UW Shoulder and Elbow Academy: Inlay total shoulder arthroplasty: does this innovation add value for the patient?

Inlay Total Shoulder Arthroplasty for Primary Glenohumeral Arthritis

These authors (two of which have received stock options from Arthrosurface) hypothesized that patients with advanced glenohumeral arthritis demonstrate significant improvements in pain and function after insertion of a total shoulder arthroplasty with an inlay glenoid prosthesis, OVO Primary Stemless Total Shoulder System, Arthrosurface.

They reviewed thirty-nine shoulders in 36 patients (3 bilateral) with a mean age of 65.9 years (17 males, 13 females) and a mean follow-up of 41.0 months.

The glenoid Walsh classification included A1 (25%), A2 (25%), B1 (22%), B2 (25%) and C (3%).

One intraoperative glenoid rim fracture led to advanced radiolucency; no other clinically relevant lucency was observed.

The mean ASES improvement was from 30.4 to 77.1 for these 36 patients. This is in comparison to the mean improvement in ASES score from 36.3 to 83.4 in 3667 receiving a standard glenoid implant (see this link).

Comment: While, like many other total shoulder designs, this small series shows improvement in patient reported outcomes, it does not demonstrate added value over designs in more common use. See this link.

See related post below:

Clinical and Radiographic Outcomes of Total Shoulder Arthroplasty With a Nonspherical Humeral Head and Inlay Glenoid in Elite Weight Lifters A Prospective Case Series

These authors point out that weight lifting after total shoulder arthroplasty (TSA) can place significant stresses on prosthetic glenoid implants potentially leading to instability, loosening, and wear.

They sought to evaluate the clinical and radiographic outcomes of a TSA system with nonspherical humeral head resurfacing and an inlay glenoid in 16 weight lifters (mean ± SD age, 57.2 ± 7.8 years; 15 male) undergoing primary anatomic TSA (n . 17 shoulders, 1 staged bilateral) for glenohumeral

osteoarthritis. Exclusion criteria were rotator cuff deficiency, revision TSA, posttraumatic

arthritis, and inflammatory arthritis.

Follow-up was obtained on all patients at a mean of 38 months (range, 14-63 months). All patients returned to weight lifting at 15.6 ± 6.9 weeks. Compared to the preoperative weight lifting level, at last follow-up patients reported performance at the following level: lighter weight, 1 (6%); same weight, 8 (50%); heavier weight, 7 (44%). The quantitative values for these levels are not provided.

Preoperative eccentric posterior glenoid wear was common (71% Walch B2 classification; 12/17).

Posterior humeral subluxation improved at follow-up according to the Walch index (mean, 55.5% preoperative vs 48.5% postoperative), and contact point ratio (mean, 63.9% preoperative vs 50.1% postoperative).

Significant pre- to postoperative improvements were seen shoulder outcome scores.

No signs of radiographic loosening were detected in follow-upimages, nor were there any postoperative instability episodes or revision surgeries.

Comment: This article does not report the amount (pounds) of weight being lifted by these patients before and after surgery, so that the loads involved cannot be quantitated.

The authors propose that the inlay glenoid component provides a more stable glenoid arthroplasty than the onlay glenoid commonly used in total shoulder arthroplasty.

The inlay glenoid does not completely cover the glenoid articular surface as seen in this illustration from the technique guide

and this intraoperative photo

and this post operative film.

The small surface area of the glenoid component may be an issue. In the figure below from this article, the humeral head is not articulating at all with the prosthetic glenoid component that lies between the two red arrows.

The value of the inset glenoid component is yet to be demonstrated in comparison to the ream and run glenohumeral arthroplasty in which no glenoid component is used (how to do this procedure is seen in this link). See also