Continuous sagittal radiological evaluation of stair-climbing in cruciate-retaining and posterior-stabilized total knee arthroplasties using image-matching techniques

Stair climbing ability and postoperative activity in patient-reported outcomes after CR-TKA are more related to handgrip strength than sagittal knee stability

INTRODUCTION

Stair ascent and descent are physically demanding tasks requiring higher functional ability of the lower extremity muscles and joint range of motion than level walking, and are associated with patient satisfaction after total knee arthroplasty (TKA). This study aimed to investigate stair ascent and descent ability after cruciate-retaining (CR)-TKA using the patient-reported outcomes, and to examine the role of knee sagittal stability and handgrip strength in postoperative stair ascent and descent ability.

MATERIALS AND METHODS

This study included 84 female patients who underwent primary unilateral CR-TKA for knee osteoarthritis at our institute between April 2015 and February 2019. Patients were classified according to ascending and descending stair difficulty using the New Knee Society Score into those with (group D) and those without difficulty ascending and descending stairs (group A). The two groups were compared for age, height, weight, body mass index, postoperative grip strength, pre-operative and postoperative knee range of motion, anterior and posterior tibial drawer on stress radiography, and the New Knee Society Score (KSS).

RESULT

Group D and A consisted of 48 and 36 patients, respectively. The mean follow-up period was 2.9 years (range 1-5 years). Group D was significantly older (74.1 vs. 70.0 years old, p = 0.01) and shorter (148.6 vs. 153.3 cm, p = 0.017) than group A. The two groups demonstrated no significant differences in the range of motion preoperatively and postoperatively and in the amount of anterior tibial drawer at 20°, anterior and posterior drawer at 90°, and total anterior-posterior movement at 90°. Postoperative handgrip strength (19.6 vs. 24.1, p < 0.01) and New KSS score (107 vs. 137, p < 0.01) were lower in group D than in group A.

CONCLUSIONS

Handgrip strength was associated with stair ascent and descent ability and postoperative activity in the patient-reported outcomes, rather than CR-TKA knee sagittal stability.

Preoperative tibiofemoral contact point on standing lateral radiograph predicts anteroposterior knee kinematics in total knee arthroplasty

Purpose

This study investigated the tibiofemoral contact point (CP) on standing lateral radiographs in knee osteoarthritis and assessed the relationship between CP and pre- and postoperative knee kinematics in total knee arthroplasty (TKA).

Methods

The intraoperative knee status of 46 knees with varus deformity that underwent bicruciate stabilized TKA using a navigation system was investigated. The intraoperative anteroposterior (AP) position of the femur relative to the tibia at maximum extension, 15°, 30°, 45°, 60° and 90° was evaluated by the navigation system before and after TKA. The CP, defined as the CP between the femur and tibia, was assessed on standing lateral radiographs at the maximum extension of the knee before and 1 year after TKA. CP was expressed as the ratio of tibial plateau distance on a scale of 0-1, with 0 indicating the most anterior position of the femur relative to the tibia.

Results

The mean CP on standing lateral radiographs was 0.54 ± 0.12 and 0.46 ± 0.08 before and after TKA, respectively. The postoperative CP was significantly more anterior than the preoperative CP (p = 0.0002). The mean AP position of the femur relative to the tibia moved anteriorly during early knee flexion both before and after TKA, representing nonanatomical AP movement. The preoperative posterior CP group (CP > 0.54) showed more nonanatomical AP movement from 15° to 60° before and after TKA compared with the preoperative anterior CP group (CP < 0.54).

Conclusion

Preoperative posterior deviation of the femur relative to the tibia in the standing position was a predictive factor for nonanatomical AP knee kinematics. Biomechanical analysis of postoperative knees will be necessary; however, surgeons should focus on preoperative tibiofemoral CP on standing lateral radiographs to predict knee kinematics.

Level of Evidence

Level Ⅲ.

Changes in the anteroposterior position of the femur relative to the tibia impact patient satisfaction in total knee arthroplasty

BACKGROUND

In this study, we aimed to investigate the preoperative and postoperative anteroposterior position (AP) of the femur relative to the tibia in total knee arthroplasty (TKA) and assess the influence of change in the AP position on clinical outcomes.

METHODS

We evaluated 49 knees that underwent bi-cruciate-substituted TKA using a navigation system. The preoperative and postoperative AP position of the femur relative to the tibia at maximum extension, 15°, 30°, 45°, 60°, 90°, 105°, and 120° and maximum flexion angles were calculated. The 2011 Knee Society Score was evaluated preoperatively and 1 year postoperatively. The Wilcoxon signed rank and Spearman's rank correlation tests were performed, with statistical significance set at P < 0.05.

RESULTS

The postoperative AP position was significantly correlated with the preoperative AP position at each measured angle. The postoperative AP positions were statistically more anterior than those preoperatively. Furthermore, the changes in the AP position after TKA negatively correlated with the symptom (P = 0.027 at 30°, P = 0.0018 at 45°, P = 0.0003 at 60°, P = 0.01 at 90°, and P = 0.028 at 105°) and patient satisfaction (P = 0.018 at 60° and P = 0.009 at 90°) scores at 1 year postoperatively.

CONCLUSION

The postoperative AP position of the femur relative to the tibia was strongly influenced by the preoperative those in TKA. Postoperative anterior deviation of the femur relative to the tibia from mid-flexion to deep flexion could worsen clinical outcomes.

Comparison of knee kinematics and ligament forces in single and multi-radius cruciate-retaining total knee arthroplasty: A computer simulation study

BACKGROUND

The single-radius design in total knee arthroplasty has been designed to develop a more fixed flexion-extension axis without mid-flexion instability compared with the multi-radius design. It remains unclear whether differences between the multi-radius and single-radius designs can affect kinematics and collateral ligament forces. This study aimed to simulate knee kinematics and kinetics between single-radius and multi-radius models using a musculoskeletal computer model.

METHODS

The single-radius and multi-radius femoral components were virtually implanted in a computer simulation using the same tibial insert. The effects of implant design on kinematics and medial collateral ligament forces during squatting and gait activities were analyzed.

RESULTS

During squatting, the multi-radius model exhibited paradoxical anterior translation on both the medial and lateral flexion facet center where peak anterior translation was 2.4 mm for medial flexion facet center and 2.2 mm for the lateral flexion facet center, while the peak anterior translation of the single-radius model was less than 1 mm at early flexion. A rapid decrease in medial collateral ligament tension was observed in the early flexion phase in the multi-radius model, which occurred simultaneously with paradoxical anterior translation, whereas the relatively constant medial collateral ligament tension was observed in the single-radius model. During gait activity, the single-radius model exhibited a more posterior position than the multi-radius model.

CONCLUSION

These suggest that abrupt changes in the medial collateral ligament force influence anterior sliding of the femur, and that the single-radius design is a reasonable choice for prevention of mid-flexion instability.

Interaction between functional capability and sleep quality at midterm after total knee arthroplasty: a Japanese retrospective cohort study

No report has clarified the frequency and interacting factors affecting sleep disturbance among Asian patients at midterm after total knee arthroplasty (TKA). This study aimed to evaluate the frequency of sleep disturbance at midterm after TKA in a Japanese cohort and to identify intervening factors for sleep. We hypothesized that residual knee pain and decreased functional capability negatively interact with sleep quality after TKA. A total of 209 Japanese participants (average age: 77.1 ± 8.3 years; postoperative follow-up period: 4.5 ± 1.9 years) who underwent primary TKA for knee osteoarthritis were included in this study. Sleep quality, satisfaction, pain, functional capability, joint awareness, and mental condition were evaluated using the Pittsburgh Sleep Quality Index (PSQI), Knee Society Score (KSS) 2011, Forgotten Joint Score (FJS)-12, and 12-Item Short-Form Health Survey (SF-12) Mental Component Summary (MCS). Multivariable analysis was performed to determine the influencing factors on PSQI. The scores for the PSQI, satisfaction with pain level while lying in bed, pain during level walking, functional activity category in the KSS 2011, awareness of the artificial joint in bed at night in the FJS-12, and SF-12 MCS were 6.7 ± 3.0, 5.8 ± 1.8, 1.6 ± 2.3, 62 ± 22, 1.5 ± 1.4, and 56 ± 9.3 on average, respectively. Sleep disturbance (PSQI ≥ 5.5) occurred in 54% of the Japanese participants. Multivariable analysis revealed that high functional capability was a significant factor associated with sleep quality improvement (p < 0.05). Decreased functional capability, not residual knee pain, negatively interacted with sleep quality. The sleep disturbance rate was high during the middle postoperative period after TKA in the Japanese cohort.

Relationship between the Femoral and Tibial Component Positions and Postoperative Knee Range of Motion after Posterior-Stabilized Total Knee Arthroplasty in Varus-Aligned Knees

This study aimed to evaluate the relationship between the femoral and tibial component positions and postoperative knee range of motion after posterior-stabilized total knee arthroplasty (TKA). Forty-four patients (48 knees in total: 9 men, 9 knees; 35 women, 39 knees) who underwent posterior-stabilized TKA using a navigation system were included. The femoral and tibial component positions were measured from the preoperative and postoperative computed tomography data with three-dimensional evaluation software. We investigated the relationship between the knee range of motion, including extension restriction and maximum flexion angles at 2 years postoperatively, and the femoral and tibial component positions. Patients with knee extension restriction of 10° or more at 2 years postoperatively showed greater posterior flexion position of the tibial component than those with knee extension restriction less than 10° (6.2° and 3.9°, respectively, p=0.018). The postoperative knee flexion angle was positively associated with the internal rotational position of the femoral component (p=0.032, 95% confidence interval: 0.105-2.178). Patients with a knee flexion angle more than 120° at 2 years postoperatively had greater internal rotational position of the femoral component than those with 120° or less (5.2° and 1.5°, respectively, p=0.002). In conclusions, after posterior-stabilized TKA, the postoperative knee extension restriction angle was associated with the posterior flexion position of the tibial component, and the knee flexion angle was positively related to the internal rotational position of the femoral component.

Progression of varus deformity in osteoarthritic knees induces anterior paradoxical motion of the femur during early knee flexion

PURPOSE

The purpose of this study was to investigate the position of the femur relative to the tibia throughout range of motion in the osteoarthritic knee to evaluate knee kinematics and assess its relationship with the degree of varus deformity.

METHODS

In this study, 116 preoperative knees with varus deformity were evaluated using a navigation system. The internal-external, anteroposterior, and mediolateral positions of the femur relative to the tibia were measured at maximum extension, 15°, 30°, 45°, 60°, 90°, 105°, and 120°, and maximum flexion angles. From these parameters, two-dimensional translation of the surgical epicondylar axis was projected onto the tibial axial plane, and the femoral movement was evaluated relative to the tibia. In addition, the knees were retrospectively classified into three groups according to their degrees of preoperative hip-knee-ankle angle: mild (< 10°), moderate (10°-20°), and severe (> 20°). Then, the differences in each parameter between these groups were investigated. The Steel-Dwass test was performed to identify the difference among three groups. Statistical significance was set at p values < 0.05.

RESULTS

There was a significant difference in the anteroposterior position of the femur relative to the tibia among the three groups, especially from extension to early flexion (p < 0.05). The anteroposterior position at knee extension deviated posteriorly according to the progression of varus deformity. Rotational and mediolateral translation were not significantly different among the groups. Normal knee kinematics were diminished in almost all cases in each group. In addition, anterior paradoxical motion of the femur during early knee flexion was observed in 45.6% (n = 26), 57.1% (n = 28), and 80.0% (n = 8) of cases in the mild, moderate, and severe groups, respectively. The anteroposterior position of the femur relative to the tibia at knee extension was significantly more posterior in patients with than in those without anterior paradoxical motion (p < 0.0001).

CONCLUSION

The anteroposterior position of the femur relative to the tibia changed according to the progression of varus deformity in osteoarthritic knees, especially from knee extension to early flexion. Posterior deviation of the femur at knee extension induced its anteroposterior movement relative to the tibia, resulting in anterior paradoxical motion.

LEVEL OF EVIDENCE

III.

A Comparative Study of Clinical Outcomes Between Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty: A Propensity Score-Matched Cohort Study

INTRODUCTION

We investigated a comparison of clinical outcomes between cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty. However, it is still controversial which design leads to better clinical results. In clinical settings, choosing either CR or PS is likely based on the surgeon's preferences. In this study, short-term clinical outcomes between CR and PS in patients who received a single knee prosthesis were compared using propensity score matching.

METHODS

Two hundred and twelve CR and 43 PS of a single knee prosthesis were enrolled in this study. After propensity score matching, 34 knees each in the CR and PS groups were chosen and were without significant differences in age at operation, gender, BMI, preoperative range of motion (ROM), preoperative femorotibial angle (FTA), and presence or absence of patellar replacement. Clinical scores, including ROM, Knee Society score (KSS), knee injury and osteoarthritis outcome score (KOOS), except for the sports subscale, were compared between the CR and PS groups preoperatively and two years postoperatively.

RESULTS

Postoperatively, there were no significant differences in FTA, ROM, or KSS. Preoperative scores for the KOOS except for the pain subscale were comparable between the groups. Postoperatively, however, the PS group had a significantly higher score in the ADL subscale compared to the CR group (PS: 89.5 vs. CR: 80.8, p = 0.017). The KOOS subscales other than activities of daily living (ADL) were comparable between the groups.

CONCLUSIONS

In this propensity score-matched cohort study, PS showed a better outcome for the ADL than the CR design. These findings suggest that choosing either CR or PS should not depend on the surgeon's preferences. A PS design may be preferable to CR for elderly patients.

Cruciate-Retaining Total Knee Arthroplasty: Current Concepts Review

Posterior cruciate-retaining (CR) total knee arthroplasty for osteoarthritis of the knee is a popular implant choice. At present, there is no consensus on whether sacrifice or retention of the posterior cruciate ligament (PCL) offers superior outcomes. This review explores the current literature available on CR total knee arthroplasty (TKA). PubMed was searched by keyword to find relevant articles for inclusion. Additional sources came from article references and joint registry reports. CR design knees have distinct kinematic gait patterns from posterior-stabilizing (PS) knees and exhibit paradoxical anterior femoral movement with less femoral rollback. While CR implants offer less flexion than PS designs, the difference is not clinically detectable as clinical scores are similar in the short and long term. CR implants have better long-term survival compared to PS knees, likely due to lower risk of aseptic loosening. CR total knee arthroplasties also have shorter operating times and lower risk of peri-prosthetic fractures. Because the CR implant is unconstrained, there may be an increased risk of instability compared to PS designs, but the literature is mixed. Overall, the current literature supports the continued use of CR TKAs due to their lower risk of complications, durability, and demonstrated equivalence in function to posterior-substituting models.

No difference in clinical outcomes between functionally aligned cruciate-retaining and posterior-stabilized robotic-assisted total knee arthroplasty

PURPOSE

To compare the clinical outcomes of subjects undergoing primary robotic-assisted total knee arthroplasty (RA-TKA), following functional alignment (FA) principles, with cruciate-retaining (CR) or posterior-stabilized (PS) bearing designs, at a minimum of 24 months of follow-up.

METHODS

This observational, retrospective study included 167 consecutive patients undergoing RA-TKA with cemented PS and cementless CR implants performed with a CT-base robotic-arm assisted system (Mako, Stryker), following FA principles, between 2017 and 2020. Patients were followed up with a clinical and radiographic assessment and were administered the Forgotten Joint Score-12 (FJS-12), Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS-JR), and the 5-level Likert scale (5-LLS).

RESULTS

Three TKA revisions were performed (2 PS, 1 CR); therefore, a total of 164 knees with a mean age of 71.7 years (SD 8.9) were considered (80 cemented PS; 84 cementless CR). No statistically significant differences were recorded between study groups relative to FJS-12, KOOS-JR, and 5-LLS at a minimum of two year follow-up (FJS-12 89.3 ± 9.2 vs 87.5 ± 12.8, p-value 0.46; KOOS-JR 88.8 ± 10.0 vs 86.7 ± 14.0, p-value 0.31; 5-LLS 4.5 ± 0.7 vs 4.5 ± 0.8, p-value 0.34).

CONCLUSION

No significant outcome differences were reported between patients undergoing PS and CR RA-TKA at a minimum of two year follow-up. RA-TKA achieves excellent clinical results and high satisfaction scores, regardless of the implant design used.

Similar rate of return to sports activity between posterior-stabilised and cruciate-retaining primary total knee arthroplasty in young and active patient

PURPOSE

Cruciate-retaining and posterior-stabilised implant designs are available for primary total knee arthroplasty. However, whether the implant design is associated with a difference in the level of activity still remains unclear. This clinical trial compared posterior-stabilised and cruciate-retaining implants in sport-related patient-reported outcome measures, range of motion, rate of return to sport, and weekly time dedicated to sport in active adults. It was also hypothesised that in young and active patients both implants lead to a similar rate of return to sport in terms of hours per week, type of sport, and joint mobility.

METHODS

All patients were evaluated preoperatively and for a minimum of 36 months follow-up. The University of California Los Angeles activity scores, High-Activity Arthroplasty Score, and Visual Analogue Scale were administered preoperatively and at the last follow-up. The range of motion was investigated at admission and the last follow-up. Data concerning the hours per week dedicated to sports and the type of sport practiced were also collected at admission and at the last follow-up. The Kaplan-Meier Curve was performed to compare implant survivorship.

RESULTS

Data from 227 procedures (cruciate-retaining: 109, posterior-stabilised: 118) were prospectively collected. At the last follow-up, no difference was reported in The University of California Los Angeles activity scores (p = 0.6), High-Activity Arthroplasty Score (p = 0.1), Visual Analogue Scale (p = 0.9), flexion (p = 0.7) and extension (p = 0.4). No difference was found in the rate of return (p = 0.1) and weekly hours dedicated to sport (p = 0.3). The Kaplan-Meier curve evidenced no statistically significant difference in implant survivorship (p = 0.6).

CONCLUSIONS

At approximately five years of follow-up, no difference was reported between cruciate-retaining and posterior-stabilised implants in active adults in sport-related patient-reported outcomes measures, range of motion, pain, weekly time dedicated to sport, rate of return to sport, and implant survivorship.

LEVEL OF EVIDENCE

Level II, prospective study.

Effect of Posterior Tibial Slope Change on Postoperative Range of Motion and Clinical Outcomes after Posterior Cruciate-Substituting Total Knee Arthroplasty

The posterior tibial slope (PTS) is usually adjusted by less than 5 degrees, without considering its individual difference, during posterior cruciate-substituting (PS) total knee arthroplasty (TKA). The effect of these individual changes of PTS would be important because clinical results depending on postoperative PTS were reported conflictingly. We investigated the effect of the change in PTS on the postoperative range of motion (ROM) and clinical scores after PS TKA. We retrospectively reviewed 164 knees from 107 patients who underwent PS TKA with a 2-year follow-up. We analyzed the preoperative and postoperative PTS, ROM, visual analog scale pain scale, Western Ontario and McMaster University Index (WOMAC), Hospital for Special Surgery Knee Score, Knee Society Score, and Forgotten Joint Score (FJS). The association of the absolute change in PTS with ROM and clinical scores was analyzed using correlation analysis and multiple regression analysis. As a result, the mean PTS and mean ROM changed from 9.6 ±  3.4 and 120.1 ±  15.4 degrees preoperatively to 2.0 ±  1.3 and 128.4 ±  9.3 degrees postoperatively, and the mean PTS change was 7.6 ±  3.5 degrees. The PTS change had no statistically significant association with the postoperative ROM and clinical scoring systems, although it did have a weak positive correlation with WOMAC function, No 10 (difficulty in rising from sitting) (correlation coefficient = 0.342, p = 0.041), and moderate positive correlation with the FJS, No. 6 (awareness when climbing stairs) (correlation coefficient = 0.470, p = 0.001). The authors concluded that the amount of change in PTS did not affect the postoperative ROM and clinical scores, although proximal tibial resection with a constant target of PTS resulted in individually different changes in the PTS after PS TKA.

Posterior-stabilized total knee arthroplasty kinematics and joint laxity: A hybrid biomechanical study

BACKGROUND

Posterior-stabilized (PS)-total knee arthroplasty (TKA) arose as an alternative to cruciate-retaining (CR)-TKA in the 1970s. Since then, it has become a popularly utilized TKA design with outcomes comparable to CR-TKA. The post-cam mechanism is unique to PS-TKA as it substitutes the function of the posterior cruciate ligament (PCL). The study aimed to understand the kinematic and laxity changes in PS-TKA with under- and overstuffing of the tibiofemoral joint space with the polyethylene (PE) insert.

METHODS

This study employed a hybrid computational-experimental joint motion simulation on a VIVO 6 degrees of freedom (6-DoF) joint motion simulator (AMTI, Watertown, MA, USA). Physical prototypes of a virtually-performed TKA in mechanical alignment (MA) and kinematic alignment (KA) based on cadaveric CT scans and a virtual ligament model were utilized. The reference, understuffed (down 2 mm) and overstuffed (up 2 mm) joint spaces were simulated, neutral flexion and laxity testing loads and motions were performed for each configuration.

RESULTS

The PE insert thickness influenced post-cam engagement, which occurred after 60º in the overstuffed configurations, after 60º-75º in the reference configurations and after 75º in the understuffed configurations. The understuffed configurations, compared to the reference configurations, resulted in a mean 2.0º (28%) and 2.0º (31%) increase in the coronal laxity in MA and KA respectively. The overstuffed configurations, compared to the reference configuration, resulted in an increase in the mean joint compressive forces (JCFs) by 73 N (61%) and 77 N (62%) in MA and KA models, respectively.

CONCLUSIONS

The under- and overstuffing in PS-TKA alter the kinematics with variable effects. Understuffing decreases the stability, JCFs and inverse with overstuffing. Subtle changes in the PE insert thickness alter the post-cam mechanics.

Polyethylene Components in Primary Total Knee Arthroplasty: A Comprehensive Overview of Fixed Bearing Design Options

The articular design of a polyethylene insert influences the kinematics and overall function of a total knee arthroplasty (TKA). Standard symmetric posterior-stabilized and cruciate-retaining polyethylene designs have a long track record of high patient satisfaction and longevity in TKA. However, the number and variety of polyethylene inserts and articulations have continued to evolve in an attempt to better replicate native knee kinematics or provide additional constraint. Ultracongruent polyethylene designs have been touted as increasing stability while maintaining the benefits of cruciate-retaining knees. Medial pivot and lateral/dual pivot polyethylene designs were introduced to mimic more normal knee kinematics with regard to femoral rollback. Further, with increasing recognition of knee instability as a cause for persistent symptoms and revision TKA, the utilization of midlevel constraint polyethylene inserts has been increasing, with multiple implant companies offering an insert design with increased constraint for use with a primary femoral component. In this rapidly evolving arena in with a myriad of options available, surgeons should be knowledgeable about the design concepts and their applicable uses for specific patient scenarios. Future research is needed to better understand whether a particular type or design of polyethylene insert and articulation leads to improved patient reported outcomes, improved replication of knee kinematics, and long-term durable implant survivorship.

Outcomes are Better With a Medial-Stabilized vs a Posterior-Stabilized Total Knee Implanted With Kinematic Alignment

BACKGROUND

There is no consensus whether a posterior-stabilized (PS) total knee device is superior to a more congruent, cruciate-substituting, medial-stabilized device (MS). This study compared the clinical outcomes of these devices. The primary hypothesis was that the clinical outcomes would be better in the MS group implanted with kinematic alignment.

METHODS

This prospective, randomized, single-center Level 1 study compared the outcomes of 99 patients who received a PS device and 101 patients who received an MS device implanted with kinematic alignment. Institutional Review Board approval and informed consent were obtained. Clinical and radiographic assessments were performed preoperatively, 6 weeks, 6 months, and annually.

RESULTS

All subjects reached the minimum follow-up of 2 years. There were no statistically significant differences in demographic characteristics, preoperative scores, or alignment (preoperative or postoperative). Tourniquet time was 7.24% longer for the PS group (40.28 min vs 37.56 min, P < .0086). There were significant differences between groups for the 1-year and 2-year Knee Society scores, Forgotten Joint Score, and ROM; in every case favoring the MS group. The FJS was 68.3 in the MS group at 2 years and 58.3 in the PS group (P = .02). The maximum flexion at 2 years was 132° in the MS group and 124° in the PS group (P < .0001).

CONCLUSION

The clinical outcomes of the MS group at 1 and 2 years were better. At the minimum 2-year follow-up, the results demonstrate the superiority of the medial-stabilized device in terms of multiple clinical outcomes.

LEVEL OF EVIDENCE

I.

Gradual-radius femoral component with s-curve post-cam provides stable kinematics at mid-flexion after total knee arthroplasty

BACKGROUND

Mid-flexion instability is the one of the reasons for patient dissatisfaction after total knee arthroplasty (TKA). The purposes of this study were to evaluate in vivo knee kinematics and clinical outcomes using a novel TKA design with a gradual femoral radius component and s-curve post-cam, which are intended to prevent the instability initiated by sudden reductions in the femoral radius observed with conventional components.

METHODS

We used radiographic-based, image-matching techniques to analyze femorotibial anteroposterior translation, axial rotation, and anterior/posterior cam-post contact during two dynamic movements, squatting and stair climbing, in 20 knees that had undergone posterior-stabilized fixed-bearing TKA with an improved sagittal profiles of the femoral component and post-cam mechanism. We also evaluated patient-reported outcomes assessed by the 2011 Knee Society Score (KSS 2011).

RESULTS

Squatting and stair climbing produced a similar trend in anteroposterior translation and a relatively small standard deviation at mid-flexion. Although the rotation angles varied widely during squatting and stair climbing, the femoral component was consistently externally rotated. Anterior/posterior cam-post contact during squatting and stair climbing were observed in 0/17 knees and 0/0 knees, respectively. The "Symptoms", "Satisfaction", and "Functional activities" subscales of the KSS 2011 were significantly (P < 0.05) improved postoperatively compared to preoperatively ("Symptoms", 10 to 21; "Satisfaction", 15 to 26; "Functional activities", 25 to 71).

CONCLUSION

A gradual femoral radius component with an s-curve post-cam provided stable kinematics and favorable clinical results during squatting and stair climbing at 1 year after surgery.

Comparison of posterior cruciate retention and substitution in total knee arthroplasty during gait: a systematic review and meta-analysis

Background

To compare the gait patterns between posterior cruciate retention and substitution in total knee arthroplasty (TKA).

Methods

Electronic databases including the PubMed, Embase, CINAHL, Web of Science, and Cochrane databases were searched to identify clinical trials investigating posterior cruciate retention versus substitution in TKA. The outcome measurements were the kinematic gait parameters (flexion at heel strike, maximum flexion during loading response, flexion range during loading, minimal flexion at terminal stance, maximal flexion at the swing, and total flexion during the gait cycle), Knee Society Score (KSS), knee flexion, knee extension, and walking speed. Statistical software Review Manager 5.4 and Stata 14.0 were used for data analysis.

Results

There were finally 9 studies included in this meta-analysis. The results did not reveal differences between posterior cruciate retention (CR) and posterior cruciate substitution (PS) groups in TKA, in terms of kinematic gait parameters, knee extension, walking speed, and KSS. However, the PS group had a significantly larger knee flexion angle than that in the CR group [weighted mean difference = − 3.20, 95% CI − 6.13 to − 0.28, P = 0.03].

Conclusion

Both the posterior cruciate retention and posterior cruciate substitution lead to obvious improvements in patient function and have their advantages in getting a good cup position. The PS design is significantly better on the knee flexion, while there are no statistical differences in kinematic gait parameters and outcome scores between them. This might indicate that surgeons do not necessarily need a PS design to substitute the posterior cruciate ligament during TKA.

Obtaining anatomic motion and laxity characteristics in a total knee design

BACKGROUND

Since the introduction of the first total knee designs, a frequent design goal has been to reproduce normal knee motion. However, studies of many currently used total knee designs, have shown that this goal has not been achieved. We proposed that Guided Motion total knee designs, could achieve more anatomic motion than present standard designs.

METHODS

Several Guided Motion knees for application without cruciate ligaments were designed using a computer method where the bearing surfaces were generated by the motion required. A knee testing machine was constructed where physiological forces including compressive, shear and torque were applied during knee flexion. The neutral path of motion and the laxity about the neutral path were measured. This evaluation method was a modification of the ASTM standard Constraint Test.

RESULTS

The motions of the Guided Motion knees and a standard PS knee were compared with the anatomic motion of knee specimens determined in an earlier study The Guided Motion knees showed motion patterns which were closer to anatomic than the PS knee.

CONCLUSIONS

The results provided justification for carrying out further evaluations of functional conditions, using either knee simulators or computer modelling. If anatomic motions could be reproduced in vivo, it is possible that clinical outcomes could be improved.

Return to Play and Performance in Golfers After Total Knee Arthroplasty: Does Component Type Matter?

BACKGROUND

Golf is a popular sport among patients undergoing total knee arthroplasty (TKA). The golf swing requires significant knee rotation, which may lead to changes in golfing ability postoperatively. The type of implant used may alter the swing mechanics or place different stresses on the knee. The purpose of this study was to evaluate golf performance and subjective stability after TKA and compare outcomes between cruciate-retaining (CR) and posterior-stabilized (PS) implants.

HYPOTHESIS

Patients with CR implants will experience better stability during the golf swing compared to patients with PS implants.

STUDY DESIGN

Retrospective cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Patients who underwent primary TKA were identified from the medical record and sent an electronic questionnaire focusing on return to play (RTP), performance, pain, and stability during the golf swing. Knee injury and Osteoarthritis Outcome Scores (KOOS) were collected before and at multiple time points after surgery. Patients were surveyed postoperatively and asked to evaluate overall performance, pain, and stability before and after surgery. Outcomes were compared based on implant type.

RESULTS

Most patients (81.5%) were able to return to golf at an average of 5.3 ± 3.1 months from surgery. The average postoperative KOOS was 74.6 ± 12.5 in patients able to RTP compared with 64.4 ± 9.5 in those who were not (P < 0.05). Knee pain during golf significantly improved from 6.4 ± 2.1 to 1.8 ± 2.2 (P < 0.01). There were no significant differences in pain, performance, or stability between the CR and PS patients.

CONCLUSION

Most patients can successfully return to golfing after TKA. Knee replacement offers patients reliable pain relief during the golf swing and fewer physical limitations during golf, with no detriment to performance. There is no difference in performance or subjective knee stability based on component type.

CLINICAL RELEVANCE

Understanding associated outcomes of different TKA knee systems allows for unbiased and confident recommendations of either component to golfers receiving total knee replacement.

No difference of survival between cruciate retaining and substitution designs in high flexion total knee arthroplasty

The aim of this study was to compare the long-term implant survival and outcomes in patients with high-flexion cruciate-retaining (CR) or high-flexion posterior cruciate-substituting (PS) knee implants. A total of 253 knees (CR group: 159 vs. PS group: 94) were available for examination over a mean follow-up of 10 years. Clinical outcomes were assessed including the Hospital for Special Surgery score, Knee Society score and Western Ontario and McMaster Universities Osteoarthritis Index score at the final follow-up. Radiologic measurements were also assessed including the hip-knee-ankle angle and radiolucent lines according to the KSS system at the final follow-up. The survival rate was analyzed using the Kaplan–Meier method. At the final follow-up, the mean total HSS scores were similar between the two groups (p = 0.970). The mean hip-knee-ankle angle at the final follow-up was similar between groups (p = 0.601). The 10- and 15-year survival rates were 95.4% and 93.3% in the CR group and 92.7% and 90.9% in the PS group, respectively, with no significant difference. Similar clinical and radiographic outcomes could be achieved with both the high-flexion CR and high-flexion PS total knee designs without a difference in survival rate after a 10-year follow-up.

Retention of Posterior Cruciate Ligament Alone May Not Achieve Physiological Knee Joint Kinematics After Total Knee Arthroplasty: A Retrospective Study

BACKGROUND

The apparently physiological kinematics of the bicruciate-stabilized total knee arthroplasty (BCS TKA) systems have been attributed to the anterior and posterior post-cam mechanism. Although comparisons between TKA designs with either a retained or a sacrificed cruciate ligament have been conducted, we are not aware of any analyses of 2 implants with identical bearing geometry but different cruciate-ligament strategies under equal loading conditions. Knowledge about the kinematic effect of the different cruciate ligament strategies would potentially be valuable to facilitate preoperative planning and decision-making with regard to selecting the most appropriate implant for a patient.

METHODS

This retrospective study included 20 patients: 10 treated with a BCS and 10 treated with a cruciate retaining (CR) TKA. Fluoroscopic analyses during high-flexion activities (unloaded flexion-extension and loaded lunge) were conducted at 24 months postsurgery. All patients completed the Knee Society Score, Forgotten Joint Score, and High-Flexion Knee Score questionnaires preoperatively and postoperatively.

RESULTS

The BCS cohort showed greater femoral lateral rollback as well as a medial pivot in both activities. In contrast, the CR cohort showed a significant increase in anterior translation on the medial compartment as well as almost absent femoral lateral rollback. Higher clinical scores were observed in the BCS cohort.

CONCLUSIONS

At 24 months postsurgery, despite equal bearing geometry, retention of the posterior cruciate ligament in the CR cohort apparently was insufficient to reduce anterior shift. The BCS cohort showed expected knee joint kinematics; however, the kinematics in this cohort could eventually benefit from a smooth transition between the interchanging surfaces. Further investigation should be focused on the surgical technique and its interaction with the TKA design.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

The extensor efficiency of unicompartmental, bicompartmental, and total knee arthroplasty

Aims

Unicompartmental knee arthroplasty (UKA) and bicompartmental knee arthroplasty (BCA) have been associated with improved functional outcomes compared to total knee arthroplasty (TKA) in suitable patients, although the reason is poorly understood. The aim of this study was to measure how the different arthroplasties affect knee extensor function.

Methods

Extensor function was measured for 16 cadaveric knees and then retested following the different arthroplasties. Eight knees underwent medial UKA then BCA, then posterior-cruciate retaining TKA, and eight underwent the lateral equivalents then TKA. Extensor efficiency was calculated for ranges of knee flexion associated with common activities of daily living. Data were analyzed with repeated measures analysis of variance (α = 0.05).

Results

Compared to native, there were no reductions in either extension moment or efficiency following UKA. Conversion to BCA resulted in a small decrease in extension moment between 70° and 90° flexion (p < 0.05), but when examined in the context of daily activity ranges of flexion, extensor efficiency was largely unaffected. Following TKA, large decreases in extension moment were measured at low knee flexion angles (p < 0.05), resulting in 12% to 43% reductions in extensor efficiency for the daily activity ranges.

Conclusion

This cadaveric study found that TKA resulted in inferior extensor function compared to UKA and BCA. This may, in part, help explain the reported differences in function and satisfaction differences between partial and total knee arthroplasty.

Cite this article: Bone Joint Res 2021;10(1):1–9.

Posterior tibial slope and anterior post-cam contact can change knee kinematics in extension in bi-cruciate stabilized total knee arthroplasty

Aims

This study aims to investigate the effects of posterior tibial slope (PTS) on knee kinematics involved in the post-cam mechanism in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) using computer simulation.

Methods

In total, 11 different PTS (0° to 10°) values were simulated to evaluate the effect of PTS on anterior post-cam contact conditions and knee kinematics in BCS TKA during weight-bearing stair climbing (from 86° to 6° of knee flexion). Knee kinematics were expressed as the lowest points of the medial and lateral femoral condyles on the surface of the tibial insert, and the anteroposterior translation of the femoral component relative to the tibial insert.

Results

Anterior post-cam contact in BCS TKA was observed with the knee near full extension if PTS was 6° or more. BCS TKA showed a bicondylar roll forward movement from 86° to mid-flexion, and two different patterns from mid-flexion to knee extension: screw home movement without anterior post-cam contact and bicondylar roll forward movement after anterior post-cam contact. Knee kinematics in the simulation showed similar trends to the clinical in vivo data and were almost within the range of inter-specimen variability.

Conclusion

Postoperative knee kinematics in BCS TKA differed according to PTS and anterior post-cam contact; in particular, anterior post-cam contact changed knee kinematics, which may affect the patient’s perception of the knee during activities.

Cite this article: Bone Joint Res 2020;9(11):761–767.

J-curve design total knee arthroplasty: the posterior stabilized shows wider medial pivot compared to the cruciate retaining during chair raising

PURPOSE

Which total knee arthroplasty (TKA) design represents the better solution to restore a correct knee biomechanics is still debated. The aim of this study was to compare posterior stabilized (PS) and cruciate retaining (CR) version of the same TKA design (femoral component with an anatomic sagittal radius-J-curve design) by the use of dynamic Roentgen stereophotogrammetric analysis (RSA). The hypothesis was that the two models influence differently in vivo knee kinematic.

METHODS

A cohort of 16 randomly selected patients was evaluated 9 months after surgery: Zimmer PERSONA® was implanted, eight with CR design and eight with PS design. The kinematic evaluations were performed using a Dynamic RSA (BI-STAND DRX 2) developed in our Institute, during the execution of the sit-to-stand motor task. The motion parameters were obtained using the Grood and Suntay decomposition and the low-point kinematics methods.

RESULTS

PS TKA lateral femoral compartment had a wider anterior translation (17 ± 2 mm) than the medial one (11 ± 2 mm), while the two compartments of CR TKA showed a similar anterior translation (medial: 9 ± 2 mm/lateral: 11 ± 2 mm). T test for comparison between CR and PS TKA of antero-posterior translation showed a statistically significant difference (p < 0.05) in the flexion range between 15° and 40°. The CR prosthesis did not anteriorly translate during flexion. The PS design translated anteriorly showing a roll-forward mechanism during extension from 80° to 18° of flexion and a posterior translation from 18° to 0°. The same significant differences (p < 0.05) between the PS and CR groups were found comparing the low-point positions of the femoral condyles in the range of flexion between 25° and 40° for the medial compartment and between 15° and 25° for the lateral compartment.

CONCLUSIONS

Dynamic RSA was able to investigate for the first time in vivo the kinematic behaviour of PS and CR version of the same TKA J-curve design. PS type showed a medial pivot during sit-to-stand motion task, while the CR type showed a cylindrical movement. Further studies are needed to evaluate the impact of different TKA designs on clinical results.

LEVEL OF EVIDENCE

IV.

Comparison of Contact Kinematics in Posterior-Stabilized and Cruciate-Retaining Total Knee Arthroplasty at Long-Term Follow-Up

BACKGROUND

There is controversy regarding the superiority of posterior-stabilizing (PS) total knee arthroplasty (TKA) and cruciate-retaining (CR) TKA. Substantial work has made comparisons between PS and CR TKA at follow-ups of less than 5 years. It was the goal of the present study to compare the kinematics at greater than 5 years postoperatively between CR and PS TKA, with a secondary goal of comparing patient function.

METHODS

A total of 42 knees were investigated, with equal representation in the PS and CR TKA groups. Patients underwent radiostereometric analysis imaging at 0°, 20°, 40°, 60° 80°, and 100° of flexion. Contact position, magnitude of excursion, and condylar separation on each condyle were measured. A Timed-Up-and-Go functional test was also performed by patients, with the total test time being measured. Preoperative and postoperative clinical outcome scores were also collected.

RESULTS

There were differences in contact position on both the medial and lateral condyles at multiple angles of flexion (P < .05). There was no difference (P = .89) in medial excursion; however, PS TKA had greater lateral excursion than CR TKA (P < .01). No difference (P > .99) was found in frequency of condylar separation. PS TKA was associated with faster (P = .03) total Timed-Up-and-Go test times. There were no differences in clinical outcome scores between the groups preoperatively or postoperatively.

CONCLUSION

We found kinematic and functional differences that favor PS TKA. Our results suggest posterior cruciate ligament insufficiency in CR TKA, indicating that perhaps the cam/post systems in PS TKA better maintain knee kinematics and function long term.

What to Know for Selecting Cruciate-Retaining or Posterior-Stabilized Total Knee Arthroplasty

There has been continuing debate about the superiority of cruciate-retaining (CR) total knee arthroplasty (TKA) versus posterior-stabilized (PS) TKA for obtaining knee joint stability with functional improvement. Many surgeons tend to select the type of prosthesis on the basis of their own training and experience. However, the selection must be based on a great store of knowledge rather than on the surgeon's preconceptions or preferences. CR TKA may not be feasible in certain settings: posterior cruciate ligament insufficiency, severe deformity, and history of trauma or surgery. The risk of conversion from a CR type prosthesis to a PS type prosthesis might be high in patients with severe flexion contracture, steep posterior slope, and small femoral component size. The above factors should be carefully considered for an appropriate selection of the type of prosthesis. The surgeon should have a clear understanding on the technical differences between CR and PS TKAs. The amount of distal femoral resection, femoral component size, and tibial slope are particularly crucial for successful TKA. Unless they are meticulously determined, stiffness or instability will ensue, which can be difficult to resolve afterwards. There was no notable difference in functional outcome, range of motion, kinematics, and survival rate between CR and PS TKAs in most previous studies. Strict adherence to surgical indications and solid understanding of differences in surgical principles might be more important than the selection of either a CR or PS prosthesis.

Motion type and knee articular conformity influenced mid-flexion stability of a single radius knee prosthesis

PURPOSE

Single radius knee implants were introduced to reduce the level of paradoxical anterior femoral translation (AFT) during mid-flexion after total knee arthroplasty. Findings from clinical and experiment studies are inconsistent, which may be due to the different loading conditions and articular conformities of the knee implants studied. The aim of this study is to analyze how variations in these two factors affect the mid-flexion stability of a single radius knee prosthesis.

METHODS

Six daily activities (walking, stair ascent, stair descent, sit-to-stand, pivot turn and crossover turn), and three articular conformity ratios (low, moderate and high) were considered. The resulting AFTs from the 18 finite element models were analyzed.

RESULTS

For low conformity knees, the worst case activity (the greatest AFT) was sit-to-stand with an AFT of 6.2 mm, while for the moderate conformity the worst case was crossover turn and pivot turn. For high conformity, all activities produced a relatively small AFT ranging from 0 mm to 1.8 mm, which more closely resembles natural knee motion. In addition, no AFT was recorded during stair ascent for all three conformities (low, moderate, high).

CONCLUSIONS

This study demonstrated that the amount of AFT is highly dependent on the activity being undertaken and the articular conformity of the knee prosthesis, and the worst case activity depends on the knee conformity. The clinical relevance of this study is that it offers valuable information towards the design of improved knee prostheses and selection of knee implants for clinical use.

LEVEL OF EVIDENCE

II.

Anterior Tibial Post Impingement During Stair Climbing: A Kinematic Analysis and Clinical Outcomes

BACKGROUND

Anterior tibial post impingement during gait and stair ambulation was reported in knees with posterior-stabilized prostheses. However, the link between anterior post impingement and knee kinematics and between anterior post impingement and the clinical outcome has not been well investigated. Therefore, the purpose of this study was to assess the anterior impingement to clarify the relevant kinematics and clinical results including patient-reported outcomes.

METHODS

We analyzed 40 well-functioning knees in 20 patients with a posterior-stabilized prosthesis due to osteoarthritis and who were followed up for 2 years or more. Dynamic lateral radiographs during stair-climbing activity were analyzed using a shape-matching technique, and anterior post impingement and the clinical outcome were assessed.

RESULTS

Anterior impingement of the tibial post was observed in 13 knees (33%) during the latter half of the stance phase and at the beginning of the swing phase with the average implant flexion angle of -2.4°. Implant flexion was significantly smaller, while the femoral component was located more posterior in the impingement knees. The posterior tibial slope was significantly greater in the impingement group (6.7° ± 2.0°, 5.3° ± 1.9°, respectively; P = .041); however, no significant differences were demonstrated in anteroposterior laxity and patient-derived assessments.

CONCLUSION

To avoid anterior post impingement, the posterior tibial slope should be made at 5° or less. Femoral notch-anterior post articulation should be designed to have good congruency in order to act as an anterior stabilizer in the case of impingement at knee extension.

Posterior-stabilized versus cruciate-retained implants for total knee arthroplasty: a meta-analysis of clinical trials

AIM

A meta-analysis comparing the outcomes of patients undergoing cruciate retaining (CR) versus posterior stabilized (PS) in primary total knee arthroplasty was performed. The outcomes of interest were the Knee Society Rating System, clinical (KSCS) and functional (KSFS) subscales, joint range of motion (ROM), surgical duration and further complications (anterior knee pain, instability and revision rate).

MATERIALS AND METHODS

The search was conducted in July 2018, accessing the following databases: Cochrane Systematic Reviews, Scopus, PubMed, EMBASE, CINAHL, AMED and Google Scholar. We included only clinical trials level of evidence I and II. During the statistical analysis, we excluded all the studies that affect negatively the I² test, in order to achieve more reliable results. For the methodological quality assessment we referred to the PEDro score. The risk of publication's bias was evaluated by the funnel plots across all the comparisons.

RESULTS

The PEDro score reported a good methodological quality assessment. The funnel plot detected a very low risk of publication's bias. We included in this study 36 articles, counting a total of 4052 patients and 4884 procedures. The mean follow-up term for both groups was 3.39 years. The ROM resulted in an overall estimate effect of 2.18° in favor of the PS group. The overall WOMAC showed a result in favor of the PS group. The overall estimate effect of the KSCS was 0.02% higher in the CR group. The KSFS showed an overall estimate effect of 2.09% in favor of the PS group. Concerning the surgical duration, the estimate effect resulted in 6.87 min shorter in the CR group. No differences were reported across the two groups regarding anterior knee pain, knee joint instability or revision rate.

CONCLUSION

Both the prosthetic implants provided to be a safety and feasible solution to treat end-stage knee joint degeneration. The PS implants reported improvements in the knee range of motion and a prolongation of the surgical time. No clinically relevant dissimilarities concerning the analyzed scores were evidenced. No statistically significant relevant differences in complications were detected.

Bicruciate Substituting Total Knee Arthroplasty Improves Stair Climbing Ability When Compared with Cruciate-Retain or Posterior Stabilizing Total Knee Arthroplasty

PURPOSE

The purpose of this study was to compare stair climbing and descent ability following bicruciate substituting (BCS), cruciate retaining (CR), and posterior stabilizing (PS) total knee arthroplasties (TKAs).

MATERIALS AND METHODS

Sixty-three participants undergoing BCS-TKA (journey II: Smith and Nephew), 47 participants undergoing CR-TKA (FINE: Teijin Nakashima Medical), and 38 participants undergoing PS-TKA (FNK: Teijin Nakashima Medical) were included in this study. Before and 12 months after surgery, a questionnaire was administered to assess daily stair climbing and descent ability. In the questionnaire, stair climbing and descent ability were classified as (1) stair climbing and descent one step at a time, (2) stair climbing and descent two steps at a time, and (3) unable to climb or descend stairs. The necessity of a handrail was also evaluated and classified as: (1) necessary, (2) unnecessary, and (3) unable to climb or descend stairs with handrail. Statistical analysis (χ ²-test) was performed to compare these data between the types of TKA.

RESULTS

Preoperatively, no significant differences in stair climbing and descent ability or between handrail classifications were observed between the three different TKA groups. Postoperatively, the percentage of patients able to climb stairs one step at a time was significantly higher in BCS-TKA group (89%), when compared with CR (72%) or PS (58%) TKA groups. No significant differences in stair descent ability or among the handrail necessity classifications were observed between the types of TKA.

CONCLUSION

BCS-TKA resulted in significantly better stair climbing ability when compared with CR or PS-TKA. This may indicate that the design of BCS-TKA better reproduces native anterior cruciate ligament and posterior cruciate ligament function and improves knee stability during stair climbing activity.

Comparison of Kinematics in Cruciate Retaining and Posterior Stabilized for Fixed and Rotating Platform Mobile-Bearing Total Knee Arthroplasty with respect to Different Posterior Tibial Slope

Reconstructed posterior tibial slope (PTS) plays a significant role in kinematics restoration after total knee arthroplasty (TKA). However, the effect of increased and decreased PTS on prosthetic type and design has not yet been investigated. We used a finite element model, validated using in vitro data, to evaluate the effect of PTS on knee kinematics in cruciate-retaining (CR) and posterior-stabilized (PS) fixed TKA and rotating platform mobile-bearing TKA. Anterior-posterior tibial translation and internal-external tibial rotation were investigated for PTS ranging from -3° to 15°, with increments of 1°, for three different designs of TKA. Tibial posterior translation and external rotation increased as the PTS increased in both CR and PS TKAs. In addition, there was no remarkable difference in external rotation between CR and PS TKAs. However, for the mobile-bearing TKA, PTS had less effect on the kinematics. Based on our computational simulation, PTS is the critical factor that influences kinematics in TKA, especially in the CR TKA. Therefore, the surgeon should be careful in choosing the PTS in CR TKAs.

Bi-cruciate stabilized total knee arthroplasty can reduce the risk of knee instability associated with posterior tibial slope

PURPOSE

The purpose of this study was to evaluate the relationship between posterior tibial slope and knee kinematics in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA), which has not been previously reported.

METHODS

This computer simulation study evaluated Journey 2 BCS components (Smith & Nephew, Inc., Memphis, TN, USA) implanted in a female patient to simulate weight-bearing stair climbing. Knee kinematics, patellofemoral contact forces, and quadriceps forces during stair climbing (from 86° to 6° of flexion) were computed in the simulation. Six different posterior tibial slope angles (0°-10°) were simulated to evaluate the effect of posterior tibial slope on knee kinematics and forces.

RESULTS

At 65° of knee flexion, no anterior sliding of the tibial component occurred if the posterior tibial slope was less than 10°. Anterior contact between the anterior aspect of the tibial post- and the femoral component was observed if the posterior tibial slope was 6° or more. An increase of 10° in posterior tibial slope (relative to 0°) led to a 4.8% decrease in maximum patellofemoral contact force and a 1.2% decrease in maximum quadriceps force.

CONCLUSION

BCS TKA has a wide acceptable range of posterior tibial slope for avoiding knee instability if the posterior tibial slope is less than 10°. Surgeons should prioritize avoiding adverse effects over trying to achieve positive effects such as decreasing patellofemoral contact force and quadriceps force by increasing posterior tibial slope. Our study helps surgeons determine the optimal posterior tibial slope during surgery with BCS TKA; posterior tibial slope should not exceed 10° in routine clinical practice.

Knee kinematics in bi-cruciate stabilized total knee arthroplasty during squatting and stair-climbing activities

This study aimed to evaluate clinical outcomes and in vivo kinematics of bi-cruciate stabilized (BCS) total knee arthroplasty (TKA), using image-matching techniques. We analyzed tibiofemoral anteroposterior translation, axial rotation, and anterior/posterior cam-post contact for 22 BCS TKAs during squatting and stair-climbing. The functional activities on the 2011 Knee Society Score were significantly improved from 36 to 71. The tibiofemoral translation and axial rotation during squatting/stair-climbing were 16.1 mm/7.1 mm and 2.5° external/1.1° internal, respectively. Anterior/posterior cam-post contacts were observed during squatting (14%/96%) and stair-climbing (27%/96%). In conclusion, BCS TKA produced physiological sagittal plane kinematics during activities with favorable clinical outcomes.

In vivo kinematics of gait in posterior-stabilized and bicruciate-stabilized total knee arthroplasties using image-matching techniques

PURPOSE

This study aimed to evaluate the effects of two types of total knee arthroplasty (TKA) designs: posterior-stabilized (PS) and bicruciate-stabilized (BCS) on in vivo kinematics during gait.

METHODS

Continuous X-ray images of the gait were taken using a flat panel detector for 23 PS and BCS TKAs. We analyzed the tibiofemoral implant flexion angle, anteroposterior (AP) translation, axial rotation, and anterior/posterior cam-post contact using image-matching techniques.

RESULTS

Double knee actions were demonstrated for the PS and BCS design (35 and 61%, respectively, p = 0.08). The tibiofemoral AP positions were significantly more posterior at peak extension (- 1.7 ± 2.2 and 1.0 ± 2.5 mm, respectively, p < 0.01) and anterior at peak flexion (1.3 ± 2.3 and - 0.8 ± 2.8 mm, respectively, p = 0.01) for the PS design than for the BCS design, with a significant difference in AP translation (3.0 ± 3.9 mm anterior and 1.7 ± 2.8 mm posterior, respectively, p < 0.01). Anterior/posterior tibial post contacts were found in 83/4% and 74/30% for the PS and BCS designs, respectively, with a significant difference in posterior contact (p = 0.72/0.04, respectively).

CONCLUSION

The knee flexion pattern, tibiofemoral AP translation, axial rotation, and cam-post contact during gait varied, depending on the type of implant, the PS and BCS designs.

Kinematic analysis of stair climbing in rotating platform cruciate-retaining and posterior-stabilized mobile-bearing total knee arthroplasties

INTRODUCTION

The aim of our study was to compare and contrast the effects of two types of mobile-bearing total knee arthroplasties (TKA), namely, the cruciate-retaining (CR) and posterior-stabilized (PS) TKAs, on clinical outcomes and in vivo kinematics during stair climbing.

MATERIALS AND METHODS

The Press-Fit Condylar Sigma rotating platform was used for both CR and PS TKAs. Patient-reported outcomes were assessed using the 2011 Knee Society Score. Quadriceps muscle strength was evaluated by isokinetic dynamometry. In vivo kinematics were evaluated using periodic sagittal plane radiographic images obtained during stair climbing to quantify anteroposterior (AP) tibiofemoral translation, implant flexion and axial rotation angles using image-matching techniques. Outcomes were evaluated in 20 TKAs, which had been undergone with clinical success, including ten knees with CR types and ten knees with PS types.

RESULTS

There were no significant differences between the CR and PS TKA groups (p > 0.05) in isometric extensor torque (1.0 ± 0.2 and 1.1 ± 0.6 N m/kg, respectively) or patient-reported score for stair climbing function (4.0 ± 0.5 and 3.8 ± 0.9, respectively). Both types of TKAs showed stable AP translation in the mid range of knee flexion and paradoxical translation in the low range of flexion, with limited rotation, during stair climbing. There were no significant differences between the CR and PS TKA groups (P > 0.05) in anterior translation from 80° to 40° of knee flexion (4.2 ± 1.2 and 3.5 ± 1.6 mm, respectively), posterior translation from 40° to 10° of knee flexion (2.3 ± 1.9 and 2.0 ± 1.5 mm, respectively), and total external rotation (2.8° ± 4.9° and 0.5° ± 5.0°, respectively).

CONCLUSIONS

Both CR and PS types of rotating platform mobile-bearing TKAs provided reproducible knee joint kinematics during stair climbing and equivalent clinical outcomes.

LEVEL OF EVIDENCE

IV.

Distinctions of introarticular force distribution between genesis-II posterior stabilized and cruciate retaining total knee arthroplasty: An intraoperative comparative study of 45 patients

BACKGROUND

Although both the posterior stabilized and cruciate retaining total knee arthroplasty have been proven to effectively relieve pain and restore basic functions, the joint gap width during flexion was reported to be different due to the presence or absence of posterior cruciate ligament, which may lead to different intra-articular force distribution. In this study, we investigated the distinctions in intra-articular force distribution between the two types of TKA designs in patients with varus knee osteoarthritis.

METHODS

Forty five patients (50 knees) with varus knee osteoarthritis were prospectively included, with each 25 knees receiving cruciate retaining and posterior stabilized total knee arthroplasty, respectively. With an intra-articular force measurement system, the intra-articular force distribution with knee flexion at 0°, 30°, 45°, 60°, 90°, and 120° were recorded in all patients.

FINDINGS

The total force was similar for posterior stabilized and cruciate retaining knees at all flexion degrees. However, force in the medial compartment accounted for 59.8%-84.0% of total force in posterior stabilized knees, while 27.4%-65.7% in cruciate retaining knees. In cruciate retaining knees, no significant difference was found between forces in the two compartments at 30° flexion (P=0.444), but force was significantly concentrated in the lateral side during 45°-120° flexion (P=0.000-0.028).

INTERPRETATION

Although the entire intra-articular forces were similar between CR and PS knees at different flexion angles, medial part had higher force than lateral part when PS knee was used. The posterior cruciate ligament do a role in soft balance, and make the force more evenly distributed.