Lower extremity strength and hopping and jumping ground reaction forces in children with neurofibromatosis type 1

Area of Science:

• Pediatric Orthopedics
• Neuromuscular Disorders
• Biomechanical Analysis

Background:

• Neurofibromatosis type 1 (NF1) is a genetic disorder associated with various musculoskeletal complications.
• Previous research indicated reduced grip strength in children with NF1, but lower extremity strength remains less understood.
• Assessing functional capacity alongside muscle strength is crucial for understanding the impact of NF1 on daily activities.

Purpose of the Study:

• To investigate lower extremity muscular force production in children with NF1, extending prior grip strength findings.
• To examine the relationship between isometric muscle strength and functional performance in children diagnosed with NF1.
• To evaluate the utility of combining hand-held dynamometry with functional tasks for comprehensive assessment.

Main Methods:

• Compared force production in hip extension, knee extension, and ankle plantar flexion using hand-held dynamometry (HHD) between 26 children with NF1 and 48 typically developing controls.
• Assessed functional performance through hopping and jumping tasks measured on a force plate.
• Analyzed data for statistical significance in strength differences and correlations between isometric strength and functional task performance.

Main Results:

• Children with NF1 exhibited significantly lower isometric force production during hip extension compared to controls (p<0.01).
• No significant differences in force production were observed for knee extension or ankle plantar flexion between groups.
• A significant relationship was identified between ground reaction forces during hopping/jumping and knee extensor strength in the NF1 cohort.

Conclusions:

• Children with NF1 present with specific deficits in hip extensor strength, while other lower limb muscle groups maintain comparable strength to peers.
• The integration of functional tasks with traditional dynamometry provides valuable insights into the functional capabilities of children with NF1.
• This combined assessment approach aids in understanding the link between clinical strength measures and real-world functional activities in NF1.