Introduction. Tibial tuberosity and trochlear groove (TT-TG) distance has been investigated for the patients with primary patellofemoral subluxation/dislocation. To date, TT-TG distance after TKA has not been evaluated, and the effect of postoperative TT-TG distance on patellar tracking is unknown. The purpose of the current study was to investigate the effect of TT-TG distance and rotational position of the femoral and tibial components on patellar tilt after TKA. Methods. Consecutive 115 knees for the diagnosis of osteoarthritis were included in the current study. TKA was performed using posterior cruciate ligament sacrificed prosthesis. A total of 17 men and 96 women with an average age of 75.3 years were included at the time of the surgery. Computed tomography (CT) was taken after TKA in full extension. Postoperative TT-TG distance was measured as a reference of surgical epicondylar axis (SEA) of the femur. Patellar tilt was defined as the angle of the patellar component relative to SEA. Femoral and tibial component rotation was measured as the angle relative to SEA and tibial antero-posterior (AP) axis. Tibial AP axis was defined as the line connecting medial one-third of the tibial tuberosity and center of medial-lateral width. Pearson correlation coefficients were calculated to determine the correlations between patellar tilt and TT-TG distance and between patellar tilt and femoral and tibial component rotation. Results. TT-TG distance had significant correlation with patellar tilt (Figure 1; r = 0.254, p = 0.006), whereas femoral component rotation (p = 0.092) and tibial component rotation (p = 0.062) were not correlated with patellar tilt. Concerning the effect on TT-TG distance, femoral component rotation (r = 0.248, p = 0.008) and tibial component rotation (r = −0.567, p < 0.001) were correlated with TT-TG distance. Conclusion. The current study investigated the effect of TT-TG distance on patellar tilt with postoperative CT scan. Greater TT-TG distance resulted in more patellar tilt, which might have negative effects on patellar tracking. In previous clinical studies, femoral component and tibial component rotation affected patellar maltracking. In the current study, however, component rotation itself did not affect patellar tilt. Postoperative TT-TG distance includes information of rotational and medial-lateral positioning of the femoral and tibial components, and can be a useful indicator to predict patellar maltracking after TKA. For any figures or tables, please contact authors directly

Statement of purpose. To determine whether the Q-angle, measured in a defined and reproducible manner, correlates with the TT-TG distance in patients with patellar instability. Methods and results. The Q-angle represents the angle between the vector of action of the quadriceps and patellar tendon. The normal angle is 14. +/−. 3° in males and 17. +/−. 3° in females. An increased Q-angle is associated with an increased risk of patellar instability, although there is disagreement on its reliability and validity. It can be affected by the anatomical points used to record the measurement, the position of the limb and whether the quadriceps are relaxed or contracted. TT-TG is ascertained by axial CT scanning, with a value exceeding 20mm associated with patellar instability. Q-angles were measured in patients presenting to the patella clinic who had previously undergone Lyon protocol CT scanning for patellar instability. Patients were positioned supine with both feet in neutral rotation taped to a specially designed wooden board (the same position used for CT scanning). The anatomical landmarks were the anterior superior iliac spine, the centre of the patella and the centre of the tibial tuberosity. Both knees were measured with the quadriceps relaxed (relaxed Q-angle) and contracted (contracted Q-angle). Thirty-four knees were measured, 24 pathological and 10 non-pathological. Pearson moment correlation demonstrated a significant correlation between relaxed Q-angle and TT-TG in all knees (R=-0.377; p=0.028). In pathological knees, contracted Q-angle also demonstrated a significant correlation with TT-TG but to a lesser extent than relaxed Q-angle (R=-0.428; p=0.037, R=-0.578; p=0.003 respectively). Linear regression analysis demonstrated relaxed Q-angle as a significant predictor of TT-TG distance in pathological knees. Contracted Q-angle was not significant. Conclusion. The relaxed Q-angle, when measured as above, reliably correlates with and is a significant predictor of TT-TG distance in patients with symptomatic patellar instability

Aims

The aim of this study was to establish consensus statements on the diagnosis, nonoperative management, and indications, if any, for medial patellofemoral complex (MPFC) repair in patients with patellar instability, using the modified Delphi approach.

Aims

Trochlear dysplasia is a significant risk factor for patellofemoral instability. The Dejour classification is currently considered the standard for classifying trochlear dysplasia, but numerous studies have reported poor reliability on both plain radiography and MRI. The severity of trochlear dysplasia is important to establish in order to guide surgical management. We have developed an MRI-specific classification system to assess the severity of trochlear dysplasia, the Oswestry-Bristol Classification (OBC). This is a four-part classification system comprising normal, mild, moderate, and severe to represent a normal, shallow, flat, and convex trochlear, respectively. The purpose of this study was to assess the inter- and intraobserver reliability of the OBC and compare it with that of the Dejour classification.