Diagnosing Posterior Labral Tears
Diagnosing a posterior labral tear of the shoulder can be difficult for physicians. These tears can present with a wide variety of symptoms and there are multiple physical exam tests of undetermined significance. Posterior shoulder instability is less commonly seen than anterior instability and the incidence is 2-5% (3). The labrum is a fibrocartilaginous structure that helps deepen the glenoid and is involved in joint stabilization (7). Tears to the posteroinferior labrum occur due to tension on the posterior band of the IGHL (inferior glenohumeral ligament) during abduction and internal rotation or with compression forces (7). Tears to the posteroinferior portion of the labrum can lead to recurrent shoulder dislocation (7). This review aims to look at how to successfully diagnosis a posterior labral tear.
Case Question
You are evaluating a football lineman with vague shoulder pain. Clinically, you suspect a posterior labral tear. Which of the following tests is most likely to be positive with a posterior labral tear?
A) Kim Test
B) Sulcus Sign
C) Apprehension Test
D) Speeds Test
Image 1. General gloind labrum anatomy (8)
History
Symptoms can vary widely with posteroinferior labral lesions. Patients can complain of recurrent shoulder instability, while others complain of vague shoulder discomfort after sports (2). Baseball hitters, offensive lineman, weightlifters, and rowers have the highest rates of posteroinferior labral pathology (6). Overhead throwers typically complain of pain during the cocking phase and through ball release (6).
Rates of posterior labral tears are also thought to be more commonly found in football players (4). Offensive lineman who are blocking a player have a posteriorly directed force upon their shoulder, which can lead to a shear force against the posterior labrum (4). In the American Journal of Roentgenology, a group of radiologists looked at 171 shoulder arthrograms performed in their hospital (4). They found that of those MRIs, 27 were from football players (4). Fifteen of the 27 MRIs showed a posterior labral tear (4).
Physical Exam
The Jerk test and Kim test are both used to detect posterior and posteroinferior instability in the shoulder (1). The Kim test is done with the patient in a seated position. The provider then places the patient’s arm in 90 degrees of abduction and grasps the patient’s elbow and lateral proximal arm (1). Then, an axial loading force and a 45 degree diagonal force is applied to the arm (1). A positive test is a posterior clunk (1).
Figure 2. Kim Test (1)
The Jerk test is also performed with the patient in a seated position. The patient’s arm is abducted to 90 degrees and internally rotated to 90 degrees (1). The patient’s elbow is grasped and an axial force is applied to the shoulder (1). Pain or a clunk is a positive test (1).
Figure 3. The Jerk Test (2)
Both the Kim test and the Jerk test were evaluated for their accuracy in diagnosing posteroinferior labral tears in a study published in the American Journal of Sports Medicine (1). The study found 33 positive Kim tests and of these, 24 were confirmed with a posteroinferior labral lesion on arthroscopy (1). They found that the sensitivity of the test was 80% and specificity was 94% (1). The Jerk test had 25 positive tests and of these, 22 had a posteroinferior labral lesion on arthroscopy (1). This led to a sensitivity of 73% and specificity of 98% (1).
A study published in the American Journal of Sports Medicine in 2004 looked at the presence of pain as a predictor of success for nonoperative treatment with posterioinferior labral lesion (2). They broke their groups up into 33 patients with a painful jerk test and 48 patients with a nonpainful jerk test (clunking without pain). Using an MRI arthrogram as a confirmatory test, they found the sensitivity of a posteroinferior labral tear to be 89.7% for a painful jerk and a specificity of 85% (2).They also found that a painful jerk test led to higher rates of failed nonoperative treatment (2).
The Modified dynamic labral shear test also has a specificity of 98% for detecting posterior labral pathology (6).
Imaging
MRI without contrast can more accurately detect anteroinferior labral tears than posteroinferior labral tears (1). As a result, an MRI arthrogram is the test of choice to diagnose lesions of the glenoid labrum (5). Placing the shoulder in a FADIR (Flexed, adducted, internally rotated) position during the arthrogram has been found to improve the accuracy of diagnosis (5). A single nondisplaced tear of the posterior labrum is usually due to microtrauma and multiple episodes of a posterior shear force (8).
Figure 4. Labrum tear with arm in FADIR position (5)
When reading an MRI arthrogram, the labrum is typically a triangular structure, but can also be rounded (7). A normal labrum is completely hypointense due to the homogenous make up of fibrocartilage (7). It is easy to be fooled by the magic angle effect when evaluating the posterosuperior labrum (7). The magic angle is the angle in which the posterosuperior labrum collagen fibers are oriented at 57 degrees which leads to increased signal intensity within the labrum (7).
Figure 5. MRI Image of posteroinferior labrum tear (4)
An MRI athrogram will also identify capsular injury, but these findings may be less evident than anterior capsular injury (8).
In summary, Posteroinferior labral tears can be difficult to diagnosis. Physical exam techniques such as the Jerk test and Kim test can aid in narrowing your differential. Despite all of our physical exam and imaging techniques, sometimes the test is only diagnosed during surgery.
– Read More @ Wiki Sports Medicine: https://wikism.org/Glenoid_Labrum_Lesions
Case Answer
Correct answer is A. In a study published in the American Journal of Sports Medicine, the authors found 33 positive Kim tests and of these, 24 were confirmed with a posteroinferior labral lesion on arthroscopy. They found that the sensitivity of the test was 80% and specificity was 94%. The Kim test is performed by abducting the arm to 90°, applying a strong axial force, and elevating the arm upward and forward and then downward and backward. A positive test is reproduction of pain with or without a clunk. The sulcus sign tests for inferior labral tears or instability, the apprehension test evaluates the anterior labrum and speeds test evaluates for proximal biceps tendon injuries or SLAP tears.
References
1) Kim, Seung-Ho, et al. “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, vol. 33, no. 8, Aug. 2005, pp. 1188–92. PubMed, doi:10.1177/0363546504272687.
2) Kim, Seung-Ho, et al. “Painful Jerk Test: A Predictor of Success in Nonoperative Treatment of Posteroinferior Instability of the Shoulder.” The American Journal of Sports Medicine, vol. 32, no. 8, Dec. 2004, pp. 1849–55. PubMed, doi:10.1177/0363546504265263.
3) Christensen, Daniel L., et al. “Risk Factors for Failure of Nonoperative Treatment of Posterior Shoulder Labral Tears on Magnetic Resonance Imaging.” Military Medicine, vol. 185, no. 9–10, 18 2020, pp. e1556–61. PubMed, doi:10.1093/milmed/usaa122.
4) Escobedo, Eva M., et al. “Increased Risk of Posterior Glenoid Labrum Tears in Football Players.” AJR. American Journal of Roentgenology, vol. 188, no. 1, Jan. 2007, pp. 193–97. PubMed, doi:10.2214/AJR.05.0277.
5) Chiavaras, Mary M., et al. “MR Arthrographic Assessment of Suspected Posteroinferior Labral Lesions Using Flexion, Adduction, and Internal Rotation Positioning of the Arm: Preliminary Experience.” Skeletal Radiology, vol. 39, no. 5, May 2010, pp. 481–88. PubMed, doi:10.1007/s00256-010-0907-3.
6) Sheean, Andrew J., et al. “Posterior Labral Injury and Glenohumeral Instability in Overhead Athletes: Current Concepts for Diagnosis and Management.” The Journal of the American Academy of Orthopaedic Surgeons, May 2020. PubMed, doi:10.5435/JAAOS-D-19-00535.
7) De Coninck, Tineke, et al. “Imaging the Glenoid Labrum and Labral Tears.” Radiographics: A Review Publication of the Radiological Society of North America, Inc, vol. 36, no. 6, Oct. 2016, pp. 1628–47. PubMed, doi:10.1148/rg.2016160020.
8) Zlatkin, Michael B., and Timothy G. Sanders. “Magnetic Resonance Imaging of the Glenoid Labrum.” Radiologic Clinics of North America, vol. 51, no. 2, Mar. 2013, pp. 279–97. PubMed, doi:10.1016/j.rcl.2012.11.003.
