Abstract
Background
The improvement of the rib cage deformity (RCD) after surgery correction has not been correlated in detail with the correction of vertebral axial rotation (AR). The loss of at the rib cage after correction has been never monitored. The hypothesis of this work was that the aesthetic improvement of RCD in adolescent idiopathic scoliosis (AIS) does not follow completely the reduction of thoracic AR after correction surgery. Moreover, lesser correction of thorax deformity could be expected in mature patients with more rigid curves.
Methods
Multicenter prospective study of the modifications of the rib cage deformity in 24 patients operated because of AIS Lenke type 1A. RDC was assessed in the preoperative MRI exams including the thoracic perimeter. Vertebral AR was quantified by the RaSac angle. Anterior and posterior rib hump, and the translation of the sternum were measured in mm according to standard protocols. All these parameters were assessed in the immediate post-op period and 2-years after surgery using CT-scan axial slides. In all cases, a vertebral derotation technique performed by asymmetric rod bending was used. Immature (Risser 0–2) and mature (Risser 3–4) patients were compared.
Results
Mean age of patients was 14±2 years. The preoperative curve magnitude was 56.2±8.3 Cobb degrees. RaSac at the apex was 27.2±2.8 degrees. There were 10 immature and 14 mature patients. There were no differences between the two groups in all the radiological measurements of the curves. Immature patients showed lesser posterior rib hump as compared to mature cases (14.9±4.1 mm versus 38.1±22.9; p<0.001). Postoperative vertebral AR was lesser in immature patients (2.0±1.2 versus 7.9±2.4 degrees) and increased slightly at 2-year check-up. The posterior rib hump showed also a slightly increased 2 years after surgery. In 18 cases (75%), a contralateral anterior rib hump less than 3 mm emerged after surgery that diminished but not disappeared at 2-year check-up.
Conclusions
The rib cage deformity showed a lesser correction than the vertebral axial rotation. Besides this finding, immature patients showed more rib cage plasticity showing both greater modifications after surgery, and higher loss of correction during follow-up.
Level of evidence
Level IV
