Traumatic Anterior Shoulder Instability
By: Chaitu S. Malempati, D.O. and Connor Donley, M.S.-IV
Anterior shoulder instability is currently the most common form of shoulder instability. It usually occurs after a traumatic event such as a motor vehicle accident, a contact event/collision or a fall with an outstretched arm with the shoulder in abduction and external rotation.1,2 These events are becoming more common in high-level contact sports as well. The inherent minimal bony restriction of the glenohumeral joint gives the shoulder maximum mobility, but stability relies on the comprehensive integrity between the static and dynamic bony and soft-tissue stabilizers. This brief synopsis will serve as a general overview of the present diagnosis and management of these injuries.
Traumatic anterior shoulder dislocations, a common culprit of anterior shoulder instability requiring closed reduction, has an incidence of 23 in 100,000 person-years, and an incidence of 98 in 100,000 person-years in the greater than 20 years age group.3,4 Furthermore, these injuries are almost three times more frequent in men. Nonsurgical treatment of anterior shoulder dislocations can have recurrent instability rates as high as 75%.3,4 While there appears to be various ideas and paradigms on managing anterior shoulder instability, how can we as an orthopaedic community identify patients with a high risk of recurrence who will benefit the most from operative stabilization?
Due to the traumatic etiology that occurs in collisions and high-level contact sports presenting with anterior shoulder instability, the identification of concomitant injuries through a detailed history and physical exam, along with X-ray, CT and MRI findings, will allow the correct intervention to be chosen. While the most observed injury following anterior shoulder dislocation is a Bankart lesion,4 Mohtadi et al. showed no difference in recurrence rates following an open or arthroscopic approach to repairing a Bankart lesion.5 Regarding return to sport, a systemic review by Abdul-Rassoul et al. found arthroscopic Bankart repair to have the highest return to sport rate at 97.5% among surgical intervention for anterior shoulder stabilization.6 Also, a Bankart fracture or glenoid bony disruption is seen in 33% of first-time anterior shoulder dislocations and if left untreated, can result in an increased rate of instability recurrence and a greater amount of glenoid bone loss (GBL).7 Furthermore, Hill-Sachs lesions (HSLs) are seen in 90% of first-time anterior shoulder dislocations and become significant in patients who present with recurrent instability.7 A three-dimensional CT scan is the most useful diagnostic method to define the percent of GBL present and determine if the HSL is on track or off track.8 These distinctions will allow surgeons to determine which operative treatment option will be the most beneficial.
When GBL is less than 13.5% and the HSL is on track, arthroscopic Bankart repair provides adequate results and offers numerous advantages such as quicker recovery, decreased operation time and improved cosmetic outcome.9 A bony Bankart injury can be repaired with newer generation arthroscopic suture techniques with good results.10 Lee et al. noted that prior dislocations, duration of instability, GBL and an off-track HSL were risk factors for recurrent stability after arthroscopic Bankart repair.11 When an off-track HSL is present along with GBL, adjunct procedures to the Bankart repair or a Latarjet bony augmentation are recommended to reduce the recurrence of anterior shoulder instability.9 An arthroscopic Bankart repair, in addition to a Remplissage or an open inferior capsular shift, should be considered to improve outcomes. However, these adjunct procedures should be used in caution with high-level overhead athletes due the risk of decreased external rotation following these procedures.9
Bony glenoid reconstruction with a bony Latarjet augmentation remains the gold standard with a GBL greater than 25%, regardless if the HSL is on or off track.9 When GBL is between 13.5% and 25%, regardless of an on or off-track HSL, either an adjunct Bankart repair or a Latarjet procedure can also be performed with positive outcomes.9 When deciding between an arthroscopic Bankart repair or the Latarjet augmentation, one should consider the Instability Severity Index Score (ISIS) which is a valuable preoperative tool to assist in surgical decision-making.12 The Glenoid Track Instability Management Score (GTIMS) is a relatively newer preoperative score developed by Di Giacomo et al., whose team compared it to the ISIS and found the GTIMS was able to better predict failure of an arthroscopic Bankart repair and resulted in fewer Latarjet procedures.13 The Latarjet augmentation procedure has been documented to have complication rates near 30% and a revision rate of 7%, primarily due to malunion, graft resorption and hardware complications with a recurrence rate of 12%.14 Both distal tibial allograft and iliac crest bone graft transfers have shown great results when compared to the Latarjet alone and should be considered in failed Latarjet procedures.15,16
Whether to treat first-time anterior dislocators with nonoperative management versus surgical intervention remains controversial in today’s orthopaedic landscape. Nonsurgical management consists of a short period of immobilization and subsequent rehabilitation followed by return to sport in one to three weeks. Dickens et al. followed 39 intercollegiate athletes after an initial anterior shoulder instability event during their season. Of the 10 who were treated nonoperatively, 40% succeeded with return to sport the following season without recurrence17. This is compared to the 29 surgical patients of which 90% successfully returned to sport without recurrence.17 On the contrary, Shanley et al. noted 85% of high school athletes who were treated nonoperatively remained injury free the following season.18 Ultimately, further investigation and research is needed to properly identify which subgroup of athletes will benefit the most from acute surgical intervention. GBL remains an important aspect of both anterior shoulder instability and short/long-term outcomes; therefore, management and treatment algorithms need to be directed towards minimizing further bone less in order to achieve improved results and decreased recurrences.
- Dumont, G.D. et al. “Anterior Shoulder Instability: A Review of Pathoanatomy, Diagnosis and Treatment.” Current Reviews in Musculoskeletal Medicine. 2011;4:200-207.
- Hovelius, L. et al. “Primary Anterior Dislocation of the Shoulder in Young Patients: A 10-Year Prospective Study.” Journal of Bone and Joint Surgery – American Volume. 1996;78:1677-1684.
- Leroux, T. et al. “Epidemiology of Primary Anterior Shoulder Dislocation Requiring Closed Reduction in Ontario, Canada.” American Journal of Sports Medicine. 2014;42(2):442-50.
- Owens, B.D. et al. “Pathoanatomy of First-Time, Traumatic, Anterior Glenohumeral Subluxation Events.” Journal of Bone and Joint Surgery – American Volume. 2010;92(7):1605-11.
- Mohtadi, N.G. et al. “A Randomized Clinical Trial Comparing Open and Arthroscopic Stabilization for Recurrent Traumatic Anterior Shoulder Instability: Two-Year Follow-Up With Disease-Specific Quality-of-Life Outcomes.” Journal of Bone and Joint Surgery – American Volume. 2014;96(5):353-60.
- Abdul-Rassoul, H. et al. “Return to Sport After Surgical Treatment for Anterior Shoulder Instability: A Systematic Review.” American Journal of Sports Medicine. 2019;47(6):1507-1515.
- Nakagawa, S. et al. “The Development Process of Bipolar Bone Defects From Primary to Recurrent Instability in Shoulders With Traumatic Anterior Instability.” American Journal of Sports Medicine. 2019;47(3):695-703.
- Yamamoto, N. et al. “Contact Between the Glenoid and the Humeral Head in Abduction, External Rotation and Horizontal Extension: A New Concept of Glenoid Track.” Journal of Shoulder and Elbow Surgery” 2007;16(5):649-56.
- Provencher, M.T. et al. “Diagnosis and Management of Traumatic Anterior Shoulder Instability.” Journal of the American Academy of Orthopaedic Surgeons. 2021;29(2):e51-e61.
- Godin, J.A. et al. “Midterm Results of the Bony Bankart Bridge Technique for the Treatment of Bony Bankart Lesions.” American Journal of Sports Medicine. 2019;47(1):158-164.
- Lee, S.H. et al. “Risk Factors for Recurrence of Anterior-Inferior Instability of the Shoulder After Arthroscopic Bankart Repair in Patients Younger Than 30 Years.” Arthroscopy. 2018;34(9):2530-2536.
- Balg, F. et al. “The Instability Severity Index Score: A Simple Preoperative Score to Select Patients for Arthroscopic or Open Shoulder Stabilization.” Journal of Bone and Joint Surgery – British Volume. 2007;89(11):1470-7.
- Di Giacomo, G. et al. “Glenoid Track Instability Management Score: Radiographic Modification of the Instability Severity Index Score.” Arthroscopy. 2020;36(1):56-67.
- Sivakumar, B.S. et al. “A Systematic Review and Meta-Analysis of Clinical and Patient-Reported Outcomes Following Two Procedures for Recurrent Traumatic Anterior Instability of the Shoulder: Latarjet Procedure Versus Bankart Repair.” Journal of Shoulder and Elbow Surgery. 2016;25(5):853-63.
- Moroder, P. et al. “Neer Award 2019: Latarjet Procedure Verus Iliac Crest Bone Graft Transfer for Treatment of Anterior Shoulder Instability With Glenoid Bone Loss: A Prospective Randomized Trial.” Journal of Shoulder and Elbow Surgery” 2019;28(7):1298-1307.
- Frank, R.M. et al. “Outcomes of Latarjet Versus Distal Tibia Allograft for Anterior Shoulder Instability Repair: A Matched Cohort Analysis.” American Journal of Sports Medicine. 2018;46(5):1030-1038.
- Dickens, J.F. et al. “Successful Return to Sport After Arthroscopic Shoulder Stabilization Versus Nonoperative Management in Contact Athletes With Anterior Shoulder Instability: A Prospective Multicenter Study.” American Journal of Sports Medicine. 2017;45(11):2540-2546.
- Shanley, E. et al. “Return to Sport as an Outcome Measure for Shoulder Instability: Surprising Findings in Nonoperative Management in a High School Athlete Population.” American Journal of Sports Medicine. 2019;47(5):1062-1067.