Introduction: We hypothesized that posterior approach (PA) dissecting the short external rotators and anterior approach (AA) not dissecting these have different influences on the pelvic floor muscles and subsequently affect urinary incontinence. The objective of this study was to investigate whether AA advantageously influences symptoms of urinary incontinence.
Patients and methods: The subjects were 76 female patients who underwent their primary total hip arthroplasty. The presence or absence of urinary incontinence before and after surgery was surveyed by a direct interview at the time of outpatient examination within a period from 1.5 year after surgery using the international consultation on incontinence questionnaire-short form.
Results: Urinary incontinence improved after surgery in eight patients (22.2%), slightly improved in one (2.8%), remained unchanged in 26 (72.2%), slightly aggravated in one (2.8%) in the AA group. In the PA group, urinary incontinence improved after surgery in one (2.5%), remained unchanged in 30 (75%), slightly aggravated in four (10%), and aggravated in five (12.5%). Symptoms of urinary incontinence were significantly improved in the AA group and aggravated in the PA group (Mann-Whitney U test, P = 0.0057).
Conclusions: As the anatomical characteristic of the short external rotators, the root of the internal obturator muscle is connected to the levator ani muscle. Among the pelvic floor muscles, this levator ani muscle is closely involved in supporting the pelvic organs. Since the short external rotators may have been atrophied due to hip joint dysfunction before surgery, if the strength of this muscle group recovers, support of the pelvic organs and urinary incontinence may be improved. It was assumed that surgery through AA improved external rotation contracture of the hip joint and leg length, which increased tension of the internal obturator muscle, with which tension of the pelvic floor muscle also increased and improved urinary incontinence.