Radiographic/MR Imaging Correlation of the Wrist

In this review article, the authors discuss the imaging features of the most common pathologic conditions of the wrist by putting the emphasis on radiographic and MR imaging correlations. A topographic approach based on the 3 functional columns of the wrist (radial, central, and ulnar) serves as a framework. The pathologic conditions are classified, based on the structures involved, as fractures, ligament injuries, arthropathies, bone abnormalities, and tendinopathies. The authors describe and evaluate classic radiographic signs and explain how they correlate with MR imaging. The advantages and limitations of each technique are thoroughly discussed as well as other imaging modalities.

Radiological identification and analysis of soft tissue musculoskeletal calcifications

Abstract

Musculoskeletal calcifications are frequent on radiographs and sometimes problematic. The goal of this article is to help radiologists to make the correct diagnosis when faced with an extraosseous musculoskeletal calcification. One should first differentiate a calcification from an ossification or a foreign body and then locate the calcification correctly. Each location has a specific short differential diagnosis, with minimal further investigation necessary. Intra-tendon calcifications are most frequently associated with hydroxyapatite deposition disease (HADD). In most cases, intra-articular calcifications are caused by calcium pyrophosphate dihydrate (CPPD) crystal deposition disease. Soft tissue calcification can be caused by secondary tumoural calcinosis from renal insufficiency, or collagen vascular diseases and by vascular calcifications, either arterial or venous (phlebolith).

Teaching Points

• Calcifications have to be differentiated form ossification and foreign body.

• A musculoskeletal MRI study must always be correlated with a radiograph.

• The clinical manifestations of calcifications may sometimes mimic septic arthritis or sarcoma.

• HADD and CPPD crystal deposition have a distinct appearance on radiograph.

• Calcinosis is more frequently caused by chronic renal failure and scleroderma.

A practical guide for planning pelvic bone percutaneous interventions (biopsy, tumour ablation and cementoplasty)

Percutaneous approaches for pelvic bone procedures (bone biopsies, tumour ablation and cementoplasty) are multiple and less well systematised than for the spine or extremities. Among the different imaging techniques that can be used for guidance, computed tomography (CT) scan is the modality of choice because of the complex pelvic anatomy. In specific cases, such as cementoplasty where real-time evaluation is a determinant, a combination of CT and fluoroscopy is highly recommended. The objective of this article is to propose a systematic approach for image-guided pelvic bone procedures, as well as to provide some technical tips. We illustrate the article with multiple examples, and diagrams of the approaches and important structures to avoid to perform these procedures safely.

TEACHING POINTS

• Pelvic bone procedures are safe to perform if anatomical landmarks are recognised. • The safest approach varies depending on the pelvic level. • CT is the modality of choice for guiding pelvic percutaneous procedures. • Fluoroscopy is recommended when real-time monitoring is mandatory. • MRI can also be used for guiding pelvic percutaneous procedures.

Phonomyography as a non-invasive continuous monitoring technique for muscle ischemia in an experimental model of acute compartment syndrome

BACKGROUND

In acute compartment syndrome (ACS), clinicians have difficulty diagnosing muscle ischemia provoked by increased intra-compartmental pressure in a timely and non-invasive manner. Phonomyography records the acoustic signal produced by muscle contraction. We hypothesize that alterations in muscle contraction caused by muscle ischemia can be detected with phonomyography, serving as a potential non-invasive technique in the detection of ACS.

METHODS

The left hind limb of 15 Sprague-Dawley rats was submitted to a reversible ischemic model of limb injury for 30min and 1, 2, 4, 6h (3 rats in each group). The right limb served as control. Phonomyography microphones were placed over the posterior calf of both limbs and the sciatic nerve was stimulated percutaneously at 10-min intervals to evaluate muscle contraction. Histopathological analysis of muscles and nerves biopsies was performed and correlation was made between duration of injury, phonomyography output and degree of muscle and nerve necrosis.

RESULTS

There was a statistically significant decrease in the phonomyography signal output in the ischemic limb that correlated with the duration of ischemia and histological findings of muscle and nerve necrosis. The phonomyography signal decrease and histological findings were respectively: 55.5% (n=15;p=0.005) with rare muscle and nerve necrosis at 30min, 65.6% (n=12;p=0.005) with 5-10% muscle necrosis at 1h, 68.4% (n=9;p=0.015) with 100% muscle necrosis and little nerve damage at 2h, 72.4% (n=6;p=0.028) with 100% muscle necrosis and severe nerve damage at 4h, and 92.8% (n=3;p=0.109) with 100% muscle necrosis and severe nerve degeneration at 6h.

CONCLUSION

Changes in phonomyography signal are observed in early ischemic injury prior to the onset of nerve or muscle necrosis. Therefore, phonomyography could serve as a non-invasive technique to detect early ischemic muscle changes in acute compartment syndrome.

CLINICAL RELEVANCE

The detection of abnormal muscle contraction in a timely fashion and non-invasive manner is of interest in clinical settings where the presence of ischemia is not easy to diagnose.

Ultrasound-Guided Cervical Facet Joint Injections: A Viable Substitution for Fluoroscopy-Guided Injections?

OBJECTIVES

To evaluate the feasibility of ultrasound (US)-guided cervical facet injections and to identify the potential obstacles to routine use of this technique.

METHODS

After Institutional Review Board approval, 4 cadavers were used in this study. Age, sex, body mass index, and neck circumference were recorded. A total of 40 facet injections were performed from C2-C3 to C6-C7 under US guidance with radiodense colored latex. Visibility of cervical tissues and the needle was graded as complete, partial, or null (no injection was performed in this case). Frontal and lateral radiographs were taken, followed by cadaveric dissection to assess contrast and the latex distribution, which were recorded as intra-articular (success), peri-articular (success), or absent (failure). A 2-tailed Fisher exact test and Pearson χ(2)test were used to evaluate difference between success and failure rates for qualitative variables.

RESULTS

Seventy-eight percent (31 of 40) of US-guided facet joint injections were successful. No statistically significant differences were found regarding body mass index, neck circumference, needle caliber, operators, and between left and right sides. All failures involved C2-C3 and C6-C7 levels, and this result was statistically significant (Pearson χ(2) = 20.645; P < .001).

CONCLUSIONS

Although US-guided cervical facet joint injections are feasible, substantial obstacles may prevent their routine use. The main obstacle is to effectively identify and target the correct cervical level in a prone position.

Assessment of femur geometrical parameters using EOS™ imaging technology in patients with atypical femur fractures; preliminary results

Atypical femur fractures (AFF) arise in the subtrochanteric and diaphyseal regions. Because of this unique distribution, we hypothesized that patients with AFF demonstrate specific geometrical variations of their lower limb whereby baseline tensile forces applied to the lateral cortex are higher and might favor the appearance of these rare stress fractures, when exposed to bisphosphonates. Using the low irradiation 2D-3D X-ray scanner EOS™ imaging technology we aimed to characterize and compare femur geometric parameters between women who sustained bisphosphonate-associated AFF and those who had experienced similar duration of exposure to bisphosphonates but did not sustain fractures. Conditional logistic regression models were constructed to estimate the association between selected geometric parameters and the occurrence of AFF. We identified 16 Caucasian women with AFF and recruited 16 ethnicity-, sex-, age-, height- and cumulative bisphosphonate exposure-matched controls from local osteoporosis clinics. Compared to controls, those with AFF had more lateral femur bowing (-3.2° SD [3.4] versus -0.8° SD [1.9] p=0.02). In regression analysis, lateral femur bowing was associated with the risk of AFF (aOR 1.54; 95% CI 1.04-2.28, p=0.03). Women who sustained a subtrochanteric AFF demonstrated a lesser femoral neck shaft angle (varus geometry) than those with a fracture at a diaphyseal site (121.9 [3.6]° versus 127.6 [7.2]°, p=0.07), whereas femur bowing was more prominent in those with a diaphyseal fracture compared to those with a subtrochanteric fracture (-4.3 [3.2]° versus -0.9 [2.7]°, p=0.07). Our analyses support that subjects with AFF exhibit femoral geometry parameters that result in higher tensile mechanical load on the lateral femur. This may play a critical role in the pathogenesis of AFF and requires further evaluation in a larger size population.

A practical guide for performing arthrography under fluoroscopic or ultrasound guidance

Abstract

We propose a practical approach for performing arthrography with fluoroscopic or ultrasound guidance. Different approaches to the principal joints of the upper limb (shoulder, elbow, wrist and fingers), lower limb (hip, knee, ankle and foot) as well as the facet joints of the spine are discussed and illustrated with numerous drawings. Whenever possible, we emphasise the concept of targeting articular recesses, which offers many advantages over traditional techniques aiming at the joint space.

Teaching Points

• Arthrography remains a foremost technique in musculoskeletal radiology

• Most joints can be successfully accessed by targeting the articular recess

• Targeting the recess offers several advantages over traditional approaches

• Ultrasound-guidance is now favoured over fluoroscopy and targeting the recess is equally applicable

Carpal angles as measured on CT and MRI: can we simply translate radiographic measurements?

OBJECTIVE

To determine the reliability of carpal angles measured on CT and MRI compared to radiography and assess if these measurements are interchangeable.

MATERIALS AND METHODS

Our institutional ethic research committee approved this study. For this retrospective study, two independent observers measured the scapholunate (SL), capitolunate (CL), radiolunate (RL), and radioscaphoid (RS) angles on 21 sets of exams, with each set including a radiograph, CT, and MRI of the same wrist. Inter- and intra-observer agreements were evaluated with the intraclass correlation coefficient (ICC). Linear mixed models and two-way contingency tables were used to determine if the angles measured on cross-sectional modalities were significantly different from those obtained on radiography.

RESULTS

Inter-observer agreement was strong (ICC >0.8) for all angles, except for the RL angle measured on MRI (ICC 0.68). Intra-observer agreement was also strong for all angles, except for the CL angle measured on CT (ICC 0.66). SL angles measured on CT and MRI were not statistically different from those measured on radiographs (p = 0.37 and 0.36, respectively), unlike CL, RL, and RS angles (p < 0.05). Accuracy between modalities varied between 76 and 86% for the SL angle and ranged between 43 and 76% for the other angles.

CONCLUSIONS

CL, RL, and RS angles showed large intermodality variability. Therefore, their measurements on CT or MRI could potentially lead to miscategorization. Conversely, our data showing no significant difference between modalities, SL angle could be measured on CT and MRI to assess wrist instability with a lower risk of error.