Previous studies on the anatomy of the lumbar spine have not clarified the precise relationship of the origin of the lumbar roots to their corresponding discs or their angulation to the dural sac. We studied 33 cadavers (25 formalin-preserved and eight fresh-frozen) and their radiographs to determine these details.

All cadavers showed a gradual decrease in the angle of the nerve root from L1 to S1. The origin of the root was found to be below the corresponding disc for the L1 to L4 roots. In the formalin-preserved cadavers 8% of the L5 roots originated above, 64% below and 28% at the L4/L5 disc. In the fresh cadavers the values were 12.5%, 62.5% and 25%, respectively. For the S1 root 76% originated above and 24% at the L5-S1 disc in the formalin-preserved cadavers and 75% and 25%, respectively, in the fresh cadavers.

A herniated disc usually compresses the root before division of the root sleeve. Thus, compression of the thecal sac before the origin of the root sleeve is common for L1 to L5 whereas compression at the root sleeve is common for S1.

Our findings are of value in understanding the pathophysiology of prolapse of the disc and in preventing complications during surgery.

The upper three-quarters of the fibula is commonly used as a non-vascularised autograft. Subsequent to this isolated weakness of extensor hallucis longus may occur. We have studied 26 patients in whom the upper and middle thirds of the fibula had been harvested as a graft through Henry’s posterolateral approach.

Isolated weakness of extensor hallucis longus was found after operation in ten patients but not in the remainder. EMG and nerve-conduction studies confirmed injury of the nerve to extensor hallucis longus in those with weakness. We dissected 40 cadaver limbs and found that those in which the nerve to extensor hallucis longus ran close to the fibular periosteum were at risk. The injury is mostly incomplete and recovery occurs within four to six months.