Access the accompanying videos for this chapter online. Available on ExpertConsult.com .
The treatment of pectus carinatum has evolved in the last two decades. Nowadays, the first line of treatment is a nonoperative remodeling of the chest by means of dynamic compression. This approach has increased the number of patients interested in receiving treatment for their chest deformity, and consultations for treatment of this condition have significantly increased over the last 10 years.
However, some patients are still candidates for operative management because they do not want to wear the compression systems as much as necessary, or because their thoracic cages are very rigid and too much pressure is required to reshape their ribs and sternum with adverse consequences to the overlying soft tissues. The rationale for performing minimally invasive surgical (MIS), nonresective operations in this population is based on the fact that this approach results in less blood loss, better cosmesis, no excision of tissues, and a shorter operative time than an open and/or resective approach.
The first MIS technique for pectus carinatum was described by Abramson, also known as the “reverse Nuss” technique. His original technique consists of the placement of a subcutaneous steel bar that is positioned anterior to the sternum and is introduced through lateral thoracic incisions. It is stabilized with two lateral steel devices and steel wire tied tightly around the ribs.
We have introduced many modifications to the original Abramson procedure. We have also developed a process of design and manufacture of custom-made, personalized implants. Our surgical planning of the procedure now includes the creation of 3D printed templates that are tried on each patient before manufacturing the final bar(s), thus diminishing the possibility of an inappropriate bar being used. Also, we have developed a modification aimed at reducing bar dislocation. Finally, to completely avoid the use of wires and lateral stabilizers, we have created the “Zip-Back” technique, which fixes the implant to the ribs with specially designed polymer zip ties.
Indications for Workup and Operation
Pectus carinatum is a condition seldom diagnosed at birth, so it is believed to be an acquired condition. Patients are typically adolescents with low self-esteem, sometimes bordering on depression, who tend to isolate themselves. Symptoms of dyspnea and reduced exercise tolerance can be observed as well, although less frequently than in pectus excavatum.
The deformity can be classified as chondrogladiolar and chondromanubrial. The chondrogladiolar is the most frequent type in which the protrusion of the sternum is located in the mid and lower segments, whereas the chondromanubrial type consists of a superior protrusion of the sternum, a peculiar anomaly called “pectus arcuatum.” When pectus arcuatum is associated with cardiac anomalies, it is often referred to as Currarino-Silverman syndrome.
Workup is done in the context of a multidisciplinary team. The rigidity of the thoracic cage is determined by means of a pressure-measuring device. A pressure of initial correction of 12 pounds per square inch or more is indicative that nonoperative compression treatment will likely fail and operative treatment will be needed.
Complementary studies include a chest computed tomography (CT) scan with 3D reconstruction. In particular, the relative position of the sternum and ribs; the size, length, and width of the sternum; the presence of normal joints in the sternal body; and the lateral symmetry of the thoracic cage are evaluated. Characteristics such as the presence of pectus arcuatum, marked asymmetry, or important rib flares may require alternative or complementary procedures, so all these characteristics and parameters should be noted for proper operative planning.
The CT scan is also used to determine the position and shape of the implant as the initial step of the surgical planning. Bar design is accomplished by means of a 3D processing software using the digital information available on the chest CT scan ( Fig. 41-1 ). A 3D plastic printed template is manufactured as part of the process of 3D surgical planning. This plastic template is tried on the patient at the outpatient clinic several weeks before operation ( Fig. 41-2 ). Once the template is considered appropriate, the final metallic implant is manufactured in steel or titanium, depending on the results of allergy testing.
A directed psychological interview provides the final evaluation for surgery and helps the attending physicians understand whether the patient’s expectations match with the expected results of the planned operation. A cardiac assessment is mandatory in cases with pectus arcuatum.
Zip to the Rib Sternal Pullback (“Zip-Back”) Technique
Materials: The Zip-Back technique implies the preoperative design of a custom-made, personalized metal bar, which will be made of steel or titanium, depending on the patient’s nickel allergy test. This strategy avoids the need for measuring the patient’s chest and bending the implant at the time of the operation. In this way, we hope to decrease the possibility of errors and determine the best operative approach prior to the operating room. Also, a special fixation device is designed, manufactured, and utilized to avoid bar dislocation.
Bar Design: The process of bar design starts with 3D software processing of the patient’s CT scan to produce a 3D printed template. This model is 3D printed into a plastic template. An ambulatory fitting session is scheduled in our Pectus Clinic before the final manufacture of the custom-made, personalized, metal bar implant(s). Once the design is approved, the implant is manufactured. The design and manufacture of polyamide 6.6 zip ties that are attached to a special pericostal needle are then done to fix the bar around the ribs ( Fig. 41-3 ).