Objectives. External fixators are the traditional fixation method of choice for contaminated open fractures. However, patient acceptance is low due to the high profile and therefore physical burden of the constructs. An externalised locking compression plate is a low profile alternative. However, the biomechanical differences have not been assessed. The objective of this study was to evaluate the axial and torsional stiffness of the externalised titanium locking compression plate (ET-LCP), the externalised stainless steel locking compression plate (ESS-LCP) and the unilateral external fixator (UEF). Methods. A fracture gap model was created to simulate comminuted mid-shaft tibia fractures using synthetic composite bones. Fifteen constructs were stabilised with ET-LCP, ESS-LCP or UEF (five constructs each). The constructs were loaded under both axial and torsional directions to determine construct stiffness. Results. The mean axial stiffness was very similar for UEF (528 N/mm) and ESS-LCP (525 N/mm), while it was slightly lower for ET-LCP (469 N/mm). One-way analysis of variance (ANOVA) testing in all three groups demonstrated no significant difference (F(2,12) = 2.057, p = 0.171). There was a significant difference in mean torsional stiffness between the UEF (0.512 Nm/degree), the ESS-LCP (0.686 Nm/degree) and the ET-LCP (0.639 Nm/degree), as determined by one-way ANOVA (F(2,12) = 6.204, p = 0.014). A Tukey post hoc test revealed that the torsional stiffness of the ESS-LCP was statistically higher than that of the UEF by 0.174 Nm/degree (p = 0.013). No catastrophic failures were observed. Conclusion. Using the LCP as an external fixator may provide a viable and attractive alternative to the traditional UEF as its lower profile makes it more acceptable to patients, while not compromising on axial and torsional stiffness. Cite this article: B. F. H. Ang, J. Y. Chen, A. K. S. Yew, S. K. Chua, S. M. Chou, S. L. Chia, J. S. B. Koh, T. S. Howe. Externalised locking compression plate as an alternative to the unilateral external fixator: a biomechanical comparative study of axial and torsional stiffness. Bone Joint Res 2017;6:216–223. DOI: 10.1302/2046-3758.64.2000470

Ring frames have the advantage of allowing progressive correction. However, the available frames for complex deformities are heavy and bulky leading to poor compliance by patients. Also, the mounting procedure requires considerable expertise and skill. On the other hand, a unilateral external fixator has the advantages of less bulk and a lighter weight. Thus, it causes less disability and can achieve better patient compliance even with bilateral application. However, previous unilateral fixators have had various limitations with respect to deformity correction, such as restricted placement of hinges, restricted correction planes, and a limited range of correction angles. In addition, it was impossible to achieve progressive correction while fixation was maintained. To overcome these disadvantages of existing unilateral fixators, we developed a new fixator for gradual correction of multi-plane deformities including translational and rotation deformities. This unilateral external fixator is equipped with a universal bar link system. The link is constructed from three dials and two splines that are connecting the dials. The pin clamps are able to vary the direction of a pin cluster in the three dimensional planes. The system allows us to correct angulation, translation, rotation, and the combination of the above. In addition, open or closed hinge technique is available because the correction hinge can be placed right on the center of rotational angulation (CORA), or at any desired location, by adjusting the length of the link spline. By increasing the spline length, the virtual hinge can also be set far from the fixator. Gradual correction can be performed by rotating the three dials using a worm gear goniometer that is temporarily attached. A 3D reconstructed image of the bone is generated preoperatively. Preoperative planning can be done using this image. Mounting parameters are determined by postoperative AP and lateral computed radiography images. These postoperative images are matched with the pre-operative 3D CT image by 2D and 3D image registration. Then, the fixator can be virtually fixed to the bone. By performing virtual correction, it is possible to plan the correction procedure. The fixator is manipulated by rotating each of the three dials to the predetermined angles calculated by the software. Static load testing disclosed that the fixator could bear a load of 1700 N. No breakage or deformation of the fixator itself was recognized. Mechanical testing demonstrated that this new fixator has sufficient strength for full weight bearing, as well as sufficient fatigue resistance for repeated or prolonged use. The results of clinical application in patients with multi-plane femoral deformities were excellent, and correction with very small residual deformity was achieved in each plane

PURPOSE: There is an argument in the literature regarding the use of intramedullary nail or the external fixation followed by intramedullary nail in tibial fractures with severe damage of soft tissues, threatened compartment syndrome, open type IIIA fractures and in polytrauma patients. The purpose of this retrospective study was to evaluate the results of non-jointed external fixators as a definite treatment for these type of tibial shaft fractures. MATERIAL AND METHOD: 86 patients (91 tibial shaft fractures) were treated at the authors’ institute with a non-jointed external fixator. The mean patient age was 35 years (range, 15–80). There were 70 male and 16 female patients. The average time of surgery from the accident was 10 hours. The indications for application an external fixator was: severe damage of the soft tissues in 11 fractures, an incipient compartment syndrome in 12 fractures, open type III Gustilo fractures in 57, and 11 tibia fractures in polytrauma patients. According to AO classification 46 fractures were type A, 32 type B and 13 type C. RESULTS: The average follow up was 2.9 years (ranged, 1–5 years). The average operative time was 50 min. Complications included: 3 non-unions, 5 delayed unions, 1 malunions, 1 tibia shortening, 3 superficial infections of soft tissues in open fractures, 26 pin infections and 1 osteomyelitis in open fractures. In 2 patients fat embolism was diagnosed while pulmonary embolism was a complication in 2 patients. Deep venous thrombosis (DVT) developed in 5 patients. A re-operation was performed in 11 out of 91 fractures. Change of the method was necessary in 2 out of 91 fractures. The primary callus in 10 out of 91 fractures was due to the stiffness of the unilateral non-jointed external fixators and did not influence the final results. Mean time of fracture union for the open fractures that did not require change of the method nor bone graft was 25 weeks, while for the closed fractures was 18 weeks. The dynamization of the system and partial weight bearing was started at 6 weeks and all the patients had full weight bearing by the 12th week. CONCLUSION: The unilateral external fixators were the definite treatment in 88 out of 91 fractures. The unilateral external fixators can be used as a definite treatment for tibial shaft fractures in the majority of the cases. Re-operation or change of the method is unusual and must be performed only when there is a delay in callus formation

Segmental bone transport (SBT) with an external fixator has become a standard method for treatment of large bone defect. However, a long time-application of devices can be very troublesome and complications such as nonunion is sometimes seen at docking site. Although there have been several studies on SBT with large animal models, they were unsuitable for conducting drug application to improve SBT. The purpose of this study was to establish a bone transport model in mice. Six-month-old C57BL/6J mice were divided randomly into bone transport group (group BT) and an immobile control group (group EF). In each group, a 2-mm bone defect was created in the right femur. Group BT was reconstructed by SBT with external fixator (MouseExFix segment transport, RISystem, Switzerland) and group EF was fixed simply with unilateral external fixator (MouseExFix simple). In group BT, a bone segment was transported by 0.2 mm per day. Radiological and histological studies were conducted at 3 and 8 weeks after the surgery. In group BT, radiological data showed regenerative new bone consolidation at 8 weeks after the surgery, whereas high rate of nonunion was observed at the docking site. Histological data showed intramembranous and endochondral ossification. Group EF showed no bone union. In this study, experimental group showed good regenerative new bone formation and was similar ossification pattern to previous large animal models. Thus, the utilization of this bone defect mice model allows to design future studies with standardized mechanical conditions for analyzing mechanisms of bone regeneration induced by SBT

To report the results of the intramedullary skeletal kinetic distractor (iskd) in patients with established leg length discrepancy following lower limb trauma. 12 patients with significant leg length discrepancy (> 20mm) following lower limb trauma were operated on using the iskd nail between september 2004 and december 2007. patients were followed up clinically and radiologically at minimum 18 months (mean: 27months range: 18–24 months). 8 femurs and 4 tibias were operated using the iskd nail. all patient in the series had successful completed treatements. the average leg length discrepancy was 38mm (91mm–21mm) and the average gained length was 37mm (76m–22mm). radiological union and bone consolidation were slow to occur. early weight bearing was permitted allowing earlier functional capacity. 6 patients required additional operations; 3 manipulation under anaesthesia for failed lengthening and 3 bone grafting for poor regenerate, 1 patient required more than one additional operation. The iskd nail is an effective and reliable alternative technique for correcting leg length discrepancy in patients who have suffred lower limb trauma. it appears to mimic the results achieved with the use of a fine wire external fixator or a unilateral external fixator. the convenience of a fully implanted device is substantial. the complications are frequent but manageable with standard techniques

Purpose: We reviewed all isolated tibial shaft fractures treated by operative means, with focus on prolonged healing and infection. Design; Retrospective Case Control Study; level of evidence; Prognostic level III. Methods: Patients: 821 isolated tibial shaft fractures, with a drop-out of 5.6% Open fractures: 400 (grade I & II 280, grade IIIa,b,c 120) Type A,B fractures: 597 Type C fractures: 224 Skeletal Fixation Modes: Ex;Fix (unilateral-one plane): 192, UTN(Synthes): 337, Plate(LCDCP): 129, RTN(Synthes): 163. Outcome measurements: Union time, requirement for secondary treatment, and development of deep infection. Results: Infections: 94 (11,4%), Closed # which became infected: 21 (5%) Open # which became infected: 73 (18%) Ex.Fix: 56 (29%) Plate: 15 (12%) UTN: 16 (5%) RTN: 7 (5%) In a multiple logistic regression analysis, only Soft tissue damage had a statistical significant interference with the outcome infection (point estimate 0.117, 95% CI 0.053–0.262) Prolonged healing: 285 (34%)? Delayed union 191 ? Non-union 94 Closed fractures which develop a delayed healing: 56 (13%) Open fractures which develop a delayed healing: 135 (34%) Closed fractures which develop a non-union: 20 (5%) Open fractures which develop a non-union: 74 (19%) In a multiple logistic regression analysis, infection & fracture type had a statistical significant interference with the outcome prolonged healing. Conclusions: The use of an unilateral external fixator as a definitive treatment for tibial fractures is obsolete. For a contaminated tibial fracture the use of the UTN diminish the risk of infection. Looking for the healing time, UTN & Ex.Fix. are associated with a significant prolonged bone healing time

31 cases of high-energy proximal tibial fractures were retrospectively analysed. The series included 22 cases of Schatzker VI and 9 cases of proximal tibial extraarticular fractures. There were 7 females and 24 males, with average age being 45years(26–94). There were 12 open fractures ( 1 Gustilo grade1, 10 grade 3b and one 3c); while 19 cases had Tcherne’s grade 2–3 injury. 4 patients developed compartment syndromes requiring fasciotomy. All fractures were treated with preliminary ligamentotaxis using a unilateral external fixator. In addition, Open fractures underwent radical debridement with the one case of 3c requiring vascular reconstruction. CT scan was then done to assess the joint incongruity ,anatomy of the fracture, and to aid in decision making. The fractures were then fixed using percutaneous techniques and a circular external fixator. Minimal open reduction was resorted to in cases with significant joint depression. In all, 26 cases were managed using percutaneous techniques alone while 5 required minimal open reduction and screw fixation. Bone grafting was done in 6 cases and 11 required a plastics procedure for soft tissue reconstruction. The results were assessed using the radiological Rasmussen’s criteria and the clinically using he IKSS knee score. At a mean follow-up of 31mths, the mean time to metaphyseal union was 18weeks (6–25weeks);. 28 patients had good to excellent clinical scores, while 3 had a fair result. The radiologic assessment graded 12 cases as excellent and 19 as good. Complications included 2 cases with flap edge necrosis, 2 with severe pin tract sepsis, 1 with proximal DVT and one case with septic arthritis. We conclude that the above treatment protocol yields promising results, preserving good knee function without prejudicing future need for arthroplasty

31 cases of high-energy proximal tibial fractures were retrospectively analysed. The series included 22 cases of Schatzker VI and 9 cases of proximal tibial extraarticular fractures There were 7 females and 24 males, with average age being 45 years (26–94). There were 12 open fractures (1 Gustilo grade1, 10 grade 3b and one 3c); while 19 cases had Tcherne’s grade 2–3 injury. 4 patients developed compartment syndromes requiring fasciotomy. All fractures were treated with preliminary ligamentotaxis using a unilateral external fixator. In addition, open fractures underwent radical debridement with the one case of 3c requiring vascular reconstruction. CT scan was then done to assess the joint incongruity, anatomy of the fracture, and to aid in decision making. The fractures were then fixed using percutaneous technique and a circular external fixator. Minimal open reduction was resorted to in cases with significant joint depression. In all, 26 cases were managed using percutaneous techniques alone while 5 require minimal open reduction and screw fixation. Bone grafting was done in 6 cases and 11 required a plastics procedure for soft tissue reconstruction. The results were assessed using the radiological Rasmussen’s criteria and the clinically using the IKSS knee score. At a mean follow-up of 31mths, the mean time to metaphyseal union was 18 weeks (6–25 weeks); 28 patients had good to excellent clinical scores, while 3 had a fair result. The radiologic assessment graded 12 cases as excellent and 19 as good. Complications included 2 cases with flap edge necrosis, 2 with severe pin tract sepsis, 1 with proximal DVT and one case with septic arthritis. We conclude that the above treatment protocol yields promising results, preserving good knee function without prejudicing future need for arthroplasty

Aims An estimated 5–10% of fractures fail to heal adequately. Novel therapies in the treatment of problem fractures include the use of culture expanded cells. An animal model of delayed fracture union is required to parallel the clinical scenario so that variations in cell therapy techniques can be rapidly assessed. Material and Methods A simple unilateral external fixator was designed for use in the rat. The fixator was applied following open osteotomy of the femur and a reproducible externally fixated femoral fracture model was established (n=41). Fracture union was assessed by digital radiography, histology and biomechanical strength testing (four point bending) at weeks 4, 6 and 8. Histological examination was also undertaken at day 4 and weeks 1 and 2. A delayed union in the fracture model was created by periosteal and endosteal stripping (n=14). Radiography and biomechanical strength testing were performed at week 8. The use of cell therapy was tested in the delayed union model. Osteogenic cells were culture expanded for 6 weeks before re-implantation. Reimplantation was facilitated by the use of a drill hole through the fracture site . Animals were randomized to one of three groups – i) drill hole & cells in a carrier ii) drill hole & carrier only iii) no drill hole, cells or carrier. Results In the fracture model radiological and histological evidence of fracture union was apparent at week 6. Biomechanical testing showed a significant difference in load to failure and stiffness of the fracture between weeks 4 and 8 (p=0.009 and 0.008 respectively). There was also a significant difference in biomechanical properties between the fracture model and the delayed union model at week 8. Drilling with the injection of a carrier significantly improved the biomechanical properties (p=0.03) of a delayed union at week 14. Surprisingly this effect was negated by the introduction of cells. Conclusion A fracture and delayed union model in the rat has been established for the testing of cell therapy. The application of cell therapy to a delayed union has been less advantageous in improving union than expected. This prompts the need for further work required in optimising cell culture techniques and cell delivery

Introduction: Fusion of the knee joint should be the last option for salvage of infected total knee arthroplasty (TKA). Although knee arthrodesis implies lost of function, it is a successful treatment in eradicating the infection and in decreasing pain. External fixation compression devices have been an excellent method for gaining fusion but, there is no documentation about its ability for obtaining adequate limb alignment with a stable fusion of the knee joint. Material and Methods: We have retrospectively reviewed the results of knee arthrodesis after infection of TKA using an anteriorly placed unilateral external fixator. In addition, we have assessed patient self-satisfaction. Postoperative radiographs have been evaluated to digitally measure loss of femoral and tibial bone stock using Engh radiological classification. Moreover, we have quantified tibiofemoral alignment and the section of bony fusion. Fusion of the knee joint was assessed with CT. Patients were interviewed and pain was graded using a Visual Analog Scale (VAS) and self-satisfaction as well as current health status using the 12-item social function survey form (SF12). Results: From 1992 to 2003, 52 arthrodeses were done for treatment of infected TKA. The average age was 71 years (range, 37–83 years). Type III bone defect according with Engh classification, in femur and/or in tibia, was present in 50% of the patients. The average postoperative tibiofemoral alignment was 1.2° (SD 3.79). The mean time to fusion was 11.26 months (range, 3–30 months). Time to fusion was statistical related with severe bone loss and with the tibiofemoral contact section. The average score according VAS was 1.6 (SD 2.60). Conclusions: Knee arthrodesis using a monolateral external fixator for infected TKA is an effective method to control infection as well as to obtain knee fusion and pain relief. Severe bone loss, frequently present in infected TKA, was found to be the most relevant factor in achieving tibiofemoral union. The individual clinical result according to SF12 shows a lower quality of life both for physical and mental components compare with general population

Background & Objectives: The objective of this study was to develop a rat model of fracture repair. Fixation of experimental fractures is generally internal {Kirschner wire/intramedullary (IM) nail} or external (single/double plane devices). Internal fixation using the IM-fixated model of a standard closed fracture is well described in rats. However, nail insertion can disrupt fracture site morphology and limit x-ray analysis. We planned to create an externally fixated femoral model, to optimise our outcome measures and facilitate the further investigation of bone healing within the department. Methods: A simple four pin unilateral external fixator was designed and constructed from four stainless steel pins, secured to a stainless steel plate with nuts. Forty-one female Sprague-Dawley rats, (12–18wks), were used. Following anaesthesia the right femur was exposed and a mid-femoral osteotomy made prior to fixator application. Post-operative x-rays were taken to confirm reduction. Animals were assigned to groups for biomechanical strength testing (BST) or histology. Fifteen animals (fractured and contralateral limbs) were sacrificed at 4, 6 or 8 weeks for BST (four-point bending). Maximum load to failure was recorded and stiffness calculated from the load displacement curve obtained. Both parameters were standardised as a percentage of the contralateral limb. Twenty-five fractured limbs were used for histological analysis at day 4, and 1, 2, 4, 6 or 8 weeks. Results: Satisfactory reduction was confirmed in all animals post operatively and no complications were noted. Histological assessment at day 4 demonstrated a predominantly lymphocytic inflammatory response within the fracture haematoma. This was replaced with endosteal and periosteal new bone between weeks 1 and 2. Bridging of the fracture gap was seen at week 6. Stiffness and load to failure increased with increasing time. There was a statistically significant improvement in the percentage stiffness (p=0.035) and load to failure (p=0.012) between 4 and 8 weeks. Conclusion: A simple reproducible externally fixated rat model has been established and characterised by radiography, histology and four point bending. This model has since proven to be of value in the study of the role of lipid lowering and anti-inflammatory drugs as well as cell therapy on fracture repair

What was the question? The treatment of multi-injured patients requires initial stabilization of general conditions and vital parameters. The first stage in orthopedic management of the fractures in trauma involves stabilization of the bone segments to reduce blood loss and allow nursing. External fixators are fast, versatile and essential in the emergency situation in cases of multiple fractures, especially with soft tissue loss. According to damage control orthopedics (DCO) concepts, it is possible to replace an external fixator (EF) with internal synthesis (ORIF) after a period of time to reduce the risks of ORIF. However, surgery can be difficult to perform and pin sites can be the source of bone infection, in which the EF as a definitive treatment option may be considered. How did you answer the question? In trauma surgery, instability of the hardware, fractures near the joint, frame extending across the knee and the ankle, initial fixation was converted to definitive treatment with circular frames according to the Ilizarov method. Fourteen patients (2 female and 12 males; age 24 to 80 yrs, average age 43,4 y/o) were treated with various circular framses as definitive treatment: Ilizarov (2), Sheffield (7), Taylor Spatial Frame (TSF) (4) and TrueLok (1) between November 2002 and December 2007 in multiply injured patients with ISS > 20. Seven cases were femoral and seven tibial. The femoral group had four knee spanning fixator configurations and three unilateral external fixators. The tibial group had 4 unilateral frames, 1 hybrid EF, 1 across the knee EF and 1 across the ankle EF. Five patients had temporary femoral and tibial hardwares in the same side. Three patients had unilateral tibial and femoral fractures. What are the results? All patients achieved consolidation. The mean duration of femoral EF was 7.6 months (5–9 months). One bone loss in a distal femoral shaft treated with Sheffield EF had lengthening (5 cm) after acute short-hening. Two patients had a gradual distal femoral fracture reduction and a mechanical axis correction by TSF. Three patients with tibial bone loss had 2 trifocal bone transport (17,5 and 9 cm) and 1 bifocal bone transport 5 cm. The TSF had no additional pre-operative planning and major post-operative frame adjustments. The intra-operative devices was easier for the TSF. What are your conclusions? Circular frame osteosynthesis following initial EF, is a reliable and effective strategy for treatment in severe open femur and tibia fractures and post traumatic reconstruction

Background: The occurrence of congenitally short metatarsals is associated with an abnormal gait and an aesthetically displeasing appearance. Similarly, short metacarpals result in severe cosmetic disfigurement, particularly in young female patients. Methods: We examined and performed bone lengthening surgery in 13 female and 2 male patients. Of these, procedures were conducted on 12 metatarsals of 8 patients, 4 metacarpals and 1 metatarsal of a single patient, 1 metacarpal and 1 metatarsal of a single patient and 7 metacarpals of 5 patients. The mean age of the patients who underwent metacarpal procedures was 14.5 (10–21) years while the mean age of those who underwent metatarsal procedures was 17.5 (10–25) years. The callotasis method was employed for these procedures and we used either a unilateral external fixator and/or a circular external fixator. Results: The mean healing index and increase in metacarpal length was 1.6 (1.1–2.3) months/cm and 17.6 (13–26) mm, respectively. The mean follow-up period for patients who underwent metacarpal lengthening was 57.5 (12–96) months. The mean healing index and increase in metatarsal length was 1.6 (1.0–2.0) months/cm and 24.3 (20–30) mm respectively. The mean follow-up period for patients who underwent metatarsal lengthening was 48.3 (12–72) months. The preoperative AOFAS (American Orthopaedic Foot and Ankle Society) scores were good in 5 and excellent in 9 cases. The functional scores of metatarso-phalangial (MTP) joint of lengthened metatarsals for the lesser toe were excellent in 12 and good in 2 cases based on the AOFAS scoring system. All patients who underwent metacarpal lengthening reported that they were satisfied and could conduct their daily activities with good functional and aesthetic results. Complications included 4 angulations, 1 subluxation and 1 non-union and were seen in 6 of the metatarsal lengthening cases that exceeded 40% (or > 20 mm) of the total length of the original bone. Interpretation: There are recommendations in the literature that allow for the avoidance of severe complications and for the shortening of the consolidation period. We conclude that the periosteum must be protected with percutaneus osteotomy and lengthening should be performed at a rate of 0.25 mm twice a day, should not exceeding 40% of the original bone length (or > 20 mm). If the anticipated lengthening exceeds these predefined values then we suggest that the procedure should be performed using a circular external fixator with temporary fixation of the MCP or the MTP joint and the inclusion of the proximal phalanx in the frame

Background & Objectives: Osteoporosis is one of the most prevalent bone diseases worldwide with fractures its major clinical consequence. Studies on the effect of osteoporosis on fracture repair are contradictory and although it might be expected for fracture repair to be delayed in osteoporotic individuals, a definitive answer still eludes us. Subsequently, the aim of this study was to attempt to clarify any such effect. Methods: Osteoporosis was induced in 53 female Sprague-Dawley rats by ovariectomy (OVX) at 3 months. A femoral fracture was produced in these animals 12 weeks later {OVX+Fracture group (OVX+F)}. A control group received the fracture only group (F) at 6 months. The fracture consisted of an open osteotomy held with a unilateral external fixator. Outcome measures include histology, motion detector analysis, pQCT, biomechanical strength testing (BST) and digital radiography. Digital radiographs were taken at time of OVX, fracture (confirming satisfactory reduction) and sacrifice from which relative bone density (BMD) measurements were calculated. Results: OVX+F animals were significantly heavier than F animals at fracture and sacrifice (p< 0.001 for both) and moved significantly less in days 1-4 (p=0.032) and 5-9 (p=0.020) post-fracture. Relative BMD measured in distal femur at fracture and sacrifice was significantly greater in F group (p< 0.001 for both). Furthermore, there was a significant decrease in relative BMD from fracture to sacrifice in OVX+F group (p< 0.001). pQCT showed a significantly greater total BMD {contralateral (p=0.021) and fractured femora (p< 0.001)} and trabecular BMD (p< 0.001 both limbs) in the distal femur of the F group. Histologically, no statistical differences were found, however, the F group generally displayed the most advanced repair. In the contralateral limb, the F group had significantly greater load to failure at 6 (p=0.026) and 8 (p=0.042) weeks and was significantly stiffer at 8 weeks (p=0.050). In the fractured leg, stiffness was significantly greater in the F group at 8 weeks (p=0.001). Conclusion: OVX was linked to increased body weight, decreased motion, decreased BMD (with particular loss in trabecular BMD), and reduced mechanical properties. OVX did not have a significant effect on fracture healing and although there was no reduction in BMD at the fracture site, histology and reduced stiffness suggest it was delayed

Introduction: Pin loosening is a common complication associated with external fixation. Various attempts such as coating the pins with calcium phosphates, have been made to modify the pin surface in order to reduce pin loosening and provide good fixation. Animal and clinical studies showed that fixation using tapered external fixation pins coated with hydroxyapatite is superior to standard pins. However, there is no data on cylindrical pins either fully or partially coated with HA. A partial coating could be a solution to optimize pin fixation with the advantage of easier removal compared to fully coated pins. Our purpose was to compare standard and partially coated cylindrical Apex pins implanted in a sheep model at 2 and 6 weeks. As controls we included fully coated tapered pins. Materials/Methods: Five groups of pins were studied. Group A included standard cylindrical Apex pins implanted in sheep which were euthanized 2 weeks after surgery; Group B included partially coated Apex pins implanted in sheep which were euthanized 2 weeks after surgery; Group C included tapered pins fully coated with HA implanted in sheep which were euthanized 2 weeks after surgery; Group D included Standard Apex pins implanted in sheep which were euthanized 6 weeks after surgery; Group E included partially coated Apex pins implanted in sheep which were euthanized 6 weeks after surgery. With the tapered pins, full contact between the coated surface and both cortices was obtained. After pin implantation, a unilateral external fixator was mounted onto the pins (Stryker carbon blue monotube Ø 20/250mm). A 5mm long removal osteotomy was performed in the mid-part of the tibial diaphysis, so that 3 pins were situated above the gap and 3 below to ensure load transfer through the bone-pin interface. Extraction torque and tibial torque resistance and histological analyses were obtained after pin removal. Results: At 2 weeks, mean insertion torque was significantly higher for group C compared to group A (p = 0.03). Mean extraction torque was statistically higher for group B compared to group A (p = 0.001). A statistically significant difference was found in the Pettine index (p = 0.03) between groups A and B. At 6 weeks, no differences in extraction torque were seen. Discussion: We believe that the partial application of the coating reduced the potential for osteointegration and the ultimate fixation of the coated Apex pins

Introduction: The aim of this research project was to establish a simple, reliable and repeatable externally fixed femoral fracture model. The rat was selected, as it was a suitable animal for use in a model of fracture repair and ovariectomy induced osteoporosis, both of which were to be investigated in future experiments. There are femoral fracture models described in the literature based on the insertion of an intramedullary nail prior to inducing a fracture. We felt, based on our experience of the unilateral externally fixed mouse fracture model, that external fixation would allow us to carry out radiographical and histological analysis of fracture healing without any of the tissue trauma caused by the insertion and removal of the intramedullary device. Materials and Methods: A unilateral external fixator was chosen due to its simplicity. Four threaded stainless steel pins pass through holes in an aluminium plate with nuts placed on the pin above and below the plate. The holes in the plate were 0.1mm bigger than the pins and unthreaded allowing the plate to slide freely over the pins. Tightening of the upper nut compressed the plate against the lower nut holding the pin securely. 41 female Sprague-Dawley rats, aged between 12 and 18 weeks, were used. They were anaesthetised using a standard mixture of hypnorm and midazolam and analgesia, fluids and antibiotic were administered subcutaneously prior to surgery. The femur was exposed through a lateral approach and a standardised osteotomy was made prior to the application of the fixator plate. Accurate reduction was confirmed visually at the time of surgery and also by way of a post-op x-ray. 25 animals were sacrificed at 4 days and 1, 2, 4, 6 and 8 weeks for histology. The fractured limbs were harvested, fixed, decalcified and paraffin embedded as per standard protocol and serial sections were cut. These were stained with H& E and alcian blue and analysed 15 animals were sacrificed at 4,6 or 8 weeks for biomechanical strength testing. Four-point bending was carried out on freshly harvested femurs stored in normal saline between harvest and testing. Both limbs were tested and the fractured limbs were standardised relative to the unfractured limb. Maximum load to failure was recorded and stiffness was calculated from the load-displacement curve. Results: No post-operative complications of fixation failure or infection occured. On histological assessment at D4 a predominantly lymphocytic inflammatory response was seen within the fracture haematoma. This inflammatory response was replaced with endosteal and periosteal new bone between wks 1 and 2. Bridging of the fracture gap was seen at week 6. Both stiffness and load to failure increased with increasing time. There was a statistically significant improvement in the percentage stiffness and percentage load to failure between 4 and 8 weeks (p=0.03 and p=0.018 respectively). The difference in load to failure between 6 and 8 weeks was also significantly different (p=0.042). Discussion: A simple, reliable and repeatable externally fixed rat femoral fracture model has been established

During the process of distraction osteogenesis new bone is formed rapidly and undergoes remodelling almost immediately. Little is known about the regulatory mechanisms governing the removal of the redundant callus in this process. Tissue homeostasis is achieved by a delicate balance between the processes of cell death (apoptosis) and cell proliferation. The aim of this study was to test the hypothesis that apoptosis is involved during distraction osteogenesis. Mid-tibial osteotomies were performed in 6 adult male NZW rabbits (age; 24 weeks, weight; 3.0 −3.5 kg), and the tibiae stabilised with unilateral external fixators (Orthofix M-100). 7 days later, twice daily distraction was initiated at rates of 0.7 mm/day for 3 weeks. BrdUrd (40mg/kg) was injected intravenously to the rabbit 1h before killing. The regenerate bone was collected, fixed in 10% buffered formalin and decalcified for paraffin embedding. Some fresh regenerate bone tissues were also prepared for examination under transmission electronic microscopy (TEM). BrdUrd immunohistochemistry has been used to detect proliferating cells and the terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-biotin nick end-labelling (TUNEL) method was used to identify cells undergoing apoptosis. To detect bone-resorbing cells, tartrate-resistant acid phosphatase (TRAP) staining was also performed. BrdUrd positive cells and TUNEL-positive cells were shown to coexist in most of the areas in the regenerates. In the mineralisation front, the majority of the TUNEL-positive cells were present in the transitional region between the fibrous tissue and the new bone. The TUNEL-positive cells were close to or on bone surfaces, and some of the newly formed osteocytes in the new trabeculae were also positive. The TUNEL-positive cells were also seen in the cartilage region of the regenerate. However, the TUNEL labelling was greatly reduced in the new bone close to the osteotomised bone ends, TUNEL-positive labelling were not detected in the cortical bone of the osteotomised bone ends and in the adjacent surrounding periosteum. TRAP staining in the regenerate revealed similar patterns of distribution to those of the TUNEL staining. There were more TRAP-positive cells in the new bone near the mineralisation front than in that of the new bone region, which was close to the osteotomised bone ends. TEM examinations have demonstrated characteristic signs of apoptotic changes in the fibroblast, osteoblast and osteocytes in the specific regions of the distraction regenerate. The study provided evidence that in the process of rapid bone formation during distraction osteogenesis, superfluous cells are removed by apoptotic mechanisms. The demonstration of a mixture of proliferative and apoptotic cell populations in the regenerating tissue, indicates that apoptosis and cell proliferation may be regulated by local factors. The neovascularisation of the regenerate and withdrawal of growth factors and cytokines may be responsible for apoptosis occurring in some parts of the regenerating tissue. The changes of distribution of apoptotic cells in the different regions of the regenerate, together with the observed patterns of osteoclast activities, suggest that bone cells undergoing apoptosis may initiate rapid bone remodelling seen during distraction osteogenesis

Aims

Distraction osteogenesis (DO) is a useful orthopaedic procedure employed to lengthen and reshape bones by stimulating bone formation through controlled slow stretching force. Despite its promising applications, difficulties are still encountered. Our previous study demonstrated that pulsed electromagnetic field (PEMF) treatment significantly enhances bone mineralization and neovascularization, suggesting its potential application. The current study compared a new, high slew rate (HSR) PEMF signal, with different treatment durations, with the standard Food and Drug Administration (FDA)-approved signal, to determine if HSR PEMF is a better alternative for bone formation augmentation.

Aims

Loosening is a well-known complication in the fixation of fractures using devices such as locking plates or unilateral fixators. It is believed that high strains in the bone at the bone-screw interface can initiate loosening, which can result in infection, and further loosening. Here, we present a new theory of loosening of implants. The time-dependent response of bone subjected to loads results in interfacial deformations in the bone which accumulate with cyclical loading and thus accentuates loosening.

The October 2012 Trauma Roundup³⁶⁰ looks at: which patients die from pelvic ring fractures; monolateral distraction osteogenesis; surgical management of pelvic and peroneal blast injuries; weekend warriors at risk of going AWOL; early experience with the locking attachment plate; and fibula nailing - an alternate, and viable technique.