Systemic Absorption Resulting from Tobramycin-Loaded Antibiotic Cement Spacers Used in the Treatment of Prosthetic Joint Infection.

Purpose: Antimicrobial cement spacer (ACS) placement has been a cornerstone of two-stage management of prosthetic hip and knee infection. Pharmacokinetic modelling has described peak systemic antibiotic concentrations within the first 24-48 h post-operatively, followed by rapid clearance. A few studies have, however, identified detectable tobramycin levels in patients with a post-operative decline in creatinine clearance. Our study sought to determine how frequently detectable serum tobramycin levels occurred within the first 72 h following ACS placement in all patients regardless of baseline or subsequent changes in renal function, whether these levels correlated with tobramycin spacer dosage, creatinine clearance, or potential nephrotoxicity risk factors, and whether any patients developed acute kidney injury within the 14-day post-operative period. Methods: We prospectively enrolled patients with prosthetic hip or knee infections and subsequent ACS placement from October 2017 to February 2020. Patient comorbidities (chronic kidney disease, diabetes mellitus, chronic liver disease, chronic obstructive pulmonary disease, and atrial fibrillation), Charleston Comorbidity Index score, risk factors for post-operative nephrotoxicity (perioperative hypotension and nephrotoxic agent receipt), total tobramycin dosage, post-operative days 1 and 3 serum tobramycin concentrations, and serum creatinine and creatinine clearance throughout a 14-day post-operative period were recorded. Results: A total of 20 patients were enrolled, comprising 20 spacers with a median total tobramycin dosage of 4.80 g with an interquartile range (IQR) of 4.13-7.20 g. Thirteen patients had a median detectable post-operative day 1 serum tobramycin concentration of 0.80 (IQR 0.50-1.60) mcg/mL. Five of these 13 patients had a median detectable post-operative day 3 serum tobramycin concentration of 0.80 (IQR 0.50-1.10) mcg/mL. A correlation was not found between serum tobramycin drug levels and patient comorbidities, receipt of nephrotoxic medications, or baseline and subsequent post-operative creatinine clearance up to day 14. Conclusion: The majority of patients who underwent tobramycin ACS placement had detectable serum tobramycin levels in the immediate post-operative period, but most reached undetectable levels within 72 h. There were no reliable perioperative predictors of detectable drug levels.

Bacterial Identification and Visualization of Bacterial Biofilms Adjacent to Fracture Sites After Internal Fixation.

Objectives: The primary aims of this study were to determine if any correlation exists in cases of fracture fixation among: (1) bacterial profiles recovered from the instrumentation and adjacent tissues; (2) the type of orthopedic injury; and (3) the clinical outcome-union versus nonunion. A secondary goal was to compare culture and molecular diagnostics for identifying the bacterial species present following fracture fixation. Design: Single-institution, prospective case-control cohort study. Setting: Single level 1 trauma center. Patients: Forty-nine bony nonunion cases undergoing revision internal fixation and 45 healed fracture controls undergoing removal of hardware. Intervention: Bacterial infection was detected by standard microbial culture methods and by a pan-eubacterial domain, molecular diagnostic (MDx) assay. Confirmation of culture and MDx results was achieved with bacterial ribosomal 16S rRNA fluorescence in situ hybridization (FISH) to visualize bacterial biofilms. Main Outcome Measurements: MDx and microbial culture methods results were the primary study outcomes. Results: Ninety-four percent of the nonunion cohort and 93% of the union cohort had bacteria detected by the MDx. Seventy-eight percent of the nonunion cases and 69% of the controls were culture negative, but MDx positive. Although no significant differences in bacterial composition were observed between the cases and controls, differences were observed when cases were divided by comorbidities. Conclusion: The MDx is more sensitive than microbial culture in detecting bacterial presence. The lack of significantly different findings with regard to bacterial profile identified between the cases and controls suggests that host factors and environmental conditions are largely responsible for determining if bony union will occur. Level of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Use of Tantalum Trabecular Metal Cones for Management of Nonunion of the Distal Femur with Segmental Bone Defects: Technique and Case Series.

INTRODUCTION: Segmental bone loss in the distal femur presents a challenge for reconstruction regardless of etiology. Use of tantalum trabecular metal cones with intramedullary fixation and autologous bone graft may be used as a salvage technique in difficult situations where other options have either been exhausted or are unavailable. CASE REPORT: Surgical planning and technique for this approach to reconstruction are described. A retrospective review of five cases with >1 year of follow-up was performed to provide radiographic and clinical outcomes. All five patients had satisfactory outcomes with clinical union and retention of implants at final follow-up (average >4 years). CONCLUSIONS: Use of tantalum metal cones for reconstruction of distal femur nonunion with segmental bone defects can be a successful technique in a complex group of patients.

Patient Characteristics and Surgical Start Time Affect Length of Stay Following Anterior Total Hip Arthroplasty.

BACKGROUND: Currently, no consensus exists for selection criteria of appropriate candidates for outpatient total hip arthroplasty (THA). This study evaluates patient characteristics associated with same-day discharge, examined surgical start time's effect on rates of same-day discharge, and compares readmission and reoperation rates between groups. METHODS: All patients who underwent a THA by one surgeon at a single quaternary care hospital between February 2016 and May 2018 were captured. All patients were given the option for same-day discharge. Patient characteristics and perioperative variables were analyzed. RESULTS: A total of 429 patients met inclusion criteria, 153 (36%) were discharged on the day of surgery. In a multivariate analysis, age (P = .000), multiple comorbidities (P = .004), and start time remained statistically significant (P = .000). Patients with start times prior to 9 AM had odds ratio of 11.56 of being discharged same day when compared to those with start times after 12 PM. Patients discharged the day of surgery were less likely to have a 90-day emergency room visit (P = .010), a readmission within 30 days (P = .001) or 90 days (P = .000), or a reoperation (0 vs 14, P = .003). CONCLUSION: Same-day discharge following THA is safe and feasible. Patient's age and number of comorbidities should be considered when developing selection criteria for same-day discharge programs. Patients selected for same-day discharge should receive earlier operating room start times.

Using Double-Contrast CT Arthrography to Confirm Suspected Dissociation of a Cemented Polyethylene Liner in the Setting of Revision Total Hip Arthroplasty: A Case Report.

CASE: A 67-year-old woman who underwent a re-revision of a total hip arthroplasty with a cemented polyethylene liner fell 14 months after surgery. The patient had symptoms of pain and weakness; however, clinical, laboratory, and radiographic evaluation did not disclose fracture, infection, osteolysis, or component migration. Liner dissociation was suspected, and a double-contrast computed tomography (CT) arthrogram confirmed failure at the cement-liner interface. She underwent additional revision surgery and was doing well at the 3-year follow-up. CONCLUSION: Double-contrast CT arthrography confirmed failure at the cement-liner interface and is an effective diagnostic tool in identifying suspected dissociations of cemented polyethylene liners.

Progressive Cardiomyopathy in a Patient With Elevated Cobalt Ion Levels and Bilateral Metal-on-Metal Hip Arthroplasties.

Systemic cobalt toxicity is a rare complication after metal-on-metal (MOM) total hip arthroplasty. Here we present a case of progressive cardiomyopathy, as evidenced by biopsy and cardiac magnetic resonance imaging (MRI), in a patient with bilateral MOM total hip arthroplasties. To our knowledge, it is one of the first cases in which cardiomyopathy resulting from systemic cobalt disease has been shown on MRI. While there is no guideline to unequivocally diagnose cobalt cardiomyopathy, the constellation of findings, including pathologic, biologic, blood levels, imaging, and surgical, all uniformly indicate a unifying diagnosis. The lack of improvement after removal of the prosthetic device supports a diagnosis of permanent myocardial damage, which is consistent with cardiomyopathy of advanced toxic etiology.

Survival of primary condylar-constrained total knee arthroplasty at a minimum of 7 years.

The purpose of the present study is to retrospectively analyze clinical and radiographic outcomes in primary constrained condylar knee arthroplasty at a minimum follow-up of 7 years. Given the concern for early aseptic loosening in constrained implants, we focused on this outcome. Our cohort consists of 127 constrained condylar knees. The mean age of patients in the study was 68.3 years, with a mean follow-up of 110.7 months. The diagnosis was primary osteoarthritis in 92%. There were four periprosthetic distal femur fractures, with a rate of revision of 0.8%. No implants were revised for aseptic loosening. Kaplan-Meier survivorship analysis with removal of any component as the end point revealed that the 10-year rate of survival of the primary CCK was 97.6% (95% CI, 94%-100%).

Can we trust intraoperative culture results in nonunions?

OBJECTIVES: To identify the presence of bacterial biofilms in nonunions comparing molecular techniques (multiplex polymerase chain reaction and mass spectrometry, fluorescent in situ hybridization) with routine intraoperative cultures. METHODS: Thirty-four patients with nonunions were scheduled for surgery and enrolled in this ongoing prospective study. Intraoperative specimens were collected from removed implants, surrounding tissue membrane, and local soft tissue followed by standard culture analysis, Ibis's second generation molecular diagnostics (Ibis Biosystems), and bacterial 16S rRNA-based fluorescence in situ hybridization (FISH). Confocal microscopy was used to visualize the tissue specimens reacted with the FISH probes, which were chosen based on the Ibis analysis. RESULTS: Thirty-four patient encounters were analyzed. Eight were diagnosed as infected nonunions by positive intraoperative culture results. Ibis confirmed the presence of bacteria in all 8 samples. Ibis identified bacteria in a total of 30 of 34 encounters, and these data were confirmed by FISH. Twenty-two of 30 Ibis-positive samples were culture-negative. Four samples were negative by all methods of analysis. No samples were positive by culture, but negative by molecular techniques. CONCLUSIONS: Our preliminary data indicate that molecular diagnostics are more sensitive for identifying bacteria than cultures in cases of bony nonunion. This is likely because of the inability of cultures to detect biofilms and bacteria previously exposed to antibiotic therapy. LEVEL OF EVIDENCE: Diagnostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Molecular techniques to detect biofilm bacteria in long bone nonunion: a case report.

BACKGROUND: Biofilms cause chronic infections including those associated with orthopaedic hardware. The only methods that are Food and Drug Administration-approved for detecting and identifying bacterial infections are cultures and selected DNA-based polymerase chain reaction methods that detect only specific pathogens (eg, methicillin-resistant Staphylococcus aureus). New DNA-based technologies enable the detection and identification of all bacteria present in a sample and to determine the antibiotic sensitivities of the organisms. CASE DESCRIPTION: A 34-year-old man sustained an open tibia fracture. He experienced 3 years of delayed healing and episodic pain. In addition to his initial treatment, he underwent three additional surgeries to achieve fracture healing. During the last two procedures, cultures were taken and samples were tested with the IBIS T5000 and fluorescence in situ hybridization (FISH). In both cases, the cultures were negative, but the IBIS and FISH confirmed the presence of a biofilm within the tibial canal. LITERATURE REVIEW: Examinations of tissues from biofilm infections, by DNA-based molecular methods and by direct microscopy, have often found bacteria present despite negative cultures. Infections associated with orthopaedic hardware may be caused by bacteria living in biofilms, and these biofilm organisms are particularly difficult to detect by routine culture methods. PURPOSES AND CLINICAL RELEVANCE: Rapid DNA-based detection methods represent a potentially clinically useful tool in the detection of bacterial biofilms. The sensitivity and clinical impact of the technology has yet to be established.

Arthrodesis of the knee with a long intramedullary nail following the failure of a total knee arthroplasty as the result of infection. Surgical technique.

BACKGROUND: Knee arthrodesis can be an effective treatment option for relieving pain and restoring some function after the failure of a total knee arthroplasty as the result of infection. The purpose of the present study was to review the outcome of a staged approach for arthrodesis of the knee with a long intramedullary nail after the failure of a total knee arthroplasty as the result of infection. METHODS: We reviewed the results for twelve patients who underwent knee arthrodesis after the removal of a prosthesis because of infection. The study group included seven women and five men who had an average age of sixty-eight years at the time of the arthrodesis. All patients were managed with a staged protocol. Implant removal, débridement, and insertion of antibiotic cement spacers was followed by the administration of systemic antibiotics. Provided that clinical and laboratory data suggested eradication of the infection, arthrodesis of the affected knee with use of a long intramedullary nail was carried out. Clinical and laboratory evaluation and radiographic analysis were performed after an average duration of follow-up of 4.1 years. RESULTS: Solid union was achieved in ten of the twelve knees. The average time to union was 5.5 months. One patient had an above-the-knee amputation because of recurrence of infection. In another patient, nail breakage occurred three years following implantation. The average limb-length discrepancy was 5.5 cm. The mean Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score improved from 41 to 64 points. None of the seven patients who underwent arthrodesis with a technique involving convex-to-concave reamers had a complication, and the average time to union for these seven patients was shorter than that for the remaining five patients (4.3 compared with 7.4 months). CONCLUSIONS: We believe that obtaining large surfaces of bleeding contact bone during arthrodesis following staged treatment of an infection at the site of a failed total knee arthroplasty contributes to stability and enhances bone-healing. Staged arthrodesis with use of a long intramedullary nail and convex-to-concave preparation of bone ends provided a painless functional gait with low complication and reoperation rates in this challenging group of patients.

CT-guided iliosacral screw placement: technique and clinical experience.

OBJECTIVE: The purpose of this study was to describe the technique of and experience in using CT guidance for percutaneous iliosacral screw placement in patients with unstable pelvic fractures. CONCLUSION: CT-guided iliosacral screw placement is a safe and accurate procedure that can be performed by radiologists in a radiology suite.

Using intraoperative pelvic landmarks for acetabular component placement in total hip arthroplasty.

Dislocation after total hip arthroplasty is frequently due to acetabular malpositioning. Positioning of the acetabular component using anatomical landmarks may reduce the incidence of dislocation from improper acetabular orientation. The pelvis provides 3 bony landmarks (ilium, superior pubic ramus, and superior acetabulum), which, when used to define a plane, allows cup orientation in abduction and version. Landmarks evaluated in 24 cadaveric acetabuli allowed slightly increased abduction and anteversion of the cup, compared with native acetabuli. Six hundred seventeen primary total hip arthroplasties were performed between 1996 and 2003 using this technique. Mean cup abduction was 44.4 degrees with 13.2 degrees of anteversion. This technique allows satisfactory reproducible cup orientation based on individual pelvic morphology. Review of patient outcome data suggest high patient satisfaction and lower dislocation rate without additional equipment, time, or cost.

Revision total hip arthroplasty with a custom cementless stem with distal cross-locking screws. Early results in femora with large proximal segmental deficiencies.

BACKGROUND: Revision total hip arthroplasty in the setting of a large proximal segmental femoral deficiency and/or discontinuity between the proximal and distal parts of the femur remains a challenging problem. We describe the use of a cementless stem with distal cross-locking screws to provide stability of the femoral implant in this situation. METHODS: Seventeen custom fully porous and hydroxyapatite-coated titanium femoral stems with distal cross-locking titanium screws were implanted in sixteen patients during revision total hip arthroplasty. Preoperatively, all of the patients had Paprosky grade-IIIB or IV femoral deficiencies. At the time of follow-up, the Harris hip scores were calculated and radiographs were made. A successful result was defined as a postoperative increase in the Harris hip score of >20 points, a radiographically stable implant, and no additional femoral reconstruction. RESULTS: At the time of final follow-up, at a mean of 5.3 years postoperatively, the result was successful in sixteen of the seventeen hips, the mean Harris hip score had improved from 35 to 76 points, and all implants were clinically and radiographically stable. There were no postoperative infections or hip dislocations. CONCLUSIONS: The use of a custom femoral stem with distal cross-locking screws can provide at least intermediate-term clinical and radiographic stability in patients with Paprosky grade-IIIB or IV femoral deficiencies. Longer follow-up will be required to determine the longevity of these implants.

Arthrodesis of the knee with a long intramedullary nail following the failure of a total knee arthroplasty as the result of infection.

BACKGROUND: Knee arthrodesis can be an effective treatment option for relieving pain and restoring some function after the failure of a total knee arthroplasty as the result of infection. The purpose of the present study was to review the outcome of a staged approach for arthrodesis of the knee with a long intramedullary nail after the failure of a total knee arthroplasty as the result of infection. METHODS: We reviewed the results for twelve patients who underwent knee arthrodesis after the removal of a prosthesis because of infection. The study group included seven women and five men who had an average age of sixty-eight years at the time of the arthrodesis. All patients were managed with a staged protocol. Implant removal, débridement, and insertion of antibiotic cement spacers was followed by the administration of systemic antibiotics. Provided that clinical and laboratory data suggested eradication of the infection, arthrodesis of the affected knee with use of a long intramedullary nail was carried out. Clinical and laboratory evaluation and radiographic analysis were performed after an average duration of follow-up of 4.1 years. RESULTS: Solid union was achieved in ten of the twelve knees. The average time to union was 5.5 months. One patient had an above-the-knee amputation because of recurrence of infection. In another patient, nail breakage occurred three years following implantation. The average limb-length discrepancy was 5.5 cm. The mean Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score improved from 41 to 64 points. None of the seven patients who underwent arthrodesis with a technique involving convex-to-concave reamers had a complication, and the average time to union for these seven patients was shorter than that for the remaining five patients (4.3 compared with 7.4 months). CONCLUSIONS: We believe that obtaining large surfaces of bleeding contact bone during arthrodesis following staged treatment of an infection at the site of a failed total knee arthroplasty contributes to stability and enhances bone-healing. Staged arthrodesis with use of a long intramedullary nail and convex-to-concave preparation of bone ends provided a painless functional gait with low complication and reoperation rates in this challenging group of patients.