Background Most knee surgeons have believed during TKA neutral mechanical alignment should be restored.

One year after treatment, characterized chondrocyte implantation was associated with a tissue regenerate that was superior to that after microfracture. Short-term clinical outcome was similar for both treatments. The superior structural outcome may result in improved long-term clinical benefit with characterized chondrocyte implantation. Long-term follow-up is needed to confirm these findings.

O ur purpose was to determine the mechanism which allows the maximum knee flexion in vivo after a posterior-cruciate-ligament (PCL)-retaining total knee arthroplasty. Using three-dimensional computer-aided design videofluoroscopy of deep squatting in 29 patients, we determined that in 72% of knees, direct impingement of the tibial insert posteriorly against the back of the femur was the factor responsible for blocking further flexion.In view of this finding we defined a new parameter termed the 'posterior condylar offset'. In 150 consecutive arthroplasties of the knee, the magnitude of posterior condylar offset was found to correlate with the final range of flexion. Total knee arthroplasty (TKA) gives good subjective and objective results during the first 15 years after implantation. Nevertheless, it is clear that the function and subjective findings do not match those of the normal knee. The range of flexion of the knee obtained after TKA is often limited and may be determined by several factors, including the length of the quadriceps, capsular tightness, surgical technique, postoperative physiotherapy and the design of the implant.

Background Recently, patient-specific guides (PSGs) have been introduced, claiming a significant improvement in accuracy and reproducibility of component positioning in TKA. Despite intensive marketing by the manufacturers, this claim has not yet been confirmed in a controlled prospective trial. Questions/purposes We (1) compared three-planar component alignment and overall coronal mechanical alignment between PSG and conventional instrumentation and (2) logged the need for applying changes in the suggested position of the PSG. Methods In this randomized controlled trial, we enrolled 128 patients. In the PSG cohort, surgical navigation was used as an intraoperative control. When the suggested cut deviated more than 3°from target, the use of PSG was abandoned and marked as an outlier. When cranial-caudal position or size was adapted, the PSG was marked as modified. All patients underwent long-leg standing radiography and CT scan. Deviation of more than 3°from the target in any plane was defined as an outlier. Results The PSG and conventional cohorts showed similar numbers of outliers in overall coronal alignment (25% versus 28%; p = 0.69), femoral coronal alignment (7% versus 14%) (p = 0.24), and femoral axial alignment (23% versus 17%; p = 0.50). There were more outliers in tibial coronal (15% versus 3%; p = 0.03) and sagittal 21% versus 3%; p = 0.002) alignment in the PSG group than in the conventional group. PSGs were abandoned in 14 patients (22%) and modified in 18 (28%). Conclusions PSGs do not improve accuracy in TKA and, in our experience, were somewhat impractical in that the procedure needed to be either modified or abandoned with some frequency. Level of Evidence Level I, therapeutic study. See instructions for authors for a complete description of levels of evidence.

Many surgeons believe that increasing the tibial slope in total knee arthroplasty (TKA) is beneficial with regard to maximal postoperative flexion. Review of the clinical literature, however, does not confirm this hypothesis, neither does it give an answer to the question of how much flexion gain can be expected per degree extra tibial slope. The purpose of this study was, therefore, to evaluate and quantify the influence of tibial slope on maximal postoperative flexion in contemporary posterior cruciate ligament (PCL)-retaining TKA. Twenty-one cadaver simulations of a standard PCL-retaining TKA were studied while reproducing identical deep flexion femorotibial kinematics as documented by three-dimensional computer-aided videofluoroscopy from patients with well-functioning TKAs of the same design. In each knee the tibial component was consecutively implanted with 0 degrees posterior slope, 4 degrees posterior slope, and 7 degrees posterior slope. Maximal flexion was recorded for each configuration. Average maximal flexion at 0 degrees tibial slope was 104 degrees, and increased significantly to 112 degrees when the same knees were implanted with 4 degrees tibial slope. Increasing the slope further to 7 degrees again significantly improved average maximal flexion to 120 degrees. When postoperative radiographic tibial slope was compared to maximal flexion, an average gain of 1.7 degrees flexion for every degree extra tibial slope was noted. Increasing the tibial slope in PCL-retaining TKA does indeed improve maximal flexion before tibial insert impingement occurs against the femoral bone. The surgeon can expect an average gain of 1.7 degrees flexion for every degree extra tibial slope.