The effect of calcaneus and metatarsal head offloading insoles on healthy subjects' gait kinematics, kinetics, asymmetry, and the implications for plantar pressure management: A pilot study

BACKGROUND

The global number of people with diabetes is estimated to reach 643 million by 2030 of whom 19-34% will present with diabetic foot ulceration. Insoles which offload high-risk ulcerative regions on the foot, by removing insole material, are the main contemporary conservative treatment to maintain mobility and reduce the likelihood of ulceration. However, their effect on the rest of the foot and relationship with key gait propulsive and balance kinematics and kinetics has not been well researched.

PURPOSE

The aim of this study is to investigate the effect of offloading insoles on gait kinematics, kinetics, and plantar pressure throughout the gait cycle.

METHODS

10 healthy subjects were recruited for this experiment to walk in 6 different insole conditions. Subjects walked at three speeds on a treadmill for 10 minutes while both plantar pressure and gait kinematics, kinetics were measured using an in-shoe pressure measurement insole and motion capture system/force plates. Average peak plantar pressure, pressure time integrals, gait kinematics and centre of force were analysed.

RESULTS

The average peak plantar pressure and pressure time integrals changed by -30% (-68% to 3%) and -36% (-75% to -1%) at the region of interest when applying offloading insoles, whereas the heel strike and toe-off velocity changed by 15% (-6% to 32%) and 12% (-2% to 19%) whilst walking at three speeds.

CONCLUSION

The study found that offloading insoles reduced plantar pressure in the region of interest with loading transferred to surrounding regions increasing the risk of higher pressure time integrals in these locations. Heel strike and toe-off velocities were increased under certain configurations of offloading insoles which may explain the higher plantar pressures and supporting the potential of integrating kinematic gait variables within a more optimal therapeutic approach. However, there was inter-individual variability in responses for all variables measured supporting individualised prescription.

Effects of indoor slippers on plantar pressure and lower limb EMG activity in older women

Open-toe mule slippers are popular footwear worn at home especially by older women. However, their biomechanical effects are still poorly understood. The objective of this study is to therefore evaluate the physical properties of two typical types of open-toe mule slippers and the changes in plantar pressure and lower limb muscle activity of older women when wearing these slippers. Five walking trials have been carried out by ten healthy women. The results indicate that compared to barefoot, wearing slippers results in significant increases in the contact area of the mid-foot regions which lead to plantar pressure redistribution from metatarsal heads 2-3 and the lateral heel to the midfoot regions. However, there is no significant difference in the selected muscle activity across all conditions. The findings enhance our understanding of slipper features associated with changes in biomechanical measures thereby providing the basis of slipper designs for better foot protection and comfort.

Effect of overground vs treadmill running on plantar pressure: influence of fatigue

The differences produced when running on a treadmill vs overground may call into question the use and validity of the treadmill as a piece of equipment commonly used in research, training, and rehabilitation. The aim of the present study was to analyze under pre/post fatigue conditions the effect of treadmill vs overground on plantar pressures. Twenty-seven recreational runners (17 men and 10 women) ran on a treadmill and overground at two speeds: S1=3.33 m/s and S2=4.00 m/s, before and after a fatigue protocol consisting of a 30-min run at 85% of their individual maximal aerobic speed (MAS). Contact time (CT in seconds), peak pressure (PP in kPa), and relative load (RL in %) were analyzed under nine foot zones of the left foot using an in-shoe plantar pressure device. A two-way repeated measures ANOVA showed that running on a treadmill increases CT (7.70% S1 and 9.91% S2), modifies the pressure distribution and reduces PP (25.98% S1 and 31.76% S2), especially under the heel, medial metatarsals, and hallux, compared to running overground. Moreover, on both surfaces, fatigue (S2) led to a reduced stride frequency (2.78%) and reduced PP on the lateral heel and hallux (15.96% and 16.35%, respectively), and (S1) increased relative load on the medial arch (9.53%). There was no significant interaction between the two factors analyzed (surface and fatigue). Therefore, the aforementioned surface effect, which occurs independently of the fatigue state, should be taken into account when interpreting the results of studies that use the treadmill in their experimental protocols, and when prescribing physical exercise on a treadmill.

An experimental model for studying the biomechanics of embryonic tendon: Evidence that the development of mechanical properties depends on the actinomyosin machinery

Tendons attach muscles to bone and thereby transmit tensile forces during joint movement. However, a detailed understanding of the mechanisms that establish the mechanical properties of tendon has remained elusive because of the practical difficulties of studying tissue mechanics in vivo. Here we have performed a study of tendon-like constructs made by culturing embryonic tendon cells in fixed-length fibrin gels. The constructs display mechanical properties (toe-linear-fail stress-strain curve, stiffness, ultimate tensile strength, and failure strain) as well as collagen fibril volume fraction and extracellular matrix (ECM)/cell ratio that are statistically similar to those of embryonic chick metatarsal tendons. The development of mechanical properties during time in culture was abolished when the constructs were treated separately with Triton X-100 (to solubilise membranes), cytochalasin (to disassemble the actin cytoskeleton) and blebbistatin (a small molecule inhibitor of non-muscle myosin II). Importantly, these treatments had no effect on the mechanical properties of the constructs that existed prior to treatment. Live-cell imaging and (14)C-proline metabolic labeling showed that blebbistatin inhibited the contraction of the constructs without affecting cell viability, procollagen synthesis, or conversion of procollagen to collagen. In conclusion, the mechanical properties per se of the tendon constructs are attributable to the ECM generated by the cells but the improvement of mechanical properties during time in culture was dependent on non-muscle myosin II-derived forces.

Modified Evans technique improves plantar pressure distribution in lateral ankle instability

OBJECTIVES

Efficiency of the modified Evans technique based on clinical and radiological evaluations was determined by plantar pressure measurement.

PATIENTS AND METHODS

Eleven patients (2 females, 9 males; mean age 29 years; range 19 to 39 years) with chronic lateral ankle instability were surgically treated using the modified Evans technique. Plantar pressures of nine patients were measured pre- and post-operatively.

RESULTS

Plantar pressure below the first metatarsal head decreased in seven of the patients after surgery. Furthermore, in all of the patients, the time of initial contact decreased significantly and the pathology returned to normal limits in the postoperative period.

CONCLUSION

Modified Evans technique, despite its controversial long-term outcomes in lateral ankle instability, decreases first metatarsal head pressure and initial contact time significantly.

Foot and ankle kinematics and ground reaction forces during ambulation

BACKGROUND

Assessing patients with foot and ankle disorders by observation of gait is dependent on the examiner's experience and cannot provide information about three-dimensional movement, forces, or motion of segments of the foot. Gait analysis models usually consider the foot as a rigid body and study the foot and ankle as a unit. These models are adequate to describe ankle sagittal plane mechanics but are limited in their ability to provide accurate analysis in the other planes or of segments of the foot. They are, therefore, less effective for objective assessment of foot and ankle disorders than multisegment foot models.

METHODS

We performed gait analysis using foot-specific analysis methods and evaluated kinematics, ground reaction forces, temporal force factors, and time-related gait factors in 20 normal subjects during level walking. Eleven reflective markers were applied to the foot and leg, and ten cameras and force plates were used. Subjects were tested in athletic shoes.

RESULTS

A three-segment model was constructed to determine three-dimensional motion in the sagittal, coronal, and transverse planes. This model enabled the determination of calcaneal-tibial (ankle-hindfoot complex) and metatarsal-calcaneal (midfoot) movement in three planes. Ground reaction forces, temporal force factors, cadence, stance time, swing time, and percentage of stance time were determined.

CONCLUSIONS

These data provide baseline information for assessment of patients with disorders of the ankle and foot.

On the influence of soft tissue coverage in the determination of bone kinematics using skin markers

Accurate measurement of underlying bone positions is important for the understanding of normal movement and function, as well as for addressing clinical musculoskeletal or post-injury problems. Non-invasive measurement techniques are limited by the analysis technique and movement of peripheral soft tissues that can introduce significant measurement errors in reproducing the kinematics of the underlying bones when using external skin markers. Reflective markers, skeletally mounted to the right hind limb of three Merino-mix sheep were measured simultaneously with markers attached to the skin of each segment, during repetitions of gait trials. The movement of the skin markers relative to the underlying bone positions was then assessed using the Point Cluster Technique (PCT), raw averaging and the Optimal Common Shape Technique (OCST), a new approach presented in this manuscript. Errors in the position of the proximal joint centre, predicted from the corresponding skin markers, were shown to be phasic and strongly associated with the amount soft tissue coverage, averaging 8.5 mm for the femur, 2.8 for the tibia and 2.0 for the metatarsus. Although the results show a better prediction of bone kinematics associated with the Optimal Common Shape Technique, these errors were large for all three assessment techniques and much greater than the differences between the various techniques. Whilst individual markers moved up to 4 mm from the optimal marker set configuration, average peak errors of up to 16, 5 and 3 mm (hip, knee and tibio-metatarsal joints respectively) were observed, suggesting that a large amount of kinematic noise is produced from the synchronous shifting of marker sets, potentially as a result of underlying muscle firing and the inertial effects of heel impact. Current techniques are therefore limited in their ability to determine the kinematics of underlying bones based on skin markers, particularly in segments with more pronounced soft tissue coverage.

Verringerung des plantaren Spitzendrucks beim Diabetiker durch Verk�rzung der Schrittl�nge

Plantar peak pressure is a diagnostically significant parameter for the evaluation of the risk of foot ulceration in patients with diabetic neuropathy. The prophylaxis and therapy of the diabetic foot therefore is to a large extent oriented on peak pressure, and is aimed at an extensive reduction in this parameter. This is mainly accomplished with protective footwear including shoe modifications and cushioning. In comparison, other approaches affecting the loading and motion pattern of the patient are of minor importance--as for example control of gait pattern. In this study we examined shortening of stride length as a possible measure in reducing plantar peak pressure during gait. In 17 diabetic patients without acute foot ulcerations, stride length was reduced to 33% of leg length using an elastic hobble. This led to a reduction in stride length of 23%. At the same time, the walking speed was significantly reduced by 27% and the cadence by 5.7%. As a consequence, the peak pressure was reduced in nearly all regions of the foot--except the small toes. In the metatarsal region peak pressure is reduced by 14.5%. Thus, a reduction in stride length offers the possibility of reducing plantar peak pressure as a supplementary measure in addition to orthopaedic footwear. However, at present clinical feasibility has not yet been established.

Progression of human body sway during successive walking studied by recording sole–floor reaction forces

Strain gauge transducers were firmly attached to five points of the human sole: calcaneus, 1st, 3rd, and 5th metatarsals and great toe. Forces from these five points were recorded during treadmill walking at different speeds. With this method it is possible to obtain data of several dozen steps successively. Lateral-medial force change (x-vector) during progression was obtained from the 5th and 1st metatarsals and posterior-anterior force change (y-vector) was obtained from the calcaneus and 3rd metatarsal. Lateral balance and medial balance were differentiated in x-vector and rearfoot phase and forefoot phase were distinguished in y-vector. The percentage of the forefoot phase among the stance period shows a linear increase with speed of progression. It was concluded that the phase of body sway forward is regulated by walking speeds.

Evaluation of the transverse metatarsal arch of the foot with gait analysis

BACKGROUND

The existence of the transverse metatarsal arch (TMA) of the foot is a point of controversy. According to Kapandji, TMA of the foot elevates the 2(nd) to 4(th) metatarsal heads. Some authors suggest the existence of TMA, while others suggest that there is no functional metatarsal arch of the foot. In this study, we evaluated the existence of TMA of the foot and weight distribution on the metatarsal heads with the EMED-SF (Novel H, Munich, Germany) plantar pressure analysis system.

METHODS

The test was performed with 16 volunteers. According to the three functional columns of the foot, the metatarsal region of pressure picture obtained from the EMED-SF system was divided into three regions called 'masks'. Mean pressures in the masks were calculated at the mid-stance phase.

RESULTS

The highest mean pressure recorded was located at the 2nd to 3rd metatarsal heads (7.96 N/cm(2)), and the second highest pressure was at the heel (6.55 N/cm(2)). The pressures of the 1st metatarsal and 4th-5th metatarsal heads were 4.86 and 6.26 N/cm(2), respectively. The difference between the pressure distributions under metatarsal heads was statistically significant ( p=0.000).

CONCLUSION

According to our results, TMA of the foot does not exist as described by Kapandji.

Characteristics of habituation of the sympathetic skin response to repeated electrical stimuli in man

OBJECTIVES

To study the effect of repeating electrical peripheral nerve stimulation on latency, duration and amplitude of the sympathetic skin response (SSR).

METHODS

SSRs were elicited in all limbs by median and peroneal nerves stimuli. In 10 subjects, 20 stimuli were applied at random time intervals (15-20 s). Another test was performed in 7 subjects using the same protocol, but switching the stimulation site every 5 or 10 stimuli without warning.

RESULTS

The mean amplitude of right palmar response to right peroneal nerve stimulation decreased from 5.05+/-0.76 (SEM) mV at the first stimulus to 1.23+/-0.42 mV at the 20th stimulus (P<0.001). The latency did not change significantly (1473+/-82 to 1550+/-90 ms, P>0.1), while the duration increased (1872+/-356 to 3170+/-681 ms, P<0.001). Stimulation and recording at other sites showed similar trends. Changing the stimulation site failed to alter the adaptation process in terms of amplitude, latency or duration.

CONCLUSIONS

Changes in amplitude and duration of the SSRs to repeated electrical stimuli can occur in presence of constant latency and appear to be independent of the source of sensory input. Peripheral sweat gland mechanisms may be involved in the loss of amplitude and increase in duration of the SSR during habituation.

Low-intensity ultrasound stimulates endochondral ossification in vitro

Animal and clinical studies have shown an acceleration of bone healing by the application of low-intensity ultrasound. The objective of this study was to examine in vitro the influence of low-intensity ultrasound on endochondral ossification of 17-day-old fetal mouse metatarsal rudiments. Forty-six triplets of paired metatarsal rudiments were resected 'en block' and cultured for 7 days with and without low-intensity ultrasound stimulation (30 mw/cm2). At days 1, 3, 5, and 7, the total length of the metatarsal rudiments, as well as the length of the calcified diaphysis were measured. Histology of the tissue was performed to examine its vitality. The increase in length of the calcified diaphysis during 7 days of culture was significantly higher in the ultrasound-treated rudiments compared to the untreated controls (P = 0.006). The growth of the control diaphysis was 180 +/- 30 microm (mean +/- SEM), while the growth of the ultrasound-treated diaphysis was 530 +/- 120 microm. The total length of the metatarsal rudiments was not affected by ultrasound treatment. Histology revealed a healthy condition of both ultrasound-treated and control rudiments. In conclusion, low-intensity ultrasound treatment stimulated endochondral ossification of fetal mouse metatarsal rudiments. This might be due to stimulation of activity and/or differentiation of osteoblasts and hypertrophic chondrocytes. Our results support the hypothesis that low-intensity ultrasound activates ossification via a direct effect on osteoblasts and ossifying cartilage.

Contributions of bone density and geometry to the strength of the human second metatarsal

We investigated, at the whole bone level, the contribution of bone density and geometry to the fracture load of the second metatarsal, a bone that is prone to stress fracture. Dual-energy X-ray absorptiometry (DXA) was used to determine the areal bone mineral density (BMD), projected area of bone, and bone mineral content. Peripheral quantitative computed tomography (pQCT) was used to determine the volumetric cortical bone mineral density (vCtBMD) and cross-sectional moment of interia. Various metatarsal linear dimensions were also measured. The load at failure in cantilever bending was determined. The only linear dimension that had a significant correlation with load at failure was the height of the metatarsal base (r(2) = 0.30, p = 0.008). Utilizing all of the information provided by DXA gave no greater indication of whole bone strength than just BMD alone (adjusted r(2) = 0.40, p = 0.001). Using all of the information provided by pQCT gave no greater indication of whole bone strength than just vCtBMD alone (r(2) = 0. 46, p < 0.001). Volumetric cortical density and BMD were strongly correlated (r(2) = 0.81, p < 0.001). Our data suggest that, in the human second metatarsal, a variable such as material strength (as inferred from cortical density), and not geometry, may be the major factor in determining cantilever load to failure.

High-impact exercise and growing bone: relation between high strain rates and enhanced bone formation

We investigated whether high-impact drop jumps could increase bone formation in the middiaphyseal tarsometatarsus of growing rooster. Roosters were designated as sedentary controls (n = 10) or jumpers (n = 10). Jumpers performed 200 drop jumps per day for 3 wk. The mechanical milieu of the tarsometatarsus was quantified via in vivo strain gauges. Indexes of bone formation and mechanical parameters were determined in each of twelve 30 degrees sectors subdividing the middiaphyseal cortex. Compared with baseline walking, drop jumping produced large peak strain rates (+740%) in the presence of moderately increased peak strain magnitudes (+30%) and unaltered strain distributions. Bone formation rates were significantly increased by jump training at periosteal (+40%) and endocortical surfaces (+370%). Strain rate was significantly correlated with the specific sites of increased formation rates at endocortical but not at periosteal surfaces. Previously, treadmill running did not enhance bone growth in this model. Comparing the mechanical milieus produced by running and drop jumps revealed that jumping significantly elevated only peak strain rates. This further emphasized the sensitivity of immature bone to high strain rates.

An in vitro comparison of bone deformation measured with surface and staple mounted strain gauges

Chicken tibiae were chosen as a model for human second metatarsals. Local surface bone deformation in a 4-point bending configuration was measured in vitro by both strain gauge instrumented staples and strain gauges bonded to the bone's cortical surface. A series of staple bridge dimensions (0.5, 0.6, 0.8 and 1.0 mm) was compared to test for staple influence on bone characteristics and greatest measurement validity and reliability. Thicker staple inhibition of bone deformation was the greatest but differences to thinner staples were not statistically significant (p > 0.05). All staples except 0.5 mm had maximum deviations from linearity less than 1%. The 1.0 mm staple had an R2 value of 0.992 +/- 0.006 plotted against the 4-point bending input force and 0.994 +/- 0.002 plotted against the surface strain gauge signal. The mean intraclass correlation coefficients (ICC) calculated with four input forces (30, 60, 90 and 120 N) and for loading and unloading conditions for the 0.5, 0.6, 0.8 and 1.0 mm staples were 0.75, 0.83, 0.87 and 0.92, respectively. Finally, the differences in slope of the staple strain gauge signal plotted against surface strain gauge signal between input force loading and unloading conditions (0.32), and between input compression and tension conditions (0.79) was least for the 1.0 mm staple which also resulted in the lowest standard deviations. These results suggested the appropriateness of the 1.0 mm staple for in vivo application.

Mobility of the first tarsometatarsal joint in relation to hallux valgus deformity: anatomical and biomechanical aspects

Hypermobility of the first tarsometatarsal (TMT 1) joint is suggested to be an important factor in the cause and progression of hallux valgus deformity. Hypermobility of the TMT 1 joint is tested clinically in the sagittal plane, but an important deformation also exists in the transversal plane: metatarsus primus varus. This in vitro study was undertaken to investigate the relation between the mobility of the TMT 1 joint in these two planes and to investigate the correlation of the mobility with morphological variables. A second aim was to study the possible stabilizing effect of the tibialis anterior muscle, flexor hallucis longus muscle, and peroneus longus muscle on the TMT 1 joint. Nine embalmed human specimens were tested under standardized conditions. A 30-N force was applied to the head of the first metatarsal (MT 1) to pull in either the dorsal or medial direction. To simulate muscle force, 21 N was applied to the three tendons: all seven possible combinations of muscle action were tested in each plane of motion. Angular displacements were measured using 2-dimensional LED video registration. TMT 1 mobility is a relevant factor in MT 1 mobility in the sagittal and transversal planes, the peroneus longus has a stabilizing effect on this joint, and the effect of the flexor hallucis longus on this joint is different in both planes. When considering a Lapidus procedure for surgically correcting a hallux valgus, the mobility of MT 1 in the transversal plane should also be assessed, but so far no objective clinical test in this plane has been described.

Differences in second-intention wound healing between horses and ponies: macroscopic aspects

Second-intention healing of deep wounds was studied in 5 horses and 5 ponies. Standardised wounds were created on the distal limbs and hind quarters. Wounds on the metatarsi extended onto the metatarsal bone; the depth of the wounds in the femoral biceps muscle was 18 mm. The wound margins were marked by tattoos. Photographs were taken at weekly intervals to determine the wound area. The relative contribution of contraction and epithelialisation to wound closure was quantified by means of the tattoos. Swelling of the limbs was measured; and regularity and aspect of the granulation tissue were semi-quantitatively scored. Second-intention wound healing occurred significantly faster in ponies than in horses, and muscle wounds healed significantly faster than metatarsal wounds. These marked differences reflected the greater contribution of contraction to wound healing. Moreover, demarcation was seen earlier and a healthy granulation bed developed more rapidly in ponies, whereas in horses the granulation tissue remained irregular and purulent for longer. Healing of the metatarsal wounds of horses differed markedly from that of all other wounds: these wounds increased to almost twice their original size in the first 2 weeks, exuberant granulation tissue was persistent, epithelialisation started later, and contraction played a minor role in wound closure. Limb swelling was greater in horses than in ponies. Periosteal new bone formation was more extensive, and was active over a longer period in the metatarsal bones of horses than of ponies. From this study it is concluded that second-intention healing of deep wounds occurs faster in ponies than in horses. This difference can be largely attributed to a more pronounced and faster wound contraction in ponies than in horses. Therefore, attempts to improve second-intention wound healing in clinical practice should be directed at stimulation of wound contraction.

Differences in second-intention wound healing between horses and ponies: histological aspects

The histological aspects of second-intention healing were studied in 5 horses and 5 ponies. Biopsies were taken weekly from standardised wounds on the metatarsus and femoral biceps muscle of one horse and one pony. Sections were stained to enable cell counting and the detection of DNA synthesis, fibrin, smooth muscle actin (SMA), collagen, and bacteria. In the ponies, the number of polymorphonuclear leucocytes (PMNs) was high during the first 3 weeks and subsequently decreased rapidly. In the horses, the initial number of PMNs was lower, but remained persistently elevated during the evaluation period. PMNs were found mainly in the superficial zones. Significantly more fibrin was present in the wounds of the horses. No significant differences were observed in the number of fibroblasts, the amounts of SMA and collagen. However, myofibroblasts were significantly less regularly organised in the wounds of the horses, particularly in the metatarsal wounds. The mitotic activity of the epithelium was temporally reduced in week 3. The mitotic activity of the granulation tissue was initially high but declined rapidly from week 1 onwards, with the exception of the metatarsal wounds of the horses, in which mitotic activity remained significantly higher. Histology confirmed and explained the macroscopical differences in wound healing between horses and ponies by the strict organisation of the myofibroblasts and the more effective acute inflammation in the ponies. Stimulation of the organisation of myofibroblasts and improvement of the efficacy of the inflammatory response in horses may therefore result in better second-intention wound healing in horses in clinical practice.

Hypertrophic osteopathy (Marie's disease) in Equidae: a review of twenty-four cases

The case records of 23 horses and one donkey affected by hypertrophic osteopathy (HO) (Marie's disease) were reviewed. All affected animals presented with limb swellings, which were bilaterally symmetrical and usually involved both fore- and hindlimbs. Associated signs included stiffness/lameness and weight loss. Radiological features included periosteal new bone formation over the diaphyses and metaphyses of affected bones. The metacarpal and metatarsal bones were most frequently affected. Articular surfaces remained free of disease. Seventeen animals were destroyed on humane grounds, 3 horses recovered after successful treatment of the primary disease, 3 horses recovered after symptomatic treatment and one horse was lost to follow-up. Significant primary diseases that were believed to predispose to HO were identified (pre- or post mortem) in 14 cases. In each of these cases, an intrathoracic disease was identified, although co-existing extrathoracic disease was present in 3 cases. Granulomatous inflammatory lesions were present in 9 of these 14 cases. In 4 horses, which underwent necropsy examination, no significant underlying disease was identified.

An evaluation of various response criteria in assessing biological availability of phosphorus for broilers

The relative bioavailability of P from seven sources was determined in relation to a standard dicalcium phosphate dihydrate (CaHPO4.2H2O) in a 21-d assay involving 1,320 broiler male chicks using several response criteria. The seven sources (Lucaphos-48, Lucaphos-40, Rukana, Cefkaphos-N, phosphoric acid, monocalcium phosphate monohydrate, or Biophos) were added to the basal diet (.40% total P and 1.10% Ca) at levels to supply .05, .08, .12, .17, .23, and .32% P. Two additional levels (.44 and .66%) of P from dicalcium phosphate dihydrate were included for the standards. The criteria selected to evaluate included tibia ash, tibia specific gravity, tibia shear force, toe shear force, and metatarsal shear force. Other criteria: weight, length, diameter, and volume of tibia; weight, volume, and specific gravity of metatarsus; and weight, volume, and specific gravity of toe were not selected because their response to increasing P levels were inconsistent and quite variable. Nonlinear (asymptotic and sigmoidal) regression equations were fitted to the data than linear equations. The ratios of regression coefficients were used to determine the bioavailability of various test phosphates relative to the reference standard. The results indicated that the response criteria used for the determination will considerably influence the relative bioavailability estimates of a P source. Body weight gain and toe ash percentage were found to be an equally or a more sensitive criteria for assessment of P availability than tibia ash. Tibia specific gravity, tibia shear force, toe shear force, and metatarsal shear force were of limited value as response criteria in P bioavailability assays based on standard error and difference required for significance.

[Form and structure of the metatarsal head arch in adults. Ultrasonographic and podometric studies]

Ultrasonic measurements (n = 172) and plantar pressure investigations (n = 119) are performed on the forefeet of healthy adults, in order to constitute a correlation between shape and function of the anterior metatarsal arch. The thickness of the sole of the foot has its maximum beneath the 2nd metatarsal head and its minimum beneath the 1st and 5th ray. The highest pressure values are found at the 2nd and 3rd metatarsal head. It is concluded that despite the arch like configuration of the forefoot there is no structural arch function. The biological principle of adequate padding of pressure points results-depending on the load-in a different thickness of the soft tissues of the sole of the foot. The higher pressure under the central metatarsal heads is accompanied by thicker soft tissue pads and a more dorsal position of these rays.

Stiffness of screw fixation and role of cortical hinge in the first metatarsal base osteotomy

The authors investigated various factors that affect stiffness of screw fixation in the oblique first metatarsal osteotomy. One screw versus two screw fixation with intact medial cortical hinge, and two screw fixation without hinge were tested on the same metatarsal specimen. Mechanical properties of the fixation patterns were measured on a materials testing apparatus. Each metatarsal was tested at below failure threshold for stiffness within the elastic range of the specimen. Load versus displacement curves and fixation stiffness values were generated for axial loading, valgus torque, and plantar-to-dorsal cantilever bending. Osteotomies with an intact hinge demonstrated superior stiffness in most parameters as compared to osteotomies without a hinge. Two screw fixation with intact hinge showed significantly increased axial stiffness as compared to one screw fixation. There was no statistical difference between one and two screws in cantilever bending and torsional stiffness with an intact hinge. The major stabilizing factor of the first metatarsal base osteotomy is the medial cortical hinge.

Plantar pressures during level walking compared with other ambulatory activities

This study was designed to determine the magnitude of plantar pressures during level walking in comparison to other activities. These activities included climbing up stairs, going down stairs, a simple pivot while walking, and a crossover pivot while walking in normal individuals. Twelve volunteers, six men and six women, mean age 28 years, served as subjects. Data were collected on the dominant foot with an EMED-SF pressure sensor platform as each subject walked barefoot and did each of the five activities. Maximum plantar pressure (MPP) and pressure-time integral (PTI) was found in the metatarsal and heel regions. The results of repeated-measures analysis of variance tests showed that the five experimental conditions were statistically different for both MPP and PTI in the metatarsal and heel regions. Post hoc analysis indicated that MPP and PTI were decreased during the going down stairs condition in the heel and increased during the crossover pivot while walking and pivot while walking conditions for the metatarsal region.

[Phlebology and podiatry]

By their tensing and relaxation, the muscles of the leg are thought to be responsible for compressing and relaxing the vascular walls and the lumen of vessels. In order to study the way the muscle structure of the lower limb (in particular the leg and the foot) functions, it is necessary to understand the step and break down its components. The weight of the body is transmitted to the ground by the astralagus which distributes the different forces throughout the fives systems of ossei trabeculae of the astralagus and the heel. The valgus heel determines a continuous traction on the tendon and the hind leg muscle which determines with time a dragging of the foot. When the body goes forward, the weight levels the transverse fore arch. The flexor muscles of the toes bend the phalanxes, gripping them to the ground, they avoid the falling forward of the body with the proximal insertion on the tibia. The sesamoids increase the muscles power as well as that of the kneecap on the quadriceps. The internal curvature of the foot on the ground is furthered by the decreasing length of the metatarsal bones. This is counterbalanced by the long fibular muscle which lowers the medial axis and raises the external axis. The supination of the forefoot depends only in part on the varus valgus of the rear of the foot. The plantar aponeurosis and the flexor tendons have an impact on the metatarsi because they increase the power and bring the insert closer. The complex articular system of the feet depends on the extrinsic and intrinsic muscle structure which, at the same time as a position variation can also play an important part in the venous alteration.

The role of the plantar first metatarsal first cuneiform ligament in weightbearing on the first metatarsal

Twelve below the knee amputation specimens were examined while a dorsally directed force was applied to the first metatarsal. Seven specimens were tested with serial removal of soft tissues, followed by cutting the plantar first metatarsocuneiform ligament. Five specimens had only the plantar first metatarsocuneiform ligament cut, leaving the other structures intact. In both groups, dorsal displacement of the distal first metatarsal was noted to be more than 5 mm after sectioning of the ligament, with no marked change noted during removal of other soft tissues. This study demonstrates that the plantar first metatarsocuneiform ligament is the major component in the stabilization of the first metatarsal during weightbearing.

An investigation of injection techniques for local analgesia of the equine distal tarsus and proximal metatarsus

A positive radiographic contrast agent was injected into the tarsometatarsal (TMT) joints of both hindlimbs of 10 horses. Lateromedial radiographic views were obtained at 5, 15 and 30 mins after injection. Injection was successful in 19 of 20 limbs. Communication between the centrodistal (CD) and TMT joints was identified in 7 limbs (35%). Contrast agent extended around the tendons of tibialis cranialis (TC) and fibularis tertius (FT) in 18 limbs, and in 7 limbs some contrast entered the tarsal sheath. Slight to moderate plantar and/or distal extension of contrast agent was identified in 13 limbs. On a subsequent occasion positive contrast agent was injected subtarsally using one of two techniques and radiography was repeated. Contrast agent was principally distributed on the plantar aspect of the 3rd metatarsal bone, the plantar aspect of the suspensory ligament and between the superficial and deep digital flexor tendons. Extension of contrast agent into the TMT joint was identified in only 1 limb but in 8 limbs contrast agent extended into the tarsal sheath. The practical implications of these results include the possibility that local anaesthetic solution injected into the TMT joint may alleviate pain from the CD joint, the insertions of TC and FT or the tarsal sheath. It may also result in perineural analgesia of the dorsal metatarsal nerves or the plantar metatarsal nerves. In some cases subtarsal injection of local anaesthetic solution may result in alleviation of pain from the tarsal sheath. False negative results for subtarsal analgesia may be achieved by inadvertent injection into the tarsal sheath or into a blood or lymphatic vessel.

[Helal's metatarsal osteotomy. Indication and technic with reference to shape and function of the foot]

Metatarsal osteotomy according to Helal is a successful method of treating metatarsalgia. Using this method, 72% of our patients, followed up between 1974 and 1986, (114 patients with a total of 336 osteotomies) were relieved of pain, the result depending on the patients' age. On reviewing the unsuccessful results using pedobarographic measuring, the major part of failures was due to an unequal distribution of weight on the forefoot. Two main types of faulty weight-bearing were stated: 1. Excessive weight-bearing on non-osteotomized adjacent metatarsals (domino-effect). In concern of the overall-result no difference could be found between cases with routine osteotomy II-IV and ones with single or double osteotomy. 2. Excessive weight-bearing on the complete fore-foot as a consequence of missing support by contracted metatarsophalangeal joints. When planning an operation, the length of all metatarsals in relation to each other, as well as the mobility of the toes should therefore be taken into consideration.

Failure of normal osteoclasts to resorb calcified cartilage from osteosclerotic (oc/oc) mice in vitro

Osteosclerosis is an osteopetrotic mutation in the mouse characterized by reduced bone resorption, numerous small osteoclasts lacking elaborate ruffled borders, and resistance to cure by bone marrow transplants from normal littermates. The failure of osteosclerotic mice to be cured by bone marrow transplants could be due to the production of bone that is not resorbable by normal osteoclasts. We tested this hypothesis using a modification of the metatarsal organ culture system of Burger et al. (1982), in which metatarsals are cultured with various tissues that act as sources of osteoclast precursors. Metatarsals from neonatal mutants were isolated, and live bone rudiments were cultured with small cubes of liver or spleen from normal littermates for 7 days. Controls included normal and mutant metatarsals cultured alone or with spleen or liver from littermates of the same or different genotype. Mutant metatarsals cultured alone or with mutant tissue had small osteoclasts, no marrow spaces, and no evidence of bone resorption. Mutant metatarsals cultured with normal liver or spleen had larger osteoclasts, evidence of resorption of bone but not cartilage, and no marrow spaces because the calcified cartilage cores of metaphyseal trabeculae persisted. Normal metatarsals cultured with normal liver had large osteoclasts, bone resorption, and marrow spaces. By transmission EM, mutant trabeculae contained a layer of amorphous material between the central core of calcified cartilage and the surrounding bone matrix. This material was not present in normal metatarsals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of age and diet on the development of mechanical strength by the third metacarpal and metatarsal bones of young horses

The application of transmission ultrasonics to the equine cannon holds promise as a method of monitoring metacarpal and metatarsal development, quality and integrity under a variety of experimental and field conditions. The validity of relating the velocities of sound pulses transmitted through the cannon to the mechanical breaking strengths of these bones was tested in two studies. Breaking strengths calculated from the sound velocities through sections of the metacarpal bones from 14 yearling ponies and 12 yearling horses were highly correlated with the mechanical breaking strengths of those sections (r = .907 and .927, respectively; P less than .01). Sound velocities through the cannons of the horses before sacrifice ranged from 2,453 to 3,130 m/s and were correlated with their mechanically determined breaking strengths (193 to 262 X 10(6) N/M2; r = .673; P less than .01). The correlation coefficient increased to .912 when the sound velocities were adjusted for the sound-delaying effects of the overlying soft tissues. In a third study, 13 horses were weaned at 2 to 4 mo of age and were fed diets providing either 100 or 130% of National Research Council (NRC) energy and protein recommendations. Metacarpal and metatarsal development was monitored monthly for 15 mo via transmission ultrasonics. Sound velocities, breaking strengths calculated from velocities adjusted for estimated soft tissue cover, measured bone mediolateral diameters and cannon diameters minus estimated soft tissue increased as quadratic functions of chronologic age (r greater than .840; P less than .0001). None of these variables was significantly affected by diet, leg or sex. These studies have demonstrated that the use of transmission ultrasonics to estimate and monitor metacarpal and metatarsal breaking strengths in the live horse is reliable, reproducible, simple, accurate and valid. They also suggest that NRC energy and protein recommendations meet the requirements for maximum bone growth and development in well-managed young equines.

The practical biomechanics of running

The foot and ankle is a complex structure made of many small bones with capsular and ligamentous constraints. The physiology, kinematics, and muscle interaction of the walking, jogging, and running cycles will be discussed and the current biomechanical literature reviewed. To analyze the pathologic state, one must be aware of the normal stresses and functions of the running cycle. This knowledge establishes a rational basis for the interpretation of problems in providing medical and orthotic treatment.

Role of the metatarsophalangeal (MTP) joints of the foot in level walking

This study investigates the motion and function of the metatarsophalangeal joints of the foot in customary, slow, fast and longer stride styles of level walking. Electromyograms of the tibialis posterior (TP), extensor hallucis longus (EHL), extensor digitorum longus (EDL), flexor hallucis longus (FHL), flexor digitorum longus (FDL), tibialis anterior (TA), gastrocnemius (TS) and peroneous longus (PL) and ground reaction forces, foot switch signals and electrogoniometers of the ankle and metatarsophalangeal (MTP) joints were recorded simultaneously. In customary and fast walking, the role of the long toe flexors is to act as an aid and they also act as roll off agents maintaining floor contact. In slow walking styles the function of the toes is not to exert propulsion forces but stabilizing forces. In longer stride walking it is suggested that the toes are required to exert propulsion forces. It is important to research multilaterally the causal relation of many parameters.

The relationship between foot structure and intermetatarsal neuromas

Intermetatarsal neuromas are caused by trauma secondary to biomechanical factors. A review of the literature concerning intermetatarsal neuromas is presented. The authors discuss foot structure as a possible cause and present data from 292 radiographs that substantiate the proposed theory. They suggest that intermetatarsal neuromas are caused by a combination of factors.

Endogenous ionic currents traverse intact and damaged bone

Living bone drives an electric current through itself and into sites of damage. Such "fracture currents" consist of two components: an intense, decaying current dependent on bone deformation and a stable, persistent current driven by a cellular battery. The latter is carried by chloride ions and, to a lesser extent, by sodium, magnesium, and calcium ions. Endogenous fracture currents are of the same polarity and similar magnitude as clinically applied currents that are successful in treating chronic nonunions in fractured bones. This suggests that the defect in biological nonunions may reside in the electrophysiology of repair.

Surgical treatment of metatarsalgia. Long-term evaluation of 105 cases

The authors present a long-term evaluation of a special treatment of metatarsalgia. The results are based on clinical findings, footprints and radiographs. The postoperative results provide a satisfactory evaluation of our technique and understanding of the biomechanics in the foot.

[The intercapital metatarsal space. Anatomical and pathological aspects]

The metatarsal intercapital space is located in the forefoot, between two metatarsal heads and above the transverse inter-metatarsal ligament. The 2nd space is the narrowest, the 1st is the widest and the 3rd is the most mobile. It contains a connective tissue bursa which facilitates the sliding of the metatarsal heads. The existence of this bursa was confirmed in two cases of rheumatoid arthritis (at operation). As the bursa hypertrophies, it gradually extends beyond its normal site towards the dorsal or plantar region of the foot. The metatarsal intercapital space, like the metatarso-phalangeal joint, warrants thorough clinical investigation.

[The importance of the long tensile system of the sole of the foot for the action of the metatarsus (optical potential study of a model)]

The importance of the plantar tensile systems of the foot are studied by the means of photoelasticity. In a plastic (VP 1527) model of the sagittal section of a foot skeleton the distribution of stressing under load has been visualized in photographs of the isochromes as seen in the polarized light. This examination has been carried out with and without tension in the long plantar tensile systems of the model. It has clearly been shown that by the influence of the tensile systems the resultant force for the forefoot runs approximately in the axis of the bony elements of the metatarsus. In absence of these plantar tensions on the contrary the metatarsal elements undergo considerable bending stresses.

Forces acting on the metatarsals during normal walking

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Supernumerary epiphyses in the macaque (Macaca nemestrina)

The frequency, age distribution and development of supernumerary epiphyses in the hand and foot were radiographically documented in 98 macaque fetuses and infants. Extra epiphyses were observed only on distal metacarpal 1 and metatarsal 1, and were present in 15% of a cross-sectional sample and 20% of a longitudinal sample. They appeared coincidentally with the ossification of other secondary epiphyses of the hand and foot. Development of extra epiphyses in this species seems to be a normal phenomenon.

The effect of dynamic loading on the growth of epiphyseal cartilage in the rat

The Hueter-Volkmann law of epiphyseal pressures describes an inverse relationship between static compressive forces parallel to the axis of epiphyseal growth and the rate of growth of that cartilage. Studies of histological sections of the epiphyseal plate of the fourth metatarsals of (a) control, (b) bipedal and (c) bipedal rats with amputation of the fifth metatarsal show that dynamic compressive forces can stimulate epiphyseal cartilage growth. Within certain parameters, both the relief and increase of dynamic compression accelerate epiphyseal growth. It is the amount and kind of loading that are important factors to accelerate epiphyseal growth.