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Multidirectional Instability

- Discussion:
    - multidirectional instability implies three-way subluxations or dislocations either anteriorly, posteriorly, or inferiorly;
    - these patients usually have no true Bankart lesion and incontrast patients have a capacious axillary pouch; 
           - ref: The Effect of Variation in Definition on the Diagnosis of Multidirectional Instability of the Shoulder. 
    - affects overhead throwing atheletes, gymnasts, swimmers;
    - stabilizers of the shoulder:
           - in multidirectional instability, static stabilizers may be stretched and dynamic stabilizers may be atrophied;
    - arthroscopic "drive-through" sign is usually present;
    - associated conditions: collagen disorders
    - diff dx: (conditions which can be confused w/ multidirectional instability):
           - impingement syndrome
           - rotator cuff tear
           - thoracic outlet syndrome
           - biceps tendinitis 
           - cervical disc herniation
           - syringomyelia 
                 - Syringomyelia presenting as shoulder instability
    - natural history:
           - A longitudinal study of patients with multidirectional instability of the shoulder with seven- to ten-year follow-up.

- Exam:
    - exam for anterior instability;
    - look for generalized hyper-elasticity (thumbs can be hyperextended to the distal radius);
    - diagnosis is made by demonstrating instability in at least two planes;
    - sulcus sign is often seen in pts with multidirectional instability;
           - look for prominent depression below acromion when inferior traction is applied to wrist;
           - is an indication of deficient rotator interval capsule

- Treatment: 
    - multidirectional instability is not well suited to operative treatment;
    - initial treatment should consist of intensive rehabilitation with rotator cuff strengthening (dynamic stabilizers) for
             at least one year;
    - surgical treatment options:
           - arthroscopic reconstruction:
                  - involves posterior & anterior plication of inferior capsule, followed by possible rotator interval plication; 
                  - with intact labram (anterior / posterior), the suture passer/shuttle device can be passed underneath the labrum, allowing the imbricated capsule to be anchored against the labrum;

           - anterior shoulder reconstruction:
                  - mutlidirectional instability can be successfullly managed w/ an anterior shoulder reconstruction combined with a verticle (upward) shift of the inferior capsule;
                  - theoretically over-tightening of the anterior capsule might result in posterior subluxation of the humeral head;
           - combined anterior and posterior approach:
                  - Hamada K, et al (1999), 64% of shoulders w/ combined procedure developed a posterolateral humeral head defect at one year postop, despite absence of subluxation;
                          - the authors concluded that over tightening of the anterior capsule resulted in subclinical anterior subluxation;
           - inferior capsular shift using either an anterior vs posterior approaches:
                  in the report by Pollock  RG, et al (2000), the authors treated 52 shoulders w/ multidirectional instability w/ an inferior capsular shift using either an ant / posterior - depending on direction major instability (determined from intra-op exam);
                  - essential feature of this procedure is adequate separation of the muscle from the capsule inferiorly to prevent tethering and to allow effective shifting of the capsule and reduction of joint volume;
                         - careful separation of the capsule from the overlying musculotendinous layer (the subscapularis anteriorly or the infraspinatus and teres minor posteriorly) in order to allow effective shifting of the ligaments to reduce capsular redundancy;
                  - in this manner, the region of maximum capsular redundancy is most directly approached anteroinferiorly with the anterior approach and posteroinferiorly with the posterior approach;
                  - 30 (61 %) had an excellent overall result, 16 (33 %) had a good result, one (2 percent) had a fair result, and two (4 percent);
                  - 47 (96 %) of the 49 shoulders remained stable at the time of follow-up;
                  - 2 of the 34 shoulders that had been repaired through an anterior approach began to subluxate anteroinferiorly again; 
                  - references:
                          - The inferior capsular-shift procedure for multidirectional instability of the shoulder.
                          - Inferior capsular shift for involuntary inferior and multidirectional instability of the shoulder. A preliminary report
                          - The inferior capsular shift for instability of shoulder. Long term results in 34 shoulders.  
                          - Operative results of the inferior capsular shift procedure for multidirectional instability of the shoulder.

           - posterior capsular imbrication:
                  - Arthroscopic posteroinferior capsular plication and rotator interval closure after Bankart repair in patients with traumatic anterior glenohumeral instability—A minimum follow-up of 5 years. 

           - closure of rotator interval (see rotator interval capsule)
                  - may be determined during intraop exam, w/ excessive inferior translation (sulcus sign) w/ arm positioned in adduction and external rotation;
                  - the decision to perform a rotator interval closure should be performed only after the inferior capsular reconstruction (since theoretically the sulcus sign may be eliminated with the inferior shift);
                  - references:
                         - Effects of Capsular Plication and Rotator Interval Closure in Simulated Multidirectional Shoulder Instability
                         - Arthroscopic posteroinferior capsular plication and rotator interval closure after Bankart repair in patients with traumatic anterior glenohumeral instability—A minimum follow-up of 5 years. 

Involuntary inferior and multidirectional instability of the shoulder: etiology, recognition, and treatment.

Arthroscopic treatment of multidirectional shoulder instability with minimum 270 degrees labral repair: minimum 2-year follow-up.

Sequential volume reduction with capsular plications: relationship between cumulative size of plications and volumetric reduction for multidirectional instability of the shoulder.

- Misc:

Arthroscopic capsular shrinkage of the shoulder for the treatment of patients with multidirectional instability: minimum 2-year follow-up

Arthrodesis as a salvage procedure for recurrent instability of the shoulder

Thermal Capsular Shrinkage for Treatment of Multidirectional Instability of the Shoulder.