Operative Approach to Adult Hallux Valgus Deformity: Principles and Techniques.

Hallux valgus deformity is a progressive forefoot deformity consisting of a prominence derived from a medially deviated first metatarsal and laterally displaced great toe, with or without pronation. Although there is agreement that the deformity is likely caused by multifactorial intrinsic and extrinsic factors, the best method of operative management is debated despite the creation of basic algorithms. Our understanding of the deformity and the development of newer techniques is continuously evolving. Here, we review the general orthopaedic principles of operative decision-making and management of hallux valgus deformity.

AOFAS Position Statement Regarding Patient-Reported Outcome Measures.

Outcome measures evaluate various aspects of patient health, and when appropriately utilized can provide valuable information in both clinical practice and research settings. The orthopedic community has placed increasing emphasis on patient-reported outcome measures, recognizing their value for understanding patients' perspectives of treatment outcomes. Patient-reported outcomes are information directly reported by patients regarding their perceptions of health, quality of life, or functional status without interpretation by healthcare providers. The American Orthopaedic Foot & Ankle Society (AOFAS) supports the use of validated patient-reported outcome (PRO) instruments to assess patient general health, functional status, and outcomes of treatment. It is not possible to recommend a single instrument to collect quality orthopedic data as the selection is dependent on the population being examined and the question being asked. We support the use of the PROMIS Physical Function Computerized Adaptive Test (PF CAT) or Lower Extremity Computerized Adaptive Test (LE CAT), which can be assessed with other domains such as Pain Interference. In addition, a disease-specific measure can be used when available.

Management of Bunionette Deformity.

Bunionette deformity, historically known as tailor's bunion, is a forefoot protuberance laterally, dorsolaterally, or plantarlaterally along the fifth metatarsal head. Although bunionette deformity has been compared to hallux valgus deformity, it is likely due to a multifactorial, anatomic interplay between fifth metatarsal bony morphology and forefoot soft-tissue imbalance. Friction generated between the bony prominence, soft tissue, and associated constrictive footwear can result in keratosis, inflammation, pain, and ulceration. Symptomatic bunionettes are usually responsive to nonsurgical management. Surgical options are available based on the underlying bony deformity when nonsurgical treatment fails.

Posterior tibial tendon dysfunction and flatfoot: analysis with simulated walking.

Many biomechanical studies investigated pathology of flatfoot and effects of operations on flatfoot. The majority of cadaveric studies are limited to the quasistatic response to static joint loads. This study examined the unconstrained joint motion of the foot and ankle during stance phase utilizing a dynamic foot-ankle simulator in simulated stage 2 posterior tibial tendon dysfunction (PTTD). Muscle forces were applied on the extrinsic tendons of the foot using six servo-pneumatic cylinders to simulate their action. Vertical and fore-aft shear forces were applied and tibial advancement was performed with the servomotors. Three-dimensional movements of multiple bones of the foot were monitored with a magnetic tracking system. Twenty-two fresh-frozen lower extremities were studied in the intact condition, then following sectioning peritalar constraints to create a flatfoot and unloading the posterior tibial muscle force. Kinematics in the intact condition were consistent with gait analysis data for normals. There were altered kinematics in the flatfoot condition, particularly in coronal and transverse planes. Calcaneal eversion relative to the tibia averaged 11.1±2.8° compared to 5.8±2.3° in the normal condition. Calcaneal-tibial external rotation was significantly increased in flatfeet from mean of 2.3±1.7° to 8.1±4.0°. There were also significant changes in metatarsal-tibial eversion and external rotation in the flatfoot condition. The simulated PTTD with flatfoot was consistent with previous data obtained in patients with PTTD. The use of a flatfoot model will enable more detailed study on the flatfoot condition and/or effect of surgical treatment.

The role of ankle ligaments and articular geometry in stabilizing the ankle.

BACKGROUND: Ankle joint stability is a function of multiple factors, but it is unclear to what extent extrinsic factors such as ligaments and intrinsic elements such as geometry of the articular surfaces play a role. The purposes of this study were to determine the contribution of the ligaments and the articular geometry to ankle stability and to determine the effects of ankle position and simulated physiological loading upon ankle stability. METHODS: Sixteen cadaveric lower extremities were studied in unloaded and with axial load equivalent to body weight. Anterior-posterior, medial-lateral translation and internal-external rotation tests were performed in neutral, dorsiflexion and plantarflexion ankle positions. Intact ankle stability was measured; ankle ligaments were serially sectioned and retested. FINDINGS: For unloaded condition, the lateral ligament accounted for 70% to 80% of anterior stability and the deltoid ligaments for 50% to 80% of posterior stability. Both ligaments contributed 50% to 80% to rotational stability; however, the ligaments did not provide the primary restraints to medial-lateral stability. For loaded ankle condition, articular geometry contributed 100% to translational and 60% to rotational stability. The ankle was less stable in plantarflexion and more stable in dorsiflexion. INTERPRETATION: The contribution of extrinsic and intrinsic elements to ankle stability is dependent upon the load and direction of force applied. This study underscores the importance of restoring soft tissues about the ankle to the anatomic condition during reconstruction operations for instability, trauma and arthritis.

Analysis of ankle-hindfoot stability in patients with ankle instability and normals.

PURPOSE: We devised a testing apparatus for in vivo analysis of ankle stability. The purpose of the study was to test the reliability of this apparatus and to determine the stability pattern of the ankle-hindfoot complex in healthy, asymptomatic volunteers and in patients with ankle instability. METHODS: Ten healthy individuals were studied, and testing was repeated on the same day and different days. Three patients with symptomatic, unstable ankles were also tested on both involved and uninvolved sides. Constant inversion torque was applied, then internal rotation torque, while moving the ankle throughout the range of sagittal motion. Three-dimensional kinematics of the ankle-hindfoot complex were measured by an electromagnetic tracking system. RESULTS: Measurements were repeatable, with intraclass correlation coefficients 0.9 or better. Variability was observed among controls, but motion curve patterns were consistent. Motion curve slopes were sensitive in differentiating between unstable and stable ankles. CONCLUSIONS: Most previous reports are in vitro studies conducted with the ankle in one position, manual stress applied, or joint positions estimated with planar radiographs. Our study indicated that more accurate diagnosis of severity of ankle ligament injuries may be possible.

Moment arms of the ankle throughout the range of motion in three planes.

BACKGROUND: The moment, a force applied at a distance, is responsible for movement and balance. A key component of the moment is the moment arm. The moment arms of nine muscles surrounding the ankle complex during motion in three planes, were studied. MATERIALS AND METHODS: Five cadaveric feet were mounted in a testing device that created moments in the sagittal, coronal and transverse planes. Axial and tendon loads were applied as the foot was passively moved in these planes. Tendon excursions and bone kinematics were monitored. The moment arm was calculated using the tendon excursion method and averaged across all specimens. RESULTS: The largest average moment arm during plantarflexion/dorsiflexion, was the Achilles (mean, 53.1; SD, 5.1 mm). During internal/external rotation the largest moment arm was the peroneus brevis (mean, 20.5; SD, 6.4 mm). During inversion/eversion, the largest moment arm was the peroneus longus (31 mm; SD, 2.3 mm). CONCLUSION: This study quantified the functional moment arms of nine tendons of the ankle/foot. The involvement of multiple tendons in multiple planes of motion should be considered in computational models and when deciding treatments. CLINICAL RELEVANCE: The correlation between moment arms and muscle function has significant effects on treatment efficacy. Information on the balance of moments around the ankle will assist in achieving optimal biomechanical behavior following operative treatments.

Ankle stability in simulated lateral ankle ligament injuries.

BACKGROUND: We performed a laboratory-based study of the ankle-hindfoot complex in normal cadaveric ankles with simulated lateral ankle ligament injuries, utilizing an ankle stability testing device. The ankle stability testing device distinguished between intact, injury to anterior talofibular ligament (ATFL) and combined injury to ATFL and calcaneofibular ligament (CFL). MATERIALS AND METHODS: Ankles were tested in an ankle stability testing device, with a specified inversion torque applied through the range of sagittal plane motion, then internal rotation torque applied through the entire range of sagittal plane motion. Three-dimensional motion of the calcaneus and talus in relation to the tibia were determined with a magnetic tracking system. The specimens were tested in the intact condition, then after sectioning the ATFL, then the CFL. RESULTS: Upon sectioning the ATFL, there was a significant increase in the internal rotation motion at the tibiotalar joint. Subsequent sectioning of the CFL did not significantly increase ankle-hindfoot internal rotation, but it did significantly increase the motion in inversion testing. This increase occurred primarily at the tibiotalar level. CONCLUSION: The isolated ATFL injury was clearly distinguished from the intact condition by increased talar-tibial internal rotation, but not inversion. The more severe combined ATFL/CFL injury was distinguished from the ATFL injury condition with inversion torque. CLINICAL RELEVANCE: Inversion torque may disclose combined ATFL/CFL injury, and internal rotation torque may be the key to distinguish isolated ATFL and combined ATFL/CFL injuries.

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.

Effects of foot orthoses on the work of friction of the posterior tibial tendon.

BACKGROUND: Posterior tibial tendon dysfunction is a significant contributor to flatfeet. Non-operative treatments, like in-shoe orthoses, have varying degrees of success. This study examined changes to the work of friction of the posterior tibial tendon under three conditions: intact, simulated flatfoot, and flatfoot with an orthosis. It was hypothesized that work of friction of the posterior tibial tendon would significantly increase in the flatfoot, yet return to normal with an orthosis. Changes to bone orientation were also expected. METHODS: Six lower limb cadavers were mounted in a foot simulator, that applied axial and a posterior tibial tendon load. Posterior tibial tendon excursion, gliding resistance, and foot kinematics were monitored, and work of friction calculated. Each specimen moved through a range of motion in the coronal, transverse, and sagittal planes. FINDINGS: Mean work of friction during motion in the coronal plane were 0.17 N cm (SD 0.07 N cm), 0.25 N cm (SD 0.09 N cm), and 0.23 N cm (SD 0.09 N cm) for the intact, flatfoot, and orthosis conditions, respectively. Motion in the transverse plane yielded average WoF of 0.36 N cm (SD 0.28 N cm), 0.64 N cm (SD 0.25 N cm), and 0.57 N cm (SD 0.38 N cm) in the same three conditions, respectively. The average tibio-calcaneal and tibio-metatarsal valgus angles significantly increased in the flatfoot condition (5.8 degrees and 9 degrees , respectively). However, the orthosis did slightly correct this angle. INTERPRETATION: The prefabricated orthosis did not consistently restore normal work of friction, though it did correct the flatfoot visually. This implies that patients with flatfeet may be predisposed to developing posterior tibial tendon dysfunction due to abnormal gliding resistance, though bone orientations are restored.

Analysis of joint laxity after total ankle arthroplasty: cadaver study.

BACKGROUND: Clinical results of total ankle arthroplasty with early designs were disappointing. Recently-developed ankle prostheses have good mid-term results; however, limited information is available regarding effects of total ankle arthroplasty on ankle laxity. METHODS: Eight cadaveric lower extremities were tested with a custom device which enabled measurement of multi-axial forces, moments, and displacement during applied axial, shear, and rotational loading. Tests consisted of anterior-posterior and medial-lateral translation and internal-external rotation of the talus relative to the tibia during axial loads on the tibia simulating body weight (700 N) and an unloaded condition (5 N). Tests were performed in neutral, dorsiflexion, and plantarflexion. Laxity was determined for the intact ankle, and following insertion of an unconstrained total ankle implant, comparing load-displacement curve. FINDINGS: Laxity after total ankle arthroplasty did not approximate the normal ankle in most conditions tested. Displacement was significantly greater for total ankle arthroplasty in both posterior and lateral translation, and internal rotation, with 5 N axial loading, and anterior-posterior, medial-lateral translation, and internal-external rotation for 700 N axial loading. For the 700 N axial load condition, in the neutral ankle position, total anterior-posterior translation averaged 0.4 mm (SD 0.2 mm), but 6.0 mm (SD 1.5 mm) after total ankle arthroplasty (P<0.01). This study demonstrated more laxity in the replaced ankle than normal ankle for both unloaded and 700 N axially loaded conditions. INTERPRETATION: These data indicate the increased responsibility of the ligaments for ankle laxity after total ankle arthroplasty and suggest the importance of meticulous ligament reconstruction with total ankle arthroplasty operations.

Midfoot arthritis.

Foot and ankle complaints are commonly encountered in orthopedic practice. Midfoot arthritis has the potential to cause a significant amount of pain and disability. A variety of conditions can cause or lead to midfoot arthritis. Treatment consists of either conservative management or surgical arthrodesis of the painful joints. In this article, we review the midfoot (its basic anatomy and biomechanics) and midfoot arthritis (its clinical presentation and etiology, radiographic evaluation, and treatment options).

The effect of flatfoot deformity and tendon loading on the work of friction measured in the posterior tibial tendon.

BACKGROUND: There is limited information regarding the mechanical factors contributing to the progression of posterior tibial tendon dysfunction. Therefore, an investigation of the mechanical forces on the posterior tibial tendon may improve our understanding of this pathology. METHODS: The gliding resistance and excursion of the posterior tibial tendon in the retromalleolar region was measured in seven cadaveric lower limbs in the coronal, transverse, and sagittal planes. These data were used to calculate the work of friction and to characterize the effect of different tendon loading levels (0.5, 1.0, and 2.0 kg) in the intact and flatfoot conditions. FINDINGS: Flatfoot deformity significantly increased the excursion of the posterior tibial tendon (P<0.05), increased forefoot and hindfoot range of motion in the coronal and transverse planes (P<0.05) and the work of friction in the coronal and transverse planes (P<0.05), but not in the sagittal plane. There was a significant increase in the work of friction between 0.5 and 2 kg (P<0.05) in all three planes of motion. INTERPRETATION: The motions in the coronal and transverse planes have a greater effect on the work of friction of the posterior tibial tendon than sagittal plane motion in the flatfoot condition. This study suggests that aggressive treatment of early stage PTT dysfunction with bracing designed to limit coronal and transverse motions, while permitting sagittal motion should be investigated further. Such bracing may decrease the potential of progressive deformity while allowing for more normal ambulation.

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.

Gliding resistance of the posterior tibial tendon.

BACKGROUND: Abnormal gliding of the posterior tibial tendon may lead to mechanical trauma, degeneration, and eventually posterior tibial tendon dysfunction. Our study analyzed the gliding resistance of the posterior tibial tendon in intact feet and in feet with simulated flatfoot deformity. METHODS: An experimental system was developed that allowed direct measurement of gliding resistance at the tendon-sheath interface. Seven normal fresh-frozen cadaver foot specimens were studied, and gliding resistance between the posterior tibial tendon and sheath was measured. The effects of ankle and hindfoot position and the effect of flatfoot deformity on gliding resistance were analyzed. Gliding resistance was measured for 4.9 N applied load to the tendon. RESULTS: Mean gliding resistance for the neutral position was 77 +/- 13.1 (x10(-2) N). Compared to neutral position, dorsiflexion increased gliding resistance and averaged 130 +/- 38.9 (x10(-2) N), and plantarflexion decreased gliding resistance and averaged 35 +/- 12.6 (x10(-2) N). Flatfoot deformity increased gliding resistance compared to normal feet, averaging 104 +/- 17.0 (x10(-2) N) for neutral, 205 +/- 55.0 (x10(-2) N) for dorsiflexion, and 58 +/- 21.3 (x10(-2) N) for plantarflexion. CONCLUSIONS: The findings indicate that patients with a preexisting flatfoot deformity may be predisposed to develop posterior tibial tendon dysfunction because of increased gliding resistance and trauma to the tendon surface.

Effects of ankle-foot orthoses on ankle and foot kinematics in patients with subtalar osteoarthritis.

OBJECTIVE: To determine whether different foot orthoses have a similar effect on foot kinematics in subjects with subtalar osteoarthritis (OA) when walking on various ground conditions. DESIGN: Within-subject comparison study. SETTING: Biomechanics research laboratory. PARTICIPANTS: Ten subjects with unilateral subtalar OA. INTERVENTIONS: Custom-made ankle foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A) were used by subjects walking on level, ascending, and descending ramp, and side slope conditions. MAIN OUTCOME MEASURES: The triplanar range of motion of the calcaneus relative to tibia (hindfoot) and metatarsal relative to calcaneus (forefoot) was measured using an 8-camera motion analysis system when subjects with subtalar OA wore different foot orthoses. RESULTS: Braces tended to perform similarly in reducing motion of the forefoot and hindfoot for all ground conditions when compared with unbraced but wearing shoes. The AFO significantly restricted frontal plane hindfoot motion during ramp descent (P<.01) and on a side slope when the arthritic subtalar joint was higher than the unaffected side (P=.02). The HFO-A provided significant frontal plane hindfoot motion restriction during ramp descent (P<.01) and on a side slope when the arthritic subtalar joint was lower than the unaffected side (P=.03). The HFO-R significantly restricted frontal plane hindfoot motion in all ground conditions except ramp ascent (P<.05). CONCLUSIONS: The HFO-R provides significant subtalar joint motion restriction while walking. The HFO-R may be considered an optimal orthosis for patients with subtalar OA pain arising from subtalar motion.

Comparison of modified Broström and Evans procedures in simulated lateral ankle injury.

PURPOSE: The purpose of this study was to compare the modified Broström and Evans procedures for simulated lateral ankle instability in cadaveric lower extremities. METHODS: Six normal cadaveric ankles were loaded with inversion and internal rotation stress through the range of ankle flexion, and three-dimensional motion of the calcaneus and talus relative to the tibia were measured. An ankle stability testing device and a magnetic tracking system were used. Testing was performed in the intact condition, unstable condition after sectioning both the anterior talofibular (ATFL) and calcaneofibular ligaments (CFL), after the Gould modification of the Broström procedure, and after the Evans procedure. RESULTS: With inversion loading, both operations resulted in a significantly more stable ankle-hindfoot complex (calcaneal-tibial) than the unstable condition, but there was restricted motion after the Evans operation from neutral to plantarflexion. Tibiotalar inversion motion approximated normal after both operations, but subtalar motion was markedly restricted in the Evans procedure throughout the range of ankle flexion. With internal rotation loading, the Broström operation stabilized the ankle-hindfoot joint complex in plantarflexion. The Evans operation improved internal rotation stability, but restricted motion in all positions. Both operations improved tibiotalar internal rotation stability, but not to normal. The subtalar internal rotation was the same as the intact condition after the Broström operation, but markedly restricted after the Evans operation through the range of ankle flexion. CONCLUSIONS: Both operations improved ankle-hindfoot stability, but neither was successful in restoring it to normal as determined with the ankle stability testing device. The Evans procedure improved stability at the expense of creating abnormal subtalar function. The Broström operation improved stability without excessively restricting subtalar movement, but was not effective in addressing the internal rotation laxity.

Effects of ankle-foot orthoses on ankle and foot kinematics in patient with ankle osteoarthritis.

OBJECTIVE: To determine if different foot orthoses have a similar effect on foot kinematics in subjects with ankle osteoarthritis (OA) when walking on various ground conditions. DESIGN: Within-subject comparisons study. SETTING: Biomechanics research laboratory. PARTICIPANTS: Thirteen subjects with unilateral ankle OA. INTERVENTIONS: Custom-made ankle-foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A) were used by subjects when walking on level, ascending and descending ramp, and side-slope conditions. MAIN OUTCOME MEASURES: The range of motion of the hindfoot (calcaneus relative to tibia) and forefoot (metatarsal relative to calcaneus) was measured using an 8-camera motion analysis system. RESULTS: The AFO and HFO-R provided the best sagittal plane hindfoot motion restriction over all ground conditions (P<.001). The HFO-R allowed the greatest sagittal plane forefoot motion when walking over level (P=.01) and side-slope (P<.02) conditions, the greatest frontal plane forefoot motion walking down the ramp (P=.003), and the greatest transverse plane forefoot motion when walking over level (P=.011) and ramp-ascending conditions (P=.005). The HFO-A restricted motion of the unaffected joint and did not effectively restrict hindfoot motion. CONCLUSIONS: The HFO-R not only provides selective restriction to the ankle-hindfoot motion, but also allows sufficient forefoot motion compared with the AFO. We consider the HFO-R to be the best option of all tested orthoses for treating patients with ankle OA pain arising from ankle motion.

The effect of custom-made braces for the ankle and hindfoot on ankle and foot kinematics and ground reaction forces.

OBJECTIVE: To assess the effects on gait of custom-made polypropylene orthoses: ankle-foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A). DESIGN: Experimental assessment. SETTING: Institutional practice, motion analysis laboratory. PARTICIPANTS: Twenty asymptomatic normative subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Three-dimensional kinematics, ground reaction force, and time-related factors in 4 conditions: shoe only, and shod with the AFO, HFO-R, and HFO-A. RESULTS: The AFO and HFO-R limited sagittal and coronal plane ankle-hindfoot motion. The HFO-A limited hindfoot coronal motion while allowing normal sagittal motion. At the midfoot, the AFO and HFO-A limited transverse motion, but the HFO-A also limited sagittal and coronal motion. Use of the HFO-R resulted in exaggerated midfoot sagittal and coronal motion. Braces that limited motion to a greater degree were associated with more atypical kinetic variables, indicative of less dynamic gait. The HFO-A resulted in ground reaction forces most similar to unbraced conditions. CONCLUSIONS: Alteration in gait was affected by orthosis design. Orthoses with a rigid component crossing a joint restricted motion at that joint, but potentially compromised typical gait kinetic factors. For immobilizing the hindfoot, the HFO-A may be more comfortable and still provide more stability than the HFO-R or AFO.

Pathomechanics of hallux valgus: biomechanical and immunohistochemical study.

BACKGROUND: One factor believed to contribute to the development of hallux valgus is an abnormality in collagen structure and makeup of the medial collateral ligament (MCL) of the first metatarsophalangeal joint (MTPJ). We hypothesized that the mechanical properties of the MCL in feet with hallux valgus are significantly different from those in normal feet and that these differences may be related to alterations in the type or distribution of collagen fibers at the interface between the MCL and the bone. MATERIALS AND METHODS: Seven normal fresh-frozen cadaver feet were compared to four cadaver feet that had hallux valgus deformities. The MCL mechanical properties, structure of collagen fibers, and content proportion of type I and type III collagen were determined. RESULTS: The load-deformation and stress-strain curves were curvilinear with three regions: laxity, toe, and linear regions. Laxity of the MCL in feet with hallux valgus was significantly larger than that of normal feet (p = 0.022). Stiffness and tensile modulus in the toe region in feet with hallux valgus were significantly smaller than those in normal feet (p = 0.004); however, stiffness and tensile modulus in the linear region were not significantly different. The MCL collagen fibrils in the feet with hallux valgus had a more wavy distribution than the fibrils in the normal feet. CONCLUSIONS: In general, strong staining for collagen III and to a lesser extent, collagen I was observed at the interface between the MCL and bone in the feet with hallux valgus but not in the normal feet. These results indicate that the abnormal mechanical properties of the MCL in feet with hallux valgus may be related to differences in the organization of collagen I and collagen III fibrils.