Total hip replacement: increasing femoral offset improves functional outcome

Abstract

IntroductionThe 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.MethodsA 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.ResultsThere 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).ConclusionThis study supports the long-held biomechanical theory of medialisation of the acetabular component with compensatory increased femoral offset results in improved functional outcome.

A comparison of radiographic leg-length and offset discrepancies between 2 intraoperative measurement techniques in anterior total hip arthroplasty

“…Restoring or maintaining equivalent leg lengths and offset after THA is an important goal for maximizing the postoperative function of a patient [3] , [7] , [8] , [9] , [10] , [16] , [17] , [18] , [19] . While the anterior approach to the hip affords the opportunity to routinely utilize intraoperative fluoroscopy, it is unclear if there is a superior method for assessing intraoperative leg length and offset.…”

“…Recreating hip offset, the difference between the center of rotation of the femoral head and the axis of the femur, is another consideration in THA, as appropriately increased offset has been associated with greater abductor muscle strength, [16] , [17] improved pelvic stability, [16] superior gait, [18] and higher patient-reported outcomes. [10] , [19] …”

Comparison of Patient-Reported Outcomes of Total Hip Arthroplasty between a Neck-Preserving Short-Stem Implant and a Conventional Neck-Sacrificing Implant

“…Second, it is widely held that increased femoral offset results in an improved moment arm, abductor strength, gait, and range of motion, leading to better PROs. [29][30][31][32][33] It has been described that NPS stem implants can offer a greater increase in femoral offset in comparison to conventional neck-sacrificing stems. 31 However, femoral offset was not measured in patients of either implant group, as this comparison is beyond the scope of the study.…”

Restoring global offset and lower limb length with a 3 offset option double-tapered stem

“…FO is defined as the distance from the center of rotation of the femoral head to the anatomical axis of the femur [2]. AO is defined as the distance from the center of rotation of the femoral head to the perpendicular line passing through the medial edge of the ipsilateral teardrop [3].…”