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Distal clavicle osteolysis

Introduction

Distal clavicular osteolysis is a well-known complication of repetitive upper-extremity trauma, most often occurring during a bench-press weight lifting routine. Since the condition is very common, mostly benign and self-limiting, many clinicians agree the condition is underdiagnosed.

The condition was first described in 1936 by Dupas who believed that direct trauma was the culprit of the condition. As time has passed and theories have been presented, most clinicians believe that repetitive microtrauma is the most likely etiology.

Anatomy

    AC Joint
The acromioclavicular joint (AC joint) is a synovial joint with supportive ligaments that prevent forward and backward motion of the distal clavicle (specifically, the superior and inferior AC ligaments). A fibrocartilaginous disk (meniscus) exists between the convex, distal end of the clavicle and the flat, medial edge of the acromion.

    CC Joint
The coracoclavicular joint (CC joint) contains some of the strongest ligaments in the body, namely the trapezoid (lateral) and conoid (medial) ligaments. This joint supports the weight of the arm as it hangs from the shoulder girdle and prevents superior and inferior motion. However, in the event of AC joint dislocation, the CC ligaments will take over the role of resisting anterior-posterior motion.

    Neurovascular Structures
Any operative procedure around the clavicle requires an in-depth knowledge of the neurovascular structures in the area. Most notably, the posterior triangle (formed by the lateral border of the sternocleidomastoid, the medial border of the trapezius and the superior edge of the clavicle) houses the subclavian vessels and the brachial plexus. The brachial plexus also gives anterior, middle and posterior branches (supraclavicular nerves) that run posterior to anterior over the superior edge of the clavicle. These supraclavicular nerves must be identified and retracted to prevent injury.

Pathogenesis

The exact pathogenesis of the condition has been under debate for many years. Although the debate continues, it is generally believed that repetitive microtrauma is the most likely etiology.

A cycle of subchondral micro fractures followed by bone remodeling is the current theory. Fissuring of the articular cartilage on the clavicle-side of the AC joint results in in-growth of the synovium. Subchondral micro cysts and, later, joint space widening occurs.

Other, less-popular theories have been developed over the years. Dysautonomia was once described in a series of patients with distal clavicular osteolysis who also had anisicoria. An idiopathic synovial hyperplasia has also been described. However, neither entity has been proven to be causative of the condition. At this point, repetitive microtrauma seems to be the most likely etiology, especially since most patients are involved in repeated over-head motion or shoulder extension.

Natural History

In 1936, Dupas first described distal clavicular osteolysis as a result of a specific traumatic injury. As investigation continued through the years, researchers and clinicians have separated the entity into atraumatic and traumatic classes.

Repetitive trauma, or the "atraumatic version", is largely asymptomatic until a threshold of articular damage has been reached, beginning with insidious aching over the AC joint and exacerbated by weight training (especially bench press, military press and power cleans).

In the traumatic version, the patient will generally recall a specific incident that was closely followed by a similar discomfort as in the atraumatic condition.

In most cases, the condition is self-limiting. If the patient does not seek medical attention, the pain will disappear as the distal clavicle will ultimately resorb itself. This process takes a few years to complete.

Clinical Presentation

The patient generally presents with point tenderness over the AC joint with pain over the same area during cross-body abduction. Crepitation (clicking/popping) may also be present. Bilateral involvement should give a clue to an alternate, systemic diagnosis such as rheumatoid arthritis, malignancy, gout, or others.

In general, shoulder pain can be very complex have many etiologies. It is important to rule out rotator cuff and glenohumeral joint pathology. In the case of distal clavicular osteolysis, the patient should have a full range of motion with most other special tests/exams being negative.

Imaging and Diagnostic Studies

   X-Rays
To diagnose distal clavicular osteolysis, there are two main imaging studies to be obtained. These are the plain AP film and the Zanca view. The Zanca view is an AP film with a 15-20 degree cephalic tilt. This view prevents the spine of the scapula from overlapping the AC joint, providing excellent visualization.

The classic findings are AC joint widening and subchondral cysts on the clavicular side of the joint. There are two important points to note: First, involvement of the acromion should lead you to an alternate diagnosis such as AC joint arthritis. Second, x-rays may be negative for weeks to months after the initial insult (if traumatic).

    Bone Scan
If x-rays are non-diagnostic, it is sometimes useful to perform a technetium-labeled bone scan. Increased radio-tracer uptake in the region of the distal clavicle may be present.

It has been argued that younger patients and athletes will have increased uptake in all joints, including that of the distal clavicle. However, with further experience, it has been noted that patients with distal clavicle osteolysis have asymmetric patterns of tracer uptake, revealing an abnormality of the AC joint.

    MRI
MRI studies have limited usefulness in diagnosis. However, it is helpful in ruling out musculotendinous sources of shoulder pathology such as a rotator cuff tear. Remember that a good physical exam should be able to rule out most other entities.

    Lidocaine Injection
Immediate relief of symptoms after lidocaine injection into the AC joint will therefore localize the condition to the AC joint, thereby ruling out other nearby structures as the cause of pain.

Classification

Distal clavicular osteolysis is generally broken down into traumatic and atraumatic categories.

Treatment

Conservative Management
Basic, conservative therapy is generally sufficient to treat the condition. These include ice, NSAIDS and avoiding provocative maneuvers such as the bench press. The success rate of such therapy is upwards of 80%.

Modification of the bench press is a way to avoid undo stress on the distal clavicle during hyper-extension of the shoulder. Not only does this help alleviate symptoms, but it also allows the weight-lifter to return to weight training activities. The main idea is to prevent the elbows from descending beyond the level of the AC joint. One such way to do this is to place towels on the chest that restrict the distance of barbell descent during the exercise (this is known as the Honing technique).  Performing the exercise with the hands closer together may also prevent extreme shoulder hyperextension.

Complete avoidance of the supine bench press is helpful. Alternatives may include the declined or inclined bench press and the cable crossover.

However, convincing a power-lifter to modify his or her weight training routine for a self-limiting, benign condition is often difficult. Also, many patients never present to the office and tend to push themselves through the pain. Continuing the exacerbating maneuver for a period of time will result in self-surgery, as the distal clavicle will lyse on its own and ultimately resect itself.
    

Surgical Management
Distal clavicle resection (Mumford procedure) has long been the surgical treatment of choice for this condition. The procedure may be performed either open or arthroscopically. As with any other treatment modality, open versus arthroscopic distal clavicle resection have their pros and cons.

        Open Mumford
The advantages of the open procedure include improved visualization allowing an adequate amount of the distal clavicle to be removed. The disadvantages are increased surgical trauma that prevent early range of motion exercises. Arthroscopic procedures require a bit more experience and precision. In other words, technical inexperience with arthroscopic procedure is an indication for the open procedure.

There are two approaches to the distal clavicle that are most commonly used: the strap approach (vertical incision that utilizes the lines of Langer for improved cosmesis) and the horizontal approach. The decision to use either approach is usually as simple as the surgeon's preference.

Following resection, there are several options for closure. One method requires suturing the deltoid fascia to the AC joint capsule, thereby eliminating dead space. Another is to partially detach the coracoacromial ligament from the acromion and transfer it to the distal clavicle, providing more stability for the athlete.

In general, active range of motion exercises are delayed until at least one week has passed after surgery.

        Arthroscopic Mumford
The advantages of the arthroscopic Mumford procedure are minimal scarring, less soft tissue dissection and a quicker recovery. Early active range of motion exercises can be started within the first week after surgery. The main disadvantage is that less bone can be removed arthroscopically.

There are two basic arthroscopic approaches to distal clavicle resection. The first is the superior approach and the second is the subacromial approach.

The subacromial approach preserves the integrity of the superior AC ligament which diminishes the possibility of post-operative instability. This also allows for visualization of any other shoulder pathology. However, this approach requires removal of the subacromial bursa.

The superior approach is mainly used to avoid trauma to the subacromial space, especially if no pathology is expected in that area. It also involves disruption of the superior AC ligament, which may necessitate removal of more bone than the subacromial approach. Removal of more bone is required to prevent abutment of the acromion into the distal clavicle because the joint is less stable after removal of the superior AC ligament.

In general, postoperative therapy involves early passive range of motion such as pendulum exercises. If the procedure was open, delay active range of motion until after the first week. If it was arthroscopic, active range of motion can begin within the first week.

Outcome

As outlined above, distal clavicle osteolysis is a self-limiting condition that will resolve within 2 years , but resof activity modification. Some patients experience either a return of symptoms or contralateral involvement if the inciting maneuver is continued.

Both surgical and conservative treatments have excellent results, especially if the etiology is atraumatic. The traumatic version may have a slightly increased risk of unfavorable results, such as continued pain.

Complications

As with any surgical procedure, certain risks are always present. These include infection, anesthesia, and neuromuscular injuries that may result from surgical dissection. Surgery around the clavicle always involves a risk to the subclavian vessels, brachial plexus and supraclavicular nerves that reside in the posterior triangle of the neck.

Limited postoperative mobility and/or excessive sling usage may result in frozen shoulder (aka adhesive capsulitis) that may permanently impede mobility of the glenohumeral joint. It is therefore necessary to start range of motion exercises in the early postoperative period to prevent this complication.

Pearls and Pitfalls

Controversy

The actual pathogenesis of distal clavicle osteolysis is controversial. However, it is now widely accepted that repetitive microtrauma is most likely involved.

A more recent controversy involves the amount of clavicle resection that is required to alleviate symptoms. In the open procedure, it has generally been routine to resect 1-2 cm of the distal clavicle. However, it is nearly impossible to resect that amount of clavicle in the arthroscopic procedure (often less than 1 cm). After much debate and research, it is now generally accepted to resect at least 4mm of clavicle in order to provide relief of symptoms. In general, enough of the clavicle needs to be removed in order to allow full range of motion of the shoulder without impingement of the acromion onto the clavicle.

References

DeLee, Jesse C., et al. "Osteolysis of the Distal Clavicle". DeLee and Drez's Orthopaedic Sports Medicine, 3rd Edition. Philadelphia. Elsevier, Inc. Copyright 2010.

Owens, Brett D. "Distal Clavicle Osteolysis".  Medscape Reference. Keenan, Mary Ann. Updated 15 July 2011. Accessed 14 Oct 2011 <http://emedicine.medscape.com/article/1262297-overview>.

Schwarzkopf, R., et al. "Distal Clavicular Osteolysis: A Review of the Literature". Bulletin of the NYU Hospital for Joint Diseases. 2008. Volume 66. pp94-101.

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