Ann Thorac Surg 1999;67:765-768
© 1999 The Society of Thoracic Surgeons
Original Articles
Bioabsorbable poly-L-lactide costal coaptation pins and their clinical application in thoracotomy
Akitoshi Tatsumi, MDa,
Naoki Kanemitsu, MDa,
Tatsuo Nakamura, MDa,
Yasuhiko Shimizu, MDa
a Department of General Thoracic Surgery, Kochi Municipal Hospital, Kochi, Japan
Accepted for publication July 14, 1998.
Address reprint requests to Dr Tatsumi, Department of General Thoracic Surgery, Kochi Municipal Hospital, 1-7-45 Marunouchi, Kochi 780-0850, Japan
e-mail: akt{at}bronze.ocn.ne.jp
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Abstract
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Background. To gain a wider operation field, ribs often are fractured as the intercostal retractor is expanded. Thoracotomy through the periosteal bed and other procedures have been performed to prevent rib fractures, and rib resections occasionally have been required.
Methods. We designed a poly-L-lactide costal coaptation pin. We used this pin in 184 thoracotomies and carried out long-term observation after insertion to evaluate its clinical efficacy and safety. Postoperative observation periods ranged from 1 to 58 months (mean ± standard error, 21.6 ± 1.2 months). We evaluated the costal pin according to its degree of fixation, categorizing it as "good," "fair," or "poor" in this respect. We also judged its lateral shift.
Results. We judged fixation as "good" in 130 cases (70.7%), and found no lateral shift in 103 cases (56%). Our overall evaluation indicated satisfactory results in 172 cases (93.5%).
Conclusions. Rib fixation was secured in nearly all cases, and no side effects were encountered. We can confirm that the poly-L-lactide costal coaptation pin is a highly effective and safe device.
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Introduction
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Thoracotomy and incision closure are the basic surgical techniques used in the field of thoracic surgery. Most surgeons prefer to perform a posterolateral thoracotomy (termed a "standard" thoracotomy) through the intercostal space for pulmonary resection because it provides an excellent intraoperative view for hilum exposure. However, it often is associated with accidental rib fractures.
Since 1991, poly-L-lactide (P-L-LA) costal coaptation pins have been used at our center. Poly-L-lactide is degraded and absorbed through hydrolysis generated under humid conditions. This polymer material causes minimal tissue reaction and has clinical applications as a bioabsorbable suture that does not require removal or the use of fixation devices. We used P-L-LA costal coaptation pins in numerous thoracotomies and carried out long-term observation after insertion to determine their efficacy.
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Patients and methods
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Two types of P-L-LA costal coaptation pins manufactured by Gunze Ltd, (Kyoto, Japan) with dimensions of 3 x 3 x 27 mm and 3 x 4 x 27 mm (Fig 1), were used. The molecular weight of the P-L-LA was 2 x 105. The drawing of long-axis bearings gave the P-L-LA pins greatly increased elasticity and strength. Their bending strength was 18 to 22 kilogram-force per square millimeter and their bending elasticity was 550 kilogram-force per square millimeter, approaching the properties of human cortical bone. The P-L-LA costal coaptation pins retained 80% of their elasticity 2 months after insertion and approximately 50% after 4 months. Their tapered shape allowed for easy insertion into the rib marrow and helped prevent intercostal slippage and lateral shift from the flank trench process. They were sterilized with ethylene oxide gas.
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Fig 1. Two types of P-L-LA costal coaptation pins with dimensions of 3 x 3 x 27 mm and 3 x 4 x 27 mm were used.
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The current study was performed between March 1992 and December 1996 at the Department of General Thoracic Surgery, Kochi Municipal Hospital, Kochi, Japan. The characteristics of the study patients and the types of operations performed are outlined in Table 1.
The fifth or sixth rib usually was cut at the costal angle (Fig 2, top) and a thoracotomy was performed through the periosteal bed. In closure, pins were inserted into the bone marrow of the cut rib (Fig 2, center), and the rib was ligated with an absorbable (1-0 polyglactin) suture (Fig 2, bottom).
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Fig 2. The rib is cut at the costal angle (top) and a thoracotomy is performed. In closure, the coaptation pin is inserted into the bone marrow (center) and the rib is ligated with an absorbable suture (bottom).
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The costal pins were evaluated based on the degree of fixation resulting from distraction levels in the coapted ribs, the results of healing, and the occurrence of lucent zones and side effects. Fixation was categorized as "good" if no distraction occurred and fixation resulted in the coapted section, as "fair" if distraction of up to 4 mm occurred, and as "poor" if distraction of 5 mm or more occurred. In addition, three categories were used to judge lateral shift: "none" if no dislocation occurred, "slight" if dislocation of up to half of a rib’s width occurred, and "moderate" if displacement of more than half of a rib’s width occurred.
This study was approved by the Ethics Committee of the Kochi Municipal Hospital, and all patients gave their informed consent before operation.
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Results
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Radiologic and clinical findings
The outcomes of the 184 cases are outlined in Table 2. The postoperative observation period ranged from 1 to 58 months (mean ± standard error, 21.6 ± 1.2 months; median, 17.5 months). Computed tomographic scanning revealed no distraction (Fig 3). Fixaton was judged to be good in 130 cases, fair in 47 cases, and poor in 7 cases. Lateral shift was judged as none in 103 cases, slight in 74 cases, and moderate in 7 cases. Good fixation and no lateral shift were found in 82 cases (44.6%). Poor coaptation, with both poor fixation and moderate lateral shift, occurred in 2 cases (1.1%). There were no cases of lucent zones with delayed bone formation around the coaptation pins. Moreover, throughout the entire observation period, there were no side effects caused by the coaptation pins. The overall evaluation indicated satisfactory results in 172 cases (93.5%), with 12 cases of poor fixation or a moderate lateral shift.
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Fig 3. Ten months after operation, the rib showed no side displacement and was firmly fixed, and an anchoring callus was visible. Immature fiber bone was buried in the crevice at the edge of the fracture.
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Pathohistologic findings
A 47-year-old man showed steady improvement in the postoperative period. However, 10 months after operation, the right sixth rib showed "nail-headed" swelling in the coapted area (Fig 4, top). The fixation was judged to be fair. With the patient’s consent, a 4-cm section that included the coapted area of the rib was removed. Pathohistologic examination showed that a cartilage layer had formed on the exterior of the section, and the presence of bone tissue was confirmed. There were no signs of apparent inflammation, and no tumorous tissue or other foreign substances were encountered (Fig 4, bottom).
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Fig 4. "Nail-headed" swelling in the coapted area (top). On pathohistologic evaluation, fragments of material (arrow) remained in the central section of the rib and were surrounded by a fibrin-like substance (bottom). (Hematoxylin and eosin; original magnification x20 then 52.2% reduction.)
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Comment
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Thoracotomy through the periosteal bed and other procedures have been performed in an attempt to prevent rib fracture, and rib resection occasionally has been required. Most surgeons in the United States and western Europe commonly resect a 1-cm portion of the rib in the subperiosteal plane, and others do not reapproximate an incised rib.
We use a thoracotomy procedure in which the rib is cut at the costal angle in an attempt to obtain a wide operating view without rib removal. In addition, we use P-L-LA costal coaptation pins during closure of the incision because anatomic restoration of a severed rib is more desirable than removal of even a small portion of the rib. Patients with well-aligned ribs had less severe postoperative pain that resolved more quickly. Previously, nonabsorbable fixation materials such as metallic wire or ceramic pins were used for coaptation of rib fractures [1]. Although these materials provide sufficient strength, they can cause connective tissue coating around the pins. These areas are seen as lucent zones on roentgenograms when delayed bone formation occurs in the rib area. Nonabsorbent materials remain as foreign substances and can lead to lateral shift. Moreover, they produce artifacts on roentgenograms. Metal wire, ceramic pins, and similar materials also have been used for rib fixation in patients with chest injuries [1–3].
Polymeric biodegradable operative materials resulted from studies of polyglycolic acid fibers beginning in 1962. The conventional process of manufacture prevents sufficient mechanical strength for costal coaptation. Thus, axial drawing treatment was added to enhance the mechanical properties of the polymer to the level of human cortical bone [4]. In the case of biomedical polymers, hydrolysis is generated uniformly in vitro through humid conditions. Poly-L-lactide plate has been studied for biomedical application [5]. Pihlajamäki and colleagues [6] and other investigators [7–10] have reported on the clinical use of P-L-LA pins in the treatment of fractures and osteotomies. They identified the usefulness of the pins in the fixation of small fragments. In the field of general thoracic surgery, it has been reported that P-L-LA is effective when used as bioabsorbable struts for the treatment of chest deformities [11]. The drawn P-L-LA rods maintain a bending strength exceeding that of human cortical bone in the medullary canal for a period of 8 weeks [12]. After that, the P-L-LA is absorbed gradually in small fragments. It maintains the same initial strength as human cortical bone for a period of 12 weeks, providing sufficient time for complete rib adhesion [12]. In one case, the implanted pin was removed 10 months after insertion and many fragments still remained, as expected. It has been estimated that it takes more than 2 years for the fragments to disappear completely. This finding was consistent with our expectations.
In conclusion, clinical studies were undertaken on P-L-LA costal coaptation pins. They were easy to insert, secured rib fixation in nearly all cases, and produced no side effects. Clinical results and pathohistologic findings indicated that healing was satisfactory. We can confirm from our clinical studies that the P-L-LA costal coaptation pin is a highly effective device.
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Acknowledgments
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We would like to acknowledge that the fundamental research was performed at the Research Center for Biomedical Engineering in Kyoto University, Kyoto. We thank the staff of the Kyoto Research Institute and Gunze Ltd, especially Mr Takeshi Shimamoto and Mr Takashige Oka, for their technical assistance.
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References
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Abstract
Introduction
