The utility of multi-stack alignment and 3D longitudinal image registration to assess bone remodeling in rheumatoid arthritis patients from second generation HR-pQCT scans

BACKGROUND

Medical imaging plays an important role in determining the progression of joint damage in rheumatoid arthritis (RA). High resolution peripheral quantitative computed tomography (HR-pQCT) is a sensitive tool capable of evaluating bone microarchitecture and erosions, and 3D rigid image registration can be used to visualize and quantify bone remodeling over time. However, patient motion during image acquisition can cause a "stack shift" artifact resulting in loss of information and reducing the number of erosions that can be analyzed using HR-pQCT. The purpose of this study was to use image registration to improve the number of useable HR-pQCT scans and to apply image-based bone remodeling assessment to the metacarpophalangeal (MCP) joints of RA patients.

METHODS

Ten participants with RA completed HR-pQCT scans of the 2nd and 3rd MCP joints at enrolment to the study and at a 6-month follow-up interval. At 6-months, an additional repeat scan was acquired to evaluate reliability. HR-pQCT images were acquired in three individual 1 cm acquisitions (stacks) with a 25% overlap. We completed analysis first using standard evaluation methods, and second with multi-stack registration. We assessed whether additional erosions could be evaluated after multi-stack registration. Bone remodeling analysis was completed using registration and transformation of baseline and follow-up images. We calculated the bone formation and resorption volume fractions with 6-month follow-up, and same-day repositioning as a negative control.

RESULTS

13/57 (23%) of erosions could not be analyzed from raw images due to a stack shift artifact. All erosions could be volumetrically assessed after multi-stack registration. We observed that there was a median bone formation fraction of 2.1% and resorption fraction of 3.8% in RA patients over the course of 6 months. In contrast to the same-day rescan negative control, we observed median bone formation and resorption fractions of 0%.

CONCLUSIONS

Multi-stack image registration is a useful tool to improve the number of useable scans when analyzing erosions using HR-pQCT. Further, image registration can be used to longitudinally assess bone remodeling. These methods could be implemented in future studies to provide important pathophysiological information on the progression of bone damage.

Longitudinal Effects of Acute Anterior Cruciate Ligament Tears on Peri-Articular Bone in Human Knees Within the First Year of Injury

Anterior cruciate ligament (ACL) tears are common sports-related knee injuries that increase the risk of developing post-traumatic osteoarthritis. ACL tears are rarely an isolated injury but are often associated with traumatic bone marrow lesions (BMLs). While early loss of bone mass following the ACL injury has been previously described, to date, microarchitectural information has not been reported due to the limited resolution of clinical imaging systems. In this study, we provide the first evidence of detailed bone mass and microarchitectural changes in the first 10 months following an acute ACL tear, and localized to traumatic BMLs. Fifteen participants with an acute unilateral ACL tear were assessed at four-time points using dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography, and traumatic BMLs were identified with magnetic resonance imaging. Loss of bone mass was localized to the injured knee (-4.6% to -15.8%, depending on bone and depth) and was accelerated immediately following the injury before suggesting a recovery phase. This loss of bone was accelerated even greater in traumatic BMLs (-18.2% to -20.6%, depending on bone). Bone loss was accompanied by microstructural degeneration of trabecular bone. For example, in the lateral femur of the injured knee, the subchondral bone plate decreased in thickness (-9.0%). This study confirmed loss of bone mass in the months following ACL tears and described the underlying bone microstructural changes. The presented bone changes were accelerated in regions of traumatic BMLs. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2325-2336, 2019.

Differences in subchondral bone plate and cartilage thickness between women with anterior cruciate ligament reconstructions and uninjured controls

OBJECTIVE

Anterior cruciate ligament (ACL) tears increase early onset osteoarthritis (OA) risk leading to cartilage and bone degradation. While the contribution of bone in OA development is unclear, evidence suggests that bone changes accompany cartilage degradation. This study aims to assess if regions with differences in subchondral bone plate thickness have differences in cartilage thickness when comparing ACL reconstructed (ACLR) knees of women ≥5 years post-injury to contralateral and controls with uninjured knees.

DESIGN

Magnetic resonance imaging (MRI) assessed cartilage and high resolution peripheral quantitative computed tomography (HR-pQCT) assessed subchondral bone in both knees. Multimodal 3D image registration aligned anatomy. Maps of the spatial distribution of thickness on the articular surfaces were generated to compare women with ACL reconstructions to contralateral and controls with uninjured knees.

RESULTS

ACLR knees had a thicker subchondral bone plate in the posterior and central lateral femur compared to contralateral knees (10.4% and 4.2% thicker, P = 0.032 and 0.032, W = 108 and 107, respectively) and in the posterior lateral femur compared to control knees (17.1% thicker, P = 0.014, W = 177). Cartilage differences were not detected (P > 0.05) in these regions.

CONCLUSIONS

This study demonstrates that subchondral bone plate thickness differences are prominent following knee injury, as measured by HR-pQCT, but no statistically significant differences in cartilage morphology, measured by MRI, were found between ACLR knees compared to contralateral and control knees. These data provide novel insight into post-traumatic knee injuries that may be signs of early OA pathogenesis.

Subchondral bone microarchitecture in ACL reconstructed knees of young women: A comparison with contralateral and uninjured control knees

Anterior cruciate ligament (ACL) tears are a common sports-related knee injury that increases the risk of developing post-traumatic osteoarthritis (OA). During OA progression bone microarchitecture changes in the affected knee, however, little is known about bone microarchitecture in knees with early stage OA. The purpose of this study is to investigate in a cohort of females predisposed to develop OA how bone microarchitecture in ACL reconstructed knees differs from uninjured contralateral knees as well as healthy control knees and how this relates to early changes in OA. Bone microarchitecture was directly assessed in ACL reconstructed knees of injured female participants (n=15) with a median age of 25.4years (age range: 22.5-28.5) and compared to their uninjured contralateral knees, as well as to a healthy age-matched female control sample (n=14) with a median age of 25.2years (age range: 22.2-27.1). ACL reconstructed knees had lower trabecular bone mineral density (compared to contralateral: -7.7% to -10.4%, p<0.05; control knees: -7.1% to -13.9%, p<0.05) and altered trabecular bone microarchitecture in the medial femur compared to contralateral and control knees. The subchondral bone plate in the lateral femur was thicker in ACL reconstructed knees compared to contralateral (29.6%, p=0.009) and control knees (47.9% to 53.7%, p<0.05). Contralateral knees did not differ from control knees. Loss of trabecular bone and increased subchondral bone plate thickness in the ACL-reconstructed knees are consistent with changes associated with OA progression. Most differences in bone microarchitecture were found in the femur, with few differences in the tibia. The bone microarchitecture of contralateral knees did not differ from control knees in our participants, suggesting the potential to use them as control references in future longitudinal studies.

Cortical porosity exhibits accelerated rate of change in peri- compared with post-menopausal women

The rate of change in bone density was not different between peri- and post-menopausal women. Differences in rate of change were observed in bone microarchitecture, specifically cortical porosity (Ct.Po), where peri-menopausal women increased +9% per year compared with the +6% per year for post-menopausal women.

INTRODUCTION

The purpose of this study was to compare changes in bone density and microarchitecture in peri- and post-menopausal women over 6 years.

METHODS

Peri- (n = 26) and post- (n = 65) menopausal women were selected from the Canadian Multicenter Osteoporosis Study. Caucasian women were scanned on dual x-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) at baseline and follow-up, an average 6 years later. To compare repeat scans, automated 3D image registration was conducted. At the radius and tibia, total volumetric BMD (Tt.BMD), total bone area (Tt.Ar) and cortical porosity (Ct.Po) were assessed, and finite element analysis estimated apparent bone strength.

RESULTS

At the tibia, the rate of change for Ct.Po and Tt.Ar was different between groups. Peri-menopausal women had a + 9% per year increase in Ct.Po, but this increase was slower for post-menopausal women at +6% per year (p = 0.049). In addition, post-menopausal women had an increase in Tt.Ar of +0.13% per year compared with a slower increase of +0.06% per year for peri-menopausal women (p = 0.017). The rate of change of density between groups was not significantly different and was approximately -1% per year at the hip by DXA, and -1% per year at the radius and -0.5% per year tibia by HR-pQCT.

CONCLUSION

This is a 6-year prospective HR-pQCT study exploring rate of change in Caucasian peri- and post-menopausal women. The microarchitectural features represented by Ct.Po and Tt.Ar changed at a significantly different rate between groups, but group differences were not detected by density measures.