Biomechanical Failure Research Articles

Effects of graft rotation on initial biomechanical failure characteristics of bone-patellar tendon-bone constructs.

Graft-tunnel mismatch is a potential problem during single-incision technique for anterior cruciate ligament reconstruction with the central third of the patellar tendon. Mismatch is present when the graft is too long to fit appropriately in the tunnels that have been created. Graft rotation is one method for addressing this problem. To determine the results of graft rotation up to 540 degrees on initial graft biomechanical properties and graft length. Controlled laboratory study. Forty porcine bone-patellar tendon-bone constructs were divided into four groups and constructs were rotated to 0 degrees, 90 degrees, 180 degrees, and 540 degrees, respectively, for each group. Biomechanical testing to failure was performed with the constructs under tension at an elongation rate of 5 cm/sec. Lengths were measured after a 1-kg load was applied to the grafts. No statistical difference in ultimate failure strength was encountered between any of the groups (P = 0.915). The grafts that were twisted to 540 degrees shortened an average of 5.41 mm, which represented an average shortening of 10% of the initial tendon length. Graft rotation up to 540 degrees does not result in loss of initial graft strength, and may be a solution for graft-tunnel mismatch.

Molecular and antibiofilm approaches to prosthetic joint infection.

The majority of patients with prosthetic joint replacement (arthroplasty) experience dramatic relief of pain and restoration of satisfactory joint function. In the United States, more than.5 million people have a primary arthroplasty each year. Less than 10% of prosthesis recipients have complications develop during their lifetime, commonly as a result of aseptic biomechanical failure, followed by prosthetic joint infection. The pathogenesis of prosthetic joint infection is related to bacteria in biofilms, in which they are protected from antimicrobial killing and host responses rendering these infections difficult to eradicate. Current microbiology laboratory methods for diagnosis of prosthetic joint infection depend on isolation of a pathogen by culture. However, these methods have neither ideal sensitivity nor ideal specificity. Therefore, culture-independent molecular methods have been used to improve the diagnosis of prosthetic joint infection. In the research setting, detection of 16S ribosomal deoxyribonucleic acid by polymerase chain reaction has been used in the molecular diagnosis of prosthetic joint infection. Various antibiofilm strategies directed at disruption of adherent bacteria are the focus of intense research to improve the detection of biofilm organisms and their eradication. In this article, molecular and antibiofilm approaches to prosthetic joint infection are reviewed.

COMPARISON OF CULTURE OF SYNOVIAL FLUID, PERIPROSTHETIC TISSUE AND PROSTHESIS SONICATE FOR THE DIAGNOSIS OF KNEE PROSTHESIS INFECTION

Background. Synovial fluid and periprosthetic tissue specimens are the standard specimens cultured for the diagnosis of prosthetic joint infection (PJI). We hypothesize that ultrasonication of the explanted prosthesis may improve diagnosis of PJI by dislodging biofilm bacteria from the prosthesis surface and improve the sensitivity and specificity of diagnosis of PJI. Methods. Included were patients undergoing knee prosthesis exchange for septic or biomechanical failure and have not received antimicrobial therapy in the last 2 weeks prior specimen collection. Cultures of synovial fluid and periprosthetic tissue specimens were performed per the usual clinical practice. Additionally, explanted joint components were sonicated for 5 minutes at frequency 40 kHz in sterile Ringer’s solution; aliquots of 0.5 ml sonicate were plated onto five aerobic and five anaerobic blood agar plates, and incubated at 37 °C and examined for the next seven days. The number and identity of each colony morphology was recorded. Results. 35 patients undergoing knee replacement have been studied (24 for aseptic biomechanical failure and 11 for suspected PJI). In patients with PJI, coagulase-negative staphylococci (7 cases), Corynebacterium spp. (2 cases), Staphylococcus aureus (1 case), and viridans group streptococcus (1 case) were recovered. Culture sensitivity and specificity were for synovial fluid 88% and 100%, for periprosthetic tissue 83% and 81%, and for explant sonicate 91% and 100%, respectively. In sonicate cultures higher numbers of microorganisms than in periprosthetic tissue cultures were consistently detected. Conclusions. Using synovial fluid, periprosthetic tissue, and explant sonicate cultures, 12%, 17% and 9% of PJI were missed, respectively. Explant sonicate cultures were the most sensitive with respect to the diagnosis of PJI, indicating that explant ultrasonication may improve bacterial recovery. In sonicate cultures, infecting organisms were detected in high numbers, typically concentrated on only one of the prosthetic components. These findings indicate that explant ultrasonication may improve bacterial recovery and support the importance of biofilms in, and the focal nature of, PJI.

Advances in the laboratory diagnosis of prosthetic joint infection

Prosthetic joint implant surgery (arthroplasty) provides restoration of movement to almost half a million people each year in the USA, with major health and economic benefits. While the majority of recipients experience dramatic relief of preoperative pain at the arthroplasty site, some prostheses fail to achieve this result. This is most commonly the result of aseptic biomechanical failure or prosthetic joint infection (PJI), both of which are associated with significant morbidity. Because the management of PJI differs from that of aseptic failure, it is important to accurately differentiate these two entities. Current laboratory methods for diagnosis of PJI depend on isolation of a pathogen by culture from a clinical specimen (e.g., synovial fluid, periprosthetic tissue). However, as PJI is typically a low organism burden and focal infection caused by commensal micro-organisms, these methods have neither ideal sensitivity nor ideal specificity. Therefore, culture-independent molecular methods have been used to improve the diagnosis of PJI. In the research setting, detection of 16S ribosomal DNA (rDNA) by polymerase chain reaction has been the prime focus of the molecular diagnosis of PJI. In this article, advantages and limitations of conventional and molecular methods for the laboratory diagnosis of PJI are reviewed, as is the use of methods that may improve detection of organisms in the biofilm environment. The diagnosis of PJI remains challenging and a rapid, sensitive and specific method is needed for appropriate surgical and medical treatment decisions in the growing arthroplasty population.

Premature biomechanical failure of the distal fixation screws of the IC Nail—case report

Treatment of closed fractures of the tibial shaft by intramedullary nailing has become standard practice [1]. However, broken implants such as a plastic medullary tube [2] or a broken nail or broken screws can occur either intraor postoperatively. This is a report of a case of premature failure of the two distal screws of the IC Nail in a patient with fractured distal third of the tibia. Although bony healing was prompt after the application of compression, it was noted that one of the two distal screws was significantly bent. Compression was applied immediately after the operation by the method recommended by the developers of the IC Nail1. Serial follow up showed early breakage of the bent screw, and bending of the other remaining distal screw as well. The opportunity is taken to discuss the biomechanical basis of the early failure of the two distal screws, and the necessary precautions needed in the use of the IC Nail are highlighted.

Epithelial-induced intrapulpal denticles in B6C3F1 mice.

Multiple intrapulpal denticles were observed in maxillary incisors of control and treated B6C3F1 mice used in a chronic inhalation study. Histologically, the denticles originated from multiple small budlike projections emanating from the epithelial sheath, immediately adjacent to the pulp chamber. The denticles were round to ovoid in shape with a central cavity surrounded by tubular dentin. Immature denticles contained epithelial cells within the central cavity, whereas mature denticles were either devoid of cells or contained cell fragments. A layer of columnar odontoblasts surrounded the outer surface of each denticle. Denticles advanced in a coronal direction as the incisors grew. With continued incisor growth, some denticles impacted the tooth wall and were associated with defects in dentinogenesis, altered tooth shape, and microfractures. Some denticles became partly or entirely incorporated into the dentin of the tooth. Intrapulpal denticle formation may represent a previously unidentified alteration that could contribute to the development of dental dysplasia in mice by interfering with normal tooth development and predisposing affected teeth to malformation and biomechanical failure with fracture.

Acquired Degenerative Changes of the Intervertebral Segments at and Supradjacent to the Lumbosacral Junction

In earlier evolutionary times, mammals were primarily quadrupeds, although other bipeds have been represented during the course of the Earth's several billion-year history. In many cases, either the bipedal stance yielded a large tail and hypoplastic upper extremities (e.g., Tyrannosaurus rex, the kangaroo), or it culminated in hypoplasia of the tail and further development and specialization of the upper extremities (e.g., nonhuman primates and human beings). In the human species this relatively recently acquired posture resulted in a more or less pronounced lumbosacral lordosis. In turn, certain compensatory anatomic features have since occurred. These include the normal characteristic posteriorly directed wedge-shape of the L5 vertebral body and the L5-S1 intervertebral disc; the L4 vertebral body and the L4-L5 and L3-4 disc may be similarly visibly affected. These compensatory mechanisms, however, have proved to be functionally inadequate over the present long-term of the human life span. Upright posture leads to increased weight bearing in humans that progressively causes excess stresses at and suprajacent to the lumbosacral junction. These combined factors result in accelerated aging and degenerative changes and a predisposition to frank biomechanical failure of the subcomponents of the spinal column in these spinal segments. One other specific problem that occurs at the lumbosacral junction that predisposes toward premature degeneration is the singular relationship that exists between a normally mobile segment of spine (i.e., the lumbar spine), and a normally immobile one (i.e., the sacrum). It is well known that mobile spinal segments adjacent to congenitally or acquired fused segments have a predilection toward accelerated degenerative changes. The only segment of the spine in which this is invariably normally true is at the lumbosacral junction (i.e., the unfused lumbar spine adjoining the fused sacrum). Nevertheless, biomechanical failures of the human spine are not lethal traits; in most cases today, mankind reaches sexual maturity before spinal biomechanical failure precludes sexual reproduction. For this gene-preserving reason, degenerative spinal disorders will likely be a part of modern societies for the foreseeable eternity of the race. The detailed alterations accruing from the interrelated consequences of and phenomena contributing to acquired degenerative changes of the lumbosacral intervertebral segments as detailed in this discussion highlight the extraordinary problems that are associated with degenerative disease in this region of the spine. Further clinicoradiologic research in this area will progressively determine the clinical applications and clinical efficacy of the various traditional and newer methods of therapy in patients presenting with symptomatic acquired collapse of the intervertebral discs at and suprajacent to the lumbosacral junction and the interrelated degenerative alterations of the nondiscal structures of the spine.

Genetic engineering of meniscal allografts.

Allograft meniscal transplantation represents one of the few available treatment options after menisectomy. Despite acceptable early results, a considerable controversy exists with regard to poor graft regeneration, shrinkage and biomechanical failure of transplanted menisci. Transfer of specific growth factor genes may improve the regeneration process of meniscal allografts. The aim of this study was to investigate the feasibility of gene transfer in meniscal allografts in rabbits. Four different viral vectors encoding marker genes, including lacZ, luciferase, and green fluorescence protein were used to investigate viral transduction in 50 lapine menisci for 4 weeks in vitro. Subsequently, 16 unilateral meniscus replacements were performed with ex vivo retrovirally transduced meniscal allografts, and the expression of the lacZ gene was examined histologically at 2, 4, 6, and 8 weeks after transplantation. Gene expression in the superficial cell layers of the menisci can be detected for up to 4 weeks in vitro, but the level of gene transfer declined over time. The transduction with retrovirus showed better persistence and deep penetration of the menisci with infected cells. In vivo, declining numbers of beta-galactosidase-positive cells were also detected in retrovirally transduced allografts up to 8 weeks. Consistently, transduced cells were found at the menisco-synovial junction of the transplants and in deeper layers of the menisci. There was no evidence of cellular immune response in the transduced transplants. This investigation showed a prospective for growth factor delivery in auto- and allografts. In further experiments, vectors expressing therapeutic proteins such as growth factors will be investigated to assess their potential to improve remodeling and healing of meniscal allografts.

Relative Safety Factors against Global Buckling, Anchorage Rotation, and Tissue Rupture in Wheat

The objective of this study was to quantify the effect of specific physical and biological factors on the relative likelihood of biomechanical failure in wheat. Wind-related crop damage is a major obstacle to wheat production that costs several billion dollars per year. The four factors varied in this study were breeding line, dwarfing gene dose, soil type, and fertilization. A theoretical model describing the dynamic structural response of living plants was used to define margins of safety against global buckling, anchorage rotation, and tissue rupture. These relative safety factors were defined for each treatment in comparison with a tall wheat variety selected from a breeding line called Seri and grown in sandy soil with low fertilization. Compared to this reference, the relative safety factor against global buckling was increased (+39%,p <0.01), and the relative safety factor against anchorage rotation was decreased (−11%,p <0.025), by one allele of the dwarfing gene. The relative safety factor against tissue rupture was unaffected by the dwarfing gene but was consistently lower (−26%, p<0.01) in a second breeding line called Kauz. Soil type and fertility did not affect the relative safety factors and this negative finding was significant at p<0.05. The key finding was that the strength of wheat was affected more by genetic rather than by environmental factors, which suggests that some varieties are intrinsically more robust than others. Also, the relative safety factor against anchorage rotation was inversely proportional to the relative safety factor against buckling, which suggests that there are competing constraints on the dynamic structural behavior of wheat.

Acquired Degenerative Changes Of The Intervertebral Segments At And Suprajacent To The Lumbosacral Junction: A Radioanatomic Analysis of the Nondiskal Structures of the Spinal Column and Perispinal Soft Tissues

In earlier evolutionary times, mammals were primarily quadrupeds. However, other bipeds have also been represented during the course of the Earth's several billion year history. In many cases, either the bipedal stance yielded a large tail and hypoplastic upper extremities (e.g., Tyrannosaurus rex and the kangaroo), or it culminated in hypoplasia of the tail and further development and specialization of the upper extremities (e.g., nonhuman primates and human beings). In the human species this relatively recently acquired posture resulted in a more or less pronounced lumbosacral kyphosis. In turn, certain compensatory anatomic features have since occurred. These include the normal characteristic posteriorly directed wedge-shape of the L5 vertebral body and the L5-S1 intervertebral disk; the L4 vertebral body and the L4-L5 disk may be similarly visibly affected. These compensatory mechanisms, however, have proved to be functionally inadequate over the long term of the human life span. Upright posture also leads to increased weight bearing in humans that progressively causes excess stresses at and suprajacent to the lumbosacral junction. These combined factors result in accelerated aging and degenerative changes and a predisposition to frank biomechanical failure of the subcomponents of the spinal column in these spinal segments. One other specific problem that occurs at the lumbosacral junction that predisposes toward premature degeneration is the singular relationship that exists between a normally mobile segment of spine (i.e., the lumbar spine) and a normally immobile one (i.e., the sacrum). It is well known that mobile spinal segments adjacent to congenitally or acquired fused segments have a predilection toward accelerated degenerative changes. The only segment of the spine in which this is invariably normally true is at the lumbosacral junction (i.e., the unfused lumbar spine adjoining the fused sacrum). Nevertheless, biomechanical failures of the human spine are not lethal traits; in most cases today, mankind reaches sexual maturity before spinal biomechanical failure precludes sexual reproduction. For this gene-preserving reason, degenerative spinal disorders will likely be a part of modern societies for the foreseeable eternity of the race. The detailed alterations accruing from the interrelated consequences of and phenomena contributing to acquired degenerative changes of the lumbosacral intervertebral segments as detailed in this discussion highlight the extraordinary problems that are associated with degenerative disease in this region of the spine. Further clinicoradiologic research in this area will progressively determine the clinical applications and clinical efficacy of the various traditional and newer methods of therapy in patients presenting with symptomatic acquired collapse of the intervertebral disks at and suprajacent to the lumbosacral junction and the interrelated degenerative alterations of the nondiskal structures of the spine.

Pertrochanteric pseudarthrosis. Implant failure - technical error - destiny?

Pain is not always the leading symptom of a failed union. High primary stability often allows full weight bearing in spite of fracture instability. The difficult diagnosis of a pseudarthrosis is a reason for late intervention. Implant failure and implant breakage are typical signs of surgical underestimation. Finally, the diagnosis "pseudarthrosis" is a fluent one and is defined as a failed fracture healing despite implant stability. Recognition of biological and biomechanical failure, this demands correct evaluation of the global situation and extensive experience in revision surgery on the part of the surgeon.

MOLECULAR DETECTION OF INFECTION IN TOTAL KNEE ARTHROPLASTY: A CLINICAL CORRELATION

Total knee arthroplasty patients displaying symptoms consistent with either implant biomechanical failure or periprosthetic infection, and requiring revision surgery, had synovial fluid aspirated from the affected joint and subjected to standard microbiological culture testing for bacterial infection. In this study, an aliquot of each synovial fluid specimen was analyzed for infection using the rapid, sensitive molecular assay of polymerase chain reaction (PCR), designed to selectively amplify bacterial deoxyribonucleic acid. Decisions concerning surgical procedures performed during revision surgery were based entirely on clinical criteria, including standard preoperative evaluation for infection, independent of PCR results. In total, on the basis of pre- and/or intraoperative clinical data in conjunction with postoperative information, septic failure was determined in 31 of 50 patients, all of whom tested positive using the PCR assay. This correlative study validates the application of the PCR assay for clinical evaluation of arthroplasty infections.

Limb Salvage Surgery for Osteosarcoma of the Proximal Humerus: Outcome in 17 Dogs

To describe function and identify factors that affect outcome in dogs undergoing limb salvage surgery for osteosarcoma (OS) of the proximal humerus. A retrospective study of dogs in which OS of the proximal humerus was treated with limb salvage surgery. 17 client-owned dogs. Records were analyzed for functional outcome, recurrence, metastasis, and survival. Outcome was good to excellent in 12% of dogs. Recurrence, metastasis, and survival were significantly affected by completeness of surgical margins. Double plating of the distal allograft-host junction significantly reduced frequency of biomechanical failure. Limb salvage surgery for OS of the proximal humerus did not result in acceptable function and was fraught with postoperative complications. Outcome was significantly affected by completeness of surgical margins. Limb salvage surgery for OS of the proximal humerus in dogs cannot be recommended until improvement in functional outcome and reduction in postoperative complications can be achieved. The dependence of outcome on completeness of surgical margins supports aggressive en bloc resection and marking and evaluating surgical margins.

Ageing and zonal variation in post-translational modification of collagen in normal human articular cartilage: The age-related increase in non-enzymatic glycation affects biomechanical properties of cartilage

A biomechanical failure of the collagen network is postulated in many hypotheses of the development of osteoarthritis with advancing age. Here we investigate the accumulation of non-enzymatic glycation (NEG) products in healthy human articular cartilage, its relation to tissue remodelling and its role in tissue stiffening. Pentosidine levels were low up to age 20 years, and increased linearly after this age. This indicates extensive tissue remodelling at young age, and slow turnover of collagen after maturity has been reached. The slow remodelling is supported by the finding that enzymatic modifications of collagen (hydroxylysine, hydroxylysylpyridinoline, and lysylpyridinoline) were not related to age. The high remodelling is supported by levels of the crosslink lysylpyridinoline (LP) as a function of distance from the articular surface. LP was highest at the surface in mature cartilage (>20 years), whereas in young cartilage (<10 years) the opposite was seen; highest levels were close to the bone. LP levels in cartilage sections at age 14 years are high at the surface and close to the bone, but they are low in the middle region. This indicates that maturation of cartilage in the second decade of life starts in the upper half of the tissue, and occurs last in the tissue close to the bone. The effect of NEG products on instantaneous deformation of cartilage was investigated as a functional of topographical variations in pentosidine levels in vivo and in relation to in vitro induced NEG. Consistently, higher pentosidine levels were associated with a stiffer collagen network. A stiffer and more crosslinked collagen network may become more brittle and more prone to fatigue.

The effect of muscle architecture on the biomechanical failure properties of skeletal muscle under passive extension

This study investigates the biomechanical failure properties of five architecturally different skeletal muscles and examines the role muscle structure plays in the passive extension characteristics of musculotendinous units. The muscles used in this study fall into four morphologic categories: fusiform, unipennate, bipennate, and multipennate. Each muscle was pulled to failure at three different rates of strain (1, 10, and 100 cm/min). Specimens of fusiform, unipennate, and bipennate muscles were pulled from their proximal as well as distal attachments. The relationship of elongation to failure of the entire musculotendinous unit to resting muscle fiber length was examined to determine the effect of angle of pennation and fiber length on the failure properties. Our results demonstrate that all four muscle types tested show injury and rupture at the musculotendinous junction whether pulled from proximal or distal attachment, regardless of muscle structure and rate of strain. There was a statistically significant difference (P less than 0.005) in the degree of elongation to failure relative to resting muscle fiber length, with a tendency to greater elongation relative to fiber length for muscles with more pennate structure (tibialis anterior, 72.7% +/- 1.0%; extensor digitorum longus, 113.1% +/- 3.5%; rectus femoris, 225.5% +/- 3.7% elongation in percent resting fiber length).

Effect of freezing on histologic and biomechanical failure patterns in the rabbit capital femoral growth plate.

Ten pairs of proximal femora were harvested from 8-week-old New Zealand white rabbits. Experimental shear fractures were then created in vitro, and load-displacement curves were recorded. One specimen from each animal was tested within 4 h of death, whereas the contralateral specimen was frozen for 10 to 20 days and thawed prior to testing. Histologic sections of the fractured specimens were studied. No statistically significant differences could be demonstrated between the fresh and the frozen/thawed specimens in either the histologic patterns or the shear load or stress to failure.

Collagenolytic Enzyme Systems in Human Intervertebral Disc

Changes in the macromolecular matrix of the intervertebral disc may predispose to biomechanical failure of the disc. Such changes would involve extracellular enzymes capable of altering the collagen and proteoglycan of the disc matrix. In this study, extracts from homogenates of both annuli fibrosi and nuclei pulposi of human lumbar discs were found to contain neutral collagenolytic, gelatinolytic, and elastinolytic enzymes in all samples assayed. The specific activity of the collagenase was higher in extracts from nuclear than from annular tissue, a difference not seen with gelatinase or elastase. The collagenase was present as both a latent and active enzyme, the other enzymes being fully active. Human intervertebral discs therefore contain enzymes capable of degrading their extracellular macromolecular matrix.