Medial plantar flap based distally on the lateral plantar artery to cover a forefoot skin defect

The authors report a simple, single-step procedure to promote the distal transfer of the instep island flap for coverage of the submetatarsal weight-bearing zone. First described in 1991 by Martin et aI, this procedure remained unknown. As opposed to the medial plantar flap, this technique proposes an instep island flap based on the lateral plantar artery. The inflow and outflow of blood is assured by the anastomosis between the dorsalis pedis and lateral plantar vessels. This approach allows for the transfer of similar tissue and provides adequate coverage of the weight-bearing zone of the distal forefoot.     

Region-specific constitutive modeling of the plantar soft tissue

Recent research has shown that hyperelastic properties of the plantar soft tissue consisting of adipose tissue and fibrous septa change from region to region. However, relatively little research has been conducted to develop analytical or computational models to describe the region-specific behavior of the plantar soft tissue. The objective of the research is to develop a region-specific constitutive model of the plantar soft tissue. Plantar soft tissue specimens were dissected from six regions [subcalcaneal (CA), sublateral (LA), subnavicular (Nav), 1st, 3rd, and 5th submetatarsal (M1, M3, M5)] from cadaveric foot samples, and a picrosirius red staining technique was used to visualize the collagen fibers in fibrous septa. The volume fractions of adipose tissue and fibrous septa and the volume fractions of the principal orientations of the fibrous septa were calculated with the intensity gradient method. Region-specific constitutive models were then developed in finite element analysis considering the microstructure of the plantar soft tissue. The hyperelastic region specific material properties of the plantar soft tissue were validated with experimental unconfined compression tests and indentation tests from the literature. The results show that the models give reasonable predictions of the stiffness of the soft tissue within a standard deviation of the tests. The region-specific constitutive models help to explain how changes in the constituents are related to mechanical behavior of the soft tissue on a region specific basis.     

Ageing and isokinetic plantar flexion

Isokinetic torques (Cybex II) of the plantar flexors in 25 healthy men were compared at 5 angular velocities (30, 60, 90, 120 and 180 degrees X s-1). The purposes were to compare plantar flexion torques in young and old subjects, and to determine whether the expected decrease was significantly associated with age, physical activity, or aerobic fitness. Four groups were studied: young (21.7 +/- 2.0 years) and older (63.3 +/- 2.8 years), active and sedentary. Measurements of height, weight, % body fat, VO2max, and daily leisure energy expenditure (questionnaire) were determined for each subject. Statistical measures of analysis of variance were used to determine significant differences among groups; product moment correlation and stepwise regression analysis were used to describe the degree of association between the dependent variable of plantar flexion torque and the independent variables at each velocity. A decline in torque was observed as the isokinetic velocity of angular motion increased. Age alone was a significant determinant of plantar flexion torque, whereas at the slowest speed, when VO2max was used as an explanatory variable, age was not a significant determinant of torque. At 30 degrees X s-1 47% of the variance in torque was explained by VO2max while at 180 degrees X s-1 49% of the variance was explained by age.     

The compressive material properties of the plantar soft tissue

The plantar soft tissue is the primary means of physical interaction between a person and the ground during locomotion. Dynamic loads greater than body weight are borne across the entire plantar surface during each step. However, most testing of these tissues has concentrated on the structural properties of the heel pad. The purpose of this study was to determine the material properties of the plantar soft tissue from six locations beneath: the great toe (subhallucal), the 1st, 3rd and 5th metatarsal heads (submetatarsal), the lateral midfoot (lateral submidfoot) and the heel (subcalcaneal). We obtained specimens from these locations from 11 young, non-diabetic donors; the tissue was cut into 2 cm x 2 cm blocks and the skin was removed. Stress relaxation experiments were conducted and the data were fit using the quasi-linear viscoelastic (QLV) theory. To determine tissue modulus, energy loss and the effect of test frequency, we also conducted displacement controlled triangle waves at five frequencies ranging from 0.005 to 10 Hz. The subcalcaneal tissue was found to have an increased relaxation time compared to the other areas. The subcalcaneal tissue was also found to have an increased modulus and decreased energy loss compared to the other areas. Across all areas, the modulus and energy loss increased for the 1 and 10 Hz tests compared to the other testing frequencies. This study is the first to generate material properties for all areas of the plantar soft tissue, demonstrating that the subcalcaneal tissue is different than the other plantar soft tissue areas. These data will have implications for foot computational modeling efforts and potentially for orthotic pressure reduction devices.     

The V-Y plantar flap for reconstruction of the forefoot

Stable reconstruction of the forefoot remains a formidable challenge. The present study reviews our experience with a flap of plantar skin and fascia advanced in a V-Y manner to cover metatarsal head ulcers. Although this technique was used in a variety of clinical situations, 71 percent of the 38 patients were diabetic with neurotrophic wounds. The anatomic basis for flap design is reported based on 10 fresh cadaver dissections. Flap survival was 100 percent. Ulcer recurrence was related to the problems inherent in the hypesthetic foot. We feel that judicious manipulation of the bony architecture along with weight-dispersion shoe inserts assists in preventing recurrent ulceration.     

Anatomic basis of plantar flap design

Safe planes exist for plantar incisions that minimize the possibility of subcutaneous nerve injury and are therefore useful in flap design. Nerve branch orientation in the plantar subcutaneous tissue is specific and guides dissection so as to avoid producing anesthesia in weight-bearing areas. An extensive proximal plantar subcutaneous plexus exists that permits elevation of plantar flaps in a superficial plane. This is due to the major contribution that the dorsal circulation makes to the skin of the plantar surface. The blood supply to the non-weight-bearing midsole area is not from the medial plantar artery exclusively. This is a watershed area with important lateral plantar artery and dorsalis pedis artery contributions as well. It is not necessary or desirable to base plantar flaps on a myocutaneous or fasciocutaneous supply with its required deep dissection. Local plantar flaps can be designed to include sensation and abundant blood supply without the need for "subfascial" dissection. Subcutaneous sensory plantar flaps designed in accordance with these principles promise a more ideal solution for the treatment of plantar defects.     

Genetics of plantar interdigital ridge counts

The genetics of interdigital ridge counts of soles has been studied in a homogeneous Brahmin population of Andhra pradesh, India. The parameters considered are a-b, b-c and c-d ridge counts. A new measure - total plantar interdigital ridge counts (TPtIRC) - has been defined and an attempt has been made to evaluate the mode of inheritance of this trait. The results of the present study do not fully support the earlier conclusions regarding the genetics of a-b, b-c and c-d ridge counts.     

Scaling of plantar pressures in mammals

The interaction of the limbs with the substrate can teach a lot about an animal's gait mechanics. Unlike ground-reaction forces, plantar pressure distributions are rarely studied in animals, but they may provide more detailed information about the loading patterns and locomotor function of specific anatomical structures. With this study, we aim to describe pressures for a large and diverse sample of mammalian species, focusing on scaling effects. We collected dynamic plantar pressure distributions during voluntary walking in 28 mammal species. A dynamic classification of foot use was made, which distinguished between plantiportal, digitiportal and unguliportal animals. Analysis focused on scaling effects of peak pressures, peak forces and foot contact areas. Peak pressure for the complete mammal sample was found to scale to (mass)^1/2, higher than predicted assuming geometric similarity, and we found no difference between the different types of foot use. Only the scaling of peak force is dependent on the dynamic foot use. We conclude that plantar peak pressure rises faster with mass than expected, regardless of the type of foot use, and scales higher than in limb bones. These results might explain some anatomical and behavioural adaptations in graviportal animals.     

Regeneration of mammalial plantar skin]

Two sole tubers of rat's hind leg were excised together with the surrounding skin and one of the hind tubers of hind and fore legs in hedgehogs were excised without the surrounding skin. During healing the skin wounds in rats and hedgehogs new skin proved to form with the papillary layer typical of the sole skin. In hedgehogs the new skin covered the regenerated sole tuber; in rats the sole tubers failed to regenerate.     

Versatility of the medial plantar flap: our clinical experience

The medial plantar flap presents an ideal tissue reserve, particularly for the reconstruction of the plantar and palmar areas, which require a sensate and unique form of skin. In the past 5 years, the authors performed 16 free flaps, 10 locally pedicled flaps, and five cross-leg flaps on 31 patients for the reconstruction of palmar and plantar defects. All flaps transferred to the palmar area survived, providing good color match and sufficient bulkiness. The overall results were satisfactory in terms of function and sensation, and no complications related to flap survival in the plantar area were observed. All flaps used to cover defects in the heel and ankle region adapted well to their recipient areas, and all lower extremities remained functional. Because the medial plantar flap presents glabrous, sensate skin with proper bulkiness and permits the movement of underlying structures, the authors advocate its use and view this procedure as an excellent alternative in the reconstruction of palmar and plantar weight-bearing areas.     

Angle dependency in strength measurements of the ankle plantar flexors

Muscle strength (or muscular moment) generated during dynamic contractions varies with joint angle. This raises the question about the choice of a representative angle in the evaluation of strength capacity. To assess this angle dependency in strength measurements, dynamic moment-angle curves for plantar flexor muscles were obtained in 43 healthy subjects (28 men and 15 women) with a controlled acceleration dynamometer at 0.52 rad s-1 (30 degrees s-1) and using maximal static preloading before the beginning of movement to attenuate the force development phase. Differences between gender and correlations between strength and anthropometric measures were calculated at each 0.087 rad (5 degrees). The plantar flexion moment was larger in men, in general, but this difference was largest when the ankle was most dorsiflexed. The correlations between moment and anthropometric measures were also higher in the first half of the plantar flexion movement. These results stress the importance of reporting joint angles at which moment of force measures were made. Furthermore, they show that the maximal strength capacity of the plantar flexors is best represented by the moment measured in dorsiflexion angles when the muscles are lengthened.     

Fatigue of the plantar intrinsic foot muscles increases navicular drop

Our purpose was to assess the effect of foot intrinsic muscle fatigue on pronation, as assessed with navicular drop, during static stance. Twenty-one healthy young adults participated. Navicular drop was measured before and after fatiguing exercise of the plantar foot intrinsic muscles. Surface electromyography of the abductor hallucis muscle was recorded during maximum voluntary isometric contractions (MVIC) in order to find the baseline median frequency (MedF). Subjects then performed sets of 75 repetitions of isotonic flexion contractions of the intrinsic foot muscles against a 4.55 kg weight on a custom pulley system. After each set an MVIC was performed to track shifts in MedF. After a MedF shift of at least 10%, navicular drop measurements were repeated. Subjects exhibited 10.0 ± 3.8 mm of navicular drop at baseline and 11.8 ± 3.8 mm after fatigue (p < 0.0005). The change in navicular drop was significantly correlated with change in MedF (r = .47, p = .03). The intrinsic foot muscles play a role in support of the medial longitudinal arch in static stance. Disrupting the function of these muscles through fatigue resulted in an increase in pronation as assessed by navicular drop.     

A viscoelastic ellipsoidal model of the mechanics of plantar tissues

Several assessments of the mechanics of plantar tissues, using various material models in conjunction with representing plantar regions using simple geometry, have been proposed. In this study, the plantar tissues were divided into eight regions to account for the various tissue characteristics. The plantar tissue model described each region as an ellipsoid, with a viscoelastic material model. The model combined varying elliptical contact areas with nonlinear tissue stiffness and damping. The main instruments used in this research were pressure-measuring insoles, which were used to determine the ground reaction force, as well as contact areas. The measured contact areas were fitted as elliptical areas to describe the compression of the corresponding ellipsoids. The approach was tested using walking data collected from 26 individuals: four men, 22 women, 24.4 ± 6.9 years old, 66.9 ± 21.4 kg of mass, 1.66 ± 0.12 m tall. The geometric and material variables of the proposed ellipsoidal model were optimized for each participant to match the ground reaction forces. Results suggest that the ellipsoid model is able to reproduce ground reaction force with reasonable accuracy. The largest errors were seen in heel and toe regions and were due to high-rate forces and small comparative areas, respectively. The model also showed that there are regional differences in the mechanical characteristics of plantar tissue, which confirms earlier research.