Why large-head metal-on-metal hip replacements are painful

Author:

Cobb J. P.1,Davda K.1,Ahmad A.1,Harris S. J.1,Masjedi M.1,Hart A. J.1

Affiliation:

1. Imperial College, Charing Cross Campus, Fulham Palace Road, London W6 8RF, UK.

Abstract

Large-head metal-on-metal total hip replacement has a failure rate of almost 8% at five years, three times the revision rate of conventional hip replacement. Unexplained pain remains a feature of this type of arthroplasty. All designs of the femoral component of large-head metal-on-metal total hip replacements share a unique characteristic: a subtended angle of 120° defining the proportion of a sphere that the head represents. Using MRI, we measured the contact area of the iliopsoas tendon on the femoral head in sagittal reconstruction of 20 hips of patients with symptomatic femoroacetabular impingement. We also measured the articular extent of the femoral head on 40 normal hips and ten with cam-type deformities. Finally, we performed virtual hip resurfacing on normal and cam-type hips, avoiding overhang of the metal rim inferomedially. The articular surface of the femoral head has a subtended angle of 120° anteriorly and posteriorly, but only 100° medially. Virtual surgery in a normally shaped femoral head showed a 20° skirt of metal protruding medially where iliopsoas articulates. The excessive extent of the large-diameter femoral components may cause iliopsoas impingement independently of the acetabular component. This may be the cause of postoperative pain with these implants.

Publisher

British Editorial Society of Bone & Joint Surgery

Subject

Orthopedics and Sports Medicine,Surgery

Reference8 articles.

1. No authors listed. National Joint Registry for England and Wales: 7th annual report, 2010. http://njrcentre.org.uk (date last accessed 2 April 2011).

2. Jeffers JR, Roques A, Taylor A, Tuke MA. The problem with large diameter metal-on-metal acetabular cup inclination. Bull NYU Hosp Jt Dis 2009;67:189–92.

3. Failure of the Durom Metasul® Acetabular Component

4. The painful metal-on-metal hip resurfacing

5. No authors listed. Medical Device Alert: ARMTM hip replacement implants manufactured by DePuy International Ltd (MDA/2010/069). http://www.mhra.gov.uk/Publications/Safetywarnings/MedicalDeviceAlerts/CON093789 (date last accessed 23 May 2011).

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