Over the past 5 years, published literature regarding treatment of pediatric limb deformity and limb length discrepancy demonstrates much interest in better understanding, categorizing and treating these challenging problems. Many studies explore expanding and refining indications for traditional treatment methods like guided growth techniques. Other studies have evaluated the results of new techniques such as lengthening via mechanized intramedullary nails. Additionally, series comparing older and newer techniques such as lengthening with external devices versus mechanized nails are becoming increasingly available.

Primary treatment for Blount disease has changed in the last decade from osteotomies or staples to tension band plate (TBP)-guided hemiepiphysiodesis. However, implant-related issues have been frequently reported with Blount cases. The purpose of our study is to evaluate the surgical failure rates of TBP in Blount disease and characterize predictors for failure.

We performed an Institutional Review Board-approved retrospective chart-review of pediatric patients with Blount disease to evaluate the results of TBP from 2008 to 2017 and a systematic literature review. Blount cases defined as pathologic tibia-vara with HKA (hip-knee-ankle) axis and MDA (metaphyseal-diaphyseal angle) deviations ≥11 degrees were included in the analysis. Surgical failure was categorized as mechanical and functional failure. We studied both patient and implant-related characteristics and compared our results with a systematic review.

In 61 limbs of 40 patients with mean follow-up of 38 months, we found 41% (25/61) overall surgical failure rate and 11% (7/61) mechanical failure rate corresponding to 11% to 100% (range) and 0% to 50% (range) in 8 other studies. Statistical comparison between our surgical failure and nonfailure groups showed significant differences in deformity (P=0.001), plate material (P=0.042), and obesity (P=0.044) in univariate analysis. The odds of surgical failure increased by 1.2 times with severe deformity and 5.9 times with titanium TBP in the multivariate analysis after individual risk-factor adjustment. All 7 mechanical failures involved breakage of cannulated screws on the metaphyseal side.

Most of the studies have reported high failure rates of TBP in Blount cases. Besides patient-related risk factors like obesity and deformity, titanium TBP seems to be an independent risk factor for failure. Solid screws were protective for mechanical failure, but not for functional failure. In conclusion, efficacy of TBP still needs to be proven in Blount disease and implant design may warrant reassessment.

Level III-retrospective comparative study with a systematic review.

This retrospective cohort study examined 20 patients (48 physes), 11 boys and nine girls, who were treated with hinge-plate or eight-plate. The mean age of the patients at surgery was 11.9±2.6 years. The mean follow-up duration was 13±2.7 months. The radiographic measurement of both distal femoral and proximal tibial deformity showed significant correction, with no difference between the hinge-plate and the eight-plate. Both screw divergence angle and the hinge angle showed significant changes at the last follow-up. The deformity correction of the distal femoral physis was quicker than the proximal tibial physis. The rate of mechanical femoral-tibial angle correction was 0.97°/month if both femoral and tibial physes were treated.

III.

Although the core principles of managing infantile Blount disease generally remain unchanged, treatment modalities have evolved over the years. Consensus has yet to be reached regarding the efficacy of bracing. Children with Blount disease commonly have advanced bone age, which may impact the timing and magnitude of (over) correction of angular deformity. Techniques of growth modulation, based on the tension band principle, continue to gain popularity. Although there are limited reports in the last decade on proximal tibial osteotomy for this developmental disorder, both acute and gradual correction remain viable treatment options in the appropriate setting. In certain older children (>7 y old) with advanced stages of the disease, a medial hemiplateau elevation combined with lateral proximal tibial hemiepiphysiodesis may be needed to address the epiphyseal deformity. Given the possibility of unpredictable proximal tibial physeal activity, all children with Blount disease should be followed at regular intervals till skeletal maturity. To provide sufficient granularity for pooled analyses and help establish evidence-based clinical guidelines, standardization of reporting clinical outcomes among children with Blount disease is encouraged.