Ex vivo biomechanical evaluation of a bone-screw-fastener for tibial plateau leveling osteotomy

Introduction

The objective of this study was to investigate the effect of a novel screw type on stiffness and failure characteristics of a tibial plateau leveling osteotomy (TPLO) construct under cyclic loading conditions. The authors hypothesized that bone-screw-fasteners (BSF) would result in superior biomechanical stability compared with locking buttress screws (LBS).

Materials and Methods

Twelve pairs of canine cadaveric pelvic limbs were included in this ex vivo biomechanical study. A TPLO was performed using a 3.5mm locking TPLO plate and stabilized using either LBS or BSF. Cyclic loading was performed for 30,000 cycles at 4Hz with a peak-load of 1000N (50N valley). The cyclic test was then continued by stepwise incremental increase of peak-load at a rate of 75N per 500 cycles until failure.

Results

Cycles to failure for LBS (44,260 ± 5,770) and BSF (41,540 ± 7,686) were not significantly different (p = 0.36). Maximum force for LBS (3,134 ± 797N) and BSF (2,940 ± 831N) was not significantly different either (p = 0.58). Dynamic stiffness for LBS (1,778 ± 932 N/mm) and BSF (1,574 ± 677 N/mm) was not significantly different (p = 0.58).

Discussion

Stabilization of the TPLO with BSF provided similar biomechanical stability under cyclic axial loading conditions as the LBS. BSF may be an acceptable alternative to traditional locking screws for TPLO.

Decreased Surgical Time with a Vessel Sealing Device Versus a Surgical Stapler in Performance of Canine Splenectomy

The purpose of this retrospective study of 72 dogs was to compare a vessel sealing device with a surgical stapling device for performance of splenectomy. The results of this study demonstrate a statistically significant shorter surgical time for splenectomy, without an adverse effect on outcomes, performed in dogs with the vessel sealing device (mean time, 58.4 min ± 3.3 min; median time, 60 min; range, 22–131 min) compared with a traditional stapling device (mean time, 66.9 min ± 2.4 min; median time, 66 min; range, 40–100 min). No other significant differences were found between the two groups of patients.

Immunohistochemical and clinical evaluation of p53 in canine cutaneous mast cell tumors

One hundred twenty-six cutaneous mast cell tumors obtained by excisional biopsy from 106 dogs were evaluated using immunohistochemical staining for the presence of p53 protein. A standard avidin-biotin immunohistochemical protocol was used incorporating a polyclonal antibody of rabbit origin (CM-1) as the primary antibody. Histopathologic grading of tumors was performed on hemotoxylin and eosin-stained samples. There was a significant difference in the percentage of cells staining positive for p53 for the histopathologic grades (P = 0.0005). Grade III tumors had a significantly greater p53 content than did grade I or II tumors (P < 0.05). Clinical data obtained retrospectively was available for 54 dogs. Tumor recurred in 19 of 54 (35.2%) dogs. Twenty-nine dogs died by the end of the study; 9 of 29 (31.0%) died of mast cell tumor disease. Histopathologic grade showed a significant negative association with survival time. Both clinical stage and histopathologic grade showed a significant negative association with time to recurrence. The percentage of cells staining positive for p53 did not significantly improve the forward analysis. Immunohistochemical detection of p53 did not appear useful in characterizing the clinical association between cutaneous mast cell tumor cellular features and survival time or time to tumor recurrence in dogs.

Deionised water as an adjunct to surgery for the treatment of canine cutaneous mast cell tumours

Medical records of 55 dogs with a diagnosis of cutaneous mast cell tumour were reviewed. Twenty-seven of the dogs were treated with surgery plus deionized water and the remaining 28 with surgery alone. A survival analysis was performed to determine whether deionized water, as an adjunct to surgery for cutaneous mast cell tumour, affected survival time or time to tumour recurrence. Dogs in which mast cell tumour recurred had a significantly shorter survival time compared with dogs with no recurrence (P = 0.05), regardless of the method of treatment. A significant negative association between tumour recurrence and method of treatment (P = 0.0097) and clinical stage (P = 0.0223) was observed. Dogs treated with surgery and deionized water had a significantly shorter time to recurrence of their mast cell tumour (P = 0.0113). Based on these results, deionized water does not appear to be beneficial in prolonging survival time or time to tumour recurrence for dogs with cutaneous mast cell tumours.

Extensive venous thrombosis and hind-limb edema associated with adrenocortical carcinoma in a dog

A 10-year-old, spayed female, mixed-breed dog was referred for evaluation of bilateral hindlimb edema and weakness. Abdominal ultrasonography showed increased echogenicity of the lumen of the caudal vena cava from the level of the urinary bladder to the level of the cranial pole of the right kidney. Bilateral saphenous venograms displayed numerous filling defects in the caudal vena cava, right external iliac vein, right femoral vein, and the right common iliac vein. Extensive venous thrombosis was diagnosed, and the animal was euthanized. Necropsy confirmed the presence of venous thrombosis and revealed a right adrenocortical carcinoma that had invaded the caudal vena cava.

CT evaluation of suspected hepatic metastases: comparison of techniques for i.v. contrast enhancement

Although IV injection of contrast material is widely used for detection and follow-up of hepatic metastases on CT, the optimal method of contrast enhancement has not yet been defined. A prospective study was performed in 50 consecutive patients with suspected hepatic metastases. Lesion size and detectability were compared on unenhanced CT scans, scans obtained during a bolus injection of contrast material (early bolus phase), and scans obtained during a rapid infusion after the loading bolus. A total of 60 hepatic lesions were evaluated in 26 patients, 19 with histologic confirmation of metastases and seven with strong supportive evidence. The bolus phase allowed detection of 15% more lesions than did examination during the rapid-infusion phase. Lesion size varied, depending on the timing and method of contrast administration; the largest measurements were obtained during bolus injection of contrast material. In addition, bolus administration of contrast material subjectively resulted in the best lesion detection. Because the three techniques of IV contrast enhancement may produce different size measurements, sequential examinations must be tailored appropriately. Scanning during the bolus phase is technically possible with current CT equipment and is recommended as the primary CT screening examination for hepatic metastases.

Pancreatic pseudotumor in pancreas divisum: CT characteristics

We report a case in which a focally spared area of pancreatic tissue in a gland otherwise replaced by fat created a "pseudomass" mimicking neoplasm on sonography and CT. The "pseudomass" appearance was related to the anomalous ductal anatomy in pancreas divisum. The spared area of pancreas creating a "pseudomass" was drained by the dorsal duct and the remainder of the pancreas that had undergone relative fatty replacement was drained by the ventral duct.

Use of endoscopic ultrasound in patients with esophageal motility disorders

New technology has combined the endoscope with ultrasound in an effort to enhance the visualization of the gastrointestinal tract. With a modified standard endoscope that has an ultrasound transducer built into the tip, high frequency ultrasonic beams can be targeted in close proximity to existing lesions. This results in better quality resolution which enhances the evaluation of the targeted lesion. In addition, esophageal wall thickness can be evaluated and assessed as to its role in esophageal function.

Pancreatic pseudotumors associated with multifocal idiopathic fibrosclerosis

Two patients with multifocal idiopathic fibrosclerosis and sclerosing cholangitis developed biliary obstruction due to a fibrotic pancreatic pseudotumor. The masslike fibrosis mimicked pancreatic carcinoma on sonography and cholangio-pancreatography. In one patient sonography was successfully used to assess the response of the pseudotumor to corticosteroid therapy.

Pancreas divisum: thin-section CT

Twelve patients with known pancreas divisum underwent thin-section computed tomography (CT) to determine the capability of CT to depict this pancreatic anomaly. Focal pancreatic enlargement was present in five patients. Two distinct pancreatic moieties separated by a fat cleft were noted in three patients; a fourth patient had focal atrophy in the distribution of the dorsal pancreas. The two pancreatic moieties were identified at the same craniocaudal level in all four of these patients. The dorsal duct was depicted in all 12 patients, while the short ventral duct was seen in only five of the 12 patients. Failure of the ventral and dorsal pancreatic ducts to fuse was identified in all five patients in whom both ducts were seen. CT may not enable specific diagnosis of pancreas divisum in the majority of patients. If, however, distinct pancreatic moieties or unfused ductal systems are evident, the diagnosis may be confidently suggested.

Renal cell carcinoma: dynamic thin-section CT assessment of vascular invasion and tumor vascularity

Dynamic thin-section computed tomography (CT) was used to evaluate renal cell carcinoma in 80 patients. The lesion was correctly staged with CT in 90% of patients. With use of the dynamic technique, the ipsilateral renal vein was depicted in 99% of patients. Extension of the tumor to the renal vein or the inferior vena cava was correctly detected in 18 of 19 patients. Actual depiction of tumor thrombus was a far more accurate indicator of renal vein invasion than was the identification of isolated renal vein enlargement. Dynamic thin-section CT of the kidney should be considered the routine method for comparison studies with other newer cross-sectional techniques in the evaluation of renal cell carcinoma.

CT of the liver: a survey of prevailing methods for administration of contrast material

The members of the Society of Body Computed Tomography were surveyed to determine the most frequently used method of administering contrast material in CT studies of the liver. The respondents represented CT departments performing liver examinations in 22 institutions. No department relied solely on noncontrast scans. In 12 (54%) of 22 institutions, only contrast-enhanced scans were performed. The preferred dose for enhancement was 150 ml of 60% contrast material. Eight (36%) of the 22 respondents obtained images during the administration of a bolus of contrast material, whereas nine (41%) obtained images during the administration of a sustained drip infusion given after a loading bolus. Follow-up in 1987 revealed that two departments had switched to obtaining images during the administration of a bolus. The availability of CT power injectors and refinements in the rapid-scanning capabilities of CT scanners have increased the popularity of obtaining images of the liver during the administration of a bolus of contrast material. Despite this, in many departments, contrast material is still administered via drip infusion in CT studies of the liver.

Esophageal malignancy: imaging results and complications of combined endoscopic-radiologic palliation

Fifty-one patients with advanced cancer of the esophagus underwent 191 endoscopic palliative procedures, including bouginage, laser therapy, bipolar electrocoagulation, and stent placement. In three patients free perforations developed; these were treated immediately and no sequelae developed. Perforations confined within the tumor mass were diagnosed with CT in two patients and did not require treatment. Methods of endoscopic palliation are discussed with reference to the radiologic studies and techniques. The radiologist must evaluate tumor topography and esophageal wall thickness with computed tomography and esophagography to aid in the choice of palliative therapy. Knowledge of each technique and its risks by the radiologist is essential for useful consultation with the endoscopist before, during, and after the procedure.

Renal metastases: clinicopathologic and radiologic correlation

The clinical and radiologic features of 27 patients with renal metastases arising from eight different types of nonlymphomatous primary malignancies are presented. Renal metastases were generally detected late in the course of the malignancy. In 23 patients there were no symptoms referable to the kidney. Urinalysis was normal in nine patients and showed microscopic hematuria in nine, gross hematuria in four, and proteinuria in four. Radiologically, metastases were usually multifocal; however, metastases arising from colon, lung, and breast carcinoma were sometimes large, solitary, and otherwise indistinguishable from primary renal cell carcinoma. Three of four melanoma metastases and three of seven lung metastases infiltrated the perinephric space. Computed tomography was the most sensitive modality, depicting renal metastases in all 24 cases in which it was employed, followed by ultrasound and intravenous urography. In patients with a history of malignancy, renal metastases outnumbered renal cell carcinomas by approximately 4:1. This study indicates that a new renal lesion in a patient with advanced, noncurable cancer is more likely metastatic than primary and that biopsy in this setting is unlikely to be of aid.

Prevesical hematoma: a complication of prostatic biopsy

Pelvic hematomas following prostatic biopsy are rare. We describe 2 cases of hematomas occurring in the prevesical space (space of Retzius) following transrectal biopsy. Computed tomography (CT) was useful in defining the extent of the hematoma and showing density changes related to the age and suppuration of the hematoma. While cystography has been used to diagnose prevesical hematomas, CT better assesses the size of the hematoma and changes that may occur over time.

Computed tomography appearance of a right cervical aortic arch

The clinical diagnosis of cervical aortic arch rests on the detection of a pulsatile mass in the supraclavicular fossa. Unfortunately, clinical differentiation of a cervical arch from an aneurysm of the great vessels can be difficult. Dynamic computed tomography (CT) can aid in this differentiation and avert the need for angiography.

Gastric tuberculosis: a manifestation of acquired immunodeficiency syndrome

A Haitian man with acquired immunodeficiency syndrome (AIDS), fever, malaise, and diarrhea is described. A computed tomographic (CT) scan showed a retrogastric mass with an associated ulcer. An upper gastrointestinal tract study showed an ulcer with both benign and malignant features. Endoscopy revealed a malignant-appearing ulcer, but cultures and histologic examinations of surgical biopsy specimens indicated gastric tuberculosis. The relationship between tuberculosis and AIDS is discussed.

Computed tomography of renal masses: pitfalls and anatomic variants

An awareness of potential pitfalls in CT imaging of renal masses helps to reduce needless imaging procedures and surgery.

Controversies in the radiologic diagnosis of pelvic malignancies

Although vast differences exist among the many pelvic malignancies, several unifying concepts emerge from this discussion. First, there is a different role for diagnostic imaging for each type of pelvic malignancy. The radiologist should be aware that although the radiographic findings may be similar, the clinical impact varies greatly with a particular tumor. Second, although clinical staging is notoriously inaccurate, nevertheless diagnostic imaging techniques only improve upon but do not replace it because of false-positive and false-negative results. Third, because of the high false-negative rates of most of the modalities in use, negative studies do not in fact rule out the presence of disease. A surgical procedure may still be needed. Finally, several new techniques, including MRI and transrectal or transurethral ultrasound, may improve the accuracy rates. These developments will probably further enliven the controversies surrounding the radiologic evaluation of pelvic malignancies.

Postcholecystectomy syndrome: evaluation using biliary scintigraphy and endoscopic retrograde cholangiopancreatography

We prospectively studied 30 patients with postcholecystectomy syndrome to determine the efficacy of biliary scintigraphy in the detection of stenosis of the sphincter of Oddi. All patients underwent endoscopic retrograde cholangiopancreatography (ERCP). Biliary scintigraphy disclosed stenosis of the sphincter by agreement with the ERCP or surgical findings in nine (90%) of ten patients and in eight (100%) of eight patients with biliary obstruction from other causes. Retention of activity at 2 hours in visually prominent ducts was the best predictor of abnormal biliary drainage. Biliary scintigraphy is a useful, noninvasive screening test for the detection of postcholecystectomy biliary obstruction.

Imaging approach to the suspected renal mass

The authors present their algorithmic approach to the detection, characterization, and staging of renal masses. Based on classification of urographic findings, the patient may be triaged to the appropriate cross-sectional or invasive imaging modality that will result in the most cost-effective management.

Hepatic imaging: current status

The radiologist needs to be aware of the varied appearance of hepatic mass lesions and be prepared to recommend the most cost-effective imaging approach. In this article, the authors discuss their hepatic imaging experience, common pitfalls, and current recommendations.

Pancreatic imaging

In this article, the pancreas is evaluated with regard to the controversies surrounding this organ from a clinical standpoint, and an approach to imaging modalities is examined. The roles of computed tomography, ultrasound, endoscopic retrograde cholangiopancreatography, and magnetic resonance imaging are put into proper perspective.

Iatrogenic sclerosing cholangitis following hepatic arterial chemotherapy infusion

A case of common hepatic duct stricture secondary to hepatic artery chemotherapy infusion is described. CT and endoscopic retrograde cholangiopancreatography (ERCP) may be used in concert to differentiate this entity from other causes of jaundice--namely, hepatic replacement by tumor, porta hepatis adenopathy, and chemotherapy hepatotoxicity.

Enhanced pancreatic CT imaging utilizing a geometric magnification technique

Computed tomography (CT) using a geometric magnification technique was found to improve spatial resolution in phantom studies when compared with conventional third-generation geometry images. The clinical feasibility of using geometric magnification, small focal spot size, and dynamic contrast enhancement was studied in 143 patients referred to CT for clinically suspected pancreatic disease. This population included 46 patients with a normal pancreas and 36 patients subsequently proven to have primary pancreatic carcinoma. Using this new technique in conjunction with dynamic contrast enhancement resulted in high quality pancreatic images. Despite the limitations in tube current associated with a small focal spot size and low total heat capacity of the system, clinical imaging was not adversely affected. Use of the geometric magnification technique is recommended in departments where it is technically feasible.

Computed tomography of acute renal failure secondary to rhabdomyolysis

Two patients with rhabdomyolysis and renal failure were imaged with CT. The presence of a striate nephrogram, nephromegaly, and perinephric fluid has not previously been described on CT. Although nonspecific, these findings suggest the diagnosis of acute tubular blockade, and, once identified, administration of additional urographic contrast medium should be avoided.

The clinical and imaging spectrum of pancreaticoduodenal lymph node enlargement

Pancreaticoduodenal lymph node enlargement, regardless of cause, has been a source of imaging confusion because of its propensity to mimic pancreatic malignancy yet not cause biliary obstruction. Thirty-eight patients with pancreaticoduodenal adenopathy were imaged with several methods. Pancreaticoduodenal lymphadenopathy could be distinguished from intrinsic pancreatic abnormality on only 44% (14/32) of CT scans and 54% (6/11) of sonograms. Demonstration of intact tissue planes separating adenopathy from pancreas and, to a lesser degree, extrapancreatic vascular displacement were the most helpful diagnostic signs. Surprisingly, 31% of patients had biliary obstruction. Care must be taken in distinguishing metastatic lymphadenopathy from primary pancreatic tumors. The presence or absence of jaundice should not be considered a helpful sign.

Perirenal cobwebs: the expanding CT differential diagnosis

Although initially described as representing collateral venous structures, perirenal cobwebs may be due to a variety of benign and malignant conditions. Six representative cases illustrating the broad differential diagnosis are presented.

Hepatobiliary scintigraphy and sonography in early biliary obstruction

The authors examined 139 patients thought to have early, partial, or intermittent biliary obstruction, using sonography, hepatobiliary scintigraphy, and in selected cases contrast cholangiography. Of 125 patients with a well-established final diagnosis, sonography and scintigraphy disagreed in 29 (23%). Scintigraphy revealed early or low-grade obstruction in 13 patients who had no evidence of dilated ductules, while 7 patients with dilatation from prior stone passage or biliary surgery showed normal clearance. The authors conclude that in a preselected population in whom early or low-grade biliary obstruction may be present, disagreement between sonography and scintigraphy is not rare, and the absence of sonographically detectable dilatation does not exclude obstruction.

Imaging of the liver, biliary tract, and pancreas

The interaction between the various noninvasive and invasive imaging modalities used to evaluate the liver, biliary tract, and pancreas is demonstrated in this article. By understanding this interaction and correlating noninvasive studies, the clinician will avoid diagnostic redundancy and the need for invasive testing may be reduced.

Natural history of neonatal periventricular/intraventricular hemorrhage and its complications: sonographic observations

Cranial sonography is an established procedure for the detection of neonatal intracranial hemorrhage. A 3 year experience in imaging such infants is reviewed. Representative examples are presented to comprehensively illustrate the spectrum of sonographic appearances of intracranial hemorrhage and its complications from the initial hemorrhage to resolution. Diagnostic problems in the initial staging of the grade of hemorrhage and in evaluating subsequent ventricular changes are addressed.

Noninvasive imaging of the gastrointestinal tract

Numerous radiographic and scintigraphic imaging modalities are now available for evaluating the gastrointestinal system. With a well-formulated plan based on patient history, physical examination, and laboratory values, together with knowledge of patient preparation techniques and consultation, an efficient customized approach to gastrointestinal disease can be accomplished.

Endoscopic retrograde computed tomography of the pancreas

Endoscopic retrograde cholangiopancreatography (ERCP) and computed tomography (CT) are well established diagnostic studies for pancreatic evaluation. We conducted a study to determine whether performing these examinations in tandem increased diagnostic accuracy. Patients undergoing ERCP with successful cannulation of the pancreatic duct and who could be placed in the gantry of our CT scanner within 30 min were included in the study. The combined examination, or endoscopic retrograde computed tomography of the pancreas (ERCTP), provided additional useful information in several types of patients including those who had intrapancreatic air without clinical abscess, those with apparent total obstruction of the pancreatic duct on ERCP, and those who were post partial pancreatectomy and were being considered for additional surgery. No additional useful information was provided in patients with a normal ERCP or in routine cases of pancreatitis.

Sonographic features of uterine leiomyomas: analysis of 41 proven cases

The relative frequencies of the different sonographic features and patterns of uterine leiomyomas have been examined by prospective and retrospective analyses of the sonograms in 41 proven cases. The original sonographic reports correctly predicted the presence of myomas in 27/45 studies (sensitivity = 60 per cent). Retrospective analyses of the sonograms revealed abnormalities in 32/41 patients (sensitivity = 78 per cent). Most myomatous uteri had two or more sonographic abnormalities, most frequently uterine contour irregularity (76 per cent), altered echo texture (68 per cent) and/or enlargement (66 per cent). Minimal contour irregularity at the interface between the uterus and the bladder deserves emphasis as a subtle diagnostic sign of leiomyoma. Careful attention to the uterus in examining a patient referred for an adnexal mass should improve the diagnostic accuracy of myoma detection by sonography.

Sonography of adrenal pheochromocytomas

The sonographic features of eight surgically confirmed pheochromocytomas are described and correlated with pathologic findings. The purely solid masses were homogeneous or heterogeneous sonographically. Pathologic examination of the gross specimen provided explanations for the variety of sonographic findings. Two tumors had large cystic components due to old blood. Other hypoechoic areas corresponded to necrosis pathologically. Hyperechoic areas represented hemorrhage. Generally, pheochromocytomas are quite large, sharply marginated, and usually have a significant solid component with or without central necrosis or hemorrhage. Recognition of these features should facilitate their identification on sonography.

Wilms tumor: ultrasonic features, pathologic correlation, and diagnostic pitfalls

The gray-scale ultrasonic features of Wilms tumor are reported with pathologic comparison. The most consistent ultrasonic features are large size, sharp margination, and echogenic heterogeneity. The frequently observed anechoic areas correlated with hemorrhage and necrosis. A rare case of mesoblastic nephroma is included for comparison. Pitfalls in diagnosis are discussed.