ACROMIOCLAVICULAR JOINT INJURIES

ACROMIOCLAVICULAR JOINT INJURIES

Mechanism of Injury:
1. Direct force is the commonest cause due to fall on the shoulder with arm adducted
2. It can also occur with indirect force due to fall on the outstretched hand

Features of Acromioclavicular joint:
• Is a diarthrodal (synovial) joint
• Horizontal stability is provided by the acromioclavicular ligaments
• The AC joint has a thin capsule that is stabilized by anterior, posterior, superior, and inferior AC ligaments. Superior AC ligament is the most important of all ligaments
• A fibrocartilaginous disk of varying size and shape exists inside the joint
• Vertical stability is by the coracoclavicular ligaments
• Normal coracoclavicular distance is 1.1 to 1.3 cm

Rockwood Classification
• Type I: Sprain of the AC ligament
Normal radiograph
• Type II: AC ligament tear, coracoclavicular ligaments sprained
Radiograph demonstrates AC joint widening (normal AC joint distance is 1 to 3mm). Stress views show identical coracoclavicular distance compared to uninvolved side
• Type III: AC and coracoclavicular ligament torn.
Radiograph demonstrates loss of AC joint relationship and increased coracoclavicular distance in stress view (25% to 100% greater than the normal side.).
• Type IV: Type III with distal clavicle displaced posteriorly into or through the trapezius
• Type V: Type III with the distal clavicle grossly displaced superiorly.
• Type VI: AC dislocated with the clavicle displaced inferior to the acromion or the coracoid.

Clinical Features:
• As in all fractures pain, tenderness and difficulty in moving the affected part is seen.
• An apparent step-off deformity is seen at the AC joint
• There may tenting of the skin over the distal clavicle

X Rays:
• AP view of the shoulder, scapular Y view and axillary views
• Zanca view: A 15 degree upward tilt view best visualizes the AC joint
• Stress views of the AC joint are obtained by tying 10 to 15 lb weight to the wrists and taking an AP view. The Acromioclavicular and coracoclavicular distances are compared with the normal shoulder.
• Stryker notch view: will rule out an associated coracoid fracture. A coracoid fracture is suspected when there is an AC joint dislocation on the AP projection but the coracoclavicular distance is normal, or equal to that on the opposite, uninvolved side

Treatment
• Type I: Sling immobilisation
• Type II: Sling immobilisation
• Type III: Inactive, non-labouring patient: -nonoperative treatment with sling. Operative treatment in heavy labourers.

• Type IV, V, VI: Open reduction and surgical repair of coracoclavicular ligaments.

• When surgical repair is done, open reduction is performed and acromioclavicular joint is fixed with K wires or indirect fixation is achieved by coracoclavicular fixation with a Bosworth screw.
• Reconstruction of the coracoclavicular ligaments is performed by using the coracoacromial ligament as a substitute, and by the placement of a synthetic augmentation device (such as a band made of absorbable braid or ribbon, Dacron tape) between the coracoid and clavicle

Clavicular HOOK PLATE:
• The clavicular hook plate was developed for treatment of AC joint dislocations and claviCLe fractures in which the distal fragment is too small to allow conventional plate fixation .
• The plate has an offset lateral hook, designed to engage distal to the posterior aspect of the acromion.
• It has been used with some success for displaced lateral-end clavicular fractures, but there are concerns that the plate may induce shoulder stiffness and osteoarthritis of the acromioclavicular joint, and there is also a risk of skin slough and infection.
• Improper positioning of the hook may lead to inadequate fixation.
• Osteolysis has been noted around the hole for the hook as shoulder movement increases, and most surgeons advise routine plate removal at three months after implantation, which necessitates a second operation.
• The timing of plate removal is critical, as early removal may result in nonunion or refracture due to instability at the fracture site, whereas delayed removal can lead to shoulder stiffness or even fracture medial to the plate


Advantages and disadvantages of AC joint dislocation fixation methods:
a)Intra-articular AC fixation
Adv: Anatomic reduction
Disadv: Hardware failure or migration
Distal clavicle osteolysis

b)Extra-articular coracoclavicular repairs
Adv: Superior strength of initial fixation (screw)
Disadv: Screw failure
Bone resorption secondary to hardware
Does not address soft tissue injury

c)Ligament reconstruction
Adv: Anatomic repair
No risk of metallic hardware failure or retention
Disadv: Less initial fixation strength
Harvest coracoacromial ligament

Chronic AC joint dislocations:

Type 1: nonoperative treatment will suffice
Type 2: initial conservative, on failure surgery.
Surgery involves distal clavicle excision combined with AC joint capsule reconstruction with CA ligament transfer
Type 3 to 6: Surgical treatment, distal clavicle excision with CA(coracoacromial) ligament transfer. The acromial attachment is detached and transferred to the resected end of clavicle


Complications:
1. Pneumothorax and pulmonary contusion are common with type VI injuries
2. Osteolysis of distal clavicle
3. Coracoclavicular ossification (disability is minimal)
4. AC joint arthritis is treated by Weaver Dunn technique: distal clavicle excision with CA(coracoacromial) ligament transfer
5. Complications of surgery include migration of pins as far as posterior mediastinal vessels and even carotids.
6. Failure of fixation is common

Role of Arthroscopy:
• The CA ligament can be released from the acromion during routine subacromial decompression and this will facilitate AC ligament reconstruction, including transfer of the coracoacromial ligament by decreasing the necessary size of the incision in the deltotrapezial fascia
• Wolf and Pennington described an all-arthroscopic technique of AC joint reconstruction(7)



Ref:

1. Nuber GW, Bowen MK. Acromioclavicular joint injuries and distal clavicle fractures. J Am Acad Orthop Surg 1997;5:11–18.
2. Lemos MJ. The evaluation and treatment of the injured acromioclavicular joint in athletes. Am J Sports Med 1998;26:137–144
3. Weaver JK, Dunn HK. Treatment of acromioclavicular injuries, especially complete acromioclavicular separation. J Bone Joint Surg [Am] 1972;54:1187-1194
4. Galatz LM, Williams GR, .Injuries to the acromioclavicular joint. In Rockwood and Green’s Fractures in adults, 6th Ed.
5. Kumar S, Sethi A, Jain AK. Surgical treatment of complete acromioclavicular dislocation using the coracoacromial ligament and coracoclavicular fixation: report of a technique in 14 patients. J Orthop Trauma 1995;9:507-510
6. Snyder S, Banas M, Karzel R. The arthroscopic Mumford procedure: an analysis of results. Arthroscopy 1995;11:157-164
7. Wolf EM, Pennington WT. Arthroscopic reconstruction for acromioclavicular joint dislocation. Arthroscopy 2001;17(5):558-563