Surgical decompression in diabetic peripheral neuropathy

Dear Editor,

Diabetic peripheral neuropathy is one of the most debilitating neurological complications for diabetic patients.^[1] Approximately 50% of those with long-term diabetes will develop neuropathy during their disease course, and one in five of these patients will experience a diabetic ulcer on their limbs.^[2,3] Glycaemic control can help limit the development of neuropathy in type 1 diabetes; however, evidence regarding its effectiveness in type 2 diabetes is limited.^[3] A less commonly used surgical procedure for these patients is surgical decompression of peripheral nerves, as originally described by Dellon in 1992.^[4] The pathophysiology of nerve decompression involves relieving the compression of the nerves caused by increased water content and inflammatory reactions in the nerves of diabetic patients, as well as their passage through narrow fibro-osseous tunnels (double crush). This process enhances blood and axoplasmic flow across the nerves. Surgical indications for diabetic patients primarily involve the treatment of ulcers, gangrene, and amputations. Surgical decompression of the peripheral nerves may serve as a prophylactic option for these patients. Dellon.^[4] The first described a procedure for external neurolysis for upper and lower limb nerves, which showed significant improvement in pain, with better results observed in upper limb nerves than in lower limb nerves. There are prospective studies conducted to evaluate the efficacy of neurolysis, primarily for the lower extremities.^[5-7] Among these, Dellon et al. ^[7] included a large sample size of more than 500 patients. Siemionow et al. (2006)^[8] and Nickerson and Rader^[9] were retrospective studies. Most of these studies demonstrated good responses with external neurolysis, with or without internal neurolysis of peripheral nerves in the limbs. All these studies included adults with both type 1 and type 2 diabetes, with some also including non-diabetic patients.^[10] Most studies focused on patients with good glycaemic control and pain that was unmanageable with medication for at least one year, excluding those who had already experienced ulcers or amputations. Tinel’s sign was identified as a prognostic factor in the selection of patients across these studies.

However, only one study by van Maurik et al.^[11] presented results and Best et al.^[12], was a case series encompassing ten patients, while Zhang et al. ^[13] was a non-randomised comparative trial with very few patients in the control group (560 in the surgical group compared to 40 in the non-surgical group). Liao et al.^[14], which was not included in the review, was also a non-randomised comparative trial with a significant difference in sample sizes between cases and controls. Additionally, the controls were selected from patients who refused surgery for various reasons, making the findings less reliable. Rozen et al.^[3] was the latest study, which was a randomised controlled trial (RCT). van Maurik et al.^[11] used the contralateral limb as a control, while Rozen et al.^[3] used sham surgery on the contralateral limb to avoid bias. Rozen et al.^[3]observed a placebo effect in the sham surgery limbs; however, a follow-up at 56 months showed lower pain scores in decompressed limbs. van Maurik et al.^[11] noted improvement in pain scores, but nerve conduction studies showed no significant results. These two randomised trials also highlighted potential complications such as wound infection and dehiscence, even though all cases were managed conservatively.

In summary, neurolysis of peripheral nerves has shown potential in selected patients with diabetic peripheral neuropathy, but its use remains limited due to a lack of high-quality evidence. There is a clear need for large randomised controlled trials to definitively assess the role, risks, and benefits of nerve decompression and to exclude the placebo effect. Unlike other surgical procedures where randomisation is difficult, this procedure can feasibly be randomised to compare outcomes with the opposite limb.