Swiss Orthopaedic Company Mathys Ag Bettlach has issued an urgent field safety notice, which warns of an incorrect instruction in its size determination table for the balanSys® Knee. Following the existing directions could result in incompatible femoral and tibial components being implanted.
Mathys says it was one of its distributors that spotted a problem in its Size Determination Table, which has resulted in this action. It seems the table, which is found in the Surgical Technique guide indicates that femoral component of size “C” can be used in conjunction with tibial inlay/tibial plateau size 67. This is definitively not the case, the size 67 tibial component only being compatible with the smaller femoral components, labelled size A or B.
The company says its size 67 tibial component was only made available in September 2012 and it has not been made aware of any complications
Having said which, the theoretical risk exists that by being unable to optimally equilibrate the knee, due to incongruence between the tibial and femoral components, this could lead to pain and instability. Furthermore it points to the long term risk of increased wear of the polyethylene, which may lead to pain, osteolysis, tibial loosening, instability and the need for revision surgery.
Unsurprisingly then, the company states that no implantation of the combination of tibial component size 67 with femoral component size C should be performed. Furthermore it recommends that users of the balanSys knee system review the case files of all previously treated patients. If a patient file indicates that a tibial inlay/tibial component size 67 was used in combination with a femoral component size C, the following measures are recommended:
- Search the patient file for medical symptoms that might have been caused by the incompatibility, then:
- Assess the knee joint’s objective and subjective stability
- Check for implant-specific pain
- Perform X-ray for signs of increased abrasion/osteolysis, if possible
- Make a note in the patient file indicating the incompatible combination
- Notify the local Mathys agency using the form in Annex D
- Carry out a follow-up examination if deemed necessary by the attending physician
For its part Mathys says it will develop specific after-care measures in cooperation with Medical Advisor and make them
available to the attending physicians of patients affected.
Full Field Safety Notice here.
Source: Mathys Ag Bettlach