ABSTRACT
Two cases of fracture of the coracoid process associated with acromioclavicular joint dislocation are described. This type of injury is uncommon with only 32 cases reported in the English literature. Both cases were treated operatively, with good results. The management and outcome of other cases described in the literature are reviewed and discussed. We also try to analyse the importance of operative fixation of the coracoid process.
Key Words: Acromioclavicular joint, Coracoid process, Dislocation
中文摘要
喙突骨折與肩鎖關節脫位之兩個病例報告和文獻回顧
俞江山、陳平德、倪偉傑
本文報告兩例喙突骨折和同時有肩鎖關節脫位病例，翻查英文文獻發現同樣情況只曾報道32例。本文嘗試分析手術固定喙突骨的重要性。
INTRODUCTION
Isolated fracture of the coracoid process is not common. In the literature, it has been infrequently described.2,4,17,18,25 The association of fracture of the coracoid process with acromioclavicular joint dislocation is even more uncommon with only 32 cases reported in the English literature.1,3,5-8,10,12-14,19-24,26 Two additional cases are reported, and the literature is reviewed, with comparison of the treatment methods and the ultimate outcomes.
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CASE REPORT
Case 1
A 19-year-old jeep driver sustained a road traffic accident in which the car toppled over. He had a head injury with loss of consciousness for 10 minutes and also sustained an injury to his right shoulder. He could not recall the exact mechanism. Physical examination revealed a prominent right distal clavicle and tenderness over the acromioclavicular joint and the coracoid process. The range of motion of the shoulder joint was restricted due to pain. The neurological examination of the upper limb was normal. There was no other major injury. Radiological examination of the shoulder revealed a third-degree acromioclavicular joint dislocation (Fig. 1). Stryker view showed a fracture through the base of the coracoid process (Fig. 2). He was treated operatively, namely open reduction and internal fixation of the acromioclavicular joint with two 2.0 mm smooth Kirschner wires and a tension band wire. The coracoclavicular ligaments were intact. The coracoid process was well reduced and was stable, therefore fixation of the coracoid process was not performed (Fig. 3). The patient had an uneventful postoperative course and was discharged on the sixth day with his arm in a sling.
Active shoulder motion exercise was started. Four months after operation, the patient resumed full activity with mild pain. Radiographic examination at 3 months showed distinct fracture line of the coracoid process. The implants were kept until there was radiographic evidence of union of the coracoid process which was definite at 6 months after operation (Fig. 4). The patient was met 2 years after the operation. Radiological assessment showed the acromioclavicular joint remained congruent, but with evidence of osteolysis of the distal clavicle (Fig. 5). He resumed normal manual duty and showed normal shoulder function with only minimal pain.
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Case 2
A 25-year-old decoration worker suffered from trauma to his left shoulder after he fell from bicycle and landed on the left side of the body. He had no other major injury. Physical examination showed a prominent distal clavicle and tenderness over the acromioclavicular joint and the coracoid process. Motion range of the left shoulder was decreased due to pain. The neurovascular examination was essentially normal. Radiographs showed a fracture of the base of the coracoid process and a third-degree acromioclavicular joint dislocation (Fig. 6).
He was treated operatively with open reduction and internal fixation of the acromioclavicular joint by two 2.0 mm smooth Kirschner wires. The coracoid process was fixed with a 6.7 mm diameter-cannulated screw (Alphatec cannulated cancellous screw system, Alphatec) (Fig. 7,8). Position of the coracoid process and the screw was confirmed with intraoperative radiographic screening. The patient made an uneventful postoperative course and was discharged on the second day with an arm sling.
A regimen of active shoulder mobilisation exercise was started and 2 months later the patient resumed nearly full activity without pain. The Kirschner wires were removed 3 months after the operation. The last follow-up took place 5 months after operation and showed that he had normal shoulder without pain. He defaulted subsequent follow-up.
LITERATURE REVIEW
With the addition of the two cases, there were 34 cases of coracoid process fracture associated with acromioclavicular dislocation reported in the English literature. These cases are correlated and summarised in table 1. All patients reported were male, except in five cases.5,8,14,20,26 This injury usually occurs in the second or the third decade of the life. Only four cases occur at ages older than 30 years.5,8,10,12 The aetiology of the injuries included motor vehicle accident (12 cases, including case 1),3,5,8,10,12-14,21,22 football injury (seven cases),3,6,13,14,24,26 fall (six cases),5,8,19,20,26 bicycle accident (three cases, including case 2),7,14 direct blow to shoulder (one case),21 skiing (one case),1 skating (one case),12 casualty (one case),12 Judo training (one case)12 and unknown mechanism (one cases).23 Follow-up ranged from 6 weeks to 2.5 years.
Eighteen patients were treated conservatively with either a sling, shoulder immobiliser or a plaster splint.3,5-7,10,12-14,20,21 Most of the cases had painless full range of motion despite the occasional cosmetic deformity. One patient had mild pain with residual acromioclavicular joint dislocation and he required no analgesics treatment.12 Another patient complained of some pain at the acromioclavicular joint with activity and was distressed by the cosmetic deformity of the high-riding clavicle.13
Fourteen of the reported cases were treated operatively by various methods. In five cases, both the coracoid process and the acromioclavicular joint were internally fixed. 20,22,26 In the other four cases, the acromioclavicular joint alone was internally fixed by pins.3,8,14,19 One case was treated by reattachment of the coracoid epiphysis back to the coracoid process with nonabsorbable sutures.13 Another case was treated operatively with an unmentioned method.23 Three cases were initially treated conservatively but required subsequent reconstructive operative treatment: one patient required the operation due to persistent pain.8 The results of operative treatment were in general good with painless full range of motion at follow-ups. However, one patient who had open reduction and internal fixation of his acromioclavicular joint with two smooth pins had minimal pain at 6 weeks postoperatively.3 Another patient had poor pain relief 1 year after an unmentioned method of open reduction and internal fixation.23
DISCUSSION
Injury to the acromioclavicular joint is common. Most injuries occurred during a fall with the arm adducted, striking the shoulder against the ground or some other firm object.15 The resultant force produced inferior displacement of the scapula in relation to the clavicle. The two cases reported in this paper had the same mechanism of injury.
The acromioclavicular joint injuries consist of a continuum of ligament injuries, beginning with injury to only the acromioclavicular ligaments. With increasing force, the coracoclavicular ligaments become involved, followed by the deltoid and trapezius musculature, and ultimately the overlying fascia is torn.15 In adult, the coracoid process and the clavicle are stronger than the coracoclavicular ligaments and are usually not damaged.13 Therefore, in adults, almost all the complete acromioclavicular joint dislocation involve a tear of the coracoclavicular ligament instead of the fracture of coracoid process, resulting in only limited cases reported in literature.
Treatment for the injury varies, depending on both local and systemic factors. Local factors include the site and degree of displacement of coracoid process fractures, the degree of displacement of acromioclavicular joint, the integrity of coracoclavicular ligament and the presence of associated neurovascular compression or skin lesion. Systemic factors include the age of patients, the presence of associated injuries or medical diseases. There is no universally agreed treatment as both surgical and conservative options appear to offer equally favorable results.3
Conservative treatment has been adopted when the acromioclavicular dislocation is not complete,14 or when the fracture consists of a small avulsion fragment with minimal displacement,13,14 or for old patients who have low demand and have significant associated injuries.10
Operative treatment is primarily reserved for patients who perform heavy labour.7 This combination of injuries preludes the use of coracoclavicular methods of fixation as a method of treatment for acromioclavicular joint dislocation.19 Indeed acromioclavicular fixation must be used to stabilise the acromioclavicular joint.15 Like Jacobs and Lizaur, we believe that early acromioclavicular degeneration is not caused by articular perforation with wires. Therefore, transacromial fixation with two smooth wires was chosen as the primary fixation device.9,11 However, most authors agree that reduction of the acromioclavicular dislocation seems to reduce the coracoid fracture well and allows subsequent healing.19 This is also confirmed by our first case. But it took 6 months to achieve radiographic evidence of union. Addition of a coracoid screw to fix coracoid process fracture allows earlier removal of the transacromial fixation wires without redisplacement as shown by case 2. This may be part of the reasons for having better functional results with case 2. He did not have any residual pain.
CONCLUSION
Complete acromioclavicular joint dislocation with fracture separation of the base of the coracoid process is uncommon. This is a report of operative treatments in two young and active male patients. Both cases had transacromial fixation and case 2 had an additional coracoid process fixation with a cannulated screw. This allows earlier removal of transacromial wires. Both cases yielded favourable results with good power and full range of motion. It is also recommended that for young and active patients who accept operative treatment, coracoid fixation should be added to allow earlier removal of transacromial wires.
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The Authors
YU Kong-San, FHKCOS, FHKAM (Orth Surg), Senior Medical Officer, Department of Orthopaedics and Traumatology, North District Hospital, Hong Kong.
CHAN Ping-Tak, FRCSEd, FCSHK, Medical Officer, Department of Orthopaedics and Traumatology, North District Hospital, Hong Kong.
NGAI Wai-Kit, FRACS, FHKAM (Orth Surg), Consultant, Department of Orthopaedics and Traumatology, North District Hospital, Hong Kong.