Acetabular dysplasia after treatment for developmental dysplasia of the hip. Implications for secondary procedures.

Untreated acetabular dysplasia following treatment for developmental dysplasia of the hip (DDH) leads to early degenerative joint disease. Clinicians must accurately and reliably recognise dysplasia in order to intervene appropriately with secondary acetabular or femoral procedures. This study sought early predictors of residual dysplasia in order to establish empirically-based indications for treatment. DDH treated by closed or open reduction alone was reviewed. Residual hip dysplasia was defined according to the Severin classification at skeletal maturity. Future hip replacement in a subset of these patients was compared with the Severin classification. Serial measurements of acetabular development and subluxation of the femoral head were collected, as were the age at reduction, type of reduction, and Tonnis grade prior to reduction. These variables were used to predict the Severin classification. The mean age at reduction in 72 hips was 16 months (1 to 46). On the final radiograph, 47 hips (65%) were classified as Severin I/II, and 25 as Severin III/IV (35%). At 40 years after reduction, five of 43 hips (21%) had had a total hip replacement (THR). The Severin grade was predictive for THR. Early measurements of the acetabular index (AI) were predictive for Severin grade. For example, an AI of 35 degrees or more at two years after reduction was associated with an 80% probability of becoming a Severin grade III/IV hip. This study links early acetabular remodelling, residual dysplasia at skeletal maturity and the long-term risk of THR. It presents evidence describing the diagnostic value of early predictors of residual dysplasia, and therefore, of the long-term risk of degenerative change.

A predictive model for outcome after conservative decompression surgery for lumbar spinal stenosis.

This study was designed to develop predictive models for surgical outcome based on information available prior to lumbar stenosis surgery. Forty patients underwent decompressive laminarthrectomy. Preop and 1-year postop evaluation included Waddell's nonorganic signs, CT scan, Waddell disability index, Oswestry low back pain disability questionnaire, low back outcome score (LBOS), visual analog scale (VAS) for pain intensity, and trunk strength testing. Statistical comparisons of data used adjusted error rates within families of predictors. Mathematical models were developed to predict outcome success using stepwise logistic regression and decision-tree methodologies (chi-squared automatic interaction detection, or CHAID). Successful outcome was defined as improvement in at least three of four criteria: VAS, LBOS, and reductions in claudication and leg pain. Exact logistic regression analysis resulted in a three-predictor model. This model was more accurate in predicting unsuccessful outcome (negative predictive value 75.0%) than in successful outcome (positive predictive value 69.6%). A CHAID model correctly classified 90.1% of successful outcomes (positive predictive value 85.7%, negative predictive value 100%). The use of conservative surgical decompression for lumbar stenosis can be recommended, as it demonstrated a success rate similar to that of more invasive techniques. Given its physiologic and biomechanical advantages, it can be recommended as the surgical method of choice in this indication. Underlying subclinical vascular factors may be involved in the complaints of spinal stenosis patients. Those factors should be investigated more thoroughly, as they may account for some of the failures of surgical relief. The CHAID decision tree appears to be a novel and useful tool for predicting the results of spinal stenosis surgery

A prospective study on CT scan outcomes after conservative decompression surgery for lumbar spinal stenosis.

This is a prospective study analyzing CT scan imaging outcomes after conservative decompression in patients with lumbar spinal stenosis. Forty patients (18 males and 22 females) initially underwent a laminarthrectomy surgical procedure to decompress the central canal as well as the neuroforamina and nerve root canals while respecting the integrity of the neural arches, facet joints, and most muscle attachments. Morphologic features of preoperative CT scan images were compared with postoperative CT scans of the operative levels, obtained for 36 patients (17 males and 19 females) after a minimum follow-up of 1 year (mean 1.7 years). Successful surgical outcome was defined as an improvement in at least three of the following four criteria: self-reported pain on a visual analog scale, self-reported functional status measured by LBOS, reduction of pain while walking, and reduction of leg pain. Fifty-five percent of patients met the successful surgical outcome criteria, including 14 subjects who met all four success criteria. Overall, there was a statistically significant increase in the interfacet bony canal diameter of the operated levels (3.9 mm, p < 001). However, patients categorized as successful surgical outcomes had a substantially, but not significantly, lower interfacet canal diameter increase postsurgically (mean 3.41 mm) in comparison with patients categorized as failures (mean postoperative increase 4.52 mm). Midsagittal canal diameters remained unchanged in the failure group but increased in the success group. The CT scan canal measures used in this study cannot be advocated for evaluation of outcome in conservative lumbar spinal canal decompression.

Somatosympathetic reflexes from the low back in the anesthetized cat.

In the appendicular skeleton, substantial evidence demonstrates that somatosensory input from deep tissues including limb muscles and joints elicits somatosympathetic reflexes. Much less is known about the presence and organization of these reflexes from the axial skeleton. We determined if mechanical loading of the lumbar spine and lumbar paraspinal muscle irritation reflexively affects postganglionic sympathetic nerve discharge (SND) to the spleen and kidney. In 27 alpha-chloralose-anesthetized cats, the L2-4 multifidus muscles were injected with the inflammatory irritant mustard oil (20%, 60 microl total) and a vertebral load (100% body weight) was applied dorsal-ventral at the L3 spinous process. Mustard oil injection alone without vertebral loading (n = 7) increased mean splenic SND (60%), renal SND (30%), and heart rate (HR; 52 bpm). Mustard oil injection accompanied by the vertebral load (n = 7) increased mean splenic SND (55%), renal SND (16%), and HR (27 bpm). Blood pressure changes were biphasic and could not account for these changes. When the vertebral load accompanied mustard oil, the increases in splenic SND, renal SND, and HR remained elevated in a pattern significantly different from when the vertebral load was absent. Vehicle injection combined with the mechanical load (n = 3) did not change any of the autonomic responses. Similarly, mustard oil injection combined with a mechanical load did not change these responses when either the medial branches of the dorsal rami from T11-L5 had been cut (n = 4) or when the spinal cord had been transected between the second and third cervical vertebrae (n = 6). The results indicate that inflammatory stimulation of multifidus muscle in the low back evokes a somatosympathetic reflex integrated supraspinally in the upper cervical spinal cord or higher. The reflex's afferent arm travels in the medial branch of the dorsal ramus, and its efferent arm can affect sympathetic outflow to the spleen and the kidney as well as HR and BP. A static mechanical load applied to the lumbar spine accompanying the inflammatory stimulus appears to sustain the inflammatory-induced reflex activity.

Clinical and psychofunctional measures of conservative decompression surgery for lumbar spinal stenosis: a prospective cohort study.

Less invasive decompressive surgery has emerged as a logical surgical treatment alternative to wide decompression of spinal stenosis. The clinical outcomes of such conservative surgical treatment, however, are not well known. The aim of the study was to evaluate short-term psychometric and functional outcomes after conservative decompressive surgery for lumbar canal stenosis. Forty patients had a lumbar laminectomy procedure, which preserved the integrity of the neural arches, facet joints and most muscle attachments. Pre-operative clinical evaluation of the patients included: Waddell's non-organic signs (NOS) performed by an independent surgeon observer; three self-report questionnaires--the Waddell Disability Index (WDI), the Oswestry Low Back Pain Disability Questionnaire (ODI), and the Low Back Outcome Score (LBOS); and a general questionnaire that included a visual analog pain intensity scale (VAS). Post-operative clinical evaluations and questionnaires were obtained in 36 subjects (mean age 59.8 years) after a 1.7-year follow-up (range 1-2.6 years). Pre-operative versus post-operative statistical comparisons of the data were performed using adjusted error rates within families of predictors. Successful surgical outcome was defined as an improvement in at least three of the following four criteria: self-reported pain on a VAS, self-reported functional status measured by LBOS, reduction of pain during walking and reduction of leg pain. At follow-up, there was a statistically significant improvement in VAS pain intensity, ODI, WDI, and LBOS. Patients classified as having mixed stenosis had a higher incidence of continuous pain symptoms in comparison with acquired stenosis, but there was no differential improvement with treatment depending upon stenosis classification and/or number of operative levels. Overall, 58% (21/36) of patients met the successful surgical outcome criteria, including 14 subjects who met all four success criteria. Based upon a stringent definition of successful surgical outcome, the results of a conservative laminectomy were as good as those of more aggressive decompressive procedures presented in the literature. Our findings indicate that, even in a highly organic disorder such as spinal stenosis, illness behavior plays an important role in predicting surgical outcome.

Radiologic abnormalities and low back pain in elite skiers.

Lumbar radiographs of 120 adolescent elite skiers were evaluated for radiologic abnormalities by two independent observers. All athletes had no symptoms before the study. Radiographs were taken before enrollment of the students in elite level training. To determine the clinical significance of these abnormalities, all athletes were observed prospectively during the subsequent 2-year period for development of low back pain under high performance training. Anterior end plate lesions, Schmorl's nodes, posterior end plate lesions, spondylolysis, scoliosis, and spina bifida occulta were found. The depth of anterior end plate lesions showed a two-peak distribution, with peaks at 11% and 22% and a valley at 18% vertebral body height. The overall low back pain incidence was 12.5%. Students with severe anterior lesions (greater than 18% vertebral body height, n = 25) had significantly more low back pain (incidence, 32%) than did students without severe anterior lesions (incidence, 7.4%). Accordingly, students with severe anterior lesions had a significantly higher risk of having low back pain develop. Moderate end plate lesions and other abnormalities were not related to an increased incidence of low back pain. Adolescent students of elite sports with severe lumbar anterior end plate lesions have an increased risk of having low back pain develop under high performance training.

Footwear affects the behavior of low back muscles when jogging.

Use of modified shoes and insole materials has been widely advocated to treat low back symptoms from running impacts, although considerable uncertainty remains regarding the effects of these devices on the rate of shock transmission to the spine. This study investigated the effects of shoes and insole materials on a) the rate of shock transmission to the spine, b) the temporal response of spinal musculature to impact loading, and c) the time interval between peak lumbar acceleration and peak lumbar muscle response. It was hypothesised that shoes and inserts a) decrease the rate of shock transmission, b) decrease the low back muscle response time, and c) shorten the time interval between peak lumbar acceleration and peak lumbar muscle response. Twelve healthy subjects were tested while jogging barefoot (unshod) or wearing identical athletic shoes (shod). Either no material, semi-rigid (34 Shore A), or soft (9.5 Shore A) insole material covered the force plate in the barefoot conditions and was placed as insole when running shod. Ground reaction forces, acceleration at the third lumbar level, and erector spinae myoelectric activity were recorded simultaneously. The rate of shock transmission to the spine was greater (p < 0.0003) unshod (acceleration rate: Means +/- SD 127.35 +/- 87.23 g/s) than shod (49.84 +/- 33.98 g/s). The temporal response of spinal musculature following heel strike was significantly shorter (p < 0.023) unshod (0.038 +/- 0.021 s) than shod (0.047 +/- 0.036 s). The latency between acceleration peak (maximal external force) and muscle response peak (maximal internal force) was significantly (p < 0.021) longer unshod (0.0137 +/- 0.022s) than shod (0.004 +/- 0.040 s). These results suggest that one of the benefits of running shoes and insoles is improved temporal synchronization between potentially destabilizing external forces and stabilizing internal forces around the lumbar spine.

The Boeing prospective study and beyond.

STUDY DESIGN: The Boeing prospective study was reviewed. The Boeing prospective study, comprising two articles, was a large field study that explored why workers would or would not report occupational back pain problems. OBJECTIVES: The most immediate objective was to determine the extent to which conclusions drawn from the Boeing prospective study withstand critical examination. The ultimate purpose of this review was to develop guidelines for field studies of back pain in industry. SUMMARY OF BACKGROUND DATA: For more than a century, researchers have noted great variability among individuals in the reporting of back pain, but the explanations posed for this variability have been inconsistent. Because findings gain credibility roughly to the extent that they bear on the world outside the laboratory, field studies in particular hold great potential for clarifying the underlying explanation for individual variability in back pain reporting. The Boeing prospective study was a large and ambitious field study that examined this issue. METHODS: The Boeing prospective study was examined through the lens of research conducted since it was published. The review used both the methodological and substantive literature. RESULTS: The Boeing prospective study, based on a minority of workers originally solicited to participate in it (33-41%), accounted for 7% of the variation in why workers would or would not report a back pain problem. A number of issues that may have biased its results toward the null are examined. CONCLUSIONS: The highlighting of the Boeing prospective study's limitations may be instructive not so much to criticize this one particular study but, rather, to anticipate problems that in general may be encountered in field studies of back pain in industry. Looking beyond the Boeing prospective study, the following guidelines for the conduct of such studies may be proposed: 1) Study designs should be based on explanations from which testable hypotheses may be derived; 2) Subgroups within the more general category of "back pain" should be delineated; 3) Both occupational exposures and psychosocial factors should be entered into the analysis; 4) Factors not apparent at the workplace should be considered; 5. Abstracts of articles should be carefully crafted.

The pathomechanism of spondylolytic spondylolisthesis in immature primate lumbar spines in vitro and finite element assessments.

STUDY DESIGN: Immature Chacma baboon (Papio ursinus) spine specimens were used to determine load-displacement behavior as related to disc injury. This was accomplished through the application of A-P shear force until failure of FSUs with pars defects. Several finite element models (FEMs) of the FSU were developed to study the mechanism of slippage in immature baboon lumbar spines. OBJECTIVES: The purpose was to show that spondylolisthesis (olisthesis) always occurs through the growth plate using a model similar to immature human lumbar spines. Using FEMs, the roles of facet orientation, pars interarticularis thickness, and a weak growth-plate in producing slippage were examined. SUMMARY OF BACKGROUND DATA: Progression from spondylolysis (lysis) to olisthesis occurs, most often, during the adolescent growth spurt. The biomechanical literature dealing with the slippage mechanism in the immature lumbar spine does not provide a clear understanding and is sparse. METHODS: Several groups of FSUs were subjected to A-P shear force until failure. The results provided displacement at failure as a function of disc injury and flexion-extension fatigue. A bilateral pars defect was created in each specimen prior to application of A-P shear force using an MTS machine. Failure sites were assessed radiographically and histologically. A nonlinear 3-D FEM of the intact L4-L5 was created from CT scans. The model was modified to predict the effects of a pars fracture, a thin pars, a weak growth plate, and facet orientation on the shear load through the growth plate and stresses in the pars. RESULTS: Experimentally, failures always occurred through the growth-plate in the disc intact and disc-incised groups. In the intact FEM, the growth plate carried21% of the applied A-P shear force. The load increased when the facets were more sagittally oriented. The effect of thin pars and/or weaker growth plate was an increase in stresses in the pars. Changes in the load through the growth plate were minimal. CONCLUSIONS: The weakest link in immature baboon lumbar functional spinal units (FSUs) with lysis during an A-P shear load was the growth plate, between the cartilaginous and osseous end plates. Surgeons may assess this lesion on MRI views, thereby predicting the possible development and preventing progression of olisthesis. Finite element model results predict that more sagittally orientated facets and/or a pars fracture are prerequisites for olisthesis to occur.

Biomechanic evaluation of the Rola Stretcher as a passive distraction device.

INTRODUCTION: Many devices have been marketed claiming to increase the mobility of the articulations of the spine with active or passive distraction. In this study, the Rola Stretcher (Unique Relief, Inc, Davenport, Iowa) and an earlier version, the True Back II (True Back, Inc, Clearwater, Fla), were evaluated to see if they have a measurable biomechanic effect on the spine. METHODS: Two studies were conducted, each with 6 male participants and 6 female participants, using a stadiometer to accurately measure a person's sitting height. The increase in sitting height after using the True Back II or Rola Stretcher for 10 minutes was compared with that after lying supine for 10 minutes. A third intervention, a firm foam block cut to the same size and shape as the True Back II, was also used in this study. RESULTS: The Rola Stretcher had a significantly greater lengthening effect on the spine compared with supine rest (P <0050). The True Back II had a similar but lesser effect (P <.0509). Women demonstrated a greater height gain than men. CONCLUSION: The True Back II and the Rola Stretcher in particular appear to lengthen the spine after a single use of 10 minutes. The observed discrepancy between the effects in men and women may be an experimental artifact occurring as a result of less effective resetting of the posturing mechanisms in men compared with women. A trend showed the Rola Stretcher to be more effective than the foam block.

Stability analysis of an enhanced load sharing posterior fixation device and its equivalent conventional device in a calf spine model.

STUDY DESIGN: An in vitro test of calf spine lumbar segments to compare biomechanical stabilization of a rigid versus a dynamic posterior fixation device. OBJECTIVES: To compare flexibility of a dynamic pedicle screw fixation device with an equivalent rigid device. SUMMARY OF BACKGROUND DATA: Dynamic pedicle screw device studies are not as prevalent in the literature as studies of rigid devices. These devices contain the potential to enhance load sharing and optimize fusion potential while maintaining stability similar to that of rigid systems. METHODS: Load-displacement tests were performed on intact and stabilized calf spines for the dynamic and rigid devices. Stability across a destabilized L3-L4 segment was restored by insertion of either a 6 mm x 40 mm dynamic or rigid pedicle screw fixation device across the L2-L4 segment. The screws then were removed, 7 mm x 45 mm pedicle screws of the opposite type were inserted, and the construct then was re-tested. Axial pull-out tests were performed to assess the likely effects of pedicle screw replacement on the load-displacement data. RESULTS: Results indicated a 65% reduction in motion in flexion-extension and a 90% reduction in lateral bending across the destabilized level for both devices, compared with intact spine values. Reduction in axial rotation motion was much smaller than in other modes. Axial pull-out tests showed no weakening of the bone-screw interface. CONCLUSIONS: Both devices provided significant stability of similar magnitudes in flexion, extension, and lateral bending. In axial rotation, the devices only could restore stability to levels similar to those in an intact spine. The dynamic device offers a design that may enhance load sharing without sacrificing construct stability.

Stulberg classification system for evaluation of Legg-Calvé-Perthes disease: intra-rater and inter-rater reliability.

BACKGROUND: Researchers and clinicians commonly use the classification system of Stulberg et al. as a basis for treatment decisions during the active phase of Legg-Calvé-Perthes disease because of its putative utility as a predictor of long-term outcome. It is generally assumed that this system has an acceptable degree of reliability. This assumption, however, is not convincingly supported by the literature. METHODS: The purpose of the present study was to assess the inter-rater and intra-rater reliability of the classification system of Stulberg et al. with use of a pre-test, post-test design. During the pre-test phase, nine raters independently used the system to evaluate the radiographs of skeletally mature patients who had been managed for Legg-Calvé-Perthes disease. The intervention between the pre-test and post-test phases consisted of a consensus-building session during which all raters jointly arrived at standardized definitions of the various joint structures that are assessed with use of the classification system. The effect of these definitions on reliability then was assessed by reevaluating the radiographs during the post-test phase. RESULTS: The pre-test intra-rater reliability coefficients ranged from 0.709 to 0.915, and the post-test coefficients ranged from 0.568 to 0.874. The pre-test inter-rater reliability coefficients ranged from 0.603 to 0.732, and the post-test coefficients ranged from 0.648 to 0.744. Contributing to the variance was a lack of agreement concerning the assessment of joint structures and the way in which the raters translated these evaluations into a classification according to the system of Stulberg et al. CONCLUSIONS: Although intra-rater reliability was marginally acceptable, the degree of variability between the classifications assigned by different raters even after the intervention - calls into question the reliability of the system of Stulberg et al.; consequently, the validity of any treatment decisions, outcome evaluations, or epidemiological studies based on this system is also in question.

Range of motion and motion patterns in patients with low back pain before and after rehabilitation.

STUDY DESIGN: Data were collected from 27 patients who were participating in a rehabilitation program for chronic low back pain. The patients were tested on day 2 and day 11 of a 2-week rehabilitation program. OBJECTIVES: To determine specific characteristics of trunk motion associated with long-term dysfunction caused by low back pain of various origin, to determine if a neural network analysis system can be effective in distinguishing between patterns, and to determine if the rehabilitation has an effect on range and pattern of motion. SUMMARY OF BACKGROUND DATA: There is a lack of objective measures for evaluating the efficacy of rehabilitation programs. Numerous studies have established the difficulty of evaluating low back pain. Existing techniques, such as imaging methods, are in many cases either very rough and inaccurate or expensive and ineffective. A technique for evaluation of motion patterns in low back pain was developed based on analysis of dynamic motion features such as shape, velocity, and symmetry of movements. METHODS: Dynamic motion data were collected before and after rehabilitation from 27 patients with low back pain by using a triaxial goniometer. Range of motion and features of the movement, such as shape, velocity, and repetitiveness, were extracted for analysis. RESULTS: Motion features showed significant improvement after the rehabilitation program. CONCLUSIONS: A neural network based on kinematic data is an excellent model for classification of low back pain dysfunction. Such a system could markedly improve the management of low back pain for an individual patient.

The role of steroids and their effects on phospholipase A2. An animal model of radiculopathy.

STUDY DESIGN: The possible role of phospholipase A2 in an animal model for lumbar radiculopathy and mechanisms of epidural steroid injections were studied. OBJECTIVES: To clarify the pathophysiologic mechanism of the recently proved animal model for lumbar radiculopathy and to characterize further the mechanisms of action of steroids. SUMMARY OF BACKGROUND DATA: There have been several reported animal models of peripheral neuropathy. Recently an animal model that shows reliable behavioral and neurochemical changes was proposed, and epidural steroid injections in this model were effective in the reduction of thermal hyperalgesia and allodynia. METHOD: In a behavioral study, 24 rats were divided into 4 groups: Group I, loose ligature of the left L4 and L5 nerve roots with 4-0 chromic gut sutures and an epidural injection of 0.1 mL of saline at 3 days after surgery; Group II, same as Group I but with an epidural injection of 0.1 mL of betamethasone on the day before the operation; Group II, same as Group II except injection at 1 day after surgery; Group IV, same as Group II except injection at 3 days after surgery. To test the phospholipase A2 activity in the nerve roots and dorsal root ganglia after the operation, eight rats were killed at given intervals. Analysis of variance techniques were used to test behavioral pattern changes and phospholipase A2 activity across time in each group. RESULTS: Thermal hyperalgesia reached its maximal point at 3 weeks after surgery in Group I, but in steroid injection groups, the recovery from hyperalgesia was faster than in Group I. However, there was no significant difference in recovery time among steroid injection groups. The level of phospholipase A2 activity was at its maximum at 1 week after surgery in Groups I and IV. It showed a steady reduction in the steroid group, whereas it remained relatively high and dropped rapidly after 3 weeks in the saline-treated group, and returned to the level of a normal nerve root at 6 weeks after surgery. CONCLUSION: These results suggest that the behavioral pattern changes observed in the irritated nerve root model are caused in part by a high level of phospholipase A2 activity initiated by inflammation, and that the mechanism of action of epidural steroid injection in this model is inhibition of phospholipase A2 activity.

The effect of epidural injection of betamethasone or bupivacaine in a rat model of lumbar radiculopathy.

STUDY DESIGN: The effect of epidural injection of betamethasone or bupivacaine was investigated in an animal model of lumbar radiculopathy. OBJECTIVE: To investigate the effects of an epidural steroid (betamethasone) or a local anesthetic (bupivacaine) in an animal model of radiculopathy produced by nerve root irritation. SUMMARY OF BACKGROUND DATA: Epidural injections are commonly used for the treatment of low back pain and sciatica. However, efficacy remains controversial, and there is a paucity of basic information to support clinical use or the injections. METHODS: Fifty-one rats were used. The left L4 and L5 nerve roots were loosely ligated with chromic gut, and either betamethasone, bupivacaine, betamethasone in combination with bupivacaine, or saline was injected using an epidurally placed catheter. The effects of epidural injection were evaluated using response to noxious stimuli and immunohistochemical methods. RESULTS: In betamethasone-treated rats (either alone or in combination with bupivacaine), thermal hyperalgesia was significantly less (P < 0.010 after surgery than that in saline- or bupivacaine-treated groups, in which the hyperalgesia was maximum at 2-3 postoperative weeks before resolving 5 weeks after surgery. Immunohistochemical analysis did not correlate with these results. CONCLUSIONS: Epidural steroid injection has a significant effect on the thermal hyperalgesia produced in a model of radiculopathy, which may provide clinical support for advocates of epidural steroids.

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.

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.

Consensus summary of the diagnosis and treatment of lumbar disc herniation.

Clinicians must not simply decide that a patient with symptoms and a positive diagnostic test has a reason for a specific treatment, and likewise clinicians must not decide that a patient with symptoms and a negative test does not have a clinically important problem. We must also consider the sensitivity, specificity and predictive value of the diagnostic test and the individual characteristics of the patient. Treatment outcome depends on many factors. Point of service decisions vs population based decisions are obviously different. Each patient presents to the treating practitioner on a given day, at a given time, and it is this picture upon which a plan of care is formulated.

Hyperextension and spine height changes.

STUDY DESIGN: The effect on spine height changes from different combinations of time and angle of static prone hyperextension, and one intervention of dynamic hyperextension was explored. OBJECTIVES: To explore whether controlled hyperextension would cause an height increase with greater duration than previously shown, and to find an optimal combination of hyperextension angle and duration of the intervention. SUMMARY OF BACKGROUND DATA: Hyperextension is a METHODS: Ten subjects were exposed to hyperextension in the prone position for different time periods and with different amounts of hyperextension. The effect was measured using the stadiometer for measurement of spine height changes. RESULTS: The study showed that time was the most important variable, and also that for a given time, there was an increased recovery with increased angle. CONCLUSIONS: The results indicate that hyperextension can be a beneficial maneuver to unload temporarily the spine after loading and to rehydrate the discs, providing enough time is given for the procedure. The optimal time and angle combination was 20 degrees for 20 minutes because this intervention resulted in the largest recovery that lasted for a relatively long period of time.

Muscular response to sudden load. A tool to evaluate fatigue and rehabilitation.

STUDY DESIGN: Subjects were exposed to fatiguing and restorative interventions to assess their response to sudden loads. OBJECTIVES: To investigate the erector spinae and rectus abdominis response characteristics to "sudden load" and the effect of fatigue and rehabilitation. SUMMARY OF BACKGROUND DATA: Unexpected loads which people often experience, can lead to high forces in the spine and may be a cause of low back injury. METHODS: Muscle responses to sudden load were mediated by fatigue, walking, expectation, method of load application, exposure to vibration, and cognitive-behavioral rehabilitation in patients with chronic low back pain. A novel technique, perfected in this work, called wavelet analysis, was used to analyze these data. RESULTS: Reaction time was affected by fatigue and expectation. Vibration exposure significantly increased the muscle response time. Walking was able to ameliorate that effect. Back muscles responded differently, depending on whether loads were applied to the back through the hands or through the trunk. Electromyographic reaction time and magnitude decreased in patients after a 2-week rehabilitation program. CONCLUSIONS: Sudden loads can exacerbate fatigue effects. Walking after driving reduces the risk to the back caused by handling unpredictable loads. Vibration exposure guidelines should be more conservative. Patients have longer response times than healthy subjects, but patients can improve their response to sudden loads via rehabilitation. Patients exhibit a flexion-extension oscillation at 5 Hz in response to a sudden load, suggesting that the 5-Hz, seated, natural frequency observed during whole-body vibration may result from neurophysiologic control limits.