What is multidirectional instability of the shoulder joint?
Multidirectional instability of the shoulder, also known as non-traumatic instability of the shoulder, is a loosening of the glenohumeral joint of the shoulder in multiple directions. Multidirectional instability of the shoulder develops when the ligaments around the shoulder joint become lax. This laxity can be a natural condition (present at birth) or can develop later in life. Many MDI patients are avid overhead athletes (e.g., gymnastics, swimming, throwing sports, baseball, tennis, etc.) who repeatedly stretch the shoulder capsule to the limits of its range of motion. These ligaments are overstretched, allowing for subluxation or subluxation of the shoulder, and this increased mobility leads to repeated small traumas, which in severe cases result in tears of the glenoid labrum or rotator cuff.
Patients with MDI often have other ligamentous laxities of the joint, with hyperextension of the knee and elbow being more common. These patients often suffer from bilateral MDI of the shoulder joint, and because so many athletes with MDI are very successful, there is a debate as to whether it is the joint laxity that allows these athletes to excel or the laxity caused by the repetitive pulling of the joint by athletic exercise.
What are the symptoms of multidirectional instability of the shoulder joint?
The symptoms and problems of multidirectional instability of the shoulder are generally associated with recurrent episodes of dislocation, and repeated subluxations often cause patients to harbor a sense of dread about certain daily activities.
The symptoms described are more vague, such as pain in an unclear position of the shoulder. The patient feels some kind of abnormality and discomfort when the arm is moved to certain positions.
Pain due to inflammation within the joint.
The patient may have signs of glenoid labrum and/or rotator cuff injuries that can result from repeated increases in mobility.
How is multidirectional instability of the shoulder joint diagnosed?
A detailed history and physical examination are key to the diagnosis.
1. Typical medical history includes
History of polyarticular laxity
History of shoulder dislocation without violence leading to dislocation
Recent occurrence of instability
2. Taking a history may reveal a recent injury, significant dislocation, or a change in motion (or training) that has caused instability in a previously healthy shoulder joint.
3. Examination of shoulder mobility is very important. By moving the arm, the physician can assess the maximum mobility of the shoulder joint. Although only one side may be symptomatic, multidirectional instability laxity may be present in both shoulders. In patients with multidirectional shoulder instability, the affected shoulder has increased mobility in multiple directions and may move in one or more directions to produce symptoms. The diagnosis of MDI is based on the assessment of the overall shoulder mobility, the elicitation of symptoms during the physician’s examination, and the sulcus test.
4. Further examination is mainly based on imaging.
X-rays are mainly used to rule out any combined injuries that require treatment. Occasionally, congenital deformities leading to shoulder instability can be detected
MRI can reveal other different causes of shoulder pain, when rehabilitation alone is not enough
5. Shoulder arthroscopy Shoulder arthroscopy allows the physician to see the internal structures of the glenoid shoulder joint through small optical fibers and can detect associated injuries such as increased shoulder mobility and repeated trauma resulting in glenoid labral injury and non-total rotator cuff injury. These injuries may be treated simultaneously through arthroscopy. The patient then undergoes rehabilitation to achieve a pain-free shoulder.
How is multidirectional instability of the shoulder treated?
The treatment of multidirectional instability of the shoulder joint should be individualized, and different treatment plans should be developed for each patient.
1.Non-surgical treatment
Most patients with MDI can be treated with non-surgical treatment, i.e. physical therapy that emphasizes muscle rehabilitation. Rehabilitation exercises focus on strengthening the rotator cuff muscles and the muscles around the scapula. The strengthened muscles provide dynamic stabilization of the shoulder joint, which is especially relevant for the shoulder joint that lacks static (ligamentous) stabilization.
The vast majority of patients (about 90%) will eliminate pain symptoms after at least six months of consistent rehabilitation. Continuing to exercise daily or weekly as prescribed by the physician is likely to result in a successful recovery.
Patients whose symptoms do not resolve after physical therapy are a challenge to treat. Only about 70-80% of patients eventually achieve long-term stabilization of the shoulder joint, with 60-70% of them reaching the level of motion before the instability occurred.
2. Surgical treatment
The most difficult patients to treat are athletes whose symptoms persist after rehabilitation. Athletes are often successful in their sport because of the increased mobility of the joint, so surgery should only be considered if the patient is well informed about MDI and they are aware that they will have to lose some mobility while gaining stability in the shoulder joint through surgery. Patients who are able to dislocate the shoulder at will are the least suitable for surgical treatment and surgery is difficult for them to be successful.
(1) Traditional surgical approach
The traditional surgical method for treating MDI is to reduce the shoulder capsule and reduce the mobility of the glenohumeral joint. This open surgical operation is called extensive release and overlap of the lower shoulder capsule.
The lower shoulder capsule is incised and overlapped to tighten the ligaments and reduce the capsule size.
During this procedure, the subscapularis stop is disconnected to access the shoulder capsule and reattached at the end of the procedure.
The success rate of this procedure is about 75% in carefully selected patients. (Patients considered suitable for surgery after detailed history and physical examination) The postoperative shoulder joint loss of mobility is high, so the athlete may not be able to return to play.
(2) Arthroscopic techniques
New arthroscopic techniques have been developed in recent years to treat multidirectional instability of the shoulder joint. Overlapping capsules are sutured with arthroscopic sutures to reduce the joint capsule. This technique is very exciting and is especially attractive to athletes who need shoulder stability while preserving joint mobility.
(3) What are the complications of surgical treatment?
The most common complication is recurrence of shoulder instability, even in carefully selected patients with a recurrence rate of 20% or more, as well as post-operative stiffness and partial loss of mobility, although partial loss of mobility while gaining stability is acceptable. The average loss of external rotation is 10°, with approximately 5% of patients losing more than 10° of external rotation. Other complications are infection, nerve damage, or vascular injury, common to most surgeries.
Functional rehabilitation of multidirectional instability of the shoulder joint
1. Rehabilitation of non-surgical treatment
The rehabilitation process for multidirectional instability of the shoulder is long, usually requiring a 6-month physiotherapy rehabilitation program. If physiotherapy is successful, a maintenance physiotherapy program is required to prevent recurrence of instability. If the instability is not controlled by 6 months of physical therapy, surgical treatment is required.
2.Recovery from surgical treatment
4-6 weeks after surgery, the patient wears a sling to protect the repaired tissue during the healing period
Gently move the elbow and wrist joints during this braking period
After the initial healing period is complete, the patient begins a slow, progressive physical therapy program to restore joint mobility and finally strengthen the shoulder joint with strength exercises.
The rehabilitation program for patients undergoing open surgery should protect the subscapularis muscle (as this muscle stop was severed and reattached during surgery)
Patients undergoing arthroscopic heat stabilization require longer periods of braking (usually up to 8 weeks) to allow scar tissue to replace heat-treated tissue. Scar tissue formation is necessary for the success of this procedure because of the risk of elongation of the heat treated tissue
Limit full participation in sports from 9-12 months after the repair
Answers to frequently asked questions
1. What is MDI?
A: MDI refers to multi-directional laxity of the shoulder joint with instability. This instability is often due to laxity and elongation of the supporting ligaments of the shoulder joint, which leads to increased mobility of the glenohumeral joint.
2. Can physical therapy successfully treat MDI?
A: Studies have shown that many patients (80%) can improve their symptoms with physical therapy alone. Patients are most likely to have success with a daily maintenance physical therapy program.
3. If I need surgery to stabilize the shoulder joint, how much mobility am I likely to lose?
A: It is not certain how much mobility will be lost. The normal mobility of the shoulder joint is 80-120° of external rotation at 90° external booth (elbow pointing outward) (the angle of external rotation increases in throwing athletes with increased shoulder mobility). The average external rotation angle in the shoulder joint that was stabilized after surgery was 90° at the 90° external booth. Early arthroscopic findings suggest a reduction in lost mobility, but further evaluation is needed.
4. If I do not want a large surgical incision, can the procedure be performed arthroscopically?
A: Arthroscopic techniques continue to evolve and advance, and short-term follow-up results indicate that arthroscopic success rates are comparable to those of open surgery. Although the initial results are encouraging, long-term studies are needed for further confirmation.