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N P Haas

Publications and source records attributed to N P Haas.

At least 19 recordsLinked to original sources
PubMed2002

Recombinant species-specific growth hormone increases hard callus formation in distraction osteogenesis.

The effect of growth hormone (GH) on secondary fracture healing and callus formation has been demonstrated in several previously investigated animal models. The aim of this study was to investigate and quantify the effects of GH on bone regenerates in a distraction osteogenesis model. In 20 mature female Yucatan micropigs, the tibia and fibula were osteotomized, stabilized with an external fixator, and distracted at 2 mm/day for 10 days after a 4 day latency period. The regenerates were allowed to consolidate for 10 days. Micropigs in the study group (ten animals) received a daily injection of 100 microg per kilogram body weight of recombinant porcine growth hormone (r-pGH). Micropigs in the control group (ten animals) received sodium chloride as placebo. After killing on day 25, a quantitative histomorphometrical analysis of the formed callus and the adjacent cortical bone was performed and the results of polychrome in vivo labeling were assessed. The regenerates of the r-pGH-treated animals showed a significantly larger callus area but no change in callus structure. We found islands of cartilage tissue in the regenerates of both groups; the calli from the control group exhibited a higher fraction of cartilage compared with the r-pGH group, but this was not significant. Quantification of the fluorescent in vivo labeling revealed that the distraction gap in GH-treated group showed significant ossification even during distraction. These results demonstrate that growth hormone can accelerate the maturation of the regenerate in distraction osteogenesis without changing the callus microstructure. This may prove to be a useful clinical tool for shortening the healing time in limb lengthening and bone segment transport.

Animals↗
PubMed2002

Insulin-like growth factor-1 and transforming growth factor-beta1 accelerates osteotomy healing using polylactide-coated implants as a delivery system: a biomechanical and histological study in minipigs.

Stimulation of bone healing and bone formation through local application of growth factors from implants may improve the clinical outcome in fracture treatment. Previous studies demonstrated a high mechanical stability of a thin poly(D,L-lactide) (PDLLA) coating on metallic implants that can withstand the process of intramedullary insertion. Following an initial peak, 80% of incorporated insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1) were released continuously, within 42 days. The goal of the present study is evaluation of the coated implants on fracture healing in a large animal model. A midshaft osteotomy (1 mm gap) of the right tibia of Yucatan minipigs was stabilized with uncoated vs. coated titanium interlocking nails (5 mm). X-ray examinations and blood analyses (including IGF-1 and IGF-binding proteins) were performed, and body weight and body temperature were taken throughout the experiment. After 28 days, both tibiae were dissected for mechanical torsional testing and histomorphometric analyses. No differences were found in the blood analyses, body weight, or temperature due to the coating or the incorporated growth factors between the groups. X-ray examinations revealed a faster consolidation of the osteotomy in the growth factor-treated group. Biomechanical testing showed a significantly higher torsional stiffness and maximum load. Progressive remodeling was observed in the histological and histomorphometric analyses with a larger callus volume in the growth factor group compared with the control groups. We conclude that local application of growth factors from a biodegradable PDLLA coating of intramedullary implants accelerates bone healing in a large animal model without systemic side effects.

Animals↗
PubMed2001

Biomechanical comparison of cervical spine interbody fusion cages.

STUDY DESIGN: An in vitro biomechanical study of cervical spine interbody fusion cages using a sheep model was conducted. OBJECTIVES: To evaluate the biomechanical effects of cervical spine interbody fusion cages, and to compare three different cage design groups. SUMMARY AND BACKGROUND DATA: Recently, there has been a rapid increase in the use of cervical spine interbody fusion cages as an adjunct to spondylodesis. These cages can be classified into three design groups: screw, box, or cylinder designs. Although several comparative biomechanical studies of lumbar interbody fusion cages are available, biomechanical data for cervical spine constructs are lacking. Additionally, only limited data are available concerning comparative evaluation of different cage designs. METHODS: In this study, 80 sheep cervical spines (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method using a nonconstrained testing apparatus. Three-dimensional displacement was measured using an optical measurement system (Qualysis). Complete discectomy (C3-C4) was performed. Cervical spine interbody fusion cages were implanted according to manufacturers' information. Eight spines in each of the the following groups were tested: intact, autologous iliac bone graft, two titanium screws (Novus CTTi; Sofamor Danek, Koln, Germany), two titanium screws (BAK-C 8 mm; Sulzer Orthopedics, Baar, Switzerland), one titanium screw (BAK-C 12 mm; Sulzer Orthopedics), carbon box (Novus CSRC; Sofamor Danek), titanium box (Syncage; Synthes, Bochum, Germany), titanium mesh cylinder (Harms; DePuy Acromed, Sulzbach, Germany), titanium cylinder (MSD; Ulrich, Ulm, Germany), and titanium cylinder (Kaden; BiometMerck, Berlin, Germany). The mean apparent stiffness values were calculated from the corresponding load-displacement curves. Additionally, cage volume and volume-related stiffness was determined. RESULTS: After cervical spine interbody fusion cage implantation, flexion stiffness increased, as compared with that of the intact motion segment. On the contrary, rotation stiffness decreased after implantation of a cervical spine interbody fusion cage, except for the Novus CSRC, Syncage, and Kaden-Cage. If two screws were inserted (Novus CTTi and BAK-C 8 mm), there was no significant difference in flexion stiffness between screw and cylinder design groups. If one screw was inserted (BAK-C 12 mm), flexion stiffness was higher for cylinder designs (P < 0.05). Extension and bending stiffness were always higher with cylinder designs (P < 0.05). Volume-related stiffness for flexion extension and bending was highest for the Harms cage (P < 0.05). There was no difference for rotation volume-related stiffness between Harms and Syncage. CONCLUSIONS: The biomechanical results indicate that design variations in screw and cylinder design groups are of little importance. In this study, however, cages with a cylinder design were able to control extension and bending more effectively than cages with a screw design.

Animals↗
PubMed2001

Biodegradable poly(D,L-lactide) coating of implants for continuous release of growth factors.

Local application of growth factors like insulin like growth factor-I (IGF-I) and transforming growth factor-beta 1 (TGF-beta1) from a biodegradable thin layer of poly(D,L-lactide) (PDLLA) coated implants could stimulate fracture healing. A new "cold coating technique" for metallic implants was established to produce a biodegradable coating with a high mechanical stability that provides a continuous release of incorporated growth factors. The properties of this bioactive coating were investigated in vitro and in vivo. Scanning electron microscope analysis revealed a coating thickness of in average 14.8 microm on titanium and 10.7 microm on steel wires. Intramedullary implantation and extraction experiments depicted a loss of PDLLA coating from titanium and steel implants of less than 5%. After explantation of the implants, the coating displayed a complete and regular layer without any defects of PDLLA uncovering the metallic surface. Smear tests demonstrate that the coating can be performed under sterile conditions. The PDLLA depicted a reduction of about 8% within 6 weeks in vitro and in vivo. The growth factors were incorporated in a stable form and demonstrated a loss of stability of less than 3% within 42 days and less than 5% within one year. In an elution experiment, 54% IGF-I and 48% TGF-beta1 were released within the first 48 h. After 42 days, 76% of IGF-I and 71% of TGF-beta1 were detected in the elution fluid by ELISA. Comparable results were obtained in the in vivo experiments after 42 days.

Animals↗
PubMed2001

[LISS--internal plate fixator].

The LISS DF (less invasive stabilisation system) is a new internal fixator for the operative treatment of distal femur fractures following the principles of minimally invasive surgery. The fixation of the implant is based on screws providing angular stability, which are inserted percutaneously guided by an aiming device. A large exposure of the fracture zone is not necessary. Between December 1996 and November 1998 a multicentre study were defined including finally 112 patients with 116 distal femur fractures treated with a LISS system. A follow up rate of 93% could be achieved, showing a fractures consolidation in 96% of all cases after 12 months. The results of the study showed a low rate of secondary bone grafting. The LISS system is a secure device for the treatment of all distal femur fractures including complex articular fractures types.

Adult↗
PubMed2001

[Mechanical comparison of biodegradable intervertebral lumbar cages].

INTRODUCTION: A biodegradable interbody cage for lumbar spine fusion would be able to solve several problems associated with the use of metallic cages. In a biomechanical in vitro study using human lumbar spines three different biodegradable poly(L-lactide-co-D,L-lacitide)(PLDLLA) cages were compared to metallic cages of the same design. MATERIAL AND METHOD: 40 human cadaver lumbar specimens (L3-S1) were tested in flexion, extension, rotation, and bending with a non-destructive flexibility method using a nonconstrained testing apparatus. Seven different groups were examined: (1) control group (intact) (n = 40); (2) unstable group (after discectomy L4/5) (n = 40), (3) autologous iliac crest bone graft (n = 8), (4) BAK-Cage (n = 8), (5) BIO-Cage 1 (PLDLLA) (n = 8), (6) BIO-Cage 2 (PLD-LLA/hydroxylapatite-buffer) (n = 8) and (7) BIO-Cage 3 (PLDLLA/hydroxylapatite particles of different size) (n = 8). Additionally, destructive compression tests of all implants were performed. RESULTS: In comparison to the intact motion segment all cages showed significantly lower range of motion (ROM) in all test modes (P < 0.01). There was no significant difference in stiffness values and ROM between BIO-Cages and metallic cages. Axial compression stiffness and failure load were significantly highest for metallic BAK-cages (P < 0.05). No significant difference for failure load was observed between BIO-cage 1 and the intact motion segment. However, in comparison to the intact motion segment failure load was significantly lower for BIO-cage 2 and 3 (P < 0.05). CONCLUSION: The results of this study are encouraging, because the biodegradable cages were able to limit lumbar spine motion similar to the metallic cages. Especially, the biodegradable PLDLLA cage consisting of pure polymer (BIO-Cage 1) showed adequate initial compression strength. However, further in vivo animal experiments are essential prior to the clinical application of biodegradable lumbar interbody fusion cages.

Absorbable Implants↗
PubMed2001

[Transoral atlanto-axial plate fixation in the treatment of a malunited dens fracture and secondary atlanto-axial instability].

INTRODUCTION: A case of a 22-year-old patient with a malunited dens fracture and secondary atlanto-axial instability is presented. The significant narrowing of the spinal canal due to the atlanto-axial instability was associated with anterior myelon compression and neurological deficit. METHODS: A transoral approach with odontoid resection and anterior atlanto-axial plate fixation was performed. With this technique the atlanto-axial subluxation was reduced and the myelon was decompressed. RESULTS: The postoperative course was uneventful. The follow-up showed a complete remission of the neurological deficit and a bony fusion of the atlanto-axial joints. CONCLUSIONS: The presented case illustrates the importance of an accurate initial diagnosis of the degree of instability and the need for short-term follow-up examinations. If atlanto-axial pseudarthrosis or malunion with anterior spinal cord compression occurs, a transoral procedure with odontoid resection and atlanto-axial plate fixation seems to be an excellent salvage procedure.

Adult↗
PubMed2001

[Navigation assisted by image conversion. An experimental study on pelvic screw fixation].

Within an experimental trial the new method of fluoroscopy based navigation was tested for percutaneous pelvic screw fixations. A regular C-arm was used and the navigation system developed by Medivision. In a first step appropriate C-arm projections were defined for five standardized screw positions. Then precision and fluoroscopy time of 60 screws in 6 artificial pelves were evaluated. For the sacroliacal screw in S1, S1 screw in S2, anterior column screw, posterior column screw and the supraacetabular ilium screw three to four appropriate projections were defined. These were all combinations of the known special pelvic views inlet/outlet and iliac/obturator. Using these standardized views the average fluoroscopy time was 6 seconds per screw. 51 screws (85%) were inserted correctly. In five cases there was a slight deviation without perforating the cortex, four times the cortex was perforated.

Acetabulum↗
PubMed2001

[Biomechanical study of angle-stable anterior atlanto-axial spondylodesis plate].

The optimum fixation method to achieve atlantoaxial fusion after odontoid resection is still subject to discussion. Isolated posterior surgical procedures for treatment of irreducible atlantoaxial kyphosis with spinal cord compression are associated with a high rate of morbidity and mortality. Transoral atlantoaxial plate fixation has been described by Harms as a fixation technique after odontoid resection. The purpose of this study was to compare biomechanically a new anterior atlantoaxial locking plate (AALP) with the Harms plate and the atlantoaxial transarticular screw fixation described by Magerl. Sixteen human cadaver craniocervical specimens were tested in flexion, extension, rotation, and bending with a nondestructive flexibility method using a nonconstrained testing apparatus. Five different groups were examined: (1) control group (intact) (n = 16), (2) unstable group (after dissection of the atlantoaxial ligaments and odontoidectomy) (n = 16), (3) Harms group (transoral atlantoaxial plate fixation) (n = 8), (4) AALP group (anterior atlantoaxial locking plate fixation) (n = 8), and (5) Magerl group (transarticular atlantoaxial screw fixation) (n = 16). Stiffness in any direction was significantly higher in the AALP specimens and those fixated with the Magerl method than in the Harms, control, or unstable specimens. The difference in stiffness between the AALP and Magerl reconstruction groups was not statistically significant. Experimentally, the AALP was significantly stiffer than the Harms plate. The AALP provided stiffness equal to transarticular screw fixation according to Magerl. A question that cannot be answered by this in vitro study concerns the level of rigidity required to obtain long-term stability and fusion by atlantoaxial fixation methods. However, it may be assumed that the more spinal motion is eliminated the greater the chance of definite spinal fusion. Therefore, it seems reasonable that the most reliable and rigid fixation method would be the method of choice.

Aged↗
PubMed2001

Mechanical boundary conditions of fracture healing: borderline indications in the treatment of unreamed tibial nailing.

Unreamed nailing favors biology at the expense of the achievable mechanical stability. It is therefore of interest to define the limits of the clinical indications for this method. The extended usage of unreamed tibial nailing resulted in reports of an increased rate of complications, especially for the distal portion of the tibia. The goals of this work were to gain a thorough understanding of the load-sharing mechanism between unreamed nail and bone in a fractured tibia, to identify the mechanical reasons for the unfavorable clinical results, and to identify borderline indications due to biomechanical factors. In a three-dimensional finite element model of a human tibia, horizontal defects were stabilized by means of unreamed nailing for five different fracture locations, including proximal and distal borderline indications for this treatment method. The loading of the bone, the loading of the implant and the inter-fragmentary strains were computed. The findings of this study show that with all muscle and joint contact forces included, nailing leads to considerable unloading of the interlocked bone segments. Unreamed nailing of the distal defect results in an extremely low axial and high shear strain between the fragments. The results suggest that mechanical conditions are advantageous to unreamed nailing of proximal and mid-diaphyseal defects. Apart from biological reasons, clinical problems reported for distal fractures may be due to the less favorable mechanical conditions in unreamed nailing. From a biomechanical perspective, the treatment of distal tibial shaft fractures by means of unreamed nailing without additional fragment contact or without stabilizing the fibula should be carefully reconsidered.

Biomechanical Phenomena↗
PubMed2001

Musculo-skeletal loading conditions at the hip during walking and stair climbing.

Musculo-skeletal loading plays an important role in the primary stability of joint replacements and in the biological processes involved in fracture healing. However, current knowledge of musculo-skeletal loading is still limited. In the past, a number of musculo-skeletal models have been developed to estimate loading conditions at the hip. So far, a cycle-to-cycle validation of predicted musculo-skeletal loading by in vivo measurements has not been possible. The aim of this study was to determine the musculo-skeletal loading conditions during walking and climbing stairs for a number of patients and compare these findings to in vivo data. Following total hip arthroplasty, four patients underwent gait analysis during walking and stair climbing. An instrumented femoral prosthesis enabled simultaneous measurement of in vivo hip contact forces. On the basis of CT and X-ray data, individual musculo-skeletal models of the lower extremity were developed for each patient. Muscle and joint contact forces were calculated using an optimization algorithm. The calculated peak hip contact forces both over- and under-estimated the measured forces. They differed by a mean of 12% during walking and 14% during stair climbing. For the first time, a cycle-to-cycle validation of predicted musculo-skeletal loading was possible for walking and climbing stairs in several patients. In all cases, the comparison of in vivo measured and calculated hip contact forces showed good agreement.Thus, the authors consider the presented approach as a useful means to determine valid conditions for the analysis of prosthesis loading, bone modeling or remodeling processes around implants and fracture stability following internal fixation.

Aged↗
PubMed2001

Influence of femoral anteversion on proximal femoral loading: measurement and simulation in four patients.

OBJECTIVE: The aim of this study was to determine the loading of the proximal femur during daily activities and to quantify the influence of femoral anteversion. DESIGN: This study combined experimental and analytical approaches to determine the in vivo loading at the hip joint. A numerical musculo-skeletal model was validated against measured in vivo hip contact forces and then used to analyse the influence of anteversion on the loading conditions in the femur. BACKGROUND: Musculo-skeletal loading of long bones is essential for joint replacement and fracture healing. Although joint contact forces have previously been measured in selected patients, the interaction between femoral anteversion and the associated musculo-skeletal loading environment remains unknown. METHODS: The gait of four patients with force measuring hip prostheses was analysed during walking and stair-climbing. Musculo-skeletal loading was determined using individual numerical models by minimising the sum of the muscle forces. RESULTS: Experimentally and numerically determined hip contact forces agreed both qualitatively and quantitatively. Muscle activity resulted in compression of the femur and small shear forces in the meta- and epi-physeal regions. Increasing the anteversion to an angle of 30 degrees increased hip contact forces and bending moments up to 28%. CONCLUSIONS: This study has shown that femoral anteversion has a strong influence on the musculo-skeletal loading environment in the proximal femur. RELEVANCE: Detailed musculo-skeletal modelling may allow pre-surgical, patient specific optimisation of loading on implant, bone and soft tissues.

Biomechanical Phenomena↗
PubMed2001

Three-dimensional ultrasonography of bone and soft tissue lesions.

BACKGROUND: The aim of this study was to investigate feasibility and potential applications of three-dimensional (3D) ultrasonography in the evaluation of musculoskeletal disorders. METHODS: 3D ultrasonography was performed in 83 patients with bone (n = 50) or soft tissue lesions (n = 33). Volume data were obtained using two volume probes (1-8.5 and 8.5-12 MHz) and a 3D ultrasound unit. The results of 3D ultrasonography were compared to two-dimensional ultrasound and radiological imaging. RESULTS: The system enabled acquisition of 3D ultrasound data in diagnostic quality. 3D image-processing permits to analyse ultrasound data interactively in three orthogonal planes (section mode) or in realistic 3D views (rendering mode). Compared to conventional ultrasonography 3D image analysis improved assessment of details, provided better spatial orientation and facilitated image interpretation in 23, 44 and 49 cases, respectively. Additional findings that had significant influence on patient management were obtained in 16 of 83 patients (19%). Multiplanar reformating provided additional scan planes and increased the comparability of follow up examinations by standardized display and measurement. 3D surface reconstructions were very helpful to understand the morphology of bone lesions e.g. tortuous fracture lines. CONCLUSION: Our preliminary experience shows that 3D ultrasonography of musculoskeletal disorders is feasible. The ability to assess previously unattainable scan planes and lifelike surface projections may be particularly valuable for imaging of bone lesions. Further studies will be required to assess the exact role of this new technique for the evaluation of musculoskeletal disorders.

Adult↗
PubMed2001

Local application of growth factors (insulin-like growth factor-1 and transforming growth factor-beta1) from a biodegradable poly(D,L-lactide) coating of osteosynthetic implants accelerates fracture healing in rats.

In vitro and in vivo studies have demonstrated an osteoinductive effect of growth factors such as insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1). However, for therapeutic use in fracture treatment, questions remain with regard to the local application of these proteins. A controlled, local release of growth factors from a biodegradable polylactide coating of osteosynthetic implants may have a stimulating effect on fracture healing. Such implants could stabilize the fracture and their bioactive surface could function simultaneously as a local drug-delivery system. Previous studies have demonstrated the high mechanical stability of an approximately 10-14-microm-thick poly(D,L-lactide) (PDLLA) coating on metallic implants, which can even withstand the process of intramedullary insertion. Following an initial peak, 80% of incorporated growth factors IGF-1 and TGF-beta1 were continuously released within 42 days. The effect of locally applied IGF-1 and TGF-beta1 from a biodegradable PDLLA coating of intramedullary implants on fracture healing was investigated in a rat model. Midshaft fractures of the right tibia of 5-month-old female Sprague-Dawley rats (n = 127) were stabilized with coated vs. uncoated titanium Kirschner wires. X-ray examinations and blood analyses were performed, and body weight and body temperature measurements were taken throughout the experimental period. After 28 and 42 days, respectively, tibiae were dissected for mechanical torsional testing and histomorphometrical analyses. X-rays demonstrated an almost completely consolidated fracture, biomechanical testing showed a significantly higher maximum load and torsional stiffness, and histological and histomorphometric analyses demonstrated progressed remodeling after 28 and 42 days in the group treated with growth factors as compared with controls. Interestingly, the PDLLA coating itself revealed a positive effect on fracture healing even without incorporated growth factors. No systemic changes of serum parameters, including IGF-1 and IGF binding proteins, and no differences in body weight and body temperature were observed within and between groups. These findings suggest that the local application of growth factors from a biodegradable PDLLA coating of osteosynthetic implants accelerates fracture healing significantly without systemic side effects.

Animals↗
PubMed2001

The effect of growth hormone on insulin-like growth factor I and bone metabolism in distraction osteogenesis.

Limb lengthening in the left tibia of 30 mature female Yucatan micropigs was performed using distraction osteogenesis. A treatment group of 15 animals received recombinant porcine growth hormone (r-pGH) (100 microg/kg/day) while the others served as controls. Serial serum measurements of total insulin-like growth factor I (IGF-I), free IGF-I, IGF binding proteins -1, -2, -3 and -4 (IGFBP-1 to -4) were performed. Bone-specific alkaline phosphatase (bone-ALP) and the serum carboxyl-terminal telopeptide of type I collagen (ICTP) were measured as bone turnover markers. The GH-treated animals showed a significant increase in total IGF-I, free IGF-I and IGFBP-3 after surgery (P<0.001). Similarly, the treated animals showed a significantly higher level of bone-ALP (P<0.001) throughout the experiment compared to the controls. There was a significant correlation between bone-ALP and total IGF-I (r=0.76) in the GH-treated group and an even higher correlation for free IGF-I (r=0.90). There was no difference in the ICTP serum levels between the two groups. These data indicate that the application of species-specific growth hormone results in a stimulation of bone formation in distraction osteogenesis which may be mediated by IGF-I. The stronger correlation between free IGF-I and bone-ALP indicates that the anabolic effect of IGF-I may be regulated through the IGFBPs by binding and inactivating IGF-I.

Alkaline Phosphatase↗
PubMed2001

[Management of thoracic trauma in multiple injuries in the clinic].

Injuries to the chest and lung are common in the polytraumatized patient. Clinical series have shown that on average 20% of all deaths following a polytrauma are caused by a chest trauma. The most common chest injuries are rip- and serial rip fractures with an unstable chest as well as pneumo- and hematothorax. Further common injuries to the lung parenchyma are lung contusions, lacerations and lung hematoma. The clinical outcome of chest injuries is closely related on a clear treatment strategy, with a sufficient preclinical assessment and early intubation, early temporary or definitive fracture stabilisation and implementation of intensive care and lung protective treatment rules.

Critical Care↗