Purpose of the study: The survival of a total hip arthroplasty (THA) depends mainly on the choice of the implant and the quality of the implantation. Mini-incisions have been criticised because of the increased risk of complications and the uncertainty concerning implant position. The main objective of this work was to assess this later feature.

Material and method: This was a prospective series of consecutive patients attending different centres from January 2008 to January 2009 comparing 100 THA implanted via the reduced Watson-Jones approach (2 centres) and 520 THA implanted in a third centre via the anterior hemimyotomy. Objective assessment (PMA, Harris) and early functional outcome (WOMAC, SF12), biological aggression (myoglobinaemia, CPK, blood loss), complications, and scanographic position of the implants were analysed.

Results: For the mini-Watson-Jones arthroplasties, there was a longer operative time (p< 0.0001), smaller scar, less consumption of analgesics the first postoperative day (p=0.003), and better objective and functional recovery at six weeks (PMA: p < 0.0001; Harris: p = 0.004; WOMAC: p < 0.0001; SF12: p = 0.007). Conversely, there was no significant difference for intraoperative or postoperative blood loss, intraoperative and early postoperative complications, elevation of serum muscle markers, or duration of hospital stay. Regarding implant position, significantly greater acetabular and cumulated anteversion was observed with the mini-incision (p=0.03 and p=0.002 respectively). Nevertheless, the proportion of well positioned implants (Lewinnek criteria) was not significantly different.

Discussion: This series confirms the contribution of the mini-incision to more rapid recovery. We did not find any difference in implant malposition related to approach. The first analyses did however show that the position of the implants is more reproducible with the conventional approach.

Purpose of the study: The purpose of this study was to assess traumatic damage to muscles using biological markers. Two approaches were evaluated: a modified Hardinge approach (anterior hemimyotomy) and a reduced anterolateral approach (Rottinger).

Material and method: This was a multicentric prospective study conducted in three centres in 2008. The first 50 patients in each centre were included. Total creatinine phosphokinase (CPK) and serum myoglobulin levels were used to evaluate muscle damage. Blood samples were taken ten hours after surgery for myoglobulaeia and at one and two postoperative days for CPK. Student’s t test was used for the statistical analysis.

Results: There was no statistically significant difference in serum myoglobulin levels 10 hours postoperatively (p=0.25) or for CPK level at day 1 (p=0.098) and day 2 (p=0.105). Objective clinical recovery (Postel-Merle-d’Aubigné, Harris) and function (WOMAC and SF-12) were better at six weeks with the reduced anterolateral approach.

Discussion: These findings show that muscle aggression after mini-incision is to the same order as with the standard approach. The damage is however different: section for the Hardinge type approaches, stretching and contusion for the mini-incisions.

Conclusion: Use of biological markers specific for muscle tissue appears to be a simple way of quantifying muscle damage. However, adjunction of an imaging technique (MRI) might provide a more precise assessment of muscle injury.