The effect of trochlear dysplasia on patellofemoral biomechanics: a cadaveric study with simulated trochlear deformities.
BACKGROUND
Trochlear dysplasia appears in different geometrical variations. The Dejour classification is widely used to grade the severity of trochlear dysplasia and to decide on treatment.


OBJECTIVE
To investigate the effect of trochlear dysplasia on patellofemoral biomechanics and to determine if different types of trochlear dysplasia have different effects on patellofemoral biomechanics.


METHODS
Controlled laboratory study.


METHODS
Trochlear dysplasia was simulated in 4 cadaveric knees by replacing the native cadaveric trochlea with different types of custom-made trochlear implants, manufactured with 3-dimensional printing. For each knee, 5 trochlear implants were designed: 1 implant simulated the native trochlea (control condition), and 4 implants simulated 4 types of trochlear dysplasia. The knees were subjected to 3 biomechanical tests: a squat simulation, an open chain extension simulation, and a patellar stability test. The patellofemoral kinematics, contact area, contact pressure, and stability were compared between the control condition (replica implants) and the trochlear dysplastic condition and among the subgroups of trochlear dysplasia.


RESULTS
The patellofemoral joint in the trochlear dysplastic group showed increased internal rotation, lateral tilt, and lateral translation; increased contact pressures; decreased contact areas; and decreased stability when compared with the control group. Within the trochlear dysplastic group, the implants graded as Dejour type D showed the largest deviations for the kinematical parameters, and the implants graded as Dejour types B and D showed the largest deviations for the patellofemoral contact areas and pressures.


CONCLUSIONS
Patellofemoral kinematics, contact area, contact pressure, and stability are significantly affected by trochlear dysplasia. Of all types of trochlear dysplasia, the models characterized with a pronounced trochlear bump showed the largest deviations in patellofemoral biomechanics.


CONCLUSIONS
Investigating the relationship between the shape of the trochlea and patellofemoral biomechanics can provide insight into the short-term effects (maltracking, increased pressures, and instability) and long-term effects (osteoarthritis) of different types of trochlear dysplasia. Furthermore, this investigation provides an empirical explanation for better treatment outcomes of trochleoplasty for Dejour types B and D dysplasia.
Department of Industrial Technology and Construction, Ghent University, Ghent, Belgium Department of Construction and Production, Ghent University, Ghent, Belgium Monica Orthopaedic Research (MORE) Institute, Antwerp, Belgium mvhaver@hotmail.com.
Annemieke
A
Van Haver
Department of Physical medicine and orthopaedic surgery, Ghent University, Ghent, Belgium.
Karel
K
De Roo
Department of Civil Engineering, IBiTech-bioMMeda, Ghent University, Ghent, Belgium.
Matthieu
M
De Beule
Department of Mechanical Engineering-Division of Biomechanics, Catholic University Leuven, Leuven, Belgium.
Luc
L
Labey
Department of Construction and Production, Ghent University, Ghent, Belgium.
Patrick
P
De Baets
Department of Orthopaedics, Lyon-Ortho-Clinic, Clinique de la Sauvegarde, Lyon, France.
David
D
Dejour
Department of Industrial Technology and Construction, Ghent University, Ghent, Belgium.
Tom
T
Claessens
Department of Physical medicine and orthopaedic surgery, Ghent University, Ghent, Belgium Antwerp Orthopedic Center, Monica Hospitals, Antwerp, Belgium.
Peter
P
Verdonk
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008297:Male; D010003:Osteoarthritis / Q000473:pathology; D010329:Patella / Q000473:pathology*; D057071:Patellofemoral Joint / Q000473:pathology*; D011312:Pressure; D012399:Rotation
experimental testing; patellofemoral dislocation; patellofemoral kinematics; patellofemoral pressures; rapid prototyping