SLR - February 2021 - Dominick J. Casciato
Bone Density of the Calcaneus Correlates with Radiologic and Clinical Outcomes After Calcaneal Fracture Fixation
Reference: Lee SM, Seo JS, Kwak SH, Shin WC, Bae JY, Woo SH. Bone Density of the Calcaneus Correlates with Radiologic and Clinical Outcomes after Calcaneal Fracture Fixation. Injury. 2020 Aug;51(8):1910-1918.
Level of Evidence: Level III, Retrospective Case Series
Scientific Literature Review
Reviewed By: Dominick J. Casciato, DPM
Residency Program: Grant Medical Center – Columbus, OH
Podiatric Relevance: Assessing bone quality in patients provides insight into appropriate fixation type and location for orthopedic injuries. One such measure of bone quality, bone mineral density, relies on the use of dual X-ray absorptiometry (DXA). DXA scans in the foot, however, prove less homogenous than conventional use in the lumbar spine. As an alternative, the linear attenuation coefficient of tissue in Computed Tomography (CT) scans, measured in Hounsfield Units (HU), provides an indirect measure of bone quality without added cost or radiation. The purpose of this study was to investigate the utility of HU in predicting post-operative outcomes in patients with displaced intraarticular calcaneal fractures (DIACF). The authors hypothesized that the bone mineral density described in HU would be similar between the injured and uninjured calcaneus and would prove a predictor for radiologic and clinical outcomes.
Methods: Fifty-two patients who underwent a unilateral Sanders type two or three fracture met inclusion criteria. These fractures were treated with screw fixation using a sinus tarsi approach followed by six to eight weeks non-weightbearing then return to protected weightbearing depending on bone quality. All patients received a DXA scan of their lumbar spine and femur as well as pre and postoperative CT scans of the injured and uninjured calcaneus. Two observers averaged three consecutive measurements of the largest elliptical region of interest under the widest portion of the posterior facet of the talus in a semi-coronal orientation on the uninjured calcaneus. A minimum of one year follow up was maintained. Clinical outcomes were measured using the Foot and Ankle Outcome Score (FAOS). Complications including wound healing and joint penetration of screws were recorded. The relationship between radiologic and clinical outcomes as well as BMD at each anatomic site with mean HU values was then examined.
Results: A high intraclass correlation coefficient was reported between observers. Preoperative mean HU of the uninjured calcaneus significantly correlated with DXA scan obtained BMD. Decreased Bohler’s angle and calcaneal widening from the post-operative period to the final follow up visit were significantly correlated with decreased HU of the uninjured calcaneus. Increased mean HU of the uninjured calcaneus significantly correlated with the clinical outcomes of activities of daily living, quality of life, and sports as defined by the FAOS. No wound problems, posterior facet screw penetration, or posttraumatic arthritis of the subtalar joint were reported during this study period.
Conclusions: This study revealed that low HU observed in the uninjured calcaneus significantly correlated with poor radiologic outcomes while high HU resulted in favorable clinical outcomes. One explanation for this outcome includes a strong correlation between bone density with fixation stability. The concordance between BMD in DXA scans and HU in CT show the ease of this routine imaging study in patients ineligible for DXA scans. Limitations include the retrospective nature of this study and the heterogeny of the cancellous bone found in the calcaneus, which could be better assessed using volumetric analysis. Future studies can expand on the application of this technique in other foot and ankle pathology.