4. Discussion
The goals of this study were to evaluate the impact of TOT on hip joint and lower extremity function. According to our findings, TOT was associated with an objective decrease in the ROM of most of the cardinal movements of the hip joint, increased limb length, and a tendency towards reduced strength of the lower limb in the 6-8 weeks following surgery. Functional tests’ results and patient’s perception of hip joint pain were not affected by the procedure.
TOT, a trans-obturator approach for midurethral sling placement, is considered one of the most effective surgical procedures for SUI, with subjective long-term cure rates of over 90% (27, 28). As compared with other surgical procedures for SUI, it is associated with less serious complications that are considered relatively mild and resolvable (29). Previous studies have carefully delineated complications such as bladder perforation (30), urinary tract infections (31), postoperative voiding dysfunction (32), erosion of the mesh through the vaginal mucosa (33) and groin pain (34). Yet, information regarding the association between TOT and hip dysfunction is limited. Baines et al. reported a case of obturator neuralgia following a retro-pubic sling placement, with weakness in adduction and internal rotation that resulted in a wide-based gait (35). Martínez Franco et al. also described a limitation of hip abduction in a patient who underwent a TOT, but this resulted from a sub-acute abscess spreading from the labia major deep into the thigh muscle (36). Midurethral sling placement involves passing the trocars through the ischiorectal fossa while their distal ends exit via the obturator canal and out through the genitofemoral creases (37). Various tissue layers including muscles and nerves in the proximity of the sling may be injured during this procedure and can potentially cause musculoskeletal dysfunction (38, 39). These structures mainly include the obturator nerve passing through the obturator foramen and the muscles and tendons of the medial thigh (pectineus, gracilis, adductor longus, adductor brevis, adductor magnus, obturator externus and obturator internus muscles). Retro-pubic slings are additionally associated with potential injury to the pudendal, ilioinguinal, and iliohypogastric nerve branches (40).
Indeed, our measurements have shown decreased strength in hip adduction following the procedure. Possible mechanisms of nerve injury are compression, direct injury or stretching of the nerve during surgery that may account for these findings, leading to transient or permanent neuropathy (39, 41). Muscle strain or protective spasm of thigh muscles due to traumatic sling insertion can contribute to the limitation in ROM (42, 43) as well. Psoas muscle spasm could have shifted the ASIS upwards to result in apparent leg lengthening in the early phase following surgery, although the functional significance of this observation remains unclear (44). Interestingly, these changes in hip movement, strength and length did not translate into impairment in the various performance tests, thus highlighting the fact that effective gait functionality and speed are more than just the sum of the individual muscles and nerves. Groups of muscles unaffected by the procedure (45), as well as adequate analgesia given routinely to patients following vaginal surgeries (46), could have attenuated specific musculoskeletal limitations.
The strengths of our study include its novelty of objective measurements as well as subjective patient’s assessment of hip function, its prospective design, and the high rate of compliance with follow-up especially during the COVID-19 period. There were no inter-observer differences in measurements because all were performed by the same examiner who is a licensed physical therapist. Limitations include the relatively small number of participants that precluded stratification for possible confounding factors and generalizability of the results although we have met the requirements of the sample size calculation that we conducted. In addition, postoperative patient evaluation was done once. Spontaneous resolution of symptoms or further deterioration of hip function could have occurred thereafter.
In conclusion, our findings provide support for a yet underestimated association between MUS for SUI and potential hip dysfunction. Pending confirmatory larger trials, it is reasonable to inform patients who intend to undergo a TOT about this potential complication and help prepare for physical rehabilitation. If there is a substantial impairment in hip motility after TOT, the role of physiotherapy before and immediately after surgery should be explored.