External Joint Research Articles

Effects of the implant design on peri-implant bone stress and abutment micromovement: three-dimensional finite element analysis of original computer-aided design models.

Occlusal overloading causes peri-implant bone resorption. Previous studies examined stress distribution in alveolar bone around commercial implants using three-dimensional (3D) finite element analysis. However, the commercial implants contained some different designs. The purpose of this study is to reveal the effect of the target design on peri-implant bone stress and abutment micromovement. Six 3D implant models were created for different implant-abutment joints: 1) internal joint model (IM); 2) external joint model (EM); 3) straight abutment (SA) shape; 4) tapered abutment (TA) shapes; 5) platform switching (PS) in the IM; and 6) modified TA neck design (reverse conical neck [RN]). A static load of 100 N was applied to the basal ridge surface of the abutment at a 45-degree oblique angle to the long axis of the implant. Both stress distribution in peri-implant bone and abutment micromovement in the SA and TA models were analyzed. Compressive stress concentrated on labial cortical bone and tensile stress on the palatal side in the EM and on the labial side in the IM. There was no difference in maximum principal stress distribution for SA and TA models. Tensile stress concentration was not apparent on labial cortical bone in the PS model (versus IM). Maximum principal stress concentrated more on peri-implant bone in the RN than in the TA model. The TA model exhibited less abutment micromovement than the SA model. This study reveals the effects of the design of specific components on peri-implant bone stress and abutment displacement after implant-supported single restoration in the anterior maxilla.

Evidence for joint moment asymmetry in healthy populations during gait

The purpose of this study was to determine the presence and prevalence of asymmetry in lower extremity joint moments within and across healthy populations during overground walking. Bilateral gait data from several studies performed at two institutions were pooled from 182 healthy, pain-free subjects. Four distinct populations were identified based on age, activity level and body mass index. Mean peak external joint moments were calculated from three to six trials of level overground walking at self-selected speed for each subject. Right and left limb moments were reclassified as “greater” or “lesser” moment for each subject to prevent obscuring absolute asymmetry due to averaging over positive and negative asymmetries across subjects. A clinically relevant asymmetry measure was calculated from the peak joint moments with an initial chosen cutoff value of 10%. Confidence intervals for the proportion of subjects with greater than 10% asymmetry between limbs were estimated based on the binomial distribution. We found a high amount of asymmetry between the limbs in healthy populations. More than half of our overall population exceeded 10% asymmetry in peak hip and knee flexion and adduction moments. Group medians exceeded 10% asymmetry for all variables in all populations. This may have important implications on gait evaluations, particularly clinical evaluations or research studies where asymmetry is used as an outcome. Additional research is necessary to determine acceptable levels of joint moment asymmetry during gait and to determine whether asymmetrical joint moments influence the development of symptomatic pathology or success of lower extremity rehabilitation.

Improper Trunk Rotation Sequence Is Associated With Increased Maximal Shoulder External Rotation Angle and Shoulder Joint Force in High School Baseball Pitchers

Background: In a properly coordinated throwing motion, peak pelvic rotation velocity is reached before peak upper torso rotation velocity, so that angular momentum can be transferred effectively from the proximal (pelvis) to distal (upper torso) segment. However, the effects of trunk rotation sequence on pitching biomechanics and performance have not been investigated. Purpose: The aim of this study was to investigate the effects of trunk rotation sequence on ball speed and on upper extremity biomechanics that are linked to injuries in high school baseball pitchers. The hypothesis was that pitchers with improper trunk rotation sequence would demonstrate lower ball velocity and greater stress to the joint. Study Design: Descriptive laboratory study. Methods: Three-dimensional pitching kinematics data were captured from 72 high school pitchers. Subjects were considered to have proper or improper trunk rotation sequences when the peak pelvic rotation velocity was reached either before or after the peak upper torso rotation velocity beyond the margin of error (±3.7% of the time from stride-foot contact to ball release). Maximal shoulder external rotation angle, elbow extension angle at ball release, peak shoulder proximal force, shoulder internal rotation moment, and elbow varus moment were compared between groups using independent t tests (α < 0.05). Results: Pitchers with improper trunk rotation sequences (n = 33) demonstrated greater maximal shoulder external rotation angle (mean difference, 7.2° ± 2.9°, P = .016) and greater shoulder proximal force (mean difference, 9.2% ± 3.9% body weight, P = .021) compared with those with proper trunk rotation sequences (n = 22). No other variables differed significantly different between groups. Conclusion: High school baseball pitchers who demonstrated improper trunk rotation sequences demonstrated greater maximal shoulder external rotation angle and shoulder proximal force compared with pitchers with proper trunk rotation sequences. Clinical Relevance: Improper sequencing of the trunk and torso alter upper extremity joint loading in ways that may influence injury risk. As such, exercises that reinforce the use of a proper trunk rotation sequence during the pitching motion may reduce the stress placed on the structures around the shoulder joint and lead to the prevention of injuries.

Surgically Relevant Bony and Soft Tissue Anatomy of the Proximal Femur.

Background:Hip endoscopy facilitates the treatment of extra-articular disorders of the proximal femur. Unfortunately, current knowledge of proximal femur anatomy is limited to qualitative descriptions and lacks surgically relevant landmarks.Purpose:To provide a quantitative and qualitative analysis of proximal femur anatomy in reference to surgically relevant bony landmarks.Study Design:Descriptive laboratory study.Methods:Fourteen cadaveric hemipelvises were dissected. A coordinate measuring device measured dimensions and interrelationships of the gluteal muscles, hip external rotators, pectineus, iliopsoas, and joint capsule in reference to osseous landmarks.Results:The vastus tubercle, superomedial border of the greater trochanter, and femoral head-neck junction were distinct and reliable osseous landmarks. The anteroinferior tip of the vastus tubercle was 17.1 mm (95% CI: 14.5, 19.8 mm) anteroinferior to the center of the gluteus medius lateral insertional footprint and was 22.9 mm (95% CI: 20.1, 25.7 mm) inferolateral to the center of the gluteus minimus insertional footprint. The insertions of the piriformis, conjoint tendon of the hip (superior gemellus, obturator internus, and inferior gemellus), and obturator externus were identified relative to the superomedial border of the greater trochanter. The relationship of the aforementioned footprints were 49% (95% CI: 43%, 54%), 42% (95% CI: 33%, 50%), and 64% (95% CI: 59%, 69%) from the anterior (0%) to posterior (100%) margins of the superomedial border of the greater trochanter, respectively. The hip joint capsule attached distally on the proximal femur 18.2 mm (95% CI: 14.2, 22.2 mm) from the head-neck junction medially on average.Conclusion:The vastus tubercle, superomedial border of the greater trochanter, and the femoral head-neck junction were reliable osseous landmarks for the identification of the tendinous and hip capsular insertions on the proximal femur. Knowledge of the interrelationships between these structures is essential for endoscopic navigation and anatomic surgical repair and reconstruction.Clinical Relevance:The qualitative and quantitative clinically relevant anatomic data presented here will aid in the diagnosis of proximal femur pathology and will provide a template for anatomic repair or reconstruction.

Effects of Strength Training Program on Shoulder External Rotators Muscle and Joint Balance

Effects of Strength Training Program on Shoulder External Rotators Muscle and Joint Balance

Strain energy in the femoral neck during exercise

Physical activity is recommended to mitigate the incidence of hip osteoporotic fractures by improving femoral neck strength. However, results from clinical studies are highly variable and unclear about the effects of physical activity on femoral neck strength. We ranked physical activities recommended for promoting bone health based on calculations of strain energy in the femoral neck. According to adaptive bone-remodeling theory, bone formation occurs when the strain energy (S) exceeds its homeostatic value by 75%. The potential effectiveness of activity type was assessed by normalizing strain energy by the applied external load. Tensile strain provided an indication of bone fracture. External force and joint motion data for 15 low- and high-load weight-bearing and resistance-based activities were used. High-load activities included weight-bearing activities generating a ground force above 1 body-weight and maximal resistance exercises about the hip and the knee. Calculations of femoral loads were based on musculoskeletal and finite-element models. Eight of the fifteen activities were likely to trigger bone formation, with isokinetic hip extension (ΔS=722%), one-legged long jump (ΔS=572%), and isokinetic knee flexion (ΔS=418%) inducing the highest strain energy increase. Knee flexion induced approximately ten times the normalized strain energy induced by hip adduction. Strain and strain energy were strongly correlated with the hip-joint reaction force (R2=0.90–0.99; p<0.05) for all activities, though the peak load location was activity-dependent. None of the exercises was likely to cause fracture. Femoral neck mechanics is activity-dependent and maximum isokinetic hip-extension and knee-flexion exercises are possible alternative solutions to impact activities for improving femoral neck strength.

EFFECT OF AN INTERNALLY VERSUS EXTERNALLY FOCUSED ACL INJURY PREVENTION PROGRAM ON INJURY RISK

BackgroundAnterior cruciate ligament (ACL) injury prevention programs have shown mixed results, which may be in part due to suboptimal training components.ObjectiveDetermine effects of a prevention program with external and internal...

INTERVENTIONS TO PREVENT SPORTS RELATED INJURIES: A SYSTEMATIC REVIEW AND META-ANALYSIS OF RANDOMISED CONTROLLED TRIALS

BackgroundThe effects of methods to prevent injuries have been studied in several systematic reviews. However, no meta-analysis taking into account all randomised controlled intervention trials aiming at prevention of sports...

SPORTS AND EXERCISE SAFETY IN FINLAND – LIVE: AN IMPLEMENTATION PROGRAM TO SPORT CLUBS AND SCHOOLS

BackgroundNumber of sports injuries has increased in Finland during the past decades. Today sports injuries are the most common injury type. Especially children and youth are at high risk.ObjectiveThe purpose...

Is midsole thickness a key parameter for the running pattern?

Many studies have highlighted differences in foot strike pattern comparing habitually shod runners who ran barefoot and with running shoes. Barefoot running results in a flatter foot landing and in a decreased vertical ground reaction force compared to shod running. The aim of this study was to investigate one possible parameter influencing running pattern: the midsole thickness. Fifteen participants ran overground at 3.3ms−1 barefoot and with five shoes of different midsole thickness (0mm, 2mm, 4mm, 8mm, 16mm) with no difference of height between rearfoot and forefoot. Impact magnitude was evaluated using transient peak of vertical ground reaction force, loading rate, tibial acceleration peak and rate. Hip, knee and ankle flexion angles were computed at touch-down and during stance phase (range of motion and maximum values). External net joint moments and stiffness for hip, knee and ankle joints were also observed as well as global leg stiffness. No significant effect of midsole thickness was observed on ground reaction force and tibial acceleration. However, the contact time increased with midsole thickness. Barefoot running compared to shod running induced ankle in plantar flexion at touch-down, higher ankle dorsiflexion and lower knee flexion during stance phase. These adjustments are suspected to explain the absence of difference on ground reaction force and tibial acceleration. This study showed that the presence of very thin footwear upper and sole was sufficient to significantly influence the running pattern.

Influence of the implant-abutment connection design and diameter on the screw joint stability.

PURPOSEThis study was conducted to evaluate the influence of the implant-abutment connection design and diameter on the screw joint stability.MATERIALS AND METHODSRegular and wide-diameter implant systems with three different joint connection designs: an external butt joint, a one-stage internal cone, and a two-stage internal cone were divided into seven groups (n=5, in each group). The initial removal torque values of the abutment screw were measured with a digital torque gauge. The postload removal torque values were measured after 100,000 cycles of a 150 N and a 10 Hz cyclic load had been applied. Subsequently, the rates of the initial and postload removal torque losses were calculated to evaluate the effect of the joint connection design and diameter on the screw joint stability. Each group was compared using Kruskal-Wallis test and Mann-Whitney U test as post-hoc test (α=0.05).RESULTSThe postload removal torque value was high in the following order with regard to magnitude: two-stage internal cone, one-stage internal cone, and external butt joint systems. In the regular-diameter group, the external butt joint and one-stage internal cone systems showed lower postload removal torque loss rates than the two-stage internal cone system. In the wide-diameter group, the external butt joint system showed a lower loss rate than the one-stage internal cone and two-stage internal cone systems. In the two-stage internal cone system, the wide-diameter group showed a significantly lower loss rate than the regular-diameter group (P<.05).CONCLUSIONThe results of this study showed that the external butt joint was more advantageous than the internal cone in terms of the postload removal torque loss. For the difference in the implant diameter, a wide diameter was more advantageous in terms of the torque loss rate.

Influence of Hip Joint Position on Muscle Activity during Prone Hip Extension with Knee Flexion.

[Purpose] This study investigated the selective activation of the gluteus maximus during a prone hip extension with knee flexion exercise, with the hip joint in different positions. [Subjects] The subjects were 21 healthy, male volunteers. [Methods] Activities of the right gluteus maximus, right hamstrings, bilateral lumbar erector spinae, and bilateral lumbar multifidus were measured using surface electromyography during a prone hip extension with knee flexion exercise. Measurements were made with the hip joint in each of 3 positions: (1) a neutral hip joint position, (2) an abduction hip joint position, and (3) an abduction with external rotation hip joint position. [Results] Gluteus maximus activity was significantly higher when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. Gluteus maximus activity was also significantly higher in the abduction hip joint position than in the neutral hip joint position. Hamstring activity was significantly lower when the hip was in the abduction with external rotation hip joint position than when it was in the neutral hip joint and abduction hip joint positions. [Conclusion] Abduction and external rotation of the hip during prone hip extension with knee flexion exercise selectively activates the gluteus maximus.

Interventions to Prevent Sports Related Injuries: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

The effects of methods to prevent injuries have been studied in several systematic reviews. However, no meta-analysis taking into account all randomised controlled intervention trials aiming at the prevention of sports injuries has been published. To summarise the effects of sports injury prevention interventions. Systematic review and meta-analysis of randomised controlled trials. PubMed, MEDLINE, SPORTDiscus, the Cochrane Central Register of Controlled Trials, CINAHL, PEDro, and Web of Science, searched in September 2013. The reference lists of retrieved articles and reviews were hand searched. To be selected articles had to examine the effects of any preventive intervention on sports injuries, be randomised/quasi-randomised and controlled trials, published in a peer-reviewed journal. The outcome of the trial had to be injury rate or the number of injured individuals. Of the 5580 articles retrieved after a search of databases and the relevant bibliography, 68 randomised controlled trials were included in the systematic review and 60 trials were included in the meta-analysis. Insoles (OR 0.51, 95% CI 0.32-0.81), external joint supports (OR 0.40, 95% CI 0.30-0.53), and specific training programmes (OR 0.55, 95% CI 0.46-0.66) appeared to be effective in reducing the risk of sports injuries. Stretching (OR 0.92, 95% CI 0.80-1.06), modified shoes (OR 1.23, 95% CI 0.81-1.87), and preventive videos (OR 0.86, 95% CI 0.44-1.68) seemed not to be effective. This meta-analysis showed that certain interventions can reduce the risk of sports injuries. There were limitations regarding the quality of the trials, generalisability of the results, and heterogeneity of the study designs. In future, the mechanisms behind effective methods and the most beneficial elements of preventive training programmes need to be clarified.

Evo‐Devo of Specialized Bone Joints Formed During Pre‐Natal and Post‐Natal Ontogeny in Turtles With Shell‐Closing Systems

The evolution of complex skeletal traits is often the result of functional variation in developmental genes during pre‐natal life stages. However, in some vertebrates, the development of such traits extends into post‐natal ontogeny, during which the relationship between functional genetic variation and phenotypic change is less clear. The objective of this study was to characterize pre‐natal and post‐natal development of a complex skeletal trait in turtles. We focused on phylogenetic comparisons of turtles with shell‐closing systems, an adaptation that enables some turtles to fully conceal appendages during predator attacks. We combined classical embryological approaches with modern geometric morphometrics to describe and quantify developmental change in bone tissues of deeply divergent lineages. We validated previous observations on the embryonic development of a specialized bone joint that articulates the dorsal scapula with the ventral shell. This joint is critical for the function of shell‐closing systems and forms via secondary subdivision of cartilage tissue. We then quantified a dramatic anatomical transformation associated with the post‐natal development of an external bone joint on the ventral shell of a lineage with the most derived form of the shell‐closing phenotype. This joint was not present in neonate turtles but likely developed in sub‐adult/adult age classes via tissue remodeling that was mechanically induced (due to muscle abduction). Remarkably, the turtle shell‐closing system is a complex skeletal trait that could feature both genetically‐ and epigenetically‐activated developmental programs. We are currently studying the genetic basis of this phenotype but will explore options to test hypotheses on epigenetic mechanisms.Grant Funding Source: NSF

Baseline bone marrow lesion volume and bone marrow lesion regression are associated with knee osteoarthritis progression: data from the osteoarthritis initiative

gait between asymptomatic individuals and symptomatic individuals diagnosed with moderate knee OA, all with Kellgren-Lawrence (KL) osteoarthritis (OA) radiographic grade 2 or 3. Methods: Individuals withmoderate medial compartment knee OA and asymptomatic adults underwent gait testing. Three-dimensional joint angles and net external knee joint moments of the affected (OA) or randomized (asymptomatic) knee were calculated from a synchronized motion capture and force platform system during self-selected speed gait. KL grades of standard anterior-posterior knee radiographs were scored by an orthopaedic surgeon (WDS). Principal component analysis (PCA) extracted major patterns of variability from the angle and moment waveforms individually (i.e. 6 PCA analyses). Participant waveforms were projected onto each principal component to calculate a set of PC scores. Asymptomatic and symptomatic PC scores were compared using an ANOVA. Results: Twenty-seven asymptomatic individuals and 37 symptomatic individuals diagnosed with moderate OA had a KL score of 2 or 3. There were no significant group differences in age, or in any features of the frontal and transverse plane knee angles. The asymptomatic group walked with a significantly faster self-selected walking speed, had smaller BMI, and lower WOMAC and higher SF-36 total and physical function scores (Table 1). The only significant kinematic difference between the groups was in the overall magnitude of the knee flexion angle (PC1, p 1⁄4 0.0006), with the asymptomatic group having higher flexion angles. The asymptomatic group had lower overall magnitude of the knee adduction moment (PC1, p <0.0001), and greater difference between the first peak and themid-late stance adductionmoment (PC2, p 1⁄4 0.05) than the OA group. The asymptomatic group had earlier peak extension moments prior to toe-off (PC3, p <0.0001), as well as more constant internal rotation moment (PC1, p <0.0001) and earlier peak rotation moments (PC3, p 1⁄4 0.01) during stance (Figure 2). Conclusions: It was interesting that twenty-seven of 28 asymptomatic individuals tested had radiographic evidence (KL 2,3) of OA in their knee joints. Compared to the gait patterns of those diagnosed with moderate OA with the same radiographic scores, the asymptomatic group walked faster with higher overall knee flexion angles, earlier peak extension moments, lower and less constant knee adduction moment loading and more constant knee rotation moment loading during gait. The lower overall adduction moment would suggest that high adduction moments may be a symptomatic feature of OA and not an early mechanism of OA development. The sagittal and frontal plane pattern differences have been previously associated with higher walking speeds and may be a reflection of a less symptomatic joint. The altered rotation moment pattern difference is not speed or function related according to previous study and may support hypotheses that altered rotational joint mechanics is a factor in early knee OA development, prior to the onset of symptoms.

Pre-operative self-efficacy and pain catastrophizing are associated with knee biomechanics during gait post-meniscectomy

s / Osteoarthritis and Cartilage 21 (2013) S63–S312 S99 in IE rotation (r21⁄40.33) and total reaction moments (r21⁄40.66). There were no differences in walking speed or step-length for any treatment. Conclusion: The shift towards greater tibia internal rotation and the association with external joint moments suggests that with treatment of Celecoxib there may be a lessening of bracing or co-contraction around the joint that results from pain and inflammation. A rotational shift in joint kinematics has previously been linked with patterns of cartilage thinning. The different kinematic response between the two treatment arms suggest potential differences in the impact of these drugs on ambulation and may have implications for different rates of disease progression that require further study. 171 PRE-OPERATIVE SELF-EFFICACY AND PAIN CATASTROPHIZING ARE ASSOCIATED WITH KNEE BIOMECHANICS DURING GAIT POSTMENISCECTOMY C.-J. Hsieh, S.Z. George, J.A. Dominguez, M.W. Moser, T.L. Chmielewski. Univ. of Florida, Gainesville, FL, USA Purpose: Meniscectomy is a risk factor for developing knee osteoarthritis (OA) and potentially leads to altered gait. Altered gait (e.g. reduced knee angle excursion and knee extensor moment and lower peak vertical ground reaction force) can change articular cartilage loading and contribute to the onset of OA. A variety of impairments could lead to altered gait, including abnormal psychosocial factors. Few studies have investigated the effect of psychosocial factors on gait, particularly in people with meniscectomy. From a clinical perspective, such research could help identify rehabilitation targets for the recovery of normal gait to possibly minimize the risk of knee OA. Therefore, the purpose of this study was to 1) examine gait biomechanics after meniscectomy, and 2) determine if pre-operative psychosocial factors are associated with post-meniscectomy knee biomechanics during gait. Methods: Fifteen subjects with traumatic meniscal tear and meniscectomy were recruited (14 males; mean age: 20.1 2.9yrs; 10 lateral/5 medial meniscectomy). Questionnaires for psychosocial constructs were administered pre-operatively and included pain catastrophizing [Pain Catastrophizing Scale, PCS; range1⁄40-52 points], fear of movement/re-injury [Tampa Scale for Kinesiophobia, TSK-11; range1⁄411-44 points], and self-efficacy for knee activity [Knee Activity Self-Efficacy Scale, KASES; range1⁄40-100 points]. Higher scores indicate higher levels of the given construct. Gait analysis was conducted after rehabilitation was complete (mean 1⁄4 7.5 weeks post-operative). Retro-reflective markers were placed prior to five walking trials at a self-selected speed. Marker position was recorded with a motion capture system (Motion Analysis Corp), and ground reaction forces were recorded with two force platforms (Advanced Mechanical Technology Inc). Sagittal plane knee angle excursion, knee extensor moment and peak vertical ground reaction force (PVGRF) were analyzed bilaterally during weight acceptance. Gait biomechanical variables were compared between sides with paired t-tests. Pearson's Product Moment correlation determined the association between pre-operative questionnaire scores and postoperative gait biomechanical variables on the surgical side. Results: Compared to the non-surgical side, the surgical side showed reduced sagittal plane knee angle excursion and knee extensor moment during weight acceptance (p1⁄4.001 and p1⁄4.002, respectively, Table). Gait biomechanical variables and questionnaire scores Variable Surgical side Non-surgical side Points Knee angle excursion ( ) 13.05 (4.51) 16.48(4.37) Knee extensor moment (N-m/kg) 0.07(0.17) 0.18(0.18) Peak vertical ground reaction force (N) 996.51(316.28) 1005.53(283.43) Pain Catastrophizing Scale (PCS) 10.93(8.32)

STATIC BEHAVIOUR OF DIFFERENT TYPES OF R.C BEAM-COLUMN CONNECTIONS AS AFFECTED BY BOTH VALUE OF ACTING AXIAL NORMAL FORCE AND GRADE OF USED CONCRETE (THEORETICAL STUDY)

This paper describes a theoretical study of the effect of both acting axial loads and grade of concrete on the static behaviour of (32) thirty two Reinforced Concrete (RC) Beam-column joints. ABAQUSCAE version 6.7, a nonlinear finite element analysis software package, was developed specifically for the analysis of reinforced concrete structures under plane stress conditions. Variable axial loads were applied and increased gradually with constant lateral load, which was applied maintaining at the top of the column at internal and external beam-column joint only the ultimate and cracking axial loads were recorded as well as the corresponding versus vertical displacement, the maximum joint shear stresses, axial, stresses strains, and absorbed energy, mode of failure using different grades of concrete C250, C400, C600 and C1200 were evaluated and recorded.

Decision Making and Experience Level Influence Frontal Plane Knee Joint Biomechanics During a Cutting Maneuver

The purpose of this study was to examine the combined impact of experience and decision making on frontal plane knee joint biomechanics during a cutting maneuver. Kinematic and kinetic data were collected from 12 recreationally active and 18 NCAA Division I female athletes during execution of anticipated and unanticipated single-leg land-and-cut maneuvers. Knee joint abduction angles and external knee joint abduction torques were calculated and discrete peak stance-phase variables were extracted. Angle and torque time-series data were also submitted to separate functional data analyses. Variables derived from the functional data analyses indicated that decision making influenced knee abduction angle and torque time series in the recreational group only. Specifically, these variables pointed to greater knee abduction at the end of stance as well as a greater, albeit delayed peak in knee abduction torque at the beginning of landing in the recreational athletes during the unanticipated condition. In addition, the recreational athletes displayed greater discrete peak knee abduction angles than the Division I athletes regardless of condition. Discrete peak knee abduction torque did not differ between groups or conditions.

Biomechanical Contributions of Posterior Deltoid and Teres Minor in the Context of Axillary Nerve Injury: A Computational Study

To determine whether transfer to only the anterior branch of the axillary nerve will restore useful function after axillary nerve injury with persistent posterior deltoid and teres minor paralysis. We used a computational musculoskeletal model of the upper limb to determine the relative contributions of posterior deltoid and teres minor to maximum joint moment generated during a simulated static strength assessment and to joint moments during 3 submaximal shoulder movements. Movement simulations were performed with and without simulated posterior deltoid and teres minor paralysis to identify muscles that may compensate for their paralysis. In the unimpaired limb model, teres minor and posterior deltoid accounted for 16% and 14% of the total isometric shoulder extension and external rotation joint moments, respectively. During the 3 movement simulations, posterior deltoid produced as much as 20% of the mean shoulder extension moment, whereas teres minor accounted for less than 5% of the mean joint moment in all directions of movement. When we paralyzed posterior deltoid and teres minor, the mean extension moments generated by the supraspinatus, long head of triceps, latissimus dorsi, and middle deltoid increased to compensate. Compensatory muscles were not fully activated during movement simulations when posterior deltoid and teres minor were paralyzed. Reconstruction of the anterior branch of the axillary nerve only is an appropriate technique for restoring shoulder abduction strength after isolated axillary nerve injury. When shoulder extension strength is compromised by extensive neuromuscular shoulder injury, reconstruction of both the anterior and posterior branches of the axillary nerve should be considered. By quantifying the biomechanical role of muscles during submaximal movement, in addition to quantifying muscle contributions to maximal shoulder strength, we can inform preoperative planning and permit more accurate predictions of functional outcomes.

108 ヤコビ行列を用いた静力学による着地動作解析(負荷のモデル化と緩和)

In many sports, it is necessary to exert external forces for generating joint torques which accelerate body. Since there is a strong relation between performance and joint torque generation, inverse dynamics problem (IDP) has been used for joint torque estimation. If external forces are dominant in dynamic equations, dynamic terms can be neglected, which leads to force equilibrium. These equations of force equilibrium express geometric mapping between external force and joint torque with Jacobian matrix in statics. The authors examined validity of the equations as a tool for joint torque estimation in comparison to IDP in landing motion experiment. The results showed estimated ankle and knee torque was comparable to that of IDP. The authors theorized and established the benefit to apply equations of force equilibrium for dynamic motion analysis.