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Biomedical subjects

J D Towers

Publications and source records attributed to J D Towers.

At least 19 recordsLinked to original sources
PubMed2001

Anterior approach for knee arthrography.

OBJECTIVE: To develop a new method of magnetic resonance arthrography (MRA) of the knee using an anterior approach analogous to the portals used for knee arthroscopy. DESIGN: An anterior approach to the knee joint was devised mimicking anterior portals used for knee arthroscopy. Seven patients scheduled for routine knee MRA were placed in a decubitus position and under fluoroscopic guidance a needle was advanced from a position adjacent to the patellar tendon into the knee joint. After confirmation of the needle tip location, a dilute gadolinium solution was injected. RESULTS AND CONCLUSION: All the arthrograms were technically successful. The anterior approach to knee MRA has greater technical ease than the traditional approach with little patient discomfort.

Adult↗
PubMed2001

Carpal impaction with the ulnar styloid process: treatment with partial styloid resection.

Carpal impaction with the ulnar styloid process (stylocarpal impaction) occurs less frequently than with the ulnar head (ulnocarpal impaction), and more commonly develops in wrists with negative ulnar variance. Physical examination, radiographic evaluation, and wrist arthroscopy are all helpful in excluding alternative causes of ulnar wrist pain. When an ulnocarpal stress test elicits pain, and radiographs suggest that this is due to carpal impaction with the ulnar styloid, partial resection of the styloid process provides successful treatment, so long as the insertion of the triangular fibrocartilage at the base of the styloid is not disrupted.

Adolescent↗
PubMed2000

Multipoint rank-order study methodology: observer issues.

RATIONALE AND OBJECTIVES: We performed a multipoint rank-order experiment to evaluate variability in observers' sensitivity to small differences in image presentation and to assess observers' performance as a function of the type and number of tasks included. METHODS: Five experienced observers were presented with four sets of chest images that had been compressed at five different levels. Each set contained six images ranging from noncompressed to approximately 60:1-compressed images. Observers were asked to review all images of each case side by side and rank-order the "quality" of each to enable determination of the presence or absence of interstitial disease and/or pneumothoraces. RESULTS: Observers varied significantly in their ability to detect very small differences among the images (P < 0.001). Those who performed well did so regardless of whether they ranked a specific abnormality in a multidisease or a single-disease setting. CONCLUSIONS: Selected observers can reliably detect very small differences among similar images. These readers could be used to confirm or rule out the need for objective observer-performance-type studies.

Humans↗
PubMed1999

Retrograde drilling of osteochondral lesions of the medial talar dome.

Sixteen patients (16 ankles) with symptomatic osteochondral lesions of the medial talar dome were treated arthroscopically with percutaneous retrograde drilling through the sinus tarsi. The surgical technique allows preservation of intact articular cartilage, in contrast to traditional methods. All patients treated with this technique during a 24-month period were included in the study. Patient age ranged from 16 to 44 years (mean, 33 years). Follow-up ranged from 19 to 38 months (mean, 24 months). A staging system based on magnetic resonance imaging examination was used to grade the lesions preoperatively. Outcome was evaluated using the American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Scale. Preoperative scores ranged from 35 to 75 points, with a mean of 53.9 points. Postoperative American Orthopaedic Foot and Ankle Society scores ranged from 48 to 100 points, with a mean of 82.6 points. Mean improvement was 25 points. There were no surgical complications. Short-term results were comparable to results reported with other available techniques.

Adolescent↗
PubMed1999

Familial resemblance of bone mineral density (BMD) and calcaneal ultrasound attenuation: the BMD in mothers and daughters study.

The familial resemblance in bone mineral density (BMD) and calcaneal broadband ultrasound attenuation (BUA) was examined in 207 mother-daughter pairs. Mothers were participants in the Study of Osteoporotic Fractures. Three groups of daughters were recruited based on their maternal history of "fracture," "low BMD" without fracture (< 0.58 g/cm2, t-score < -2.5), and "normal BMD" without fracture (> 0.67 g/cm2, t-score > -1.6). Data on other potentially heritable factors known to influence BMD and BUA were also collected. BMD was measured at the hip, spine, whole body, and calcaneus. Calcaneal BUA was assessed using the Walker-Sonix UBA 575. Total hip and femoral neck BMD were significantly lower (5.0-8.0%, p < 0.017) among daughters, in particular premenopausal daughters, of mothers with established osteoporosis ("fracture" or "low BMD") compared with daughters of mothers at lower risk of osteoporosis ("normal BMD"). BUA did not differ across daughter groups. Lifestyle characteristics (dietary calcium, smoking, physical activity) were not highly correlated in mothers and daughters. Height, weight, and body composition were significantly correlated within mother-daughter pairs and could be a potential mechanism by which BMD is inherited. Among pre- and postmenopausal daughters, heritability estimates ranged from 50-63% and 34-48%, respectively. Heritability for calcaneal BUA (53%) was evident among postmenopausal daughters only. In conclusion, familial association in BMD was strongest among premenopausal daughters. Estimates of heritability suggest that maternal BMD and BUA are important independent predictors of BMD and BUA among daughters, reinforcing the importance of prevention and early intervention among women with a positive family history of osteoporosis.

Adult↗
PubMed1998

MR imaging of knees having isolated and combined ligament injuries.

OBJECTIVE: Although clinical evaluation and MR imaging both accurately reveal injuries in knees with isolated ligament tears, physical examination becomes progressively less reliable when multiple lesions exist. We investigated the accuracy of MR imaging of knees having varying degrees and numbers of ligament injuries. SUBJECTS AND METHODS: We prospectively interpreted the MR images of 340 consecutive injured knees and compared these interpretations with the results of subsequent arthroscopy or open surgery, which served as the gold standard. Our interpretations of MR images focused on five soft-tissue supporting structures (the two cruciate ligaments, the two collateral ligaments, and the patellar tendon) and the two menisci. Patients were divided into three groups: no ligament injuries, single ligament injuries, and multiple ligament injuries. RESULTS: Using MR imaging, we found overall sensitivity and specificity for diagnosing ligament tears to be 94% and 99%, respectively, when no or one ligament was torn and 88% and 84%, respectively, when two or more supporting structures were torn. The difference in specificity was statistically significant (p < .0001). Sensitivity for diagnosing meniscal tears decreased as the number of injured structures increased, but the relationship achieved statistical significance (p = .001) only for the medial meniscus. For all categories of injury, MR imaging was more accurate than clinical evaluation, statistics for which were taken from the orthopedic literature. CONCLUSION: In knees with multiple ligament injuries, the diagnostic specificity of MR imaging for ligament tears decreases, as does the sensitivity for medial meniscal tears.

Adolescent↗
PubMed1997

The use of intravenous contrast in MRI of extremity infection.

Infection of the musculoskeletal system encompasses a variety of conditions, affecting skin, fascia, muscle, joints, tendon sheaths, and bone. In addition to features unique to each tissue site, these processes vary with respect to organism virulence, overall host condition, and the condition of the extremity itself, particularly its circulation. Treatment of musculoskeletal infection varies according to these features, and with respect to the presence of devitalized tissue. Unfortunately, while clinical examination is accurate for the presence of infection as a process in most circumstances, it lacks specificity for the variety of disorders within the spectrum of extremity infection. MRI examination using intravenous contrast is becoming the preferred modality to study complicated extremity infections, since it provides an accurate portrayal of the extent of osseous and non osseous involvement, and identifies areas of necrosis. This information provides a basis from which clinicians may more accurately choose from among treatment options.

Adult↗
PubMed1997

Anterolateral soft-tissue impingement in the ankle: diagnosis using MR imaging.

OBJECTIVE: This study was performed to elucidate the MR imaging findings and pitfalls for the diagnosis of anterolateral soft-tissue impingement in the ankle, a cause of chronic ankle pain that can be relieved by arthroscopic resection. MATERIALS AND METHODS: We retrospectively reviewed MR imaging examinations of 18 patients with arthroscopically confirmed anterolateral ankle impingement. The MR images of 18 additional subjects with symptoms that could mimic anterolateral impingement, but who had a surgically confirmed alternate diagnosis (instability, peroneal tendon injury, osteochondral defect, normal arthroscopy) and no evidence of impingement at arthroscopy, served as controls. RESULTS: On the MR imaging studies, nine patients had an ankle effusion, eight of whom showed an abnormal soft-tissue structure in the anterolateral gutter, 2-15 mm in maximal diameter. No soft-tissue mass was seen in the patients without joint fluid. Four control subjects with instability had a similar soft-tissue structure in the anterolateral gutter, but in the control subjects the finding represented a portion of the torn anterior talofibular ligament. CONCLUSION: Anterolateral soft-tissue impingement of the ankle can be suggested by MR imaging when fluid in the lateral gutter outlines an abnormal soft-tissue structure separate from the anterior talofibular ligament.

Adolescent↗
PubMed1996

Subjective quality assessment of computed radiography hand images.

To evaluate the sensitivity of a non-receiver-operating characteristic (ROC) study in assessing small differences of perceived image quality of hand images acquired by computed radiography (CR) and conventional screen-film systems, hand images were acquired on 12 patients with both conventional screen-film and CR. Each CR image was then processed with three different edge-enhancement algorithms. One conventional film and four CR images were then viewed side by side by five radiologists. Observers rated perceived image quality of each radiograph using a 10-category discrete scale. The study was repeated after 6 weeks using a different block randomization scheme. Despite the small sample size, significant differences (P < .05) in assigned image quality were detected among CR images acquired at low, medium, and high resolutions. Image processing routines did not fully compensate for differences in quality between conventional film and CR-acquired images. The quality rating of the reference conventional image was found to be dependent on the quality of images with which it was compared. Small, highly sensitive study designs can be used to identify radiologists' perceived differences in image quality. "Reference" or "gold standard" quality are important in such studies. Edge-enhancement schemes cannot fully compensate for perceived image quality degradations because of reduced image resolution.

Algorithms↗
PubMed1996

Change in trabecular architecture as measured by fractal dimension.

The objective of this work was to expose dried trabecular bone material to a decalcifying environment and to quantify the change in the spatial distribution of the bone with a fractal measure. Digitized radiographic images were produced from four separate slices of human vertebral bone as they dissolved within a solution of nitric acid. Pixel data from a region of interest (ROI) within the trabecular bone were used to estimate the time-dependent change in fractal dimension of the ROI as the bone dissolved. Results demonstrated that a change in the spatial distribution of trabecular material may be expressed in terms of a concurrently changing estimate of the fractal dimension.

Algorithms↗
PubMed1996

The seronegative spondyloarthropathies.

The four seronegative spondyloarthropathies can be divided into two main groups by their pattern of sacroiliitis and spondylitis (Table 1). The axial skeletal changes of ankylosing spondylitis and enteropathic arthropathy are often indistinguishable, as are those of psoriatic arthritis and Reiter's syndrome. Early proximal appendicular joint involvement in ankylosing spondylitis is a poor prognostic sign except in women where peripheral arthritis is more common, but has a more benign course. Peripheral joint destruction in enteropathic arthropathy is rare because treatment of the bowel disease also treats the arthritis. Distal appendicular involvement is characteristic of psoriatic arthritis and Reiter's syndrome. Proliferative erosions and enthesitis, periostitis, and normal mineralization aid in differentiating psoriatic arthritis and Reiter's syndrome from rheumatoid arthritis. The distribution of arthritis also differs from that seen in classic rheumatoid arthritis, with asymmetry and involvement of the distal interphalangeal joints more common in psoriatic disease and Reiter's syndrome.

Arthritis, Psoriatic↗
PubMed1996

Revision total hip arthroplasty with a retroperitoneal approach to the iliac vessels.

Although vascular complications during revision total hip arthroplasty are rare, the results can be devastating. Reports in the literature describe staged operations, with the first procedure being abdominal to remove cement and/or the acetabular component followed by a second joint reconstruction procedure. A protocol was developed that combines a retroperitoneal approach with revision total hip arthroplasty in one operative procedure in patients at risk for vascular injury. The patient first undergoes a retroperitoneal incision and the iliac artery and vein are dissected free of surrounding tissue. A silicone loop is placed around the iliac artery and vein and brought out through the wound. The wound is temporarily closed using staples. Revision total hip arthroplasty then proceeds in the usual fashion. If hemorrhage is encountered, bleeding can be rapidly controlled by tensioning the abdominal vessel loops and opening the incision for exposure to the vessels. No complications have been encountered in 23 patients when using this approach.

Aged↗
PubMed1996

Are MR imaging signs of meniscocapsular separation valid?

PURPOSE: To define the positive predictive value (PPV) for the magnetic resonance (MR) imaging diagnosis of meniscocapsular separation in the knee. MATERIALS AND METHODS: The MR reports of 52 patients aged 16-75 years who had a prospective MR diagnosis of meniscocapsular injury were correlated with arthroscopic results. MR images obtained in 50 of these patients were retrospectively reviewed for specific signs of meniscocapsular separation, which included meniscal displacement, peripheral meniscal corner tears, increased perimeniscal signal intensity, fluid deep to the medial collateral ligament, and abnormal lateral fascicles. MR findings were correlated with arthroscopic findings. RESULTS: For the prospective MR interpretations, the PPV for meniscocapsular separation was 9% medially and 13% laterally. Meniscal displacement (measured from the meniscal edge to the tibia) was as great as 10 mm medially or 13 mm laterally without meniscocapsular tears at arthroscopy. Meniscal displacement did not correlate with effusion. Meniscal corner tears had a PPV of 0% medially and 50% laterally. Fluid at the meniscocapsular border and fluid deep to the medial collateral ligament were poor predictors of meniscocapsular abnormalities. Abnormal-appearing meniscal fascicles had a PPV of 8% for lateral meniscocapsular separation. CONCLUSION: The PPV for the MR diagnosis of meniscocapsular separation is low; the reported MR signs correlate poorly with arthroscopic findings.

Adolescent↗
PubMed1996

MR imaging of the foot: utility of complex oblique imaging planes.

Successful MR imaging of the foot presents special challenges to the radiologist. Accurate and confident diagnosis presupposes the ability to produce high-resolution images of obliquely oriented, relatively small structures. Orienting the foot within an appropriate local coil to bring such structures into an orthogonal imaging plane, or even into a conventional oblique plane, may be impossible or intolerably uncomfortable for the patient. The frequent result is motion artifacts, which are accentuated when using a small field of view. However, when patients are comfortably positioned, the anatomy of interest often lies in a plane that is not orthogonal to any of the conventional imaging planes. Fortunately, commercially available MR imaging equipment can produce images in complex oblique planes with relative ease. In this pictorial essay, we discuss the technical considerations for expedient diagnostic MR imaging of the complex anatomy of the foot and illustrate our experiences with this technique.

Adolescent↗
PubMed1995

The pronator quadratus: a distinct forearm space?

The pronator quadratus sign is associated with fractures of the distal radius and ulna and is believed to be due to accumulation of fluid within the pronator quadratus muscle. This anatomic study based on dye injection and x-ray film examination shows that the pronator quadratus occupies a distinct forearm space without intramuscular communication.

Cadaver↗
PubMed1995

Selection of processing algorithms for digital image compression: a rank-order study.

RATIONALE AND OBJECTIVES: We investigated non-receiver operating characteristic (non-ROC) methods for the selection of processing algorithms for digital image compression. METHODS: We performed a multipoint, rank-order study with 20 posteroanterior chest images, each processed using four different algorithms. Seven radiologists reviewed these alongside the digitized noncompressed image. Observers were forced to rank order the similarity and/or difference of the processed images to the nonprocessed image in each case. RESULTS: A two-way analysis of variance of the rankings was statistically significant (p = .025), indicating that one processing scheme yielded images that were clearly perceived as the most similar to the nonprocessed images. The selected processing scheme was not the one that yielded the lowest quantitative difference from the nonprocessed images as measured by root mean square error. CONCLUSION: Non-ROC study designs that are highly sensitive to small differences among similar images can be used to select processing algorithms.

Algorithms↗
PubMed1995

A cadaveric and radiologic assessment of catheter placement for the measurement of forearm compartment pressures.

The diagnosis of compartment syndrome is essentially a clinical one. In recent years, much interest and research has focused on the development of intracompartmental pressure monitoring devices to help in the diagnosis of this condition. Proper placement of the catheter is essential for accurate monitoring, because an incorrect result is potentially more dangerous than no reading at all. In the forearm, measurement in the flexor digitorum profundus is thought to be a more sensitive way of assessing rising pressure. One of the risks of catheter placement is inadvertent damage to a neurovascular structure, particularly when monitoring pressures in deeper muscle bellies. Standard anatomic texts and outpatient magnetic resonance scans of the forearm were studied to define a safe pathway for the introduction of a catheter into the volar forearm. An approach from the midline to the ulna, between the tendons of the flexor carpi radialis and palmaris longus, seemed the safest. Ten cadaveric forearms had 100 cc of gastrograffin injected into the deep forearm through a dorsal approach. The median and ulnar nerves were cannulated with a fine wire from the elbow to the wrist. Two cannulae were passed, using the suggested approach, at 2 locations between the wrist and the mid forearm. All limbs then were scanned with computed tomography, and the images were reviewed. In all forearms, the cannulae passed between the median and ulnar nerves into the belly of the flexor digitorum profundus and posed no risk to the neurovascular structures.

Cadaver↗