Biomechanical Effects Of Nuss Procedure On Thoracic Wall

Objective To assess the biomechanical effect of Nuss procedure on the thoracic wall. Pectus excavatum is a most common deformity of anterior chest wall and accounting for about 90% of chest wall deformity in children.Their breastbone and bilateral costal cartilage have sunk from front to back toward backbone, forming forward open-ended funnel deformity. Development of deformity is increasing and may lead to diminution of thoracic cavity volume so that this deformity has affected the function of breath and circulatory system. 90% of children with chest wall deformity can be found one year after birth, and some children do not have chest wall deformity at birth, but they are usually found during the period of infant and young children. Pectus excavatum is mainly treated by operation, including traditional surgery and minimally invasive surgery, that is Nuss produce(minimally invasive technique for repair of pectus excavatum, MIRPE). Be compared with tradition surgery, Nuss operation have a lot of merits, but it have many defects.Our study purpose is mainly biomechanical effects of Nuss procedure on thoracic wall.Methods From 2004 to 2008, we followed up 33 patients with pectus excavatum who underwent Nuss procedure in our hospital, male 25 examples , female 8 examples, operation age, from 2.7 years to 10.6 years, average age 5.6 years, weight 11.5-26 kilograms , average 18.3 kilograms. There are 3 examples with Asymmetric thoracic wall; 2 examples have symptoms such as the dyspnea after exercise, repeated pneogaster infection; Thoracic deformity of 10 examples is increasing. The children with pectus excavatum must have many examinations after operation such as X-ray and 3DCT of thoracic wall, ECG, ultrasound of heart, pulmonary function tests and Haller index. Haller indexs are all beyond 3.2 in 33 examples. The examinations after operation include appearance of thoracic wall; X-ray of Orthotopic and lateral thoracic wall; 3DCT of thoracic wall for whose Nuss bars have been removed; ultrasound of thoracic wall to inspect the first to sixth costochondral joints (CCJ) and sternocostal joints (CSJ) to know if CCJ, CSJ ,Costal Cartilage and Rib were injuried or moved away,and if Costal Cartilage were ossified. Results Eight cases (24%) were found to have different degree injury of costosternal joints (CSJ) and costochondral joints (CCJ) shortly after operation. one case was found left third costochondral joint separated four days after operation. We have also found that the bilateral costocartilage junction area dropped below the Nuss bar in 6 (18%) patients. Bizarre bony protrusion immediately after the procedure was found in 4(12%) patients. The Nuss bar displacement was found in 2 patients. There have costal cartilage fracture in two (6%) cases and one patient had an old fracture detected by sonography at right fourth rib near the costochondral junction at 3 years and 4 months after operation, the other case had traverse fracture with right fifth Costal one week after surgery. The Knife-edge infection was found in 2(6%) cases. Another patient had dot-like ossification at fifth costal cartilage.Conclusions Although the Nuss procedure has many merits, but it also bring some biomechanical damages on the chest wall. In addition to the bar displacement and unexpected chest wall disfiguration, the damages on the chest wall included: separation or displacement of costosternal joints (CSJ) and costochondral joints (CCJ), ossification of costal cartilage, fracture of the ribs and anisotropy of thoracic wall. The long-term effects of Nuss procedure are to be observed, discussed and studied in the future.