Stand-alone Anterior Lumbar Interbody Fusion Research Articles

A Radiological Comparison of Anterior Fusion Rates in Anterior Lumbar Interbody Fusion

Aim To compare anterior fusion in standalone anterior lumbar interbody fusion (ALIF) using cage and screw constructs and anterior cage–alone constructs with posterior pedicle screw supplementation but without posterior fusion. Methods Eighty-five patients underwent single- or two-level ALIF procedure for degenerative disk disease or lytic spondylolisthesis (SPL). Posterior instrumentation was performed without posterior fusion in all cases of lytic SPL and when the anterior cage used did not have anterior screw through cage fixation. Results Seventy (82%) patients had adequate radiological follow-up at a mean of 19 months. Forty patients had anterior surgery alone (24 single level and 16 two levels) and 30 had front-back surgery (15 single level and 15 two levels). Anterior locked pseudarthrosis was only seen in the anterior surgery–alone group when using the STALIF cage (Surgicraft, Worcestershire, UK) (37 patients). This occurred in five of the single-level surgeries (5/22) and nine of the two-level surgeries (9/15). Fusion was achieved in 100% of the front-back group and only 65% (26/40) of the anterior surgery–alone group. Conclusion Posterior pedicle screw supplementation without posterolateral fusion improves the fusion rate of ALIF when using anterior cage and screw constructs. We would recommend supplementary posterior fixation especially in cases where more than one level is being operated.

Stand-alone Anterior Versus Anteroposterior Lumbar Interbody Single-level Fusion After a Mean Follow-up of 41 Months

Prospective cohort study comparing evaluations of single-level anterior lumbar interbody fusion (ALIF) versus anteroposterior lumbar fusion (APLF). To clinically and radiologically compare the outcome after angle-stable, locked, stand-alone ALIF with that obtained after APLF, in cases with degenerative disc disease (DDD). Fusion rates have been reported to be highest after interbody fusion with transpedicular fixation. However, transpedicular fixation is linked to significant damage of the paravertebral muscles, to screw displacement-related neurological and vascular complications, and to an increased rate of adjacent segment degeneration. When performed as a stand-alone procedure, the disadvantages of transpedicular fixation can be completely avoided by ALIF. Eighty patients with chronic low-back pain due to a single-level DDD (Modic ≥2) and facet joint arthritis (Fujiwara ≥3) were enrolled in this study. Forty patients received an anteroposterior fusion (ALIF with transpedicular fixation: APLF group) and 40 patients (ALIF group) were treated with a stand-alone ALIF using the Synfix-LR device. At 7 days, 3, 6, 12, and 24 months, and at a mean follow-up of 41 months, patients were clinically (visual analog scale, Oswestry Low Back Pain Disability Index, satisfaction) and radiologically (x-ray, and at 12 months, thin-slice computed tomography) compared. Blood loss and duration of surgery were significantly lower in the ALIF group (P<0.001). Visual analog scale and Oswestry Low Back Pain Disability Index improved significantly over time (analysis of variance, P<0.001) in both groups, but both scores were significantly better in ALIF group (analysis of variance, P<0.001). Patients' satisfaction consistently ranked higher in the ALIF group (P=0.042 at 12 mo). No significant difference was found in the fusion rate throughout the study. Stand-alone ALIF leads to better clinical results than APLF, without differences in fusion rates after 41 months. Therefore, when a posterior approach is not needed for decompression or reposition, we suggest performing a stand-alone ALIF in cases with single-level DDD.

Stand-Alone Anterior Lumbar Interbody Fusion for Degenerative Disc Disease of the Lumbar Spine: Results with a Two-Year Follow-Up

Stand-Alone Anterior Lumbar Interbody Fusion for Degenerative Disc Disease of the Lumbar Spine: Results with a Two-Year Follow-Up

Are stand‐alone cages sufficient for anterior lumbar interbody fusion?

Anterior lumbar interbody fusion (ALIF) has increased in popularity because it has advantages over posterior fusion. Because there is disagreement about the stability of stand-alone cage ALIF, some surgeons use various types of supplementary fixation, including anterior plates, pedicle screw systems and translaminar screws, to increase segmental stability. Many factors associated with both the cages and endplates influence the time of onset and extent of subsidence after use of stand-alone cage ALIF. A large round cage with an adequate central opening is recommended to facilitate maximum contact with the periphery of the endplate. With regard to the relationship between radiographic fusion and recurrence of symptoms with the development of subsidence, most researchers have reported finding no correlation. Subsidence may be due to a process of bone incorporation between cages and endplates. Does subsidence or nonfusion really matter clinically? Further prospective, randomized controlled trials are very much needed to answer these questions.

Sacral fractures following stand-alone L5–S1 anterior lumbar interbody fusion for isthmic spondylolisthesis

Recent studies have demonstrated excellent results in treating isthmic spondylolisthesis via an anterior lumbar interbody fusion (ALIF). The authors describe 3 patients with isthmic spondylolisthesis at L5-S1 who experienced sacral fractures after insertion of a unique, stand-alone anterior interbody fixation device. Three consecutive patients at a single institution were treated for Grade I spondylolisthesis at L5-S1 via a standalone ALIF with insertion of a novel biomechanical interbody device. This device is made of polyetheretherketone and has an integrated system for internal fixation into the vertebral bodies. In each patient a bone morphogenetic protein-soaked sponge was placed for the fusion. The indications for treatment in each patient were back and radicular pain that had been unsuccessfully treated with conservative measures. All 3 patients had reduction of their spondylolisthesis and resolution of their unilateral radiculopathies immediately postoperatively. Within 1 month of surgery, all 3 patients had failure of the device and recurrence of their symptoms. In each case the failure was due to fracture of the anterior portion of the S-1 body. Each patient underwent reduction and pedicle screw fixation at L5-S1. In all cases, there was successful reduction in their recurrent spondylolisthesis and resolution of their radiculopathies. Treatment of Grade I isthmic spondylolisthesis at L5-S1 with stand-alone ALIF and fixation can lead to sacral fracture from high stress loads at that level in the spine, and consideration should be made either for supplemental pedicle screw fixation or a completely posterior approach.

Injury of the right and left inferior epigastric artery during the implantation of a stand-alone ALIF cage through a left retroperitoneal approach: a case report

Various perioperative vascular complications of anterior lumbar spine procedures have been described in orthopaedic literature. We report the unusual case of a perioperative bleeding from the right and left epigastric inferior artery occurring when using a stand-alone ALIF device (Synfix, Synthes, Oberdorf, Switzerland) at the L5/S1 level through an anterior left retroperitoneal approach. The primary stability of the Synfix is achieved by four divergent screws which are inserted through the anteriorly located plate into the neighbouring vertebral endplates. For the screw insertion the surrounding structures have to be mobilized more extensively than during a “standard” anterior lumbar interbody fusion (ALIF) procedure. The epigastric inferior arteries were embolized by applying polyvinyl alcohol particles and metal coils. The retroperitoneal haematoma caused herniation of the external rectus sheath. Hence revision surgery with removal of the haematoma and resuturing of the rectus sheath were performed. Insertion of divergent screws of the Synfix device may cause severe distension and rupture of the epigastric vessels. This case shows that a lesion of the right epigastric artery may be a hazard even in left retroperitoneal approaches. To the author’s knowledge this is the first case describing a lesion of the right epigastric artery during an ALIF procedure through a left retroperitoneal approach.

Anterior Lumbar Interbody Fusion in the Treatment of Mechanical Low Back Pain

A number of options exist for patients with intractable back pain and degenerative disc disease (DDD). Interbody fusion techniques exploit the mechanical advantages of the disc space anteriorly, including a large fusion bed, excellent blood supply and graft compression. Unlike posterior approaches, the anterior, retroperitoneal technique affords wide access to the disc space without necessitating significant retraction on the lumbar extensor muscles. Instrumentation options are rapidly advancing, but remain more limited than posterior approaches. The failure rate of stand-alone anterior lumbar interbody fusion (ALIF) remains a concern and a variety of percutaneous or less invasive posterior approaches have been devised to augment ALIF procedures. This article examines the role of stand-alone and posteriorly stabilized ALIF in the management of DDD.

Finite Element Analysis of Anterior Lumbar Interbody Fusion

Pedicle screw fixation (PSF) has been used for the setting of a lumbar interbody fusion. To investigate analytically the effects of additional PSF to the anterior lumbar interbody fusion (ALIF) with the cylindrical cages (Ray TFC) in the immediate postoperative state. An addition of PSF to the stand-alone ALIF increases segmental stiffness. A finite element model of ALIF (L4,-L5) was constructed. Finite element analyses were performed to investigate relative motion and bone stress at the bone-cage interface. The results were then compared with those of the stand-alone ALIF. Bone stress surrounding pedicle screws was also predicted. An addition of PSF to the stand-alone ALIF led to higher segmental stiffness, smaller relative motion, smaller bone deformation, and lower bone stress level at the cage-bone interface. The bone stress level at the interface reduced substantially during extension. The bone stress level at the bone-screw tip interface was much lower than that of the bone-cage interface. The articulating facet had no significant load-bearing capacity because of stiff PSF. Little gap opening at the bone-cage interface was found during a compressive preload over 400 N; an excessive extension without preload caused considerable gap opening. Slip less than 0.15 mm occurred during all the loading modes except axial rotation; an excessive axial rotation caused to slip over 0.15 mm. Geometric constraints caused by PSF will reduce substantially the bone stress level and the relative motion, and therefore be more likely to allow bone ingrowth at the bone-cage interface, compared with the stand-alone ALIF. The use of pedicle screw stabilization would have significant beneficial effects on the rate of interbody fusion, regardless of whether ALIF or PLIF was used.

Bone Dowels in Anterior Lumbar Interbody Fusion

Since the Food and Drug Administration approved the Babgy-Kuslich BAK cage for anterior lumbar interbody fusion (ALIF), various threaded interbody fusion devices have been introduced. Bone dowels offer several theoretical advantages over cages with regard to stress shielding; the purpose of this study was to assess the efficacy of bone dowels in interbody fusion. All patients undergoing ALIF performed by the senior author between 1998 and 2001 were retrospectively reviewed. Patients' preoperative and postoperative neurologic status, functional status, and both back and radicular pain were assessed according to a previously published outcome measure. Between 1998 and 2000, 23 patients underwent ALIF with cortical femoral allograft bone dowels. One patient underwent simultaneous bone dowel and titanium cage placements and was therefore excluded from further analysis. The 22 remaining patients underwent a total of 33 fused segments; of these, 21 patients were available for follow-up. Mean clinical follow-up was 30.6 months. Mean imaging follow-up was 21 months. There were 5 instances of radiographic nonunion (3 symptomatic and 2 asymptomatic). The incidence of technical failures and complications related to the bone dowels was 17%. Bone dowels failed and caused symptoms only in patients with a stand-alone ALIF. There were no clinical failures in patients treated with supplemental anterior or posterior spinal fixation. These data demonstrate that marginal fusion rates and functional success rates can be achieved using stand-alone bone dowels for ALIF. The clinical success and fusion rates are significantly higher if ALIF dowels are shielded from stress with rigid spinal instrumentation.

Graft Resorption With the Use of Bone Morphogenetic Protein: Lessons From Anterior Lumbar Interbody Fusion Using Femoral Ring Allografts and Recombinant Human Bone Morphogenetic Protein-2

This is a prospective cohort study examining the results and radiographic characteristics of anterior lumbar interbody fusion (ALIF) using femoral ring allografts (FRAs) and recombinant human bone morphogenetic protein-2 (rhBMP-2). This was compared to a historical control ALIF using FRAs with autologous iliac crest bone graft (ICBG). To determine whether the use of rhBMP-2 can enhance fusion ALIF with stand-alone FRAs. ALIF is a well-accepted procedure in reconstructive spine surgery. Advances in spinal surgery have produced a multitude of anterior interbody implants. The rhBMP-2 has promoted fusion in patients undergoing ALIF with cages and threaded allograft dowels. The FRA still remains a traditional alternative for anterior support. However, as a stand-alone device, the FRA has fallen into disfavor because of high rates of pseudarthrosis. With the advent of rhBMP-2, the FRA may be more attractive because of its simplicity and remodeling potential. It is important to understand the implications when rhBMP-2 is used with such structural allografts. A total of 36 consecutive patients who underwent ALIF with stand-alone FRAs by a single surgeon (E.G.D.) at 1 institute were included. A cohort of 9 consecutive patients who received FRAs filled with rhBMP-2 was followed prospectively. After noticing suboptimal results, the senior author terminated this method of lumbar fusion. A total of 27 prior consecutive patients who received FRAs filled with autogenous ICBG were used for comparison. Analyzing sequential radiographs, flexion-extension radiographs, and computerized tomography with multiplanar reconstructions determined nonunions. Minimum follow-up was 24 months. Pseudarthrosis was identified in 10 of 27 (36%) patients who underwent stand-alone ALIF with FRAs and ICBG. Nonunion rate was higher among patients who received FRAs with rhBMP-2 (i.e., 5 of 9 [56%]). Statistical significance was not established because of the early termination of the treatment group (P > 0.3). Of interest, radiographs and computerized tomography revealed early and aggressive resorption of the FRAs when used with rhBMP-2. This preceded graft fracture and even disintegration, resulting in instability and eventual nonunion. The use of rhBMP-2 did not enhance the fusion rate in stand-alone ALIF with FRAs. In fact, the trend was toward a higher nonunion rate with rhBMP-2, although this was not significant with the numbers available. This result appears to be caused by the aggressive resorptive phase of allograft incorporation, which occurs before the osteoinduction phase.

Supplementary Stabilization With Anterior Lumbar Intervertebral Fusion–A Radiologic Review

A radiologic assessment of the success of anterior lumbar interbody fusion (ALIF) using thin-section computerized tomography (CT) was performed. To assess the effect of different types of posterior stabilization on the fusion rate of ALIF. Thin-section CT has shown a higher rate of pseudarthrosis with ALIF than previously reported with standard radiologic methods. Cadaveric studies have shown that posterior stabilization would increase stiffness of the motion segment and is likely to enhance the rate of fusion with ALIF. To our knowledge, the results of thin-section CT of ALIF, with and without posterior stabilization, has not been reported previously. Patients with discogenic back pain confirmed by diskography underwent ALIF surgery, either as a stand-alone procedure or with posterior stabilization, using translaminar, unilateral pedicle, or bilateral pedicle screws. The 4 cohorts were followed up prospectively, and thin-section CT was used to assess interbody fusion. The fusion rate for stand-alone ALIF was 51%, for patients with supplementary stabilization with translaminar screws 58%, with unilateral pedicle screws 89%, and with bilateral pedicle screws 88%. A significant difference in the fusion rate was found when ALIF was combined with pedicle screw stabilization (P < 0.01). The addition of pedicle screw fixation at ALIF produces a significant increase in the rate of interbody fusion.

Biomechanical Assessment of Anterior Lumbar Interbody Fusion With an Anterior Lumbosacral Fixation Screw-Plate: Comparison to Stand-Alone Anterior Lumbar Interbody Fusion and Anterior Lumbar Interbody Fusion With Pedicle Screws in an Unstable Human Cadaver Model

Human lumbosacral cadaveric specimens were tested in an in vitro biomechanical flexibility experiment using physiologic loads in 5 sequential conditions. To determine the biomechanical differences between anterior lumbar interbody fusion (ALIF) using cylindrical threaded cages alone or supplemented with an anterior screw-plate or posterior pedicle screws-rods. Clinically and biomechanically, stand-alone ALIF performs modestly in immobilizing the unstable spine. Pedicle screws improve fixation stiffness significantly, but supplementary anterior instrumentation has not been studied. There were 7 specimens tested: (1) intact, (2) after discectomy and facetectomy to induce moderate rotational and translational hypermobility, (3) with 2 parallel ALIF cages, (4) with cages plus a triangular anterior screw-plate, and (5) with cages plus pedicle screws-rods. Pure moments without preload induced flexion, extension, lateral bending, and axial rotation; linear shear forces induced anteroposterior translation. Angular and linear motions were measured stereophotogrammetrically, and range of motion (ROM) and stiffness were quantified. Compared to the destabilized spine, interbody cages alone reduced ROM by 77% during flexion, 53% during extension, 60% during lateral bending, 69% during axial rotation, and 71% during anteroposterior shear (P < 0.001, analysis of variance/Fisher least significant difference). Addition of an anterior plate or pedicle screws-rods, respectively, further reduced ROM by 8% or 13% during flexion (P = 0.21), 21% or 28% during extension (P = 0.15), 5% or 25% during lateral bending (P = 0.04), 11% or 18% during axial rotation (P = 0.13), and 18% or 18% during anteroposterior shear (P = 0.17). Compared to stand-alone ALIF, both the anterior screw-plate and pedicle screw-rod fixation reduced vertebral ROM to less than 1.2 degrees of rotation and less than 0.1 mm of translation. The anterior screw-plate and pedicle screws-rods both substantially reduced ROM and increased stiffness compared to stand-alone interbody cages. There was no significant difference in the amount by which the supplementary fixation devices limited flexion, extension, axial rotation, or anteroposterior shear; pedicle screws-rods better restricted lateral bending.

Biomechanical Changes at Adjacent Segments Following Anterior Lumbar Interbody Fusion Using Tapered Cages

A biomechanical evaluation of anterior cages in a calf lumbar spine model. To determine changes in spinal motion and intradiscal pressures at immediately adjacent lumbar motion segments following anterior insertion of tapered cages. Stand-alone anterior lumbar interbody fusion (ALIF) is an effective approach in the treatment of discogenic low back pain. A tapered lumbar (LT) cage design attempts to restore physiologic lordosis and sagittal balance. We are not aware of any previous biomechanical evaluation of the effects of LT cages on adjacent motion segments. Nine fresh calf spines (L2-L5) were procured for the study. Pure moments (up to 8.5 Nm) in flexion, extension, and lateral bending were applied to the L2 vertebra in five steps through a nonconstrained loading system. With each step of loading, three-dimensional rotation at three intervertebral disc levels was obtained through a three-camera motion analysis system, and intradiscal pressures within the nucleus pulposus of the two nonoperated discs were measured with miniature transducers. The spines were tested initially intact and following paired anterior LT cage insertion. Following ALIF, small to moderate increase in motion was found at both adjacent segments in flexion (superior: 12.5%, P < 0.05; inferior: 11.3%, P < 0.02) and lateral bending (superior: 7.8%, P < 0.02; inferior: 6.6%, P < 0.02). An increase in intradiscal pressure was noted at the superior adjacent segment under flexion (21%, P < 0.01) and lateral bending (16%, P < 0.03). Intradiscal pressure changes at the inferior adjacent level were not significant. Statistically significant changes in intradiscal pressures and motion were found at the adjacent levels following a single-level stand-alone ALIF procedure using paired LT cages.

The Correlation Between Preoperative Disc Space Height and Clinical Outcomes After Anterior Lumbar Interbody Fusion

To determine whether preoperative disc space height (DSH) influences the clinical outcomes of patients diagnosed with single-level symptomatic discogenic disease and treated with a stand-alone anterior lumbar interbody fusion with two tapered threaded fusion cages, we performed a retrospective analysis of 392 patients. Preoperative radiographs were used to establish four study groups based on the patients' DSH: the tall disc group: DSH >15 mm; the intermediate tall group: DSH ranging from 10 to 15 mm; the intermediate collapsed group: DSH ranging from 5 to 10 mm; and the collapsed disc group: DSH <5 mm. All of the patient groups exhibited improvement in their clinical outcomes. However, patients in the collapsed disc group (DSH of <5 mm) tended to have earlier and greater improvement in Oswestry Disability Index scores, Physical Component Summary scores of the Short Form-36, and Visual Analog Scale scores for low back pain. Symptomatic disc degeneration can be readily identified with plain radiographic findings, and patients' symptoms can often be relieved predictably with a stand-alone interbody fusion procedure.

6:00 176. Salvage posterolateral fusion for failed anterior interbody fusion with titanium and bone cages

BACKGROUND CONTEXT: Some patients who undergo stand-alone anterior lumbar interbody fusion (ALIF) with bone or titanium cages fail to improve. One cause of clinical failure is pseudarthrosis, which may or may not be apparent on radiographs. Posterolateral fusion (PLF) with transpedicular instrumentation may be an effective salvage surgery for these patients.

Bilateral Pedicle Fractures Following Anterior Dislocation of the Polyethylene Inlay of a ProDisc® Artificial Disc Replacement

An unusual complication resulting from an artificial disc replacement for lumbar degenerative disc disease and its treatment are reported To describe the clinical circumstance, radiologic findings, treatment, and outcome of bilateral pedicle fractures associated with dislocation of the polyethylene inlay of a ProDisc replacement at L5/S1 level. To the authors' knowledge, no published reports in the English literature have described bilateral pedicle fractures following a single level artificial lumbar total disc replacement. A 30-year-old male underwent a ProDisc total disc replacement at L5/S1 level for discogenic pain. Six-week postoperative assessment showed improvement in the visual analog and Oswestry scores. Assessment at 18 weeks postoperatively for acute pain revealed an anterior slip of the superior plate component, and computerized tomography showed bilateral pedicle fractures of the fifth lumbar vertebra. At surgery, the poly insert was found to have dislocated anteriorly. A salvage interbody fusion was then performed using the stand-alone anterior lumbar interbody fusion cage. The most recent review confirmed radiologic evidence of fusion with improvement in the subjective evaluation scores We hypothesize that the current implant design in which the contribution to lordosis angle is purely from the superior component may be responsible for the reported complication. We suggest that dividing the contribution equally between both endplates might increase the stability, and this has been discussed with the manufacturers.

A new classification system for degenerative disc disease of the lumbar spine based on magnetic resonance imaging, provocative discography, plain radiographs and anatomic considerations

Prior attempts to classify degenerative disc disease (DDD) of the lumbar spine have been based on magnetic resonance imaging (MRI) signal intensity. Internal disruption of the disc is not reliably diagnosed by MRI alone. No attempt has been made to include provocative discography and plain radiographs. The intervertebral joint is a three-joint complex consisting not only of the end plate–disc–end plate joint of the anterior column, but also the two facet joints of the posterior column. To date, no classification system for lumbar DDD has taken into account the state of degeneration of the facet joints. In the past this may not have been important with regard to arthrodesis. But as early experience indicates, the degree of degeneration of the facet joints is paramount to the clinical success of an artificial disc replacement. As we transition from intervertebral joint fusion to intervertebral joint replacement, it is imperative that the state of degeneration of the three-joint complex be classified in such a way that all can evaluate lumbar DDD using the same terminology. A new classification system for lumbar DDD is presented. The intervertebral segment is graded in two parts: the anterior column and the posterior column, based on MRI, discography and plain radiographs. The system will be validated through a blinded study of 100 patients requiring stand-alone anterior lumbar interbody fusion or circumferential fusion. Although the debate over which discs are best treated surgically with indication for total disc replacement, or with indication for fusion will continue for some time, the basic understanding of intervertebral disc and posterior facet joint pathology, classified and validated in a simple forthright manner, is essential as we move forward with artificial disc technology.

A Prospective, Randomized Controlled Clinical Trial of Anterior Lumbar Interbody Fusion Using a Titanium Cylindrical Threaded Fusion Device

A prospective, randomized, controlled clinical trial comparing a cylindrical threaded titanium cage to a femoral ring allograft control for anterior lumbar interbody fusion. To compare these two implants with regard to arthrodesis. Secondary outcome measures included pain relief, neurological status, and general health status. Anterior lumbar interbody fusion is a well-accepted procedure using trapezoidal femoral ring allografts or cylindrical titanium cages. Clinical and biomechanical studies evaluating these two distinct constructs are numerous; however, no prospective, randomized study comparing them has been done. A multicenter trial of 140 patients: 78 were randomized to the cylindrical threaded titanium cage device treatment arm and 62 patients randomized into the control group. All had autogenous iliac crest bone graft packed into the device. All patients had a single-level stand-alone anterior lumbar interbody fusion at either the L4-L5 or L5-S1 interspace for symptomatic degenerative disc disease. Radiographic fusion data were collected as well as multiple types of outcome data, including pain/disability scores, neurologic status, and overall health. At 12 months, 97% of the cylindrical threaded titanium cage device group and 40% of the control group demonstrated radiographic fusion. At 24 months, 97% of the cylindrical threaded titanium cage group and 52% of the control group showed radiographic fusion. These fusion rate differences are statistically significant (P < 0.001). The Oswestry and neurologic scores were not significantly different between groups. This is the first prospective, randomized, multicenter clinical trial that compares fusion cage results to control data. Cylindrical threaded titanium cages have a higher fusion rate, comparable improvements in clinical outcome (Oswestry, Low Back Pain Questionnaire, SF-36), and fewer secondary supplemental fixation procedures compared to the femoral ring allograft control.

Anterior lumbar interbody fusion with processed sea coral (coralline hydroxyapatite) as part of a circumferential fusion.

A retrospective review of 20 patients undergoing circumferential lumbar fusion with coralline hydroxyapatite blocks anteriorly and autograft with transpedicular or translaminar facet screw fixation posteriorly. To examine the efficacy of coralline hydroxyapatite as a bone graft substitute for anterior lumbar interbody fusion. Autograft is the gold standard for bone grafting in the anterior lumbar spine. Harvesting bone from the iliac crest leads to significant postoperative pain and morbidity. Femoral ring allograft is a widely used alternative to autograft but has some inherent problems. Coralline hydroxyapatite was shown to be 100% successful for anterior cervical fusion when combined with rigid plating. A retrospective review of 20 patients with low back pain and indicated for surgical intervention. A circumferential instrumented fusion was performed with coralline hydroxyapatite blocks anteriorly and transpedicular or translaminar facet fixation and autograft posteriorly. All patients reached a minimum 3-year clinical and radiologic follow-up. Radiographic follow-up yielded a solid arthrodesis rate of 93.8% by level (30 of 32 disc spaces) and 90% by patient (18 of 20). Clinical follow-up generated a mean pain reduction of 61.8% with clinical success demonstrated in 80% (16 of 20) of all patients who reported good or excellent pain relief. Eight of 12 (66.7%) patients employed before surgery returned to work in some capacity. Coralline hydroxyapatite is a practicable anterior lumbar interbody fusion alternative to autograft and allograft as part of a circumferential fusion with rigid posterior fixation. It is not recommended for stand-alone anterior lumbar interbody fusion without further study.

An economic analysis of bone morphogenic protein

Purpose of study: An economic model was developed to compare costs of bone morphogenic protein (BMP) versus autogenous iliac crest bone graft (AICBG) for spinal fusion. Fusion and complications rates were based on two multicenter, randomized, clinical trials comparing stand-alone anterior lumbar interbody fusion with BMP (recombinant human BMP-2 [rhBMP-2]) on an absorbable collagen sponge versus AICBG in either a tapered cylindrical cage (LT-CAGE clinical trial) or a threaded cortical bone dowel (Bone Dowel clinical trial). The objective of this study was to determine the effect of use of BMP on the process of care and costs of spinal fusion during the index hospitalization and in the subsequent 2 years. The economic model was developed based on data from clinical trials, peer-reviewed literature and expert opinion.Methods used: We identified and assigned costs to medical resources that would increase or decrease with the use of BMP. Direct medical costs in two distinct contexts were considered: those incurred by the hospital during the index hospitalization and those incurred during both the index hospitalization and 2 years afterwards. The price of BMP in the base case analyses was $3,380. The costs are reported in 2001 US dollars.of findings: In the base case analysis over a period of 2 years, total direct medical costs for spinal fusion were similar for BMP and AICBG ($9 difference favoring BMP) using clinical trial fusion rates of 94.5% and 88.7%, respectively (LT-CAGE clinical trial). In a sensitivity analysis over a period of 2 years using fusion rates of 100% for rhBMP-2 and 68.4% for AICBG, respectively (Bone Dowel clinical trial), BMP resulted in $4,564 in savings. In the base case analysis from a hospital perspective (index hospitalization only), nearly half of the $3,380 price of BMP was offset.Relationship between findings and existing knowledge: The upfront price of BMP is likely to be offset to a significant extent by reductions in the use of other medical resources, particularly if costs incurred during the 2-year period after the index hospitalization are taken into account.Overall significance of findings: Under the base case assumptions (fusion success rates of 94.5% for rhBMP-2 and 88.7% for AICBG; LT-CAGE clinical trial) over a 2-year period, cost-neutrality was achieved at a BMP price of $3,389. Sensitivity analyses indicate that under an alternative scenario about the fusion success rates (100.0% for rhBMP-2 and 68.4% for AICBG; Bone Dowel clinical trial), cost-neutrality would be achieved over a 2-year period at a BMP price of $7,944.Disclosures: Device or drug: rhBMP-2. Status: not approved.Conflict of interest: David Polly, Jr., grant research support: Medtronic Sofamor Danek and De Puy Acromed.