Q&A: Minimally invasive total knee replacements

Q: What is a minimally invasive total knee replacement and is it coded differently from a traditional total knee replacement?

A: A minimally invasive total knee replacement is a surgery similar to a traditional total knee replacement, but there's less cutting of the tissue surrounding the knee. It helps avoid trauma to the quadricep muscle, which decreases recovery time.

The implants are the same as the implants that are used for traditional total knee replacements, but specifically designed surgical instruments are used to prepare the femur and the tibia, and to place the implants properly.

It's performed through a shorter incision, typically four to six inches versus eight to ten inches for the traditional total knee replacement. The smaller incision allows for less tissue disturbance. The technique used to open the knee is less invasive. Those are considered quadricep-sparing, meaning that they avoid trauma to the quadricep tendon and muscle in front of the thigh. So, lower risk of complications and more rapid return of knee function.

Other minimally invasive techniques, called midvastus or subvastus, make smaller incisions in the muscle but are also less invasive than traditional total knee replacements. These techniques used to expose the joint involve less disruption, so the patient may have less postoperative pain and reduced recovery time.

Are minimally invasive total knee replacements coded differently than traditional total knee replacements? There really isn't any generally accepted definition of “minimally invasive.” The CPT codes don't explicitly distinguish between minimally invasive and traditional approaches. The coding depends on the compartments that are replaced: medial, lateral, or both. So, the code is going be the same as a traditional total knee replacement:

• 27446 (Arthroplasty, knee, condyle and plateau; medial or lateral compartment)
• 27447 (Arthroplasty, knee, condyle and plateau; medial and lateral compartments with or without patella resurfacing [total knee arthroplasty])

Editor’s note: This Q&A was originally published in JustCoding. It was answered by Adrienne Commeree, MLS, RHIA, CPC, CPMA, CCS, CEMC, CPIP, during JustCoding’s webinar, “CPT Coding for Outpatient Knee Replacement Surgery.”