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- Pullout strength of cancellous screws in human femoral heads depends on applied insertion torque, trabecular bone microarchitecture and areal bone mineral density. [JOURNAL ARTICLE]
- J Mech Behav Biomed Mater 2014 Sep 16.:354-361.
For cancellous bone screws, the respective roles of the applied insertion torque (TInsert) and of the quality of the host bone (microarchitecture, areal bone mineral density (aBMD)), in contributing to the mechanical holding strength of the bone-screw construct (FPullout), are still unclear. During orthopaedic surgery screws are tightened, typically manually, until adequate compression is attained, depending on surgeons' manual feel. This corresponds to a subjective insertion torque control, and can lead to variable levels of tightening, including screw stripping. The aim of this study, performed on cancellous screws inserted in human femoral heads, was to investigate which, among the measurements of aBMD, bone microarchitecture, and the applied TInsert, has the strongest correlation with FPullout. Forty six femoral heads were obtained, over which microarchitecture and aBMD were evaluated using micro-computed tomography and dual X-ray absorptiometry. Using an automated micro-mechanical test device, a cancellous screw was inserted in the femoral heads at TInsert set to 55% to 99% of the predicted stripping torque beyond screw head contact, after which FPullout was measured. FPullout exhibited strongest correlations with TInsert (R=0.88, p<0.001), followed by structure model index (SMI, R=-0.81, p<0.001), bone volume fraction (BV/TV, R=0.73, p<0.001) and aBMD (R=0.66, p<0.01). Combinations of TInsert with microarchitectural parameters and/or aBMD did not improve the prediction of FPullout. These results indicate that, for cancellous screws, FPullout depends most strongly on the applied TInsert, followed by microarchitecture and aBMD of the host bone. In trabecular bone, screw tightening increases the holding strength of the screw-bone construct.
- Exploring the Effects of Seated Whole Body Vibration Exposure on Repetitive Asymmetric Lifting Tasks. [JOURNAL ARTICLE]
- J Occup Environ Hyg 2014 Sep 29.:0.
ABSTRACT This study investigated changes in the physiological and behavioral responses to repetitive asymmetric lifting activity after exposure to whole body vibrations. Seventeen healthy volunteers repeatedly lifted a box (15% of lifter's capacity) positioned in front of them at ankle level to a location on their left side at waist level at the rate of 10 lifts/minute for a period of 60 minutes. Prior to lifting, participants were seated on a vibrating platform for 60 minutes; in one of the two sessions the platform did not vibrate. Overall, the physiological responses assessed using near-infrared spectroscopy signals for the erector spinae muscles decreased significantly over time during the seating and the lifting tasks (p < 0.001). During repetitive asymmetric lifting, behavioral changes included increases in peak forward bending motion, twisting moment and three-dimensional movement velocities of the spine. The lateral bending moment of the spine and the duration of each lift decreased significantly over the 60 minutes of repetitive lifting. With exposure to whole body vibration, participants twisted further (p = 0.046) and twisted faster (p = 0.025). These behavioral changes would suggest an increase in back injury risk when repetitive lifting tasks are preceded by whole body vibration exposure.
- Sex-Specific Effects of Surface Instability on Drop Jump and Landing Biomechanics. [JOURNAL ARTICLE]
- Int J Sports Med 2014 Sep 29.
This study investigated sex-specific effects of surface instability on kinetics and lower extremity kinematics during drop jumping and landing. Ground reaction forces as well as knee valgus and flexion angles were tested in 14 males (age: 23±2 years) and 14 females (age: 24±3 years) when jumping and landing on stable and unstable surfaces. Jump height was found to be significantly lower (9%, p<0.001) when drop jumps were performed on unstable vs. stable surface. Significantly higher peak ground reaction forces were observed when jumping was performed on unstable versus stable surfaces (5%, p=0.022). Regarding frontal plane kinematics during jumping and landing, knee valgus angles were higher on unstable compared to stable surfaces (19-32%, p<0.05). Additionally, at the onset of ground contact during landings, females showed higher knee valgus angles than males (222%, p=0.027). Sagittal plane kinematics indicated significantly smaller knee flexion angles (6-35%, p<0.05) when jumping and landing on unstable vs. stable surfaces. During drop jumps and landings, women showed smaller knee flexion angles at ground contact compared to men (27-33%, p<0.05). These findings imply that knee motion strategies were modified by surface instability and sex during drop jumps and landings.
- Arthroscopic technique for treatment of combined pathology associated with femoroacetabular impingement syndrome using traction sutures and a minimal capsulotomy. [Journal Article]
- Arthrosc Tech 2014 Aug; 3(4):e527-32.
The use of hip arthroscopy is gaining popularity for diagnostic and therapeutic purposes. With our increasing understanding of hip biomechanics and pathophysiology, our techniques for treatment are evolving as well. The main aim is to preserve the joint and prolong the degenerative process associated with femoroacetabular impingement (FAI). In general, combined pathology is encountered when a diagnosis of FAI is established. In our experience, we have seen large number of patients with a combination of cam and pincer lesions with or without associated labral tears. It is optimal to address all symptomatic pathology with one surgical intervention. The described technique shows the feasibility of dealing with the hip FAI pathology by using traction sutures on the capsule through a 2-portal technique.
- Fluoroscopy-guided implantation of subacromial "biodegradable spacer" using local anesthesia in patients with irreparable rotator cuff tear. [Journal Article]
- Arthrosc Tech 2014 Aug; 3(4):e455-8.
Treatment of massive rotator cuff tears can be challenging, especially when tears are considered irreparable or, when repaired, at significant risk of retear. A surgical technique is described using a biodegradable subacromial balloon-shaped spacer (InSpace; Ortho-Space, Caesarea, Israel) that, when implanted between the humeral head and acromion, permits smooth, frictionless gliding, supporting shoulder biomechanics. The specific insertion technique described herein is a simple procedure that can be performed in a day-care or outpatient setting with patients under local anesthesia, thus providing a treatment option for patients with multiple comorbidities complicating or contraindicating surgery, such as reverse arthroplasty under general anesthesia.
- Accuracy of Individualized Custom Tibial Cutting Guides in UKA. [Journal Article]
- HSS J 2014 Oct; 10(3):260-5.
Component malposition is one of the major reasons for early failure of unicompartmental knee arthroplasty (UKA).It was investigated how reproducibly patient-specific instrumentation (PSI) achieved preoperatively planned placement of the tibial component in UKA specifically assessing coronal alignment, slope and flexion of the components and axial rotation.Based on computer tomography models of ten cadaver legs, PSI jigs were generated to guide cuts perpendicular to the tibial axis in the coronal and sagittal planes and in neutral axial rotation. Deviation ≥3° from the designed orientation in a postoperative CT was defined as outside the range of acceptable alignment.Mean coronal alignment was 0.4 ± 3.2° varus with two outliers. Mean slope was 2.8 ± 3.9° with six components in excessive flexion. It was noted that the implants were put in a mean of 1.7 ± 8.0° of external rotation with seven outliers.PSI helped achieve the planned coronal orientation of the component. The guides were less accurate in setting optimal tray rotation and slope.
- A Novel Lateral Lumbar Integrated Plate-Spacer Interbody Implant: In-Vitro Biomechanical Analysis. [JOURNAL ARTICLE]
- Spine J 2014 Sep 25.
Lateral spacers (LS) are the standard of care for a lateral lumbar interbody fusion. However, various types of fixation, such as bilateral pedicle screws (BPS), unilateral pedicle screws (UPS), bilateral facet screws (BFS), and lateral plates (LP) have been reported to increase the stability of LSs. The biomechanics of a novel lateral interbody implant, which is an interbody spacer with an integrated plate and two bone screws (IPS-L), has not been investigated yet.To compare the biomechanical stability of IPS-L and LS with and without supplemental instrumentation.Human lumbar cadaveric study evaluating the biomechanical stability of a lateral integrated plate-spacer.Each of the six (L2-L5) spines was sequentially tested in; 1) Intact; 2) IPS-L; 3) IPS-L+UPS; 4) IPS-L+BPS; 5) IPS-L+BFS; 6) LS+BFS; 7) LS+UPS; 8) LS+BPS; 9) LS; 10) LS+LP, using a load control protocol in which a ±8Nm moment was applied, for three cycles each, in flexion-extension (FE), lateral bending (LB) and axial rotation (AR). Data results were obtained from the third cycle.The IPS-L construct significantly reduced ROM by 75% in FE, 70% in LB, and 57% in AR, compared to intact. IPS-L demonstrated similar biomechanical stability as LS+LP, and higher stability than the LS alone construct, but the difference was not statistically significant.The lateral integrated plate-spacer evaluated in the present study demonstrated equivalent biomechanical stability compared to standard lateral interbody fusion constructs. The addition of bilateral pedicle screws to the lateral integrated plate-spacer showed significant reduction in ROM in flexion-extension, and the addition of bilateral facet screws showed significant reduction in ROM in flexion-extension and axial rotation, compared to the integrated plate-spacer alone construct. The lateral integrated plate-spacer with supplemental fixation may be a viable option for lateral interbody fusion. Long term clinical studies are further required to confirm these results.
- Effect of combining traction and vibration on back muscles, heart rate and blood pressure. [JOURNAL ARTICLE]
- Med Eng Phys 2014 Sep 25.
Eighty-five percentage of the population has ever experienced low back pain (LBP), which would result in decreasing of muscle strength and endurance, functional capacity of the spine and so on. Traction and vibration were commonly used to relieve the low back pain. It was investigated that the effect of the combing traction and vibration on back muscles, heart rate (HR) and blood pressure (BP) in this study. Thirty healthy subjects participated in 12 trials lying supine on the spine combing bed with different tilt angle (0°, 10°, 20° and 30°) and vibration modes (along with the sagittal and coronal axis with 0Hz, 2Hz and 12Hz separately). EMG was recorded during each trial. Power spectral frequency analysis was applied to evaluate muscle fatigue by the shift of median power frequency (MPF). Pulse pressure (PP) was calculated from BP. HR and PP were used to estimate the effect of the combination of traction and vibration on cardio-vascular system. It was shown that vibration could increase HR and decrease PP. The combination of traction and vibration (2Hz vibration along Z-axis and 12Hz vibration along Y-axis) might have no significant effect on cardio-vascular system. The MPF of LES and UT decreased significantly when the angle reached 20° under the condition of 2Hz vibration along Z-axis compared with it of 0°. What's more, the MPF also decreased significantly compared with it of static mode at 20° for LES and at 30° for UT. However at 12Hz vibration along Y-axis, the MPF had significant increase when the angle reached 20° in LES and 30° in UT compared to it of 0°. For LES, the MPF also had significant difference when the angle was added from 10° to 20°. Therefore, when the 2Hz vibration along Z-axis and traction (tilt angles that less than 20°) were combined, it was helpful to reduce muscle fatigue both for LES and UT compared with only vibration or traction. When the 12Hz vibration along Y-axis and traction (tilt angles that more than 10° for LES and more than 20° for UT) were combined, it could provide good treatment with lower muscle fatigue for back pain compared with only vibration or traction. It is helpful to provide biomechanical quantitative basis for the selection of the clinical treatment methods.
- Effects of aging on mechanical efficiency and muscle activation during level and uphill walking. [JOURNAL ARTICLE]
- J Electromyogr Kinesiol 2014 Sep 16.
Purpose: The metabolic cost of walking is greater in old compared to young adults. This study examines the relation between metabolic cost, muscular efficiency, and leg muscle co-activation during level and uphill walking in young and older adults. Procedures: Metabolic cost and leg muscle activation were measured in young (22.3±3.6years) and older adults (74.5±2.9years) walking on a treadmill at six different slopes (0.0-7.5% grade) and a speed of 1.3ms(-1). Across the range of slopes, 'delta mechanical efficiency' of the muscular system and antagonist muscle co-activation were quantified. Main findings: Across all slopes, older adults walked with a 13-17% greater metabolic cost, 12% lower efficiency, and 25% more leg muscle co-activation than young adults. Among older adults, co-activation was weakly correlated to metabolic cost (r=.233) and not correlated to the lower delta efficiency. Conclusion: Lower muscular efficiency and increased leg muscle co-activation contribute to the greater metabolic cost of uphill slope walking among older adults but are unrelated to one another.