Shoulder Instability and Dislocation

01  The injury

What shoulder instability is

The shoulder trades stability for motion. The ball of the humerus sits against a shallow socket, the glenoid, and most of what keeps it centered comes from soft tissue: a rim of cartilage called the labrum that deepens the socket, and the ligaments of the joint capsule. When the ball is forced out of the socket, it is a dislocation. When it slips partway and returns on its own, it is a subluxation. Both count, and both can damage the joint.

Most instability is anterior, meaning the ball comes out the front. It usually happens with the arm out to the side and rotated back, as in an arm tackle or a fall on an outstretched hand. Two injuries tend to come with it.

The Bankart lesion

The labrum and capsule tear away from the front of the socket. When a piece of the socket rim breaks off with them, it is called a bony Bankart. Repeated dislocations wear the front of the socket down further, which is why the number of events matters.

The Hill-Sachs lesion

As the ball comes out, the back of it strikes the front edge of the socket and leaves a compression defect. Small ones are common and harmless. Large ones can catch on the socket edge and lever the shoulder back out.

Posterior and multidirectional instability

Less often the shoulder slips out the back. I see this in offensive and defensive linemen, in lifters who bench and push heavy, and in baseball players, where the lead shoulder can sublux during the swing. That last condition has its own name, batter's shoulder, and I have written about how it is evaluated and treated. A smaller group has loose shoulders in several directions without a single major injury. That pattern usually starts with physical therapy rather than surgery.

02  The first decision

Surgery or rehab after a first dislocation

This is the question I am asked most, and the answer depends on who is asking.

For young athletes, the evidence is consistent. In a prospective study of 252 patients between 15 and 35 who were treated with a sling and physical therapy, the shoulder became unstable again in 56% within two years and in 67% by five years, and young men carried the highest risk. In a randomized trial of patients under 30 with a first traumatic dislocation, early arthroscopic stabilization cut the redislocation rate from 47% to 16% and produced better shoulder-specific quality of life.

Waiting for a second or third dislocation is not free. Each event can tear more labrum and take more bone off the front of the socket, and enough bone loss changes which operation you need.

Surgery is not the right answer for everyone. Older or less active patients, people whose shoulders subluxed without structural damage, and patients with generalized looseness often do well with a focused strengthening program. The factors I weigh are:

• Your age and sex
• Your sport, position, and level, especially contact and collision sports
• Where you are in your season and your career
• Dislocation or subluxation, and how many events you have had
• How much bone is missing from the socket and the ball
• What your exam shows, including how apprehensive the shoulder is in the at-risk position

03  In season

Finishing the season with an unstable shoulder

Many athletes want to finish the season, and in the right situation that is a reasonable plan. Return to play after an in-season event is guided by restored motion and strength, a shoulder that is no longer apprehensive, and sometimes a brace, depending on position.

The trade-off should be clear before you go back out. In a prospective study of 45 collegiate contact athletes managed without surgery after an in-season instability event, 73% returned to play, after a median of five days. Only 27% finished the season without another episode. Athletes who had subluxed were more likely to return than those who had fully dislocated.

When an athlete chooses to finish the season, I plan the stabilization for the end of it, and I work with the team's athletic trainers so everyone is watching for the same warning signs. If the shoulder comes out again, we reassess the bone before deciding anything further.

04  The workup

Measuring the bone before choosing the operation

The workup starts with x-rays and an MRI, often an MR arthrogram, to see the labrum, capsule, and cartilage. When there is any concern for bone loss, which is common after more than one dislocation, I add a CT scan with 3D reconstruction. CT is the most reliable way to measure how much of the socket is missing and how large the Hill-Sachs defect is.

Two measurements drive the decision.

Glenoid bone loss

For years, losing 20 to 25% of the socket width was treated as the point at which a soft-tissue repair alone was no longer enough. Later work showed the real threshold is lower. In active patients, outcomes after an isolated arthroscopic repair began to decline once bone loss passed about 13.5%, even in shoulders that never dislocated again. In an early study of contact athletes, arthroscopic repairs failed in 89% when a significant bone defect was present, against 6.5% when it was not.

The glenoid track

The glenoid track describes the contact zone between the ball and the socket as the arm moves. If the Hill-Sachs defect stays inside that zone, it is on-track and unlikely to catch. If it falls outside, it is off-track and can lever the shoulder out. Socket and ball defects interact, so I measure both together rather than either one alone.

05  Treatment

Matching the operation to the problem

No single operation fits every unstable shoulder. The goal is to rebuild what is actually missing, whether that is soft tissue, bone on the socket side, bone on the ball side, or a combination.

Arthroscopic Bankart repair

Through small incisions, I reattach the torn labrum to the socket with suture anchors and retension the stretched capsule, a step called a capsular shift. This is the standard operation when bone loss is minimal.

Remplissage

When the Hill-Sachs defect is off-track or borderline, I fill it by securing the back of the rotator cuff tendon into the defect so it can no longer catch on the socket. Remplissage is added to an arthroscopic Bankart repair rather than performed alone.

Latarjet procedure

When the socket has lost a meaningful amount of bone, or a prior soft-tissue repair has failed, I transfer a piece of the coracoid, a hook of bone at the front of the shoulder blade, to the front of the socket. The bone block restores socket width, and the tendons attached to it act as a sling across the front of the joint when the arm is in the at-risk position.

Distal tibial allograft reconstruction

For large bone loss, revision cases, and failed Latarjet procedures, I rebuild the socket with donor bone from the lower tibia. Its cartilage surface is curved, so it restores the depth of the socket as well as its width. With my colleagues at the Hospital for Special Surgery, I studied this in cadaveric shoulders. Distal tibia reconstruction restored more of the socket's natural concavity than a classic Latarjet and gave equivalent stability once the Latarjet's sling effect was included. A follow-up study found that where the capsule is repaired during the reconstruction changes how the ball sits in the socket, and repairing it to the native socket overtightened the joint in testing. Both were laboratory studies at time zero. They inform how I do the operation, and the clinical outcome data are still developing.

Humeral head reconstruction

When the Hill-Sachs defect is too large for remplissage, the ball itself can be rebuilt with a shaped bone graft, such as talus allograft.

Posterior labral repair

For posterior instability, including linemen and batter's shoulder, the labrum and capsule at the back of the socket are repaired arthroscopically. Most patients with batter's shoulder never need surgery. Those who do generally return to play at a high level.

06  Recovery

Phase by phase after stabilization

These ranges describe a typical course after an arthroscopic stabilization. Bone procedures follow a similar sequence, with return to contact tied to confirmed graft healing. Your program depends on your procedure, your sport, and how the shoulder responds.

1. Day 0

   Surgery and the sling

   Most stabilizations are outpatient, and you go home the same day in a sling. The sling protects the repair while the labrum heals back to bone.

2. Weeks 0–6

   Protection

   You stay in the sling for three to six weeks, depending on the procedure, except for therapy and hygiene. Elbow, wrist, and hand motion start right away, and shoulder motion progresses within limits that protect the repair, especially rotation away from the body. Lower body and core training continue.

3. Weeks 6–12

   Restoring motion and early strength

   Once the sling is off, we work toward full motion while beginning rotator cuff and shoulder blade strengthening.

4. Months 3–5

   Building strength and power

   Strengthening progresses to sport-specific and plyometric work. Throwing and contact remain off limits.

5. Months 5–6

   Return to throwing and contact

   Throwing athletes begin an interval throwing program. Return to full contact depends on measured strength, motion, and functional testing rather than the calendar. For bone procedures, I also want evidence that the graft has healed.

07  Revision

When a previous stabilization has failed

A shoulder that dislocates again after surgery needs a fresh workup, not a repeat of the same operation. The most common reasons a stabilization fails are bone loss that was underestimated or developed afterward, a new injury, and soft tissue that was not strong enough to hold.

Revision evaluation starts with a CT scan to measure the socket and the ball, a review of the original operative findings when they are available, and an exam. Revision surgery usually means restoring bone, through a Latarjet, a distal tibial allograft reconstruction, or a humeral-sided graft, rather than another soft-tissue repair.

I see patients for second opinions after failed stabilization, including after a failed Latarjet. If you live outside the Baton Rouge area, call the office and we can arrange for your imaging to be reviewed before your visit.

08  Common questions

Questions about shoulder instability