Process and Tubercle Fractures of the Hindfoot Abstract Process and tubercle fractures of the talus and calcaneus can be a source of significant pain and dysfunction. Successful management requires extensive knowledge of the complex osseoligamentous anatomy of the hindfoot. The large posterior process of the talus is composed of a medial and a lateral tubercle; an os trigonum may exist posterior to the lateral tubercle. The talus has a lateral process that articulates with the fibula and subtalar joint; the calcaneus possesses a frequently injured anterior process that articulates with the cuboid. Injury to these hindfoot structures is caused by inversion and eversion of the ankle, which can occur during athletic activity. These injuries often are misdiagnosed as ankle sprains. A high degree of clinical suspicion is warranted, and specialized radiographs or other imaging modalities may be required for accurate diagnosis. Nonsurgical management with cast immobilization is frequently successful when the fracture is correctly diagnosed acutely. Large fragments may be amenable to open reduction and internal fixation. Untreated, chronic injuries can cause significant pain and functional impairment that may be improved substantially with late surgical intervention. T he calcaneus and talus are the most frequently fractured tarsal bones. 1 Most attention in the ortho- paedic literature has been devoted to fractures of the neck of the talus and the posterior facet of the calcaneus. Other hindfoot fractures have not been as well studied; fractures in- volving the peripheral processes and tubercles of the talus and calcaneus have been relatively neglected. Con- sequently, questions persist regard- ing these fractures. The mechanisms of injury remain incompletely un- derstood, and misdiagnosis is not uncommon. Uncertainty persists re- garding optimal treatment and prog- nosis. In treating patients with hind- foot symptomatology, it is helpful to have an organized approach to eval- uating and managing the most com- mon process and tubercle fractures of the hindfoot, including the later- al and posterior processes of the ta- lus, the medial and lateral tubercles of the posterior talus, the os tri- gonum, and the anterior process of the calcaneus. Anatomy The osseoligamentous anatomy of the hindfoot is complex and often confusing (Figure 1). Several process- es and tubercles project from the main body of the talus and calca- neus. These structures serve as sites of ligamentous attachment and con- tribute to the subtalar and calca- neocuboid articulations. Because Mark J. Berkowitz, MD, MAJ, MC, USA, and DavidH.Kim,MD Dr. Berkowitz is Chief, Foot and Ankle Section, Orthopaedic Surgery Service, Tripler Army Medical Center, Honolulu, HI. Dr. Kim is Assistant Clinical Professor, Orthopaedic Surgery, University of Colorado School of Medicine, Denver, CO, and Orthopaedic Foot and Ankle Surgeon, Colorado Permanente Medical Group, Denver. None of the following authors or the departments with which they are affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Berkowitz and Dr. Kim. Reprint requests: Dr. Berkowitz, Tripler Army Medical Center, 1 Jarrett-White Road, Honolulu, HI 96859-5000. J Am Acad Orthop Surg 2005;13:492- 502 Copyright 2005 by the American Academy of Orthopaedic Surgeons. 492 Journal of the American Academy of Orthopaedic Surgeons these osseous projections are located along the periphery of the talus and calcaneus, they are referred to as the peripheral structures of the hind- foot. The talus has five peripheral structures that may be fractured. The two talar processes, the lateral and the posterior, project from the body of the talus. The lateral process is a wide, wedge-shaped prominence extending from the lateral aspect of the body of the talus. 2 It possesses two distinct articular facets: the dor- solateral and the inferomedial. The dorsolateral facet articulates with the distal fibula; the inferomedial facet forms the anterolateral portion of the subtalar joint. The lateral pro- cess is the site of insertion of the lat- eral talocalcaneal ligament. The posterior process is relative- ly large (Figure 1, B), and its inferior surface composes the posterior 25% of the subtalar articulation. 3 It is the most variable aspect of hindfoot anatomy. 4 The posterior process is composed of two tubercles: the me- dial and the lateral. These tubercles are separated by a groove within which lies the flexor hallucis longus tendon. Forming a roof over this groove is the Y-shaped, bifurcate talocalcaneal ligament, which in- serts onto each tubercle. 5 The later- al tubercle (ie, Stieda’s process) is Figure 1 Osseous anatomy of the hindfoot. A, Lateral view of the talus and calcaneus. B, Posterior view of the ankle and hindfoot. C, Superior view of the talus. Mark J. Berkowitz, MD, MAJ, MC, USA, and David H. Kim, MD Volume 13, Number 8, December 2005 493 larger than the medial tubercle and projects more posteriorly. The poste- rior talofibular ligament inserts onto the lateral tubercle of the talus. The posterior talotibial portion of the deltoid ligament attaches to the me- dial tubercle. The os trigonum is located direct- ly posterior to the lateral tubercle (Figure 1, C). It is an accessory bone of variable size and shape that arises from a secondary ossification center between the ages of 8 and 11 years. In most persons, it fuses to the later- al tubercle within 1 year of its ap- pearance. However, it may persist as a separate ossicle, attached to the ta- lus by a cartilaginous synchondro- sis. 4 Burman and Lapidus 6 observed a distinct os trigonum in 64 of 1,000 radiographs of feet as well as a “fused os trigonum” in the form of an elongated lateral tubercle in 429 of the 1,000 radiographs. The anterior process is the most commonly fractured peripheral structure of the calcaneus. 1 This pro- cess is a saddle-shaped projection of bone at the superior aspect of the calcaneal body that extends toward the navicular 7 (Figure 1, A). Its infe- rior surface articulates with the cuboid. The bifurcate ligament in- serts on the anterior process and connects the cuboid and navicular bones. Additionally, the extensor digitorum brevis muscle takes at least a portion of its origin from the anterior process. Other peripheral structures of the calcaneus include the sustentacu- lum tali, the peroneal tubercle, and the medial and lateral calcaneal tu- bercles. 8 Injuries to these structures are rare. Mechanism of Injury Process and tubercle fractures of the hindfoot occur in two distinct pat- terns. These fractures may be caused by high-energy trauma, such as a fall from a height or a motor vehicle ac- cident. 9 In this setting, they are o ften found concomitantly with fracture- dislocations of the subtalar and an- kle joints. 10 Process and tubercle fractures also may be caused by low- energy sprains, such as those occur- ring during athletic participation. 11 In both types, the position o f the foot and the vector of the forces applied to it are critical in producing the fracture. Fractures of the lateral talar pro- cess initially were believed to occur after forced ankle dorsiflexion and inversion, usually because of a fall o r motor vehicle accident. 9,12,13 Snow- boarding now accounts for most lateral talar process fractures, with approximately 2,000 occur ring an- nually. 14 The mechanism of injury appears to be related to the forces transferred to the ankle while the foot is strapped to the board. Boon et al 2 produced cadaveric “snowboard- er’s fractures” only when external rotation force was applied to the dor- siflexed, inverted foot. Similarly, Funk et al 14 demonstrated that ever- sion of an axially loaded, dorsiflexed ankle may produce a lateral process fracture. The medial tubercle of the poste- rior process may be fractured when the foot is suddenly forced into a po- sition of combined dorsiflexion and pronation. 11,15 This places the poste- rior talotibial component of the del- toid ligament under tension, causing avulsion of the tubercle. In 1974, Cedell 15 originally described this in- jury and its mechanism in four pa- tients injured during sports activity. This injury also has been reported af- ter motor vehicle accidents and falls in association with subtalar disloca- tion, talar neck fracture, and total t a- lar dislocation. 16,17 Fractures of the posterior talar process most likely are caused by forceful plantar flexion of the ankle. Maximum plantar flexion produces a nutcracker-like compression of the posterior process between the poste- rior malleolus and the calcaneus 18,19 (Figure 2). The entire posterior pro- cess, the lateral talar tubercle, or the os trigonum may be injured in this way. The os trigonum may be injured by repetitive plantar flexion, similar to a stress fracture. 20 This injury is often refer red to as either os trigo- Figure 2 Axial (A) and sagittal (B) computed tomography scans demonstrating fracture of the entire posterior process of the talus. Forceful plantar flexion compresses the posterior process of the talus between the calcaneus and the tibia, resulting in fracture (arrows). Process and Tubercle Fractures of the Hindfoot 494 Journal of the American Academy of Orthopaedic Surgeons num syndrome or posterior ankle impingement. It is seen most often in professional ballet dancers, soccer players, and runners. 19,21,22 More commonly, the synchondrosis is acutely disrupted by a plantar flex- ion–inversion mechanism, similar to an ankle sprain. 21,23 This same mechanism also may cause a frac- ture of the lateral tubercle of the pos- terior talar process. Ankle inversion tensions the posterior talofibular lig- ament, producing avulsion of the lat- eral tubercle (Figure 3). Shepherd first described this fracture and mechanism in 1883, and some au- thors still refer to it as “Shepherd’s fracture.” 24 Fractures of the anterior calcaneal process also occur after inversion of the plantarflexed ankle. 7 This mech- anism of injury stretches the bifur- cate ligament and avulses the anteri- or process. Alternatively, forced dorsiflexion and eversion may com- press the anterior process between the cuboid and the talus, resulting in a shear fracture 7 (Figure 4). Diagnosis A high level of suspicion is required when diagnosing process and tuber- cle fractures of the hindfoot. These fractures can be challenging to dis- cern on standard radiographs and physical examination. Unfortunate- ly, misdiagnosis and delayed diagno- sis are frequent complications. 25 Lateral talar process fractures mimic lateral ankle sprains. 13,19,26 Missed lateral talar process fractures were found retrospectively in 0.86% of patients initially diagnosed as having a lateral ankle sprain (13/ 1,500 patients). 13 In a series of 25 an- terior calcaneal process fractures, the diagnosis was initially incorrect in 9 patients, with 7 initially mis- diagnosed with a sprain of the an- terior talofibular ligament. 7 In Figure 3 A, Lateral view of the ankle (taken for unrelated reasons before injury) demonstrat- ing an intact lateral tubercle of the posterior process of the talus. B, Repeat lateral radiograph of the same patient after a plantar flexion–inversion injury demonstrating fracture of the lateral tubercle with angulation of the fragment (arrow). Figure 4 Mechanism of injury of a fracture of the anterior process of the calcaneus. A, Inversion of the plantarflexed ankle (arrow) results in anterior process avulsion by the bifurcate ligament (inset). B, Dorsiflexion and eversion (arrow) may create a shear fracture of the anterior process of the calcaneus (inset). (Courtesy of the Mayo Foundation. Copyright 1980.) Mark J. Berkowitz, MD, MAJ, MC, USA, and David H. Kim, MD Volume 13, Number 8, December 2005 495 Cedell’s 15 original article on frac- tures of the medial tubercle of the posterior talar process, each of the four patients was initially misdiag- nosed with a sprain and treated with a compression bandage and rest. Paulos et al 5 reported on 20 patients with avulsion fractures of the poste- rior talus, all of which were initially diagnosed as ankle sprain. The aver- age number of physician visits per patient before correct diagnosis was made was 5.8; one patient was seen 17 times. Failure to diagnose also occurs with multiple trauma. Process and tubercle fractures occur in associa- tion with significant lower extremi- ty injuries, such as subtalar and an- kle fracture-dislocations, total talar dislocations, and lower extremity long bone fractures. 17,27,28 In treating these injuries, process or tubercle fractures may be easily missed. Un- fortunately, delayed detection of these fractures increases the likeli- hood of painful nonunion and ar- throsis. 7,11,17 Physical Examination The initial step in diagnosing these fractures is eliciting the mech- anism of injury. The position of the foot and the force applied should raise suspicion that a particular frac- ture may have occurred. Once the mechanism of injury has been deter- mined, a focused physical examina- tion is performed to elicit the maxi- mal point of tenderness. The maximal point of tenderness repre- sents the most important diagnostic feature in distinguishing a peripher- al fracture from an uncomplicated ankle sprain. 11 It can be difficult to discern in a patient with an acute, swollen ankle, and the patient may need to be reexamined 10 to 14 days later. Lateral talar process fractures can be particularly difficult to differenti- ate from sprains on physical exami- nation. However, careful palpation just anterior and inferior to the later- al malleolus should raise suspicion of this injury. The patient with pos- terior process fracture demonstrates deep tenderness anterior to the Achilles tendon but posterior to the talus. Fracture of the lateral tubercle of the posterior talar process and of the os trigonum provokes point ten- derness over the posterolateral an- kle, just medial to the peroneal ten- dons. Fracture of the medial tubercle of the posterior talar process demon- strates localized tenderness medial- ly, just posterior to the medial mal- leolus. 11 Forced plantar flexion is another important test. The patient with posterior talar process or os trigo- num fracture frequently reports pain when the posterior talus is com- pressed against the tibia during this maneuver. Likewise, resisted mo- tion of the great toe can elicit pain as the flexor hallucis longus tendon slides past a medial or lateral tuber- cle fracture of the posterior talar pro- cess. 5 Anterior calcaneal process frac- ture usually produces tenderness in an area approximately 2 cm anterior and 1 cm inferior to the anterior talofibular ligament. 7 Swelling and ecchymosis localized to this area are signs of anterior calcaneal process fracture. Radiographic Evaluation Radiographs must be carefully scrutinized to ensure prompt and ac- curate diagnosis of process and tu- bercle fractures. As mentioned, these fractures are difficult to detect on standard plain radiographs; there- fore, the use of specialized oblique radiographs, computed tomography (CT), magnetic resonance imaging (MRI), or bone scans may be re- quired. Plain Radiographs Lateral talar process fractures are best seen on mortise or anteroposte- rior ankle radiographs, in which a fragment just inferior to the lateral malleolus can be visualized 2,13 (Fig- ure 5). Occasionally, an avulsed frag- ment is visible on a lateral radio- graph. Dorsiflexing and inverting the ankle while taking the lateral radio- graph may further improve visual- ization of the fragment. 29 Posterior talar fractures are par- ticularly difficult to detect and dif- ferentiate on standard radiographs. Large posterior process fractures may demonstrate a prominent frac- ture line on a standard lateral radio- graph, but distinguishing between medial and lateral tubercle frac- tures and differentiating them from a normal os trigonum can be chal- lenging. 17 Paulos et al 5 described us- ing a special 30° subtalar oblique view to better visualize lateral tu- bercle and os trigonum fractures. Kim et al 30 likewise used a medial oblique view to evaluate suspected posteromedial talus fractures (Fig- ure 6). Anterior calcaneal process frac- tures are not well visualized on stan- dard anteroposterior views of the foot or ankle. A lateral radiograph may reveal the fracture, but direct- ing the beam 20° superior and poste- rior to the midportion of the foot can project the anterior process away from the neck of the talus, enabling Figure 5 Anteroposterior radiograph of the ankle demonstrating a fracture of the lateral process of the talus, which is visible just inferior to the lateral malleolus. Process and Tubercle Fractures of the Hindfoot 496 Journal of the American Academy of Orthopaedic Surgeons visualization of the fracture 7 (Fig- ure 7). Computed Tomography When clinical suspicion is high but radiographs are negative, CT scans are very useful for detecting hindfoot process and tubercle frac- tures. Multiplanar CT imaging with fine 1-mm cuts allows accurate as- sessment of fragment location, size, displacement, and comminution 10 (Figure 8). Additionally, CT provides adequate cortical detail to distin- guish the smooth, sclerotic margins of an os trigonum from the jagged, ir- regular contour of an acute lateral tubercle fracture. This important distinction is frequently not possible with standard lateral radiographs. CT is also sensitive for early degen- erative changes that may not be de- tectable on plain radiographs. 21,31 CT especially should be considered when subtalar dislocation is suspect- ed. 28 Subtalar dislocation rarely oc- curs in isolation, and CT often re- veals associated process or tubercle fractures not visualized on plain ra- diographs. 17 Ebraheim et al 10 used CT to eval- uate 10 patients with fracture of the talus. Eight process or tubercle frac- tures were initially identified on plain radiographs, but CT was re- quired to determine size, displace- ment, subtalar joint involvement, and treatment. Two fractures initial- ly missed on plain radiographs were diagnosed using CT 6 months and 1 year, respectively, after injury. In several cases, the surgical approach was determined based on the CT findings. Magnetic Resonance Imaging The ability of fluid-sensitive mag- netic resonance sequences to dem- onstrate edema adjacent to injured structures makes it a useful modal- ity, particularly in the chronic set- ting 32,33 (Figure 9). Wakeley et al 32 performed sagittal and coronal spin- echo sequences on three patients with chronic posterior ankle pain. Based on the MRI results, os trigo- num syndrome was accurately diag- nosed in each case. Sanders et al 33 re- ported on a 59-year-old man who underwent MRI for evaluation of Figure 8 Axial computed tomography scan demonstrating a fragment medial to the flexor hallucis longus groove (arrow), consistent with a fracture of the medial tubercle of the posterior process of the talus. Compare with the lateral radiograph in Figure 6, A, in which it is difficult to determine whether there is an os trigonum, a lateral tubercle fracture, a medial tubercle fracture, or a posterior process fracture. Figure 6 A, Lateral radiograph demonstrating nonspecific fracture of the posterior process of the talus. B, Medial oblique view demonstrating avulsion fracture of the medial tubercle fracture of the posterior process of the talus (arrow). (Reproduced with permission from Kim DH, Hrutkay JM, Samson MM: Fracture of the medial tubercle of the posterior process of the talus: A case report and literature review. Foot Ankle Int 1996;17:186-188.) Figure 7 Oblique lateral view allowing visualization of fracture of the anterior process of the calcaneus (arrow). Mark J. Berkowitz, MD, MAJ, MC, USA, and David H. Kim, MD Volume 13, Number 8, December 2005 497 chronic lateral ankle pain. MRI re- vealed a previously undetected later- al talar process fracture for which the patient eventually underwent surgical excision. MRI also may pro- vide useful information regarding adjacent soft-tissue structures, such as tenosynovitis of the flexor hallu- cis longus tendon or peroneal tendi- nopathy. Nuclear Medicine Imaging Technetium Tc-99m bone scan- ning is another important technique for evaluation of hindfoot process and tubercle fractures. 21,22 In the presence of an acute or chronically symptomatic fracture, a bone scan demonstrates an area of focal radio- isotope uptake. This may be useful in detecting occult fractures and in distinguishing fractures from nor- mal ossicles 34 (Figure 10). Paulos et al 5 consider technetium Tc-99m bone scanning to be the de- finitive test for diagnosing occult fractures of the posterior talus. They found it particularly useful for differ- entiating an acute lateral tubercle fracture from a normal os trigonum. Abramowitz et al 21 likewise report- ed that 32 of 35 patients with os trig- onum injury demonstrated increased focal uptake in the posterolateral as- pect of the talus on bone scan. However, bone scanning may in- dicate false positives and false nega- tives. Sopov et al 35 evaluated the scintigraphic findings of 100 consec- utive soldiers. Of 200 feet, 27 (13.5%) demonstrated uptake in the region of the os trigonum; however, only 10 of the 27 feet (37%) were symptomatic. They concluded that a positive Tc-99m bone scan is a fre- quent finding in active individuals and may even be considered a nor- mal variant in this population. Sim- ilarly, i n three patients with negative bone scans, Abramowitz et al 21 iden- tified and removed symptomatic os trigonum with excellent results, leading the authors to reject the no- tion that a normal bone scan elimi- nates the possibility of os trigonum injury. Fluoroscopic Injection Injection of lidocaine under fluo- roscopic guidance is another useful diagnostic tool. 34 When physical ex- amination reveals a point of maxi- mum tenderness suspicious of a process or tubercle fracture, a fluoro- scope can be used to precisely guide the placement of local anesthetic. Significant relief of symptoms after injection strongly points to that structure as the source of pain. A flu- oroscopically guided injection also may have predictive value with re- spect to surgical treatment. Jones et al 36 used fluoroscopic injection of lidocaine into the synchondrosis of Figure 9 Sagittal T2-weighted magnetic resonance image of a patient with chronic posterior ankle pain demonstrating intraosseous edema in the os trigonum and adjacent talus and calcaneus (asterisks), which is consistent with posterior ankle impingement. Figure 10 Lateral projection in a patient with an os trigonum demonstrating focal intense radioisotope Tc-99m uptake in the posterior aspect of the talus and adjacent tibia as well as in the calcaneus, consistent with os trigonum syndrome. Process and Tubercle Fractures of the Hindfoot 498 Journal of the American Academy of Orthopaedic Surgeons an os trigonum in four patients with chronic posterior ankle pain. Each patient experienced transient pain relief and subsequently underwent excision of the os trigonum with complete resolution of symptoms. Management The optimal management of process and tubercle fractures remains con- troversial. Relatively simple classifi- cation schemes have been proposed to help guide treatment (Tables 1 and 2). The most critical factors in- clude the size of the fragment, dis- placement, comminution, and de- gree of articular involvement. 7,14 Nonsurgical Management Nonsurgical management should be considered for acute process and tubercle fractures with small (<1 cm), minimally displaced (<2 mm) fragments. 1,8 The small size of the fragment leaves the adjacent articu- lar surface almost completely intact. Therefore, talofibular, subtalar, or calcaneocuboid incongruity usually is not a problem. Nonsurgical man- agement also is appropriate for larg- er fragments that are either non- displaced or minimally displaced. These fractures are likely to heal or result in a stable, asymptomatic fi- brous union. 11 When these requirements are met, immobilization in a below- knee, non–weight-bearing cast can result in a favorable outcome. 5,7,9,30 Generally, 6 weeks of non–weight- bearing and cast immobilization is recommended. When the patient is asymptomatic after 6 weeks, transi- tion into a removable walking boot and progressive weight bearing with crutches is allowed. When the pa- tient remains symptomatic after 6 weeks of protected weight bearing and immobilization, continued re- striction of activity may be warrant- ed for several months. Early diagnosis and management of hindfoot process and tubercle frac- tures appear to be critical factors af- fecting the success of nonsurgical management. 1,5,7,9,11,26,29,30 Degan et al 7 successfully used immobilization for a mean of 5.4 weeks to treat 18 of 25 patients with early diagnosed acute anterior calcaneal process frac- tures. A satisfactory result consist- ing of no or minimal pain and full re- turn to activity was achieved in those 18 patients. Kim and colleagues 11,30 described successful management of acutely diagnosed posterior medial talar tu- bercle fractures. The patients under- went immediate immobilization in a non–weight-bearing cast for an aver- age of 6 weeks. At 2-year follow-up, the average AOFAS ankle-hindfoot score was 95 of a total of 100 points. One patient who healed with a radio- graphic fibrous union nevertheless achieved a score of 97. 11 Certain peripheral hindfoot frac- tures do less well with nonsurgical management. 5,7,9-11,13,16,17,23,37,38 Later- al talar process fractures have been reported to result in generally poor outcomes when managed with casting alone. 9,13,26,39 For this rea- son, Kirkpatrick et al 38 recommend against nonsurgical management of all but the truly nondisplaced later- al talar process fracture. Neverthe- less, fractures that are acute, extra- articular, smaller than 1 cm, and displaced <2 mm may be considered for conservative management with 6 to 8 weeks of immobilization in a non–weight-bearing cast 14 (Figure 11). Large fragments, particularly those resulting from high-energy trauma, do not reliably respond to nonsurgical management. Although Kim and colleagues 11,30 reported suc- cess with nonsurgical treatment of patients with acute posterior medial talar tubercle fractures, Giuffrida et al 17 reported failure in each of their patients despite prompt cast immo- bilization. A comparison of the two series, however, highlights impor- tant differences. Each of the patients in the report by Kim et al 11 sustained low-energy athletic injuries that re- sulted in small avulsion fragments with minimal articular disruption. In the report by Giuffrida et al, 17 six fractures occur red in association with medial subtalar dislocation. This high-energy mechanism pro- duced much larger fracture frag- ments and a high rate of subtalar subluxation and incongruity. This comparison emphasizes that, even for a single type of fracture, no uni- versal treatment prescription can be given. Chronic injuries seem to have the worst outcome when managed with casting. Failure to promptly diag- nose and initiate proper immobiliza- tion frequently results in a chroni- cally painful nonunion. Paulos et al 5 found that only 6 of 17 chronic lateral talar tubercle and os trigo- num injuries responded to a regi- men of rest, nonsteroidal anti- inflammatory drugs, stretching, and activity restriction. In the series of anterior calcaneal process fractures reported on by Degan et al, 7 the Table 1 Classification of Fractures of the Anterior Process of the Calcaneus 7 Type I Nondisplaced tip avulsion Type II Displaced avulsion fracture not involving the calcaneocuboid articulation Type III Displaced, larger fragments involving the calcaneocuboid joint Table 2 Classification of Fractures of the Lateral Process of the Talus 14 Type A Small, minimally displaced, extra-articular avulsion Type B Medium-sized fracture involving only the talocalcaneal articular surface Type C Larger fracture involving both talocalcaneal and talofibular articulations Mark J. Berkowitz, MD, MAJ, MC, USA, and David H. Kim, MD Volume 13, Number 8, December 2005 499 worst outcomes were found in pa- tients with the longest delay in diag- nosis and treatment. Surgical Management Surgical management of hindfoot process and tubercle fractures should be strongly considered for large (>1 cm), displaced (>2 mm) frag- ments with significant articular in- volvement. 1,8 Surgery generally con- sists of open reduction and internal fixation (ORIF) for large fragments, primary excision for highly commi- nuted fractures, and delayed exci- sion for chronic nonunions. The sur- gical approach is tailored to the particular fracture being treated. Open Reduction and Internal Fixation Noncomminuted, displaced frac- tures that compromise articular con- gruity should be considered for pri- mary ORIF. Unreduced large, displaced, articular fragments have a high propensity for nonunion, and the subsequent articular malunion may progress to arthrosis. 12,16,17,29,40 Accurate assessment of fragment size and comminution is necessary to determine whether ORIF is appro- priate and feasible. CT is frequently required to make this determina- tion. CT also precisely localizes the fracture and helps determine the most appropriate surgical ap- proach. 10 Fractures most commonly ame- nable to ORIF include large lateral talar process fractures, medial talar tubercle fractures, and fractures of the entire posterior talar process. Stable fixation usually may be achieved with small or mini- fragment screws or with Kirschner wires. Although anterior calcaneal process fractures may be considered for ORIF, they are rarely of sufficient size to warrant this approach. 7 ORIF has been recommended in several small case series for large, noncomminuted fractures of the lat- eral talar process that disrupt either the talocalcaneal or talofibular artic- ulations. 9,13,26,29,38 Although results of ORIF are considered to be superi- or to those of nonsurgical manage- ment, persistence of symptoms is not uncommon even in fractures managed surgically. 1 The fracture is exposed via an incision over the tar- sal sinus, with distal reflection of the extensor digitorum brevis muscle. ORIF is also the best treatment for medial tubercle fractures of the posterior talus that affect a signifi- cant amount of the subtalar joint. Kanbe et al 41 performed ORIF on two patients with posterior talar medial tubercle fractures. Neither patient reported pain at 2-year follow-up, and radiographs demonstrated no subtalar arthrosis. Conversely, fail- ure to anatomically restore this frac- ture may result in subtalar sublux- ation and arthrosis. 17 This fracture is approached through a posteromedial dissection between the flexor digi- torum longus tendon anteriorly and the neurovascular bundle posterior- ly. 11 The fractured tubercle is visual- ized medial to the tendon of the flex- or hallucis longus. Fracture of the entire posterior talar process is rare, but it frequently requires ORIF because of the relatively large size and signifi- cant involvement of the subtalar joint. 18,42-44 Several case reports doc- ument good results after anatomic fixation of these fractures. 3,18,42-45 Ei- ther a posteromedial or posterolat- eral approach may be used. When the major displacement is posterome- dial, the fracture is approached through a posteromedial dissection between the flexor digitorum longus tendon anteriorly and the neurovas- cular bundle posteriorly. 3 When the major displacement is posterolateral, an approach between the peroneal tendons and the Achilles tendon should be performed. 43 This ap- proach requires identification and protection of the sural nerve. Like- wise, dissection medial to the flexor hallucis longus tendon should be performed cautiously to avoid injury to the medial neurovascular bundle. Figure 11 A, Initial coronal computed tomography scan of a fracture of the lateral process of the talus shown in Figure 5 demonstrating moderate comminution, minimal displacement, and no significant subtalar incongruity. B, Coronal computed tomography scan 6 months later demonstrating healing of the fracture fragments with preservation of subtalar congruity. The patient was asymptomatic. Process and Tubercle Fractures of the Hindfoot 500 Journal of the American Academy of Orthopaedic Surgeons Primary Excision Displaced, intra-articular process and tubercle fractures that are too comminuted to fix internally can be considered for primary excision. Pri- mary excision allows early mobiliza- tion without the risk of developing painful nonunion. 1,8 This approach has been recommended primarily for comminuted fractures of the lateral talar process. 9,13,29 The surgical ap- proach is identical to that for ORIF, except that all loose articular frag- ments are removed. Immobilization usually consists of 2 to 3 weeks in a weight-bearing cast or a removable boot. Late Excision Patients who develop symptom- atic nonunion of a peripheral hind- foot fracture may improve signifi- cantly with late fragment excision. Abramowitz et al 21 excised the os trigonum via a posterolateral ap- proach in 41 patients who had failed nonsurgical management. Improve- ment in the 100-point AOFAS ankle- hindfoot score averaged 36 points, with the best results in patients who had been symptomatic for fewer than 2 years. Marumoto and Fer- kel 31 documented an average 41- point improvement in the AOFAS ankle-hindfoot score after arthro- scopic excision in 11 patients with os trigonum syndrome. Similar im- provement has been repor ted after late excision of the medial tubercle of the posterior talar process and anterior calcaneal process frac- tures. 7,11,23 Results of late excision seem to deteriorate the longer symp- toms have been present. 7,21 Complications The primary complications associat- ed with process and tubercle frac- tures of the hindfoot are chronic pain and late arthrosis. Chronic symptomatic nonunion is particu- larly likely when these fractures are not diagnosed and treated acute- ly. 5,7,11,30 Even when treated appropri- ately, patients may remain symp- tomatic for a prolonged period (up to 2 years in one report 7 ). Persistence of mild pain and stiffness after union also may occur. 1 Although small fractures frequently respond favor- ably to excision, large fracture frag- ments tend to produce articular in- congruity, and arthrosis of the subtalar joint can develop (Figure 12). In these cases, subtalar arthro- desis may be required. 9,16,17 Summary Process and tubercle fractures of the hindfoot are challenging to diagnose and manage. An understanding of the complex anatomy of the hind- foot is required. The clinician must be diligent and knowledgeable in the interpretation of plain radiographs and in the use of additional studies, such as specialized oblique views, CT, MRI, and bone scanning. The most critical prognostic factor is cor- rect initial diagnosis. Prompt man- agement, whether cast immobiliza- tion, ORIF, or primary excision, provides the best opportunity for complete recovery. Delay in diagno- sis increases the likelihood of chron- ic pain and disability. In these pa- tients, late excision can provide significant improvement in symp- toms, but arthrodesis of the involved joints also may be considered. Im- proved understanding of peripheral hindfoot anatomy and injury pat- terns should increase physician awareness of and vigilance for these fractures. References 1. Heckman J: Fractures of the talus, in Bucholz R, Heckman J (eds): Rock- wood and Green’s Fractures in Adults, ed 5. Philadelphia,PA: Lippin- cott Williams & Wilkins, 2001, vol 2, pp 2091-2132. 2. Boon AJ, Smith J, Zobitz ME, Amrami KM: Snowboarder’s talus fracture: Mechanism of injury. Am J Sports Med 2001;29:333-338. 3. Nadim Y, Tosic A, Ebraheim N: Open reduction and internal fixation of fracture of the posterior process of the talus: A case report and review of the literature. Foot Ankle Int 1999;20: 50-52. 4. Grogan DP, Walling AK, Ogden JA: Anatomy of the os trigonum. J Pediatr Orthop 1990;10:618-622. 5. Paulos LE, Johnson CL, Noyes FR: Posterior compartment fractures of the ankle: A commonly missed ath- letic injury. Am J Sports Med 1983; 11:439-443. 6. Burman MS, Lapidus PW: The func- tional disturbances caused by the in- constant bones and sesamoids of the foot. Arch Surg 1931;22:936-975. 7. Degan TJ, Morrey BF, Braun DP: Sur- gical excision for anterior-process fractures of the calcaneus. J Bone Joint Surg Am 1982;64:519-524. 8. Fitzgibbons T, McMullen S, Mormino M: Fractures and dislocations of the calcaneus, in Bucholz R, Heckman J (eds): Rockwood and Green’s Frac- tures in Adults, ed 5. Philadelphia, PA: Lippincott Williams & Wilkins, 2001, vol 2, pp 2131-2179. 9. Hawkins LG: Fracture of the lateral process of the talus. J Bone Joint Surg Figure 12 Coronal computed tomography image demonstrating sclerosis, subchondral cysts, and irregularity of the subtalar and talofibular articulations of the lateral process of the talus. These findings are consistent with degenerative arthrosis (arrows). Mark J. Berkowitz, MD, MAJ, MC, USA, and David H. Kim, MD Volume 13, Number 8, December 2005 501 . scan elimi- nates the possibility of os trigonum injury. Fluoroscopic Injection Injection of lidocaine under fluo- roscopic guidance is another useful diagnostic tool. 34 When physical ex- amination. predictive value with re- spect to surgical treatment. Jones et al 36 used fluoroscopic injection of lidocaine into the synchondrosis of Figure 9 Sagittal T2-weighted magnetic resonance image of a patient. the relatively large size and signifi- cant involvement of the subtalar joint. 18,42-44 Several case reports doc- ument good results after anatomic fixation of these fractures. 3,18,42-45 Ei- ther a posteromedial