Abstract
Blount's disease is a multi-planar deformity affecting the pediatric population which leads to varus alignment of the lower extremities. The Multi-Axial Correction (MAC) monolateral external fixation system (Biomet, Parsippany, NJ, USA) is a non-circular fixator that was developed as a response to the technical difficulty for both patients and physicians of placing, managing, and tolerating a circular fixator. The purpose of this study was to determine the efficacy of the MAC system for the treatment of pediatric patients with Blount's disease. A retrospective analysis of 17 consecutive patients with surgically corrected Blount's disease using the MAC system with tibial and fibular osteotomies was identified. Patient charts and radiographs at three different time points (pre-operative, fixator removal, and final follow-up) were reviewed. The mechanical axis deviation (MAD), tibial-femoral angle (TFA), medial proximal tibial angle (MPTA), and posterior proximal tibial angle (PPTA) were measured in the MAC group at the three time points mentioned previously. The total wear time, total operative time, and post-operative complications were noted. The MAC system was able to correct the deformity of Blount's disease as measured by a decrease in the MAD (40.2 +/- 29.3 mm; P </= 0.001) and TFA (15.9 +/- 13.7 degrees ; P </= 0.001), as well as an increase in the MPTA (15.7 +/- 14.6 degrees ; P = 0.001) at the time of fixator removal. The correction was maintained for these parameters at the time of final follow-up (P </= 0.025). The absolute values obtained at final follow-up for MAD (20.5 +/- 12.7 mm medial), TFA (8.0 +/- 4.1 degrees varus), and MPTA (83.7 +/- 8.1 degrees ) after correction with the MAC system were close to what is considered as normal for these indices. The most common complications noted were superficial pin tract infections and/or cellulitis, with no patients having nerve palsy, compartment syndrome, non-union, or leg length discrepancies. The total time that the fixator was on the patients prior to removal was 130.6 days (standard deviation [SD] = 44.8). The mean operative time was 120.6 min (SD = 21.2). Correction of Blount's disease with osteotomy of the tibia and fibula as well as dynamic fixation with the MAC system achieved deformity correction as measured by radiographic indices with minimal intra- and post-operative complications. The ease of application and adjustment of the MAC system makes it an attractive option for Blount's deformity correction.
Highlights
Blount, in 1937 [1], described tibia vara as a developmental condition of the proximal tibia involving the epiphysis, physis, and metaphysis
The total time that the fixator was on the patients prior to removal was 130.6 days
It is essentially a multi-planar deformity that leads to progressive varus and rotational malalignment of the proximal tibia, with the distal femur involved to a certain extent as well [5,6,7,8]
Summary
In 1937 [1], described tibia vara as a developmental condition of the proximal tibia involving the epiphysis, physis, and metaphysis. Based on the age of onset and radiographic features, it is sub-classified into early-onset/ infantile, juvenile, and adolescent varieties [2,3,4] It is essentially a multi-planar deformity that leads to progressive varus and rotational malalignment of the proximal tibia, with the distal femur involved to a certain extent as well [5,6,7,8]. Hosalkar The Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
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