Cruciate-retaining Total Knee Arthroplasty Research Articles

Knee injury and osteoarthritis outcome score and knee society score for the minimal clinically important differences after cruciate-retaining total knee arthroplasty: Two-year follow up.

This study investigated changes in the Knee Injury and Osteoarthritis Outcome Score (KOOS), 2011 Knee Society Score (KSS), and minimal clinically important differences (MCIDs) of these scores preoperatively to 2years after total knee arthroplasty (TKA). This single-center retrospective study included 168 patients who underwent primary cruciate-retaining (CR) TKA using the subvastus approach. The KOOS and KSS were assessed preoperatively and during the 3-month, 6-month, 1-year, and 2-year follow ups. The MCIDs of the KOOS and KSS were calculated using distribution-based methods with standard deviation. All patient-reported outcome measures improved considerably from preoperatively to 3months postoperatively. KOOS pain and symptom scores considerably improved at approximately 2years postoperatively, with KOOS activities of daily living (ADL) and sports/recreation subscale scores showing rapid improvement within 3months, followed by smaller gains. MCID thresholds for KOOS subscales were as follows: pain, 14.3-15.3; symptoms, 14.1-15.6; ADL, 15.2-16.0; sport/recreation, 11.7-11.8; and quality of life, 13.6-14.4. KSS objective knee indicators and satisfaction improved considerably approximately 2years postoperatively; however, scores on the expectation and functional activity subscales did not improve after 1year. MCID thresholds for KSS subscales were as follows: objective knee indicators, 4.6-4.7; satisfaction, 4.9-5.0; expectation, 2.4; and functional activities, 12.0-12.3. Improvements in the KSS objective knee indicators and KOOS subjective pain and symptom scores were similar over the 2-year follow up. These findings may help better understand the expected outcomes of CR-type TKA, especially in severe osteoarthritis cases, thereby informing patient counseling.

The CR Versus PS Debate: A Throwback Throw-Down in Total Knee Arthroplasty: Commentary on an article by Young-Hoo Kim, MD, et al: "No Discernible Difference in Revision Rate or Survivorship Between Posterior Cruciate-Retaining and Posterior Cruciate-Substituting TKA".

The CR Versus PS Debate: A Throwback Throw-Down in Total Knee Arthroplasty: Commentary on an article by Young-Hoo Kim, MD, et al: "No Discernible Difference in Revision Rate or Survivorship Between Posterior Cruciate-Retaining and Posterior Cruciate-Substituting TKA".

Effect of posterior-stabilized and cruciate-retaining implants on three-dimensional kinematic characteristics after total knee arthroplasty.

This study aimed to analyze the effects of posteriorstabilized (PS) and cruciate-retaining (CR) total knee arthroplasty (TKA) on early postoperative three-dimensional (3D) dynamic and kinematic characteristics in patients with unilateral knee osteoarthritis (OA). A retrospective analysis of prospectively collected data from 90 patients with unilateral TKA between February 2021 and September 2021 was conducted using a 3D kinematic analysis system before and six months after TKA. This patient group included 57 patients (10 males, 47 females; mean age: 69.5±7.5 years; range, 53 to 85 years) who underwent PS TKA and 33 patients (11 males, 22 females; mean age: 67.9±8.8 years; range, 45 to 86 years) who underwent CR TKA. The kinematic characteristics and clinical results of the two groups were compared. Clinical evaluation included the Hospital for Special Surgery knee score and range of motion (ROM). Twenty-eight healthy controls (9 males, 19 females; mean age: 64.5±2.9 years; range, 61 to 75 years) without knee OA matched for age, weight, height, and body mass index were recruited. The kinematic characteristics of the healthy control group were also evaluated. The PS group exhibited significant changes in basic gait parameters after TKA, including cadence (p=0.046), stride time (p=0.011), opposite foot off (p<0.001), opposite foot contact (p=0.038), step time (p=0.005), double support period (p<0.001), and foot off (p=0.004). No significant differences were observed in the kinematic parameters before and after TKA between the PS and CR groups, such as knee angle, moment, and force. The dynamic ROM of the CR group was greater than that of the PS group (p<0.001). Both the PS and CR groups showed significant deficiencies in flexion and extension function, including knee flexion moment, extension force, maximum flexion angle, and dynamic ROM, compared to healthy individuals. Throughout the gait cycle, both the PS and CR groups showed better knee joint stability compared to healthy individuals. At six months postoperatively, both the PS and CR groups' gait patterns did not recover to a healthy state, and the CR group's gait pattern was more similar to OA. Compared to PS TKA, CR TKA allowed for greater dynamic ROM during gait. Despite exhibiting superior knee stability during gait, both implants' knee kinematics function remained inferior compared to healthy individuals.

Low-constraint insert with a medial pivot design as a potential predictor of favourable outcomes in cruciate-retaining total knee arthroplasty: A propensity score-matched analysis.

The influence of polyethylene insert conformity on the outcomes of cruciate-retaining (CR) total knee arthroplasty (TKA) with a medial pivot design remains uncertain. Therefore, this study aimed to evaluate the effects of polyethylene insert conformity in CR-TKA on patient-reported outcomes. The data of 255 knees (FINE Total Knee System) from 255 patients were retrospectively analysed to compare outcomes for high- or low-constraint medial pivot inserts, as determined through historical controls, over an average follow-up period of 2.2 years (range, 2.0-5.5 years). Multivariate logistic regression analysis was used to identify predictors of achieving the patient-acceptable symptom state (PASS) for the Forgotten Joint Score-12 (FJS-12). Propensity score-matched cohorts for age, sex, body mass index, Kellgren-Lawrence grade, Charlson Comorbidity Index, knee flexion contracture, FJS-12 and follow-up duration were created for between-group comparison (n = 50 in each group). Low-constraint insert (p = 0.031) and age (p = 0.043) were independent predictors of achieving the PASS for the FJS-12 (>33, 153/255). After successful matching, compared to the high-constraint insert, the low-constraint insert improved patient satisfaction (p = 0.029 for pain on going up or downstairs, and p = 0.047 for the function of going upstairs) and increased the likelihood of achieving the minimal clinically important difference (p = 0.019) and PASS (p = 0.025) for the FJS-12. A significant correlation was observed between the posterior tibial slope and the FJS-12 in the low-constraint insert group (p < 0.001), indicating that a greater posterior tibial slope was associated with better functional outcomes in this group. Compared with high-constraint inserts, low-constraint medial pivot inserts yielded higher functional outcomes and patient satisfaction. Therefore, insert conformity may play a crucial role in CR-TKA outcomes. Level III.

Reoperations After Operatively and Non-Operatively Treated Periprosthetic Knee Fractures: A Nationwide Study on 1,931 Fractures After Primary Total Knee Arthroplasty

BackgroundPeriprosthetic knee fracture (PPKF) following total knee arthroplasty (TKA) can be difficult to treat. A PPKF can be treated both operatively and nonoperatively, and the treatment varies between fracture sites. This study aimed to assess the risk of reoperation according to the fracture site and treatment of the PPKF. MethodThis study is a nationwide cohort study using register data from 1997 to 2022. Cruciate-retaining or posterior-stabilized primary TKA were identified from the Danish Knee Arthroplasty Register. Subsequent PPKFs, fracture treatments, and later reoperations were identified through the International Classification of Diseases, tenth edition (ICD-10) diagnosis and procedure codes in the Danish National Patient Register. In addition, indications for revision total knee arthroplasty (rTKA) in the Danish Knee Arthroplasty Register were used to identify PPKFs and the reason for reoperation. ResultsWe included 1,931 PPKFs (1,494 femoral, 207 patellae, and 230 tibial) with an overall two-year reoperation risk of 20% (95% confidence interval (CI): 18 to 23). Femoral PPKFs had a two-year reoperation risk of 16% (CI: 12 to 22) after nonoperative treatment and 21% (CI: 18 to 24) after operative treatment. Patellar PPKFs had a two-year reoperation risk in five to 17 after nonoperative treatment and 46% (CI: 30 to 69) after operative treatment. Tibial PPKFs had a two-year reoperation risk of 17% (CI: 11 to 27) after nonoperative treatment and 36% (25 to 53) after operative treatment. ConclusionsThe overall two-year reoperation risk was 20% (CI: 18 to 23). Operative-treated PPKFs had a higher risk of reoperation across all fracture locations. The highest reoperation risk was found after operatively treated patella and tibial PPKFs (46 and 36%, respectively), and the lowest reoperation risk was found after nonoperative-treated patella PPKFs.

No Increased Risk of Patella-Related Revisions When Comparing Ultra-Congruent versus Cruciate-Retaining Polyethylene Liners in Primary Total Knee Arthroplasties With an Unresurfaced Patella: An Australian Registry Study of 42,105 Knee Arthroplasties

BackgroundUltra-congruent (UC) polyethylene liners are designed to add additional anterior-posterior stability in primary total knee arthroplasties (TKAs), compensating for actual or potential posterior cruciate ligament incompetence, somewhat like a posterior-stabilized knee. The literature supports patella resurfacing in primary posterior-stabilized compared to cruciate-retaining (CR) TKA due to higher revision rates with nonresurfaced patella. However, it is unclear if UC liners alter patella-related revisions. The aim of the study was to compare patella revision rates and survivorship of UC versus CR liners in primary TKA without patella resurfacing using two common prostheses in patients who had osteoarthritis. MethodsThis was a retrospective cohort analysis of data from the Australian Orthopedic Association National Joint Replacement Registry. Patients who underwent primary TKA utilizing one of two common knee systems with cemented tibial fixation for osteoarthritis and did not have their patella resurfaced between January 1, 2007, and December 31, 2022, were included for analysis. A total of 42,105 primary TKA procedures were included (UC, n = 18,989 and CR, n = 23,116). The risk of patella-related revision and survivorship for primary TKA procedures with UC compared to CR liners were analyzed. ResultsThe cumulative revision at 14 years was 5.7% (95% confidence interval [CI] 4.7 to 6.9) and 5.4% (95% CI 4.8 to 6.1) for the CR and UC group, respectively, with no difference between groups (entire period: HR [hazard ratio] = 1.07 (95% CI 0.95 to 1.20), P = 0.256). When revision TKA for patella-related diagnoses was analyzed, there was no difference between the CR and UC groups (entire period: HR = 1.10 (95% CI 0.88 to 1.38), P = 0.406). The prosthesis-specific analyses did not produce any differences between the groups for all-cause or patella-related revisions. ConclusionsThe use of UC compared to CR liners in primary TKA without patella resurfacing was not associated with an increased rate of all-cause or patella-related revisions. Surgeons should make clinical decisions on the need for patella resurfacing based on other patient, surgical, and implant factors.

Using Video-Fluoroscopy and Multibody Modelling to Unveil the Influence of a Gradually Reducing Femoral Radius on Ligament Elongation Patterns Following Posterior Cruciate-Retaining Total Knee Arthroplasty

Stability in total knee arthroplasties (TKAs) is mainly provided by soft tissue structures and the implant geometry. Paradoxical anterior translation could be decreased with a gradually reducing femoral radius compared to a dual-radii design. However, the influence of the sagittal curvature of the femoral condyles on knee ligaments remains unclear. This study quantified the length change patterns of the medial and lateral collateral ligaments (MCL and LCL) and posterior cruciate ligament (PCL) in 15 subjects with a gradually reducing radius and 15 subjects with a dual-radii TKA. Kinematics obtained from video-fluoroscopy were used to drive personalised multibody knee models. The ligament lengths were analysed throughout complete cycles of level gait, stair descent, and sit-to-stand-to-sit activity. Regardless of the implant design, our results indicated flexion-dependent elongation patterns in all ligament bundles. Importantly, however, subjects with the dual-radii implant design exhibited higher ligament strains during the mid-flexion phase compared to those with gradually reducing designs. Our findings, therefore, emphasise the importance of the impact of subtle changes in implant geometry on the loading patterns of the knee soft tissues, which need to be acknowledged by implant manufacturers and orthopaedic surgeons.

Linear and Volumetric Polyethylene Wear Patterns after Primary Cruciate-Retaining Total Knee Arthroplasty Failure: An Analysis Using Optical Scanning and Computer-Aided Design Models.

(1) Background: Analyses of retrieved inserts allow for a better understanding of TKA failure mechanisms and the detection of factors that cause increased wear. The purpose of this implant retrieval study was to identify whether insert volumetric wear significantly differs among groups of common causes of total knee arthroplasty failure, whether there is a characteristic wear distribution pattern for a common cause of failure, and whether nominal insert size and component size ratio (femur-to-insert) influence linear and volumetric wear rates. (2) Methods: We digitally reconstructed 59 retrieved single-model cruciate-retaining inserts and computed their articular load-bearing surface wear utilizing an optical scanner and computer-aided design models as references. After comprehensively reviewing all cases, each was categorized into one or more of the following groups: prosthetic joint infection, osteolysis, clinical loosening of the component, joint malalignment or component malposition, instability, and other isolated causes. The associations between volumetric wear and causes of failure were estimated using a multiple linear regression model adjusted for time in situ. Insert linear penetration wear maps from the respective groups of failure were further processed and merged to create a single average binary image, highlighting a potential wear distribution pattern. The differences in wear rates according to nominal insert size (small vs. medium vs. large) and component size ratio (≤1 vs. >1) were tested using the Kruskal-Wallis test and the Mann-Whitney test, respectively. (3) Results: Patients with identified osteolysis alone and those also with clinical loosening of the component had significantly higher volumetric wear when compared to those without both causes (p = 0.016 and p = 0.009, respectively). All other causes were not significantly associated with volumetric wear. The instability group differentiated from the others with a combined peripheral antero-posterior wear distribution. Linear and volumetric wear rates showed no significant differences when compared by nominal insert size (small vs. medium vs. large, p = 0.563 and p = 0.747, respectively) or by component (femoral-to-insert) size ratio (≤1 vs. >1, p = 0.885 and p = 0.055, respectively). (4) Conclusions: The study found increased volumetric wear in cases of osteolysis alone, with greater wear when combined with clinical loosening compared to other groups. The instability group demonstrated a characteristic peripheral anterior and posterior wear pattern. Insert size and component size ratio seem not to influence wear rates.

Medial soft tissue release is also related to the anterior stability of cruciate-retaining total knee arthroplasty: a cadaveric study.

Medial soft tissue release is occasionally performed to achieve mediolateral ligament balance in total knee arthroplasty (TKA), whose sequential effect on mediolateral and anteroposterior stability remains unclear. This study aimed to quantitatively evaluate the difference in mediolateral and anteroposterior stability according to a sequential medial soft tissue release in TKA. Cruciate-retaining TKA was performed in six cadaveric knees. Medial and lateral joint gaps, varus-valgus angle, and tibial anterior and posterior translations relative to the femur with pulling and pushing forces, respectively, were measured. All measurements were performed at full extension and 45° and 90° flexion after release of the deep medial collateral ligament (MCL) (stage 1), the posteromedial capsule (stage 2), and the superficial MCL (stage 3). Mediolateral and anteroposterior stability were compared between stages, and correlations between mediolateral and anteroposterior stability were analyzed. Medial joint gap significantly increased from stages 1 to 3 by 3.2mm, 6.8mm, and 7.2mm at extension, 45° flexion, and 90° flexion, respectively, and from stages 2 to 3 by 3.5mm at extension. Varus-valgus angle was varus at stage 2, which turned to valgus at stage 3 (-2.7° to 0.8°, -2.2° to 4.3°, and -5.5° to 2.5° at extension, 45° flexion, and 90° flexion, respectively). Anterior translation at 90° flexion significantly increased from stages 1 and 2 to stage 3 by 11.5mm and 8.2mm, respectively, which was significantly correlated with medial gap (r = 0.681) and varus-valgus angle (r = 0.495). Medial soft tissue release also increased tibial anterior translation as well as medial joint gap, and medial joint gap and tibial anterior translation were significantly correlated. Surgeons should be careful not to create too large medial joint gap and tibial anterior translation in flexion by excessive medial release up to the superficial MCL for achieving an equal mediolateral joint gap in extension.

WOMAC, Kujala Score, and Knee Injury and Osteoarthritis Outcome Score for Quality of Life Thresholds for Predicting Increased and Decreased Likelihood of Failure to Improve Quality of Life After Total Knee Replacement.

Background Improvement in quality of life is the primary goal following total knee arthroplasty (TKA). Patient-reported outcome measures (PROMs) have become the standard for evaluating TKA results, capturing the patient's perspective. However, PROMs face challenges such as inconsistent presurgery data collection and ambiguity in determining clinical significance. Establishing reliable thresholds for success and failure is crucial for comparing outcomes. Purpose To determine cutoff values for the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Kujala score, and Knee Injury and Osteoarthritis Outcome Score for Quality of Life (KOOS-QL) that significantly change the likelihood of success (TIS) or failure (TIF) to improve self-reported quality of life one year after TKA compared to the baseline probability of the studied cohort. Methods A retrospective study was conducted to evaluate PROMs following conventional cruciate-retaining (CR) TKA without patellar replacement. Patients were evaluated during 2022 and 2023, with a minimum one-year follow-up. A total of 161 successful evaluations were identified, representing 81% of all CR TKA procedures without patellar replacement performed between January 2018 and June 2022 at a single university hospital. Assessments included the three dimensions of the WOMAC scale (pain, stiffness, and function), Kujala score, and KOOS-QL. The primary outcome was to determine the threshold value of each PROM that significantly reduced or increased the likelihood of "same or worse" self-perceived improvement in quality of life compared to the cohort. Logistic regression with 200 iterations was used for statistical analysis. Results The threshold for improvement success was <4 for WOMAC-Pain, <1 for WOMAC-Stiffness, <15 for WOMAC-Function, >70 for Kujala, and >62 for KOOS-QL. Meanwhile, the threshold for increased failure was >7 for WOMAC-Pain, >3 for WOMAC-Stiffness, >26 for WOMAC-Function, <55 for Kujala, and <41 for KOOS-QL. Conclusions The study successfully established significant thresholds for success and failure in improving quality of life following CR TKA without patellar replacement. The identified thresholds for WOMAC-Pain, WOMAC-Function, and Kujala scores have good-excellent discrimination and can be confidently used to estimate sample sizes and compare quality of life improvements post-TKA.

Patient height is a predictive factor for good postoperative knee flexion after cruciate-retaining total knee arthroplasty with GRADIUS design.

A gradually reducing radius (GRADIUS) design implant can facilitate a smooth transition from stability through full range of motion in total knee arthroplasty (TKA). Nonetheless, patient-specific factors associated with good knee flexion remain unclear. This study aimed to determine the factors associated with good knee flexion after cruciate-retaining TKA with a GRADIUS prosthesis in an Asian population. This retrospective study included 135 patients that were stratified according to postoperative knee flexion angle (KFA) into Group F (⩾ 120∘; 85 patients [63.2%]) and Group NF (< 120∘; 50 patients [36.8%]). Patients in Group F were taller and had a lower body mass index (BMI) smaller preoperative hipkneeankle angle and better preoperative extension and flexion angle than Group NF patients. The multivariable analysis revealed that patients' height (odds ratio [OR]: 1.07, P= 0.0150), BMI (OR: 0.85, P= 0.0049), and preoperative flexion angle (OR: 1.06, P= 0.0008) predicted good KFA. The ROC curve analysis showed that the cutoff values of a good KFA were height 155.1 cm, BMI 22.1 kg/m2, and preoperative KFA 120∘. Patient height, BMI, and preoperative KFA were independent factors affecting good postoperative KFA in patients of Asian descent who underwent cruciate-retaining TKA with a GRADIUS design.

Bilateral Cruciate-retaining Image-free Robot-assisted Total Knee Arthroplasty Using Extended Restricted Kinematic Alignment in a Patient with Severe Varus Deformities

The management of severe coronal deformities during total knee arthroplasty (TKA) is challenging. Although conventionally considered to be a contraindication for cruciate-retaining TKA, severe varus deformities of ≥15° can be managed using cruciate-retaining prostheses and result in satisfactory outcomes if appropriate alignment and gap balance can be achieved. Robotic technology has enhanced the correction of complex deformities through virtual surgical planning, alternative alignment strategies, superior soft-tissue management, and personalized surgery. We present a case of bilateral osteoarthritis of the knees with severe varus deformities, managed through image-free robot-assisted TKA using extended restricted kinematic alignment and cruciate-retaining prostheses. Arthroplasty surgeons in developing countries need to be well-versed in multiple techniques for the management of osteoarthritis of the knee with severe coronal deformities. The technique presented by the authors would be a valuable tool in their armamentarium.

Internal rotational patellar resection and patella alta induced patellar maltracking in total knee arthroplasty: intraoperative measurement of the patellofemoral pressure

BackgroundAnterior knee pain due to patellar maltracking following total knee arthroplasty (TKA) reduces patients’ satisfaction. This study aimed to determine the patellofemoral pressure (PFP) in patients with favorable patellar tracking (FT) and impaired patellar tracking (IT) following TKA, the factors causing patellar maltracking, and the effect of lateral retinacular release (LRR) on patients with IT.MethodsForty-four patients with varus knee osteoarthritis undergoing cruciate-retaining TKA were enrolled. After component implantation, patients with a separation of ≥ 2 mm of the patellar medial facet from the medial femoral trochlea throughout knee range of motion were classified into the IT group; meanwhile, the others were classified into the FT group. PFP was measured intraoperatively in three phases: (1) with the resurfaced patella (RP); (2) with the resurfaced patella and knee (RPK); and (3) when LRR was performed in IT (post-LRR). The PFPs at 0°, 90°, 120°, and 135° knee flexion were compared between FT and IT using the Mann–Whitney U test. Pairwise comparison of the PFP in IT between RPK and post-LRR was performed using the Wilcoxon signed-rank test. Correlations between PFP and pre- and postoperative radiographic parameters, such as hip–knee–ankle angle, lateral distal femoral angle, medial proximal tibial angle, anterior femoral offset, Insall–Salvati ratio (ISR), patellar tilt, and patellar resection angle (PRA), were evaluated using Spearman’s rank correlation coefficients.ResultsHigh lateral PFP in the knee flexion position led to patellar maltracking. Patients with IT (n = 24) had higher lateral and lower medial PFP than did patients with FT (n = 20) at 90°, 120°, and 135° knee flexion in RP and RPK. LRR in IT reduced the lateral PFP in the knee flexion position. PRA and ISR were correlated with the lateral PFP at no less than 90° in RP and RPK.ConclusionsThis study demonstrated that internal rotational patellar resection, which resulted in a thick medial patellar remnant and a thin lateral counterpart, and patella alta were the causative factors of high lateral PFP, which induced patellar maltracking after TKA. Surgeons should avoid internal rotational patellar resection to achieve FT and perform LRR in patients with patellar maltracking.

Coronal plane stability of cruciate-retaining total knee arthroplasty in valgus gonarthrosis patients: A mid-term evaluation using stress radiographs.

Total knee arthroplasty (TKA) using implants with a high level of constraint has generally been recommended for patients with osteoarthritis (OA) who have valgus alignment. However, studies have reported favorable outcomes even with cruciate-retaining (CR) implants. To evaluate the coronal plane stability of CR-TKA in patients with valgus OA at the mid-term follow-up. Patients with primary valgus OA of the knee who underwent TKA from January 2014 to January 2021 were evaluated through stress radiography using a digital stress device with 100 N of force on both the medial and lateral side. Gap openings and degrees of angulation change were determined. Descriptive statistical analysis was performed for both continuous and categorical variables. Inter-rater reliability of the radiographic measurements was evaluated using Cronbach's alpha. This study included 25 patients (28 knees) with a mean preoperative mechanical valgus axis of 11.3 (3.6-27.3) degrees. The mean follow-up duration was 3.4 (1.04-7.4) years. Stress radiographs showed a median varus and valgus gap opening of 1.6 (IQR 0.6-3.0) mm and 1.7 (IQR 1.3-2.3) mm and varus and valgus angulation changes of 2.5 (IQR 1.3-4.8) degrees and 2.3 (IQR 2.0-3.6) degrees, respectively. No clinical signs of instability, implant loosening, or revision due to instability were observed throughout this case series. The present study demonstrated that using CR-TKA for patients with valgus OA of the knee promoted excellent coronal plane stability.

No Difference in 10-year Clinical or Radiographic Outcomes Between Kinematic and Mechanical Alignment in TKA: A Randomized Trial.

There is continuing debate about the ideal philosophy for component alignment in TKA. However, there are limited long-term functional and radiographic data on randomized comparisons of kinematic alignment versus mechanical alignment. We present the 10-year follow-up findings of a single-center, multisurgeon randomized controlled trial (RCT) comparing these two alignment philosophies in terms of the following questions: (1) Is there a difference in PROM scores? (2) Is there a difference in survivorship free from revision or reoperation for any cause? (3) Is there a difference in survivorship free from radiographic loosening? Ninety-nine patients undergoing primary TKA for osteoarthritis were randomized to either the mechanical alignment (n = 50) or kinematic alignment (n = 49) group. Eligibility for the study was patients undergoing unilateral TKA for osteoarthritis who were suitable for a cruciate-retaining TKA and could undergo MRI. Patients who had previous osteotomy, coronal alignment > 15° from neutral, a fixed flexion deformity > 15°, or instability whereby constrained components were being considered were excluded. Computer navigation was used in the mechanical alignment group, and patient-specific cutting blocks were used in the kinematic alignment group. At 10 years, 86% (43) of the patients in the mechanical alignment group and 80% (39) in the kinematic alignment group were available for follow-up performed as a per-protocol analysis. The PROMs that we assessed included the Knee Society Score, Oxford Knee Score, WOMAC, Forgotten Joint Score, and EuroQol 5-Dimension score. Kaplan-Meier analysis was used to assess survivorship free from reoperation (any reason) and revision (change or addition of any component). A single blinded observer assessed radiographs for signs of aseptic loosening (as defined by the presence of progressive radiolucent lines in two or more zones), which was reported as survivorship free from loosening. At 10 years, there was no difference in any PROM score measured between the groups. Ten-year survivorship free from revision (components removed or added) likewise did not differ between the groups (96% [95% CI 91% to 99%] for the mechanical alignment group and 91% [95% CI 83% to 99%] for the kinematic alignment group; p = 0.38). There were two revisions in the mechanical alignment group (periprosthetic fracture, deep infection) and four in the kinematic alignment group (two secondary patella resurfacings, two deep infections). There was no statistically significant difference in reoperations for any cause between the two groups. There was no difference with regard to survivorship free from loosening on radiographic review (χ2 = 1.3; p = 0.52) (progressive radiolucent lines seen at 10 years were 0% for mechanical alignment and 3% for kinematic alignment). Like the 2-year and 5-year outcomes previously reported, 10-year follow-up for this RCT demonstrated no functional or radiographic difference in outcomes between mechanical alignment and kinematic alignment TKA. Anticipated functional benefits of kinematic alignment were not demonstrated, and revision-free survivorship at 10 years did not differ between the two groups. Given the unknown long-term impact of kinematic alignment with regard to implant position (especially tibial component varus), we must conclude that mechanical alignment remains the reference standard for TKA. We could not demonstrate any advantage to kinematic alignment at 10-year follow-up. Level I, therapeutic study.

Five-year migration of uncemented femoral components in total knee arthroplasty with either highly cross-linked or conventional polyethylene inserts: a blinded randomized controlled trial using radiostereometric analysis.

The aim of this study was to compare the migration of the femoral component, five years postoperatively, between patients with a highly cross-linked polyethylene (HXLPE) insert and those with a conventional polyethylene (PE) insert in an uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary aims included clinical outcomes and patient-reported outcome measures (PROMs). We have previously reported the migration and outcome of the tibial components in these patients. A double-blinded randomized controlled trial was conducted including 96 TKAs. The migration of the femoral component was measured with radiostereometry (RSA) at three and six months and one, two, and five years postoperatively. PROMs were collected preoperatively and at all periods of follow-up. There was no clinically relevant difference in terms of migration of the femoral component or PROMs between the HXLPE and PE groups. The mean difference in migration (maximum total point motion), five years postopeatively, was 0.04 mm (95% CI -0.06 to 0.16) in favour of the PE group. There was no clinically relevant difference in migration of the femoral component, for up to five years between the two groups. These findings will help to establish a benchmark for future studies on migration of femoral components in TKA.

An Advanced Knee Simulator Model Can Reproducibly Be Used for Ligament Balancing Training during Total Knee Arthroplasty.

A critical and difficult aspect of total knee arthroplasty (TKA) is ligamentous balancing for which cadavers and models have played a large role in the education and training of new arthroplasty surgeons, although they both have several shortcomings including cost, scarcity, and dissimilarity to in vivo ligament properties. An advanced knee simulator (AKS) model based on computed tomography (CT) scans was developed in the setting of these challenges with cadavers and previous models. In this study, we compared the ligament balancing between AKS and human cadaveric knees to assess the validity of using the AKS for ligament balancing training during TKA. A CT scan of a TKA patient with varus deformity was used to design the AKS model with modular components, using three-dimensional printing. Three fellowship-trained arthroplasty surgeons used technology-assisted TKA procedure to plan and balance three cadaver knees and the AKS model. Medial and lateral laxity data were captured using manual varus and valgus stress assessments for cadavers and the model in an extension pose (10 degrees of flexion from terminal extension) and between 90 and 95 degrees for flexion. After preresection assessments, surgeons planned a balanced cruciate-retaining TKA. Following bony cuts and trialing, extension and flexion ligament laxity values were recorded in a similar manner. Descriptive statistics and Student's t-tests were performed to compare the cadavers and model with a p-value set at 0.05. Preresection medial/lateral laxity data for both extension and flexion were plotted and showed that the highest standard deviation (SD) for the cadavers was 0.67 mm, whereas the highest SD for the AKS was 1.25 mm. A similar plot for trialing demonstrated that the highest SD for the cadavers was 0.6 mm, whereas the highest SD for the AKS was 0.61 mm. The AKS trialing data were highly reproducible when compared with cadaveric data, demonstrating the value of the AKS model as a tool to teach ligament balancing for TKA and for future research endeavors.

No evidence of mid-flexion instability after robotic-assisted total knee arthroplasty as assessed by intraoperative pressure sensors

PurposeMid-flexion instability has been identified as a cause for dissatisfaction following total knee arthroplasty (TKA). Robotic-assisted surgery using the Mako robot only allows for assessment of stability at 10° and 90°. This study aimed to investigate any evidence of mid-flexion instability in Mako-assisted TKA.MethodsData from 72 TKA in 59 patients from 2018 to 2022 were collected. All patients underwent an RA (Mako, Stryker, Fort Lauderdale, FL, USA), single-radius design, cruciate-retaining TKA. Intraoperatively, medial, and lateral pressures were measured at 10°, 45° and 90° of flexion using a pressure sensor (Verasense, OrthoSensor, 59 Inc., Dania Beach, FL, USA). The knee was considered balanced if the difference in pressures between compartments was less than 15 pounds-force (lbf).ResultsThere was no significant difference between the pressures measured in the medial compartment at 10°, 45° and 90° of flexion (P = 0.696). A statistically significant difference was found between the pressures measured in the lateral compartment at 10°, 45° and 90° of flexion, with the 10° value being significantly higher (P < 0.001), but this did not exceed the threshold of 15 lbf. None of the patients had a pressure difference of more than 15 lbf when pressures at 45° were compared to that at 10° and 90°, medially or laterally.ConclusionThis study showed no evidence of mid-flexion instability in Mako-assisted TKA, using a single radius, cruciate-retaining prosthesis whilst maintaining the joint height.Level of evidenceLevel III retrospective cohort study.

Comparison of postoperative clinical outcomes and knee stability of cruciate-retaining total knee arthroplasty using the tibia-first gap navigation technique with a computer-aided system and measured-resection technique: A retrospective analysis of a propensity-matched cohort.

This study aimed to clarify whether the range of motion (ROM), anterior and posterior (AP) stabilityand other clinical measures changed in patients who underwent tibia-first total knee arthroplasty (TF-TKA) using navigation with a computer-aided system after surgery. This is a retrospective study and we conducted a matched cohort analysis of 60 measured resection (MR)-TKAs and 52 TF-TKAs performed by a single surgeon. All the surgeries used the same implant and approach. Baseline differences between the groups were adjusted using propensity score matching. We compared each patient's measured ROM and Oxford Knee Score (OKS) and performed knee AP laxity measurements by using a device during routine follow-ups. A total of 40 MR-TKAs with a mean age of 73.5 ± 5.6 years and sex (male 10, female 30) were compared to 40 TF-TKAs with a mean age of 74.0 ± 5.7 years and sex (male 13, female 27) at 2-year follow-ups. Two years postoperatively, there was a significant difference in the AP laxity at 30° of knee flexion between both groups (7.0 ± 3.4 mm vs. 5.2 ± 2.3 mm, p < 0.01). In contrast, no differences were found between both groups for knee flexion (120.8 ± 9°vs. 116.7 ± 9.8°, p = 0.07) and OKS score (41.8 ± 6.9 vs. 41.0 ± 5.9, p = 0.61). The AP stability in the midflexion obtained using the tibia-first technique remained consistent even after 2 years. However, OKS and ROM were not significantly different from those of the MR-TKA group. Retrospective comparative LEVEL III study.

Kinematic Alignment Achieves a More Balanced Total Knee Arthroplasty Than Mechanical Alignment among CPAK Type I Patients: A Simulation Study

Background: There is no consensus on whether mechanical alignment (MA) or kinematic alignment (KA) should be chosen for total knee arthroplasty (TKA) for coronal plane alignment of the knee (CPAK) Type I with a varus arithmetic HKA (aHKA) and apex distal joint line obliquity (JLO). The aim of this study was to investigate whether MA or KA is preferable for soft tissue balancing in TKA for this phenotype. Method: This prospective cohort study included 64 knees with CPAK Type I osteoarthritis that had undergone cruciate-retaining TKA. Using optical tracking software, we simulated implant placement in the Mako system before making the actual bone cut and compared the results between MA and KA. Extension balance (the difference between medial and lateral gaps in extension) and medial balance (the difference in medial gaps in flexion and extension) were examined. These gap differences within 2 mm were defined as good balance. Achievement of overall balance was defined as an attainment of good extension and medial balance. The incidence of balance in each patient was compared with an independent sample ratio test. Results: Compared with the MA group, the KA group achieved better soft tissue balance in extension balance (p &lt; 0.001). A total of 75% of the patients in the KA group achieved overall balance, which was greater than the 38% achieved in the MA group (p &lt; 0.001). Conclusions: In robot-assisted TKA for CPAK Type I osteoarthritis, KA achieved knee balance during extension without soft tissue release in a greater percentage of patients than MA.