Internal fracture fixation in patients with osteoporosis

Local drug delivery for enhancing fracture healing in osteoporotic bone

Fragility fractures can cause significant morbidity and mortality in patients with osteoporosis and inflict a considerable medical and socioeconomic burden. Moreover, treatment of an osteoporotic fracture is challenging due to the decreased strength of the surrounding bone and suboptimal healing capacity, predisposing both to fixation failure and non-union. Whereas a systemic osteoporosis treatment acts slowly, local release of osteogenic agents in osteoporotic fracture would act rapidly to increase bone strength and quality, as well as to reduce the bone healing period and prevent development of a problematic non-union. The identification of agents with potential to stimulate bone formation and improve implant fixation strength in osteoporotic bone has raised hope for the fast augmentation of osteoporotic fractures. Stimulation of bone formation by local delivery of growth factors is an approach already in clinical use for the treatment of non-unions, and could be utilized for osteoporotic fractures as well. Small molecules have also gained ground as stable and inexpensive compounds to enhance bone formation and tackle osteoporosis. The aim of this paper is to present the state of the art on local drug delivery in osteoporotic fractures. Advantages, disadvantages and underlying molecular mechanisms of different active species for local bone healing in osteoporotic bone are discussed. This review also identifies promising new candidate molecules and innovative approaches for the local drug delivery in osteoporotic bone.

Use of screw locking elements improves radiological and biomechanical results of femoral osteotomies

BACKGROUND

Dynamic compression plate (DCP) constructs provide inadequate fixation in cases of poor bone quality and early weight-bearing. Screw locking elements (SLE) are flat locking nuts placed at the end of the screw to prevent screw stripping from the bone, improving fixation stability. The purpose of this work was to compare biomechanical and radiological evaluations of femoral ovine osteotomies fixed using DCP constructs with and without SLE.

METHOD

A dyaphyseal femoral osteotomy was performed in sixteen adult sheep and fixed with a DCP and cortical screws. Half of the animals were operated on with a SLE on each side of the osteotomy and the rest without the addition of SLE. Four animals of each group were euthanized after 8 weeks, and the remaining after 16 weeks. Both femora of each animal were radiographed and mechanically tested in torsion.

RESULTS

Radiologically femoral malalignment or screw loosening was observed in six out of the eight animals operated on without SLE. In contrast, all animals subjected to the operation with SLE showed complete radiological consolidation of the osteotomy. Seven of these eight animals showed normal femoral alignment and no osteosynthesis failure. Stiffness of the bones fixed with SLE was among 145% and 177% the value of their contralateral non-operated femurs (all animals of this group showed greater stiffness on the operated bone than its contralateral non-operated femur). However, stiffness of the bones operated on without SLE was among 58% and 87% the value of the stiffness of their contralateral non-operated bone (all animals of this group showed greater stiffness on the non-operated bone than the osteotomized ones).

CONCLUSIONS

Use of SLE avoided loosening of the system and stimulated stronger osteotomy consolidation. Clinical application of this improved system may thus be a feasible and cost-effective alternative to other more rigid and expensive bone fixation techniques.

A New Method to Intra-Operatively Measure Local Bone Strength in Osteoporotic Bone Using a Modified Surgical Tool

The aim of this study was to test a novel method for intra-operative assessment of osteoporotic bone fracture strength using a surgical tool instrumented with a strain gauge and compare the device with cortical width (CW) measurements in the distal radius. The force needed to puncture the cortex (FNP) was quantified with the device and found to strongly correlate with bone mineral density (BMD) in the diaphysis (adj. R2 = 0.66, p < 0.001). Screw pullout studies were performed and correlation between FNP and screw pullout strength (SPS) was modest (adj. R2 = 0.34 with p < 0.05). CW correlated well with BMD (adj. R2 = 0.7, p < 0.0001) and SPS (adj. R2 = 0.5, p = 0.002) in the diaphysis. This technology may allow objective intra-operative assessment of bone strength to provide surgeons another tool for decision making on fixation strategies appropriate to the area of bone treated.

Role of sclerostin in bone and cartilage and its potential as a therapeutic target in bone diseases

Sclerostin is a small protein expressed by the SOST gene in osteocytes, bone cells that respond to mechanical stress applied to the skeleton and appear to play an important role in the regulation of bone remodeling. When sclerostin binds to its receptors on the cell surface of osteoblasts, a downstream cascade of intracellular signaling is initiated, with the ultimate effect of inhibiting osteoblastic bone formation. Recent studies have shown that the SOST gene is also expressed by articular chondrocytes and that modulation of its activity may have effects on articular cartilage and subchondral bone. The role of sclerostin in the pathogenesis of osteoarthritis in humans has not yet been defined, and the potential utility of treating osteoarthritis with interventions that alter sclerostin is not known. Rare genetic skeletal disorders in humans with low sclerostin levels, such as sclerosteosis and van Buchem disease, have been associated with a high bone mineral density (BMD) phenotype and low risk of fractures. This has led to the concept that antisclerostin interventions might be useful in the treatment of patients with osteoporosis and skeletal disorders associated with low bone mass. Compounds that inhibit sclerostin have been shown to stimulate bone formation and reduce bone resorption, with a robust increase in BMD. Investigational monoclonal antibodies to sclerostin, including romosozumab, blosozumab, and BPS804, have advanced to phase II clinical trials or beyond. If antisclerostin therapy is found to have beneficial effects on clinical endpoints, such as reduction of fracture risk or improvement in quality of life in patients with osteoarthritis, with a favorable balance of benefit and risk, then this class of compounds may become a prominent addition to the options for therapy of osteoporosis and other skeletal disorders.

Conservative treatment of a femoral neck fracture following nail removal

With increased longevity, the management of fragility fractures in the elderly is becoming more frequent. In particular, hip fractures have considerable importance due to the significant morbidity and mortality. A 67-year-old woman underwent intramedullary nail (IMN) removal inserted for a pertrochanteric fracture that had occurred 20 months earlier. This was indicated due to continuous discomfort related to the protruding apex of the implant over the great trochanter. Due to pain persistence two days after surgery, a computed tomography (CT) scan was performed, documenting a minimally displaced impacted subcapital femoral neck fracture. Conservative management with close radiographic follow-up was conducted. After six months, the patient had returned to previous daily activities and a satisfactory range of motion was achieved without pain on walking. The purpose of our paper is to discuss the decision of removing hardware in the elderly osteoporotic patient and to analyze the possibility to conservatively treat an impacted minimally displaced subcapital fracture occurring after the removal of an IMN inserted previously for the treatment of a trochanteric fracture. In the elderly population with decreased bone quality, the removal of intramedullary implants of the proximal femur should be carefully evaluated, and osteoporotic patients undergoing reduction and fixation of femoral fractures should be encouraged to start antiosteoporotic therapy (bisphosphonate, teriparatide) to reduce the risk of further bone loss. Conservative treatment should be considered for the management of lesser symptomatic minimally displaced impacted fractures, where the inherent stability of the fracture allows rapid healing without further surgical attempts.

Biomaterial scaffolds for treating osteoporotic bone

Healing fractures resulting from osteoporosis or cancer remains a significant clinical challenge. In these populations, healing is often impaired not only due to age and disease, but also by other therapeutic interventions such as radiation, steroids, and chemotherapy. Despite substantial improvements in the treatment of osteoporosis over the last few decades, osteoporotic fractures are still a major clinical challenge in the elderly population due to impaired healing. Similar fractures with impaired healing are also prevalent in cancer patients, especially those with tumor growing in bone. Treatment options for cancer patients are further complicated by the fact that bone anabolic therapies are contraindicated in patients with tumors. Therefore, many patients undergo surgery to repair the fracture, and bone grafts are often used to stabilize orthopedic implants and provide a scaffold for ingrowth of new bone. Both synthetic and naturally occurring biomaterials have been investigated as bone grafts for repair of osteoporotic fractures, including calcium phosphate bone cements, resorbable polymers, and allograft or autograft bone. In order to re-establish normal bone repair, bone grafts have been augmented with anabolic agents, such as mesenchymal stem cells or recombinant human bone morphogenetic protein-2. These developing approaches to bone grafting are anticipated to improve the clinical management of osteoporotic and cancer-induced fractures.

Locked plating of comminuted distal femur fractures: does unlocked screw placement affect stability and failure?

OBJECTIVES

Locked plates provide greater stiffness, possibly at the expense of fracture healing. The purpose of this study is to evaluate construct stiffness of distal femur plates as a function of unlocked screw position in cadaveric distal femur fractures.

METHODS

Osteoporotic cadaveric femurs were used. Four diaphyseal bridge plate constructs were created using 13-hole distal femur locking plates, all with identical condylar fixation. Constructs included all locked (AL), all unlocked (AUL), proximal unlocked (PUL), and distally unlocked (DUL) groups. Constructs underwent cyclic axial loading with increasing force per interval. Data were gathered on axial stiffness, torsional stiffness, maximum torque required for 5-degree external rotation, and axial force to failure.

RESULTS

Twenty-one specimens were divided into AL, AUL, PUL, and DUL groups. Axial stiffness was not significantly different between the constructs. AL and PUL demonstrated greater torsional stiffness, maximum torque, and force to failure than AUL and AL showed greater final torsional stiffness and failure force than DUL (P < 0.05). AL and PUL had similar axial, torsion, and failure measures, as did AUL and DUL constructs. All but 2 specimens fractured before medial gap closure during failure tests. Drop-offs on load-displacement curves confirmed all failures.

CONCLUSIONS

Only the screw nearest the gap had significant effect on torsional and failure stiffness but not axial stiffness. Construct mechanics depended on the type of screw placed in this position. This screw nearest the fracture dictates working length stiffness when the working length itself is constant and in turn determines overall construct stiffness in osteoporotic bone.

Low-modulus Mg/PCL hybrid bone substitute for osteoporotic fracture fixation

In this paper, we describe a new biodegradable composite composed of polycaprolactone and magnesium. Incorporation of magnesium micro-particles into the polycaprolactone matrix yields mechanical properties close to those of human cancellous bone, and in vitro studies indicate that the silane-coated Mg/PCL composites have excellent cytocompatibility and osteoblastic differentiation properties. The bioactivity of the composites is manifested by the formation of calcium and phosphate after immersion in simulated body fluids. The bulk mechanical properties can be maintained for 2 months before obvious degradation takes place. The in vivo animal study reveals a larger amount of new bone formation on the silane-coated Mg/PCL composites compared to conventional PMMA and pure polycaprolactone and our results suggest potential clinical applications of the sliane-coated Mg/PCL composites.

The osteoporotic acetabular fracture

Fractures of the acetabulum are some of the most challenging fractures that face orthopedic surgeons. In geriatric patients, these challenges are enhanced by the complexity of fracture patterns, the poor biomechanical characteristics of osteoporotic bone, and the comorbidities present in this population. Nonsurgical management is preferable when the fracture is stable enough to allow mobilization, and healing in a functional position can be expected. When significant displacement and/or hip instability are present, operative management is preferred in most patients, which may include open reduction and internal fixation with or without total hip arthroplasty.

Currents of plate osteosynthesis in osteoporotic bone

Osteoporotic fractures are becoming more prevalent with ageing of populations worldwide. Inadequate fixation or prolonged immobilization after non-surgical care leads to serious life-threatening events, poor functional results and lifelong disability. Thus, a stable internal fixation and rapid initiation of rehabilitation are required for faster return of function. Conventional internal fixation attempts to achieve the exact anatomy, often with extended soft-tissue stripping and compression of the periosteum, causing disturbance of the metaphyseal and comminuted fracture's bone blood supply. This technique relies on frictional forces between bone and plate. Osteoporotic bone might not be able to generate enough torque with the screw to securely fix the plate to bone. Thus, this surgical management have resulted in increased incidence of poor results in elderly, osteoporotic patients. The newly developed locked internal fixators, locking compression plates and less invasive stabilization system, consist of plate and screw systems where the screws are locked in the plate, minimizing the compressive forces exerted between plate and bone. Thus, the plate does not need to compress the bone nor requires precise anatomical contouring of a plate disturbing the periosteal blood supply. These fixators allowed the development of the minimal invasive percutaneous osteosynthesis. Nowadays, locking plates are the fixation method of choice for osteoporotic, diaphyseal or metaphyseal, severely comminuted fractures.

Preoperative vitamin D status of adults undergoing surgical spinal fusion

STUDY DESIGN

Retrospective investigation of cross-sectional data.

OBJECTIVE

To define the prevalence and determinants of preoperative vitamin D deficiency among adults undergoing spinal fusion.

SUMMARY OF BACKGROUND DATA

Vitamin D plays a critical role in establishing optimal bone health, which, in turn, is vital to the success of spinal arthrodesis. Recently, hypovitaminosis D was documented in 43% of adults undergoing any orthopedic surgery.

METHODS

Serum 25-hydroxyvitamin D levels were routinely measured in adults undergoing spinal fusion at a single institution. Between January 2010 and March 2011, 313 patients were retrospectively identified for inclusion. Risk factors for vitamin D deficiency (<20 ng/mL) were analyzed using univariate analysis and multivariate logistic regression.

RESULTS

The rates of inadequacy (<30 ng/mL) and deficiency were 57% and 27%, respectively. Although 260 patients were diagnosed with degenerative disease (spondylosis), 99 had deformity, and there were 73 revision cases. There was a higher rate of smoking (P = 0.03) and lower age (P < 0.01) in the vitamin D-deficient subset. There was no sex difference. Increasing body mass index (P < 0.01), increasing Neck and Oswestry Disability Index scores (P = 0.03), and lack of vitamin D and/or multivitamin supplementation (P < 0.01) remained predictors of deficiency after multivariate analysis. Those with previous supplementation were older (P < 0.01) and more likely to be at least 50 years old than those without repletion (P < 0.01).

CONCLUSION

Our investigation revealed a substantially high prevalence of vitamin D abnormality in the analyzed population. Although advanced age is a well-established risk factor for hypovitaminosis, young adults undergoing fusion should not be overlooked with regard to vitamin D screening; this age bracket is less likely to have been previously supplemented. In the absence of better-recognized determinants, spinal disability indices may also be useful in identifying those with deficiency.

Accelerated fracture healing with teriparatide

Satisfactory healing of the osteoporotic fracture is critically important to functional recovery, morbidity, and quality of life. Some therapies for osteoporosis may affect the processes associated with bone repair. For example, bisphosphonates in experimental models are associated with increased callus size and mineralization, reduced callus remodeling, and improved mechanical strength. Local and systemic bisphosphonate treatment may improve implant fixation. No negative impact on fracture healing has been observed, even after major surgery or when administered immediately after fracture. For the osteoanabolic agent teriparatide, case reports and a randomized trial have produced mixed results, but they are consistent with a positive impact of teriparatide on fracture healing. Some of the agents currently being developed for osteoporosis, notably sclerostin and DKK1 antibodies have shown a beneficial effect on fracture healing. At this point, therefore, there is no evidence that osteoporosis therapies are detrimental to fracture healing with some promising experimental evidence for positive effects on healing, notably for those agents whose actions are primarily anabolic.

A three-dimensional comparison of intramedullary nail constructs for osteopenic supracondylar femur fractures

OBJECTIVES

This study developed a new 6 degree-of-freedom, unconstrained biomechanical model that replicated the in vivo loading environment of femoral fractures. The objective of this study was to determine whether various distal fixation strategies alter failure mechanisms and/or offer mechanical advantages when performing retrograde intramedullary nail (IMN) stabilization of supracondylar femur fractures in osteoporotic bone.

METHODS

Forty fresh-frozen human femora were allocated into 2 groups of matched pairs: "locked" (fixed angle locking construct with both distal locking screws rigidly attached to the IMN) versus "unlocked" (conventional locking technique with 2 distal locking screws targeted through the distal locking screw holes of the IMN) and "locked" versus "washer" (fixed angle locking with the most distal screw exchanged for a bolt with condyle washers) distal fixation of a retrograde IM nails. A comminuted fracture (OTA 33-A3) was simulated with a wedge osteotomy. Bone density measurements were completed on all specimens before instrumentation. Instrumented femurs were loaded axially to failure, whereas 6 degree-of-freedom translations and angulations were measured using Roentgen stereophotogrammetric analysis.

RESULTS

Mean (± SD) load born by "locked" specimens (1609 ± 667 N) at clinical failure was 38.1% greater (P = 0.09) than the corresponding mean load born by "unlocked" specimens (1165 ± 772 N). Clinical failure for the "washer" group (1738 ± 772 N) was 29.9% greater (P = 0.07) than the corresponding mean of the "locked" counterparts (1338 ± 822 N). Failure load was most clearly related to bone density in the "unlocked" fixation group.

CONCLUSIONS

Predicting failure load based on bone density using a least squares estimate suggests that the washer construct provides superior fixation to other treatment techniques. The failure mechanism for a comminuted, supracondylar fracture cannot be analyzed accurately with a 1-dimensional measurement. The most common failure mechanism in this model was medial translation and varus angulation.

Delayed fracture healing in aged senescence-accelerated P6 mice

BACKGROUND

Osteoporosis is characterized by poor bone quality. However, it is still controversially discussed whether osteoporosis compromises fracture healing. Herein, we studied whether the course of healing of a femur fracture is affected by osteoporosis or age.

METHODS

Using the senescence-accelerated osteoporotic mouse, strain P6 (SAMP6), and a closed femur fracture model, we studied the process of fracture healing in 5- and 10-month-old animals, including biomechanical, histomorphometric, and protein biochemical analysis.

RESULTS

In five-month-old osteoporotic SAMP6 mice, bending stiffness, callus size, and callus tissue distribution as well as the concentrations of the bone formation marker osteocalcin and the bone resorption markers tartrate-resistant acid phosphatase form 5b (TRAP) and deoxypyridinoline (DPD) did not differ from that of non-osteoporotic, senescence-resistant, strain 1 (SAMR1) controls. In contrast, femur fractures in 10-month-old SAMP6 mice showed a significantly reduced bending stiffness and an increased callus size compared to fractures in age-matched SAMR1 controls. This indicates a delayed fracture healing in advanced age SAMP6 mice. The delay of fracture healing was associated with higher concentrations of TRAP and DPD. Significant differences in osteocalcin concentrations were not found between SAMP6 animals and SAMR1 controls.

CONCLUSION

In conclusion, the present study indicates that fracture healing in osteoporotic SAMP6 mice is not affected in five-month-old animals, but delayed in animals with an age of 10 months. This is most probably due to the increased osteoclast activity in advanced age SAMP6 animals.

Outcomes for four-part proximal humerus fractures treated with a locking compression plate and an autologous iliac bone impaction graft

OBJECTIVES

The study aims to evaluate outcomes of autologous iliac bone impaction grafts (AIBIGs) with locking-compression plates (LCPs) in four-part proximal humeral fracture.

METHODS

Between October 2004 and October 2008, 21 AIBIG with LCP osteosyntheses were done for four-part proximal humeral fractures. Patients included seven males and 14 females. Their mean age at the time of the operation was 66.3±16.9 years (range: 24-87 years). Five patients had high-energy fractures other than fall from standing height. There were two fracture-dislocation cases, and three valgus-impacted fractures. The length of the calcar segment attached to the articular segment was 7.04±6.10mm; 13 of the 21 cases had lengths less than 8mm. Medial-hinge displacement was 16.77±15.84mm; 19 of the 21 cases had displacements more than 2mm.

RESULTS

There was no avascular necrosis of the humeral head and union was achieved in all cases. Varus collapse and hardware-related complications were not observed. Postoperative neck-shaft angles were found to be 129±9° (range: 109-146°). Neer scores were 92.0±6.3 (range: 81-100).

CONCLUSION

The results of using AIBIG with LCP for four-part proximal humeral fractures are excellent. There are significant bone defects in osteoporotic or comminuted fractures and LCP alone does not always provide reliable fixation. Therefore, meticulous technique and use of AIBIG in this complicated type of fracture can ensure a favourable outcome.

In-vitro comparison of LC-DCP- and LCP-constructs in the femur of newborn calves - a pilot study

Background

To compare the biomechanical in-vitro characteristics of limited-contact dynamic compression plate (LC-DCP) and locking compression plate (LCP) constructs in an osteotomy gap model of femoral fracture in neonatal calves. Pairs of intact femurs from 10 calves that had died for reasons unrelated to the study were tested. A 7-hole LC-DCP with six 4.5 mm cortical screws was used in one femur and a 7-hole LCP with four 5.0 mm locking and two 4.5 mm cortical screws was used in the corresponding femur. The constructs were tested to failure by cyclic compression at a speed of 2 mm/s within six increasing force levels.

Results

The bone-thread interface was stripped in 21 of 80 cortical screws (26.3%) before a pre-set insertion torque of 3 Nm was achieved. Only 3 corresponding intact pairs of constructs could be statistically compared for relative structural stiffness, actuator excursion and width of the osteotomy gap. Relative structural stiffness was significantly greater, actuator excursion and width of the osteotomy gap were significantly smaller in the LCP constructs. While failure occurred by loosening of the screws in the LC-DCP constructs, locking constructs failed by cutting large holes in the soft distal metaphyseal bone.

Conclusions

An insertion torque sufficient to provide adequate stability in femurs of newborn calves could not be achieved reliably with 4.5 mm cortical screws. Another limiting factor for both constructs was the weak cancellous bone of the distal fracture fragment. LCP constructs were significantly more resistant to compression than LC-DCP constructs.

Does bone mineral density affect hip fracture severity?

The association between hip fracture and reduced bone mineral density is well documented, with reduced bone mineral density predisposing to fracture. However, it is unknown whether an association exists between the magnitude of bone density lost and the severity of the hip fracture sustained. One hundred forty-two patients (96 women, 46 men) with a mean age of 74 years (range, 49-92 years) who sustained a hip fracture following a simple ground-level fall and were treated for this injury were reviewed. All patients had undergone dual-energy x-ray absorptiometry bone scanning of the contralateral hip and lumbar spine. Fractures were classified as intra- or extracapsular or subtrochanteric and then subclassified by degree of severity as simple (stable) or multifragmentary (unstable) fracture patterns.Although a low hip bone mineral density (T- or Z score <2.5) was associated with an increased risk of extracapsular fracture (P=.025) compared with other fracture types, no association existed between bone mineral density and the severity of the resultant hip fracture. Although an association exists between bone mineral density and the risk of fragility fractures, the results of the current study suggest that the severity of hip fractures does not follow this correlation. Therefore, no assumption can be made about bone mineral density of the proximal femur based on the severity of the fracture observed on plain radiographs.

Implications for fracture healing of current and new osteoporosis treatments: an ESCEO consensus paper

Osteoporotic fracture healing is critical to clinical outcome in terms of functional recovery, morbidity, and quality of life. Osteoporosis treatments may affect bone repair, so insights into their impact on fracture healing are important. We reviewed the current evidence for an impact of osteoporosis treatments on bone repair. Treatment with bisphosphonate in experimental models is associated with increased callus size and mineralization, reduced callus remodeling, and improved mechanical strength. Local and systemic bisphosphonate treatment may improve implant fixation. No negative impact on fracture healing has been observed, even after major surgery or when administered immediately after fracture. Experimental data for denosumab and raloxifene suggest no negative implications for bone repair. The extensive experimental results for teriparatide indicate increased callus formation, improved biomechanical strength, and greater external callus volume and total bone mineral content and density. Case reports and a randomized trial have produced mixed results but are consistent with a positive impact of teriparatide on clinical fracture healing. Studies with strontium ranelate in models of fracture healing indicate that it is associated with improved bone microstructure, callus volume, and biomechanical properties. Finally, there is experimental evidence for a beneficial effect of some of the agents currently being developed for osteoporosis, notably sclerostin antibody and DKK1 antibody. There is currently no evidence that osteoporosis treatments are detrimental for bone repair and some promising experimental evidence for positive effects on healing, notably for agents with a bone-forming mode of action, which may translate into therapeutic applications.

The lateral decubitus approach for complex proximal femur fractures: anatomic reduction and locking plate neutralization: a technical trick

Unstable intertrochanteric or subtrochanteric fractures with significant proximal or distal extension or comminution are often a challenge for achieving stable fixation. In recent years, locked proximal femoral plates have been developed that aid fixation of these complex fractures often permitting the biological advantages of minimal contact or minimally invasive application. Although previously described with success using a standard lateral approach in the supine position, we describe a lateral decubitus position for the locked plating of proximal femur fractures. We have found that lateral positioning neutralizes the gravitational forces acting on the bone and soft tissues, facilitating reduction and exposure while continuing to be compatible with intraoperative image intensification. We present lateral positioning as a technical trick for anatomic and stable reduction of complex proximal femur fractures with proximal femoral locking plates and present a series of 10 cases that were treated with this combination of approach and internal fixation.

Influence of screw holes and gamma sterilization on properties of phosphate glass fiber-reinforced composite bone plates

Polymers prepared from polylactic acid (PLA) have found a multitude of uses as medical devices. For a material that degrades, the main advantage is that an implant would not necessitate a second surgical event for removal. In this study, fibers produced from a quaternary phosphate-based glass (PBG) in the system 50P2O5-40CaO-5Na2O-5Fe2O3 were used to reinforce PLA polymer. The purpose of this study was to assess the effect of screw holes in a range of PBG-reinforced PLA composites with varying fiber layup and volume fraction. The flexural properties obtained showed that the strength and modulus values increased with increasing fiber volume fraction; from 96 MPa to 320 MPa for strength and between 4 GPa and 24 GPa for modulus. Furthermore, utilizing a larger number of thinner unidirectional (UD) fiber prepreg layers provided a significant increase in mechanical properties, which was attributed to enhanced wet out and thus better fiber dispersion during production. The effect of gamma sterilization via flexural tests showed no statistically significant difference between the sterilized and nonsterilized samples, with the exception of the modulus values for samples with screw holes. Degradation profiles revealed that samples with screw holes degraded faster than those without screw holes due to an increased surface area for the plates with screw holes in PBS up to 30 days. Scanning electron microscope (SEM) analysis revealed fiber pullout before and after degradation. Compared with various fiber impregnation samples, with 25% volume fraction, 8 thinner unidirectional prepreg stacked samples had the shortest fiber pull-out lengths in comparison to the other samples investigated.

Effect of osteoporosis on clinical outcomes in intertrochanteric hip fractures treated with a proximal femoral nail

The effect of osteoporosis on clinical outcomes following surgical treatment of intertrochanteric hip fractures was investigated. A total of 80 patients aged 65-97 years with intertrochanteric hip fractures underwent insertion of a proximal femoral nail. Osteoporosis severity was measured using the Singh index in the unaffected hip. Screw cut-out occurred in four patients, reverse Z-effect in three patients and Z-effect in one patient. Four patients were lost to follow up. Clinical results were evaluated according to the Harris hip scoring system. The mean Harris hip score was 73.58 (range 25-100). When divided according to Singh index grade (I-II versus III-V), there were no significant differences in mean age, type of fracture, American Society of Anesthesiologists classification or frequency of technical failures between the two groups. The mean Harris hip score, however, was significantly lower in patients with grades I-II compared with grades III-V, suggesting that the presence of osteoporosis had a negative effect on clinical outcome after hip fracture.

Pinealectomy affects bone mineral density and structure--an experimental study in sheep

Background

Osteoporosis and associated fractures are a major public health burden and there is great need for a large animal model. Melatonin, the hormone of the pineal gland, has been shown to influence bone metabolism. This study aims to evaluate whether absence of melatonin due to pinealectomy affects the bone mass, structure and remodeling in an ovine animal model.

Methods

Female sheep were arranged into four groups: Control, surgically ovariectomized (Ovx), surgically pinealectomized (Px) and Ovx+Px. Before and 6 months after surgery, iliac crest biopsies were harvested and structural parameters were measured using μCT. Markers of bone formation and resorption were determined. To evaluate long term changes after pinealectomy, bone mineral density (BMD) was analyzed at the distal radius at 0, 3, 9, 18 and 30 months.

Results

Cancellous bone volume (BV/TV) declined after 6 months by -13.3% Px and -21.5% OvxPx. The bone loss was due to increased trabecular separation as well as decreased thickness. The histomorphometric quantification and determination of collagen degradation products showed increased bone resorption following pinealectomy. Ovariectomy alone results in a transient bone loss at the distal radius followed by continuous increase to baseline levels. The bone resorption activity after pinealectomy causes a bone loss which was not transient, since a continuous decrease in BMD was observed until 30 months.

Conclusions

The changes after pinealectomy in sheep are indicative of bone loss. Overall, these findings suggest that the pineal gland may influence bone metabolism and that pinealectomy can be used to induce bone loss in sheep.

A comparison of parallel and diverging screw angles in the stability of locked plate constructs

We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm(3)) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10° and 20° divergent) and 5 mm self-tapping locking screws underwent pull-out and cyclical pull and bending tests. The bovine cancellous blocks were only subjected to static pull-out testing. We also performed finite element analysis for the static pull-out test of the parallel and 20° configurations. In both the foam model and the bovine cancellous bone we found the significantly highest pull-out force for the parallel constructs. In the finite element analysis there was a 47% more damage in the 20° divergent constructs than in the parallel configuration. Under cyclical loading, the mean number of cycles to failure was significantly higher for the parallel group, followed by the 10° and 20° divergent configurations. In our laboratory setting we clearly showed the biomechanical disadvantage of a diverging locking screw angle under static and cyclical loading.

Evidence for success with locking plates for fragility fractures

Fixation of fragility fractures with plates and screws often results in loss of fixation and need for revision surgery. Locking plates and screw were introduced to improve fixation of fragility fractures and have been in use for a decade. This review was conducted to compile evidence that locking plates and screws improve fixation of fragility fractures. A search of PubMed was performed to identify biomechanical studies as well as clinical series of fragility fractures treated with locking plates. Biomechanics papers had to use models of osteoporotic bone and had to directly compare locking plates with traditional plates. Clinical studies included case series in which locking plates were applied to elderly patients with fractures of the proximal humerus and periprosthetic distal femur fractures. Most studies are retrospective case series. Locking plates lead to greater stability and higher loads to failure than traditional plates. When applied to proximal humerus fractures, uncomplicated healing occurs in 85% of patients. Constant and Dash scores approach normal values. For distal femoral periprosthetic fractures, union rates of 75% are reported with a malunion rate of 10%. Early evidence suggests that locking plates improve results of treatment of proximal humerus fractures and distal femoral periprosthetic fractures in the elderly. Loss of fixation is associated with failure to achieve stability at the fracture site. Principles of fracture fixation in osteoporotic bone defined prior to the introduction of locking plates should still be applied.

Displaced proximal humeral fractures: an Indian experience with locking plates

Background

The treatment of displaced proximal humerus fractures, especially in elderly, remains controversial. The objective of this study was to evaluate functional outcome of locking plate used for fixation of these fractures after open reduction. We also attempted to evaluate the complications and predictors of loss of fixation for such an implant.

Methods

Over two and a half years, 56 patients with an acute proximal humerus fracture were managed with locking plate osteosynthesis. 47 of these patients who completed a minimum follow up of 1 year were evaluated using Constant score calculation. Statistical analysis was done using SPSS 16 and a p value of less than 0.05 was taken as statistically significant.

Results

The average follow up period was around 21.5 months. Outcomes were excellent in 17%, good in 38.5%, moderate in 34% while poor in 10.5%. The Constant score was poorer for AO-OTA type 3 fractures as compared to other types. The scores were also inferior for older patients (> 65 years old). Complications included screw perforation of head, AVN, subacromial impingement, loss of fixation, axillary nerve palsy and infection. A varus malalignment was found to be a strong predictor of loss of fixation.

Conclusion

Locking plate osteosynthesis leads to satisfactory functional outcomes in all the patients. Results are better than non locking plates in osteoporotic fractures of the elderly. However the surgery has steep learning curve and various complications could be associated with its use. Nevertheless we believe that a strict adherence to the principles of locking plate use can ensure good result in such challenging fractures.

Less rigid stable fracture fixation in osteoporotic bone using locked plates with near cortical slots

INTRODUCTION

Locked plating leads to improved fixation in osteoporotic bone. In addition, experimental data suggest that overall construct stiffness is increased. Ideal stiffness may be significantly less than that achieved with these locked constructs, and overly stiff constructs may lead to impaired fracture healing and stress concentration at the ends of the plate. In osteoporotic bone, this stiffness mismatch can be even more pronounced. We hypothesized that substituting slots for holes in the near cortex under a locked plate would lead to predictably lower stiffness without diminishing implant stability.

METHODS

Osteoporotic bone substitute segments were used. Locking screws and plates were applied to each specimen using either standard holes or near cortical slots. The slots were designed to allow axial displacement of the screw in the near cortex only, while continuing to provide some torsional stability. Mechanical testing was performed using a progressive dynamic displacement load protocol to determine failure and stiffness. Next, cyclic axial loading was performed with a physiologic load for 10,000 cycles to determine change in stiffness with cycling. Outcomes were compared between groups using Mann-Whitney U tests.

RESULTS

In the dynamic displacement tests, the slotted specimens reached both maximum load and failure load at a significantly greater displacement than the non-slot group (p=0.008), indicating later failure. The magnitude of the maximum load achieved was no different between groups. In the cyclic loading tests, the axial stiffness in the slotted group was significantly lower (1199 N/mm) than the non-slotted group (3538 N/mm; p<0.05 at all cycles). Stiffness did not change significantly in either group over the course of cycling.

DISCUSSION

The ability to predictably adjust the axial stiffness of locked plating constructs is critical, particularly in osteoporotic bone. The use of near cortical slots decreases axial stiffness of locking plates, while maintaining fixation stability. This may allow the surgeon to more closely tailor the construct stiffness to the clinical situation to minimize stiffness mismatches and complications.

Influence of defective bone marrow osteogenesis on fracture repair in an experimental model of senile osteoporosis

Bone marrow osteogenesis in senile osteoporotic bone is impaired and, as such, may have significant implications on the successful outcome of fracture repair. Here we utilize a well-established murine model of senile osteoporosis, the P6 strain of senescence-accelerated mice (SAMP6), to investigate fracture healing in aged osteoporotic bone. A femoral osteotomy was created in SAMP6 and in non-osteoporotic age-matched control R1 senescence-resistant mice (SAMR1). The course of fracture healing was evaluated over a period of 42 days using quantitative microCT and histological analysis. The differentiation capabilities of bone mesenchymal progenitor cells derived from SAMP6 and SAMR1 mice was examined, and their osteogenic potential determined. Although preliminary in vitro analysis confirmed that bone marrow-derived stem cells (BMSC) isolated from SAMP6 mice had a reduced osteogenic capacity, no significant deficit in fracture repair as determined by quantitative microCT could be detected. This was supported by histology assessment, where complete bridging of the fracture gap was evident by day 28 and was fully healed day 42 in both SAMP6 and SAMR1 mice. Further in vitro studies revealed that periosteal-derived progenitor cells (PDPC) isolated from SAMP6 mice had an osteogenic potential comparable to that observed in SAMR1 mice. In conclusion, fracture healing in SAMP6 mice is not detrimentally affected by impairment of BMSC osteogenesis, suggesting that bone marrow-mediated repair processes are dispensable for normal bone healing in this senile osteoporotic fracture model. Furthermore, the influence of PDPC in the repair process may partly explain the absence of any detectable deficits in fracture repair in SAMP6 mice.

Proximal humerus fracture rotational stability after fixation using a locking plate or a fixed-angle locked nail: the role of implant stiffness

BACKGROUND

Fixed-angle locked devices have been developed to improve internal fixation of proximal humerus fractures. Available low-profile precontoured locking plates and intramedullary nails with fixed-angle interlocks are currently favored by most surgeons in this setting. The aim of this study was to assess the relative stability of these two methods of fixation under torsion load.

METHODS

A surgical neck osteotomy was created in six pairs of embalmed humeri. In each pair, one specimen was secured with a titanium locking-compression plate, and the contralateral was secured with a titanium nail with a proximal locked spiral blade. The specimens were first tested cyclically in internal-external rotation for 10,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cyclic testing, the specimens were loaded to failure in external rotation to measure torque to failure and construct stiffness (static study).

FINDINGS

There were no significant differences in interfragmentary motion between the two fixation devices in the dynamic study. When tested to failure, fixation with the locking plate tolerated on average 20 more degrees in torsion before failure, and demonstrated higher torsional load to failure and less torsional stiffness (P<0.05).

INTERPRETATION

Both locking plates and locked intramedullary nails may provide enough stability to avoid secondary displacement of proximal humerus fractures during early physical therapy. Locking plates demonstrated superior biomechanical properties under high rotational loads than locked intramedullary nails in a cadaveric proximal humerus two-part osteotomy model, and could provide more protection against unexpected high torsion loads.

Irradiated human chondrocytes expressing bone morphogenetic protein 2 promote healing of osteoporotic bone fracture in rats

Bone morphogenetic protein 2 (BMP2) was selected as a transgene to regenerate osteoporotic bone defects after several BMPs were tested using a bone formation study in nude mice. Human chondrocytes were transduced with a BMP2-containing retroviral vector, and single clones were selected. The cells were characterized over numerous passages for growth and BMP2 expression. The single clones were irradiated and tested for viability. BMP2 expression lasted for 3 weeks before dying off completely after approximately 1 month. Irradiated and non-irradiated transduced chondrocytes successfully healed fractures in osteoporotic rats induced by ovariectomy. The osteoinducing effect of irradiated cells was better than that of their non-irradiated counterparts or a chondrocytes-only control. This study showed that delivering BMP2 from the transduced and irradiated chondrocytes could be an effective and safe method of repairing osteoporotic bone fractures.

Hydroxyapatite particles maintain peri-implant bone mantle during osseointegration in osteoporotic bone

In osteoporotic bones, resorption exceeds formation during the remodelling phase of bone turnover. As a consequence, decreased bone volume and bone contact result in the peri-implant region. This may subsequently lead to loss of fixation. In this study we investigated whether the presence of nonresorbable, osteoconductive hydroxyapatite (HA) particles could help maintain a denser and more functional peri-implant bone structure. Titanium screws were implanted into the proximal tibial metaphysis of four months old, ovariectomized Wistar rats (n=60). In the right tibia, the drill hole was first filled with HA particles, while the left tibia served as a control without HA particles. Histological analysis demonstrated that during the remodelling phase the amount of newly formed bone was significantly higher on the HA over the control side. Micro-CT analysis corroborated the significant changes over time as well as differences in peri-implant bone volume density between treatment and control group. Mechanical tests demonstrated that the pull-out force was greater with HA particles. These results indicate that HA particles are able to induce and maintain for a longer time a denser peri-implant bone mantle in osteoporotic bone, which may have important implications in the prevention of implant migration and cut-outs.

Failure of fracture plate fixation

Failure of fracture fixation after plating often leads to challenging surgical revision situations. Careful analysis of all patient and fracture variables is helpful in both determining the causes of the fixation failure and maximizing the success of subsequent interventions. Biologic and mechanical factors must be considered. Biologic considerations include traumatic soft-tissue injury and atrophic fracture site. Common mechanical reasons for failure include malreduction, inadequate plate length or strength, and excessive or insufficient construct stiffness. Reliance on laterally based implants in the presence of medial comminution may be a cause of fixation failure and subsequent deformity, particularly with conventional nonlocking implants. Management of dead space with cement or beads has been effective in conjunction with staged approaches. An antibiotic cement rod in the diaphysis may provide fracture stabilization. Locking full-length constructs should be considered for osteoporotic fractures.

Relative stability of conventional and locked plating fixation in a model of the osteoporotic femoral diaphysis

BACKGROUND

This study investigated the stiffness and strength of bridge plating with uni-cortical and bi-cortical locking plate constructs relative to a conventional, non-locked construct in the osteoporotic femoral diaphysis.

METHODS

Four bridge plating configurations were applied to a validated model of the osteoporotic femoral diaphysis. A non-locked conventional configuration served as baseline. Locked configurations included bi-cortical locked plating, uni-cortical locked plating and mix-mode locked plating, which combined uni and bi-cortical locking screws. For all configurations, an 11-hole plate was applied with 4.5-mm screws placed in the 1st, 3rd, and 5th plate hole. Five specimens of each configuration were dynamically loaded until failure in torsion, axial compression, and bending to determine construct stiffness, strength and failure modes.

FINDINGS

In torsion and bending, locked plating constructs provided a significantly lower stiffness and strength than the conventional construct. The uni-cortical locked construct was 69% weaker (P<0.001) in torsion than the conventional construct, but its torsional strength improved 73% (P<0.001) by adding one bi-cortical locked screw. In axial compression, construct stiffness varied by less than 10% between the four groups. However, the bi-cortical and mixed-mode locked constructs provided a significant increase in strength of 12% (P=0.001) and 11% (P=0.002), respectively, compared to the conventional construct.

INTERPRETATIONS

Locked plating in the osteoporotic diaphysis can improve fixation strength under axial loading, but may reduce fixation strength in bending and torsion compared to conventional plating. Adding one bi-cortical locked screw to an otherwise uni-cortical construct is recommended to improve torsional strength.

A sheep model for fracture treatment in osteoporosis: benefits of the model versus animal welfare

Animal models are necessary to evaluate new options for the treatment of fractures in osteoporotic bone. They permit both the biological response of a living system and the influence of the pathological processes to be taken into account. A sheep model for osteoporosis was established by combining oestrogen deficiency, calcium and vitamin D-deficient diet with steroid medication. Bone mineral density (BMD) was reduced by >30% after 12 weeks of combined treatment. Osteoporosis similar to the human situation with corresponding changes in the micro-architecture and mechanical properties of bone was observed. This publication focuses on the impressive results obtained with the model and contrasts them with considerations of animal welfare. Considerable side-effects associated with steroid medication became manifest. Animals in the treatment groups showed signs of infection of various degrees due to the immunosuppressive effect of the medication. The infections were mostly caused by Corynebacterium pseudotuberculosis. Antibody testing revealed a 100% prevalence of infection in this breed of sheep. A modification of the steroid treatment, i.e. less-frequent injections, reduced the incidence of side-effects. This sheep model shows a significant and reproducible reduction in cancellous BMD of >30%, including relevant changes in biomechanical properties and increased fracture risk. However, the severity of the side-effects cannot be overlooked. The model must be improved if it is to be used in the future. Options to reduce the side-effects are discussed.

The use of locked plating in skeletally immature patients

The philosophy and techniques for the management of fractures in the pediatric patient have changed over the past several decades. The immature skeleton has unique properties, and injuries in children have different characteristics, management options, and complications than do similar injuries in adults. The basic surgical techniques used in the management of pediatric fractures include closed reduction and casting, closed or open reduction with internal fixation, and external fixation. The concept of bridging plate osteosynthesis has evolved based on scientific insight into bone biology and the importance of blood supply to bone. The use of locked plating is gaining favor in the treatment of certain fractures in adults. However, the role for this technique in the skeletally immature patient has not been described.

Controlled plastic deformation for the fastening mechanism of an internal fixation device. The new Mennen 3 PeriPro plate

The Mennen femur plate is a fixation device used for the treatment of femoral periprosthetic fractures. It features a novel fastening method where curved prongs are plastically deformed securing the implant to the bone. Although this "clamp-on" method has been successfully used to treat fractures of long bones, there are no literature data assessing the nature of the required plastic deformation. In the present study, the parameters influencing the performance of the prongs were identified and further explored using numerical modeling. The new Mennen 3 PeriPro plate is briefly discussed focusing on the new sculpted formation of the prongs. Their design was optimized to effectively control the magnitude and position of the required plastic deformation achieving enhanced anchorage on the fractured bone with minimum effort. The work presented contains all the necessary steps in analysing a clinical problem using finite elements and illustrates how effective use of simulation techniques can accurately predict and effectively control the required plastic deformation of a structure.

Pullout strength and load to failure properties of self-tapping cortical screws in synthetic and cadaveric environments representative of healthy and osteoporotic bone

BACKGROUND

The parameters of self-tapping screw (STS) performance in normal and osteoporotic bone have been defined in representative environments, but the question remains as to the clinical application of such findings. The goal of this study was to analyze the biomechanical performance of STSs in cadaveric and synthetic environments representative of healthy and osteoporotic bone.

METHODS

Ninety-six Synthes STSs were inserted into cadaveric and synthetic models representative of osteoporotic and healthy bone. Screws were inserted to depths of 1 mm short of the far cortex, flush and 1 mm and 2 mm beyond the far cortex. Screws were tested with an Instron 8511 material testing system utilizing axial pullout forces. A SAS procedure was used to conduct analysis of variance for unbalanced datasets.

RESULTS

Substantial differences were appreciated with respect to screw performance between osteoporotic and healthy bone specimens. Although a similar pattern of increased pullout strength and loading energy with increasing depth of insertion was demonstrated, absolute values were lower in osteoporotic specimens. Although performance trends were similar in cadaveric and synthetic testing models for both osteoporotic and healthy bone, values obtained during testing were different. Incomplete insertion of STSs resulted in a 21.5% and 37% reduction of biomechanical properties in osteoporotic and normal bone, respectively.

CONCLUSIONS

These results indicate that previously published findings on the performance of STSs in synthetic models cannot reasonably be applied to the clinical realm. Although trends may be similar, screw performance in synthetic, as compared with cadaveric, models is markedly different.

The anterolateral acromial approach for fractures of the proximal humerus

Displaced and unstable fractures of the proximal humerus are notoriously difficult to manage. Successful surgical treatment requires finding the appropriate balance between adequate exposure for reduction and rigid fixation and minimizing soft tissue dissection. The anterolateral acromial approach was developed to allow less invasive treatment of proximal humerus fractures. The plane of the avascular anterior deltoid raphe is utilized, and the axillary nerve is identified and protected. Anterior dissection near the critical blood supply is avoided, substantial muscle retraction is minimized, and the lateral plating zone is directly accessed. Over a 4-year period, 52 patients with acute displaced fractures of the proximal humerus were treated with the anterolateral acromial approach and either a locking plate or an intramedullary nail. Twenty-three patients were evaluated clinically at a minimum follow-up of 1 year (average, 28 months) by clinical examination for range of motion and nerve function and a QuickDASH score. There were no axillary nerve deficits postoperatively related to the approach, and the average QuickDASH score was 25.2 (0, best; 100, worst). This approach allowed direct access to the lateral fracture planes for fracture reduction and plate placement or safe nail and interlocking screw placement.

Occurrence and pattern of long bone fractures in growing dogs with normal and osteopenic bones

A retrospective study was undertaken to record the occurrence and pattern of long bone fractures, and the efficacy of Intramedullary (IM) Steinmann pin fixing in growing dogs. All the records of growing dogs during a 10-year-period were screened to record the cause of trauma, the age and sex of the animal, the bone involved, the type and location of the fracture, the status of fixation, alignment, maintenance of fixation and fracture healing. The results were analysed and comparisons were made between growing dogs with normal and osteopenic bones. Among the 310 cases of fractures recorded, the bones were osteopenic in 91 cases (29%). Minor trauma was the principal cause of fracture in dogs with osteopenia (25%), and indigenous breeds were most commonly affected (38%). Fractures in dogs with osteopenic bones were most commonly recorded in the age group of 2-4 months (53%), whereas fractures in normal dogs were almost equally distributed between 2 and 8 months of age. Male dogs were affected significantly more often in both groups. In osteopenic bones, most fractures were recorded in the femur (56%), and they were distributed equally along the length of the bone. Whereas in normal bones, fractures were almost equally distributed in radius/ulna, femur and tibia, and were more often recorded at the middle and distal third of long bones. Oblique fractures were most common in both groups; however, comminuted fractures were more frequent in normal bones, whereas incomplete fractures were more common in osteopenic bones. Ninety-nine fracture cases treated with IM pinning (66 normal, 33 osteopenic) were evaluated for the status of fracture reduction and healing. In a majority of the cases (61%) with osteopenic bones, the diameter of the pin was relatively smaller than the diameter of the medullary cavity (<70-75%), whereas in 68% of the cases in normal bones the pin diameter was optimum. The status of fracture fixing was satisfactory to good in significantly more osteonormal (59%) than osteopenic dogs (42%). Fracture healing, however, was satisfactory in significantly more cases with osteopenic than normal bones. The appearance of callus was relatively early and the amount of bridging callus was relatively large in greater number of osteopenic bone fractures. Mal-union and non-union were recorded more often in osteopenic cases than in normal cases. However, the incidence of bone shortening and osteomyelitis was significantly higher in normal bones than in osteopenic bones.