Nele Arnout

Patient-specific Guides Do Not Improve Accuracy in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial

BackgroundRecently, 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/purposesWe (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.MethodsIn 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.ResultsThe 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%).ConclusionsPSGs 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 EvidenceLevel I, therapeutic study. See instructions for authors for a complete description of levels of evidence.

Post-cam mechanics and tibiofemoral kinematics: a dynamic in vitro analysis of eight posterior-stabilized total knee designs

PurposePosterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA) designs were introduced to avoid paradoxical roll forward of the femur and to optimize knee kinematics. The aim of this in vitro study was to investigate post-cam function and contact mechanics and relate it to knee kinematics during squatting in eight contemporary posterior-stabilized TKA designs.MethodsAll prostheses were fixed on custom-designed metal fixtures and mounted in a knee rig and five sequential-loaded squats were performed between 30° and 130° of flexion. Contact pressure and contact area were measured using pressure-sensitive Tekscan sensors on the posterior face of the post. Kinematics was recorded with reflective markers and infrared light-capturing cameras.ResultsThe post-cam mechanisms analyzed in this study are very variable in terms of design features. This leads to large variations in terms of the flexion angle at which the post and cam engage maximal contact force, contact pressure and contact area. We found that more functional post-cam mechanisms, which engage at lower flexion angle and have a similar behavior as normal PCL function, generally show more normal rollback and tibial rotation at the expense of higher contact forces and pressures. All designs show high contact forces. A positive correlation was found between contact force and initial contact angle.ConclusionPost-cam contact mechanics and kinematics were documented in a standardized setting. Post-cam contact mechanics are correlated with post-cam function. Outcomes of this study can help to develop more functional designs in future. Nevertheless, a compromise will always be made between functional requirements and risk of failure. We assume that more normal knee kinematics leads to more patient satisfaction because of better mobility. Understanding of the post-cam mechanism, and knowing how this system really works, is maybe the clue in further development of new total knee designs.

A New Prediction Model for Patient Satisfaction After Total Knee Arthroplasty

BACKGROUND Total knee arthroplasty (TKA) is a proven and cost-effective treatment for osteoarthritis. Despite the good to excellent long-term results, some patients remain dissatisfied. Our study aimed at establishing a predictive model to aid patient selection and decision-making in TKA. METHODS Using data from our prospective arthroplasty outcome database, 113 patients were included. Preoperatively and postoperatively, the patients completed 107 questions in 5 questionnaires: Knee Injury and Osteoarthritis Outcome Score, Oxford Knee Score, Pain Catastrophizing Scale, Euroqol questionnaire, and Knee Scoring System. First, outcome parameters were compared between the satisfied and dissatisfied group. Second, we developed a new prediction tool using regression analysis. Each outcome score was analyzed with simple regression. Subsequently, the predictive weight of individual questions was evaluated applying multiple linear regression. Finally, 10 questions were retained to construct a new prediction tool. RESULTS Overall satisfaction rate in this study was found to be 88%. We identified a significant difference between the satisfied and dissatisfied group when looking at the preoperative questionnaires. Dissatisfied patients had more preoperative symptoms (such as stiffness), less pain, and a lower quality of life. They were more likely to ruminate and had a lower preoperative Knee Scoring System satisfaction score. The developed prediction tool consists of 10 simple but robust questions. Sensitivity was 97% with a positive-predictive value of 93%. CONCLUSIONS Based upon preoperative parameters, we were able to partially predict satisfaction and dissatisfaction after TKA. After further validation, this new prediction tool for patient satisfaction following TKA may allow surgeons and patients to evaluate the risks and benefits of surgery on an individual basis and help in patient selection.

Correction to: Surgeon experience with dynamic intraligamentary stabilization does not influence risk of failure

The original version of this article unfortunately contains mistake in Table 4.