Correction of Cubitus Varus After Pediatric Supracondylar Elbow Fracture: Alternative Method Using the Taylor Spatial Frame.

BACKGROUND: Cubitus varus is a well-reported complication of supracondylar fracture of the humerus potentially resulting in cosmetic problems, impaired function, and malpractice claims. Traditional methods of correcting malunited distal humeral fractures involve complex osteotomies that have a high complication rate, require a large exposure, and challenging fixation. We present a technique of gradual correction using a percutaneous transverse osteotomy and 3 dimensional correction with a Taylor Spatial Frame. METHODS: This was a retrospective, IRB-approved study of 12 patients between 2006 and 2010, with cubitus varus after a malunited pediatric supracondylar fracture. The average age at initial injury was 5+8 years. The average age of the patients at surgery was 8+8 years. We measured technical (radiographic parameters and complications), functional (clinical carrying angle, range of motion, QuickDash), and satisfaction domain (questionnaire) outcomes at a minimum follow-up of 6 months. RESULTS: The osteotomy healed in all patients by 10 weeks after the index surgery. The mean external fixator time was 10 weeks. The average preoperative and postoperative humeroulnar angles for the affected elbow were 23 degrees varus and 5.8 degrees valgus, respectively. This was statistically significant (P<0.001). The mean preoperative and postoperative carrying angles were 22 degrees of varus and 5.8 degrees of valgus. This was statistically significant (P<0.001). The results of the QuickDash assessment showed that patients were doing very well with regard to the use of their upper extremity. The mean symptom/disability score was 0.80. No major complications or neurovascular complications were encountered. Overall satisfaction with the procedure was high. CONCLUSIONS: The Taylor Spatial Frame as used in this case series provides the experienced surgeon another safe, accurate, and reliable method to correct cubitus varus after pediatric supracondylar fracture. We used in 7 of our 12 cases, a previously unreported pattern of distal humeral pin fixation that allows for a very distal metaphyseal osteotomy, close to the deformity apex. This is a biplanar delta configuration that straddles the olecranon fossa and is appropriate for both children and adults. LEVEL OF EVIDENCE: Level IV.

Two regions in the N-terminal domain of ionotropic glutamate receptor 3 form the subunit oligomerization interfaces that control subtype-specific receptor assembly.

The N-terminal domain (NTD) of alpha-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) and kainate glutamate receptors plays an important role in controlling subtype specific receptor assembly. To identify NTD subdomains involved in this process we generated AMPA glutamate receptor 3 (GluR3) mutants having intra-NTD substitutions with the corresponding regions of the kainate receptor GluR6 and tested their ability to form functional heteromers with wild-type subunits. The chimeric design was based on the homology of the NTD to the NTD of the metabotropic GluR1, shown to form two globular lobes and to assemble in dimers. Accordingly, the NTD was divided into four regions, termed here N1-N4, of which N1 and N3 correspond to the regions forming lobe-1 and N2 and N4 to those forming lobe-2. Substituting N1 or N3 impaired functional heteromerization but allowed protein-protein interactions. Conversely, exchanging N2 or N4 preserved functional heteromerization, although it significantly decreased homomeric activity, indicating a role in subunit folding. Moreover, a deletion in GluR3 corresponding to the hotfoot mouse mutation of the glutamate receptor delta2, covering part of N2, N3, and N4, impaired both homomeric and heteromeric oligomerization, thus explaining the null-like mouse phenotype. Finally, computer modeling suggested that the dimer interface, largely formed by N1, is highly hydrophobic in GluR3, whereas in GluR6 it contains electrostatic interactions, hence offering an explanation for the subtype assembly specificity conferred by this region. N3, however, is positioned perpendicular to the dimer interface and therefore may be involved in secondary interactions between dimers in the assembled tetrameric receptor.