Influence of Medial Patellofemoral Ligament Reconstruction on Patellofemoral Contact in Patients With Low-Flexion Patellar Instability: An MRI Study

Markus Siegel; Elham Taghizadeh; Thomas Lange; Andreas Fuchs; Tayfun Yilmaz; Philipp Maier; Hans Meine; Hagen Schmal; Kaywan Izadpanah

doi:10.1177/23259671231160215

Influence of Medial Patellofemoral Ligament Reconstruction on Patellofemoral Contact in Patients With Low-Flexion Patellar Instability: An MRI Study

Orthop J Sports Med. 2023 May 16;11(5):23259671231160215. doi: 10.1177/23259671231160215. eCollection 2023 May.

Authors

Markus Siegel¹, Elham Taghizadeh², Thomas Lange³, Andreas Fuchs¹, Tayfun Yilmaz¹, Philipp Maier¹, Hans Meine², Hagen Schmal^{1

4}, Kaywan Izadpanah¹

Affiliations

¹ Department of Orthopedic Surgery and Traumatology, Freiburg University Hospital, Albert Ludwigs University of Freiburg, Freiburg, Germany.
² Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany.
³ Division of Medical Physics, Department of Diagnostic and Interventional Radiology, Medical Center-University of Freiburg, Faculty of Medicine, Albert Ludwigs University of Freiburg, Freiburg, Germany.
⁴ Department of Orthopedic Surgery, University Hospital Odense, Odense, Denmark.

Abstract

Background: Medial patellofemoral ligament (MPFL) reconstruction is a well-established procedure for the treatment of patients with patellofemoral instability (PFI) at low flexion angles (0°-30°). Little is known about the effect of MPFL surgery on patellofemoral cartilage contact area (CCA) during the first 30° of knee flexion.

Purpose/hypothesis: The purpose of this study was to investigate the effect of MPFL reconstruction on CCA using magnetic resonance imaging (MRI). We hypothesized that patients with PFI would have a lower CCA than patients with healthy knees and that CCA would increase after MPFL reconstruction over the course of low knee flexion.

Study design: Cohort study; Level of evidence, 2.

Methods: In a prospective matched-paired cohort study, the CCA of 13 patients with low-flexion PFI was determined before and after MPFL reconstruction, and the data were compared with those of 13 healthy volunteers (controls). MRI was performed with the knee at 0°, 15°, and 30° of flexion in a custom-designed knee-positioning device. To suppress motion artifacts, motion correction was performed using a Moiré Phase Tracking system via a tracking marker attached to the patella. The CCA was calculated on the basis of semiautomatic cartilage and bone segmentation and registration.

Results: The CCA (mean ± SD) at 0°, 15°, and 30° of flexion for the control participants was 1.38 ± 0.62, 1.91 ± 0.98, and 3.68 ± 0.92 cm², respectively. In patients with PFI, the CCA at 0°, 15°, and 30° of flexion was 0.77 ± 0.49, 1.26 ± 0.60, and 2.89 ± 0.89 cm² preoperatively and 1.65 ± 0.55, 1.97 ± 0.68, and 3.52 ± 0.57 cm² postoperatively. Patients with PFI exhibited a significantly reduced preoperative CCA at all 3 flexion angles when compared with controls (P ≤ .045 for all). Postoperatively, there was a significant increase in CCA at 0° of flexion (P = .001), 15° of flexion (P = .019) and 30° of flexion (P = .026). There were no significant postoperative differences in CCA between patients with PFI and controls at any flexion angle.

Conclusion: Patients with low-flexion patellar instability showed a significant reduction in patellofemoral CCA at 0°, 15°, and 30° of flexion. MPFL reconstruction increased the contact area significantly at all angles.

Keywords: MPFL reconstruction; cartilage contact area; dynamic MRI evaluation; patellofemoral instability.