Vibrotactile perception thresholds at the sole of the foot: effects of contact force and probe indentation

When using vibrotactile thresholds to investigate neuropathy in the fingers, the indentation of a vibrating probe, and the force applied to a static surround around a vibrating probe, affect thresholds. This study was designed to investigate the effects on vibrotactile perception thresholds at the sole of the foot of probe indentation (i.e. height of a vibrating probe relative to a static surround) and the force applied to the static surround. Thresholds at 20 Hz (expected to be mediated by the NP I channel) and at 160 Hz (expected to be mediated by the Pacinian channel) were obtained at the hallux (i.e. greater toe) and the ball of the foot on 14 healthy subjects. In one condition, the height of the vibrating probe was varied to 0, 1, 2, 3, and 4 mm above a static surround with 4-N force applied to the surround. In a second condition, the force applied to the surround was varied to 1, 2, 3, 4, 5, and 6 N while using a probe height of 1mm. Thresholds at 20 Hz decreased with increasing probe height from 0 to 1 mm but showed no significant variation between 2, 3, and 4mm at either the hallux or the ball of the foot. Thresholds at 160 Hz decreased with increasing probe height from 0 to 4 mm at both the hallux and the ball of the foot. Thresholds at 20 Hz obtained with 1-N surround force were higher than thresholds obtained with 2 N, but there was no significant difference with surround forces from 2 to 6 N at either the hallux or the ball of the foot. Thresholds at 160 Hz were unaffected by variations in surround force at the ball of the foot but tended to decrease with increasing force at the hallux. It is concluded that a vibrating probe flush with a static surround, and a surround force in the range 2-4 N, are appropriate when measuring vibrotactile thresholds at the hallux and the ball of the foot with a 6-mm diameter contactor and a 2-mm gap to the static surround.     

Modification of human pain threshold by specific tactile receptors.

The effects of conditioning vibrotactile stimulation of particular tactile receptor groups on thresholds to painful electric stimuli were studied in seven healthy adults. Preferentially Pacinian afferents were activated with conditioning sinusoidal vibration of 240 Hz at 20 and 200 micrometers amplitudes and preferentially non-Pacinian tactile fibers were activated with conditioning sinusoidal vibration of 20 Hz at 200 and 400 micrometers amplitudes. None of the subjects showed pain threshold elevation during activation of non-Pacinian tactile fibers. However, 6 of the 7 subjects showed significant pain threshold elevation with conditioning vibration stimulus of 240 Hz at 200 micrometers amplitude, and 4 subjects showed significantly elevated pain thresholds with conditioning stimulus of 240 Hz at 20 micrometers amplitude. It is concluded that the activation of Pacinian afferents causes inhibition of pain conducting pathways.     

Modification of human pain threshold by specific tactile receptors

The effects of conditioning vibrotactile stimulation of particular tactile receptor groups on thresholds to painful electric stimuli were studied in seven healthy adults. Preferentially Pacinian afferents were activated with conditioning sinusoidal vibration of 240 Hz at 20 and 200μm amplitudes and preferentially non-Pacinian tactile fibers were activated with conditioning sinusoidal vibration of 20 Hz at 200 and 400 μm amplitudes. None of the subjects showed pain threshold elevation during activation of non-Pacinian tactile fibers. However, 6 of the 7 subjects showed significant pain threshold elevation with conditioning vibratory stimulus of 240 Hz at 200 μm amplitude, and 4 subjects showed significantly elevated pain thresholds with conditioning stimulus of 240 Hz at 20 μm amplitude. It is concluded that the activation of Pacinian afferents causes inhibition of pain conducting pathways.     

Determination of backrest inclination based on biodynamic response study for prevention of low back pain

Whole-body vibration experiments with subjects under vertical vibration were performed to examine and evaluate effects of backrest inclination on vibration transmitted through seats to the human body by using biodynamic response parameters represented by apparent mass (APMS) and vibration power absorption (VPA). The biodynamic response parameters of twelve male subjects, exposed to vertical random vibration at 0.8 m/s² r.m.s., were characterized under three different backrest support conditions, with the upper body supported against backrest inclined at angles of 0° (vertical), 10°, and 30° with respect to the vertical axis. An increased backrest inclination angle resulted in reduction of the total power absorption calculated particularly the frequency range of 1–20 Hz. Normalized APMS magnitudes showed a principal resonance at about 5 Hz for each subject for a backrest supported vertically. A second resonant peak appeared at about 7.5 Hz in addition to the primary resonant peak for a backrest inclined at an angle of 10° and then became much steeper for a backrest inclined at angle of 30°. For a backrest inclined at an angle of 30°, the resonant peak at 5 Hz was less apparent than in other backrest inclination postures. All subjects showed the second resonant peak at about 7.5 Hz in the double-normalized VPA for a backrest inclined at an angle of 30°. According to the evaluation of vibration absorption behavior performed in this study, backrest inclination angle is preferable between 10° and 30° from the viewpoint of prevention of low back pain disorder.     

Reductions in finger blood flow induced by 125-Hz vibration: effect of area of contact with vibration

To investigate whether the Pacinian channel is involved in vibration-induced reductions of finger blood flow (FBF), vibrotactile thresholds and vasoconstriction have been studied with 125-Hz vibration and two contact areas: 3- or 6-mm-diameter vibrating probes with 2-mm gaps to fixed surrounds. Fifteen subjects provided thresholds for perceiving vibration at the thenar eminence of the right hand with both contact areas. With both contact areas, FBF was then measured in the middle fingers of both hands during five successive 5-min periods: (i) no force and no vibration, (ii) force and no vibration, (iii) force with vibration 15 dB above threshold, (iv) force and no vibration, and (v) no force and no vibration. Thresholds were in the ranges of 0.16–0.66 ms^?2 r.m.s. (6-mm probe) and 0.32–1.62 ms^?2 r.m.s. (3-mm probe). With the magnitude of vibration 15 dB above each individual’s threshold with the 3-mm probe, the median reduction in FBF with the 6-mm probe (to 70 and 77 % of pre-exposure FBF on the exposed right hand and the unexposed left hand, respectively) was greater than with the 3-mm probe (79 and 85 %). There were similar reductions in FBF when vibration was presented by the two contactors at the same sensation level (i.e. 15 dB above threshold with each probe). The findings are consistent with reductions in FBF arising from excitation of the Pacinian channel: increasing the area excited by vibration increases Pacinian activation and provokes stronger perception of vibration and greater vasoconstriction.     

Peripheral tactile sensory perception of older adults improved using subsensory electrical noise stimulation

Loss of tactile sensory function is common with aging and can lead to numbness and difficulty with balance and gait. In previous work we found that subsensory electrical noise stimulation (SENS) applied to the tibial nerve improved tactile perception in the soles of the feet of healthy adults. In this work we aimed to determine if SENS remained effective in an older adult population with significant levels of sensory loss.Older adult subjects (N = 8, female = 4, aged 65–80) had SENS applied via surface electrodes placed proximally to the medial and lateral malleoli. Vibration perception thresholds (VPTs) were assessed in six conditions, two control conditions (no SENS) and four SENS conditions (zero mean ± 15 µA, 30 µA, 45 µA and 60 µA SD). VPT was assessed at three sites on the plantar aspect of the foot.Vibration perception was significantly improved in the presence of ± 30 µA SENS and by 16.2 ± 2.4% (mean ± s.e.m.) when optimised for each subject. The improvement in perception was similar across all VPT test sites.     

Vibrotactile thresholds in mechanoreceptive afferents innervating the foot pad of the cat. The importance of stimulus frequency and duration

Vibrotactile thresholds were determined for non-Pacinian (SA and RA) and Pacinian (PC) mechanoreceptive units innervating the foot pad of the cat with vibratory stimuli of varying frequency (20, 80, and 240 Hz) and duration (100, 400, and 800 ms). Both the absolute (1 impulse/stimulus train) and the tuning (1 impulse/cycle) thresholds of SA and RA units were elevated and those of PC units were decreased as a function of increasing vibration frequency. PC units had the lowest thresholds at 80 and at 240 Hz whereas RA units had the lowest thresholds at 20 Hz. Larger atonal intervals (the range between the absolute and the tuning thresholds) were obtained for all unit types with increasing vibration frequency and PC units had the smallest atonal intervals at all frequencies. The absolute thresholds of all unit types were independent of stimulus duration. The tuning thresholds of SA and RA units were elevated with increasing stimulus duration whereas the tuning thresholds of PC units were independent of stimulus duration. Consequently, larger atonal intervals were obtained for RA and SA but not for PC units with increasing stimulus duration. The results indicate that there are both differences (effect of frequency) and similarities (effect of stimulus duration and the width of atonal intervals) in response characteristics of non-Pacinian mechanoreceptors innervating the hairy skin and the glabrous foot pad of the cat.     

Vibrotactile thresholds in mechanoreceptive afferents innervating the foot pad of the cat: The importance of stimulus frequency and duration

Vibrotactile thresholds were determined for non-Pacinian (SA and RA) and Pacinian (PC) mechanoreceptive units innervating the foot pad of the cat with vibratory stimuli of varying frequency (20, 80, and 240 Hz) and duration (100, 400, and 800 ms). Both the absolute (1 impulse/stimulus train) and the tuning (1 impulse/cycle) thresholds of SA and RA units were elevated and those of PC units were decreased as a function of increasing vibration frequency. PC units had the lowest thresholds at 80 and at 240 Hz whereas RA units had the lowest thresholds at 20 Hz. Larger atonal intervals (the range between the absolute and the tuning thresholds) were obtained for all unit types with increasing vibration frequency and PC units had the smallest atonal intervals at all frequencies. The absolute thresholds of all unit types were independent of stimulus duration. The tuning thresholds of SA and RA units were elevated with increasing stimulus duration whereas the tuning thresholds of PC units were independent of stimulus duration. Consequently, larger atonal intervals were obtained for RA and SA but not for PC units with increasing stimulus duration. The results indicate that there are both differences (effect of frequency) and similarities (effect of stimulus duration and the width of atonal intervals) in response characteristics of non-Pacinian mechanoreceptors innervating the hairy skin and the glabrous foot pad of the cat.     

The effect of vertical whole-body vibration on lower limb muscle activation in elderly adults: Influence of vibration frequency,amplitude and exercise

ObjectiveThis study aimed to investigate how whole-body vibration (WBV) and exercise and their interactions influenced leg muscle activity in elderly adults.Study designAn experimental study with repeated measures design that involved a group of ambulatory, community-dwelling elderly adults (n = 30; 23 women; mean age = 61.4 ± 5.3 years).Main outcome measuresMuscle activity of the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GS) was measured by surface electromyography (EMG), while participants were performing seven different exercises during 4 WBV conditions (condition 1: frequency = 30 Hz, amplitude = 0.6 mm, intensity = 2.25 units of Earth’s gravity (g); condition 2: 30 Hz, 0.9 mm, 3.40 g; condition 3: 40 Hz, 0.6 mm, 3.65 g; condition 4: 40 Hz, 0.9 mm, 5.50 g) and a no-WBV condition in a single experimental session.ResultsSignificantly greater muscle activity was recorded in VL (3%–148%), BF (16%–202%), and GS (19% –164%) when WBV was added to the exercises, compared with the same exercises without WBV (p ≤ 0.015). The effect of vibration intensity on EMG amplitude was exercise-dependent in VL (p = 0.002), and this effect was marginally significant in GS (p = 0.052). The EMG activity induced by the four WBV intensities was largely similar, and was the most pronounced during static erect standing and static single-leg standing.ConclusionsThe EMG amplitude of majority of leg muscles tested was significantly greater during WBV exposure compared with the no-WBV condition. Low-intensity WBV can induce muscle activity as effectively as higher-intensity protocols, and may be the preferred choice for frail elderly adults.     

Effect of combining traction and vibration on back muscles,heart rate and blood pressure

Eighty-five percent of the population has experienced low back pain (LBP), which may result in decreasing muscle strength and endurance, functional capacity of the spine, and so on. Traction and vibration are commonly used to relieve the low back pain. The effect of the combing traction and vibration on back muscles, heart rate (HR) and blood pressure (BP) was investigated 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 0 Hz, 2 Hz and 12 Hz 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 the cardio-vascular system. It was shown that vibration could increase HR and decrease PP. The combination of traction and vibration (2 Hz vibration along Z-axis and 12 Hz vibration along Y-axis) had no significant effect on the cardio-vascular system. The MPF of lumbar erector spinae (LES) and upper trapezius (UT) decreased significantly when the angle reached 20° under the condition of 2 Hz vibration along Z-axis compared with it of 0°. Furthermore, the MPF also decreased significantly compared with it of static mode at 20° for LES and at 30° for UT. However at 12 Hz vibration along Y-axis, the MPF had significant increase when the angle reached 20° in LES and 30° in UT compared to 0°. For LES, the MPF also had significant difference when the angle was increased from 10° to 20°. Therefore, combining 2 Hz vibration along Z-axis and traction (tilt angles that less than 20°) may to reduce muscle fatigue both for LES and UT compared with either vibration or traction alone. The combination of 12 Hz vibration along Y-axis and traction (tilt angles greater than 10° for LES and more than 20° for UT) could provide good treatment of lower muscle fatigue for back pain compared with either vibration or traction alone. It is helpful to provide biomechanical quantitative basis for the selection of the clinical treatment methods.     

Whole body vibration training reduces plantar foot sensitivity but improves balance control of healthy subjects

The goal of this study was to investigate the effects of short-time whole body vibration (WBV) training on foot vibration sensitivity of healthy subjects. Furthermore, the effects of WBV on a balance task (one-leg stand) were also evaluated. 30 young healthy subjects participated in the study. Vibration perception thresholds and balance were measured prior and after a single session of a 4-min WBV training (27 Hz, 2 mm horizontal amplitude). Thresholds were measured at 200 Hz at three anatomical locations of the plantar foot area (first and fifth metatarsal heads and heel). Body balance was quantified using the length as well as the area described by the center of pressure (COP) at quiet, one-leg standing. Whereas vibration thresholds significantly increased after WBV training at all measured locations, there was a significant decrease in the balance related parameters after WBV exercise. The results indicate that the above-threshold, sinusoidal vibration used during WBV training is not an adequate strategy to stimulate/improve vibration sensitivity. The improvements seen in balance after WBV are likely to have neuromuscular mechanisms as their main component rather than increased foot sensitivity.     

ACL reconstruction: Effect of bone dowel on tibial tunnel enlargement

PurposeTo evaluate prospectively if the impaction of a bone dowel in the tibial tunnel prevents the tunnels from enlarging beyond their original diameter.MethodsSeventeen patients underwent arthroscopically assisted ACL reconstruction with hamstring autologous graft. All patients underwent CT of the knee on the day of surgery, at 3 months and 12 months post-op.ResultsOn the day of surgery, the median cross-sectional areas of the tunnels were 77.0 and 79.0 mm², respectively at 15 mm and 20 mm from the tip of the posterior wall of the tunnel. At 3 months, the median cross-sectional areas of the tunnels were 70.0 and 65.0 mm², at 15 mm and 20 mm. At 12 months post-op, the median cross-sectional areas of the tunnels were 69.0 and 69.0 mm². The median enlargement of the tunnels between 3 months and 12 months post-op was 0.0 mm² at 15 mm and ? 2.0 mm² at 20 mm.ConclusionsThe impaction of an autologous bone dowel in the tibial tunnel during hamstring ACL reconstruction keeps the tunnels from enlarging beyond their original diameter, and there is no further enlargement of the tunnels after 3 months post-op.     

Marker-based validation of a biplane fluoroscopy system for quantifying foot kinematics

IntroductionRadiostereometric analysis has demonstrated its capacity to track precise motion of the bones within a subject during motion. Existing devices for imaging the body in two planes are often custom built systems; we present here the design and marker-based validation of a system that has been optimized to image the foot during gait.MethodsMechanical modifications were made to paired BV Pulsera C-arms (Philips Medical Systems) to allow unfettered gait through the imaging area. Image quality improvements were obtained with high speed cameras and the correction of image distorting artifacts. To assess the system's accuracy, we placed beads at known locations throughout the imaging field, and used post processing software to calculate their apparent locations.ResultsDistortion correction reduced overall RMS error from 6.56 mm to 0.17 mm. When tracking beads in static images a translational accuracy of 0.094 ± 0.081 mm and rotational accuracy of 0.083 ± 0.068° was determined. In dynamic trials simulating speeds seen during walking, accuracy was 0.126 ± 0.122 mm.DiscussionThe accuracies and precisions found are within the reported ranges from other such systems. With the completion of marker-based validation, we look to model-based validation of the foot during gait.     

Altered dynamic foot kinematics in people with medial knee osteoarthritis during walking: A cross-sectional study

BackgroundFootwear and insoles are used to reduce knee load in people with medial knee osteoarthritis (OA), despite a limited understanding of foot function in this group. The aim of this study was to investigate the differences in foot kinematics between adults with and without medial knee OA during barefoot walking.MethodsFoot kinematics were measured during walking in 30 adults; 15 with medial knee OA (mean age was 67.0 with a standard deviation (SD) of 8.9 years; height was 1.66 with SD of 0.13 m; body mass was 84.2 with SD of 15.8 kg; BMI was 30.7 with SD of 6.2 kg/m²; K–L grade 3: 5, grade 4: 10) and 15 aged and gender matched control participants with 12 motion analysis cameras using the IOR multi-segment foot model. Motion of the knee joint, hindfoot, midfoot, forefoot and hallux were compared between groups using clustered linear regression.ResultsThe knee OA group displayed reduced coronal plane range of motion of the midfoot (mean 3.8° vs. 5.4°, effect size = 1.1, p = 0.023), indicating reduced midfoot mobility. There was also a reduced sagittal plane range of motion at the hallux in the knee OA group compared to the control group (mean 29.6° vs. 36.3°, effect size = 1.2, p = 0.008). No statistically significant differences in hindfoot or forefoot motion were observed.ConclusionsPeople with medial knee OA display altered foot function compared to healthy controls. As foot and knee function are related, it is possible that altered foot function in people with knee OA may influence the effects of footwear and insoles.     

A new metaphyseal bone defect model in osteoporotic rats to study biomaterials for the enhancement of bone healing in osteoporotic fractures

The intention of this study was to establish a new critical size animal model that represents clinically relevant situations with osteoporotic bone status and internally fixated metaphyseal defect fractures in which biomaterials for the enhancement of fracture healing in osteoporotic fracture defects can be studied. Twenty-eight rats were ovariectomized (OVX) and treated with a calcium-, phosphorus-, vitamin D3-, soy- and phytoestrogen-free diet. After 3 months Dual-energy X-ray absorptiometry measurements showed statistically significant reductions in bone mineral density of the spine of ?25.9% and of the femur of ?21.3% of the OVX rats compared with controls, confirming osteoporosis in the OVX rats. The OVX rats then underwent either 3 or 5 mm wedge-shaped osteotomy of the distal metaphyseal area of the femur that was internally stabilized with a T-shaped mini-plate. After 42 days biomechanical testing yielded completely unstable conditions in the 5 mm defect femora (bending stiffness 0 N mm^?2) and a bending stiffness of 12,500 N mm^?2 in the 3 mm defects, which showed the beginning of fracture consolidation. Micro-computed tomography showed statistically significant more new bone formation in the 3 mm defects (4.83 ± 0.37 mm²), with bridging of the initial fracture defect area, compared with the 5 mm defects (2.68 ± 0.34 mm²), in which no bridging of the initial defect was found. These results were confirmed by histology. In conclusion, the 5 mm defect can be considered as a critical size defect model in which biomaterials can be tested.     

Impact of sampling rate for time domain analysis of continuous intracranial pressure (ICP) signals

Time domain analysis of the intracranial pressure (ICP) waveform is critically dependent on the exact reproduction of the ICP waveform. This study explored how the sampling rate of the ICP signal affects the time domain analysis. It was also assessed through this study how upsampling (interpolation) improves the time domain analysis. From the hospital database, a set of 55 ICP waveforms were retrieved from 48 patients (28 children and 20 adults). First, the ICP signals originally sampled at 200 or 100 Hz were compared with the ICP signals downsampled to 5, 10, 20, 25, 50 Hz (and 100 Hz). Second, the original ICP signals were compared with ICP signals upsampled (i.e. interpolated) to 100 Hz (from 5, 10, 20, 25 or 50 Hz). For each ICP recording the output of time domain analysis was the average value and the quantitative distribution of mean ICP wave amplitudes determined every six second (6 s) time window. The total material incorporated a total of 373,371 6 s time windows. Downsampling revealed that the time domain analysis could be most faithfully applied to ICP signals sampled at 50 Hz or above, while ICP signals sampled at 25 Hz deviated more from the original signal than we would accept from a clinical perspective. The use of interpolation gave better representation of the peaks, and should be applied to all ICP signals sampled at lower rate than 100 Hz.     

Anatomy of the anterior cruciate ligament related to hamstring tendon grafts. A cadaveric study

BackgroundThe aim of modern techniques for anatomic reconstruction of the ACL is to reproduce ACL footprints, in order to restore anatomy and therefore normal biomechanics. Is there an oversizing of the hamstring grafts related to ACL dimensions?MethodsTwenty-two paired cadaver knees were dissected. ACL dimensions at mid-portion and ACL footprints were measured after removing the synovial membrane.Hamstrings were harvested and prepared in a quadruple strand graft in order to measure the mean circumference.ResultsThe average ACL tibial and femoral insertion site areas of the ACL were 117.9 mm² (range, 90 to 130 mm) and 96.8 mm² (range, 80 to 121 mm), respectively.The average diameter and cross sectional area of the ACL tendon at mid-portion were 6.1 mm (range, 5 to 7 mm) and 29.2 mm² (range, 20 to 38.9), respectively. The average diameter and cross-sectional area of the 4-stranded hamstring tendons were 6.7 (range, 5 to 8) and 35.3 mm² (range, 20 to 50), respectively.There was a correlation between the 4-stranded hamstring grafts and ACL dimensions (footprints, ligament at mid substance, p < 0.01). The cross sectional area of hamstring tendon was significantly larger than the ACL area at mid-portion (mean 20.9%, p < 0.05).ConclusionWith current ACL reconstruction techniques, the graft is oversized at a mean of 21%, despite a good correlation between the ACL and the hamstring tendon, especially among small subjects and women. The question arises whether the anatomic reconstruction of the ACL should fill ACL footprints or mimic the ligament itself.Clinical relevanceHamstrings grafts are significantly larger than native ACL.     

The effect of dual frequency cyclic compression on matrix deposition by osteoblast-like cells grown in 3D scaffolds and on modulation of VEGF variant expression

As a strategy to optimise osteointegration of biomaterials by inducing proper extracellular matrix synthesis, and specifically angiogenic growth factor production and storage, we tested the effects of cyclic mechanical compression on 3D cultures of human osteoblast-like cells. MG-63 cells were seeded into 3D porous hydroxyapatite ceramics under vacuum to enable a homogenous cellular distribution. A four-day culture period allowed cell proliferation throughout the scaffolds. Low amplitude cyclic compressions were then applied to the scaffolds for 15 min with different regimens generated by the ZetOS? system. A 3 Hz sinusoidal (sine) signal increased slightly collagen and fibronectin expression. When 50 Hz or 100 Hz vibrations were superimposed to the 3 Hz signal, matrix protein expression was down-regulated. In contrast, adding a 25 Hz vibration up-regulated significantly collagen and fibronectin. Moreover, expression of a matrix-bound variant of vascular endothelial growth factor-A (VEGF-A) was specifically stimulated compared to control or 3 Hz sine, and non-soluble VEGF protein was increased. Our study enabled us to identify low-amplitude, high-frequency strain regimen able to increase major matrix proteins of bone tissue and to regulate the expression of VEGF variants, showing that an appropriate combined loading has the potential to functionalise cellularized bone-like constructs.     

Anterior tibiofemoral intersegmental forces during landing are predicted by passive restraint measures in women

BackgroundPassive restraint capabilities may influence sagittal plane knee joint mechanics during activity. This study aimed to determine if measures associated with passive restraint of anterior translation of the tibia are predictive of peak anterior knee shear force during landing.MethodsPassive restraint measures were assessed via joint arthrometry and during 40% body weight simulated weight acceptance using recreationally active students (73 F, 42 M; 21.8 ± 2.9 yr, 1.69 ± 0.1 m, 68.9 ± 14.1 kg). Anterior knee laxity (mm) at 133 N and initial (0–20 N) and terminal (100–130 N) anterior stiffnesses (N/mm) were calculated from arthrometer data. Peak anterior tibial acceleration (m?s^?2) relative to the femur was assessed via electromagnetic position sensors during 40% body weight acceptance trials. Peak knee shear force was assessed during double-leg drop jumps.ResultsSex specific linear stepwise regressions revealed that in females, increasing peak tibial acceleration (5.1 ± 1.8 m·s^? 2) (R²? = 7.3%, P? = 0.021), increasing initial anterior stiffness (31.0 ± 14.0 N/mm) (R²? = 5.9%, P? = 0.032), and decreasing terminal anterior stiffness (43.4 ± 17.4 N/mm) (R²? = 4.9%, P? = 0.046) collectively predicted greater peak knee shear forces (66.6 ± 12.03% BW) (multiple R² = 18.1%). No male regressions were significant.ConclusionsSagittal laxity measures are associated with anterior knee shear loads during landing in females. Greater tibial acceleration during early axial load along with greater initial and lesser terminal anterior stiffnesses predicted increasing anterior knee shear forces. Future work should investigate the combined contribution of passive and active restraints to high-risk ACL biomechanics.     

Suitability of DCPs with Screw Locking Elements to allow sufficient interfragmentary motion to promote secondary bone healing of osteoporotic fractures

This paper analyses the suitability of a system comprising a Dynamic Compression Plate (DCP) and Screw Locking Elements (SLEs) to allow sufficient interfragmentary motion to promote secondary bone healing in osteoporotic fractures.Four fixation systems were mounted on bone-simulating reinforced epoxy bars filled with solid rigid polyurethane foam. Group 1, used for comparison purposes, represents a system comprised of a Locking Compression Plate (LCP) and eight locking screws. Groups 2 and 3 represent a system comprised of a DCP plate with eight cortical screws and two SLEs placed on the screws furthest from (group 2) and nearest to (group 3) the fracture. Group 4 represents the system comprised of a DCP plate with SLEs placed on all eight cortical screws. Cyclic compression tests of up to 10,000 load cycles were performed in order to determine the parameters of interest, namely the stiffnesses and the interfragmentary motion of the various configurations under consideration. Tukey's multiple comparison test was used to analyse the existence or otherwise of significant differences between the means of the groups.At 10,000 cycles, interfragmentary motion at the far cortex for group 2 was 0.60 ± 0.04 mm and for group 3 0.59 ± 0.03 mm (there being no significant differences: p = 0.995). The mean interfragmentary motion at the far cortex of the LCP construct was 70% less than that of the two groups with 2SLEs (there being significant differences: p = 1.1 × 10^?8). In the case of group 4 this figure was 45% less than in groups 2 and 3 (there being significant differences: p = 5.6 × 10^?6). At 10,000 cycles, interfragmentary motion at the near cortex for group 2 was 0.24 ± 0.06 mm and for group 3 0.24 ± 0.03 mm (there being no significant differences: p = 1.000). The mean interfragmentary motion at the near cortex of the LCP construct was 70.8% less than that of the two groups with 2SLEs (there being significant differences: p = 0.011). In the case of group 4 this figure was 66.7% less than in groups 2 and 3 (there being significant differences: p = 0.016). The mean stiffness at 10,000 cycles was 960 ± 110 N mm^?1 for group 2 and 969 ± 53 N mm^?1 for group 3 (there being no significant differences: p = 1.000). For group 1 (the LCP construct) the mean stiffness at 10,000 cycles was 3144 ± 446 N mm^?1, 3.25 times higher than that of groups 2 and 3 (there being significant differences: p = 0.00002), and 1.6 times higher than that of the DCP + 8SLEs construct (1944 ± 408 N mm^?1, there being significant differences: p = 0.007).It is concluded that using the DCP + 2SLEs construct sufficient interfragmentary motion is ensured to promote secondary bone healing. However, if too many SLEs are used the result may be, as with the LCP, an excessively rigid system for callus formation.