Total Knee Arthroplasty
This procedure is done mainly for osteoarthritis however, other reasons for having this procedure performed can be AVN (AVascular Necrosis) where the blood supply to the bone is lost, as well as old injuries that led to damage to the patients articular surface, which in turn led to early arthritis.
There are two main ways this procedure can be performed
- CR (Cruciate Retaining)
- PS (Posterior Stabilized)
When doing the procedure either way, the ACL (Anterior Cruciate Ligament) is sacrificed. However, what happens to the PCL (Posterior Cruciate Ligament) determines the type of implant that will be used in the patient. A CR Knee keeps the PCL intact, while, when doing a PS Knee the PCL is sacrificed.
The photos below will be showing the steps involved to perform a Smith & Nephew Legion (Gen II) Primary Knee Arthroplasty, both CR & PS. The particular pans used are Gen II however, the same instrumentation is available for the Legion Pans (just different configuration of instruments in the pans)
The 9mm Drill Bit is used to enter the femoral canal. After the canal is opened this will allow the Valgus Alignment Guide to be placed down the canal to determine the placement of the distal cut of the femur.
Valgus Alignment Guide. After guide is assembled & handed to the surgeon 2 pins will be placed into the Distal Cutting Block to secure it in place (TIP**a Kocher may be placed on one of the pins to prevent the block from vibrating out of place while the surgeon is sawing the distal femur). A fan shaped saw blade is used to make this cut.
The individual pieces to make up the Valgus Alignment Guide Are:
• Alignment Guide
• Valgus Bushing (degree of bushing is determined by surgeon preference)
• Distal Cutting Block
• IM Rod (IntraMedullary Rod) (there are two length IM Rods in this pan. A long & a short. The length used is based on surgeon preference. However, if the patient has an excessively bowed femur or, there is an existing implant in the patient at the hip; the shorter rod is preferred.
Femoral Sizing Block. This block determines the size and rotation of the femoral cutting block & component. This guide is comprised of two pieces. This guide IS side specific, so be sure to choose the appropriate block based on the side you are doing. When handing this block, make sure the posterior paddles are set to 3° of rotation.
• Left or Right Femoral Sizing Guide
• Sizing stylus
The 4-in1 Femoral Cutting Block is the block that will give the femur shape it needs to accept the femoral trials & implants. This cutting block is not side specific, so whatever size the surgeon determined the femur was in the previous step, is the same size block you will hand him to make his femoral cuts. This block is malleted on and secured with anywhere from 2-4 pins. A fan shaped sawblade is used to make these cuts. After cuts are made pins are removed, the Slap Hammer is used to remove the 4-in-1 cutting block and an osteotome (½” to ¾”) is used to help extract the pieces of sawed off bone.
Femoral Trial. These ARE side specific, so be careful to choose that appropriate size & side for the particular procedure being done. This trial will be secured onto the femoral trial handle.
• Femoral Trial
• Femoral Trial Handle (has Gold locking collet)
If you are doing a CR Knee, this construct will be placed to the side until it’s time for trialing.
If you are doing a PS Knee, this construct will be placed & secured w/ a pin onto the femur to facilitate the next step of cleaning out the femoral notch where the ACL & PCL reside.
In a PS Knee the ACL & PCL are removed, the implants will compensate for the removal of these ligaments & keep stability in the knee. After the femoral trial is secured onto the femur, the PS housing is secured on the trial, then the ACL & PCL are removed with the PS reamer. The remaining bone is shaped using the box osteotome.
• PS Housing
• PS Reamer Dome
• Patella Reamer Shaft
• Box Chisel / Osteotome
• Slap Hammer
Tibial Alignment Guide. The tibial cutting block IS side specific, make sure to use the correct side for the procedure being performed. The cutting block is secured with 2-3 pins & a fan shaped saw blade is used for this cut. This guide can be constructed 2 different ways, Extramedullary or Intramedullary. Always remember before handing this guide that the Popliteal Artery is Protected. This can be achieved a bunch of different ways. Some different ways I’ve seen with the surgeons I work with are using a Hohman Retractor, Cobb Elevator, or PCL Retractor (pickle fork).
Extramedullary Tibial Alignment Guide . The IM canal is not entered & depth, rotation, & slope are determined by external landmarks, such as tibial crest, 2nd metatarsal alignment.
• Tibial Extramedullary Alignment Tube
• Ankle Clamp w/ Locking Screw
• Non-Spiked Fixation Rod
• Tibial Cutting Block
• Long Non-Spiked Fixation Rod (optional)
Intramedullary Tibial Alignment Guide is where depth, rotation, & slope of the cut is determined using the intramedullary canal, then if surgeon prefers can be rechecked extramedullary before making the tibial cut.
• 9mm Drill Bit (same one used to enter the femoral canal in 1st step of the procedure)
• T-Handle (same one used to enter the femoral canal in 1st step of the procedure)
• IM Rod (same one used to enter the femoral canal in 1st step of the procedure)
• Intramedullary Alignment Guide
• Tibial Cutting Block
• Long Non-Spiked Fixation Rod (optional)
Tibial Trial Base Plate. The base plate is side specific so make sure you select the correct side for the procedure being performed. The size of the base plate is determined by the size of the bone removed from the tibia. You can lay your metal trial on top to the cut piece of bone, there should be a small rim of bone showing around the base plate. This is to accommodate for potential osteophytes the patient may have had as well as the fact that the tibia narrows. Another important thing to look for when determining the size of the tibial is that there is NO A/P Overhang (Anterior to Posterior Overhang) for the base plate. Once the correct tibial size has been dertermined, the surgeon may want to create the Fin Punch (locks in tibial rotation), of Trial the whole Knee, then create the fin punch (surgeon preference)
• Tibial Base Plate
• Quick Connect Handle
• 11mm Tibial Drill (optional)
• Fin Punch
• Slap Hammer
Tibial Insert Trials. These plastic inserts will be the surface that the femoral prosthesis will articulate with & are NOT side specific. The inserts come in a varitity of widths (most common are 9-13). The appropriate width will be chosen by the surgeon during the trialing phase. The surgeon is looking to see that the leg fully extends (no contractures), not too tight or loose when place in varus or valgus stress, or when placed in traction.
• Orange CR Tibial Inserts (various widths)
• Purple PS Tibial Inserts (various widths)
The black wafer is added onto the 9mm inserts to transform them into 13mm inserts.
Time to put the trials in.
The row of photos w/ the Orange inserts is the CR Knee. in the last photo is the Lug Punch, this control medial / lateral migration in the implant.
The row of photos w/ the Purple inserts is the PS Knee. In the last photo is the PS Box Module, this controls medial / lateral migration.
Patella Button (optional). If the surgeon chooses to replace the patella it can be done 2 ways, either Inlay (not shown) or Onlay
Onlay Patella Button uses the following items:
• Cutting Clamp (Resection Guide)(optional)
• Reamer / Drill / Impactor Guide
• Patella Drill Guide (size determined after bone resected)
• Patella Drill
• Red Patella Onlay Trial (same size as drill guide)
2nd Femoral Impactor
CR Primary Femoral Impactor
CR Primary Femoral Impactor Loaded
PS Primary Femoral Impactor
PS Primary Femoral Impactor Loaded
Look for any areas of extruded cement, remove, irrigate, then CLOSE!!!!