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Management of Space Constraints in Sternal Cleft Repair

Man Mohan Harjai
New Delhi, India

 

Correspondence

Man Mohan Harjai
Department of Paediatric Surgery
Division of Surgery
Army College of Medical Sciences
Base Hospital, Delhi Cantt 110 010, India
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Tel:   91-11-28638049
Fax: 91-11-25693490


Abstract

Cleft sternum is a rare congenital anomaly often asymptomatic at birth. Clinical outcome may be unfavorable when an intracardiac anomaly coexists with the defect. Primary repair should be employed in the neonatal period because the flexibility of the chest wall is maximal and compression of underlying structures is minimal. Primary repair some times is difficult and may require some form of prosthetic material. To meet the space limitation, partial thymectomy was accomplished successfully in our case to close the sternum without causing mediastinal compression.

Key words: Cleft sternum, partial thymectomy, space limitation, neonate, early surgery

 

Introduction

Sternal cleft is the separation of the sternum with orthotopic normal heart and normal skin coverage [1]. Clefts located at any level of the sternum occur in approximately one in 50,000 live births. Sternal clefts appear equally in males and females. They may be classified as complete or incomplete. Isolated sternal clefts, however, have a favorable prognosis because they present without intracardiac anomalies that allows a potential for primary repair of the defect. Repair of a sternal cleft should preferably be employed early in the neonatal period when the thorax is relatively more compliant, and the primary closure is generally safe and easy. We report herein a case of newborn baby presenting with a sternal cleft who underwent a successful surgical repair with partial removal of thymus to avoid cardio-respiratory compromise.

Case report:

A 5 days old baby was transferred to our institution with a bony defect in the central upper part of her chest wall since birth. On physical examination, a wide gap at the upper part of the sternum was observed. Pulsations of the great vessels and heart could easily be seen through the defect, which was covered by a thin layer of skin lined with a benign epidermoid cyst. Laboratory examinationswere within normal limits. A chest roentgenogram showed widening between the medial ends of the clavicles. Ultrasonography revealed a large thymus underneath a thin cutaneous coverage. Echocardiography did not reveal any coexisting cardiac abnormality. The patient was taken up for surgery on the same day. The skin overlying the sternal defect was incised along the midline corresponding with the virtual suprasternal notch to the epigastric region. Skin flaps were developed with sharp dissection laterally to expose entire sternum. The dissection was carried out in the plane superficial to the sternum and pectoralis muscles. The sternal edges were mobilized from underlying mediastinal structures with blunt dissection and freshened up. Sutures were then passed and crossed for a trial apposition of the sternum. There was fall in blood pressure and disappearance of peripheral pulses. Part of thymus gland (one lobe) was excised in view of space constraints and again trial was given. There was no cardiopulmonary compromise this time; hence the edges were approximated in the mid line with four interrupted 2-0 Polyester braided non absorbable sutures (Ethibond ®). Pectoralis major muscles were also approximated in the midline along with sternohyoid, sternothyroid and sternocleidomastoid muscles. The skin and the subcutaneous tissues were primarily closed over closed wound suction (Romovac®) drain. Patient remained hemodynamically stable throughout the procedure and in the postoperative period. Baby is progressing well on follow up without any evidence of infection.

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Figure 1. Clinical Photograph showing upper sternal defect with benign epidermoid cyst

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Figure 2. Operative photograph showing four interrupted 2-0 Polyester braided non absorbable sutures (Ethibond ®) in position with partial removal of thymus

Discussion

Sternal clefts result from fusion failure. It may be V-shaped when the cleft reaches the xiphoid process as in our case, or broad and U-shaped, with a bony bridge joining the two edges, ending at the third or fourth costal cartilages. The embryology of the sternal cleft remains obscure. In embryonic life, the sternum originates from the lateral plate mesoderm. Cells from two bands of mesoderm on either side of the anterior chest wall migrate toward the midline, and become fused by the tenth week to form the sternum. The manubrium is formed by primordia between the ventral ends of the developing clavicles. The sternal bars may sometimes fail to join in the midline, which results in a complete sternal cleft [2]. The process of fusion begins at the cephalic end and progresses caudally. An upper sternal cleft with fusion of the distal part is the most common form. An early disturbance in the development of midline mesodermal structures that interferes with fusion of the lateral sternal bands and overlying cutaneous tissue has also been postulated to explain the association of sternal malformation and vascular dysplasia [3]. The extremes of cleft sternum can present as absence of sternum and pericardium with just skin cover [4]. Sternal fusion defects are malformations that often present as an isolated finding. An association with multiple malformations has also been reported in the literature [5].

The diagnosis of sternal cleft is easily done at birth by inspection and palpation. Diagnostic investigations are directed only to exclude the infrequent associated anomalies. The cardiopulmonary system progressively accommodates to the size of the thorax following the first 3 months of age, and the chest wall becomes firm. Thus, numerous authors agree that the optimal choice of treatment is the primary direct closure in the neonatal period with autogenous tissues, when flexibility of the chest wall is maximal and compression of underlying structures is minimal. Sternal defects should be corrected as lack of bony cage makes the mediastinal structures vulnerable to trauma and unsightly appearance. Delayed correction of defect is difficult and may result in disturbance in respiratory and cardiac functions. Many methods for repair of cleft sternum have been described ranging from sliding chondrotomies, repair of the defect with autologous grafts (costal cartilage, ribs, parietal bone) and prosthetic materials (Marlex mesh, teflon, silicone prosthesis). Direct approximation of the sternal halves or primary repair is preferable, because this technique reduces the problems with the prosthetic material and the difficulties in the osteocartilaginous cicatrisation, which occurs in the chondrocostal division procedures [6]. However, the age of the patients is the prime determinant for the feasibility of this procedure. Even in neonatal period, there can be signs of mediastinal compression which need to be addressed. Moreover prosthetic materials do not grow with the individual and may cause chest deformity. We modified the space constraints by partial removal of thymus gland. Children with congenital heart diseases routinely undergo thymectomy during cardiac surgery for better visualization of structures. Brearley S et al stated that the thymectomy in infants younger than 3 months of age resulted in impaired immunity in late childhood [7]. On the contrary, the Turan T. et al and Madhok A. B. et al haddemonstrated that partial excision of the thymus had no effect on immunodeficiency in children [8, 9]. After the neonatal period and certainly after one year of life, primary repair of sternal cleft become very difficult [10]. A literature search did not reveal any articles on partial removal of thymus for space creation and management of the sternal cleft. Our case reiterates that early surgery with partial removal of thymus for space constraints in such cases is a feasible alternative in the armamentarium of sternal cleft surgery.

 

 

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