title: The effects of femoral component design on the patello-femoral joint in a PS total knee arthroplasty.
abstract: BACKGROUND
  Anterior knee pain following TKA performed utilizing the PFC Sigma system still represents a cause of failure. The purpose of this study was to evaluate whether or not a recent change in the femoral design (PFC Sigma PS) had a positive impact on the patello-femoral complication rate.
  
  
  METHODS
  A consecutive series of 100 TKA using the PFC Sigma PS system was followed prospectively for a minimum of 3 years. All patellae were replaced and a standard lateral release was never performed. Radiographic analysis following the Knee Society Score (KSS) included antero-posterior weight-bearing, lateral and bilateral axial radiographs. TKA rotational alignment was recorded at the final follow-up in 30 consecutive knees by performing a CT evaluation.
  
  
  RESULTS
  Good to excellent clinical results according to the KSS were achieved in 94% of the knees. Survival without need of reoperation for any reason was 98% at 3 years minimum follow-up; two reoperations were done for removal of fibromatous intra-articular tissue ("Clunk syndrome"). There were no revisions for septic or aseptic loosening of the components. The mean ROM improved from 104° preoperatively to 115° (97°-132°) postoperatively: postoperative flexion was 120° or more in 58 % of the knees. Severe anterior knee pain was present in 9% of patients. Radiographic evaluation showed 90 knees with a tibio-femoral anatomical axis between 8° and 2° of valgus (±3° from the intraoperative goal). CT evaluation of 30 consecutive knees showed that the femoral component positioning in relationship to the trans-epicondylar axis had only 2.80° of external rotation (±2.10°) with respect to a planned external rotation of 3°. This difference was statistically significant.
  
  
  CONCLUSIONS
  Although the PFC Sigma PS system provides good and predictable results for tricompartmental arthritis of the knee, anterior mechanism complications still represent a reason for dissatisfaction in a substantial group of patients.
authors.affiliation: Centro Eccellenza Sostituzioni Articolari Toscana (CESAT), Clinica Ortopedica Universita' di Firenze, Florence, Italy, pierfrancesco.indelli@unifi.it.
authors.forename: Pier Francesco
authors.initials: PF
authors.lastname: Indelli
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Marcucci
authors.forename: Gennaro
authors.initials: G
authors.lastname: Pipino
authors.forename: Sophie
authors.initials: S
authors.lastname: Charlton
authors.forename: Christian
authors.initials: C
authors.lastname: Carulli
authors.forename: Massimo
authors.initials: M
authors.lastname: Innocenti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018771:Arthralgia / Q000209:etiology*; D001168:Arthritis / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005260:Female; D005269:Femur; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D057071:Patellofemoral Joint; D017060:Patient Satisfaction; D011474:Prosthesis Design