The Founder’s Lecture 2009: advances in imaging of osteoporosis and osteoarthritis

The objective of this review article is to provide an update on new developments in imaging of osteoporosis and osteoarthritis over the past three decades. A literature review is presented that summarizes the highlights in the development of bone mineral density measurements, bone structure imaging, and vertebral fracture assessment in osteoporosis as well as MR-based semiquantitative assessment of osteoarthritis and quantitative cartilage matrix imaging. This review focuses on techniques that have impacted patient management and therapeutic decision making or that potentially will affect patient care in the near future. Results of pertinent studies are presented and used for illustration. In summary, novel developments have significantly impacted imaging of osteoporosis and osteoarthritis over the past three decades

Bone Marrow Lesions and Subchondral Cysts in Association with Severity of Structural Degeneration in Hip Osteoarthritis

This item is only available electronically.Thesis (BHlthMSc(Hons)) -- University of Adelaide, Adelaide Medical School, YEA

Relationships between image-based and mechanical bone properties with pain in knee osteoarthritis

Pain is the predominant symptom of OA, a debilitating disease marked by changes in cartilage and subchondral bone, but pain pathophysiology is poorly understood. Bone is densely innervated and may be linked to OA-related knee pain. Quantitative computed tomography (QCT) is an in vivo image-based technique with the potential to quantify bone mineral density (BMD) to explore the role of bone in OA-related pain. When coupled with subject-specific finite element (FE) modeling, it may be possible to clarify the mechanical role of bone in OA-related knee pain. The objectives of this study were to assess if: 1) tibial subchondral BMD is associated with OA-related nocturnal knee pain using depth-specific QCT image processing, 2) tibial epiphyseal and metaphyseal BMD is associated with OA-related knee pain using a modified depth-specific CT image processing tool, 3) subchondral cyst characteristics are associated with OA-related knee pain, and 4) FE-derived mechanical outcomes at the proximal tibia are associated with OA-related pain. Lateral focal subchondral BMD was 33% higher in participants with severe nocturnal pain than participants with no nocturnal pain at the 2.5-5mm depth (p=0.028) and 32% higher at 5-10mm from the subchondral surface (p=0.049). At the epiphyseal and metaphyseal depths, higher total pain was associated with lower medial epiphyseal BMD (R2=-0.40, p=0.002), and lower metaphyseal BMD (R2=-0.35, p=0.017). At the lateral region, subchondral cyst number (r=0.55, p<0.001) and cyst number per proximal tibial volume (r=0.52, p<0.001) were both associated with BMD, and lateral cyst number and volume were associated with joint space narrowing (r=0.52 to 0.68, p<0.001) and alignment (r=0.44 to 0.62, p<0.001). In our FE study, principal compressive stress was associated with nocturnal pain at most lateral regions (r=0.33 to 0.50, p<0.05). Principal compressive stress at the lateral region ranged from 47% to 67% higher (p<0.05) in participants with severe nocturnal pain than participants with no pain. This series of studies suggests that pain in patients with knee OA may be associated with BMD throughout various depths at the proximal tibia as well as FE-based bone mechanical outcomes, such as principal compressive stress. These findings suggest previously unexplored associations between OA-related knee pain and BMD or mechanical outcomes, emphasizing that bone may have a mechanical role in OA-related pain pathogenesis

Deficits in trabecular bone microarchitecture in young women with Type 1 diabetes mellitus

Context: The pathophysiological mechanism of increased fractures in young adults with Type 1 Diabetes Mellitus (T1DM) is unclear. Objective: Case:control study of trabecular bone microarchitecture and vertebral marrow adiposity in young women with T1DM. Patients and Settings: 30 women with T1DM with a median (range) age of 22.0yrs (16.9, 36.1) attending one outpatient clinic with a median age at diagnosis of 9.7yrs (0.46, 14.8) were compared to 28 age-matched healthy women who acted as controls. Methods and Main Outcome Measures: Measurements included MRI-based assessment of proximal tibial bone volume/total volume (appBV/TV), trabecular separation (appTb.Sp), vertebral bone marrow adiposity (BMA) and abdominal adipose tissue and biochemical markers of GH/IGF-1 axis (IGF-1, IGFBP3, ALS) and bone turnover. Results: Median appBV/TV in cases and controls was 0.3 (0.22, 0.37) and 0.33 (0.26, 0.4), respectively (p = 0.018) and median appTb.Sp in T1DM was 2.59 (2.24, 3.38) and 2.32 (2.03, 2.97), respectively (p = 0.012). The median appBV/TV was 0.28 (0.22, 0.33) in those cases with retinopathy (n,15) compared to 0.33 (0.25, 0.37) in those without retinopathy (p = 0.02). Although median visceral adipose tissue in cases was higher than in controls at 5,733mm3 (2030, 11,144) and 3,460mm3 (1,808, 6,832), respectively (p = 0.012), there was no difference in median BMA which was 31.1% (9.9, 59.9) and 26.3% (8.5, 49.8) in cases and controls, respectively (p = 0.2). Serum IGF-1 and ALS were also lower in cases and the latter showed an inverse association to appTbSp (r = -0.30, p = 0.04). Conclusion: Detailed MRI studies in young women with childhood-onset T1DM have shown clear deficits in trabecular microarchitecture of the tibia. Underlying pathophysiological mechanisms may include a microvasculopathy

MECHANICAL METRICS OF THE PROXIMAL FEMUR ARE PRECISE AND ASSOCIATED WITH HIP MUSCLE PROPERTIES: A MAGNETIC RESONANCE BASED FINITE ELEMENT STUDY

Proximal femoral (hip) fractures are a life-threatening injury which affects 30,000 Canadians annually. Improved muscle and bone strength assessment methods may reduce fracture occurrence rates in the future. Magnetic resonance (MR) imaging has potential to assess proximal femoral bone strength in vivo through usage of finite element (FE) modeling. Though, to precisely assess bone strength, knowledge of a technique’s measurement error is needed. Hip muscle properties (e.g., lean muscle and fat area) are intrinsically linked to proximal femoral bone strength; however, it is unclear which muscles and properties are most closely associated with bone strength. This thesis is focused on MR-based FE modeling (MR-FE) of the proximal femur and surrounding muscle properties (e.g., hip abductor fat area, hip extensor muscle area). The specific objectives of this research were 1) to characterize the short-term in vivo measurement precision of MR-FE outcomes (e.g., failure load) of the proximal femur for configurations simulating fall and stance loading, and 2) explore associations between upper thigh muscle and fat properties (e.g., hip abductor fat area, knee extensor muscle area) with MR-FE failure loads of the proximal femur. In vivo precision errors (assessed via root mean square coefficient of variation, CV%RMS from repeated measures) of MR-FE outcomes ranged from 3.3-11.8% for stress and strain outcomes, and 6.0-9.5% for failure loads. Hip adductor muscle area and total muscle area correlated with failure load of the fracture-prone neck and intertrochanteric region under both fall and stance loading (correlation coefficients ranged from 0.416-0.671). This is the first study to report the in vivo short-term precision errors of MR-FE outcomes at the proximal femur. Also, this is the first study to relate upper-thigh muscle and fat properties with MR-FE derived failure loads. Results indicate that MR-FE outcomes have comparable precision to computed tomography (CT) based FE outcomes and are related to hip muscle area

The relationship between adiposity, bone density and microarchitecture is maintained in young women irrespective of diabetes status

Background: The relationship between bone health and adiposity and how it may be affected in people with chronic metabolic conditions is complex. Methods: 17 women with Type 1 diabetes mellitus (T1DM) and 9 age-matched healthy women with a median age of 22.6 yrs (range, 17.4, 23.8) were studied by 3T-MRI and MR spectroscopy to assess abdominal adiposity, tibial bone microarchitecture and vertebral bone marrow adiposity. Additional measures included DXA-based assessments of total body (TB), femoral neck (FN) and lumbar spine (LS) bone mineral density (BMD) and fat mass (FM). Results: Although women with T1DM had similar BMI and bone marrow adiposity to the controls, they had higher visceral and subcutaneous adiposity on MRI (p&lt;0.05) and total body FM by DXA (p=0.03). Overall, in the whole cohort, a clear inverse association was evident between bone marrow adiposity and BMD at all sites (p&lt;0.05). These associations remained significant after adjusting for age, BMI, FM, and abdominal adiposity. In addition, visceral adiposity, but not subcutaneous adiposity, showed a positive association with bone marrow adiposity (r,0.4, p=0.03), and a negative association with total body BMD (r,0.5, p=0.02). Apparent trabecular separation as assessed by MRI showed an inverse association to total body BMD by DXA (r,–0.4, p=0.04). Conclusion: Irrespective of the presence of an underlying metabolic condition, young women display a negative relationship between MRI-measured bone marrow adiposity and DXA-based assessment of bone mineral density. Furthermore, an association between bone marrow adiposity and visceral adiposity supports the notion of a common origin of these two fat depots

Quantifying the Tibiofemoral Joint Space Using X-ray Tomosynthesis

Purpose: Digital x-ray tomosynthesis (DTS) has the potential to provide 3D information about the knee joint in a load-bearing posture, which may improve diagnosis and monitoring of knee osteoarthritis compared with projection radiography, the current standard of care. Manually quantifying and visualizing the joint space width (JSW) from 3D tomosynthesis datasets may be challenging. This work developed a semiautomated algorithm for quantifying the 3D tibiofemoral JSW from reconstructed DTS images. The algorithm was validated through anthropomorphic phantom experiments and applied to three clinical datasets. Methods: A user-selected volume of interest within the reconstructed DTS volume was enhanced with 1D multiscale gradient kernels. The edge-enhanced volumes were divided by polarity into tibial and femoral edge maps and combined across kernel scales. A 2D connected components algorithm was performed to determine candidate tibial and femoral edges. A 2D joint space width map (JSW) was constructed to represent the 3D tibiofemoral joint space. To quantify the algorithm accuracy, an adjustable knee phantom was constructed, and eleven posterior–anterior (PA) and lateral DTS scans were acquired with the medial minimum JSW of the phantom set to 0–5 mm in 0.5 mm increments (VolumeRadTM, GE Healthcare, Chalfont St. Giles, United Kingdom). The accuracy of the algorithm was quantified by comparing the minimum JSW in a region of interest in the medial compartment of the JSW map to the measured phantom setting for each trial. In addition, the algorithm was applied to DTS scans of a static knee phantom and the JSW map compared to values estimated from a manually segmented computed tomography (CT) dataset. The algorithm was also applied to three clinical DTS datasets of osteoarthritic patients. Results: The algorithm segmented the JSW and generated a JSW map for all phantom and clinical datasets. For the adjustable phantom, the estimated minimum JSW values were plotted against the measured values for all trials. A linear fit estimated a slope of 0.887 (R2¼0.962) and a mean error across all trials of 0.34 mm for the PA phantom data. The estimated minimum JSW values for the lateral adjustable phantom acquisitions were found to have low correlation to the measured values (R2¼0.377), with a mean error of 2.13 mm. The error in the lateral adjustable-phantom datasets appeared to be caused by artifacts due to unrealistic features in the phantom bones. JSW maps generated by DTS and CT varied by a mean of 0.6 mm and 0.8 mm across the knee joint, for PA and lateral scans. The tibial and femoral edges were successfully segmented and JSW maps determined for PA and lateral clinical DTS datasets. Conclusions: A semiautomated method is presented for quantifying the 3D joint space in a 2D JSW map using tomosynthesis images. The proposed algorithm quantified the JSW across the knee joint to sub-millimeter accuracy for PA tomosynthesis acquisitions. Overall, the results suggest that x-ray tomosynthesis may be beneficial for diagnosing and monitoring disease progression or treatment of osteoarthritis by providing quantitative images of JSW in the load-bearing knee