Growth Retardation (Hemiepiphyseal Stapling) and Growth Acceleration (Periosteal Resection) as a Method to Improve Guided Growth in a Lamb Model.

BACKGROUND

Guided growth corrects pediatric limb deformity by inhibiting growth on the convexity of the bone. Both modular and rigid implants have been used; we endeavor to determine whether a clear advantage of one implant exists. We further hypothesize that improved correction could be realized by accelerating growth with resection of the periosteum.

METHODS

Sixteen lambs underwent guided growth of the medial proximal tibia (the opposite limb served as a control). Group 1 used a rigid staple (n=5); group 2 a modular plate and screw construct (n=5), and group 3 had a similar device plus periosteal resection (n=6). Radiographs tracked the progression of deformity in the coronal plane. Before sacrifice, pulsed fluorochrome labels allowed for temporal and spatial growth rate analysis. At sacrifice, True Deformity was calculated (and compared with control tibia) from standardized radiographs in the coronal and sagittal planes. Device Efficiencies were normalized by dividing True Deformity produced (degrees) by the Expected Growth gain (mm) from the control limb.

RESULTS

Group 3 produced greater coronal plane deformity than group 1 by an average of 2.2 degrees per month (P=0.001) and group 2 by an average of 2.4 degrees per month (P=0.0007). At sacrifice, groups 1 and 2 were equally effective at limiting growth to 75% of control; no differences in growth retardation were noted. No differences in Device Efficiency were noted between groups 1 and 2. The Device Efficiency was significantly different between groups 1 and 2 with comparison with group 3 (P=0.05 and P=0.022); with a 2.5 degree/mm faster deformation in the stripped cohort.

CONCLUSIONS

Rigid implants initially produced deformity quicker than modular constructs; yet ultimately, both implants were equally effective at guiding growth. Device Efficiency for the modular group improved significantly with the addition of periosteal stripping as method to accelerate growth.