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. 2016 Sep;136(9):1317-1323.
doi: 10.1007/s00402-016-2527-4. Epub 2016 Aug 2.

Total hip replacement: increasing femoral offset improves functional outcome

N D Clement  1 , R S Patrick-Patel  2 , D MacDonald  2 , S J Breusch  3
Affiliations

Total hip replacement: increasing femoral offset improves functional outcome

N D Clement et al. Arch Orthop Trauma Surg. 2016 Sep.

Abstract

Introduction: The aim of this study was to assess the independent effect of radiographic measures of implant position, relative to pre-operative anatomical assessment, on the functional outcome of total hip arthroplasty according to change in the Oxford hip score (OHS) 1 year post surgery.

Methods: A prospective cohort study was preformed to assess whether improvement in functional outcome (change in OHS at 1 year) and the relationship with femoral offset and length, and acetabular offset and height. After a power calculation 359 patients were recruited to the study and radiographic measures were performed by blinded observers. Regression analysis was used to assess the independent effect of the four radiographic measurements after adjusting for confounding variables.

Results: There was a significant (p < 0.001) decrease in acetabular offset [5.3 mm, 95 % confidence interval (CI) 4.4-6.2] and increase in femoral offset (6.1 mm, 95 % CI 5.4-6.8). Hence there was no significant change in overall offset. Femoral offset was the only radiographic measure to be achieved statistical significance (r = 0.198, 95 % CI 0.063-0.333, p = 0.004) in relation to clinical outcome, with increasing offset being associated with a greater improvement in the OHS. On combining femoral and acetabular offset increasing offset was associated with a greater improvement in the OHS (r = 0.10, 95 % CI 0.01-0.19, p = 0.04).

Conclusion: This study supports the long-held biomechanical theory of medialisation of the acetabular component with compensatory increased femoral offset results in improved functional outcome.

Keywords: Arthroplasty; Hip; Offset; Outcome; Oxford hip score.

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Figures

Fig. 1
Fig. 1
Diagrams defining the radiographic measurements-obtained [femoral offset (red dashed line) and length (red line), and acetabular offset (blue line) and height (blue dashed line)]
Fig. 2
Fig. 2
Correlation between changes in femoral offset and the OHS at 1 year post THA (dashed line represent 95 % confidence intervals)
See this image and copyright information in PMC

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