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Mechanism of bar displacement and corresponding bar fixation techniques in minimally invasive repair of pectus excavatum
Journal of Pediatric Surgery (2008) 43, 74–78
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Mechanism of bar displacement and corresponding bar fixation techniques in minimally invasive repair of pectus excavatum Hyung Joo Park⁎, Won-Jae Chung, In Sung Lee, Kwang Taik Kim Department of Thoracic and Cardiovascular Surgery, Korea University Medical Center, Seoul 425-707, Republic of Korea Received 28 August 2007; accepted 2 September 2007
Index words: Pectus excavatum; Minimally invasive technique; Bar displacement mechanism; Bar fixation technique
Abstract Purpose: Bar displacement is a major complication in repair of pectus excavatum with the Nuss technique. Mechanisms of bar displacement have been elucidated by case-by-case analysis, and specific bar fixation techniques have been developed to deal with each mechanism. The efficacy of our bar fixation techniques is appraised. Methods: Data from 725 consecutive patients between 1999 and 2006 who were repaired with our modifications to the Nuss procedure were retrospectively analyzed. Results: The mechanism of bar displacement consisted of one or a combination of the following types: type 1, “bar flipping”—rotation of the bar along the axis of hinge; type 2, “lateral sliding”—horizontal slipping of the bar to one side in asymmetric pectus excavatum; and type 3, “hinge-point disruption”—a dorsal shift of the bar owing to tearing of the supporting intercostal musculature. Specific bar fixation techniques have been tailored to compensate for potential mechanisms of bar displacement according to pectus morphology: multipoint pericostal bar fixation (MPF) (n = 496) for type 1 displacement; incorporation of a stabilizer on the depressed side (n = 169) for type 2 displacement; and hinge point reinforcement and the crane technique (n = 122) for type 3 displacement. The bar displacement rate was decreased with our mechanism-based approach (4.6% before MPF vs 1.8% after MPF, P = .045). In addition, the major complication rates (6.8% before MPF vs 2.0% after MPF, P = .001) and reoperation rates (5.5% before MPF vs 1.6% after MPF, P = .019) decreased. Conclusions: Mechanism-based bar fixation techniques, especially multipoint pericostal wire fixation, seems to be effective in preventing bar displacement following pectus excavatum repair. © 2008 Elsevier Inc. All rights reserved.
Bar displacement is a serious complication following minimally invasive repair of pectus excavatum. After introduction of the Nuss technique [1], bar displacement rates was Presented at the 38th annual meeting of the American Pediatric Surgical Association, Orlando, Florida, May 24-27, 2007. ⁎ Corresponding author. Tel.: +82 31 412 5060; fax: +82 31 414 3249. E-mail address: [email protected] (H.J. Park). 0022-3468/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2007.09.022
unacceptably high [2,3], when the principal bar fixation technique was with absorbable sutures to the subcutaneous tissue, as proposed by Donald Nuss. However, bar displacement mechanisms had yet to be studied and thus were not incorporated into the bar fixation techniques. We have also experienced serious challenges with this problem [4,5]. Consequently, we started to examine every case of bar displacement to deduce the underlying
Mechanism of bar displacement and corresponding bar fixation techniques
75
mechanisms and subsequently developed bar fixation techniques tailored to each potential mechanism. As a result, the “multipoint pericostal fixation technique” (MPF) was set up in 2001, and bar displacement rate began to decrease significantly as a consequence [6].
1. Materials and methods Data were collected from 725 consecutive patients who underwent minimally invasive repair of pectus excavatum performed by the principal author between August 1999 and December 2006. The average age was 10.4 (range, 16 months to 51) years, and the male-female ratio was 5.2. Bar displacement rates, major complication rates (hemothorax, pericardial effusion, and major bar displacement), and reoperation rates were compared between 2 groups (before MPF [n = 219] vs after MPF [n = 506]). Statistical analysis was performed using χ2 test (SPSS 10.0, SPSS Inc, Chicago, Ill). P values less than .05 were considered significant. Bar displacement was defined as minor when there was a slight chest wall contour change accompanied by a minor degree (less than 30°) of bar dislocation. Major displacement was defined as a remarkable contour change or total flipping of the bar, these cases required immediate repositioning of the bar.
2. Results 2.1. Bar displacement mechanisms Types and the mechanisms of bar displacement are illustrated in Table 1 and Fig. 1. Type 1 bar displacement occurs most often and is owing to unstable positioning of the bar's apex at the underside of the sternum. Two factors are related with this event: the surgeon's failure to properly position the bar at the deepest point of the depressed chest wall and the morphology of the patient's sternum that has too pointy and sharp undersurface that induce the bar to slip away. Type 2 bar displacement occurs in cases of severe eccentric deformities Table 1 Three types of bar displacement and tailored preventive techniques for each type Types
Mechanisms
Preventive techniques (no. of patients)
Type 1 Type 2
Bar flipping Lateral sliding
Type 3
Hinge point disruption
Multipoint fixation (496) Multipoint fixation Stabilizer (169) Hinge-point reinforcement Crane technique (122)
Fig. 1 Bar displacement mechanisms. A, Type1: flipping of the bar rotation of the bar along the axis of hinge. D indicates downward turnover of the bar; U, upward turnover of the bar. B, Type 2: lateral sliding (2)—horizontal slipping of the bar to one side in asymmetric pectus excavatum. Type 3, hinge-point disruption (3)—dorsal shift of the bar owing to stripping of supporting intercostal musculature.
(morphological type 2A). Uneven pressure exerted on the bar on each side causes lateral sliding of the bar toward the more depressed side. Type 3 bar displacement typically is an intraoperative problem, particularly in adult patients with heavier chests. During rotation of the bar to lift the depressed chest, intercostal muscles of the hinge points strip as a result of excessive pressure, and the bar sinks downward. Because the intercostal musculature is torn-making, it impossible to elevate the depressed chest, type 3 bar displacement may result in a completely failed procedure.
2.2. Bar fixation techniques Bar displacement mechanism for each patient could be anticipated specific to his or her chest wall morphology, and
76 therefore, fixation techniques were devised to counteract each mechanism. In type 1 bar displacement, the bar moves in a cephalad or caudad direction—both the center and tips of the bar in opposite direction (flipping). To prevent these movements, the tips as well as the center of the bar need to be fixed. However, the center of the bar is not readily accessible; therefore, the hinge point—the most accessible central point—is selected for fixation (near-central fixation). This is the MPF, typically the “5-point fixation method” (4 end-hole fixations plus a hinge point fixation), and has been the author's preferred approach for bar fixation. To prevent type 2 bar displacement, lateral sliding of the bar must be blocked on the depressed side of eccentric deformities. In most cases, 5-point fixation method is sufficient, but in severe cases, reinforcement with a stabilizer is necessary as a “slide-block.” For type 3 bar displacement, wire suture reinforcements of the disrupted hinge points with or without stabilizer use are the only remedy. Currently, to prevent this serious problem that may cause incomplete or unsuccessful repair, the “crane technique” is included in the armamentarium for heavy adults and severely asymmetric patients [6]. Sternal elevation with a crane, before the rotation of the bar, alleviates pressure on the hinge points, thus preventing the tearing of intercostal muscles. (Fig. 2) All pericostal sutures
H.J. Park et al. were made using the “through-the-skin suture technique” (TTS) (Fig. 3). There were 19 cases (2.6%) of bar displacement of 725 patients. Of these, 4 cases (0.6%) were major displacement, and 15 cases (2.1%) were minor displacement. Bar fixation techniques used included multipoint fixation (n = 496) to prevent type 1 bar displacement, stabilizers (n = 169) to prevent type 2 bar displacement, and hinge point reinforcement or the crane technique (n = 122) to prevent type 3 bar displacement. With the multipoint bar fixation technique, bar displacement rate was decreased (4.6% [10/219] before MPF vs 1.8% [9/506] after MPF, P = .045). Notably, there were no cases of major bar displacement after the setup of multipoint bar fixation technique. There were no complications directly related with the TTS in the multipoint bar fixation technique. Major complication rate was lower (6.8% [15/219] before MPF vs 1.6% [8/506] after MPF, P = .001). Reoperation rate also decreased (5.5% [12/219] before MPF vs 2.0% [10/506] after MPF, P = .019). Reoperation owing to bar displacement (major and minor) was required in 17 cases (2.3%). Other causes of reoperation included progressive deterioration of the chest contour that required reinsertion of bar to a different level in 3 patients, postoperative bleeding in 1 patient, and skin perforation owing to a stabilizer in 1 patient.
3. Discussion
Fig. 2 The crane technique is elevation of the sternum before the procedure. A percutaneous wire suture is passed through the bony tissue at the xiphi-sternal area, and the wire is connected to a table-mounted crane system. By lifting the sternum off of the underlying viscera with a crane, the entire procedure is safe and easy, and type 3 bar displacement (intercostal muscle stripping) can be prevented.
The prototype Nuss technique for bar fixation is fixing the bar to the subcutaneous tissue with absorbable sutures [1]. This technique could have been successful in limited cases owing to its fixation strength. To overcome this serious bar displacement problem, several new techniques were proposed, but most of these techniques require a larger or additional skin incision and the routine use of stabilizers [7] or other special equipment [8]. These techniques would be cumbersome and may not fulfill the goal of minimally invasive surgery. Furthermore, these techniques are not based on the exact underlying mechanisms of bar displacement. Bar displacement rate of our early experience of 4.6% was comparable to that of other series, but our further development of the “multipoint pericostal wire fixation technique” in conjunction with the “crane technique” achieved the bar displacement rate of 1.8% and no major bar displacement in 506 patients. From the beginning of the author's experience, the lateral incisions for bar insertion were strictly maintained at a size of 1 cm, which is only for the bar passage. This small incision or even a larger incision may not be able to accommodate all the necessary pericostal sutures. To overcome this problem, we developed the TTS, and we could make successfully as
Mechanism of bar displacement and corresponding bar fixation techniques
77
Fig. 3 Through-the-skin suture technique for pericostal bar fixation—the entire suturing process is performed outside the small lateral incisions for bar insertion: (1) the targeted rib is first palpated and the suture needle is pierced directly through the overlying skin, passed around the rib and taken out, once again, through the skin (A); (2) the sutured wires are then retrieved via subcutaneous dissection and finally pulled out through the incision (B and C); (3) the hinge point fixation suture is made with the same technique (D and E); (4) Pericostal sutures are passed through the end-hole of the bar and tied within the incision (F, G); (5) skin incision remains small (1 cm)—the size just allows the bar passage—after all pericostal fixation sutures are made (H).
78 many pericostal sutures as necessary, whereas 2 tiny lateral skin incisions were maintained. Our approach with the “mechanism-based bar fixation techniques,” especially the multipoint pericostal wire fixation, seems to be effective and safe method of bar fixation in minimally invasive pectus excavatum repair.
References [1] Nuss D, Kelly Jr RE, Croitoru DP, et al. A 10-year review of a minimally invasive technique for the correction of pectus excavatum. J Pediatr Surg 1998;33:545-52. [2] Hebra A, Swoveland B, Egbert M, et al. Outcome analysis of minimally invasive repair of pectus excavatum: review of 251 cases. J Pediatr Surg 2000;35:252-8.
H.J. Park et al. [3] Molik KA, Engum SA, Rescorla FJ, et al. Pectus excavatum repair: experience with standard and minimally invasive techniques. J Pediatr Surg 2001;36:324-8. [4] Park HJ, Lee SY, Lee CS, et al. The Nuss procedure for pectus excavatum: an evolution of techniques and results on 322 patients. Ann Thorac Surg 2004;77:289-95. [5] Park HJ, Lee SY, Lee CS. Complications associated with the Nuss procedure: analysis of risk factors and suggested measures for prevention of complications. J Pediatr Surg 2004;39:391-5. [6] Park HJ. Technical innovations in minimally invasive approach for pectus excavatum: a paradigm shift through 630 patients. Innovations 2007;2:25-8. [7] Nuss D, Croitoru DP, Kelly Jr RE, et al. Review and discussion of the complications of minimally invasive pectus excavatum repair. Eur J Pediatr Surg 2002;12:230-4. [8] Hebra A, Gauderer MW, Tagge EP, et al. A simple technique for preventing bar displacement with the Nuss repair of pectus excavatum. J Pediatr Surg 2001;36:1266-8.
www.elsevier.com/locate/jpedsurg
Mechanism of bar displacement and corresponding bar fixation techniques in minimally invasive repair of pectus excavatum Hyung Joo Park⁎, Won-Jae Chung, In Sung Lee, Kwang Taik Kim Department of Thoracic and Cardiovascular Surgery, Korea University Medical Center, Seoul 425-707, Republic of Korea Received 28 August 2007; accepted 2 September 2007
Index words: Pectus excavatum; Minimally invasive technique; Bar displacement mechanism; Bar fixation technique
Abstract Purpose: Bar displacement is a major complication in repair of pectus excavatum with the Nuss technique. Mechanisms of bar displacement have been elucidated by case-by-case analysis, and specific bar fixation techniques have been developed to deal with each mechanism. The efficacy of our bar fixation techniques is appraised. Methods: Data from 725 consecutive patients between 1999 and 2006 who were repaired with our modifications to the Nuss procedure were retrospectively analyzed. Results: The mechanism of bar displacement consisted of one or a combination of the following types: type 1, “bar flipping”—rotation of the bar along the axis of hinge; type 2, “lateral sliding”—horizontal slipping of the bar to one side in asymmetric pectus excavatum; and type 3, “hinge-point disruption”—a dorsal shift of the bar owing to tearing of the supporting intercostal musculature. Specific bar fixation techniques have been tailored to compensate for potential mechanisms of bar displacement according to pectus morphology: multipoint pericostal bar fixation (MPF) (n = 496) for type 1 displacement; incorporation of a stabilizer on the depressed side (n = 169) for type 2 displacement; and hinge point reinforcement and the crane technique (n = 122) for type 3 displacement. The bar displacement rate was decreased with our mechanism-based approach (4.6% before MPF vs 1.8% after MPF, P = .045). In addition, the major complication rates (6.8% before MPF vs 2.0% after MPF, P = .001) and reoperation rates (5.5% before MPF vs 1.6% after MPF, P = .019) decreased. Conclusions: Mechanism-based bar fixation techniques, especially multipoint pericostal wire fixation, seems to be effective in preventing bar displacement following pectus excavatum repair. © 2008 Elsevier Inc. All rights reserved.
Bar displacement is a serious complication following minimally invasive repair of pectus excavatum. After introduction of the Nuss technique [1], bar displacement rates was Presented at the 38th annual meeting of the American Pediatric Surgical Association, Orlando, Florida, May 24-27, 2007. ⁎ Corresponding author. Tel.: +82 31 412 5060; fax: +82 31 414 3249. E-mail address: [email protected] (H.J. Park). 0022-3468/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2007.09.022
unacceptably high [2,3], when the principal bar fixation technique was with absorbable sutures to the subcutaneous tissue, as proposed by Donald Nuss. However, bar displacement mechanisms had yet to be studied and thus were not incorporated into the bar fixation techniques. We have also experienced serious challenges with this problem [4,5]. Consequently, we started to examine every case of bar displacement to deduce the underlying
Mechanism of bar displacement and corresponding bar fixation techniques
75
mechanisms and subsequently developed bar fixation techniques tailored to each potential mechanism. As a result, the “multipoint pericostal fixation technique” (MPF) was set up in 2001, and bar displacement rate began to decrease significantly as a consequence [6].
1. Materials and methods Data were collected from 725 consecutive patients who underwent minimally invasive repair of pectus excavatum performed by the principal author between August 1999 and December 2006. The average age was 10.4 (range, 16 months to 51) years, and the male-female ratio was 5.2. Bar displacement rates, major complication rates (hemothorax, pericardial effusion, and major bar displacement), and reoperation rates were compared between 2 groups (before MPF [n = 219] vs after MPF [n = 506]). Statistical analysis was performed using χ2 test (SPSS 10.0, SPSS Inc, Chicago, Ill). P values less than .05 were considered significant. Bar displacement was defined as minor when there was a slight chest wall contour change accompanied by a minor degree (less than 30°) of bar dislocation. Major displacement was defined as a remarkable contour change or total flipping of the bar, these cases required immediate repositioning of the bar.
2. Results 2.1. Bar displacement mechanisms Types and the mechanisms of bar displacement are illustrated in Table 1 and Fig. 1. Type 1 bar displacement occurs most often and is owing to unstable positioning of the bar's apex at the underside of the sternum. Two factors are related with this event: the surgeon's failure to properly position the bar at the deepest point of the depressed chest wall and the morphology of the patient's sternum that has too pointy and sharp undersurface that induce the bar to slip away. Type 2 bar displacement occurs in cases of severe eccentric deformities Table 1 Three types of bar displacement and tailored preventive techniques for each type Types
Mechanisms
Preventive techniques (no. of patients)
Type 1 Type 2
Bar flipping Lateral sliding
Type 3
Hinge point disruption
Multipoint fixation (496) Multipoint fixation Stabilizer (169) Hinge-point reinforcement Crane technique (122)
Fig. 1 Bar displacement mechanisms. A, Type1: flipping of the bar rotation of the bar along the axis of hinge. D indicates downward turnover of the bar; U, upward turnover of the bar. B, Type 2: lateral sliding (2)—horizontal slipping of the bar to one side in asymmetric pectus excavatum. Type 3, hinge-point disruption (3)—dorsal shift of the bar owing to stripping of supporting intercostal musculature.
(morphological type 2A). Uneven pressure exerted on the bar on each side causes lateral sliding of the bar toward the more depressed side. Type 3 bar displacement typically is an intraoperative problem, particularly in adult patients with heavier chests. During rotation of the bar to lift the depressed chest, intercostal muscles of the hinge points strip as a result of excessive pressure, and the bar sinks downward. Because the intercostal musculature is torn-making, it impossible to elevate the depressed chest, type 3 bar displacement may result in a completely failed procedure.
2.2. Bar fixation techniques Bar displacement mechanism for each patient could be anticipated specific to his or her chest wall morphology, and
76 therefore, fixation techniques were devised to counteract each mechanism. In type 1 bar displacement, the bar moves in a cephalad or caudad direction—both the center and tips of the bar in opposite direction (flipping). To prevent these movements, the tips as well as the center of the bar need to be fixed. However, the center of the bar is not readily accessible; therefore, the hinge point—the most accessible central point—is selected for fixation (near-central fixation). This is the MPF, typically the “5-point fixation method” (4 end-hole fixations plus a hinge point fixation), and has been the author's preferred approach for bar fixation. To prevent type 2 bar displacement, lateral sliding of the bar must be blocked on the depressed side of eccentric deformities. In most cases, 5-point fixation method is sufficient, but in severe cases, reinforcement with a stabilizer is necessary as a “slide-block.” For type 3 bar displacement, wire suture reinforcements of the disrupted hinge points with or without stabilizer use are the only remedy. Currently, to prevent this serious problem that may cause incomplete or unsuccessful repair, the “crane technique” is included in the armamentarium for heavy adults and severely asymmetric patients [6]. Sternal elevation with a crane, before the rotation of the bar, alleviates pressure on the hinge points, thus preventing the tearing of intercostal muscles. (Fig. 2) All pericostal sutures
H.J. Park et al. were made using the “through-the-skin suture technique” (TTS) (Fig. 3). There were 19 cases (2.6%) of bar displacement of 725 patients. Of these, 4 cases (0.6%) were major displacement, and 15 cases (2.1%) were minor displacement. Bar fixation techniques used included multipoint fixation (n = 496) to prevent type 1 bar displacement, stabilizers (n = 169) to prevent type 2 bar displacement, and hinge point reinforcement or the crane technique (n = 122) to prevent type 3 bar displacement. With the multipoint bar fixation technique, bar displacement rate was decreased (4.6% [10/219] before MPF vs 1.8% [9/506] after MPF, P = .045). Notably, there were no cases of major bar displacement after the setup of multipoint bar fixation technique. There were no complications directly related with the TTS in the multipoint bar fixation technique. Major complication rate was lower (6.8% [15/219] before MPF vs 1.6% [8/506] after MPF, P = .001). Reoperation rate also decreased (5.5% [12/219] before MPF vs 2.0% [10/506] after MPF, P = .019). Reoperation owing to bar displacement (major and minor) was required in 17 cases (2.3%). Other causes of reoperation included progressive deterioration of the chest contour that required reinsertion of bar to a different level in 3 patients, postoperative bleeding in 1 patient, and skin perforation owing to a stabilizer in 1 patient.
3. Discussion
Fig. 2 The crane technique is elevation of the sternum before the procedure. A percutaneous wire suture is passed through the bony tissue at the xiphi-sternal area, and the wire is connected to a table-mounted crane system. By lifting the sternum off of the underlying viscera with a crane, the entire procedure is safe and easy, and type 3 bar displacement (intercostal muscle stripping) can be prevented.
The prototype Nuss technique for bar fixation is fixing the bar to the subcutaneous tissue with absorbable sutures [1]. This technique could have been successful in limited cases owing to its fixation strength. To overcome this serious bar displacement problem, several new techniques were proposed, but most of these techniques require a larger or additional skin incision and the routine use of stabilizers [7] or other special equipment [8]. These techniques would be cumbersome and may not fulfill the goal of minimally invasive surgery. Furthermore, these techniques are not based on the exact underlying mechanisms of bar displacement. Bar displacement rate of our early experience of 4.6% was comparable to that of other series, but our further development of the “multipoint pericostal wire fixation technique” in conjunction with the “crane technique” achieved the bar displacement rate of 1.8% and no major bar displacement in 506 patients. From the beginning of the author's experience, the lateral incisions for bar insertion were strictly maintained at a size of 1 cm, which is only for the bar passage. This small incision or even a larger incision may not be able to accommodate all the necessary pericostal sutures. To overcome this problem, we developed the TTS, and we could make successfully as
Mechanism of bar displacement and corresponding bar fixation techniques
77
Fig. 3 Through-the-skin suture technique for pericostal bar fixation—the entire suturing process is performed outside the small lateral incisions for bar insertion: (1) the targeted rib is first palpated and the suture needle is pierced directly through the overlying skin, passed around the rib and taken out, once again, through the skin (A); (2) the sutured wires are then retrieved via subcutaneous dissection and finally pulled out through the incision (B and C); (3) the hinge point fixation suture is made with the same technique (D and E); (4) Pericostal sutures are passed through the end-hole of the bar and tied within the incision (F, G); (5) skin incision remains small (1 cm)—the size just allows the bar passage—after all pericostal fixation sutures are made (H).
78 many pericostal sutures as necessary, whereas 2 tiny lateral skin incisions were maintained. Our approach with the “mechanism-based bar fixation techniques,” especially the multipoint pericostal wire fixation, seems to be effective and safe method of bar fixation in minimally invasive pectus excavatum repair.
References [1] Nuss D, Kelly Jr RE, Croitoru DP, et al. A 10-year review of a minimally invasive technique for the correction of pectus excavatum. J Pediatr Surg 1998;33:545-52. [2] Hebra A, Swoveland B, Egbert M, et al. Outcome analysis of minimally invasive repair of pectus excavatum: review of 251 cases. J Pediatr Surg 2000;35:252-8.
H.J. Park et al. [3] Molik KA, Engum SA, Rescorla FJ, et al. Pectus excavatum repair: experience with standard and minimally invasive techniques. J Pediatr Surg 2001;36:324-8. [4] Park HJ, Lee SY, Lee CS, et al. The Nuss procedure for pectus excavatum: an evolution of techniques and results on 322 patients. Ann Thorac Surg 2004;77:289-95. [5] Park HJ, Lee SY, Lee CS. Complications associated with the Nuss procedure: analysis of risk factors and suggested measures for prevention of complications. J Pediatr Surg 2004;39:391-5. [6] Park HJ. Technical innovations in minimally invasive approach for pectus excavatum: a paradigm shift through 630 patients. Innovations 2007;2:25-8. [7] Nuss D, Croitoru DP, Kelly Jr RE, et al. Review and discussion of the complications of minimally invasive pectus excavatum repair. Eur J Pediatr Surg 2002;12:230-4. [8] Hebra A, Gauderer MW, Tagge EP, et al. A simple technique for preventing bar displacement with the Nuss repair of pectus excavatum. J Pediatr Surg 2001;36:1266-8.