15 Total Knee Arthroplasty
Summary
Total knee arthroplasty is one of the most common and successful surgical procedures performed in medicine. This procedure involves replacing the articulating surface in an arthritis knee joint with titanium-based implants that provide improved knee joint alignment and weight-bearing stability, all while eliminating osteoarthritic pain. Total knee arthroplasty is indicated for the treatment of severe arthritis (osteoarthritis or rheumatoid arthritis) that has not improved with conservative management (activity modification, non-steroidal anti-inflammatory drugs (NSAIDs), joint injections, and physical therapy). Total knee arthroplasty is a highly complex procedure that involves precise measurements of angles and accurate resection of bone to implant a prosthesis that is optimally aligned within the lower extremity mechanical axis. This chapter will explore the process of total knee arthroplasty.
15.1 Preop
Radiographic templating. Can use preoperative imaging (CT scan, X-rays) and templating software to measure the patient’s articular surface and plan for expected implant sizes prior to operating room.
Surgical instrumentation. Important to understand the system that is being used and nuances of instrumentation between the systems.
Operating table. Standard operating room table often used; sometimes, can use radiolucent table if taking intraoperative images.
Patient positioning. Supine position with a bump under the ipsilateral hip (minimizes external rotation when operating at knee).
Leg hold can be used to hold the knee at approximately 90 degrees of flexion at certain parts of the procedure.
Tourniquet. Although recent studies have questioned efficacy, apply tourniquet as proximally as possible to allow for adequate clearance for operating and draping.
15.2 Approach
15.2.1 Medial Parapatellar Approach to Knee
Mark the relevant anatomy using a sterile marking pen once draped—mark out the patella, patellar tendon, tibial tubercle, joint line, and quadriceps tendon insertion to patella.
Mark out incision. Draw straight line beginning 5–7 cm proximal to proximal aspect of patella and carry to point just distal to tibial tubercle.
Incise skin along drawn out incision line, carrying incision deep to the deep fascia (level of patellar and quadriceps tendons).
Create skin flaps medially and laterally. These are important for skin mobilization and visualization throughout surgery.
15.2.2 Entering Joint and Creating Adequate Visualization
Mark out the medial aspect of the patellar tendon, the medial aspect of the patella, and the medial aspect of the quadriceps tendon (but lateral to the vastus medialis oblique).
Beginning proximally, perform the arthrotomy by carrying incision along medial aspect of quadriceps tendon, patella, and patellar tendon.
Leave approximately 5 mm of soft tissue on the medial aspect of patella—will aid in wound closure.
Avoid disruption of the patellar tendon by incision along medial border of tendon without disrupting tendon itself.
15.2.3 Proximal Tibial Exposure and Preparation
The medial capsular tissue (and often medial collateral ligament [MCL]) must be cleared—use sharp dissection to clear this region and provide exposure (usually dissect posterior to the mid-coronal plane). Remove any osteophytes.
Severe varus deformity may require more extensive release of the MCL/capsule.
Severe valgus deformity will have medial laxity present at start—begin with conservative medial release and only extend as needed.
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