Vol.:(0123456789) 1 3 Knee Surgery, Sports Traumatology, Arthroscopy https://doi.org/10.1007/s00167-019-05413-6 KNEE Fluoroscopic guided tunnel placement during medial patellofemoral ligament reconstruction is not accurate in patients with severe trochlear dysplasia Kaywan Izadpanah 1  · Hans Meine 2,3  · Johanna Kubosch 1  · Gernot Lang 1  · Andreas Fuchs 1  · Dirk Maier 1  · Peter Ogon 1,4  · Norbert P. Südkamp 1  · Matthias J. Feucht 1,5 Received: 8 August 2018 / Accepted: 13 February 2019 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2019 Abstract Purpose Accurate femoral tunnel placement is of great importance during medial patellofemoral ligament (MPFL) recon- struction. Purpose of the present study was to investigate the infuence of trochlear dysplasia on the accuracy of fuoroscopic guided femoral tunnel placement. Methods CT-Scans of 30 knees (fve with regular shaped trochlea, 10 with a Type A and fve each with a Type B, C, or D trochlear dysplasia) were imported into the image analysis platform MeVisLab. A 3D Bone Volume Rendering (VR) and a virtual lateral radiograph was created. The anatomic femoral MPFL insertion was identifed on the 3D VR. On virtual lateral radiographs, the MPFL insertion was identifed based on landmarks described by Schöttle et al. using three diferent perspectives: Best possible overlap of the femoral condyles (BC) and a tangent along posterior border of the posterior femoral cortex (pBC); a tangent along the anterior border of the posterior cortex (aBC); and best possible overlap of the distal part of the posterior femoral cortex (BF). Distances between the anatomic attachment and radiographically obtained insertions were measured on the 3D VR and compared according to the type of trochlear dysplasia. Results Signifcantly lower accuracy of fuoroscopy guided tunnel placement in MPFL reconstruction was found in knees with Type C and D dysplasia. This efect was observed irrespectively from the radiologic perspective (pBC, aBC, and FC). In the pBC view (highest accuracy), the mean distance from the centre of the anatomic MPFL attachment to the radiographically defned location was 4.3 mm in knees without trochlear dysplasia and increased to 4.8 mm in knees with Type A dysplasia, 3.8 mm in knees with Type B dysplasia, 6.7 mm (p < 0.001) in knees with Type C dysplasia, and 7.3 mm (p < 0.001) in knees with Type D dysplasia. Conclusion Radiographic landmark-based femoral tunnel placement in the pBC view provides highest accuracy in knees with a normal shaped trochlea or low grade trochlear dysplasia. In patients with severe dysplasia, fuoroscopy guided tunnel placement has a low accuracy, exceeding a critical threshold of 5 mm distance to the anatomic MPFL insertion irrespective of the radiographic perspective. In these patients, utilization of anatomic landmarks may be benefcial. Level of evidence IV. Abbreviations BC Best condylar ft pBC Best condylar ft with a tangent to the posterior femoral cortex aBC Best condylar ft with a tangent to the anterior femoral cortex BF Best femoral MPFL Medial patellofemoral ligament * Kaywan Izadpanah izadpanaha@me.com 1 Faculty of Medicine, Medical Center, Albert- Ludwigs-University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany 2 Medical Image Computing Group, Department of Informatics, University of Bremen, Enrique-Schmidt-Straße 5, 28359 Bremen, Germany 3 Institute for Medical Image Computing, Fraunhofer MEVIS Bremen, Am Fallturm 1, 28359 Bremen, Germany 4 Center of Orthopedic Sports Medicine Freiburg, Breisacher Strasse 84, 79110 Freiburg, Germany 5 Department of Orthopaedic Sports Medicine, Klinikum Rechts der Isar, TU Munich, Ismaninger Str. 22, 81675 Munich, Germany