Louis Dagneaux1, Raphael Allal2, Martine Pithioux2, Patrick Chabrand2, Matthieu Ollivier2, Jean-Noël Argenson2. 1. Aix Marseille University, APHM, CNRS, ISM, Sainte-Marguerite Hospital, Institute for Locomotion, Department of Orthopaedics and Traumatology, Marseille, France; Department of Orthopaedic Surgery, Lower Limb Surgery Unit, Lapeyronie University Hospital, Montpellier Cedex 05, France; Aix Marseille University, CNRS, ISM, Inst Movement Sci, France. Electronic address: louisdagneaux@gmail.com. 2. Aix Marseille University, APHM, CNRS, ISM, Sainte-Marguerite Hospital, Institute for Locomotion, Department of Orthopaedics and Traumatology, Marseille, France.
Abstract
BACKGROUND: Malrotation of the femur is a frequent complication in the management of a diaphyseal fracture. It is often responsible for pain and adverse functional results. Among these complications, contact stress effects on the patellofemoral joint are recognized as predictive factors of impaired results. The purpose of this study was to analyze the effect of malrotation on stress distribution on the patellofemoral joint, using radiological measurement and three-dimensional finite element models. METHODS: Functional analysis of the patellofemoral joint was evaluated in eight knee pairs from patients with unilateral femoral fractures and subsequent femoral malrotation. A computed tomography-based protocol allowed patellofemoral joint analysis. A finite element model of the healthy (contralateral) knee was then created from 3D reconstruction at 30° flexion. In a finite element model, incremental rotational malalignment was simulated to observe changes in stress distribution on the patellar surface. RESULTS: Femoral malrotation was associated with anomalies of patellofemoral joint rotational alignment. Internal rotation resulted in increased stress on the lateral side of the patella, and external rotation increased inferior medial side stress. CONCLUSIONS: Rotational disorders of the distal femur resulted in increased stress on the patellofemoral joint and alignment changes. Malrotation in internal and external rotation might cause patellofemoral pain syndrome from rotations <10°. Care should be taken especially for internal malrotation in the management of femoral shaft fracture.
BACKGROUND: Malrotation of the femur is a frequent complication in the management of a diaphyseal fracture. It is often responsible for pain and adverse functional results. Among these complications, contact stress effects on the patellofemoral joint are recognized as predictive factors of impaired results. The purpose of this study was to analyze the effect of malrotation on stress distribution on the patellofemoral joint, using radiological measurement and three-dimensional finite element models. METHODS: Functional analysis of the patellofemoral joint was evaluated in eight knee pairs from patients with unilateral femoral fractures and subsequent femoral malrotation. A computed tomography-based protocol allowed patellofemoral joint analysis. A finite element model of the healthy (contralateral) knee was then created from 3D reconstruction at 30° flexion. In a finite element model, incremental rotational malalignment was simulated to observe changes in stress distribution on the patellar surface. RESULTS:Femoral malrotation was associated with anomalies of patellofemoral joint rotational alignment. Internal rotation resulted in increased stress on the lateral side of the patella, and external rotation increased inferior medial side stress. CONCLUSIONS: Rotational disorders of the distal femur resulted in increased stress on the patellofemoral joint and alignment changes. Malrotation in internal and external rotation might cause patellofemoral pain syndrome from rotations <10°. Care should be taken especially for internal malrotation in the management of femoral shaft fracture.