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A Simple Critical-sized Femoral Defect Model in Mice
Published on: March 15, 2015
Pathologic morphology of the dislocated proximal femur in children with cerebral palsy
Insights
Children with neuromuscular imbalance experience hip deformities due to muscle forces. These forces cause femoral head deformation, cartilage loss, and progressive hip subluxation, leading to bone pain.
Area of Science:
- Orthopedics
- Pediatric Orthopedics
- Pediatric Rheumatology
Background:
- Neuromuscular imbalance in children, such as spastic diplegia and tetraplegia, can lead to significant musculoskeletal complications.
- Hip joint deformities are a common and challenging issue in these pediatric populations, impacting mobility and quality of life.
Purpose of the Study:
- To investigate the gross, microscopic, and radiographic anatomical changes in the proximal femur of children with neuromuscular imbalance.
- To elucidate the deforming forces and mechanisms leading to hip subluxation and dislocation in this patient group.
Main Methods:
- Evaluation of twelve resected proximal femora from children with spastic diplegia or tetraplegia.
- Detailed gross, microscopic, and radiographic analysis of the resected specimens to identify anatomical alterations.
Main Results:
- Consistent wedge-shaped epiphyses and deformed femoral heads were observed in all specimens.
- Significant articular cartilage loss and furrowed erosion of epiphyseal bone indicated sustained blunt force.
- Histological examination revealed irregular capital femoral physis and hypertrophic lesser trochanter physis.
- Muscle imbalances, particularly spastic adductors and iliopsoas, contribute to proximal femur subluxation.
Conclusions:
- The interaction of spastic muscles and hip structures leads to progressive proximal femur subluxation.
- Acetabular rim and capsular deformation of the femoral head creates a fulcrum, causing progressive subluxation.
- This mechanism prevents complete dislocation but results in bone pain due to cartilage erosion.
Abstract:
We describe the gross and microscopic anatomic changes in the hip that result from the deforming forces in children with neuromuscular imbalance. Twelve dislocated proximal femora that had been resected from children with spastic diplegia or tetraplegia were evaluated with respect to their gross, microscopic, and radiographic structure. The epiphyses were wedge shaped with deformation of the femoral head apparent in all cases. In addition to a severe loss of articular cartilage, a furrowed erosion of epiphyseal bone suggested a sustained, blunt, band-like force across the surface of the hip where it opposed the acetabular labrum. The underlying physis of the capital femur was irregular with aberrant histologic structure, whereas that of the lesser trochanter was hypertrophic and angulated in a superior and anterior direction. A significant degree of valgus was not noticeable in most specimens. In summary, the spastic adductor and iliopsoas, responsible for the changes in the lesser trochanter, work in conjunction with the hip flexor and internal rotator muscles to subluxate the proximal femur. In the process, the superior rim of the acetabulum and capsule causes focal deformation of the superolateral femoral head, creating a fulcrum upon which the hip then progressively subluxates. The indentation locks the femoral head at the lateral acetabular margin, preventing complete dislocation, but leading to bone pain consequent to cartilage erosion.
