Chest Deformity

Pectus excavatum (Funnel chest); pectus carinatum (Pigeon chest); chest deformity due to scoliosis

This is thought to be caused by an abnormality of connective tissue, which results in depression of the sternum. It is sometimes associated with Marfan and Ehlers Danlos syndromes.

Epidemiology

Pectus excavatum is a congenital anomaly. It is the most common deformity of the anterior chest in children and is present in between 1 in 400 and 1000 live births. It is thought to be an inherited condition.¹

Investigations²

• Radio-imaging with chest xray is the first line investigation.
• Two new clinical methods have recently been developed:³
  • Chest cytometry involves measuring the circumference of the chest in the region of the distal third of the sternum or at the site of greatest deformity with the patient in the orthostatic position and inspiring deeply.
  • Calculation of the anthropomorphic index - this involves taking to measurements. Firstly, the maximum anteroposterior measurement in the region of greatest deformity or of the distal third of the sternum (A) is assessed. Secondly, the greatest depth of the defect is measured with the highest point of the anterior costal wall and the lowest point of the pre-sternal region at the site of greatest deformity being used as reference (B). The index is calculated as B/A.
• Standardised cardiopulmonary function tests may be useful, particularly in assessing whether patients would benefit from surgery.
• CT chest scanning may be indicated to assess the degree of sternal deformity, the severity of lung compression and the presence of mediastinal displacement.
• Echocardiography may be clinically indicated in patients with dyspnoea to evaluate cardiac compression.
• Pulmonary function tests may be required to assess lung capacity.

Management²

• Mild cases may not require treatment as the deformity can be hidden under clothing.
• The treatment to correct functional disability has for many years been the Ravitch operation in which the anterior chest wall is exposed, skin and muscle flaps are created, the affected cartilages are excised and sternal osteotomy is performed.
• A newer minimally -invasive procedure called the Nuss technique has been developed which involves the insertion of a retrosternal metal bar via two incisions using a thorascope. The bar is removed 2-3 years later. It is mainly used in 12-14 year olds but can be performed in younger children and in adults, in whom two bars may be required.⁴ The technique may lower the threshold for surgical treatment which was previously hampered by the high incidence of keloid formation of the anterior chest wall which bedevilled the Ravitch procedure. The Nuss technique has also been shown to reduce the length of hospital stay.⁵
• Autologous fat transplantation has been reported⁶ as has polyethylene implant for patients with mild deformity who required aesthetic improvement.⁷
• A survey of patients who have had surgery showed considerable improvement in body image and function.⁸

In this condition, the sternum is raised (carina = keel). It used to be associated with rickets. Nowadays there is usually an associated history of severe asthma in childhood sometimes with a ventricular septal defect (VSD). 20% of patients have an associated scoliosis. Pectus carinatum complicating surgical treatment for pectus excavatum has been reported.⁹

The large forces needed for inspiration lead to an in-drawing of the lower portion of the ribs giving a Harrison's sulcus.

Epidemiology

This is much less common than pectus excavatum. The prevalence in the United States has been assessed at 0.06% with one third of patients having a positive family history.¹⁰

Investigations

• Pulmonary function tests should be performed if reduced lung capacity is suspected.
• Electrocardiography and echocardiography may be needed to rule out cardiac abnormalities and assess cardiac function.
• A scoliosis series should be arranged if this condition is suspected.

Management¹⁰

• Many patients have a mild deformity with no associated morbidity requiring treatment.
• Various physical methods of correcting the deformity have been tried including casting, bracing and chest compressors.
• Endoscopic resection of costal cartilage and sternal osteotomy is available for patients who require cosmetic correction, but this procedure does nothing to correct any functional disability.
• Rarely, if there is significant pulmonary and/or cardiac dysfunction, open surgical repair is performed. Various techniques have been tried.

There are many different causes of scoliosis including neuromuscular, congenital vertebral deformity and idiopathic, which is the largest group of all. Idiopathic scoliosis usually presents at the pubertal growth spurt. In 80% of the cases the curve is convex to the right. The lateral curvature of the spine also has a rotational element. The chest defect is sometimes greater than the spinal one with one shoulder lower than the other.
The rib rotation leads to abnormal articulation, reducing both vital capacity and compliance of the lungs. The reduction in total vital capacity is accompanied by reduction in forced expiratory volume.
The condition is diagnosed radiologically by measuring the Cobb angle (the angle made by a line drawn between the top of T9 and the bottom of L3 vertebral bodies.¹¹

Epidemiology¹²

There is 4:1 female to male ratio. Studies of prevalence vary because some researchers use a Cobb angle of 6° and others 10°. One study of children aged 6-14 years (Cobb angle 10° ) suggests a prevalence rate of 0.5%.

Investigations¹²

• Thoracic spine xrays with the patient bending over a fulcrum are thought to be the best method of diagnosis.
• MRI is reserved for patients with unusual symptoms, e.g. headaches.
• Lung function tests are indicated for patients with significant chest deformity and/or respiratory symptoms.¹³

Management¹²

• Monitoring with serial radiographs is all that may be required in some patients.
• A variety of orthosis have been developed to correct the spinal deformity, e.g. the Milwaukee brace.
• The reduction in forced expiratory volume does not respond to inhaled bronchodilators because this is a mechanical problem.
• Severe chest deformities which affect lung capacity may require thoracotomy and spinal correction.