The tibial tubercle-trochlear groove distance (TT-TG) is an
established measurement to assist diagnosis and treatment of
patellofemoral instability. However, little is known about the
distribution of TT-TG in osteoarthritic knees. The purpose of the
current study is to investigate the TT-TG in a large cohort of
osteoarthritic knees and to analyse, in particular, the association
of knee alignment and TT-TG.
Data from 962 consecutive patients [455 male, 507 female; mean
age ± SD 70.8 ± 9.3 (37-96)] who
had undergone 3D-CT and preoperative knee planning with validated
commercial 3D planning software before total knee arthroplasty (TKA)
were collected prospectively. The TT-TG, coronal hip knee ankle
angle (HKA), femoral anteversion (AVF), external tibial torsion
(ETT), and femorotibial rotation (Rot FT) were analysed. Pearson
correlations were performed to assess correlations between TT-TG,
mechanical axis, and rotational parameters
(p < 0.05).
HKA showed a strong correlation with TT-TG (r = 0.488;
p < 0.001) with 98 (67.1%) and 45 (30.8%) of valgus
knees having respective abnormal and pathological TT-TG values.
There were no significant correlations between parameters of
rotational alignment (AVF, ETT, Rot FT) and TT-TG. Mean TT-TG was
12.9 ± 5.6 mm, ranging from 0.0 to
33.7 mm. 325 (33.8%) of all patients had abnormal
(> 15 mm) and 101 (10.5%) had pathological
(> 20 mm) values. A varus alignment was present in
716 (74.4%) of the cases (HKA < - 1.5°), a
neutral alignment in 100 (10.4%), and a valgus alignment in 146
(15.2%) (HKA > 1.5°).
LEVEL OF CLINICAL EVIDENCE
A wide variation of TT-TG values in osteoarthritic knees was shown
by our results. There was a relevant influence of coronal limb
alignment on the TT-TG-the more valgus the higher and more
pathological the TT-TG. With the aim of having a more personalised
TKA, the individual TT-TG should be taken into account to improve
III. Retrospective cohort study.