Abstract
We present a new technique for TKA implantation which utilizes patient-specific femoral and tibial positioning guides developed from MRI to offer an individualized approach to total knee replacement.
This is a prospective non controlled study which aims to analyse the precision of this technique, its advantages and inconvenients in comparison with the conventional instrumented technique.
Material
The MRI provides a consistent three-dimensional data set of the patient's anatomy which allows for 3D axis identification.
The ideal position and sizing is performed by the surgeon on this 3D model and the patient specific guides are manufactured in advance in order to reproduce the bone cuts corresponding to this positioning and implant size. There are no intramedullary nor extramedullary instruments during the surgery.
Method
We compared 20 patients operated with this technique with 20 patients operated with the conventional technique.
The hypothesis was a difference < 2° between the 2 techniques
The measured parameters were:
HKS, HKA, tibial slope, femoral rotation on CT
Duration, bleeding, pain on VAS and morphine consumption, active flexion, KSS, Oxford score, recovery of independant walking and delay of return to home.
Both groups were identical for gender, age, BMI, etiology, comorbidities, pain and rehabilitation protocols.
Results
There were no significant differences on HKA, HKS angles, femoral rotation, active flexion, pain, length of hospital stay.
The surgery with the patient specific instruments was 10 minutes shorter than the conventional one (p < 0,05) and the bleeding was inferior with a ratio of 1/3 (p=0,02).
There were no complications with this technique and the use of the conventional guides were never necessary with the patient specific instrumentation.
Discussion and Conclusion
The patient specific instrumentation for TKA has a precision identical to that of the conventional technique, including for femoral rotation and ligament balance.
The advantages of this method are:
Reduced per and post operative bleeding
Shortening of the operative procedure
It is reproducible, including for less experimented surgeons and allows teaching and assistance in a lower technological institution.
The number of implant sizes is much inferior (2/9) just as the quantity of instruments to be sterilised.
These advantages induce a cost reduction which could be inferior to the price of the procedure.
