Tensile load on the flexor digitorum profundus tendon during palmar and lateral blocking exercises: Influence on blocking force and distal interphalangeal joint flexion angle.

STUDY DESIGN: This is a basic science research. INTRODUCTION: Isolating excursion of the flexor digitorum profundus (FDP) in zones I and II is common practice in the current management after flexor tendon repair. During this procedure, the proximal interphalangeal joint is sometimes fully extended with unmeasured external forces at the middle phalanx when the distal interphalangeal joint is actively flexed. PURPOSE OF THE STUDY: The purpose of the study was to investigate the incremental effect of external force with palmar blocking versus lateral blocking and increased angles of flexion on internal tendon forces at the repair site for a safer application of force by the treating therapist. METHODS: Eight human cadaveric fingers were studied. To simulate palmar or lateral finger blocking, a compression force of blocking was applied from 5N (510 grams) to 25N (2,550 grams) on the skin surface of the palmar or the lateral aspect of each of these middle phalanges in 5N increments. The tensile load on the FDP tendon during distal interphalangeal joint flexion from 0° to 60° was measured in 10° increments. RESULTS: During palmar blocking, the tensile load was significantly increased with increases in palmar blocking force. However, no significant increase in the tensile load on the FDP tendon was observed at any lateral blocking. DISCUSSION: Lateral blocking exercise can be performed with less tensile force on the FDP tendon when performing blocking exercise after flexor tendon injury repair. CONCLUSIONS: This study supports the concept that lateral blocking with incremental joint angles allows a safer application of force for the healing tendon.

Distribution of sole Pacinian corpuscles: a histological study using near-term human feet.

INTRODUCTION: Fast-adapting afferent input from the sole Pacinian corpuscles (PCs) is essential for walking. However, the distribution of PCs in the plantar subcutaneous tissue remains unknown. MATERIALS AND METHODS: Using histological sections tangential to the plantar skin of eight near-term fetuses, we counted 528-900 PCs per sole. RESULTS: Almost half of the sole PCs existed at the level of the proximal phalanx, especially on the superficial side of the long flexor tendons and flexor digitorum brevis. Conversely, the distribution was less evident on the posterior side of the foot. The medial margin of the sole contained fewer PCs than the lateral margin, possibly due to the transverse arch. In contrast to a cluster formation in the anterior foot, posterior PCs were almost always solitary, with a distance greater than 0.5 mm to the nearest PC. DISCUSSION AND CONCLUSION: Because a receptive field of PCs is larger than that of the other receptors, fewer solitary PCs might cover the posterior sole. In infants, the amount of anterior sole PCs seemed to determine the initial walking pattern using the anterior foot without heel contact. Anterior PCs concentrated along flexor tendons might play a transient role as tendon organs during the initial learning of walking. During a lesson in infants, mechanical stress from the tendon and muscle was likely to degrade the PCs. In the near term, the sole PCs seemed not to be a mini-version of the adult morphology but suggested an infant-specific function.

Stabilization of postural sway on a sideward slope using cuboid support insoles.

[Purpose] The purpose of this study was to elucidate whether insoles alter postural sway on a sideward slope rather than on level ground. [Participants and Methods] This study involved 20 flat-footed individuals and 20 normal-footed individuals. The postural sway was determined based on the total length of the locus and the body sway area, which were measured using the Zebris system. The participants were divided into three groups: the BMZ insoles, Superfeet insoles, and no insole groups. These insoles were worn by the participants with their normal shoes worn daily. [Results] The total length of the locus of the BMZ group was significantly lower than those of the Superfeet and no-insole groups. The body sway area did not significantly differ based on the insole condition. [Conclusion] BMZ insoles improve postural sway in both normal-footed and flat-footed individuals on a sideward slope.

Can an insole for obese individuals maintain the arch of the foot against repeated hyper loading?

BACKGROUND: Insoles are often applied as preventive therapy of flatfoot deformity, but the therapeutic effects on obese individuals are still controversial. We aimed to investigate the effect of insole use on time-dependent changes in the foot arch during a repeated-loading simulation designed to represent 20,000 contiguous steps in individuals with a BMI value in the range of 30-40 kg/m2. METHODS: Eighteen cadaveric feet were randomly divided into the following three groups: normal, obese, and insole. Ten thousand cyclic loadings of 500 N (normal group) or 1000 N (obese and insole groups) were applied to the feet. We measured time-dependent change in arch height and calculated the bony arch index (BAI), arch flexibility, and energy absorption. RESULTS: The normal group maintained more than 0.21 BAI, which is the diagnostic criterion for a normal arch, throughout the 10,000 cycles; however, BAI was less than 0.21 at 1000 cycles in the obese group (mean, 0.203; 95% confidence interval [CI] 0.196-0.209) and at 6000 cycles in the insole group (mean, 0.200; 95% CI, 0.191-0.209). Although there was a significant time-dependent decrease in flexibility and energy absorption in both the obese and insole groups (P < 0.001), the difference between 1 and 10,000 cycles were significantly smaller in the insole group than in the obese group (P = 0.024). CONCLUSIONS: Use of insoles for obese individuals may help to slow time-dependent foot structural changes. However, the effect was not enough to maintain the foot structure against repeated hyper loadings.

Impact of double-tiered subchondral support procedure with a polyaxial locking plate on the stability of distal radius fractures using fresh cadaveric forearms: Biomechanical and radiographic analyses.

BACKGROUND: The present study compared the changes in biomechanical and radiographic properties under cyclic axial loadings between the 'double-tiered subchondral support' (DSS) group (wherein two rows of screws were used) and the 'non-DSS' (NDSS) group (wherein only one row of distal screws was used) using cadaveric forearm models of radius fractures fixed with a polyaxial locking plate. MATERIAL AND METHODS: Fifteen fresh cadaveric forearms were surgically operated to generate an Arbeitsgemeinschaft für Osteosynthesefragen (AO) type 23-C2 fracture model with the fixation of polyaxial volar locking plates. The model specimens were randomized into two groups: DSS (n = 7) and NDSS (n = 8). Both the groups received 4 locking screws in the most distal row, as is usually applied, whereas the DSS group received 2 additional screws in the second row inserted at an inclination of about 15° to support the dorsal aspect of the dorsal subchondral bone. Cyclic axial compression test was performed (3000 cycles; 0-250 N; 60 mm/min) to measure absolute rigidity and displacement, after 1, 1000, 2000 and 3000 cycles, and values were normalized relative to cycle 1. These absolute and normalized values were compared between those two groups. Radiographic images were taken before and after the cyclic loading to measure changes in volar tilt (ΔVT) and radial inclination (ΔRI). RESULTS: The DSS group maintained significantly higher rigidity and lower displacement values than the NDSS group during the entire loading period. Radiographic analysis indicated that the ΔVT values of the DSS group were lower than those of the NDSS group. In contrast, the fixation design did not influence the impact of loading on the ΔRI values. CONCLUSIONS: Biomechanical and radiographic analyses demonstrated that two rows of distal locking screws in the DSS procedure conferred higher stability than one row of distal locking screws.

The adductor part of the adductor magnus is innervated by both obturator and sciatic nerves.

The hip adductor group, innervated predominantly by the obturator nerve, occupies a large volume of the lower limb. However, case reports of patients with obturator nerve palsy or denervation have described no more than minimal gait disturbance. Those facts are surprising, given the architectural characteristics of the hip adductors. Our aim was to investigate which regions of the adductor magnus are innervated by the obturator nerve and by which sciatic nerve and to consider the clinical implications. Twenty-one lower limbs were examined from 21 formalin-fixed cadavers, 18 males and 3 females. The adductor magnus was dissected and was divided into four parts (AM1-AM4) based on the locations of the perforating arteries and the adductor hiatus. AM1 was supplied solely by the obturator nerve. AM2, AM3, and AM4 received innervation from both the posterior branch of the obturator nerve and the tibial nerve portion of the sciatic nerve in 2 (9.5%), 20 (95.2%), and 6 (28.6%) of the cadavers, respectively. The double innervation in more than 90% of the AM3s is especially noteworthy. Generally, AM1-AM3 corresponds to the adductor part, traditionally characterized as innervated by the obturator nerve, and AM4 corresponds to the hamstrings part, innervated by the sciatic nerve. Here, we showed that the sciatic nerve supplies not only the hamstrings part but also the adductor part. These two nerves spread more widely than has generally been believed, which could have practical implications for the assessment and treatment of motor disability.

Fetal development of ligaments around the tarsal bones with special reference to contribution of muscles.

Through a histological examination of eight mid-term human fetuses (10-15 weeks) and seven late-stage fetuses (30-34 weeks), we attempted to determine how and when fetal ligaments around the tarsal bones form the regular arrangement seen in adults. Ligaments along the dorsal aspect of the tarsal bones developed early as an elongation of the perichondrium, in contrast to the late development of the plantar-sided ligaments. In contrast, a distal elongation of the tibialis posterior tendon was a limited plantar ligament in the early stage; finally, it extended from the navicular, ran obliquely to cross the dorsal side of the fibularis longus tendon, and inserted to the lateral cuneiform and fourth metatarsal. In the late stage, the adductor hallucis muscle origin provided multiple ligamentous structures along the cuneiforms and metatarsals. The tarsal sinus contained multiple fibrous bundles (possibly, the putative interosseous talocalcanean ligaments) that were derived from (1) insertion tendons of the extensor digitorus brevis muscle and (2) the fibrous sheath of the extensor digitorus longus tendon. The aponeurotic origin of the quadratus plantae muscle seemed to contribute to formation of the long plantar ligament. Therefore, tarsal ligaments appeared likely to develop from the long tendons, their fibrous sheaths and aponeuroses and intramuscular tendons of the proper foot muscles. Under in utero conditions with little or no stress from the plantar side of the foot, the muscle-associated connective tissue seems to play a crucial role in providing a regular arrangement of the ligaments in accordance with tensile stress from muscle contraction.

Standing balance on the ground -the influence of flatfeet and insoles.

[Purpose] The aim of this study was to determine whether insoles change standing balance on the ground in normal and flat-footed subjects. [Subjects] Twenty subjects with flatfeet and 20 subjects with normal feet were included in this study. [Methods] Body sway was evaluated based on the center of pressure while subjects stood on the ground. Body sway was measured during upright standing with the feet 10 cm apart for 30 seconds. The total locus length and the area of body sway were then measured using a zebris system. Measurements were made under three sets of conditions: using BMZ insoles, which supported the cuboid; using Superfeet insoles, which supported the medial longitudinal arch; and with no insoles. [Results] The 3 insole conditions were compared. On level ground, the total locus length for the Superfeet insole was significantly less than those for the BMZ insole and no insole. [Conclusion] On level ground, Superfeet feet insoles were effective in stabilizing standing balance in both flat-footed and normal-footed subjects.

Wearing high-heeled shoes on a side slope makes standing balance unstable.

INTRODUCTION: Many women wearing high-heeled footwear are at high risk of falls. Past studies have examined the balance on level ground or balance during walking. We measured the standing balance on the ground and side slopes for 18 healthy women. METHOD: Body sway was evaluated based on the center of pressure (COP) while participants stood on level ground on a side slope. The total locus length as well as rectangular and outer peripheral areas were then measured using a Zebris system. Measurements were compared under bare feet, normal shoe, and high-heeled shoe conditions. RESULTS: On level ground, there were no significant differences among the three conditions. On the side slope, the total locus length (TLL), rectangular area (RA) and outer peripheral areas (OPA) were significantly greater for the high-heeled shoes than for the bare feet and normal shoes. Standing on the side slope caused larger body sway than on the level ground, along with a higher risk of falling. DISCUSSION: In TLL, OPA, and RA, the COP moved outside substantially when participants stood on a slope in high heels than in shoes. High heels were highly unstable for standing on a slope since the ankle joint of one leg is in plantar flexion, the foot is pronated, and the other side is plantarflexed at the ankle with pronation of the foot. CONCLUSION: High-heeled shoes significantly alter a person's balance when standing on a side slope, suggesting a high risk of falling.

Recovery process of the muscle activities during walking with efficient early quadriceps training and gait exercises after total knee arthroplasty.

BACKGROUND: Total knee arthroplasty (TKA) by the trivector approach is less invasive to the knee extensor mechanism; early quadriceps training is possible and a good prognosis is expected after surgery. However, investigations regarding lower limb muscle activity during gait have not been reported after using the trivector approach. To determine an effective postoperative rehabilitation program, we analyzed the recovery processes of leg muscle activities during walking. METHODS: Fourteen subjects with severe knee osteoarthritis (OA) who underwent early exercises after TKA by trivector approach were included in the TKA group. The control group consisted of eight patients with mild knee OA. Surface electromyography of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles were recorded and gait speed and step length were measured. The TKA group was measured postoperatively at 3, 12, and 24 weeks. RESULTS: Gait speed of TKA group significantly increased at 12 weeks post-surgery and recovered equal to the control group at 24 weeks. Additionally, step length reached the level of control subjects at 24 weeks. Postoperative activity of VM returned to that of the control group at 12 weeks. VL continued decreasing until 12 weeks compared with the preoperative values, but gradually increased and became equal to the control group at 24 weeks. RF slightly increased at 3 weeks postoperation and remained stable. CONCLUSIONS: VM injury by the trivector approach might be small and temporary.Functional recovery of VL was important and early starting rehabilitation program up to 24 weeks is appropriate.

The influence of flatfoot deformity on the gliding resistance of tendons about the ankle.

BACKGROUND: Various tendinopathies occur about the ankle, but there are few publications investigating their etiology or pathoanatomy. The purpose of this investigation was to determine the gliding resistance of the tendons about the posteromedial ankle: the posterior tibial (PT), flexor digitorum longus (FDL), and flexor hallucis longus (FHL) tendons. MATERIALS AND METHODS: The gliding abilities of the posterior tibial, flexor digitorum longus, and flexor hallucis longus tendons at the ankle-hindfoot level were compared, in terms of gliding resistance, with use of a system that was developed in this laboratory. Six cadaveric specimens were used and tested in a dorsiflexed position, then in simulated flatfoot in a dorsiflexed position. RESULTS: The gliding resistance was found to be significantly greater in the simulated flatfoot in dorsiflexion compared to the dorsiflexed position with an intact arch for the PT, FDL, and FHL tendons. The gliding resistance was significantly higher in the PT tendon than FDL or FHL tendons in the flatfoot/dorsiflexion condition. There was no significant difference between the FDL and FHL tendons in resistance in either condition. CONCLUSION: We concluded that the gliding ability of the PT tendon was inferior to that of the FDL and FHL tendons in a simulated flatfoot model. CLINICAL RELEVANCE: The findings of the present study are consistent with the clinical observations that tendinitis and rupture of the PT tendon commonly occurs at the malleolar level, whereas FDL and FHL ruptures do not. A pre-existing flexible flatfoot deformity may be associated with PT tendon dysfunction in the adult due to poor gliding ability of the PT tendon.

The range of glenohumeral joint motion in activities of daily living after rotator cuff repair: a cadaveric biomechanical study.

This study was conducted to quantify the restriction of glenohumeral motion and activities of daily living (ADL) after rotator cuff repair. Eight fresh cadaveric shoulders were used. The ranges of passive shoulder motions in models of the intact cuff tendon, and repaired small cuff and large cuff tears were measured using a 6-degree-of-freedom electromagnetic tracking device. The range of motion for reach, perineal care, hair combing, and washing the axilla were also measured as simulated ADL. Elevation, horizontal adduction, and abduction were significantly restricted in the repaired small-tear model, whereas glenohumeral motion in all directions was significantly restricted in the repaired large-tear model. The repair of the small tear significantly restricted perineal care alone, whereas the repair of the large tear significantly restricted all ADL except hair combing. These findings could be helpful in managing restricted shoulder motion and in instructing patients in acceptable ADL after rotator cuff repair.

Macroscopic and histotopographic study of the deep transverse perineal muscle (musculus transversus perinei profundus) in elderly Japanese.

Although the deep transverse perineal (DTP) muscle is welt known as the core of the urogenital diaphragm, most recent studies have denied its existence. In students' dissection classes, we cut the surfaces of 93 macroscopically identified urogenital diaphragms (59 male cadavers) and found the distinct sheet-like DTP in 24.7% (23 of 93 sides). Another 17 cadavers (mean age 81.4 years) were used for histology. In histology of 12 males, we consistently identified the DTP as a small muscle bundle immediately lateral to the bulbourethral gland. Thus, the macroscopicically unclear morphology of the DTP (19.4%, 18 of 93 sides) seemed to be overestimated. The histologically proven DTP was continuous with a "tail" or inferolateral protrusion of the external urethral sphincter or urethral rhabdospincter. However, the histology revealed that a sheet-like DTP was not usual (16.7%, two of 12 cadavers). Likewise, in histology of five females, the tail always continued to a muscle mass immediately lateral to the greater vestibular gland and far dorsal to the external urethral sphincter. Thus, the female topohistology seemed to be consistent with the male unclear DTP. Because of the limited incidence of a sheet-like DTP and the unclear fascial structure containing numerous vessels around the rather small DTP, in most elderly cadavers the urogenital diaphragm was likely to be a macroscopic entity rather than a histologic one. However, we believed that the histologically proven DTP was present in elderly men and women even if it had changed as a result of degeneration with aging.

Muscle strain on the radial wrist extensors during motion-simulating stretching exercises for lateral epicondylitis: a cadaveric study.

The purpose of this study is to measure muscle strain on the extensor carpi radialis longus (ECRL) and extensor carpi radialis brevis (ECRB) in cadavers and to identify effective stretching positions. In 12 frozen/thawed cadaveric arms, a strain gauge was attached to the ECRL and ECRB muscles, and increases in muscle strain were measured from a standard position (45 degrees elbow flexion, neutral forearm, and neutral wrist) to 12 sequential arm and wrist positions. Muscle strain on the ECRL and ECRB with the elbow at 45 degrees flexion was less than 10% regardless of forearm and wrist positions, whereas the majority of it was greater than 10% with the elbow extended. Maximal muscle strain on the ECRL and ECRB was obtained with elbow extension, forearm pronation, and wrist flexion-ulnar deviation, with mean values of 17.8% and 13.8%, respectively (greater than standard position, P < .05). Muscle stretching of the wrist extensors for lateral epicondylitis should be performed in this position.

Measurement of strain and tensile force of the supraspinatus tendon under conditions that simulates low angle isometric elevation of the gleno-humeral joint: Influence of adduction torque and joint positioning.

BACKGROUND: Recently, supraspinatus muscle exercise has been reported to treat rotator cuff disease and to recover shoulder function. However, there have been no report on the direct measurement of strain on the supraspinatus tendon during simulated isometric gleno-humeral joint elevation. METHODS: Ten fresh-frozen shoulder specimens with the rotator cuff complex left intact were used as experimental models. Isometric gleno-humeral joint elevation in a sitting position was reproduced with low angle of step-by-step elevation in the scapular plane and strain was measured on the surface layer of the supraspinatus tendon. FINDINGS: In isometric conditions, applied tensile force of the supraspinatus tendon increased significantly with increases in adduction torque on the gleno-humeral joint. Significant increases in the strain on the layer were observed by increase in adduction torque, which were recorded in isometric elevation at -10° and 0°, but little increase in the strain was observed at 10° or greater gleno-humeral elevation. INTERPRETATION: Increased strain on the surface layer of the supraspinatus tendon was observed during isometric gleno-humeral elevation from -10 to 0°. These findings demonstrate a potential risk of inducing overstretching of the supraspinatus tendon during supraspinatus muscle exercise.

The effect of arm position on stretching of the supraspinatus, infraspinatus, and posterior portion of deltoid muscles: a cadaveric study.

BACKGROUND: The stretching of the supraspinatus and infraspinatus muscles is important to prevent shoulder injuries. Although several authors have advocated various stretching techniques, a general opinion has not been reached owing to the lack of quantitative analysis. METHODS: Nine fresh cadaveric shoulders were used to measure the strain on the supraspinatus, the middle and inferior portions of the infraspinatus, and the posterior portion of the deltoid muscles during eleven arm positions. The strain on the muscles was measured by precise displacement sensors attached to the center of each muscle belly. FINDINGS: In case of the supraspinatus muscle, abduction at extension showed significantly larger strain than that in the neutral position (P < 0.05). Internal rotation at extension showed significantly larger strain in the middle portions of the infraspinatus (P < 0.05). Internal rotation at 30 degrees and 60 degrees elevation as well as extension showed significantly larger strain in the inferior portion of the infraspinatus (P<0.05). Adduction at 60 degrees elevation did not show large strain in the infraspinatus muscle; however, significantly larger strain was observed in the posterior portion of the deltoid muscle. INTERPRETATION: Shoulder stretching techniques that are based on these experimental data can enhance the selective stretching of the corresponding muscles. Application of these techniques is considered to be useful for the prevention and treatment of shoulder injuries.

Morphometrical study of arteries and veins in the human sheet-like muscles (pectoralis major, latissimus dorsi, gluteus maximus and trapezius) with special reference to a paradoxical venous merging pattern of the trapezius.

The trapezius is one of the critical targets of physical therapy for shoulder functional disorder because this muscle plays a great role in fixation and elevation of the shoulder. Trapezius (n = 63), latissimus dorsi (n = 5), pectoralis major (n = 7) and gluteus maximus (n = 7) muscles were obtained from 43 donated cadavers, and vascular morphologies were compared. An artery without a concomitant vein was found in 35 of 63 trapezius muscles. Moreover, twice as many venous merging sites as arterial branching sites were present in the trapezius. Notably, peripheral or distal venous tributaries were larger in caliber than the proximally located vein in 6.2% of all 404 venous merging sites in the trapezius. Moreover, similar paradoxical venous merging, in which tributaries were relatively thicker than drainage capacity of the venous trunk after merging according to Poisueille's law (peripheral or distal thickness >0.85 x proximal thickness), was observed in 39.1% (158 of 404 merging sites) in the trapezius, compared to 8-9% in the other 3 muscles. Given this vascular morphology, trapezius muscle seems likely to frequently display venous blood retention. Interestingly, venous valves were not observed in the trapezius, compared to 1-7 valves per one of the other 3 muscles. Abundant venous mergings without valves might form a venous network acting as a reservoir. Therefore, for the trapezius, collateral venous routes such as the external vertebral plexus are essential to provide additional peripheral drainage. However, sufficient muscle-pump function does not seem to be expected for trapezius muscle, given the venous courses parallel to muscle fibers.

Distal fibular length needed for ankle stability.

BACKGROUND: The fibula is commonly used for bone grafts. Previous clinical and biomechanical studies have suggested that the length of the residual portion of the distal part of the fibula has an important effect on the long-term stability of the ankle joint. However, we cannot find clear-cut guidelines for the amount of bone that can be harvested safely. METHODS: Using six normal fresh-frozen cadaver legs, motions of the tibia, talus and calcaneus were measured. The fibula was cut sequentially 3 cm from the proximal tip of the fibula and distally 10 cm, 6 cm, and 4 cm from the distal tip of the lateral malleolus. The angular motion of each bone was measured while a medial and lateral traction force of 19.6 N was applied to the proximal tibia. Angles of the tibia, talus, and calcaneus were measured. RESULTS: Sequential resection of the fibula increased the inversion angles of the ankle joint. The proximal 3-cm cut increased the inversion angle from 42.1 +/- 6.2 degrees to 49.6 +/- 3.6 degrees, and the distal 4-cm cut increased the angle from 57.6 +/- 6.6 degrees to 67.4 +/- 5.9 degrees. The rotational angles were almost constant with sequential resections of the fibula; however, the distal 4-cm cut increased the rotational angle from 11.3 +/- 25.1 degrees to 78.7 +/- 37.5 degrees. CONCLUSIONS: The whole fibula including the head is essential for the stability of the ankle joint complex, and the distal fibula is responsible for stabilizing the ankle mortise during external rotation and inversion. We recommend fixation of the syndesmosis or bracing to prevent ankle joint instability with rotation of the talus in the mortise, especially when the distal fibula is shortened 6 cm or more.

Ankle ligament tensile forces at the end points of passive circumferential rotating motion of the ankle and subtalar joint complex.

BACKGROUND: Ankle ligament injuries and instability are commonly observed. Knowledge of the relationship between the foot position and tensile forces of the ankle ligaments could be useful for treatment of ankle ligament disorders. The aim of this study was to measure the tensile forces of the ankle ligaments at the end points of passive circumferential rotating motion of the ankle and subtalar joint complex in various foot positions. METHODS: Ligament tensile forces of the anterior talofibular (ATF), calcaneofibular (CF), posterior talofibular (PTF), and tibiocalcaneal (TC) ligaments were measured simultaneously in eight cadaver specimens, with a force probe in each ligament in a custom-made ankle ligament testing device. Weights of 0.5 kg and 1 kg were applied to the foot through a loading arm to provide axial compression and a bending moment to the foot and ankle. The position of the loading arm was changed circumferentially in 10-degree increments. RESULTS: Maximal tensile force in the ATF ligament was observed in supination with plantarflexion (108 +/- 62.8 N at 0.5 kg and 130 +/- 39.1 N at 1 kg). The maximal tensile force in the CF ligament was observed in pronation with plantarflexion (68 +/- 48.6 N at 0.5 kg and 135 +/- 92.9 N at 1 kg). The maximal tensile force in the PTF ligament was observed in dorsiflexion (131 +/- 80.1 N at 0.5 kg and 109 +/- 36.3 N at 1 kg). The maximal tensile force of the TC ligament was observed in pronation with plantarflexion (49.0 +/- 80.1 N at 0.5 kg and 67.4 +/- 69.6 N at 1 kg). Relatively high magnitudes of tensile force were observed in the ankle ligaments, and the peak forces were related to the anatomic position of individual ligaments. CONCLUSIONS: The ATF ligament has an important role in the supination position in plantarflexion, CF and TC ligaments also are important for pronation in plantarflexion, and the PTF is an important stabilizer in dorsiflexion. This study provides baseline information for further research related to ligament instability and reconstruction operations.