Thursday, November 28, 2013

Lack of demonstrated advantage of cementless metal backed glenoid components

Effect of glenoid cementation on total shoulder arthroplasty for degenerative arthritis of the shoulder.

A prior report based on the Australian Joint registry showed poorer results with a metal-backed glenoid with a high incidence of breakage and dissociation.

These authors used the New Zealand National Joint Registry compare the outcomes of uncemented and cemented glenoids in TSA performed for degenerative arthritis in 1596 patients followed for a mean of 3.5 years (range 2-10.7 years).  1065 had a cemented glenoid. This study does not identify the reasons surgeons decided to use one type of fixation or other.

There were no significant differences in any preoperative factors between the 2 groups. The revision rate for uncemented glenoids was 4.4 times higher than for cemented glenoids (1.92 vs 0.44 revisions per 100 component-years, P < .001).

Noting that some patients had more than one reason for failure, the most common reasons for failure were different between the metal backed and the cemented poly components.

We have previously posted comments on why this might be.

It is of interest that the traditional '2 years followup' does not reveal the actual problem with glenoid component failure, which continues with time. Note that the apparent plateau in the survivorship curve for metal backed uncemented is probably related to the lack of longer term followup for these components.

The authors also observed that age <55 years was an independent risk factor for revision (P < .001). For both uncemented and cemented components, the failure rate for patients <55 was over twice that for individuals >55 years.

The effect of age and of component type were independent of each other.

The results do not provide evidence in support of the use of metal backed components (a finding similar to prior studies that have been posted previously).

The increased revision rate for younger patients is also a consistent finding and suggests that in some young patients a glenohumeral arthroplasty without a glenoid prosthesis may be considered.

Consultation for those who live a distance away from Seattle.

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