Clinical Biomechanics

The wear of the biomaterial/cartilage interface is vital for the development of innovative chondroplasty therapies. The aim of this study was to investigate potential chondroplasty biomaterials when sliding against natural articular cartilage under uniaxial reciprocating and multi-directional rotation/reciprocating motions. Three biphasic hydrogels were compared to articular cartilage (negative control) and stainless steel (positive control). Friction was measured by means of a simple geometry friction and wear simulator. All tests were completed in 25% bovine serum at 20 degrees C. Mechanical alterations to the surface structure were quantified using surface topography. Articular cartilage produced a constant friction value of 0.05 (confidence interval=0.015) with and without rotation. Stainless steel against articular cartilage produced an increase in friction over time resulting in a peak value of 0.7 (confidence interval=0.02) without rotation, increasing to 0.88 (confidence interval=0.03) with rotation. All biphasic hydrogels produced peak friction values lower than the positive control and demonstrated no difference between uni- and multi-directional motion. Degradation of the opposing cartilage surface showed a significant difference between the positive and negative controls, with the greater cartilage damage when sliding against stainless steel under uni-directional motion. The lower friction and reduction of opposing cartilage surface degradation with the potential chondroplasty biomaterials can be attributed to their biphasic properties. This study illustrated the importance of biphasic properties within the tribology of cartilage substitution materials and future work will focus on the optimisation of biphasic properties such that materials more closely mimic natural cartilage.

Normative gait data is essential for diagnosing and treating abnormal gait patterns. The examination of the onset of adult-like kinetic gait patterns in children has generated inconsistent results. The purpose of this study was to identify age-related differences in kinematic and kinetic gait parameters across children aged 3-13 years old. A motion capture system and three force plates were employed to compute sagittal joint angles and joint kinetics during walking and compare results between children aged 3-4 years (n=13), 5-6 years (n=10), 7-8 years (n=12), and 9-13 years (n=12). Anthropometric data was estimated using a mathematical model (elliptical cylinder method). Peak flexion and extension joint angles and moments, and peak concentric and eccentric joint powers were analyzed using multivariate analyses of variance. For most of the variables examined, similar results were obtained across age groups. Reduced peak hip flexion moments and knee extension moments were observed in the 3-4 year olds compared to the oldest group of walkers. Compared to the 9-13 year olds, reduced ankle joint moments and power were observed in most age groups. The results suggest that adult-like kinetic patterns for the hip and knee were attained by 5 years of age. However, for the ankle joint, adult-like patterns are not achieved until nine years of age or older. These findings stress the importance of using age-matched normative data for clinical gait analysis.

OBJECTIVE: To compare the strength of two types of fixation method for calcaneal fractures. DESIGN: A biomechanical testing examined the stability of 12 fractured calcaneal specimens fixed with two different methods. BACKGROUND: Though anatomic reduction and internal fixation for the treatment of intra-articular fractures of the calcaneus has become popular, biomechanical data on the fixation strength is lacking. METHODS: Twenty fresh frozen specimens of amputated human legs were impacted by a 20 kg weight dropped from a 155 cm height to create calcaneal fractures. Twelve specimens which demonstrated a longitudinal and a transverse primary fracture lines were selected for open reduction and internal fixation. Group 1: a lateral buttress plate and parallel screws placed in the latero-medial direction were used. Group 2: a longitudinal screw was added in addition to the fixation used in group 1. Biomechanical testing was performed by applying a tibial shank load until the internal fixation failed. RESULTS: All mechanical failures of the reconstructed calcaneus occurred through the transverse primary fracture line. The average failure load was 805+/-356 N in group 1 and 2905+/-910 N in group 2 (Wilcoxon p<0.05). CONCLUSIONS: A longitudinal transfixing screw could significantly improve the stability of the transverse primary fracture line in calcaneal fractures.

Objective: To determine the effect of quadriceps strength and joint stability on gait patterns after anterior cruciate ligament injury and reconstruction. Design: Cross-sectional comparative study in which four groups underwent motion analysis with surface electromyography. Background: Individuals following anterior cruciate ligament rupture often demonstrate reduced knee angles and moments during the early stance phase of gait. Alterations in gait can neither be ascribed to instability nor to quadriceps weakness alone when both are present. Methods: Twenty-eight individuals with complete anterior cruciate ligament rupture (10 patients with acute rupture, 8 patients following reconstruction with quadriceps strength >90% of the uninvolved side [strong-anterior cruciate ligament reconstructed group], and 10 patients after reconstruction with quadriceps strength <80% of the uninvolved side [weak-anterior cruciate ligament reconstructed group]), and 10 uninjured subjects underwent an examination of their lower extremity to collect kinematics, kinetics, and electromyography during walking and jogging. Anterior cruciate ligament reconstruction was arthroscopically assisted and a double loop semitendinosis-gracilis autograft or allograft was used as a graft source. All reconstructed subjects had stable knees, full range of motion, and no effusion or pain at the time of testing (more than three months after surgery). Results: Knee angles and moments of the strong group were indistinguishable from the uninjured group during early stance of both walking and jogging. The weak subjects had reduced knee angles and moments during walking, and jogged similarly to the deficient subjects. Regression analysis revealed a significant effect between early stance phase knee angles and moments and quadriceps strength during both walking and jogging. Conclusion: Inadequate quadriceps strength contributes to altered gait patterns following anterior cruciate ligament reconstruction. Relevance: Rapid strengthening following anterior cruciate ligament injury or reconstruction may contribute to a safe return to high-level activities.

INTRODUCTION:: Reviewing the management of calcaneus fractures, conservative and operative treatment are known without a generally accepted, well proven therapeutical strategy or tactics compared to other types of fractures. The purpose of this study is to define the parameters of the differences between the fractured calcaneus and the intact one, as well as the two types of treatments using the gait analysis method. MATERIALS AND METHODS:: Retrospective clinical investigation and gait analysis have been performed on 217 patients with calcaneus fractures. An analysis of the X-rays was also included. The Novel 101 B pedobarography analyser with platform 102H (4 sensor/cm(2)) was used for pressure distribution analysis. The region of the foot was divided into four masks, Mask 1 (M1) the area of the heel, Mask 2 (M2), the mid-foot, Mask 3 (M3), metatarsal region, and Mask 4 (M4) the region of the toes. The total area of the foot (TOT) included all four masks. Eighteen bilateral fractured calcanei have been omitted from the evaluation, owing to the lack of control foot, and 28 patients were excluded for the other complications of the fractures foot, complications of the control foot or complications extending to both feet. The data on the 171 fractures (68 patients treated conservatively and 103 patients treated operatively) of the calcaneus were compared with their control feet. The average age was 52.0 years (+/- 2.7) and the average follow up time was 49.9 months (+/- 17.5). The statistical analysis was performed using SPSS for Windows. Examination of correlation, repeated measurement analysis of variance, ANOVA, and multiple comparisons were performed by Bonferoni. Linear discriminating analysis was also performed. Significance level was defined as p<0.05 in each case. RESULTS:: All investigated parameters (area, max.F, max.P, absolute and relative contact time, FTI, PTI.) of M2 were significantly higher on the fractured side than on the intact one. The investigation of the whole foot showed significant increase concerning the area, and significant decrease in the max. force, FTI and PTI values. The differences between the conservatively treated and the intact foot values, as well as the differences between operatively treated foot and the intact one, demonstrated a significant decrease in the FTI TOT and the PTI TOT in both groups. A significantly higher difference was also demonstrated when the difference in the value of PTI TOT in the operative group was compared to the conservative one. Therefore, the values of the fractured side of the operative group were significantly lower than the values of the intact one, but significantly higher than the values of the conservative group. CONCLUSIONS:: The gait analysis parameters for the calcaneus fractured and the intact sides allowed for separation of the data according to significant differences. The results of the gait analysis comparing the conservative and operative method of the treatment showed that the surgical method was the better choice.

The resonant frequency of the wrist has been measured in hemiplegic subjects and was higher on the spastic side, indicating greater stiffness. The increased stiffness is associated with stretch reflex activity, which is absent in normal subjects. The increased stiffness of spasticity in most of the patients did not exaggerate the sharpness of tuning as there was a compensatory rise in damping. Increased damping will contribute to the subjective assessment of muscular hypertonicity. Measurements of resonant frequency and damping are essential in assessing muscular hypertonicity.

The "180° turning and sitting down task" is a very conscious movement that requires focusing on turning at the exact moment, and very few studies address on this topic in older adults. The purpose of the study was to compare kinematics and electromyography of the head, lumbar and knee joints during 180°turning in older and young adults. Twenty older adults and 20 younger adults were assessed. A 16-channel telemetry electromyography system with electrogoniometers and an inclinometer were used to record the head, lumbar and knee joint kinematic and electromyography data during the 180° turning. This movement had been further divided into 4 phases (braking, mid-stance, swing, and terminal loading) for analysis. There were significant differences in the joint displacement and muscular activity among the different phases. Comparison between groups showed that the older adults group had less lateral lumbar flexion, less knee flexion and lower velocity of the head and knee flexion compared to young adults during turning. The electromyography data of the left biceps femoris, left gastrocnemius and left erector spinae muscles in the older adults group showed significantly higher levels than in the young adults. Older adults need to adjust velocities of moving joints and increase the extensor synergy muscles of the back and the stance leg to provide posture stability. Kinematics and neuromuscular modulations of the head, lumbar and knee are required according to the various phases of the turn movements and change with aging.

Preservation of hip geometry is important for treatment success in endoprosthesis implantation. Digital planning can be used to estimate postoperative hip geometry. This study examined whether digital planning accurately predicts surgical outcomes for two femoral neck resecting short stem implants, Mayo® (Zimmer) and Metha® (Aesculap). Preoperative digital planning of the short stem and acetabular cup was performed for 191 patients (197 endoprostheses) with hip osteoarthritis. Digital planning was done with mediCAD II (Hectec) to evaluate types of prosthesis stems and sizes, leg lengthening and offset, and angle of stem inclination within the femur. The predicted values for these parameters were compared to the postoperative measurements. A double coordinate system was developed to measure pelvic and femoral distances separately. Individual scale factors were applied to minimize measurement bias. Implantation of the planned short stem prostheses resulted in a mean femoro-acetabular leg lengthening of 4.2mm (SD 5.8mm) and a mean femoro-acetabular offset-reduction of 4.2mm (SD 5.9mm) in comparison with preoperative planning. Implantation of both stems resulted in increased valgization compared to planning (Metha®, mean 5.4° (SD 3.7°); Mayo®, mean -3.2° (SD 3.4°)). Differences between preoperative planning and postoperative outcomes were greater for femoro-acetabular than for cup-related leg length and offset. On average, leg length was longer than predicted and there was loss of femoro-acetabular offset. Compared with the planning, valgization of the implanted stems was frequently observed. Copyright © 2013 Elsevier Ltd. All rights reserved.