8. Foot and Ankle MCQs

Normal syndesmotic relationships include a tibiofibular clear space smaller than 6 mm on both AP and mortise views. In a 1989 cadaveric study by Harper and Keller, a tibiofibular clear space exceeding 6 mm on both the AP and mortise views was the most reliable predictor of early syndesmotic widening. Tibiofibular overlap is measured 1 cm proximal to the plafond. Normal values exceed 6 mm or 42% of the width of the fibula on the AP view, or 1 mm on the mortise view.

The main function of the Tib. Post. Tendon is inversion of the subtalar joint and adduction of the forefoot. This initial inversion stabilizes the subtalar joint allowing the gastrosoleus complex to forcibly invert the joint while plantarflexing the ankle. Heel inversion begins during flatfoot when the Tib Post. fires at 7% of the walking cycle. The gastrosoleus kicks in at 30% of the cycle to maintain inversion, which locks the midfoot for push-off.

Placement of long lateral tibial plates has been shown to have a risk of iatrogenic injury to the superficial peroneal nerve, which has a sensory distribution to the dorsal foot and the first dorsal webspace. This risk is seen especially with percutaneous approaches, such as those used with the LISS plate. Deangelis et al. found a risk of superficial peroneal injury with percutaneous screw placement of holes 11-13 in the LISS plate.

The term turf toe includes a range of injuries of the capsuloligamentous complex of the first metatarsophalangeal joint with or without osteochondral fracture of the first metatarsal head or one of the sesamoids. The mechanism of injury is hyperextension.

The partial foot amputation through the talonavicular and calcaneocuboid joints is also known as the Chopart amputation. The Chopart amputation may result in significant equinovarus deformity with anterior weight bearing through the scar line, predisposing to skin breakdown over time. Therefore, lengthening of the Achilles tendon and transfer of the tibialis anterior to the talar neck should also be performed in conjunction with this disarticulation. The tibialis anterior transfer results in dorsiflexion and distributes the weight-bearing portion more centrally, and the lengthening of the Achilles tendon is necessary to accommodate this posteriorly. Transfer of the tibialis anterior or posterior tibialis to the calcaneus would exacerbate the equinovarus deformity. Shortening of the Achilles tendon would also exacerbate the anterior loading of the scar.

The peroneal tubercle is often a good landmark at which to identify the peroneus longus tendon surgically, and a hypertrophic tubercle has been associated with peroneus longus tendinopathy. Both peroneal tendons curve anteriorly around the tip of the fibula, with the peroneal tubercle separating the two tendons at the level of the calcaneus. The peroneus brevis runs in front of the tubercle and the longus behind. The flexor hallucis longus runs through a fibro-osseous tunnel posterior to the hindfoot formed by the posterolateral (os trigonum) and posteromedial tubercle of the talus. The calcaneofibular ligament attaches to the calcaneus below the posterior facet of the subtalar joint and deep to the peroneal tendons.

The main function of the EDL is extension of the MTP joints of the lesser toes, so injury results in a claw toe deformity if left unrepaired. The EDL originates on the lateral tibial condyle, the anterior crest of the fibula, and the interosseous membrane and inserts on the base of the terminal phalanges of the four lesser toes. Innervated by the deep peroneal nerve, the EDL functions to extend the toes at the DIP joint and to dorsiflex and evert the foot. The EDL divides into two separate tendons beneath the superior retinaculum and then further divides into two lateral tendons to the fourth and fifth toes and two medial tendons to the second and third toes. The individual tendon of the EDL to each toe is joined on the lateral aspect by the tendon of the EDB. They are anchored at the level of the MTP joint by a fibroaponeurotic structure.The EDB originates on the distal lateral and superior surface of the calcaneus and inserts on thelateral aspect of the flexor digitorum longus tendon and also on to the base of the proximal phalanx of the first through fourth toes. There is no EDB tendon to the fifth toe. If an EDB laceration is easily identified at the time of an EDL repair, than it may be repaired as well, otherwise repair of the EDL alone is sufficient.Heckman JD: Fractures and dislocation of the foot, in Rockwood CA Jr, Green DP, Bucholz RW, Heckman JD (eds):Rockwood and Green’s Fractures in Adults, ed 3. Philadelphia, PA, JB Lippincott, 1991, pp 2166-2169.Coughlin MJ: Disorders of tendons, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, ed 7. St Louis, MO, Mosby, 1999, pp 787-788.back to this question    next question

DISCUSSION: The MRI scans clearly show an extruded L4-5 disk that is affecting the L5 nerve root on the left side. In addition, the L5 nerve root has a cutaneous distribution in the first dorsal web space. S1 affects the lateral foot. L4 affects the medial calf.

DISCUSSION: The peroneus tertius, although absent in 10% of the population, originates on the distal third of the extensor surface of the fibula and inserts onto the base of the fifth metatarsal, possibly extending to the fascia over the fourth interosseous space. The muscle is located in the anterior compartment of the leg and is innervated by the deep peroneal nerve. The tendon produces dorsiflexion and eversion when walking and can be used as an insertion point during tendon transfers to assist dorsiflexion. This tendon is peculiar to humans and is a proximally migrated deep extensor of the fifth toe.

DISCUSSION: Flexor hallucis longus tendinitis is a common cause of posterior ankle pain in dancers. It tends to be more posteromedial and is characterized by a clicking or catching sensation posteromedially with motion of the great toe. A painful os trigonum typically causes more posterolateral ankle pain and may occur after an ankle sprain or plantar flexion injury where there may be a fracture of the os trigonum.

DISCUSSION: Early postoperative wound infections after open reduction and internal fixation should be treated with aggressive debridement and maintenance of stability of the fracture. If infection persists following healing of the fracture, the hardware should be removed.

DISCUSSION: The injury radiographs reveal a supination external rotation IV ankle fracture with evidence of medial clear space widening exceeding 4 mm and an increase relative to the superior tibiotalar clear space. This indicates injury to the deltoid ligament and necessitates surgical reduction and fixation to restore and maintain ankle stability. Following stabilization of the fibula, an intraoperative stress examination of the syndesmosis such as an external rotation stress test under fluoroscopy or lateral pull on the fibula (the Cotton test) should be performed to determine the integrity of the syndesmosis. Radiographic evidence of tibiofibular clear space widening, medial clear space widening with external rotation, and lateral displacement of the distal fibula when pulled is consistent with syndesmotic injury. In contrast to the presurgical stress test, once the fibula has been reduced and stabilized lateral talar translation can occur only if the syndesmosis is injured in addition to the deltoid ligament. Failure of the syndesmotic screw without evidence of malalignment of the mortise and a pain-free ankle are not indications for further surgery because these patients have satisfactory outcomes when compared to those who have intact or removed screws. Hardware removal following fibula ORIF is indicated when patients have pain directly related to hardware prominence. Resolution of joint pain or stiffness is not a reliable outcome following hardware removal. Although fibular fracture can occur, this is a rare complication. Malreduction of the syndesmosis is the most common complication following ORIF of the syndesmosis and is improved with direct visualization; however, malreduction still may occur with direct visualization.

The superomedial fragment of an intra-articular calcaneus fracture is also referred to as the sustentacular fragment or “constant fragment.” In their CT analysis of acute calcaneal fractures, Gilmer et al describe that the superomedial piece typically does not move in these fractures due to its strong ligamentous attachments to the talus. For this reason, it is commonly referred to as the "constant fragment." The superomedial fragment is important during ORIF of calcaneal fractures, because fixation from the lateral side is typically based off this "constant" fragment as a guide to provide anatomic fixation. Additionally, the flexor hallucis longus (FHL) tendon wraps inferiorly around this piece within an osseous groove.

The patient has calcaneal apophysitis, an overuse syndrome common in children ages 9 to 12 years. Symptoms are usually the result of excess tension and a tight heel cord. Management includes activity modification, as well as heel cord stretching, nonsteroidal anti-inflammatory drugs, icing, and other modalities. Radiographs are typically negative; MRI is unnecessary. Custom orthotics are not indicated. The condition is self-limiting, in that the symptoms fully resolve once the apophyses fuses, such that surgery is rarely indicated.

Synovitis of the second MTP occurs in association with instability of the joint. This can be idiopathic or secondary to an external deforming force (such as a hallux valgus or shoe wear causing a claw toe). The primary stabilizer of the MTP joint for translation in the vertical plane is the plantar plate. The flexor digitorum brevis flexes the MTP joint, and the flexor digitorum longus flexes all joints of the toe. The collateral ligaments are primary stabilizers in the transverse plane and secondary stabilizers in the sagittal plane.

The radiograph reveals a displaced calcaneal tuberosity fracture. Displacement of a large tuberosity fragment necessitates urgent fracture reduction and stabilization. Delayed reduction results in compromise of the skin and soft tissues at the posterior heel. This injury occurs frequently in patients with diabetes. Protected weight-bearing activity does not address the displaced fragment or the threatened skin. Closed reduction, if possible, will not maintain the tuberosity fragment in a reduced position and will likely result in redisplacement. The fragment is large enough that it may be fixed and not excised. The Achilles tendon inserts on the displaced tuberosity fragment, so tuberosity reduction and fixation is necessary to achieve proper Achilles function.

The radiographs show an isolated posterior malleolus fracture which, given the injury mechanism, is highly suspicious for a Maisonneuve injury. As with any suspected extremity injury, radiographs including the joints above and below the level of injury are acutely indicated. Although MRI may reveal a ligamentous injury to the ankle and CT may show asymmetry of the ankle mortise or syndesmosis, both studies are considerably more costly and are not indicated in the absence of a complete radiographic work-up. Technetium bone scan is nonspecific and would be of limited value in this instance, as would repeat radiographs of the ankle.

DISCUSSION: A significant bunionette deformity that fails to respond to conservative management is best addressed surgically, in this case with the bunion deformity. The radiograph reveals a prominent lateral condyle at the fifth metatarsal head without a significant increase in the intermetatarsal angle. Simple exostectomy is preferred with less risk of complications. Complete excision would risk transfer lesions to the medial metatarsals.

Ice hockey injuries demand a thorough assessment because they have the potential to be significant. In hockey players, bone injuries in the foot and ankle can be missed or improperly diagnosed through routine radiographic imaging. MRI can display bone injuries that are not found radiographically; this is becausesome fractures and contusions involve the medial ankle and midfoot bones.

DISCUSSION: Depending on the type of materials used, an orthotic can be fabricated to achieve a variety of results. While a rigid fixed deformity can be stabilized or cushioned, an orthotic will not correct a deformity that is not passively correctable.