Determination of the Offset of Tibial Plateau in relation to the Tibial Shaft in Indian Population

INTRODUCTION: Total knee arthroplasty is one of the most common surgeries being done for arthritis of knee joint. The long-standing success of the surgery relies on the life of the prosthesis which in turn depends on the accurate placement of the implant. There exist an offset between the proximal tibia and the tibial shaft. This offset varies with various ethnic groups. The presently available implants are based on the anatomic studies of the western population. This study will help to design an ideal tibial component to suit the anatomy of the Indian population. So that there will be no mismatch between the tibial implant and the tibia. AIM OF THE STUDY: To determine the relation of the tibial plateau offset in relation to tibial shaft in normal Indian population using 124 slice computed tomography. OBJECTIVES: 1. To find the offset of the tibial plateau in relation to the tibial shaft using CT images of the proximal tibia in adult Indian population. 2. To design an ideal tibial component of knee prosthesis to match the anatomy of Indian population. STUDY TYPE: Cross-Sectional study. STUDY PERIOD: January 2015 to December 2019. RESULTS: The mean age of the participants was 60.21 with the age. The Mean Lateral Medial Dimension of the Tibial Plateau was found to be 7.3± 0.04 cm. The Mean Posterior Anterior Dimension of the Tibial Plateau was found to be 5.11 ± 0.03 cm. The Mean Lateral Medial Distance of the Tibial Plateau was found to be 3.89 ± 0.03 cm. The Mean Posterior Anterior Offset of the Tibial Plateau was found to be 0.67 ± 0.03 cm towards the Anterior direction. The Mean Lateral Medial Offset of the Tibial Plateau was found to be 0.10 ± 0.02 cm towards the Medial direction. DISCUSSION: In total knee arthroplasty, long stems are used so that they can provide support for a tibial component. It is advantageous in certain circumstances like a fracture, revision total knee arthroplasty. The offset stems have been made available so that there can be given maximal tibial coverage with or without minimal overhang. The designs of most of these stems are based on anatomic data of Western populations. western studies have revealed that the axis of the tibial shaft is, on the average, located anteromedial in our study we observed there was a large variation in the offset of the tibial shaft from the tibial plateau, ranging from 0mm to 17.8 mm, so it would be desirable to have a wide range of offset stems available from 0 to 20 mm, in 2-mm or 4-mm increments. In our studies, the tibial shaft axis was located lateral to the center of the tibial plateau in 39 (1mm or more) out of 172 knee which shows the need for lateral offset stem. The tibial shaft axis was located anterior to the center of the tibial plateau in 155 (1mm or more) out of 172 knees. Which shows the need for anterior with medial and also lateral offset stem. CONCLUSION: In conclusion, we have described the morphology of the proximal part of the tibia as measured on computed tomography, we observed a large variation and mostly the tibial shaft axis is in offset from the tibial plateau. The tibial shaft axis was located anterior to the center of the tibial plateau in a majority of our Indian subjects. Accordingly, an anterior offset tibial keel or stem seems to be a more suitable choice for Indian patients undergoing primary or revision total knee arthroplasty. In the case of medial-lateral offset, we need both medial and lateral offset stemmed implant as the medial offset is seen in 86 knees and the lateral offset is seen in 39 knees almost ¼th of the study subjects