Faculty Bibliography

BACKGROUND:The Coronal Plane Alignment of the Knee (CPAK) classification method describes knee phenotypes. The rise in robotic-assisted total knee arthroplasties (RA-TKA) has enabled surgeons to fine-tune bony cuts, minimizing soft tissue release while prioritizing balanced gaps rather than predetermined alignment targets, a technique known as functional alignment (FA). As a patient’s preoperative CPAK changes when using FA, our aim was to assess which preoperative CPAK phenotypes are maintained post-TKA and further define this change with a simplified classification. METHODS:We retrospectively reviewed 1,028 primary RA-TKA cases performed using functional alignment (FA) technique from 2023 to 2024. Arithmetic hip-knee-ankle (aHKA) and joint line obliquity (JLO) angles were obtained using robotic software, with boundaries in accordance with CPAK. Demographics, CPAK phenotypes, and planned resections were collected and analyzed. RESULTS: < 0.001). Based on results, we classified preoperative alignment according to final functional coronal alignment that would reflect tibia and aHKA angles and propose a new, simplified Functional Coronal Alignment (FCA) classification composing of four categories. CONCLUSION:This study highlighted the clinical usefulness of robotics for FA and described the FCA classification system to guide surgeons in optimizing kinematics using robotic assistance for FA.

BACKGROUND:Varying degrees of flexion contracture appear commonly in total knee arthroplasty (TKA) patients and can be corrected using increasing distal femoral bone resection. Robotic-assisted (RA) technology aims to avoid ligament release through optimized bony resections. This study evaluated the influence of preoperative flexion contracture on the magnitude of resections surgeons perform to balance knees in RA-TKA. MATERIALS AND METHODS/METHODS:We reviewed 789 primary RA-TKAs from 2023 to 2024 using cruciate-retaining (CR) implants. The cohort was divided by native flexion deformity into three groups: <0° flexion ("hyperextension", n = 157), 0-9.9° flexion ("minimal contracture", n = 457), and ≥ 10° flexion ("clinically important contracture", n = 175). Mean preoperative flexion contracture was - 3.8, 4.1, and 13.5° for the hyperextension, minimal contracture, and clinically important contracture cohorts, respectively. Demographics, implants, and intraoperative data were collected and analyzed. The arithmetic hip-knee-ankle (aHKA) angle was used to determine native deformity groups for additional subanalyses. RESULTS:Significant differences were found between cohorts for mean distal femur and proximal tibia resections, with the clinically important contracture group having the largest resections. After accounting for implanted polyethylene thickness, differences in mean tibia resections were quite small, varying by 0.9 millimeters (mm) laterally and 0.7 mm medially. Similarly, the mean distal femoral resection varied by only 1.4 mm laterally and 0.7 mm medially between the hyperextension and clinically important contracture cohorts. Indeed, 85% of cases with clinically important contractures were managed with less than 2 mm of additional distal femoral resection compared to the minimal contracture cohort. CONCLUSION/CONCLUSIONS:With robotic-assisted TKA, bone resections can be guided by collateral ligament tension in flexion and extension. Our data suggest that surgeons can follow this strategy and successfully address flexion contractures with very small increases in resection magnitudes, which may help to maintain the joint line.

BACKGROUND:Computer navigation and robotic assistance may reduce total hip arthroplasty (THA) dislocations by improving the accuracy and precision of component positioning. We investigated dislocation rates for THAs using conventional techniques, robotic assistance, and computer navigation, while controlling for surgical approach, dual mobility (DM) use, and fluoroscopic guidance. METHODS:We reviewed 11,740 primary THAs performed between June 2016 and December 2022, including 5,873 conventional, 1,293 with robotic-arm assistance, and 4,574 with navigation. The approach was posterior in 6,580 (56.0%), anterior in 4,342 (37.0%), and lateral in 818 (7.0%). A DM was used in 10.4%. Fluoroscopy was used in 3,653 cases and only with the anterior approach. Multivariate analyses yielded odds ratios (OR) for dislocation and revision. Additional regression analyses for dislocation were performed for approach and DM. RESULTS:Raw dislocation rates were as follows: conventional 1.2%, robotic 0.4%, navigation 0.9%, anterior with fluoroscopy 0.4%, anterior without fluoroscopy 2.3%, posterior 1.3%, and lateral 0.5%. Upon multivariate analysis, use of robotics was found to be associated with significantly reduced dislocation risk compared to conventional (OR: 0.3), as did anterior (OR: 0.6) compared to posterior approach; navigation and lateral approach were not found to be associated with a significant reduction in risk. For the anterior approach, multivariate analysis demonstrated that fluoroscopy significantly reduced dislocation risk (OR: 0.1), while DM, robotics, and navigation were not significant. For the posterior approach, the dislocation risk was lower with robotics than with conventional (OR: 0.2); the use of navigation or DM did not demonstrate a significant reduction in risk. CONCLUSIONS:The use of robotics was associated with a reduction in dislocations for this cohort overall. Further, fluoroscopy in the anterior approach and robotic assistance in the posterior approach were both associated with decreased dislocation risk. The role of imageless computer navigation and DM implants requires further study.

Image-based robotic-assisted total knee arthroplasty (RA-TKA) allows three-dimensional surgical planning informed by osseous anatomy, with intraoperative adjustment based on a dynamic assessment of ligament laxity and gap balance. The aim of this study was to identify ranges of implant alignment and bone resections with RA-TKA. We retrospectively reviewed 484 primary RA-TKA cases, stratified by preoperative coronal alignment. Demographics and intraoperative data were collected and compared using Chi-square and ANOVA tests. Planned limb, femoral, and tibial alignment became increasingly varus in a progressive order from valgus to neutral to the highest in varus knees (p < 0.001). Planned external transverse rotation relative to the TEA was lowest in the valgus cohort; relative to the PCA, whereas the varus cohort was highest (p < 0.001, both). Planned resections of the lateral distal femur and of the medial posterior femur were greater in the varus group compared to neutral and valgus (p < 0.001). There were significant differences between cohorts in planned tibia resections, laterally and medially. Varus knees demonstrated higher variability, while valgus and neutral had more metrics with low variability. This study demonstrated trends in intraoperative planned alignment and resection metrics across various preoperative coronal knee alignments. These findings contribute to the understanding of RA-TKA and may inform surgical decision-making.

BACKGROUND/UNASSIGNED:The utilization of technology, including robotics and computer navigation, in total hip arthroplasty (THA) has been steadily increasing; however, conflicting data exists regarding its effect on short-term clinical and patient-reported outcomes. Therefore, this study sought to explore the association between different surgical technologies and postoperative outcomes following THA. METHODS/UNASSIGNED:We retrospectively reviewed 9892 primary THA cases performed by 62 surgeons from a single institution from September 2017 to November 2022. Three cohorts were created based on the utilization of technology: conventional (no technology), navigation, or robotics. Patient demographics, clinical outcomes, and patient-reported outcome measures were collected over the first 90 days following surgery. This data was compared using analysis of variance and multivariate logistic regressions. In total, 4275 conventional, 4510 navigation, and 1107 robotic cases were included in our analyses. RESULTS/UNASSIGNED:< .001) compared to no technology use in THA. Hip dysfunction and Osteoarthritis Outcome Score, Joint Replacement and Patient-Reported Outcomes Measurement Information System Pain Interference scores showed the greatest improvement in the robotic cohort at both 6 weeks and 3 months following surgery. CONCLUSIONS/UNASSIGNED:The present study demonstrates favorable clinical and patient-reported outcomes in the first 90 days following surgery for patients undergoing robot-assisted THA compared to conventional and navigation-assisted THA.

BACKGROUND:Soft tissue balancing is integral in providing stability following total knee arthroplasty (TKA). Although intraoperative contact load sensors are providing insights into the effects of soft tissue balancing, there is still a lack of understanding of the relationship between the knee's ligamentous tensions and joint surface contact loads. This study reports on the development of a multifunctional testing apparatus that can quantify the effects of ligamentous tension on joint contact loads in a controlled repeatable environment. METHODS:The functional knee apparatus was constructed to act as an anatomical substitute for the benchtop assessment of intraoperative soft tissue balancing. The system was calibrated through reproduction of results from a cadaveric study that employed intraoperative load sensors. Experimentation was then conducted to quantify the effects of tensile pretension variation on measured contact loads throughout the full range of flexion. RESULTS:A linear relationship between the ligamentous tensions and contact loads was observed, with ligaments contributing to 74-80% of the measured contact loads. Ligamentous tensions could be approximated from measured contact loads to within ± 23 N. CONCLUSION/CONCLUSIONS:The proposed apparatus can prove to be a valuable tool in the continued exploration of currently undocumented effects (e.g. surgical alteration) in soft tissue balancing. In addition to quantifying the relationship between ligamentous tensions and joint contact loads, soft tissue loading conditions where bicondylar contact was lost (i.e. known sign of kinematic instability) were identified. As a corollary, this system may be able to provide insights on soft tissue balancing standards predictive of patient outcomes.

Total joint arthroplasty (TJA) is one of the most performed and successful surgeries in the United States for advanced degenerative and inflammatory arthritis with most patients reporting excellent outcomes. However, a large number of patients are still dissatisfied following TJA. To improve outcomes, new technologies such as patient-specific instrumentation and custom implants; smart implant trials; radiologic, computer, and portable accelerometer-based navigation systems; and robotics have been developed. Their overall goals are to avoid the drawbacks of conventional arthroplasty surgery, to simplify the procedures, to improve the accuracy of surgical techniques, to improve outcomes, and to decrease costs. This chapter provides an overview of the current technologies and their applications in TJA.

BACKGROUND:The 2013 American Academy of Orthopedic Surgeons evidence-based guidelines recommend against the use of preoperative narcotics in the management of symptomatic osteoarthritic knees; however, the guidelines strongly recommend tramadol in this patient population. To our knowledge, no study to date has evaluated outcomes in patients who use tramadol exclusively as compared with narcotics naive patients. METHODS:This is a retrospective study of prospectively collected data for patients who underwent unilateral primary total knee arthroplasty between January 2017 and March 2018. PRO scores were obtained using a novel electronic patient rehabilitation application, which pushed PRO surveys via email and mobile devices within 1 month prior to surgery and 3 months postoperatively. RESULTS:One hundred and thirty-six patients were opiate naïve, while 63 had obtained narcotics before the index operation. Of those, 21 patients received tramadol. The average preoperative Knee Disability and Osteoarthritis Outcome Scores were 50.4, 49.95, and 48.01 for the naïve, tramadol, and narcotic populations, respectively, (P = .60). The tramadol cohort had the least gain in 3 months postoperative Knee Disability and Osteoarthritis Outcome Scores, improving on average 12.5 points in comparison to the 19.1 and 20.1 improvements seen in the narcotic and naïve cohorts, respectively (P = .09). This difference was statistically significant when comparing the naïve and tramadol populations alone in post hoc analysis (P = .016). CONCLUSIONS:When comparing patients who took tramadol preoperatively to patients who were opiate naïve, patients that used tramadol trended toward significantly less improvement in functional outcomes in the short-term postoperative period.

Background/UNASSIGNED:The purpose of the study was to investigate the accuracy of balancing which could be achieved at total knee surgery and its relation to functional outcomes. Methods/UNASSIGNED:During surgery, the forces on the medial and lateral plateaus were measured at 10-15 degrees flexion in 101 patients, using an instrumented tibial trial, with equal forces being targeted. Of the initial 101 cases, 71 cases completed all follow-up visits to 1 year. At each follow-up visit, the function was measured using the Knee Society Scoring System, and varus and valgus laxity angles were measured. Results/UNASSIGNED:The mean medial/(medial + lateral) compartmental force ratio was 0.52, with a standard deviation of 0.09. The total contact force was 217 Newtons, with a standard deviation of 72 Newtons. No correlations were found between the functional scores and the compartmental force ratio or total contact force. However, the mean varus and valgus laxity angles, 2.8 and 2.3 degrees, respectively, were very close to the angles of normal intact knees. Conclusions/UNASSIGNED:The likely reason for the lack of correlation of function was that the large majority of the balancing ratios were within the range 0.4-0.6 but with a wide spread of functional scores typical of total knee study groups. However, the normal varus and valgus angles achieved at follow-up indicated that equal balancing in early flexion was a reasonable surgical target. Using instrumented tibial trials enabled accurate and consistent balancing values to be achieved, as well as normal varus and valgus laxity angles, which may be important in obtaining optimal outcomes.

BACKGROUND:Spacer blocks, tensors, or instrumented tibial trials are current methods of balancing the knee during surgery but there are no current techniques for measuring ligament forces. Our goal was to study the relationship between the collateral ligament forces and the condylar contact forces to determine whether there was equivalence. METHODS:A test rig was constructed modeling an artificial knee joint with collateral ligaments. The ligament forces as well as the lateral and medial tibial contact forces were measured during flexion for different positions of the femoral component on the femur, producing a set of forces for the simulated conditions. A regression analysis was used to study the correlation between the ligament and contact forces. RESULTS:The combined medial and lateral ligament and contact forces showed a linear relation with a correlation coefficient of 0.98. For the medial and lateral sides separately, the correlations were 0.85 and 0.88, respectively, with more than 80% of points within a ±25% deviation from the linear relations. This deviation from the linear correlation is linked to differences in medial-lateral femoral-tibial contact point locations at different flexion angles. CONCLUSION/CONCLUSIONS:Within balancing accuracies generally achieved at surgery, the collateral ligament forces were linearly correlated to the condylar contact forces. These forces can also be equally correlated to the distraction forces as well as the moments at which condylar liftoff would occur from varus-valgus moments. This indicated a unification of the different balancing parameters, and hence such quantitative methods can be used interchangeably.