A scintigraphic classification of Legg-Calvé-Perthes disease

Detection of early metaphyseal changes in a piglet model of Legg-Calvé-Perthes disease using quantitative mapping of MRI relaxation times

Legg-Calvé-Perthes disease (LCPD) is a childhood hip disorder characterized by ischemic injury to the epiphysis of the femoral head, but changes to the metaphysis have also been implicated in its pathogenesis. Quantitative magnetic resonance imaging (MRI) relaxation time mapping techniques are potentially useful to detect injury in LCPD, but studies to date have focused on the epiphysis. The purpose of this study was to assess whether T2, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation times can detect early metaphyseal changes in an LCPD piglet model. Complete epiphyseal ischemia of one femoral head was surgically induced and confirmed using contrast-enhanced MRI in n = 10 6-week-old piglets; the contralateral side was unoperated. The bilateral hips were imaged 1 week after surgery in vivo at 3T MRI using relaxation time mapping and contrast-enhanced MRI. Relaxation times and thicknesses of the metaphyseal primary and secondary spongiosa were measured and compared between the ischemic and contralateral-control femoral heads using paired t-tests. In the ischemic femoral heads, T2 relaxation times were significantly increased in the primary spongiosa (6.7 ± 9.8 ms, p = 0.029), and T2, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation times were significantly decreased in the secondary spongiosa (respectively: -13.3 ± 9.3 ms, p = 0.013; -32 ± 23 ms, p < 0.001; -43 ± 41 ms, p = 0.009; and -39 ± 13 ms, p < 0.001). The secondary spongiosa thickness was also significantly decreased in the ischemic femoral heads (p < 0.001). In conclusion, T2, T1ρ, adiabatic T1ρ, and adiabatic T2ρ relaxation time mapping techniques can detect early changes in the metaphysis following ischemic injury to the epiphysis of the femoral head in a piglet model of LCPD.

Epidemiology, natural evolution, pathogenesis, clinical spectrum, and management of Legg-Calvé-Perthes

Background

Legg-Calvé-Perthes disease is a self-limiting disorder that develops in children following interruption of the blood supply to the capital femoral epiphysis. This review outlines the current knowledge on the epidemiology, natural evolution, clinical spectrum, and management of the disease.

Methods

The literature pertaining to these aspects of the disease were studied and summarized in this review.

Results

Epidemiological studies suggest that environmental factors contribute to the causation of the disease. Incidence rates monitored over time indicate that the incidence of Legg-Calvé-Perthes disease is declining. The natural evolution followed on sequential plain radiographs enables division of the disease into Stages Ia, Ib, IIa, IIb, IIIa, IIIb, and IV. Reversible deformation of the capital occurs in Stages Ia-IIa simply on standing while irreversible deformation may occur in Stages IIb and IIIa. Treatment of Legg-Calvé-Perthes disease in Stages Ia-IIa aims to prevent the femoral head from getting deformed by containment and avoidance of weight-bearing. In Stages IIb and IIIa, treatment aims to remedy the effects of early irreversible deformation of the femoral head. In Stage IIIb and IV, treatment is directed to correcting the altered shape of the femoral head. The impression that these treatment methods are helpful is based on poor quality evidence.

Conclusion

There is an urgent need to undertake Level I studies to establish the efficacy of currently treatment.

Level of evidence

level V.

Prolonged non-weightbearing treatment decreases femoral head deformity compared to symptomatic treatment in the initial stage of Legg-Calvé-Perthes disease

The purpose of this study is to investigate the potential benefit of using prolonged non-weightbearing (PNWB) as a treatment option for early-stage Legg-Calvé-Perthes disease (LCPD). An Institutional Review Board (IRB) approved this retrospective study of patients with LCPD and ≥2-year follow-up. Patients 6-12 years of age were included if treatment began in Waldenstrom stage 1 or 2A. PNWB consisted of ≥6 months of non- or toe-touch weightbearing. PNWB was recommended if perfusion MRI demonstrated ≥40% hypoperfusion of the femoral head and parents decided against operative treatment. The control group consisted of symptomatically treated patients. Deformity index and epiphyseal quotient were measured at 2-year follow-up. Stulberg classification and sphericity deviation score (SDS) were determined at skeletal maturity or at a minimum of 5-year follow-up. When treatment was initiated in Waldenstrom stage 1, the PNWB group had significantly less femoral head deformity, including deformity index (0.21 vs. 0.52; P < 0.001), epiphyseal quotient (69% vs. 43%; P < 0.001), SDS (18 vs. 52; P = 0.004), and Stulberg (50% good vs. 0% good; P = 0.044). The PNWB group mean hypoperfusion was 68%, indicating severe hypoperfusion. Duration of recommended non-weight bearing in the PNWB group was 11.5 months (range 7-17 months). Despite severe femoral head hypoperfusion, PNWB begun during the initial stage of LCPD decreased femoral head deformity. PNWB should be considered a treatment option for patients/parents who do not wish to pursue operative intervention in early-stage LCPD with substantial hypoperfusion. Level of Evidence III - retrospective comparative study.

Microarray analysis of lncRNA and mRNA expression profiles in patients with Legg-Calve-Perthes disease

BACKGROUND

The etiology and underlying pathogenic mechanisms of Legg-Calve-Perthes disease (LCPD) still remain unclear. A disruption of blood supply to the femoral head, producing ischemic necrosis, appears to be the critical pathological event. The lncRNAs play crucial roles in many biological processes and are dysregulated in various human diseases. However, its expression profiles and the potential regulatory roles in the development of LCPD have not been investigated.

METHODS

In this study, differentially expressed lncRNA and mRNA of Legg-Calve-Perthes disease patients were profiled. Several GO terms and pathways that play important roles in the regulation of vascular structure, function or coagulation were selected for further analysis. The lncRNA -mRNA interacting networks in LCPD tissues were constructed to identify novel potential targets for further investigation.

RESULTS

The microarray analysis revealed that 149 lncRNAs and 37 mRNAs were up-regulated, and 64 lncRNAs and 250 mRNAs were down-regulated in LCPD tissues. After filtering, we finally found 14 mRNAs and constructed an mRNA-lncRNA interacting network. Through the analysis of the interaction network, we finally found 13 differentially expressed lncRNAs, which may be implicated in the pathogenesis of LCPD. These mRNAs/lncRNAs were further validated with qRT-PCR.

CONCLUSION

The findings of this study established a co-expression network of disease-related lncRNAs and mRNAs which screened out from the concerned G.O. terms and Pathways, which may provide new sights for future studies on molecular mechanisms of LCPD.

Transient synovitis of the hip : is systematic radiological screening necessary for the detection of Perthes disease?

Current imaging guidelines in Belgium advise a systematic X-ray screening of the hips after an episode of transient synovitis of the hip, in order to detect Perthes disease. The aim of this study was to analyze whether systematic radiological screening is necessary for all children or whether the X-ray indication could be guided by clinical symptoms. A retrospective single center study including all children with the diagnosis of transient synovitis of the hip between 2013 and 2018 was performed. 242 patients with the diagnosis of one or more transient synovitis episodes were included, 102 of whom underwent a follow up X-ray. Persistence or recurrence of symptoms were recorded for all patients, as well as the results of follow-up hip X-rays. 12 children did not remain symptom-free after the episode of transient synovitis. Of these patients 10 had a normal follow-up X-ray and 3 were diagnosed with Perthes disease. 1 patient of those 3 had a normal X-ray but was diagnosed with Perthes disease on MRI. Of the children which remained symptom-free after the episode of transient synovitis, none were diagnosed with Perthes disease afterwards. A follow-up X-ray to exclude Perthes disease after a diagnosis of transient hip synovitis appears to be necessary only in patients with persistent or recurrent symptomatology.

Evolution of Legg-Calvé-Perthes disease following proximal femoral varus osteotomy performed in the avascular necrosis stage:a prospective study

PURPOSE

This prospective study was undertaken to describe patterns of fragmentation of the femoral epiphysis following a proximal femoral varus osteotomy (PFVO) done during stage I of LCPD and to assess the disease duration and outcome in each pattern.

METHODS

A total of 25 children treated by a PFVO in stage I of LCPD were followed until healing. The MRI Perfusion Index, radiographic changes in the femoral epiphysis, disease duration and the Sphericity Deviation Score (SDS) at healing were documented. The reproducibility of classification of the pattern of fragmentation, estimation of disease duration and SDS were assessed. The duration of the disease and SDS in the patterns of fragmentation were compared.

RESULTS

Four patterns of fragmentation were noted, namely, typical fragmentation, bypassing fragmentation, abortive fragmentation and atypical fragmentation with horizontal fissuring. The reproducibility of classifying the pattern of fragmentation was moderate (Kappa: 0.48) while the reproducibility of other continuous variables was excellent. The Perfusion Index was less than 50% in every affected hip. The duration of the disease and SDS were lowest in children in whom the stage of fragmentation was bypassed but these differences were not statistically significant.

CONCLUSION

Following a proximal femoral osteotomy during stage I of LCPD the fragmentation stage may be bypassed partially or completely and the chances of a good outcome appear to be very good if fragmentation is bypassed.

LEVEL OF EVIDENCE

Level II Prognostic Study.

Revascularization of the necrotic femoral head after traumatic open anterior hip dislocation in a child: a case report

INTRODUCTION

Avascular necrosis of the femoral capital epiphysis is the most serious complication after traumatic dislocation of the hip in children. This case report discusses the localization and revascularization of the necrotic femoral head following rarely experienced traumatic open anterior hip dislocation in children.

CASE PRESENTATION

Our patient was an 11-year-old Japanese boy who had open anterior hip dislocation sustained in a traffic accident. Reduction of the hip joint was performed in an emergency operation, and he was evaluated using serial gadolinium-enhanced magnetic resonance imaging. T1-weighted magnetic resonance images showed two bands with low signal intensity in the femoral capital epiphysis on coronal and oblique axial planes, indicating the existence of avascular osteonecrosis of the femoral head. We observed gadolinium enhancement in the central region of the epiphysis, where the area between the two bands with low signal intensity was located. Serial assessment with enhanced magnetic resonance images during a non-weight-bearing period of 1.5 years after injury showed revascularization starting from the central region and converging toward the peripheral region. Although the patient had leg-length discrepancy due to the early epiphyseal closure, non-weight-bearing treatment for the avascular osteonecrosis of the femoral head achieved a favorable outcome without any hip joint dysfunction, pain, or sign of secondary osteoarthritic change within 4.5 years after injury.

CONCLUSION

We confirmed the revascularization process of the necrotic lesion in the femoral capital epiphysis in an 11-year-old boy using serial gadolinium-enhanced magnetic resonance imaging. Conservative non-weight-bearing treatment achieved a favorable outcome.

Diffusion-weighted MRI for outcome prediction in early Legg-Calvé-Perthes disease: Medium-term radiographic correlations

BACKGROUND

Outcome prediction at the early sclerotic stage of Legg-Calvé-Perthes disease (LCPD) is valuable to select patients likely to benefit from early surgery. The metaphyseal apparent diffusion coefficient (ADC) ratio correlated significantly with Herring's classification of LCPD in a preliminary study of 49 MRIs, in which values greater than 1.63 were associated with poor outcomes. The objective of this study was to determine whether the femoral neck ADC ratio, with the 1.63 cut-off, determined at the initial stage of LCPD correlated with medium-term radiographic outcomes.

HYPOTHESIS

The metaphyseal ADC ratio correlates significantly with medium-term radiographic outcomes of LCPD.

MATERIALS AND METHODS

A prospective study was performed in 27 children (mean age, 13 years; range, 9.5-16 years) who underwent 49 MRIs at the sclerosis or fragmentation stage of unilateral LCPD. ADCs measured bilaterally at the femoral head and neck were used to compute the corresponding ADC ratios between the affected and unaffected sides. The patients received regular follow-up for at least 5 years. The correlation between the ADC ratios and Stulberg grade at last follow-up was assessed.

RESULTS

After a mean follow-up of 6.8 years (range, 5.2-8.4 years) from the date of the first MRI, 13 hips were Stulberg 1 or 2, 13 were Stulberg 3 or 4, and 1 was Stulberg 5. The metaphyseal ADC ratio increased significantly with the Stulberg grade (p<0.01). When only MRIs obtained at the early stage of sclerosis were considered, the correlation remained significant (p=0.03). It was also significant in the subgroup of surgically treated patients (p<0.0001) but was not significant in the subgroup without surgery (p=0.51). A metaphyseal ADC ratio greater than 1.63 was associated with a worse Stulberg grade (p=0.02).

DISCUSSION/CONCLUSION

Diffusion-weighted MRI is a non-irradiating and non-invasive investigation that contributes to the management of LCPD when used in combination with morphological MRI sequences. Elevation of the femoral neck ADC is a finding of adverse prognostic significance that correlates with Herring's grade at the fragmentation stage and with Stulberg's grade at the healed stage. Early ADC elevation in the affected femoral neck can serve to select those patients most likely to benefit from early surgery before the fragmentation stage, i.e., before Herring's classification can be applied.

LEVEL OF EVIDENCE

III, prospective uncontrolled study 3.

A comparison of subtraction MRI with the standard contrast-enhanced imaging in Perthes' disease

PURPOSE

Perthes' disease (PD) results from loss of blood supply to the hip and can progress to femoral head deformity. MRI in the early course of the disease can provide data on the initial extent of infarct. Vascularity of the femoral head is assessed by gadolinium-enhanced MRI (contrast MRI), which may be improved by the digital subtraction technique (subtraction MRI). We hypothesized that gadolinium-enhanced MRI without subtraction was comparable with subtraction MRI in depicting the femoral head perfusion.

METHODS

In all, 34 patients (34 hips) with unilateral PD had gadolinium-enhanced MRI as part of a prospectively randomized study. Nine patients had three MRIs, 15 had two and ten had a single MRI. Measurement of perfusion of the femoral head (MRI perfusion index) was obtained using digital image analysis on all the MRIs, including both before and after subtraction. A paired sample t-test was performed to compare the measurements.

RESULTS

The mean age of the patients was 8.9 years (sd 1.6). At the time of diagnosis, the subtraction MRI did not elicit a statistically significant difference in MRI perfusion index measurements when compared with the contrast MRI (p = 0.19). The same findings were found when including all patients at various stages of the disease (p = 0.30). Qualitatively, although some subtraction MRI images showed superior delineation of epiphysis, there are no significant differences throughout the whole series.

CONCLUSION

Although the current literature supports the increasing role of the subtraction MRI for PD management, our study proposed that the contrast MRI without subtraction technique appears adequate in assessing femoral head perfusion.

LEVEL OF EVIDENCE

Level I - Diagnostic study.

Bone Scintigraphy: A Review of Technical Aspects and Applications in Orthopedic Surgery

Due to its high sensitivity, low cost, accessibility, and ease of use, bone scintigraphy is used in orthopedic surgery for the diagnosis and management of varied pathology. It is commonly used for insufficiency fractures, metastatic neoplasia, staging and surveillance of sarcoma, and nonaccidental trauma. It augments diagnoses, including stress or occult fractures, musculoskeletal neoplasia or infection, and chronic regional pain syndrome, in patients presenting with normal results on radiographs. Bone scan images are resistant to metal-based implant artifact, allowing effective evaluation of failed total joint prostheses. Bone scintigraphy remains an underused tool in the evaluation and management of orthopedic patients. [Orthopedics. 2019; 42(1):e14-e24.].

The Pathogenesis and Treatment of Legg-Calvé-Perthes Disease

Legg-Calvé-Perthes disease is a childhood hip condition in which the blood supply to the capital femoral epiphysis is interrupted, causing osteonecrosis and chondronecrosis that lead to progressive deformity of the femoral head and secondary degenerative osteoarthritis in later life. The etiology of Legg-Calvé-Perthes disease remains unclear, with both biological and mechanical factors playing important roles in the pathogenesis of the condition. The treatment of Legg-Calvé-Perthes disease remains controversial but is dependent on several salient factors, including the age at clinical onset, the extent of epiphyseal involvement, the stage of the disease, and the degree of femoral head deformity. The literature supports operative containment treatment in the early stage of disease. Such treatment has led to improved femoral head sphericity with better patient outcomes in multicenter prospective cohort studies. The number of hips that need to be treated operatively in order to achieve a modest treatment effect remains high. Multicenter prospective cohort studies have shown that 6 to 7 patients need to be managed to create 1 spherical femoral head that would not have otherwise occurred.

Role of Advanced Imaging in the Diagnosis and Management of Active Legg-Calvé-Perthes Disease

Since the first description of Legg-Calvé-Perthes disease a century ago, the diagnosis, staging, prognosis, and treatment decisions have been based on plain radiographs. The goal of treatment is prevention of femoral head deformity, yet radiographic prognostic classifications are applied in the fragmentation stage, often after deformity occurs. These classifications are assigned too late in the progression of the disease to maximize the effects of intervention. Thus, alternative mechanisms to determine femoral head involvement earlier in the disease course are warranted. Increasingly, MRI has been used in the study of the disease. Gadolinium-enhanced and diffusion-weighted MRI has shown promising results that correlate with radiographic classifications and the early radiographic outcome. Advanced imaging has improved the assessment of hinge abduction, yet the exact definition remains controversial. The role of imaging in the management of Legg-Calvé-Perthes disease is rapidly evolving. New or refined imaging techniques may eventually allow earlier prognosis and treatment.

What's New in Pediatric Hip?

BACKGROUND

Developmental dysplasia of the hip (DDH), which encompasses a wide spectrum of disease from mild dysplasia to frank dislocation, is one of the most common developmental deformities of the lower extremities and one of the leading causes of future osteoarthritis and hip arthroplasty. Legg-Calvé-Perthes disease (LCPD) results from a vascular insult to the growing femoral epiphysis, which in turn can create permanent morphologic changes to the hip joint. Slipped capital femoral epiphysis (SCFE) occurs when the proximal femoral physis fails allowing the epiphysis to displace in relation to the metaphysis. Infections about the hip also create significant morbidity in the pediatric hip.

METHODS

We searched the PubMed database for all studies related to DDH, LCPD, SCFE, and pediatric hip infections that were published between July 1, 2014 and August 31, 2017. The search was limited to English articles and yielded 839 papers. This project was initiated by the Pediatric Orthopaedic Society of North America Publications Committee and was reviewed and approved by the Pediatric Orthopaedic Society of North America Presidential Line.

RESULTS

A total of 40 papers were selected for review based upon new and significant findings. Select historical manuscripts are also included to provide sufficient background information.

CONCLUSIONS

DDH, LCPD, SCFE, and infections about the hip continue to be important topics in pediatric orthopaedics and areas of vital research. This manuscript reviews the most important recent literature on the diagnosis and treatment of these pediatric hip conditions.

LEVEL OF EVIDENCE

Level V.

A simple, precocious, and reliable way to assess future clinical outcome in children with Perthes disease and mild femoral head involvement: correlation between MRI with diffusion-weighted and dynamic gadolinium-enhanced subtraction and Catterall and Herring classifications

BACKGROUND

In children older than 5 years with a mild form of Legg-Calvé-Perthes disease, the outcome is difficult to predict. In this study, we retrospectively correlated gadolinium-enhanced subtracted (DGS) and diffusion (DWI) MRI findings to the radiographic assessment according to the Catterall and Herring et al. classifications and to the final score according to Stulberg et al.: the aim was to identify a precocious, simple, and objective criterion to differentiate between forms evolving favourably and forms requiring an early surgical treatment in order to avoid femoral head deformity and subsequent osteoarthritis.

METHODS

Twelve boys with unilateral mild femoral head involvement (Catterall grade 2 or grade 3) underwent DSG and DWI MR during the early phase of the disease. The absence of enhancement of the external pillar on DSG MRI and the presence of metaphyseal hyperintensity on DWI were considered to be the signs of poor outcome. These findings were correlated with the Catterall and Herring et al. classifications at the initial sclerotic stage and early fragmentation phase and with the Stulberg et al. classifications at least 5 years after the onset of the disease.

RESULTS

DSG MRI findings correctly discriminated three out of four patients with a good outcome but underestimated two out of eight patients with a poor outcome. DWI findings correlated with the Catterall and Herring et al. classifications in 12 out of 12 cases. In only one case, DWI findings did not correlate with the Stulberg et al. classification.

CONCLUSION

DWI MR provides an objective and accurate prognostic criterion that is relatively easy to recognise. DGS MR findings are less accurate, thus underestimating the gravity of the disease in one-fourth of the patients with a poor outcome.

Evaluation of femoral head viability via bone scintigraphy in the postoperative pediatric patient

BACKGROUND

Evaluating postoperative patients with hardware is challenging following surgical intervention for hip maladies such as femoral neck fractures and slipped capital femoral epiphysis (SCFE). These children are at increased risk of developing avascular necrosis, and imaging may be requested to confirm or exclude this diagnosis. Children with Legg-Calvé-Perthes disease can be monitored for restoration of blood flow to the capital femoral epiphysis to guide management and help with prognosis. Although MRI is sensitive for detecting early avascular necrosis, the presence of hardware degrades image quality.

OBJECTIVE

This report examines the utility of bone scans for evaluating femoral head perfusion in children who have undergone surgery for femoral neck fractures, SCFE or Legg-Calvé-Perthes disease.

MATERIALS AND METHODS

A retrospective review of 20 patients (22 scans) after fixation for femoral neck fracture, SCFE or Legg-Calvé-Perthes disease from 2012 to 2015 was performed. The bone scan findings were correlated with the intraoperative findings or clinical follow-up.

RESULTS

Twenty-one of the 22 (95%) bone scans in 19 of the 20 (95%) patients demonstrated findings consistent with clinical outcomes and/or the intraoperative appearance of the femoral head. Four of 20 patients (20%) had bone scan features of avascular necrosis, defined as "absent" or "moderately diminished" femoral head activity, which were confirmed intraoperatively and resulted in poor outcomes.

CONCLUSION

Radionuclide imaging of hips in the postoperative setting is a valuable modality for assessing the risk of avascular necrosis, a complication of femoral neck fractures and SCFE and for evaluating the restoration of flow to the capital femoral epiphyses of children with Legg-Calvé-Perthes disease.

Legg-Calvé-Perthes disease: classifications and prognostic factors

INTRODUCTION

Legg-Calvé-Perthes Disease (LCPD) represents idiopathic avascular necrosis of femoral head in pediatric population. Indications for treatment depend mostly on prognosis about femoral head sphericity and hip congruence at the end of growth. The aim of this review is to highline prognostic factors of LCPD.

METHODS

Bibliographic search in PubMed allowed selection of 33 articles concerning prognostic factors and/or classification of LCPD.

CONCLUSION

Clinical factors of poor prognosis are overweight, female sex, age exceeding 6 years old, and lack of hip abduction. Radiologically, Herring's classification is consensual because of its high prognostic value and very good reproducibility. The other signs of femoral head "at-risk" and the assessment of the reduction in abduction of the femoral head in the acetabulum are also prognostic of late evolution. MRI seems to be a future tool in assessing the fate of hips in LCPD. It is likely that a better understanding of LCPD etiology would precise the prognosis of this disease.

Assessment of Femoral Head Revascularization in Legg-Calvé-Perthes Disease Using Serial Perfusion MRI

BACKGROUND

Legg-Calvé-Perthes disease is a juvenile form of osteonecrosis of the femoral head. The purpose of this study was to use serial perfusion magnetic resonance imaging (MRI) to determine the pattern and rate of revascularization of the femoral heads of patients with the active stage of Legg-Calvé-Perthes disease.

METHODS

We performed a prospective study of 29 patients (30 hips) with a mean age (and standard deviation) of 8.4 ± 1.9 years who were diagnosed with Waldenström Stage-1 or 2 Legg-Calvé-Perthes disease. All patients had ≥2 perfusion MRIs, and 21 patients (22 hips) had ≥3. Perfusion percentages of the femoral epiphyses were measured by 2 independent observers. Statistical analyses included calculation of the intraclass correlation coefficient, the paired t test, the Mann-Whitney U test, and the Kruskal-Wallis test.

RESULTS

Initial perfusion MRIs showed the percent perfusion in the affected femoral heads to range from 5% to 70%. The average percent perfusion (and standard deviation) was 35% ± 16% on the first MRI, which increased to 77% ± 14% on the follow-up MRI acquired at an average of 10.5 ± 2.9 months later (p < 0.01). Serial assessment showed a general pattern of revascularization starting from the periphery of the posterior, lateral, and medial aspects of the femoral epiphysis and converging toward the anterocentral region. The average rate of revascularization was 4.9% ± 2.3% per month with a wide range among the patients (0.6% to 10.4% per month).

CONCLUSIONS

Revascularization of the necrotic femoral head increased over time in a horseshoe pattern, starting from the posterior, lateral, and medial aspects of the femoral epiphysis. The rate of revascularization was highly variable among patients.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Management of Perthes' disease

The main complication of Perthes' disease is femoral head deformation. Evidence from the literature highlights two important factors related to the cause and timing of this complication. (1) Extrusion of the femoral head appears to be a major factor that leads to femoral head deformation. (2) Deformation of the femoral head occurs in the latter part of the stage of fragmentation. The likelihood of preventing femoral head deformation is over 16 times higher if extrusion is reversed or prevented by the early stage of fragmentation than if done later. Several treatment options have been described in children who present later in the course of the disease but the outcomes of all these measures do not compare with those of early intervention.

MR perfusion index as a quantitative method of evaluating epiphyseal perfusion in Legg-Calve-Perthes disease and correlation with short-term radiographic outcome: a preliminary study

BACKGROUND

Current radiographic prognosticators of the outcome of Perthes disease can only be applied after femoral head deformity has occurred. Quantification of femoral head perfusion using the gadolinium-enhanced subtraction magnetic resonance imaging (MRI) technique may serve as an early prognosticator of outcome. The purposes of this study were 2-fold: (1) to develop a reliable method to quantify femoral head perfusion using this MRI technique; and (2) to determine whether the perfusion at early stages of Perthes disease correlates with radiographic deformity after a 2-year follow-up.

METHODS

A total of 20 patients meeting the following inclusion criteria were studied: radiographs and MRI obtained of femoral heads predeformity, age between 5 and 13 years, and unilateral disease. MR perfusion index, a measure of perfusion in the epiphysis, was obtained using digital image analysis of subtraction gadolinium-enhanced MRI. Intraobserver and interobserver agreement of this index was assessed by 2 independent observers. MR perfusion index was correlated with a radiographic deformity index (a measure of femoral head deformity) obtained after a minimum of 2 years.

RESULTS

The intraobserver agreement assessed by the intraclass correlation coefficient was 0.96 for observer 1 and 0.97 for observer 2. The interobserver agreement of the MR perfusion index was 0.90 for trials 1 and 2. MR perfusion index in the early stages of Perthes disease was highly variable, ranging from 0 to 0.70. After a minimum of 2 years following MRI acquisition, radiographs were obtained and evaluated using the deformity index, a continuous measure of femoral head deformity, by 2 blinded observers. Deformity index at 2-year follow-up showed moderate correlation with predeformity MR perfusion index (r=-0.56, P=0.01, R=0.31). In those patients who were treated nonoperatively, the correlation was stronger (r=-0.79, P=0.006, R=0.63).

CONCLUSIONS

MR perfusion index obtained from gadolinium-enhanced subtraction MR images showed a high interobserver agreement. MR perfusion index is highly variable at early stages of Perthes disease, and a lower MR perfusion index correlated with greater radiographic deformity at the 2-year follow-up. This pilot study shows the promise of predeformity MR perfusion index as a possible early prognosticator of outcome in Perthes disease.

LEVELS OF EVIDENCE

Prognostic level II.

Prognosis value of early diffusion MRI in Legg Perthes Calvé disease

PURPOSE

To evaluate diffusion MRI of the proximal femoral epiphysis and metaphysis as a prognosis factor in Legg Calvé Perthes (LCP) disease.

METHODS

Thirty-one children (mean age 5.5 years, range 2.5-10.5) with unilateral LCP were included in a prospective, consecutive series. Radiographs were analysed and classified as per Herring criteriae. Mean follow-up was 19 months (range 6-30). Forty-nine MRI scans were performed at either the condensation or fragmentation stage. Apparent Diffusion Coefficient (ADC) of both the femoral epiphysis and metaphysis were measured bilaterally and ADC ratio were calculated, then compared to the Herring group.

RESULTS

Sixteen hips were rated Herring A or B, 3 Herring B-C and 12 Herring C. ADC was increased in affected hips compared to unaffected sides, both at the femoral epiphysis (P<0.001) and metaphysis (P<0.0001). ADC ratio of the femoral metaphysis was positively correlated to Herring classification: if superior to 1.63, it was associated with a bad prognosis (Herring B-C or C) (P=0.0017, sensitivity=89%, specificity=58%). Interobserver reliability of ADC measurement was excellent. The 1.63 threshold could be determined as early as the condensation stage.

CONCLUSIONS

Diffusion presents several advantages including being non radiating and non invasive. It does not need contrast medium administration and it can be performed without anaesthesia. The origin of the increased ADC remains unknown. Basically, it reflects molecular changes (true diffusion) but it is also influenced by the vascular supply (pseudo-diffusion). ADC ratio could provide an early prognosis before Herring classification is applicable.

LEVEL OF EVIDENCE

Level III. Prospective uncontrolled study.

Evaluation of bone viability

Bone scintigraphy is an excellent tool to assess bone viability. The functional information provided is crucial in several clinical settings, like the detection of avascular necrosis, septic embolism, frostbite lesions and osteonecrosis, and to evaluate the results of surgical treatment in cases of avascular necrosis. Mechanisms to obtain molecular images, as well as different kind of techniques, are detailed. Comparative and multimodality imaging to focus on any clinical problem and a review of the clinical indications reflect the multidisciplinary approach with close collaboration between orthopaedists, radiologists and nuclear medicine physicians. Finally, an effort has been made to list the most important points of imaging of bone viability in children.

Comparison between innominate osteotomy and arthrodistraction as a primary treatment for Legg-Calvé-Perthes disease: a prospective controlled trial

PURPOSE

Legg-Calvé-Perthes (LCP) disease is currently managed by mechanical containment of the femoral head in the hip socket. As evidence suggests that hip distraction may offer a new treatment strategy, we used arthrodistraction as a primary treatment for active forms of LCP disease and prospectively compared the results with the Salter innominate osteotomy.

METHODS

A total of 54 children, six years or older of both genders with severe forms of LCP disease in the stages of necrosis or revascularisation, were enrolled. Patients were submitted to either Salter innominate osteotomy (n = 28) or hip arthrodistraction (n = 26). Final radiographs were used to evaluate the Mose index, Wiberg angle, extrusion index and the Stulberg et al. classification.

RESULTS

There were no significant differences in gender, age, lateral pillar classification and average follow-up time between the two groups. The osteotomy group progressed without major complications, but children in the joint distraction group experienced episodes of pin tract pain and infection, leading to the early removal of the external device in one case. Two patients developed joint stiffness, treated by physiotherapy or manipulation, and one child developed subluxation of the femoral head. The average time in distraction was 4.44 months (2.53-7.23 months). In the final evaluation the osteotomy group showed better containment of the femoral head. The Mose index and the Stulberg et al. classification were statistically similar between the two groups.

CONCLUSIONS

Despite similar final radiological results, arthrodistraction was associated with a higher morbidity. Consequently, we do not recommend hip distraction as a primary treatment for the early stages of LCP disease.

Vascular safe zones for surgical dislocation in children with healed Legg-Calvé-Perthes disease

BACKGROUND

Legg-Calvé-Perthes disease consists of idiopathic osteonecrosis of the femoral head, causing proximal femoral growth deformity. Recent advances in surgical technique have permitted safe surgical dislocation of the hip, allowing for correction of femoracetabular impingement. The purpose of this study was to characterize the location and number of lateral epiphyseal arteries supplying the femoral head in children with healed Legg-Calvé-Perthes disease.

METHODS

This retrospective study included nineteen children (twenty-two hips) with a diagnosis of Legg-Calvé-Perthes disease (the LCPD group) and a matched control group of seventeen children (twenty hips) with developmental hip dysplasia. All patients underwent high-resolution contrast-enhanced magnetic resonance imaging (MRI) to visualize the path of the medial femoral circumflex artery and the lateral epiphyseal artery branches supplying the femoral head.

RESULTS

All patients in the LCPD group were classified as having Waldenström grade-4 disease. Their average age at the time of MRI was fifteen years (range, eleven to eighteen years). The lateral epiphyseal arteries reliably inserted on the posterior-superior aspect of the femoral neck from a superior-anterior to a superior-posterior position in both groups. An average of 2.63 (standard deviation [SD], 1.47) retinacular vessels were visualized in the LCPD group, compared with 5.20 (SD, 1.06) retinacular vessels in the dysplasia group (p &lt; 0.0001).

CONCLUSIONS

The lateral epiphyseal arteries of the femoral head reliably insert in a narrow anatomic window on the femoral neck. Reperfusion of the medial femoral circumflex artery does occur in patients with Legg-Calvé-Perthes disease; however, the overall number of vessels is decreased as compared with that in patients with developmental hip dysplasia.

Pathophysiology and new strategies for the treatment of Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease is a juvenile form of idiopathic osteonecrosis of the femoral head that can lead to permanent femoral head deformity and premature osteoarthritis. According to two recent multicenter, prospective cohort studies, current nonoperative and operative treatments have modest success rates of producing a good outcome with a spherical femoral head in older children with Legg-Calvé-Perthes disease. Experimental studies have revealed that the immature femoral head is mechanically weakened following ischemic necrosis. Increased bone resorption and delayed new bone formation, in combination with continued mechanical loading of the hip, contribute to the pathogenesis of the femoral head deformity. Biological treatment strategies to improve the healing process by decreasing bone resorption and stimulating bone formation appear promising in nonhuman preclinical studies.

Diffusion-weighted MRI reveals epiphyseal and metaphyseal abnormalities in Legg-Calvé-Perthes disease: a pilot study

BACKGROUND

Legg-Calvé-Perthes disease (LCP) is thought to be associated with ischemic events in the femoral head. However, the types and patterns of reperfusion after these ischemic events are unclear.

PURPOSES

We therefore determined whether (1) there would be any age-related diffusion changes; (2) diffusion-weighted MR imaging would reveal ischemic damage; and (3) diffusion changes are correlated with prognostic MR findings in patients with LCP.

METHODS

We prospectively performed conventional, perfusion, and diffusion-weighted MR imaging studies in 17 children with unilateral LCP. We then measured the apparent diffusion coefficient (ADC) values in the epiphysis and the metaphysis, and compared them with those of the contralateral normal side. Based on perfusion MR imaging, we assessed reperfusion to the epiphysis as either periphyseal or transphyseal. We studied T2-signal intensity changes in the metaphysis and the presence of focal physeal irregularity. We correlated diffusion changes with reperfusion to the epiphysis, T2-signal intensity change, and focal physeal irregularity.

RESULTS

Normal diffusion decreased with age. In LCP hips, epiphyseal diffusion increased early and remained elevated through the healing stage. Six of the 17 patients who had a metaphyseal ADC greater than 50% over the normal side had 13 times greater odds of having an association with transphyseal reperfusion to the epiphysis. The increase of metaphyseal ADC also was associated with an increased T2-signal intensity in the metaphysis and presence of focal physeal irregularity.

CONCLUSIONS

Diffusion-weighted MR imaging can be used as a complimentary modality to evaluate ischemic tissue damage with a potential prognostic value in patients with LCP.

Pathophysiology, classifications, and natural history of Perthes disease

Since the original reports of Legg-Calvé-Perthes disease (LCPD), much research effort has been undertaken to improve understanding of this idiopathic hip disorder. This article focuses on the current knowledge of the pathophysiology, classifications, and natural history of LCPD. Although the cause of LCPD remains largely unknown, some insight has been gained on its pathophysiology through experimental studies using animal models of ischemic necrosis. The few available clinical studies on the natural history of LCPD suggest that femoral head deformity is well tolerated in short and intermediate terms, but 50% of patients develop disabling arthritis in the sixth decade of life.

Imaging in Legg-Calvé-Perthes disease

Imaging in Legg-Calvé-Perthes disease should help assess the severity and the stage of the disease, detect severe forms earlier, and provide guidance to therapy. However, due to the complexity of the disease, not all examinations can be performed at the same time with the same goals. The scope of this work is to provide an overview of all imaging techniques available today, and to help understand when to use a particular examination. Advantages and limitations of plain radiographs, bone scintigraphy, magnetic resonance imaging, arthrography, computed tomography, and ultrasonography are identified.

Prognostic factors and outcome measures in Perthes disease

The shape of the femoral head at the time when Perthes disease heals is the most important determinant of the risk for degenerative arthritis; hence, the shape of the femoral head and congruence of the hip are the most useful outcome measures. Although several prognostic factors that predict femoral head deformation may be identified during the course of Perthes disease, only two prognostic factors may be identified early enough to institute preventive intervention: femoral head extrusion and the age at onset of the disease. Femoral head extrusion is the only factor that may be influenced by treatment.

Principles of containment treatment aimed at preventing femoral head deformation in Perthes disease

The aim of treatment of Perthes in the early part of the disease is to prevent the femoral head from getting deformed by muscular forces and weight-bearing stresses transmitted across the acetabular margin. To achieve this, femoral head extrusion must be preempted in children who are older than 8 years at onset of the disease by ensuring containment as soon as the disease is diagnosed. In children younger than 8 years in whom femoral head extrusion occurs, containment must be obtained by the early stage of fragmentation.

Guidelines for paediatric bone scanning with 99mTc-labelled radiopharmaceuticals and 18F-fluoride

The purpose of these guidelines is to offer nuclear medicine teams a framework that could prove helpful in daily practice. The guidelines include information related to the indications, acquisition, processing and interpretation of bone scans in children, focusing primarily on (99m)Tc-labelled diphosphonate scintigraphy, and also recommendations with regard to the emerging use of PET with (18)F-fluoride.

[Bone scintigraphy in evaluation of bone vascularisation at wrist and hand]

Diphosphonate bone scintigraphy is used since the 1970s for studying bone pathology; it is increasingly common because of increased physical activity of the population. The disphosphonate uptake in bone requires the preservation of bone vascularity and reflects osteoblastic activity; it allows studying the viability of bone. Using data from the literature and our experience, we tried to take stock of its main uses in routine emphasizing the study of vascular and describe its use in fractures of the scaphoid and in the study of vascularised bone transfers. If the value of scintigraphy is well known, the use made by means of pinhole collimator and the market entry of new and more sensitive detectors with better resolution could allow the side of the imaging anatomy of improving the study of the vascularisation of small bone transfers which are increasingly used, particularly at wrist and hand.

Diffusion-weighted imaging findings in Perthes disease with dynamic gadolinium-enhanced subtracted (DGS) MR correlation: a preliminary study

BACKGROUND

Legg-Calvé-Perthes disease (LCP) is necrosis of the proximal femoral epiphysis of vascular origin. Clinical course and outcome in LCP disease varies considerably between different patients. Earlier prognostic criteria than those offered by conventional radiography are necessary to identify children who require prompt surgical treatment.

OBJECTIVE

To assess the significance of signal alteration on diffusion-weighted MR imaging (DWI MR) in LCP.

MATERIALS AND METHODS

Twelve boys with unilateral LCP disease (Catterall grade 2 and 3), at the initial sclerotic stage and early fragmentation phase, underwent dynamic gadolinium-enhanced subtracted (DGS) and DWI MR. For DGS MR, the lateral pillar enhancement was recorded. For DWI imaging, we measured ADC values in the diseased and the unaffected epiphyses and metaphyses. Receiver operating characteristic curves were performed to analyze the performance of DWI in establishing agreement with the results of DGS MR, which is the gold standard for prognosis.

RESULTS

Femoral epiphysis increased diffusivity was observed in the affected hip in all cases. Increased metaphysis diffusivity in the affected side was observed in all cases with absent lateral pillar enhancement at DGS MR.

CONCLUSION

DWI seems to be a noninvasive means of distinguishing between Perthes disease with favourable and unfavourable prognosis.

MRI of Legg-Calve-Perthes disease

OBJECTIVE

Legg-Calvé-Perthes disease is a common cause of hip pain in children that may be initially clinically and radiographically difficult to diagnose and stage. The purpose of this article is to describe and illustrate the various MRI appearances of this condition.

CONCLUSION

MRI may show proximal femoral abnormalities before radiography in the setting of Legg-Calvé-Perthes disease, allowing appropriate diagnosis and prompt treatment. MRI can also assess for revascularization, healing, and multiple complications.

Perthes' disease: prognosis in children under six years of age

Children presenting with Perthes' disease before their sixth birthday are considered to have a good prognosis. We describe 166 hips in children in this age group. The mean age at onset of the disease was 44 months (22 to 72). Mild forms (Catterall I and II) were treated conservatively and severe forms (Catterall III and IV) either conservatively or operatively. The aim of the former treatment was to restrict weight-bearing. Operative treatment consisted of innominate osteotomy and was indicated by a Conway type-B appearance on the bone scan. All the patients were followed to skeletal maturity with a mean follow-up of 11 years (8 to 15). The end results were evaluated radiologically using the classifications of Stulberg and Mose. A total of 50 hips were Catterall grade-I or grade-II, 65 Catterall grade-III and 51 Catterall grade-IV. All hips with mild disease had a good result at skeletal maturity. Of the hips with severe disease 78 (67.3%) had good (Stulberg I and II), 26 (22.4%) fair (Stulberg III) and 12 (10.3%) poor results (Stulberg IV and V). Of the Catterall grade-III hips 38 were treated conservatively of which 31 (81.6%) had a good result, six (15.8%) a fair and one (2.6%) a poor result. Operative treatment was carried out on 27 Catterall grade-III hips, of which 21 (77.8%) had a good, four (14.8%) a fair and two (7.4%) a poor result. By comparison conservative treatment of 19 Catterall grade-IV hips led to ten (52.7%) good, seven (36.8%) fair and two (10.5%) poor results. Operative treatment was carried out on 32 Catterall grade-IV hips, of which 16 (50.0%) had a good, nine (28.1%) a fair and seven (21.9%) a poor result. We confirm that the prognosis in Perthes' disease is generally good when the age at onset is less than six years. In severe disease there is no significant difference in outcome after conservative or operative treatment (p > 0.05). Catterall grade-III hips had a better outcome according to the Stulberg and Mose criteria than Catterall grade-IV hips, regardless of the method of treatment.

Dynamic gadolinium-enhanced MRI in early ischaemia of the proximal femoral epiphysis--a preliminary study

AIM

To compare the sensitivities of dynamic Gadoteridol (Gd)-enhanced magnetic resonance imaging (MRI) and conventional Gd-enhanced spin-echo (SE) T1-weighted imaging (WI) in the detection of decreased perfusion of early epiphyseal ischaemia, and to determine the contribution of metaphyseal vascularity to physeal perfusion in epiphyseal vascular occlusion by dynamic Gd-enhanced MRI.

MATERIALS AND METHODS

Twenty-eight 2-week-old piglets were divided evenly into four groups: control groups A and B, and ischaemic groups A and B (seven animals in each). In the ischaemic groups, MRI was performed bilaterally on hips in persistent hyperabduction for 30 min. In the control and ischaemic group A the piglets underwent dynamic Gd-enhanced MRI, and in control and ischaemic group B the piglets were subjected to Gd-enhanced SE T1WI.

RESULTS

In ischaemic group A, the enhancement ratio (ER) and enhancement speed (ES) of the various tissues (except the metaphysis) were significantly lower than those in control group A on dynamic Gd-enhanced MRI (p<0.05). However, in ischaemic group B, no significant decrease in the ER of each tissue was found, compared with the ER in control group B as viewed using Gd-enhanced SE T1WI (p>0.05). On dynamic Gd-enhanced MRI, the ER and ES of the physis were less than those of metaphysis in the ischaemic group A (p<0.05); however, the ER and ES of the physis were similar to those of metaphysis in control group A (p>0.05).

CONCLUSION

Dynamic Gd-enhanced MRI is more sensitive than conventional Gd-enhanced SE T1WI in the detection of early epiphyseal ischaemia. Physeal perfusion might be from the metaphysis in epiphyseal vascular occlusion.

Legg-Calvé-Perthes disease: multipositional power Doppler sonography of the proximal femoral vascularity

BACKGROUND

Selection of the most appropriate sonographic scanning approaches for evaluation of hips can improve the method efficacy and decrease the scanning time.

OBJECTIVE

To determine the sonographic scanning planes that best assess the proximal femoral vascularity in asymptomatic and pathologic hips of children with Legg-Calvé-Perthes disease (LCPD) and evaluate the frequency (number of hips with evidence of perfusion) and intensity (number of color pixels per region) of color pixels representing superficial cartilaginous and deep transphyseal vascularity in different anatomic regions of pathologic and asymptomatic hips using multipositional power Doppler approaches.

MATERIALS AND METHODS

Seven scanning approaches (anterior-sagittal, anterior-transverse, coronal, adduction, perineal, 30 degrees and 70 degrees of abduction) were applied in 26 pathologic hips of 26 children with LCPD (age range 3-11 years) and in 25 contralateral asymptomatic hips. The color Doppler signals seen within the proximal femur were analyzed both qualitatively (overall/regional frequency) and quantitatively (intensity).

RESULTS

The coronal (P=0.009) and 30 degrees abduction (P=0.047) approaches demonstrated a higher frequency of color pixels in pathologic than in asymptomatic hips. The anterior-sagittal, 30 degrees abduction, adduction and anterior-transverse planes performed best of all approaches (P=0.02) to assess deep transphyseal perfusion. The physis demonstrated a greater intensity of color signals representing intraosseous vascularity than other regions in pathologic hips (P=0.027), as noted with the anterior-sagittal approach. There was a tendency (P=0.06) towards a greater intensity of pixels representing cartilaginous vascularity in pathologic hips' physes with the coronal approach.

CONCLUSION

Specific sonographic scanning planes are recommended for assessment of the proximal femoral vascularity of LCPD hips. The physis is the anatomic region that presents with the greatest intensity of color signals in pathologic hips.

[Nuclear medicine techniques in the diagnosis of orthopaedic diseases]

Nuclear medicine techniques show metabolic processes, allowing the diagnoses of many bone and joint disorders. For most orthopaedic indications three-phase bone scintigraphy is used, showing inflammatory bone and joint diseases, traumatic and post-operative disorders as well as necrotic or malignant changes. In addition to bone scintigraphy, there are radiopharmaceuticals to depict inflammatory processes. Finally, positron emission tomography is a modern imaging technique used mainly for tumor diagnostics, but also for detection of inflammation.

Serial bone scintigraphy in Legg-Calvé-Perthes disease: correlation with the Catterall and Herring classification

Radiographic classifications in Legg-Calvé-Perthes disease are difficult to use in the early stage of the disease. Changes on bone scintigraphy (revascularization versus recanalization pathway) precede the radiographic changes. Our purpose was to study the correlation between serial bone scintigraphy and radiographic classifications in Legg-Calvé-Perthes disease. In 86 patients, 95 hips that presented with Legg-Calvé-Perthes disease in the early stage were followed with serial bone scintigraphy and radiographs. Forty-four hips showed recanalization: pathway A on bone scintigraphy. Of these hips 96% were classified as Herring A or B and 66% as Catterall 2. Thirty-five hips showed revascularization: pathway B on bone scintigraphy. Of this group 82.8% were classified as Herring C and 17.1% as Herring B. All pathway B hips have Catterall 3 or 4. Sixteen hips showed pathway C: regression from pathway A to pathway B. They presented in 56% of cases with Herring B, 44% with Herring C, and in 81% with Catterall 3 or 4 classifications. We can conclude that there is a significant correlation between the vascularization pattern and the radiographic classification of Herring and Catterall.

Computer-assisted image analysis of the rat postosteonecrotic remodeled femoral head

Osteonecrosis of rat femoral heads was induced by stripping the periosteum of the neck and cutting the ligamentum teres. The epiphyseal marrow and bone were necrotic on the 5th postoperative day. Specimens obtained 18 and 36 days postoperatively showed fibrous and hematopoietic-fatty tissue in the intertrabecular spaces, osteoclastic bone resorption, osteogenesis, and degeneration of the joint cartilage. Morphometrically, the means of the height-to-length ratios of the control, 6-day, 18-day, and 36-day femoral heads were 0.26, 0.28, 0.48, and 0.29, respectively. The shape factor of the femoral heads of the control rats was higher than 0.81 in 80% of the cases, while those of rats killed on the 6th, 18th, and 36th postoperative day were higher than 0.81 in 65, 60, and 50% of cases, respectively. Statistically, the means of the height-to-length ratios and the values of the shape factors of the femoral heads of the rats killed 18 days postoperatively differed significantly from those of the other three groups of rats. The quantitatively gauged data of the remodeled epiphyses negate the authors' subjective impression concerning early flattening of the femoral heads after surgically produced osteonecrosis.

Imaging of pediatric hip disorders

Developmental and acquired abnormalities of the hips are common in childhood. Radiographs, MR imaging, CT, and nuclear medicine play an important role in the diagnosis and management of these disorders. Knowledge of the surgical and clinical treatments of these disorders is important to interpret accurately the radiology studies and impact treatment of the children.

The role of single photon emission computed tomography in bone imaging

Single photon emission computed tomography (SPECT) of the bone is the second most frequently performed SPECT examination in routine nuclear medicine practice, with cardiac SPECT being the most frequent. Compared with planar scintigraphy, SPECT increases image contrast and improves lesion detection and localization. Studies have documented the unique diagnostic information provided by SPECT, particularly for avascular necrosis of the femoral head, in patients with back pain, for the differential diagnosis between malignant and benign spinal lesions, in the detection of metastatic cancer in the spine, for the diagnosis of temporomandibular joint internal derangement, and for the evaluation of acute and chronic knee pain. Although less rigorously documented, SPECT is being increasingly used in all types of situations that demand more precise anatomic localization of abnormal tracer uptake. The effectiveness of bone SPECT increases with the selection of the proper collimator, which allows one to acquire adequate counts and minimize the patient-to-detector distance. Low-energy, ultrahigh-resolution or high-resolution collimation is preferred over all-purpose collimators. Multihead gamma cameras can increase the counts obtained or shorten acquisition time, making SPECT acquisitions more practical in busy departments and also increasing image quality compared with single-head cameras. Iterative reconstruction, with the use of ordered subsets estimation maximization, provides better quality images than classical filtered back projection algorithms. Three-dimensional image analysis often aids lesion localization.

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.