Faculty Bibliography

OBJECTIVE: We investigated the ability of sonography to reveal the polyethylene liner used in total knee arthroplasty with the hopes of establishing a possible relationship between the sonographic measurement of the actual thickness of the polyethylene liner and the estimated thickness based on conventional radiography. MATERIALS AND METHODS: Twenty-four consecutive patients who were referred for Doppler screening for deep venous thrombosis after total knee arthroplasty were evaluated. The polyethylene liner was identified on sonography, and three measurements were obtained from four locations: anteromedial joint line (just medial to the midline incision), along the medial joint line, anterolateral joint line (just lateral to the midline incision), and along the lateral joint line. These sonographic measurements were compared with radiographic measurements of the radiolucent polyethylene liner and with the manufacturers' stated size of the polyethylene liner. Linear regression analyses were then performed. RESULTS: The polyethylene liner is seen on sonography as a strong linear echogenic interface with posterior acoustic shadowing. Linear regression analyses showed a high correlation (r = 0.8) between the sonographic measurements and the radiographic measurements. A relatively poor correlation (r = 0.2) was noted between the manufacturers' stated size of the liner and the sonographic measurements. CONCLUSION: We found that the polyethylene liner used in total knee arthroplasty can be clearly identified during sonographic evaluation of the knee. We also found a high correlation between the longitudinal measurement of the polyethylene liner with the thickness of the radiolucent polyethylene as measured on conventional radiographs. We propose that sonography could potentially be a useful noninvasive imaging modality to screen for subtle cases of polyethylene wear.

Ultrasound is an established modality for the evaluation of neuromas, particularly Morton's neuromas. It has also had success in the assessment of amputation stump neuromas. While ultrasound localization for steroid injection has proven useful in the conservative treatment of Morton's neuromas, it has not yet been established as a localization technique for steroid injection to successfully treat amputation stump neuromas.

OBJECTIVE: The objective of our study was to review our experience using sonography to evaluate the rotator cuff after arthroplasty. Diagnostic reliability, with respect to surgical findings, as well as subjective assessment of the examinations, including the usefulness of applications such as extended field-of-view imaging, photopic imaging, and tissue harmonic imaging, were reviewed. CONCLUSION: We found sonography to be a useful method of imaging the rotator cuff after arthroplasty. Extended field-of-view imaging and tissue harmonic imaging aided in diagnosis by improving visualization of regional anatomic landmarks and increasing conspicuity of small tendon tears.

Ultrasound guidance is an accurate method for the delivery of therapeutic injections in the musculoskeletal system. The visualization of the needle in real time allows for reliable placement of the needle tip in the tendon sheath, bursa, or joint of interest. Both superficial and deep articulations and tendon sheaths can be targeted for diagnostic or therapeutic interventions. In addition, intratendinous calcifications, the plantar fascia, and interdigital (Morton's) neuromas can also be visualized and injected directly under real-time guidance. Performing percutaneous interventions with ultrasound ensures accurate needle tip placement and helps direct the needle away from other regional soft-tissue structures such as nearby neurovascular bundles.

Both chronic as well as acute foot and ankle pain are common indications for visits to general practitioners, rheumatologists, and orthopedic surgeons. The causes for foot and ankle pain are varied and can include osseous pathology (fractures), yet the far greater majority are secondary to soft-tissue injuries and inflammation. Regional corticosteroid injections, traditionally performed using anatomic landmarks, can be inaccurate and miss intended targets. The use of ultrasound for guidance for interventional radiologic procedures is well known, including guidance for vascular as well as visceral interventions. Using sonography to guide for interventions in the musculoskeletal system, specifically the foot and ankle, yields accurate placement of the needle tip and subsequent anesthetic/steroid injection as well as diagnostic aspiration of tendon sheaths, joint spaces, and bursae.

The radiographic diagnosis of calcium pyrophosphate dihydrate (CPPD) deposition disease is usually made by observing calcifications in the articular cartilage of large joints or, in the knee, noting calcification in the menisci. Sonography is useful in evaluating the patellofemoral joint, including the trochlear cartilage, which is often difficult to image adequately on conventional radiographs, as true tangential views of the patellofemoral joint may be difficult to obtain. We describe a case of sonographic detection of cartilage calcification in the trochlea of the knee which was radiographically occult.

Estimation of mean transit time, along with tissue blood volume, are important factors in determining soft tissue perfusion. Recently, power mode decorrelation techniques have been successfully used to estimate mean transit time of red blood cells or contrast material through a region-of-interest (ROI) both in laminar flow phantoms and in vivo. The previously described theory for power mode decorrelation derives from a phenomenological stochastic differential equation (Langevin equation) based on conservation of matter, relating the detected signal power to the measured rate of decorrelation. Given the experimental support for power mode decorrelation as a method to estimate mean transit time, it becomes important to determine the relationship between the phenomenological parameters that appear in the corresponding stochastic equation and system parameters, such as the transducer point response function. With this equation as a starting point, and using the fact that the pressure amplitude is a Gaussianly distributed random process, the following stochastic differential equation for the pressure amplitude p(t) is derived, a necessary first step in establishing the relationship between the measured decorrelation rate and system parameters (i.e., point response function): dp(t)/dt = -(v/2+2ik x v)p(t)+f(t), where v/2 represents the rate of decorrelation, 2k x v is the Doppler shift for an insonating wave vector k and particle velocity v.f(t) is a stationary, white noise Gaussian random process.

We have evaluated the utility of ultrasonographic guidance for intervention in the musculoskeletal system. All interventional musculoskeletal procedures using ultrasonographic guidance performed at our institution from July 1998 through November 1999 were reviewed. Examinations were performed using either a linear or curved phased array transducer, based on depth and local geometry. The choice of needle was likewise optimized for specific anatomic conditions. One hundred ninety-five procedures were performed on 167 patients from July 1998 through November 1999. Thirty-one procedures had magnetic resonance correlation within 6 months beforehand. Excluding large-joint aspirations and injections, we found that 180 of the procedures were more readily performed using ultrasonography than any other imaging modality. These included therapeutic injections into tendon sheaths (biceps, flexor digitorum longus, posterior tibial, and iliopsoas), Morton's neuromas, plantar fascia, wrist ganglia, and tarsal tunnel cysts; peritendinous hamstring injections; and synovial cyst and muscle biopsies. In all cases, the target of interest was identified easily with ultrasonography, and needle position was documented readily. Also in all cases, aspiration or medication delivery to the site of interest was observed during real time and was documented on postprocedure images of the area. No significant complications (e.g., bleeding, infection, and neurovascular compromise) were encountered during or immediately after any procedure. Ultrasonography is a readily available imaging modality useful for guiding interventional procedures in the musculoskeletal system. The ability to document exact needle placement in real time confirms accurate placement of therapeutic injections, fluid aspiration, and soft tissue biopsies.

OBJECTIVE. The objective of this study was to describe the sonographic appearance of tears of the distal biceps brachii tendon. CONCLUSION. Sonography can reveal complete and partial tears of the distal biceps tendon, thus providing an alternative technique to MR imaging.

OBJECTIVE: We assessed the usefulness of sonography in evaluating the glenoid labrum in cadaveric specimens using arthroscopy as a standard of reference. MATERIALS AND METHODS: Eighty labral quadrants in 20 cadaveric shoulders were examined by two musculoskeletal radiologists using 5- to 7-MHz linear and curvilinear transducers. Agreement was reached by consensus. After sonography, arthroscopy was performed by an experienced orthopedic surgeon. Each labral quadrant was classified at the time of sonography and arthroscopy as normal, degenerated, or torn. RESULTS: Concordance between sonography and arthroscopy was 86% (69/80 quadrants). In differentiating abnormal labrum (tear or degeneration) from normal labrum using sonography, sensitivity was 63%, specificity was 98%, positive predictive value was 94%, negative predictive value was 86%, and accuracy was 88%. In differentiating labral tears from other labral conditions (degeneration or normality), sensitivity was 67%, specificity was 99%, positive predictive value was 67%, negative predictive value was 99%, and accuracy was 98%. CONCLUSION: Sonography has a promising role in the evaluation of the glenoid labrum, particularly in excluding labral tears when the labra appear normal on sonography. Further studies are required using normal and symptomatic patients to determine the usefulness of sonography in the diagnosis of labral abnormalities.