Preoperative Planning/Templating/Limb Alignment for Primary Total Knee Arthroplasty
Timothy B. Alton
Mark W. Pagnano
Preoperative planning in total knee arthroplasty helps surgeons visualize the bone cuts and decrease intraoperative errors regarding implant size and alignment (Figure 44.1).
Preoperative planning can identify the need for nonstandard implants and identify major extra-articular deformities that require osteotomy or an alternative surgical technique.
Digital templating allows fast, precise, calibrated measurements and digital storage in the electronic medical record for access at the time of surgery.
Weight bearing radiographs in the anteroposterior and posteroanterior projections are very helpful for accurate planning.
Full-length radiographs of the hip-knee-ankle are particularly useful when substantial extra-articular deformity is present or suspected and serve as a useful reminder to rule out hip pathology in every patient presenting with knee pain.
Detailed medical history to identify risks for bony abnormalities
Prior trauma or infection in hip, femur, tibia, ankle, or foot
History of Paget disease, rickets, congenital or developmental conditions
Think specifically about extra-articular deformity
Detailed surgical history focused on lower extremity
Prior hip, femur, tibia, ankle, or foot surgery that might impact overall limb alignment or have caused a neurovascular problem.
Observe patient standing and walking.
Identify and document gait abnormalities, coronal plane deformities, foot drop, pes planovalgus, knee hyperextension, etc.
Examination of operative knee.
Evaluate ipsilateral hip to rule out hip pathology manifesting as knee pain.
Evaluate knee range of motion; identify and document preoperative contractures, coronal plane instability, and patellar stability.
Carefully examine the skin for open sores and prior incisions, then treat or plan accordingly.
Standing AP, PA weight bearing flexed, lateral, and patella sunrise views (Figure 44.2A-D).
Consider full-length hip-knee-ankle AP radiographs when evaluating coronal plane deformity (Figure 44.3). Another choice is EOS to image the entire body (Figure 44.4A and B). Full-length radiographs are particularly valuable in patients with substantial extra-articular deformity in whom a decision between intra-articular correction alone or combined osteotomy and total knee are being contemplated.
Extra-articular deformities further from the knee joint or smaller in angular deviation are more likely to be correctable with total knee alone (“correction through the joint”). In contrast, those deformities that are closer to the joint or that are larger in angular deviation are more likely to require osteotomy (“correction outside the joint”) either staged or combined with the total knee.
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