Development of subject-specific tibiofemoral and patellofemoral joint kinematic models for children and adolescents with recurrent patellar dislocation
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Modenese, Luca
da Luz, Simao Brito
Maine, Sheanna
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Abstract
Patellar dislocation is a complex pathoanatomical condition that affects
approximately 1:1000 children and adolescents. Up to 71% of those affected are at risk
of recurrent dislocations, that can lead to long-term complications, such as persistent knee
pain, decreased activity levels and impairment of knee function. The cause of patellar
dislocation is believed to be multifactorial, including lower limb misalignment, abnormal
patellofemoral morphology and inadequate soft tissue restraints. While anatomical risk
factors and thresholds for typical measures have been well established in adults, there is
a paucity of normative and pathoanatomical data that contribute to patellar dislocation in
paediatric populations, where the morphology of the patellofemoral joint (PFJ), as well
as lower limb alignment, change with growth. Moreover, many surgical techniques
common in adults (e.g., trochleoplasty) cannot be performed in a paediatric population
due to the risk of growth disruption. Given the challenges in managing recurrent patellar
dislocation in paediatric populations, treatment is often unsuccessful and commonly
results in poor functional outcomes for the patient while incurring substantial costs.
Poor treatment outcomes may be due to limitations in current diagnosis and
treatment methods. Nowadays, clinicians use static measures from medical imaging to
inform diagnosis and treatment of recurrent patellar dislocation. These measures, despite
providing valuable insights on the PFJ anatomy, are unable to provide understanding of
the patellar dislocation mechanism during dynamic tasks. Conversely, subject-specific
computational models of the musculoskeletal system, with individualised geometries and
anatomical structures, have the potential to capture the complex functional relationship
between multiple risk factors for patellar dislocation on an individual basis. Creating fully
subject-specific models requires accurate personalisation of the joint kinematics, which
will improve estimates of all the dependent quantities of interest for musculoskeletal
modelling (e.g., muscle moment arms, articular contact points and ligament kinematics).
Therefore, the general purpose of this thesis was to develop subject-specific rigid-body
models of the tibiofemoral and patellofemoral joints in children and adolescents with
recurrent patellar dislocation.
The first study systematically reviewed the current literature to characterise lower
limb alignment, patellofemoral morphology and soft tissue restraints of the PFJ through
medical imaging measurements in paediatric recurrent patellar dislocators (RPD) and
age-matched typically developing (TD) participants. Moreover, the data were synthesised to stratify the factors that influence PFJ stability and recommendations on the assessment
and reporting of PFJ parameters in this patient population were provided. Results from a
meta-analysis conducted on measures reported in two or more studies that included both
a control and a patellar dislocator group showed that the tibial tuberosity to trochlear
groove (TT-TG) distance and bony sulcus angle can be confidently used to predict the
risk of recurrence in the paediatric population. These results can streamline the patient
evaluation and best inform clinical decision-making. The paper describing these results
was published as Barzan, M., Maine, S., Modenese, L., Lloyd, D.G., Carty, C.P.,
Patellofemoral joint alignment is a major risk factor for recurrent patellar dislocation in
children and adolescents: a systematic review. JISAKOS 2018, 0:1-11.
doi:10.1136/jisakos-2017-000189.
The aim of the second study was to analyse the differences in lower limb
alignment, patellofemoral alignment and trochlea dysplasia between paediatric RPD
patients and TD participants using magnetic resonance imaging (MRI). This was essential
as results from the previous study revealed that there is a paucity of reported radiological
parameters to define normal and pathoanatomical paediatric cohorts. A prospective crosssectional
study was conducted on 24 RPD children and adolescents and 25 age-matched
TD participants. Significant differences between the two groups were found for
acetabular inclination, tibial-femoral torsion, TT-TG distance, lateral patellar tilt,
congruence angle and cartilaginous sulcus angle. TT-TG distance and cartilaginous
sulcus angle were included in the final predictive model, which correctly classified 84.4%
of cases of recurrent patellar dislocation. Therefore, these measures should be included
in the evaluation of paediatric patients who present with recurrent patellar dislocation.
The paper describing these results was submitted as Ngo-Nguyen, C., Maine, S., Barzan,
M., Stockton, C.A., Modenese, L., Lloyd, D.G., Carty, C.P. Radiological predictors of
paediatric patellofemoral joint dislocation from medical imaging. The Knee.
The purpose of study three was to develop three subject-specific tibiofemoral
(TFJ) kinematic models, with either rigid or extensible ligament constraints, and a
subject-specific PFJ model for eight healthy paediatric participants. The estimated joint
and ligament kinematics from the three models were also validated against in vivo
kinematics measured from MRIs at four different TFJ flexion angles. The three TFJ
models were created from MRIs and used to solve the TFJ kinematics: (i) 5-rigid-link
parallel mechanism with rigid surface contact and isometric anterior cruciate (ACL),
posterior cruciate (PCL) and medial collateral (MCL) ligaments (Δ!"), (ii) 6-link parallel
mechanism with minimised ACL, PCL, MCL and lateral collateral ligament (LCL) length changes (Δ!
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Subject
Patellofemoral
Joint
Kinematic models
Patellar dislocation