Little League Shoulder

Little League Shoulder (Proximal Humeral Epiphysiolysis) is an overuse injury affecting the proximal humeral growth plate in skeletally immature throwing athletes.

Pathophysiology:

• Essentially a Salter-Harris Type I stress fracture of the proximal humerus physis
• Occurs due to repetitive rotational shear and distraction forces
• The physis (growth plate) is the "weak link" in the kinetic chain of the young athlete
• The proximal humerus contributes 80% of longitudinal growth of the arm
• Rapid growth spurts increase susceptibility as the physis widens and weakens

Epidemiology (largest series, Heyworth et al. 2016, n=95):

• Age: mean 13.1 years (range 8-16); skeletally immature with an open proximal humeral physis.
• Gender: strongly male-predominant (93 of 95 patients male) but not exclusive to males.
• Sport: 97% baseball players (86% pitchers, 8% catchers); ~3% tennis players. Reported in other overhead athletes (volleyball, cricket).
• Associated findings: glenohumeral internal rotation deficit (GIRD) in ~30%; concomitant elbow pain in ~13%.
• Trend: diagnosed with increasing frequency, attributed to early sport specialisation and year-round play (Ina et al. 2026; Heyworth et al. 2016).
• Mechanism: repetitive overhead throwing generating high rotational torque at the physis (Sabick et al. 2005).

Proximal Humerus Development:

• Ossification centers:
  • Head (appears 6 months)
  • Greater Tuberosity (appears 3 years)
  • Lesser Tuberosity (appears 5 years)
• Coalescence: Centers merge at age 5-7 to form single epiphysis
• Physeal Closure: Typically closes at age 14-17 (females earlier) or 16-19 (males)
• Contributes 80% of humeral length

Mechanics of Injury:

• Late Cocking Phase: Maximal external rotation places rotational shear stress across the physis.
• Deceleration Phase: Distraction forces pull the epiphysis.
• The physis is weaker against shear and tension than compression.
• Repetitive microtrauma leads to widening of the hypertrophic zone of the physis, failure of calcification, and eventual stress fracture.

Blood Supply Considerations:

• The proximal humeral epiphysis is supplied by the arcuate artery (ascending branch of the Anterior Humeral Circumflex Artery).
• The physis acts as a barrier to blood flow from the metaphysis.
• Although damage to the physis can theoretically disrupt supply, avascular necrosis (AVN) is extremely rare in Little League Shoulder because the fracture is usually Type I (slipped) without significant displacement or vessel disruption.

Adaptive Changes (Humeral Retrotorsion):

• Throwers normally develop increased humeral retroversion (bony adaptation).
• The proximal humerus "twists" during growth to allow the hand to reach further back in late cocking.
• This results in increased External Rotation (ER) and decreased Internal Rotation (IR).
• Total Arch of Motion (ER + IR) should remain equal to the contralateral side.
• This allows greater external rotation range without checking the capsule.
• In Little League Shoulder, "Opening Up Early" (anterior trunk rotation) causes the arm to lag behind, increasing the torque on the physis beyond its limits.
• Biomechanical analysis often reveals that the pitcher relies too much on the arm and not enough on the legs/trunk ("Arm Thrower").

History:

• Patient: Young male pitcher (11-16 years)
• Pain: Progressive onset shoulder pain
• Location: Proximal humerus / Lateral shoulder (Deep ache)
• Timing: Initially only with throwing, progresses to ADLs
• Volume: History of high pitch counts, recent increase in play, or "showcase" events
• Mechanics: Often reports fatigue or "dead arm" sensation

Physical Examination:

• Inspection: Usually normal. Mild atrophy in chronic cases.
• Palpation: Maximal tenderness over the proximal humeral physis. This is the hallmark. (Lateral aspect, just below acromion).
• ROM:
  • GIRD (Glenohumeral Internal Rotation Deficit) common
  • Increased External Rotation (adaptive)
• Strength: Often normal, but pain with resisted abduction/rotation.
• Special Tests:
  • Neer/Hawkins: Negative (or false positive due to extensive irritability)
  • O'Brien's: Usually negative
  • Scapular Dyskinesis: Check for winging/dysrhythmia (predisposing factor)

Plain Radiographs (Mandatory):

• Views: AP (Internal/External Rotation), Axillary Lateral.
• Must order COMPARISON VIEWS of the contralateral shoulder.

MRI:

• Usually not necessary if X-rays are diagnostic.
• Indicated if:
  • X-rays normal but high clinical suspicion (early stress reaction)
  • Unusual presentation (rule out tumor/infection)
  • Assessing healing/return to sport (sometimes)
• Findings:
  • Physeal edema (high T2 signal)
  • Metaphyseal edema usually extending into shaft
  • Periosteal edema

CT Scan:

• Rarely indicated. Avoid radiation in children.

Growth Arrest:

• The most feared complication.
• Continued throwing through pain leads to bar formation.
• Result: Shortened humerus or varus deformity.
• Usually humerus shortening is well tolerated functionally but cosmetically apparent.

For Standard Nonoperative Cases: (Refer to the Management section, Nonoperative Protocol)

If Surgery was performed (Acute Fraction Fixation):

• 0-4 Weeks: Sling immobilization. Pendulums only.
• 4 Weeks: Pin removal (if K-wires used). Start Active Assist ROM.
• 6-12 Weeks: Strengthening phases.
• Return to Sport: Delayed compared to stress fracture (often 6 months+).

Prognosis (Heyworth et al. 2016):

• Excellent with rest and physiotherapy.
• Mean time to symptom resolution 2.6 months; mean time to return to competition 4.2 months.
• Recurrent symptoms in 7% at a mean of 7.6 months after diagnosis.
• Key determinant: patient/parent compliance with throwing rest; GIRD increases recurrence risk and should be corrected before return.

Long term:

• Premature physeal closure / growth arrest is reported but rare in the published series.
• Adaptation of humeral retroversion (a normal throwing adaptation) persists.

Counseling for Growth Arrest:

• Although rare (less than 1%), premature closure can occur if warnings are ignored.
• Resultant shortening is usually 1-2cm if near skeletal maturity.
• If young (e.g., 10-12 years), shortening can be significant (5cm+).

Global epidemiology:

• Concentrated in baseball-playing regions (USA, Japan, Latin America, Caribbean, parts of East Asia) where youth pitching volume is high; the largest published cohorts come from US paediatric sports-medicine centres (Heyworth et al. 2016).
• Less common where baseball participation is low, but the same physeal overuse mechanism is seen in other overhead-loading sports: tennis (kick/topspin serve with extreme external rotation), volleyball (spikers/jump servers) and cricket (bowlers, although lumbar spondylolysis is the dominant fast-bowler injury).
• Incidence is reported to be rising, attributed to early single-sport specialisation and year-round play without an off-season (Ina et al. 2026).

Major guidelines and consensus, side by side:

Registry / large-cohort evidence:

• No dedicated implant registry applies (this is a non-operative, non-implant condition). The relevant high-quality evidence comes from prospective youth-pitcher cohorts: Fleisig et al. 2011 (n=481, 10-year follow-up, 5% serious-injury incidence) and Lyman et al. 2002 (n=476), plus the Heyworth et al. 2016 case series (n=95).

Global practice variation:

• In high-baseball-volume regions, ultrasound screening of youth pitchers and formal pitch-count enforcement are increasingly used; in low-baseball regions the condition is rare and may be under-recognised, with cricket/tennis/volleyball being the more likely contexts.
• Workload-management frameworks differ by sport (pitch counts in baseball, over/spell limits in cricket, serve volume in tennis) but share the same principle: limit cumulative load on the immature physis and rest at the first sign of arm pain or fatigue.

Prevention principles (sport-agnostic):

• Adhere to age-appropriate pitch/over/serve count limits and mandatory rest days.
• Build in an annual off-season (no competitive throwing for roughly 3-4 months).
• Avoid "showcase" events that demand maximal-intensity throwing without a build-up.
• Address fatigue, mechanics and GIRD proactively, since overuse and fatigue are the strongest modifiable risk factors (Olsen et al. 2006).