Prevalence of saphenous nerve injury after adductor-canal-blockade in patients receiving total knee arthroplasty.

BACKGROUND: Adductor-canal-blockade is a new technique for pain relief after knee surgery. This block could cause nerve injury and the aim of this follow-up study was to determine the prevalence of saphenous nerve injury in patients receiving adductor-canal-blockade for pain treatment after total knee arthroplasty.

METHODS: All patients included in two former studies of adductor-canal-blockade following total knee arthroplasty were invited to participate in this follow-up study 3-6 months after surgery. We examined the cutaneous area on the medial aspect of the lower leg (medial crural branch of the saphenous nerve), as well as the anterior, posterior, lateral and infrapatellar part of the affected and contralateral lower leg. Sensory function was tested with pinprick (sharp and blunt needle), temperature discrimination (cold disinfectant swabs) and light brush.

RESULTS: We included 97 patients. None of the patients [0-5.3% (99% confidence interval)] had sensory changes related to temperature or light brush corresponding to the medial crural branch of the saphenous nerve, but 10 patients could not discriminate between blunt and sharp stimulation with a needle. In the infrapatellar area of the operated knee, 76 patients could not discriminate between blunt and sharp stimulation with a needle, 81 patients could not discriminate between cold and warmth, and 82 patients displayed an altered sensation to light brush.

CONCLUSION: We found no indications of saphenous nerve injury caused by the adductor-canal-blockade at the mid-thigh level. However, 84% of the patients had signs of injury to the infrapatellar branch of the saphenous nerve in the operated leg. Such findings are well-known complications to the surgical procedure.