ANTHROPOMETRIC MEASUREMENTS OF KNEE JOINT IN INDIAN POPULATION: CO-RELATION WITH CURRENT KNEE ARTHROPLASTY SYSTEMS

Abstract

Purpose: There is no data concerning morphological dimensions of distal femur(DF), proximal tibia(PT) and thickness of patella(TP) in Indian population and our objective was to analyse the anthropometric data in Indian knees and to correlate them with existing knee arthroplasty systems.

Methods: MRI scans of 25 patients(15M;10F) who underwent bilateral knee scans for ligamental injuries were collected. Patients with arthritis, bone loss, varus/ valgus deformity of > 150 and those with immature skeleton were excluded. The mean age was 32 years (range 18–53y). Three surgeons independently measured medio-lateral(ML), antero-posterior(AP) lengths & aspect ratio(AR) of DF, PT and TP on three occasions one week apart to account for intra & inter-observer variability. The resultant data of 50 knees was analysed using SPSS v16.0 and compared with five different knee arthroplasty systems (PFC sigma/NexGen/Scorpio/IB-II/ Gender specific knee).

Results: The mean ML & AP for proximal tibia was 73.3±5.3 & 47.8±4.3 mm. The mean ML & AP (lateral condyle) for distal femur was 74.3±5.9 & 65.4±5.0 mm. The mean unresected thickness of patella was 24.7 & 21.8 mm in males & females respectively. The ML & AP showed a statistically significant positive correlation with person’s height (ML®=0.55;AP®=0.50 & p=0.01). A decrease in AR for increasing AP dimension was noted for both distal femur and proximal tibia (Tibia®=0.153;p=0.29 & Femur:®=−0.91;p=0.001).

Discussion: None of the prosthesis designs mimicked this decrease in AR and NexGen infact showed increase in AR.

Only Gender specific knee closely mimicked normal variation in AR and is available only for females (in India). Most of the available TKR prosthesis designs differ from true knee morphometry of Indian population. These data provides the basis for designing optimal prosthesis for people of Indian/Asian origin in UK/overseas.