Evaluation of two different semi-automated homogenization techniques in microbiological diagnosis of periprosthetic joint infection: disperser vs. bead milling method.

BACKGROUND: In microbiological diagnosis of periprosthetic joint infection (PJI) there is no consensus regarding the most suitable and optimal number of specimens to be cultured or the most effective technique of tissue processing. This comparative study analysed the accuracy of two semi-automated homogenization methods with special focus on the volume and exact origin of each sample. METHODS: We investigated a total of 722 periprosthetic tissue samples. PJI was defined according to the new scoring system for preoperative and intraoperative criteria. We compared the performance of our routinely used single tissue processing by disposable high-frequency disperser with the bead milling method. RESULTS: Eighty patients were included. Among forty classified PJIs, 34 patients yielded positive culture results. In 23 cases (68%) exact concordant results were generated with both techniques. However, in seven cases (20%) processing by the disperser and in four cases (12%) by bead milling provided additional positive samples, but without significant difference since the major definition criteria were met in all cases. The percentage of positive results was influenced by the volume and origin of the tissue samples. Results for small tissue samples tended to be better using the bead milling method. This might lead to improved preoperative arthroscopic diagnosis, as the volume of biopsies is generally limited. Six patients had negative results due to previous antimicrobial therapy. Forty other patients were classified as aseptic failures. Neither procedure resulted in any contamination. CONCLUSION: Both methods enable reliable processing of tissue samples for diagnosis of PJI and are suitable for routine use.

Sonicate fluid inoculated into blood culture bottles does not improve diagnosis of periprosthetic joint infection caused by anaerobes. A retrospective analysis.

BACKGROUND: In microbiological diagnosis of periprosthetic joint infection (PJI) there is much controversial discussion about culture media and incubation time, especially if anaerobic bacteria are the causative agents. This retrospective analysis was conducted to compare the results obtained by inoculation of sonicate fluid from prosthetic components into BD Bactec blood culture bottles with those obtained by our culture method using sensitive supplemented growth media. METHODS: Twenty-eight cases were included in this study. For definition of PJI, the criteria of the Musculoskeletal Infection Society (MSIS) were considered. The quantity and time to positivity of anaerobes detected in sonicate fluid were monitored both from inoculated supplemented liver thioglycollate broth and anaerobic blood culture bottles. Furthermore, phenotypic testing was performed on the antimicrobial activity within the sonicate fluid. RESULTS: The most frequently isolated microbes were Cutibacterium species, followed by Finegoldia magna, Parvimonas micra, Robinsoniella peoriensis, Clostridium species, Peptoniphilus harei and Slackia exigua. In 24 cases, the microorganisms became detectable within five days (median time 3.2 days) when sonicate fluid was incubated in supplemented liver thioglycollate broth, regardless of whether the patients had taken antimicrobial agents prior to surgery. However, when sonicate fluid was inoculated into anaerobic Bactec bottles, the median time to positivity was 7.4 days and only 12 cases (43%) were correctly identified. Sixteen cases remained negative after 14 days of incubation. CONCLUSION: Depending on the pathogen, incubation of sonicate fluid using blood culture bottles can support diagnosis of PJI but compared with our culture medium it is less efficient if anaerobes are the suspected cause of infection. Microbiological expertise is therefore indispensable to ensure reliable detection of these microorganisms in PJI until a gold standard for laboratory handling of anaerobes has been established.

Application of Rapid Prototyping Pelvic Model for Patients with DDH to Facilitate Arthroplasty Planning: A Pilot Study.

Total hip arthroplasty (THA) is challenging in cases of osteoarthritis secondary to developmental dysplasia of the hip (DDH). Acetabular deficiency makes the positioning of the acetabular component difficult. Computer tomography based, patient-individual three dimensional (3-D) rapid prototype technology (RPT)-models were used to plan the placement of acetabular cup so that a surgeon was able to identify pelvic structures, assess the ideal extent of reaming and determine the size of cup after a reconstructive procedure. Intraclass correlation coefficients (ICCs) were used to analyze the agreement between the sizes of chosen components on the basis of preoperative planning and the actual sizes used in the operation. The use of the 3-D RPT-model facilitates the surgical procedures due to better planning and improved orientation.

Inhibition of the PI3K/AKT pathway reduces tumor necrosis factor-alpha production in the cellular response to wear particles in vitro.

Joint replacement is the most effective treatment for end-stage osteoarticular disease. However, macrophage-mediated aseptic loosening of joint prosthesis severely hampers the clinical effects of joint replacement. Until now, the mechanism by which macrophages regulate the secretion of inflammatory cytokines after particle stimulation is not clear. It is well known that the PI3K/AKT pathway participates in multiple cellular processes, including cell growth, survival, and inflammation. However, whether the PI3K/AKT pathway participates in the proinflammatory response of macrophages after particle stimulation and secondary aseptic loosening is still unknown. In this study, ceramic and titanium particles of different sizes were prepared to stimulate macrophages. LY294002, a specific inhibitor of PI3K, was pretreated prior to particle stimulation. The expression of tumor necrosis factor-alpha (TNF-α) and all the subunits of PI3K and AKT were detected by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blot. The result showed that LY294002 could suppress the RNA and protein expression of TNF-α in RAW264.7 cells after stimulation of different particles. The subunits of PI3K (p110ß and p85ß), followed by activation of phosphor-AKT (Ser473), participated in the regulation of activating macrophages by wear particles, ultimately resulting in the secretion of TNF-α.

The decrease of particle-induced osteolysis after a single dose of bisphosphonate.

The most common cause of implant failure in joint replacement is aseptic loosening due to particle-induced osteolysis. Bisphosphonates have been shown to be effective against particle-induced osteolysis when administered daily. We investigated the effect of a single subcutaneous dose of a more potent third generation bisphosphonate on particle-induced osteolysis. We utilized the murine calvaria osteolysis model in C57BL/J6 mice. Bone resorption was measured as resorption within the midline suture using Giemsa staining. Twenty-eight mice were used, seven per group. Seven animals were treated with a single dose of zoledronic acid (ZA) directly after surgery and seven animals were treated four days postoperatively. For statistical analysis one-way ANOVA and a Student's t-test were used. Bone resorption was 0.26+/-0.09 mm(2) in animals with particle implantation, 0.14+/-0.05 mm(2) in animals with particle implantation and ZA treatment directly after surgery (p = 0.0047), and 0.15+/-0.05 mm(2) in animals with particle implantation and ZA treatment on the fourth postoperative day (p = 0.006). In conclusion, particle-induced bone resorption was markedly decreased by a single s.c. dose of a third generation bisphosphonate. This important new finding holds great promise, because single dose treatment of particle-induced osteolysis may reduce side effects compared to repeated application of bisphosphonates.

The diagnostic value of digital subtraction arthrography and radionuclide arthrography in revision total hip arthroplasty.

An analysis of plain radiographs, digital subtraction arthrography, and radionuclide arthrography was performed in 25 revision hip arthroplasties to evaluate the efficacy and usefulness of these methods in the diagnosis of loosening. The findings by each method were compared with intraoperative assessment of the status of components and expressed in terms of sensitivity, specificity, and predictive accuracy. Overall accuracy for the acetabular component by plain radiographs was 80%; by digital subtraction arthrography, 88%; by radionuclide arthrography, 68%. Overall accuracy for the femoral component by plain radiographs was 92%; by digital subtraction arthrography, 84%; radionuclide arthrography, 76%. We consider subtraction arthrography and radionuclide arthrography to be adjuvant diagnostic tools which may be indicated in individual cases of suspected implant loosening of total hip arthroplasty. The routine use of these two methods is not warranted when compared to plain radiographs.

The clinical value of combined use of MR imaging and multi-slice spiral CT in limb salvage surgery for orthopaedic oncology patients: initial experience in nine patients.

BACKGROUND: The purpose of this prospective study was to evaluate the value of the combined use of MR imaging and multi-slice spiral CT for limb salvage surgery in orthopaedic oncology patients. PATIENTS AND METHODS: Nine consecutive patients with lower/upper limb malignant bone tumours (7 osteosarcomas and 2 chondrosarcomas) were treated with limb-salvaging procedures. Preoperative planning including determination of the osteotomy plane and diameters of the prosthesis was performed basing on the preoperative CT and MR images. The histopathology was performed as golden diagnostic criteria to evaluate the accuracy of CT and MR-based determination for tumour's boundary. RESULTS: The tumour extension measured on MRI was consistent with the actual extension (P>0.05, paired Student's t test), while the extension measured on CT imaging was less than the actual extension. The length, offset and alignment of the affected limb were reconstructed accurately after the operation. An excellent functional outcome was achieved in all patients. CONCLUSIONS: In the present study, MRI was found to be superior to CT for determining the tumour extension, combined use of MRI and CT measurement provided high precision for the fit of the prosthesis and excellent functional results.

The long-term clinical sequelae of incidental durotomy in lumbar disc surgery.

STUDY DESIGN: A retrospective, long-term follow-up study. OBJECTIVES: To find out whether incidental durotomy in lumbar disc surgery is associated with long-term sequelae. SUMMARY OF BACKGROUND DATA: Incidental durotomy is a frequent complication during spinal surgery. Little is known about the clinical long-term outcome. METHODS: The study population comprised 1,280 patients who underwent standard discectomy of a lumbar disc herniation. A total of 41 patients with incidental durotomies (Group A) were compared with a control group (n = 41) (Group B) matched for age, sex, spinal level, and duration of follow-up. After a mean follow-up period of 10.2 years (Group A) or 10.3 years (Group B), the patients reported complaints, headache, and low back or leg pain. The patients' activity was assessed by means of a questionnaire concerning hindrance in daily activities, the Tegner score for general activities in daily life, and the Hannover Functional Ability Questionnaire for Measuring Back Pain-Related Functional Limitations (FFbH-R). The frequency of reoperation and the intake of analgesics were included. Furthermore, the patients' inability to work, change of profession, and retirement were registered. RESULTS: Patients with incidental durotomy had a poorer outcome after surgery. The Tegner score was significantly decreased for the group with dural tears. Furthermore, significant more patients with incidental durotomy complained about headaches after surgery. A strong tendency for worse outcome in Group A was shown in regard to reported complaints and daily activity. The patients with incidental durotomy had a tendency to more reoperations, a longer duration of inability to work, more back-pain, and functional limitations related to back-pain (FFbH-R). CONCLUSION: Our study revealed that incidental durotomy in lumbar disc surgery was associated with long-term clinical sequelae. We therefore conclude that dural tears bring about poor clinical outcome at the long-term follow-up.

Strut allografts for failed treatment of periprosthetic femoral fractures: good outcome in 13 patients.

Strut allografts are not recommended after a femoral shaft exposure, because they may endanger the femoral blood supply. Up till now, we have seen no clinical reports on this problem. We treated 13 consecutive patients with very large anteromedial and anterolateral femoral strut allografts to restabilize periprosthetic fractures which had become loose after a previous attempt at surgical fixation (Vancouver type B fractures with severe bone loss). In 8 cases, the stem was revised in conjunction with the use of strut allografts and in 5 cases, strut allografts alone were used. All refractures and nonunions healed without further treatment. At a mean follow-up of 3 (1.2-7) years, the mean Harris Hip Score was 78 (65-92). All strut grafts showed ingrowth with augmentation of periprosthetic bone on the radiographs. There were 3 complications, 1 nonprogressive subsidence of a revision stem (fibrous stable), 1 deep hematoma and 1 partial lesion of the sciatic nerve. In this series, strut grafts gave reliable healing with augmentation of the host bone stock despite previous femoral exposure, severe bone loss, adverse type of fracture, and persistent instability at the index operation.

Rotating platform components for revisions of hinged knee prostheses.

If hinged prostheses are revised with smaller and nonhinged prostheses, do these implants provide adequate fixation, do massive bone grafts in combination with smaller implants reinforce host bone stock, do less constrained prostheses restore ligament tension, and do they avoid problems of the extensor mechanism? To answer these questions, 20 failed hinges were revised to rotating platform revision prostheses with short intramedullary stems in a prospective study. Meticulous soft tissue release techniques and extensive bone grafts were used (tibia, impaction grafting in 16 cases, and structural grafts in four cases; femur, impaction grafting in four cases and structural grafts in 16 cases). The mean followup was 5.3 years (range, 2.3-10.5 years). The Knee Society score improved from a preoperative mean of 21 points (range, 7-49 points) to a mean 81.2 points (range, 59-94 points). One cementless tibial component with extensive impaction grafting became loose. The remaining components (95%) were well-fixed. All cancellous bone grafts showed trabecular remodeling. All structural grafts united to the host bone without resorption. All knees had ligamentous stability after surgery. There were no problems of the extensor mechanism. In this series the rotating platform revision prostheses were used successfully for failed hinged prostheses.