Comparison of 99mTc ciprofloxacin, 99mTc white blood cell and three-phase bone imaging in the diagnosis of hip prosthesis infections: improved diagnostic accuracy with extended imaging time.

The purpose of this study was to compare the utility of 99mTc labelled ciprofloxacin (Infecton) imaging with the 99mTc white blood cell and three-phase bone imaging procedures for identifying hip prosthesis infection. We studied 30 symptomatic patients in whom infection was confirmed in eight and excluded in 22 cases based on clinical and microbiological findings. 99mTc ciprofloxacin images were obtained at 1, 4 and 24 h after the injection of the tracer, and the data were compared to those obtained from 99mTc leukocyte and three-phase bone imaging. The 99mTc ciprofloxacin imaging correctly identified all true infections. In 13 (59%) of the non-infected patients, non-specific uptake of 99mTc ciprofloxacin was found in the 1-h and 4-h images, which disappeared, however, in the 24-h images. When the early and late 99mTc ciprofloxacin images were compared, the specificity was found to improve from 41% to 95%, positive predictive value from 38% to 89%, and the diagnostic accuracy from 57% to 97%. The accuracy of the conventional 99mTc leukocyte imaging was 90%. Dynamic bone imaging also yielded abnormal findings in all the infected patients although also in 23% of the non-infected patients. Current data indicate that 99mTc ciprofloxacin is a useful method for confirming hip prosthesis infection. The diagnostic efficiency of this method is improved when the imaging time is extended to 24 h post-injection of the tracer.

99m Tc-ciprofloxacin (Infecton) imaging in the diagnosis of knee prosthesis infections.

The purpose of this study was to evaluate the usefulness of 99mTc labelled ciprofloxacin imaging in detecting the presence of infection in patients with symptomatic knee prostheses. Among 16 randomly selected patients of whom seven had infection based on clinical and microbiological findings and nine did not, 99mTc-ciprofloxacin images were obtained at 1, 4 and 24h after the injection of the tracer. While there was some diffuse non-specific accumulation of 99mTc-ciprofloxacin in large synovial joints and in prosthetic knee joints, the infected knee prostheses were found to show more intensive focal uptake, which also extended outside the synovial cavity. The infection related uptake remained visible in the 24h images, whereas non-specific uptake had a fading tendency at this time point. 99mTc-ciprofloxacin imaging showed diagnostic sensitivity of 86% and a specificity of 78% for correctly classifying the presence of infection. The data indicate that 99mTc-ciprofloxacin imaging may be used in the diagnosis of knee prosthesis infections. Infection-related uptake remains visible in the 24h images and is typically found also outside the synovial cavity, which should be noted in the evaluation of the images.

Improved method for detecting knee replacement infections based on extended combined 99mTc-white blood cell/bone imaging.

The purpose of this study was to evaluate whether an extension of the imaging time to 24 h post-injection improves the diagnostic accuracy of technetium-99m-hexamethylpropyleneamine oxime (99mTc-HMPAO) leucocyte imaging in detecting knee replacement infections. Thirty patients were studied, with infection confirmed in eight (27%) and excluded in 22 on the basis of clinical and microbiological findings. Leucocyte imaging was carried out at 2-4 h (routine images) and at 24 h (late images) post-injection. For comparison, bone imaging with technetium-99m-hydroxydiphosphonate (99mTc-HDP) was carried out at arterial, soft tissue and metabolic phases. Late leucocyte imaging was found to be more sensitive (100% vs. 87.5%) and more specific (82% vs. 77%) than routine leucocyte imaging in detecting infections. All the bone imaging methods showed a sensitivity of 100%, whereas the specificity varied from only 5% to 23%. All procedures had high negative predictive values (NPVs) (94 to 100%) for excluding infection. However, the positive predictive value (PPV) was only 28 to 32% for bone imaging and 58% for routine leucocyte imaging, whereas late leucocyte imaging showed a PPV of 67% and a diagnostic accuracy of 87%. The data indicate that late leucocyte imaging may be superior to routine leucocyte imaging for examining patients with symptomatic knee replacements.

A proximal fixed anatomic femoral stem reduces stress shielding.

In 24 patients with total hip replacement using a short anatomic femoral stem, bone mineral density (BMD) was measured after a 7-year follow-up using dual-energy X-ray absorptiometry. The contralateral side was used as a control. The BMD on the side of the prosthesis was lower by a mean of 7% than that on the control side. The difference was greatest in the area of the calcar and laterally and proximally around the stem. BMD at the metaphyseal and diaphyseal areas were the same as on the contralateral side. The bone loss around the proximal aspect of the stem may be related to the proximal porous coating. It is concluded that stress shielding can be diminished by appropriate design of the femoral component.

Extended combined 99mTc-white blood cell and bone imaging improves the diagnostic accuracy in the detection of hip replacement infections.

Although the diagnosis of hip prosthesis infection is clinically important, X-ray studies, blood chemistry and synovial fluid aspiration may be unreliable for this purpose. The aim of this study was to evaluate whether extending the time for technetium-99m labelled leucocyte imaging to 24 h post injection improves the accuracy of diagnosis of hip replacement infections. We studied 64 symptomatic patients with hip prostheses. The presence of infections was verified by intraoperative bacterial cultures, and infection was excluded either by negative operative findings or by follow-up for at least 1 year. Leucocyte imaging was done with 99mTc-hexamethylpropylene amine oxime (HMPAO)-labelled leucocytes at 2-4 h (routine images) and at 24 h (late images) after the injection of the leucocytes. In addition, bone imaging was carried out with 99mTc-hydroxydiphosphonate (HDP) at the arterial, soft tissue and metabolic phases. A standardised method was used to compare leucocyte images with bone metabolic images. In this material, there were six confirmed infections. All the bone imaging methods had a sensitivity of 100% in detecting prosthesis infections whereas the specificity varied from only 2% to 82%. Routine leucocyte imaging was less sensitive (50% vs 83%) and less specific (90% vs 100%) than late leucocyte imaging. All tests had a high negative predictive value for excluding infection (95%-100%). However, both bone (10%-38%) and routine leucocyte imaging (33%) showed a poor positive predictive value (PPV), whereas late leucocyte imaging had a PPV of 100% and a diagnostic accuracy of 98%. We conclude that late leucocyte imaging improves the specificity of diagnosis of infected hip prostheses. This type of imaging procedure should be combined with three-phase bone scintigraphy in studies of patients with painful joint replacement.

Penetration of Ullevaal hip screw into the pelvis.

The fracture of the femoral neck is usually treated operatively with screw osteosynthesis or prosthesis. There have been reported a rare complication both with screws and lag screws used in hip fractures, both can penetrate into the pelvis postoperatively. We present two cases with this similar rare complication when using Ullevaal screws. Both patients were reoperated on with a total hip arthroplasty (THA). We think that the exact anatomical reposition and good operation technique should make this complication even more rare. The canal should always be drilled only to the line of the fracture, so that there is no canal for the screw to squeeze further. To prevent penetration some kind of cap fixed the lateral end of the screw could also be worth while.

Bone healing and mineralization, implant corrosion, and trace metals after nickel-titanium shape memory metal intramedullary fixation.

Its shape memory effect, superelasticity, and good wear and damping properties make the NiTi shape memory alloy a material with fascinating potential for orthopedic surgery. It provides a possibility for making self-locking, self-expanding, and self-compressing implants. Problems, however, may arise because of its high nickel content. The purpose of this work was to determine the corrosion of NiTi in vivo and to evaluate the possible deleterious effects of NiTi on osteotomy healing, bone mineralization, and the remodeling response. Femoral osteotomies of 40 rats were fixed with either NiTi or stainless steel (StSt) intramedullary nails. The rats were killed at 2, 4, 8, 12, 26, and 60 weeks. Bone healing was examined with radiographs, peripheral quantitative computed tomography, (pQCT) and histologically. The corrosion of the retrieved implants was analyzed by electron microscopy (FESEM). Trace metals from several organs were determined by graphite furnace atomic absorption spectrometry (GF-AAS) or by inductively coupled plasma-atomic emission spectrometry (ICP-AES). There were more healed bone unions in the NiTi than in the StSt group at early (4 and 8 weeks) time points. Callus size was equal between the groups. The total and cortical bone mineral densities did not differ between the NiTi and StSt groups. Mineral density in both groups was lower in the osteotomy area than in the other areas along the nail. Density in the nail area was lower than in the proximal part of the operated femur or the contralateral femur. Bone contact to NiTi was close. A peri-implant lamellar bone sheet formed in the metaphyseal area after 8 weeks, indicating good tissue tolerance. The FESEM assessment showed surface corrosion changes to be more evident in the StSt implants. There were no statistically significant differences in nickel concentration between the NiTi and StSt groups in any of the organs. NiTi appears to be an appropriate material for further intramedullary use because it has good biocompatibility in bone tissue.

Role of metaphyseal cancellous bone defect size in secondary displacement in Colles' fracture.

The purpose of this study was to evaluate the role of the metaphyseal cancellous bone defect size in secondary dislocation of Colles' fracture. Thirty-five patients with a dislocated Colles' fracture were examined by computed tomography (CT) for metaphyseal bone defects. The size of the defect was assessed and related to the surface area of the cross-section of the distal radius at the site of the defect. The relative size of the defect correlated with the severity of dorsal angulation of the fracture but not with the shortening of the radius seen after cast immobilization. We concluded that secondary displacement of the distal radius is partly mediated through the metaphyseal cancellous bone defect, and to prevent malunion in dorsal angulation, operative treatment or possibly filling of the defect should be considered even as early as during primary reduction if a large defect is suspected.

MR imaging in tibial shaft fractures. A potential method for early visualization of delayed union.

PURPOSE: To evaluate the relationship between MR findings at the fracture site during the healing process and the outcome of patients with tibial shaft fracture. MATERIAL AND METHODS: Twelve consecutive patients with an uncomplicated tibial fracture treated conservatively were imaged by MR 1 to 3 days, 1 week, 3 weeks, 6 weeks and 12 weeks after the trauma. MR imaging consisted of sagittal/coronal T1-weighted, T2-weighted, proton density, short-tau inversion recovery, and contrast-enhanced T1-weighted spin-echo images. The images were analysed for the extent of signal pathology in the bone marrow adjacent to the fracture, the extent of soft tissue oedema, and the intensity and homogeneity of the contrast enhancement of the callus. RESULTS: The differences between normal (n=7) and delayed union (n=5) were observed within 3 to 6 weeks after the trauma, mainly in the homogeneity of the callus in T2-weighted and contrast-enhanced images. CONCLUSION: MR imaging is a potentially valuable method for early visualization of delayed union in tibial shaft fractures.

Bone modeling and cell-material interface responses induced by nickel-titanium shape memory alloy after periosteal implantation.

The purpose of this study was to evaluate the new bone formation, modeling and cell-material interface responses induced by nickel-titanium shape memory alloy after periosteal implantation. We used a regional acceleratory phenomenon (RAP) model, in which a periosteal contact stimulus provokes an adaptive modelling response. NiTi has thermal shape memory and superelasticity properties uncommon in other implant alloys. So far, there are insufficient data concerning the biocompatibility of NiTi as a bone implant. NiTi was compared to stainless steel (stst) and Ti-6Al-4V. The test implant was placed in contact with the intact femur periosteum, but it was not fixed inside the bone. Histomorphometry with digital image analysis was used to determine the bone formation and resorption parameters. The ultrastructural features of cell-material adhesion were analysed with scanning electron microscopy (FESEM). A typical peri-implant bone wall modelation was seen due to the normal RAP. The maximum new woven bone formation started earlier (2 weeks) in the Ti-6Al-4V group than in the NiTi (P < 0.01) group, but also decreased earlier, and at 8 weeks the NiTi (P < 0.05) and stst (P < 0.005) groups had greater cortical bone width. At 12 and 26 weeks no statistical differences were seen in the histomorphometric values. The histological response of the soft tissues around the NiTi implant was also clearly non-toxic and non-irritating. Cell adhesion and focal contacts were similar between the materials studied by FESEM. We conclude that NiTi had no negative effect on total new bone formation or normal RAP after periosteal implantation during a 26-week follow-up.

The formation of the demarcation line at experimental frostbite.

Experiments were carried out to gain a better understanding of the pathogenesis of frostbite and changes at the demarcation line after freezing and thawing and to determine the forming demarcation line as early as possible. These changes were investigated by histochemical techniques, by histofluorescence, by determining noradrenaline content in the tissue and nerve, by scintigraphy and thermography. The experimental animal was New Zealand white rabbit. The frostbite was produced using a small laboratory bottle filled with liquid nitrogen pressing against the shaved skin in the middle of the proximal part of the ear. Enzyme histochemistry was good in demonstrating the demarcation line between irreversibly damaged and healing frostbitten tissue. Especially the reaction to esterase was the clearest, the demarcation line was visible already after one week. The glyoxylic acid-induced fluorescence method was available for showing adrenergic nerves around the vessels and the accumulation of catecholamines in these nerves in the demarcation line. The result of quantitative measurement of catecholamines in the nerve and tissue was similar and the reaction was the most powerful during the first three days. Scintigraphy was better than thermography and necrotic areas in the middle of the frostbitten area became clearly visible after three weeks. It seems that many changes caused by frostbite happen both in tissue and cells. The role of catecholamines in vascular circumstances is important and that's why chemical or surgical sympathectomy could be useful.

In vivo biocompatibility evaluation of nickel-titanium shape memory metal alloy: muscle and perineural tissue responses and encapsule membrane thickness.

Nickel-titanium shape memory alloy (Nitinol) has properties that could be very useful in surgical applications. Thermal shape memory, superelasticity, and high damping properties make such alloys behave differently compared to other implant metals. There has previously been a lack of sufficient evidence on the biocompatibility of Nitinol. The purpose of this study was to evaluate general soft tissue response and biocompatibility to Nitinol in vivo, and to clarify neural and perineural responses, previously unreported. Seventy-five rats were randomized into three groups. Test specimens were implanted into paravertebral muscle and near the sciatic nerve. A comparison was made between Nitinol, stainless steel, and Ti-6Al-4V. The animals were euthanized at 2, 4, 8, 12, and 26 weeks after implantation. General morphologic and histologic observations were made under light microscopy. Semiautomatic computerized image analysis was used to measure the encapsule membrane thickness around the implants. The muscular tissue response to Nitinol was clearly nontoxic, regardless of the time period. The overall inflammatory response to Nitinol was very similar to that of stainless steel and Ti-6Al-4V alloy. There were no necroses, granulomas, or signs of dystrophic soft tissue clacification. The immune cell response to Nitinol remained low. Only a few foreign-body giant cells were present. The detected neural and perineural responses were also clearly nontoxic and nonirritating with Nitinol. No qualitative differences in histology between the different test materials could be seen. At 8 weeks, the encapsule membrane of Nitinol was thicker than that of stainless steel (mean 62 +/- 25 microns vs. 41 +/- 8 microns). At the end of the study, the encapsule thickness was equal to all the materials tested. We concluded that Nitinol had good in vivo biocompatibility after intramuscular and perineural implantation in rats in the 26-week follow-up. Based on the results of the present study, Nitinol appears to have good potential for clinical use.

Multiplanar and 3D CT of acetabular fractures.

PURPOSE: To establish a standard protocol for the multiplanar (MPR) and 3D shaded surface display (SSD) reconstruction of CT data on acetabular fractures, and to assess the usefulness of these reformats. MATERIAL AND METHODS: Acetabular fractures in 15 patients were imaged by means of plain radiographs, transaxial CT, MPR reformats, and SSD reformats. RESULTS: The classification of the acetabular fracture was revised in 7/15 cases when the transaxial CT images were read after the plain radiographs. Although the MPR and SSD reformats did not alter the classification, they did add to the degree of confidence in the diagnosis in 9/15 cases. In 2 patients, the MPR and SSD reformats indicated operative instead of conservative treatment. In the MPR reformats, the following views were considered essential in all cases: (a) along the anterior column; (b) along the posterior column; and (c) along both columns and the inferior ramus. In the SSD reformats, the following views were considered essential in all cases: (d) the latero-caudal en face view into the acetabulum; and 180 degrees opposite to this, (e) the medio-cranial view (facing the quadrilateral plate). In 10/15 cases, these views were all that was needed for classification. It was, however, essential to remove the femur from the images before reconstructing the SSD views. CONCLUSION: Complex acetabular fractures with displacement should be evaluated by means of transaxial CT and additional MPR and SSD reformats. The use of appropriate standard MPR and SSD views shortens the time required to produce the reformats and thereby maximizes the benefit gained.

A simple device for the stereoscopic display of 3D CT images.

We describe a simple device for creating true 3D views of image pairs obtained at 3D CT reconstruction. The device presents the images in a slightly different angle of view for the left and the right eyes. This true 3D viewing technique was applied experimentally in the evaluation of complex acetabular fractures. Experiments were also made to determine the optimal angle between the images for each eye. The angle varied between 1 degree and 7 degrees for different observers and also depended on the display field of view used.

Epidural abscess after lumbar discography. A case report.

STUDY DESIGN: The patient who suffered from pain in both lower legs and in whom discography was performed experienced a rare complication after discography. The findings and method of discography is described, as is usefulness of magnetic resonance imaging to image this rare complication. OBJECTIVES: To establish the possibility of getting a spinal epidural abscess after discography, how to make the diagnosis, and how to treat the complication. SUMMARY OF BACKGROUND DATA: Discitis after discography is a well-known complication, but epidural abscess is rare. METHODS: C-reactive protein concentration was measured and was more than 100 mg/L. Infection was suspected, and antibiotic therapy was started immediately. Magnetic resonance imaging was performed, and the diagnosis became clear. A laminotomy was performed. RESULTS: Symptoms due to epidural abscess disappeared soon after laminotomy. CONCLUSIONS: Some harmful and unpleasant complications are possible after discography. Antibiotic prophylaxis and stiletted needles should be used. Magnetic resonance imaging is the best radiologic procedure to image the complication, and surgery must be performed as soon as possible.

Image technique optimization in MR imaging of a titanium alloy joint prosthesis.

The purpose of this study was to explore systematically the effect of the imaging parameters changeable by the user in spin-echo (SE) imaging sequences to minimize image distortion when imaging joint prostheses. A titanium alloy hip joint prosthesis was studied at I.O.T. The SE imaging parameters were bandwidth/pixel(BW/ p), TE, strength of encoding gradients (matrix size), echo train length (ETL), and direction of phase and frequency encoding. The effect of ETL in rapid acquisition relaxation enhanced (RARE) sequences was also evaluated with a turbo-SE sequence using a different ETL with the same TR and an effective TE. It is concluded that an optimized image quality can be achieved in SE imaging by using a high bandwidth/pixel value (at least 130 Hz/pixel), a high resolution matrix (256-512), sequences with multiple refocusing, and a frequency-encoding axis parallel to the long axis of the prosthesis. The degree of distortion is reduced with this optimized technique.

Short communication: distal adrenergic innervation remains normal after perivascular sympathectomy.

Perivascular sympathectomy, which has been used for vasospastic disorders of the hands, was examined in experimental models. Perivascular sympathectomy was performed on the central ear vessels and forepaw metacarpal vessels of the rabbit and on the common digital vessels in the monkey. The effects on adrenergic nerves were studied using a glyoxylic acid-induced fluorescence method. Adrenergic nerves were removed only at the site of the perivascular sympathectomy and the distal adrenergic innervation appeared normal. Because the distal sympathetic nerves appeared normal after the operation, it should rather be called adventitectomy and we feel its clinical effects should be reevaluated.

Assessment of tissue viability by thermography after experimentally produced frostbite of the rabbit ear.

Since it is difficult and time-consuming to monitor the formation of a demarcation line in frostbite by visual inspection only, thermography was used to study experimental freezing injuries of the rabbit ear. In 8 rabbits, anesthetized with ketamine hydrochloride and xylazine hydrochloride, frostbite was induced by pressing the bottom of a glass bottle 2 cm in diameter, filled with liquid nitrogen against the shaved ear skin. Thermography was performed on both ears after 2, 24, and 48 hours, and one and 3 weeks. At 2 to 48 hours the frost-bitten area was clearly warmer than the surroundings, after one week there were ill-defined diffuse cold spots in the injured area, and after 3 weeks a cold area had become clearly demarcated with a warm zone between the cold area and the surroundings. Thermography is an easy, noninvasive method for monitoring thermal changes after experimental frostbite, but its clinical value is as yet unresolved.

Changes in adrenergic nerves and tissue perfusion after freezing injury to the ear skin of rabbits.

The aim of the present study was to investigate by a combined trypan blue and catecholamine fluorescence technique the sequential changes in cutaneous adrenergic nerves, the distribution of blood flow, and vascular permeability at the demarcation line that occurred after experimental cold injury. Nine New Zealand white rabbits weighing 4.0-4.4 kg had frostbite induced by pressing the bottom of a glass bottle 2 cm in diameter filled with liquid nitrogen against the shaved skin of the ear. All the rabbits were anaesthetised with ketamine hydrochloride (Ketamine) and xylazine hydrochloride (Rompun). Specimens were taken one and three days, and two weeks after frostbite. Control samples were taken from the opposite normal ear. Trypan blue was injected into a saphenous vein just before the specimens were taken. The specimens were always taken in the same way and selected so that the probable demarcation line of the frostbite ran across the middle. The glyoxylic acid-induced fluorescence method was used to show the adrenergic nerves. There were no adrenergic nerves around the vessels and no arteriovenous anastomoses in the central area of the injury after one day, but catecholamines had started to accumulate in the adrenergic nerve endings at the margins of the injured area. This accumulation was still more obvious three days after frostbite. Some fluorescent regenerating adrenergic nerves could already be seen at the probable demarcation line two weeks after frostbite. There was increased trypan blue fluorescence near the margin of the injured area after one day, indicating extravasation and vascular damage.(ABSTRACT TRUNCATED AT 250 WORDS)