Coronal alignment of patellofemoral arthroplasty.
BACKGROUND
Patellofemoral arthroplasty (PFA) can yield successful results in appropriately selected patients. The varus-valgus position or coronal alignment of the trochlear implant is determined by how its transitional edges articulate with the condylar cartilage. Whilst variation in condylar anatomy will not influence the axis of the lower limb in PFA, it can impact on the Q-angle of the PF joint. The aim of this study was to analyze how the coronal alignment can be influenced by the choice of anatomical landmarks.


METHODS
Retrospective analysis of 57 PFAs with measurements of alignment from full leg radiographs.


RESULTS
Coronal alignment following anterior condylar anatomy leads to a mean (SD) proximal valgus alignment of 100° (9°). Aligning the component with Whiteside's line gives a better alignment with less variance 89° (3°).


CONCLUSIONS
A trochlear component with a higher Q-angle compensates for patellar maltracking if the condylar anatomy would tend to put the implant in a more proximal varus or neutral position. If the trochlear component is proximally aligned in valgus this may have the opposite effect. Aligning the trochlear component with the AP-axis in the coronal plane avoids maltracking and optimally utilizes the design features of the implant.


METHODS
Level III.
Department of Orthopaedic Surgery, University Hospital Saint Luc, Av. Hippocrate 10, 1200 Brussels, Belgium. Electronic address: emmanuel.thienpont@uclouvain.be.
Emmanuel
E
Thienpont
Department of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, 925 Chestnut St, Philadelphia, PA 19107, USA.
Jess H
JH
Lonner
D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D006801:Humans; D007720:Knee Prosthesis; D057071:Patellofemoral Joint / Q000601:surgery*; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012189:Retrospective Studies
Patellar tracking; Patellofemoral alignment; Patellofemoral arthritis; Patellofemoral arthroplasty; Trochlear dysplasia