Failed, Unsatisfactory Shoulder Joint Arthroplasty - glenoid component loosening

As we saw in the June 27 post 59% of patients coming to us for consultation because they were dissatisfied with their total shoulder joint replacement arthroplasty had loose or worn glenoid components.

The concern about glenoid component failure comes from careful followup of patients having shoulder replacements in the past using a variety of older component designs and older techniques. 

Our shoulder fellow Lazarus published a nice paper pointing to the challenges of achieving a perfect glenoid component insertion and the effect of surgeon experience.

Ideal contouring of the bone beneath the glenoid component (as shown below) is essential as pointed out by shoulder fellow Collins.

When the bone is not properly prepared, there is a tendency to pack in a bit of cement to fill in the defect ('putty carpentry'). This is commonly seen in the posterior (back) half of the glenoid as shown below left. However, this wedge of cement is brittle and not fixed to either the component or bone so it can slip out leaving the component unsupported and at risk for loosening (below right).

The earliest sign of loosening is a dark line (radiolucency) seen on the x-ray as shown below at the "L".

From a very well done study of 333 total shoulders, here is a graph showing a 50% radiographic survivorship of glenoid components put in 10 years ago.

Loosening seems to be particularly common when the glenoid design consists of a keel that is fixed into the bone of the shoulder blade using a wad of cement as shown below left and in the color photograph of a retrieved glenoid component

Cement cures with an exothermic reaction - this heats the bone to an amount determined by the amount of cement used. Excessive cement can result in thermal death of the bone with loss of fixation as shown by the thermal camera images below.

Removing a loose glenoid component leaves a big hole in the glenoid bone, making subsequent reconstruction difficult.

We have vigorously investigated the causes of failure and ways in which the security of the component can be optimized. We continue to use a modern glenoid component in the majority of our shoulder joint replacements, because it provides predictable recovery of shoulder comfort and function

Time will tell whether the newer design and our modern techniques will improve the long term durability of the glenoid component.

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