Friday, February 10, 2017

New shoulder arthroplasty components, new uncertainties

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

These authors suggest that in comparison to standard total shoulder arthroplasty (TSA), total shoulder surface replacement (TSSR) may offer the advantage of preservation of bone stock and shorter surgical time, possibly at the expense of glenoid component positioning and increasing lateral glenohumeral offset.

They conducted a retrospective cohort study comparing 29 patients having a TSA using an anatomical humeral stem with 20 having TSSR with a humeral surface replacement.

This report excluded shoulders with type B2 glenoids, one of the most common arthritic pathoanatomies. It is unclear how patients were allocated to either the TSSR or TSA groups.

After 29 and 34 months of mean follow-up, the two groups showed similar outcome scores and radiographic outcomes. However, one intraoperative glenoid fracture occurred in the TSSR group.

Comments:  At breakfast today, we discussed the issues surrounding new technologies with the editor of a leading orthopedic journal, Seth Leopold. He pointed out that in addition to the added costs of research, development, marketing, consultants, and the learning curve, another added cost of a new technology is the uncertainty introduced by deviating from what we are used to doing.  Thus most shoulder surgeons are adept at the proper positioning of a stemmed humeral component. However, the use of resurfacing implants can introduce uncertainty in the positioning of the humeral articular surface as shown in the cases below.

Furthermore, most shoulder surgeons are adept at gaining good exposure to the glenoid so that a safe, well-seated and well-fixed prosthetic glenoid arthroplasty can be accomplished. 

However, without the standard resection of the entire humeral head, the ability to gain the necessary access to the glenoid becomes less certain as shown below.

A few additional points are worth recognizing. First, the great majority of complications of total shoulder arthroplasty relate to failure of the glenoid (and not problems with the humerus); thus an effort to preserve humeral bone should not make the glenoid arthroplasty less certain. Second, the results shown here are at two to three years, whereas glenoid arthrplasty problems typically do not show up until five to seven years after surgery. In their discussion, the authors point out that "Case series with longer follow-up have found 98% and 100% 5-year survival for TSA compared with 63% and 78% 10-year survival for TSSR."

In this study 1 of 20 patients with the most straightforward type A glenoids having a TSSA by surgeons experienced in the method sustained a glenoid fracture. 

In summary, unless the new technology is clearly superior to the accepted norm for which substantial outcome data are available, the incremental costs and uncertainties may be difficult to justify.