Friday, December 12, 2014

Patient specific surgical guides - are they of value in improving clinical outcomes?

Small improvements in mechanical axis alignment achieved with MRI versus CT-based patient-specific instruments in TKA: a randomized clinical trial.

There is enthusiasm in some quarters for the application of 'patient-specific' instruments for shoulder arthroplasty (see here and here), however the value of this technology in improving patient outcomes has yet to be demonstrated. Because total knee arthroplasty (TKA) is performed more commonly than total shoulder arthroplasty and because the effects of non-anatomic alignment have been well documented for TSA, it seems of interest to include a study of the effect of MRI- and CT-based patient-specific instrumentation on validated outcomes scores for knee arthroplasty.

These authors conducted a randomized clinical trial in which 90 patients were enrolled and divided into three groups: CT-based, MRI-based patient-specific instrumentation, and conventional instrumentation. The groups were not different regarding age, male/female sex distribution, and BMI. 

Compared with conventional instrumentation MRI- and CT-based patient-specific instrumentation showed higher accuracy regarding
(1) the coronal limb axis (MRI versus conventional, 1.0°; CT versus conventional, 3.0°,
(2) femoral rotation (MRI versus conventional; CT versus conventional, 1.0°)
(3) tibial slope (MRI versus conventional, 1.0°, CT versus conventional, 1.0°), 

While these differences were statistically significant, they were small.

There were no differences in the postoperative Knee Society pain and function and WOMAC scores among the groups.

The authors concluded that patient-specific instrumentation increased accuracy in comparison to conventional instrumentation, the differences were only subtle and of questionable clinical relevance. In the absence of differences in the long-term clinical outcome or survivorship, the authors do not recommend widespread use of this technique.

Comment: The results and conclusions of this study are similar to those of another study covered in a previous post. The authors do not present the cost and time necessary for the patient-specific instrument approach. It would be of interest to know how much extra resource was consumed in the effort to improve alignment by a few degrees. 


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