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ABSTRACT Objective Methods Results Conclusion Pseudo‐patella baja (PPB) was one of the complications after total knee arthroplasty (TKA). This complication may be closely related to the occurrence of knee joint movement limitation and pain after TKA. This study aimed to investigate whether PPB affects clinical outcomes after TKA and to study the biomechanical effects of PPB after TKA.This study was a retrospective case series of 462 eligible patients (563 knees). Clinical evaluation was performed using the visual analogue scale (VAS), the Hospital for Special Surgery (HSS), the Western Ontario McMaster University Osteoarthritis Index (WOMAC) scoring systems, the 5‐Level EuroQol Generic Health Index (EQ‐5D‐5L), the Forgotten Joint Score‐12 (FJS‐12), and patient satisfaction. CT and MRI scans of two healthy left knees and TKA prostheses were taken; 3D models including PPB, True patella baja (TPB), normal patella, and patella alta (PA) were created in FEA and applied load along the direction of quadriceps femoris. T‐test, Mann–Whitney U‐test, chi‐squared (χ2) test, and analysis of variance (ANOVA) were performed using GraphPad Prism (Version 8, GraphPad Software, USA). A statistically significant difference was considered at p < 0.05 with bilateral α.The VAS, HSS, WOMAC, EQ‐5D‐5L, FJS‐12, and patient satisfaction scores in the PPB and TPB groups were significantly worse than those in the patella normal (PN) group (p < 0.05). The PPB group found a positive correlation between Blackburne–Peel index (BPI) and FJS‐12 score. PPB showed lower contact stress of patellofemoral joint compared to TPB when knee flexion was less than < 90° (p < 0.01), but no significant difference when flexion was more than > 90° (p > 0.05) in the finite element model with Patella baja (PB). The contact area of the patellofemoral joint tended to increase with the deepening of knee flexion, and decreased after reaching the peak value. The contact area of the patellofemoral joint tended to decrease with the increase in patellar height. There was no significant difference in the contact area of the patellofemoral joint among different patellar heights and different degrees of knee flexion (p > 0.05).PPB after TKA may increase patellofemoral joint stress and postoperative complications like anterior knee pain. [ABSTRACT FROM AUTHOR]

Purpose: Joint line (JL) position change in total knee arthroplasty (TKA) may alter knee biomechanics and impact function. The purpose of this study was to compare the change in JL position between robotic-assisted TKA (RA-TKA) and conventional TKA (C-TKA). Methods: A retrospective, radiographic analysis was conducted of patients who underwent RA-TKA and C-TKA to compare JL position change. JL position was measured in consecutive RA-TKAs and C-TKAs performed by four fellowship-trained arthroplasty surgeons. Statistical analysis was done utilizing t-tests and Mann Whitney U tests, with statistical significance being defined as a p value < 0.05. Results: Six hundred total RA-TKAs and 400 total C-TKAs were included in the analysis. There were no significant differences in patient baseline characteristics such as body mass index, range of motion, and tibiofemoral coronal alignment. RA-TKAs were associated with an average of 0.04 (2.2) mm JL position change, and C-TKAs were associated with an average 0.5 (3.2) mm JL position change (p = 0.030). There were inter-surgeon differences when comparing the change in JL position for RA-TKAs and C-TKAs between the four participating surgeons. Conclusion: RA-TKA leads to better preservation of the JL position than C-TKA, and this seems to be dependent on the arthroplasty surgeon's preferences and techniques during TKA. Whether this statistically significant difference is clinically relevant needs to be further investigated. [ABSTRACT FROM AUTHOR]

Objective: The purpose of our study was to determine joint line (JL), posterior condylar offset ratio (PCOR), and patellar height alterations following revision total knee arthroplasty (RTKA) and evaluate the functional results according to the critical limits defined in the literature. Material and Method: Fifty-one patients with a minimum of two years of follow-up were retrospectively reviewed. Demographic data and operative reports were evaluated. Joint line change was measured according to the method of Figgie. Patellar height was measured using the Insall–Salvati Index and the Blackburn–Peel Index. The effect of JL, patellar height alteration, and PCOR on functional outcomes was analyzed using the Knee Society Score (KSS), knee range of motion (ROM), SF-12, and visual analog scale score as functional results. Result: Patients whose joint lines were not reconstructed had a lower KSS than those whose JLs were restored in accordance with the crucial limit of 5 mm. The other functional results were similar. Functional outcomes were similar between patients with PCORs under 0.44 and those with PCORs higher than 0.44. There was also no significant difference in functional results for the group of patients whose PCOR was lower than 0.5 and those whose PCOR was higher than 0.5. The patients with patella baja had significantly lower knee ROMs, KSS, and SF-12 PCS scores than those without patella baja (p:0.012,p:0.03, and p:0.01, respectively). Conclusion: In this study, joint line change >5 mm and patella baja negatively affected clinical outcomes after RTKA. [ABSTRACT FROM AUTHOR]

Purpose: It was hypothesized that robotic arm‐assisted total knee arthroplasty (RA‐TKA) using additionally a gap‐balancing instrumentation will show high accuracy in executing the planning in femoral and tibial component placement throughout the range of knee motion (ROM) during TKA surgery. Methods: Prospectively collected data were analysed for patients undergoing RA‐TKA. A cruciate retaining cemented design was implanted using the MAKO® robotic system. Lower limb alignment at 0°, 30°, 45°, 60° and 90° of flexion was recorded at the beginning of surgery and finally after implantation of the components. A ligament tensioner was inserted after tibial precut to measure the extension and flexion gap, and final component placement was planned based on 3D CT images. Femoral and tibial component placement was measured in all three planes. Results: A total of 104 patients were included (mean age 69.4 ± 9 years; 44 male, 60 female). The difference in component placement after planning and final implantation showed less valgus of 0.7° ± 1.4° (p < 0.001), less external rotation of 0.6° ± 1.9° (p = 0.001) and less flexion of 0.9° ± 1.8° (p < 0.001) for the femoral component. The tibial component was placed in more varus of 0.2° ± 0.9° (p = 0.056) and more posterior slope of 0.5° ± 0.9° (p < 0.001). The lower limb alignment in extension was 4.4° ± 5.2° of varus of the native knee and changed to 1.2° ± 1.9° of varus after TKA (p < 0.01). Conclusion: Robotic‐assisted TKA helps to achieve the target of alignment and component placement very close to the planning. It allows optimal component placement of off‐the‐shelf implants respecting patient's specific anatomy. Level of Evidence: Level II. [ABSTRACT FROM AUTHOR]

Introduction: Controversy regarding which variables should be prioritized for better outcomes in revision total knee arthroplasty (RTKA) exists. This study aimed to comprehensively analyze the variables affecting RTKA outcomes. Materials and methods: We retrospectively identified 87 RTKAs in 82 patients who were performed between March 2014 and February 2020. Range of motion (ROM), including flexion contracture (FC) and further flexion (FF), was analyzed according to the covariates. The covariates included mode of failure, joint line position, anteroposterior (AP) position, rotational alignment of the femoral component, and patellofemoral alignment. The differences between the final follow-up values of each RTKA variable and those of the native knee were evaluated. The clinical outcomes were evaluated. Results: No significant differences were observed between the joint line positions of the RTKA and native knees. The patellar and AP positions of the femoral component were restored to pre-TKA values. The femoral component had an external rotation of 2.78° compared with the native knee. In multivariable stepwise regression analysis, restoration of the adductor tubercle joint line and posterior condylar offset (PCO) were significant variables affecting ROM. Septic RTKA (33 knees) resulted in poor FF outcomes (p = 0.030) and Western Ontario and McMaster Universities Osteoarthritis Index stiffness (WOMAC S) scores (p < 0.001), compared with aseptic RTKA (54 knees). Conclusions: Restoration of the joint line position and PCO are crucial factors for improved ROM in RTKA. Joint line elevation in RTKA resulted in worse ROM than joint line lowering. In addition, RTKA due to septic failure had inferior ROM and WOMAC S scores compared with RTKA due to aseptic failure. Level of evidence: Level III, cohort study. [ABSTRACT FROM AUTHOR]

Background: The effect of tibiotalar joint line level (TTJL) on patient outcomes following total ankle arthroplasty (TAA) remains unclear. It was previously reported that patients with end-stage ankle arthritis have an elevated TTJL compared with nonarthritic ankles, and the TTJL post-TAA remains elevated compared with nonarthritic ankles. The objectives of this study were to (1) propose a reliable radiographic method to measure the TTJL absolute value and (2) determine the effect of TTJL alterations on tibiotalar range of motion (ROM) following TAA. Methods: A retrospective review was performed on patients who underwent TAA between January 2018 and April 2021 with a minimum of 1-year postoperative follow-up and complete perioperative ROM radiographs. Radiographic TTJL and ROM measurements were performed by 2 observers. The proposed TTJL measuring technique computes 4 measurements: high, low, center of the talus (center), and center of the axis (axis). Reliability of measurements and correlation between TTJL measurements and ROM were assessed. Results: A total of 33 patients were included. Postoperatively, 22 patients had a lowered TTJL compared to 11 patients with an elevated TTJL (2.2 ± 1.3 mm lowered vs 1.9 ± 1.2 mm elevated; P <.0001). Of the 4 TTJL measurements, 3 (low, center, axis) demonstrated a significant positive correlation between lowering the TTJL and improved tibiotalar dorsiflexion and 2 (low, axis) for total ROM (all P <.05). Plantarflexion was not significantly affected by TTJL alterations. Compared to patients with an elevated TTJL, patients with a lowered TTJL had improved tibiotalar dorsiflexion (8.8 vs 2.5 degrees; P =.0015) and total ROM (31.0 vs 22.9 degrees; P =.0191), respectively. The interrater reliability was nearly perfect (intraclass correlation r = 0.96-0.99). Conclusion: In this small series, we found that lowering the TTJL level may more closely reestablish the native TTJL and correlates with improved tibiotalar dorsiflexion and total ROM following TAA. Level of Evidence: Level IV, case series. [ABSTRACT FROM AUTHOR]

Introduction:Two-stage revision arthroplasty is the gold standard treatment for infected knee arthroplasty. The primary objectives of this treatment approach are to eradicate the infection and restore a pain-free and well-functional joint. In this retrospective study of case series from a single center, we aimed to evaluate the clinical and radiological results of patients who underwent two-stage revision knee replacement with the diagnosis of infected knee prosthesis and share the results.Methods:The data of patients between 2011 and 2016 were analyzed in this retrospective study. Twenty-four patients who were followed up for at least six months were included in the study. Infection markers, Knee Society Score (KSS), pain scores, range of motion (ROM), and flexion contractures were recorded before and after treatment. Radiologically, changes in the patellar tendon length, the Insall-Salvati (IS) ratio, and the joint line (JL) were evaluated.Results:Sixteen female and eight male patients with a mean age of 68.0±8.6 years were studied. The patients were followed up for 31.0±18.9 months on average. The mean clinical KSS of the patients before and after treatment was 44.7 and 76.3, respectively, while the functional KSSs were 31.7 and 63.5, respectively. The patients had a mean ROM of 60.5° and 84.8°, pain score of 8 and 2.25, and knee flexion contracture of 1.38° and 0.21° before and after the treatment. Pre- and post-treatment IS and JL values did not have a statistically significant effect on the clinical and functional outcomes.Conclusion:The early- tomid-term results of patients who underwent two-stage knee revision arthroplasty were satisfactory in terms of clinical and functional results. Postoperative JL position and IS ratio had no significant effect on functional outcomes. The use of dynamic spacers and the short time between two stages had a positive effect on the results.

Purpose: A key part of kinematic alignment (KA) and functional alignment (FA) is to restore the natural femoral joint line, in particular the medial joint line. KA is known to reproduce the femoral joint line accurately; however, direct comparisons with other surgical techniques such as FA are currently lacking. The purpose of this study was to evaluate differences of alignment parameters in KA and FA techniques with a special focus given to the femoral joint line. Methods: We performed a retrospective radiological analysis of pre- and postoperative long leg radiographs of 221 consecutive patients with varus or neutral leg alignment, who underwent primary total knee arthroplasty (TKA) procedures from 2018 to 2020. Patients were assigned to one of four groups: (1) FA: image-based robotic-assisted TKA, (2) FA: imageless robotic-assisted TKA, (3): restricted KA: 3D cutting block-assisted (patient-specific instruments, PSI) TKA, (4): unrestricted KA: calipered technique. Patients' radiographs were (re)-analyzed for overall limb alignment, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), as well as medial and lateral femoral joint line alteration. Statistical significance was determined using unpaired t testing (FA vs. KA group) and one-way ANOVA (subgroup analyses). Results: Comparisons of KA vs. FA, as well as individual subgroups of KA and FA did not show any differences in the accuracy of medial joint line reconstruction (< 2 mm, p = 0.384, p = 0.744, respectively) and LDFA alteration (< 2°, p = 0.997, 0.921, respectively). Correction of MPTA (3.4° vs. 2.2°) and lateral femoral joint line (2.1 mm vs. 1.5 mm) was higher for FA and FA subgroups compared to KA and KA subgroups (both p < 0.001). Conclusion: Kinematic and functional alignments showed a comparable accuracy in reconstruction of the medial femoral joint line and femoral joint line orientation. Increased correction of MPTA and lateral femoral joint line was recorded with FA techniques. Level of evidence: III. [ABSTRACT FROM AUTHOR]

Introduction: The results of revision total knee arthroplasty (rTKA) may be compromised by excessive joint line (JL) elevation. It is critical but challenging in reestablishing the JL in rTKA. Previous studies have confirmed that, biomechanically and clinically, JL elevation should not exceed 4 mm. Image-based studies described several approaches to locate the JL intraoperatively, however magnification errors could occur. In this cadaveric study, we aim to define an accurate and reliable method to determine the JL. Materials and methods: Thirteen male and eleven female cadavers were used, with an average age of death being 48.3 years. The transepicondylar width (TEW), the distance from the medial (MEJL) and lateral (LEJL) epicondyle, adductor tubercle (ATJL), fibular head (FHJL) and tibial tubercle (TTJL) to the JL were measured in 48 knees. Intra- and interobserver reliability and validity were tested prior to any additional analysis. Pearson correlation and linear regression analysis were used to examine the correlations between landmark-JL distances (LEJL, MEJL, ATJL, FHJL and TTJL) and the TEW, and to further derive models for intraoperative JL determination. The accuracy of different models, quantified by errors between estimated and measured landmark-JL distances, was compared using the Friedman and post hoc Dunn tests. Results: The intra- and inter-observer measurements for TEW, MEJL, LEJL, ATJL, TTJL and FHJL did not differ significantly (p > 0.05). Between genders, significant differences were found on TEW, MEJL, LEJL, ATJL, FHJL and TTJL (p < 0.05). There was no association between TEW and either FHJL or TTJL (p > 0.05), while ATJL, MEJL, and LEJL were found to be correlated with TEW (p < 0.05). Six models were derived: (1) MEJL = 0.37*TEW (r = 0.384), (2) LEJL = 0.28*TEW (r = 0.380), (3) ATJL = 0.47*TEW (r = 0.608), (4) MEJL = 0.413*TEW − 4.197 (R2 = 0.473), (5) LEJL = 0.236*TEW + 3.373 (R2 = 0.326), (6) ATJL = 0.455*TEW + 1.440 (R2 = 0.556). Errors were defined as deviations between estimated and actual landmark-JL distances. The mean absolute value of the errors, created by Model 1–6 was 3.18 ± 2.25, 2.53 ± 2.15, 2.64 ± 2.2, 1.85 ± 1.61, 1.60 ± 1.59 and 1.71 ± 1.5, respectively. The error could be limited to 4 mm in 72.9%, 83.3%, 72.9%, 87.5%, 87.5%, and 93.8% of the cases by referencing Model 1–6, respectively. Conclusion: Compared to previous image-based measurements, the current cadaveric study most closely resembles a realistic view of intraoperative settings and could circumvents magnification errors. We recommend using Model 6, the JL can be best estimated by referencing the AT and the ATJL can be calculated as ATJL (mm) = 0.455*TEW (mm) + 1.440 (mm). [ABSTRACT FROM AUTHOR]

Introduction: Two-stage revision arthroplasty is the gold standard treatment for infected knee arthroplasty. The primary objectives of this treatment approach are to eradicate the infection and restore a pain-free and well-functional joint. In this retrospective study of case series from a single center, we aimed to evaluate the clinical and radiological results of patients who underwent two-stage revision knee replacement with the diagnosis of infected knee prosthesis and share the results. Methods: The data of patients between 2011 and 2016 were analyzed in this retrospective study. Twenty-four patients who were followed up for at least six months were included in the study. Infection markers, Knee Society Score (KSS), pain scores, range of motion (ROM), and flexion contractures were recorded before and after treatment. Radiologically, changes in the patellar tendon length, the Insall-Salvati (IS) ratio, and the joint line (JL) were evaluated. Results: Sixteen female and eight male patients with a mean age of 68.0±8.6 years were studied. The patients were followed up for 31.0±18.9 months on average. The mean clinical KSS of the patients before and after treatment was 44.7 and 76.3, respectively, while the functional KSSs were 31.7 and 63.5, respectively. The patients had a mean ROM of 60.5° and 84.8°, pain score of 8 and 2.25, and knee flexion contracture of 1.38° and 0.21° before and after the treatment. Pre- and post-treatment IS and JL values did not have a statistically significant effect on the clinical and functional outcomes. Conclusion: The early- tomid-term results of patients who underwent two-stage knee revision arthroplasty were satisfactory in terms of clinical and functional results. Postoperative JL position and IS ratio had no significant effect on functional outcomes. The use of dynamic spacers and the short time between two stages had a positive effect on the results. [ABSTRACT FROM AUTHOR]

Abstract Background Discrepancies in bone resection between the medial and lateral compartments are very common in total knee arthroplasty (TKA) when mechanical alignment (MA) is used. The purpose of this study was to explore whether and how joint line orientation affects the initial bone resection in mechanically aligned TKA. Methods A total of 194 patients (225 knees) diagnosed with osteoarthritis (OA) were included. Virtual bone resection was conducted in the coronal view using full-length weight-bearing radiographs according to the technical requirements of MA, and the reliability of the virtual resection was verified via intraoperative caliper measurements. Correlation and regression analyses were conducted between the initial bone resection within the extension gap (EG) and various parameters, including the hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), joint line congruence angle (JLCA), and medial proximal tibial angle (MPTA). Moreover, the correlation between intraoperative bone resection adjustments and joint line orientation parameters was also investigated. Results All knees in the current case series were artificially divided into 4 subgroups: subgroup 1, containing 148 varus knees (65.8%) with valgus femurs; subgroup 2, containing 48 varus knees (21.3%) with varus femurs; subgroup 3, containing 17 valgus knees (7.6%) with varus tibias; and subgroup 4, containing 12 valgus knees (5.3%) with valgus tibias. In subgroup 1, the mLDFA and MPTA were positively correlated with the initial bone resection with regression coefficients of 0.670 and 0.089, respectively. Moreover, in all varus knees, intraoperative bone resection adjustments were negatively correlated with mLDFA and MPTA, with categorical regression coefficients of -0.426 and − 0.230, respectively. Conclusion When MA-TKAs are performed in varus knees with valgus femurs, the initial bone resection within the EG is mainly positively correlated with mLDFA, while the intraoperative bone resection adjustment is significantly correlated with mLDFA and MPTA in all varus knees.

Objective Ankle joint line orientation (AJLO) is influenced by the subtalar foot and frontal leg alignment. However, the influence of axial leg alignment on AJLO remains unclear. The study aimed to analyze the influence of frontal, axial leg alignment on AJLO in healthy subjects. Methods Thirty healthy subjects (60 legs) without prior surgery underwent standing biplanar long leg radiograph (LLR) between 2016 and 2020. AJLO was measured in standing long‐leg radiographs relative to the ground. Meary's angle and calcaneal pitch were measured. Hip‐knee‐ankle angle (HKA), femoral antetorsion, and tibial torsion were assessed with SterEOS software (EOS Imaging, Paris, France). LLR was acquired with the feet directing straight anteriorly, which corresponds to a neutral foot progression angle (FPA). The influence of subtalar, frontal, and axial alignment on AJLO was analyzed in a multiple regression model. Results An increase in knee valgus increased relative valgus AJLO by 0.5° (95% CI: 0.2° to 0.7°) per 1° (P

Background. The need for revision knee replacement is increasing every year. Technical difficulties are the determination of the correct level of the joint line in case of femoral defects. The purpose of the study is to determine the average coefficients of the joint line distalization. Materials and Methods. The parameters of the knee joint determined by X-ray were studied. Based on these parameters, the coefficients of the relationship of anatomical structures depending on gender were determined. Results. Using these data, the average coefficients of the joint line distalization were obtained. Conclusions. The proposed method for determining the joint line distalization is universal, since the studied parameters are relative, which makes it possible to level the error between them when measuring the studied values by the X-ray method and during the surgical intervention.

Background: Discrepancies in bone resection between the medial and lateral compartments are very common in total knee arthroplasty (TKA) when mechanical alignment (MA) is used. The purpose of this study was to explore whether and how joint line orientation affects the initial bone resection in mechanically aligned TKA. Methods: A total of 194 patients (225 knees) diagnosed with osteoarthritis (OA) were included. Virtual bone resection was conducted in the coronal view using full-length weight-bearing radiographs according to the technical requirements of MA, and the reliability of the virtual resection was verified via intraoperative caliper measurements. Correlation and regression analyses were conducted between the initial bone resection within the extension gap (EG) and various parameters, including the hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), joint line congruence angle (JLCA), and medial proximal tibial angle (MPTA). Moreover, the correlation between intraoperative bone resection adjustments and joint line orientation parameters was also investigated. Results: All knees in the current case series were artificially divided into 4 subgroups: subgroup 1, containing 148 varus knees (65.8%) with valgus femurs; subgroup 2, containing 48 varus knees (21.3%) with varus femurs; subgroup 3, containing 17 valgus knees (7.6%) with varus tibias; and subgroup 4, containing 12 valgus knees (5.3%) with valgus tibias. In subgroup 1, the mLDFA and MPTA were positively correlated with the initial bone resection with regression coefficients of 0.670 and 0.089, respectively. Moreover, in all varus knees, intraoperative bone resection adjustments were negatively correlated with mLDFA and MPTA, with categorical regression coefficients of -0.426 and − 0.230, respectively. Conclusion: When MA-TKAs are performed in varus knees with valgus femurs, the initial bone resection within the EG is mainly positively correlated with mLDFA, while the intraoperative bone resection adjustment is significantly correlated with mLDFA and MPTA in all varus knees. [ABSTRACT FROM AUTHOR]

Purpose : Implant malpositioning, joint line (JL) lowering, and malalignment have been identified as risk factors for implant failure in unicompartmental knee arthroplasty (UKA). The aims of this study were to compare the accuracy of implant positioning in robotic-assisted UKA versus conventional UKA in a large cohort and examine the correlation with implant survival at mid-term follow-up. Methods: This retrospective study included 356 medial UKAs from 2011 to 2019. The radiological measurements performed were coronal positioning of tibial implant according to Cartier angle (Δ Cartier), posterior tibial slope (PTS), residual hip-knee-ankle (HKA), and JL restoration. Outliers were defined as follows: post-operative HKA < 175° or > 180°, Δ Cartier > 3° or < − 3°, JL change ≥ 2 mm, and PTS < 2° or > 8°. The survival probability was reported at the last follow-up. Results: Out of the 356 knees included, 159 underwent conventional UKA (44.5%) and 197 (55.5%) robotic-assisted UKA. The mean follow-up was 61.3 months ± 24.0. Robotic UKA was associated with better accuracy compared to conventional UKA in relation to HKA (67% vs 56%, p = 0.023), JL restoration (70% vs 44%, p < 0.0001), PTS (83% vs 55%, p < 0.0001), and tibial varus restoration (65% vs 55%, p = 0.049). Implant survival in the robotic group was found to be superior at the last follow-up (96.4% versus 87.3% at 9 years, p = 0.004). Conclusion: Robotic assistance in patients undergoing medial UKA was associated with better accuracy compared to conventional UKA with respect to tibial implant positioning, post-operative limb alignment, and JL restoration. This was translated in improved survival at mid-term follow-up favouring the robotic group. [ABSTRACT FROM AUTHOR]

Purpose: The use of total ankle arthroplasty (TAA) is increasing over time, as so will the need for revision TAAs in the future. Restoration of the ankle joint line (JL) in revision TAA is often difficult due to severe bone loss. This study analyzed the accuracy of a three-dimensional (3D) registration of the contralateral tibia and fibula to restore the ankle joint line (JL) and reported side-to-side differences of anatomical landmarks. Methods: 3D triangular surface models of 96 paired lower legs underwent a surface registration algorithm for superimposition of the mirrored contralateral lower leg onto the original lower leg to approximate the original ankle JL using a proximal, middle and distal segment. Distances of the distal fibular tip, anterior and posterior medial colliculus to the JL were measured and absolute side-to-side differences reported. Anterior lateral distal tibial angle (ADTA) and lateral distal tibial angle (LDTA) were measured. Results: Mean JL approximation was most accurate for the distal segment (0.1 ± 1.4 mm (range: -3.4 to 2.8 mm)) and middle segment (0.1 ± 1.2 mm (range: -2.8 to 2.5 mm)) compared to the proximal segment (-0.2 ± 1.6 mm (range: -3.0 to 4.9 mm)) (p = 0.007). Distance of the distal fibular tip, the anterior, and posterior medial colliculus to the JL, ADTA and LDTA yielded no significant side-to-side differences (n.s.). Conclusion: 3D registration of the contralateral tibia and fibula reliably approximated the original ankle JL. The contralateral distal fibular tip, anterior and posterior medial colliculi, ADTA and LDTA can be used reliably for the planning of revision TAA with small side-to-side differences reported. Level of Evidence: IV. [ABSTRACT FROM AUTHOR]

Objective: Ankle joint line orientation (AJLO) is influenced by the subtalar foot and frontal leg alignment. However, the influence of axial leg alignment on AJLO remains unclear. The study aimed to analyze the influence of frontal, axial leg alignment on AJLO in healthy subjects. Methods: Thirty healthy subjects (60 legs) without prior surgery underwent standing biplanar long leg radiograph (LLR) between 2016 and 2020. AJLO was measured in standing long‐leg radiographs relative to the ground. Meary's angle and calcaneal pitch were measured. Hip‐knee‐ankle angle (HKA), femoral antetorsion, and tibial torsion were assessed with SterEOS software (EOS Imaging, Paris, France). LLR was acquired with the feet directing straight anteriorly, which corresponds to a neutral foot progression angle (FPA). The influence of subtalar, frontal, and axial alignment on AJLO was analyzed in a multiple regression model. Results: An increase in knee valgus increased relative valgus AJLO by 0.5° (95% CI: 0.2° to 0.7°) per 1° (P < 0.001). A decrease in femoral antetorsion increased relative valgus AJLO by 0.2° (95% CI: 0.1° to 0.2°) per 1° (P < 0.001), whereas Meary's angle and calcaneal pitch did not influence AJLO. Conclusion: A link between frontal, axial leg alignment, and AJLO could be demonstrated, indicating that a valgus leg alignment and relative femoral retrotorsion are associated with an increase of valgus AJLO in healthy subjects when placing their feet in a neutral position. Alteration of the frontal, or rotational profile after realignment surgery or by implant positioning might influence the AJLO, when the FPA is kept constant. [ABSTRACT FROM AUTHOR]

Background During a conventional measured resection using the posterior reference method for total knee arthroplasty (TKA) in varus knees, proximal tibia is resected from the lateral joint surface for the same thickness as the implant. Distal femur is resected from the worn medial surface for the same thickness as the implant. Posterior femur is resected using the posterior reference method with an external rotation for appropriate degrees. In this situation, although the joint line of the tibia is leveled to the height of lateral joint surface, the posterior joint line of the femur is leveled to the center of medial and lateral posterior condyle, which is a few millimeters lower than the lateral posterior condyle. This discrepancy between the proximal tibia‐posterior femoral joint line causes a tight flexion gap in cruciate‐retaining TKA. Therefore, downsizing of the femur is necessary to adjust the posterior joint line to the level of the lateral condyle. Perspectives To avoid this circumstance, the postoperative joint line should be leveled to the center of the original medial and lateral joint surface. Proximal tibia is resected from the lateral joint surface 1 mm to 2 mm thicker than the implant. Distal femur is resected from the worn medial surface 1 mm to 2 mm thinner than the implant. Posterior femur is resected using the posterior reference method with an external rotation for appropriate degrees. In this situation, all the joint lines are leveled to the center of the medial and lateral joint surface. Otherwise, use of an anatomically shaped implant with a physiologic joint line is another option to avoid joint line discrepancy. Conclusions Adopting joint line theory for bone resection can prevent the flexion gap tightness that likely occurs in cruciate‐retaining TKA.

Abstract Purpose The use of total ankle arthroplasty (TAA) is increasing over time, as so will the need for revision TAAs in the future. Restoration of the ankle joint line (JL) in revision TAA is often difficult due to severe bone loss. This study analyzed the accuracy of a three‐dimensional (3D) registration of the contralateral tibia and fibula to restore the ankle joint line (JL) and reported side‐to‐side differences of anatomical landmarks. Methods 3D triangular surface models of 96 paired lower legs underwent a surface registration algorithm for superimposition of the mirrored contralateral lower leg onto the original lower leg to approximate the original ankle JL using a proximal, middle and distal segment. Distances of the distal fibular tip, anterior and posterior medial colliculus to the JL were measured and absolute side‐to‐side differences reported. Anterior lateral distal tibial angle (ADTA) and lateral distal tibial angle (LDTA) were measured. Results Mean JL approximation was most accurate for the distal segment (0.1 ± 1.4 mm (range: ‐3.4 to 2.8 mm)) and middle segment (0.1 ± 1.2 mm (range: ‐2.8 to 2.5 mm)) compared to the proximal segment (‐0.2 ± 1.6 mm (range: ‐3.0 to 4.9 mm)) (p = 0.007). Distance of the distal fibular tip, the anterior, and posterior medial colliculus to the JL, ADTA and LDTA yielded no significant side‐to‐side differences (n.s.). Conclusion 3D registration of the contralateral tibia and fibula reliably approximated the original ankle JL. The contralateral distal fibular tip, anterior and posterior medial colliculi, ADTA and LDTA can be used reliably for the planning of revision TAA with small side‐to‐side differences reported. Level of Evidence IV.

Aims: Nearly 99,000 total knee arthroplasties (TKAs) are performed in UK annually. Despite plenty of research, the satisfaction rate of this surgery is around 80%. One of the important intraoperative factors affecting the outcome is alignment. The relationship between joint obliquity and functional outcomes is not well understood. Therefore, a study is required to investigate and compare the effects of two types of alignment (mechanical and kinematic) on functional outcomes and range of motion. Methods: The aim of the study is to compare navigated kinematically aligned TKAs (KA TKAs) with navigated mechanically aligned TKA (MA TKA) in terms of function and ROM. We aim to recruit a total of 96 patients in the trial. The patients will be recruited from clinics of various consultants working in the trust after screening them for eligibility criteria and obtaining their informed consent to participate in this study. Randomization will be done prior to surgery by a software. The primary outcome measure will be the Knee injury and Osteoarthritis Outcome Score The secondary outcome measures include Oxford Knee Score, ROM, EuroQol five-dimension questionnaire, EuroQol visual analogue scale, 12-Item Short-Form Health Survey (SF-12), and Forgotten Joint Score. The scores will be calculated preoperatively and then at six weeks, six months, and one year after surgery. The scores will undergo a statistical analysis. Discussion: There is no clear evidence on the best alignment for a knee arthroplasty. This randomized controlled trial will test the null hypothesis that navigated KA TKAs do not perform better than navigated MA TKAs. Cite this article: Bone Jt Open 2021;2(11):945–950.

Background: Despite numerous advances in the implant design and surgical technique, improvement in patient satisfaction following total knee arthroplasty (TKA) has plateaued. Various TKA alignment strategies have been introduced that impact the coronal positioning of the tibial component relative to the native joint line. This study aims to analyze if postoperative variance of the joint line from preoperative native alignment is correlated with changes in patient-reported outcomes following primary TKA.Methods: A retrospective review of an academic center's patient population identified all primary TKAs between 2013 and 2021 with full-length, standing radiographs and patient-reported outcome measures (PROMs) data. These measures included the Knee injury and Osteoarthritis Outcome Score for Joint Replacement, Patient-Reported Outcome Measurement Information System, and Veterans RAND 12 scores. Preoperative and postoperative radiographic measurements for hip-knee angle, tibia-metaphyseal angle, tibial-axis orientation angle, and joint-line obliquity angle were recorded. Three-month, 1-year, and 2-year PROM scores were correlated with the change in degrees for each of the angles using a Spearman's correlation. A Mann-Whitney U-test was used to compare angular changes with a change in PROM scores.Results: One hundred and ninety nine patients (204 knees) with a mean age of 67 years were included. Average follow-up was 23 months. Three-month, 1-year, and 2-year follow-up rates were 93%, 64%, and 34%, respectively. Improvements were seen across all PROMs regardless of an angular change.Conclusion: There were no clear correlations between PROMs and variation in joint line obliquity in the coronal plane. These data suggest that the magnitude of the variation in coronal tibial alignment from native alignment does not impact PROMs. Further study is indicated to correlate an angular change with functional measures. [ABSTRACT FROM AUTHOR]

Purpose: One of the key factors to the successful revision of total knee arthroplasty (rTKA) is the reconstruction of the joint line, which can be determined using the epicondylar ratio (ER). The measurement is established in X-ray and MRI. However, it is not known whether computed tomography (CT) allows a more reliable determination. The objective was to assess the reliability of the ER in CT and to determine the correlation between the ER in CT and a.p. X-ray of the knee. Methods: The ER was determined on X-ray and CT images of a consecutive series of 107 patients, who underwent rTKA. Measurements were made by two blinded observes, one measured twice. The inter- and intraobserver agreement, as well as the correlation between the two methods, were quantified with the Intraclass Correlation Coefficient. Results: The average lateral ER was 0.32 (± 0.04) in X-ray and 0.32 (± 0.04) in CT. On the medial side, the average ER was 0.34 (± 0.04) in X-ray and 0.35 (± 0.04) in CT. The interobserver agreement for the same imaging modality was lateral 0.81 and medial 0.81 in X-ray as well as lateral 0.74 and medial 0.85 in CT. The correlation between the two methods was lateral 0.81 and medial 0.79. Conclusions: The ER can be reliably determined in X-ray and CT. Measurements of the two image modalities correlate. Prior to rTKA, the sole use of the X-ray is possible. [ABSTRACT FROM AUTHOR]

Background: Joint line elevation in revision total knee arthroplasty (rTKA) is considered a risk factor for inferior outcomes, engendering a dogmatic protocol of joint line restoration. However, this precedent is based on historical data using rudimentary revision systems and unvalidated outcome measures. This study's purpose was to evaluate the effect of joint line height elevation on validated patient-reported outcome measures (PROMs) using modern revision implants.Methods: A total of 327 rTKAs performed at a single institution were reviewed. Surgical technique prioritized flexion-extension gap balancing and accepted joint line elevation if necessary to achieve a balanced flexion space. Radiographic measurements included changes in joint line height (from preoperative and calculated "intended" anatomic/native) and change in posterior condylar offset. Prospectively collected PROMs were evaluated using multivariate regression.Results: The mean joint line elevation from preoperative and "intended" to postoperative joint line was 4.9 ± 5.7 mm and 7.2 ± 6.6 mm, respectively. The mean increase in posterior condylar offset was 1.0 ± 4.6 mm. Patients within ±5 mm of preoperative joint line height were 3.88× more likely to achieve the substantial clinical benefit for Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (P = .004). An increase from intended joint line height >5 mm was not associated with differences in any other PROMs (P ≥ .165).Conclusions: In contemporary rTKA, recreating the joint line within 5 mm of preoperative improves knee-specific health outcomes. These data support approximating native joint line height as a viable technique to optimize flexion gap balance and subsequent patient outcomes in rTKA.Level Of Evidence: Level III retrospective cohort study. [ABSTRACT FROM AUTHOR]

Background: During a conventional measured resection using the posterior reference method for total knee arthroplasty (TKA) in varus knees, proximal tibia is resected from the lateral joint surface for the same thickness as the implant. Distal femur is resected from the worn medial surface for the same thickness as the implant. Posterior femur is resected using the posterior reference method with an external rotation for appropriate degrees. In this situation, although the joint line of the tibia is leveled to the height of lateral joint surface, the posterior joint line of the femur is leveled to the center of medial and lateral posterior condyle, which is a few millimeters lower than the lateral posterior condyle. This discrepancy between the proximal tibia‐posterior femoral joint line causes a tight flexion gap in cruciate‐retaining TKA. Therefore, downsizing of the femur is necessary to adjust the posterior joint line to the level of the lateral condyle. Perspectives: To avoid this circumstance, the postoperative joint line should be leveled to the center of the original medial and lateral joint surface. Proximal tibia is resected from the lateral joint surface 1 mm to 2 mm thicker than the implant. Distal femur is resected from the worn medial surface 1 mm to 2 mm thinner than the implant. Posterior femur is resected using the posterior reference method with an external rotation for appropriate degrees. In this situation, all the joint lines are leveled to the center of the medial and lateral joint surface. Otherwise, use of an anatomically shaped implant with a physiologic joint line is another option to avoid joint line discrepancy. Conclusions: Adopting joint line theory for bone resection can prevent the flexion gap tightness that likely occurs in cruciate‐retaining TKA. [ABSTRACT FROM AUTHOR]

Purpose: Joint line orientation (JLO) plays an important role in total knee arthroplasty (TKA), but its influence on patient-reported outcomes (PROs) is unclear. The purpose of this study was to examine JLO impact as measured by the forgotten joint score (FJS-12). The hypothesis was that restoring the joint line (JL) parallel to the floor would influence joint awareness favorably, i.e., allow the patient to forget about the joint in daily living. Methods: All computer-navigated primary TKAs using a cemented, cruciate-retaining (CR) design implanted between January 2018 and September 2019 were reviewed in this retrospective single-center analysis. Primary endpoints were: clinical [range of motion (ROM)], and patient-reported (FJS-12) and radiographical outcomes [tibia joint line angle (TJLA), hip knee axis (HKA), mechanical medial proximal tibia angle (mMPTA) as well as mechanical lateral distal femoral angle (mLDFA)]. Results: Seventy-six patients (mean age: 70.3 ± 9.7 years, mean BMI: 29.7 ± 5.2 kg/m2) were included. Postoperative ROM averaged 118.7 ± 9.6°. The mean FJS-12 improved from 16.4 ± 15.3 (preoperatively) to 89.4 ± 16.9 (1-year follow-up; p < 0.001). Clinical outcomes and PROs did not correlate with JLO (p = n.s.). Cluster analysis using six measures revealed that a medially opened TJLA was associated with significantly better postoperative FJS-12. Conclusion: Tibial JLO was found to have no effect on PROs. Considering the JLO in the coronal plane alone probably has questionable clinical relevance. Lower limb alignment should be assessed in all three planes and correlated with the clinical outcome. Level of clinical evidence: Level IV. [ABSTRACT FROM AUTHOR]

Purpose: Correct positioning and alignment of the prosthesis is a very important factor for durability of prosthesis and implant survival which is improved with the use of technology in total knee arthroplasty. However, the long-term functional outcomes and survivorship are unclear. For this study, it was hypothesized that mechanical axis alignment of lower limb, post-operative joint line restoration, femoral and tibial component alignment is more accurate with the new handheld semi-active robotic-assisted TKA. Method: From April-2019 to March-2020, 60 patients with unilateral knee osteoarthritis who underwent total knee arthroplasties were included in this prospective randomised controlled study. Computer generated randomization was used. Study included 48 female patients and 12 male patients. Pre-operative and post-operative radiographic measurements were done and compared between the two groups. Results: There was a significant difference between two groups with respect to mechanical axis deviation, joint line deviation and coronal alignment of femoral and tibial prosthesis. Mechanical axis deviation > 3° was seen in eight cases (28.5%) in C-TKA group compared to one case (3.1%) in RA-TKA (p 0.019). Joint line deviation of 3.5 mm was noted in C-TKA group as compared to 0.9 mm in RA-TKA group (p < 0.001) which was statistically significant. However, whether this difference of 2.6 mm of joint line elevation between C-TKA and RA-TKA leads to any difference in clinical outcome in terms of knee kinematics and knee flexion needs to be investigated with further studies. Clinically restoring normal joint line is important for improved knee function after primary TKA. No significant difference was noted in femoral component rotation on post-operative computed tomography (CT) scan. Conclusion: The novel imageless, handheld semi-autonomous robotic system for TKA is highly accurate with respect to component positioning in coronal plane and mechanical alignment as compared to conventional TKA. Joint line is elevated in conventional TKA but is accurately restored using the robotic-assisted TKA which may lead to better patellofemoral kinematics. Level of evidence: I. [ABSTRACT FROM AUTHOR]

Abstract A considerable proportion of patients (19%) are dissatisfied after total knee arthroplasty (TKA). Possible factors contributing to this dissatisfaction are decreased posterior condylar offset (PCO) with subsequent joint line elevation, leading to mid-flexion instability. Secondly, the pre-disease mechanical alignment is changed into a neutral alignment. The Flexion First Balancer was developed to avoid these problems. This technique aims to maintain MCL isometry by restoring medial PCO and medial joint line to its pre-disease level. Also, to reconstruct the pre-disease mechanical alignment by adjusting the distal femoral angle. In this study we provide a detailed technical overview of the Flexion First Balancer technique.

Background: Lower limb coronal alignment was thought to be a predictive factor for Unicompartmental Knee Arthroplasty (UKA) result. The tibial bony resection and implant position lead to joint line change postoperatively. Analysis was done to find out the correlation between these factors., Methods: From 2019 to 2021, 90 medial Oxford UKA were implanted by a single surgeon. Hip Knee Ankle Angle (HKAA), Lateral Distal Femoral Angle (LDFA), Medial Proximal Tibial Angle (MPTA), and intraoperative bony resection thickness were measured. The medial joint line change was calculated. The correlation between joint line change and alignment change was evaluated., Results: The mean tibial resection thickness was 4.3 mm. The mean tibial joint line was elevated by 2.3 mm, while the mean femoral joint line proximalized by 0.8 mm. HKAA changed from 8.4° varus preoperatively to 3.6° varus postoperatively. LDFA changed from 89.0° to 86.7°. MPTA changed from 85.6° to 86.6°. Preoperative HKAA showed a strong correlation with postoperative HKAA (p < 0.001), and preoperative MPTA showed a positive correlation with postoperative HKAA (p < 0.001). While preoperative LDFA had a negative correlation with postoperative HKAA (p < 0.001). The femoral joint line change and LDFA change had a significant correlation with HKAA change (p < 0.05)., Conclusion: The change of joint line had no correlation with postoperative HKAA in Oxford UKA. Preoperative HKAA strongly correlated with postoperative HKAA; while preoperative smaller LDFA and larger MPTA had a moderate correlation with postoperative HKAA. The femoral joint line change and LDFA change had a weak to moderate correlation with HKAA change., Competing Interests: Conflicts of interest The authors declare no conflicts of interest., (Copyright © 2024 HCFMUSP. Published by Elsevier España, S.L.U. All rights reserved.)

Background: This study aimed to investigate the difference in lateral distal femoral angle (LDFA) between knees with medial osteoarthritis (mOA) and knees without osteoarthritis, and to explore the validity of the assumption that there is no bone wear on the femoral articular surface in kinematic alignment total knee arthroplasty (KA-TKA)., Methods: The study included 69 patients with mOA on one side of the knee and but no OA on the other side. LDFA, medial proximal tibial angle (MPTA), mechanical hip-knee-ankle angle (mHKA), and arithmetic hip-knee-ankle angle (aHKA) were measured and compared between the knees. Pearson's correlation coefficient and paired t-tests were used for statistical analysis., Results: The LDFA and MPTA were significantly more varus in mOA knees than in knees non-OA knees, with differences of 1.0° ± 2.3° and 0.9° ± 2.0°, respectively. The difference between mHKA of the non-OA side and aHKA of the mOA side was not significant, indicating that it is appropriate to use aHKA as an estimation of postoperative alignment after kinematically-aligned total knee arthroplasty without anatomical correction. However, there was a significant difference in MPTA and aHKA between male and female patients in both mOA and non-OA knees., Conclusions: The assumption that there is no bone wear on the femoral articular surface is rejectable, and the constant compensation thickness of 2 mm for cartilage wear may not be sufficient. Further research is needed to estimate the amount of bone wear in both femur and tibia side to develop more individualized surgical planning strategies in KA-TKA., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Introduction: Functional alignment (FA) in total knee arthroplasty (TKA) has been introduced to restore the native joint line obliquity, respect the joint line height and minimize the need of soft tissue releases. The purpose of this study was to assess the intraoperative joint line alignment and compare it with the preoperative epiphyseal orientation of the femur and tibia in patients undergoing robotic-arm-assisted (RA)-TKA using FA. Materials and Methods: This retrospective study included a consecutive series of patients undergoing RA-TKA between February 2019 and February 2021. The joint line orientation of the femur and tibia in the three-dimensions was calculated and classified on preoperative CT-scans and compared with the intraoperative implant alignment. The tibial cut was performed according to the tibial preoperative anatomy. The femoral cuts were fine-tuned based on tensioned soft tissues, aiming for balanced medial and lateral gaps in flexion and extension. Results: A total of 115 RA-TKAs were assessed. On average, the tibial component was placed at 1.8° varus (SD 1.3), while the femur was placed at 0.8° valgus (SD 2.2) and 0.6° external rotation (SD 2.6) relative to the surgical transepicondylar axis. Moderate to strong, statistically significant relationships were described between preoperative tibial coronal alignment and tibial cut orientation (r = 0.7, p < 0.0001), preoperative femoral orientation in the coronal and axial planes and intraoperative femoral cuts alignment (r = 0.7, p < 0.0001 and r = 0.5, p < 0.0001, respectively). One case (0.9%) of slight tibial component varus subsidence was reported 45-days post-operatively, but implant revision was not necessary. Conclusions: The proposed robotic-assisted functional technique for TKA alignment, with a restricted tibial component coronal alignment, based on the preoperative phenotype and femoral component positioning as dictated by the soft tissues, provided joint line respecting resections. Further studies are needed to assess long-term implant survivorship, patient satisfaction and alignment-related failures. [ABSTRACT FROM AUTHOR]

Purpose: To assess a novel method of three-dimensional (3D) joint line (JL) restoration based on the contralateral tibia and fibula. Methods: 3D triangular surface models were generated from computed tomographic data of 96 paired lower legs (48 cadavers) without signs of pathology. Three segments of the tibia and fibula, excluding the tibia plateau, were defined (tibia, fibula, tibial tuberosity (TT) and fibular tip). A surface registration algorithm was used to superimpose the mirrored contralateral model onto the original model. JL approximation and absolute mean errors for each segment registration were measured and its relationship to gender, height, weight and tibia and fibula length side-to-side differences analyzed. Fibular tip to JL distance was measured and analyzed. Results: Mean JL approximation did not yield significant differences among the three segments. Mean absolute JL error was highest for the tibia 1.4 ± 1.4 mm (range: 0 to 6.0 mm) and decreased for the fibula 0.8 ± 1.0 mm (range: 0 to 3.7 mm) and for TT and fibular tip segment 0.7 ± 0.6 (range: 0 to 2.4 mm) (p = 0.03). Mean absolute JL error of the TT and fibular tip segment was independent of gender, height, weight and tibia and fibula length side-to-side differences. Mean fibular tip to JL distance was 11.9 ± 3.4 mm (range: 3.4 to 22.1 mm) with a mean absolute side-to-side difference of 1.6 ± 1.1 mm (range: 0 to 5.3 mm). Conclusion: 3D registration of the contralateral tibia and fibula reliably approximated the original JL. The registration of, TT and fibular tip, as robust anatomical landmarks, improved the accuracy of JL restoration independent of tibia and fibula length side-to-side differences. Level of evidence: IV [ABSTRACT FROM AUTHOR]

Abstract Background The adductor tubercle (AT) has been used intraoperatively as a landmark to evaluate the joint line position in knee arthroplasty. The purpose of this study was to determine whether the AT could be clearly identified on radiographic imaging as well as if the AT to joint line distance could be accurately measured for use as a radiographic landmark. Methods The distance from the AT to the joint line was measured on each of 78 knees during total knee arthroplasty. Next, the AT was marked with a metal marker for radiographic analysis. On the postoperative radiograph, the location of the AT was determined by tracing the metal marker. Subsequently, the radiographic joint line distance (RJLD) was measured and compared with the intraoperative joint line distance (IJLD) to test the agreement of the measurements. Results Location analysis indicated that the inflection point on the radiographic contour of the distal femur was the predicted location for the AT. The mean IJLD was 45 ± 3 mm and the RJLD was 45 ± 4 mm. The intraclass correlation coefficient was used to evaluate the inter-rater reliability between the two methods; that coefficient was 0.751, indicating good agreement between them. Measurements on the radiograph were comparable to the intraoperative measurements of the operated knees. Conclusions In addition to being an intraoperative landmark, the AT may also be an eligible radiographic landmark for analyzing joint line level. The RJLD measurement may be obtained to plan the joint line position in knees with significant bone loss preoperatively and to follow up the results of surgery postoperatively.

Abstract Purpose This study aimed to validate a new joint line measurement technique in total knee arthroplasty for separated assessment of the medial and lateral femoral joint line alteration with 3D‐surface scan technology. Separate assessment of the medial and lateral joint line alteration may improve TKA alignment assessment regarding to joint line restoration in kinematic alignment and use of robotic‐assisted TKA surgery. Methods The medial and lateral joint line difference after TKA implantation on an artificial bone model was analyzed and compared with a 3D‐scan and full femoral radiographs pre‐ and postoperatively. Radiographic analysis included the perpendicular distance between the most distal point of the medial and lateral condyle and the reproduced preoperative lateral distal femoral angle (LDFA). For evaluation of validity and reliability, radiographs were captured initially with true anteroposterior view and subsequently with combined flexion and rotation malpositioning. Reliability of the introduced measurement technique in between three observers was tested with intraclass correlation coefficient (ICC). Results Radiographic measurement showed a mean difference of 0.9 mm on the medial side and 0.6 mm on the lateral side when compared to the 3D‐surface scan measurement. The reliability of measurement accuracy was ≤ 1 mm in x‐rays with

Abstract Purpose To assess a novel method of three‐dimensional (3D) joint line (JL) restoration based on the contralateral tibia and fibula. Methods 3D triangular surface models were generated from computed tomographic data of 96 paired lower legs (48 cadavers) without signs of pathology. Three segments of the tibia and fibula, excluding the tibia plateau, were defined (tibia, fibula, tibial tuberosity (TT) and fibular tip). A surface registration algorithm was used to superimpose the mirrored contralateral model onto the original model. JL approximation and absolute mean errors for each segment registration were measured and its relationship to gender, height, weight and tibia and fibula length side‐to‐side differences analyzed. Fibular tip to JL distance was measured and analyzed. Results Mean JL approximation did not yield significant differences among the three segments. Mean absolute JL error was highest for the tibia 1.4 ± 1.4 mm (range: 0 to 6.0 mm) and decreased for the fibula 0.8 ± 1.0 mm (range: 0 to 3.7 mm) and for TT and fibular tip segment 0.7 ± 0.6 (range: 0 to 2.4 mm) (p = 0.03). Mean absolute JL error of the TT and fibular tip segment was independent of gender, height, weight and tibia and fibula length side‐to‐side differences. Mean fibular tip to JL distance was 11.9 ± 3.4 mm (range: 3.4 to 22.1 mm) with a mean absolute side‐to‐side difference of 1.6 ± 1.1 mm (range: 0 to 5.3 mm). Conclusion 3D registration of the contralateral tibia and fibula reliably approximated the original JL. The registration of, TT and fibular tip, as robust anatomical landmarks, improved the accuracy of JL restoration independent of tibia and fibula length side‐to‐side differences. Level of evidence IV

Instability is an increasingly common cause and symptom of failure of Total Knee Arthroplasty (TKA). Patients seek 'Functional Stability', which is the sum of both a balanced joint and, if necessary, mechanical constraint. The objective of this paper is to classify the different types of TKA instability and their causes. Based on this classification, the authors give methodical recommendations for instability management. Instability in revision TKA can be classified into 3 types based on the management of bone loss and ligamentous deficiency which directs the level of constraint required to achieve functional stability. Bone deficiency: Revision with restoration of joint line and rebuilding the bony anatomy results in a balanced joint. No increased constraint is needed. Ligament and soft tissue deficiency: Requires increased constraint to overcome instability Composite (Total) deficiency: (combined Type 1 and 2). The multiple causes of instability are outlined for each Instability type along with an algorithm for restoring the joint line and adding titrated constraint to restore functional stability. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to validate a new joint line measurement technique in total knee arthroplasty for separated assessment of the medial and lateral femoral joint line alteration with 3D-surface scan technology. Separate assessment of the medial and lateral joint line alteration may improve TKA alignment assessment regarding to joint line restoration in kinematic alignment and use of robotic-assisted TKA surgery. Methods: The medial and lateral joint line difference after TKA implantation on an artificial bone model was analyzed and compared with a 3D-scan and full femoral radiographs pre- and postoperatively. Radiographic analysis included the perpendicular distance between the most distal point of the medial and lateral condyle and the reproduced preoperative lateral distal femoral angle (LDFA). For evaluation of validity and reliability, radiographs were captured initially with true anteroposterior view and subsequently with combined flexion and rotation malpositioning. Reliability of the introduced measurement technique in between three observers was tested with intraclass correlation coefficient (ICC). Results: Radiographic measurement showed a mean difference of 0.9 mm on the medial side and 0.6 mm on the lateral side when compared to the 3D-surface scan measurement. The reliability of measurement accuracy was ≤ 1 mm in x-rays with < 10° flexion error regardless to malrotation in these images. The ICC test showed very good reliability for the medial joint line evaluation and good reliability for lateral joint line evaluation (ICC 0.92, ICC 0.86 respectively). Conclusion: The new introduced joint line measurement method showed a sufficient reliability, accuracy and precision. It provides separated information about medial and lateral joint line alteration in TKA surgery in absolute values. Level of evidence: V - Experimental Study [ABSTRACT FROM AUTHOR]

Although Oxford unicompartmental knee arthroplasty is often used to successfully treat patients with knee osteoarthritis isolated at the medial compartment, we present a case of fracture just below the tibial keel caused by either a shift in medial loading position or an increased amount of tibial osteotomy. Finite element analysis was used to determine which factor was more important. First, a 3D-surface model of the patient's tibia and the implant shape were created using computed tomography-Digital Imaging and Communications in Medicine (CT-DICOM) data taken preoperatively. The finite element analysis found that following unicompartmental knee arthroplasty, the cortical stress (normal, 5.8 MPa) on the medial tibial metaphyseal cortex increased as the load point moved medially (3 and 12 mm medially: 7.0 and 10.7 MPa, respectively) but was mild with increased tibial bone resection (2 and 6 mm lower: 6.1 and 6.5 MPa, respectively). Implanting the femoral component more medially than the preoperative plan increases stresses in the medial cortex of the tibia and may cause fractures., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Imada et al.)

Introduction Optimal repair of the joint line (JL) in total knee arthroplasty (TKA) is critical for knee joint motion reconstruction and ligament balance. Identification of JL may be difficult, particularly in revision or primary cases of severe femoral condylar bone loss. We aimed to define the relationship between the epicondyles and the articular surface (AS) of the femur using computed tomography-based three-dimensional digital templating software. Methods The study included 127 knees with osteoarthritis of the knee below grade 2 on the Kellgren-Lawrence index. A perpendicular line was drawn from the medial and lateral femoral epicondylar processes to the most distal point of the AS, and the distance was measured in the axial and coronal planes. Femoral width was measured as the distance between the medial and lateral epicondyles. All distances described above were converted to a ratio by division with femoral width. Results On the axial plane, the distance from epicondyles to the posterior ASs was 29.4 ± 2.2 mm medially and 21.3 ± 2.1 mm laterally. The width of the distal femur was 75.2 ± 4.2 mm. On the coronal plane, the distances from epicondyles to the distal ASs were 25.2 ± 2.9 mm on the medial side and 21.3 ± 2.5 mm on the lateral side. The ratio of the distance from epicondyles to the distal and posterior ASs divided by the width of the femur was 0.39 ± 0.02, 0.28 ± 0.03, 0.34 ± 0.03, and 0.28 ± 0.03. Conclusions The distance from the epicondyles to the distal and posterior JLs correlates with the distal femur width. These findings may be useful in determining an appropriate JL., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Institutional Review Board of Oita University Hospital issued approval 1850. The study protocol for this retrospective and noninvasive study was approved by the institutional review board of our hospital (Approval No.: 1850). Informed consent was obtained in the form of an opt-out, and the need to obtain informed consent from individual patients was waived by the ethics committee of our institution. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Hirakawa et al.)

Abstract Background Restoration of the natural joint line is a cornerstone for kinematically aligned total knee arthroplasty (TKA). The purpose of this study was to investigate the relative orientation of the tibial growth plate (GP) with respect to the tibial plateau (TP) for possible application in predicting natural joint line for knees with highly advanced osteoarthritis patient at the time of kinematically aligned TKA. Methods Images from computed tomography (CT) of 27 normal knees (9 males, 18 females; mean age, 31.6 years) were studied. Geometry of the GP was extracted from CT images, and its moment-of-inertia axes were calculated for the whole GP and the medial and lateral halves. Angular orientations of each GP axis with respect to the TP plane were measured in anatomical coordinates. Results The TP and GP planes were oriented in 2.3 ± 1.8° of varus and 1.1 ± 1.9° of valgus relative to the tibial mechanical axis, respectively. With respect to the TP plane, the whole GP plane was inclined in 3.4 ± 1.5° of valgus. Orientation of the GP plane differed drastically between medial and lateral halves. The medial GP was in 4.9 ± 2.9° of varus and 1.8 ± 2.5° of anterior inclination, and the lateral half was in 10.4 ± 2.4° of valgus and 18.6 ± 4.0° of anterior inclination relative to the TP. Conclusions Angular orientation of the original TP plane can be predicted in reference to the GP plane and may provide reasonable guidance for the target bone resection angle of the tibia in kinematically aligned TKA.

Purpose: Previous cadaver studies showed that the additional bone cuts in the distal and posterior femur and joint line elevation resulted in laxity at mid-flexion after total knee arthroplasty (TKA). However, these results are not always applicable to TKA candidates because the related studies used cadaver knees with no osteoarthritis. It was hypothesized that the joint line elevation results in mid-flexion laxity after TKA in patients with knee osteoarthritis. The purpose of this study was to analyze the relationship between joint line elevation and mid-flexion laxity in patients with knee osteoarthritis.Methods: 30 knees with varus osteoarthritis undergoing TKA were evaluated. Two femoral trial component models were prepared: (1) normal model with a thickness of the distal and posterior femoral components of 9 mm, and (2) 2-mm joint line elevation model with a thickness of the distal and posterior femoral components of 9 - 2 = 7 mm. This 2-mm joint line elevation model simulated an additional bone cut in the distal and posterior femur, and joint line elevation, without an additional bone cut. The femoral trial component models were set before implantation and measured the joint gap kinematics using a tensor device through the full knee range of motion.Results: The differences in joint gap change from 30° to 90° were not statistically significant between the two models. However, the joint line elevation model decreased the joint gap laxity at 120° (p = 0.02) and at 145° (p = 0.01).Conclusions: This study showed that a 2-mm joint line elevation was not associated with mid-flexion laxity in patients with varus osteoarthritis in the knee. The results of this study differed from the results in previous cadaver studies.Level Of Evidence: Therapeutic study, level II, prospective comparative study. [ABSTRACT FROM AUTHOR]

Purpose: Flexion deformity after total knee arthroplasty (TKA) is associated with poor function and dissatisfaction and should, therefore, be avoided. In the case of preoperative flexion deformity, an increased distal resection of the femur may be necessary. The degree of resection required has only been determined for cruciate-retaining (CR) prostheses to date and varies considerably from study to study. Although, for many surgeons, the algorithm for the treatment of a flexion deformity includes the resection of the posterior cruciate ligament (PCL) before additional distal resection, the degree of resection necessary for posterior-stabilized (PS)-type prostheses is not known.Methods: Fifty consecutive patients (50 knees) who were due to undergo navigated TKA were included in this prospective study. At the end of the operation, the flexion deformity resulting from different sizes of distal femoral augmentations on the trial implants (0-8.5 mm) was determined using the navigation system.Results: A linear relationship of 2.2° ± 0.3° flexion deformity per mm distal femoral augmentation was found. This was not dependent on age, sex, the preoperative coronal alignment, or the preoperative flexion deformity.Conclusions: In conclusion, after the removal of posterior osteophytes and posterior capsule release, around 5 mm of the distal femur must be further resected in the case of 10° flexion deformity and 9 mm in the case of 20° flexion deformity.Level Of Evidence: II (Prospective cohort study). [ABSTRACT FROM AUTHOR]

A considerable proportion of patients (19%) are dissatisfied after total knee arthroplasty (TKA). Possible factors contributing to this dissatisfaction are decreased posterior condylar offset (PCO) with subsequent joint line elevation, leading to mid-flexion instability. Secondly, the pre-disease mechanical alignment is changed into a neutral alignment. The Flexion First Balancer was developed to avoid these problems. This technique aims to maintain MCL isometry by restoring medial PCO and medial joint line to its pre-disease level. Also, to reconstruct the pre-disease mechanical alignment by adjusting the distal femoral angle. In this study we provide a detailed technical overview of the Flexion First Balancer technique. [ABSTRACT FROM AUTHOR]