Abstract
BackgroundMeasurements of plantar loading reveal foot-to-floor interaction during activity, but information on bone architecture cannot be derived. Recently, cone-beam computer tomography (CBCT) has given visual access to skeletal structures in weight-bearing. The combination of the two measures has the potential to improve clinical understanding and prevention of diabetic foot ulcers. This study explores the correlations between static 3D bone alignment and dynamic plantar loading.MethodsSixteen patients with diabetes were enrolled (group ALL): 15 type 1 with (N, 7) and without (D, 8) diabetic neuropathy, and 1 with latent autoimmune diabetes. CBCT foot scans were taken in single-leg upright posture. 3D bone models were obtained by image segmentation and aligned in a foot anatomical reference frame. Absolute inclination and relative orientation angles and heights of the bones were calculated. Pressure patterns were also acquired during barefoot level walking at self-selected speed, from which regional peak pressure and absolute and normalised pressure-time integral were worked out at hallux and at first, central and fifth metatarsals (LOAD variables) as averaged over five trials. Correlations with 3D alignments were searched also with arch index, contact time, age, BMI, years of disease and a neuropathy-related variable.ResultsLateral and 3D angles showed the highest percentage of significant (p < 0.05) correlations with LOAD. These were weak-to-moderate in the ALL group, moderate-to-strong in N and D. LOAD under the central metatarsals showed moderate-to-strong correlation with plantarflexion of the 2nd and 3rd phalanxes in ALL and N. LOAD at the hallux increased with plantarflexion at the 3rd phalanx in ALL, at 1st phalanx in N and at 5th phalanx in D. Arch index correlated with 1st phalanx plantarflexion in ALL and D; contact time showed strong correlation with 2nd and 3rd metatarsals and with 4th phalanx dorsiflexion in D.ConclusionThese preliminary original measures reveal that alteration of plantar dynamic loading patterns can be accounted for peculiar structural changes of foot bones. Load under the central metatarsal heads were correlated more with inclination of the corresponding phalanxes than metatarsals. Further analyses shall detect to which extent variables play a role in the many group-specific correlations.
Highlights
Measurements of plantar loading reveal foot-to-floor interaction during activity, but information on bone architecture cannot be derived
Sixteen patients with diabetes performed two data acquisition sessions, the cone-beam computer tomography (CBCT) static scan and the plantar pressure analysis during gait. These patients were grouped as follows: 8 type 1 diabetes without (D) and 7 with (N) neuropathy, and 1 with latent autoimmune diabetes of the adults (LADA), all together in the All patients (ALL) group. Those patients with two out of the following three conditions [21] were assigned to the neuropathic group N: Michigan Neuropathy Screening Instrument (MNSI) > 2, Michigan Diabetes Neuropathy Score > 7, and biothesiometer Vibration Perception Threshold (VPT) > 25 Volt
Because the foot bones and the ground were in their original technical frame of the CBCT device, not along the anatomical planes, a foot anatomical reference frame was first defined as follow: the vertical axis was orthogonal to the ground, the antero/posterior axis was the line segment on the ground plane joining the projections of the most plantar points of the calcaneus and of the second metatarsal head; these two axes define the lateral plane of the foot, and their cross product the medio-lateral axis
Summary
Measurements of plantar loading reveal foot-to-floor interaction during activity, but information on bone architecture cannot be derived. Cone-beam computer tomography (CBCT) has given visual access to skeletal structures in weight-bearing. The combination of the two measures has the potential to improve clinical understanding and prevention of diabetic foot ulcers. Knowledge and prevention of diabetic foot disorders are important and may be improved by biomechanical measurements in real patients. The cone-beam computed tomography (CBCT) technology has given access to three-dimensional (3D) measures of bone alignment in weight-bearing condition [8,9,10,11,12,13], overcoming traditional 2D measurements from radiographs [14, 15] and standard computed tomography scans in supine position. It has been demonstrated that, with respect to standard computed tomography, radiation doses are smaller, device ergonomics and portability are better, and overall costs are smaller with the new technique [17,18,19] and these instruments are expected to be used extensively for clinical and biomechanical measurements of the foot in the decades
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