Leg Length and Offset following hip Resurfacing and Hip Replacement

Abstract

We measured and compared critical parameters on antero-posterior radiographs from 28 patients who had undergone hybrid hip replacement (CPS/EPF), with 28 patients who had undergone cemented hip resurfacing (Cormet). All operations were performed by a single surgeon or under his supervision. We measured the femoral offset, acetabular offset, cup height and leg length on pre and post operative radiographs. The mean difference in femoral offset post-operatively was 3.52 mm (95% CI: -1.10 to 8.14 mm) in the hybrid group and -1.30 mm (95%CI: -2.88 to 0.29 mm) in the resurfacing group. Using the independent sample t test (two-tailed), the difference between these means was significant, test statistic t 2.025, p<0.05. This suggests that resurfacing restored the femoral offset more accurately than hybrid hip replacement. The mean difference in leg length post-operatively was 11.91 mm (95% CI: 8.21 to 15.62 mm) in the hybrid group and 4.87 mm (95% CI: 3.32 to 6.42 mm) in the resurfacing group. Using the independent sample t test (two-tailed), the difference between the means was significant, test statistic t 3.597, p<0.001. This suggests that resurfacing produced less change in leg length post-operatively than hybrid hip replacement. We found no statistically significant difference in ideal pre and post operative centre of rotation in the two groups. Proximal femoral anatomy was restored during hip resurfacing by resecting bone of a thickness determined by corresponding preoperative templating and implant thickness rather than relying on placement of the cutting ring at the head-neck junction. No femoral neck fractures occurred in the resurfacing group.

Computed tomography evaluation of hip geometry restoration after total hip resurfacing

“…FO was restored within ±4 mm in 57% of cases after HR compared to only 25% after THA (P < 0.001); corresponding proportions for LLL restoration within 4 mm were 86% and 60%, respectively (P < 0.001). Similarly, in a retrospective comparison of THA and HR [18], restoration of FO and LLL was significantly better after HR (mean variation in FO, 1.3 mm after HR vs. 3.5 mm after THA; corresponding values for LL, 4.9 mm and 11.9 mm, respectively). In another comparison of THA (n = 50) and HR (n = 40) [19] performed during the same period by the same surgeon, restoration of FO and LL was more reliable with HR.…”

“…Before surgery At last follow-up P value Oxford hip score [12] 39.5 ± 4.2 (28-50) 14.1 ± 1.9 (12)(13)(14)(15)(16)(17)(18)(19) < 0.001 a Harris hip score [13] 42.3 ± 8.2 95.4 ± 7.9 (74-100) < 0.001 a Merle d'Aubigné-Postel score [14] 11.1 ± 1.5 (6)(7)(8)(9)(10)(11)(12)(13)(14) 17.6 ± 0.7 (15-18) < 0.001 a Devane activity score [15] 3.0 ± 0.7 (2-5) 4 ± 0.7 (2-5) < 0.001 a UCLA activity score [16] 5.9 ± 1.3 (3-10) 8 ± 1.4 (5-10) < 0.001 a…”

State of the art in hard-on-hard bearings: how did we get here and what have we achieved?

“…Several authors have reported decreased mean horizontal offsets following hip resurfacing arthroplasty of between 3.3 and 8.4 mm when compared with disease-free contralateral hips [154,157,158]. However, other authors have reported that resurfacing more accurately reproduced native horizontal femoral offset compared with total hip arthroplasty [154,[158][159][160], which frequently produced a larger increase in this measurement. Most authors have reported postoperative mean femoral offset values within a few millimeters of the anatomic values, suggesting that any differences are clinically unimportant in properly selected patients.…”

Results of Conserve Plus® Metal-On-Metal Hip Resurfacing for Post-Traumatic Arthritis and Osteonecrosis

“…Recent evidence has suggested that the evolution of HR designs and surgical techniques has led to HRs with lower wear and improved survivorship (6). Hip resurfacing is associated with less alteration in host anatomy and biomechanics, resulting in less change in leg length and offset (7). There is evidence that HR can be safely converted to a THA should there be a failure on the femoral side (8).…”