Comparison of the different approaches to saphenous nerve block.

BACKGROUND: The authors compared the efficacy of the different approaches to saphenous nerve block.

METHODS: The following approaches to saphenous nerve block were compared in 10 volunteers: perifemoral, transsartorial, block at the medial femoral condyle, below-the-knee field block, and blockade at the level of the medial malleolus. Each volunteer underwent all five blocks, and the interval between blocks was 3-7 days. The sequence of injection was randomized by Latin square design. Sensory blockade at the medial aspects of the leg and foot and the strength of the anterior thigh muscles were noted.

RESULTS: The transsartorial, perifemoral, and below-the-knee field block approaches were more effective than block at the medial femoral condyle in providing sensory anesthesia to the medial aspect of the leg. The transsartorial approach was more effective than block at the medial femoral condyle and below-the-knee field block in providing sensory anesthesia to the medial aspect of the foot. Compared with the perifemoral approach, the transsartorial approach did not cause weakness of the hip flexors and the knee extensors. In volunteers with partial numbness in the medial aspect of the foot, supplemental block of the medial dorsal cutaneous branch of the superficial peroneal nerve resulted in complete sensory blockade.

CONCLUSIONS: Sensory blockade in the medial aspects of the leg and foot is best achieved with the transsartorial approach. In some subjects, supplementary block of the medial dorsal cutaneous branch of the superficial peroneal nerve may have to be performed to assure complete numbness of the medial aspect of the foot.