title: Patellar Height Decreasing After Distal Femur Endoprosthesis Reconstruction Does Not Affect Functional Outcome.
abstract: BACKGROUND
  The patellar height can influence extensor mechanism and the knee function. Thus, during knee arthroplasty, the surgeon seeks to maintain the correct patellar height. However, it is more difficult to define and maintain the correct patella height in megaprosthesis reconstructions after tumor resections. The objective of this study was to evaluate patellar height after distal femur endoprosthesis reconstruction and its association to knee function.
  
  
  METHODS
  This retrospective analysis included 108 patients who underwent distal femur resections and endoprosthesis reconstruction. The minimum follow-up was 1 year or until the patients underwent patellar resurfacing or endoprosthesis revision. Patellar height was calculated using Insall-Salvati ratio (ISR) and Insall-Salvati patellar tendon insertion ratio (PTR) at 2 different times: postoperatively and at the final follow-up. The postoperative ratio was calculated using the best postoperative radiograph taken at least 1 month after the procedure. The final measures were based on the radiograph available at the last follow-up consultation. The ISR and PTR were associated to anterior knee pain (AKP), range of motion (ROM), and extension lag (EXL).
  
  
  RESULTS
  The average follow-up was 4.5years. The mean postoperative ISR was 1.02, and the mean ISR at final follow-up was 0.95 (P<.0001). The mean postoperative PTR was 1.45, and the mean PTR at final follow-up was 1.40 (P=.016). There was no association between patellar height and AKP, ROM, and EXL. Patellar height decreases significantly after distal femur resections but does not affect AKP, ROM, and EXL.
authors.affiliation: Department of Orthopaedic Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Department of Orthopaedics and Traumatology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Etchebehere
authors.affiliation: Department of Orthopaedic Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Patrick P
authors.initials: PP
authors.lastname: Lin
authors.affiliation: Department of Orthopaedic Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Bryan S
authors.initials: BS
authors.lastname: Moon
authors.affiliation: Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Jun
authors.initials: J
authors.lastname: Yu
authors.affiliation: Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Orthopaedic Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
authors.forename: Valerae O
authors.initials: VO
authors.lastname: Lewis
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018771:Arthralgia / Q000209:etiology*; D002648:Child; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010329:Patella; D017847:Patellar Ligament / Q000502:physiology; D019919:Prosthesis Implantation / Q000009:adverse effects*; D016059:Range of Motion, Articular; D012086:Reoperation; D012189:Retrospective Studies; D013710:Tendons / Q000601:surgery; D055815:Young Adult
keywords: bone tumor; distal femur; endoprosthesis reconstruction; knee function; patellar height