Showing papers in "Spine in 1993"
TL;DR: A multiple logistic regression model was developed, based on biomechanical plausibility, and indicated that a combination of five trunk motion and workplace factors distinguished between high and low risk of occupationally-related low back disorder risk well (odds ratio: 10.7).
Abstract: Current ergonomic techniques for controlling the risk of occupationally-related low back disorder consist of static assessments of spinal loading during lifting activities. This may be problematic because several biomechanical models and epidemiologic studies suggest that the dynamic characteristics of a lift increase spine loading and the risk of occupational low back disorder. It has been difficult to include this motion information in workplace assessments because the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of low back disorder during occupational lifting in industry. More than 400 repetitive industrial lifting jobs were studied in 48 varied industries. Existing medical and injury records in these industries were examined so that specific jobs historically categorized as either high-risk or low-risk for reported occupationally-related low back disorder could be identified. A triaxial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers lifted in these high-risk or low-risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model was developed, based on biomechanical plausibility, and indicated that a combination of five trunk motion and workplace factors distinguished between high and low risk of occupationally-related low back disorder risk well (odds ratio: 10.7). These factors included 1) lifting frequency, 2) load moment, 3) trunk lateral velocity, 4) trunk twisting velocity, and 5) the trunk sagittal angle. This analysis implies that by suitably varying these five factors observed during the lift collectively, the odds of high-risk group membership may decrease by almost 11 times. The predictive power of this model was found to be more than three times greater than that of current lifting guidelines. This study, though not proving causality, indicates an association between the biomechanical factors and low back disorder risk. This model could be used as a quantitative, objective measure to design the workplace so that the risk of occupationally-related low back disorder is minimized.
839 citations
TL;DR: One hundred, twenty-four patients undergoing lumbar or lumbosacral fusion for degenerative conditions were entered into a prospective study and clinical results were rated as excellent if the patients were pain-free and had returned to work; good if the Patients had mild backache requiring non-narcotic analgesics and had return toWork; fair if continuing back pain prevented a return to work.
Abstract: One hundred, twenty-four patients undergoing lumbar or lumbosacral fusion for degenerative conditions were entered into a prospective study. The patients were randomly assigned to one of three treatment groups. Group I underwent posterolateral fusion using autogenous bone graft. Group II had autogenous posterolateral fusions supplemented by a semi-rigid pedicle screw/plate fixation system (Luque II; Danek Medical, Memphis, Tennessee). Group III patients underwent posterolateral autogenous fusion with a rigid pedicle screw/rod fixation system (Texas Scottish Rite Hospital [TSRH]-Danek Medical, Memphis, Tennessee). All the patients were operated on by the same surgeon, identical bone grafting technique was used in all, and all were treated in an identical fashion postoperatively. Fusion status was determined from the anteroposterior, oblique, and flexion-extension radiographs obtained at 1 year. Clinical results were rated as excellent if the patients were pain-free and had returned to work; good if the patients had mild backache requiring non-narcotic analgesics and had returned to work; fair if continuing back pain prevented a return to work; or poor if the pain was worse than that which the patient experienced preoperatively or the patient required revision surgery. Nine patients who were originally assigned to Group II or Group III were placed in Group I intraoperatively. This change was due to the identification of severe osteopenia and the determination that pedicle screw purchase was poor. One patient was lost to follow-up. Thus, 51 patients were in Group I, 35 in Group II, and 37 in Group III. Follow-up ranged from 9 to 28 months, averaging 16 months.(ABSTRACT TRUNCATED AT 250 WORDS)
750 citations
TL;DR: It is concluded that pedicle screw placement may be associated with significant intraoperative and postoperative complications and is of value to surgeons using pedicle implant systems as well as to their patients.
Abstract: A limited survey analysis of 617 surgical cases in which pedicle screw implants were used was undertaken to ascertain the incidence and variety of associated complications. The different implant systems used included variable spinal plating (n = 249), Edwards (n = 143), and AO fixateur interne (n = 101). The most common intraoperative problem was unrecognized screw misplacement (5.2%). Fracturing of the pedicle during screw insertion and iatrogenic cerebrospinal fluid leak occurred in 4.2% of cases. The postoperative deep infection rate was 4.2%. Transient neuropraxia occurred in 2.4% of cases, and permanent nerve root injury occurred in 2.3% of cases. Previously unreported injury to nerve roots occurred late in the postoperative course in three cases. Screw breakage occurred in 2.9% of cases. All other complications had an incidence of less than 2%. The authors conclude that pedicle screw placement may be associated with significant intraoperative and postoperative complications. This information is of value to surgeons using pedicle implant systems as well as to their patients. Repeat surgery is associated with greater numbers of complications.
672 citations
TL;DR: According to radiologic, neurophysiologic, and muscle biopsy evidence most patients suffering from the severe postoperative failed back syndrome had dorsal ramus lesions in one or more segments covered by the scar and local paraspinal muscle atrophy at the corresponding segments.
Abstract: Impairment and disability after back surgery is a common diagnostic and therapeutic problem. For the most part the reasons are unclear. Of 178 patients who had undergone laminectomies 2-5 years earlier, 14 patients with good recovery and 21 patients with poor recovery but no evidence of restenosis o
563 citations
TL;DR: The results demonstrate that nucleus pulposus may induce nerve tissue injury by mechanisms other than mechanical compression and may be based on direct biochemical effects of nucleus pulPOSus components on nerve fiber structure and function and microvascular changes including inflammatory reactions in the nerve roots.
Abstract: Epidural application of autologous nucleus pulposus in pigs, without mechanical nerve root compression, induced a pronounced reduction in nerve conduction velocity in the cauda equina nerve roots after 1-7 days, compared to epidural application of retroperitoneal fat in control experiments. Histologically, the nerve fiber injury was more pronounced after application of nucleus pulposus than after control tissue application. The results demonstrate that nucleus pulposus may induce nerve tissue injury by mechanisms other than mechanical compression. Such mechanisms may be based on direct biochemical effects of nucleus pulposus components on nerve fiber structure and function and microvascular changes including inflammatory reactions in the nerve roots.
546 citations
TL;DR: These are the first results to indicate that certain psychiatric syndromes appear to precede chronic iow-back pain (substance abuse and anxiety disorders), whereas others (specifically, major depression) develop either before or after the onset of chronic low- back pain.
Abstract: Two hundred chronic low-back pain patients entering a functional restoration program were assessed for current and lifetime psychiatric syndromes using a structured psychiatric interview to make DSM-III-R diagnoses. Results showed that, even when the somewhat controversial category of somatoform pain disorder was excluded, 77% of patients met lifetime diagnostic criteria and 59% demonstrated current symptoms for at least one psychiatric diagnosis. The most common of these were major depression, substance abuse, and anxiety disorders. In addition, 51% met criteria for at least one personality disorder. All of the prevalence rates were significantly greater than the base rate for the general population. Finally, and most importantly, of these patients with a positive lifetime history for psychiatric syndromes, 54% of those with depression, 94% of those with substance abuse, and 95% of those with anxiety disorders had experienced these syndromes before the onset of their back pain. These are the first results to indicate that certain psychiatric syndromes appear to precede chronic low-back pain (substance abuse and anxiety disorders), whereas others (specifically, major depression) develop either before or after the onset of chronic low-back pain. Such findings substantially add to our understanding of causality and predisposition in the relationship between psychiatric disorders and chronic low-back pain. They also clearly reveal that clinicians should be aware of potentially high rates of emotional distress syndromes in chronic low-back pain and enlist mental health professionals to help maximize treatment outcomes.
531 citations
TL;DR: The authors hypothesize that TrPs are caused by sympathetically activated intrafusal contractions.
Abstract: Monopolar needle electromyogram (EMG) was recorded simultaneously from trapezius myofascial trigger points (TrPs) and adjacent nontender fibers (non-TrPs) of the same muscle in normal subjects and in two patient groups, tension headache and fibromyalgia. Sustained spontaneous EMG activity was found in the 1-2 mm nidus of all TrPs, and was absent in non-TrPs. Mean EMG amplitude in the patient groups was significantly greater than in normals. The authors hypothesize that TrPs are caused by sympathetically activated intrafusal contractions.
507 citations
TL;DR: The carbon implant achieved successful fusion in 6/6 (100%) of followed patients treated for a failed ETO allograft interbody fusion, and a prospective controlled multi-centered study is being initiated.
Abstract: Posterior lumbar interbody fusion (PLIF), pioneered by Ralph Cloward in the 1940’s [1,2] is a biomechanically optimum fusion. A successful PLIF maintains the disk height, protects the nerve roots, restores weight bearing to anterior structures, restores the annulus to tension, and immobilizes the unstable de-generated intervertebral disk area. A successful PLIF restores every mechanical function of the functional spinal unit except motion. Problems with PLIF have included excessive bleeding (usually epidural), the need for donor bone (with risk of AIDS and hepatitis), prolonged healing time of donor bone, the difficulty of cutting precise bony channels, the difficulty of providing sterile donor bone of precise dimensions, the potential of instability, the risk of retropulsion of graft and consequent neural damage, and post-operative collapse of the donor bone and pseudarthrosis.
443 citations
TL;DR: The outcome of back pain was predicted by pain- related disability and days in pain rather than by recency of onset, so it may be more meaningful to distinguish characteristic levels of pain intensity, pain-related disability, and pain persistence than to classify patients as acute or chronic.
Abstract: Outcomes of primary care back pain patients (N = 1128) were studied at 1 year after seeking care. Changes in depression depending on outcome, and predictors of poor outcome were evaluated. Less than one back pain patient in five reported recent onset (first onset within the previous 6 months). One year after seeking care, the large majority of both recent and nonrecent-onset patients reported having back pain in the previous month (69% vs. 82%). A significant minority of both recent and nonrecent-onset patients had either a poor functional outcome (14% vs. 21%) or continuing high intensity pain without appreciable disability (10% vs. 16%). Predictors of poor outcome included pain-related disability, days in pain, lower educational attainment, and female gender. Among initially dysfunctional patients with persistent pain, one half were improved and one third had a good outcome at the 1-year follow-up. Among initially dysfunctional patients who experienced a good outcome, elevated depressive symptoms improved to normal levels at follow-up. The outcome of back pain was predicted by pain-related disability and days in pain rather than by recency of onset, so it may be more meaningful to distinguish characteristic levels of pain intensity, pain-related disability, and pain persistence than to classify patients as acute or chronic.
414 citations
TL;DR: Indications for fusion among older patients require better definition, preferably based on outcomes from prospective controlled studies, and results were similar in most diagnostic subgroups.
Abstract: Regional variations in lumbar spinal fusion rates suggest a poor consensus on surgical indications. Therefore, complications, costs, and reoperation rates were compared for elderly patients undergoing surgery with or without spinal fusion. Subjects were Medicare recipients who underwent surgery in 1985, with 4 years of subsequent follow-up. There were 27,111 eligible patients, of whom 5.6% had fusions. Mean age was 72 years. Patients undergoing fusion had a complication rate 1.9 times greater than those who had surgery without fusion. The blood transfusion rate was 5.8 times greater, nursing home placement rate 2.2 times greater, and hospital charges 1.5 times higher (all P < 0.0005). Six-week mortality was 2.0 times greater for patients undergoing fusions (P = 0.025). Reoperation rates at 4 years were no lower for patients who had fusion surgery and results were similar in most diagnostic subgroups. Indications for fusion among older patients require better definition, preferably based on outcomes from prospective controlled studies.
409 citations
TL;DR: The radiographic changes that occurred at spinal levels adjacent to fused vertebrae after anterior cervical fusion affected late neurologic results, and patients with multilevel fusions notably exhibited these radiographic abnormalities at adjacent levels.
Abstract: A retrospective study was performed to evaluate the radiographic changes that occurred at spinal levels adjacent to fused vertebrae after anterior cervical fusion. One hundred six patients with cervical spondylotic myeloradiculopathy (88 men, 18 women) were followed for an average of 8.5 years. The average age at follow-up was 64 years. Forty-two patients underwent a single-level fusion, 52 had a two-level fusion, and 12 had three levels fused. Seventeen patients who underwent additional surgery after anterior fusion also were reviewed, with an average follow-up period of 2.9 years. Postoperatively, cervical flexion-extension resulted in significantly increased movement about the vertebral interspace at the upper adjacent level. An increment of posterior slip of the vertebra immediately above the fusion level, with associated spinal canal compromise of less than 12 mm, significantly affected neurologic results. Patients with multilevel fusions notably exhibited these radiographic abnormalities at adjacent levels. Spinal canal stenosis, when associated with dynamic spinal canal stenosis in the vertebra above the fusion level, affected late neurologic results. Results of salvage laminoplasty were not satisfactory. Unnecessarily extended longer fusion must be avoided.
TL;DR: Nonoperative management yields acceptable results; following nonoperative management, bony deformity progresses marginally relative to the rate of canal area remodeling; incidence of subsequent neurologic deficits is quite low; and initial radiographic severity of injury or residual deformity following closed management does not correlate with symptoms at follow-up.
Abstract: There continues to be considerable controversy regarding the management of thoracolumbar burst fractures. Most feel that failure of the middle osteoligamentous complex, particularly with retropulsion of fragments into the spinal canal, is an indication for operative management. Others advocate postural reduction and prolonged bedrest for such injuries. The purpose of this study was to 1) review the clinical outcome and efficacy of closed management of thoracolumbar burst fractures; and 2) quantify what, if any, remodeling occurs in the bony canal as measured by serial CT. Forty-one patients who presented with a burst fracture of the thoracolumbar spine without neurologic deficit were reviewed clinically and radiographically following nonoperative management. At injury, canal compromise averaged 37% (range, 16-66%); 26 patients had at least 30% canal compromise. During treatment, one patient developed neurologic deterioration that prompted surgery; all other patients remained neurologically intact. At average follow-up of 2 years, an overall outcome evaluation indicated that 49% of the patients had excellent outcomes relative to pain and function; 17%, good; 22%, fair; and 12%, poor. Approximately 90% of the patients had a satisfactory work status relative to factors associated with their burst fracture. Serial roentgenograms documented significant progression in body collapse, which averaged 8% (P < 0.0001) from injury to follow-up. On the other hand, serial CTs documented significant improvement from injury to follow-up for canal compromise and midsagittal diameter. Average improvements in canal compromise and midsagittal diameter were 22% (P < 0.0001) and 11% (P < 0.0001), respectively. Only three patients had canal compromise greater than 30%, no patients had canal compromise greater than 40%, and no patients experienced canal area deterioration over time. On average, nearly two-thirds of the fragment occluding the canal resorbed, with most remodeling complete within one year. For patients with burst fractures presenting neurologically intact, we obtained the following findings: 1) nonoperative management yields acceptable results; 2) following nonoperative management, bony deformity (i.e., kyphosis and body collapse) progresses marginally relative to the rate of canal area remodeling; 3) incidence of subsequent neurologic deficits is quite low; and 4) initial radiographic severity of injury or residual deformity following closed management does not correlate with symptoms at follow-up. This pattern of results suggests nonoperative management as the preferred treatment in these circumstances.
TL;DR: It is proposed that both inactivity and axonal injury (mainly of neurapraxia type) contribute to the selective type 2 atrophy and inner structure changes in disc patients' multifidus muscle that are reversible and can be diminished by adequate therapy.
Abstract: Biopsy specimens of the lumbar multifidus were obtained from 18 patients with lumbar disc herniation at operation and after a postoperative follow-up period of 5 years. The structure and morphometry of the muscle fibers were analyzed and these data were compared with intraoperative biopsy results and the clinical outcome of the operation. The main findings were: 1) on the basis of occupational handicap score 10 patients belonged in the "positive" and 8 in the "negative" outcome group; 2) the intraoperatively recorded selective type 2 muscle fiber atrophy and the extent of pathologic inner structure changes both decreased in the "positive" outcome group, whereas they persisted in the "negative" group; 3) grouping as a definite sign of reinnervation was seen in only two versus four patients of the "positive" versus "negative" outcome group; 4) the relative amount of adipose tissue within the muscle decreased more markedly in the "positive" outcome group. The authors propose that both inactivity and axonal injury (mainly of neurapraxia type) contribute to the selective type 2 atrophy and inner structure changes in disc patients' multifidus muscle. These pathologic structural changes correlated well with the clinical outcome, and most importantly they are reversible and can be diminished by adequate therapy.
TL;DR: The quantitative anatomy of the facets may improve the understanding of the spinal anatomy, help improve the clinical diagnosis and treatment, and provide the necessary data for constructing more realistic mathematical models of the spine.
Abstract: This study provides the quantitative three-dimensional surface anatomy of the articular facets for the entire human vertebral column based on a study of 276 vertebrae. Means and standard errors of the means for linear, angular, and area dimensions of the superior and inferior articular facets were measured for all vertebrae from C2 to L5. Facet orientations were described as angles with respect to the sagittal and transverse planes and also as card angles. The plane angles are similar to the angles seen on traditional radiographic views--radiographs and computed tomographic scans. The card angles, a new concept, are better at helping visualize the three-dimensional orientations of the facets. Excluding the superior C2 facet, the following minimum and maximum dimensions were found for the facets from C3 to L5: width = 9.6-16.3 mm; height = 10.2-18.4; surface area = 72.3-211.9 mm2; interfacet width = 20.8-40.6; interfacet height = 12.2-33.0 mm; transverse plane angle = 41.0-86.0; sagittal plane angle = 67.4-154.8; X-card angle = 41.0-86.0; and Y-card angle = 5.8-66.1. The quantitative anatomy of the facets may improve the understanding of the spinal anatomy, help improve the clinical diagnosis and treatment, and provide the necessary data for constructing more realistic mathematical models of the spine.
TL;DR: The hypothesis that patients developing degenerative spondylolisthesis are predisposed to this by a developmental sagittal orientation of the L4-5 facet joints is supported.
Abstract: This study examined the role of facet joint morphology in the etiology of both degenerative spondylolisthesis and isthmic spondylolysis. To this end, the axial facet joint morphology of the lower lumbar spine in a normal population and in populations of patients with spinal stenosis or degenerative spondylolisthesis at L4-5 and in patients with isthmic spondylolysis at the L5 level were characterized. Computed tomographic scans were digitized, defining the axial morphology of the normal facet joint at five stations from proximal to distal within the joint. Assessments were made of facet joint orientation, transverse articular dimension, depth of the articular surface, and shape of the articular surface at levels L3-4, L4-5, and L5-S1. There was a gradually more coronal orientation from proximal to distal among the stations at each level, and a maximal transverse articular dimension at the level of the superior endplate of the caudad vertebra. Minimal error in the recording process at this level. In addition to the maximal joint dimension, made this level the most representative of the overall morphology and most useful for further studies. At the L4-5 level, a significantly more sagittal facet orientation was found in the degenerative spondylolisthesis group when compared to both the normal population and spinal stenosis groups (P < 0.01). At L5-S1, the only significant morphologic difference between the normal population and the patients with isthmic spondylolysis was reduced transverse articular dimension. These results support the hypothesis that patients developing degenerative spondylolisthesis are predisposed to this by a developmental sagittal orientation of the L4-5 facet joints.
TL;DR: The lumbar intervertebral discs and the maximum isometric strength and size of the trunk muscles of middle-aged healthy volunteers and low back pain patients were evaluated and disc degeneration was more frequently seen in patients than in the healthy volunteers.
Abstract: This study aimed to evaluate the lumbar intervertebral discs and the maximum isometric strength and size of the trunk muscles of middle-aged healthy volunteers (60 persons) and low back pain patients (48 persons). Disc degeneration was more frequently seen in the patients than in the healthy volunteers. The psoas and back muscles (erector spinae and multifidus) of the patients were smaller than those of the volunteers. Patients had also more fat deposits in the back muscles than controls. The maximum isometric strength of trunk muscles of the patients was on average weaker than that of the volunteers. However, the size of the back muscles was not related to the maximum isometric extension strength of the trunk.
TL;DR: Although the authors are unaware of any major long-term morbidity from this complication in their patient group, they believe the true incidence of this potentially quite serious complication may be underestimated.
Abstract: Anterior approaches to the lumbar spine are rapidly gaining popularity for decompressive and reconstructive procedures. A recognized hazard to this approach to the spine is possible injury to the great vessels. This retrospective study is a review of 102 consecutive anterior lumbar spinal procedures. All approaches were performed by one of two fellowship-trained vascular surgeons. Both have extensive experience with this approach. All injuries to the inferior vena cava, common iliac vein, or other great vessels that required suture repair were recorded. The authors were surprised to note an overall rate for this vascular complication of 15.6%. These injuries included 11 tears of the common iliac vein, four tears of the inferior vena cava, and one avulsion of the iliolumbar vein. Two different approaches were used during this study. Twenty-six cases were performed through a flank incision, with the dissection proceeding through the external and internal oblique muscles as well as the transversus abdominis. The average number of levels exposed was 2.3. Two vascular complications resulted, for an incidence of 7.7%. Seventy-six procedures were carried out through a small (5-10 cm) incision overlying the rectus abdominis muscle. The retroperitoneal space was entered through the posterior rectus sheath without division of any muscle tissue. This resulted in 14 vascular complications, for an incidence of 18.4%. Although the authors are unaware of any major long-term morbidity from this complication in their patient group, they believe feel that the true incidence of this potentially quite serious complication may be underestimated.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: A concomitant double-blind investigation of the effect of the nonsteroidal anti-inflammatory drug piroxicam was performed and results measured by visual analog scale and Roland's functional tests showed a satisfactory improvement throughout the 4 weeks of observation.
Abstract: To study the natural history of acute sciatica, 208 patients with obvious symptoms and signs of a lumbar radiculopathy (L5 and S1) were examined within 14 days of onset. A concomitant double-blind investigation of the effect of the nonsteroidal anti-inflammatory drug piroxicam was performed. The res
TL;DR: It is suggested that insertional torque is a good predictor of bone-metal interface failure and Bone mineral density of the vertebral body was less effective as a predictor of failure.
Abstract: This study was designed to correlate several parameters regarding pedicle screw bone/metal interface strength. The insertional torque measured during tapping and placement of pedicle screws was correlated with the bone mineral density of the vertebral body, the dimensions of the pedicle, the method of preparation of the pedicle, and the amount of load and number of cycles to failure of the bone/metal interface. Thirty human cadaveric lumbar vertebrae were instrumented with 6.5-mm pedicle screws. The maximum torque achieved during insertion was digitally recorded. A cyclic pedicle screw pullout test was performed. A linear correlation existed between both the insertional torque when tapping or when inserting a screw and the number of cycles to ultimate pedicle screw pullout. An inverse linear relationship was found between the pedicle width and cycles to failure. There was no linear correlation found when comparing the number of cycles to failure to bone mineral density. These findings suggest that insertional torque is a good predictor of bone-metal interface failure. Bone mineral density of the vertebral body was less effective as a predictor of failure. Smaller pedicle width correlated with increased insertional torque and cycles to failure. This may explain why patients with osteoporosis on radiography may still obtain stable fixation with pedicle screws. Other factors, such as pedicle dimensions and shape, affect screw purchase as much as vertebral body bone density. Insertional torque less than 4.0 inch-pounds led to early pedicle screw pullout. This study forms the basis for the authors' clinical use of an instrumented torque screwdriver to measure insertional torque in the operating room.
TL;DR: In patients with intact posterior elements and thoracolumbar burst fractures, early mobilization in a total contact TLSO can lead to satisfactory functional results and attribute the good results of nonoperative management to the exclusion of patients with posterior column disruption.
Abstract: Eighteen neurologically intact patients with burst fractures at the thoracolumbar junction were treated with early ambulation in a total contact orthosis. No attempt was made to reduce the associated deformity. Selection criteria excluded patients with posterior column disruption. Hospital stay averaged 10 days. Follow-up averaged 19 months. Mean kyphosis was 19 at time of injury and 20 at follow-up. At follow-up, 15 patients rated their pain as little or none. Seventeen patients had little or no restriction of activity. Follow-up computed tomography (CT) scans obtained in eight patients showed significant resorption of retropulsed bone. No deterioration of neurologic function developed in any patient. In patients with intact posterior elements and thoracolumbar burst fractures, early mobilization in a total contact TLSO can lead to satisfactory functional results. Prolonged bed rest was not required in this series. The authors attribute the good results of nonoperative management to the exclusion of patients with posterior column disruption.
TL;DR: The results showed that posterior instrumentation surgery was not a hazard to spinal tuberculosis infection when combined with radical debridement and intensive anti-tuberculosis chemotherapy.
Abstract: The risk of persistence and recurrence of infection in posterior spinal instrumentation surgery for spinal tuberculosis was studied clinically and microbiologically. Eleven patients with thoracic, thoracolumbar, and lumbar spinal tuberculosis treated by debridement, anterior fusion, and combined posterior instrumentation surgery were analyzed. Seven patients had tuberculosis in both anterior and posterior spinal elements. There were no cases of persistence or recurrence of infection after surgery, and instrumentation provided immediate stability and protected against development of kyphotic deformity. The adherence properties of Mycobacterium tuberculosis to stainless steel (SUS 316) was evaluated experimentally. The results showed that posterior instrumentation surgery was not a hazard to spinal tuberculosis infection when combined with radical debridement and intensive anti-tuberculosis chemotherapy.
TL;DR: It is indicated that immobilization of long segments of the spine influences the remaining mobile segments by increasing the load and motion not only at the immediately adjacent segment but also at the distal segments.
Abstract: Long levels of spinal instrumentation and fusion are common in surgery for spinal deformity, the effect on the remaining mobile segments is not wall understood. The changes in lumbar facet loading and lumbosacral motion were valuated as the number of immobilized levels increased. Four fresh canine c
TL;DR: Lumbar extension exercise is beneficial for strengthening the lumbar extensors and results in decreased pain and improved perceptions of physical and psychosocial functioning in chronic back pain patients, however, these improvements were not related to changes in activities or psychological distress.
Abstract: The effects of exercise for isolated lumbar extensor muscles were examined in 54 chronic low-back pain patients. Subjects were randomly assigned to a 10-week exercise program (N = 31) or a wait-list control group (N = 23). Results indicated a significant increase in isometric lumbar extension strength for the treatment group and a significant reduction in reported pain compared with the control group (P 0.05). Treated subjects reported less physical and psychosocial dysfunction whereas the control group increased in pain, and physical and psychosocial dysfunction. There were no concomitant changes in reported daily activity levels. These results show that lumbar extension exercise is beneficial for strengthening the lumbar extensors and results in decreased pain and improved perceptions of physical and psychosocial functioning in chronic back pain patients. However, these improvements were not related to changes in activities or psychological distress.
TL;DR: The model predictions, in conjunction with the degenerative cascade concept, support the observation that the osteoarthritis of facets may follow disc degeneration and provide quantitative data on the stabilizing effects of muscles on the mechanics of a ligamentous spine.
Abstract: A combined finite element and optimization approach to study the effects of muscles on the biomechanics of the lumbar spine was initiated. Briefly, a three-dimensional, nonlinear, finite element model of a ligamentous L3-4 motion segment was formulated (LIG model) for the predictions of stresses, etc., in the motion segment. A separate, biomechanical optimization-based force model with experimental input was developed to predict the forces in muscles and disc across the L3-4 segment in response to a person holding 90 N in his hands with spine flexed 30 degrees, and knees straight. The predicted muscle forces from the optimization model were then incorporated into the L3-4 finite element model as nodal forces to simulate the muscle action (MUS model). The predicted responses from the muscles active (MUS) finite element model were compared to the corresponding results from the ligamentous (LIG) finite element model subjected to an equivalent load. The biomechanical parameters compared were: translation and rotation of L3, disc bulge, intervertebral foramen gap, intradiscal pressure, facet loading, ligament tension, compressive disc load, and stresses in the vertebral body. The addition of muscular forces in the MUS model led to a decrease in the anteroposterior translation and flexion rotation (displacements in the sagittal plane) of the segment compared to the corresponding LIG model predictions. Thus, the muscles imparted stability to the ligamentous segment. The presence of muscles also led to a decrease in stresses in the vertebral body, the intradiscal pressure and other mechanical parameters of importance. However, the load bearing of the facets increased compared to the ligamentous model. Thus, facets play a significant role in transmitting loads in a normal intact spine. These results, for the first time, provide quantitative data on the stabilizing effects of muscles on the mechanics of a ligamentous spine. The results also provide a scientific explanation in support of the "degenerative cascade" concept proposed in the literature. The model predictions, in conjunction with the degenerative cascade concept, also support the observation that the osteoarthritis of facets may follow disc degeneration. Future research directions based on the current model are presented.
TL;DR: Subgroups of patients could be identified according to their treatment responses: physiotherapy was the superior treatment for the male participants, whereas the intensive back exercises appeared to be most efficient for the female participants.
Abstract: In a randomized, observer-blind trial, 150 men and women, aged 21-64 years, with chronic/subchronic low-back pain, followed one of these three treatment regimens: 1) intensive, dynamic back-muscle exercises; 2) conventional physiotherapy, including isometric exercises for the trunk and leg muscles; and 3) placebo-control treatment involving semihot packs and light traction. Eight treatment sessions were given during the course of 4 weeks, each session lasting 1 hour. The short-term effect was evaluated at the end of the treatment period and 1 month later, and the long-term effect at 6 and 12 months. The evaluations included recording of changes in pain level and assessment of overall treatment effect, which were indicated on visual interval scales. Subgroups of patients could be identified according to their treatment responses: physiotherapy was the superior treatment for the male participants, whereas the intensive back exercises appeared to be most efficient for the female participants. Patients with moderate or hard physical occupations tended toward a better response with physiotherapy, whereas intensive back exercises seemed most effective for those with sedentary/light job functions.
TL;DR: A stochastic (probabilistic) model of trunk muscle activation was developed that predicted the possible combinations of time-dependent trunk muscle coactivations that could be expected given a set of trunk bending conditions and could help explain how some repetitive lifting motions could increase the risk of acquiring a low back disorder.
Abstract: Biomechanical models of the spine have traditionally assumed that workplace lifting conditions (weight, posture, motion, etc.) precisely dictate the magnitude of individual muscle forces necessary to maintain a biomechanical balance within the trunk. However, because there are a large number of muscle groups within the trunk there is also an infinite number of possible combinations of muscle forces that can satisfy this biomechanical balance requirement for a given condition. Currently there are no methods available to predict this possible variability in muscle activity. Such variability in a multiple muscle system can result in variations in spinal loading. To quantitatively capture this trunk muscle variability during bending motions, such as those involved in lifting, a stochastic (probabilistic) model of trunk muscle activation was developed. The model was based on a simulation of experimentally derived data and predicted the possible combinations of time-dependent trunk muscle coactivations that could be expected given a set of trunk bending conditions. These simulated muscle activities were then used as input to an electromyographically assisted biomechanical model so that the magnitude and variability of the spine reaction forces could be estimated. This procedure allows one to assess the range of spinal loads that would be expected with a particular task. Significant variability in muscle activities was observed for each specific lifting condition and explained biomechanically. The results indicated that the variability in trunk muscle force had a small effect on spinal compression variability (+/- 7% of the mean compression), but greatly influenced both lateral (+/- 90% of mean) and anteroposterior shear forces (+/- 40% of mean). A validation study confirmed that the model predictions were reasonable estimates of muscle activity variability under previously untested conditions. This work could help explain how some repetitive lifting motions could increase the risk of acquiring a low back disorder and the simulation model could help drive electromyographically assisted models without the need for recording actual electromyographic activity.
TL;DR: It is suggested that in one of five cases the plain radiographs underestimate the degree of fusion, and this finding agrees with the authors' knowledge of osteoid and mineralized bone.
Abstract: Controversy centers on the determination of surgical fusion in lumbar spinal patients. What method best determines the nature of surgical arthrodesis remains unanswered. Numerous studies have investigated the accuracy of different radiologic tests. Although the best method has not been determined, plain radiography is certainly the most widely used in many centers and reported in scientific articles. In most of the literature a poor agreement between radiographic interpretation and surgical findings was observed. The main reasons seemed to be the lack of an accurate method to assess the radiographs. The authors rely on a radiologist or spinal surgeon to estimate the success of bony fusion by reviewing a two-dimensional radiograph. The purpose of this study was to determine the accuracy of plain radiographs to predict the presence of a surgical fusion. Forty-nine patients underwent fusion site exploration in the course of hardware removal. All patients had a one- or two-level posterolateral fusion and posterior lumbar interbody fusion with pedicle screw/link rod instrumentation. Immediate preoperative anteroposterior and lateral radiographs were taken before hardware removal that included both visual assessment and a Kocher mechanical test. Two spinal surgeons and two musculoskeletal radiologists blindly judged the preoperative radiographs as to the absolute presence or absence of successful arthrodesis. A second review was repeated at 3 months. The overall agreement between radiographic assessment and actual surgical findings was 69%. The range among observers was 57-77%. The overall false positive rate was 42% (0-75%), while the false-negative rate was 29% (20-51%). Success of observed surgical arthrodesis at the time of the second look was 90% and this number was used as the standard in the agreement process. In comparing the radiographic observations with the surgical findings it is suggested that in one of five cases the plain radiographs underestimate the degree of fusion. This finding agrees with the authors' knowledge of osteoid and mineralized bone. The premineralized osteoid may be functionally fused, but appear radiolucent on radiographic film. Once solid trabecular bony bridging occurs radiographic identification of fusion is easier to determine.
TL;DR: The authors studied 200 patients older than ago 50 years with back pain and recent onset of secolicsis and found that a Cobb angle of 30 or more, lateral vertebral translation of 6 mmor more, and the prominence of L5 in relation to the intercrest line were important factors in predicting curve progression.
Abstract: Scoliosis with progressive deformity can develop late in life. The authors studied 200 patients older than age 50 years with back pain and recent onset of scoliosis. Seventy-one percent of patients were women, and no patient had undergone spinal surgery. The curves involved the area from T12 to L5 with the apex at L2 or L3 and did not exceed 60 degrees. Degenerative facet joint and disc disease always were present, and the curves were associated with a loss of lumbar lordosis. Forty-five patients with severe pain and neurologic deficits were studied using myelography. Indention of the column of contrast medium was seen at several levels but was most severe at the apex of the curve. It was least severe at the lumbosacral joint. The curves progressed an average of 3 degrees per year over a 5-year period in 73% of patients. Grade 3 apical rotation, a Cobb angle of 30 or more, lateral vertebral translation of 6 mm or more, and the prominence of L5 in relation to the intercrest line were important factors in predicting curve progression.
TL;DR: The morphologic changes and signal intensity of the spinal cord on preoperative magnetic resonance images were correlated with postoperative outcomes in 74 patients undergoing decompressive cervical surgery for compressive myelopathy and a multiple regression equation was developed to predict surgical outcomes.
Abstract: The morphologic changes and signal intensity of the spinal cord on preoperative magnetic resonance images were correlated with postoperative outcomes in 74 patients undergoing decompressive cervical surgery for compressive myelopathy. The transverse area of the spinal cord on T1-weighted images at the level of maximum compression was closely correlated with the severity of myelopathy, duration of disease, and recovery rate as determined by the Japanese Orthopaedic Association score. In patients with ossification of the posterior longitudinal ligament or cervical spondylotic myelopathy, the increased intramedullary T2-weighted magnetic resonance imaging signal at the site of maximal cord compression and duration of disease significantly influenced the rate of recovery. A multiple regression equation was then developed with these three variables to predict surgical outcomes.
TL;DR: The results suggest that preoperative measurement of BMD is necessary for transpedicle screwing in osteoporotic cases, and that the cyclic tilting motion decrease its mechanical stability.
Abstract: The influence of bone mineral density on the stability of transpedicle screwing was studied in the human cadaveric lumbar vertebrae. The pull-out force correlated with bone mineral density. The tilting moment (load needed to tilt the screw 4 degrees cranially at the screw-plate junction) and the cut-up force (load needed to tip the end plate up by the screw) correlated with bone mineral density. A correlation was also found between the maximum insertion torque of the screw and bone mineral density. The maximum insertion torque correlated with the pull-out force, the tilting moment, and the cut-up force. In the cyclic tilting test (200 cycles), the mean value of the tilting moment at the 200th cycle was 67.4 +/- 6.1%, compared with the first cycle. The results suggest that preoperative measurement of BMD is necessary for transpedicle screwing in osteoporotic cases, and that the cyclic tilting motion decrease its mechanical stability. The authors have also concluded that the maximum insertion torque could predict the mechanical stability.