Polyaxial Screws in Locked Plating of Tibial Pilon Fractures.

This study examined the axial and torsional stiffness of polyaxial locked plating techniques compared with fixed-angle locked plating techniques in a distal tibia pilon fracture model. The effect of using a polyaxial screw to cross the fracture site was examined to determine its ability to control relative fracture site motion. A laboratory experiment was performed to investigate the biomechanical stiffness of distal tibia fracture models repaired with 3.5-mm anterior polyaxial distal tibial plates and locking screws. Sawbones Fourth Generation Composite Tibia models (Pacific Research Laboratories, Inc, Vashon, Washington) were used to model an Orthopaedic Trauma Association 43-A1.3 distal tibia pilon fracture. The polyaxial plates were inserted with 2 central locking screws at a position perpendicular to the cortical surface of the tibia and tested for load as a function of axial displacement and torque as a function of angular displacement. The 2 screws were withdrawn and inserted at an angle 15° from perpendicular, allowing them to span the fracture and insert into the opposing fracture surface. Each tibia was tested again for axial and torsional stiffness. In medial and posterior loading, no statistically significant difference was found between tibiae plated with the polyaxial plate and the central screws placed in the neutral position compared with the central screws placed at a 15° position. In torsional loading, a statistically significant difference was noted, showing greater stiffness in tibiae plated with the polyaxial plate and the central screws placed at a 15° position compared with tibiae plated with the central screws placed at a 0° (or perpendicular) position. This study showed that variable angle constructs show similar stiffness properties between perpendicular and 15° angle insertions in axial loading. The 15° angle construct shows greater stiffness in torsional loading.

In situ comparison of varying composite tibial tunnel interference screws used for ACL soft tissue graft fixation.

PURPOSE: This mechanical study using an in vitro porcine model compared composite interference screw fixation of soft tissue ACL grafts in tibial tunnels. METHODS: Forty-eight porcine profundus tendons and tibiae were divided into four groups of 12 closely matched specimens. Equivalent diameter grafts were assigned to each group. Tibial bone tunnels were drilled to 0.5mm greater than graft diameter. Grafts were fixed in tunnels using one 10 × 35 mm composite interference screw designed by four different manufacturers. Maximal insertion torque and perceived within group mechanical testing outcome predictions were recorded. Constructs were potted and loaded into a six degrees of freedom clamp that placed the servohydraulic device tensile loading vector in direct tunnel alignment. Constructs were pre-loaded to 25 N, pre-conditioned between 0 and 50 N for 10 cycles (0.5 Hz), submaximally tested between 50 and 250 N for 500 cycles (one hertz) and load to failure tested at 20mm/min. RESULTS: Statistically significant differences were not observed between groups for displacement during submaximal cyclic loading, yield load, displacement at yield load, stiffness, ultimate load at failure and displacement at ultimate load. One composite screw group displayed a slightly greater proportion of specimens that required use of more than one screw during insertion. CONCLUSIONS: Under highly controlled conditions groups displayed comparable fixation.

Progressive resistance, whole body long-axis rotational training improves kicking motion motor performance.

OBJECTIVES: To evaluate lower extremity muscle activation, peak resultant ground reaction force (GRF) production and quickness during performance of a kicking motion following progressive resistance, whole body long-axis rotational training. DESIGN: Randomized, controlled study. SETTING: Kinesiological research laboratory. PARTICIPANTS: Thirty-six healthy subjects were assigned to a training (Group 1) or to a control (Group 2) group. MAIN OUTCOME MEASURES: Time-synchronized EMG (1000 Hz), peak resultant GRF (1000 Hz) and two-dimensional kinematic (60 Hz) data were collected as subjects responded to an audio cue by kicking a cone. Group mean change differences (MCD) were compared using independent sample t-tests. Fisher's exact tests were used to determine group differences in the proportion of subjects that displayed earlier activation responses post-training. RESULTS: Group 1 MCD revealed earlier gluteus maximus, gluteus medius, rectus femoris, medial hamstrings, and biceps femoris activation timing than Group 2 (P ≤ 0.006) and more Group 1 subjects displayed earlier activation of these muscles post-training (P ≤ 0.041). Group 1 MCD also revealed earlier peak resultant GRF timing and improved "kick quickness" than Group 2 (P ≤ 0.014) and more Group 1 subjects displayed earlier response timing for these variables post-training (P = 0.035). CONCLUSION: Progressive resistance, whole body long-axis rotational training may improve performance during sports movements that require quick, integrated trunk-lower extremity function.

The development of an experimental multiple serogroups vaccine for Neisseria meningitidis.

A native outer membrane vesicles (NOMV) vaccine was developed from three antigenically diverse strains of Neisseria meningitidis that express the L1,8, L2, and L3,7 lipooligosaccharide (LOS) immunotypes, and whose synX, and lpxL1 genes were deleted.. Immunogenicity studies in mice showed that the vaccine induced bactericidal antibody against serogroups B, C, W, Y and X N. meningitidis strains. However, this experimental NOMV vaccine was not effective against serogroup A N. meningitidis strains. N. meningitidis capsular polysaccharide (PS) from serogroups A, C, W and Y were effective at inducing bactericidal antibody when conjugated to either tetanus toxoid or the fHbp1-fHbp2 fusion protein fHbp(1+2). The combination of the NOMV vaccine and the N. meningitidis serogroup A capsular polysaccharide (MAPS) protein conjugate was capable of inducing bactericidal antibodies against a limited number of N. meningitidis strains from serogroups A, B, C, W, Y and X tested in this study.

Outside-in continuous suturing is superior to interrupted suturing for repairing peripheral meniscus lesions: an in vitro biomechanical study using a porcine model.

PURPOSE: This in vitro biomechanical study using a porcine model compared peripheral longitudinal vertical meniscus lesion (PLVML) outside-in suture repair fixation strength using either interrupted or continuous "N" configuration No. 2-0 braided polyester sutures. METHODS: Porcine lateral menisci were randomly assigned to group 1 (continuous) or group 2 (interrupted). Standardized PLVMLs were created in each specimen. Repaired specimens were placed in a specially designed clamp and loaded into a servohydraulic device. Specimens underwent preconditioning for 10 cycles (0.1 Hz, 5 to 20 N) and 500 submaximal loading cycles (0.5 Hz, 5 to 20 N), before load-to-failure testing (12.5 mm/s). A 30-second pause after preconditioning and after 10, 100, and 500 submaximal loading cycles enabled standardized digital photographs to be taken for gapping measurement determination. The failure mode was documented. RESULTS: Displacement and gapping during preconditioning and submaximal loading cycles did not differ between groups. Group 1 withstood a greater failure load (mean, 118.3 N; 95% confidence interval [CI], 97.2 to 139.4 N) than group 2 (mean, 63.7 N; 95% CI, 51.2 to 76.2 N) (P < .0001) and displacement during load-to-failure testing (mean, 5.3 mm; 95% CI, 4.2 to 6.5 mm) than group 2 (mean, 3.2 mm; 95% CI, 2.1 to 4.3 mm) (P = .005). Group 1 failed by suture breakage or suture pulling through tissue, whereas group 2 primarily failed by knot slippage (P < .0001). CONCLUSIONS: Group displacement and gapping differences were not observed after 500 submaximal loading cycles. PLVMLs repaired with a continuous N configuration, however, withstood greater load at failure and greater displacement before failure than repairs that used interrupted sutures. CLINICAL RELEVANCE: Continuous suture in an N configuration may improve PLVML repair fixation strength.

Repair of peripheral vertical meniscus lesions in porcine menisci: in vitro biomechanical testing of 3 different meniscus repair devices.

BACKGROUND: All-inside meniscus repair eliminates the need for an extra incision and decreases neurovascular injury risk. Biomechanical testing can help delineate the efficacy of all-inside device use. HYPOTHESIS: There would be no group differences between 4 peripheral meniscus repair techniques and 3 different devices tested. STUDY DESIGN: Controlled laboratory study. METHODS: Equivalent-sized menisci with attached tibiae were randomly assigned to 1 of 4 test groups (8 specimens each), as follows: group 1, Fast-Fix using No. 0 braided polyester suture; group 2, inside-out repair using 2-0 braided polyester suture; group 3, Sequent using No. 0 ultra-high molecular weight polyethylene (UHMWPE) suture in a continuous "N" configuration; and group 4, Sequent using No. 0 UHMWPE suture in an interrupted configuration. After placement in a clamp, specimens underwent preconditioning from 5 to 20 N for 10 cycles (0.1 Hz), 500 submaximal loading cycles from 5 to 20 N (0.5 Hz), and load-to-failure testing at 12.5 mm/s. A 30-second pause after 10 preconditioning cycles and after 10, 100, and 500 submaximal loading cycles enabled digital photographs to be taken for gapping measurements. Failure mode was recorded. RESULTS: Specimens in group 3 withstood greater failure loads than did those in groups 1 and 4 (P ≤ .027), and group 3 specimens were stiffer than those in groups 2 and 4 (P ≤ .048). Displacement during submaximal loading and load-to-failure testing did not differ between groups. Groups 1, 3, and 4 each gapped less than group 2 during submaximal cyclic loading (P ≤ .05). Groups 1 and 2 failed primarily by suture breakage (P < .0001), while groups 3 and 4 failed primarily by the suture pulling free from an implant (P < .0001). CONCLUSION: Sequent using No. 0 UHMWPE suture in a continuous "N" configuration displayed superior load at failure compared with repairs using Fast-Fix with No. 0 braided polyester suture and displayed greater stiffness and less gapping than inside-out repair using 2-0 braided polyester suture. The suture pulling free from an implant was the primary failure mode for Sequent using No. 0 UHMWPE suture regardless of whether a continuous "N" or an interrupted configuration was used. Study groups that used No. 0 UHMWPE sutures (groups 3 and 4) had more specimens fail by the suture pulling free from an implant. Compared with the weaker braided polyester suture in the inside-out and Fast-Fix groups, the No. 0 UHMWPE suture used in the Sequent groups likely influenced study results, as this suture has stronger material properties. However, the continuous "N" configuration likely also improved the performance of the Sequent with No. 0 UHMWPE suture, as failure load was significantly less with an interrupted configuration. CLINICAL RELEVANCE: All-inside meniscus repair with continuous suture function may translate into improved patient outcomes.

Cyclic test comparison of all-inside device and inside-out sutures for radial meniscus lesion repair: an in vitro porcine model study.

PURPOSE: To compare biomechanical fixation and gapping characteristics of a new all-inside meniscus repair method for radial meniscus lesion repair versus conventional inside-out suture repair under submaximal cyclic loading and load-to-failure test conditions. METHODS: Fresh-frozen porcine tibiae with attached lateral menisci and joint capsules were harvested and stored for 48 hours at -20°C. After thawing for 12 hours, equivalent-size healthy specimens were randomly assigned to 2 groups of 8 specimens each. Standardized radial lesions were repaired with the Sequent device (ConMed Linvatec, Largo, FL) (group 1) or conventional inside-out suturing with No. 2-0 braided polyester suture (group 2). Repaired specimens were placed in custom clamps and mounted on a servohydraulic device. After a 2-N preload, specimens were cycled from 5 to 20 N (0.1 Hz), before undergoing 1,000 submaximal loading cycles between 5 and 20 N (0.5 Hz). A 40-second delay at 100, 500, and 1,000 cycles enabled digital photographs to be taken for gapping measurement determination. Specimens then underwent load-to-failure testing (12.5 mm/s). Fixation failure mode was documented. RESULTS: Group displacement did not differ after 1, 100, 500, and 1,000 submaximal loading cycles. Group peak gapping did not differ at 100, 500, and 1,000 submaximal loading cycles. Load at failure and displacement and stiffness during load-to-failure testing did not differ between groups. During load-to-failure testing, all-inside specimens failed by implant dislodgement from the meniscus periphery whereas the inside-out repaired specimens failed by suture rupture. CONCLUSIONS: Under controlled in vitro biomechanical test conditions, the all-inside device provided radial meniscus lesion fixation that was comparable, but not superior, to conventional inside-out suturing. CLINICAL RELEVANCE: The all-inside radial lateral meniscus lesion repair method may provide comparable fixation to conventional inside-out suturing without the need for additional incisions and their associated neurovascular injury risks.

Analysis of the bactericidal response to an experimental Neisseria meningitidis vesicle vaccine.

Rabbit immunogenicity studies on an experimental trivalent native outer membrane vesicle vaccine derived from three serogroup B strains were conducted to evaluate the effectiveness of this vaccine at inducing an antibody response with serum bactericidal activity against meningococcal strains of other serogroups in addition to serogroup B strains. The results showed that the vaccine was capable of inducing an effective broad-based bactericidal antibody response in rabbits against a small sample of Neisseria meningitidis strains of serogroups C, W135, and X and, to a lesser extent, serogroups A and Y. Analysis of antibody specificity using a bactericidal depletion assay revealed that antibodies to lipooligosaccharide (LOS), PorA, and NadA induced in rabbits by the experimental trivalent outer membrane vesicle vaccine were responsible for most of the bactericidal activity against strains of the other N. meningitidis serogroups. In the case of serogroup A N. meningitidis strains, the outer membrane antigen NadA was primarily responsible for protection. The outer membrane antigens fHbp and OpcA were also effective in removing some bactericidal activity from the sera.

Bone loss following spinal cord injury in a rat model.

The current study was undertaken to follow the time course of bone loss in the proximal tibia of rats over several weeks following thoracic contusion spinal cord injury (SCI) of varying severity. It was hypothesized that bone loss would be more pronounced in the more severely injured animals, and that hindlimb weight bearing would help prevent bone loss. Twenty-six female Sprague-Dawley rats (200-225 g, 6-7 weeks old) received standard thoracic (T9) injuries at energies of 6.25, 12.5, 25, or 50 g-cm. The rats were scored weekly for hindlimb function during locomotion. At 0, 2 or 3, and 8 weeks, high-resolution micro-CT images of each right tibia were obtained. Mechanical indentation testing was done to measure the compressive strength of the cancellous bone structure. The 6.25 g-cm group showed near normal locomotion, the 12.5 and 25 g-cm groups showed the ability to frequently or occasionally generate weight-supported plantar steps, respectively, and the 50 g-cm group showed only movement without weight-supported plantar stepping. The 6.25, 12.5 and 25 g-cm groups remained at the same level of bone volume fraction (cancBV/TV=0.24±0.07), while the 50 g-cm group experienced severe bone loss (67%), resulting in significantly lower (p<0.05) bone volume fraction (cancBV/TV=0.11±0.05) at 8 weeks. Proximal tibia cancellous bone strength was reduced by approximately 50% in these severely injured rats. Instead of a linear proportionality between injury severity and bone loss, there appears to be a distinct functional threshold, marked by occasional weight-supported stepping, above which bone loss does not occur.

An experimental outer membrane vesicle vaccine from N. meningitidis serogroup B strains that induces serum bactericidal activity to multiple serogroups.

A trivalent native outer membrane vesicle vaccine that has potential to provide broad based protection against Neisseria meningitidis serogroup B strains has been developed. Preliminary immunogenicity studies in mice showed that the vaccine was capable of inducing an effective broad based bactericidal antibody response against N. meningitidis serogroup B strains. These findings in mice have been repeated with a cGMP trivalent NOMV vaccine and extended to show that the bactericidal antibody response induced by the vaccine in mice is effective against strains belonging to serogroups C, Y, W135, X, and NadA-expressing serogroup A strains. Taken together these results suggest that this experimental vaccine may provide protection against both serogroup B and non-serogroup B N. meningitidis strains.

Anterolateral and medial locking plate stiffness in distal tibial fracture model.

BACKGROUND: The purpose of this study was to compare the axial and torsional stiffness between anterolateral and medial distal tibial locking plates in a pilon fracture model. MATERIALS AND METHODS: The biomechanical stiffness of anterolateral or medial plated pilon fracture models was evaluated. Six Sawbones Composite Tibiae with a simulated pilon fracture representing varus or valgus comminution (OTA 43-A2.2) were plated with a Synthes 3.5-mm contoured LCP anterolateral or medial locking distal tibia plate. Load as a function of axial displacement and torque as a function of angular displacement were recorded. Each tibia was tested with a fracture wedge in place and removed with a medial and then anterolateral plate. RESULTS: Loading the tibial plateau medial to the central axis, no significant difference in mean stiffness between the anterolateral and medial plates was demonstrated with the fracture wedge in place. A significant difference was demonstrated with the wedge removed. Loading the plateau posterior to the central axis, no significant difference in mean stiffness between plates was demonstrated with the wedge in place or removed. With the wedge in place, there was a significant difference in mean torsional stiffness for clockwise rotation, but not counterclockwise rotation. With the wedge removed, no significant difference appeared in mean stiffness for clockwise and counterclockwise rotation. CONCLUSION: Distal tibia extra-articular fractures stabilized with anterolateral or medial locking plate constructs demonstrated no statistically significant difference in biomechanical stiffness in compression and torsion testing. CLINICAL RELEVANCE: We believe this study indicates the primary concern when treating a pilon fracture may be soft-tissue considerations. Further clinical studies are required before definitive changes can be recommended regarding pilon fracture fixation.

Xenograft bone inclusion improves incorporation of hydroxyapatite cement into cancellous defects.

OBJECTIVES: Hydroxyapatite cement (HAC) is biocompatible and osteoconductive, but its slow resorption limits new bone formation. The purpose of this investigation was to determine the effects of adding partially demineralized xenograft cortical bone in an established animal model. METHODS: Eight 6-month-old female New Zealand white rabbits were used. Drill-hole defects (8.0 mm long, 5.0 mm diameter) were prepared and filled with either HAC alone or HAC mixed with processed xenograft bone particles from young pigs (XBC) at a volumetric ratio of approximately 25%. The particles were approximately 5 mm long and 1 mm diameter and were extensively washed, demineralized in dilute hydrochloric acid, and rewashed. Microcomputed tomography scanning and histology were performed after 10 weeks. New bone and inflammatory/immune response were graded on a 0 to 3 scale and calcein labeling was quantified as percent area new bone. Statistical analyses were by Student's t tests. RESULTS: XBC showed significantly more new bone formation than HAC throughout the defect (P < 0.05). XBC also showed significantly more inflammatory/immune response than HAC (P < 0.05). The three-dimensional microcomputed tomography reconstructions showed that the HAC was basically inert, whereas the XBC took on an appearance suggestive of more extensive incorporation. CONCLUSIONS: Adding xenograft to HAC creates a bioactive composite that is more rapidly incorporated, resorbed, and replaced by new bone. The presence of processed xenograft particles creates a vigorous inflammatory response, but there may be some benefit to the resorption rate of the HAC as a result of the infiltration of cells. Future research should focus on the longer-term incorporation and remodeling of XBC.

Whole body, long-axis rotational training improves lower extremity neuromuscular control during single leg lateral drop landing and stabilization.

BACKGROUND: Poor neuromuscular control during sports activities is associated with non-contact lower extremity injuries. This study evaluated the efficacy of progressive resistance, whole body, long-axis rotational training to improve lower extremity neuromuscular control during a single leg lateral drop landing and stabilization. METHODS: Thirty-six healthy subjects were randomly assigned to either Training or Control groups. Electromyographic, ground reaction force, and kinematic data were collected from three pre-test, post-test trials. Independent sample t-tests with Bonferroni corrections for multiple comparisons were used to compare group mean change differences (P≤0.05/21≤0.0023). FINDINGS: Training group gluteus maximus and gluteus medius neuromuscular efficiency improved 35.7% and 31.7%, respectively. Training group composite vertical-anteroposterior-mediolateral ground reaction force stabilization timing occurred 1.35s earlier. Training group knee flexion angle at landing increased by 3.5°. Training group time period between the initial two peak frontal plane knee displacements following landing increased by 0.17s. Training group peak hip and knee flexion velocity were 21.2°/s and 20.1°/s slower, respectively. Time period between the initial two peak frontal plane knee displacements following landing and peak hip flexion velocity mean change differences displayed a strong relationship in the Training group (r(2)=0.77, P=0.0001) suggesting improved dynamic frontal plane knee control as peak hip flexion velocity decreased. INTERPRETATION: This study identified electromyographic, kinematic, and ground reaction force evidence that device training improved lower extremity neuromuscular control during single leg lateral drop landing and stabilization. Further studies with other populations are indicated.

Single leg jumping neuromuscular control is improved following whole body, long-axis rotational training.

Improved lower extremity neuromuscular control during sports may decrease injury risk. This prospective study evaluated progressive resistance, whole body, long-axis rotational training on the Ground Force 360 device. Our hypothesis was that device training would improve lower extremity neuromuscular control based on previous reports of kinematic, ground reaction force (GRF) or electromyographic (EMG) evidence of safer or more efficient dynamic knee stability during jumping. Thirty-six healthy subjects were randomly assigned to either training (Group 1) or control (Group 2) groups. Using a pre-test, post-test study design data were collected from three SLVJ trials. Unpaired t-tests with adjustments for multiple comparisons were used to evaluate group mean change differences (P≤0.05/25≤0.002). During propulsion Group 1 standardized EMG amplitude mean change differences for gluteus maximus (-21.8% vs. +17.4%), gluteus medius (-28.6% vs. +15.0%), rectus femoris (-27.1% vs. +11.2%), vastus medialis (-20.2% vs. +9.1%), and medial hamstrings (-38.3% vs. +30.3%) differed from Group 2. During landing Group 1 standardized EMG amplitude mean change differences for gluteus maximus (-32.9% vs. +11.1%) and rectus femoris (-33.3% vs. +29.0%) also differed from Group 2. Group 1 peak propulsion vertical GRF (+0.24N/kg vs. -0.46N/kg) and landing GRF stabilization timing (-0.68 vs. +0.05s) mean change differences differed from Group 2. Group 1 mean hip (-16.3 vs. +7.8°/s) and knee (-21.4 vs. +18.5°/s) flexion velocity mean change differences also differed from Group 2. Improved lower extremity neuromuscular efficiency, increased peak propulsive vertical GRF, decreased mean hip and knee flexion velocities during landing, and earlier landing stabilization timing in the training group suggests improved lower extremity neuromuscular control.

Are they just lazy? Student teachers' attitudes about dyslexia.

It is highly likely that teachers' abilities in dealing with different forms of learning difficulties will be affected by their knowledge about and attitudes towards those difficulties. Ajzen's Theory of Planned Behaviour (TPB) provides a useful framework within which to explore such attitudes and was used as the starting point for investigating trainee teachers' attitudes towards aspects of dyslexia. It is assumed that new teachers will enter the profession with a set of intentions according to personal beliefs, normative views within the teaching profession and the sense of competence and power they feel in dealing with dyslexic difficulties. The purpose of this study was to probe student teachers' attitudes at a prestigious School of Education in the Southwest of England. Four hundred and eight primary and secondary Post Graduate Certificate in Education (PGCE) students responded to a survey asking about their attitudes toward dyslexia. The student teachers expressed strongly positive attitudes toward the construct of dyslexia, with the majority expressing confidence in their ability to support dyslexic pupils. Females held significantly more positive attitudes toward dyslexia than males, but there were no significant differences according to PGCE course subject. Students who took the survey before and after teaching practice demonstrated some small but significant changes in attitude scores over that time. It is proposed that a new breed of teachers may be entering the teaching profession with positive beliefs about their ability to help dyslexic pupils, but who remain unclear as to how this can be accomplished. Some implications for action and suggestions for future research are provided.

Is dyslexia necessarily associated with negative feelings of self-worth? A review and implications for future research.

This paper will provide an overview of research in the past 20 years into the relationship between dyslexia and various aspects of self-perception, including self-concept, self-esteem, self-efficacy and locus of control. Problems are identified relating to the measurement of some of the most widely used constructs, as is the need for more precise identification of key variables relating to them. Critical issues concerning the assumptions that can be drawn from largely correlational data are highlighted also. The conclusion is drawn that an alternative approach to research in this area is required to enhance our understanding of how those suffering from learning disabilities of a dyslexic nature develop a positive or negative sense of identity. Suggestions are made as to how this can be achieved by drawing upon attribution theory and other aspects of social psychology.

In vivo micro-CT scanning of a rabbit distal femur: repeatability and reproducibility.

Before in vivo micro-CT scanning can be used to investigate femoral trabecular microarchitecture over time in rabbits, its repeatability and reproducibility must be demonstrated. To accomplish this, both distal femurs of two 6-month-old New Zealand white rabbits were scanned five times each in 1 day under different conditions (repeatability). Scanning was done at 28 microm isotropic voxel size to produce five image stacks of each femur. Three operators then followed a standard image processing protocol (reproducibility) to isolate two separate cubes from each anterior femoral condyle [total n = (8 cube sites)(5 scans)(3 operators) = 120]. Bone volume fraction (BV/TV) of the eight different cube sites (sample) ranged from 0.408 to 0.501 (mean: 0.453); trabecular thickness (Tb.Th) ranged from 158.1 to 185.5 microm (mean: 168.6 microm); and trabecular separation (Tb.Sp) ranged from 179.4 to 233.1 microm (mean: 204.7 microm). Using ANOVA and the variance component method, the total process variation was +/- 14.1% of the mean BV/TV of 0.453. The sample variation was +/- 13.9% (p < 0.001), the repeatability was +/- 2.1% (p < 0.001), and the reproducibility was +/- 0.1% (p > 0.05). Results were similar for Tb.Th and Tb.Sp. Though the contribution due to repeatability was statistically significant for each of the three indices, the natural sample differences were far greater than differences caused by repeated scanning under different conditions or by different operators processing the images. These findings suggest that in vivo micro-CT scanning of rabbit distal femurs was repeatable and reproducible and can be used with confidence to measure differences in trabecular bone microarchitecture at a single location in a longitudinal study design.

Cyclic loading comparison of Bio-SutureTak-#2 FiberWire and Bio Mini-Revo-#2 Hi-Fi suture anchor-sutures in cadaveric scapulae.

This study compared tap-in Bio-SutureTak suture anchor-#2 FiberWire suture (Group 1) and screw-in Bio Mini-Revo suture anchor-#2 Hi-Fi suture (Group 2) fixation in the glenoid region of interest for Bankart repair, in addition to evaluation of isolated suture loop biomechanical properties under progressive incremental cyclic loads. With knowledge of glenoid apparent bone mineral density (BMD), implant preparation and fit characteristics, and following application of a light manual tensile load, the primary investigator scored each specimen for perceived within group biomechanical test performance using a 0-10 point modified visual analog scale. After scoring, 12 paired constructs were placed in a servo hydraulic device clamp, preloaded to 25 N, and cycled between 25 and 50 Hz with a 25 N load increase every 25 cycles. Group 2 withstood greater load (104.1 +/- 56 vs. 70 +/- 36.9 N, P = 0.04) and displaced more at failure (13 +/- 4.5 vs. 8.6 +/- 3.3 mm, P = 0.04). All Group 1 specimens failed prior to reaching 150 N, whereas 25% of Group 2 specimens (n = 3) failed at 200 N. All specimens failed by anchor pullout except for three Group 2 specimens that failed by eyelet breakage at 200 N. Isolated suture testing revealed that Group 1 sutures displaced less at each cyclic load (P = 0.028) and withstood greater failure loads (P = 0.028) than that of Group 2 sutures. Group 2 constructs displayed moderately strong relationships between perceived within group biomechanical test performance and ultimate load (r (2) = 0.55) and displacement at failure (r (2) = 0.67). Group 1 did not display significant relationships. Similar biomechanical performance between 50 and 125 N, greater load at failure, and superior biomechanical test prediction accuracy suggest that the screw-in type Bio Mini-Revo suture anchor-#2 Hi-Fi suture combination may be preferred for Bankart lesion repair in low apparent BMD glenoid processes. The #2 Hi-Fi suture, however, allowed significantly greater displacement than the #2 FiberWire suture at each progressive cyclic load interval.

Evaluation of BioCorkscrew and Bioknotless RC suture anchor rotator cuff repair fixation: an in vitro biomechanical study.

This in vitro biomechanical study used cadaveric specimens to compare the rotator cuff repair fixation provided by BioCorkscrew and Bioknotless RC suture anchors. Three cm wide by 1-cm long full-thickness supraspinatus defects were repaired using either two BioCorkscrew suture anchors with combined vertical and horizontal mattress sutures (n = 7) or three Bioknotless RC suture anchors with simple sutures (n = 7). Therefore, the BioCorkscrew suture anchor group had two sutures per anchor (four total sutures), while the Bioknotless RC suture anchor group had one suture per anchor (three total sutures). Two-phase cyclic (5-100 N, 1,000 cycles and 5-180 N, 2,000 cycles) and load to failure tests (31 mm/s) were performed. Non-parametric statistics were used to compare group differences (P < 0.05). All of the BioCorkscrew group specimens (seven of seven) completed the two phase cyclic test regimen without failure or gapping >/= 5 mm, compared to only three of seven of the Bioknotless RC group (Fisher's Exact test = 0.03). Groups did not differ for repair site gapping during the 5-100 N cyclic test phase (Fisher's Exact test = 0.77), however more of the Bioknotless RC group displayed gapping >/= 5 mm during the 5-180 N cyclic test phase than the BioCorkscrew group (P = 0.02). The BioCorkscrew group also displayed greater yield load during load to failure testing (492.2 +/- 204 N vs. 296.4 +/- 155 N, P = 0.03). In this in vitro biomechanical study, the BioCorkscrew group with combined vertical and horizontal mattress sutures displayed greater cyclic test survival, less repair site gapping, and superior yield load compared to the Bioknotless RC group with simple sutures. These results in human cadaveric rotator cuff-humerus specimens suggest better immediate post-operative repair site strength and a reduced need for post-operative restrictions. Clinical studies are needed to determine how these rotator cuff repair modes withstand the forces of early rehabilitation and activities of daily living that potentially influence patient outcomes.

Soft tissue tendon graft fixation in serially dilated or extraction-drilled tibial tunnels: a porcine model study using high-resolution quantitative computerized tomography.

BACKGROUND: Tibial tunnel preparation may contribute to improved soft tissue graft fixation. HYPOTHESIS: Step dilation produces greater tunnel wall bone volume than does extraction drilling and increases fixation strength. Bioabsorbable interference screw divergence decreases fixation strength, regardless of tunnel preparation method. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty porcine tibias were divided into 2 groups of 10 with matching mean apparent bone mineral density. One group received 9-mm-diameter extraction-drilled tunnels, and the other group received 7-mm-diameter extraction-drilled tunnels followed by step dilation to 9 mm. High-resolution quantitative computerized tomography scans and voxel analysis techniques determined tunnel wall bone volume fraction. Screws secured 8.5-mm-diameter porcine grafts in the tunnels. Repeat scans were used to determine screw divergence. Cyclic loading was performed in a servohydraulic device before load to failure testing. RESULTS: The step dilation group had greater tunnel wall bone volume/total volume than did the extraction drilled group; however, a significant increase in fixation strength was not detected. Specimens with screw divergence angles less than 15 degrees had superior fixation and insertion torques compared with specimens with angles 15 degrees or more. Screw divergence correlated more strongly with fixation strength than did mean apparent bone mineral density or screw insertion torque. CONCLUSION: Step dilation increased tunnel wall bone volume/total volume, but fixation strength did not improve. Screw divergence >or=15 degrees decreases graft-bone tunnel fixation whether or not step dilation is performed. CLINICAL RELEVANCE: Screw alignment plays a greater role in anterior cruciate ligament graft fixation than does extraction drilling or step dilation tunnel preparation methods in healthy bone.