Surgical offloading procedures for diabetic foot ulcers compared to best non-surgical treatment: a study protocol for a randomized controlled trial

Abstract

Background: Diabetic foot ulcers are frequently related to elevated pressure under a bony prominence. Conservative treatment includes offloading with orthopaedic shoes and custom made orthotics or plaster casts. While casting in plaster is usually effective in achieving primary closure of foot ulcers, recurrence rates are high. Minimally invasive surgical offloading that includes correction of foot deformities has good short and long term results. The surgery alleviates the pressure under the bony prominence, thus enabling prompt ulcer healing, negating the patient's dependence on expensive shoes and orthotics, with a lower chance of recurrence. The purpose of this protocol is to compare offloading surgery (percutaneous flexor tenotomy, mini-invasive floating metatarsal osteotomy or Keller arthroplasty) to non-surgical treatment for patients with diabetic foot ulcers in a semi-crossover designed RCT.

Methods: One hundred patients with diabetic neuropathy related foot ulcers (tip of toe ulcers, ulcers under metatarsal heads and ulcers under the hallux interphalangeal joint) will be randomized (2:3) to a surgical offloading procedure or best available non-surgical treatment. Group 1 (surgery) will have surgery within 1 week. Group 2 (controls) will be prescribed an offloading cast applied for up to 12 weeks (based on clinical considerations). Following successful offloading treatment (ulcer closure with complete epithelization) patients will be prescribed orthopaedic shoes and custom made orthotics. If offloading by cast for at least 6 weeks fails, or the ulcer recurs, patients will be offered surgical offloading. Follow-up will take place till 2 years following randomization. Outcome criteria will be time to healing of the primary ulcer (complete epithelization), time to healing of surgical wound, recurrence of ulcer, time to recurrence and complications.

Discussion: The high recurrence rate of foot ulcers and their dire consequences justify attempts to find better solutions than the non-surgical options available at present. To promote surgery, RCT level evidence of efficacy is necessary.

Trial registration: Israel MOH_2017-08-10_000719. NIH: NCT03414216.

Keywords: Diabetic foot ulcers; Minimally invasive surgery; Surgical offloading.

Fig. 1

Treatment Flowchart - Time Schedule. Note that crossover patients will start afresh from the beginning

Fig. 2

Protocol group flowchart

Fig. 3

A schematic representation of the mechanism of tip of toe ulcer formation and treatment. a The normal toe. Note how the interosseii (and lumbricals, not delineated) pass below the center of the head of the metatarsal (marked with a cross) inserting into the extensor hood. They act as flexors of the metatarso-phalangeal joint and extensors of the proximal and distal inter-phalangeal joints [45].. b In absence of the flexing moment of the interosseii, the extensor digitorum longus forces the metatarso-phalangeal joint into extension. In absence of the extending moment of the interosseii and lumbricals through the extensor sheath, the flexor digitorum longus forces the proximal and distal inter-phalangeal joints into flexion. c The flexor tenotomy with the Beaver knife straightens the toe, relieving pressure from the ulcer sites. Reproduced with permission from Foot & Ankle International [15]

Fig. 4

Minimally invasive floating metatarsal osteotomy. Surgical technique with Shannon burr

Fig. 5

Minimally invasive floating metatarsal osteotomy. Post-operative x-ray demonstrating an osteotomy of the neck of the 4th metatarsal

Fig. 6

Schematic outline of Keller resection arthroplasty that includes shortening the toe by osteotomy of the proximal phalanx and detaching the flexor hallucis brevis tendon. Reproduced with permission from Foot & Ankle International [29]

Fig. 7

Fiberglass cast with heel for metatarsal head ulcers