The Effect of Patella Height and Trochlear Grove Depth on Patella Lateral Tilt
Brian Noehren1 Steve Duncan1, Christopher Powers2, Christian Lattermann1
1
University of Kentucky, Lexington, Kentucky, USA
2
University of Southern California, Los Angeles, California, USA
email for correspondence: b.noehren@uky.edu
Introduction
Excessive lateral tilting of the patella has been linked to
lateral patella compression syndrome and is thought to
be one factor that may underlie the development of
patellofemoral pain (PFP). Although excessive lateral
tilting of the patella is a common finding in persons with
PFP, the underlying cause of this anomaly is not fully
understood. From a structural standpoint, 2 structural
predispositions have been discussed in the literature: 1)
patella alta, and 2) trochlear dysplasia. Both of these
conditions result in diminished patella stability typically
afforded by the lateral femoral condyle of the distal
femur. Additionally, Hvid et al., has proposed that during
development a higher riding patellar would result in a
shallower trochlear grove (1). However, few reports have
assessed this relationship. To date, a clear
understanding of how altered bony structure of the distal
femur relates to lateral patella tilt is lacking. The purpose
of the current study was to assess the association
between patella height, trochlear groove depth and
lateral patella tilt (LPT). We hypothesized that patella
height and trochlear grove depth would significantly
predict patellar tilt.
As a secondary aim we also
assessed the relationship between patella height and
trochlear grove depth.
Methods
Thirty two subjects participated in this study. Subjects
could not have any previous history of patellar
dislocations of instability. Pre-operative x-rays for
patients scheduled to undergo either an anterior cruciate
ligament reconstruction or cartilage repair surgery were
used. Axial and lateral x-rays of the patellofemoral joint
were obtained in weight bearing with the knee flexed to
30 degrees. The vertical height of the patella was
quantified using the Insall-Savati ratio (ISR) which
measures the length of the patella tendon relative to the
length of the patella. The depth of the trochlear groove
was assessed by measuring the sulcus angle (SA) which
was quantified as the angle formed by the intersection of
lines defining the medial and lateral slopes of the
trochlear groove. LPT was quantified as the angle
formed between a line drawn along the lateral facet of
the patella and a line along the posterior aspects of the
medial and lateral femoral condyles. Using this measure,
a smaller angle was representative of greater LPT. The
relationship between the ISR, SA, and LPT was
assessed using a step wise linear regression model. The
relationship between the ISR and the SA was assessed
using pearson product moment correlation coefficient.
Results
The ISR and SA predicted 54% of the variance in patellar
tilt. The model with SA and ISR resulted in r= 0.734 and
p=0.000. There was also a non significant correlation
between SA and ISR (r=-0.25, p=0.17).
Discussion
The purpose of this study was to evaluate if patella tilt
could be predicted by the ISR and the SA. We found
that these two measures predicted over 50% of the
varience in patellar tilt which has implications for various
populations with PFP. A higher riding patella and a
shallower troclear grove lessens the ability of the
osseous structures of the distal femur to resist the lateral
pull of the quadriceps and the iliotibial band. This could
lead to greater shear across the patellofemoral joint and
result in pain. Additionally, the effectiviness of bracing
and taping to alter lateral patellar tilt may be restricted
by osseous structures of the patellofemoral joint. Future
studies should consider the effectivness of these
treatments with different types of boney aligment.
Interestingly, one the greatest causes of revisions for
total knee arthoplasty is PFP (2). Good patellofemoral
articulation has previously been cited to be an important
but overlooked contributer to reducing PFP after surgery
(3). Establishing a proper patellar to trochlear
relationship is key to a successful revision knee
arthroplasty. With newer generation knee implants,
deeper trochlear grooves have been designed to help
promote improved patellar tracking. We also found no
relationship between the ISR and the SA. The
differences in the current study as compared to Hvid et
al, could be do in part to the partipants in Hvid et al,
study having patella instabiilty wheras we did not. The
relationship between these variables maybe stronger in
more pronounced cases. However, within our sample we
had individuals with a high riding patella (figure 1) that
were not associated with a shallow trochlear grove.
Acknowledgments:
These results were in part presented at the 2011
combined sections meeting of the American Physical
Therapy Association
References
1. Hvid, I et al (1983) ACTA ORTHOP ,54:91-93.
2. Cooney, W, et al (2005). CORR,440:117-121.
3. McPerson, (2006). Instr Course Lect, 55:439-448