Keywords
3D printing - chest wall reconstruction - sternal cleft
Introduction
Complete sternal cleft (SC) is an uncommon congenital chest wall malformation. Chest
wall reconstruction provides protection to the mediastinal structures, additionally
aiding in the restoration of the aesthetic appearance.
Case Report
A 9-month-old female child born out of nonconsanguineous marriage reported to us with
a history of visible pulsations in the chest. On clinical evaluation, a 5 × 5 cm wide,
“V”-shaped complete SC was noted converging toward the xiphisternum with visible mediastinal
pulsation ([Fig. 1]). Clavicles were 5 cm apart with medial ends floating. There was an associated midline
contracture band in the neck which restricted complete neck extension. Supraumbilical
midline raphe was present.
Fig. 1 Image showing “V”-shaped complete sternal cleft with visible pulsation covered by
skin.
Contrast-enhanced CT chest was suggestive of the absence of midline fusion of sternum,
with the presence of the xiphoid process ([Fig. 2]). US abdomen was within normal limits. Two-dimensional (2D) echocardiogram showed
a 8 mm ostium secundum atrial septal defect (ASD) with left to right shunt. Genetics
workup was done to rule out syndromic (pentalogy of Cantrell and posterior fossa malformations,
hemangioma, arterial anomalies, coarctation of the aorta/cardiac defects, and eye
abnormalities [PHACE] syndrome) association.
Fig. 2 Image displaying axial section of CECT thorax displaying 5 cm of sternal cleft between
the two medial ends of clavicle.
3D Printing
3D printing of the available rib cage and the costal cartilage was done in a 3D printing
laboratory within our institution. Materialise Mimics InPrint software was used to
segment the region. Ribs and spine were printed in polylactic acid (PLA) material
using fusion deposition modelling (FDM) printer (Ultimaker 3), and cartilage was separately
printed using clear resin material on a sterolithography printer (Formlabs Form2),
creating a realistic 3D model. Additionally, the 7th and 8th ribs were printed ([Fig. 3]). Incisions of the sternum for bringing the rib cage together were decided on the
model. The site, direction, length of incision, and additional rib graft length were
preplanned, resulting in minimal incisional approach. To get the proper contour of
the upper anterior chest wall, it was decided that 4 cm of the 7th rib from right
side had to be harvested just anterior to the anterior axillary line.
Fig. 3 Image showing 3D-printed model of rib cage with costal cartilage.
Surgical Technique
Midline chest incision was placed, and the skin flaps were raised off the precordium.
A 5 × 5 cm wide “V”-shaped complete SC was visualized. The deep cervical fascia was
seen extending from the neck along the inner aspect of the sternal cleft edges till
the inferior limit of the cleft. Herniation of mediastinal contents through the defect
in the extended deep cervical fascia was seen. The fascia was found to be tough and
of good quality and strength. Inferiorly xiphoid process was well-formed. Bilateral
pectoralis major muscle flap (left side was islanded) was raised.
The anterior perichondrium on either side of the 1st to 4th costal cartilage was raised
like a perichondrial flap from the costochondral junction till the edge of SC. The
xiphoid process bone block was excised. In the lower part of sternum, the cartilage
was incised in a straight line. The edges were approximated in an overriding fashion
and 10 × 15 mm cartilage was excised without causing respiratory compromise. Central
venous pressure (CVP) (7–8 mm of Hg) and pO2 (110–120 mm of Hg) were maintained in the overriding position for 5 minutes. Thereafter,
the lower edges of the sternum were primarily approximated using No.1 stainless steel
sternal wires. The size of the cleft in the upper sternum was reduced to 4 cm.
Herniated mediastinal contents were reduced by approximating the deep cervical fascia
in two layers, with 2–0 ticron continuous sutures. The perichondrial flaps were reflected
medially and approximated in crisscross fashion over the deep cervical fascia ([Fig. 4]). A 5 cm graft of right seventh rib was harvested through a separate incision, just
medial to the anterior axillary line. The 4 cm upper sternal defect was bridged using
a rib graft with No.1 stainless steel sternal wires ([Fig. 5]). The residual defect was filled with xiphoid process bone block and diced cartilage.
Bilateral pectoralis major muscle flap was advanced and approximated in the midline
using 2–0 ticron. Skin was closed with 4–0 monocryl subcuticular sutures. Postoperatively,
the child was on ventilator support for 3 days and discharged on the 10th postoperative
day. Follow-up at 1 year reveals no complications with acceptable cosmesis ([Figs. 6] and [7] and [Video 1]).
Fig. 4 Intraoperative image showing anterior perichondrial flap from 1st to 4th rib was
raised on either side and sutured over the sternal defect in a crisscross fashion
bridging the defect and primary approximation of lower portion of sternum.
Fig. 5 Intraoperative image showing bridging of upper sternal defect with 4 cm 7th rib graft
and xiphoid bone block interspersed with diced cartilage.
Fig. 6 Postoperative image showing no visible pulsation at 1-year follow-up.
Fig. 7 X-ray at 1-year follow-up showing osseointegration of rib graft with xiphoid process
bony block.
Video 1
Video displaying visible pulsation during expiration and V-shaped sternal cleft (SC)
during inspiration with supraumbilical raphe and postoperative outcome. Online content
including video sequences viewable at: https://www.thieme-connect.com/products/ejournals/html/10.1055/s-0040-1721547.
Discussion
SC can be classified as complete or partial, based on the extent of absence of sternum.[1] Complete SC can be “U”- or “V”-shaped.
In a “U”-shaped cleft, sternal bars are parallel to each other, which is managed easily
by primary approximation. In a “V”-shaped cleft, sternal bars are converging inferiorly;
hence, primary approximation becomes difficult without the excision of the bridging
segment ([Algorithm 1]).
Algorithm 1 for surgical approaches for complete sternal cleft (SC).
There are several surgical approaches described such as primary closure, closure using
autogenous material (cartilage/bone graft/muscle interposition), prosthetic materials,
and biological tissue grafts. Primary closure can be achieved, owing to the chest
wall elasticity in infants less than 3 months of age, without causing respiratory
compromise. As the age progresses, the rigidity of chest wall and the physiologic
accommodation of the intrathoracic organs limits the primary approximation, which
is facilitated by resection of costal cartilage/fracturing the clavicle or sliding
chondrotomy. Prosthetic reconstruction carries risk of extrusion, infection and lacks
growth with child, contrary to autologous material.[2]
[3]
Kabiri et al and[4] Sapiri et al[5] reported complete SC in adolescence and adults associated with pectus excavatum,
where resection of the deformed cartilage for correction of pectus excavatum facilitated
primary SC approximation.
Biswas et al reported a case of 7-year-old with 4 × 6 cm “V”-shaped defect, which
was reconstructed with a split iliac bone graft and sternocostal portion of pectoralis
major muscle flap.[6] Jadhav et al reported a case of 12-year-old with 2.8 to 3.1 cm “U”-shaped defect,
which was corrected with anterior perichondrial flap and pectoralis major advancement
flap.[7] Jabbad et al repaired a 6-cm defect in a 35-year-old with titanium plates.[8]
In our case, the correction was done in four layers, using the deep cervical fascia,
the anterior perichondrial flap with the autologous rib graft, and the bilateral pectoralis
major muscle flap. Considering the age of the child (9 months), and the size and shape
of the defect (“V”-shaped, 5 cm at upper end), which was wide for the age of the child,
primary closure would increase intrathoracic pressure; hence, the alternative repair
was done. 3D printing provided additional aid with its features of virtual image of
the operative site, preplanning, assistance in counselling and reducing operative
duration.
Age at presentation for the management has been described in the literature as preliminary
factor in choosing the appropriate surgical technique.[3] But none of the published literature emphasizes on the defect size in relation to
the age of presentation as the decisive factor in determining the surgical technique.
Conclusion
Besides the age at presentation, the size and shape of the defect in relation to the
age can be considered as an additional factor in deciding the appropriate surgical
technique for repair in complete SC.
