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In Which Arm Position Is a Hill-Sachs Lesion Created?
Jun Kawakami1, Nobuyuki Yamamoto1, Taku Hatta1
1Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
The American Journal of Sports Medicine
|June 28, 2019
Summary
A Hill-Sachs lesion (HSL) is created in a mid-range arm position (74° abduction, 27° external rotation) during shoulder dislocation. This finding clarifies the timing of HSL formation, regardless of when the dislocation occurs.
Area of Science:
- Orthopedics
- Biomechanics
- Radiology
Background:
- The exact arm position during the creation of a Hill-Sachs lesion (HSL) during shoulder dislocation is not well-established.
- Previous beliefs suggested HSLs form with the arm in abduction and external rotation, but empirical data was lacking.
Purpose of the Study:
- To precisely determine the arm position responsible for creating a Hill-Sachs lesion (HSL).
Main Methods:
- A descriptive laboratory study analyzed CT scans of 100 shoulders with recurrent anterior shoulder dislocation.
- Three-dimensional bone models of the scapula and humerus were created.
- The humerus was manipulated to perfectly align the HSL with the anterior glenoid rim to record the specific arm position.
Main Results:
- The optimal fit between the Hill-Sachs lesion and the anterior glenoid rim occurred at an average arm position of 74° abduction, 27° external rotation, and 3° horizontal flexion.
- This specific arm positioning is identified as the likely position for HSL creation.
Conclusions:
- The study identifies a distinct mid-range arm position (74° abduction, 27° external rotation) as the critical point for Hill-Sachs lesion formation.
- This suggests HSLs are created in this mid-range position, distinct from the potential end-range position of the initial dislocation event.
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