OPTIMUM ACETABULAR COMPONENT POSITION FOR REDUCED ION LEVELS IN HIP RESURFACING

Grammatopoulos G, Pandit H, Taylor A, et al. OPTIMUM ACETABULAR COMPONENT POSITION FOR REDUCED ION LEVELS IN HIP RESURFACING. Orthop Procs. 2011;93-B(SUPP_IV):546-546. doi:10.1302/0301-620X.93BSUPP_IV.0930546a

Grammatopoulos, G., et al. “OPTIMUM ACETABULAR COMPONENT POSITION FOR REDUCED ION LEVELS IN HIP RESURFACING.” Orthopaedic Proceedings, vol. 93-B, no. SUPP_IV, 2011, pp. 546-546., https://doi.org/10.1302/0301-620X.93BSUPP_IV.0930546a

Grammatopoulos, G., Pandit, H., Taylor, A., Whitwell, D., Glyn-Jones, S., Gundle, R., McLardy-Smith, P., Murray, D., & Gill, H. (2011). OPTIMUM ACETABULAR COMPONENT POSITION FOR REDUCED ION LEVELS IN HIP RESURFACING. Orthopaedic Proceedings, 93-B(SUPP_IV), 546-546. https://doi.org/10.1302/0301-620X.93BSUPP_IV.0930546a

Grammatopoulos, G., Pandit, H., Taylor, A., Whitwell, D., Glyn-Jones, S., Gundle, R. et al. (2011) “OPTIMUM ACETABULAR COMPONENT POSITION FOR REDUCED ION LEVELS IN HIP RESURFACING.” Orthopaedic Proceedings, 93-B(SUPP_IV), pp. 546-546. Available at: https://doi.org/10.1302/0301-620X.93BSUPP_IV.0930546a

Grammatopoulos, G., H. Pandit, A. Taylor, D. Whitwell, S. Glyn-Jones, R. Gundle, P. McLardy-Smith, D.W. Murray, and H.S. Gill. “OPTIMUM ACETABULAR COMPONENT POSITION FOR REDUCED ION LEVELS IN HIP RESURFACING.” Orthopaedic Proceedings 93-B, no. SUPP_IV (2011): 546-546. https://doi.org/10.1302/0301-620X.93BSUPP_IV.0930546a

Grammatopoulos G, Pandit H, Taylor A, Whitwell D, Glyn-Jones S, Gundle R, et al. OPTIMUM ACETABULAR COMPONENT POSITION FOR REDUCED ION LEVELS IN HIP RESURFACING. Orthop Procs. 2011 Nov 1;93-B(SUPP_IV):546-546. https://doi.org/10.1302/0301-620X.93BSUPP_IV.0930546a

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Abstract

Introduction: Metal-on-metal-hip-resurfacing-arthroplasty (MoMHRA) has been associated with the development of inflammatory pseudotumours(IP), especially in females. IPs have been linked to wear debris, which can be related to metal-ion blood levels. Acetabular component position has been shown to influence wear. We have identified an optimum component orientation minimising IP risk around an inclination/anteversion of 40°/20°±10°. Our aim was to see if this optimal position results in lower metal ions and to identify the boundary of an optimal placement zone for low wear.

Methods: A cohort of 104 patients(60M:44F) with unilateral MoMHRA was studied. Blood tests were obtained at a mean follow up of 3.9 years and serum Co/Cr levels were measured(ICPMS). High metal ion concentrations were defined as Co> 4.1ppb and Cr> 5.2ppb. Radiographic cup inclination/anteversion were measured using EBRA. The differences in ion levels between different orientation zones were investigated. Three orientation zones were defined centered on 40°/20°: Z1-within ±5°, Z2-outside ±5°/within ±10° and Z3-within ±10°.

Results: There was a wide range of cup placements. Females had significantly (p< 0.001) smaller components(mean:51, 44–60) than males(mean: 56, 52–64). Cr levels, but not Co, were higher in females(p=0.002) and those with small femoral components(< 50mm, p =0.03). Patients with cups within Z1 (n=13) had significantly lower Co(p=0.005) and Cr(p=0.001). Males with cups within Z3(n=27) had lower ion levels in comparison to those outside, which were significantly lower for Co(p=0.049) but not Cr(p=0.084). Females had similar ion levels within and out of Z3(Cr/Co: p=0.83/0.84). Co levels were significantly lower in Z1(n=13) in comparison to Z2(n=33)(p=0.048) but Cr levels were not different (p=0.06).

Discussion: MoMHRA cups placed within ±5° of the optimum(40°/20°) had significantly lower metal ions indicating lower wear within this narrow zone. This safe zone, could extend to ±10° for males only. The narrower safe zone coupled with smaller components implanted are possible factors contributing to the increased IP incidence seen in females.

Correspondence should be addressed to: British Hip Society, 35–43 Lincoln’s Inn Fields, London, WC2A 3PE, England. Email: c.wilson@boa.ac.uk