Early success has been reported using a long-stem cemented femoral component in total hip arthroplasty (THA). The same patient group reported by the authors' institution at five years were reviewed again at ten years postarthroplasty. Certain trends can now be defined, including gradual deterioration in the Harris hip score, tendency toward failure of acetabular fixation (8.4% loosening rate requiring revision), and increased calcar resorption. Overall, the cemented femoral component has performed admirably, with a 97% success rate at ten-years' post-THA (3.1% revision rate). In this study, success was defined as arthroplasties that did not require revision. Ninety percent of observed patients were rated as good or excellent using the Harris hip score. The Clayton femoral component provides excellent durability by virtue of design.
Revision total knee arthroplasty presents numerous technical challenges and decisions for the operating surgeon. Preoperative planning includes critically reviewing radiographs and ordering necessary equipment, including prosthetic components, extraction devices, and bone graft materials. In some cases, surgical exposure requires the use of extensile exposure techniques. Component removal is facilitated by the use of appropriate tools (eg, specialized osteotomes) as well as by the patience to ensure preservation of host bone. Bone loss is managed with bone grafts or prosthetic augmentation. Attention to balancing the flexion and extension gaps is essential to avoid problems with instability as well as excessively constrained prosthetic components. Intramedullary stem extensions improve long-term clinical results. Intraoperative extensor mechanism complications can be avoided with meticulous surgical technique; late complications may require surgical intervention.
The Rocky Mountain Musculoskeletal Research Laboratory uses in vivo video fluoroscopy to evaluate kinematics of total knee arthroplasty. This method allows us to evaluate in vivo weight bearing activity for a variety of knee designs, as well as kinematics of the normal knee. Our proprietary method of automated model fitting allows for three-dimensional analysis obtained from two-dimensional fluoroscopic images with minimal error. This article outlines the details of our kinematic analysis of the Low Contact Stress (LCS) Total Knee System (DePuy Orthopaedics lnc, Warsaw, Ind) rotating platform total knee and compares this design with fixed-bearing posterior cruciate-retaining and posterior cruciate-substituting total knee and normal knee kinematics.
Introduction: Previously, in vivo kinematic studies have determined the in vivo kinematics of the femur relative to the metal base-plate. These kinematic studies have reported posterior femoral rollback in posterior stabilized (PS) TKA designs, but the actual time of cam/post engagement was not determined. The objective of this present study was to determine, under in vivo conditions, the time of cam/post engagement and the kinematics of the femur relative to the polyethylene insert.
Methods: Femorotibial contact positions for twenty subjects having a PS TKA, implanted by two single surgeons, were analyzed using video fluoroscopy. Ten subjects were implanted with a PS TKA that is designed for early cam/post engagement (PSE) and ten subjects with a PS TKA designed for later cam/post engagement (PSL). Each subject, while under fluoroscopic surveillance, performed a weight-bearing deep knee bend to maximum flexion. Video images were downloaded to a workstation computer and analyzed at ten-degree increments of knee flexion. Femorotibial contact paths for the medial and lateral condyles, axial rotation and condylar lift-off were then determined using a computer automated model-fitting technique.
Results: Subjects implanted with the PSE TKA experienced, on average, the cam engaging the post at 48° (10 to 80°). Subjects having the PSL TKA experienced more consistent results and did experience engagement in deep flexion (Average 75°). Subjects having the PSE TKA experienced, on average, −5.5 mm (1.5 to −9.3) of posterior femoral rollback (PFR), while subjects having the PSL TKA experienced only −2.6 mm (8.5 to −9.0) of PFR. Subjects having the PSE TKA experienced more normal axial rotation patterns. Nine subjects having the PSE TKA experienced condylar lift-off (maximum = 1.9 mm), while only 4/10 having the PSL TKA experienced condylar lift-off (maximum = 2.7 mm).
Discussion: This is the first study to determine the in vivo contact position of the cam/post mechanism. Subjects having a PSE TKA experienced earlier cam/post engagement than subjects having the PSL TKA. Some subjects did not experience any cam/post engagement throughout knee flexion. Subjects having the PSE TKA experienced more PFR and better axial rotation patterns, but subjects having a PSL TKA experienced lesser incidence of condylar lift-off. Results from this study suggest that there may be an advantage to early cam/post engagement, which leads to more normal axial rotation patterns caused by the medial condyle moving in the anterior direction as the lateral condyle rolls in the posterior direction.
Introduction: Obtaining accurate anatomic and mechanical alignment in total knee arthroplasty (TKA) is correlated with improved long-term results. Whether computer-assisted total knee arthroplasty (CAS-TKA) more reliably produces a neutral mechanical and anatomic alignment and improves functional outcomes over traditional total knee arthroplasty (T-TKA) remains debatable. This report evaluates the results of CAS-TKA vs. T-TKA in a series of patients who underwent bilateral TKA performed at the same surgical operation. Methods: Sequential bilateral TKA were performed on 36 patients utilizing CAS-TKA in one knee and T-TKA in the contralateral knee by two high volume, fellowship trained surgeons. A review and statistical analysis of prospectively collected data was performed after a mean follow-up of 2.2 years. Results: Knee Society Scores (KSS) improved from 42.9 to 96.3 in the CASTKA group vs. 46.0 to 94.8 in the T-TKA group. Range of motion (ROM) improved from 116.8° to 126.9° in the CAS-TKA group vs. 118.3° to 125.4° in the T-TKA group. With numbers available, there were no differences between the groups with regard to change in KSS (p=0.38), ROM (p=0.42), mean postoperative anatomic alignment (5.78° vs. 5.50°, p=0.37), femoral angle (5.56° vs. 5.61°, p=0.84), or tibial angle (89.89° vs. 89.69°, p=0.46). There was a non-significant trend towards fewer outliers in the CASTKA group with respect to anatomic alignment (2.8% vs. 13.9%, p=0.09) and tibial angle (0% vs. 5.6%, p=0.46). Conclusion: There is not an apparent benefit to the use of CAS-TKA with regards to KSS, ROM, or alignment in the hands of high-volume, fellowship-trained total joint specialists. The clinical relevance of the non-sig-nificant trend towards fewer outliers in the CAS-TKA group is unknown at the current follow-up interval. These results may not preclude the benefits of CAS-TKA in lower-volume or less experienced TKA surgeons.
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