Aim

Treatment algorithms for fracture-related nonunion depend on the presence or absence of bacterial infection. However, the manifestation of septic nonunion varies. Low-grade infections, unlike manifest infections, lack clinical signs of infection and present similarly to aseptic nonunion. The clinical importance of low-grade infection in nonunion is not entirely clear. Therefore, the aim of this study was to evaluate the clinical relevance of low-grade infection in the development and management of femoral or tibial nonunion.

Tibial shaft fractures require surgical stabilization preferably by intramedullary nailing. However, patients often report functional limitations even years after the injury. This study investigates the influence of the surgical approach (transpatellar vs. parapatellar) on gait performance and patient reported outcome six months after surgery.

Twenty-two patients with tibial shaft fractures treated by intramedullary nailing through a transpatellar approach (TP: n=15, age 41±15, BMI 24±3) or a parapatellar approach (PP: n=7, age 34±15, BMI 23±2) and healthy, matched controls (n=22, age 39±13, BMI 24±2) were assessed by instrumented motion analysis six months after intramedullary nailing. Short musculoskeletal function assessment questionnaire (SMFA) as well as kinematic and kinetic gait data were collected during level walking. Comparisons among approach methods and control group were performed by analysis of variance and Mann-Whitney test.

Six months after surgery, knee kinetics in both groups differed significantly compared to controls (p <.04). The approach method affected gait speed (TP: p = .002; PP: p = .08) and knee kinematics in the early stance phase (TP: p = .011; PP: p = .082), with the parapatellar approach showing a more favorable outcome. However, the difference between patient groups was not significant for any of the assessed gait parameters (p > .2). Also, no differences could be found in the bother index (BI) or function index (FI) of SMFA between surgical approach methods (BI: TP: Mdn = 7.2, PP: Mdn = 9.4; FI: TP: Mdn = 10.3, PP: Mdn = 9.2, p > .7).

Our study demonstrates, that six months after surgery for tibial shaft fractures functional limitations remain. These limitations appear not to be different for either a trans- or a parapatellar approach for the insertion of the intramedullary nail. The findings of this study are limited by the relatively short follow up time period and small number of patients. Future studies should investigate the source of the functional limitation after intramedullary nailing of tibial shaft fractures.

Implant manufacturers develop new products to improve existing fracture fixation methods or to approach new fracture challenges. New implants are commonly tested and approved with respect to their corresponding predecessor products, because the knowledge about the internal forces and moments acting on implants in the human body is unclear. The aim of this study was to evaluate and validate implant internal forces and moments of a complex physiological loading case and translate this to a standard medical device approval test.

A finite elements model for a transverse femur shaft fracture (AO/OTA type 32-B2) treated with a locked plate system (AxSOS 3 Ti Waisted Compression Plate Broad, Stryker, Kalamazoo, USA) was developed and experimentally validated. The fractured construct was physiologically loaded by resulting forces on the hip joint from previously measured in-vivo loading experiments (Bergmann et. al). The forces were reduced to a level where the material response in the construct remained linear elastic. Resulting forces, moments and stresses in the implant of the fractured model were analysed and compared to the manufacturers’ approval data.

The FE-model accurately predicted the behaviour of the whole construct and the micro motion of the working length of the osteosynthesis. The resulting moment reaction in the working length was 24 Nm at a load of 400 N on the hip. The maximum principle strains on the locking plate were predicted well and did not exceed 1 %.

In this study we presented a protocol by the example of locked plated femur shaft fracture to calculate and validate implant internal loading using finite element analysis of a complex loading. This might be a first step to move the basis of development of new implants from experience from previous products to calculation of mechanical behaviour of the implants and therefore, promote further optimization of the implants’ design.

Abstract

Aims

Evaluate if treating an unstable femoral neck fracture with a locking plate and spring-loaded telescoping screw system would improve construct stability compared to gold standard treatment methods.

Hip osteoarthritis (OA) is a disorder of high socio-economic relevance. The causes of hip osteoarthritis are multifactorial; however, the epidemiological literature regularly cites occupational tasks, such as heavy lifting and carrying, as a risk factor for the development of hip OA. The level of mechanical stresses upon the hip joint caused by occupational tasks remain largely unclear, however. This project sought to quantify the levels of stresses upon the hip joint during occupational tasks. In particular we were interested in comparing load as well as stress levels from everyday activities with occupational tasks typically performed by blue collar workers.

Sectors and occupational activities presenting a high potential for stress upon the hip joint were identified by means of a survey conducted among accident insurance institutions. Lifting, carrying and load transfer (25 to 50 kg), ladder climbing and stair climbing (without additional load and with an additional load of 25 kg) were selected from among these sectors and activities for the purpose of the study. Laboratory measurements were performed in which motion capturing and a range of force measurement apparatus were used to record and evaluate the performance of the selected tasks by 12 skilled workers from a number of sectors. multi-body simulation was used to calculate the stress in the form of hip-joint contact forces. The contact pressures and their geometric distribution on the cartilage surfaces of the hip joint were then calculated from these results by means of finite-element analysis. This produced an indicator for the strain upon the hip joint.

The highest hip-joint forces, at (637±148)% of the body weight, occurred during handling of the 50 kg load. This corresponded to 1.7 times the stress arising during walking, at (368±78)% of the body weight. Significantly higher hip-joint forces compared to those arising during walking were observed for the carrying of loads of 40 kg and 50 kg, the handling of loads of 25 kg, 40 kg and 50 kg, and stair climbing with an additional load of 25 kg. Maximum contact pressures of 24.1 MPa were computed during the finite-element analysis (lifting of 50 kg); only very small regions of the joint surface were however affected by these high pressures. During walking, the maximum pressure reached 15 MPa.

The results obtained provide a quantitative overview of the strains upon the hip joint during occupational and everyday tasks. They constitute an aid to future quantitative exposure assessments in a range of sectors and occupational fields, and thus contribute to improving estimation of the relevance of stresses of occupational origin to the incidence of hip OA.

Introduction

Metabolic disorders are among known risk factors for tendinopathies or spontaneous tendon ruptures. However, the underlying cellular and molecular mechanisms remain unclear. We have previously shown that human and rat tendon cells produce and secrete insulin upon glucose stimulation. Therefore, we hypothesize that nutritional glucose uptake affects tendon healing in a rat model.

Background

The inherently high stiffness of locked plate constructs is increasingly recognized as a potential cause of deficient healing observed in patients with periarticular locked plating systems.

The objective of this study is to perform a biomechanical comparison of distal femur locked plating systems.

Introduction

Metatarsocuneiform (MTC) fusion is a standard treatment for arthritis, instability, and deformity of these joint. The MTC fusion achieves a good clinical outcome, but nonunion rates up to 12% have been reported. There are different methods for fixation of first MTC joint arthrodesis. Our aim was to compare the biomechanical characteristic of internal and external fixation constructs.

Hypothesis

The proximal geometry and design of trochanteric nails affects initial construct stiffness, fatigue survival, and preservation of biomechanical stability over time.

Common cell based strategies for treating bone defects require time-consuming and expensive isolation and expansion of autologous cells. We developed a novel expedited technology creating gene activated muscle grafts. We hypothesized that BMP-2 activated muscle grafts provide healing capabilities comparable to autologous bone grafting, the clinical gold standard.

Two male, syngeneic Fischer 344 rats served as tissue donors. Muscle tissue was harvested from hind limbs and incubated with an adenoviral vector carrying the cDNA encoding BMP-2. Bone tissue was harvested from the iliac crest. Segmental bone defects were created in the right femora of 12 rats and were filled with either BMP-2 activated muscle tissue or bone grafts. After 8 weeks, femora were evaluated by radiographs, microCT, and biomechanical tests.

BMP-2 activated muscle grafts and autologous bone grafts resulted in complete mineralization and healing, as documented by radiographs and microCT. Bone volume in the muscle graft defects (33+/-12mm3) was similar to autologous bone graft defects (39+/-5mm3). Torque at failure of the two groups was statistically indistinguishable (240+/-115 Nmm vs. 232+/-108Nmm).

In previous experiments we demonstrated that the large segmental defect model in this study will not heal with either empty defects or non-activated muscle grafts. Our findings therefore demonstrate that BMP-2 gene activation of muscle tissue effectively stimulates defect healing similar to autologous bone grafts.

Alpine ski sports changed rapidly in the last decade. Complex fractures of the proximal tibia, typically seen in high energy trauma, has been seen more frequently and more often related to alpine skiing.

The aim of our study was to identify reasons for proximal tibia fracture in alpine skiing and observe the outcome.

All patients with proximal tibia fractures related to alpine skiing, which were treated in our two trauma centers were included. The patients received a questionnaire at the emergency department, dealing with accident details and the skiing habits. The fractures were classified according to the AO fracture classification scheme. The follow up was performed at least one year after trauma with the Lysholm, the Tegner activity, as well as the WOMAC VAS Score.

Between 2007 and 2010 a total of 188 patients with proximal tibia fractures caused by alpine skiing were treated. 43 patients had a type A, 96 patients a type B and 49 a type C injury. The incidence was increasing over the period continuously. The main trauma mechanism was an accident without a third party involvement with an increased rotational and axial compression impact. All outcome scores were related to fracture severity with significant worse results for the type C fractures.

In conclusion, proximal tibia fractures are an increasing and serious injury during alpine skiing. Further technical progress in skiing material should focus on these knee injuries in future.

Objectives: Goal of this retrospective study is to evaluate risk factors, which lead to an osteitis of the tibia depending on the fracture location.

Methods: The study was initiated 01/2002. The study population consists of 104 patients including 14 women (13%). All of them suffered from an osteitis of the tibial. All of them are complications after traumatic open or closed fractures of the tibia, treated surgical. The average age of the patients has been 48 (± 18) years. In 28 cases there has been an acute osteitis of the tibia. In the other 76 patients the infection was not noticed before the ninth week after trauma. In all patients the risk factors were analyzed depending on the fracture configuration, the soft tissue situation, and the fracture location.

Results: All infections have been localized at the fracture level. The majority of the patients suffered from open tibial fractures (77.4%). 7.9% have been first, 23.6% second, and 68.5% third degree open fractures. Almost half of the fractures (48.1%) were located at the distal third of the tibia. Equally, 25.9% of the infections were localized in the medial and proximal third of the tibia. The percentage of open fractures leading to an osteitis was significant highest (p < 0.01) at the medial third of the tibia (91.3%), whereas the percentage of open proximal fractures has been 61.1% and open distal fractures 62%. The complexity of the fractures of the proximal, medial, and distal third of the tibia was very similar. The proportion of osteosynthesis with fixateur externe, plating, or naling showed no significant differences. 37.8% of the patients were smoker. The percentage of smoker was significant highest (p < 0.05) in the subgroup osteitis after closed tibial fracture (69.9%). The number of the other risk factors (Diabetes mellitus, hypertension, alcohol consumption, adipositas, PAD) was similar in all subgroups. There have been no differences between the 28 acute versus the 76 chronic osteitis.

Conclusion: The majority of the posttraumatic tibial osteitis is localised in the distal third. The most important risk factor for the development of a posttraumatic tibial osteitis is the dimension of the soft tissue defect. This is particularly true for the medial third of the tibia where the percentage of open fractures is significant highest. Additionally nicotine consumption is a major risk factor for the development of a posttraumatic tibial osteitis, particularly in cases of closed distal tibial fractures.

Introduction: Because of strong loads acting in the elbow joint, intraarticular fractures with a methaphyseal comminuted fracture site at the distal humerus demand a lot from the osteosynthetic care.

Ambiguities arise concerning to the anatomic position of the implants and the resulting mechanic performance.

Aim of this study was the comparison of three anatomic variations of one angle stable plate system as to their mechanic stability.

Material and Methods: As a fracture model an AO C 2.3-fracture on an artificial bone (4th Gen. Sawbone) was simulated via double osteotomy in sagittal and transversal plane. The fractures were equipped with a prototypical version of the Variax Elbow System (Stryker) in the variations 90° (lat+post), 90° (med+post) and 180° (med+lat).

A physiological load distribution (Capitulum Humeri 60%, Trochlea humeri 40%) could be guaranteed for by a therefore designed test set up. In three test series, the load to failure (static), the system rigidity (static) and the median fatigue limit (dynamic) were determined. The tests were conducted under 75° flexion and 5° extension and the relative displacements were recorded.

Results: In extension, the 180° (med+lat) alternative achieved the highest load to failure (2959 N), stiffness (1126 N ± 127 N) and median fatigue limit (1046 N ± 46 N) followed by the 90° (lat+post) alternative.

Great differences could be stated with the 180° (me d+lat) alternative in extension in comparison to the flexion (p< 0,05): under flexion the failure already appeared at 1077N and the stiffness reduced to 116 N ± 10 N. The highest stiffness (202 N ±19 N) under flexion load could be determined for 90° (med+post). As to stiffness, the 90° (lat+post) alt ernative lay in between. Decreases of fracture gaps due to a failure of screw bone interface and a bending of plates could be determined as failure patterns in case of static load. Under dynamic load especially fatigue fractures occurred at the implant system in terms of broken plates and screws.

Conclusion: In vivo the highest loads occur at the distal humerus in extension direction which can best be transferred, in static as well as in dynamic regard, by a 180° alternative. An alternative to that is the 90° (lat+post) variation due to its advantageous me chanic performance under static and dynamic extension load. But still the nature of fracture with size and position of the fragments useable remains decisive for the choice of an osteosynthesis.

The mechanic superiority of the 180° alternative (minimized gap displacement and high stiffness of the system respectively) in extension direction in comparison to a 90° alternative can be explained by the 90° position of the plates and hence reduced moment of inertia. Less stiffness under flexion direction arises from the long levers, which cause high bending moments.

Introduction: Patients who are prescribed bisphosphonates are still at risk to endure a fracture from weak and brittle bones. The question is what pharmacologic strategy should be taken to accelerate fracture healing when the patient is currently taking a bisphosphonate. Ibandronate, was tested in an osteoporotic rat model to determine how it modified the callus healing and resistance to torsion after a transverse fracture was produced in a femur.

Materials and Methods: 36 female rats were divided into 3 groups; ovariectomized (OVX) placebo control, non-OVX control and Ibandronate. Prior to the osteotomy, the Ibandronate treatment group was injected with the drug over 21 days healing. Each sample was scanned by the SCANCO uCT 80 to measure volume of the callus and quality of the trabeculae in the proximal femur. Instron testing recorded the modulus of rigidity and torque until failure. Yield point and toughness were also calculated.

Results: uCT images taken over the fracture gap showed that the Ibandronate rats had greater bone volume fraction of woven callus by ANOVA compared to control groups (p< 0.05). Significant in total callus volume for Ibandronate, were shown to be 32% larger than the non-OVX control group and 45% larger than the placebo group. Ibandronate also increased BMD of woven bone in the callus by 14%. Ibandronate showed the highest polar moment of inertia as well.

The torsion testing in Ibandronate had 51% greater toughness than placebo and 69% greater than the non-OVX group. Ibandronate increased trabecular number significantly over the placebo and was not significantly different from the non-OVX group. Trabecular separation was less in Ibandronate compared to the placebo group. Volume in the trabecular neck increased by 35% for the Ibandronate over the placebo.

Discussion: Ibandronate had an anabolic effect to produce more callus tissue at the fracture site, most likely by suppressing osteoclast remodelling activity. A large callus with more bone would increase fracture stability and reduce risk of non union. This is supported by a larger polar moment of inertia. Ibandronate had greater resistance to torsion, which could indicate better healing. However increased rigidity would not entirely benefit the healing unless the bone could handle load plastically. The toughness results showed that Ibandronate can absorb more energy than the control groups before refracturing. Continued treatment with this drug after a fracture could form a larger callus with greater mechanical toughness while also treating the disease of osteoporosis in other fracture risk sites of the body.

Introduction: The aim of this study was to evaluate direct mechanical measurements from an external fixator as an alternative method to DEXA to examine the healing progress of patients undergoing distraction osteogenesis (DO).

Methods: Five patients were evaluated concurrently by BMD estimates and direct mechanical measurements from an external fixator to examine bone consolidation approximately every six weeks after the end of distraction. For mechanical measurements, all rods were removed from the external fixator and replaced with three load cells. An axial load of 10 kg was applied to the tibia and the load recorded from the three load cells was used to calculate the proportion of the load supported by the fixator (Load Share Ratio, LSR), which indicates the stiffness of the newly developed bone.

Results: The LSR decreased significantly for all patients (r2=0.63, p < 0.01), indicating increased bone stiffness. DEXA based BMD estimates decreased for two of five patients despite normal healing progress and likewise BMD and LSR were weakly correlated (r2=0.22, p > 0.05).

Discussion: Bone consolidation is often accompanied by changes in bone geometry, which can make DEXA based BMD estimates inaccurate for this application. Mechanical measurements from external fixators are not subject to this error and therefore could be a more reliable method to evaluate the healing progress of patients undergoing DO.

Conclusion: Direct mechanical measurements from an external fixator may be an alternative procedure to improve the evaluation of healing progress during DO.

Introduction: The SonicPin technology uses ultrasonic energy to weld polymer into bone (BoneWelding), thus forming a bond between implant and bone. The aim of this study was to determine the mechanical capabilities of the SonicPin in comparison to conventional techniques using generic mechanical load conditions.

Methods: Blocks of cancellous bone served as test specimens for generic tests. Two blocks respectively were fixed using either the SonicPin, a titanium cancellous bone screw (ASNIS) or a PLLA pin-screw system (Inion OTPS). The samples were then clamped into a test device and mechanically tested. Tests included pull-out, shear and 4-point-bending.

To examine the mechanical performance of the Son-icPin in a realistic fracture model 12 fresh frozen tibiae were osteotomized through the medial apex of the pla-fond, simulating a horizontal fracture of the medial malleolus. The tibiae were treated with either the Son-icPin or with 4.0-millimeter partially threaded titanium screws. Mechanical testing was performed by applying a compressive load 17 degrees from the long axis of the tibia to simulate supination-adduction loading.

Results: The bond between implant and bone exceeded the strength of the SonicPin itself. Using 2 SonicPins load levels were similar to those obtained with the cancellous screw or the PLLA fixation (p> 0,05).

Discussion: Ultrasonic welding of polymer into bone seems to be a promising technology to be used in orthopaedic surgery. Applying the SonicPin in fractures of the medial malleolus may be considered after slight modifications such as larger diameter or longer pins.

Introduction: It has recently been observed that around the site of a fracture bone loss of up to 10% can occur during the healing process. We hypothesized that trabecular bone around the site of a diaphyseal fracture is considerably diminished during the course of fracture healing and that this loss can be partly compensated by antiresorptive therapy.

Methods: 45 Sprague Dawley rats were randomly divided into 3 groups: Ovariectomy (OVX), sham operation (NON-OVX) and OVX with bisphosphonate (ibandonate) treatment (OVX+BIS). All animals received a standard closed mid diaphyseal fracture of the left femur fixed with an intramedullary pin. After 4 weeks of healing both femurs were excised and scanned with Micro CT to analyze bone architecture in the femoral head.

Results: There was significant osteopenia due to ovariectomy (p< 0.001). BV/TV was reduced by 30%. The fracture itself induced a similar osteopenia at the ipsilateral femur. In OVX animals the fracture induced osteopenia was potentiated by ovariectomy and amounted in a total bone deficit of 60% compared to healthy cancellous bone. Bisphosphonate treatment significantly reduced both the OVX and fracture induced osteopenia.

Discussion: A fracture leads to significant localized osteopenia at locations adjacent to the fracture site. Our findings suggest that the increased risk of secondary fractures after a first osteoporotic fracture might be related to the loss of trabecular bone caused by the fracture healing process. Therefore it is important to consider prevention measures for osteoporosis during the course of fracture healing in osteoporotic patients

In vitro experiments have shown, that stabilisation of the fibula in complete fractures of the lower leg give more stability compared to a single stabilisation of the tibia. However it is not known how this biomechanical conditions influence the bone healing process. To investigate the effect of fibula stability in tibia fracture healing tibial osteotomies in rats with and without fibula fractures were compared.

Male wistar rats (n=18) were operated by a transverse osteotomy of the proximal tibia of the left leg. Fracture was stabilised by intramedullary nailing. In 8 cases an additional closed fibula fracture was performed. The healing period was 21 days.

Each whole leg was examined by x-ray. After explantation of the tibia and removing of the nail and the fibula, the tibia was examined by CT-Scan, three-point-bending and histological evaluation.

Animals, who had a fibula fracture along with the tibia fracture presented with delayed healing. Density in CT-scan was 30% lower (p=0,0002) in animals with a fibula fracture (405mg/ccm, SD:64) compared to those without a fibula fracture (mean=577mg/ccm, SD:17). In three point bending the bending stiffness was 79% lower (p=0,0006) in animals with a fibula fracture (mean=252Nmm/mm, SD:118) compared to animals without a fibula fracture (mean=1219Nmm/mm, SD:478). The breaking force was 59% lower (p=0,0004) in animals with a fibula fracture (mean=17,5N, SD:6) compared to animals without a fibula fracture (mean=42,4N, SD:14).

Complete fractures of the lower leg healed considerably worse than solitary fractures of the tibia. We conclude that the missing of rotational stability of our k-wire fixation of the tibia with a unfixed fibula fracture is one of the reasons for the delay in fracture repair. The results support the in vitro findings of the biomechanical importance of the fibula for the stability of tibia fractures.

Non-steroidal anti-rheumatics (NSAR) are often used in patients with fractured bones for analgetic reasons. This animal experiment was performed to determine the influence of NSAR on the process of fracture healing. As an alternative central acting analgetic without peripheral effect Tramadol was included in this experiment.

Wistar rats were operated by a transverse osteotomy of the proximal tibia of the left leg, fracture was stabilized by intramedullary nailing (healing period 21 days). All therapeutics were applied orally, twice a day. The animals were divided in 4 groups, 10 rats each: Group 1 was treated with placebo, group2 with tramadol (20mg/kg bodyweight/day), group3 with Diclofenac-Colestyramin (5mg/kg/bw./day) over 7 days followed by 14 days placebo, group4 with Diclofenac-Colestyramin (5mg/kg/bw./day) over 21 days. On day 21 the rats were sacrificed and each leg was examined by x-ray, than the tibia was examined by CT-Scan, three-point-bending and histological evaluation.

There were no significant differences between group1 and 2 and between group3 and 4, respectively. Therefore the data of group1 and 2 as well as group3 and 4 are put together.

The results of CT and 3-point-bending showed, that rats treated by Diclofenac presented with delayed fracture healing compared to those treated by placebo or Tramadol. Bone density was 30% lower (p = 0,0001) in animals treated with Diclofenac (mean = 577mg/ccm, SD:53,1 in group1 and 2 vs. mean = 404,3mg/ccm, SD:27,3 in group3 and 4).

The breaking force was 45% (p = 0,0009) lower (mean = 42,4N, SD:14,2 vs. mean = 23,3N, SD:8,2) and the bending stiffness 56% (p = 0,0039) lower (mean = 1218,9Nmm/mm, SD:477,9 vs. mean = 532,6Nmm/mm, SD:389,9) in animals, treated with diclofenac. Diclofenacserumlevels on day 21 in rats with longtime diclofenac application (mean = 242ng/ml, SD:47,7) were comparable to those in humans.

Oral application of Diclofenac significantly delayed fracture healing in rats. This effect might be comparable to other NSAR and fracture healing in humans.