Non-Medial Ulnar Collateral Ligament Elbow Pathology in the Thrower

Injury rates in baseball players reach as high as 5.8 per 1000 at the professional level. Recent data have singled out the elbow as the leading cause of injured list necessitating injuries and the costliest injury location in professional baseball. While the medial ulnar collateral ligament (MUCL) has gained the largest notoriety in this population, elbow injury in the thrower occurs as a spectrum of pathologies. These pathologies may encompass other injuries often resulting from or occurring in conjunction with MUCL insufficiency. These conditions include valgus extension overload syndrome, osteochondritis dissecans, olecranon stress fractures, and ulnar nerve pathology.

Key points

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The thrower’s elbow undergoes significant repetitive forces that lead to distinct injury patterns.
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Non-medial ulnar collateral ligament (MUCL) elbow injuries in throwers are often overshadowed by the MUCL but significantly impact athletic performance and return to play capacity.
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Clinicians must recognize and address the multifaceted landscape of elbow injuries in order to adequately treat the overheard thrower.

Valgus extension overload syndrome

The complex motion of throwing places unique demands on the elbow that result in valgus forces and angular velocities reaching as high as 64 N-m and 5000 deg/sec. As the elbow approaches terminal extension during deceleration, it undergoes a triad of forces seen as tensile stress along the medial elbow (medial ulnar collateral ligament [MUCL], flexor–pronator mass, medial epicondyle apophysis, and ulnar nerve), compression stress along the lateral radiocapitellar joint, and compression and shearing stress along the posteromedial olecranon and trochlea. ^, ^, Over time, these repetitive forces result in predictable injury patterns discussed in this article. Poor dynamic muscular control, throwing mechanic issues, and MUCL insufficiency can further amplify these forces and result in posteromedial pathologies to both the olecranon and trochlea such as symptomatic olecranon or trochlear stress reactions, transverse/proximal olecranon stress fractures, olecranon tip exostosis (with or without fragmentation), trochlear marginal exostoses, trochlear chondromalacia and osteochondral lesions (with subchondral insufficiency fractures and collapse), osteophytes, and loose bodies. ^, This constellation of repetitive force dissipation and resulting pathology is collectively referred to as valgus extension overload syndrome (VEOS).

With isolated VEOS, patients will typically present with elbow pain localized to the posteromedial olecranon after ball release. Symptoms are typically preceded by decreases in pitch velocity, control, and early fatiguability. Additional findings may include loss of terminal extension due to posterior osteophyte impingement, mechanical symptoms due to loose bodies/chondromalacia, history of prior MUCL/flexor–pronator injury, and ulnar nerve neuritis and/or subluxation. ^, A valgus extension overload test of repeatedly forcing a flexed elbow into rapid extension with a valgus stress will often reproduce pain with impingement of the posteromedial tip of the olecranon. Understanding the intricacies of this condition is crucial for accurate diagnosis and effective management.

Lesions of the posterior compartment, olecranon osteophytes, and loose bodies have historically been the most common pathologies resulting from VEOS that require operative management in throwers. Andrews and Timmerman reported posteromedial olecranon impingement, which is a term that describes the compression of structures on the posteromedial side of the elbow, to be the most common diagnosis requiring surgery in baseball athletes, while Reddy and colleagues reported it to be the most common diagnosis requiring arthroscopic treatment in athletes overall. Plain radiographs of the elbow may reveal these posteromedial osteophytes or loose bodies, typically best seen on a modified anterior–posterior (AP) humerus fully flexed elbow film with 40° of external rotation ( Fig. 1 ). ^, Radiographs may also demonstrate calcification/ossification of the MUCL, possibly indicating prior injury or MUCL insufficiency. ^, MRI can further assess injury to the soft tissues and chondral surfaces, MUCL, and is also useful in evaluation of loose bodies, osteophytes, and neurologic pathologies/complaints. ^,

Initial conservative treatment of VEOS consists of activity modification and throwing rest, nonsteroidal anti-inflammatory medication, intra-articular corticosteroid and/or platelet-rich plasma injections, detailed assessment of pitching mechanics, and a progressive return to throw program. However, minimal evidence-based literature is available on the outcomes following conservative care for posteromedial impingement, especially in those without overt compromise of the articular cartilage, subchondral bone, or MUCL. Piraino and Davis demonstrated a case report of conservative treatment in a 15 year old baseball player with VEOS, highlighting the capabilities and importance of a systematic movement examination and comprehensive rehabilitation program to address specific kinesiopathology.

Surgical intervention for VEOS is indicated when throwers fail to obtain symptom relief after a trial of conservative management. Arthroscopic posteromedial debridement and osteophyte excision have ultimately become a safe and reliable method to treat VEOS in throwers, with many results demonstrating high patient satisfaction and high rates of return to play (RTP). ^, ^, ^, ^, Andrews and colleagues first demonstrated an RTP rate of 70% at 24 months in 56 professional baseball players with posterior osteophyte excision; however, 41% required reoperation for repeat debridement. Five years later, Reddy and colleagues showed an RTP rate of 85% in baseball players undergoing arthroscopic treatment of posterior impingement. More recently, Koh and colleagues and Matsuura and colleagues both demonstrated RTP rates as high as 97% and 100% in 36 and 15 throwers, respectively, undergoing elbow arthroscopy with posteromedial olecranon osteophyte resection. It is important to note, however, that olecranon spurs are routinely found in asymptomatic throwers (especially professional baseball players), and thus posteromedial decompression is only indicated in patients with positive provocative testing.

Historically, the goal of surgical management for posteromedial impingement was to resect the olecranon tip in its entirety. However, modern thought and techniques now advocate against the removal of any portion of the normal olecranon margin ( Fig. 2 ). Kamineni and colleagues first demonstrated that sequential partial resection of the posteromedial olecranon resulted in a stepwise increase in valgus angulation as the amount of resection increased in 12 cadaveric elbows, challenging the rationale of removing any amount of normal olecranon in throwing athletes. In a follow-up study, Kamineni and colleagues demonstrated increased strain on the MUCL with olecranon resections greater than 3 mm, supporting MUCL insufficiency as a relative contraindication to posteromedial decompression in fear of exacerbating valgus instability. Paul and colleagues validated this fear by reporting that 18% of 28 baseball pitchers that underwent isolated arthroscopic posteromedial osteophyte resection for posteromedial impingement went on to require MUCL reconstruction surgery.

While RTP after arthroscopic debridement alone has been validated and studied, there is a paucity of literature regarding RTP after combined medial ulnar collateral ligament reconstruction (MUCLR) and arthroscopic debridement for VEOS. Osbahr and colleagues reviewed 29 baseball players who were treated for combined posteromedial chondromalacia and MUCL injury, demonstrating a lower RTP rate of 76% when compared to players with isolated MUCL injuries. However, Heaps and colleagues showed an RTP of 83% in throwers undergoing MUCLR with concomitant arthroscopic posterior compartment debridement, additionally demonstrating no difference in statistical performance in pitchers before or after surgery. They concluded that the addition of an arthroscopic posterior impingement procedure does not diminish an athlete’s ability to successfully return to sport (RTS) or perform at their prior level.

Overall, the goal of arthroscopic debridement in throwers with VEOS should be restoration of the normal contour of the posteromedial compartment without removal of any portion of the normal olecranon margin, along with concomitant procedures of MUCL reconstruction or ulnar nerve transposition as indicated. It is critical to work up and recognize MUCL injury and valgus laxity in these patients in order to not worsen medial-sided pain and instability in the future. Advances in instrumentation and arthroscopy technique continue to improve the safety and efficacy of elbow arthroscopy in throwers. Surgeon’s experience, knowledge, strategic preoperative planning, and expectation management remain paramount in the treatment of these athletes.

Osteochondritis dissecans

Osteochondritis dissecans (OCD) of the elbow is a localized disorder of articular cartilage and subchondral bone that results in a loss of structural support. ^, While the exact etiology is unclear and likely multifactorial, the widely accepted theory is that of repetitive microtrauma from excessive valgus creates stress along the radiocapitellar joint during development and throwing. ^, ^, This stress manifests as compressive and shear forces, likely compromising an already tenuous blood supply, and resulting in separation between cartilage and bone beneath the epiphyseal cartilage, most commonly in the capitellum. This in turn leads to inflammation, edema, and ossification arrest of the articular fragment with subsequent fibrocartilage formation and eventual subchondral bone and articular cartilage fracture/fragmentation. ^, Because of this proposed mechanism, the overhead athlete is often affected. The general incidence of elbow OCD is reported as 2.2 per 100,000 (6.8 times greater in male individuals), with reported incidences ranging from 1% to 7% in youth baseball players.

Patients with OCD will initially present with an insidious onset of activity-related, poorly localized lateral elbow pain, decreased range of motion, mechanical symptoms (suggestive of intra-articular loose bodies), and tenderness of the radiocapitellar joint. It is important to note that in 82 baseball players with an OCD lesion, Kida and colleagues reported that only 32.9% reported elbow pain at diagnosis, but 81.7% had a history of prior elbow pain. The active radiocapitellar compression test will often be positive, eliciting lateral elbow pain upon rotation of the forearm with the elbow extended.

Standard orthogonal radiographs have been reported to miss up to half of all OCD lesions and are less than 50% sensitive when compared to MRI. ^, Thus, routine radiographs are not typically useful for treatment planning or follow-up imaging. First described by Takahara and colleagues and Conway, the 45° flexed AP “capitellum view” is widely accepted as the standard of care for initial imaging workup in these patients as it is better able to visualize the capitellum. In baseball players, it is our recommendation that flexed views are obtained at 40° and 60° in throwers as they have been found have larger lesions with higher inclination angles. Advanced imaging modalities such as computed tomography (CT) and MRI have been shown to be more valuable in not only identifying lesions but also evaluating and characterizing their stability. MRI scans are almost always performed with intra-articular contrast with a high spatial resolution magnet, narrow slices (2–3 mm) with 3 dimensional reformats. It is our recommendation that MRI scans are performed with “40° up-oblique” sequences, allowing slices to be appropriately aligned with the OCD lesion ( Fig. 3 ). CT scans are typically only useful for complex, late-stage reconstruction planning, and recent studies have begun to suggest that ultrasonography may even provide an improved screening tool capable of detecting asymptomatic lesions. ^,

The treatment of OCD is still largely evolving but is mainly predicated on the stability of the overlying cartilage, the size and location of the lesion, and the lesions capacity to heal (often related to age). Many classification systems exist for a multitude of imaging modalities seeking to grade these lesion characteristics to guide treatment; however, they are typically unreliable and difficult to apply. Overall, general signs of instability on imaging include fluid beneath the lesion, increased T2 signal at the fragment/bed interface, sclerosis, and fragmentation of the cartilage or subchondral plate with associated loose bodies ( Fig. 4 ). ^, ^,

Conservative management mainly involves rest from throwing with occasional immobilization. Some have advocated for bracing (including a range of motion brace or activity cast) as well as follow-up imaging at 6 to 12 week intervals to evaluate healing. Takahara and colleagues in particular advocates for immobilization with casting (mean: 3.7 weeks) followed by splinting (mean: 7.3 weeks) which was shown to enable earlier RTS (mean: 4.4 months) along with faster and more complete healing. This is our recommended first-line treatment of choice for young throwers with open physes. Evidence-based indications for nonoperative care include younger age and an open lateral epicondylar physis (more growth remaining healing potential), smaller, stable, and central grade I lesions, and the absence of radial head migration. ^, In a retrospective review of 93 elbows, Niu and colleagues demonstrated a healing rate of 53.8% at a mean of 8.3 months, concluding that over half of “stable” OCD lesions have the capacity to heal with activity restriction. Smaller lesions and the absence of cysticlike lesions were independent predictors of healing. In one of the only studies to report on RTP in nonoperative OCD management, Sakata and colleagues reported a RTP rate of 70.4% in 81 youth baseball players at a mean time of 6.3 months. Proximal radial translation length on AP radiographs was significantly greater (less proximal migration) in the RTS group. Funakoshi and colleagues performed a multivariate regression on 245 elbows with OCDs concluding that radial head enlargement and asymmetrically advanced skeletal age were significant predictors of lack of healing and advanced stage lesion. This study suggests that a history of radiocapitellar joint stress (such as from repetitive throwing) may lead to OCD and thus cause a more advanced skeletal age in the involved elbow.

Numerous authors have concluded that many capitellar OCD lesions lack innate healing potential and thus conservative care may lead to poor outcomes especially in high-risk, overhead athletes trying to RTS. ^, Surgical management of OCD is largely guided by size and location of the lesion. Predictors of poor outcomes with nonoperative care are unstable lesions, older age, longer duration of symptoms, closed lateral epicondylar physes, higher stage lesion classification findings, larger lateral lesions (especially uncontained lesions—lesions extending lateral to the radial head center line and including the lateral margin ; Fig. 5 ), as well as radiocapitellar incongruity and radial head hypertrophy/migration. ^, Surgical options include arthroscopic debridement, drilling/microfracture and loose body (LB) removal for smaller lesions, and fragment fixation and open complex reconstruction procedures for larger lesions.

Multiple studies have demonstrated mixed results with regard to arthroscopic debridement with or without drilling. Lewine and colleagues reported a return to primary sport rate of 66.7% in 21 adolescents with Grade IV OCD lesions (defined in this study as detachment of the lesion and intra-articular LB formation) treated with LB removal and drilling/microfracture. Bexkens and colleagues reported a lower rate of 55% in 77 patients treated with debridement and LB removal, citing open physes and shorter duration of symptoms as being correlated with improved outcomes. More recently, Matsuura and colleagues and Rothermich and colleagues reported RTS rates of 87% (only 20% in pitchers) in Grade IV and V lesions and 93% in lesions ranging from “small, moderate and large” in size, respectively. While many of these results support non-reconstructive surgical care, they also demonstrate that while debridement and drilling can be effective for some, it is not successful for all, especially overhead throwers.

With the high demand of the throwing athlete and the average-to-moderate outcomes of arthroscopic debridement and drilling, complex cartilage reconstruction and restoration procedures may be the preferred option for large unstable lateral lesions. At the forefront of these procedures is osteochondral autograft (OAT) and allograft transplantations ( Fig. 6 ). Autograft harvest sites have included the ipsilateral or contralateral elbow and knee (lateral trochlea, notch, costochondral), and allograft donors have ranged from precut fresh osteochondral plugs or knee condyle/trochlea to multiple other sources such as the humeral head, distal humerus, femoral head, and talar head. In a systematic review from 2016 comparing RTS rates in athletes (primarily baseball players and gymnasts) undergoing OCD debridement, fixation or OAT procedures, Westermann and colleagues found that the return to the highest preoperative level of sport was most common after OAT (94%). They also demonstrated that fragment fixation had a lower RTS and higher reoperation rate than both debridement and OATS. Since that time, multiple other systematic reviews and studies have also supported high (>90%) successful RTS and graft incorporation rates, as well as reliable outcomes with few complications and low donor-site morbidity. ^,

OCD lesions of the elbow remain a difficult and controversial pathology to treat. To date, no controlled prospective studies that consider lesion stage or standardized therapy exist, and there are few studies that prospectively compare OCD treatment options. Overall, we recommend using an evidence-/algorithm-based approach in the treatment of these athletes. Conservative care has the potential to be successful in young, premature, stable, small, central, short duration lesions, while operative management is typically indicated in larger, more mature, unstable lesions with indications for OATS for large lateral lesions. Nonoperative progress can be followed with selective, flexed AP radiographs and specific OCD sequence MRI scans; however, they should not be followed for more than 3 months without considerable concern and discussion of operative intervention. Arthroscopic debridement/drilling and fragment fixation may be acceptable for smaller, shallow-contained lesions without evidence of radial head pathology. However, there is growing evidence that these procedures may not work as well or as predictively as OATS procedures and have lower RTS and higher reoperation rates.

Olecranon stress fracture

Olecranon stress fractures (OSFs) are a rare upper extremity fractures that primarily impact the overheard thrower. As the olecranon is repeatedly driven into the fossa during the throwing motion, shear and impaction forces are created along the medial tip/fossa leading to the development of stress reactions, fractures, and osteophytes. ^, ^, Typically deemed an injury of overuse, the olecranon is the site of injury for 58% of stress fractures in baseball players with pitchers being the most at-risk position. ^, Athletes will typically present with an insidious onset of vague, activity-related posterior elbow pain that is progressive over the course of weeks, often occurring with elbow extension at ball release. ^, Point tenderness to palpation over the posteromedial or posterolateral olecranon is a key physical examination finding. ^, In throwers specifically, repetitive valgus loads on the elbow can cause additional attenuation of the MUCL with increased reliance on the posterior elbow for stability and a compensatory increase in posteromedial compression during the throwing motion. ^,

Initial workup begins with plain radiographs. While often initially normal and nondiagnostic, characteristic findings can include new periosteal bone formation, enthesopathy, endosteal thickening, cortical radiolucency and sclerosis, and even late fracture lines. ^, Early detection and diagnosis of OSF is imperative as prior literature has demonstrated a statistically significant difference in return time to sport in athletes when the stress injury was diagnosed within 3 weeks of symptom onset (return time 10.4 vs 18.4 weeks). Lateral radiographs with the humerus internally rotated 20° (“hand down lateral”) may enhance visualization of the posteromedial olecranon ( Fig. 7 ). ^, If stress injury is suspected but radiographs appear normal, advanced imaging with CT, MRI, and 3 phase bone scan may be helpful with early diagnosis. CT scan is often useful in identifying cortical abnormalities and early signs of fatigue damage. It should be performed on a minimum 128 slice scanner with true axial, sagittal, and coronal alignments and may also be used to follow stress reaction healing postoperatively. Bone scintigraphy is quite sensitive for early detection of stress reactions within 3 to 5 days after symptom onset due to its capacity to detect areas of subtle osseous turnover and stress remodeling. However, MRI has remained the gold standard for diagnosis due to its enhanced sensitivity and specificity. With its sequencing-dependent capacity to detect early bone edema, it also provides a more comprehensive evaluation of the bone and surrounding soft tissue, making it especially critical in throwers when considering and evaluating the relationship between olecranon stress injury and MUCL damage. ^, However, it is also important to note that MRI may provide a delayed positive or false negative especially in olecranon tip and sublime tubercle fractures. ^,