Intraoperative Analysis of Collateral Ligament Elongation Patterns by Coronal Plane Alignment of the Knee Classification Using Augmented Reality Navigation in Japanese Osteoarthritic Knees.

Introduction This study investigates the elongation patterns of native knee collateral ligaments across various coronal plane alignment phenotypes (CPAK classification), aiming to refine soft tissue balancing in Total Knee Arthroplasty (TKA). Materials and methods In this cross-sectional study, 84 patients were analyzed prior to undergoing TKA using a computer-assisted surgery (CAS) system. CPAK types were determined using pre-operative standing full-leg radiographs. The CAS system facilitated real-time tracking of the native medial (MCL) and lateral (LCL) collateral ligament elongation throughout passive knee motion. Data were normalized and analyzed using a linear mixed model to assess the impact of knee alignment on ligament elongation, with ANOVA and Fisher's LSD method applied at a 95% confidence level. Results A significant correlation was observed between aHKA and MCL length changes during deep flexion (90°-110°), with the MCL shortening in valgus-aligned knees and lengthening in varus/neutral knees. CPAK III (valgus knees with high JLO) showed significantly more MCL shortening than CPAK I, II, and IV at 90° flexion (p < 0.05). Knees with similar aHKA values exhibited comparable MCL behavior. Across all CPAK types, the LCL displayed a consistent pattern of progressive loosening with flexion. Valgus knees, particularly CPAK III, demonstrated a significantly tighter LCL in full extension compared to other types (p < 0.05). No significant effect of aHKA or JLO on LCL behavior was found. Conclusion This study demonstrates that MCL and LCL elongation patterns are phenotype-dependent. While the LCL consistently loosens with flexion across types, MCL behavior varies significantly with coronal alignment. These findings suggest that alignment-based ligament behavior must be considered for optimal soft tissue balance and support a shift toward personalized TKA strategies aimed at replicating native knee kinematics.

PurposeThe purpose was to compare intraoperative versus postoperative coronal, sagittal and axial alignment in total knee arthroplasty (TKA) performed using augmented reality (AR) navigation, and determine whether imperfect implant positioning affects postoperative alignment.MethodsA retrospective assessment was conducted on a study cohort of 70 patients (70 knees), who received unrestricted kinematic aligned TKA using AR navigation between February 2022 and April 2023. Implant positioning was assessed on postoperative frontal (divergence between the proximal tibial resection and baseplate) and sagittal radiographs (gaps between the distal femoral resection and implant) to distinguish between knees with adequate and imperfect implant positioning. The deviation between intraoperative and postoperative alignment measurements (lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), hip knee ankle angle (HKA), posterior tibial slope (PTS) and femoral rotation) was assessed, and the number of outliers calculated using thresholds of 1° and 3°.ResultsThere were considerable proportions of knees with deviations between intraoperative and postoperative LDFA (>1°, 43 [61%]; >3°,14 [20%]), MPTA (>1°, 42 [60%]; >3°, 5 [7%]), HKA angle (>1°, 42 [60%]; >3°, 17 [24%]), and PTS (>1°, 47 [67%]; >3°, 15 [21%]). It is worth noting, however, that most of the relevant deviations were observed in knees that had imperfectly positioned implants (19 of 70, 27%), where the femoral component was inadequately impacted during surgery (15 of 19, 79%) and/or the tibial baseplate had an uneven cement distribution (8 of 19, 42%).ConclusionThe use of AR facilitates precise bone resections during TKA, yet it may not reduce deviations between intraoperative and postoperative LDFA, MPTA, HKA angle or PTS. As with any assistive technology, accurate bone resections alone are not sufficient to grant adequate implant positioning during TKA, which requires meticulous attention from surgeons to ensure sufficient component impaction and uniform cement distributions.Level of EvidenceIV.

The abstracts are presented here as prepared by the authors. The accuracy and content of each abstract remain the responsibility of the authors. In the identification number above each abstract, OPL designates an Orthopaedic platform presentation. J Orthop Sports Phys Ther 2010;40(1):A12–A39. doi:10.2519/jospt.2010.40.1.A12

Update This article was updated on February 6, 2019, because of a previous error. On page 105, in the subsection titled “Outcomes and Design” the sentence that had read “Furthermore, in a retrospective review, Houdek et al. 48 , at a mean follow-up of 8 years, demonstrated improved survivorship of 9,999 metal-backed compared with 1,645 all-polyethylene tibial components, over all age groups and most BMI categories” now reads “Furthermore, in a retrospective review, Houdek et al. 48 , at a mean follow-up of 8 years, demonstrated inferior survivorship of 9,999 metal-backed compared with 1,645 all-polyethylene tibial components, over all age groups and most BMI categories.” An erratum has been published: J Bone Joint Surg Am. 2019 Mar 20;101(6):e26.

System Physical Function (PROMIS-PF) measure based on rising popularity and the amount of research dedicated for its use in a variety of knee conditions. A basic summary of the properties of the different measures is displayed in table 1. Psychometric data pertaining to the floor and ceiling effects, validity, reliability, responsiveness, and minimum clinically important difference of each patient reported outcome is displayed in table 2. Floor and ceiling effects were considered to be absent if no participants scored the bottom or top score, respectively, and acceptable if <15% of the cohort scored the bottom or top score, respectively. Validity was measured by assessing content, face, and construct validity. Content validity was present if patients were involved in development. Face validity was present if expert reviewers made a similar assessment and considered the measured items adequate. Construct validity was considered adequate if expected correlations were found with existing measures that assess similar (convergent construct validity) and dissimilar (divergent construct validity) constructs. Internal consistency was considered adequate if Cronbach's alpha was at least 0.7 (1), and test-retest (intrarater) reliability was adequate if the intraclass correlation coefficient was at least 0.8 for groups and 0.9 for individuals. Responsiveness was determined with a measures ability to detect change over a period of time or intervention. Minimum clinically important difference is the amount of change of a patient-reported outcome that represents a meaningful change to the patient. Since 2011, there have been numerous studies evaluating the psychometric properties of the above studies. There has also been ample research assessing the utility and psychometric properties of the PROMIS-PF function. Extensive work has been performed to add available translations and culturally adapted versions of the above measures. Our review summarizes the available information about how these measures perform for different patient populations in different settings.

Elongation of the collateral ligaments after cruciate retaining total knee arthroplasty and the maximum flexion of the knee

The in-vivo medial and lateral collateral elongation correlated with knee functional score and joint space following unicompartmental knee arthroplasty

Objective To use soft-tissue balancing navigation for real-time quantitative observation of medial soft-tissue releasing in total knee arthroplasty (TKA) for the varus knee. Methods From October 2006 through September 2010,25 patients with knee osteoarthritis plus knee varus received TKA under soft-tissue balancing navigation.The soft-tissue balancing navigation system was used in the knee after routine bone cutting.The soft tissue stresses and balancing status observed and documented before and during the releasing under the guidance of the navigation system.Clinical outcomes were followed up. Results In this series,the mean operating time was 62 minutes (from 48 to 80 minutes) and the mean intraoperative blood loss was 320 mL ( from 100 to 500 mL).An average follow-up of 36.4 months (from 12 to 54 months)revealed no revision due to infection or loosening.The mean HSS scores were imuproved significantly from preoperative 53.4 ± 12.8 to 89.2 ± 17.3 at the last follow-up( t =17.411,P =0.000 ).The alignment of the lower limb decreased significantly from preoperative varus of 16.4°± 10.0° to postopcrative varus of 1.8° ± 2.1°(t=7.526,P=0.000).The differences in the medial and lateral stresses of the soft tissue at the knee extension and flexion were significant between pre-releasing and post-releasing ( P ＜ 0.05).In releasing the posterior portion of medial collateral ligament (MCL),the decreasc in medial and lateral stresses at the knee extension (42.33％ ± 20.88％ ) was significantly greater than that at the knee flexion ( 12.33％ ± 9.75％ ) ( t =6.714,P =0.000).In releasing both the anterior and posterior portions of MCL.the decrease in medial and lateral stresses at the knee extension (50.33％ ± 18.82％ ) was significantly smaller than that at the knee flexion (59.42％ ± 21.46％ ) ( t =2.492,p =0.021 ). Conclusion The soft-tissue balancing uavigation system is capable of real-time quantitative measurement of the soft tissue stress and balance in TKA for the varus knee. Key words: Osteoarhritis, knee; Surgcry, computer-assisted; Arthroplasty, replacement,knee; Soft tissue balamce

This study aims to (1) develop an augmented reality (AR) navigation platform for craniomaxillofacial (CMF) and head and neck surgery; (2) apply it to a range of surgical cases; and (3) evaluate the advantages, disadvantages, and clinical opportunities for AR navigation. A multi-center retrospective case series. Four tertiary care academic centers. A novel AR navigation platform was collaboratively developed with Xironetic and deployed intraoperatively using only a head-mounted display (Microsoft HoloLens 2). Virtual surgical plans were generated from computed tomography/magnetic resonance imaging data and uploaded onto the AR platform. A reference array was mounted to the patient, and the virtual plan was registered to the patient intraoperatively. A retrospective review of all AR-navigated CMF cases since September 2023 was performed. Thirty-three cases were reviewed and classified as either trauma, orthognathic, tumor, or craniofacial. The AR platform had several advantages over traditional navigation including real-time 3D visualization of the surgical plan, identification of critical structures, and real-time tracking. Furthermore, this case series presents the first-known examples of (1) AR instrument tracking for midface osteotomies, (2) AR tracking of the zygomaticomaxillary complex during fracture reduction, (3) mandibular tracking in orthognathic surgery, (4) AR fibula cutting guides for mandibular reconstruction, and (5) integration of real-time infrared visualization in an AR headset for vasculature identification. While still a developing technology, AR navigation provides several advantages over traditional navigation for CMF and head and neck surgery, including heads up, interactive 3D visualization of the surgical plan, identification of critical anatomy, and real-time tracking.

BackgroundComputer-navigated knee arthroplasty has been shown to improve accuracy over conventional instruments. The next generation of computer assistance is being developed using augmented reality. The accuracy of augmented reality navigation has not been established.MethodsFrom April 2021 to October 2021, a prospective, consecutive series of 20 patients underwent total knee arthroplasty utilising an augmented reality-assisted navigation system (ARAN). The coronal and sagittal alignment of the femoral and tibial bone cuts was measured using the ARAN and the final position of the components was measured on postoperative CT scans. The absolute difference between the measurements was recorded to determine the accuracy of the ARAN.ResultsTwo cases were excluded due to segmentation errors, leaving 18 cases for analysis. The ARAN produced a mean absolute error of 1.4°, 2.0°, 1.1° and 1.6° for the femoral coronal, femoral sagittal, tibial coronal and tibial sagittal alignments, respectively. No outliers (absolute error of >3°) were identified in femoral coronal or tibial coronal alignment measurements. Three outliers were identified in tibial sagittal alignment, with all cases demonstrating less tibial slope (by 3.1°, 3.3° and 4°). Five outliers were identified in femoral sagittal alignment and in all cases, the component was more extended (3.1°, 3.2°, 3.2°, 3.4° and 3.9°).The mean operative time significantly decreased from the first nine augmented reality cases to the final nine cases by 11 minutes (p<0.05). There was no difference in the accuracy between the early and late ARAN cases.ConclusionAugmented reality navigation can achieve accurate alignment of total knee arthroplasty with a low rate of component malposition in the coronal plane. Acceptable and consistent accuracy can be achieved from the initial adoption of this technique, however, some sagittal outliers were identified and there is a clear learning curve with respect to operating time.The level of evidence was IV.

What's New in Adult Reconstructive Knee Surgery.

The primary aim of this study was to assess the effects of total knee arthroplasty (TKA) implant design on collateral ligament elongation patterns that occur during level walking, downhill walking, and stair descent. Using a moving fluoroscope, tibiofemoral kinematics were captured in three groups of patients with different TKA implant designs, including posterior stabilized, medial stabilized, and ultra-congruent. The 3D in vivo joint kinematics were then fed into multibody models of the replaced knees and elongation patterns of virtual bundles connecting origin and insertion points of the medial and lateral collateral ligaments (MCL and LCL) were determined throughout complete cycles of all activities. Regardless of the implant design and activity type, non-isometric behavior of the collateral ligaments was observed. The LCL shortened with increasing knee flexion, while the MCL elongation demonstrated regional variability, ranging from lengthening of the anterior bundle to slackening of the posterior bundle. The implant component design did not demonstrate statistically significant effects on the collateral elongation patterns and this was consistent between the studied activities. This study revealed that post-TKA collateral ligament elongation is primarily determined by the knee flexion angle. The different anterior translation and internal rotation that were induced by three distinctive implant designs had minimal impact on the length change patterns of the collateral ligaments.

PurposeKinematic alignment (KA) total knee arthroplasty (TKA) aims to restore native knee kinematics by aligning prosthetic components with each patient's constitutional anatomy. While femoral resurfacing is well established, tibial resection in KA‐TKA remains largely subjective, particularly in cases with advanced deformity or bone loss. This study introduces a novel augmented reality (AR)–based technique for tibial resection that utilises real‐time ligament elongation patterns to support personalised alignment.MethodsMore than 200 consecutive KA‐TKA procedures were performed using an AR navigation system (NextAR, Medacta) with medial‐stabilised implants (GMK Sphere). After femoral resurfacing and osteophyte removal, trial femoral components were inserted to restore functional intraoperative reference configuration, thereby defining a ‘zero‐position’ baseline. Real‐time elongation data of the medial and lateral collateral ligaments were visualised throughout the full range of motion via AR smart glasses. Tibial resection parameters—including varus/valgus angle and posterior slope—were quantitatively adjusted according to elongation patterns to replicate physiological soft‐tissue tension. Spacer blocks were used intraoperatively to verify bone‐gap balance.ResultsIntraoperative tibial adjustments guided by ligament elongation patterns enabled patient‐specific resection strategies without reliance on ambiguous osseous landmarks or purely subjective gap assessments. This approach facilitated consistent intraoperative evaluation of medial and lateral soft‐tissue behaviour in both extension and flexion.ConclusionThis AR‐based KA‐TKA technique enables individualised tibial resection guided by real‐time ligament behaviour. It provides a reproducible and objective framework to support soft‐tissue‐informed intraoperative decision‐making, particularly in patients with complex deformities. This approach may complement existing KA principles and serve as a foundation for future outcome‐based investigations.Level of EvidenceNA.

To assess the symmetry of coronal alignment in the lower limbs of patients with knee osteoarthritis to evaluate whether the contralateral lower limb can serve as a reliable reference for guiding coronal positioning and alignment in total knee arthroplasty (TKA) surgery. This is a multicentric cross-sectional observational study. Preoperative full-leg weight-bearing radiographies from patients with knee osteoarthritis treated with a TKA between 2022 and 2024 were analyzed. Radiological parameters were measured in both lower limbs: medial proximal tibial angle, tibial mechanical angle (TMA), lateral distal femoral angle, femoral mechanical angle (FMA), hip-knee-ankle angle (HKA) and Kellgren-Lawrence. Lower limb coronal symmetry was assessed using the HKA, coronal plane alignment of the knee (CPAK) and phenotypes classifications. The relationship between concordance rates and osteoarthritis severity and symmetry was also analyzed. Seventy-six patients were included. The operated-to-contralateral concordance for the HKA classification was 57%. It was higher when the operated knee was neutral (81%), compared to varus (58%) or valgus (27%). The CPAK concordance was 38%; it was similar across different CPAK types. The phenotype classification concordance was only 11%; 30% for the HKA parameter, 39% for FMA and 34% for TMA. There was no relationship between osteoarthritis severity or symmetry and coronal concordance rates. Patients with knee osteoarthritis have poor side-to-side symmetry in lower limb coronal alignment. The concordance rate was 56% for the HKA classification, 39% for the CPAK classification and 11% for the phenotype classification. Therefore, the contralateral lower limb may not be a reliable reference for guiding coronal positioning and alignment in TKA surgery. Level III.

The emergence of patient specific instrumentation has seen an expansion from simple radiographs to plan total knee arthroplasty (TKA) with modern systems using computed tomography (CT) or magnetic resonance imaging scans. Concerns have emerged regarding accuracy of these non-weight bearing modalities to assess true mechanical axis. The aim of our study was to compare coronal alignment on full length standing AP imaging generated by the EOS acquisition system with the CT coronal scout image.Eligible patients underwent unilateral or bilateral primary TKA for osteoarthritis under the care of investigating surgeon between 2017 and 2022, with both EOS X-Ray Imaging Acquisition System and CT scans performed preoperatively. Coronal mechanical alignment was measured on the supine coronal scout CT scan and the standing HKA EOS.Pre-operative lower limb coronal alignment was assessed on 96 knees prior to TKA on the supine coronal scout CT scan and the standing HKA EOS. There were 56 males (56%), and 44 right knees (44%). The mean age was 68 years (range 53-90). The mean coronal alignment was 4.7 degrees (SD 5.3) on CT scan and 4.6 degrees (SD 6.2) on EOS (p=0.70). There was a strong positive correlation of coronal alignment on CT scan and EOS (pearson0.927, p=0.001). The mean difference between EOS and CT scan was 0.9 degrees (SD 2.4). Less than 3 degrees variation between measures was observed in 87% of knees. On linear regression for every 1° varus increase in CT HKA alignment, the EOS HKA alignment increased by 0.93° in varus orientation. The model explained 86% of the variability.CT demonstrates excellent reliability for assessing coronal lower limb alignment compared to EOS in osteoarthritic knees. This supports the routine use of CT to plan TKA without further weight bearing imaging in routine cases.