Abstract
Aim
The aim of this paper is to analyse the cause of neuropathic diabetic foot ulcers and discuss their preventive measures.
Methods
Review of patients with foot ulcers managed in our diabetic MDT clinics since Feb 2018 were analysed. Based on this observation and review of pertinent literature, following observations were made.
Results
Forefoot
Progressive hindfoot equinus from contraction of gastroc-soleus-tendo-Achilles complex, with additional contraction of tibialis posterior and peroneal longus muscles and, progressive plantar flexed metatarsal heads secondary to claw toe deformity results in increased forefoot plantar pressures. In patients with insensate feet, this result in ulcer formation under the metatarsal heads from shear stress when walking.
Callosity under the metatarsal heads is the earliest clinical sign. Most patients by this time have fixed tightness of the muscle groups as assessed by negative Silfverskiold test. Percutaneous tendo-Achilles lengthening (TAL) has shown to reduce the mid-forefoot plantar pressures by 32% and ulcer healing in 96% of patients within 10 weeks (± 4 weeks). Additional z-lengthening of peroneal longus and tibialis posterior tendons helped in patients with big-toe and 5th metatarsal head ulcers. Proximal metatarsal osteotomies further reduce the forefoot pressures to near normality.
Midfoot
Midfoot ulcers are secondary to rocker-bottom deformity a consequence of Charcot neuroarthropathy (CN). Hindfoot equinus as described and relative osteopenia from neurally mediated increased blood flow (neurovascular theory) and repeated micro-trauma (neurotraumatic theory) result in failure of medial column osseo-ligamentous structures. As the disease progress to the lateral column, the cuboid height drops resulting in a progressive rocker bottom deformity. The skin under this deformity gradually breaks down to ulceration.
In the pre-ulcerative stages of midfoot CN, TAL has shown to stabilise the disease progression and in some patents’ regression of the disease process was noted. The lump can excised electively and the foot accommodated in surgical shoes.
Hindfoot
These develop commonly at the pressure areas and bony exostosis in non-ambulatory patients. In ambulatory patients, the most common cause are factors that result in over lengthening of tendo-Achilles such as after TAL, spontaneous tears, or tongue-type fractures.
Conclusions
Early identification of factors that result in plantar skin callosity and treating the deforming forces prevent progression to ulceration. Total contact cast without treatment of these deforming forces results in progression of these callosities to ulceration while in the cast or soon after completion of cast treatment.
