Current peri-operative imaging concepts surrounding shoulder arthroplasty

Glenohumeral osteoarthritis is a prevalent degenerative disease that can lead to excruciating pain and debility. End-stage osteoarthritis can be treated by both conservative and surgical interventions. Along with a comprehensive history and physical exam, pre-operative imaging with plain radiographs, computerized tomography, and magnetic resonance imaging plays an essential role in the decision-making process guiding whether the patient undergoes a shoulder hemiarthroplasty, anatomic total shoulder arthroplasty, or a reverse total shoulder arthroplasty. The most important pre-operative imaging factors are the integrity of the rotator cuff and presence of significant glenoid erosion. Imaging is also critical postoperatively, as signs of prosthetic loosening, rotator cuff failure (especially involving the subscapularis), periprosthetic fracture, and stress fractures are important entities to recognize. This article will review pertinent imaging findings related to the pre- and post-operative management of patients with glenohumeral osteoarthritis.

Variations in jump height explain the between-sex difference in patellar tendon loading during landing

Patellar tendinopathy is the most common overuse knee injury in volleyball, with men reporting more than twice the injury prevalence than women. Although high patellar tendon loading is thought to be a causative factor of patellar tendinopathy, it is unknown whether between-sex variations in landing technique account for differences in patellar tendon loading. It was hypothesized that male volleyball players would display differences in landing technique and would generate higher patellar tendon loading than their female counterparts. The landing technique and patellar tendon loading of 20 male and 20 female volleyball players performing a lateral stop-jump block movement were collected. Independent t-tests were used to identify any between-sex differences in landing technique with the data grouped to account for differences in jump height and in anthropometry. Male volleyball players were taller and heavier, landed from a higher height, displayed differences in landing kinematics, generated a significantly greater knee extensor moment, and experienced higher patellar tendon loading than female players when all 40 participants were compared. However, when participants were matched on jump height, they generated similar patellar tendon loading, irrespective of their sex. These results imply that jump height is a more important determinant of patellar tendon loading than sex.

Determining the osmolality of over-concentrated and supplemented infant formulas

BACKGROUND

Hyperosmolar infant feeds can cause osmotic diarrhoea and may be a risk factor for necrotising enterocolitis; the osmolality of infant formula is therefore usually <400 mOsm kg(-1) . However, in fluid-restricted infants and those needing nutritional support, formulas may be over-concentrated or supplemented. The present study aimed to determine the effect of these practices on osmolality.

METHODS

A clinical laboratory osmometer was used to measure the osmolality of infant formulas. The effect of over-concentration and supplementation on osmolality was then determined using three and seven different infant formulas, respectively. Osmolalities were measured in triplicate.

RESULTS

The effect of over-concentration was shown to be linear using Pepti Junior (Cow & Gate, Trowbridge, UK) at concentrations of 12.8% (standard), 17% and 19%. This linear relationship was also demonstrated with Enfamil A.R. (Mead Johnson Nutritionals, Uxbridge, UK) (15%) and Neocate (SHS International Ltd, Liverpool, UK) (21%). The effect of individual additives on osmolality was found to be similar for the seven infant formulas. All preparations of SMA High Energy (SMA Nutrition, Maidenhead, UK) and five of the 12 preparations of Nutriprem 1 (Cow & Gate) exceeded an osmolality of 400 mOsm kg(-1) .

CONCLUSIONS

The effect of over-concentrating infant formulas was shown to be linear, meaning that the osmolality at different concentrations can be predicted accurately. The over-concentrated infant formulas that were measured in the present study did not exceed 400 mOsm kg(-1) , with the exception of 21% Neocate, which would not be used in practice. When supplemented, some infant formulas exceeded an osmolality of 400 mOsm kg(-1) ; this may be relevant in cases of feed intolerance or in those at risk of necrotising enterocolitis.

The impact of child and adolescent obesity treatment interventions on physical activity: a systematic review

Efforts to treat obesity in childhood and adolescence would benefit from a greater understanding of evidence-based strategies to modify physical activity behaviour. A systematic review was conducted to examine the impact of child and adolescent obesity treatment interventions on physical activity. Studies included were randomized controlled trials or controlled trials, with overweight and obese youth (aged < 18 years), which reported statistical analysis of free-living physical activity at pretreatment and post-treatment. Two independent reviewers assessed each study for methodological quality. Seventeen child and three adolescent studies were retrieved, half of which were conducted in the USA. Studies were characterized by small samples of limited cultural and economic diversity. Fifteen studies reported an increase in at least one physical activity outcome at post-test or follow-up. Overall, study quality was rated as low (child median score = 3/10, range = 0-9; adolescent median score = 3/10, range = 2-5) with three child studies classified as high quality (>or=6/10). Research evaluating the effect of child and adolescent obesity treatment trials on physical activity is limited in both quantity and quality. Studies testing innovative, theoretically driven treatment approaches that use robust methodologies are required to better understand generalizable approaches for promoting physical activity participation among obese youth.

How do respiratory state and measurement method affect bra size calculations?

OBJECTIVES

To investigate the effects of respiratory state and measurement method on bra size calculation.

METHODS

The bra sizes of 16 large-breasted women were measured during two respiratory states, end voluntary inspiration and relaxed voluntary expiration, and using two sizing methods, which were compared against subject-reported bra sizes.

RESULTS

Both respiratory state and measurement method significantly affected bra size estimations, whereby measuring chest circumference during inspiration increased both band and decreased cup size. However, whereas bra size calculated using the standard method differed significantly from subject-reported bra size, cup size calculated using the breast hemi-circumference method did not differ significantly from subject-reported cup size.

CONCLUSIONS

As respiratory state significantly affects bra sizes, it should be standardised during bra size measurements. A more valid and reliable bra sizing method should be developed, possibly using the breast hemi-circumference method for cup size estimations and raw under-bust chest circumference values for band size.

Musculoskeletal disorders associated with obesity: a biomechanical perspective

Despite the multifactorial nature of musculoskeletal disease, obesity consistently emerges as a key and potentially modifiable risk factor in the onset and progression of musculoskeletal conditions of the hip, knee, ankle, foot and shoulder. To date, the majority of research has focused on the impact of obesity on bone and joint disorders, such as the risk of fracture and osteoarthritis. However, emerging evidence indicates that obesity may also have a profound effect on soft-tissue structures, such as tendon, fascia and cartilage. Although the mechanism remains unclear, the functional and structural limitations imposed by the additional loading of the locomotor system in obesity have been almost universally accepted to produce aberrant mechanics during locomotor tasks, thereby unduly raising stress within connective-tissue structures and the potential for musculoskeletal injury. While such mechanical theories abound, there is surprisingly little scientific evidence directly linking musculoskeletal injury to altered biomechanics in the obese. For the most part, even the biomechanical effects of obesity on the locomotor system remain unknown. Given the global increase in obesity and the rapid rise in musculoskeletal disorders, there is a need to determine the physical consequences of continued repetitive loading of major structures of the locomotor system in the obese and to establish how obesity may interact with other factors to potentially increase the risk of musculoskeletal disease.

The impact of childhood obesity on musculoskeletal form

Despite the greater prevalence of musculoskeletal disorders in obese adults, the consequences of childhood obesity on the development and function of the musculoskeletal system have received comparatively little attention within the literature. Of the limited number of studies performed to date, the majority have focused on the impact of childhood obesity on skeletal structure and alignment, and to a lesser extent its influence on clinical tests of motor performance including muscular strength, balance and locomotion. Although collectively these studies imply that the functional and structural limitations imposed by obesity may result in aberrant lower limb mechanics and the potential for musculoskeletal injury, empirical verification is currently lacking. The delineation of the effects of childhood obesity on musculoskeletal structure in terms of mass, adiposity, anthropometry, metabolic effects and physical inactivity, or their combination, has not been established. More specifically, there is a lack of research regarding the effect of childhood obesity on the properties of connective tissue structures, such as tendons and ligaments. Given the global increase in childhood obesity, there is a need to ascertain the consequences of persistent obesity on musculoskeletal structure and function. A better understanding of the implications of childhood obesity on the development and function of the musculoskeletal system would assist in the provision of more meaningful support in the prevention, treatment and management of the musculoskeletal consequences of the condition.

The biomechanics of restricted movement in adult obesity

In spite of significant advances in the knowledge and understanding of the multi-factorial nature of obesity, many questions regarding the specific consequences of the disease remain unanswered. In particular, there is a relative dearth of information pertaining to the functional limitations imposed by overweight and obesity. The limited number of studies to date have mainly focused on the effect of obesity on the temporospatial characteristics of walking, plantar foot pressures, muscular strength and, to a lesser extent, postural balance. Collectively, these studies have implied that the functional limitations imposed by the additional loading of the locomotor system in obesity result in aberrant mechanics and the potential for musculoskeletal injury. Despite the greater prevalence of musculoskeletal disorders in the obese, there has been surprisingly little empirical investigation pertaining to the biomechanics of activities of daily living or into the mechanical and neuromuscular factors that may predispose the obese to injury. A better appreciation of the implications of increased levels of body adiposity on the movement capabilities of the obese would afford a greater opportunity to provide meaningful support in preventing, treating and managing the condition and its sequelae. Moreover, there is an urgent need to establish the physical consequences of continued repetitive loading of major structures of the body, particularly of the lower limbs in the obese, during the diverse range of activities of daily living.

What are the effects of obesity in children on plantar pressure distributions?

OBJECTIVE

This study examined the effects of obesity on static and dynamic plantar pressure distributions displayed by children.

DESIGN

Field-based experimental data on body mass index (BMI) and plantar pressures were collected for 10 obese children and 10 nonobese controls.

SUBJECTS

In all, 10 obese (age 8.8+/-2.0 y, BMI 25.8+/-3.8 kg m(-2)) children matched to 10 nonobese children (age 8.9+/-2.1 y, BMI 16.8+/-2.0 kg m(-2)), for gender, age and height.

MEASUREMENTS

Height and weight were measured to calculate BMI. Right and left foot plantar pressures were obtained using an AT-4 emed pressure platform (Novel(gmbh), Munich) to calculate the peak force and pressure experienced under areas of each child's feet during static and dynamic conditions.

RESULTS

While standing, the obese children generated significantly higher forces over a larger foot area and experienced significantly higher plantar pressures compared to their nonobese counterparts (41.8+/-17.7; 30.1+/-12.0 N cm(-2), respectively; P<0.022). Similarly, while walking, the obese children generated significantly higher forces over all areas of their feet, except the toes. Despite distributing these higher forces over a significantly larger foot area when walking, the obese children experienced significantly higher plantar pressures in the midfoot (P<0.003) and under the second to fifth metatarsal heads (P<0.006) compared to the nonobese children.

CONCLUSIONS

It is postulated that obese children are at an increased risk of developing foot discomfort and/or foot pathologies due to increased plantar loads being borne by the small forefoot bones. Furthermore, continual bearing of excessive mass by children appears to flatten the medial midfoot region during walking. As the long-term consequences of these increased plantar loads are currently unknown, it is recommended that the effects of obesity on the structural and functional characteristics of obese children's feet be further investigated.

The force–velocity relationship of the human soleus muscle during submaximal voluntary lengthening actions

In experiments on isolated animal muscle, the force produced during active lengthening contractions can be up to twice the isometric force, whereas in human experiments lengthening force shows only modest, if any, increase in force. The presence of synergist and antagonist muscle activation associated with human experiments in situ may partly account for the difference between animal and human studies. Therefore, this study aimed to quantify the force-velocity relationship of the human soleus muscle and assess the likelihood that co-activation of antagonist muscles was responsible for the inhibition of torque during submaximal voluntary plantar flexor efforts. Seven subjects performed submaximal voluntary lengthening, shortening(at angular, velocities of +5, -5, +15, -15 and +30, and -30 degrees s(-1)) and isometric plantar flexor efforts against an ankle torque motor. Angle-specific (90 degrees ) measures of plantar flexor torque plus surface and intramuscular electromyography from soleus, medial gastrocnemius and tibialis anterior were made. The level of activation (30% of maximal voluntary isometric effort) was maintained by providing direct visual feedback of the soleus electromyogram to the subject. In an attempt to isolate the contribution of soleus to the resultant plantar flexion torque, activation of the synergist and antagonist muscles were minimised by: (1) flexing the knee of the test limb, thereby minimising the activation of gastrocnemius, and (2) applying an anaesthetic block to the common peroneal nerve to eliminate activation of the primary antagonist muscle, tibialis anterior and the synergist muscles, peroneus longus and peroneus brevis. Plantar flexion torque decreased significantly ( P<0.05) after blocking the common peroneal nerve which was likely due to abolishing activation of the peroneal muscles which are synergists for plantar flexion. When normalised to the corresponding isometric value, the force-velocity relationship between pre- and post-block conditions was not different. In both conditions, plantar flexion torques during shortening actions were significantly less than the isometric torque and decreased at faster velocities. During lengthening actions, however, plantar flexion torques were not significantly different from isometric regardless of angular velocity. It was concluded that the apparent inhibition of lengthening torques during voluntary activation is not due to co-activation of antagonist muscles. Results are presented as mean (SEM).

Effect of verbal instructions on muscle activity and risk of injury to the anterior cruciate ligament during landing

BACKGROUND

Minimising the likelihood of injury to the anterior cruciate ligament (ACL) during abrupt deceleration requires proper synchrony of the quadriceps and hamstring muscles. However, it is not known whether simple verbal instructions can alter landing muscle activity to protect the knee.

OBJECTIVE

To assess the efficacy of verbal instructions to alter landing muscle activity.

METHODS

Twenty four athletes landed abruptly in single limb stance. Sagittal plane motion was recorded with an optoelectric device, and ground reaction force and surface electromyographic data were recorded for the rectus femoris, vastus lateralis, biceps femoris, and semimembranosus muscles. Subjects performed 10 landings per condition: normal landing (N); repeat normal landing (R); landing after instruction to increase knee flexion (K); and landing after instruction to recruit hamstring muscles earlier (M). Muscle bursts immediately before landing were analysed relative to initial foot-ground contact (IC).

RESULTS

The K condition resulted in significantly (p</=0.05) greater knee flexion at IC compared with the other conditions. The M condition did not result in earlier hamstring muscle activity, but instead caused significantly (p</=0.05) earlier rectus femoris onset relative to IC, with a similar trend for the vastus lateralis. As these muscles are ACL antagonists, earlier onset times would be detrimental to the ACL.

CONCLUSIONS

Subjects successfully increased knee flexion during landing following the K condition instruction. However, further research is warranted to establish the efficacy of more extensive lower limb muscle retraining programmes to ensure landings that decrease susceptibility to ACL injury.

The biomechanics of adiposity--structural and functional limitations of obesity and implications for movement

Obesity is a significant health problem and the incidence of the condition is increasing at an alarming rate worldwide. Despite significant advances in the knowledge and understanding of the multifactorial nature of the condition, many questions regarding the specific consequences of the disease remain unanswered. For example, there is a dearth of information pertaining to the structural and functional limitations imposed by overweight and obesity. A limited number of studies to date have considered plantar pressures under the feet of obese vs. non-obese, the influence of foot structure on performance, gait characteristics of obese children and adults, and relationships between obesity and osteoarthritis. A better appreciation of the implications of increased levels of body weight and/or body fat on movement capabilities of the obese would provide an enhanced opportunity to offer more meaningful support in the prevention, treatment and management of the condition.

H-reflex modulation during passive lengthening and shortening of the human triceps surae

1. The present study investigated the effects of lengthening and shortening actions on H-reflex amplitude. H-reflexes were evoked in the soleus (SOL) and medial gastrocnemius (MG) of human subjects during passive isometric, lengthening and shortening actions performed at angular velocities of 0, +/-2, +/-5 and +/-15 deg s(-1). 2. H-reflex amplitudes in both SOL and MG were significantly depressed during passive lengthening actions and facilitated during passive shortening actions, when compared with the isometric H-reflex amplitude. 3. Four experiments were performed in which the latencies from the onset of movement to delivery of the stimulus were altered. Passive H-reflex modulation during lengthening actions was found to begin at latencies of less than 60 ms suggesting that this inhibition was due to peripheral and/or spinal mechanisms. 4. It is postulated that the H-reflex modulation seen in the present study is related to the tonic discharge of muscle spindle afferents and the consequent effects of transmission within the Ia pathway. Inhibition of the H-reflex at less than 60 ms after the onset of muscle lengthening may be attributed to several mechanisms, which cannot be distinguished using the current protocol. These may include the inability to evoke volleys in Ia fibres that are refractory following muscle spindle discharge during rapid muscle lengthening, a reduced probability of transmitter release from the presynaptic terminal (homosynaptic post-activation depression) and presynaptic inhibition of Ia afferents from plantar flexor agonists. Short latency facilitation of the H-reflex may be attributed to temporal summation of excitatory postsynaptic potentials arising from muscle spindle afferents during rapid muscle lengthening. At longer latencies, presynaptic inhibition of Ia afferents cannot be excluded as a potential inhibitory mechanism.

Is lower limb muscle synchrony during landing affected by gender? Implications for variations in ACL injury rates

This study examined whether lower limb muscle synchrony during abrupt landings was affected by gender, thereby predisposing females to a higher incidence of non-contact anterior cruciate ligament (ACL) injuries than males. Seven males and 11 females landed in single-limb stance on a force platform after receiving a chest-height netball pass and decelerating abruptly. Ground reaction force and electromyographic data for rectus femoris, vastus lateralis, vastus medialis, semimembranosus (SM), biceps femoris, and gastrocnemius were sampled (1000 Hz) during landing. Subjects' sagittal plane motion was also filmed (200 Hz). Knee joint reaction forces and sagittal planar net moments of force were estimated using Newtonian equations of motion and inverse dynamics. Tibiofemoral shear forces (F(s)) were obtained and muscle bursts temporally analysed with respect to initial foot-ground contact (IC) and peak F(s) times. Males displayed significantly delayed SM onset relative to IC (113+/-46 ms) compared to females (173+/-54 ms; p=0.03), and significantly delayed SM peak activity relative to peak F(s) (54+/-27 ms) compared to females (77+/-15 ms; p=0.03). Delayed SM activity during landing was suggested to allow peak muscle activity to better coincide with high anterior F(s), thereby acting as an ACL synergist via increased joint compression and posterior tibial drawer. It was concluded that females displayed muscle synchrony less protective of the ACL than males, possibly increasing their susceptibility to non-contact ACL injuries.

Does obesity influence foot structure and plantar pressure patterns in prepubescent children?

OBJECTIVE

This study examined the effects of obesity on plantar pressure distributions in prepubescent children.

DESIGN

Field-based, experimental data on BMI (body mass index), foot structure and plantar pressures were collected for 13 consenting obese children and 13 non-obese controls.

SUBJECTS

Thirteen obese (age 8.1+/-1.2 y; BMI 25.5+/-2.9 kg/m(2)) and 13 non-obese (age 8.4+/-0.9 y; BMI 16.9+/-1.2 kg/m(2)) prepubescent children, matched to the obese children for gender, age and height.

MEASUREMENTS

Height and weight were measured to calculate BMI. Static weight-bearing footprints for the right and left foot of each subject were recorded using a pedograph to calculate the footprint angle and the Chippaux-Smirak index as representative measures of the surface area of the foot in contact with the ground. Right and left foot plantar pressures were then obtained using a mini-emed(R) pressure platform to calculate the force and pressure experienced under each child's foot during static and dynamic loaded and unloaded conditions.

RESULTS

Obese subjects displayed significantly lower footprint angle (t=4.107; P=<0.001) values and higher Chippaux-Smirak index values (t=-6.176; P=<0.001) compared to their non-obese counterparts. These structural foot changes were associated with differences in plantar pressures between the two subject groups. That is, although rearfoot dynamic forces generated by the obese subjects were significantly higher than those generated by the non-obese subjects, these forces were experienced over significantly higher mean peak areas of contact with the mini-emed(R) system. Therefore, rearfoot pressures experienced by the two subject groups did not differ. However, the mean peak dynamic forefoot pressures generated by the obese subjects (39.3+/-15.7 N.cm(-2); q=3.969) were significantly higher than those generated by the non-obese subjects (32.3+/-9.2 N.cm(-2)).

CONCLUSIONS

It is postulated that foot discomfort-associated structural changes and increased forefoot plantar pressures in the obese foot may hinder obese children from participating in physical activity and therefore warrants immediate further investigation.

The effect of upper-limb motion on lower-limb muscle synchrony. Implications for anterior cruciate ligament injury

BACKGROUND

A high prevalence of rupture of the anterior cruciate ligament is associated with activities that incorporate both abrupt deceleration and catching a ball. In the present study, we examined whether the upper-limb motion involved in catching a ball affected the synchrony of the lower-limb muscles during tasks known to stress the anterior cruciate ligament-namely, abrupt decelerative landings.

METHODS

Seven male and eleven female subjects decelerated abruptly to land in single-limb stance after catching a chest-height pass and after no catching. Ground-reaction force and electromyographic data for six lower-limb muscles were sampled while the subjects' landing technique was filmed. The joint-reaction forces and the sagittal planar net moments for the knee then were calculated to derive the tibiofemoral shear forces. The muscle onsets and peak muscle activities were temporally analyzed with respect to the time of initial foot-ground contact, the peak resultant ground-reaction force, and the peak tibiofemoral shear force.

RESULTS

When catching a pass, the subjects demonstrated significantly (p < 0.05) earlier rectus femoris onset relative to the timing of the initial foot-ground contact and of the peak tibiofemoral shear force, and they showed delayed biceps femoris onset relative to the timing of the peak tibiofemoral shear force compared with the findings in the trials without catching.

CONCLUSIONS

We concluded that catching a ball during an abrupt landing could increase the potential for an anterior cruciate ligament injury by limiting the time available for the hamstring muscles to generate posterior tibial-drawer force before the onset of the quadriceps-induced anterior tibial translation.

CLINICAL RELEVANCE

The integrity of the anterior cruciate ligament during landing relies on the proper coordination of the lower-limb muscles, particularly the quadriceps and the hamstrings. The present study demonstrated that motion of the upper-limbs may interfere with recruitment of these muscles, thereby predisposing the anterior cruciate ligament to injury.

A preliminary investigation of injury prevention strategies in Netball: are players heeding the advice?

All netball players who sought treatment for injury during the three-day 1995 New South Wales State Netball Championships were surveyed. Of 940 participants, 131 incurred injuries (139.4 injuries per 1,000 players; 23.8 injuries per 1,000 playing hours). Ankle and knee injuries were most frequent, with ligament sprains, bruising/contusions, and muscle strains presenting as the most common injury types. The most frequent causes of injury were incorrect landings, collisions with players, being struck by the ball, or repetitive movements. Although most players heeded advice pertaining to warm-up, occurrence of injuries during warm-up and cool-down suggested that activities performed during these periods may be inappropriate. To reduce risk of ankle ligament sprain in netball, high-cut netball shoes have been advocated. However, only 5.1% of players surveyed wore high-cut shoes. Furthermore, although players have been advised to seek immediate treatment when injured, 54.7% of players finished the game before seeking treatment. Relative to previous netball injury investigations, the frequency and nature of injuries, and the injury prevention behaviours of players have not changed. Therefore, wider promotion of injury prevention resources, combined with research into the effectiveness of these resources and how players can be encouraged to adopt appropriate injury prevention strategies in netball, is recommended.

Does obesity influence foot structure in prepubescent children?

OBJECTIVE

This study examines the relationship between obesity and foot structure in prepubescent children.

DESIGN

Field-based, experimental data on BMI (body mass index) and foot structure were collected for 431 consenting children from 18 randomly selected primary schools.

SUBJECTS

Of the 431 participants, 62 obese (BMI>95th percentile) and 62 non-obese (10th percentile<BMI>90th percentile) children (age = 8.5+/-0.5 y) were selected.

MEASUREMENTS

Height and weight were measured to calculate BMI. Static weight-bearing footprints for the right and left foot of each subject were then taken using a pedograph to calculate the Footprint Angle and the Chippaux-Smirak Index as representative measures of the surface area of the foot in contact with the ground.

RESULTS

A significant difference was found between the Footprint Angle of the obese and non-obese subjects for both the left (t = 3.663; P<0.001) and right (t = 3.742; P<0.001) feet whereby obese subjects displayed a reduced angle. Chippaux-Smirak Index scores were also significantly different for both the left (t = -6.362; P<0.001) and right (t=-5.675; P<0.001) feet between the two subject groups where a greater score for the obese subjects was evident. A decreased footprint angle and an increased Chippaux-Smirak Index are characteristic of structural foot changes that have been associated with compromised foot function.

CONCLUSIONS

Excess body mass appears to have a significant effect on the foot structure of prepubescent children whereby young obese children display structural foot characteristics which may develop into problematic symptoms if excessive weight gain continues. Further investigation into possible consequences, particularly any effects on foot function, is warranted.

Tension regulation during lengthening and shortening actions of the human soleus muscle

In the present study we investigated tension regulation in the human soleus (SOL) muscle during controlled lengthening and shortening actions. Eleven subjects performed plantar flexor efforts on an ankle torque motor through 30 degrees of ankle displacement (75 degrees -105 degrees internal ankle angle) at lengthening and shortening velocities of 5, 15 and 30 degrees. S(-1). To isolate the SOL from the remainder of the triceps surae, the subject's knee was flexed to 60 degrees during all trials. Voluntary plantar flexor efforts were performed under two test conditions: (1) maximal voluntary activation (MVA) of the SOL, and (2) constant submaximal voluntary activation (SVA) of the SOL. SVA trials were performed with direct visual feedback of the SOL electromyogram (EMG) at a level resulting in a torque output of 30% of isometric maximum. Angle-specific (90 degrees ankle angle) torque and EMG of the SOL, medial gastrocnemius (MG) and tibialis anterior (TA) were recorded. In seven subjects from the initial group, the test protocol was repeated under submaximal percutaneous electrical activation (SEA) of SOL (to 30% isometric maximal effort). Lengthening torques were significantly greater than shortening torques in all test conditions. Lengthening torques in MVA and SVA were independent of velocity and remained at the isometric level, whereas SEA torques were greater than isometric torques and increased at higher lengthening velocities. Shortening torques were lower than the isometric level for all conditions. However, whereas SVA and SEA torques decreased at higher velocities of shortening, MVA torques were independent of velocity. These results indicate velocity- and activation-type-specific tension regulation in the human SOL muscle.

Does fatigue induced by repeated dynamic efforts affect hamstring muscle function?

PURPOSE

The purpose of this study was to determine the effects of hamstring fatigue induced by repeated maximal efforts on hamstring muscle function during maximal sprint running.

METHODS

Twelve subjects performed three maximal 40-m sprints during which time high-speed film of the subjects' sprint action and EMG of five lower extremity muscles were recorded (nonfatigued condition, NFC). Subjects then performed specific and general hamstring fatigue tasks followed by three final 40-m sprints (fatigued condition, FC) during which time high-speed film and EMG of the same muscles were again recorded.

RESULTS

Statistical analysis of the kinematic data indicated the following significant (P < 0.05) changes in the subjects' running action from the NFC to the FC: decreased hip and knee flexion at maximum knee extension in the swing phase of the sprint cycle, decreased leg angular velocity immediately before foot-ground contact (FGC), and decreased angular displacement of the trunk, thigh, and leg segments during the late swing phase. Statistical analysis of the EMG data indicated a significant increase in the duration of hamstring activity and earlier cessation of rectus femoris activity during the swing phase of the sprint stride.

CONCLUSIONS

It was concluded that these changes in the kinematic and EMG parameters of sprint running primarily served as protective mechanisms to reduce stress placed on the hamstring muscles at critical phases of the stride cycle.

Does using an ejector chair affect muscle activation patterns in rheumatoid arthritic patients? A preliminary investigation

The present study examined knee and arm extensor muscle activation patterns displayed by 12 elderly female rheumatoid arthritic patients (mean age = 65.5 +/- 8.6 yr) rising from an instrumented Eser ejector chair under four conditions: high seat (540 mm), low seat (450 mm), with and without ejector assistance. Electromyographic (EMG) signals were sampled (1000 Hz) for vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF) and triceps brachii (TB) using a Noraxon Telemyo System (bandwidth 0-340 Hz). Muscle onset, offset and peak activity relative to loss of seat contact (SS), and integrated EMG, were calculated for each muscle burst before SS. A high seat significantly (p < or = 005) decreased VL and TB intensity but did not change muscle activation patterns compared with rising from a low seat. Ejector assistance significantly increased VM and RF burst duration and RF intensity but had no effect on vastii muscle intensity. It was concluded that concerns pertaining to muscle disuse when rising with ejector assistance were unfounded in the present study. However, further research is required to investigate the effects of habitual use of a mechanical ejector device on muscle activation patterns.

Household-shoe wearing and purchasing habits. A survey of people aged 65 years and older

A mail survey was conducted to assess the types of household footwear currently being worn by a random sample of independently living men and women aged 65 years and older as well as their needs related to the purchase and wearing of household footwear. Questionnaires were completed by 128 people. The greatest number of respondents wore slippers all day around the home, purchasing these shoes because of their convenience and comfort. Respondents were not willing to purchase expensive shoes for household wear and infrequently replaced them, despite the fact that such footwear was worn for extended periods each day. It was concluded that further research is required to design a household shoe that fits well and accommodates a variety of foot pathologies typical of the elderly foot; the shoe should be comfortable, relatively inexpensive, and safe for typical household surfaces.

Transrectal versus transvaginal abscess drainage: survey of patient tolerance and effect on activities of daily living

PURPOSE

To evaluate patient perception of pain related to transrectal and transvaginal drainage and the catheter's effect on activities of daily living.

MATERIALS AND METHODS

From July 1993 to August 1997, 22 male and 40 female patients (mean age, 41 years; age range, 4-80 years) underwent transrectal or transvaginal aspiration or drainage. Fifty-seven drainages were performed. In a follow-up survey, patients were asked to score pain experienced during the procedure and afterward on a scale of 1-10 and to rate the effect of the catheter on their activities of daily living.

RESULTS

Twenty-two patients participated in the telephone survey. For those able to recall the insertion procedure, the mean pain score was 3.2 for transrectal and 5.9 for transvaginal drainage. Mean indwelling catheter pain was 1.6 for transrectal and 4.8 for transvaginal drainage. Pain after removal was 1.4 for transrectal and 2.3 for transvaginal drainage. Only one patient with a transrectal catheter reported severe limitation (bowel movement), with no reports of any serious effect on urinating, bathing, sitting, or walking. Transvaginally placed catheters caused marked limitation in all categories and were more painful than transrectal catheters (P < .05).

CONCLUSION

Of the transrectal and transvaginal approaches, transrectal is better tolerated.

Warm-up effect on active and passive arthrometric assessment of knee laxity

OBJECTIVE

To determine the influence of a warm-up protocol suitable for use in clinical settings on tibial displacement and muscle activity during arthrometric knee laxity assessment.

DESIGN

Intervention study in which the subjects served as their own controls.

SETTING

The Biomechanics Research Laboratory, University of Wollongong, Wollongong, New South Wales, Australia.

SUBJECTS

Ten volunteers who reported no history of knee trauma or disease.

INTERVENTION

A warm-up consisting of 10 minutes of ergometer cycling (60rpm) followed by two sets of three hamstring muscle stretches.

MAIN OUTCOME MEASURES

Outcome measures were: (1) anterior tibial translation and knee extension force assessed using a Dynamic Cruciate Tester for each subject's right knee during active and passive testing, and (2) intensity of quadriceps and hamstring muscle activity during knee laxity testing.

RESULTS

There was significantly less quadriceps activity after warm-up (t = 2.419, p = .039). However, there was no significant difference between anterior tibial translation, knee extension force, or hamstring muscle activity results before and after warm-up in either active or passive tests.

CONCLUSION

A warm-up suitable for use in a clinical setting is not required before arthrometric assessment of knee laxity.

Effects of chronic anterior cruciate ligament deficiency on muscle activation patterns during an abrupt deceleration task

OBJECTIVE

This study examined the influence of chronic anterior cruciate ligament deficiency on muscle activation patterns displayed during abrupt deceleration, relative to timing of tibiofemoral shear forces (Fs) generated during the task.

DESIGN

Experimental data were collected for both limbs of 11 chronic functional anterior cruciate ligament deficient subjects and 11 matched controls.

METHODS

Electromyographic, high speed film and ground reaction force data were sampled as subjects landed in single-limb stance on a force platform after receiving a chest level pass and decelerating abruptly. Temporal characteristics of each muscle burst relative to initial foot-ground contact were derived and Fs were calculated from net joint reaction forces and the patellar tendon force occasioned by the net moments and inertial forces predicted about the knee.

RESULTS

Compared to controls, anterior cruciate ligament deficient subjects displayed a delay in hamstring activation so that peak hamstring activity was more synchronous with initial contact and with the high Fs which occurred after initial contact.

CONCLUSIONS

It was concluded the delayed hamstring activation was an adaptation developed to enable peak muscle activity to better coincide with the high anterior Fs, thereby stabilizing the injured limb against a giving-way episode via increased joint compression and posterior tibial drawer.

Breast motion and sports brassiere design. Implications for future research

Exercise usually results in a large displacement of the breasts, often leading to breast pain. Although breast pain is a common concern of exercising females, little research has been conducted in the area of breast pain. It has been suggested that a cause of breast pain is excessive breast motion. As the female breast does not contain strong intrinsic structural support, this breast motion is difficult to reduce. It is suggested that the primary anatomical support for the breast is the Cooper's ligaments; however, their true functional properties are unknown. Because of the lack of internal breast support it has been suggested that the skin covering the breast may also act as a support structure for the breast, but this has not been quantified. In an attempt to reduce breast motion, external breast supports (brassieres) have been developed. This article discusses components of current sports brassieres with implications for future research required to improve brassiere design and performance.

Reproducibility of knee laxity assessment results using the dynamic cruciate tester

The purpose of the study was to examine reproducibility of knee laxity measurements obtained using the Dynamic Cruciate Tester (DCT) from day-to-day, set-to-set, and trial-to-trial. In Part I, peak anterior tibial translation (ATT) was assessed for 1 anterior cruciate ligament (ACL) deficient and 16 control subjects during two sets of three active trials (maximal isometric quadriceps contractions) and three passive trials (240 N load) conducted over four consecutive days. In Part II, peak ATT was recorded for 12 chronic ACL deficient subjects during one set of five active and five passive trials within one day. Results were analysed using mixed repeated measures ANOVA designs with intraclass reliability coefficients (ICC) calculated from the ANOVA results. There were no significant differences in the mean peak ATT results among the four tests days or between the two test sets conducted within a day, with ICC ranging from R1 = 0.939 to 0.980. It was concluded peak ATT measurements obtained using the DCT were reproducible from day-to-day and set-to-set. A significant main effect of trial was found on both active (F(2,32) = 13.93; p < 0.001) and passive (F(2,32) = 57.21; p < 0.001) peak ATT results. It was therefore recommended a full pretrial should be conducted before knee laxity assessment using the DCT to ensure reproducible results.

Foot-care awareness. A survey of persons aged 65 years and older

The authors conducted a mail survey that examined foot problems, rates of utilization of foot-health services, and the perception of foot problems as medical conditions in a sample of people aged 65 years and older who lived independently. Although 71% of the 128 respondents reported suffering from foot problems, only 39% had consulted medical personnel about their feet, and only 26% identified their foot pathologies as medical conditions. More female than male respondents experienced foot problems and had visited medical personnel about their feet. Increased education of older individuals about their foot-care requirements, as well as increased access to podiatric medical services, is recommended.

A kinematic and kinetic analysis of the sit-to-stand transfer using an ejector chair: implications for elderly rheumatoid arthritic patients

Twelve elderly female rheumatoid arthritis patients (mean age = 65.5 +/- 8.6 yr) were assessed rising from an instrumented Eser Ejector chair under four conditions: high seat (540 mm), low seat (450 mm), with and without the ejector mechanism operating. Sagittal plane motion, ground reaction forces, and vertical chair arm rest forces were recorded during each trial with the signals synchronised at initial subject head movement. When rising from a high seat, subjects displayed significantly (p < 0.05) greater time to seat off; greater trunk, knee and ankle angles at seat off; increased ankle angular displacement; decreased knee angular displacement; and decreased total net and normalised arm rest forces compared to rising from a low seat. When rising using the ejector mechanism, time to seat off and trunk and knee angle at seat off significantly increased, whereas trunk and knee angular displacement, and total net and normalised arm rest forces significantly decreased compared to rising unassisted. Regardless of seat height or ejector mechanism use, there were no significant differences in the peak, or time to peak horizontal velocity of the subjects' total body centre of mass, or net knee and ankle moments. It was concluded that increased seat height and use of the ejector mechanism facilitated sit-to-stand transfers performed by elderly female rheumatoid arthritic patients. However, using the ejector chair may be preferred by these patients compared to merely raising seat height because it does not necessitate the use of a footstool, a possible obstacle contributing to falls.

The MR appearance of volume overload in the lower extremities

PURPOSE

Our goal was to describe the MR findings of volume overload (VO) in the lower extremities.

METHOD

Fifteen individuals were studied, including eight healthy controls and seven patients with VO (four cardiac, three renal). MR evaluation included various SE techniques. Edema detection, localization, and symmetry were assessed subjectively. Relaxation time estimates were also made of the subcutaneous tissue, marrow, and three muscles.

RESULTS

Subcutaneous tissue was markedly edematous in seven of seven patients and asymmetric in four of seven, whereas marrow was normal in all patients. Muscle edema was mild and asymmetric in six and two of seven patients, respectively. Perifascial fluid collections were identified in six of seven patients.

CONCLUSION

Subcutaneous tissue edema is the dominant feature of VO in the lower extremities. Perifascial fluid is common but does not necessarily distribute symmetrically. Muscle edema is relatively mild. These findings should aid in identifying VO as the potential cause of swelling in patients with swollen legs.

Biomechanics of the sprint start

Many variables have been studied pertaining to the block sprint start. Research suggests that the adoption of a medium block spacing is preferred, with front and rear knee angles in the set position approximating 90 and 130 degrees, respectively, with the hips held moderately high. The sprinter must be capable of developing a high force rate combined with a high maximum force, especially in the horizontal direction. This ability to create high force underlies other important indicators of starting performance such as minimum block clearance time, maximum block leaving velocity and maximum block leaving acceleration. Once the sprinter has projected him/herself from the blocks at a low angle (40 to 45 degrees) relative to the ground, the following 2 post-block steps should occur with the total body centre of gravity ahead of the contacting foot at foot strike to minimise potential horizontal braking forces.

An injury profile of elite ironman competitors

An injury questionnaire was administered to the 30 elite ironman competitors (mean age = 25.7 +/- 4.6 yrs) participating in a commercially sponsored seven race national series. Responses provided retrospective data from the preceding three years indicating the type, location, frequency, cause and severity of injuries sustained by ironmen, and associated these injuries with particular race components (run, swim, board, ski). Twenty self-reported questionnaires were returned for analysis that described a total of 67 injuries incurred by 19 subjects. Results indicated the following: (i) the most frequently injured body parts were the knee (n = 18) and shoulder (n = 14) with the lower extremity accounting for 55% of all injuries reported; (ii) knee, shin and calf injuries had a significant association with the run component and upper extremity injuries had a significant association with the swim component; (iii) running was perceived to be the most injurious race component in terms of the frequency and severity of injury; (iv) overtraining was perceived to be the main cause of injury; (v) tendinitis was perceived to be the main type of injury; (vi) athletes adjusted their training mode to accommodate injury so that total training volume could be maintained; and (vii) injury did not result in withdrawal from competition. Further research investigating the techniques used in the ironman event and their relationship to injury is recommended.

Effect of torso position on arthrometric assessment of anterior knee laxity

The purpose of the study was to examine the effect of changes in torso position on arthrometric assessment of knee laxity. Anterior tibial translation (ATT) of 12 control and 12 ACL deficient subjects was assessed using a Dynamic Cruciate Tester during five maximal isometric knee extensions and five passive tests (240 N load) on the right and left knee in each of three torso positions: vertical, reclined, and supine. Electromyographic activity of rectus femoris, vastus lateralis, biceps femoris, and semimembranosus were sampled during arthrometric assessment. Results indicated there was no significant difference in mean ATT as a function of torso position. However, subjects demonstrated significantly greater hamstring activity when seated vertically compared to reclined or supine and significantly greater hamstring activity when reclined compared to supine.

Traumatic anterior dislocation of the hip: spectrum of plain film and CT findings

Traumatic anterior dislocation of the hip represents 11% of all hip dislocations and is classified into superior and inferior types [1]. Whereas inferior anterior hip dislocation is easily recognized on an anteroposterior radiograph of the pelvis, the radiographic appearance of superior anterior hip dislocation is less straightforward, often leading to an initial misdiagnosis of posterior hip dislocation. Misdiagnosis of the direction (anterior versus posterior) of a hip dislocation can result in failed closed reduction or an improper surgical approach to open reduction. In addition, recognition of associated impaction fractures is important, as patients with this finding have a greater tendency to develop traumatic arthritis [2, 3]. This pictorial essay, which is based on our experience with 20 cases of anterior hip dislocation, including five of the rare superior type, illustrates the spectrum of radiographic findings and distinguishing features associated with anterior hip dislocation.

Effect of work station design on sitting posture in young children

The purpose of the study was to compare muscular activity levels and sitting posture displayed by 10 children (mean age = 4.7 years) when performing tracing tasks while seated at a traditional work station (level desk top, 5 degrees backward sloping seat) and at an ergonomically designed work station (15 degrees sloping desk top, 15 degrees forward sloping seat). EMG profiles of latissimus dorsi (LD), erector spine (ES), and superior trapezius (ST) were sampled using Medi-trace disposable surface electrodes for 10 min on the non-dominant side. Muscle activity was sampled (1000 Hz) every 2 min for 5000 ms while the subjects performed the tracing tasks at each station. Raw EMG signals of the five trials for each muscle were processed by removing signal offset, full-wave rectification, and integration. The subjects' posture was monitored from a lateral view using a Panasonic VHS video camera while the children were seated at each work station. Neck flexion angle and the angle between the torso and thigh (hip angle) were manually sampled from the video images each 1 min as an indication of the posture adopted by the subjects during the tracing tasks. Use of t-tests for dependent means indicated that there was no significant difference in either mean ES or ST muscle activity as a function of work station design. However, subjects demonstrated significantly less LD activity when seated at the ergonomic work station (mean = 20.9 V ms) compared with the traditional work station (mean = 24.4 V ms, t = -2.88, p = 0.018).(ABSTRACT TRUNCATED AT 250 WORDS)

A three-dimensional representation of an athletic female knee joint using magnetic resonance imaging

Intense interest in knee joint mechanics has resulted in the development of numerous models to predict forces acting at the knee. However, few models have accounted for the unique geometric characteristics of the knee joint's articular surfaces when predicting the mechanical response of the joint. The purpose of this study was to stimulate accurately the complex geometric characteristics of the tibiofemoral joint for input into a finite element model representing the knee joint of athletic females. The right knee of an athletic female with no history of knee joint trauma was imaged using a 0.5 T magnetic resonance imaging (MRI) unit. Twelve cross-sectional slices of the knee were scanned in each of three orthogonal planes (coronal, sagittal and axial) at slice intervals of 6 mm, 7 m, and 8 mm respectively. A scan plan (two coronal images and an axial image) was also generated to enable calculation of the orthogonal scans with respect to one another. Select anatomical reference points representing cancellous and compact bone, major ligament attachment areas, and articular cartilage of the distal femur and proximal tibia were digitized from the processed shadowgraphs. The processed digitized data were input into a computer graphics program which was the pre- and post-processing software for the finite element analysis package. Contours of the cancellous and compact bone of the tibial and femoral condyles were generated using beta and cubic spline curves. Bezier quadratic and cubic polynomials were used to reconstruct the tibial and femoral shafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical factors affecting performance in netball. Implications for improving performance and injury reduction

Despite netball having one of the largest number of participants of any team game within the Commonwealth there has been limited research conducted which biomechanically analysed skills of the game. However, information presented from biomechanical analyses of skills can provide coaches with the necessary theoretical basis to teach netball fundamentals to junior players. Biomechanical information can also be used to refine the existing techniques of experienced netball players so they may achieve optimal technical performance of game skills while minimising the potential for injury. Changes to footwork rules and to the material properties of court surfaces and footwear could reduce stress placed on the musculoskeletal system. However, the factor which influences musculoskeletal stress to the greatest extent is a player's landing technique. Thus, the first concern for all netball coaches must be to teach all players to land correctly. The magnitude and rate of loading of the high vertical and horizontal ground reaction forces generated when players execute abrupt landings in netball are reduced more effectively by encouraging players to throw higher passes, requiring the receiver to jump upward to catch the ball. However, to maximise the reduction in stress placed on the musculoskeletal system on landing, players should be encouraged to land with the foot neutrally aligned (not abducted or adducted), ensure adequate hip and knee flexion, and reduce the foot-hip displacement by eliminating an exaggerated 'striding out' position often adopted by netball players. Apart from landing techniques, the only netball skill that has been objectively analysed is goal shooting. To improve shooting accuracy players should demonstrate greater flexion of the knees and shooting elbow when preparing to shoot, sufficient but not excessive hyperextension of the hand to stabilise the ball, minimisation of trunk, arm and forearm movements during the shooting action in favour of increased hand motion, greater release height and greater release velocity. If the potential for injury from poorly executed skills in netball is to be minimised, further research is required to identify the most efficient methods of performing all skills involved in the game, including pivoting, rebounding, defensive movement patterns, and attacking movement strategies.