A review of demineralized bone matrices for spinal fusion: the evidence for efficacy.

BACKGROUND AND PURPOSE: Autologous Iliac Crest Bone Grafting (ICBG) is considered the gold-standard graft choice for spinal arthrodesis; however, it is associated with donor site morbidity and a limited graft supply. Bone graft alternatives to replace autograft and augment arthrodesis are a topic of ongoing research. This article will review properties of Demineralized Bone Matrix (DBM) and review the evidence for its use, including animal models and human clinical trials. METHODS: A systematic and critical review of the English-language literature was conducted on Pubmed, Cochrane, CINAHL, and Google Scholar using search key terms such as 'Demineralized Bone Matrix', 'Spine' and 'Fusion'. Papers that were included were original research articles in peer-reviewed journals that investigated fusion outcomes. Scientific validity of articles was appraised using the PRISMA methodology. Articles were critically examined and compared according to study design, DBM type, outcomes, and results. Primary outcome of interest was fusion rate. Secondary outcomes included Oswestry Disability Index; Short Form-36 survey; Odom's criteria; Visual Analog Scale neurologic pain score; Japanese Orthopedic Association myelopathy score; Neck Disability and Ishihara Curvature Indices; and pseudarthrosis and surgical failure rates. RESULTS: Demineralized Bone Matrix has been evaluated in animal models and human clinical trials of spine fusion. Results of animal studies indicate variation in performance within and among DBM products. The majority of human clinical trials report high fusion rates when DBM is employed as a graft extender or a graft enhancer. Few prospective randomized controlled trials have been performed comparing DBM to autologous iliac crest bone graft in spine fusion. CONCLUSIONS: Although many animal and human studies demonstrate comparable efficacy of DBM when combined with autograft or compared to autograft alone, additional high level of evidence studies are required to clearly define the indications for its use in spine fusion surgeries and the appropriate patient population that will benefit from DBM.

Dynamic changes of the ligamentum flavum in the cervical spine assessed with kinetic magnetic resonance imaging.

The purpose of this article is to quantify changes in thickness of the ligamentum flavum (LF) associated with motion of the cervical spine and to compare the thickness of the LF at each cervical level using kinetic magnetic resonance imaging (kMRI). Two hundred fifty-seven symptomatic patients (129 men; 128 women) underwent kMRI in neutral, flexion, and extension positions. Midsagittal images were digitally marked and electronically analyzed by spine surgeons. Thickness of LF in the cervical region from C2-3 to C7-T1 was measured in all three positions. LF at C7-T1 was significantly thicker than C2-3 to C6-7 in neutral, flexion, and extension positions (p < 0.05). LF was significantly thicker in extension than in flexion at C3-4 to C6-7. LF thickness increases with extension and decreases with flexion. LF is uniquely thick at C6-7 and at C7-T1 in the extension position, which may predispose these levels to cord compression syndromes and associated neuropathies.

Gasless endoscopic anterior lumbar interbody fusion utilizing the B. E.R.G. approach.

BACKGROUND: Several authors have reported success using a gas-mediated transperitoneal approach for lumbar interbody fusion. However, this approach has not been shown to reliably and predictably address segments above L4-5. METHODS: The B.E.R.G. approach was attempted in 202 patients who required anterior lumbar interbody fusion (ALIF). Of those, 168 were completed successfully without conversion to an open procedure. The anterior retroperitoneal approach required no gas insufflation. The gasless environment allowed for the use of standard anterior instrumentation and a variety of fusion grafts and devices. RESULTS: Mean hospital stay was 1.95 days, with 73% of patients discharged in <47 h following surgery. Clinical results from the first 50 patients, with a minimum 2-year follow-up, include a 92% fusion rate and 78% of patients reporting significant pain relief of greater than 50%. CONCLUSIONS: The B.E.R.G. approach offers significant technical advantages over the standard gas-mediated transperitoneal approach for ALIF. The clinical results are similar to those reported for open approaches and the gas-mediated transperitoneal approach.

Surgical anatomy of the cervical pedicles: landmarks for posterior cervical pedicle entrance localization.

The posterior entrance to the cervical pedicle is described using quantitative and descriptive parameters. Fifty-three spines (C2-C7) were evaluated using a digital caliper and by visual inspection using four bony landmarks: the lateral vertebral notch and inferior articular process (C2-C7), the medial pedicle cortex at C2, and the transverse process at C7. Three distances were defined. (1) At C2, the average medial pedicle cortex-pedicle distance was 7.2 mm. (2) The lateral vertebral notch-pedicle distances showed that the entrances were located close to the notch at C2, almost at the notch at C3 and C4, and gradually moved medially away from the notch from C5 to C7. The pedicles were rarely located lateral to the lateral vertebral notch. (3) The inferior articular process-pedicle distance was large at C2, the shortest at C3, and gradually increased toward C7. Three relations were defined. (1) The pedicles were located mostly in the intermediate third of the inferior facet at C2; in the lateral third at C3, C4, and C7; or in the lateral or intermediate thirds at C5 and C6. Only C2 and C6 pedicles were located in its medial third. (2) The pedicles were located mostly below the lateral vertebral notch at C2, at C3-C6, or almost equally above and at the notch at C7. (3) Most of the C7 pedicles were located below the midline of the transverse process. The location of the pedicle entrance was unique at each cervical level. Their distribution followed the cervical spinal cord enlargement. These landmarks should assist with safe placement of pedicle screws.

Morphologic characteristics of human cervical pedicles.

STUDY DESIGN: Cervical pedicle morphology was investigated using manual and computed tomography measurements. OBJECTIVES: Normal anatomic variations of the cervical pedicles were measured to evaluate their safety as anchors for posterior cervical fixation systems. SUMMARY OF BACKGROUND DATA: There have been no cervical pedicle measurements on a large number of specimens. No study has ever measured the inner pedicle diameter. METHODS: Fifty-three spinal columns (C2-C7) of Euro-American origin identified by age, sex, and height (318 vertebrae or 636 pedicles) were measured using a digital caliper, a goniometer, and computed tomography scanning. RESULTS: The pedicle axis lengths were similar from C3 to C7 (except for shorter C2 pedicles). In the horizontal plane, the medial inclination of the pedicles followed the cervical spinal cord enlargement. In the sagittal plane, the pedicles were directed superiorly in the upper spine and inferiorly in the lower cervical spine. Some pedicles had no medullary canal (i.e., were solid cortical bone: 0.9% C2, 2.8% C3 and C4, and 3.8% C5 pedicles). The outer pedicle width was smaller than the height in most of the pedicles. The inner pedicle width was equal to or smaller than 2 mm in 13.2% C2, 72.6% C3, 67.0% C4, 62.3% C5, 51.9% C6, and 16.0% C7. The outer pedicle width was equal to or smaller than 4 mm in 8.5% C2, 75.5% C3, 35.8% C4, 13.2% C5 and C6, and 6.6% C7 pedicles. The thinnest pedicle cortex was always the lateral cortex, which protects the vertebral artery. Measurements of the posterior pedicle projection also were taken. CONCLUSIONS: These data provide anatomic limitations to pedicle screw use in the cervical spine.