Charcot foot in diabetes: farewell to the neurotrophic theory.

Neuropathic osteoarthropathy is characterised by relatively painless swelling together with extensive damage in bones and joints, predominantly in the feet and ankles. The uncontrolled natural course of the condition leads to gross foot deformity, skin pressure ulceration, spreading infections, and sometimes amputation. Jean-Martin Charcot in 1883 described "Charcot foot" named after him in patients with tabes dorsalis insensitivity. Charcot believed that intrinsic bone weakness was the underlying condition, and was caused by neurogenic deficiencies in bone nutrition. His followers believed such dystrophy to be mediated by sympathetic denervation of the bone vasculature (neurotrophic, or neurovascular theory). Attempts to prove this theory were futile. A neurogenic circulatory disorder potentially relevant to bone nutrition could not be identified. Nowadays, Charcot foot is mostly seen in diabetic neuropathy, which has replaced syphilis as a frequent cause of peripheral nerve dysfunction. Recent studies in the diabetic Charcot foot and bone turnover indicate that the neurotrophic theory is a myth. The assumption of bone resorption due to sympathetic denervation proved to be false--sympathetic activity increases osteoclastic activity and thereby bone loss (sympathomimetic bone resorption). Except for the transient, inflammatory stage of the diabetic Charcot foot, there is no evidence of relevant osteoporosis or demineralisation of the foot skeleton in diabetes.     

Differential diagnosis of Charcot arthropathy and osteomyelitis

Foot problems are common causes of morbidity in patients with diabetes mellitus. Foot ulcers are the leading cause of hospitalization in diabetic patients. Bones may be involved in two different clinical conditions: osteomyelitis and Charcot osteoarthropathy. Osteomyelitis usually develops by spreading from contiguous soft tissue to underlying bone. Charcot foot is deformation of foot as a result of muscle athrophy, bone and joint structure changes in a joint as a secondary complication of neuropathy. To distinguish bone infection from non-infectious bone disorders as in Charcot joint may be difficult, especially if there is no skin ulceration. So, the mere absence of skin ulcers does not exclude the diagnosis of osteomyelitis.     

Mirror foot

Mirror image polydactyly is a rare congenital abnormality that may occur in isolation, or in association with multiple congenital anomalies. A case of unilateral mirror foot with an ipsilateral short, broad tibia is described. The clinical, radiologic, and operative findings are presented, and current theories of embryo-pathogenesis are reviewed.     

Diabetic foot infections: fate of the contralateral foot

Following an initial report urging conservative management of severe diabetic foot infections, the authors have managed 45 patients with a minimum 3-year follow-up. By using standard principles for soft-tissue infection, 78 percent of the patients healed minor amputation sites and maintained biped ambulation following the initial foot involvement. Only 22 percent required a major amputation at the time of the initial foot involvement. The 45 patients were followed and 22 (or 49 percent) developed a severe infection involving the contralateral foot within 18 months. Although 15 of the 22 patients developing contralateral infection (or 33 percent of the total series) required some type of amputation on the contralateral foot, the conservative approach allowed 64 percent of the patients with severe infections in both feet to maintain biped ambulation. This included 40 percent of the patients who required amputation of some portion of both feet.     

Natural gaits of the non-pathological flat foot and high-arched foot

There has been a controversy as to whether or not the non-pathological flat foot and high-arched foot have an effect on human walking activities. The 3D foot scanning system was employed to obtain static footprints from subjects adopting a half-weight-bearing stance. Based upon their footprints, the subjects were divided into two groups: the flat-footed and the high-arched. The plantar pressure measurement system was used to measure and record the subjects' successive natural gaits. Two indices were proposed: distribution of vertical ground reaction force (VGRF) of plantar and the rate of change of footprint areas. Using these two indices to compare the natural gaits of the two subject groups, we found that (1) in stance phase, there is a significant difference (p<0.01) in the distributions of VGRF of plantar; (2) in a stride cycle, there is also a significant difference (p<0.01) in the rate of change of footprint area. Our analysis suggests that when walking, the VGRF of the plantar brings greater muscle tension to the flat-footed while a smaller rate of change of footprint area brings greater stability to the high-arched.     

Parametric study of orthopedic insole of valgus foot on partial foot amputation

Orthopedic insole was important for partial foot amputation (PFA) to achieve foot balance and avoid foot deformity. The inapposite insole orthosis was thought to be one of the risk factors of reamputation for foot valgus patient, but biomechanical effects of internal tissues on valgus foot had not been clearly addressed. In this study, plantar pressure on heel and metatarsal regions of PFA was measured using F-Scan. The three-dimensional finite element (FE) model of partial foot evaluated different medial wedge angles (MWAs) (0.0°–10.0°) of orthopedic insole on valgus foot. The effect of orthopedic insole on the internal bone stress, the medial ligament tension of ankle, plantar fascia tension, and plantar pressure was investigated. Plantar pressure on medial heel region was about 2.5 times higher than that of lateral region based on the F-Scan measurements. FE-predicted results showed that the tension of medial ankle ligaments was the lowest, and the plantar pressure was redistributed around the heel, the first metatarsal, and the lateral longitudinal arch regions when MWA of orthopedic insole ranged from 7.5° to 8.0°. The plantar fascias maintained about 3.5% of the total load bearing on foot. However, the internal stresses from foot bones increased. The simulation in this study would provide the suggestion of guiding optimal design of orthopedic insole and therapeutic planning to pedorthist.     

A thin foot switch

A common problem in determining a number of important gait parameters is a convenient means for indicating foot/floor contact. Various foot switches have been used in many forms, but still an ideal, commercially available switch has yet to materialize. This note describes one method for constructing very thin, (1 mm), durable, switches that have worked well in the Gait Analysis Lab at Texas Scottish Rite Hospital.