Ulnar Collateral Ligament Reconstruction: Where Do We Stand In 2021? Brandon J. Erickson, MD Section Chief, Shoulder & Elbow Surgery: Phelps Hospital Assistant Professor, Department of Orthopaedic Surgery Sidney Kimmel Medical College of Thomas Jefferson University Assistant Professor, Department of Orthopaedic Surgery Zucker School of Medicine, Hofstra University Assistant Team Physicians: Philadelphia Phillies Disclosures
• AOSSM, AAOS, ASES committee member
• Hospitality/education payments: Arthrex, Smith & Nephew, Linvatec, Stryker, DePuy Synthes
• Consulting: Arthrex Lineup
• Dines: UCL epidemiology, risk factors
• Dugas: UCL Repair in 2021: Which patients, technique, RTS and outcomes
• Schickendantz: UCLR in 2021: Which patients, technique, RTS and outcomes
• Ahmad: Sometimes it's more than the UCL: Concomitant procedures with UCL surgery
• Erickson: Discussion and case presentations Meet Our Faculty – Joshua Dines
• Undergrad: Dartmouth • Medical School: Cornell • Residency: HSS • Sports Fellowship: KJOC
• Current Practice: Hospital for Special Surgery
• Topic: UCL Epidemiology and Risk Factors
• Team Physician: • New York Mets Meet Our Faculty – Jeffrey Dugas
• Undergrad: North Carolina State • Medical School: Duke • Residency: HSS • Sports Fellowship: ASMI
• Current Practice: ASMI
• Topic: UCL Repair in 2021
• Team Physician (too many to list them all): • Troy Trojans • WWE • USA Cheer Meet Our Faculty – Mark Schickendantz
• Undergrad: ??? • Medical School: St. Louis University • Residency: Cleveland Clinic • Sports Fellowship: Steadman Hawkins
• Current Practice: Cleveland Clinic
• Topic: UCLR in 2021
• Team Physician: • Cleveland Indians Meet Our Faculty – Christopher Ahmad
• Undergrad: Columbia • Medical School: ??? • Residency: Columbia • Sports Fellowship: KJOC
• Current Practice: Columbia
• Topic: Sometimes it's more than the UCL
• Team Physician: • New York Yankees • Rockland Boulders Meet The Faculty – Brandon Erickson
• Undergrad: Notre Dame • Medical School: Tufts • Residency: Rush • Fellowship: HSS
• Current Practice: Rothman
• Assistant Team Physician: • Philadelphia Phillies Bringing It Home
• UCL injuries are on the rise
• UCLR is a good procedure with reliable outcomes
• While there are many surgical variables, most of these do not effect outcomes
• Players should be cautioned about RTS too quickly following UCLR Objectives
• Understand history and physical exam findings that are seen with UCL tears
• Understand basic anatomy and function of the UCL
• Understand the various treatment options for UCL injuries, and which patients would benefit from which treatment
• Understand the rehabilitation process following surgery for UCL tears 2013
• Created a database of all UCLR in MLB players from 1974 until 2013
• 179 MLB Pitchers underwent UCLR
• 83% RTS in MLB
• 97.2% RTS in MLB or minors
• No significant decline in performance upon RTS 2013
Tommy John Surgeries in MLB Pitchers by Year
35
30
25
20
15
10
5
Number of UCLR Performed UCLR of Number 0 1980 1985 1990 1995 2000 2005 2010 2015
Year of Surgery 2015
PearlDiver Database Study from 2007 – 2011
790 patients underwent UCLR 695 males, 95 females
Avg annual incidence: 3.96 per 100,000 for the overall population 22 per 100,000 for patients aged 15 to 19 years
Overall average annual growth was 4.2%.
Incidence of UCLR in 15- to 19-year-olds increased at an average rate of 9.12% per year (P = .009) 2015
P<0.001 Bottom Line…It’s A Problem Our Patient
17 y/o LHD M high school junior
Has been a pitcher all his life
No prior elbow injuries
L medial elbow pain started after a specific pitch Player History: Let’s Define Risk Factors 2011 201 6 • 28 males between 13-16 threw a simulated game
• Shoulder ROM was assessed before and after the game
• Velocity and accuracy were measured for every pitch, and every 15th pitch was videotaped from 2 views
• Quantitative and qualitative mechanics were measured from these videos
• Perceived fatigue and pain were assessed after each inning using a visual analog scale 201 6 • The model functioned well: • Pitchers became progressively more fatigued (0.3 → 3.5), had more pain (0.1 →1.6), and pitched with a lower velocity (73 mph → 71 mph) as pitch number increased (all significant)
• No upper extremity kinematics changed with fatigue
• Knee flexion angle at ball release significantly increased with increasing pitch number (49° → 53°)
• Hip to shoulder separation significantly increased with increasing pitch number (90% at pitch 15 to 40% at pitch 90) Erickson, B. J., Sgori, T., Chalmers, P. N., Vignona, P., Lesniak, M., Bush-Joseph, C. A., et al. (2016). The Impact of Fatigue on Baseball Pitching Mechanics in Adolescent Male Pitchers. Arthroscopy • 247 MLB Pitchers Underwent UCLR as of June 1, 2014
• State/country where MLB pitcher played Baseball was used to determine warm vs. cold
• Cold states were north of 33rd parallel; warm states were south
• Why the 33rd parallel? • Avg temperature in “warm weather” states was above freezing in January
2014 • 139 MLB Pitchers from warm weather areas
• 108 MLB Pitchers from cold weather areas
• A higher proportion of MLB pitchers undergoing UCLR are from warm weather areas p<.0001
2014 Pitchers from warm weather areas had UCLR one year earlier than cold weather pitchers
Pitchers from warm weather areas pitched significantly fewer MLB season prior to UCLR
2014 2014
• 505 examinations on 296 pitchers for 8 consecutive years (2008-2005) ➢ Measured pROM of throwing/non-throwing shoulder
• 49 elbow injuries and 8 elbow surgeries in 38 players ➢ Missed 2551 days because of this
• Pitchers w/ deficits of >5° in total rotation in their throwing shoulder had a 2.6 times greater risk for injury
• Pitchers w/ deficit of >5° in flexion of the throwing shoulder had a 2.8 times greater risk for injury
• In this study, GIRD was not correlated w/ injury • Purpose: determine factors predictive of UCLR among MLB pitchers
• Pitch velocity, number, and type (fastball, curveball, etc.) for every pitcher and game within MLB from 2007 to 2015
• 1327 pitchers included; 309 (26.8%) had undergone UCLR
• Peak pitch velocity was significantly higher among preinjury pitchers than control pitchers: 93.3 vs. 92.1 mph P<.001
• Same w/ avg pitch velocity: 87.8 vs. 86.9 mph P=.001
2016
2019 2010 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Fastball Velocity is INCREASING 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Percentage of Fastballs Thrown is DECREASING 2002
• Purpose: evaluate association between pitch counts, pitch types, and pitching mechanics and shoulder and elbow pain in young pitchers
• Followed 476 baseball pitchers (ages 9 to 14 years) for one season
• Authors collected data from pre- and postseason questionnaires, injury and performance interviews after each game, pitch count logs, and video analysis of pitching mechanics
• 50% experience shoulder or elbow pain during the season
• Significant association between the number of pitches thrown per game and during the season, and rate of elbow pain and shoulder pain How much of a difference in pitch counts leads to injury?
Variable History of injury No history of P injury Pitches/Game 64±21 54±22 <0.001 Pitches/Year 1978±1679 1408±1491 0.001 10 pitches per game 500 pitches per year Current Pitch Count Recommendations
Age Pitch Counts Rest 17-18 105/day 31-45 pitches = 1 day rest 46-60 pitches = 2 days rest 15-16 95/day 61-75 pitches = 3 days rest 76+ pitches = 4 days rest 13-14 95/day 21-35 pitches = 1 day rest 12-13 85/day 36-50 pitches = 2 days rest 51-65 pitches = 3 days rest 10-11 75/day 66+ pitches = 4 days rest 9-10 50/day Risk Factor Summary
• Pitching with higher velocity • High pitch counts • Pitching >100 innings per year • Pitching on consecutive days • Pitching for multiple teams • Pitching while fatigued • Geography (pitching while growing up in warmer climates) • Pitching with a loss of total arc of shoulder motion • Loss of hip rotation
We are still learning other risk factors Physical Exam ROM: 0°-145°, 80°/80°
TTP over sublime tubercle
No discernable increase in laxity of UCL compared to left elbow
Pain w/ Moving Valgus Stress Test, Milking Maneuver
Pain with arm bar and forced elbow extension
No ulnar nerve symptoms Other Diagnoses To Consider…
• Ulnar Collateral Ligament Injury
• Valgus Extension Overload
• Osteochondral Lesion
• Ulna or Medial Epicondyle Fracture
• Medial Epicondylitis/Little Leaguer’s Elbow
• Ulnar Neuropathy/Instability
• Flexor/Pronator Injury What Is The UCL?
Primary restraint to valgus force between 30°-120° of elbow flexion
Anatomy was described by Morrey in 1983
Recent work has expanded our understanding on UCL insertion What Is The UCL?
3 Bundles
Anterior Bundle Ant/Post Bands Posterior Bundle Transverse Bundle
Hypertrophy in MLB Pitchers 2019 • Cadaver study evaluating the contribution of the varying parts of the distal UCL to valgus stability of the elbow
• Dissected the UCL in 15 cadavers and sectioned the UCL in three different sections: proximal, middle, and distal thirds
• The middle and distal thirds of the UCL insertion on the ulna did not significantly contribute to gap resistance at 5 Nm of valgus load. The proximal third of the footprint is the primary resistor of valgus load 2019 2019 • Excellent elbow anatomic dissection study that found two tendinous septa: one between PT and FDS and one between FDS and FCU. Both are connected to the medial part of the brachialis tendon, deep aponeurosis of the FDS, and FCU to form the tendinous complex, which linked the ulnohumeral joint
• Determined the PT, FDS, FCU, and brachialis muscles work together and transmit the muscular power to the ulnohumeral joint via the tendinous complex Pitch Cycle Imaging X-Ray Findings Seen In Throwers What About If The Medial Epicondyle Is Off? Contralateral Elbow Very Different Discussion And Treatment… 2018
• 9 fellowship-trained specialists from 7 institutions independently completed 4 surveys consisting of 60 elbow MRI scans with UCL tears using a newly proposed 6- stage classification system
• Intra- and interobserver reliability demonstrated near perfect and substantial agreement respectively Sometimes It Looks Like This… Diagnosis Partial Thickness Distal Ulnar Collateral Ligament Tear Treatment Options
• Non Operative: • Rest, rehabilitation, return to throwing program • Addition of biologic augmentation ?
• Operative: • UCL Repair with Internal Brace • UCL Reconstruction 2017
• Purpose: survey ASES members to assess current trends related to the comprehensive treatment of athletes presenting with UCL injury via 7 clinical scenarios
• 159 members responded (24% of the active membership)
• 65 respondents (40.9%) reported >15 years of clinical experience
• Of the 7 case scenarios presented, a consensus was reached to indicate the patient for surgery in 4 cases Does Imaging Help Dictate Treatment? 2017
• 32 professional baseball pitchers w/ UCL tears underwent trial of non-op treatment • Avg age: 22.3 years
• 66% (21/32) successfully RTS without UCLR while 34% failed and required subsequent UCLR
• Likelihood of failing nonoperative management was 12.40 times greater (P = .020) with a distal tear
• 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 combining high-grade tear and distal location, 88% (7/8) failed non-op management 2018
• Assess relationship of MRI classification system for UCL tears and nonoperative vs. operative management
• 85 patients were included w/ minimum 1 year follow up
• 51 patients underwent surgery
• 29 patients completed nonoperative management 2018 2018
• In baseball players • 59% of the proximal tears were treated nonoperatively • 97% of the distal tears were treated operatively • 100% of the proximal partial-thickness tears were treated non-operatively • 100% of the distal complete tears were treated operatively, respectively
• Patients with distal (P < .0001) and complete (P = .004) tears were more likely to undergo surgery 2016
• 44 baseball players (6 pro, 14 college, 24 high school) treated with PRP for partial UCL tears • 16 patients had 1 injection, 6 had 2, and 22 had 3 • Mean age was 17.3 years (range, 16-28 years) • All patients were available for follow-up after injection (mean, 11 months)
• 15 (34%) had an excellent outcome, 17 had a good outcome, 2 had a fair outcome, and 10 had a poor outcome • After injection, 4 (67%) of the 6 professional players returned to professional play. 2013
• 34 patients w/ partial thickness UCL tears
• Avg age 18 years old
• All received PRP followed by PT and throwing program
• 70 week avg follow up
• 88% returned to same level of play • Avg time to RTP was 12 weeks
• One player underwent UCLR 2019 • Included 544 professional baseball players treated non-op for UCL tears from 2011 – 2015 • 133 received PRP injections and 411 did not
• Nonoperative treatment of UCL injuries resulted in an overall 54% RTS rate
• Players who received PRP took longer to return to throwing (P < .001) and RTS (P = .012)
• Survival analysis did not reveal significant differences between groups over time
• The use of PRP, MRI grade, and tear location did not predict RTP or progression to surgery Our Patient
• Shut down from throwing for 6 weeks
• Began a throwing progression program once pain free
• Started basketball and played without issue
• Tried to throw again and had continued pain at sublime tubercle
• No ulnar nerve symptoms
• Elected to undergo UCL Repair w/ Internal Brace and elbow arthroscopy to debride posteromedial osteophyte Posteromedial Impingement Posteromedial Impingement Debridement Expose the Flexor Pronator Fascia Avoid The MABCN Make A Split In The Flexor Pronator Fascia Bluntly Dissect Down To Native UCL Make A Split In The Native UCL…See The Gapping Place The First Anchor To Repair The Tear Place The Second Anchor Check ROM 2015
REPAIR MODIFIED JOBE UCLR
RESITANCE TO GAPPING 0.35±0.16 mm 0.53±0.23 mm ✓ 2015
REPAIR MODIFIED JOBE UCLR
No statistical significant differences found between: -Max torque at failure -Torsional stiffness -Gap formation during failure 2015
REPAIR MODIFIED JOBE UCLR
*Augmented UCL Repair replicates the time-zero failure strength of traditional UCLR, and appears more resistant to gapping at low cyclic loads* 2019
• Included 111 overhead athletes
• All failed nonoperative treatment with imaging suggestive of a complete or partial UCL avulsion from the sublime tubercle or medial epicondyle, with good quality ligament tissue
• The final decision on UCL repair vs. reconstruction was determined intraoperatively
• 92%(102/111) RTS at the same or higher level at a mean time of 6.7 months
• These patients had a mean KJOC score of 88.2 at final follow-up What About UCLR? What Does UCLR Involve?
• Harvesting a graft – commonly ipsilateral palmaris longus or hamstring
• Technique – Docking vs. ASMI most common
• Ulnar nerve – Transpose or leave alone? 2010
743 patients w/ UCL repair (10) or reconstruction (733)
Avg age 21.5 years old
38.4 month avg follow up
Return to Play: • 83% returned to same or higher level of play after recon • 70% returned to same or higher level of play after repair 2016 2016 2017
When MLB team physicians were surveyed, significantly more harvest the hamstring from the landing leg (72.5%) than the drive leg (27.5%) (p=0.007) Are they correct???? 2017 • Prospective controlled laboratory study
• Study was powered to detect a 50% change in semitendinosus activation • Needed 15 subjects; 16 completed the study
• Inclusion criteria: • Pitchers age 16-21 • Collegiate and High School both included • No history of hamstring injuries • Currently pitching without pain 2017
• On the within pitcher analysis, 14 out of 16 pitchers (88%) had significantly more sum semimembranosus/semitendinosus activity in the drive leg than the landing leg (p=0.043)
• On a within pitcher analysis, 11 out of 16 pitchers had significantly more time above 20% MVIC in the semimembranosus/semitendinosus in the drive leg than the landing leg (p=0.043)
2019
• Included all players from 2010 - 2015 who underwent UCLR with hamstring autograft
• Players with hamstring UCLR were compared with a matched control group of players who underwent UCLR with palmaris autograft
• 195 players underwent UCLR with hamstring autograft
• No differences in RTS rates or timing to RTS were found between the hamstring and palmaris groups 2019
• Significantly more subsequent injuries to the lower extremity were seen in the hamstring group versus the palmaris group (25 vs 13, respectively) (P = .040)
• More subsequent injuries to the upper extremity were found in the palmaris group versus the hamstring group (73 vs 55, respectively), although this difference was not significant (P = .052)
• No significant difference in WAR, WHIP, or FIP existed between groups postoperatively. 2019
• Included all players from 2010 - 2015 who underwent UCLR with hamstring autograft
• Outcomes for UCLR with hamstring autograft harvested from the drive leg were compared with UCLR with the graft harvested from the landing leg
• 191 players underwent UCLR with hamstring autograft • Drive leg, n = 58, 30% • Landing leg, n = 133, 70% 2019
• No differences in subsequent ipsilateral or contralateral hamstring injuries occurred between players who underwent UCLR with hamstring autograft from the drive leg or the landing leg (P = .999 and P = .460, respectively)
• No difference in overall upper or lower extremity injury rates existed between groups (all P >.05), and no difference in performance metrics existed between groups upon RTS Slide Courtesy of Kevin Wilk Slide Courtesy of Kevin Wilk Slide Courtesy of Kevin Wilk Slide Courtesy of Kevin Wilk Slide Courtesy of Kevin Wilk Slide Courtesy of Kevin Wilk Slide Courtesy of Kevin Wilk Slide Courtesy of Kevin Wilk My Post-Op Protocol My Post-Op Protocol When Should We Allow Players to RTS? 2017
• 569 pitchers underwent UCLR and were included • Both minor and major league pitchers included • Average age 24.8 +/- 4.1 years
• Average time to RTS following UCLR: • Any professional level: 479 +/- 365 days or 15.3 +/- 12.0 months • Same professional level as prior to surgery: 540 +/- 396 days or 17.3 +/- 13.0 months
• No difference in length of time to RTS between pitchers who underwent revision UCLR and those who didn’t 2017 2020
• Included all professional position players who underwent UCLR between 2010 and 2018
• Time to batting milestones and batting performance after UCLR was analyzed
• 141 UCLRs (96% performed on the dominant arm) in 137 position players were included
• 86% were Minor League players
• Of the surgeries, 76% were on the trail/back arm in regards to hitting 2020
• While 91% of players were able to return to some form of hitting, there was a progressive gradual decrease in the percent returning to each subsequent milestone during the rehabilitation process such that 77% were able to return to hitting in a real game and 75% were able to return to fielding in a real game
• Players generally saw a decrease in their utilization, with fewer at bats (P<.001) translating into fewer hits (P<.001) and runs (P<.001)
• On average, players hit in a real game 20 days before fielding in a real game. 2020
Are There Limits We Need to Set Once Players RTS? RTS 2016
• 154 pitchers were included • MLB pitchers who pitched 1 full season after UCLR
• 135 pitchers did not require revision UCLR
• 19 underwent revision UCLR RTS 2016 On The Horizon Thank You References
• Ahmad CS, Conway JE. Elbow arthroscopy: valgus extension overload. Instr Course Lect. 2011;60:191-197. • Ahmad CS, ElAttrache NS. Valgus extension overload syndrome and stress injury of the olecranon. Clin Sports Med. 2004;23(4):665-676, x. • Blake JJ, Block JJ, Hannah GA, Kan JH. Unusual stress fracture in an adolescent baseball pitcher affecting the trochlear groove of the olecranon. Pediatr Radiol. 2008;38(7):788-790. • Cain EL, Jr., Andrews JR, Dugas JR, et al. Outcome of ulnar collateral ligament reconstruction of the elbow in 1281 athletes: Results in 743 athletes with minimum 2-year follow-up. Am J Sports Med. 2010;38(12):2426-2434. • Cain EL, Jr., Dugas JR, Wolf RS, Andrews JR. Elbow injuries in throwing athletes: a current concepts review. Am J Sports Med. 2003;31(4):621-635. • Erickson BJ, Bach BR, Jr., Cohen MS, et al. Ulnar Collateral Ligament Reconstruction: The Rush Experience. Orthop J Sports Med. 2016;4(1):2325967115626876. • Frank RM, Lenart BA, Cohen MS. Olecranon physeal nonunion in the adolescent athlete: identification of two patterns. J Shoulder Elbow Surg. 2017;26(6):1044-1051. • Fujioka H, Tsunemi K, Takagi Y, Tanaka J. Treatment of stress fracture of the olecranon in throwing athletes with internal fixation through a small incision. Sports Med Arthrosc Rehabil Ther Technol. 2012;4(1):49. • Furushima K, Itoh Y, Iwabu S, Yamamoto Y, Koga R, Shimizu M. Classification of Olecranon Stress Fractures in Baseball Players. Am J Sports Med. 2014. • Jones TB, Karenz AR, Weinhold PS, Dahners LE. Transcortical screw fixation of the olecranon shows equivalent strength and improved stability compared with tension band fixation. J Orthop Trauma. 2014;28(3):137-142. • Kovach J, 2nd, Baker BE, Mosher JF. Fracture separation of the olecranon ossification center in adults. Am J Sports Med. 1985;13(2):105-111. • Maffulli N, Chan D, Aldridge MJ. Overuse injuries of the olecranon in young gymnasts. J Bone Joint Surg Br. 1992;74(2):305-308. • Nuber GW, Diment MT. Olecranon stress fractures in throwers. A report of two cases and a review of the literature. Clin Orthop Relat Res. 1992(278):58-61. • Paci JM, Dugas JR, Guy JA, et al. Cannulated screw fixation of refractory olecranon stress fractures with and without associated injuries allows a return to baseball. Am J Sports Med. 2013;41(2):306-312. • Rettig AC, Wurth TR, Mieling P. Nonunion of olecranon stress fractures in adolescent baseball pitchers: a case series of 5 athletes. Am J Sports Med. 2006;34(4):653-656. • Cain EL, Jr., Andrews JR, Dugas JR, et al. Outcome of ulnar collateral ligament reconstruction of the elbow in 1281 athletes: Results in 743 athletes with minimum 2-year follow-up. Am J Sports Med. 2010;38(12):2426-2434. • Dines JS, Yocum LA, Frank JB, ElAttrache NS, Gambardella RA, Jobe FW. Revision surgery for failed elbow medial collateral ligament reconstruction. Am • Erickson BJ, Bach BR, Jr., Cohen MS, et al. Ulnar Collateral Ligament Reconstruction: The Rush Experience. Orthop J Sports Med. 2016;4(1):2325967115626876. • Erickson BJ, Chalmers PN, Bush-Joseph CA, Verma NN, Romeo AA. Ulnar Collateral Ligament Reconstruction of the Elbow: A Systematic Review of the Literature. Orthop J Sports Med. 2015;3(12):2325967115618914. • Erickson BJ, Gupta AK, Harris JD, et al. Rate of Return to Pitching and Performance After Tommy John Surgery in Major League Baseball Pitchers. Am J Sports Med. 2013. • Erickson BJ, Harris JD, Chalmers PN, et al. Ulnar Collateral Ligament Reconstruction: Anatomy, Indications, Techniques, and Outcomes. Sports Health. 2015;7(6):511-517. • 1Erickson BJ, Nwachukwu BU, Rosas S, et al. Trends in Medial Ulnar Collateral Ligament Reconstruction in the United States: A Retrospective Review of a Large Private-Payer Database From 2007 to 2011. Am J Sports Med. 2015;43(7):1770-1774. • 1Erickson BJ, Romeo AA. The Ulnar Collateral Ligament Injury: Evaluation and Treatment. J Bone Joint Surg Am. 2017;99(1):76-86. • Fleisig GS, Andrews JR, Dillman CJ, Escamilla RF. Kinetics of baseball pitching with implications about injury mechanisms. Am J Sports Med. 1995;23(2):233-239. • Fleisig GS, Barrentine SW, Escamilla RF, Andrews JR. Biomechanics of overhand throwing with implications for injuries. Sports Med. 1996;21(6):421-437. • Frostick SP, Mohammad M, Ritchie DA. Sport injuries of the elbow. Br J Sports Med. 1999;33(5):301-311. • Ciccotti MG, Atanda A, Jr., Nazarian LN, Dodson CC, Holmes L, Cohen SB. Stress sonography of the ulnar collateral ligament of the elbow in professional baseball pitchers: a 10-year study. The American journal of sports medicine. 2014;42(3):544-51. • Magee T. Accuracy of 3-T MR arthrography versus conventional 3-T MRI of elbow tendons and ligaments compared with surgery. AJR American journal of roentgenology. 2015;204(1):W70-5. • Podesta L, Crow SA, Volkmer D, Bert T, Yocum LA. Treatment of partial ulnar collateral ligament tears in the elbow with platelet-rich plasma. The American journal of sports medicine. 2013;41(7):1689-94. • Rettig AC, Sherrill C, Snead DS, Mendler JC, Mieling P. Nonoperative treatment of ulnar collateral ligament injuries in throwing athletes. The American journal of sports medicine. 2001;29(1):15-7. • Moraes VY, Lenza M, Tamaoki MJ, Faloppa F, Belloti JC. Platelet-rich therapies for musculoskeletal soft tissue injuries. The Cochrane database of systematic reviews. 2014;4:CD010071. • Walsh WR, Wiggins ME, Fadale PD, Ehrlich MG. Effects of a delayed steroid injection on ligament healing using a rabbit medial collateral ligament model. Biomaterials. 1995;16(12):905-10. • Cohen SB, Woods DP, Siegler S, Dodson CC, Namani R, Ciccotti MG. Biomechanical comparison of graft fixation at 30 degrees and 90 degrees of elbow flexion for ulnar collateral ligament reconstruction by the docking technique. Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons [et al]. 2015;24(2):265-72.