The radiographic quantification of scapular malalignment after malunion of displaced clavicular shaft fractures

BACKGROUND: Malunion after displaced fractures of the clavicle can result in varying degrees of scapular malalignment and potentially scapular winging. The purpose of our study was to quantify the scapular malalignment in patients with midshaft clavicle malunions showing scapular winging. METHODS: Eighteen patients with symptomatic midshaft clavicle malunions showing scapular winging were identified and underwent standardized computed tomography scanning of the thorax. Specific bony landmarks on the clavicle and scapula were digitized, allowing generation of 3-dimensional points. These points were acquired bilaterally so that relative translations comparing the malunited side with the contralateral side could be obtained. Statistical analysis using a paired t test was performed. RESULTS: The mean time from fracture to examination was 42.9 months. There were 15 men and 3 women with a mean age of 41.6 years. The mean clavicular shortening was 21.1 mm (P = .0000004). The acromion of the affected scapula on average translated 24.3 mm. The components of this translation were medial, 11.9 mm (P = .00008); inferior, 20.7 mm (P = .0009); and anterior, 4.6 mm (P = .02). Posterior bony landmarks on the scapula including the superior and inferior angles of the scapula translated a total of 9.9 mm and 5.9 mm, respectively. CONCLUSION: This is the first study to document the degree of scapular malalignment in patients with symptomatic clavicle malunions showing scapular winging. The acromion closely follows the distal clavicular fragment and translates medially, inferiorly, and anteriorly. The translations of the superior and inferior angles of the scapula are quite variable in magnitude and direction, and on average, these angles translate substantially less than the acromion.