Use of orthopedic markers for quantitative determination of proximal radial and ulnar growth in foals.

This study investigates the growth of the proximal (uppermost) parts of the radius and ulna bones in foals, using bone screws as markers for radiographic measurement. The findings shed light on the growth patterns and relations between the two bones, underscoring the damaging impact of unnecessary fixation and its potential repercussions on the elbow’s function.

Research Methodology

• The researchers conducted an experiment with six newborn Quarter Horse foals. They inserted cortical bone screws into the top sections of their right and left radius and ulna as radiographic markers.
• The distance between the respective markers was measured with the help of lateral radiographic views. The imaging data was collected at different time intervals until the foals were 72 weeks old.
• Radiographs were taken at two-week intervals for the first eight weeks, four-week intervals until they were 48 weeks old, and finally at 12-week intervals until they turned 72 weeks old.

Study Findings

• The results showed that the proximal radius and ulna grew at similar rates throughout the 72-week period, with the radius growing 3.5 cm and the ulna growing 3.4 cm.
• However, the growth in the ulnar physis (growth plate) only contributed to the length of the olecranon (the bony prominence of the elbow), and not to the ulnar diaphysis (the shaft of a long bone) below the cubital joint.
• The proximal radius moved lower relative to the ulna as it grew from the proximal radial physis (growth plate at the end of the bone). This emphasises the elbow joint’s continuous evolution and modification as the horse ages and grows.

Implications

• The study highlights the potential harm of transfixing the ulna to the radius while the proximal radial physis is still growing. This unnatural fixation impedes the natural shifting process within the joint, leading to potential subluxation (partial dislocation) of the elbow.
• The severity of the subluxation would be inversely related to the horse’s age at the time of fixation; meaning, the younger the horse at the time of treatment, the more significant the subluxation can be as it grows.
• The findings of the research, thereby, suggest caution against unnecessary orthopaedic interventions that could interrupt normal bone growth in foals and lead to impaired joint function.