Sunday, June 14, 2015

Shoulder joint replacement arthroplasty - does three dimensional imaging and templating get us closer to the goal?

Three-dimensional imaging and templating improve glenoid implant positioning.

Preoperative quantitative assessment of glenoid bone loss, selection of the glenoid component, and definition of its desired location can be challenging. Placement of the glenoid component in the desired location at the time of surgery is difficult, especially with severe glenoid pathological conditions.

These authors randomly assigned 46 patients to three-dimensional computed tomographic preoperative templating with either standard instrumentation or with patient-specific instrumentation and were compared with a nonrandomized group of seventeen patients with two-dimensional imaging and standard instrumentation used as historical controls. All patients had postoperative three-dimensional computed tomographic metal artifact reduction imaging to measure and to compare implant position with the preoperative plan.

They found that three-dimensional imaging and templating with or without patient-specific instrumentation, yielded a significant improvement achieving the desired implant position within 5° of inclination or 10° of version when compared with two-dimensional imaging and standard instrumentation.

Comment: Consistent with our experience, these patients with primary osteoarthritis were categorized as showing a wide range of pathoanatomies. The issue is how these variations might best be managed. These authors indicate that one method is to 'correct' glenoid version and inclination between 0 and 10 degrees relative to the plane of the scapula, using augmented glenoid components if deemed necessary. As Figure 2 of this article demonstrates, this approach may lead to the removal of a substantial amount of glenoid bone and may require not only a special glenoid component, but also special instruments to guide and prepare the glenoid bone for the receipt of this component. The alternative, most commonly used in our practice, is to use nubbed reamers to convert the glenoid articular face to a single concavity while preserving the maximal amount of glenoid bone as described here.

If we accept the premise that glenoid version and inclination should be corrected, these authors found that glenoid inserted with three-dimensional imaging and  'three-dimensional intelligent reusable instruments' had a mean difference of 3 degrees in inclination (CI  2 - 4) from the planned position, while the two-dimensional imaging group had a mean difference of 11 (CI 8 - 14). The respective data for version were 4 (CI 3 - 5) and 7 (CI 5 - 9). The question becomes whether the differences of 7 and 3 degrees are worth the time and expense of the three-dimensional imaging and  three-dimensional intelligent reusable instrument system in terms of value to the patient. Time will tell.


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