Eur J Cardiothorac Surg 2008;34:510-513. doi:10.1016/j.ejcts.2008.05.019
Copyright © 2008, European Association for Cardio-thoracic Surgery. Published by Elsevier. All rights reserved.
Clinical application of costal coaptation pins made of hydroxyapatite and poly-L-lactide composite for posterolateral thoracotomy
Riken Kawachi,
Shun-ichi Watanabe,
Kenji Suzuki,
Hisao Asamura*
Thoracic Surgery Division, National Cancer Center Hospital, 1-1 Tsukiji 5-chome, Chuo-ku, Tokyo 104-0045, Japan
Received 22 November 2007;
received in revised form 7 May 2008;
accepted 19 May 2008.
* Corresponding author. Address: Thoracic Surgery Division, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. Tel.: +81 3 3542 2511; fax: +81 3 3542 3815. (Email: hasamura{at}ncc.go.jp).
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Abstract
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Background: Costal coaptation pins made of hydroxyapatite and poly-L-lactide (HA/PLLA) composite are used to prevent slippage of the connected ribs in posterolateral thoracotomy. The objective of this study was to evaluate rib fixation achieved by HA/PLLA costal coaptation pins. Methods: Between September 2005 and January 2006, HA/PLLA costal coaptation pins were used in 106 consecutive patients who underwent posterolateral thoracotomy at the National Cancer Center Hospital, Tokyo, Japan. Among these, 96 patients who were followed for one year were analyzed. Fixation was assessed on chest X-ray at one week, two months, and one year after surgery, and classified into four types: no displacement, vertical displacement, lateral displacement, and combined vertical with lateral displacement. Results: The incidence of displacement at one week, two months, and one year after surgery was 22%, 19%, and 31%, respectively. No severe adverse events leading to the removal of HA/PLLA pins occurred. At one year, the most frequent type of displacement was vertical displacement (15%), which reflected a delay in bone formation. The use of analgesics among patients with different types of displacement was not significantly different (p
= 0.97). Conclusions: Based on the results of this study, the fixation of cut ribs with HA/PLLA costal coaptation pins may be less advantageous in posterolateral thoracotomy, as displacement and delay of bone formation appear to occur frequently.
Key Words: Chest wall • Lung cancer • Pain • Tissue engineering • Thoracotomy
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1. Introduction
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A fixation device made of hydroxyapatite and poly-L-lactide (HA/PLLA) composite is a newly developed modality that is being increasingly used in thoracic surgery. Costal coaptation pins made of HA/PLLA are absorbable, easy to handle, and safe to use. Costal coaptation pins are used for rib fixation during posterolateral thoracotomy and to reposition multiple rib fractures [1–5]. There have been few reports on the use of HA/PLLA costal coaptation pins for thoracotomy, and in particular it has not been well documented whether such costal pins are beneficial for rib fixation. The objective of the present study was to evaluate post-thoracotomy rib displacement over time based on radiographic findings.
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2. Materials and methods
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2.1 Patients
Between September 2005 and January 2006, 135 lung resections were performed at the National Cancer Center Hospital, in Tokyo, Japan. Costal coaptation pins made of HA/PLLA composite were used in 106 consecutive patients who underwent posterolateral thoracotomy during the same period. Costal pins were not applied for the following reasons: wedge resection without rib resection in 12 patients, and complicated resection, such as chest wall resection, in 17 patients. The patient characteristics are shown in Table 1
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2.2 PLLA costal coaptation pins and the surgical procedure
Two sizes of HA/PLLA costal coaptation pins (SuperFIXSORB®: Ethicon Inc., Somerville, NJ) were used: 2 mm x 2 mm x 27 mm (thin) and 3 mm x 3 mm x 34 mm (thick) (Fig. 1
). During posterolateral thoracotomy, the ribs were usually cut at the costal angle. The caliber was measured by a calibrator, and the bone marrow space was dilated using a reamer, if necessary. Small holes were made on both sides of the cut ribs using a drill. An absorbable suture was threaded through the rib holes, and the pins were inserted into the bone marrow of the cut rib. The cut ribs were connected and ligated (Fig. 2
).
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Fig. 1. Costal coaptation pins were used to close the posterolateral thoracotomy. The pin sizes were 2 mm x 2 mm x 27 mm (thin) and 3 mm x 3 mm x 34 mm (thick).
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Fig. 2. A hand-drill was used to make holes on both sides of the cut rib (a). The caliber was measured by a calibrator, and a reamer was used to dilate the bone marrow space (b). Costal coaptation pins were inserted into the bone marrow (c). The ribs were ligated with absorbable sutures, and connected (d).
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2.3 Radiographic evaluation
Chest X-rays (posteroanterior view) were obtained at one week, two months, and one year after surgery. Based on the degree of fixation, the patients were classified into four groups: no displacement, vertical displacement, lateral displacement, and combined vertical with lateral displacement (Fig. 3
). Displacement was defined as being vertical when the shift was more than one third of a rib's width, and as being lateral when the shift was 
5 mm.
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Fig. 3. The degree of fixation was categorized as no displacement, vertical displacement, lateral displacement, or combined vertical with lateral displacement.
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2.4 Statistical analysis
Statistical analyses were performed using SPSS software, version 13.0J (SPSS Inc., Chicago, IL). The chi-square test and Mann–Whitney's U-test were used to determine the relationship between rib displacement and clinical factors. A p-value 
0.05 was considered significant.
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3. Results
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3.1 Clinical findings
Of the 106 patients, 93 were followed for one year. In 13 patients, the follow-up was not complete: 9 patients had recurrence or died, and 4 patients were followed only with computed tomography. Displacement according to the clinical and surgical factors of the 106 patients who were followed for one year is shown in Table 2
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3.2 Radiographic findings of displacement
The radiographic findings according to the type of displacement are shown in Table 3
. The characteristic features were the incidence of displacement and the variation of displacement over time. Displacement occurred in 20 patients (22%) at one week, 18 patients (19%) at two months, and 29 patients (31%) at one year after surgery. Vertical displacement was more common during the early period after surgery, and lateral displacement was more frequent one year after surgery. Of the 73 patients who did not have displacement one week after surgery, 24 developed some displacement during follow-up; in 15 (63%), displacement was noted between one week and two months. In contrast, displacement improved in 12 patients between one week and two months.
One year after surgery, 12 patients had lateral displacement; in these patients, the chest X-ray showed a lucent zone at the connection of the ribs. In patients who had lateral displacement, computed tomography showed that the ribs were completely separated, and no bone tissue was observed (Fig. 4
).
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Fig. 4. The arrow shows the rib connection. The edge of the cut rib is clubbed, and the pin is not covered with bone tissue; a bare costal coaptation pin is present.
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3.3 Clinical findings and displacement
With respect to the results associated with different surgical procedures, 29 patients with rib displacement (32%) had lobectomy or pneumonectomy, and 1 patient had a limited resection (14%); the difference in rib displacement between surgical procedures was not significant (p
= 0.56).
The effect of rib displacement on pain was assessed. Surgical wounds, which included the rib connection, were considered painful when oral analgesics were required two months after surgery. Nineteen patients were prescribed oral analgesics two months after surgery. Of these 19 patients, 13 had no displacement (20%), and 6 had displacement (21%); 2 patients had vertical displacement, 3 had lateral displacement, and 1 had the combined type. Thus, there was no significant difference in analgesic use among the groups (p
= 0.97). Moreover, complications (parenchymal lung injury and sputum retention with atelectasis) which induced excessive cough and subsequent costal dislocation were not seen in our series.
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4. Comment
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Absorbable fixation devices made of hydroxyapatite and poly-L-lactide (HA/PLLA) composite are increasingly being used in orthopedic surgery for procedures such as fractured bone fixation and bone grafting. In thoracic surgery, costal pins are used for fixation of the sternum and ribs in procedures for chest deformity, chest trauma, and thoracotomy. However, only a few reports have dealt with the use of costal coaptation pins [1–6]. The trend in thoracic surgery is toward a minimally invasive approach, and rib separation is not routinely performed, even in posterolateral thoracotomy in the present series, despite its widespread indication for intrathoracic diseases. When ribs are separated in thoracotomy, the need for rib coaptation has been controversial among thoracic surgeons, and the advantages of rib coaptation have not yet been defined [1,2]. The efficacy of coaptation pins has also not been adequately described. The present study focused on the use of HA/PLLA pins for the closure of posterolateral thoracotomy with regard to the incidence of displacement after surgery at the immediate, intermediate, and late postoperative periods.
The most remarkable finding of the present study was the high incidence of costal displacement even at the immediate postoperative period (one week after surgery) as high as 21%. Throughout the observation period, the incidence continued to be higher than 20%. In the literature, the incidence of displacement has been reported to be 2% by Tatsumi et al. and 1.3% by Tsunezuka et al. [1,2]. These reports concluded that PLLA costal coaptation pins were effective for the fixation of separated rib. Thus, there are large differences in the incidence of displacement between our study and these previous studies. The timing and method of postoperative evaluation might account for these differences. In the two previous studies, the timing of roentgenological evaluation varied, and chest CT was mainly used to evaluate displacement. For example, in Tatsumi's report, evaluation was performed with chest CT at 1–58 months after surgery [1]. The status of costal adaptation might be greatly influenced by the time after surgery, and the study should have incorporated a uniform timing for evaluation. Furthermore, the images on chest CT scan do not seem to be suitable for the evaluation of displacement in a vertical dimension. In fact, this method cannot detect displacement of less than 1 cm. Our strict criteria in the evaluation of displacement at scheduled time-points could have detected even small displacement which might have been overlooked in previous studies.
Another important observation was the increase in the incidence of displacement during the follow-up period. The incidence varied from 21% at the immediate point to 31% at the late point postoperatively. The 21% incidence at the immediate postoperative period clearly indicated that fixation is not enough to ensure stability of the ribs. The increase in displacement at the late period might be caused by a decrease in the tension of the suture materials (absorbable strings). With regards to the ligation technique, ligation was performed with a single suture in our series. If double ligation had been made for tightening the cut rib, the rate of displacement might have decreased in the early period. The cut ribs were too small and too thin for double ligation, especially in the Japanese female patients. Regardless of the cause, the increased incidence in the late period, when bone coaptation should have been achieved, is a substantial problem in practice.
In this study, the status of rib displacement was classified into four patterns according to the images on postoperative chest X-rays. The most common pattern of displacement was lateral displacement (15%), followed by vertical displacement (11%), and combined lateral and vertical displacement (5%) at one year after surgery. On the other hand, two other reports did not show any differences in the incidence of displacement according to patterns [1,2]. The chest CT images of cases with lateral displacement in this series showed the complete separation of both costal ends and their bony clubbing. These findings suggested that bone formation around the costal pins was impaired. The costal pins could induce the proliferation of connective tissue around the pins, as reported previously, which results in impaired bone formation due to a foreign body reaction [7,8].
In summary, ribs connected with costal coaptation pins appear to deviate in a high percentage of patients, although the effect of such displacement on pain is likely minimal and no adverse events, such as parenchymal lung injury requiring reoperation to remove the pins, were noted. Rib fixation with HA/PLLA costal pins may be considered to be less advantageous in posterolateral thoracotomy.
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References
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Abstract
1. Introduction
