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Component malrotation may result in unsuccessful total knee arthroplasty. We asked whether revision improves function in patients with malrotated total knee arthroplasty components. We retrospectively reviewed 22 revision total knee arthroplasties performed for femoral and/or tibial component malrotation. Revision surgery was performed within 2 years of the primary arthroplasty in 81% of the cases (18 of 22) with the remainder within 5 years. Although all patients had pain, 32% of patients had associated instability and 36% of patients had poor range of motion. Average Knee Society Scores improved from 42 preoperatively to 77 postoperatively. Average Oxford Knee Scores improved from 38 preoperatively to 29 postoperatively. Although clinical and functional improvement was observed, these results are inferior to those for primary knee arthroplasty, and they emphasize the need for proper component rotational positioning during primary total knee arthroplasty. Internal component malrotation leads not only to patellofemoral problems, but also to difficulty in gap balancing and femoral component sizing, which may in turn lead to either poor range of motion or symptoms of knee instability.

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The short-term high rate of corrosion-related revision with Rejuvenate modular-neck stems is striking.

Background Traditionally, the placement of the tibial component in total knee arthroplasty (TKA) has focused on maximizing coverage of the tibial surface. However, the degree to which maximal coverage affects correct rotational placement of symmetric and asymmetric tibial components has not been well defined and might represent an implant design issue worthy of further inquiry. Questions/purposes Using four commercially available tibial components (two symmetric, two asymmetric), we sought to determine (1) the overall amount of malrotation that would occur if components were placed for maximal tibial coverage; and (2) whether the asymmetric designs would result in less malrotation than the symmetric designs when placed for maximal coverage in a computer model using CT reconstructions. Methods CT reconstructions of 30 tibial specimens were used to generate three-dimensional tibia reconstructions with attention to the tibial anatomic axis, the tibial tubercle, and the resected tibial surface. Using strict criteria, four commercially available tibial designs (two symmetric, two asymmetric) were placed on the resected tibial surface. The resulting component rotation was examined. Results Among all four designs, 70% of all tibial components placed in orientation maximizing fit to resection surface were internally malrotated (average 9°). The asymmetric designs had fewer cases of malrotation (28% and 52% for the two asymmetric designs, 100% and 96% for the two symmetric designs; p \ 0.001) and less malrotation on average (2°and 5°for the asymmetric designs, 14°for both symmetric designs; p \ 0.001). Conclusions Maximizing tibial coverage resulted in implant malrotation in a large percentage of cases. Given similar amounts of tibial coverage, correct rotational positioning was more likely to occur with the asymmetric designs. Clinical Relevance Malrotation of components is an important cause of failure in TKA. Priority should be given to correct tibial rotational positioning. This study suggested that it is easier to balance rotation and coverage with asymmetric tibial baseplates; clinical research will need to determine whether the observed difference affects patellar tracking, loosening rates, or the likelihood of revisions after TKA.

Strain was measured in the normal anterior talofibular ligament (ATF) and the calcaneofibular ligament (CF) using Hall effect strain transducers in five cadaveric ankles. These measurements were made in both ligaments with the ankle in neutral position and with the foot moving from 10 degrees dorsiflexion to 40 degrees plantarflexion in an apparatus that permits physiologic motion. The ankle ligaments were then tested with the foot placed in six different positions that combined supination, pronation, external rotation, and internal rotation. In the neutral position, through a range of motion of 10 degrees dorsiflexion to 40 degrees plantarflexion, the anterior talofibular ligament underwent an increasing strain of 3.3%. No significant strain increase was found with internal rotation. The only significant difference from the strains at the neutral position was in external rotation, which decreased strain 1.9%. In all positions, increased strain occurred with increased plantarflexion. The calcaneofibular ligament was essentially isometric in the neutral position throughout the flexion arc. The calcaneofibular ligament strain was significantly increased by supination and external rotation. However, with increasing plantarflexion in these positions, the strain in the calcaneofibular ligament decreased. Therefore, plantarflexion has a relaxing effect on the calcaneofibular ligament. Thus, the anterior talofibular and calcaneofibular ligaments are synergistic, such that when one ligament is relaxed, the other is strained and vice versa.

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