The prevention of neural complications in the surgical treatment of scoliosis: the role of the neurophysiological intraoperative monitoring.

Iatrogenic spinal cord injury is the most feared complication of scoliosis surgery. The importance of combined somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) monitoring during spine surgery is well known. The current authors retrospectively evaluated the results of neurophysiological intraoperative monitoring (IOM) in a large population of patients who underwent surgical treatment for spinal deformity. Intraoperative monitoring of SEPs and transcranial electrical stimulation MEPs (TES-MEP) was performed in 172 successive patients who underwent surgical treatment of idiopathic (128 pts), congenital (15 pts) or syndromic (29 pts) scoliosis. The first 106 patients (Group 1) underwent only SEP monitoring, while the other 66 patients (Group 2) underwent combined SEP and TES-MEP monitoring, when the technique was introduced in the current authors' institution. Halogenate anaesthesia (Sevoflurane, MAC 0.6-1.2) was performed in Group 1 cases, total intravenous anaesthesia (Propofol infusion, 6-10 mg/kg/h) in Group 2 patients. A neurophysiological "alert" was defined as a reduction in amplitude (unilateral or bilateral) of at least 50% for SEPs and of 65% for TES-MEPs compared with baseline. In Group 1, two patients (1.9%) developed postoperative neurologic deficits following surgical correction of spinal deformity, consisting of permanent paraparesis in one case and transient paraparesis secondary to spinal cord ischaemia in the other. Twelve patients presented intraoperative significant changes of neurophysiological parameters that improved following corrective actions by surgeons and anaesthesiologists, and did not show any postoperative neurologic deficits. In ten cases the alert was apparently unrelated to surgical manoeuvres or to pharmacological interventions and no postoperative neurologic deficits were noted. Considering the patients of Group 2, two patients (3.0%) presented transient postoperative neurologic deficits preceded by significant intraoperative changes in SEPs and TES-MEPs. In five cases a transient reduction in the amplitudes of SEPs (1 patient) and/or TES-MEPs (5 patients) was recorded intraoperatively with no postoperative neurologic deficits. In conclusion, in the current series of 172 patients the overall prevalence of postoperative neurologic deficit was 2.3% (4 patients). When combined SEP and TES-MEP monitoring was performed, the sensitivity and specificity of IOM for sensory-motor impairment was 100 and 98%, respectively. Combined SEP and TES-MEP monitoring must be regarded as the neurophysiological standard for intraoperative detection of emerging spinal cord injury during corrective spinal deformity surgery. Early detection affords the surgical team an opportunity to perform rapid intervention to prevent injury progression or possibly to reverse impending neurologic sequelae.

Fueling the debate: Are outcomes better after posterior lumbar interbody fusion (PLIF) or after posterolateral fusion (PLF) in adult patients with low-grade adult isthmic spondylolisthesis?

STUDY DESIGN: Retrospective cohort study. CLINICAL QUESTION: Do more adult patients affected by low grade isthmic spondylolisthesis have significant clinical and radiological improvement following posterior lumbar interbody fusion (PLIF) than those who receive posterolateral fusion (PLF)? METHODS: One hundred and fourteen patients affected by adult low grade isthmic spondylolisthesis, treated with posterior lumbar interbody fusion or posterolateral fusion, were reviewed. Clinical outcome was assessed by means of the questionnaires ODI, RMDQ and VAS. Radiographic evaluation included CT, MRI, and x-rays. The results were analyzed using the Student t-test. RESULTS: The two groups were similar with respect to demographic and surgical characteristics. At an average follow-up of 62.1 months, 71 patients were completely reviewed. Mean ODI, RMDQ and VAS scores didn't show statistically significant differences. Fusion rate was similar between the two groups (97% in PLIF group, 95% in PLF group). Major complications occurred in 5 of 71 patients reviewed (7%): one in the PLIF group (3.6%), four in the PLF group (9.3%). Pseudarthrosis occurred in one case in the PLIF group (3,6%) and in two cases in PLF group (4.6%). CONCLUSIONS: In our series, there does not appear to be a clear advantage of posterior lumbar interbody fusion (PLIF) over posterolateral fusion (PLF) in terms of clinical and radiological outcome for treatment of adult low grade isthmic spondylolisthesis.

Selective thoracic surgery in the Lenke type 1A: King III and King IV type curves.

Pedicle screw fixation enables enhanced three-dimensional correction of spinal deformities and effectively shortens the distal fusion level. However, the choice of distal fusion level is still controversial in single thoracic idiopathic scoliosis with the lumbar compensatory curve not crossing the middle line (Lenke type 1 with modifier A or King type III and IV curves).The authors retrospectively analyzed 31 patients treated by segmental pedicular instrumentation alone, affected by a single thoracic adolescent idiopathic scoliosis with a compensatory lumbar curve not crossing the midline (Lenke 1A), with an average age of 16.3 years (range 10-22 years). The patients with regard to the King classification were also assessed. A statistical analysis was performed to determine whether the two groups (King III, King IV) presented differences concerning the level of the stable vertebra (SV), end vertebra (EV), and neutral vertebra (NV) and were also analyzed the results at follow-up regarding the relationships between the SV, EV, and lowest instrumented vertebra (LIV). The statistical analysis showed a significant difference between the two curve types. In the King III type curve the SV, EV, and NV appeared to be more proximal than those of the King IV type curve and the segments between the SV, EV, and NV appeared to be reduced in King III curves compared with King IV curves. At a follow-up of 3.2 years (range 2.2-5) the thoracic curve showed a correction of 58.4% (from 62.3 degrees to 26.6 degrees ) and compensatory lumbar curve an average spontaneous correction of 52.4% (from 38.1 degrees to 18.1 degrees ).The position of the LIV was shorter than the position of the SV in 30 patients (97%) with an average "salvage" of 2.1 (from 1 to 4) distal fusion levels. Four cases (13%), all affected by a King IV type curve, presented at follow-up an unsatisfactory results due to an "adding on" phenomenon. The statistical analysis confirmed that this phenomenon was correlated with The King IV curve (P = 0.043; Chi-square test) and that the only predictive parameter for its onset was the LIV-SV difference (odds ratio = 0.093; with a confidence interval of 0.008-1): every time that in King IV curve type the LIV was three or more levels shorter than the stable vertebra at follow-up the "adding on" phenomenon was present. The authors conclude that Lenke's type 1 with modifier A includes two kinds of curves, King III and King IV and that the Lenke's type 2 curves and King V with the lumbar curve not crossing the middle line have a similar behavior. Therefore, it is of authors' opinion that "the adding on phenomenon" could be prevented by more rigidly defining K. IV versus K. III curves. In Lenke's 1/2 A-K. IV/V type with the rotation of the first vertebra just below the thoracic lower EV in the same direction as the thoracic curve, and when SV and EV show more than two levels of difference, it is necessary to extend the lower fusion down to L2 or L3 (not more than two levels shorter than the SV). Whereas in Lenke's 1/2 A-K. III/V with the rotation of the first proximal vertebra of lumbar curve in the opposite direction to the thoracic apex and when SV and EV show not more than two level gap differences, the position of the lowest instrumented vertebra can be two or three levels shorter than the stable vertebra with satisfactory postoperative spinal balance. Therefore, the stable vertebra and the rotation of lumbar curve are considered to be a reliable guide for selecting the lower level of fusion.

Thoracoplasty in the surgical treatment of adolescent idiopathic scoliosis.

A consecutive series of 40 adolescents surgically treated between 1998-2001, by posterior spinal fusion and thoracoplasty were compared with a similar group of 40 adolescents treated in the same period by posterior only segmental fusion. Clinical and radiographic analysis was performed, including the SRS-30 questionnaire and Pulmonary Function Tests (PFT). Minimum five years follow-up was requested. No statistical differences were found between the two groups in PFT's both pre-operatively and at latest follow up. Our findings suggest that thoracoplasty did not adversely affected long-term PFT's in AIS patients treated by posterior spinal fusion alone.

An innovative diagnostic procedure of vertebral deformities without exposure to X-rays.

The objective of the study was to compare standard manual X-ray measurements of vertebral deformities and values obtained from the Ortelius 800. 52 Patients (41 females and 11 males: mean age 20.35 years) with adolescent vertebral deformities, was studied. The patients were evaluated with standard radiographic views and the Ortelius 800. The parameters considered for the comparison were the angles of scoliosis and kyphosis and the values of global axial deformity, shoulder asymmetry and pelvic tilt. We also evaluated the modification of pelvic/shoulder angle after surgery (this parameter allows to evaluate vertebral rotation and can be derived only from the Ortelius 800). This study allowed us to conclude that there is a perfect agreement between measurements with the Ortelius 800 and those resulting from standard x-rays. The system has also proved to have the capability of quantifying changes in vertebral rotation.

Biological assessment of the bone-screw interface after insertion of uncoated and hydroxyapatite-coated pedicular screws in the osteopenic sheep.

The sheep seems to be a promising model of osteoporosis and biomaterial osteointegration in osteopenic bone. The long-term ovariectomized sheep model was used for the biological investigation of bone healing around uncoated and hydroxyapatite (HA)-coated pedicle screws in osteopenic bone. Four sheep were ovariectomized and four sheep were sham-operated. Twenty-four months after surgery, the animals were implanted with uncoated and HA-coated stainless steel screws in the lumbar vertebral pedicles. Four months later, bone-to-implant contact, bone ingrowth, and bone hardness were measured around screws. Uncoated stainless steel presented significantly (p < 0.0005) lower bone-to-implant contact in healthy and osteopenic bone compared with HA-coated stainless steel. HA significantly improved bone ingrowth in healthy bone (p < 0.05) compared with uncoated stainless steel. Osteopenia significantly (p < 0.05) reduced the area of bone ingrowth around the screw threads for both types of implants. In the inner thread area, bone microhardness significantly increased (p < 0.05) in HA-coated surface versus uncoated for healthy and osteopenic bone. HA coating significantly enhances bone-to-implant contact also in osteopenic bone in comparison with uncoated stainless steel surfaces. Bone ingrowth and mineralization are ameliorated by the osteoconductive HA coating. However, osteopenia seems to greatly influence bone ingrowth processes around the implanted screws regardless of the characteristics of the material surface.

Pedicular fixation in the osteoporotic spine: a pilot in vivo study on long-term ovariectomized sheep.

Spinal instrumentation success is greatly affected by the presence of osteoporosis. To date, however, no data exist on in vivo investigations on biomaterial and surgical techniques in the osteoporotic spine. In the present study 24 uncoated and 24 HA-coated screws were implanted in the L3, L4 and L5 pedicles of eight sheep (four ovariectomized, OVX Group; four sham-operated, Control Group). At four months, uncoated screws showed a significant decrease of about -22% in the extraction torque of the OVX Group as compared to the Control Group (p < 0.005). The extraction torque of HA-coated screws significantly (p < 0.0005) improved in both groups when compared to that of uncoated screws and showed increases ranging from 133% to 157%. Pedicle trabecular bone of OVX sheep showed a significant decrease in BV/TV (-30%; p < 0.05) and Tb.Th (-33%; p < 0.01). The affinity index (AI) results revealed significant (p < 0.0005) differences between uncoated and HA-coated screws for both groups: values were lower for uncoated than HA-coated screws by about -35%. A significant difference was also found for the AI data of uncoated screws between the OVX and Control Groups (-13%, p < 0.005). The current findings have demonstrated that long-term ovariectomized sheep can be used to study in vivo osteointegration in the osteoporotic spine. The HA coating has proven to improve bone purchase and bone-screw interface strength in healthy and osteopenic animals.

Lumbar disc excision in children and adolescents.

STUDY DESIGN: The authors examined a case series of patients under the age of 18 years treated for lumbar intervertebral disc herniation. OBJECTIVES: To evaluate postoperative and long-term results of surgery in patients younger than 18 years. SUMMARY OF BACKGROUND DATA: There are only a few series, with controversial results, available on the surgical treatment of disc herniation in growing patients. METHODS: Between 1975 and 1991, a consecutive series of 129 patients 9-18 years of age (average age, 16.2 years) underwent surgery for lumbar intervertebral disc herniation. Low back pain associated with leg pain was the main clinical symptom in 106 subjects (82%), back pain in 17 (13%), and leg pain in 6 (5%). RESULTS: Short-term results were excellent or good for 123 cases (95%), with complete pain relief in 97 (75%) and moderate but incomplete relief in 26 (20%). A total of 98 (76%) long-term responses obtained at a mean follow-up of 12.4 years revealed excellent outcomes in 40% of the cases, good in 47%, and poor in 13%. Ten patients (10%) underwent reintervention after 9 years on average (2 fusions and 8 re-explorations for herniated disc). CONCLUSIONS: Results have confirmed a tendency for outcomes to deteriorate between the short-term and long-term follow-up in young patients treated by discectomy: this tendency and the rate of reintervention (10%) confirmed the need for long-term follow-up of children and adolescents treated for disc herniation.

Circumferential fusion by posterior approach in lumbosacral instability with or without pedicle screw fixation: a comparison of methods.

Lumbosacral circumferential fusion, a method which is widely adopted for the treatment of the different causes of lumbar pain, may be carried out in a single stage by posterior approach, associating interbody fusion with cages with posterolateral fusion. During the same operation, pedicle screw fixation may also be performed. In order to evaluate the need for this final surgical stage represented by pedicle screws, a comparison was conducted in 2 groups of patients affected with lumbosacral instability, treated at the Division of Vertebral Surgery at the Rizzoli Orthopaedic Institute between May 1995 and May 1997. The best clinical results were obtained in the first group (where pedicle fixation was associated). Because of the persistance of pain symptoms, successive pedicle fixation was instead required in a high percentage of patients (45%) in the second group (without pedicle fixation).

Lumbar disc herniation in the elderly patient.

It was the purpose of this study to clinically follow-up 78 patients affected with lumbar disc herniation, aged from 60 to 81 years (mean 66 years), hospitalized in several wards at the Rizzoli Orthopaedic Hospital between 1987 and 1996, for surgical treatment. A minimum of 24 months after surgery (maximum 61 months), sciatic pain (present in all of the patients prior to surgery) had regressed in 90% of the patients and was reported to occur only occasionally in 10%. Low back lumbar pain was still present in 21%. Results concerning recovery of motor deficit (30%), deficit in reflexes (31%), and sensory deficit (24%) were good. Better results were obtained when the surgical findings were sequestered hernia and expulsed hernia, with excellent results observed in 70% and 60%, respectively (based on the Smiley-Webster scale), as compared to contained hernia, the results for which were excellent in 54% of patients. Complications were observed in 9 cases (11%); 5 of the cases (6%) after a period of time ranging from 20 to 45 days postsurgery required further surgery because of an error in level in 3 and a residual nerve root compression in 2.

Intra-operative spinal cord monitoring in orthopaedics.

The surgical correction of spinal deformities carries a small but significant risk of injury to the spinal cord. To detect the onset and possibly reverse the effects of surgical complication, a variety of neurophysiological monitoring procedures can be employed. The purpose of this review is to provide information regarding the various methodologies available for monitoring spinal cord and nerve root function during orthopaedic procedures. Intra-operative monitoring of cortically recorded somatosensory evoked potentials (SEPs) by peripheral nerve stimulation is of value during orthopaedic surgery and is the state-of-the-art in terms of non-invasiveness, versatility, time requirement, lateral discrimination, and ease of electrode placement. Monitoring of motor evoked potentials (MEPs) is useful particularly in combination with SEPs but is still considered investigational. Root function monitoring has limited application and requires more clinical research.

Biomaterials in spinal fixation. An experimental animal study to improve the performance.

Different pedicle screws were biomechanically and morphologically studied and compared through the use of an animal model to determine their efficacy and resistance in spinal fixation. The principal objective was to compare biomechanical and histomorphological aspects of HA-coated screws to uncoated ones. Fourty-eight cylindrical transpedicular self-tapping screws divided into three groups of sixteen each were employed; Group A: stainless steel screws; Group B: titanium screws; Group C: HA-coated titanium screws. The screws were implanted bilaterally and randomly into the L3, L4, and L5 pedicles of eight adult mongrel sheep. The final insertion torque was measured in all the implants. After one and four months, upon euthanization, four samples per group were extracted from the surrounding bone and the screw extraction torque was measured. The remaining samples were examined and processed for histological and histomorphological evaluations. No differences were observed at one month among the extraction torque of the three groups. After four months the only significance between insertion and extraction values was for the HA group, i.e. p=0.001. Comparing the extraction torque values of the three groups after four months of healing, the HA-coated group showed a greater than twofold increase (p<0.0005). No differences were observed at one month among the percentages of bone-implant contact in the three groups. After four months the percentage was significant only for the C group (p<0.0005). At four months a correlation was found between the morphological and the biomechanical data of group C (p<0.0005). The use of hydroxyapatite-coated screws could act as an effective method to improve the bone-implant interface, thus obtaining a strong fixation of the implant independently of the arthrodesis achieved with bone graft.

Surgical correction of dystrophic spinal curves in neurofibromatosis. A review of 56 patients.

STUDY DESIGN: A presentation of the results from 56 patients with dystrophic spinal deformities caused by neurofibromatosis surgically managed from 1971 to 1992. OBJECTIVES: To focus on the need for combined anterior and posterior fusion in the presence of severe spinal dystrophic changes. SUMMARY OF BACKGROUND DATA: It has been stated that the most effective management for dystrophic curves is early and aggressive surgery. METHODS: The patients were divided into two groups: Type I scoliosis (kyphosis < 50 degrees) and Type II kyphoscoliosis (kyphosis > 50 degrees). Results were evaluated in relation to the type of surgery performed: single posterior instrumented fusion or preplanned combined anterior and posterior fusion. RESULTS: At a mean follow-up period of 15 years (range, 5-22 years), all patients appeared to be stabilized, after a total of 120 surgical interventions. In Group I, the posterior instrumented fusion failed in nine patients (47%), and in Group II it failed in seven patients (63%). The preplanned combined anterior and posterior fusion failed in two patients (33%) in Group I and in four patients (20%) in Group II. The failure incidence of the posterior instrumented fusion alone and of the planned anterior and posterior fusion was 53% (16 patients) and 23% (6 patients), respectively. CONCLUSIONS: The severe dystrophic curve with anterior vertebral scalloping always requires combined anterior and posterior stabilization, particularly in younger patients, even if the sagittal curves have not become pathologic by the time of presentation.

Posterior surgery for the treatment of thoracolumbar pathologic fractures in metastatic patients.

A total of 25 pathologic fractures in patients affected with thoracolumbar vertebral metastases associated with neurologic deficit are reported. None of the pathologic fractures were stable, while 14 were unstable and 11 were very unstable. Decompression with intralesional excision of the neoplastic mass compressing the dural sac was performed in all of the cases. Posterior stabilization was performed in the first cases using systems of sublaminar segmental fixation, and thereafter using systems of pedicle fixation. Removal of the vertebral body followed by anterior fusion after preventive posterior stabilization was performed in 2 cases. Pain symptoms regressed in 85% of the cases and in more than 50% of the patients there was improvement in the neurologic findings and in vertebral deformity consequent to fracture. Mean survival rate was 12 months. Despite the limited number of cases posterior stabilization of pathological fractures is a good choice of treatment in patients with severe neurologic deficit.

Diastematomyelia in congenital scoliosis. A review of the literature and description of one clinical case.

The authors present a case of diastematomyelia, a malformation of the neurospinal axis, frequently associated with congenital vertebral deformities. Often asymptomatic, its site different from that of the vertebral deformity, it may go unrecognized if specific imaging diagnosis is not used, thus exposing the patient who is then submitted to surgery for the correction of vertebral deformity to a high risk of neurological complications.

Scoliosis in Escobar syndrome (multiple pterygium syndrome). Description of two cases.

The authors report two cases of scoliosis in Escobar syndrome. Both of the patients were submitted to surgical treatment. A fair amount of correction was obtained in the first case, simple stabilization of the deformity was obtained in the second. Our experience confirms the fact that scoliosis may progress considerably in Escobar syndrome, requiring early surgical treatment.

The surgical treatment of vertebral deformities in achondroplastic dwarfism.

The authors analyzed 15 patients affected with achondroplastic dwarfism with vertebral deformity treated surgically between 1976 and 1994. The forms represented were: achondroplasia; diastrophic dwarfism; spondyloepiphyseal achondroplasia. The types of vertebral deformity were: kyphosis: 12 (angular: 6; regular: 6); scoliosis: 1; kyphoscoliosis: 2. Neurological symptoms were present in 10 patients. Treatment was as follows: laminectomy: 8; posterior fusion with instrumentation: 2; anterior fusion: 2; anterior fusion with laminectomy and posterior fusion: 3. There were postoperative neurological complications in 4 cases (27%). Fusion must be performed early in angular kyphosis in the adult in order to prevent neurological symptoms. Wide laminectomies do not require associated fusion because they do not cause late vertebral instability.

Neurological complications in segmental spinal instrumentation: analysis of 750 patients.

The authors report on neurological damage caused by the use of sublaminar segmental fixation in the correction of vertebral deformities. Three groups were reviewed: 600 patients instrumented with Harrington rods and segmental wiring, 50 patients treated with the Hartshill system and 100 patients instrumented with Luque bars. All of the patients were operated on using sublaminar wiring fixation. We report two transitory neurological complications among the 600 patients with Harrington rod instrumentation and segmental wiring, two permanent neurological deficits among the 50 cases treated with the Hartshill system and none among the 100 patients instrumented using Luque bars. The purpose of this study is to analyse the causes of these neurological complications, which occurred late in all four of the cases described.

Lumbosacral fusion with pedicular osteosynthesis.

A total of 40 patients affected with lumbosacral degenerative pathology and submitted to pedicular synthesis and laminectomy were followed-up. There was an 86% success rate after an average of 2 years. The authors conclude by recognizing the effectiveness of pedicular fixation, and the need to associate laminectomy with fusion because of the frequent association of instability and stenosis in degenerative low back pain.