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The stability assessment after bone plate fixation is an important link to ensure the smooth healing of fractures and the restoration of limb function. It requires comprehensive consideration from multiple aspects. The following is a detailed introduction for you:
Imaging assessment
X-ray examination: In the early postoperative period, X-ray films should be rechecked regularly to observe the position of the fracture end and the shape of the bone plate. Under normal circumstances, there should be no obvious displacement at the fracture end, and the bone plate should not be deformed or fractured. If widening of the gap, angulation deformity, bending of the bone plate or loosening of the screws are found at the fracture end, it indicates that the stability may be insufficient. For instance, when re-examining X-ray films after tibial fracture surgery, if it is observed that the cortical bones on both sides of the fracture line no longer closely align and show obvious separation, it may indicate unstable fixation.
CT examination: For complex fractures, such as intra-articular fractures or multi-segment fractures, CT examination can provide more detailed three-dimensional information on the fracture ends and bone plate fixation. It can clearly display the splicing situation of fracture blocks, the degree of adhesion between the bone plate and the bone surface, as well as the distribution and depth of screws. If the CT images show that there are large gaps between the fracture blocks or the screws fail to effectively fix the fracture blocks, it indicates poor fixation stability.
MRI examination: Although MRI is relatively less used in evaluating the stability of bone plate fixation, in some cases, such as when there is suspicion of occult nonunion of fractures or surrounding soft tissue damage affecting the stability of fixation, MRI can help observe the soft tissue conditions at the fracture site, such as whether there is hematoma, edema, etc., indirectly reflecting the stability of fixation.
Assessment of clinical signs
Pain condition: The patient’s pain should gradually ease after the operation. If the patient still has persistent pain for a period of time after the operation, especially the pain intensifies when moving the limbs, it may indicate unstable fixation. For instance, after bone plate fixation of femoral shaft fractures, if the patient experiences significant pain in the affected limb when walking and the pain does not completely subside even after rest, it is necessary to be vigilant about whether there is a problem with the fixation.
Limb swelling: Under normal circumstances, limb swelling after the operation will gradually subside over time. If the swelling persists or worsens instead, it may be related to unstable fixation leading to local bleeding and aggravated inflammatory response. For instance, after the fixation of the bone plate for an ankle fracture, if the swelling in the ankle persists for a long time and is accompanied by an increase in skin temperature, it might be a manifestation of local circulatory disorders caused by unstable fixation.
Abnormal movement: When performing palpation at the fracture site or having the patient move the limb, if abnormal movement can be felt at the fracture end, such as a bone rubbing sensation or a bone rubbing sound, this is direct evidence of unstable fixation. For instance, after the forearm fracture bone plate is fixed, if the doctor can feel abnormal movement between the fracture ends during the examination, it indicates that the fixation effect is not good.
Biomechanical assessment
Stress test: Apply a certain stress to the fixed area through a specific instrument and observe the response of the fracture end and the fixation system. For example, axial pressure, torsional force, etc. are applied to the femoral fracture plate fixation model using a biomechanical testing machine to measure the displacement of the fracture end and the deformation of the fixation system. If the displacement is too large or the fixing system is damaged prematurely, it indicates insufficient fixing stability.
Finite element analysis: By using computer technology to establish finite element models for fractures and bone plate fixation, simulate the force conditions under different physiological states, and analyze the stress distribution and deformation of the fracture ends and the fixation system. The stability of the fixed system can be predicted through finite element analysis, providing a reference for clinical treatment. For example, for the fixation of complex hip fracture plates, finite element analysis can reveal the stress concentration areas at the fracture ends and on the plates under different motion states, thereby evaluating the stability of the fixation.
Functional evaluation
Joint range of motion: Assess the range of motion of the joints around the fracture site. If the fixation is unstable, joint movement may be restricted, or pain and instability may occur during the movement. For example, after the bone plate of a knee fracture is fixed, the flexion and extension range of motion of the patient’s knee joint is significantly less than the normal range, and the knee joint feels unstable during movement, which may be related to the unstable fixation.
Muscle strength assessment: Observe the recovery of muscle strength in the affected limb. Unstable fixation may lead to muscle atrophy and decreased muscle strength, as the instability at the fracture site can affect the normal contraction and functional exercise of the muscles. For example, after the fixation of the bone plate for upper limb fractures, the muscle strengths such as grip strength and elbow flexion strength of the affected limb are significantly lower than those of the healthy side, suggesting that there may be problems with the fixation and affecting the normal functional recovery of the muscles.
Gait analysis: For patients with lower extremity fractures, gait analysis can assess the stability and coordination of their walking. Unstable fixation may lead to conditions such as limping and abnormal gait when patients walk. For example, after the bone plate of a foot fracture is fixed, the patient shows obvious lameness when walking, and the affected limb dares not bear full weight, indicating that the fixation may be unstable and affect the patient’s normal walking function.