Case Study: Genu Valgum - Dysplasia
Presented by Peter M. Stevens, MD
University of Utah
Salt Lake City, Utah
Clinical Presentation
A four-and-a-half-year-old girl presented with progressive and painful knock knee deformities. She has a bone growth disorder called spondylometaphyseal dysplasia contributing to her genu valgum. While the growth plates (physes) are weakened by this condition, the displacement of gravity beyond the confines of the knee tends to accelerate the damage and limits her vertical growth.
The mechanical axis (or center of gravity) is represented by a dotted line drawn from the center of the hip to the center of the ankle. Normally this should bisect the knee. That would provide balance of forces across the knee and spare the adjacent ligaments from undue stress. However, in her condition, the mechanical axis, and thus the forces of gravity, are lateral to the knee. This pulls the patella outward, causing knee pain. The unbalanced forces cause ligament stress and inhibit the growth of the outer portion of both the femur and the tibia. Left untreated, the natural history is one of progressive deformity, awkward gait, and knee pain.
Operative Technique
Using the guided growth technique with the eight-Plate, the bones were never cut, neurovascular risk was avoided, instability was avoided, and there was no healing interval. Correction occured gradually through growth. As growth occured, the screws were free to diverge but the plate resisted longitudinal expansion on the instrumented side of the growth plate.
Post-Op Course
Through guided growth, the deformities correct gradually and safely over a period of eleven months following eight-Plate application. There is no cast and immediate mobilization is permitted. The mechanical axis is successfully restored to neutral whereupon the pain resolves and the gait pattern normalizes. The ligaments, cartilage and physes are alleviated of the harmful effects of eccentric loading. The plates are then removed; subsequent growth will be monitored. In the event that deformity reoccurs, the plating procedure may be safely repeated.
Through understanding and patience, even complex deformities may be gradually and safely corrected through redirecting the physis without the risks and problems associated with traditional methods requiring osteotomy and immobilization. This minimally invasive and biologically sound technique represents a powerful new tool in the orthopedic armamentarium.
eight-Plate is applicable to virtually any angular deformity of any etiology, in any size child, providing the physis has not closed. Patient and parent acceptance is uniformly enthusiastic compared to other available techniques.
