Thursday, November 28, 2013

The arthritic shoulder before surgery and after the ream and run: the axillary x-ray

Axillary View: Arthritic Glenohumeral Anatomy and Changes After Ream and Run.

The technique and results of shoulder arthroplasty are influenced by glenohumeral pathoanatomy, especially the glenoid type (Walch), the glenoid retroversion and the amount of posterior subluxation of the humeral head on the glenoid.

Although some authors advocate a routine preoperative CT scan to define this anatomy, a CT scan substantially increases the cost and increases the radiation exposure to the patient by 2600%. This study asked (1) whether the pathoanatomy of arthritic shoulders can be reliably characterized on a standardized axillary view, (2) whether  postoperative radiographs can reliably show the changes in glenoid anatomy and glenohumeral relationships after shoulder arthroplasty, and (3) whether the axillary view can show differences in glenohumeral pathoanatomy in the different sexes and different types of shoulder arthritis.

These questions were addressed using cross-sectional studies of 344 shoulders with different types of arthritis and of 128 osteoarthritic shoulders having a ream and run arthroplasty (a glenohumeral arthroplasty that combines a noncemented humeral hemiarthroplasty with concentric reaming of the glenoid bone without implantation of a prosthetic glenoid component). 

Measurements of glenoid type, glenoid version, and the point of glenohumeral contact were made on standardized axillary radiographs. 
Shown below are axillary views of an A2 and a B1 glenoid on the top row and two B2 glenoids on the bottom row.

Shown below is a simple method for measuring glenoid version (left) and the point of glenhumeral contact (right) on the axillary view.

These measurements showed a high degree of interobserver reliability and sensitivity to the changes effected by arthroplasty. Male shoulders and shoulders with osteoarthritis had more type B glenoids (ie, those with posterior erosion and biconcavity of the glenoid), more retroversion, and a greater degree of posterior displacement of the point of glenohumeral contact.

Avoiding the use of a plastic glenoid component, the ream and run procedure significantly improved the centering of the glenohumeral contact point from an average of 65% ± 13% posterior to 54% ± 7% posterior (50% represents the centered position) (p< 0.001).  The ream and run procedure resulted in a significant change in the glenohumeral type: the percentage of type A glenoids improved from 26% before surgery to 94% after surgery (p< 0.001).

Shown below are typical preoperative and postoperative films.

The authors concluded that the axillary view provides a practical method of characterizing glenohumeral anatomy before and after surgery that is less costly and exposes the patient to less radiation than a CT scan. While the CT scan may provide more detail, there is no evidence that this additional detail leads to improved patient outcomes.

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