Symptomatic Nonunion of the Coracoid Process Following Osteosynthesis Using a Suture Button for Coracoid Process and Distal Clavicle Fracture: A Case Report

Introduction

Coracoid process fractures are relatively rare injuries that occur in 0.4–1% of all fractures [1,2]. These fractures are often associated with shoulder girdle injuries, including acromioclavicular dislocation, distal clavicle fracture, and acromion fracture [3,4]. However, owing to their rarity, a treatment strategy for coracoid process fractures combined with distal clavicle fractures has not been fully established.

Recently, intraosseous suture button devices have increasingly been used to treat distal clavicle fractures. Some studies have reported that suture buttons combined with plate fixation resulted in early bone union and satisfactory functional outcomes [5,6]. However, no reports have described the use of suture buttons for fractures of the distal clavicle and coracoid process.

We report a case of symptomatic nonunion of the coracoid process after osteosynthesis using a suture button for fractures of the coracoid process and distal clavicle.

Case Report

A 60-year-old man presented to our hospital with pain in his left shoulder after falling from the back of a truck. The patient had no remarkable medical history, and his occupation was manual labor. Owing to severe pain, he had difficulty moving the shoulder joint. There were no findings suggestive of nerve or vascular injury. Plain radiography exhibited fractures of the left distal clavicle and left coracoid process (Figure 1A, 1B). The modified costoclavicular distance ratio [7] was 1.4. Computed tomography (CT) revealed a fracture line extending from the coracoid process base to the glenoid fossa, corresponding to a type I Ogawa classification [4] and type V Eyres classification [8] fracture (Figure 1C–1E). Osteosynthesis was performed for the distal clavicle and coracoid process fractures.

Surgery was performed under general anesthesia with the patient in the beach chair position. We began by making a skin incision extending from the distal clavicle to the coracoid process, exposing the superior surface of the clavicle and coracoid processes. We exposed the fracture site of the clavicle and found partial rupture of the conoid ligament; the trapezoid ligament was intact. Subsequent articular arthroscopy revealed a displacement of the glenoid articular surface (Figure 2A), but no rotator cuff tear or degeneration of the long-head biceps tendon. Using an intra-articular arthroscopic view, we reduced the articular surface by moving the coracoid process with bone-grasping forceps (Figure 2B). Subsequently, we used 2 cannulated cancellous screws inserted from the superior aspect of the glenoid fossa for fixation. After reducing the clavicle fracture, ZipTight™ (Zimmer Biomet, Warsaw, IN, USA) was passed from the clavicle to the coracoid process. A plate (HOYA Technosurgical, Tokyo, Japan) was also placed on the superior clavicular surface (Figure 3).

Postoperatively, passive range of motion training was initiated within 90° elevation of the shoulder joint. Full shoulder range of motion training was allowed 5 weeks postoperatively. Five months after the surgery, the patient underwent plate removal because of severe irritation (Figure 4). The irritation disappeared after implant removal; however, the patient continued to experience shoulder pain and limited movement. One year postoperatively, the patient experienced pain around the coracoid and a positive painful arc sign. The shoulder range of motion (right/left) was recorded as follows: 150/120° for anterior elevation (Figure 5A), 60/40° for external rotation (Figure 5B), and 120/95° for horizontal adduction (Figure 5C). The patient had difficulty working because of muscle weakness when the shoulder joint was elevated > 90°. Plain radio-graphs revealed a bone union of the distal clavicle fracture (Figure 6A, 6B), while CT demonstrated nonunion of the coracoid process (Figure 6C, 6D). Owing to the severe functional impairment of the patient, surgical intervention was recommended for the nonunion; however, the patient refused the surgery. At 1.5 years postoperatively, the patient continued to experience shoulder pain and a limited range of motion. The constant score was 54, and the American Shoulder and Elbow Surgeon scores were 22.

Discussion

We report a rare symptomatic nonunion of the coracoid process following its osteosynthesis. In the present study, the suture button used for complicated distal clavicle fracture reduction may have caused the coracoid process nonunion.

Nonunion of the coracoid process is rare, with approximately 30 cases reported in the English literature to date [9]. The common causes of nonunion include oversight by a previous physician and conservative treatment [9], and nonunion after osteosynthesis for coracoid process fractures has not been reported. Nonunion of the coracoid process is often asymptomatic; however, it may present with severe shoulder pain during movement, pain around the coracoid, and subacromial impingement due to coracoacromial arch rupture [9], similar to the symptoms observed in this case.

The coracoid process is rich in blood supply; the vertical part of coracoid process is nourished by the supra-scapular artery, while the horizontal part is nourished by branches of the axillary artery [10,11]. The supra-scapular artery runs below and behind the clavicle toward the coracoid notch, and the branch to the coracoid process runs medial to the vertical part of the coracoid process as an intraosseous nutrient artery [10,11]. The lack of blood supply is one of the causes of nonunion; however, the fracture pattern in this case does not indicate a disruption of blood supply to the fracture site of the coracoid process.

Using suture-button devices for unstable distal clavicle fractures can provide satisfactory functional outcomes and prevent postoperative coracoclavicular separation [12–17]. However, complications have also been reported, including secondary coracoid process fractures [16,18,19] and clavicle fractures [20–22].

On acute coracoid process fractures, Ogawa type I fractures with scapuloclavicular dissociation, and displaced Eyres type IV or V fractures are considered indications for surgery [21]. Accordingly, we performed osteosynthesis because there was an Ogawa type I fracture with distal clavicle fracture or displaced Eyres type V fracture. For Ogawa type I coracoid process fractures, osteosynthesis with a cannulated cancellous screw provides a high union rate, and nonunion has not been reported [4,23,24]. However, in this case, despite using 2 cannulated screws for coracoid process fixation from the superior aspect of the glenoid, coracoid nonunion was observed, suggesting that the tractional force from the suture-button device on the coracoid process inhibits its bone union.

Although fractures of the coracoid process and distal clavicle, such as in this case, are rare, previous reports have demonstrated that tension band wiring or transacromial fixation using a Kirschner wire for distal clavicle fractures and fixation using canulated cancellous screws for coracoid process fractures have provided satisfactory outcomes [23,25]. Considering these reports, performing tension band wiring or plate fixation with transacromial fixation using a Kirschner wire for the distal clavicle fracture and fixation using cannulated cancellous screws for the coracoid process fracture in this case may have been better. Alternatively, if a symptomatic delayed bone union of coracoid process is observed in early postoperative imaging, suture button removal would have been considered.

In the present study, we only evaluated the postoperative reduction of fracture with arthroscopic findings and did not obtain a postoperative CT until 1 year postoperatively. Therefore, the lack of postoperative follow-up CT to evaluate the anatomical reduction and bone union of the coracoid process caused the delay in detecting the nonunion of the coracoid process. This suggests that frequent evaluation with CT in addition to radiographs is necessary.

Conclusions

This case report provides new information on symptomatic coracoid process nonunion following osteosynthesis for a fracture of the coracoid process and distal clavicle. In this case, using a suture-button device for distal clavicle fractures may have caused coracoid process nonunion. To prevent postoperative nonunion of the coracoid process, postoperative CT evaluation is necessary. If a symptomatic delayed bone union of coracoid process is observed, considering early removal of the suture button is recommended.