Kinematically Aligned Total Knee Arthroplasty Research Articles

A Restriction Boundary-Based Coronal Plane Alignment of the Knee (CPAK) Classification for Restricted Kinematic Alignment Total Knee Arthroplasty.

Background Coronal plane alignment of the knee (CPAK) classification was proposed as a means of understanding the knee phenotype in leg alignment and joint line obliquity (JLO). However, when it is adapted to restricted kinematic alignment total knee arthroplasty (rKA-TKA), the boundaries of CPAK and those of rKA-TKA phenotype are different. We therefore reappraise the boundary between the CPAK classification and restriction protocol and propose a restriction boundary-based CPAK (Rb-CPAK). Methods Between May 2020 and March 2022, 143 knees in 95 patients underwent rKA at our institution and were included in this study. In Rb-CPAK, we set the following ranges: 6° varus to 3° valgus for arithmetic hip-knee-ankle angle (aHKA), 0° to 6° varus for the medial proximal tibial angle (MPTA), 0° to 5° valgus for the lateral distal femoral angle (LDFA), and 169° to 180° for JLO. The pre- and postoperative alignments were classified using the original CPAK and Rb-CPAK. Results There were significant differences in pre- and postoperative distributions between original CPAK and Rb-CPAK (p < 0.0001). Postoperative Rb-CPAK primarily led to neutral aHKA (116 of 143 knees), and decreased MPTA varus (pre: 83.9 ± 3.4, post: 87.0 ± 2.3, p < 0.0001) and stable LDFA values (pre: 88.7 ± 3.1, post: 88.5 ± 2.7, p = 0.4) were observed. Among cases with neutral JLO, 78 knees required MPTA or LDFA corrections. Postoperatively, 67 (64%) out of 119 knees categorized as neutral JLO fell within MPTA and LDFA ranges. Conclusion The Rb-CPAK modification more effectively outlined knees that required restriction, and the restriction was properly performed compared with the original CPAK. However, JLO does not effectively indicate if a knee requires restriction or not, and thus individual evaluation of LDFA and MPTA might be necessary.

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

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. 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. 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. 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. IV, continuous case series with no comparison group.

A bone graft from the tibial resection or patella that rectified a tibial over-resection reliably healed and improved clinical outcome scores: A retrospective study of kinematically aligned TKA.

During kinematically aligned (KA) total knee arthroplasty (TKA), the surgeon may need to rectify an over-resection of the medial, lateral or posterior tibia. This study tested the hypothesis that a bone graft taken from the tibial resection or patella and impacted beneath a tibial baseplate would heal, regardless of whether the tibial component and knee were in outlier ranges according to mechanical alignment (MA) criteria. The study also tested the hypothesis that the Oxford Knee Score (OKS) and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) would improve beyond the substantial clinical benefit and that the source and thickness of the bone graft would not influence their improvement. This retrospective study radiographically assessed the healing of a bone graft from the tibial resection (n = 19) or patella (n = 10) in 29 KA TKAs (18 females, mean age 65 years). The tibial component and knee alignment were categorized as in-range or outliers based on reported MA criteria for bone graft healing and implant survival. The one-sample t test identified differences in the improvement of the OKS and KOOS JR from their reported substantial clinical benefit of 16 and 20 points, respectively. At an average follow-up of 37 months, all bone grafts healed even though ≥55% of tibial components and 34% of knees were varus outliers according to MA criteria for bone healing and implant survival. Amongst the 29 patients, the mean OKS and KOOS JR improvements of 25 ± 11 and 47 ± 21 points, respectively, surpassed the threshold of their respective substantial clinical benefit (p < 0.01) and were not influenced by the bone graft's source and thickness (p ≥ 0.51). During cemented KA TKA, the surgeon can use a bone graft from the tibial resection or patella to rectify a tibial over-resection. This technique led to consistent bone healing and improved outcome scores. Level IV.

Two-Year Outcomes are Equal in Kellgren-Lawrence Osteoarthritis Grades 1-4 after Total Knee Arthroplasty with Medial-Pivot Implants and Kinematic Alignment.

Introduction While risks exist with total knee arthroplasty (TKA) and survivorship is not indefinite, delaying surgery may lead to further deterioration of the knee joint, functional outcomes, and health status. Most studies report that patients with high-grade osteoarthritis (OA) scores have higher satisfaction and functional scores, cautioning against TKA in those with lower OA grades. This study correlates Kellgren-Lawrence (KL) OA scores with outcomes following kinematically-aligned TKA. Methods Preoperative anteroposterior weight-bearing radiographs of 168 patients enrolled in a prospective trial were scored for KL grade. Patients were segregated into two groups: the low-grade OA group had KL scores of 1 or 2, the high-grade OA group had a KL score of 3 or 4. Outcomes as measured with Forgotten Joint Score (FJS), Knee Society Score (KSS), and Range of motion were compared up to 2-years. Results There were 29 subjects with low-grade KL scores and 127 with high-grade KL scores. There were no differences in BMI, age, or gender distribution. The only statistically significant difference was in the preoperative KSS Pain/Motion score, 60.6 in the low-grade OA group vs. 46.4 in the high-grade group (P&lt;0.008). There were no significant differences between the groups in FJS at one or two-year follow-up. There were no differences in KSS Functional or Composite Scores, or in range of motion (ROM) at pre-op, 1-year or 2-years, and in KSS Pain/Motion at 1 or 2-years. Conclusion There were no significant differences in FJS, KSS, and ROM in patients with low- vs. high-grade OA up to 2-year follow-up. Patients with lower grade OA demonstrated substantial improvements in their FJS, KSS scores, and ROM indistinguishable from the higher-grade OA cohort up to 2-years, suggesting no shorter-term downside to earlier intervention with kinematically-aligned medial-pivot (MP) TKA.

Effect of inverse kinematic alignment total knee arthroplasty on coronal alignment of the ankle joint in patients with varus knee deformity

IntroductionVarus or valgus knee deformities influence ankle coronal alignments. The impact of Total Knee Arthroplasty (TKA) on ankle joint alignment has not been entirely illustrated. Inverse Kinematic Alignment (iKA) is a surgical philosophy that aims to restore soft tissue balance, function, and native anatomy within validated boundaries to restore restrictive native kinematics. Therefore, this study aimed to investigate the postoperative association of patient-specific alignment on the coronal alignment of the ankle in patients with varus knee deformity who underwent iKA TKA. We hypothesized that greater preoperative varus malalignments would correlate with significant postoperative ankle coronal alignment changes.MethodsThis retrospective study of a prospective collected cohort assessed patients who underwent imageless navigation assisted robotic TKA using a single implant design for primary osteoarthritis between January 2022 and August 2023. Preoperative and postoperative full-length standing anteroposterior X-ray imaging was used to measure Hip-Knee-Ankle (HKA), Tibial Plafond Inclination (TPI), Talar inclination (TI), and Tibiotalar Tilt (TTT) angles. Patients were subsequently divided into groups of neutral varus) < 10°) and severe varus (≥ 10°) according to the preoperative HKA angle.ResultsSignificant changes in preoperative and postoperative HKA angles were found in the severe varus (14.5° vs. 6.4°, p < 0.001) group. Changes were also significant between preoperative and postoperative TPI and TI angles in the severe varus group; however, TTT did not reach statistical significance. Delta change from pre- to postoperative HKA was significantly higher for the severe varus group (8.1° vs. 0.8°, p < 0.019). Delta change of TPI, TI and TTT did not differ between groups.ConclusionCoronal knee alignment after TKA affects coronal alignment of the ankle. iKA technique in TKA for varus knee deformity preserves or minimizes substantial coronal alignment changes of the ankle joint. These findings may add to the benefits reported for patient specific alignment TKA techniques.Level of evidenceIII.

A Novel Technique for Restricted Kinematic Alignment Total Knee Arthroplasty Without Computer-Assisted Devices

A Novel Technique for Restricted Kinematic Alignment Total Knee Arthroplasty Without Computer-Assisted Devices

No difference in postoperative patient satisfaction rates between mechanical and kinematic alignment total knee arthroplasty: A systematic review.

The purpose of this systematic review was to compare patient satisfaction patient-reported outcomes (PROMs) levels after mechanically aligned (MA) and kinematically aligned (KA) total knee arthroplasty (TKA). A systematic literature search following PRISMA guidelines was conducted on PubMed, Embase, Medline and Scopus to identify potentially relevant articles for this review, published from the beginning of March 2013 until the end of October 2023. Only articles reporting satisfaction after KA TKA, MA TKA or both were included, which use valid and reliable tools for the evaluation and reporting of satisfaction after TKA. Title, authors, year of publication, study design, level of evidence, follow-up period, patients' demographic data, sample size, type of satisfaction score, postoperative satisfaction score, postoperative alignment, statistical significance, as well as other variables, were extracted for analysis. An Agency for Healthcare Research and Quality's (AHRQ) design-specific scale was used for assessing randomized control trials (RCTs). The nonrandomized control trials were evaluated by using the Joanna Briggs Institute's (JBI) Critical Appraisal Tool. The Newcastle-Ottawa Scale (NOS) was also used to assess cohort studies, while case series were evaluated using the NIH Quality Assessment Tool for Case Series Studies. The initial search identified 316 studies, of which 178 were considered for screening. Eleven studies completely fulfilled the inclusion criteria, including one RCT, five nonrandomized control trials/quasi-experiments, three case series, and two cohort studies. The total number of patients recruited for MA TKA was 1740. Conversely, 497 patients were enrolled for KA TKA. Five studies used the visual analogue scale (VAS) for assessing postoperative patient satisfaction, four used the Knee Society Score (KSS) 2011 version and two Likert-based types of scores. Overall, the highest mean satisfaction score of KSS 2011 was 31.5 ± 6.6 in the MA group, and 29.8 ± 80 in the KA group in four studies. All of them showed high postoperative patient satisfaction rates for both MA and KA TKA, but with no statistically significant difference between them (p > 0.05). Both mechanically aligned total knee arthroplasty, as well as kinematically aligned total knee arthroplasty led to high rates of postoperative patient satisfaction, with no statistically significant differences between them. Level III, systematic review.

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

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. 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. 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). KA restored native patellar tracking patterns more closely compared to MA. Level I, therapeutic study.

The Trochlear Bisector as a New Landmark for Kinematic Alignment in Total Knee Arthroplasty: A Radiographic Study.

Background: In recent years, there has been considerable interest in prosthetic alignment techniques for total knee arthroplasty (TKA), particularly in the so-called kinematic alignment, which aims to restore the knee's native alignment. However, implementing this technique requires specialized instruments and procedural steps that can be laborious. This study introduces the bisector of the trochlear groove as a reliable landmark for performing the distal femoral cut while maintaining parallelism with the native femoral joint line. Methods: Three orthopedic specialists assessed 110 X-ray images of full-leg, weight-bearing lower limbs obtained from healthy individuals between January 2021 and December 2022. The bisector of the trochlear groove was identified on the X-ray images, and the angle between this bisector and the femoral joint line was measured. The consistency of these measurements across repeated assessments and different examiners was evaluated. Results: The bisector of the trochlear groove was found to be perpendicular to the femoral joint line, with a mean angle of 89.4°. The inter-rater reliability was 68% within ±1.3° from the mean, while the intra-rater reliability was 82% within ±1.5° from the mean. Conclusions: These results suggest that by performing a femoral cut perpendicular to the bisector of the trochlear groove, surgeons can inherently restore the femoral joint line of the native knee in patients where the native joint line is no longer identifiable due to the effect of osteoarthritis. This method may offer a viable and straightforward alternative to the standard surgical technique currently practiced for kinematic alignment in TKA.

Limitations of the knee society score in kinematically aligned total knee arthroplasty.

The Knee Society Scoring System (KSS) is a frequently used outcome score which quantifies functional patients' outcomes before and after total knee arthroplasty (TKA). Several problems arise when trying to implement KSS for obtaining postoperative outcomes after more personalised aligned TKAs. Scoring for valgus femorotibial angle (FTA) intervals outside moderate ranges is often poorly explained, the specific version of KSS used for outcome collection is frequently unclear and the exact measuring methods are typically not described in the literature. The aims of this systematic review were to investigate the latest user practice, the application of KSS and its limitations after kinematically aligned (KA) TKA. A systematic literature search following PRISMA guidelines was conducted on PubMed, Embase, Medline and Scopus to identify potentially relevant articles for this review, published from the beginning of January 2013 until the end of January 2023. Broad Mesh terms such as 'kinematic alignment', 'total knee arthroplasty' and 'knee society score' were used for building search strategy in each database accordingly. Articles reporting postoperative values of the objective surgeon-assessed KSS after KA TKA or KA and mechanically aligned TKA were included. For assessing included randomised control trials (RCTs), an Agency for Healthcare Research and Quality's design-specific scale for assessing RCTs was used. The non-RCTs were assessed by using the Joanna Briggs Institute Critical Appraisal Tool. The Ottawa-Newcastle Score system was also used. Studies were additionally evaluated for their radiological methodology by using a five-question checklist (Radiological Assessment Qualit criteria). The initial search identified 167 studies, of which 129 were considered for screening. Ten studies reporting outcomes after KA TKA did not use the objective surgeon-assessed part of KSS for clinical outcome measurement, and 30 studies reporting outcomes after KA TKA did not use KSS at all for clinical and/or functional outcomes. From the 10 included studies, only six have used the latest KSS score (2011), the rest using its 1989 variant; and out of these six studies, only two presented values of the FTA, which is needed for calculating the KSS's 'alignment' subcomponent, the rest presenting hip-knee-ankle angle (HKA) values. Additionally, when converting these HKA values to FTA intervals, the authors of this systematic review found that KA TKA FTA intervals display limits, which tend to be outside the 'well-scored' KSS anatomical alignment interval. The inconsistent and nonstandardised use of the surgeon-assessed KSS across studies reviewed compromises assessment reliability and patient outcome scores. To enhance precision and comparability, it is crucial to standardise the KSS application, incorporating personalised alignment strategies for more accurate patient evaluations. Level III.

Maintaining the Physiological Lateral Flexion Gap in the Kinematically Aligned TKA Does Not Compromise Clinical Outcomes at One-Year Follow-Up.

Background: Instability is a common cause of (total knee arthroplasty) TKA failure, which can be prevented by achieving proper gap balance during surgery. There is no consensus on the ideal gap balance in TKA, and different alignment philosophies result in varying soft-tissue tightness. Traditional TKA aims for symmetric compartment balance, while kinematic alignment (KA) restores anatomy and accepts asymmetric flexion gaps. This study evaluated the impact of these philosophies on the flexion gap balance and clinical outcomes. Methods: A retrospective review of 167 patients who received true or restricted KA robotic-assisted TKA with at least one year of follow-up was conducted. The groups were based on intraoperative flexion gap differences: symmetric (0-1 mm) (n = 94) and asymmetric (2-5 mm) (n = 73). Results: Preoperative demographics and postoperative clinical and functional scores were compared. Both groups were similar in demographics and preoperative scores. True KA alignment was more likely to result in an asymmetric flexion gap, while restricted KA produced symmetric gaps. Conclusions: The study found no adverse effects from the physiological asymmetric flexion gap, with clinical and functional outcomes comparable to symmetric gaps. A 5 mm difference between the medial and lateral gap width did not negatively impact the outcomes. True KA more frequently results in a physiological asymmetric flexion gap.

Similar Recovery Rate for Patients Aged between 50 and 89 Years That Go Home on the Surgery Day and Self-Administer Their Rehabilitation after Kinematically Aligned Total Knee Arthroplasty.

for kinematic alignment (KA) total knee arthroplasty (TKA), it was unknown whether 'the pace of recovery' at six weeks was different for patients with ages ranging between 50-59, 60-69, 70-79, and 80-89 years who were discharged on the surgery day and self-administered their rehabilitation. a single surgeon treated 206 consecutive patients with a KA-designed femoral component and an insert with a medial ball-in-socket, lateral flat articulation, and PCL retention. Each filled out preoperative and six-week Oxford Knee Score (OKS), Knee Society Score (KSS), Knee Function Score (KFS), and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS, JR) questionnaires. The six-week minus preoperative value indicated improvement. between age cohorts, the improvement was not different (p = 0.2319 to 0.9888). The mean improvement/six-week postoperative value was 6°/-2° for knee extension, 0°/119° for knee flexion, 7/31 for the OKS, 39/96 for the KSS, 7/64 for the KFS, and 13/62 for the KOOS. The 30-day hospital readmission rate was 1%. surgeons who perform KA TKA can counsel 50 to 89-year-old patients that they can be safely discharged home on the surgery day with a low risk of readmission and can achieve better function at six weeks than preoperatively when performing exercises without a physical therapist.

Phenotype-considered kinematically aligned total knee arthroplasty for windswept-deformity-associated osteoarthritis: surgical strategy and clinical outcomes

BackgroundWindswept deformity (WSD) in relation to advanced osteoarthritis (OA) presents a significant surgical challenge in total knee arthroplasty (TKA). The primary goal of this study is to investigate the Prevalance of WSD associated osteoarthritis who have undergone total knee arthroplasty. The secondary goal is to explore the causes of WSD and its association with spinal deformity or leg length discrepancy in these patients. Finally, we evaluate the surgical outcomes of phenotype-considered kinematically aligned TKA (KA-TKA) in treating patients with WSD.MethodsA review was conducted on data from 40 knees of 33 WSD patients who underwent phenotype-considered KA-TKA from August 2016 to December 2020. Patient demographics, associated diseases, preoperative and postoperative knee alignment angles, range of motion (ROM), Oxford Knee Score (OKS), and Knee Society Score (KSS) were collected and analyzed. Subgroup analysis for comparing the results between valgus and varus knees were also performed.ResultsWithin the studied cohort of WSD patients, a substantial 64% displayed concomitant coronal spinal imbalance and 21% evidenced leg length discrepancy. Postoperative improvements were notable in knee alignments, ROM, OKS, and KSS following the application of the phenotype-considered KA-TKA approach. There were significant differences in the knee alignment angles, including mHKA, LDFA, and MPTA, between the valgus and varus side of knees (P = 0.018). However, no statistically significant difference were observed in the functional scores, comprising ROM, OKS, and KSS, between valgus and varus knees.ConclusionsA high percentage of patients with WSD exhibited coronal spinal imbalance and leg length discrepancy. Phenotype-considered KA-TKA effectively provided alignment targets for the treatment of both varus and valgus knees in patients with WSD, achieving excellent short-term outcomes and acceptable knee alignment.

Risk of tibial baseplate loosening is low in patients following unrestricted kinematic alignment total knee arthroplasty using a cruciate-retaining medial conforming insert: A study using radiostereometric analysisat 2 years.

Assessing the risk of tibial baseplate loosening in patients after unrestricted kinematically aligned (unKA) total knee arthroplasty (TKA) using a medially conforming insert is important because baseplates generally are aligned in varus which has been linked to an increased incidence of aseptic loosening following mechanically aligned TKA. Two limits that indicate long-term stability in patients are a change in maximum total point motion between 1 and 2 years (ΔMTPM) < 0.2 mm and anterior tilt at 2 years < 0.8°. The purposes were to determine: (1) the number of patients with ΔMTPM > 0.2 mm, (2) the number of patients with anterior tilt > 0.8°and (3) whether increased varus baseplate and limb alignment were associated with increased migration. Thirty-five patients underwent cemented, caliper-verified, unKA TKA using a medially conforming tibial insert with posterior cruciate ligament (PCL) retention. Biplanar radiographs acquired on the day of surgery and at 1.5, 3, 6, 12and 24 months were processed with model-based radiostereometric analysis (RSA) software to determine migration and the number of patients with migration above the two stability limits. Medial proximal tibial angle (MPTA), hip-knee-ankle angle (HKAA)and posterior slope angle (PSA) were analyzed for an association with migration in six degrees of freedom and in MTPM. Thirty-two of 35 patients were available for analysis at 2 years. One patient exhibited ΔMTPM > 0.2 mm. The same patient exhibited anterior tilt > 0.8°. Varus rotation (p = 0.048, r ≤ 0.34) and medial translation (p = 0.0273, r ≤ 0.29) increased with increased varus baseplate alignment. The results indicate low risk of long-term baseplate loosening in patients. Although varus rotation and medial translation increased with increased varus baseplate alignment, the magnitudes of the migrations were minimal and did not increase ΔMTPM and anterior tilt. Level II, therapeutic prospective cohort study.

Caliper-Based Restricted Kinematic Alignment Total Knee Arthroplasty.

Restricted kinematic alignment total knee arthroplasty (rKA-TKA) is a reasonable selection for avoiding an extreme alignment that has been conceded to induce implant failure. However, computer-aided devices (CAS), such as navigation, robotics, and patient-specific instrumentation, are necessary to perform rKA-TKA. This paper reports on the surgical technique of kinematic alignment total knee arthroplasty (KA-TKA) using mechanical instruments. The lateral distal femoral angle (LDFA) and the medial proximal tibial angle (MPTA) are measured from preoperative long radiographs or CT of the lower limb, and the arithmetic hip-knee-ankle angle (aHKA) is calculated from the MPTA - LDFA. The predefined restriction boundaries are used to determinethe osteotomy angle. In our practice, the LDFA is 85° to 93°, the MPTA is 85° to 90°, and the aHKA is 5° varus to 3° valgus. If correction of the femoral osteotomy is required, this can be achieved by changing the thickness of the paddle set on the distal articular surface or by adjusting the angle of the variable angle femoral cutting guide. For the tibia, the distal end of the extramedullary rod, with the proximal part placed in the center of the knee joint, should be adjusted so that it does not exceed the lateral malleolus. This limits the medial tilt of the osteotomy plane to within 5.5°. These techniques allow restricted KA to be performed with existing mechanical instruments without using CAS.

Functional knee phenotypes: A helpful classification tool for visualizing potential femoral varus in restricted kinematic alignment total knee arthroplasty in Japan.

Restricted kinematic alignment (rKA) is a modified technique of kinematically aligned total knee arthroplasty (TKA) within a safe alignment range for long-term implant survivorship. The purpose of this study was to clarify (1) the distribution of functional knee phenotypes in patients who underwent TKA in Japan and (2) whether the application of this classification results in anatomically neutral alignment after rKA TKA. Overall, 114 TKA surgeries (mechanical alignment [MA]: 49; rKA: 65) were performed. The joint line orientation angle (JLOA), hip-knee-ankle angle (HKA), femoral mechanical angle (FMA)and tibial mechanical angle (TMA) were obtained. The knees were categorized using a functional knee phenotype classification. Clinical evaluations, including the Knee Injury and Osteoarthritis Outcome, 12-question Forgotten Jointand Oxford Knee Scores, were performed 3 years postoperatively. Between-group comparisons were made. The most common preoperative functional knee phenotype was VARHKA 3° + NEUFMA 0° + VARTMA 3° (11.4%). In the preoperative population, 51 knees (44.7%) had VARFMA ≥ 3°. Postoperatively, the most common functional knee phenotype was NEUHKA 0° + VARFMA 3° + VALTMA 3° (14 knees, 28.6%) in the MA and NEUHKA 0° + NEUFMA 0° + NEUTMA 0° in the rKA group. The percentage of postoperative JLOA within ±3° from the floor was 27% and 72% in the MA and rKA groups, respectively (p < 0.001). The functional knee phenotype after rKA TKA was neutrally reproduced, and the joint line was more parallel to the ground in the standing position than that of MA. Between-group differences in clinical outcomes were not significant. The application of functional knee phenotyping to knee osteoarthritis in Japan suggested the presence of racial morphological characteristics. This classification could help better visualize potential femoral varus, contributing to protocol deviation in applying restricted KA TKA. Level IV.

Effects of Unrestricted Kinematically Aligned Total Knee Arthroplasty with a Modified Soft-Tissue Respecting Technique on the Deformity of Limb Alignment in Japanese Patients.

Background and Objectives: Unrestricted kinematic alignment total knee arthroplasty (KA-TKA) with a soft-tissue respecting technique (STRT) is a soft-tissue-dependent tibial resection entailing the restoration of the original soft-tissue tension using ligamentotaxis after resurfacing the femur, based on the concept of restoring the native or pre-osteoarthritis alignment in each patient. However, there is no consensus on the indications of unrestricted KA-TKA with the STRT. We modified the STRT, followed by an investigation of the effects of surgery on the postoperative hip-knee-ankle angle (HKAA). Materials and Methods: We retrospectively analyzed the clinical background data, including the preoperative and postoperative HKAA, of 87 patients who underwent unrestricted KA-TKA with the modified STRT. Univariate and multivariate analyses were performed to determine the factors affecting the postoperative HKAA. A receiver operating characteristic (ROC) curve was plotted to investigate the change in the cut-off values of preoperative HKAA with respect to the safe zone of the postoperative HKAA. We generated two regression models, the linear regression model and generalized additive model (GAM) using machine learning, to predict the postoperative HKAA. Results: Univariate and multivariate analyses revealed the preoperative HKAA as the factor most relevant to the postoperative HKAA. ROC analysis revealed that the preoperative HKAA exhibited a high predictive utility, with a cut-off value of -10°, when the safe range of postoperative HKAA was set at ±5°. The GAM was the superior machine learning model, indicating a non-linear association between the preoperative and postoperative HKAA. Patients with preoperative HKAAs ranging from -18° to 4° were more likely to fall within the ±5° safe range of the postoperative HKAA. Conclusions: The preoperative HKAA influences the postoperative HKAA in unrestricted KA-TKA with the modified STRT. Machine learning using the GAM may contribute to the selection of patients eligible for the surgical approach.

Alignment strategy for different types of varus knee with generic instruments: Mechanical alignment or kinematic alignment?

ObjectiveA thorough examination of the available approaches is crucial to comprehensively understand the variance among the alignment strategies employed in total knee arthroplasty (TKA). In this study, we assessed the functional outcomes during the perioperative and postoperative periods of TKA in patients using generic instruments with varus knee to compare the mechanical alignment (MA) and kinematic alignment (KA) procedures.MethodsA total of 127 patients from the First Affiliated Hospital of Wannan Medical College who had undergone unilateral TKA between November 2019 and April 2021 were included. The patients with varus knee deformity were categorized into two groups [type I (n = 64) and type IV (n = 63)] based on the modified coronal plane alignment of the knee (mCPAK) classification. The type I and IV groups were further subdivided into MA (n = 30 and n = 32) and KA subgroups (n = 34 and n = 21), respectively. The clinical information collected included sex, surgical side, age, body mass index, and perioperative data [including operation time, intraoperative blood loss, length of hospital stay, and the American Society of Anesthesiologists (ASA) classification]. All patients were monitored for 12 months post-surgery to evaluate the recovery of knee joint function. During this period, the Knee Disability and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR) and the active range of motion (AROM) and visual analog scale (VAS) pain scores were compared at different time points, i.e., before the operation and 6 weeks, 6 months, and 12 months post-operation. Additionally, the patients’ subjective experiences were assessed at 6 and 12 months post-surgery using Forgotten Joint Score Knee (FJS-12 Knee), while complications were recorded throughout the monitoring period.ResultsNo significant variances were observed in ASA classification, operation duration, blood loss volume during surgery, and hospital stay length between the patients who underwent KA TKA and those who received MA TKA (P > 0.05). During the initial 6 weeks post-operation, the KA group exhibited a significantly reduced average VAS pain score (P < 0.05), with no such differences at 6 months and 1 year after the surgery (P > 0.05). Furthermore, the KA group had significantly higher scores on the KOOS JR at 6 weeks, 6 months, and 1 year following the surgery (P < 0.05). Moreover, the AROM score of the KA group significantly improved only at 6 weeks after the surgery (P < 0.05); however, no prominent differences were found at 6 months and 1 year after the operation (P > 0.05). The KA cohort also exhibited a significant increase in FJS-12 Knee at 1 year following the operation (P < 0.05), whereas no such difference was detected at 6 months following the surgery (P > 0.05). Thus, compared to the MA method, the KA procedure provided pain relief and improved active motion range within 6 weeks after the surgery in patients undergoing TKA. Further, the KOOS JR exhibited significant increases at 6 weeks, 6 months, and 1 year while the FJS-12 Knee demonstrated a significant increase at 1 year after the KA TKA procedure.ConclusionTherefore, our study results suggest that the KA approach can be considered in patients using generic instruments with varus alignment of the knee, particularly those with mCPAK type I and IV varus knees, to help improve patient satisfaction.

Better forgotten joint scores when the angle of the prosthetic trochlea is lateral to the quadriceps vector in kinematically aligned total knee arthroplasty.

The primary aim was to analyze unrestricted kinematic alignment (unKA) total knee arthroplasty (TKA) and determine the frequency of medial deviation of the prosthetic trochlear angle (PTA) of the femoral component relative to the quadriceps vector (QV) that terminates at the anterior inferior iliac spine (AIIS), and whether patients with medial deviation had a worse Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) relative to those with lateral deviation. The secondary aim was to determine the frequency of medial deviation for mechanical alignment (MA) TKA simulations. From a database of a single surgeon, the study extracted de-identified data on 147 patients with a CT scanogram showing the pelvis and AIIS, a limb with an unKA TKA, and a native (i.e., healthy) opposite limb. On the scanogram, an examiner, blinded to the PROMs, measured the PTA-QV angle on the unKA TKA and on the opposite limb simulated MA TKA by drawing the PTA at 6° valgus relative to the femoral mechanical axis and measuring the PTA-QV angle. Medial deviation of the PTA occurred in 86% of patients with unKA TKA, and the 126 with medial deviation had a 17/1 point worse median FJS/OKS than the 21 with lateral deviation at a mean follow-up of 47 ± 8 months, respectively (p < 0.0001, p = 0.0053). In addition, 21%, 17%, and 8% of MA TKA had medial deviation after radiographic simulation using reported surgical errors for manual, patient-specific, and robotic instrumentation, respectively. In most patients with unKA TKA and a smaller proportion with MA TKA, a PTA of 6° valgus was medial to the QV, which, by excluding the patient's Q-angle, might alter patellofemoral kinematics like an incorrectly oriented trochleoplasty. The 17-point worse FJS in the patients with an unKA TKA and medial deviation of the PTA suggests the surgical target should be to orient the PTA lateral to the QV. IV.

Laxity, Balance, and Alignment of a Simulated Kinematic Alignment Total Knee Arthroplasty.

Kinematic alignment (KA) and related personalized alignment strategies in total knee arthroplasty (TKA) target restoration of native joint line obliquity and alignment. In practice, deviations from exact restoration of the prearthritic joint surface are tolerated for either the femur or tibia to achieve ligamentous balance. It remains unknown what laxity, balance, and alignment would result if a pure resurfacing of both femur and tibia were performed in a KA TKA technique. We used data from 382 robot-assisted TKA performed with a digital joint tensioner to simulate TKA with a pure resurfacing KA technique for both femur and tibia. All knees had the posterior cruciate ligament retained. Knees were subdivided into 4 groups based on preoperative coronal alignment: valgus, neutral, varus, and high varus. Medial and lateral laxity in extension and flexion, balance in extension and flexion, and coronal plane alignment were compared between groups using analysis of variance testing. In simulated pure resurfacing KA TKA across a range of preoperative coronal plane deformities, only 11%-31% of knees would have mediolateral extension ligament balance within ±1 mm, and 20%-41% would have a medial flexion gap that is looser than the lateral flexion gap. Over 45% of knees would have coronal hip-knee-ankle angle >3 degrees from mechanical neutral. In simulations of pure resurfacing KA TKA, there was wide variability in the resulting laxity and alignment outcomes. Most knees had alignment and balance outcomes outside of normally accepted ranges. Techniques that deviate from pure resurfacing in order to achieve balance appear favorable.