Desai B, Willard JG, Assid E, Hall C, Renshaw A, Schoofs E, Wilder JH, Hatcher L, Tupler R, Jones D. Missouri osteochondral preservation system transplantation: Outcome scores from 24 months to 60+ months. World J Orthop 2026; 17(9): 114039 [DOI: 10.5312/wjo.114039]
Corresponding Author of This Article
Deryk Jones, MD, Chief Physician, Principal Investigator, Department of Orthopedics and Sports Medicine, Sutter Health Orthopedics and Sports Medicine Service Line, 1201 S. Clearview Pkwy., Bldg. B., Ste. 104, New Orleans, LA 70121, United States. deryk.jones@sutterhealth.org
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Desai B, Willard JG, Assid E, Hall C, Renshaw A, Schoofs E, Wilder JH, Hatcher L, Tupler R, Jones D. Missouri osteochondral preservation system transplantation: Outcome scores from 24 months to 60+ months. World J Orthop 2026; 17(9): 114039 [DOI: 10.5312/wjo.114039]
Bhumit Desai, Eric Assid, Andrew Renshaw, James Heath Wilder, Department of Orthopaedic Surgery, Ochsner Health System, Jefferson, LA 70121, United States
Jonathan Gerard Willard, Chad Hall, Eden Schoofs, Lakin Hatcher, Department of Sports Medicine, Ochsner Health System, Jefferson, LA 70121, United States
Richard Tupler, Department of Radiology, Ochsner Health System, Jefferson, LA 70121, United States
Deryk Jones, Department of Orthopedics and Sports Medicine, Sutter Health Orthopedics and Sports Medicine Service Line, Emeryville, CA 94705, United States
Deryk Jones, Department of Orthopaedic Surgery, University of Queensland-Ochsner Clinical School, Jefferson, LA 70121, United States
Co-corresponding authors: Jonathan Gerard Willard and Deryk Jones.
Author contributions: Desai B, Willard JG, Assid E, Hall C, Schoofs E, and Hatcher L contributed to drafting the article and revising it critically for important intellectual content; Desai B, Willard JG, Assid E, Hall C, Renshaw A, Schoofs E, Wilder J, Hatcher L, Tupler R, and Jones D contributed to final approval of the version to be submitted; Renshaw A, Schoofs E, Wilder J, and Jones D contributed to the conception and design of the study; Renshaw A, Wilder J, and Jones D contributed to revising it critically for important intellectual content; Schoofs E contributed to acquisition of data, analysis and interpretation of data; Tupler R contributed to analysis and interpretation of data. Willard JG and Jones D are designated as co-corresponding authors because they shared senior leadership throughout the study and publication process. As the clinical research fellow, Willard JG oversaw manuscript preparation, revisions, and coordinated the submission. Additionally, he was responsible for the primary communication with the journal throughout the peer review and publication process. Jones D served as the senior author and assumed responsibility for the publication transaction fee. Their complementary roles were both essential to the successful completion and submission of this work.
AI contribution statement: The authors certify that no artificial intelligence tools were used in the production of this manuscript.
Institutional review board statement: This investigation was approved by the Ochsner Health Human Research Protection Program, IRB No. 2018.247.
Informed consent statement: This study involved secondary research of existing data and was determined to be exempt from informed consent requirements by the Ochsner Clinic Foundation Institutional Review Board IRB ID No. 2018.247.
Conflict-of-interest statement: All authors declare that they have no conflict of interest to disclose.
Data sharing statement: All data generated or analyzed during this study are included in this published article. Additional details are available from the corresponding author upon reasonable request.
Corresponding author: Deryk Jones, MD, Chief Physician, Principal Investigator, Department of Orthopedics and Sports Medicine, Sutter Health Orthopedics and Sports Medicine Service Line, 1201 S. Clearview Pkwy., Bldg. B., Ste. 104, New Orleans, LA 70121, United States. deryk.jones@sutterhealth.org
Received: September 11, 2025 Revised: July 6, 2026 Accepted: August 20, 2026 Published online: September 18, 2026 Processing time: 364 Days and 9 Hours
Abstract
BACKGROUND
The Missouri osteochondral preservation system (MOPS) prolongs chondrocyte viability in osteochondral allografts for up to 60 days. Improved chondrocyte viability is linked to improved graft incorporation and functional outcomes.
AIM
To discover the clinical impact of MOPS allograft transplantation on patient reported outcomes.
METHODS
A retrospective review of 76 patients (78 knees) with symptomatic knee chondral lesions treated with MOPS were evaluated for safety, incorporation, survivorship, and improvement in functional outcomes. Short Form-12 (SF-12), subjective International Knee Documentation Committee (IKDC) score, Knee injury and Osteoarthritis Outcome Subscale Scores (KOOS), Lysholm Knee Scoring System, Visual Analogue Scale (VAS) Pain Severity and Frequency scores were collected.
RESULTS
Twenty-nine knees (28 patients) meeting inclusion criteria had a minimum 24 months follow up. Lysholm, IKDC, SF-12, and KOOS: Pain, symptoms, activities of daily living, sports, quality of life, VAS Pain frequency scores improved at each follow up compared to pre-operative baseline (POB). These trends were maintained at the most recent follow up (average 51.87 ± 17.31 months) with statistically significant increases compared to POB demonstrated. Radiographic evaluation revealed excellent incorporation at last follow up with an average interval change of 0.48 in Kellgren-Lawrence scores in 29/29 knees from preoperative radiographs. Magnetic resonance imaging analysis was performed in 22/29 knees with an average MOCART 2.0 score of 72.
CONCLUSION
Our results demonstrate significant increases in functional scores at latest follow-up with MOPS grafts compared to POB. MOPS grafts incorporated well without evidence of radiographic deterioration 2 years following transplantation.
Core Tip: This retrospective study evaluated Missouri osteochondral preservation system (MOPS) allograft transplantation for symptomatic knee chondral lesions. MOPS preserves chondrocyte viability, which may contribute to improved graft incorporation and functional outcomes. Patients showed significant, sustained improvements in functional scores, with excellent radiographic incorporation and no evidence of deterioration at two years. These results support the safety and efficacy of MOPS allografts for long-term knee cartilage repair.
Citation: Desai B, Willard JG, Assid E, Hall C, Renshaw A, Schoofs E, Wilder JH, Hatcher L, Tupler R, Jones D. Missouri osteochondral preservation system transplantation: Outcome scores from 24 months to 60+ months. World J Orthop 2026; 17(9): 114039
The functional integrity of a joint is dependent on healthy articular cartilage. Without healthy and intact articular cartilage, patients may develop pain, effusion, and mechanical symptoms - inevitably progressing to arthritis in the absence of other intervention[1]. Uni-compartmental knee arthroplasty and total knee arthroplasty are successful in older patients with osteoarthritis[2]. However, the results are not as promising in younger patients less than 55 years old based on complications, level of activity, morbidity, likelihood of revision, and decreased satisfaction rates[3].
Treatment recommendations for symptomatic osteochondral lesions range from non-operative to operative management. Non-operative measures include weight loss, physical therapy to strengthen muscles around the knee to help absorb load across the joint, orthosis, anti-inflammatory and other analgesic medications, as well as steroid and biologic injection therapies[1]. If non-operative treatment fails to relieve symptoms, operative management is generally recommended. Based on the size, location, nature of injury, and activity demands of the patient, this treatment can range from debridement and marrow stimulation techniques with or without augmentation, cell-based regenerative techniques, transfer of osteochondral autograft or transplantation of osteochondral allograft (OCA) to fill the articular defects[4].
There is a myriad of surgical options to address the difficulty of treating symptomatic osteochondral lesions. Arthroscopic debridement (chondroplasty) and microfracture have been successful in small lesions (< 2 cm2), in low-demand patients, and in combination with concomitant procedures[5,6]. Microfracture requires penetration of the vascular subchondral bone, which stimulates fibrocartilage formation characterized by type 1 collagen, irregular, limited cellular organization, and heterogeneous proteoglycan matrix composition[7,8]. This tissue has demonstrated inferior mechanical properties compared to the native cartilage characterized by type 2 collagen, homogeneous proteoglycan content, and columnar cellular orientation[8,9]. Microfracture is a straightforward procedure with relatively low cost, low risk of morbidity, and improved symptoms in well-contained lesions, but the fibrocartilaginous repair site can deteriorate after 2 years. This may require revision surgery, potentially complicating the outcomes of revision interventions[7,10,11]. Osteochondral autograft transfer or mosaicplasty is another single-staged procedure used to treat small to intermediate (1-3 cm2) sized lesions with the advantage of transfer of normal osteoarticular grafts[12,13]; however, there can be donor site morbidity, potential subchondral cyst formation, and graft damage due to impaction at the time of implantation[14]. Matrix autologous chondrocyte implantation can treat larger and multiple lesions but necessitates a two-stage procedure with cartilage biopsy followed by subsequent processing and proliferation with implantation on a matrix carrier[15]. The procedure has demonstrated improved patient-reported outcome measures over microfracture out to five years, but has a potentially longer rehabilitation time and can be less effective in chronic conditions with poor containment[16].
For larger, chronic, and poorly contained lesions (> 2-4 cm2), fresh size-matched OCA are durable with graft survival rates between 79% and 100% in short-term follow-up studies[17]. Several studies have shown that OCA transplantation of large femoral condyle lesions > 2.5 cm2 has demonstrated an 88% return-to-sport rate[18,19]. Numerous studies have also shown greater than 75% 10-year survival rates for OCA transplantation of large femoral condyle lesions > 2.5 cm2[20-23]. OCAs are also suited for larger lesions (> 4 cm2), multiple defects, uncontained lesions, and in revisions[24,25]. Initial OCA transplantations were performed using grafts transplanted within 72 hours to 2 weeks of donation[20,26,27]. Current American Association of Tissue Banks and United States Food and Drug Administration policies and procedures for donor screening, serologic and microbiologic testing for infectious agents in allografts have impacted the time from donation to transplantation[28]. Consequently, due to these mandatory screening protocols and patient-specific size-matching requirements, fresh OCA grafts are typically not available to surgeons and patients earlier than 21-42 days from donation[29]. The current standard practice for tissue processors is preservation of OCAs in defined solutions at 4 °C[30]. The initial theory was that preservation of OCAs at 4 °C would slow down the metabolism of chondrocytes, maintain sterility, and improve the shelf life of the graft. However, studies have shown that chondrocytes are temperature sensitive to cold and heat fluctuations[31-34]; storage at 4 °C has a detrimental effect on the superficial zone of cartilage, causing matrix degeneration and decreasing cell viability if not implanted early following donation[33,35]. LaPrade et al[25] reported a dramatic decrease in chondrocyte viability after 14 days, with 70% remaining viable after 28 days. Time from donation to distribution using OCA preserved with standard techniques creates a narrow window for surgical implantation; this can be an inconvenient situation for clinicians and patients while potentially resulting in financial losses and waste of donor tissue[36,37].
The MOPS was developed and validated to address this shortcoming[2,38-40]. In the MOPS protocol, OCAs are preserved in a proprietary solution at room temperature (25 °C). This temperature has been reported to maintain articular cartilage extracellular matrix (ECM) composition, sufficient chondrocyte viability, and material properties for at least 60 days after procurement and has demonstrated successful functional outcomes in a preclinical canine model[39,40]. Stoker et al[37] validated the effectiveness of the MOPS protocol in maintaining sufficient chondrocyte viability, ECM composition, and material properties in human femoral condyle OCAs. In their study, MOPS preserved essential OCA viability and quality at significantly higher levels than the standard preservation techniques. MOPS maintained over 70% day-0 viable chondrocyte density at least 56 days after procurement. There is limited literature on clinical outcomes following surgical utilization of MOPS for symptomatic chondral lesions despite its ability to maintain a significantly higher chondrocyte viability at longer storage periods compared to the standard protocol[41]. The purpose of this study was to evaluate whether MOPS graft utilization may demonstrate improvement in functional outcomes of large symptomatic chondral lesions of the knee at short to intermediate term follow up.
MATERIALS AND METHODS
A retrospective study was undertaken at a tertiary care center specializing in orthopedic sports medicine to examine the effects of the MOPS medium in the treatment of osteochondral defects of the knee. The study was approved by the institutional review board (IRB No. 2018.247). Active patients presenting with focal osteochondral defects of the knee were treated between March 2016 and April 2021. All procedures using the MOPS grafts were performed by the senior author, a fellowship-trained sports medicine orthopedic surgeon. The decision to implant was made by considering the patient’s age and pre-injury activity level as well as International Cartilage Repair Society (ICRS) grade, size, location, and chronicity of the lesion(s). Only cartilage defects greater than 2 cm2 (range 2-18 cm2) were evaluated for treatment with an allograft. Patients followed up in clinic at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, 2 years, and yearly intervals after 24 months post-operatively to assess function and progress, and objective functional outcome surveys were administered at each follow-up visit. Outcome measures included the Lysholm score, Knee Injury and Osteoarthritis Outcome (KOOS) subscale scores, Short Form-12 (SF-12), and International Knee Documentation Committee (IKDC) questionnaires, along with pain frequency and severity assessment (VAS). Eligible patients had functional scores taken and filed in a prospective registry dedicated to the storage of patient outcome scores confidentially. Pre-surgery symptom duration was obtained through chart review. Exclusion criteria included patients undergoing concomitant meniscal transplantation, complex operations denoted at the time of the surgery, and those who had concomitant cartilage restoration procedures (cartilage allograft matrix or viable cartilage allograft matrix) in addition to MOPS OCA. Patients with prior complex surgical history involving the affected joint, history of joint infection in the ipsilateral lower extremity, malunion of the operative lower extremity, systemic inflammatory pathologies, ligamentous instability of the knee, or lack of follow-up were also excluded. Bipolar OCA for articulating osteochondral (kissing) lesions were included specifically.
Cartilage allografts harvested for repair were stored using the MOPS obtained from MTF Biologicsâ (Edison, NJ, United States). All allografts underwent mandatory disease testing over a 14-day period immediately following harvest per American Association of Tissue Banks policies and procedures. Allografts were subsequently stored in custom closed containers with defined media in a strictly temperature-controlled environment at room temperature (25 °C) until implantation.
Osteochondral allografts were implanted using a subvastus approach targeted at the site of the chondral lesion following an initial diagnostic arthroscopy (Figure 1). Patients were maintained in a knee immobilizer locked at 10° hyperextension with gait until adequate quadriceps function was obtained. Toe-touch-weight-bearing to 25% partial weight-bearing (PWB) was initiated immediately, with advancement to 25%-50% PWB at 4 weeks and full weight-bearing as tolerated (WBAT) in femoral chondral lesions at 6 weeks. Patellofemoral patients were allowed to progress to full WBAT at 10 days to 2 weeks, locked at 10° hyperextension for 4-6 weeks, with gait advancement from the immobilizer based on quadriceps and extensor mechanism functional return. Range of motion began at 1-3 days following surgical treatment; standard motion consisted of 10° hyperextension to 30°-45° flexion, advancing by 15° per week, with a goal of 90° by 4 weeks and 120° by 6 weeks. Closed-chain rehabilitation and core strengthening protocols were initiated at 6 weeks, with advancement to higher levels of activity based on single-leg balance ability at 3-4 months; progression to cutting and sports-specific training activities was allowed at 6-9 months and individualized based on patient goals and milestone achievements under physical therapy guidance. All patients were advised to follow up in clinic post-operatively at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, 2 years, and yearly intervals after 24 months. Radiographic assessments were performed at all postoperative visits with antero-posterior (AP) and lateral views at 2 weeks and bilateral AP, posterior-anterior, Merchant, and lateral views at all other visits. Magnetic resonance imaging (MRI) assessments were performed at either the 6-month or 12-month follow-up (Figures 2 and 3). Hip-knee-angle was also assessed preoperatively with standing long-leg radiographs. All radiographic studies used to determine Kellgren-Lawrence and MOCART scores were evaluated and graded by a trained musculoskeletal radiologist on staff at our institution. Functional scores were recorded at each clinic visit. The primary outcome was assessment of change from baseline to a minimum of two years in functional scores (KOOS, IKDC, and Lysholm, SF-12) evaluating for achievement of a minimally clinically important difference (MCID)[42]. Secondary assessment of graft survivorship, incorporation rates, and adverse events was performed.
Figure 1 Intra-operative images demonstrating an ICRS grade 4 lesion.
A: Patella; B: Preparing the lesion site; C: Progressing to the transplantation of the allograft.
Figure 2 Non-contrast magnetic resonance showing sagittal and axial T2 slices.
A-C: Patella at pre-operative state (A), at 6 months post-operative (B), and at 1-year post-operation (C), demonstrating a retained osteochondral allograft with maintained articular congruity and intact subchondral bone bed with overall improved fluid accumulation at the base of the allograft.
Figure 3 Non-contrast magnetic resonance.
A-C: Showing sagittal and axial T2 slices of the patella 32 months post-operation demonstrating a retained osteochondral allograft with maintained articular congruity and intact subchondral bone bed. With overall improved fluid accumulation at the base of the allograft.
Descriptive statistics were reported as the mean with standard deviations. Data analysis of functional scores was conducted using a Student’s t-test with significance defined as P < 0.05. Statistical analyses were performed using R software (Version 3.6.3; R Core team).
RESULTS
Demographics
76 patients (78 knees) underwent osteochondral defect repair using an allograft stored with the MOPS. Concomitant meniscal transplantation, complex procedures, and concomitant additional cartilage restoration procedures (cartilage allograft matrix or viable cartilage allograft matrix) in addition to MOPS OCA were excluded. Complex surgical history involving the affected joint, history of joint infection in the ipsilateral lower extremity, malunion of the operative lower extremity, systemic inflammatory pathologies, ligamentous instability of the knee, or lack of follow up were excluded from this study. Bipolar OCA for articulating osteochondral (kissing) lesions were included despite being known to be associated with inferior outcomes[43]. A total of 29 knees (20 female, 9 male) implanted with allografts were included in final data analysis (Table 1). Mean clinical follow-up was 51.87 ± 17.31 months. The mean patient age at time of surgery was 38.9 years ± 9.5 (range 21-58). Mean body mass index was 28.94 ± 5.88 (range 21.10-48.10) (Table 1). The mean time from symptom onset to surgery was 14.0 ± 14.3 months (range 1-62) (Table 1). Of the 29 knees, 17 had available preoperative long-leg radiographs; 9 demonstrated varus deformity, and 8 demonstrated valgus deformity. The mean degree of deformity in the varus and valgus groups was 178.7° and 178.3°, respectively. Meniscal status was evaluated intraoperatively, with 3 patients (10%) requiring concurrent meniscectomies and 6 patients (21%) having had prior meniscectomies. All patients included had undergone a prior surgery of the index knee; these procedures included chondroplasty (69%), microfracture (31%), synovectomy (24%), meniscectomies (21%), anterior cruciate ligament reconstruction (14%), and medial patellar femoral ligament reconstruction (14%) (Table 2). Of those included, 55% had more than one prior procedure on the index knee. Chondral defect size ranged from 1.5 cm2 to 18 cm2 with an average defect size of 8.05 cm2. Osteochondral lesions were ICRS grade II (2.6%), III (10.5%), or IV (87%) (Table 1). MOPS Allografts from the patella, distal femur, and tibia were used. Grafts preserved with standard preservation techniques were excluded. Diagnostic arthroscopy was performed in all cases. Sub-group analysis included patients treated with concomitant high tibial osteotomy (4), patellofemoral realignment (9), and multiple OCA (8).
Functional score data were collected for 78 MOPS procedures, which involved 76 unique patients. Twenty-nine of the seventy-eight procedures met the minimum two-year post-operative follow-up and inclusion criteria. Pain frequency and pain severity scores improved from 8.69 and 5.36 pre-operatively to 3.31 and 4.28 at the most recent follow-up (P < 0.001, P = 0.082 respectively). Progressive increases in functional scores were noted and trends were maintained at most recent follow up with significant improvements compared to baseline KOOS pain (47.41 ± 22.33 vs 80.75 ± 17.97, P < 0.001), KOOS symptom (48.58 ± 24.17 vs 78.08 ± 19.90, P < 0.001), KOOS activities of daily living (ADLs) (54.77 ± 23.60 vs 87.07 ± 15.81, P < 0.001), KOOS sports (25.89 ± 23.02 vs 62.93 ± 28.96, P < 0.001), KOOS quality of life (QOL) (21.55 ± 15.99 vs 56.90 ± 25.02, P < 0.001), Lysholm (39.78 ± 19.30 vs 69.48 ± 21.16, P < 0.001), IKDC (32.18 ± 16.83 vs 66.23 ± 19.92, P < 0.001), Physical Short Form-12 (PSF-12) (33.18 ± 9.41 vs 44.99 ± 11.27, P < 0.001), and Mental Short Form-12 (MSF-12) scores (47.98 ± 8.94 vs 52.97 ± 9.13, P = 0.009). Statistically significant improvements in mean score were noted for every functional score modality recorded and ten out of eleven functional scores (Table 3, Figure 4). When observing interval time points, eleven out of eleven scores demonstrated improved scores beyond 60 months (n = 11) (Table 4, Figure 5). Three out of three subgroups showed significant improvements in at least one sub score across timepoints despite additional procedures (Tables 5, 6, and 7). Additionally, MCIDs were met in all KOOS subscales, Lysholm, IKDC, and VAS frequency[44].
Patients with significant adverse events included post-operative infection (1) and non-union (1); these two patients and one patient with pre-existing avascular necrosis (1) were excluded from the study based on exclusion criteria. Two patients were treated with a lysis of adhesion procedure within the 3-months post-operative period, and one patient required repeat arthroscopy 4 years postoperatively. One patient progressed to patellofemoral arthroplasty. One patient treated initially with patellar OCA received another OCA in the trochlea of the same knee. Fourteen patients included in the study were reported to have higher pain severity from preoperative baseline within the first 3 months post-surgery. One patient had long coronavirus disease 2019 symptomatology and was excluded due to this confounding variable. One patient injured her contralateral leg and back; her scores after the injury were not included.
Radiographic findings
Kellgren-Lawrence grade on baseline imaging was 1.5 on average vs 2.14 at 24 months and 2.33 at 60 months. The mean interval change from pre-operative baseline to final follow-up was 0.48. MRI evaluation was obtained in 22 out of 29 knees with an average MOCART 2.0 score of 72.
DISCUSSION
In this study, we employed MOPS in 28 patients (29 knees) with symptomatic articular cartilage deficits, observing significant enhancements in outcome measures compared to preoperative baseline. Our findings affirm the effectiveness of the MOPS, with notable improvements in mean IKDC by 31 points (32.18 ± 16.83 vs 66.23 ± 19.92, P < 0.001), KOOS pain by 33 points (47.41 ± 22.33 vs 80.75 ± 17.97, P < 0.001), KOOS symptom by 30 points (48.58 ± 24.17 vs 78.08 ± 19.90, P < 0.001), KOOS ADL by 32 points (54.77 ± 23.60 vs 87.07 ± 15.81, P < 0.001), KOOS sports by 37 points (25.89 ± 23.02 vs 62.93 ± 28.96, P < 0.001), KOOS QOL by 35 points (21.55 ± 15.99 vs 56.90 ± 25.02, P < 0.001), Lysholm by 30 points (39.78 ± 19.30 vs 69.48 ± 21.16, P < 0.001), PSF-12 by 12 points (33.18 ± 9.41 vs 44.99 ± 11.27, P < 0.001), and MSF-12 by 5 points (47.98 ± 8.94 vs 52.97 ± 9.13, P = 0.009) compared to baseline scores, at a mean follow-up. The visual analog scale of 51.87 ± 17.31 months. Notably, VAS pain did not exhibit significant improvement despite enhanced functional scores. There are documented limitations to this scoring system, as there is the potential for measurement errors due to imprecise marking by the patient, as well as a lack of clear anchors leading to ceiling/floor effects[45].
In the present study, we utilized MOPS in 28 patients (29 knees) with symptomatic articular cartilage deficits and noted significant improvement in outcome measures compared to preoperative baseline. When considering treatment for high-grade focal chondral lesions, OCA transplantation is considered an effective surgical procedure in improving functional and clinical outcomes[46]. However, there are several disadvantages of using OCA. To have a successful OCA transplantation procedure, a size-matched allograft is utilized, and the donor tissue must go through extensive screening for diseases. Additionally, cell viability can impact successful OCA implantation, with some studies showing that > 70% chondrocyte viability at implantation is strongly recommended for best results; under standard OCA storage techniques, surgeons and patients have a 28-42 days window from donation to transplantation to ensure adequate chondrocyte viability dramatically[39,47].
When considering treatment for high-grade focal chondral lesions, OCA transplantation is considered an effective surgical procedure in improving functional and clinical outcomes[46,48,49]. However, there are several disadvantages of using OCA. To have a successful OCA transplantation procedure, a size-matched allograft is utilized, and the donor tissue must go through extensive screening for diseases. Additionally, it was found that successful graft implantation must have > 70% chondrocyte viability at implantation, and under standard OCA storage techniques, this gives surgeons and patients 2 weeks to 4 weeks from donation to transplantation to ensure adequate chondrocyte viability dramatically[25,39].
The MOPS preserves fresh OCA twice as long as OCA preserved using current preservation methods[40]. Stoker et al[37] and Cook et al[40] demonstrated that MOPS preserved essential chondrocyte viability and quality at significantly higher levels than current tissue bank protocols[37,40]. Stoker et al[37] and Cook et al[40] reported viable chondrocyte density was maintained at nearly 90% of day 0 values through 56 days of MOPS preservation with or without media change. MOPS utilizes a storage temperature of 22-25 °C or room temperature. Preservation temperatures above 25 °C raise concerns for microbial contamination as microbes grow faster in warmer temperatures and demonstrate chondrocyte apoptosis rates like those found in grafts preserved at 4 °C[31,32,40,47]. Recent data, however, indicate that OCA preservation at room temperature does not increase potential risk for microbial contamination and persistent chondrocyte viability compared to preservation at 4 °C[37,39,40]. Amidst concerns of potential loss of tissue ECM architecture and composition with storage temperatures above 4 °C, Stoker et al[37] showed that long-term storage of OCA using the MOPS protocol at room temperature did not affect OCA architecture and composition.
There is limited literature on evaluating clinical and functional outcomes of large symptomatic chondral lesions with MOPS graft utilization. Buyuk et al[41] conducted a study evaluating patient outcomes and graft survival rate at 24-60 months following whole-surface OCA transplantation using MOPS shell grafts for patellofemoral lesions compared to standard preservation technique. The study found that there were meaningful improvements in patient reported pain and function level and that the 2-year graft survival rate was higher in MOPS grafts than grafts utilizing standard preservation. Similar results were found of improved pain and functional scores through 3 years to 4 years following OCA transportation using MOPS combined with modified surgical techniques and postoperative patient management[50]. However, a poster presentation found no difference in patient reported outcomes post OCA transplantation regardless of preservation technique utilized[51].
Our study is not without several limitations. It is a retrospective case series, not randomized, and without a control arm. There is potential for selection bias as our treatment focused on patients with articular cartilage defects considered good candidates for OCA transplantation vs other treatment options available in the current algorithm available in the United States. We did not perform a direct comparison in the same facility to a cohort of patients treated with OCA stored in the traditional method. Our study is also limited to a mean follow up of 51.87 months, and although there were improvements in outcome scores at each follow up, it is uncertain if these outcome scores will continue to improve beyond 5 years, prompting the need for continued long-term follow-up. Further analysis of complex procedures would also add value to the overall study, while stratifying out with sub-analysis. Additionally, analysis of imaging limitations exist as long-term imaging was difficult to evaluate secondary to follow up, cost of MRI, and resources.
Nonetheless, our study shows promising results in symptomatic patients with cartilage defects treated with MOPS grafts in the short to intermediate-term, prompting further studies to elucidate and corroborate the efficacy of the MOPS. At a minimum, we have demonstrated that OCA performed with grafts preserved using the MOPS are safe, effective, incorporate, and survive while demonstrating functional improvements equal to or better than previously published studies[44]. Further, this preservation technique has the practical benefit of allowing more time for surgeon and patient from donation to transplantation. Future studies directly comparing functional outcomes with MOPS grafts to the standard preserved grafts are indicated.
Regardless, equivalence or improvement in outcomes using the MOPS allografts when compared to allografts stored with the traditional 4 °C technique is an improvement for the surgeon and the patient. The time from donation to transplantation of these valuable gifts is significantly increased. The pressure for surgical decision making based on clinical and social factors has been lessened, allowing for improved scheduling and preparation prior to implantation of the graft. Pre-habilitation, peri-operative pain management, brace fitting, and post-operative care can potentially be improved. The senior author has noticed an easier discussion with the patient once the decision has been made to perform the procedure. Previous time limitations created a more difficult discussion due to the short 14-day window recommended for transplantation as discussed above.
We included patellofemoral patients treated for kissing lesions effectively performing a biological reconstruction of the articulating surfaces. In our study, there was no detrimental impact of placing MOPS grafts on adjacent surfaces. Specific focus was placed intra-operatively to limit bone load to 8-10 mm and treat the subchondral bone with carbon dioxide prior to implantation to limit the impacts of antigenic load from the donor metaphyseal bone[52,53].
CONCLUSION
Our study shows significant improvement in IKDC, KOOS subscales, Lysholm, pain frequency, and PSF-12 scores in symptomatic patients with knee articular cartilage defects treated with MOPS allograft transplantation. These improvements were maintained at a minimum of two years and maintained up to 60 months following surgical treatment.
ACKNOWLEDGEMENTS
The authors would like to thank Graylin Jacobs, Senior Clinical Research Coordinator, and Joseph Laurent, Clinical Research Coordinator, for their administrative support of this research project.
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