Reduction in Early Dislocation Rate With Large-Diameter Femoral Heads in Primary Total Hip Arthroplasty

104

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.

Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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

Lombardi¹,

Skeels

Berend

et al. 2011

104

“…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.

“…Large-head metal-on-metal (MoM) THAs have the theoretical advantages of superior wear characteristics [9,12] and improved stability [6,7,17,21,22]. However, their routine use is currently discouraged as a result of concerns regarding elevated serum metal ions and their local [3-5, 8, 13, 19, 20, 25] and systemic side effects [2,10,12,15,18,23,26].…”

Section: Introductionmentioning

confidence: 99%

What Is the Natural History of Asymptomatic Pseudotumors in Metal-on-metal THAs at Mid-term Followup?

Konan

Duncan

Masri

et al. 2017

Background The risk of early revision because of pseudotumors in patients who have undergone large-head metal-on-metal (MoM) total hip arthroplasty (THA) is well documented. However, the natural history of asymptomatic pseudotumors or of MoM articulations without pseudotumors is less well understood. The aim of our study was to investigate the natural history of primary MoM THA at mid-term followup. Questions/purposes The purposes of this study were: (1) Did previously detected pseudotumors persist or worsen in asymptomatic patients at mid-term followup; and if so, did any of them require revision THA? (2) Did new pseudotumors form in asymptomatic patients at mid-term followup? (3) What happened to serum trace metal ions at mid-term followup? (4) Were postoperative patient-reported outcome measures (PROMs) maintained at midterm followup? Methods Seventy-one patients who underwent a MoM THA using a Metasul LDH implant with a Durom acetabular cup and an M/L Taper stem between September 2005 and October 2008 were reviewed. All patients for this study were part of two previously published studies from our early followup. Data from the previous studies were used for comparison only. Two of the 71 patients (2.8%) were lost to followup. The mean age at operation was 56 years (range, 34-68 years). There were 24 female patients. All patients had serum trace metal ions testing, ultrasound imaging, and PROMs at a mean 3.5 years (early followup) after the index operation (range, 3-5 years) and delayed followup at a mean 7 years (range, 6.5-9 years). The indication to undertake revision THA was based on clinical evaluation and not solely on the investigation results. Results Twenty-three of 71 patients (32%) had a positive ultrasound scan for pseudotumor at early followup. Of these, eight patients underwent revision THA (11% of MoM THA or 35% of patients with an early positive ultrasound scan). The mean time between positive ultrasound scan and revision surgery was 13 months (range, 5-22 months). Of the remaining 15 patients with pseudotumor noted on early ultrasound, 12 had persistent pseudotumor, two resolved, and one was lost to followup. Six patients (13%) with a normal ultrasound scan at early followup showed new ultrasound findings at delayed followup. Of these, four (8%) were conclusively diagnosed as pseudotumor and one was revised. Serum trace metal ion increased at mid-term followup in the seven cases that showed an increase in volume of pseudotumor. Of the five patients in whom the volume of pseudotumor decreased on ultrasound at mid-term followup, three showed a decrease Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research1 editors and board members are on file with the pub...