Gap Balancing Throughout the Arc of Motion With Navigated TKA and a Novel Force-Controlled Distractor: A Review of the First 273 Cases.

BACKGROUND: This study evaluated the ability to achieve the targeted soft-tissue balance in terms of medio-lateral (ML) laxity and gap values when using a computer-assisted orthopedic surgery (CAOS) system featuring an intra-articular force-controlled distractor and assessed learning curves associated with the adoption of this technology. METHODS: The first 273 cases using this technology were reported without exclusions comparing 1) final ML laxity and 2) final average gap to their predefined targets. For both parameters, the signed and unsigned differentials were reported. The linear mixed model was used to evaluate laxity curve differences between surgeons. A cumulative sum control chart (CUSUM) was applied to assess surgeon learning curves regarding surgical time. RESULTS: Both the average signed ML laxity and gap differentials were neutral throughout the full arc of motion. Both the average unsigned ML laxity and gap differentials were linear. Signature of ML laxity and gap differential curves tended to be surgeon-specific. The CUSUM analyses of surgical times demonstrated either a short learning curve or the absence of a discernible learning pattern for surgeons. CONCLUSION: Data from all users involved with the pilot release of the balancing device were considered to capture variability in familiarity with the technique and learning curve cases were included. A high ability to achieve targeted gap balance throughout the arc of motion using the proposed method was observed.

Posterior tibial slope impacts intraoperatively measured mid-flexion anteroposterior kinematics during cruciate-retaining total knee arthroplasty.

PURPOSE: Posterior tibial slope (PTS) for cruciate-retaining (CR) total knee arthroplasty (TKA) is usually pre-determined by the surgeon. Limited information is available comparing different choices of PTS on the kinematics of the CR TKA, independent of the balancing of the extension gap. This study hypothesized that with the same balanced extension gap, the choice of PTS significantly impacts the intraoperatively measured kinematics of CR TKA. METHODS: Navigated CR TKAs were performed on seven fresh-frozen cadavers with healthy knees and intact posterior cruciate ligament (PCL). A custom designed tibial baseplate was implanted to allow in situ modification of the PTS, which altered the flexion gap but maintained the extension gap. Knee kinematics were measured by performing passive range of motion (ROM) tests from full extension to 120° of flexion on the intact knee and CR TKAs with four different PTSs (1°, 4°, 7°, and 10°). The measured kinematics were compared across test conditions to assess the impact of PTS. RESULTS: With a consistent extension gap, the change of PTS had significant impact on the anteroposterior (AP) kinematics of the CR TKA knees in mid-flexion range (45°-90°), but not so much for the high-flexion range (90°-120°). No considerable impacts were found on internal/external (I/E) rotation and hip-knee-ankle (HKA) angle. However, the findings on the individual basis suggested the impact of PTS on I/E rotation and HKA angle may be patient-specific. CONCLUSIONS: The data suggested that the choice of PTS had the greatest impact on the mid-flexion AP translation among the intraoperatively measured kinematics. This impact may be considered while making surgical decisions in the context of AP kinematics. When using a tibial component designed with "center" pivoting PTS, a surgeon may be able to fine tune the PTS to achieve proper mid-flexion AP stability.

Accuracy and precision in resection alignment: Insights from 10,144 clinical cases using a contemporary computer-assisted total knee arthroplasty system.

BACKGROUND: Studies on total knee arthroplasty (TKA) with computer-assisted orthopedic surgery (CAOS) are limited by sample size or overlooked longitudinal performance of the system. This study aimed to assess resection accuracy across the entire TKA application history of a modern CAOS system considering multiple factors. METHODS: A retrospective analysis was performed based on a database that archives technical logs of all TKAs performed using a CAOS system. Coronal resection errors and percentage of outliers (<2° alignment error) in the proximal tibia and distal femur were assessed. Multilevel modeling was used to understand whether and where the resection error variability was located in the grouping categories, which included geographic region, individual established surgeon, preoperative alignment, adoption phase (learning/proficient), and version of the CAOS software application. RESULTS: A total of 10,144 cases were reviewed. The accuracy (mean) and precision (standard deviation) of the coronal alignment for both the tibia and femur were at the sub-degree level. High percentages of acceptable resections were observed across the pooled and each grouping category. The accountability for the amounts of total variability in tibial and femoral resection errors was negligible for all grouping categories, demonstrated by ICC values less than the common variations in observational studies. CONCLUSIONS: The study applied advanced analyses to assess alignment outcome in TKA bony resection alignment across the history of a specific CAOS system. The results demonstrated high resection alignment accuracy insensitive to geographic region, CAOS software application, adoption phase, preoperative alignment, and inter-surgeon differences.

A soft-tissue preserving method for evaluating the impact of posterior tibial slope on kinematics during cruciate-retaining total knee arthroplasty: A validation study.

BACKGROUND: The reconstructed posterior tibial slope (PTS) plays a significant role in restoring knee kinematics in cruciate-retaining total knee arthroplasty. However, conventional methods for the investigation of PTS can be limited by sample size or prone to errors due to damages to the bone and/or soft tissues. The purpose of this study was to validate a novel method for the evaluation of the effects of PTS on knee kinematics. METHODS: Seven computer-assisted cruciate-retaining TKAs were performed by two surgeons on healthy cadaveric knees. The implanted tibial baseplates allowed precise and easy modification of the PTS in situ. Knee kinematics were evaluated during passive full range of motion test. The evaluation was performed three times at each of the five PTSs in the order of 10°, seven degrees, four degrees, one degree, and back to ten degrees. The variability of the repeated measurements, inter-surgeon variation of the data, and test reproducibility were investigated. RESULTS: The test method was shown to be highly repeatable (low root-mean-squared errors) and has low sensitivity to surgeon variability (ANOVA). No statistical difference was found in the knee kinematics between the first and last measurements at 10° PTS (paired t-test). CONCLUSION: The results suggested that the developed method can be used to investigate the impact of PTS on knee kinematics without disrupting the soft-tissue environment of the knee. The use of the novel tibial baseplate allowed for adjusting the PTS without re-cutting the tibia and removing the components. The method may be applied to improve the future investigation of PTS.