全膝关节置换详解

A 76-year-old woman presented with bilateral knee pain, left worse than right. Pre-operative radiographs of the left knee show severe, end-stage osteoarthritis. The radiographic hallmarks of osteoarthritis are: joint space narrowing, sclerosis of the subchondral bone, osteophyte formation and eventually cystic changes in the adjacent bone Standing "alignment views" are used to determine the patient's weight bearing and mechanical axis. The technical goals of Total Knee Arthroplasty include re-establishing the patients mechanical axis and restoring the joint line. Often times, patients will have developed severe "varus" deformity (bowed legs) or less commonly, "valgus deformity (knock kneed). After a sterile prep, the limb is draped, landmarks are identified and the mid-line knee incision is planned unless patients have old scars which are not compatible with this standard incision The leg is exsanguinated and a tourniquet is used to maintain hemostasis throughout the case. Once the incision is made, the quadriceps tendon, the patella and the patellar tendon are identified. A medial para-patellar arthrotomy is made and the soft tissues are elevated from the tibia. Great care must be taken not to strip to much medially or laterally as this may result in disruption of the medial collateral ligament or the patellar tendon, respectfully. Both are disastrous complications. The patella and patellar tendon are released from the underlying fat pad and other soft tissues so the patella may be everted laterally to expose the distal femur and proximal tibia. After the patella and tendon are everted (under rake in photo), remaining capsular tissues are released. The patellar-femoral ligament above the clamp is about to be divided. Only a single cut is made to prepare the tibia. An extramedullary alignment guide is placed and secured with pins in the proximal tibia. This guide is used to resect the proper amount of bone and create the proper surface angulation for the new tibial joint line Several pins are placed to secure the guide. Once the guide is secure, the arthritic articulating surface of the tibia is resected using an oscillating saw After the cut is made with the oscillating saw, the section of tibia is removed. The resected arthritic articular surface of proximal tibia is shown After the tibial bone is resected, edges and any remaining bone are removed. Unlike the tibia, an intra-medullary guide is used to make the resection cuts on the femur. A hole is reamed from distal to proximal in the femur so the guide may be placed. The femoral guide hole is shown The placement of the intra-medullary guide with cutting block is shown. Once the alignment and rotation of the cutting block are determined, the block is secured into place with pins In contrast to the tibia, a series of cuts are made to prepare the distal aspect of the femur. The first and most important is the distal femoral cut. This will be used to determine soft tissue balancing and proper positioning of the replacement components Osteophytes are resected after the distal cut is completed. The knee is then extended and a "spacer block" is positioned to check the accuracy of the proximal tibia and distal femoral cuts. These cuts ultimately determine the position of the knee replacement components, the adequacy of the soft tissue balancing and the overall success of the arthroplasty. A tensioning device is used to determine if adjustments are required Next, a series of blocks are used to determine the proper size of implant to be selected. The sizing block is pinned to assure proper size and positioning The sizing block is removed. The pins are left in place and are used to position the cutting block. The anterior aspect of the femur is then resected?nbsp ...followed by the posterior aspect?nbsp; ...and finally the champfer cuts (angled cuts connecting anterior and posterior surfaces with the distal surface). Soft tissue and excess bone are removed The diagram demonstrates the planes of the anterior, posterior and champfer cuts The notch of the distal femur is prepared using a series of guides as well The anterior part of the notch is completed with a V-shaped cut The bottom notch cut is shown. Once all the cuts are completed the surfaces are prepared for placement of trial components. The trial components are placed to determine if final adjustments are needed and occasionally to determine if a larger or smaller sized component should be used. Here, the femoral trial is placed. The femoral trial component is shown in place Once the femoral trial component is positioned the posterior capsule of the knee is released and osteophytes are removed The femoral component is then removed to gain access to the tibial surface. A sizing guide is used to determine the fit for the tibial component The tibial guide is pinned into place The tibial guide has an extension through which an alignment rod is placed. This is yet another built in way to continually reassess the positioning of the final implants A cavity is created in the cancellous bone of the proximal tibia. The actual tibial implant has a stem to provide greater stability. Then, both femoral and tibial components are placed together to assess how they function in unison The undersurface of the patella is also resected?nbsp; ...measured with a caliper?nbsp ...sized appropriately?nbsp ...and fitted with a trial component. Any adjustments are made after taking the knee through a series of motion and stability tests The trial components are removed for a final time All prepared surfaces are inspected for a final time. The raw bone surfaces are the irrigated with antibiotic solution using a pulsatile lavage system. This removes loose bony fragments and particles. After irrigating, the bony surfaces are dried and polymethyl methacrylate bone cement is applied to the end of the femur. The actual femoral stainless steel implant is then positioned and impacted for a perfect fit. Excess bone cement is removed. The final implant is inspected Cement is then applied to the proximal tibia and pressed into the interstices of the tibial bone The actual tibial implant is then pressed into position The tibial implant is also impacted for a perfect fit. Excess cement is removed Bone cement is applied to the patella last The cement is pressed into the bone The polyethylene patellar button is then held in position with a clamp The knee is extended and irrigated a final time. The newly placed implants are taken through a series of motion and stability tests and then inspected again The quadriceps tendon and retinaculum/capsular layer are repaired using using #2 PDS interrupted, figure-of-eight sutures Once the arthrotomy is repaired maximum knee extension and flexion are measured. This is the best way to predict potential post-operative range of motion. Incomplete extension or inadequate flexion may result in gait abnormalities and problems with activities of daily living. After motion assessment, the subcutaneous tissues are closed and the skin approximated. Staples are used for skin closure and removed in two weeks time. Range of motion is begun immediately and a standard therapy protocol is begun. The patient will be allowed to bear full weight with assistance for balance.