Conversion hip arthroplasty for posttraumatic conditions is associated with greater rates of intraoperative and postoperative complications than total hip arthroplasty for primary osteoarthritis.[4,36] Arthroplasty after prior surgeries on a joint is associated with a higher risk of infection. This condition is particularly true in the setting of retained implants and impaired vascularity from previous trauma and soft-tissue dissection. As a result of the greater dissection required for implant removal and reconstruction, a higher incidence of bleeding, need for transfusion, and hematoma is observed.
These patients also face higher risks of dislocation (Figure 6) because of multiple causes. The greater trochanter and abductor mechanism may be deficient from prior trauma or surgeries. Furthermore, residual deformity may make accurate implant positioning during reconstruction more difficult, in terms of femoral and acetabular version. The risk of instability may be mitigated by using a larger diameter femoral head or a dual mobility articulation.
Dislocation is one of the complications observed after conversion hip arthroplasty. A, This patient had a trochanteric nonunion with implant cutout. B, She had a noncemented reconstruction through an anterolateral approach. She had two episodes of dislocation managed by closed means with reduction and a brace with no subsequent instability episodes.
In instances of prior trauma, heterotopic ossification may be an issue and is prone to recur if not addressed. Perioperative prophylaxis in the form of radiation therapy or indomethacin is indicated if prior heterotopic ossification is excised.
Lastly, sciatic nerve injury is more common after posttraumatic conversion hip arthroplasty. This injury can be as a result of scarring of the surgical field making the nerve more difficult to identify and prone to direct iatrogenic injury, particularly from a posterior approach. Care must be taken intraoperatively to avoid aberrant retractor placement and to identify and protect the nerve when possible. Secondarily, posttraumatic osteonecrosis or degenerative arthrosis may result in notable extremity shortening, necessitating lengthening at the time of reconstruction. If notable lengthening is necessary, intraoperative neuromonitoring or a subtrochanteric shortening osteotomy may be performed. A well-defined threshold for which lengthening can be safely undertaken does not exist. This likely varies depending on the etiology of shortening and how long the limb has been short. Studies have quoted 1.7 to 4 cm for amount of lengthening posing a risk for postoperative nerve palsy. A postoperative hematoma may be another risk factor for sciatic nerve palsy. If a hematoma is identified, it must be evacuated and the sciatic nerve decompressed as early as possible to facilitate neurologic recovery.
J Am Acad Orthop Surg. 2019;27(8):275-285. © 2019 American Academy of Orthopaedic Surgeons