Direct Suturing of Sciatic Nerve Defects in High-degree Knee Flexion: An Experimental Study

We sought to elucidate the conditions of direct suturing of sciatic nerve defects in high-degree knee flexion. We aimed to establish a correlation among the defect length, defect location, degree of knee flexion, and eventual need for hip immobilization in extension.

We performed an experimental study by completing bilateral dissection of the sciatic nerve in 6 cadavers. Three groups of lesions were identified: at the buttock (BG), in the thigh (TG), and in the popliteal fossa (PG). For each defect, a direct, tensionless suture was performed with minimal knee flexion. Next, the hip was progressively flexed until rupture. The nerve defect length correlated with the degree of knee flexion and hip extension required to perform and protect the installed sutures.

A 30° knee flexion allowed for direct suturing of defects >2 cm in the 3 groups. The largest suturable nerve defects measured 7 cm in the TG and PG and 6 cm in the BG. When considering the same-size defects, the required knee flexion tended to be significantly greater in the BG. A bowstringing effect was noted at the buttock and popliteal levels. Hip flexion placed tension on the nerve suture at all locations.

The middle third of the thigh was the most compliant level, because the largest defects will be suturable without a visible bowstringing effect. Hip immobilization should be considered as soon as the defect has exceeded 2 cm, regardless of the location.