Accuracy of soft tissue balancing in total knee arthroplasty using surgeon-defined assessment versus a gap-balancer or electronic sensor

Background Soft tissue balancing is essential for the success of total knee arthroplasty (TKA) and is mainly dependent on surgeon-defined assessment (SDA) or a gap-balancer (GB). However, an electronic sensor has been developed to objectively measure the gap pressure. This study aimed to evaluate the accuracy of soft tissue balancing using SDA and GB compared with a sensor. Methods Forty-eight patients undergoing TKA (60 knees) were prospectively enrolled. Soft tissue balancing was sequentially performed using SDA, a GB, and an electronic sensor. We compared the SDA, GB, and sensor data to calculate the sensitivity, specificity, and accuracy at 0°, 45°, 90°, and 120° flexion. Cumulative summation (CUSUM) analysis was performed to assess the surgeon’s performance during the sensor introductory phase. Results The sensitivity of SDA was 63.3%, 68.3%, 80.0%, and 80.0% at 0°, 45°, 90°, and 120°, respectively. The accuracy of the GB compared with sensor data was 76.7% and 71.7% at 0° and 90°, respectively. Cohen’s kappa coefficient for the accuracy of the GB was 0.406 at 0° (moderate agreement) and 0.227 at 90° (fair agreement). The CUSUM 0° line achieved good prior performance at case 45, CUSUM 90° and 120° showed a trend toward good prior performance, while CUSUM 45° reached poor prior performance at case 8. Conclusion SDA was a poor predictor of knee balance. GB improved the accuracy of soft tissue balancing, but was still less accurate than the sensor, particularly for unbalanced knees. SDA improved with ongoing use of the sensor, except at 45° flexion.

Robotic Arm-Assisted Lateral Unicompartmental Knee Arthroplasty: How Are Components Aligned?

The purpose of this multicenter, retrospective, observational study was to investigate the association between intraoperative component positioning and soft tissue balancing, as reported by robotic technology for a cohort of patients who received robotic arm-assisted lateral unicompartmental knee arthroplasty (UKA) as well as short-term clinical follow-up of these patients. Between 2013 and 2016, 78 patients (79 knees) underwent robotic arm-assisted lateral UKAs at two centers. Pre- and postoperatively, patients were administered the Knee Injury and Osteoarthritis Score (KOOS) and the Forgotten Joint Score-12 (FJS-12). Clinical results were dichotomized based upon KOOS and FJS-12 scores into either excellent or fair outcome, considering excellent KOOS and FJS-12 to be greater than or equal to 90. Intraoperative, postimplantation robotic data relative to computed tomography-based components placement were collected and classified. Following exclusions and loss to follow-up, a total of 74 subjects (75 knees) who received robotic arm-assisted lateral UKAs were taken into account with an average follow-up of 36.3 months (range: 25.0–54.2 months) postoperative. Of these, 66 patients (67 knees) were included in the clinical outcome analysis. All postoperative clinical scores showed significant improvement compared with the preoperative evaluation. No association was reported between three-dimensional component positioning and soft tissue balancing throughout knee range of motion with overall KOOS, KOOS subscales, and FJS-12 scores. Lateral UKA three-dimensional placement does not seem to affect short-term clinical performance. However, precise boundaries for lateral UKA positioning and balancing should be taken into account. Robotic assistance allows surgeons to acquire real-time information regarding implant alignment and soft tissue balancing.

Which Pre- and Postoperative Coronal Plane Laxity Parameters Influence Patient Satisfaction and Function after Primary Total Knee Arthroplasty?

Soft tissue balancing, while accepted as crucial to total knee arthroplasty (TKA) outcomes, is incompletely defined as the subject of broad recommendations. We analyzed 120 computer-assisted, posterior stabilized TKA undertaken for osteoarthritis. Coronal plane laxity was measured, in the 91 varus and 29 valgus knees, prior to any bone resection or soft tissue release, and again after implant insertion. Soft tissue laxity parameters were correlated to the American Knee Society Score (2011) at a minimum follow-up of 12 months with a focus on patient function and satisfaction. Thirteen specific laxity parameters showed a significant correlation to satisfaction, one parameter correlated to function, and another to both functional and satisfaction outcomes. Most correlations were weak, the strongest related to postoperative decreases in coronal plane laxity. Greater preoperative varus but not valgus deformity was associated with higher satisfaction scores. Additionally, 30 patients who reported 40 of 40 satisfaction and that their TKA knee felt normal at all times did not have soft tissue balancing parameters distinguishing them from other subjects. Patient satisfaction and function outcomes demonstrated limited correlation to coronal plane soft tissue parameters. It appears that optimizing TKA satisfaction and function is not as simple as producing a narrow range of coronal laxity parameters. The ongoing debate around optimal coronal plane alignment and its subsequent effect on coronal plane soft tissues may not be as independently important as currently argued. Soft tissue balance may need to be considered as a more complex global envelope.

Posteromedial Corner Release with the Knee in Figure-of-Four Position vs Conventional Position for Varus Knee Arthroplasty

Backgroud: The objective of this study is to introduce posteromedial corner release with the knee in the figure-of-four position versus the conventional position for varus knee arthroplasty. Methods : From March 2015 to September 2019, 123 patients (139 knees) with varus knee were randomly and blindly allocated to experimental group (60 patients; 68 knees) and control group (57 patients; 65 knees). Patients in experimental group underwent posteromedial corner release with the knee in the figure-of-four position; and patients in control group with the knee in the conventional position. Time for soft tissue balancing was defined as the time from the start of spacer test to the end of balance test. Length of release was defined as the distance from the osteotomy surface of the tibial plateau to the farthest structures released. The rating system of Hospital for Special Surgery (HSS) knee score was used to evaluate the clinical results. Differences were considered statistically significant at p < 0.05. Results: The mean time for soft tissue balancing was 8.4±3.3 minutes and 8.4±3.3 minutes in experimental and control group, respectively ( p <0.05). The mean length of releasing posteromedial corner structures was 35.5±13.4 mm and 27.3±9.7 mm in experimental and control group, respectively ( p <0.05). HSS scores 5 years after surgery were 95.1±16.9 and 94.8±17.2 respectively ( p >0.05). Conclusion: During varus knee arthroplasty, the posteromedial corner can be released more extensively and thoroughly when the knee is placed in the figure-of-four position.