Expert Insights On Peripheral Nerve Surgery For Tarsal Tunnel Syndrome

Author(s): 
By Stephen L. Barrett, DPM

In my opinion, meticulous dissection is imperative and requires 3.5 x to 4 x surgical loupes and bipolar cautery. When it comes to peripheral nerve surgery, one should avoid monopolar cautery as there is a cone of destruction that one cannot control. However, when you employ bipolar cautery, you can be assured there will be ideal hemostasis with no damage to adjacent tissues. Be careful not to burn the skin edges with any cautery. In my opinion, using a thigh tourniquet is mandatory.
There is little place for sharp dissection in peripheral nerve surgery, especially when it comes to tarsal tunnel decompressions. Using blunt Steven’s tenotomy scissors, one can carefully spread the subcutaneous tissues apart without damaging the nerves. You’ll often find that a medial calcaneal nerve branch can run right through the fatty tissues and there is no way to spare that nerve with sharp dissection.
Once you are down to the flexor retinaculum, you must be extremely careful as the neurovascular bundle is just below. Again, if you employ the aforementioned surgical technique, you minimize the risk of damage to these structures. It is important to note this anatomical area is rarely the site of true entrapment. However, it is imperative to complete the dissection of this portion of the posterior tibial nerve as it allows you to see the origin of the medial calcaneal nerve or nerves. This also gives you the ability to identify the proximal portion of the medial and lateral plantar nerve tunnels. You will almost always find large veins in and around the posterior tibial nerve. Keep in mind that these should rarely, if ever, be ligated.6

Identify the superficial fascia of the abductor hallucis muscle and incise it without damaging the underlying muscle belly. Proceed to retract the muscle plantarly. Doing so will expose the deep fascia of the abductor hallucis muscle. This fascial tissue forms the roof of the medial and lateral plantar tunnels, and acts as the termination of the septum, which separates the medial and lateral neurovascular bundles.
You must remove this septum and divide the fascial roof, which will allow for adequate decompression. Determine if there has been an adequate release by passing a finger into the area. You shouldn’t notice any tightness and you should be able to pass your finger into the plantar aspect of the arch of the foot. With this stage of the procedure complete, proceed to identify the medial calcaneal nerve tunnel or tunnels, and decompress these, alleviating any distal compression on the nerve.7

Key Tips For Closing Tarsal Tunnel Incisions
Closure of the tarsal tunnel incision is very important and failure to pay close attention to this step can lead to disastrous consequences. We have found that by using intradermal 5-0 Monocril suture in an interrupted manner with the knots buried deep and combining this with surgical staples makes for an ideal skin closure. Since adopting this method of closure, we have seen no wound dehiscence, which may be the most frequent complication of the surgery.
By dorsiflexing the foot at the time of skin closure, we have also noted better cosmetic results.

How To Ensure Sound Postoperative Management
Proper postoperative management is essential for an optimal outcome with any type of peripheral nerve surgery. With tarsal tunnel decompression, it is imperative to move the patient immediately after surgery. All peripheral nerves slide and glide similar to tendons. If a patient is immobilized after a neurolysis/decompression, there will likely be fibrosis of the nerve with a less than optimal surgical result.
With a large Robert Jones-type dressing, patients are able to bear some weight on their feet immediately with the aid of crutches or a walker. This allows for movement of the nerve in addition to the active non-weightbearing range of motion exercises that I encourage for the patient. It must be emphasized that patients cannot do too much because they could tear their incisions.

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