Monday, July 9, 2018

Scapular notching with the Delta Xtend

Scapular notching refers to the loss of bone from the inferior glenoid neck resulting from contact with the humeral component of a reverse total shoulder.

These authors evaluated patients with preoperative computed tomography (CT) scans who underwent reverse total shoulder with the Delta Xtend; 155 humeral neck-shaft angle and 38-mm [n = 10] or 42-mm [n = 19] glenosphere at a minimum of 2 years of follow-up with video motion analysis (VMA), postoperative threedimensional (3D) CT, and standard radiographs. 

The glenohumeral range of motion demonstrated by the VMA and the postoperative implant location on the CT were used in custom simulation software to determine areas of osseous contact between the humeral implant and the scapula and their relationship to scapular notching on postoperative CT. Patients with and without notching were compared with one another by univariable and multivariable 

Seventeen patients (59%) had scapular notching, which was along the posteroinferior aspect of the scapular neck in all of them and along the anteroinferior aspect of the neck in 3 of them. Osseous contact occurred in external rotation with the arm at the side in 16 of the 17 patients, in internal rotation with the arm at the side in 3, and in adduction in 12. 

Placing the glenosphere in a position that was more inferior (by a mean of 3.4 ± 2.3 mm) or lateral (by a mean of 6.2 ± 1.4 mm) would have avoided most impingement in the patients’ given range of motion. 

Their results suggest that for the Delta Xtend system with its medialized center of rotation, placing the glenosphere in a maximally inferior position while maximizing posterior and lateral placement may help minimize notching.

Comment: While the bony changes of notching can be assessed by x-rays, it is also important to consider changes on the humeral component resulting from the unwanted contact.

Notching can proceed to the point where fixation of the glenoid component is jeopardized.

It is apparent that the design of different prostheses affects the risk of notching. Lateralization of the baseplate can be effective in that regard.
Finally, as a part of the surgical technique with any prosthesis, while the trial components are in place it is important to check for unwanted contact between the humeral component and the scapula with the arm in adduction and in the full range of rotation. If this unwanted contact is present, modification of the prosthesis or its position can be effected.
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