An, Kai‐Nan

A major limitation of operations commonly performed for acquired flatfoot is inadequate correction of alignment. The authors defined the efficacy of two operations, deltoid ligament reconstruction and flexor digitorum longus tendon transfer, for treatment of posterior tibial tendon dysfunction with flatfoot deformity. Twelve fresh-frozen foot specimens were used. A flatfoot deformity was created, and, to simulate the midstance phase of gait, loads were applied axially to the plantar surface of the foot and to appropriate tendons. Foot position improved substantially after deltoid ligament reconstruction but not after flexor digitorum longus tendon transfer. The average increase in arch height after deltoid ligament reconstruction was 10.3 ± 8.9 mm and after flexor digitorum longus tendon transfer, −0.6 ± 2.0 mm. Mean arch height after deltoid ligament reconstruction was 2.2 ± 1.7 mm less than intact arch height and, after flexor digitorum longus tendon transfer, 13.2 ± 9.0 mm less than intact arch height. Improvement in metatarsal-talar, calcaneal-talar, and talar-tibial positions was significantly greater after deltoid ligament reconstruction than after flexor digitorum longus tendon transfer. Although the authors do not advocate clinical use, the deltoid ligament reconstruction was more effective than flexor digitorum longus tendon transfer in restoring arch alignment in flatfoot.

We defined the mechanical behavior of the foot after an operation for treatment of the flatfoot deformity, subtalar arthrodesis, and compared results with those from flexor digitorum longus tendon transfer. Twelve fresh-frozen human foot specimens were used. Supporting elements were sectioned to create a flatfoot deformity. To simulate midstance phase of gait, loads were applied axially to the plantar foot and to five tendons. Reduction of deformity in metatarsal-talar, calcaneal-talar, and talar-tibial positions was achieved and was significantly greater after subtalar arthrodesis operation than after flexor digitorum longus transfer.

We defined the relative contributions of six ligaments in stabilizing the arch of the foot: plantar aponeurosis, long-short plantar ligaments, plantar calcaneonavicular ligament (spring ligament), medial talocalcaneal ligament, talocalcaneal interosseous ligament, and tibionavicular portion of the deltoid ligament. Nineteen fresh-frozen human foot specimens were used. A load of 445 N was applied axially to simulate standing-at-ease posture. Three-dimensional positions of tarsal bones before and after ligament sectioning were determined with the use of a magnetic tracking device. The motions were presented in the form of screw axis displacements, quantitating rotation, and axis of rotation orientation. After sectioning one structure, the arch did not collapse on any specimen and there was no obvious change by visual inspection. There were, however, measurable changes in tarsal bone position. Metatarsal-to-talus total rotation difference was greatest with spring ligament and deltoid ligament sectioning, with an average of 2.1° ± 1.7° and 2.0° ± 0.2° difference, respectively. Calcaneus-to-talus rotation difference was greatest with talocalcaneal interosseous ligament sectioning, with an average of 1.7° ± 1.5°. The spring ligament, deltoid ligament, and talocalcaneal interosseous ligament were most important for arch stability.

Ligaments surrounding the hindfoot joints play an important role in hindfoot stability. This in vitro study investigated anatomical and biomechanical characteristics of nine major ligamentous structures, including length and orientation at neutral position and physiological elongation with the foot in five different positions relative to the neutral position. The results showed that ligament elongation depended on the ligament length, orientation in neutral position, and movement of bones to which they were attached.

We studied six fresh frozen cadaver feet to define the three-dimensional motion of the hallux proximal phalanx in relation to the first metatarsal and to describe the contact features of the first metatarsophalangeal joint. Six tendons to the hallux were loaded to simulate dynamic loading of the hallux. A magnetic tracking system was used to monitor the three-dimensional movement of the proximal phalanx while the toe position was changed from a neutral position to full extension by adjusting the tendon loads. The average surface area was 0.38 ± 0.08 cm 2 in the neutral position; it decreased with toe extension and was the lowest (0.04 ± 0.03 cm 2 ) at the full extension position. Contact distribution of the proximal phalanx did not change substantially throughout the arc of motion. However, for the metatarsal articular surface, the contact distribution shifted dorsally with increasing degrees of extension. These data are consistent with the observation that chondral erosions associated with hallux rigidus and degenerative arthritis initially affect the dorsal articular surface of the metatarsal, and implant arthroplasty often fails from component loading dorsally. The current technique of determining joint contact characteristics is applicable not only for the first metatarsophalangeal joint but also other joints that have not been studied because of shortcomings with more conventional methods.

A cadaver study was performed to determine the effect of the posterior tibial tendon (PTT) on the stability of the foot in simulated midstance phase of gait. Thirteen fresh-frozen human foot specimens were used. Loads were applied axially and to each tendon. Three-dimensional positions of tarsal bones before and after tendon loading were determined with the use of a magnetic tracking device. Significant differences in tarsal bone positions were observed with application of loads to the Achilles, posterior tibial, flexor digitorum longus, peroneus longus, and peroneus brevis tendons at the metatarsotalar, calcaneotalar, and talotibial joints and in overall arch height. These tendon loads caused position changes toward arch flattening or mild pes planus deformity. Significant differences in tarsal bone positions were observed with PTT loading compared with no PTT loading in metatarsotalar, calcaneotalar, and talotibial levels as well as arch height. The PTT caused position changes toward restoring the arch alignment. These data suggest that the PTT is an important stabilizer of the arch of the foot.

The change in position of the bones of the foot was studied in three dimensions after plantar fascia release in intact and destabilized feet. Fifteen fresh-frozen human foot specimens were used. Physiologic loads of 445 newtons were applied axially to simulate standing at ease, and the three-dimensional position of tarsal bones was determined with a magnetic tracking device. The positions were presented in the form of screw axis displacements, quantitating rotation, and axis of rotation orientation. After fasciotomy in the six intact feet, significant differences in rotation were observed at the talotibial and calcaneotalar levels. After fasciotomy in the four unstable feet with three supporting elements sectioned, significant differences in position were observed at the talotibial joint and a significant decrease in arch height was observed. After fasciotomy in the five unstable feet with five supporting elements sectioned, significant differences in rotation were observed at the talotibial joint (mean, 5.5 ± 1.6° P = 0.001), calcaneotalar joint (mean, 6.1 ± 2.1° P = 0.003), and metatarsotalar level (mean, 9.3 ± 4.1° P = 0.007). The average decrease in arch height was 7.4 ± 4.1 mm ( P = 0.015). Displacement of all joints tested occurred after fasciotomy, with rotation about all three axes. These changes in displacement were more pronounced in unstable or destabilized feet. The data suggest that operations involving fasciotomy affect arch stability and should not be performed in patients with evidence of concomitant pes planus deformity, because of the likelihood of further deformation.

We studied 15 cadaver feet to determine three-dimensional motion of selected tarsal bones under axial loading at three different loading levels. We determined the motion of individual joints and also the rotation of the tarsal bones in relation to the tibia. Joint rotations increased consistently with higher loads. The navicular-talar joint had the greatest total screw axis rotation, which averaged 9.4° ± 2.2° at 667 N of load, followed by the first metatarsal-navicular (mean, 7.2° ± 1.5°), talar-tibial (mean, 5.2° ± 1.6°), and calcaneal-talar (mean, 4.4° ± 1.7°) joints. The observed changes indicate the need for assessment of foot and ankle alignment clinically and radiologically while the patient is weightbearing.

In spite of the common occurrence of pes planus and multiple operations that have been reported to relieve the associated symptoms, there is little published on the relative contribution of various structures to stabilization of the arch of the foot. Twelve fresh-frozen human cadaveric feet were loaded along the tibial axis with compressive loads of 230, 460, and 690 newtons with the specimens intact and after sequential sectioning of plantar fascia, plantar ligaments, and spring ligament. Structures were sectioned in six different sequences and changes in vertical and horizontal dimensions of the medial arch were measured. The highest relative contribution to arch stability was provided by the plantar fascia, followed by plantar ligaments and spring ligament. Plantar fascia was a major factor in maintenance of the medial longitudinal arch. Its division in the cadaveric feet decreased arch stiffness by 25%.

Background We have recently reported that interpositional synovium grafts from tendon sheath have a potential to accelerate tendon healing when implanted at the repair site. The purpose of this study was to investigate the effect of orientation of the synovium after synovium graft transplantation, by comparing the ability of cells from the visceral and parietal surfaces to migrate into the tendon in a canine tissue culture model. Methods The synovium graft was placed within a complete tendon laceration, with either the visceral or parietal surface facing the proximal end of the lacerated tendon. The number of migrating cells was quantified by a cell migration assay. Qualitative immunohistochemistry and confocal laser microscopy were also used at day 10. Results Many labeled synovial cells were observed within the tendon to which the visceral surface of the synovium graft was facing. Migrated cells were also observed on the parietal side, but there were fewer cells compared to visceral surface cells. Migrating cells all expressed α-smooth muscle actin. Conclusion We found that graft orientation affected cell migration. Whether this finding has clinical significance awaits in vivo study.