Total hip arthroplasty (THA) is considered to be one of the most successful orthopedic interventions of its generation.1 In 2010, 332,000 THAs were performed in the U.S.2 Although used to correct advanced joint diseases in the elderly, the THA procedure has become increasingly common in a younger population for posttraumatic fractures and conditions that lead to early onset secondary arthritis such as avascular necrosis, juvenile rheumatoid arthritis, hip dysplasia, Perthes disease, and femoro-acetabular impingement.
Current hip replacements are expected to function at least 10 to 20 years in 90% of patients.3 As increasing numbers of young patients have these procedures and as seniors continue to live longer, patients will outlast their implants. Younger and more active patients have a higher rate of revision, because the longevity of the prosthesis is usually a function of usage.3 The number of revision THAs is projected to increase 137% by 2030.4
Hip resurfacing has been developed as a bone preserving surgical alternative to THA. The first system for use in the U.S. received FDA approval in 2006, but concerns about the metal on metal bearing surfaces, high failure and revision rates, and early catastrophic modes of failure compared with THAs has resulted in the recall of many of these devices. Hip resurfacing may offer some advantages compared with those of a THA in a carefully selected population, but its use will not be further discussed in this case study.5 Periprosthetic osteolysis and aseptic loosening are 2 of the long-term consequences of THA.6 Bone loss is felt to be secondary to a biologic reaction to particulate debris from implants.6 Some patients, especially those with loosening, complete wear, or fracture, will be symptomatic with pain. However, wear and osteolysis is a silent disease unless there is mechanical failure. Other patients may not experience discomfort. Radiographic studies may reveal significant changes, which warrant the recommendation for a hip revision.
Hip revision surgery has 3 major purposes: relieving pain in the affected joint, restoring the patient’s mobility, and removing a loose or damaged prosthesis before irreversible harm is done to the joint. It’s anticipated that most primary care providers (PCPs) will encounter patients who seek advice on the need for a revision hip arthroplasty.
This case will present an asymptomatic patient who underwent a THA in 1997 at age 37, to address developmental dysplasia of the hip (DDH) and was advised to undergo a revision hip arthroplasty due to abnormal radiographic findings at age 55 years. A discussion will follow that includes a brief review of the history of THA, the materials and bearings commonly used, the presenting symptoms or radiographic changes that signal the need for a revision, and the current options available for a patient such as this.
Case Report
A man aged 55 years presented to a new orthopedic surgeon for his first orthopedic appointment in 10 years. The patient had a left metal-on-polyethylene (M-on-PE) THA 18 years prior due to early onset secondary degenerative joint disease from DDH. The patient’s M-on-PE THA was a titanium acetabular socket and femoral stem with a cobalt-chromium alloy femoral head and a polyethylene liner. The patient remained physically active with an exercise routine consisting of walking, swimming, and weight training.
The patient’s orthopedic history was notable for a right knee arthroscopy for intervention due to a torn medial and lateral meniscus, and birth history was noteworthy for a breech presentation. The physical exam was unremarkable except for a slight leg length discrepancy, but the patient did not exhibit a Trendelenburg gait.
Plain X-rays and a computed tomography (CT) scan showed eccentric PE wear and superior migration of the femoral head, which was indicative of significant PE liner wear. No significant osteolysis or periprosthetic loosening was observed on the X-rays or CT scan. He was advised that a hip revision procedure would need to be done, optimally, within the next 6 months to a year.
Discussion
Hip dysplasia represents a broad group of disorders and generally means abnormal development of the hip joint. The term is most commonly used to refer to DDH with inadequate coverage of the femoral head. In one study, 25% of hip replacements performed in patients aged ≤ 40 years were due to underlying hip dysplasia.7
Developmental dysplasia of the hip occurs more often in children who present in the breech position.8 One theory argues that packaging issues in utero may account for the increased incidence of DDH.9 The earliest recorded attempts at hip replacement occurred in Germany, in 1891, when ivory was used to replace the femoral heads of patients whose hip joints had been destroyed by tuberculosis.1