Three-dimensional analysis of subchondral cysts in hip osteoarthritis: an ex vivo HR-pQCT study

Outcomes of Total Ankle Arthroplasty After Periprosthetic Cyst Curettage and Bone Grafting

Total ankle arthroplasty (TAA) has become a popular management option for ankle arthritis. Periprosthetic osteolysis is one of the most common causes for reoperation in TAA. A CT scan should be done in all suspected osteolysis cases to confirm location, quantify size and aid in surgical planning. These patients are often asymptomatic with limited evidence regarding appropriate management. Smaller lesions should be monitored for progression in size. Periprosthetic cysts measuring 10-15mm in all three axes should be considered for debridment and curettage with autogenous bone grafting. The authors believe that bone grafting of large asymptomatic periprosthetic cysts could prevent implant failure.

Evaluation of subchondral bone cysts in canine elbows with radiographic osteoarthritis secondary to elbow dysplasia

OBJECTIVE

To investigate whether subchondral bone cysts (SBCs) were present in dogs with radiographic elbow osteoarthritis (OA) and to investigate their relationship with radiographic OA severity.

STUDY DESIGN

Retrospective cross-sectional study.

SAMPLE POPULATION

Thirty-eight Labrador retrievers (total of 76 elbows).

METHODS

Elbow computed tomography (CT) images of 18 young (≤2 years old) and 20 old (>2 years old) Labrador retrievers, which presented for elbow-associated lameness, were reviewed. Radiographic elbow OA was graded into four groups based on the largest osteophyte size on CT. The presence, number, and maximum diameter of SBCs were determined.

RESULTS

Subchondral bone cysts were only identified in elbows with osteophytic new bone formation. The number and size of SBCs were associated with radiographic OA severity (p < .001 and p = .041 respectively). Specifically, the rate at which SBCs were present increased for both moderate and severe OA in comparison with the mild OA (moderate OA RR = 2.46, 95% CI 2.08-2.92, p < .001; severe OA RR = 5.60, 95% CI 4.79-6.55, p < .001). For dogs with severe OA, there was an increased likelihood that their SBCs were larger than SBCs from dogs with mild OA (OR = 1.056, 95% CI 1.012-1.101, p = .012). No SBCs were observed in elbows without radiographic evidence of OA.

CONCLUSION

Subchondral bone cysts were identified as a feature of radiographic elbow osteoarthritis in Labrador retrievers, and their number and size were indicative of the presence and severity of radiographic elbow OA.

CLINICAL SIGNIFICANCE

Subchondral bone cysts are a potential imaging biomarker for quantitative assessment for canine OA.

Systematic review of computed tomography parameters used for the assessment of subchondral bone in osteoarthritis

OBJECTIVE

To systematically review the published parameters for the assessment of subchondral bone in human osteoarthritis (OA) using computed tomography (CT) and gain an overview of current practices and standards.

DESIGN

A literature search of Medline, Embase and Cochrane Library databases was performed with search strategies tailored to each database (search from 2010 to January 2023). The search results were screened independently by two reviewers against pre-determined inclusion and exclusion criteria. Studies were deemed eligible if conducted in vivo/ex vivo in human adults (>18 years) using any type of CT to assess subchondral bone in OA. Extracted data from eligible studies were compiled in a qualitative summary and formal narrative synthesis.

RESULTS

This analysis included 202 studies. Four groups of CT modalities were identified to have been used for subchondral bone assessment in OA across nine anatomical locations. Subchondral bone parameters measuring similar features of OA were combined in six categories: (i) microstructure, (ii) bone adaptation, (iii) gross morphology (iv) mineralisation, (v) joint space, and (vi) mechanical properties.

CONCLUSIONS

Clinically meaningful parameter categories were identified as well as categories with the potential to become relevant in the clinical field. Furthermore, we stress the importance of quantification of parameters to improve their sensitivity and reliability for the evaluation of OA disease progression and the need for standardised measurement methods to improve their clinical value.

Relationship between the degree of subchondral collapse and articular surface irregularities in osteonecrosis of the femoral head

Articular surface irregularities are often observed in collapsed femoral heads with osteonecrosis, while the effects of the degree of collapse on the articular surface are poorly understood. We first macroscopically assessed the articular surface irregularities on 2-mm coronal slices obtained using high-resolution microcomputed tomography of 76 surgically resected femoral heads with osteonecrosis. These irregularities were observed in 68/76 femoral heads, mainly at the lateral boundary of the necrotic region. The mean degree of collapse was significantly larger for femoral heads with articular surface irregularities than for those without (p < 0.0001). Receiver operating characteristic analysis showed that the cutoff value for the degree of collapse in femoral heads with articular surface irregularities at the lateral boundary was 1.1 mm. Next, for femoral heads with <3-mm collapse (n = 28), articular surface irregularities were quantitatively assessed based on the number of automatically counted negative curvature points. Quantitative evaluation showed that the degree of collapse was positively correlated with the presence of articular surface irregularities (r = 0.95, p < 0.0001). Histological examination of articular cartilage above the necrotic region (n = 8) revealed cell necrosis in the calcified layer and abnormal cellular arrangement in the deep and middle layers. In conclusion, articular surface irregularities of the necrotic femoral head depended on the degree of collapse, and articular cartilage was already altered even in the absence of macroscopically determined gross irregularities.

Subchondral Bone Cyst Development in Osteoarthritis: From Pathophysiology to Bone Microarchitecture Changes and Clinical Implementations

Osteoarthritis is a degenerative joint disease affecting middle-aged and elderly patients. It mainly involves weight-bearing joints such as the hip, knee and spine as well as the basilar joint of the thumb, causing dysfunction and painful symptoms. Often, joint arthritis is accompanied by cartilage defects, joint space narrowing, osteophytes, bone sclerosis and subchondral bone cysts (SBC). The aim of the present study was to explore the pathophysiology responsible for the development of SBCs as well as the association between SBCs and disease progress, the level of clinical symptoms and their impact on postoperative outcomes and risk of possible complications following joint replacements if left untreated. A literature review on PubMed articles was conducted to retrieve and evaluate all available evidence related to the main objective mentioned above. A few theories have been put forth to explain the formation process of SBCs. These involve MMPs secretion, angiogenesis, and enhanced bone turnover as a biological response to abnormal mechanical loads causing repeated injuries on cartilage and subchondral tissue during the development of arthritis. However, the application of novel therapeutics, celecoxib-coated microspheres, local administration of IGF-1 and activated chondrocytes following surgical debridement of SBCs hinders the expansion of SBCs and prevents the progression of osteoarthritis.

Comparison of clinical-CT segmentation techniques for measuring subchondral bone cyst volume in glenohumeral osteoarthritis

PURPOSE

This study aimed to assess the accuracy and reproducibility of four common segmentation techniques measuring subchondral bone cyst volume in clinical-CT scans of glenohumeral OA patients.

METHODS

Ten humeral head osteotomies collected from cystic OA patients, having undergone total shoulder arthroplasty, were scanned within a micro-CT scanner, and corresponding preoperative clinical-CT scans were gathered. Cyst volumes were measured manually in micro-CT and served as a reference standard (n = 13). Respective cyst volumes were measured on the clinical-CT scans by two independent graders using four segmentation techniques: Qualitative, Edge Detection, Region Growing, and Thresholding. Cyst volume measured in micro-CT was compared to the different clinical-CT techniques using linear regression and Bland-Altman analysis. Reproducibility of each technique was assessed using intraclass correlation coefficient (ICC).

RESULTS

Each technique outputted lower volumes on average than the reference standard (-0.24 to -3.99 mm³). All linear regression slopes and intercepts were not significantly different than 1 and 0, respectively (p < 0.05). Cyst volumes measured using Qualitative and Edge Detection techniques had the highest overall agreement with reference micro-CT volumes (mean discrepancy: 0.24, 0.92 mm³). These techniques showed good to excellent reproducibility between graders.

CONCLUSIONS

Qualitative and Edge Detection techniques were found to accurately and reproducibly measure subchondral cyst volume in clinical-CT. These findings provide evidence that clinical-CT may accurately gauge glenohumeral cystic presence, which may be useful for disease monitoring and preoperative planning.

LEVEL OF EVIDENCE

Retrospective cohort Level 3 study.

Structural features of subchondral bone cysts and adjacent tissues in hip osteoarthritis

OBJECTIVE

Focal lesions within the subchondral bone, termed subchondral bone cysts (SBCs), are clinically accepted radiographic markers of advanced osteoarthritis (OA), but their etiology in the hip is not well understood.

DESIGN

This study used micro-computed tomography (μCT), and histological and immunocytological analysis to examine the prevalence, size, location, and morphological and cellular features of SBCs found within 34 femoral heads (14 male, 20 female; age range = 43-80 years) obtained from total hip arthroplasty procedures.

RESULTS

SBCs were common-present in 91% of the femoral heads examined-and frequently commuted with the surface of the femoral head, but otherwise showed no preferred anatomical location. Few associations were found between SBC features and patient characteristics such as BMI, age and sex. SBCs were also heterogenous in composition, ranging from fibrous (most common) to predominantly fatty (least common) and often containing vasculature, nerve fibers, cartilage islands, and bony spicules. Despite this heterogeneity, focal abnormalities in bone density and cartilage thickness were consistently observed. Bone adjacent to SBCs was denser than that in the primary compressive group, and cartilage thickness in regions overlying SBCs was lower than in non-overlying regions. In contrast to these local bony changes, μCT-based finite element analyses indicated that the stiffness of the primary compressive group was only mildly affected by SBCs.

CONCLUSIONS

These findings indicate that SBCs in the femoral head involve extensive perturbations in cellular activity, culminating in myriad skeletal tissue types and spatially heterogenous changes in bone and cartilage morphology that are likely to affect OA progression.

Spatial assessment of femoral neck bone density and microstructure in hip osteoarthritis

Osteoarthritis (OA) is known to involve profound changes in bone density and microstructure near to, and even distal to, the joint. Critically, however, a full, spatial picture of these abnormalities has not been well documented in a quantitative fashion in hip OA. Here, micro-computed tomography (44.8 μm/voxel) and data-driven computational anatomy were used to generate 3-D maps of the distribution of bone density and microstructure in human femoral neck samples with early (6F/4M, mean age = 51.3 years), moderate (14F/8M, mean age = 60 years), and severe (16F/6M, mean age = 63.3 years) radiographic OA. With increasing severity of radiographic OA, there was decreased cortical bone mineral density (BMD) (p=0.003), increased cortical thickness (p=0.001), increased cortical porosity (p=0.0028), and increased cortical cross-sectional area (p=0.0012, due to an increase in periosteal radius (p=0.018)), with no differences detected in the total femoral neck or trabecular compartment measures. No OA-related region-specific differences were detected through Statistical Parametric Mapping, but there were trends towards decreased tissue mineral density (TMD) in the inferior femoral neck with increasing OA severity (0.050 < p ≤ 0.091), possibly due to osteophytes. Overall, the lack of differences in cortical TMD among radiographic OA groups indicated that the decrease in cortical BMD with increasing OA severity was largely due to the increased cortical porosity rather than decreased tissue mineralization. As porosity is inversely associated with stiffness and strength in cortical bone, increased porosity may offset the effect that increased cortical cross-sectional area would be expected to have on reducing stresses within the femoral neck. The use of high-resolution imaging and quantitative spatial assessment in this study provide insight into the heterogeneous and multi-faceted changes in density and microstructure in hip OA, which have implications for OA progression and fracture risk.

Why do subchondral cysts occur at the medial aspect of the femoral head in hip dysplasia?

INTRODUCTION

Osteoarthritis in dysplastic hips should develop from the lateral side of the acetabulum and the femoral head just below. However, the existence of subchondral cysts located more on the medial side contradicts the weight-loading theory. The aim of this study was to confirm the presence of medial cysts at the femoral head and to investigate the relationship between medial cysts and injuries of the ligamentum teres in hip dysplasia.

METHODS

A retrospective analysis was conducted on 257 cases of hip dysplasia. All patients had x-rays and 3-dimensional computed tomographies (3D CT) preoperatively and 123 patients had magnetic resonance arthrographies. A comparison was performed between cases with and without medial cysts according to the severity of damage to the ligamentum teres, the presence of bony spurs around the fovea capitis, and the Tönnis grade.

RESULTS

Medial subchondral cysts around the fovea capitis were found in 100 cases. Mild osteoarthritis (Tönnis grade 0 or 1) was present in 89% of cases in the medial cyst group. A significant difference between the groups was observed in the incidence of bony spurs around the fovea capitis (p < 0.05) and injuries of the ligamentum teres (p < 0.05).

CONCLUSIONS

The formation of subchondral cysts at the medial femoral head in hip dysplasia may be related to damage in the ligamentum teres. Considering that subchondral cysts develop in early osteoarthritis, the progression of arthritis in hip dysplasia appears to correlate with damage to the ligamentum teres, as well as compressive pressure on the joint.

Bone Cysts and Osteolysis in Ankle Replacement

BACKGROUND

Total ankle replacements (TARs) have higher rates of osteolysis than hip or knee replacements. It is unclear whether this is a pathologic immunologic process in response to wear debris, or expansion of pre-existing osteoarthritic bone cysts. We aimed to determine the incidence of bone cysts in patients with end-stage ankle arthritis prior to surgery and review the literature on bone cysts and osteolysis in relation to TAR.

METHODS

This is a descriptive/prevalence study in which all patients with end-stage ankle arthritis underwent plain radiographic imaging and computed tomographic (CT) scans prior to TAR surgery. Their imaging was assessed for the presence of cysts, measured on sagittal, axial, and coronal slices of the CT scan at the widest diameter. All cysts that would be removed as a result of the bone resection for the implant were excluded using digital analysis software. We assessed 120 consecutive patients with mean age of 63.4 years.

RESULTS

Seventeen patients (14%) did not have any bone cysts based on CT images. Ten patients (8%) had cysts that would have been completely removed by surgery, leaving 93 patients for analysis (78%). In 60% of these cases, the cysts were not seen on the plain radiographs. In 39 patients (33%), the cysts were greater than 5 mm in size. The medial (36%) and lateral malleoli (33%) were the most common location for the cysts (mean diameter 4.6±2.0 and 4.2±2.3 mm, respectively).

CONCLUSION

Bone cysts outside of the resection margins for a TAR were present in 78% of patients with ankle arthritis prior to undergoing surgery. In 30% of cases, cysts were greater than 5 mm in size. In 60% of cases, the cysts were not seen on plain radiographs. Preoperative 3-dimensional imaging can provide a foundation to observe and quantify cyst presence, expansion, and time of onset in the postoperative setting.

LEVEL OF EVIDENCE

Level IIc, diagnostic/prevalence study.

Bone marrow lesions: etiology and pathogenesis at the hip

Bone marrow lesions (BML) are painful changes in subchondral bone which can be reliably identified on magnetic resonance imaging and have been identified in patients suffering from hip osteoarthritis (OA) and related conditions. Created via repetitive microdamage at the articular surface and dysregulated subchondral healing, BML have been linked to traumatic, inflammatory, degenerative, metabolic and neoplastic processes. While BML are known to be a common pathology throughout the body, BML at the hip have not been extensively studied in comparison to those at the knee. Due to the hip’s unique biomechanical architecture, function and loading, and independent risk factors leading to hip OA, hip BMLs must be independently understood. The identification of BML in the setting of a pre-osteoarthritic condition may provide a target for treatment and prevention of joint degeneration. By continuing to define and refine the relationships between BML, subchondral bone cysts and OA, prevention, diagnosis and treatment of OA could shift, leading to an improved quality of life and increased longevity of individuals’ native hips.

Cyst formation in the subchondral bone following cartilage repair

Subchondral bone cysts represent an early postoperative sign associated with many articular cartilage repair procedures. They may be defined as an abnormal cavity within the subchondral bone in close proximity of a treated cartilage defect with a possible communication to the joint cavity in the absence of osteoarthritis. Two synergistic mechanisms of subchondral cyst formation, the theory of internal upregulation of local proinflammatory factors, and the external hydraulic theory, are proposed to explain their occurrence. This review describes subchondral bone cysts in the context of articular cartilage repair to improve investigations of these pathological changes. It summarizes their epidemiology in both preclinical and clinical settings with a focus on individual cartilage repair procedures, examines an algorithm for subchondral bone analysis, elaborates on the underlying mechanism of subchondral cyst formation, and condenses the clinical implications and perspectives on subchondral bone cyst formation in cartilage repair.

Differences in subchondral trabecular bone microstructure and finite element analysis-based biomechanical properties between osteoporosis and osteoarthritis

Background/Objective

The microstructure of the subchondral trabecular bone, including the composition and distribution of plates and rods, has an important influence on the disease progression and mechanical properties of osteoarthritis (OA) and osteoporosis (OP). We aimed to determine whether differences in plates and rods influence the variations in the quantities and qualities of the subchondral trabecular bone between OA and OP.

Materials and methods

Thirty-eight femoral head samples [OA, n = 13; OP, n = 17; normal control (NC), n = 8] were collected from male patients undergoing total hip arthroplasty. They were scanned using microcomputed tomography, and subchondral trabecular structures were analysed using individual trabecular segmentation. Micro-finite element analysis (μFEA) was applied to assess the mechanical property of the trabecular bone. Cartilage changes were evaluated by using histological assessment. Analysis of variance was used to compare intergroup differences in structural and mechanical properties and cartilage degradation. Pearson analysis was used to evaluate the relationship between the trabecula microstructure and biomechanical properties.

Results

Compared with the OP and NC group, there was serious cartilage damage in the OA group. With respect to the microstructure results, the OA group had the highest plate and rod trabecular microstructures including number and junction density among the three groups. For the mechanical properties detected via μFEA, the OA group had higher stiffness and failure load than did the OP group. Pearson analysis revealed that compared with OP, OA had a higher number of microstructure parameters (e.g., rod bone volume fraction and rod trabecular number) that were positively correlated with its mechanical property.

Conclusions

Compared with OP, the OA subchondral bone has both increased plate and rod microarchitecture and has more microstructures positively related with its mechanical property. These differences may help explain the variation in mechanical properties between these bone diseases.

The translational potential of this article

Our findings suggested that changes in the plates and rods of the subchondral trabecular bone play a critical role in OA and OP progression and that the improvement of the subchondral trabecular bone may be a promising treatment approach.

Correlation between vertebral bone microstructure and estimated strength in elderly women: An ex-vivo HR-pQCT study of cadaveric spine

PURPOSE

A vertebral fracture is the most common complication of osteoporosis, and various factors are involved in its occurrence. The purpose of this study was to investigate the role of trabecular and cortical bone microstructure on vertebral strength using high-resolution peripheral quantitative computed tomography (HR-pQCT).

METHODS

Three female cadaveric spines were investigated (average age: 80.3 years). The whole spine (T1-L4) was scanned by second-generation HR-pQCT at a voxel size of 60.7 μm. Bone microstructure analysis and micro finite element analysis were performed after excluding the upper and lower endplates and posterior elements of a total of 48 vertebrae. Correlations between trabecular and cortical bone microstructure parameters and estimated vertebral strength were analyzed by univariate and multivariate regression models.

RESULTS

Cortical thickness (Ct.Th) and trabecular thickness (Tb.Th) were strongly correlated with estimated failure load on univariate analysis (r = 0.89, 0.82). Trabecular volumetric bone mineral density (Tb.vBMD), bone volume fraction (BV/TV), trabecular number (Tb.N), and Ct.Th were correlated with estimated failure load on multivariate regression analysis.

CONCLUSIONS

It was suggested that, in addition to trabecular bone (Tb.vBMD, BV/TV, Tb.N), cortical bone (Ct.Th) contributed significantly to vertebral strength in elderly women.

Knee osteoarthritis patients with more subchondral cysts have altered tibial subchondral bone mineral density

Background

Subchondral bone cysts are a widely observed, but poorly understood, feature in patients with knee osteoarthritis (OA). Clinical quantitative computed tomography (QCT) has the potential to characterize cysts in vivo but it is unclear which specific cyst parameters (e.g., number, size) are associated with clinical signs of OA, such as disease severity or pain. The objective of this study was to use QCT-based image-processing techniques to characterize subchondral tibial cysts in patients with knee OA and to explore relationships between proximal tibial subchondral cyst parameters and subchondral bone density as well as clinical characteristics of OA (alignment, joint space narrowing (JSN), OA severity, pain) in patients with knee OA.

Methods

The preoperative knee of 42 knee arthroplasty patients was scanned using QCT. Patient characteristics were obtained, including OA severity, knee pain, JSN, and alignment. We used 3D image processing techniques to obtain cyst parameters including: cyst number, cyst number per proximal tibial volume, cyst volume per proximal tibial volume, as well as maximum and average cyst volume across the proximal tibia, as well as regional bone mineral density (BMD) excluding cysts. We used Spearman’s correlation coefficients to explore associations between patient characteristics and cyst parameters.

Results

At both the medial and lateral compartments of the proximal tibia, greater cyst number and volume were associated with higher BMD. At the lateral region, cyst number and volume were also associated with lateral OA severity, lateral JSN, alignment and sex. Pain was not associated with any cyst parameters at any region.

Conclusion

Cyst number and volume were associated with BMD at both the medial and lateral compartments. Lateral cyst number and volume were also associated with joint alignment, OA severity, JSN and sex. This is the first study to use clinical QCT to explore subchondral tibial cysts in patients with knee OA and provides further evidence of the relationships between subchondral cysts and clinical OA characteristics.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2388-9) contains supplementary material, which is available to authorized users.

Osteoclast-related markers in the hip joint fluid with subchondral insufficiency fracture of the femoral head

Similar to the radiological findings in rapidly destructive arthrosis of the hip joint (RDA), subchondral insufficiency fracture of the femoral head (SIF) can result in progressive femoral head collapse of unknown etiology. We thus examined the osteoclast activity of hip joint fluid in SIF with progressive collapse in comparison with that in RDA. Twenty-nine hip joint fluid samples were obtained intraoperatively with whole femoral heads from 12 SIF patients and 17 RDA patients. SIF cases were classified into subgroups based on the presence of ≥2 mm collapse on preoperative radiographs: SIF with progressive collapse (n = 5) and SIF without progressive collapse (n = 7). The levels of tartrate-resistant acid phosphatase (TRACP)-5b, interleukin-8, vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)-9 were measured. The number of multinuclear giant cells at the subchondral region was histopathologically assessed using mid-coronal slice of each femoral head specimen. The median levels of all markers and the median number of multinuclear giant cells in SIF with progressive collapse were significantly higher than those in SIF without progressive collapse, while there were no significant differences in SIF with progressive collapse versus RDA. Regression analysis showed that the number of multinuclear giant cells was positively correlated with the level of TRACP-5b in joint fluid. The present study demonstrated the possible association of increased osteoclast activity with the existing condition of progressive collapse in SIF, which was quite similar to the findings in RDA, indicating that increased osteoclast activity may reflect the condition of progressive collapse in SIF as well as RDA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2987-2995, 2018.

Radiological analysis of cystic lesion in osteonecrosis of the femoral head

PURPOSE

Cystic lesions are a common complication in osteonecrosis of the femoral head (ONFH). This study will discuss the cause of cystic lesion formation and the feature of cystic lesion distribution in ONFH. According to the feature of cystic lesion in ONFH, we will discuss the possible mechanisms of cystic lesions and their  influence on collapse of the femoral head.

MATERIALS AND METHODS

We retrospectively gathered 102 ONFH patients (168 hips) from November in 2015 to August in 2016 on China-Japan Friendship Hospital. Three categories of patients' medical information were collected: demographic characteristics, bone cystic lesion location, and pathological finding on CT and MRI imaging (microfracture, collapse, crescent sign). On mid-coronal and mid-axial CT section, the femoral head was divided into four quadrants for locating the cystic lesion. And we classified the location relationship of cystic lesion and sclerosis rim as G1 type, G2 type, and G3 type on coronal CT section.

RESULTS

A significant difference was found between ONFH group with cystic lesion and ONFH group without cystic lesion in terms of microfracture (P < 0.001), collapse (P < 0.001), and crescent sign (P < 0.001). Forty-four cystic lesions (70%) are located in anterior hip area and 19 cystic lesions (30%) are located in posterior hip area. There were 14, 24, and seven cystic lesions (31, 53, 16%) locating in lateral, central, and medial pillars of the femoral head. G2 type was the most common pattern of location relationship between cystic lesion and sclerosis rim.

CONCLUSION

Cystic lesions are often found near sclerosis rim in ONFH. The femoral head with osteonecrosis complicating by cystic lesions is more likely to accompany microfracture, collapse, and crescent sign which indicate structural instability in the femoral head. Cystic lesion in ONFH plays an important role in aggravating the progression of femoral head collapse. The peak stress from sclerosis rim may be a main factor inducing the formation of cystic lesion in ONFH via an OA-like mechanism.

Longitudinal morphological change of acetabular subchondral bone cyst after total hip arthroplasty in developmental dysplasia of the hip

PURPOSE

The purpose of this study is to clarify morphological changes of acetabular subchondral bone cyst after total hip arthroplasty for osteoarthritis secondary to developmental dysplasia of the hip.

METHODS

Two hundred and sixty-one primary cementless total hip arthroplasties of 208 patients, 18 males, 190 females, were retrospectively reviewed. Morphological changes of subchondral bone cyst were evaluated by computed tomography (CT). The mean cross-sectional area of the cyst from CT scans at 3 months postoperatively and after 7-10 years (average 8.4 years) were compared.

RESULTS

Acetabular subchondral bone cysts were found in 49.0% of all cases in preoperative CT scans. There was no cyst which was newly recognized in CT scan performed after postoperative 7-10 years. All the cross-sectional areas of the cysts evaluated in this study were reduced postoperatively.

CONCLUSIONS

This study revealed that acetabular subchondral bone cysts do not increase or expand after total hip arthroplasty and indicated that the longitudinal morphological change of acetabular bone cysts in patients of developmental dysplasia of the hip do not influence long-term implant fixation in total hip arthroplasty.

Diffusion Tensor Imaging of Lumbar Vertebras in Female Adolescent Idiopathic Scoliosis: Initial Findings

OBJECTIVE

The purpose of this study was to characterize diffusion tensor imaging (DTI) features of lumbar vertebras in adolescent idiopathic scoliosis (AIS) patients.

METHODS

Fifty-two AIS patients and 20 healthy volunteers underwent 3-T magnetic resonance scanning including DTI sequence. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values on the convex and concave sides of lumbar vertebras were obtained and compared.

RESULTS

The FA and ADC values differed significantly between the convex and concave side of lumbar vertebras in AIS (P < 0.01). The ADC values in AIS differed significantly with healthy volunteers (P < 0.01). The FA values on the convex side of L1 to L2 were significantly lower than L4 to L5 in AIS. The difference of FA values between the concave and convex sides of the apex vertebra correlated significantly with Cobb angle (r = 0.436, P < 0.01).

CONCLUSIONS

The convex and concave sides of lumbar vertebras in AIS patients showed different DTI features.

Proximal tibial trabecular bone mineral density is related to pain in patients with osteoarthritis

Background

Our objective was to examine the relationships between proximal tibial trabecular (epiphyseal and metaphyseal) bone mineral density (BMD) and osteoarthritis (OA)-related pain in patients with severe knee OA.

Methods

The knee was scanned preoperatively using quantitative computed tomography (QCT) in 42 patients undergoing knee arthroplasty. OA severity was classified using radiographic Kellgren-Lawrence scoring and pain was measured using the pain subsection of the Western Ontario and McMaster Universities Arthritis Index (WOMAC). We used three-dimensional image processing techniques to assess tibial epiphyseal trabecular BMD between the epiphyseal line and 7.5 mm from the subchondral surface and tibial metaphyseal trabecular BMD 10 mm distal from the epiphyseal line. Regional analysis included the total epiphyseal and metaphyseal region, and the medial and lateral epiphyseal compartments. The association between total WOMAC pain scores and BMD measurements was assessed using hierarchical multiple regression with age, sex, and body mass index (BMI) as covariates. Statistical significance was set at p < 0.05.

Results

Total WOMAC pain was associated with total epiphyseal BMD adjusted for age, sex, and BMI (p = 0.013) and total metaphyseal BMD (p = 0.017). Regionally, total WOMAC pain was associated with medial epiphyseal BMD adjusted for age, sex, and BMI (p = 0.006).

Conclusion

These findings suggest that low proximal tibial trabecular BMD may have a role in OA-related pain pathogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1415-9) contains supplementary material, which is available to authorized users.

Optimizing finite element predictions of local subchondral bone structural stiffness using neural network-derived density-modulus relationships for proximal tibial subchondral cortical and trabecular bone

BACKGROUND

Quantitative computed tomography based subject-specific finite element modeling has potential to clarify the role of subchondral bone alterations in knee osteoarthritis initiation, progression, and pain. However, it is unclear what density-modulus equation(s) should be applied with subchondral cortical and subchondral trabecular bone when constructing finite element models of the tibia. Using a novel approach applying neural networks, optimization, and back-calculation against in situ experimental testing results, the objective of this study was to identify subchondral-specific equations that optimized finite element predictions of local structural stiffness at the proximal tibial subchondral surface.

METHODS

Thirteen proximal tibial compartments were imaged via quantitative computed tomography. Imaged bone mineral density was converted to elastic moduli using multiple density-modulus equations (93 total variations) then mapped to corresponding finite element models. For each variation, root mean squared error was calculated between finite element prediction and in situ measured stiffness at 47 indentation sites. Resulting errors were used to train an artificial neural network, which provided an unlimited number of model variations, with corresponding error, for predicting stiffness at the subchondral bone surface. Nelder-Mead optimization was used to identify optimum density-modulus equations for predicting stiffness.

FINDINGS

Finite element modeling predicted 81% of experimental stiffness variance (with 10.5% error) using optimized equations for subchondral cortical and trabecular bone differentiated with a 0.5g/cm³ density.

INTERPRETATION

In comparison with published density-modulus relationships, optimized equations offered improved predictions of local subchondral structural stiffness. Further research is needed with anisotropy inclusion, a smaller voxel size and de-blurring algorithms to improve predictions.

Bone turnover and articular cartilage differences localized to subchondral cysts in knees with advanced osteoarthritis

OBJECTIVE

To investigate changes in bone structure, turnover, and articular cartilage localized in subchondral bone cyst (SBC) regions associated with knee osteoarthritis (OA).

METHODS

Tibial plateaus (n = 97) were collected from knee OA patients during total knee arthroplasty (TKA). SBCs were identified using micro-computed tomography, and the specimens were divided into non-cyst (n = 25) and bone cyst (n = 72) groups. Microstructure of subchondral bone was assessed using bone volume fraction (BV/TV), trabecular number (Tb.N), structure model index (SMI) and bone mineral density (BMD). In bone cyst group, the cyst subregion, which contained at least one cyst, and the peri-cyst subregion, which contained no cysts, were further selected for microstructure analysis. Articular cartilage damage was estimated using the Osteoarthritis Research Society International (OARSI) score. The numbers of TRAP(+) osteoclasts, Osterix(+) osteoprogenitors, Osteocalcin(+) osteoblasts and expression of SOX9 were evaluated by immunohistochemistry.

RESULTS

Bone cyst group presented higher BV/TV, Tb.N and SMI at subchondral bone than non-cyst group. Furthermore, cyst subregion displayed increased BV/TV and Tb.N but lower BMD and SMI than peri-cyst subregion. Histology revealed a higher OARSI score in bone cyst group. SBC exhibited a weak relationship with BV/TV, etc. The numbers of TRAP(+) osteoclasts, Osterix(+) osteoprogenitors, Osteocalcin(+) osteoblasts and expression of SOX9, were higher in bone cyst group.

CONCLUSION

SBCs within knee OA are characterized by focally increased bone turnover, altered bone structure and more severe articular cartilage damage. The increased bone turnover possibly contributes to altered bone structure localized in SBC areas, and thus aggravates articular cartilage degeneration.

Knee osteoarthritis patients with severe nocturnal pain have altered proximal tibial subchondral bone mineral density

OBJECTIVE

Our objective was to investigate relationships between proximal tibial subchondral bone mineral density (BMD) and nocturnal pain in patients with knee osteoarthritis (OA).

METHODS

The preoperative knee of 42 patients booked for knee arthroplasty was scanned using quantitative computed tomography (QCT). Pain was measured using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and participants were categorized into three groups: 'no pain', 'moderate pain', and 'severe pain' while lying down at night. We used depth-specific image processing to assess tibial subchondral BMD at normalized depths of 0-2.5 mm, 2.5-5.0 mm and 5-10 mm relative to the subchondral surface. Regional analyses of each medial and lateral plateau included total BMD and maximum BMD within a 10 mm diameter core or 'focal spot'. The association between WOMAC pain scores and BMD measurements was assessed using Spearman's rank correlation. Regional BMD was compared pairwise between pain and no pain groups using multivariate analysis of covariance using age, sex, and BMI as covariates and Bonferroni adjustment for multiple comparisons.

RESULTS

Lateral focal BMD at the 2.5-5 mm depth was related to nocturnal pain (ρ = 0.388, P = 0.011). The lateral focal BMD was 33% higher in participants with 'severe pain' than participants with 'no pain' at 2.5-5 mm depth (P = 0.028) and 32% higher at 5-10 mm depth (P = 0.049). There were no BMD differences at 0-2.5 mm from the subchondral surface.

CONCLUSION

This study suggests that local subchondral bone density may have a role in elucidating OA-related pain pathogenesis.