JORT

Results

A total of 33 patients (30 after sternotomy with deep sternal wound healing disorder, 2 after sternal fracture, 1 after syndesmosis infection) were treated with 43 sternal clips between 6/2017 and 10/2024. Two patients had a traumatic sternal fracture (16.3.2.A AO/OTA classification of sternal fractures). One patient had a primary spontaneous infection of the syndesmosis between the manubrium and corpus sterni. In 30 patients, sternal clips were used for osteosynthesis after sternotomy. All patients had previously undergone heart surgery using the extracorporeal circulation, including CABG surgery (n=19), ascending aorta replacement (n=5), aortic valve replacement (n=3), combined CABG surgery and aortic valve replacement (n=3). The aim was always to insert at least 1 sternal clip, preferably a three-segment clip. This was achieved in all 30 patients (Figure 5). In 8 patients, an additional clip had to be inserted. In one patient, 3 double clips were used. As described previuosly, all patients received at least 2 PDS cords. In addition, a titanium plate was inserted in 17 patients (all patients with deep sternal wound infection). These were always positioned at the manubrium or the costal arch. The reason for such a titanium plate was: 1. the width of the manubrium that did not allow the clip implantation, 2. an insufficiently large intercostal gap at the level of the costal arch. The mean age of our study cohort was 63 ± 11 years, the gender distribution was 26 men and 7 women. The only inclusion criterion for the use of the sternal clip was an adequate bone quality allowing implantation of a sternal clip. All sternal clips were implanted at the University Hospital Augsburg, Clinic for Cardiac and Thoracic Surgery by 3 experienced surgeons.

The following one-segment, two-segment or three-segment clips combinations were used (Table 1):

Table 1: Number and type of clips used

The implantation was uneventful for all patients. The two single clips were inserted in combination with a multi-segment clip. No clips had to be removed or repositioned. Of note, the clips enabled good bridging and stabilization of transverse sternal fractures and smaller bone defects, which typically may occur after disruption of the sternal wires. Clinically, all secondary osteosyntheses using the sternal clips were stable both intraoperatively and at the functional examination postoperatively. There were no serious complications. There were three minor intraoperative complications, such as bleeding from an intercostal vessel, which was stopped by electrocoagulation. One sternal clip became dislocated after the patient fell out of bed. At the same time, the PDS cords and a titanium plate, which was fixed by screws, tore out simultaneously. No fracture of the sternal clip was observed. In a total of five patients, the sternal clips were removed again due to persistent osteomyelitis. The causes for the removal were a persistent sternal infection in all cases, induced by the same microbiological pathogen. The interval between implantation and the removal was at least 6 weeks in all patients, so that the former osteotomy had become osseous in the meantime and the thorax was functionally stable. The explantation was possible without any problems in all five patients. The sternal clips were all still in their original position without any recognizable deformation or fracture.

Discussion

The use of wires for sternal osteosynthesis is considered a standard of care. It is quick to perform, has few complications and is costeffective. By using wires, the lateral forces on the rib cage can be sufficiently compensated. However, the shear forces are not sufficiently addressed by wires that are not connected to each other in most cases. The use of the figure of eight wire osteosynthesis could be a possible solution to address this drawback. Another disadvantage of the wire osteosynthesis is the fact that the bone is penetrated by the wire and the contact surface for the force distribution is very limited. This has a particularly negative effect in older female people with advanced osteporosis. There is a risk that the wire will tear through the bone tissue and lose its hold. To avoid this, Robbiczek has developed a special wiring method. However, this surgical technique may impair the blood supply to the sternum. There are several osteosynthesis systems available to overcome the limitation of wires. Sternal bands have a larger contact surface and, therefore, a superior force distribution. In addition, they are usually placed around the bone so that the bone does not have to be pierced and there is broad contact with the stable compacta. However, individual ligaments can also only cope poorly with shear forces along the osteosynthesis [10]. Alternatively, there are plates that are anchored in the bone with locking screws. These systems can absorb shear forces well as they have several anchor points on each half of the sternum. However, sufficiently firm bone tissue is required to fix the plates. A combination of both systems (ligament and plate) was also available. An ideal osteosynthesis system should fulfill the following requirements: a) the sternum should not be additionally injured during the osteosynthesis, b) there is a wide contact surface of the osteosynthesis to the bone that distributes the forces well; c) the system has several holding points that absorb shear forces; d) the osteosynthesis system can be customized; e) when implanting the osteosynthesis system, there is no necessity to dissect the dorsal side of the sternum which can be risky due to dence adhesions between the sternum and the heart or vascular structures (e.g., bypass graft).

All abovementioned requirements are addressed by the sternal clips. The main advantage of this system is the anchoring around the bone without perforating it with screws or wires. Furthermore, the system is suitable for bridging transverse fractures and smaller bone defects. Based on our preliminary experience in a limited consecutive patient’s series, the sternal clips are safe to use. An anatomical study has shown that the clips accomomodate well to the sternum in terms of length and available widths [11]. The fact that the clips can be adapted to the individual patient in terms of both the size of the opening (Small, Medium and Large) and their length has proven to be advantageous. The titanium can also be adapted to the shape of the sternum. When treating a sternal fracture with a sternal clip, the entire fracture gap must be bridged with the clip. This is only possible for 2-segment clips in the case of a horizontal fracture of the corpus sterni (AO/OTA 16.3.2.A) exactly between the intercostal spaces. For all other fractures, i.e. a horizontal fracture (AO/OTA 16.3.2.A) at the intercostal space or an oblique fracture (AO/OTA 16.3.2.B), a 3-segment clip must be inserted. Therefore, it is common sense that a 3-segment clip should always be used when treating fractures. The advantage of the sternal clip in the treatment of sternal fractures is also that the length of the clip can be adjusted again after implantation of the clip. By subsequently shortening the clip, further pressure can be applied to the fracture halves in the fracture gap. This procedure has proven to be very helpful for bridging bone defects.

However, the shortening option is limited to a few millimeters. Thus, this is sufficient for treating the defect after a Sydesmos defect or smaller bone defects after DSWI. The limitation of the sternal clip is that it can be very well implanted only on the corpus immediately caudal to the Angle of Lewis. It can be often successfully used on the manubrium in the first intercostal space, although the manubrium might be too wide for the largest opening (Large) of the clip to encompass it. Caudal to the corpus directly at the costal arch, implantation is often not possible due to the anatomical conditions. This is only possible if the ribs are still horizontal in this region. If the ribs and the associated intercostal clefts are already very steep, there is not enough space to insert the necessary bending pliers. This is also reflected by our findings; in sternal closure after median sternotomy, only 4 patients had 2 clips inserted at the same time. This is of course sufficient to counteract shear forces, but in order to achieve sufficient stability of the osteosynthesis, further osteosynthesis procedures must be used for the required 6 bridges between the two halves of the sternum. PDS cords have proven to be the optimal combination here.

To the best of our knowledge, our case series represent the largest experience published with the sternal clips. In this regard, no complications such as material breakage or surgery-associated complications occurred. As far as this retrospective analysis allows, the sternal clips described can be used safely and reproducibly within the described framework. In some indications such as osteomyelitis, osteoporosis or if retrosternal preparation is to be avoided, they may even be the first choice as an osteosynthesis procedure. The limitation is, however, the cost factor. In comparison with the wires, osteosynthesis plates or clips are more expensive. However, given the advantages and indications described above, individualized and patient-centered decision-making process is strongly appreciated.

Figure 5: 2 examples of complete osteosynthesis with sternal clips after deep sternal wound infection.

References

1. Brookes JG, Dunn RJ, Rogers IR (1993) Sternal fractures: a retrospective analysis of 272 cases. J Trauma 35(1): 46-54.
2. Khoriati AA, Rajakulasingam R, Shah R (2013) Sternal fractures and their management. J Emerg Trauma Shock 6(2):113-116.
3. Schulz-Drost S, Krinner S, Langenbach A, Oppel P, Lefering R, et al. (2017) Concomitant Sternal Fracture in Flail Chest: An Analysis of 21,741 Polytrauma Patients from the Trauma Register DGU®. Thorac Cardiovasc Surg 65(7): 551-559.
4. Rodríguez Lorenzo P, Fernández Martínez B, Pérez Alba M, Ramírez Jaén C, Meana Morís AR, et al. (2023) Primary sternal osteomyelitis. Arch Argent Pediatr 121(5): e202201449.
5. Gerbode F, Braimbridge MV, Melrose DG (1958) Median sternotomy for open cardiac surgery during total heart-lung by-pass. AMA Arch Surg 76(5): 821-824.
6. Çiçek S (2018) Sternal closure: Wires are still the king. J Thorac Cardiovasc Surg 156(4): 1596-1597.
7. Omer SJ (2018) Polymer cable tie closure of the sternum: Is it an acceptable fix? Thorac Cardiovasc Surg 156(4): 1611-1612.
8. Reiss N, Schuett U, Kemper M, Bairaktaris A, Koerfer R (2007) New method for sternal closure after vacuum-assisted therapy in deep sternal infections after cardiac surgery. Ann Thorac Surg 83(6): 22467.
9. Wiese MN, Kawel Boehm N, Moreno de la Santa P, Al Shahrabani F, Toffel M, et al. (2015) Functional results after chest wall stabilization with a new screwless fixation device. Eur J Cardiothorac Surg 47(5): 868-875.
10. Marasco SF, Fuller L, Zimmet A, McGiffin D, Seitz M, et al. (2018) Prospective, randomized, controlled trial of polymer cable ties versus standard wire closure of midline sternotomy. J Thorac Cardiovasc Surg 156(4):1589-1595.
11. Reindl S, Schuller P, Meller M, Beyer M, Decker J, et al. (2022) Morphometry of The Sternum in Osteosynthetic Reconstruction. J Orthop Res Ther 7: 1242.