Local Bone Density Research Articles

2313: Changes in local bone density after pelvic radiotherapy in patients with pelvic malignancies

2313: Changes in local bone density after pelvic radiotherapy in patients with pelvic malignancies

Application of topical 5-Fluorouracil to reduce the recurrence of odontogenic keratocyst: A prospective study with 2-year follow-up

ObjectivesThe purpose of this prospective study was to evaluate the effect of topical 5-Fluorouracil as an adjunct therapy in reducing the recurrence of odontogenic keratocyst. MethodsForty-eight patients with proven incisional biopsy as odontogenic keratocyst were included in this clinical study. The patients were divided into two equal groups, the test group patients were treated with 5-Fluorouracil cream after cyst enucleation. However, the control group patients were treated with cyst enucleation only. Recurrence (yes/no) was the primary outcome variable evaluated by clinical signs of inflammation, swelling, or pain within a 2-year follow-up. The pain was measured on a visual analogue scale, and swelling was measured pre-surgically using vertical and horizontal references, 1 week, 1 month, 3 months, 6 months, 12 months, and 24 months. Computed tomography was performed pre-surgically and 24 hours post-surgically, at 12-month, and 24-month intervals to evaluate local bone density. The T-test was used to compare between two studied groups. ResultsPost-surgical follow-up showed uneventful wound healing in both groups with no clinical signs of recurrence or swelling, pain results demonstrated that patients have decreased records throughout the observation periods with no significant difference between both groups. Normal sensation was encountered in all patients except for one patient in the control group who showed no sensation (score 2). Post-surgical radiographic findings revealed a considerable shift in bone density in all patients of both groups at the site of excised lesions during the follow-up periods compared with immediate post-surgical radiographs. However, the test group patients demonstrated a significant increase of bone density between different evaluation periods (P = 0.001) than the control group. ConclusionConservative enucleation of odontogenic keratocyst combined with topical application of 5-Fluorouracil is an effective treatment with lower recurrence rates, less morbidity, and normal bone healing.

Mid- to long-term outcomes of proximal humerus fractures treated with open reduction, plate fixation, and iliac bone autograft augmentation.

Open reduction and internal fixation (ORIF) using locking plates is a widely adopted treatment for displaced proximal humerus fractures. Various augmentation techniques have been developed to enhance the stability of plate fixation. Among these, iliac bone autograft is notable for its advantages over allografts, such as ready availability and the elimination of costs and risks associated with disease transmission. Despite its potential benefits, data on the outcomes of iliac bone autograft augmentation (IBAA) are still limited. This study aims to present the mid- to long-term results of treating proximal humerus fractures with ORIF using locking plates and IBAA. The study included 15 patients treated with ORIF and IBAA. We classified fracture patterns using the Neer classification and estimated local bone density via the deltoid tuberosity index. We measured the neck shaft angle (NSA) and humeral head height (HHH) on both immediate postoperative and most recent X-ray images to assess the maintenance of reduction. Clinical outcomes were evaluated using the DASH (Disabilities of the Arm, Shoulder, and Hand) and Constant scores. The average follow-up duration was 59.56 months, ranging from 24 to 93 months. A majority of fractures were classified as four-part (53%). The average immediate and late postoperative NSAs were 132.6±8.19 and 131.6±7.32 degrees, respectively. The average HHH on the immediate postoperative and latest follow-up images were 16.46±6.07 and 15.10±5.34, respectively. None of the patients exhibited any radiological signs of avascular necrosis or loss of reduction at the latest follow-up. The mean postoperative Constant and DASH scores at the latest follow-up were 79.6 and 11.5, respectively. Our findings suggest that ORIF with IBAA is an effective method for managing three- or four-part proximal humerus fractures, yielding excellent outcomes.

Deltoid tuberosity index for proximal humerus fracture: reliability and a predictor of systemic osteoporosis in an Asian population

Our study investigates the reliability of deltoid tuberosity index (DTI) and DTI as a predictor of systemic osteoporosis. The proximal humerus is a common fragility fracture. Current literature suggests that poor local bone density is a significant predictor for surgical fixation failure. The DTI is a simple radiographical tool that is strongly correlates with local humeral BMD aiding surgical planning to consider adjuncts or arthroplasty. However, there is a lack of data in the reliability of assessment of DTI, as well as its correlation to systemic osteoporosis. Respective cohort of patients with PHF treated at a trauma center in Singapore from August 2017 to July 2018 were recruited. Four raters at different levels of varying clinical seniority measured DTI using shoulder radiographs. The dual energy X-ray Absorptiometry (DEXA) bone mineral density (BMD) scan of the hip and lumbar spine was used to diagnose osteoporosis. Area under receiver operating characteristics (AUROC) analysis was conducted to study the diagnostic utility of DTI to predict the risk of osteoporosis. Our study had 87 patients consisting 18 males and 69 females, mainly of Chinese ethnicity (84%) and mean age of 69.7 years (SD 9.52, range 39-92yrs). For assessment of DTI, there was good intra-rater reliability amongst four raters (correlation coefficient range 0.805- 0.843) and excellent inter-rater reliability between al raters (intraclass correlation coefficient = 0.898; 95% CI 0.784-0.950, p-value <0.001). Based on BMD, 55.2% (n=48) were osteoporotic using T-score <-2.5. The highest correlation of DTI to BMD was with femoral neck density at 0.580. The DTI cut-off of 1.6 had the highest combined sensitivity and false positive rate, with area under curve (AUC) = 0.682 (95% CI, 0.564-0.799) for the overall population and AUC =0.706 (95% CI, 0.569-0.842) for patients <75 years. The DTI is a simple and reliable tool, strengthening its applicability in clinical practice to enhance preoperative planning in the surgical fixation of PHF. DTI with a cut off of 1.6 may be helpful tool prompting clinicians to workup and manage underlying osteoporosis.

Preoperative glenoid bone density is associated with systemic osteoporosis in primary shoulder arthroplasty

BackgroundIn shoulder arthroplasty, poor bone mineral density can impact humeral and glenoid fixation, as well as increase the risk of periprosthetic fracture. The purposes of this study were to (1) determine the association between preoperative glenoid and humeral Hounsfield units (HUs) with systemic bone density in primary shoulder arthroplasty, (2) determine a threshold for HU on preoperative shoulder computed tomography (CT) to classify patients as osteoporotic, and (3) identify which anatomic T-score locations were significantly associated with glenoid and/or humeral HU measurements. MethodsConsecutive patients who had both a preoperative shoulder CT and a dual-energy x-ray absorptiometry (DEXA) scan were included. HU measurements of the glenoid vault and proximal humerus were recorded. DEXA T-scores from the spine, hip, and femoral neck were recorded, and osteoporosis was defined as a T-score of −2.5 or lower in any of the anatomic sites. Patients were grouped into osteoporosis and nonosteoporosis cohorts and these cohorts were compared using standard statistical tests. To assess the association between HUs and DEXA T-score, linear regression analysis was performed. Additional receiver operating characteristic analysis was performed to evaluate the ability of HUs to classify patients as osteoporotic. ResultsA total of 162 patients undergoing primary shoulder arthroplasty with both preoperative CT and DEXA scores were included. The osteoporosis cohort had significantly lower body mass index (P = .001), although no other significant differences in demographics were found between the 2 cohorts. The osteoporosis cohort was associated with significantly lower glenoid vault bone density in HUs (183 ± 104 vs. 303 ± 157, P = .004) and trended toward significantly lower proximal humeral bone density in HUs (34.3 ± 54.8 vs. 64.5 ± 58.2, P = .058). Glenoid HU threshold of 175 had an area under the curve of 0.75, with sensitivity of 80.8% and specificity of 62.5% for classifying systemic osteoporosis. HUs of both the glenoid (P = .031) and proximal humerus (P = .003) were significantly associated with femoral neck T-scores on linear regression analysis. Similarly, HUs of both the glenoid (P < .001) and proximal humerus (P = .009) were significantly associated with spine T-scores on linear regression analysis. DiscussionThis study found that glenoid vault HU is significantly associated with systemic osteoporosis and can be used as a screening tool for detecting osteoporosis preoperatively. In addition to implications for component fixation and periprosthetic fracture, local bone density evaluation on shoulder CT prior to shoulder arthroplasty represents an opportunity for osteoporosis screening.

Predictive value of the deltoid tuberosity index for assessing the risk of screw cut-out

Abstract Background Reconstruction of the proximal humerus with a locking plate is often the first surgical approach for proximal humerus fractures. Screw cut-out is a common complication and is relevant in osteoporotic bone of older adults. The Deltoid Tuberosity Index (DTI) is an indirect measure for assessing local bone quality and failure rate before surgery, providing important information for surgical planning. This was the first independent, large-sample retrospective analysis of the correlation between local bone density, indirectly measured through the DTI, and screw cut-out. Methods In total, 306 cases of proximal humerus fractures treated with the PHILOS plate (DePuy Synthes, Oberdorf, Switzerland) were retrospectively analyzed. The DTI was measured on anteroposterior x‑rays. The primary endpoint was screw cut-out defined as the intra-articular position of at least one screw associated with a reduction loss after surgery. Results The mean clinical follow-up was 935 days. The DTI varied from 1.10 to 2.28 (average: 1.45). Screw cut-out occurred on average in 8% of the cases and was positively correlated with a DTI of ≤ 1.44 (p = 0.003). However, the rate of cut-out and correlation with DTI varied widely according to age group: for ages 65–80 years, a DTI of ≤ 1.44 increased the cut-out rate from 0% to 17% (p = 0.02); in younger ages (&lt; 65 years) the DTI did not correlate with cut-out and in the oldest group (&gt; 80 years) cut-out rates were high (17–20%) independently of the DTI. Conclusion We confirm the correlation between a DTI of ≤ 1.44 and screw cut-out. High-risk groups for screw cut-out are patients over 65 years with a DTI of ≤ 1.44 or any patient older than 80 years. Applying the DTI in the age group of 65–80 years offers relevant information for surgical planning in the trauma setting via a fast, cheap, and easy-to-use tool. Level of Evidence: Level 3, Retrospective Cohort Study.

SOST gene suppression stimulates osteocyte Wnt/β-catenin signaling to prevent bone resorption and attenuates particle-induced osteolysis

The most common cause for prosthetic revision surgery is wear particle-induced periprosthetic osteolysis, which leads to aseptic loosening of the prosthesis. Both SOST gene and its synthetic protein, sclerostin, are hallmarks of osteocytes. According to our previous findings, blocking SOST induces bone formation and protects against bone loss and deformation caused by titanium (Ti) particles by activating the Wnt/β-catenin cascade. Although SOST has been shown to influence osteoblasts, its ability to control wear-particle-induced osteolysis via targeting osteoclasts remains unclear. Mice were subjected to development of a cranial osteolysis model. Micro CT, HE staining, and TRAP staining were performed to evaluate bone loss in the mouse model. Bone marrow-derived monocyte-macrophages (BMMs) made from the C57BL/6 mice were exposed to the medium of MLO-Y4 (co-cultured with Ti particles) to transform them into osteoclasts. Bioinformatics methods were used to predict and validate the interaction among SOST, Wnt/β-catenin, RANKL/OPG, TNF-α, and IL-6. Local bone density and bone volume improved after SOST inhibition, both the number of lysis pores and the rate of skull erosion decreased. Histological research showed that β-catenin and OPG expression were markedly increased after SOST inhibition, whereas TRAP and RANKL levels were markedly decreased. In-vitro, Ti particle treatment elevated the expression of sclerostin, suppressed the expression of β-catenin, and increased the RANKL/OPG ratio in the MLO-Y4 cell line. TNF-α and IL-6 also elevated after treatment with Ti particles. The expression levels of NFATc1, CTSK, and TRAP in osteoclasts were significantly increased, and the number of positive cells for TRAP staining was increased. Additionally, the volume of bone resorption increased at the same time. In contrast, when SOST expression was inhibited in the MLO-Y4 cell line, these effects produced by Ti particles were reversed. All the results strongly show that SOST inhibition triggered the osteocyte Wnt/β-catenin signaling cascade and prevented wear particle-induced osteoclastogenesis, which might reduce periprosthetic osteolysis.Key messagesSOST is a molecular regulator in maintaining bone homeostasis.SOST plays in regulating bone homeostasis through the Wnt/β-catenin signaling pathway.SOST gene suppression stimulates osteocyte Wnt/β-catenin signaling to prevent bone resorption and attenuates particle-induced osteolysis.

RESULTS OF STUDIES OF COMPUTED TOMOGRAPHY IN PLANNING DENTAL IMPLANTATION IN PATIENTS WITH ADENTIA

Computed tomography is an accurate study of determining bone density at the site of the proposed implantation. Local bone density has a predominant influence on the primary stability of the implant, which is an important factor for the success of the treatment. On the basis of indicators of dual-energy X-ray absorptiometry, the relationship between the state of the skeletal system and the coefficient of absorption of jaw density - indicators on the Hounsfield scale was studied. There is a directly proportional relationship between the data of densitometry of double X-ray absorptiometry of the axial skeleton and the density of the jaws.

Изучение взаимосвязи состояния костной системы по данным двойной энергетической рентгеновской абсорбциометрии и локальной плотности челюстей у пациентов с адентией при планировании дентальной имплантации

Background. Timely an accurate diagnostics before the implant placement allows to get a correct anatomical rehabilitation and a satisfactory functional result. The success of dental implants in patients with osteoporosis depends primarily on the quality of the jaw bones. Aims. To study the relationship between the state of the skeletal system according to double energy X-ray absorptiometry and local density of the jaws in patients with adentia when planning dental implantation. Materials and methods. By using a densitometric method 690 patients aged between 18 to 84 years were examined prior the dental implantation. The 547 of 690 patients were women (79.3%) and 143 men (20.7%). Measurements of bone mineral density were carried out on a bone densitometer "QDR-4500A" ("Hologic"), which allows to evaluate the following parameters: elasticity, density and stiffness of the bone tissue. The study of the local density of the jaw bones was carried out by the method of cone-beam computed tomography(CBCT). Local bone density measurements were recorded in Hounsfield units (HU). Results. There is a directly proportional relationship between the results of densitometry of the axial skeleton and the density of the bone tissue of the jaws – the lower the mineral density of the bone tissue of the axial skeleton, the lower the absorption coefficient of the jaw – the Hounsfield index. As an effective sign, indicators of the state of the bone of the alveolar ridge of the lower jaw were used. The correlation between the mineral density of the skeletal system from the alveolar process of the jaws was r=0.88, which indicates a high level of feedback of these indicators. Conclusions. Diagnosis of the normal bone density, osteopenia, osteoporosis by using bone densitometry allows to determine the indications for implantation with great accuracy. There is a directly proportional relationship between the results of densitometry of the axial skeleton and the local density of the bone tissue of the jaws. Keywords: osteoporosis, densitometry (dual energy x-ray absorptiometry), dental implantation, cone beam computed tomography

Local Bone Dencity in Neglected Ankle Fractures

Objective: determining the neglected ankle fractures clinical stages based on the analysis of computed tomograms (CT) at various time from the injury and radiological findings in different types of ankle injury. Material and methods. An open randomized multicenter study included 48 patients with Weber type B and C ankle fractures (15 males, 33 females) aged from 27 to 68 years old (mean age 45 years old). The result of the CT analysis for each patient was the ratio of bone density on the damaged side to the bone density of the intact ankle. Next, the correlation was defined between the attitude and time from injury (in days) as well as diastasis (in millimeters) and age (in years). Results. Mean bone density in the period up to 15 days was 403.25 ± 63.74 HU, in the period between 15 and 32 days – 359.85 ± 71.34 HU, in the period more than 32 days – 271.91 ± 73.34 HU. Local bone density is inversely proportional to the time from injury (correlation coefficient –0.678) and the fracture gap (correlation coefficient –0.396). There was no significant dependence of local bone density on the patient’s age (correlation coefficient –0.177). Local bone density significantly (p = 0.05) decreased in the period of more than 14 days from the injury and was 80% and less from intact bone density in the period of more than 32 days from the injury (p = 0.0004). Signs of fracture healing appeared, in average, on the 28 th day after the injury with the fracture gap less than 1 mm. Conclusion. From the point of view of preoperative planning, neglected ankle fractures bone density critical points are 14 th and 32 nd days after injury.

Remotely-activatable extracellular matrix-mimetic hydrogel promotes physiological bone mineralization for enhanced cranial defect healing

The biomineralization of calcium ions and phosphate ions in the extracellular matrix (ECM) is a key event in bone regeneration, and it’s of therapeutic significance to develop biomaterials capable of mimicking the physiological biomineralization process, which is especially desirable in cranial defect repairing. For this purpose, we design a composite remotely-activatable ECM-mimetic chitosan/collagen-based hydrogel incorporated with mesenchymal stem cell (MSC)-membrane-coated black phosphorus (BP), which is a photothermal material with versatile utility. Here, the MSC membrane-coated BP nanosheets could induce mild photothermal effect under near-infrared (NIR) light to stimulate the osteoblast recruitment via activating the heat shock proteins (HSPs)-mediated matrix metalloproteinase (MMP) and ERK-Wnt/β-catenin-RUNX2 axis. Meanwhile, the thermal decomposition of BP would release phosphate ions into the surrounding medium to attract calcium ions to form hydroxyapatite in the ECM in an in-situ manner, which is beneficial for osteoblast migration and osteogenic differentiation. After the implantation in to the cranial defect site on Sprague Dawley (SD) rats, it was evidently observed that the hydrogel treatment substantially enhanced the local bone density and promoted new bone formation. Overall, the ECM-mimetic BP-incorporated hydrogel could enhance osteoblast migration/differentiation and stimulate the biomineralization process under remote NIR activation to promote bone healing, which offers new opportunities for repairing cranial defect in the clinics.

A study of screw placement to obtain the optimal pull-out resistance of lumbar pedicle screws\u2014analysis of Hounsfield units measurements based on computed tomography

ObjectiveThe screw path of lumbar pedicle screws in the vertebral body has certain variability. It is not clear whether the screw paths in different directions can obtain the same pull-out resistance. This study intends to use CT (Computed Tomography) to measure the Hounsfield unit (HU value) around the screw paths in different parts of the lumbar vertebral body to obtain the bone mineral density value of the corresponding parts which will provide some reference for the direction of lumbar pedicle screw placement.MethodsThis retrospective study included 200 patients with lumbar degenerative diseases selected randomly from the case base and the patient’s basic information was recorded. L1-L5 vertebral body was divided equally into the upper, middle and lower 1/3, which was consistent with the three sagittal entry directions of the pedicle screw head tilt, parallel endplate and caudal tilt, and the HU values were measured by CT cross-sectional scanning to indirectly reflect the local bone density values. The paired t-test (randomized block experiment) was used to compare the HU values of the upper, middle and lower 1 / 3 parts, with P < 0.05 being considered statistically significant.ResultsComparison of HU values in different parts of each vertebral body revealed that HU values in the middle 1/3 of the L1,L2 (163.88 ± 58.44 and 152.94 ± 59.45) and in the lower 1/3 of the L4 (149.86 ± 60.18) were higher than in the other two parts of the vertebral body of the same segment(P < 0.0001,P = 0.0069 and P = 0.0024, respectively); According to the results of each stratification, patients with younger age and better bone condition had higher HU values in the middle 1/3 of L1 and L2, and higher HU values in the lower 1/3 of L3, L4 and L5; With the increase of age, the decrease of bone condition and the difference of HU value in each vertebral body gradually decreased.ConclusionAlthough further follow-up studies are needed, based on the analysis of the statistical results, we speculate that from the perspective of obtaining the best pull-out resistance of the lumbar pedicle screws, the placement direction of L1 and L2 in the sagittal position may be as parallel to the endplate as possible; L3, L4, and L5 may be as appropriate as possible to the tail tilt theoretically.

The effect of cement augmentation on pedicle screw fixation under various load cases

AimsAnchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques.MethodsMicro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S4). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads.ResultsExperimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R2 > 0.87) and FV (R2 > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient (R) = -0.95).ConclusionThis combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone.Cite this article: Bone Joint Res 2021;10(12):797–806.

CORRELATION BETWEEN LOCAL BONE DENSITY AND INSERTION TORQUE AS PREDICTORS OF IMMEDIATE IMPLANT LOADING. A BIBLIOGRAPHIC REVIEW

Title: Correlation between local bone density and insertion torque as predictor of immediate implant loading. A bibliographic review.&#x0D; Background: Implants have become an alternative to rehabilitate lost teeth. One of the prerequisites for immediate loading is to determine primary stability by analyzing bone density and insertion torque.&#x0D; Aims: A bibliographic review is conducted to correlate local bone density and insertion torque as predictors of the immediate loading of an implant.&#x0D; Materials and methods: Review using PubMed databases of systematic reviews, meta-analyses, randomized clinical studies, non-randomized clinical studies, in vitro studies, cohort studies, cross-sectional studies, and clinical trials, either in English or in Spanish. The focus was on the correlation between local bone density and insertion torque.&#x0D; Results: Local bone density is a useful guide for determining insertion torque and predicting initial implant stability.&#x0D; Discussion: The insertion torque and bone density values determine whether immediate loading of the implant is possible or not, and therefore predict this possibility.&#x0D; Conclusions: A correlation between local bone density and insertion torque was established, and this correlation predicts immediate loading of an implant. Therefore, to reach a consensus, further studies should consider all the factors influencing this concept.

Finite Element Investigation of Fracture Risk Under Postero-Anterior Mobilization on a Lumbar Bone in Elderly With and Without Osteoporosis

Postero-anterior (PA) mobilization is widely used to manage low back pain by physiotherapists. The PA load is applied through the spinous process of a vertebra. Low bone density is a counter-indication of PA mobilization, whether PA mobilization may cause fractures in fragile vertebrae is unclear. Therefore, the aim of this study was to quantify the role of bone density on a fracture risk in the first lumbar vertebra subjected to PA load. A finite element model of the first lumbar (L1) vertebra of an elderly female was created to predict the fracture risk of the PA mobilization. The von Mises stress and minimum principal strain were used as the assessment indicators. Three different bone density cases were evaluated to reflect healthy, osteoporotic, and severe osteoporotic conditions by assuming heterogeneous moduli based on local bone density converted from computed tomographic images. In the severe osteoporotic condition under PA load, the maximum von Mises stress and largest compressive strain occurred in the pedicles and spinous process. These stress and strain exceeded the yield stress and yield strain indicating a high risk for failure. The resulted stress and strain were also excessive in the pedicles for healthy and moderate osteoporotic conditions. PA mobilization can increase the risk of vertebra fracture in elderly with osteoporosis. The pedicles and spinous process of osteoporotic L1 vertebra are the critical regions prone to fracture. We recommend that it is crucial to be reduce force when applying the PA mobilization to elderly with osteoporosis.

Gray value measurement for the evaluation of local alveolar bone density around impacted maxillary canine teeth using cone beam computed tomography.

Background To investigate whether any relationship between local alveolar bone density and maxillary canine impaction using gray values from cone beam computed tomography.Material and Methods The cone beam computed tomography images of 151 patients were retrospectively evaluated. Maxillary canine was defined as an impacted tooth when root formation was complete and the patient’s age older than 13 or the other side of the maxillary canine has completely erupted. Similarly, complete eruption was defined as the tooth in its expected occlusion and position. Using the cone beam computed tomography software, the region of interest which was 5 mm2 in area, was placed in the trabecular bone on cross sectional cone beam computed tomography images and the gray value measurements were recorded. After measuring the gray values of all the teeth, the images were grouped according to the field of view size. Comparison of the gray values of impacted and non-impacted teeth was made between images with the same field of view size.Results A total of 151 patients, 101 (66.9%) female and 50 (33.1%) male, were included in the study. The mean age of the patients was 24.94 ±13.9. In images with a 40X40 field of view, the gray values of the impacted canine teeth were higher than the gray values of the non-impacted ones and statistically significant difference was found between them (p=0.003). However no statistically significant difference was found between the gray values of impacted and non-impacted canine teeth in 60x60 and 100x50 field of view (p=0.197, p=0.170, respectively).Conclusions We suggest using the smallest field of view size when evaluating bone density using gray values from cone beam computed tomography images and we support the idea that the local increased bone density may influence on impaction. Key words:Cone-beam computed tomography, tooth, impacted, bone density, maxilla, image processing, computer-assisted.

Microarchitecture and stress patterns of the mandibular condyle: a micro-computed tomographic study

Introduction: Mandible condyle fractures commonly present in the oral and maxillofacial (OMFS) clinic. We hypothesised a positive correlation between the prevalence of fractures and local bone density reflecting a lifelong adaptive process adhering to Wolff's law, as physiological loads are transmitted along similar lines of force to traumatic impacts.

Misaligned spinal rods can induce high internal forces consistent with those observed to cause screw pullout and disc degeneration

BACKGROUND CONTEXTManual contouring of spinal rods is often required intraoperatively for proper alignment of the rods within the pedicle screw heads. Residual misalignments are frequently reduced by using dedicated reduction devices. The forces exerted by these devices, however, are uncontrolled and may lead to excessive reaction forces. As a consequence, screw pullout might be provoked and surrounding tissue may experience unfavorable biomechanical loads. The corresponding loads and induced tissue deformations are however not well identified. Additionally, whether the forced reduction alters the biomechanical behavior of the lumbar spine during physiological movements postoperatively, remains unexplored. PURPOSETo predict whether the reduction of misaligned posterior instrumentation might result in clinical complications directly after reduction and during a subsequent physiological flexion movement. STUDY DESIGNFinite element analysis. METHODSA patient-specific, total lumbar (L1–S1) spine finite element model was available from previous research. The model consists of poro-elastic intervertebral discs with Pfirrmann grade-dependent material parameters, with linear elastic bone tissue with stiffness values related to the local bone density, and with the seven major ligaments per spinal motion segment described as nonlinear materials. Titanium instrumentation was implemented in this model to simulate a L4, L5, and S1 posterolateral fusion. Next, coronal and sagittal misalignments of 6 mm each were introduced between the rod and the screw head at L4. These misalignments were computationally reduced and a physiological flexion movement of 15° was prescribed. Non-instrumented and well-aligned instrumented models were used as control groups. RESULTSPulling forces up to 1.0 kN were required to correct the induced misalignments of 6 mm. These forces affected the posture of the total lumbar spine, as motion segments were predicted to rotate up to 3 degrees and rotations propagated proximally to and even affect the L1–2 level. The facet contact pressures in the corrected misaligned models were asymmetrical suggesting non-physiological joint loading in the misaligned models. In addition, the discs and vertebrae experienced abnormally high forces as a result of the correction procedure. These effects were more pronounced after a 15° flexion movement following forced reduction. CONCLUSIONSThe results of this study indicate that the correction of misaligned posterior instrumentation can result in high forces at the screws consistent with those reported to cause screw pullout, and may cause high-tissue strains in adjacent and downstream spinal segments. CLINICAL SIGNIFICANCEProper alignment of spinal posterior instrumentation may reduce clinical complications secondary to unfavorable biomechanics.

P14. Analysis of the segmental and adjacent level impacts of forcing the connection of misaligned pedicle screws and rods and subsequent unintended forces applied to the construct and spine: a finite element analysis

BACKGROUND CONTEXT Manual contouring of rods is often required intraoperatively for proper alignment of the rods within the pedicle screw heads. Residual malalignments are frequently reduced by using dedicated reduction devices. The forces exerted by these devices, however, are uncontrolled and may lead to excessive reactive forces. As a consequence, the pedicle screw-bone interface may become compromised and surrounding tissue may experience unfavorable biomechanical loads. The biomechanical loads on surrounding tissue and induced deformations from the reduction have not been well described previously. Additionally, it is unexplored whether the correction of the malalignment alters the biomechanical behavior of the lumbar spine during physiological movements postoperatively. PURPOSE The aim of this computational study is to predict the loads and deformations in the instrumentation and surrounding tissues directly after the reduction is applied and during physiological flexion following successful fusion. STUDY DESIGN/SETTING N/A PATIENT SAMPLE N/A OUTCOME MEASURES N/A METHODS A patient-specific, total lumbar (L1-S1) spine finite element model was available from previous research. The model consists of poro-elastic intervertebral discs with Pfirrmann grade dependent material parameters, linear elastic bone tissue with stiffness values related to the local bone density, and the seven major ligaments per spinal motion segment described with a hypo-elastic stress-strain relationship. Titanium instrumentation was implemented in this model to simulate a L4, L5, and S1 posterolateral fusion. Next, a misalignment of six millimeters was introduced between the rod and the screw head at L4 in the coronal and sagittal plane respectively. These misalignments were computationally reduced after which a physiological flexion movement of 15° was prescribed. Non-instrumented and well-aligned instrumented models were added as control groups. RESULTS Forces of up to 1.0 kN were required to correct the induced misalignment of six millimeters. These forces affect the posture of the total lumbar spine as motion segments were observed to rotate at adjacent segments and propagate up to and include the L1-2 segment. Asymmetrical increased facet contact pressures of up to 6 MPa were encountered cranial to L4-5 after the correction of the misalignment. In addition, the discs and vertebrae demonstrated significant increased abnormal forces as a result of the correction procedure. Although these effects are more pronounced after inducing a 15° flexion movement, similar trends can be found when inducing the same flexion for a lumbar spine with well-aligned posterior instrumentation. The facet contact pressures in the misaligned model are substantial and asymmetrical suggesting unnatural joint loading in the misaligned models. CONCLUSIONS The estimated forces required to correct a small (6mm) misalignment between a rod and screw will compromise the screw-bone interface and induce asymmetrical forces at the adjacent segments that propagate at least 3 levels proximal to the upper instrumented vertebrae. The tissue volume at risk (discs and vertebrae) during flexion is larger for the misaligned models in which reduction was performed. The deformations induced by reducing this small misalignment produce substantial unintended asymmetrical forces that demonstrate a ‘domino effect’ on the adjacent segments and theoretically could negatively impact patient outcome in the clinical setting. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Biomechanical comparison of knotless vs. knotted suture anchors in the acetabular rim with respect to bone density

BackgroundAcetabular labral tears are managed with suture anchors providing good clinical outcomes. Knotless anchors are easier to use and have a quicker insertion time compared to knotted anchors. The purpose of this study was to compare the biomechanical behavior of two different anchor designs (knotted vs. knotless) in ultimate load testing in correlation with bone density in the acetabular rim. MethodsEighteen knotted Bio-FASTak and seventeen knotless PushLock anchors (both: Arthrex Inc., Naples, FL, USA) were inserted in the rims of two human acetabula, with known bone density distribution. The anchors were subjected to load-to-failure tests. Anchors were additionally tested in solid polyurethane foam with defined densities. FindingsThe Bio-FASTak group showed higher survival rates at 1, 2, and 3 mm displacement and was able to withstand significantly higher loads at 3 mm displacement (p = 0.031). There was no statistically significant difference in stiffness (p = 0.087), yield- (p = 0.190), and ultimate load (p = 0.222) between the two groups. Only the PushLock group showed correlation between bone volume over total volume (BV/TV) and stiffness (R = 0.750, p = 0.086) and between BV/TV and yield load (R = 0.838, p = 0.037). Experiments on solid polyurethane foam confirmed the correlation between the mechanical properties and tissue density for the same anchor. InterpretationPushLock shows similar biomechanical properties to the Bio-FASTak, but eliminates knot tying and potentially abrasive knots. In addition, biomechanical properties of the PushLock are governed by local bone density.