Patient - implant dimension mismatch in total knee arthroplasty: Is it worth worrying? An Indian scenario

Do age, gender, and region affect tibial slope? A multi-center study

INTRODUCTION

Tibial slope is a parameter that is important to recognize in knee kinematics and knee surgery. A very wide range of values governing posterior tibial slope exist in the literature. This study is based on the hypothesis that age, gender and region may have an effect on the tibial slope.

MATERIALS AND METHODS

A total of 1800 lateral knee radiographies from five different countries [Turkey, Germany, Italy, Spain, and the United Kingdom (UK)] were utilized to measure the native posterior tibial slope. Participants were categorized in deciles with each decade of age after 40 years determined as a separate age group. Accordingly, four different age categories were formed in total, namely, the 40- to 49-, 50- to 59-, 60-69, and 70- to 79-year-old groups. Patients with severe knee osteoarthritis, those with a history of arthroscopic and open surgery around the knee, and those with severe morbid obesity and those outside the specified age group were excluded from the study. The angle between the line tangential to the medial tibial plateau and the proximal anatomical axis of the tibia was measured.

RESULTS

The tibial slope values of both males and females in the Turkish population were found to be higher than those in other populations. It was observed that tibial slope values increased with age in females in all populations, except for those in the Spanish and UK populations. In the male population, it was found that tibial slope values increased with age in all populations except in the Spanish population.

CONCLUSIONS

Region, age, and gender affect tibial slope in different populations in various ways. Our study shows that the region an individual lives in and living conditions affect the tibial slope.

Sub-optimal femoral fit in total knee arthroplasty, a systematic review of human femoral data vs off-the-shelf contemporary femoral components

PURPOSE

The purpose of the current study is to investigate the inadequacy of fit between the human distal femur and the knee implants offerings and describe the available strategies to overcome this issue.

METHODS

A systematic research of the literature was performed to identify studies reporting morphologic measures of the distal femur. Studies were excluded if they included unhealthy knees or the morphological analysis did not report the two key dimensions to identify the patient's unique anatomy: AP length and mediolateral (ML) width. Clinically relevant component overhang or underhang was considered when the metal-bone mismatch was > 3 mm as described in the literature.

RESULTS

Six studies with anthropometric analysis of 1395 distal femurs met the inclusion criteria. The analysis revealed that by employing the available sizes of four current "state-of-the-art" primary off-the shelf (OTS) femoral implants up to 13-41% would show underhang and 9-27% overhang clinically relevant and the introduction of narrower sizes did not reduce this percentage of underhang but improved the overhang rate of 10-15%.

CONCLUSIONS

Whenever an ML/AP mismatch in encountered in the operating room, adaptations are needed, and these bring about deleterious biomechanical and clinical complications. Therefore, this study highlights the need for implants design with multiple ML offerings per AP size, since they provide not only more sizes options but more femoral shapes to match the different ML sizes of the distal femur, compared to designs with single ML offerings for a given femoral AP dimension.

A computed tomographic evaluation of femoral and tibial rotational reference axes in total knee arthroplasty

INTRODUCTION

 The surgical trans epicondylar axis (sTEA) is considered the gold standard for optimum rotation of the femoral component; however, no consensus exists on tibial component positioning. The objectives of this study were to determine the relationship of sTEA to various femoral and tibial reference axes in varus osteoarthritis (OA) knees and (ii) to study the intra-observer and inter-observer variability of the axis relationships.

MATERIALS AND METHODS

 The study was done on preoperative computerised tomogram (CT) scans of 110 varus knees to assess the rotational relationships respectively of femoral side sTEA with whitesides line (WSL), posterior condylar axis (PCA), clinical trans epicondylar axis (cTEA) and on the tibial side sTEA with posterior tibial margin (PTM), anterior condylar axis (ACA), Akagi's line and line from the geometric centre of the tibial plateau to 1/3rd tibial tubercle (line GC 1/3rd TT).

RESULTS

 On the femoral side the mean angles of sTEA with WSL, PCA, cTEA were 95.64° ± 2.85°, 1.77° ± 1.88°, 4.19° ± 0.99° respectively. On the tibial side, the mean angles of sTEA with, PTM, ACA, Akagi's line, and line GC 1/3rd TT were 1.10° ± 4.69°, 11.98° ± 4.51°, 2.43° ± 4.35°, 16.04° ± 5.93° respectively.

CONCLUSION

 Contrary to the generalization, TEA has variable relationships. The surgical trans epicondylar axis was not at the assumed 3° of external rotation to PCA in 85% of knees, nor perpendicular to WSL in >95% of knees. Of the four tibial axes, Akagi's line was the least variable with sTEA. Furthermore, surgeons should also be aware of the multiple reference axes and the range of deviation from sTEA to optimize the rotational alignment of components.

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.

Medial Ball and Socket Total Knee Arthroplasty in Indian Population: 5-Year Clinical Results

Background

Medial pivot total knee arthroplasty aims to restore native knee kinematics through highly conforming medial tibiofemoral articulation with survival comparable to contemporary knee designs. The aim of this study was to report preliminary clinical results of medial pivot total knee arthroplasty in an Indian population.

Methods

A retrospective analysis of 45 patients (average age, 62 years; 40 women and 5 men) with end-stage arthritis (Kellgren-Lawrence grade 4) operated with a medial pivot prosthesis was done. All patients were assessed using Knee Society Score (satisfaction, expectation, and functional scores) and Oxford Knee Score, and range of motion was recorded at the end of 5-year postoperative follow-up. In addition, all patients underwent standardized radiological assessment.

Results

At the final follow-up, patients reported significant improvement in mean Knee Society Score (satisfaction, expectation, and functional scores) and Oxford Knee Score (p < 0.05). The mean range of motion achieved at the end of 5 years ranged from 0° (extension) to 118.4° (further flexion). There was no evidence of loosening or osteolysis at a minimum follow-up of 5 years.

Conclusions

These results demonstrated satisfactory clinical and radiological outcomes at 5 years after total knee arthroplasty with a medial pivot design, which may be related to better replication of natural knee kinematics with the medial pivot knee and inherent advantages of this design.

Validity of the Novel Radiological Classification System of the Distal Femur

OBJECTIVE

Aseptic loosening (AL) is among the most important causes of failure after total knee arthroplasty (TKA). However, while there are numerous underlying causes of AL, the morphometry of the distal femur and intramedullary canal has not been sufficiently demonstrated. This study aimed to show the interobserver and intraobserver reliability and validity of the Citak classification, which has been recently defined according to the morphometry of the distal femur and provides a risk factor definition for AL.

MATERIALS AND METHODS

A total of 200 patients whose standardized anteroposterior (AP) and lateral images of the knee joint were obtained between October 2019 and April 2020 were retrospectively evaluated in this study. Patients with a history of extra-articular deformity and knee surgery were excluded from the study. For AL, morphologies of the distal femur were identified by two observers using the new radiological classification system of the distal femur. Mean pairwise Cronbach's alpha coefficient was used to assess the intra- and interobserver agreement of the classification.

RESULTS

There was excellent interobserver agreement for the 20 cm proximal and 2 cm proximal to the lateral joint line (PLJL) and adductor tubercle (PAD), respectively. The mean Cronbach's alpha coefficient was 0.96 (range 0.764-0.944) for the PAD and 0.98 (range 0.734-0.929) for the PLJL. There was also an excellent intraobserver agreement, with 93% average pairwise percent agreement for the index group and 95.5% average pairwise percent agreement for the anatomical classification group.

CONCLUSIONS

The level of inter- and intraobserver agreement for the morphology of the distal femur was excellent in the new radiological classification system, which was shown to be beneficial in the planning of revision knee arthroplasty for AL. However, there is a need for further studies in order to make a correlation of the classification with specific intraoperative findings.

Anthropometry of Nonarthritic Asian Knees: Is It Time for a Race-Specific Knee Implant?

Background

This study was done to study the anthropometry of nonarthritic Asian knees; to determine the differences in morphology between knees of different ethnicities and to compare the knee anthropometry values with sizes of available knee implants.

Methods

Magnetic resonance imaging scans of 100 nonarthritic Indian knees were analyzed. Anteroposterior (AP) length, mediolateral (ML) length, and aspect ratio of the distal femur and proximal tibia, patellar length, and patellar tendon length were measured. These values were compared with values of other ethnicities from literature. The values were also compared with sizes of available knee implants and evaluated for mismatch.

Results

All the parameters of female knees were significantly smaller than those of male knees (p < 0.05). The distal femur of Indian knees resembled that of Chinese knees with similar AP and ML lengths and aspect ratio. The distal femur of Indian knees had a significantly smaller AP, ML, and aspect ratio than those of Hispanic knees did. In comparison to Caucasian distal femur, Indian knees had smaller AP and ML lengths and larger aspect ratio. In terms of the proximal tibia, the Indian knees were smaller than Chinese (only ML), Caucasian (AP and ML) and Hispanic (AP and ML) knees. On comparison with implant sizes, there was a mismatch between the distal femur morphology and the dimensions of all implants. For a given AP length, the ML dimensions of all implants were smaller than the measured ML length of the knee. However, the tibial components of all the studied implants correlated well with the tibial morphology.

Conclusions

Distinct anthropometric differences exist between knees of different ethnicities. The knees of females were smaller than the knees of males. In Indian knees, the ML-AP aspect ratio of the distal femur was higher than that of the currently available femoral components. These results suggest the need for race-specific knee implants.

Posterior tibial slope of the knee measured on X-rays in a Turkish population

PURPOSE

Posterior tibial inclination of the knee joint should be considered during anterior cruciate ligament reconstruction and total knee replacement surgery. This inclination is called the posterior tibial slope (PTS) angle. The PTS differs among populations and the aim of this study was to determine the mean PTS in a Turkish population.

METHODS

PTS was measured retrospectively on lateral knee X-rays (n = 1024). The angle between the line connecting the anterior and posterior points of the lateral tibial plateau and the tibial longitudinal axis was taken as the PTS angle. Intra- and inter-observer agreement regarding the measurements on 20 X-rays were checked.

RESULTS

The mean PTS angle for the entire cohort was 8.36 ± 3.3° (range: 2.1-18.7°); it was 8.57 ± 3.4° (range: 2.3-17.4°) in men and 8.16 ± 3.2° (range: 2.1-18.7°) in women. Although no significant correlation was detected between PTS and age, PTS was higher in men than in women.

CONCLUSION

The increasing number of total knee replacement surgeries has increased the need for studies on implant mismatch. In this study, reference PTS values were determined for a Turkish population. It may be beneficial to use patient-specific implants in some cases.

Wider femoral and mediolaterally narrower tibial components are required for total knee arthroplasty in Turkish patients

PURPOSE

To evaluate the knee morphologic parameters in the Turkish population, compare them with known data, and identify new morphologic parameters.

METHODS

Magnetic resonance (MR) images of 1000 healthy subjects aged 18-50 years were included. One orthopedic surgeon and one experienced musculoskeletal radiologist reviewed MR images and measured 22 morphologic parameters. Sex and side differences were evaluated. Correlations between age and measurement parameters were assessed. The measured parameters were compared with known data. Femoral and tibial condylar height differences were identified.

RESULTS

A strong correlation was found among regarding all measurement parameters (p = 0.000 and k > 0.985 for all measurements) by both observers. A significant difference between the female and male subjects regarding the measurement parameters (p = 0.000) was found, except for the tibial coronal slope, posterior condylar angle (PCA), medial and lateral tibial slopes (MTS and LTS), and medial plateau depth. No measurement parameter was significantly correlated with age (n.s.). The femur surface ratio in male and female subjects was 1.29 ± 1.04 and 1.28 ± 1.12, respectively (n.s.). The tibial plateau aspect ratio was 61.4 ± 1.09 in males and 59.8 ± 1.57 in females (p = 0.004). The mean medial and lateral femoral condylar cartilage and bone height differences were 3.3 ± 1.1 and 3.1 ± 0.9 mm, respectively. The mean medial and lateral tibial condylar cartilage and bone height differences were 2.3 ± 0.3 and 1.6 ± 0.1 mm, respectively.

CONCLUSION

Compared to current designs, wider femoral and mediolaterally narrower tibial components are needed to provide well-fitting prosthesis and improve functional outcomes, especially in women. The data on femoral and tibial condylar height differences will be useful for future research on component design. In the clinical practice, the components developed based on these findings will have a substantial effect on postoperative outcomes and patient satisfaction.

LEVEL OF EVIDENCE

II.