Sunday, October 30, 2016

Resurfacing total shoulder arthroplasty - what are the advantages?

Radiological and functional 24-month outcomes of resurfacing versus stemmed anatomic total shoulder arthroplasty

These authors compared clinical and radiographic outcomes of patients undergoing resurfacing total shoulder arthroplasty (RES) (Promos® resurfacing prosthesis)

with those treated with a multi-pieced stemmed TSA (STA) (Promos® standard prosthesis),

 between 2006 and 2014. They age and sex matched 37 of 44 RES shoulders with 37 of 137 STA shoulders with two-year followup. Shoulders in both groups showed significant functional improvement and similar outcome scores, revision rates and radiographic scores at 24 months.

At 24 months post-surgery, 89 % RES and 95 % STA patients reported that they would undergo the same operation again.

Comment: While the 37 shoulders in each group were age and sex matched, the authors do not explain why the use of the standard stemmed prosthesis was over three times that of the resurfacing prosthesis during the period of study. The reader must wonder what the differences in surgeon, shoulder and patient characteristics might have been between the 137 and the 44. For example 35% of the shoulders in the RES group had type B glenoids while 54% of the STA shoulders had this glenoid pathology.

The average preoperative scores were not the same between the two groups, so that even though the postoperative scores were similar, the improvement in the scores were not the same as shown for the Constant score below.

Positioning the resurfacing humeral component is not always straightforward and the preservation of the humeral head may interfere with access to the glenoid leading to suboptimal positioning. In this example it appears that a superiorly placed humeral component contacts the upper edge of an inferiorly placed glenoid component.

One STA patient not included in the 2-year followup group required an exchange of the inclination set and humeral head due to spontaneous malrotation of the humeral head component after 14 months – users of this rather complex prosthesis design should keep this potential problem in mind.

While it is stated that the intent of a resurfacing design is to avoid intra- and post-operative stem-related complications, and preserve bone stock for future revisions, we find that these same goals can be achieved without impairing glenoid access by using an impaction grafted thin stemmed two-piece prosthesis inserted with impaction autografting.