Citations

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.

Intramedullary tibiotalocalcaneal arthrodesis (IMTCA) is an increasingly used procedure for salvage of complex hindfoot and ankle disorders. 1 , 2 To avoid injury to vital plantar neurovascular structures, it is important to begin with an appropriate insertion site during retrograde IMTCA. We use a simple, reproducible method to determine this site based on anatomic landmarks.

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.

An intramedullary fixation device was devised by the senior author (K.A.J.) to use in conjunction with a previously described method for tibiotalocalcaneal arthrodesis. Satisfactory results were obtained in approximately 87% of the initial 30 patients; union was radiographically or clinically evident in all but two patients. Many of these patients had been offered or were considering below the knee amputation; only two ultimately chose this reconstructive option at a follow-up that ranged from 4 to 27 months.

Nineteen patients underwent surgical synovectomy and debridement for the clinical diagnosis of stage I posterior tibial tendon (PTT) dysfunction. Stage I PTT dysfunction is characterized by pain and swelling along the medial aspect of the ankle. Fourteen patients (74%) reported complete relief of pain, 3 patients (16%) reported minor pain, and 1 patient (5%) had moderate pain, and 1 (5%) had continued severe pain. Sixteen (84%) of the patients subjectively reported being “much better” and had a return of function of the PTT, as evidenced by their ability to perform a single limb-heel-rise test. Two patients (10%) underwent subtalar arthrodesis for progressive foot deformity and continued pain. Based on these results, surgical release, tenosynovectomy, and debridement are recommended for the treatment of stage I PTT dysfunction.

The chevron osteotomy for hallux valgus was modified by addition of screw fixation and change of the osteotomy angle. Thirty-six patients underwent this modified osteotomy. All had mild to moderate symptomatic hallux valgus deformities. No other forefoot procedures were performed. Standing radiographs were taken before surgery, at 1 month after surgery, and, for the 15 patients who returned for long-term follow-up, at 1 year or more after surgery. Overall, 35/42 procedures were rated as satisfactory without reservations and 7 were rated as satisfactory with mild reservations. All patients stated that they had some improvement in their preoperative symptoms, which included pain, cosmetic concerns, and shoe wear difficulties. Radiographically, none of the capital fragments displaced and there were no malunions, nonunions, nor evidence of avascular necrosis. The average metatarsophalangeal-1 angle improved 8° and the average intermetatarsal 1–2 angle improved 4°. This modification is relatively simple, increases stability, and allows early weightbearing. In our experience, the modified chevron osteotomy has been a very reliable procedure for mild to moderate symptomatic hallux valgus deformity.

Material properties of the plantar aponeurosis were determined by a two-dimensional video tracking method to simultaneously measure the aponeurosis deformation. Failure loads averaged 1189 ± 244 N and were higher in men. Average stiffness of the intact fascia was 203.7 ± 50.5 N/mm at a loading rate of 11.12 N/sec and it did not vary significantly for the loading rates of 11.12 to 1112 N/sec. The high tensile loads required for failure were consistent with clinical and biomechanical studies and indicated the importance of the aponeurosis in foot function and arch stability.

Four rating systems were developed by the American Orthopaedic Foot and Ankle Society to provide a standard method of reporting clinical status of the ankle and foot. The systems incorporate both subjective and objective factors into numerical scales to describe function, alignment, and pain.