Hip joint fluid: detection and distribution at MR imaging and US with cadaveric correlation

Synovial Fluid Derived from Human Knee Osteoarthritis Increases the Viability of Human Adipose-Derived Stem Cells through Upregulation of FOSL1

Knee osteoarthritis (Knee OA) is an irreversible condition that causes bone deformity and degeneration of the articular cartilage that comprises the joints, resulting in chronic pain and movement disorders. The administration of cultured adipose-derived stem cells (ADSCs) into the knee joint cavity improves the clinical symptoms of Knee OA; however, the effect of synovial fluid (SF) filling the joint cavity on the injected ADSCs remains unclear. In this study, we investigated the effect of adding SF from Knee OA patients to cultured ADSCs prepared for therapeutic use in an environment that mimics the joint cavity. An increase in the viability of ADSCs was observed following the addition of SF. Gene expression profiling of SF-treated ADSCs using DNA microarrays revealed changes in several genes involved in cell survival. Of these genes, we focused on FOSL1, which is involved in the therapeutic effect of ADSCs and the survival and proliferation of cancer stem cells. We confirmed the upregulation of FOSL1 mRNA and protein expression using RT-PCR and western blot analysis, respectively. Next, we knocked down FOSL1 in ADSCs using siRNA and observed a decrease in cell viability, indicating the involvement of FOSL1 in the survival of ADSCs. Interestingly, in the knockdown cells, ADSC viability was also decreased by SF exposure. These results suggest that SF enhances cell viability by upregulating FOSL1 expression in ADSCs. For therapy using cultured ADSCs, the therapeutic effect of ADSCs may be further enhanced if an environment more conducive to the upregulation of FOSL1 expression in ADSCs can be established.

The Presence of Hip Joint Effusion on MRI Is Predictive of a Grade 4 Femoral Neck Stress Injury

INTRODUCTION

One of the most debilitating types of bone stress injuries is those occurring at the femoral neck. This problem occurs in the military population with much higher incidence than in the normal population and is of great concern to military medical providers. Early detection and accurate diagnosis are key in protecting soldiers and recruits from sustaining a potentially career-ending fracture. In a case study, a 16-year-old elite male distance runner presented with hip pain. MRI found hip joint effusion but was unremarkable for marrow edema and a low-signal fracture line. The initial diagnosis was acute arthritis; however, a follow-up radiograph 1 month later, after the patient had been refraining from running, confirmed a significant non-displaced compression-side Grade 4 femoral neck stress injury (FNSI). In light of the case study and our similar clinical experience, we tested the hypothesis that an MRI study positive for an FNSI, combined with the evidence of a hip joint effusion, is indicative of a Grade 4 FNSI, even without visualization of a low-signal intensity fracture line on T1 or short tau inversion recovery images.

MATERIALS AND METHODS

Recruits in Army Basic Combat Training were included in the investigation if 1) diagnosed with a unilateral FNSI, 2) had an initial positive MRI for an FNSI, 3) had a positive bone scan for uptake in the femoral neck area (to validate the diagnosis), 4) had no other hip/pelvis injuries, and 5) had a follow-up MRI within 60 days. Hip joint effusion was defined as 1) ≥2-mm measurable difference in the thickness of fluid along the length of the involved femoral neck when compared to the contralateral uninvolved femoral neck on the initial MRI; 2) visibly assessed as a prominent collection of fluid distending the posterior hip joint capsule on the initial MRI coronal short tau inversion recovery sequence (called the "flash sign").

RESULTS

A total of 162 recruits met the study inclusion criteria. For the detection of a Grade 4 FNSI on the first MRI, the sensitivity, specificity, and positive predictive value of the measured joint effusion criteria were 0.52, 0.94, and 0.89, respectively. or the non-measured flash sign, these values were 0.70, 0.83, and 0.80, respectively.

CONCLUSIONS

Both the measured hip joint effusion criteria and the non-measured flash sign were predictive of a Grade 4 FNSI and may be useful in clinical evaluation.

The parallels between particle induced lung overload and particle induced periprosthetic osteolysis (PPOL)

Background: When particles deposit for instance in the lung after inhalation or in the hip joint after local release from a hip implant material they can initiate a defense response. Even though these particles originate from inert materials such as polyethylene (PE) or titanium, they may cause harm when reaching high local doses and overwhelming local defense mechanisms. Main body: This paper describes the parallels between adverse outcome pathways (AOP) and particle properties in lung overload and periprosthetic osteolysis (PPOL). It is noted that in both outcomes in different organs , the macrophage and cytokine orchestrated persistent inflammation is the common driver of events, in the bone leading to loss of bone density and structure, and in the lung leading to fibrosis and cancer. Most evidence on lung overload and its AOP is derived from chronic inhalation studies in rats, and the relevance to man is questioned. In PPOL, the paradigms and metrics are based on human clinical data, with additional insights generated from in vitro and animal studies. In both organ pathologies the total volume of particle deposition has been used to set threshold values for the onset of pathological alterations. The estimated clinical threshold for PPOL of 130 mg/ml is much higher than the amount to cause lung overload in the rat (10 mg/ml),although the threshold in PPOL is not necessarily synonymous to particle overload. Conclusions: The paradigms developed in two very different areas of particle response in the human body have major similarities in their AOP. Connecting the clinical evidence in PPOL to lung overload challenges relevance of rat inhalation studies to the human lung cancer hazard. .

Normal range of motion at the hip show different pressure behavior in the lateral and acetabular compartments: a cadaveric investigation

Purpose

The techniques used previously to assess intracapsular pressures did not allow the assessment of pressure variations in both compartments throughout the entire range of motion without puncturing the capsular tissue. Our hypothesis was that the intra-capsular pressure would be different in the lateral and acetabular compartment depending on the movement assessed.

Methods

Eight hip joints from four cadaveric specimens (78.5 ± 7.9 years) were assessed using intra-osseous tunnels reaching the lateral and acetabular compartments. Using injector adaptors, 2.7 ml of liquid were inserted in both compartments to simulate synovial liquid. Optic pressure transducers were used to measure pressure variations. We manually performed hip adduction, abduction, extension, flexion and internal rotation at 90° of flexion.

Results

Hip extension and internal rotation show the highest intra-capsular pressures in the lateral compartment with increases of 20.56 ± 19.29 and 19.27 ± 18.96 mmHg, respectively. Hip abduction and hip internal rotation showed depressurisations of − 16.86 ± 18.01 and − 31.88 ± 30.71 mmHg in the acetabular compartment, respectively. The pressures measured in the lateral compartment and in the acetabular compartment were significantly (P < 0.05) different for the hip abduction, 90° of flexion and internal rotation. Pressure variations showed that maximum intracapsular fluid pressures in the lateral compartment occur at maximum range of motion for all movements.

Conclusion

As an increase in pressure may produce hip pain, clinician should assess pain at maximum range of motion in the lateral compartment. The pressure measured in the acetabular compartment vary depending on the hip position. The movements assessed are used in clinical practice to evaluate hip integrity and might bring pain. The pressure variations throughout the entire range of motion are a relevant information during hip clinical assessment and might help clinicians to better understand the manifestations of pain.

Intracapsular pressures in the flexion-abduction-external rotation and flexion-adduction-internal rotation tests and their comparison with classic hip range of motion: A cadaveric assessment

Background Flexion-Abduction-External-Rotation and Flexion-Adduction-Internal-Rotation tests are used to reproduce pain at the hip during clinical assessment. As pain can be elicited by high intracapsular pressure, no information has been provided regarding intracapsular pressure during these pain provocative tests. Methods Eight hip joints from four cadaveric specimens (78.5 ± 7.9 years) were assessed using intra-osseous tunnels reaching the lateral and acetabular compartments. To simulate synovial liquid, 2.7 ml of liquid were inserted in both compartments using adaptor injectors. Optic pressure transducers were used to measure pressure variations. Pressures were compared between compartments in each test and between tests for each compartment. Both tests were compared with uniplanar movements. Findings The Flexion-Adduction-Internal-Rotation test showed a significant difference between pressure measured in the lateral (27.17 ± 42.63 mmHg) and acetabular compartment (-26.80 ± 29.26 mmHg) (P < 0.006). The pressure measured in the lateral compartment during the Flexion-Adduction-Internal-Rotation test (27.17 ± 42.63 mmHg) was significantly higher than in the Flexion-Abduction-External-Rotation test (-8.09 ± 15.09 mmHg) (P < 0.010). The pressure measured in the lateral compartment in the Flexion-Abduction-External-Rotation test was significantly lower than during internal rotation (P = 0.011) and extension (P = 0.006). Interpretation High intracapsular pressure is correlated with greater pain at the hip. Clinicians should assess pain with caution during the Flexion-Adduction-Internal-Rotation test as this test showed high intracapsular pressures in the lateral compartment. The Flexion-Abduction-External-Rotation is not influenced by high intra-capsular pressures.

The wettability of electron spun membranes by synovial fluid

Aseptic loosening due to periprosthetic osteolysis has been accepted as one of the leading causes of revision procedures in patients with previous joint arthroplasty. Recently, several strategies for suppression of osteolysis were proposed, mostly based on biological treatment such as mitigation of chronic inflammatory reactions. However, these biological treatments do not stop the debris migration but only reduce the inflammatory reaction. To address this shortcoming, we propose the concept of ultrahigh molecular weighted polyethylene particles filtration storage by electrospun membranes. Firstly, the surface tension of synovial fluid (SF) is obtained by use of a pendant droplet. Secondly, the contact angle of the electrospun membranes wetted by two different liquids is measured to obtain the free surface energy using of the Owens-Wendt model. Additionally, the wettability of electrospun membranes by SF as a function of technology parameters is studied.

Automatic Assessment Of Hip Effusion From MRI

Joint effusion is a hallmark of osteoarthritis (OA) associated with stiffness, and may relate to pain, disability, and long-term outcomes. However, it is difficult to quantify accurately. We propose a new Deep Learning (DL) approach for automatic effusion assessment from Magnetic Resonance Imaging (MRI) using volumetric quantification measures (VQM). We developed a new multiplane ensemble convolutional neural network (CNN) approach for 1) localizing bony anatomy and 2) detecting effusion regions. CNNs were trained on femoral head and effusion regions manually segmented from 3856 images (63 patients). Upon validation on a non-overlapping set of 2040 images (34 patients) DL showed high agreement with ground-truth in terms of Dice score (0.85), sensitivity (0.86) and precision (0.83). Agreement of VQM per-patient was high for DL vs experts in term of Intraclass correlation coefficient (ICC)= 0.88[0.80,0.93]. We expect this technique to reduce inter-observer variability in effusion assessment, reducing expert time and potentially improving the quality of OA care.Clinical Relevance- Our technique for automatic assessment of hip MRI can be used for volumetric measurement of effusion. We expect this to reduce variability in OA biomarker assessment and provide more reliable indicators for disease progression.

Development of a technique for MRI gold-standard direct volumetric measurement of complex joint effusion, and validation at the hip

OBJECTIVE

Accurate joint fluid quantification on MRI cannot simply rely on measuring the maximum fluid depth or using an ellipsoid approximation as this does not fully characterize the complex shape of a fluid-filled joint. As per the Outcome Measurement in Rheumatology (OMERACT) filter, we sought to evaluate the feasibility, reliability, and validity of a semi-automated supervised technique to quantify hip effusion volume.

MATERIALS AND METHODS

Ninety-three hip osteoarthritis patients were imaged with coronal short TI inversion recovery (STIR) and sagittal intermediate weighted fat-suppressed (IWFS) sequences at two time points (Fig. 1). Volumetric quantitative measurement (VQM) of joint fluid and measurement of the largest femoral neck fluid thickness (FTM) was performed using the custom MATLAB software. Self-reported Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and clinical measures of pain, stiffness, and function were recorded.

RESULTS

Inter-observer reliability was significantly higher for VQM than FTM (ICC = 0.96 vs. 0.85, p < 0.05). VQM and FTM correlated moderately (r = 0.76, p < 0.0001). There was significantly more articular fluid in symptomatic than asymptomatic hips at baseline (mean = 9.8 vs. 5.9 mL). Volumetric quantitative measurement generally displayed more frequent and stronger correlations to clinical parameters than FTM. Volumetric quantitative measurement required 3.9 min/hip vs. < 1 min/hip for femoral neck fluid thickness.

CONCLUSION

Volumetric quantitative measurement of joint effusion can serve as an MRI gold-standard, could apply to other joints and collections, and is highly suited to future automation.

Normal hip joint fluid volumes in healthy children of different ages, based on MRI volumetric quantitative measurement

BACKGROUND

While magnetic resonance imaging (MRI) of the pelvis and hips is common in pediatric patients, to date there are no data on the quantification of normal hip joint fluid volume in this patient population.

OBJECTIVE

We sought to assess the feasibility and reliability of quantitative hip joint fluid measurement in the pediatric population to estimate the normal volume of fluid in a pediatric hip joint.

MATERIALS AND METHODS

Seventy healthy children ages 8-17 years underwent a pelvic MRI including a large field of view coronal T2 fat-saturated sequence where hips were entirely imaged. Following 3 training sessions, 2 readers with experience in musculoskeletal imaging performed volumetric quantitative measurements of hip fluid (140 hips) using semiautomated pixel-based thresholding on custom MATLAB software.

RESULTS

The mean processing time per hip was 2 min, 41 s. The mean volume of fluid in a hip joint was 2.1 mL (range: 0.38-5.41 mL), increasing slightly with age. Volumes were also greater in boys than in girls (P=0.004). Intra-observer and interobserver agreement were high (intra-class correlation coefficients 0.93 and 0.98, respectively), with mean volume differences of 0.04 mL for intra-observer and 0.09 mL for interobserver.

CONCLUSION

A semiautomated pixel-based thresholding approach was feasible and reliable for measuring joint fluid in pediatric hip MRI. The average fluid volume of 2.1 mL can represent a visually substantial quantity of fluid per MRI slice, particularly in small children, and should not be misinterpreted as a joint effusion.

Comparison of the effectiveness of high resolution ultrasound with MRI in patients with temporomandibular joint dısorders

OBJECTIVES

To assess the effectiveness of a high resolution ultrasound for temporomandibular joint (TMJ) evaluation in comparison to MRI in patients with TMJ disorders.

METHODS

Our study comprised 50 patients (35 female and 15 male) with a mean age of 30.61. Clinical examination was performed. Bilateral imaging of TMJ was conducted by using a high-resolution ultrasound and 1.5 Tesla MR. Diagnostic accuracy of ultrasound was assessed for disc displacement and joint effusion in comparison to MRI. Sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), and accuracy (Ac) were calculated for ultrasound. Measurements were compared by Bland & Altman and intraclass correlation coefficient (ICC). Significance level was set at p < 0.05.

RESULTS

Most frequent complaints were noise 42 (84%) and 34 (68%) pain. For disc position assessment with ultrasound for both sides and closed-open mouth, sensitivity, specificity, PPV, NPV and accuracy ranged between, 0.88 - 1, 0.60 - 0.87, 0.70 - 0.97, 0.75 - 1, and 0.84 - 0.98, respectively. For the diagnosis of effusion with ultrasound for both sides, sensitivity, specificity, PPV, NPV and accuracy ranged between 0.65 - 0.81, 0.91 - 1, 0.96 - 1, 0.45 - 0.46 and 0.72 - 0.84, respectively. ICC values calculated for intraobserver agreement for right and left TMJ for all measurements were found to be statistically significant (p < 0.001). ICC values ranged between 0.964 and 0.995 suggesting excellent correlation among ultrasound and MRI. In general, for ultrasound measurements we found a mean difference ranging between -0.182 and +0.130 mm in comparison to MRI.

CONCLUSION

Ultrasound can be suggested as an adjunct to common imaging modalities in the assessment of TMJ.

Aseptic lymphocyte-dominated vasculitis-associated lesions are related to changes in metal ion handling in the joint capsules of metal-on-metal hip arthroplasties

Objectives

We have encountered patients who developed large joint fluid collections with massive elevations in chromium (Cr) and cobalt (Co) concentrations following metal-on-metal (MoM) hip arthroplasties. In some cases, retrieval analysis determined that these ion concentrations could not be explained simply by the wear rates of the components. We hypothesized that these effects may be associated with aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL).

Patients and Methods

We examined the influence of the ALVAL grade on synovial fluid Co and Cr concentrations following adjustment for patient and device variables, including volumetric wear rates. Initially restricting the analysis to include only patients with one MoM hip resurfacing device, we performed multiple regression analyses of prospectively collected data. We then repeated the same statistical approach using results from a larger cohort with different MoM designs, including total hip arthroplasties.

Results

In the resurfacing cohort (n = 76), the statistical modelling indicated that the presence of severe ALVAL and a large fluid collection were associated with greater joint fluid Co concentrations after adjustment for volumetric wear rates (p = 0.005). These findings were replicated in the mixed implant group (n = 178), where the presence of severe ALVAL and a large fluid collection were significantly associated with greater fluid Co concentrations (p < 0.001).

Conclusion

The development of severe ALVAL is associated with elevations in metal ion concentrations far beyond those expected from the volumetric loss from the prosthetic surfaces. This finding may aid the understanding of the sequence of events leading to soft-tissue reactions following MoM hip arthroplasties.

Cite this article: D. J. Langton, R. P. Sidaginamale, T. J. Joyce, J. G. Bowsher, J. P. Holland, D. Deehan, A. V. F. Nargol, S. Natu. Aseptic lymphocyte-dominated vasculitis-associated lesions are related to changes in metal ion handling in the joint capsules of metal-on-metal hip arthroplasties. Bone Joint Res 2018;7:388–396. DOI: 10.1302/2046-3758.76.BJR-2018-0037.

Musculoskeletal ultrasound for intra-articular bleed detection: a highly sensitive imaging modality compared with conventional magnetic resonance imaging

Essentials The best imaging modality for joint blood detection in hemophilia is unknown. Blood appearance and detection thresholds were studied with ultrasound and conventional MRI. Ultrasound is sensitive to low volume and concentration of blood, whereas conventional MRI is not. The findings establish the validity of ultrasound for rapid bleed detection in hemophilia care.

SUMMARY

Background There is increasing demand for musculoskeletal ultrasound (MSKUS) to detect hemophilic joint bleeding, but there is uncertainty regarding blood detection concentration thresholds or if magnetic resonance imaging (MRI) is more accurate. Aims Compare the sensitivity of blood detection by MSKUS and MRI. Methods Increasing blood concentrations in plasma were imaged with MSKUS and MRI 1-2 h, 3-4 days and 7 days after blood withdrawal in vitro, and after injection into cadaveric pig joints. Additionally, effusions in the joints of two patients with hemophilia joints were imaged, followed by aspiration. MSKUS was performed using an 8-18-MHz linear transducer; MRI was performed at 3T using T1-weighted and T2-weighted fat-suppressed sequences. Images were reviewed by a hematologist certified in MSKUS and a musculoskeletal radiologist. Results MSKUS permitted the detection of blood in vitro and in pig joint spaces at concentrations as low as 5%, demonstrated by the presence of echogenic signals that were absent with plasma alone. In contrast, no differences between fluids were discernible on the T1-weighted or T2-weighted MRI images. Results were confirmed in the two patients with hemophilia. Blood clots demonstrated varying and dynamic echogenicity patterns over time and, using MRI, were visualized best with T2 sequences. Conclusion MSKUS is extremely sensitive in detecting low concentrations of intra-articular blood and in discriminating between bloody and non-bloody fluid, whereas conventional MRI is not. These observations demonstrate the advantages of MSKUS over MRI in detecting intra-articular blood, and show that MSKUS is ideal for rapid bleed detection in the clinic.

Success of ultrasound-guided versus landmark-guided arthrocentesis of hip, ankle, and wrist in a cadaver model

PURPOSE

The objectives of this study were to evaluate emergency medicine resident-performed ultrasound for diagnosis of effusions, compare the success of a landmark-guided (LM) approach with an ultrasound-guided (US) technique for hip, ankle and wrist arthrocentesis, and compare change in provider confidence with LM and US arthrocentesis.

METHODS

After a brief video on LM and US arthrocentesis, residents were asked to identify artificially created effusions in the hip, ankle and wrist in a cadaver model and to perform US and LM arthrocentesis of the effusions. Outcomes included success of joint aspiration, time to aspiration, and number of attempts. Residents were surveyed regarding their confidence in identifying effusions with ultrasound and performing LM and US arthrocentesis.

RESULTS

Eighteen residents completed the study. Sensitivity of ultrasound for detecting joint effusion was 86% and specificity was 90%. Residents were successful with ultrasound in 96% of attempts and with landmark 89% of attempts (p=0.257). Median number of attempts was 1 with ultrasound and 2 with landmarks (p=0.12). Median time to success with ultrasound was 38s and 51s with landmarks (p=0.23). After the session, confidence in both US and LM arthrocentesis improved significantly, however the post intervention confidence in US arthrocentesis was higher than LM (4.3 vs. 3.8, p<0.001).

CONCLUSIONS

EM residents were able to successfully identify joint effusions with ultrasound, however we were unable to detect significant differences in actual procedural success between the two modalities. Further studies are needed to define the role of ultrasound for arthrocentesis in the emergency department.

Measurement outcomes from hip simulators

Simulation of wear in total hip replacements has been recognised as an important factor in determining the likelihood of clinical success. However, accurate measurement of wear can be problematic with factors such as number and morphology of wear particles produced as well as ion release proving more important in the biological response to hip replacements than wear volume or wear rate alone. In this study, hard-on-hard (CoCr alloy, AgCrN coating) and hard-on-soft (CoCr alloy and CrN coating on vitamin E blended highly cross-linked polyethylene) bearing combinations were tested in an orbital hip simulator under standard and some adverse conditions. Gravimetric wear rates were determined for all bearings, with cobalt and where applicable, silver release determined throughout testing. Isolation of wear particles from the lubricating fluid was used to determine the influence of different bearing combinations and wear conditions on particle morphology. It was found that cobalt and silver could be measured in the lubricating fluid even when volumetric wear was not detectable. In hard-on-hard bearings, Pearson’s correlation of 0.98 was established between metal release into the lubricating fluid and wear volume. In hard-on-soft bearings, coating the head did not influence the polyethylene wear rates measured under standard conditions but did influence the cobalt release; the diameter influenced both polyethylene wear and cobalt release, and the introduction of adverse testing generated smaller polyethylene particles. While hip simulators can be useful to assess the wear performance of a new material or design, measurement of other outcomes may yield greater insight into the clinical behaviour of the bearings in vivo.

Dissolution behaviour of silicon nitride coatings for joint replacements

In this study, the dissolution rate of SiNx coatings was investigated as a function of coating composition, in comparison to a cobalt chromium molybdenum alloy (CoCrMo) reference. SiNx coatings with N/Si ratios of 0.3, 0.8 and 1.1 were investigated. Electrochemical measurements were complemented with solution (inductively coupled plasma techniques) and surface analysis (vertical scanning interferometry and x-ray photoelectron spectroscopy). The dissolution rate of the SiNx coatings was evaluated to 0.2-1.4 nm/day, with a trend of lower dissolution rate with higher N/Si atomic ratio in the coating. The dissolution rates of the coatings were similar to or lower than that of CoCrMo (0.7-1.2 nm/day). The highest nitrogen containing coating showed mainly Si-N bonds in the bulk as well as at the surface and in the dissolution area. The lower nitrogen containing coatings showed Si-N and/or Si-Si bonds in the bulk and an increased formation of Si-O bonds at the surface as well as in the dissolution area. The SiNx coatings reduced the metal ion release from the substrate. The possibility to tune the dissolution rate and the ability to prevent release of metal ions encourage further studies on SiNx coatings for joint replacements.

The lubrication performance of the ceramic-on-ceramic hip implant under starved conditions

Lubrication plays an important role in the clinical performance of the ceramic-on-ceramic (CoC) hip implant in terms of reducing wear and avoiding squeaking. All the previous lubrication analyses of CoC hip implants assumed that synovial fluid was sufficiently supplied to the contact area. The aim of this study was to investigate the lubrication performance of the CoC hip implant under starved conditions. A starved lubrication model was presented for the CoC hip implant. The model was solved using multi-grid techniques. Results showed that the fluid film thickness of the CoC hip implant was affected by fluid supply conditions: with the increase in the supplied fluid layer, the lubrication film thickness approached to that of the fully blooded solution; when the available fluid layer reduced to some level, the fluid film thickness considerably decreased with the supplying condition. The above finding provides new insights into the lubrication performance of hip implants.

Sonographic evaluation of hip joint effusion in osteoarthritis with correlation to radiographic findings

PURPOSE

Hip joint effusion is expected in rapidly destructive osteoarthritis, a diagnosis often only made retrospectively at the end stage of the disease. This study assesses whether the presence of an effusion identified during routine ultrasound-guided hip injection may suggest a more aggressive process such as rapidly destructive osteoarthritis.

METHODS

After the observation of 10 index cases of rapidly destructive osteoarthritis in patients who presented with a joint effusion on ultrasound, we retrospectively reviewed 94 hips from 89 patients who underwent ultrasound-guided hip injection for pain. Preinjection longitudinal ultrasound images of the anterior capsule adjacent to the femoral neck and inferior to the femoral head were reviewed to determine if a joint effusion was present and the size of the effusion if one was there. Comparison of effusion size was then made between those hips that had a clinical and radiographic diagnosis of osteoarthritis and those who had rapidly destructive osteoarthritis by comparing the severity of joint effusion, if one was present.

RESULTS

Patients with rapidly destructive osteoarthritis were more likely to have a large joint effusion 60% (3/5) than were those with osteoarthritis 6.7% (6/89) (p = 0.013).

CONCLUSIONS

Large joint effusions identified sonographically correlate well with radiographic findings of rapidly destructive osteoarthritis. Given rapid onset and severity of the disease, when a large joint effusion is identified on routine hip intervention, patients should be forewarned of the potential for this disease process.

Septic arthritis of the neonatal hip: acute management and late reconstruction

Septic arthritis of the hip in neonates is rare but can have devastating consequences. Presenting signs and symptoms may differ from those encountered in older children, which may result in diagnostic challenge or delay. Many risk factors predispose neonates to septic arthritis, including the presence of transphyseal vessels and invasive procedures. Bacterial infection of the joint occurs via hematogenous invasion, extension from an adjacent site, or direct inoculation. A strong correlation exists between younger age at presentation and severity of residual hip deformity. Diagnosis is based on clinical examination, laboratory markers, and ultrasound evaluation. Early management includes parenteral antibiotics and surgical drainage. Late-stage management options include femoral and pelvic osteotomies, trochanteric arthroplasty, arthrodesis, pelvic support procedures, and nonsurgical measures. Early diagnosis and management continues to be the most important prognostic factor for a favorable outcome in the neonate with septic arthritis.

High-tech hip implant for wireless temperature measurements in vivo

When walking long distances, hip prostheses heat up due to friction. The influence of articulating materials and lubricating properties of synovia on the final temperatures, as well as any potential biological consequences, are unknown. Such knowledge is essential for optimizing implant materials, identifying patients who are possibly at risk of implant loosening, and proving the concepts of current joint simulators. An instrumented hip implant with telemetric data transfer was developed to measure the implant temperatures in vivo. A clinical study with 100 patients is planned to measure the implant temperatures for different combinations of head and cup materials during walking. This study will answer the question of whether patients with synovia with poor lubricating properties may be at risk for thermally induced bone necrosis and subsequent implant failure. The study will also deliver the different friction properties of various implant materials and prove the significance of wear simulator tests. A clinically successful titanium hip endoprosthesis was modified to house the electronics inside its hollow neck. The electronics are powered by an external induction coil fixed around the joint. A temperature sensor inside the implant triggers a timer circuit, which produces an inductive pulse train with temperature-dependent intervals. This signal is detected by a giant magnetoresistive sensor fixed near the external energy coil. The implant temperature is measured with an accuracy of 0.1°C in a range between 20°C and 58°C and at a sampling rate of 2-10 Hz. This rate could be considerably increased for measuring other data, such as implant strain or vibration. The employed technique of transmitting data from inside of a closed titanium implant by low frequency magnetic pulses eliminates the need to use an electrical feedthrough and an antenna outside of the implant. It enables the design of mechanically safe and simple instrumented implants.

Influence of Co-Cr particles and Co-Cr ions on the growth of staphylococcal biofilms

PURPOSE

In the last decades, hip prostheses with a metal-on-metal (MOM) bearing have been implanted by orthopedic surgeons worldwide. However, concerns are now raised towards the metal particles and degradation products released by MOM-bearings into surrounding tissue, although effects of Co-Cr wear on infection are also unknown. Therefore, we here determine the viable volumes of staphylococcal biofilms formed on polystyrene in the absence and presence of Co-Cr particles and Co-Cr ions.

METHODS

Three clinically derived and two commercially available staphylococcal strains were grown in the presence of 2 mg/mL Co-Cr particles or 1000/500 µg/L Co-Cr ions derived from Co-Cr salts or from particle supernatant, under static and dynamic growth conditions. A dynamic model simulates the conditions that apply for biofilm formation in the human body, as synovial fluid in mobile patients with hip prostheses is in constant motion with accompanying shear rates. Images of 24 h old biofilms were made with confocal laser scanning microscopy and analyzed with the mathematical computer program COMSTAT, yielding the biovolume of a biofilm. X-ray photoelectron spectroscopy was performed on the particles to study their elemental surface composition.

RESULTS

Most isolates showed a tendency of reduced biofilm growth in the presence of Co-Cr particles compared to growth during exposure to metal ions, but this was only significant in one strain under the dynamic growth condition (Staphylococcus aureus 7388). Characterization of the outer surface of the particles revealed a Co-Cr oxide layer enriched by Mo relative to the bulk concentration.

CONCLUSIONS

MOM bearings produce metal particles which were found to possess antibacterial characteristics under dynamic growth conditions. Further research is needed towards the clinical relevance of this finding.

Ultrasonographic evaluation of knee joints in patients with Lyme disease

OBJECTIVE

The aim of this study was to evaluate the ultrasonographic images of patients with chronic knee pain and serologic features of Lyme disease.

METHODS

Seventy-six patients hospitalized in The Department of Infectious Diseases and Neuroinfections of the Medical University in Białystok, Poland were included in the study. Patients were divided into two groups: (1) the Lyme disease group included patients with pain in one or both knees and anti-Borrelia burgdorferi antibodies with symptoms lasting for over 6 months; (2) the control group included patients suffering from pain in one or both knees for over 6 months, but for whom B. burgdorferi infection was excluded.

RESULTS

The most frequent ultrasonographic finding in the Lyme disease group was effusion, and its frequency was significantly higher than in the control group. No patient in the control group presented with synovitis or cartilage damage, while these were quite frequent findings in the Lyme disease group. Baker's cysts were more frequent in the Lyme disease group, but this was statistically non-significant.

CONCLUSIONS

Ultrasonography may be useful in following the sequelae of Lyme disease. The abnormalities found in Lyme disease patients are non-specific and ultrasonography is not useful in the differential diagnosis.

Fully automated system for the quantification of human osteoarthritic knee joint effusion volume using magnetic resonance imaging

INTRODUCTION

Joint effusion is frequently associated with osteoarthritis (OA) flare-up and is an important marker of therapeutic response. This study aimed at developing and validating a fully automated system based on magnetic resonance imaging (MRI) for the quantification of joint effusion volume in knee OA patients.

METHODS

MRI examinations consisted of two axial sequences: a T2-weighted true fast imaging with steady-state precession and a T1-weighted gradient echo. An automated joint effusion volume quantification system using MRI was developed and validated (a) with calibrated phantoms (cylinder and sphere) and effusion from knee OA patients; (b) with assessment by manual quantification; and (c) by direct aspiration. Twenty-five knee OA patients with joint effusion were included in the study.

RESULTS

The automated joint effusion volume quantification was developed as a four stage sequencing process: bone segmentation, filtering of unrelated structures, segmentation of joint effusion, and subvoxel volume calculation. Validation experiments revealed excellent coefficients of variation with the calibrated cylinder (1.4%) and sphere (0.8%) phantoms. Comparison of the OA knee joint effusion volume assessed by the developed automated system and by manual quantification was also excellent (r = 0.98; P < 0.0001), as was the comparison with direct aspiration (r = 0.88; P = 0.0008).

CONCLUSIONS

The newly developed fully automated MRI-based system provided precise quantification of OA knee joint effusion volume with excellent correlation with data from phantoms, a manual system, and joint aspiration. Such an automated system will be instrumental in improving the reproducibility/reliability of the evaluation of this marker in clinical application.

Ultrasonography of the temporomandibular joint: a literature review

This review summarizes knowledge on the accuracy and clinical usefulness of ultrasonography (US) for the diagnosis of temporomandibular joint (TMJ) disorders. A systematic search in the National Library of Medicine's Database was performed to identify all peer-reviewed papers in the English literature that assessed the accuracy of US with respect to magnetic resonance (MR), computerized tomography (CT), clinical assessment or autopsy specimens for the diagnosis of TMJ disk displacement, effusion and osteoarthrosis. The combined search words "ultrasonography" and "temporomandibular joint", "temporomandibular disorders", "effusion", "disk displacement", "condyle", yielded 20 papers. Most studies (N=17) focused on detecting disk displacement, with less emphasis on assessing joint effusion (N=6) and osteoarthrosis (N=7). US accuracy was 54-100% for diagnosing disk displacement, 72-95% for joint effusion and 56-93% for osteoarthrosis. US is operator-dependent. Better standardization of the technique is required and normal parameters must be set. Standardization is also required for the taxonomic aspects of pathologies. Despite these limitations, US remains potentially useful as an alternative imaging technique for monitoring TMJ disorders, particularly the presence of intrarticular effusion.

Does running cause metatarsophalangeal joint effusions? A comparison of synovial fluid volumes on MRI in athletes before and after running

OBJECTIVE

The metatarsophalangeal joints (MTPJ) are the only joints that bear weight directly through synovium. The purpose of this study was to determine whether there is an association between synovial stresses during running and increases in volume of joint fluid.

MATERIALS AND METHODS

This was a prospective case controlled study (nine healthy athlete volunteers acting as own controls). High-resolution coronal 3D T2W magnetic resonance imaging of the MTPJs were obtained following 24 h rest and after a 30-min run. The volume of joint fluid in each MTPJ (n = 90) was measured by two independent observers using an automated propagating segmentation tool.

RESULTS

The median volume of synovial fluid in the MTPJs at rest was 0.018 ml (inter-quartile range (IQ) range 0.005-0.04) and after running 0.019 ml (IQ range 0.005-0.04, p = 0.34, 99% confidence interval (CI), 0.330.35). The volume of fluid in the MTPJs of the great toes was substantially larger than other toes (0.152 ml at rest, 0.154 ml after exercise, p = 0.903). Median volumes decrease from second to fifth MTPJs (0.032-0.007 ml at rest and 0.035-0.004 ml after exercise). Subset analysis for each toe revealed no significant difference in volumes before and after running (p = 0.39 to p = 0.9). The inter-rater reliability for observer measurements was good with an intra-class correlation of 0.70 (95% CI, 0.60 to 0.78).

CONCLUSION

It appears to be normal to find synovial fluid, particularly in the MTPJs of the great toes, of athletes at rest and after running. There does not appear to be an association between moderate distance running and an increase in the volume of synovial fluid.

Accuracy of sonographically guided intra-articular injections in the native adult hip

OBJECTIVE

The purpose of this study was to determine the accuracy of sonographically guided intra-articular injections performed in the native adult hip using contrast-enhanced fluoroscopy as a reference standard.

METHODS

Twenty-eight consecutive patients (ages 32-91 years; mean, 68 years) referred to the pain clinic for intra-articular hip injections were recruited to participate. In each case, a 2- to 6-MHz curvilinear array transducer was used to place the needle into the hip joint at the femoral head-neck junction using an oblique sagittal approach. A contrast-enhanced fluoroscopic examination was then completed and assessed by an independent observer to determine needle placement accuracy. Once accurate placement was confirmed, the therapeutic injection proceeded.

RESULTS

Thirty hip injections were completed in 15 women and 13 men (1 man and 1 woman received bilateral injections). The patients' body mass index (BMI) ranged from 20 to 39 kg/cm(2) (mean, 28 kg/cm(2)) and procedure time from initial scanning to injection averaged 112 seconds (range, 47-187 seconds). Overall, 97% of sonographically placed needles were accurate. The single inaccurate placement resulted from inadvertent needle withdrawal from the joint capsule during connection of the extension tubing for contrast agent injection in a young patient with a BMI of 28 kg/cm(2) and no hip effusion.

CONCLUSIONS

Sonographic guidance can be used to inject the native adult hip joint with acceptable accuracy. When using the oblique sagittal approach, operators must be aware of the possibility of needle withdrawal from the joint due to the limited intra-articular space within the target region, particularly in the absence of effusion.

Treatment of early septic arthritis of the hip in children: comparison of results of open arthrotomy versus arthroscopic drainage

PURPOSE

The goal of this study was to compare results of open arthrotomy versus arthroscopic drainage in treating septic arthritis of the hip in children.

METHODS

This prospective controlled study was conducted on twenty patients (20 hips) with acute septic arthritis of the hip. Diagnosis was suspected if there was: a history of fever, non-weight-bearing on the affected limb, erythrocyte sedimentation rate (ESR) of at least 40 mm/h, and white blood cell count of more than 12,000 cells per cubic millimeter. Diagnosis was established by ultrasonographic examination of the affected hip followed by ultrasound-guided aspiration of the joint. Patients were allocated to have either open arthrotomy or arthroscopic drainage of the joint. There were ten patients (ten hips) in each treatment group. The mean age of the patients was 7.3 years in the arthrotomy group, and 8 years in the arthroscopy group. The mean temperatures for the arthrotomy and arthroscopy groups were 38.8 and 38.7 degrees C, respectively. All the children were unable to bear weight on the affected limb.

RESULTS

Staphylococcus aureus was the most common causative microorganism in both groups. The mean duration of the children's hospital stay was 6.4 days in the arthrotomy group and 3.8 days in the arthroscopy group. The difference was highly significant. Infection could be eradicated in all patients of both groups. At the latest follow-up, seven children in the arthrotomy group (70%) had excellent results and three children (30%) had good results. In the arthroscopy group, nine children (90%) had excellent results and one child (10%) had good results. The difference was not statistically significant.

CONCLUSIONS

Arthroscopic drainage is an effective method in treating septic arthritis of the hip. It is a minimal invasive procedure which is associated with less hospital stay. Arthroscopic drainage of septic arthritis of the hip in children is a valid alternative procedure in early uncomplicated cases and for orthopedic surgeons skilled in pediatric arthroscopy.

MR arthrography of the shoulder, hip, and wrist: evaluation of contrast dynamics and image quality with increasing injection-to-imaging time

OBJECTIVE

The purpose of our study was to investigate the contrast dynamics and the relationship between visualization of intraarticular structures and time elapsed between intraarticular injection of contrast agent and MRI in symptomatic patients referred for MR arthrography of the shoulder, hip, and wrist.

SUBJECTS AND METHODS

Our local ethics committees and the national drug administration approved this multicentric study. We prospectively studied 11 shoulders, 11 hips, and 10 wrists. After the intraarticular gadolinium injection, patients underwent a baseline MR arthrography protocol (time point [TP] 1) and subsequent MRI at another four time points (TP 2-TP 5) up to 240 minutes. The course of contrast-to-noise ratio (CNR) over time was calculated. Three observers assessed the degree of visualization of different intraarticular structures and the overall image quality at each time point using a 3-point scale and a 5-point scale, respectively.

RESULTS

For all joints, CNR measurements showed peak CNR at TP 1 (21 minutes) and TP 2 (45 minutes) with a subsequent, near-logarithmic decline of CNR values over time. Visualization of different anatomic structures decreased over time. Overall image quality was insufficient for diagnostic purposes at TP 3 (96 minutes) in three (27%) of 11 shoulders and in three (27%) of 11 hips. In two (20%) of 10 wrists, image quality was insufficient at TP 2 (45 minutes).

CONCLUSION

For MR arthrography, the degree of visualization of intraarticular structures depends on the time elapsed between contrast injection and MRI. MR arthrography of the shoulder and hip should be performed within 90 minutes, and MR arthrography of the wrist should be performed within 45 minutes, after intraarticular injection.

Whole body MR imaging in ankylosing spondylitis: a descriptive pilot study in patients with suspected early and active confirmed ankylosing spondylitis

Background

Ankylosing spondylitis is a chronic inflammatory rheumatic disorder which usually begins in early adulthood. The diagnosis is often delayed by many years. MR imaging has become the preferred imaging method for detection of early inflammation of the axial skeleton in ankylosing spondylitis.

The goal of this study was to assess the frequency and distribution of abnormalities on whole body MR imaging in patients with suspected early ankylosing spondylitis and with active confirmed ankylosing spondylitis.

Methods

Ten patients with suspected early ankylosing spondylitis and ten patients with confirmed ankylosing spondylitis were enrolled. On an 18-channel MR system, coronal and sagittal T1 weighted and STIR sequences were acquired covering the entire spine, sacrum, anterior chest wall, shoulder girdle, and pelvis. The total examination time was 30 minutes.

Results

In both groups inflammatory lesions of the lower thoracic spine were frequent (number of patients with suspected early/confirmed ankylosing spondylitis: 7/9). In confirmed ankylosing spondylitis the upper thoracic spine (3/6) and the lumbar spine (4/8) were more commonly involved. The inferior iliac quadrant of the sacroiliac joints was frequently altered in both groups (8/8). The superior iliac (2/5), inferior sacral (6/10) and superior sacral (3/6) quadrants were more frequently affected in confirmed ankylosing spondylitis. Abnormalities of the manubriosternal joint (2/4), the sternoclavicular joints (1/2) and hip joint effusion (4/3) were also seen.

Conclusion

In both suspected early ankylosing spondylitis and confirmed ankylosing spondylitis, whole body MR examinations frequently demonstrate inflammatory lesions outside the sacroiliac joints. These lesions are similarly distributed but occur less frequently in suspected early compared to confirmed ankylosing spondylitis. Due to the small sample size in this pilot study these results need to be confirmed in larger studies with this emerging technique.

Clinical examination and ultrasound of self-reported snapping hip syndrome in elite ballet dancers

BACKGROUND

Although snapping hip syndrome is commonly reported in ballet dancers, the prevalence, impact, and underlying mechanism of this condition have not been formally studied within a cohort of dancers.

PURPOSE

To determine the prevalence, associated factors, and mechanisms of snapping hip and to investigate self-reported snapping with physical and ultrasound examination.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A snapping hip questionnaire was completed by 87 unselected elite ballet dancers at 2 institutions. Twenty-six of the dancers (50 hips) who were able to voluntarily snap their hips were selected from this group for further physical examination by 2 clinicians to determine whether there was a palpable snap, and each underwent an ultrasound examination of his or her hips.

RESULTS

Ninety-one percent of dancers reported snapping hip, of which most (80%) had bilateral symptoms. Fifty-eight percent had pain associated with the snap, and 7% had taken time off dance because of this condition. Sixty percent of the dancers could voluntarily snap their hip. One or more of 3 dance movements elicited the snapping in 81%. The clinicians could palpate 46 of the 50 self-reported snapping hips. Ultrasound showed a snapping iliopsoas tendon in 59% of the hips and the iliotibial band snapping in 4%. In one third of cases, ultrasound was not helpful in identifying the cause of the snapping.

CONCLUSION

Snapping hip is extremely common in ballet dancers. Some dancers have significant pain, yet many are asymptomatic. Self-reported snapping is likely to be palpable by the clinician. Iliotibial band snapping is evident by physical examination and ultrasound. Iliopsoas snapping was most common and required ultrasonic confirmation.

Ultrasound-guided hip arthrocentesis in the ED

In patients presenting with atraumatic joint pain and swelling, diagnosis is typically made by synovial fluid analysis. Management of an acute suspected hip joint arthritis can present a challenge to the emergency physician (EP). Hip joint effusions are somewhat more difficult to identify and aspirate than effusions in other joints that are commonly managed by EPs. Identification and aspiration of a hip joint effusion under ultrasound guidance is a well-established procedure in the fields of orthopedic surgery and interventional radiology. Here, we report 4 cases of ultrasound-guided hip arthrocentesis at the bedside by EPs; relevant technical details of the procedure are reviewed. These cases demonstrate the feasibility of ultrasound-guided hip arthrocentesis in the emergency department (ED) by EPs. With increasing availability of bedside ultrasound in the ED, suspected hip joint arthritis or infection may be evaluated and managed by the trained EP in a fashion similar to other joint arthritides.

Quantitative evaluation of the relaxivity effects of iodine on GD-DTPA enhanced MR arthrography

PURPOSE

To quantify the effect of iodine on the gadolinium (Gd) contrast-enhanced signal in MR arthrography.

MATERIALS AND METHODS

Saline solutions of Gd contrast agent (0-1 mmol/liter) were mixed with iodinated contrast agent (0-185 mmol/liter). The T1 and T2 relaxation constants of these solutions were measured at 1.5T. Different types of commonly used iodinated contrast agents as well as sodium iodide (NaI) solutions were also analyzed.

RESULTS

Iodine caused significant T2 shortening and some T1 shortening in Gd contrast solutions. Both contrast agents independently obeyed the standard relaxation relation, and their mixture obeyed a modified version of this relation. The side chains in various iodine molecules and their viscosities affected the relaxation properties differently. For various spin-echo (SE) sequences, the signal from synovial fluid containing different concentrations of the two contrast agents was calculated. The T2-weighted signal appeared to be most affected by the increase in iodine concentrations. In the absence of Gd contrast, all SE sequences showed an initial increase in signal from iodine contrast.

CONCLUSION

A generalized relation for the relaxivities of Gd contrast in the presence of iodine was established. The side chains of iodine contrast were found to alter the relaxivities of Gd contrast. Imaging with proton density (PD)-weighted SE with only iodine contrast agent was found to be feasible.

Ultrasound-guided Adult Hip Injections

PURPOSE

The authors believe that ultrasound as a primary method of image guidance for performing hip aspirations is underutilized, and the authors report their experience in performing ultrasound-guided hip injections in 358 patients, using a free-hand technique.

MATERIALS AND METHODS

A retrospective review of all adult ultrasound-guided hip injections performed at the authors' institution over a four-year period was performed.

RESULTS

Retrospective review of an ultrasound database revealed 358 adult hip aspirations/injections were performed at the authors' institution from October 2000-October 2004. All procedures were performed using a longitudinal, anterior approach and without the use of a needle guide. There were no reported cases of inadvertent vascular or femoral nerve puncture.

CONCLUSIONS

To the authors' knowledge, this is the largest reported series of sonographically-guided adult hip aspirations/injections without the use of a needle guide. The authors believe that ultrasound as a primary method of image guidance for performing hip aspirations is underutilized. The absence of radiation and relatively short procedure time of ultrasound-guided hip injections are favorable factors to both the authors' referring clinician population as well as the patients.

The role of ultrasound in the diagnosis and management of psoriatic arthritis

Psoriatic arthritis (PsA) presents many diagnostic, management and research challenges for rheumatologists who wish to obtain early diagnosis, differentiate synovitis and enthesitis, monitor disease activity accurately and objectively, prevent the development of structural damage, deliver local therapy accurately, and obtain PsA tissue for research purposes. Musculoskeletal ultrasound (MSUS) is widely used by European rheumatologists in their clinical practice to meet these challenges and has the potential to become the rheumatologist's stethoscope in Europe and North America. This paper examines the evidence that MSUS can improve clinical evaluation of patients with PsA for synovitis and enthesitis, that MSUS is more sensitive than plain radiography in detecting structural damage in joints, that MSUS can improve the success of joint aspiration and guide biopsy of PsA tissues. Recent exciting developments in the management of PsA are detailed including the role of power Doppler in the diagnosis of enthesitis in PsA, the role of MSUS in objective monitoring of disease activity, the evaluation of MSUS in the diagnosis of sacroiliitis, and the use of MSUS to guide therapeutic injection of the sacroiliac joints.

Reactive Carpal Synovitis: Initial Experience with MR Imaging

PURPOSE

To retrospectively evaluate the accuracy of various magnetic resonance (MR) imaging findings in the diagnosis of reactive carpal synovitis.

MATERIALS AND METHODS

Institutional review board approval was obtained, and the need for informed consent was waived. This study was compliant with the Health Insurance Portability and Accountability Act. Thirty-five consecutive patients (19 male and 16 female patients; age range, 13-57 years) who underwent arthroscopy and MR imaging within 4 weeks of surgery were evaluated by two reviewers for the following potential findings of synovitis: (a) distention of the pisotriquetral recess by fluid, (b) distention of the radial and/or prestyloid recess, (c) synovial enhancement (in patients who received contrast material), (d) amount of dorsal capsule distention, and (e) the location of bone marrow edema, if any. The chi2 and paired t tests were used to assess these findings in patients with and patients without arthroscopically proved synovitis. The sensitivity, specificity, positive and negative predictive values, and accuracy of these findings in the detection of synovitis were calculated.

RESULTS

Fluid in the pisotriquetral recess was seen in nine of the 14 patients with synovitis and five of the 21 patients without synovitis (P = .018). Distention of the radial and/or prestyloid recess was observed in six of the 14 patients with synovitis and two of the 21 patients without synovitis (P = .027). Among the 24 patients who received contrast material, synovial enhancement was seen in seven of eight patients with synovitis and three of 16 patients without synovitis (P = .002). The dorsal capsule measured 1-7 mm (mean, 3.07 mm) in the 14 patients with synovitis and 2-7 mm (mean, 3.76 mm) in the 21 patients without synovitis (P = .193). Although bone marrow edema was seen globally in similar frequencies (nine of 14 patients with synovitis, nine of 21 patients without synovitis), pisotriquetral bone marrow edema was seen only in patients with synovitis (two of nine patients).

CONCLUSION

Fluid in the pisotriquetral recess, enhancing synovium, and, less commonly, pisotriquetral bone marrow edema are MR imaging findings that may help in the diagnosis of reactive carpal synovitis.

Treatment of septic arthritis of the hip joint by repeated ultrasound-guided aspirations

Arthrotomy of the hip joint followed by a variable period of drainage or continuous irrigation and drainage is considered the accepted treatment of septic arthritis of the hip joint (SAHJ). The authors reviewed the results of a cohort of children with SAHJ with repeated aspirations of the hip joint. Thirty-four children diagnosed with SAHJ were treated with repeated aspirations of the hip joint. The aspirations were performed under ultrasound guidance and topical anesthesia or under sedation. After the aspiration the joint was irrigated using the same needle, and the procedure was repeated daily. Six of the patients were operated on and then treated with aspirations because of drain dislodgement or clogging. Twenty-eight of the patients were treated primarily with repeated aspirations. Four of those patients did not improve and underwent arthrotomies, and 24 were treated only by repeated aspirations and healed completely. The mean number of aspirations was 3.6 (range 3-5), and 75% of the patients resumed walking after 24 hours. The mean follow-up time was 7.4 years (range 3-18). No complications were seen. Repeated aspiration is a safe and efficacious method of treatment for SAHJ. This method of treatment is not associated with surgery and its complications and prevents scarring of the skin and the need for general anesthesia. Faster return to normal activity was noted in this series.

Standard reference values for musculoskeletal ultrasonography

OBJECTIVES

To determine standard reference values for musculoskeletal ultrasonography in healthy adults.

METHODS

Ultrasonography was performed on 204 shoulders, elbows, hands, hips, knees, and feet of 102 healthy volunteers (mean age 38.4 years; range 20-60; 54 women) with a linear probe (10-5 MHz; Esaote Technos MP). Diameters of tendons, bursae, cartilage, erosions, hypoechoic rims around tendons and at joints were measured with regard to established standard scans. Mean, minimum, and maximum values, as well as two standard deviations (2 SD) were determined. Mean values +/-2 SD were defined as standard reference values.

RESULTS

Hypoechoic rims were normally present in joints and tendon sheaths owing to physiological synovial fluid and/or cartilage. Similarly, fluid was found in the subdeltoid bursa in 173/204 (85%), at the long biceps tendon in 56 (27%), in the suprapatellar recess in 158 (77%), in the popliteal bursae in 32 (16%), and in the retrocalcaneal bursa in 49 (24%). Erosions of >1 mm were seen at the humeral head in 47 (23%). Values for important intervals were determined. The correlation between two investigators was 0.96 (0.78-0.99). The reliability of follow up investigations was 0.83 (0.52-0.99).

CONCLUSIONS

Fluid in bursae as well as hypoechoic rims within joints and around tendons are common findings in healthy people. This study defines standard reference values for musculoskeletal ultrasonography to prevent misinterpretation of normal fluid as an anatomical abnormality.

Ultrasound assessment of increased capsular width as a predictor of temporomandibular joint effusion

OBJECTIVES

The aim of this study was to evaluate whether an increased capsular width evidenced by ultrasound (US) could be an indirect marker of temporomandibular joint (TMJ) effusion.

METHODS

138 TMJs were evaluated by US and magnetic resonance imaging (MRI) by two blinded calibrated investigators. US measures of capsular width (in mm) and MRI diagnosis of TMJ effusion (presence/absence) were used to perform a receiver operating characteristic (ROC) curve analysis in order to assess the most accurate cut-off value of capsular width that was able to discriminate between joints with and without MRI effusion.

RESULTS

Diagnostic accuracy of US to detect MRI-depicted TMJ effusion was good (area under the ROC curve=0.817). US sensitivity was high for values below the cut-off value of 1.950 mm (true positive rate (TPR)=83.9%; false positive rate (FPR)=26.3%), while specificity was high for values above the cut-off value of 2.150 mm (TPR=71.0%; FPR=11.8%).

CONCLUSIONS

Analysis of ROC curve appears to reveal that the critical area is around the 2 mm value for TMJ capsular width. These findings need to be refined by further studies assessing the smallest detectable difference in capsular width, with attention to reliability of interobserver observations.

Obturator externus bursa: anatomic origin and MR imaging features of pathologic involvement

PURPOSE

To investigate the anatomy of the obturator externus bursa of the hip and describe the magnetic resonance (MR) imaging features of pathologic involvement.

MATERIALS AND METHODS

The authors dissected eight cadaver hemipelvises to assess for the presence of periarticular bursae of the hip and bursal communication with the fascial plane of the obturator externus muscle. In addition, 10 consecutive patients with obturator externus bursa enlargement were prospectively identified with MR imaging. A bursa was considered present when a fluid collection was seen extending along the obturator externus muscle, continuous with the posterior inferior hip joint. The direction, extent, contour, and thickness of the bursa and hip capsule were recorded. Surgical findings were available for eight of the 10 patients, with histopathologic correlation between the bursal lining and hip capsule.

RESULTS

At cadaveric dissection, one specimen showed a bursa communicating with and extending from the posteroinferior aspect of the hip joint deep to the obturator externus tendon. In all 10 patients, MR images showed a hip joint effusion with a continuous bursa extending medially and displacing the obturator externus inferiorly. At surgery, a bursa was seen displacing the obturator externus muscle inferiorly and originating from the posteroinferior aspect of the hip joint in all eight patients. Results of pathologic analysis confirmed disease identical to the primary hip abnormality in all eight patients.

CONCLUSION

The obturator externus bursa is a potential posteroinferior communication of the hip joint capsule, can be a site of disease spread from the hip joint, and can be accurately identified with MR imaging.

MR imaging of sports-related hip disorders

Hip arthroscopy is being used increasingly for the diagnosis and treatment of hip disorders. MR imaging performed with appropriate technical considerations may aid not only in preoperative planning but in the appropriate selection of patients, which tends to lead to better postoperative results. Although the painful hip is imaged most commonly by radiography, MR imaging is considered the next imaging test of choice for evaluation of most common hip abnormalities in athletes, including labral injuries, ligament injuries, osteochondral injuries, fractures, bursitis, and musculotendinous injuries. MR arthrography can be a particularly useful technique for dedicated assessment of hip joint internal derangements.

Rheology of joint fluid in total knee arthroplasty patients

While the properties of joint fluid may affect the tribology of joint replacement prostheses, the flow parameters of joint fluid have not yet been examined in the context of total knee arthroplasty (TKA). The objective of this study was to evaluate the flow properties of joint fluids in patients undergoing index TKA or revision TKA. We hypothesized that an alteration of the properties of joint fluid would result from TKA. The steady-shear viscosity and storage and loss moduli were evaluated in joint fluid from 35 arthritis patients undergoing TKA, 14 patients undergoing revision of a previous TKA, and two patients presenting with joint effusion after TKA. The same properties were also evaluated in two commercially available sodium hyaluronate preparations and bovine serum, which is used as a lubricant in joint simulators. The steady-shear viscosity varied over three orders of magnitude among samples obtained from patients undergoing TKA, spanning previously established "normal" and "diseased" ranges. Fluid obtained at index TKA was more likely to exhibit normal viscous properties than fluid obtained at revision TKA (p = 0.01). Other viscous parameters distinguished the two groups, but the difference did not reach statistical significance. Both groups exhibited degenerate flow properties when compared to synovial fluid from healthy individuals. Further examination of the connection between flow properties and the tribology of joint replacement prostheses is warranted.