Operations on the lungs, esophagus, trachea and chest wall are all part of thoracic surgery. Some simpler operations are performed with a minimally-invasive technique (video-assisted thoracotomy). These include biopsies of lung or lymph nodes and resection of lung blebs for recurrent pneumothorax (collapsed lung from an air leak). Removal of larger portions of the lung, or of tumors in the chest, requires an open procedure. Repair of congenital and acquired chest-wall deformities demand special experience. Defects in the chest may need reconstruction using the patient's own bone and cartilage. The most common defect, pectus excavatum, no longer requires an extensive operation but can be repaired using the Nuss procedure, a new minimally-invasive technique (see below).