Shoulder Instability

By admin On Mar 3, 2024

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.

Title: 5-Minute Orthopaedic Consult, 2nd Edition

> Table of Contents > Shoulder Instability

Shoulder Instability

Adam J. Farber MD

Basics

Description

Because of the shoulder’s extensive ROM, it is prone to instability.
The term encompasses a spectrum of disorders of varying degree, direction, and cause.
Instability should be distinguished from laxity.
- “Laxity” is the symmetric translation of the humeral head over the surface of the glenoid without symptoms.
- “Instability” occurs when the degree of translation becomes excessive and leads to symptoms.
Shoulder joint stability depends on various static and dynamic anatomic restraints.
- Static restraints: Osseous anatomy
  (glenoid fossa and humeral head), joint capsule, glenohumeral ligaments
  (superior, middle, and inferior), and glenoid labrum
- Dynamic restraints: The muscles and tendons of the rotator cuff, the scapular stabilizers
Shoulder instability is classified by:
- Direction of dislocation: Anterior, posterior, or multidirectional
- Degree: Dislocation, subluxation, microinstability
- Force: Traumatic versus atraumatic
- Patient contribution: Voluntary versus involuntary

Risk Factors

Anterior shoulder instability is common.
- Risk of recurrence after a traumatic anterior shoulder dislocation varies with patient age:
  - 50–85% risk in those initially affected when <20 years old (1,2)
  - 20% risk in those initially affected when >40 years old (1)
Recurrent posterior shoulder instability
most commonly presents with repeated episodes of subluxation with no
history of shoulder injury.
- Usually affects active males (<30 years old)
- Many patients can demonstrate voluntary posterior shoulder instability.
MDI:
- Usually atraumatic
- Is poorly understood and typically results from a combination of excessive tissue laxity and muscular discoordination
- Frequently, history of incidental or no trauma

Pathophysiology

Shoulder instability is associated with injury to the capsuloligamentous labral complex.
- The Bankart lesion is a detachment of the anterior glenoid labrum and capsuloligamentous attachments.
- Patients with recurrent anterior instability also often have anterior capsular redundancy.
Recurrent posterior instability may have
a detached posteroinferior labrum (reverse Bankart lesion), a patulous
posteroinferior capsule, and excessive glenoid retroversion.
Patients with MDI usually have a generalized increase in joint laxity and redundant capsule.

Etiology

Mechanisms of “shoulder dislocation” are addressed elsewhere (see “Shoulder Dislocation” chapter).

Diagnosis

Signs and Symptoms

Keys to accurate diagnosis of shoulder instability are a thorough history and physical examination.

History

Key information for the clinician to identify:
- Initial episode of major, minor, or no trauma
- Arm position at the time of the initial
  event (for determining direction of instability) but, more importantly,
  which arm positions reproduce symptoms
- The necessity of a formal reduction maneuver for a dislocation and the presence of radiographs documenting a dislocation
- Symptoms, pain location, exacerbating activities, and any voluntary component to the instability episodes
Patients with anterior instability typically:
- Have a history of traumatic anterior shoulder dislocation (see “Shoulder Dislocation” chapter).
- Report symptoms, such as pain or apprehension, during arm abduction, extension, and external rotation.
Patients with posterior instability:
- Present with a sense of shoulder instability and looseness or episodes of recurrent subluxation, seldom dislocation
- Experience symptoms with the arm flexed, adducted, and internally rotated (e.g., when pushing a heavy cart or during a seizure)
Patients with inferior instability may become symptomatic when carrying heavy objects, such as a suitcase, at the side.
Patients with MDI (3):
- May have a family history of similar findings and personal history of other joint problems
- Typically have history of minimal or no trauma
- Commonly complain of pain, rather than episodes of subluxation or dislocation
- Experience most symptoms in midrange rather than extreme shoulder motions

Physical Exam

Examine and compare both shoulders: Laxity, strength, and ROM.
Include inspection, palpation, ROM, and a thorough neurovascular examination.
- Inspection may reveal atrophy or mild scapular dyskinesis.
- Palpation may reveal focal tenderness.
Ask the patient to demonstrate the positions and actions that produce the symptoms.
- Symptoms in extension, abduction, and external rotation suggest anterior instability
- Symptoms in flexion, adduction, and internal rotation suggest posterior instability.
Patients with MDI often have generalized ligamentous laxity.
Evaluate shoulder laxity with the
load-and-shift test (assesses amount of humeral head translation on the
glenoid fossa in the anterior or posterior direction).
- Patients with instability often have excessive translation and pain.
- Patients with MDI may have excessive laxity bilaterally.
Assess inferior laxity with the sulcus
test: Pull downward on the neutrally positioned arm, assess amount of
inferior translation and presence of an anterior dimple (or sulcus)
beneath the acromion.
- Often increases translation or reproduces symptoms in patients with MDI
Reproduction of symptoms by provocative tests helps confirm the diagnosis of instability.
- For anterior instability: Apprehension test:
  - Place the patient supine and abduct the
    shoulder 90°, flex the elbow 90°, and gradually externally rotate the
    arm until the patient reports pain or apprehension.
  - Relief of symptoms with the application
    of a posteriorly directed force on the anterior humeral head
    constitutes a positive relocation test, another sign of anterior
    instability.
- For posterior instability:
  - Arm in 90° of elevation and internal rotation
  - Move the arm from the coronal to the sagittal plane and back while applying an axial load to the humerus.
  - Positive test: Humeral head subluxates over the glenoid rim, reproducing symptoms.

Tests

Imaging

Radiographic evaluation should include AP and axillary views of the shoulder.
- Plain radiographs frequently are negative, especially in subtle forms of instability.
- Findings suggestive of anterior instability:
  - A posterolateral impression defect of the humeral head (Hill-Sachs lesion) suggests traumatic anterior dislocation.
  - An anterior-inferior glenoid rim fracture (a bony Bankart lesion)
- Findings suggestive of posterior instability:
  - An anterior impression defect of the humeral head (reverse Hill-Sachs lesion)
  - Posterior lesions of the glenoid rim
CT scanning can help define humeral or glenoid abnormalities.
MRI is useful in identifying labral or capsuloligamentous pathology.

Diagnostic Procedures/Surgery

Examination under anesthesia and diagnostic arthroscopy are not routinely necessary, but they can be helpful in selected cases.

Differential Diagnosis

Conditions such as internal impingement syndrome or SLAP
lesions may be confused with subtle forms of instability, especially in
overhead athletes.

P.397

Treatment

General Measures

Nonsurgical treatment is recommended for most 1st-time anterior dislocations (see “Shoulder Dislocation” chapter) and for posterior shoulder instability, MDI, and voluntary dislocators.
- Modalities: Joint reduction (in the case
  of shoulder dislocation), followed by a period of activity restriction,
  immobilization, and rehabilitative exercises
- The duration of immobilization is controversial.
Surgery may be recommended for recurrent
traumatic anterior shoulder instability and for posterior instability
or MDI after unsuccessful nonoperative treatment (6 months).

Special Therapy

Psychologic evaluation and treatment for patients with habitual voluntary shoulder instability

Physical Therapy

Rehabilitative programs emphasize
strengthening of the shoulder’s dynamic stabilizers (particularly
rotator cuff muscles and scapular stabilizers), regaining full ROM,
restoring normal shoulder mechanics, improving proprioception, and
avoiding provocative arm activities.
- Progression of the rehabilitation
  protocol varies with the direction of instability, quality of the
  tissue, type of repair, and requirements of the patient.
- In general, return to sports is
  restricted for 6–9 months after surgery for anterior instability and
  9–12 months after surgery for posterior instability and MDI.

Medication

Patients with posterior instability from seizures should be treated with medication adjustment to reduce the seizure frequency.

Surgery

The key concept in surgical treatment is
the anatomic repair of the capsuloligamentous or labral abnormality
rather than nonanatomic reconstructions.
Capsulorrhaphy (capsular tightening) enhances correction of instability by reducing capsular laxity and excessive joint volume.
Arthroscopic surgery:
- For traumatic anterior instability:
  - Treatment of choice is Bankart repair
    (reattachment of capsulolabral structures to the glenoid rim) with
    suture anchors and supplemental anterior capsulorrhaphy.
  - Capsular tightening achieved with capsular plication or thermal shrinkage
- For posterior shoulder instability: Arthroscopic capsulolabral repair and posterior capsulorrhaphy
- For MDI: Arthroscopic plication or capsular shift procedures
Nonanatomic open reconstructive procedures:
- Result in failure, loss of motion, and arthritis
- Exception is the Bristow procedure
  (transfer of the coracoid process to the antero-inferior glenoid rim)
  for patients with large bony defects in the glenoid rim
Anatomic open reconstructive procedures:
- For anterior shoulder instability, the classic is the open Bankart procedure.
  - Most commonly used surgical technique
  - Reattaches capsulolabral structures to the glenoid rim
  - Often combined with open capsulorrhaphy to reduce capsular redundancy
- For symptomatic recurrent posterior instability:
  - Posterior capsulorrhaphy
  - Posterior bone block procedures (glenoid bone stock deficiency)
  - Rotational osteotomy of the proximal humerus (excessive retrotorsion of the proximal humerus)
  - Posterior glenoid osteotomy (abnormal glenoid retroversion)
- For MDI:
  - Most common procedure is inferior capsular shift with associated closure of the rotator interval defect.
  - Postoperative immobilization with the arm in neutral rotation and 10–15° of abduction
Because of psychologic problems, surgery is contraindicated for patients with voluntary instability.

Follow-up

Prognosis

Prognosis is excellent after surgical treatment of recurrent anterior shoulder instability.
Posterior shoulder instability and MDI
that fail to respond to nonoperative treatment have a good prognosis
with surgical treatment.

Complications

The risk of recurrent instability after surgical treatment is ~3–10% (4).
The risk of recurrence is lower after
open than after arthroscopic surgical procedures, particularly in
contact athletes with recurrent instability (5).
Complications of open procedures include
pain, decreased ROM, infection, neurovascular injury, late degenerative
arthritis, subscapularis over tightening or rupture, and
hardware-related problems (breakage, loosening, migration, and
intra-articular penetration).
Complications of arthroscopic procedures
include neurovascular injury, adhesive capsulitis, synovial fistula,
and hardware-related problems.

References

1. Hovelius
L, Eriksson K, Fredin H, et al. Recurrences after initial dislocation
of the shoulder. Results of a prospective study of treatment. J Bone Joint Surg 1983;65A:343–349.

2. Simonet WT, Cofield RH. Prognosis in anterior shoulder dislocation. Am J Sports Med 1984;12: 19–24.

3. Schenk TJ, Brems JJ. Multidirectional instability of the shoulder: Pathophysiology, diagnosis, and management. J Am Acad Orthop Surg 1998;6: 65–72.

4. Freedman
KB, Smith AP, Romeo AA, et al. Open Bankart repair versus arthroscopic
repair with transglenoid sutures or bioabsorbable tacks for recurrent
anterior instability of the shoulder: A meta-analysis. Am J Sports Med 2004;32: 1520–1527.

5. Pagnani MJ, Dome DC. Surgical treatment of traumatic anterior shoulder instability in American football players. J Bone Joint Surg 2002;84A: 711–715.

Additional Reading

Matsen FA, III, Thomas SC, Rockwood CA, Jr, et al. Glenohumeral instability. In: Rockwood CA, Jr, Matsen FA, III, eds. The Shoulder, 2nd ed. Philadelphia: WB Saunders, 1998:611–754.

Robinson CM, Dobson RJ. Anterior instability of the shoulder after trauma. J Bone Joint Surg 2004;86B:469–479.

Robinson CM, Aderinto J. Recurrent posterior shoulder instability. J Bone Joint Surg 2005;87A:883–892.

Miscellaneous

Codes

ICD9-CM

718.81 Shoulder instability
831.1 Shoulder dislocation, anterior
831.2 Shoulder dislocation, posterior
831.3 Shoulder dislocation, inferior

FAQ

Q: Should patients with voluntary instability undergo surgery?

A:
Generally, no. Most patients with voluntary instability have underlying
psychologic problems that the surgery cannot help and, thus, make poor
surgical candidates.

Q: What are the indications for arthroscopic anterior shoulder stabilization?

A:
Patients with acute traumatic anterior dislocation, without multiple
dislocations, who have a Bankart lesion are the ideal candidates for
arthroscopic stabilization. Assessing capsular laxity arthroscopically
requires advanced surgical skills. Arthroscopic stabilization is
preferred in overhead athletes (e.g., pitchers), but it has a higher
failure rate than open repairs in contact athletes (e.g., football
players).