Shoulder

A bone sticking up on top of my shoulder: AC joint dislocation and the hook plate

Hee Seung Nam, MD, Orthopedic Surgeon · October 31, 2026

Some people come in after falling on the shoulder while cycling or exercising and say, “a bone is sticking up on top of my shoulder.” Often the joint where the outer end of the collarbone meets the acromion of the shoulder blade, the acromioclavicular (AC) joint, has been knocked out of place.

How far it is out of place decides the treatment

Several ligaments hold the collarbone in this joint. Depending on which ligaments are torn and how badly, we usually use the Rockwood classification, from type 1 to type 6.

In short, types 1–2 with little displacement almost never need surgery, type 3 is the range where doctors disagree, and from type 4 up the balance tips toward surgery.

If surgery is done, what are the options?

There are two main approaches.

• Hook plate: a metal plate is laid on top of the collarbone and its hook is passed under the acromion to press the collarbone down. It is easy to align while looking directly at the joint, and because it has been used for a long time its results are well known.
• Suspension fixation (TightRope, “dog bone,” etc.): holes are drilled in the collarbone and the coracoid process beneath it, and the two are tied together with a strong cord and button-shaped anchors. In many cases the hardware does not need to be removed later.

How do the results of the two methods differ?

A meta-analysis that pooled studies comparing the two methods in acute type 3–5 dislocations that needed surgery found no meaningful difference in shoulder function scores (Constant, UCLA). Pain scores were slightly lower with suspension fixation.

The hook plate also has clear weaknesses.

• Because the hook sits under the acromion, it can catch or hurt when you raise the arm high.
• Rarely, the bone of the acromion where the hook rests is worn away.
• For that reason, once bone and ligaments have healed, usually within a few months, a second operation to remove the plate is needed.

Suspension fixation, on the other hand, often needs no hardware removal, but drilling through the coracoid is tricky and loosening of the fixation or re-dislocation has been reported, rarely.

So is surgery always better?

Not necessarily. In a multicenter randomized study in Canada that split acute type 3–5 dislocations between hook plate surgery and non-surgical treatment, the operated side looked better on X-ray but shoulder function at two years was similar, and in the first few months recovery was actually faster in the non-surgical group. Reoperations were more common on the surgical side.

So I do not operate on types 1–2, and for type 3 I decide after talking through job, activity, pain and concerns about appearance. When I do operate, I choose the method that gives that patient the most dependable result; I mostly use the hook plate, whose results are well known and which lets me align the joint precisely while looking at it directly. In return, I always tell patients before surgery that a plate removal operation will be needed.

In closing

• Types 1–2 mostly get better without surgery.
• Type 3 can go either way, surgical or non-surgical, and we decide together based on your life.
• If surgery is done, functional results are similar with a hook plate or suspension fixation, and each has pros and cons. Whichever method is used, what matters is that it is one the operating surgeon is familiar with and can do well.

This article is general medical information. Treatment can differ depending on the degree of dislocation, associated injuries, age and activity level, so please confirm with an examination.