Citation: Nett MH, Richardson ML. Open reduction and internal fixation of a distal clavicle fracture using a clavicle hook plate. Radiology Case Reports. [Online] 2009;4:325.
Copyright: © 2009 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 2.5 License, which permits reproduction and distribution, provided the original work is properly cited. Commercial use and derivative works are not permitted.
Abbreviations: acromioclavicular (AC) joint
Matthew Nett is a resident and Michael Richardson is a Professor in the Department of Radiology, University of Washington School of Medicine, Seattle WA.
Published: September 12, 2009
Historically, fractures of the clavicle have been treated nonoperatively. However, it is becoming much more common for orthopedic surgeons to treat clavicle fractures with open reduction and internal fixation--particularly fractures of the lateral clavicle with high rates of nonunion, such as the Neer type II. Several techniques and devices are currently being used for clavicle fixation. We present a case of a recently developed and increasingly popular fixation device called a clavicle hook plate, used to repair a Neer type II clavicle fracture.
A 51 year-old right-hand-dominant engineer crashed his bicycle at approximately 24-35 mph and sustained a distal right clavicle fracture. There were no other significant or life-threatening injuries. Initial radiographs showed a grossly malaligned distal clavicle fracture (Fig. 1A, B). The medial clavicle was elevated, while the distal fracture fragments maintained a normal distance to the coracoid, indicating intact acromioclavicular and coracoclavicular ligaments that were attached to the distal fragments. These findings were consistent with a Neer type II distal clavicle fracture.
Figure 1A, B. 51-year-old patient with clavicle fracture. Initial anteroposterior (top) and apical oblique (above) radiographs demonstrate a distal clavicle fracture with a normal acromioclavicular and coracoclavicular distances but with elevation of the medial segment.
The initial plan was for nonoperative management. However, due to the nature of the injury and the patient's desire to return to activity, open reduction and internal fixation were planned. A Synthes hook plate was used, with planned removal in four to six months following surgery (Figs. 2 and 3).
Figure 2A, B. 51-year-old patient with clavicle fracture. Intraoperative images of the right shoulder demonstrate placement of a hook plate.
Figure 3A, B. 51-year-old patient with clavicle fracture. Anteroposterior (top) and apical oblique (above) radiographs taken two weeks following surgery show the clavicular hook plate bridging the clavicular fragments in near-anatomic alignment.
Clavicle fractures are a common injury, representing approximately 2.6-4% of adult fractures and approximately 35% of injuries to the shoulder girdle (1). They tend to occur in young males during sports activities when a direct force is applied to the point of the shoulder. A second incidence peak in older patients is related to falls, particularly in women with osteoporosis.
Clavicle fractures can often be diagnosed based on history and physical exam alone. However, radiographs remain a mainstay of initial evaluation in order to classify the fracture, evaluate for other injuries, and obtain a baseline exam for future followup. Lateral clavicle fractures make up approximately 12-15% of all clavicle fractures (2).
There are several schemes for classification of lateral clavicle fractures. Of these, the Neer classification is widely used (3). Neer type I fractures are minimally displaced fractures that occur lateral to or between the intact coracoclavicular ligaments. Neer type II fractures occur at the level of coracoclavicular ligaments, with the trapezoid ligament remaining attached to the distal segment. Type II fractures can be further divided into type IIA, in which the conoid and trapezoid ligaments both remain attached to the distal fragment, and type IIB, in which the conoid ligament is torn. Type III injuries occur distal to the coracoclavicular ligament and enter the acromioclavicular (AC) joint. Because they are unstable and prone to nonunion, type II distal clavicle fractures are often treated surgically (4). Type I and III fractures are typically treated nonoperatively, but type III injuries have a greater risk of osteoarthritis due to the joint trauma.
A number of surgical techniques have been developed for Neer type II fractures. These include coracoclavicular screws, Kirschner wire fixation, and rigid metal plating. These have all had significant problems with hardware failure and migration. In addition, plate fixation cannot be used if the distal fragment will not support two or more cortical screws.
In the late 1980s and early 1990s, a new clavicular hook plate was developed for the treatment of these fractures. This device is marketed and manufactured by Synthes (West Chester PA). It is gaining increased acceptance and use by orthopedists, although it may not be familiar to most radiologists. The device is inserted by selecting the appropriate plate size and then inserting the hook underneath the acromion, posterior to the acromioclavicular joint. The plate portion is then fixed to the medial clavicle with multiple screws.
Biomechanical studies have confirmed that rotational movement occurs between the clavicle and acromion, which results in problems for rigid fixation methods. The clavicle hook plate is designed to address this problem by maintaining the biomechanics of the acromioclavicular joint. This allows a degree of early mobilization and avoids the need for reconstruction of the coracoclavicular ligaments (4). Studies comparing the Kirschner wire fixation and hook plate techniques have shown that the clavicle hook plate has fewer complications and allows earlier mobilization (5, 6).
Despite these advantages, complications can occur if the hook plate is retained. Over time, osteolysis can occur around the hook as the shoulder is mobilized. The medial end of the plate can act as a stress riser, resulting in clavicle fracture medial to the plate (7). Other complications include rotator cuff damage, plate failure, unhooking from under the acromion, infection, nonunion, screw loosening or fracture, skin sloughing, pain, and potential osteoarthritis of the AC joint (1, 4). Because of these complications, clavicle hook plates are typically removed approximately three months after their placement.
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