Regional Distribution Prevalence of Heterotopic Ossification in the Elbow Joint: A 3D Study of Patients After Surgery for Traumatic Elbow Injury

BACKGROUND:Heterotopic ossification (HO) is a common complication after elbow fracture surgery and can lead to severe upper extremity disability. The radiographic localization of postoperative HO has been reported previously. However, there is no literature examining the distribution of postoperative HO at the three-dimensional (3D) level. This study aimed to investigate 1) the distribution characteristics of postoperative HO and 2) the possible risk factors affecting the severity of postoperative HO at a 3D level. METHODS:A retrospective review was conducted of patients who presented to our institution with HO secondary to elbow fracture between 13 January 2020 and 16 February 2023. CT scans of 56 elbows before elbow release surgery were reconstructed in three dimensions (3D). HO was identified using density thresholds combined with manual identification and segmentation. The elbow joint and HO were divided into six regions according to three planes: the transepicondylar plane (TEP), the lateral ridge of the trochlear plane (LTP), and the radiocapitellar joint and coronoid facet plane (RCP). The differences in the volume of regional HO associated with different initial injuries were analyzed. RESULTS:Postoperative HO was predominantly present in the medial aspect of the capsule in 52 patients (93%), in the lateral aspect of the capsule in 45 patients (80%), in the medial supracondylar in 32 patients (57%), and in the lateral supracondylar, radial head, and ulnar region in the same number of 28 patients (50%). The median and interquartile range (IQR) volume of total postoperative HO was 1683 (777∼4894) mm3. The median and IQR volume of regional postoperative HO were: 584 (121∼1454) mm3 at medial aspect of capsule, 207 (5∼568) mm3 at lateral aspect of capsule, 25 (0∼449) mm3 at medial supracondylar, 1 (0∼288) at lateral supracondylar, 2 (0∼478) at proximal radius and 7 (0∼203) mm3 at the proximal ulna. In the subgroups with Injury Severity Score (ISS) >or= 16, Gustilo-Anderson II, normal uric acid levels, elevated alkaline phosphatase (ALP), and Body Mass Index (BMI) >or= 24, the median HO volume exceeds that of the respective control groups. CONCLUSION:The medial aspect of the capsule was the area with the highest frequency and median volume of postoperative HO among all initial elbow injury types. Patients with higher Gustilo-Anderson grade, ISS, ALP or BMI had higher median volume of postoperative HO.