Biomedical subjects

M Ogon

Publications and source records attributed to M Ogon.

30 records · Page 2Linked to original sources

PubMed1997

A dynamic approach to spinal instability. Part I: Sensitization of intersegmental motion profiles to motion direction and load condition by instability.

STUDY DESIGN: Human lumbar functional spinal units (FSUs) were moved throughout their range of motion in sagittal and lateral bending while the dynamics of this movement were computed in vitro. Functional spinal units were tested intact and after subsequent discectomy and unilateral facetectomy. OBJECTIVE: To establish "normal" velocity and acceleration curves during lumbar intersegmental bending in the intact FSU and then evaluate the changes of this dynamic behavior due to surgically induced component instability. SUMMARY OF BACKGROUND DATA: In preliminary clinical studies, researchers have provided evidence that dynamic motion measurements may be useful in the assessment of spinal impairment. METHODS: Human lumbar FSUs moved from extension to flexion, flexion to extension, left to right, and right to left a pure moment. Range of motion, as well as velocity and acceleration patterns of the main and coupled motions, were evaluated in six degrees of freedom by position changes of attached infrared light-emitting diodes recorded by cameras. Functional spinal units were tested in three surgical conditions (intact, discectomy, and unilateral facetectomy) under two preload conditions (no preload and 400 N preload). RESULTS: Motion of intact FSUs progressed with velocity and acceleration patterns that were relatively independent from motion direction and preload condition. After surgery, however, the dynamic motion became unequal between opposite motion directions (even if range of motion was equal between directions) and more sensitive to preload condition. CONCLUSION: The results suggest that equilibrium of dynamic motion parameters within a range of motion is an element of segmental stability. From this approach, segmental instability appears to change intersegmental acceleration and velocity patterns as a function of motion direction and load conditions. Whereas dynamic motion patterns in an intact FSU are relatively invariable between reversed motion directions, instability is characterized by a considerable diversity of dynamic motion parameters between reversed motion directions.

Acceleration↗

PubMed1997

A dynamic approach to spinal instability. Part II: Hesitation and giving-way during interspinal motion.

STUDY DESIGN: Human lumbar functional spinal units (FSUs) were moved throughout their range of motion in sagittal and lateral bending, while the dynamics of this movement were computed in vitro. Functional spinal units were tested intact and after subsequent discectomy and unilateral facetectomy. OBJECTIVE: To determine whether the patterns of small jerks observed during intersegmental motion are sensitive to spinal instability. SUMMARY OF BACKGROUND DATA: Small jerks have been observed as hesitation during increasing velocity and as giving way during decreasing velocity in the experiments described in Part I of this study. METHODS: Human lumbar functional spinal units were moved from extension to flexion, flexion to extension, left to right, and right to left, by a pure moment. Range of motion and velocity and acceleration patterns of the main and coupled motions were evaluated in six degrees of freedom by position changes of attached infrared light-emitting diodes recorded by cameras. Functional spinal units were tested in three surgical conditions (intact, discectomy, and unilateral facetectomy) under two preload conditions (no preload and 400-N preload). Discontinuous accelerations and decelerations (jerks) were computed in these motions and their location in relation to the main angular motion determined. RESULTS: Jerks were observed in almost all motions, in the intact functional spinal units and after surgery. The parameters describing the magnitude of the jerk decreased with increasing component instability. In the sagittal plane, there was a surgical condition by motion direction interaction (P < 0.014) regarding the location of the jerk. Independent from the motion direction, the jerk occurred around the neutral position (in relation to the primary angular motion) in the intact functional spinal units, whereas it shifted from the neutral position toward the beginning of the motion with increasing component instability. CONCLUSION: The results suggest that a small jerk is a normal component of fast intersegmental motion. The jerk has a certain magnitude and location in an intact functional spinal unit, whereas both of the parameters describing the jerk are sensitive to component instability.

Acceleration↗

PubMed1997

[Biomechanics of lumbar instability].

Several authors have tried to define segmental lumbar instability. Their definitions: increased antero-posterior translation, pathologic coupled motion, increased neutral zone, pathologic instantaneous center of rotation describe some mechanic findings occurring in the aging spine. However, there is no evidence that they help to differentiate the pathologic entity of segmental lumbar instability from the normal aging process. Dynamic explanation models are promising but at the moment they cannot be used clinically for diagnosis of instability as well. The most important structure to maintain lumbar stability is the intervertebral disc. In the third and fourth decade, more than 50 percent of specimen show peripheral tears of the anulus. It was shown in animal experiments that these tears develop to radial tears, which are accompanied by nuclear volume loss and decreased height. The facets degenerate one or two decades later. Corresponding with the loss of discal function, they increasingly contribute to spinal stability. In conclusion, the concept of lumbar segmental instability is not very helpful in clinical practise. It is recommended to base the decision of lumbar fusion on a painful degenerated disc, and additional findings promising a good result.

Animals↗

PubMed1997

[Minimally invasive approach and surgical procedures in the lumbar spine].

The history of minimally invasive lumbar spine surgery began in 1963 with the introduction of chemonucleolysis. Like this technique, the later development of mechanical nucleotomy and lasernucleotomy aimed primarily at reduction of the disc pressure. Miniature optical systems offered the opportunity for more specific decompression by discoscopy or, more recently, by transforaminal epiduroscopy. Initially, nucleotomy was the only feasible minimally invasive procedure. In recent years, however, minimally invasive spinal fusion became possible due to the development of new devices (Cages) and advanced transperitoneal (laparoscopic) and retroperitoneal approaches.

Decompression, Surgical↗

PubMed1997

[Advantages and disadvantages of retro- and transperitoneal approach for fusion of the presacral intervertebral disk].

In a retrospective study, we evaluated 180 patients treated for painful spondylolisthesis with combined anterior and posterior fusion. Group I included 90 patients treated by anterior fusion with the transperitoneal approach. Group II included 90 patients operated on with a retroperitoneal approach. Group II showed a higher incidence of pseudarthrosis L5/S1 (4%), tear of the common iliac vein (1%), postsympathectomy syndrome (4%) and reversible L4 nerve-root lesion (3%). On the basis of our findings, we recommend the transperitoneal approach for anterior interbody fusion L5 to S1 or L4 to S1.

Adolescent↗

PubMed1997

[Lumbar fusion in adults--dorsal or combined ventral/dorsal approach?].

A retrospective study was conducted to compare the results of posterior with combined anterior/posterior lumbar fusion in adults. Seventy-six consecutive posterior cases fused with pedicle screws and 46 combined cases were included and followed for at least 2 years. Subjective assessment was based on the Visual Analogue Scales, Waddel Disability and Impairment Score and the GBB for objective quantification of complaints. Furthermore, a thorough clinical examination was done and X-rays including flexion/ extension radiographs, were taken. Questions were asked about the occupational status as well. Pain decreased significantly more in the combined cases than in the posterior fusion cases. In one case a lesion of the common iliac vein occurred during a retroperitoneal approach. Only about half the patients working preoperatively returned to work again. In conclusion, the benefit of better pain relief after combined fusion must be regarded in relation to a higher complication rate due to a second approach.

Adult↗

PubMed1997

AP-translation in the proximal disc adjacent to lumbar spine fusion. A retrospective comparison of mono- and polysegmental fusion in 120 patients.

120 consecutive patients with painful spondylolisthesis underwent combined anterior and posterior fusion. Patients were divided retrospectively into two groups. In group I, 46 patients were treated with monosegmental fusion. In group II, 74 had polysegmental fusion. The mean follow-up time was 3 (2-7) years. Anterior posterior (AP)-translation in the first disc superior to fusion was measured according to Wiltse and Winter (1983). In group I, 3 and in group II, 10 patients developed an AP-translation of more then 3 mm in the disc adjacent to the fusion. AP-translation correlated with the number of fused segments and the follow-up time.

Adolescent↗

PubMed1997

Conservative treatment of tuberculous spondylitis: a long-term follow-up study.

A retrospective follow-up study was performed on 40 patients, in which tuberculous spondylitis was treated conservatively between 1969 and 1985 with orthotic supports for an average of 16 months (range, 10-30 months) and with anti-tuberculous agents. All had persistent back pain, but none had neurological deficits. The mean follow-up period was 17 years (range, 10-26 years). Diagnosis was confirmed histopathologically. The spinal segments involved ranged from T5 to L5. The kyphotic angle was calculated according to Cobb. At final follow-up, 22 patients were pain free, 11 had occasional pain, 6 complained of pain in the morning, and 1 had chronic pain and needed frequent analgesics. Solid bony union was found in 75% of patients. The kyphotic deformity occurred in the thoracic spine with a mean angle of 20 degrees (range, 13-28 degrees) and in the lumbar spine with a mean angle 12 degrees (range, 5-26 degrees). The long-term follow-up of conservative treatment showed only slightly increased kyphosis. Conservative treatment is an alternative to surgical intervention in cases with kyphosis < 35 degrees.

Adult↗

PubMed1996

Comparison between single-screw and triangulated, double-screw fixation in anterior spine surgery. A biomechanical test.

STUDY DESIGN: The advantage to fixation strength of triangulated, double-screw fixation compared with that of single-screw instrumentation in anterior spine surgery was evaluated by in vitro testing. OBJECTIVES: To compare the fixation strength of single-screw instrumentation with ventral derotation spondylodesis screws with the fixation strength of triangulated, double-screw instrumentation with Cotrel-Dubousset-Hopf screws. Resistance against pull-out load and against load perpendicular to the axis of the screws was evaluated. To avoid the bias caused by different screw design, the pull-out strength of single screws of both devices was compared first. SUMMARY OF BACKGROUND DATA: To the authors' knowledge, no study comparing anterior single with triangulated screws has been published. METHODS: A pull-out test was performed when one vertebra in each spine specimen was instrumented with a ventral derotation spondylodesis screw, one with an isolated Cotrel-Dubousset-Hopf screws, and one with two triangulated, Cotrel-Dubousset-Hopf screws linked by a Cotrel-Dubousset-Hopf block. Load perpendicular to the axis of the screw was applied on the bone-device interface after instrumentation of further specimens with ventral derotation spondylodesis and triangulated, Cotrel-Dubousset-Hopf devices. RESULTS: Use of isolated Cotrel-Dubousset-Hopf screws compared with ventral derotation spondylodesis screws showed no significant differences in pull-out strength. The use of triangulated, double-screw fixation with Cotrel-Dubousset-Hopf screws led to a significant 79% increase in resistance against pull-out and a 73% increase in resistance against load perpendicular to the screw axis compared with the resistance produced using ventral derotation spondylodesis single-screw instrumentation. CONCLUSION: In anterior surgery, fixation of the vertebra-device interface can be improved considerably by application of two triangulated screws.

Aged↗

PubMed1996

The possibility of creating lordosis and correcting scoliosis simultaneously after partial disc removal. Balance lines of lumbar motion segments.

STUDY DESIGN: The feasibility of correcting scoliosis and creating lordosis simultaneously in the thoracolumbar and lumbar spine by anterior instrumentation was investigated by in vitro testing. OBJECTIVES: To evaluate the vertebral zones in which a compressive load applied in a motion segment creates side bending and lordosis in intact motion segments and after partial disc removal. SUMMARY OF BACKGROUND DATA: Most investigators have observed a kyphogenic effect of anterior scoliosis instrumentation and recommended dorsal placement of screws and the use of wedge grafts, although wedge grafts were not used routinely by all surgeons. METHODS: Zones of lordosization and side bending were determined by evaluation of balance lines between extension-flexion and side bending, respectively, by axial loading on ligamentous human motion segments with intact discs and after partial disc removal. RESULTS: In lumbar motion segments with intact discs, it is possible to achieve ipsilateral side bending and lordosization by anterior instrumentation. After partial disc removal, the balance line between extension and flexion runs through the ipsilateral pedicle, and, therefore, a compressive load between the vertebral bodies always creates kyphosis. CONCLUSIONS: After partial disc removal, it is not possible to create lordosis and correction of scoliosis simultaneously by ipsilateral anterior instrumentation without the use of intervertebral wedge grafts.

Adult↗

PubMed1996

Early migration predicts late aseptic failure of hip sockets.

We report a prospective, stratified study of 60 PCA-cups and 60 RM-polyethylene cups which have been followed for a median time of 90 months, with annual radiography. The radiological migration of cups was measured by the computer-assisted EBRA method. A number of threshold migration rates from 1 mm in the first year to 1 mm in five years have been assessed and related to clinically determined revision rates. A total of 28 cups showed a total migration of 1 mm or more within the first two years; 13 of these cups have required revision and been exchanged. The survival curves of cups which had previously shown early migration were considerably different from those without early migration. For cups with a migration of less than 1 mm within the first two years the mean survival at 96 months was 0.96 +/- 0.02; for migrating cups, it was 0.63 +/- 0.11 (log-rank test, p=0.0001; chi-square value=39.4). Early migration is a good predictor for late loosening of hip sockets.

Aged↗

PubMed1991

[Recurrent sciatica caused by "conjoined nerve roots". Diagnosis, therapy, follow-up].

This study reports about 10 patients, with low back pain and sciatica caused by conjoined nerve roots. The described nerve root anomaly could produce sciatica even without the presence of a disc prolaps or another impingement. On computed tomography it is difficult to distinguish conjoined nerve roots from a disc prolaps. Two of these patients have been operated, eight of them have had conservative treatment. Our experiences show that the best results could be achieved with conservative treatment, especially with stabilising gymnastics and with transcutaneous nerve stimulation.

Adult↗