Tuesday, February 9, 2016

Patient-specific Instrumentation - No Functional Benefit

The John Insall Award: No Functional Benefit After Unicompartmental Knee Arthroplasty Performed With Patient-specific Instrumentation: A Randomized Trial.

The authors hypothesized that unicompartmental knee arthroplasty (UKA) performed with Patient-specific Instrumentation (PSI) would result in improved level gait as ascertained with three-dimensional analysis, implant positioning, and patient-reported outcomes measured by a validated scoring system when compared with conventional instrumentation 3 months and 1 year after surgery.

They randomized 60 patients into two groups using either the PSI technique or a conventional technique. All patients were operated on using the same technique and the same cemented metal-backed implant.

For the patients allocated to the PSI group,MRIs were obtained after randomization. All patients had their MRI completed  using a standardized protocol validated by the protocol manufacturer (MaterialiseTM , Leuven, Belgium). After segmentation, the engineers planned the UKA and submitted the plan to the surgeon. Based on the clinical examination and standing full-length hip-to-ankle radiographs, the plan was scrutinized and modified by the surgeon to set the appropriate depth of the distal femoral and tibial cuts, flexion of the femoral implant, and slope of the tibial plateau.

One year after surgery, there were no differences between the two groups in the analyzed gait spatiotemporal parameters, in terms of lower limb alignment,  implant positioning on mediolateral and anteroposterior radiographs, or in the functional scores.

Their observations suggest that PSI may confer small, if any, advantage in alignment, pain, or function after UKA. This argument can therefore not be used to justify the extra cost and uncertainty related to this technique.

Comment: When new technologies are brought forward, it is important to ask 'who will benefit'? The possibilities might include the manufacturer, the designer, the product champion, the medical center, the surgeon and/or the patient. In that the incremental cost of these technologies is ultimately borne by the patient and the patient's insurance, their use should be justified in term of benefit to the patient.This Level I randomized controlled study was unable to determine a value of PSI to the patient.

We include this total knee article in the Shoulder Blog because it shows the type of high quality clinical research that is necessary to evaluate the value of new technologies, including the many different forms of patent specific instrumentation, that are being introduced yearly to the shoulder marketplace.