title: A comparison of lateral radiograph of the knee in extended weight bearing and 30 degrees flexion to predict a patellar tendon length.
abstract: BACKGROUND
  Anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstruction with bone patellar tendon bone graft (BPTB) are commonly performed. Lack of precision in patellar tendon length measurement may result in a graft-tunnel mismatch. Presently, preoperative planning needs to evaluate the limb alignment from knee extended weight bearing radiograph and the length of the patellar tendon from knee 30 degrees flexion radiograph.
  
  
  OBJECTIVE
  To compare knee extended weight bearing radiograph and knee 30 degrees flexion radiograph to find which one can predict the patellar tendon length with more precision.
  
  
  METHODS
  Cross-sectional diagnostic study.
  
  
  METHODS
  Thirty-six patients who received a cruciate ligament reconstruction with BPTB graft at Phramongkutklao Hospital were enrolled. Patellar tendon lengths were measured from knee extended weight bearing radiograph and knee 30 degress flexion radiograph and then compared to a real intraoperative patellar tendon length. Analysis using intra-class correlation coefficient and paired t-test was done.
  
  
  RESULTS
  The mean patellar tendon length from radiographic taken at 30 degrees of knee flexion and extended weight bearing were 43.90 mm and 42.95 mm respectively. The difference was less than 1 mm which might not be clinically significant. The prediction of patellar tendon length from 30 degrees flexed film is statistically closer (ICC 0.760: 0.717, p-value < 0.001). By the way, they were both in intermediate reliability level (0.6 < ICC < 0.8). It also seems not clinically different.
  
  
  CONCLUSIONS
  Preoperative film knee extended weight bearing alone is enough for evaluation both limb alignment and length of the patella tendon leading to decreasing cost, time and radiation exposure of patients.
authors: Department of Orthopaedics, Phramongkutklao Hospital, Bangkok, Thailand. nwrbl@yahoo.com
authors: Nitis
authors: N
authors: Reeboonlap
authors: Worapong
authors: W
authors: Pongpatarat
authors: Korakot
authors: K
authors: Charakom
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D001178:Arthroplasty; D001696:Biomechanical Phenomena; D050376:Bone-Patellar Tendon-Bone Grafting; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017847:Patellar Ligament / Q000033:anatomy & histology*; D016119:Posterior Cruciate Ligament / Q000293:injuries; D011859:Radiography; D016474:Weight-Bearing