Saphenous neurectomy and application of the Polyganics Neurocap surgical technique
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The geniculate branches of the saphenous nerve are at risk of injury during surgery to the knee. The branches cross obliquely from medial to lateral and may be injured through transection, direct blunt trauma, traction or tether in scar. Injury to the geniculate branches is associated with numbness in the anterior knee, pain at the site of injury and sometimes allodynia. A Tinel’s sign is positive with pain elicited by tapping at the site of suspected nerve injury. Injury to these nerve branches may be a cause of unexplained pain after knee surgery and can be confirmed when the pain resolves after an ultrasound guided block to the saphenous nerve.
Surgical exposure of the nerve may be required for patients with persistent pain and altered sensation that is resistant to physical therapy strategies. Neurolysis of intact branches may improve nerve glide and reduce pain. However the surgeon must be prepared for identifying an end neuroma from transection injury to one or more of the infrageniculate nerve branches and in such cases the treatment options include nerve graft or allograft reconstruction if the distal nerve stump can be identified. In cases where the distal stump is not available, a capping procedure can be performed after neuroma resection using the Polyganics Neurocap device. The Neurocap is a bioresorbable device manufactured from Polycaprolactone. It has a chamber to protect the nerve stump from the surrounding surgical bed to prevent scar tether and pain. Its absorption is complete by 18 months.
In cases of extensive scarring or multiple neuromata of the infra-geniculate branches a saphenous neurectomy may be performed, however the sensory loss that results involves the whole of the anteromedial leg below the knee and this functional loss and risk of marginal hypersensitivity must be balanced against the need to improve the local pain on the extensor aspect of the knee.
Author: Dominic Power FRCS Orth, Consultant Hand and Peripheral Nerve Surgeon
Institution: Peripheral Nerve Injury Service, Queen Elizabeth Hospital, Birmingham, UK