Ultrasound evaluation shows increase in laxity after partial common extensor origin detachment but not after additional lesion of the radial band of the lateral collateral ligament

Ultrasound evaluation shows increase in laxity after partial common extensor origin detachment but not after additional lesion of the radial band of the lateral collateral ligament

REVIEWED BY Bridie Roche, AFASA | ASA SIG: Musculoskeletal

REFERENCE | Authors: Paolo Arrigoni, Davide Cucchi, Francesco Luceri, Andrea Zagarella, Michele Catapano, Alessandra Menon, Valentina Bruno, Mauro Gallazzi, Pietro Simone Randelli

WHY THE STUDY WAS PERFORMED

Dynamic stress ultrasound is widely used in the setting of ulnar collateral ligament injury for detecting valgus instability of the elbow. Stress ultrasound, however, has not yet been validated in the lateral elbow for detection of varus instability. Little is known of the contribution of the radial collateral ligament (RCL) versus the common extensor origin (CEO) to varus stability. The sequential release of the extensor carpi radialis brevis (ECRB), followed by release of the RCL, was performed to investigate the degree of joint space widening under varus stress.

HOW THE STUDY WAS PERFORMED

The degree of lateral joint space widening before and after surgically introduced CEO and RCL tears was investigated in cadavers. The annular ligament and lateral ulnar collateral ligament were left intact.

Positioning of each cadaveric arm during stress ultrasound was as follows:

• The humerus was internally rotated 90 degrees and fixated as if positioned prone.

• The forearm was neutral with the lateral elbow facing up.

• The elbow was either flexed to 60 degrees or fully extended.

• The transcondylar axis was perpendicular to the floor.

Varus stress was applied using both gravity and with 0.5 kg of weight at the level of the hand. A longitudinal imaging plane over the midpoint of the radiohumeral joint was used to measure the distance from the capitellum to radial head.

“Damage to the CEO of the lateral elbow, and not only the radial collateral ligament, has a massive impact on elbow instability.”

WHAT THE STUDY FOUND

Release of the anterior half of the CEO contributed significantly to varus instability causing joint space widening of 200% (an increase of approximately 3 mm) with the elbow at 60 degrees of flexion.

Detachment of the proximal RCL origin following CEO release contributed less than 1 mm additional joint widening.

Prior to either release, lateral joint space widening with either gravity or 0.5 kg on an extended elbow was insignificant. With the elbow at 60 degrees flexion, 0.5 kg did produce significant joint space widening, although minimal.

While detection of the degree of joint widening via stress ultrasound may not help distinguish an RCL tear from an anterior CEO tear, stress ultrasound can indirectly confirm the presence of a significant anterior CEO tear. This study was the first of its kind establishing the significant contribution of the anterior CEO to varus stability of the elbow.

Ultrasound evaluation shows increase in laxity after partial common extensor origin detachment but not after additional lesion of the radial band of the lateral collateral ligament

RELEVANCE TO CLINICAL PRACTICE

Ultrasound guided intratendinous CEO injections aimed at treating recalcitrant lateral elbow pain can cause long-term damage to the CEO and this tendon weakening may contribute to RCL overload. RCL overload will also further compromise the ligament and therefore elbow stability. The authors advise against repeat hydrocortisone injections into the ECRB.

Isolated injuries of the RCL may be arthroscopically addressed; however, the success of reconstruction is contingent on an intact overlying CEO. The sonographer therefore plays an important role in detection of any tendinous injury or avulsion prior to surgical management of a lateral ligament tear.

The results of the study led the authors to advise against open surgical approaches for lateral ligament repair since any iatrogenic injury to the ECRB may escalate instability.