Summary

In view of the wide dispersions in proximal tibia in anteroposterior and mediolateral dimensions, the implant sizes should ideally accommodate change in aspect ratios along with usual ML and AP dimensions.

Abstract

Introduction

Total knee arthroplasty (TKA) success depends on accurate bony cuts and soft tissue balancing. However an anthropometrically well matched prosthesis is a challenge for surgeons. A wide variety of implants are available in market, so this study was undertaken to evaluate the compatibility of western implants in Indian population.
Materials & methods:
Prospective study included 304 knees of 192 Indian patients (44 male and 148 female patients) who underwent TKA. Patients with congenital anomaly of tibia, previous fractures around proximal tibia, history of knee surgery with implants in situ, severe bone loss or deformity >25 degrees and revision TKR patients were excluded from our study. Anthropometric measurements were performed according to Akagi’s method. Out of 192 patients, 153 patients were implanted with Press Fit Condylar PFC Sigma and Attune was used in 39 patients in this study. Also, tibial implant sizes of NexGen, Persona, Genesis II were used for comparison with proximal tibial cut surface measurements.

Results

The average ML dimension was 71.3 ± 6.1 mm (range, 62-95 mm),78.0 ± 6.7 mm (range, 62-95 mm), and 69.5 ± 4.4 mm (range,62-82 mm) for the total, male, and female patients, respectively. The average AP dimensions were 47.3 ± 4.9 mm (range, 39-80 mm), 51.3 ± 3.0 mm (range, 46- 58 mm), and 46.2 ± 4.7 mm (range, 39-56 mm) for the total, male, and female patients, respectively. The mAP dimensions were significantly longer than lAP dimensions by 5.2 ± 1.0 mm on average. A significant positive correlation was found between lAP & mAP and lAP & ML dimensions. Amongst, ML incompatibilities, it was found that ML dimension was undersized in 14 males and 22 female patients with smaller AP and overhang was observed in 5 male patients and 7 female patients for larger AP dimensions.

Conclusion

In view of the wide dispersions in proximal tibia in anteroposterior and mediolateral dimensions, the implant sizes should ideally accommodate change in aspect ratios along with usual ML and AP dimensions. Also, Western implants are not suitable for Indian population as the aspect ratio (AR) decreases in Indian patients with increase in anteroposterior dimensions.