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FOOT & ANKLE INTERNATIONAL Copyright  2009 by the American Orthopaedic Foot & Ankle Society DOI: 10.3113/FAI.2009.1037 Fractures of the Sustentaculu...

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FOOT & ANKLE INTERNATIONAL Copyright  2009 by the American Orthopaedic Foot & Ankle Society DOI: 10.3113/FAI.2009.1037

Fractures of the Sustentaculum Tali: Injury Characteristics and Surgical Technique for Reduction Gregory J. Della Rocca, MD, PhD; Sean E. Nork, MD; David P. Barei, MD, FRCSC; Lisa A. Taitsman, MD; Stephen K. Benirschke, MD Seattle, WA

ABSTRACT

involving distal retraction of the digital flexors and neurovascular bundle, allowing for an anatomical extraarticular cortical reduction.

Background: The sustentaculum tali of the calcaneus is a vital load-bearing structure. Isolated sustentacular fractures are rare and may have implications for future hindfoot function. This retrospective cohort study describes sustentacular fracture patterns and characteristics, associated foot injuries, and a method of surgical treatment via a medial approach to the calcaneus. Materials and Methods: During a 7-year period, 19 surgically-treated sustentacular fractures without calcaneal posterior facet involvement were identified from a prospectively-collected database at a single Level 1 regional trauma center. Of these, 15 underwent open reduction and internal fixation utilizing a medial approach to the calcaneus. Patient charts, plain radiographs, and CT scans were reviewed for injury characteristics/morphology and associated musculoskeletal injuries. Results: Fourteen patients had associated ipsilateral foot/ankle injuries, and nine had other musculoskeletal injuries. Seven patients had intra-articular middle facet involvement, and seven had subtalar joint subluxation or dislocation. The medial approach to the calcaneus involves distal retraction of the neurovascular bundle and toe flexors. This allowed for an accurate indirect articular reduction using the extraarticular medial calcaneal cortex, as well as reduction of any associated subluxations. No complications were related to the surgical approach. Reduction was maintained through fracture healing. Conclusion: Fractures of the sustentaculum tali are rare injuries associated with high energy mechanisms, and associated ipsilateral foot injuries are common. Open reduction and internal fixation of these fractures was reliable and possible through a medial approach

Level of Evidence: IV, Retrospective Case Series Key Words: Sustentaculum Tali; Calcaneus; Fracture; Open Reduction and Internal Fixation; Foot Injuries INTRODUCTION

Isolated fractures of the calcaneus involving the sustentaculum tali are rare. Historically, they have been regarded as extra-articular fractures, despite the fact that displaced fractures invariably lead to incongruity of the subtalar joint. Few published series exist and most publications are limited to case reports.8 The sustentaculum tali represents a medial triangular projection of the calcaneus, and includes the middle facet of the subtalar joint. Occasionally, this middle facet may be contiguous with the anterior facet of the subtalar joint.12 The sustentaculum serves as an attachment point of the plantar calcaneonavicular ligament (spring ligament) and of the deltoid ligament. The flexor hallucis longus tendon sits in a groove on the plantar surface of the sustentaculum. Fractures of the sustentaculum can lead to incongruity of extra-articular surfaces, possibly compromising stability of the transverse tarsal joint and of the subtalar joint. Malunited sustentacular fractures can adversely affect the flexor hallucis longus tendon. In addition, incongruity of the subtalar joint that may result from displaced sustentacular fractures can potentially lead to subtalar arthrosis and hindfoot stiffness, as with any intra-articular fracture. Operative treatment should be considered in displaced sustentacular fractures in an attempt to improve long term outcomes. The optimal method of surgical treatment for fractures of the sustentaculum tali has not been defined. Given the medial anatomical location of the sustentaculum tali, an accurate reduction of a displaced fracture through a classical extensile lateral approach to the calcaneus,

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Corresponding Author: Gregory J. Della Rocca, MD, PhD University of Missouri-Columbia Orthopaedic Surgery 213 McHaney Hall One Hospital Drive Columbia, MO 65212 E-mail: [email protected] For information on pricings and availability of reprints, call 410-494-4994, x232.

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as described by Benirschke,1 can be difficult. A medial approach allows for direct exposure of the medial cortical fracture extensions.6 The purpose of this manuscript is to report the fracture morphology, associated foot and ankle injuries, and a method of treatment involving a medial surgical approach for reduction and fixation of displaced sustentacular fractures. MATERIALS AND METHODS

After approval by our Institutional Review Board, a retrospective review of isolated fractures of the sustentaculum tali of the calcaneus was undertaken. A prospectively obtained database of fracture patients was reviewed for the 7-year period culminating in the year 2007. The Orthopaedic Trauma Association/AO classification of fractures was used,11 with patients being screened for inclusion on the basis of a classification of OTA/AO types 73-B fractures (partial articular calcaneus fractures) and 73-C fractures (complete articular calcaneus fractures). All database entries had been accomplished prospectively at the time of patient treatment by orthopaedic traumatology fellows at our institution. Radiographs and operative notes were reviewed to determine the fracture classification, location and treatment. Of over 300 operative calcaneus fractures, 19 were identified as isolated fractures of the sustentaculum tali which underwent surgical treatment, and 15 of these were treated with a medial approach to the calcaneus —these represented the study group. The remaining patients were treated with a lateral approach due to associated extra-articular fractures of the calcaneal neck, cuboid fractures or dislocations, or talus fractures, all of which required reduction and fixation. The average age of the 15 patients in the study group was 32 (range, 18 to 50) years. Ten patients sustained right-sided fractures and five sustained left-sided fractures. Mechanisms of injury included a motor vehicle crash in five, a fall from a substantial height in five, a motorcycle crash in one, a pedestrian struck by motor vehicle in one, a motocross crash in one, a skateboarding accident in one, and a kite-boarding accident in one. In two patients (13%) there was an associated open traumatic medial wound. All patients underwent operative management of their calcaneus fractures by an orthopaedic trauma fellowshiptrained attending physicianat a single regional Level 1 trauma center. All patients had basic demographic characteristics recorded, such as age, side of injury (right versus left), mechanism of injury, smoking status, and associated musculoskeletal injuries. Operative summaries were reviewed for surgical technique and implant utilization. Injury radiographs and CT scans, as well as clinical notes, were reviewed for fracture patterns, associated dislocations/subluxations, and associated foot/ankle injuries. When available, final followup radiographs were also reviewed for radiographic signs of

subtalar joint arthrosis. Subtalar joint arthritis was defined as a dichotomous variable —either present or absent —given the short term followup and the limited number of patients in the study. Presence of subtalar arthritis was defined as narrowing of posterior facet joint space, subchondral osteosclerosis, and/or subchondral bone cyst formation. The surgical technique for approaching the medial aspect of the calcaneus has been previously described.4 For the medial approach to reduction and fixation of the sustentacular fractures, a longitudinal incision is made plantar to the medial malleolus, parallel to the path of the posterior tibial tendon sheath (Figure 1). The posterior tibial tendon sheath is then incised and the tendon mobilized. The posterior tibial tendon is retracted plantarly for access to any cephalad extra-articular fracture cortical involvement and implant placement. However, for the primary reduction of the fracture using the extraarticular cortical extensions along the medial aspect of the calcaneus, the posterior tibial tendon is retracted cephalad, and the interval between the posterior tibial tendon and the flexor digitorum longus developed. The neurovascular bundle, plantar and posterior to the approach, is retracted plantarly and protected. If necessary, the flexor hallucis longus tendon is similarly mobilized and retracted plantarly to allow access to the inferior cortical exit point of the fracture. Fixation is typically accomplished with a combination of small and minifragment screws and plates as necessary. RESULTS

Associated ipsilateral foot and ankle injuries were common. Six patients sustained talar neck fractures, and four of these had associated talar body fractures. An additional six patients sustained fractures of the talar body without talar neck involvement. Five patients had an associated talonavicular dislocation. One patient sustained a fracture of the talar head. An associated distal fibula fracture was present in one, and one patient had an associated cuboid fracture. Five patients sustained one or more of the following associated injuries: anterior tibial plafond fracture, extraarticular calcaneal neck fracture, navicular fracture, calcaneocuboid dislocation, and/or tibiotalar dislocation. Only one patient’s sustentacular fracture represented an isolated ipsilateral foot/ankle fracture or dislocation (although this patient had a contralateral talus fracture). Other musculoskeletal injuries in this patient population were common. These included contralateral foot injuries in four patients (talus fractures in two, calcaneus fracture in one, multiple midfoot fractures in one), ipsilateral patella fracture in one, vertebral fractures in two, and one or more upper extremity fractures in three others. Scrutiny of injury radiographs and CT scans yielded a description of fracture characteristics (Figure 2). Two of the patients did not have injury radiographs or preoperative CT scan available for review. Of the remaining 13 patients, six

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B

C

D

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Fig. 1: Illustration of surgical approach to sustentaculum tali. A, relationship of skin incision to soft tissue anatomy of the ankle and hindfoot. Dashed line: planned skin incision; a: tendon of flexor digitorum longus; b: tendon of tibialis posterior; c: posterior tibial artery; d: tibial nerve. B, relationship of skin incision to osseous anatomy of the ankle and hindfoot. A rendering of the sustentacular fracture is illustrated. Dashed line: planned skin incision. C, skin incision made in line with posterior tibial tendon. Skin retraction reveals the posterior tibial tendon sheath. The flexor digitorum longus tendon is seen posteriorly. Dotted line: planned incision in posterior tibial tendon sheath. D, retraction of the posterior tibial tendon dorsally and of the flexor digitorum longus tendon plantarly exposes the medial face of the calcaneus and the sustentacular fracture line.

were noted to have widening of the calcaneus, as assessed on Harris axial radiography. Six patients were noted to have subtalar dislocations associated with the sustentacular fracture, and one more patient was noted to have posterior facet subluxation without frank dislocation. Seven patients had a fracture line which involved either the middle facet or the extreme medial aspect of the posterior facet; in five of these patients, articular comminution was present, and in four, articular depression was present (three patients had both). Positioning of the calcaneal tuberosity and fracture patterns were evaluated. Fracture displacement was varus in seven patients (47%) and valgus in one. All patients underwent open reduction and internal fixation of their sustentacular fractures at an average of 12.9 days after injury (range, 0 to 58 days). Fourteen patients were treated exclusively through a medial approach, and one patient was treated with combined medial and lateral approaches. Nine of these patients underwent plate-andscrew fixation medially, and six of these patients were treated with medial screws only. No wound complications were noted. Two patients eventually required implant removal due to irritation of overlying soft tissues. Twelve of the 15 patients had radiographic followup of an average of 14.3 (range, 4 to 36) months. Three patients did not followup at our center after hospital discharge. All twelve patients exhibited radiographic healing at a minimum of three months. Only six patients had a minimum followup

of 12 months, and of these patients, radiographic evidence of subtalar arthrosis was present in one. DISCUSSION

Isolated sustentacular fractures of the calcaneus are relatively rare, as illustrated by the paucity of reports available in the literature. Nevertheless, they do occur, and little has been written about their characteristics and treatment methods. As the sustentaculum tali is a medial structure, the standard lateral extensile approach to the calcaneus does not provide visualization of the fracture line(s), and indirect reduction methods are required. This series describes a method of treatment for sustentacular fractures that involves direct reduction of fracture fragments via a medial approach. As sustentacular fractures have historically been considered to be extra-articular fractures, conservative management has been advocated, especially in the setting of minimal displacement of the fracture lines.12,14 However, nonoperative management may not be appropriate in displaced fractures or in patterns that are actually intraarticular in location. Our series demonstrated that approximately half of these fractures (seven of 15 with adequate radiographs or CT scans for review) involved the subtalar joint articular surface. Also, the flexor hallucis longus tendon may become interposed within the fracture line, creating mechanical difficulties and perhaps predisposing to nonunion.13 Tarsal tunnel syndrome

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C B

A

D F E

Fig. 2: A and B, Lateral and Harris axial radiographs, respectively, of a calcaneus fracture isolated to the sustentaculum tali. C and D, Representative computed tomography axial section and coronal section, respectively, through the hindfoot of same calcaneus with isolated sustentacular fracture. E and F, Lateral and Harris axial radiographs, respectively, obtained after open reduction and internal fixation of isolated sustentacular fracture via a medial approach to the calcaneus, utilizing plate and screws.

has also been reported with hypertrophy of the sustentaculum tali and after nonunion of a sustentacular fracture.7,10 In the setting of displaced sustentacular fractures, direct reduction and rigid fixation may help to minimize these possible late sequelae. Biomechanical studies have been performed to better describe the relative contribution of the middle facet to the total weightbearing forces seen by the subtalar joint during normal ambulation. Wagner et al. performed a biomechanical cadaveric study on load distribution between the anteromedial facets and the posterior facet of the subtalar joint. They determined that the contact area for the anteromedial facets was only 31% of the total for the subtalar joint, despite the load being carried by the anteromedial facets equaling 63% of that of the subtalar joint. Mean contact pressures were 1.44 MPa for the anteromedial facets and 0.93 MPa for the posterior facet.16 This indicates that the middle facet sees disproportionately high loads as pressure increases across the ankle and hindfoot. Sangeorzan et al. demonstrated that contact areas across the posterior facet were significantly decreased with calcaneus fracture displacement of 2 mm or more, leading to the suggestion that this degree of displacement of posterior facet fractures should be

addressed with operative reduction.15 With knowledge of the increased contact pressures and small surface area for the middle facet of the subtalar joint, it seems reasonable also to suggest that small displacements of sustentacular fractures perhaps should be addressed surgically. Calcaneus fractures are traditionally approached through an extensile, L-shaped incision over the lateral surface of the heel.1,2 However, the sustentaculum is a medial structure, and direct visualization of medial fracture lines via a lateral approach can be obstructed by the intact calcaneal tuberosity. Medial approaches to the calcaneus have been described. McReynolds initially described a medial approach for reduction and fixation of calcaneus fractures,9 and this was expanded upon by Burdeaux.3 Although some patients in Burdeaux’ series required an additional lateral exposure for reduction and fixation of calcaneus fractures, overall results after using the medial approach were satisfactory.4 Zwipp et al. described a “mandatory” medial approach in over twothirds of cases for open reduction and internal fixation of displaced intra-articular calcaneus fractures, citing the sustentacular fragment as the “key” to reduction.17 Burdeaux then subsequently published a review of 61 calcaneus fractures treated through a medial approach at a mean followup of

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4.4 years, and demonstrated good-to-excellent results in 46 patients, as assessed with the American Orthopaedic Foot and Ankle Society (AOFAS) scoring system.5 When the main, or only, fracture line in a calcaneus fracture exits medially, and restoration of the calcaneal tuberosity to the sustentacular fragment is the goal, then a medial approach provides excellent visualization of the extra-articular medial cortex. Obtaining a good reduction in this location can yield a good indirect reduction of the articular surface in fractures involving the subtalar joint. Careful scrutiny of alignment in the coronal plane, however, via axial radiographs is essential to help prevent fixation of the fracture in varus or valgus malalignment. This study has several limitations, including the small number of patients treated and the lack of good followup data. The small number of patients is a testament to the infrequency of this injury. We only identified 19 patients that underwent open reduction and internal fixation of isolated sustentacular fractures from a database that included over 300 operative calcaneus fractures during the 7-year collection period. As our database does not routinely collect fractures that do not require operative management, the true total number of sustentacular fractures presenting to our center during the 7-year collection period is unable to be determined. Gatha et al. reported only four cases from the 15-year practice of a single trauma surgeon.8 Although we have limited followup data and can draw few conclusions regarding outcomes of surgical treatment of displaced sustentacular fractures, the rarity of the injury coupled with the regional nature of our trauma center makes obtaining followup exceedingly difficult. A multi-center, prospective cohort study would likely be required for a more in-depth exploration of outcomes of patients who sustain isolated sustentacular fractures of the calcaneus. CONCLUSION

Fractures of the sustentaculum tali are rare injuries that often occur in conjunction with ipsilateral foot and ankle injuries. Displaced sustentacular fractures can be safely approached from the medial aspect of the heel, retracting the neurovascular bundle distally. This exposure provides good visualization of the extra-articular cortical reduction, allowing for indirect reduction of involved articular surfaces. The surgical approach was not associated with any complications. Radiographically, evidence of subtalar arthrosis was minimal at approximately 1 year of average followup. Due to the rarity of these injuries, a multi-center prospective study would be necessary for adequate determination of ideal

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methods of treatment and of outcomes in patients with calcaneus fractures isolated to the sustentaculum tali. REFERENCES 1. Benirschke, SK; Sangeorzan, BJ: Extensive intraarticular fractures of the foot: Surgical management of calcaneal fractures. Clin Orthop. 292:128 – 134, 1993. 2. Borrelli Jr., J; Lashgari, C: Vascularity of the lateral calcaneal flap: A cadaveric injection study. J Orthop Trauma. 13:73 – 77, 1999. http://dx.doi.org/10.1097/00005131-199902000-00001 3. Burdeaux Jr., BD: Reduction of calcaneal fractures by the McReynolds medial approach technique and its experimental basis. Clin Orthop. 177:87 – 103, 1983. 4. Burdeaux Jr., BD: The medial approach for calcaneal fractures. Clin Orthop. 290: 96 – 107, 1993. 5. Burdeaux Jr., BD: Fractures of the calcaneus: Open reduction and internal fixation from the medial side a 21-year prospective study. Foot Ankle Int. 18:685 – 692, 1997. 6. Carr, JB: Surgical treatment of intra-articular calcaneal fractures: A review of small incision approaches. J Orthop Trauma. 19:109 – 117, 2005. http://dx.doi.org/10.1097/00005131-200502000-00007 7. Garchar, DJ; Lewis, JE; DiDomenico, LA: Hypertrophic sustentaculum tali causing a tarsal tunnel syndrome: A case report. J Foot Ankle Surg. 40:110 – 112, 2001. http://dx.doi.org/10.1016/S10672516%2801%2980053-3 8. Gatha, M; Pedersen, B; Buckley, R: Fractures of the sustentaculum tali of the calcaneus: A case report. Foot Ankle Int. 29:237 – 240, 2008. http://dx.doi.org/10.3113/FAI.2008.0237 9. McReynolds, IS: The case for operative treatment of fractures of the os calcis. In Leach, RE; Hoaglund, FT; Riseborough, EJ: Controversies in Orthopaedic Surgery, Philadelphia, Saunders, 1982. 10. Myerson, MS; Berger, BI: Nonunion of a fracture of the sustentaculum tali causing a tarsal tunnel syndrome: A care report. Foot Ankle Int. 16: 740 – 742, 1995. 11. Orthopaedic Trauma Association Committee for Coding and Classification: Fracture and dislocation compendium. J Orthop Trauma. 10 Suppl 1:109 – 113, 1996. 12. Rockwood Jr., CA; Green, DP; Bucholz, RW; et al.: Fractures in Adults, 2nd edition, Philadelphia, Lippincott-Raven, 1996. 13. Romash, MM: Fracture of the calcaneus: An unusual fracture pattern with subtalar joint interposition of the flexor hallucis longus. A report of two cases. Foot Ankle Int. 13:32 – 41, 1992. 14. Rowe, CR; Sakellarides, HT; Freeman, PA; et al.: Fractures of the os calcis. JAMA. 184: 920 – 923, 1963. 15. Sangeorzan, BJ; Ananthakrishnan, D; Tencer, AF: Contact characteristics of the subtalar joint after a simulated calcaneus fracture. J Orthop Trauma. 9:251 – 258, 1995. http://dx.doi.org/10.1097/00005131199506000-00012 16. Wagner, UA; Sangeorzan, BJ; Harrington, RM; et al.: Contact characteristics of the subtalar joint: Load distribution between the anterior and posterior facets. J Orthop Res. 10:535 – 543, 1992. http://dx.doi.org/10.1002/jor.1100100408 17. Zwipp, H; Tscherne, H; Thermann, H; et al.: Osteosynthesis of displaced intraarticular fractures of the calcaneus: Results in 123 cases. Clin Orthop. 290: 76 – 86, 1993.

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