Total hip and knee arthroplasty after lower extremity amputation in a military population

Introduction: The military includes lower extremity amputees requiring arthroplasty; however, there is little literature on this population. The primary aim of this study was to report demographics and clinical factors in amputees who undergo total hip or knee arthroplasty (THA/TKA) in the Military Health System (MHS). Second, patient-reported outcome measures (PROMs) are reported.

Methods: The Military Data Repository was queried for patients with lower extremity amputations and TKA or THA between 1 October 2014 and 12 October 2020. The medical records were reviewed and patients were contacted to complete PROMs. Mean follow-up for TKA and THA was 5.5 and 2.5 years, respectively.

Results: Nineteen TKAs (76%) and eight THAs (28%) were performed in 25 patients. Mean age of TKA and THA patients at the time of arthroplasty was 57 years old. A majority of TKA (68%) and THA (57%) patients underwent amputations secondary to trauma. Nearly all TKAs were performed on the contralateral side to the amputation (95%), while half of THAs were performed on the ipsilateral side (50%). Two THAs (29%) were revised due to periprosthetic fractures, whereas six TKAs (32%) were revised or reoperated on due to infection. Ten TKA patients completed PROMs. The mean score on Knee Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) was 41.8 and Patient-Reported Outcomes Measurement Information System Global-10 (PROMIS-10) was 41.6 (Global Physical Health) and 49.6 (Global Mental Health).

Conclusions: Most TKAs were performed on the contralateral limb, suggesting increased demand on the joint. The most common indication for amputation and post-TKA complication was trauma and infection, respectively. KOOS JR may not accurately capture the outcomes of this population, or they simply do worse. However, PROMIS-10 scores were similar to the non-amputee population, suggesting that the PROMIS-10 may be more useful than the KOOS JR.