Differentiating Occult <italic>Propionibacterium acnes</italic> Infection From Aseptic “Biologic” Interference Screw Hydrolysis After Anterior Cruciate Ligament Reconstruction

Kathryn Metcalf; Jia-Wei Kevin Ko; Samantha Quilici; Penelope Barnes; Dennis C. Crawford

摘要

Historically, arthroscopic anterior cruciate ligament (ACL) reconstruction has a low rate of infection, with a reported prevalence of 0.14% to 5.7%.~( 12 , 14 , 21 )While uncommon, these infections generally occur early and are characterized by either cellulitis at the graft insertion site and/or septic arthritis.~( 5 )Subacute infections are less well characterized. Although bioabsorbable interference screws have the potential advantages of osseointegration, limited postoperative imaging artifact, and decreased hardware removal rates, the potential for acting as the nidus for a sterile abscess, which can both mimic and/or set the stage for infection, exists.~( 2 )Typically, distinguishing a sterile abscess from infection is clinically apparent. However, we describe 2 patients with subacute postsurgical medial tibial pain in which this distinction was not evident. Application of a novel culture protocol taken from the prosthetic joint infection literature~( 6 )identified infection by a low-virulence organism and directed therapeutic treatment. Cases Initial Presentation and Treatment A 25-year-old male pedestrian (patient 1) was struck by an automobile and sustained an isolated right knee ACL tear. A 54-year-old woman (patient 2) sustained a right knee ACL tear while dancing. Both patients underwent arthroscopic ACL reconstruction performed by the same surgeon using an identical transtibial technique with suspense fixation (Endobutton; Smith & Nephew) and tibial fixation using the bioabsorbable Bio-INTRAFIX (DePuy Mitek) system. The bioabsorbable implant was composed of a proprietary combination of polylactic acid and tricalcium phosphate. Tibialis anterior allograft (Community Tissue Services) was used in both cases. The procedures were uncomplicated and were followed by routine rehabilitation and uneventful recovery with unrestricted activity at 6 months. Patient 1 Eight months postoperatively, patient 1 developed new onset erythema and swelling around the tibial incision (2 × 2 cm) with a central eschar and associated tenderness. He had no fever, effusion at the knee, or systemic signs of infection. Radiographs ( Figure 1 ) and magnetic resonance images ( Figure 2, A and B ) were obtained. The presence of diffuse hyperintense signal within the proximal tibia ( Figure 2 ), in contrast with soft tissue edema, and minimal signal in the uninfected proximal tibia ( Figure 3, A and B ) suggested the presence of infection, and the infectious disease (ID) service was consulted. Recommended blood tests were obtained, and results were within normal limits ( Table 1 ). Figure 1. No significant abnormalities were seen on anteroposterior knee radiographs in patient 1. The interference screw is apparent, without significant bone resorption. Figure 2. (A) Coronal and (B) sagittal plane T2-weighted magnetic resonance images for patient 1 indicating subtle changes adjacent to the interference screw and presenting an extensive hyperintense signal within the proximal tibia adjacent to the implant. Figure 3. Example of (A) coronal and (B) sagittal plane T2-weighted magnetic resonance images that exhibit a fragmented distal screw in association with soft tissue edema and minimal hyperintense signal in the proximal tibia. TABLE 1 Presurgical Laboratory Blood Test Results ~(a) Test Patient 1 Patient 2 WBC, ×10~(3)/mm~(3) 6.56 9.24 Neutrophil, ×10~(3)/mm~(3) 3.85 6.46 Lymphocyte, ×10~(3)/mm~(3) 1.87 2.16 Monocyte, ×10~(3)/mm~(3) 0.62 0.51 EOS, ×10~(3)/mm~(3) 0.18 0.07 BASO, ×10~(3)/mm~(3) 0.03 0.02 Immature granulocyte, ×10~(3)/mm~(3) 0.01 0.02 ESR, mm/h Not performed 17 C-reactive protein, mg/dL <0.5 <0.5 ~(a) BASO, basophil count; EOS, eosinophil count; ESR, erythrocyte sedimentation rate; WBC, white blood cell count. Surgical debridement of the tibial tunnel and interference screw removal proceeded within 1 week. At surgery, healthy bleeding tissue was found with no evidence of purulence or necrosis. The intact interference screw was removed in 1 piece with its surrounding sheath adjacent to minimal serous-appearing fluid. The graft was healed to bone, and no evidence of intra-articular extension of fluid or infection was apparent. Multiple cultures and pathology specimens were taken from the adjacent granulation tissue using our standard orthopaedic biopsy protocol (Oregon Health and Science University), which is an institution-wide tissue culture protocol specifically developed to improve detection of occult infections in association with orthopaedic implants.~( 6 )This protocol dictates obtaining a minimum of 5 tissue specimens (from the region of greatest suspicion) to be sent for culture. Each specimen is taken with a separate clean instrument; no swabs are used. An additional specimen is sent for surgical pathology analysis. Each microbiology specimen is separately incubated on blood agar and chocolate media plates aerobically and anaerobically for 5 days (conventional incubation) and in thioglycolate broth anaerobica

机译：从历史上看，关节镜下前交叉韧带（ACL）重建的感染率低，据报道患病率为0.14％至5.7％。（（12，14，21）虽然不常见，但这些感染通常较早发生，并且以蜂窝织炎为特征在移植物插入部位和/或败血性关节炎中。（5）亚急性感染的特征较差。尽管可生物吸收的干扰螺钉具有骨整合，术后影像伪影少和硬件去除率降低的潜在优势，但仍有可能用作无菌脓肿的病灶，可模仿和/或设定感染的阶段。（2）通常，将无菌脓肿与感染区分开在临床上是显而易见的。但是，我们描述了2例亚急性手术后胫骨内侧疼痛患者，其中这种区别并不明显。从人工关节感染文献中获得的新型培养方案的应用〜（6）鉴定了低毒力生物体的感染并进行了定向治疗。病例的初步介绍和治疗一名25岁的男性行人（患者1）被汽车撞倒，并遭受孤立的右膝ACL撕裂。一名54岁的女性（患者2）在跳舞时遭受了右膝ACL撕裂。两名患者均由同一位外科医生采用相同的胫骨技术进行悬吊固定（Endobutton; Smith＆Nephew），并使用可生物吸收的Bio-INTRAFIX（DePuy Mitek）系统进行胫骨固定，并进行了关节镜ACL重建。可生物吸收的植入物由聚乳酸和磷酸三钙的专有组合组成。在两种情况下均使用胫骨前同种异体移植（社区组织服务）。手术并不复杂，随后进行常规康复和平稳康复，六个月后活动不受限制。患者1术后8个月，患者1出现新的红斑并在胫骨切口（2×2 cm）周围肿胀，并伴有中央es骨和压痛。他没有发烧，膝盖积液或全身感染的迹象。获得了射线照片（图1）和磁共振图像（图2，A和B）。与软组织水肿相反，在胫骨近端存在弥散性高信号（图2），而在未感染胫骨近端存在最小信号（图3，A和B）表明存在感染和传染病（ID）。）咨询了服务。获得推荐的血液测试，结果在正常范围内（表1）。图1.患者1的膝后X线片未见明显异常。明显可见干涉螺钉，无明显骨吸收。图2.患者1的（A）冠状面和（B）矢状面T2加权磁共振图像，显示邻近干涉螺钉的细微变化，并在邻近植入物的胫骨近端内呈现广泛的高强度信号。图3.（A）冠状面和（B）矢状面T2加权磁共振图像的示例，这些图像显示了远端螺钉断裂，伴有软组织水肿和胫骨近端的最小高强度信号。表1.术前实验室血液测试结果〜（a）测试患者1患者2 WBC，×10〜（3）/ mm〜（3）6.56 9.24中性粒细胞，×10〜（3）/ mm〜（3）3.85 6.46淋巴细胞， ×10〜（3）/ mm〜（3）1.87 2.16单核细胞，×10〜（3）/ mm〜（3）0.62 0.51 EOS，×10〜（3）/ mm〜（3）0.18 0.07 BASO，×10 〜（3）/ mm〜（3）0.03 0.02未成熟的粒细胞，×10〜（3）/ mm〜（3）0.01 0.02 ESR，mm / h未执行17 C反应蛋白，mg / dL <0.5 <0.5〜（a）BASO，嗜碱性粒细胞计数; EOS，嗜酸性粒细胞计数; ESR，红细胞沉降率;白细胞，白细胞计数。 1周内进行了胫骨隧道的外科清创术和去除了干扰螺钉。在手术中，发现健康的出血组织没有化脓或坏死的迹象。完整的干涉螺钉被拆下为一件，其周围的鞘与极少出现浆液的液体相邻。移植物已愈合至骨头，并且没有明显证据显示关节腔内积液或感染。使用我们的标准骨科活检协议（俄勒冈卫生科学大学）从邻近的肉芽组织中获取多种培养物和病理学标本，该协议是专为改善与骨科植入物相关的隐匿性感染的检测而专门开发的全机构范围的组织培养协议。（6）该协议规定至少要从可疑区域中取出5个组织标本进行培养。每个标本都用单独的清洁仪器采集;不使用拭子。另外的标本被送去进行手术病理分析。每个微生物标本分别在需氧和厌氧的血琼脂和巧克力培养基板上孵育5天（常规孵育），并在巯基乙酸盐厌氧菌培养基中孵育

Differentiating Occult Propionibacterium acnes Infection From Aseptic “Biologic” Interference Screw Hydrolysis After Anterior Cruciate Ligament Reconstruction

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