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PubMed2000

Efficacy and validity of radiofrequency neurotomy for chronic lumbar zygapophysial joint pain.

STUDY DESIGN: A prospective audit. OBJECTIVE: To establish the efficacy of lumbar medial branch neurotomy under optimum conditions. SUMMARY OF BACKGROUND DATA: Previous reports of the efficacy of lumbar medial branch neurotomy have been confounded by poor patient selection, inaccurate surgical technique, and inadequate assessment of outcome. METHODS: Fifteen patients with chronic low back pain whose pain was relieved by controlled, diagnostic medial branch blocks of the lumbar zygapophysial joints, underwent lumbar medial branch neurotomy. Before surgery, all were evaluated by visual analog scale and a variety of validated measures of pain, disability, and treatment satisfaction. Electromyography of the multifidus muscle was performed before and after surgery to ensure accuracy of the neurotomy. All outcome measures were repeated at 6 weeks, and 3, 6, and 12 months after surgery. RESULTS: Some 60% of the patients obtained at least 90% relief of pain at 12 months, and 87% obtained at least 60% relief. Relief was associated with denervation of the multifidus in those segments in which the medial branches had been coagulated. Prelesion electrical stimulation of the medial branch nerve with measurement of impedance was not associated with outcome. CONCLUSIONS: Lumbar medial branch neurotomy is an effective means of reducing pain in patients carefully selected on the basis of controlled diagnostic blocks. Adequate coagulation of the target nerves can be achieved by carefully placing the electrode in correct position as judged radiologically. Electrical stimulation before lesioning is superfluous in assuring correct placement of the electrode.

Adult↗
PubMed2001

Long-term effects of specific stabilizing exercises for first-episode low back pain.

STUDY DESIGN: A randomized clinical trial with 1-year and 3-year telephone questionnaire follow-ups. OBJECTIVE: To report a specific exercise intervention's long-term effects on recurrence rates in acute, first-episode low back pain patients. SUMMARY OF BACKGROUND DATA: The pain and disability associated with an initial episode of acute low back pain (LBP) is known to resolve spontaneously in the short-term in the majority of cases. However, the recurrence rate is high, and recurrent disabling episodes remain one of the most costly problems in LBP. A deficit in the multifidus muscle has been identified in acute LBP patients, and does not resolve spontaneously on resolution of painful symptoms and resumption of normal activity. Any relation between this deficit and recurrence rate was investigated in the long-term. METHODS: Thirty-nine patients with acute, first-episode LBP were medically managed and randomly allocated to either a control group or specific exercise group. Medical management included advice and use of medications. Intervention consisted of exercises aimed at rehabilitating the multifidus in cocontraction with the transversus abdominis muscle. One year and three years after treatment, telephone questionnaires were conducted with patients. RESULTS: Questionnaire results revealed that patients from the specific exercise group experienced fewer recurrences of LBP than patients from the control group. One year after treatment, specific exercise group recurrence was 30%, and control group recurrence was 84% (P < 0.001). Two to three years after treatment, specific exercise group recurrence was 35%, and control group recurrence was 75% (P < 0.01). CONCLUSION: Long-term results suggest that specific exercise therapy in addition to medical management and resumption of normal activity may be more effective in reducing low back pain recurrences than medical management and normal activity alone.

Adult↗
PubMed2002

Fatigue-related changes in torque output and electromyographic parameters of trunk muscles during isometric axial rotation exertion: an investigation in patients with back pain and in healthy subjects.

STUDY DESIGN: A cross-sectional case-control study. OBJECTIVES: To examine the effect of fatigue on torque output as well as electromyographic frequency and amplitude values of trunk muscles during isometric axial rotation exertion in back pain patients and to compare the results with a matched control group. SUMMARY OF BACKGROUND DATA: Back pain patients exhibited different activation strategies in trunk muscles during the axial rotation exertions. Fatigue changes of abdominal and back muscles during axial rotation exertion have not been examined in patients with back pain. METHODS: Twelve back pain patients and 12 matched controls performed isometric fatiguing axial rotation to both sides at 80% maximum voluntary contraction in a standing position. During the fatiguing exertion, electromyographic changes of rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum, and multifidus were recorded bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were also measured. RESULTS: No difference in the endurance capacity was found between back pain and control groups. At the initial period of the exertion, back pain patients demonstrated a statistical trend (P = 0.058) of greater sagittal coupling torque as well as lower activity of rectus abdominis and multifidus and higher activity in external oblique. During the fatigue process similar changes of coupling torque were demonstrated in both sagittal and coronal planes, but a smaller fatigue rate for right external oblique, increase in median frequency for latissimus dorsi, and lesser increase in activity for back muscles were found in the back pain group compared with the control group. CONCLUSIONS: Alterations in electromyographic activation and fatigue rates of abdominal and back muscles demonstrated during the fatigue process provide insights into the muscle dysfunctions in back pain and may help clinicians to devise more rational treatment strategies.

Abdomen↗
PubMed2002

The effect of different standing and sitting postures on trunk muscle activity in a pain-free population.

STUDY DESIGN: A normative, single-group study was conducted. OBJECTIVE: To determine whether there is a difference in electromyographic activation of specific lumbopelvic muscles with the adoption of common postures in a pain-free population. SUMMARY OF BACKGROUND DATA: Clinical observations indicate that adopting passive postures such as sway standing and slump sitting can exacerbate pain in individuals with low back pain. These individuals often present with poor activation of the lumbopelvic stabilizing musculature. At this writing, little empirical evidence exists to document that function of the trunk and lumbopelvic musculature are related to the adoption of standardized standing and sitting postures. METHODS: This study included 20 healthy adults, with equal representation of the genders. Surface electromyography was used to measure activity in the superficial lumbar multifidus, internal oblique, rectus abdominis, external oblique, and thoracic erector spinae muscles for four standardized standing and sitting postures. RESULTS: The internal oblique, superficial lumbar multifidus, and thoracic erector spinae muscles showed a significant decrease in activity during sway standing (P = 0.027, P = 0.002, and P = 0.003, respectively) and slump sitting (P = 0.007, P = 0.012, and P = 0.003, respectively), as compared with erect postures. Rectus abdominis activity increased significantly in sway standing, as compared with erect standing (P = 0.005). CONCLUSIONS: The findings show that the lumbopelvic stabilizing musculature is active in maintaining optimally aligned, erect postures, and that these muscles are less active during the adoption of passive postures. The results of this study lend credence to the practice of postural retraining when facilitation of the lumbopelvic stabilizing musculature is indicated in the management of specific spinal pain conditions.

Abdomen↗
PubMed2006

The Wiltse paraspinal approach to the lumbar spine revisited: an anatomic study.

The paraspinal posterior approach to the lumbar spine initially was described for spinal fusion, particularly for treatment of lumbosacral spondylolisthesis. Despite the technical details described by Wiltse et al, the exact location of the sacrospinalis muscle that must be split remains unclear. We sought to clarify the anatomic description of the paraspinal posterior approach to the lumbar spine, and to provide topographic landmarks for facilitating this surgical approach. Fifty cadavers were dissected using an anatomic transmuscular paraspinal approach. The level of the natural cleavage plane between the multifidus and the longissimus parts of the sacrospinalis muscle was noted, and measurements were taken between this level and the midline at the level of the spinous process of L4. A natural cleavage plane between the multifidus and the longissimus parts of the sacrospinalis muscle was present in all specimens. There was a fibrous separation between the two muscular parts in 88 of 100 cases. The mean distance between the level of the cleavage plane and the midline was 4.04 cm (range, 2.4-7 cm). Small arteries and veins were present at the level of the cleavage plane in all specimens. These vascular landmarks make it easier to locate the muscular cleavage plane and reach the articular and transverse processes during the paraspinal approach.

Cadaver↗
PubMed2005

The use of magnetic resonance imaging to evaluate lumbar muscle activity during trunk extension exercise at varying intensities.

STUDY DESIGN: Descriptive, repeated measures analysis of exercise-induced changes in lumbar muscle transverse relaxation time (T2). OBJECTIVES: To use muscle functional magnetic resonance imaging (MRI) to characterize the activity levels and recruitment patterns of the lumbar extensor muscles during trunk extension exercise over 3 intensities. SUMMARY OF BACKGROUND DATA: Contrast shifts in T2 are indicative of skeletal muscle activity during resistance exercise and are used to characterize the function of a variety of muscles. The use of muscle functional MRI for the lumbar muscles has been limited. METHODS: In 11 healthy participants, T2 was calculated for the lumbar quadratus lumborum, iliocostalis lumborum, longissimus thoracis, and multifidus at rest and following dynamic trunk extension exercise at 3 exercise intensities (40%, 50%, and 70% peak intensity). RESULTS: The multifidus displayed the largest T2 increase at each of the 3 exercise intensities, followed by the erector spinae and, finally, the quadratus lumborum. At the lowest intensity, the medial erector spinae (longissimus thoracis) displayed a higher T2 increase than the lateral group (iliocostalis lumborum), while at the higher intensities, this pattern was reversed. In general, the T2 increase was higher during exercise at 50% and 70% intensities than at 40%, while there was no difference in T2 increase between 50% and 70%. CONCLUSIONS: Muscle functional MRI can be used to characterize lumbar muscle function during trunk extension exercise. The levels and recruitment patterns of the lumbar extensors, as measured by muscle T2 shifts, vary with exercise intensity. Future research is needed to assess the mechanism of the nonlinear relationship between T2 shifts and exercise intensity, and to clarify the effects of fatigue and the order of exercise presentation on the T2 response of the lumbar extensors.

Adult↗
PubMed2006

Cadaver evaluation of EMG needle insertion techniques used to target muscles of the thorax.

STUDY DESIGN: Measure the accuracy of needle insertion in thoracic muscles of human cadavers. OBJECTIVES: Evaluate the effectiveness of known EMG techniques for sampling thoracic innervated muscles. SUMMARY OF BACKGROUND DATA: The evaluation of thoracic radiculopathies requires accurate electrodiagnostic techniques for evaluating the thoracic myotomes. METHODS: An American Board of Electrodiagnostic Medicine certified physician placed needles into pertinent muscles of the thorax and an anatomist serving as a blinded dissector recorded the path and accuracy of needle. RESULTS: Needle examination of thoracic muscles was as accurate as limb needle examination. No notable risks are noted in multifidus sampling. However, in the cadaver, some risks were noted in association with placements in the intercostal muscles. The target muscle was reliably sampled, but the rib or vertebral level was difficult to landmark in the cadaver. CONCLUSIONS: Needle examination of the thoracic multifidus and intercostals is reliable, although further confirmation is needed to accurately verify the appropriate vertebral or rib level being sampled.

Adult↗
PubMed2006

Effect of different upright sitting postures on spinal-pelvic curvature and trunk muscle activation in a pain-free population.

STUDY DESIGN: A normative within-subjects single-group study. OBJECTIVE: To compare spinal-pelvic curvature and trunk muscle activation in 2 upright sitting postures ("thoracic" and "lumbo-pelvic") and slump sitting in a pain-free population. SUMMARY OF BACKGROUND DATA: Clinical observations suggest that both upright and slump sitting postures can exacerbate low back pain. Little research has investigated the effects of different upright sitting postures on trunk muscle activation. METHODS: Spinal-pelvic curvature and surface electromyography of 6 trunk muscles were measured bilaterally in 2 upright (thoracic and lumbo-pelvic) sitting postures and slump sitting in 22 subjects. RESULTS: Thoracic, compared to lumbo-pelvic, upright sitting showed significantly greater thoracic extension (P < 0.001), with significantly less lumbar extension (P < 0.001) and anterior pelvic tilt (P = 0.03). Furthermore, there was significantly less superficial lumbar multifidus (P < 0.001) and internal oblique (P = 0.03) activity, with significantly higher thoracic erector spinae (P < 0.001) and external oblique (P = 0.04) activity in thoracic upright sitting. There was no significant difference in superficial lumbar multifidus activity between thoracic upright and slump sitting. CONCLUSIONS: Different upright sitting postures resulted in altered trunk muscle activation. Thoracic when compared to lumbo-pelvic upright sitting involved less coactivation of the local spinal muscles, with greater coactivation of the global muscles. These results highlight the importance of postural training specificity when the aim is to activate the lumbo-pelvic stabilizing muscles in subjects with back pain.

Adult↗
PubMed1976

Exteroceptive influences on the lumbar back muscle tone and reflexes in the cat.

The exteroceptive influences on tonic activity and on stretch reflexes of the longissimus dorsi and multifidus spinae muscles were investiagted in decerebrate, spinal and chloralose-anesthetized cats. Adequate skin stimulation was used to map out facilitatory and inhibitory skin areas on the trunk and the extremities. On the trunk facilitatory areas are relatively large and located at the dorsal side while inhibitory areas are confined to the ventrolateral part of the contralateral body half. The facilitatory skin fields are of approximately the same size in decerebrate and spinal cats. On leg skin stimulation facilitation can be evoked from the ipsilateral hind limb while inhibition results from stimulation of the other limbs. Spinal cord transection increased excitatory effects of ipsilateral hind limb stimulation. Reflex responses in the back muscles to applied stretch are described. These reflexes were used as test reflexes in experiments with conditioning stimulation of the peripheral nerves supplying skin areas from which effects on back muscle activity were evoked by adequate stimulation. The conditioning-test experiments and those using adequate stimulation show that the longissimus dorsi and multifidus spinae are activated or facilitated by an ipsilateral stimulus to skin afferents. The extent of the effects induced by stimulation of skin differs in the types of preparation used. These differences may be accounted for by assuming a supraspinal control of the reflex pathways studied.

Anesthesia, General↗
PubMed2002

External perturbation of the trunk in standing humans differentially activates components of the medial back muscles.

During voluntary arm movements, the medial back muscles are differentially active. It is not known whether differential activity also occurs when the trunk is perturbed unpredictably, when the earliest responses are initiated by short-latency spinal mechanisms rather than voluntary commands. To assess this, in unpredictable and self-initiated conditions, a weight was dropped into a bucket that was held by the standing subject (n = 7). EMG activity was recorded from the deep (Deep MF), superficial (Sup MF) and lateral (Lat MF) lumbar multifidus, the thoracic erector spinae (ES) and the biceps brachii. With unpredictable perturbations, EMG activity was first noted in the biceps brachii, then the thoracic ES, followed synchronously in the components of the multifidus. During self-initiated perturbations, background EMG in the Deep MF increased two- to threefold, and the latency of the loading response decreased in six out of the seven subjects. In Sup MF and Lat MF, this increase in background EMG was not observed, and the latency of the loading response was increased. Short-latency reflex mechanisms do not cause differential action of the medial back muscles when the trunk is loaded. However, during voluntary tasks the central nervous system exerts a 'tuned response', which involves discrete activity in the deep and superficial components of the medial lumbar muscles in a way that varies according to the biomechanical action of the muscle component.

Adult↗
PubMed2002

Accuracy of abnormal paraspinal muscle findings on contrast-enhanced MR images as indirect signs of unilateral cervical root-avulsion injury.

PURPOSE: To evaluate the accuracy of abnormal magnetic resonance (MR) findings in the paraspinal muscles as indirect signs of nerve-root avulsion injury. MATERIALS AND METHODS: Forty-three consecutive patients suspected of having unilateral root-avulsion injury underwent MR imaging and were evaluated. Paraspinal muscles were evaluated for abnormal signal intensity on T1- and T2-weighted images, abnormal enhancement on images obtained after contrast material enhancement, and muscle volume loss. MR images were interpreted independently by two observers for interobserver variability. MR findings were compared with findings of root continuity, determined with a combination of surgery and clinical evaluation. Sensitivities, specificities, and kappa values of the findings were calculated. RESULTS: Sensitivities of MR findings in the paraspinal muscles indicating root-avulsion injury were 88% (36 of 41 patients) for abnormal enhancement, 83% (34 of 41 patients) for high signal intensity on T2-weighted images, 37% (15 of 41 patients) for high signal intensity on T1-weighted images, and 71% (29 of 41 patients) for muscle volume loss. Specificities for all findings were 100% (two of two patients). Of the paraspinal muscles, findings in the multifidus muscle were the most accurate and provided the highest interobserver agreement (kappa = 0.81). CONCLUSION: Contrast material-enhanced abnormal MR findings in the paraspinal muscles are accurate in indicating root-avulsion injuries, and abnormal enhancement in the multifidus muscle is the most accurate among paraspinal muscle findings.

Adolescent↗
PubMed2003

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.

Anesthesia↗
PubMed2005

Effects of pelvic stabilization on lumbar muscle activity during dynamic exercise.

Many commonly utilized low-back exercise devices offer mechanisms to stabilize the pelvis and to isolate the lumbar spine, but the value of these mechanisms remains unclear. The purpose of this study was to examine the effect of pelvic stabilization on the activity of the lumbar and hip extensor muscles during dynamic back extension exercise. Fifteen volunteers in good general health performed dynamic extension exercise in a seated upright position on a lumbar extension machine with and without pelvic stabilization. During exercise, surface electromyographic activity of the lumbar multifidus and biceps femoris was recorded. The activity of the multifidus was 51% greater during the stabilized condition, whereas there was no difference in the activity of the biceps femoris between conditions. This study demonstrates that pelvic stabilization enhances lumbar muscle recruitment during dynamic exercise on machines. Exercise specialists can use these data when designing exercise programs to develop low back strength.

Adult↗
PubMed1989

Lumbar muscles: structure and function.

We review new data derived from careful dissection studies on the macroscopic anatomy, innervation and function of the lumbar muscles, as well as information on the fibres in these muscles. The new findings correct previous misconceptions of the functional anatomy of the lumbar muscles. The innervation and function of the erector spinae and multifidus muscles are so different that they cannot be classified as a single unit. The new interpretation of the innervation of multifidus muscle is of importance, for example, for the neurophysiological examination of the lumbar muscles. The relative number of the slow and fast type of muscle fibres in lumbar muscles varies considerably, and selective atrophy of the fast fibres seems to ensue from inactivity, not only in patients with back pain but also in sedentary controls. The atrophy may be corrected by adequate exercise. Both the fibre type composition and degree of atrophy may well influence a person's susceptibility to low back pain arising from the muscles.

Adult↗
PubMed2002

Oxidative stress and heat shock protein response in human paraspinal muscles during retraction.

OBJECT: The need for wide dissection and forceful retraction of paraspinal muscles often required for posterolateral lumbar fusion and fixation may severely jeopardize the muscles, structurally and functionally. The underlying pathophysiology of muscle damage may involve both mechanical and ischemic mechanisms. On the other hand, the surgery-related stress may trigger certain protective responses within the insulted paraspinal muscles. This study was conducted to assess the relationship between the oxidative stress and the stress response mediated by heat shock protein 70 (HSP70) induction within paraspinal muscles being retracted. METHODS: Multifidus muscle specimens were surgically obtained before, during, and after retraction in patients with lumbar spondylolisthesis undergoing posterolateral lumbar fusion, pedicle fixation, and laminectomy. Muscle samples were analyzed to determine HSP70 and malondialdehyde (MDA) levels. Both HSP70 expression and MDA production within multifidus muscle cells were increased significantly by retraction. Expression of HSP70 then decreased after a peak at 1.5 hours of retraction, whereas MDA levels remained elevated even after release of retractors for reperfusion of the muscles. Analysis of histopathological and immunohistochemical evidence indicated that the decline of HSP70 synthesis within muscle cells after prolonged retraction was the result of severe muscle damage. CONCLUSIONS: Results of this study highlight the deleterious effect of intraoperative retraction on human paraspinal muscles at the cellular and molecular levels. The authors also found that intraoperative maneuvers aimed at reducing the oxidative stress within the paraspinal muscles may help to attenuate surgery-related paraspinal muscle damage.

Aged↗
PubMed1999

Sacroiliac joint involvement in activation of the porcine spinal and gluteal musculature.

In the search for causes of low back pain, the sacroiliac joint has gained renewed interest as a possible pain generator. There is reason to believe that the sacroiliac joint plays a regulatory role involving reflex muscle activation, which controls trunk mobility and stability, as well as locomotion. The aim of this experimental study was to determine whether stimulation of nerves in the sacroiliac joint and joint capsule could elicit contractions in porcine gluteal or lumbar spinal muscles. Via a lateral retroperitoneal approach and using hypodermic needles, bipolar stimulating wire electrodes were inserted into the ventral area of the sacroiliac joint and directly under the surface of the capsular membrane, in 10 adolescent pigs (45 kg). This procedure was performed bilaterally, thus establishing two bilateral stimulation sites in the joints. Six electromyographic electrodes were unilaterally inserted into the following muscles: multifidus, gluteus medius, gluteus maximus, and quadratus lumborum. On stimulation within the ventral area of the joint, predominant responses occurred in both the gluteus maximus and quadratus lumborum muscles. However, when stimulating the capsule, the greatest muscular responses were detected in the multifidus muscles. This study addressed the possible regulatory function of the sacroiliac joint, namely, its involvement in activation of the spinal and gluteal muscles, which help control locomotion and body posture, as well as provide stability on the segmental level in the lumbar spine.

Animals↗
PubMed2001

[How I explore ... lumbar paraspinal muscle electromyography in the assessment of radiculopathy].

Lumbar paraspinal muscles examination is an interesting part of the electrodiagnostic evaluation of patients with suspected lumbosacral radiculopathy. However, many electromyographers hesitate to routinely include that technique in their study of lower limbs. The purpose of this paper is to specify the anatomy and electrophysiologic data of multifidus lumbar paraspinal muscle. Previous anatomic studies indicate that the medial lumbar multifidus and lumbar interspinalis muscles share unisegmental innervation by the dorsal ram of the spinal nerve. Electromyography of these muscles can improve the sensitivity of lumbosacral radiculopathy detection. Multi-MUP analysis of quantitative electromyographic parameters in lumbar paraspinal muscles, in a population of 75 healthy subjects without back pain, allowed to set up normal values for the L5 myotome.

Action Potentials↗
PubMed2003

Radiofrequency lumbar zygapophysial (facet) joint denervation: a preliminary report of a new concept.

This is a preliminary report of a new concept of lumbar medial branch neurotomy by measurement of minimal sensory threshold. This technique is not recommended for routine clinical use until further controlled data are available. The lumbar zygapophysial joints (Z-joint) or facet joints, are a potential source of low back pain. In general, the principle innervation of the Z-joint is the medial branch of the posterior primary ramus of the same level as the target Z-joint as well as the level above. Denervation of the multifidus as evaluated by electromyography has become a measurement of successful Z-joint denervation. Two drawbacks to this method are that it takes one to several weeks for denervation potentials to develop and thus does not give the physician any sense of successful denervation intra-operatively. The other is that the Z-joint is innervated by the sensory fibers of the medial branches. As a result, the multifidus may be successfully denervated as demonstrated by electromyography but the Z-joints may be inadequately denervated. As a result, this technique describes measurement of minimal sensory threshold prior to lesioning and seeking to double that threshold as an additional, intra-operative measure of successful sensory denervation of the Z-joint.

Journal Article↗