How to assess glenohumeral bone loss

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Assessment of Glenohumeral Bone Loss

Glenohumeral bone loss occurs on both sides of the joint — the glenoid (anteroinferior) and the humerus (posterosuperior Hill-Sachs lesion). Accurate pre-operative assessment of both is essential because significant bone loss predicts failure of soft-tissue stabilization and dictates the need for bony augmentation.

1. Clinical Context

Some degree of glenoid bone loss is present in 40% of first-time dislocations and 85% of recurrent dislocations.
A Hill-Sachs lesion is seen in 40% of patients with recurrent subluxation, 90% after first dislocation, and approaching 100% with recurrent dislocations.
Bipolar lesions (combined glenoid + Hill-Sachs) occur in 33% of primary instability and 62% of recurrent instability cases.

2. Imaging Modalities

Plain Radiography

Several special views improve sensitivity:

View	Technique	Purpose
Stryker Notch	Supine, arm over head, beam 10° cephalad	Detects Hill-Sachs lesion
West Point	Prone, forearm hanging, beam 25° downward + 25° medial	Detects anteroinferior glenoid rim (bony Bankart)
Bernageau (Glenoid Profile)	Arm flexed, beam along scapular spine at 30-40°	Glenoid profile, anterior rim loss
True AP (Grashey)	Standard shoulder series	Overall joint assessment

CT Scan (Primary Modality)

CT is the standard for evaluating bone loss. High-resolution thin-slice acquisition with 3D volume-rendered reconstructions and digital subtraction of the humeral head provides the best visualization.

Identifies smallest osseous fragments and glenoid asymmetry
3D CT with humeral subtraction: gold standard for glenoid bone loss quantification
Also detects Hill-Sachs lesions with accuracy comparable to arthroscopy
Essential when bipolar lesions are suspected

3D CT reconstruction showing Hill-Sachs lesions (stars) on the posterolateral humeral head

3D CT reconstruction showing Hill-Sachs lesions (★) on the posterolateral humeral head — Rockwood & Green's Fractures in Adults, 10th ed.

3D CT reconstruction of glenoid showing ~20% anterior bone loss

3D CT reconstruction of the glenoid and scapula demonstrating approximately 20% anterior glenoid bone loss — Miller's Review of Orthopaedics, 9th ed.

MRI / MR Arthrogram (MRA)

MRA preferred over plain MRI for greater sensitivity for labral and ligamentous lesions
ABER position (abduction-external rotation) increases sensitivity for anteroinferior labral injuries
Circle method on MRI is accurate to within 1.3% of 3D CT for measuring glenoid bone loss
Demonstrates capsular volume, glenoid version, and associated soft-tissue pathology

3. Quantifying Glenoid Bone Loss

A. Circle Method (most widely used)

A best-fit circle is drawn over the intact posterior glenoid on the en face view (CT or sagittal MRI). The missing segment anteriorly represents the bone loss.

% Bone loss = (diameter of best-fit circle − remaining anterior-posterior width) / diameter × 100

B. Burkhart Bare-Spot Arthroscopic Method

Arthroscopic measurement using a calibrated probe:

Distance from bare spot to posterior glenoid margin = Dp
Distance from bare spot to anterior glenoid margin = Da
% Bone loss = (Dp − Da) / (2 × Dp) × 100

C. Width-Based Formula (Owens et al.)

Predicts normal glenoid width from height measurements on MRI:

Males: Normal glenoid width = ⅓ height + 15 mm
Females: Normal glenoid width = ⅓ height + 13 mm

4. Critical Thresholds

Threshold	Significance
≥20–25% glenoid bone loss (≈6–8 mm)	"Critical" defect → recurrence rate after arthroscopic Bankart repair rises to 67%; bony augmentation (Latarjet, bone graft) required
>21% of glenoid length	Biomechanically causes instability and ROM limitation after Bankart repair
Inverted-pear glenoid morphology	Corresponds to ~25–27% anteroinferior width loss

5. Hill-Sachs Lesion Assessment and the Glenoid Track Concept

A Hill-Sachs lesion is not just quantified by size but by whether it is on-track or off-track — whether it will engage the anterior glenoid rim in functional positions.

Glenoid Track Calculation

Glenoid Track (GT) = 0.84 × actual glenoid width

(The 84% factor accounts for the medial glenoid insertion of the inferior glenohumeral ligament, which limits how far laterally the humeral head can translate.)

Hill-Sachs Interval (HSI)

Measured on coronal MRI as the distance from the rotator cuff footprint to the medial margin of the Hill-Sachs lesion.

Classification

On-track (safe): HSI < GT → no engagement risk → arthroscopic Bankart repair alone is appropriate
Off-track (high risk): HSI ≥ GT → engagement occurs → requires remplissage or Latarjet in addition

Glenoid track and Hill-Sachs interval measurement on MRI — showing on-track/off-track assessment

(A) Sagittal oblique MRI: best-fit circle on glenoid; glenoid track = 24 mm × 0.84 = 20.1 mm with 17% bone loss. (B) Coronal MRI: Hill-Sachs interval = 23.1 mm. Since HSI (23.1 mm) > GT (20.1 mm) → off-track lesion at high risk for engaging. (Miller's Review of Orthopaedics, 9th ed.)

6. Summary Algorithm

Plain XR (Stryker Notch, West Point, Bernageau)
        ↓
   Suspected bone loss?
        ↓
3D CT with humeral subtraction  ←  primary quantification
+/- MRI/MRA (soft tissue, labrum, version)
        ↓
  Measure glenoid bone loss (circle method)
        ↓
< 20%          20–25%          > 25%
  ↓               ↓               ↓
Arthroscopic   Borderline:     Bony augmentation
Bankart repair  glenoid track  (Latarjet / bone graft)
                analysis
                  ↓
            On-track → ABR
            Off-track → ABR + remplissage or Latarjet

Sources:

Rockwood and Green's Fractures in Adults, 10th ed., 2025 — Chapter 35
Miller's Review of Orthopaedics, 9th ed. — Chapter 4, Anterior Instability

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