Clinical History: A 51 year old female with a history of lateral relax for therapy of lateral epicondylitis presents through posterolateral ache and challenge achieving complete elbow extension. The patient was reported together being really anxious when extending the elbow throughout positioning because that the MRI examination. Fat-suppressed T2-weighted coronal (1a) and also T2-weighted sagittal (1b) images are made easily accessible for review. What room the findings? What is her diagnosis?


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1a
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1b
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Figure 2:

The fat suppressed T2-weighted coronal image demonstrates one attenuated usual extensor tendon (arrow). The LUCL is lacking at its origin (arrowhead).

You are watching: The ligament that stabilizes and encircles the head of the radius is the:


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Figure 3:

The sagittal T2-weighted photo demonstrates proof for radiocapitellar instability. The long axis that the radius (red line) is directed posterior come the facility of the capitellum (dot), and widening that the radiocapitellar joint an are is noticeable (blue).

Diagnosis

Lateral ulnar collateral ligament tear with posterolateral rotatory instability of the elbow.

Introduction

Posterolateral rotatory instability of the elbow is the most common chronic elbow instability. O’Driscoll originally defined the concept of posterolateral rotatory instability (PLRI), a certain instability pattern which results as soon as the ulna rotates ~ above its lengthy axis, distracting the radial element of the ulnotrochlear joint.1 due to the fact that the proximal radioulnar joint is stabilized by an intact annular ligament, the radius stays tightly combination to the ulna. Therefore the rotation of the ulna istransfer to the radius bring about posterior displacement that the radius loved one to the capitellum (4a). This sample of instability commonly follows a history of significant elbow trauma, but may likewise be watched in other clinical settings. Subtle PLRI may reason functional impairment yet may be difficult to diagnose.


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Figure 4:

3D renderings the the posterolateral elbow demonstrate the concept of posterolateral rotatory instability. ~ above the left the common alignment that the ulnohumeral and radiocapitellar joints is demonstrated. Top top the appropriate posterolateral rotatory instability occurs when loss of sensible stability permits the ulnohumeral share to rotate open up laterally (red arrow). With an undamaged annular ligament shown in red, the radius moves in conjunction through the ulna and also is displaced posterior to the capitellum (blue arrow).

Anatomy and Function

Posterolateral stability of the elbow is kept by the static and also dynamic interaction of the articular contours and also the sustaining ligamentous and also soft tissues at the elbow. The main constraint to PLRI is the lateral collateral ligament complex (LCL), which is consisted of of the radial collateral ligament (RCL), lateral ulnar collateral ligament (LUCL), annular ligament, and accessory lateral collateral ligament.2 O’Driscoll figured out that the an essential anatomic structure staying clear of this sample of instability is the lateral ulnar collateral ligament, i m sorry extends from the lateral epicondyle to the supinator comb of the ulna, traversing the posterolateral aspect of the radial head.1,3 succeeding anatomic studies have questioned the function of the LUCL as the main stabilizer versus PRLI, rather emphasizing the prestige of the entire lateral collateral ligament complex4,5,6 the overlying extensor musculotendinous structures,7 and the osseous anatomy in ~ the elbow. Nevertheless, the primary focus of correcting PRLI is the restoration or augmentation that that section of the lateral collateral ligament facility which extends native the lateral epicondyle come the ulna, the course of the lateral ulnar collateral ligament.

The anatomy that the lateral collateral ligament facility varies significantly among individuals. The RCL and also LUCL stand for capsular thickenings the originate indigenous a common origin, measuring approximately 5 mm at the distal portion of the lateral epicondyle.5 At their origin, the LUCL and also RCL room deep to and also slightly distal come the common extensor tendon origin. The LUCL and also RCL blend through the overlying extensor tendons and also intermuscular fascia.8 The RCL and also LUCL space inseparable proximal to the annular ligament. The anterior yarn are frequently thinner and also comprise the RCL, fanning the end distally to insert on the annular ligament and also blend v the origin of the supinator muscle. The more posteriorly arising fibers originate at the facility of the elbow’s axis that rotation1,2,9,10 and also pass posterolateral come the head of the radius, proceeding medially and distally come insert top top the proximal ulna in ~ the supinator crest. This bundle that capsuloligamentous tissue comprises the LUCL (D).2 at its mid-portion, the LUCL fibers lie deep to the intermuscular fascia between the supinator and extensor carpi ulnaris muscles and blends v the fibers of the annular ligament. Macroscopically, the LUCL is most unique at that is insertion through a commonly well-defined, solid anterior band inserting at the tubercle of the supinator crest. A thinner fan-like insertion extends proximally follow me the supinator crest, adjacent to the basic of the annular ligament.2 in ~ the tubercle insertion, the LUCL is deep and adherent to the fascia that the anconeus, supinator, and also extensor carpi ulnaris muscles.14

The annular ligament encircles the radial head and also tapers distally as it extends end the proximal section of the radial neck. The annular ligament originates from the anterior and also posterior spare part of the lesser sigmoid notch the the ulna and also acts to stabilize the radial head come the ulna transparent the variety of pronation and supination the the forearm.10 The annular ligament has been displayed to be crucial in preserving stability at the elbow (D). Number of studies have shown instability patterns similar to PRLI resulting from defects of the annular ligament, alone or in mix with defects that the LUCL and RCL.4,5 The accessory lateral collateral ligament occurs from the distal annular ligament anteriorly and also attaches distally in ~ the tubercle that the supinator crest. The accessory lateral collateral ligament stabilizes the annular ligament, specifically during varus anxiety (5a).5,11


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Figure 5:

Lateral (left) and posterior (right) 3D makes of the elbow show the anatomic relationship of the lateral ulnar collateral ligament (blue), annular ligament (red), radial collateral ligament (yellow), and the accessory lateral collateral ligament (green).

The key osseous anatomy and also articular contours contributing to security at the elbow room the coronoid process of the ulna and also the radiocapitellar joint. The coronoid procedure is coming to be increasingly well-known as crucial structure in preserving elbow stability, serving as a constraint come posterior ulnohumeral displacement.12 Fractures of the coronoid procedure are most typically the result of elbow dislocation. Indeed, visualization of a coronoid procedure fracture can be regarded as proof of a ahead subluxation or dislocation.13 In one cadaver study, fractures involving 50% or higher of the coronoid height resulted in a 28% rise in exterior rotation that the forearm family member to the humerus.14 Clinical results show that bone grafting and reconstruction the the coronoid have actually successfully restored stability in those patients through PRLI adhering to an ununited coronoid fracture.15 The radiocapitellar share assists in giving stability by the congruency of the radial head with the capitellum. In addition, a normal size of the proximal radius is necessary for keeping normal anxiety of the lateral ligament complex. Resection of the radial head can an outcome in laxity that the lateral ligament complex and instability.16

Clinical background and Presentation

Patients through PRLI may present with a wide range of complaints, ranging from vague symptoms to frank posterolateral dislocation. Mechanical symptoms space common, consisting of painful clicking, locking or snapping, or a sense of giving means when the elbow is placed in an unstable place resulting from external rotation the the forearm with valgus and also axial loading, which frequently occurs as soon as pushing increase from a chair. Components that may add to PRLI incorporate a history of ahead trauma, chronic resistant lateral epicondylitis, front lateral elbow surgery, serial steroid injections, and also chronic malalignment at the elbow.

PRLI most generally results indigenous elbow trauma bring about posterolateral dislocation or subluxation the the elbow. Disruption of the supporting frameworks occurs in a circular fashion indigenous lateral come medial. In phase I, the lateral ligament facility is disrupted. Phase II injuries result from progression of the tear to involve the anterior and also posterior capsule, evidenced by a perched incomplete elbow dislocation.17 In stage III, the medial collateral ligament complicated ruptures and there is complete elbow dislocation. Linked fractures the the coronoid procedure or radial head or avulsion fractures in ~ the origin of the collateral ligaments may complicate the ligamentous injury.18 In a little subset that patients, sufficient healing of the lateral supporting structures does no occur and posterolateral rotatory instability may ensue.

Lateral epicondylitis resistant to conservative measures is generally the result of coexisting LUCL injury. LUCL abnormalities space seen in approximately 63% that patients v lateral epicondylitis through MRI.19 The recurring varus stresses and degenerative transforms that cause the typical extensor tendon tears are felt to involve the subjacent LUCL, leading to ligamentous weakening and also potential rupture. Once such transforms of the LUCL and also instability are not recognized preoperatively, surgical release of the extensor tendon may then further destabilize the elbow. Therapy of lateral epicondylitis with serial steroid injections may likewise compromise the truth of the LUCL.20

Arthrotomy that the elbow may an outcome in PRLI, because surgical philosophies to the lateral elbow may damage the LUCL. To minimize this risk, arthrotomy anterior come the LUCL is favored to preserve ulnohumeral stability. When greater exposure is required, a posterior capsular flap release from the humerus might be performed, followed by a transosseous ligament repair.21 Recently arisen surgical ideologies to the radiocapitellar joint focus on keeping the lateral collateral ligament complicated proximally by gaining exposure through an osteotomy in ~ the ulnar attachments of the ligament complex, which is consequently reattached.22

Physical Examination

The diagnosis of PLRI is a clinical one based on history and physics exam. Numerous clinical tests because that diagnosing PLRI have actually been described, including the lateral pivot-shift test and also the posterolateral rotatory drawer test. This provocative maneuvers location the elbow in a position of maximal instability, v a mix of exterior rotation the the forearm, valgus, and also axial loading, which shot to give birth the symptoms or radial head subluxation.1 In the wake up patient, these maneuvers typically cannot be tolerated to a suggest of subluxation or dislocation that the radial head because of patience discomfort.23 general anesthesia is commonly required in stimulate to show subluxation or dislocation that the radius making use of these maneuvers.

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Plain movie Findings

Plain radiography may show an avulsion fracture in ~ the origin or insertion that the lateral collateral ligament complex, and can demonstrate the verity of the radial head, capitellum, and also coronoid process. Fractures of the radial head and also of the capitellum might be seen on level films secondary to posterior dislocation of the radial head impacting the capitellum. The drop authorize has likewise been described, which is seen with an ulnohumeral street of higher than 4mm top top the level lateral film of the unrelated elbow.24

MRI Findings

In the acute or chronic setting, MRI deserve to directly demonstrate tears the the lateral collateral ligament facility and injuries the the nearby soft tissue and osseous structures.

Because injuries that the LUCL most frequently occur together avulsions native the distal humerus,25 an understanding of the anatomy and also normal MRI appearance, concentrating on the ligament origin enables a more precise assessment of basic lesions of the lateral collateral ligament complex and the overlying tendinous structures. The common lateral ulnar collateral and radial collateral ligaments room low in signal on all sequences. A bilaminar appearance might be demonstrated end the proximal ligament (6a), i m sorry presumably delineates the ligamentous from the overlying tendinous structures, yet the LUCL, RCL, and also the typical extensor tendon and also fascial frameworks are frequently inseparable together discrete structures on MR photos at the level that the epicondyle (7a). Coronal or coronal oblique imaging planes are best for assessing the verity of the lateral ulnar collateral ligament and also radial collateral ligament. Top top coronal images, the LUCL does no occupy a single plane, and also sequential pictures are important for finish visualization. Coronal oblique images are posteriorly angled approximately 20 levels in relationship to the humeral shaft with elbow prolonged (8a).26