With the development of new arthroscopic approaches over the last decade, one innovation that has facilitated this trend has been the introduction of high-tensile-strength sutures. These nonabsorbable sutures allow for the reliable and secure fixation of soft tissues, such as the glenoid labrum and rotator cuff, to bone by means of anchors1,2. Similarly, these sutures have gained great acceptance in open procedures, such as tendon repairs and suture fixation of fracture fragments3. FiberWire (Arthrex, Naples, Florida) is one of the first members of this family of sutures. Currently, it is one of the most commonly used high-tensile-strength sutures in orthopaedic surgery.
FiberWire is composed of an ultra-high molecular weight polyethylene multifilament core surrounded by a braided polyester jacket4. A silicone coating has been added to the surface of the polyester jacket to improve the handling and knot-tying characteristics of the suture. Ticron (Tyco, Waltham, Massachusetts) is the only other high-tensile-strength suture sold in the United States that has an outer silicone coating. The remaining high-tensile-strength sutures all employ proprietary blends of polyethylene and polyester without the use of a silicone coating.
Over a two and a half-year period, we performed or revised 193 lower-extremity amputations at our institution in our treatment of injured soldiers. Because of its strength and the excellent documented clinical experience with FiberWire, we used it to suture the myodesis in 178 (92%) of the 193 transtibial and transfemoral amputations. Recently, five patients with similar-appearing draining sinuses through previously well-healed incisions presented during follow-up visits for the lower-extremity amputations. In all five patients, FiberWire had been used to secure the myodesis. This clustering of similar complications suggested a common cause. Thus, a quality assurance review was initiated. The purpose of this case series is to present the results of that review.
This study is a case series, in which all intraoperative findings and histologic analyses were collected retrospectively. The patients were informed that data concerning their cases would be submitted for publication, and they consented. Institutional review board approval was obtained for this study. From March 2003 until January 2006, 193 lower-extremity amputations were performed at our institution by eight different orthopaedic surgeons. A myodesis was performed with use of FiberWire suture in 178 (92%) of 193 patients, while Ethibond (Ethicon, Somerville, New Jersey) was used in fifteen patients (8%). During this time, a multidisciplinary amputation team was developed. A single orthopaedic surgeon was assigned to this team and was responsible for the postoperative follow-up and management of all patients who had a traumatic amputation. During the course of follow-up, five patients whose amputations had been performed by four different surgeons presented to the amputation clinic at a mean of 9.1 months (range, five to eleven months) postoperatively with similar sinus tracts through otherwise well-healed incisions. In all five patients, the suture used to secure the myodesis was FiberWire. An illustrative case summary of one of the patients is presented below. It accurately reflects the clinical course and findings of the five patients in our series.
Pathology Methods
Hematoxylin and eosin-stained tissue from around each sinus tract was examined by routine light microscopy and under polarized light for birefringence. In addition, a section was stained immunohistochemically for CD68 (which stains macrophages and foreign-body-type giant cells). Unstained tissue sections were mounted on carbon discs for scanning electron microscopy with energy dispersive x-ray analysis (a procedure for elemental analysis that routinely allows the identification of elements with atomic numbers as low as that of carbon on the basis of their characteristic x-ray energies). Unstained sections mounted onto aluminum slides were examined by infrared spectroscopy (an analysis that provides information on the molecular characteristics of a material). The scanning electron microscopy with energy dispersive x-ray analysis and infrared spectroscopy methods used in the present study were similar to those previously described in the literature5,6. Portions of the formalin-fixed excised suture were also prepared for scanning electron microscopy with energy dispersive x-ray analysis and infrared spectroscopy analysis, and they were compared with the results from a sample of unused, intact FiberWire suture.
One patient (Case 5), a twenty-nine-year-old male soldier in the U.S. Army, was injured when his military vehicle was hit by an explosive ordnance in January 2005. He sustained massive blast injuries to the left lower extremity. The injuries included an open, severely comminuted calcaneal fracture with extensive plantar soft-tissue loss, open talar body and neck fractures, as well as an open type-IIIB, comminuted, segmental fracture of the mid-to-distal one-third of the tibial shaft. After serial irrigation and débridement procedures and extensive counseling, the patient elected a transtibial amputation as the definitive reconstruction procedure. The transtibial amputation included the creation of a long posterior myocutaneous flap with myodesis of the gastrocnemius tendon to the residual tibial shaft by means of two drill-holes on the medial and anterolateral tibial cortices with use of FiberWire suture with the knots tied deep to the subcutaneous layer of the leg. A myoplasty of the remaining anterior and lateral compartment musculature was performed with Vicryl sutures (polyglactin; Ethicon). The myoplasty was used to cover the myodesis sutures, and it was followed by delayed primary skin closure of the long posterior flap, leaving the suture line proximal to the level of the residual tibia. The amputation wound healed, and the skin sutures were removed two weeks postoperatively, without evidence of acute complication. The patient advanced through limb shrinking and prosthetic fitting over the following four weeks without event. Subsequently, he progressed to full independent walking ability with use of a prosthetic limb.
Ten months after the injury, the patient returned to the clinic noting a punctuate sinus tract over the previously well-healed suture line, which had appeared and started draining clear, serous fluid one week prior to presentation. The patient denied the presence of fevers or other constitutional symptoms. Laboratory evaluation on presentation included a white blood-cell count of 10.6 × 103 cells/mm3 (10.6 × 109/L) (normal, 3.6 to 10.6 × 103 cells/mm3 [3.6 to 10.6 × 109/L]) with 62.4% polymorphonuclear cells (normal, 40.7% to 76.4%), an erythrocyte sedimentation rate of 13 mm/hr (normal, 1 to 19 mm/hr), and a C-reactive protein value of 0.481 mg/dL (normal, 0.071 to 0.500 mg/dL). On physical examination, the patient had a 1-mm punctuate sinus tract centered over the otherwise well-healed amputation suture line. There was no surrounding erythema, induration, or expressible purulence from the small sinus, and suture knots were not clinically palpable. A radiograph of the residual limb was made, and it did not show a spur or heterotopic ossification about the residual tibia and fibula.
The patient was returned to the operating room for débridement and irrigation of the sinus tract and possible transtibial amputation revision. The sinus tract extended from the skin through the subcutaneous layer, directly down to a FiberWire suture at the myodesis site (Fig. 1). The suture was surrounded by tissue that appeared soft and amorphous in nature, without any sign of gross purulence. Intraoperative deep wound cultures were sent to assess for aerobic and anaerobic bacteria, mycobacteria, and/or fungal growth. Final culture results were negative for all growth. A rim of tissue surrounding the sinus tract, including the suture, was excised and sent for microbiologic, histologic, and environmental toxicologic analysis. The sinus tract, myoplasty, and myodesis were opened and explored in the area about the tract. Débridement and irrigation was performed, the gastrocnemius myodesis was revised through drill-holes in the residual tibia with number-5 Ethibond suture, and the wound was closed primarily. The length of the residual tibia and fibula were not revised. Antibiotics were administered intraoperatively and perioperatively for a twenty-four-hour period and were then discontinued. The wound healed well and without complication. The patient again returned to independent walking with the use of the prosthetic limb.
Four additional patients presented in a similar manner to that of the first patient described (Case 5), with a draining sinus at the site of a previously well-healed lower-extremity amputation. Again, neither systemic symptoms nor physical signs of infection were present. Laboratory evaluation demonstrated normal white blood-cell counts and differentials (Table I). A preoperative erythrocyte sedimentation rate and C-reactive protein value were obtained for three of the four patients and were normal in all three. Wound culture specimens obtained from the five patients at serial surgical wound débridements prior to the primary amputation were positive in two patients (one had Escherichia coli, and one had Acinetobacter baumannii), but, at the time of the primary amputation and myodesis, all wound cultures were negative. Intraoperative wound culture specimens at the time of the revision amputation were negative in four of the five patients. One patient had a positive culture at the time of revision for coagulase-negative Staphylococcus. This was not the same organism (Escherichia coli) that had been isolated prior to the primary amputation. In this patient, the tissue at the base of the sinus, adjacent to a FiberWire suture, was grossly similar to that seen in the other four patients with negative wound cultures. Likewise, there was no pus or other evidence of active infection. As was the case for the other four patients, this patient was not treated with postoperative antibiotics following the twenty-four-hour perioperative period. Following excision of the suture and adjacent inflammatory tissue, the wound healed without complication.
All five patients in the series underwent wound exploration and excision of the sinus tract and suture-related granuloma, with irrigation, débridement, revision myodesis, and primary closure of the wound. All of the patients were noted to have soft, amorphous tissue surrounding a FiberWire suture at the previous myodesis site. There was no evidence of frank infection or purulence in any patient. The myodesis was revised in each patient with use of a number-5 Ethibond suture, which is a synthetic, braided, nonabsorbable, polyester-coated polyester suture, and the skin was closed primarily. No further wound complications had been noted in these patients at a mean follow-up of 29.4 months (range, twenty-six to thirty-three months). All patients returned to walking in their prostheses without the aid of assistive devices.
Pathological Evaluation
The materials that were reviewed include formalin-fixed wet tissue and paraffin-embedded tissue with grossly apparent suture material, as well as hematoxylin and eosin-stained glass slides. In addition, an intact and unused FiberWire suture was obtained for comparative analysis. Grossly, the excised sutures from our patients resembled the structure of an intact FiberWire. With use of light microscopy, both the excised and intact FiberWire sutures were shown to have a central core of white fibers surrounded by a braided "jacket" of round blue fibers and white, more angular fibers resembling the fibers of the core. Infrared spectroscopy was performed on the blue and white bundles of the intact FiberWire as well as the FiberWire sutures excised in the tissue specimens. Both demonstrated the same spectral characteristics of a polyester (polyethylene terephthalate in the blue fibers) and polyethylene (white fibers). Furthermore, when the tissue specimens were viewed under polarized light, both the polyethylene and polyethylene terephthalate fibers demonstrated bright birefringence.
Scanning electron microscopy with energy dispersive x-ray analysis demonstrated that the surface of the intact FiberWire suture contained silicon (a component of silicone), and the different bundles of braided fibers demonstrated the presence of carbon and oxygen (consistent with a polyester such as polyethylene terephthalate) or carbon only (consistent with polyethylene). In the same manner, scanning electron microscopy with energy dispersive x-ray analysis was performed on the sutures within the tissue specimens that also demonstrated the presence of carbon and oxygen (consistent with polyethylene terephthalate) and focally a small peak for silicon. Other fiber bundles demonstrated the presence of carbon only (consistent with polyethylene).
Hematoxylin and eosin-stained sections of the excised tissue demonstrated fragments of amorphous soft-tissue with an abundant foreign-body-type giant-cell reaction. Within the cytoplasm of the foreign-body-type multinucleated giant cells located adjacent to the sinus tract, irregularly shaped, colorless gel-like material was identified. This material was refractile but not birefringent when viewed under polarized light (Fig. 2). Of note, neither the birefringent polyethylene nor polyethylene terephthalate fibers were identified within the areas of inflammation in the excised tissue. A CD68 immunohistochemical stain was performed, which highlighted the presence of multinucleated giant cells attempting to encircle individual fibers (Fig. 3).
The gel-like material found within the giant cells on light microscopy was evaluated by scanning electron microscopy with energy dispersive x-ray analysis, which identified the presence of elemental silicon in the material, illustrated with use of mapping software. Infrared spectroscopy was then separately performed both on the intracytoplasmic refractile material from the tissue specimens as well as on the coating of the authentic FiberWire suture. The infrared spectra obtained of both materials matched the infrared spectral characteristics of silicone (polydimethylsiloxane) when compared with a computerized library of reference spectra. Therefore, this analysis confirmed the presence of silicone granulomas in the excised tissue surrounding the FiberWire suture.
The history of silicone devices implanted in humans has been a controversial one, which has sparked heated debate and inconclusive scientific findings. This debate started when silicone was implicated as the putative agent in a fulminant form of fibrosis7 and granulomatous tissue reaction8,9 that occurred in some women following breast augmentation with silicone gel-filled breast implants. While a thorough review of this literature is beyond the scope of this article, we will review some of the relevant facts.
Silicone is a synthetic plastic polymer composed of an alternating silicon and oxygen atom backbone that has hydrocarbon groups attached to silicon atoms. It is a durable, elastic material that can be used in the body as a sealant, a gel, or a solid rubbery material in multiple surgical applications. Silicone biomaterials have been used in humans for over half a century. Silicone is still a common component of cosmetic, otolaryngological, and orthopaedic implants, especially in hand and wrist surgery10. Silicone appears to be neither teratogenic nor oncogenic11,12. Likewise, there is no clear proof that silicone causes any systemic side effects. Currently, the only consistent finding has been that, like virtually all foreign material implanted in the body, it has the capability of eliciting a local inflammatory response13. The degree, frequency, and clinical consequences of this response continue to be debated.
While this study is the first, as far as we know, to report foreign-body reactions associated with the use of FiberWire, it is not the first report of a foreign-body reaction to silicone-coated high-tensile-strength suture. Ticron is the only other high-tensile-strength synthetic suture sold in the United States that has a silicone coating. Warme et al.14 reported a late (3.5-year-postoperative) foreign-body reaction after the use of Ticron to secure an inferior capsular shift. At surgery, two displaced Ticron sutures had migrated superficial to the subscapularis where they were found in a sterile seroma. Histologic evaluation of samples of the tissue adjacent to the suture revealed inflammatory cells consistent with a foreign-body reaction.
Since the complication reported in this study occurred in only 3% of the 178 lower-extremity amputations performed with a FiberWire myodesis during the study period, the silicone coating on the suture must be, at most, only one part of the problem. Mechanical issues including suture prominence combined with repetitive motion and shear at the distal aspect of the residual limb may also be linked to the inflammatory process surrounding the suture. As with the use of silicone implants in hand and wrist surgery, mechanical wear has been shown to cause the eventual generation of silicone particles with a resultant foreign-body granuloma formation15. A similar phenomenon may be occurring in these amputees, with repetitive irritation, friction, and wear of the prosthesis against a prominent suture possibly inciting silicone particle and foreign-body granuloma formation. It is possible that, if other amputation sites that have less friction and wear (such as those with better soft-tissue padding) at the suture-tissue interface were explored, this same reaction may not occur or it may occur to a lesser degree.
Infection is always a consideration when discussing the etiology of inflammatory processes in combat-related wounds. In this study, one of the five patients had a positive wound culture at the time of revision, growing coagulase-negative Staphylococcus. Although this organism is a common skin contaminant, and the patient had no signs or symptoms of infection at the time of revision, the presence of occult infection as a cofactor in the development of foreign-body reaction cannot be ruled out. Similarly, two patients demonstrated positive wound cultures at débridement prior to the primary amputation. Despite the demonstration of negative culture results for these organisms at the time of revision, it is possible that an occult infection may also be a contributing factor in the granulomatous inflammation surrounding the suture material in these patients.
Furthermore, the injuries that led to amputation in this series of patients were sustained in combat, primarily from high-energy blasts. The level of energy imparted to the soft tissue of these patients is not the same as with civilian trauma. This degree of injury may be a catalyst for an exuberant inflammatory response not seen in other patient groups. We are currently evaluating the role of high-energy trauma in the development of other inflammatory complications, such as heterotopic ossification16.
The impact of our findings is limited by our study design. Case series are typically conducted to report a rare or unique finding. Prospective studies are needed to derive generalizable information, such as incidence and relative risk of exposure, and to clearly demonstrate a cause-and-effect relationship. Likewise, when surgical complications are related to an aggressive inflammatory response, patient-specific immune system traits and the character of the wound itself must also be explored. Thus, future studies are also needed to identify patient-specific confounding factors that are prognostic of this type of complication.
FiberWire has been used in numerous orthopaedic applications, especially arthroscopic procedures, without any reported wound-related complications. However, in our patients who had a lower-extremity traumatic amputation, FiberWire-associated foreign-body reaction appears to be a real, but uncommon, complication. Although the etiology of these complications remains unclear, we no longer use FiberWire to secure myodeses in lower-extremity amputations. 
Note: The authors thank Colonel C. Adair and Colonel C.A. Prabha, Department of Pathology, Walter Reed Army Medical Center, for their contributions to this work, and Florabel G. Mullick, MD, Director, Armed Forces Institute of Pathology and Chair, Department of Environmental and Infectious Disease Sciences.
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