Primary Total Knee Arthroplasty in Patients Who Have Neuromuscular Disorders and Genu Recurvatum Using a Rotating-Hinge Implant: A Case Series with a Mean Four-Year Follow-Up.

Background: Patients who have neuromuscular disorders and quadriceps weakness may develop knee osteoarthritis along with progressive recurvatum deformity. Due to challenges in ligament balancing and the risk of knee hyperextension recurrence, the use of constrained implants may be required. The objective of this study was to report mid-term (mean four-year) clinical outcomes of patients who had neurological conditions and knee hyperextension and who underwent primary total knee arthroplasty (TKA) with a rotating-hinge implant.

Methods: Patients who had neuromuscular disorders and gonarthrosis with recurvatum deformity and who underwent primary TKA using a rotating-hinge implant between 2015 and 2021 at multiple centers were reviewed retrospectively. Inclusion criteria included neurological conditions, preoperative recurvatum > 5°, and a follow-up period of ≥ 24 months. Demographic, clinical, and radiographic data were collected, including age, Body Mass Index (BMI), underlying neurological disease, symptom duration, and previous surgeries. In total, patients (26 knees) were included. The mean age was 60 years (range, 42 to 82) and the mean preoperative hyperextension was 33.4 ± 12.6°. The most common neurological condition was poliomyelitis (40.9%), followed by idiopathic neuropathy (31.8%), Charcot neuroarthropathy (22.8%), and sequelae of childhood meningitis (4.5%). Clinical outcomes were assessed using functional scores (Knee Injury and Osteoarthritis Outcome Score (KOOS), Knee Society Score (KSS), Forgotten Joint Score (FJS), and Global Perceived Effect Scale (GPE)), postoperative complications, and radiographs to evaluate implant loosening and patella baja.

Results: The mean functional scores were: KSS 72.4, KOOS 74.3, FJS 66.9, and GPE 3.8. The failure rate was 7.7%, with two patients needing revision surgery due to aseptic loosening. Regarding complications, one intraoperative tibial shaft fracture occurred. Postoperatively, one patient developed peroneal nerve neuropraxia, and one had bilateral arthrofibrosis requiring surgical release.

Conclusion: Patients who have neuromuscular disorders and genu recurvatum can achieve favorable outcomes with rotating-hinge TKA, yielding good functional scores and acceptable complication and failure rates, considering the severity of the condition.