Expanded butterfly plots: A new method to analyze simultaneous pressure and shear on the plantar skin surface during gait.

The current method of visualizing pressure and shear data under a subject's foot during gait is the Pedotti, or "butterfly" diagram. This method of force platform data visualization was introduced in the 1970s to display the projection of the ground reaction force vector in the sagittal plane. The purpose of the current study was to examine individual sub-components of the vectors displayed in Pedotti diagrams, in order to better understand the relationship between one foot region and another. For this, new instrumentation was used that allows multiple Pedotti diagrams to be constructed at any instant during the gait cycle. The custom built shear-and-pressure-evaluating camera system (SPECS) allows for simultaneous recordings of pressure and both components of the horizontal force vector (medio-lateral and antero-posterior) at distinctive regions under one's foot during gait. Data analysis of such recordings affirms three conclusions: (i) pressure and shear values on individual sites on the plantar surface of the foot are not associated in a linear manner, (ii) force vectors in the heel and forefoot regions exhibit horizontal force components that oppose one another, and similarly, (iii) force vectors in the frontal plane transecting the forefoot region also exhibit medial-lateral shear components that counteract one another. This approach sheds light on individual vectors that collectively sum to each vector displayed in a Pedotti diagram. The results indicate that shearing between the foot and the ground is not simply a passive event. The structures of the arches and/or muscular activities are major contributors to the observed interfacial stresses.

Spatial relationships between shearing stresses and pressure on the plantar skin surface during gait.

Based on the hypothesis that diabetic foot lesions have a mechanical etiology, extensive efforts have sought to establish a relationship between ulcer occurrence and plantar pressure distribution. However, these factors are still not fully understood. The purpose of this study was to simultaneously record shear and pressure distributions in the heel and forefoot and to answer whether: (i) peak pressure and peak shear for anterior-posterior (AP) and medio-lateral (ML) occur at different locations, and if (ii) peak pressure is always centrally located between sites of maximum AP and ML shear stresses. A custom built system was used to collect shear and pressure data simultaneously on 11 subjects using the 2-step method. The peak pressure was found to be 362 kPa ± 106 in the heel and 527 kPa ± 123 in the forefoot. In addition, the average peak shear values were higher in the forefoot than in the heel. The greatest shear on the plantar surface of the forefoot occurred in the anterior direction (mean and std. dev.: 37.7 ± 7.6 kPa), whereas for the heel, peak shear the foot was in the posterior direction (21.2 ± 5 kPa). The results of this study suggest that the interactions of the shear forces caused greater "spreading" in the forefoot and greater tissue "dragging" in the heel. The results also showed that peak shear stresses do not occur at the same site or time as peak pressure. This may be an important factor in locating where skin breakdown occurs in patients at high-risk for ulceration.

Midshaft first-ray osteotomies for hallux valgus.

In this article, the authors describe the indications, contraindications, surgical technique and its fixation considerations, postoperative care, results, and potential complications of the offset V and the traditional Z osteotomies. Because of its versatility, inherent stability, minimal first metatarsal shortening, good intermetatarsal reduction, and ease of rigid internal fixation, shaft osteotomies are gaining popularity as procedures for the correction of hallux valgus. Strong and stable internal fixation allows for earlier functional recovery and primary bone healing. Shaft osteotomies can provide predictable and rewarding results for the patient and surgeon for the correction of hallux valgus.

Combined popliteal and saphenous nerve blocks at the knee: an underused alternative to general or spinal anesthesia for foot and ankle surgery.

Peripheral nerve blocks at the ankle have long been used for foot surgery. However, when local foot and ankle blocks are inappropriate or contraindicated, general and spinal anesthesia are the common alternatives. Both have disadvantages and require added equipment and monitors. Combined popliteal and saphenous nerve blocks at the knee can offer a desirable alternative to general and spinal anesthesia for foot and ankle surgery. In addition, popliteal and saphenous nerve blocks provide anesthesia of the entire lower leg, thus permitting a greater variety of procedures to be performed. This article reviews the anatomical considerations, various block techniques, and surgical applications of this useful approach to lower-leg anesthesia.

Complications of intra-articular fractures of the calcaneus.

Most complications of calcaneal fractures are due to the combination of the dynamic nature and the mechanism of the injury itself. Complications are usually secondary to three integral parts of this complex fracture pattern: 1) fracture and depression of the subtalar joint, 2) loss of the height of the calcaneal body with varus rotation, and 3) expansion of the lateral wall of the calcaneus. Other complications occur with less frequency. This article describes the complications and sequelae of old, malunited intra-articular calcaneal fractures in relation to the nature and the components of these unique fractures.