Shoulder Surgery — Melbourne

AC Joint Excision (Distal Clavicle Excision)

AC joint excision — also called distal clavicle excision or the Mumford procedure — removes a small amount of bone from the outer end of the collarbone so that the worn surfaces of the acromioclavicular joint no longer grind against each other.

It is the most common operation for AC joint arthritis that has not settled with non-operative care.

What the Operation Does

The AC joint sits at the very top of your shoulder, where the collarbone (clavicle) meets the acromion. When the cartilage lining wears away, the two bones rub directly on each other, which is what causes pain on top of the shoulder, with cross-body reaching and when lying on that side.

Rather than resurfacing the joint, the surgeon removes the last few millimetres of the collarbone. That creates a small gap so the bones can no longer make contact. The gap fills with scar tissue, and the surrounding ligaments continue to hold the collarbone in place.

When It Is Considered

This is not a first-line treatment. Surgery is generally considered when:

  • Pain has persisted despite a proper trial of non-operative care — usually at least six months of activity modification, anti-inflammatory medication, physiotherapy and, where appropriate, a corticosteroid injection.
  • Symptoms are limiting your sleep, work or sport.
  • Examination and imaging confirm the AC joint is the source of pain. A diagnostic injection into the joint can help settle this, because more than one structure in the shoulder can produce pain in the same area.

How It Is Performed

Most AC joint excisions are done arthroscopically (keyhole), through small incisions using a camera. There are two arthroscopic routes:

  • Indirect (bursal) approach — through the subacromial space. This is the more common choice, because many patients also have impingement or rotator cuff problems that can be treated at the same time.
  • Direct (superior) approach — straight into the AC joint, sparing the bursa. Suited to isolated AC joint disease.

An open procedure through a small incision remains an option in selected cases.

Typically less than a centimetre of bone is removed. The amount matters: too little and pain can persist because the bones still touch; too much and the joint can become unstable. The operation usually takes well under an hour and is generally day surgery, often combined with other shoulder procedures.

Recovery

  • Sling: usually 1–2 weeks, for comfort rather than protection.
  • Physiotherapy: gentle movement starts within the first few days.
  • Desk work: often within a few days.
  • Manual work: commonly 4–6 weeks.
  • Sport and gym: a graded return from around 6–8 weeks, with pressing and heavy overhead work later.

Recovery is quicker than rotator cuff repair, because no tendon has been reattached to bone and there is nothing that has to heal before you can load the shoulder.

Risks and Things to Weigh Up

  • Persistent pain from incomplete resection — particularly if the back of the joint has not been fully cleared. This is the most common reason for an unsatisfactory result.
  • Instability of the collarbone if too much bone is taken or the supporting ligaments are damaged, which can cause clicking and ongoing discomfort.
  • Weakness, more often after open surgery where muscle attachments are disturbed.
  • Continuing pain from another source — the commonest reason the operation disappoints is that the AC joint was not the only problem.
  • Infection, stiffness and nerve or vessel injury, all uncommon.

What the Results Look Like

Published series report good or excellent results in roughly nine out of ten patients after arthroscopic excision, with most people back to their usual activities within two to three months. Results after open surgery are reported as somewhat more variable.

These figures come from selected patients whose pain was confidently localised to the AC joint — which is why we spend time on the diagnosis before recommending the operation.

Related Services & Information

Content reviewed by our shoulder surgery and physiotherapy teams. This information is general and does not replace personalised medical advice.