AOSM Valgus extension overload syndrome

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Understanding the biomechanics of throwing is important to determine the pathophysiology of valgus extension overload syndrome and to plan an appropriate management protocol for patients with this syndrome. The elbows’ of baseball pitchers must endure repetitive and excessive valgus forces that typically lead to injuries of the medial and lateral joints and the olecranon, caused by distraction, compression, and rotatory forces, respectively. If undiagnosed or treated inappropriately, the syndrome may lead to debilitating consequences in athletes. Elbow arthroscopy has been invaluable for the diagnosis and treatment of intra-articular pathologies of the elbow. Compared to open procedures, arthroscopic surgeries have allowed not only faster rehabilitation but also expedited return-to-competition in athletes. Yet correct arthroscopic techniques and knowledge of regional elbow anatomy are needed if we are to avoid neurovascular complications and articular damage and improve surgical outcomes in patients with valgus extension overload syndrome.

Keywords: Valgus extension overload syndrome; Posterior elbow; Baseball injury

Valgus extension overload syndrome

Jin-Young Park, Jae-Hyung Lee, Atul Mahajan

Center for Shoulder, Elbow and Sports, NEON Orthopaedic Clinic, Seoul, Korea

CC This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/

by-nc/4.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received June 16, 2017; Revised October 16, 2017; Accepted November 15, 2017

Correspondence to: Jae-Hyung Lee, Center for Shoulder, Elbow and Sports, NEON Orthopaedic Clinic, 4F, Novel Bldg., 8 Seolleung- ro 131gil, Gangnam-gu, Seoul 06059, Korea. Tel: +82-2-540-3200, Fax: +82-2-540-2299, E-mail: [email protected]

Arthroscopy and Orthopedic Sports Medicine

AOSM

INTRODUCTION

Valgus extension overload syndrome (VEOS) is commonly associated with medial compartment distraction, lateral compartment compression, and posterior compartment impingement. In VEOS, patients often present with pain secondary to impingement of the posteromedial olecranon and the medial aspect of the trochlea. The impingement and the resultant force applied to these areas during particular sports activities, such as repetitive throwing, produces degenerative changes in the posterior compartment of the elbow.

Careful and optimal management based on both sub- jective and objective assessments of the elbow may allow carefully selected patients to return to throwing sports successfully after VEOS.

The purpose of this article was to discuss the anatomy and the pathomechanics of VEOS and to examine the evidence for the utility of diagnostic imaging modalities, surgical techniques, and rehabilitation for VEOS.

ANATOMY AND PATHOMECHANICS

The anterior bundle of the medial collateral ligament (MCL) provides primary stability against the extreme tensile force generated by valgus torque [1–3], while the bony constraints of the olecranon fossa and the radiocapitellar joint provide secondary stability. Because baseball pitchers are exposed to extreme tensile forces, they are at higher risk of soft tissue injury of the elbow. Excessive valgus stresses are counteracted by bony, ligamentous, and muscular restraints [1]. In particular, the anterior bundle of the MCL is often referred to as the “primary stabilizer”

[2] and the radial head as the “secondary stabilizer,”

which in the presence of a normal MCL plays no part in resisting the valgus deforming force.

Valgus stress is resisted by MCL, the capsule, and the bony constraints to equal extents during full extension of the elbow [4,5]. The contribution of the olecranon towards resistance against valgus stress was confirmed by An et al. [6] who found that sequential olecranon resection causes increased valgus instability. King et al.

[7] noted that medial ligament laxity and, therefore, the

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impingement of the posteromedial olecranon within the olecranon fossa exacerbated under excessive valgus force near full extension of the elbow. This is thought to be because the olecranon traumatically abuts the posterior compartment when the muscles fail to dynamically control deceleration as the elbow reaches full extension.

Thus, the olecranon is subject to injury from both valgus and extension forces, which is commonly described as the “valgus extension overload” [8–10].

Werner et al. [11] divided the throwing motion into six phases: windup, early cocking, late cocking, acceleration, deceleration, and follow-through. The shoulder is abducted, extended, and externally rotated to approximately 130° and the elbow is flexed to approximately 90° at the cocking phase, from which phase onwards the elbow is under severe valgus stress [12]. During the transition between cocking and acceleration, the valgus load on the medial elbow increases as the shoulder rotates internally, the forearm is in near-full supination, and the elbow flexes another 20° to 30° [12]. This transition is often described as the “moment of explosion” or “initiation of speed.”

During pitching, velocity is generated through the upper extremity kinetic chain—the internal rotation of the shoulder and the translational and rotational motion of the trunk. The power generated from the chain places significant force and torque on the elbow and shoulder.

Anz et al. [13] reported that pitchers who experience high valgus torque of the elbow and external rotation torque of the shoulder during throwing are more likely to suffer elbow injuries than those with lower levels of torque.

Manipulating pitching mechanics to lower these torque levels or using these parameters as risk factors may avoid injuries.

Ahmad et al. [14] found that the posteromedial contact force increases only during the deceleration phase of throwing, during which the elbow is at lower degrees of flexion. This finding was consistent with the pathomechanics associated with valgus extension overload, but location-specific chondromalacia within the throwing elbow was not evaluated. Osbahr et al. [15] hypothesized that posteromedial elbow impingement, associated with valgus laxity secondary to ulnar collateral ligament (UCL) insufficiency, occurs as ulnohumeral chondral and ligamentous overload develops from abnormal contact pressures incurred at any one phase of throwing. This as- sertion is consistent with findings from other studies that have suggested either a continuum or two distinct forms

of posteromedial impingement (early acceleration and deceleration), which may develop at any phase of throwing and at certain chondral lesion locations (medial crista of the posterior humeral trochlea and medial olecranon fossa) [16–19].

Despite the importance of UCL integrity, as well as the ulnohumeral articulation, against posteromedial impingement in the elbow of throwers, its role is not well defined [20,21]. In fact, Andrews and Timmerman [22] found that only 25% of competitive baseball players had developed valgus instability that required UCL reconstruction after isolated resection of symptomatic posteromedial osteophytes induced from valgus extension overload. Altogether, the findings from the previous studies highlight the complexity of posteromedial impingement in the elbow of throwers and suggest that valgus laxity, in combination with valgus extension load, may produce a “windshield-wiper effect” on the elbow, leading to medial translation of the olecranon tip along the humerus.

These findings emphasize the importance of diagnos- ing valgus instability associated with UCL insufficiency early in throwing athletes before they develop pathological chondromalacia. These chondral lesions during elbow arthroscopy may act as potential markers of UCL- insufficiency–induced valgus instability in throwing athletes.

The pathological elbows of a handball goalie or a boxer are similar to that of a pitcher with VEOS. Posterolateral impingement of the elbow is caused by repetitive hyperextension and pronation of the lower arm from missed punches. Hyperextension forces the olecranon tip into the olecranon fossa, and the subsequent impingement leads to osteophyte formation on the olecranon tip, es- pecially on the lateral side. Similarly, the mechanism of posterolateral impingement in goalkeepers appears to be repeated hyperextension [23,24] from blocking shots. This condition is also called “the handball goalie’s elbow.” Radiologic and ultrasonographic evaluation of 30 handball goalkeepers by Popovic and Lemaire [25]

revealed osteophyte formation (on mainly the tip of the olecranon), loose body formation, and periarticular calci- fication. The three syndromes differed with respect to the location of osteophytic change. Osteophyte formation at the olecranon process seemed to be a critical part of the goalkeepers’ elbow syndrome, but their exact location has not been precisely described. It was found that the pattern of osteophytic location and the mechanism

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of trauma between VEOS in pitchers and the elbow syndrome in boxers were the opposite: osteophytes occurred on the posteromedial aspect of the olecranon process in pitchers and on the posterolateral aspect of the olecranon tip in boxers. Because shear forces cause posteromedial osteophytes in overhead-throwing athletes, we may hypothesize that this phenomenon may also explain the formation of posterolateral osteophytes in boxers.

CLINICAL EVALUATION

Physical examination

The mechanics of throwing rely on a kinetic chain that involves the shoulder, and this is also the reason why the shoulder should always be closely examined in throwing athletes. Primary shoulder pathologies can affect pitching mechanics, causing the elbow to endure excessive amounts of stress. Dines et al. [26] reported an associa- tion between pathologic glenohumeral internal rotation deficit (GIRD) and UCL insufficiency; they found that baseball players with UCL injury had an average GIRD of 28.5°. Inspection of the elbow begins with an assessment of the resting position and the carrying angle, which on average is a valgus angle of 11° and 13° in men and women, respectively. An increased, that is, a more valgus, carrying angle may indicate an adaptation to repetitive valgus stress [4]. A carrying angle greater than 15° has been documented in professional pitchers [8].

Subsequent examinations should focus on the evaluation of range of motion (ROM) and loss of extension, such as the loss in terminal extension often caused by posterior osteophytes. Patients with restricted ROM and extension loss may feel pain upon forced terminal extension. Although flexion contracture of the elbow is seen in up to half of professional pitchers, its presence is not necessarily indicative of injury.

During physical examination, the elbow is palpated in the posterior direction towards the triceps tendon and the olecranon tip. Pronation, valgus, and extension forces may elicit tenderness in the posterior compartment. The olecranon is assessed for tenderness, warmth, crepitus with ROM, and bony fragments. Posteromedial olecranon tenderness and crepitus may indicate VEOS, and direct olecranon tenderness may indicate a stress fracture or apophysitis in young athletes. Signs of warmth and fluctuance may be due to olecranon bursitis, gout, or infection. Crepitus, locking, or catching is suggestive of the presence of loose body, osteophyte, or chondromalacia.

Commonly used diagnostic tests for VEOS are the extension impingement test, the arm bar test, and the moving valgus stress test. The moving valgus stress test examines the arm in full flexion and then in full extension under a constant valgus force. As the elbow quickly extends from 120° of flexion to 70° of extension, the patient re-experiences the painful symptoms (Fig. 1) [2,9,19]. The arm bar test [27] begins with the patient resting his or her hand on the shoulder of the clinician and the arm is fully and internally rotated and extended at the elbow (Fig.

2). Pain during forced extension implies the presence of posteromedial impingement. The valgus extension overload test involves applying moderate valgus stress to the elbow and simultaneously palpating the posteromedial tip of the olecranon. The elbow is maneuvered from 30°

of flexion to full extension (Fig. 3), and a positive result is noted if this maneuver, which simulates the posteromedial olecranon impingement and pain that occur in the late acceleration phase of pitching, elicits pain [7,17].

As well as the posterior compartment, it is essential to assess MCL, the flexor-pronator mass, the radiocapitellar articulation, and the ulnar nerve for concomitant injuries. This is because co-injuries such as a subluxat-

Fig. 1. Extension impingement test. With the patient’s arm in full flexion, the examiner applies a constant valgus force to the patient’s elbow and then quickly extends the elbow. This reproduces the painful symptoms with an apprehension-like response as the elbow passes from 120°

of flexion to 70° of extension in an arc.

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ing ulnar nerve may worsen with use of medial portals and because underlying conditions such as UCL- insufficiency–induced valgus instability are important factors to consider in management decisions. Injuries of the UCL can be differentiated from medial epicondyli- tis by performing the valgus stress test with the wrist in passive flexion and pronation, which relaxes the flexor- pronator mass and helps to isolate MCL pathology [28].

The milking maneuver [29] involves the patient reaching and grabbing hold of their thumb of the injured arm with their opposite hand. Continued pulling places valgus stress on the elbow of the injured arm. The MCL should be palpated with the elbow in approximately 60° of flexion, which moves the flexor pronator mass anteriorly relative to the fibers of the anterior band.

Diagnostic imaging

Evaluating VEOS and posteromedial impingement of the elbow joint often requires a multimodal approach because of the clinical importance of accurate osseous and extraosseous findings.

Imaging of overhead athletes with suspected VEOS ini- tially includes plain radiography of the elbow. Anteropos- terior, lateral, and axial views are typically chosen. Wilson et al. [9] recommends taking the axial view with the elbow

in 110° of flexion, the arm resting on the cassette, and the beam angled 45° to the ulna, because it shows the articulation of the olecranon, such as the trochlear groove, and the posteromedial osteophyte. Conventional radiographs of the elbow can detect posteromedial osteophytes, loose body, and stress fractures of the olecranon tip but not cartilaginous lesions. Therefore, computed tomography (CT) or magnetic resonance imaging (MRI) becomes necessary to diagnose complicated cases involving other posteromedial osteophytes, subchondral sclerosis, and joint space narrowing.

Stress radiography has been used adjunctively to evaluate UCL insufficiency. Valgus stress views are obtained for both the injured and uninjured elbows in 30° of flexion, and ulnohumeral widening in the injured elbow relative to the uninjured elbow is measured. Rijke et al. [30]

found that a greater than 0.5-mm side-to-side difference in joint space on stress radiography is highly indicative of a ruptured UCL in athletes. Non-enhanced MRI can be used to evaluate the size and location of concomitant intra-articular bodies and identify chondrosis, subchondral sclerosis, cystic changes, and edema. It has been reported that MRI has a sensitivity of 90% for identifying posterior loose body and osteophytes [31]. It is used to detect at- tenuation and redundancy of the anterior bundle of UCL Fig. 2. Arm bar test. The patient’s hand is rested on the clinician’s

should with the arm fully internally rotated and extended at the elbow.

Pain induced with forced extension indicates the presence of posteromedial impingement.

Fig. 3. Moving valgus stress test. Moderate valgus stress is applied to the elbow and the posteromedial tip of the olecranon is palpated simultaneously. The elbow is then moved from 30° of flexion to full extension.

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and evaluate the articular cartilage of the trochlea and olecranon fossa, the common flexor tendon, and the ulnar nerve.

In their retrospective study, Cohen and Bruno [32] observed a distinctive set of features on MRI in nine patients with a clinical diagnosis of posteromedial impingement.

All patients had degenerative changes on the articular surfaces of the posterior trochlea and the anteromedial olecranon, cartilage signal heterogeneity, focal cartilage defects, and subchondral bone marrow edema and sy- novitis within the posteromedial recess. Edema at the distal medial triceps was found in eight patients. Simi- larly, Kooima et al. [33] observed similar MRI findings in 13 of 16 asymptomatic professional baseball players with posteromedial impingement. Interestingly, they also reported that UCL thickening significantly correlated with posteromedial subchondral sclerosis.

Other common diagnostic features of posteromedial impingement on MRI are insertional tendinosis at the medial border of the triceps with sub-enthesial bone marrow edema in the olecranon [34], loose body formation, and chronic changes to UCL and to flexor and pronator tendon origins. These demonstrate the importance of corroborating findings from medical history and physical examination with those from diagnostic imaging studies of the lesion. Yet these pathological features alone should not be an indication for surgical treatment because they are considered to be incidental, not primary, findings for the diagnosis of posteromedial impingement.

Most athletes who engage in repetitive throwing motions present with abnormal MRI findings and may show signs of laxity. In their retrospective study, Del Grande et al. [35] qualitatively and quantitatively evaluated the elbow in 21 non-symptomatic professional baseball pitchers for 3-T MRI features. They found that collateral ligament thickening without full thickness tears was seen in a high proportion of pitchers, tendinosis without tears in 19%, and cartilage abnormalities infrequently. Bone abnormalities manifested as edema and humero-ulnar osteophytes in 24% of patients. They found that ulnar nerve signal and/or morphologic abnormalities occurred at very high proportions, in up to 81% of patients. Ap- proximately a third of olecranon fat pads showed scar- ring. Interestingly, previous studies have shown that throwing athletes with MRI changes to the olecranon and pain in the early acceleration phase of throwing are more likely to suffer from UCL insufficiency, whereas those with similar MRI changes but pain during the full exten-

sion phase or the follow-through phase of throwing are more likely to suffer from posteromedial impingement.

Therefore, MRI findings seem to strongly correlate with arthroscopic evaluations.

Radiological findings of VEOS such as joint space narrowing, medial olecranon subluxation, and loose body formation are significantly better diagnosed with CT [36]

than MRI. The is because joint space and medial subluxation between the bony cortices of the olecranon process and olecranon fossa are better measured on CT than MRI [37]. Also, small osseous fragments lacking fatty marrow appear hypo-intense on T1-weighted or proton density fat-suppressed MRI images and therefore cannot be identified as clearly as with CT scans. In the preoperative stages of treatment, non-contrast CT could offer helpful information concerning the evaluation and prognosis of patients with VEOS [37].

Park et al. [38] classified the tip fragment by shape: dot- like or triangular. They found that 3 out of14 patients had a dot-like fragment (type 1) (Fig. 4) and 10 out of 13 patients had a triangular fragment (type 2) (Fig. 5). The authors insisted that the olecranon tip fracture was the main pathology as opposed to osteophyte formation.

Ultrasonography can facilitate a rapid and accurate evaluation of UCL. The ultrasound scan between the medial humeral epicondyle and the ulna appears hyper- echoic in patients with a normal UCL and hypoechoic in patients with an abnormal UCL. The disrupted ligament fibers are visualized by injecting anechoic fluid into the gap. To estimate sonographic joint laxity, Kim et al. [39]

assessed the presence of three sonographic features on stress sonography—ligamentous waviness, joint gap- ping, and intra-articular ring-down artifacts—as well

Fig. 4. A dot-like type 1 fragment of valgus extension overload syndrome (arrows).

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as concomitant tenderness. The ring-down artifact and concomitant tenderness on stress sonograms may help predict the rehabilitation outcome of UCL injuries [40].

The indications for arthroscopic surgery are clinical evidence of a posteromedial compartment lesion with posteromedial pain during throwing, posteromedial tenderness on examination, a positive valgus extension overload test, and radiographic evidence of impingement. Patients who despite conservative treatment do not improve are also indicated for arthroscopic surgery.

Relative contraindications to arthroscopic treatment include severe bony or fibrous ankylosis or history of surgery, such as an ulnar nerve transposition, that distorted the native anatomy of UCL, in which case open resection may be performed.

MANAGEMENT

Nonoperative treatment

Some surgeons recommend patients to be treated non- operatively for around 3 to 6 months before choosing surgery. Rettig et al. [41] found that 42% of throwing athletes (13 of 31) were able to return-to-sports at or above pre-injury level after rehabilitation. In a retrospective review, Dodson et al. [42] found that 90% of patients who were National Football League quarterbacks successfully returned-to-professional play after non-operative treatment of UCL pathology caused by contact injury. Their results suggest that acute and traumatic UCL lesions may be more amenable to non-operative management than chronic and attritional lesions.

Dines et al. [43] found that platelet rich plasma injec- tion led to excellent outcomes such as return-to-sports to pre-injury level or enhanced level at a mean 14 weeks

of follow-up in 59% of baseball players (from a total of 27) with a partial UCL tear, diagnosed with non-contrast MRI.

Non-operative treatment aims to achieve full and non- painful ROM, absence of pain, non-tenderness upon physical examination, and satisfactory muscle strength, power, and endurance. The rehabilitation aims to improve eccentric strength and control of elbow flexors by enhancing the eccentric strength of the biceps, brachio- radialis, and brachialis muscles.

Surgical treatment

The choice of surgical procedure in overhead athletes who fail to be treated conservatively for posteromedial impingement is osteophyte excision and exploration of loose body. Originally described by Bennett et al. [44] as an open procedure, this procedure is more commonly considered an arthroscopic intervention nowadays.

Reddy et al. [45] reported that the most common preoperative diagnosis among 187 elbows that received arthroscopic surgery was posteromedial osteophyte with loose body. In general, patients with symptomatic loose body or impinged osteophytes showed the greatest im- provement after arthroscopic surgery, whereas patients with degenerative changes seemed to have less satisfactory results [19]. Ahmad et al. [14] suggested that the osteotomy may have caused an asymptomatically lax elbow to become unstable and painful or that the osteophytes may have maintained clinical stability in place of the insufficient UCL before osteotomy. These observations have prompted surgeons to avoid aggressive osteophyte resection and removal of the normal olecranon in osteotomy [37]. In line with this, excessive resection has been associated with delayed treatment of the ruptured UCL [21].

Park et al. [38] evaluated the clinical outcome after arthroscopic olecranon-osteophyte resection without ligament operation in elite baseball players who had VEOS without moderate or severe medial ulnar collateral ligament (MUCL) injury. They concluded that arthroscopic osteophyte resection is an ideal treatment that facilitate early return to pre-injury level sports activity and pain relief for patients with VEOS combined low-grade MUCL injury (Fig. 6) [38]. Park et al. [46] also retrospectively evaluated adolescent athletes with VEOS who underwent either an arthroscopic olecranon tip resection or a staged operation involving an arthroscopic olecranon tip resection and medial collateral ligament reconstruction a fort- Fig. 5. A triangular type 2 fragment of valgus extension overload syn-

drome (arrows).

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night later. They found that patients who underwent the isolated arthroscopic surgery reported less postoperative pain and a higher Conway grade than patients who underwent the staged operation. Thus, their findings indi-

cate that concomitant UCL insufficiency is associated with less favorable outcomes than isolated posteromedial impingement in patients with VEOS. Arthroscopic resection of the olecranon tip yielded favorable outcomes after at least a 2-year follow-up [46]. Rahusen et al. [47] evaluated the effectiveness of arthroscopic debridement of the posterior fossa for posterior impingement in 16 elbows of athletes and found that it leads to excellent mid-term results (Fig. 7).

Operative technique

As one of the first steps of surgical treatment, the land- marks including the radial head, the proximal radius, the capitellum, the medial and lateral humeral epicondyles, the tip of the olecranon, and the ulnar nerve are identified with a sterile marker. Before the portals are created, the affected joint is inflated by injecting 20 mL of normal saline into the posterior triangular space through a soft spot. The distention of the joint moves the neurovascular structures away from the joint surface and decreases the chance of iatrogenic neurovascular injury from portal placement. Anterior elbow arthroscopy in overhead throwers with posterior symptoms is important because throwing motions generate compressive forces at the lateral aspect of the elbow, leading to osteochondral injury to the radiocapitellar joint. Two arthroscopic portals are

A B

C

Fig. 7. Intraoperative athroscopic findings of valgus extension overload syndrome and the posterior olecranon tip fracture (A), after removing the fracture fragment (B), and after trimming off the posterior olecranon osteophyte (C).

Fig. 6. Preoperative three-dimensional computed tomography (3D- CT) scan (A) of valgus extension overload syndrome with posterior olecranon tip fracture and osteophyte formation and postoperative 3D- CT scan (B) showing definite widening between the olecranon and the olecranon fossa after removal of the fracture fragment and partial tip resection.

A B

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used to access the posterior compartment: the straight posterior (or trans-triceps) and the posterolateral. Then, the extent and dimension of the osteophyte are evaluated by using the arthroscope in the posterolateral portal and the shaver in the trans-triceps portal. Excess soft tissue, including synovial reflections, is removed from the olecranon tip with a radiofrequency device and the osteophytes are removed with a quarter inch osteotome or an arthroscopic burr [9,48]. The posterolateral portal is used as the viewing portal while the posterior portal, through which the osteotome is inserted, is used as the working portal. Approximately 5 to 10 mm of the olecranon tip is removed, cutting at the posterior cortical surface with the osteotome and a small mallet. The cut fragment is levered free by manipulating the osteotome and taken out with grasping forceps. Afterwards, the olecranon tip and fosaa is contoured with a motorized burr to prevent further impingement, keeping the underlying cartilage undamaged throughout [9,48]. The overarching goal of treatment is to re-establish and contour the coronoid and olecranon fossa with the burr, preventing further impingement in all ranges of flexion and extension. During treatment, the surgeon may switch from one portal to another depend- ing on how well the elbow pathology can be visualized and accessed.

The position of the ulnar nerve, which is just superficial to the capsule in the posteromedial gutter, is important when using a shaver near the ulnar nerve; suctioning should not be used and the radiofrequency device should be used with caution. Removing the osteophyte allows the humeral chondral surface to be visualized more com- pletely and, if present, the kissing lesion of the chondral abrasion opposite the osteophyte to be in direct view. De- bridement, and if necessary microfracture, of loose chondral flaps should be performed. The optimal amount of olecranon to be debrided has been a matter of debate.

Although a standard value has not been suggested in the literature, two recent studies have recommended limit- ing resection to the osteophyte only and preserving as much normal olecranon bone as possible, because debridement of osteophytes may potentially contribute to elbow instability and place strain on the medial collateral ligament in throwing athletes [49].

In a cadaveric study, Field et al. [50] found that arthroscopic examination of the medial joint space has a high specificity in detecting complete ruptures of the anterior bundle of UCL. Unlike complete ruptures, valgus instability due to partial ruptures of the anterior bundle

of UCL cannot be detected with stress radiography. In ad- dition, Azar [51] reported that clinical elbow examination has a low specificity in detecting partial UCL ruptures.

The possibility of a stabilizing effect of the posteromedial osteophyte has always been a concern. The buttressing effect of the posteromedial osteophyte has been partly attributed to UCL insufficiency. The concern grounds on the fact that resection of the osteophyte may lead to increased stress on the ligament, requiring some patients to undergo additional reconstruction of UCL. A crucial step in elbow arthroscopy is intra-articular evaluation of UCL [50]. An arthroscopic valgus stress test is performed with the elbow in 70° of flexion, and a medial opening, observed under direct visualization, of greater than 1 to 2 mm suggests UCL insufficiency. Then, surgical reconstruction of UCL must be considered to mini- mize recurrence and improve outcome.

In patients with a severely attenuated anterior bundle of UCL, ligament reconstruction may be additionally needed to prevent the olecranon tip from further imping- ing the medial aspect of the olecranon fossa during overhead throwing. Using pressure sensors, Hassan et al. [52]

measured the contact area, pressure, and valgus torque of the posteromedial elbow at 90° and 30° of elbow flexion in 25 cadaveric elbows from men. They made the mea- surements first with an intact UCL, second with a 50%

proximal-to-distal detachment of UCL, and then with a complete proximal-to-distal detachment of the anterior band of UCL from the ulnar attachment. Because the change in contact area and the proximal movement of the center of pressure was significant only when more than 50% of the proximal UCL was detached (i.e., not when 50% of the distal UCL was detached), these findings suggest that the proximal half of the ulnar footprint is critical to maintaining the functional biomechanics of the posteromedial elbow. Therefore, these findings also suggest that surgical reconstruction should prioritize reestablishing at least the proximal 50% of the ulnar footprint (Supplementary File 1).

COMPLICATIONS

Complications related to surgical procedures of VEOS are similar to those from any open or arthroscopic procedures of the elbow. They include neurovascular damage from either direct injury or fluid extravasation-induced compression, damage to the articular surface from poor or defective instrumentation, infection, and tourniquet-

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related problems. Other complications such as early het- erotopic bone and scar tissue formation in the posterior compartment are observed in less than 10% of patients.

These complications often occur when the recovery period is pushed forward and the thrower is hastened to return-to-throwing early. Because damage to neurovascular structures is the most common complication of elbow arthroscopy [53], surgeons must have a detailed knowledge of the techniques of arthroscopic surgery and the anatomy—the topical, neurovascular, and compart- mental anatomy—of the elbow as seen on arthroscopy [54,55].

CONCLUSION

Because elbow injuries in throwing athletes can be dif- ficult to diagnose, a thorough understanding of the anatomy, function, and biomechanics of the elbow is essential for the proper evaluation and treatment of these injuries. Current management guidelines for operative or non-operative procedures and rehabilitation protocols

require physicians to have a thorough knowledge of the biomechanics of the throwing cycle.

Elbow arthroscopy has become an invaluable tool for the diagnosis and treatment of VEOS. Performed well, elbow arthroscopy can be a powerful tool for the management of common thrower’s injuries, facilitating a quick return- to-competition with minimal morbidity. Future research should aim at furthering our understanding of the anatomy, biomechanics, and pathophysiology to help us improve the clinical outcome in patients with VEOS.

CONFLICT OF INTEREST

No potential conflict of interest relevant to this article was reported.

ACKNOWLEDGMENTS

The written informed consent for publishing photo- graphs was obtained from the patient.

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