- Email: [email protected]
Recent and Future Developments in Chest Wall Reconstruction
Author's Accepted Manuscript
Recent and Future Developments in Chest Wall Reconstruction Calvin S.H. Ng, BSc, MD, FRCS (CTh), FCCP
www.elsevier.com/locate/buildenv
PII: DOI: Reference:
S1043-0679(15)00089-1 http://dx.doi.org/10.1053/j.semtcvs.2015.05.002 YSTCS735
To appear in:
Semin Thoracic Surg
Cite this article as: Calvin S.H. Ng, BSc, MD, FRCS (CTh), FCCP, Recent and Future Developments in Chest Wall Reconstruction, Semin Thoracic Surg, http://dx.doi.org/ 10.1053/j.semtcvs.2015.05.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
News & Views Recent and Future Developments in Chest Wall Reconstruction
Calvin S.H. Ng
BSc
MD
FRCS(CTh)
FCCP
Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong SAR
Abstract word count: 168 Word count: 2516
Disclosure Statement: No competing financial interests exist
Correspondence:
Calvin S.H. Ng, BSc(Hons) MBBS(Hons) MD FRCSEd(CTh) FCCP Associate Professor Division of Cardiothoracic Surgery, The Chinese University of Hong Kong Prince of Wales Hospital, Shatin, N.T. Hong Kong SAR, China E-mail: [email protected] Tel.No.: (852) 2632 2629
Fax No.: (852) 2637 7974
Abstract Reconstruction following major chest wall resection can be challenging. Conventional methods of using mesh with or without incorporation of methyl methacrylate is slowly being replaced by chest wall reconstruction prosthetic systems that use titanium plates or bars. The most popular systems in use are the titanium STRATOS bars and MatrixRIB plates which have different systems for securing to the chest wall. In general, these new approaches are user friendly, more ergonomical, and may avoid certain complications associated with the more conventional methods of reconstruction. However, the successful implantation of these titanium prosthetic systems require the operator to be familiar with the limitations and potential pitfalls of the process. Follow-up data is only just emerging on the risk factors for implant failure of these prosthetic systems, as well as certain device specific complications, with fracture failure being increasingly recognized as a significant problem. In the future, emerging intraoperative real-time imaging and 3D printing technology, as well as development in biomaterials will allow chest wall reconstruction to become increasingly personalized.
Keywords: 3D Printing, Chest Wall, MatrixRib, STRATOS, Titanium Prostheses
Introduction Chest wall tumors usually require radical surgery with adequate surgical resection margins which can result in large defects. Complex reconstruction is sometimes required to maintain chest wall integrity and cosmesis, as well as to prevent paradoxical chest wall movement which may lead to respiratory compromise. The reconstruction should also aim to avoid defects that allow organ herniation, counteract significant chest retraction leading to thoracoplasty-like effect, and be capable of affording some protection to underlying mediastinal organs against external impact. Conventional chest wall reconstruction, particularly for large defects, may be associated with high rates of complications. [1] For many decades, methyl methacrylate have been the popular choice to reconstruct parts of the sternum, ribs and chest wall. [2] However, recent advances in rib fixation devices may simplified the reconstruction process, in particular the DePuy Synthes
MatrixRib Pre-contoured Plate and the
STRATOS™ (Strasbourg Thoracic Osteosyntheses System; MedXpert GmbH, Heitersheim, Germany) titanium systems.[3,4, 5] The implantation of new devices when executed correctly can be more user friendly, ergonomic, and may avoid certain problems associated with traditional reconstruction methods. Often the successful implantation of prosthetic rib requires knowledge of certain tips and tricks which will be discussed. In addition, specific complications relating to these systems will be highlighted. Lastly, there are exciting future developments in a more personalized approach to prosthetic chest wall reconstruction on the horizon.
Conventional Approaches A whole multitude of materials are available for chest wall reconstruction, however traditionally the most commonly used were synthetic meshes and bone substitutes, such as methyl methacrylate. The meshes and patches are easy to manipulate, handle and can be easily sutured to the ribs and surrounding connective tissue. The flexibility of the meshes usually allow a uniform distribution of tension at the defect edges, and their relative porosity can limit adjacent seroma formation. Despite being used doubled over in most situations, the meshes tend to lack rigidity which when covering large chest wall defects are unable to maintain the natural chest wall curvature. This has important implications not only for cosmesis but also for postoperative pulmonary function. Methyl methacrylate is widely used for reconstructing the rigid structures of the chest wall, and may be applied as a sandwich between two layers of mesh. However, the material can be difficult to use in inexperienced hands. Despite technical modifications introduced by Lardinois et al [6] on the methacrylate mixture and application methodology which allow better configuration of the prosthesis, problems with anchorage and dislocation remain. Other potential problems that are encountered, albeit uncommonly, include; methyl methacrylate toxicity, poor anchorage and fixation difficulties of the material, fracture of the methacrylate and associated chronic pain, as well as prosthesis infection. [1] The transition and recognition for the need of reconstructing the chest wall with “neo-ribs” that is more akin to the anatomy and perhaps physiology of the native chest wall was recognized and presented by Dahan et al. *7+ They describe the technique of using Kirschners’s wires that are inserted into the cut rib ends as the framework for holding the silicon molds, into which the viscous methyl methacrylate is injected and allowed to harden, before the molds are eventually split and removed. Compared with the nonporous large plate of methyl methacrylate, this modification allows some tissue in-growth and better fluid drainage.
Development and Use of Titanium Prostheses Utilization of metal prostheses for chest wall reconstruction may have been reported as far back as 1909 by French surgeon Gangolphe for management of a large sternal notch enchondroma. [8] Titanium implants have been more widely used since the mid-1950s, with the eventual development of the Austin Moore and Thompson orthopedic prostheses. The strength, corrosion resistance and biocompatibility of titanium make it ideal for implants. However, problems with early prostheses fracture led to modification from using “pure” titanium to the stronger titanium alloys in these devices. The first alloy used for biomedical implants was Ti-6Al-4V containing 6% aluminium and 4% vanadium, which is the same material used for construction of the NASA Space Shuttles. Unfortunately, it was found that the vanadium from Ti-6Al-4V prostheses slowly seeped out and became toxic to humans. Hence the titanium alloy Ti-6Al-7Nb containing 6% aluminium and 7% niobium became the standard for prostheses, which is the same stronger alloy currently used in hip implants of today, as well as in some of the titanium rib prostheses system, such as the DePuy Synthes
MatrixRibs.
There are numerous materials and rib prostheses systems that exist. Perhaps one of the oldest dedicated system is the Borrelly steel staple-splints system (Medicalex, Bagneux, France) which was popularized in the 1990s. The currently most favored prostheses are the STRATOS™ system and MatrixRIB Precontoured Plate system. *4,9+ The STRATOS™ titanium system may be considered an evolution of the Borrelly system by working through a similar mechanism of securing to the rib ends using clips that resemble claws at the two ends of the bar. On the other hand, the MatrixRIB Precontoured Plate system is secured by fastening the plate to the rib with locking-screws through predrilled holes. In general, most thoracic surgeons are less familiar with bone drilling and use of plates and screws than colleagues in other surgical specialties. Therefore, it is even more important to gain
knowledge of certain tips and tricks to avoid some of the pitfalls during implantation of the MatrixRIB Precontoured Plate system.
Considerations during MatrixRIB Plate Implantation Achieving good pneumostasis and hemostasis is important, as returning to the pleural space will often mean having to take down the chest wall reconstruction. A generous size chest tube should be placed through a separate port incision towards the apex. The neo-pleura is reconstructed with either doubled up polypropylene mesh or Gortex
mesh based on surgeon preference. In certain cases, the defect may
be so large that several pieces of Gortex
mesh are required, and a rapid and secure method to unite
the pieces is by utilizing the Covidien TATM 90mm stapler. [9] The mesh should be trimmed to 2cm larger than the defect in all directions to allow some “give” avoiding too much tension, while maintaining the general conformation. Interrupted horizontal mattress Ethibond 2/O sutures are placed circumferentially 3 cm apart on the mesh and then sutured to the chest wall fascia internally. Such suture distribution should provide good security and may reduce interstitial fluid accumulating in the chest wall and seroma formation by allowing drainage into the pleural space. Our practice of placing the mesh deep to the artificial ribs prevents lung herniation between implanted plates. Prior to tying all the sutures and “closing off” the pleural space with the mesh, the lung should be reexpanded under direct vision with resumption of two lung ventilation.
In considering the rib implantation, preoperative planning is paramount. Imaging should be carefully studied and the size of the post-resection defect estimated. It is noteworthy that there is limitation to the length of the artificial ribs, with the longest MatrixRib being an 18-hole plate, which given that there
should be at least two screws for securing the plate onto the rib at both ends, provides a maximum breachable rib-rib defect of 14cm. If the defect is slightly too wide for even the longest plate, a trick is to push the rib ends closer together to narrow the gap before fixation of the plate. [10] Through a drill guide, 2 holes are created at each end and locking screws firmly secure the plate to the resected rib ends. Redivac drain should be placed superficial to the mesh, with soft tissue covering applied over. It is noteworthy that these techniques are not just applicable for repair of the chest wall but is also applicable for total sternal reconstructions. [Figure 1]
Prosthetic Ribs: The Beauty and The Beast The beauty of the prosthetic rib systems is their ease of implantation and their relatively trouble free follow up. However, the surgeon should be aware of certain rare complications. Recently, there have been reports of STRATOS™ system bar fracture following chest wall reconstruction and pectus excavatum repair, [3,11] which can be between 0-11% in some series [4,5]. In addition, fracture failure of the MatrixRIB Precontour Plate system have also been reported, [12, 13] some with an accountable cause such as following an impact to the chest wall directly over the prostheses. [12] [Figure 2]
Despite the strength of modern day titanium alloy, studies have shown that repeated stress to the metal can initiate and propagate microcracks, which in the presence of fine precipitations within the metal, can eventually lead to full blown fracture failure. Therefore, fracture failure can and do still occur, although very rarely. Interestingly, the STRATOS™ system uses “pure” titanium which has less strength compared with the titanium alloys used in other modern surgical implantable prostheses. This may
partly explain the higher frequency of reports on fracture failure of the STRATOS™ system. *3,11+ One of the main reason for choosing ‘pure” titanium as the material for the STRATOS™ system is so that the metal is pliable enough for crimping of the clips by pliers at the bar ends, to secure the bar to the rib ends. In contrast, the plate and screw design of the MatrixRIB Precontour system allows the stronger titanium alloy Ti-6Al-7Nb to be used for its bars. Another possible reason for the STRATOS™ system potentially being more prone to fracture is that along the STRATOS™ bar are areas of narrower profile as well as more acute angulation that may be subjected to higher stresses, contributing to metal fatigue and fracture failure. [3,5,11,13] In contrast, the smooth contour of the MatrixRIB plate should prevent areas of focused high stress from developing, therefore reducing risk of stress fracture. Nevertheless, rare cases of fracture failure can still occur in MatrixRIB Precontour Plates when subjected to repeated stresses and excessive external forces, [12,13] and patients should be warned of this possibility during consent. Furthermore, most of the failures tend to occur in anterior chest wall implants probably because of the larger chest movement during respiration and repeated stress, and those failure usually happen early, within 14 months following the implant. [13] Surgical removal is often required following implant fracture failure because of discomfort and pain, and risk of implant migration injury. [4,12,13]
Another complication we have witnessed is prosthesis screw loosening, which is actually rarely reported in implanted prosthetic rib devices. [Figure 3] Although elderly patients with osteoporotic ribs may be more at risk, technical failure is usually the cause, and in the MatrixRIB system certain technical pitfalls can contribute to the development of such complication. The first reason concerns mismatch between screw length and measured rib thickness. The measurement of rib thickness by the system’s parallel gauge records the thickest aspect of the rib. The surgeon must ensure that the drilling, plates and screws are placed over this thickest aspect of the rib to correspond to the measured screw length to
prevent screw protrusion and loosening. [9] Secondly, to avoid screw back-out or loosening, special care should be taken during drilling to avoid “double-tap” (re-drilling the same hole) which can destroy the bone threads that lock the screw securely in place. Furthermore, to improve plate security and if the length of the plate allows, the screws should be placed into the last and third from last holes of each plate end.
A Look into the Future Although reconstruction of the chest wall with prostheses implantation is desirable and in some cases essential during chest wall surgery, unfortunately many of the cons of using such devices stem from its rigidness, uncompromising or inappropriate conformation, and also the persistent nature of the material as an indefinite foreign body. Despite the recent advances in variable angle titanium prosthetic bar design to try to accommodate different chest wall defect configurations, the prostheses are still far from ideal. [14] There have also been some successes in the use of bioabsorbable materials for reconstructing the chest wall, which is particularly important in the growing pediatric population. [15,16] In the coming years, chest wall prostheses will evolve to become more personalized, with shape and size that will exactly fit each individual patient. Preoperative computed tomography (CT) with reconstructed 3D images may be used as reference for manufacturers to customize more unusual implant configurations. [17] The rapid development in 3D printing technology may allow customized prostheses from resins, polymers, metals and degradable biomaterials to be made quickly and accurately. Not only that, the 3D printed construct may utilized a combination of materials, some that biodegrade while other parts of the prostheses may have properties that are more rigid and permanent to optimize
prostheses characteristics for that particular reconstruction. Even more exciting is the prospect of 3D printing bio-scaffolds that allow patient’s own cells to colonize and grow into. *18+ Clearly, these developments will be a huge advantage in terms of having a prostheses that fits the patient’s habitus and disease. However, often the true post-resection cavity size and shape is difficult to predict, and the measurement of chest wall defect is only known “on-table” intraoperatively. Hybrid operating room real-time cone beam CT is increasingly being use in thoracic surgery to guide and improve accuracy of procedures. [19] Perhaps not in the too distant future, we shall see the use of such facility to provide image of the post-resection chest wall defect, followed by 3D image reconstruction and immediate transfer of data for 3D printing of the chest wall prostheses within the operating theatre. By the time the mesh reconstruction of the chest wall is completed, the 3D printed prostheses will be ready to provide the ultimate in prostheses customization. (Figure 4) It is indeed exciting times for chest wall reconstruction as the marriage of innovative surgical technique, state of the art real-time imaging, and advances in technology and biomaterials will allow a highly personalized surgical treatment for each individual. As Eleanor Roosevelt (First Lady of the United States, 1933-1945) once said “The future belongs to those who believe in the beauty of their dreams.” For us, there is no need to dream. The technology described is available. It is simply a matter of ceasing this opportunity for our patients.
References
1) Mansour KA, Thourani VH, Losken A, Reeves JG, Miller JI, Carlson GW, Jones GE. Chest wall resections and reconstruction: a 25-year experience. Ann Thorac Surg 2002; 73:1720-1726
2) Bibas BJ, Bibas RA. Operative stabilization of flail chest using a prosthetic mesh and methylmethacrylate. Eur J Cardiothorac Surg 2006;29:1064-6
3) Billè A, Okiror L, Karenovics W, Routledge T. Experience with titanium devices for rib fixation and coverage of chest wall defects. Interact Cardiovasc Thorac Surg 2012;15:588-95
4) Berthet JP, Canaud L, D'Annoville T, Alric P, Marty-Ane CH. Titanium plates and Dualmesh: a modern combination for reconstructing very large chest wall defects. Ann Thorac Surg 2011;91:1709-16
5) Lardinois D, Muller M, Furrer M et al. Functional assessment of chest wall integrity after methylmethacrylate reconstruction. Ann Thorac Surg 2000;69(3):919-23
6) Thomas PA, Brouchet L. Prosthetic reconstruction of the chest wall. Thorac Surg Clin 2010;20:551-8
7) Gangolphe L. Enorme enchondrome de la fourchette sternale. Lyon Chir 1909;2:112 [in French] 8) Ng CSH, Ho AMH, Lau RWH, Wong RHL. Chest Wall Reconstruction with MatrixRib SystemAvoiding Pitfalls. Interact Cardiovasc Thorac Surg 2014;18:402-3
9) Kwok MWT, Lau RWH, Wong RHL, Ng SK, Chui PT, Wan S, Underwood MJ, Yim APC, Ng CSH. MatrixRib Reconstruction following Major Chest Wall Tumor Resection- Initial Experience. American Association for Thoracic Surgery (AATS) 94th Annual Meeting. 26-30th April 2014, Metro Toronto Convention Centre, Toronto, Canada [oral presentation]
10) Stefani A, Nesci J, Morandi U. STRATOS™ system for the repair of pectus excavatum. Interact Cardiovasc Thorac Surg 2013;17:1056-8
11) Ng CSH, Wong RHL, Kwok MWT, Yim APC. Delayed Fracture of MatrixRib Pre-contoured Plate System. Interact Cardiovasc Thorac Surg 2014; 19:512-4
12) Tuggle DW, Mantor PC, Foley DS, Markley MM, Puffinbarger N. Using a bioabsorbable copolymer plate for chest wall reconstruction. J Pediatr Surg 2004;39:626–628
13) Miller DL, Force SD, Pickens A, Fernandez FG, Luu T, Mansour KA. Chest wall reconstruction using biomaterials. Ann Thorac Surg. 2013;95:1050-6
14) Krüger M, Zinne N, Zhang R, Schneider JP, Heckmann A, Haverich A, Petersen C. Multidirectional thoracic wall stabilization: a new device on the scene. Ann Thorac Surg. 2013;96:1846-9
15) Fabre D, El Batti S, Singhal S, Mercier O, Mussot S, Fadel E, Kolb F, Dartevelle PG. A paradigm shift for sternal reconstruction using a novel titanium rib bridge system following oncological resections. Eur J Cardiothorac Surg. 2012;42:965-70
16) Berthet JP, Caro AG, Solovei L, Gilbert M, Bommart S, Gaudard P, Canaud L, Alric P, Marty-Ané CH. Titanium Implant Failure After Chest Wall Osteosynthesis. Ann Thorac Surg. 2015 Apr 24. pii: S0003-4975(15)00248-9. doi:10.1016/j.athoracsur.2015.02.040
17) Turna A, Kavakli K, Sapmaz E, Arslan H, Caylak H, Gokce HS, Demirkaya A. Reconstruction with a patient-specific titanium implant after a wide anterior chest wall resection. Interact Cardiovasc Thorac Surg. 2014;18:234-6
18) Michalski MH, Ross JS. The shape of things to come: 3D printing in medicine. JAMA. 2014;312:2213-4
19) Ng CSH, Chu CM, Kwok MWT, Yim APC, Wong RHL. Hybrid DynaCT Guided Localization Single Port Lobectomy. Chest 2015;147(3):e76-8
Legend
Figure 1. Reconstruction of whole manubrium and sternum with MatrixRIB plates following excision of post-irradiation chest wall sarcoma. An anterior lateral thigh flap was used for soft tissue coverage.
Figure 2. Chest radiograph showing a fractured MatrixRIB plate following direct chest wall impact from sports.
Figure 3. Chest radiograph showing one of the screws from MatrixRIB plate has loosened and sunk to the bottom of the left post-pneumonectomy fluid filled pleural cavity.
Figure 4. The future of customized chest wall prostheses starting with chest wall resection, intraoperative real-time cone beam CT of the defect in hybrid operating room, immediate intra-operative 3D printing of the prostheses, and implantation into the patient.
Recent and Future Developments in Chest Wall Reconstruction Calvin S.H. Ng, BSc, MD, FRCS (CTh), FCCP
www.elsevier.com/locate/buildenv
PII: DOI: Reference:
S1043-0679(15)00089-1 http://dx.doi.org/10.1053/j.semtcvs.2015.05.002 YSTCS735
To appear in:
Semin Thoracic Surg
Cite this article as: Calvin S.H. Ng, BSc, MD, FRCS (CTh), FCCP, Recent and Future Developments in Chest Wall Reconstruction, Semin Thoracic Surg, http://dx.doi.org/ 10.1053/j.semtcvs.2015.05.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
News & Views Recent and Future Developments in Chest Wall Reconstruction
Calvin S.H. Ng
BSc
MD
FRCS(CTh)
FCCP
Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong SAR
Abstract word count: 168 Word count: 2516
Disclosure Statement: No competing financial interests exist
Correspondence:
Calvin S.H. Ng, BSc(Hons) MBBS(Hons) MD FRCSEd(CTh) FCCP Associate Professor Division of Cardiothoracic Surgery, The Chinese University of Hong Kong Prince of Wales Hospital, Shatin, N.T. Hong Kong SAR, China E-mail: [email protected] Tel.No.: (852) 2632 2629
Fax No.: (852) 2637 7974
Abstract Reconstruction following major chest wall resection can be challenging. Conventional methods of using mesh with or without incorporation of methyl methacrylate is slowly being replaced by chest wall reconstruction prosthetic systems that use titanium plates or bars. The most popular systems in use are the titanium STRATOS bars and MatrixRIB plates which have different systems for securing to the chest wall. In general, these new approaches are user friendly, more ergonomical, and may avoid certain complications associated with the more conventional methods of reconstruction. However, the successful implantation of these titanium prosthetic systems require the operator to be familiar with the limitations and potential pitfalls of the process. Follow-up data is only just emerging on the risk factors for implant failure of these prosthetic systems, as well as certain device specific complications, with fracture failure being increasingly recognized as a significant problem. In the future, emerging intraoperative real-time imaging and 3D printing technology, as well as development in biomaterials will allow chest wall reconstruction to become increasingly personalized.
Keywords: 3D Printing, Chest Wall, MatrixRib, STRATOS, Titanium Prostheses
Introduction Chest wall tumors usually require radical surgery with adequate surgical resection margins which can result in large defects. Complex reconstruction is sometimes required to maintain chest wall integrity and cosmesis, as well as to prevent paradoxical chest wall movement which may lead to respiratory compromise. The reconstruction should also aim to avoid defects that allow organ herniation, counteract significant chest retraction leading to thoracoplasty-like effect, and be capable of affording some protection to underlying mediastinal organs against external impact. Conventional chest wall reconstruction, particularly for large defects, may be associated with high rates of complications. [1] For many decades, methyl methacrylate have been the popular choice to reconstruct parts of the sternum, ribs and chest wall. [2] However, recent advances in rib fixation devices may simplified the reconstruction process, in particular the DePuy Synthes
MatrixRib Pre-contoured Plate and the
STRATOS™ (Strasbourg Thoracic Osteosyntheses System; MedXpert GmbH, Heitersheim, Germany) titanium systems.[3,4, 5] The implantation of new devices when executed correctly can be more user friendly, ergonomic, and may avoid certain problems associated with traditional reconstruction methods. Often the successful implantation of prosthetic rib requires knowledge of certain tips and tricks which will be discussed. In addition, specific complications relating to these systems will be highlighted. Lastly, there are exciting future developments in a more personalized approach to prosthetic chest wall reconstruction on the horizon.
Conventional Approaches A whole multitude of materials are available for chest wall reconstruction, however traditionally the most commonly used were synthetic meshes and bone substitutes, such as methyl methacrylate. The meshes and patches are easy to manipulate, handle and can be easily sutured to the ribs and surrounding connective tissue. The flexibility of the meshes usually allow a uniform distribution of tension at the defect edges, and their relative porosity can limit adjacent seroma formation. Despite being used doubled over in most situations, the meshes tend to lack rigidity which when covering large chest wall defects are unable to maintain the natural chest wall curvature. This has important implications not only for cosmesis but also for postoperative pulmonary function. Methyl methacrylate is widely used for reconstructing the rigid structures of the chest wall, and may be applied as a sandwich between two layers of mesh. However, the material can be difficult to use in inexperienced hands. Despite technical modifications introduced by Lardinois et al [6] on the methacrylate mixture and application methodology which allow better configuration of the prosthesis, problems with anchorage and dislocation remain. Other potential problems that are encountered, albeit uncommonly, include; methyl methacrylate toxicity, poor anchorage and fixation difficulties of the material, fracture of the methacrylate and associated chronic pain, as well as prosthesis infection. [1] The transition and recognition for the need of reconstructing the chest wall with “neo-ribs” that is more akin to the anatomy and perhaps physiology of the native chest wall was recognized and presented by Dahan et al. *7+ They describe the technique of using Kirschners’s wires that are inserted into the cut rib ends as the framework for holding the silicon molds, into which the viscous methyl methacrylate is injected and allowed to harden, before the molds are eventually split and removed. Compared with the nonporous large plate of methyl methacrylate, this modification allows some tissue in-growth and better fluid drainage.
Development and Use of Titanium Prostheses Utilization of metal prostheses for chest wall reconstruction may have been reported as far back as 1909 by French surgeon Gangolphe for management of a large sternal notch enchondroma. [8] Titanium implants have been more widely used since the mid-1950s, with the eventual development of the Austin Moore and Thompson orthopedic prostheses. The strength, corrosion resistance and biocompatibility of titanium make it ideal for implants. However, problems with early prostheses fracture led to modification from using “pure” titanium to the stronger titanium alloys in these devices. The first alloy used for biomedical implants was Ti-6Al-4V containing 6% aluminium and 4% vanadium, which is the same material used for construction of the NASA Space Shuttles. Unfortunately, it was found that the vanadium from Ti-6Al-4V prostheses slowly seeped out and became toxic to humans. Hence the titanium alloy Ti-6Al-7Nb containing 6% aluminium and 7% niobium became the standard for prostheses, which is the same stronger alloy currently used in hip implants of today, as well as in some of the titanium rib prostheses system, such as the DePuy Synthes
MatrixRibs.
There are numerous materials and rib prostheses systems that exist. Perhaps one of the oldest dedicated system is the Borrelly steel staple-splints system (Medicalex, Bagneux, France) which was popularized in the 1990s. The currently most favored prostheses are the STRATOS™ system and MatrixRIB Precontoured Plate system. *4,9+ The STRATOS™ titanium system may be considered an evolution of the Borrelly system by working through a similar mechanism of securing to the rib ends using clips that resemble claws at the two ends of the bar. On the other hand, the MatrixRIB Precontoured Plate system is secured by fastening the plate to the rib with locking-screws through predrilled holes. In general, most thoracic surgeons are less familiar with bone drilling and use of plates and screws than colleagues in other surgical specialties. Therefore, it is even more important to gain
knowledge of certain tips and tricks to avoid some of the pitfalls during implantation of the MatrixRIB Precontoured Plate system.
Considerations during MatrixRIB Plate Implantation Achieving good pneumostasis and hemostasis is important, as returning to the pleural space will often mean having to take down the chest wall reconstruction. A generous size chest tube should be placed through a separate port incision towards the apex. The neo-pleura is reconstructed with either doubled up polypropylene mesh or Gortex
mesh based on surgeon preference. In certain cases, the defect may
be so large that several pieces of Gortex
mesh are required, and a rapid and secure method to unite
the pieces is by utilizing the Covidien TATM 90mm stapler. [9] The mesh should be trimmed to 2cm larger than the defect in all directions to allow some “give” avoiding too much tension, while maintaining the general conformation. Interrupted horizontal mattress Ethibond 2/O sutures are placed circumferentially 3 cm apart on the mesh and then sutured to the chest wall fascia internally. Such suture distribution should provide good security and may reduce interstitial fluid accumulating in the chest wall and seroma formation by allowing drainage into the pleural space. Our practice of placing the mesh deep to the artificial ribs prevents lung herniation between implanted plates. Prior to tying all the sutures and “closing off” the pleural space with the mesh, the lung should be reexpanded under direct vision with resumption of two lung ventilation.
In considering the rib implantation, preoperative planning is paramount. Imaging should be carefully studied and the size of the post-resection defect estimated. It is noteworthy that there is limitation to the length of the artificial ribs, with the longest MatrixRib being an 18-hole plate, which given that there
should be at least two screws for securing the plate onto the rib at both ends, provides a maximum breachable rib-rib defect of 14cm. If the defect is slightly too wide for even the longest plate, a trick is to push the rib ends closer together to narrow the gap before fixation of the plate. [10] Through a drill guide, 2 holes are created at each end and locking screws firmly secure the plate to the resected rib ends. Redivac drain should be placed superficial to the mesh, with soft tissue covering applied over. It is noteworthy that these techniques are not just applicable for repair of the chest wall but is also applicable for total sternal reconstructions. [Figure 1]
Prosthetic Ribs: The Beauty and The Beast The beauty of the prosthetic rib systems is their ease of implantation and their relatively trouble free follow up. However, the surgeon should be aware of certain rare complications. Recently, there have been reports of STRATOS™ system bar fracture following chest wall reconstruction and pectus excavatum repair, [3,11] which can be between 0-11% in some series [4,5]. In addition, fracture failure of the MatrixRIB Precontour Plate system have also been reported, [12, 13] some with an accountable cause such as following an impact to the chest wall directly over the prostheses. [12] [Figure 2]
Despite the strength of modern day titanium alloy, studies have shown that repeated stress to the metal can initiate and propagate microcracks, which in the presence of fine precipitations within the metal, can eventually lead to full blown fracture failure. Therefore, fracture failure can and do still occur, although very rarely. Interestingly, the STRATOS™ system uses “pure” titanium which has less strength compared with the titanium alloys used in other modern surgical implantable prostheses. This may
partly explain the higher frequency of reports on fracture failure of the STRATOS™ system. *3,11+ One of the main reason for choosing ‘pure” titanium as the material for the STRATOS™ system is so that the metal is pliable enough for crimping of the clips by pliers at the bar ends, to secure the bar to the rib ends. In contrast, the plate and screw design of the MatrixRIB Precontour system allows the stronger titanium alloy Ti-6Al-7Nb to be used for its bars. Another possible reason for the STRATOS™ system potentially being more prone to fracture is that along the STRATOS™ bar are areas of narrower profile as well as more acute angulation that may be subjected to higher stresses, contributing to metal fatigue and fracture failure. [3,5,11,13] In contrast, the smooth contour of the MatrixRIB plate should prevent areas of focused high stress from developing, therefore reducing risk of stress fracture. Nevertheless, rare cases of fracture failure can still occur in MatrixRIB Precontour Plates when subjected to repeated stresses and excessive external forces, [12,13] and patients should be warned of this possibility during consent. Furthermore, most of the failures tend to occur in anterior chest wall implants probably because of the larger chest movement during respiration and repeated stress, and those failure usually happen early, within 14 months following the implant. [13] Surgical removal is often required following implant fracture failure because of discomfort and pain, and risk of implant migration injury. [4,12,13]
Another complication we have witnessed is prosthesis screw loosening, which is actually rarely reported in implanted prosthetic rib devices. [Figure 3] Although elderly patients with osteoporotic ribs may be more at risk, technical failure is usually the cause, and in the MatrixRIB system certain technical pitfalls can contribute to the development of such complication. The first reason concerns mismatch between screw length and measured rib thickness. The measurement of rib thickness by the system’s parallel gauge records the thickest aspect of the rib. The surgeon must ensure that the drilling, plates and screws are placed over this thickest aspect of the rib to correspond to the measured screw length to
prevent screw protrusion and loosening. [9] Secondly, to avoid screw back-out or loosening, special care should be taken during drilling to avoid “double-tap” (re-drilling the same hole) which can destroy the bone threads that lock the screw securely in place. Furthermore, to improve plate security and if the length of the plate allows, the screws should be placed into the last and third from last holes of each plate end.
A Look into the Future Although reconstruction of the chest wall with prostheses implantation is desirable and in some cases essential during chest wall surgery, unfortunately many of the cons of using such devices stem from its rigidness, uncompromising or inappropriate conformation, and also the persistent nature of the material as an indefinite foreign body. Despite the recent advances in variable angle titanium prosthetic bar design to try to accommodate different chest wall defect configurations, the prostheses are still far from ideal. [14] There have also been some successes in the use of bioabsorbable materials for reconstructing the chest wall, which is particularly important in the growing pediatric population. [15,16] In the coming years, chest wall prostheses will evolve to become more personalized, with shape and size that will exactly fit each individual patient. Preoperative computed tomography (CT) with reconstructed 3D images may be used as reference for manufacturers to customize more unusual implant configurations. [17] The rapid development in 3D printing technology may allow customized prostheses from resins, polymers, metals and degradable biomaterials to be made quickly and accurately. Not only that, the 3D printed construct may utilized a combination of materials, some that biodegrade while other parts of the prostheses may have properties that are more rigid and permanent to optimize
prostheses characteristics for that particular reconstruction. Even more exciting is the prospect of 3D printing bio-scaffolds that allow patient’s own cells to colonize and grow into. *18+ Clearly, these developments will be a huge advantage in terms of having a prostheses that fits the patient’s habitus and disease. However, often the true post-resection cavity size and shape is difficult to predict, and the measurement of chest wall defect is only known “on-table” intraoperatively. Hybrid operating room real-time cone beam CT is increasingly being use in thoracic surgery to guide and improve accuracy of procedures. [19] Perhaps not in the too distant future, we shall see the use of such facility to provide image of the post-resection chest wall defect, followed by 3D image reconstruction and immediate transfer of data for 3D printing of the chest wall prostheses within the operating theatre. By the time the mesh reconstruction of the chest wall is completed, the 3D printed prostheses will be ready to provide the ultimate in prostheses customization. (Figure 4) It is indeed exciting times for chest wall reconstruction as the marriage of innovative surgical technique, state of the art real-time imaging, and advances in technology and biomaterials will allow a highly personalized surgical treatment for each individual. As Eleanor Roosevelt (First Lady of the United States, 1933-1945) once said “The future belongs to those who believe in the beauty of their dreams.” For us, there is no need to dream. The technology described is available. It is simply a matter of ceasing this opportunity for our patients.
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Legend
Figure 1. Reconstruction of whole manubrium and sternum with MatrixRIB plates following excision of post-irradiation chest wall sarcoma. An anterior lateral thigh flap was used for soft tissue coverage.
Figure 2. Chest radiograph showing a fractured MatrixRIB plate following direct chest wall impact from sports.
Figure 3. Chest radiograph showing one of the screws from MatrixRIB plate has loosened and sunk to the bottom of the left post-pneumonectomy fluid filled pleural cavity.
Figure 4. The future of customized chest wall prostheses starting with chest wall resection, intraoperative real-time cone beam CT of the defect in hybrid operating room, immediate intra-operative 3D printing of the prostheses, and implantation into the patient.