A simple method to rapidly assess the tibial tuberosity—trochlear groove distance using computed tomography

BACKGROUND: The tibial tuberosity–trochlear groove (TTTG) distance is used to assess patellofemoral instability (PFI) and the likelihood of the development of patellofemoral disorders. The current gold standard in the assessment of the TTTG is computed tomography (CT) or magnetic resonance imaging (MRI). The current image software used for viewing these CT images does not allow for easy assessment of the TTTG. AIMS: This study presents a simple method to measure the TTTG on any image software, utilizing easily available and affordable stationary. METHODS: Four consecutive patients with no known knee pathologies were selected from recent studies at our institution. Their TTTGs were measured using this study’s method and validated using the standard, freely available image analysis software Fiji. Pre-defined anatomical landmarks were located and marked using adhesive pieces of paper. The TTTG was defined as the distance between parallel lines through the apex of the tibial tuberosity and trough of the trochlear groove, where each of these lines is perpendicular to the Dorsal Condylar Line. RESULTS: The TTTG measured using this study’s method was found to be in agreement with the measurements made using Fiji software. CONCLUSIONS: This study demonstrates that the TTTG can be simply and quickly assessed using readily available and affordable stationery, without the need for expensive or complex secondary analysis software. This could allow for the assessment of PFI in the outpatient clinic whilst the patient is present, offering valuable assistance to the orthopaedic surgeon in clinical decision making.