Treatment of Ulcers Associated With Hammer, Mallet and Claw Toe Deformities in the Diabetic Patient Setting

1. STUDY RATIONAL Diabetes is one of the largest medical challenges facing the world today. 12% of the world's health budget is spent on diabetes, which is USD 673 billion (Euros 585 billion). It is estimated that a lower limb is amputated due to diabetes every 30 sec. on a global scale, and its known that 85% of all amputations are performed due to a diabetic ulcer1. In Denmark 320.000 citizens has a diabetes diagnosis, an additional 200.000 are estimated to have diabetes unknowingly, and 750.000 to have the pre-stages of diabetes2. These numbers have doubled in the past ten years and are estimated to cost DKK 86 million a day (or Euros 11.6 million a day)1. One of the complications to diabetes is the "diabetic foot syndrome", which is a result of neurological abnormalities, vascular complications or a combination of the two. Knowledge about the causes of the disease has been gathered since the late nineteenth century3. In recent years, preventive therapy has been the focus of treatment, resulting in several national and international guidelines4,5,6. Focus has been on education in self-care and awareness of risk factors, combined with "Foot-at-Risk" evaluation7, at least once a year and off-loading therapy crafted and applied by specialized personnel3,4.

Steno Diabetes Center Copenhagen, University of Copenhagen, Denmark is a highly-specialized treatment facility focusing on the patient with diabetes. In spite of optimized treatment for patients with diabetes, and the fact that incidence of first-time ulcers in patients with type 1 and 2 diabetes is declining, the incidence of first time ulcers is still 2.6 and 8.7 per. 1000 patient years for type 1 and 2, respectively8. Diabetic foot ulcers have a known association with increased mortality, morbidity and economic burden9,10,11, at the same time most amputations in patients with diabetes are preceded by an ulcer12.

Hammer, mallet and claw-toe deformities are some of the most common deformities associated with the diabetic foot syndrome. Prevalence has been reported between 32% and 46%13,14. These deformities are predictors of diabetic foot ulcers15,16. There are several theories on the etiology of hammer, mallet and claw toe deformities - the three classic deformities of the toes. In the diabetic patient setting, the classical theory is based on neuropathy (nerve damage associated with diabetes and other diseases), resulting in intrinsic muscle (muscles of the foot) dysfunction, changes that lead to imbalance between the flexor and extensor tendons, which in turn leads to hyperextension of the metatarsophalangeal (MTP) joint and/or flexion in the interphalangeal joints (IP), leading to the three classic deformities of the toes. The neuropathic theory is not sufficient to explain the full 4 scope of the problem, and other theories have been proposed17. In the non-diabetic patient, the neuropathic explanation is not viable, but the explanations still center on an imbalance between in- and extrinsic musculature, resulting from deformities in the foot either as flexor-substitution or stabilization deformities18. The deformities change the pressure on the plantar aspect of the foot19. These changes in pressure make specific contact point's predilection sites for ulcers. The sites have been described as tip of the toe ulcers, cock-up ulcers, kissing ulcers and plantar metatarsal ulcers20, these sites will be referred to as ulcers associated with hammer, mallet and claw toe deformities, and are defined as cock-up ulcers that are placed at the dorsal side of proximal phalangeal joint of toes 2-5 and inter phalangeal joint of the hallux. A tip of the toe ulcer is placed at the pulpa of the affected toe. Metatarsal ulcers are placed at the plantar aspect of the distal head of the metatarsal bone of the involved toe. Kissing ulcers, which are placed between toes, and is due to pressure from the deformed toe/toes.

The treatment of hammer, mallet and claw toe deformities in diabetes has classically consisted of offloading in the form of shoes, insoles and/or orthosis (i.e. silicone spacers, felt pads etc.) or flexor tendon tenotomy (cutting tendons) done by scalpel. Several studies on flexor tenotomies performed with scalpel have been performed21,22; all have reported acceptable or positive results on ulcer healing and low complication rates, including one study from our own institute23. At Diabetic Foot Study Group 2018 we presented unpublished results from a study showing that tenotomy done by needle has comparable results to the classical scalpel. However, no study has, to our knowledge, been published comparing conservative treatment with surgical approach to these deformities, let alone randomized controlled trials (RCT). At the same time no studies have, to our knowledge, looked at the effect on plantar pressure (pressure profile of the foot) and balance post flexor tenotomy in the above-mentioned setting. 2. WHAT DOES THIS TRIAL ADD TO CURRENT KNOWLEDGE? This is to our knowledge the first RCT looking at flexor tenotomies compared to conservative treatment. At the same time this is the first study looking at needle flexor tenotomies, as opposed to the classic tenotomies done by scalpel. The effect of flexor tenotomy on the balance of patients with diabetes has not been described earlier. 3. HYPOTHESIS We hypothesize that treating ulcers associated with hammer, mallet and claw toe deformities in patients with type 1 and 2 diabetes with needle tenotomy is a safe and effective treatment, and superior to offloading (conservative) treatment done by silicon spacer, insoles, felt, and/or therapeutic sandals.

I addition we hypothesize that needle tenotomy performed as a treatment for ulcers associated with hammer, mallet and claw toe deformities in patients with type 1 and 2 diabetes will not affect the patients balance or gait significantly. 4. AIM This study is a randomized controlled trial (RCT) . The aim of the RCT is to evaluate the effect of needle tenotomy when treating hammer, mallet and claw toe deformities and an associated ulcer in patients with diabetes. 5. Study 5.1 Design A prospective RCT involving patients with diabetes as well as one of the three deformities and an active ulcer associated with the mentioned deformities.