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Biomedical subjects

W J Dhert

Publications and source records attributed to W J Dhert.

At least 19 recordsLinked to original sources
PubMed2001

Traumatic lumbosacral dislocation: case report.

STUDY DESIGN: A case report of a bilateral lumbosacral dislocation without a fracture is presented. OBJECTIVE: To report the diagnosis and treatment of a traumatic lumbosacral dislocation. SUMMARY OF BACKGROUND DATA: Lumbosacral dislocations without fractures are rare injuries, with only four cases reported in literature. The recommended treatment consists of an anterior lumbar interbody fusion after posterior reduction with pedicle screw instrumentation. METHODS: The 1-year follow-up evaluation of a 17-year-old male with a traumatic lumbosacral dislocation, diagnosed with computed tomography and magnetic resonance imaging, and treated with a posterior lumbar interbody fusion procedure combined with a posterolateral fusion is reported. RESULTS: At 1 year after surgery the patient is asymptomatic and has resumed his heavy manual work. Radiologic evidence of interbody fusion is present. CONCLUSIONS: Lumbosacral dislocations are rare injuries. The authors demonstrate the feasibility of a posterior lumbar interbody fusion procedure in combination with posterolateral instrumentation and fusion.

Accidents, Occupational↗
PubMed2001

Tobramycin-containing bone cement and systemic cefazolin in a one-stage revision. Treatment of infection in a rabbit model.

The efficacy of tobramycin-containing bone cement with that of systemic cefazolin for treatment of infection in a one-stage revision model is compared. In addition, the value of detecting bacterial DNA after antibiotic treatment was investigated. An implant was inserted into the right tibia of rabbits after inoculation with Staphylococcus aureus. At 28 days, the implant was removed. Subsequently, either plain bone cement with or without systemic administration of cefazolin, or tobramycin-containing bone cement was injected into the medullary canal. The tibiae were cultured 14 days after revision (Day 42), and showed a significant decrease in bacterial counts for both antibiotic groups compared with the control group (p</=0.05). The rate of infection in the tobramycin-cement group was slightly higher (2/9) than in the cefazolin group (0/8), although the difference was not significant. Persistence of bacterial DNA after antibiotic treatment may be the result of delayed clearance of DNA and not a sign of active infection. This animal model shows that in a one-stage revision tobramycin-containing bone cement can reduce size and rate of infection, although systemic cefazolin may be more efficacious. Therefore, the use of antibiotic-containing bone cement combined with systemic antibiotic might provide optimal treatment.

Animals↗
PubMed2000

Prevention of infection with tobramycin-containing bone cement or systemic cefazolin in an animal model.

We investigated in an animal model the efficacy of tobramycin-containing bone cement and systemic cefazolin for infection prophylaxis. In 18 female rabbits, the femoral cavity was inoculated with Staphylococcus aureus before injection of bone cement. The first group of six rabbits received tobramycin-containing Simplex-P bone cement. Two other groups of six rabbits received plain Simplex-P bone cement. Preoperatively, in one of the two latter groups cefazolin was administered intravenously. The other group served as untreated controls. The rabbits were monitored for clinical signs of infection. At 7 days' follow-up, the femora were harvested and cultures from the bone adjacent to the cement plug were quantified. Cultures from the rabbits which received antibiotic prophylaxis (either cefazolin systemically or tobramycin-containing bone cement) were all negative. In contrast, all rabbits in the untreated control group had positive cultures. These rabbits also had other signs of infection such as an elevated erythrocyte sedimentation rate and loss of body weight. Culture results were confirmed by the absence of bacterial DNA in the polymerase chain reaction hybridization assay. In conclusion, we found that both tobramycin-containing bone cement and systemic cefazolin are effective in preventing implant bed infection in rabbits up to 7 days after contamination with S. aureus.

Animals↗
PubMed2000

Prophylaxis of implant-related staphylococcal infections using tobramycin-containing bone cement.

In a rabbit model, premixed tobramycin-containing bone cement was studied for its efficacy to prevent infections with two frequently encountered staphylococcal species in arthroplasty surgery. After intramedullary inoculation with staphylococci, either standard or premixed tobramycin-containing Simplex-P bone cement was injected in the right femur of 120 rabbits. Development of infection was examined by culture of femoral bone after 7 or 28 days. Loss of body weight and elevated erythrocyte sedimentation rate in the control rabbits inoculated with Staphylococcus aureus were seen in the first postoperative week, returning to normal in 28 days. Inoculation with Staphylococcus epidermidis resulted only in a low-grade infection. All rabbits receiving premixed tobramycin-containing bone cement were free of signs of infection, and all their cultures were negative. Culture yield from Staphylococcus aureus controls increased with time and inoculum dose. Staphylococcus epidermidis controls needed higher inoculum doses to establish an infection, while culture yield decreased in time. These differences in mode of prosthesis-related infection are explained by differences in virulence factors.

Animals↗
PubMed2000

Effects of hydrosyapatite coating on Ti-6A1-4V implant-site infection in a rabbit tibial model.

To investigate the effect of implant type after direct contamination, a hydroxyapatite-coated or noncoated Ti-6A1-4V implant was inserted into both tibiae of 32 New Zealand White rabbits. Prior to implantation, the left tibia was contaminated with increasing concentrations of Staphylococcus aureus (10(2)-10(5) colony-forming units), ranging from very low (10(2)) to relatively high (10(5)). Four weeks after implantation, half of the tibial bone adjacent to the implant was harvested for bacteriological examination. Bacterial counts were quantified by plating serial dilutions. For the histological evaluation, sections of the implant with the remaining tibia were examined by semiquantitative scoring of infection parameters. The bacteriological data showed the inoculum dose and implant type to have a significant effect on the culture outcome: more bacteria were retrieved from the hydroxyapatite-coated implants than from the noncoated titanium implants. Histological evaluation showed an increased score for the infected left tibiae compared with their contralateral control. In addition, with increasing inoculum dosage, the difference between the two types of implant increased. We demonstrated that infections can occur with biocompatible, noncemented implants and that they are related to the dose of the original inoculum. Bacteria were more likely to grow onto or next to the hydroxyapatite implants than on titanium implants and resulted in a more severe histopathological characterization of infection.

Aluminum↗
PubMed1999

MRI findings of thoracolumbar spine fractures: a categorisation based on MRI examinations of 100 fractures.

OBJECTIVE: To define the state of different structures of the fractured thoracolumbar spine which may play a role in the immediate and long-term mechanical stability on MR images and to investigate the relationship of these findings with the AO classification of spinal injuries. DESIGN: The state of the anterior longitudinal ligament, posterior longitudinal ligament, posterior ligamentous complex, cranial and caudal endplates, cranial and caudal discs and the vertebral body were defined using clinical, experimental and radiological data. The state of these structures was reported for each fracture on the MRI examinations and the different MRI features appropriate for different fracture classes were defined. PATIENTS: MRI examinations of 70 patients with 100 fractures of the thoracolumbar spine were used for this study. RESULTS: Wide variations were seen in the state of the structures studied. We could not find a definite pattern to relate these findings with the AO classification scheme. CONCLUSIONS: MR findings should be integrated into future classification schemes of thoracolumbar spine fractures. This would enable specific data about the structures involved in the stability of the spine to be acquired. Prospective studies using the criteria developed in this study may help resolve some of the controversies concerning the diagnosis and prognosis of these injuries as well as the development of new classification systems.

Humans↗
PubMed1999

Correlation of MR images of disc injuries with anatomic sections in experimental thoracolumbar spine fractures.

This cadaver study evaluated the value of MR images for detection of acute intervertebral disc damage associated with fractures of the thoracolumbar spine. Damage to the intervertebral disc may be a major contributor to chronic instability in non-operative treatment or failure of fixation and recurrence of deformity in posterior fixation methods. MR imaging can help us to understand the injury patterns and their prognostic significance. However, before we can justify the use of MRI in clinical cases, determination of MRI's ability to detect acute injury to the disc is necessary. Ten fresh cadaver specimens were used for this study. After obtaining radiograms and MR images, injuries were created with a weight-dropping apparatus using a variety of weights and compression angles. Post-injury radiograms and MR images were taken and the specimens were frozen at -20 degrees C. Slides of these specimens obtained with cryosection techniques were compared with MR images for evaluation of the damage to different parts of the discs. A total of 20 fractures were observed on cryosections. In 12 of the discs adjacent to fractured vertebral bodies, macroscopic damage was seen on the sections. These were all detected on the corresponding MR images. The study showed that MRI is able to detect acute, macroscopic injury to the intervertebral disc. It is therefore justified to use MR for the study of acute disc damage associated with thoracolumbar fractures.

Aged↗
PubMed1999

Critical size defect in the goat's os ilium. A model to evaluate bone grafts and substitutes.

Bone defects and their treatment are a well known problem in orthopaedic surgery. A critical size defect is a suitable model to study bone replacement materials. This study describes a critical size defect in the goal and the evaluation of three bone fillers (particulate autograft, particulate allograft, and a polyethylene oxide/polybutylene terephthalate copolymer) in this defect. The goat allows for implantation of large implants and has a metabolic rate more comparable with that of humans than small animals. The critical size defect, located in the goat's iliac wing, is easily reproducible and allows qualitative and quantitative evaluation of bone grafts and bone graft substitutes. After 3 months of healing, the unfilled defects showed 13.5% bone in the defect, the autografted defects 36.3%, and the allografted 18.5%. The copolymer gave only 1.5% bone in the defect; this is in contrast to previous reports. The described model allows for the evaluation of bone graft substitutes before introduction into clinical practice.

Animals↗
PubMed1998

Integration of press-fit implants in cortical bone: a study on interface kinetics.

The early healing phase of hard tissue implants is important to their long-term success. Problems during this phase can result in a so-called primary biological failure. In 24 New Zealand white rabbits, the healing in cortical bone of noncoated TiAlV and cpTi cylinders and of TiAlV cylinders plasma-spray-coated with hydroxyapatite (HA) of fluorapatite (FA) was investigated histologically and histomorphometrically after 3, 7, 14, and 28 days. Histomorphometry consisted of bone contact measurements and the use of a new semi quantitative scoring system that discriminated various tissues in contact with the implant. The results demonstrated that the most important parameter in initial implant healing is the bone itself and not the characteristics of the implanted material. For all implants, healing was characterized by a sequence of hematoma formation, bone resorption, and new bone formation where the initial press-fit situation revealed more bone-implant contact than after 7 and 14 days. There were only minor differences between the implant types: the new bone formation directly on the implant surface was qualitatively histologically superior to the CaP-coated implants, but this could be confirmed with the scoring method only for the HA-coated implants. It is concluded that initial press-fit fixation in cortical bones is not an end situation; rather, what happens is that as a result of interface remodeling, early postoperatively implant integration in the bone will decrease temporarily prior to a subsequent phase of new bone formation.

Animals↗
PubMed1998

[Total hip replacement arthroplasty in the Netherlands].

The total hip arthroplasty (THA) is an effective treatment of osteoarthritis of the hip joint. Each year, more than 16,000 THAs are performed in the Netherlands. The incidence of THA had doubled between 1980 and 1994. The medical indication has extended to younger and older patients. Due to the success of the THA the number of alternative treatments, such as arthrodesis and osteotomy decreased. The number of revision surgeries increased more than four folds, to 1,400 in 1994. Based on these data the increase of primary and revision hip arthroplasties is expected to continue, but it is unknown how much the exact increase will be. In view of the increased demand it is important to gain more insight into the numbers of primary and revision surgical procedures to be expected, so that a better estimation can be made of the health care capacity and financial resources required in the future.

Adolescent↗
PubMed1998

[An estimate of the intramural costs of the placement of a total hip prosthesis].

OBJECTIVE: Determining the intramural costs of the (re) placement of a total hip prostheses. DESIGN: Retrospective, descriptive. SETTING: Utrecht University Hospital (AZU) and the De Weezenlanden Hospital in Zwolle (ZWZ), the Netherlands. PATIENTS AND METHOD: From the records of 137 patients in whom an uncomplicated primary placement or revision of 151 total hip prostheses had taken place in the AZU or the ZWZ during the period 1990-93, data were collected on the number of days hospitalised, the length of the operation, the medical materials used, the number of radiological procedures, ECG's and laboratory determinations, and the visits to the outpatient clinic. The costs of a hip replacement were determined on the basis of the salary costs, tariffs and purchase prices. RESULTS: The average total cost was f 9381 for the placement of a cemented prosthesis, f 10,796 for the placement of a cement-free prosthesis, and f 17,879 for a revision operation. About 90% of the total costs were due to the price of hospitalization, surgery and prosthesis. With 14,000 primary placements and 1400 revisions annually, the cost is approximately 186 million guilders. An expected increase in the number of hip replacements and their cost should be taken into consideration.

Arthroplasty, Replacement, Hip↗
PubMed1998

[One hundred years of orthopedics in the Netherlands. VII. biomaterials].

The use of biomaterials in orthopaedics is becoming increasingly important. They are widely used in artificial joints, as bone replacement material and as resorbable material. Also (recombinant) bone morphogenetic proteins are used. Classification of biomaterials is based on composition (animal or human tissue, metals, polymers, ceramics or composites) or on biological reactions after implantation (bio-inert, bio-tolerant or bio-active). Depending on location and function biomaterials have to meet requirements with respect to durability (artificial joints), fixation (total hip prosthesis), flexibility (artificial ligaments), solubility (suture wire) and stiffness (plates and screws). The development of biomaterials is in full swing, focussing on the decrease of wear and the increase of durable fixation of artificial joints, and the induction of cells to form bone and cartilage tissue.

Biocompatible Materials↗
PubMed1998

The prevention of peridural adhesions. A comparative long-term histomorphometric study using a biodegradable barrier and a fat graft.

We studied peridural fibrosis in 16 dogs after laminectomies at the L2, L4 and L6 levels. They received either a free fat graft, a biodegradable mechanical barrier (polyethylene oxide (PEO)/polybutylene terephthalate (PBT) copolymer), or no treatment. The animals were killed after 4, 12, 26 and 52 weeks. Histomorphometry showed extensive and consistent peridural fibrosis in control and PEO/PBT groups. Fat grafts produced significantly less fibrous tissue, but the presence of the fat graft in the bony defect prevented closure. Degradation of the PEO/PBT barrier resulted in the formation of more fibrous tissue. We conclude that up to one year a free fat graft is effective in reducing the amount of peridural scarring.

Adipose Tissue↗
PubMed1998

Changes in the disc space after fractures of the thoracolumbar spine.

We have studied the intervertebral discs adjacent to fractured vertebral bodies using MRI in 63 patients at a minimum of 18 months after injury. There were 75 thoracolumbar fractures of which 26 were treated conservatively and 37 by posterior reduction and fusion with an AO internal fixator. We identified six different types of disc using criteria based on the morphology and the intensity of the MRI signal. The inter- and intraobserver variability of this system was good. Most of the discs showed predominantly morphological changes with no variation in signal intensity. Some disc types were associated with progressive kyphosis in patients treated conservatively. In those managed by operation, recurrent kyphosis appeared to result from creeping of the disc in the central depression of the bony endplate rather than from disc degeneration. Changes in the disc space after posterior fixation should not be seen as a form of chronic instability but as a redistribution of the disc tissue in the changed morphology of the space after fractures of the endplate.

Adolescent↗
PubMed1997

Periarticular aneurysm formation in haemophilia.

BACKGROUND: Spontaneous bleeding into the joints is common in haemophilia. Recurrent intra-articular bleeding leads to joint destruction. In the past 4 years we have carried out sixteen total knee replacements for haemophilic arthropathy. In three patients there was persistent bleeding with haemarthrosis, manifest skin discolouration, severe pain, and swelling, which was caused by a periarticular aneurysm. METHODS: Using angiography as part of the preoperative preparation, we initiated a prospective study. Ten angiographic examinations (six preoperative, two postoperative, one both) were carried out in seven patients without major complications. FINDINGS: In seven of the ten angiographic examinations, three preoperative and four postoperative, we found aneurysms around the knee. Since the patients with a positive postoperative finding did not have preoperative studies, we do not know whether the aneurysms existed before surgery. INTERPRETATION: Aneurysms can cause increased bleeding and other complications. The occurrence of spontaneous periarticular aneurysms in haemophilia has not been explored. In these cases, the resultant bleeding led to serious clinical symptoms that were not responsive to conservative measures. This new finding is relevant to those who surgically treat haemophilia patients. Angiography--and, when indicated, embolisation--before total knee replacement proved simple and effective as a diagnostic and therapeutic procedure.

Adult↗
PubMed1997

Healing of gaps around calcium phosphate-coated implants in trabecular bone of the goat.

Hydroxylapatite coatings are under clinical investigation in orthopaedics and dentistry. Bone formation on apatite coatings in the presence of gaps is important for clinical applications. The importance of the stability of the coating is not known at present. By varying the plasma-spray parameters, and by the addition of fluoride, the crystallinity and stability of calcium phosphates can be changed. It is suggested that bone formation is enhanced by dissolution of the apatite coating. We studied apatite coatings of varying stability with regard to their gap-healing characteristics, and we examined what the maximum gap would be that can be bridged if a coating is applied. Ti-6A1-4V implants coated with 62% crystalline hydroxylapatite, 30% crystalline hydroxylapatite or fluorapatite, or noncoated Ti-6A1-4V were implanted in 16 goats. The implants were surrounded by gaps of 1 or 2 mm, and the follow-up period was 6 weeks. Histological examination and histometry revealed that gaps of 1 mm can be bridged by bone if an apatite coating is applied. However, only a minimal amount of bone contact was seen on the apatite coatings with 2 mm gaps. Uncoated implants demonstrated no bone contact at all. Among the three different coatings there were no differences in gap healing. It can be concluded that in the goat, gaps of 2 or more mm between coated implants and host bone tissue inhibit bone deposition on the coating (p < 0.05), but the stability of the coating does not influence gap-healing characteristics.

Alloys↗
PubMed1997

Release of tobramycin from tobramycin-containing bone cement in bone and serum of rabbits.

Tobramycin release from tobramycin-containing bone cement was studied in vivo in a rabbit model. After insertion of cement into the right femur, tobramycin concentration as a function of time for up to 28 days was measured in serum and bone of rabbits. Tobramycin release in the femoral cortex adjacent to the cement was found to exceed the minimal inhibitory concentration for Staphylococcus aureus Wood 46. Serum tobramycin concentrations were below the systemic toxicity threshold.

Journal Article↗