Summary

The PFCN and its brances are at risk for injury while dissecting the hamstring fascia and retracting the glutues maximus when performing proximal hamstring repair.

Abstract

Background

and objectives
The posterior femoral cutaneous nerve (PFCN) lies lateral to the ischial tuberosity and the insertion of the common hamstring tendon, placing the nerve at risk during the surgical approach for both proximal hamstring repair and fixation of ischial tuberosity avulsion fractures. The perineal branch of the PFCN is described in surgical technique publications as often crossing the surgical field, but the variations in the location of the PFCN and its branches relative to the surgical approach during proximal hamstring repair have not yet been described in the literature. Postoperative complications including numbness and pain from injury to the PFCN and its branches have been described in the literature. The goal of our study was to identify the location of the PFCN and its branches in relation to the proximal hamstring tendon and ischial tuberosity in an effort to better understand the risk during proximal hamstring repair.

Methods

and analysis
Fifteen hip-to-knee human cadaveric specimens were dissected in the prone position. Skin and subcutaneous tissues were reflected to expose the gluteal and hamstring musculature. The distance between the ischial tuberosity and lateral border of the hamstring, PFCN, perineal branch of the PFCN, and descending femoral branch of the PFCN was measured with digital calipers. Measurements were repeated 3 times and averaged.

Results

The PFCN was 30.5 ± 11.4 mm lateral to the central tip of the ischial tuberosity (range 15.7-52 mm). The average longitudinal distance from the tip of the ischial tuberosity to the point where the perineal branch crossed the hamstrings was 24.1 ± 15.0 mm (range -9.9 to 52.2 mm). The average longitudinal distance to the point where the descending cutaneous branch crossed the hamstrings was 83.3 ± 21.3 mm (range 41.3-110.3 mm). The PFCN was nearest to the inferior border of the gluteus maximus 45.8 ± 13.6 mm lateral to the ischial tuberosity (range 13.6-62.1 mm). Eleven specimens had one identifiable perineal branch; four specimens had two distinct perineal branches. Figure 1 is an example of a dissected specimen with two distinct perineal branches crossing the proximal hamstring.

Conclusions

The PFCN is in close proximity to the surgical approach utilized during proximal hamstring repair, with the perineal branch consistently crossing the surgical field transversely. There is substantial anatomic variability in the precise location of these cutaneous nerves. Although the perineal branch in these specimens crossed an average 2.4 cm distal to the tip of the ischial tuberosity, this relationship ranged from nearly 1cm proximal to 5.2cm distal to the tip of the ischial tuberosity. Based on our findings, we advise careful dissection of the hamstring fascia in an effort to limit risk of injury to the PFCN and its branches during proximal hamstring repair. In addition, avoidance of excessive lateral retraction of the gluteus maximus is recommended.