Large-Diameter Femoral Heads in Total Hip Arthroplasty: An Evidence-Based Review
Recent advances in the wear characteristics and material properties of highly cross-linked polyethylene and fourth-generation ceramic bearings have led to increasing use of large-diameter (≥ 36 mm) femoral heads in total hip arthroplasty (THA).
In this article, we review the current concepts and principles behind use of large-diameter ceramic or cobalt-chromium femoral heads on polyethylene bearings in THA. We specifically review the biomechanics, some of the early concerns about polyethylene wear and rim fractures, recent improvements in material properties of polyethylene and ceramic bearings, dislocation rates, and clinical and functional outcomes of large-diameter heads in THA.
Recent literature suggests that the incidence of dislocation has been substantially reduced because of improvements in jump distance and impingement-free range of motion with use of large-diameter heads. Limited evidence suggests excellent short-term and midterm clinical and functional outcomes with these heads.
Use of these bearings has recently increased in the United States. Short-term and midterm follow-up data show low rates of dislocation and wear. Long-term data are to come.
Clinical and Functional Outcomes of Large-Diameter Femoral Heads
There is a paucity of long-term outcomes data on use of large-diameter heads with highly cross-linked polyethylene bearings. Short-term and midterm clinical results appear to be excellent, with low rates of wear, osteolysis, and aseptic loosening.28,41,73,89-92
Plate and colleagues91 compared the effects of large-diameter (≥ 36 mm) and small-diameter (26 mm, 28 mm) metal heads on highly cross-linked polyethylene bearings. At a mean follow-up of 5 years (range, 4-8.4 years), the large-head cohort had a mean HHS of 90 points (range, 50-100 points) and no dislocations or radiographic evidence of stem or cup loosening. Similarly, Meftah and colleagues93 reported 100% stem survivorship and excellent clinical outcomes—a mean Western Ontario and McMaster Universities Arthritis Index (WOMAC) score of 30 points—for 72 hips with use of large ceramic heads (≥ 32 mm) on highly cross-linked polyethylene at a mean follow-up of 3 years. Gagala and colleagues94 reported excellent clinical and radiographic outcomes in 50 hips (18 ceramic on ceramic, 32 ceramic on polyethylene; 36-mm heads) at a mean follow-up of 3.5 years. Mean HHS was 94 points, and there was no evidence of liner fractures, aseptic loosening, or osteolysis.
In summary, large-diameter femoral heads in THA have become increasingly popular because of improvements in the material properties and wear characteristics of highly cross-linked polyethylene and fourth-generation ceramics. Despite the potential advantages of large heads in preventing dislocations, the basic surgical tenets of placing the acetabular component in appropriate alignment remain firmly established. Implants with functionally large heads (eg, dual-mobility bearings, constrained tripolar liners) may play an important role in patients at high risk for dislocation—particularly elderly patients with poor neuromuscular muscle coordination or deficient abductors, trauma patients, and patients with prior dislocations. Short-term and midterm results are excellent; rates of wear, aseptic loosening, and osteolysis are low. However, long-term outcomes data are needed to support widespread use of large heads in younger and more active patients.
