UCL Throwing Injuries in Nonprofessional Baseball Players: A 14-Year Retrospective Study

Abstract

Background:

This study evaluated treatment modality (surgical vs nonoperative) of medial ulnar collateral ligament (UCL) injuries in nonprofessional throwing baseball athletes by comparing type, severity, and location of UCL injury.

Hypothesis:

Baseball players with closed medial epicondyle physes and concomitant throwing-related UCL injury will be more likely to undergo surgical intervention than players with open medial epicondyle physes.

Study Design:

Retrospective.

Level of Evidence:

Level 5.

Methods:

A total of 119 baseball players with a mean age of 16.9 ± 2.5 years (range, 11-25 years) were included in the study. Datapoints included sex, age at time of injury, severity, and location of UCL injury, growth plate status, operative versus conservative management, and concomitant flexor forearm injury.

Results:

A total of 75 players were treated conservatively; 43 underwent UCL reconstruction (UCL-R), and 1 had an unknown treatment outcome. No significant difference was found for age related to treatment type, UCL-R (17.2 ± 2.2) versus conservative treatment (16.8 ± 2.6). Athletes with closed medial epicondylar growth plates were more likely to undergo UCL-R than athletes with open medial epicondylar growth plates (P = 0.02). There were no significant differences between UCL injury location (42 distal, 37 proximal, 18 combined tear locations, 11 complete tears, and 11 intact UCLs with inflammation) by treatment type (P = 0.09). There was a significant difference for UCL severity (11 complete tears, 96 partial tears) by treatment type (P = 0.03).

Conclusion:

Nonprofessional athletes with closed medial epicondylar growth plates and throwing-related UCL injuries were more likely to be treated surgically. Baseball athletes with partial tears, if skeletally immature, require further long-term evaluation.

Clinical Relevance:

Continued knowledge gains in this area of throwing medicine will further improve our treatment algorithms in nonprofessional baseball players.

The occurrence and volume of ulnar collateral ligament (UCL) injuries and subsequent surgical reconstruction in the elbow in the United States has grown in recent years.^12,14,23 Overhead throwing athletes, such as baseball players, are at an increased risk to injure their UCL due to the repetitive valgus strain put on the elbow during the throwing motion. UCL injuries in professional athletes (eg, professional baseball players) draw significant media attention and public speculation due to concerns about pitchers returning to preinjury level.^{8,13,22,24,26,36} As a result, there has been substantial research into diagnosis, management, and outcomes of treatments in throwing athletes with UCL injuries at the professional level, primarily in baseball.^5-7,19,25 However, there has been less research in nonprofessional athletes, such as adolescent, high school, and collegiate athletes. Further, there is a lack of robust research in nonprofessional throwers in other throwing sports (such as cricket, handball, javelin, and softball) with respect to UCL injuries. In addition, few long-term longitudinal studies exist on volume of UCL injuries and associated outcomes in nonprofessional throwers compared with professional athletes.^{12,20,23,30,34} It is important to determine the number of nonsurgical UCL injuries and UCL injuries treated with surgery in nonprofessional baseball athletes to fill in the missing gap in epidemiological and preventative research for UCL injuries over greater periods of time. By increasing our understanding of the number of UCL injuries as well as associated characteristics (eg, location, growth plate status, and severity of UCL injury), we will attain a greater understanding and provide enhanced treatment algorithms to improve care in this athletic population.^17,33 Thus, it was the goal of this study to retrospectively assess characteristics of throwing-associated UCL injuries in nonprofessional baseball players. We further intend to identify the number of UCL injuries that were treated with nonoperative versus operative management. Finally, we will elucidate associated commonalities between UCL injury severity, age, physeal status (skeletal maturity vs open physes), location of UCL injury, concomitant proximal flexor forearm (FF) injury, and treatment modality (surgical vs nonoperative). Our hypothesis is that baseball players with closed medial epicondyles and concomitant UCL injury sustained from throwing will be more likely to undergo surgical intervention than players with open medial epicondyle physes, due to skeletal maturity and pubertal maturation allowing for greater force and power when throwing.

Methods

We conducted a retrospective analysis on athletes aged 11 to 25 years who were treated for a UCL injury at our institution between January 1, 2008 and June 30, 2022. This was a substudy on baseball athletes with the original dataset including 749 athletes (Figure 1) that sustained an elbow UCL injury from throwing during baseball playing. We utilized International Classification of Disease (ICD) and Current Procedural Terminology (CPT) codes to identify the patient population, followed by a subsequent chart review to confirm that the elbow injury was due to the inclusion criteria (a result of throwing during baseball related activity). ICD-9 and/or -10 codes included those for UCL of the elbow sprain and UCL of the elbow rupture. Queried CPT codes included those for UCL rupture reconstruction. Table 1 provides a full listing of ICD and CPT codes used.

Figure 1.

Chart review process. UCL, ulnar collateral ligament.

Table 1.

ICD and CPT code identification

	Elbow UCL Sprain	Elbow UCL Rupture	UCL Avulsion Fracture	UCL Rupture Reconstruction
ICD 9	841.1, 841.9, 842, 848.9	841.1, 905.7	812.43
ICD 10	S53.449A, S53.441A, S53.442A	S53.30XA, S53.31XA, S53.32XA	S42.441A, S42.442A, S42.443A, S42.444A, S42.445A, S42.446A, S42.447A, S42.448A, S42.449A,
CPT codes				24346

CPT, Current Procedural Terminology; ICD, International Classification of Disease; UCL, ulnar collateral ligament.

Further, we included the following datapoints: age at time of injury and evaluation, sex, handedness, month and year of injury, sprain versus rupture of the UCL, surgical reconstruction (UCL reconstruction [UCL-R]) or rehabilitation only, repeat injury, baseball player, and modality used to diagnose the injury (clinical examination alone, magnetic resonance imaging [MRI], MRI-arthrogram, and/or other). We further included location of UCL injury and medial epicondylar growth plate (ME) status. A review of advanced imaging was conducted by a board-certified and fellowship-trained musculoskeletal radiologist to further determine whether there was an injury to proximal FF muscles and tendons (flexor carpi ulnaris, palmaris longus, flexor carpi radialis, pronator teres, flexor digitorum superificialis, flexor digitorum profundus, flexor pollicus longus; pronator quadratus not examined). Definitions of UCL injury as well as FF severity were based on advanced imaging results and previously published data.^16,37,38 When there was no UCL tear, we defined UCL abnormality as an intact ligament with inflammation and/or bony edema at insertion. ¹⁶ This research plan and methodology was used in previous studies.^37,38 Figure 1 depicts our final chart review process, with 119 athletes with advanced imaging ultimately being included.

Ethics Statement

This retrospective descriptive epidemiological study was approved by our institution’s Institutional Review Board with a Health Insurance Portability and Accountability Act waiver. A report request was submitted to the University of Florida Integrated Data Repository office for a query of records to identify all subjects treated at our institution for UCL injuries.

Statistics

Descriptive statistics for continuous variables (means and standard deviations) and categorical variables (frequencies and percentages) were completed. Statistical comparisons were made using the Mann-Whitney U test between age and treatment modality. Separate chi-square tests were used to assess differences for physeal status and treatment modality, and FF injury location and treatment modality. The type 1 error rate was set a priori at 0.05.

Results

Included in the study were baseball players (N = 119, all male, 104 right-handed and 15 left-handed dominant) with a mean age of 16.9 ± 2.5 years. Location of UCL injury and severity was separate based on location (distal, proximal, or combined), complete versus partial tear, and/or whether there was an UCL abnormality with intact fibers. Players treated nonoperatively totaled 75, while 43 underwent UCL-R, and for 1 athlete the treatment type was not available. No significant difference was found for age related to treatment type, or UCL-R (17.2 ± 2.2 years) versus nonoperative treatment (16.8 ± 2.6) (P = 0.14). There were a total of 94 athletes with closed medial epicondylar growth plates and 25 with open medial epicondylar growth plates. Of the 25 athletes with open medial epicondylar growth plates, none had a complete UCL rupture (Tables 2 and 3). Of the athletes with closed growth plates (n = 94), 39 underwent reconstruction and 54 were treated nonoperatively; for 1 athlete, the treatment type was not available. Athletes with closed growth plates were significantly more likely to undergo UCL-R than athletes with open growth plates (P = 0.02, Table 4). There were 4 athletes with open growth plates who did undergo UCL-R. We found no significant differences (P = 0.09) when assessing UCL injury location by treatment type. In addition, we found no significant differences (P = 0.79) in assessment of UCL injury severity (full vs partial) by treatment type. Whereas we included all UCL injuries related to baseball throwing, we excluded the intact UCL injury cases (n = 11) from the previous analysis as intact UCL injuries did not require surgical intervention in our study.

Table 2.

Physeal status and location of partial UCL injury based on advanced imaging

	Closed Growth Plates	Open Growth Plates	P value
Proximal	29	8	0.83
Distal	32	10
Combined a	15	3

UCL, ulnar collateral ligament.

^aCombined includes proximal-distal tears, proximal-midsubstance tears, and proximal-midsubstance-distal tears.

Table 3.

Physeal status and extent of UCL injury based on advanced imaging

	Closed Growth Plates	Open Growth Plates	P value
Complete rupture	11	0	0.03
UCL abnormality a	7	4

UCL, ulnar collateral ligament.

^aUCL abnormality defined as an intact ligament with inflammation and or bony edema at insertion site. ¹⁶

Table 4.

Physeal status and treatment modality ^a

	Reconstruction	Nonoperative	P value
Closed growth plates	39	54	0.02
Open growth plates	4	21

^aN = 118 because 1 patient was lost to follow-up.

For athletes who sustained a proximal FF injury (n = 11), 6 underwent UCL-R and 5 were treated nonoperatively. No significant differences were noted for athletes (n = 11) sustaining proximal FF injuries combined with a UCL injury (P = 0.17) for treatment type (Table 5). However, it should be noted that 3 out of the 6 UCL-R with FF also sustained medial epicondylar avulsion fractures. Finally, of the 5 athletes with concomitant FF injuries who were treated nonoperatively, 3 out of the 5 had a proximal tear injury of the UCL on advanced imaging.

Table 5.

Concomitant FF injury

	FF Injury	No FF Injury	P value
UCL-R	6	37	0.17
Nonoperative treatment	5	70

FF, flexor forearm; UCL, ulnar collateral ligament; UCL-R, UCL-reconstruction.

Discussion

Our first aim was to identify the number of UCL injuries that were treated with nonoperative versus operative management in our study population. A greater number of the athletes were treated nonoperatively (75 of 119; 63%). However, while no significance difference was detected for treatment type (UCL-R vs nonoperative management) with a mean age 17.2 ± 2.2 years for those in the UCL-R group versus mean age of 16.8 ± 2.6 in the conservative group (P = 0.14), it is important to contextually consider strength and power generated as one matures physically. Baseball throwing, in particular pitching, requires precise timing to efficiently generate mechanical energy through different body segments. Given the sheer volume of elbow varus torque generated with a baseball pitch, it is imperative that appropriate pitching and throwing mechanics are taught at an early age. If mechanics are not taught before puberty, once the physical maturation process begins an athlete will be able to generate greater power and subsequent torque on the elbow. ¹⁵ This is further elucidated by recent data indicating that 86% of total pitching energy is transferred through the elbow via trunk related motion.^2,3 These data suggest that pitching mechanics potentially play an important role in reducing elbow injury risk in baseball throwers. Furthermore, velocity is also a known risk factor for elbow injury in baseball players.^1,29 Thus, it is reasonable to conclude that older athletes are able to generate more power, velocity, and elbow valgus torque, which places them at greater and more significant risk of injury (eg, a complete rupture). Our data support this inference with older athletes sustaining UCL injuries requiring reconstructions more than younger athletes.

We assessed medial epicondylar physeal growth plate status and treatment modality and noted athletes with closed growth plates were significantly more likely to suffer a complete UCL tear as well as undergo a UCL-R than athletes with open growth plates. Our data reflect earlier finding that athletes of an older age require UCL-R more often than younger athletes. ³⁷ Younger players with open physes are typically not able to create the same level of power, force, and torque that a skeletally mature person can generate. ¹⁵ In fact, in our dataset, all athletes who sustained a complete UCL rupture had closed growth plates. However, 4 athletes who had open growth plates (ages 11, 11, 14, and 14) with partial UCL injuries did undergo UCL-R. Of these 4 patients, 3 attempted but failed nonoperative management (which included physical therapy) and the fourth proceeded directly to surgery; the location of this patient’s tear was distal whereas the previous 3 were proximal. These data reinforce and complement the principles of previously published research highlighting the importance of developing proper mechanics to potentially decrease the risk of injury in baseball players as they physically mature.^9,15 Our data are consistent with previous data that older athletes sustain more severe UCL injuries than younger throwers. ³⁷ However, it is important to remember that, as opposed to severe UCL injuries, medial epicondylar physeal injuries are more common in younger athletes. ³⁷ This is due, in part, to the epiphyses, which are 2 to 5 times weaker than the neighboring osseous tissue. In addition, the medial epicondylar epiphysis does not fuse until approximately 15 to 16 years of age, putting this aspect of the elbow at risk of osseous injury in overhead throwers. ¹⁸ When analyzing our dataset, 3 of 7 players sustained medial epicondylar avulsion fractures with concomitant FF injuries. Given that the origin of the UCL is the distal medial epicondyle, UCL-R may be necessary with associated avulsion fractures, ³¹ as was the case in our dataset for all 3 fractures. Newer data have indicated the utilization of an augmented internal brace to the UCL in addition to the UCL-R when there is an associated medial epicondylar avulsion fracture, in particular if chronic. ²⁷ It should be further emphasized that, in some instances, primary UCL repair has become a newer surgical technique that has substantially shorter rehabilitation and return-to-play time. An ideal candidate for this procedure instead of UCL-R is typically a younger athlete with avulsion type UCL injury (either proximal or distal) without further UCL involvement.^10,11,32

We further examined UCL injury location and treatment modality. Our dataset did not indicate a significant difference between treatment modality and location of UCL injury (distal, proximal, and/or combined). Data at the professional baseball level have revealed that nearly 82% of distal partial tears failed nonoperative management. ¹⁷ Previous data have indicated a greater likelihood of a distal partial UCL injury with a concomitant FF injury. ³⁸ As a result of these data, we included FF concomitant injury with UCL injury in our study. Emerging data have indicated that combined FF and UCL injuries are common, given the importance of the FF providing valgus stability in throwing athletes.^21,35,38 Further, the location of the UCL injury (distal) appears to have associations with a concomitant FF injury.^21,28 Moreover, there is some concern that FF injury may indicate that nonoperative treatment of distal UCL injuries is unlikely to be successful. ²¹ Research has suggested that biomechanical valgus stability, as well as hypovascularity of the distal UCL, may contribute to these findings as well.^4,17,28,35

Limitations

The retrospective design of the study is a significant limitation. Exact data for player position were not available and there was no longitudinal controlled follow-up. There was no standardized conservative management plan or surgical plan for the study. Due to the retrospective design of the study and the challenges involved in contacting patients from as far back as 2008, outcome measures were difficult to obtain consistently. Player position was not included in the study analyses since nearly all patients were pitchers, but some athletes may have played other positions in previous years. In addition, provider decision-making based upon open physes, clinical evaluations, and failure of initial conservative management are major limitations. Finally, similar to previous research, ³⁷ our dataset was based on evaluation of athletes at our institution. It is likely that injuries were assessed in other clinical settings in our region.

Conclusion

Nonprofessional older athletes with closed growth plates and throwing related UCL injuries in baseball were more likely to be treated with surgical intervention as opposed to nonoperative management in younger athletes. By continuing to increase our understanding of UCL injuries in throwing athletes, including tracking of treatment outcomes and associated characteristics, such as location and severity of UCL injury and physical maturity of the athlete, we will improve treatment algorithms and return-to-play guidelines in nonprofessional baseball players.

Strength of Recommendation Taxonomy Practical Recommendations

• Tracking of outcomes of throwing-related UCL injuries using consistent grading systems with advanced imaging (and/or ultrasonography) is recommended (strength of recommendation taxonomy [SORT] B).

• Furthering research in other throwing sports in addition to baseball (such as softball and javelin) is important to improve the treatment algorithms of all throwing-related athletes, not just male baseball players (SORT B).

• Long-term studies that track outcomes based on location and severity of throwing-related UCL injury, while taking into account physical maturity of the athlete, may improve treatment algorithms and return-to-play guidelines in nonprofessional baseball players (SORT C).