Current Concepts In Surgical Offloading Of The Diabetic Foot
Boulton and co-workers showed that neuropathic patients had higher plantar pressures under the forefoot.3 The goal for patients with diabetic neuropathy is to mitigate these plantar pressures. Armstrong and colleagues compared peak plantar pressures after Achilles tendon lengthening.4 They found that ankle joint dorsiflexion significantly increased and peak plantar pressures were greatly reduced with percutaneous Achilles lengthening.
We prefer a triple hemi-section lengthening of the Achilles. Be careful not to over-lengthen the Achilles as it can result in uncontrolled ankle dorsiflexion after hemisection. We prefer lengthening to no more than 5 degrees past neutral. After lengthening, one can manage the Achilles in the same short leg cast that he or she would use with the forefoot ulceration. Patients need a minimum of six weeks to heal before they can walk in a shoe.
When it comes to bone resection for forefoot ulceration, the surgeon may perform an isolated metatarsal head resection, osteotomy, a plantar condylectomy or a panmetatarsal head resection. Absolute criteria for each clinical scenario are difficult to define. The foot and ankle surgeon must be cautious not to create transfer ulcerations and secondary deformity.
Sub-second metatarsal head ulceration is often the result of a dorsal dislocation of the second metatarsophalangeal joint, a long second ray or a hypermobile or unstable first ray. To address a long ray or dislocated second MPJ, we prefer a distal oblique shortening osteotomy and Girdlestone-Taylor flexor to extensor tendon transfer to the top of the second toe.
Isolated metatarsal head resections are effective in eliminating plantar ulceration but can result in the obvious transfer lesion. This is especially predictable when one has not addressed an underlying biomechanical problem such as ankle equinus. Griffiths and colleagues reviewed patients with diabetes who underwent metatarsal head resections for recalcitrant diabetic foot ulcerations.5 They found that the mean time for healing ulcerations conservatively was nine months while the mean time of healing for the ulceration following a metatarsal head resection was 2.4 months.
Often, we manage the plantar forefoot ulceration for too long unsuccessfully, resulting in radical ray resection or transmetatarsal amputation. Early and definitive surgical care can be very beneficial for patients who do not respond to non-surgical offloading. Biomechanically, a panmetatarsal head resection shortens the metatarsal parabola and distributes weight evenly across the forefoot.
One should consider panmetatarsal head resection in scenarios with large plantar ulcerations involving multiple metatarsal heads. In addition, surgeons should consider the panmetatarsal head resection if two or more lesser metatarsal heads have been removed. Cohen and colleagues showed that panmetatarsal head resection and transmetatarsal amputation had higher clinical success than a solitary partial ray resection.6
The problem with the panmetatarsal head resection is elimination of the first metatarsophalangeal joint. The loss of the first MPJ decreases the stability of the medial foot and arch height. Hamilton and colleagues reviewed patients who had ulceration due to abnormal metatarsal parabola.7 The patients underwent a gastrocnemius recession, a peroneus longus to brevis tendon transfer and resection of the second through fifth metatarsal heads. All patients achieved a healed plantigrade foot without ulcer recurrence or transfer callus.