Early Radiographic and Clinical Outcomes Study Evaluating an Integrated Screw and Interbody Spacer for One- and Two-Level ACDF.

BACKGROUND: Multiple techniques and implants can be used in ACDF, the newest of which are integrated cage and screw constructs. These devices may be beneficial over anterior plate constructs due to a negligible anterior profile that may reduce dysphagia. The goal of this study is to review the early radiographical and clinical results associated with a low profile integrated intervertebral cage in one- and two-level anterior column fusions. METHODS: Fusion rates, incidence of hardware failure and deformity correction were assessed through 1 year. Patientreported scores, including VAS for neck pain, and improvements in axial neck pain and neurologic deficit from the preoperative baseline were quantified at 3, 6 and 12 months post-operatively. The incidence of dysphagia was recorded. RESULTS: Lordosis and disc space height at the operated levels increased an average of 4.5° and 3.3mm after device placement (p<0.001). Sagittal plane correction was maintained at 1 year. VAS improved from an average of 5.1 preoperatively to 3.1 immediately postoperatively and was maintained at 12 months. At 3 months, patient-reported improvements in axial neck pain and neurologic deficit were 85% and 93%, respectively. Reported improvements were sustained for both parameters at 12 months (77% and 86%, respectively). Fusion was noted in 93% of the operated levels. There were two documented cases of dysphagia that lasted more than 5 weeks, both following two level ACDFs with the test device (3.5% rate of chronic dysphagia). CONCLUSIONS: The low profile integrated device improved lordosis at the operated level that was maintained at 1 year. Fusion rates with the new device are consistent with ACDF using anterior plating. In combination with improvements in pain and a minimal rate of dysphagia, study findings support the use of integrated interbody spacers for use in one- and two-level ACDF procedures. LEVEL OF EVIDENCE: Level IV, Case Series.

Biomechanical analysis of an interbody cage with three integrated cancellous lag screws in a two-level cervical spine fusion construct: an in vitro study.

BACKGROUND CONTEXT: Despite an increase in the clinical use of no-profile anchored interbody cages (AIC) for anterior cervical discectomy and fusion (ACDF) procedures, there is little published biomechanical data describing its stabilizing effect relative to the traditional anterior plating technique over two contiguous levels. PURPOSE: To biomechanically compare the acute stability conferred by a stand-alone interbody fusion device with three integrated fixation screws ("anchored cage") with a traditional six-hole rigid anterior plate in a two contiguous levels (C4-C5+C5-C6) fusion construct. We hypothesized that the anchored cage would confer comparable segmental rigidity to the cage and anterior plate construct. STUDY DESIGN: A biomechanical laboratory study using cadaveric human cervical spines. METHODS: Seven (n=7) cadaveric human cervical spines (C3-C7) were subjected to quasistatic, pure-moment loading (±1.5 Nm) in flexion-extension (flex/ext), right/left lateral bending (RB/LB), and right/left axial rotation (RR/LR) for the following test conditions: intact; after discectomy and insertion of the AIC at C4-C5 and C5-C6 with anchoring screws engaged; after the removal of the integrated anchoring screws and instrumentation of an anterior locking plate (ALP) over both levels; and cage-only (CO) configuration with screws and anterior plate removed. Intervertebral range of motion (ROM) at the instrumented levels was the primary biomechanical outcome. RESULTS: Flex/ext, RB/LB, and RR/LR ROMs were significantly reduced (p<.001) over both levels by AIC and ALP constructs relative to the CO construct. Significant reduction in flex/ext motion was achieved with the ALP (6.8±3.7) relative to the AIC (10.2°±4.6°) (p=.041) construct. No significant differences were seen in ROM reductions over the two levels between the AIC and APL groups in lateral bending or axial rotation (p>.826). CONCLUSIONS: The anchored cage fusion construct conferred similar acute biomechanical stability in lateral bending and axial rotation ROMs relative to rigid anterior plating. We identified a statistically significant reduction (Δ=3.4°, combined over two levels) in sagittal plane ROM conferred by the ALP relative to the AIC construct. Our biomechanical findings may support the clinical use of no-profile integrated interbody devices over two contiguous levels in ACDF.

Biomechanical analysis of impending femoral neck fractures: the role of percutaneous cement augmentation for osteolytic lesions.

BACKGROUND: Management of impending pathologic femoral neck fractures includes internal fixation, arthroplasty and megaprostheses. The study aim was to determine the augmentative effect of cement injection for minimally invasive treatment of femoral neck lesions. METHODS: Twenty-seven cadaveric femora received a simulated osteolytic lesion previously shown to decrease the femur's failure load by 50%. Specimens were allocated to three groups of nine and loaded to failure in simulated single-leg stance: (1) percutaneous cementation + internal fixation (PCIF); (2) percutaneous cementation (PC); and (3) internal fixation (IF). Lesion-only and augmented finite element models were virtually loaded and stresses were queried adjacent to the lesion. FINDINGS: PCIF resulted in the largest failure load though the increase was not significantly greater than the PC or IF groups. Inspection of the PC and PCIF specimens indicated that the generation of a cement column that spanned the superior and inferior cortices of the femoral neck increased failure loads significantly. Finite element analysis indicated that IF and PCIF constructs decreased the stress adjacent to the lesion to intact femur levels. Cementation without superior-to-inferior femoral neck cortical contact did not restore proximal femoral stress toward the intact condition. INTERPRETATION: Internal fixation alone and internal fixation with or without cementation produce similar levels of mechanical augmentation in femora containing a high-risk lesion of impending fracture. A cement injection technique that produces a cement column contacting the superior and inferior femoral neck cortices confers the highest degree of biomechanical stability, should percutaneous cementation alone be performed.

Biomechanics of an integrated interbody device versus ACDF anterior locking plate in a single-level cervical spine fusion construct.

BACKGROUND CONTEXT: No profile, integrated interbody cages are designed to act as implants for cervical spine fusion, which obviates the need for additional internal fixation, combining the functionality of an interbody device and the stabilizing benefits of an anterior cervical plate. Biomechanical data are needed to determine if integrated interbody constructs afford similar stability to anterior plating in single-level cervical spine fusion constructs. PURPOSE: The purpose of this study was to biomechanically quantify the acute stabilizing effect conferred by a single low-profile device design with three integrated screws ("anchored cage"), and compare the range of motion reductions to those conferred by a standard four-hole rigid anterior plate following instrumentation at the C5-C6 level. We hypothesized that the anchored cage would confer comparable postoperative segmental rigidity to the cage and anterior plate construct. STUDY DESIGN: Biomechanical laboratory study of human cadaveric spines. METHODS: Seven human cadaveric cervical spines (C3-C7) were biomechanically evaluated using a nondestructive, nonconstraining, pure-moment loading protocol with loads applied in flexion, extension, lateral bending (right+left), and axial rotation (left+right) for the intact and instrumented conditions. Range of motion (ROM) at the instrumented level was the primary biomechanical outcome. Spines were loaded quasi-statically up to 1.5 N-m in 0.5 N-m increments and ROM at the C5-C6 index level was recorded. Each specimen was tested in the following conditions: 1. Intact 2. Discectomy+anchored cage (STA) 3. Anchored cage (screws removed)+anterior locking plate (ALP) 4. Anchored cage only, without screws or plates (CO) RESULTS: ROM at the C5-C6 level was not statistically different in any motion plane between the STA and ALP treatment conditions (p>.407). STA demonstrated significant reductions in flexion/extension, lateral bending, and axial rotation ROM when compared with the CO condition (p<.022). CONCLUSIONS: In this in vitro biomechanical study, the anchored cage with three integrated screws afforded biomechanical stability comparable to that of the standard interbody cage+anterior plate cervical spine fusion approach. Due to its low profile design, this anchored cage device may avoid morbidities associated with standard anterior plating, such as dysphagia.

Postero-lateral disc prosthesis combined with a unilateral facet replacement device maintains quantity and quality of motion at a single lumbar level.

BACKGROUND: Mechanically replacing one or more pain generating articulations in the functional spinal unit (FSU) may be a motion preservation alternative to arthrodesis at the affected level. Baseline biomechanical data elucidating the quantity and quality of motion in such arthroplasty constructs is non-existent. PURPOSE: The purpose of the study was to quantify the motion-preserving effect of a posterior total disc replacement (PDR) combined with a unilateral facet replacement (FR) system at a single lumbar level (L4-L5). We hypothesized that reinforcement of the FSU with unilateral FR to replace the resected, native facet joint following PDR implantation would restore quality and quantity of motion and additionally not change biomechanics at the adjacent levels. STUDY DESIGN: In-vitro study using human cadaveric lumbar spines. METHODS: Six (n = 6) cadaveric lumbar spines (L1-S1) were evaluated using a pure-moment stability testing protocol (±7.5 Nm) in flexion-extension (F/E), lateral bending (LB) and axial rotation (AR). Each specimen was tested in: (1) intact; (2) unilateral FR; and (3) unilateral FR + PDR conditions. Index and adjacent level ROM (using hybrid protocol) were determined opto-electronically. Interpedicular travel (IPT) and instantaneous center of rotation (ICR) at the index level were radiographically determined for each condition. ROM, ICR, and IPT measurements were compared (repeated measures ANOVA) between the three conditions. RESULTS: Compared to the intact spine, no significant changes in F/E, LB or AR ROM were identified as a result of unilateral FR or unilateral FR + PDR. No significant changes in adjacent L3-L4 or L5-S1 ROM were identified in any loading mode. No significant differences in IPT were identified between the three test conditions in F/E, LB or AR at the L4-L5 level. The ICRs qualitatively were similar for the intact and unilateral FR conditions and appeared to follow placement (along the anterior-posterior (AP) direction) of the PDR in the disc space. CONCLUSION: Biomechanically, quantity and quality of motion are maintained with combined unilateral FR + PDR at a single lumbar spinal level.

Hip resurfacing arthroplasty in severely obese patients.

We conducted a study of outcomes of modern hip resurfacing arthroplasty (HRA) in severely obese patients. Patients who had undergone HRA and been followed for a minimum of 2 years were divided into 2 groups, those with body mass index under 35 (control, 366 hips) and those with body mass index of 35 or above (study, 63 hips). At mean follow-up of 41 months, there was no significant difference between the groups with respect to postoperative Harris Hip Scores, complication rates, and need for revision. Six revision surgeries were required in the control group (98.4% survival), and 2 were required in the study group (96.8% survival). These results suggest that severely obese patients should be considered candidates for HRA.

Regeneration of a discoid meniscus after arthroscopic saucerization.

We report the case of a 5-year-old girl who presented to the clinic with recurrent knee pain after meniscal repair and saucerization at age 3. The finding of a regenerated discoid meniscus was confirmed arthroscopically and radiographically. To our knowledge, this is the first report in the literature to confirm regeneration of a discoid meniscus after saucerization. The case has significant implications for management of pediatric discoid meniscus tears and patient counseling, and is encouraging in terms of the potential for repair and regeneration of meniscal tissue, particularly in the very young pediatric population.

Brain natriuretic peptide is not reno-protective during renal ischemia-reperfusion injury in the rat.

BACKGROUND: Acute kidney injury (AKI) occurs in 30% of patients undergoing complex cardiovascular surgery, and renal ischemia-reperfusion (I/R) injury is often a contributing factor. A recent meta-analysis observed that perioperative natriuretic peptide administration was associated with a reduction in AKI requiring dialysis in cardiovascular surgery patients. This study was designed to further clarify the potential reno-protective effect of brain natriuretic peptide (BNP) using an established rat model of renal I/R injury. METHODS: The study comprised three groups (n = 10 kidneys each): (1) control (no injury); (2) I/R injury (45 min of bilateral renal ischemia followed by 3 h of reperfusion); and (3) BNP (I/R injury plus rat-BNP pretreatment at 0.01 µg/kg/min). Glomerular filtration rate (GFR) and a biomarker of AKI, urinary neutrophil gelatinase-associated lipocalin (uNGAL), were measured at baseline and at 30 minute intervals post-ischemia. Groups were compared using two-way repeated measures analysis of variance (mean ± SD, significance P < 0.05). RESULTS: Baseline GFR measurements for control, I/R, and BNP groups were 1.07 ± 0.55, 0.88 ± 0.51, and 1.03 ± 0.59 mL/min (P = 0.90), respectively. Post-ischemia, GFR was significantly lower in I/R and BNP compared with controls at 30 min, 1.29 ± 0.97, 0.08 ± 0.04, and 0.06 ± 0.05 mL/min (P < 0.01), and remained lower through 3 h, 1.79 ± 0.44, 0.30 ± 0.17, and 0.32 ± 0.12 mL/min (P < 0.01). Comparing I/R to BNP groups, GFR did not differ significantly at any time point. There was no significant difference in uNGAL levels at 1 h (552 ± 358 versus 516 ± 259 ng/mL, P = 0.87) or 2 h (1073 ± 589 versus 989 ± 218 ng/mL, P = 0.79) between I/R and BNP. CONCLUSIONS: BNP does not reduce the renal injury biomarker, urinary NGAL, or preserve GFR in acute renal ischemia-reperfusion injury.