Interobserver variation in the measurement of patellar height after total knee arthroplasty / 中国矫形外科杂志

ABSTRACT

[Objeetive] To assess the reproducibility and accuracy of four ratios used to measure patellar height,named the Blackburne-Peel,Caton Deschamps,Insall-Salvati and modified Insall-Salvati,before and after totalknee arthroplasty.[Methods]The patellar height was measured,by means of the four ratios,on the pre-and post-operative lateral radiographs of 44 patients(45 knees)who had undergone total knee arthroplasty.Two independent observers measured the films sequentially,in identical conditions,totally 720 measurements per observer.[Results]Before operation there was greater interobserver variation using either the Insall-Salvati or modified Insall-Salvati ratios than that when using the Caton-Deschamps or Blackburne-Peel methods.This was due to difficulty in identifying the insertion of the patellar tendon.Before operation,there was a minimal difference in reliability between these methods.After operation the interobserver difference was greatly reduced using both the Caton-Deschamps and Blackburne-Peel methods,which used the prosthetic joint line,compared with the Insall-Salvati and modified Insall-Salvati,which refered to the insertion of the patellar tendon.[Conclusion]The theoretical advantage of using the Insall-Salvati and modified Insall-Salvati ratios in measuring true patellar height after total knee arthroplasty needs to be balanced against their significant interobserver variability and inferior reliability when compared with other ratios.