Surgical correction of absent sternum with homologous rib graft.
Congenital defects of the sternum are relatively infrequent anomalies. They may vary from simple notching of the manubrium and irregularities in the shape of the xiphoid to absence of the entire sternum., ,  A wide variety of sternal defects and their surgical correction has been reported in the literature. A review of the available literature shows that these anomalies can be divided into three main groups. The first group consists of varying degrees of isolated sternal defects. The second is constituted by defects of the sternum, abdominal wall and the diaphragm and the third consists of a syndrome of congenital defects, involving the abdominal wall, the sternum, diaphragm, pericardium and the heart. Out of these, the isolated sternal anomaly is the rarest entity. The type of corrective surgery performed has shown individualisation depending upon the patient's age and the size of the defect. Thus, Burton3 first reported two cases of successful repair of nonfusion of the greater portion of the sternum; one was an infant and the other, a. 12 year old child. In both his cases autogenous cartilage grafts were used to bridge the gap. Other workers have been able to approximate and primarily suture the sternal defects in younger patients. More recently, Hoffman reported the correction of a bifid sternum using marlex mesh in a 17 months' old baby.
In the case under report, there was an extensive defect in the sternum in a 16 year old girl.
An autogenous cartilage grafting was not feasible because the anterior ends of the ribs were far apart. Homogenous rib grafts were therefore used for surgical correction.
M. V. P., a 16 year old female was first seen by us on 29th August 1966 for shortness of breath and abnormal shape and movements of the chest. She was born of a full term normal delivery and her growth was uneventful. The anterior part of the chest was noticed to be abnormally soft from early childhood but no special attention was paid to it. At the age of 13 years she first noticed shortness of breath and palpitation on climbing one flight of stairs or on walking about 200-300 yards. She also noticed that the anterior chest wall moved in with each inspiration.
Examination revealed a girl of an average build, fair nourishment with a height of 4'-10" and weighing 64 lbs. She appeared to be fairly well developed and had a normal gait. Inspection of the chest wall revealed a large depression in the central portion with gross paradoxical movements on respiration. The nipple and the areola on both sides were normal but both breasts appeared flat due to the lack of bony support underneath.
On palpation, the clavicles were like fibrous strands in their medial halves; no bony tissue could be palpated in the central portion of the chest wall. The heart could be palpated directly under the skin. The medial ends of the upper eight ribs were palpable just anterior to the anterior axillary line. Palpation of the breasts revealed normal amount of breast substance.
Auscultation of the chest revealed a soft systolic murmur at the base of the heart. Air entry over both lungs was normal. Examination of the abdomen and central nervous system revealed no abnormality. The haemogram and electrocardiogram were within normal limits.
X-Ray of the chest:
The X-Ray of the chest in lateral view showed no evidence of bone at all in the region of the sternum [Fig. 1]. The tomograms of the chest taken at the depth of 6 to 10 cms, failed to reveal any bony tissue in the sternal region.
Collection and preservation of rib homografts:
The rib homografts utilized by us were taken from patients undergoing thoracotomy for mitral heart disease. No particular attention was directed to the blood group of the donors since Boyd  has clearly shown that the blood group has no significance in bone transplant.
Subperiosteal resection of the rib was performed at the operation. Each rib was then cleared of all soft tissues including any tags of periosteum and was then deposited in a gamma ray sterilized polyethelene bag containing normal saline, penicillin (1 meg unit) and streptomycin (1 g.). All the bags were then stored at 4°C in a refrigerator.
All rib homografts used in this case were collected within two weeks prior to implantation although Gordon and Welsh have reported no evidence of bacterial contamination in grafts stored under similar conditions for several months.
Operation 1-22nd February, 1967
The operation (P.K.S.) was carried out in supine position, patient being intubated under pentothal and scoline and maintained with nitrous oxide and oxygen, supplemented by tubarine. A bilateral sub-mammary incision was made and the skin flap along with both the breasts was raised upwards almost reaching the root of the neck. The lower flap was raised for a distance of about 3 cms. going down to the upper reaches of the rectus abdominis.
The place of the normal sternum was occupied by fibro-muscular tissue. No evidence of any bone or cartilage could be seen. The anterior ends of the ribs could be palpated in the lateral parts of the incision, abruptly ending underneath the moderately developed pectorals. just anterior to the anterior axillary line. Similarly, cartilagenous ends of the clavicles were felt upto the mid-clavicular line.
The pericardium was not visible and was covered by fibro-muscular tissue in the lower end of which the upper ends of the abdominal recti intermingled.
Since the bony gap was large, six preserved rib homografts were used to bridge it. Four ribs were used in the transverse axis. Two more were placed vertically, in the midline, anchoring all the other four and replacing the sternum.
The problem of fixation of donor ribs was overcome by dissecting small spaces near the patient's rib ends in the fibromuscular tissue. The grafted ribs were held in position in these pockets by suturing the soft tissue over the ribs and various places. The vertical rib grafts were also fixed in a similar manner [Fig. 2]. After proper haemostasis the flaps were closed keeping one corrugated rubber drain at either end of the incision.
The patient did not require any respiratory support and was breathing on her own. Some amount of paradox still persisted. She mad(an uneventful recovery and was discharged a month after the operation with moderate improvement in the appearance of the chest wall. The patient when seen a year later was found to have a well developed middle portion of the chest and the breasts were prominent due to skeletal support underneath. However, in the lateral part of the chest the bony tissue had almost disappeared. The paradox persisted. The centre of the chest was having a normal firm and bony appearance bringing the medial halves of both the breasts into prominence. But the lateral parts of the chest along with the part of the breasts appeared to sag in. It was therefore decided to reinforce the lateral parts of the grafts and the patient was operated upon, on 22nd March, 1968.
Second operation (P.K.S.)-22nd March, 1968.
Supine position and endotracheal anaesthesia was utilized. The old butterfly scar was excised and the upper skin flap was raised upto the nipple line. The vertical bony strut could be felt well and intact but the four transverse rib grafts were seen only as patchy bony tissue. The tips of the patient's rib were exposed and small tunnels on either side were made under the fibromuscular tissue. A small accidental puncture in the pleura was sutured. Two ribs were placed obliquely on either side and were anchored to the tips of the patient's ribs by catgut sutures. These rib grafts were covered by subcutaneous tissue. Patient made an uneventful recovery.
The patient was re-evaluated in the first week of June 1968, that is, about 3 months after the second operation. Paradox still persisted but was much less than before.
The midline and the left side of the chest appeared firm resulting in good normal rounded contour of the left breast. The postero-lateral part of the right side had sagged in resulting in a flattened appearance of the lateral half of the right breast. It was therefore decided to reconstruct the right hemithorax.
Third operation (P.K.S.)-28th June, 1968.
Patient was turned 45° right up position. Right half of the previous incision was excised and the flap reflected upto midline. Another oblique incision parallel to this was made from the inferior angle of the scapula to the midaxillary line. Three fibromuscular tunnels were made and three rib grafts were fixed through the tunnels, from the posterior to the anterior axillary line. The donor ribs were fixed to the patient's rib in the mid-axillary line and the -kin was closed.
The patient made an uneventful recovery.
Assessment: 1st February, 1969
Cosmetically the patient has improved considerably. The anterior chest wall looks almost normal with normal elevation of breasts. There has been some improvement in the exercise tolerance and she can now climb two flights of stairs without becoming dyspnoeic. The respiratory paradox is minimal and is only obvious on close inspection. The X-rays show that at least nine rib grafts have survived [Fig. 3] and [Fig. 4] . The two forming the vertical bar of bone simulating the normal sternum have strengthened into a hard and strong bony strut.
Last follow zip: October, 1978
Patient is married and has got two children. She has normal exercise tolerance and does not become dyspnoeic on exertion. On examination, her chest wall looks normal except for the operation scars. Her breasts are well and normally developed. There is no respiratory paradox. The bone grafts feel as firm and stubom as normal sternum.
The sternum is formed from paired lateral concentrations of mesenchymal cells in the throacic region of the embryo. These cannot be clearly identified prior to the fifth week. They are converted into precartilage and advance towards the midline where they fuse into a single structure.
The process of fusion begins at the cephalic end and progresses caudally. Simultaneously, rib cartilages are growing ventrally from the vertebrae and by the ninth week, the sternum is complete and the anterior rib ends have become attached.
The types of defects which could occur, fall into two maln groups. The first group consists of combination of sternocostal, diaphragmatic and intracardiac defects while the second group includes only the sternal and abdominal wall defects., , 
The sternal defects result from failure of complete migration of the paired primordial structures. The costal cartilages connect with cartilaginous plates which represent the paired sternal anlages. In most instances variable degrees of fusion occur in the cephalic portion of the thorax resulting clinically into various degrees of bifid sternum. But when there is total lack of fusion and the sternal anlages are widely separated, the clinically absent sternum results. However, this defect of absent sternum does not mean that the sternal primordia are absent. Ectopia cordis may or may not accompany this defect even in its severe forms. Thus, in our case, though the defect has presented in the severest form, there was no ectopia cordis.
Since the possible variations in the pathology are considerable in number, the modes of surgical correction have shown a wide range. It is generally agreed that the correction of the sternal defect should be done at its earliest as the problems of management increase considerably with advancing age.
The method of surgical correction is influenced to a large extent by the size of the defect, and the age of the patient. In a child with minimal defect, mobilization of all lateral tissues with primary closure may suffice, while in young children with relatively large defects, fascia lata repair may be needed and has been advocated. In older age groups but with moderate sized defects, autogenous ribs with cartilages have shown good results. Recently, Marlex mesh has been used to replace an absent portion of the sternum in an infant.
Our patient, probably the oldest reported in the literature, had a defect amounting to total absence of the sternum making it impossible to use any of the accepted methods of treatment. The use of foreign material to substitute for the sternum was considered but rejected because the large quantity required to replace the extensive defect would lead to placement of foreign material directly under the skin thus inviting infection. Also, it was debatable whether such material would provide sufficient strength and rigidity and yet allow normal growth of the chest wall.
We therefore decided to use rib homografts. They have so far given sufficient rigidity without hampering movement or growth. Neither has there been any infection. In parts, the homografts appeared to be absorbed but by far and large the greater portions have survided. There is general agreement regarding the histological picture that develops in the homografts and the host tissues but the interpretation of just how this occurs has given rise to controversial comments. It has been demonstrated that when homogenous bone grafts with dead cells or with living cells which will soon die, are transplanted the graft structure is absorbed and replaced in kind by new living bone cells and new calcified structure. Thus, osteoblastic tissue in sternal and rib anlages have by creeping substition probably replaced the homogenous graft by autogenous bone.
It is over eleven years now after the first operation and still the homografts put at that time retain their rigid structure. This appears to be an ideal yet simple method of repair for those types of extensive defects.