Fixing Cho Type IIC Distal Clavicle Fractures with Hook Plates Leads to a High Incidence of Subacromial Osteolysis: A Retrospective Study and Literature Review

Abstract

Background: This retrospective study investigates the complications, particularly subacromial osteolysis (SAO), associated with hook plate (HP) fixation, in the treatment of unstable distal clavicle fractures characterized by complete coracoclavicular (CC) ligament rupture. The decision-making process for employing HP in fractures of this nature, such as Neer types IIB and V and Cho classification IIC, involves considerations of distal fragment size and displacement. While HP offers advantages in clinical practice, it is not without complications, with SAO being a notable concern. Factors such as non-anatomic hook tip placement and fracture classification may influence the risk of SAO.

Methods: The study comprises a retrospective analysis of unstable distal clavicle fractures treated with HP at our institution from 2019 to 2022. Exclusions include non-displaced fractures, those treated with other locking plates, and pathologic fractures. A total of 91 patients with displaced distal clavicle fractures underwent open reduction and internal fixation with HP. Cho classification was employed to differentiate cases with CC ligament rupture. Patient demographics, classifications, postoperative radiographs, distal fragment size, plate position, timing of implant removal, and complications, including SAO, were recorded.

Results: Among the 91 patients, 32 were classified as Cho IIB, 43 as Cho IIC, and 16 as Cho IID. Ninety-one percent exhibited solid union before implant removal. The prevalence of SAO was 43.8%, 76.7%, and 62.5% in Cho IIB, IIC, and IID, respectively. Univariate analysis revealed a significant difference only in Cho classification (p = 0.014). Binary logistic regression identified Cho classification type IIC as the sole risk factor for SAO (p = 0.021; odds ratio, 4.48; 95% confidence interval, 1.56-12.87).

Conclusions: Cho type IIC fractures, characterized by CC ligament deficiency causing horizontal instability, demonstrated the highest SAO rate. In contrast, Neer type IIB fractures retained the trapezoid ligament, and Neer type V fractures had intact CC ligaments, resulting in lower SAO rates. Biomechanically, combining HPs with CC ligament reconstruction provided better structural stability than using HPs alone in treating Cho type IIC fractures.

Keywords: Bone; Cho’s classification; Clavicle; Fractures; Hook plate; Neer classification; Subacromial osteolysis.

Fig. 1. (A) The distal clavicle fragment size (a) and the preoperative coracoclavicular distance (CCD, b) were measured on the shoulder anteroposterior (AP) view. The contralateral side CCD was also measured with the same method on the contralateral side shoulder AP view. (B) The anteroposterior positioning of the hook tip in relation to the acromion was illustrated by the ratio of d to c. A larger ratio indicates a more posterior placement of the hook plate. (C) The hook coverage ratio, denoted as f to e, illustrates the extent of lateral placement of the hook plate relative to the acromion. A higher ratio signifies a more outward positioning of the hook plate (HP). The postoperative CCD (g) was measured. (D) The image obtained after HP removal showed presence of subacromial osteolysis, which is shown in the circle.

Fig. 2. Patient 1: a 66-year-old man presented with a Cho type IIC distal clavicle fracture. He was treated using a hook plate. The postoperative plain film revealed satisfactory reduction; however, during follow-up, there was progression of subacromial osteolysis, culminating in eventual acromion cut-through.

Fig. 3. Patient 2: A 44-year-old man presented with a Cho type IIC distal clavicle fracture. He underwent treatment with a hook plate. The postoperative plain film indicated successful reduction; however, progressive subacromial osteolysis with upper migration of the hook into the acromion was identified. Acromion perforation accompanied by peri-implant fracture was noted at postoperative 5 months of follow-up. Eventually, the plate had to be removed due to the development of severe pain.