Lumbar spondylolysis is a fatigue fracture of the pars interarticularis and correlates with Spina Bifida Oculta (SBO) in 67%. Load is normally transferred across the arch in axial rotation. Bifid arch results in increased strain across the isthmus of the loaded inferior articular process.Introduction
Hpothesis
We described a technique of measuring the flexibility of the rib prominence clinically before surgery, and aimed to analyse the results in patients with adolescent idiopathic scoliosis who underwent posterior correction with pedicle screw instrumentation. This prospective study investigated the magnitude of rib humps before and after the operation when the patient was in Adam's forward bending posture. Also preoperatively, a flexion and derotation manoeuvre was performed and the corrected rib prominence was measured. This is compared to the magnitude of the rib hump present postoperatively at three months' follow up. Seven consecutive patients with adolescent idiopathic scoliosis that underwent posterior surgical correction. Clinical measurement of rib prominence using scoliometer. The magnitude of the curve improved from a mean preoperative Cobb angle of 53.6+/−11.2° (range 45.3–72.5°) to a mean postoperative Cobb angle of 7.8+/−9.3° (range 0.4–17.6°). The mean preoperative magnitude of the rib hump was 12.3+/−6.9° (range 5-20°) which was then corrected to a mean magnitude of 1.3+/−2.2° (range 0-5°) by performing the above described flexion derotation manoeuvre. The mean postoperative magnitude of the rib hump was 3.0+/−3.1° (range 0-8°) with the patient in Adam's forward bend position. There was positive correlation between the postoperative residual rib hump and the reduced rib hump measured preoperatively using our described technique (r=0.8,p=0.05). This flexion derotation test is a useful in assessing the amount of postoperative persistent rib hump after posterior correction of adolescent idiopathic scoliosis using pedicle screw instrumentation with derotation technique.
