Case Study: Genu Varum - Dysplasia
Presented by Peter M. Stevens, MD
University of Utah
Salt Lake City, Utah
Metaphyseal Dysplasia
Clinical Presentation
A three-year-old boy developed progressive bowed leg deformities causing leg pain, difficulty running, and a waddling, awkward gait. He has a hereditary bone growth abnormality (skeletal dysplasia) contributing to his deformity. It is likely that this eccentric loading is what accounts for the patient's discomfort. The waddling gait results from the bow at the top of the femur (coxa vara).
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 (solid white line). The greater the distance between the actual vs. desired axis, the more outward force is subjected to the knee. The forces of gravity and weight-bearing combine to perpetuate the bowed deformity while subjecting the knee ligaments and cartilage to pathological overload.
Treatment Options
The natural history of this condition is one of persistence and progression.
- Bracing and physical therapy would be ineffectual. Neither method of treatment can adequately address the forces across the hip and knee or alter the established abnormal growth pattern.
- Each upper femur requires an abduction osteotomy to correct the alignment and normalize the forces across the hips.
- Osteotomy above and below each knee is also theoretically warranted. However the prospect of 6 osteotomies for this child is daunting. They would have to be staged in order to avoid complications. Furthermore the bone cuts are above and below the true deformities, necessitating the production of compensatory deformities and the use of a body cast (spica).
- Percutaneous epiphysiodesis would be contraindicated because it would result in permanent growth arrest.
- Stapling of the femur and tibia might be feasible but the likelihood of one or more staples migrating or breaking is significant.
- Hemi-epiphysiodesis is therefore, the optimal choice using the eight-Plate on the convex side of each femur and tibia to guide and redirect the physes (growth plates).
Operative Technique
Option #6 (hemi-epiphysiodesis) was selected for correction of the bowed legs. Four plates were inserted through separate 2cm incisions. This was done at the same time as the proximal femoral osteotomies. No knee immobilization or physical therapy was required.
Since the bones are never cut, there is no neurovascular risk, no instability, and no healing interval. Correction occurs gradually through growth.
As growth occurs, the screws are free to diverge but the plate resists longitudinal expansion on the instrumented side of the growth plate.
Post-Op Course
One year following surgery the center of gravity (depicted by the dotted white line) has been restored to the center of the knee. The plates were removed at that time.
The child's symptoms have completely resolved; he is able to run and pursue full activities (“function follows form”). As long as the periosteum is left undisturbed, there will be no permanent or irreversible effects upon the growth plate. By centralizing the forces of gravity and weight-bearing, the knee ligaments, cartilage, and physis are spared deleterious shear and overload. Subsequent to eight-Plate removal, further growth should be monitored. If there is recurrent deformity, guided growth 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. It 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.
