Outcomes after Bipolar Osteochondral Allograft Transplantation in the Ankle

Abstract

Category: Ankle Arthritis; Ankle Introduction/Purpose: Surgical treatment options for symptomatic, full-thickness articular cartilage loss in the ankle are not consistently effective in restoring ankle function. Osteochondral allograft transplantation provides a standard-of-care alternative for patients, however, outcomes reported to date have been only fair, with a high incidence of reoperation and revision. However, recent cartilage storage and preservation techniques have significantly improved the percent viable chondrocytes at the time of implantation in OCAs. These high-chondrocyte-viability allografts should lead to improved survivability of OCAs and improved outcome measures. This study aimed to document the initial outcomes for patients undergoing bipolar OCA transplantation in the ankle after advances in tissue preservation, transplantation techniques, and patient management strategies. Methods: Patients with symptomatic tibiotalar arthritis were prospectively enrolled into a registry designed to follow outcomes after OCA surgeries in the ankle. All patients underwent complete OCA replacement of their tibial plafond and talar dome, with most undergoing fibular articular resurfacing. All OCA were size and side matched and preserved in Missouri Osteochondral Allograft Preservation System (MOPS). Patients followed a standardized, procedure-specific rehabilitation protocol after surgery, including remaining non-weight bearing for 8 weeks, weekly therapy visits, limited step count during recovery, and avoidance of high impact activities until 1 year after surgery. Patients followed-up with their physician at regular post-operative timepoints. Radiographs and patient reported outcome measures (VAS, AAOS Foot and Ankle, PROMIS PF, PROMIS Mobility) were obtained at each follow-up visit. Demographic and operative data were collected from the electronic medical record. All reported complications, reoperations, revisions, and failures were recorded in the EMR. Results: 14 patients were included for analyses with 12 undergoing primary OCA transplantation, and 2 undergoing revision OCA transplantation. Mean age and follow up was 36 and 44.1 months, respectively. All patients underwent tibia and talus OCA transplantation, with 10/14 including a fibula OCA transplantation. Initial success was 92.9% with one documented failure (tibial OCA collapse). Radiographic assessments indicated OCA integration and maintenance of joint space in 12 patients (85.7%). AAOS and VAS pain scores improved significantly from preoperative measures at each timepoint (p=.002, p=.03), while postoperative improvements in PROMIS Mobility and PROMIS Physical Function scores did not reach significance (p>0.15) (Table 1). Patients that were non-adherent to postoperative restriction and rehabilitation protocols, all 1-year postoperative PROs were significantly lower than for patients who were adherent. Conclusion: Ankle osteoarthritis in young patients continues to present a challenging dilemma. Previous attempts at large bipolar OCAs in the ankle have yielded fair, to poor, results. However, recent advances in bulk osteochondral allograft preservation has improved chondrocyte viability. Based on the results of our study, the use of high-chondrocyte-viability allografts for OCA transplantation is a viable option for the treatment of symptomatic bipolar osteochondral defects in the ankle joint. However, post operative rehab protocols are equally important in determining outcomes, and patient selection and education is key to ensuring successful outcomes. Longer term follow up is ongoing.