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Biomedical subjects

W Puhl

Publications and source records attributed to W Puhl.

At least 55 records · Page 3Linked to original sources
PubMed1999

Biomechanical evaluation of a newly developed monocortical expansion screw for use in anterior internal fixation of the cervical spine. In vitro comparison with two established internal fixation systems.

STUDY DESIGN: The primary biomechanical stability of anterior internal fixation of the cervical spine obtained with a new monocortical expansion screw in vitro was evaluated. OBJECTIVES: To determine whether the anterior internal fixation of the spine obtained with the new monocortical expansion screw provides biomechanical stability comparable with that obtained with bicortical fixation. SUMMARY OF BACKGROUND DATA: The anterior plate instrumentation used with bicortical screw fixation in the cervical spine provides a primary stability superior to that associated with monocortical screw fixation. However, bicortical screws have the potential to perforate the posterior cortex. Therefore, monocortical instrumentation systems were developed, but without the biomechanical stability associated with bicortical systems. A new expansion screw for monocortical fixation was developed to improve biomechanical stability of monocortical systems. METHODS: Three different internal fixation systems were compared in this study: 1) H-plate with AO 3.5-mm bicortical screws, 2) cervical spine locking plate with monocortical screws, and 3) H-plate with the new monocortical expansion screws. Eight fresh human cadaver spine segments from C4 to C7 were tested in flexion-extension, axial rotation, and lateral bending using pure moments of +/- 2.5 Nm without axial preload. Five conditions were investigated consecutively: 1) intact spine; 2) uninstrumented spine with the segment C5-C6 destabilized; 3-5) instrumentation of the segment C5-C6 with the three implants mentioned above after removal of the disc and insertion of an interbody spacer. RESULTS: Between bicortical and monocortical expansion screw H-plate fixation, no significant differences were observed in all load cases concerning range of motion and neutral zone. The neutral zone and range of motion were significantly larger for the cervical spine locking plate than for bicortical and monocortical expansion screw fixation in all load cases, except neutral zone for axial rotation versus bicortical screw fixation. The instrumented cases only had a significantly lower range of motion and neutral zone than the intact cases in extension-flexion, whereas for lateral bending and axial rotation no significant differences could be observed. Because the experimental design precluded any cyclic testing, the data represent only the primary stability of the implants. CONCLUSIONS: In anterior instrumentation of the cervical spine using a H-plate, the new monocortical expansion screw provides the same biomechanical stability as the bicortical 3.5-mm AO screw and a significantly better biomechanical stability than the cervical spine locking plate. Therefore, the expansion screw may be an alternative to the bicortical fixation and does not involve the risk of penetration of the posterior vertebral body cortex.

Aged↗
PubMed1999

Epidural blood patch under fluoroscopic control: non-surgical treatment of lumbar cerebrospinal fluid fistula following implantation of an intrathecal pump system.

The treatment of lumbar cerebrospinal fluid fistula in the presence of an intrathecal catheter is known to be difficult. Open revision surgery is recommended in the literature, although the rate of recurrence is high. The epidural blood patch technique is well established as a successful treatment for post-dural-puncture headaches. Recent work about the distribution of the injected blood and theoretical considerations about the mechanism of action make this method suitable for the occlusion of spinal leakage even in the presence of an intrathecal catheter. In this note technical details are given for a successful therapy of lumbar cerebrospinal fluid fistula including the right positioning of the opening of the needle (cerebrospinal fluid can be expected intrathecally and epidurally) by injection of contrast medium first for myelography then for epidurography. In this procedure the (epidural) distribution of autologous blood can be indirectly controlled by compression of the dural sac. The method is easy to perform, and the possible risks are small.

Adult↗
PubMed1999

Reliability of radiological measurements in the assessment of hip dysplasia in adults.

Radiographic measurements are commonly used to quantify the treatment results of hip dysplasia and assess further need of operative treatment. We investigated the interobserver and intraobserver reliability of the commonest radiographic techniques in the assessment of hip dysplasia in skeletally mature adults. Three observers independently analysed 100 hip radiographs of patients with hip dysplasia aged between 16 and 32 years. We measured centre-edge angle of Wiberg, acetabular angle of Sharp, acetabular index of the weightbearing zone, acetabular index of depth to width, ACM-angle, MZ-distance, acetabular head index, lateral subluxation and neck-shaft angle. In addition, the radiographs were reviewed a second time 3 months apart by two of the observers to assess intraobserver reliability. We found a high correlation (intraclass correlation coefficient) for interobserver reliability (0.76-0.87) and intraobserver reliability (0.70-0.92) for all radiographic measurements except acetabular index of depth to width, ACM-angle and MZ-distance. Depending on the clinical question we therefore recommend the use of one of the reliable measurements to assess the radiograph of a dysplastic hip.

Adolescent↗
PubMed1998

Scoring prevalence and severity in gonarthritis: the suitability of the Kellgren & Lawrence scale.

In clinical and epidemiological studies the Kellgren & Lawrence (K&L) scale was mainly used in the past to determine the radiological prevalence and severity of gonarthritis. The dependency of this scoring system on the presence of osteophytes has been criticised, and owing to its varying reliability, its appropriateness in cross-sectional and longitudinal studies is questioned. It was the purpose of this study to test whether the dependency of the K&L scale on the presence of osteophytes is reflected in a higher correlation of the overall score with a separate scoring of 'osteophytes' than with other radiological features. Furthermore we compared the inter- and intrarater reliability with the reliability of individual radiological features. Knee radiographs of 40 patients were graded according to the K&L scale and for the presence and severity of five separate radiological features of osteoarthritis. We found a moderate correlation of the K&L scale with the radiological features of 'osteophytes', 'joint space narrowing' and 'flattening of condyles'. The intra- and inter-rater reliability of the K&L scale was higher than the reliability of the individual radiological features. The K&L scale seems not to be strongly dependent on the presence of osteophytes, i.e. there is not a higher correlation of the overall score with that feature than with other radiological features.

Aged↗
PubMed1998

[Integration properties of bone substitute materials. Experimental studies on animals].

In order to avoid the potential risks of disease transmission in allograft surgery, numerous substitute materials have been described. As the biological response to implant materials is different, we undertook the following study to assess type and amount of bone ingrowth in CaP-ceramics. 105 cylindrical bone defects with a diameter of 5.4 mm were created surgically in the femoral condyles of 53 skeletal mature NZW rabbits. The defects were filled with crushed coralline hydroxyapatite (HA) implants (n = 21), synthetically produced hydroxyapatite (n = 21) and surface-modified alpha-Tricalciumphosphate (TCP) grains (n = 21). 21 defects were left empty and other drill holes were filled with rabbit cancellous bone cylinders (n = 21) after 3 months of cryopreservation at -78 degrees C without sterilization. Following observation periods of 2, 4, 6, 8, 12, 26 and 52 weeks the femoral condyles were harvested for histological evaluation and quantitative analysis of bone ingrowth. Woven bone formation at implant periphery can be observed in all substances as early as 2 weeks postoperatively. At 4-week-intervals cryopreserved allografts show new bone apposition on surfaces of necrotic trabeculae and graft-host junctions by a predominantly osteoblastic reaction at the periphery of all cylinders, while in HA- and TCP-grains early bone formation in the center of drill holes is detectable as well. There is a direct contact between HA-/TCP-particles and newly formed bone without fibrous tissue formation at the implant surfaces. Central new bone formation in rabbit allografts can be observed after 6 to 8 weeks together with a secondary osteoclastic resorption of necrotic transplant trabeculae. The result of this remodeling process is a complete degradation of transplant cylinders with reorganization of vital trabeculae oriented in a mature pattern after 12 to 26 weeks. In contrast the HA- and TCP-implants did not show any signs of resorption.

Animals↗
PubMed1998

Prevalence of generalised osteoarthritis in patients with advanced hip and knee osteoarthritis: the Ulm Osteoarthritis Study.

OBJECTIVES: Different prevalences of generalised osteoarthritis (GOA) in patients with knee and hip OA have been reported. The aim of this investigation was to evaluate radiographic and clinical patterns of disease in a hospital based population of patient subgroups with advanced hip and knee OA and to compare the prevalence of GOA in patients with hip or knee OA, taking potential confounding factors into account. METHODS: 420 patients with hip OA and 389 patients with knee OA scheduled for unilateral total joint replacement in four hospitals underwent radiographic analysis of ipsilateral and contralateral hip or knee joint and both hands in addition to a standardised interview and clinical examination. According to the severity of radiographic changes in the contralateral joints (using Kellgren-Lawrence > or = grade 2 as case definition) participants were classified as having either unilateral or bilateral OA. If radiographic changes of two joint groups of the hands (first carpometacarpal joint and proximal/distal interphalangeal joints defined as two separate joint groups) were present, patients were categorised as having GOA. RESULTS: Patients with hip OA were younger (mean age 60.4 years) and less likely to be female (52.4%) than patients with knee OA (66.3 years and 72.5% respectively). Intensity of pain and functional impairment at hospital admission was similar in both groups, while patients with knee OA had a longer symptom duration (median 10 years) compared with patients with hip OA (5 years). In 41.7% of patients with hip OA and 33.4% of patients with knee OA an underlying pathological condition could be observed in the replaced joint, which allowed a classification as secondary OA. Some 82.1% of patients with hip and 87.4% of patients with knee OA had radiographic changes in their contralateral joints (bilateral disease). The prevalence of GOA increased with age and was higher in female patients. GOA was observed more often in patients with knee OA than in patients with hip OA (34.9% versus 19.3%; OR = 2.24; 95% CI: 1.56, 3.21). Adjustment for the different age and sex distribution in both patient groups, however, takes away most of the difference (OR = 1.32; 95% CI: 0.89, 1.96). CONCLUSION: The crude results confirm previous reports as well as the clinical impression of GOA being more prevalent in patients with advanced knee OA than in patients with advanced hip OA. However, these different patterns might be attributed to a large part to a different distribution of age and sex in these hospital based populations.

Age Factors↗
PubMed1998

Serum cholesterol and osteoarthritis. The baseline examination of the Ulm Osteoarthritis Study.

OBJECTIVE: To assess the association between serum cholesterol and osteoarthritis (OA). METHODS: OA patterns were studied in 809 patients with knee or hip joint replacement due to OA in 4 hospitals in southwest Germany. Participants had a standardized interview and examination. Radiographs of the contralateral joint as well as both hands and a blood sample were obtained. Serum cholesterol levels were divided into tertiles and hypercholesterolemia was defined as > or = 6.2 mmol/l or use of antihyperlipidemic drugs. According to the presence or absence of radiographic OA in the contralateral joint, participants were categorized as having bilateral or unilateral OA. If radiographic OA of different finger joints was present, participants were categorized as having generalized OA. Odds ratios and 95% confidence intervals for the association of serum cholesterol with OA patterns were calculated with logistic regression, adjusting for potential confounders. RESULTS: Eighty-five percent of participants with radiographs had bilateral OA and 26% generalized OA. No association was observed between hypercholesterolemia and bilateral OA. Hypercholesterolemia (OR 1.61; 95% CI 1.06-2.47) and high serum cholesterol levels (3rd versus 1st tertile: OR 1.73; 95% CI 1.02-2.92) were independently associated with generalized OA. This association was almost exclusively due to participants with knee OA. CONCLUSION: These data add to the evidence regarding the independent role of serum cholesterol as a systemic risk factor for OA. The discrepant associations observed for different OA patterns are likely due to the relative weight of other risk factors.

Aged↗
PubMed1997

[Spondylolisthesis and pseudospondylolisthesis. Treatment by segmental reposition and interbody fusion with fixateur interne].

In spondylolisthesis with an indication for fusion and with a slipping of more than 50% at least a partial reposition should be reached in general because the incidence of pseudarthrosis would increase with a fusion in situ and a large disturbance of the spinal statics would persist. Hereby with almost all methods an enlarged operative morbidity and often a longer fusion range has to be taken in account compared to the fusion in situ. Therefore, in smaller slippages the fusion in situ will be favoured because the disturbance of the statics is not so important, that such an effort combined with such methods is necessary. If the operation method with small spondylolisthesis and pseudospondylolisthesis allows the reposition without much effort and if the operative morbidity in comparison with the fusion in situ is not higher, then it is reasonable to fuse the cases with a spondylolisthesis Meyerding grade 1 and 2 in the anatomic corrected position too. Because the spinal fixator we use fills out these criteria we combine the correction of the position with the fusion also in cases of small spondylolisthesis. The incidence of neurologic complications correlates with the amount of the reposition distance and can be caused by preforaminal or extraforaminal lesions. The reduction of small malpositions could only produce preforaminal lesions. Using the spine fixator with its reposition instruments linked outside the wound and with it's un-inhibited access to the segment and to the preforaminal neural structures during the whole repositioning these lesions can be avoided.

Humans↗
PubMed1997

Complexity of IL-1 beta induced gene expression pattern in human articular chondrocytes.

The mRNA fingerprinting technique, differential display reverse transcription polymerase chain (DDRT-PCR), was used to detect changes in the overall pattern of gene expression in human articular knee chondrocytes-induced by interleukin-1 beta (IL-1 beta), the prototypical inducer of catabolic responses in degenerate joint diseases. One hundred different primer combinations generated approximately 10,000 different PCR fragments for IL-1 beta treated, as well as for untreated human chondrocytes, cultivated in alginate beads. This represented 53% of all expressed chondrocyte genes as based on statistical considerations. Side by side comparisons of differential display patterns originating from two different donor tissues yielded 44 reproducibly, differentially-displayed cDNA fragments, which were subcloned and sequenced. Sequence homology searches revealed sequence identities to the human necrosis factor alpha (TNF-alpha) and IL-1 regulated gene TSG-6, fibronectin, osteopontin, calnexin, and the DNA repair enzyme ERCC5. The differential expression was confirmed with Northern and quantitative PCR analyses. The known function of these genes and their known IL-1 responsiveness indicate that the employed model system reflects the pleiotropic effects of IL-1 on the overall gene expression in human articular chondrocytes and identifies genes involved in very different biochemical pathways. Twenty-seven cDNAs lacked sequence homologies to known genes and may represent novel genes.

Aged↗
PubMed1997

Autotransfusion--bacterial contamination during hip arthroplasty and efficacy of cefuroxime prophylaxis. A randomized controlled study of 40 patients.

40 patients undergoing primary hip arthroplasty, given autologous processed blood transfusion, were randomized a receive no antibiotic prophylaxis (group A, n 20) or cefuroxime (1.5 g single injection; group B, n 20). Bacterial contamination at various steps in the autotransfusion procedure was assessed in liquid and solid culture media. The operation field and the wound drainage blood were never contaminated either of the groups but some of the suction tips were. Parts of the Vacufix blood collection bags of group A contained bacteria, but none in group B. Processed red blood cell concentrates in both groups showed bacterial growth. Greater blood loss did not increase the contamination rate in general. Isolated bacteria included the species Staphylococcus epidermidis, coagulase-negative staphylococci and Propionibacteria in both groups, but with different cell counts. In addition, Corynebacterium bovis et minutissimum and Moraxelle were identified in group A. In conclusion, autologous blood transfusion was a safe procedure. If contamination occurred, the bacterial count was low, and the bacteria of low pathogenicity. Antibiotic prophylaxis with cefuroxime reduced this contamination of suction tips and collection bags and limited the transfer of autologous blood products.

Antibiotic Prophylaxis↗
PubMed1996

In situ rigidity of a new sliding rod for management of the growing spine in Duchenne muscular dystrophy.

STUDY DESIGN: This biomechanical, in vitro laboratory study determined the static stiffness of a new telescoping rod and the axial motion of this implant during various loading conditions. OBJECTIVES: To compare the stability of the new telescoping rod with the classic Luque instrumentation, and to determine whether the sliding rod elongates or contracts during spine motion. SUMMARY OF BACKGROUND DATA: A new telescoping rod was developed to stabilize the spine in children with Duchenne muscular dystrophy and to provide capacity for spinal growth. METHODS: The stability of 11 instrumented calf spines was determined in flexion, extension, lateral bending, and torsion to determine the stiffnesses of the spines instrumented with these two implants. The telescoping motion in the left and right rod was measured in the new rod system. RESULTS: In flexion, the spines with the telescoping rods were stiffer than those with the Luque implant. However, no significant differences in the stiffness coefficients were found for extension, lateral bending, or torsion. The restoring force of the telescoping system was greater than that of the Luque system in all directions. All modes of loading produced an accommodating change of length in the construct. CONCLUSIONS: The dynamic telescoping system provides stiffness comparable with that of established systems while allowing elongation during growth of the young patient.

Animals↗
PubMed1996

Recombinant human osteogenic protein 1 is a potent stimulator of the synthesis of cartilage proteoglycans and collagens by human articular chondrocytes.

OBJECTIVE: To study the effects of recombinant human osteogenic protein-1 (rHuOP-1; bone morphogenetic protein-7) on proteoglycan and collagen synthesis by human articular chondrocytes. METHODS: Articular chondrocytes from fetal, adolescent, and adult human donors were cultured in alginate beads for 4 days in a mixture of Ham's F-12, Dulbecco's modified Eagle's medium, 10% fetal bovine serum (FBS), then for an additional 3-10 days in the presence and absence of rHuOP-1, with and without FBS. Chondrocyte synthetic activity was measured as the amount of incorporation of 35S-sulfate into proteoglycans and 3H-proline into hydroxyproline. Sieve chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis were performed to identify specific proteoglycans and collagens. RESULTS: Recombinant human OP-1 markedly stimulated the synthesis of proteoglycans (mostly aggrecan) and collagens (predominantly type II) by all chondrocyte preparations. This did not require the presence of FBS and was associated with continued expression of the chondrocyte phenotype. CONCLUSION: Recombinant human OP-1 is a more potent stimulator of the synthesis of cartilage-specific molecules by human articular chondrocytes than are other factors tested for comparison, including TGF beta 1 and activin A.

Activins↗
PubMed1996

Influence of hemodilution on cefuroxime levels and bacterial contamination of intra- and postoperative processed wound blood during hip replacement.

MATERIALS AND METHODS: In a prospective randomized study we investigated the effect of hemodilution on cefuroxime levels and bacterial contamination of processed shed blood during hip arthroplasty. 10 patients received cefuroxime 1,5 g as single shot prophylaxis before (group A), 10 after hemodilution (15 ml/KG) (group B). Cefuroxime levels in serum 1 h after administration, at the end of operation, after 12 h and in drainage-blood after 12 h were assessed by HPLC. Bacteriological study was performed from collecting bags (Vacufix), wound drainage blood and processed red blood cell concentrates, using pour plate technique and broth culture enrichment. RESULTS AND DISCUSSION: Mean concentrations of cefuroxime were higher in group B than group A, but differed not significantly. No bacterial contamination was found in collecting bags and wound drainages in both groups. Processed red cell concentrates in group B showed no growth. In group A, however, 3/10 were contaminated with < or = CFU/ml of coagulase-negative Staphylococcus, Staphylococcus epidermidis and Propionibacterium acnes. The differences between groups did not reach the level of statistical significance and could not be related to lower cefuroxime levels. No wound infection occurred in either group.

Antibiotic Prophylaxis↗
PubMed1995

Effects of excimer laser on healing of articular cartilage in rabbits.

This study examined healing of 1.0 mm diameter defects in rabbit knee articular cartilage for as long as 14 weeks after creation of the defects by either laser or drilling. The purpose of the research was to determine the effects of laser debridement of cartilage on the intrinsic biomechanical properties of the repair tissue. We therefore imitated chondral shaving and subchondral abrasion of cartilage by creating partial-thickness and full-thickness cartilage defects of standardized size with both excimer laser and drilling. Light and scanning electron microscopic examinations of the repair tissue showed that healing of osteochondral defects created by laser may be delayed compared with defects created by drilling, for at least 6 weeks postoperatively. Even though there initially was a considerable delay in healing in the laser group, neither laser nor drilling had any appreciable effects on the mechanical properties of the repair tissue, as demonstrated by biomechanical testing at 14 weeks. Specifically, the repair cartilage in the defects in the laser group had the following material properties (mean +/- SD): aggregate modulus, 0.40 +/- 0.24 MPa; Poisson's ratio, 0.37 +/- 0.08; permeability, 3.72 +/- 4.28 x 10(-15) m4/N.s; and thickness, 0.20 +/- 0.06 mm. The corresponding values for the defects in the drilling group were 0.39 +/- 0.23 MPa, 0.34 +/- 0.09, 3.82 +/- 3.44 x 10(-15) m4/N.s, and 0.22 +/- 0.09 mm. The repair tissue from both types of defects was pooled, and the values were compared with those for contralateral (control) tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗