MRI-based assessment of the mylohyoid muscle in oral squamous cell carcinoma, a 7-point scoring method.

OBJECTIVES: To investigate preoperative MRI evaluation of the features of the mylohyoid muscle (MM) predictive of its infiltration in oral squamous cell carcinoma (OSCC) treatment planning, defining the most appropriate sequences to study its deep extension into the floor of the mouth (FOM). MATERIALS AND METHODS: We applied a 7-point score to retrospectively evaluate preoperative imaging of patients who underwent surgery for OSCC over 11 years. The results were compared with histopathological findings using Spearman's rank coefficient. Receiver operating characteristic curves were employed to assess the score's ability to predict MM infiltration, determining optimal thresholds for sensitivity, specificity, and predictive values. The Mann-Whitney U-test confirmed that infiltration judgments did not overlap around this threshold. Cohen's K statistical coefficient was used to evaluate the interobserver agreement. RESULTS: Fifty-two patients (mean age 66.4 ± 11.9 years, 36 men) were evaluated. Histopathological examination found MM infiltration in 21% of cases (n = 11), with 90% classified in the highest Score categories. A score > 4 proved to be the best cut-off for predicting the risk of MM infiltration, with a sensitivity of 91% (CI: 0.57-0.99), specificity 61% (CI: 0.45-0.76), PPV 38% (CI: 0.21-0.59), and NPV 96% (CI: 0.78-0.99). At the subsequent single-sequence assessment, the TSE-T2wi had the highest diagnostic accuracy, with sensitivity 90% (CI: 0.57-0.99), specificity 70% (CI: 0.53-0.82), PPV 45% (CI: 0.25-0.67), and NPV 96% (CI: 0.80-0.99). CONCLUSION: The 7-point score is a promising predictor of safe surgical margins for MM in OSCC treatment, with the particular benefit of T2-weighted sequences. CLINICAL RELEVANCE STATEMENT: Our scoring system for tumor infiltration of MM, which is easy to use even for less experienced radiologists, allows for uniformity in radiological language, thereby ensuring crucial preoperative information for the surgeon. KEY POINTS: The relationship of the MM to an oral lesion may impact surgical planning. As the score increases, there is a greater incidence of infiltration in the MM. Our score system improves radiologists' reporting for MM involvement by tumor.

Concurrent advanced HIV disease and viral load suppression in a high-burden setting: Findings from the 2015-6 ZIMPHIA survey.

BACKGROUND: As Zimbabwe approaches epidemic control of HIV, programs now prioritize viral load over CD4 monitoring, making it difficult to identify persons living with HIV (PLHIV) suffering from advanced disease (AD). We present an analysis of cross-sectional ZIMPHIA data, highlighting PLHIV with AD and concurrent viral load suppression (VLS). METHODS: ZIMPHIA collected blood specimens for HIV testing from 22,501 consenting adults (ages 15 years and older); 3,466 PLHIV had CD4 and VL results. Household HIV testing used the national serial algorithm, and those testing positive then received point-of-care CD4 enumeration with subsequent VL testing. We used logistic regression analysis to explore factors associated with concurrent AD and VLS (<1000 copies/mL). All analyses were weighted to account for complex survey design. RESULTS: Of the 3,466 PLHIV in the survey with CD4 and VL results, 17% were found to have AD (CD4<200cells/mm3). Of all AD patients, 30% had VLS. Concurrent AD and VLS was associated with male sex (aOR 2.45 95%CI 1.61-3.72), older age (35-49 years [aOR 2.46 95%CI 1.03-5.91] and 50+ years [aOR 4.82 95%CI 2.02-11.46] vs 15-24 years), and ART duration (<6 months [aOR 0.46 95%CI 0.29-0.76] and 6-24 months [aOR 2.07 95%CI 1.35-3.17] vs more than 2 years). The relationship between sex and AD is driven by age with significant associations among men aged 25-34, (aOR 3.37 95%CI 1.35-8.41), 35-49 (aOR 5.13 95%CI 2.16-12.18), and 50+ (aOR 12.56 95%CI 4.82-32.72) versus men aged 15-24. CONCLUSIONS: The percentage of PLHIV with AD and VLS illustrates the conundrum of decreased support for CD4 monitoring, as these patients may not receive appropriate clinical services for advanced HIV disease. In high-prevalence settings such as Zimbabwe, CD4 monitoring support warrants further consideration to differentiate care appropriately for the most vulnerable PLHIV. Males may need to be prioritized, given their over-representation in this sub-population.

Mechanical resonance spectra in human cancellous bone.

The dynamic mechanical response of fresh human cancellous bone at low audio frequencies contains two resonance spectra. The spectral frequencies in each series have the ratios 1:4:9:16 ... n(2). The frequencies are in quantitative agreement with the concept of momentum wave modes of calcium and phosphorus atoms in the lamellae, with no variable parameters.

Long-term fatigue behavior of compact bone at low strain magnitude and rate.

Fatigue behavior of compact bone at physiological strain ranges was examined in vitro. Standardized specimens of bovine compact bone were cyclically loaded in uniaxial tension of 0-1200 or 0-1500 microstrain for up to 13-37 million cycles to study the long-term fatigue properties. All specimens exhibited fatigue during the first several million cycles of loading, evidenced by a gradual decrease of specimen modulus during this initial loading period; mean modulus loss for all specimens was approximately 6%. After this initial stiffness loss, specimen modulus stabilized and did not change again for the duration of the loading. Osteonal bone specimens lost significantly more stiffness than primary bone specimens during the early loading history, but neither microstructural type progressed to fatigue failure. These data suggest that some fatigue of compact bone is a realistic expectation of the normal loading environment, but this fatigue does not progress to fatigue failure within a physiologically reasonable number of cycles when tested in vitro at strain magnitudes like those measured in living animals. Implications for fatigue/stress fractures in vivo are discussed.

Mechanical and morphological effects of strain rate on fatigue of compact bone.

Compact bone specimens were cyclically loaded in uniaxial tension for one million cycles; loading was performed at either of two physiological strain rates (0.01 s-1 or 0.03 s-1) and a physiological strain range (0-1200 microstrain). Microdamage in loaded and nonloaded control specimens was then assessed histomorphometrically. Fatigue, evidence by stiffness loss, was observed at both strain rates and was significantly greater in specimens loaded at the high experimental strain rate than in specimens loaded at the low strain rate. Morphologically, this fatigue corresponded to increased numbers of microcracks in the bone. These data show that fatigue and resultant microdamage are realistic expectations of cyclic loading within the physiological strain range. The rate at which strains are developed influences the fatigue behavior of compact bone, suggesting that cyclic loading at high physiological strain rates, characteristic of vigorous activities, is more damaging to compact bone than loading at lower physiological strain rates.

The effects of altered strain environments on bone tissue kinetics.

This study defines the alteration in bone tissue kinetics responsible for the "adaptive remodeling" response to altered strain environments. Adult beagle dogs were separated into three experimental groups: ulnar osteotomy, ulnar osteotomy with fracture fixation plate spanning the gap and sham surgery. Four sets of double fluorochrome labels were administered. Prior to sacrifice at 1, 3, and 6 months, strains were measured through rosette strain gages on the cranial and caudal surfaces of the intact radius. Histomorphometric analysis indicated that the increased bone mass in response to elevated strain results from increased activation frequency of modeling with more sites undergoing formation processes than resorption processes on periosteal and endocortical surfaces. Increased remodeling activation did not lead to increased bone mass. There was no evidence that elevated strain changes the individual vigor of osteoclasts or osteoblasts, or that the sigma period was altered by elevated strain.

Skeletal change in response to altered strain environments: is woven bone a response to elevated strain?

Studies demonstrate that geometric changes in bone architecture in response to altered mechanical strain occur through the formation of woven bone. The goal of this study was to test the hypothesis that these changes are partly the result of surgical manipulation rather than a true adaptive response to altered strain. Beagle dogs were subjected to either an ulnar osteotomy, an osteotomy with plate fixation, or sham operation. Strains on the radius were measured just prior to sacrifice 1, 3 or 6 months after surgery. Our results support the idea that woven bone can be a normal response to an abnormal strain environment if the mechanical challenge is intense enough; that elevated mechanical strains can cause the endocortical bone envelope to revert to a state of net formation; and that "adaptive remodeling" in adults in response to a change in mechanical strain may be a special case of modeling in which resorption is not required prior to formation at a particular skeletal site.

Hypothesis: joints can heal.

Although cartilage has a limited capacity for intrinsic repair, cells extrinsic to the cartilage can provide a mechanism for repair if the proper conditions exist. The new chondroid material produced, although not histologically or biochemically identical to mature hyaline articular cartilage, can nevertheless in many circumstances permit normal joint function and prevent further joint deterioration. The evidence suggests that joint healing results from establishing a source of cells, normalizing joint pressures, and encouraging joint motion. Much of the controversy surrounding the question of whether joints can heal results from a failure to view joint function, rather than cartilage appearance, as the most important component of the healing process, and to appreciate the significant role played by mechanical factors in promoting this response.

Mechanical determinants of osteoarthrosis.

The joint is an organ and functions as a mechanical bearing created of biological materials. In the joint, as in all connective tissues, there is a relationship between mechanical factors and tissue behavior. Therefore, it is not surprising that joint health and osteoarthrosis are reflections of both mechanical and biological factors. Osteoarthrosis is not a disease, but organ failure caused initially by mechanical factors. The biological changes follow. There is no habitual pathophysiological cascade. Osteoarthrosis is best thought of not as a common final pathway, but as a common end stage. The hypotheses that in osteoarthrosis substructural disorganization of the matrix proceeds chondrocytic enzyme production, that impulsive loading is an essential factor in the progressive cartilage destruction, and that tidemark advancement and horizontal cartilage splitting are the primary mechanisms in progressive cartilage loss are discussed.

A prognosis for ultra high molecular weight polyethylene.

Ultra high molecular weight polyethylene (UHMPWE) is now the material of choice for total joint replacement prostheses, in combination with a metal surface against which the polymer articulates. As this material has now been in use in this application for approximately three decades and other limiting factors (e.g. loosening of the prosthesis) have been improved upon, it is appropriate to attempt a long-term prognosis.

Synovial membrane and cartilage changes in experimental osteoarthrosis.

The Hulth instability model was performed on 25 rabbit knee joints. Electron-microscopic, light-microscopic, and histomorphometric data demonstrated consistent chondrocyte alterations and cartilage destruction. The comparison between operated, sham, and control knees shows that surgical intervention without surgically induced instability is followed by changes in the synovial membrane and cartilage. The cartilage destruction is preceded by a synovial reaction, suggesting that the inflammatory response has an important role in the onset of cartilage damage in this model. The damage was more severe in the experimental knees, suggesting that mechanical instability is also a factor in cartilage destruction.

Effects of mechanical loading on the tissues of the rabbit knee.

We studied changes in subchondral bone and articular cartilage in an animal model of osteoarthrosis. In this model we applied repetitive impulsive loads to rabbits' knees. Their legs were held in short leg splints so the rabbits were unable to dampen the peak applied load with ankle flexion. After sacrifice, at 1 day to 6 weeks, we studied proximal tibial load-bearing cartilage histologically, biochemically, and with radioactive sulfate uptake. We also studied the subchondral bone under that cartilage histologically, histomorphometrically, with bone scan (99mTc pyrophosphate), and by tetracycline labeling. An increase in 99mTc labeling of the subchondral bone was the first reliable change observed. This was followed by an increase in tetracycline labeling, bone formation, and a decrease in porosity, which has been associated with relative stiffening of bone. Horizontal splitting and deep fibrillation of the overlying articular cartilage followed the early bone changes. All of these changes preceded changes in content and characterization of cartilage proteoglycans or increased chondrocyte activity as manifested by incorporation of radioactive sulfate. In this model the early bone changes preceded changes in the articular cartilage. The deep splitting of articular cartilage occurred prior to metabolic alteration of that tissue.

Damage type and strain mode associations in human compact bone bending fatigue.

When compact bone is subjected to fatigue loading, it develops matrix microdamage, which reduces the tissue's ability to resist fracture. The relative influence of different strain modes on damage and strength in compact bone has not been characterized, to our knowledge. In this study, the nonuniform strain field produced by four-point bending was used to introduce fatigue damage into tibial bending beam specimens from men 40-49 years old. The specimens were then bulk-stained with basic fuchsin to mark damage surfaces and were examined histologically and with confocal microscopy to describe damage morphologies and position relative to tension and compression-strained regions of the specimen. Histomorphometric methods were used to quantify the amounts of different types of bone microdamage. Three major types were observed. In regions subjected to tensile strains, the bone had focal regions of diffusely increased basic fuchsin staining (i.e., diffuse microdamage). Confocal microscopy of these regions showed them to be composed of extensive networks of fine, ultrastructural-level cracks. In compressive strain regions, the tissue developed linear microcracks in interstitial areas similar to those originally described by Frost. Fine, tearing-type (wispy-appearing) cracks were observed near and in the plane of the neutral axis. The paths of these fine cracks were not influenced by microstructural boundaries. Other minor damage morphologies (sector-stained osteons, delamination of regions of lamellae, and intraosteonal cracking) were observed, but their distribution was unrelated to local strain field. Thus. in fatigue of human compact bone, the principal mechanisms of matrix failure (i.e., linear microcrack, diffuse damage foci, and tearing-type damage) are strongly dependent on local strain type.

Bone and cartilage changes following experimental varus or valgus tibial angulation.

The purpose of this work was to determine whether subchondral bone changes are an integral part of the development of osteoarthrosis of the knee following experimentally created tibial angulation. Thirty degree varus or valgus proximal tibial osteotomies were created in female New Zealand white rabbits. Bone and cartilage changes were assessed grossly, radiologically, and histologically. Thirty-four weeks following osteotomy, severe cartilage changes, including osteophytes, fibrillation, derangement of cell columns, and cloning, were evident on the overloaded condyle, accompanied by increased subchondral bone density. The pattern of cartilage deterioration was different from that found in other experimental, mechanically induced arthroses. We conclude that osteoarthrosis is a final common pathway for mechanically induced joint failure, and that progressive cartilage change is associated with increased subchondral bone density.

Relationship between lower limb dynamics and knee joint pain.

To test the hypothesis that appropriate and timely neuromuscular control of limb motions plays an important role in the preservation of joint health, we kinematically and kinetically examined the behavior of the legs of young adult subjects at heel strike during natural walking. We compared a group of 18 volunteers, who, we presumed, were preosteoarthrotic because of mild, intermittent, activity-related knee joint pain, with 14 age-matched asymptomatic normal subjects. The two groups of subjects exhibited similar gait patterns with equivalent cadences, walking speeds, terminal stance phase knee flexion, maximum (peak) swing angular velocity, and overall shape of the vertical ground reaction. However, our instrumentation detected statistically significant differences between the two groups within a few milliseconds of heel strike. In the knee pain group, the heel hit the floor with a stronger impact in this brief interval. Just before heel strike, there was a faster downward velocity of the ankle with a larger angular velocity of the shank. The follow-through of the leg immediately after heel strike was more violent with larger peak axial and angular accelerations of the leg echoed by a more rapid rise of the ground reaction force. This sequence of events represents repetitive impulsive loading, which consistently provoked osteoarthrosis in animal experiments. We refer to this micro-incoordination of neuromuscular control not visible to the naked eye as "microklutziness."

The Maquet procedure: effect of tibial shingle length on patellofemoral pressures.

The Maquet procedure--elevation of the anterior tibial tubercle--has been recommended for treatment of symptomatic osteoarthrosis of the patellofemoral joint. Although the operation was first described 30 years ago, it remains controversial, both on a clinical and on a biomechanical basis. In addition, deterioration of the long-term results has been suggested. One of the variables that has been ignored in both clinical and biomechanical studies has been tibial shingle length. In order to judge its effect, we examined contact pressures and areas in 15 cadaver knees with 7 and 20 cm tibial shingle lengths. We found significant patellofemoral pressure diminution only with 2 cm elevations. The short anterior tibial shingle with 2 cm of elevation tipped the patella on its superior pole, with a significant change in angle between the patella and the shingle. We suggest that this creates a potentially less than desirable biomechanical circumstance and believe it may explain the discrepancies among previously published reports.

Polymeric debris in synovium after total joint replacement: histogical identification.

In studying a series of synovial biopsy specimens from patients with loose joint replacements, we were able to differentiate reliably between polymethylmethacrylate and ultra high-molecular-weight polyethylene by observing alterations in their birefringence with changes in temperature. The glass transition temperature of polymethylmethacrylate (when it softens from a glass-like to a rubber-like state) is about 105 degrees centigrade. Polyethylene melts at 135 degrees centigrade. The birefringence in polyethylene returns after it has been melted and then cooled; this is not true of methylmethacrylate fragments heated above their glass transition temperature. When cooled, methacrylate fails to regain its birefringence. In addition, free particles of the two plastics were studied in vitro to validate this method of differentiation. We recommend its use routinely in histological studies of patients with loosening.

"Stiction-friction" of total hip prostheses and its relationship to loosening.

The static friction, or "stiction-friction", in McKee-Farrar and Charnley-Müller prostheses in a hip joint simulator was compared with dynamic friction determined while the prostheses were oscillated. Under physiological conditions stiction-friction differed little from dynamic friction in both metal-on-metal and metal-on-plastic prostheses, and was affected very little by the lubricant as long as some fluid was present. Stiction-friction increased significantly only after relatively long stationary periods and high loads. However, the frictional forces generated in total hip-replacement prostheses were at least forty times higher than those generated in normal joints and may well be enough to cause late loosening of acetabular components by fatigue failure.

Changes in the bone-cement interface after total hip replacement. An in vivo animal study.

UNLABELLED: In order to study the temporal sequence of radiographic, histological, mechanical, bacteriological, and chemical changes around the femoral component following total hip replacement, a model was created by implanting plastic-on-metal total hip replacements in sheep and walking the animals on a concrete surface beginning six weeks postoperatively. This model demonstrated a decreased torsional rigidity between the prosthesis and the femoral cortex in all sheep. Failure of bonding occurred at the bone-cement interface and appears from our results to be most probably due to alterations in the functional stress of the proximal end of the femur following insertion of the femoral component rather than exothermic polymerization, toxicity of free monomer residue, or infection. CLINICAL RELEVANCE: An understanding of the causes of loosening of cemented metal femoral components in total hip replacement has been thwarted by a lack of specimens at sequential times in the loosening process. Since a patient is not operated on until the prosthetic components are completely loose, such specimens are difficult to obtain clinically. For this reason a model for examining the bone-cement interface, measured by decreased torsional rigidity of the prosthesis relative to the bone, was developed in sheep. Of all the parameters studied, those inherent in the effects (mechanical or vascular, or both) of insertion of the prosthesis itself appeared to be the most likely cause of the change in the mechanical properties of the interface. This suggests that degenerative changes of the bone-cement interface may be inevitable.

Global mechanical consequences of reduced cement/bone coupling rigidity in proximal femoral arthroplasty: a three-dimensional finite element analysis.

Component loosening in total hip arthroplasty is often accompanied by substantial bony remodelling, associated initially with reduced stiffness of the cancellous bone bordering the cement, and eventually with the formation and proliferation of a compliant fibrous membrane at the bone/cement interface. An anatomically based three-dimensional finite element model has been developed to explore the salient stress changes occurring with progressive degradation of the stiffness of the cancellous bone in a thin zone bordering the cement. This border zone, modelled as a distinct linearly elastic and isotropic material layer, assumed a geometry and a range of mechanical properties inferred from eventual membrane thickness apparent in recent animal studies of component loosening. The major variables considered were: stiffness (elastic modulus) and compressibility (Poisson ratio) of the border zone, stiffness changes in the outlying cancellous bone, resultant hip contact force, and trochanteric muscle loadings. The results for the limiting case of a non-degraded border zone compared reasonably with previous studies of femoral reconstructions having rigid bone-to-cement attachment. Progressive decay of border zone stiffness produced complex changes in load transmission. Foremost among these were a generalized increase in stress levels (especially of transverse-plane tension) in the proximo-lateral cancellous bone, and a corresponding generalized decrease in stress levels in the proximo-medial cancellous bone. There were also large bending moment increases in the prosthesis and its cement mantle, especially at mid-stem. At almost all sites, the critical stress levels were those developed for peak stance-phase loading, rather than for the lower loads (and different resultant contact force directions) occurring elsewhere in the gait cycle. The elevated proximo-lateral cancellous bone stresses occurring with eventual membrane development, consistent with localized bony hypertrophy seen in recent animal studies, may be a response to hoop stresses occurring during pistoning of the tapered cement mantle.