Gerbers Test

Original Editor - User Name Top Contributors - Saumya Srivastava, Rachael Lowe, Kim Jackson, Wanda van Niekerk and George Prudden

Purpose

MRI. Partial rupture of the cranial subscapularis tendon at the insertion site

Gerber's test also known as Lift-Off Test (LOT) or Gerber's Lift-Off Test. It was first described by Gerber and Krushell(199l). It was developed to be used as a simple clinical manoeuvre, which can reliably diagnose or exclude clinically relevant rupture of the subscapularis tendon.

The Subscapularis is part of the 4 muscles, called the rotator cuff, which provide stability and strength to the shoulder joint during motion. The other 3 muscles include The Supraspinatus, The Infraspinatus, and The Teres Minor. Each of these muscles has its own special tests to check their integrity and functioning.

Another clinical test for the subscapularis was also described by Gerber et al in 1996, called the Belly Press Test (BPT) in response to patients who were unable to perform the LOT because of pain or limited joint range of motion

Technique

This test is performed in a standing position, with the examiner observing and testing from standing behind the patient.

To perform this test, the patient is asked to place the back of the affected arm (dorsum of the hand) in the mid lumbar spine area. The testing movement involves the patient performing internal rotation (IR), by lifting the hand off the back while the examiner places pressure on the hand.

The test is considered to be positive if the patient cannot resist, lift the hand off the back or if she/he compensates by extending the elbow and shoulder.

Limitations of this test involve the patient having full passive IR so that it is physically possible for the patient to place the arm in the desired position and pain is not a limiting factor during the manoeuvre.

Evidence

Greis et al 1996 EMG analysis determined the muscle activity of the shoulder muscles during the lift-off test and during resisted internal rotation. It demonstrated the activity in the upper and lower fibres of the subscapularis muscle, during a lift-off test from the region of the mid-lumbar spine, was approximately 70% of its maximum voluntary contraction, which was significantly higher than for all the other muscles tested (P < 0.05). The lift-off test resulted in one-third more electromyographic activity in the subscapularis muscle fibres than when the test was modified from the hand being placed in the region of the mid-lumbar spine, to the hand at the buttocks region. However when resistance was applied during the test, higher activities in all the muscles was noted, but only a small increase noted in the pectoralis major muscle (significantly active during resisted internal rotation with the arm in front of the body). No significant differences were noted in the upper and lower fibres during any of the tests. This study concluded with showing the importance of the subscapularis muscle during the lift-off test and suggesting that other potential internal rotators of the humerus have a limited role in maintaining internal rotation when the arm is placed behind the back.

A controlled laboratory study was conducted by Pennock et al in 2011 to determine the ideal arm and shoulder positions for isolating the subscapularis muscle while performing the bear-hug (BHT), belly-press (BPT), and lift-off tests (LOT). and the activity of 7 muscles were noted in 20 healthy participants. The muscles which were monitored include upper and lower divisions of the subscapularis, supraspinatus, infraspinatus, latissimus dorsi, teres major, triceps, pectoralis major. EMG data was collected and compared across each clinical test at varying arm positions: bear-hug (ideal position, 10° superior, 10° inferior to the shoulder line), belly-press (ideal position, maximum shoulder external rotation, and maximal shoulder internal rotation), and lift-off (ideal position, hand position 5 in. [12.7 cm] superior and 5 in. [12.7 cm] inferior to the midlumbar spine). Just like the Greis et al EMG study, Pennock et al also showed no significant differences between the upper and lower subscapularis fibres at any position within and across the 3 tests and that the upper and lower muscle fibre activities were significantly greater than all other muscles while performing each test, irrespective of the arm and shoulder position.

However, according to a level 2 study conducted by Barth et al 2012, the LOT is the test that cannot be performed most often (18%) but when positive, is a strong predictor of very severe tears. This study also shows the three tests LOT, BPT and BHT correlated to the severity of observed tears (P < 0.05) and more deficient the test results were, severe the anatomical damage was noted.

Another level 1 study was performed by Kappe et al in 2018 to evaluate the diagnostic capabilities of the five clinical SSC tests (  LOT, Internal Rotation Lag Sign, BPT, Belly Off Sign, and BHT). It showed for all tests, positive tests results were found to be dependent on subscapularis integrity (p < 0.001, respectively). The sensitivity and specificity for any type of SSC lesion for the LOT was 0.35 and 0.98 respectively.

References

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