THA: Surface replacement arthroplasty results in a more anatomical reconstruction
Biomechanical reconstruction of the hip: a randomised study comparing total hip resurfacing and total hip arthroplastyJ Bone Joint Surg Br. 2006 Jun;88(6):721-6
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104 patients with advanced unilateral degeneration of the hip undergoing unilateral primary hip replacement were randomized in this study to receive either total hip arthroplasty (THA) or surface replacement arthroplasty (SRA). Radiographs comparing the operated hip with the normal contralateral hip were taken pre and post-operatively. Results indicated that patients in the SRA group had a more precisely restored proximal femoral anatomy than those in the THA group. Significantly more SRA patients were also able to have their leg length inequality restored to within SD 4 mm.
Was the allocation sequence adequately generated?
Was allocation adequately concealed?
Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?
Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?
Blinding Patients: Was knowledge of the allocated interventions adequately prevented?
Was loss to follow-up (missing outcome data) infrequent?
Are reports of the study free of suggestion of selective outcome reporting?
Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?
Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?
Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?
Yes = 1
Uncertain = 0.5
Not Relevant = 0
No = 0
The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.
Inclusion / Exclusion
Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.
Why was this study needed now?
Superior clinical outcomes for primary hip replacement have been documented for operations in which normal anatomy of the hip could be restored, as compared to operations in which a failure of restoration occurred. For this reason, results for THA have been variable, as it can be difficult to provide anatomical restoration during this procedure. Since surface replacement arthroplasty (SRA) requires less removal of the femoral bone, it may result in superior anatomical restoration and better outcomes for patients. Randomized trials are needed to compare SRA with THA in order to explore this hypothesis.
What was the principal research question?
Does surface replacement arthroplasty result in better anatomical restoration than THA when assessed post-operatively in patients with advanced unilateral degeneration of the hip undergoing unilateral primary hip replacement?
What were the important findings?
- With respect to the horizontal centre of rotation of the hip, there was a significant difference between the groups for the percent of patients who were reconstructed within +/- 3 mm of the normal contralateral side (60% of the THA patients vs. 84% of the SRA patients; p = 0.008)
- There was no significant difference between the groups for the percent of patients with reconstruction of the vertical centre of rotation of the hip to within +/- 3 mm of the normal contralateral side (p=0.74), as well as for percent of patients with a mean angle of inclination of the acetabular component between 35 degrees and 55 degrees (p=0.2)
- The mean post-operative femoral offset was significantly increased in the THA group by 5.1 mm (95% CI [4.1, 5.8]; p<0.001) and significantly decreased in the SRA group by -3.3 mm (95% CI [-3.9, -2.6]; p<0.001); the two groups differed significantly (p=0.0001)
- 25% of the THA patients and 59% of the SRA patients had a mean femoral offset within +/- 4 mm; this difference was significant (p < 0.001)
- The leg was lengthened in the THA group by a mean of 2.6 mm (-6.04 to +12.9), and it was shortened in the SRA group by a mean of 1.9 mm (-7.1 to +2.05)
- The two groups differed significantly in the percent of patients with restoration of leg-length inequality to within SD 4 mm (60% THA vs. 86% SRA; p=0.002)
What should I remember most?
This study suggests that SRA results in superior hip anatomy restoration than THA in patients with advanced unilateral degeneration of the hip undergoing unilateral primary hip replacement.
How will this affect the care of my patients?
The results suggest that SRA may allow for a more precise anatomical restoration than THA, leading to better clinical outcomes such as superior functioning and abductor muscle strength. Further randomized trials are required to compare functional outcomes of both SRA and THA.
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