Distal femur rotation relates to joint obliquity in ACL-deficient Chinese

Spacer-based gap balancing is useful in total knee arthroplasty: a 3-year follow-up of a retrospective study

Background

Which technique, gap balancing or measured resection, can obtain better femoral component alignment and soft tissue balance in total knee arthroplasty (TKA) is still controversial. This study aimed to determine whether the gap balancing technique using a modified spacer block in TKA can result in better postoperative clinical outcomes than the measured resection technique.

Methods

A total of 124 patients who underwent consecutive primary TKA between May 2016 and August 2018 were retrospectively reviewed. The gap balancing technique assisted by a modified spacer block was used in 61 patients, and the measured resection technique was used in 63 patients. The surgical, imaging and knee function outcomes of the two groups were compared.

Results

The thickness of the posterior medial condyle bone resection using the modified spacer block tool in gap balancing was significantly larger than that of the MR technique (P = 0.001). Compared with the measured resection group, the gap balancing group had a greater external rotation resection angle of the femur (4.06 ± 1.10° vs. 3.19 ± 0.59°, P < 0.001°). Despite these differences, the mean ROM, KSS scores, and WOMAC scores at the 6-week, 1-year, and 2-year follow-ups were not significantly different. Postoperatively, there was no significant difference between the two groups in mechanical axis measurements (P = 0.275), the number of HKA outliers (P = 0.795) or the joint line displacement (P = 0.270).

Conclusion

The functional outcomes of the gap balancing technique based on the modified spacer are similar to those of measured resection at 3 years. Compared with the MR technique, the GB technique resulted in a greater external rotation resection angle and thicker posterior medial condylar cuts in TKA with knee varus.

Is there difference and correlation between medial and lateral tibial plateau coronal obliquity in native knee? A radiographic study

Background/Purpose

Knee joint line is commonly defined as a tangent to medial and lateral tibial plateaus in various radiographic measurements. We aim to investigate radiographic differences between medial and lateral knee joint line coronal obliquity. It has significant implication on radiographic analysis following unicompartmental knee arthroplasty.

Methods

We analysed the knee radiographs of 48 young patients (mean age 25.1 + /-5.6 years) with 50 anterior cruciate ligament-deficient knees. Medial and lateral tibial plateau coronal obliquity were defined as angles between femoral knee joint line and the tangent to articular surface of each tibial plateau. Mediolateral differences and linear correlation were analysed.

Results

Significant difference was found between medial (mean = -1.5, SD = 2.4 degrees) and lateral obliquity (mean =  + 0.6, SD = 3.0 degrees) ( p < 0.001). The mean mediolateral difference was 3.1 degrees (SD = 2.8, range 0–11.8 degrees), without significant correlation (r = 0.085, p = 0.56).

Conclusion

Mediolateral differences exist in knee joint line obliquity. Each compartment should be considered separately when measuring knee joint line obliquity.

Distal Femoral Rotation Correlates With Proximal Tibial Joint Line Obliquity: A Consideration for Kinematic Total Knee Arthroplasty

BACKGROUND

We hypothesized that there is a correlation between the distal femoral rotation and proximal tibial joint line obliquity in nonarthritic knees. This has significance for kinematic knee arthroplasty, in which the target knee alignment desired approximates the knee before disease.

METHODS

Fifty computed tomography scans of nonarthritic knees were evaluated using three-dimensional image processing software. Four distal femoral rotational axes were determined in the axial plane: the transepicondylar axis (TEA), transcondylar axis (TCA), posterior condylar axis (PCA), and a line perpendicular to Whiteside's anterior-posterior axis. Then, angles were measured relative to the TEA. Tibial joint line obliquity was measured as the angle between the proximal tibial plane and a line perpendicular to the axis of the tibia.

RESULTS

There was a strong positive correlation between PCA-TEA and tibial joint line obliquity (r = 0.68, P < .001) as well as TCA-TEA and tibial joint line obliquity (r = 0.69, P < .001). In addition, the tibial joint line obliquity and TCA-TEA angles were similar, 3.7° ± 2.2° (mean ± standard deviation) and 3.5° ± 1.7°, respectively (mean difference, 0.2° ± 0.2°; P = .369).

CONCLUSION

Both PCA-TEA and TCA-TEA strongly correlated with proximal tibial joint line obliquity indicating a relationship between distal femoral rotational geometry and proximal tibial inclination. These findings could imply that the native knee in flexion attempts to balance the collateral ligaments toward a rectangular flexion space. A higher tibial varus inclination is matched with a more internally rotated distal femur relative to the TEA.

Morphologic features of the distal femur and tibia plateau in Southeastern Chinese population: A cross-sectional study

Morphologic measurements of the femoral and tibial features of western population have been done in several studies, which provides the fundamental data for the design of total knee arthroplasty prosthesis used globally, including China. However, researches on anatomic and morphologic features of the knee in Chinese populations of both sexes have never been conducted. Our study was aimed at investigating the anatomic and morphologic features of the knees of the Southeastern Chinese population by magnetic resonance imaging (MRI) scans, so as to provide parameters for sex- and ethnic-specific implant designs in the future.A total of 245 knees from 244 Chinese adults (130 females and 114 males, aging from 18 to 89 years) who received knee MRI scan from November 2014 to October 2015 were recruited and analyzed. A set of linear and angular parameters, and 6 normalized ratios were measured and calculated on the distal femur and proximal tibia.The knee size was significantly different between sexes. Compared with women, men have larger (P < .01) medial-lateral (ML) and anterior-posterior (AP) dimensions in both distal femur and proximal tibia. Differences in femoral shape, represented by the femur surface ratio, between both sexes were also identified (1.23 ± 0.07 vs 1.27 ± 0.07, P < .01), whereas the ML/AP ratios of the tibia are similar between both sexes (1.44 ± 0.07 vs 1.44 ± 0.09, P = .97). We also found substantial difference in the morphology of femur and tibia plateau in Southeastern Chinese population compared with data obtained from western populations.Our study measured the anatomic and morphologic features of the knees in Southeastern Chinese population, and identified knee morphologic differences between both sexes, as well as western and Chinese population. Further clinical studies are needed to determine other essential parameters for the design of prosthesis to the Chinese populations.

Kinematics of anterior cruciate ligament-deficient knees in a Chinese population during stair ascent

Background

The purpose of this study was to measure the tibiofemoral kinematics of anterior cruciate ligament (ACL) deficiency in a Chinese population and compare the kinematics with published data about a Caucasian population.

Methods

Unilateral knees of 18 Chinese ACL-deficient (ACL-D) subjects were studied while subjects ascended stairs. Kinematic alteration was compared between ACL-D knees and contralateral ACL-intact (ACL-I) knees. The kinematic alteration of ACL deficiency was also compared between the Chinese population and published data about a Caucasian population.

Results

A statistical difference was found in the three-dimensional rotations between ACL-D and ACL-I knees. In the sagittal plane, ACL-I knees had a larger flexion angle than ACL-D knees during 40 to 50 % of the activity during stair ascent (P < 0.027) and throughout the gait cycle. A significant difference in rotational motion between ACL-D and ACL-I knees was also observed in the frontal plane during 40 to 60 % (P < 0.017) of the activity and in the transverse plane during 70 to 80 % (P < 0.028) of the activity. A greater tibial varus was demonstrated in the Chinese population while the published data revealed external tibial rotation and a statistical difference in translation in the Caucasian population.

Conclusions

ACL-D knees show different kinematics than ACL-I knees in the Chinese population. ACL-I knees had a larger flexion angle than ACL-D knees in the middle stage of the activity during stair ascent. A significant difference in rotational motion between ACL-D and ACL-I knees was also observed in the frontal plane during the middle phase and in the transverse plane during the terminal phase of the activity. A greater tibial varus was demonstrated in the Caucasian population while the published data revealed external tibial rotation and a statistical difference in translation in the Caucasian population.

Differences in anatomy and kinematics in Asian and Caucasian TKA patients: influence on implant positioning and subsequent loading conditions in mobile bearing knees

The objective of our study was to determine the mechanical stress conditions under tibiofemoral loading with an overlay of knee kinematics in deep flexion on two different mobile bearing designs in comparison to in vivo failure modes. This study investigates the seldom but severe complication of fatigue failure of polyethylene components at mobile bearing total knee arthroplasty designs. Assuming a combination of a floor-based lifestyle and tibial malrotation as a possible reason for a higher failure rate in Asian countries we developed a simplified finite element model considering a tibiofemoral roll-back angle of 22° and the range of rotational motion of a clinically established floating platform design (e.motion FP) at a knee flexion angle of 120° in order to compare our results to failure modes found in retrieved implants. Compared to the failure mode observed in the clinical retrievals the locations of the occurring stress maxima as well as the tensile stress distribution show analogies. From our observations, we conclude that the newly introduced finite element model with an overlay of deep knee flexion (lateral roll-back) and considerable internally rotated tibia implant positioning is an appropriate analysis for knee design optimizations and a suitable method to predict clinical failure modes.