Anteroposterior distance between the tibial tuberosity and trochlear groove in patients with patellar instability Miho J. Tanaka b, ⁎, Taylor D'Amore c , John J. Elias d , Gaurav Thawait e , Shadpour Demehri e , Andrew J. Cosgarea a a Department of Orthopaedic Surgery, The Johns Hopkins University School of Medicine, 5 th Floor, 601 N Caroline Street, Baltimore, MD 21287, United States b Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, 175 Cambridge St. Suite 400, Boston, MA 02114, United States c University of Rochester School of Medicine, 601 Elmwood Avenue, Rochester, NY 14642, United States d Department of Research, Cleveland Clinic Akron General, 1 Akron General Avenue, Akron, OH 44307, United States e Department of Radiology, The Johns Hopkins University School of Medicine, 1800 Orleans Street, Baltimore, MD 21287, United States article info abstract Article history: Received 22 March 2019 Received in revised form 3 July 2019 Accepted 25 August 2019 Available online xxxx Background: Our objective was to describe a measurement to assess sagittal tibial tuberosity (TT)–trochlear groove (TG) distance and to compare this between asymptomatic (control) patients and patients with symptomatic patellar instability. Methods: We compared static CT images of 22 fully extended knees of patients with symp- tomatic patellar instability with images of 22 asymptomatic knees. TT–TG distance was measured to quantify lateralization of the TT, and anteroposterior TT–TG distance was used to quantify the sagittal distance between these two points. Lateral trochlear inclination, sulcus angle, and trochlear depth were measured. Groups were compared using paired t tests (alpha = 0.05). Correlations of anteroposterior TT–TG distance with lateral trochlear inclina- tion, sulcus angle, and trochlear depth were assessed using linear and multivariate regression. Results: Mean TT–TG distances were 19.9 ± 4.4 mm (symptomatic) and 16.8 ± 5.5 mm (control) (mean ± std deviation) (P = 0.002). Mean anteroposterior TT–TG distances were 8.3 ± 7.8 mm (symptomatic) and −0.5 ± 4.6 mm (control) (P b 0.0001). The symptomatic group had greater measurements of trochlear dysplasia, with lower lateral trochlear inclination, greater sulcus angle, and lower trochlear depth (all P b 0.0001). Anteroposterior TT–TG distance and trochlear depth were strongly negatively correlated (r = 0.62, R 2 = 0.39, P b 0.0001). Conclusions: In asymptomatic patients, the anteroposterior TT–TG distance was −0.5 mm, indicating that the TG and TT were nearly in the same coronal plane. In patients with symp- tomatic patellar instability, the TG was almost nine millimeters anterior, and this distance cor- related with measurements of trochlear dysplasia. Level of evidence: III, case control study. © 2019 Elsevier B.V. All rights reserved. Keywords: Patellar instability Tibial tuberosity osteotomy Trochlear groove Trochlear dysplasia 1. Introduction Extensor mechanism alignment is an important consideration in the treatment of patellofemoral pathology. In the coronal plane, lateralization of the tuberosity has been associated with increased incidence of instability, caused by lateralizing forces on the extensor mechanism. The Knee xxx (xxxx) xxx ⁎ Corresponding author at: Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, 175 Cambridge St. Suite 400, Boston, MA 02114, United States. E-mail address: mjtanaka@gmail.com. (M.J. Tanaka). THEKNE-02885; No of Pages 8 https://doi.org/10.1016/j.knee.2019.08.011 0968-0160/© 2019 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect The Knee Please cite this article as: M.J. Tanaka, T. D'Amore, J.J. Elias, et al., Anteroposterior distance between the tibial tuberosity and troch- lear groove in patients with patella..., The Knee, https://doi.org/10.1016/j.knee.2019.08.011