Ann Thorac Surg 2008;86:1905-1908. doi:10.1016/j.athoracsur.2008.08.059
© 2008 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Usefulness of Osteosynthesis Device Made of Hydroxyapatite-Poly-L-Lactide Composites in Port-Access Cardiac Surgery
Tsutomu Ito, MD*,
Mikihiko Kudo, MD,
Ryohei Yozu, MD
Department of Surgery, School of Medicine, Keio University, Tokyo, Japan
Accepted for publication August 25, 2008.
* Address correspondence to Dr Ito, Department of Cardiovascular Surgery, Saiseikai Yokohamashi Tobu Hospital, 3-6-1 Shimosueyoshi, Tsurumi-ku, Yokohama-City, Kanagawa, 230-0012, Japan (Email: t_ito{at}tobu.saiseikai.or.jp).
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Abstract
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Background: Port-access minimally invasive cardiac surgery has been developed with the aim of reducing surgical invasion. We conduct port-access cardiac surgery, generally through an intercostal space. To ensure sufficient visual field, either the upper or lower rib may be divided. In the process of restoration of divided ribs, we have developed a bone fixation technique using a new osteosynthesis device by way of prevention of pseudoarthrosis.
Methods: Forty-five consecutive patients underwent right-sided anterior intercostal thoracotomy under the port-access method between July 2006 and July 2007. We used a totally resorbable osteosynthesis device (Super Fixsorb; Takiron Co., Ltd., Osaka, Japan) consisting of a mix of poly-L-lactide (PLLA) and particulate resorbable uncalcined hydroxyapatite (u-HA).
Results: Fixation of the rib-costal cartilage was sufficiently achieved in this manner. No clinical symptoms suggestive of inflammation or infection were identified in the areas corresponding to the site of bone junction, and no patients have suffered pseudoarthrosis perioperatively and up to one year after surgery. Computed tomographic (CT) scanning clearly visualized these devices, and their attachment to the rib surfaces was confirmed in the patient who underwent CT scanning after the longest tested interval of 133 days after surgery.
Conclusions: In this study, the possibility was suggested that the advantages of u-HA/PLLA composite, such as early osteoconductive property and bioactive property, might beneficially affect bone fusion. We conclude that this osteosynthesis device can be applied in various fields, including cardiovascular surgery, and that its use will contribute to improvement of patients' postoperative quality of life.
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Introduction
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Minimally invasive cardiac surgery (MICS) procedures are becoming increasingly established in the field of cardiovascular surgery [1, 2]. With the aim of further reducing surgical invasion, port-access MICS has been developed as a procedure that requires no sternotomy and enables intracardiac operation, generally through an intercostal space [3–5]. We have conducted port-access cardiac surgery since 1997. The fourth right intercostal small thoracotomy is normally used to approach the thoracic cavity; however, to ensure sufficient visual field, if it is limited, either the upper or lower rib may be divided near the costal cartilage. In the process of restoration of divided ribs-costal cartilage before closure of the chest, we formerly used resorbable sutures, including coated Vicryl (Ethicon, Inc., Piscataway, NJ), for suturing and fixation. This treatment occasionally resulted in the development of pseudoarthrosis. Among 220 patients assessed since 1997, pseudoarthrosis occurred in 3 patients (1.4%) and protrusion of rib fixation in 3 patients (1.4%). Besides the cosmetic issue, the pain issue is thought to be the most serious problem as a consequence of pseudoarthrosis. In light of the risk that the rapid fixation of ribs-costal cartilage might not be sufficiently achieved by fixation with sutures only, we have developed a bone fixation technique using a new osteosynthesis device.
The properties of this new osteosynthesis device (Super Fixsorb MX40; Takiron Co. Ltd., Osaka, Japan) can be summarized as follows [6–10]. (1) Its mechanical strength has been increased to a level that closely approximates the strength of the cortical bones of the living body, and its rigidity (elastic modulus) is particularly high. (2) Its decline in strength, until the 12th week after its placement in the living body, is slow. (3) Its osteoconductive property and bioactive property of fusing directly with bone have contributed to improvement of its early fixation ability. (4) It is degraded and resorbed in a uniform manner and rarely induces strong tissue reactions that result from rapid degradation. (5) It is radiopaque and the device can be observed after surgery. We report our experiences of the clinical application of this osteosynthesis device in port-access cardiac surgery.
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Patients and Methods
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Materials
The bone cement used was Super Fixorb MX40 Mesh-Type Plate (Takiron Co. Ltd.) (referred to as mesh plate). This mesh plate is a totally resorbable osteosynthesis device consisting of a mix of poly-L-lactide (PLLA) and particulate resorbable uncalcined hydroxyapatite (u-HA; weight percentage 40%), strengthened using a unique compression forging method (u-HA/PLLA composite). The mesh plate is 50 mm in length and width, and 0.7 mm in thickness (Fig 1). The size of the mesh plate was adjusted to match its application site.
Patients
The subjects were 45 consecutive patients at our institution who underwent right-sided anterior intercostal small thoracotomy, regular-approach port-access MICS, and costotomy at the costal cartilage to ensure sufficient visual field, between July 2006 and July 2007. They suffered the following diseases: atrial septal defect (n = 18), mitral insufficiency (n = 24), mitral stenosis (n = 2), and left atrial myxoma (n = 1). This study was approved by the Institutional Review Board, and the Board waived the need for patient consent.
Operative Procedure
Employing the previously reported procedure [4, 5], we conducted cardiac surgery using the port-access method. Generally, an approximately 5-cm skin incision is made immediately above the fourth right intercostal space. In female patients who wish to avoid visible surgical scars, the lower margin of the right breast is selected as the incision line and the right mammary tissues are displaced upward to permit fourth intercostal thoracotomy to be performed. The thoracic cavity can then be entered through the fourth intercostal space. In this process, the upper or lower rib may be divided near the costal cartilage to facilitate intracardiac operation if the visual field is narrow.
When all the surgical procedures are complete, the mesh plate is trimmed down to the width of the rib before closure of the chest. To restore the divided rib-costal cartilage, we bring the two ends together and secure them with the mesh plates. In this process, the finished condition is designed such that the junction of the two ends is held between the upper and lower mesh plates. An Ethiguard needle (36 mm to 40 mm; Ethicon Inc) and Coated Vicryl (suture gauge: 1-0, suture length 75 cm to 90 cm; Ethicon Inc) for fixation, which is passed through a hole in the mesh plate, is inserted directly into the rib or costal cartilage. Again, the needle is passed through a hole in the mesh plate on the opposite side. This procedure is repeated to make two parallel end-to-end sutures for fixation. The remaining suture is then wound twice around the rib fixed with the mesh plates for ligation and fixation. Tight contact between the mesh plates and the bone can thus be achieved. On confirmation of sufficient fixation of the rib-costal cartilage, the chest is closed using the conventional technique (Fig 2).
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Fig 2. The rib was held between the upper and lower mesh plates and Vicryl was used for ligation and fixation.
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Evaluation Items
In the present study, we examined the following items from the clinical aspect to evaluate the efficacy and safety of the osteosynthesis device: (1) fixedness during surgery, condition of reduction after surgery; (2) X-ray findings, especially the condition of the mesh plate, as visualized by computed tomographic (CT) scan; and (3) postoperative local symptoms, blood biochemical findings, and adverse reactions.
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Results
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Fixedness During Surgery, Condition of Reduction After Surgery
The junction of the two ends was held between the upper and lower mesh plates and two parallel sutures were made with Vicryl to ensure suture and fixation. Although this technique rarely allows upward-downward displacement, the remaining suture was wound twice around the rib fixed with the mesh plates to guarantee ligation and fixation. In this manner, fixation of the rib-costal cartilage was sufficiently achieved to the extent that it could be confirmed by manipulation. Tight contact between the mesh plate and the bone was also confirmed. The intercostal space was brought together before closure of the chest. Addition of this treatment, however, caused neither displacement of fixed mesh plates nor displacement of any fixed rib-costal cartilage. In the present study, no patients have as yet suffered pseudoarthrosis or any neurovascular complications related to the intercostal bundle being looped in the repair during the postoperative follow-up period.
X-ray Findings, Especially the Condition of the Mesh Plate as Visualized by CT Scanning
In this study, postoperative CT scanning was conducted in the following five patients: a 75-year-old female (eighth day after surgery), a 57-year-old female (ninth day after surgery; Fig 3A; B), a 42-year-old male (67th day after surgery), a 60-year-old male (79th day after surgery), and a 51-year-old male (133rd day after surgery; Fig 3C). The CT scanning clearly visualized the mesh plates, and their attachment to the rib surfaces was confirmed in the patient who underwent CT scanning after the longest tested interval of 133 days after surgery. In all these 5 patients, the ribs were tightly held between the mesh plates and no displacement was detected. This fixation technique thus appears to ensure stability.
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Fig 3. Postoperative computed tomographic scanning. (A) A 57-year-old female (ninth day after surgery). (B) Same as (A) (part). (C) A 51-year old male (133rd day after surgery).
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Postoperative Local Symptoms and Blood Biochemical Findings
No clinical symptoms suggestive of inflammation-infection (such as reddening, swelling, heat sensation or tenderness) were identified in the areas corresponding to the site of bone junction during the postoperative follow-up period. No abnormally high values suggestive of inflammatory reactions were seen in the biochemical examinations of blood, in any of the patients, perioperatively and up to one year after surgery.
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Comment
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Growing interest is being shown in resorbable materials that are absorbed into the living body and replaced by tissues, and the development of such materials as osteosynthesis devices is increasingly being promoted. They have been clinically applied in the fields of orthopedic surgery, dentistry and oral surgery, and plastic surgery [6–8]. Researchers, however, have pointed out the following disadvantages of PLLA osteosynthesis devices: (1) Because of its lower dynamic strength and lack of ability to fuse with the bone, its rapid fixation power is limited; (2) its resorption and replacement require a long period of time; and (3) its radiolucent property impedes perioperative control and evaluation of postoperative progress. Efforts were made to overcome these disadvantages, and eventually u-HA/PLLA composite material was developed by adding particulate resorbable uncalcined hydroxyapatite (u-HA) to PLLA.
We used super Fixorb MX40 mesh-type plate (Takiron Co. Ltd.) in the present study. This mesh plate is a totally resorbable osteosynthesis device consisting of a mix of PLLA and u-HA (weight percentage 40%), strengthened using a unique compression forging method. The plate-type device is 0.7 mm in thickness and its size and shape can be adjusted to match the application site. Use of a couper scissors facilitates determination of its design. Use of screws is recommended to secure the mesh plate to the bone. In the present study, however, we did not adopt the technique of screw fixation because we used the mesh plate to achieve fusion between the ends of the divided ribs, especially divided costal cartilage. Instead, we fixed the mesh plate with Vicryl. We considered that early adhesion between the mesh plate and the rib was important to be able to confirm, in the clinical setting, the advantages of the u-HA/PLLA composite (such as its osteoconductive property) and bioactive property to fuse directly with the bone. Therefore, special efforts were made to achieve fixation of the mesh plate and the rib-costal cartilage and their tight contact by using Vicryl. The mesh-type plate facilitated passing of the needle and Vicryl for fixation through its holes.
In animal experiments, direct fusion between u-HA/PLLA composite and a bone was confirmed by the fourth week postoperatively [11]. Vicryl itself is a synthetic resorbable suture. In the living body, its tensile strength decreases with the elapse of time. According to the in vivo data, the percentage of retained tensile strength is about 75% after two weeks, about 50% after three weeks, and about 25% after four weeks. Its resorption period ranges from about 56 to 70 days. We expected that adhesion between u-HA /PLLA composite and the bone surface could be achieved while the tensile strength of Vicryl was retained in the living body. In this study, we evaluated the findings of remote CT scanning and confirmed the maintenance of adhesion between the mesh plate and the bone. Accordingly, the possibility was suggested that the advantages of u-HA/PLLA composite, such as early osteoconductive property and bioactive property, might beneficially affect bone fusion. It is often difficult to achieve rapid adhesion between the ends of divided rib-costal cartilage. In this case, use of Super Fixorb MX proved advantageous due to its potentially high affinity with bone and its ability to fuse directly with bone.
In this series, we found no neurovascular complications related to the intercostals bundle being looped in the repair, and no adverse reactions (such as reddening, swelling, sensation of heat or tenderness) suggestive of inflammation-infection. No patients suffered pseudoarthrosis during the postoperative follow-up period. Because Super Fixorb MX40 is radiopaque, it can be clearly visualized by CT scan. Treatment with Super Fixorb MX40 was a technique that can be appropriately monitored by remote observation. The postoperative observation period was longest, at 133 days, in this study. During this period, no degradation-resorption was seen in CT scans and no development of delayed inflammation was reported. Shikinami and colleagues [12] confirmed some plate type devices were impalpable and buried in 4 to 5 years after implantation in their clinical experience. Our results show that the mesh plate, acting as external fixation, was extremely useful in fusing the ends of divided rib-costal cartilage; a longer observation period will be needed to fully confirm its degradation-resorption process. In March 2007, Takiron Co Ltd acquired 510(k) approval from the US Food and Drug Administration for a new generation bone-bonding material (foreign trade name: OSTEOTRANS MX; Japanese trade name: SUPER FIXSORB MX) in the cranial and maxillofacial regions. The scope of approval in the U.S. is for the maxillofacial surgery, not for orthopedic surgery and rib fixation. This study is a single institutional clinical review in a midterm postoperative observation time. Further long-term observation studies and additional data in animal experimental model are required.
In the future, the mesh plate technique has potential for more extensive application in the field of cardiovascular surgery and in the process of special sternal closure in the clinical setting. We conducted partial sternotomy (standard MICS: ministernotomy with upper full-transverse division technique, T-shaped sternotomy) to replace the aortic valve in a 56-year-old male patient. In this case, the mesh plate was used to achieve sternal fixation (Fig 4). The plate was placed over the T-shaped division of the sternal bone and the surrounding area. This treatment proved to be effective in stabilizing the sternal bone after surgery. In elderly patients, sternal fractures may be found during surgery. In the light of this possibility, we consider it possible for the mesh plate to be used for reinforcement-restoration and fixation of the sternal bone. We conclude that this osteosynthesis device can be applied in various fields, including cardiovascular surgery, and that its use will contribute to improvement of patients' postoperative quality of life.
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Fig 4. The mesh plate was used to close the divided sternal bone after partial sternotomy (T-shaped sternotomy) in this patient.
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References
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- Cosgrove III DM, Sabik JF. Minimally invasive approach for aortic valve operation Ann Thorac Surg 1996;62:596-597.[Abstract/Free Full Text]
- Gundry SR, Shattuck OH, Razzouk AJ, et al. Facile minimally invasive cardiac surgery via mini-sternotomy Ann Thorac Surg 1998;65:1100-1104.[Abstract/Free Full Text]
- Chitwood Jr WR, Elbeery JR, Moran JF. Minimally invasive mitral valve repair using transthoracic occlusion Ann Thorac Surg 1997;63:1477-1479.[Abstract/Free Full Text]
- Yozu R, Shin H, Maehara T, Iino Y, Mitsumaru A, Kawada S. Port-access cardiac surgery: experience with 34 cases at Keio University Hospital Jap J Thorac Cardiovasc Surg 2001;49:360-364.[Medline]
- Yozu R, Shin H, Maehara T. Minimally invasive cardiac surgery by the port-access method Artif Organs 2002;26:430-437.[Medline]
- Shikinami Y. Characteristics and application of poly-L-lactide as biomaterials Rheumatology 1999;21:267-278.
- Kikuchi N, Noguchi M, Yuzuriha S, et al. Clinical use of bioabsorbable devices made from composites of hydroxyapatite (HA) particles and poly-L-lactide (PLLA) J Jap Plast Reconstr Surg 2002;22:375-382.
- Matsusue Y, Niibayashi H, Aoki Y. Bone fusion using HA/PLLA composite, a material characterized by its excellent resorbability in the living body J Orthop Surg (Hong Kong) 1999;50:1405-1411.
- Shikinami Y, Okuno M. Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-L-lactide (PLLA): Part I. Basic characteristics. Biomaterials 1999;20:859-877.[Medline]
- Shikinami Y, Okuno M. Bioresorbable devices made of forged composites of hydroxyapatite (HA) particles and poly-L-lactide (PLLA): Part II. Practical properties of miniscrews and miniplates. Biomaterials 2001;22:3197-3211.[Medline]
- Yasunaga T, Matsusue Y, Furukawa T, et al. Bonding behavior of ultrahigh strength unsintered hydroxyapatite particles/poly (L-lactide) composites to surface of tibial cortex in rabbits J Biomed Mater Res 1999;47:412-419.[Medline]
- Shikinami Y, Matsusue Y, Nakamura T. The complete process of bioresorption and bone replacement using devices made of forged composites of raw hydroxyapatite particles/poly L-lactide (F-u-HA/PLLA) Biomaterials 2005;26:5542-5551.[Medline]
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Abstract
Introduction
