Preoperative synovial fluid culture poorly predicts the pathogen causing periprosthetic joint infection.

PURPOSE: We investigated the value of preoperative pathogen detection and evaluated its concordance with intraoperative cultures in patients with culture-positive periprosthetic joint infection (PJI). METHODS: Culture-positive PJI episodes with available preoperative (synovial fluid) and intraoperative cultures (periprosthetic tissue, synovial or sonication fluid) were analyzed. The pathogen detection rate in preoperative and intraoperative cultures was compared using Fisher's exact test and their concordance was calculated. RESULTS: Among 167 included PJI episodes, 150 were monomicrobial with coagulase-negative staphylococci (n = 55, 37%), S. aureus (n = 34, 23%), and streptococci (n = 21, 14%) being the most common pathogens. Seventeen episodes (10%) were polymicrobial infections. The pathogen(s) grew in preoperative culture in 110 and in intraoperative cultures in 153 episodes (66% vs. 92%, p < 0.001). The pathogen detection rate was lower in preoperative compared to intraoperative cultures for low-virulent pathogens (40% vs. 94%, p < 0.001), polymicrobial infections (59% vs. 100%, p = 0.007), and in delayed and late PJI (63% vs. 94%, and 66% vs. 91%, respectively, p < 0.001). Full concordance of preoperative and intraoperative cultures was found in 87 episodes (52%). The pathogen was detected solely preoperatively in 14 episodes (8%) and solely intraoperatively in 57 cases (34%); an additional pathogen was found in 3 episodes (2%) preoperatively and in 6 episodes (4%) intraoperatively. CONCLUSION: The concordance of preoperative and intraoperative cultures was poor (52%). The sole or an additional pathogen was found exclusively in intraoperative cultures in 38% of PJI episodes, hence preoperative synovial fluid cultures are considered unreliable for pathogen detection in PJI.

Programable Active Fixator System for Systematic In Vivo Investigation of Bone Healing Processes.

This manuscript introduces a programable active bone fixator system that enables systematic investigation of bone healing processes in a sheep animal model. In contrast to previous systems, this solution combines the ability to precisely control the mechanical conditions acting within a fracture with continuous monitoring of the healing progression and autonomous operation of the system throughout the experiment. The active fixator system was implemented on a double osteotomy model that shields the experimental fracture from the influence of the animal's functional loading. A force sensor was integrated into the fixator to continuously measure stiffness of the repair tissue as an indicator for healing progression. A dedicated control unit was developed that allows programing of different loading protocols which are later executed autonomously by the active fixator. To verify the feasibility of the system, it was implanted in two sheep with different loading protocols, mimicking immediate and delayed weight-bearing, respectively. The implanted devices operated according to the programmed protocols and delivered seamless data over the whole course of the experiment. The in vivo trial confirmed the feasibility of the system. Hence, it can be applied in further preclinical studies to better understand the influence of mechanical conditions on fracture healing.

Severity of Complications after Locking Plate Osteosynthesis in Distal Femur Fractures.

Background: Locked plating for distal femur fractures is widely recommended and used. We systematically reviewed clinical studies assessing the benefits and harms of fracture fixation with locked plates in AO/OTA Type 32 and 33 femur fractures. Methods: A comprehensive literature search of PubMed, Embase, Cinahl, Web of Science, and the Cochrane Database was performed. The studies included randomized and non-randomized clinical trials, observational studies, and case series involving patients with distal femur fractures. Studies of other fracture patterns, studies conducted on children, pathological fractures, cadaveric studies, animal models, and those with non-clinical study designs were excluded. Results: 53 studies with 1788 patients were found to satisfy the inclusion and exclusion criteria. The most common harms were nonunion (14.8%), malunion (13%), fixation failure (5.3%), infection (3.7%), and symptomatic implant (3.1%). Time to full weight-bearing ranged from 5 to 24 weeks, averaging 12.3 weeks. The average duration of follow-up was 18.18 months, ranging from 0.5 to 108 months. Surgical time ranged between 40 and 540 min, with an average of 141 min. The length of stay in days was 12.7, ranging from 1 to 61. The average plate length was ten holes, ranging from 5 to 20 holes. Conclusion: This review aimed to systematically synthesize the available evidence on the risk associated with locked plating osteosynthesis in distal femur fractures. Nonunion is the most common harm and is the primary cause of reoperation. The overall combined risk of a major and critical complication (i.e., requiring reoperation) is approximately 20%.

Convergence of scaffold-guided bone regeneration principles and microvascular tissue transfer surgery.

A preclinical evaluation using a regenerative medicine methodology comprising an additively manufactured medical-grade ε-polycaprolactone ß-tricalcium phosphate (mPCL-TCP) scaffold with a corticoperiosteal flap was undertaken in eight sheep with a tibial critical-size segmental bone defect (9.5 cm3, M size) using the regenerative matching axial vascularization (RMAV) approach. Biomechanical, radiological, histological, and immunohistochemical analysis confirmed functional bone regeneration comparable to a clinical gold standard control (autologous bone graft) and was superior to a scaffold control group (mPCL-TCP only). Affirmative bone regeneration results from a pilot study using an XL size defect volume (19 cm3) subsequently supported clinical translation. A 27-year-old adult male underwent reconstruction of a 36-cm near-total intercalary tibial defect secondary to osteomyelitis using the RMAV approach. Robust bone regeneration led to complete independent weight bearing within 24 months. This article demonstrates the widely advocated and seldomly accomplished concept of "bench-to-bedside" research and has weighty implications for reconstructive surgery and regenerative medicine more generally.

Femoral Component Rotation in Total Knee Arthroplasty Using a Tibia-First, Gap-Balancing, "Functional Alignment" Technique.

BACKGROUND: The purpose of this study was to describe the femoral component rotation in total knee arthroplasty (TKA) using a tibia-first, gap-balancing, "functional alignment" technique. METHODS: Ninety-seven patients with osteoarthritis received a TKA using computer navigation. The tibial resection was performed according to the kinematic alignment (KA) principles, while the femoral rotation was set according to the gap-balancing technique. Preoperative MRIs and intraoperative resection depth data were used to calculate the following rotational axes: the transepicondylar axis (TEA), the posterior condylar axis (PCA) and the prosthetic posterior condylar axis (rPCA). The angles between the PCA and the TEA (PCA/TEA), between the rPCA and the PCA (rPCA/PCA) and between the rPCA and the TEA (rPCA/TEA) were measured. Data regarding patellar maltracking and PROMs were collected for 24 months postoperatively. RESULTS: The mean PCA/TEA, rPCA/TEA and rPCA/PCA angles were -5.1° ± 2.1°, -4.8° ± 2.6° and -0.4° ± 1.7°, respectively (the negative values denote the internal rotation of the PCA to the TEA, rPCA to TEA and rPCA to PCA, respectively). There was no need for lateral release and no cases of patellar maltracking. CONCLUSIONS: A tibia-first, gap-balancing, "functional alignment" approach allows incorporating a gap-balancing technique with kinematic principles. Sagittal complexities in the proximal tibia (variable medial and lateral slopes) can be accounted for, as the tibial resection is completed prior to setting the femoral rotation. The prosthetic femoral rotation is internally rotated relative to the TEA, almost parallel to the PCA, similar to the femoral rotation of the KA-TKA technique. This technique did not result in patellar maltracking.

Treatment of peroneal tendon dislocation and coexisting medial and lateral ligamentous laxity in the ankle joint.

PURPOSE: Acute dislocation of the peroneal tendon is caused by massive combined flexion-torsion trauma supported by preexisting ligamentous laxity of the ankle joint. This study aimed to investigate the clinical outcome of combined treatment of peroneal tendon dislocation and lateral and medial ligamentous laxity. METHODS: Between 2005 and 2007, forty-two patients with peroneal tendon dislocation and coexisting ligamentous laxity were treated. The superior extensor retinaculum was reconstructed using anchor technique and periosteal flap repair, whereas the preexisting ligamentous laxity with regard to the extensor inferior retinaculum was addressed using anchor reconstruction. All patients underwent arthroscopy prior to surgery. Thirty-eight of a total of 42 patients (aged 17-31) completed the 24-month follow-up. Clinical and arthroscopic examination was accomplished consistently by always the same two surgeons. Postoperative follow-up comprised clinical evaluation after 3, 6, 12 and 24 months. RESULTS: Clinical results showed a significant (P<0.0001) increase in the AOFAS-Hindfoot Score as an often used but not validated outcome measure, as well as a significant decrease in the Visual Analogue Scale and in the internal and external rotation, after 3 months. The clinical outcome was confirmed at the 6-, 12- and 24-months measuring points. No dislocation of the peroneal tendon recurred within the 24-month follow-up. Subjective patient satisfaction was stated as high. CONCLUSIONS: Combined treatment of peroneal tendon dislocation and coexisting lateral and medial ligamentous laxity in the ankle joint following arthroscopy results in good clinical outcome and high patient satisfaction. LEVEL OF EVIDENCE: Case series, Level IV.

Combined medial and lateral anatomic ligament reconstruction for chronic rotational instability of the ankle.

BACKGROUND: This study aimed to extend knowledge on the arthroscopic evaluation of the unstable ankle joint and the outcome of ligament reconstruction on rotational instability. In contrast to previous studies, we investigated the combined repair of lateral and medial ligaments. METHODS: Ninety-six patients underwent medial and lateral ligament reconstruction between 2006 and 2008, 81 of whom, with a mean age of 31.9 (range, 14 to 44) years, completed the 12-month followup and were therefore included in this study (Table 1). Clinical, radiographic, and concomitant arthroscopic examination was performed prior to the ligament stabilization. Postoperative followup included clinical and radiographic evaluation after 3, 6, and 12 months. RESULTS: Arthroscopy showed a lesion of the anterior fibulotalar ligament (AFTL), calcaneofibular ligament (CFL), and tibiocalcanear ligament (TCL) (Deep part of deltoid ligament complex) in 67 patients. An avulsion of the proximal insertion point of the ATTL was additionally found in 14 cases. Clinical results 3 months after surgery showed a significant increase in the AOFAS-Hindfoot Score as well as a significant decrease of the Visual Analogue-Scale for pain (VAS) (p < 0.0001). This outcome persisted at the 12-month examination. CONCLUSION: Rotational instability of the ankle joint in most cases has an injury of the lateral ligaments and a component of the deltoid, the TCL, but rarely with a combined lesion of the TCL and the anterior tibiotalar ligament (ATTL) (Superficial part of deltoid ligament complex). The combined lateral and medial ligament reconstruction with an anchor technique had a good clinical outcome with high patient satisfaction with few complications.

Acute compartment syndrome in children: a case series in 24 patients and review of the literature.

Trauma-associated acute compartment syndrome (ACS) of the extremities is a well-known complication in adults. There are only a handful of articles that describe the symptoms, the diagnostic procedure and treatment of ACS in children. The aim of this study was to analyse the diagnostic procedures in children compared to adolescents with ACS to obtain evidence for the diagnosis, treatment and outcome of children with ACS. Twenty-four children and adolescents with ACS have been treated at the Department of Trauma Surgery of the Medical University of Vienna, Austria. Two age-related groups were investigated to compare the diagnostic and therapeutic algorithm: group A comprising children aged 2-14 years (n = 12) and group B comprising adolescents aged 15-18 years (n = 12). Patient characteristics, diagnosis and therapy-associated data, complications and clinical outcome were analysed. In both groups we found fractures in most of our patients (n = 19) followed by contusion of the soft tissues (n = 3). In group A most of our patients were injured as pedestrians in car accidents (n = 5) followed by low-energy blunt trauma (n = 3). The most common region of injury and traumatic ACS was the lower leg (n = 7) followed by the feet (n = 3). For fracture stabilisation most of the patients (n = 6) received an external fixator. The mean time from admission to the fasciotomy was 27.9 hours. In four patients a compartment pressure measurement was performed with pressure levels from 30 to 75 mmHg. A histological examination of soft tissue was performed in five patients. From fasciotomy to definitive wound closure 2.4 operations were necessary. The mean hospital stay was 18.9 days. In group B most of our patients had a motorcycle accident (n = 5). The most common region for traumatic ACS in this group was also the lower leg (n = 9). In most of the patients (n = 6) intramedullary nails could be implanted. The mean time from admission to the fasciotomy was 27.1 hours. In six patients a compartment pressure measurement was performed with pressures from 25 to 90 mmHg. In five patients a histological examination was performed. From fasciotomy to definitive wound closure 2.3 operations were necessary. The mean hospital stay was 18.4 days. Secondary fasciotomy closure was performed in all cases. A split-skin graft was only necessary in three patients (13%). We avoided primary closure in the same setting when the fasciotomy was performed. Thus, we found no difference between the two groups in the diagnostic procedures, the indication for fasciotomy, the number of operations needed from fasciotomy to definitive wound closure, time of hospitalisation and clinical outcome. The rate of permanent complications was 4.2% (one patient from group A), which means that nearly all patients experienced full recovery after fasciotomy. ACS represents a surgical emergency and the indication should be determined early even in doubtful cases to avoid complications.

Short-Term Bone Healing Response to Mechanical Stimulation-A Case Series Conducted on Sheep.

It is well known that mechanical stimulation promotes indirect fracture healing by triggering callus formation. We investigated the short-term response of healing tissue to mechanical stimulation to compare the changes in tissue stiffness during stimulation and resting phases in a preclinical case-series. Four sheep underwent a tibial osteotomy and were instrumented with a custom-made active fixator which applied a mechanical stimulation protocol of 1000 cycles/day, equally distributed over 12 h, followed by 12 h of rest. During each cycle, a surrogate metric for tissue stiffness was measured, enabling a continuous real-time monitoring of the healing progression. A daily stiffness increase during stimulation and an increase during resting were evaluated for each animal. One animal had to be excluded from the evaluation due to technical reasons. For all included animals, the stiffness began to increase within the second week post-op. A characteristic pattern was observed during daily measurements: the stiffness dropped considerably within the first stimulation cycles followed by a steady rise throughout the rest of the stimulation phase. However, for all included animals, the average daily stiffness increase within the first three weeks post operation was larger during resting than during stimulation (Sheep I: 16.9% vs. -5.7%; Sheep II: 14.7% vs. -1.8%; Sheep III: 8.9% vs. 1.6%). A continuous measurement of tissue stiffness together with a controlled fracture stimulation enabled the investigation of the short-term effects of specific stimulatory parameters, such as resting periods. Resting was identified as a potentially determining factor for bone healing progression. Optimizing the ratio between stimulation and resting may contribute to more robust fracture healing in the future.

Comparison of intra-articular administration of adenosine, lidocaine and magnesium solution and tranexamic acid for alleviating postoperative inflammation and joint fibrosis in an experimental model of knee arthroplasty.

BACKGROUND: Dysregulated inflammatory responses are implicated in the pathogenesis of joint stiffness and arthrofibrosis following total knee arthroplasty (TKA). The purpose of this study was to compare the effects of intra-articular (IA) administration of tranexamic acid (TXA), an anti-fibrinolytic commonly used in TKA, and ALM chondroprotective solution on postoperative inflammation and joint tissue healing in a rat model of knee implant surgery. METHODS: Male Sprague-Dawley rats (n = 24) were randomly divided into TXA or ALM treatment groups. The right knee of each rat was implanted with titanium (femur) and polyethylene (tibia) implants. An IA bolus (0.1 ml) of TXA or ALM was administered after implantation and capsule closure, and before skin closure. Postoperative coagulopathy, haematology and systemic inflammatory changes were assessed. Inflammatory and fibrotic markers were assessed in joint tissue, 28 days after surgery. RESULTS: Haemostasis was comparable in animals treated with TXA or ALM after knee implant surgery. In contrast to ALM-treated animals, systemic inflammatory markers remained elevated at day 5 (IL-6, IL-12, IL-10, platelet count) and day 28 (IL-1ß, IL-10) following surgery in TXA-treated animals. At day 28 following surgery, the extension range of motion of operated knees was 1.7-fold higher for ALM-treated animals compared to the TXA group. Key inflammatory mediators (NF-κB, IL-12, IL-2), immune cell infiltration (CD68+ cells) and markers of fibrosis (α-SMA, TGF-ß) were also lower in capsular tissue of ALM-treated knees at day 28. CONCLUSION: Data suggest that IA administration of ALM is superior to TXA for reducing postoperative systemic and joint inflammation and promoting restoration of healthy joint tissue architecture in a rat model of TKA. Further studies are warranted to assess the clinical translational potential of ALM IA solution to improve patient outcomes following arthroplasty.

Computer-Assisted Technologies in Arthroplasty: Navigating Your Way Today.

Computer-assisted technologies that are used in arthroplasty include navigation, image-derived instrumentation (IDI), and robotics. Computer-assisted navigation improves accuracy and allows for real-time assessment of component positioning and soft-tissue tension. It is not clear whether the implementation of these technologies improves the clinical outcome of surgery. High cost and time demands have prevented the global implementation of computer-assisted technologies.

Biomechanical comparison of knotless vs. knotted suture anchors in the acetabular rim with respect to bone density.

BACKGROUND: Acetabular labral tears are managed with suture anchors providing good clinical outcomes. Knotless anchors are easier to use and have a quicker insertion time compared to knotted anchors. The purpose of this study was to compare the biomechanical behavior of two different anchor designs (knotted vs. knotless) in ultimate load testing in correlation with bone density in the acetabular rim. METHODS: Eighteen knotted Bio-FASTak and seventeen knotless PushLock anchors (both: Arthrex Inc., Naples, FL, USA) were inserted in the rims of two human acetabula, with known bone density distribution. The anchors were subjected to load-to-failure tests. Anchors were additionally tested in solid polyurethane foam with defined densities. FINDINGS: The Bio-FASTak group showed higher survival rates at 1, 2, and 3 mm displacement and was able to withstand significantly higher loads at 3 mm displacement (p = 0.031). There was no statistically significant difference in stiffness (p = 0.087), yield- (p = 0.190), and ultimate load (p = 0.222) between the two groups. Only the PushLock group showed correlation between bone volume over total volume (BV/TV) and stiffness (R = 0.750, p = 0.086) and between BV/TV and yield load (R = 0.838, p = 0.037). Experiments on solid polyurethane foam confirmed the correlation between the mechanical properties and tissue density for the same anchor. INTERPRETATION: PushLock shows similar biomechanical properties to the Bio-FASTak, but eliminates knot tying and potentially abrasive knots. In addition, biomechanical properties of the PushLock are governed by local bone density.

A preclinical large-animal model for the assessment of critical-size load-bearing bone defect reconstruction.

Critical-size bone defects, which require large-volume tissue reconstruction, remain a clinical challenge. Bone engineering has the potential to provide new treatment concepts, yet clinical translation requires anatomically and physiologically relevant preclinical models. The ovine critical-size long-bone defect model has been validated in numerous studies as a preclinical tool for evaluating both conventional and novel bone-engineering concepts. With sufficient training and experience in large-animal studies, it is a technically feasible procedure with a high level of reproducibility when appropriate preoperative and postoperative management protocols are followed. The model can be established by following a procedure that includes the following stages: (i) preoperative planning and preparation, (ii) the surgical approach, (iii) postoperative management, and (iv) postmortem analysis. Using this model, full results for peer-reviewed publication can be attained within 2 years. In this protocol, we comprehensively describe how to establish proficiency using the preclinical model for the evaluation of a range of bone defect reconstruction options.

Early mechanical stimulation only permits timely bone healing in sheep.

Bone fracture healing is sensitive to the fixation stability. However, it is unclear which phases of healing are mechano-sensitive and if mechanical stimulation is required throughout repair. In this study, a novel bone defect model, which isolates an experimental fracture from functional loading, was applied in sheep to investigate if stimulation limited to the early proliferative phase is sufficient for bone healing. An active fixator controlled motion in the fracture. Animals of the control group were unstimulated. In the physiological-like group, 1 mm axial compressive movements were applied between day 5 and 21, thereafter the movements were decreased in weekly increments and stopped after 6 weeks. In the early stimulatory group, the movements were stopped after 3 weeks. The experimental fractures were evaluated with mechanical and micro-computed tomography methods after 9 weeks healing. The callus strength of the stimulated fractures (physiological-like and early stimulatory) was greater than the unstimulated control group. The control group was characterized by minimal external callus formation and a lack of bone bridging at 9 weeks. In contrast, the stimulated groups exhibited advanced healing with solid bone formation across the defect. This was confirmed quantitatively by a lower bone volume in the control group compared to the stimulated groups.The novel experimental model permits the application of a well-defined load history to an experimental bone fracture. The poor healing observed in the control group is consistent with under-stimulation. This study has shown early mechanical stimulation only is sufficient for a timely healing outcome. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1790-1796, 2018.

Can MRI accurately detect pilon articular malreduction? A quantitative comparison between CT and 3T MRI bone models.

BACKGROUND: Pilon fracture reduction is a challenging surgery. Radiographs are commonly used to assess the quality of reduction, but are limited in revealing the remaining bone incongruities. The study aimed to develop a method in quantifying articular malreductions using 3D computed tomography (CT) and magnetic resonance imaging (MRI) models. METHODS: CT and MRI data were acquired using three pairs of human cadaveric ankle specimens. Common tibial pilon fractures were simulated by performing osteotomies to the ankle specimens. Five of the created fractures [three AO type-B (43-B1), and two AO type-C (43-C1) fractures] were then reduced and stabilised using titanium implants, then rescanned. All datasets were reconstructed into CT and MRI models, and were analysed in regards to intra-articular steps and gaps, surface deviations, malrotations and maltranslations of the bone fragments. RESULTS: Initial results reveal that type B fracture CT and MRI models differed by ~0.2 (step), ~0.18 (surface deviations), ~0.56° (rotation) and ~0.4 mm (translation). Type C fracture MRI models showed metal artefacts extending to the articular surface, thus unsuitable for analysis. Type C fracture CT models differed from their CT and MRI contralateral models by ~0.15 (surface deviation), ~1.63° (rotation) and ~0.4 mm (translation). CONCLUSIONS: Type B fracture MRI models were comparable to CT and may potentially be used for the postoperative assessment of articular reduction on a case-to-case basis.