UW Shoulder and Elbow Academy: Stemless humeral components, is less more?

Is the humeral stem useful in anatomic total shoulder arthroplasty?

These authors reviewed forty-seven patients with an average age of 63 having a total shoulder arthroplasty using a humeral head prosthesis with a three-fin design and titanium coating. Diagnoses included: primary osteoarthritis (29), fracture sequelae (12) and avascular osteonecrosis (6).

In four women aged 62 to 72 years, the intra-operative assessment of primary fixation of the stemless component was unsatisfactory (insufficient), and the surgeons preferred to implant a classic cemented stemmed prosthesis. In the remaining 43 shoulder implants, the intra-operative assessment of primary fixation was satisfactory.

Minimum follow-up was two years (range 24–51 months).

Two patients had revision of the implants, one for persistent pain and one for secondary massive rotator cuff tear.

At the final follow-up, the mean Constant score was 69, with an average gain of 36. Mean satisfaction rate was 87%. No revisions were related to humeral component loosening.

Radiologic evaluations showed 17 cases with radiolucent areas, particularly superior and lateral to the implant (see below).

Comment: The arguments proposed for stemless prostheses include preservation of humeral bone stock for potential revisions, performance of anatomic reconstruction regardless of posterior offset in anatomic arthroplasty, facilitating arthroplasty in cases of humeral deformity, prevention of malpositioning, avoiding periprosthetic fractures, and avoiding 'violating' the humeral
through the use of metaphyseal fixation.

While there is no question that good results have been reported with these prostheses, we are unaware of evidence that patients with stemless prostheses achieve clinical outcomes that are superior to those seen with conventional prostheses. The greater amount of humeral bone retention can compromise the quality of glenoid component insertion in a total shoulder. As the series reported here reveals, a substantial percentage of shoulders do not have sufficient humeral bone quality for the use of this prosthesis. Furthermore, clinical experience indicates that stemless prostheses have their own learning curve and set of potential problems of fixation and positioning as shown in the films below.

We find in the great majority of cases, the proposed advantages of canal sparing prostheses can be achieved with impaction grafting of a thin stem: preservation of humeral bone stock for potential revisions, performance of anatomic reconstruction regardless of posterior offset in anatomic arthroplasty, facilitating arthroplasty in cases of humeral deformity, prevention of malpositioning, and avoiding periprosthetic fractures.

The variations of intramedullary anatomy are recognized

and managed by impacting humeral autograft into the canal, 'reinvesting' the patients own bone in strengthening the humeral shaft.

This approach enables precise positioning of a humeral component with a smaller stem, secure safe fixation, and ease of prosthesis exchange should revision become necessary. Note the absence of cortical contact with the tip of the prosthesis.

It also allows the use of an anteriorly eccentric humeral head to manage posterior instability, a modification not possible with stemless implant.

It is apparent that management of a post traumatic arthritic shoulder can be complicated if the humerus is malunited in varus.

because normal positioning of the humeral component would conflict with the cuff attachment to the tuberosity.

In these cases it is possible to use impaction grafting to fix a small stemmed humeral prosthesis in an amount of varus that matches the deformity, so that the humeral head is positioned in the center of the glenoid. In the case below, the fixation of the humeral component was robust - more than what we could have achieved with a stemless prosthesis.