Distal Clavicle Fracture Mimicking Type IV Acromioclavicular Joint Injury in the Skeletally Immature Athlete

INTRODUCTION Distal clavicle fractures in children may mimic an acromioclavicular (AC) joint separation, but have a very different prognosis and treatment. The distal clavicular epiphysis appears at age 19 and quickly unites to the shaft. 1 Until age 15, injuries to this region are usually physeal fractures. 1 The AC joint is intact and joins the strong periosteal tube of the clavicle, which retains its coracoclavicular ligament attachments. Only the clavicular shaft displaces, exiting the torn periosteum like a banana from its skin. Pediatric injuries that involve the distal clavicle have been classified by Dameron and Rockwood in a scheme that mirrors classification of adult AC joint injuries. 1 The type IV injury includes a fracture of the distal clavicle with posterior displacement and button-holing of the shaft through the trapezius. Given the rarity and lack of understanding of the distal clavicle fracture mimicking AC joint dislocation in the pediatric population, we present a case of a type IV distal clavicle fracture, and its subsequent treatment in a skeletally immature hockey player. CASE REPORT A 13-year-old right-handed male injured his right shoulder after being checked into the boards during a competitive hockey game. The patient had immediate pain in his right shoulder with limited range of motion. On examination, the patient had a swollen right shoulder with a posterior tender bony prominence, with significant tenting of the skin. The patient's shoulder was diffusely tender. The patient's anteroposterior (AP) and axillary X-rays revealed a fracture of the distal clavicle with greater than 100% superior and posterior displacement of the clavicle with respect to the acromion. A computed tomography (CT) scan was done to document the extent of posterior displacement of the clavicle and the stability of the AC joint. The CT scan revealed an intact AC joint with greater than 100% posterior displacement of the clavicle into the posterior soft tissues (Figure 1).FIG. 1.: Computed tomography scans post injury confirm the posterior displacement of the clavicular shaft with respect to the small remnant of distal clavicle that has remained with the intact acromioclavicular joint.The patient was taken to the operating room for reduction under a general anesthetic. As the fracture was reduced, the puckering of the skin resolved. The reduction was confirmed with the image intensifier and was stable without the need for internal fixation. The patient was initially placed in a shoulder immobilizing sling. He was started on pendulum exercises at 2 weeks, and on active range of motion at 4 weeks. Twelve weeks post reduction, the patient had full range of motion and was allowed to resume full activity. The Tarrant view, taken at 12 weeks, revealed healing via periosteal new bone formation from the intact anterior periosteum (Figure 2).FIG. 2.: Axial (Tarrant) view after 12 weeks of healing shows periosteal callus bridging between the intact acromioclavicular joint and the slightly posteriorly displaced clavicular shaft.The patient resumed competitive hockey without any significant complaints of pain, nor any loss of preinjury function or skill. DISCUSSION Injuries to the distal clavicular physis generally occur as a result of direct trauma to the shoulder and are rare in the pediatric population. 1–3 There is minimal literature that provides examples and treatments for the type IV injury. Havranek 4 reported a series of 10 AC joint equivalent injuries over a 4-year period. The majority of these cases demonstrated dorsal displacement of the distal clavicle. Black et al. 2 (n = 58) and Eidman et al. 5 (n = 25) reported moderate-sized series of AC joint injuries in the pediatric population but fail to classify these injuries according to Dameron and Rockwood. 1 The current case illustrates a posterior pseudodislocation of the AC joint (type IV) secondary to a distal clavicular fracture. Our patient presented with similar radiographic findings to Havranek's 4 patients. Recognition of the posterior displacement relies on physical findings. In addition to a posterior bony prominence in the trapezius, which in our patient was tenting the skin, there was a palpable step-off anteriorly where the acromion was present but most of the clavicle shaft absent. The bony mass of the lateral clavicle was felt in the posterior trapezius muscle, and in our patient's case was tenting the overlying skin. Standard AP radiographs did not show AP displacement well, but it could be appreciated with axial CT images, or with Tarrant views of the clavicle. 6 (A Tarrant view is a near-axial projection of the clavicle, projecting a beam from above and behind a seated patient onto a horizontal plate held on the patient's lap. The patient leans forward to project the clavicle slightly anterior to the ribs). Treatment of type I, II, and III distal clavicle fractures in the skeletally immature usually requires simple immobilization for comfort. 1 Significantly displaced type IV, V, and VI fractures may require open reduction and internal fixation, according to Rockwood. 1 One hundred percent of the cases reviewed by Eidman and his colleagues 5 were treated surgically using a variety of operative procedures. Only 10 of 58 patients had an operative repair in the Black et al. 2 series. Barber 7 contributed a case report to the literature of a 15-year-old male who sustained a complete posterior AC joint dislocation. Barber 7 treated his case operatively with a primary ligamentous repair of the coracoclavicular and acromioclavicular ligaments and with mersilene tape fixation of the clavicle to the coracoid. We successfully reduced this type IV distal clavicle fracture by closed means, in the operating room with the patient under a general anesthetic. Achieving this reduction was difficult, and only with full relaxation did the button-holed clavicle reduce back through the rent in the trapezius to its original anatomic location. Healing after closed reduction was rapid and complete, because the AC joint itself was stable and the intact periosteum quickly stabilized the clavicular fracture with new bone. Coracoclavicular ligaments are functionally intact after healing, because they maintain their insertion into the tough periosteal sleeve. This is different from adult healing of a similar injury. The literature suggests that these type IV AC joint injuries do well no matter what type of method was used to obtain the reduction. Havranek 4 states that there was no functional loss with the patients in his series. Barber's 7 patient had full range of motion at 4 weeks post operatively and could perform normal overhead activity at 8 weeks post operatively. Even with varied surgical procedures, Eidman and his associates 5 stated that all 25 patients had good results. Dartoy and colleagues describe a curiously poor result of an unreduced posterior dislocation in a 5-year-old. The posterior prominence of the displaced shaft remained, and a neoclavicle formed within the intact periosteal tube, resulting in a Y-shaped bone with persistent deformity. 8 In this case, with full relaxation from a general anesthetic, the button-holed distal clavicle could be reduced and was stable. This may not always be the case, and open reduction with internal fixation may be necessary. Minimal immobilization followed by pendulum exercises, and then active range of motion exercises allow the injured athlete to return to sporting activities quickly with no significant loss of function. As with other injuries of the distal clavicle in the skeletally immature, the healing after closed reduction was excellent because of the intact AC joint and the intact periosteal tube of the clavicle, which leads to a solid and stable union.

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