DIAGNOSIS OF AN ULNAR COLLATERAL LIGAMENT TEAR USING MUSCULOSKELETAL ULTRASOUND IN A COLLEGIATE BASEBALL PITCHER: A CASE REPORT

Abstract

Objective:

To demonstrate a comparative diagnostic approach between magnetic resonance imaging (MRI) and musculoskeletal ultrasound for detecting UCL trauma of the elbow in a collegiate baseball pitcher.

Background:

A 19 year-old male baseball pitcher with no previous history of an elbow injury presented with left medial elbow pain after experiencing a popping sensation during a bull pen throwing session. Patient initially demonstrated palpable tenderness directly over the UCL and a positive milking maneuver. Minimal swelling and no observable discoloration were noted upon examination. Diagnostic ultrasound was utilized to assess the elbow anatomical structures. The differential diagnosis included medial epicondylitis, flexor pronator muscle strain, ulnar collateral ligament tear

Treatment:

Initial treatment was conservative while preparing for a ligament reconstruction. Goals included pain control, restoration of range of motion, and reduction of inflammation.

Uniqueness:

Accurate diagnosis of UCL disruption was made using dynamic diagnostic musculoskeletal ultrasound despite a negative MRI. The ability to accurately identify the injury contributed to the timeliness of the appropriate surgical intervention and the facilitation of a timely and successful rehabilitation program.

Conclusions:

Dynamic musculoskeletal ultrasound may offer an effective option for diagnosing UCL tears of the elbow. Diagnostic musculoskeletal ultrasound is an affordable, accessible, and portable option that provides a clinician with real-time information and accurate observations in the hands of a skilled operator. Diagnostic musculoskeletal ultrasound may play an increased role as a diagnostic tool in the sports medicine community.

Shoulder and elbow injuries are the most common injuries sustained by overhead throwing athletes, particularly baseball pitchers.¹ In a long-term study of the epidemiology of college baseball injuries from 1988-2004, the incidence of upper extremity injuries was as high as 45% for all game and practice injuries with elbow related injuries noted as the second most commonly injured body part.¹ It has also been reported that upwards of 75 major league pitchers since 2001 have undergone a UCL reconstruction via the commonly performed “Tommy John Surgery”.² While previously thought of as a concern to collegiate and professional level throwers, medial elbow injuries have now become more prevalent in younger baseball pitchers when compared to previous years. A retrospective cohort study analyzing data from 1988-2003 revealed a dramatic increase in UCL injuries with an astonishing 50% increase in UCL reconstructions in high school baseball athletes, with one center reporting a rise from five to 50 procedures during this timeframe.^2,3

The medial or ulnar collateral ligament is the primary structure responsible for stability of the elbow joint against the valgus forces associated with the throwing mechanism. Anatomically, the ligament complex is composed of three bundles: the anterior, posterior, and transverse bundles with the anterior bundle being the strongest component. ^{4- 6} The anterior bundle originates on the medial epicondyle of the humerus and inserts on the tubercle of the ulna. (Figure 1) This bundle is crucial in the maintenance of joint stability during the late cocking and early acceleration phases of over-head throwing.⁵ The anterior bundle of the UCL is placed under the greatest amount of valgus stress during the throwing motion between 20-30 degrees of elbow flexion as a result of the olecranon process unlocking from the olecranon fossa.^4,5

Figure 1.

Anatomy of the medial elbow complex, courtesy of Primal Pictures, London, UK.

Diagnosing medial elbow injuries in an accurate and timely manner can be challenging to even the experienced clinician. A thorough history, knowledge of the type, volume, and level of activity, and a report of the mechanism of injury can all assist in understanding what structures may be involved. Physical examination including observation, palpation, and performance of special tests can be further incorporated to corroborate one's assessment. Plain radiographs, arthrograms, computed tomography (CT), and magnetic resonance imagining (MRI) are commonly utilized to make an accurate diagnosis. Recently, diagnostic musculoskeletal ultrasound has emerged as a valuable tool for evaluating soft tissue structures whereby clinicians can benefit from the ability to apply external forces to live imaging.^7–8 Diagnostic musculoskeletal ultrasound has the capability to identify full and partial tears in the UCL in addition to detecting localized joint swelling, joint instability, and medial joint space widening while under loaded situations.^4,5 The valgus stress test for medial elbow joint instability can be used to detect joint space gapping. In addition, providing a valgus stress with the shoulder at 90 degrees of shoulder flexion, referred to as the milking maneuver technique, allows for dynamic assessment of the ligament at normal tissue length and under tension. (Figure 2)

Figure 2.

Musculoskeletal ultrasound performed on the medial aspect of the elbow with simultaneous valgus forces applied through the milking maneuver.

CASE DESCRIPTION

A 19 year old male left-handed collegiate baseball pitcher was throwing a bullpen session during an early pre-season practice when he reported having felt a popping sensation in his throwing arm that was immediately followed by medial elbow pain. The athlete immediately discontinued his throwing session and was examined on-site by the certified athletic trainer and the orthopaedic team physician. Physical examination noted mild palpable swelling over the medial aspect of his left elbow with tenderness to touch at of the insertion of the UCL on the ulna as well as the mid-substance region of the ligament. The level of pain was subjectively rated six out of a possible ten via verbal feedback. No pain was elicited superficially over the ulnar groove or the ulnar nerve at the medial aspect of the elbow, and no neurological symptoms were identified. All range of motion was full and equal to the non-throwing elbow unaccompanied by discomfort. Valgus stress testing at both 30° and 90° of elbow flexion, revealed medial joint opening and joint laxity. A positive milking maneuver was also evident with unremarkable results on the non-involved elbow. A formal grade of instability was not determined as it was unclear as to the amount of joint gapping may have existed prior to any injury in the dominant versus non-dominant elbow.

One day following the reporting and assessment of the injury, radiographic and dynamic imaging tests were performed. All x-rays of the elbow were unremarkable with the exception of mild cartilage irregularities seen along the posteromedial aspect of the trochlea and the medial aspect of the olecranon. An MRI was read as negative for any ligamentous disruption or other tissue damage. A dynamic diagnostic musculoskeletal ultrasound was performed by the team orthopaedic surgeon with the athlete in a supine position while performing the milking maneuver test. This ultrasound revealed a disruption of the ulnar collateral ligament at its mid section and at its insertion onto the ulna.(Figure 3)

Figure 3.

Musculoskeletal ultrasound to assess the integrity of the ulnar collateral ligament at the time of injury. Arrow on the right points to the UCL injury, arrow on the left points to the medial epicondyle.

Differential Diagnosis

Based upon the clinical examination, imaging findings, and potential delayed symptoms, the differential diagnosis included the following: ulnar collateral ligament tear, medial epicondylitis and flexor pronator muscle strain, osteochondral lesion at the humeral ulnar joint articulation, and ulnar nerve subluxation.

Subsequent management of medial epicondylitis and flexor pronator muscle strains would be approached conservatively. However, addressing an ulnar collateral ligament tear, osteochondral lesion, or ulnar nerve subluxation would likely require surgical intervention. In such cases, the recovery time associated with an operative technique would be sufficiently long enough to allow for conservative healing of any concomitant muscle tissue strain. Based upon the reported symptoms and functional inability to perform, the physical examination data, and the results of the musculoskeletal ultrasound, it was decided to proceed with a surgical approach with the hypothesis that the ulnar collateral ligament may be the primary structural component of concern.

OUTCOME

Treatment Intervention

The decision to perform surgery to reconstruct the athlete's ulnar collateral ligament was made quickly and the procedure was scheduled to be performed within the week of the injury occurrence. Treatment intervention during the three days preceding the scheduled surgical procedure consisted of efforts to maintain full range of motion, minimize any subsequent muscle atrophy, reduce accompanying pain levels, and decrease localized joint swelling.

An open surgical procedure in the region of the medial aspect of the elbow confirmed the findings of the dynamic musculoskeletal ultrasound. The UCL was subsequently reconstructed and the athlete began a progressive rehabilitative program. Figure 4 provides evidence of the reconstructed ligament seen via musculoskeletal ultrasound four months post-operatively.

Figure 4.

Musculoskeletal ultrasound to assess the ulnar collateral ligament 4 months after the ligament reconstruction.

DISCUSSION

The first injuries to the UCL of the elbow sustained by javelin throwers were described in 1946.⁴ Over the last couple of decades, magnetic resonance imaging has been the gold standard for diagnosis of injury to the UCL of the elbow. These images provide clear visualization of varied parts of the ligament, adjacent bone, and associated soft tissues⁹ Despite the ability of MRI to detect ligamentous damage, it is not without limitations. Anecdotally, baseball pitchers have reported an inability to throw successfully (without pain and feelings of instability) despite the absence of a positive MRI finding of actual tissue damage to the UCL. This may be due to the tension increases in the ligament seen with joint valgus forces that can occur without recognizable ligament tearing on imaging procedures. As such, dynamic diagnostic musculoskeletal ultrasound presents the clinician with the ability to actively assess the extent of medial joint line opening while simultaneously observing the status of the medial collateral ligament fibers and their response to activity (milking technique).

There are many benefits to the inclusion of using diagnostic musculoskeletal ultrasound for assessing the UCL of the elbow. Generally speaking, the technique is non-invasive, takes just a few minutes to perform, and can be repeated as frequently as warranted without the complications of scheduling conflicts.^10,11 Furthermore, the smaller units are portable yet still possess the capability to store images and video captures that can be reproduced instantaneously for clinician viewing and comparison. Despite the initial cost ranging between $25,000 - $40,000 for a mobile unit, once owned, additional approvals from third party payers are not necessary for those in the high school, collegiate or professional setting since assessments can be performed at any time by the clinician trained to use the machine.

There are some inherent disadvantages and challenges of using musculoskeletal ultrasound. Perhaps the largest challenge is that of the time associated with learning the technique. To the novice clinician, musculoskeletal ultrasound may not necessarily be viewed as a time-saving, gold-standard approach to viewing the ulnar collateral ligament. While no standard guidelines have been established to verify competence for using the technique amongst physicians and other health care providers, it is estimated that the learning curve may be quite extensive and yield consistent and reliable results relative to the experience (or lack thereof) of the clinician. Currently, however, dynamic musculoskeletal ultrasound is the only tool available that allows for prompt image guided office-based procedures to assess the medial aspect of the elbow.^5,11

When properly used, dynamic musculoskeletal ultrasound compared to standard MRI can increase the accuracy and speed of the diagnosis and treatment, decrease the time to rehabilitative intervention, and improve patient satisfaction.¹² In some cases dynamic musculoskeletal ultrasound has been shown to be more reliable than the traditional MRI when differentiating between partial thickness and full thickness ligamentous tears⁶. Sensitivity related to diagnosing UCL tears, epicondylitis, and ulnar nerve entrapment ranges from 86% to 100% using musculoskeletal ultrasound, with computed tomography (CT) sensitivity at 86% and MRI 57%⁶ Timmerman and Andrews reported that six of seven athletes identified with incompetence of the UCL clinically and surgically demonstrated an absence of abnormal MRI studies.¹³ This supports the potential increased use of clinical musculoskeletal ultrasound as a diagnostic tool in the presence of a normal MRI finding.

De Smet et al. used dynamic musculoskeletal ultrasound performed during valgus stress testing to assess the UCL of the elbow in two baseball pitchers who had sustained elbow injuries.⁶ Their MRI images showed the ligaments to be torn, though the severity of the injury was not assessed biomechanically under dynamic load application. As in the present case, magnetic resonance imaging was found to identify irregularities such as ligament thickening, discontinuity, and edema. However, when ultrasound was used on those same athletes the practitioners were able to examine the ligamentous and joint complex with various amounts of force application that is not capable of being performed during the MRI.⁶

In the present case, the athlete's elbow injury demonstrated an outcome similar to what was identified in the Timmerman and Andrews and DeSmet studies whereby diagnostic ultrasound was effective as an evaluative tool versus MRI and CT examinations. Clinically, the suspected diagnosis was a disruption of the left UCL of the elbow. Although the MRI did not show a tear of the ligament, the dynamic ultrasound identified an area of nearly complete attenuation and medial joint space widening. This finding likely supports the athlete's complaints of dysfunction. These findings allowed the medical team to present the athlete, his family, and his advisors (coaches) with information necessary to make an informed decision regarding medical treatment options in a timely manner. Had the nature and extent of the injury not been determined using the musculoskeletal ultrasound, it is likely the athlete would have entered a time-consuming conservative course of rehabilitation while simultaneously seeking additional medical opinions and undergoing further imaging procedures.

Summary

This case report presents the description of a patient that presented the opportunity to utilize dynamic diagnostic musculoskeletal ultrasound as a diagnostic tool in order to assess the integrity of the UCL of the elbow. Ligamentous disruption was identified that was not detected by standard MRI examination. Though not considered the gold standard for examination of soft tissues such as ligaments, dynamic musculoskeletal ultrasound possesses the potential to be used as a portable and readily available, non-invasive adjunct to the more expensive and commonly used MRI. This case report demonstrates the importance and unique application of clinician assessment and simultaneous tissue imaging under controlled circumstances whereby active forces can be applied to stress the tissue being examined. Prior to confirming this technique as a gold standard approach, further studies will need to be conducted and standardized training and procedures will need to be established to demonstrate reliability of the clinician operator and the and validity of the measurement provided by the equipment.