Purpose of study:. In polytrauma patients (ISS > 16) early long bone and pelvic fracture fixation (< 24 hours post injury) has been shown to be beneficial. Surgery in the presence of subclinical hypo perfusion (SCH) (normal vital signs with a serum lactate > 2.5 mmol/L) may be detrimental. This study aimed to investigate the effect of fracture fixation in polytrauma patients with SCH. Description of methods:. We performed a retrospective database review of polytrauma patients (ISS > 16) with significant long bone or pelvic fractures (extremity NISS> 9) who underwent surgical fracture stabilisation within 48 hours of injury. In the group of patients with normal vital signs (mean arterial pressure (MAP) > 60 mmHg and heart rate (HR) < 110 beats/min) we compared outcomes of those with normal lactate (< 2.5 mmol/L) prior to surgery with patients that had a raised lactate (> 2.5 mmol/L). Results:. Of the 36 patients with normal preoperative vital signs, 17 had normal serum lactates (control group) and 19 abnormal (SCH group). The SCH group required more inotropes in the first 24 hours post-surgery (p=0.02), had higher Sequential Organ Failure Assessment (SOFA) scores on day three (p=0.003) and showed a trend towards higher SOFA scores on day seven (p=0.061). Conclusion:. Early fracture fixation in patients with SCH as evidenced by a lactate > 2.5 mmol/L is associated with worse postoperative outcomes. Consideration should be given to delaying surgery in this cohort until resuscitation is complete

Treatment of segmental bone defects remains a major clinical problem, and innovative strategies are often necessary to successfully reconstruct large volumes of bone. When fractures occur, the resulting hematoma serves as a reservoir for growth factors and a space for cell infiltration, both crucial to the initiation of bone healing. Our previous studies have demonstrated very clear ultrastructural differences between fracture hematomas formed in normally healing fractures and those formed in segmental bone defects. However, there is little information available regarding potential differences in the underlying gene expression between hematomas formed in normal fractures, which usually heal by themselves, and segmental bone defects, which do not. Therefore, the aim of this study was to identify differences in gene expression within hematomas collected from 0.5 mm (normal fracture) and 5 mm (segmental bone defect) fracture sites during the earliest stages of bone healing.

Osteotomies of 0.5 and 5 mm in the femur of Fisher 344 rats were stabilized with external fixators (RISystem AG). After 3 days the rats were sacrificed, and the fracture hematomas were collected for RNA-sequencing. Ingenuity pathway analysis (IPA) was used to identify upstream regulators and biological functions that were significantly enriched with differentially expressed genes from the RNA-sequencing analysis. Animal procedures were conducted following the IACUC protocol of the UT Health Science Center San Antonio.

Key upstream regulators of bone formation were less active (e.g. TGFB1, FGF2, SMAD3) or even inhibited (e.g. WNT3A, RUNX2, BMP2) in non-healing defects when compared to normally healing fractures. Many upstream regulators that were uniquely enriched in healing defects were molecules recently discovered to have osteogenic effects during fracture healing (e.g. GLI1, EZH2). Upstream regulators uniquely enriched in non-healing defects were mainly involved in an abnormal modulation of hematopoiesis, revealing evidence of impaired maturation of functional macrophages and cytokines (e.g. IL3, CEBPE), both essential for successful bone healing. In addition, the enrichment pattern suggested a dysregulation of megakaryopoiesis (e.g. MRTFA, MRTFB, GATA2), which directly affects platelet production, and therefore fracture hematoma formation. Remarkably, the organization of the ECM was the most significantly enriched biological function in the normally healing fractures, and implies that the defect size directly affected the structural properties within the fracture hematoma. Conversely, genes encoding important ECM components (e.g. BGN, various collagens, IBSP, TNC), cell adhesion molecules, MMPs (MMP2), and TIMPs were all significantly downregulated in non-healing defects.

Our most recent findings reveal new important key molecules that regulate defect size-dependent fracture healing. Combined with our previous results, which identified structural differences in fracture hematomas from both types of defects, current findings indicate that differential expression of genes is dictated by the structural properties of the hematomas formed during early fracture healing. Consequently, creating a bioscaffold that mimics the structure of normal fracture hematomas could be the first step towards developing new orthoregenerative treatment strategies that potentiate healing of large bone defects and non-healing fractures.

Metal-on-metal hip resurfacing prostheses are a relatively recent intervention for relieving the symptoms of common musculoskeletal diseases such as osteoarthritis. While some short term clinical studies have offered positive results, in a minority of cases there is a recognised issue of femoral fracture, which commonly occurs in the first few months following the operation. This problem has been explained by a surgeon's learning curve and notching of the femur but, to date, studies of explanted early fracture components have been limited. Tribological analysis was carried out on fourteen retrieved femoral components of which twelve were revised after femoral fracture and two for avascular necrosis (AVN). Eight samples were Durom (Zimmer, Indiana, USA) devices and six were Articular Surface Replacements (ASR, DePuy, Leeds, United Kingdom). One AVN retrieval was a Durom, the other an ASR. The mean time to fracture was 3.4 months. The AVNs were retrieved after 16 months (Durom) and 38 months (ASR). Volumetric wear rates were determined using a Mitutoyo Legex 322 co-ordinate measuring machine (scanning accuracy within 1 micron) and a bespoke computer program. The method was validated against gravimetric calculations for volumetric wear using a sample femoral head that was artificially worn in vitro. At 5mm. 3. , 10mm. 3. , and 15mm. 3. of material removal, the method was accurate to within 0.5mm. 3. Surface roughness data was collected using a Zygo NewView500 interferometer (resolution 1nm). Mean wear rates of 17.74mm. 3. /year were measured from the fracture components. Wear rates for the AVN retrievals were 0.43mm. 3. /year and 3.45mm. 3. /year. Mean roughness values of the fracture retrievals (PV = 0.754, RMS = 0.027) were similar to the AVNs (PV = 0.621, RMS = 0.030), though the AVNs had been in vivo for significantly longer. Theoretical lubrication calculations were carried out which found that in both AVN retrievals and in seven of the twelve cases of femoral fracture the roughening was sufficient to change the lubrication regime from fluid film to mixed. Three of these surfaces were bordering on the boundary lubrication regime. The results show that even before the femoral fracture, wear rates and roughness values were high and the implants were performing poorly

Introduction

The aim of this study was to compare the results and length of stay of patients of early (within 12 hours) versus conventional (after 48 hours) ankle fixation our hospital.

As a treatment for end-stage elbow joint arthritis, total elbow replacement (TER) results in joint motions similar to the intact joint; however, bearing wear, excessive deformations and/or early fracture may necessitate early revision of failed implant components. Compared to hips, knees and shoulders, very little research has been focused on the evaluation of the outcomes of TER, possible failure mechanisms and the development of optimal designs. The current study aims to develop computational models of TER implants in order to analyze implant behaviour; considering contact stresses, plastic deformations and damage progression. A geometrical model of a TER assembly was developed based on measurements from a Coonrad-Morrey TER implant (Zimmer, Inc., Warsaw, IN). Ultra high molecular weight polyethylene (UHMWPE) nonlinear elasto-plastic material properties were assigned to the humeral and ulnar bushings. A frictional penalty contact formulation with a coefficient of friction of 0.04 was defined between all of the surfaces of the model to take into account every possible interaction between different implant components in vivo. The loading scenario applied to the model includes a flexion-extension motion, a joint force reaction with variable magnitude and direction and a time varying varus-valgus (VV) moment with a maximum magnitude of 13 N.m, simulating a chair-rise scenario as an extreme loading condition. An explicit dynamic finite element solver was used (ABAQUS Explicit, Dassault Systèmes, Vélizy-Villacoublay, France), due to improved capabilities when performing large deformation analyses. Model results were compared directly with corresponding experimental data. Experimental wear tests were performed on the abovementioned implants using a VIVO (AMTI, Watertown, MA) six degree-of-freedom (6-DOF) joint motion simulator apparatus. The worn TER bushings were scanned after the test using micro computed tomography (µCT) imaging techniques, and reconstructed as 3D models. Comparisons were made based on the sites of damage and deformed geometries between the numerical results and experimental test data. In addition to that, parametric geometrical models were developed using worn geometry of the retrievals in order to account for primary wear and deformations while simulating long-term contact stress and secondary damage progression on the bushings (Fig. 1). Contact pressure distributions on the humeral and ulnar bushings correlate with the sites of damage as represented by the µCT data and gross observation of clinical retrievals. Furthermore, deformation patterns and kinematics of the components are in good agreement with the experimental results (Fig.2). Excessive plastic deformations are evident in both the numerical and the experimental results close to the regions with high contact pressures. Simulating parametric initially-worn geometries results in the formation of secondary damage zones, as well as redistribution of contact stresses and contact locations (Fig. 3). The results demonstrate UHMWPE bushing damage due to different loading protocols. Numerical results demonstrate strong agreement with experimental data based on the location of deformation and creep on bushings and exhibit promising capabilities for predicting the damage and failure mechanisms of TER implants. For figures/tables, please contact authors directly.

Aims. Compartment syndrome (CS) is a well-recognised, serious complication of long bone fractures. The association between CS and tibial shaft fractures is well documented in adult patients and in children with open or high velocity trauma. There is, however, little literature on the risk of developing CS in children with closed tibial fractures. In a number of units these children are routinely admitted for elevation and monitoring for CS. We audited our experience of managing paediatric tibial fractures to ascertain whether it may be safe to discharge a sub-group of these children. Methods. We audited all children up to the age of 12 years admitted to our hospital over a 5 year period. We reviewed radiographs and clinical notes to determine fracture pattern, modality of treatment, and complications. Results. We audited 159 tibial fractures. The mean age was 5.8 years (1–12 years), 95 boys, 64 girls. 105 (66%) closed fractures were conservatively managed: 87 of these were diaphyseal and 20 involved both tibia and fibula. Of the conservatively managed fractures, 89 (85%) were minimally displaced (< 5 degrees varus/valgus/anterior angulation, < 5 degrees rotation, < 5mm shortening, no posterior angulation). In the conservatively managed group there were 3 cases of angulation in cast, managed with wedging. There were no other complications and no cases of compartment syndrome. Conclusion. Of the 105 closed tibial fractures we managed conservatively, most were minimally displaced, diaphyseal, tibia-only fractures. No patient developed compartment syndrome. Based on our experience we suggest that children with closed, minimally displaced tibial fractures do not require admission for monitoring of CS and may go home in a plaster-slab with early fracture clinic follow-up providing suitable supervision is in place, pain is controlled, and they are able to mobilise safely

Aim. To evaluate the results and complications of bone transport in the treatment of massive tibial bone defects, using the Ilizarov method. Methods. 15 patients underwent bone transport using the Ilizarov technique to treat massive tibial bone defects. The average age of the patients was 8.7 years (3–24 years) and the mean bone defect was 10.8 cms. Following a latent period of 1 week, distraction of the transport doughnut was commenced at 1mm/24 hours in 4 quarterly turns. A docking procedure was performed in 7 cases which involved freshening of the bone ends and autogenous bone grafting from the iliac crest. Following docking the fixator was removed once the regenerate had consolidated. Results. The fixators were removed after a mean 12.3 months (range 8–21 months). 1 patient required adjustment of the frame under anaesthetic due to translation of the docking doughnut and poor alignment. All patients had at least one superficial pin site infection successfully treated with oral antibiotics. Deep infection at the docking site was seen in 1 patient needing debridement and split skin grafting. There were no neuro-vascular complications. 1 patient had a recurvatum deformity at the regenerate due to early frame removal. There were no early fractures. Re-fracture of the docking site occurred in one patient, 17 months after the removal of the original frame. This needed open reduction and internal fixation. Non union at the docking site was seen in 3 patients, needing open reduction, internal fixation with bone grafting (1 case) and excision of non-union and compression with a further frame (2 cases). Conclusion. Massive bone transport in the tibia is an orthopaedic challenge. This paper highlights the complications of this procedure. It confirms the viability of this method but emphasises careful counselling of both the patient and parents prior to the commencement of such difficult treatment

Algorithms for the treatment of multiply-injured patients with concomitant orthopaedic injuries have continued to evolve over the past several decades. Advances in surgical techniques and implants have revolutionised the treatment of specific musculoskeletal injuries. Improved understanding of the implications of applying these techniques to patients with compromised physiology has led to critical reevaluation of the issues surrounding definitive orthopaedic care. A discussion of these issues as they apply to the multiply-injured patient with associated femoral shaft fracture provides insight into how Damage Control Orthopaedics has evolved. As well as what questions remain unanswered in our ongoing efforts to decrease mortality and improve long-term functional recovery in this difficult and challenging patient population. While femur fracture patients in the 1950s and 1960s were often deemed ‘too sick’ for surgical treatment, the high morbidity and mortality associated with long-term traction as a primary treatment modality led to recognition of the benefits of early fracture care in the 1980s. Multiple studies demonstrating the benefit of early fixation of femur fractures in multiply-injured patients led to a dramatic shift in treatment protocols towards urgent, if not emergent, definitive stabilisation of the femur. However, weaknesses of these early studies exist and their results were often over-interpreted. In the late 1980s and early 1990s, evidence began to accumulate that early definitive treatment consisting of reamed intramedullary nailing of the femur might actually be detrimental in an at risk subgroup of patients. Early interpretation of these results led to a move toward ‘unreamed’ nails in multiply-injured patients in an effort to minimise the pulmonary impact of reaming. Our current level of understanding appears to indicate that there exists a much more complex interaction between multiple factors including patient characteristics, associated injuries, timing and mode of orthopaedic stabilisation employed. As the relative importance and influence of these multiple factors becomes clearer, our ability to appropriately select patients for early total care versus damage control orthopaedics should improve the potential for damaging physiological effects of treatment. In the meantime, application of the principles of damage control to those patients for whom it is clearly indicated, as well as to those for whom it may not be clear cut, appears to have minimal, if any, deleterious effect

Periprosthetic fractures present several unique challenges including gaining fixation around implants, poor bone quality and deciding on an appropriate treatment strategy. Early. With the popularity of cementless stems in primary total hip arthroplasty (THA) we have seen a concomitant rise in the prevalence of intra-operative and early post-operative fractures of the femur. While initial press-fit fixation is a requirement for osseointegration to occur, there is a fine balance between optimising initial stability and overloading the strength of the proximal femur. Hence, the risk of intra-operative fractures is intimately related to the design of the femoral component utilized (metaphyseal engaging, wedge shaped designs having the highest risk) and the strength of the bone that it is inserted into (elderly females being at highest risk). These fractures typically are associated with a loose femoral component and require revision to a stem that gains primary fixation distally. We have found a high risk of complications and problems when treating these fractures in the early post-operative period with a high risk of infection, heterotopic ossification and the requirement for subsequent surgery. Late. The Vancouver Classification is based on the location of the fracture, the fixation of the implant and the quality of the surrounding host bone. The most common pitfall in treatment is mistaking a B2 fracture (stem loose) for a B1 (stem stable); treatment of a loose implant with ORIF alone will necessarily fail

Purpose. Glenoid component loosening is a common reason for failed total shoulder arthroplasty. Multiple factors have been suggested as causes for component loosening that may be related to cement technique. The purpose of the study was to compare the load transfer across a polyethylene glenoid bone construct with two different cementing techniques. Method. Eight cadaveric specimens underwent polyethylene glenoid component implantation. Four had cement around the pegs only (CPEG) and four had cement across the entire back (CBACK) of the implant including around the pegs. Step loading was performed with a pneumatic actuator and a non-conforming humeral head construct capable of applying loads at various angles. Strain gauges were placed at the superior and inferior poles of the glenoid and position trackers were applied to the superior and inferior aspects polyethylene component. Micro CT data were obtained before and after the loading protocol. Results. During compressive loading, greater tension was recorded with the CBACK technique than with the CPEG technique. Compression was recorded superiorly when load was applied at 30 degrees while tension was recorded inferiorly. Greater displacement occurred with the CPEG group. Failure as defined on micro CT occurred more consistently with the CBACK technique than with the CPEG technique. Conclusion. Tension measurements and upward deflection of the polyethylene with compressive loading at lower angles was unexpected. Early failure of fully cemented glenoids may be due to the fragility of the cement mantle around the periphery of the implant. Tension at the bone cement interface and early cement fracture are unfavorable and this may be a mechanism of implant loosening

BACKGROUND. In vitro tests have shown that when a force is applied to the proximal femur within the range of directions spanned during physiological activities, the direction of principal strain vary by a very narrow angle (Cristofolini et al, 2009, J. Engng. Med.). This shows that the anatomy and the distribution of inhomogeneous and anisotropic material properties of the bone tissue make the structure of the proximal femur optimized to withstand a wide range of loading directions. The increasing use of hip resurfacing is associated with early neck fractures of the implanted femur. The aim of this study was to elucidate if such fractures could be caused by a non-physiological state of stress/strain post-implantation. While the possible role of notching at the neck-implant interface has already been elucidated, it is not know whether a resurfacing implant could make the principal strain vary in magnitude and direction in a way that could compromise integrity of the proximal femur. METHODS. The aim of this study was to measure if the direction of the principal strain in the proximal femur was affected by the presence of a resurfacing prosthesis. Seven human cadaver femurs were instrumented with 12 triaxial strain gauges to measure the magnitude and alignment of principal strains in the head-neck region. Each femur was implanted with a typical resurfacing prosthesis (BHR). All femurs were tested in vitro before and after implantation with a range of loading conditions to explore the range of loading directions during daily activity (Fig. 1). FINDINGS. Comparison of the strain distribution before and after implantation showed that: . In the natural conditions the principal tensile strain was significantly larger where the cortical bone was thinner; the compressive strain was larger where the cortical bone was thicker. This should be considered when designing a resurfacing prosthesis. The strain magnitude varied greatly between loading configurations both in the intact and implanted condition: this suggests that different loading configurations must be simulated for the preclinical validation of a resurfacing prosthesis. In the natural conditions, the direction of the principal strain varied significantly between measurement locations, but varied little between loading configurations (less than 10° when the hip force spanned a 21° cone, Fig. 2). This confirms that the anatomy and the distribution of anisotropic material properties enable the proximal femur to respond adequately to the changing direction of daily loading. In the resurfaced femurs, when the force spanned the same 21° cone, the direction of principal strain at each measurement location varied by less than 10° (Fig. 3), similar to the natural condition. In the resurfaced femurs, the direction of principal strain lied within less than 10° from the direction in the natural conditions. INTERPRETATION. Our results show that resurfacing does not disturb the alignment of principal strain in the proximal femur. In other words, the most critical directions of stress/strain after implantation stay aligned with the same direction as in the intact femur, which is the direction for which the inhomogeneous and anisotropic structure of the proximal femur is optimized