Avascular necrosis of the hip: comparison of contrast-enhanced and nonenhanced MR imaging with histologic correlation. Work in progress

Subchondral insufficiency fractures, subchondral insufficiency fractures with osteonecrosis, and other apparently spontaneous subchondral bone lesions of the knee-pathogenesis and diagnosis at imaging

Subchondral insufficiency fractures (SIFs) and SIFs with osteonecrosis (SIF-ONs) of the knee (previously misnamed spontaneous osteonecrosis of the knee (SONK)) are bone lesions that appear without prior traumatic, tumoral, or inflammatory event.Both conditions are characterized in the early stages by epiphyseal bone marrow edema (BME)-like signal at MRI. However, while SIFs usually heal spontaneously, they can also evolve to osteonecrosis (i.e., SIF-ON), which may progress to an irreversible collapse of the articular surface. Careful analysis of other MRI signs may help differentiate the two conditions in the early phase. In SIFs, the BME edema-like signal extends to the area immediately adjacent to the subchondral plate, while in SIF-ONs, this subchondral area shows low signal intensity on fluid-sensitive MR images due to altered bone marrow. The thickness and length of subchondral areas with low fluid-sensitive signal intensity are important factors that determine the prognosis of SIF-ONs. If they are thicker than 4 mm or longer than 14 mm, the prognosis is poor. The differential diagnosis of SIFs and SIF-ONs include bone lesions associated with the "complex regional pain syndrome" (CRPS), epiphyseal osteonecrosis of systemic origin, and those related to cartilage pathology.Clinical relevance statement Imaging plays an essential role in diagnosing subchondral insufficiency fractures (SIFs) from subchondral insufficiency fractures with osteonecrosis (SIF-ONs) and collapse, as well as in distinguishing them from other spontaneous knee subchondral bone lesions presenting with bone marrow edema-like signal.Key points• Subchondral insufficiency fractures may affect the knee, especially in older adults.• Subchondral insufficiency fractures usually heal spontaneously.• Sometimes, subchondral osteonecrosis and collapse may complicate subchondral insufficiency fractures.• Bone marrow-like edema is an aspecific sign seen in all these lesions.• Degraded marrow in osteonecrosis complicating fractures is hypointense on fluid-sensitive sequences.

Predictors of Failure for Vascularized and Nonvascularized Bone Grafting of Scaphoid Nonunions: A Systematic Review

Objective This article compares predictors of failure for vascularized (VBG) and nonvascularized bone grafting (NVBG) of scaphoid nonunions.

Methods We conducted a systematic literature review of outcomes after VBG and NVBG of scaphoid nonunion. Fifty-one VBG studies (N = 1,419 patients) and 81 NVBG studies (N = 3,019 patients) met the inclusion criteria. Data were collected on surgical technique, type of fixation, time from injury to surgery, fracture location, abnormal carpal posture (humpback deformity and/or dorsal intercalated segmental instability [DISI]), radiographic parameters of carpal alignment, prior failed surgery, smoking status, and avascular necrosis (AVN) as defined by punctate bleeding, magnetic resonance imaging (MRI) with contrast, MRI without contrast, X-ray, and histology. Meta-analysis of proportions was conducted with Freeman–Tukey double arcsine transformation. Multilevel mixed-effects analyses were performed with univariable and multivariable Poisson regression to identify confounders and evaluate predictors of failure.

Results The pooled failure incidence effect size was comparable between VBG and NVBG (0.09 [95% confidence interval [CI] 0.05–0.13] and 0.08 [95% CI 0.06–0.11], respectively). Humpback deformity and/or DISI (incidence-rate radios [IRRs] 1.57, CI: 1.04–2.36) and lateral intrascaphoid angle (IRR 1.21, CI: 1.08–1.37) were significantly associated with an increased VBG failure incidence. Time from injury to surgery (IRR 1.09, CI: 1.06–1.12) and height-to-length (H/L) ratio (IRR 53.98, CI: 1.16–2,504.24) were significantly associated with an increased NVBG failure incidence, though H/L ratio demonstrated a wide CI. Decreased proximal fragment contrast uptake on MRI was a statistically significant predictor of increased failure incidence for both VBG (IRR 2.03 CI: 1.13–3.66) and NVBG (IRR 1.39, CI: 1.16–1.66). Punctate bleeding or radiographic AVN, scapholunate angle, radiolunate angle, and prior failed surgery were not associated with failure incidence for either bone graft type (p > 0.05).

Conclusion Humpback deformity and/or DISI and increasing lateral intrascaphoid angle may be predictors of VBG failure. Time from injury to surgery may be a predictor of NVBG failure. AVN as defined by decreased contrast uptake on MRI may be a marker of increased failure risk for both bone graft types.

Neuralgia-inducing cavitational osteonecrosis - A systematic review

OBJECTIVE

To assess the aetiologic factors, proposed diagnostic means and treatment strategies for neuralgia-inducing cavitational osteonecrosis.

METHODS

A search of the literature published up to June 2020 was conducted using Medline, the Cochrane Library, PsycINFO, CINAHL and Web of Science. The scientific quality of the evidence was rated according to NIH Quality Assessment Tools.

RESULTS

4,051 articles were found, 59 were reviewed in full text, and 29 studies were included. With the exception of hereditary coagulopathies, which were identified as potential risk factors in five studies, suggestions concerning the aetiology varied widely. No gold standard diagnostic mean could be identified. Treatment was most often performed by surgical curettage of the affected bone. Surgical treatment outcomes were equally varied: significant facial pain remission was reported in 66%-100% for periods varying between 2 months to 18 years, whereas no or little relief and recurrences were reported in up to ⅓ of cases. All studies were observational in their design. All investigations were rated as poor quality because of high risk of bias and non-transparent reporting.

CONCLUSIONS

Evidence concerning the aetiology, diagnosis and treatment of NICO is poor. Prospective diagnostic and therapeutic studies are needed before the usefulness of invasive therapeutic procedures can be evaluated.

Glossary of terms for musculoskeletal radiology

Members of the International Skeletal Society compiled a glossary of terms for musculoskeletal radiology. The authors also represent national radiology or pathology societies in Asia, Australia, Europe, and the USA. We provide brief descriptions of musculoskeletal structures, disease processes, and syndromes and address their imaging features. Given the abundance of musculoskeletal disorders and derangements, we chose to omit most terms relating to neoplasm, spine, intervention, and pediatrics. Consensus agreement was obtained from 19 musculoskeletal radiology societies worldwide.

S3-Guideline non-traumatic adult femoral head necrosis

INTRODUCTION

The treatment of adult non-traumatic avascular necrosis of the femoral head (AVN; N-ANFH) within an estimated incidence of 5000-7000 cases per annum in Germany remains a challenge. Risk factors include steroids, alcohol abuse, chemotherapy and immunosuppressive medication, but a genetic predisposition has been suggested. Early diagnosis of this often bilateral disease process is essential for successful conservative or joint preserving surgical management. In this review, we present the update German consensus S3 guideline "diagnosis and management for N-ANFH" as a concise summary.

MATERIALS AND METHODS

This systematic review is based on the published literature from January 1, 1970 to April 31, 2013 (German and English language). Inclusion criteria were systematic reviews, meta-analyses and relevant peer review publications. We identified a total of 3715 related publications, of which 422 were suitable according to the SIGN criteria, but only 159 fulfilled our inclusion criteria.

RESULTS AND CONCLUSIONS

Clinical suspicion of N-ANFH mandates radiographic evaluation. If radiographs are normal MRI scans are recommended, which should be evaluated according to the ARCO-classification. Differential diagnoses include transient osteoporosis, bone bruise, insufficiency fracture and destructive arthropathy. Untreated, subchondral fractures commonly occur within 2 years, during which the risk for contralateral involvement is high-thereafter unlikely. Conservative management with Ilomedin and Alendronat can be tried, but other pharmacological or physical treatments are inappropriate. No specific joint preserving procedure can be recommended, but core decompression should be considered in early stages if necrosis is <30 %. In ARCO stages IIIc or IV total hip arthroplasty (THA) should be contemplated, which offers similar outcome compared to osteoarthritis. Young age is the main risk factor for higher revision rates after THA for N-ANFH.

MR imaging of children and young adults with classic findings of osteonecrosis on unenhanced MR images: do contrast-enhanced sequences help?

BACKGROUND

The added value of routine contrast-enhanced MR imaging in children with classic findings of osteonecrosis on unenhanced MR images has not been determined.

OBJECTIVE

Our purpose was to determine the added value of routine contrast-enhanced MR sequences for identifying complications of osteonecrosis.

MATERIAL AND METHODS

Sixty-four patients who underwent 139 contrast-enhanced MR examinations were retrospectively identified. Unenhanced images and subsequently both unenhanced and enhanced images were reviewed in consensus. The location of osteonecrosis and the presence of complicating features (epiphyseal collapse, marrow edema, joint effusion, soft tissue edema) were recorded. Cohen's kappa coefficients (κ) were calculated to assess agreement.

RESULTS

A diagnosis of classic osteonecrosis was made in 22.3% of unenhanced examinations and 28.1% of enhanced examinations (κ = 0.734, P < 0.001). Among patients with complicated osteonecrosis, unenhanced images interpreted without and with contrast-enhanced images showed epiphyseal collapse in 51.2% and 42.5% (κ = 0.796, P < 0.001), marrow edema in 50.4% and 46.8% (κ = 0.727, P < 0.001), joint effusion in 44.9% and 51.2% (κ = 0.686, P < 0.001), and soft tissue edema in 12.2% and 10.1% (κ = 0.674, P < 0.001).

CONCLUSION

The high observed agreement between the unenhanced MR images interpreted without and with contrast-enhanced images shows little marginal benefit from the use of routine contrast-enhanced imaging in children and young adults with classic findings of osteonecrosis on unenhanced MR images.

The role of magnetic resonance imaging in scaphoid fractures

Fractures of the scaphoid are the most common surgically treated carpal fracture, and early diagnosis is critical to minimize complications including osteonecrosis. If the initial radiographs after the injury are inconclusive, early magnetic resonance imaging (MRI) provides an immediate diagnosis to allow for proper management. This has been shown to be cost effective both in direct measureable costs and likely in difficult-to-measure indirect costs related to lost productivity. In the cases in which no scaphoid fracture is present, MRI provides alternate diagnoses such as identification of other fractures (eg, other carpals and distal radius), osseous contusions, and soft tissue injuries (preferably ≥ 1.5T). When MRI is contraindicated, computed tomography (CT) is a reasonable alternative after the initial and repeat negative radiographs. MRI is the best imaging modality for assessing osteonecrosis of the proximal pole in a scaphoid nonunion. Unfortunately, the most useful imaging sequences remain controversial. My institution relies on the noncontrast T1-weighted images for the primary diagnosis of osteonecrosis with dynamic contrast enhancement used in a supplemental fashion.

Is dynamic contrast-enhanced MRI useful for assessing proximal fragment vascularity in scaphoid fracture delayed and non-union?

OBJECTIVE

To assess dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) as a measure of vascularity in scaphoid delayed-union or non-union.

MATERIALS AND METHODS

Thirty-five patients (34 male, one female; mean age, 27.4 ± 9.4 years; range, 16-51 years) with scaphoid delayed-union and non-union who underwent DCE MRI of the scaphoid between September 2002 and October 2012 were retrospectively reviewed. Proximal fragment vascularity was classified as good, fair, or poor on unenhanced MRI, contrast-enhanced MRI, and DCE MRI. For DCE MRI, enhancement slope, Eslope comparison of proximal and distal fragments was used to classify the proximal fragment as good, fair, or poor vascularity. Proximal fragment vascularity was similarly graded at surgery in all patients. Paired t test and McNemar test were used for data comparison. Kappa value was used to assess level of agreement between MRI findings and surgical findings.

RESULTS

Twenty-five (71 %) of 35 patients had good vascularity, four (11 %) had fair vascularity, and six (17 %) had poor vascularity of the proximal scaphoid fragment at surgery. DCE MRI parameters had the highest correlation with surgical findings (kappa = 0.57). Proximal scaphoid fragments with surgical poor vascularity had a significantly lower Emax and Eslope than those with good vascularity (p = 0.0043 and 0.027). The sensitivity, specificity, positive and negative predictive value and accuracy of DCE MRI in predicting impaired vascularity was 67, 86, 67, 86, and 80 %, respectively, which was better than that seen with unenhanced and post-contrast MRI. Flattened time intensity curves in both proximal and distal fragments were a feature of protracted non-union with a mean time interval of 101.6 ± 95.5 months between injury and MRI.

CONCLUSIONS

DCE MRI has a higher diagnostic accuracy than either non-enhanced MRI or contrast enhanced MRI for assessing proximal fragment vascularity in scaphoid delayed-union and non-union. For proper interpretation of contrast-enhanced studies in scaphoid vascularity, one needs to incorporate the time frame between injury and MRI.

Differentiation, diagnosis, and treatment of osteoarthritis, osteonecrosis, and rapidly progressive osteoarthritis

Osteoarthritis, osteonecrosis, and rapidly progressive osteoarthritis are hip arthropathies that result in marked pain and disability. Although these diseases share features of arthritis-like symptoms and are all treated with total hip arthroplasty, they are separate diseases with distinct epidemiologic, radiographic, and histopathologic findings. In this article, the authors present clinical tips and techniques that will aid the surgeon in diagnosing and treating these different entities.

[The role of imaging in the assessment of vascularity at hand and wrist]

The viability of the bone is compromised in two main situations at the wrist: Kienböck's disease and scaphoid nonunion with avascular necrosis. Plain radiography and CT allow an accurate anatomical approach of morphological changes associated with avascular necrosis of the lunate and the scaphoid fracture with complications. CT is readily available to detect nondisplaced fractures. However, early forms of necrosis can be misdiagnosed and evaluation of bone vitality is impossible. MRI is the best imaging modality to detect avascular necrosis and the intravenous injection of gadolinium improves the specificity of diagnosis of necrosis. The lack of enhancement of the proximal fragment of the scaphoid leads the surgeon to use a vascular graft in the treatment of nonunion. The technique has its limitations. The bone necrosis is histologically complex and contrast enhancement does not mean necessarily viability. However, MRI is still the most powerful imaging modality in the assessment of the bone marrow.

Assessment of scaphoid viability with MRI: a reassessment of findings on unenhanced MR images

OBJECTIVE

The purpose of this article is to evaluate the accuracy of unenhanced T1-weighted MR images in predicting the vascular status of the proximal pole of the scaphoid in patients with chronic scaphoid fracture nonunions.

MATERIALS AND METHODS

A database search identified 29 patients with chronic scaphoid nonunions who underwent a preoperative MRI examination and intraoperative assessment of scaphoid viability from 2004 to 2009. T1-weighted MR images were evaluated by two musculoskeletal radiologists. If the proximal pole demonstrated diffusely decreased T1-weighted signal (less than or equal to that of skeletal muscle), the patient was placed in a moderate-to-high risk for avascular necrosis (AVN) category. Otherwise, the patient was placed in a viable-to-low risk for AVN category. Scaphoid viability or necrosis was diagnosed intraoperatively depending on whether punctate bleeding was present. After the patients were classified according to the T1-weighted appearance, the appearance on STIR images was recorded.

RESULTS

There were 29 patients (25 male) with a mean age of 21 years. When we compared the MRI results, using only the T1-weighted images, with the surgical findings, unenhanced MRI had a sensitivity, specificity, and accuracy of 55%, 94%, and 79%, respectively, for diagnosing AVN. Increased proximal pole STIR signal was noted with similar frequencies in patients with and without AVN.

CONCLUSION

T1-weighted unenhanced MRI is an acceptable alternative to delayed contrast-enhanced MRI in the preoperative assessment of the vascular status of the proximal pole of the scaphoid in patients with chronic fracture nonunions. STIR images were not beneficial in determining proximal pole viability.

Avascular necrosis (AVN) of the proximal fragment in scaphoid nonunion: is intravenous contrast agent necessary in MRI?

PURPOSE

The purpose of this prospective study is to assess the diagnostic value of intravenously applied contrast agent for diagnosing osteonecrosis of the proximal fragment in scaphoid nonunion, and to compare the imaging results with intraoperative findings.

MATERIALS AND METHODS

In 88 patients (7 women, 81 men) suffering from symptomatic scaphoid nonunion, preoperative MRI was performed (coronal PD-w FSE fs, sagittal-oblique T1-w SE nonenhanced and T1-w SE fs contrast-enhanced, sagittal T2*-w GRE). MRI interpretation was based on the intensity of contrast enhancement: 0 = none, 1 = focal, 2 = diffuse. Intraoperatively, the osseous viability was scored by means of bleeding points on the osteotomy site of the proximal scaphoid fragment: 0=absent, 1 = moderate, 2 = good.

RESULTS

Intraoperatively, 17 necrotic, 29 compromised, and 42 normal proximal fragments were found. In nonenhanced MRI, bone viability was judged necrotic in 1 patient, compromised in 20 patients, and unaffected in 67 patients. Contrast-enhanced MRI revealed 14 necrotic, 21 compromised, and 53 normal proximal fragments. Judging surgical findings as the standard of reference, statistical analysis for nonenhanced MRI was: sensitivity 6.3%, specificity 100%, positive PV 100%, negative PV 82.6%, and accuracy 82.9%; statistics for contrast-enhanced MRI was: sensitivity 76.5%, specificity 98.6%, positive PV 92.9%, negative PV 94.6%, and accuracy 94.3%. Sensitivity for detecting avascular proximal fragments was significantly better (p<0.001) in contrast-enhanced MRI in comparison to nonenhanced MRI.

CONCLUSION

Viability of the proximal fragment in scaphoid nonunion can be significantly better assessed with the use of contrast-enhanced MRI as compared to nonenhanced MRI. Bone marrow edema is an inferior indicator of osteonecrosis. Application of intravenous gadolinium is recommended for imaging scaphoid nonunion.

MRI evaluation of collapsed femoral heads in patients 60 years old or older: Differentiation of subchondral insufficiency fracture from osteonecrosis of the femoral head

OBJECTIVE

The purpose of this article is to verify the hypothesis that osteonecrosis and subchondral insufficiency fracture of the femoral head can be differentiated on the basis of their appearance on MRI.

SUBJECTS AND METHODS

Between May 1998 and February 2009, we reviewed 30 consecutive hips in 30 patients, 60 years old or older at the time of onset of hip pain, with radiologic evidence of subchondral collapse of the femoral head and with both MR images and histologic results available. Both clinical and radiologic appearances were investigated. The patients were divided into two groups according to the shape of low-intensity bands on T1-weighted images. The first group showed concavity of the articular surface, which is characteristic of osteonecrosis, and the second group showed an irregular convexity of the articular surface, which is characteristic of subchondral insufficiency fracture.

RESULTS

Sixteen hips (53.3%) showed evidence of osteonecrosis, and 14 (46.7%) showed evidence of subchondral insufficiency fracture, which was consistent with the corresponding histopathologic diagnoses. In all cases of osteonecrosis, the patient had a history of either corticosteroid intake or alcohol abuse. Among patients with subchondral insufficiency fracture, the proportion of women was significantly higher than that among patients with osteonecrosis. A crescent sign (subchondral fracture) was present radiographically in about half of all cases in both groups.

CONCLUSION

The results of the present study suggest that the shape of the low-intensity band on MRI is useful for the differentiating subchondral insufficiency fracture from osteonecrosis. In addition, among osteoporotic elderly women without any history of corticosteroid intake or alcohol abuse, a diagnosis of subchondral insufficiency fracture should be considered.

Contrast-enhanced MR imaging of subchondral insufficiency fracture of the femoral head: a preliminary comparison with that of osteonecrosis of the femoral head

INTRODUCTION

Subchondral insufficiency fracture of the femoral head (SIF) may be confused with osteonecrosis of the femoral head (ON) due to clinical and imaging similarities.

MATERIALS AND METHODS

Contrast-enhanced MR images in patients with SIF (ten hips in ten patients) were retrospectively reviewed and compared with those from patients with ON (ten hips in six patients).

RESULTS

Low-signal intensity bands on T1-weighted images were present within the femoral head in all hips examined. The segment proximal to the band was contrast-enhanced following IV gadolinium administration in nine of ten hips (90%) with SIF and in none of the 10 hips with ON.

CONCLUSION

These results suggest that the presence of contrast enhancement in the segment proximal to the low-signal intensity band in the femoral head may serve as a supplemental diagnostic measure for the differentiation of SIF from ON.

Bone marrow edema of the femoral head and transient osteoporosis of the hip

The current article of this issue aims at defining the generic term of bone marrow edema of the femoral head as seen at MR imaging. It must be kept in mind that this syndrome should be regarded, not as a specific diagnosis, but rather as a sign of an ongoing abnormal process that involves the femoral head and/or the hip joint. We aim at emphasizing the role of the radiologists in making a specific diagnosis, starting from a non-specific finding on T1-weighted images and by focusing on ancillary findings on T2-weighted SE or fat-saturated proton-density weighted MR images.

The relationship between osteonecrosis of the proximal femur identified by MRI and lesions proven by histological examination

Total hip replacement in patients with advanced osteonecrosis of the femoral head is often complicated by early loosening of the femoral component. Recent evidence has suggested that abnormal bone extending into the proximal femur may be responsible for the early failure of the femoral component. We aimed to identify which patients were at high risk of early failure by evaluating gadolinium-enhanced MR images of histologically-confirmed osteonecrotic lesions beyond the femoral head.

Although the MR signal intensity has been shown to correlate well with osteonecrosis in the femoral head, it was found to be relatively insensitive at identifying lesions below the head, with a sensitivity of only 51% and a predictive value of a negative result of only 48%. However, the specificity was 90%, with the predictive value of a positive MRI finding being 86%. Only those patients with osteonecrosis of the femoral head secondary to sickle-cell disease, who are known to be at high risk of early loosening, had changes in the MR signal in the greater trochanter and the femoral shaft. This observation suggests that changes in the MR signal beyond the femoral head may represent osteonecrotic lesions in areas essential for the fixation of the femoral component. Pre-operative identification of such lesions in the neck of the femur may be important when considering hip resurfacing for osteonecrosis of the femoral head, following which early loosening of the femoral component and fracture of the neck are possible complications.

Preprocedural MR imaging for percutaneous vertebroplasty: special interest in contrast enhancement

PURPOSE

The success of percutaneous vertebroplasty (PVP) depends greatly on preprocedural evaluation of the patients. The purpose of this study was to evaluate the efficacy of preprocedural magnetic resonance imaging (MRI) for the indications of PVP.

MATERIALS AND METHODS

A retrospective review of 122 osteoporotic compression fractures in 63 patients who underwent preprocedural gadolinium-enhanced MRI and PVP was performed. Based on the extent of contrast enhancement on preprocedural MRI, each case was classified into one of two groups: group 1, which represented more than 50% of the vertebral body enhanced; and group 2, which represented less than 50% of the vertebral body enhanced. The most enhancing level was evaluated in multilevel PVP sessions. We evaluated the difference of pre- and postprocedural pain scales between groups 1 and 2 using Mann-Whitney's U-test.

RESULTS

There was a trend toward higher preoperative pain score in group 1, but it was not statistically significant (P = 0.0537). In addition, the postoperative pain score in group 2 was significantly higher than that in group 1 (P = 0.0007). The difference between the pre- and postoperative pain scores was significantly higher in group 1 than in group 2 (P = 0.0001).

CONCLUSION

Contrast enhancement on MRI indicates a painful lesion and extensive contrast enhancement predicts better pain relief after PVP.

Osteonecrosis of the femoral head: etiology, imaging and treatment

Osteonecrosis of the femoral head is a disabling clinical entity affecting young adults that usually leads to destruction of the hip joint. A high index of suspicion is necessary for the diagnosis due to the insidious onset of the bone infarcts and the lack of specific clinical signs at the early stages. Many etiology-associated factors have been identified reducing thus the number of idiopathic cases. A number of joint salvaging treatment options are available if early diagnosis can be achieved. MR imaging has been proved to be a highly accurate method both for early diagnosis and for staging of the disease. Replacement of the hip joint is the last resort for pain relief and function, although non-desirable because of the young age of the affected population.

Perthes' disease in the very young child

We report two cases of very young children who presented with irritable hips and in whom magnetic resonance imaging with gadolinium-enhancement revealed ischaemic changes affecting the capital ossific nucleus. Radiological changes consistent with Perthes' disease subsequently appeared. In the published literature Perthes' disease has been reported in children as young as 24 months. Gadolinium-enhanced magnetic resonance imaging has revealed Perthes' disease in younger children which can predate the appearance of radiographic changes by up to 3 months.

MR imaging of epiphyseal lesions of the knee: current concepts, challenges, and controversies

This article focuses on spontaneous painful conditions involving the subchondral bone and marrow of mature knee epiphyses. MR imaging is the technique of choice for the work-up of these lesions and enables distinction of two main categories of lesions on the basis of T1-weighted images: avascular necrosis, and lesions presenting the bone marrow edema pattern. This latter category encompasses spontaneous osteonecrosis of the knee, and a variety of self-resolving conditions that may be differentiated by the study of the subchondral bone marrow area on T2-weighted images. Behind definite appellation of lesions, the challenge for the radiologist is to provide a prognosis: the distinction between self-resolving lesions from those that may evolve to epiphyseal collapse and joint impairment should be possible in most cases.

MRI of osteonecrosis

Osteonecrosis is a relatively common condition, which may be idiopathic or secondary to a variety of clinical situations. It may involve the subarticular region of a joint, when it is commonly referred to as ischaemic necrosis, or the metaphyseal regions of long bones, when it is referred to as bone infarction. In both situations, early lesions may be radiographically occult. However, magnetic resonance imaging (MRI) is very sensitive in identifying and characterizing osteonecrosis. This review illustrates the varied MRI features of osteonecrosis that enable a confident diagnosis to be made. Complications and differential diagnosis are also considered.

Valeur de l’IRM dans l’évaluation du potentiel de guérison des pseudarthroses du scaphoïde traitées par greffe osseuse

PURPOSE

To determine the accuracy of MR imaging in predicting bone graft healing in patients with scaphoid non-union.

MATERIAL AND METHODS

21 patients with scaphoid non-union were examined with MR imaging prior to bone grafting (conventional bone graft in 14 cases and vascularized bone graft in 7 cases). The protocol included unenhanced and Gadolinium-enhanced sequences. Signal intensity and homogeneity of the proximal fragment was analysed by two independent radiologists. MRI findings were then correlated to the postoperative rate of union.

RESULTS

Healing occurred in 17 cases and failed in 4 cases with a mean follow up of 14 months. Intraobserver agreement in MR reading was respectively 0.92 et 0.86. Interobserver agreement was 0.88. On Tl-wi, the proximal fragment was hyperintense in 1 case (with positive surgical result), heterogeneous low signal intensity in 7 cases (healing in n = 7) and homogeneous low signal intensity in 13 cases (healing in n = 9). On T2-wi, the proximal fragment was hypointense in 4 cases (healing in n = 3), homogeneous high signal in 5 cases (healing in n = 4) and heterogeneous high signal intensity in 12 cases (healing in n = 10). After Gadolinium injection, enhancement was homogeneous in 4 cases (healing in n = 4), heterogeneous in 8 cases (healing in n = 7) and absent in 9 cases (healing in n = 6). In the group with no enhancement, 5 patients were treated with vascularized bone graft (healing in n = 4) and 4 with conventional bone graft (healing in n = 2).

CONCLUSION

The absence of enhancement of the proximal scaphoid fragment leads to poor surgical results except for vascularized bone graft.

Skeletal scintigraphy in the multimodality assessment of young children with acute skeletal symptoms

The authors review the scintigraphic manifestations of acute osteomyelitis, septic arthritis, transient synovitis, Legg-Calvé-Perthes disease, fractures of toddlers, and some systemic conditions that cause skeletal symptoms during childhood. They offer suggestions regarding incorporation of skeletal scintigraphy into a multimodality approach for assessing children with skeletal symptoms.

Measurement of lesion area and volume by three-dimensional spoiled gradient-echo MR imaging in osteonecrosis of the femoral head

The purpose of this investigation is to evaluate the diagnostic ability of three-dimensional spoiled gradient-echo (3D SPGR) magnetic resonance (MR) imaging in cases of osteonecrosis of the femoral head (ONFH), and to determine the accuracy of 3D SPGR imaging in area and volume measurement of ONFH. T1-weighted spin-echo (SE) and 3D SPGR imaging were performed on 20 femoral heads obtained from patients with ONFH. After MR imaging, the femoral heads were cut parallel to the imaging plane and were evaluated histologically. Areas and volumes of necrotic lesions were measured with a computer program and the deviation between MR images and anatomical measurements was evaluated. A low signal intensity band on 3D SPGR MR images was observed in all femoral heads and corresponded histologically to repaired marrow with viable fibrous mesenchymal tissue. The area proximate to the low band area coincided with the necrotic region. Both area and volume measurements by T1-weighted SE and 3D SPGR images showed a strong correlation to histological measurements. The discrepancies between histological and imaging results were minimal in 3D SPGR imaging, especially at the anterior and posterior portions of the femoral head. Three-dimensional SPGR imaging provides more accurate measurements of the area and volume of a necrotic lesion than T1-weighted SE imaging.

Pathogenesis and natural history of osteonecrosis

BACKGROUND AND OBJECTIVES

Osteonecrosis (avascular necrosis) is a relatively common disorder seen by both rheumatologists and orthopedic surgeons. The vast majority of cases are secondary to trauma. However, for non-traumatic cases, there often remains a diagnostic challenge in defining the cause of bone death. The goal of this article is to review data extensively in the medical literature with respect to the pathogenesis of osteonecrosis, its natural history, and treatment.

METHODS

A review of 524 studies on osteonecrosis was performed, of which 213 were selected and cited.

RESULTS

Non-traumatic osteonecrosis has been associated with corticosteroid usage, alcoholism, infections, hyperbaric events, storage disorders, marrow infiltrating diseases, coagulation defects, and some autoimmune diseases. However, a large number of idiopathic cases of osteonecrosis have been described without an obvious etiologic factor. Although corticosteroids can produce osteonecrosis, careful history is always warranted to identify other risk factors. The pathogenesis of non-traumatic osteonecrosis appears to involve vascular compromise, bone and cell death, or defective bone repair as the primary event. Our understanding of the pathogenesis of osteonecrosis is now much better defined and skeletal scintigraphy and magnetic resonance imaging have enhanced diagnosis greatly. Early detection is important because the prognosis depends on the stage and location of the lesion, although the treatment of femoral head osteonecrosis remains primarily a surgical one.

CONCLUSIONS

Osteonecrosis has been associated with a wide range of conditions. Many theories have been proposed to decipher the mechanism behind the development of osteonecrosis but none have been proven. Because osteonecrosis may affect patients with a variety of risk factors, it is important that caregivers have a heightened index of suspicion. Early detection may affect prognosis because prognosis is dependent on the stage and location of the disease. In particular, the disease should be suspected in patients with a history of steroid usage, especially in conjunction with other illnesses that predispose the patient to osteonecrosis.

RELEVANCE

A better understanding of the pathophysiology, diagnosis and treatment of osteonecrosis will help the physician determine which patients are at risk for osteonecrosis, facilitating early diagnosis and better treatment options.

Subchondral insufficiency fracture of the femoral head: magnetic resonance imaging findings correlated with micro-computed tomography and histopathology

We described magnetic resonance (MR) imaging findings of subchondral insufficiency fracture of the femoral head without collapse in which micro-computed tomography (CT) and histopathologic studies were performed. Magnetic resonance imaging showed a subchondral low-signal intensity band, which corresponded to the fracture callus. Diffuse bone marrow edema with contrast enhancement effect was seen in both the proximal and distal segments of the low-signal intensity band. These features are distinct from those of avascular necrosis.

Histological findings of bone marrow edema pattern on MRI in osteonecrosis of the femoral head

Sequential magnetic resonance imaging (MRI) was performed on a 38-year-old woman with systemic lupus erythematosus who had received corticosteroid and had developed non-traumatic osteonecrosis of the femoral head. The initial MR finding was a band lesion on the T1-weighted image, which had been present before the onset of symptoms. At the onset of symptoms, a diffuse bone marrow edema pattern, with a low signal intensity on T1 and high signal intensity on T2-weighted images, was noted around the band lesion, extending to the femoral neck. Histopathologically, this region was found to consist of serous exudate, focal interstitial hemorrhage, and mild fibrosis, without any evidence of extension of osteonecrosis. It should be noted that extension of a low signal intensity area on MRI after the onset of hip pain may not be the result of the extension of osteonecrosis, but may represent concomitant edema due to collapse.

Serial magnetic resonance imaging in a non-traumatic rabbit osteonecrosis model: an experimental longitudinal study

We investigated the time-dependent natural course of experimental osteonecrosis (ON), including initial changes in ON and the reparative process, using in vivo serial repetitive magnetic resonance imaging (MRI) in a non-traumatic rabbit serum sickness ON model. Some necrotic lesions were detected at 1 week (3 of 16 femora with necrotic lesions) and some in the metaphysis were detected by 12 weeks (2 of 6 femora with lesions) on T(1)-weighted, T(2)-weighted, and fat suppression T(1)-weighted images. On contrast-enhanced MRI, extravasation of the erythrocytes was detected at 72 h (7 of 26 femora with lesions) as a small, focal enhanced area. Necrotic lesions were detected in all abnormal femora by 6 weeks (16 of 16 femora with lesions) as focal, homogeneously or inhomogeneously enhanced areas. Reparative tissue replaced with new vascular and trabecular formation in necrotic areas was detected as an extended marginal enhanced area at 12 weeks. These results suggest that the enhancement patterns on contrast-enhanced MRI may provide helpful information about the developmental and reparative process of clinical ON.

Nontraumatic osteonecrosis: MR perfusion imaging evaluation in an experimental model

RATIONALE AND OBJECTIVES

Because the nature and time course of changes in early, nontraumatic osteonecrosis at perfusion and magnetic resonance (MR) imaging are unknown, the authors evaluated this technique in the assessment of early osteonecrosis with a nontraumatic model.

MATERIALS AND METHODS

Five rabbits underwent intravenous injection of lipopolysaccharide endotoxin followed by intramuscular injection of methylprednisolone. MR imaging of the femora was performed before and at weekly intervals after endotoxin injection. Histologic findings from the areas of osteonecrosis were correlated with the findings of MR imaging and MR perfusion studies.

RESULTS

Histologic evaluation showed osteonecrosis in six femora of four animals 2-4 weeks after endotoxin injection. Findings on T1-weighted images of the femur were normal in all animals; T2-weighted images of one femur showed equivocal changes. On MR perfusion images, the baseline mean peak percentage of enhancement was 52.7% +/- 12.6. In the six areas without osteonecrosis, the mean percentage of enhancement was similar to the baseline percentage of enhancement at 1 week (62.2% +/- 31.2). In the four areas with diffuse osteonecrosis, there was essentially no contrast enhancement 1-4 weeks after endotoxin injection.

CONCLUSION

T1- and T2-weighted MR imaging is insensitive to the presence of early nontraumatic osteonecrosis. MR perfusion imaging might be useful to detect early nontraumatic osteonecrosis.

Usefulness of gadolinium-enhanced MR imaging in the evaluation of the vascularity of scaphoid nonunions

OBJECTIVE

The objective of this article is to identify the role of gadolinium-enhanced MR imaging in the preoperative evaluation of the vascular status of the proximal fragment in scaphoid nonunions.

SUBJECTS AND METHODS

Thirty consecutive patients (27 men and three women; age range, 19-52 years; mean age, 28 years) with nonunion of the scaphoid were prospectively examined with unenhanced and gadolinium-enhanced MR imaging. MR images and surgical findings were classified in four groups according to the vascular status of the proximal fragment (normal bone, moderate ischemic bone, severe ischemic bone, and avascular necrosis). Sensitivity, specificity, and accuracy of unenhanced and gadolinium-enhanced MR studies were calculated. Surgical findings were used as the gold standard. The postoperative rate of union at 12 months was evaluated for each group.

RESULTS

Unenhanced MR imaging showed a global sensitivity of 36%, specificity of 78%, and accuracy of 68% in the preoperative evaluation of the vascular status of the proximal fragment. Correlation with the surgical findings was not statistically significant (p < 0.149). Global sensitivity, specificity, and accuracy of gadolinium-enhanced MR imaging were 66%, 88%, and 83%, respectively. Correlation with the surgical findings was good (p < 0.0001). Gadolinium-enhanced sequences allowed accurate diagnosis and enabled the creation of prognostic groups having better correlation with surgical findings and postoperative results.

CONCLUSION

Gadolinium-enhanced MR imaging is the most reliable imaging method for investigating the vascularity of the proximal pole in scaphoid nonunions.

Contrast-enhanced magnetic resonance imaging in a nontraumatic rabbit osteonecrosis model

We investigated early osteonecrosis using in vivo magnetic resonance imaging in a nontraumatic rabbit model of serum-sickness osteonecrosis in which osteonecrosis was induced after two intravenous injections of horse serum with a 3-week interval. One week (group A, 17 rabbits) and 3 weeks (group B, 13 rabbits) after the second serum injection, coronal magnetic resonance images of the femur were obtained and it was removed for histological study. Some of the necrotic lesions in the diaphysis were detected on T1-weighted, T2-weighted, or fat-suppression T1-weighted images (six of 24 necrotic lesions in group A and 16 of 18 in group B), and all of the necrotic lesions in the epiphysis, metaphysis, and diaphysis were detected on T1-weighted or fat-suppression T1-weighted images enhanced with gadolinium-diethylene triamine pentaacetic acid. All focal homogeneous enhanced areas on T1-weighted or fat suppression T1-weighted images corresponded to necrotic lesions (22 of 24 necrotic lesions in group A and 18 of 18 in group B); the contours of the enhanced areas were displayed more clearly on the fat-suppression T1-weighted than on the T1-weighted images. The fat-suppression T1-weighted image enhanced with gadolinium-diethylene triamine pentaacetic acid was thus the most sensitive and specific of five kinds of magnetic resonance images for the detection of early necrotic lesions. The results suggest that this image may be useful for early diagnosis of clinical osteonecrosis and for obtaining information about the pathomechanism of osteonecrosis.

Emergency MR imaging of orthopedic trauma. Current and future directions

Fast MR imaging protocols pave the way for more widespread use of MR imaging to evaluate emergency room trauma patients. This article reviews technical developments and protocols facilitating rapid imaging, conventional applications of MR imaging to evaluate soft tissue injuries, and newer applications in which MR imaging is used to image both axial and appendicular fractures.

Idiopathic bone marrow edema lesions of the femoral head: predictive value of MR imaging findings

PURPOSE

To determine the frequency of several subchondral magnetic resonance (MR) imaging features observed in bone marrow edema lesions of the femoral head and to determine their value for differentiation of irreversible from transient lesions.

MATERIALS AND METHODS

The authors reviewed MR images of 72 femoral head lesions in 42 men and 25 women (median age, 48 years) with equivocal radiographic findings and bone marrow edema seen at MR imaging (T1- and T2-weighted images in all patients and contrast material-enhanced T1-weighted images in 39 patients). Follow-up MR images showed 57 lesions to be transient and 15 to be irreversible. The presence and size of subtle subchondral features observed on initial MR images were compared for both types of lesion.

RESULTS

Lack of any additional subchondral change on T2-weighted or contrast-enhanced T1-weighted images had 100% positive predictive value for transient lesions. For irreversible lesions, presence of a subchondral area of low signal intensity at least 4 mm thick or 12.5 mm long had positive predictive values of 85% and 73%, respectively, on T2-weighted images and 87% and 86%, respectively, on contrast-enhanced T1-weighted images.

CONCLUSION

Careful assessment of subchondral changes enables confident differentiation between early irreversible lesions and transient bone marrow edema lesions.

Imaging of elbow disorders

Numerous modalities are available for imaging the elbow. Radiographs should be the first imaging procedure performed for evaluation of an elbow abnormality. The use of advanced imaging modalities such as MR imaging, CT, and sonography also is discussed in this article.

The role of CT and MR in imaging the complications of sickle cell disease

Sickle cell disease is the most common inherited haemoglobinopathy described. Complications of sickle cell disease (SCD) are due to chronic haemolysis of fragile red cells or secondary to vascular occlusion by sickled red cells with subsequent tissue infarction. Traditionally plain film radiography has been the mainstay in the assessment of patients with SCD, but increasingly magnetic resonance (MR) imaging and computed tomography (CT) are being used. In this review the imaging features of a range of complications of SCD are demonstrated with particular emphasis on CT and MR.

Current concepts in imaging of the pelvis and hip

Over the past decade, imaging evaluation of orthopedic conditions of the pelvis and hips has become increasingly complex. Although the conventional radiograph remains the initial examination of choice, the decision between secondary tests, such as computed tomography, MR imaging, or scintigraphy is far from clear. A thorough understanding of current imaging technology is necessary for the clinician to choose the most appropriate examination for a given situation. This article reviews the current status of orthopedic imaging in the areas of acute trauma, stress injuries, osteonecrosis, arthropathies, tumors, and interventional imaging.

Avascular necrosis of bone following an intensified chemotherapy regimen including high dose steroids

We report the imaging findings and natural history of avascular necrosis of bone (AVN) that developed following a chemotherapy regimen including high dose steroid treatment. All patients had acute lymphoblastic (ALL) or non-Hodgkin's lymphoma (NHL). Symptoms followed the high dose steroid therapy and 28 joints in eight patients were involved, (11 knees, seven hips, five shoulders and five ankles). Plain radiographs at presentation were normal in most joints, whilst bone scintigraphy and magnetic resonance imaging (MRI) were positive. We believe that the development of AVN in these patients is most likely due to the high dose dexamethasone therapy as in all eight cases symptoms followed this stage of the regimen. Patients experiencing bone or joint pains while receiving high dose steroids as part of a chemotherapy regimen could be investigated by bone scintigraphy but MRI is preferable as it is more sensitive and specific for AVN. In this series of patients multiple joints were involved and all the male patients proceeded rapidly from bone infarction to joint collapse. If the MRI appearances are typical, an early diagnosis of AVN can be made enabling therapeutic interventions to prevent joint collapse and its associated morbidity.

Vascularized pedicle bone-grafting for nontraumatic avascular necrosis of the femoral head. A 5- to 11-year follow-up

We investigated the results of 31 hips in 26 patients with nontraumatic (n = 20) and steroid-induced (n = 6) avascular necrosis of the femoral head (ANFH) treated with vascularized iliac pedicle bone graft (PBG). The average age at operation was 38.3 years. Three were women and 23 men. The average follow-up was 8.0 years. The Harris hip score prior to operation and at latest follow-up improved from 62 to 83; one hip collapsed and was revised with a bipolar endoprosthesis. At the final follow-up, 19 hips (63%) were clinically rated as good to excellent, 4 fair, and 7 poor. At the final follow-up, 15 of 27 hips (56%) of stage II before operation showed progressive collapse after bone grafting. In steroid-induced ANFH, in three women, 2 of 4 hips showed poor results. These results are only slightly better than those of core decompression and no better than those obtained after decompression and simple nonvascularized grafts to provide support for the subchondral bone. We concluded that vascularized PBG is sometimes indicated for ANFH in an early stage before collapse of the femoral head.

Optimizing joint imaging: MR imaging techniques

For optimizing MR imaging of the joints, a sophisticated knowledge of MR system hard- and software conditions and coil technologies, sequence and contrast preparation techniques, and the use of paramagnetic contrast agents is necessary. This review article discusses the basic principles of the appropriate use of surface coils as well as the different conventional and fast imaging sequences, including three-dimensional (3D) MR imaging. In addition, the applications of contrast agents as well as the most important contrast preparation techniques are reviewed.

Magnetic resonance imaging of the musculoskeletal system. II. The hip

Magnetic resonance (MR) imaging of the hip joint and adjacent structures can provide valuable information under many clinical circumstances. After plain radiography, MR imaging is arguably the modality of choice for the detection of osteonecrosis, occult fractures, primary and secondary neoplasms, and in the assessment of some soft tissue abnormalities. The accuracy of MR imaging is dependent on technical factors, such as magnet field strength, surface coils, and sequence selection. Low resolution MR images generally are satisfactory for screening for osteonecrosis and for the evaluation of large bone or soft tissue abnormalities. Tailoring an examination with high resolution images, specialized sequences, or contrast may add useful information, particularly if a detailed evaluation of the joint is desired. Tailoring of the examination by an experienced radiologist requires adequate clinical information, so communication between the referring physician and radiologist is crucial for optimal results. Finally, MR imaging and radiographs are complementary examinations; MR images of the hip should not be interpreted without having recent radiographs available for comparison.