Anatomic variations between Japanese and Caucasian populations in the healthy young adult knee joint

Increased prevalence of valgus constitutional alignment subtypes in a South African arthritic population group using the coronal plane alignment of the knee (CPAK) classification

BACKGROUND

Knee alignment philosophies and patient specific models to improve patient reported outcomes are gaining increasing attention. The coronal plane alignment of the knee (CPAK) classification describes nine knee phenotypes and then proposes surgical alignment strategies to achieve constitutional alignment. The CPAK classification has been validated in Australian, European, Asian and North American population groups. To date no African data has been analyzed using CPAK.

METHODS

A total of 344 arthritic patients (608 knees) with appropriate long leg radiographs were classified based on the CPAK type. Measurements included mechanical hip-knee-angle(mHKA), medial proximal tibial angle (mMPTA) and lateral distal femoral angle (mLDFA) and the derived calculations of joint line obliquity (JLO) and arithmetic hip-knee-angle (aHKA).

RESULTS

The sample population was 77.9% (n = 268) female with a mean age of 68.4 ± 9.2 years. The most common CPAK types in order were type 3 (n = 174; 28.6%), type 2 (n = 155; 25.5%), type 1 (n = 94; 15.5%) and type 6 (n = 80; 13.2%). The most common limb alignment types were valgus (CPAK types 3,6,9; 41.8%).

CONCLUSION

This study, which investigated arthritic patients from a single institution in South Africa, shows a divergence of CPAK phenotypic knee patterns relative to other international studies, with much higher proportions of valgus phenotypes (3 and 6). This regional difference should be further investigated in other South African and African population samples and used to adapt the surgical strategies employed by local surgeons.

Radiologic Assessment of Knee Phenotypes Based on the Coronal Plane Alignment of the Knee Classification in a Korean Population

Background

The Coronal Plane Alignment of the Knee (CPAK) classification system has been developed as a comprehensive system that describes 9 coronal plane phenotypes based on constitutional limb alignment and joint line obliquity (JLO). Due to the characteristics of Asian populations, which show more varus and wider distribution in lower limb alignment than other populations, modification of the boundaries of the arithmetic hip-knee-ankle angle (aHKA) and JLO should be considered. The purpose of this study was to determine the knee phenotype in a Korean population based on the original CPAK and modified CPAK classification systems.

Methods

We reviewed prospectively collected data of 500 healthy and 500 osteoarthritic knees between 2021 and 2023 using radiographic analysis and divided them based on the modified CPAK classification system by widening the neutral boundaries of the aHKA to 0° ± 3° and using the actual JLO as a new variable. Using long-leg standing weight-bearing radiographs, 6 radiographic parameters were measured to evaluate the CPAK type: the mechanical HKA angle, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), aHKA, JLO, and actual JLO.

Results

From 2 cohorts of 1,000 knees, the frequency distribution representing all CPAK types was different between the healthy and arthritic groups. The most common categories were type II (38.2%) in the healthy group and type I (53.8%) in the arthritic group based on the original CPAK classification. The left and upward shift in the distribution of knee phenotypes in the original classification was corrected evenly after re-establishing the boundaries of a neutral aHKA and the actual JLO. According to the modified CPAK classification system, the most common categories were type II (35.2%) in the healthy group and type I (38.0%) in the arthritic group.

Conclusions

Although the modified CPAK classification corrected the uneven distribution seen when applying the original classification system in a Korean population, the most common category was type I in Korean patients with osteoarthritic knees in both classification systems. Furthermore, there were different frequencies of knee phenotypes among healthy and arthritic knees.

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

BACKGROUND

Individualized alignment techniques have gained major interest in an effort to increase satisfaction among total knee arthroplasty patients. This study aimed to compare postoperative alignment between kinematic alignment (KA) and mechanical alignment (MA) and assess whether KA significantly deviates from the principle of aligning the limb as close to neutral alignment as possible.

METHODS

There were 234 patients who underwent robotic-assisted total knee arthroplasty using an unrestricted KA and a strict MA technique (KA: 145, MA: 89). The lateral distal femoral angle, medial proximal tibia angle, and the resultant arithmetic hip-knee-ankle angle (aHKA) were measured. The aHKA < 0 indicated varus alignment, while the aHKA > 0 indicated valgus knee alignment. The primary outcome was the frequency of cases that resulted in an aHKA of ± 4° of neutral (0°), as assessed on full-leg standing radiographs obtained at 6 weeks postoperatively. The secondary outcome was the change in coronal plane alignment of the knee classification type from preoperative to postoperative between the MA and KA groups.

RESULTS

The mean preoperative aHKA was similar between the 2 groups (P = .19). The KA group had a mean postoperative aHKA of -1.4 ± 2.4°, while the MA group had a mean postoperative aHKA of -0.5 ± 2.1°. No significant difference in limb alignment was identified between KA and MA cases that resulted in hip-knee-ankle angle of ± 4° being neutral (91.7 versus 96.6%, P = .14). There were 97.2% of cases in the KA group that fell within the ± 5° range. The MA group was associated with a significantly higher rate of coronal plane alignment of the knee classification type change from preoperatively to postoperatively (P < .001).

CONCLUSIONS

Kinematic alignment achieved similar postoperative aHKA compared to MA, and thus did not significantly deviate from the principle of aligning the limb as close to neutral alignment as possible. Surgeons should feel comfortable starting to introduce individualized alignment techniques. Without being restricted by boundaries, postoperative alignment will be within 5 degrees of neutral 97% of the time.

Tibial morphology of symptomatic osteoarthritic knees varies according to location: a retrospective observational study in Japanese patients

This study analyzed 31 patients with symptomatic osteoarthritic knees scheduled to undergo knee arthroplasty or high tibial osteotomy and demonstrated shape variations in their proximal tibia using an average three-dimensional (3D) bone model. Preoperative computed tomography of the affected knees was reconstructed as 3D bone models using a triangle mesh of surface layers. The initial case was defined as the template, and the other models were reconstructed into homologous models with the same number of mesh vertices as that in the template. The corresponding mesh vertices of the other models were averaged to evaluate the spatial position on the particular mesh vertex of the template. This was applied to all the mesh vertices of the template to generate the average 3D model. To quantify the variation in surface geometry, average minimum distance from the average bone model to 31 models was recorded. The medial proximal tibial cortex (1.63 mm) revealed lesser variation compared to the tibial tuberosity (2.50 mm) and lateral cortex (2.38 mm), (p = 0.004 and p = 0.020, respectively). The medial tibial plateau (1.46 mm) revealed larger variation compared to the lateral tibial plateau (1.16 mm) (p = 0.044). Understanding 3D geometry could help in development of implants for arthroplasty and knee osteotomy.

The Lateral Malleolus Is a Simple and Reliable Landmark that Can Be Used to Reliably Perform Restricted Kinematically Aligned Total Knee Arthroplasty-Anatomical and Clinical Studies in Japanese Population

In restricted kinematic alignment total knee arthroplasty (TKA), bone resection is performed within a safe range to help protect against failure from extreme alignments. Patient-specific instrumentation, navigations, and robotics are often required for restricting bone cuts within a specified safe zone. We hypothesized that the lateral malleolus could be used as a landmark for restricting the tibial osteotomy using a mechanical jig. Here, we examine its feasibility in anatomical and clinical settings. We studied long-leg standing radiographs of 114 consecutive patients (228 knees) who underwent knee arthroplasty in our institution. We measured the lateral malleolus angle (LMA), the angle between the tibial axis and the line between the center of the knee and the lateral surface of the lateral malleolus. The medial proximal tibial angle was also measured before and after restricted kinematic alignment TKA under restriction with reference to the lateral malleolus. Mean LMA was 5.5 ± 0.5 degrees. This was relatively consistent and independent of patient's height, weight, and body mass index. The lateral malleolus is a reliable bone landmark that can be used to recognize approximately 5.5 degrees of varus intraoperatively. A surgeon can use this as a restriction of the tibial varus cut up to 6 degrees without the requirement for expensive assistive technologies.

Caliper-Based Restricted Kinematic Alignment Total Knee Arthroplasty

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

Definitions and consequences of current alignment techniques and phenotypes in total knee arthroplasty (TKA) - there is no winner yet

Dissatisfaction following total knee arthroplasty (TKA) has been extensively documented and it was attributed to numerous factors. In recent years, significant focus has been directed towards implant alignment and stability as potential causes and solutions to this issue. Surgeons are now exploring a more personalized approach to TKA, recognizing the importance of thoroughly understanding each individual patient's anatomy and functional morphology. A more comprehensive preoperative analysis of alignment and knee morphology is essential to address the unresolved questions in knee arthroplasty effectively. The crucial task of determining the most appropriate alignment strategy for each patient arises, given the substantial variability in bone resection resulting from the interplay of phenotype and the alignment strategy chosen. This review aims to comprehensively present the definitions of different alignment techniques in all planes and discuss the consequences dependent on knee phenotypes.Level of evidence V.

Both Adjustable and Fixed Loop Hamstring Tendon Graft Fixation Have Similar Clinical and Patient-Reported Outcomes in Anterior Cruciate Ligament Reconstruction

Purpose

This study aims to compare the outcomes of fixed-loop device (FLD) vs adjustable-loop device (ALD) graft fixation with up to 2-year follow-up in patients undergoing primary anterior cruciate ligament reconstruction (ACLR) in a predominantly Asian setting.

Methods

Prospectively collected outcome measures as well as clinical records of patients who underwent primary ACLR using either FLD or ALD fixation of hamstring tendon autograft performed by a single surgeon were reviewed. The surgeon in this study used a fixed-loop device from 2018 to 2019 and then changed to adjustable loop from 2019 to 2020. Suspensory fixation was performed on the femoral side, and aperture (interference screw) fixation was performed on the tibial side. Outcome measures included knee range of motion, KT-1000 arthrometer testing, Lysholm knee score, and Tegner activity scale. Patients were assessed preoperatively and postoperatively at regular intervals of 6, 12, and 24 months.

Results

A total of 105 patients were identified. Forty-six were excluded due to incomplete follow-up data, so 59 patients with full 2-year follow-up were included in the final study group. Both groups (FLD vs ALD) were similar in demographics except for age (P = .042). Out of 105, there were 59 patients remaining in the study group with 2-year follow-up data. No significant differences were observed between the 2 groups at all respective testing intervals.

Conclusions

FLDs and ALDs for suspensory fixation of hamstring tendon autograft in ACLR had similar clinical outcomes with a minimum of 2-year follow up. There is no evidence of graft loosening from loop lengthening.

Level of Evidence

Level III, retrospective comparative trial.

Geographic Variation in Knee Phenotypes Based on the Coronal Plane Alignment of the Knee Classification: A Systematic Review

BACKGROUND

The extent of geographic variation in knee phenotypes remains unclear. The Coronal Plane Alignment of the Knee (CPAK) Classification proposes 9 coronal plane phenotypes based on constitutional limb alignment and joint line obliquity. This systematic review aims to examine differences in the distributions of CPAK types across geographic regions.

METHODS

A systematic review of the literature was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies reporting distributions of knee phenotypes according to the CPAK classification for healthy and/or arthritic knees were included.

RESULTS

There were 7 studies included, accounting for 5,964 knees in 3,917 subjects. Among healthy knees (n = 1,214), CPAK type II was the most common type in Belgium (39.2%), Taiwan (39.3%), and India (25.6%). Among arthritic knees (n = 2,804), CPAK type I was the most common in France (33.4%), India (58.8%), and Japan (53.8%), whereas CPAK type II was the most common in Australia (32.8%). The proportion of CPAK type I and II knees varied significantly across geographic regions among healthy (P < .01) and arthritic knees (P < .01).

CONCLUSION

Significant variation in CPAK distributions exists between countries. Further work is needed to delineate racial and sexual differences in CPAK types, which were not explored in this article. A better understanding of population-level variability in knee phenotypes may enable orthopaedic surgeons to offer a more personalized approach to knee arthroplasty.

Patellofemoral Pain, Q-Angle, and Performance in Female Chinese Collegiate Soccer Players

Background and objective: Female sports injuries have been neglected by science, and few relevant studies have considered female subjects. Knee pain in female soccer players is more common than in male soccer players. The number of days of absence from training and competition has been shown to be higher in females than males. The reporting of knee pain is common in female soccer players, but whether knee pain is associated with morphological features is unclear. The Q-angle of the knee has been hypothesized to be a causal factor in knee pain. Asian females have shown higher levels of valgus than non-sporting Caucasian populations, but no data exist for female Chinese players. The aim of our study was to investigate whether there are associations between knee pain, the Q-angle of the lower limb, jump performance, play time, and perceived exertion in female Chinese collegiate soccer players. Materials and Methods: We measured the Q-angle, patellofemoral/anterior knee pain (SNAPPS questionnaire), and CMJ and SJ performance of 21 subjects (age: 20.09 ± 1.13 years, weight: 56.9 ± 6.26 kg, height: 164.24 ± 4.48 cm, and >10 years of practice) before and after a match; Borg scale and play time results were also recorded. Results: We found that our studied group had higher Q-angles in comparison to other ethnic groups reported in the literature, as well as an association of the Q-angle with the age, height, and weight of the players; however, contrary to other studies, we did not find any association between the Q-angle and knee pain, jumps, play time, or perceived exertion. Knee pain was not associated with any of the measured variables. Conclusions: Female Chinese soccer players showed higher Q-angles than players of other ethnic groups, a result that was associated with anthropometrics. The Q-angle was not found to be associated with knee pain, for which the sole determinant was body height.

The impact of postoperative inclination of the joint line on clinical outcomes in total knee arthroplasty using a prosthesis with anatomical geometry

The goal of this study was to investigate the impact of postoperative inclination of the joint line on clinical results after total knee arthroplasty (TKA) using a prosthesis with anatomical geometry. This study included 145 primary cruciate-retaining type of knee prosthesis with anatomical geometry. Three years postoperatively, clinical outcomes including the patient-reported outcomes (PROs) were recorded. Limb alignment was evaluated by the hip-knee-ankle (HKA) axis and inclination of the joint line was assessed by the joint line orientation angle (JLOA). Knees were divided into two groups according to the HKA: in-range (- 3 to 3°) and outlier group (< - 3° or > 3°) or the JLOA: in-range (2-4°) and outlier group (< 2° or > 4°), and clinical outcomes were compared between the groups. Postoperative Knee Society Function Score (KS-FS) was significantly higher in the HKA in-range group than the outlier group (p = 0.01). The Knee Society Knee Score and all subscales of the Knee injury Osteoarthritis Outcome Score were comparable between the groups. A multivariate analysis revealed a significant association between age at operation and postoperative KS-FS > of 80 points. Neither HKA in-range nor JLOA in-range were associated with the higher knee function. In conclusion, TKA-postoperative inclination of the joint line was not relevant to the short-term PROs. Treatment strategies that attempt to make joint line inclination in order to improve postoperative PROs should be avoided, and alignment goals such as kinematic alignment should be considered carefully.

Knee alignment and individual quadriceps femoris muscle thicknesses and their relationships with postnatal motor development and subcutaneous fat thickness: A cross-sectional study in Japanese infants

BACKGROUND

Postnatal changes in individual quadriceps femoris muscle thicknesses and the relationships between knee alignment and quadriceps thicknesses, postnatal motor development, and subcutaneous fat thickness are unclear. This study investigated knee alignment and individual quadriceps thickness ratios in Japanese infants and investigated their relationships with postnatal motor development and subcutaneous fat thickness.

METHODS

One-year-old (n = 28), 2-year-old (n = 26), and 3-year-old infants (n = 22) were included. Postnatal months when the infants began crawling, standing, and walking were assessed. The intercondylar distance was measured, and the individual quadriceps and subcutaneous fat thicknesses at the right mid-thigh were measured using ultrasonography. The individual quadriceps:total quadriceps muscle thickness ratios were calculated. Analysis of variance tests in the 3 groups were conducted for the intercondylar distances and individual quadriceps thickness ratios, and correlation coefficients between the parameters were evaluated in each group.

FINDINGS

Intercondylar distance was longer in 1-year-old infants than in 2-year-old infants (p < 0.001), without significant differences between 2-year-old and 3-year-old infants (p = 0.33). The rectus femoris thickness ratio was higher in 1-year-old infants than in 3-year-old infants (p = 0.013), whereas the vastus medialis thickness ratio was higher in 3-year-old infants than in 2-year-old infants (p = 0.024). In 3-year-old infants, a larger subcutaneous fat thickness, but not postnatal motor development, was correlated with a longer intercondylar distance and a lower vastus medialis thickness ratio (rs = 0.53, p = 0.012; rs = -0.46, p = 0.032, respectively).

INTERPRETATION

Further studies on the relationships between subcutaneous fat and knee alignment and vastus medialis in juveniles, adolescents, young adults, and elderly people are expected.

Correlation of Tibial Torsion With Lower Limb Alignment and Femoral Anteversion in Patients With Patellar Instability

BACKGROUND

Alignment and rotation of the lower extremities have been suggested to be predisposing pathologic factors for patellar instability.

PURPOSE

To elucidate the relationship between the lower limb alignment and lower extremity rotation in patients with patellar instability.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Included were 83 patients with patellar instability. Computed tomography scans and standing full-leg radiographs were used to measure the tibial tuberosity-trochlear groove (TT-TG) distance, mechanical femorotibial angle (mFTA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), femoral torsion, and tibial torsion of the different segments. The relationships between femoral torsion, tibial torsion of the different segments, and the mFTA, mLDFA, and mMPTA were evaluated. The levels of tibial torsion and femoral torsion in patients with varus, normal, or valgus alignment were compared with 1-way analysis of variance and chi-square test.

RESULTS

The total tibial torsion was significantly associated with total femoral anteversion (r = 0.329; P = .002) and mFTA (r = -0.304; P = .005). There were no significant correlations between mFTA and TT-TG distance or femoral anteversion. Compared with patients with valgus malalignment, patients with varus malalignment tended to have higher tibial torsion.

CONCLUSION

Tibial torsion was associated with leg axis alignment and femoral anteversion in patients with patellar instability. Patients with patellar instability, especially those with concurrent leg axis deformities, should undergo further radiological imaging so that tibial torsion can be assessed and a diagnosis of torsion deformity made early in the treatment pathway and the proper surgical plan formulated.

Kamath V. A study on topography of tibial plateau and its applications in knee arthroplasty

Introduction and Aim: This investigation was designed for evaluating the tibial plateau in Indian population and compares the data with other populations. The major intention is to observe if significant difference exists in diverse a demographic profile that necessitates production of population specific implants ensuring success in total knee arthroplasty.   Materials and Methods: Morphometry of 200 adult human tibial plateaus were measured in dry bones using a sliding digital caliper and data analysis was done.    Results:   The mean anteroposterior dimension of the medial condyle was 38.98 ± 4.46 mm on the left and 38.81 ± 5.05 mm on the right and the lateral condyle was 32.99 ± 4.01mm on the left and 32.42 ± 4.88 mm on the right. The mean transverse dimension of the medial condyle was 24.95 ± 3.22 mm on the left and 24.54 ± 2.69 mm on the right and the lateral condyle was 28.15 ± 4.10 mm on the left and 27.76 ± 3.50 mm on the right. The anteroposterior dimension of the intercondylar area was 44.78 ± 3.87 mm on the left and 44.19 ± 4.51mm on the right.   Conclusion: The data obtained will help in designing tibial prosthetic implants best suited for Indian population. The surgeon can assess how much a given deformity deviates from the normal values. The dimensions of the tibial plateau vary in different populations and most available prosthesis is designed based on Caucasian data. The tibial prosthetic sizing needs to be population specific to avoid a mismatch or mediolateral overhang.

Fixed 6° distal femoral cut consistently achieves neutral alignment for Asians, Caucasians, and Native Hawaiian/Pacific Islanders

BACKGROUND

Restoration of a neutral mechanical axis (MA) is important to the success of total knee arthroplasty (TKA). While known differences are present between Asians and Caucasians regarding native knee alignment, it is unknown whether such differences exist amongst Native Hawaiian/Other Pacific Islanders (NHPI) or if utilizing a fixed distal femoral cut of 6° can consistently achieve a neutral MA in these minority racial groups. This study examines the preoperative deformities presented by Asians, Caucasians, and NHPI, and the resulting knee alignment achieved following TKA when a fixed 6° distal femoral cut is targeted for all patients.

METHODS

Preoperative and postoperative MA was measured from 835 Asian, 447 Caucasian, and 163 NHPI hip-to-ankle radiographs. All patients underwent TKA in which a standard distal femoral cut of 6° valgus was targeted for all patients. Data were evaluated as continuous variables and by groupings of varus (MA < - 3°), valgus (MA > 3°), and neutral (- 3° ≤ MA ≤ 3°) alignment.

RESULTS

Preoperative deformity ranged from 38° varus to 29° valgus. The proportion of Asian and NHPI presenting with varus alignment prior to surgery was significantly greater than Caucasian patients in both males (Asians: 80.6%; Caucasians: 67.0%; NHPI: 79.0%, p = 0.001) and females (Asians: 66.1%; Caucasians: 45.7%; NHPI: 63.2%, p < 0.001). There was no difference in the proportion of patients (72-79%) achieving a neutral MA amongst all three racial groups.

CONCLUSION

NHPI appear to have similar preoperative deformities to Asians with both groups having significantly more varus alignment than Caucasians. Despite a wide range of preoperative deformity, application of a fixed distal femoral cut of 6° valgus successfully established a neutral MA equally in the majority of patients across all three racial groups.

Dynamic Taping Improves Landing Biomechanics in Young Volleyball Athletes

Poor landing biomechanics such as hip adduction, internal rotation, and knee valgus have been recognized as modifiable risk factors of anterior cruciate ligament (ACL) injury. Dynamic taping is a newly developed technique with better elasticity and extensibility, which could change the landing biomechanics. The purpose of this study was to identify whether dynamic taping could improve lower limb biomechanics in athletes. Forty-two high school volleyball athletes (21 males and 21 females) participated in the study. Biomechanical properties, including the landing error scoring system (LESS) and anterior-posterior knee laxity, were evaluated before and after the application of dynamic tape while athletes performed the jump-landing task. As a result, we found that dynamic tape significantly reduced the faulty landing strategy by an average of 0.64 errors in all volleyball athletes. The effect induced by dynamic tape was more prominent in female athletes and high-risk athletes (1.1 errors). Furthermore, the application of dynamic tape improved anterior-posterior knee laxity, especially in female athletes (p < 0.001). In conclusion, we found that dynamic tape provided a short-term, passive, and clinically significant means to normalize inadequate biomechanics during landing in athlete groups, which could have a protective effect and further alleviate the risk of ACL injury.

Lateral shift of the femoral condyle after total knee arthroplasty: simulation using 2D-templates of the medial pivot design on knee radiographs of young Japanese patients

Background

Total knee arthroplasty (TKA) is an established surgical treatment for advanced knee osteoarthritis by which patients can expect improvement of knee pain and function. Although many surgeons have investigated limb alignment after TKA, changes in coronal positional relation between the femur and tibia are not known well.

Methods

Radiographs of 105 knees of young Japanese patients between 20 and 49 years-old (60 men and 45 women) without osteoarthritic changes who received arthroscopic surgeries at our hospital were used in this study. Using 2D-templates of the medial pivot design (the FINE total knee), we simulated TKA on a SYNAPSE-PACS software. First, the femoral component was placed in normal knee alignment and then was merged to the medial concave of the insert where the tibial component was placed in neutral alignment. The length of the mediolateral shift of the femoral component was measured as an estimate of lateral shift of the femoral condyle, of which association with radiographic parameters including the femorotibial angle (FTA), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA) was analyzed. Subjects were classified into three groups according to the femoral component size that was chosen in simulation of TKA, and the lateral shift of the femoral condyle was compared between groups.

Results

The estimated mean lateral shift of the femoral condyle was 5.99 ± 1.98 mm and was greater in males than females (p < 0.05). Also, it was most highly correlated with the medial proximal tibial angle (MPTA) (r = − 0.553, p < 0.01). A group receiving larger component sizes significantly shifted more laterally compared with a group receiving smaller component sizes (p < 0.01).

Conclusions

These results suggest that the coronal positional relation between the femur and tibia is altered and subsequent ligament imbalance may occur after mechanically aligned TKA using the medial pivot design.

Kinematic Alignment in Total Knee Arthroplasty Reduces Polyethylene Contact Pressure by Increasing the Contact Area, When Compared to Mechanical Alignment—A Finite Element Analysis

Unrestricted Kinematic alignment (KA) in total knee arthroplasty (TKA) replicates the joint line of each patient by adjusting the cuts based on the anatomy of the patient. Mechanical alignment (MA) aims to restore a neutral mechanical axis of the leg, irrespective of the joint line orientation. The purpose of the present study was to compare contact pressure and contact areas of the polyethylene (PE) bearing surface as well as von Mises stress of the PE-tibial tray interface for MA and KA in the same patient, using CT data and finite element analysis. Finite element models were created from lower leg CT scans of 10 patients with knee osteoarthritis with different phenotypes. Mechanical PE properties were experimentally determined by tensile tests on dumbbell specimens. For numerical simulation purposes an adjusted non-linear material model with the maximum load to failure of 30.5 MPa, was calibrated and utilized. Contact pressure points were the deepest parts of the polyethylene inlay. Contact pressures were either very similar or were increased for MA knees throughout the gait cycle. KA either increased or had a comparable contact area, compared to MA. KA and MA produced comparable von Mises stresses, although both alignments breached the failure point of 30.5 MPa in all 3 valgus knees. This might indicate a higher probability of failure at the inlay-tibial baseplate interface. By maintaining the joint line orientation, KA reduces or has comparable contact pressures on the PE bearing surface by increasing or maintaining the contact area throughout one gait cycle in a validated finite element analysis model in 10 different knee phenotypes. The von Mises stress on the PE-tibial component interface was comparable, except for the valgus knees, where the load to failure was achieved in both alignment strategies and slightly higher stresses were observed for KA. Further studies for different knee phenotypes are needed to better understand the pressure changes depending on the alignment strategy applied.

Internal Torsion of the Knee: An Embodiment of Lower-Extremity Malrotation in Patients with Patellar Instability

BACKGROUND

Torsion of the lower extremities has been suggested to be a predisposing factor for patellar instability. However, no clear torsional factors have been clarified. This study aimed to elucidate the rotational geometry of the lower limb through segmental analysis in patients with patellar instability.

METHODS

Eighty-three patients with patellar instability were included. Computed tomography of the lower limb was acquired. Femoral and tibial torsion were measured in different segments. Femoral and tibial torsion in each segment was compared between the high- and normal-torsion groups to investigate which segment contributes the most.

RESULTS

All segments of femoral and tibial torsion except proximal femoral torsion showed significant differences between the high- and normal-torsion groups. The average proximal femoral torsion was 1.9° ± 7.1°, indicating that there was only slight torsion in the segment of the femoral neck. The angle between the femoral neck and the foot orientation in the normal-torsion, high-torsion tibial, and combined high-torsion femoral and tibial groups was 89.1° ± 12.0°, 81.3° ± 9.4°, and 98.2° ± 11.7°, respectively (p < 0.001), which suggested that the femoral neck remained nearly perpendicular to the foot orientation in the normal-torsion group. Shaft and distal femoral torsion contributed the most to total femoral torsion. For tibial torsion, from distal to proximal, internal torsion of both the proximal and distal segments contributed to the high torsion. There was no significant difference between distal femoral torsion and proximal tibial torsion, which suggested that, rather than the distal femur rotating internally on its own, the distal femur and the proximal tibia simultaneously rotated internally.

CONCLUSIONS

In patients with patellar instability, torsional deformity occurs along the length of the tibia and in the shaft and distal segments of the femur. The comprehensive embodiment of lower-extremity malrotation is an internal rotation deformity of the knee.

CLINICAL RELEVANCE

This study elucidated the rotational geometry of the lower limb through a detailed segmental analysis in patients with patellar instability. It could serve as a theoretical basis for choosing a derotational osteotomy site and may be a reference for additional clinical research.

Study on the morphological characteristics and rotational alignment axis of placement plane of the tibial component in total knee arthroplasty for hemophilia-related knee arthritis

Background

Abnormal epiphyseal growth plate development of the proximal tibia in hemophilia patients leads to notable morphological changes in the mature knee joint. This study aimed to compare the morphological characteristics of tibial component placement cut surface in patients with hemophilic arthritis (HA) and osteoarthritis (OA) and to determine the tibial component rotational alignment axis’ best position for HA patients.

Methods

Preoperative computed tomography scans of 40 OA and 40 HA patients who underwent total knee arthroplasty were evaluated using a three-dimensional (3D) software. The tibial component’s placement morphological parameters were measured. The tibial component’s rotational mismatch angles were evaluated, and the most appropriate 0°AP axis position for HA patients was investigated.

Results

In the two groups, the morphology was significantly different in some of the parameters (p < 0.05). The tibial component rotational mismatch angles were significantly different between both groups (p < 0.05). The medial 9.26° of the medial 1/3 of the patellar tendon was the point through which 0°AP axis passed for the HA patients. Similarly, the medial 13.02° of the medial 1/3 of the tibial tubercle was also the point through which the 0°AP axis passed.

Conclusions

The ratio of the anteroposterior length to the geometric transverse length of the placement section of the tibial component in HA patients was smaller than that in OA patients. The medial 9.26° of the medial 1/3 of the patellar tendon or the medial 13.02° of the medial 1/3 of the tibial tubercle seem to be an ideal reference position of the rotational alignment axis of the tibial component for HA patients.

Determining the rotational alignment of the tibial component referring to the tibial tubercle during total knee arthroplasty: the tibial tubercle-trochlear groove can be an aid

Background

There is no consensus on anatomic landmarks or reference axes with which to accurately align rotational position of tibial component. Using the tibial tubercle, commonly referring to the Akagi line and the Insall line, for anatomic reference was widely accepted. However, it is unknown about the predictors that may affect the reliability of using the tibial tubercle for aligning tibial component rotation. The aims of our study were (1) to investigate the reproducibility and accuracy of using the tibial tubercle for aligning tibial component rotation and (2) to determine predictors resulting in discrepancies of the tibial component rotation when referring to the tibial tubercle.

Method

A total of 160 patients with osteoarthritis were recruited before total knee arthroplasty. The angle α formed by the tibial anteroposterior (AP) axis and the Akagi line and the angle β formed by the tibial AP axis and the Insall line were measured to quantify the discrepancies of the Akagi line and the Insall line. Independent variables, including the tibial tubercle-to-trochlear groove distance (TT-TG), tibial tubercle to posterior cruciate ligament (TT-PCL), and knee rotation angle (KRA), hip–knee–ankle angle (HKA), medial proximal tibial angle (MPTA), and tibial bowing (TB), were measured. Pearson’s product moment correlation coefficients and multivariable linear regression analysis were calculated to assess relationships between independent variables and the two defined angles.

Results

All defined measurement were available for 140 patients. The Akagi line rotated internally with 1.03° ± 4.25° in regard to the tibial AP axis. The Insall line rotated externally in regard to the tibial AP axis with 7.93° ± 5.36°. Three variables, including TT-TG, TT-PCL, and KRA, tended to be positively correlated with the angle α and the angle β. In terms of a cutoff of TT-TG = 9 mm, 100% cases and 97% cases for using the Akagi line and Insall line, respectively, were located in the defined safe zone (− 5° to 10°).

Conclusion

The tibial tubercle (the Akagi line and Insall line) is found to be a useful and promising anatomic landmark for aligning the tibial component rotation. The TT-TG, with a cutoff value of 9 mm, is helpful to choose the Akagi line or Insall line, alternatively.

Improved surgical procedure of primary constrained total knee arthroplasty which enables use of the femoral diaphyseal straight extension stem

Background

In performing primary constrained total knee arthroplasties (TKA) to imbalanced knees, the offset stem is sometimes compelled to use, although this is associated with surgical difficulties. We developed a modified procedure which might be able to fit the anteroposterior (AP) and mediolateral (ML) position of the femoral component simultaneously with the straight stem. Purposes of this study were to evaluate usefulness of the modified procedure both in computer simulations and actual surgeries.

Methods

We included 32 knees that had undergone primary TKA using constrained implants because of the coronal imbalance. In the component-first procedure, the distal femur was prepared to fit the AP and ML position of the femoral component simultaneously at first, as in primary TKA. Finally, the stem hole is created based on the femoral component position (the component-first procedure). The femoral component and extension stem were simulated using the three-dimensional planning software (ZedKnee) following the component-first procedure. We investigated the suitability of the straight stem through computer simulation and evaluation of actual surgeries. Clinical and radiographical outcomes were also evaluated at the latest follow-up.

Results

The component-first procedure enabled the AP and ML position of the femoral component to be fitted simultaneously with the straight stem in simulations and actual surgeries in all cases. The stem diameter was not significantly different between simulations and actual surgeries (13.9 and 13.7 mm on average, respectively, p = 0.479) and almost similar from intraclass correlation coefficient analysis (kappa value 0.790). Clinical and radiographical outcomes were almost similar to primary TKA cases and there was no case of component loosening, cortical bone hypertrophy around the stem and stem-tip pain.

Conclusions

Our improved surgical procedure may facilitate use of the constrained implant for more cases of primary TKA in imbalanced knees without the usual surgical difficulties.

Trial registration

Retrospectively registered.

Current concept of kinematic alignment total knee arthroplasty and its derivatives

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal.

Prevalence of proximal tibia vara in Indonesian population with knee osteoarthritis

BACKGROUND

Proximal tibia vara has drawn interest since the concept of constitutional varus was introduced. Proximal tibia vara is a condition where the knee varus tilt the tibia condyle medially and shift the tibial articular surface medially. This condition affects medial proximal tibial angle measurements and the placement of the tibial implant in knee replacement surgery. Thus, it challenged the neutral knee arthroplasty alignment target because some people may present a proximal tibia vara. This study assesses the prevalence of the proximal tibia vara and the correlation to knee osteoarthritis grade.

METHODS

This retrospective study was carried out from January 2021 to June 2021. Eighty-five limbs were included with the following inclusion criteria: knee osteoarthritis patients who received a long view lower extremity radiograph. The exclusions criteria were (1) patients who had undergone arthroplasty and lower extremity surgery before and (2) valgus knee deformity. The outcomes in this study were HKAA, MAD, TAD, MPTA, PTRP, LDFA, and PTS. Intraclass correlation (ICC) using two-way mixed was used to assess the reproducibility of the radiographic parameters. Multiple logistic regression was used to evaluate the correlation between knee osteoarthritis grade and radiographs parameters (MAD and TAD).

RESULT

A total 85 limbs from 52 patients were assessed in this study. Proximal tibia vara was found in 18 knees (21%.). The logistic regression was performed to assess the correlation between the severity of the knee osteoarthritis and radiographic parameters (MAD, TAD, LDFA, and PTS) with an overall p-value < 0.001 and pseudo-R² = 0.29.

CONCLUSION

A significant portion of patients with knee osteoarthritis have proximal tibia vara, and it is a pre-existing condition. Since the pre-existing proximal tibia vara affects preoperative measurements, a long-standing lower extremity x-ray is recommended to be obtained as part of knee replacement preparation.

Anthropometric Comparison between Indian and Arabian Knees with Respect to Total Knee Replacement

Implants used for total knee replacement (TKR) in most Asian countries are not designed originally for the Asian population, and studies have shown anthropometric differences with respect to TKR among various ethnic groups. For this reason, implants designed for a specific population may not provide an anatomic fit when used in other populations. To avoid the consequences associated with such a misfit, the concept of ethnic-specific implant design is being introduced. In this study, the knee anthropometry of the Indian and Arabian patients was compared. They were operated with implants which were not ethnic-specific designs. Since the consequences associated with implant misfit apply equally to both the Indian and Arabian population, it is essential to compare the knee anthropometry of these two populations. Anthropometric measurements of the distal femur and proximal tibia of the Indian and Arabian knees were obtained intraoperatively using a Vernier caliper. Their respective aspect ratios (ARs) were calculated and statistically compared. It was found that the ARs of both tibia and femur of Indian and Arabian population did not show any statistical difference. There was no statistical difference between Indian and Arabian males (p = 0.345) and between Indian and Arabian females (p = 0.8210). However, a statistical difference in tibial AR (p-value = 0.049) and femoral AR (p-value = 0.003) was found significant when a comparison was made between the knees of Indian males and Indian females in the study. The above results suggested that TKR implants designed anatomically to suit the Indian population can also suit the Arabian population and vice versa. The obtained data can help implant designers to come up with ethnic-specific TKR implants.

Distribution of Coronal Plane Alignment of the Knee Classification in Patients with Knee Osteoarthritis in Japan

Coronal plane alignment of the knee (CPAK) has recently been proposed as a simple and universal classification system to determine the suitability of a particular phenotype of the knee to a specific alignment strategy for knee replacement surgery. Although racial differences may affect knee alignment, there are no reports on the racial distribution of this classification system. We aimed to clarify the distribution of CPAK classification in patients with osteoarthritis who underwent total knee arthroplasty (TKA) in Japan. Consecutive patients who underwent primary TKA were analyzed retrospectively. The knees were categorized according to the CPAK classification system which comprised of two independent variables (arithmetic hip-knee-ankle [aHKA] angle and joint-line obliquity [JLO]) with three respective subgroups to create the following nine phenotypes of the knee: type I (varus aHKA and apex distal JLO), type II (neutral aHKA and apex distal JLO), type III (valgus aHKA and apex distal JLO), type IV (varus aHKA and neutral JLO), type V (neutral aHKA and neutral JLO), and type VI (valgus aHKA and neutral JLO), type VII (varus aHKA and apex proximal), type VIII (neutral aHKA and apex proximal), and type IX (valgus aHKA and apex proximal). The distribution of the phenotypes in the Japanese population was investigated as a primary outcome. To accurately compare the results with previous studies conducted on non-Japanese patients, a sex-matched distribution was investigated as a secondary outcome. A total of 570 knees were investigated of which 500 knees were examined after exclusions. The most common distribution was type I (53.8%), followed by type II (25.4%), type III (8.2%), type IV (7.2%), type V (4.4%), and type VI (1.0%). Types VII, VIII, and IX were not distributed. The sex-matched distribution was nearly identical to the overall distribution in Japan. The majority of patients with knee osteoarthritis in Japan had medially tilted joints with constitutional varus alignment.

Ethnical Differences in Knee Phenotypes Indicate the Need for a More Individualized Approach in Knee Arthroplasty: A Comparison of 80 Asian Knees with 308 Caucasian Knees

The purpose of this study was to determine the distribution of functional knee phenotypes in a non-osteoarthritic Asian population. The Stryker Orthopaedic Modeling and Analytics (SOMA) database was searched for CT scans of the lower limb meeting the following inclusion criteria: patient age at time of image >18 and <46 years, no signs of fractures and/or previous surgery and/or degenerative changes, Asian ethnicity. A total of 80 CT scans of 40 patients were included (24 males, 16 females). The hip-knee-ankle angle (HKA), femoral mechanical angle (FMA) and tibial mechanical angle (TMA) were measured. Based on these measurements, each limb was phenotyped according to the previously introduced functional knee phenotype concept. All angles and phenotypes of the present study were compared with previously published data of a non-osteoarthritic Caucasian population (308 legs of 160 patients, 102 males, 58 females). Asian knees had a significantly lower TMA (both genders p < 0.001) but a higher FMA (males p < 0.05, females p < 0.001) than Caucasian knees but showed no difference in the HKA. Asian knees differed significantly with regard to femoral and tibial phenotypes (p < 0.01), but not with regard to limb phenotypes. The high variability of all coronal alignment parameters highlights the importance of a detailed analysis prior to TKA. Ethnical differences underline the need for a more individualized approach in TKA.

Influence of axial limb rotation on radiographic lower limb alignment: a systematic review

INTRODUCTION

The influence of limb malrotation on long-leg radiographs (LLR) is frequently discussed in literature. This systematic review aimed to describe the influence of limb rotation on alignment measurements alone and in combination with knee flexion, and determine its clinical impact.

MATERIALS AND METHODS

A literature search was conducted in June 2021 using the databases MEDLINE, Cochrane, Web of Science (Clarivate Analytics), and Embase. The search term ((radiograph OR X-ray) AND (position OR rotation) AND limb alignment) was used. Database query, record screening, and study inclusion and exclusion were performed by two reviewers independently. Experimental studies (using either specimens or synthetic bones) or clinical studies (prospective or retrospective using radiographs of patients) analyzing the influence of limb rotation on anatomic and mechanical limb alignment measurements were included. Characteristics and results of the included studies were summarized, simplified, and grouped for comparison to answer the research question. Studies were compared descriptively, and no meta-analysis was performed.

RESULTS

A total of 22 studies were included showing large heterogeneity, comprising studies with cadavers, patients, and synthetic bones. Most studies (7 out of 8) reported that external rotation (ER) causes less apparent valgus and leads to more varus and internal rotation (IR) causes more valgus and leads to less varus. However, there is no consensus on the extent of rotation influencing alignment measures. Studies reported about an average change of > 2° (n = 4) and < 2° (n = 4) hip-knee-ankle angle (HKA) between 15°IR and 15°ER. There is a consensus that the impact of rotation on mechanical alignment is higher if additional sagittal knee angulation, such as knee flexion, is present. All five studies analyzing the influence of rotation combined with knee flexion (5°-15°) showed an HKA change of > 2° between 15°IR and 15°ER.

CONCLUSION

Malrotation is frequently present on LLR, possibly influencing the measured alignment especially in knees with extension deficit. Surgeons must consider this when measuring and treating deformities (high tibial osteotomy or total knee arthroplasties), and analyzing surgical outcomes. Especially in patients with osteoarthritis with knee extension deficits or postoperative swelling, the effect of malrotation is significantly greater.

Large Individual Bilateral Differences in Tibial Torsion Impact Accurate Contralateral Templating and the Evaluation of Rotational Malalignment

OBJECTIVE

To determine individual bilateral differences (IBDs) in tibial torsion in a diverse population.

METHODS

Computed tomography scans of uninjured bilateral tibiae were used to determine tibial torsion and IBDs in torsion using 4 measurement methods. Age, sex, and self-identified race/ethnicity were also recorded for each subject. Mean tibial torsion and IBDs in torsion were compared in the overall cohort and when stratified by sex and race/ethnicity. Simple and multiple linear regression models were used to correlate demographic variables with tibial torsion and IBDs in torsion.

RESULTS

One hundred ninety-five patients were evaluated. The mean tibial torsion was 27.5 ± 8.3 degrees (range -3 to 47.5 degrees). The mean IBD in torsion was 5.3 ± 4.0 degrees (range 0-23.5 degrees, P < 0.001). 12.3% of patients had IBDs in torsion of ≥10 degrees. In the regression analysis, patients who identified as White had greater average torsion by 4.4 degrees compared with Hispanic/Latinx patients (P = 0.001), whereas age and sex were not significantly associated with absolute torsion. Demographics were not associated with significant differences in IBDs in torsion.

CONCLUSIONS

Tibial torsion varies considerably and individual side-to-side differences are common. Race/ethnicity was associated with differences in the magnitude of tibial torsion, but no factors were associated with bilateral differences in torsion. The results of this study may be clinically significant in the context of using the uninjured contralateral limb to help establish rotational alignment during medullary nail stabilization of diaphyseal tibia fractures. In addition, these findings should be considered in the evaluation of tibia rotational malalignment.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Malrotation of whole-leg radiograph less than 10 degrees does not influence preoperative planning in open-wedge high tibial osteotomy

Coronal whole-leg radiography is generally used for preoperative open-wedge high tibial osteotomy (OWHTO) planning. Nevertheless, malrotational whole-leg radiographs could affect the planning, and the effects could possibly be strengthened by the knee flexed position. Consecutive 51 varus osteoarthritis knees that underwent OWHTO were included. The digitally reconstructed radiography (DRR) images parallel to the surgical epicondylar axis (neutral rotation; NR), 5° and 10° external rotation (ER) or internal rotation (IR), were reconstructed from preoperative CT. Preoperative weight-bearing line percentage (WBL%), medial proximal tibial angle (MPTA), planned opening angle, and planned postoperative MPTA were measured with OWHTO planning in each DRR image. Correlations among the measured differences relative to NR images and knee flexion angle were investigated. As the DRR image shifted from ER to IR, the differences in preoperative WBL% and MPTA gradually increased, whereas those in the opening angle gradually decreased, although all differences in the opening angle were within 0.5° on an average. Opening angle differences remarkably correlated with knee flexion angle, and knees with >10° flexion contracture had >1° difference in 10° ER or IR images. Planned postoperative MPTA had relatively high consistency regardless of whole-leg malrotation. The opening angle measurement using malrotated radiographs less than 10° would be clinically reliable in cases without knee flexion contracture. Nevertheless, extreme care should be taken in cases with >10° knee flexion contracture. The MPTA after medial opening would be a consistent and reliable parameter in whole-leg alignment evaluation.

Healthy middle-aged Asian and Caucasian populations present with large intra- and inter-individual variations of lower limb torsion

PURPOSE

There is a lack of standardization in the measurement of lower limb torsional alignment. Normal values published in the literature are inconsistent. A 3D-CT-scan-based method was used in a healthy population to define the femoral neck version (FNV) and the tibial torsion (TT) and their relationship with demographic parameters. The study objectives were (1) to define normal values of lower limb torsional alignment, (2) to estimate inter- and intra-individual variations of torsional deformity of healthy individuals' lower limbs. The hypothesis was that FNV and TT values would be influenced by patient characteristics such as gender, age, and ethnicity, and would have low side-to-side asymmetry.

METHODS

Torsional landmarks of the lower limbs from 191 healthy subjects were automatically calculated with a 3D CT-scan-based program. The FNV was defined by the angle between the femoral neck axis and the femoral posterior condylar line. The TT angle was considered between the tibial plateau axis and the axis of the ankle. For the former, two alternatives were considered: the line connecting the more medial and lateral point of the medial and lateral plateau, respectively (method 1; TT1), or the line connecting the two more posterior points of the medial et lateral plateau (method 2; TT2). The ankle axis was defined as the line connecting the medial and lateral malleoli. These reference lines were automatically calculated. Age, gender, ethnic group, and BMI were recorded for every subject. A p value < 0.05 was considered as statistically significant.

RESULTS

Overall, the mean FNV was 15.3 ± 9.5° and the mean TT was 31.6 ± 6.3°. Female hips were more anteverted than male hips. Caucasians had less anteverted hips than Asians, but more externally rotated tibias. Age and BMI were not correlated with any anatomical parameter. A substantial side-to-side asymmetry was found for FNV [absolute difference (AD) = 6.3°; percentage of asymmetry (%As) = 47%], TT1 (AD = 3°; %As = 12%), and TT2 (AD = 4.9°; %As = 9%) (p = 0.008).

CONCLUSION

The findings showed that lower limb torsional parameters were highly variable from patient to patient and from one leg to the other for the same patient. The understanding of normal values concerning femoral version and external tibial torsion in the present healthy population will help surgeons to define pathological values of FNV and TT, as well as corrections to perform in case of torsional deformities.

LEVEL OF EVIDENCE

Level III.

Personalized alignment in total knee arthroplasty: current concepts

Traditionally in total knee arthroplasty (TKA), a post-operative neutral alignment was the gold standard. This principle has been contested as functional outcomes were found to be inconsistent. Analysis of limb alignment in the non-osteoarthritic population reveals variations from neutral alignment and consideration of a personalized or patient-specific alignment in TKA is challenging previous concepts. The aim of this review was to clarify the variations of current personalized alignments and to report their results. Current personalized approaches of alignment reported are: kinematic, inverse kinematic, restricted kinematic, and functional. The principle of “kinematic alignment” is knee resurfacing with restitution of pre-arthritic anatomy. The aim is to resurface the femur maintaining the native femoral joint line obliquity. The flexion and extension gaps are balanced with the tibial resection. The principle of the “inverse kinematic alignment” is to resurface the tibia with similar medial and lateral bone resections in order to keep the native tibial joint line obliquity. Gap balancing is performed by adjusting the femoral resections. To avoid reproducing extreme anatomical alignments there is “restricted kinematic alignment” which is a compromise between mechanical alignment and true kinematic alignment with a defined safe zone of alignment. Finally, there is the concept of “functional alignment” which is an evolution of kinematic alignment as enabling technology has progressed. This is obtained by manipulating alignment, bone resections, soft tissue releases, and/or implant positioning with a robotic-assisted system to optimize TKA function for a patient’s specific alignment, bone morphology, and soft tissue envelope. The aim of personalizing alignment is to restore native knee kinematics and improve functional outcomes after TKA. A long-term follow-up remains crucial to assess both outcomes and implant survivorship of these current concepts.

Three-Dimensionally-Printed Joint-Preserving Prosthetic Reconstruction of Massive Bone Defects After Malignant Tumor Resection of the Proximal Tibia

Joint-preserving prosthetic reconstruction for massive bone defects has the potential to be a new and revolutionary treatment option. In this paper, we discuss the case of a 30-year-old female patient who presented with pain and swelling around the knee for three months. The patient underwent this procedure. Postoperative patient satisfaction, pain scores, and range of motion results were found to be promising. We believe that this method has the potential to be the next stage in the quest for better treatment options for this condition.

Neutral alignment resulting from tibial vara and opposite femoral valgus is the main morphologic pattern in healthy middle-aged patients: an exploration of a 3D-CT database

PURPOSE

Given the goal of achieving optimal correction and alignment after knee arthroplasty or high tibial osteotomy, literature focusing on the inter-individual variability of the native knee, tibia and femur with regards to the coronal or sagittal alignment is lacking. The aim of this study was to analyse normal angular values in the healthy middle-aged population and determine differences of angular values according to inter-individual features. The first hypothesis was that common morphological patterns may be identified in the healthy middle-aged non-osteoarthritic population. The second hypothesis was that high inter-individual variability exists with regards to gender, ethnicity and alignment phenotype.

METHODS

A CT scan-based modelling and analysis system was used to examine the lower limb of 758 normal healthy patients (390 men, 368 women; mean age 58.5 ± 16.4 years) with available data concerning angular values and retrieved from the SOMA database. The hip-knee-ankle angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), posterior distal femoral angle (PDFA), posterior proximal tibial angle (PPTA) and non weight-bearing joint line convergence angle (nwJLCA) were then measured for each patient. Results were analysed for the entire cohort and based on gender, ethnicity and phenotype.

RESULTS

The mean HKA was 179.4° ± 2.6°, LDFA: 85.8° ± 2.0°, MPTA: 85.6° ± 2.4°, PDFA: 85.2° ± 1.5°, PPTA: 83.8° ± 2.9° and nwJLCA: 1.09° ± 0.9°. Gender was associated with higher LDFA and lower HKA for men. Ethnicity was associated with greater proximal tibial vara and distal femoral valgus for Asian patients. Patients with an overall global varus alignment had more tibia vara and less femoral valgus than patients with an overall valgus alignment.

CONCLUSION

Even if significant differences were found based on subgroup analysis (gender, ethnicity or phenotype), this study demonstrated that neutral alignment is the main morphological pattern in the healthy middle-aged population. This neutrality is the result from tibia vara compensated by an ipsilateral femoral valgus.

LEVEL OF CLINICAL EVIDENCE

III, retrospective cohort study.

Medio-Lateral and Flexion-Extension Gap Imbalances in Mechanically Aligned Total Knee Arthroplasty Using Measured Resection Technique in Korean Patients: 3D Simulation

Background: It is well known that the measured resection (MR) technique in mechanically aligned (MA) total knee arthroplasty (TKA) generates significant gap imbalances, but little is known about whether this applies to the knees of Asian patients. The aim of this study was to evaluate the medio-lateral and flexion-extension gap imbalances and to find the most optimal posterior femoral condyle resection method for operating on the knees of Asian patients. Methods: In total, 738 magnetic resonance imaging (MRI) scans of consecutive patients who underwent TKA were obtained. Four posterior femoral condylar resection methods were used: alignment by the surgical transepicondylar axis (TEA), Whiteside’s line (WSL), 3° external rotation to the posterior condylar axis (PCA), and flexion-extension axis (FEA). Results: For the medial compartments, there were significant differences between the flexion and extension gaps in the varus knee group in all four methods, but there were no differences between the flexion and extension gaps in the valgus knee group. For the lateral compartment, all the methods showed significant differences except for WSL of the valgus knee group and FEA of the varus knee group. Conclusions: In Asian patients, the use of the MA MR technique inevitably leads to medio-lateral or flexion-extension imbalances. Therefore, surgeons should consider which methods can minimize imbalances and choose the best method within the technically possible range.

Mismatched knee implants in Indonesian and Dutch patients: a need for increasing the size

PURPOSE

The aim of this study was to evaluate the anthropometric differences between knees of Indonesian Asians and Dutch Caucasians and the fit of nine different knee implant systems.

METHODS

A total of 268 anteroposterior (AP) and lateral knee preoperative radiographs from 134 consecutive patients scheduled for total knee arthroplasty at two different centres in Jakarta and Leiden were included. Both patient groups were matched according to age and sex and included 67 Asians and 67 Caucasians. We assessed the radiographic differences between the Asian and Caucasian anthropometric data. The dimensions of the nine knee implant designs (Vanguard, Genesis II, Persona Standard, Persona Narrow, GK Sphere, Gemini, Attune Standard, Attune Narrow, and Sigma PFC) were compared with the patients' anthropometric (distal femur and proximal tibia) measurements.

RESULTS

The Dutch Caucasian patients had larger mediolateral (ML) and AP femoral and tibial dimensions than the Indonesian Asians. The aspect ratios of the distal femur and tibia were larger in Asians than in Caucasians. The AP and ML dimensions were mismatched between the tibial components of the nine knee systems and the Asian anthropometric data. Both groups had larger ML distal femoral dimensions than the knee systems.

CONCLUSION

Absolute and relative differences in knee dimensions exist not only between Asian and Caucasian knees but also within both groups. Not all TKA systems had a good fit with the Asian and Caucasian knee phenotypes. An increase in the range of available knee component sizes would be beneficial, although TKA remains an adequate compromise.

LEVEL OF EVIDENCE

III.

Tibial Torsion and Patellofemoral Pain and Instability in the Adult Population: Current Concept Review

PURPOSE OF REVIEW

Tibial torsion is a recognized cause of patellofemoral pain and instability in the paediatric population; however, it is commonly overlooked in the adult population. The aim of this review article is to summarize the current best evidence on tibial torsion for the adult orthopaedic surgeon.

RECENT FINDINGS

The true incidence of tibial torsion in the adult population is unknown, with significant geographical variations making assessment very difficult. CT currently remains the gold standard for quantitatively assessing the level of tibial torsion and allows assessment of any associated femoral and knee joint rotational anomalies. Surgical correction should only be considered after completion of a course of physiotherapy aimed at addressing the associated proximal and gluteal weakness. Tibial torsion greater than 30° is used as the main indicator for tibial de-rotation osteotomy by the majority of authors. In patients with associated abnormal femoral rotation, current evidence would suggest that a single-level correction of the tibia (if considered to be a dominant deformity) is sufficient in the majority of cases. Proximal de-rotational osteotomy has been more commonly reported in the adult population and confers the advantage of allowing simultaneous correction of patella alta or excessive tubercle lateralization. Previous surgery prior to de-rotational osteotomy is common; however, in patients with persistent symptoms surgical correction still provides significant benefit. Tibial torsion persists into adulthood and can play a significant role in patellofemoral pathology. A high index of suspicion is required in order to identify torsion clinically. Surgical correction is effective for both pain and instability, but results are inferior in patients with very high pain levels pre-surgery and multiple previous surgeries.

Impact of joint line orientation on clinical outcomes in bilateral Oxford mobile-bearing unicompartmental knee arthroplasty

BACKGROUND

Joint line orientation angle (JLOA) is the angle between the knee joint line and the floor. It has been reported to be related to postoperative outcome after TKA. Regarding unicompartmental knee arthroplasty (UKA), although it can be horizontal after UKA because it is a resurfacing surgery, there are few reports about the JLOA after UKA and its impact on clinical outcomes.

PURPOSE

The purpose of this study was to reveal the relationship between JLOA and clinical outcome after UKA.

METHODS

This study included 106 knees in 53 consecutive patients with osteoarthritis who underwent simultaneous bilateral mobile-bearing UKA. Their pre- and postoperative JLOAs were measured by full-leg-length standing coronal radiographs. We also evaluated the tibial component height (TCH) as the factor which we assumed could influence JLOA. We analyzed the patients' JLOAs, TCHs and clinical outcomes.

RESULTS

Pre- and postoperative JLOA were 0.4 ± 2.4° and 2.7 ± 2.6°, respectively. The JLOA significantly tilted medially (P < 0.0001). The JLOA significantly negatively correlated with the improvement of the clinical outcomes (Oxford Knee Score (OKS): r = 0.40, P < 0.0001, Knee Society Knee Score (KSKS): r = 0.25, P < 0.01, Knee Society Function Score (KSFS): r = 0.22, P = 0.02). The TCH showed a positive correlation with postoperative JLOA and with the postoperative JLOA change (r = 0.45, P < 0.001; r = 0.25, P < 0.01, respectively).

CONCLUSION

The JLOA significantly tilted medially after UKA. An excessive medial tilt of the JLOA was associated with poorer postoperative outcomes of UKA. It is therefore recommended to keep the JLOA horizontal and to avoid a lower tibial cut.

Internal tibial torsion is related to syndesmosis injury in a large osteological collection

BACKGROUND

The long-term consequences of tibial torsion remain unclear. This study evaluated whether syndesmotic injuries are associated with tibial torsion.

METHODS

A collection of over 3000 cadaveric skeletons was screened for irregular bony prominence along the lateral distal tibia, consistent with previous syndesmosis injury. Tibial torsion was measured and compared to 1034 control cadaveric tibiae.

RESULTS

Mean torsion of 236 specimens with syndesmotic injury was 6.2±8.9 degrees, while that of control specimens was 7.9±8.8 degrees (P = 0.008). Multiple regression analysis showed a non-statistically significant trend toward internal torsion and syndesmotic injury (standardized beta=-0.051, P=0.059). Syndesmosis injury was present in 48/200 specimens (24.0%) with internal torsion and 31/199 specimens (15.6%) with external torsion (P=0.035).

CONCLUSION

This association between internal tibial torsion and syndesmotic injury suggests that internal tibial torsion might not be an entirely benign condition and merits further study.

Editorial Commentary: Revision Anterior Cruciate Ligament Surgery, Unlike Cheese, Is Not Improved With Age but Nationality and Culture May Matter

Recurrent instability and future joint damage occur if there is a repeated anterior cruciate ligament injury after reconstruction. This prognostic declaration is said to those who have sustained a rupture to the repaired anterior cruciate ligament. Both younger and older patients seek stable knees to allow a return to stability and twisting activity without the risk of added joint damage. To achieve this goal, revision ligament surgery is needed.

Increasing hospital admissions for patellar instability: a national database study from 2004 to 2017

Objectives: Epidemiology of patellar instability is not fully characterized, as some studies have produced conflicting information or been drawn from limited populations. In this study, we used the Pediatric Health Information System (PHIS) database to examine trends in admissions for patellar instability throughout the United States. We hypothesized that there would be an increasing rate of patellar instability admissions in recent years. Secondarily, we examined how demographic factors and insurance status relate to admissions for patellar instability.Methods: This study queried the Pediatric Health Information System (PHIS). Patients with ICD 9 & 10 codes 8363, 8364, 71,785, M221.0, S83.001, S83.002, S83.003, S83.004, S83.005, and S83.006, were abstracted from PHIS. We included all patients admitted with patellofemoral dislocations that were reported in the PHIS database between 1 January 2004 and 30 April 2017. The rate of patellar instability admissions was examined as well as demographic factors and insurance status.Results: An estimated total of 25,413 admissions for patellar instability were identified by the search of the PHIS database; 15,444 (60.8%) were female patients and 9,966 (39.2%) were male. The adjusted number of admissions per reporting hospital significantly increased over the years studied (r = 0.775, p < 0.001), from 14.5 admissions per reporting hospital in 2004 to 86.0 admissions per reporting hospital in 2016. Of all patellar instability admissions, 55.0% were white, 20.4% were black, 1.7% were Asian, and 22.9% were unknown race. A larger number of admissions occurred in patients with insurance status other than Medicaid in every year data were collected.Conclusions: Based on a PHIS database search, pediatric hospital admissions for patellar instability are steadily increasing. The majority of patients admitted for patellar instability are female, white, and have insurance other than Medicaid. Males admitted for patellar instability tended to be older than females admitted for the same.Level of evidence: II.

The Medial Eminence Line for Predicting Tibial Fracture Risk after Unicompartmental Knee Arthroplasty

Backgroud

Tibial fracture after cementless Oxford unicompartmental knee arthroplasty (OUKA) is a rare but serious complication. It is reported more frequently in Asian countries. The aim of this retrospective study was to assess the morphological characteristics of the tibia by using a simple novel measurement method in patients with tibial fractures after OUKA.

Methods

Six knees (all women) with tibial fractures after cementless OUKA (fracture group) and 150 knees without an obvious complication after cementless OUKA (control group) were examined retrospectively at our institution between January 2016 and April 2017. We drew a medial eminence line (ME line) defined as a line extending from the tip of the medial intercondylar eminence parallel to the tibial axis. The ME line was classified into two types (intramedullary type [type I] and extramedullary type [type E]), and the proportion of each type was compared between fracture patients and controls.

Results

In the fracture group, there were four (66.7%) type E cases and two (33.3%) type I cases; in the control group, there were 18 (12%) type E cases and 132 (88%) type I cases. Fisher exact tests showed that the proportion of type E was higher in the fracture group than in the control group (p < 0.01).

Conclusions

Measurement of the ME line can be recommended as a useful method to assess the risk of postoperative fracture after cementless OUKA.

Revisiting the tibial crest as reference for the mechanical alignment of the tibial component in total knee arthroplasty: a cadaveric study on Caucasian tibiae

PURPOSE

The accuracy of the tibial crest (TC) in guiding the mechanical alignment of the tibial component in total knee arthroplasty (TKA) has been investigated in a few studies on Asian patients. No study analyzed the anatomical variants of the TC. We analyzed the morphological types of the TC in cadaveric tibiae of Caucasian subjects and assessed whether the TC may be considered an accurate guide for the mechanical alignment of the tibial component in TKA.

METHODS

The TC and mechanical axis (MA) were identified in 86 dried cadaveric tibiae by placing metal landmarks along the TC course and a guidewire overlapping the MA. Coronal view radiographs were taken in different positions of tibial axial rotation, and the relationships between the TC and MA were analyzed.

RESULTS

The TC showed three different patterns, comprising a curved, mixed and straight course in 47 (54.6%), 21 (24.4%) and 18 (20.9%) tibiae, respectively. When a curved course was found, the TC intersected the MA at proximal and distal points located, on average 22.4% and 63.3% along the tibial length, respectively. When a straight course was found, the mean angle between the TC and MA was 2.9°. In 35% of the cases, the two axes differed by more than 3°.

CONCLUSION

The TC of Caucasian subjects exhibits a marked variability in its course and relationship with the MA. Unlike the TC in Asian subjects, the TC of Caucasians cannot be considered an accurate anatomical reference to guide the coronal alignment of the tibial component in TKA.

Improving the accuracy of tibial component placement during total knee replacement in varus knees with tibial bowing: A prospective randomised controlled study

BACKGROUND

Lateral tibial bowing leads to varus placement of the tibial component during total knee replacement in varus knees. Lateralised tibial jig placement can improve the accuracy of the tibial cut.

METHODS

A total of 227 patients (300 knees) undergoing total knee replacements were randomised into two groups. In the study group, the point of intersection of the distal tibial diaphyseal line at the tibial plateau drawn on long films was represented by zones. Knees with femoral bowing >5° (28%) were excluded. Tibial jig placement on the proximal tibia was lateralised according to the zones. In the control group, the mid-point of the tibial plateau was taken as a reference. Femoral and tibial bowing, postoperative limb alignment and component placement were assessed.

RESULTS

Of the 216 knees that were studied, 106 were in the study group and 110 in the control group. Bowing ≥3° had a significant positive correlation with lateralisation of the proximal tibial reference (p < 0.001). The Incidence of tibial bowing ≥3° was 57.33%. The mean postoperative hip-knee-ankle (HKA) angle was 178.31 ± 2.88° and 176.53 ± 2.88° (p < 0.001), whereas the mean medial proximal tibial angle (MPTA) was 89.91 ± 1.42° and 88.79 ± 1.72° (p < 0.001) in the study and control groups, respectively. Considering bowed tibiae alone, HKA angle and MPTA in the study group were 178.08 ± 2.81° and 89.72 ± 1.39° compared with 175.88 ± 2.87° and 88.38 ± 1.38° in the control group (p < 0.001).

CONCLUSION

There is a high incidence of tibial bowing in varus knees. Lateralised tibial jig placement improved tibial component placement and postoperative limb alignment in total knee arthroplasty in varus knees with tibial bowing.

Phenotyping of hip-knee-ankle angle in young non-osteoarthritic knees provides better understanding of native alignment variability

PURPOSE

There is a lack of knowledge about the native coronal knee alignment in 3D. The currently used classification system (neutral, valgus and varus) oversimplifies the coronal knee alignment. The purpose of this study was therefore (1) to investigate the coronal knee alignment in non-osteoarthritic knees using 3D-reconstructed CT images and (2) to introduce a classification system for the overall knee alignment based on phenotypes.

METHODS

The hospital registry was searched for patients younger than 45 years and older than 16, who received a CT according to the Imperial Knee Protocol. Patients with prosthesis, osteoarthritis, fractures or injury of the collateral ligaments were excluded. Finally, 308 non-osteoarthritic knees of 160 patients remained (102 males and 58 females, mean age ± standard deviation (SD) 30 ± 7 years). The overall lower limb alignment was defined as the hip-knee-ankle angle (HKA), which is formed by lines connecting the centers of the femoral head, the knee and the talus. The angle was measured using a commercially planning software (KneePLAN 3D, Symbios, Yverdon les Bains, Switzerland). Descriptive statistics, such as means, ranges, and measures of variance (e.g., standard deviations) are presented. Based on these results, the currently used classification system was evaluated and a new system, based on phenotypes, was introduced. These phenotypes consist of a phenotype-specific mean value (a HKA value) and cover a range of ± 1.5° from this mean (e.g., 183° ± 1.5°). The mean values represent 3° increments of the angle starting from the overall mean value (mean HKA = 180°; 3° increments = 183° and 177°, 186° and 174°). The distribution of these limb phenotypes was assessed.

RESULTS

The overall mean HKA was 179.7° ± 2.9° varus and values ranged from 172.6° varus to 187.1° valgus. The mean HKA values for male and female were 179.2° ± 2.8° and 180.5° ± 2.8°, respectively, which implied a significant gender difference (r² = 0.23). The most common limb phenotype in males was NEU_HKA0° (36.4%), followed by VAR_HKA3° (29.2%) and VAL_HKA3° (23.1%). The most common limb phenotype in females was NEU_HKA0° (36.4%), followed by VAL_HKA3° (22.1%) and VAR_HKA3° (15.0%).

CONCLUSION

The measurements using 3D-reconstructed CT images confirmed the great variability of the overall lower limb alignment in non-osteoarthritic knees. However, the currently used classification system (neutral, varus, valgus) oversimplifies the coronal alignment and therefore the introduced classification system, based on limb phenotypes, should be used. This will help to better understand individual coronal knee alignment.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Functional knee phenotypes: a novel classification for phenotyping the coronal lower limb alignment based on the native alignment in young non-osteoarthritic patients

PURPOSE

The currently used system to classify the lower limb alignment (neutral, varus, valgus) does not consider the orientation of the joint line or its relationship to the overall lower limb alignment. Similarly, current total knee arthroplasty (TKA) alignment concepts do not sufficiently consider the variability of the native coronal alignment. Therefore, the purpose of this study was (1) to introduce a new classification system for the lower limb alignment, based on phenotypes, and (2) to compare the alignment targets of different TKA alignment concepts with the native alignment of non-osteoarthritic patients.

METHODS

Two recent articles phenotyped the lower limb, the femur and tibia of 308 non-osteoarthritic knees of 160 patients [male to female ratio = 102:58, mean age ± standard deviation 30 ± 7 years (16-44 years)]. The present study introduces functional knee phenotypes, which are a combination of all previously introduced phenotypes. The functional knee phenotypes therefore enable an evaluation of all parameters in relation to each other and thus a comprehensive analysis of the coronal alignment. The existing functional knee phenotypes in the female and male population were investigated. In addition, how many non-osteoarthritic knees had an alignment within the range of current TKA alignment targets (mechanical, anatomical and restricted kinematic alignment) was investigated. Therefore, it was defined which functional knee phenotypes represented a target of the TKA alignment concepts and which percentage of the population had such a phenotype.

RESULTS

Out of 125 possible functional knee phenotypes, 43 were found (35 male, 26 and 18 mutual). The most common functional knee phenotype in males was NEU_HKA0° + NEU_FMA0° + NEU_TMA0° (19%), followed by VAR_HKA3° + NEU_FMA0° + VAR_TMA0° (8.2%). The most common functional knee phenotype in females was NEU_HKA0° + NEU_FMA0° + NEU_TMA0° (17.7%), closely followed by NEU_HKA0° + NEU_FMA0° + VAL_TMA0° (16.6%). The functional knee phenotype representing a mechanical alignment target was found in 5.6% of the males and 3.6% of the females. The phenotype representing an anatomical alignment target was found in 18% of the males and 17% in females. Five of the nine phenotypes representing a restricted kinematic alignment target were found in this population (male 5, female 4, mutual 4). They represented 31.3% of all males and 45.1% of all females.

CONCLUSION

A more individualized approach to TKA alignment is needed. The functional knee phenotypes enable a simple, but detailed assessment of a patient's individual anatomy and thereby could be a helpful tool to individualize the approach to TKA.

LEVEL OF CLINICAL EVIDENCE

III, retrospective cohort study.

Native non-osteoarthritic knees have a highly variable coronal alignment: a systematic review

PURPOSE

Coronal alignment of the knee is defined by the hip-knee-ankle angle (HKA), the femoral mechanical angle (FMA), the tibial mechanical angle (TMA), and the joint line convergence angle (JLCA). To date, there is still a lack of knowledge about the variability of native coronal knee alignment. The purpose of this paper is to present a systematic review of the current literature about the variability of coronal knee alignment (HKA, FMA, TMA, and JLCA) in non-osteoarthritic knees.

METHODS

The electronic databases MEDLINE, EMBASE, and Google Scholar were searched from database inception to search date (November 1, 2018) and screened for relevant studies. The PRISMA guidelines were followed. Inclusion criteria were studies that reported the coronal alignment of the native, non-osteoarthritic knee.

RESULTS

A total of 15 studies met the inclusion criteria. Thirteen studies performed the measurements on weight-bearing long-leg standing radiographs (LLR), one study used MRI, and one study used the EOS imaging system. The mean HKA ranged from 176.7° ± 2.8° (male) to 180.7° (female). The mean FMA ranged from 92.08° ± 1.78° (female) to 97.2° ± 2.7° (female). The mean TMA ranged from 84.6° ± 2.5° (female) to 89.6° (female). The mean JLCA ranged from - 0.47° ± 0.98° (male) to - 1.9° ± 1.4° (female).

CONCLUSION

This systematic review provides a detailed overview about the variability of the coronal knee alignment in non-osteoarthritic knees. The broad variability of all coronal alignment parameters highlights the necessity for a more anatomic and individualized approach in knee arthroplasty. It also offers the fundament to understand the changes in osteoarthritic knees.

LEVEL OF CLINICAL EVIDENCE

Systematic review, Level IV.

Phenotyping the knee in young non-osteoarthritic knees shows a wide distribution of femoral and tibial coronal alignment

PURPOSE

There is a lack of knowledge about the joint line orientation of the femur and tibia in non-osteoarthritic knees. The primary purpose of the present study was to evaluate the orientation of the joint lines in native non-osteoarthritic knees using 3D-reconstructed CT scans. The secondary purpose was to identify knee phenotypes to combine the information of the femoral and tibial alignment.

METHODS

A total of 308 non-osteoarthritic knees of 160 patients (male to female ratio = 102:58, mean age ± standard deviation 30 ± 7 years (16-44 years) were retrospectively included from our registry. All patients received CT of the knee according to the Imperial Knee Protocol. The orientation of the femoral and tibial joint line was measured in relation to their mechanical axis (femoral mechanical angle, FMA, and tibial mechanical angle, TMA) using a commercially planning software (KneePLAN 3D, Symbios, Yverdon les Bains, Switzerland). The values of FMA and TMA were compared between males and females. Descriptive statistics, such as means, ranges, and measures of variance (e.g. standard deviations), were presented. Based on these results, phenotypes were introduced for the femur and tibia. These phenotypes, based on FMA and TMA values, consist of a mean value and cover a range of ± 1.5° from this mean (3° increments). The distribution of femoral and tibial phenotypes, and their combinations (knee phenotypes) were calculated for the total group and for both genders.

RESULTS

The overall mean FMA ± standard deviation (SD) was 93.4° ± 2.0° and values ranged from 87.9° varus to 100° valgus. The overall mean TMA ± SD was 87.2° ± 2.4° with a range of 81.3° varus to 94.6° valgus. FMA and TMA showed significant gender differences (p < 0.01). Females showed more valgus alignment than males. The most common femoral phenotype was neutral in both genders. The most common tibial phenotype was neutral in the male knees (62.8%) and valgus (41.6%) in the female knees. In males, the most frequent combination (knee phenotype) was a neutral phenotype in the femur and a neutral phenotype in the tibia (25.6%). In females, it was a neutral femoral phenotype and a valgus tibial phenotype (28.3%).

CONCLUSION

3D-reconstructed CT scans confirmed the great variability of the joint line orientation in non-osteoarthritic knees. The introduced femoral and tibial phenotypes enable the evaluation of the femoral and tibial alignment together (knee phenotypes). The variability of knee phenotypes found in this young non-osteoarthritic population clearly shows the need for a more individualized approach in TKA.

LEVEL OF EVIDENCE

III.

The native coronal orientation of tibial plateaus may limit the indications to perform a kinematic aligned total knee arthroplasty

PURPOSE

To investigate the coronal alignment of tibial plateaus in normal and osteoarthritic knees and to simulate the effects of a tibial cut performed in total knee arthroplasty (TKA) using a kinematic alignment technique with standard instrumentation.

METHODS

The coronal alignment of tibial plateaus was measured in three groups including group 1 (reference group), 50 cadaveric tibiae showing no evidence of degenerative changes of tibial plateaus; group 2, 49 patients who underwent MR of the knee, showing no or mild degenerative changes of the knee joint and, group 3, 54 patients with knee osteoarthritis who underwent computer-assisted total knee arthroplasty.

RESULTS

The coronal alignment of tibial plateaus averaged 2.4° with no significant differences between groups. The mean coronal orientation of tibial plateaus was 3° ± 2° in men and 1.6° ± 2° in women (p = 0.03). A coronal alignment of tibial plateaus of 3° or more was found in 69 cases (45%) and 5° or more in 23 (14.7%). The simulation of a tibial cut performed with an error of 3° in varus in 15% of the subjects showing a native coronal orientation of tibial plateaus of 3° or more, led to a final tibial cut greater 6° in 13.7% of cases.

CONCLUSIONS

A coronal alignment of tibial plateaus of 3° or more in varus was found in near half of normal subjects and osteoarthritic patients. A preoperative measurement of the coronal alignment of tibial plateaus is advisable in any patients scheduled for kinematic aligned TKA. As errors in the alignment of the tibial component of 3° or more may occur using standard instrumentations, the results of this study raise questions on performing a kinematic aligned TKA with standard instrumentations.

LEVEL OF EVIDENCE

IV.