Complicated Muscle-Bone Interactions in Children with Cerebral Palsy

Abstract

Purpose of review: The goal of this review is to highlight the deficits in muscle and bone in children with cerebral palsy (CP), discuss the muscle-bone relationship in the CP population, and identify muscle-based intervention strategies that may stimulate an improvement in their bone development.

Recent findings: The latest research suggests that muscle and bone are both severely underdeveloped and weak in children with CP, even in ambulatory children with mild forms of the disorder. The small and low-performing muscles and limited participation in physical activity are likely the major contributors to the poor bone development in children with CP. However, the muscle-bone relationship may be complicated by other factors, such as a high degree of fat and collagen infiltration of muscle, atypical muscle activation, and muscle spasticity. Muscle-based interventions, such as resistance training, vibration, and nutritional supplementation, have the potential to improve bone development in children with CP, especially if they are initiated before puberty. Studies are needed to identify the muscle-related factors with the greatest influence on bone development in children with CP. Identifying treatment strategies that capitalize on the relationship between muscle and bone, while also improving balance, coordination, and physical activity participation, is an important step toward increasing bone strength and minimizing fractures in children with CP.

Keywords: Bone; Cerebral palsy; Fragility fracture; Mechanical loading; Muscle; Pediatrics.

Figure 1.

The figure summarizes the deficit in trabecular bone microarchitecture observed in children with cerebral palsy (CP). Trabecular bone microarchitecture was assessed in the lateral distal femur immediately above the growth plate (A), as indicated by the dotted rectangle, using magnetic resonance imaging. Binarized magnetic resonance images show the remarkable underdevelopment of trabecular bone microarchitecture in a nonambulatory boy with CP (B) when compared to typically developing boy of the same age and near the 50^th percentile for height and body mass (C). The images were modified from Modlesky et al. (49).

Figure 2.

Raw T1-weighted magnetic resonance images of the midtibia and the surrounding leg musculature and adipose tissue taken from an ambulatory boy with mild CP (A) and a typically developing boy not different in age or race (B). The images demonstrate the marked deficit in cortical bone architecture (small arrow indicating a thin tibia cortex) and muscle size (gray) and the high infiltration of fat within (intramuscular; medium arrow) and adipose tissue around (intermuscular; large arrow) the musculature. The figure was modified from Whitney et al. (22).

Figure 3.

A raw coronal magnetic resonance image of thigh muscles and femurs (A) and segmented images showing the smaller and thinner cortical bone of a nonambulatory boy with CP (black ring; B) compared to the cortical bone of a typically developing boy not different in age or race (C). The images were generated from participants in Modlesky et al. (47). Also shown (D) are the theoretical changes in bone in: 1) typically developing children, 2) children with CP involved in a muscle-based intervention (e.g., resistance training) and not receiving a common treatment that adversely affects muscles, and 3) children with CP not involved in a muscle-based intervention and receiving a common treatment that adversely affects muscle. The figure was modified from Modlesky and Lewis (125).