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Ann Thorac Surg 2004;77:210-213
© 2004 The Society of Thoracic Surgeons

Original article: cardiovascular

A modified parasternal wire technique for prevention and treatment of sternal dehiscence

Rajeev Sharma, MCha, Deepak Puri, MCha*, Bishnu P. Panigrahi, MDa, Inderjeet S. Virdi, FRCSa

a Department of Cardiothoracic Surgery, Indraprastha Apollo Hospital, New Delhi, India

Accepted for publication July 17, 2003.

* Address reprint requests to Dr Puri, Department of Cardiothoracic Surgery, Forti's Heart Institute, Mohali, Punjab, India
e-mail: drdeepakpuri2{at}rediffmail.com


   Abstract
Top
 Abstract
Introduction
 Patients and methods
 Results
 Comment
 References
 
BACKGROUND: Sternal dehiscence with or without mediastinitis is a devastating complication of median sternotomy. Various techniques of sternotomy closure including ‘figure of eight’ wire sutures, nylon bands, and custom-made titanium-H plates have been described. We have devised and tested a new method of sternal closure to prevent sternal wound complications in patients at high risk of sternal dehiscence.

METHODS: 1336 patients underwent sternotomy for various cardiac operations from January 1996 to January 2002. Patients were divided into two groups. Group I consisted of 560 patients who did not have any high risk factors for sternal dehiscence and received a standard six wire closure. Group II comprised of patients at high risk of sternal dehiscence and were divided randomly into subgroup II A (n = 390), which included patients who had conventional sternal closure. While in subgroup II B (n = 386) patients had a modified parasternal wire closure according to the finalized protocol.

RESULTS: Sternal instability was noticed in 1/560 and none had sternal dehiscence in group I, but 16/390 patients had sternal instability and 3/390 had sternal dehiscence in subgroup II A, whereas only one patient in high risk subgroup II B developed sternal dehiscence with mediastinitis and required a pectoral flap advancement for sternal closure.

CONCLUSIONS: Use of modified parasternal wire closure in patients with a high risk of sternal dehiscence is a safe, effective, technically easily reproducible, as well as economical, method of preventing and treating sternal dehiscence.


   Introduction
Top
 Abstract
 Introduction
Patients and methods
 Results
 Comment
 References
 
There has been a recent increase in enthusiasm for minimal access incisions, yet the ease of access and excellent exposure provided by median sternotomy for all mediastinal structures has made it the most popular approach employed in cardiac surgery. The physical forces of coughing and breathing, however, generate constant mobility which makes immobilization of the two halves of divided sternum very difficult after closure. This lack of immobilization can result in progression of a seemingly "innocent" wound discharge with a barely perceptible sternal instability to sternal dehiscence with or without fulminant mediastinitis.

Mediastinitis occurs in 1% to 2.5% of patients undergoing a median sternotomy [1]. The risk of mediastinitis after valvular procedures is higher [1.8%] compared to that after coronary artery bypass procedures [2]. Concomitant procedures, longer duration of hospital stay, sternal rewiring, prolonged ventilation, and female sex lead to a greater incidence of sternal wound complications [2].

Although there is an increasing enthusiasm for use of arterial grafts, the incidence of sternal wound complications may increase with the use of internal mammary artery if the blood supply to sternum is jeopardized. The incidence approaches 5% if both the internal mammary arteries are used [3].

All the complications, may it be sternal wound discharge, instability, or mediastinitis increase the hospital stay, physical pain, and mental agony of the patients. Even a barely noticeable sternal instability can compromise wound healing and facilitate bacterial infection. It appears rational therefore to aim at a perfect and absolute immobilization of the sternal halves in an endeavor to eliminate the sternal closure technique related risk factor for development of mediastinitis and sternal dehiscence. With this aim a new technique was developed by us for closure of the sternum; especially for patients at high risk of sternal dehiscence.


   Patients and methods
Top
 Abstract
 Introduction
 Patients and methods
Results
 Comment
 References
 
Between January 1996 to January 2002 we did a sternotomy in 1336 patients (Table 1). These patients were divided into group I and group II depending on the absence or presence of the following high risk factors for sternal wound complications:


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  		Table 1. Clinical Profile of Patients Who Had Sternotomy for Various Cardiac Procedures During the Study

 
(i) Age above 65 years; (ii) diabetes mellitus; (iii) bilateral internal mammary artery is harvested; (iv) reoperations; (v) eccentric sternotomy; (vi) sternal reclosure for mediastinitis or dehiscence; (vii) obesity (body weight > 20% higher than expected); and (viii) chronic obstructive pulmonary airway disease.

The patients who did not have any of these risk factors were placed in group I and all of them had a standard six wire closure of sternotomy. The patients having any of these high risk factors were placed in group II and were randomly divided into subgroup II A (consisting of those patients who again had standard closure of sternotomy) while in the remaining patients (subgroup II B) our modified parasternal wire technique was used in addition to the standard six transverse wires used for closure of sternotomy. In this technique, two additional wires were placed parasternally in a longitudinal manner craniocaudally, followed by the routine six transversely placed wires. The patients were randomized by including every alternate patient from group II to subgroup II A and every other alternate patient to subgroup II B. Three patients who developed sternal dehiscence in subgroup A also subsequently had a modified parasternal wire closure similar to the patients in subgroup II B.

For statistical analysis, the incidence of various risk factors present in subgroup II A and subgroup II B were compared using a {chi}2 test (Table 2). Fischer's exact test was used to compare the incidence of sternal wound complications between these two subgroups. The incidence of sternal wound complications in low risk subgroup I was also compared with high risk subgroups II A and II B separately using a {chi}2 test.


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  		Table 2. The Incidence of Various Risk Factors for Sternal Dehiscence in Patients Included in Subgroup II A and II B

 
Operative technique
The technique of sternotomy closure adopted in group I and subgroup II A comprised of passage of No. 6 stainless steel wires transversely in the intercostal spaces, starting from the sixth intercostal space and progressively going up. Care was taken to pass the wires grazing the lateral edge of the sternum and the upper edge of the lower rib in each intercostal space. The topmost wire was passed through the manubrium sternii. After elevating the operating table and retraction of the sternal edges, hemostasis was ensured and the wires were tightened.

For patients in subgroup II B, belonging to the high-risk category, the modified parasternal wire technique devised by us was used. Two lengths of No. 6 stainless steel wires were used "parasternally" in a longitudinal fashion starting from the lower end of each side from the 7th intercostal space. The wire was drawn anterior and posterior to alternalte ribs in such a fashion that both ends of the wire were drawn out near the rostral ends and the caudal ends of the sternum (Fig 1). The standard six wires were then passed in the usual transverse fashion lateral to the longitudinal wires so that the longitudinal wires acted as struts to the transverse wires.



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  		Fig 1. The parasternal wires drawn anterior and posterior to alternate ribs. Both ends were drawn out near the caudal and rostral end of the sternum.

 
After adequate hemostasis the six transversely placed wires were tightened. Subsequently the parasternal wires were tightened so that the rostral end of one wire was tied to the rostral end of the opposite wire. Similarly the caudal end of one wire was tied to the caudal end of the other (Fig 2). The tightened wires were cut short and the remaining stubs were buried carefully under the soft tissues. The soft tissues were then closed in two layers using Vicryl sutures.



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  		Fig 2. The parasternal wires tightened with the rostral end of one side tied to the rostral end of the opposite side and similar caudal end of one side tied to the caudal end of the opposite side.

 

   Results
Top
 Abstract
 Introduction
 Patients and methods
 Results
Comment
 References
 
Among the 560 patients belonging to group I who did not have any risk factor for sternal wound complications, only one patient had sternal instability after conventional sternal wire closure and none of them developed sternal dehiscence. In subgroup IIA (n = 390), the patients who had one or more high risk factors but had conventional closure the incidence of sternal wound complications was significantly higher compared to subgroup I (p = 0.0002) and subgroup II B (p = 0.00065) and sternal instability occurred in 16 patients, 3 of them later developed sternal dehiscence. One patient developed sternal dehiscence on the fourth postoperative day, which was preceded by superficial wound infection. Another patient developed sternal dehiscence 42 days after surgery and had an associated sternal fracture. The third patient was an obese female who developed sternal dehiscence on the eighth postoperative day, which later progressed to frank mediastinitis. All three of these patients were diabetics and after debridement all three subsequently had a parasternal wire technique closure of the sternum.

In subgroup II B (n = 386) the ‘parasternal wire technique’ was used for sternal closure in all patients. Though the patients were having one or more associated high risk factors for sternal dehiscence, the incidence of sternal wound complications was extremely low and comparable to that seen among normal risk patients of group I (p = 0.64771). Only one of the patients in this group developed sternal dehiscence. The patient was an elderly diabetic lady who developed wound discharge with low-grade fever after being discharged from the hospital. She came back after 2 months with necrosis of the sternum and fulminant mediastinitis. Pectoral muscle advancement flap was used for reclosure after adequate debridement. Uncontrolled diabetes was the predisposing factor for fulminant infection in this case.

One patient in each subgroup, II A and II B, came back with infected sternal wires and were treated successfully with appropriate antibiotics and wire removal. All the patients who had developed sternal dehiscence and mediastinitis were successfully treated with this new technique and are now symptom free in a follow-up ranging from 22 to 58 months. There was no increase in incidence of postoperative bleeding, pain, discomfort, or wound infection in the parasternal wire group. There was not a single incidence of accidental injury to the internal thoracic artery by this technique as the longitudinal wires were carefully passed close to the sternal border. The incidence of infected wires was also comparable in both subgroups, II A and II B (one in each subgroup). The mean hospital stay was prolonged by 12 ± 3 days in patients with sternal dehiscence and 5 ± 2 days in the sternal instability group. There was no mortality related to sternal wound dehiscence in either of the groups.


   Comment
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Comment
References
 
Ever since Milton [4] first used steel wires for sternal closure, median sternotomy has now become the standard approach to heart and great vessels during most of the cardiac procedures. It has now also gained application for pulmonary resections for bilateral lesions. The complications of median sternotomy range from superficial wound infections to chronic osteomyelitis, costochondritis, sternal dehiscence to frank mediastinitis posing risk of vein graft occlusion, or prosthetic valve endocarditis [5]. These complications are associated with 19% to 39% mortality in spite of adequate treatment and without treatment the mortality may be 100% due to generalized sepsis, endocarditis, fatal hemorrhage, and multiorgan failure [6].

The most important factor in preventing sternal wound complications is a stable sternal approximation; as bony union depends on adequate reduction and immobilization of the sternocostal junctions. Various innovative techniques have been described to achieve maximum sternal stability and each technique has its own merits and demerits. The Robicsek weave technique has been used to close the fragile and fractured sternum [7]. The disadvantage of this technique is that it produces a constrictive weave which can disrupt the collateral blood supply of sternum and effective approximation of the top and bottom of a gaping sternum cannot be obtained. Modified Robicsek closure with two vertical weaves on each side of the sternum with bilateral pectoralis major advancement flaps has also been described to successfully treat mediastinitis after aggressive sternal debridement [6].

Surgeons have also used "figure of eight" pericostal wire sutures [5], nylon bands [8], and custom made titanium-H plates [9] to achieve a stable sternal fixation. Sternal plates have been also used for sternal nonunion [10]. None of these techniques offers an objective advantage over steel wire encirclage. Besides, the use of bands and custom-made plates may have an additional disadvantage of restricted availability, consequent increase in cost of surgery, and leaving an avoidable foreign material within the body. In addition, custom-made H-plates until now have not been used in human subjects. The delay to "unscrew" and remove plates could be potentially catastrophic when emergent entry into the chest is warranted in ICU settings. Moreover, the drilling of holes in the sternum may actually cause small fractures, especially in thin and osteoporotic sternums and the fractured segments act as foci for infection.

Sternal halves fixed with wire fixation techniques have proven to be more stable biomechanically than other methods of sternal closure [11]. Despite this, there are incidences of sternal wire closure failure because of composite play of forces which ultimately results in wires cutting through the bones transversely. This results in sternal separation because of increased movements between the two halves of the sternum, increased pain at the sternotomy site, inadequate respiratory excursions for expectoration, various respiratory complications, and consequently further interplay of forces that deteriorate sternal healing. The advantage of "figure of 8" technique is that it allows oblique and horizontal angle of shearing forces instead of direct perpendicular forces. Thus these wires are less likely to loosen or fracture [5].

The advantage of our "modified parasternal wire" technique is that it reinforces the lateral sternal table to allow tight closure which decreases the likelihood of the wires cutting through. These parasternal wires act by providing a metal "strut" for the transversely placed wires, so that the disrupting forces are distributed over a wider surface of sternum. In addition, the longitudinal wires provide an equal resistance to the cutting forces of transverse wire, thereby preventing direct burrowing of wires into the sternum. This method has an added advantage over conventional Robicsek's closure in that the blood supply of sternum is not "strangulated" by the ring formed by encircling wires around the costal cartilages by anterior and posterior longitudinal wires [12]. In addition, the knotting of the left and right parasternal wire at the rostral and caudal ends provides an additional support mechanism with two extra transversely supporting wires in addition to the six transverse wires.

This modified ‘parasternal wire technique’ was successfully used by us for prevention of sternal wound complications in those patients who were at high risk of sternal dehiscence. Thus, among the high risk patients who had conventional closure of sternum, the incidence of sternal wound complications was significantly higher (16/390) compared to the negligible incidence (1/386) observed in patients in whom this new technique was used. Our overall experience in the high risk group II is that the patients who have insulin dependent diabetes mellitus, obesity, and COPD have a very high risk of postoperative sternal dehiscence. All four patients in group II who had sternal dehiscence (including 3 in subgroup II A and 1 in subgroup II B) were diabetics dependent on insulin, three were obese, and three were having COPD with persistent cough. In all three patients who had sternal dehiscence after conventional closure in subgroup III A, the transverse wires had cut through the sternum causing multiple fractures in the sternum. This did not happen in any of the patients who had closure with our modified parasternal wire technique. Moreover, in three of the patients who had sternal dehiscence after conventional sternal wire closure in group II A, successful sternal reclosure was achieved after appropriate debridement with this new technique.

This study shows the clinical efficacy of adopting the longitudinal parasternal wires placement as a safe and easily reproducible method for prevention and treatment of sternal dehiscence. We therefore, recommend this technique for sternal closure in patients who are at high risk for sternal wound complications and also in patients who undergo reoperation for sternal dehiscence.


   References
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Comment
 References
 

  1. Loop F.D., Lyttle B.W., Cosgrove M.D., Mahfood S., et al. Sternal wound complications after isolated coronary artery bypass grafting: early and late mortality, morbidity and cost of care. Ann Thorac Surg 1990;49:179-187.[Abstract]
  2. Ottino G., De Paulis R., Pansini S., Rocca G., et al. Major sternal wound infection after open heart surgery: a multvariate analysis of risk factors in 2,579 consecutive operative procedures. Ann Thorac Surg 1987;44:173-179.[Abstract]
  3. Culliford A.T., Cunningham J.N., Zeff R.H., Isom O.W., Teiko P., et al. Sternal and costochondral infections following open heart surgery. A review of 2,594 cases. J Thorac Cardiovasc Surg 1976;72:714-726.[Abstract]
  4. Milton A.F. Tratatad de tecruca operatoria generally especial. Barcelona: Editorial Labor 1944;4:756-760.
  5. Di Marco R.F., Lee M.W., Bekoe S., Grant K.J., et al. Interlocking figure-of-8 closure of the sternum. Ann Thorac Surg 1989;47:927-929.[Abstract]
  6. El Gamel A., Yonen N.A., Hassan R., Jones M.T., et al. Treatment of mediastinitis. Early modified Robicsek closure and pectoralis major advancement flaps. Ann Thorac Surg 1998;65:41-47.[Abstract/Free Full Text]
  7. Robicsek F., Dangherty H., Cook J. The prevention and treatment of sternum separation following open heart surgery. J Thorac Cardiovasc Surg 1977;73:267-268.[Abstract]
  8. Sanfellipo P.M., Danielson G.K. Nylon bands for closure of median sternotomy closure of median sternotomy incisions. Ann Thorac Surg 1972;13:404-406.[Medline]
  9. Sherman J.E., Salzberg A., Raskin N.M., Beattie E.J. Chest wall stabilization using plate fixation. Ann Thorac Surg 1988;46:467-469.[Abstract]
  10. Hendrickson S.C., Koger K.E., Morea C.J., Aponte R.L., et al. Sternal plating for the treatment of sternal nonunion. Ann Thorac Surg 1996;62:512-518.[Abstract/Free Full Text]
  11. Cheng W., Cameron D.E., Warden K.E., Fonger J.D., et al. Biomechanical study of sternal wire techniques. Ann Thorac Surg 1993;55:737-740.[Abstract]
  12. Arnold M. The surgical anatomy of sternal blood supply. J Thorac Cardiovasc Surg 1972;64:596-610.[Medline]



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