Monday, October 31, 2016

Is there an advantage of using a humeral surface replacement in total shoulder arthroplasty?

Comparative study of total shoulder arthroplasty versus total shoulder surface replacement for glenohumeral osteoarthritis with minimum 2-year follow-up.

These authors compared patients having a Tornier conventional total shoulder arthroplasty (TSA - cemented anatomical humeral stem)

performed with a complete resection of the humeral head

with those having a Tornier total shoulder with a surface replacement of the humeral head  (TSSR)

used with the goal of preserving a bit more of the humeral head

Both types of humeral component were paired with a cemented, curved, keeled, all-poly glenoid component.

They suggest that TSSR may offer advantage of preservation of bone stock and shorter surgical time, possibly at the expense of glenoid component positioning and increasing lateral glenohumeral offset. 

In the TSSA shoulders the authors state that extensive releases of the posterior and inferior capsule had to be performed to gain exposure of the glenoid.

After 29 and 34 months of mean follow-up, respectively, TSA (n = 29) and TSSR (n = 20) groups showed similar median adjusted Constant Scores (84% vs. 88%), Oxford Shoulder Scores (44 vs. 44), Disabilities of the Arm, Shoulder and Hand scores (22 vs. 15), and Dutch Simple Shoulder Test scores (10 vs. 11). 

One intraoperative glenoid fracture occurred in the TSSR group. They point out that with the resurfacing implant,the "surgeon is presented with challenges related to a more difficult exposure because less humeral bone is resected. Indeed, the glenoid fracture in our TSSR group was probably caused by a more forceful glenoid exposition."

Comment: It is unclear what criteria led to the use of a resurfacing vs a standard humeral  component in this series of cases.

In that most total shoulder failures are related to the glenoid component, it would seem that safely optimizing glenoid exposure is a high priority, outweighing the theoretical advantage of preserving a bit more of the humeral head.