Evaluation of Differences in Imaging Findings on Stress-MRI in Throwing Athletes With and Without a History of Ulnar Collateral Ligament Reconstruction

Abstract

Background:

Ulnar collateral ligament (UCL) reconstruction (UCLR) of the elbow is common in throwing athletes and reliably allows return to play. The literature supports stress imaging of the elbow to evaluate the integrity of the UCL. The FEVER view (flexion, external rotation, and valgus stress) was developed to improve the diagnostic accuracy of UCL pathology in throwing athletes with stress magnetic resonance imaging (MRI).

Hypothesis/Purpose:

The present study sought to evaluate FEVER MRI imaging findings, primarily ulnohumeral joint space widening, in patients with and without a history of UCLR. The authors hypothesize that on the FEVER view there would be no difference in joint space widening between pitchers with a history of UCLR and those without.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Pitchers in 2 Major League Baseball franchises who underwent preseason screening MRIs with standard and FEVER views were included. All images were read by 2 fellowship-trained musculoskeletal radiologists. Findings included gross UCL appearance, UCL edema, location of edema, type of signal, grade of injury, ligament retraction, and amount of ulnar-sided joint space opening (absolute opening, the joint space widening in the FEVER stress view; relative opening, the difference between joint space widening in the FEVER view and standard view joint space widening). Time from surgery was evaluated for impact on imaging findings.

Results:

There was a statistically significant increase in absolute medial-sided joint space opening in players with a history of UCLR (n = 18; mean, 4.5 ± 3.4 years between UCLR and MRI) versus no UCLR (n = 76) (4.3 vs 3.8 mm; P = .04) and increased grade of UCL signal (P = .034) in patients with a history of UCLR. There was no difference in the other imaging parameters, including relative joint space opening (2.2 vs 1.9 mm; P = 0.11). Time from surgery was not associated with any outcome variables.

Conclusion:

Valgus stress MRI (the FEVER view) showed a slight, but significant increase in absolute joint space opening after UCLR and an increased grade of intrasubstance UCL signal. However, there was no difference in relative joint space opening, and the clinical significance of these findings is unclear and warrants further study.

Keywords

baseball stress imaging of elbow throwing athletes ulnar collateral ligament

Injuries to the ulnar collateral ligament (UCL) followed by surgical reconstruction are increasingly common in both Major and Minor League professional baseball players.^1,10 Pitchers have a higher incidence of UCL injuries than position players, given the biomechanics of throwing that deliver a large amount of valgus stress to the elbow during a high-velocity pitch.^8,11 Studies have found that over a quarter of Major League Baseball (MLB) pitchers have a history of UCL reconstruction surgery (UCLR), with UCL tears being the most common cause of season-ending injuries within the league.^2,10 UCLR is proven to be an effective surgery with 80% of MLB pitchers returning to their same level of play after reconstruction.¹

Diagnosis of UCL injury consists of clinical examination findings, such as medial pain with valgus stress, followed by imaging with radiographs, magnetic resonance (MR) arthrography, magnetic resonance imaging (MRI), or ultrasound. MRI has been established as the gold standard for advanced imaging and diagnosis.^3,15 MRI findings consistent with UCL tears include focal or diffuse increased T2 signal, ligament thinning, retraction, and partial or complete fiber discontinuity of the UCL. While the use of direct and indirect MR arthrography for UCL injuries has declined recently, previous studies have shown a small increase in sensitivity and specificity for pre- and postoperative UCL evaluation, particularly for partial thickness tears.^13,19 Given the continued challenge in accurately understanding UCL injuries and competence, there has been continued interest in improving imaging techniques.

Given previous evidence for the utility of stress views using modalities, such as radiography and ultrasound,^4,17,18 the Flexed Elbow Valgus External Rotation (FEVER) view was developed by Lund et al¹² as a stress-view MRI sequence. The FEVER view applies reproducible valgus stress across the ulnohumeral joint, with the accuracy and heightened soft-tissue resolution of MRI.¹² The FEVER view has shown greater inter-reader agreement (intraclass correlation coefficient, 0.92 vs 0.54) for mean joint space widening, and overall radiologist reader confidence in the ability to measure signal intensity, grade of injury, and retraction, and overall classification as abnormal versus normal, compared with the standard view.¹² Additionally, patients with and without a history of UCLR reported minimal pain during imaging, making the technique a promising addition to the evaluation of MLB pitchers’ musculoskeletal health.¹² Figure 1 demonstrates an example of standard and FEVER MRI views on a player with a history of UCLR.

Figure 1.

23-year-old right-handed professional baseball pitcher, 3 years status after palmaris longus UCL autograft reconstruction. (A) Standard COR PD/T2FS (TR = 4500/TE = 55) with 2.1-mm subchondral bone-bone ulnohumeral joint space (green line), small indistinct signal proximal graft (arrow), and normal linear fluid between sublime tubercle and ulnar attachment (arrowhead). (B) Scout localizer for standard 90° sagittal PD/T2FS COR (green lines) with elbow in extension and arm overhead “superman” position. (C) FEVER COR PD/T2FS (TR = 4500/TE = 55) with 4.2-mm subchondral bone-bone ulnohumeral joint space (green line), small indistinct signal proximal graft (arrow), and absent fluid between sublime tubercle and ulnar attachment (arrowhead). (D) Scout localizer sagittal for standard PD/T2FS COR (A) with elbow in FEVER position showing a 30° angle along the anterior bundle UCL (green lines). COR, coronal; FEVER, fast echo with variable echo train; PD/T2FS, proton density/T2 fat-suppressed; TE, echo time; TR, repetition time; UCL, ulnar collateral ligament.

Methods

Study Population

This was a retrospective cohort study of all pitchers in 2 MLB organizations. Pitchers who consented to participate during their preseason screening in 2019 and 2020 (n = 94) were included and underwent standard and FEVER MRI. The imaging protocol has previously been described by Lund et al¹² and Patel et al.¹⁶ FEVER view MRI imaging was obtained with the patient in the lateral decubitus position lying on the throwing arm (Figure 2). MRI was performed with a 3T system (Mangetom Vida, Siemens Healthineers) with sequences in 2- to 3-mm slice intervals with a 0.3-mm interslice gap.^12,16 Standard sequences (non-FEVER view) were performed with a 16-channel elbow flex coil with the arm in an overhead “superman” position. MRI sequencing included coronal T1-weighted (TR/TE, 600-700/10), fat-saturated (FS) proton density-weighted (PDW) (repetition time [TR]/echo time [TE], 3000/40-50), FS T2-weighted (TR/TE, 4000/80-120) imaging, with axial T1-weighted and FS PDW imaging, and sagittal T1-weighted and FS T2-weighted imaging. For the FEVER-view, imaging was performed with the same MRI and coil.^12,16 The affected shoulder was placed in a flexed position, with the shoulder and elbow both flexed to 90°, palm up. Two foam pads and a sandbag elevated the elbow 4 inches from the table, with 2 sandbags placed on the distal forearm, adding 7.6 lb (3.4 kg) to the total weight to create valgus stress. An oblique coronal FS PDW sequence (TR/TE, 3000/40-50) with 2-mm slice intervals with no interslice gap was obtained of the UCL in an oblique angle of 35°, approximating the anterior bundle of the UCL.^12-16

Figure 2.

Flexed elbow valgus external rotation (FEVER) view patient positioning. The volunteer was placed in the lateral decubitus position with the elbow elevated. Sandbags are used to create valgus stress.

Institutional review board approval was obtained (TUNIRB000070), and players provided written informed consent before participation. All players with preseason imaging, paid for by their respective franchises, were included. Exclusion criteria included position players and those who did not consent to the FEVER view. Pitchers were separated into 2 cohorts: those with a history of UCLR (UCLR) and those without (non-UCLR).

Data Acquisition

All images were read by 2 fellowship-trained musculoskeletal radiologists (P.L., M.S.), and the mean of these 2 readings was utilized with readings sensitive to 0.1 mm on the Picture Archiving and Communication System software. Findings included gross appearance of UCL, UCL edema, location of edema (if applicable), type of signal present (low, intermediate, high), grade of injury (1-5, with 1 being the lowest), presence of UCL retraction, and amount of absolute and relative ulnar-sided joint space opening (absolute opening defined as the joint space widening in the FEVER stress view, and relative opening the difference between the FEVER view minus joint space widening in the standard view). The grading system has previously been described in the literature by Lund et al¹² in the original description of the FEVER view.¹² The date of surgery was also obtained from records for pitchers who underwent previous UCLR to document the time between current imaging and previous surgery to assess for differences in outcomes based on time from surgery. Of the 18 pitchers in the UCLR group, 1 did not have a surgery date and was excluded from the time from surgery analysis.

Statistical Analysis

Statistical analysis consisted of 2-sample t tests for quantitative variables and chi-square tests for qualitative variables to compare UCLR and no UCLR cohorts. Linear regression was used to calculate differences between joint space opening and time from surgery. P < .05 were considered significant.

Results

A total of 94 pitchers from 2 MLB organizations were included, 18 with a history of UCLR and 76 without any prior UCL surgery. The mean time from UCLR was 4.5 ± 3.4 years (range, 1-11 years). The mean age was 25.6 years (range, 20-38 years), and the UCLR group had a higher mean age (28.9 [20-38] vs 24.8 [20-36]; P = .001).

FEVER view MRI findings demonstrated a statistically significant increase in the UCLR group versus the non-UCLR group for absolute joint space opening, but not relative joint space opening (4.3 vs 3.8 mm; P = .04; 2.2 vs 1.9 mm; P = 0.11, respectively) (Table 1).

Table 1

Comparison of Joint Space Opening Between Pitchers With Prior UCLR and No UCLR With 2-Sample T Tests ^a

	Overall	UCLR	No UCLR	P
Age, years	25.6 (20-38)	28.9 (20-38)	24.8 (20-36)	.001
Absolute opening, mm	3.9 (2.1-6.8)	4.3 (3.3-6.1)	3.8 (2.1-6.8)	.04
Relative opening, mm	2 (0.55-5.1)	2.2 (1.4-4.35)	1.9 (0.55-5.1)	.11

Data are presented as mean (range). UCLR, ulnar collateral ligament reconstruction.

With respect to MRI findings, there were no significant differences in ligament retraction, edema, location, signal grade, or injury type (Table 2). There was no significant relationship between time since surgery and absolute and relative joint space opening (Table 3). Also, 0.5% of the variability in absolute opening and 2.1% of the variability in relative opening were explained by time since surgery.

Table 2

Comparison of FEVER View MRI Findings Between Pitchers With UCLR and No UCLR With Chi-Square Tests ^a

		UCLR	No UCLR	P
Retraction	Yes	1	7	.52
Retraction	No	17	69	.52
Edema	Yes	4	17	.63
Edema	No	14	59	.63
Location	Proximal	10	32	.84
	Distal	3	17
	Both	1	8
	n/a	4	19
Type	L	0	1	.20
	Int	3	29
	H	11	27
	n/a	4	19
Grade	0	4	19	.40
	1	2	24
	2	3	9
	3	5	11
	4	3	10
	5	1	3
Appearance	Normal	4	19	.54
Appearance	Abnormal	14	57	.54
Edema	Yes	4	17	.63
Edema	No	14	59	.63

MRI, magnetic resonance imaging; UCLR, ulnar collateral ligament reconstruction.

Table 3

Absolute and Relative Joint Space Opening Compared With Time From Surgery in UCLR Cohort (n = 17) ^a

	R ²	Coefficient (SE)	95% CI	P
Absolute opening	0.005	0.019 (0.07)	[–0.13 to 0.17]	.79
Relative opening	0.021	0.037 (0.06)	[–0.10 to 0.18]	.58

UCLR, ulnar collateral ligament reconstruction.

Discussion

In the present study, we found that MLB pitchers with a history of UCLR demonstrated an increased absolute joint space widening (4.3 vs 3.8 mm; P = .04) but no difference in relative joint space widening (2.2 vs 1.9 mm; P = .11) compared with those without a history of UCLR; this difference was ≤0.5 mm for both measures. There were no significant differences in any other imaging parameters, including grade of UCL signal, edema, retraction, location, and type. There was no relationship between the time from surgery and any of the imaging parameters.

While several studies evaluate risk factors for UCL injury, there are limited imaging data describing the findings and changes that occur in patients after UCLR. One study compared stress ultrasound findings with a moving valgus stress arc and found that professional pitchers with a history of UCLR at least 18 months before testing had less gapping and a thicker ligament than those without UCLR.⁹ Another study evaluated patients (only 23% [n = 6] of whom were overhead athletes) who underwent stress ultrasound at a mean of 3 years after UCLR and found increased medial laxity, although this was not specifically quantified.¹⁴ These findings are similar to the present study, which shows slightly increased relative and absolute joint space in patients with a history of UCLR. However, the lack of concrete measurements makes it difficult to directly compare, and differing patient populations could contribute to differences between the 2 studies above and the present study. In contrast, a more recent study compared 8 MLB pitchers who had undergone UCLR with 8 matched controls and found that at a mean 2-year follow-up, there were no differences in resting joint space, stressed joint space, or laxity on stress ultrasound.⁷

There are conflicting data on the impact of stress-imaging findings on the risk of UCL injury among pitchers. Shanley et al¹⁸ showed that absolute opening of the joint >5.6 mm during stress ultrasound had a 6 times higher chance of subsequent UCL injury; they also found a statistically significant difference in the absolute ulnar-sided joint space between patients who injured their UCL and those who did not: 6.5 versus 5.3 mm, respectively. In contrast, Hanna et al⁷ evaluated pitchers who underwent preseason stress ultrasounds of their dominant and nondominant arms and noted that increased resting joint space relative to the nondominant arm and hypoechoic foci were correlated with risk of injury; however, ligament thickness, joint space opening at rest, and relative joint space opening with stress were not different between injured and uninjured players.⁶ A previous study evaluated a cohort of pitchers who underwent FEVER MRI for risk of injury, and found no correlation between absolute and relative joint space opening with subsequent injury. However, increased joint space was associated with decreased innings pitched.¹⁶

When specifically considering imaging findings and performance metrics, Gutierrez et al⁵ evaluated 26 asymptomatic MLB pitchers and found no specific MRI findings that were predictive of being on the disabled list for the following season or number of innings pitched, including UCL remodeling, partial UCL tears, ossification at the sublime tubercle, posteromedial articular cartilage loss, insertional triceps tendinitis, common extensor and/or flexor origin degeneration, and joint effusion.⁵ While performance metrics were not addressed in the present study, this presents a future question for investigation: whether FEVER view measurements may better correlate with performance metrics compared with standard MRI views.

To our knowledge, this is the first study to compare MRI stress-view findings between players with no prior UCLR and those with a prior UCLR, and to examine their correlation with time since surgery. The UCLR players also showed increased absolute joint space opening but decreased intrasubstance edema compared with those without. We found no association between time since surgery and joint space opening, or with any other imaging parameters, suggesting no significant impact of time since reconstruction. However, this was limited by sample size. While the FEVER view is growing in utilization, the relationship between stress-imaging findings on MRI, the importance of these specific measurements, and correlation with time since surgery is not well understood, and further study is warranted.

The authors believe that relative joint space opening will be an important metric, as it demonstrates the ability of the UCL under stress to prevent laxity in the joint. At present, however, it is unclear what threshold of laxity would be defined as normal, adaptive, or pathological on the FEVER view.

Limitations

The present study does have limitations. While we did not find many significant differences in imaging measures between UCLR and no UCLR cohorts, this study was limited to professional pitchers. It may not be generalizable to other throwing sports, other levels of baseball, positions other than pitcher, or players who underwent repairs or internal brace surgeries, which were excluded. Additionally, we did not have baseline data on pre-UCLR baseline imaging findings for the included pitchers. We were unable to account for the differences that may have existed both between players and for each player's imaging findings pre- and post-UCLR. Regarding time from surgery, our sample size was small, also limiting statistical analysis. Another limitation was the radiologists not being blinded to UCLR given postsurgical findings and hardware seen on MRI.

As the FEVER view becomes more prevalent, future studies should seek to understand the correlation between MRI findings and performance metrics, as well as stress MRI values in identified UCL graft injuries. Additionally, it remains to be determined how these imaging findings change over time after UCLR or how findings vary after revision UCLR. Therefore, comparison of pre- and post-UCLR within the same player will have significant utility in future investigations.

Conclusion

Valgus stress MRI (the FEVER view) showed a significant increase in absolute and joint space opening after UCLR and increased grade of intrasubstance UCL signal; however, there was no difference in relative joint space opening or correlation with time from surgery, yet the clinical significance of these findings is unclear and warrants further study.

Footnotes

Final revision submitted April 16, 2026; accepted April 19, 2026.

One or more of the authors has declared the following potential conflict of interest or source of funding: E.L. is a consultant for Arthrex. No internal or external funding was utilized for this project. Institutional review board approval was obtained from Tuoro University Institutional Review Board (Protocol No.: TUNIRB000070).

ORCID iDs

Midhat Patel

Kendall Schwartz

Evan Lederman

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