Drew A. Bednar

Procurement of Bone Graft from the Iliac Crest. An Operative Approach with Decreased Morbidity

We compared the donor site morbidity in fifty-seven consecutive patients in whom a bone graft had been procured from the iliac crest through an incision parallel to the superior cluneal nerves and perpendicular to the posterior iliac crest (the study group) with that in fifty-three consecutive patients in whom the graft had been procured through an oblique incision parallel to the posterior iliac crest (the control group). Numbness, tenderness, and pain at the donor site one and six months postoperatively were assessed by means of an interview with the patient and a review of the records. The prevalence of symptoms in the control group was greater than that in the study group. At one month, thirty-nine patients (74 per cent) in the control group had numbness, compared with twenty-five (44 per cent) in the study group (p = 0.001). At six months, thirty-one patients (58 per cent) in the control group had numbness, compared with fourteen (25 per cent) in the study group (p = 0.0002). Thirty-six patients (68 per cent) in the control group and twenty-four (42 per cent) in the study group had tenderness over the incision at one month (p = 0.005), and twenty-seven (51 per cent) and eleven (19 per cent), respectively, had tenderness at six months (p = 0.0003). Forty patients (75 per cent) in the control group and forty-six patients (81 per cent) in the study group had deep pain in the region of the iliac crest at one month, compared with thirty-two (60 per cent) and thirty-one (54 per cent), respectively, at six months. The mean analog score for pain at the donor site was 7 of 10 points in the control group and 6 points in the study group (p = 0.001) at one month and 3 and 2 points, respectively, at six months (p = 0.001).

Relationship between pain and vertebral motion in chronic low-back pain subjects

OBJECTIVES To investigate the relationship between intervertebral motion, intravertebral deformation and pain in chronic low-back pain patients. DESIGN This study measured vertebral motion of the lumbar spine and associated pain in a select group of chronic low-back pain patients as they performed a standard battery of motions in all planes. BACKGROUND Numerous studies have demonstrated that individuals with low-back pain have impaired spinal motion, yet few studies have examined the specific relationship between pain and motion parameters. Although it is accepted that the pain in mechanical low-back patients is due to specific spinal motions, no studies have related specific motions to pain measures. METHODS Percutaneous intra-pedicle screws were placed into the right and left L4 (or L5) and S1 segments of nine chronic low-back pain patients. The external fixator frame was removed following the clinical external fixation test. The 3D locations of the pedicle screws and the level of pain were recorded as the subjects performed a battery of motions. The relationship between the pain and motion parameters was assessed using linear discriminant analysis and neural network models. RESULTS The neural network model showed a strong relationship between observed and predicted pain (R(2)=0.997). The discriminant analysis showed a weak relationship (R(2)=0.5). CONCLUSIONS Vertebral motion parameters are strongly predictive of pain in this select group of chronic low-back pain patients. The nature of the relationship is nonlinear and involves interactions; neural networks are able to effectively describe these relationships. RELEVANCE Specific patterns of intervertebral motion and intravertebral deformation result in pain in chronic low-back pain patients. This substantiates the mechanical back pain aetiology.

Pullout strength of pedicle screws augmented with particulate calcium phosphate: An experimental study

BACKGROUND CONTEXT Pressure-injected and in situ curing bone cements have been studied as alternatives in augmenting lumbar pedicle screw fixation but are frequently found to leak outside the confines of the target vertebra. PURPOSE The objective is set to determine the mechanical efficacy of a porous granular/particulate calcium phosphate (CP) bone augmentation product (Skelite) applied manually without pressurized injection in this application. STUDY DESIGN/SETTING The biomechanical analysis compared the axial pullout strength and insertional torque of augmented and nonaugmented pedicle screws in cellular polyurethane foams. METHODS The insertion torque and pullout strength of 6.5-mm pedicle screws inserted (via 3.5-mm pilot holes) into polyurethane blocks mimicking the porosity of cancellous bone were measured. New pilot holes were then packed with granular particles of Skelite and retested. Last, those blocks initially tested to failure without augmentation were packed with Skelite and retested. Measurements were performed for polyurethane densities of 0.16 and 0.32 g/cc (corresponding to the porosity of osteoporotic and normal bone) and strain rates of 0.5 and 5mm/min. RESULTS Peak pullout force averaged 2132.5+/-119.3 N and 1840.1+/-216.7 N in high density samples without and with augmentation and 688.2+/-91.4 N and 861.6+/-74.5 N in low density samples without and with augmentation. After failure, approximately 50% and 77% of the peak pullout force of original high and low density samples was regained by augmentation. Statistical analysis revealed significant (p<.0001) correlation between the addition of CP, peak pullout resistance, and insertion torque. CONCLUSION Granular CP augmentation improved the pullout strength in both failed (pulledout) samples and low density (porosity of osteoporotic cancellous bone) polyurethane blocks.

Tranexamic acid for hemostasis in the surgical treatment of metastatic tumors of the spine.

Study Design. This is a retrospective study of sequential cohorts. Objective. To assess the efficacy of tranexamic acid in decreasing operative blood loss and the need for intraoperative transfusion in metastatic spine surgery. Summary of Background Data. Significant published data have established the efficacy of antifibrinolytic drugs in limiting surgical bleeding during heart surgery and total joint replacement. One study in scoliosis suggested benefit in spine surgery as well. Methods. During a 6-month trial period, 14 patients with spine cancer undergoing palliative intralesional tumor excision and concomitant instrumentation to stabilize the spine in the hands of a single surgeon were administered tranexamic acid intraoperatively in the attempt to minimize operative blood loss. They were then compared to the immediately preceding 14 patients. Results. Estimated operative blood loss was 1385 mL in the study group treated with tranexamic acid and 1815 mL in controls not receiving the drug, and was not found to be significantly decreased in this study. Conclusions. Control of operative bleeding in metastatic spine surgery can be problematical. Optimum protocol might include routine preoperative angiographic tumor embolization to decrease lesion vascularity in all cases, but angiography is not without risk. Noninvasive prophylaxis of tumor bleeding would have obvious desirable advantages but was, unfortunately, not achieved in this study.

New insight into the mechanics of the lumbar interspinous ligament.

Study Design Repeated in vitro mechanical tests were performed on porcine and human interspinous ligament specimens with progressive disruption of the collagen fiber network to evaluate the existence of mechanical interactions between collagen fibers. Objective To evaluate the existence of a load pathway in the interspinous ligament whereby loads are transmitted between collagen fibers. Summary of Background Data Mechanical tests demonstrate that the interspinous ligament resists spinal flexion, but the collagen fibers are not oriented to oppose separation of the spinous processes. This seeming contradiction could be explained by the existence of mechanical interactions between collagen fibers of the interspinous ligament. Methods In vitro mechanical tests were performed on porcine and human bone‐interspinous ligament‐bone specimens. The collagen network of the ligament substance was disrupted by passing a scalpel blade though the ligament substance. Repeated tests were performed with progressive disruption of the collagen fiber network. Results The stiffness of the interspinous ligament specimens was reduced as the collagen fiber network was disrupted, but approximately half of the initial stiffness was maintained when the collagen fiber network was severely disrupted. In this case, no intact collagen fibers remained. Conclusions Mechanical interactions exist between collagen fibers in the interspinous ligament. The mechanism of the interactions is unknown.

Failure of external spinal skeletal fixation to improve predictability of lumbar arthrodesis

Background: Whether lumbar arthrodesis can relieve isolated low-back pain in the absence of focal neurological findings or instability is unclear. The results of published studies are also inconsistent with regard to whether temporary back-pain relief with external spinal skeletal fixation can predict lasting back-pain relief after arthrodesis. This report presents the results, with regard to clinical benefit and complications, of more than 100 external spinal skeletal fixation procedures undertaken as a prelude to lumbar arthrodesis. Methods: The records of all patients who underwent external spinal skeletal fixation between 1989 and 1999 were reviewed with attention to perioperative complications, pain relief from the test procedure, the clinical benefit from a subsequent arthrodesis, and the functional status after the arthrodesis. Analyzed data included the frequency of neurological complications and infections and the benefit (Prolo score) after staged spinal arthrodesis in patients who underwent arthrodesis after temporarily experiencing pain relief with the test procedure. Results: A total of 103 external spinal skeletal fixation procedures were undertaken. Neurological complications occurred in two procedures (2%); one resulted in permanent sciatica. Infections occurred in five patients (5%). Sixty patients experienced pain relief during the external fixation test, but only twenty-seven of forty-nine patients who went on to have an arthrodesis and had sufficient follow-up reported that they were doing well at a minimum of one year later. In no case did the external spinal skeletal fixation procedure cause a permanent increase in low-back pain. Conclusions: On the basis of this analysis, external spinal skeletal fixation should not be used as a predictor of pain relief after lumbar arthrodesis.

Failure of reconstitution of open-section, posterior iliac-wing bone graft donor sites after lumbar spinal fusion. Observations with implications for the etiology of donor site pain

The objective of this cohort study—conducted at a regional trauma unit in southern Ontario, Canada—was to review the imaging history of open-section, iliac-wing bone graft donor sites in lumbar fusion patients. Intervention entailed review of available X-ray and CT scan images for all patients undergoing lumbar fusion with iliac autograft in the senior author’s practice over a 4-year period. Outcome was radiographic confirmation of the absence of bony reconstitution at the iliac harvest site. Of 239 primary fusions performed, 209 complete imaging records were available for review. The images of a further 20 patients who had surgery with the senior author prior to the study period and who presented at the office in the first half of 2000 were also assessed. All cases showed persistence of the iliac donor harvest site defect. Only minimal marginal sclerosis to suggest attempted remodeling was observed. We conclude that iliac-wing bone graft donor sites do not remodel. Given that iliac harvesting is known to increase strain in the pelvis, and that lumbosacral stabilization increases stress in the pelvis, permanent deficiency of iliac bone stock at donor harvest site may be a factor in both primary donor site pain and the observed high frequency of this problem in lumbosacral fusion patients.

Solitary C1 Posterior Fixation for Unstable Isolated Atlas Fractures: Case Report and Systematic Review of the Literature.

Study Design A systematic review of the literature. Objectives To review the published results to date of motion-preserving direct reconstruction of C1 ring fractures with combined coronal plane displacement of at least 7 mm (rule of Spence) and so at risk for Dickman type I or II disruption of the transverse atlantal ligament (TAL). Methods A structured literature review prompted by successful management of a typical case. Results To date only 65 such cases are reported and follow-up is almost uniformly short. Although reported clinical success is uniform, the case mix is heterogenous and confirmation/classification of ligamentous injury at baseline is often lacking. Conclusions Direct C1 stabilization shows promise as a “more selective” option in managing displaced atlas fractures with probable TAL disruption but cannot yet be recommended as a practice standard. Prospective clinical studies are indicated and should be structured so as to differentiate between Dickman type I and type II injuries of the TAL.

Sacral Stress Fracture Mimicking Lumbar Radiculopathy in a Mounted Police Officer: Case Report and Literature Review

Study Design Case report and review of the literature. Objective To present a unique case of L5 radiculopathy caused by a sacral stress fracture without neurologic compression. Methods We present our case and its clinical evolution and review the available literature on similar pathologies. Results Relief of the unusual mechanical loading causing sacral stress fracture led to rapid resolution of radiculopathy. Conclusion L5 radiculopathy can be caused by a sacral stress fracture and can be relieved by simple mechanical treatment of the fracture.

Cauda equina syndrome from lumbar disc herniation

The syndrome can progress to paraplegia with rectal and urinary incontinence and represents a surgical emergency.[1][1] Sixty percent of patients are male with a mean age of 42 years, and 82% have a history of chronic low-back pain. In two-thirds of patients, the syndrome is associated with trauma