Fixation of Chondral-only Shear Fractures of the Knee in Pediatric and Adolescent Athletes

Purpose: Attempted fixation of acute osteochondral shear injuries of the knee, though rare, is generally pursued in young, active patients, provided the adequately-sized fragment contains substantial bony tissue. Traditional biological principles suggest cartilage alone cannot be reaffixed to bone. However, due to several case reports of successful fixation of chondral-only fragments, this concept remains controversial and incompletely explored. The purpose of the current study was therefore to evaluate the presenting features, techniques, rates of healing, clinical, and radiological results in a cohort of youth athletes who underwent fixation of chondral-only fragments. Methods: An IRB-approved departmental database review at a regional tertiary care children’s hospital identified patients=18 years old who underwent fixation of a “chondral-only” fragment in the knee, which was defined by the inability to visualize the fragment on injury radiographs or discern bone on the fragment intra-operatively. Mechanism of injury, fragment features, fixation technique, timing of sports clearance, healing on postoperative MRI, and any complications/re- operations were assessed. Descriptive statistics were reported as medians and interquartile ranges (IQR) in order to minimize the skew effect of outliers, which is of concern in reports of rare conditions. Results: Ten patients met inclusion and exclusion criteria. Median age at the time of surgery was 12.5 years old (IQR:11.7-13.3), and median follow-up was 12 months (IQR:6-22▒mo). All patients sustained an acute knee injury prior to surgery, including self-reported patellofemoral instability events (N=6), fall onto flexed knee (N=2), and hyperextension (N=2). Injury sites were trochlea (N=4), patella (N=3), and lateral femoral condyle (N=3). Median fragment size was 484▒mm2 (IQR:400-600▒mm2). Arthrotomy, with or without preceding arthroscopy, was pursued in all cases, which were performed at a median of 1.3 weeks (IQR:1.0-2.0▒wk) post-injury. Fixation implants included bioabsorbable tacks alone (N=7), bioabsorbable screw and suture (N=1), bioabsorbable screw and tacks (N=1), absorbable suture alone (N=1). One patient (10%) sustained a reinjury 8 weeks postoperatively, requiring secondary surgery for fragment excision, and one (10%) underwent patellar stabilization surgery 3.4 years post-operatively, at which time the fragment was found to be stable. Postoperative MRI to assess the fragment was performed in 6/10 subjects at a median of 1.0 years postoperatively, with 3 (50%) showing restoration of cartilage contour and subchondral edema resolution. 1/6 showed thinning of cartilage with an intact contour, 1/6 had cartilage thickening, and 1/6 had subchondral edema, fissuring, and cystic changes. Median time to return to sports was 25.9 weeks (IQR:24.1-24.8▒wk). Conclusion: There is minimal literature to guide treatment of chondral-only shear fractures of the knee. The results of this study suggest that acute fixation of chondral-only fragment using absorbable implants should be considered in pediatric or adolescent athletes and may result in successful healing in the majority of patients.