The incidence of Tibia vara, or Blount disease, is greater if the child is black, obese, has an affected family, and resides in certain geographical locations such as the southeastern part of United States. The cause is unknown but it has been theorized that in susceptible individuals mechanical stress damages the proximal medial growth plate, thus converting physiologic bow legs into tibia vara.
Evaluation Two clinical patterns of tibia vara are seen. Radiographs in early infantile tibia vara may be difficult to differentiate from physiologic bowing.
The metaphyseal–diaphyseal angle is often used. This angle shows considerable overlap between physiologic and tibia vara cases. If the angle exceeds 15°, tibia vara is likely. Differentiation is made by following radiographs made every 3–6 months. Physiologic varus usually improves after the child’s second birthday. Tibia vara progresses and shows diagnostic metaphyseal changes.
Bone scan is seldom necessary but will show increased uptake on the medial side of the proximal tibial physis.
MRI studies show considerable deformation, which might be helpful for complex deformity management.
Langenskiöld stages These are stages of the disease with transition from one to the next over time.
Treatment of Tibia vara
Management is based on the stage of tibia vara and the age of the child.
Bracing Mild deformities may resolve without treatment, so the beneficial effect of the brace is uncertain. Often braces are used to treat stage 1 and 2 disease. If treatment is elected, order a long-leg brace with a fixed-knee that incorporates valgus loading. The brace should be worn during active play and at nighttime.
Operative Correction Operative correction may be achieved by an osteotomy or by initiating asymmetrical growth to correct the deformity. This asymmetrical growth may be achieved by a permanent hemiepipysiodesis or by a reversible stapling procedure. See the next two pages.
Osteotomy in the child If tibia vara progresses or is first seen in stages 3 and 4, osteotomy is indicated. Perform the osteotomy before age 4 years if possible. Deformities of stages 5 and 6 are more complex and may require a double-level osteotomy to correct both the genu varum and the articular incongruity. Also assess the shape of the distal femur as varus or valgus deformity may contribute to the deformity. Medial tibial torsion is also a common associated deformity. Correct the varus and torsion by a simple closing wedge with rotation or by an oblique osteotomy. Correct the thigh-foot angle to about +10 degrees and overcorrect the varus to about 10 degrees of valgus. Use a sterile tourniquet so the entire limb can be seen to ensure appropriate correction. Release the anterior compartment fascia to reduce the risk of a compartment syndrome. Fix the osteotomy with crossed pins and supplement the fixation with a long-leg cast.
Hemistapling may be an alternative to osteotomy for stage 2 or 3 deformities.
Physeal bridge resection Rarely, a physeal bridge is suspected in unilateral involvement in mid to late childhood. CT or MRI studies confirm the presence of the bridge. Resect the bridge, fill the defect with fat, and correct the tibial deformity by osteotomy.
Surgery in the adolescent Operative correction in the older child or adolescent is usually complicated by obesity. Stabilize the osteotomy with an external fixator. External fixation provides adequate immobilization without need for a cast and allows the option to adjust alignment during the postoperative period.
Stapling Stapling is a convenient method for correction. The disadvantages are the larger scar, the risk of staple extrusion, and a second operation for staple removal. The advantage is simplicity. The staples (usually two) are placed, the patient carefully followed, and when the deformity is corrected the staples are removed. If the staples are placed extraperiosteal, growth can be expected to resume. The zone system is commonly used to determine the need for correction. A zone 3 deformity may be an indication for stapling. A rebound often occurs after staple removal, undoing some correction, so overcorrect slightly in anticipation of this common problem.
Hemiepiphysiodesis With accurate timing, hemiepiphysiodesis has several advantages. The scar is short and the procedure simple and definitive. Bowen has developed a table to aid in timing. Careful follow-up is essential because if the deformity appears to be destined for overcorrection, arresting the entire epiphysis becomes necessary.
Timing The timing of the stapling is not critical. When correction is acheived, the staples are removed. Timing of epiphysiodesis is critical, and tables have been developed to help estimate the appropriate timing.
Prognosis The prognosis depends upon the severity, stage, and treatment. Recurrence of varus and increasing shortening are common during childhood. Persisting articular deformity often leads to degenerative arthritis in adult life.