Anthropometry of the proximal tibia to design a total knee prosthesis for the Japanese population

Arthroscopic debridement improves range of motion for heterotopic ossification after total knee replacement: a retrospective cohort study

The presence of heterotopic ossification (HO) after primary total knee replacement (TKR) is rare and associated with limited mobility and stiffness of the knee. This study aimed to identify if the arthroscopic debridement after TKR could decrease HO and improve the function and range of motion. Thirty HO patients after TKR were retrospectively separated into 2 cohorts. 15 patients of group A accepted the arthroscopic debridement, while 15 patients of group B only had non-operative treatment, mainly including oral nonsteroidal anti-inflammatory drugs (NSAIDs) and rehabilitative treatment. Visual analog scale (VAS) scores, knee society knee scores (KSS), range of motion (knee flexion and knee extension) were obtained before treatment and at 1 month, 3 months, and 6 months after treatment. Radiography of after-treatment was also evaluated to assess the changes in HO. There were 3 males and 27 females with a mean age of 67.4 ± 0.8 years in group A and 68.2 ± 1.3 in group B. The onset time of HO was 3-6 months. The maximum size of the ossification was < 2 cm in 23 knees, 2 cm < heterotopic bone < 5 cm in 6 knees and > 5 cm in 1 knee. The size of HO decreased gradually in all knees by X-ray film at the last follow-up. There were no significant differences in VAS scores after replacement between two groups (p > 0.05). The average range of motion preoperatively in group A was - 15.2-90.6°, which postoperatively increased to - 4.2-110.0°. Meanwhile, the KSS scores and average range of motion of the group A were better than those of the group B at each follow-up time after treatment. Arthroscopic debridement can decrease HO seen from postoperative X-rays, improve the function and range of motion, as well as the pain remission between two groups are comparable. Consequently, arthroscopic resection of HO after TKR is recommended as soon as there is aggravating joint stiffness.

Sexual dimorphism of the posterior condylar offset of the femur and the medial posterior slope of the tibia in non-arthritic knees of Egyptian adults: an MRI study

BACKGROUND

The aim of this magnetic resonance imaging (MRI) study was to investigate controversial sexual dimorphism of the posterior condylar offset of the femur (the offset) and the posterior slope of the tibia (the slope) in non-arthritic knees of Egyptian adults.

METHODS

On 100 male and 100 female MRIs of non-arthritic knees, linear measurements of the distal part of the femur (the offset) and the angular measurements of the proximal part of the tibia (the slope) were performed and compared regarding sex and ethnicity. The intraclass correlation coefficient (ICC) was used to test the interrater agreement.

RESULTS

Both offsets and the lateral offset ratio were larger in males (p < 0.001), the medial offset ratio, and the medial slope in females (p from < 0.001 to 0.007), whereas the lateral slope was sex-free (p = 0.41). Irrespective of sex, however, the medial offset with its ratio, and the medial slope were larger than their counterparts (p < 0.001). Our means of the offsets, their ratios, and the slopes mostly differed from those of other ethnicities (p from ≤ 0.001 to 0.004). ICCs > 0.8 proved MRI's precision was high.

CONCLUSION

There was a sexual dimorphism of both the offset and the medial slope in non-arthritic knees of Egyptian adults. We believe future designs of knee implants should consider these differences in order to improve postoperative range of motion and patients' satisfaction after total knee arthroplasty. Level of evidence Level III Retrospective Cohort Study. Trial registration ClinicalTrials.gov identifier: NCT03622034, registered on July 28, 2018.

Reappraisal of the proximal tibia anatomy in Turkish population

OBJECTIVE

Total knee arthroplasty has been popular in recent years. Morphometry of proximal tibia is important for surgeons to perform successful total knee arthroplasty. Aim of this study was to reappraise the proximal tibia morphometry.

METHODS

In this study, 57 human dry tibia were evaluated. Anteroposterior and mediolateral dimensions of tibial condyles, maximum width of superior articular surface and length of tibia were measured. Furthermore, morphometric measurements of the intercondylar area and Gerdy's tubercle (infracondylar tibial tubercle) were done. All measurements were performed by two observers using a digital caliper.

RESULTS

Mean anteroposterior and mediolateral dimensions of medial tibial condyle were found 39.76 and 23.27 mm, respectively. Mean anteroposterior and mediolateral dimensions of lateral tibial condyle were measured 34.72 and 21.83 mm, respectively. Mean anteroposterior dimension of intercondylar area was 41.62 mm. Shape of the Gerdy's tubercle was oval in 76.8%, irregular in 12.5%, and triangular in 10.7%. Texture of the tubercle was smooth in 85.7% and rough in 14.3%. Mean superoinferior and mediolateral dimensions of Gerdy's tubercle were 12.28 and 10.27 mm, respectively. Anteroposterior and mediolateral dimensions of tibial condyles were significantly higher (p < 0.05) for the medial condyle. Positive and statistically significant correlations were found between the tibial length and the other parameters (p < 0.05, r > 0.40).

CONCLUSION

The morphometric data of tibial plateau are important for surgeons during total knee arthroplasty. The superoinferior and mediolateral dimensions of the Gerdy's tubercle, the distance between Gerdy's tubercle and tibial tuberosity, the distance between Gerdy's tubercle and lateral tibial plateau were measured for the first time in our study. The data obtained from this study can be used as a guideline in designing tibial component of the total knee prosthesis in Turkish population. In arthroplasty, patient-specific prosthetic implants may eradicate implant mismatch in the near future.

Evaluation of Anthropometric Measurements of the Aspect Ratio of Knee in Indian Population and its Correlation with the Sizing of Current Knee Arthroplasty System

BACKGROUND

Most of the commercially available TKR implants are designed for western populations, which are known to have larger build and stature compared to Asian counterparts often leading to mismatch between resected bony surfaces and implant components. There is paucity of morphometric data of distal femur and proximal tibia in the Indian population. Thus, it becomes important to obtain anthropometric data to achieve the best stability and long-term success of implant.

MATERIALS AND METHODS

Intraoperative morphological measurements of 100 knees (59 female and 41 males) were done using vernier calliper during TKR. The anteroposterior (AP) and mediolateral (ML) dimensions of cross-section of the femur and tibia were noted before bony resection. The aspect ratios were calculated and compared with that of implant used (DePuy, Stryker, Maxx).

RESULTS

We have found that Indian males have larger dimensions of distal femur as well as proximal tibia than females. There exists some degree of mismatch in patients' dimensions and the sizes of all the three commercially available implant system as well their aspect ratios.

CONCLUSION

Specific designing of implants with dimensions in accordance with the morphometric measurements of Indian population should be done. Also gender specific implant designing should be done.

Does One Size Really Fit All? Morphometric Analysis of Distal Femur and Proximal Tibia in an Ethnic Indian Population and Correlation to the Sizing of Existing Total Knee Arthroplasty Implants

BACKGROUND

Total knee arthroplasty (TKA) has been proven to be a highly efficacious procedure for patients with end-stage osteoarthritis who have persistent symptoms not managed by conservative treatment. A large percentage of standard commercially available total knee arthroplasty (TKA) implants are imported and designed based on morphometric data of Western populations, which are known to have a larger build compared to their Asian counterparts. Hence, these prostheses may sometimes not be the best fit for Indian patients. We conducted this study to examine the anthropometry of osteoarthritic knees of Indian patients, analyze anatomical differences between males and females, and compare these measurements with commercially available five TKA implants.

METHODS

Morphometric data were collected from 150 Indian patients with osteoarthritis of the knee using computed tomography (CT) scans. The mediolateral (ML) and anteroposterior (AP) dimensions of the distal femur and proximal tibia were measured, and aspect ratios (ML/AP) were calculated. These measurements were correlated with current commercially available implant sizes.

RESULTS

We examined CT scans of 100 female and 50 male patients' knees with a combined average age of 58.2 ± 7.5 years. The mean mediolateral and anteroposterior dimensions of the distal femur for Indian knees were 74.5 ± 5.8 mm and 58.0 ± 4.2 mm, respectively, whereas for the proximal tibia, 69.1 ± 5.5 mm and 43.8 ± 3.6, respectively. The mean aspect ratio for the femur was 129.0 ± 6.0 and for the tibia was 158.1 ± 9.1. Male dimensions were found to be greater than female dimensions in all measured aspects of the distal femur and proximal tibia for the Indian population. However, the aspect ratio of the tibia was not found to vary with gender. When compared with the dimensions of other ethnic groups, the size of Indian knees was found to be smaller than Caucasians.

CONCLUSIONS

There is a mismatch between the anatomy of Indian knees and currently available TKA implants, and these implants may have drawbacks when implanted in Indian patients. The obtained anthropometric data may provide useful directions for designing TKA implants of more suitable sizes and aspect ratios for Indian patients.

Early Results of Bone-Conserving High Flexion Posterior-Stabilized Total Knee System in Indian Population

Background

A number of total knee arthroplasty (TKA) systems are used across a variety of markets in which outcome will be influenced by patient factors, surgical technique and implant characteristics. The aim of the current study was to report the early functional results of a primary TKA system in support of the component design characteristics adapted for achieving increased functional expectations of the patients.

Materials and Methods

A prospective, continuous series of 304 primary posterior-stabilized (PS) TKAs were performed in 208 patients by a single surgeon. Inclusion criterion was patients undergoing primary TKA with Freedom Total Knee system and willing to participate in the study. Exclusion criteria were patients undergoing revision TKA, patients not willing to participate and patients who were lost to follow-up. Patients were clinically and radiologically assessed for a minimum of 5 years post-operatively. Oxford Knee score (OKS) and range of motion (ROM) were assessed for the entire study population and by gender.

Results

There were no patients who were lost to follow-up. Two patients (Two knees) required incision and secondary suturing for superficial skin wound complication. At minimum 5-year follow-up, there was no radiographic evidence of component loosening/failure. Clinical evaluation at 5 years post-operatively showed statistically significant increase in the OKS and ROM as compared to pre-operative values (OKS pre-operative 19.27 ± 1.86, post-operative 38.76 ± 1.5, p value < 0.001, ROM pre-operative 94.57 ± 3.49, post-operative 127.69 ± 3.65, p value < 0.001). There was no statistically significant difference in the clinical outcome between male and female genders as well as between unilateral and bilateral TKA.

Conclusion

The study showed encouraging early results for the bone-conserving high flexion TKA system in 208 patients at minimum 5-year follow-up. The adapted design characteristics for improved functional expectations are confirmed in this reported Indian population study group cohort. Further continued evaluation is warranted for this primary TKA system across Indian and other ethnic population.

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.

Sexual dimorphism and racial diversity render bone-implant mismatch inevitable after off-the-shelf total knee arthroplasty: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to investigate the variability in femoral geometric ratios among knees of different sexes and races, and to appreciate whether the observed variability is accommodated by commonly implanted total knee arthroplasty (TKA) components. The hypothesis was that the anthropometric studies report considerable variability of femoral geometric ratios among sexes and races.

METHODS

This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) criteria. Two authors independently conducted an electronic search using MEDLINE^® and Embase^® on 6 July 2020 for clinical studies reporting on femoral geometric ratios among sexes and races. Femoral geometric ratios were graphically represented as means and 2 standard deviations, and compared to those of 13 commonly implanted femoral components.

RESULTS

A total of 15 studies were identified that reported on a combined total of 2627 knees; all reported the aspect ratio, and 2 also reported the asymmetry ratio and trapezoidicity ratio. Men had wider knees than women, and compared to Caucasian knees, Arabian and Indian knees were wider, while East Asian were narrower. There were no differences in asymmetry ratio between men and women, nor among Caucasian and East Asian knees. Men had more trapezoidal knees than women, and East Asian knees were more trapezoidal than Caucasian knees. The commonly implanted femoral components accommodated less than a quarter of the geometric variability observed among sexes and races.

CONCLUSION

Anthropometric studies reported considerable sexual dimorphism and racial diversity of femoral geometric ratios. Since a surgeon generally only uses one or a few TKA brands, bone-implant mismatch remains unavoidable in a large proportion of knees. These findings support the drive towards personalized medicine, and accurate bone-implant fit may only be achievable through customisation of implants, though the clinical benefits of custom TKA remain to be confirmed.

LEVEL OF EVIDENCE

IV.

Investigation of morphotypes of the knee using cluster analysis

BACKGROUND

Objects that manifest in several characteristic shapes, or morphotypes, are typically caused by some hidden variable. For example, the gender of a person influences the width of their pelvis. This is important when reconstructing natural shapes, e.g., in knee implant design. The aim of this study was to identify such morphotypes.

METHODS

This work investigated the shapes of roughly 1000 knee joints acquired from computed tomography, including the distal femur and proximal tibia. Two comprehensive feature sets were utilized to describe the bone shapes, one based on morphological measurements and the other on statistical shape model (SSM) weights. We normalized the data by size and performed a cluster analysis with different algorithms, namely k-means and high dimensional data clustering. The clusters were evaluated using several metrics.

RESULTS

The data showed a low tendency to form clusters. Only one of 12 experiments slightly exceeded the thresholds for actual clusters suggested by the literature. k-Means outperformed high dimensional data clustering in all cases.

CONCLUSION

After anisotropic normalization by size, which removes size and aspect ratio related differences, the data exhibited no morphotypes. This showed that there are no relevant hidden variables, e.g., gender, body type or ethnicity, which influence the shape of the knee joint. Instead, knee shape is highly individual. Investigating the three-dimensional shape, variations occur for a wide range of different shape parameters, not just for anterior-posterior and mediolateral size.

Anthropometry of the knee of the Turkish population and the comparison to implant sizes in total knee arthroplasty

BACKGROUND

Total knee arthroplasty (TKA) is one of the most common orthopaedic surgical procedures in the advanced stages of knee arthritis.

OBJECTIVE

The purpose of this study was to define the sex differences in the Turkish population's morphological measurements of the distal femoral and proximal tibial surfaces that form the knee joint and to compare their compatibility with conventional prosthetic implants commonly used in TKA for advanced-stage knee arthritis.

METHODS

Anthropometric data for a total of 240 knees from 240 patients were measured using 3-dimensional computed tomography (3D CT). All morphological data were compared with the dimensions of four conventional knee prostheses commonly used in Turkey.

RESULTS

A comparison of the four tibial components revealed that the majority of female proximal tibias matched with smaller-sized tibial components, whereas those of males matched the larger sizes. Comparing the morphological data with similar values for the four femoral components currently used in Turkey, we found that all the prostheses had similar values.

CONCLUSION

The four conventional prosthetic brands included in this study matched the distal femoral dimensions of both sexes. On the other hand, we need smaller size tibial components for our female population.

Morphometric measurement of the proximal tibia to design the tibial component of total knee arthroplasty for the Thai population

Purpose

This study evaluates the morphology of the Thai proximal tibia based on three-dimensional (3D) models to design the tibial component.

Methods

The 3D models of 480 tibias were created using reverse engineering techniques from computed tomography imaging data obtained from 240 volunteers (120 males, 120 females; range 20–50 years). Based on 3D measurements, a digital ruler was used to measure the distance between the triangular points of the models. The morphometric parameters consisted of mediolateral length (ML), anteroposterior width (AP), medial anteroposterior width (MAP), lateral anteroposterior width (LAP), central to a medial length (CM), central to a lateral length (CL), medial anterior radius (MAR), lateral anterior radius (LAR), and tibial aspect ratio (AR). An independent t-test was performed for gender differences, and K-means clustering was used to find the optimum sizes of the tibial component with a correlation between ML length and AP width in Thai people.

Results

The average morphometric parameters of Thai proximal tibia, namely ML, AP, MAP, LAP, CM, and CL, were as follows: 72.52 ± 5.94 mm, 46.36 ± 3.84 mm, 49.22 ± 3.62 mm, 43.59 ± 4.05 mm, 14.29 ± 2.72 mm, and 15.28 ± 2.99 mm, respectively. The average of MAR, LAR, and AR was 24.43 ± 2.11 mm, 21.52 ± 2.00 mm, and 1.57 ± 0.08, respectively. All morphometric parameters in males were significantly higher than those of females. There was a difference between the Thai proximal tibia and other nationalities and a mismatch between the size of the commercial tibial component and the Thai knee. Using K-means clustering analysis, the recommended number of ML and AP is seven sizes for the practical design of tibial components to cover the Thai anatomy.

Conclusion

The design of the tibial component should be recommended to cover the anatomy of the Thai population. These data provide essential information for the specific design of Thai knee prostheses.

Do the distal femur and the proximal tibia have narrower aspect ratios in smaller knees? : A morphological analysis of osteoarthritic knees in the Japanese population using computed tomography

BACKGROUND

Whether the distal femur and the proximal tibia have narrower aspect ratios in smaller knees has not been clarified. The purpose of this study was to confirm the dimensional characteristics of the distal femur and the proximal tibia using a novel method for consistently determining knee size.

METHODS

A total of 220 Japanese osteoarthritic knees (160 female and 60 male knees) were analyzed using computed tomography. The mediolateral (ML) and the anteroposterior (AP) dimensions of the distal femur (fML, fAP) and the proximal tibia (tML, tAP) were measured. The aspect ratios (ML/AP) of the distal femur (fML/fAP) and the proximal tibia (tML/tAP) were assessed against the product of AP × ML as a consistent determination of knee size.

RESULTS

The fML/fAP ratios positively correlated with knee size (fAP × fML) (r = 0.420, p < 0.001), only in the combined cohort, attributable to the narrower aspect ratios of female knees. No correlations were found between the tML/tAP ratios and knee size (tAP × tML) among females, males, nor all subjects (p = 0.299, 0.994, and 0.996, respectively). Aspect ratio correlations to knee size diverged between the three knee size indices, AP, ML, and AP × ML.

CONCLUSIONS

AP × ML was the meaningful option for knee size indexing in our morphological analyses. The distal femur, but not the proximal tibia, was found to have a narrower aspect ratio in female knees in the Japanese population.

Hybrid Oxford unicompartmental knee arthroplasty has lower residual cement extrusion than cemented arthroplasty in treating end-stage unicompartmental knee osteoarthritis

Background

Hybrid Oxford unicompartmental knee arthroplasty (OUKA) consists of cementless femoral prostheses and cemented tibial prostheses. Although a hybrid OUKA has been used in clinical practice, the clinical outcome has not been reported. The purpose of this study was to compare the short-term clinical outcomes and rate of residual bone cement extrusion between hybrid and cemented prostheses and analyse the possible reasons for differences between outcomes.

Methods

A total of 128 knees (118 patients) with end-stage osteoarthritis were included in this study, of which underwent consecutive operations using unicondylar Oxford phase 3 implants from July 2017 and September 2019 in our centre. Follow-up was performed at 6 weeks, 3 and 6 months, 1 year and every year after operation, and complications and changes in the Oxford knee score (OKS) were recorded. The OKS of the two groups was analysed by the generalized estimating equation approach. Prosthesis-based standard fluoroscopy was performed in a timely manner after each operation, and the rate of residual cement extrusion of the two groups was estimated using T-tests and a multivariate regression analysis.

Results

Excluding the cases that lost follow-up, a total of 120 knees (65 in hybrid group and 55 in cemented group) were included in the analysis. There was no statistically significant difference in patient characteristics between the two groups (p > 0.05). The average follow-up time was 23.4 months (and ranged from 12 to 38 months). As of the last follow-up, there were no complications, such as dislocation, fracture, prosthesis loosening and subsidence, but one patient in the cemented group experienced symptoms caused by residual loose cement. Postoperative OKS in both groups improved significantly (p < 0.001). There was no significant difference in the OKS at any point during the follow-up or in the improvement of the OKS between the two groups (p > 0.05). Residual cement was mainly extruded behind the tibial prosthesis. The rate of hybrid periprosthetic residual cement extrusion was significantly lower in the hybrid group than in the cemented group, and the difference was statistically significant (OR = 3.38; p = 0.014).

Conclusions

Hybrid OUKA is as effective as cemented OUKA in the short term after operation and can significantly reduce the residual cement extrusion rate around the tibial prosthesis.

Anthropometric measurements of non-arthritic knees in an Egyptian population: an MRI-based study

Background

Knee anthropometric characteristics were evaluated for different ethnicities; however, data from North African populations are deficient. The primary aim was to investigate the Egyptian knees’ anthropometric characteristics as a representative of North African populations. Secondary aims are as follows: (1) to study the anthropometric gender difference, (2) to compare results with other ethnic groups, and (3) to study the mismatch in comparison to geometric characteristics of modern TKA implant designs.

Methods

Two hundred normal knee MRI scans (100 females and 100 males, aging from 18 to 60) were obtained for analysis. Linear measurements (anteroposterior (AP), mediolateral (ML), and aspect ratio (AR)) of the planned cut surface of the distal femur (f) and the proximal tibia (t) were evaluated.

Results

A significant difference between both sexes was found, males had larger measurements in anteroposterior [fAP: 60.97 ± 3.1 vs 54.78 ± 3.3 (P < 0.001), tAP: 46.89 ± 3.0 vs 41.35 ± 2.9 (P < 0.001)] and mediolateral [fML: 74.89 ± 3.2 vs 67.29 ± 3.7 (P < 0.001), tML: 76.01 ± 3.0 vs 67.26 ± 3.2 (P < 0.001)], the mean femoral and tibial AP and ML measurements were different from other ethnic groups. None of the seven studied TKA systems matched the largest ML or the smallest AP dimensions of the distal femur in the current study population.

Conclusion

A significant difference was found between males’ and females’ knee anthropometric characteristics. Some of the commonly used TKA implants in our area could not provide a perfect fit and coverage.

Trial registration

ClinicalTrials.gov identifier: NCT03622034, registered on July 28, 2018.

CT Morphometric Analysis of Medial Tibial Condyles: Are the Currently Available Designs of Unicompartmental Knee Arthroplasty Suitable for Indian Knees?

BACKGROUND

The main purpose of this study is to assess the compatibility of medial tibial condyle (MTC) morphometry of Indian population with that of six contemporary UKA prostheses tibial components. We hypothesized that from the currently available UKA designs at least one would fit the MTC morphometry optimally as per the manufacturer's recommendation.

METHODS

We used CT morphometric data of 100 (66 males and 34 females) consecutive nonarthritic adult knees with reference to the MTC to assess the compatibility of currently available (in India) UKA prostheses. Each MTC was measured in the anteroposterior dimension, mediolateral at pre-defined points and the MTC aspect ratio calculated. Proportion of knees which could be optimally fitted with the existing UKA tibial components was calculated.

RESULTS

The mean age was 39.6 (SD 15.9) years. Anteroposterior and mediolateral dimensions in males were higher as compared to females (p < 0.001). As the anteroposterior dimension increased, the MTC aspect ratio decreased. There was asymmetry of anteroposterior halves with maximum mediolateral width being posterior to the central mediolateral width by 5.5 (SD 2.8) mm. Optimal anteroposterior fit ranged from 66 to 93%. However, optimal mediolateral fit as well, ranged from 5 to 37% with underhang present in 17-61% and > 2 mm medial overhang present in 0-35% cases. In 23% of cases, not a single implant could be fitted optimally.

CONCLUSION

Currently available UKA implants do not provide optimal tibial fit in nearly 25% of Indian patients. A surgeon needs to be aware of these limitations of existing implants when considering UKA.

Morphometric analysis of medial and lateral tibia plateau and adaptability with Oxford partial knee replacement in a Japanese population

AIMS

In unicompartmental knee arthroplasty (UKA), tibial components must be correctly sized and positioned so that tibial cut surfaces are well covered without marked under- or overhang with impingement of the surrounding soft tissue. We used morphometric data of both medial and lateral tibial plateaus separately to plan UKA and evaluated the compatibility of the measurement data to the dimensions of six currently available tibial prostheses in a Japanese population.

MATERIALS AND METHODS

Using computed tomography, we preoperatively examined 60 patients (30 medial and 30 lateral osteoarthritis (OA)) scheduled for primary UKA at our hospital between 2013 and 2017. Each tibial cutting surface was measured in the transverse plane at 2 mm below the respective joint line. We used anteroposterior and mediolateral length to calculate the mediolateral length/anteroposterior ratio of both medial and lateral compartments. We then compared measurements across six current UKA systems: Oxford fixed tibia and fixed lateral tibia, Triathlon, TRIBRID, JOURNEY UNI, and HLS Uni Evolution.

RESULTS

We found no significant differences in morphometric data between the medial and the lateral OA. The cutting surface of lateral plateau, however, had smaller anteroposterior dimensions, greater mediolateral length, and higher mediolateral length/anteroposterior ratio than those of medial plateau. Therefore, in this Japanese population-based study, Oxford lateral tibia had good compatibility with the measurement data of lateral compartments.

CONCLUSIONS

Lateral compartments had lower anteroposterior length, greater mediolateral length, and higher mediolateral length/anteroposterior ratio than those of medial compartments. We, therefore, strongly recommend using Oxford fixed lateral tibia for lateral OA over other current tibial prostheses because of superior coverage.

A landmark-based 3D analysis reveals a narrower tibial plateau and patella in trochlear dysplastic knees

PURPOSE

The trochlear dysplastic femur has a specific morphotype previously characterised by not only dysplastic features of the trochlea but also by specific features of the notch and posterior femur. In this study the morphology of the tibia and patella was investigated to gain further insight in the complete geometrical complexity of the trochlear dysplastic knee.

METHODS

Arthro-CT scan-based 3D models of 20 trochlear dysplastic and 20 normal knees were uniformly scaled and landmarks and landmark-based reference planes were created to quantify a series of morphometric characteristics of the tibia and patella.

RESULTS

In the mediolateral direction, the 3D-analysis revealed a 3% smaller medial tibial plateau (30.4 ± 1.6 mm vs 31.5 ± 1.6 mm), a 3% smaller overall width of the tibial plateau (73.6 ± 2.0 mm vs 75.7 ± 2.0 mm), a 16% smaller medial facet (17.3 ± 2.2 mm vs 20.1 ± 1.3 mm) and a 4% smaller overall width of the patella (41.7 ± 2.5 mm vs 43.4 ± 2.3 mm) in trochlear dysplastic knees. In the anteroposterior direction, the lateral tibial plateau of trochlear dysplastic knees was 5% larger (37.2 ± 2.3 mm vs 35.5 ± 3.1 mm). A correlation test between the width of the femur and the width of the tibia revealed that trochlear dysplastic knees show less correspondence between the femur and tibia compared to normal knees.

CONCLUSION

Significant differences in the morphology of the tibial plateau and patella were detected between trochlear dysplastic and normal knees. Both in the trochlear dysplastic tibial plateau and patella a narrower medial compartment leads to a significant smaller overall mediolateral width. These findings are important for the understanding of knee biomechanics and the design of total knee arthroplasty components.

LEVEL OF EVIDENCE

III.

Comparative study of existing knee prosthesis with anthropometry of Indian patients and other races, a computer tomography 3D reconstruction-based study

Background: Appropriate component sizing plays an important role in determining the functional outcome following total knee arthroplasty. Comparative studies of different populations have shown significant differences in the anthropometric parameters of knees in different race groups which negates the possibility of using a single sized implant system across different ethnic groups. This study evaluates the dimensions of femoral and tibial articular surfaces of Indian patients and compares the parameters with other ethnic groups and correlates the dimensions with five different commercially available knee systems.Material & Methods: Computerized tomography (CT) scans of contralateral normal knees of patients who underwent the scan for various ailments of the knee were retrieved retrospectively from the hospital database and 3D reconstruction of the images was done. Mediolateral dimensions (fML,tML), Anteroposterior dimensions (fAP, tAP) and aspect ratio (fML/fAP, tML/tAP) of the femur and tibia respectively were calculated and compared with the dimensions of different ethnic groups as well as the femoral and tibial components of five different knee prosthesis systems.

RESULTS

The average fML in the study group was less than that of Caucasian knees but was marginally larger than other ethnic groups. The fAP, tML and tAP was found to be smaller than all other ethnic groups but a larger femoral aspect ratio was reported than other ethnic groups. Among the implant systems, only NexGen LPS and Scorpio NRG implant femoral components closely matched the femoral dimensions in the study group whereas all implant systems showed significant mismatch with tibial component dimensions when compared to the study populations.

CONCLUSION

This study concludes that the dimensions of Indian knees are different from other ethnic groups and the use of commercially available knee Implants designed based on measurements in Caucasian populations can lead to significant mismatch between implant and resected bone surfaces.

Anthropometric measurements of patella and its clinical implications

INTRODUCTION

Early patellar failures in tricompartmental total knee arthroplasty (TKA) have been related to universal designing of implants. Establishing the appropriate patellar bone-prosthesis composite thickness is one of the important steps in ensuring functional success in arthroplasty. Since there is a paucity of data concerning the anthropometric measurements of Indian patella, the objective of this study was to obtain anatomic information of the patella of the northern Indian population and to analyze how it differs from western patellae that will improve patellar component design and implantation in TKA.

MATERIALS AND METHODS

A total of 266 consecutive knee radiographs were evaluated. All data were collected by a single doctor using X-ray console, where height (mm) and breadth (mm) were taken in anteroposterior views and thickness (mm) in lateral view.

RESULTS

The mean, standard deviation, 95% confidence interval and P value of the measurements were calculated. It was found that Indians had thinner and smaller patella as compared to westerners and also males had significantly (P < .001) larger patella as compared to females.

CONCLUSION

Anthropometric patellar dimensions can influence implant design and surgical outcomes and can be used as a guideline for future designing of more regional and gender-specific patellar component and patellar plate.

Morphometric Study of Lower End Femur by Using Helical Computed Tomography

BACKGROUND

A mismatch between the prosthesis size and bone may result in a number of complications. Keeping this in view, it is essential to analyze the morphological differences of the knee observed across various ethnic groups to improve the performance of total knee arthroplasty (TKA). The current study was aimed at studying the computed tomography (CT) profile of distal femur in Indian population and evaluates it morphologically.

MATERIALS AND METHODS

This descriptive study was conducted on 62 patients presenting to the Department of Orthopedics in a tertiary care center in rural north-west India for features suggestive of osteoarthritis and trauma of knee from September 17, 2015 to September 16, 2016. Helical CT of both knees was done, and the data were analyzed using Statistical Package for Social Sciences Version 17.0 statistical significance was assessed with the help of t-test and the value of P < 0.05 was considered to be statistically significant.

RESULTS

The mean mediolateral (ML) value in male patients was 72.74 ± 4.45 while the mean ML value in female patients was lower (63.59 ± 2.61). The mean anteroposterior (AP) value in male patients was significantly (statistically) higher (49.62 ± 3.86) in comparison to mean AP value in female patients (45.11 ± 4.4). The mean anterior lateral condylar height (ALCH) value in male patients was higher (17.53 ± 2.72) in comparison to mean ALCH value in female patients (14.63 ± 3.42).

CONCLUSIONS

The current study highlights the need to develop components and implants for use in TKA and fractures of distal femur keeping the age- and sex-specific anatomical features of people of different ethnic origins in view.

Anthropometric Measurements of Knee Joints in the Hispanic Population

BACKGROUND

Total knee arthroplasty (TKA) systems provide a set of incrementally sized tibial and femoral components intended to accommodate most knee parameters. However, the most commonly used systems in the United States were developed using data from Caucasian patients which might not lead to the best fit in non-Caucasians. Therefore, we wanted to evaluate whether these TKA systems proportionally match femoral and tibial measurements in Hispanics.

METHODS

All lower extremity magnetic resonance imaging performed at our institution between January 2007 and October 2015 were screened. A total of 500 nonarthritic knees from the same number of Hispanic patients were included in this retrospective descriptive radiographic study. Intraoperative osseous TKA resections were simulated on magnetic resonance imaging. Linear regression analyses were used to contrast the mediolateral (ML) width/anteroposterior (AP) length of simulated resected femoral condyle and tibia with the ML/AP dimensions of components offered by 4 current TKA systems.

RESULTS

Simulated resected male femurs tended to be wider than most TKA system components for a given AP size, probably leading to component ML underhang. Altogether, systems studied accommodated most AP and ML measurements of female condyles. However, we identified subsets of Hispanic female patients with certain AP lengths and/or ML widths that particular knee systems could not accommodate. Resected male and female tibias tended to be slightly narrower than all TKA systems for a given AP size.

CONCLUSION

The results of our study provide valuable data concerning the unique morphology of the Hispanic knee. These data can assist surgeons in the selection of the most suitable TKA systems for these patients.

How Much Does the Anatomical Tibial Component Improve the Bony Coverage in Total Knee Arthroplasty?

BACKGROUND

Recently, anatomical designs in total knee arthroplasty are introduced to address asymmetry of the resected tibia cutting surface. It is still not well known how much improvement would be achieved in total knee arthroplasty, especially in Asian knees.

METHODS

We evaluated the bony coverage of 4 commercially available posterior-stabilized tibial designs (3 symmetrical: NexGen, Attune, and Vega; 1 anatomical: Persona) by measuring uncovered areas over 3 different regions: lateroposterior (LP), medioposterior (MP), and mediolateral (ML) areas. The implant size was chosen based on lateral anteroposterior dimension of the implant that most closely matched the corresponding surface of tibia. The knee with over coverage <1 mm and under coverage <2 mm was regarded as having optimal fit.

RESULTS

The optimal fit of anatomical design in LP dimension was achieved in 76% of the cases, which was not significantly different from other symmetrical designs (P > .05). The anatomical tibial implant had a more optimal fit in MP and ML dimensions (48% and 42%, respectively) compared to all symmetric designs (P < .05). All symmetrical tibial designs had significant absolute underhang in MP (62%-78%) and ML (24%-34%) areas without difference. The anatomical tibial design had significant improvement for posteromedial coverage by about 69.8%-74.3% compared with the symmetrical designs.

CONCLUSION

Recently introduced anatomical tibial design improves surface coverage at the medioposterior dimension in Asian knees. Moreover, there is small improvement in ML fit compared with the symmetrical designs.

The Anteroposterior Axis of the Proximal Tibia Can Change After Tibial Resection in Total Knee Arthroplasty: Computer Simulation Using Asian Osteoarthritis Knees

BACKGROUND

We evaluated the effect of cutting surface on the anteroposterior (AP) axis of the proximal tibia using a 3-dimensional (3D) bone model to ensure proper tibial rotational alignment in total knee arthroplasty.

METHODS

3D bone models were reconstructed from the preoperative computed tomography data of 93 Japanese osteoarthritis knees with varus deformity. The AP axis was defined as the perpendicular bisector of the medial and lateral condylar centers in a 3D coordinate system. Bone cutting of the proximal tibia was performed with various tibial posterior slopes (0°, 3°, 7°) to the mechanical axis, and we compared the AP axes before and after bone cutting.

RESULTS

The AP axis before bone cutting crossed a point at about 16% (one-sixth) of the distance from the medial edge of the patellar tendon at its tibial attachment. The AP axis after bone cutting was significantly internally rotated at all posterior slopes: 4.1° at slope 0°, 3.0° at slope 3°, and 2.1° at slope 7°. The percentages of cases with differences of more than 3° or 5° were 66.7% and 34.4% at slope 0°, 53.8% and 24.7% at slope 3°, and 38.3% and 11.8% at slope 7°, respectively.

CONCLUSION

The AP axis of the proximal tibia may be rotated internally after resection of the proximal tibia in total knee arthroplasty. Hence, surgeons should recognize the effect of changes in the cutting surface on rotational alignment of the proximal tibia.

What Differences in Morphologic Features of the Knee Exist Among Patients of Various Races? A Systematic Review

BACKGROUND

Most TKA prostheses are designed based on the anatomy of white patients. Individual studies have identified key anthropometric differences between the knees of the white population and other major ethnic groups, yet there is limited understanding of what these findings may indicate if analyzed collectively.

QUESTION/PURPOSE

What are the differences in morphologic features of the distal femur and proximal tibia among and within various ethnicities?

METHODS

A systematic review of the PubMed database and a hand-search of article bibliographies identified 235 potentially eligible English-language studies. Studies were excluded if they did not include morphology results or had insufficient data for analysis, were unrelated to the distal femur or proximal tibia, were conducted in pediatric patients or those undergoing unicondylar knee arthroplasty, or bone surface measurements were obtained for trauma products. This left 30 eligible studies (9050 knees). Study quality was assessed and reported as good, fair, or poor according to the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Morphometric data for the distal femur and proximal tibia were available for four ethnic groups: East Asian (23 studies; 5543 knees), white (11 studies; 3111 knees), Indian (three studies; 283 knees), and black (three studies; 113 knees). Although relatively underrepresented, the knees from the Indian and black studies were maintained for hypothesis-generating purposes and to highlight crucial gaps in the data. The two key dimensions for selecting a suitable implant based on a patient's unique anatomy-AP length and mediolateral (ML) width-were assessed for the femur and tibia, in addition to aspect ratio, calculated by dividing the ML width by the AP length. Study measurement techniques were compared visually when possible to ensure that each pooled study conducted a similar measurement process. Any significant measurement outliers were reviewed for eligibility to determine if the measurement techniques and landmarks used were comparable to the other studies included.

RESULTS

White patients had larger femoral AP measurements than East Asians (62 mm, [95% CI, 57-66 mm] vs 59 mm, [95% CI, 54-63 mm]; mean difference, 3 mm; p < 0.001), a smaller femoral aspect ratio than East Asians (1.20, [95% CI, 1.11-1.29] vs 1.25, [95% CI, 1.16-1.34]; mean difference, 0.05; p = 0.001), and a larger tibial aspect ratio than black patients (1.55, [95% CI, 1.40-1.71] vs 1.49, [95% CI, 1.33-1.64]; mean difference, 0.06; p = 0.005).

CONCLUSIONS

This analysis uncovered differences of size (AP height and ML width of the femur and tibia) and shape (tibial and femoral aspect ratios) among knees from white, East Asian, and black populations. Future research is needed to understand the clinical implications of these discrepancies and to provide additional data with underrepresented groups.

Morphologic analysis of the proximal tibia after open wedge high tibial osteotomy for proper plate fitting

Background

After open wedge high tibial osteotomy (OWHTO), the proximal fragment resembles the anatomy of the proximal tibia that is aligned in the anterior-posterior direction and the distal fragment resembles the anatomy of the mid shaft that is aligned in the proximal-distal direction. In addition, the medial portion of the proximal fragment becomes aligned medially and the medial portion of the distal fragment, laterally, depending on the magnitude of the posterior opening gap. Therefore, there would be a mismatch between the post-correction bony surface and the previous pre-contoured plate geometry. The purpose of this study was to devise a new plate that best fit the post-contoured anatomy of the tibia by evaluating the surface geometry of the plate positioning site after OWHTO.

Methods

Thirty-one uni-planar and 38 bi-planar osteotomies were evaluated. Surgical indications were age of under 70 years, relatively active patient who performs recreational sports activities. Other indications were similar with general recommendation of HTO. Computed tomography (CT) of the operated knees was performed and it was used for the reconstruction of the 3D model. Bone model axis re-alignment was performed with coronal, sagittal, and axial plane. Morphologic analysis of the proximal tibia was performed using the following parameters: (1) radii in axial plane, 2) radii in coronal plane, and 3) angle and horizontal distance (Distance X) between the proximal and distal fragments. These were also analyzed according to the correction degree. The Analysis of Variance (ANOVA) test was conducted to verify the change depending on the correction amount of the posterior opening gap. The values obtained for the uni- and bi-planar osteotomy were compared by the independent t-test.

Results

There were 9 male and 60 female patients were recruited to this study; the mean age was 58.3 ± 8 and 56.9 ± 7.6 years, respectively. Preoperative weight bearing line (WBL) was 21.59 ± 11.36 and 22.32 ± 10.55 %, respectively. Mean correction degree was 10.9 ± 2.7 and 11.1 ± 2.6 mm, respectively. The radii of the tibial cross-sectional contour at the head portion tended to increase from the proximal to distal direction. The radii of the tibial cross-sectional contour at the neck portion tended to decrease from the proximal to distal direction. The radii of the coronal plane tended to increase from the proximal to distal direction. The angle between the proximal fragment and the distal one varied with the correction amount of the posterior opening gap. Shaft_Mid and Distance X of GroupI (110.08 mm and 6.11 mm, respectively) which had lower correction angle were lower than those of GroupII (130.05 mm and 6.41 mm, respectively) and those of GroupIII (136.35 mm, 8.01 mm, respectively) in coronal plane. There were significant differences (p = 0.023 < 0.05 and p = 0.009 < 0.01, respectively).

Conclusion

Current plate design should be modified to the surface geometry of the post-correction for the proper fitting. As the correction degree increases, the plate should be bended at the both end of the opening gap in coronal plane.

Trial registration

‘retrospectively registered (ISRCTN97792440).

Comparison of intraoperative anthropometric measurements of the proximal tibia and tibial component in total knee arthroplasty

BACKGROUND

Precise matching of the tibial component and resected bony surfaces and proper rotational implanting of the tibial component are crucial for successful total knee arthroplasty. We aimed to analyze the exact anthropometric proximal tibial data of Japanese patients undergoing total knee arthroplasty and correlate the measurements with the dimensions of current total knee arthroplasty systems.

METHODS

A total of 703 knees in 566 Japanese patients who underwent total knee arthroplasty for osteoarthritis were included. The bone resection in the proximal tibia was performed perpendicular to the tibial axis in the frontal plane. Measurements of the proximal tibia were intraoperatively obtained after proximal tibial preparation.

RESULTS

There were significant positive correlations between the lateral anteroposterior and medial anteroposterior and mediolateral dimensions. A progressive decrease in the mediolateral/lateral anteroposterior ratio with an increasing lateral anteroposterior dimension or the mediolateral/anteroposterior ratio with an increasing anteroposterior dimension was observed. The lateral anteroposterior dimension was smaller than the medial anteroposterior dimension by a mean of 4.8 ± 2.0 mm. The proximal tibia exhibited asymmetry between the lateral and medial plateaus. A comparison of the morphological data and dimensions of the implants, one of which was a symmetric tibial component (NexGen) and the others were asymmetric (Genesis II and Persona), indicated that an asymmetric tibial component could be beneficial to maximize tibial plateau coverage.

CONCLUSIONS

This study provided important reference data for designing a proper tibial component for Japanese people. The proximal tibial cut surface was asymmetric. There was wide dispersion in the lateral anteroposterior, medial anteroposterior, and mediolateral dimensions depending on the patient. Our data showed that the tibial components of the Genesis II and Persona rather than that of the NexGen may be preferable for Japanese people because of their asymmetric design.

Anthropometric measurements of tibial plateau and correlation with the current tibial implants

PURPOSE

The aim of the study was to make an anthropometric analysis at the resected surfaces of the proximal tibia in the Turkish population and to compare the data with the dimensions of tibial components in current use. We hypothesized that tibial components currently available on the market do not fulfil the requirements of this population and a new tibial component design may be required, especially for female patients with small stature.

METHODS

Anthropometric data from the proximal tibia of 226 knees in 226 Turkish subjects were measured using magnetic resonance imaging. We measured the mediolateral, middle anteroposterior, medial and lateral anteroposterior dimensions and the aspect ratio of the resected proximal tibial surface. All morphological data were compared with the dimensions of five contemporary tibial implants, including asymmetric and symmetric design types.

RESULTS

The dimensions of the tibial plateau of Turkish knees demonstrated significant differences according to gender (P < 0.05). Among the different tibial implants reviewed, neither asymmetric nor symmetric designs exhibited a perfect conformity to proximal tibial morphology in size and shape. The vast majority of tibial implants involved in this study tend to overhang anteroposteriorly, and a statistically significant number of women (21 %, P < 0.05) had tibial anteroposterior diameters smaller than the smallest available tibial component.

CONCLUSION

Tibial components designed according to anthropometric measurements of Western populations do not perfectly meet the requirements of Turkish population. These data could provide the basis for designing the optimal and smaller tibial component for this population, especially for women, is required for best fit.

LEVEL OF EVIDENCE

II.

Oversizing the tibial component in TKAs: incidence, consequences and risk factors

PURPOSE

The incidence of anteroposterior overhang of the tibial component after TKA and its effect on clinical outcome were investigated, and the morphometric characteristics of the knees in which tibial baseplates were oversized were identified.

METHOD

One hundred and fourteen consecutive TKAs were retrospectively assessed. The dimensions of the tibia were measured on a pre-operative CT scan and were compared with those of the implanted tibial component. We analysed the effect of anteroposterior and mediolateral size variations on clinical outcomes 1 year after surgery.

RESULTS

An anteroposterior overhang was observed in 87 % of cases on the lateral plateau, in 88 % on the central plateau and in 25 % on the medial tibial plateau. The mean post-pre-operative size differences were 3.2 ± 2.7, 2.8 ± 2.7 and -1.6 ± 2.3 mm, respectively. (Positive value means oversizing). A mediolateral overhang of the tibial component was found in 61 % of the patients. Oversizing was significantly greater and more frequent in females. Patients oversized in the anteroposterior dimension had lower post-operative pain scores. Patients with mediolateral oversizing had decreased flexion 1 year after surgery. Anteroposterior oversizing was observed more frequently in patients with asymmetric tibial plateaus, while mediolateral oversizing was observed more frequently in patients with small tibias.

CONCLUSIONS

This study demonstrates that the incidence of oversized tibial plateau components is surprisingly high and that functional outcomes are lower in the case of mediolateral or anteroposterior oversizing. The risk of oversizing could be predicted as it occurs predominantly in patients with asymmetric proximal tibia and/or small tibia.

LEVEL OF EVIDENCE

IV.

Evaluation of the screw position and angle using a post-contoured plate in the open wedge high tibial osteotomy according to the correction degree and surgical technique

BACKGROUND

The purpose of the present study was to evaluate the screw insertion angle and orientation with an anatomical plate that is post-contoured to the surface geometry of the proximal tibia after open wedge high tibial osteotomy.

METHODS

From March 2012 to June 2014, 31 uni-planar and 38 bi-planar osteotomies were evaluated. Postoperative computed tomography data obtained after open wedge high tibial osteotomy using a locking plate were used for reconstruction of the 3 dimensional model with Mimics v.16.0 of the proximal tibia and locking plate. Measurement data were compared between 2 groups (gap lesser than or equal to 10mm (Group 1) and gap greater than 10mm(Group 2)). These data were also compared between the uniplanar (Group 3) and bi-planar (Group 4) osteotomy groups.

FINDINGS

Dimensions of the medial proximal tibia of the sagittal plane, positions of the screw hole in the sagittal plane, and angles of screw insertion of all planes were not statistically different, regardless of the correction degree and operative technique. Additionally, angles of screw insertion were larger at the most anterior and posterior screw in the axial plane and most inferior screw showed smallest angle in the coronal plane.

INTERPRETATION

Using a post-contoured plate, the position and angle of the screw insertion were not different in the direction of the lateral hinge, regardless of the correction degree and operative technique. This could imply that it could be used universally in the open wedge high tibial osteotomy.

Anthropometry of Arabian Arthritic Knees: Comparison to Other Ethnic Groups and Implant Dimensions

BACKGROUND

We aim to measure the proximal tibia and distal femur of the osteoarthritic knees of Arab patients and to compare these measurements with data on other ethnic groups available in literature and with the dimensions of 6 knee implants.

METHODS

Anteroposterior and mediolateral measurements of tibia and femur were done on 3-dimensional computed tomography reconstructions of 124 osteoarthritic knees undergoing total knee arthroplasty with patient-specific instruments.

RESULTS

Average mediolateral and anteroposterior dimensions of the tibia for Arab knees were 74.36 ± 6 mm and 48.94 ± 4.57 mm, respectively, whereas for femur, 72.04 ± 6.6 and 68.1 ± 7.75, respectively. Average aspect ratio for tibial was 152.62 ± 12.66 and for femur 106.37 ± 14.34.

CONCLUSION

The size of Arab knees was generally smaller than Caucasian and larger than Asian. There is significant asymmetry of proximal tibial plateau and femur condyles.

Distal Femur Morphology of Iranian Population and Correlation With Current Prostheses

Background:

Maintaining proper size and rotation of components of total knee arthroplasty is mandatory for optimal longevity. Ethnical differences may affect the fitness of prostheses that were manufactured mainly based on Caucasian dimensions.

Objectives:

To evaluate the distal femur morphology of the Iranian population at the level of standard cuts simulated via computed tomography.

Patients and Methods:

During 2013, 150 consecutive patients (96 males and 54 females) from the outpatient Department of Orthopedic Surgery of Rasoul Akram Hospital with knee CT scans were studied. We entered cases with apparent normal extremity alignment and bone maturity. Exclusion criteria were history of fracture or conditions affecting knee profile. Standard cuts were simulated on the CT scan using the Marco Pacs program. For each bone, anteroposterior (AP), mediolateral (ML), and aspect ratio (ML/AP) were measured. Values were compared with the sizing of four currently available prostheses.

Results:

The mean age of the patients was 43 years (range: 17 to 80). All isolated parameters were higher in men significantly (P < 0.001). However, the aspect ratio did not show any significant difference (1.51 ± 0.11 vs 1.46 ± 0.1), suggestive of a similar configuration of distal femur profiles between genders. Ultimately, close correlations were observed among simulated cuts and size-matched femoral components of the prostheses. For females, however, components were mostly overhang mediolaterally except for one gender-specific subset. Decrement in the aspect ratio for larger knees was another mismatch with current prostheses that preserve an almost constant ratio throughout all sizes.

Conclusions:

Our findings may be applied by manufacturers to design prostheses more compatible with Asian populations. Alterations to the shape of components should be considered to provide optimal coverage.

Morphology of the Proximal Tibia at Different Levels of Bone Resection in Japanese Knees

The purpose was to measure the morphology of the proximal tibia at different levels for consideration of tibial tray design and placement. The morphology was analysed in 51 knees at 10, 15, 20, and 25 mm below the centre of the lateral tibial plateau. Surface rotation was measured by fitting an ellipse on the resection surface. The anteroposterior (AP), mediolateral (ML), medial AP (MAP) and lateral AP (LAP) dimensions were also measured. The resection surface showed internal rotation of 22.9° from the 10 mm level to the 25 mm level. More distally, the ML/AP and MAP/LAP ratios showed significant changes. Surgeons should pay attention to morphological changes for patients with gross tibial bone defects in primary and revision total knee arthroplasty.

Anthropometric difference of the knee on MRI according to gender and age groups

The purpose of this study was to analyze the anthropometric data from MRI images that were obtained from the non-arthritic knees in Asian adults, and to identify the existence of morphologic differences between age groups. This cross-sectional study included knee MR images of 535 patients (273 males, 262 females) taken for the evaluation of soft-tissue injuries, excluding cases with cartilage defect and malalignment. The age, gender, height, and BMI were also assessed. The patients were grouped into three different 20-year age groups (20-39, 40-59, and 60-79). The MRI analysis was performed on the anthropometric parameters of distal femur and posterior tibial slope. Age-related differences were found in femoral width, distance from the distal and posterior cartilage surface to the medial/lateral epicondyle, medial posterior condylar offset (PCO), and posterior condylar angle (PCA) (all P < 0.001), but not in lateral PCO, and medial/lateral tibial slopes. In the analysis of covariance analyses, significant interaction between gender and age groups was found in most parameters, but not in PCA, distance from the posterior cartilage surface to the medial epicondyle, or medial tibial slope. We found anthropometric differences among age groups exist in most of distal femoral parameters, but not in posterior tibial slope. The results of this study can be used by manufacturers to modify prostheses to be suitable for the future Asian elderly population.

Intraoperative anthropometric measurements of tibial morphology: comparisons with the dimensions of current tibial implants

PURPOSES

This study analyzed morphological differences in the resected proximal tibial surfaces of Chinese males and females undergoing total knee arthroplasty (TKA) and compared the measurements with the dimensions of five currently used tibial implants.

METHODS

The mediolateral (ML), middle anteroposterior (AP), medial anteroposterior (MAP), and lateral anteroposterior (LAP) dimensions of the resected tibial surfaces of 976 Chinese TKA knees (177 male, 799 female) were measured. The ML/AP ratio of every knee was calculated. These morphological data were compared with the dimensions of five currently used tibial implants.

RESULTS

The ML, AP, MAP, and LAP dimensions of the resected proximal tibias showed significant differences according to gender. Compared with currently used tibial implants, the smaller implants showed tibial ML undersizing and the larger implants showed tibial ML overhang. The ML/AP aspect ratio progressively decreased with increasing AP dimension in the resected proximal tibias, which contrasts with the relatively constant or increased (NexGen) aspect ratio in currently used tibial implants. Males showed a higher ML/AP aspect ratio than females for a given AP dimension. This indicates that for an implant with a given AP dimension, the tibial ML dimension tends to be undersized in males and to overhang in females.

CONCLUSION

The results of this study may provide fundamental data for designing suitable tibial implants for use in the Chinese population, especially for design of gender-specific prostheses.

LEVEL OF EVIDENCE

II.

Morphological measurements of the posterior surface of the normal proximal tibia in a healthy Chinese population

BACKGROUND

To measure and calculate the morphological parameters and determine the anatomical characteristics of the posterior surface of the proximal tibia in a healthy Chinese population.

METHODS

A total of 150 volunteers with normal knees were enrolled. The parameters in the multi-slice spiral computed tomography (MSCT) three-dimensional (3-D) reconstruction images were measured and calculated by two independent qualified observers. The differences and correlation were investigated. The intraclass correlation coefficient (ICC) was used to assess inter-observer reliability.

RESULTS

The posterior margin of the tibial plateau is presented as two superior arc-shapes. The central angles of these arcs were 118°±14° (medial) and 106°±20° (lateral). The radii of these arcs both showed a skewed distribution. The median radii of the arcs were 22 mm in the medial and 20mm in the lateral. There were two significant angles present in the sagittal plane of the posterior cortex of the proximal tibia. The first angles were 39°±7° (medial) and 47°±7° (lateral). The second angles were 39°±4° (medial) and 41°±5° (lateral). Significant differences were observed in the central angles and the first angles but not in the second angles between the medial and lateral. There were no significant differences between different gender groups, and between left and right limbs. All of these parameters exhibited excellent to moderate ICC.

CONCLUSION

Due to the varying anatomic morphology between the postero-medial and postero-lateral surface of the proximal tibia, the internal fixation implants of these two parts should be designed differently.

Anatomic tibial component design can increase tibial coverage and rotational alignment accuracy: a comparison of six contemporary designs

PURPOSE

The aim of this study was to comprehensively evaluate contemporary tibial component designs against global tibial anatomy. We hypothesized that anatomically designed tibial components offer increased morphological fit to the resected proximal tibia with increased alignment accuracy compared to symmetric and asymmetric designs.

METHODS

Using a multi-ethnic bone dataset, six contemporary tibial component designs were investigated, including anatomic, asymmetric, and symmetric design types. Investigations included (1) measurement of component conformity to the resected tibia using a comprehensive set of size and shape metrics; (2) assessment of component coverage on the resected tibia while ensuring clinically acceptable levels of rotation and overhang; and (3) evaluation of the incidence and severity of component downsizing due to adherence to rotational alignment and overhang requirements, and the associated compromise in tibial coverage. Differences in coverage were statistically compared across designs and ethnicities, as well as between placements with or without enforcement of proper rotational alignment.

RESULTS

Compared to non-anatomic designs investigated, the anatomic design exhibited better conformity to resected tibial morphology in size and shape, higher tibial coverage (92% compared to 85-87%), more cortical support (posteromedial region), lower incidence of downsizing (3% compared to 39-60%), and less compromise of tibial coverage (0.5% compared to 4-6%) when enforcing proper rotational alignment.

CONCLUSIONS

The anatomic design demonstrated meaningful increase in tibial coverage with accurate rotational alignment compared to symmetric and asymmetric designs, suggesting its potential for less intra-operative compromises and improved performance.

LEVEL OF EVIDENCE

III.

Anthropometric measurements of the human distal femur: a study of the adult Malay population

The distal femurs of 100 subjects (50 men, 50 women) from the Malay population aged between 19 and 38 years were scanned to measure the anterior-posterior (AP) and medial-lateral (ML) width. The mean AP values were 64.02 ± 3.38 mm and 57.33 ± 3.26 mm for men and women, respectively, and the mean ML values were 74.91 ± 3.52 mm and 64.53 ± 3.07 mm. We compared our data to that published previously for the Chinese and Indian populations. It was found that the Malay population had smaller distal femur than that of the Chinese but was larger than that of the Indian population (P < 0.05). In conclusion, although it is well established that Asians have a smaller distal femur size than that of the Western population, the variations in different Asian ethnicities may need to be considered when designing the appropriate knee implant.

Comprehensive assessment of tibial plateau morphology in total knee arthroplasty: Influence of shape and size on anthropometric variability

Better understanding of proximal tibia morphology can lead to improvements in total knee arthroplasty (TKA) through development of tibial tray families that adequately reflect the diversity of global anatomy using an appropriate number of components. We quantified variations in proximal tibial morphology at the TKA level and characterized differences attributable to gender and ethnicity. Virtual TKA was performed on digital models of 347 tibiae, spanning both genders and multiple ethnicities. The geometry of the resection profile was quantified using both a comprehensive set of morphological measurements (reflecting size and shape) and principal component analysis (PCA). The dominant statistical modes of variation were associated primarily with size (plateau dimensions, radii, and area), with lesser contributions associated with asymmetry and aspect ratios. Medial and lateral AP dimensions were strongly correlated with plateau ML width, with minimal differences in correlations due to gender or ethnicity. In conclusion, clinically relevant differences in proximal tibia morphology at the level of TKA resections across genders and multiple ethnicities can be attributed largely to variations in overall proximal tibial size, not gender- or ethnic-specific shape variations.

Computed tomography morphometric study of gender differences in osteoarthritis proximal tibias

One hundred and thirty osteoarthritic knees(65 males, 65 females) from a Chinese population were measured by computed tomography for tibial mediolateral (ML), middle anteroposterior (AP), medial anteroposterior (MAP), lateral anteroposterior (LAP) dimensions and ML/AP aspect ratio. The ML/AP aspect ratio were classified into 3 groups based on AP dimensions(<48 mm, 48-52 mm, >52 mm) to compare the morphologic differences of proximal tibia between males and females. The mean ML, AP, MAP and LAP dimensions of proximal tibia showed significant differences for sex (P < .01). We found a progressively decreased in the ML/AP aspect ratio with an increasing AP dimension, and males have larger ML/AP aspect ratio than that of females under a given AP dimension (P < .01). This indicates that under a given AP dimension prosthesis, the tibial ML dimension have the potential to be undersized in males and to overhang in females. This study may provide important reference in designing proper gender-specific tibia prosthesis with different ML/AP aspect ratio for Chinese males and females.

Anthropometry of the proximal tibia of patients with knee arthritis in Shanghai

We measured the resected bony surface of the proximal tibia from reconstructed 3D models of the 179 arthritis knees using CT data. We found that the mediolateral (ML) dimension (69.6 ± 9.2 mm) and anteroposterior (AP) dimension (46.1 ± 6.1 mm) were less than those of Westerners. It was observed the medial anteroposterior (MAP) dimension (47.1 ± 7.2 mm) was much larger and closer to middle point of ML dimension than lateral anteroposterior (LAP) dimension (42.9 ± 6.3 mm). The aspect ratio (AR) (1.5 ± 0.07) was constant in Shanghai population. Only half of the prostheses we used in clinic mostly matched the resected bony surface of Shanghai population very well in ML, AP and AR dimension.

Tibia vara affects the aspect ratio of tibial resected surface in female Japanese patients undergoing TKA

BACKGROUND

Tibia vara seen in Japanese patients reportedly influences the tibial component alignment when performing TKA. However, it is unclear whether tibia vara affects the component position and size selection.

QUESTIONS/PURPOSES

We therefore determined (1) the amount of medial tibial bow, (2) whether the tibia vara influences the aspect ratio of the tibial resected surface in aligning the tibial component with the tibial shaft axis, and (3) whether currently available tibial components fit the shapes of resected proximal tibias in terms of aspect ratio.

METHODS

We measured the tibia vara angle (TVA), proximal varus angle (PVA), and the mediolateral and middle AP dimensions of the resected surface using three-dimensional preoperative planning software in 90 knees of 74 female patients with varus osteoarthritis. We determined the correlations of the aspect ratio with TVA or PVA and compared the aspect ratios to those of five prosthesis designs.

RESULTS

The mean TVA and PVA were 0.6° and 2.0°, respectively. The aspect ratio negatively correlated with both TVA and PVA (r = -0.53 and -0.55, respectively). The mean aspect ratio of the resected surface was 1.48 but gradually decreased with increasing AP dimension, whereas four of the five prostheses had a constant aspect ratio.

CONCLUSIONS

The aspect ratio of resected tibial surface was inversely correlated to the degree of tibia vara, and currently available prosthesis designs do not fit well to the resected surface in terms of aspect ratio.

CLINICAL RELEVANCE

The design of a tibial component with a smaller aspect ratio could be developed to obtain better bone coverage in Japanese patients.

Gender differences of the morphology of the distal femur and proximal tibia in a Korean population

PURPOSE

We conducted this study to determine whether the sizes of distal femurs and proximal tibiae in Korean men and women are different, and to assess suitability of the sizes of prostheses currently used in Korea.

MATERIALS AND METHODS

We performed morphological analysis of proximal tibia and distal femur on 115 patients (56 male, 59 female) using MRI to investigate a gender difference. Tibial mediolateral dimension (tMAP), tibial medial anteroposterior dimension (tMAP), tibial lateral anteroposterior dimension (tLAP) femoral mediolateral dimension (fML), femoral medial anteroposterior dimension (fMAP), and femoral lateral anteroposterior dimension (fLAP) were measured. The ratio of tMAP and tLAP to tML (plateau aspect ratio, tAP/tML×100%), and that of fMAP and fLAP to fML (condylar aspect ratio, fAP/fML×100%) were calculated. The measurements were compared with the similar dimensions of four total knee implants currently used.

RESULTS

The tML and tAP lengths showed a significant gender difference (P<0.05). The plateau aspect ratio (tMAP/tML) revealed a significant difference between male (0.74±0.05) and female (0.68±0.04, P<0.05). For morphotype of distal femur, males were found to have significantly large values (P<0.05) in the parameters, except for fLAP. With regards to the ratio of the ML width to the AP length, the women showed a narrower ML width than the men. Both genders were distributed within the range of the dimensions of the prostheses currently used prostheses.

CONCLUSIONS

Korean population revealed that women have smaller dimensions than male counterparts. In both genders, a relatively small size of prostheses matches distal femur and proximal tibia better among the implants currently used in Korea.

Influence of landmark and surgical variability on virtual assessment of total knee arthroplasty

Given advances in recent years in imaging modalities and computational hardware/software, virtual analyses are increasingly valuable and practical for evaluating total knee arthroplasty (TKA). However, the influence of variabilities at each step in computational analyses on predictions of TKA performance for a population has not yet been thoroughly investigated, nor the relationship between these variabilities and expected variations in surgical practice. Understanding these influences is nevertheless essential for ensuring the clinical relevance of theoretical predictions. Here, a morphological analysis of proximal tibial resections within TKA is proposed and investigated. The goals of this analysis are to quantify the influence of variability in landmark detection on resection parameters and to evaluate this sensitivity relative to expected clinical variability in TKA resections. Results here are directly applicable to population-level computational analyses of morphological and functional TKA performance.

Morphometrical measurement of resected surface of medial and lateral proximal tibia for Chinese population

PURPOSE

The objective of this study was to analyze the morphology of the medial tibial plateau and lateral tibial plateau in Chinese knees and compared these measurements and features with those of commercial unicondylar tibial baseplates.

METHODS

Three-dimensional knee models were reconstructed from computed tomography slices of 81 subjects. Among the series, 27 knees were from male subjects and 54 knees from female subjects. The dimensions and shape of the medial and lateral tibial plateaus were measured and compared with six commercially available unicondylar tibial baseplates.

RESULTS

The results showed significant differences between the shapes of the medial and lateral tibial plateaus. For the lateral tibial plateau, the shape was symmetric about the mediolateral axis. The medial plateaus presented their widest mediolateral width in an obviously more posterior position than the lateral compartment. Additionally, the plateau aspect ratio decreased with increasing mediolateral dimensions, in contrast to the constant aspect ratio shown by conventional unicondylar knee prostheses.

CONCLUSION

Compartment-specific designs may optimize coverage between the prosthesis and resected tibial surface. The morphometrical measurements presented may allow manufacturers to design tibial baseplates that accommodate the structural variability between different ethnic groups.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

The correctness of fit of current total knee prostheses compared with intra-operative anthropometric measurements in Korean knees

We aimed to obtain anthropometric data on Korean knees and to compare these with data on commonly available total knee arthroplasties (TKAs). The dimensions of the femora and tibiae of 1168 knees were measured intra-operatively. The femoral components were found to show a tendency toward mediolateral (ML) under-coverage in small femurs and ML overhang in the large femurs. The ML under-coverage was most prominent for the small prostheses. The ML/anteroposterior (ML/AP) ratio of Korean tibiae was greater than that of tibial components. This study shows that, for different reasons, current TKAs do not provide a reasonable fit for small or large Korean knees, and that the 'gender-specific' and 'stature-specific' components help for large Korean femurs but offer less satisfactory fits for small femurs. Specific modifications of prostheses are needed for Asian knees.

Gender differences in distal femoral morphology and the role of gender specific implants in total knee replacement: a prospective clinical study

Gender differences in distal femoral morphology may affect femoral component fit using a standard range of prostheses. The clinical relevance of this is controversial. Standardised measurements were taken from the distal femora of 50 males and 50 females during total knee replacement (TKR). Corresponding measurements were taken from the respective gender specific and standard femoral components. No demographic differences were noted. Significant differences in both frequency and magnitude existed in the medial-lateral femoral component overhang between the sexes. In females, standard implants overhung at the anterior flange width (AFW) by >2mm in 24/50 (48%) and by >3mm in 17/50 (34%) (p<0.001). Also at the anterior medial-lateral width (MLA) 29/50 (58%) overhung by >2mm and 24/50 (48%) by >3mm (p<0.001). In males, standard implants overhung by >2mm in 1/50 (2%). In females, gender specific implants overhung by >2mm in 3/50 (6%). Females had a mean aspect ratio of 1.02 (0.82 to 1.35) and men 0.98 (0.79 to 1.19). Femoral component overhang can occur in females undergoing TKR and a gender specific implant would reduce the potential for medial-lateral overhang. Long term studies are awaited to quantify the clinical implications of overhang.

Three-dimensional morphology of the knee reveals ethnic differences

BACKGROUND

Studies have demonstrated sex differences in femoral shape and quadriceps angle raising a question of whether implant design should be sex-specific. Much of this research has addressed shape differences within the Caucasian population and little is known about differences among ethnic groups.

QUESTIONS/PURPOSES

We therefore asked: Do shape differences in the distal femur and proximal tibia exist among different ethnic groups and between the sexes in each ethnic population? And if ethnic differences exist, do they have a clinical impact on current TKA design?

SUBJECTS AND METHODS

We analyzed 1000 normal adult knees (80 African American, 80 East Asian, and 860 Caucasian). Three-dimensional surface models were created for each bone and added to three-dimensional statistical bone atlases. Statistical shape analysis was conducted with a process combining principal components and multiple discriminate analyses. Eleven femoral and nine tibial measurements were calculated.

RESULTS

We found differences in mean measurements between the sexes and ethnicities. Males had larger knees, with a mean 5-mm-larger anteroposterior dimension than females in all ethnicities. African American females had a 7.4-mm-deeper patellar groove, 2.3-mm-smaller tibial mediolateral dimension, and 2.5-mm-larger tibial anteroposterior dimension than Caucasian females. African American males had a 4.3-mm-larger femoral anteroposterior dimension, 10.1-mm-larger tibial mediolateral dimension, and 6-mm-larger tibial anteroposterior dimension than Asian males.

CONCLUSIONS

We identified differences in three-dimensional knee morphology among Caucasian, African American, and East Asian populations. Clinical studies will be required to determine whether these differences are important for implant design.