1000 C OPYRIGHT Ó 2014
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Anatomic Alignment and Integrity of the Sustentaculum Tali in Intra-Articular Calcaneal Fractures Is the Sustentaculum Tali Truly Constant? Ida Leah Gitajn, MD, Mostafa Abousayed, MD, Rull James Toussaint, MD, Beverlie Ting, MD, Jenny Jin, MD, and John Y. Kwon, MD Investigation performed at the Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts
Background: In an intra-articular calcaneal fracture, the sustentaculum tali is generally thought to remain tightly bound to the talus by the interosseous talocalcaneal ligaments, spring ligament, and deltoid ligament, providing a ‘‘constant’’ fragment that remains anatomically aligned. The extensile lateral approach is commonly used for reduction based on this assumption, but because it provides only limited access to the medial aspect of the calcaneus, indirect fracture reduction is required to restore an anatomic relationship of these fragments to the sustentacular fragment. The purpose of this study was to determine the prevalence and displacement of sustentacular fractures in patients with an intra-articular calcaneal fracture, and thus determine whether the sustentacular fragment can be accurately considered as constant and can be consistently relied on to maintain anatomic alignment. Methods: All patients with an intra-articular calcaneal fracture who presented to two level-I trauma centers from 2006 to 2012 were included in the study if computed tomography scanning was performed. The presence or absence of a sustentacular fracture was documented, along with the displacement and the comminution of any such fracture and the subluxation or dislocation of the sustentaculum tali. Results: Sustentacular fractures were present in ninety-four (44.3%) of the 212 patients who met the inclusion criteria. Seventy-two (76.6%) of the sustentacular fractures were nondisplaced, eleven (11.7%) were displaced, and ten (10.6%) were comminuted. The articulation between the sustentaculum tali and the talus was anatomically aligned in 166 (78.3%) of the calcaneal fractures, subluxated in forty-three (20.3%), and dislocated in two (0.9%). Conclusions: This study provides a detailed description of the frequency of sustentacular fractures, the displacement of such fractures, and articular subluxation or dislocation associated with intra-articular calcaneal fractures. Fixation by means of a lateral approach may be compromised when the sustentaculum tali is fractured or subluxated. A medial approach or combined medial and lateral approaches may be considered in such circumstances. Special attention should be paid to the integrity and alignment of the sustentacular fragment prior to surgical fixation. Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
A
dvances in conventional imaging studies, soft-tissue management, and internal fixation methods have enabled better outcomes of surgical treatment of intraarticular calcaneal fractures1-9. One of the keys to fracture reduction and rigid fixation is the superomedial fragment including the sustentaculum tali. The sustentaculum tali is
a triangular projection from the medial surface of the calcaneus and supports the talus. In an intra-articular calcaneal fracture, the sustentaculum tali is thought to remain tightly bound to the talus by the interosseous talocalcaneal ligaments, spring ligament, and deltoid ligament, yielding a fragment that is believed to remain anatomically aligned and is therefore often referred to
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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http://dx.doi.org/10.2106/JBJS.M.00330
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as the ‘‘constant’’ fragment. During surgical fixation, this constant fragment is often used as a scaffold to which other fracture fragments are reduced to restore congruity of the subtalar joint. The commonly used extensile lateral surgical approach is based on this reduction technique but allows only limited access to the medial aspect of the calcaneus. Consequently, anatomic reduction of the posterior facet and extra-articular fragments to the sustentaculum tali must be performed in an indirect fashion with the aid of intraoperative fluoroscopy7,10-17. Although the concept of anatomic constancy of the sustentaculum tali in intra-articular calcaneal fractures has long been held, little has been published to verify it. The purpose of the present study was to determine the prevalence and displacement of sustentacular fractures in patients with an intra-articular calcaneal fracture, and thus determine whether the sustentacular fragment can be accurately considered as constant and can be consistently relied on to maintain anatomic alignment. In addition, we evaluated possible associations between various patient and fracture-related variables and injuries affecting the sustentaculum tali. Materials and Methods
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fter obtaining institutional review board approval, we conducted a retrospective review of patients presenting to two level-I trauma centers from 2006 to 2012 with an intra-articular calcaneal fracture. All such patients were included if computed tomography (CT) scans were available. A trauma registry was used to identify the patients, and all clinical information (including age, sex, and side and mechanism of the injury) was collected from medical records. Fractures were classified according to both the Essex18 19 Lopresti and Sanders classification systems, and the CT scans were reviewed to evaluate the integrity of the sustentacular fragment. According to an ana18 tomic study of fifty calcaneal specimens by Sarrafian , the sustentaculum tali forms approximately one-third of the transverse width of the calcaneus and averages 13 mm in length in the transverse plane of the calcaneus. We therefore defined the sustentaculum tali as the portion of the calcaneus extending 13 mm from the most medial prominence and evaluated it on axial, sagittal, and coronal CT images (Fig. 1). The presence or absence of a sustentacular fracture was documented, along with the displacement and the comminution of any such fracture and the subluxation or dislocation of the sustentaculum tali. Displacement was defined as translation of the fracture fragments by ‡2 mm in any plane. Subluxation of the middle facet was quantified by measuring the angulation of the talar and calcaneal articular surfaces in both the sagittal and coronal planes (Figs. 2-A and 2-B). Any angulation (incongruency) of >5° between these articular surfaces was considered subluxation. Dislocation of the sustentaculum tali was defined as complete lack of articular congruency.
Statistical Methods Descriptive statistics were calculated to provide a general overview of the population. Bivariate statistics (chi-square and Fisher exact tests for categorical variables, and independent-sample t tests for continuous variables) were used to identify associations between the predictor variables and sustentacular fractures. The Bonferroni procedure was used as appropriate to correct for chance associations when multiple comparisons were made. A p value of 3 mm, a 20% prevalence of fracture diastasis of the middle facet, and an overall 42% prevalence of sustentacular displacement. They noted an increased prevalence of such injuries with high-grade Sanders fractures as well as with Sanders subtype-B and C injuries.
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Our findings are consistent with the work of Berberian et al. in that a substantial number of patients with an intraarticular calcaneal fracture sustained injuries to the sustentaculum tali that challenge the notion of anatomic constancy. Although our study included more than twice as many patients as the study by Berberian et al., any comparison of the results should be made with care because of slight methodologic differences. We believe that a definition of the sustentaculum tali that is based on length is more accurate than one based on width, given the difficulties in measuring width in a fractured and distorted heel. Furthermore, we examined nonanatomic positioning in both the coronal and sagittal planes, which more accurately characterizes displacement. We report separately on true fractures of the sustentaculum tali proper and on angulation or displacement of the sustentaculum tali. We analyzed the association of these phenomena with the less commonly used Essex-Lopresti classification system as well as the Sanders system; furthermore, with our larger series, we were able to report on the prevalence of sustentacular injury in Sanders type-I fractures, which was not reported by Berberian et al. Regardless of these methodologic differences, our work supports the conclusions of Berberian et al. in that the high prevalences of sustentacular displacement and fracture disprove the notion of the constant fragment. The sustentaculum tali is not a discrete anatomic structure but rather a medial prominence confluent with the tuberosity, forming the middle facet and supporting the talus. Sarrafian18 performed an anatomic review of fifty calcaneal specimens and described multiple variations in length, width, and confluence with the anterior facet. Using dual definitions, Sarrafian described the mean length of the sustentaculum tali as 13 mm (range, 8 to 18 mm) and the mean width as one-third of the total width of the calcaneus. The present study demonstrated that a sustentacular fracture was present in nearly one-half of patients with an intra-articular calcaneal fracture, and 12% of the sustentacular fractures were displaced ‡2 mm. Sustentacular fractures were significantly more likely to be associated with joint-depression injuries and with higher-order Sanders types. This might reflect the presence of only a small or no part of the posterior facet being attached to the sustentaculum tali, which may increase its risk of fracture, or it may simply reflect a higher-energy injury mechanism. Sanders et al. developed their commonly used classification system on the basis of the number and location of articular fracture fragments seen on semicoronal CT imaging19. They further subdivided fractures into subtypes A, B, and C on the basis of the location of the primary fracture line. Subtype-C fractures were described as those in which the primary fracture line was the farthest medial, and diagrammatically these were depicted as being located at the base of the sustentaculum tali. However, interpretation of our data, which were based on our described methodology, should not lead to the conclusion that the relatively common sustentacular fractures seen in our series were actually Sanders subtype-C fractures rather than not true sustentacular fractures. Understanding that the sustentaculum tali is a projection confluent with the calcaneal body, we chose to define the sustentacular portion of the calcaneus according to
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Fig. 3
Example of severe angulation of the sustentaculum tali in the coronal plane.
Sarrafian’s definition of length. Upon review of all cases in our series, the sustentacular fractures were not at junction of the sustentaculum tali and the calcaneal body. Thus, the sustentacular fractures that we described were distinguished from Sanders subtype-C fractures. However, incongruity of the middle facet as defined in our series may have resulted from either true sustentacular fractures or Sanders subtype-C fractures. The presence of a fracture, particularly a displaced fracture, raises concerns regarding stability. The dense bone of the sustentaculum tali provides excellent screw purchase. The integrity of this structure, which provides strong medial support during operative fixation, is therefore important14,17. The sustentacular fragment, frequently used as a constant fragment during fixation, may not be stable enough for rigid internal fixation, depending on the amount of comminution present. Additionally, the articulation between the sustentaculum tali and the talus was subluxated (incongruent) in 20% of the intra-articular calcaneal fractures in our study (Fig. 3), and it was dislocated in 1%. In all of these cases, it is likely that there was damage to the surrounding ligaments, challenging the idea that this fragment remains anatomically aligned and consistently bound to the talus by the interosseous and deltoid ligaments. Fixation and/or anatomic reduction utilizing the extensile lateral approach may be compromised in the presence of a fractured or subluxated sustentacular fragment. It would seem reasonable to consider a medial approach or combined medial and lateral approaches when the sustentaculum tali is seen to be fractured or subluxated on preoperative CT scans (Fig. 4). Several authors have described medial or combined medial and lateral techniques for calcaneal fixation, although the indications for such alternative approaches have been neither clearly defined nor generally accepted3,10,11,21,22,24. An isolated medial approach allows anatomic reduction of the tuberosity to the sustentacular fragment; however, visualization and anatomic reduction of depressed posterior-facet fragments
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Fig. 4
Example of a comminuted sustentacular fracture that compromises lateral-to-medial fixation.
is not possible11,17,24,25. Stephenson described combined medial and lateral approaches, using the medial approach for reduction of the tuberosity to the sustentacular fragment and the lateral approach for accurate reduction of the posterior facet26. Treatment of calcaneal fractures by means of medial or combined medial and lateral approaches to the calcaneus is often dependent on surgeon familiarity with these approaches, and the indications for these approaches are not well established. However, the results of the present study suggest that certain patients with a sustentacular injury may benefit from use of such combined approaches. This study has several limitations. Evaluation was limited to imaging and did not explicitly evaluate the functional implications of, or the outcomes associated with, these imaging findings. No outcome measures were used to determine whether treatment of an intra-articular calcaneal fracture with an associated sustentacular injury yields results that differ from those
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obtained when such an injury is not present. In addition, postoperative CT scans were not obtained and the quality of calcaneal reduction in patients with sustentacular compromise was not determined. Furthermore, although Sanders fracture types I through IV were represented in our series, the series included only fractures that were investigated with use of CT. Fractures deemed to not require CT for treatment purposes were not included, and their inclusion might have changed the findings of the study. The present study provides a detailed description of the sustentaculum tali with respect to the prevalence of fracture and fracture displacement as well as articular subluxation or dislocation in patients with an intra-articular calcaneal fracture. Much of the literature emphasizes the value of the sustentaculum tali as a constant fragment in the treatment of a displaced intraarticular calcaneal fracture. In the popular lateral approach, this concept serves as the rationale for using the sustentacular fragment as the foundation from which to reassemble the fracture fragments. However, clinicians should be aware that the sustentacular fragment was fractured relatively frequently, in almost one-half of the intra-articular calcaneal fractures in the present study. Additionally, the articulation between the sustentacular fragment and the talus was subluxated (incongruent) in 20% of intra-articular calcaneal fractures and was dislocated in 1%. When reviewing imaging, surgeons should not assume that the sustentacular fragment is uninjured or anatomically aligned. Fixation utilizing the lateral approach may be compromised when the sustentaculum tali is fractured or subluxated. A medial approach or combined medial and lateral approaches may be considered in such circumstances. Special attention should be paid to the integrity and alignment of the sustentacular fragment prior to surgical fixation. n
Ida Leah Gitajn, MD Mostafa Abousayed, MD Rull James Toussaint, MD Beverlie Ting, MD Jenny Jin, MD John Y. Kwon, MD Department of Orthopaedic Surgery, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114. E-mail address for I.L. Gitajn: [email protected]
References 1. Buckley R, Tough S, McCormack R, Pate G, Leighton R, Petrie D, Galpin R. Operative compared with nonoperative treatment of displaced intra-articular calcaneal fractures: a prospective, randomized, controlled multicenter trial. J Bone Joint Surg Am. 2002 Oct;84(10):1733-44. 2. Thordarson DB, Krieger LE. Operative vs. nonoperative treatment of intra-articular fractures of the calcaneus: a prospective randomized trial. Foot Ankle Int. 1996 Jan;17(1):2-9. 3. Zwipp H, Tscherne H, Thermann H, Weber T. Osteosynthesis of displaced intraarticular fractures of the calcaneus. Results in 123 cases. Clin Orthop Relat Res. 1993 May;290:76-86.
4. Sanders R. Displaced intra-articular fractures of the calcaneus. J Bone Joint Surg Am. 2000 Feb;82(2):225-50. 5. Leung KS, Yuen KM, Chan WS. Operative treatment of displaced intra-articular fractures of the calcaneum. Medium-term results. J Bone Joint Surg Br. 1993 Mar;75(2):196-201. 6. Sanders R, Gregory P. Operative treatment of intra-articular fractures of the calcaneus. Orthop Clin North Am. 1995 Apr;26(2):203-14. 7. Benirschke SK, Sangeorzan BJ. Extensive intraarticular fractures of the foot. Surgical management of calcaneal fractures. Clin Orthop Relat Res. 1993 Jul;292:128-34.
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8. Paley D, Hall H. Intra-articular fractures of the calcaneus. A critical analysis of results and prognostic factors. J Bone Joint Surg Am. 1993 Mar;75(3):342-54. 9. B`ezes H, Massart P, Delvaux D, Fourquet JP, Tazi F. The operative treatment of intraarticular calcaneal fractures. Indications, technique, and results in 257 cases. Clin Orthop Relat Res. 1993 May;290:55-9. 10. Burdeaux BD Jr. Fractures of the calcaneus: open reduction and internal fixation from the medial side a 21-year prospective study. Foot Ankle Int. 1997 Nov;18(11):685-92. 11. Burdeaux BD Jr. The medical approach for calcaneal fractures. Clin Orthop Relat Res. 1993 May;290:96-107. 12. Stephenson JR. Displaced fractures of the os calcis involving the subtalar joint: the key role of the superomedial fragment. Foot Ankle. 1983 Sep-Oct;4(2):91-101. 13. Stephenson JR. Treatment of displaced intra-articular fractures of the calcaneus using medial and lateral approaches, internal fixation, and early motion. J Bone Joint Surg Am. 1987 Jan;69(1):115-30. 14. Banerjee R, Nickisch F, Easley M, DiGiovanni C. Skeletal trauma. Philadelphia: Elsevier; 2009. p 26-69. 15. Sanders R. Intra-articular fractures of the calcaneus: present state of the art. J Orthop Trauma. 1992;6(2):252-65. 16. Eastwood DM, Langkamer VG, Atkins RM. Intra-articular fractures of the calcaneum. Part II: open reduction and internal fixation by the extended lateral transcalcaneal approach. J Bone Joint Surg Br. 1993 Mar;75(2):189-95. 17. Barei DP, Bellabarba C, Sangeorzan BJ, Benirschke SK. Fractures of the calcaneus. Orthop Clin North Am. 2002 Jan;33(1):263-85, x.
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18. Sarrafian S. Anatomy of the foot and ankle: descriptive, topographic, functional. Philadelphia: JB Lippincott; 1983. p 54-62. 19. Sanders R, Fortin P, DiPasquale T, Walling A. Operative treatment in 120 displaced intraarticular calcaneal fractures. Results using a prognostic computed tomography scan classification. Clin Orthop Relat Res. 1993 May;290:87-95. 20. Heger L, Wulff K, Seddiqi MS. Computed tomography of calcaneal fractures. AJR Am J Roentgenol. 1985 Jul;145(1):131-7. 21. Della Rocca GJ, Nork SE, Barei DP, Taitsman LA, Benirschke SK. Fractures of the sustentaculum tali: injury characteristics and surgical technique for reduction. Foot Ankle Int. 2009 Nov;30(11):1037-41. 22. Burdeaux BD. Reduction of calcaneal fractures by the McReynolds medial approach technique and its experimental basis. Clin Orthop Relat Res. 1983 JulAug;177:87-103. 23. Berberian W, Sood A, Karanfilian B, Najarian R, Lin S, Liporace F. Displacement of the sustentacular fragment in intra-articular calcaneal fractures. J Bone Joint Surg Am. 2013 Jun 5;95(11):995-1000. 24. Mcreynolds I. The case for operative treatment of fractures of the os calcis. In: Leach RE, Hoaglund FT, Riseborough EJ, editors. Controversies in orthopaedic surgery. Philadelphia: WB Saunders; 1982. 25. Burdeaux BD. Calcaneus fractures: rationale for the medial approach technique of reduction. Orthopedics. 1987 Jan;10(1):177-87. 26. Stephenson JR. Surgical treatment of displaced intraarticular fractures of the calcaneus. A combined lateral and medial approach. Clin Orthop Relat Res. 1993 May;290:68-75.
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Anatomic Alignment and Integrity of the Sustentaculum Tali in Intra-Articular Calcaneal Fractures Is the Sustentaculum Tali Truly Constant? Ida Leah Gitajn, MD, Mostafa Abousayed, MD, Rull James Toussaint, MD, Beverlie Ting, MD, Jenny Jin, MD, and John Y. Kwon, MD Investigation performed at the Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts
Background: In an intra-articular calcaneal fracture, the sustentaculum tali is generally thought to remain tightly bound to the talus by the interosseous talocalcaneal ligaments, spring ligament, and deltoid ligament, providing a ‘‘constant’’ fragment that remains anatomically aligned. The extensile lateral approach is commonly used for reduction based on this assumption, but because it provides only limited access to the medial aspect of the calcaneus, indirect fracture reduction is required to restore an anatomic relationship of these fragments to the sustentacular fragment. The purpose of this study was to determine the prevalence and displacement of sustentacular fractures in patients with an intra-articular calcaneal fracture, and thus determine whether the sustentacular fragment can be accurately considered as constant and can be consistently relied on to maintain anatomic alignment. Methods: All patients with an intra-articular calcaneal fracture who presented to two level-I trauma centers from 2006 to 2012 were included in the study if computed tomography scanning was performed. The presence or absence of a sustentacular fracture was documented, along with the displacement and the comminution of any such fracture and the subluxation or dislocation of the sustentaculum tali. Results: Sustentacular fractures were present in ninety-four (44.3%) of the 212 patients who met the inclusion criteria. Seventy-two (76.6%) of the sustentacular fractures were nondisplaced, eleven (11.7%) were displaced, and ten (10.6%) were comminuted. The articulation between the sustentaculum tali and the talus was anatomically aligned in 166 (78.3%) of the calcaneal fractures, subluxated in forty-three (20.3%), and dislocated in two (0.9%). Conclusions: This study provides a detailed description of the frequency of sustentacular fractures, the displacement of such fractures, and articular subluxation or dislocation associated with intra-articular calcaneal fractures. Fixation by means of a lateral approach may be compromised when the sustentaculum tali is fractured or subluxated. A medial approach or combined medial and lateral approaches may be considered in such circumstances. Special attention should be paid to the integrity and alignment of the sustentacular fragment prior to surgical fixation. Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a final review by the Editor-in-Chief prior to publication. Final corrections and clarifications occurred during one or more exchanges between the author(s) and copyeditors.
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dvances in conventional imaging studies, soft-tissue management, and internal fixation methods have enabled better outcomes of surgical treatment of intraarticular calcaneal fractures1-9. One of the keys to fracture reduction and rigid fixation is the superomedial fragment including the sustentaculum tali. The sustentaculum tali is
a triangular projection from the medial surface of the calcaneus and supports the talus. In an intra-articular calcaneal fracture, the sustentaculum tali is thought to remain tightly bound to the talus by the interosseous talocalcaneal ligaments, spring ligament, and deltoid ligament, yielding a fragment that is believed to remain anatomically aligned and is therefore often referred to
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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http://dx.doi.org/10.2106/JBJS.M.00330
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as the ‘‘constant’’ fragment. During surgical fixation, this constant fragment is often used as a scaffold to which other fracture fragments are reduced to restore congruity of the subtalar joint. The commonly used extensile lateral surgical approach is based on this reduction technique but allows only limited access to the medial aspect of the calcaneus. Consequently, anatomic reduction of the posterior facet and extra-articular fragments to the sustentaculum tali must be performed in an indirect fashion with the aid of intraoperative fluoroscopy7,10-17. Although the concept of anatomic constancy of the sustentaculum tali in intra-articular calcaneal fractures has long been held, little has been published to verify it. The purpose of the present study was to determine the prevalence and displacement of sustentacular fractures in patients with an intra-articular calcaneal fracture, and thus determine whether the sustentacular fragment can be accurately considered as constant and can be consistently relied on to maintain anatomic alignment. In addition, we evaluated possible associations between various patient and fracture-related variables and injuries affecting the sustentaculum tali. Materials and Methods
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fter obtaining institutional review board approval, we conducted a retrospective review of patients presenting to two level-I trauma centers from 2006 to 2012 with an intra-articular calcaneal fracture. All such patients were included if computed tomography (CT) scans were available. A trauma registry was used to identify the patients, and all clinical information (including age, sex, and side and mechanism of the injury) was collected from medical records. Fractures were classified according to both the Essex18 19 Lopresti and Sanders classification systems, and the CT scans were reviewed to evaluate the integrity of the sustentacular fragment. According to an ana18 tomic study of fifty calcaneal specimens by Sarrafian , the sustentaculum tali forms approximately one-third of the transverse width of the calcaneus and averages 13 mm in length in the transverse plane of the calcaneus. We therefore defined the sustentaculum tali as the portion of the calcaneus extending 13 mm from the most medial prominence and evaluated it on axial, sagittal, and coronal CT images (Fig. 1). The presence or absence of a sustentacular fracture was documented, along with the displacement and the comminution of any such fracture and the subluxation or dislocation of the sustentaculum tali. Displacement was defined as translation of the fracture fragments by ‡2 mm in any plane. Subluxation of the middle facet was quantified by measuring the angulation of the talar and calcaneal articular surfaces in both the sagittal and coronal planes (Figs. 2-A and 2-B). Any angulation (incongruency) of >5° between these articular surfaces was considered subluxation. Dislocation of the sustentaculum tali was defined as complete lack of articular congruency.
Statistical Methods Descriptive statistics were calculated to provide a general overview of the population. Bivariate statistics (chi-square and Fisher exact tests for categorical variables, and independent-sample t tests for continuous variables) were used to identify associations between the predictor variables and sustentacular fractures. The Bonferroni procedure was used as appropriate to correct for chance associations when multiple comparisons were made. A p value of 3 mm, a 20% prevalence of fracture diastasis of the middle facet, and an overall 42% prevalence of sustentacular displacement. They noted an increased prevalence of such injuries with high-grade Sanders fractures as well as with Sanders subtype-B and C injuries.
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Our findings are consistent with the work of Berberian et al. in that a substantial number of patients with an intraarticular calcaneal fracture sustained injuries to the sustentaculum tali that challenge the notion of anatomic constancy. Although our study included more than twice as many patients as the study by Berberian et al., any comparison of the results should be made with care because of slight methodologic differences. We believe that a definition of the sustentaculum tali that is based on length is more accurate than one based on width, given the difficulties in measuring width in a fractured and distorted heel. Furthermore, we examined nonanatomic positioning in both the coronal and sagittal planes, which more accurately characterizes displacement. We report separately on true fractures of the sustentaculum tali proper and on angulation or displacement of the sustentaculum tali. We analyzed the association of these phenomena with the less commonly used Essex-Lopresti classification system as well as the Sanders system; furthermore, with our larger series, we were able to report on the prevalence of sustentacular injury in Sanders type-I fractures, which was not reported by Berberian et al. Regardless of these methodologic differences, our work supports the conclusions of Berberian et al. in that the high prevalences of sustentacular displacement and fracture disprove the notion of the constant fragment. The sustentaculum tali is not a discrete anatomic structure but rather a medial prominence confluent with the tuberosity, forming the middle facet and supporting the talus. Sarrafian18 performed an anatomic review of fifty calcaneal specimens and described multiple variations in length, width, and confluence with the anterior facet. Using dual definitions, Sarrafian described the mean length of the sustentaculum tali as 13 mm (range, 8 to 18 mm) and the mean width as one-third of the total width of the calcaneus. The present study demonstrated that a sustentacular fracture was present in nearly one-half of patients with an intra-articular calcaneal fracture, and 12% of the sustentacular fractures were displaced ‡2 mm. Sustentacular fractures were significantly more likely to be associated with joint-depression injuries and with higher-order Sanders types. This might reflect the presence of only a small or no part of the posterior facet being attached to the sustentaculum tali, which may increase its risk of fracture, or it may simply reflect a higher-energy injury mechanism. Sanders et al. developed their commonly used classification system on the basis of the number and location of articular fracture fragments seen on semicoronal CT imaging19. They further subdivided fractures into subtypes A, B, and C on the basis of the location of the primary fracture line. Subtype-C fractures were described as those in which the primary fracture line was the farthest medial, and diagrammatically these were depicted as being located at the base of the sustentaculum tali. However, interpretation of our data, which were based on our described methodology, should not lead to the conclusion that the relatively common sustentacular fractures seen in our series were actually Sanders subtype-C fractures rather than not true sustentacular fractures. Understanding that the sustentaculum tali is a projection confluent with the calcaneal body, we chose to define the sustentacular portion of the calcaneus according to
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Fig. 3
Example of severe angulation of the sustentaculum tali in the coronal plane.
Sarrafian’s definition of length. Upon review of all cases in our series, the sustentacular fractures were not at junction of the sustentaculum tali and the calcaneal body. Thus, the sustentacular fractures that we described were distinguished from Sanders subtype-C fractures. However, incongruity of the middle facet as defined in our series may have resulted from either true sustentacular fractures or Sanders subtype-C fractures. The presence of a fracture, particularly a displaced fracture, raises concerns regarding stability. The dense bone of the sustentaculum tali provides excellent screw purchase. The integrity of this structure, which provides strong medial support during operative fixation, is therefore important14,17. The sustentacular fragment, frequently used as a constant fragment during fixation, may not be stable enough for rigid internal fixation, depending on the amount of comminution present. Additionally, the articulation between the sustentaculum tali and the talus was subluxated (incongruent) in 20% of the intra-articular calcaneal fractures in our study (Fig. 3), and it was dislocated in 1%. In all of these cases, it is likely that there was damage to the surrounding ligaments, challenging the idea that this fragment remains anatomically aligned and consistently bound to the talus by the interosseous and deltoid ligaments. Fixation and/or anatomic reduction utilizing the extensile lateral approach may be compromised in the presence of a fractured or subluxated sustentacular fragment. It would seem reasonable to consider a medial approach or combined medial and lateral approaches when the sustentaculum tali is seen to be fractured or subluxated on preoperative CT scans (Fig. 4). Several authors have described medial or combined medial and lateral techniques for calcaneal fixation, although the indications for such alternative approaches have been neither clearly defined nor generally accepted3,10,11,21,22,24. An isolated medial approach allows anatomic reduction of the tuberosity to the sustentacular fragment; however, visualization and anatomic reduction of depressed posterior-facet fragments
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Fig. 4
Example of a comminuted sustentacular fracture that compromises lateral-to-medial fixation.
is not possible11,17,24,25. Stephenson described combined medial and lateral approaches, using the medial approach for reduction of the tuberosity to the sustentacular fragment and the lateral approach for accurate reduction of the posterior facet26. Treatment of calcaneal fractures by means of medial or combined medial and lateral approaches to the calcaneus is often dependent on surgeon familiarity with these approaches, and the indications for these approaches are not well established. However, the results of the present study suggest that certain patients with a sustentacular injury may benefit from use of such combined approaches. This study has several limitations. Evaluation was limited to imaging and did not explicitly evaluate the functional implications of, or the outcomes associated with, these imaging findings. No outcome measures were used to determine whether treatment of an intra-articular calcaneal fracture with an associated sustentacular injury yields results that differ from those
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obtained when such an injury is not present. In addition, postoperative CT scans were not obtained and the quality of calcaneal reduction in patients with sustentacular compromise was not determined. Furthermore, although Sanders fracture types I through IV were represented in our series, the series included only fractures that were investigated with use of CT. Fractures deemed to not require CT for treatment purposes were not included, and their inclusion might have changed the findings of the study. The present study provides a detailed description of the sustentaculum tali with respect to the prevalence of fracture and fracture displacement as well as articular subluxation or dislocation in patients with an intra-articular calcaneal fracture. Much of the literature emphasizes the value of the sustentaculum tali as a constant fragment in the treatment of a displaced intraarticular calcaneal fracture. In the popular lateral approach, this concept serves as the rationale for using the sustentacular fragment as the foundation from which to reassemble the fracture fragments. However, clinicians should be aware that the sustentacular fragment was fractured relatively frequently, in almost one-half of the intra-articular calcaneal fractures in the present study. Additionally, the articulation between the sustentacular fragment and the talus was subluxated (incongruent) in 20% of intra-articular calcaneal fractures and was dislocated in 1%. When reviewing imaging, surgeons should not assume that the sustentacular fragment is uninjured or anatomically aligned. Fixation utilizing the lateral approach may be compromised when the sustentaculum tali is fractured or subluxated. A medial approach or combined medial and lateral approaches may be considered in such circumstances. Special attention should be paid to the integrity and alignment of the sustentacular fragment prior to surgical fixation. n
Ida Leah Gitajn, MD Mostafa Abousayed, MD Rull James Toussaint, MD Beverlie Ting, MD Jenny Jin, MD John Y. Kwon, MD Department of Orthopaedic Surgery, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114. E-mail address for I.L. Gitajn: [email protected]
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18. Sarrafian S. Anatomy of the foot and ankle: descriptive, topographic, functional. Philadelphia: JB Lippincott; 1983. p 54-62. 19. Sanders R, Fortin P, DiPasquale T, Walling A. Operative treatment in 120 displaced intraarticular calcaneal fractures. Results using a prognostic computed tomography scan classification. Clin Orthop Relat Res. 1993 May;290:87-95. 20. Heger L, Wulff K, Seddiqi MS. Computed tomography of calcaneal fractures. AJR Am J Roentgenol. 1985 Jul;145(1):131-7. 21. Della Rocca GJ, Nork SE, Barei DP, Taitsman LA, Benirschke SK. Fractures of the sustentaculum tali: injury characteristics and surgical technique for reduction. Foot Ankle Int. 2009 Nov;30(11):1037-41. 22. Burdeaux BD. Reduction of calcaneal fractures by the McReynolds medial approach technique and its experimental basis. Clin Orthop Relat Res. 1983 JulAug;177:87-103. 23. Berberian W, Sood A, Karanfilian B, Najarian R, Lin S, Liporace F. Displacement of the sustentacular fragment in intra-articular calcaneal fractures. J Bone Joint Surg Am. 2013 Jun 5;95(11):995-1000. 24. Mcreynolds I. The case for operative treatment of fractures of the os calcis. In: Leach RE, Hoaglund FT, Riseborough EJ, editors. Controversies in orthopaedic surgery. Philadelphia: WB Saunders; 1982. 25. Burdeaux BD. Calcaneus fractures: rationale for the medial approach technique of reduction. Orthopedics. 1987 Jan;10(1):177-87. 26. Stephenson JR. Surgical treatment of displaced intraarticular fractures of the calcaneus. A combined lateral and medial approach. Clin Orthop Relat Res. 1993 May;290:68-75.
