Excellent results of restricted kinematic alignment total knee arthroplasty at a minimum of 10 years of follow-up.

PURPOSE: While restricted kinematic alignment (rKA) total knee arthroplasty (TKA) with cemented implants has been shown to provide a similar survivorship rate to mechanical alignment (MA) in the short term, no studies have reported on the long-term survivorship and function. METHODS: One hundred four consecutive cemented cruciate retaining TKAs implanted using computer navigation and following the rKA principles proposed by Vendittoli were reviewed at a minimum of 10 years after surgery. Implant revisions, reoperations and clinical outcomes were assessed using knee injury and osteoarthritis outcome score (KOOS), forgotten joint score (FJS), patients' satisfaction and joint perception questionnaires. Radiographs were analyzed to identify signs of osteolysis and implant loosening. RESULTS: Implant survivorship was 99.0% at a mean follow-up of 11.3 years (range: 10.3-12.9) with one early revision for instability. Patients perceived their TKA as natural or artificial without limitation in 50.0% of cases, and 95.3% were satisfied or very satisfied with their TKA. The mean FJS was 67.6 (range: 0-100). The mean KOOS were as follows: pain 84.7 (range: 38-100), symptoms 85.5 (range: 46-100), function in daily activities 82.6 (range: 40-100), function in sport and recreation 35.2 (range: 0-100) and quality of life 79.1 (range: 0-100). No radiological evidence of implant aseptic loosening or osteolysis was identified. CONCLUSION: Cemented TKA implanted with the rKA alignment protocol demonstrated excellent long-term implant survivorship and is a safe alternative to MA to improve patient function and satisfaction. LEVEL OF EVIDENCE: IV, continuous case series with no comparison group.

Superiority of kinematic alignment over mechanical alignment in total knee arthroplasty during medium- to long-term follow-up: A meta-analysis and trial sequential analysis.

PURPOSE: To compare and determine the reliability and conclusiveness of the medium- and long-term efficacy in terms of patient-reported outcome measures and the risk of revisions or reoperations (RRRs) of kinematic alignment (KA) and mechanical alignment (MA) in total knee arthroplasty. METHODS: A comprehensive search was conducted in Medline, EMBASE, Web of Science and Cochrane Database Library to identify relevant literature. Only randomised clinical trials (RCTs) published before July 2023 were included. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and RRR were compared. Additionally, OKS and RRR were subjected to a trial sequential analysis. RESULTS: Seven RCTs involving 572 knees were identified. The pooled analysis of the included studies demonstrated that KA showed better medium-term WOMAC and OKS (mean difference [MD] = -6.3, 95% confidence interval [CI]: -9.52 to -2.99, p < 0.05 and MD = 1.1, 95% CI: 0.05-2.15, p < 0.05), respectively), but no significant differences were observed in the long-term follow-up (MD = 2.1, 95% CI: -3.21 to 7.31, not significant [n.s.] and MD = 0.01, 95% CI: -2.43 to 2.46, n.s., respectively). FJS (standardised MD = -0.03, 95% CI: -0.25 to 0.19, n.s.) and RRR (risk ratio = 1.0, 95% CI: 0.57 to 1.74, n.s.) showed no significant intergroup differences (n.s.). The evidence quality ranged from moderate to high, and the trial sequential analysis indicated the need for additional high-quality RCTs to draw more conclusive results. CONCLUSIONS: KA showed better medium-term WOMAC and OKS, while KA and MA had similar FJS without increasing the RRR in medium- and long-term follow-up. Further research is needed for more conclusive results. LEVEL OF EVIDENCE: Level II (meta-analyses).

Personalized alignment techniques better restore the native trochlear groove compared to systematic alignment techniques in total knee arthroplasty.

PURPOSE: The relationship between constitutional coronal alignment and implant positioning on trochlear groove restoration in total knee arthroplasty (TKA) is poorly understood. This study aimed to determine whether the choice of alignment philosophy significantly affects the restoration of the trochlea groove. METHODS: Sixty-one imageless robotic TKAs performed by a single orthopaedic surgeon were retrospectively reviewed. In each case, the entire native trochlea was digitized to generate the native femoral anatomy, and implants were planned according to a functional alignment (FA) technique. Final implant position was recorded using the validated bone resection planes from the navigation system. Simulated femoral component positions were generated according to previously described alignment techniques: mechanical alignment (MA), gap balancing (GB), kinematic alignment (KA), restricted kinematic alignment (rKA) and restricted inverse kinematic alignment (riKA). Trochlear angle (TA), trochlear under/overstuffing and mediolateral sulcus offset were compared between the six simulated alignment techniques, as well as the final implanted technique. Further analyses investigated the effect of preoperative coronal alignment on trochlear position. Comparisons were assessed with an analysis of variance and Welch's t-tests or Wilcoxon's rank-sum tests with Bonferroni corrections. RESULTS: The implanted and simulated techniques all resulted in greater TA valgus compared to the native groove (p < 0.001). The implanted technique, KA and rKA were closer to the native TA than GB, MA and riKA (p > 0.001). All alignment philosophies understuffed the native trochlea groove. KA and rKA understuffed less than all other techniques (p < 0.001), and GB understuffed more than all other techniques (p < 0.001). In extension, all techniques shifted the trochlear sulcus laterally, while in flexion, they medialized it. These effects were most prominent in GB and MA. CONCLUSION: Personalized alignment techniques such as KA and rKA, which consider variations in individual anatomy, best restore the native patellar groove compared to systematic alignment techniques when using a standardized femoral component. LEVEL OF EVIDENCE: Level III, retrospective review.

Sparse and inconsistent reporting of pre- and post-operative radiographic angles of total knee arthroplasty using true unrestricted kinematic alignment: An umbrella review and secondary meta-analysis.

PURPOSE: To identify, synthesise and critically appraise findings of systematic reviews and meta-analyses on pre- and post-operative radiographic angles (lateral distal femoral angle [LDFA], medial proximal tibial angle [MPTA] and hip-knee-ankle [HKA] angle) of unrestricted kinematic alignment versus mechanical alignment in total knee arthroplasty (TKA). METHODS: Two authors searched MEDLINE, EMBASE and Epistemonikos for systematic reviews, with or without meta-analyses, that reported on TKA outcomes using unrestricted kinematic alignment. The methodological quality of the included systematic reviews and meta-analyses was independently assessed using A MeaSurement Tool to Assess systematic Reviews (AMSTAR-2). The effect size with its 95% confidence interval (CI) for radiographic angles was extracted from the systematic reviews and meta-analyses. The characteristics of clinical studies included in systematic reviews were listed and tabulated. Pre- and post-operative MPTA, LDFA and HKA angles were summarised using meta-analytic random-effects models. RESULTS: Nineteen records were eligible for data extraction. Systematic reviews and meta-analyses included 44 clinical studies, of which 31 were on unrestricted kinematic alignment and 13 were on restricted versions of kinematic alignment. None of the included systematic reviews or meta-analyses fulfiled all seven critical AMSTAR-2 domains. Few comparative studies reported both pre- and post-operative angles (LDFA, n = 3; MPTA, n = 4; and HKA angle, n = 10). Mean pre- and post-operative LDFAs were 88.0° (range, 83-94°) and 88.0° (range, 80-96°) for the kinematic alignment group, and 88.2° (range, 83-95°) and 90.2° (range, 84-97°) for the mechanical alignment group. Mean pre- and post-operative MPTAs were 86.0° (range, 78-93°) and 87.1° (range, 78-94°) for the kinematic alignment group and 86.4° (range, 77-94°) and 89.6° (range, 84-95°) for the mechanical alignment group. Mean pre- and post-operative HKA angles were -3.3° (range, -24° to 24°) and -0.3° (range, -10° to 8°) for the kinematic alignment group and -6.9° (range, -25° to 7°) and -0.9° (range, -8° to 7°) for the mechanical alignment group. CONCLUSION: Most systematic reviews and meta-analyses that report outcomes of TKA using kinematic alignment do not distinguish between the different versions of kinematic alignment. The clinical studies included in systematic reviews are limited and inconsistent in their reporting of radiographic angles. Different alignment strategies are often grouped under the umbrella term of kinematic alignment, which contributes to conflicting reports, confusion and unresolved questions regarding the efficacy of true unrestricted kinematic alignment. LEVEL OF EVIDENCE: Level IV.

Kinematical alignment better restores native patellar tracking pattern than mechanical alignment.

PURPOSE: The purpose of this study was to assess whether kinematic alignment (KA) outperforms mechanical alignment (MA) in restoring patellar tracking to native patterns by using a clustering algorithm. METHODS: Twenty cadavers (40 knees) were evaluated. For each cadaver, one knee was randomly assigned to KA and the other to MA. KA total knee arthroplasty (TKA) procedures were performed using a caliper-verified technique, while MA TKA procedures utilized a measured resection technique. Subsequently, all specimens were mounted on a customized knee-testing system, and patellar tracking was measured using a motion analysis system. All patellar tracking data were clustered using the density-based spatial clustering of applications with noise algorithm. Differences in patellar tracking patterns and the restoration of native patellar tracking were compared between the two alignment strategies. RESULTS: Patellar tracking patterns following KA were considerably different from MA. Pre- and post-TKA patellar tracking patterns following MA were grouped into separate clusters, whereas a substantial proportion of patellar tracking patterns following KA were grouped into the pre-TKA dominant cluster. Compared to MA, a greater proportion of patellar tracking patterns following KA showed similar patterns to native knees (p < 0.05) and more patellar tracking patterns following KA paired with preoperative patterns (p < 0.01). CONCLUSION: KA restored native patellar tracking patterns more closely compared to MA. LEVEL OF EVIDENCE: Level I, therapeutic study.

Functional alignment maximises advantages of robotic arm-assisted total knee arthroplasty with better patient-reported outcomes compared to mechanical alignment.

PURPOSE: Robotic arm-assisted total knee arthroplasty (RTKA) enables adjustment of implant position to achieve the surgeon's preferred alignment. However, the alignment concept that most effectively enhances patient satisfaction remains unclear. This study compares the clinical outcomes of patients who underwent functionally aligned RTKA (FA-RTKA), mechanically aligned conventional TKA (MA-CTKA) and mechanically aligned RTKA (MA-RTKA). METHODS: A prospectively collected database was retrospectively reviewed for patients who underwent primary TKA for knee osteoarthritis. One hundred and forty-seven knees were performed with MA-CTKA, followed by 72 consecutive knees performed with MA-RTKA, and subsequently, 70 consecutive knees performed with FA-RTKA were enrolled. After 1:1 propensity score matching of patient demographics, 70 knees were finally included in each group. The extent of additional soft tissue release during surgery was identified, and the Coronal Plane Alignment of the Knee classification was utilised to categorise the alignment. At the 1-year follow-up, patient-reported outcomes, including the pain Visual Analogue Scale, Knee Society Score, Western Ontario and McMaster Universities Arthritis Index and Forgotten Joint Score-12, were also compared among the groups. RESULTS: The FA-RTKA group showed significantly less additional soft tissue release than the MA-CTKA and MA-RTKA groups (15.7%, 38.6% and 35.7%, respectively; p = 0.006). Statistically significant differences in functional scores were observed in the postoperative 1-year clinical outcomes in favour of the FA-RTKA group, which had a significantly larger percentage of knees that maintained constitutional alignment and joint line obliquity than those of the other groups. CONCLUSIONS: Functionally aligned TKA showed superior 1-year postoperative patient-reported outcomes compared with those of conventional and robotic arm-assisted mechanically aligned TKA. Therefore, the advantage of RTKA is maximised when the implant positioning is based on functional alignment. The application of RTKA with mechanical alignment has been proven ineffective in improving the clinical outcomes of patients. LEVEL OF EVIDENCE: Level III.

Mechanically aligned total knee arthroplasty does not yield uniform outcomes across all coronal plane alignment of the knee (CPAK) phenotypes.

PURPOSE: Patient dissatisfaction rates following total knee arthroplasty (TKA) reported in the literature reach 20%. The optimal coronal alignment is still under debate. The aim of this retrospective study was to compare clinical outcomes in different coronal plane alignment of the knee (CPAK) phenotypes undergoing mechanically aligned (MA) TKA. The hypothesis was that knees with preoperative varus arithmetic hip-knee-ankle angle (aHKA) would achieve inferior clinical outcomes after surgery compared to other aHKA categories. Additionally, another objective was to assess CPAK phenotypes distribution in the study population. METHODS: A retrospective selection was made of 180 patients who underwent MA TKA from April 2021 to December 2022, with a 1-year follow-up. Coronal knee alignment was classified according to the CPAK classification. Clinical outcome evaluations were measured using the Knee Society Score (KSS), Oxford Knee Score (OKS), Short Form Survey 12 and Forgotten Joint Score (FJS). Differences in clinical outcomes were considered statistically significant with a p value <0 .05. RESULTS: Patients with varus aHKA achieved significantly inferior outcomes at final follow-up compared to other aHKA categories in KSS pt. 1 (79.7 ± 17.2 vs. 85.6 ± 14.7; p = 0.028), OKS (39.2 ± 9.2 vs. 42.2 ± 7.2; p = 0.019) and FJS (75.4 ± 31.0 vs. 87.4 ± 22.9; p =0 .003). The most common aHKA category was the varus category (39%). The most common CPAK phenotypes were apex distal Types I (23.9%), II (22.8%) and III (13.3%). CONCLUSION: MA TKA does not yield uniform outcomes across all CPAK phenotypes. Varus aHKA category shows significantly inferior results at final follow-up. The most prevalent CPAK categories are varus aHKA and apex distal JLO, with phenotypes I, II and III being the most common. However, their gender distribution varies significantly. LEVEL OF EVIDENCE: Level IV.

Higher satisfaction and function scores in restricted kinematic alignment versus mechanical alignment with medial pivot design total knee arthroplasty: A prospective randomised controlled trial.

PURPOSE: Restricted kinematic alignment (rKA) in total knee arthroplasty (TKA) and medial pivot (MP) knee designs already showed superior outcomes in independent comparative studies. The objective of this study was to assess whether rKA with MP TKA provides better clinical and functional outcomes compared to mechanical alignment (MA) with MP TKA. METHODS: This is a randomised, parallel two group study involving a total of 98 patients with end-stage knee osteoarthritis. Patients were randomly allocated to either rKA or MA TKA procedures conducted with a MP prothesis using patient-specific instruments between 2017 and 2020. Final follow-up was at 2 years postoperatively. Demographic data and clinical and functional scores (Oxford knee score, knee society score [KSS], Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], forgotten joint score [FJS]) were collected and compared preoperative, 1 year postoperative and 2 years postoperative. Coronal plane alignment of the knee and functional knee phenotype classification were recorded. RESULTS: A total of 47 patients (rKA) and 51 patients (MA) were included in final analysis. Superior joint awareness scores (FJS) were found at 1 year postoperative for rKA (62.2 vs. 52.4, p = 0.04). KSS subscores (expectation score, satisfaction score) improved with rKA with significant differences at both 1 and 2 years postoperatively. Major differences between rKA and MA were found in subgroup analysis of varus and neutral CPAK phenotypes. Both 1 year and 2 years postoperatively, FJS was significantly better in KA compared with MA in varus CPAK phenotypes (63.1 vs. 44.9, p = 0.03; 71.1 vs. 46.0, p = 0.005). Further clinical and functional scores showed improvement in the varus CPAK phenotypes with predominantly significant improvement in the expectation and satisfaction KSS subscores. No significant differences were found in the comparison of rKA and MA in neutral CPAK phenotypes. CONCLUSION: The rKA of MP TKA design shows superior patient satisfaction and self-reported function when compared to MA MP TKA. Furthermore, rKA MP TKA shows superior joint awareness at early postoperative stage. The most important clinical relevance of this study is the clear superiority of rKA in varus phenotypes. LEVEL OF EVIDENCE: Level II.

CPAK classification detect the real knee joint apex position in less than half of the knees.

PURPOSE: Accurate assessment of the knee joint line is essential for surgeries involving the knee. The knee joint line obliquity (KJLO) is a radiological measurement that evaluates the position of the knee joint relative to the ground and is frequently used in preoperative planning and clinical follow-up. On the other hand, coronal plane alignment of the knee (CPAK) classifications assesses the joint line as the summation of the medial proximal tibial angle (MPTA) and mechanical lateral distal femoral angle (mLDFA). The purpose of this study is to determine the concordance of these two measurement techniques. METHODS: This cross-sectional study evaluated the long-leg standing radiographs (LSRs) of 164 healthy knees. The extremity KJLO and CPAK classification JLO were measured twice by two observers at 8-week intervals. The knee joint line apex positions (proximal, neutral and distal) of the two measurement techniques are compared (concordance or discordant). The intraobserver and interobserver reliability were examined using the intraclass correlation coefficient (ICC). Possible causes of the discordant were evaluated with univariate and multivariate logistic regression analysis. RESULTS: CPAK classification detected the KJLO apex position in 70 extremities (42.7%) only. Subgroups CPAK JLO detected 13.6% of the proximal apex, 20.4% of the neutral, and 90.7% of the distal apex (p < 0.01). Upon multivariate logistic regression analysis, the variable KJLO apex position (proximal, neutral vs. distal, odds ratio (OR) = 10.291, 95% confidence interval [CI] = 2.225-25.656, and (p < 0.01) was determined as a risk factor for discordant. CONCLUSION: The CPAK JLO measurement technique can be misleading in defining the KJLO apex position and the concordance between them is less than 50%. It has a high tendency to misleadingly predict proximal and neutral apex positions, which can potentially have negative implications for assessing the joint line. LEVEL OF EVIDENCE: Level I.

CPAK classification cannot be used to determine segmental coronal extra-articular knee deformity.

PURPOSE: While the coronal plane alignment of the knee (CPAK) classification serves as a useful guide in personalising total knee arthroplasty (TKA), the extent of its correlation with segmental coronal extra-articular knee deformities remains uncertain. This study aims to investigate the potential correlation between CPAK matrix groups and segmental coronal extra-articular deformities in prearthritic knees, shedding light on the relationship between these two factors that seems to be both essential to perform personalised TKA. MATERIALS AND METHODS: A radiological assessment of 1240 nonarthritic knees was performed by evaluating lower limb measurements following the protocol established by Paley et al. Subsequently, all knees were classified into their respective CPAK matrix groups. In our quest to discern any correlation between the CPAK matrix groups and the presence of segmental coronal extra-articular knee deformities, nine potential coronal extra-articular deformity phenotype (CEDP) groupswere identified based on medial proximal tibial angle (MPTA) and mechanical lateral distal femoral angle (mLDFA). Neutral values for MPTA and mLDFA were set at 90.0° ± 3.0° and then at 87.0° ± 2.0°. Each CPAK matrix group underwent detailed coronal morphology analysis and then, segmental coronal extra-articular deformities were assessed by comparing them with the CEDP groups. RESULTS: The study revealed a mean hip-knee-ankle angle (HKA) of 178.6° ± 4.4°, mLDFA of 86.9° ± 2.5°, MPTA of 85.4° ± 2.4°, arithmetic HKA of -1.4° ± 3.2° and joint line obliquity of 172.5° ± 3.7°. The varus CPAK groups (I/IV/VII) included 435 patients, the neutral groups (II/V/VIII) comprised 630 patients and the valgus groups (III/VI/IX) had 175 patients. Notably, CPAK matrix groups were not distinctly associated with specific coronal extra-articular deformity phenotype (CEDP) groups. Particularly among the most common CPAK matrix groups (I/II/III/IV/V), there was a significant variation in segmental coronal extra-articular deformity patterns. Moreover, when neutral MPTA/mLDFA values were set at 87.0° ± 2.0°, the CPAK matrix groups exhibited even greater variability in coronal extra-articular deformities. CONCLUSION: The CPAK matrix groups do not exhibit a direct correlation with a specific extra-articular deformity pattern (CEDP), thus rendering them unsuitable for determining segmental coronal extra-articular knee deformities. LEVEL OF EVIDENCE: Level III, retrospective diagnostic study.

Equivalent Clinical Outcomes Between Anatomical Alignment Versus Mechanical Alignment of Simultaneous Bilateral Total Knee Arthroplasty Using a Posterior-Stabilized Prosthesis During an Average Follow-Up of Five Years: A Prospective Randomized Clinical Trial.

BACKGROUND: This study aimed to investigate the differences in clinical outcomes between anatomical alignment and mechanical alignment in each knee, respectively, in patients who underwent bilateral total knee arthroplasty. METHODS: Bilateral simultaneous total knee arthroplasty using a posterior-stabilized prosthesis was performed between June 2016 and May 2018, with one knee undergoing anatomical alignment and the contralateral knee undergoing mechanical alignment, which was randomized. There were 80 knees in 40 patients (mean age 75 years, range 60 to 87, with 4 men and 36 women) followed up for at least 2 years (mean follow-up 4.9 years, range 2 to 7 years). On the anatomical side, the distal femoral cut was set 2° more valgus to the mechanical axis, and the tibial cut was set to 2 or 3° varus using a specific guide. Implant position and lower extremity alignment were measured using postoperative radiographs and computed tomography images. The range of motion before and after surgery, Knee Society score, patient satisfaction, postoperative 2011 Knee Society questionnaire, and Knee Injury and Osteoarthritis Outcome Scores were evaluated. RESULTS: A significant difference was observed in joint line orientation (0.6 versus 2.9°, P < .001), but not in the postoperative hip-knee-ankle angle between 2 groups. There was one knee in the mechanical alignment group that required revision surgery at 5 years due to implant loosening. Before surgery, the anatomical alignment group had a significantly lower knee extension angle (-7.2 versus -6.0°, P = .035) and Knee Society Score (46.1 versus 49.1, P = .046). No significant difference was observed between the groups except for the 2011 Knee Society Questionnaire satisfaction scores (26.7 versus 25.7, P = .035). More participants preferred the anatomical alignment side postoperatively. CONCLUSIONS: Anatomical and mechanical alignments had similar clinical outcomes in patients undergoing bilateral total knee arthroplasty at a mean of 4.9 years follow-up. LEVELS OF EVIDENCE: Level Ⅰ (Randomized control study).

No Difference in Limb Alignment Between Kinematic and Mechanical Alignment Robotic-Assisted Total Knee Arthroplasty.

BACKGROUND: Individualized alignment techniques have gained major interest in an effort to increase satisfaction among total knee arthroplasty patients. This study aimed to compare postoperative alignment between kinematic alignment (KA) and mechanical alignment (MA) and assess whether KA significantly deviates from the principle of aligning the limb as close to neutral alignment as possible. METHODS: There were 234 patients who underwent robotic-assisted total knee arthroplasty using an unrestricted KA and a strict MA technique (KA: 145, MA: 89). The lateral distal femoral angle, medial proximal tibia angle, and the resultant arithmetic hip-knee-ankle angle (aHKA) were measured. The aHKA < 0 indicated varus alignment, while the aHKA > 0 indicated valgus knee alignment. The primary outcome was the frequency of cases that resulted in an aHKA of ± 4° of neutral (0°), as assessed on full-leg standing radiographs obtained at 6 weeks postoperatively. The secondary outcome was the change in coronal plane alignment of the knee classification type from preoperative to postoperative between the MA and KA groups. RESULTS: The mean preoperative aHKA was similar between the 2 groups (P = .19). The KA group had a mean postoperative aHKA of -1.4 ± 2.4°, while the MA group had a mean postoperative aHKA of -0.5 ± 2.1°. No significant difference in limb alignment was identified between KA and MA cases that resulted in hip-knee-ankle angle of ± 4° being neutral (91.7 versus 96.6%, P = .14). There were 97.2% of cases in the KA group that fell within the ± 5° range. The MA group was associated with a significantly higher rate of coronal plane alignment of the knee classification type change from preoperatively to postoperatively (P < .001). CONCLUSIONS: Kinematic alignment achieved similar postoperative aHKA compared to MA, and thus did not significantly deviate from the principle of aligning the limb as close to neutral alignment as possible. Surgeons should feel comfortable starting to introduce individualized alignment techniques. Without being restricted by boundaries, postoperative alignment will be within 5 degrees of neutral 97% of the time.

Alignment in Total Knee Arthroplasty: Avoid Crossing Over From Varus to Valgus.

BACKGROUND: Ideal target limb alignment remains a debated topic in total knee arthroplasty (TKA). We aimed to determine the effect of limb alignment correction on patient-reported outcomes and knee range of motion (ROM) following TKA. METHODS: In this retrospective analysis, patients (N = 409) undergoing primary TKA at a single institution were studied. Using full leg-length radiographs, limb alignment was measured preoperatively and postoperatively. Patients were categorized by preoperative (Preop) alignment (varus > 0°; valgus < 0°). Preop varus patients were then divided as follows based on postoperative alignment: neutral (VAR-NEUT, 0°± 2), remaining in varus (VAR-rVAR, ≥3°), and cross-over to valgus (VAR-CO, ≤-3°). Similarly, Preop valgus patients were divided as follows for postoperative alignment: neutral (VAL-NEUT, 0°± 2), remaining in valgus (VAL-rVAL, ≤-3°), and cross-over to varus (VAL-CO, ≥3°). The Knee Injury and Osteoarthritis Outcome Score for Joint Replacement survey scores were collected at preoperatively as well as at 6 weeks, 3, 6, and 12 months postoperatively. Knee ROM was collected at 2 weeks, 6 to 12 weeks, and >6 months postoperatively. An analysis of variance repeated on time followed by a Bonferroni post hoc test was used to compare outcomes for the postoperative alignment subgroups. RESULTS: Preop Varus patients: Those in the VAR-CO group (overcorrected to -4.03° ± 1.95valgus) were observed to have lower Knee Injury and Osteoarthritis Outcome Score for Joint Replacement scores at 3, 6, and 12 months postoperatively compared to those in the NEUT group (P < .05). This finding was paired with reduced ROM at 6 to 12 weeks postoperatively in the VAR-CO group compared to VAR-NEUT and VAR-rVAR (P < .05). Preop Valgus patients: Those in the VAL-rVal group (left in -4.39° ± 1.39valgus) were observed to have reduced knee flexion at 6 to 12 weeks postoperatively compared to VAL-NEUT and VAL-CO. CONCLUSIONS: These findings indicate that postoperative valgus alignment via either crossing over to valgus (VAR-CO) or remaining in valgus (VAL-rVAL) alignment may result in less preferable outcomes than correction to neutral or slightly varus alignment.

Restoring the Preoperative Phenotype According to the Coronal Plane Alignment of the Knee Classification After Total Knee Arthroplasty Leads to Better Functional Results.

BACKGROUND: Mechanical alignment after total knee arthroplasty (TKA) is still widely used in the surgical community, but the alignment finally obtained by conventional techniques remains uncertain. The recent Coronal Plane Alignment of the Knee (CPAK) classification distinguishes 9 knee phenotypes according to constitutional alignment and joint line obliquity (JLO). The aim of this study was to assess the phenotypes of osteoarthritic patients before and after TKA using mechanical alignment and to analyze the influence of CPAK restoration on functional outcomes. METHODS: This retrospective multicenter study included 178 TKAs with a minimum follow-up of 2 years. Patients were operated on using a conventional technique with the goal of neutral mechanical alignment. The CPAK grade (1 to 9), considering the arithmetic Hip-Knee-Ankle angle (aHKA) and the JLO, was determined before and after TKA. Functional results were assessed using the following patient-reported outcome measures: Knee Injury and Osteoarthritis Outcome Score, the Simple Knee Value, and the Forgotten Joint Score. RESULTS: A true neutral mechanical alignment was obtained in only 37.1%. Isolated restoration of JLO was found in 31.4%, and isolated restoration of the aHKA in 44.9%. Exact restoration of the CPAK phenotype was found in 14.6%. Restoration of the CPAK grade was associated with an improvement in the "daily living": 79.2 ± 5.3 versus 62.5 ± 2.3 (R2 = 0.05, P < .05) and "Quality of life" Knee Injury and Osteoarthritis Outcome Score subscales: 73.8 ± 5.0 versus 62.9 ± 2.2 (R2 = 0.02, P < .05). CONCLUSIONS: This study shows that few neutral mechanical alignments are finally obtained after TKA by conventional technique. A major number of patients present a postoperative modification of their constitutional phenotype. Functional results at 2 years of follow-up appear to be improved by the restoration of the CPAK phenotype, JLO, and aHKA. LEVEL OF CLINICAL ART EVIDENCE: III, Retrospective Cohort Study.

Kinematic Alignment Technique Outperforms Mechanical Alignment in Simultaneous Bilateral Total Knee Arthroplasty: A Randomized Controlled Trial.

BACKGROUND: The aim of this study was to compare the clinical results of kinematic alignment (KA) with those of mechanical alignment (MA) in single-stage bilateral total knee arthroplasty. METHODS: In this double-blinded randomized controlled trial, 65 patients who had bilateral knee osteoarthritis underwent simultaneous bilateral total knee arthroplasty. One knee was randomly selected to be operated on with the calipered-KA technique and the other with MA. The participants were assessed via the Oxford Knee Score, Western Ontario and McMaster Universities Osteoarthritis Index questionnaire, and visual analog scale before the surgery and the same plus the Forgotten Joint Score at their last follow-up visit, 2 years postoperatively. Maximum knee flexion and the time reaching maximum knee flexion, named the recovery time, were also recorded. Hip-knee-ankle angle, medial proximal tibial angle, and lateral distal femoral angle were measured before and after the surgery using 3-joint-view radiographs. RESULTS: At 2 years, there were significant differences between the KA and MA techniques in terms of duration of surgery, recovery time, and final Western Ontario and McMaster Universities Osteoarthritis Index, Forgotten Joint Score, and maximum flexion range in favor of KA (P < .05), but no significant difference in visual analog scale score or Oxford Knee Score. In patients who have a preferred knee, the KA knee was preferred over the MA knee by most patients. No prosthetic failure or revision was reported in either group. CONCLUSIONS: The KA technique yields acceptable functional outcomes compared to the MA technique. The KA technique was associated with a shorter surgery time, a faster recovery time, and higher patient satisfaction in 2-year follow-ups. Larger multicenter studies with longer follow-ups are warranted to confirm these findings. LEVEL OF EVIDENCE: I.

Restoration of constitutional alignment optimizes outcomes of computer navigated total knee arthroplasty: a prospective randomized controlled trial.

PURPOSE: The value of computer navigation in total knee arthroplasty (TKA) for arthritic knees continues to be debated. The purpose of this study was to evaluate the value of navigated TKA associated with updated alignment philosophy. METHODS: This prospective randomized controlled trial enrolled 38 consecutive patients (76 knees) and were randomly assigned to both groups. The demographic data and perioperative data were recorded. The coronal plane alignment of the knee (CPAK) classification was used to classify knee alignment phenotypes. Radiographic outcomes were measured and subgroup analysis was further performed. Clinical outcomes were evaluated using patient-reported outcome measures (PROMs). Surgery-related complications were recorded. RESULTS: The distribution of CPAK phenotypes following constitutional aligned TKA was equivalent to the native cohort, whereas the mechanical aligned TKA dramatically altered the phenotype distribution from type I and type II to type V and type IV. Final implant positioning was different between groups, with constitutional aligned TKA having larger cTCA (P = .004), joint line obliquity (P = .006), joint line distance (P = .033) and smaller sFCA (P = .013). Subgroup analysis showed higher actual accuracy of component positioning was achieved in navigated TKA, especially in knees with deformity of > 10° (P < .05). Patients reported higher HSS score at three months postoperatively in constitutional aligned group (P = .002). One patient in navigated group suffered femoral pin site fracture caused by a minor trauma. CONCLUSION: Computer navigated TKA allows for restoration of constitutional alignment and minimizes soft tissue release, which when compared to mechanical alignment may be associated with superior early outcomes.

Better restoration of joint line obliquity in tibia first restricted kinematic alignment versus mechanical alignment TKA.

INTRODUCTION: In total knee arthroplasty (TKA), suboptimal restoration of joint line obliquity (JLO) and joint line height (JLH) may lead to diminished implant longevity, increased risk of complications, and reduced patient reported outcomes. The primary objective of this study is to determine whether restricted kinematic alignment (rKA) leads to improved restoration of JLO and JLH compared to mechanical alignment (MA) in TKA. MATERIALS AND METHODS: This retrospective study assessed patients who underwent single implant design TKA for primary osteoarthritis, either MA with manual instrumentation or rKA assisted with imageless navigation robotic arm TKA. Pre- and post-operative long standing AP X-ray imaging were used to measure JLO formed between the proximal tibial joint line and the floor. JLH was measured as the distance from the femoral articular surface to the adductor tubercle. RESULTS: Overall, 200 patients (100 patients in each group) were included. Demographics between the two groups including age, sex, ASA, laterality, and BMI did not significantly differ. Distribution of KL osteoarthritis classification was similar between the groups. For the MA group, pre- to post-operative JLO significantly changed (2.94° vs. 2.31°, p = 0.004). No significant changes were found between pre- and post-operative JLH (40.6 mm vs. 40.6 mm, p = 0.89). For the rKA group, no significant changes were found between pre- and post-operative JLO (2.43° vs. 2.30°, p = 0.57). Additionally, no significant changes were found between pre- and post-operative JLH (41.2 mm vs. 42.4 mm, p = 0.17). Pre- to post-operative JLO alteration was five times higher in the MA group compared to the rKA group, although this comparison between groups did not reach statistical significance (p = 0.09). CONCLUSION: rKA-TKA results in high restoration accuracy of JLO and JLH, and demonstrates less pre- and post-operative JLO alteration compared to MA-TKA. With risen interest in joint line restoration accuracy with kinematic alignment, these findings suggest potential advantages compared to MA. Future investigation is needed to correlate between joint line restoration accuracy achieved by rKA and enhanced implant longevity, reduced risk of post-operative complications, and heightened patient satisfaction.

Alignment Techniques in Total Knee Arthroplasty: Where do We Stand Today?

Achieving optimal alignment in total knee arthroplasty (TKA) is a critical factor in ensuring optimal outcomes and long-term implant survival. Traditionally, mechanical alignment has been favored to achieve neutral post-operative joint alignment. However, contemporary approaches, such as kinematic alignments and hybrid techniques including adjusted mechanical, restricted kinematic, inverse kinematic, and functional alignments, are gaining attention for their ability to restore native joint kinematics and anatomical alignment, potentially leading to enhanced functional outcomes and greater patient satisfaction. The ongoing debate on optimal alignment strategies considers the following factors: long-term implant durability, functional improvement, and resolution of individual anatomical variations. Furthermore, advancements of computer-navigated and robotic-assisted surgery have augmented the precision in implant positioning and objective measurements of soft tissue balance. Despite ongoing debates on balancing implant longevity and functional outcomes, there is an increasing advocacy for personalized alignment strategies that are tailored to individual anatomical variations. This review evaluates the spectrum of various alignment techniques in TKA, including mechanical alignment, patient-specific kinematic approaches, and emerging hybrid methods. Each technique is scrutinized based on its fundamental principles, procedural techniques, inherent advantages, and potential limitations, while identifying significant clinical gaps that underscore the need for further investigation.

The Distribution of Coronal Plane Alignment of the Knee Classification in a Sample of Spanish Southeast Osteoarthritic Population: A Retrospective Cross-Sectional Observational Study.

Background and Objectives: The Coronal Plane Alignment of the Knee (CPAK) classification is a pragmatic distribution of nine phenotypes for coronal knee alignment that can be used on healthy and arthritic knees. Our study aimed to describe the CPAK distributions in a Spanish southeast osteoarthritic population and compare them to other populations' published alignment distributions. Method and Materials: Full-leg standing X-rays of the lower limb from 528 cases originating from the so-called Vega Alta del Segura (southeast of the Iberian Peninsula) were retrospectively analysed. We measured the mechanical hip-knee-ankle, lateral distal femoral, and medial proximal tibial angles. We calculated the arithmetic hip-knee-ankle angle and the joint line obliquity to classify each case according to the criteria of the CPAK classification. Results: Based on the aHKA result, 59.1% of the cases were varus (less than -2°), 32.7% were neutral (0° ± 2°), and 8.2% were valgus (greater than +2°). Based on the JLO result, 56.7% of the cases had a distal apex (less than 177°), 39.9% had a neutral apex (180° ± 3°), and 3.4% had a proximal apex (greater than 183°). The most common CPAK distribution in our Spanish southeast osteoarthritic population was type I (30.7%), followed by type IV (25.9%), type II (21%), type V (11.2%), type III (5%), type VI (2.8%), type VII (2.4%), type VIII (0.6%), and type IX (0.4%). Conclusions: We described the distribution according to the CPAK classification in a sample of the osteoarthritic population from southeastern Spain. In our sample, more than 75% of the patients were classified as type I, II, and IV.

Postoperative clinical outcomes for kinematically, restricted kinematically, or mechanically aligned total knee arthroplasty: a systematic review and network meta-analysis of randomized controlled trials.

BACKGROUND: Mechanically aligned total knee arthroplasty (MATKA) is a well-established procedure. Kinematically aligned TKA (KATKA) has been proposed to restore and preserve pre-arthritic knee anatomy. However, normal knee anatomy varies widely, and there have been concerns regarding restoring unusual anatomy. Accordingly, restricted KATKA (rKATKA) was introduced to reproduce constitutional knee anatomy within a safe range. This network meta-analysis (NMA) aimed to evaluate the clinical and radiological outcomes of the surgeries. METHODS: We performed a database search on August 20, 2022, which included randomized controlled trials (RCTs) comparing any two of the three surgical TKA techniques for knee osteoarthritis. We conducted a random-effects NMA within the frequentist framework and evaluated confidence in each outcome using the Confidence in Network Meta-Analysis tool. RESULTS: Ten RCTs with 1,008 knees and a median follow-up period of 1.5 years were included. The three methods might result in little to no difference in range of motion (ROM) between methods. In patient-reported outcome measures (PROMs), the KATKA might result in a slight improvement compared with the MATKA (standardized mean difference, 0.47; 95% confidence interval [CI], 0.16-0.78; very low confidence). There was little to no difference in revision risk between MATKA and KATKA. KATKA and rKATKA showed a slight valgus femoral component (mean difference [MD], -1.35; 95% CI, -1.95-[-0.75]; very low confidence; and MD, -1.72; 95% CI, -2.63-[-0.81]; very low confidence, respectively) and a slight varus tibial component (MD, 2.23; 95% CI, 1.22-3.24; very low confidence; and MD, 1.25; 95% CI, 0.01-2.49; very low confidence, respectively) compared with MATKA. Tibial component inclination and hip-knee-ankle angle might result in little to no difference between the three procedures. CONCLUSIONS: KATKA and rKATKA showed similar ROM and PROMs and a slight variation in the coronal component alignment compared with MATKA. KATKA and rKATKA are acceptable methods in short- to mid-term follow-up periods. However, long-term clinical results in patients with severe varus deformity are still lacking. Surgeons should choose surgical procedures carefully. Further trials are warranted to evaluate the efficacy, safety, and subsequent revision risk.