R. Timothy Greene and Spero G. Karas
DEFINITION
A number of pathologic processes may affect the acromioclavicular (AC) joint, altering anatomy, biomechanics, and normal function.
The most common of these are primary osteoarthritis, posttraumatic arthritis, and distal clavicle osteolysis.
ANATOMY
The AC articulation is a diarthrodial joint composed of the medial end of the acromion and the distal end of the clavicle. The joint supports the shoulder girdle through the clavicular strut.
A fibrocartilaginous intra-articular disc is present in variable shape and size.
The average size of the AC joint is 9 × 19 mm.11 The sagittal orientation of the joint surface varies, ranging from an almost vertical orientation to a downsloping medial angulation of 50 degrees.11
The stability of the AC joint is provided by capsular (AC) ligaments, the extracapsular (coracoclavicular) ligaments, and the fascial attachments of the overlying deltoid and trapezius.
The AC ligaments are the primary restraint to anteroposterior translation.
The superior AC ligament, reinforced by attachments of the deltoid and trapezius fascia, resists vertical translation at small physiologic loads. However, the coracoclavicular ligaments are the primary restraint to superior displacement under large loads.
PATHOGENESIS
Degeneration of the AC joint is a natural part of aging.
DePalma11 has shown degeneration of the fibrocartilaginous disc as early as the second decade of life and degenerative changes in the AC joint commonly by the fourth decade.
The superficial location of the joint may predispose it to traumatic injury.
The clavicle acts as a supporting strut for the scapula, helping maintain its orientation and biomechanical advantage for glenohumeral motion. Large forces may be transmitted from the extremity to the axial skeleton through the small surface area (9 × 19 mm) of the AC joint.
Repetitive transmission of large forces, such as weightlifting or heavy labor, may result in degeneration of the joint.
Repetitive microtrauma to the AC joint may cause subchondral fatigue fractures that undergo a subsequent hypervascular response, resulting in reabsorption and osteolysis (distal clavicular osteolysis).
NATURAL HISTORY
Despite the frequency of radiographically evident AC joint degeneration, symptomatic arthritis of the AC joint is relatively uncommon.
Studies have shown that 8% to 42% of patients with type I and II AC joint injuries develop chronic AC symptoms from posttraumatic arthritis.2,3
Distal clavicle fractures may also result in posttraumatic arthritis.
Patients with symptomatic AC joint degeneration have been successfully treated nonoperatively with activity modification.12
PATIENT HISTORY AND PHYSICAL FINDINGS
Patients with isolated AC pathology typically experience pain over the anterior or superior aspect of the shoulder in an area between the midpart of the clavicle and the deltoid insertion.
Pain occurs with activities of daily living that involve internal rotation and adduction such as putting on a coat sleeve, hooking a brassiere, or washing the opposite axilla.
Younger patients may complain of pain with weightlifting, golf swing follow-through, swimming, or throwing.
Physical examination of the AC joint includes.
Palpation: Tenderness on direct palpation suggests AC pathology.
Cross-arm adduction test: This test is highly sensitive but not specific for AC pathology; it is often positive with impingement syndrome. Pain should be confirmed anteriorly because this maneuver will cause posterior pain if posterior capsular tightness is present.
Paxinos test: Combined with a bone scan, this test was found to be the most predictive factor for AC joint pathology.16
Diagnostic AC injection: Elimination of symptoms is diagnostic of AC pathology and prognostic for successful distal clavicle resection.
A complete physical examination of the shoulder should be done to evaluate associated pathology and to rule out other differential diagnoses (as described below).
Impingement syndrome commonly coexists with or may mimic AC pathology, and awareness of this possibility should be used to rule out its existence.
IMAGING AND OTHER DIAGNOSTIC STUDIES
The AC joint is best evaluated radiologically with a Zanca view. This provides an unobstructed view of the AC joint by tilting the x-ray beam 10 to 15 degrees cephalad of the normal shoulder AP (FIG 1A).
Characteristic radiographic changes of primary and posttraumatic arthritis of the AC joint include osteophyte formation with trumpeting of the distal clavicle, sclerosis, and subchondral cyst formation. Narrowing of the AC joint will also be present; however, this occurs as a normal part of aging.
FIG 1 • A. Dedicated AC joint view of the shoulder best shows AC joint arthropathy or subluxation. Patients with degenerative changes on plain film or MRI, however, frequently have no symptoms. B.Edema in the AC joint. AC joint edema is a common finding in patients with symptomatic AC joint disease. Capsular distention and hypertrophy are also present.
Rheumatoid arthritis affecting the AC joint would typically show periarticular erosions and osteopenia with less spurring than osteoarthritis.
Distal clavicle osteolysis characteristically shows osteopenia, cystic changes of the distal clavicle, and widening of the joint space with narrowing of the distal clavicle.
The supraspinatus outlet view may show inferior clavicular osteophytes, which may contribute to an impingement syndrome.
The axillary lateral view of the shoulder may show anterior or posterior displacement of the clavicle, indicative of trauma to the AC joint.
Three-phase technetium bone scan is highly sensitive and specific for AC joint pathology.
Bone scan is especially useful in diagnosing AC pathology that is not evident with conventional radiography.
Magnetic resonance imaging (MRI) is sensitive in identifying AC pathology but has poor specificity, as AC abnormalities are frequently observed in clinically asymptomatic patients. Reactive edema in the AC joint is more predictive of clinical symptoms than are MRI findings of degenerative changes in the AC joint (FIG 1B).13
DIFFERENTIAL DIAGNOSIS
Intrinsic AC patholog.
Primary osteoarthritis
Posttraumatic arthritis
Inflammatory arthritis
Crystal-induced arthritis
Septic arthritis
Distal clavicle osteolysis
Intrinsic shoulder patholog.
Impingement syndrome
Rotator cuff tears
Biceps lesions
Glenohumeral arthritis
Early adhesive capsulitis
Musculoskeletal tumors of the distal clavicle and proximal acromion
Extrinsic conditions
Cervical spine disorder
Referred visceral problems (cardiac, pulmonary, or gastrointestinal disorders)
NONOPERATIVE MANAGEMENT
The initial management of painful AC pathology should be conservative and should include a combination of activity modification, ice or heat therapy, nonsteroidal anti-inflammatory medications, corticosteroid injection, and physical therapy.
Activity modification should focus on avoiding the inciting painful activities. Some patients may be successfully treated nonoperatively with activity modification.
Intra-articular corticosteroid injection with 1 mL of 1% lidocaine and 1 mL of corticosteroid is effective in relieving AC joint pain, but the duration of relief is variable. Patients may receive multiple injections.
Physical therapy consisting of terminal stretching and rotator cuff strengthening may be effective if a concomitant impingement syndrome exists. Isolated AC pathology typically does not respond to physical therapy.
Patients should undergo 3 to 6 months of conservative management before operative intervention.
SURGICAL MANAGEMENT
Patients with continued AC joint symptoms despite adequate conservative management over a 3- to 6-month period are appropriate candidates for surgical intervention.
Significant pain relief from an AC joint injection should be documented before surgery, as this is prognostic for a good result after distal clavicle excision.
Preoperative Planning
Preoperative history, physical examination, and imaging studies should be reviewed before operative intervention.
A lidocaine injection test should be completed preoperatively and the patient should experience significant pain relief.
If the diagnosis is in doubt and the patient does not receive significant pain relief from the lidocaine injection, a more detailed workup should be completed before surgery.
Error in diagnosis accounts for a significant number of failures of distal clavicle resections.12
Positioning
The patient may be placed in the beach-chair or lateral decubitus position.
We prefer the beach-chair position, as it facilitates conversion to an open procedure such as biceps tenodesis. The beach-chair position also places the AC joint in its more customary in vivo orientation, which may aid the surgeon during arthroscopy.
Approach
There are two methods to resect the distal clavicle: the indirect (subacromial) approach and the direct (superior) approach.
The choice of approach depends on the presence of concomitant shoulder pathology and the status of the AC joint.
The indirect approach is used when there is coexisting shoulder pathology, such as an impingement syndrome or a rotator cuff tear, allowing the patient to undergo simultaneous subacromial decompression and rotator cuff repair. The indirect approach is also helpful for markedly narrow AC joints, allowing wider exposure and thus better visualization of the AC joint surfaces.
The direct approach may be used for patients with isolated AC pathology or if there is adequate joint space to place the burr.
We prefer the indirect (subacromial) approach to resect the distal clavicle because associated pathology can be addressed, fewer incisions are made, and the joint can be easily and adequately resected from this approach.
TECHNIQUES
INDIRECT (SUBACROMIAL) DISTAL CLAVICLE RESECTION
A complete diagnostic arthroscopy of the glenohumeral joint is performed.
The arthroscope is redirected into the subacromial space through the posterior portal.
A complete bursectomy and diagnostic subacromial arthroscopy is performed, as described in the previous section on subacromial decompression.
If an impinging spur from the acromion or an osteophyte from the inferior AC joint is present, subacromial decompression and coplaning of the AC joint are performed, as previously described.
The AC joint may be difficult to orient due to variations in patient anatomy. An 18-gauge spinal needle may be placed percutaneously into the AC joint to facilitate orientation (TECH FIG 1A).
If coplaning of the AC joint has not been previously performed with the subacromial decompression, an electrocautery device is used to remove the soft tissue from the undersurface of the AC joint.
A 5- to 6-mm burr is then inserted in the lateral portal and the acromial side of the AC joint is resected. This will expose the distal aspect of the clavicle (TECH FIG 1B).
Both the acromial and clavicular sides of the AC joint should be beveled. This maneuver will create more working space and will allow easier access to the AC joint once the burr is introduced into the anterior portal. Inferiorly directed pressure over the distal clavicle will also enhance its visualization.
TECH FIG 1 • A. A spinal needle may be placed in the AC joint to help orient the surgeon. B. View of the AC joint from the posterior portal. The burr is in the lateral portal and is used to take down the acromial side of the AC joint. This maneuver will decompress the subacromial space and help expose the distal clavicle. C. Beveling the distal clavicle. With the burr in the lateral portal, the undersurface of the distal clavicle is scored. The surgeon can base the amount of clavicular resection on the length of the burr. D. The arthroscope is placed in the lateral portal and the burr is introduced into the AC joint via the anterior portal. The resection is completed using the landmarks established when previously beveling the distal clavicle. E. The completed AC joint resection is viewed “end on” from the lateral portal. F.The arthroscope is introduced into the anterior portal to view the adequacy of the posterior AC resection. The resection is adequate. The posterior AC joint capsule is left intact.
The burr tip is about 10 to 12 mm long. Thus, when approaching the distal clavicle from the lateral portal, the length of the burr tip can be used to measure the length of distal clavicle to be resected, typically 8 to 10 mm (TECH FIG 1C).
Care should be taken to preserve the anterior and posterior AC ligaments if possible. The inferior joint capsule will be resected with the indirect approach.
The arthroscope is now placed in the lateral portal and the 5.5-mm burr is placed in the anterior portal (TECH FIG 1D).
The burr is placed in the beveled area previously established via the lateral portal.
Resection of the remaining dorsal two thirds of the distal clavicle is accomplished starting at the anteroinferior aspect of the distal clavicle and working in a posterosuperior direction.
Again, care is taken to preserve the superior and posterior AC ligaments and superior joint capsule.
About 1 cm of the distal clavicle is resected. Again, this can be estimated by comparing the size of the resection with the size of the burr (TECH FIG 1E).
The arthroscope is then placed in the anterior portal to evaluate the adequacy of resection (TECH FIG 1F).
The arm may be placed in maximal cross-body adduction with the arthroscope in the anterior portal to confirm that the ends of the acromion and clavicle do not touch.
DIRECT (SUPERIOR) DISTAL CLAVICLE RESECTION
A portal for the arthroscope is placed superiorly, 1 cm posterior to the AC joint. A 5-mm incision is made to introduce the trocar for the arthroscope.
Once the arthroscope is introduced, the anterior working portal is placed under direct visualization starting superior and 1 cm anterior to the AC joint (TECH FIG 2A).
A smaller arthroscope (2.7 mm) and soft tissue resector (2.0 mm) may be needed initially if the AC joint is significantly narrowed (TECH FIG 2B).
An electrocautery device is used to remove the soft tissue on the AC joint undersurface.
The AC joint is progressively resected until a larger burr (5.5 mm) will fit into the joint space.
The anterior distal clavicle is resected first starting inferior and working superiorly.
Again, care is taken to preserve the anterior, posterior, and superior AC ligaments and capsule.
When the anterior resection is completed, the arthroscope is placed in the anterior portal and the burr is placed in the posterior portal.
Resection of the posterior distal clavicle is completed from inferior to superior (TECH FIG 2C).
The arthroscope is then placed in the anterior portal and the adequacy of resection is assessed.
A cross-body adduction maneuver may be performed to ensure that no contact remains between the clavicle and acromion.
TECH FIG 2 • A. Portals for the direct technique of AC joint resection. B. A 2.7-mm shaver in the anterior AC joint. The arthroscope is in the posterior portal. Narrowing of a degenerative AC joint frequently precludes the use of a larger burr for the initial resection. C. Completion of the posterior clavicular resection with the direct technique. The initial resection is completed with small joint instruments, and a 5.5-mm burr may then be introduced into the posterior portal to complete the resection. Again, the posterior AC joint capsule is preserved.
WOUND CLOSURE
As much fluid as possible is drained from the subacromial and intra-articular space. Suction may be placed on the arthroscopic cannula's outflow port to speed the extrication of superfluous fluid.
Wounds are closed subcutaneously with 3.0 Monocryl suture.
Steri-Strips and a sterile dressing are applied.
POSTOPERATIVE CARE
Patients are placed in a sling for comfort postoperatively but are encouraged to discontinue the sling immediately when the interscalene block wears off.
Patients are started on passive range-of-motion exercises for the first postoperative week. Therapy is advanced to active range of motion with terminal stretching in the second postoperative week. A resisted rotator cuff and periscapular strengthening program is initiated the third week postoperatively. Terminal stretching is continued for the next several months postoperatively, especially posterior capsule stretches.
The therapy regimen is advanced as rapidly as motion and pain allow.
Patients can typically return to sport in 2 to 3 months. Graduated return is advised. For example, golfers should only chip and putt for the first month postoperatively. Weightlifters can begin training with lighter weights and avoid pressing motions until comfortable.
OUTCOMES
The published success rates of arthroscopic distal clavicle resection are generally good and parallel the results of open distal clavicle resection.
Good or excellent outcomes have been reported in 83% to 100% of patients undergoing arthroscopic distal clavicle resection for primary osteoarthritis, posttraumatic osteoarthritis, or distal clavicle osteolysis.1,5,7–10,14,15,17
The results of open versus arthroscopic distal clavicle resection have been retrospectively reviewed in the literature.
Several authors have found equivalent long-term results of open and arthroscopic distal clavicle resections; however, a significantly quicker recovery time has been observed with the arthroscopic resection.4,6
The quicker recovery time is a result of deltoid attachment preservation, which eliminates postoperative protection of the deltoid and allows for rapid advancement of physical therapy.
COMPLICATIONS
Infection
Bleeding
Neurovascular injury
AC joint instability
Painful scar formation
Heterotopic ossification at the resection site
REFERENCES
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