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

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.

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.

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).

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.