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.