Postoperative Infection Caused by a Resorbable Plate used to Treat a Zygomatic Fracture

Case Report

Postoperative Infection Caused by a Resorbable Plate used to Treat a Zygomatic Fracture

Sukegawa S^1*, Kanno T^1,2, Kawai H³, Shibata A¹, Sukegawa-Takahashi Y¹ and Furuki Y¹
¹Division of Oral and Maxillofacial Surgery, Kagawa Prefectural Central Hospital,Japan
²Department of Oral and Maxillofacial Surgery, Shimane University Faculty of Medicine, Japan
³Department of Oral Pathology and Medicine, Okayama University, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Japan

^*Corresponding author: Shintaro Sukegawa, Division of Oral and Maxillofacial Surgery, Kagawa Prefectural Central Hospital, 1-2-1, Asahi-cho, Takamatsu, Kagawa 760-8557, Japan

Published: 12 May, 2016
Cite this article as: Sukegawa S, Kanno T, Kawai H, Shibata A, Sukegawa-Takahashi Y, Furuki Y. Postoperative Infection Caused by a Resorbable Plate used to Treat a Zygomatic Fracture. Clin Surg. 2016; 1: 1002.

Abstract

A 58-year-old female patient was referred to our division of Oral and Maxillofacial Surgeryby a general dental practitioner with swelling symptoms in the left cheek. Five months earlier, she had fractured her left zygomatic bone, which was fixed using a resorbable plate. A maxillofacial computed tomographic scan taken upon the first visit showed a clear swelling of the soft tissue next to the left maxillary sinus and a maxillary sinusitis. In addition, the plate at the zygomaticomaxillary buttress showed bone resorption surrounding the plate and the screws, possibly because of an infection affecting the area around both the plate and the screws. These were removed, and their molecular weight and average molecular weight measured following extraction. These measurements showed that the plate and the screws had progressively degraded. All symptoms immediately diminished after the operation and no evidence of infection was observed after 3 months after the operation.
Keywords: Resorbable plate; Postoperative infection; Molecular weight

Introduction

Maxillofacial fractures are commonly fixed using titanium mini plates because they are strong, easy to handle, and are not prone to dimensional changes [1,2]. However, fracture fixation using titanium plates present some disadvantages, including potential difficulties associated with the subsequent removal surgery, facial growth [3,4], thermal sensitivity [5,6], and plate migration [7,8], ultimately leading to the development of resorbable bone fixation devices as a trend.
Bioresorbable plates are designed to be absorbed by the surrounding tissue through chemical interactions; therefore, negative foreign body reactions and infection throughout the resorption process are theoretically possible [5]. However, there are little complications involved and it is used by clinicians as a major device [9,10].
This report presents a case of infection, following zygomatic fracture fixation using a resorbable plate, suspected of being caused by the resorption process.

Presentation of Case

In June 2014, a 58-year-old female patient who did not present any note worthy past medical condition was referred to our division of Oral and Maxillofacial Surgery, Kagawa Prefectural Central Hospital, Takamatsu, Kagawa, Japan by a general dental practitioner because of swelling in the left cheek. Five months earlier, the patient underwent surgery to fit a Lactosorb^® 1.5 resorbable fixation system (Lorenz Surgical, Jacksonville, FL, USA) to fix a zygomatic bone fracture at another general hospital. The patient never suffered any discomfort or presented any problems in the operative site before the fracture. Osteosynthesis was achieved by a fixation technique using three points along to the orbital rim, the frontozygomatic suture, and the zygomaticomaxillary buttress. During her first visit to the general dental practitioner, an intraoral examination revealed the presence of pus, discharged from the gingivobuccal area (Figure 1). Furthermore, a probe showed that the bone could be easily reached. A maxillofacial computed tomographic scan taken during the first visit showed as welling of the soft tissue next to the left maxillary sinus and a maxillary sinusitis. In addition, the plate at the zygomaticomaxillary buttress showed bone resorption surrounding the plate and the screws (Figure 2).
These clinical symptoms did not improve after initial treatment with Clarithromycin for 2 weeks, followed by Cefcapenepivoxil hydrochloride hydrate for 2 weeks together with continuous local irrigation. Based on these symptoms the patient was diagnosed with an infection caused by the fitted resorbable plate and screw, and the full removal of biomaterials was recommended. The patient was operated to remove the plate and the screws under local anesthesia. The operation involved a vestibular incision on the left side of the mandible to locate and remove the free resorbed plate and the screws on the buttress. In addition, the operative team cleaned the area of bone resorption surrounding the bioresorbable plate and the maxillary sinus front wall for abscess formation of the maxillary sinus (Figure 3). During the operation, we took samples from the affected area; Streptococcus milits and anaerobic bacteria were cultured from these samples. The patient reported an immediate relief of the symptoms after the operation, and no evidence of infection was detected after 3months of follow-up.

Figure 1

Figure 1
(A) Frontal aspect at admission, showing the intact facial skeleton with enophthalmos of the left eye. (B) Coronal and (C) Sagittal computed tomography images showing a defect in the mid-left orbital floor, with herniation of the orbital contents into the underlying maxillary sinus.

Figure 2

Figure 2
A titanium mesh plate with high three-dimensional flexibility was designed to create a basic hexagonal polygon shape.

Figure 3

Figure 3
The implant was designed using a rapid prototype threedimensional model that mirrored the shape of the intact opposite orbit. It was designed to precisely cover the bony defect and support the orbital globe.

Figure 4

Figure 4
The preshaped titanium mesh plate was positioned to support the orbital globe in the left orbital floor. Because the implant conformed perfectly to the shape of the intact bone around the defect, positioning of the plate was easy.

Measurement of the Molecular Weight

To measure the molecular weight (Mw) of the extracted plate and screws, they were dissolved in tetrahydrofuran. Gel permeation chromatography using a TOSOH Build-up GPC system 8020 and a TOSOH Co, Japan) and a TSK-GELGMHHR-H (TOSOH Co, Japan) was used to estimate the molecular weight. This technique is able to separate polymers based on their size. Polystyrene (SM-105 by Showa Denko Co, Japan) was used for Mw calibration. For comparative purposes, the molecular weight of an intact Lactosorb^® plate and screws were also measured following the same protocol.
The average molecular weight (Mn) was calculated using the following equation:
Mn=Σ (Mi·Ni)/ΣNi
Where Mi represents the molecular weight and Ni the number of numerators of the polymer.
The weighted average molecular weight (Mw) was calculated using the following equation.
Mw=Σ (Mi2·Ni)/Σ(Mi·Ni)
The plate removed 5 months after the initial surgery showed an average molecular weight and a weighted average molecular weight of 2.28 × 10⁴ and 5.36 × 10⁴ , respectively. This represents a 53% decrease in Mn and a 54% decrease in Mw compared with an intact plate. Mn and Mw of the two screws removed were 2.01 × 10⁴ , and 2.19 × 10⁴, and 5.27 × 10⁴ , and 5.59 × 10⁴ , respectively. These values indicated that Mn decreased by 58% and 54% for the first and second screw, respectively, and Mw had decreased by 56% and 54% compared with intact screws (Table 1).

Table 1

Table 1
Diagnostic situations (staging or follow-up) and skeletal metastasis extent (EOD).

Discussion

Resorbable Osteosynthes is systems were well developed to replace titanium fixation systems in craniofacial, oral, maxillofacial, plastic, and reconstructive surgery [1,2]. The resorbable materials used are ideally able to meet the biomechanical demands and to provide enough initial strength; however, these materials are able to degrade in a predictable manner throughout the healing process, providing sufficient strength and biomechanical stability to ensure the full healing of the fractured section. This resorption process has the added advantage of eliminating the need to remove the plate or the screws because no deleterious bodily response is associated with the presence of these materials or the resorption process [11]. The resorbable materials are designed to undergo a biphasic degradation process, including an early degradation step via hydrolysis of ester bonds [9,12]. The resulting degradation products subsequently crystallize and undergo a secondary hydrolysis, which strongly determines the rate of degradation of the material [12]. Throughout this process, the molecular weight of the material progressively decreases to eventually disappear. This degradation process is associated with a decrease in polymer strength [11], a reduction in molecular weight, and strength and mass loss. The implants lose the clinical biomechanical properties long before the loss of a significant amount of mass. The final end products of this degradation process, CO₂ and H₂O, are ultimately metabolized by the liver [9]. In this case, a LactoSorb (Lorenz/Biomet Inc.) bioresorbable system was used, which was composed by a substantially amorphous linear copolymer and consisted of 82% PLLA and 18% PGA. This material is able to retain 70% of its initial strength for the first 6–8 weeks, and it has been reported to dissolve entirely within the first year [13]. In this case, the patient had healed well after 5 months, and the bioresorbable system appeared to be efficient as Osteosynthesis material. However, bone resorption was observed around the bioresorbable plate and the screws fitted to the zygomatic and the maxillary bones. Inflammation could be expected for those cases where the degradation rate is too high and debris particles are produced faster than the body can tolerate [14]. The strong inflammatory reaction in the implantation site observed in this case was possibly caused by an increase in degradation products. This degradation probably caused the disintegration of the implanted materials, leading to the infiltration of the polymer into the adjacent tissues, overwhelming local clearance mechanisms. The molecular weight of the removed plate was 53% lower (58 and 52% lower for the screws) compared with intact plates, indicating that the absorption of the Osteosynthesis material had progressed as expected. The severe inflammation reaction observed could have led to periimplant osteolysis. In addition, the mobility of the plate and the screw as a result of the bone resorption could have further exacerbated the maxillary infection. A buccal buttress requires an occlusal stress. Resorption of a plate progresses 5 months postoperatively and the plate strength decreases. Because an occlusal force is recovered 2 months postoperatively for zygomatic fractures [15], it may lead to instability of a plate by a strong occlusal stress. Therefore, during zygomatic fracture treatment, we have to consider buccal buttress of the resorptive plate in which strength temporally reduces. To prevent the plate surge by an incongruity, it is required to firmly fit a plate to a bone.
This plate system has been widely and successfully used as an Osteosynthesis material [9]. In this case, the same plate system was used for other sites, such as the orbital rim and the zygomaticofrontal suture; however, bone resorption was only observed in the zygomaticomaxillary suture, connected to the side of the oral cavity. The presence of an oral Streptococcus sp. infection suggests an oral origin of the infection. This bacterial infection may have promoted the resorption of the bone surrounding the plate system, worsening the situation. Although inflammation by a foreign-body reaction occurs, there is generally little bacterial infection at areas other than the oral cavity. Because the oral-cavity is always exposed to the oral origin bacteria, we should be cautious regarding infections occurring at a relatively early stage.

Conclusions

Here postoperative complications related to the biodegradation of resorbable materials are reported. This study shows that there is a need to widen our understanding on the characteristics and use of these resorbable materials based on clinical observations.

No.	Specimen name	Number average molecular weight	Mn pace of decrease	Weight average molecular weight	Mw pace of decrease
1	intact screw	4.74 x 10⁴		1.21 x 10⁵
2	intact plate	4.81 x 10⁴		1.16 x 10⁵
3	removal screw	2.01 x 10⁴	58	5.27 x 10⁴	56
		2.19 x 10⁴	52	5.59 x 10⁴	54
4	removal plate	2.28 x 10⁴	53	5.36 x 10⁴	54

Case Report