What is Patient Specific Instrumentation?
Patient Specific Instrumentation is one of the new and visionary technologies in total knee replacement surgery.
Combination of long standing X-rays of both lower limbs and MRI is used to create a virtual model of the patient knee, based on which, patient specific bone cutting zigs (custom block) are made. These blocks provide a "hand in glove" fit during surgery as they "exactly matches the patient's unique tibial and femoral anatomy".
During surgery they provide accurate bony cuts thus allowing precision to the final implant position. These "Blocks" are patient specific (even to the individual knee) and disposable.
Virtual model of Femur and Tibia with cutting zigs
What is the need of Patient Specific Instrumentation?
There is a close correlation between poor implant alignment and poor clinical outcome in total knee replacement surgery. Most surgeons strive to ensure that implant alignment is optimal for excellent outcome. CAS (Computer Assisted Surgery) offered this as its advantage but cost of systems, extended surgical time, array fixation methods are some of the disadvantages of the system.
Patient Specific Instrumentation is a good alternative to CAS as a technology to replicate the performance of CAS with minimal disadvantages of CAS.
What are the advantages of Patient Specific Instrumentation?
Patient Specific Instrumentation is advantageous to patients, Surgeons and Hospitals alike.
For patients: improves accuracy of alignment without putting extra pin in the bones thereby giving good results. Reduce incidence of DVT & Fat embolism, as femoral canal is not violated in conventional surgery and also reduces blood loss. Even in High Risk category patients the surgical time and anesthesia time is significantly reduced.
For Surgeons: More efficient surgery. Patient Specific Instrumentations not only reduces the number of instruments on the operation table but also reduces the number of surgical steps required to do knee replacement surgery.
Greater accuracy – Patient Specific Cutting Blocks are made from patient's own x-rays images and MRI and nothing can be more accurate for assessing patient's alignment and size. Greater accuracy is expected to give lasting outcome to patients Knee replacement
What are the disadvantages of Patient Specific Instrumentation?
The main disadvantage of Patient specific instrumentation at the moment is waiting period of approximately 4 weeks (time taken to deliver custom bock after patient X-rays & MRI) and additional cost of approx., Rs 45000/- (or approx. 1000$) each knee.