STRATOS™ system for the repair of pectus excavatum

Abstract

Open techniques represent a valid repair option for severe asymmetric pectus excavatum in adults. The use of metal supports is recommended to reduce the risk of recurrence. A wide variety of metal supports have been proposed, with pre-, trans- or retrosternal fixation. A novel open technique using titanium bars fixed to the ribs with clips has been recently introduced (STRATOS™ system) for chest wall reconstruction, rib fracture fixation and chest wall malformation repair. We employed this technique in two adult patients with severe asymmetric pectus excavatum: after sternal mobilization, one bar is passed below the body of the sternum and secured with clips bilaterally to two ribs. In the first case, the results remained excellent 5 years after surgery. In the second case, the initial results were satisfying but the bar ruptured after 30 months: removal of the bars and clips was performed and a subsequent recurrence of the deformity occurred. The experiences reported in literature are still too limited to draw firm conclusions about the use of the STRATOS™ system in pectus excavatum repair, but it seems that the use of two bars may reduce the risk of rupture. At present, we are the only ones who reported long-term results.

INTRODUCTION

Pectus excavatum (PE) can be surgically corrected with open techniques or with the minimally invasive repair technique (MIRPE). The feasibility of MIRPE in adults is controversial, especially in cases of severe and asymmetric deformity. These patients may be better served with a modified Ravitch repair, which employs metal struts to hold the sternum in the correct position. A wide variety of metal supports have been proposed, with pre-, trans- or retrosternal fixation. A new technique using a retrosternal titanium bar (Strasbourg Thorax Osteosyntheses System—STRATOS™, MedXpert GmbH, Heitersheim, Germany) was proposed in 2007 [1]. Here, we report our experience with this technique in two adult patients with severe asymmetric deformity.

CASE REPORT

A 20-year old woman and a 20-year old man underwent surgery in September and in November 2007, respectively. Both patients presented with severe asymmetric PE (Fig. 1A) and complained of psychological troubles; the woman also experienced reduced exercise tolerance and shortness of breath. Spirometry revealed restrictive deficits: predicted forced vital capacity and forced expired volume in one second were 67 and 65% as well as 66 and 67% for the first and the second patient, respectively. Echocardiogram showed anterior compression of the right ventricle and heart displacement to the left in both patients, as well as mitral valve prolapse in the woman.

Figure 1:

(A) Preoperative computed tomography scan of the first patient and (B) intraoperative picture showing a STRATOS system placement behind the sternum. (C and D) Chest X-rays showing the implant and the final result in the first patient.

The operative technique was as follows. A transverse skin incision was made within the inframammary crease. The xiphoid process was resected and two small cylinders of costal cartilage were subperichondrially resected, to the chondrosternal and chondrocostal junctions. Resection extended bilaterally from the third to the seventh costal cartilages. A wedge osteotomy is created through the anterior cortex of the sternal body, at the site of angulation, just above the third chondrocostal junction. We used the STRATOS™ system for the internal fixation of the sternum: a titanium bar was passed below the body of the sternum and secured with clips bilaterally to two ribs (Fig. 1B). The clips were angled with dedicated surgical pliers and then fixed bilaterally to the anterior arc of the fourth rib. The osteotomy was closed and the perichondrial sheaths were sutured.

Postoperative pain was easily controlled and no complications were observed. A satisfying correction of the deformity was obtained in both cases (Fig. 1C and D). The woman referred significant improvement in exercise tolerance, and both patients were satisfied with the aesthetic results. Spirometric and echocardiographic alterations disappeared. Five years after surgery, there was no deformity recurrence in the woman. In the man, the clinical and radiological results remained satisfying until November 2009, but in a routine visit in May 2010 a chest X-ray revealed a rupture of the left lateral edge of the bar (Fig. 2A). Removal of the bars and clips was performed under general anaesthesia (Fig. 2B), and a recurrence of the deformity progressively occurred over 12 months.

Figure 2:

(A) Chest X-rays revealing the ruptured bar and (B) picture of the implant after removal.

DISCUSSION

Open techniques remain a valid option for PE correction, especially in adult patients and in cases of severe and asymmetric deformity. The use of metal struts is recommended to maintain the correction in good shape during the healing process of cartilages; the major concerns include the risk of displacement, the need for a second intervention for removal and the risk of recurrence after removal. Moreover, complications such as pain, infections, bleeding, pleural effusion or pneumothorax can occur while the bar is in place or at the time of removal.

The STRATOS™ system is a novel technique for chest wall surgery, which is comprised of a titanium bar fixed to two rib clips [1]. Compared with other implants, titanium is easily and precisely adaptable to the shape of the thoracic wall, corrosion free, chemically inert and better tolerated and it is associated with fewer radiological artefacts. Therefore, titanium is especially indicated for long-term or permanent implants.

The use of this system is well established in chest wall reconstruction and rib fracture fixation, where good results have been described [1–3], but the experience in PE repair is very limited. Wihlm et al. [1] reported the feasibility of this technique in 12 Ravitch procedures and described good early results using two bars in each procedure. Mier et al. [4] reported a case of successful repair using a single bar to correct a recurrent deformity.

Our standard technique consists of a modified Ravitch procedure, with the use of two steel supports, which are removed 6 and 12 months after operation [5]. We obtained good results but found an increased rate of recurrence in adults compared with younger patients after support removal (18 vs 7%). Moreover, we observed a case of migration of a support into the abdomen [5]. In an attempt to reduce the risks of displacement and recurrence after removal, we employed the STRATOS™ technique in two adult patients. We implanted a single bar in each case, to reduce the amount of permanent prosthetic material in these young patients. In the first case, we obtained excellent results, whereas in the second case, although the initial results were satisfying, a delayed rupture of the bar occurred. The rupture occurred on the left edge, at a point of minor resistance of the system (the joint), where the clip is angled to be adapted to the rib angle. It is likely that the pressure the sternum applied over the bar finally caused the rupture, favoured by the manoeuvre of angulation of the joint. Berthet et al. [2] described 2 cases of delayed titanium bar rupture, in his series of 19 reconstructions for chest wall tumours; in both cases, only one bar was implanted and rupture occurred at the joint. Aware of this eventuality, Wihlm et al. [1] implanted two bars in each patient. However, neither Wihlm et al. [1] nor Mier et al. [4] described long-term follow-up of their patients. The experiences reported in the literature are too limited to draw firm conclusions about the STRATOS™ system in PE repair. Even if a single bar may be sufficient to correct and stabilize the repaired chest wall, it is likely that two bars are needed to better distribute forces and pressures, thus reducing the risk of support rupture. Although we were concerned about the large amount of prosthetic material if 2 bars were employed, we acknowledge that this might represent a minor problem, taking into account the good titanium tolerability.

Conflict of interest: none declared.