Large versus small femoral heads in metal-on-metal total hip arthroplasty

Background A relatively high percentage of monoblock metal-on-metal total hip arthroplasties (THAs) undergo early revision. Revision of these THAs poses challenges unique to this implant type. The early complications after these revisions remain unreported as do the clinical and demographic factors associated with these complications. Questions/purposes We describe (1) the frequency of early complications after revision of monoblock metal-onmetal THA; and (2) the clinical and demographic factors associated with complications. Methods A review of our institution's total joint registry identified 107 patients who underwent 114 revisions of monoblock metal-on-metal THAs. Mean patient age at revision was 60 years (range, 17-84 years), and 65% of the patients were women. Mean followup after revision was 14 months (range, 0-122 months). Revision diagnoses included metallosis (51%), aseptic loosening (27%), infection (7%), pain (6%), malposition (4%), instability (3%), iliopsoas impingement (2%), and periprosthetic fracture (1%). Major complications (instability, infection, aseptic loosening, and wound complications) were documented and included in the analysis. Minor postoperative complications such as urinary tract infection were excluded. Results Twenty-three of 114 procedures (20%) involved at least one early complication after revision of monoblock metal-on-metal THA with 18 (16%) undergoing at least one additional subsequent surgery. The most common complications included aseptic loosening (6%), deep infection (6%), dislocation (4%), and acetabular fracture (3%). Patients who sustained a complication after revision

Section: Introductionmentioning

confidence: 99%

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

Stryker

Odum

Fehring

et al. 2015

“…Thin-walled acetabular cup designs are advantageous in that they offer the ability to preserve bone stock while accommodating larger femoral head sizes for increased ROM [7], lower volumetric wear rates [1,9], and reduced likelihood of femoral head dislocation [2,12,15]. Thin-walled press-fit acetabular cups, however, are susceptible to substantial deformation after implantation [5].…”

Section: Introductionmentioning

confidence: 99%

Acetabular Cup Design Influences Deformational Response in Total Hip Arthroplasty

Meding

Small

Jones³

et al. 2013

Background Press-fit acetabular components are susceptible to deformation in an underreamed socket, with excessive deformation of metal-on-metal (MOM) components potentially leading to increased torsional friction and micromotion. Specifically, however, it remains unclear how cup diameter, design, and time from implantation affect shell deformation. Questions/purposes We asked whether (1) changes in component geometry and material altered maximum shell deformation and (2) time-dependent deformational relaxation processes occurred. Methods Diametral deformation was quantified after press-fit implantation of metal shells into a previously validated polyurethane model. Experimental groups (n = 6-8) consisted of 48-, 54-, 60-, and 66-mm MOM cups of 6-mm wall thickness, 58-mm cups of 10-mm wall thickness, and CoCrMo and Ti6Al4V 58-mm modular cups. Results Greater cup diameter, thinner wall construction, and Ti6Al4V modular designs generated conditions for maximum shell deformation ranging from 0.047 to 0.267 mm. Relaxation (18%-32%) was observed 120 hours postimplantation in thin-walled and modular designs. ConclusionsOur findings demonstrate a reduction of shell deformation over time and suggest, under physiologic loading, early component deformation varies with design. Clinical Relevance Component deformation should be a design consideration regardless of bearing surface. Designs neglecting to adequately address deformational changes in vivo could be susceptible to diminished cup survival, increased wear, and premature revision.

“…The benefit of increased head size was seen in a study of 22-mm and 40-mm femoral heads; the displacement required for dislocation increased by approximately 5 mm with 40-mm heads when the acetabular component is in 45°of abduction [10]. A number of studies document increasing femoral head size increases implant stability, thereby reducing postoperative dislocations [1,3,[9][10][11]30]. We previously reported an incidence of 12 dislocations in 1518 primary THAs (0.8%) with femoral heads 32 mm or less through a standard direct lateral approach [24].…”

Section: Introductionmentioning

confidence: 99%

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

Lombardi¹,

Skeels

Berend

et al. 2011

Self Cite

102

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.