Sugaya (2003) — Glenoid rim morphology in recurrent anterior glenohumeral instability

Glenoid Rim Morphology in Recurrent Anterior Glenohumeral Instability

Sugaya, Tsuchiya·J Bone Joint Surg Am·2003·815 citations·Shoulder & Elbow

This study introduces a 3D-CT method that digitally removes the humeral head to visualize and measure glenoid rim bone loss in recurrent anterior shoulder instability. It asks how often glenoid bone loss occurs and how to quantify it before surgery. 100 unstable shoulders were compared with 75 normal glenoids and then checked arthroscopically.

Study Snapshot

Design

Diagnostic case-control

Blinding: Open-label

Setting: Sports medicine center, Chiba, Japan

Funding: None

Objective

Whether 3D-CT with the humeral head removed can quantify glenoid bone loss in recurrent anterior instability

Outcome(s)

Glenoid rim morphology and defect size on 3D-CT, confirmed arthroscopically

Subjects

100 unstable shoulders; 75 normal glenoids

Inclusion

Recurrent unilateral anterior instability
Initial traumatic dislocation or subluxation

Exclusion

Bilateral shoulder involvement

Statistics

Descriptive quantification

Key Findings

Normal glenoids showed no side-to-side difference, so the contralateral shoulder is a valid template for the injured glenoid's normal circular contour. This is the basis for using the healthy side as an internal control when reading bone loss.
Abnormal rim morphology was found in 90 of 100 unstable shoulders, and only 10 looked normal. Bone loss in recurrent instability is the rule, not the exception.
A discrete osseous fragment was present in 50 of 100 shoulders, graded by the Sugaya system:
–Large (>20%): 1 fragment, 26.9%
–Medium (5-20%): 27 fragments, avg 10.6%
–Small (<5%): 22 fragments, avg 2.9%
–Overall average fragment size was 7.7% of the glenoid fossa.
The other 40 of 100 shoulders had no fragment but showed a straight anteroinferior contour (en face) and an obtuse or rounded rim (oblique) versus the normally sharp edge. This is attritional erosion or mild compression, which shows bone loss is a spectrum rather than fragment-or-nothing.
Arthroscopy confirmed a Bankart lesion in 97 of 100 shoulders, and the 3 misses had been read as normal on CT.
Fragments were confirmed arthroscopically in 45 of 50 CT-positive shoulders, and the 5 missed at arthroscopy were all small (avg 2.3%) and buried in soft tissue. Because fragments only appeared after releasing the labrum off the glenoid neck, CT can detect bone loss that direct scope inspection hides.

Board PearlIn recurrent anterior instability, 90% of glenoids show rim bone loss: 50% a discrete osseous Bankart fragment, 40% attritional erosion without a fragment.

Clinical Relevance

The practical model here: on 3D-CT with the humeral head subtracted, the inferior glenoid should trace a true circle. A flat or missing anteroinferior arc means bone loss, and you compare against the patient's own normal contralateral side.

The prevalence numbers change how you think preoperatively. If 90% of recurrent instability shoulders have some rim bone loss and half have a real fragment, you cannot assume a clean soft-tissue Bankart from history alone.

Size drives the plan in this paper: large fragments push toward bone-grafting, while medium and small fragments were treated with arthroscopic fixation to restore the glenoid arc. A key pitfall: arthroscopy underestimated bone loss, missing small fragments buried under the labroligamentous complex until it was released. Do not let a normal-looking scope talk you out of what CT shows.

Core

Glenoid Rim Morphology in Recurrent Anterior Glenohumeral Instability

Sugaya·J Bone Joint Surg Am·2003·815 citations·Shoulder & Elbow

Glenoid Rim Morphology in Recurrent Anterior Glenohumeral Instability

Study Snapshot

Key Findings

Clinical Relevance

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Glenoid Rim Morphology in Recurrent Anterior Glenohumeral Instability

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