Posterior shoulder instability, though less common than anterior instability, presents a unique challenge in orthopedic care. It involves the backward slipping or dislocation of the shoulder joint, often causing pain, weakness, or dysfunction. Recent advances in arthroscopic techniques now allow for a minimally invasive and highly effective approach to treating this condition.
Understanding Posterior Shoulder Instability
Posterior shoulder instability is rare and can be hard to diagnose, often misinterpreted as general shoulder pain or weakness. It occurs when the shoulder joint shifts or slips backward, and can be caused by a traumatic injury or repetitive microtrauma—such as repetitive lifting or pushing exercises.
Historically, both open and arthroscopic surgeries have been used to treat this condition. The study by Provencher et al. evaluated arthroscopic stabilization specifically, examining how different patient and surgical factors influenced outcomes.
Diagnostic Evaluation
Before surgery, patients underwent a full physical examination, X-rays, and magnetic resonance arthrograms (MRAs). These imaging tests helped detect:
- Posterior labral tears (in 52% of patients),
- Excessive capsular laxity (“billowing” of the posterior capsule),
- Other coexisting shoulder conditions like SLAP lesions or partial-thickness rotator cuff tears.
Even when MRAs appeared normal, physical findings often confirmed instability requiring surgical intervention.
Surgical Approach: Arthroscopic Stabilization
All patients were positioned on their side under anesthesia, and the shoulder was examined to determine the degree of posterior translation. Depending on findings, surgeons either:
- Repaired torn labrum using suture anchors (in 17 patients), or
- Tightened the capsule through plication stitches (in 16 patients).
Other procedures performed when necessary included:
- Biceps tenodesis,
- SLAP repairs,
- Closure of the rotator interval capsule in select cases.
Rehabilitation and Recovery
Following surgery:
- Patients wore a sling in neutral rotation for six weeks.
- Shoulder movement was restricted during early recovery.
- Physical therapy began at six weeks to restore full motion and strengthen muscles.
- Full activity, including return to sports or military duties, was typically allowed after four months.
Key Factors Affecting Success
- Better Outcomes: Involuntary instability, first-time surgery, traumatic cause.
- Worse Outcomes: Voluntary subluxation, prior surgery (especially thermal capsular shrinkage), microtrauma without labral tears.
- Capsulolabral Repair vs. Plication: Patients with labral repair using anchors generally had better results than those with plication only.
Should the Rotator Interval Be Closed?
The rotator interval (RI) was closed in 2 patients—both of whom failed treatment. The study suggests that RI closure is not routinely necessary unless specific indications are present. Most patients had good outcomes without RI intervention.
Safety and Complications
There were:
- No nerve injuries,
- No infections,
- No issues with the surgical wounds,
showing that arthroscopic techniques are relatively safe when performed properly.
Final Thoughts and Conclusion
Arthroscopic treatment for posterior shoulder instability is a safe and effective method, especially for patients with traumatic and involuntary instability who have not undergone prior surgery.
While some patients may not achieve full relief—particularly those with voluntary instability or prior procedures—the majority experience significant improvement in stability, strength, and return to function.
This minimally invasive approach represents a modern solution to a historically difficult problem.
If you’re experiencing shoulder instability, especially if it’s interfering with your daily life or athletic performance, consult with an orthopedic specialist experienced in arthroscopic shoulder procedures. With proper diagnosis and treatment, most patients can expect excellent outcomes and a return to their active lifestyles.
Do you have more questions?
Q. What is posterior shoulder instability?
A. Posterior shoulder instability occurs when the ball of the shoulder repeatedly slips out of the back of the socket.
Q. What are common causes of posterior shoulder instability?
A. It can result from repetitive overhead activities, trauma, or congenital conditions that lead to looseness in the joint.
Q. What are the symptoms of posterior shoulder instability?
A. Symptoms include pain, a feeling of looseness, and episodes where the shoulder feels like it is slipping out of place.
Q. How is posterior shoulder instability diagnosed?
A. Diagnosis involves a detailed history, physical examination, and imaging such as X-rays and MRIs.
Q. What are the non-surgical treatments for posterior shoulder instability?
A. Non-surgical options include physical therapy to strengthen shoulder muscles and activity modification.
Q. When is surgery recommended for posterior shoulder instability?
A. Surgery is recommended when non-operative treatments fail or when instability significantly affects daily life or sports performance.
Q. What does arthroscopic treatment of posterior shoulder instability involve?
A. It involves the use of a camera and small instruments inserted through tiny incisions to repair and tighten the damaged structures in the shoulder.
Q. How is the torn labrum treated during surgery?
A. The torn labrum is reattached to the bone using suture anchors during the arthroscopic procedure.
Q. How long does the arthroscopic surgery take?
A. The surgery typically takes about 1 to 2 hours.
Q. What type of anesthesia is used for the procedure?
A. General anesthesia combined with a regional nerve block is usually used.
Q. Will I need to wear a sling after surgery?
A. Yes, a sling is typically worn for 4 to 6 weeks to protect the repair.
Q. When can physical therapy start after surgery?
A. Physical therapy usually begins after the sling is removed to help restore motion and strength.
Q. How long is the recovery after arthroscopic posterior shoulder stabilization?
A. Full recovery typically takes about 4 to 6 months, depending on the individual and the extent of the injury.
Q. Can patients return to sports after surgery?
A. Most patients can return to sports after completing rehabilitation, usually around 4 to 6 months post-surgery.
Q. What are the risks of arthroscopic shoulder surgery?
A. Risks include infection, stiffness, nerve injury, recurrence of instability, and the need for further surgery.
Q. What are the benefits of arthroscopic surgery compared to open surgery?
A. Arthroscopic surgery is less invasive, results in smaller scars, and typically allows for a quicker recovery.
