Quantitative analysis of the medial ulnar collateral ligament ulnar footprint and its relationship to the ulnar sublime tubercle

Influence of flexor pronator muscle contraction on medial elbow joint space distance in high school baseball players: a cross-sectional study

BACKGROUND/HYPOTHESIS

The contraction of the flexor pronator muscles (FPMs) plays an important role in stabilizing the elbow joint in baseball players. However, the influence of different types of contractions on the medial joint space (MJS) in high school baseball players is not well understood. This study aimed to elucidate the effects of individual or combined contractions of the FPMs, specifically the flexor carpi ulnaris, flexor digitorum superficialis (FDS), pronator teres (PT), palmaris longus, and flexor carpi radialis, on the MJS in high school baseball players. We hypothesized that contractions, particularly of the FDS, PT, and flexor carpi radialis, would lead to a narrowing of the MJS.

METHODS

The study included 36 high school baseball players who executed 9 different contraction tasks related to the FPMs (including a resting state) in a randomized order. The MJS was measured using ultrasound equipment and compared with the resting state. The Friedman test, as a repeated-measures one-way analysis of variance, was performed, followed by Steel's test for multiple comparisons. All analyses were conducted using EZR software, with a significance level set at 5%.

RESULTS

The repeated-measures one-way analysis of variance and the Friedman test revealed a significant difference among the 9 contraction tasks (P < .001). Using Steel's test, a significant reduction in the MJS (mean ± standard deviation) was observed compared with the resting state (4.8 ± 1.2 mm), particularly in contraction tasks involving the PT (4.0 ± 1.0 mm, P = .017), FDS and PT (4.0 ± 1.1 mm, P = .007), and flexor carpi ulnaris, FDS, and PT (4.0 ± 1.1 mm, P = .008).

CONCLUSIONS

Incorporating the PT into contraction tasks significantly reduced the MJS, emphasizing the important role of the PT in elbow joint stability. More work is required to see if the results of this study can be used to develop injury prevention and rehabilitation strategies.

Ulnar Collateral Ligament Injuries in Overhead Athletes: Diagnosis, Management, and Clinical Outcomes

Ulnar collateral ligament (UCL) injuries are a common source of pain and disability in overhead and throwing athletes. The prolonged nature of healing often results in notable time lost from competitive sports regardless of the definitive management strategy. A thorough history and physical examination are critical in the diagnosis of UCL injury and understanding patient goals and expectations. In carefully selected patients, nonsurgical management, including rest and slow progression back to activities, can result in successful return to sport. Recent literature has suggested that administration of platelet-rich plasma may be effective in aiding in the healing process, particularly in proximal and partial-thickness tears; however, additional study is warranted. UCL reconstruction has been the benchmark for tears not amendable to nonsurgical treatment, with flexor-pronator complex preservation being important. UCL repair has historically been most commonly used in partial avulsions, but indications have yet to be completely well defined. Knowledge regarding appropriate UCL treatment continues to evolve with patient-specific treatment being essential.

Anatomic Study of the Medial Collateral Ligament in Thai Population: A Cadaveric Study of 56 Elbows

PURPOSE

This study aims to elucidate basic anatomic and geometric features of MCL, providing more accurate and detailed information, as guidance for surgeons, to improve patient's outcome of the treatment.

METHODS

The anterior bundle (AB), posterior bundle (PB) and transverse bundle (TB) ligament of 56 fresh frozen Thai cadaveric elbows, were measured and recorded, comprise key ligament's geometric features, footprints and dimensions, and its relation to bony landmarks. Sagittal and coronal planes were used in respect of the anatomical position.

RESULTS

The mean distance between the center of AB origin and the apex of medial epicondyle is as follows: 2.97 ± 2.21 mm anteriorly, 4.73 ± 1.60 mm inferiorly in the sagittal plane, and 4.23 ± 1.13 mm deep from the epicondyle in the coronal plane. Its dimension is 6.23 ± 1.02 mm in width and 45.97 ± 6.75 mm in length. The ligament's insertion triangular shape has its base located 28.44 ± 3.51 mm anterior from the posterior olecranon border, and 22.52 ± 2.49 mm superior from the inferior ulnar border. The tip located 50.79 ± 4.86 mm anterior from the posterior olecranon border and 17.64 ± 2.80 mm superior from the inferior ulnar border.

CONCLUSION

Apprehension of the precise geometries and distances of the ligament's footprint relative to key anatomical point is crucial. This stereographically comprehended data are useful for surgeon as reference points to obtain stability, motion, kinetic, and kinematic properties of the elbow.

LEVEL OF EVIDENCE

Level V evidence.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43465-022-00648-x.

Biomechanical Comparison of Anatomic Restoration of the Ulnar Footprint vs Traditional Ulnar Tunnels in Ulnar Collateral Ligament Reconstruction

BACKGROUND

Current techniques for ulnar collateral ligament (UCL) reconstruction do not reproduce the anatomic ulnar footprint of the UCL. The purpose of this study was to describe a novel UCL reconstruction technique that utilizes proximal-to-distal ulnar bone tunnels to better re-create the anatomy of the UCL and to compare the biomechanical profile at time zero among this technique, the native UCL, and the traditional docking technique.

HYPOTHESIS

The biomechanical profile of the anatomic technique is similar to the native UCL and traditional docking technique.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten matched cadaveric elbows were potted with the forearm in neutral rotation. The palmaris longus tendon graft was harvested, and bones were sectioned 14 cm proximal and distal to the elbow joint. Specimen testing included (1) native UCL testing performed at 90° of flexion with 0.5 N·m of valgus moment preload, (2) cyclic loading from 0.5 to 5 N·m of valgus moment for 1000 cycles at 1 Hz, and (3) load to failure at 0.2 mm/s. Elbows then underwent UCL reconstruction with 1 elbow of each pair receiving the classic docking technique using either anatomic (proximal to distal) or traditional (anterior to posterior) tunnel locations. Specimen testing was then repeated as described.

RESULTS

There were no differences in maximum load at failure between the anatomic and traditional tunnel location techniques (mean ± SD, 34.90 ± 10.65 vs 37.28 ± 14.26 N·m; P = .644) or when including the native UCL (45.83 ± 17.03 N·m; P = .099). Additionally, there were no differences in valgus angle after 1000 cycles across the anatomic technique (4.58°± 1.47°), traditional technique (4.08°± 1.28°), and native UCL (4.07°± 1.99°). The anatomic group and the native UCL had similar valgus angles at failure (24.13°± 5.86° vs 20.13°± 5.70°; P = .083), while the traditional group had a higher valgus angle at failure when compared with the native UCL (24.88°± 6.18° vs 19.44°± 5.86°; P = .015).

CONCLUSION

In this cadaveric model, UCL reconstruction with the docking technique utilizing proximal-to-distal ulnar tunnels better restored the ulnar footprint while providing valgus stability comparable with reconstruction with the docking technique using traditional anterior-to-posterior ulnar tunnel locations. These results suggest that utilization of the anatomic tunnel location in UCL reconstruction has similar biomechanical properties to the traditional method at the time of initial fixation (ie, not accounting for healing after reconstruction in vivo) while keeping the ulnar tunnels farther from the ulnar nerve. Further studies are warranted to determine if an anatomically based UCL reconstruction results in differing outcomes than traditional reconstruction techniques.

CLINICAL RELEVANCE

Current UCL reconstruction techniques do not accurately re-create the ulnar UCL footprint. The UCL is a dynamic constraint to valgus loads at the elbow, and a more anatomic reconstruction may afford more natural joint kinematics. This more anatomic technique performs similarly to the traditional docking technique at time zero, and the results of this study may offer a starting point for future in vivo studies.

Biomechanical Evaluation of a Low-Invasive Elbow Medial Collateral Ligament Reconstruction Technique With Fascia and Tendon Patches

Background: Injury to the medial collateral ligament (MCL) of the elbow has become increasingly common in sports, and the elbow is prone to contracture and ossification in trauma. Effective reconstruction of the MCL with reduction of irritation to the elbow has rarely been reported. This study introduces a minimally invasive elbow MCL reconstruction technique and evaluates the valgus stability.

Methods: Eight fresh-frozen elbow specimens underwent reconstruction of the anterior bundle of the MCL (AMCL) first with the flexor carpi ulnaris fascia patches, followed by reconstruction of the posterior bundle of the MCL (PMCL) with the triceps tendon patches. The valgus angles of each specimen were examined in three stages as follows: intact MCL, reconstruction of the AMCL alone, and reconstruction of the MCL (including AMCL and PMCL). Finally, specimens were loaded to failure, and failure modes were recorded.

Results: AMCL reconstruction alone had similar valgus stability at all testing angles (p = 0.080, 30° flexion; p = 0.064, 60° flexion; p = 0.151, 90° flexion; p = 0.283, 120° flexion) compared with the intact MCL, as did MCL reconstruction (p = 0.951, 30° flexion; p = 0.739, 60° flexion; p = 0.841, 90° flexion; p = 0.538, 120° flexion). More importantly, a significant difference existed between the MCL reconstruction and the AMCL reconstruction alone at 30° flexion (p = 0.043) and 60° flexion (p = 0.013) but not at the 90° flexion (p = 0.369) and 120° flexion (p = 0.879). The mean maximum failure torque of MCL reconstruction was 24.02 Nm at 90° elbow flexion.

Conclusion: Both AMCL reconstruction alone and MCL reconstruction provided valgus stability comparable with the native MCL, and importantly, MCL reconstruction provided more valgus stability than AMCL reconstruction alone at 30° flexion and 60° flexion of the elbow. Therefore, the new MCL reconstruction technique might be a useful guide for the treatment of elbow MCL injuries or deficiencies.

Elbow Ulnar Collateral Ligament Injuries in Throwing Athletes: Diagnosis and Management

Ulnar collateral ligament (UCL) injuries of the elbow are common in overhead throwing athletes. With throwing, the elbow experiences substantial valgus stress and repetitive microtrauma can lead to injury. Increasing rates of injury among both youth and professional throwers has resulted in a "UCL epidemic." Ulnar collateral ligament reconstruction ("Tommy John Surgery") became a part of the public consciousness after Tommy John returned to professional baseball after a UCL reconstruction with Dr Frank Jobe for what was once considered a career-ending injury. Partial tears and some athletes with complete UCL injuries can be managed without surgery. Since the introduction of UCL reconstruction, technical modifications have aimed to decrease complications and increase return-to-play rates. Ulnar collateral ligament repair has reemerged as a potential surgical option for some throwers. Future prospective and comparative studies are necessary to better define the optimal operative treatment for these injuries.

Comparison of a Novel Anatomic Technique and the Docking Technique for Medial Ulnar Collateral Ligament Reconstruction

BACKGROUND

Current reconstruction techniques do not re-create the distal ulnar collateral ligament (UCL) insertion. Reconstructing the distal extension of the anterior band ulnar footprint may increase elbow stability and resistance against valgus stress after UCL reconstruction (UCLR).

PURPOSE/HYPOTHESIS

The purpose was to test a new technique for UCLR, a modification of the docking technique, aimed at re-creating the distal ulnar footprint anatomy of the anterior band. We hypothesize that this novel "anatomic" technique will provide greater resistance to valgus stress after UCLR when compared with the docking technique.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Eighteen unpaired cadaveric arms were dissected to capsuloligamentous elbow structures and potted. With use of a servohydraulic load frame, 5 Nċm of valgus stress was placed on the UCL-intact elbows at 30°, 60°, 90°, and 120° of flexion. UCLR was performed on each elbow, randomized to either the docking technique or the anatomic technique. After UCLR, the elbow was again tested at 30°, 60°, 90°, and 120° of flexion. Ulnohumeral joint gapping was calculated using a 3-dimensional motion capture system applied to markers attached to the ulna and humerus. Differences in gapping among the intact state and docking and anatomic techniques were compared using a 2-way analysis of variance with significance set to P < .05.

RESULTS

There was no significant difference in gapping between the anatomic and docking technique groups regardless of elbow flexion angle. All reconstructed groups showed increased gapping relative to intact, but all increases were below the clinically relevant level of 1 mm.

CONCLUSION

Ulnohumeral joint gapping and resistance to valgus stress were similar between the anatomic technique and the docking technique for UCLR.

CLINICAL RELEVANCE

This study provides evidence that the anatomic technique is a viable alternative UCLR method as compared with the docking technique in a cadaveric model.

The dynamic rotation axis of ulnohumeral joint during active flexion-extension: an in vivo 4-dimensional computed tomography analysis

Background

As the collateral ligament reconstruction becomes more common to perform, the knowledge between the collateral ligament reconstruction and the elbow rotation axis is still ambiguous. The purpose of this study was to investigate the location of the intersections between the elbow rotation axis and medial and lateral aspect of the humerus.

Methods

Four-dimensional computed tomography (4D CT) scan was designed to obtain the images from 8 participants. The instantaneous rotation axis was created according to the trochlea notch of the ulna in the Rapidform XO software. Then the intersections between the instantaneous rotation axis and the medial and lateral aspect of the humerus were identified in the Geomagic Wrap software. Landmark coordinate systems of the distal humerus was created.

Result

The intersections in the medial aspect of the humerus were mostly located in the superior and posterior quadrant and showed the trend from anterior-superior to posterior-superior with the increment of the elbow flexion. The intersections in the lateral aspect of the humerus were mostly located in the middle half of the anterior quadrant and showed the trend from posterior-inferior to anterior-superior with the increment of the elbow flexion.

Conclusion

There’s no isometric point for medial collateral ligament (MCL) and lateral ulnar collateral ligament (LUCL) reconstruction. The isometric area for MCL reconstruction should be considered at the superior and posterior quadrant of the medial aspect of the humerus. The isometric area for LUCL reconstruction should be considered at the middle half of the anterior quadrant of the lateral aspect of the humerus.

Trial registration

This work was supported by the National Natural Science Foundation of China [No.81911540488] in 07/01/2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05102-5.

Acute Ligament Injuries of the Elbow

Ulnar collateral, radial collateral, lateral ulnar collateral, and annular ligaments can be injured in an acute trauma, such as valgus stress in athletes and elbow dislocation. Recognizing normal anatomy in magnetic resonance imaging and ultrasonography studies is important to identify ligamentous abnormalities in these imaging modalities.

Elbow valgus stability of the transverse bundle of the ulnar collateral ligament

Background

The purpose of this study was to clarify elbow valgus stability of the transverse bundle (TB). We hypothesized that the transverse bundle is involved in elbow valgus stability.

Methods

Twelve elbows of six Japanese Thiel-embalmed cadavers were evaluated. The skin, subcutaneous tissue and origin of forearm flexors were removed from about 5 cm proximal to the elbow to about 5 cm distal to the elbow, and the ulnar collateral ligament was dissected (intact state). The cut state was defined as the state when the TB was cut in the middle. The joint space of the humeroulnar joint (JS) was measured in the intact state and then in the cut state. With the elbow flexed to 30°, elbow valgus stress was gradually increased to 30, 60 N using the Telos Stress Device, and the JS was measured by ultrasonography under each load condition. Paired t-testing was performed to compare the JS between the intact and cut states under each load.

Results

No significant difference in JS was identified between the intact and cut state at start limb position. The JS was significantly higher in the cut state than in the intact state at both 30 N and 60 N.

Conclusion

The findings from this study suggested that the TB may be involved in elbow valgus stability.

Imaging of Elbow Injuries

Familiarity with throwing mechanics during elbow range of motion allows accurate diagnosis of sports-related elbow injuries, which occur in predictable patterns. In addition, repetitive stress-related injuries are often clinically apparent; however, imaging plays an important role in determining severity as well as associated injuries that may affect clinical management. A detailed understanding of elbow imaging regarding anatomy and mechanism of injury results in prompt and precise treatment.

Ulnar Collateral Ligament Repair of the Elbow-Biomechanics, Indications, and Outcomes

PURPOSE OF REVIEW

Traditionally medial elbow injuries in overhead athletes have been treated with ulnar collateral ligament (UCL) reconstruction as first described by Dr. Frank Jobe. Recent literature has shown favorable outcomes in select patients treated with UCL repair. Newer techniques utilizing suture augmentation demonstrate biomechanical profiles as good or better than the native state and/or reconstruction. This review aims to evaluate these biomechanical studies and the clinical outcomes of ulnar collateral ligament repair with suture augmentation.

RECENT FINDINGS

UCL repair has favorable outcomes in select patients with specific tear type patterns. Clinical outcomes have shown return to play rates of 92-97% with mean time of 2.5-6 months post-operatively. Biomechanical data comparing UCL repair to reconstruction techniques have shown improved resistance to common forces applied to the elbow during overhead activities. Additionally, suture tape augmentation dramatically improves stability of ligament repair without over-constraining the elbow. Initial ulnar collateral ligament repair data was poor, and thus UCL reconstruction became the mainstay of treatment for overhead athletes. Recent studies evaluating the biomechanical properties as well as clinical outcomes have demonstrated favorable data when UCL repair is performed. When considering the drawbacks of a prolonged recovery associated with reconstruction, UCL repair is a viable option in select patients.

Investigation of site and frequency of asymptomatic injury in medial structures of the elbow in adolescent baseball players using dedicated magnetic resonance imaging

PURPOSE

Medial epicondyle (ME) and elbow joint proximal (UCL-p) and distal ulnar collateral ligament (UCL-d) asymptomatic injuries are frequently observed using magnetic resonance imaging (MRI). However, the injury rates vary among these structures in elbow screening of adolescent baseball players, despite being adjacent medial structures of the elbow. This study aimed to retrospectively determine the actual injury site and rate, and investigate the underlying reason for discrepancies anatomically and biomechanically.

MATERIALS AND METHODS

Forty-four male adolescent baseball players were scanned using MRI. Two interpreters independently and retrospectively assessed the ME, UCL-p, and UCL-d injuries using the gradient echo axial, sagittal, and coronal planes.

RESULTS

The injury prevalence was significantly higher in the ME and UCL-p (> 50% of the participants) than in the UCL-d (22.7%), P < 0.01 and P < 0.01, respectively. Additionally, there was a tendency toward a high-frequency injury rate of the ME or UCL-p.

CONCLUSION

The injury site of the medial structures tended to be proximal. The ME and UCL-p were observed to be more frequently injured compared to the UCL-d in adolescent baseball players according to the dedicated MRI findings in this study.

Morphological Features of the Ulnar Collateral Ligament of the Elbow and Common Tendon of Flexor-Pronator Muscles

Background:

The anterior bundle (AB) of the ulnar collateral ligament is the most important structure for valgus stabilization of the elbow. However, anatomic relationships among the AB, posterior bundle (PB) of the ulnar collateral ligament, and common tendon (CT) of the flexor-pronator muscles have not been fully clarified.

Purpose:

To classify the AB, PB, and CT and to clarify their morphological features.

Study Design:

Descriptive laboratory study.

Methods:

This investigation examined 56 arms from 31 embalmed Japanese cadavers. The CT investigation examined 34 arms from 23 embalmed Japanese cadavers with CTs remaining. Type classification was performed by focusing on positional relationships with surrounding structures. Morphological features measured were length, width, thickness, and footprint for the AB and PB and attachment length, thickness, and footprint for the CT.

Results:

The AB was classified as type I (44 elbows; 78.6%), can be separated as a single bundle, or type II (12 elbows; 21.4%), cannot be separated from the PB and joint capsule. The PB was classified as type I (28 elbows; 50.0%), can be separated as a single bundle; type IIa (6 elbows; 10.7%), posterior edge cannot be separated; type IIb (7 elbows; 12.5%), anterior edge cannot be separated; or type III (15 elbows; 26.8%), cannot be separated from the joint capsule. The CT was classified as type I (18 elbows; 52.9%), can be separated from the AB, or type II (16 elbows; 47.1%), cannot be separated from the AB. Significant differences in frequencies of AB, PB, and CT types were identified between men and women. Morphological features were measured only for type I of each structure, and reliability was almost perfect.

Conclusion:

These results suggest that the AB, PB, and CT each can be classified into an independent form and an unclear form. Presence of the unclear form was suggested as one factor contributing to morphological variation.

Clinical Relevance:

This study may provide basic information for clarifying functional roles of the AB, PB, and CT.

Ulnar Collateral Ligament Tear Location May Affect Return-to-Sports Rate but Not Performance Upon Return to Sports After Ulnar Collateral Ligament Reconstruction Surgery in Professional Baseball Players

BACKGROUND

The number of ulnar collateral ligament (UCL) tears in professional baseball players is increasing. UCL reconstruction (UCLR) is the treatment of choice in players with failed nonoperative treatment who wish to return to sports (RTS). It is unknown if UCL tear location influences the ability of players to RTS or affects their performance upon RTS.

PURPOSE/HYPOTHESIS

The purpose was to compare the RTS rate and performance upon RTS in professional baseball players who underwent UCLR based on UCL tear location (proximal vs distal). It was hypothesized that no difference in RTS rate or performance upon RTS will exist between players with proximal or distal UCL tears.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All professional baseball players who underwent primary UCLR by a single surgeon between 2016 and 2018 were eligible for inclusion. Players with purely midsubstance tears or revision UCLR were excluded. Tear location was determined based on preoperative magnetic resonance imaging (MRI) and intraoperative findings. RTS rate and performance were compared between players with proximal versus distal UCL tears.

RESULTS

Overall, 25 pitchers (15 proximal and 10 distal tears) and 5 position players (2 proximal and 3 distal) underwent primary UCLR between 2016 and 2018. Of the 25 pitchers, 84% were able to RTS. Of the 5 position players, 80% were able to RTS. Among the total cohort of pitchers and position players, 12 out of 17 (71%) players with proximal tears were able to RTS, while of the 13 distal tears, 13 out of 13 (100%) players were able to RTS (P = .05). With regard to performance data, pitchers with distal tears had higher utilization postoperatively and, as such, allowed statistically more hits (P = .03), runs (P = .015), and walks (P = .021) postoperatively. However, the WHIP ([walks + hits]/innings pitched) was not different between players with proximal or distal tears, indicating that efficacy in games was not significantly different between groups.

CONCLUSION

Professional baseball players who sustain a distal UCL tear and undergo UCLR may be more likely to RTS than those who sustain a proximal UCL tear and undergo UCLR. Players with distal UCL tears who underwent UCLR saw higher utilization postoperatively than those with proximal UCL tears. Further work is needed in this area to confirm this result.

Magnetic resonance imaging of the elbow

Elbow pain can cause disability, especially in athletes, and is a common clinical complaint for both the general practitioner and the orthopaedic surgeon. Magnetic resonance imaging (MRI) is an excellent tool for the evaluation of joint pathology due to its high sensitivity as a result of high contrast resolution for soft tissues. This article aims to describe the normal imaging anatomy and biomechanics of the elbow, the most commonly used MRI protocols and techniques, and common MRI findings related to tendinopathy, ligamentous and osteochondral injuries, and instability of the elbow.

The History and Evolution of Elbow Medial Ulnar Collateral Ligament Reconstruction: from Tommy John to 2020

PURPOSE OF REVIEW

The purpose of this review article is to discuss the evolution of surgical reconstruction of the anterior bundle of the UCL, otherwise known as Tommy John surgery, from Dr. Jobe's initial description in 1986 to present day. In particular, the unique changes brought forth by each new surgical technique, and the reasons that these changes were implemented, are highlighted.

RECENT FINDINGS

The incidence of UCL reconstruction surgery continues to increase significantly, particularly in the 15- to 19-year-old age group. New anatomic understanding of the anterior bundle of the UCL, including the importance of the central fibers and the broad and tapered ulnar insertion, may affect optimal UCL reconstruction techniques in the future. Although return to play rates are generally quite high (80-95%), the mean time to return to play (typically 12-18 months for pitchers) is longer than desired. Accordingly, many authors feel that there remains room for improvement in the treatment of this common injury. The Tommy John surgery has evolved in many ways with the development of novel techniques over the last 35 years. Currently, overhead throwing athletes undergoing UCL reconstruction have high return to play and low complication rates. Future modifications to the surgery may aim to further improve outcomes and, more importantly, expedite the length of postoperative rehabilitation.

State of the Union on Ulnar Collateral Ligament Reconstruction in 2020: Indications, Techniques, and Outcomes

PURPOSE OF REVIEW

There has been a marked increase in the number of ulnar collateral ligament reconstructions performed annually and an associated increase in the amount of recent literature published. It is paramount that surgeons remain up to date on the current literature, as modern indications and surgical techniques continue to improve clinical outcomes.

RECENT FINDINGS

Our understanding of ulnar collateral ligament (UCL) injuries, treatment indications, and surgical techniques for UCL reconstruction continues to evolve. Despite the rapidly increasing amount of published literature on the topic, a clear and concise surgical algorithm is lacking. Studies have suggested a trend towards improved clinical outcomes and decreased complications with various modifications in UCL reconstruction techniques. Current sport-specific outcome studies have reported conflicting results regarding the effect of UCL reconstruction on an athlete's performance upon returning to sport. With the rising incidence of UCL reconstruction and growing media attention, UCL injuries, reconstruction techniques, and return to sport following UCL surgery are timely topics of interest to clinicians and overhead throwing athletes. Several technique modifications have been reported, and these modifications may lead to improved outcomes and lower complication rates. Studies assessing sport-specific outcome measures will be necessary to provide a more critical and informative analysis of outcomes following UCL reconstruction.

Comprehensive Update of Elbow Magnetic Resonance Imaging

We present a comprehensive update of elbow magnetic resonance imaging, detailing the complex anatomy and pathology of the elbow. A variety of pathologies may affect the elbow joint, and many of the symptoms overlap. As such, magnetic resonance imaging of the elbow serves as an invaluable clinical tool for the clinician in the diagnosis and management of patients presenting with elbow pain.

Clinical Value of an Acute Popping Sensation in Throwing Athletes With Medial Elbow Pain for Ulnar Collateral Ligament Injury

Background:

Throwing athletes sustaining an ulnar collateral ligament (UCL) injury may recall a popping sensation originating from the medial elbow at the time of injury. There are no studies available that inform clinicians how to utilize this salient anamnestic information and what amount of diagnostic weight to afford to it.

Purpose:

To assess the diagnostic value of a popping sensation for significant UCL injury in throwing athletes who sustained an injury causing medial elbow pain.

Study Design:

Cohort study (prognosis); Level of evidence, 3.

Methods:

A total of 207 consecutive patients with throwing-related medial elbow pain were evaluated for UCL injury by the senior author between 2011 and 2016. The presence or absence of a popping sensation was routinely reported by the senior author. Magnetic resonance imaging was evaluated for UCL injury severity and classified into intact, edema/low-grade partial-, high-grade partial-, and full-thickness tears.

Results:

The overall frequency of a pop was 26%. The proportion of patients who reported a pop significantly increased with UCL tear severity (P < .001), from 13% in patients with low-grade UCL injuries to 26% in patients with high-grade partial-thickness tears and 51% in patients with full-thickness tears. The positive likelihood ratio, negative likelihood ratio, and odds ratio of a popping sensation for significant UCL injury were 3.2, 0.7, and 4.4 (P < .001), respectively (P < .001). A pop was not associated with either distal or proximal UCL tears (P ≥ .999).

Conclusion:

A popping sensation at the time of injury in throwing athletes with medial elbow pain was associated with UCL injury severity. When a throwing athlete reports a pop, this should moderately increase a clinician’s suspicion for a significant UCL injury. Conversely, absence of a pop should not substantially decrease suspicion for significant UCL injury. The findings of this study allow for the clinical interpretation of the salient anamnestic finding of a pop at the time of injury, which can be used for diagnostic purposes as well as patient counseling. This study provides reference foundation for future studies of predictive and diagnostic factors for UCL injury in throwing athletes.

Review of Anatomy of the Medial Ulnar Collateral Ligament Complex of the Elbow

PURPOSE OF REVIEW

The importance of both the static and dynamic stabilizers of the medial elbow for the throwing athlete has been demonstrated in recent studies. Furthermore, recent anatomic studies have demonstrated the insertion of the anterior bundle (UCL) to be more distal and elongated, which has implications for surgical reconstruction of the UCL. The purpose of this review is to highlight recent anatomic and biomechanical studies evaluating the anatomy and reconstructions of the medial elbow.

RECENT FINDINGS

Recent literature has highlighted the crucial role of the dynamic stabilizers in resisting valgus force, especially during the throwing motion. The dynamic stabilizers of the medial elbow include the flexor pronator mass, specifically the flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS). The clinical importance of these findings cannot be under stated, as unrecognized dynamic stabilizer injury can lead to increased stress on a native or reconstructed UCL in the throwing athlete. The medial ulnar collateral ligament complex of the elbow has a crucial role in providing both static and dynamic elbow stability. Most notably, the anterior bundle (UCL) provides the primary resistance to valgus and rotational stresses, especially during throwing motion. An understanding of the humeral and ulnar footprints and their relationships with surrounding structures is necessary to restore the native isometry of the medial complex of the elbow during UCL reconstruction. The flexor pronator musculature plays an essential role in dynamic stability, and the intimate relationship of the FCU and FDS with the ulnar insertion of the UCL should be considered to optimize recovery and outcomes with repair or reconstruction.

Anatomic and Biomechanical Evaluation of Ulnar Tunnel Position in Medial Ulnar Collateral Ligament Reconstruction

BACKGROUND

Although numerous techniques of reconstruction of the medial ulnar collateral ligament (mUCL) have been described, limited evidence exists on the biomechanical implication of changing the ulnar tunnel position despite the fact that more recent literature has clarified that the ulnar footprint extends more distally than was appreciated in the past.

PURPOSE

To evaluate the size and location of the native ulnar footprint and assess valgus stability of the medial elbow after UCL reconstruction at 3 ulnar tunnel locations.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eighteen fresh-frozen cadaveric elbows were dissected to expose the mUCL. The anatomic footprint of the ulnar attachment of the mUCL was measured with a digitizing probe. The area of the ulnar footprint and midpoint relative to the joint line were determined. Medial elbow stability was tested with the mUCL in an intact, deficient, and reconstructed state after the docking technique, with ulnar tunnels placed at 5, 10, or 15 mm from the ulnotrochlear joint line. A 3-N·m valgus torque was applied to the elbow, and valgus rotation of the ulna was recorded via motion-tracking cameras as the elbow was cycled through a full range of motion. After kinematic testing, specimens were loaded to failure at 70° of elbow flexion.

RESULTS

The mean ± SD length of the mUCL ulnar footprint was 27.4 ± 3.3 mm. The midpoint of the anatomic footprint was located between the 10- and 15-mm tunnels across all specimens at a mean 13.6 mm from the joint line. Sectioning of the mUCL increased elbow valgus rotation throughout all flexion angles and was statistically significant from 30° to 100° of flexion as compared with the intact elbow (P < .05). mUCL reconstruction at all 3 tunnel locations restored stability to near intact levels with no significant differences among the 3 ulnar tunnel locations at any flexion angle.

CONCLUSION

Positioning the ulnar graft fixation site up to 15 mm from the ulnotrochlear joint line does not significantly increase valgus rotation in the elbow.

CLINICAL RELEVANCE

A more distal ulnar tunnel may be a viable option to accommodate individual variation in morphology of the proximal ulna or in a revision setting.

Establishing Safe Extra-articular Parameters for Cortical Button Distal Fixation During Ulnar Collateral Ligament Reconstruction

BACKGROUND

A variety of methods exist for fixation during ulnar collateral ligament (UCL) reconstruction on the ulna for the overhead throwing athlete. Current biomechanical evidence suggests that cortical button fixation may fail at a higher load and under more cycles than interference screw fixation alone, while also minimizing the risk of fracture. A safe angle for placement of this cortical button has not yet been determined.

PURPOSE

To define a safe angle for cortical button deployment during UCL reconstruction to avoid violation of the proximal radioulnar joint (PRUJ).

STUDY DESIGN

Descriptive laboratory study.

METHODS

Measurements on 100 cadaveric ulna bones, 50 women and 50 men, were obtained referencing the entry point for ulnar fixation, which is 1 cm distal to the ulnar humeral joint line along the medial UCL ridge. Ulnar width at the entry point and distance to the PRUJ were obtained to calculate safe distal angulation, while distance from the entry point to the posterior ulnar crest ulnarly and distance from the PRUJ to the posterior ulnar crest radially were obtained to calculate safe posterior angulation. Ten bony measurements on the same group of specimens were performed by 3 authors to establish an interobserver reliability. Means, quartiles, and outliers were obtained for the calculated angles. Finally, recommended angles of entry were determined to be approximately 1 interquartile range above the upper limit.

RESULTS

The mean distal angle of entry that was obtained was 11.32° (SD, ±4.80°; 95% CI, 10.37°-12.27°; P < .001). Three upper limit outliers were discovered: 24.20°, 23.4°, and 21.1°. The mean posterior angle of entry was 40.44° (SD, ±6.18°; 95% CI, 39.22°-41.67°; P < .001). There were no outliers for the posterior angle of entry. Interobserver reliabilities were strong for the 4 measurements.

CONCLUSION

To be safely outside of the PRUJ utilizing a cortical button construct, we recommend 30° distal angulation and 60° posterior angulation for ulnar fixation during UCL reconstruction. Both parameters are 1 quartile above the highest calculated angle of entry.

CLINICAL RELEVANCE

These data define safe parameters for distal fixation during UCL reconstruction and highlight a clear entry point for reference.

The pathoanatomy of the anterior bundle of the medial ulnar collateral ligament

BACKGROUND

The purpose of this study was to increase our understanding of the pathoanatomy of the ulnar collateral ligament (UCL) by performing a descriptive analysis of the surgical inspection of the anterior bundle in patients undergoing reconstruction.

METHODS

A single-surgeon series of 163 patients who underwent UCL reconstruction between 2009 and 2017 was retrospectively analyzed. Descriptions of the pathoanatomy of injury were obtained from the operative reports. Magnetic resonance imaging data were reviewed to assess whether the presence and location of tissue disruptions were accurately recognized. Demographic and clinical characteristics were obtained from medical records and correlated to observed pathoanatomy.

RESULTS

Injuries to the anterior bundle were characterized by a single tissue disruption (65%), tissue disruptions at more than 1 location (23%), or injuries without distinct fiber tissue disruptions (12%). The presence and location of tissue disruptions matched magnetic resonance imaging findings in 124 of 153 patients (81%). Partial tears more frequently affected the anterior band of the anterior bundle distally as opposed to the posterior band of the anterior bundle proximally (P = .012). Patients with single tissue disruptions more frequently reported a popping sensation than patients with non-tear insufficiency (P = .030).

CONCLUSIONS

This study shows the heterogeneity of anterior bundle injuries in patients undergoing UCL reconstruction. A variety of injury configurations and chronic attritional damage to the anterior bundle were observed, as well as distinct tear patterns at the distal and proximal attachment sites. Future research may elucidate the diagnostic value of a pop sign for UCL injury.

Reconstruction of the Medial Ulnar Collateral Ligament of the Elbow: Biomechanical Comparison of a Novel Anatomic Technique to the Docking Technique

Background:

In recent years, understanding of the anatomy of the ulnar collateral ligament (UCL) has evolved, demonstrating that the insertional footprint of the UCL on the ulna is more elongated and distally tapered than previously described. Current UCL reconstruction configurations do not typically re-create this native anatomy, which may represent a potential area for improvement.

Purpose/Hypothesis:

The purposes of this study were (1) to describe a novel anatomic UCL reconstruction technique designed to better replicate the native UCL anatomy and (2) to biomechanically compare this with the docking technique. The hypothesis was that the ultimate load to failure for the anatomic technique would not be inferior to the docking technique.

Study Design:

Controlled laboratory study.

Methods:

A total of 16 fresh-frozen cadaveric upper extremities (8 matched pairs) were utilized. One elbow in each pair was randomized to receive UCL reconstruction via the docking technique or the novel anatomic UCL reconstruction technique with palmaris tendon autograft. Following reconstruction, biomechanical testing was performed by applying valgus rotational torque at a constant rate of 5 deg/s until ultimate mechanical failure of the construct occurred. Maximal torque (N·m), rotation stiffness (N·m/deg), and mode/location of failure were recorded for each specimen.

Results:

The mean ultimate load to failure for elbows in the docking technique group was 23.8 ± 6.1 N·m, as compared with 31.9 ± 8.4 N·m in the anatomic technique group (P = .045). Mean rotational stiffness was 1.9 ± 0.7 versus 2.3 ± 0.9 N·m/deg for the docking and anatomic groups, respectively (P = .338). The most common mode of failure was suture pullout from the graft, which occurred in all 8 (100%) docking technique specimens and 7 of 8 (88%) specimens that underwent the anatomic UCL reconstruction technique.

Conclusion:

Ultimately, the anatomic UCL reconstruction technique demonstrated superior strength and resistance to valgus torque when compared with the docking technique, and this was comparable with that of the native UCL from prior studies. Increased initial strength may allow for earlier initiation of throwing postoperatively and potentially shorten return-to-play times.

Clinical Relevance:

Current UCL reconstruction techniques do not accurately reproduce the UCL insertional anatomy on the ulna. The novel anatomic technique described may result in more natural joint kinematics. This study demonstrated load-to-failure rates that are significantly higher than with the docking technique and consistent with the native ligament, as reported from previous studies. These findings may serve as a foundation for future clinical study and optimization of this technique.

Approach to Medial Elbow Pain in the Throwing Athlete

PURPOSE OF REVIEW

Injury to the ulnar collateral ligament is the most common, significant injury affecting the medial elbow of the overhead athlete. However, there are many other significant sources of pathology that should be considered. This review seeks to present a broad range of conditions that providers should consider when evaluating the overhead athlete with medial elbow pain.

RECENT FINDINGS

Recent biomechanical studies have deepened understanding of the anatomy and function of the anterior bundle of the ulnar collateral ligament germane to the overhead athlete. Orthobiologics hold potential for expanding the role of non-operative treatment for ulnar collateral ligament injuries. In addition to injury to the ulnar collateral ligament, providers should be prepared to diagnose and treat valgus extension overload, proximal olecranon stress fracture, ulnar nerve pathology, common flexor - pronator mass injury, and, in adolescents, medial epicondylar avulsion, when managing medial elbow pain in the overhead athlete.

The Middle and Distal Aspects of the Ulnar Footprint of the Medial Ulnar Collateral Ligament of the Elbow Do Not Provide Significant Resistance to Valgus Stress: A Biomechanical Study

Background

The medial ulnar collateral ligament (UCL) insertion of the elbow has been shown to extend distally beyond the sublime tubercle. The contribution to valgus stability of the distal aspect of the footprint is unknown.

Purpose/Hypothesis

The purpose of this study was to determine the contribution of each part of the UCL footprint to the elbow valgus stability provided by the UCL. It was hypothesized that the distal two-thirds of the ulnar UCL footprint would not contribute significantly to valgus stability provided by the UCL.

Study Design

Descriptive laboratory study.

Methods

Fifteen cadaveric arms were dissected to the capsuloligamentous elbow structures and potted. A servohydraulic load frame was used to place 5 N·m of valgus stress on the intact elbow at 30°, 60°, 90°, and 120° of flexion. The UCL insertional footprint was measured and divided into thirds (proximal, middle, and distal). One-third of the UCL footprint was elevated off the bone (leaving the ligament in continuity), and the elbow was retested at the same degrees of flexion. This was repeated until the entire UCL footprint on the ulna was sectioned. Each elbow was randomized for how the UCL would be sectioned (sectioning the proximal, then middle, and then distal third or sectioning the distal, then middle, and then proximal third). Ulnohumeral joint gapping (millimeters) was recorded with a 3-dimensional motion capture system using physical and virtual markers. Two-group comparisons were made between each sectioned status versus the intact condition for each flexion angle.

Results

When the UCL was sectioned from distal to proximal, none of the ligaments failed prior to complete sectioning. When the UCL was sectioned from proximal to distal, 3 of the 6 ligaments failed after sectioning of the proximal third, while 2 more failed after the proximal and middle thirds were sectioned. Of the specimens with the distal third of the ligament sectioned first, no significant differences were found between intact, distal third cut, and distal plus middle thirds cut at all flexion angles.

Conclusion

The middle and distal thirds of the insertional footprint of the UCL on the ulna did not significantly contribute to gap resistance at 5 N·m of valgus load. The proximal third of the footprint is the primary resistor of valgus load.

Clinical Relevance

This cadaveric biomechanical study demonstrated that the middle and distal thirds of the native UCL insertion onto the ulna did not significantly contribute to valgus resistance at the elbow. When a UCL reconstruction is performed, the proximal third of the UCL insertion may be the most clinically important portion of the ligament to reconstruct.

Mechanical Properties and Microstructural Collagen Alignment of the Ulnar Collateral Ligament During Dynamic Loading

BACKGROUND

The ulnar collateral ligament (UCL) microstructural organization and collagen fiber realignment in response to load are unknown.

PURPOSE/HYPOTHESIS

The purpose was to describe the real-time microstructural collagen changes in the anterior bundle (AB) and posterior bundle (PB) of the UCL with tensile load. It was hypothesized that the UCL AB is stronger and stiffer with more highly aligned collagen during loading when compared with the UCL PB.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The AB and PB from 34 fresh cadaveric specimens were longitudinally sectioned to allow uniform light passage for quantitative polarized light imaging. Specimens were secured to a tensile test machine and underwent cyclic preconditioning, a ramp-and-hold stress-relaxation test, and a quasi-static ramp to failure. A division-of-focal-plane polarization camera captured real-time pixelwise microstructural data of each sample during stress-relaxation and at the zero, transition, and linear points of the stress-strain curve. The SD of the angle of polarization determined the deviation of the average direction of collagen fibers in the tissue, while the average degree of linear polarization evaluated the strength of collagen alignment in those directions. Since the data were nonnormally distributed, the median ± interquartile range are presented.

RESULTS

The AB has larger elastic moduli than the PB ( P < .0001) in the toe region (median, 2.73 MPa [interquartile range, 1.1-5.6 MPa] vs 0.65 MPa [0.44-1.5 MPa]) and the linear region (13.77 MPa [4.8-40.7 MPa] vs 1.96 MPa [0.58-9.3 MPa]). The AB demonstrated larger stress values, stronger collagen alignment, and more uniform collagen organization during stress-relaxation. PB collagen fibers were more disorganized than the AB during the zero ( P = .046), transitional ( P = .011), and linear ( P = .007) regions of the stress-strain curve. Both UCL bundles exhibited very small changes in collagen alignment (SD of the angle of polarization) with load.

CONCLUSION

The AB of the UCL is stiffer and stronger, with more strongly aligned and more uniformly oriented collagen fibers, than the PB. The small changes in collagen alignment indicate that the UCL response to load is due more to its static collagen organization than to dynamic changes in collagen alignment.

CLINICAL RELEVANCE

The UCL collagen organization may explain its susceptibility to injury with repetitive valgus loads.

Biomechanical analysis of elbow medial ulnar collateral ligament tear location and its effect on rotational stability

BACKGROUND

Recent anatomic and clinical studies have shown that the location of the injury to the elbow ulnar collateral ligament (UCL) is an important variable in deciding on surgical intervention; however, no studies have evaluated these findings biomechanically.

METHODS

This study tested 16 intact elbow specimens. Valgus torques of 2.5 and 5 Nm were applied to the elbow at various flexion angles, and the resulting valgus angles were measured. The valgus angles were applied to the elbows in their intact states and again after partial and complete cuts were made on the proximal and distal insertions of the UCL. Resulting valgus torques were measured, and stiffness was calculated for each elbow flexion angle. Unpaired t tests were used to evaluate the effects of cut location and flexion angle on joint rotational stability and stiffness.

RESULTS

The posterior-distal insertion contributed the most to stability. At valgus angles generated from 2.5 Nm intact torques, the posterior-distal insertions contributed to 51% ± 26% (P < .03) intact rotational stability, and at valgus angles generated from 5 Nm intact torques, the posterior-distal insertions contributed to 41% ± 17% (P < .02) intact rotational stability. For overall stiffness, the posterior-distal insertions contributed to 31% ± 12% (P < .045) intact stiffness.

CONCLUSION

Overall, the posterior distal insertion of the UCL contributed most to rotational stability and stiffness of the medial elbow when subjected to valgus stress at 90° and 120° of elbow flexion. At higher elbow flexion angles, the posterior insertions contributed more to stability, whereas the anterior insertions had a greater effect at lower flexion angles.

Understanding the medial ulnar collateral ligament of the elbow: Review of native ligament anatomy and function

The medial ulnar collateral ligament complex of the elbow, which is comprised of the anterior bundle [AB, more formally referred to as the medial ulnar collateral ligament (MUCL)], posterior (PB), and transverse ligament, is commonly injured in overhead throwing athletes. Attenuation or rupture of the ligament results in valgus instability with variable clinical presentations. The AB or MUCL is the strongest component of the ligamentous complex and the primary restraint to valgus stress. It is also composed of two separate bands (anterior and posterior) that provide reciprocal function with the anterior band tight in extension, and the posterior band tight in flexion. In individuals who fail comprehensive non-operative treatment, surgical repair or reconstruction of the MUCL is commonly required to restore elbow function and stability. A comprehensive understanding of the anatomy and biomechanical properties of the MUCL is imperative to optimize reconstructive efforts, and to enhance clinical and radiographic outcomes. Our understanding of the native anatomy and biomechanics of the MUCL has evolved over time. The precise locations of the origin and insertion footprint centers guide surgeons in proper graft placement with relation to bony anatomic landmarks. In recent studies, the ulnar insertion of the MUCL is described as larger than previously thought, with the center of the footprint at varying distances relative to the ulnar ridge, joint line, or sublime tubercle. The purpose of this review is to consolidate and summarize the existing literature regarding the native anatomy, biomechanical, and clinical significance of the entire medial ulnar collateral ligament complex, including the MUCL (AB), PB, and transverse ligament.

Functional Classification of the Medial Ulnar Collateral Ligament: An In Vivo Kinematic Study With Computer-Aided Design

Background:

It has been widely accepted that the anterior and posterior bundles of the medial ulnar collateral ligament (MUCL) tighten at extension and flexion, respectively. However, this belief is based on anatomic data acquired from cadaveric studies. The advancement of 3-dimensional (3D) model technology has made possible the simulation of dynamic movement that includes each ligament bundle fiber to analyze its functional properties. To date, no study has analyzed ligament kinematics at the level of the fibers while also focusing on their functional properties.

Purpose:

To propose a new classification for functional properties of the MUCL based on its kinematic pattern.

Study Design:

Descriptive laboratory study.

Methods:

Five healthy elbow joints were scanned by use of computed tomography, and 3D models were rendered and translated into vertex points for further mathematical analysis. The humeral origin and ulnar insertion of the MUCL fiber groups were registered. Each vertex point on the origin side was randomly connected to the insertion side, with each pair of corresponding points defined as 1 ligament fiber. Lengths of all the fibers were measured at 1° increments of elbow range of motion (ROM). Ligament fibers were grouped according to their patterns. Mean coverage area for each group, expressed as the percentage of ligament fibers per group to the total number of fibers, was calculated.

Results:

Four major bundle groups were found based on fiber length properties. Kinematic simulation showed that each group had a different kinematic function throughout elbow ROM. Mean coverage area of groups 1, 2, 3, and 4 was 8% ± 4%, 10% ± 5%, 42% ± 6%, and 40% ± 8%, respectively. Each group acted as a dominant stabilizer in certain arcs of motion. Reciprocal activity was observed between groups 1 and 3 along with groups 2 and 4 to produce synergistic properties of maintaining elbow stability.

Conclusion:

Detailed analysis of fibers of the MUCL allows for further understanding of its kinematic function. This study provides MUCL group coverage area and kinematic function for each degree of motion arc, allowing selective reconstruction of the MUCL according to mechanism of injury.

Clinical Relevance:

Understanding the dominant functional fibers of the MUCL will benefit surgeons attempting MUCL reconstruction and will enhance further anatomic study.

Quantitative Anatomic Analysis of the Medial Ulnar Collateral Ligament Complex of the Elbow

Background

A more detailed assessment of the anatomy of the entire medial ulnar collateral ligament complex (MUCLC) is desired as the rate of medial elbow reconstruction surgery continues to rise.

Purpose

To quantify the anatomy of the MUCLC, including the anterior bundle (AB), posterior bundle (PB), and transverse ligament (TL).

Study Design

Descriptive laboratory study.

Methods

Ten unpaired, fresh-frozen cadaveric elbows underwent 3-dimensional (3D) digitization and computed tomography with 3D reconstruction. Ligament footprint areas and geometries, distances to key bony landmarks, and isometry were determined. A surgeon digitized the visual center of each footprint, and this location was compared with the geometric centroid calculated from the outline of the digitized footprint.

Results

The mean surface area of the AB was 324.2 mm², with an origin footprint of 32.3 mm² and an elongated insertional footprint of 187.6 mm² (length, 29.7 mm). The mean area of the PB was 116.6 mm² (origin, 25.9 mm²; insertion, 15.8 mm²), and the mean surface area of the TL was 134.5 mm² (origin, 21.2 mm²; insertion, 16.7 mm²). The geometric centroids of all footprints could be predicted within 0.8 to 1.3 mm, with the exception of the AB insertion centroid, which was 7.6 mm distal to the perceived center at the apex of the sublime tubercle. While the PB remained relatively isometric from 0° to 90° of flexion (P = .606), the AB lengthened by 2.2 mm (P < .001).

Conclusion

Contrary to several historical reports, the insertional footprint of the AB was larger, elongated, and tapered. The TL demonstrated a previously unrecognized expansive soft tissue insertion directly onto the AB, and additional analysis of the biomechanical contribution of this structure is needed.

Clinical Relevance

These findings may serve as a foundation for future study of the MUCLC and help refine current surgical reconstruction techniques.

Qualitative and Quantitative Analyses of the Dynamic and Static Stabilizers of the Medial Elbow: An Anatomic Study

BACKGROUND

The anterior bundle of the medial ulnar collateral ligament (UCL) and the forearm flexors provide primary static and dynamic stability to valgus stress of the elbow in overhead-throwing athletes. Quantitative anatomic relationships between the dynamic and static stabilizers have not been described.

PURPOSE

To perform qualitative and quantitative anatomic evaluations of the medial elbow-UCL complex with specific attention to pertinent osseous and soft tissue landmarks.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Ten nonpaired, fresh-frozen human cadaveric elbows (mean age, 54.1 years [range, 42-64 years]; all male) were utilized for this study. Quantitative analysis was performed with a 3-dimensional coordinate measuring device to quantify the location of pertinent bony landmarks and tendon and ligament footprints on the humerus, ulna, and radius.

RESULTS

The anterior bundle of the UCL attached 8.5 mm (95% CI, 6.9-10.0) distal and 7.8 mm (95% CI, 6.6-9.1) lateral to the medial epicondyle, 1.5 mm (95% CI, 0.5-2.5) distal to the sublime tubercle, and 7.3 mm (95% CI, 6.1-8.5) distal to the joint line on the ulna along the ulnar ridge. The flexor digitorum superficialis (FDS) ulnar tendinous insertion was closely related and interposed within the anterior bundle of the UCL, overlapping with 45.6% (95% CI, 38.1-53.6) of the length of the anterior bundle of the UCL. The flexor carpi ulnaris (FCU) attached 1.9 mm (95% CI, 0.8-2.9) posterior and 1.3 mm (95% CI, 0.6-3.2) proximal to the sublime tubercle and overlapped with 20.9% (95% CI, 7.2-34.5) of the area of the distal footprint of the anterior bundle of the UCL.

CONCLUSION

The anterior bundle of the UCL had consistent attachment points relative to the medial epicondyle and sublime tubercle. The ulnar limb of the FDS and FCU tendons demonstrated consistent insertions onto the ulnar attachment of the anterior bundle of the UCL. These anatomic relationships are important to consider when evaluating distal UCL tears both operatively and nonoperatively. Excessive stripping of the sublime tubercle should be avoided during UCL reconstruction to prevent violation of these tendinous attachments.

CLINICAL RELEVANCE

The findings of this study enhance the understanding of valgus restraint in throwing athletes and provide insight into the difference in nonoperative outcomes between proximal and distal tears of the UCL.

Anterior and posterior bands of the anterior bundle in the elbow ulnar collateral ligament: ultrasound anatomy

BACKGROUND

The anterior oblique bundle (AOL) of the ulnar collateral ligament (UCL) is composed of anterior and posterior bands. This study evaluated the anatomy of the anterior and posterior bands in the AOL of the UCL for their separate visualization with ultrasound (US).

METHODS

We dissected 18 cadaveric elbow joints and recorded the direction of each band from the lateral view to determine the proper position for the US transducer. To determine the proper inclination of the transducer, we measured the inclinations of each band at the proximal and distal insertions from the transverse view. A paired t test was used for comparisons between both bands. Values of P < .05 were considered statistically significant.

RESULTS

The mean angles of the directions in the anterior and posterior bands were 10° ± 4° and 24° ± 9°, respectively. At the medial epicondyle, the mean inclination angles of both bands were 61° ± 5° and 67° ± 5°, respectively. At the sublime tubercle, the mean inclination angles of both bands were 14° ± 7° and 44° ± 9°, respectively. The inclination angles at the proximal ulna and the directions in both bands were significantly different (P < .001).

CONCLUSIONS

This study shows that the directions of both bands and inclination angles of the bony attachments in both bands can assist with correct placement of the US transducer and allow for separate visualization of each band.

Medial Elbow Injuries in the Throwing Athlete

Medial elbow injuries in the throwing athlete are common and increasing in frequency. They occur due to repetitive supraphysiologic forces acting on the elbow during the overhead throw. Overuse and inadequate rest are salient risk factors for injury. Most athletes improve substantially with rest and nonoperative treatment, although some athletes may require surgical intervention to return to play. Because of advances in conservative and surgical treatments, outcomes after medial elbow injury have improved over time. Currently, most athletes are able to return to a high level of play after ulnar collateral ligament reconstruction and experience a low rate of complications.

Elbow Injuries in Adult Overhead Athletes

OBJECTIVE

The purpose of this article is to review common elbow injuries found in overhead athletes with focus on mechanism, clinical features, imaging appearance, and treatment options.

CONCLUSION

The overhead throwing motion subjects the elbow to a variety of complex forces, which places both osseous and soft-tissue structures at high risk for injury.

Ulnar Collateral Ligament Reconstruction: Anatomy, Indications, Techniques, and Outcomes

Context:

Ulnar collateral ligament (UCL) injuries lead to pain and loss of performance in the thrower’s elbow. Ulnar collateral ligament reconstruction (UCLR) is a reliable treatment option for the symptomatic, deficient UCL. Injury to the UCL usually occurs because of chronic accumulation of microtrauma, although acute ruptures occur and an acute-on-chronic presentation is also common.

Evidence Acquisition:

Computerized databases, references from pertinent articles, and research institutions were searched for all studies using the search terms ulnar collateral ligament from 1970 until 2015.

Study Design:

Clinical review.

Level of Evidence:

Level 5.

Results:

All studies reporting outcomes for UCLR are level 4. Most modern fixation methodologies appear to be biomechanically and clinically equivalent. Viable graft choices include ipsilateral palmaris longus tendon autograft, gracilis or semitendinosus autograft, and allograft. Clinical studies report excellent outcomes of UCLR for both recreational and elite level athletes with regard to return to sport and postoperative performance. Complications, although rare, include graft rerupture or attenuation, ulnar nerve symptoms, stiffness, pain, and/or weakness leading to decreased performance.

Conclusion:

Injuries to the UCL have become commonplace among pitchers. Nonoperative treatment should be attempted, but the limited studies have not shown promising results. Operative treatment can be performed with several techniques, with retrospective studies showing promising results. Complications include ulnar neuropathy as well as failure to return to sport. Detailed preoperative planning, meticulous surgical technique, and a comprehensive rehabilitation program are essential components to achieving a satisfactory result.

Elbow US: Anatomy, Variants, and Scanning Technique

As with other musculoskeletal joints, elbow ultrasonography (US) depends on the examination technique. Deep knowledge of the relevant anatomy, such as the bone surface anatomy, tendon orientation, nerves, and vessels, is crucial for diagnosis. It is important to be aware of the primary imaging pitfalls related to US technique (anisotropy) in the evaluation of deep tendons such as the distal biceps and peripheral nerves. In this article, US scanning technique for the elbow as well as the related anatomy, primary variants, and scanning pitfalls are described. In addition, an online video tutorial of elbow US describes a possible approach to elbow evaluation. Online supplemental material is available for this article.

Optimal Elbow Angle for Sonographic Visualization of the Ulnar Collateral Ligament

OBJECTIVE

To formally examine the sonographic appearance of the elbow ulnar collateral ligament (UCL) at 30° versus 70° of elbow flexion in asymptomatic baseball pitchers.

DESIGN

A prospective, cross-sectional design.

SETTING

Sports medicine clinic in a tertiary academic medical center.

PARTICIPANTS

Thirty asymptomatic adolescent baseball pitchers 13-18 years of age (mean 15.8 years), with at least 3 years of continuous pitching experience and no significant history of elbow pain or injury.

METHODS

Static sonographic images of the bilateral UCLs were obtained at 30° and 70° of elbow flexion by a single experienced examiner. Images were anonymized and randomized into a slide set. Three clinicians with different levels of ultrasound experience reviewed the static 30° and 70° images for each elbow and chose their preferred image based on UCL conspicuity. The clinicians reviewed a re-randomized slide set 1 week later. A different study co-investigator measured UCL cross-sectional area (CSA) on all images using ultrasound machine electronic calipers.

MAIN OUTCOME MEASURES

Preference for the sonographic conspicuity of the UCL at 30° versus 70° of elbow flexion, and UCL CSA at 30° versus 70° of flexion.

RESULTS

Each clinician demonstrated a significant preference for UCL images obtained at 70° of flexion when compared to those obtained at 30° (80.3% overall preference for 70°, P < .001). There was no statistically significant effect of clinician experience or arm dominance on image preference. The sonographically determined CSA of the UCLs were on average 1.4 mm(2) greater at 70° than at 30° of flexion (P < .001) when combining dominant and nondominant arms.

CONCLUSIONS

Static sonographic evaluation of the UCL at 70° of elbow flexion should be integrated into UCL imaging protocols. Furthermore, when performing sonographically guided procedures targeting the UCL, clinicians should consider positioning the elbow at >30° of flexion to optimize UCL conspicuity and CSA.

A sonographic technique to evaluate the anterior bundle of the ulnar collateral ligament of the elbow: imaging features and anatomic correlation

OBJECTIVES

The aim of this study was to test a sonographic technique used to view the anterior bundle of the ulnar collateral ligament (UCL), describe its sonographic characteristics in healthy volunteers, and verify these characteristics by determining interobserver variability and their correlations in cadavers.

METHODS

Sonographic studies of the anterior bundle of the UCL were performed on 48 elbows of asymptomatic healthy volunteers. The participants were examined by 3 experts, who identified the insertion sites of the anterior bundle and subjectively evaluated its echogenicity and echo texture. A sonographic examination of the anterior bundle of the UCL in a cadaveric elbow was performed, and the same aspects were evaluated.

RESULTS

In all cases, the anterior bundle of the UCL appeared as a triangular structure in the coronal plane and had a hyperechoic homogeneous echo texture in most of these cases. The cadaveric elbow had the same sonographic characteristics as the volunteers.

CONCLUSIONS

As shown by examining the interobserver variability and determining the correlation with cadaveric tissue, sonography proved to be a reliable tool for evaluating the normal aspects of the anterior bundle of the UCL.

Reliability and precision of stress sonography of the ulnar collateral ligament

OBJECTIVES

Musculoskeletal sonography has emerged as an additional diagnostic tool that can be used to assess medial elbow pain and laxity in overhead throwers. It provides a dynamic, rapid, and noninvasive modality in the evaluation of ligamentous structural integrity. Many studies have demonstrated the utility of dynamic sonography for medial elbow and ulnar collateral ligament (UCL) integrity. However, evaluating the reliabilityand precision of these measurements is critical if sonography is ultimately used as a clinical diagnostic tool. The purpose of this study was to evaluate the reliability and precision of stress sonography applied to the medial elbow.

METHODS

We conducted a cross-sectional study during the 2011 baseball off-season. Eighteen National Collegiate Athletic Association Division I pitchers were enrolled, and 36 elbows were studied. Using sonography, the medial elbow was assessed, and measurements of the UCL length and ulnohumeral joint gapping were performed twice under two conditions (unloaded and loaded) and bilaterally.

RESULTS

Intraclass correlation coefficients (0.72-0.94) and standard errors of measurements (0.3-0.9 mm) for UCL length and ulnohumeral joint gapping were good to excellent. Mean differences between unloaded and loaded conditions for the dominant arms were 1.3 mm (gapping; P < .001) and 1.4 mm (UCL length; P < .001).

CONCLUSIONS

Medial elbow stress sonography is a reliable and precise method for detecting changes in ulnohumeral joint gapping and UCL lengthening. Ultimately, this method may provide clinicians valuable information regarding the medial elbow's response to valgus loading and may help guide treatment options.

Effect of distal ulnar collateral ligament tear pattern on contact forces and valgus stability in the posteromedial compartment of the elbow

BACKGROUND

It is not known whether the pattern of ulnar collateral ligament (UCL) tear affects elbow biomechanics.

HYPOTHESIS

There will be a significant change in elbow biomechanics with 50% proximal but not 50% distal simulated rupture of the UCL.

STUDY DESIGN

Controlled laboratory study.

METHODS

Pressure sensors in the posteromedial elbow joint of 25 male cadaveric elbows (average age, 54.9 years; range, 26-66 years) were used to measure contact area, pressure, and valgus torque at 90° and 30° of elbow flexion. Thirteen specimens were tested with the UCL intact, then with proximal-to-distal detachment of 50%, and then with proximal-to-distal detachment of 100% of the anterior band of the UCL from the ulnar attachment. This method was repeated in the remaining 12 specimens in a distal-to-proximal direction.

RESULTS

With 50% proximal-to-distal detachment, contact area decreased significantly versus intact at 90° (91.3 ± 23.6 vs 112.2 ± 26.0 mm(2); P < .001) and 30° (69.3 ± 14.8 vs 83.1 ± 21.6 mm(2); P < .001) of elbow flexion; the center of pressure (COP) moved significantly proximally versus intact at 90° (3.8 ± 2.5 vs 5.4 ± 2.3 mm; P < .001) and 30° (5.9 ± 2.8 vs 7.4±1.9 mm; P < .001). With 50% distal-to-proximal UCL detachment versus intact, no significant change was observed in contact area, movement of the COP, or valgus laxity at either flexion position. With 100% proximal-to-distal and distal-to-proximal detachment, significant change in contact area, movement of the COP, and valgus laxity versus intact was found at 90° and 30° of elbow flexion (P < .05). No significant difference in contact pressure was observed in any test conditions.

CONCLUSION

Significant change in contact area and proximal movement of the COP with 50% proximal UCL detachment and the lack of significant change with 50% distal UCL detachment suggest that the proximal half of the UCL ulnar footprint has a primary role in maintaining posteromedial elbow biomechanics.

CLINICAL RELEVANCE

The findings suggest that surgical reconstruction should aim to reestablish at least the proximal 50% of the UCL ulnar footprint.

Three-dimensional analysis of elbow soft tissue footprints and anatomy

BACKGROUND

Tendinous and ligamentous injuries commonly occur in the elbow. This study characterized the location, surface areas, and origin and insertional footprints of major elbow capsuloligamentous and tendinous structures in relation to bony landmarks with the use of a precision 3-dimensional modeling system.

METHODS

Nine unpaired cadaveric elbow specimens were dissected and mounted on a custom jig. Mapping of the medial collateral ligament (MCL), lateral ulnar collateral ligament (LUCL), triceps, biceps, brachialis, and capsular reflections was then performed with 3-dimensional digitizing technology. The location, surface areas, and footprints of the soft tissues were calculated.

RESULTS

The MCL had a mean origin (humeral) footprint of 216 mm(2), insertional footprint of 154 mm(2), and surface area of 421 mm(2). The LUCL had a mean origin footprint of 136 mm(2), an insertional footprint of 142 mm(2), and a surface area of 532 mm(2). Of the tendons, the triceps maintained the largest insertional footprint, followed by the brachialis and the biceps (P < .001-.03). The MCL, LUCL, and biceps footprint locations were consistent, with little variability. The surface areas of the anterior (1251 mm(2)) and posterior (1147 mm(2)) capsular reflections were similar (P = .82), and the anterior capsule extended farther proximally.

CONCLUSION

Restoring the normal anatomy of key elbow capsuloligamentous and tendinous structures is crucial for effective reconstruction after bony or soft tissue trauma. This study provides the upper extremity surgeon with information that may aid in restoring elbow biomechanics and preserving range of motion in these patients.

Sonographic assessment of the medial ulnar collateral ligament distal ulnar attachment

OBJECTIVES

The purpose of this study was to determine whether the long distal attachment of the medial ulnar collateral ligament (MUCL) can be delineated on sonography.

METHODS

We used 12 fresh-frozen cadaveric elbows for this study. We performed sonography of the elbow using a coronal-equivalent long-axis view of the MUCL. All sonographic examinations and measurements were performed by a board-certified, fellowship-trained musculoskeletal radiologist. Measurements were performed from the anteroinferior aspect of the medial epicondyle to the sublime tubercle and then from the sublime tubercle to the terminal fibers of the MUCL long ulnar attachment. We then measured the length of the MUCL from its attachment at the medial epicondyle of the humerus to the sublime tubercle and then from the sublime tubercle to the distal extent of its terminal fibers at the ulnar attachment with digital calipers.

RESULTS

On sonography, the average length of the MUCL from its humeral attachment to the sublime tubercle (transarticular) was 19.6 mm. The average length of the ulnar attachment was 27.9 mm. The MUCL was thickest (mediolateral dimension) at its humeral attachment and tapered as it coursed distally along the ulnar attachment. The MUCL was clearly identified on sonography and in all anatomic specimens. On gross measurement, the average lengths of the transarticular portion of the MUCL and its ulnar footprint were 21.5 and 30.2 mm, respectively.

CONCLUSIONS

We have successfully shown that the distal ulnar attachment of the MUCL can be visualized on high-resolution sonography. This preliminary work provides a framework for developing protocols for diagnosis of injuries to the distal ulnar collateral ligament.