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Key Features

Etiology

  • Laxity vs Instability
  • Instability in midrange
  • Activities of daily living
  • 3 directions of dislocation/subluxation
  • Past
  • Atruamatic (AMBRI)
  • Most common
  • Traumatic (TUBS)
  • Current
  • Symptomatic multidirectional with/without hyperlaxity
  • Laxity
  • Congenital (Ehlers-Danlos, Marfans)
  • Acquired
  • Cycle of instability - fatigue - weakness - neuromotor coordination loss - disuse

History

  • Neer and Foster - 1980
  • Recurrent instability and pain
  • Large, redundant inferior capsule
  • 3 directions of instability
  • Operative patients
  • Still no standardized definition

Pathophysiology

  • Large, inferior capsular pouch
  • Rotator interval cleft
  • Loss of muscle strength
  • Proprioception
  • Shoulder joint vacuum
  • Neuromuscular control
  • Acquired condition
  • repetitive overhead activities

Patient History

  • 10-30 yo
  • Recurrent pain and instability
  • Reproducible symptoms
  • Activities of daily living
  • 12% bilateral
  • Reducible dislocation
  • Inferior instability
  • Failed shoulder surgery for instability

Anatomy

  • Dynamic stabilizers
  • Rotator Cuff: 4 muscles
  • Supraspinatus, ifraspinatus, teres minor, subscapularis
  • Proprioception and neuromuscular coordination
  • Scapulothoracic muscles
  • Static stabilizers
  • Glenohumeral ligaments
  • Labrum
  • Glenoid fossa
  • Rotator interval
  • Supraspinatus and subscapularis

Multidirectional Instability

of the Shoulder

By Brian "Jason, Jew-Morm, CHF, DJ Scribbles" Scrivens

Western University of Health Sciences

Diagnosis

  • Exam
  • Muscle atrophy
  • Generalized ligamentous laxity
  • Sulcus Test (rotator interval, (+) >1-2 cm)
  • Abduct 90 + inferior translation (redundant inf. capsule)
  • Load and shift test (grade 1-3)
  • Sensory and Vascular
  • Radiographs to rule out other issues
  • Magnetic resonance arthrography (large capsule, increased volume)

Works Cited

Gaskill, Trevor, MD, Dean Taylor, MD, and Peter Millett, MD. "Management of Multidirectional Instability of the Shoulder." Journal of the American Academy of Orthopedic Surgeons 19 (2011): 758-67. Print.

Jaggi, Anju, and Ali Noorani. "Muscle Activation Patterns in Patients with Recurrent Shoulder Instability." International Journal of Shoulder Surgery 6.4 (2012): 101-07. Print.

Lee, Hui J., and Na R. Kim. "Multidirectional Instability of the Shoulder: Rotator Interval Dimension and Capsular Laxity Evaluation Using MR Arthrography." Skeletal Radiology 42 (2013): 231-38. Print.

Lubiatowski, Przemyslaw, and Piotr Ogrodowicz. "Arthroscopic Capsular Shift Technique and Volume Reduction." European Journal of Orthopaedic Surgery and Traumatology 22 (2012): 437-41. Print.

McKean, Jaon. "Multidirectional Shoulder Instability." Orthobullets.com. N.p., 8 Aug. 2013. Web. 3 Oct. 2013.

Schenk, Thomas, MD, and John Brems, MD. "Multidirectional Instability of the Shoulder: Pathophysiology, Diagnosis, and Management." Journal of the American Academy of Orthopedic Surgeons 6 (1998): 65-72. Print.

Non-operative Treatment

  • Gold standard
  • Strength and neuromotor coordination
  • 2 phases
  • Progressive resistance
  • Muscle coordination
  • Minimum 6 months

What's New

  • Korean study, Aug. 2013
  • MR arthrogarphy shows enlarged rotator interval (p <0.001) and posterior capsule (p <0.05) in MDI
  • Width >15.2mm or depth >6.4mm
  • sensitivity ~90%, specificity ~70%
  • United Kingdom, Dec. 2012
  • Muscle activation (latissimus dorsi and pectoralis major) increased in MDI
  • Latissimus dorsi - 80% ant/post instability
  • Pectoralis major - 60% ant

Operative Treament

  • Classic - open inferior capsular shift
  • First described by Neer and Foster
  • Others
  • Arthroscopic capsular plication
  • Glenoid osteotomy
  • Thermal capsulorrhaphy
  • Less effective in connective tissue disorders

Inferior Capsular Shift

  • Interscalene block
  • Anterior deltopectoral approach
  • Dissect 2/3 of subscapularis tendon near lesser trochanter insertion
  • Rotator interval imbrication
  • T-incision of capsule and plication
  • Spica for 6 weeks, then sling from 6-10
  • Stretching exercises at week 10
  • Studies show >90% satisfaction with surgical procedures
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