[Comparison of Abductor Muscle Strength and Harris Hip Score after Total Hip Arthroplasty].

Purpose of the study: The study aimed to compare the postoperative outcomes of patients with total hip arthroplasty performed through Watson-Jones anterolateral approach and Röttinger minimally invasive anterolateral approach (MIS-AL). The hypothesis was that the MIS-AL approach enables faster recovery and better clinical outcomes in terms of abductor muscle strength and Harris Hip Score (HHS).

Material and methods: The prospective comparative study included 136 patients who underwent surgery between 2018 and 2021. In 88 patients the Watson-Jones procedure was performed and in 48 patients Röttinger minimally invasive procedure was opted for. The Harris Hip Score (HHS) was used to evaluate the outcomes at three time points (before surgery, at 3 and 6 months after surgery) and the abductor muscle strength was measured using the dynamometer at four time points (before surgery, at 17 days, 3 and 6 months after surgery). The statistical analyses were conducted using the independent samples t-test at the level of significance p < 0.05.

Results: In the MIS-AL group, the HHS after 3 months was 86.32 ± 4.8 points, which was a higher score than that achieved in the Watson-Jones group (78.76 ± 5.6; p = 0.0015). After 6 months the difference remained in favour of MIS-AL (94.68 ± 4.7 vs. 90.28 ± 5.4; p = 0.0078). The maximum abductor muscle strength after 6 months improved from 125.52 ± 14.8 N to 170.91 ± 16.2 N in the Watson-Jones group and from 142.78 ± 15.3 N to168.11 ± 15.8 N in the MIS-AL group, with no statistically significant difference between the two groups (p > 0.05).

Discussion: The results show that the differences in abductor muscle strength between the MIS-AL approach and the Watson-Jones anterolateral approach were statistically insignificant. However, better results of the Harris Hip Score in patients in whom the MIS-AL approach was used are supported by the trend of faster functional recovery and higher satisfaction rate of patients undergoing less invasive surgical procedures.

Conclusions: The Röttinger minimally invasive anterolateral approach provides faster improvement of the HHS during the first six months after surgery. The differences in abductor muscle strength between the groups were statistically insignificant.