Acute angle deformity refers to a specific type of localized deformity where a sharp angle forms in areas of significant protrusion or depression of the chest wall. This malformation does not exist independently but rather manifests as a feature within a diverse range of chest wall deformities, encompassing single deformity such as pectus excavatum and pectus carinatum, as well as various complex deformities.

Acute angle deformity is most commonly seen in cases where pectus excavatum surgery has failed. Due to the unreasonable placement of the bars during the operation, the original depression not only fails to disappear, but squeezed to one side of the chest wall, eventually forming acute-angle deformities at the base and one edge of the depression.

Illustration of acute angle deformity: the lowest point of the depressed area forms an acute angle (angle a).

Illustration of acute angle deformity: the highest point of the protruding deformity forms an acute angle (angle a).

Illustration of acute angle deformity: the lowest point of the depressed region and the highest point of the protruding region each form an acute angle (angle a).

The defining characteristic of acute angle deformity is the extreme hardness and concentrated stress in the affected bones. Attempting to correct the deformity directly with bars can lead to numerous complications, such as fractures, alteration or even breakage of the bars. These issues not only significantly affect the correction results but also directly lead to surgical failure and various complications.

To better correct chest wall deformities, especially acute angle deformity, the concept of pre-shaping was developed. Pre-shaping is generally performed through a small subxiphoid incision, using various methods and instruments to apply external force to the deformed region, adjusting the bone structure to a more normal appearance. This helps release localized stress in the deformed area in advance, making the subsequent bar shaping proceed more smoothly.

For adolescents with pectus excavatum, due to relatively flexible bones, the sternum is typically lifted with a thyroid retractor or specialized instrument before the bars are inserted.

Intraoperative view of severe pectus excavatum: subxiphoid incision (left) and sternal lift for pre-shaping (right).

For adults with extremely severe pectus excavatum, however, it is usually necessary to first soften part of the ribs (transection, osteotomy, and external force shaping) or perform osteotomy on the costal cartilages, and then use instruments to lift the sternum and insert bars.

Through these approaches, pre-shaping significantly reduces the difficulty and risks of bar shaping, leading to more effective surgical outcomes

Learn more:  Pre-shaping: revolutionizing the treatment of severe and complex chest wall deformities