The effect of hubbing on the pull-out strength of lateral mass screws in the cervical spine: a biomechanical experiment.

STUDY DESIGN: This was a cadaveric biomechanical experiment. OBJECTIVE: To compare the pull-out strength of polyaxial screws that are either hubbed or not hubbed when inserted into the lateral mass. SUMMARY OF BACKGROUND DATA: It has been shown in a study on pedicle screws in the thoracic spine that "hubbing" the head of the screw against the dorsal laminar cortex results in significantly lower pull-out strength of the screws. MATERIALS AND METHODS: Fifteen segments of the human cervical spine (from C3 to C7) were prepared. Polyaxial screws 3.5 mm in diameter were used. On one side screws 12 mm in length were inserted until the screw head touched the lateral mass; they were then turned 2.5 more times until they were fully hubbed (hubbed screws). On the other side screws 14 mm in length were inserted until the screw head just touched the lateral mass (nonhubbed screws). The 2 mm difference in length was to ensure that the screws were buried to the same length. All screws inserted into the lateral masses underwent tensile pull-out by applying a tensile force down the long axis of the screw. The difference in pull-out strength between the 2 groups was evaluated using a nonparametric paired test (the Wilcoxon signed rank test), which compared side to side on each vertebra. RESULTS: One specimen was excluded because of cement breakage during the biomechanical test. A total of 14 vertebrae were tested. Four vertebrae in the hubbed group showed small fractures or cracks around the screw hole after screw insertion. In a side to side comparison, the hubbed screws had significantly lower pull-out strengths as compared with the nonhubbed screws (P=0.033). CONCLUSIONS: Hubbing of lateral mass screws lowers the potential pull-out strength of the screws as compared with the pull-out strength of nonhubbed screws. Thus, hubbing of lateral mass screws, on the basis of the parameters applied in this study, is not recommended.

Apatite-coated collagen sponge for the delivery of bone morphogenetic protein-2 in rabbit posterolateral lumbar fusion.

Bone morphogenetic proteins (BMPs) need an effective delivery system for efficient bone regeneration. In this study, we evaluated the efficiency of an apatite-coated collagen sponge for the long-term delivery of BMP-2 in a rabbit model of lumbar posterolateral fusion. A total of 15 rabbits, divided into three groups, underwent posterolateral lumbar fusion. The first group (control group) received uncoated collagen sponges without BMP-2. The second group (uncoated group) received uncoated collagen sponges with BMP-2 (40 µg each side). The third group (apatite-coated group) received apatite-coated collagen sponges with the same level of BMPs (40 µg each side). All rabbits were euthanized 6 weeks after operation, and the fusion status was assessed by radiographic study, micro-CT, manual palpation, biomechanical study, and histological examination. Fusion rates as determined by radiographic study, micro-CT, and manual palpation showed that the apatite-coated group had a significantly higher rate of fusion than the control group (P = 0.024), while the uncoated group did not (P = 0.083). Biomechanical study showed significantly higher tensile strength in the apatite-coated group than the uncoated group (P = 0.032). Denser trabeculations were found in the apatite-coated group compared with the uncoated group. It is concluded that the use of apatite-coated collagen sponges for BMP-2 delivery enhanced bone regeneration.

Controlled delivery of low-dose bone morphogenetic protein-2 using heparin-conjugated fibrin in the posterolateral lumbar fusion of rabbits.

The heparin-conjugated fibrin (HCF) system has been developed to deliver bone morphogenetic proteins (BMPs) for a long-term period and thus enhance bone regeneration. In the present study, we tested the effectiveness of the delivery system for spinal fusion with a very low dose of BMP-2. A total of 15 rabbits underwent posterolateral lumbar spine, divided into three groups. The control group received only collagen sponges without BMP-2, another group (BMP-only group) received collagen sponges loaded with BMP-2 (10 µg each side), and the last group (BMP/HCF group) received collagen sponges filled with HCF loaded with BMP-2 (10 µg each side). All animals were euthanized 8 weeks after surgery, and the fusion was assessed by radiographs, manual palpation, computed tomography scan, and mechanical testing. No case in the BMP/HCF group or in the control group achieved solid fusion, while all cases in BMP-only group showed evidence of solid fusion. BMP/HCF group had significantly lower fusion rate and tensile strength than BMP-only group at the dose of 10 µg of BMP-2. The HCF long-term delivery system with the low dose of BMP-2 (10 µg) is ineffective for the induction of lumbar posterolateral fusion in the rabbits.

Effects of alendronate on lumbar posterolateral fusion using hydroxyapatite in rabbits.

There are controversies regarding the effect of alendronate on spine fusion. In order to study the effects of alendronate on fusion with porous hydroxyapatite, a total of 47 rabbits underwent posterolateral lumbar fusion. The rabbits received saline (control group), alendronate 0.5 mg/kg/week (low-dose group), or alendronate 1 mg/kg/week (high-dose group) per oral beginning 2 weeks before surgery. All animals were euthanized 12 weeks after surgery, and the extent of fusion was assessed by radiographs, manual palpation, computed tomography (CT) scan, mechanical testing, and histologic examination. The fusion rates by manual palpation, radiography, and CT scan were similar in all groups. There was no significant difference in pixel optic density from the CT scan. Biomechanical testing showed the tensile strength of the control group was higher than that of the treatment group including the low- and high-dose group. In histologic examination, the fusion masses of control animals were characterized by a higher predominance of well-incorporated, trabeculated bone with a prominent marrow element. The treatment group showed a higher proportion of woven bone structures and thicker bony trabeculae. There was no significant difference in the fusion rate, but the tensile strength of treatment group was significantly lower. Histologic examination showed that alendronate inhibited bone resorption and remodeling.

Lumbar posterolateral fusion using heparin-conjugated fibrin for sustained delivery of bone morphogenic protein-2 in a rabbit model.

We had devised a heparin-conjugated fibrin (HCF) system to deliver bone morphogenic proteins (BMPs) for a long-term period to enhance bone regeneration. In the present study, we tested the effectiveness of the delivery system for spinal fusion in a rabbit model. A total of 15 rabbits underwent posterolateral lumbar spine fusion with BMP-2 (50 µg per collagen sponge). The control group received only collagen sponges without BMP-2, another group (short-term delivery [SD] group) received collagen sponges filled with fibrin gel loaded with BMP-2, and the third group (long-term delivery [LD] group) received collagen sponges filled with HCF loaded with BMP-2. All animals were euthanized 8 weeks after surgery, and the fusion was assessed by radiographs, manual palpation, computed tomography, and mechanical testing. The fusion rate was significantly higher in the LD group using HCF than in the SD group or in the control group. Biomechanical testing showed the tensile strength was also significantly higher in the LD group using HCF than in other groups. The HCF system can provide a good option for the delivery of BMP-2 on posterolateral lumbar spine fusion.

Efficacy of Postural Reduction of Vertebral Compression Fracture with Extension Lateral Radiograph Before Vertebroplasty.

OBJECTIVE: This retrospective comparative study aimed to evaluate the efficacy of postural reduction of vertebral compression fracture (VCF) using the hyperextension posture before vertebroplasty (VP). METHODS: Sixty-five consecutive patients who underwent VP were retrospectively reviewed. Thirty patients who underwent passive expansion of compression fracture before VP (postural reduction vertebroplasty [PRV] group) were compared with 35 patients who underwent in situ vertebroplasty (ISV group). Patient characteristics, complications, local kyphosis angle (LKA), Cobb angle, sagittal index (SI), anterior body height (ABH), and posterior body height were assessed. RESULTS: LKA and SI significantly improved from preoperative measurements at the final follow-up in the ISV and PRV groups. ABH significantly improved only in the PRV group and ABH improvement at the final follow-up was significantly greater in the PRV group. However, there were no significant differences in LKA, Cobb angle, SI, ABH, and posterior body height at the final follow-up. Within the subgroup analysis of patients with preoperative ABH ≤15 mm, ABH and amount of ABH improvement at final follow-up were significantly greater in the PRV group. CONCLUSIONS: Hyperextension postural reduction showed superior ABH improvement. It also showed higher ABH at the final follow-up when performed on patients with preoperative ABH ≤15 mm. Although routine hyperextension postural reduction should be carefully approached, postural reduction using supine extension lateral radiography would provide more effective vertebral body height restoration in patients with moderate collapse of vertebral compression fracture with ABH ≤15 mm.

Efficacy of Escherichia coli-derived recombinant human bone morphogenetic protein-2 in posterolateral lumbar fusion: an open, active-controlled, randomized, multicenter trial.

BACKGROUND CONTEXT: The efficacy and safety of recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone graft substitute in spinal fusion has been widely researched. However, no study of the efficacy and safety of Escherichia coli-derived rhBMP-2 (E.BMP-2) with a hydroxyapatite (HA) carrier has been proposed. PURPOSE: This study aimed to compare the efficacy and safety of fusion materials between E.BMP-2 and autogenous iliac bone graft in posterolateral fusion (PLF). STUDY DESIGN/SETTING: An open, active-controlled, randomized, multicenter trial was carried out. PATIENT SAMPLE: This study included 93 patients who underwent single-level lumbar or lumbosacral PLF. OUTCOME MEASURES: The primary outcome measure was computed tomography (CT)-based fusion rate at 12 and 24 weeks. Secondary outcome measures were fusion grade by radiographs and CT at 12 and 24 weeks and changes in Oswestry Disability Index (ODI), Short Form-36 (SF-36) Health Survey, and visual analogue scale (VAS). METHODS: Patients who underwent 1-level PLF (between L1 and S1) for severe spinal stenosis or grade 1 spondylolisthesis were randomized to receive E.BMP-2 with an HA carrier (E.BMP-2 group) or autogenous iliac bone graft (AIBG group). Thin-section CT (<2 mm), VAS, ODI, and SF-36 were obtained pre- and postoperatively at 12 and 24 weeks. Outcome measures were compared between the groups. RESULTS: A total of 100 patients were enrolled in this trial. Among them, 93 patients underwent planned surgery. Preoperative demographic and clinical data showed no difference between groups. CT-based fusion rates were 100.0% (41/41) for the E.BMP-2 group and 90.2% (46/51) for the AIBG group (p=.062) at 12 weeks and 100.0% (41/41) and 94.1% (48/51) (p=.251) at 24 weeks, respectively. Fusion grade based on radiographs and CT showed non-inferiority of the E.BMP-2 group compared with the AIBG group. All clinical parameters improved postoperatively. However, there was no difference in changes in VAS, ODI, or SF-36 between the groups. No serious adverse event related to E.BMP-2 was found. CONCLUSIONS: The fusion rate of E.BMP-2 was comparable with that of AIBG following PLF. Good clinical efficacy and safety of E.BMP-2 in spinal fusion were also revealed. It was also suggested that HA shows suitability as a carrier for E.BMP-2. Thus, E.BMP-2 with an HA carrier can be an alternative bone graft material in spinal fusion.

Comparison of fusion rate and clinical results between CaO-SiO2-P2O5-B2O3 bioactive glass ceramics spacer with titanium cages in posterior lumbar interbody fusion.

BACKGROUND CONTEXT: The CaO-SiO2-P2O5-B2O3 glass ceramics spacer generates chemical bonding to adjacent bones with high mechanical stability to produce a union with the end plate, and ultimately stability. PURPOSE: The authors aimed to compare the clinical efficacy and safety of CaO-SiO2-P2O5-B2O3 glass ceramics with a titanium cage that is widely used for posterior lumbar interbody fusion (PLIF) surgery in the clinical field. STUDY DESIGN/SETTING: This is a prospective, stratified randomized, multicenter, single-blinded, comparator-controlled non-inferiority trial. PATIENT SAMPLE: The present study was conducted in four hospitals and enrolled a total of 86 patients between 30 and 80 years of age who required one-level PLIF due to severe spinal stenosis, spondylolisthesis, or huge disc herniation. OUTCOME MEASURES: The Oswestry Disability Index (ODI), Short Form-36 Health Survey (SF-36), and pain visual analog scale (VAS) were assessed before surgery and at 3, 6, and 12 months after surgery. The spinal fusion rate was assessed at 6 and 12 months after surgery. METHODS: The spinal fusion rate and the area of fusion, subsidence of each CaO-SiO2-P2O5-B2O3 glass ceramics and titanium cage, and the extent of osteolysis were evaluated using a dynamic plain radiography and a three-dimensional computed tomography at 12 months after surgery. The present study was supported by BioAlpha, and some authors (JHL, C-KL, and B-SC) have stock ownership (<10,000 US dollars). RESULTS: From the plain radiography results, the 6-month fusion rates for the bioactive glass ceramics group and the titanium group were 89.7% and 91.4%, respectively. In addition, the 12-month fusion rates based on CT scan were 89.7% and 91.2%, respectively, showing no significant difference. However, the bone fusion area directly attached to the end plate of either bioactive glass ceramics or the titanium cage was significantly higher in the bioactive glass ceramics group than in the titanium group. The ODI, SF-36, back pain, and lower limb pain in both groups significantly improved after surgery, with no significant differences between the groups. No significant differences between the two groups were observed in the extent of subsidence and osteolysis. CONCLUSIONS: In lumbar posterior interbody fusion surgery, CaO-SiO2-P2O5-B2O3 glass ceramics spacer showed a similar fusion rates and clinical outcomes compared with titanium cage.

Comparison of clinical and physiological efficacies of different intermittent sequential pneumatic compression devices in preventing deep vein thrombosis: a prospective randomized study.

BACKGROUND: There are few comparative studies about the optimal method of pneumatic compression to prevent deep vein thrombosis (DVT). The aim of this prospective randomized study was to compare venous hemodynamic changes and their clinical influences between two graded sequential compression groups (an alternate sequential compression device [ASCD] vs. a simultaneous sequential compression device [SSCD]). METHODS: In total, 34 patients (68 limbs) undergoing knee and spine operations were prospectively randomized into two device groups (ASCD vs. SSCD groups). Duplex ultrasonography examinations were performed on the 4th and 7th postoperative days for the detection of DVT and the evaluation of venous hemodynamics. Continuous data for the two groups were analyzed using a two-tailed, unpaired t-test. Relative frequencies of unpaired samples were compared using Fisher exact test. Mixed effects models that might be viewed as ANCOVA models were also considered. RESULTS: DVT developed in 7 patients (20.6%), all of whom were asymptomatic for isolated calf DVTs. Two of these patients were from the ASCD group (11.8%) and the other five were from the SSCD group (29.4%), but there was no significant difference (p = 0.331). Baseline peak velocity, mean velocity, peak volume flow, and total volume flow were enhanced significantly in both device groups (p < 0.001). However, the degrees of flow and velocity enhancement did not differ significantly between the groups. The accumulated expelled volumes for an hour were in favor of the ASCD group. CONCLUSIONS: Both graded sequential compression devices showed similar results both in clinical and physiological efficacies. Further studies are required to investigate the optimal intermittent pneumatic compression method for enhanced hemodynamic efficacy and better thromboprophylaxis.

Recurrence rate of lumbar disc herniation after open discectomy in active young men.

STUDY DESIGN: A retrospective clinical study. OBJECTIVE: To estimate the recurrence rate of lumbar disc herniation after open discectomy in active young men using survival analysis. SUMMARY OF BACKGROUND DATA: There are few reports on the recurrence rate of lumbar disc herniation in young adults, even though this age group shows a higher incidence of disc herniation than the other age groups. In addition, most of the studies on the recurrence rate of disc herniation have reported percentages without regard to the effect of the time course. METHODS: Medical records were retrospectively reviewed and phone call surveys were undertaken for 241 patients aged from 20 to 39 who had undergone open discectomies over a period of 14 years. A diagnosis of recurrence was based on the development of new symptoms and magnetic resonance imaging showing compatible lesions in the same segment as the initial diagnosis. The recurrence rate was calculated using a survival analysis based on the Kaplan-Meier product-limit method and the log-rank test was used to evaluate the effect of patient age, level of occurrence, and type of herniated disc on the recurrence rate. RESULTS: The overall recurrence rate was 7.1% (17 patients) at a mean follow-up of 8.55 years, and the cumulative survival rate was 91.5% at a follow-up of 14 years. Survival analysis estimated a higher rate of recurrence at longer follow-up, although there was no recurrence after ninth year from the primary surgery. The recurrence rate was significantly higher for protruded discs compared with other types. CONCLUSION: Survival analysis provides a more accurate estimation of true recurrence rate. Protruded discs are more likely to show recurrence than other types.