Posterior Shoulder Instability: What We Know and What’s Needed to Improve

 

By: Peter S. Vezeridis, M.D. and Felix H. Savoie III, M.D.

 

Posterior glenohumeral joint instability is an increasingly relevant diagnosis, particularly in the athletic population. While posterior shoulder instability is less common than anterior shoulder instability, there are certain patient populations that are at higher risk, including football players, rugby players and military service members.1,2,3 Female athletes also represent an increasingly more common patient population with posterior instability, especially in volleyball, softball and gymnastics. Accurate diagnosis of posterior instability might be delayed as patients often do not present with a clear history of a traumatic shoulder injury. Our understanding of this pathology has increased over the past several years with a growing body of research dedicated to improving our diagnosis and treatment of this challenging condition.

 

The small osseus static restraint and the high mobility of the glenohumeral joint result in the shoulder being particularly prone to instability. Disrupting the balance between dynamic and static stabilizers can lead to instability including subluxations or dislocations. The glenohumeral joint stabilizers most important in posterior instability include the posterior labrum, posterior capsule, glenoid and humeral head morphology, rotator cuff and rotator interval. The role of the rotator interval in posterior instability is highly controversial. Additionally, the scapula and its position play a tremendous role in allowing the dynamic stabilizers to effectively prevent posterior subluxation. Scapular winging or protraction may produce posterior subluxation, and posterior instability may be the root cause of posterior subluxation. As a result, each examination maneuver should be performed with and without scapular assist.

 

A thorough history, physical examination and imaging evaluation are essential to arrive at an accurate diagnosis and optimize the treatment plan. Frequently, patients with posterior shoulder instability will not present with the classic history of a traumatic posterior glenohumeral joint dislocation. Instead, their presentation can be highly variable. It is important to determine the predisposing factors that have resulted in the patient’s posterior instability. Deep pain within the joint’s posterior aspect is the most common symptom, and mechanical symptoms may or may not be present.4 Physical examination typically demonstrates full range of motion. Specific physical examination tests including the Kim Test, Jerk Test and Posterior Stress Test. The Load and Shift Test is also helpful in diagnosing posterior instability.5,6,7 Imaging studies include X-rays and magnetic resonance arthrograms. CT scans are also useful in further evaluating patients with abnormal osseus morphology.

 

Managing posterior instability is highly individualized, and there is a lack of clear consensus regarding a treatment algorithm. Nonsurgical treatment consists of activity modification and physical therapy including proprioceptive training and dynamic stabilization. Postural correction bracing and taping may help with nonoperative treatment. A recent device, the shoulder pacemaker, might have some value in correcting posterior subluxation associated with scapular maltracking.8 Surgical treatment can be considered for patients who have failed conservative management and for patients with an acute traumatic posterior instability event with labral and/or osseus pathology. Unlike anterior instability, there is no “essential lesion” anatomically in posterior instability.9 Posterior labral tears are common, but so are reverse humeral avulsion lesions, laxity of the posterior band of the inferior glenohumeral ligament, glenoid dysplasia, glenoid retroversion, and, in our young patients, fractures of an unfused posterior cartilage analog. While open labral repair and capsular plication were previously utilized, arthroscopic techniques have become more prevalent in recent years.10,11 In appropriately indicated patients, arthroscopic posterior labral repair with capsular plication can be a reliable treatment option.12,13,14,15 In the setting of a failed arthroscopic posterior instability procedure and/or when aberrant glenoid morphology is encountered, osseus augmentation can be considered. There is a lack of evidence-based data to guide when osseous augmentation is recommended, particularly since glenoid morphology (increased retroversion and/or hypoplasia) may lower the threshold at which osseous augmentation may be necessary. Distal tibial allograft and iliac crest autograft are options when osseous augmentation is needed.16,17

 

Outcomes following posterior shoulder stabilization can be difficult to interpret due to both the high variability amongst this patient population and differences amongst surgical techniques. In one of the largest series consisting of 200 shoulders, Bradley et al. found that 90% of athletes returned to play (with 64% able to return to their preinjury level of play) following arthroscopic posterior labral repair.15 This study also found significantly higher return to play rates in those patients treated with suture anchor repair as compared with those patients treated with an anchorless fixation technique. A systematic review and meta-analysis including over 1,000 patients found lower recurrence rates and higher rates of return to play favoring arthroscopic approaches over open stabilization.14 One study comparing throwing athletes with nonthrowing athletes found similar outcomes between the two groups, with throwing athletes less likely to return to their preinjury levels of sport (55%) compared with nonthrowing athletes (71%).18 McClincy et al. found comparable outcomes scores, stability, strength and range of motion when comparing throwing athletes to nonthrowing athletes who underwent arthroscopic posterior stabilization.19 Improved return to play in this series was associated with identifying a discrete labral tear intraoperatively and using suture anchor fixation, as compared with anchorless repair. Football players treated with arthroscopic posterior stabilization experienced a 93% return to play and 96.5% excellent or good results in one series of 56 athletes.20

 

While recent studies have demonstrated overall successful outcomes following arthroscopic posterior stabilization, further investigation is required to optimize treatment approaches and results for patients with posterior glenohumeral joint instability.

 

References:

  1. Mannava, S., Frangiamore, S.J., Murphy, C.P., Sanchez, A., Sanchez, G., Dornan, G.J., Bradley, J.P., LaPrade, R.F., Millett, P.J., Provencher, M.T. “Prevalence of Shoulder Labral Injury in Collegiate Football Players at the National Football League Scouting Combine.” Orthopaedic Journal of Sports Medicine. 2018;6(7):2325967118783982.
  2. Javed, S., Gheorghiu, D., Torrance, E., Monga, P., Funk, L., Walton, M. “The Incidence of Traumatic Posterior and Combined Labral Tears in Patients Undergoing Arthroscopic Shoulder Stabilization.” The American Journal of Sports Medicine. 2019;47(11):2686-2690.
  3. Swan, E.R., Lynch, T.B., Sheean, A.J., Schmitz, M.R., Dickens, J.F., Patzkowski, J.C. “High Incidence of Combined and Posterior Labral Tears in Military Patients With Operative Shoulder Instability.” The American Journal of Sports Medicine. 2022;50(6):1529-1533.
  4. Millett, P.J., Clavert, P., Hatch III, G.F., Warner, J.J. “Recurrent Posterior Shoulder Instability.” Journal of the American Academy of Orthopaedic Surgeons. 2006;14(8):464-476.
  5. Kim, S.H., Park, J.S., Jeong, W.K., Shin, S.K. “The Kim Test: A Novel Test for Posteroinferior Labral Lesion of the Shoulder: A Comparison to the Jerk Test.” The American Journal of Sports Medicine. 2005;33(8):1188-1192.
  6. Pollock, R.G., Bigliani, L.U. “Recurrent Posterior Shoulder Instability: Diagnosis and Treatment.” Clinical Orthopaedics and Related Research. 1993;(291):85-96.
  7. Gerber, C., Ganz, R. “Clinical Assessment of Instability of the Shoulder With Special Reference to Anterior and Posterior Drawer Tests.” The Journal of Bone and Joint Surgery – British Volume. 1984;66(4):551-556.
  8. Moroder, P., Plachel, F., Van-Vliet, H., Adamczewski, C., Danzinger, V. “Shoulder Pacemaker Treatment Concept for Posterior Positional Functional Shoulder Instability: A Prospective Clinical Trial.” The American Journal of Sports Medicine. 2020;48(9):2097-2104.
  9. Papendick, L.W., Savoie IIII, F.H. “Anatomy-Specific Repair Techniques for Posterior Shoulder Instability.” Journal of the Southern Orthopaedic Association. 1995;4(3):169-176.
  10. Lenart, B.A., Sherman, S.L., Mall, N.A., Gochanour, E., Twigg, S.L., Nicholson, G.P. “Arthroscopic Repair for Posterior Shoulder Instability.” Arthroscopy. 2012;28(10):1337-1343.
  11. Savoie III, F.H., Holt, M.S., Field, L.D., Ramsey, J.R. “Arthroscopic Management of Posterior Instability: Evolution of Technique and Results.” Arthroscopy. 2008;24(4):389-396.
  12. Kercher, J.S., Runner, R.P., McCarthy, T.P., Duralde, X.A. “Posterior Labral Repairs of the Shoulder Among Baseball Players: Results and Outcomes With Minimum Two-Year Follow-Up.” The American Journal of Sports Medicine. 2019;47(7):1687-1693.
  13. Lacheta, L., Goldenberg, B.T., Horan, M.P., Millett, P.J. “Posterior Bony Bankart Bridge Technique Results in Reliable Clinical Two-Year Outcomes and High Return to Sports Rate for the Treatment of Posterior Bony Bankart Lesions.” Knee Surgery, Sports Traumatology, Arthroscopy. 2021;29(1):120-126.
  14. DeLong, J.M., Jiang, K., Bradley, J.P. “Posterior Instability of the Shoulder: A Systematic Review and Meta-Analysis of Clinical Outcomes.” The American Journal of Sports Medicine. 2015;43(7):1805-1817.
  15. Bradley, J.P., McClincy, M.P., Arner, J.W., Tejwani, S.G. “Arthroscopic Capsulolabral Reconstruction for Posterior Instability of the Shoulder: A Prospective Study of 200 Shoulders.” The American Journal of Sports Medicine. 2013;41(9):2005-2014.
  16. Frank, R.M., Shin, J., Saccomanno, M.F., Bhatia, S., Shewman, E., Bach Jr., B.R., Wang, V.M., Cole, B.J., Provencher, M.T., Verma, N.N., Romeo, A.A. “Comparison of Glenohumeral Contact Pressures and Contact Areas After Posterior Glenoid Reconstruction With an Iliac Crest Bone Graft or Distal Tibial Osteochondral Allograft.” The American Journal of Sports Medicine. 2014;42(11):2574-2582.
  17. Van Spanning, S.H., Picard, K., Buijze, G.A., Themessl, A., Lafosse, L., Lafosse, T. “Arthroscopic Bone Block Procedure for Posterior Shoulder Instability: Updated Surgical Technique.” Arthroscopy Techniques. 2022;11(10):e1793-e1799.
  18. Radkowski, C.A., Chhabra, A., Baker III, C.L., Tejwani, S.G., Bradley, J.P. “Arthroscopic Capsulolabral Repair for Posterior Shoulder Instability in Throwing Athletes Compared With Nonthrowing Athletes.” The American Journal of Sports Medicine. 2008;36(4):693-699.
  19. McClincy, M.P., Arner, J.W., Bradley, J.P. “Posterior Shoulder Instability in Throwing Athletes: A Case-Matched Comparison of Throwers and Nonthrowers.” Arthroscopy. 2015;31(6):1041-1051.
  20. Arner, J.W., McClincy, M.P., Bradley, J.P. “Arthroscopic Stabilization of Posterior Shoulder Instability Is Successful in American Football Players.” Arthroscopy. 2015;31(8):1466-1471.
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