A Comparative Radiological Analysis of Patellar Height Indices from Digital Radiography in the Northern and Eastern Regions from India

Introduction: Patella height measurement is used to study knee biomechanics, physiopathology of knee diseases and planning of Deformity correction surgery or Total Knee Arthroplasty. Patellar indices variables differ due to morphological, structural, and functional differences amongst population from different regions, making the implementation and universal standardization of indices difficult, moreover data from subcontinent is lacking. We evaluated Patellar Height Indices in Northern and Eastern Indian Population to study the ethnical and morphological differences.

Aims: To compare patella Alta and Baja incidence, concordance amongst patellar indices amongst Northern and Eastern Indian population and investigate whether classical limits of IS ratio applies to Eastern Population.

Methods: Prospective multicenter study from June’2014 and December’2022 to study patellar height profile using IS, MIS, BP,CD and PPA.

Results: 1702 knee radiographs in 900 patients. Incidence of Patella Alta and Baja was 29.4% and 19%. TL, PL and PL1 were 3.34 +/- 0.75 cm, 4.23 +/- 0.45 cm and 2.14 +/- 0.72 cm respectively. Mean IS ratio was 1.46 (SD-0.32). IS higher in females (1.28 vs 1.25, p<0.01). Mean CD index was 1.12 (SD-0.40), Mean BP index was 0.82 (SD-0.38) and Mean PPA was 280 (SD-0.67). Sensitivity for Patella Alta and Baja was BP>CD>PPA>MIS>IS and PPA>BP> CD>IS respectively.

Conclusion: Patella Alta and mean IS ratio higher in Eastern India than Northern population and Central India, Chinese, Emirati and Western populations. IS ratio is less applicable to eastern population. We propose IS range: 1.14-1.78 in Eastern India population and recommend use of BP, PPA with IS for a comprehensive patellar height profiling.