These authors obtained preoperative and postoperative CT scans on 37 patients having total shoulder arthroplasty to measure glenohumeral offset (GHO) to determine its effect on shoulder function.
They found a mean increase in GHO of 4.3 mm (standard deviation, 4.6; range, from -10.6 to +10.8) after surgery. No associations were observed between change in offset and functional or strength scores.
Comment: Two observations are worth making about this study. (1) the range in offset was huge, varying from 1 cm of increased medicalization to 1 cm of lateralization. (2) the change in offset did not significantly effect the change in Constant score.
In our practice, we routinely insert a standard thickness all polyethylene glenoid component with minimal reaming of the glenoid bone. This may result in an increase of 2 to 3 millimeters of lateral offset. On the humeral side, the thickness of the humeral head component is selected to allow internal rotation to 60 degrees with the arm abducted to 90 degrees, 50% posterior translation on the drawer test. and 150 degrees of flexion. Thus the net change in glenohumeral offset is determined by the preoperative pathoanatomy and the soft tissue balance.
Determining the change position of the tuberosity in relation to the scapula can be a helpful tool for assessing (a) the degree of medial erosion preoperatively and (b) the degree to which the tuberosity is lateralized after surgery (recognizing that excessive tuberosity lateralization can placed increased tension on the rotator cuff, "overstuffing").
Rather than obtaining CT scans we use the lateral acromial line on the plain film AP in the plane of the scapula (Grashey view) to indicate the relative position of the tuberosity and scapula as shown in the images below.
We have a new set of shoulder youtubes about the shoulder, check them out at this link.
Be sure to visit "Ream and Run - the state of the art" regarding this radically conservative approach to shoulder arthritis at this link and this link
Use the "Search" box to the right to find other topics of interest to you.
You may be interested in some of our most visited web pages arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'
