Do Large Heads Enhance Stability and Restore Native Anatomy in Primary Total Hip Arthroplasty?

Abstract

Background Dislocation remains a serious complication in hip arthroplasty. Resurfacing proponents tout anatomic femoral head restoration as an advantage over total hip arthroplasty. However, advances in bearings have expanded prosthetic head options from traditional sizes of 22, 26, 28, and 32 mm to diameters as large as 60 mm. Large heads reportedly enhance stability owing to increased range of motion before impingement and increased jump distance to subluxation. Available larger diameter material combinations include metal-or ceramic-on-highly crosslinked polyethylene and metal-on-metal, each with distinct advantages and disadvantages. Questions/purposes We sought to determine (1) if using larger diameter heads has lowered our dislocation rate; and (2) how closely an anatomic metal-on-metal bearing with diameters to 60 mm replicates native femoral head size. Methods We retrospectively reviewed 2020 primary arthroplasties performed with large heads (C 36 mm) in 1748 patients and noted dislocation incidence. In a prospective subset of 89 cases using anatomic heads, native femoral head diameter was measured intraoperatively with calipers by an independent observer and later compared with implanted size. Results One dislocation has occurred in 2020 hips for an incidence of 0.05%. The prosthetic head averaged 0.7 mm larger than the native head with 68 of 89 (76%) reconstructed to within ± 2 mm of native size. Conclusions Larger diameter heads have contributed to lower dislocation rates and large-diameter metal-on-metal articulation can provide close anatomic restoration in primary THA.

Revisions of Monoblock Metal-on-metal THAs Have High Early Complication Rates

“…However, limitations associated with polyethylene bearings such as wear, osteolysis, and late instability, in conjunction with advances in metallurgy, improved understanding of articulation mechanics, and implant manufacturer marketing bolstered the resurgence of MoM THA. In addition to the potential for obviating polyethylene-associated complications, MoM bearing surfaces allowed for larger head sizes, thereby affording increased ROM, reduced impingement, and lower dislocation rates [11,20,26,34]. Because of these apparent advantages, use of MoM implants increased, and by 2006, they accounted for more than one-third of the US market [9,36].…”

Causes of Failure of Ceramic-on-Ceramic and Metal-on-Metal Hip Arthroplasties

“…MOM articulations allow for larger head-neck ratios than current options for MOP, which allows for a larger ROM before impingement and stability [31]. Recent studies demonstrated largerdiameter metal heads decreased dislocation rates to as low as 0.05% and were able to better approximate anatomic femoral heads in primary arthroplasty [21], while other studies found a higher rate of revision for dislocation, up to 0.8% in hard-on-hard THA, particularly with the use of smaller head sizes [26].…”

No Difference in Gait Recovery After THA With Different Head Diameters: A Prospective Randomized Study

“…With the advent of new materials designed to reduce wear (crosslinked polyethylene) [8,13,21] and hard bearings to reduce wear and frictional torque (ceramic-on-ceramic, metal-on-metal) [11,17,18,22], the number of THAs with larger diameter heads has increased in recent years. Larger heads may offer distinct advantages, including reduced risk of dislocation and component impingement, as well as increased ROM in some cases [1,6,10,15,20]. Furthermore, larger femoral heads have been theorized to improve joint biomechanics and perhaps better approximate a more normal-feeling hip [10].…”

“…Larger heads may offer distinct advantages, including reduced risk of dislocation and component impingement, as well as increased ROM in some cases [1,6,10,15,20]. Furthermore, larger femoral heads have been theorized to improve joint biomechanics and perhaps better approximate a more normal-feeling hip [10].…”