The incidence of bent dorsal fins in free-ranging cetaceans.

Laterally bent dorsal fins are rarely observed in free-ranging populations of cetaceans, contrary to captivity, where most killer whale Orcinus orca adult males have laterally collapsed fins. This topic has been poorly explored, and data/information on its occurrence and possible causes are limited. The present study: (i) undertakes a review of the available information on bent dorsal fins in free-ranging cetaceans, and updates it with new records, (ii) reports on the proportion of bent fins in different study populations, and (iii) discusses possible causes. An empirical approach based on bibliographic research and compilation of 52 new records collected worldwide resulted in a total of 17 species of cetaceans displaying bent dorsal fins. The species with the highest number of records (64%) and from most locations was O. orca. On average, individuals with bent dorsal fins represent < 1% of their populations, with the exception of false killer whales Pseudorca crassidens and O. orca. While line injuries associated with fisheries interactions may be the main cause for P. crassidens, and the vulnerability to health issues caused by the evolutionary enlargement of the fin may be the cause for O. orca adult males, factors contributing to this abnormality for other species are still unclear. The occurrence of bent dorsals could be influenced by a set of variables rather than by a single factor but, irrespective of the cause, it is suggested that it does not directly affect the animals' survivorship. While still rare in nature, this incident is more common (at least 101 known cases) and widespread (geographically and in species diversity) than hypothesized, and is not confined only to animals in captive environments. Investigation into the occurrence of bent fins may be an interesting avenue of research.

Meniscal root injury and spontaneous osteonecrosis of the knee: an observation.

We describe injuries to the posterior root of the medial meniscus in patients with spontaneous osteonecrosis of the medial compartment of the knee. We identified 30 consecutive patients with spontaneous osteonecrosis of the medial femoral condyle. The radiographs and MR imaging were reviewed. We found tears of the posterior root of the medial meniscus in 24 patients (80%). Of these, 15 were complete and nine were partial. Complete tears were associated with > 3 mm of meniscal extrusion. Neither the presence of a root tear nor the volume of the osteonecrotic lesion were associated with age, body mass index (BMI), gender, side affected, or knee alignment. The grade of osteoarthritis was associated with BMI. Although tears of the posterior root of the medial meniscus were frequently present in patients with spontaneous osteonecrosis of the knee, this does not prove cause and effect. Further study is warranted.

The posterior transtriceps approach for elbow arthrography: a forgotten technique?

OBJECTIVE: To evaluate the technical feasibility of performing elbow MR arthrography via a posterior approach through the triceps. MATERIALS AND METHODS: The images of 19 patients with elbow MR arthrography via a posterior transtriceps approach were retrospectively studied. The injections were performed by four musculoskeletal radiologists, using fluoroscopic guidance and a 22- or 25-gauge needle. The fluoroscopic and subsequent MR images were reviewed by two musculoskeletal radiologists and evaluated for adequacy of joint capsular distention, degree and location of contrast leakage, and presence of gas bubbles. RESULTS: The injection was diagnostic in all 19 patients, with a sufficient amount of contrast agent seen in the elbow joint. No significant contrast leakage occurred in 12 patients who received injections of 8 cc or less of contrast agent, but moderate contrast leakage occurred in 6/7 patients who received injections of greater than 8 cc. Contrast leakage generally occurred within the triceps myotendinous junction. No gas bubbles were identified in the injected joints. CONCLUSION: Patients often present for MR arthrography of the elbow with medial or lateral elbow pain. Contrast leakage during a radiocapitellar approach may complicate evaluation of the lateral collateral ligament or the common extensor tendon origin. Transtriceps MR arthrography offers an alternative to the more commonly used radiocapitellar approach. With injected volumes not exceeding 8 cc, the risk of significant contrast leakage is small. An advantage of the transtriceps injection is that contrast leakage through the posterior needle tract does not interfere with evaluation of the lateral structures.

Iliosacral screw fixation of the posterior pelvic ring using local anaesthesia and computerised tomography.

Various techniques have been used for the fixation of the posterior pelvis, each with disadvantages specific to the technique. In this study, a new protocol involving the placement of posterior pelvic screws in the CT suite is described and evaluated. A total of 66 patients with unstable pelvic ring injuries was stabilised under local anaesthesia with sedation. The mean length of time for the procedure was 26 minutes per screw. There were no technical difficulties or misplaced screws and no cases of infection or nonunion. All patients stated that they would choose to have the CT scan procedure again rather than a procedure requiring general anaesthesia. The charges for the procedure were approximately 1840 pounds sterling (2800 dollars) per operation. CT-guided placement of iliosacral screws is a safe, feasible, and cost-effective alternative to radiologically-guided placement in the operating theatre in selected patients.

Shoulder imaging abnormalities in individuals with paraplegia.

Shoulder pain and rotator cuff tears are highly prevalent in individuals with paraplegia (PP). The purpose of this study was to use magnetic resonance imaging (MRI), plain radiographs, questionnaires, and physical examination to gain insight into the prevalence of shoulder disorders in individuals with PP. A total of 28 individuals with PP was recruited (mean age=35; mean year from injury=11.5). Each subject completed a questionnaire designed to identify arm pain, had a standard physical examination focusing on the shoulder, and underwent imaging studies (radiographic and MRI). Nine of the thirty-two subjects (36 percent) experienced shoulder pain in the month prior to testing. The MRI studies documented only one rotator cuff tear. Five subjects showed osteolysis of the distal clavicle by plain radiographic study. In two subjects this was seen bilaterally. Although no relationship was seen between pain and imaging abnormalities, stepwise linear regressions found a statistically significant positive relationship between imaging abnormalities and body mass index (BMI) (radiographic: beta= 0.56, p<0.01; MRI: beta=0.52, p<0.01). This study found a low prevalence of rotator cuff tears and a high prevalence of distal clavicle osteolysis in a sample of relatively young individuals with PP. Although there was only one tear identified by MRI, a number of subclinical abnormalities were seen and found to correlate with BMI.

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.

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.

Statistical test to assess rank-order imaging studies.

RATIONALE AND OBJECTIVES: Rank-order experiments often provide a reasonable method of determining whether a large-scale receiver operating characteristic study can be justified. The authors' purpose was to formalize a proposed method for analyzing rank-order imaging experiments and provide methods that can be used in determining sample sizes for both cases and raters. MATERIALS AND METHODS: Simulations were conducted to determine the adequacy of the normal approximation of a statistic used to test the null hypothesis of random ordering. For a multireader experiment, formulas are presented and guidelines are provided to enable investigators to determine the number of required readers (raters) and cases for a specific study. RESULTS: When there are at least five ordered images per case, 10 cases are sufficient to test a random rank order. When there are only three or four images for a case, 20 cases are required. The authors constructed tables of statistical power for selected numbers of ordered images, numbers of cases, and degrees of trend, and they also provide an approximation for use in situations that are not tabled. CONCLUSION: The statistical methods for analyzing rank-order experiments and estimating sample sizes for study planning are relatively simple to implement. The derived formulas for sample size estimation, when applied to typical imaging experiments, indicate that modest numbers of cases and readers are required for rank-order studies.

Intraneural ganglion of the peroneal nerve: importance of timely diagnosis.

Peroneal nerve ganglion cysts typically present because of a palpable mass or symptoms and signs of entrapment neuropathy, including pain, diminished sensation, and motor weakness. Surgical treatment is usually successful when performed early, but, when diagnosis is delayed, intraneural growth and invasion may cause irreversible axonal injury and footdrop. This case report illustrates the importance of timely diagnosis when treating a ganglion of the peroneal nerve and reviews the appropriate workup, differential diagnosis, and treatment.

Transsacral versus modified pelvic landmarks for percutaneous iliosacral screw placement--a computed tomographic analysis and cadaveric study.

The alar roots of the first sacral body are the usual confines for iliosacral screw (IS) placement when stabilizing a sacroiliac joint injury or sacral fracture. The traditional transsacral method of IS placement aligns the screw horizontally through the sacral ala on both the inlet and outlet views of the sacrum. A modified oblique method of IS placement aligns the screw in an oblique fashion, directed inferiorly to superiorly and posteriorly to anteriorly. The purpose of this investigation was to first define the S-1 segment boundaries for both methods of placement by analyzing the 3-dimensional (3-D) composites of 40 pelvic computed tomography (CT) scans, and then to evaluate the actual placement of ISs under fluoroscopy in 10 cadaveric pelves comparing the transsacral with the modified oblique techniques. Critical dimensions of 7.3 mm and 14.6 mm were considered as the diameter sizes of one and two cannulated screws, respectively. From the 3-D CT composites, the mean anterior/posterior (A/P) measurements were 10.9 mm and 18.0 mm, comparing transsacral with modified oblique methods, respectively. Moreover, 9/40 (22.5%) of the transsacral A/P measurements were <7.3 mm, while all of the modified oblique A/P measurements were >7.3 mm. The mean superior/inferior (S/I) measurements were 18.0 mm for transsacral and 26.2 mm for modified oblique placement. Out of 40 transsacral S/I measurements, 4 (10%) were <14.6 mm, while all the modified oblique S/I measurements were >14.6 mm. In the second part of this study, 10 uninjured cadaveric pelves had unilateral percutaneous IS placed under fluoroscopic guidance (inlet, outlet, and lateral projections) by one orthopedic traumatologist. The final position of all 10 screws was confirmed on fluoroscopy by two independent orthopedic trauma surgeons. The first 5 screws were placed by using transsacral pelvic landmarks. Modified landmarks guided the other 5 screws. The accuracy of final screw position was determined by "postoperative" CT scans interpreted by a blinded musculoskeletal radiologist. The screws inserted using transsacral pelvic landmarks were errant in 3 of the 5 cases. Neurovascular complications could be expected from the extraosseous position of all 3 screws. All 5 screws were located within the confines of the S-1 segment by means of the modified oblique technique. Thus, the modified oblique placement technique allowed greater accuracy and reliability over transsacral landmarks in placing percutaneous ISs. The use of the modified oblique pelvic landmarks is warranted during percutaneous iliosacral screw stabilization of the posterior pelvis.

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.

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.

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.

The use of magnetic resonance imaging in posterior tibial tendon dysfunction.

The role of magnetic resonance imaging in the evaluation of the patient with posterior tibial tendon dysfunction is discussed. Considerations for the proper positioning of the patient and optimal technique to obtain appropriate images of the posterior tibial tendon and associated joint abnormalities are highlighted. Cases are presented to show the effectiveness of magnetic resonance imaging in different clinical situations. The treatment algorithm for posterior tibial tendon dysfunction should include magnetic resonance imaging as a diagnostic tool when appropriate.

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.

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.

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.