Do large heads enhance stability and restore native anatomy in primary total hip arthroplasty?
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.


OBJECTIVE
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 (≥ 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.
Joint Implant Surgeons, Inc, 7277 Smith's Mill Road, Suite 200, New Albany, OH 43054, USA. LombardiAV@joint-surgeons.com
Adolph V
AV
Lombardi
Michael D
MD
Skeels
Keith R
KR
Berend
Joanne B
JB
Adams
Orlando J
OJ
Franchi
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D005260:Female; D005270:Femur Head; D005500:Follow-Up Studies; D005548:Foreign-Body Migration / Q000453:epidemiology / Q000209:etiology*; D006617:Hip Dislocation / Q000453:epidemiology / Q000209:etiology*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011475:Prosthesis Failure; D012189:Retrospective Studies; D012307:Risk Factors; D013499:Surface Properties; D014481:United States / Q000453:epidemiology; D055815:Young Adult