With the introduction of the pedicle screw-rod system and intervertebral cages, posterior spinal fusion has increasingly become a standard procedure in the treatment of degenerative spinal conditions. The aim of this study is to investigate the influence of rod persuading in lumbar spinal fusion constructs on the pullout strength of pedicle screws, considering different bone qualities.

Ten fresh-frozen lumbar spines (L1-5) from 10 cadaveric donors were initially included. All specimens were examined at the beginning of the study both macroscopically and by computed tomography scans (HR-CT, Siemens) to ensure specimen integrity, and the mineral bone density by using Hounsfield units. One specimen had to be excluded prior to biomechanical testing due to a vertebral fracture extending into the pedicle, leaving a total of 9 specimens available for the study.

The displacement of the screws during the pullout test was significantly greater in the osteoporotic specimens after rod persuader use (Group 2), compared to the non-osteoporotic specimens (3.7 ± 0.7 mm vs. 5.5 ± 0.4 mm, p = 0.0486). This difference was not observed in the non-rod persuader group. Overall, rod persuading decreased the displacement distance until tensile load to screw failure by 29 %.

The use of the rod persuader reduces the pedicle screw pullout strength, thereby compromising the construct stability. This reduction is particularly significant in osteoporotic vertebral bodies, highlighting the need for careful consideration of rod persuader use in this patient population.

Surgical fusion through posterior instrumentation and pedicle screw placement is a long established method for stabilising traumatic spinal fractures. Post-surgical complications include infection and metal work failure, the most common aetiology of which is pedicle screw fracture. Metal work failure rates vary from 15% to 60%. Research relating to factors which predict metal work failure in post-traumatic thoracolumbar spinal fixation is lacking. This study aimed to identify potential risk factors for metalwork failure in patients who had posterior fixation for traumatic thoracolumbar spine fractures.

This retrospective cohort analysis was conducted by interrogating the hospital database for neurosurgical post-traumatic thoracolumbar fixation cases between 2015 and 2018 with at least 2 years follow up. Data was collected through electronic medical notes and PACS. Nineteen different patient factors (gender, age, mechanism of injury, presence of concomitant injury spinal or extra-spinal injury, pedicle cross-sectional area, pedicle cancellous bone density, pedicle total bone density, vertebral body bone density, erector spinae muscle density and lumbar spine subcutaneous fat thickness, Charlson comorbidity index, fracture location, surgical approach, long/short segment fixation, whether decompression was done, whether the index level was fixed, and presence of wound infection) were compared.

We identified 92 patients with 97 operations, and 9 cases of metal work failure. Two factors were statistically significantly associated with metal work failure: Post-operative wound infection (p = 0.029) and lumbar spine fat thickness (p = 0.024). The relative risk calculated in patients with a wound infection was 3.76. Lumbar spine fat thickness was on average 11.9 mm greater than patients not experiencing metal work failure.

This study has identified two factors associated with increased rates of metal work failure: Post-operative wound infection and lumbar spine fat thickness. When assessing surgical candidates these factors may be incorporated into surgical planning.

Osteoporotic vertebral compression fracture (OVCF) causes pain, kyphosis and neurological damage, which significantly affect patients' quality of life. Patients with OVCF are often elderly and have severe osteoporosis, which makes preoperative symptom more serious, postoperative recovery worse and the incidence of postoperative complications high. The paraspinal muscles have been well studied in adult spinal deformities, but there is no conclusive evidence that their findings can be applied to OVCF. The purpose of this study was to evaluate the associations between multifidus (MF) parameters including fat infiltration (FI), relative functional sectional area (rFCSA), relative gross cross-sectional area (rGCSA) and the sagittal parameters, symptom score, and postoperative complications.

To figure out the potential associations between multifidus muscle (MF) degeneration and patients' quality of life (QoL), sagittal parameters and mechanical complications in osteoporotic vertebral compression fracture (OVCF) patients with kyphosis deformity.

Retrospective cohort study.

OVCF patients with kyphosis deformity who underwent corrective surgery between 2008 to 2021.

MF fat infiltration (MFFI), relative functional cross-sectional area (MFrFCSA), MF relative gross cross-sectional area (MFrGCSA), VAS, ODI, JOA, SRS-22, preoperative, postoperative and last-follow up spine sagittal parameters, postoperative mechanical complications.

The study included 108 OVCF patients with kyphosis deformity who underwent corrective surgery and were followed for 2 years. MRI were performed preoperatively to evaluate the paraspinal muscle morphology, including MF fat infiltration (MFFI), relative functional cross-sectional area (MFrFCSA), and MF relative gross cross-sectional area (MFrGCSA). VAS, ODI, JOA, and SRS-22 were conducted preoperatively. Preoperative, postoperative and last-follow up spine sagittal parameters were recorded, as well as sagittal balance, loss of correction results and improvement and deterioration of sagittal parameters. The occurrence of postoperative mechanical complications, including adjacent segment disease, screw loosening, proximal junctional kyphosis, and distal junctional problem were recorded. We analyzed the relationship between MF degeneration and the above parameters.

Strong correlation was observed in VAS and MFFI (rr=0.597, p=.000),MF rFCSA (rr=-0.520, p=.001) and MF rGCSA (rr=-0.461, p=.005), as well as ODI and MF rFCSA (rr=-0.336, p=.042). Preoperatively, strong correlations were observed between MF rFCSA and LL (rr=-0.320, p=.010), TLK (rr=-0.271, p=.026), TK (rr=-0.251, p=.048). MF rGCSA and LL (rr=-0.259, p=.039), TLK (rr=-0.247, p=.043), TK (rr=-0.273, p=.030), GK (rr=-0.381, p=.002) were also strongly correlated. Our study showed strong correlations between MF FI and TLK loss (rr=0.406, p=.003), TK loss (rr=0.332, p=.045);MF rGCSA and SVA loss (rr =-0.367, p=.050), TPA loss (rr =-0.404, p=.030); MF rGCSA and TPA loss (rr =-0.401, p=.031), MF FI and GK loss(rr =0.397, p=.027). MF FI was significantly higher in the complication-presence group (p=.045).

Multifidus degeneration is significantly associated with QoL, sagittal parameters and mechanical complications in OVCF patients with kyphosis deformity. The pathological changes of paravertebral muscles should be included in the surgical strategy and postoperative paravertebral muscle rehabilitation should be adopted to improve the clinical outcomes of OVCF patients.

Retrospective, observational study.

To determine the frequency and predictors of implant-related complications in adults after posterior cervical fusion.

Published literature on lumbosacral fusion suggest that implant-related complications are not uncommon. Although posterior cervical fusion is a common operation, data on frequency and predictors of implant-related complications after posterior cervical fusion is still scarce.

86 patients (with 740 screws) who underwent posterior cervical fusion were included. Implant-related complications were identified by the presence of: (1) halo sign, (2) screw pull-out/breakage (3) post-operative kyphosis and (4) implant-related complications requiring revision surgery. These were stratified into two groups: (a) minor - isolated halo sign or screw pull-out/breakage (b) major - post-operative kyphosis > 10 degrees, and revision surgery. Demographic, operative and radiological data was collected. Rates of implant-related complications were determined and associated risk factors identified.

33 (38.4%) patients had signs of implant-related complications. Of these, 29 (87.9%) had minor complications and 4 (12.1%) had major complications. Charlson Comorbidity Index (CCI) (p = 0.03179) and pre-op C2-C7 sagittal vertical alignment (SVA) (p = 0.02449) were the only significant risk factors for all-cause implant-related complications during multivariate logistic regression. Other intraoperative parameters (type of screw, length of fusion, levels decompressed, and extension of fusion beyond the levels decompressed) were not significantly associated with implant-related complications.

Implant-related complications are not uncommon but rarely require revision surgery. Higher pre-operative SVA and CCI were significant risk factors; length of construct and extent of decompression were not. These findings may assist clinicians when deciding the extent of fusion and in selecting patients for closer follow-up.

To clarify the ability of the preoperative CT Hounsfield units (HU) of the vertebrae and MRI-based vertebral bone quality (VBQ) score in predicting screw loosening following lumbar interbody fusion.

Patients with lumbar degenerative disease who underwent single-level lumbar interbody fusion at five hospitals were enrolled. The HU were assessed at vertebral body and pedicle. The VBQ score was assessed on the T1-weighted sagittal image and defined as the quotient of the median signal intensity of the vertebrae from L1 to L4 divided by the signal intensity of the cerebrospinal fluid. Screw loosening was evaluated by the postoperative CT scans at 12 months or more. Patients were divided into the screw loosening group and no loosening group, and the HU and the VBQ score were compared between the groups.

A total of 107 patients (mean age, 67.8 ± 10.1 years, 62 men) were included. At the vertebral body, the HU of L1, the average HU from L1 to L4, from L1 to L5, and from L1 to S1, and the HU of the upper instrumented vertebra showed a statistically significant difference between the two groups. The average HU of the vertebral body from L1 to L4 showed the highest AUC of 0.651 and sensitivity of 0.818. No significant difference was found in the HU of the pedicle and VBQ score.

The preoperative CT HU of the vertebral bodies could reliably predict screw loosening following lumbar interbody fusion. In contrast, the VBQ score did not predict screw loosening.

Study DesignRetrospective series.ObjectiveScrew loosening in the surgical treatment of lumbar spine disease is a major complication of osteopenia or osteoporosis. This study investigated the risk of screw loosening following either MIS-TLIF or pedicle screw-based dynamic stabilization (DS) in patients with osteopenia or osteoporosis.MethodsWe retrospectively enrolled patients receiving 1- or 2-level MIS-TLIF or DS in a single institute. All patients were diagnosed as having lumbar spondylosis without concurrent spondylolisthesis and found by dual-energy X-ray absorptiometry to have osteopenia or osteoporosis. Screw loosening was identified by X-ray and CT. Clinical outcomes were also assessed.ResultsA total of 103 patients (50 MIS-TLIF and 53 DS) were confirmed to have osteopenia (-2.5 Collapse

Osteoporotic vertebral compression fractures (OVCFs) are common fractures and pedicle screw system gains dissatisfactory results since bone mass loss. Cement augmentation (CA) is the most applied surgery modality for OVCFs but with shortcomings. Pedicle screw fixation plus CA (PSF + CA) has been reported superior to CA. This study aims to investigate the impact of PSF + CA on OVCFs.

We approached databases of PubMed, Europe PMC, Web of Science, CENTRAL, and Embase for studies published up to November 2023. Clinical outcomes (hospital stay, blood loss, cement volume, cement leakage, secondary fracture), radiological outcomes (local kyphotic angle and anterior vertebral height), and subjective outcomes (visual analog scale and Oswestry Disability Index) were extracted. We tested the sensitivity and publication bias, rated evidence, calculated total effect sizes with prediction intervals, and explained heterogeneity.

Six studies were included with 255/339 patients in the PSF + CA group/CA-only group. The result is as follows: the PSF + CA group showed better in local kyphotic angle; anterior vertebral height claimed insufficient support favoring PSF + CA. The CA-only group showed better clinical outcome of hospital stay, blood loss, and operative time. Cement volume and cement leakage difference were not significant. Secondary fractures occurred more in the CA-only group. Visual analog scale scores favored the PSF + CA group, and Oswestry Disability Index results were too inaccurate to conclude.

PSF + CA and CA-only procedures achieved efficient clinical outcomes in OVCFs. PSF + CA showed better strength in deformity correction and long-term maintenance, less strength in incidence of secondary fracture, and more pain relief at the cost of length of hospital stay, blood loss, and operative time.

Investigate whether S1 vertebral bone quality (VBQ) score serves as a viable substitute for the traditional VBQ score in predicting screw loosening in patients undergoing transforaminal lumbar interbody fusion (TLIF) for lumbar spondylolisthesis using quantitative computed tomography (QCT) as a standard reference.

We reviewed 165 patients undergoing single-segment TLIF for lumbar spondylolisthesis at our center from 2012 to 2021. Demographic and radiographic data were collected. To determine the independent factors affecting pedicle screw loosening, univariate analysis and multivariate logistic regression were conducted. Receiver operating characteristic analysis was carried out to assess the predictive ability.

16.3% of patients experienced screw loosening at a minimum of 24 months of follow-up. Statistically significant differences in the 2 groups were observed in surgery level (L5-S1), traditional VBQ, S1 VBQ, and QCT values. QCT values, traditional VBQ score, and the S1 VBQ score were independent risk factors for screw loosening. The receiver operating characteristic analysis showed that area under the curve (AUC) of QCT was 0.839 (95% confidence interval [CI]: 0.771-0.907) and the cut-off value was 119 (sensitivity: 85.2% and specificity: 76.8%); AUC of VBQ scores was 0.787 (95% CI: 0.699-0.875) and the cut-off value was 3.585 (sensitivity: 88.9% and specificity: 69.6%), while AUC of S1 VBQ score was 0.823 (95% CI: 0.739-0.908) and the cut-off value was 3.72 (sensitivity: 81.5% and specificity: 76.8%).

The elevated S1 VBQ score was identified as an independent risk factor for screw loosening and exhibits greater predictive capability compared to the traditional VBQ score in forecasting screw loosening following TLIF for lumbar spondylolisthesis.

Pedicle screws are commonly used in spinal surgeries, but screw loosening remains a major concern, even in non-osteoporotic patients. Predicting pedicle screw stability via the insertion torque is a controversial topic, mainly studied on osteoporotic cadavers. Whether the insertion torque is suitable for patients with healthy bone mineral density (BMD) remains unknown. The aim was to investigate the influencing factors, namely insertion torque, BMD, screw diameter, length, surface area, volume, screw-in rotations, vertebral level, on the screw loosening stability during distractions and to understand if intra-operative predictions are possible.

Non-osteoporotic thoraco-lumbar vertebrae (n = 50) were used to implant five different pedicle screws (n = 100) while measuring the insertion torque. After embedding the endplates, the force needed to distract the screw head by 1 mm was tested.

The insertion toque (2.3 ± 0.9 Nm) showed the highest influence on the distraction force (324.8 ± 84.4 N) followed by the screw size and vertebral level. BMD did not show any effects.

The linear correlation of insertion torque and the bending force suggests an alternative prediction metric for screw loosening which could improve the outcome of surgeries and patients' safety. This is potentially a simple, intra-operative method, which can be used in future.

Screw loosening is one of the most frequent complications after instrumented spine surgery, which constitutes a heavy burden for patients and the health care system. Low-virulent colonialization with biofilm formation has been identified as a possible cause for screw loosening. The aim of this study was to investigate the rate of low virulent infections in recurrent screw loosening after revision surgery.

Seventy-nine patients from January 2015-July 2018 undergoing revision surgery due to clinically aseptic implant loosening were included in our observational study. Sonication of the loosened implant was performed. All identified patients received clinical and radiographic follow-up. Screw loosening was evaluated in computed tomography scans carried out at least 12 months after revision surgery. Patients were differentiated into the following 3 groups: 1) all patients with low virulent colonialization, who received antibiotic treatment (Co + ABX); 2) all patients with colonialization without postoperative antibiotic treatment (Co-ABX); and 3) reference cohort containing all patients without colonialization (noCo).

Seventy-nine patients (51 females; mean age, 65.12 years) were identified. Forty-two patients (51.2%) received radiologic follow-up with computed tomography scan for implant control. These patients were assigned to 3 groups (Co + ABX: n = 5 [12%]; Co-ABX: n = 8 [19%]; noCo: n = 29 [69%]). In 10 of 13 patients with positive sonication results (Co + ABX and Co-ABX), recurrent screw loosening occurred (76.9%). Antibiotic administration had no influence on screw loosening rates (4 of 5 patients [80%] in Co + ABX and 6 of 8 [75%] patients in Co-ABX; P > 0.05). In the reference group, noCo, in 11 of 29 patients (37.9%), recurrent screw loosening was identified (P = 0.043).

In patients with screw revision surgery, incidence of low-virulent microorganism colonialization is high and may play a role in the incidence of screw loosening. New therapeutic approaches addressing low-virulent infections and biofilm formation may be helpful.

To retrospectively analyze screw loosening rates following dynamic fixation with polyetheretherketone (PEEK) rods and rigid fixation with titanium rods and assess mid-term outcomes of loosened screws.

This retrospective analysis included 203 patients who underwent lumbar pedicle screw fixation between March 2017 and June 2020 (57 with PEEK rods, 146 with titanium rods). Patients were followed for at least 48 months to evaluate screw loosening postoperatively and investigate outcomes of loosened screws. Multivariate logistic regression identified factors influencing screw restabilization.

Both PEEK rod and titanium rod groups exhibited peak screw loosening rates approximately 1 year after surgery, decreasing with longer follow-up. At 48 months, screw loosening rates were 5.3% and 15.8% for PEEK and titanium rods, respectively (P < 0.05). Among patients experiencing early loosening (within 12 months), the proportion of stabilized screws was significantly higher with PEEK rods (84% vs. 34%, P < 0.001). Regression analysis revealed dynamic fixation (odds ratio 4.579; 95% confidence interval 1.611-12.519), lowest fixed vertebra S1 (odds ratio 3.151; 95% confidence interval 1.352-9.233), and L1-L4 average computed tomography value (odds ratio 1.132; 95% confidence interval 1.015-1.263) as independent risk factors for screw restabilization. The area under the receiver operating characteristic curve for L1-L4 average computed tomography value predicting restabilization was 0.713 (P < 0.05), with an optimal threshold of 106 Hounsfield units (sensitivity 0.771, specificity 0.803).

Following PEEK rod dynamic fixation surgery, a certain proportion of screw loosening may occur in the short term. With prolonged follow-up, screws gradually restabilize at the bone interface, with most loosened screws returning to a stable state.

Retrospective cohort study.

To evaluate the effectiveness of pedicle screw trajectory planning based on artificial intelligence (AI) software in patients with different levels of bone mineral density (BMD).

AI-based pedicle screw trajectory planning has potential to improve pullout force (POF) of screws. However, there is currently no literature investigating the efficacy of AI-based pedicle screw trajectory planning in patients with different levels of BMD.

The patients were divided into 5 groups (group A-E) according to their BMD. The AI software utilizes lumbar spine CT data to perform screw trajectory planning and simulate AO screw trajectories for bilateral L3-5 vertebral bodies. Both screw trajectories were subdivided into unicortical and bicortical modes. The AI software automatically calculating the POF and pullout risk of every screw trajectory. The POF and risk of screw pullout for AI-planned screw trajectories and AO standard trajectories were compared and analyzed.

Forty-three patients were included. For the screw sizes, AI-planned screws were greater in diameter and length than those of AO screws ( P <0.05). In groups B-E, the AI unicortical trajectories had a POF of over 200N higher than that of AO unicortical trajectories. POF was higher in all groups for the AI bicortical screw trajectories compared with the AO bicortical screw trajectories ( P <0.05). AI unicortical trajectories in groups B-E had a lower risk of screw pullout compared with that of AO unicortical trajectories ( P <0.05).

AI unicortical screw trajectory planning for lumbar surgery in patients with BMD of 40-120 mg/cm 3 can significantly improve screw POF and reduce the risk of screw pullout.

Pedicle screw loosening is one of the common complications in elderly patients undergoing transforaminal lumbar interbody fusion (TLIF) for lumbar spine disease. Malnutrition, prevalent among elderly patients, has been shown to be associated with increased complications. The Geriatric Nutritional Risk Index (GNRI) serves as a simple indicator of nutritional status. However, the relationship between malnutrition, particularly GNRI, and pedicle screw loosening has not been adequately investigated. This study aims to investigate the relationship between GNRI and pedicle screw loosening following TLIF to guide the perioperative nutritional management of patients and prevent postoperative complications.

A retrospective review was conducted on clinical data from patients who underwent single-level TLIF between 2014 and 2022. Data collection encompassed patient demographics, preoperative laboratory parameters, surgery-related data, perioperative radiographic data, and patient-reported outcomes were comprehensively documented. All patients were followed up for a minimum of 12 months. The relationship between GNRI and pedicle screw loosening was evaluated by univariate and multivariate Cox regression analysis, restricted cubic spline (RCS) analysis, receiver operating characteristic (ROC) analysis, and Kaplan-Meier survival analysis.

A total of 426 patients were included in the study. The rate of pedicle screw loosening rate was 16.4% at a minimum follow-up of 12 months. Patients with pedicle screw loosening exhibited significantly lower GNRI (89.0 ± 8.0 vs. 99.2 ± 9.3, p < 0.001) and volumetric bone mineral density measured by quantitative computed tomography (QCT-vBMD) (84.2 [interquartile range (IQR) 79.6-92.2] vs. 104.0 [IQR 88.2-126.0] mg/cm3, p < 0.001) compared with those in the non-loosening group. Multivariate Cox regression analysis identified sex (hazard ratio [HR] 1.433, 95% confidence interval [CI] 0.714-2.876, p = 0.027), age (HR 1.062, 95% CI 1.014-1.113, p = 0.012), GNRI (HR 0.841, 95% CI 0.711-0.994, p = 0.043), and QCT-vBMD (HR 0.982, 95% CI 0.967-0.997, p = 0.019) as independent risk factors for screw loosening. RCS analysis showed that GNRI was negatively correlated with screw loosening (p < 0.0001). The area under the curve (AUC) for the GNRI in predicting pedicle screw loosening was 0.794, with a cut-off value of 95.590 (sensitivity, 85.7%; specificity 65.2%). Kaplan-Meier survival analysis identified that the lower-level GNRI group exhibited a higher cumulative incidence of screw loosening (log-rank test, p < 0.0001).

The GNRI was an independent risk factor for postoperative screw loosening in elderly patients undergoing TLIF for lumbar spine disease. Preoperative GNRI may potentially serve as a valuable tool in predicting postoperative screw loosening in elderly patients undergoing TLIF.

Screw-loosening is a common instrumentation-related complication following fusion. Patients who present with pain and neurological symptoms due to screw-loosening require revision. It has been reported that fat-infiltrated and/or atrophied paraspinal muscles were associated with low back pain, disability, radiculopathy, and instrumentation-related failures. However, there is limited and conflicting knowledge regarding the association of paraspinal muscles with screw-loosening. In the present study, we aimed to identify whether fatty infiltration in the paraspinal muscles was associated with screw-loosening.

A retrospective analysis of the clinical and radiological data of the patients who underwent short-segment decompression and fusion for lumbar spinal stenosis (LSS) at a tertiary spine clinic between 2013 and 2023. Goutallier's classification system was used for grading fatty infiltration in the paraspinal muscles.

Patients with screw-loosening had fattier multifidus at the upper lumbar spine (particularly L2-L3, cephalad to the upper instrumented level of L3-L4) compared to those without screw-loosening. In univariate analysis fatty multifidus at L2-L3 level, elder age, and male sex had ORs of 1.509 (p = 0.008), 1.116 (p = 0.001) and 4.702 (p = 0.004), respectively. In multivariate analysis fatty multifidus at L2-L3 level, elder age and male sex had ORs 1.428 (p = 0.043), 1.109 (p = 0.003), and 5.911 (p = 0.004), respectively.

Fatty infiltration in the multifidus muscle (particularly in the one at the cranial end of the fusion mass) is predictive for screw-loosening following short-segment lumbar decompression and fusion for LSS. Preserving multifidus in subjects is essential to prevent future long-term complications of spine surgery.

Pedicle screw loosening (PSL) is a frequent complication in osteoporotic patients undergoing spinal fixation, yet effective risk assessment methods are limited. This study explores the impact of craniocaudal cyclic load on pedicle screw fixation strength using computed tomography-based finite element analysis (CT-FEA) and evaluates its predictive value for PSL.

A total of 23 PSL cases (7 men and 16 women) and 29 matched controls were analyzed using CT-FEA. Both a simple axial pullout load and a pullout load with a preset craniocaudal cyclic load were applied to calculate the pullout force. Hounsfield unit (HU) values and volumetric bone mineral density (vBMD) of the screw trajectory were also assessed for osteoporosis evaluation. The pullout force and osteoporotic assessment value were compared between PSL and controls.

Craniocaudal cyclic loading significantly reduced the pullout force (924.3 ± 195.1 N vs. 745.2 ± 188.7 N, p < 0.0001). The PSL group had a lower pullout force under cyclic load (629.6 ± 188.2 N vs. 836.9 ± 131.6 N, p < 0.0001) and lower HU value of screw trajectories (183.7 ± 42.6 vs. 206.7 ± 29.72, p = 0.026) than controls, while simple axial pullout force and vBMD showed no significant differences. Receiver operating characteristic (ROC) analysis indicated that pullout force under cyclic load (AUC = 0.806) was a better predictor of PSL than HU values (AUC = 0.629).

This study demonstrates the critical role of craniocaudal cyclic loading in pedicle screw fixation strength and its predictive value for PSL. Craniocaudal cyclic load reduces screw fixation strength significantly. Pullout force under cyclic load assessed by CT-FEA enhances the predictive accuracy for PSL risk.

To explore incidence and predictive factors for distal pedicle screw loosening (DPSL) followed posterior corrective surgery for degenerative lumbar scoliosis (DLS).

The diagnostic criteria for DPSL developed by X-ray including radiolucent area around screw and "double halo" sign. According to occurrence of DPSL at two-year follow-up, 153 patients were divided into two groups: study group (screw loosening) and control group (without screw loosening). To investigate predictive factors for DPSL, three categorized factors including general data, surgical data and radiological data were analyzed statistically.

DPSL was detected in 72 patients at two-year follow up (study group). Hounsfield unit (HU) value was lower in study group than that in control group. Fusion level was longer in study group than that in control group. Lower instrumented vertebrae on L5 was less in study group than that in control group. Posterolateral fusion was less in study group than that in control group. Preoperative Cobb angle, postoperative Cobb angle, Cobb angle correction, preoperative lumbosacral coronal angle (LSCA), LSCA correction, preoperative thoracolumbar junction (TL), postoperative TL were larger in study group than those in control group. Logistic regression analysis revealed that low Bone mineral density (BMD) (< 169 HU), posterolateral fusion, Cobb angle correction (> 16 degrees), LSCA correction (> 9 degrees) were independently associated with DPSL.

The incidence of DPSL following posterior decompression and instrumented fusion for DLS is 47.1%. Low BMD, large correction of both main curve and fractional curve are predictive factors for DPSL, posterolateral fusion is a protective factor.

Screw loosening remains a serious complication for patients undergoing pedicle screw fixation surgeries. An accurate risk prediction is significant for prevention of screw loosening through preoperative planning. In this study, we proposed a novel index, namely the bone mineral density surrounding the screw thread (thread BMD), and tested its predictability in screw loosening.

86 screws (18 loosening and 68 non-loosening) from L3-L5 of 20 patients who experienced pedicle screw loosening were analyzed. The preoperative and postoperative quantitative CT scans of the same vertebra were spatially registered and a helix-based approach was developed to extract the thread BMD. BMDs of the vertebral body, the pedicle and the screw trajectory were also measured from the preoperative CT scans. Finite element analysis was conducted to determine pullout strength and tissue failure around the screw. Receiver operating characteristic (ROC) curve analysis was used to assess the performances of all BMD indices and pullout strength in predicting screw loosening. Linear regression was used to examine correlations between different BMD indices and screw pullout strength.

The thread BMD had the greatest value of area under the curve (AUC = 0.73, p = 0.004) compared to vertebral BMD (AUC = 0.51, p = 0.923), pedicle BMD (AUC = 0.56, p = 0.474) and trajectory BMD (AUC = 0.67, p = 0.020). Also, the thread BMD showed a stronger correlation with the pullout strength (r = 0.83, p < 0.001) than vertebral BMD (r = 0.59, p < 0.001), pedicle BMD (r = 0.65, p < 0.001) and trajectory BMD (r = 0.60, p < 0.001).

We developed a novel approach to measure a newly-defined thread BMD, which indicates superior capacities over other BMD indices in predicting pedicle screw loosening.

Osteoporosis is a crucial risk factor for screw loosening. Our studies indicate that the bone mineral density (BMD) in the screw trajectory is a better predictor of screw loosening than the BMD of the lumbar spine or the screw insertion position. Research has shown that anchorage on the screw tip is the most significant factor for screw anchorage ability, while others argue that decreased bony quality in the pedicle poses a significant risk for screw loosening. This study aimed to determine whether the bony quality of the screw tip, pedicle, or screw-anchored vertebral body plays the most significant role in screw anchorage ability.

A total of 73 patients who underwent single-segment bilateral pedicle screw fixation, along with posterior and transforaminal lumbar interbody fusion (PLIF and TLIF), from March 2019 to September 2020 were included in this retrospective study. The Hounsfield unit (HU) value of the fixed vertebral bodies, the entire screw trajectory, screw tip, screw-anchoraged vertebral body, and pedicles were measured separately. Data from patients with and without screw loosening were compared, and regression analyses were conducted to identify independent risk factors. Additionally, the area under the curve (AUC) values were computed to assess the predictive performance of different parameters. Furthermore, fixation strength was calculated in numerical models with varying bony densities in different regions.

HU values were found to be significantly lower in the loosening group across most measuring methods (HU values in the pedicle, 148.79 ± 97.04, 33.06 ± 34.82, p < 0.001). Specifically, the AUC of screw loosening prediction was notably higher when using HU values of the pedicle compared to other methods (AUC in the pedicle > 0.9 and in the screw insertion position > 0.7). Additionally, computational results for fixation strength revealed a clear decline in screw anchorage ability in models with poor BMD in the pedicle region.

Pedicle bone quality plays a more significant role in screw anchorage ability than that in other regions. The innovation of bony augmentation strategies should pay more attention to this region to optimize the screw anchorage ability effectively.

Pedicle screw loosening (PSL) after spinal fusion surgery is one of the most frequently reported complications and leads to poor clinical outcomes.

This study aimed to develop and validate a risk prediction model for PSL within two years in patients undergoing lumbar instrumented fusion surgery based on their risk profiles.

Retrospective, observational study.

Patients who underwent lumbar instrumented fusion surgery at a single academic institution between May 2015 and February 2019.

Risk assessment of PSL and development of a rating score based on patient characteristics.

The demographic profiles and radiographic parameters using computed tomography were obtained. These factors were analyzed to determine possible risk factors related to postoperative PSL after 2 years. A scoring system was developed using these independent risk factors and validated using prospectively collected data from another center between May 2019 and December 2021.

The occurrence of PSL within 2 years postoperation was 12.7% (40/315). PSL was significantly predicted by smoking, low Hounsfield units (HU) of the pedicle tract at the index level (P), and a low psoas-lumbar vertebral index (PLVI). The risk of PSL according to the categories of the risk score was 1.1% for those with a score of 0-1, 15.1% for a score of 2-3, and 61.5% for a score of 4-6. In validation, this model demonstrated both good discrimination and calibration results. The area under the curve was 0.887 (95% CI 0.830-0.938) for the derivation cohort and 0.835 (95% CI 0.738-0.918) for the external validation cohort.

This PSL risk score, including smoking, Index P HU, and PLVI, is a novel approach to predict PSL 2 years post-surgery. This approach highlights the role of factors associated with osteoporosis and sarcopenia in the development of PSL and could aid in preoperative decision-making and surgical planning.

Metallic implants often produce artifacts in computed tomography (CT) imaging, complicating the interpretation of postoperative findings. This case report describes a 63-year-old male with a history of cervical and lumbar spine surgeries who presented with worsening radicular pain. The patient underwent cervical decompression laminectomy and posterior instrumented fusion. Postoperative CT, processed with an iterative metal artifact reduction (iMAR) algorithm, revealed unexpected hypodense lucencies surrounding pedicle screws and fixation hardware, initially suggestive of hardware loosening or infection. However, these lucencies were not seen in non-processed images, indicating their artifactual nature. This case highlights the potential for iMAR to generate misleading findings that may mimic clinical conditions, emphasizing the need for a careful approach when interpreting iMAR-processed images in conjunction with clinical context and pre-processed datasets to prevent unnecessary interventions.

Multicenter retrospective cohort study.

To evaluate the efficacy and safety of using cement-augmented pedicle screw (CAPS) fixation only for the cephalad and caudal vertebral bodies.

Pedicle screw fixation is less effective in patients with low-quality bone. Although CAPS fixation has shown promise in improving stability and reducing screw loosening in such cases, cement leakage can have serious consequences.

This study included 65 patients who underwent spinal surgery using CAPS and were followed up for >3 months. Four CAPSs were used in each patient, and 254 CAPSs were included in the analysis.

Of the 65 patients, 36.9% showed intravenous cement leakage, and a low bone mineral density (BMD) was associated with a higher risk of cement leakage. The use of a CAPS on the right side was also potentially associated with a higher risk of leakage. However, the shape and location of the leaked cement remained stable over time. Screw loosening occurred in 3.5% of the CAPSs and was associated with a lower cement volume.

Cement leakage was related to lower BMD. Using CAPS exclusively at the lower or upper instrumentation levels might minimize the risk of cement leakage in osteoporotic patients.

This study aimed to identify whether the ratio of the vertebral Hounsfield unit to serum pentosidine (H/P ratio), which reflects bone density and quality, can predict screw loosening after spinal fusion surgery.

A retrospective case-control study was conducted in 35 patients (mean age 71 ± 10.4 years, 18 men) who underwent spinal interbody fusion for lumbar spine disease between June 2020 and February 2022. Screw loosening was evaluated by computed tomography at 12 months postoperatively. Information was collected on patient background characteristics, including age, sex, body mass index, diagnosis, dialysis status, smoking history, diabetes, steroid use, and osteoporosis. Imaging parameters, the surgical method used, number of fixed intervertebral segments, intervertebral level (including L5/S1 or not), and the H/P ratio were also investigated. Risk factors associated with screw loosening and pseudarthrosis were examined in univariable and multivariable logistic regression analyses. A P-value of < 0.05 was considered statistically significant.

Screw loosening occurred in 14 of 35 patients (40%). Multivariate analysis revealed that the H/P ratio (odds ratio 0.09, confidence interval 0.02-0.53, P = 0.007) was a significant risk factor for screw loosening at 12 months postoperatively.

This study demonstrates that the H/P ratio, which reflects both bone density and deterioration of bone quality in the vertebral body, may serve as a predictor of screw loosening at 12 months after lumbar spinal surgery.

Pedicle screws have long been established as the gold standard for spinal bone fixation. However, their fixation strength can be compromised in cases of low bone density, particularly in osteoporotic bone, due to the reliance on a micro-shape lock between the screw thread and the surrounding bone. To address this challenge, we propose augmenting conventional pedicles screws with a curved compliant anchor. This anchor integrates a curved super-elastic nitinol rod that is advanced through a canulated pedicle screw, forming a macro-shape lock within the vertebral body to aid the fixation strength. Both placement safety and fixation strength of this novel spinal bone anchor were validated on tissue phantoms (Sawbones). The radius of the curved compliant anchor's path demonstrates high precision while exhibiting strong dependence on the bone density in which the anchor is placed. When the curved compliant anchor is combined with a conventional pedicle screw, the mean maximum pull-out force elevated to 290 N, marking a 14% enhancement in pull-out resistance compared to using pedicle screw alone. Further augmentation with multiple curved compliant anchors holds promise for even greater fixation. The application of a curved compliant spinal bone anchor offers a promising means of increasing the fixation strength of pedicles screws, which is especially relevant in challenging clinical scenarios such a patient suffering from osteoporosis.

Retrospective Cohort.

(1) To determine if vertebral HU values obtained from preoperative CT predict postoperative outcomes following one to three level lumbar fusion and (2) to investigate whether decreased BMD values determined by HU predict cage subsidence and screw loosening.

In light of suboptimal screening for osteoporosis, vertebral computerized tomography (CT) Hounsfield Units (HU), have been investigated as a surrogate for bone mineral density (BMD).

In this retrospective study, adult patients who underwent one to three level posterior lumbar decompression and fusion (PLDF) or transforaminal lumbar interbody and fusion (TLIF) for degenerative disease between the years 2017 and 2022 were eligible for inclusion. Demographics and surgical characteristics were collected. Outcomes assessed included 90-day readmissions, 90-day complications, revisions, patient-reported outcomes (PROMs), cage subsidence, and screw loosening. Osteoporosis was defined as HU of ≤110 on preoperative CT at L1.

We assessed 119 patients with a mean age of 59.1, of whom 80.7% were white and 64.7% were nonsmokers. The majority underwent PLDF (63%) compared with TLIF (37%), with an average of 1.63 levels fused. Osteoporosis was diagnosed in 37.8% of the cohort with a mean HU in the osteoporotic group of 88.4 compared with 169 in nonosteoporotic patients. Although older in age, osteoporotic individuals did not exhibit increased 90-day readmissions, complications, or revisions compared with nonosteoporotic patients. A significant increase in the incidence of screw loosening was noted in the osteoporotic group with no differences observed in subsidence rates. On multivariable linear regression osteoporosis was independently associated with less improvement in visual analog scale (VAS) scores for back pain.

Osteoporosis predicts screw loosening and increased back pain. Clinicians should be advised of the importance of preoperative BMD optimization as part of their surgical planning and the utility of vertebral CT HU as a tool for risk stratification.

3.

Basic study.

This study aimed to utilize finite element (FE) analysis and design of experiment (DoE) techniques to propose and optimize a novel pedicle screw design and compare its pull-out force with that of a control device.

Pedicle screw-based fixation is the gold-standard treatment for spine diseases, particularly in fusion procedures. However, pedicle screw loosening and breakage still occur in osteoporotic and non-osteoporotic patients. This research investigates screw design modifications to enhance screw-bone interface strength and reduce the likelihood of loosening.

We conceptualized a novel pedicle screw considering vertebral bone morphology and strength differences. A validated FE model was developed and used in conjunction with DoE to determine the screw՚s optimum geometrical parameters. The FE model was validated through simulation and laboratory experiments using the control device. The optimized thread profiles for cortical bone and cancellous bone were determined, with pull-out force as the primary factor for screw design evaluation.

FE analysis results for the control device closely matched experimental results, with less than 5% difference. The chosen unique pitch/depth ratio showed maximum pull-out force for cortical bone, while DoE enabled the optimization of design parameters for cancellous bone. The optimized pedicle screw exhibited a 15% increase in pull-out force compared to the control device.

The study proposes a novel pedicle screw design with better pull-out strength than the control device. Combining FE analysis with DoE is an effective approach for screw design optimization, reducing the need for extensive prototyping tests. A two-variable analysis suffices for optimizing cortical bone design parameters, while a multi-variable analysis is more effective for optimizing cancellous bone design parameters.

To compare hidden blood loss (HBL) of minimally invasive transforaminal lumbar interbody fusion (Mis-TLIF) of lumbar degenerative diseases in patients with or without osteoporosis (OP) and identify the risk factors for HBL with OP.

The data from 156 patients with lumbar degenerative diseases, who underwent Mis-TLIF between January 2018 and December 2021, were retrospectively analyzed. The patients were divided into the Osteoporosis and Non-osteoporosis groups. We recorded demographic characteristics and blood-related parameters in each group. Blood loss was measured by quantifying visible blood loss and calculating HBL using preoperative hematocrit (Hctpre) and postoperative hematocrit (Hctpost). Pearson or Spearman correlation analysis was used to investigate the association between OP patient's characteristics and HBL. Multivariate linear regression analysis was used to confirm independent risk factors of HBL in patients with OP.

The mean HBL of the Osteoporosis and Non-osteoporosis groups was 608.27 ± 175.23 and 173.04 ± 67.55 ml, respectively. There were significant differences in age, BMI, subcutaneous fat thickness, muscle thickness, Hctpost, average hematocrit of preoperative and postoperative (Hctave), visible blood loss, HBL and volume of allogeneic blood transfusions between the two groups (P < 0.05). Multivariate linear regression analysis showed that Hctpost, T-score, use of tranexamic acid (TXA) and preoperative regular anti-osteoporosis treatment were independent risk factors for HBL in patients with OP.

There was significant perioperative HBL in patients with OP. Hctpost, T-score, use of TXA and preoperative regular anti-osteoporosis treatment were independent risk factors for HBL in patients with OP. More attention should be paid to the perioperative period to ensure the safety of patients with OP.

Percutaneous cement augmentation has been reported as an effective salvage procedure for frail patients with spinal instrumentation failure, such as screw loosening, hardware breakage, cage subsidence, and fractures within or adjacent to stabilized segments. Favorable results were reported during a median follow-up period of 16 months in a retrospective analysis of 31 consecutive procedures performed in 29 patients. In the present study, the long-term effectiveness of this treatment in avoiding or postponing revision surgery is reported.

Clinical and radiologic data of our original cohort of patients were retrospectively collected and reviewed to provide an extended follow-up assessment. The need for revision spinal surgery was assessed as the primary outcome, and the radiologic stability of the augmented spinal implants was considered as the secondary outcome.

An extended radiologic follow-up was available in 27/29 patients with an average of 50.9 months. Overall, 18 of 27 (66.7%) patients, originally candidates for revision surgery, avoided a surgical intervention after a cement augmentation rescue procedure. In the remaining patients, the average interval between the rescue cement augmentation and the revision surgery was 22.5 months. Implant mobilization occurred in 2/27 (7.4%) patients; rod breakage, in 1/27 (3.7%); a new fracture within or adjacent to the instrumented segment occurred in 4/27 (14.8%) patients; and screw loosening at rescued levels occurred in 5/27 (18.5%) patients.

In this cohort, cement augmentation rescue procedures were found to be effective in avoiding or postponing revision surgery during long-term follow-up.

Retrospective multicenter study.

To examine the shape change of screw-rod constructs over time after short-segment lumbar interbody fusion and to clarify its relationship to clinical characteristics.

No study has focused on the shape change of screw-rod constructs after short-segment fusion and its clinical implications.

One hundred eight patients who had single-level lumbar interbody fusion with pedicle screws and cages were enrolled. Three-dimensional (3D) images of screw-rod constructs were generated from baseline CT on the day after surgery and follow-up CT and were superposed on the right and left side, respectively, using the iterative closest point algorithm. The shape change was quantitatively assessed by computing the median distance between the 3D images, which was defined as the shape change value. Among the 5 time-course categories of follow-up CT (≤1, 2-3, 4-6, 7-12, and ≥13 months), the shape change values were compared. The relationships between the shape change values and clinical characteristics, such as age, CT-derived vertebral bone mineral density, screw and rod materials, and postoperative interbody fusion status, cage subsidence, and screw loosening, were evaluated.

A total of 237 follow-up CTs were included (≤1 [34 scans], 2-3 [33 scans], 4-6 [80 scans], 7-12 [48 scans], and ≥13 months [42 scans]) because many patients underwent multiple follow-up CTs. There were significant differences in shape change values among the time-course categories ( P <0.001 in Kruskal-Wallis test). Most shape changes occurred within 6 months postoperatively, with no significant changes observed at 7 months or more. There were no significant relationships between the shape change values and each clinical characteristic.

The temporal shape changes of screw-rod constructs following short-segment lumbar interbody fusion progressed up to 6 months after surgery but not significantly thereafter.

In orthopedic surgery, precise bone screw insertion is crucial for stabilizing fractures, necessitating a preliminary cortical bone drilling procedure. However, this process can induce temperatures exceeding 70 °C due to the low thermal conductivity of cortical bone, potentially leading to thermal osteonecrosis. Furthermore, significant cutting forces and torque pose risks of tool breakage and bone damage, underlining the need for high precision and optimal processing parameters. Traditionally, drilling relies on the surgeon's experience and often results in imprecise outcomes due to inconsistent feed rates. Therefore, this study proposes the use of a 6-axis robot for controlled drilling, offering precise control over angular velocities and consistent feed rates. Additionally, explore the use of cryogenic liquid nitrogen (LN2) as a novel cooling method compared to conventional saline solutions, examining its efficacy under various cutting conditions. The results demonstrate that LN2 cooling conditions lead to a reduction in thrust and torque under specific processing conditions, and facilitate smoother chip evacuation. Additionally, LN2 significantly lowers the peak temperature around the drilling site, thus minimizing the risk of thermal osteonecrosis. Consequently, the use of a 6-axis robot provides consistent feed rates, and LN2 cooling achieves optimal processing conditions, enabling a more controlled and effective drilling process.

The cortical bone trajectory (CBT) technology is an effective substitute for traditional pedicle screw (PS) technology. However, there is still controversy about the CBT screw technology placement strategy. The objective of this study was to simulate cortical screw placement with the help of three-dimensional (3D) software, to discuss the differences in screws between genders and vertebral segments, and to explore a safer and more efficient strategy for cortical screw placement.

Mimics Medical software was used to construct a 3D model of the lumbar spine, and the placement of CBT screws was simulated. The volume of each vertebral body from L1 to L5, the pedicle isthmus height (IH), the pedicle isthmus width (IW), and the sagittal vertebral distance (SAVD) were measured. The transverse distance (TD) and the longitudinal distance (LD) between the ideal starting point (SP) and the clinical SP (the intersection Q of the midline of the superior articular process and the horizontal line 1 mm below the transverse process) were measured. The cephalad angle (CA), lateral angle (LA), maximum screw diameter (MSD), maximum screw length (MSL) of each trajectory of the L1 to L5 vertebral bodies, and the percentage of the screw insertion depth (PSID) into the vertebral body were measured. Data were statistically analyzed using Student's t-test, one-way analysis of variance (ANOVA), and Tukey's test.

Vertebral anatomical parameters and CBT screw parameters differed between males and females. Female patients had lower IH, IW, SAVD, CA, LA, MSD, and MSL than males. IH was greatest in L1 (male, 17.81 mm; female, 16.12 mm) and the smallest in L5 (male, 14.11 mm; female, 13.05 mm). IW was smallest in L1 (male, 8.89 mm; female, 7.37 mm) and greatest in L5 (male, 16.59 mm; female, 15.43 mm). The MSD of males was smallest in L1 (6.05 mm) and greatest in L3 (7.06 mm); the MSD of females was smallest in L1 (5.13 mm) and greatest in L4 (6.64 mm). MSL was greatest at L3 (male, 33.63 mm; female, 32.28 mm) and smallest at L5 (male, 31.25 mm; female, 29.97 mm). CA was smallest in L1 (male, 22.80°; female, 21.92°) and greatest in L3 (male, 25.29°; female, 24.33°). LA was smallest in L1 (male 12.37°, female 11.27°) and greatest in L5 (male 13.56°, female 12.96°). Among the males, TD was smallest at L1 (-0.51 mm) and greatest at L5 (1.37 mm), while LD was greatest at L2 (3.46 mm) and smallest at L5 (2.40 mm). In females, TD was greatest at L1 (0.12 mm) and smallest at L3 (-0.51 mm), while LD was greatest at L1 (3.69 mm) and smallest at L5 (2.08 mm). In the overall sample, the incidence of SAVD and PSID gradually increased from L1 to L5.

The optimal screw placement strategy for CBT screws varies significantly according to sex and vertebral body segments, particularly noting the specificity of screw placement at L5. The optimal screw placement strategy should be selected based on the patient's sex and segment characteristics before surgery to maximize the safety and accuracy of CBT screw placement.

A retrospective comparative study revealed that percutaneous kyphoplasty combined with pediculoplasty (PKCPP) offers more benefits in terms of pain relief, spinal stability, and complications compared to simple percutaneous kyphoplasty. Moreover, PKCPP can augment and internally fixate the severe osteoporotic vertebral fractures.

Vertebral augmentation (VA) has emerged as a satisfactory and minimally invasive surgical approach for severe osteoporotic vertebral fractures (OVFs). However, treating severe OVFs with advanced collapse, burst morphology with MC injury, posterior wall retropulsion, high degree of osseous fragmentation, pediculo-somatic junction fracture, and large vacuum cleft presents significant challenges. This study aimed to evaluate the effectiveness of percutaneous kyphoplasty combined with pediculoplasty (PKCPP) in reducing refracture, preventing further collapse and bone cement displacement, reconstructing vertebral body (VB) stability, and providing internal fixation of the anterior column (AC), middle column (MC), and the bilateral pedicles.

The current study was designed as a retrospective review of clinical and radiologic parameters. From July 2018 to September 2021, ninety-six patients with severe OVFs and without neurological deficit were treated either with simple percutaneous kyphoplasty (simple PKP group, n = 54) or with percutaneous kyphoplasty combined with pediculoplasty (PKCPP group, n = 42). All patients were followed up for at least 1 year, and clinical and radiological outcomes were assessed. Surgery duration and bone cement volume were compared between the two groups, as well as analgesic dosage and hospital stay. Anterior wall height (AWH), posterior wall height (PWH), and Cobb angle (CA) were measured and analyzed before and after surgery.

The simple PKP group had significantly shorter surgery duration and lower bone cement volume compared to the PKCPP group (P < 0.05). Conversely, the simple PKP group had significantly higher analgesic dosage and longer hospital stay than the PKCPP group (P < 0.05). Both groups showed significant improvements in AWH, PWH, and CA after surgery (P < 0.05). At the final follow-up, the PWH in the simple PKP group was significantly lower than the preoperative measurement (P < 0.05), and the difference in PWH between the two groups was statistically significant (P > 0.05). Moreover, both groups demonstrated a significant reduction in CA after surgery, with the PKCPP group showing a greater reduction compared to the simple PKP group throughout the postoperative period to the final follow-up (P < 0.05). VAS and ODI scores significantly decreased in both groups after surgery (P < 0.05), with no significant difference between the groups at the final follow-up (P > 0.05). However, the PKCPP group achieved better VAS scores than the simple PKP group at postoperative 1 day, 1 month, and 3 months (P < 0.05), and the ODI in the PKCPP group was lower than the simple PKP group at 1 month after surgery (P < 0.05). Furthermore, the overall complication rate in the PKCPP group was significantly lower than that in the simple PKP group (P < 0.05).

If performed by appropriately trained surgeons, both PKP and PKCPP are safe and effective treatments for patients with severe OVFs. However, PKCPP offers additional benefits in the setting of bothersome fractures, including rapid pain relief, improved spinal stability, satisfactory restoration of vertebral body height, and better correction of kyphotic deformity. These promising results have been tested in a single center but require further confirmation in multiple centers.

Thread shape is regarded as an important factor influencing the fixation strength and osseointegration of bone screws. However, commercial pedicle screws with a V-shaped thread are prone to generating stress concentration at the bone-screw interface, thereby increasing the risk of screw loosening. Thus, modification of the pedicle-screw thread is imperative.

This study aimed to investigate the fixation stability of pedicle screws with the new undercut thread design in comparison to pedicle screws with a V-shaped thread.

In vitro cadaveric biomechanical test and finite element analysis (FEA).

Pedicle screws with the undercut thread (characterized by a flat crest feature and a tip-facing undercut feature) were custom-manufactured, whereas those with the V-shaped thread were procured from a commercial supplier. Fixation stability was assessed by the cyclic nonpullout compressive biomechanical testing on cadaveric female osteoporotic vertebrae. The vertical displacement and rotation angle of the 2 types of pedicle screws were calculated every 100 cycles to evaluate their resistance to migration and rotation. FEA was conducted to investigate the stress distribution and bone damage at the bone-screw interface for both types of pedicle screws.

Biomechanical testing revealed that the pedicle screws with the undercut thread exhibited significantly lower vertical displacement and rotation angles than the pedicle screws with the V-shape thread (p<0.05). FEA results demonstrated a more uniform stress distribution in the bone surrounding the thread in the undercut design than in the V-shape design. Additionally, bone damage resulting from the pedicle screw was lower in the undercut design than in the V-shape design.

Pedicle screws with an undercut thread are less prone to migration and rotation and thus more stable in the bone than those with a V-shape thread.

The undercut thread design may reduce the incidence of pedicle-screw loosening.

Screw loosening is a common complication of pedicle screw internal fixation surgery. This study aimed to investigate whether the application of a porous scaffold structure can increase the contact area between screws and bone tissue by comparing the bone ingrowth and screw-bone interface of porous scaffold core pedicle screws (PSCPSs) and hollow lateral hole pedicle screws (HLHPSs) in the lumbar spine of Bama pigs.

Sixteen pedicle screws of both types were implanted into the bilateral pedicles of the L1-4 vertebrae of 2 Bama pigs. All Bama pigs were sacrificed and the lumbar spine was freed into individual vertebrae at 16 weeks postoperatively. After the vertebrae were made into screw-centered specimens, micro-computed tomography analysis and histological observation were performed to assess the screw-bone interface and bone growth around and within the screws.

We found that the bone condition around PSCPSs and HLHPSs did not show significant differences on micro-computed tomography three-dimensional reconstruction images. CT transverse views showed different bone growth inside the 2 screws. In PSCPSs, bone tissue was seen to fill the internal pores and was evenly distributed around each strut. Inside HLHPSs, bone growth was confined to 1 side of the screw and did not fill the entire cavity. Osteometric analysis showed that bone volume fraction and trabecular number, the parameters representing bone mass, were higher in PSCPSs than in HLHPSs. These differences were not statistically significant (P > 0.05). Histological observations visualized that the osseointegration within PSCPSs was superior to that of HLHPSs, and the tight integration of bone tissue with the porous scaffold resulted in a larger screw-bone integration area in PSCPSs than in HLHPSs.

Compared with HLHPSs, PSCPSs possessing a porous scaffold core could promote bone ingrowth and osseointegration, resulting in an effective enhancement of the combined area of the screw-bone interface.

To compare predictive performance for pedicle screw loosening between computed tomography (CT)-based Hounsfield units (HU) and magnetic resonance imaging (MRI)-based vertebral bone quality score (VBQ) after lumbar surgery.

A retrospective study was conducted on patients who received transforaminal lumbar interbody fusion continuously at our institution from May 2018 to September 2020. On the basis of 12 months' follow-up lumbar radiographs, screw loosening was defined as a clear zone of minimal thickness of ≥1 mm around the pedicle screw on radiography. VBQ score and HU value were measured using preoperative MRI and CT, respectively. Then, we evaluated the predictive performance of these 2 parameters by comparing the receiver operating characteristic curve.

In all patients, area under the curve (AUC) of the VBQ score (AUC = 0.752; 95% confidence interval [CI] 0.663-0.841; P < 0.001) was larger than those of the CT HU value (AUC = 0.652; 95% CI 0.558-0.746; P = 0.005), but there was no significant difference between them (PAUC = 0.076). In patients with lumbar spinal stenosis, AUC of VBQ score (AUC = 0.863; 95% CI 0.764-0.961; P < 0.001) was larger than those of the CT HU value (AUC = 0.673; 95% CI 0.513-0.833; P = 0.043), with significant difference (PAUC = 0.003).

MRI-based VBQ score and CT-based HU value have similar performance in predicting pedicle screw loosening after lumbar surgery. Furthermore, in patients with lumbar spinal stenosis, VBQ score demonstrated better predictive ability than HU value.

Lumbar spine disorders often cause lower back pain, lower limb radiating pain, restricted movement, and neurological dysfunction, which seriously affect the quality of life of middle-aged and older people. It has been found that pathological changes in the spine often cause changes in the morphology and function of the paraspinal muscles (PSMs). Fatty infiltration (FI) in PSMs is closely associated with disc degeneration and Modic changes. And FI causes inflammatory responses that exacerbate the progression of lumbar spine disease and disrupt postoperative recovery. Magnetic resonance imaging can better distinguish between fat and muscle tissue with the threshold technique. Three-dimensional magnetic resonance imaging multi-echo imaging techniques such as water-fat separation and proton density are currently popular for studying FI. Muscle fat content obtained based on these imaging sequences has greater accuracy, visualization, acquisition speed, and utility. The proton density fat fraction calculated from these techniques has been shown to evaluate more subtle changes in PSMs. Magnetic resonance spectroscopy can accurately reflect the relationship between FI and the degeneration of PSMs by measuring intracellular and extracellular lipid values to quantify muscle fat. We have pooled and analyzed published studies and found that patients with spinal disorders often exhibit FI in PSMs. Some studies suggest an association between FI and adverse surgical outcomes, although conflicting results exist. These suggest that clinicians should consider FI when assessing surgical risks and outcomes. Future studies should focus on understanding the biological mechanisms underlying FI and its predictive value in spinal surgery, providing valuable insights for clinical decision-making.

Spinal metastases occur in up to 40% of patients with cancer. Of these cases, 10% become symptomatic. The reported incidence of spinal metastases has increased in recent years due to innovations in imaging modalities and oncological treatments. As the incidence of spinal metastases rises, so does the demand for improved treatments and treatment algorithms, which now emphasize greater multidisciplinary collaboration and are increasingly customized per patient. Uniquely, we discuss the potential clinical applications of AI and NGS in the treatment of spinal metastases. Material and Methods: A PubMed search for articles published from 2000 to 2023 regarding spinal metastases and artificial intelligence in healthcare was completed. After screening for relevance, the key findings from each study were summarized in this update. Results: This review summarizes the evidence from studies reporting on treatment modalities for spinal metastases, including minimally invasive surgery (MIS), external beam radiation therapy (EBRT), stereotactic radiosurgery (SRS), CFR-PEEK instrumentation, radiofrequency ablation (RFA), next-generation sequencing (NGS), artificial intelligence, and predictive models.

A prospective experimental study.

This biomechanical in vitro study aimed to examine the extent to which the use of a rod persuader (RP) leads to additional mechanical stress on the screw-rod system and determine its influence on the bony anchoring of primary pedicle screws.

Degenerative spine diseases and deformities are the most common indications for the stabilization and fusion of spinal segments. The pedicle screw-rod system is considered the gold standard for dorsal stabilization, and an RP is also increasingly being considered to fit the spondylodesis material.

Ten lumbar spines from body donors were examined. Bisegmental dorsal spinal lumbar interbody fusion of the L3-L5 segments was performed using a pedicle screw-rod system (ROCCIA Multi-LIF Cage; Silony Medical, Germany). In group 1, the titanium rod was inserted without tension, whereas in group 2, the rod was attached to the pedicle screws at the L4 and L5 levels, creating a 5-mm gap. To attach the rod, the RP was used to press the rod into the pedicle screw. The rod was left in place for 30 minutes and then removed.

The rod reduction technique significantly increased the mechanical load on the overall construct measured by strain gauges (p<0.05) and resulted in outright implant failure with pedicle screw pullout in 88.9%.

In cases where the spondylodesis material is not fully attached within the pedicle screw, an RP can be used with extreme caution, particularly in osteoporotic bones, to avoid pedicle screw avulsion and screw anchor failure.