8. Foot and Ankle MCQs

The question asks for the recommended orientation for syndesmotic screw fixation with respect to the coronal plane of the tibia. The standard recommendation is to place the screw 2 to 4 cm proximal to the tibial plafond, directed from the fibula to the tibia, angled 25 to 30 degrees anteriorly to account for the orientation of the syndesmosis.

The radiographic findings show 30 degrees of talar tilt (severe) and 10 mm of anterior translation that typically involves laxity of both of the major lateral ligaments of the ankle (anterior talofibular and calcaneofibular). There is no evidence of deltoid laxity.

The patient has a rim avulsion fracture that is the result of a forceful twisting injury as the superior peroneal retinaculum is avulsed from its fibular attachment along with a small rim of bone. Injuries to the anterior talofibular ligament or calcaneal fibular ligament would show cortical avulsions more anteriorly or distally at the fibular tip. Deltoid ligament injuries would reveal medial radiographic changes. In a true injury to the syndesmosis, if osseous structures do show avulsion, it would be more directly posterior or anterior on the distal fibula or would occur on the tibial surface.

The clinical photograph shows a skin infection with an appearance consistent with methicillin-resistantStaphylococcus aureus. This infection should be clinically incised and allowed to drain and a course of antibiotics should follow. If this infection is not promptly treated with debridement, it likely will worsen and potentially spread to other teammates. Antibiotics are secondary to surgical debridement but are a necessary adjunct. Although this patient has a history of severe sprain, his malaise and skin appearance do not correlate with a ligament injury or fracture. Debridement in the training room is not appropriate and would likely not fully decompress the fluid collection.

The most common deformity after a midfoot amputation as shown in Figure A is an equinuovarus deformity due to the pull of the Achilles and plantarflexors in face of loss of the common extensors and distal insertion of the tibialis anterior.Ng et al. review foot and ankle amputations, and review the issues inherent with each amputation level, including prosthesis fitting and use. They also mention that careful repair of all released or transected tendons is needed to maintain a plantigrade foot.Early reviews the importance of soft tissue balancing with midfoot amputations. They note that the attachment of the resected tendons into the more proximal retained bones is critical for success in restoration of foot position and ambulation capabilities.Figure A shows a midfoot amputation as the result of trauma. Illustration A shows the lateral view of the amputation, with an obvious equinus deformity.Incorrect Answers:

The patient has the classic symptoms, examination findings, and radiographs for a painful accessory navicular. Initial treatment should always be nonsurgical, specifically cast immobilization. Surgery should be reserved for those patients who fail nonsurgical management. Corticosteroids should not be injected into a posterior tibial tendon or insertion point because they can weaken the tendon and possibly cause tendon rupture. Triple arthrodesis and biopsy have no role in the management of a painful accessory navicular.

CMT is characterized by a cavovarus foot position that increases weight-bearing stresses along the lateral border. Removal of the fifth metatarsal head carries the risk of creating a transfer lesion at the fourth metatarsal head, particularly with a cavovarus foot. Claw toes are common in CMT, but the fifth toe would be flail in this situation. Ulceration is unlikely given the lack of underlying bone. Peroneal atrophy is associated with CMT but would not be a complication of this procedure. Charcot arthropathy is a neuropathic process frequently seen in individuals with diabetes mellitus.

Chronic lateral instability is commonly associated with a longitudinal split tear of the peroneus brevis tendon. The interrelationship of lateral ankle instability with superior retinacular laxity and resultant peroneus brevis split can account for persistent lateral ankle pain in this patient. Surgical treatment must identify and correct the underlying tendon pathology and should attempt to repair or debride the peroneus brevis tendon, reconstruct the superior peroneal retinaculum, flatten the posterior edge of the fibula by removing the sharp bony prominence, or deepening the fibular groove, along with addressing lateral ankle ligamentous instability. The laboratory values are not consistent with infection. A negative anterior drawer test confirms stability of the repair. Ankle arthritis is not seen on radiographs and usually takes longer than 3 months to develop.

DISCUSSION: The figures show a longitudinal split within the peroneus brevis tendon as it courses posterior to the fibula. The peroneus longus tendon has been driven between the medial and lateral components of the peroneus brevis tendon. Peroneal split syndrome is a cause of lateral ankle pain. It may be associated with tendon subluxation following a tear of the superior peroneal retinaculum. REFERENCE: Mink JH: Tendons, in Deutsch AL, Mink JH, Kerr R (eds): MRI of the Foot and Ankle. New York, NY, Raven Press, 1992, pp 135-172.

The patient has a moderately displaced distal diaphyseal fracture of the fifth metatarsal, and the most appropriate treatment is brief immobilization and symptomatic management. Attempts at closed reduction are unlikely to appreciably alter the position of the fracture. Surgical techniques for either reduction of the fracture or fixation have not been shown to result in improved functional outcomes.

Prospective studies, including randomized and randomized multicenter reports, have shown that percutaneous or mini-open acute Achilles tendon repair has comparable functional results when compared to traditional open techniques. Calder and Saxby reported one superficial infection out of 46 patients with a mini-open repair; Assal and associates and Cretnik and associates had no wound complications or infections. The other complications have not proved to be less likely with the mini-open or percutaneous technique.

The radiographs reveal a hindfoot deformity that developed following a severe, comminuted, intra-articular fracture of the calcaneus. There is deformity of the calcaneal body and collapse of the talus into the calcaneus, leading to dorsiflexion of the talus and anterior ankle joint impingement. Distraction bone block subtalar joint arthrodesis will assist with correction of the calcaneal height and will allow for an improved talar declination angle. With this procedure, care must be taken to avoid placing the hindfoot into further varus. A similar reconstruction option not listed would be a calcaneal osteotomy and arthrodesis as described by Romash. Talectomy and tibiocalcaneal arthrodesis are not warranted because the primary structure of the talus and ankle joint is well preserved. In situ subtalar joint arthrodesis will not correct the deformity, and symptoms about the ankle and hindfoot would most likely persist. Lateral wall calcaneal exostectomy may decrease pain from subfibular impingement but will not deal directly with subtalar joint arthrosis and deformity.

The distal tibiofibular syndesmosis is a ligamentous complex that consists of the AITFL, PITFL, intertransverse ligament (ITL), and IOL. The PITFL originates on the posterior inferior aspect of the tibia (Volkmann tubercle) and inserts on the lateral malleolus. The AITFL originates on the anterolateral aspect of the tibia (Chaput tubercle) and inserts on the distal anterior aspect of the fibula (Wagstaffe tubercle). The ITL is a group of fibers running transversely just inferior to the PITFL. As a group, these structures maintain the appropriate tibial plafond and talus relationship throughout physiologic range of motion.

Continuous fluoroscopy and cineradiography exposes the patient and personnel to markedly increased levels of direct and scatter radiation exposure. Continuous fluoroscopy should be limited to only what is absolutely needed for safe completion of the procedure. By orienting the cathode ray tube beneath the patient and placing the image intensifier as close as clinically possible to the patient, scatter radiation exposure to the personnel is minimized.

Claw toe and hammer toe deformities are associated with dorsal subluxation of the interossei, which can no longer serve to flex the metatarsophalangeal joint. The extensor digitorum longus then loses its tenodesing effect on the proximal interphalangeal and distal interphalangeal joints and works unopposed to extend the metatarsophalangeal joint and the proximal phalanx. Without the antagonistic action of the extensor digitorum longus, the extrinsic flexors become unopposed flexors of the proximal and distal interphalangeal joints.

DISCUSSION: In an ankle syndesmosis injury, the fibula is most unstable in an anterior and posterior direction. This is whether or not there is an accompanying ankle fracture. Most commonly, the fibula will subluxate anterior in an ankle fracture model. The first referenced article by Xenos et al found that stress lateral radiographs have more interobserver reliability than stress AP/mortise radiographs and that two syndesmotic screws are stronger than one. The referenced article by Candal-Couto et al is a biomechanical study that found more anterior-posterior instability in a syndesmosis injury model, and more ankle instability is noted with syndesmosis injury and a concomitant deltoid injury. The referenced article by Zalavras et al is an excellent review article on ankle syndesmosis injuries.

DISCUSSION: It is imperative to recognize the need for a position screw (syndesmosis screw) to hold the syndesmosis in proper alignment when surgically stabilizing an ankle fracture. Although many different fracture patterns are suspicious for a disrupted syndesmosis, the only sure way to assess the syndesmosis is to stress it with abduction and external rotation of the talus and attempt to displace the fibula from the incisura fibularis. Under fluoroscopy, the talus will move laterally and displace the fibula, show a valgus talar tilt, or show an increase in the medial clear space. If any or all of these signs occur, a syndesmosis screw is inserted after making sure that the fibula is reduced into the incisura fibularis.

DISCUSSION: The images demonstrate an L5 selective root block as it exits the L5-S1 foramen. This root block best helps relieve pain or paresthesias in the L5 distribution, which is the dorsal first web space and the great toe. The lateral foot is an S1 distribution and would need to be blocked through the posterior first sacral foramen. The anterior shin and thigh represent the L4 root which exits a level above this at the L4-5 foramen. A stocking distribution is nonanatomic and not indicative of a specific root.

The child has an up-to-date tetanus; therefore, a booster is not recommended. Pseudomonas coverage is most likely not needed because the child was barefoot. It is too early to evaluate for abscess or osteomyelitis with MRI, and a formal debridement is rarely indicated without signs of an abscess or a retained foreign body. Radiographs with soft-tissue penetration should be obtained to check for a retained foreign body. References: Richardson EG (ed): Orthopaedic Knowledge Update: Foot and Ankle 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 199-205. DeCoster TA, Miller RA: Management of traumatic foot wounds. J Am Acad Orthop Surg 1994;2:226-230.

DISCUSSION: Gouty arthritis, pseudogout, and infection can all present with inflammatory arthritis and periarticular erosions. Strongly negative birefringent crystals are seen in gout. The histologic image shows elongated “needle-like” crystals of gout. Epidermal inclusion cysts are rarely painful and usually have a history of localized penetrating trauma.