Relationship between the lateral acromion angle and postoperative persistent pain of distal clavicle fracture treated with clavicle hook plate

Background The clavicular hook plate is an accepted surgical procedure for distal clavicle fractures. The relationship of the characteristics of the hook plate, acromioclavicular joint and acromion morphology, and clinical outcome has remained poorly understood. We reviewed the clinical records of patients who had distal clavicle fractures with different lateral acromion angles treated using a clavicle hook plate and evaluated their clinical outcomes with respect to shoulder pain and acromial morphology. Methods We retrospectively reviewed 102 patients with distal clavicle fractures treated with hook plates at our institution from 2010 to 2017. They were divided into four groups according to lateral acromion angle on shoulder AP view X-rays. The angle was defined as the incline angle between the superior surface of distal clavicle and the inferior facet of acromion on coronal plane. We reviewed their clinical features, including Neer’s impingement sign, MRI findings, and outcomes using Japanese Orthopaedic Association Scores. The mean follow-up was 25.5 months (range, 24 to 28 months). Results All patients in group D (large lateral acromion angle (α) > 40°, acromion coronal angle (β) < 60°) complained of postoperative symptoms. Compared to those with common lateral acromion angle, the incidence of postoperative impingement in group D was undoubtedly much higher (100%). Japanese Orthopaedic Association (JOA) scores in group D were worse at 3 months post-surgery, 3 months post plate removal, and at the last follow-up despite a slightly earlier removal in this group. Conclusion Lateral acromion angle appears to be an important factor in the development of postoperative pain and worse outcomes (JOA scores) in patients treated with the hook plate. The incidence of subacromial impingement and rotator cuff lesion (RCL) increased with the α angle. Early limited mobility and removal of the implant may improve the prognosis and resolve the postoperative shoulder pain. Study design Retrospective review, level of evidence IV.