Highly variable tibial tubercle–trochlear groove distance (TT–TG) in osteoarthritic knees should be considered when performing TKA
Hochreiter, B., Hirschmann, M.T., Amsler, F. et al.Knee
Purpose
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.
Methods
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).
Results
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°).
Conclusion
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 the outcome.
Level of clinical evidence
III. Retrospective cohort study.
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