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ABSTRACT: Total hip arthroplasty imparts significant physical forces on the patient at the time of surgery. We report a case of an injury to the superior mesenteric vein that is thought to have occurred at the time of impaction of the acetabular component of a total hip arthroplasty. This complication has been reported previously only from high-energy nonpenetrating trauma, such as motor vehicle accidents.
The Journal of Arthroplasty 09/2001; 16(5):671-3. · 2.38 Impact Factor
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ABSTRACT: An established rabbit posterolateral lumbar fusion model was used to evaluate the ability of osteogenic protein-1 to overcome the inhibitory effect of nicotine.
To determine whether osteogenic protein-1 should be considered as a bone graft alternative for the patient who smokes.
Smoking interferes with the success of posterolateral lumbar fusion. This inhibitory effect has been attributed to nicotine and confirmed in a New Zealand white rabbit model. Osteoinductive protein-1 has been shown to induce posterolateral spine fusion reliably in the rabbit model. The effectiveness with which osteogenic protein-1 induces fusion in the presence of nicotine has not been studied previously.
Single-level posterolateral intertransverse process fusions were performed at L5-L6 in 18 New Zealand white rabbits. Either autograft or osteogenic protein-1 was used as grafting material. Nicotine was administered via subcutaneous mini-osmotic pumps. The animals were killed 5 weeks after surgery, and the resulting fusion masses were studied.
Three rabbits (17%) were excluded because of complications. By manual palpation, two of the eight nicotine-exposed autograft rabbits (25%) and all of the nicotine-exposed osteogenic protein-1 rabbits (100%) were found to be fused. These results correlated well with those obtained from biomechanical testing. Histologically, the fusion zones of the nicotine-exposed autograft rabbits were distinctly less mature than the fusion masses of the nicotine-exposed osteogenic protein-1 rabbits.
Osteoinductive protein-1 was able to overcome the inhibitory effects of nicotine in a rabbit posterolateral spine fusion model, and to induce bony fusion reliably at 5 weeks.
Spine 09/2001; 26(15):1656-61. · 2.08 Impact Factor
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ABSTRACT: Biomechanics of posterolateral spinal fusion were studied in an in vivo rabbit model.
To determine the extent of stabilization produced by posterolateral lumbar fusion and to test the hypothesis that motions are not completely eliminated after successful fusion.
Previous human cadaveric studies, clinical studies, and animal studies have attempted to characterize the biomechanics of posterolateral fusion. Such studies have been limited by either methods of fusion modeling or methods of stability testing. No previous study has examined biologic fusion with a physiologic biomechanical testing technique.
Ten adult New Zealand white rabbits underwent L5-L6 intertransverse process fusion using autogenous iliac crest bone graft. Rabbits were killed 5 weeks after surgery. Only one time point was studied. This time point was chosen because previous pull-apart studies have shown plateauing of rabbit fusion mass strength and stiffness around this time. Spines were then harvested and evaluated with manual palpation and an established flexibility testing protocol. Resulting data were compared with previously acquired, nonoperative spine flexibility data.
Two animals were excluded because of complications. Of those that were fused (n = 5), biomechanical testing revealed significant decreases in flexion (81%), extension (61%), and right and left lateral bending (67% and 83%, respectively) (P < 0.01).
These findings define the amount of motion reduction that can be expected with posterolateral fusions in the rabbit model at 5 weeks. These results suggest that motion was significantly decreased but was not eliminated.
Spine 05/2001; 26(10):1125-30. · 2.08 Impact Factor
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ABSTRACT: This article presents a technical description of a novel dorsal technique of arthroscopic reduction and percutaneous fixation of scaphoid fractures. Background highlighting the evolution of this technique is described. A series of patients treated in this manner, all of whom have healed without complications, is presented.
Orthopedic Clinics of North America 05/2001; 32(2):247-61. · 1.25 Impact Factor
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ABSTRACT: An established rabbit intertransverse process lumbar fusion model was used to evaluate osteogenic protein (OP)-1 as a potential graft substitute.
To determine whether OP-1 is effective in producing intertransverse process lumbar fusion in a rabbit model.
Autogenous iliac crest bone is the gold standard in grafting material for inducing intertransverse process fusion. However, bone graft substitutes are being considered as supplementary or alternative means to achieve such fusion with less morbidity. Relatively little research has been undertaken to investigate the efficacy of OP-1 in this role.
Single-level intertransverse process lumbar fusions were performed at L5-L6 of 31 New Zealand White rabbits. These were divided into three study groups: autograft, carrier alone, and carrier with OP-1. The animals were killed 5 weeks after surgery. Resultant fusion masses were evaluated by manual palpation, radiography, biomechanical multidirectional flexibility testing, and histology.
Seven rabbits (23%) were excluded because of complications. Of the remaining 24 rabbits, 5 (63%) of the 8 in the autograft group had fusion detected by manual palpation, none (0%) of the 8 in the carrier-alone group had fusion, and all 8 (100%) in the OP-1 group had fusion. Radiographs were 55% sensitive and 92% specific for determining fusion. Biomechanical testing results correlated well with those of manual palpation. Histologically, autograft specimens were predominantly fibrocartilage, OP-1 specimens were predominantly maturing bone, and carrier-alone specimens did not show significant bone formation.
OP-1 was found to reliably induce solid intertransverse process fusion in a rabbit model at 5 weeks.
Spine 02/2001; 26(2):127-33. · 2.08 Impact Factor
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ABSTRACT: Physiologic motions of the human, sheep, and calf lumbar spines have been well characterized. The size, cost, and ease of care all make the rabbit an attractive alternative choice for an animal lumbar spine model. However, comparisons of normal biomechanical characteristics of the rabbit lumbar spine have not been made to the spines of larger species. The purpose of this study was to establish baseline physiologic kinematic data for the rabbit lumbar spine. Ten skeletally mature New Zealand white rabbit osteoligamentous spines were obtained. L4-L7 spine segments were harvested and mounted. Multi-directional flexibility testing was performed by applying pure moments up to 0.27 Nm. Resulting rotations were measured using an Optotrak system. Data were analyzed for each intervertebral level in the three planes of rotation. The three levels tested had roughly similar range of motion (ROM). The mean (SD) angular ROMs in flexion for L4-L5, L5-L6, L6-L7 were 12.10 degrees (2.59 degrees), 12.38 degrees (2.70 degrees), and 15.17 degrees (3.22 degrees), respectively. The ROMs in extension were 5.86 degrees (1.21 degrees), 5.58 degrees (1.48 degrees), and 6.13 degrees (2.03 degrees). Lateral bending and axial rotation were roughly symmetric due to the symmetric nature of the spine. For right lateral bending, the ROMs were 8.25 degrees (2.44 degrees), 4.96 degrees (1.70 degrees ), and 4.25 degrees (1.20 degrees). For left axial rotation, the ROMs were 1.23 degrees (1.16 degrees), 0.35 degrees (0.61 degrees), 0.87 degrees (0.64 degrees ). Neutral zone (NZ) was on average 60% (29%) of ROM for the motions studied. The physiologic ROM of the New Zealand white rabbit lumbar spine was found to be similar between the rabbit and human. This relatively conserved physiologic flexibility supports the use of the rabbit as a model of the lumbar spine for kinematic studies. However, the overall NZ was found to be a greater percentage of ROM in the rabbit than the corresponding percentage in the human (60% as compared to 25%). This suggested that the rabbit lumbar spine has a greater laxity than that of the human.
European Spine Journal 07/2000; 9(3):250-5. · 1.97 Impact Factor
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ABSTRACT: The article reports a new hypothesis of whiplash injury based on a series of experimental studies using isolated human cadaveric specimens. Although the clinical symptoms of whiplash are widely known, the understanding of the underlying injury mechanism is poor. The prevailing view of neck-hyper-extension as the essential injury mechanisms was not supported by recent experiments. In a series of experiments using eight human cadaveric specimens which underwent experimental stepwise whiplash acceleration from 2.5 to 10.5 g functional radiographs and flexibility tests were performed at the end of each acceleration step. Ligament strains, vertebral alignment and elongation of the vertebral artery were monitored during the whiplash trauma by highspeed cinematography and specially designed transducers. After the trauma CT- and MRI-scans were taken and specimens were sectioned using Cryomicrotomy. We found a distinct biphasic kinematic response of the cervical spine to whiplash trauma. In the first phase the spine formed an S-shaped curve with flexion at the upper levels and hyper-extension at the lower levels. This phase was found to be the vulnerable phase of whiplash trauma. The largest dynamic elongation of the capsular ligaments was observed at the C6-C7 level during this initial S-shaped phase of whiplash. The maximum elongation of the vertebral artery could be observed synchronously in the first S-shaped curve of the cervical spine. In the second phase of whiplash all levels of the cervical spine were extended, so that the head reached is maximum extension. No injuries were observed in the second phase. We propose, based on our experimental findings, that with low accelerations the anterior structures of the lower cervical spine are injured during the first phase of whiplash, when the cervical spine forms an S-shaped curve and before the neck is fully extended. At higher trauma accelerations there is also a tendency for the injuries to occur at upper levels of the cervical spine. Based on our findings the traditional view of whiplash as hyper-extension injury can be modified by a differentiated, time dependent, biphasic biomechanical model of the injury, thus allowing better and more effective injury prevention, diagnosis and therapy.
Der Orthopäde 01/1999; 27(12):813-9. · 0.51 Impact Factor
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ABSTRACT: Knowledge of precise head kinematics during whiplash trauma is important for identifying possible injury mechanisms and their prevention. This study reports a comprehensive data set describing head kinematic response to horizontal accelerations simulating whiplash. Seven isolated fresh human cervical spine specimens (C0 to T1 or C7), each carrying a surrogate head designed to represent a 50th percentile human head, were mounted on the sled and subjected to incremental trauma by horizontal sled accelerations of 2.5, 4.5, 6.5, 8.5, and 10.5 g. Sled and head kinematics were measured with potentiometers and accelerometers. The incremental sled accelerations resulted in average (standard deviations) sled velocity changes (delta V) ranging from 5.8 (0.2) to 15.8 (0.2) km/h. Generally, all the peak head kinematic parameters increased with increasing sled acceleration, except for the peak head angular displacement, which decreased. In the initial phase of a whiplash trauma, the head translated posteriorly with respect to T1, without rotation. In the later phase, the head rotated backwards, but much less than its physiological limit. Maximum head rotation of 31.5 (23.9) degrees occurred in a 2.5 g trauma class, and this was less than the maximum physiological head extension of 55.1 (13.3) degrees. Head kinematics expressed in the T1 or shoulder coordinate system is better suited to study potential neck injury in whiplash.
Accident Analysis & Prevention 08/1998; 30(4):469-79. · 1.87 Impact Factor
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ABSTRACT: A bench-top trauma sled was used to apply four intensities of whiplash trauma to human cadaveric cervical spine specimens and to measure resulting intervertebral rotations using high-speed cinematography.
To determine the cervical spine levels most prone to injury from whiplash trauma and to hypothesize a mechanism for such injury.
Whiplash injuries traditionally have been ascribed to hyperextension of the head, but other mechanisms such as hypertranslation also have been suggested.
Six occiput to T1 (or C7) fresh cadaveric human spines were studied. Physiologic flexion and extension motions were recorded with an Optotrak motion analysis system by loading up to 1.0 Nm. Specimens then were secured in a trauma sled, and a surrogate head was attached. Flags fixed to the head and individual vertebrae were monitored with high-speed cinematography (500 frames/sec). Data were collected for 12 traumas in four classes defined by the maximum sled acceleration. The trauma classes were 2.5 g, 4.5 g, 6.5 g, and 8.5 g. Significance was defined at P < 0.01.
In the whiplash traumas, the peak intervertebral rotations of C6-C7 and C7-T1 significantly exceeded the maximum physiologic extension for all trauma classes studied. The maximum extension of these lower levels occurred significantly before full neck extension. In fact, the upper cervical levels were consistently in flexion at the time of maximum lower level extension.
In whiplash, the neck forms an S-shaped curvature, with lower level hyperextension and upper level flexion. This was identified as the injury stage for the lower cervical levels. A subsequent C-shaped curvature with extension of the entire cervical spine produced less lower level extension.
Spine 11/1997; 22(21):2489-94. · 2.08 Impact Factor
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ABSTRACT: Clinical signs of whiplash are presently not well understood. Vertebral artery (VA) stretch during trauma is a possible pathomechanism that could explain some aspects of the whiplash symptom complex. This study quantified the VA elongation during whiplash simulation using an in vitro model. Seven fresh human cadaveric specimens (occiput to C7 or T1) were carefully dissected, preserving the osteoligamentous structures. The right VA was replaced with a thin nylon-coated flexible cable. This cable was fixed at one end to the occipital bone and at the other end to a specially designed VA transducer. Physiological motion of the occiput and physiological elongation of the VA were measured with a standard flexibility test. Next the specimen was mounted on a specially designed sled and subjected to 2.5, 4.5, 6.5, and 8.5 g (1 g = 9.81 m/s2) horizontal accelerations. Elongation of the VA was continuously recorded from the start of the trauma. The average (standard deviation) physiological VA elongation was 5.8 (1.6) mm in left lateral bending and 4.7 (1.8) mm in left axial rotation. Flexion and extension did not result in any appreciable elongation of the VA. The maximum VA elongation during the whiplash trauma significantly correlated with the horizontal acceleration of the sled (R2 = 0.7, P < 0.05). The VA exceeded its physiological range by 1.0 (2.1), 3.1 (2.6), 8.9 (1.6), and 9.0 (5.9) mm in the 2.5-, 4.5-, 6.5-, and 8.5-g trauma classes respectively.
European Spine Journal 01/1997; 6(4):286-9. · 1.97 Impact Factor
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ABSTRACT: Increasing evidence suggests that beta-carotene, retinol (vitamin A), and alpha-tocopheral (vitamin E) may have important protective effects in the lung. However, surprisingly little is known about their storage and metabolism in human lung. Levels of beta-carotene, retinol, and alpha-tocopherol in human lung tissues and bronchoalveolar lavage (BAL) cells were determined with reverse-phase high-pressure liquid chromatography (HPLC). Fresh lung tissue, serum, and dietary questionnaires were obtained from 21 patients undergoing open lung surgery, and BAL cells from 12 of these patients. Dietary and serum levels of carotenoids, beta-carotene, retinol, and alpha-tocopherol were consistent with previously reported values. Lung tissue levels of total carotenoids, beta-carotene, retinol, and alpha-tocopherol were respectively 0.34 +/- 0.36 microg/g, 0.13 +/- 0.27 microg/g, 0.15 +/- 0.06 microg/g, and 9.60 +/- 4.86 microg/g tissue. Levels of these nutrients were also measured in BAL cells to establish potential markers for their lung tissue levels. Correlations between serum, BAL-cell, tissue, and dietary levels of the nutrients were determined. Lung tissue levels of total carotenoids, beta-carotene, and alpha-tocopherol, but not retinol, correlated well with their serum levels. Lung tissue levels of retinol and alpha-tocopherol correlated with their BAL-cell levels. These studies demonstrate quantifiable levels of retinol, alpha-tocopherol, and total carotenoids or beta-carotene in human lung tissue and BAL cells, and show that serum and/or BAL-cell levels of these nutrients can potentially be used to predict their lung tissue levels.
American Journal of Respiratory and Critical Care Medicine 12/1996; 154(5):1436-43. · 11.08 Impact Factor
