AC Joint Separation Specialist

The AC joint is where the collarbone meets the shoulder blade, and it is small, barely mobile, and structurally essential. The entire arm hangs from it. When a fall onto the point of the shoulder tears the ligaments holding that connection together, the collarbone rises and the arm effectively drops away from it, which is why a complete separation produces a visible step deformity that does not correct itself.

Steven Struhl, MD did not learn the acromioclavicular reconstruction described on this page, he invented it. The United States Patent and Trademark Office granted him Patent 8,162,997 in 2012, the orthopedic device manufacturer Smith and Nephew subsequently acquired the design, and he published his long term outcomes in The American Journal of Sports Medicine after performing more than 200 of these reconstructions. He is board certified in orthopedic surgery and separately in sports medicine, and he treats AC joint injuries at his Manhattan and White Plains offices.

Acromioclavicular Joint (AC Joint) Separation

The more severe the injury the more the joint is disrupted.

AC Joint Separation Symptoms by Grade

The symptoms of a separated shoulder depend almost entirely on how many of the supporting ligaments have failed, which is what the grading system measures. A stable separation and a complete one produce different problems, follow different courses, and are treated differently.

Complete AC Joint Separation, Grades 3 Through 6

An acute shoulder separation usually follows a direct fall onto the point of the shoulder. That force overwhelms the ligaments supporting the AC joint, and in severe cases both the acromioclavicular and the coracoclavicular ligaments rupture together, producing an immediate visible deformity.

Without surgery that deformity is permanent, because the entire weight of the arm continues to pull the acromial side of the injury downward and nothing remains to hold it up. Depending on the severity, the separation can be dramatic, with the joint pulled apart by as much as two inches.

The immediate symptoms are pain, weakness, and visible deformity at the top of the shoulder.

For a detailed breakdown of each grade, see [AC joint separation grading]([GRADING URL]).

Late Symptoms of an Untreated Complete Separation

Once the pain of the initial injury settles, the course diverges. Some patients go on to have comfortable, satisfactory shoulder function, though the deformity itself never resolves.

In the majority, however, the mismatched joint produces ongoing and disabling symptoms:

Physical therapy can overcome some of these symptoms. It cannot correct the underlying problem, because the anatomy itself has been permanently disrupted, and for many patients shoulder function remains compromised.

Stable AC Joint Separation, Grades 1 and 2

In less severe injuries the anatomy is left either partially intact, in a grade 2, or completely intact, in a grade 1. Any amount of deformity present will be permanent for the same reason described above.

Pain can be quite severe even where there is little or no visible deformity, which frequently surprises patients. Despite that, simple treatment resolves the large majority of these injuries: a sling for comfort, ice, rest, and early rehabilitation.

Late Symptoms After an Incomplete Separation

A smaller number of patients develop persistent symptoms after an incomplete separation, and some of them have entirely normal radiographs.

The explanation is that the initial impact can cause cell death within the articulating cartilage of the joint, which leads to a later breakdown of the cartilage tissue. This traumatically induced arthritis can produce chronic pain and, in rare cases, requires surgical treatment.

Fortunately the surgery needed here is minor. A repair or reconstruction is rarely indicated, and simple debridement of the end of the clavicle resolves these symptoms reproducibly.

When AC Joint Surgery Should Be Performed

Timing is the single most important variable in AC joint surgery. An acute repair is a considerably simpler operation than the reconstruction required once a separation has become chronic, and the window between them is measured in weeks.

Acute AC Joint Repair, the First 3 to 6 Weeks

Once an AC joint has completely separated, the downward pull of the arm prevents the dislocation from reducing on its own, and it certainly prevents the torn ligaments from healing in the correct position.

The goal of an acute repair is therefore to reduce the deformity with a mechanical device and hold it there while the body does the healing. An acute ligament disruption provokes an intense healing response, and if the bones can be brought into alignment and held reliably, natural ligament healing follows. In this early period the torn ligament ends can also be sewn together, reinforcing and adding to that response.

Early attempts at this used simple screw fixation and were largely successful, but the rigidity of that construct led to hardware breakage and occasional slippage. Our technique is extremely strong and rigid in the direction of the deformity while still allowing motion in other planes, so ligament healing can occur without over constraining the shoulder.

The result is a procedure that is straightforward, restores the anatomy to its original state, and requires no grafting or tissue transfer. That window lasts roughly three to six weeks. After it closes, a more complex procedure becomes necessary.

Chronic AC Joint Reconstruction

Once the initial healing response has passed, the torn ligament ends scar into contracted lumps and the injury site loses its biological ability to heal. New ligament tissue then has to be brought into the repair site and sewn into place, which requires an extended period of healing and tissue incorporation before it can function normally.

In these cases the coracoacromial ligament is detached from the acromion, swiveled over to the front of the clavicle, and surgically reattached. That supplies ample vascularized tissue capable of initiating a healing response, and a thick growth of scar tissue forms between the clavicle and the coracoid, stabilizing the AC joint.

Alternative techniques use a donor tendon graft, meaning cadaveric tissue, though this is rarely necessary except in revision surgery. Removing the end of the clavicle is frequently recommended alongside other techniques and is rarely necessary here, since it risks weakening the repair site and adds complexity to the procedure.

Deciding Whether to Have AC Joint Surgery

For many patients this is a genuinely complex decision rather than a clear one.

One consideration deserves particular weight. An unsuccessful attempt at nonsurgical treatment results in the need for a more complex surgical procedure later, because the acute window will have closed. Each patient has to weigh their own needs and expectations carefully before deciding what is right for them.

The Patented Double Endobutton AC Joint Repair Technique

The technique described here is the subject of United States Patent 8,162,997, which the orthopedic manufacturer Smith and Nephew subsequently acquired. It restores the anatomy to its original state, requires no grafting or tissue transfer, and uses a construct with no knots, which removes knot slippage as a mode of failure.

The joint is reduced to its anatomical location and held there by two small plates, called endobuttons, connected by a continuous loop of extremely strong suture. The device follows the anatomic path of the original ligaments.

Why the Construct Is Designed This Way

The forces disrupting an AC joint are powerful, which sets a demanding requirement for any repair. The construct has to be extremely strong in the direction of those deforming forces and, at the same time, flexible in other planes so the shoulder can move normally.

Connecting two small metal plates with a continuous loop of suture accomplishes both. There are no knots anywhere in the loop, which eliminates the weak links other constructs contain and provides reliable stability throughout the months the body needs to achieve true biological healing.

Surgical Exposure

A small incision, one to two inches, is made over the front of the shoulder, exposing the top of the clavicle and the top of the coracoid. No muscle is cut off the bone. The deltoid is simply split in line with its fibers to visualize the repair site. A downward force then reduces the distal clavicle so that it lines up with the acromion.

Bone Preparation

A drill hole is made through the clavicle and continued into the coracoid process. This hole is placed in the same location as the native coracoclavicular ligament that has torn.

Endobutton Passage

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

Fixation

Two suture tails anchored in the first endobutton, the one beneath the coracoid, are passed through opposite holes of the second endobutton on top of the clavicle. That endobutton is seated flat against the bone and the sutures are tied over it, holding it in place.

A second suture is then passed through a separate drill hole, positioned between the main drill hole and the AC joint, and tied. This adds further fixation and stability to the construct.

Final Ligament Repair

The torn acromioclavicular and coracoclavicular ligaments are then sutured and tied. This provides additional fixation and recreates the original anatomy of the joint.

Frequently Asked Questions About AC Joint Separation Surgery

Will the bump on my shoulder go away without surgery?

For a complete separation, no. Once both sets of ligaments have failed, the collarbone stays elevated because nothing is holding it down, and the deformity is permanent without surgical reconstruction. Lower grade separations, meaning grades one and two, are a different situation entirely and settle with a sling, ice, rest, and early rehabilitation in most cases. The distinction between a stable and a complete separation is what the grading system exists to establish.

How soon after the injury does surgery need to happen?

There is a window of roughly three to six weeks in which an acute repair is possible, and it is worth taking seriously. Within that period the torn ligament ends can still be brought together and sewn, and the reconstruction restores the original anatomy without grafting or tissue transfer. After that window the ligaments have scarred and retracted, and reconstruction becomes a more involved procedure requiring a ligament transfer. The operation is still successful later. It is simply a larger one.

What makes the double endobutton technique different?

The construct connects two small metal plates, one seated beneath the coracoid and one on top of the clavicle, with a continuous loop of very strong suture. There are no knots in the loop, which removes knot slippage as a mode of failure, and the device follows the anatomic path of the original ligaments. The result is a repair that is rigid in the direction the deformity wants to go while still permitting motion in other planes, holding the reduction during the months the body needs for true biological healing.

Do I need surgery for a grade 3 AC separation?

Grade 3 is the genuinely individualized decision, which is why it generates more discussion than any other grade. Grades 4 and 5 are strongly recommended for surgery, and grades 1 and 2 are not. For grade 3 the factors that matter are how physically demanding your work is, whether you are an overhead athlete, how much the deformity bothers you, and how the shoulder performs after a trial of rehabilitation. It is worth noting that a patient who tries nonsurgical treatment first and then wants surgery months later needs the more complex chronic reconstruction rather than the acute repair.

What symptoms mean an old AC separation still needs attention?

Localized pain over the top of the shoulder, painful clicking or popping with motion, shoulder fatigue, and a loss of endurance are the late symptoms that bring patients back, particularly manual laborers and athletes. These frequently appear well after the initial injury has stopped hurting. An old separation that has become symptomatic can still be reconstructed, and post traumatic arthritis at the joint is sometimes treated with debridement of the distal clavicle instead, depending on what the examination and imaging show.

Is a cadaver graft used in AC joint reconstruction?

Rarely, and not in a standard acute repair. The acute technique uses your own tissue, sewing the torn ligament ends together over the endobutton construct, with no graft required. Chronic reconstructions typically use a transfer of the coracoacromial ligament, again your own tissue, moved and reattached. Donor tendon graft is generally reserved for revision surgery where the previous options have been used.

Schedule an AC Joint Consultation in New York City

A separated shoulder is one of the few injuries where the calendar genuinely matters, because the repair available in the first month is smaller and more anatomic than the one available in the third. If you have a visible step at the top of your shoulder after a fall, it is worth being seen promptly rather than waiting to see whether it settles. Dr. Struhl evaluates AC joint injuries at his Manhattan and White Plains offices. Contact our practice to schedule an appointment.

Dr. Struhl’s article

Read Dr. Struhl’s published article on Double Endobutton Technique for Repair of Complete Acromioclavicular Joint Dislocations

Contact our practice today to schedule your consultation with Dr. Struhl.

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