Fixators dynamization for delayed union and non-union of femur and tibial fractures: a review of techniques, timing and influence factors

The optimal balance between mechanical environment and biological factors is crucial for successful bone healing, as they synergistically affect bone development. Any imbalance between these factors can lead to impaired bone healing, resulting in delayed union or non-union. To address this bone healing disorder, clinicians have adopted a technique known as "dynamization" which involves modifying the stiffness properties of the fixator. This technique facilitates the establishment of a favorable mechanical and biological environment by changing a rigid fixator to a more flexible one that promotes bone healing. However, the dynamization of fixators is selective for certain types of non-union and can result in complications or failure to heal if applied to inappropriate non-unions. This review aims to summarize the indications for dynamization, as well as introduce a novel dynamic locking plate and various techniques for dynamization of fixators (intramedullary nails, steel plates, external fixators) in femur and tibial fractures. Additionally, Factors associated with the effectiveness of dynamization are explored in response to the variation in dynamization success rates seen in clinical studies.

The use of circular and hybrid external skeletal fixation systems to repair open tibial fractures in large ruminants: a report of six clinical cases

A prospective clinical study consisting of six bovines (200-300 kg body weight) undergoing open tibial fractures was carried out, to evaluate the use of circular and hybrid external skeletal fixation (ESF) systems for open tibial fracture repair in large ruminants. The ESF systems consisting of 4 full rings (n = 2), 8 half-rings (n = 1), 2 full rings with 2 sidebars (n = 2) or 2 full rings with 4 sidebars (n = 1) were used to treat open tibial fractures. The healing progress of the animals was evaluated based on different clinical and radiographic examinations. The level of fracture reduction, alignment, and fixation ranged between satisfactory to adequate in all the animals. The fixators were well tolerated and maintained by the animals till the complete repair of the fracture. Adequate fracture healing with satisfactory functional recovery was observed in all the animals in about 3-4 months. The different designs of ESFs were found to provide adequate stability in open tibial fractures in animals weighing 200-300 kg. However, the fixators need to be evaluated in numerous clinical cases to establish their suitability in routine clinical settings.

Biomechanical analysis of the role of hinge support fixators on hinge stability in medial closing wedge distal femoral osteotomy

BACKGROUND

This study aimed to examine the hinge-stabilizing biomechanical effects of hinge support fixators, applied for lateral hinge fractures sustained following distal femoral osteotomy.

METHODS

Medial closing wedge distal femoral osteotomy was performed using a locking plate on 10 cadaveric limbs. The limbs were divided into two groups: the non-fracture group and the lateral hinge fracture group. A cyclic axial load of 400 N was applied to the knee to keep it extended and flexed at 45°. The hinge-stabilizing effects of adding a screw or a short support plate to the lateral fracture site were examined by measuring the translation and rotational angles of the anterodistal and posterodistal hinge positions as well as the surface strains of the medial locking plate.

FINDINGS

Translation and rotation in the fracture group were significantly more pronounced than in the non-fracture group, at the anterodistal and posterodistal positions. Translations at both positions were significantly reduced, by adding the support plate, during both extension and 45-degree flexion in the fracture group. The rotation at the posterodistal position upon extension and the anterodistal position upon 45-degree flexion was significantly reduced by the support plate. The surface strain of the medial plate in the fracture group was significantly reduced by the support plate upon both extension and 45-degree flexion.

INTERPRETATION

Lateral hinge fractures caused abnormal hinge movements, which were significantly reduced by the short support plate. A short support plate could be used if a hinge fracture occurs during distal femoral osteotomy, to improve lateral hinge stability.