Adipocyte lineage differentiation potential of MSCs isolated from reaming material.

Mesenchymal stem cells (MSCs) obtained from various sources have been used for different therapeutic applications including tissue regeneration. Reamer/irrigator/aspirator (RIA) has been increasingly used in recent years for the derivation of MSCs. Here in this investigation we have comparatively analyzed MSCs obtained from iliac crest bone marrow (ICBM) and RIA for their morphology, cluster determinant (CD) markers, and adipogenic differentiation capacity. MSCs were isolated, cultured, and purified from both sources and then flow cytometric studies were performed to study their characteristics. The differentiation potential of RIA and ICBM was examined by an Oil Red O staining protocol. Moreover, the tissue-specific markers related to adipogenesis were analyzed by real-time polymerase chain reaction (RT-PCR). The cells were cultured in the relevant induction medium and then adipogenic lineage differentiation was tested and confirmed for all MSC preparations. Additionally, analysis by flow cytometer was indicative of RIA derived MSCs (RIA-MSCs) having a more homogenous population than ICBM derived MSCs. The RIA-MSCs differentiation toward adipogenic lineage was more efficient compared with ICBM-MSCs. Direct comparative analysis of RIA to ICBM-MSCs indicated that the RIA-MSCs had a higher potential toward adipocyte lineage differentiation compared with ICBM-MSCs.

Iliac and mandible osteoblasts exhibit varied responses to LMHF vibration.

The facial and long bones have distinct developmental origins, structures, and cellular compositions. This study aimed to compare the in vitro responses of human mandible and long bone osteoblasts to low-magnitude, high-frequency (LMHF) mechanical vibration in terms of expression of mediators of bone remodeling. Osteoblast-like cell cultures were prepared from iliac crest and mandibular bone specimens from three individuals and cultured in osteogenic induction media. Induction of mature osteoblastic phenotypes was confirmed by analysis of DNA content, alkaline phosphatase activity and gene expression every 3 days for 27 days. Based on gene expression, mature osteoblasts formed by day 15 of induction culture. After 15 days of culture in induction media, mature osteoblasts were subjected to vibration (0, 30, or 60 Hz) for 30 min every 24 h. After 48 h, RANKL, OPG, IL-1ß, IL-6 and TGF-ß gene, and protein expression were determined by real-time PCR analysis of total cellular mRNA and ELISAs of the cell supernatants. Both iliac and mandible osteoblasts responded to LMHF vibration: IL-1ß and RANKL mRNA were downregulated and IL-6 mRNA was upregulated. However, TGF- ß mRNA was unaltered and OPG mRNA was upregulated in iliac osteoblasts, whereas both TGF-ß and OPG mRNA were downregulated in mandible osteoblasts. As a result, LMHF reduced the RANKL/OPG mRNA ratio in iliac osteoblasts but did not alter the RANKL/OPG mRNA ratio in mandible osteoblasts. This study suggests mature iliac osteoblasts exhibit a more potent anti-resorptive response to vibration, while this tendency was not obviously apparent in mature mandible osteoblasts.

Biomechanical analysis of iliac crest loading following cortico-cancellous bone harvesting.

BACKGROUND: Iliac crest bone harvesting is a frequently performed surgical procedure widely used to treat bone defects. The objective of this study is to assess the biomechanical quantities related to risk for pelvic fracture after harvesting an autologous bone graft at the anterior iliac crest. METHODS: Finite element models with a simulated harvest site (sized 15 × 20 mm, 15 × 35 mm, 30 × 20 mm and 30 × 35 mm) in the iliac wing are created. The relevant loading case is when the ipsilateral leg is lifted off the ground. Musculoskeletal analysis is utilized to compute the muscle and joint forces involved in this motion. These forces are used as boundary conditions for the finite element analyses. Bone tissue stress is analyzed. RESULTS: Critical stress peaks are located between the anterior superior iliac spine (ASIS) and the anterior edge of the harvest site. Irrespective of the graft size, the iliac wing does not show any significant stress peaks with the harvest site being 20 to 25 mm posterior to the ASIS. The harvest area itself inhibits the distribution of the forces applied on the ASIS to extend to the posterior iliac wing. This leads to a lack of stress posterior to the harvest site. A balanced stress distribution with no stress peaks appears when the bone graft is taken below the iliac crest. CONCLUSION: A harvest site located at least 20 to 25 mm posterior to the ASIS should be preferred to minimize the risk of iliac fatigue fracture.

Vertebral body versus iliac crest bone marrow as a source of multipotential stromal cells: Comparison of processing techniques, tri-lineage differentiation and application on a scaffold for spine fusion.

The potential use of bone progenitors, multipotential stromal cells (MSCs) helping spine fusion is increasing, but convenient MSC sources and effective processing methods are critical factors yet to be optimised. The aim of this study was to test the effect of bone marrow processing on the MSC abundance and to compare the differentiation capabilities of vertebral body-bone marrow (VB-BM) MSCs versus iliac crest-bone marrow (IC-BM) MSCs. We assessed the effect of the red blood cell lysis (ammonium chloride, AC) and density-gradient centrifugation (Lymphoprep™, LMP), on the extracted VB-BM and IC-BM MSC numbers. The MSC abundance (indicated by colony counts and CD45lowCD271high cell numbers), phenotype, proliferation and tri-lineage differentiation of VB-BM MSCs were compared with donor-matched IC-BM MSCs. Importantly, the MSC attachment and osteogenesis were examined when VB-BM and IC-BM samples were loaded on a beta-tricalcium phosphate scaffold. In contrast to LMP, using AC yielded more colonies from IC-BM and VB-BM aspirates (p = 0.0019 & p = 0.0201 respectively). For IC-BM and VB-BM, the colony counts and CD45lowCD271high cell numbers were comparable (p = 0.5186, p = 0.2640 respectively). Furthermore, cultured VB-BM MSCs exhibited the same phenotype, proliferative and adipogenic potential, but a higher osteogenic and chondrogenic capabilities than IC-BM MSCs (p = 0.0010 and p = 0.0005 for calcium and glycosaminoglycan (GAG) levels, respectively). The gene expression data confirmed higher chondrogenesis for VB-BM MSCs than IC-BM MSCs, but osteogenic gene expression levels were comparable. When loaded on Vitoss™, both MSCs showed a similar degree of attachment and survival, but a better osteogenic ability was detected for VB-BM MSCs as measured by alkaline phosphatase activity (p = 0.0386). Collectively, the BM processing using AC had more MSC yield than using LMP. VB-BM MSCs have a comparable phenotype and proliferative capacity, but higher chondrogenesis and osteogenesis with or without using scaffold than donor-matched IC-BM MSCs. Given better accessibility, VB-BM could be an ideal MSC source for spinal bone fusion.

Comprehensive biomechanical analysis of three reconstruction techniques following total sacrectomy: an in vitro human cadaveric model.

OBJECTIVE Aggressive sacral tumors often require en bloc resection and lumbopelvic reconstruction. Instrumentation failure and pseudarthrosis remain a clinical concern to be addressed. The objective in this study was to compare the biomechanical stability of 3 distinct techniques for sacral reconstruction in vitro. METHODS In a human cadaveric model study, 8 intact human lumbopelvic specimens (L2-pelvis) were tested for flexion-extension range of motion (ROM), lateral bending, and axial rotation with a custom-designed 6-df spine simulator as well as axial compression stiffness with the MTS 858 Bionix Test System. Biomechanical testing followed this sequence: 1) intact spine; 2) sacrectomy (no testing); 3) Model 1 (L3-5 transpedicular instrumentation plus spinal rods anchored to iliac screws); 4) Model 2 (addition of transiliac rod); and 5) Model 3 (removal of transiliac rod; addition of 2 spinal rods and 2 S-2 screws). Range of motion was measured at L4-5, L5-S1/cross-link, L5-right ilium, and L5-left ilium. RESULTS Flexion-extension ROM of the intact specimen at L4-5 (6.34° ± 2.57°) was significantly greater than in Model 1 (1.54° ± 0.94°), Model 2 (1.51° ± 1.01°), and Model 3 (0.72° ± 0.62°) (p < 0.001). Flexion-extension at both the L5-right ilium (2.95° ± 1.27°) and the L5-left ilium (2.87° ± 1.40°) for Model 3 was significantly less than the other 3 cohorts at the same level (p = 0.005 and p = 0.012, respectively). Compared with the intact condition, all 3 reconstruction groups statistically significantly decreased lateral bending ROM at all measured points. Axial rotation ROM at L4-5 for Model 1 (2.01° ± 1.39°), Model 2 (2.00° ± 1.52°), and Model 3 (1.15° ± 0.80°) was significantly lower than the intact condition (5.02° ± 2.90°) (p < 0.001). Moreover, axial rotation for the intact condition and Model 3 at L5-right ilium (2.64° ± 1.36° and 2.93° ± 1.68°, respectively) and L5-left ilium (2.58° ± 1.43° and 2.93° ± 1.71°, respectively) was significantly lower than for Model 1 and Model 2 at L5-right ilium (5.14° ± 2.48° and 4.95° ± 2.45°, respectively) (p = 0.036) and L5-left ilium (5.19° ± 2.34° and 4.99° ± 2.31°) (p = 0.022). Last, results of the axial compression testing at all measured points were not statistically different among reconstructions. CONCLUSIONS The addition of a transverse bar in Model 2 offered no biomechanical advantage. Although the implementation of 4 iliac screws and 4 rods conferred a definitive kinematic advantage in Model 3, that model was associated with significantly restricted lumbopelvic ROM.

Relationships between age and microarchitectural descriptors of iliac trabecular bone determined by microCT.

AIM: Estimation of age at death is a major issue in anthropology. The main anthropological histological methods propose studying the architecture of cortical bone. In bone histomorphometry, researches on metabolic bone diseases have provided normative tables for trabecular bone volume (BV/TV) according to age and gender of individuals on trans-iliac bone biopsies. We have used microCT, a non-destructive tool for measuring bone volume and trabecular descriptors to compare the French tables to a series of forensic anthropological population and if the two iliac bones could be used interchangeably. METHODOLOGY: Coxal bone of a personal forensic collection whose age and gender were known (DNA identification) were used. Bone samples, centered on the same area than bone biopsy. MicroCT (pixel size: 36µm) was used to measure BV/TV and morphometric trabecular parameters of microarchitecture. An adjusted Z-score was calculated for BV/TV to compare with normative tables and a right/left comparison of trabecular parameters was provided. RESULTS: Twenty-seven iliac bones, which 20 forming 10 complete pelvises, aged between 24 and 73y.o. (average of 47.7 y.o.) were used. All adjusted Z-score were within normal values. There was a strong positive correlation between right and left sides for Tb.Th, Tb.N and Tb.Sp, but an insignificant correlation was obtained for BV/TV. CONCLUSION: Normative tables between age and BV/TV are valid and therefore usable in anthropology. They may represent an alternative to determine the age at death. Nevertheless, it requires a precise technique that could be a drawback in current practice.

Biomechanical and histologic basis of osseodensification drilling for endosteal implant placement in low density bone. An experimental study in sheep.

A bone drilling concept, namely osseodensification, has been introduced for the placement of endosteal implants to increase primary stability through densification of the osteotomy walls. This study investigated the effect of osseodensification on the initial stability and early osseointegration of conical and parallel walled endosteal implants in low density bone. Five male sheep were used. Three implants were inserted in the ilium, bilaterally, totaling 30 implants (n=15 conical, and n=15 parallel). Each animal received 3 implants of each type, inserted into bone sites prepared as follows: (i) regular-drilling (R: 2mm pilot, 3.2mm, and 3.8mm twist drills), (ii) clockwise osseodensification (CW), and (iii) counterclockwise (CCW) osseodensification drilling with Densah Bur (Versah, Jackson, MI, USA): 2.0mm pilot, 2.8mm, and 3.8mm multi-fluted burs. Insertion torque as a function of implant type and drilling technique, revealed higher values for osseodensification relative to R-drilling, regardless of implant macrogeometry. A significantly higher bone-to-implant contact (BIC) for both osseodensification techniques (p<0.05) was observed compared to R-drilling. There was no statistical difference in BIC as a function of implant type (p=0.58), nor in bone-area-fraction occupancy (BAFO) as a function of drilling technique (p=0.22), but there were higher levels of BAFO for parallel than conic implants (p=0.001). Six weeks after surgery, new bone formation along with remodeling sites was observed for all groups. Bone chips in proximity with the implants were seldom observed in the R-drilling group, but commonly observed in the CW, and more frequently under the CCW osseodensification technique. In low-density bone, endosteal implants present higher insertion torque levels when placed in osseodensification drilling sites, with no osseointegration impairment compared to standard subtractive drilling methods.

A new sagittal parameter to estimate pelvic tilt using the iliac cortical density line and iliac tilt: a retrospective X-ray measurement study.

BACKGROUND: When spinal kyphosis increases, the compensatory mechanism activates and the pelvic position changes. Increasing the pelvic tilt, which is the orientation of the pelvis with respect to the femoral head, is known to associate with the clinical symptoms in kyphosis in the aging population. It is often difficult to detect the femoral head on radiographs, limiting the ability to determine the pelvic tilt. Therefore, there is a need to establish another parameter independent of the femoral head which closely correlates with the pelvic tilt. METHODS: Eighty-two adult patients with full-length lateral standing spine radiographs were recruited (mean age: 73.0 years). A new parameter, the iliac cortical density line (a component of the arcuate line of the ilium) and the iliac tilt (defined as the angle between the iliac cortical density line and the vertical), was analyzed to determine the correlation with the pelvic tilt. RESULTS: Both the pelvic tilt (PT) and iliac tilt (IT) could be identified in 67 patients, and a significant correlation was observed between the PT and IT (r = 0.86, P < 0.0001). The PT could be estimated using the following formula: PT = IT - 12.9 (in females), PT = IT - 16.7 (in males). CONCLUSIONS: The iliac tilt, which can be easily and directly measured using the iliac cortical density line, is a new parameter that can reliably estimate the pelvic tilt even when the femoral head is not detectable on the radiograph.

Relationship of calcaneal and iliac apophyseal ossification to peak height velocity timing in children.

BACKGROUND: Ossification of the calcaneal apophysis has never been fully characterized. We examined the ossification sequence of the calcaneus in relation to ossification of the iliac apophysis and the timing of the peak height velocity (PHV). METHODS: Ninety-four healthy children (forty-nine girls and forty-five boys), from three to eighteen years old, were followed longitudinally through growth with annual serial radiographs and physical examinations. These were done at least annually from ten to fifteen years of age. The PHV was calculated using the height measurements of each child. We measured and compared calcaneal and iliac crest apophyseal ossification using foot and pelvic radiographs made on the same day. We correlated the PHV with the degree of calcaneal and iliac ossification. RESULTS: Ossification of the calcaneal apophysis occurred in an orderly fashion, with the ossification center first appearing a mean of 4.7 years (95% confidence interval [CI], 5.2 to 4.2 years) before the PHV. The apophysis spread across the plantar surface more quickly than the dorsal surface. The apophysis extended completely over the plantar surface a mean of 0.86 year (95% CI, 1.0 to 0.7 year) before the PHV. Fusion of the apophysis followed complete plantar extension over the next two years and was typically complete a mean of 2.1 years (95% CI, 2.0 to 2.2 years) after the PHV. Fusion began in the middle of the apophysis and proceeded outward. Iliac apophyseal ossification did not appear prior to the PHV in any subject. CONCLUSIONS: The calcaneal apophysis ossifies in a consistent fashion characterized by six different stages. The calcaneal stages occur during narrow intervals in relation to the PHV, allowing the calcaneal system to be used for assessment of skeletal maturity. The PHV occurs prior to iliac ossification, whereas the calcaneal apophysis has four stages of ossification before and two stages after the PHV.

BDNF and its TrkB receptor in human fracture healing.

Fracture healing is a physiological process of repair which proceeds in stages, each characterized by a different predominant tissue in the fracture gap. Matrix reorganization is regulated by cytokines and growth factors. Neurotrophins and their receptors might be of importance to osteoblasts and endothelial cells during fracture healing. The aim of this study was to examine the presence of brain-derived neurotrophic factor (BDNF) and its tropomyosin-related kinase B receptor (TrkB) during human fracture healing. BDNF and TrkB were investigated in samples from human fracture gaps and cultured cells using RT-PCR, Western blot, and immunohistochemistry. Endothelial cells and osteoblastic cell lines demonstrated a cytoplasmic staining pattern of BDNF and TrkB in vitro. At the mRNA level, BDNF and TrkB were expressed in the initial and osteoid formation phase of human fracture healing. In the granulation tissue of fracture gap, both proteins--BDNF and TrkB--are concentrated in endothelial and osteoblastic cells at the margins of woven bone suggesting their involvement in the formation of new vessels. There was no evidence of BDNF or TrkB during fracture healing in chondrocytes of human enchondral tissue. Furthermore, BDNF is absent in mature bone. Taken together, BDNF and TrkB are involved in vessel formation and osteogenic processes during human fracture healing. The detection of BDNF and its TrkB receptor during various stages of the bone formation process in human fracture gap tissue were shown for the first time. The current study reveals that both proteins are up-regulated in human osteoblasts and endothelial cells in fracture healing.

Early bone resorption of free microvascular reanastomized bone grafts for mandibular reconstruction--a comparison of iliac crest and fibula grafts.

OBJECTIVES: Patients with continuous bone defects of the mandible after ablative tumor surgery need bony reconstruction for proper function and aesthetics. Free microvascular reanastomized bone grafts provide a clinically proven option for such patients, yet the optimal source of donor tissue has not yet been established. The aim of this study was to evaluate and compare the bone volume stability of vascularized bone grafts, particularly in the early highly resorptive phase, from the iliac crest (DCIA) and the fibula and to assess the implantologic rehabilitations. MATERIALS AND METHODS: Thirty-six patients with mandibular continuity defects due to tumor resection were reconstructed by the use of vascularized bone grafts; 21 patients received DCIA flaps and 15 patients received a composite free fibular flap, depending on the size and location of the defect. Bone resorption was assessed using digital panographs. Radiographs were taken immediately after bone reconstruction, 6 months postoperatively, prior to implant surgery, and at prosthetic loading. RESULTS: After a mean observation period of 6 months, vertical bone resorption was 6.79% for the patients of the iliac crest group (DCIA), 10.20% after 11 months, and 12.58% after 17 months. Fibular grafts showed a bone resorption of 5.30% after a mean observation time of 6 months, 8.26% after 11 months, and 16.95% after 17 months. Eighteen patients received 71 implants for implant-retained dental reconstructions. CONCLUSIONS: Microvascular reanastomized bone grafts represent a reliable treatment option for reconstruction in cases of large defects of the mandible, with low graft resorption in the early healing phase. Additionally, the compared grafts provide sufficient bone volume to permit implant rehabilitation.

A biomimetic growth factor delivery strategy for enhanced regeneration of iliac crest defects.

The importance of provision of growth factors in the engineering of tissues has long been shown to control the behavior of the cells within the construct and several approaches were applied toward this end. In nature, more than one type of growth factor is known to be effective during the healing of tissue defects and their peak concentrations are not always simultaneous. One of the most recent strategies includes the delivery of a combination of growth factors with the dose and timing to mimic the natural regeneration cascade. The sequential delivery of bone morphogenetic proteins BMP-2 and BMP-7 which are early and late appearing factors during bone regeneration, respectively, was shown in vitro to enhance osteoblastic differentiation of bone marrow derived mesenchymal stem cells. In the present study, the aim was to study the effectiveness of this delivery strategy in a rabbit iliac crest model. 3D plotted poly(ε-caprolactone) scaffolds were loaded with BMP carrying nanoparticles to achieve: (a) single BMP-2 or BMP-7 delivery, and (b) their combined delivery in a simultaneous or (c) sequential (biomimetic) fashion. After eight weeks of implantation, computed tomography and biomechanical tests showed better mineralized matrix formation and bone-implant union strength at the defect site in the case of sequential delivery compared to single or simultaneous delivery modes. Bone mineral density (BMD) and push-out stress were: 33.65±2.25 g cm(-3) and 14.5±2.28 MPa, respectively, and almost 2.5 fold higher in comparison to those without growth factors (BMD: 14.14±1.21 g cm(-3); PS: 6.59±0.65 MPa). This study, therefore, supports those obtained in vitro and emphasizes the importance of mimicking the natural timing of bioavailability of osteogenic factors in improving the regeneration of critical-sized bone defects.

Structural stability of different reconstruction techniques following total sacrectomy: a biomechanical study.

BACKGROUND: The biomechanical stability of spino-pelvis structure after varying reconstruction methods following total sacrectomy remains poorly defined. The objective of this study was to compare the structural stability of different reconstruction techniques. METHODS: Six fresh human cadavers (L2-pelvis-femora) were used to compare biomechanical stability after reconstruction using four different techniques: (1) sacral rod reconstruction; (2) bilateral fibular flap reconstruction; (3) four-rod reconstruction; and (4) improved compound reconstruction. After total sacrectomy, the construction was carried out using each method once in each cadaver. Structural stiffness was evaluated by linear and angular ranges of motion. L5 relative shift-down displacement, abduction angle on the coronal plane and rotation angle on the sagittal plane, were calculated based on displacement of the identification point under 500N axial loading. Overall stiffness was estimated using load displacement curve. FINDINGS: Improved compound reconstruction resulted in significantly higher stiffness than all three other techniques. The structural stability following bilateral fibular flap reconstruction was superior to that after sacral rod reconstruction. Four-rod reconstruction achieved worst stability due to the lack of anterior bracing applied in three other methods. INTERPRETATION: Improved compound reconstruction produces optimal structural stability after total sacrectomy. This finding suggests that both anterior bracing and alternation of screw trajectory are important in achieving optimal structural stability.

Age-related changes in iliac crest cortical width and porosity: a histomorphometric study.

Although age-related changes in cancellous bone structure in human are relatively well characterized, few studies have addressed changes in cortical bone. We have investigated age-related changes in iliac crest bone biopsy specimens from 54 normal subjects, 23 men and 31 women, aged 18-90 years. A significant decrease in cortical width and area was seen (P =0.002 and <0.001 respectively), with no difference between sexes. Haversian canal density increased significantly with age by approximately 9% per decade (P = 0.032) but Haversian canal area tended to be lower, resulting in no overall age-related difference in cortical porosity. Haversian canal area was significantly higher in the endosteal section than in the periosteal section of the cortex (P = 0.019) but the Haversian canal density was lower, resulting in similar overall porosity in the two sections. In conclusion, our results demonstrate an age-related decrease in iliac crest cortical width in men and women and an increase in Haversian canal density, but no overall change in cortical porosity.

Proliferation and osteoblastic differentiation of bone marrow stem cells: comparison of vertebral body and iliac crest.

Bone marrow stem cells (BMSCs) can be obtained from the vertebral body (VB) and iliac crest (IC) for augmenting spinal arthrodesis. However, it is still not evaluated, which of the two sites would have a better BMSCs potential on Proliferation and osteoblastic differentiation is still not evaluated. Fourteen patients (10 men and 4 women) undergoing posterolateral lumbar arthrodesis and pedicle screw instrumentation were involved. The mean age was 54.7 years (range 31-75 years). Bone marrow aspirates were obtained from the vertebral body through the bilateral pedicle and were quantified relative to matched, bilateral aspirates from the iliac crest that were obtained from the same patient and at the same time. The mononuclear cell count and concentration of BMSCs were calculated and compared. Proliferation and osteoblastic differentiation of each of the BMSCs were characterized using biochemical and molecular biology techniques. Concentration (cells/mL) of BMSCs from VB and IC were 3.73 × 10(3) and 3.19 × 10(3), respectively (P > 0.05). VB and IC exhibited similar proliferation pattern at 3, 5 and 7 days, but BMSCs from the VB exhibited an increased mineralization staining with Alizarin Red S at 14 days. BMSCs from both anatomic sites expressed comparable levels of CD29, CD34, CD44, CD90 and CD105. VB and IC displayed similar levels of expression of ALP, type I collagen and osterix, but VB expressed higher level of osteocalcin and Runx-2, especially at 14 and 21 days. Our studies show that BMSCs from VB have osteogenic differentiation potential similar to IC. Based on these findings, we suggest that BMSCs from VB would be comparable candidates for osseous graft supplementation especially in spinal fusion procedures.

The effect of screw length and bone cement augmentation on the fixation strength of iliac screws: a biomechanical study.

STUDY DESIGN: Comparison of the biomechanical fixation strengths offered by 3 iliac screw fixation techniques: short screw, short screw augmented with cement, and long screw. OBJECTIVE: Evaluate the effect of screw length and bone cement augmentation on the fixation strength of iliac screw upon fatigue loading. SUMMARY OF BACKGROUND DATA: Iliac screws have been used in treating spinal disorders such as spinal deformity, spondylolisthesis, and sacral tumor. In clinical practices, both short screws and long screws are being used. It has been reported that short iliac screws have a higher rate of loosening. Therefore, short iliac screws are being used with bone cement augmentation to improve fixation. To date, no biomechanical study has compared the strengths of these 3 different iliac screw fixation techniques. METHOD: Fresh, frozen human cadaveric pelvis specimens (n = 18, 12 males, 6 females, average age 61 y) were used. Bone density was measured to characterize bone quality. The specimens were randomly divided into 2 groups. In group 1 (n = 8), short screws of 7.0-mm diameter and 70 + or - 4 mm length (as the length of exceeding over ischial notch) and long screw of 7.0-mm diameter and 120 + or - 4 mm length were placed on either side of the pelvis (left and right). In group 2 (n = 10), short iliac screws were placed after augmentation with polymethyl methacrylate bone cement on 1 side of the pelvis and long iliac screw were placed on the other side (left and right). Cyclic loading ranging from 20 to 200 N was applied to each screw at a frequency of 2 Hz up to 5000 cycles. Pullout tests were then conducted at the rate of 5 mm/min after the fatigue test, and the maximum pullout strength for each screw was recorded and analyzed. RESULTS: The maximum pullout strength of the long screw and short screw groups after fatigue conditioning were 2386 + or - 1470 and 833 + or - 681 N respectively. Significant difference was found between the 2 groups (P < 0.05). The short iliac screw had a higher loosening rate. The pullout force of the short screw fixation with augmentation and the long screw fixation after cyclic loading were 2436 + or - 915 and 2529 + or - 1055 N, respectively. No significant difference was found between the 2 groups (P > 0.05). CONCLUSIONS: Short iliac screws are susceptible to loosening after cyclic loading. Bone cement augmentation of short screws has demonstrated a significant increase in the fixation strength of short screws to an extent similar to that of long iliac screws. Thus, short iliac screw fixation after augmentation with bone cement will be a viable clinical option for spino-pelvic reconstruction.

A biomechanical comparison of different types of lumbopelvic fixation.

STUDY DESIGN: Comparative biomechanical testing in calf spines. OBJECTIVE: To biomechanically evaluate 4 techniques of lumbosacral fixation. SUMMARY OF BACKGROUND DATA: Pelvic fixation is a problematic area, and currently, the preferred method of pelvic fixation is controversial. Clinically, iliac screws have demonstrated decreased rod breakage rates, and better correction of pelvic obliquity than unthreaded rods (Galveston technique), but several modern methods of iliac fixation have not been compared. METHODS: A total of 32 male calf spines were tested under axial rotation, flexion/extension, and lateral bending. Following intact testing, specimens were instrumented in the following groups: group 1-Modified Galveston technique with rods connected directly to iliac screws (no S1 fixation); group 2-S1 screws and iliac screws with offset connectors distal to S1; group 3-S1 screws and iliac screws with offset connectors coupled to the longitudinal rod between L6 and S1; and group 4-S1 and S2 screws without iliac fixation. Pedicle screws were placed from L3 to L6. Following nondestructive testing, specimens were fixed at the cephalad aspect of the construct and flexed to failure, with peak failure moment (Nm). RESULTS: Group 1 demonstrated significantly more flexion/extension than groups 2, 3, 4 (P<0.001). There were no significant differences between groups for lateral bending or axial rotation at L3-S1 or L6-S1. During destructive testing, group 4 showed a significant reduction in peak failure compared to group 1 (P<0.001), group 2 (P=0.001), and group 3 (P<0.001). There was no significant difference between groups 1, 2, and 3 and all specimens failed at the distal fixation. CONCLUSION: With extension of instrumentation across the lumbosacral junction, our results indicate significant improvement in stability with the use of S1 screws and iliac screw fixation. Furthermore, there does not appear to be any significant difference in the location of the connector for the iliac screw.

Teriparatide following bisphosphonates: initial and long-term effects on microarchitecture and bone remodeling at the human iliac crest.

Since the approval of teriparatide for clinical application, a number of iliac crest studies have focused on increases in bone volume or changes in structural parameters with microCT and numerical changes in histomorphometry. This investigation is based on individual histopathological observations related to early and late effects of teriparatide treatment in humans. A total of 44 (18 paired) iliac crest biopsies (ICB) from 41 patients receiving teriparatide (10 months +/- 6 months) following bisphosphonate (BP) treatment were investigated for hematopoietic changes, bone turnover, and description of microarchitectural changes using histology and selective microCT. Fully 71% of the ICB showed a normal or high bone turnover; 56% of the paired ICB presented an increase in bone turnover following teriparatide treatment. Early teriparatide stimulation (<1 month) resulted in peritrabecular fibroblast-like formations. Rare findings (<9%) included reactive hematopoietic changes, osteoidosis, endosteal fibrosis, microcallus, or woven bone. Round mast cells were frequently observed within marrow spaces. A total of 14% had an increase in cortical porosity, approximately 20% demonstrated signs of intratrabecular resorption sites. Teriparatide treatment resulted in an increase in remodeling units as early as 1 week after the first application with a continuous stimulation up to 18 months of rhPTH treatment despite previous BPs. Subgroups of patients developed increased cortical and/or intratrabecular resorption pattern, with unclear biomechanical significance. This mechanism could potentially result in new trabecular structures with an increase in trabecular number. Some individuals presented histological findings (e.g., fibrosis) that may require adjustment of treatment that could be of importance for clinical efficacy.

Iliac crest fresh frozen homografts used in pre-prosthetic surgery: a retrospective study.

In the case of severe jaw atrophy several options are available to restore the alveolar crest. Aim of the present study was to evaluate the resorption over time of homologous fresh frozen bone used to restore the alveolar ridge. Specifically factors influencing (1) graft survival, (2) type, and (3) degree of bone resorption were evaluated. One hundred and thirteen maxillae and 27 mandibles were grafted. The surgical techniques used were 102 inlay, 27 onlay, and 11 veneer. Measurements were taken on pre-operative, post-operative, and follow-up radiographs. Data were processed by using three statistical methods: Kaplan-Meier algorithm, Cox regression, and curve estimation. As regards graft survival, Cox regression output showed a statistically significant effect only on surgical technique (P = 0.0312) and Kaplan-Meier algorithm demonstrated a worse outcome for veneer surgical technique (Log rank test = 0.0242). The Curve estimation demonstrated an inverse correlation between degree of bone resorption over time, with a progressive decrease. In conclusion FFB is a reliable material for alveolar bone restoration with a predicable average of resorption.

Trabecular bone microarchitecture in mild primary hyperparathyroidism.

Primary hyperparathyroidism (PHPT) is a common endocrine disease. High levels of PTH cause demineralization of bone and increased risk of fracture. On the other hand, the effect of PHPT on bone structure is more ambiguous. The aim of this study was to evaluate the effect of PHPT on cancellous bone volume, structure, and microarchitecture. Thirteen transiliac biopsy specimens taken in untreated post-menopausal women aged 65+/-5 yr with primary hyperparathyroidism were compared with 13 biopsies taken in normal women aged 66+/-6 yr. None of the patients presented any other disorder affecting bone metabolism. In these samples we evaluated the direct and indirect histomorphometric parameters of bone microarchitecture using an image analysis system consisting of an epifluorescent microscope (Leica DMR) connected to an analogic 3 CCD camera (Sony DXC 390P) and a computer equipped with specific software for histomorphometric analyses. No significant differences between PHPT patients and controls in cancellous bone volume, trabecular thickness, and number were found. Two-dimensional parameters showed a preserved microarchitecture in PHPT patients. On the other hand, indirect parameters of microarchitecture [Marrow Star Volume (MSV) and Trabecular Bone Pattern Factor (TBPf)] showed a significant compromising of microarchitecture in these patients. PHPT patients have similar structural parameters to normal subjects. Concerning microarchitecture, indirect approach by MSV and TBPf shows a significant compromising of connectivity. These results can explain trabecular fragility observed in clinical studies on PHPT.