Biomechanical Analysis of Cortical Versus Pedicle Screw Fixation Stability in TLIF, PLIF, and XLIF Applications.

STUDY DESIGN: Cadaveric biomechanical study. OBJECTIVES: Medial-to-lateral trajectory cortical screws are of clinical interest due to the ability to place them through a less disruptive, medialized exposure compared with conventional pedicle screws. In this study, cortical and pedicle screw trajectory stability was investigated in single-level transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), and extreme lateral interbody fusion (XLIF) constructs. METHODS: Eight lumbar spinal units were used for each interbody/screw trajectory combination. The following constructs were tested: TLIF + unilateral facetectomy (UF) + bilateral pedicle screws (BPS), TLIF + UF + bilateral cortical screws (BCS), PLIF + medial facetectomy (MF) + BPS, PLIF + bilateral facetectomy (BF) + BPS, PLIF + MF + BCS, PLIF + BF + BCS, XLIF + BPS, XLIF + BCS, and XLIF + bilateral laminotomy + BCS. Range of motion (ROM) in flexion-extension, lateral bending, and axial rotation was assessed using pure moments. RESULTS: All instrumented constructs were significantly more rigid than intact (P < .05) in all test directions except TLIF + UF + BCS, PLIF + MF + BCS, and PLIF + BF + BCS in axial rotation. In general, XLIF and PLIF + MF constructs were more rigid (lowest ROM) than TLIF + UF and PLIF + BF constructs. In the presence of substantial iatrogenic destabilization (TLIF + UF and PLIF + BF), cortical screw constructs tended to be less rigid (higher ROM) than the same pedicle screw constructs in lateral bending and axial rotation; however, no statistically significant differences were found when comparing pedicle and cortical fixation for the same interbody procedures. CONCLUSIONS: Both cortical and pedicle trajectory screw fixation provided stability to the 1-level interbody constructs. Constructs with the least iatrogenic destabilization were most rigid. The more destabilized constructs showed less lateral bending and axial rotation rigidity with cortical screws compared with pedicle screws. Further investigation is warranted to understand the clinical implications of differences between constructs.

The effects of prebiotics on growth performance and in vitro immune biomarkers in weaned pigs.

The objective of the experiment was to investigate the effects of prebiotics in nursery pigs on growth performance and immune biomarkers. Sixty-four weaned pigs (31 ± 1 d; BW 8 ± 0.1 kg) of mixed gender were housed (4 pigs/pen) in an environmentally controlled nursery with ad libitum access to feed and water over a 35-d study. Pigs were randomly assigned to one of four treatments: control (53% corn, 32% SBM, 7% fishmeal, 8% others), control + 2.5% GroBiotic-S (GS), control + 0.05% chicory (CL), or control + 0.5% chicory (CH). Feeders and pigs were weighed weekly. On day 21, blood samples were obtained from three pigs/treatment for collection of peripheral blood mononuclear cells (PBMC). Isolated PBMC were cultured and subsequently challenged with lipopolysaccharide (LPS; 20 ng/mL). Cell culture supernatants were collected for quantification of the pro- and anti-inflammatory cytokines, interleukin (IL)-8 and IL-10, respectively. Dietary treatment had no effect on BW. At days 28 to 35, pigs fed GS (790 ± 15 g), CL (704 ± 15 g), or CH (692 ± 15 g) had greater (P < 0.05) ADG compared with control (643 ± 15 g) pigs. In addition, overall (days 0-35), pigs fed GS (823 ± 18 g), CL (783 ± 18 g), or CH (782 ± 18 g) had greater (P < 0.05) ADFI compared with control, and ADFI for GS-fed pigs was greater (P < 0.05) than either CL or CH. There was no difference in G:F among treatments. In vitro LPS challenge increased (P < 0.05) IL-8 secretion from PBMC isolated from CL (23,731 ± 3,221 pg/mL) pigs compared with control (10,061 ± 3,221 pg/mL) and CH (12,411 ± 3,221 pg/mL) pigs. Secretion of IL-10 from PBMC isolated from CL (63 ± 9 pg/mL) pigs was greater (P < 0.05) compared with control (22 ± 9 pg/mL) pigs and tended (P < 0.1) to be greater compared with CH (34 ± 9 pg/mL) pigs. Results indicate that inclusion of prebiotics in nursery pig diets has positive effects on growth performance and may have immunomodulatory effects (in vitro) on cells isolated from prebiotic-fed pigs.

Effects of spray-dried porcine plasma on fecal microbiota in nursery pigs.

Spray-dried porcine plasma (SDPP) has been considered as an alternative for in-feed antibiotics to improve pig growth performance; however, the effect of SDPP on gut microbiota is unknown. The objective of this study was to evaluate effects of feeding SDPP on fecal microbial communities of nursery pigs. Ninety-six weaned pigs were assigned to 16 pens, which were allotted to two dietary treatments, including the control or the control + SDPP (5% and 2.5% SDPP inclusion in phase 1 and 2, respectively) diet. Fecal samples were collected at d 0, 7, 14, 21, and 28. Multiplex sequencing of V3 region of the 16S rRNA gene was used to characterize the bacterial community structure of fecal samples. Pearson's correlation tests were performed in Calypso to identify bacterial taxa that were either positively or negatively associated with overall growth performance. Feeding SDPP altered microbial structure at family, genus, and operational taxonomic unit (OTU) classifications; however, fecal microbes shifted with time. At the family level, Clostridiaceae increased (P < 0.001) on d 14, but decreased (P < 0.05) on d 28 in SDPP-fed pigs compared with control pigs. Decreased Veillonellaceae (P < 0.05; d 14) and Lachnospiraceae (P = 0.001; overall) were observed in SDPP-fed pigs compared with control pigs. Feeding SDPP increased lactic acid-producing bacteria (Lactobacillus delbrueckii, d 7) and cellulolytic bacteria (Ruminococcus albus, d 7; Clostridium thermocellum, d 7 and 14; and Clostridium saccharoperbutylacetonicum/beijerinckii, d 14; and Megasphaera elsdenii, d 21). On d 28, feeding SDPP decreased (P < 0.05) Clostridium difficile compared with control pigs. In conclusion, feeding SDPP altered fecal microbial communities in nursery pigs. The results of this study may provide information to help explain the positive effects associated with feeding SDPP on nutrient digestibility and gut health of nursery pigs.

MIS Expandable Interbody Spacers: A Literature Review and Biomechanical Comparison of an Expandable MIS TLIF With Conventional TLIF and ALIF.

STUDY DESIGN: Biomechanical study and review of literature on expandable lumbar interbody fusion constructs. OBJECTIVE: To evaluate the biomechanical stability of expandable interbody devices. SUMMARY OF BACKGROUND DATA: Lumbar interbody implants placed from an anterior or lateral approach are desirable due to their large size, providing a stable fusion environment. Posterior implants are typically limited by their access corridor. Expandable footprint transforaminal lumbar interbody fusion (TLIF) interbodies may allow for a minimally invasive TLIF approach with the biomechanical benefits of an anterior lumbar interbody fusion (ALIF)-sized graft; however, this requires experimental investigation. METHODS: Six cadaveric L1-sacrum segments were tested intact with pure moments of  ± 7.5  N m in flexion-extension, lateral bending, and axial rotation. Specimens received at L4-5 either a medial-lateral expandable TLIF cage (MLX-TLIF) or a conventional polyether ether ketone (PEEK) banana-shaped TLIF cage (Conv-TLIF) first. Both were tested with unilateral and bilateral pedicle screw (PS) fixation. Testing was repeated with the alternate cage and fixation. Motion marker arrays were fixed to L4 and L5 to assess range of motion. Results were compared with published data for a PEEK ALIF cage with anterior plate and a PEEK ALIF cage with bilateral PS fixation, tested under the same conditions. RESULTS: The most rigid construct was ALIF with bilateral PS fixation in flexion-extension and axial rotation, whereas MLX with bilateral PS was most rigid in lateral bending. Conv-TLIF with unilateral PS was the least rigid construct. MLX-TLIF with unilateral PS provided similar range of motion to Conv-TLIF with bilateral PS in flexion-extension and lateral bending, and ALIF with anterior plate in lateral bending. CONCLUSION: The MLX-TLIF cage with unilateral PS fixation provided comparable stability to conventional TLIF with bilateral PS fixation and ALIF with anterior plate treatments. The large footprint of the expandable cage may reduce the TLIF supplemental fixation demands and facilitate minimally invasive single-position surgery. If needed, additional stability may be achieved by using bilateral PS. LEVEL OF EVIDENCE: N/A.

A modified Bohlman technique using a novel implant for treatment of high-grade spondylolisthesis.

Several surgical options for managing high-grade spondylolisthesis have been described in the literature and range from posterior-only in situ fusion to circumferential fusion with complete reduction of the dislocation. The level of evidence supporting any one technique is weak, and to date there is no Level I or II evidence supporting any current surgical treatment option. Techniques have evolved as implant technology has advanced and surgeons have gained experience with deformity correction. Still, the paucity of cases at any one institution limits the ability to perform clinical studies in a prospective and randomized fashion. To the authors' knowledge, the use of the AxiaLif bolt in a modified Bohlman technique has not been described. In the setting of a case of symptomatic high-grade spondylolisthesis refractory to nonoperative management, the authors describe a modified Bohlman technique in which they used the AxiaLif bolt rather than the fibula graft that was originally described. They then supplemented this with pedicle screw instrumentation and an iliac crest autograft. At the 2-year follow-up exam, the patient exhibited relief of his preoperative back and leg pain and he had returned to all activities. The latest radiographs demonstrated successful fusion. A single-stage, posterior instrumented fusion in which the AxiaLif bolt is used in lieu of fibula autograft or allograft in a modified Bohlman technique is technically less demanding, does not have the morbidity associated with harvesting a fibula autograft, and carries no risk of disease transmission associated with the use of allograft.

Variation in time and magnitude of immune response and viremia in experimental challenges with Porcine circovirus 2b.

BACKGROUND: Porcine circovirus 2 is the primary agent responsible for inducing a group of associated diseases known as Porcine Circovirus Associated Diseases (PCVAD), which can have detrimental effects on production efficiency as well as causing significant mortality. The objective of this study was to evaluate variation in viral replication, immune response and growth across pigs (n = 974) from different crossbred lines. The approach used in this study was experimental infection with a PCV2b strain of pigs at an average of 43 days of age. RESULTS: The sequence of the PCV2b isolate used in the challenge was similar with a cluster of PCV2b isolates known to induce PCVAD and increased mortality rates. The swine leukocyte antigen class II (SLAII) profile of the population was diverse, with nine DQB1 haplotypes being present. Individual viremia and antibody profiles during challenge demonstrate variation in magnitude and time of viral surge and immune response. The correlations between PCV2 specific antibodies and average daily gain (ADG) were relatively low and varied between - 0.14 to 0.08 for IgM and -0.02 and 0.11 for IgG. In contrast, PCV2 viremia was an important driver of ADG decline following infection; a moderate negative correlation was observed between viral load and overall ADG (r = - 0.35, P < 0.001). The pigs with the lowest 10% level of viral load maintained a steady increase in weekly ADG (P < 0.0001) compared to the pigs that had the 10% greatest viral load (P < 0.55). In addition, the highly viremic group expressed higher IgM and IgG starting with d 14 and d 21 respectively, and higher tumor necrosis factor - alpha (TNF-α) at d 21 (P < 0.005), compared to low viremic group. CONCLUSIONS: Molecular sources of the observed differences in viremia and immune response could provide a better understanding of the host factors that influence the development of PCVAD and lead to improved knowledge of swine immunity.

The effect of body mass index on lumbar lordosis on the Mizuho OSI Jackson spinal table.

STUDY DESIGN: Prospective cohort study. CLINICAL QUESTION: Does the patients' body mass index (BMI) influence the degree of intraoperative lumbar lordosis in patients undergoing operative treatment on the Mizuho Orthopedic Systems Incorporated (OSI) Jackson spinal table? METHODS: Twenty-four consecutive patients undergoing posterior spinal instrumentation and fusion on the Jackson table, excluding those with sagittal malalignment, underwent standing preoperative and prone intraoperative lateral x-rays. Intervertebral body angle measurements were obtained from L1-S1 using the modified method of Cobb. Changes in angle measurements were compared to BMI using linear regression and ANOVA. RESULTS: We found a mean lordosis of 52.6° in standing preoperative x-rays compared to a prone position mean lordosis of 61.5° on the Jackson table. The mean change was 8.88° with a range of 0°-18°. A linear association between lordosis and BMI was demonstrated (P < .0022). As BMI increased, so did lordosis (correlation coefficient, 0.59). CONCLUSIONS: The current study is the first in which a correlation of patient body mass and use of the Jackson table has been evaluated. These data suggest that BMI influences lumbar lordosis on the Jackson table and that care must be used when dealing with a population with large BMI on the Jackson table. [Table: see text] The definiton of the different classes of evidence is available on page 83.

Failure of Orthofix eight-Plate for the treatment of Blount disease.

BACKGROUND: Hemiepiphysiodesis is a well-established treatment option for angular deformities of the knee. Recently, our institution began using the eight-Plate tension band device by Orthofix (McKinney, Tex) as an alternative to staples. However, several patients have returned with broken screws necessitating revision surgery. METHODS: Charts and radiographs of all patients who were treated with the eight-Plate (Orthofix) at our institution were reviewed. The diagnosis, age, amount of angular deformity, weight, and body mass index were analyzed with respect to eventual implant failure. RESULTS: Implant failure occurred in 8 (26%) of 31 proximal tibia constructs. All 8 failures occurred in patients with Blount disease and involved breakage of the tibial metaphyseal screw. The mean time to failure was 13.6 months. Eight hardware failures in 18 Blount disease extremities represent a failure rate of 44%. No implant failures occurred in the remaining diagnoses. Neither age nor degree of deformity correlated with implant failure. The failure group was significantly heavier than the nonfailure group, and the patients with Blount disease were found to be heavier than the other patients. However, no significant difference in weight was found within the Blount group regarding implant failure. In all patients whose plates did not fail, rate of correction was equal to or better than previously reported hemiepiphysiodesis studies. CONCLUSIONS: The eight-Plate (Orthofix) is a reasonable option for hemiepiphysiodesis but has an unacceptable failure rate in Blount disease (44%). There were no instances of failure in patients with other diagnoses. In Blount disease, stronger implants should be considered. Future implant designs should include stronger screws to decrease implant failure complications.