Tuesday, August 8, 2017

Stemless humeral components - do they solve a problem? (Part 2)

Is the stemless humeral head replacement clinically and radiographically a secure equivalent to standard stem humeral head replacement in the long-term follow-up? A prospective randomized trial

These authors used a stemless humeral component in 20 patients (Group 1) and a stemmed design in 20 patients (Group 2).

Twenty-nine patients were examined clinically and radiographically at a minimum follow-up of 2 years and a minimum follow-up of 5 years.

The postoperative CS improved significantly in both groups, with no significant difference between the minimum of 2-year and 5-year follow-up. There were no significant differences in final Constant score or range of motion between the two groups. However, the patients receiving the stemmed design (Group 2) had substantially lower preoperative Constant scores and poorer range of motion:

Thus the amount of improvement at two years in the relative Constant score was 12.9 for the stemless and 55.7 for the stemmed component.  The amount of improvement at two years in flexion was 19.3 degrees for the stemless and 47.4 degrees for the stemmed component.

With this particular stemmed implant there was lower bone density adjacent to the humeral calcar in 41% and there were significantly more frequent radiolucent lines.  No diminished density was seen with this stemless particular stemless implant. However, the group receiving the stemmed implant were older and had a higher percentage of females, both of which factors may have contributed to the radiographic findings.

No complication concerning the humeral implant was observed in group 1 (stemless). For the glenoid implant, atraumatic loosening of the glenoid component was noted in 2 patients, which led to a revision and exchange of the glenoid component. One rotator cuff deficiency, which led to a revision with conversion to a reverse prosthesis, was observed. 

In group 2 (stemmed), a fracture of the greater tuberosity resulted in 1 traumatic loosening of the humeral implant. There were no complications at the glenoid implant in group 2.

Comment: In this comparative series, patients in the stemless group appear to have realized less functional improvement and experienced a higher complication rate than those in the stemmed group.
We continue to use impaction grafting of a relatively thin smooth humeral stem because of the simplicity of use, the maximal bone preservation, the broad load distribution that minimizes stress shielding and the ease of revision, should that ever become necessary. 

Note in these two year followup films the preservation of the humeral bone stock, the stable fixation of the long stem achieved with impaction autografting, and the absence of stress shielding/bone resorption.
Note also the absence of radiolucent lines around the all polyethylene glenoid component, the absence of cement on the back side of the glenoid component, and the bone ingrowth between the flanges of the central peg of the glenoid component (arrow). 

On the postoperative 'truth' axillary view, note again the bone ingrowth, the absence of back side cement, and the absence of radiolucent lines as well as the centering of the humeral head in the glenoid and the preservation of glenoid bone stock.

This technique provides a dependable, adaptable and bone-preserving approach to total shoulder arthroplasty.

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