We aimed to investigate the effect of Seprafilm®, a synthetic biomembran, on the intra-articular adhesion formation in an experimental arthrofibrosis model. Twenty male white rabbits were randomly allocated into two groups of 10 animals in each. A standard surgical procedure aiming at the development of arthrofibrosis and including medial parapatellar arthrotomy, lateral eversion of the patella, partial synovectomy and debridement of anterior of supracondylar area and patella joint surface by scalpel was performed on all rabbits' right knees. Group 1 rabbits served as controls, and in Group 2 rabbits a Seprafilm®, barrier placed into the described area. In both groups, after surgery, knee joint was immobilized by a no.5 wire suture passing from the ankle and groin and keeping the joint in 140° of flexion. At 6th week, all animals were sacrificed and adhesion formation was evaluated both macroscopically and histo-pathologically. All data were semi-quantified and analyzed statistically by Fisher's exact test. While all rabbits in control group displayed different rates of adhesion macroscopically (62.5% severe, 25% moderate, 12.5% mild), none in the study group had it. The average macroscopic adhesion score was 2.5 ± 0.75 in control group, and 0 in Seprafilm® group. Histopathologic evaluation also revealed microscopic adhesion in all rabbits in control group, but none in Seprafilm® group. Fibroblast proliferation in Seprafilm® group (100% mild) was significantly lower than in control group (62.5% severe, 37.5% moderate) (p<0.05). In conclusion, use of Seprafilm® as a mechanical barrier may be of value against the formation of arthrofibrosis in risky knees such as septic and traumatic ones

Aims. Despite long-standing dogma, a clear relationship between the timing of surgical irrigation and debridement (I&D) and the development of subsequent deep infection has not been established in the literature. Traditionally, I&D of an open fracture has been recommended within six hours of injury based on animal studies from the 1970s, however the clinical basis for this remains unclear. Using data from a multicentre randomized controlled trial of 2,447 open fracture patients, the primary objective of this secondary analysis is to determine if a relationship exists between timing of wound I&D (within six hours of injury vs beyond six hours) and subsequent reoperation rate for infection or healing complications within one year for patients with open limb fractures requiring surgical treatment. Methods. To adjust for the influence of patient and injury characteristics on the timing of I&D, a propensity score was developed from the dataset. Propensity-adjusted regression allowed for a matched cohort analysis within the study population to determine if early irrigation put patients independently at risk for reoperation, while controlling for confounding factors. Results were reported as odds ratios (ORs), 95% confidence intervals (CIs), and p-values. All analyses were conducted using STATA 14. Results. In total, 2,286 of 2,447 patients randomized to the trial from 41 orthopaedic trauma centres across five countries had complete data regarding time to I&D. Prior to matching, the patients managed with early I&D had a higher proportion requiring reoperation for infection or healing complications (17% vs 13%; p = 0.019), however this does not account for selection bias of more severe injuries preferentially being treated earlier. When accounting for propensity matching, early irrigation was not associated with reoperation (OR 0.71 (95% CI 0.47 to 1.07); p = 0.73). Conclusion. When accounting for other variables, late irrigation does not independently increase risk of reoperation. Cite this article: Bone Joint J 2021;103-B(6):1055–1062

Most animal studies indicate that early irrigation and debridement reduce infection after an open fracture. Unfortunately, these studies often do not involve antibiotics. Clinical studies indicate that the timing of initial debridement does not affect the rate of infection but these studies are observational and fraught with confounding variables. The purpose of this study was to control these variables using an animal model incorporating systemic antibiotics and surgical treatment. We used a rat femur model with a defect which was contaminated with Staphylococcus aureus and treated with a three-day course of systemic cefazolin (5 mg/kg 12-hourly) and debridement and irrigation, both of which were initiated independently at two, six and 24 hour time points. After 14 days the bone and hardware were harvested for separate microbiological analysis. No animal that received antibiotics and surgery two hours after injury had detectable bacteria. When antibiotics were started at two hours, a delay in surgical treatment from two to six hours significantly increased the development of infection (p = 0.047). However, delaying surgery to 24 hours increase the rate of infection, but not significantly (p = 0.054). The timing of antibiotics had a more significant effect on the proportion of positive samples than earlier surgery. Delaying antibiotics to six or 24 hours had a profoundly detrimental effect on the infection rate regardless of the timing of surgery. These findings are consistent with the concept that bacteria progress from a vulnerable planktonic form to a treatment-resistant biofilm

Aim To develop a militarily relevant complex extremity wounding model. Study Design Controlled laboratory study with New Zealand White Rabbits. Method Phase One: Injury Development. Under general anaesthesia, the flexor carpi ulnaris of the right forelimb was exposed and high energy, short duration impact delivered via drop test rig. Anaesthesia was maintained for three hours, the animal was recovered and saline soaked gauze and supportive bandaging applied. 48 hrs later, the animal was culled and muscle harvested for histological analysis. Analgesia was administered daily, animals checked by experienced staff at least twice daily and temperatures recorded by subcutaneous transponder. Phase Two: Contamination. Sequential groups of animals had inoculums of 1×102, 1×106 and 1×108/100μl of Staphylococcus aureus administered to the muscle immediately after injury. Animals were recovered as phase one. At 48 hours, animals were culled, muscle harvested and axillary lymph nodes sampled. Quantitative microbiological analysis was performed on the muscle. Results: Six animals given a loading of 0.5kg yielded consistent injury with 20% of the muscle becoming necrotic. Representative of injury from ballistic trauma, this was adopted as standard. Twenty-two subsequent animals were exposed to the injury and inoculated with the challenge doses. 1×106/100μl S.aureus provided the greatest consistency in recovered yield. There were no adverse effects on animal welfare and body temperatures were always within normal limits. Discussion. This model enables a consistent, contaminated soft tissue injury to be delivered in vivo. It will allow the investigation of complex wound management including wound coverage and fracture fixation

Aims. Little is known about the effect of haemorrhagic shock and resuscitation on fracture healing. This study used a rabbit model with a femoral osteotomy and fixation to examine this relationship. Materials and Methods. A total of 18 male New Zealand white rabbits underwent femoral osteotomy with intramedullary fixation with ‘shock’ (n = 9) and control (n = 9) groups. Shock was induced in the study group by removal of 35% of the total blood volume 45 minutes before resuscitation with blood and crystalloid. Fracture healing was monitored for eight weeks using serum markers of healing and radiographs. Results. Four animals were excluded due to postoperative complications. The serum concentration of osteocalcin was significantly elevated in the shock group postoperatively (p < 0.0001). There were otherwise no differences with regard to serum markers of bone healing. The callus index was consistently increased in the shock group on anteroposterior (p = 0.0069) and lateral (p = 0.0165) radiographs from three weeks postoperatively. The control group showed an earlier decrease of callus index. Radiographic scores were significantly greater in the control group (p = 0.0025). Conclusion. In a rabbit femoral osteotomy model with intramedullary fixation, haemorrhagic shock and resuscitation produced larger callus but with evidence of delayed remodelling. Cite this article: Bone Joint J 2018;100-B:1234–40

Compartment syndrome, a devastating consequence of limb trauma, is characterised by severe tissue injury and microvascular perfusion deficits. We hypothesised that leucopenia might provide significant protection against microvascular dysfunction and preserve tissue viability. Using our clinically relevant rat model of compartment syndrome, microvascular perfusion and tissue injury were directly visualised by intravital video microscopy in leucopenic animals. We found that while the tissue perfusion was similar in both groups (38.8% (standard error of the mean (. sem). 7.1). , 36.4. % (. sem. 5.7), 32.0% (. sem. 1.7), and 30.5% (. sem. 5.35) continuously-perfused capillaries at 45, 90, 120 and 180 minutes compartment syndrome, respectively versus 39.2% (. sem. 8.6), 43.5% (. sem. 8.5). , . 36.6% (. sem. 1.4) and 50.8% (. sem. 4.8) at 45, 90, 120 and 180 minutes compartment syndrome, respectively in leucopenia), compartment syndrome-associated muscle injury was significantly decreased in leucopenic animals (7.0% (. sem. 2.0), 7.0%, (. sem. 1.0), 9.0% (. sem. 1.0) and 5.0% (. sem. 2.0) at 45, 90, 120 and 180 minutes of compartment syndrome, respectively in leucopenia group versus 18.0% (. sem. 4.0), 23.0% (. sem. 4.0), 32.0% (. sem. 7.0), and 20.0% (. sem. 5.0) at 45, 90, 120 and 180 minutes of compartment syndrome in control, p = 0.0005). This study demonstrates that the inflammatory process should be considered central to the understanding of the pathogenesis of cellular injury in compartment syndrome. Cite this article: Bone Joint J 2015;97-B:539–43

Aims

Tobacco, in addition to being one of the greatest public health threats facing our world, is believed to have deleterious effects on bone metabolism and especially on bone healing. It has been described in the literature that patients who smoke are approximately twice as likely to develop a nonunion following a non-specific bone fracture. For clavicle fractures, this risk is unclear, as is the impact that such a complication might have on the initial management of these fractures.

INTRODUCTION. Surgical correction of spinal deformities in the growing child can be applied with or without fusion. Sublaminar wiring, first described by Luque, allows continuation of growth of the non-fused spine after correction of the deformity. Neurological complications and wire breakage are the main clinical problems during the introduction and removal of currently used sublaminar wires. In this pilot study a posterior hybrid construction with the use of a medical-grade UHMWPE (Dyneema Purity®) sublaminar wire was assessed in an ovine model. We hypothesized that such a hybrid construction can safely replace current titanium laminar wires, while providing sufficient stability of the non-fused spinal column with preservation of growth. MATERIALS AND METHODS. This study included 6 Tesselaar sheep, age 7±2months. Two pedicle screws (Legacy system, Medtronic) were placed at lumbar level. Four consecutive laminae were attached to two titanium bars (4.5 mm) using 3 mm diameter UHMWPE (Dyneema Purity®) on the left side and 5 mm diameter on the right side. The sublaminar wires were fixed with a double loop sliding knot and tightened with a tensioning device. As a control, in one animal titanium sublaminar wires (Atlas cable, Medtronic) were applied. After sacrifice the spine of the animals was harvested. Radiographs were taken and CT scans were performed. The vertebrae were dissected and placed in formaldehyde for macroscopic and histological evaluation. RESULTS. The animals were sacrificed after a (minimal) postoperative period of 15 weeks. One animal developed a wire fistula and one animal died the first postoperative day due to complications of the anesthesia. None of the 3 or 5 mm knots loosened and no neurological complications occurred. An average of 8.7 mm growth was seen over the segment operated on. Computed tomography confirmed the preserved stability. Even though no decortication was performed, variable bone bridges with fused levels were seen on CT. Macroscopic and histological analysis showed no inflammation at lamina and dura levels containing Dyneema Purity®, with the exception of the case with the fistula where it was observed locally. DISCUSSION. This pilot animal model study shows that the UHMWPE laminar wire made by Dyneema Purity® has good handling and tensioning properties and can provide sufficient stability in fusionless spinal instrumentation while allowing substantial growth. The examined model showed to be a feasible spinal study model, without occurrence of neurological problems. Reactive periostal bone formation with fusion levels led to some restrictions in this model. In the future it will be necessary to test the described construction in a large animal scoliosis model

Since osteoimmunology is gaining increasingly interest and evidence for involvement of complement in bone biology was found, the role of complement in bone biology and fracture healing was evaluated. After characterizing the bone phenotype, a fracture healing experiment with C3- and C5- deficient mice was performed. After osteotomy of the right femur and external fixation, healing was analyzed after 1, 3, 7 and 21 days. Bone characterization revealed a reduced number of osteoclasts in C5-deficient animals with a significantly reduced resorption activity. While bone mineral density was significantly higher in complement-deficient strains, stiffness was significantly reduced. After 21 days of fracture healing, C5-deficient animals showed reduced stiffness and a smaller callus volume compared to controls. Interestingly, C3- more than C5-deficient animals showed reduced bone formation. Altogether, bone phenotype of complement-deficient animals resembles a mild form of osteopetrosis. This might be due to the resorption defect seen in C5-deficient mice. A reason for the minor involvement of C3-deficient mice compared to the C5-deficient animals could be the cross-talk between the coagulation cascade with side activation of complement factor C5 by thrombin. These results indicate for the first time an essential role of complement in bone biology and fracture healing. Future studies should focus on the molecular basis of complement involvement and the osteoclastic resorption defect

Aims

Ankle fractures are common injuries and the third most common fragility fracture. In all, 40% of ankle fractures in the frail are open and represent a complex clinical scenario, with morbidity and mortality rates similar to hip fracture patients. They have a higher risk of complications, such as wound infections, malunion, hospital-acquired infections, pressure sores, veno-thromboembolic events, and significant sarcopaenia from prolonged bed rest.

Objective. To assess the beneficial use of polypropylene mesh impregnated with vancomycin in an experimental model open fractures Gustilo IIIa in rabbits. Material and Method. We worked with 15 New Zeland White rabbits. All of them were carried out under general anaesthetic, a 5-cm incision longitudinal was made at the back of the right thigh. The femur was aproached and a fracture was performed with a shear, giving rise to a multifragment fracture. The wound remained open for 6 hours with the bone exposed, in a non-surgical ambient. Subsequently underwent surgical cleaning of the open fractures in two stages. The fracture was stabilized with an intramedular pin. The animals were sorted in 3 different therapeutic groups:. Group 1: (5 rabbits) without other treatment. Group 2: (5 rabbits) a polypropylene mesh was placed around the fracture. Group 3: (5 rabbits) a polypropylene mesh with vancomycin was placed around the fracture. The wound was closed with nylon stiches. Three weeks postoperative, the animals were intervened surgically under general anesthesia, after aseptic cure and placement of surgical fields, femoral bone biopsies, soft tissue and mesh were taken. The rabbits were sacrified. The samples were sent to pathology and bacteriology labs. Results. The bacteria isolated were as follows: Escherichia coli, Pasteurella multocida, Staphylococcus spp., Clostridium spp. Mamheinia spp. The Clostridium spp. is a common contaminant in the exposed fractures present in the environment. The Pasteurella mustocida is a microorganism present in the oral cavity of rabbits, as well as Escherichia coli is a germ present in the animal's digestive tract. Mannheimia spp. It is a beta-hemolytic organism, found in the nasal flora of these animals and their pathological role is not elucidated. Staphylococcus spp. is a germ that is found in the normal flora of the animals skin. Group 1 showed a relative risk for an infection. For Group 2 the relative risk was substantially greater than 1.4, while in Group 3, the relative risk was 0.6, significantly lower than the previous two groups. The results have shown a beneficial effect of the use of impregnated polypropylene mesh with vancomycin in this animal group. Conclusion. The use of polypropylene meshes with vancomycin could be useful in the treatment of muscle and ligamentary deficits in patients with open fractures Gustillo IIIa

Objectives. One commonly used rat fracture model for bone and mineral research is a closed mid-shaft femur fracture as described by Bonnarens in 1984. Initially, this model was believed to create very reproducible fractures. However, there have been frequent reports of comminution and varying rates of complication. Given the importance of precise anticipation of those characteristics in laboratory research, we aimed to precisely estimate the rate of comminution, its importance and its effect on the amount of soft callus created. Furthermore, we aimed to precisely report the rate of complications such as death and infection. Methods. We tested a rat model of femoral fracture on 84 rats based on Bonnarens’ original description. We used a proximal approach with trochanterotomy to insert the pin, a drop tower to create the fracture and a high-resolution fluoroscopic imager to detect the comminution. We weighed the soft callus on day seven and compared the soft callus parameters with the comminution status. Results. The mean operating time was 34.8 minutes (. sd. 9.8). The fracture was usable (transverse, mid-shaft, without significant comminution and with displacement < 1 mm) in 74 animals (88%). Of these 74 usable fractures, slight comminution was detected in 47 (63%). In 50 animals who underwent callus manipulation, slight comminution (n = 32) was statistically correlated to the amount of early callus created (r = 0.35, p = 0.015). Two complications occurred: one death and one deep infection. Conclusions. We propose an accurate description of comminution and complications in order to improve experiments on rat femur fracture model in the field of laboratory research. Cite this article: Bone Joint Res 2013;2:149–54

Our unpublished data has indicated that the perivascular stem cells (PSCs) have increased chondrogenic potential compared to mesenchymal stem cells (MSCs) derived in culture. There has been a recent change in the theory that stem cells work by a paracrine effect rather than differentiation. There are minimal data demonstrating the persistence of implanted stem cells when used for engraftment. This study aimed to develop an autologous large animal model for perivascular stem cells as well as to determine if cells were retained in the articular cartilage defects. The reactivity of anti-human and anti-ovine antibodies was ascertained using immunohistochemistry and fluorescence-activated cell sorting (FACS). A panel of antibodies were combined and used to identify and purify pericytes (CD34-CD45-CD146+) and adventitial cells (CD34+CD45-CD146-) using FACS. The purified cells were cultured and their identity checked using FACS. These cultured cells demonstrated osteogenic, adipogenic and chondrogenic potential. Autologous ovine PSCs (oPSCs) were isolated, cultured and transfected using a GFP virus. The transfection rate was 88%. The cells were implanted into an articular cartilage defect on the medial femoral condyle using a hydrogel, four weeks following implantation the condyle was explanted and confocal laser scanning microscopy demonstrated the presence of oPSCs in the defect. Histology did not demonstrate any repair tissue at this early time point. These data have confirmed the viability our large animal model and that the implanted stem cells were retained in the defect four weeks following implantation

Systemic antibiotics reduce infection in open fractures. Local delivery of antibiotics can provide higher doses to wounds without toxic systemic effects. This study investigated the effect on infection of combining systemic with local antibiotics via polymethylmethacrylate (PMMA) beads or gel delivery. An established Staphylococcus aureus contaminated fracture model in rats was used. Wounds were debrided and irrigated six hours after contamination and animals assigned to one of three groups, all of which received systemic antibiotics. One group had local delivery via antibiotic gel, another PMMA beads and the control group received no local antibiotics. After two weeks, bacterial levels were quantified. . Combined local and systemic antibiotics were superior to systemic antibiotics alone at reducing the quantity of bacteria recoverable from each group (p = 0.002 for gel; p = 0.032 for beads). There was no difference in the bacterial counts between bead and gel delivery (p = 0.62). . These results suggest that local antibiotics augment the antimicrobial effect of systemic antibiotics. Although no significant difference was found between vehicles, gel delivery offers technical advantages with its biodegradable nature, ability to conform to wound shape and to deliver increased doses. Further study is required to see if the gel delivery system has a clinical role. Cite this article: Bone Joint J 2015;97-B:1423–7

Introduction. Following tear of its tendon, the muscle undergoes retraction, atrophy and fatty infiltration. These changes are inevitable and considered irreversible and limit the potential of successful repair of musculotendinous units. It was the purpose of this study to test the hypothesis that administration of anabolic steroids can prevent these muscular changes following experimental supraspinatus tendon release in the rabbit. Methods. The supraspinatus tendon was experimentally released in 20 New Zealand rabbits. Musculotendinous retraction was monitored over a period of 6 weeks. The seven animals in group I had no additional intervention, six animals in group II had local and seven animals in group III had systemic administration of nandrolone deconate during six weeks of retraction. At the time of sacrifice, in-vivo muscle performance as well as radiologic and histologic muscle changes were investigated. Results. Supraspinatus retraction was significantly higher in group I (1.8 ± 0.2cm) than in group II (1.5 ± 0.3cm, p = 0.044) or III (1.2 ± 0.3cm, p = 0.001). The reduction in radiological cross sectional area, as a measure for atrophy, was significant in groups I (p = 0.013) and II (p = 0.030) and insignificant in group III (p = 0.149). Histologically, there was no fatty infiltration in the treated groups II (p = 1.000) and III (p = 0.812), but in the untreated group I (p = 0.0312). The work of the respective muscle during one standardized contraction with supramaximal stimulation decreased markedly in groups I (p = 0.056) and II (p = 0.0528), and also but less in group III (p = 0.23). Conclusion. This is the first documentation of prevention of important muscle alterations after chronic retraction of the musculotendinous unit caused by rotator cuff tear. Nandrolone deconate administration in the post tendon release phase prevented fatty infiltration of the supraspinatus muscle and reduced functional muscle impairment caused by myo-tendinous retraction

Aims

Our objective was to conduct a systematic review and meta-analysis, to establish whether differences arise in clinical outcomes between autologous and synthetic bone grafts in the operative management of tibial plateau fractures.

Objectives. Small animal models of fracture repair primarily investigate indirect fracture healing via external callus formation. We present the first described rat model of direct fracture healing. Methods. A rat tibial osteotomy was created and fixed with compression plating similar to that used in patients. The procedure was evaluated in 15 cadaver rats and then in vivo in ten Sprague-Dawley rats. Controls had osteotomies stabilised with a uniaxial external fixator that used the same surgical approach and relied on the same number and diameter of screw holes in bone. Results. Fracture healing occurred without evidence of external callus on plain radiographs. At six weeks after fracture fixation, the mean stress at failure in a four-point bending test was 24.65 N/mm. 2. (. sd. 6.15). Histology revealed ‘cutting-cones’ traversing the fracture site. In controls where a uniaxial external fixator was used, bone healing occurred via external callus formation. Conclusions. A simple, reproducible model of direct fracture healing in rat tibia that mimics clinical practice has been developed for use in future studies of direct fracture healing

Aims

The modified Radiological Union Scale for Tibia (mRUST) fractures score was developed in order to assess progress to union and define a numerical assessment of fracture healing of metadiaphyseal fractures. This score has been shown to be valuable in predicting radiological union; however, there is no information on the sensitivity, specificity, and accuracy of this index for various cut-off scores. The aim of this study is to evaluate sensitivity, specificity, accuracy, and cut-off points of the mRUST score for the diagnosis of metadiaphyseal fractures healing.

Fracture repair occurs by two broad mechanisms: direct healing, and indirect healing with callus formation. The effects of bisphosphonates on fracture repair have been assessed only in models of indirect fracture healing. A rodent model of rigid compression plate fixation of a standardised tibial osteotomy was used. Ten skeletally mature Sprague–Dawley rats received daily subcutaneous injections of 1 µg/kg ibandronate (IBAN) and ten control rats received saline (control). Three weeks later a tibial osteotomy was rigidly fixed with compression plating. Six weeks later the animals were killed. Fracture repair was assessed with mechanical testing, radiographs and histology. The mean stress at failure in a four-point bending test was significantly lower in the IBAN group compared with controls (8.69 Nmm. -2. (. sd. 7.63) vs 24.65 Nmm. -2. (. sd. 6.15); p = 0.017). On contact radiographs of the extricated tibiae the mean bone density assessment at the osteotomy site was lower in the IBAN group than in controls (3.7 mmAl (. sd. 0.75) vs 4.6 mmAl (. sd. 0.57); p = 0.01). In addition, histological analysis revealed progression to fracture union in the controls but impaired fracture healing in the IBAN group, with predominantly cartilage-like and undifferentiated mesenchymal tissue (p = 0.007). . Bisphosphonate treatment in a therapeutic dose, as used for risk reduction in fragility fractures, had an inhibitory effect on direct fracture healing. We propose that bisphosphonate therapy not be commenced until after the fracture has united if the fracture has been rigidly fixed and is undergoing direct osteonal healing. Cite this article: Bone Joint J 2013;95-B:1263–8

There is evidence that fracture healing is delayed in severely injured patients. We recently demonstrated that a blunt chest trauma, which induced posttraumatic systemic inflammation, considerably impaired fracture healing in rats. Because the complement anaphylatoxin C5a is an important trigger of systemic inflammation, we tested the hypothesis, whether the impairment of fracture healing observed after a severe trauma resulted from systemically activated complement. 16 male Wistar rats received a thoracic trauma and a femur osteotomy stabilized by an external fixator. Immediately and 12 h after the trauma, half of the animals received a C5aR-antagonist to prevent the C5a-dependent systemic inflammation. Control rats received a nonsense peptide, which does not provoke any biological effect. The animals were killed after 35 days and the calli were analyzed by three point bending testing, μCT and histomorphometry. Statistics: Mann-Whitney U test, level of significance to p<0.05. The treatment with the C5aR-antagonist increased flexural rigidity significantly by 55%, improved bony bridging of the fracture gap and led to a slightly larger and qualitatively improved callus as evaluated by μCT and histological measurements. This study shows, that the immunomodulation by a C5aR-antagonist significantly reduced the deleterious effects of a thoracic trauma on fracture healing. C5a could possibly represent a target to prevent delayed bone healing in patients with severe trauma