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Saturday, February 26, 2005

Surgeons must watch for LFCN in minimal incision THA

Minimal incision surgery is becoming increasingly popular. However, the limited field requires surgeons to be particularly careful, according to researchers for Poster P068. They investigated the risk of injury to the lateral femoral cutaneous nerve (LFCN) when a surgeon uses an anterior approach dual incision minimally invasive hip replacement.

The study examined both cadavaric and clinical evidence to track the morphology of the LFCN. Researchers used an anterior approach in 97 cadaver hips and documented LFCN morphology. They found that in 31 percent of the cadavers, the LFCN displayed an arborization pattern with two large trunks, while 53 percent of the cadvers had a "classical" plattern of a single large trunch and a smaller lateral branch.

Researchers also conducted a prospective study and follow-up of patients who had a dual-incision, minimally invasive hip replacement while enrolled in a randomized controlled trial. They questioned patients about LFCN symptoms and time to resolution, outlined the distribution pattern and photographed the area.

A high incidence (38 percent) of patients described a significant paraesthesia in the distribution of the LFCN after the surgical procedure. The area of proximal and lateral sensory loss was approximately the size of the patient's hand span. Although the situation resolved in six months in about half of these patients, a significant number continued to have paraesthesia at the one-year follow up.

Researchers concluded that the cadaveric study supported the existence of a significant lateral branch to the LFCN, which is at risk for neurotmesis. While the dual incision approach attempts to preserve the medial trunk of the LFCN, it does not acknowledge the significant lateral branch.

To reduce the risk of permanent damage, researchers recommend a modified technique and emphasize the the need for judicious retraction and exposure as well as the use of a mobile surgical window.

The research team was led by Daniel Fick, MD, of Perth, Western Australia, and included Ms Samantha Haebich, Professor Bo Nivbrant, and Professor David Wood, all of Perth, Western Australia, and Mr Riaz Khan, of Norwich, United Kingdom.

Area of paraesthesia of the lateral femoral cutaneous nerve lateral branch, postop.

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