Use of Botulinum Toxin A to Manage Hamstring-Induced Flexion Contracture Following Total Knee Arthroplasty: A Case Series.

Introduction Flexion contractures following total knee arthroplasty (TKA) greatly affect patient function and satisfaction. Botulinum toxin A (BTX) has been described in the literature as a means of addressing post-operative flexion contractures due to hamstring muscle rigidity. Methods We retrospectively report a case series of eight patients with range of motion (ROM) who developed a flexion contracture status post-TKA and were managed with the use of physical therapy, diagnostic hamstring lidocaine injections, and therapeutic hamstring BTX injections. Results All patients had an improvement in extension ROM following diagnostic lidocaine hamstring injections and were therefore considered candidates for therapeutic hamstring BTX injections. Prior to therapeutic hamstring BTX injections, patients had an average flexion contracture of 19° (range: 15°-22°). All patients had an improvement in extension ROM two to four weeks following the therapeutic hamstring BTX injection, with an average improvement in ROM of 7° (range: 2°-19°). At the final follow-up, all patients continued to sustain an improvement in extension ROM with an average deficit of 9° (range: 0°-17°). Conclusion Our case series highlights the use of diagnostic hamstring lidocaine injections to confirm hamstring rigidity as an etiology for flexion contracture following TKA. In addition, we showed a persistent improvement in flexion contracture for all patients after hamstring BTX injections. Therefore, when the appropriate patient is selected, BTX may provide an additional treatment option for a flexion contracture following TKA.