Association of intraoperative changes in brain-derived neurotrophic factor and postoperative delirium in older adults.

BACKGROUND: Delirium is common after surgery, although the aetiology is poorly defined. Brain-derived neurotrophic factor (BDNF) is a neurotrophin important in neurotransmission and neuroplasticity. Decreased levels of BDNF have been associated with poor cognitive outcomes, but few studies have characterized the role of BDNF perioperatively. We hypothesized that intraoperative decreases in BDNF levels are associated with postoperative delirium. METHODS: Patients undergoing spine surgery were enrolled in a prospective cohort study. Plasma BDNF was collected at baseline and at least hourly intraoperatively. Delirium was assessed using rigorous methods, including the Confusion Assessment Method (CAM) and CAM for the intensive care unit. Associations of changes in BDNF and delirium were examined using regression models. RESULTS: Postoperative delirium developed in 32 of 77 (42%) patients. The median baseline BDNF level was 7.6 ng ml -1 [interquartile range (IQR) 3.0-11.2] and generally declined intraoperatively [median decline 61% (IQR 31-80)]. There was no difference in baseline BDNF levels by delirium status. However, the percent decline in BDNF was greater in patients who developed delirium [median 74% (IQR 51-82)] vs in those who did not develop delirium [median 50% (IQR 14-79); P =0.03]. Each 1% decline in BDNF was associated with increased odds of delirium in unadjusted {odds ratio [OR] 1.02 [95% confidence interval (CI) 1.00-1.04]; P =0.01}, multivariable-adjusted [OR 1.02 (95% CI 1.00-1.03); P =0.03], and propensity score-adjusted models [OR 1.02 (95% CI 1.00-1.04); P =0.03]. CONCLUSIONS: We observed an association between intraoperative decline in plasma BDNF and delirium. These preliminary results need to be confirmed but suggest that plasma BDNF levels may be a biomarker for postoperative delirium.

Tract-Specific Diffusion Tensor Imaging in Cervical Spondylotic Myelopathy Before and After Decompressive Spinal Surgery: Preliminary Results.

PURPOSE: Diffusion tensor imaging (DTI) metrics of the cervical spinal cord in patients with cervical spondylotic myelopathy (CSM) were compared to those measured in healthy volunteers, using tract-specific region of interests (ROIs) across all cervical intervertebral disc levels. METHODS: Magnetic resonance (MR) imaging of the cervical spinal cord was performed in four patients with CSM and in five healthy volunteers on a 3-T MR scanner. Region-specific fractional anisotropy (FA) and mean diffusivity (MD) were calculated on axial imaging with ROI placement in the anterior, lateral, and posterior regions of the spinal cord. FA and MD were also calculated on sagittal acquisitions. Nonparametric statistical tests were used to compare controls and patients before and after surgery. RESULTS: FA values were significantly lower (p = 0.050) and MD values were significantly higher (p = 0.014) in CSM patients measured at level of maximal compression before surgery than in healthy controls in lateral and posterior ROIs, respectively. In posterior ROIs, MD values were significantly higher in patients before surgery compared to controls at all levels except C7-T1. CONCLUSION: Patients with CSM may demonstrate region-specific changes in DTI metrics when compared to healthy controls. Changes in DTI metrics may also occur at levels remote from site of compression.

The effect of neuromuscular blockade on pedicle screw stimulation thresholds.

STUDY DESIGN: Nerve root stimulation thresholds were studied relative to the level of neuromuscular blockade in patients undergoing lumbar decompression surgery. OBJECTIVES: To determine what levels of intraoperative neuromuscular blockade can be used during pedicle screw stimulation. BACKGROUND DATA: Previous studies of intraoperative pedicle screw stimulation thresholds have failed to determine the effect of neuromuscular blockade on the stimulation threshold. METHODS: Twenty-one roots in 10 patients undergoing lumbar decompression surgery were studied at different levels of neuromuscular blockade. Ninety-five nerve root thresholds were determined relative to level of blockade. RESULTS: Neuromuscular blockade below 80% provides nerve root thresholds similar to thresholds without blockade. CONCLUSIONS: Neuromuscular blockade should be less than 80% when using pedicle screw electrical stimulation testing.

Nerve injuries in total hip arthroplasty.

Nerve injury occurs in 1% to 2% of patients who undergo total hip arthroplasty and is more frequent in patients who need acetabular reconstruction for dysplasia and those undergoing revision arthroplasty. Injury to the peroneal division of the sciatic nerve is most common, but the superior gluteal, obturator, and femoral nerves can also be injured. Nerve injury can be classified as neurapraxia, axonotmesis, or neurotmesis. The worst prognosis is seen in patients with complete motor and sensory deficits and in patients with causalgic pain. Prevention is of overriding importance, but use of ankle-foot orthoses and prompt management of pain syndromes can be useful in the treatment of patients with nerve injury. Electrodiagnostic studies hold promise in complex cases; however, their intraoperative role requires objective, prospective, controlled scientific study before routine use can be recommended.

Prophylactic antibiotics for spine surgery: description of a regimen and its rationale.

Cefazolin, an antibiotic commonly used for surgical prophylaxis, may not adequately penetrate the intervertebral disk or cerebrospinal fluid. The combination of gentamicin and cefuroxime has been found to penetrate both structures in adequate levels and was used in 40 consecutive elective spine cases without a postoperative infection or antibiotic-related complications.

Laparoscopic assisted fusion of the lumbosacral spine. A biomechanical and histologic analysis of the open versus laparoscopic technique in an animal model.

STUDY DESIGN: An animal model for laparoscopic lumbosacral fusion. OBJECTIVES: To compare the biomechanical and histologic results of open to laparoscopic lumbosacral discectomy and fusion in an animal model. BACKGROUND DATA: Early clinical reports of laparoscopic lumbosacral fusions are encouraging, but animal experiments have not been reported. METHODS: Ten pigs (50-80 kg) were divided into two groups. Group 1 underwent an open anterior lumbosacral discectomy and fusion at L7-S1 using autologous bone graft and a titanium MOSS (DePuy Motech) cage. Group 2 was identical to Group 1 except that a laparoscopic technique was used. The animals were killed at 3 months, and the lumbosacral spines were harvested for biomechanical and histologic testing. RESULTS: Estimated blood loss and average length of operation, respectively, for the two groups were: Group 1, 50 mL, 2 hours 50 minutes; and Group 2, 40 mL, 3 hours 40 minutes. There were no perioperative or postoperative complications in either group. Motion analysis results showed less motion in lateral bending, flexion, and extension than in the intact specimen in both groups. Tensile testing showed that the stiffness was significantly greater in the open group than in the laparoscopic group (P < 0.004). Histologic examination showed a less extensive discectomy and less bone growth in the implant in the laparoscopic group. Inadequate decortication of end-plates occurred in two animals who underwent laparoscopy. CONCLUSIONS: Although lumbosacral discectomy and implant insertion can be performed using the laparoscopic technique, the construct may not have the same biomechanical strength as that attained with the open procedure. Laparoscopic-assisted lumbosacral fusion surgery requires additional investigation before it is widely used in clinical situations.

The thoracolumbar spine in Marfan syndrome.

We analyzed the prevalence, inheritance, progression, and functional implications of spinal deformity in Marfan syndrome using four different groups of patients. We studied 113 patients who had Marfan syndrome, eighty-two of whom were skeletally immature, in order to characterize the alignment and function of the spine. The patients were selected from a clinic that provides total care with no bias toward the presence of orthopaedic conditions. Scoliosis was identified in fifty-two of the eighty-two patients, and the prevalences for the sexes were equal. The thoracic portion of the curve was convex to the right in all but two patients. The mean kyphosis was greater than that in the general population. Five distinct sagittal profiles were identified on the basis of whether the thoracic kyphosis was within, greater than, or less than normal limits and whether the transition between the kyphosis and lordosis occurred at or caudad to the normal level or whether the curves were reversed. Spondylolisthesis was present in five patients (6 per cent), with a mean slip of 30 per cent. Fourteen pedigrees were studied in depth. There was no familial pattern of the scoliosis. A separate group of fifty-six patients with scoliosis, for whom serial follow-up radiographs were available, was studied for progression. Patients who had a curve of more than 30 degrees had mild progression, and those who had a curve of more than 50 degrees had marked progression (mean, 3 +/- 4 degrees per year). Pain and function of the back were studied in thirty patients who were thirty-five to forty-five years old; these patients were found to be more impaired than matched controls. The presence of scoliosis was associated with pain in the region of the curve in these patients.

Considerations in the comparison of cemented and cementless total hip prostheses.

Based on conservative models of the revision rates for cemented and uncemented hip arthroplasties, the required number of patients for a study to show significant uncemented superiority was determined using standard statistical techniques. A review of the literature was done to ascertain the revision rates for cemented total hip arthroplasties. Patients with osteoarthritis who were older than 50 years had an average revision rate of 1% per year, while those younger than 50 years had revision rates in excess of 2% per year. Specific conditions of the hip were also associated with increased failure rates, most notably the implantation of a revision arthroplasty for a previously failed total hip arthroplasty. Assuming that the uncemented hip had a long-term revision rate of 0.5% per year and an early lack of biologic fixation in 1% of patients, it was found that a 5-year study would have to include at least 2,800 patients (1,400 in each group) if the study population had a cemented failure rate of 1% per year and a total of 230 patients in those having a cemented failure rate of 2% per year. The patients needed for a 10-year evaluation would be 700 and less than 100, respectively. Altering the long- or short-term revision rate for uncemented total hip arthroplasty had relatively little effect on the study size. This analysis indicates that a comparison study would be best done in patients who have high failure rates with cemented total hip arthroplasties. Multicenter trials involving younger patients or those undergoing revision surgery are ideally suited for such an investigation.

A histologic comparison of aseptic loosening of cemented, press-fit, and biologic ingrowth prostheses.

The histology of interface membranes from aseptic loosened prostheses of various types including cemented, press-fit, and biologic ingrowth varieties was compared. Pseudosynovial implant-facing surfaces were present in specimens from all types. The remaining portions of these membranes showed distinct characteristics as well. Cemented implant membranes contained many macrophages and giant cells and evidenced frequent granuloma formation. Press-fit membranes consisted of poorly vascularized, dense fibrous tissue within the loosened press-fit membrane. Macrophages and giant cells were rare, except in one specimen containing ceramic debris particles. Biologic ingrowth membranes were the most vascular and contained loosely organized connective tissue and islands of woven bone. Macrophages were common. One out of six specimens from patients with rheumatoid arthritis contained massive numbers of lymphocytes and plasma cells but not mast cells. The greatest numbers of mast cells were present in membranes from patients with osteoarthritis and in all cases were associated with the presence of stainless steel and/or chrome cobalt particles.

The anterior retropharyngeal approach to the upper part of the cervical spine.

Since 1959, we have used a superior extension of the anterior approach to the cervical spine of Robinson and Smith in a consecutive series of seventeen patients. This approach provided anterior access to the neural elements from the clivus to the body of the third cervical vertebra, without the need for posterior dissection of the carotid sheath or entrance into the hypopharynx or oral cavity. It also provided adequate exposure for the insertion of iliac or fibular strut grafts, which was necessary in thirteen patients. The approach gave excellent exposure for anterior intralesional excision of a tumor in ten patients, marginal excision of an osteochondroma, two corpectomies of the second cervical vertebra combined with removal of the odontoid process, corpectomy of the second cervical vertebra for the treatment of fixed atlanto-axial subluxation, removal of a bullet anterior to the clivus, reduction of a dislocation of the second on the third cervical vertebra secondary to an unstable fracture of the pedicles of the second cervical vertebra, and anterior débridement for treatment of pyogenic vertebral osteomyelitis. In contrast to the reported results of transmucosal approaches to the atlas and axis, there were no infections or iatrogenic neurological deficits of the spine in the present series. Twelve patients who were followed for two years or more had a solid anterior fusion and no subsequent loss of cervical stability. Pain in the neck was relieved in all of the patients who had had a pathological or traumatic fracture.

Pyogenic osteomyelitis of the occiput, the atlas, and the axis. A report of five cases.

Pyogenic osteomyelitis rarely affects the first and second cervical vertebrae, and when it does it can progress to abscess formation, compressing the spinal cord. If the process is unrecognized, it can be fatal. The cases of five patients are reported. Two patients were treated by anterior débridement and posterior cervical-occipital arthrodesis; one, by transoral drainage; one, by posterior cervical-occipital arthrodesis; and the fifth, by posterior atlanto-axial arthrodesis. The causative organism was Staphylococcus aureus in four patients and Pasteurella multocida in one. In all patients, intravenous antibiotics were used, followed by prolonged administration of oral antibiotics. All five patients recovered.

High tibial valgus osteotomy. A clinical review.

Thirty-one consecutive high tibial valgus osteotomies for varus gonarthrosis performed by one surgeon using one technique were evaluated to determine correction of deformity, functional result, subjective impression, and subsequent surgery for the same problem. Twenty-five patients had satisfactory follow-up evaluations. Preoperative tibiofemoral angulation averaged 7 degrees varus. Postoperative tibiofemoral angulation averaged 5 degrees valgus. Ninety-two percent had excellent or good results, according to Coventry's criteria and the H.S.S. knee score. Eighty-eight percent claimed postoperative improvement, 8% were unchanged, and one patient was worse. Eighty-eight percent had had no further surgery. Excellent/good results deteriorated from 92% at two years to 88% at five years, to 91% at seven years, and to 80% at nine years. This is a smaller rate of deterioration than noted in other series. Analgesic and antiinflammatory drug use was significantly reduced after operation. No significant differences were noted in patients older than or younger than 60 years of age at the time of surgical correction. Factors contributing to success included careful patient selection; correction of the limb to the mechanical axis; and precise surgical technique. Osteotomy proved a successful alternative to total knee replacement for treatment of varus gonarthrosis in a carefully selected group of patients.

Focal lytic lesions associated with femoral stem loosening in total hip prosthesis.

Focal lytic lesions may occur in the proximal femur associated with loosening of the femoral component of a total hip prosthesis. During long-term follow-up of 62 patients with total hip prostheses, five such lesions developed. Histologically the lesions appear to be a histiocytic response to fragmented methylmethacrylate. Radiographically the lesions may suggest infection or neoplasm. Pathologic fracture may occur through large lesions. Experience in one case suggests that thorough removal of the tissue at the time of revision may be necessary to prevent recurrence. The recent reports of several malignant neoplasms developing in association with the femoral components of total hip replacements makes recognition of these benign focal lytic lesions even more important.

Skeletal changes during prolonged external irradiation: alterations in marrow, growth plate and osteoclast populations.

This report describes hematologic and skeletal changes in young mice subjected to continuous external whole body irradiation (45 rads/day) for 4 days to 12 weeks. Irradiation caused a rapid depletion of hematopoietic stem cells, marrow aplasia and pancytopenia, all of which persisted during the period of irradiation but resolved afterward. In spite of suppressed cellular proliferation and disarray of cartilage cell columns in metaphyseal plates, linear bone growth appeared to continue at physiologic rates. Histologic and morphometric studies provided no evidence of impaired osteoblast function, but the presence of thickended trabeculae beneath the growth plate and of cartilagenous islands within cortical shafts of long bones indicated that bone remodeling was deficient. Direct osteoclast counts demonstrated that marrow aplasia was followed by a progressive decline that could not be reversed by parathormone injections or infusions with mature macrophages and lymphocytes but that resolved once the bone marrow recovered following cessation of irradiation. Therefore, the altered bone remodeling probably resulted from radiation injury to osteoclast precursors in the hematopoietic compartment.

Geometric total knee replacement for treatment of the rheumatoid knee.

The results of fifty-four geometric total knee arthroplasties in forty-four patients with definite or classic rheumatoid arthritis were analyzed twenty-four to sixty-four months after the surgical procedure. There were no operative deaths, no postoperative infections, and no known pulmonary emboli. Three patients required additional operative procedures on the knee: one, a patellectomy for pain one year after arthroplasty; the second, resection of tibial bone and reinsertion of the tibial component to correct a flexion contracture; and the third, replacement of the tibial component because of loosening. The relief of pain and increase in ability to carry out the activities of daily living were dramatic in these patients, who, because of the limitations imposed by their rheumatoid arthritis, applied minimum stress on the prosthetic knees. Postoperatively, the average arc of knee flexion was 104 degrees.