Outcomes of Hybrid Total Hip Arthroplasty for Subchondral Insufficiency Fracture of the Femoral Head

Background

The purpose of this study was to evaluate functional outcomes, radiologic results, and complications after hybrid total hip arthroplasty (THA) in patients with subchondral insufficiency fractures (SIFs) of the femoral head.

Methods

From June 2009 to December 2020, among 985 patients who underwent hybrid THA at our hospital, 19 patients diagnosed with SIF through a retrospective chart review were included. Those under 50 years of age, with radiographic findings of osteonecrosis on the contralateral side of surgery, a history of organ transplantation, and alcohol abuse, were excluded. Functional evaluation was performed using a modified Harris Hip Score (HHS). After surgery, inclination and anteversion of the acetabular cup and version of the femoral system were measured using postoperative x-ray. The outpatient follow-up was performed at 6 weeks, 3 months, 9 months, and 12 months after surgery and every year thereafter. Complications including dislocation, implant loosening, stem subsidence, and periprosthetic infection were observed on follow-up radiographs.

Results

The average follow-up time was 29.3 ± 9.1 months (range, 24-64 months) with no loss to follow-up. The mean modified HHS was 83.4 ± 9.6 (range, 65-100) at the last outpatient clinic follow-up. The average inclination of the acetabular cup was 41.9° ± 3.4° (range, 37°-48°), and the anteversion was 27.5° ± 6.7° (range, 18°-39°). The version of the femoral stem was 19° ± 5.7° (range, 12°-29°). There was no case of intraoperative fracture. There were no cases of dislocation, loosening of the cup, subsidence of the femoral stem, intraoperative or periprosthetic fracture, or periprosthetic infection on the follow-up radiographs.

Conclusions

In our study, hybrid THA showed favorable outcomes in patients diagnosed with SIF, and there were no further special considerations as for THA performed due to other diseases or fractures.

Are there associations between hip geometry and bone quality? An analysis on 3074 adults from a general population

INTRODUCTION

Patients with reduced bone mineral density and altered hip geometry are susceptible for hip pathologies. Knowledge on associations between bone properties and hip geometric parameters might facilitate identification of patients at risk for hip pathologies. The aim of the present study was to identify associations of bone properties assessed by quantitative ultrasound (QUS) at the heel and hip geometric parameters like center-edge angle (CE), neck-shaft angle (NSA) and alpha angle.

MATERIALS AND METHODS

Hip geometric parameters (CE, NSA and alpha angle) of 3074 participants from the population-based Study of Health in Pomerania were assessed on magnetic resonance imaging. QUS was performed on both calcanei providing broadband ultrasound attenuation (BUA), speed of sound (SOS) and stiffness-index. Based on the stiffness-index the individual osteoporotic fracture risk (low, moderate or high) was determined. Associations between QUS-based and hip geometric parameters were calculated in linear regression models adjusted for age, sex, body height and weight. Interactions of QUS markers with age and sex on hip geometric parameters were tested.

RESULTS

Significant inverse associations between BUA (β = - 0.068), SOS (β = - 0.024) as well as stiffness-index (β = - 0.056) and CE were present, while fracture risk was positively associated with CE (β for high = 1.28 and moderate = 2.54 vs. low fracture risk). Interactions between BUA and sex as well as between SOS and age were detected in the models for CE. Furthermore, there was an inverse relation between fracture risk and NSA that was restricted to the moderate risk (β for moderate vs. low fracture risk = - 0.60). There were no significant associations between QUS parameters and alpha angle.

CONCLUSIONS

In the general population, several associations between QUS-based bone properties or fracture risk and hip geometry are present. Less dysplastic hips had a lower stiffness-index and a higher fracture risk, whereas more valgus hips had a lower fracture risk.

Subchondral fatigue fracture of the femoral head in young military recruits: Potential risk factors

BACKGROUND

Subchondral fatigue fracture of the femoral head (SFFFH) mainly occurs in young military recruits and might be confused with osteonecrosis of the femoral head. However, less research focuses on the risk factor for SFFFH.

AIM

To evaluate the intrinsic risk factors for SFFFH in young military recruits.

METHODS

X-ray and magnetic resonance imaging data were used for analysis. Acetabular anteversion of the superior acetabulum, acetabular anteversion of the center of the acetabulum (AVcen), anterior acetabular sector angle (AASA), posterior acetabular sector angle, superior acetabular sector angle, neck-shaft angle (NSA), inferior iliac angle (IIA), and ischiopubic angle were calculated. Then, logistic regression, receiver operating characteristic curve analysis, and independent samples t-test were performed to identify the risk factors for SFFFH.

RESULTS

Based on the results of logistic regression, age [odds ratio (OR): 1.33; 95% confidence interval (95%CI): 1.12-1.65; P = 0.0031] and treatment timing (OR: 0.86; 95%CI: 0.75-0.96; P = 0.015) could be considered as the indicators for SFFFH. AVcen (P = 0.0334), AASA (P = 0.0002), NSA (P = 0.0007), and IIA (P = 0.0316) were considered to have statistical significance. Further, AVcen (OR: 1.41; 95%CI: 1.04-1.95) and AASA (OR: 1.44; 95%CI: 1.21-1.77), especially AASA (area under curve: 66.6%), should be paid much more attention due to the higher OR than other indicators.

CONCLUSION

We have for the first time unveiled that AASA and age could be key risk factors for SFFFH, which further verifies that deficient anterior coverage of the acetabulum might be the main cause of SFFFH.

Cementless Hip Arthroplasty in Patients with Subchondral Insufficiency Fracture of the Femoral Head

BACKGROUND

Subchondral insufficiency fracture of the femoral head (SIFFH) occurs in elderly patients and might be confused with osteonecrosis of the femoral head (ONFH). Subchondral insufficiency fracture of the femoral head is an insufficiency fracture at the dome of the femoral head and has been known to be associated with osteoporosis, hip dysplasia, and posterior pelvic tilt. This study's aims were to evaluate (1) surgical complications, (2) radiological changes, (3) clinical results, and (4) survivorship of THA in patients with SIFFH.

METHODS

From November 2010 to June 2017, 21 patients (23 hips); 5 men (5 hips) and 16 women (18 hips) underwent cementless THA due to SIFFH at our institution. Their mean age was 71.9 years (range, 57 to 86) at the time of surgery, and mean T-score was -2.2 (range, -4.2 to 0.2). The mean lateral center-edge angle, abduction, and anteversion of the acetabulum were 29.9° (range, 14.8° to 47.5°), 38.5° (range, 31° to 45°), and 20.0° (range, 12° to 25°), respectively. The mean pelvic incidence, lumbar kyphotic angle and posterior pelvic tilt were 56.4° (range, 39° to 79°), 14.7° (range, -34° to 43°), and 13.0° (range, 3° to 34°), respectively.

RESULTS

An intraoperative calcar crack occurred in 1 hip. The mean anteversion and abduction of cup were 29.0° (range, 17° to 43°) and 43.3° (range, 37° to 50°), respectively. One patient sustained a traumatic posterior hip dislocation 2 weeks after the procedure, and was treated with open reduction. At a mean follow-up of 35.4 months (range, 24 to 79 months), no hip had prosthetic loosening or focal osteolysis. At the latest follow-up, the mean modified Harris hip score was 79.1 (range, 60 to 100) points, and mean UCLA activity score was 4.2 (range, 2 to 7) points. The survivorship was 95.7% (95% CI, 94.9% to 100%) at 6 years.

CONCLUSIONS

Cementless THA is a favorable treatment option for SIFFH in elderly patients.

LEVEL OF EVIDENCE

3.

The Discrepancy in the Posterior Boundary of Necrotic Lesion Between Axial and Oblique Axial Slices of MRI in Patients with Osteonecrosis of the Femoral Head

BACKGROUND

Little is known concerning differences in assessment of anteroposterior osteonecrotic lesion of the femoral head (ONFH) between the axial plane parallel to the body axis (axial) and the axial plane parallel to the femoral neck axis (oblique axial) using magnetic resonance imaging (MRI). This study aimed to compare the posterior boundary of necrotic lesions between the axial and oblique axial planes on MRI.

METHODS

This study retrospectively reviewed 120 consecutive hips in 71 patients (47 males and 24 females; mean age, 42 years) with ONFH, for which both axial and oblique axial MRI slices were available. The posterior boundaries of the necrotic lesions were calculated as the ratio of posterior intact circumference to anteroposterior circumference of the femoral head using mid-axial and mid-oblique axial MRI slices. The necrotic angles, calculated using the modified Kerboul method, were compared between cases with progression and nonprogression of collapse.

RESULTS

The mean posterior intact ratio in the axial slice was 49.2% (range, 8.6 to 85.1%), while that in the oblique axial slice was 33.5% (7.5 to 79.2%). The posterior intact ratio in the oblique axial slice significantly decreased compared to that in the axial slice (p < 0.0001). In cases with progression of collapse, the mean necrotic angle was significantly larger in the oblique axial slice than in the axial slice (p < 0.0001). The sensitivity and specificity of the necrotic angle with regard to the prognosis of the femoral head were both higher when using the oblique axial slice (sensitivity: 88.4%, specificity: 82.3%) than when using the axial slice (sensitivity: 85.1%, specificity: 62.0%). The posterior intact ratio at a mean of 6.8 mm superior to the mid-axial slice corresponded to that of the mid-oblique axial slice.

CONCLUSION

Our findings suggest that the posterior boundaries of necrotic lesions differ between axial and oblique axial slices, and examination of the oblique axial MRI slice might be more suitable for predicting the prognosis of the femoral head.

LEVEL OF EVIDENCE

Diagnostic-Investigating a diagnostic test. Level IV (Case series).

Subchondral fracture of the femoral head in children: Differential diagnosis of pediatric hip pain

This report describes clinical and radiographic characteristics of two pediatric patients with a presumptive diagnosis of subchondral fracture of the femoral head made based on their clinical course and imaging findings. An 8-year-old boy and an 8-year-old girl had subchondral fracture in the femoral head without osteonecrosis, which was verified by contrast-enhanced magnetic resonance imaging. Although complete disappearance of the fracture line was confirmed in the boy, the girl had a residual femoral head deformity after conservative treatment. Subchondral fracture of the femoral head should be included in the differential diagnosis of pediatric hip pain.

Spontaneous osteonecrosis of the knee (SONK): The role of MR imaging in predicting clinical outcome

Background/aim

We try to investigate the association between patterns of imaging findings in patients who had a diagnosis of subchondral fracture around the knee, formerly known as SONK and their clinical outcome.

Materials and methods

We retrospectively identified 43 knees of 37 patients (28 males, 15 females) who had diagnosis of subchondral fractures around the knee. The mean age is 56-year-old (range 17-83). Musculoskeletal fellowship trained radiologist evaluated all 43 knee MRI in: 1)location of marrow edema 2)peri-osseous edema; 3) subchondral fracture line; 4) subchondral articular surface contour; 5)meniscal tear and extrusion; 6)adjacent soft tissue edema; 7) joint effusion. Independent clinical chart review was performed for clinical outcome with follow up time average of 13.3 months (range 0-88 months). Bad outcome was defined as worsening on imaging, continued complaint with surgical management and knee replacement or another episode of SONK. Chi-square analysis and Student's T tests were conducted to test the statistical significance of association between MR findings and outcomes. Statistical significance was set at p = 0.05 level.

Results

Of 43 knees, 6 patients had another episodes of SONK (14%), 11 patients were not improving or needed injection vs arthroscopy (26%), 4 patients required arthroplasty (9%), 22 patients had no negative outcome (51%). Gender, age, diabetic status, and location of the subchondral fracture show no influence on outcome. Worse outcome group had a significantly higher average BMI (31.7 vs. 28.0, P = 0.02). Positive change of subchondral articular surface contour is the only imaging finding with positive association with worse outcome (80% vs. 39.9%, P = 0.02). Presence of positive findings of above 3), 4), 5) and 6) had higher percentage of bad outcome (77.8%) compared to those with less positive findings (47.2%).

Conclusion

MR imaging findings may help at identifying SONK patient with potential risk of developing bad outcome.

Distribution of Femoral Head Subchondral Fracture Site Relates to Contact Pressures, Age, and Acetabular Structure

OBJECTIVE. Nontraumatic subchondral fracture of the femoral head (FH) is often seen in elderly patients with osteoporosis and acetabular dysplasia. Although this injury can also occur in young people, even those without osteoporosis, it remains unclear who is at risk. We examined the acetabular structure and sites of subchondral fracture of the FH in young patients compared with those in middle-aged and older patients. MATERIALS AND METHODS. Forty-eight hips with nontraumatic subchondral fracture of the FH were divided into two groups according to patient age: young (< 40 years) and middle-aged and older (≥ 40 years). Dysplasia and retroversion were defined as a lateral center-edge angle of < 20° and crossover sign on anterosuperior radiographs, respectively. Locations and extents of fracture were evaluated by measuring the edge location of low-signal-intensity bands on coronal T1-weighted MR images. Stress distribution on subchondral bone in young patients was evaluated in contralateral unaffected hips with the same acetabular structure using finite element modeling based on CT. RESULTS. Twelve hips were in young patients and 36 were in middle-aged and older patients. Hips in young patients showed retroversion in 41.7%, whereas those in middle-aged and older patients had dysplasia in 38.9%. Young patients had larger mediolateral fractures; fractures in middle-aged and older patients were laterally located. Anterosuperior fractures were seen in both groups. Contact stress in patients with retroversion was mainly distributed on the mediolateral and superior sides but was concentrated laterally and superiorly in one patient with dysplasia. CONCLUSION. Mediolateral and anterosuperior fractures and stress distribution by retroversion were commonly observed in young patients, suggesting partial involvement of retroversion in the mechanism of injury of nontraumatic subchondral fractures of the FH in young patients.

Nomenclature of Subchondral Nonneoplastic Bone Lesions

OBJECTIVE. The purpose of this article is to summarize the nomenclature of nonneoplastic conditions affecting subchondral bone through a review of the medical literature and expert opinion of the Society of Skeletal Radiology Subchondral Bone Nomenclature Committee. CONCLUSION. This consensus statement summarizes current understanding of the pathophysiologic characteristics and imaging findings of subchondral nonneoplastic bone lesions and proposes nomenclature to improve effective communication across clinical specialties and help avoid diagnostic errors that could affect patient care.

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.

The depth of the low-intensity band on the T1-weighted MR image is useful for distinguishing subchondral insufficiency fracture from osteonecrosis of the collapsed femoral head

PURPOSE

To verify the hypothesis that depth of the low-intensity band on T1-weighted MR image is useful for distinguishing subchondral insufficiency fracture (SIF) from osteonecrosis of the collapsed femoral head (ON).

PATIENTS AND METHODS

We reviewed 35 consecutive hips in 35 patients with radiological evidence of subchondral collapse of the femoral head and available MR images and histology between May 2013 and January 2016. Both clinical and radiological appearances were investigated. The ratios of distance from articular surface of the femoral head to the T1 low-intensity band to femoral head diameter (band depth ratio: BDR) on (1) mid-coronal slice of MR images and that on (2) coronal slice of MR images in which the highest BDR was observed, were calculated.

RESULTS

The mean age in SIF group was significantly higher than that in ON group (SIF: 68 years, ON: 49 years, P = 0.0017). The rates of history of steroid intake or alcohol consumption in SIF group were significantly lower than those in ON group (P = 0.0022 and P = 0.0408, respectively). The mean BDRs in SIF group were (1) 0.16 and (2) 0.23, which were significantly lower than those in ON group [(1) 0.42 and (2) 0.59] (P < 0.0001 for both). The cut-off BDR values to differentiate SIF from ON were (1) 0.22 and (2) 0.38, respectively.

CONCLUSION

The results of the study suggest that depth of the low-intensity band on T1-weighted MR image is useful for distinguishing SIF from ON in cases with collapsed femoral heads.

Computed tomography findings of subchondral insufficiency fractures of the femoral head

Objectives

The objective of this study was to describe the appearance of Subchondral insufficiency fracture (SIF) by computed tomography (CT).

Methods

Images of 52 consecutive patients diagnosed with SIF were retrospectively reviewed. CT was available for five patients (7 cases).

Results

Corresponding to a low-intensity band on MR images, a radiolucent or sclerotic band was observed on CT images.

Conclusion

The present study is the first to report CT findings of SIF. A radiolucent or sclerotic band was observed on CT images. The results of the present study provide useful information for diagnosis of SIF.

Understanding Bone Strength Is Not Enough

Increases in fracture risk beyond what are expected from bone mineral density (BMD) are often attributed to poor "bone quality," such as impaired bone tissue strength. Recent studies, however, have highlighted the importance of tissue material properties other than strength, such as fracture toughness. Here we review the concepts behind failure properties other than strength and the physical mechanisms through which they cause mechanical failure: strength describes failure from a single overload; fracture toughness describes failure from a modest load combined with a preexisting flaw or damage; and fatigue strength describes failure from thousands to millions of cycles of small loads. In bone, these distinct failure mechanisms appear to be more common in some clinical fractures than others. For example, wrist fractures are usually the result of a single overload, the failure mechanism dominated by bone strength, whereas spinal fractures are rarely the result of a single overload, implicating multiple loading cycles and increased importance of fatigue strength. The combination of tissue material properties and failure mechanisms that lead to fracture represent distinct mechanistic pathways, analogous to molecular pathways used to describe cell signaling. Understanding these distinct mechanistic pathways is necessary because some characteristics of bone tissue can increase fracture risk by impairing fracture toughness or fatigue strength without impairing bone tissue strength. Additionally, mechanistic pathways to failure associated with fracture toughness and fatigue involve multiple loading events over time, raising the possibility that a developing fracture could be detected and interrupted before overt failure of a bone. Over the past two decades there have been substantial advancements in fracture prevention by understanding bone strength and fractures caused by a single load, but if we are to improve fracture risk prevention beyond what is possible now, we must consider material properties other than strength. © 2017 American Society for Bone and Mineral Research.

Favorable Clinical and Radiographic Results of Transtrochanteric Anterior Rotational Osteotomy for Collapsed Subchondral Insufficiency Fracture of the Femoral Head in Young Adults

Background:

Subchondral insufficiency fracture of the femoral head (SIF) occurs infrequently in young adults. As the collapsed SIF lesion is usually located at the anterior portion of the femoral head, young adults with SIF are considered to be candidates for transtrochanteric anterior rotational osteotomy, similar to patients with osteonecrosis of the femoral head (ON). In the present study, we assessed the clinical and radiographic results of anterior rotational osteotomy for the treatment of SIF as compared with ON.

Methods:

We retrospectively reviewed 28 consecutive patients who underwent anterior rotational osteotomy for the treatment of unilateral SIF (7 patients) or unilateral ON (21 patients). The mean duration of follow-up was 3.7 years (range, 2.0 to 6.2 years). Clinical and radiographic assessments were performed with use of the Harris hip score (HHS), sequential radiographs, and single-photon emission computed tomography/computed tomography (SPECT/CT) with ^99mTc-hydroxymethylene diphosphonate performed 5 weeks after surgery.

Results:

The mean HHS (and standard deviation) in the SIF group improved significantly from 51.6 ± 11.7 preoperatively to 91.9 ± 7.1 at 1 year after surgery and to 96.9 ± 3.8 at the time of the latest follow-up (p = 0.0010 and 0.0002, respectively). Similarly, the mean HHS in the ON group improved significantly from 52.4 ± 13.7 preoperatively to 80.7 ± 10.0 at 1 year after surgery and to 88.2 ± 12.6 at the time of the latest follow-up (p < 0.0001 for both). The HHS was significantly higher in the SIF group than in the ON group at 1 year after surgery (p = 0.019), but there was no significant difference between the groups at the time of the latest follow-up (p = 0.10). A postoperative intact ratio (calculated as the intact area of the femoral head divided by the weight-bearing area of the acetabulum on an anteroposterior radiograph) of >80% was achieved in association with smaller femoral neck-shaft varus angles in the SIF group (10.0° ± 4.2°) as compared with the ON group (15.3° ± 8.2°). Postoperative progression of collapse at the anteriorly rotated subchondral lesion was observed in 5 patients (23.8%) in the ON group but no patients in the SIF group. SPECT/CT images showed that rate of increased tracer uptake at the collapsed lesions in the SIF group was significantly higher than that in the ON group (p < 0.0001).

Conclusions:

The present study suggested that the absence of progression of collapse and a sufficient postoperative intact ratio without the need for marked varus realignment may be associated with favorable results following anterior rotational osteotomy for the treatment of SIF in young adults.

Level of Evidence:

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Fat-suppressed T2-weighted MRI appearance of subchondral insufficiency fracture of the femoral head

OBJECTIVE

Our aims were to investigate the imaging appearance of subchondral insufficiency fracture (SIF) of the femoral head based on fat-suppressed T2-weighted MRI, and evaluate its correlation with the clinical outcomes following conservative treatment.

MATERIALS AND METHODS

We retrospectively evaluated 40 hips in 37 patients with SIF of the femoral head (12 males and 25 females; mean age 55.8 years, range 22-78 years). MRI examinations were performed within 3 months after the onset of hip pain. Using fat-suppressed T2-weighted imaging, we evaluated the hips for the intensity of the subchondral bone (corresponding to the area superior to the low intensity band on T1-weighted images) as well as bone marrow edema, joint effusion, and presence of the band lesion. We then correlated the intensity of the subchondral bone with clinical outcomes.

RESULTS

The hips were classified into three types based on subchondral intensity on fat-suppressed T2-weighted images: type 1 (21 hips) showed high intensity, type 2 (eight hips) showed heterogeneous intensity, and type 3 (11 hips) showed low intensity. The mean period between pain onset and MRI examination was significantly longer for type 2 hips than for type 1. Healing rates were 86 % for type 1, 75 % for type 2, and 18 % for type 3.

CONCLUSION

SIF cases were classified into three types based on subchondral intensity on fat-suppressed T2-weighted imaging performed within 3 months after pain onset. Type 3 SIF tended to be intractable to conservative treatment compared to type 1 and type 2.

Decreased Lumbar Lordosis and Deficient Acetabular Coverage Are Risk Factors for Subchondral Insufficiency Fracture

Subchondral insufficiency fracture (SIF) of the femoral head occurs in the elderly and recipients of organ transplantation. Osteoporosis and deficient lateral coverage of the acetabulum are known risk factors for SIF. There has been no study about relation between spinopelvic alignment and anterior acetabular coverage with SIF. We therefore asked whether a decrease of lumbar lordosis and a deficiency in the anterior acetabular coverage are risk factors. We investigated 37 patients with SIF. There were 33 women and 4 men, and their mean age was 71.5 years (59-85 years). These 37 patients were matched with 37 controls for gender, age, height, weight, body mass index and bone mineral density. We compared the lumbar lordosis, pelvic incidence, pelvic tilt, sacral slope, acetabular index, acetabular roof angle, acetabular head index, anterior center-edge angle and lateral center-edge angle. Lumbar lordosis, pelvic tilt, sacral slope, lateral center edge angle, anterior center edge angle, acetabular index and acetabular head index were significantly different between SIF group and control group. Lumbar lordosis (OR = 1.11), lateral center edge angle (OR = 1.30) and anterior center edge angle (OR = 1.27) had significant associations in multivariate analysis. Decreased lumbar lordosis and deficient anterior coverage of the acetabulum are risk factors for SIF as well as decreased lateral coverage of the acetabulum.

Clinical outcomes in relation to locations of bone marrow edema lesions in patients with a subchondral insufficiency fracture of the hip: a review of fifteen cases

OBJECTIVE

The prognosis of patients with a subchondral insufficiency fracture remains unclear. The purpose of this study was to investigate the correlation between locations of bone marrow edema (BME) lesions and clinical outcome in patients with a subchondral insufficiency fracture of the hip.

METHODS

We retrospectively reviewed 15 consecutive hips in 14 patients who were diagnosed with subchondral insufficiency fracture of the hip at our institution between April 2013 and September 2014. This study included five males (six hips) and nine females (nine hips), ranging from 36 to 83 years of age (mean age: 66 years). The mean duration from the onset of hip pain to MRI examination was 1.8 months (range 0.5-5 months). Both clinical and imaging findings were investigated.

RESULTS

Based on the findings of MR images, BME lesion in the femoral head alone was observed in six patients (six hips), BME lesion in the acetabulum alone was observed in one patient (two hips) and BME lesions in both the femoral head and acetabulum were observed in seven patients (seven hips). 3 of 15 hips resulted in rapidly destructive arthrosis and their BME lesions were observed in both the femoral head and acetabulum. 8 of 15 hips successfully healed by conservative treatment and BME lesions in 7 of these 8 hips were observed in only the femoral head or acetabulum.

CONCLUSION

The results of this study indicate that the locations of BME lesions (femoral side alone, acetabular side alone or both) may be related to the clinical outcome in patients with a subchondral insufficiency fracture of the hip.

ADVANCES IN KNOWLEDGE

Patients with subchondral insufficiency fracture of the hip in whom BME lesions were observed in both the femoral head and acetabulum may have a higher risk to need to undergo total hip arthroplasty.

Does the relative density of periarticular bone influence the failure pattern of intra-articular fractures?

INTRODUCTION

The architecture of joints almost certainly influences the nature of intra-articular fractures, and the concavity is much more likely to fail than the associated convexity. However, local differences in periarticular bone density potentially also plays a critical role. The purpose of this study was to investigate if there was any difference in periarticular bone density in intra-articular fractures between the two opposing joint surfaces, comparing the convexity to the concavity.

MATERIALS AND METHODS

We retrospectively identified a series of 1003 intra-articular fractures of the hip, knee, and ankle; 129 of these patients had previously undergone CT scanning during their routine clinical assessment. Periarticular bone density was assessed using Hounsfield Units (HU) as a measure of the composite density of the adjacent bone. Bone density was compared between the opposite sides of each joint, to determine if a relationship exists between local bone density and the risk of articular surface fracture.

RESULTS

There was a statistically significant difference in density between the two opposing surfaces, with the convexity 19% more dense than the concavity (p=0.0001). The knee exhibited the largest difference (55%), followed by the hip (18%); in the ankle, an inverse relationship was observed, and the concave surface was paradoxically denser (5%). There was no significant difference between those cases where the concavity failed in isolation compared to those where the convexity also failed (p=0.28).

CONCLUSION

When the results were pooled for all three joints, there was a statistically significant higher local bone density demonstrated on the convex side of an intra-articular fracture. However, while this relationship was clearly exhibited in the knee, this was less evident in the other two joints; in the ankle the reverse was true, and the local bone adjacent to the concavity was found to have greater density. This suggests local bone density plays only a minor role in determining the nature of intra-articular fractures.

Common site of subchondral insufficiency fractures of the femoral head based on three-dimensional magnetic resonance imaging

OBJECTIVES

The objective of this study was to investigate the common sites of subchondral insufficiency fractures of the femoral head (SIF) based on three-dimensional (3-D) reconstruction of MR images.

MATERIALS AND METHODS

In 33 hips of 31 consecutive patients diagnosed with SIF, 3-D reconstruction of the bone, fracture, and acetabular edge was performed using MR images. These 3-D images were used to measure the fractured areas and clarify the positional relationship between the fracture and degree of acetabular coverage.

RESULTS

The fractured area in the anterior portion was significantly larger than in the posterior area. In 11 cases, the fractures contacted the acetabular edge and were distributed on the lateral portion. The indices of acetabular coverage (center-edge angle and acetabular head index) in these cases were less than the normal range. In the remaining 22 cases, the fractures were apart from the acetabular edge and distributed on the mediolateral centerline of the femoral head. The majority of these cases had normal acetabular coverage.

CONCLUSIONS

The common site of SIF is the anterior portion. In addition, two types of SIF are proposed: (1) Lateral type: the contact stress between the acetabular edge and lateral portion of the femoral head causes SIF based on the insufficient acetabular coverage, and (2) Central type: the contact stress between the acetabular surface and the mediolateral center of the femoral head causes SIF independent from the insufficiency of acetabular coverage. These findings may be useful for considering the treatment and prevention of SIF.

Subchondral insufficiency fractures of the femoral head: associated imaging findings and predictors of clinical progression

OBJECTIVES

To characterize the morphology and imaging findings of femoral head subchondral insufficiency fractures (SIF), and to investigate clinical outcomes in relation to imaging findings.

METHODS

Fifty-one patients with hip/pelvis magnetic resonance (MR) images and typical SIF characteristics were identified and reviewed by two radiologists. Thirty-five patients had follow-up documentation allowing assessment of clinical outcome. Subgroup comparisons were performed using regression models adjusted for age and body mass index.

RESULTS

SIF were frequently associated with cartilage loss (35/47, 74.5 %), effusion (33/42, 78.6 %), synovitis (29/44, 66 %), and bone marrow oedema pattern (BMEP) (average cross-sectional area 885.7 ± 730.2 mm(2)). Total hip arthroplasty (THA) was required in 16/35 patients, at an average of 6 months post-MRI. Compared to the THA cohort, the non-THA group had significantly (p < 0.05) smaller overlying cartilage defect size (10 mm vs. 29 mm), smaller band length ratio and fracture diameters, and greater incidence of parallel fracture morphology (p < 0.05). Male gender and increased age were significantly associated with progression, p < 0.05.

CONCLUSIONS

SIF were associated with synovitis, cartilage loss, effusion, and BMEP. Male gender and increased age had a significant association with progression to THA, as did band length ratio, fracture diameter, cartilage defect size, and fracture deformity/morphology.

KEY POINTS

• Femoral head subchondral insufficiency fractures (SIF) frequently require total hip arthroplasty (THA). • SIF frequently coexist with synovitis, cartilage loss, and bone marrow oedema pattern. • SIF cartilage defect size, band length ratio, and fracture diameter/morphology can predict progression risk.

MRI of subchondral fractures: a review

Several authors have recently emphasized the role of magnetic resonance imaging (MRI) in the diagnosis of subchondral fractures. There is increasing interest about this type of fractures, mostly because they have been implicated in the genesis of some well-known destructive articular conditions whose cause was previously undetermined, such as distal clavicular osteolysis, rapidly progressive osteoarthritis of the hip, spontaneous osteonecrosis of the knee and adult-type Freiberg's infraction. Subchondral fractures may ultimately lead to bone collapse, secondary osteonecrosis and severe articular damage, and there may be rapid progression of joint destruction over a period of weeks to months. It has been suggested that timely diagnosis might potentially improve the outcome and avoid the onset of destructive joint disease, making MRI even more important in this setting. The fracture line usually appears as a band of low signal intensity in the subchondral bone plate, adjacent to the articular surface, most often surrounded by bone marrow edema. In this article the authors review the most relevant imaging features of subchondral fractures in several joints, stressing the importance of early recognition for a better outcome.