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Study Design: An experimental study., Objective: To evaluate the effectiveness of freeze-dried bone allograft (FDBA) with basic fibroblast growth factor (bFGF) fused with the polycystic kidney disease domain (PKD) and the collagen-binding domain (CBD) of Clostridium histolyticum collagenase, for the acceleration of lumbar posterolateral fusion in rats., Summary of Background Data: Reports indicate bFGF is an effective growth factor with osteogenic potential for promoting bone regeneration, although its efficiency decreases rapidly following its diffusion in body fluid from the host site. We developed a bFGF fusion protein containing the PKD and the CBD of C histolyticum collagenase (bFGF-PKD-CBD), which markedly enhanced bone formation at a relatively low concentration when applied to the surface of rat femurs in a previous study. The potential of this novel protein to accelerate bone fusion in a rat model of lumbar posterolateral fusion has yet to be investigated., Methods: Bilateral L4-L5 posterolateral fusions were performed, using 150 mg of FDBA powder per side. A total of 20 male Sprague-Dawley rats weighing 200 to 250 g/each were divided into two groups of 10 rats: FDBA was incubated with either phosphate-buffered saline (control group) or 0.58 nmol bFGF-PKD-CBD (bFGF-PKD-CBD group) before fusion surgery. The effect of bFGF-PKD-CBD was estimated using radiographs, microcomputed tomography, and histology (hematoxylin-eosin and von Kossa staining)., Results: Both grafted bone volume in the posterolateral lesion and the volume of new bone formation on the surface of laminae and spinal processes were significantly higher in the bFGF-PKD-CBD group than in the control group. Histologically, new bone formation and surrounding chondrocytes and fibroblasts were prominent in the bFGF-PKD-CBD group., Conclusion: FDBA infused with bFGF-PKD-CBD may be a promising material for accelerating spinal fusion, and the FDBA-based delivery system for localizing bFGF-PKD-CBD may offer novel therapeutic approaches to augment spinal fusion., Level of Evidence: N/A.

Study Design: Retrospective cohort analysis., Objective: To compare clinical outcomes after spine instrumentation and fusion using 3 different bone grafts in children with adolescent idiopathic scoliosis (AIS)., Summary of Background Data: Autogenous iliac crest bone graft (AIC) is the "gold standard" to promote fusion in posterior AIS operations, although the morbidity of harvest is a concern. There is limited data comparing outcomes after AIS surgery based on types of bone grafts., Methods: Children (10-18 yr) with AIS who underwent deformity correction via a posterior approach were identified in the Spinal Deformity Study Group database. All had a minimum of 2-year follow-up. Patients were subdivided into 3 groups based on bone graft used: AIC, allograft, and bone substitute (BS). Clinical data included patient demographics, operative details, postoperative analgesic use, and perioperative complications. Lenke curve type and curve magnitude changes were radiographically analyzed. The Scoliosis Research Society-30 questionnaire was used to assess clinical outcomes., Results: 461 patients met inclusion criteria (girls: 381, boys: 80; average age 14.7 ± 1.7) and consisted of 152 AIC patients (124 girls, 28 boys), 199 allograft patients (167 girls, 32 boys), and 110 BS patients (90 girls, 20 boys). There was no difference in age (P = 0.41) or gender (P = 0.82). The BS group had significantly smaller preoperative curves and shorter operative times. Postoperatively, patients who received BS had significantly longer hospital stays, used higher quantities of patient-controlled intravenous analgesia and used epidurals longer. The AIC group used patient-controlled intravenous analgesia significantly longer. There were no differences between the groups in regards to curve type, number of levels fused, postoperative infections, pseudarthrosis, reoperations for any indication, and Scoliosis Research Society-30 scores at the latest follow-up., Conclusion: Outcomes after primary posterior spinal fusion with instrumentation are not influenced by type of bone graft or substitute., Level of Evidence: 3.

Study Design: A prospective study., Objective: The aim of this study was to compare clinical and radiological efficacy of anterior cervical microdiscectomy and fusion done by the newly designed low-profile interbody spacer in cases of symptomatic cervical spine spondylosis., Summary of Background Data: There are basically 2 ways to provide interbody fusion in the degenerative cervical spine; the first is by way of an unanchored "stand-alone" bone graft or cage, and the second is with bone graft or a cage anchored with a plate. Both concepts have their own benefits as well as potential drawbacks. Low-profile angle-stable spacer Zero-P is an implant that can potentially limit the drawbacks of both these procedures. METHODS.: Prospective study collecting clinical and radiological data of 77 patients undergoing anterior cervical interbody fusion of 1 or 2 motion segments from C3-C7 was performed. Zero-P spacer was used in 44 patients (55 segments) and in 33 cases (41 segments), stabilization was done using interbody spacer and dynamic anterior cervical plate. Patients were followed a minimum of 2 years after surgery., Results: There was no significant difference in neck disability index values, presence of dysphagia (P = 0.308), and Cobb C values during follow-up (P = 0.051) between both groups. A significant difference in the first 2 values of Cobb S was found (P < 0.001), but the next course of Cobb S changes showed no difference in either group. No difference was found in the radiological stability during follow-up, and no revision surgery was done., Conclusion: The results of this study confirm biomechanical assumptions associated with the Zero-P spacer. Implantation of this new cage results in setting required biomechanical conditions in the treated segment that are comparable with those when the segment is treated with a dynamic plate. However, the potential of the mentioned implant to reduce the incidence of postoperative dysphagia was not proven on this sample of patients.

Study Design: Prospective, randomized, controlled animal study., Objective: To determine the efficacies of 2 ceramic composite bone graft extenders for promoting spinal fusion., Summary of Background Data: Although autogenous bone is still considered the "gold standard" graft material for fusion procedures, its use is associated with a number of limitations. Synthetic ceramic composites represent a class of osteoconductive materials that may be employed as supplements or even alternatives to autograft. In this study, we compared the fusion rates generated by 2 ceramic composite bone graft extenders (MasterGraft and Mozaik Strips) with that obtained with autograft in a rabbit bone paucity model., Methods: Thirty-two New Zealand white rabbits undergoing noninstrumented posterolateral lumbar fusion were randomized to 1 of the following 4 groups: 100% autograft, 50% autograft, 50% autograft with Mozaik Strip, and 50% autograft with MasterGraft Strip. The rabbits were followed postoperatively for 8 weeks at which time the spinal segments were explanted and assessed for the presence of a solid fusion., Results: The arthrodesis rates by manual palpation of the 100% and 50% autograft controls were 75% (6 of 8 animals) and 12.5% (1 of 8), respectively (P < 0.01). In the 50% autograft/Mozaik and 50% autograft/MasterGraft groups, 3/8 and 1/8 of the rabbits were determined to have fused successfully, respectively (P = 0.569). However, there were no significant differences between the fusion rate of the 50% autograft cohort and those exhibited by the Mozaik or MasterGraft animals (P = 0.569 and 1.00, respectively)., Conclusion: This study provides further evidence that the quantity of autograft may influence the process of spinal fusion such that the arthrodesis rate was significantly lower when less bone was implanted. Neither of the ceramic composite scaffolds seemed to enhance the fusion response compared to an equivalent amount of autograft alone, suggesting that these substances may need to be combined with other osteogenic materials to optimize bone production.

Study Design: A retrospective matched cohort study with control group., Objective: To compare the infection rate after posterior spinal fusion with unit rod instrumentation with or without gentamicin-impregnated allograft bone in children with cerebral palsy (CP)., Summary of Background Data: Previous studies evaluating wound infection rates after spinal fusion surgery in children with CP report an 8.7% to 10% wound infection rate. The concept of using antibiotic-loaded bone graft (AbBGF) to provide local antibiotics has been explored in high risk patients, such as those with osteomyelitis or infected joint arthroplasty. There have been no reports of using AbBGF prophylactically in spine surgery., Methods: After IRB approval, the medical records of 220 children with CP who underwent spinal fusion with unit rod instrumentation for a primary spinal deformity between January 2000 through December 2006 at a single institution were retrospectively reviewed. We evaluated the incidence of postoperative wound infection in patients with AbBGF and those without bone graft (BGF)., Results: One hundred fifty-four patients received AbBGF during spinal fusion surgery and 6 patients (3.9%) developed a deep wound infection. Ten (15.2%) of the 66 patients without AbBGF developed a deep wound infection. The difference between groups was statistically different (P = 0.003). The mean age at surgery, preoperative Cobb angle, correction rate, operative time, and estimated blood loss were not statistically different between the 2 groups (P > 0.05). The length of hospital stay was decreased in the AbBGF group (P < 0.05)., Conclusion: The incidence of deep wound infection after spinal fusion in 220 children with CP scoliosis decreased from 15% to 4% with the use of prophylactic antibiotics in the corticocancellous allograft bone.

Study Design: An in vitro biomechanical study using a calibrated distractor and a subminiature load cell in a cadaveric cervical corpectomy construct., Objective: To study the inter-relationships of defect height, graft height, and compressive and distractive forces in an anterior cervical corpectomy model., Summary of Background Data: The effects of graft size on compressive and distractive forces in cervical corpectomy remain unknown. Larger grafts afford neural decompression through anterior column distraction, but may subject the graft and vertebral bodies to excessive loads, increasing graft fracture, and subsidence risk., Methods: The intended corpectomy defect was measured radiographically in 17 specimens. A C6 corpectomy was performed and the specimens embedded in polyester resin. A distractive force was applied through a strain gauge fitted distractor to allow introduction of allograft struts fixed to a subminiature load cell. After distraction was removed, immediate compressive force was measured. The specimen was then placed in a loading frame to simulate head weight., Results: Distractive forces of 36.65, 70.90, and 118.10 N were required to insert 23, 25, and 27 mm grafts, respectively. On removal of this distraction, immediate compressive loads of 2.87, 4.74, and 8.95 N were noted. No statistically significant relationship between the intended corpectomy height and graft distraction forces was found. A statistically significant relationship was observed between distractive force required for graft insertion and immediate graft compressive force. Distractive force was also significantly related to the compressive force borne by the loaded strut graft., Conclusion: Significantly higher distractive and compressive forces were recorded with larger grafts. Intended corpectomy height was not an accurate predictor of graft loads.

Study Design: A retrospective clinical study., Objective: To assess the results of anterior strut grafting and the loss of the reduction in anterior interbody fusion and anterior interbody fusion combined with posterior instrumental fusion in pyogenic spondylodiscitis., Summary of Background Data: Resorption of the anterior graft is an ominous sign following most anterior surgery. Thus, additional posterior instrumentation has been used to prevent collapse of the anterior graft. However, its effect is controversial, and few studies have examined the fate of the anterior strut graft., Methods: Twenty-four consecutive patients underwent surgical treatment for pyogenic spondylodiscitis. The patients were divided into Group I (anterior interbody fusion) and Group II (anterior interbody fusion + posterior instrumented fusion). The sagittal angle, intervertebral height, and complications relating to the anterior graft were compared., Results: Solid bone fusion was achieved in 23 (95.8%) patients. The sagittal angle and the intervertebral height were similar in Groups I and II (P = 0.61, P = 0.89, respectively). In Groups I and II, the postoperative sagittal angle was maintained until 1 month after surgery (P > 0.05), but it decreased significantly by 3 months after surgery (P < 0.05). In Groups I and II, intervertebral height correction was maintained until 1 month after surgery (P > 0.05), but by 3 months after surgery, it had collapsed significantly (P < 0.05). Subsidence of the graft occurred through the damaged endplate. Group I included 1 case of graft dislodgement necessitating revision; there were no such cases in Group II. There were no recurrences of infection in either group., Conclusion: Reduction of intervertebral height and loss of sagittal profile occurred in both groups. Complications relating to the bone graft were more common in Group I than in Group II. Despite loss of correction, both groups had a high fusion rate without recurrence of infection. The reduction of intervertebral graft height appears to be the result of destruction of the endplate either due to surgical debridement or the infective process.

Study Design: To determine the effect of cage/spacer stiffness on the stresses in the bone graft and cage subsidence., Objective: To investigate the effect of cage stiffness on the biomechanics of the fused segment in the lumbar region using finite element analysis., Summary of Background Data: There are a wide variety of cage/spacer designs available for lumbar interbody fusion surgery. These range from circular, tapered, rectangular with and without curvature, and were initially manufactured using titanium alloy. Recent advances in the medical implant industry have resulted in using medical grade polyetheretherketone (PEEK). The biomechanical advantages of using different cage material in terms of stability, subsidence, and stresses in bone graft are not fully understood., Methods: A previously validated 3-dimensional, nonlinear finite element model of an intact L3-L5 segment was modified to simulate posterior interbody fusion spacers made of PEEK ("E" = 3.6 GPa) and titanium ("E" = 110 GPa) at the L4/5 disc with posterior instrumentation. Bone graft ("E" = 12 GPa) packed between the spacers in the intervertebral space was also simulated. The posterior lumbar interbody fusion spacer with instrumentation and graft represent a simulation of the condition present immediately after surgery., Results: The peak centroidal Von Mises stresses in the graft bone increased by at least 9-fold with PEEK spacers as compared to titanium spacer. The peak centroidal Von Mises stresses in the endplates increased by at least 2.4-fold with titanium spacers over the PEEK spacers. These stresses were concentrated at places where the spacer interfaced with the endplate. The stiffness of the spacer did not affect the relative motion (stability) across the instrumented (L4/5) segment., Conclusions: Spacers less stiff than the graft will: (1) provide stability similar to titanium cages in the presence of posterior instrumentation, (2) reduce the stresses in endplates adjacent to the spacers, and (3) increase the load transfer through the graft, as evident from the increase in stresses in graft.

Study Design: Fourteen sheep were fused using anterior interbody implants at C2-C3 and C4-C5 and followed for 6 months., Objective: To evaluate the effect of absorbable and nonabsorbable implants on fusion rate, cage migration, and implant integrity., Summary of Background Data: Despite the high clinical success rate with metallic plates and interbody grafting, complications such as dysphagia, imaging artifacts, and revision difficulties exist. Less permanent and lower profile implants could minimize these problems., Methods: Four treatments were studied: 1) carbon fiber-reinforced polymer (CFRP) cage alone, 2) CFRP cage with an absorbable tension band, 3) absorbable cage with an absorbable tension band, and 4) absorbable cage with a titanium plate. Fusion was assessed using radiographs, biomechanical testing, and micro-CT analysis., Results: Treatments with the CFRP cage alone had the lowest fusion rate at 3 months (2/6) and 6 months (4/6). The CFRP cage with the absorbable strap treatments had 5/6 fusions at 6 months. The absorbable cage with absorbable strap also had 5/6 fusions, but two of the cages fractured. The absorbable cage with titanium plate had 5/6 fusions, but the one partial fusion was attributed to poor screw and plate placement., Conclusion: Using both absorbable and nonabsorbable implants, high fusion rates were achieved in the challenging sheep cervical spine model. However, the absorbable cages were not able to withstand the mechanical forces during the 6-month survival period.

Study Design: This is a retrospective, sequential cohort study of 34 patients treated by anterior instrumented fusion with single solid rod, single screw constructs with at least 2-year follow-up. Sixteen of the patients received structural grafts as interbody spacers in disc levels below T12, while the other 18 patients received only morselized rib autograft., Objective: To determine if structural interbody grafts preserve sagittal alignment better than morselized rib autograft., Summary of Background Data: Some studies have shown that structural grafts are more effective in preserving sagittal alignment, while others have found them to be no more effective than morselized rib graft., Methods: Anterior-posterior radiographs were measured for primary, secondary, and fractional Cobb curves, and C7-sacrum plumb lines. Lateral radiographs were measured for: T5-HIV (highest instrumented vertebrae), instrumented levels, LIV (lowest instrumented vertebrae)-S1, T12-LIV, and T12-S1 angles, C7-sacrum plumb lines, and LID-A (lowest instrumented disc-angle)., Results: The increase in kyphosis from preoperative to follow-up radiographs of the angle between T12-LIV was significantly more for the patients with morselized rib graft compared with those with structural grafts, 9 degrees and 1 degree, respectively (P < 0.05)., Conclusions: The structural grafts placed in disc spaces below T12 were able to maintain sagittal alignment over this region, while the spines that received only morselized rib graft collapsed into kyphosis.

Study Design: A finite-element study of posterior alone or anterior/posterior combined instrumentation following total spondylectomy and replacement with a titanium mesh cage used as an anterior strut., Objectives: To compare the effect of posterior instrumentation versus anterior/posterior instrumentation on transmission of the stress to grafted bone inside a titanium mesh cage following total spondylectomy., Summary of Background Data: The most recent reconstruction techniques following total spondylectomy for malignant spinal tumor include a titanium mesh cage filled with autologous bone as an anterior strut. The need for additional anterior instrumentation with posterior pedicle screws and rods is controversial. Transmission of the mechanical stress to grafted bone inside a titanium mesh cage is important for fusion and remodeling. To our knowledge, there are no published reports comparing the load-sharing properties of the different reconstruction methods following total spondylectomy., Methods: A 3-dimensional finite-element model of the reconstructed spine (T10-L4) following total spondylectomy at T12 was constructed. A Harms titanium mesh cage (DePuy Spine, Raynham, MA) was positioned as an anterior replacement, and 3 types of the reconstruction methods were compared: (1) multilevel posterior instrumentation (MPI) (i.e., posterior pedicle screws and rods at T10-L2 without anterior instrumentation); (2) MPI with anterior instrumentation (MPAI) (i.e., MPAI [Kaneda SR; DePuy Spine] at T11-L1); and (3) short posterior and anterior instrumentation (SPAI) (i.e., posterior pedicle screws and rods with anterior instrumentation at T11-L1). The mechanical energy stress distribution exerted inside the titanium mesh cage was evaluated and compared by finite-element analysis for the 3 different reconstruction methods. Simulated forces were applied to give axial compression, flexion, extension, and lateral bending., Results: In flexion mode, the energy stress distribution in MPI was higher than 3.0 x 10 MPa in 73.0% of the total volume inside the titanium mesh cage, while 38.0% in MPAI, and 43.3% in SPAI. In axial compression and extension modes, there were no remarkable differences for each reconstruction method. In left-bending mode, there was little stress energy in the cancellous bone inside the titanium mesh cage in MPAI and SPAI., Conclusions: This experiment shows that from the viewpoint of stress shielding, the reconstruction method, using additional anterior instrumentation with posterior pedicle screws (MPAI and SPAI), stress shields the cancellous bone inside the titanium mesh cage to a higher degree than does the system using posterior pedicle screw fixation alone (MPI). Thus, a reconstruction method with no anterior fixation should be better at allowing stress for remodeling of the bone graft inside the titanium mesh cage.

Study Design: A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate modifications to a plain collagen sponge to deliver recombinant human bone morphogenetic protein-2 (rhBMP-2)., Objectives: To evaluate the feasibility of enhancing the delivery of rhBMP-2 with the established collagen sponge carrier by adding biphasic ceramic phosphate (BCP) granules (15% hydroxyapatite, 85% tricalcium phosphate) or allograft chips to provide compression resistance for posterolateral spine arthrodesis., Summary of Background Data: Recombinant human bone morphogenetic protein-2 was successfully delivered with a resorbable collagen sponge in a rabbit intertransverse process fusion model. Success in nonhuman primates required a higher dose (6-9 mg) of rhBMP-2 and a more compression-resistant matrix (ceramic) than plain collagen. The limitation of the ceramic carrier was its radiopacity, which made radiographic detection of new bone formation difficult., Methods: Nine adult rhesus monkeys underwent bilateral posterolateral intertransverse process arthrodesis at L4-L5. The animals were divided into three groups (n = 3 each) based on the graft material implanted: 1) autogenous iliac crest bone (5 cm3/side); 2) collagen sponge and 15:85 BCP granules loaded with rhBMP-2 (3 mg/side); and, 3) collagen sponge and allograft chips loaded with rhBMP-2 (3 mg/side). The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, computed tomographic scans, and histology were used to assess fusion., Results: All six monkeys with rhBMP-2 delivered in the collagen/15:85 BCP carrier and the collagen/allograft chips carrier achieved solid spine fusions, whereas only one of three animals fused with autogenous bone graft. Histologic analysis of the bone induced by rhBMP-2 showed normal trabecular bone and bone marrow elements., Conclusions: The addition of either 15:85 BCP granules or allograft bone chips to the existing resorbable collagen sponge matrix enhanced delivery of rhBMP-2 in the posterolateral spine. The combination matrices were more compression resistant and had improved radiographic resorption properties that permitted easy radiographic visualization of new bone. In addition, a lower dose of rhBMP-2 (3 mg/side) was successful compared with the dose previously used with the plain collagen sponge (6 mg/side).

Objectives: To elucidate the cause of late operative site pain in six cases of scoliosis managed with Isola posterior instrumentation that required removal of the implants., Method: Microbiologic examination of wound swabs and enriched culture of operative tissue specimens was undertaken in all cases. Histologic study of the peri-implant membranes also was conducted., Results: The presentation in all cases was similar: back pain appearing between 12-20 months after surgery, followed by a local wound swelling leading to a wound sinus. In only one of these cases was the discharge positive for bacterial growth. Implant removal was curative. Histologic examination of tissue specimens revealed a neutrophil-rich granulation tissue reaction suggestive of an infective etiology despite the failure to isolate organisms. Within the granulation tissue was metallic debris that varied from very sparse to abundant from fretting at the distal cross-connector junctions. A review of recent literature describing similar problems suggests that late onset spinal pain is a real entity and a major cause of implant removal., Conclusions: On reviewing the evidence for an infective etiology versus a metallurgic reaction etiology for these cases of late onset spinal pain, it was concluded that a subacute low-grade implant infection was the main cause. Histologic findings would seem to confirm low-grade infection. There may be more than one causative factor for late operative site pain, as it is possible that fretting at cross connection junctions may provide the environment for the incubation of dormant or inactive microbes.

The strength of saw-harvested vs. osteotome-harvested Smith-Robinson iliac crest grafts from five fresh frozen cadavers was compared. Matched pairs of grafts were harvested, one with a saw and the other with an osteotome from equivalent locations on the two iliac crests of each pelvis. Grafts were tested to failure in axial compression, and load-displacement curves were recorded for each test. Yield load and displacement, ultimate load, and stiffness were calculated, and statistical analysis was performed with the Student t test and three-way analysis of variance. Evaluation of the 66 pairs of grafts revealed that saw-harvested grafts were consistently stronger than were matched grafts harvested with an osteotome. The middle third of the iliac crest produced significantly stronger grafts, and those harvested from younger donors were significantly stronger than those obtained from older donors. Of even greater clinical relevance, saw-harvested grafts were stiffer than osteotome-harvested grafts. Based on these findings, it is recommended that iliac crest grafts harvested for spine fusion be obtained with an oscillating saw rather than with an osteotome.