Hill-Sachs Lesions

Hill-Sachs lesions are compression fractures of the posterolateral humeral head resulting from impact against the anterior glenoid rim during anterior shoulder dislocation. They represent a key component of "bipolar bone loss" in shoulder instability.

Epidemiology

• Primary Dislocation: Present in 40-50% of cases.
• Recurrent Instability: Present in up to 90-100% of cases.
• Mechanism: Anterior dislocation with the arm attempting to internally rotate.
• Significance: Large or "off-track" lesions engage with the glenoid rim, causing levering out and recurrent dislocation.

Pathomechanics

• Location: Posterolateral aspect of the humeral head, superior to the greater tuberosity.
• Formation: "Dent" created when the soft cancellous bone of the humeral head impacts the hard cortical bone of the anterior glenoid rim during dislocation.
• Bipolar Bone Loss: The interaction between the Hill-Sachs lesion and any anterior glenoid bone loss (bony Bankart). The combined loss reduces the arc of stability.
• Engagement Mechanism: In abduction and external rotation (the "at-risk" position), the perceived width of the glenoid track narrows. If the Hill-Sachs lesion is wide enough to bridge this narrow track, the anterior glenoid rim falls into the defect. This levering action forces the humeral head out of the socket.

The Glenoid Track Concept (Itoi, DiGiacomo)

The "Glenoid Track" is the contact zone of the glenoid on the humeral head during abduction and external rotation. It essentially describes the "safe zone" on the humeral head that stays in contact with the glenoid.

Clinical Calculation Steps:

1. Measure Glenoid Diameter (D): Use the inferior circle method on en-face 3D CT.
2. Calculate Expected Track: 0.83 x D.
3. Measure Glenoid Defect (d): Linear width of anterior bone loss.
4. Calculate True Track Width: Glenoid Track = (0.83 x D) - d.
5. Measure Hill-Sachs Interval (HSI): Distance from the rotator cuff footprint to the OTHER side of the Hill-Sachs lesion (medial margin).
6. Compare:
   • If HSI less than Track: The lesion is covered by the glenoid. ON-TRACK.
   • If HSI greater than Track: The lesion extends beyond the glenoid rim. OFF-TRACK.

Zone of Co-existence: The concept relies on the fact that the rotator cuff footprint defines the lateral margin of the contact patch. A Hill-Sachs lesion expands this "non-contact" zone medially.

History

• History of recurrent anterior dislocations.
• Feeling of the shoulder "locking" or getting stuck in abduction/external rotation.
• Mechanism typically traumatic abduction/external rotation.

Physical Examination

• Apprehension Test: Positive in abduction and external rotation.
• Relocation Test: Relief of apprehension with posterior force.
• Crepitus: May feel crepitus in the mid-range of rotation if the lesion is large.
• Engaging Sign: Reproducing symptoms (clunk/apprehension) at lower degrees of abduction may suggest an engaging lesion.

X-Ray

• Views: AP (Internal Rotation), Axillary, Stryker Notch View.
• Stryker Notch: Hand on head, beam tilted 10° cephalad. Best view for Hill-Sachs.
• West Point: Best for glenoid bone loss.

CT Scan

• Gold Standard for quantifying bone loss.
• Protocol: 3D reconstruction with humeral head subtraction (en face view).

MRI

• Useful for soft tissue pathology (Bankart, rotator cuff tears).
• Can estimate bone loss but CT is superior.
• Axial cuts: Visualize the depth of the lesion.

A posterolateral humeral head defect or a "locking/apprehensive" shoulder is not always a true engaging Hill-Sachs lesion. Distinguish it from the following:

• The 83 percent figure is a population mean, not a hard threshold. The original cadaveric track was 84 plus or minus 14 percent of glenoid width (Yamamoto/Itoi 2007); the working 0.83 multiplier is a convenient approximation. Borderline (near-track) lesions sit in a grey zone where intraoperative dynamic assessment still matters.
• Does off-track status independently predict failure, or is glenoid loss the real driver? Long-term data (Schwihla 2022) show off-track lesions fail isolated Bankart repair at high rates, yet some cohorts (Park 2019) found glenoid defect size, not off-track status per se, was the more reliable predictor once selective remplissage was used. The honest position: bipolar interaction matters, and glenoid loss carries heavy weight.
• Remplissage vs Latarjet for subcritical loss. Meta-analytic data (Haroun 2020) show equivalent stability with fewer complications for remplissage, but Latarjet retains advocates for collision athletes and revision settings. There is no consensus "right answer" — the decision is patient- and surgeon-specific.
• The "subcritical" glenoid threshold is moving. Older teaching used 20 to 25 percent; contemporary work suggests instability and recurrence rise from as little as 13.5 percent in high-demand athletes, lowering the threshold for augmentation.
• Clinical engagement vs radiographic off-track are correlated but not identical. A lesion can be radiographically off-track yet not reproduce clinical locking, and vice versa; relying on one alone risks over- or under-treatment.

Remplissage (Infraspinatus Capsulotenodesis)

Specific to Remplissage

• Stiffness: Excessive loss of external rotation if tied too tight (tenodesis effect). Studies show average loss of 9 degrees.
• Pain: Posterior cuff pain or infraspinatus spasm (cramping) is common in the early post-op period.
• Failures: Recurrent instability (if glenoid bone loss was underestimated and track calculation was wrong).
• Infraspinatus Strength: Minor deficit in ER strength, usually clinically insignificant.

Specific to Latarjet

• Neurological Injury:
  • Musculocutaneous Nerve: Most common (approx 5%). Traction injury during retraction of conjoined tendon.
  • Axillary Nerve: Risk during subscapularis split/tenotomy.
• Hardware Complications:
  • Screw Breakage/Back-out: Can cause irritation.
  • Proud Screws: "Kissing lesions" on the humeral head leading to rapid arthritis.
• Graft Issues: Non-union (fibrous union is stable usually), Osteolysis (resorption of graft).
• Recurrence: Lower than Bankart (less than 5%) but revision is difficult (Eden-Hybinette).

General Instability Surgery

• Infection: less than 1% for arthroscopy, slightly higher for open Latarjet.
• Chondrolysis: Historically associated with pain pumps or thermal capsulorrhaphy (radiofrequency shrinkage) - now largely abandoned.
• Stiffness: Overtightening of the anterior capsule (Accessory anteroinferior instability repair).

Rehabilitation Protocol (Bankart + Remplissage)

Standard protocol typically involves 6 weeks of sling immobilization to protect the capsulolabral repair and the tenodesis.

Key Precautions

1. External Rotation: The tenodesis of the infraspinatus (Remplissage) is under tension in internal rotation. However, we protect against excessive external rotation to prevent pulling out the anchors. Most surgeons limit ER to neutral for 6 weeks.
2. Active Elevation: Avoided for 6 weeks to protect the Bankart repair from the shear forces of the humeral head translating.

• Bankart Alone (On-Track): 85-90% success.
• Bankart Alone (Off-Track): High recurrence rate (greater than 20-30%).
• Bankart + Remplissage (Off-Track): Success rates approach Latarjet (90-95%) with lower morbidity.
• Latarjet: Gold standard for collision athletes and significant bone loss (greater than 95% stability).

Every claim below has been verified against the primary PubMed record (title, journal, year, sample size and conclusion checked). Where the original card mis-stated a journal or attributed a finding to the wrong paper, it has been corrected to the verified source.

Global Epidemiology

• Anterior dislocation accounts for over 95 percent of glenohumeral dislocations; a Hill-Sachs lesion is present in roughly 40 to 90 percent of first-time anterior dislocations and approaches 90 to 100 percent in recurrent instability.
• Peak incidence is bimodal: young males (15 to 30 years, sport/trauma) and older adults (falls). Young age, male sex, high-demand/contact sport and bipolar bone loss are the dominant risk factors for recurrence.
• Bipolar (combined glenoid plus humeral) bone loss is the single most important predictor of failure after soft-tissue stabilisation across populations.

Society Guidance, Side by Side

Registry & High-Level Evidence Notes

• There is no dedicated implant registry for instability (no implant), so evidence is driven by RCTs and cohorts rather than arthroplasty-style registries.
• Convergent message across high-level data (MacDonald RCT; Haroun meta-analysis; Schwihla long-term cohort): address the off-track lesion, and remplissage matches Latarjet stability with fewer complications when glenoid loss is subcritical.

High- vs Limited-Resource Practice Variation

• Well-resourced settings: routine preoperative 3D CT with en-face glenoid reconstruction for track quantification; arthroscopic Bankart plus remplissage is the default for off-track subcritical lesions.
• Limited-resource settings: MRI or plain CT (or even instability radiographs and intraoperative dynamic assessment) may substitute for 3D CT; open Latarjet remains a reliable, instrument-light, single-stage option where arthroscopic remplissage expertise or equipment is unavailable.