Aims. To report the development of the technique for minimally invasive lumbar decompression using robotic-assisted navigation. Methods. Robotic planning software was used to map out bone removal for a laminar decompression after registration of CT scan images of one cadaveric specimen. A specialized acorn-shaped bone removal robotic drill was used to complete a robotic lumbar laminectomy. Post-procedure advanced imaging was obtained to compare actual bony decompression to the surgical plan. After confirming accuracy of the technique, a minimally invasive robotic-assisted laminectomy was performed on one 72-year-old female patient with lumbar spinal stenosis. Postoperative advanced imaging was obtained to confirm the decompression. Results. A workflow for robotic-assisted lumbar laminectomy was successfully developed in a human cadaveric specimen, as excellent decompression was confirmed by postoperative CT imaging. Subsequently, the workflow was applied clinically in a patient with severe spinal stenosis. Excellent decompression was achieved intraoperatively and preservation of the dorsal midline structures was confirmed on postoperative MRI. The patient experienced improvement in symptoms postoperatively and was discharged within 24 hours. Conclusion. Minimally invasive robotic-assisted lumbar decompression utilizing a specialized robotic bone removal instrument was shown to be accurate and effective both in vitro and in vivo. The robotic bone removal technique has the potential for less invasive removal of laminar bone for spinal decompression, all the while preserving the spinous process and the posterior ligamentous complex. Spinal robotic surgery has previously been limited to the insertion of screws and, more recently, cages; however, recent innovations have expanded robotic capabilities to decompression of neurological structures. Cite this article: Bone Jt Open 2024;5(9):809–817

Informed consent is a very important part of surgical treatment. In this paper, we report a number of legal judgements in spinal surgery where there was no criticism of the surgical procedure itself. The fault that was identified was a failure to inform the patient of alternatives to, and material risks of, surgery, or overemphasizing the benefits of surgery. In one case, there was a promise that a specific surgeon was to perform the operation, which did not ensue. All of the faults in these cases were faults purely of the consenting process. In many cases, the surgeon claimed to have explained certain risks to the patient but was unable to provide proof of doing so. We propose a checklist that, if followed, would ensure that the surgeon would take their patients through the relevant matters but also, crucially, would act as strong evidence in any future court proceedings that the appropriate discussions had taken place. Although this article focuses on spinal surgery, the principles and messages are applicable to the whole of orthopaedic surgery.

Cite this article: Bone Joint J 2019;101-B:355–360.

Surgical decision-making in lumbar spinal stenosis involves assessment of clinical parameters and the severity of the radiological stenosis. We suspected that surgeons based surgical decisions more on dural sac cross-sectional area (DSCA) than on the morphology of the dural sac. We carried out a survey among members of three European spine societies. The axial T2-weighted MR images from ten patients with varying degrees of DSCA and morphological grades according to the recently described morphological classification of lumbar spinal stenosis, with DSCA values disclosed in half the assessed images, were used for evaluation. We provided a clinical scenario to accompany the images, which were shown to 142 responding physicians, mainly orthopaedic surgeons but also some neurosurgeons and others directly involved in treating patients with spinal disorders. As the primary outcome we used the number of respondents who would proceed to surgery for a given DSCA or morphological grade. Substantial agreement among the respondents was observed, with severe or extreme stenosis as defined by the morphological grade leading to surgery. This decision was not dependent on the number of years in practice, medical density or specialty. Disclosing the DSCA did not alter operative decision-making. In all, 40 respondents (29%) had prior knowledge of the morphological grading system, but their responses showed no difference from those who had not. This study suggests that the participants were less influenced by DSCA than by the morphological appearance of the dural sac.

Classifying lumbar spinal stenosis according to morphology rather than surface measurements appears to be consistent with current clinical practice.

Recurrence of back or leg pain after discectomy is a well-recognised problem with an incidence of up to 28%. Once conservative measures have failed, several surgical options are available and have been tried with varying degrees of success. In this study, 42 patients with recurrent symptoms after discectomy underwent less invasive posterior lumbar interbody fusion (LI-PLIF). Clinical outcome was measured using the Oswestry Disability Index (ODI), Short Form 36 (SF-36) questionnaires and visual analogue scales for back (VAS-BP) and leg pain (VAS-LP). There was a statistically significant improvement in all outcome measures (p < 0.001). The debate around which procedure is the most effective for these patients remains controversial.

Our results show that LI-PLIF is as effective as any other surgical procedure. However, given that it is less invasive, we feel that it should be considered as the preferred option.

Purpose: Perispinal core muscle strength has been theorized to be an important component in the pathogenesis of back pain. Recent research has demonstrated a strong association between preoperative perispinal musculature, adjusted for fatty infiltration and prospective outcomes and improvements in back pain in patients undergoing lumbar laminectomy without fusion. The purpose of this study is to determine if a similar relationship exists in patients undergoing elective posterior lumbar fusion and decompression (PLFD) surgery. Method: A retrospective observational study of prospectively collected outcomes data was conducted in which pre-operative function and patient variables of those undergoing PLFD were derived from a functional status questionnaire and medical records. ImageJ Digital Imaging Software was utilized to measure the total (CSA) and percentage of fatty infiltration of the psoas, multifidus, and erector spinae muscles in pre-operative L4 axial CT images. Pre-operative and post-operative lateral images were evaluated for degree of post-operative adjacent level degeneration. Follow-up consisted of a functional status questionnaire. Outcomes measured were improvements in back pain, leg pain, and Oswestry disability scores. Results: Twenty-three patients were analyzed with a mean follow-up of 2 years (range 1 – 5 years). Outcomes improved following surgery. There were strong to moderate correlations between percentage of fat in the pre-operative posterior spinal muscles and improvements in leg pain (r = 0.63, p = < 0.001) and improvements in back pain (r = 0.41, p = 0.05). There was a moderate trend towards greater adjacent level degeneration (r = 0.37, p = 0.1) in patients with higher percentage of fat in the pre-operative posterior spinal muscles. There was a strong relationship between greater adjacent level degeneration and pre-operative disability as measured by the Oswestry (r = 0.62, p = 0.03). Conclusion: The results demonstrate that a potential relationship exists between pre-operative fatty infiltration of posterior perispinal muscles and post-operative outcomes, and adjacent level degeneration following lumbar fusion surgery. This suggests that perispinal muscle atrophy and conditioning may play a role in these outcomes. Results may be used for prognostication, surgical candidate selection, and interventional strategies

The purpose of this study was to evaluate whether epidural fibrosis formation around the spinal cord was affected by endogenous oestrogen deficient state after lumbar laminectomy in the rats. Thirty-six 12-month-old adult female Sprague-Dawley rats were used in this study. Bilaterally ooferectomy were done in 18 rats. Rats were divided into two groups: oophrectomised (oestrogen deficient) group and sham operated (oestrogen maintained) group. Three weeks after the ooferectomy each rat underwent complete bilaterally laminectomy at the L2 and L3 vertebral levels (two levels per rat). The rats were randomly divided into three equal groups (12 rats in each group). The rats were sacrificed at four, eight, and twelve weeks postoperatively and the lumbar spine excised en bloc, fixed and decalcified. Section stained with hematoxylin and eosin and Masson’s trichrome were used to evaluate epidural fibrosis, acute inflammatory cells, chronic inflammatory cells and vascular proliferation. Sections were analyzed by investigator blinded to the study and graded on a five-point grading system. Statistic were performed using Mann-Whitney U test when compare two variable and Kruskal-Wallis test when compare more than two variables. Compared with the oopherectomised group, the sham operated group showed decreased rate of epidural fibrosis and higher acute and chronic inflammatory cells response at four and eight weeks but this was no statistically significant (p> 0.05). The results of this study revealed that endogenous oestrogen may decrease epidural fibrosis formation after lumbar laminectomy in the rats

Background: A common complication of lumbar spine surgery is incidental tear of the dural sac and subsequent leakage of the cerebrospinal fluid intraoperatively. Studies have reported a wide variation in the rates of dural tears in spine surgery (1%–17%). The rates were higher after revision surgery. Objective: To establish a baseline rate of incidence of dural tears after lumbar surgery in Morriston Hospital Neurosurgical Unit and to compare it with the results reported in the literature. Methods and Results: A prospective review of the operation notes of 65 consecutive patients who had undergone lumbar surgery (Primary lumbar discectomy, primary lumbar laminectomy and revision lumbar discectomy) over a period of 3 months from Jan 2008. Patients were operated on by different neurosurgical consultants. 40 patients had primary lumbar discectomy of which 2 (5%) had dural tears. 20 patients had primary lumbar laminectomy of which 1 (5%) had a dural tear and 5 patients had revision lumbar discectomy of which 1 (20%) had a dural tear. All dural tears were repaired intraoperatively. Conclusion: This study shows that the highest percentage of incidental durotomy was in revision lumbar surgery which was also slightly higher than the reported rates (8.1%–17.4%). The percentage of dural tears after primary discectomy and primary laminectomy was within range of the percentages reported in the literature (1%–7.1%) and (3.1%–13%) respectively. A multicentre prospective larger study which includes all different surgical procedures performed on the lumbar spine is needed to establish a more accurate incidence rate for this common complication

Purpose: The goal of laminectomy is to relieve spinal stenosis and improve radiculopathy. Back pain related to poor trunk muscular conditioning may negatively affect post-operative outcomes. A better understanding of this relationship is important to improve the selection of appropriate surgical candidates. The purpose of this study was to assess the association between cross-sectional lumbar paraspinal muscle area as measured by CT or MRI and outcomes following laminectomy. Method: Prospective observational study of 23 patients undergoing primary elective lumbar laminectomy without fusion who were assessed with pre-operative CT scans. Clinical outcomes were measured with Numerical Pain Scale (NPS) for back and leg pain and the Oswestry Low Back Disability Index (ODI) at baseline and follow-up at a minimum of one year. Lumbar paraspinal muscle cross-sectional area was measured using digital imaging software and adjusted for percent fat infiltration; CT scans evaluations were blinded to clinical outcomes. Results: There were significant improvements in clinical outcomes following laminectomy. ODI decreased from 53.9±11.8 (mean±standard deviation) at baseline to 27.3±20.6 after a follow-up of 15.2±3.5 months. A strong correlation existed between cross-sectional lumbar paraspinal muscle area after adjusting for infiltrating fat content an improvement in ODI (r=0.51, p< 0.02) or back pain NPS (r=0.55, p< 0.02). These relationships remained statistically significant after adjusting for age and body mass index. No significant associations were identified for improvements in leg pain NPS. Conclusion: This study suggests a possible relationship between cross-sectional lumbar paraspinal muscle area and outcomes following laminectomy. This raises important questions regarding the role of trunk muscular conditioning in the etiology of back pain and success of surgery. Further research is required to refine this measurement as a tool to improve patient selection for surgery

A lumbar laminectomy is a commonly performed surgical procedure for the decompression of neural structures. The aim of this human cadaveric study is to establish the extent of pars interarticularis remaining at each lumbar level when a laminectomy is performed to the medial edge of the pedicle. Seven human cadavers with intact lumbar spines were obtained for this study. The lumbar spine was dissected from the body and segmental disarticulation of each level was performed. The isolated lumbar levels had laminectomies performed exposing the neural canal. The vertical alignment of the laminectomy was orientated in line with the medial aspect of the ipsilateral pedicle. The remaining lateral pars interarticularis was measured with a calliper. The procedure was performed bilaterally at each isolated lumbar segment. Five males and two female cadavers with an age range of sixty-eight years to ninety-five years at the time of death. Fourteen lumbar segments of each respective level were available for study except at L5, where only twelve was possible due the presence of a transitional vertebra in one of the specimens. Taken to the nearest mms, the average width of the remnant pars interarticularis at the L1 level was 4 mm, range 3–6 mm (SD 0.95); L2 6 mm, range 5–7 mm (SD 0.77); L3 8mm, range 4–9mm (SD 1.34); L4 11mm, range 9–14 mm (SD 1.31) and L5 16mm, range 13–17 mm (SD 1.15). One way analysis of variance for each of the groups were performed to establish that the difference recorded was greater than that expected by chance (p< 0.05). The results predictably established the gradual narrowing of the pars interarticularis as the levels ascend cranially from L5. The medial wall of the pedicle could be used as an indirect means to establish a satisfactory remnant of the pars interarticularis following a laminectomy in the lower lumbar spine, at the levels of L3 to L5. However in the upper two levels direct visualisation of the pars is recommended

Introduction: Thickened ligamentum flavum (LF) is a major contributor to the clinical syndrome of lumbar canal stenosis (LCS). The patho-mechanisms responsible for this phenomenon remain unclear. Cysts adjacent to facet joints (FJ) in the spine are regarded as rare entities that may uncommonly contribute to LCS. Inaccurate pathological interpretation and unawareness of a key anatomical feature has generated erratic terminology and confusion about their origin. Methods: Twenty-seven consecutive patients with radiologically confirmed central canal or lateral recess stenosis underwent lumbar laminectomy for neurogenic symptoms. Surgical specimens comprising en bloc excision of LF and medial inferior facet (to retain LF and FJ relationships) were examined microscopically following staining with haematoxylin-eosin and Miller’s elastic stain. Controls were facet/LF specimens from 89 cadaver lumbar spines. Results: Mean LF thickness was 8.9 mm (+/− 0.3 mm SEM) at the operated levels and 2.9 mm (+/− 0.3 mm) at the non-operated, adjacent levels (p < 0.01). Twenty-eight synovial cysts (8 bilateral, 12 unilateral) were present at a single level in 20 (74%) patients. Synovial cysts per spine level were: L1/2 = 0; L2/3 = 3; L3/4 = 7; L4/5 = 16; L5/S1 = 2. The cyst levels all showed advanced osteoarthritis and LF degeneration. Ten patients (50 %) with cysts had pre-existing degenerative spondylolisthesis (DS). Only 5 patients had pre-operative radiological apperances of unilateral facet cysts. Therefore 82 % of our observed synovial cysts were microscopic or occult. The synovial cysts communicated with the FJ via a bursa-like cleft within the LF, and their linings of synoviocytes and other cells contained fragments shed from the articular surface. The control cadaver specimens revealed that a synovial bursa or intra-ligamentous out-pouching from the synovial cavity was present in 90% of normal LF at L4/5 and was up to 12 mm in length. This intra-ligamentous synovial recess, either wholly or partially lined by synoviocytes, was only present in 55% of specimens at L1/2 with a maximum length of 5 mm. Several other juxtafacet cyst types were observed in the experimental group and a novel classification based upon pathological findings is presented. Discussion: Para-facetal intraspinal cysts are common in degenerative lumbar spinal stenosis. DS is also a frequent finding but is statistically unrelated to cyst formation (Chi-square: p=0.187). We have found that debris from osteoarthritic facet joints enters a bursa-like cleft within the LF where it becomes incorporated into the wall where it excites a granulomatous reaction leading to blockage and synovial cyst formation. The existence of this channel has not been reported previously. We suggest that microscopic synovial cysts contribute significantly to the ligamentous thickening seen in LCS. We also present a novel classification of juxtafacet cysts based on our pathological findings

Objective: Measuring outcomes from chronic disease in terms of generic, health-related quality of life (HRQoL) instruments is of increasing importance to allow valid comparison of interventions and to accurately assess efficacy of treatment from the patient’s perspective. In this context we sought to establish the role of the generic SF-36 health survey in measuring outcomes from spinal surgery. Method: A prospective observational study of patients undergoing elective cervical discectomy, lumbar discectomy, and lumbar laminectomy using both disease specific (Myelopathy Disability Index [MDI], Roland Morris Disability Scale [RMDS], Visual Analogue Scales [VAS], Hospital Anxiety and Depression Scales [HADS]) and SF-36 assessment pre-operatively and at 3 months and 12–24 months following surgery. The generic instrument was tested for the components of construct validity in comparison to the established specific measures. Analysis was performed with non-parametric statistics within SPSS. Results: Six-hundred and twenty patients were followed between 1998 and 2005 (median age 53 years; 203 lumbar discectomy, 177 lumbar laminectomy, 240 cervical discectomy). The principal SF-36 physical domains (Physical Functioning, Bodily Pain) strongly correlated with disease specific scores in all patients (Spearman’s ρ=0.5–0.74, p< 0.001) and similarly SF-36 mental domains correlated with the HADS subscales (ρ=0.30–0.45, p< 0.001) indicating concurrent/convergent validity. Discriminant validity was confirmed by the absence of significant correlation between SF-36 physical domains and the HADS (ρ=0.014–0.14, p> 0.05). In the lumbar laminectomy and cervical discectomy patients disease-specific physical scores prior to surgery strongly predicted early and late outcome (area under the receiver-operating characteristics curve [AUC] = 0.79–0.86, p< 0.001) and the same pattern was mirrored in the SF-36 physical domains (AUC = 0.76–0.78, p< 0.001) demonstrating the predictive validity of the generic measure. Physical Function and Bodily Pain SF-36 domains both had excellent response to change by Cohen’s criteria with effect sizes (standardised mean difference) of 0.86–1.57. Conclusion: The SF-36 has been shown to possess the necessary features of construct validity in relation lumbar and cervical surgery to be considered as a suitable adjunct or alternative to measuring outcome with disease specific scores. As a widely employed HRQoL instrument the SF-36 should be a convenient means of assessing patients with spinal morbidity in all healthcare settings and the generic measure will permit easier comparison of the clinical and economic efficacy of different interventions

The continuous leakage of cerebrospinal fluid in the mielomeningocele (MMC) area produces the Chiari II malformation. The aim of our study was to assess the effect of preterm delivery and prenatal corticosteroids administration in the degree of Chiari malformation. Seventy-five out of 148 foetuses from 17 pregnant New Zealand White rabbits underwent lumbar three-level laminectomy and wide opening of dura-mater (surgical MMC). Animals were distributed in five groups: group T, foetuses with MMC, delivery at term and no other treatment; group TC, foetuses with MMC, delivery at term and prenatal administration of corticosteroids; group P, foetuses with MMC, delivery preterm and no other treatment; group PC, foetuses with MMC, delivery preterm and prenatal administration of corticosteroids; group C, controls. The degree of herniation was measured in percentage of decrease of the cerebellum between the inferior limit of the skull and the superior limit of the first vertebra, and compared among groups. We obtained 7T, 5TC, 10P, 6PC, and 28C alive newborns. All groups with prenatal delivery or prenatal corticosteroids showed statistically significant minor degree of herniation than T-group: group TC IC 95% between 25.7 and 47.2% minor (p=0.000), group P IC 95% between 30.4 and 47.7% minor (p=0.000), group PC IC 95% between 32.6 and 55.4 minor (p=0.000). There were no statistically significant differences among groups TC and P (p=0,577), TC and PC (p=0,227) or P and PC (p=0,311). Preterm delivery and prenatal administration of corticosteroids, together or separately, result in lower degree of Chiari malformation in a model of surgical MMC in rabbit fetuses

Open fetal surgery for reparation in myelomeningocele reverses Chiari II malformation and protects exposed neural elements from secondary lesion, but the technique is associated with a high rate of complications. The aim of our study was to assess whether a simple and fast technique of coverage produces the same results as a complete and longer technique of reparation in terms of neural protection. Twelve sheep’s foetuses underwent lumbar three-level laminectomy and opening of the dura-mater on the 75th day of the gestation. Four of them were not-repaired (NR group). Eight of them underwent coverage with inert material sheet and synthetic surgical sealant on the 95th day (R group). At birth, clinical and histological examination and comparison between groups was performed. None NR animal were able to stand or to walk nor had sphincter continence; all of them showed a wide defect of closure in the lumbar area, continuous leakage of cerebrospinal fluid (CSF), and histological neural damage; the mean vermis herniation was 75%. All R animals were able to stand and to walk and all of them showed sphincter continence; none of them showed leakage of CSF and showed coverage of the 93% of the defect; all of them showed regeneration of dura-mater, muscle and skin; the mean vermis herniation was 10%. A simplified technique of coverage produces the same clinical results than a more complex reconstruction in a model of surgical MMC in sheep and the histological study reveals the regeneration of several layers of soft tissues

Study design. A retrospective study design. Objective. To comprehensively compare the 2-year clinical outcome of lumbar laminectomy alone versus lumbar laminetomy supplemented with dynamic stabilization (Dynesys system) in degenerative lumbar stenosis in elderly patients. Material and Methods. A total of 60 elderly patients with an average age of 65.1 years (range, 50 to 78 yrs) affected by lumbar stenosis that underwent lumbar laminectomy alone (30 cases) or lumbar laminectomy with supplementary Dynesys system (30 cases) at our Department were sorted and matched according to three criteria : similar patient age, similar degenerative lumbar desease, and identical operative methods (i.e. levels of laminectomy). Patients were compared according to Oswestry Disability Index (ODI), Roland Morris, SF-36 and VAS outcomes scores. Results. The two cohorts were well matched at 2-years follow-up. Patients treated with lumbar laminectomy alone presented reduced operative time and intraoperative blood loss and reduced postoperative complications, with better clinical outcome compared with patients that received laminectomy with supplementary Dynesys system, for ODI score (28.9 vs 31), Roland Morris (8.25 vs 9.1) and VAS scores (leg pain 36 vs 44.3; back pain 31 vs 38.7), while SF-36 scores resulted similar in both groups of patients. Conclusions. In degenerative lumbar stenosis, supplementary dynamic stabilization in addition to decompressive laminectomy did not presented significant advantages, with respect to functional outcome, in comparison to lumbar laminectomy alone

Introduction: Preliminary studies suggest that prolonged retraction of the paraspinal muscle during spinal surgery may produce ischaemic damage. We describe the continuous measurement of intramuscular pressures (IMP) during decompressive lumbar laminectomy and the relationship to back pain and disability. Methods: In this prospective interventional study, 28 patients undergoing surgery for lumbar canal stenosis were recruited. Back pain and function were assessed using the Visual Analogue Score (VAS), Oswestry Disability Index (ODI) and Short Form 36 (SF36) health survey. During surgery, IMP was continuously recorded from the multifidus muscle using a pressure transducer. The intramuscular perfusion pressure (IPP) was derived as the difference between the patient’s mean arterial pressure (MAP) and IMP (IPP = MAP − IMP). The data was analysed using repeated measures ANOVA (SPSS package). Results: The mean age was 60.4 ± 3 years and the mean duration of symptoms of 31.0 ± 6 months. The predominant symptoms were neurogenic claudication (14) and/or sciatica (13). Patients underwent 1 (N=3), 2 (N=20) or 3 (N=5) level laminectomies. The muscle retractors used were Norfolk and Norwich (N=16) and McCullock (N=12). The mean duration of deep muscle retraction was 68.5 ± 9 mins (range 19–240). On application of deep muscle retraction, there was a rapid and sustained increase in IMP (F=26.8; p< 0.001; repeated measures ANOVA), and overall the calculated mean IPP approached 0 mmHg or less during this period (F=36.8; p< 0.001). On release of deep muscle retraction there was a rapid decrease in IMP to pre-operative levels. The IPP was greater with Norfolk and Norwich than McCullock retractors (F=12.2; p< 0.001). Compared to pre-operative values, there was a decrease in ODI (F=18.6; p< 0.001) and VAS for back pain (F=9.9; p< 0.001) at discharge, 4–6 weeks and 6 months, post-operatively. Compared to pre-operative values, there was a decrease in SF36 scores at 6 months (F=26.7; p< 0.001). Total duration of muscle retraction over 60 mins was associated with higher VAS scores for back pain at 4–6 weeks and 6 months postoperatively (F=3.7; p< 0.01). There was no relationship between IPP and post-operative ODI or VAS for back pain. Conclusions: This study demonstrates a simple technique for the continuous monitoring of IMP during spinal surgery, from which the IPP can be derived. Comparison of two muscle retractors has shown that the McCullock retractor generates a higher IMP than Norfolk and Norwich retractor. Decompressive lumbar laminectomy improves the VAS for back pain and ODI and SF36 outcome scores in these patients. The results show that duration of muscle retraction, rather than extent of the pressure generated by the retractor, is related to postoperative back pain

In order to identify the risk factors and the incidence of post-operative spinal epidural haematoma, we analysed the records of 14 932 patients undergoing spinal surgery between 1984 and 2002. Of these, 32 (0.2%) required re-operation within one week of the initial procedure and had an International Classification of Diseases (ICD)-9 code for haematoma complicating a procedure (998.12). As controls, we selected those who had undergone a procedure of equal complexity by the same surgeon but who had not developed this complication. Risks identified before operation were older than 60 years of age, the use of pre-operative non-steroidal anti-inflammatories and Rh-positive blood type. Those during the procedure were involvement of more than five operative levels, a haemoglobin < 10 g/dL, and blood loss > 1 L, and after operation an international normalised ratio > 2.0 within the first 48 hours. All these were identified as significant (p < 0.03). Well-controlled anticoagulation and the use of drains were not associated with an increased risk of post-operative spinal epidural haematoma.

We have developed criteria to determine the appropriate indications for lumbar laminectomy, using the standard procedure developed at the RAND corporation and the University of California at Los Angeles (RAND-UCLA). A panel of five surgeons and four physicians individually assessed 1000 hypothetical cases of sciatica, back pain only, symptoms of spinal stenosis, spondylolisthesis, miscellaneous indications or the need for repeat laminectomy. For the first round each member of the panel used a scale ranging from 1 (extremely inappropriate) to 9 (extremely appropriate). After discussion and condensation of the results into three categories laminectomy was considered appropriate in 11% of the 1000 theoretical scenarios, equivocal in 26% and inappropriate in 63%. There was some variation between the six categories of malalignment, but full agreement in 64% of the hypothetical cases. We applied these criteria retrospectively to the records of 196 patients who had had surgical treatment for herniated discs in one Swiss University hospital. We found that 48% of the operations were for appropriate indications, 29% for equivocal reasons and that 23% were inappropriate. The RAND-UCLA method is a feasible, useful and coherent approach to the study of the indications for laminectomy and related procedures, providing a number of important insights. Our conclusions now require validation by carefully designed prospective clinical trials, such as those which are used for new medical techniques

1 . Standard lumbar laminectomy was performed at multiple levels in thirty dogs, and manipulations were carried out in the spinal canal to observe their effects on periradicular adhesion formation. The canal was scarified, packed with Gelfoam, or treated with three varieties of Silastic membranes. The results were serially assessed from three days to twelve weeks by gross observation, nerve conduction studies, histological examination of transverse sections of the spine, myelin study of lumbar roots and micropaque study of the arterial supply to the roots. 2. The results were consistent biologically. The principal source of scar is dorsally in the fibrous tissue elements of the erector spinae muscle mass. This scar, the laminectomy membrane, covers the laminectomy defect and extends into the canal bilaterally to adhere to the dura and nerve roots. 3. Gelfoam does not contribute to scar formation, but instead acts as an effective interposing membrane. Silastic membranes are capable of providing protection against nerve root adhesions without interfering with the anatomical or physiological integrity of the nerves. 4. Certain clinical implications of the study are discussed