8. Foot and Ankle MCQs

Risk factors for a poor outcome after bar resection are adult age and a bar that encompasses more than 50% of the middle facet of the subtalar joint. Because this patient has both risk factors, the appropriate procedure is a subtalar fusion.

Becker muscular dystrophy is an X-linked inherited disorder present in approximately 1 in 30,000 live male births. The responsible gene is located on the xp21 region of the X chromosome including sixty-five exons that encode for the protein dystrophin. Duchenne muscular dystrophy is also related to a mutation of the dystrophin gene. Muscle biopsies for dystrophin have been extremely successful for identifying these dystrophies and distinguishing them from other clinically similar autosomal recessive myopathies. (Ref: Shapiro, Hoffman)Question 18 -A 25-year-old woman with spastic diplegia has a painful progressive bunion deformity that has failed to respond to nonsurgical treatment. Examination reveals tenderness and erythema over the bunion prominence; however, the hallux metatarsophalangeal joint has full range of motion. A standing AP radiograph shows a hallux valgus angle of 30 degrees and a 1-2 intermetatarsal angle of 13 degrees. Treatment should now consist ofarthrodesis of the hallux metatarsophalangeal joint.arthrodesis of the first tarsometatarsal joint.excision of the medial eminence and medial capsular reefing of the metatarsophalangeal joint.osteotomy of the distal first metatarsal.proximal metatarsal osteotomy with distal soft-tissue realignment.Treatment of hallux valgus in a patient with cerebral palsy is largely dependent on the degree of spasticity and the pattern of gait. The only way to adequately eliminate spastic deforming forces is with an arthrodesis of the MTP joint. Any other procedure will most likely lead to a high incidence of either hallux varus or recurrent hallux valgus.The optimal arthrodesis angle is 25-30 degrees, and the metatarsal inclination angle should be 25-30 degrees also. Sagittal plane position should be checked intraoperatively and the proximal phalanx should clear the table by 5-10mm with simulated WB

DISCUSSION: The patient has posttraumatic subtalar joint arthrosis that developed following a calcaneal fracture. Because there is no hindfoot deformity, in situ subtalar joint arthrodesis is the treatment of choice. Calcaneal osteotomy or distraction bone block arthrodesis is beneficial in patients with severe talar dorsiflexion or malunion of the calcaneal body.

DISCUSSION: The patient has macrodactyly involving the second ray, with significant enlargement of the width and height of the foot. The radiographs show widening of the interval between the first and second metatarsal and between the second and third metatarsal. With this degree of involvement, amputation of the second ray with excision of the overgrowth of affected soft tissue provides the most consistent desired reduction in foot size.

DISCUSSION: The ankle dorsiflexor muscles have been denervated for too long a period to expect reinnervation to be successful. Even if the extensor hallucis longus tendon was functional, it is unlikely to have sufficient strength to achieve dynamic ankle dorsiflexion. The tibialis posterior tendon transfer has been shown to predictably achieve these goals in a high percentage of patients. Successful ankle fusion is likely to fail with time due to the development of forefoot equinus.

DISCUSSION: With the use of CT scans, adults with symptomatic flatfoot deformity have been noted to develop subluxation of the talocalcaneal joint with resulting lateral hindfoot pain. Impingement of the talus and calcaneus in the sinus tarsi and/or between the tip of the fibula and the calcaneus may occur. This impingement is known as lateral impaction syndrome. Hindfoot motion is painless; therefore, this patient does not have symptomatic subtalar arthritis. Middle facet and calcaneonavicular coalitions are not present (hindfoot motion is present).

DISCUSSION: Intrinsic muscles of the foot function to flex the metatarsophalangeal joints and extend the interphalangeal joints.

In the setting of a knee dislocation, an ABI of < 0.90 is highly sensitive for an occult vascular injury, even in the presence of palpable pedal pulses. The standard of care mandates that an ABI < 0.90 requires an immediate vascular imaging study, most commonly a CT angiogram (CTA), to rule out a popliteal artery intimal tear or other injury. Immediate exploration is reserved for hard signs of vascular injury (e.g., absent pulses after reduction, expanding hematoma, pulsatile bleeding).

An ABI < 0.9 in the setting of a knee dislocation is highly suspicious for a vascular injury and warrants advanced imaging, specifically a CT angiogram, to locate the arterial lesion. Immediate surgical exploration is reserved for 'hard signs' of arterial injury, such as absent pulses, expanding hematoma, pulsatile hemorrhage, or distal ischemia. Serial examinations are appropriate only if the ABI > 0.9 and pulses are symmetric.

An Ankle-Brachial Index (ABI) of less than 0.9 following a knee dislocation is a hard indication for advanced vascular imaging. CT angiography is the standard next step to rule out an intimal flap or flow-limiting popliteal artery injury.

In the setting of a knee dislocation, an ABI less than 0.9 is highly indicative of a vascular injury. Although the limb is perfused, the abnormal ABI mandates an advanced imaging study, primarily a CTA, to rule out intimal flap or flow-limiting popliteal artery injury.

Nonsurgical management of OCD of the talus in skeletally immature individuals frequently results in a fairly rapid decrease in symptoms, but radiographic abnormalities can frequently be found even 6 months after treatment. Spontaneous resolution of this condition is rare.

DISCUSSION: The patient has a stage II posterior tibial tendon tear with a supple foot; therefore, the treatment of choice is flexor digitorum longus transfer with medial displacement calcaneal osteotomy. Triple arthrodesis is not indicated, and isolated tendon transfer will stretch out in the face of persistent heel valgus. Direct repair of the posterior tibial tendon or repair of the spring ligament is not sufficient to correct the deformity. REFERENCES: Myerson MS, Corrigan J: Treatment of posterior tibial tendon dysfunction with flexor digitorum longus tendon transfer and calcaneal osteotomy. Orthopedics 1996;19:383-388. Mosier-LaClair S, Pomeroy G, Manoli A II: Operative treatment of the difficult stage 2 adult acquired flatfoot deformity. Foot Ankle Clin 2001;6:95-119.

DISCUSSION: Cadaver and clinical studies have shown that the sural nerve is at the highest risk for injury with a percutaneous repair of the Achilles tendon. REFERENCE: Hockenbury RT, Johns JC: A biomechanical in vitro comparison of open versus percutaneous repair of tendon Achilles. Foot Ankle 1990;11:67-72.

DISCUSSION: The presence of recurrent breakdown over the medial eminence despite shoe wear modifications is an indication for surgery. A number of factors must be considered when deciding on an appropriate course of treatment. These include age, activity level, joint congruency, joint degeneration, and the patient’s symptoms and expectations. The indications for a simple bunionectomy are rather limited. In this patient, the goal of surgery is to alleviate the recurrent infection by removal of a large medial eminence. REFERENCES: Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 123-134. Abidi NA, Conti SF: The clinical and radiographic anatomy of hallux valgus and surgical algorithm. Foot Ankle Clin 1997;2:599-626.

DISCUSSION: The tibiofibular overlap is measured between the medial border of the fibula and the lateral border of the anterior tibial tubercle. Plain radiographic assessment of the distal tibiofibular syndesmosis requires AP and mortise views. It has been recommended to obtain the first three measurements on the mortise view and the other three on the AP view.

DISCUSSION: In the treatment of ankle fractures, the superficial peroneal nerve is most commonly injured by the use of a direct lateral approach to the ankle. The superficial peroneal nerve and its branches exit the fascial hiatus approximately 9 cm to 10 cm proximal to the tip of the distal fibula, and their course is typically anterior to the midlateral plane of the fibula.

Even though the patient has a grade 3 ankle ligament injury, studies have shown that 95% of patients with a grade 3 injury that may include a complete tear of the ligaments will heal successfully with conservative functional management. Extensive diagnostic evaluation with stress radiographs, CT, and MRI is not indicated. Surgical reconstruction is not indicated because of the overwhelming success of conservative management; however, in the few patients where late instability develops, surgical reconstruction offers an excellent outcome.

Unopposed action of the tibialis anterior with weakness of the peroneus longus will lead to a dorsal bunion and supination deformity. Overpull of the gastrocnemius-soleus complex and posterior tibialis with weakness of the peroneus brevis will cause equinovarus deformity. A strong posterior tibialis with weakness of the peroneals will cause varus of the hindfoot. Unopposed peroneus brevis and incompetence of the posterior tibialis will lead to a flatfoot deformity. The etiology of a cavus foot is complex, but findings usually include a contracted plantar fascia and weakness of the tibialis anterior.

Generally, patients cannot tolerate more than 5 degrees of hindfoot posting.