Osteochondral Lesions of the Ankle and Occult Fractures of the Foot and Ankle

Introduction

Fractures of the foot and ankle are a common occurrence in the athletic population. Sometimes fractures may not be obvious on x-rays, and one must be on the lookout for occult fractures. Ankle fractures are approximately 7% of all sport-related fractures, and as high as 11% in National Football League (NFL) players evaluated at the combine. Disability due to foot and ankle stress fractures is a major source of injuries in athletes, and is seen to be as high as 15% in the running population.

Occult Fractures of the Hindfoot

Occult fractures of the hindfoot are a significant and common cause of injury and can often be misdiagnosed as a soft-tissue injury without having a high level of suspicion. In-depth knowledge of the anatomy, coupled with a thorough history and physical examination, and a keen differential diagnosis will assist the clinician in an accurate diagnosis. Often, further diagnostic testing, such magnetic resonance imaging (MRI) or computed tomography (CT) scans, can confirm a diagnosis.

Occult fractures of the hindfoot include anterior process of the calcaneus, talonavicular avulsion injuries, cuboid fractures, navicular stress fractures, distal tibia or fibular stress fracture, and calcaneal or talar stress fractures.

Clinical Anatomy

The foot and ankle are comprised of 28 bones, multiple joints, and connecting ligaments. The foot and ankle are vulnerable to compression and avulsion injuries with many complex and diverse movements during competitive sports. The hindfoot is made up of the tibia, fibula, talus, calcaneus, navicular, and cuboid. Often, the talus is prone to injury during athletics as it moves through both dorsiflexion/plantarflexion and inversion/eversion motions. The talus is connected at the ankle joint to the tibia medially through the deltoid ligament ( Fig. 16.1A ) and to the fibula laterally through the anterior talofibular ligament (ATFL) and posterior talofibular ligament ( Fig. 16.1B ). The posterior talofibular ligament attaches at the posterior talus, on the Stieda process (posterolateral) or os trigonum.

Fig. 16.1, Hindfoot anatomy of the ankle. Note the (A) medial attachment of the talus the tibia with the deltoid and (B) laterally to the fibula with the anterior and posterior talofibular ligaments.

The talus is connected to the calcaneus by the talocalcaneal interosseous ligament and the cervical ligament ( Fig. 16.2A ). The dorsal (see Fig. 16.2A ) and plantar ( Fig. 16.2B ) talonavicular ligaments connect the talus and navicular. Approximately 60% to 70% of the talar surface is articular, with the ankle joint superiorly, the talonavicular joint anteriorly, and the subtalar joint inferiorly. Blood supply to the talus therefore is limited, coming from its ligamentous attachments and a leash of vessels surrounding the talar neck that receive contributions from the artery to the tarsal canal medially, the dorsalis pedis artery anteriorly, and the artery to the sinus tarsi laterally ( Fig. 16.3A-C ). The internal vasculature of the talus varies considerably ( Fig. 16.4 ). External athletic injuries to the talus that involve disruption of the vascular leash or the ligamentous attachments often produce vascular insult to the talar body or neck and may produce talar fractures or compression injuries that have delayed healing. The talus is unique in that it has no direct muscular attachments. It has seven articular surfaces along with the head, neck, body, and two processes: posterior and lateral. The lateral process of the talus is a wide, triangular-shaped process that slopes down to meet the lateral calcaneus (see Fig. 16.5A ). On the lateral view it is wedge-shaped and articulates superiorly with the fibular surface and inferiorly with the calcaneus, forming the lateral portion of the subtalar joint (see Fig. 16.5A ). The lateral talocalcaneal ligament attaches to the lateral process ( Fig. 16.5B ).

Fig. 16.2, Hindfoot anatomy of the subtalar joint. Note the attachment of the talus to the calcaneus via the (A) talocalcaneal and cervical ligaments and the talus to the navicular via the (A) dorsal and (B) plantar talonavicular ligaments.

Fig. 16.3, Vasculature supply anatomy for the talus. Note contributions from the (A-C) dorsal pedis artery, (A-C) peroneal (artery to the sinus tarsi), (A) artery to the tarsal canal, and (A and C) posterior tibial artery.

Fig. 16.4, Internal vasculature anatomy of the talus.

Fig. 16.5, Anatomy of the talus. Note the (A) predominance of articular surface and (B) laterally the attachment of the talocalcaneal ligament to the lateral process.

The posterior process of the talus originates from the convex-curved posterior half of the talar dome and slopes down and back to form the posterior talar ‘‘beak’’ or the Stieda process. Saraffian calls it the trigonal process. Inferiorly, it is concave and articulates with the posterior subtalar facet of the calcaneus. The posterior process has both a posteromedial tubercle and posterolateral tubercle. In between lies the flexor hallucis longus, which is commonly involved in posterior talar injuries ( Fig. 16.6 ). This posterior process is widely variable in shape, from a short, rounded end to a long ‘‘beak’’ that is prone to injury.

Fig. 16.6, Posterior anatomy of the talus. Note the (A) posterior process of the talus, the (B) flexor hallucis longus between the two tubercles of the posterior talus, and (C) the posterior ligamentous anatomy.

The posterolateral tubercle (Stieda’s process) is larger than the posteromedial tubercle. In approximately 7% to 10% of humans a separate os trigonum may exist, connected to the posterolateral tubercle by a fibrous cartilaginous synchondrosis ( Fig. 16.7A and B). The posterior talofibular ligament attaches the fibula, to the posterolateral tubercle, or the os trigonum (see Fig. 16.7B ). The posterior third of the deltoid or posterior talotibial ligament attaches the posterior tibia to the posteromedial tubercle of the talus. The Y-shaped transverse or bifurcate talocalcaneal ligament is a thickening in the posterior ankle capsule that holds the two tubercles together and restrains the flexor hallucis longus ( Fig. 16.8 ). Hallux saltans can develop at this site due to a stenosing tenosynovitis of the flexor hallucis longus that creates pain and triggering.

Fig. 16.7, (A) Lateral view. Anatomy of the os trigonum. Note that the os trigonum is the posterior process that is attached to the talus via a synchondrosis and (B) is attached to the posterior talofibular ligament (axial view).

Fig. 16.8, Anatomy of the posterior hindfoot, including the ankle and subtalar joint. a = tibia; b = fibula; C = calcaneus; d = talus; e = medial talar process; f = lateral talar process; g = posterior tibiotalar ligament; h = posterior talofibular ligament; i = calcaneofibular ligament; j = fibrous tunnel for passage of the flexor hallucis longus tendon

The calcaneus is a complex, bony structure, the largest in the foot, providing attachment for the Achilles posteriorly and the plantar fascia and plantar intrinsic muscles of the foot inferiorly. It articulates with the talus superiorly, as well as with the cuboid and navicular anteriorly. The peroneal tubercle is prominent laterally and serves as a point at which the peroneal longus and brevis tendon sheath separate. The anterolateral process of the calcaneus extends forward to form the calcaneocuboid joint. The saddle-shaped anterior surface articulates with the cuboid anteriorly, and the superior tip articulates to a varying degree with the lateral navicular. The extensor digitorum brevis also originates from this calcaneal process. The blood supply to the calcaneus is quite robust, and fractures of the calcaneus tend to heal more easily than other fractures. The ligamentous attachments at the calcaneus are the talocalcaneal interosseous ligament, lateral talocalcaneal ligament, and cervical ligament to the talus and the calcaneofibular ligament laterally ( Fig. 16.9 ). The posterior, lateral, and anterior calcaneocuboid ligaments and the plantar calcaneonavicular (spring ligament) and lateral calcaneonavicular ligaments connect the calcaneus anteriorly to the cuboid and navicular, respectively. The strong plantar calcaneonavicular or ‘‘spring’’ ligament acts as a ‘‘sling’’ to hold the talar head in place. The bifurcate ligament (Y-ligament) is composed of the anterior and lateral calcaneocuboid ligament ( Fig. 16.10A and B) and is commonly injured during ‘‘sprain-type’’ inversion injuries, producing an avulsion fracture at the anterolateral process of the calcaneus. Inversion/adduction injuries of the midfoot also may produce avulsion fractures at the base of the cuboid.

Fig. 16.9, Calcaneal ligaments. Note laterally the calcaneofibular, cervical, and lateral talocalcaneal ligaments.

Fig. 16.10, Lateral plantar transverse tarsal ligaments.

The saddle-shaped cuboid forms the base of the lateral column and articulates with the anterior process of the calcaneus and may be involved in either compression or avulsion tension-type injuries. The peroneus longus tendon courses along the lateral border of the cuboid.

The tarsal navicular is a ‘‘C’’ or saucer-shaped bone articulating with the talus posteriorly and the cuboid laterally. The dorsal talonavicular ligament and capsule can be injured in avulsion-type injuries of the navicular from plantarflexion-type injuries. Compression-type injuries also may be produced by the impact of the talar head on the navicular. The blood supply to the midportion of the navicular is poor ( Fig. 16.11 ) and may contribute to delayed healing or nonunion of such fractures. The articulation between the cuboid and the navicular varies from a true articulating joint to a fibrous connection to a bony bridge (tarsal coalition). Various important and powerful tendons attach to the hindfoot; these produce considerable forces during athletic activities and can create injuries. The posterior tibial tendon attaches to the navicular ( Fig. 16.12A and B), producing inversion/supination and adduction while elevating the arch. It fires twice during each gait cycle or step—both eccentrically as a shock absorber and concentrically during push-off. The anterior tibial tendon, with attachments to the cuneiform and first metatarsal, is the primary dorsiflexor for the ankle and also inverts the foot. It also fires eccentrically during heel strike to decelerate and cushion the landing foot. The peroneus brevis and longus tendons ( Fig. 16.13 ) both evert the foot and ankle and resist inversion injuries. The peroneus brevis attaches to the base of the fifth metatarsal. The peroneus longus wraps around the cuboid at the trochlea to insert broadly underneath the foot near the base of the first metatarsal, which allows the longus also to help plantarflex and stabilize the medial foot.

$Fig. 16.11, Vasculature anatomy of the tarsal navicular. Note the central area of decreased blood supply corresponding to areas of navicular stress fractures.$

Fig. 16.12, Posterior tibial tendon anatomy. Note the attachment to the medial navicular, medial cuneiform, and lateral cuneiform that produces inversion, supination, and adduction.

Fig. 16.13, Anatomy lateral ankle depicting peroneus longus and brevis tendons.

Occult Fractures of the Calcaneus

The majority of fractures of the calcaneus occur from high- energy trauma, such as a motor vehicle accident or a fall from height, but there are many commonly missed calcaneal fractures and related injuries seen in the sporting population.

Sustantaculum Tali Fractures

Mechanism of Injury

Sustantaculum tali fractures are rare, extra-articular fractures of the calcaneus. The sustantaculum tali is a medial projection of the calcaneus that serves as an attachment of the plantar calcaneonavicular ligament (spring ligament) and for the deltoid ligament. It is also important in that the flexor hallucis longus tendon runs in a plantar groove of the sustantaculum tali. Fractures of this can lead to subtalar joint discordance that can possibly lead to subtalar joint and hindfoot stiffness, flexor hallucis longus (FHL) entrapment, and medial sided ankle pain. Isolated fractures are rare but can occur with a direct trauma or a fall onto an axial loaded, rotated foot and can be associated with a talus fracture. Misdiagnosis of this fracture can lead to a nonunion, tarsal tunnel syndrome, chronic FHL impingement, and progressive pes planovaglus deformity.

Presentation and Physical Exam

The patient will often present with medial sided ankle pain, swelling, and ecchymosis. One should assess the flexor hallucis longus for direct trauma to the tendon or entrapment.

Imaging

Plain foot and ankle radiographs may show a normal Bohler’s angle; however, a Harris axial x-ray can often assist with the diagnosis and show the fracture. CT is most useful to identify the fracture displacement and determine the need for surgical management.

Treatment

Operative management of these fractures should be considered in cases of any displacement. Open reduction internal fixation of these fractures is best done with a direct medial approach and lag screw construct with a cannulated partially threaded screw fixation while protecting the FHL and neurovascular bundle.

Rehabilitation and Return to Sports

Rehabilitation will usually consist of nonweight bearing in a splint or cast for the first month, followed by a boot and nonweight bearing until 6 weeks postop. Thorough follow-up with axial Harris x-rays will allow one to determine union (or a CT scan if the plain imaging is inconclusive) and the beginning of weight bearing. The athlete should focus on joint mobilization and specifically focus on the FHL tendon to prevent adhesions.

Anterolateral Process of the Calcaneus Fractures

Mechanism of Injury

The anterior process of the calcaneus makes up 23% of fractures of the calcaneus. The injury occurs via an inversion injury mechanism with the ankle in plantarflexion, which can lead to an avulsion injury at the tip of the anterolateral process through tension of the bifurcate ligament that connects the anterior process to the cuboid and navicular ( Fig. 16.14 ).

Fig. 16.14, Diagram of right foot demonstrating supination and inversion of hindfoot causing avulsion of anterior process of calcaneus with tension on bifurcate ligament.

A second injury mechanism is forced dorsiflexion, eversion, abduction injury leading to a compression fracture of the anterior process between the cuboid and talus.

Presentation and Physical Exam

When an athlete presents with pain over the hindfoot following a mechanism of injury as stated above, it is crucial to have a high level of suspicion to avoid delayed diagnosis of the fracture. Typically, the patient will present with ecchymosis and swelling with tenderness 2 cm anterior and 1 cm inferior to the ATFL ( Fig. 16.15 ). Often pain may be produced by inversion stress through the subtalar joint (distracting the fragment). There may be instability of the transverse tarsal joint, which is tested by holding the heel stable with one hand and pronating and supinating the midfoot with the other hand ( Fig. 16.16A and B ).

$Fig. 16.15, Clinical photograph of right foot demonstrating area of hindfoot that is tender with underlying anterior process fracture of calcaneus.$

Fig. 16.16, Clinical photograph of right foot demonstrating assessment of transverse tarsal instability by stressing the hindfoot in (A) supination and (B) pronation.

Imaging

X-rays may present as negative if the fracture is nondisplaced. If displaced, the fracture through the tip of the anterolateral process of the calcaneus is best seen with the bean directed 20 degrees superior and posterior to the midportion of the foot ( Fig.16.17 ).

$Fig. 16.17, Lateral radiograph of hindfoot demonstrating small anterior process fracture (arrows) of calcaneus.$

A CT scan is useful to evaluate displacement of the fracture, and in severe cases, the advanced imaging is necessary to plan for surgical management. ( Fig. 16.18A-C )

$Fig. 16.18, (A) Sagittal reconstruction, (B) coronal, and (C) axial computed tomography view of occult anterior process fracture (arrows) of calcaneus. Plain radiographs did not reveal fracture, but athlete had tenderness over anterior process.$

Classification

Degan et al. proposed the following classification for fractures of the anterior lateral process of the calcaneus, which is useful in the diagnosis and treatment ( Table 16.1 ).

Table 16.1

Classification of Fractures of the Anterior Process of the Calcaneus

Type I	Nondisplaced tip avulsion
Type II	Displaced avulsion fracture not involving the calcaneocuboid articulation
Type III	Displaced, larger fragments involving the calcaneocuboid joint

Treatment

Small nondisplaced fractures and those less than 2 mm can be treated in a cast and boot for 6 weeks of nonweight-bearing management until the fracture has fully healed.

In cases of chronic nonunion of the anterolateral process of the calcaneus, asymptomatic athletes are treated with observation only. For large fragments, greater than 1 cm or involving a significant portion of the articular surface, the fracture site is debrided and internal fixation is applied. For smaller fragments, the fragment is excised. The calcaneocuboid joint is inspected and debrided if necessary. The bifurcate ligament may be repaired back to the calcaneal process if any instability of the transverse tarsal joint exists (though this is not common).

For cases of malunited fractures, arthritic changes in the superior portion of the calcaneocuboid joint and/or the junction between the process of the calcaneus and navicular may exist. In these cases, a trial injection of cortisone in the calcaneocuboid joint and calcaneonavicular space may provide relief or help to establish the diagnosis of arthritic changes. Surgical treatment involves open resection of a portion of the anterolateral process of the calcaneus, trimming it back to a point at which a healthy calcaneocuboid joint is present. Recently, arthroscopic resection through a subtalar approach has been described. We prefer a limited debridement of the area and arthroscopic excision of the nonunion. If the fracture is quite large, a small open incision is made rather than arthroscopically removing a large amount of soft tissue to gain access to the anterior subtalar joint.

Rehabilitation and Return to Sports

In cases in which excision is required, boot immobilization and nonweight bearing are used for 2 weeks, followed by gentle active range of motion (AROM) of the foot and protected weight bearing in the boot for an additional 4 weeks. General ankle rehabilitation then is begun, followed by sports-specific exercises.

Athletes with anterolateral process fractures treated by open reduction internal fixation (ORIF) or excision and ligament repair are placed in a nonweight-bearing boot for 6 weeks until healed. They then begin general ankle rehabilitation followed by sports-specific exercises. Return to sports usually occurs within 8 to 12 weeks.

OS Peroneum Avulsion Fractures(See also Chapter 8 )

Mechanism of Injury

Os perineum fractures are a rare but often overlooked diagnosis in athletes that can be associated with complete rupture of the peroneus longus tendon and requires a high index of suspicion. The os peroneum is a sesamoid bone that can be found in the peroneus longus tendon, often found adjacent to the plantar-lateral aspect of the cuboid. It has been reported in 5% to 26% of the population. It is important to recognize this injury early to plan for management of an associated tendon injury.

Presentation and Physical Exam

Patients will often present after an inversion ankle injury with a swollen, painful, and occasionally ecchymotic foot and ankle. Clinicians will observe point tenderness plantar-laterally along the inferior lateral cuboid area and pain with inversion and eversion of the hindfoot.

Imaging

Plain x-rays will reveal a proximally migrated bony fragment that may be misread as a “benign” avulsion, or different accessory ossicles. Radiographic features of an acute fracture of the os peroneum will demonstrate the presence of “cortical discontinuity with nonsclerotic margins” and a “pieces of a puzzle” appearance. A normal-appearing os perineum will appear as an oval, well-corticated ossicle near the calcanealcuboid joint.

MRI imaging is essential to evaluate the appearance and possible retraction of the peroneus longus tendon and rule out any other surrounding soft tissue injury. A retracted os peroneum is highly suggestive of a complete peroneus longus rupture.

Treatment

Treatment for an os peroneum fracture can include nonoperative management when the os perineum fracture is minimally displaced. Excision of the ossicle with primary repair of the peroneal longus or tenodesis of the peroneus longus to the brevis is most often the preferred method for managing this injury in the athlete. Repair or tenodeses helps the athlete to avoid loss of eversion strength, and first metatarsal plantarflexion strength. Postoperatively, the ankle is immobilized in a cast nonweight bearing for 3 weeks in slight eversion, followed by a boot or cast for another 3 weeks. Therapy will begin at 6 weeks with the focus on ankle and subtalar mobilization.

Occult Fractures of the Cuboid

Mechanism of Injury

Midfoot injuries, specifically of the cuboid, are rare in the athlete, but can often be overlooked as a midfoot sprain. They can be observed in two different variants in athletes: as either a capsular avulsion injury or a compression cuboid injury. Capsular avulsion injuries are seen during an adduction/inversion injury when the patient lands in plantarflexion. This is common in sports like basketball, volleyball, and dancing. In an avulsion cuboid injury, the calcaneocuboid capsule and plantar calcaneocuboid ligament are torn producing a small avulsion fragment off the plantar posterior cuboid. Alternatively, a compression injury can occur, creating a nutcracker mechanism of acute compression of the cuboid between the anterior process of the calcaneus and the base of the fourth and fifth metatarsal, accompanied by medial column distraction injury of the midfoot. It is important to rule out injuries to the Chopart joint in this situation, which can be seen by widening of the talonavicular joint.

Presentation and Physical Exam

The patient will typically present with lateral foot pain (just proximal to the insertion of the peroneus brevis), ecchymosis, and swelling with difficulty walking, especially with plantar-flexion.

Imaging

X-rays can show a small lateral cuboid avulsion injury or will reveal compression fractures ( Fig. 16.19 ). CT scan imaging is best used to more clearly visualize the fracture, its pattern and its extent. CT imaging can help establish the extent of fracture and the amount of joint depression that can be involved with the impaction injury.

$Fig. 16.19, Oblique radiograph of foot demonstrating small fracture of cuboid.$

Treatment

Surgery will be required when there is significant shortening of the cuboid in an impaction injury. Surgery is also required if displacement results in destabilization of the lateral column. This can be performed with mini-fragment screws with or without bone graft and plating to restore the lateral column.

Conservative management is typically used to treat most types of painful cuboid injuries. Cast and boot treatment are preferred with pain and a return to sports is advised when the patient is pain free.

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