What are the roles of hip labrum innervation in both nociception and proprioception? Canadian researchers tackled this question by studying hip joints that were harvested during total hip replacement or hip resurfacing surgery. Twenty labrums were harvested and the structures in the labrum were divided into four quadrants including antero-superior (AS), postero-superior (PS), antero-inferior (AI), and postero-inferior (PI). The mean age of the subjects was near 60. The authors reported the following:
•Labral innervation is from a branch of the nerve to the quadratus femoris and the obturator nerve.
•All labrum samples had abundant free nerve endings according to the authors. These nerve endings are responsible for nociception transmission.
•Three different types of nerve end organs were noted: Vater-Pacini, Golgi-Mazonian, and Ruffini corpuscles. These nerve end organs operate to provide proprioception through their roles in pressure, deep sensation, and temperature.
•The free nerve endings and nerve end organs were observed more often in the AS and PS zones.
•The nerve endings were noted to be abundant in the superficial zones of the acetabular labrum which were for the most part avascular.
•The antero-superior zone of the labrum has abundant free nerve endings, a fact that correlates with the location of common labral tears and that also fits with the pain produced using a maneuver to test impingement in the hip (flexion, adduction, internal rotation).
•No significant differences in age was noted with respect to the innervation.
The study further states that a labral debridement may ease pain with removal of the free nerve endings, yet the labral repair may best allow for proprioceptive abilities and higher function in the injured hip. The authors also describe the findings that there are abundant myofibroblasts in the labrum that may account for the labrum's ability to heal. To learn more about healing labrums and getting patients moving, check out faculty member Ginger Garner's continuing education course on Extra-Articular Pelvic and Hip Labrum Injury: Differential Diagnosis and Integrative Management. The next opportunity to take the course is in March in Houston.