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Bone & Joint Expert Care

Acromio-Clavicular joint (ACJ) Instability and Dislocation


A shoulder separation is a fairly common injury, especially in certain sports. Most shoulder separations are actually injuries to the acromioclavicular (AC) joint. The AC joint is the connection between the scapula (shoulder blade) and the clavicle (collarbone). Shoulder dislocations and AC joint separations are often mistaken for each other. But they are very different injuries.


The Acromio-Clavicular Joint (ACJ) is formed by the articulation (joint) between the outer (distal) end of the collarbone (Clavicle) and the Acromion of the shoulder blade (Scapula). The joint is stabilised by 2 main ligament groups. The Acromio-Clavicular ligaments are essentially thickenings of the joint capsule above (superior) and below (inferior) the joint. The main stabilisers of the Joint are the two Coraco-Clavicular ligaments, which bind the Clavicle to the Scapula. The Trapezoid lies towards the outer end of the collarbone (laterally) and the Conoid more medially.

Structures damaged.

The ACJ is commonly injured following a fall onto the hand, elbow or the point of the shoulder.

The Joint may be injured resulting in pain but the ligaments and joint capsule may remain structurally sound. If the force of the injury is sufficient the Acromio-Clavicular ligaments may be disrupted and a partial dislocation or subluxation may occur. If the force is sufficient to damage both the Acromio-Clavicular and the Coraco-Clavicular ligaments an ACJ separation or dislocation develops.

Signs and symptoms:

Complete separation (types 3,4,5, and 6)

Initial symptoms

An acute shoulder separation usually results from a direct fall on the point of the shoulder. This severe direct force on the supporting ligaments of the AC joint causes these ligaments to fail resulting in a separation of the AC joint. In severe cases, both the acromioclavicular ligaments as well as the coracoclavicular ligaments are ruptured and there is an immediate deformity that occurs. Without surgery this deformity remains permanent as the entire weight of the arm continues to pull the acromial side of the injury downward and the trapezius muscle pulls the clavicular side upward. Depending on the severity of the injury this deformity can be quite dramatic as the joint can be pulled apart as much as two inches. Initially the primary symptoms of this injury are pain, deformity, and weakness.

Complete separation (types 3,4,5, and 6)

Late symptoms

After the symptoms of the initial trauma subside many patients will go on to have pain-free and satisfactory function of the shoulder, although the deformity will always be present. In a substantial percentage of cases, however, the mismatch of the joint will create ongoing and disabling symptoms. This includes localized pain, painful clicking and popping, and shoulder fatigue. High demand patients such as those involved in manual labor, repetitive tasks or athletes may notice either a generalized weakness or lack of endurance. While physical therapy may overcome some of these symptoms, the permanent derangement of the anatomy leaves the shoulder function compromised for many patients.

Stable or incomplete separation (types 1 and 2)

Initial symptoms

In less severe case the anatomy is left either somewhat (type 2) or completely (type 1) intact. Any amount of deformity even in incomplete ruptures will be permanent for the reasons mentioned above. Pain can be quite severe even in cases with little deformity; however, simple treatment with a sling for comfort, ice, rest, and early rehab will result in resolution in most cases.

Late symptoms

In some cases of incomplete separation or even in cases with normal x-rays there can be persistent symptoms. The initial impact may cause cell death of the articulating cartilage of the joint causing late breakdown of cartilage tissue. This type of traumatically induced arthritis can cause chronic pain and require surgical treatment in rare cases. Fortunately, a repair or reconstruction is rarely indicated and a simple debridement of the end of the clavicle will reproducibly resolve these symptoms.


Pain may be generalised to the shoulder region and arm. Typically the site of the pain or maximal pain is localised to the region of the ACJ at the top of the shoulder.


If the ACJ is subluxed there may be a bump, or more pronounced bump over the top of the shoulder. If the joint is dislocated the shoulder may appear drooped with a prominence of the end of the collarbone (clavicle). The deformity may not be pronounced but may become more so as the arm is moved particularly across the chest when a lump formed by the end of the collarbone may appear at the back of the shoulder.

Diagnosis and investigations:

The diagnosis is typically apparent from the history and the examination.

X-Rays (plain radiographs) are usually taken to confirm the diagnosis and grade the severity of the injury. It is important to identify associated fractures or injuries. Stress X-Rays may used to identify the maximal extent of the deformity.

Occasionally further investigations in the form of Ultrasound scans (USS), Magnetic Resonance Imaging (MRI) and Computerised Tomography (CT) may be undertaken.


Treatment Timing

Timing of surgery is critical as the procedure for an acute repair is much simpler than the reconstruction required for a chronic separation.

Acute repair:

Once an AC joint has a complete separation, the deforming forces of the arm (downward) and the clavicle (upward) prevent any chance of reducing the dislocation, much less the proper healing of the torn ligaments. The primary goal of an acute repair is to reduce the deformity with a mechanical device so that the tissues can heal. An acute disruption of the ligaments provokes an intense healing response in the body. If the bones can be brought into alignment and held there reliably, natural ligament healing can occur. In the early period after a complete separation, the ends of the ligaments can also be sewn together reinforcing and adding to the body's healing response. Early attempts to do this with simple screw fixation were largely successful; however, the rigidity of this construct did lead to hardware breakage and occasion slippage. Our technique is extremely strong and rigid in the direction of the deformity but allows for motion in other planes. Thus ligament healing can occur without overly constraining the anatomy.

The technique is simple, restores the anatomy to its original state, and requires no grafting or other tissue transfer. Once the initial period (about 3-6 weeks) of healing response has passed, however, a more complex procedure is required.

Chronic repair:

Once the initial period of healing response has passed the torn ligaments ends scar up into contracted lumps of scar tissue and the injury site no longer has the biologic ability to heal. In this setting, new ligament tissue has to be brought into the repair site and sewn into place, requiring an extended period of healing and tissue incorporation before it can function normally. In most cases this requires obtaining a tendon graft from either a tissue donor (cadaver graft) or from the patient (usually from the hamstring tendon behind the knee). In addition, it is often necessary to remove the outer end of the clavicle before repairing it. Once the clavicle has been in a dislocated state for several months the cartilage degenerates and must be removed before the bone is brought back down and fixed. This not only adds more complexity to the procedure but also puts more abnormal forces on the site of healing adding to the risk of late stretching or outright failure of the graft.

Surgical Decision Making

Deciding whether or not to have early surgery is a complex decision in many cases. For cases of very severe deformity (type 4 and type 5 separations) and for extremely active patients surgery is strongly recommended. In those less active or with only a type 3 separation, decision making needs to be individualized. It is difficult to predict ahead of time which patients will be satisfied without surgery and which won't. An unsuccessful attempt at nonsurgical treatment does, however, result in the need for a more complex surgical procedure. Therefore, each patient will have to consider their needs and expectations carefully before deciding on what is best for them.

Pain relief.

Simple painkillers (analgesics) and anti-inflammatories may be helpful.


It is reasonable to provide support for the shoulder with a broad arm sling or Polysling. There are a wide variety of straps and braces designed to reduce ACJ dislocations. There is little evidence that any offer any advantage over symptomatic relief with a simple sling.

The shoulder and arm can be used a pain allows and the sling can be discarded as discomfort settles.

The majority of these injuries will settle without further treatment and are likely to give a satisfactory long-term result.

If the ACJ is significantly displaced either vertically or horizontally then surgical stabilisation may offer some benefit with regard to function as well as offering correction of the deformity.

Surgical Treatment.

There are numerous methods of stabilising or reconstructing the ACJ.

Surgical treatment may be divided into early (acute) stabilisation procedures and later (chronic) reconstruction procedures. Severely displaced fractures may have better long term function and outcome with surgery. The management of less severe dislocations remains somewhat controversial but there is increasing evidence supporting earlier surgical stabilisation.


The joint is reduced to its anatomical location and held in place with two small plates (endobuttons) connected by a continuous loop of extremely strong suture. The course of the device is anatomically placed and there are no knots, eliminating the possibility of knot slippage.

Technique detail.

Because of the powerful deforming forces disrupting the AC joint, the repair technique must be extremely strong in the direction of the deforming forces yet flexible in other planes to allow for normal shoulder movement. This is accomplished by connecting two small metal plates (endobuttons) with a continuous loop of suture. This unique construct eliminates any "weak links" in the system providing reliable stability during the time it takes for the body to provide true biological healing.


A small incision (1-2 inches) is made over the front of the shoulder, exposing the top of the clavicle and the top of the coracoid. It is not necessary to cut any muscle off the bone. The deltoid muscle is simply split in line with its fibers in order to visualize the repair sige. With a downward force the distal clavicle is reduced so that it lines up with the acromion.

Bone preparation:

A drill hole is made in the clavicle and then into the coracoid process. This drill hole is in the same location as the native (but torn) coracoclavicular ligament.

Endobutton passage:

The endobutton and its associated sutures are then pushed through both drill holes and out the bottom of the coracoid process. Then the endobutton is "deployed" so that it seats flush against the underside of the bone. The loop of correct length is then pulled up through the clavicular hole and a second endobutton slid under the small bit of loop protruding out the top of the clavicle.


Two suture tails that are anchored in the first (coracoid) endobutton are now passed through opposite holes of the second (clavicular) endobutton. The endobutton is now seated flat on top of the clavicle and the sutures tied on top, thereby holding this endobutton into place. A second suture is passed into a separate drill hole in between the main drill hole and the AC joint and tied giving additional fixation and stability.

Final Repair

At this point the torn acromioclavicular and coracoclavicular ligaments are sutured and tied, providing additional fixation and recreating the original anatomy.

Pros and Cons of Surgery


Anatomic restoration of damaged tissue

Restored cosmesis

Eliminate need for more complex surgery

Simple procedure

Small incision


Satisfactory result may be possible without surgery

Requires surgery

Requires commitment to post-op therapy


What is the AC joint, and how does it work?

The shoulder is made up of three bones: the scapula (shoulder blade), the humerus (upper arm bone), and the clavicle (collarbone).

The part of the scapula that makes up the top of the shoulder is called the acromion. The AC joint is where the acromion and the clavicle meet. Ligaments hold these two bones together.

Ligaments are soft tissue structures that connect bone to bone. The AC ligaments surround and support the AC joint. Together, they form the joint capsule. The joint capsule is a watertight sac that encloses the joint and the fluids that bathe the joint. Two other ligaments, the coracoclavicular ligaments, hold the clavicle down by attaching it to a bony knob on the scapula called the coracoid process.

AC joint separations are graded from mild to severe, depending on which ligaments are sprained or torn. The mildest type of injury is a simple sprain of the AC ligaments. Doctors call this a grade one injury. A grade two AC separation involves a tear of the AC ligaments and a sprain of the coracoclavicular ligaments. A complete tear of the AC ligaments and the coracoclavicular ligaments is a grade three AC separation. This injury results in the obvious bump on the shoulder.


How does AC joint separation happen?

The most common cause of an AC joint separation is falling on the shoulder. As the shoulder strikes the ground, the force from the fall pushes the scapula down. The collarbone, because it is attached to the rib cage, cannot move enough to follow the motion of the scapula. Something has to give. The result is that the ligaments around the AC joint begin to tear, separating (dislocating) the joint.


What symptoms does this condition cause?

Symptoms range from mild tenderness felt over the joint after a ligament sprain to the intense pain of a complete separation. Grade two and three separations can cause a considerable amount of swelling. Bruising may make the skin bluish several days after the injury.

In grade three separations, you may feel a popping sensation due to shifting of the loose joint. Grade three separations usually cause a noticeable bump on the shoulder.


What tests will my doctor run?

Your doctor will need to get information about your injury and a detailed medical history. You will need to answer questions about past injuries to your shoulder. You may be asked to rate your pain on a scale of one to 10.

Diagnosis is usually made by the physical examination. Your doctor may move and feel your sore joint. This may hurt, but it is very important that your doctor understand exactly where your joint hurts and what movements cause you pain.

Your doctor may order X-rays. X-rays can show an AC joint disruption, and they may be necessary to rule out a fracture of the clavicle. In some cases, X-rays are taken while holding a weight in each hand to stress the joint and show how unstable it is.


What treatment options are available?

Nonsurgical Treatment

Treatment for a grade one or grade two separation usually consists of pain medications and a short period of rest using a shoulder sling. Your rehabilitation program may be directed by a physical or occupational therapist.

The treatment of grade three AC separations is somewhat controversial. Many studies show no difference whether a person is treated with surgery or conservative treatment. Even with surgery, a bump may still be present where the separation occurred. And a significant portion of people who undergo surgery will need another operation later.

Several studies have looked at what happens to the AC joint after this injury. It appears that many people, whether they had the joint repaired surgically or not, will need an operation at some time in the future. The injured joint degenerates faster than normal. Over time it becomes arthritic and painful. This process may take years to develop, but sometimes it happens within one or two years.


Acute Acromio-Clavicular Joint (ACJ) Stabilisation

Indication for surgery:

The indication for AC joint stabilisation is current or anticipated future symptomatic impairment of shoulder function or pain as a consequence of an AC Joint dislocation. If the AC Joint is markedly displaced upwards or backwards then surgery may well improve the long-term outcome. When the deformity is less marked the benefit of surgical stabilisation is less clear. If there is concern regarding the appropriateness of surgery it is best to seek early advice.

Acute stabilisation is generally considered to be within 2-3 weeks of the injury and may involve reduction and stabilisation of the AC Joint allowing the Coraco-Clavicular ligaments to heal or scar at the appropriate length.

Stabilisation of a chronic injury (beyond a few weeks) typically involves a reconstructive procedure, where ligaments or tendons are transferred from elsewhere to reconstruct the Coraco-Clavicular ligaments. This is sometimes termed a Weaver-Dunn procedure after one of the early techniques described.


Surgery is typically undertaken as a day-case procedure, that is you come into hospital and are discharged the same day. If the surgery is undertaken in the afternoon or evening then you may wish to stay in over night and go home first thing the next morning.

The operation is undertaken with a general anaesthetic often with an interscalene nerve block, that is you are fully asleep with further pain relief from a local anaesthetic injection above the Clavicle (collarbone) block. The block typically results in arm numbness and pain relief for 12 to 48 hours following the operation.

Acute Stabilisation:

Acute stabilisation may be obtained using a TightropeTM technique. This can be undertaken as a keyhole (arthroscopic) or mini-open technique.


The arthroscopic technique typically involves three or four, half to one-centimetre incisions. One at the back of the shoulder, one or two at the front of the shoulder and one over the top of the shoulder near the AC joint itself.

The mini-open technique uses a single three to four centimetre scar at the top of the shoulder near the AC Joint. The scar typically lies under clothing straps and is usually cosmetically acceptable.

There is little cosmetic difference between the arthroscopic and mini-open techniques


Arthroscopic Technique:

The arthroscopic (keyhole) technique allows assessment of the Gleno-Humeral Joint with a camera. The Coracoid is cleared and the undersurface exposed through a small incision or portal at the front of the shoulder. A special jig is used to guide a wire and then a drill through the Clavicle and then through the Coracoid. The TightropeTM system allows a strong pulley mechanism to be pulled though both bones before being ‘flipped’, securing a hold on both the top of the Clavicle and bottom of the Coracoid. The TightropeTM pulley can then be tightened to the appropriate length and by so doing the AC Joint can be reduced and held in the correct position. A second TightropeTM may be passed to offer improved strength and stiffness of the reduction and stabilisation.

Mini-Open Technique:

A small incision is made over the end of the Clavicle (Collarbone). The top of the clavicle is exposed. To allow one or two drill holes to be placed in the optimal positions. The top of the coracoid can be readily identified and exposed without extensive tissue clearance. One or two drill holes can then be drilled through the coracoid with appropriate care. One or two TightropesTM can then be pulled through the Clavicle. The Coracoid button may then be pushed through Coracoid drill holes at which point the button will ‘flip’ spontaneously securing the TightropeTM to both the Clavicle and Coracoid. The pulley mechanism then allows reduction and stabilisation of the AC Joint in the correct position. This technique allows the placement of two Tightropes under direct vision with minimal soft tissue disturbance. The soft tissue attachments to the distal clavicle, which may stripped at the time of the dislocation may also be repaired using this technique.

Wound Closure:

Arthroscopic wounds are typically closed using SteriStripsTM, small butterfly paper stitches, but a single absorbable stitch may be used which does not require removal. These wounds are then typically covered by a number of OpsiteTM dressings.

A mini-open incision is typically closed with an absorbable stitch that does not require removal. Occasionally the ends of this suture need to be trimmed when the dressing is removed at 10 to 14 days. The wound is then usually covered with a number of SteriStripsTM to protect the wound and minimise scarring. The wound is then covered by an OpsiteTM dressing

Following surgery:

The arm is typically placed in a sling, which is worn for three to four weeks. It is important to follow the rehabilitation protocols for AC Joint stabilistion supervised by a physiotherapist.

Risks associated with the operation:

All operations are associated with a degree of risk but complications associated with an Acute stabilisation are uncommon

Infection (<1%)

Anaesthetic Risks (Anaestheic complications are rare but include Heart Attack (Myocardial Infarction, MI), Stroke (Cerbero-Vascular Accident, CVA) and a clot in the leg (Deep Vein Thrombosis, DVT) or lungs (Pulmonary Embolus, PE).

Damage to nerve or blood vessels (Neuro-Vascular Damage). There may be a small patch of numbness beyond the shoulder scar. These patches when they do occur do not normally cause an issue. More significant injury is very rare.

Stiffness. There is a small risk of developing a stiff or frozen shoulder after the surgery. This should get better on its own but does occasionally require treatment.

Deformity. There is a small risk that the reduction of the joint will be lost resulting in recurrence of the deformity.

Fracture. Further injury to the shoulder may result in a fracture (break) of either the Coracoid or Clavicle. The likelihood of this may be increased by the presence of the small drill holes.

While the probability of symptom improvement is high it remains possible that symptoms may remain unchanged or deteriorate.

Further surgery (Re-operation)


What should I expect after treatment?

Nonsurgical Rehabilitation

If you don't need surgery, range-of-motion exercises should be started as pain eases, followed by a program of strengthening. At first, exercises are done with the arm kept below shoulder level. The program advances to include strength exercises for the rotator cuff and shoulder blade muscles. In most cases, the pain goes away almost completely within three weeks. Full recovery can take up to six weeks for grade two separations and up to 12 weeks for grade three separations. Since there is little danger of making the condition worse, you can usually do whatever activities you can tolerate.

After Surgery

Your surgeon may have you wear a sling to support and protect the shoulder for a few days. A physical or occupational therapist will probably direct your recovery program. The first few therapy treatments will focus on controlling the pain and swelling from surgery. Ice and electrical stimulation treatments may help. Your therapist may also use massage and other types of hands-on treatments to ease muscle spasm and pain.

Therapists usually wait four weeks before starting range-of-motion exercises. You will probably begin with passive exercises. In passive exercises, the shoulder joint is moved, but your muscles stay relaxed. Your therapist gently moves your joint and gradually stretches your arm. You may be taught how to do passive exercises at home.

Active therapy starts six to eight weeks after surgery, giving the ligaments time to heal. Active range-of-motion exercises help you regain shoulder movement using your own muscle power. You might begin with light isometric strengthening exercises. These exercises work the muscles without straining the healing joint.

After about three months, you will start more active strengthening. Exercises will focus on improving strength and control of the rotator cuff muscles and the muscles around the shoulder blade. Your therapist will help you retrain these muscles to keep the ball of the humerus centered in the socket. This helps your shoulder move smoothly during all your activities.

Recovery from shoulder surgery can take some time. You will need to be patient and stick to your therapy program. Some of the exercises you'll do are designed get your shoulder working in ways that are similar to your work tasks and sport activities. Your therapist will help you find ways to do your tasks that don't put too much stress on your shoulder. Before your therapy sessions end, your therapist will teach you a number of ways to avoid future problems.

What is the AC joint?

The AC joint is where the acromion process and the clavicle meet and form a joint. It is a small joint, but commonly sprained in car accidents, bicycling and in contact sports. There are several ligaments surrounding the joint and depending on the severity of your injury you may have torn one or all of the ligaments.

What are the different injuries one can get around the AC joint? The ligaments can either partially tear or fully tear around the AC joint. When you fully tear the ligaments the clavicle "rides" up and is seeing/felt higher at the top of the shoulder.

You can also fracture the outer part of the clavicle and/or the acromion process and this may also look like the clavicle is riding up. Luckily, most of the injuries are mild ligament strains and not full fledged tears causing the upward displacement of the clavicle.

What is the treatment for the AC joint injuries?

Proper diagnosis is imperative. With this we can tailor your therapy accordingly. A large majority of the patients do great with a sling for comfort and early range of motion with physical therapy.

There are some fractures and or ligament injuries that need to have surgical intervention. Again, these patients are the minority, but the goal is the same and that is to get you back to your pre-injury state.

What is the AC Joint in the shoulder?

The top of the wing bone or scapula is the acromion. The joint formed where the acromion connects to the collar bone or clavicle is the AC joint. Usually there is a protuberance or bump in this area, which can be quite large in some people normally. This joint, like most joints in the body, has a cartilage disk or meniscus inside and the ends of the bones are covered with cartilage. The joint is held together by a capsule, and the clavicle is held in the proper position by two heavy ligaments called coracoclavicular ligaments.

How is the AC Joint usually injured?

The AC joint is injured most often when one falls directly on the point of the shoulder. The trauma will separate the acromion away from the clavicle, causing a sprain or a true AC joint dislocation. In a mild injury, the ligaments which support the AC joint are simply stretched (Grade I), but with more severe injury, the ligaments can partially tear (Grade II) or completely tear (Grade III). In the most severe injury, the end of the clavicle protrudes beneath the skin and is visible as a prominent bump.

How is an AC Joint separation diagnosed?

Most often the clinical exam will demonstrate tenderness or bruising around the top of the shoulder near the AC joint, and the suspected diagnosis can be confirmed using an x-ray, which compares the injured side with the patient's other joint.

What is the proper treatment for a sprained AC Joint?

When a joint is first sprained, conservative treatment is certainly the best. Applying ice directly to the point of the shoulder is helpful to inhibit swelling and relieve pain. The arm can be supported with a sling which also relieves some of the weight from the shoulder. Gentle motion of the arm can be allowed to prevent stiffness, and exercise putty is very helpful to improve function of the elbow, wrist, and hand, but any attempts at vigorous shoulder mobilization early on will probably lead to more swelling and pain.

How long does it take for a shoulder separation to heal?

Depending on how severe the injury is, it may heal adequately in two to three weeks. In severe cases, the shoulder may not heal without surgery.

When and why is surgery necessary for AC Joint separations?

Usually surgery is reserved for those cases where there is residual pain or unacceptable deformity in the joint after several months of conservative treatment. The pain can occur with direct pressure on the joint, such as with straps from underwear or work clothing. Sometimes there will be catching, clicking, or pain with overhead activities, such as lifting, throwing, or reaching. Finally, in some people with very thin skin and very little muscular and soft tissue padding above their shoulders, the prominent clavicle after the separation may be considered unattractive, since the shoulder can appear to be unbalanced.

Are there other causes of AC Joint pain and disability?

Arthritis can occur as an isolated event in the AC joint, causing stiffness, aching, and sometimes swelling. Another condition called DCO, or distal clavicle osteolysis, gives a similar picture, usually in young people who lift heavy weights. This is called "Weightlifter's Shoulder."

What type of surgery can repair AC Joint problems?

The simplest type of surgery for AC joint injury involves resection or removal of the end of the clavicle using arthroscopic (mini-surgical) techniques (called a Mumford procedure). If the joint becomes painful because of DCO (weightlifter's shoulder) or arthritis, or the separation is only minor, this technique can be very satisfactory. When the joint is severely displaced, then a more complex procedure is needed to restore the position of the clavicle. Usually this operation, called a Weaver-Dunn procedure, is done using a two-inch incision over the joint. The end of the clavicle is removed, and ligament is transferred from the underside of the acromion into the cut end of the clavicle to replace the ligaments torn during the dislocation. Soon an arthroscopic procedure should be available to restore the position of the joint, but at this point, only open surgery techniques are available.

What is the postoperative treatment and rehabilitation?

Postoperatively, treatment depends on the type of surgery performed. Usually, when the Mumford procedure is performed using arthroscopic techniques, the arm can be treated with a sling. Bathing is allowed in three days' time, and elbow, wrist, and hand exercises are begun immediately. Lifting is limited for three weeks, but following that, progressive exercise and motion activities proceed as the symptoms allow.

When a Weaver-Dunn procedure (rebuilding of the torn ligaments) is needed, approximately two or three weeks is added to the immobilization time before motion exercises are begun. This time allows the ligament to heal. Otherwise, the exercise program is the same as that for the Mumford procedure above.