Efficacy and Complications of External Fixator-Assisted Correction in Cubitus Varus Deformity

Untreated cubitus varus results in cosmetic deformity as well as posterolateral rotatory instability at the elbow if longstanding. French osteotomy with its modifications is the most commonly done osteotomy and relies on a medial intact hinge and these osteotomies fail to address the lateral prominence. Intraoperative fixator assistance to adjust the translation and fine tune the osteotomy is a novel method to address the lateral prominence. This prospective study analyses the efficacy of the same.

A total of 16 consecutive patients presenting with unilateral cubitus varus resulting from mal-united supracondylar fracture of humerus were included. The humero-ulnar angle correction required, size of lateral closing wedge and amount of translation required were calculated. After a lateral surgical approach, one Schanz pin of size 2.5mm-3.5mm depending on age, was passed just above the level of distal humerus physis, lateral to medial; a second pin was inserted in the shaft of humerus, again lateral to medial. Pre-calculated wedge of bone was removed, angular correction as well as translation done; fine tuning of the osteotomy was achieved using fixator assistance. Rotational and hyperextension deformities were corrected simultaneously. Fixation of the osteotomy was done by multiple K wires or plates, depending on the age of the patient.

The mean carrying angle corrected to 10.4 degrees valgus from a preoperative value of 19.8 degrees varus. The mean humero-ulnar angle corrected to 9.6 degrees valgus from a preoperative value of 19.6 degrees varus. The mean lateral prominence index reduced to - 3.8% from a preoperative value of - 5.5%. The mean cosmetic correction score was 9 (Max 10) from a preoperative value of 1.9. No patient had an 'S' shaped deformity in the operated elbow. No nerve palsies were observed in any of the operated patients.

Fixator assistance during surgery allows angular, translation and rotational control of the fragments to fully correct the deformity. It also allows fine tuning of the osteotomy during surgery.