Background. Charcot neuropathic osteoarthropathy is a rare, destructive process affecting the bones and joints of feet in patients with diabetic peripheral neuropathy. The aetiology of Charcot remains unknown, although it has been suggested that it is triggered by the occurrence of inflammation in the foot of a susceptible individual, and that the inflammation results in increased osteoclastic activity. Hypothesis. The increased bone turnover in acute Charcot is associated with increased concentrations of pro-inflammatory cytokines, related signalling peptides and bone turnover markers. Methods. 17 patients newly presenting with acute Charcot in diabetes and 16 non-diabetic patients without neuropathy undergoing elective forefoot surgery provided informed consented to participate. Samples of bone were taken by needle biopsy, and were stained with H&E to determine bone architecture and bone remodelling. Serum ALP, CTX, OPG and sRANKL TNF, IL1-beta, IL6 and CRP were measured by immunoassay. Blood was taken from the dorsal foot vein of both the affected and the unaffected foot, as well as an antecubital vein. Results. Classic histopathology features of fracture and bone remodelling were evident in Charcot bone biopsies. Systemic circulating concentrations in the Charcot group antecubital vein for both IL6 and OPG were significantly greater than in controls (p<0.05). There were no significant differences between the dorsal vein concentrations of any analyte when the affected and unaffected feet were compared. However, in patients with an acute Charcot foot the concentration of OPG, ALP and CTX was higher in sera from the dorsal vein of affected foot when compared to controls (p<0.05), this difference was highly significant for IL6 (p<0.001). Conclusion. The elevation in CTX observed in the affected foot in patients with an acute Charcot foot reflects the bone breakdown and remodelling which is present. The higher circulating concentration of IL-6 in the Charcot patient group, reflects the inflammation which is present and which is thought to be central to the development of the condition. Although OPG values were significantly greater in Charcot than control group, circulating concentrations of OPG are known to be higher in diabetes

Using the transverse processes of fresh porcine lumbar spines as an experimental model we evaluated the heat generated by a rotating burr of a high-speed drill in cutting the bone. The temperature at the drilled site reached 174°C with a diamond burr and 77°C with a steel burr. With water irrigation at a flow rate of 540 ml/hr an effective reduction in the temperature was achieved whereas irrigation with water at 180 ml/hr was much less effective. There was a significant negative correlation between the thickness of the residual bone and the temperature measured at its undersurface adjacent to the drilling site (p < 0.001).

Our data suggest that tissues neighbouring the drilled bone, especially nerve roots, can be damaged by the heat generated from the tip of a high-speed drill. Nerve-root palsy, one of the most common complications of cervical spinal surgery, may be caused by thermal damage to nerve roots arising in this manner.

This study was designed to test the hypothesis that the sensory innervation of bone might play an important role in sensing and responding to low-intensity pulsed ultrasound and explain its effect in promoting fracture healing. In 112 rats a standardised mid-shaft tibial fracture was created, supported with an intramedullary needle and divided into four groups of 28. These either had a sciatic neurectomy or a patellar tendon resection as control, and received the ultrasound or not as a sham treatment. Fracture union, callus mineralisation and remodelling were assessed using plain radiography, peripheral quantitative computed tomography and histomorphology.

Daily ultrasound treatment significantly increased the rate of union and the volumetric bone mineral density in the fracture callus in the neurally intact rats (p = 0.025), but this stimulating effect was absent in the rats with sciatic neurectomy. Histomorphology demonstrated faster maturation of the callus in the group treated with ultrasound when compared with the control group. The results supported the hypothesis that intact innervation plays an important role in allowing low-intensity pulsed ultrasound to promote fracture healing.