Patellofemoral Pressure Changes After Static and Dynamic Medial Patellofemoral Ligament Reconstructions.
BACKGROUND
Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue fixation. Static MPFL reconstruction is most commonly used. However, dynamic reconstruction deforms more easily and presumably functions more like the native MPFL.


OBJECTIVE
The aim of the study was to evaluate the effect of the different MPFL fixation techniques on patellofemoral pressures compared with the native situation. The hypothesis was that dynamic reconstruction would result in patellofemoral pressures closer to those generated in an intact knee.


METHODS
Controlled laboratory study.


METHODS
Seven fresh-frozen knee specimens were tested in an in vitro knee joint loading apparatus. Tekscan pressure-sensitive films fixed to the retropatellar cartilage measured mean patellofemoral and peak pressures, contact area, and location of the center of force (COF) at fixed flexion angles from 0° to 110°. Four different conditions were tested: intact, dynamic, partial dynamic, and static MPFL reconstruction. Data were analyzed using linear mixed models.


RESULTS
Static MPFL reconstruction resulted in higher peak and mean pressures from 60° to 110° of flexion (P < .001). There were no differences in pressure between the 2 different dynamic reconstructions and the intact situation (P > .05). The COF in the static reconstruction group moved more medially on the patella from 50° to 110° of flexion compared with the other conditions. The contact area showed no significant differences between the test conditions.


CONCLUSIONS
After static MPFL reconstruction, the patellofemoral pressures in flexion angles from 60° to 110° were 3 to 5 times higher than those in the intact situation. The pressures after dynamic MPFL reconstruction were similar as compared with those in the intact situation, and therefore, dynamic MPFL reconstruction could be a safer option than static reconstruction for stabilizing the patella.


CONCLUSIONS
This study showed that static MPFL reconstruction results in higher patellofemoral pressures and thus enhances the chance of osteoarthritis in the long term, while dynamic reconstruction results in more normal pressures.
Department of Orthopaedics, Radboud University Medical Center, Nijmegen, the Netherlands akrood@hotmail.com.
Akkie
A
Rood
Orthopaedic Research Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands.
Gerjon
G
Hannink
Department of Orthopaedics, Radboud University Medical Center, Nijmegen, the Netherlands.
Anke
A
Lenting
Orthopaedic Research Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands.
Karlijn
K
Groenen
Department of Orthopedic Surgery, Canisius Wilhelmina Hospital, Nijmegen, the Netherlands.
Sander
S
Koëter
Orthopaedic Research Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands Laboratory of Biomechanical Engineering, University of Twente, Enschede, the Netherlands.
Nico
N
Verdonschot
Department of Orthopaedics, Radboud University Medical Center, Nijmegen, the Netherlands.
Albert
A
van Kampen
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D008023:Ligaments, Articular / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery*; D010329:Patella / Q000601:surgery*; D011312:Pressure; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures / Q000379:methods*
MPFL reconstruction; medial patellofemoral ligament; patella; patellofemoral pressure; trochlea