Distal Ulnar Collateral Ligament Research Articles

Biomechanical Characteristics of Ulnar Collateral Ligament Injuries Treated With and Without Augmentation: A Network Meta-analysis of Controlled Laboratory Studies

Background: Treatment of ulnar collateral ligament (UCL) tears with suture tape augmentation has gained interest given preliminary reports of favorable biomechanical characteristics. No study to date has quantitatively assessed the biomechanical effects of multiple augmentation techniques relative to the native UCL. Purpose: To perform a systematic review and meta-analysis of controlled laboratory studies to assess and comparatively rank biomechanical effects of UCL repair or reconstruction with or without augmentation. Study Design: Systematic review and meta-analysis; Level of evidence, 4. Methods: PubMed, OVID/Medline, and Cochrane databases were queried in January 2023. A frequentist network meta-analytic approach was used to perform mixed-treatment comparisons of UCL repair and reconstruction techniques with and without augmentation, with the native UCL as the reference condition. Pooled treatment estimates were quantified under the random-effects assumption. Competing treatments were ranked in the network meta-analysis by using point estimates and standard errors to calculate P scores (greater P score indicates superiority of treatment for given outcome). Results: Ten studies involving 206 elbow specimens in which a distal UCL tear was simulated were included. UCL reconstruction with suture tape augmentation (AugRecon) restored load to failure to a statistically noninferior magnitude (mean difference [MD], –1.99 N·m; 95% CI, –10.2 to 6.2 N·m; P = .63) compared with the native UCL. UCL reconstruction (Recon) (MD, –12.7 N·m; P < .001) and UCL repair with suture tape augmentation (AugRepair) (MD, –14.8 N·m; P < .001) were both statistically inferior to the native UCL. The AugRecon condition conferred greater load to failure compared with Recon (P < .001) and AugRepair (P = .002) conditions. AugRecon conferred greater torsional stiffness relative to all other conditions and was not statistically different from the native UCL (MD, 0.32 N·m/deg; 95% CI, –0.30 to 0.95 N·m/deg; P = .31). Medial ulnohumeral gapping was not statistically different for the AugRepair (MD, 0.30 mm; 95% CI, –1.22 to 1.82 mm; P = .70), AugRecon (MD, 0.57 mm; 95% CI, –0.70 to 1.84 mm; P = .38), or Recon (MD, 1.02 mm; 95% CI, –0.02 to 2.05 mm; P = .055) conditions compared with the native UCL. P-score analysis indicated that AugRecon was the most effective treatment for increasing ultimate load to failure and torsional stiffness, whereas AugRepair was the most effective for minimizing medial gapping. Conclusion: AugRecon restored load to failure and torsional stiffness most similar to the parameters of the native UCL, whereas Recon and AugRepair did not restore the same advantageous properties at time zero. Medial ulnohumeral gapping during a valgus load was minimized by all 3 treatments. Based on network interactions, AugRecon was the superior treatment approach for restoring important biomechanical features of the UCL at time zero that are jeopardized during a complete distal tear.

Reliability of ulnar collateral ligament findings in magnetic resonance imaging.

Ulnar collateral ligament (UCL) tears are common in baseball players. Although magnetic resonance imaging (MRI) is the most used imaging modality for UCL injuries, the inter-rater reliability of MRI analyzing specific characteristics of UCL pathology has not been defined. The purpose of this study was to define the inter-rater reliability of MRI for evaluating UCL characteristics. Three surgeons analyzed 45 noncontrast MRIs: 15 without UCL tears, 15 with intraoperatively confirmed partial-thickness tears, and 15 with intraoperatively confirmed full-thickness tears. Findings evaluated included ligament characteristics (periligamentous or osseous edema, ligament hypertrophy, calcifications, and partial- or full-thickness tearing) and location of the pathology (proximal, midsubstance, or distal). Fleiss' κ coefficients were used to assess interobserver reliability. There were high rates of agreement for midsubstance (κ: 0.50) and distal (κ: 0.69) ligament edema and proximal osseous edema (κ: 0.48). There were low rates of agreement for proximal ligament edema (κ: 0.08), ligament thickening (κ: -0.02 to 0.20), and proximal to midsubstance calcifications (κ: -0.04 to 0.10). Midsubstance (κ: 0.55) and distal full-thickness tears (κ: 0.63) demonstrated higher agreement than proximal (κ: 0.29). Proximal partial-thickness tears (κ: 0.45) had higher agreement than midsubstance (κ: -0.02) or distal (κ: -0.02). In our study, there was high inter-rater reliability regarding proximal osseous edema, midsubstance, and distal ligament edema and full-thickness tears. There was no agreement for midsubstance and distal partial-thickness UCL tears, but fair agreement for proximal tears. UCL tissue characteristics including ligament thickening and calcifications demonstrated low agreement. Challenges remain in effectively evaluating UCL tissue characteristics on noncontrast MRIs.

Sites of flexor-pronator muscle injury and relationship between ulnar collateral ligament injury and flexor-pronator muscle injury in baseball players: a retrospective cohort study.

Ulnar collateral ligament (UCL) and flexor-pronator muscle (FPM) injuries are common in baseball players. However, the sites of FPM injuries and the relationship between UCL and FPM injuries in baseball players have not been fully clarified. The purpose of this study was to identify the sites of FPM injuries and to determine the relationships of location and severity of UCL injury with the presence of FPM injuries in baseball players. UCL and FPM injuries were diagnosed using magnetic resonance imaging in 99 baseball players. The sites of FPM injuries were identified on coronal, sagittal, and axial images. UCL injury severity was classified into four grades: chronic changes, low-grade partial tear, high-grade partial tear, and complete tear. UCL injury location was classified as proximal UCL tear or distal UCL tear. All images were assessed by a musculoskeletal radiologist and an orthopedic surgeon. Combined UCL and FPM injuries were observed in 45 of 99 players, of which 40 of 45 (89%) involved injury of the flexor digitorum superficialis (FDS). All FDS injuries were in the deep layer of the muscle belly. There was no significant difference between the severity of UCL injury and presence of FPM injuries (P=.352). There was a significant association of distal UCL tears with FPM injuries (P<.001). FDS injury occurs most commonly in the muscle belly of the second and fifth digits. There may be no relationship between the severity of UCL injury and presence of FPM injury in baseball players. FPM injuries may be a contributing factor in the failure of nonoperative management of distal UCL tears in baseball players.

Sonographic morphological and qualitative deficits in the elbow ulnar collateral ligament and ulnohumeral joint in throwing arms of asymptomatic collegiate baseball pitchers.

The ulnar collateral ligament (UCL) supports the medial elbow against valgus torque and is commonly injured in baseball pitchers. Changes in UCL morphology and pathology occur with long-term pitching, with more severe findings at higher competition levels. We examined the bilateral differences and the relationship between UCL morphology, pathology, and ulnohumeral joint laxity in asymptomatic collegiate pitchers using ultrasound. Division I college pitchers (n = 41) underwent ultrasound scans of their bilateral medial elbows, both at rest and in a valgus-stressed position. The presence of enthesopathy, calcifications, and degeneration was assessed qualitatively. UCL thickness and ulnohumeral joint gap were measured with online calipers. The bilateral differences were analyzed using paired t-tests and chi-square analysis, and the relationships between thickness, gapping, and degenerative changes were analyzed using regression analyses. The throwing arm demonstrated greater distal UCL thickness (mean difference (MD) = 0.2mm (95%CI = 0.1-0.3), p < 0.01), resting and stressed gap (MD = 0.3mm (95%CI = 0.0-0.7), p = 0.04; MD = 0.4 (95%CI = 0.0-0.9), p = 0.02), and greater prevalence of degeneration and enthesopathy (p = 0.03) compared bilaterally. Enthesopathy and calcifications predicted increased distal UCL thickness (p = 0.04; p = 0.02). Degenerative scores predicted increased stressed-resting ulnohumeral joint gap (p < 0.01). In the throwing arms of collegiate pitchers, ultrasound demonstrated UCL thickening, enthesopathy/intra-ligamentous calcification, and greater laxity of the ulnohumeral joint relative to the non-throwing arm. Degeneration of the UCL, not thickness, was related to greater elbow joint gapping. This study demonstrates the utility of ultrasound for examining sonographic characteristics of the UCL in a sample of college pitchers.

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.

Pre-Draft Elbow Magnetic Resonance Imaging in Major League Baseball Pitchers (127)

Objectives:Evaluate pre-draft elbow MRI on baseball pitchers who were entering the MLB draft to determine the presence or absence of pathology, and the associations between these pathologies and UCL tears, and inter-observer reliability regarding common MRI pathology.Methods:Pre-draft elbow MRI and X-Rays on prospective MLB pitchers between 2011-2017 were deidentified and reviewed by two separate authors. The authors graded the X-Rays MRI on several factors including presence or absence of ulnar collateral ligament (UCL) ossification, UCL appearance (heterogeneous or not), UCL thickening (and location), UCL tear (partial vs. full thickness and location), muscle strain, flexor tendon tear, posteromedial osteophyte, sublime tubercle enthesophyte, and osseous stress reactions.Results:Overall, 245 pre-draft elbow X-Rays and MRI were reviewed. On X-Ray: 12 (4.9%) had ossification within the UCL; 34 (13.9%) had an olecranon osteophyte; 14 (5.7%) had a sublime tubercle enthesophyte. MRI abnormalities were found in 70% (171/245) of pitchers. UCL thickening was found in 20% of pitchers. Regarding UCL tears, 3% had a full thickness tear and 24% had a partial thickness tear. Of full thickness tears, 86% were distal and one was midsubstance. Of partial thickness tears, 41% (24/58) were distal, 12% (7/58) were midsubstance, and 47% (27/58) were proximal. Periligamentous edema was present in 36% of pitchers while 14% had a flexor pronator muscle strain. Stress reactions were seen in 27% and most commonly involved the sublime tubercle. Based upon the presence of periligamentous edema, distal UCL pathology was more likely to be chronic than acute while proximal UCL pathology was more likely to be acute.Conclusions:The majority (70%) of pitchers entering the MLB draft had abnormal findings on their MRI, most commonly involving changes to the UCL. Interobserver reliability was acceptable following definition of pathology when reading pre-draft elbow MRI on MLB prospects.

Forearm flexor injury is associated with medial ulnar collateral ligament injury in throwing athletes.

Elbow ulnar collateral ligament (UCL) injuries have become increasingly common in throwing athletes. The forearm flexors (FF) have been studied as biomechanical stabilizers for the medial elbow. However, there are no studies investigating the association of concomitant UCL injuries and FF injuries in throwing athletes. To determine if throwing athletes with a complete UCL injury had a greater likelihood of concomitant FF injury than those with a partial UCL injury. Descriptive retrospective epidemiological study. Academic, tertiary care medical center. Throwing related UCL injuries in patients aged 12-24 years. Electronic medical records and key word searches identified all patients from January 1, 2010 to December 31, 2019. A board certified and fellowship trained musculoskeletal radiologist reviewed all advanced imaging studies. Fifty-four patients (46 male, 8 female, mean age 17.1 years, SD 2.3) were included. Fifty-four UCL injuries (21 complete ruptures, 16 proximal partial injuries, 17 distal partial injuries) were confirmed by magnetic resonance imaging (MRI). Twenty-eight FF injuries (22 strains, 6 tears) were diagnosed with MRI and/or MRI-arthrogram. There was a significant association between sustaining a FF injury and UCL reconstruction (UCL-R) (X2 = [1, N= 54], = 3.97, P= .046) (15/22, 68.2%), as well as FF injury and UCL injury location (X2 = [1, N= 33], = 3.86, P= .049) (10/17, distal partial UCL injury, 58.8%). Analysis of FF injury and complete UCL tear is not significant (X2 = [1, N= 54], = 3.02, P= .08) (14/21, 66.7%). The data indicate that FF injury is associated with UCL injury in throwing athletes. Future prospective studies should investigate causation versus correlation of FF and UCL injury in throwing athletes. The results of this study have applications to multiple sports medicine areas that include but are not limited to surgical, nonsurgical, prehabilitation, rehabilitation, and sports performance. This study reveals a strongly significant association between FF injury and concomitant UCL injury in throwing athletes.

Biomechanical assessment of docking ulnar collateral ligament reconstruction after failed ulnar collateral ligament repair with suture augmentation

Ulnar collateral ligament (UCL) repair with single-strand suture augmentation has been introduced as a viable surgical option for throwers with acute UCL tears. For the original single-strand suture augmentation construct, revision UCL reconstructions can be challenging owing to the bone loss at the site of anchor insertion in the center of the sublime tubercle. This biomechanical study assessed a small-diameter (1.5-mm) ulnar bone tunnel technique for double-strand suture-augmented UCL repair that may be more easily converted to salvage UCL reconstruction if necessary, as well as a salvage UCL reconstruction with a docking technique after a failed primary suture-augmented UCL repair. In 7 fresh-frozen cadaveric upper extremities (mean age, 66.3 years), a custom shoulder testing system was used to simulate the late cocking phase of throwing. The elbow valgus opening angle was evaluated using a MicroScribe 3DLX device for sequentially increasing valgus torque (from 0.75 to 7.5 Nm in 0.75-Nm increments) at 90° of flexion. Valgus angular stiffness (in newton-meters per degree) was defined as the correlation of sequentially increasing valgus torque with the valgus opening angle through simple linear regression (slope of valgus torque - valgus opening angle curve). Four conditions were tested: intact elbow, distal UCL avulsion, primary UCL repair with double-strand suture augmentation using small-diameter bone tunnels, and subsequent docking UCL reconstruction in the same specimen. Load-to-failure tests were performed for primary UCL repair with double-strand suture augmentation and subsequent docking UCL reconstruction. With increasing elbow valgus torque, the valgus opening angle increased linearly in each condition (R2 ≥ 0.98, P < .001). Distal UCL avulsion resulted in significantly decreased angular stiffness compared with the intact UCL (P < .001). Both UCL repair with double-strand suture augmentation and subsequent UCL reconstruction showed significantly increased angular stiffness values compared with distal UCL avulsion (P < .001 and P < .001, respectively). On load-to-failure testing, there was no significant difference in stiffness, yield torque, and ultimate torque between the primary suture-augmented UCL repair and the subsequent UCL reconstruction (P = .11, P = .77, and P = .38, respectively). In all specimens undergoing the small-diameter ulnar bone tunnel technique for double-strand suture-augmented UCL repair, failure occurred by retear of the repaired ligament without causing an ulnar bone bridge fracture. Primary UCL repair with double-strand suture augmentation using small-diameter bone tunnels was able to restore valgus stability. When failure occurs, this technique retains enough cortical bone to permit subsequent docking UCL reconstruction.

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

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. 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. 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. 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.

Medial Elbow Instability Resulting From Partial Tears of the Ulnar Collateral Ligament: Stress Ultrasound in a Cadaveric Model

Background: There is consensus that most complete ulnar collateral ligament (UCL) injuries in throwers would benefit from surgical intervention. Optimal treatment for partial UCL tears remains controversial. Stress ultrasonography has become a well-accepted diagnostic modality for assessing UCL injury. Hypothesis: Partial UCL tears will result in an intermediate increase in ulnohumeral joint space gapping as compared with that of an intact UCL and a complete UCL tear, but the degree of joint space gapping will vary by anatomic location of the partial tear. Study Design: Controlled laboratory study. Methods: Twenty-one cadaveric elbows were divided into 7 groups representing different anatomic locations of UCL partial tears. Partial tears were simulated by cutting 50% of the measured width of the UCL at 6 locations: distal anterior/posterior, midsubstance anterior/posterior, and proximal anterior/posterior. A seventh partial tear was created by partially elevating the undersurface of the distal UCL to simulate the radiographic “T-sign.” Valgus stress (15 daN) was applied to each cadaveric elbow at 30° of flexion using a standardized device. Each specimen was tested intact, partially torn, and completely torn. At each state, joint space was measured using stress ultrasonography, and the difference in joint space from unstressed to stressed (delta) was recorded. Results: There were 10 right and 11 left upper extremity specimens. The mean delta was 0.58 mm for the intact state and <0.75 mm in all groups. Both distal partial tear groups had mean deltas <0.75 mm, similar to intact elbows. Proximal tears and the T-sign demonstrated intermediate deltas (0.99-1.23 mm). Midsubstance partial tears demonstrated the largest deltas (1.57-2.03 mm), similar to those of the complete tears. All complete tear groups had a mean delta >1.5 mm (1.54-3.03 mm). Conclusion: These findings suggest that partial tears introduce a spectrum of instability from functionally intact to completely torn. As a result, some may be biomechanically amenable to nonoperative treatment, while others would be indicated for early reconstruction. Further research into the biological and biomechanical determinants of nonoperative treatment failure will assist with more precise treatment recommendations. Clinical Relevance: Describing the biomechanical consequences of different, clinically significant partial UCL tears potentially allows more precise recommendations for operative and nonoperative treatment.

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.

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.

Variations in Blood Supply from Proximal to Distal in the Ulnar Collateral Ligament of the Elbow: A Qualitative Descriptive Cadaveric Study

Objectives: The vascular supply of the ulnar collateral ligament (UCL) is unknown. Previous studies have reported varying success in return to play rates after non-operative management of partial UCL tears and suggest a varying healing capacity as possibly related to UCL injury location. The purpose of this study was to analyze the macroscopic vascular anatomy of the ulnar collateral ligament of the elbow. Methods: Eighteen, fresh-frozen, male cadaveric elbows from nine donors were sharply dissected 15 cm proximal to the medial epicondyle. Sixty mL of India Ink was injected through the brachial artery of each elbow. Arms were then frozen at -10°C, radial side down in 15-20° of elbow flexion. A bandsaw was used to section the frozen elbows into 5 mm coronal or sagittal sections. Sections were cleared for visualization using the modified Spalteholz technique. Images of specimens were taken and the qualitative description of the UCL vascularity was undertaken. Results: We consistently found a dense blood supply to the proximal UCL, while the distal UCL was hypovascular. We observed a possible osseous contribution to the proximal UCL from the medial epicondyle in addition to an artery from the flexor/pronator musculature that consistently appeared to provide vascularity to the proximal UCL. The degree of vascular penetration moving from proximal to distal in the UCL ranged from 39-68% of the overall UCL length, with a 49% average length of vascular penetration of the UCL. Conclusion: Our study found a difference in the vascular supply of the ulnar collateral ligament. The proximal UCL was well vascularized, while the distal UCL was hypovascular. This difference in vascular supply may be a factor in the differential healing capacities of the UCL based on the location of injury. An improved understanding of the macroscopic vascular supply of the UCL may aid in the clinical management of partial UCL tears and suggest an indication for treatments with respect to location of UCL injuries.

Variations in Blood Supply From Proximal to Distal in the Ulnar Collateral Ligament of the Elbow: A Qualitative Descriptive Cadaveric Study

Background: The vascular supply of the ulnar collateral ligament (UCL) is unknown. Previous studies reported varying success in return-to-play rates after nonoperative management of partial UCL tears and suggested a varying healing capacity as possibly related to the location of the UCL injury. Purpose: To analyze the macroscopic vascular anatomy of the UCL of the elbow. Study Design: Descriptive laboratory study. Methods: Eighteen fresh-frozen male cadaveric elbows from 9 donors were sharply dissected 15 cm proximal to the medial epicondyle. Sixty milliliters of India ink was injected through the brachial artery of each elbow. Arms were then frozen at −10°C, radial side down, in 15° to 20° of elbow flexion. A band saw was used to section the frozen elbows into 5-mm coronal or sagittal sections. Sections were cleared for visualization with the modified Spalteholz technique. Images of the specimens were taken, and qualitative description of UCL vascularity was undertaken. Results: The authors consistently found a dense blood supply to the proximal UCL, while the distal UCL was hypovascular. They also observed a possible osseous contribution to the proximal UCL from the medial epicondyle in addition to an artery from the flexor/pronator musculature that consistently appeared to provide vascularity to the proximal UCL. The degree of vascular penetration from proximal to distal in the UCL ranged from 39% to 68% of the overall UCL length, with a 49% mean length of vascular penetration of the UCL. Conclusion: This study found a difference in the vascular supply of the UCL. The proximal UCL was well vascularized, while the distal UCL was hypovascular. This difference in vascular supply may be a factor in the differential healing capacities of the UCL based on the location of injury. Clinical Relevance: An improved understanding of the macroscopic vascular supply of the UCL may aid in the clinical management of partial UCL tears and suggests an indication for these treatments with respect to location of UCL injuries.

Evaluation of Endothelial and Vascular-Derived Progenitor Cell Populations in the Proximal and Distal UCL of the Elbow: A Comparative Study.

Background:Vascular-derived progenitor and endothelial cell populations (CD31, CD34, CD146) are capable of multipotent differentiation at the site of injured ligamentous tissue to aid in the intrinsic healing response. Proximal ulnar collateral ligament (UCL) tears have been reported to have better healing capability when compared with distal UCL tears.Purpose:To compare the vascular composition of the proximal and distal insertions of the anterior bundle of the UCL of the elbow via known markers of endothelial and vascular-derived progenitor cells (CD31, CD34, CD146).Study Design:Descriptive laboratory study.Methods:UCLs were harvested from 10 nonpaired fresh-frozen human cadaveric elbows and transected into proximal and distal portions. Endothelial and vascular-derived progenitor cell densities were assessed with 4 staining groups: CD31 (immunohistochemistry) and CD31/α-smooth muscle actin (α-SMA), CD34/α-SMA, and CD146/α-SMA (immunofluorescence). CD31 immunohistochemistry identified endothelial progenitor cells in the UCL. Later staining of the same slides with α-SMA demonstrated the relationship of progenitor cells to the surrounding vasculature. Fluorescent staining was quantified by calculating the proportion of positively stained nuclei versus the total number of nuclei in the proximal and distal UCL.Results:CD31+ cells were present in the proximal and distal sections of all 10 UCLs. Fluorescent staining revealed no significant differences in the ratio of CD31 to total nuclei between the distal (median, 36% [range, 23%-53%]) and proximal UCL (39% [22%-56%]) (P = .432, Wilcoxon signed-rank test). Similarly, no differences were seen between CD34 distal (39% [24%-64%]) and proximal regions (46% [28%-63%]) (P = .846, Wilcoxon signed-rank test) or CD146 distal (40% [12%-65%]) and proximal regions (40% [22%-51%]) (P ≥ .999, Wilcoxon signed-rank test).Conclusion:Analysis of UCL tissues demonstrated equal distributions of vascular endothelial and vascular-derived progenitor cell markers throughout the proximal and distal UCL. Unlike that of the medial collateral ligament of the knee, the microvascular composition of the proximal and distal UCL insertions was not different, suggesting a well-vascularized ligament throughout its course.Clinical Relevance:These findings investigate one of the possible contributors to UCL healing after injury, which may provide insight into operative and nonoperative management of UCL injuries in the future. This study also indicates that reasons other than differences in progenitor cell density alone may explain the clinical healing differences seen between proximal and distal UCL tears. A better understanding of the microvascular environment and associated blood supply is warranted to understand the healing capability of the UCL.

Ulnar Collateral Ligament Reconstruction Versus Repair With Internal Bracing: Comparison of Cyclic Fatigue Mechanics.

Background:Ulnar collateral ligament (UCL) injuries have increased significantly in recent years, and reconstruction has become the preferred treatment for UCL injury over ligament repair. In a recent study, UCL repair with internal bracing demonstrated significantly greater resistance to gap formation in biomechanical tests, even at low cycles of valgus loading.Purpose/Hypothesis:The purpose of this study was to compare the fatigue and failure mechanics of traditional UCL reconstruction with UCL repair and internal bracing. We hypothesized that repaired specimens would have less gap formation, closer return to native gap formation, and greater maximum torque to failure versus traditionally reconstructed specimens.Study Design:Controlled laboratory study.Methods:Ten matched pairs of cadaveric elbows were positioned at 90° of flexion and the native UCL subjected to 500 cycles of subfailure valgus loading. A simulated tear was created, and the 10 cycles were repeated. Each pair of specimens was next given repair with internal bracing on 1 side and a modified Jobe reconstruction on the contralateral side, followed by 100 manual cycles of flexion-extension, 500 cycles of valgus rotation, and, finally, rotation to failure.Results:The specimens that received the repair unexpectedly experienced significantly less gapping in the torn state than did those in the reconstruction group. At the 10th cycle, repaired UCL injuries had significantly less gap formation than the reconstructed UCLs. At the 100th and 500th cycles, repaired UCL injuries continued to experience significantly less gap formation as compared with the reconstructed injuries.Conclusion:When compared with the gold standard reconstruction technique, UCL repair with internal bracing is more resistant to gap formation under fatigue loading. However, the unexpected early difference between the torn states may have confounded this finding. Time-zero failure properties of this repair technique are on par with those of traditional reconstruction, even after 500 cycles of valgus loading.Clinical Relevance:UCL reconstruction has become a common procedure among adolescent and elite-level throwers. Recent data suggest that UCL repair may be a viable option for younger athletes with acute proximal or distal UCL tears, allowing a faster return to play.

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.

Magnetic Resonance Imaging Predictors of Failure in the Nonoperative Management of Ulnar Collateral Ligament Injuries in Professional Baseball Pitchers

Background: A medial ulnar collateral ligament (UCL) injury of the elbow is an increasingly common injury in professional baseball pitchers. Predictors of success and failure are not well defined for the nonoperative management of these injuries. Purpose: To evaluate the efficacy of objective measures to predict failure of the nonoperative management of UCL injuries. Study Design: Case-control study; Level of evidence, 3. Methods: Thirty-two professional pitchers (82%) met inclusion criteria and underwent an initial trial of nonoperative treatment for UCL tears based on clinical and radiological findings. Age, preseason physical examination results, magnetic resonance imaging (MRI) characteristics, and performance metrics were analyzed for these pitchers. Successful nonoperative management was defined as a return to the same level of play or higher for >1 year. Failure was defined as recurrent pain or weakness requiring a surgical intervention after a minimum of 3 months’ rest when attempting a return to a throwing rehabilitation program. Results: Thirty-two pitchers (mean age, 22.3 years) who underwent initial nonoperative treatment of UCL injuries were evaluated. Thirty-four percent (11/32) failed and required subsequent ligament reconstruction. Sixty-six percent (21/32) successfully returned to the same level of play for 1 year without a surgical intervention. There was no significant difference seen in physical examination findings or performance metrics between these patients. When comparing MRI findings between the groups, 82% (9/11) (P < .001) who failed nonoperative management had distal tears, and 81% (17/21) who did not fail had proximal tears (P < .001). When adjusting for age, location, and evidence of chronic changes on MRI, the likelihood of failing nonoperative management was 12.40 times greater (P = .020) with a distal tear. No other variable alone or in combination reached significance. When combining the parameters of a high-grade tear and distal location, 88% (7/8) failed nonoperative management. Conclusion: In professional pitchers, distal UCL tears showed significantly higher odds of failure with nonoperative management compared with proximal tears. Thus, tear location should be considered when deciding between operative and nonoperative management.

MRI Predictors of Failure in Non-operative Management of Ulnar Collateral Ligament Injuries in Professional Baseball Pitchers

Objectives:Ulnar collateral injuries (UCL) of the elbow are prevalent among professional baseball pitchers. The decision on initial operative versus nonoperative management of these injuries remains subjective in many cases, with reported success rates with nonoperative management ranging from 42 to 93% in professional throwing athletes. No studies to date have identified objective characteristics specific to success or failure of nonoperative intervention. The purpose of this study was to identify radiologic predictors for success or failure in nonoperative management of ulnar collateral ligament injuries in professional pitchers.Methods:A retrospective review of pitchers sustaining UCL injuries between 2006 and 2015 from one professional baseball organization (one major league team and all minor league teams included) was performed. UCL injuries were identified in 38 players based on clinical and radiographic findings. Six players underwent initial surgical intervention without attempted nonoperative intervention and were excluded from analysis. This left 32 (84%) professional pitchers who underwent an initial trail of nonoperative treatment for partial UCL tears. Success was defined as return to same level of play (RTSP) or higher for >1 year. Failure was defined as recurrent pain or weakness requiring surgical intervention after a minimum of 3 months’ rest when attempting a return to throw rehabilitation program. MRI findings were classified as high or low grade sprains, proximal or distal location of injury, and with or without the presence of concomitant chronic findings.Results:Of the 32 patients who underwent nonoperative management, 10 (36%) failed and required subsequent ligament reconstruction. Between the success and failure groups, there was no significant difference seen in total shoulder arc of motion (P=.7776), shoulder internal rotation deficit (P=.3846) or loss in elbow extension (P=.0644) at the time of injury. When comparing MRI findings between the groups, distal tears were found in 90% (9/10) of those who failed nonoperative management compared to 18.2% (4/22) who were successful nonoperatively (P=<.0001). No significant difference was seen with high grade tears (P=.0817) between the groups. When adjusting for age, location and evidence of chronic changes on MRI, the likelihood of failing nonoperative management was 22.7 times greater (P=.001) with distal tears. No other variable reached significance, and no combination of variables showed a greater likelihood than distal location alone.Conclusion:In professional pitchers, distal ulnar collateral ligament tears described on MRI show significantly higher rates of failure with nonoperative management compared to proximal tears. This information provides an objective measure for evaluating operative versus nonoperative management of ulnar collateral ligament injuries in throwing athletes.

Biomechanical Comparison of Ulnar Collateral Ligament Repair With Internal Bracing Versus Modified Jobe Reconstruction

Background: The number of throwing athletes with ulnar collateral ligament (UCL) injuries has increased recently, with a seemingly exponential increase of such injuries in adolescents. In cases of acute proximal or distal UCL insertion injuries or in partial-thickness injuries that do not respond to nonoperative management, UCL repair and augmentation rather than reconstruction may be a viable option. Purpose/Hypothesis: The purpose of this study was to biomechanically compare a new technique of augmented UCL repair versus a typical modified Jobe UCL reconstruction technique. The hypotheses were that (1) the repaired specimens would have less gap formation and a higher maximal torque to failure compared with the reconstruction group, and (2) while both groups would show an increase in gap formation after the simulated tear, the repair group would return closer to the native values compared with the reconstruction group. Study Design: Controlled laboratory study. Methods: Nine matched pairs of cadaveric arms were dissected to expose the UCL. Each elbow was mounted on a test frame at 90° of flexion. A cyclic valgus rotational torque was applied to the humerus with the UCL in its intact state and repeated in its surgically torn state. Finally, each specimen received either an augmented repair or reconstruction and was again put through the cyclic protocol, followed by a torque to failure. Results: Gap formation (0.51 ± 0.22 mm) in the torn state for the repair group was significantly higher (P = .04) than in the intact state (0.33 ± 0.12 mm). After the procedures, the repair group (0.35 ± 0.16 mm) showed greater resistance to gapping (P = .03) compared with the reconstruction group (0.53 ± 0.23 mm). No statistical differences were found for the maximum torque at failure, torsional stiffness, or gap formation during the failure test. Conclusion: The current study shows that this novel technique of augmented UCL repair replicates the time-zero failure strength of traditional graft reconstruction and appears to be more resistant to gapping at low cyclic loads. Clinical Relevance: This study demonstrates that this novel technique has important biomechanical properties, including time-zero strength and ultimate failure load, compared with the gold standard of UCL reconstruction. In some throwing athletes, this technique may supplant standard UCL reconstruction as the procedure of choice.