SLR - September 2014 - Michael Matthews
Reference: Gitajn IL, Abousayed M, Toussaint RJ, Ting B, Jin J, Kwon J. Anatomic Alignment and Integrity of the Sustentaculum Tali in Intra-Articular Calcaneal Fractures J Bone Joint Surg Am. 2014; 96: 1000-5.Scientific Literature Review
Reviewed By: Michael Matthews, DPM
Residency Program: Mount Auburn Hospital
Podiatric Relevance: A fundamental tenant of open reconstruction of calcaneal fractures is that the anteromedial segment containing the sustentaculum tali is “constant.” Such anatomic consistency is thought to be due to the attachments of the interosseous talocalcaneal ligament, spring ligament, and deltoid ligaments providing anatomical stability and thereby a stable surgical landmark. Such medial stability is the principal by which the lateral extensile approach was formulated, which allows the surgeon direct access to the posterior facet and other structures at the expense of limited medial exposure. The stability of the sustentaculum tali has long been established, but previously there had very little published to confirm that belief.
Methods: A retrospective review of all CT scans with calcaneal fractures that presented to two level I trauma centers between 2006 and 2012 was conducted. The inclusion criteria for this study consisted solely of an intra-articular calcaneal fracture for which a CT scan was taken. No exclusion criteria were specifically outlined. The primary outcome for the study was to assess the involvement of the sustentaculum tali in intra-articular calcaneal fractures. CT scans were reviewed for sustentaculum fractures, which were then evaluated by the Sanders and Essex Lopresti staging systems. The baseline for fracture and precise location was determined by a previous study by Sarrafian who found that the sustentaculum on average makes up the most medial third of the calcaneus and is 13mm in length. Sustentaculum tali fractures were measured based on displacement (translation of greater than 2mm), subluxation (angulation of greater than five degrees from adjacent articular surfaces), and dislocation (complete lack of articular congruency). Bivariate statiscial models consisting of the chi squared test, Fischer exact test, and independent sample t-tests were used for statistical analysis of study variables. The Bonferroni method was employed to adjust for possible chance associations. A P value of <0.5 was considered statistically significant for the uncorrected analysis, where as a P of <0.1 was considered significant post Bonferroni correction.
Results: A total of 212 fractures met the inclusion criteria. The most common fracture pattern was a Sanders II followed by a Sanders III. Sustentacular fractures were present in 94 (44.3%) of patients. Seventy-two of those fractures were nondisplaced, eleven were displaced, and ten were comminuted. The mean coronal angulation was 3.81 degrees in patients with sustentacular fracture compared to 2.05 degrees in those without (p = 0.11). Sustentacular fractures were more commonly associated with joint depression fractures (p = 0.47) and higher order Sanders fractures (p = 0.001). Articulation between the sustentaculum tali and the talus was maintained in 78.3 percent of calcaneal fractures, subluxed in 20.3 percent, and dislocated in 0.9 percent. Amongst the calcaneal fractures with a sustentacular component, the articulation between the talus and calcaneus was subluxed in 28.7% of fractures and dislocated in 2.1 percent. Mean sagittal angulation was 3.30 degrees for joint depression fractures as compared to 1.74 percent for tongue type fractures (p = 0.03). Mean coronal angulation for Sanders IV fractures was 5.49 degrees compared to 1.67 degrees for Type II fractures (p = 0.03).
Conclusions: The results of the study provide evidence that the sustentaculum tali may not be as steadfastly constant as was previously thought. Berberian et al are the only other acknowledged group to have examined the issue of sustentacular consistency critically. They reported an overall 42 percent prevalence of sustentacular displacement with regards to angulation, translation, and diastasis of the middle facet. The Berberian group also found an increased prevalence of sustentacular inconsistency with higher-grade Sanders fractures. The current study claims to not only have consistency with Berberian, but also to have greater statistical significance and depth due to a larger sample size and stricter anatomical parameters. The authors conclude that based on their evidence, it would seem reasonable to consider a medial approach or combined medial and lateral approaches when sustentacular inconsistency presents on preoperative CT scans.
The presented study has several limitations. Due to its retrospective nature, functional outcomes were not able to be evaluated. They were also not able to compare whether ORIF of a calcaneal fracture with sustentacular inconsistency produced lower functional outcomes than those calcaneal fractures without inconsistency. Additionally, postoperative CT scans were not available to evaluate the effects of sustentacular inconsistency on reduction. It should be mentioned that measurement error is possible, and the study did not mention who (one radiologist vs. multiple) measured the CT scans. Additionally, sensitivity analyses would have helped determine if those patients who did not receive a CT in the presence of a calcaneal fracture were different than those who did receive a CT scan. One possibility would have been perceived severity of the fracture on x-ray, which could have potentially significantly altered the study’s results if less severe fractures had been included.