Do serum markers correlate with invasiveness of the procedure in THA? A prospective randomized study comparing direct anterior and lateral approaches

Background: Advantages of minimally invasive approaches for total hip arthroplasty are still matter of debate. Serum markers have been assessed as objective method to quantify muscle damage after surgery but in literature ambiguous results have been reported. The aim of this prospective randomized study was to: 1) compare serum markers elevation between a minimally invasive direct anterior approach (DAA) and a direct lateral approach (DLA); 2) to establish a correlation between serum markers increase and other perioperative variables. Hypothesis: A lesser elevation of markers could be found in patients who underwent a minimally invasive DAA. Patients and methods: Seventy patients were enrolled and randomly divided in two groups according to the type of the approach. All patients were treated with the same implant by the same surgeon and received the same rehabilitation protocol. Demographic data, preoperative Harris Hip Score (HHS) and operative time were recorded. Myoglobin, creatine kinase MB (CK-MB), troponin I, C-reactive protein (CRP), haemoglobin (HB) and pain levels were measured pre-and postoperatively. Results: Mean postoperative rise were 524.9 +/- 134.6 and 667.8 +/- 409.5 for myoglobin, 4.8 +/- 2.5 and 6.6 +/- 3.7 for CK-MB, and 16.9 +/- 5.3 and 15.4 +/- 6.4 for PCR, in DAA and DLA groups, respectively. In both groups, postoperatively values were significantly higher than preoperatively (p < 0.05). Comparing the two groups, no significant differences in serum markers elevations were found. A significantly lower postoperative pain was found in DAA group than in DLA group (2.9 vs. 4.2 and 2.7 vs. 3.6 in second and third day, respectively (p < 0.05)). No significant correlation was present between the serum marker elevations and age, BMI, HHS, operative time, HB or pain levels (p > 0.05). Conclusion: Serum markers of muscle damage and inflammation increased in the postoperative period without significant differences between DAA and DLA, even though overall trend was higher in DLA group. The DAA group had significantly lower levels of postoperative pain. No significant correlation between pain and serum markers levels was found. Level of evidence: I; randomized study.