Shoulder proprioception in baseball pitchers

The effects of shoulder stabilization exercises on muscle strength, proprioceptive sensory ability and performance in office workers with shoulder protraction

Objectives. Shoulder protraction is frequently seen in office workers because of working with excessive trunk flexion for a long time. This study aimed to compare the effectiveness of stabilization exercises (SE) given in addition to office exercises (OE). Methods. Sixty office workers with shoulder protraction were divided into SE + OE (n = 30) and OE (n = 30) groups by stratified random sampling for 8 weeks and followed up for 4 weeks. Shoulder protraction was assessed with a caliper, muscle strength with a hand-held dynamometer, proprioception with an isokinetic dynamometer, vibration sense with a vibrometer and upper extremity functional performance with the closed kinetic chain upper extremity stability test. Results. There were significant improvements in all parameters in the OE + SE group, while increases in the strength of the upper trapezius, pectoralis major and infraspinatus muscles and in upper extremity functional performance were also found in the OE group (p < 0.05). During detraining, shoulder protraction, muscle strength, proprioception and upper extremity performance showed longer-term improvement with SE + OE (p < 0.05). Conclusion. The results obtained with the exercises demonstrate the importance of SE + OE in terms of maintaining proper posture and improving shoulder proprioception, muscle strength and functional performance.

The associations of physical parameters with the Closed Kinetic Chain Upper Extremity Stability Test, the Upper Quarter Y Balance Test, and the Upper Limb Rotation Test in professional overhead athletes

OBJECTIVE

To investigate the associations of glenohumeral internal (IR) and external rotation (ER), horizontal adduction (HA), and thoracic spine rotation ranges of motion (ROM), isometric muscle strength of the shoulder rotators, and trunk muscle endurance with the Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST), the Upper Quarter Y Balance Test (YBT-UQ), and the Upper Limb Rotation Test (ULRT) in overhead athletes.

DESIGN

Cross-sectional study.

SETTINGS

Laboratory.

PARTICIPANTS

One hundred twenty-one athletes were enrolled.

MAIN OUTCOME MEASURES

Independent variables were: IR, ER, HA, and thoracic spine rotation ROMs, isometric muscle strength of glenohumeral IR and ER muscles, and trunk muscle endurance. Dependent variables were: CKCUEST, YBT-UQ, ULRT.

RESULTS

IR ROM of the nondominant side was associated with the CKCUEST, the YBT-UQ, and the ULRT. IR muscle strength of the dominant side was associated with the CKCUEST and the ULRT. Trunk flexor and lateral endurance of the dominant side were associated with the CKCUEST and the YBT-UQ, respectively.

CONCLUSIONS

Many of the physical parameters influencing scores on the CKCUEST and the YBT-UQ are different. Common parameters influence the CKCUEST and ULRT scores, yet more parameters influence the CKCUEST score. We suggest the combined use of the CKCUEST and the YBT-UQ in overhead athletes.

Reduced shoulder proprioception due to fatigue after repeated handball throws and evaluation of test-retest reliability of a clinical shoulder joint position test

Background

Proprioception is vital for motor control and can be disturbed, for example, due to fatigue or injury. Clinical feasible, reliable and valid tests of shoulder proprioception are warranted. The aim was to investigate the effects of local fatigue on shoulder proprioception and the reliability of a feasible joint position sense test using an experimental repeated measures design.

Method

Forty participants repeated a shoulder joint position sense test to assess test-retest reliability. The test was then utilized on a subgroup of handball players who were subjected to five bouts of a repeated throwing task with the dominant hand. The effect of local fatigue was investigated by comparing the fatigued with the non-fatigued shoulder.

Results

There was a significant interaction for the arm × bout (p = 0.028, ηp2 = 0.20) and a significant effect for the arm (p = 0.034, ηp2 = 0.35) with a significant decrease in joint position sense for the throwing arm compared to the non-throwing arm. The intraclass correlation coefficient was 0.78 (95% CI = [0.57; 0.89]). The standard error of measurement between trials was 0.70° (range: 0.57°-0.90°).

Discussion

The results indicate that repeated throwing to fatigue disturbs shoulder joint position sense. Assessment with the modified test showed acceptable reliability and can be a valuable assessment tool in the clinic.

Handball players have superior shoulder proprioception: a prospective controlled study

BACKGROUND

Proper proprioceptive and neuromuscular control is crucial for the overhead athlete's performance. The aim of the present study was to evaluate the shoulder joint position sense (JPS) levels in overhead throwing athletes. The secondary aim was to confront the proprioceptive abilities with glenohumeral adaptive changes and pathologies among athletes.

METHODS

Ninety professional handball players and 32 healthy volunteers were recruited. JPS levels were measured by an electronic goniometer and expressed as values of an active reproduction of the joint position (ARJP) and as error of ARJP (EARJP) in 3 different reference positions for each movement (abduction and flexion at 60°, 90°, and 120°; internal [IR] and external rotation [ER] at 30°, 45°, and 60°).

RESULTS

Side-to-side differences revealed significantly better values of EARJP for the throwing shoulders in abduction at 90° and 120°, flexion at 90° and 120°, IR at 60°, and ER at 30° and 60° compared with the nonthrowing shoulders. Handball players showed significantly better proprioceptive levels in their throwing shoulder compared to the dominant shoulder of the control group in abduction at 90° (P = .037) and 120° (P = .001), flexion at 120° (P = .035), IR at 60° (P = .045), and in ER at 60° (P = .012).

DISCUSSION

Handball players present superior shoulder JPS in their dominant throwing shoulder at high range of motion angles when compared to a nonathlete population and to their own nondominant shoulder.

Measuring upper limb active joint position sense: Introducing a new clinical tool - The Upper Limb Proprioception Reaching Test

BACKGROUND

Proprioception is our sense of body awareness, including the sub-category of active joint position sense (AJPS). AJPS is fundamental to joint stability and movement coordination. Despite its importance, there remain few confident ways to measure upper limb AJPS in a clinic.

OBJECTIVE

To assess a new AJPS clinical tool, the Upper Limb Proprioception Reaching Test (PRO-Reach; seven targets), for discriminant validity, intra-rater and absolute reliability.

DESIGN

Cross-sectional measurement study.

METHODS

Seventy-five healthy participants took part in a single session with 2 consecutive evaluations (E1 and E2) (within-day reliability). Twenty participants were randomly selected to perform a dominant shoulder fatigue protocol (discriminant validity), whereafter a third evaluation was repeated (E3). The PRO-Reach was analyzed with paired t tests (discriminant validity), intra-class correlation coefficients (ICCs) and minimal detectable change [MDC]) (intra-rater: within-day and between-trial relative and absolute reliability).

RESULTS

The PRO-Reach supports moderate (mostly superior targets) to excellent (mostly inferior targets) reliability. Between-trial ICCs (T1/T2/T3) varied between 0.72 and 0.90, and within-day (E1/E2) ICCs between 0.45 and 0.72, with associated MDC95 values (3.9-5.0 cm). The overall scores (seven targets) supported the strongest within-day reliability (ICC = 0.77). The inferior targets demonstrated the highest between-trial and within-day reliability (ICCs = 0.90 and 0.72). A fatigue effect was found with the superior and superior-lateral targets (P < .05).

CONCLUSIONS

The inferior targets and overall scores demonstrate the strongest reliability. The use of the PRO-Reach tool may be suitable for clinical use upon further psychometric testing amongst pathological populations.

LEVEL OF EVIDENCE

Level III cross-sectional study.

Innovative Use of Biodex Balance System to Improve Dynamic Stabilization and Function of Upper Quarter in Recreational Weightlifters: A Randomized Controlled Trial

Background and Objectives: Following an injury, upper-body strength and proprioception training is typically suggested. To our understanding, no prior research has looked into the impact of balance training on upper-body strength and stability. So, this study investigated the effects of Biodex balance training on enhancing the dynamic stability, strength, and function of the upper quarter (UQ) in recreational weightlifters. Materials and Methods: Fifty male weightlifters were randomly assigned into two groups. The experimental group received an upper-extremity Biodex balance training program three times/week for eight weeks, while the control group underwent a regular weightlifting training routine. Pre- and post-test scores of the upper-quarter dynamic stability, strength, and function were measured for both groups using the shoulder active repositioning accuracy test, two-minute push-up test, and the upper-quarter Y-balance test (UQ-YBT) and one-arm hop test, respectively. Results: Post-test values were significantly greater for the normalized UQ-YBT test than pre-test values in both groups (p < 0.05). Post-test values of the experimental group were significantly greater than the control group (p < 0.05). Regarding the shoulder active repositioning accuracy test and the time of the one-arm hop test, post-test values were significantly lower than pre-test values for both groups (p < 0.05), and post-test values of the experimental group were significantly lower than those of the control group (p < 0.05). The post-test value of the two-minute push-up test of each group was significantly higher than the pre-test value (p < 0.05), without any significant difference between both groups (p > 0.05). Conclusions: Adding upper-body Biodex balance training to a regular weightlifting training routine was effective in enhancing the upper quarter′s dynamic stability and function.

EMG Signal Processing for the Study of Localized Muscle Fatigue-Pilot Study to Explore the Applicability of a Novel Method

This pilot study aimed to explore a method for characterization of the electromyogram frequency spectrum during a sustained exertion task, performed by the upper limb. Methods: Nine participants underwent an isometric localized muscle fatigue protocol on an isokinetic dynamometer until exhaustion, while monitored with surface electromyography (sEMG) of the shoulder's external rotators. Firstly, three methods of signal energy analysis based on primer frequency contributors were compared to the energy of the entire spectrum. Secondly, the chosen method of analysis was used to characterize the signal energy at beginning (T1), in the middle (T2) and at the end (T3) of the fatigue protocol and compared to the torque output and the shift in the median frequencies during the trial. Results: There were statistically significant differences between T1 and T3 for signal energy (p < 0.007) and for central frequency of the interval (p = 0.003). Moreover, the isometric peak torque was also different between T1 and T3 (p < 0.001). Overall, there were no differences between the signal energy enclosed in the 40 primer frequency contributors and the analysis of the full spectrum energy; consequently, it was the method of choice. The reported fatigue and the decrease in the produced muscle torque was consistent with fatigue-induced alterations in the electromyogram frequency spectrum. In conclusion, the developed protocol has potential to be considered as an easy-to-use method for EMG-based analysis of isometric muscle exertion until fatigue. Thus, the novelty of the proposed method is to explore, in muscle fatigue, the use of only the main contributors in the frequency domain of the EMG spectrum, avoiding surplus information, that may not represent muscle functioning. However, further studies are needed to investigate the stability of the present findings in a more comprehensive sample.

Correlation analysis of national elite Chinese male table tennis players’ shoulder proprioception and muscle strength

BACKGROUND

Shoulder is the most injured part in table tennis players, and it takes multiple roles in transmitting power and striking the center of the ball during the stroke. Proprioception is strongly correlated with high level of athletic performance. It is customary to assume that there is a correlation between proprioception and muscle strength and therefore proprioceptive assessment and rehabilitation is often neglected.

AIM

To investigate the correlation between isokinetic muscle strength and proprioception in the internal and external rotation muscle groups of elite Chinese male table tennis players, to provide reference for physical training and rehabilitation of elite table tennis players.

METHODS

A total of 19 national elite table tennis players from the Chinese National Table Tennis Team were recruited in this research. All of them had more than 10 years training experience and had participated major competitions such as the National Games and World Youth Championships. IsoMed 2000 was used to test the peak torque of internal and external rotation isokinetic concentric contraction of the athletes' bilateral shoulder joints at low speed (60°/s) and high speed (180°/s) respectively; IsoMed 2000 was used to conduct the Joint Position Reproduction test to evaluate the athletes' proprioceptive ability capacity at low speed (60°/s) and high speed (180°/s) respectively. If the data satisfied the normal distribution, the correlation between the differences in peak torque s and angles in different directions was analyzed using a Pearson simple linear model; otherwise, Spearman correlation analysis was used. The comparison of proprioceptive ability between the table tennis racket-holding hand and non-racket-holding hands was performed using independent samples t-test if the data satisfied a normal distribution; otherwise, the Mann-Whitney U test was used.

RESULTS

There was no direct linear correlation between the strength and proprioceptive correlation analysis at slow speed (60°/s) and fast speed (180°/s) in the racket-holding hand; At the slow speed (60°/s) and fast speed (180°/s), there was no correlation between muscle strength and proprioception in the non-racket-holding hand except for the internal rotation variable error (VE) and external rotation relative peak torque, which showed a moderate positive correlation (r = 0.477, P < 0.05), (r = 0.554, P < 0.05). The internal rotation’s constant error (CE) and VE were 1.06 ± 3.99 and 2.94 ± 2.16, respectively, for the racket-holding hand, and -3.36 ± 2.39 and 1.22 ± 0.93, respectively, for the non-racket-holding hand; the internal rotation’s CE, VE of the racket-holding hand was lower than that of the non-racket-holding hand, and there was a highly significant difference (P < 0.01).

CONCLUSION

There was no correlation between muscle strength and proprioceptive function in the internal and external rotation of the racket-holding hand’s shoulder in elite Chinese male table tennis players. These results may be useful for interventions for shoulder injuries and for the inclusion of proprioceptive training in rehabilitation programs.

Levels of Gnostic Functions in Top Karate Athletes-A Pilot Study

High-quality sensory perception and body scheme (somatognosis) are important aspects for sport performance. This study compares stereognosis, body scheme, and kinesthesia in a group of 36 competitive karate athletes against a control group of 32 general population participants. The stereognosis Petrie test, two body scheme tests, and three kinesthesia tests served as outcome measurement tools. No significant difference was found in the stereognosis Petrie test, for the dominant (p = .389) or the nondominant (p = .791) hand, nor in the kinesthesia test (dominant, p = .661 and nondominant, p = .051). Karate athletes performed significantly better in the body scheme tests, that is, fist width estimation (p = .024) and shoulder width estimation (p = .019), as well as in karate-specific kinesthesia tests, that is, single punch (p = .010) and triple punch (p = .001). This study confirms competitive karate athletes have significantly better somatognosis, and better accuracy when performing quick dynamic movements compared with the general population.

Upper limb active joint repositioning during a multijoint task in participants with and without rotator cuff tendinopathy and effect of a rehabilitation program

STUDY DESIGN

Cross-sectional and longitudinal (exploratory) studies.

INTRODUCTION

Rotator cuff (RC) tendinopathy is the most prevalent shoulder diagnosis, and proprioception deficits are often observed in individuals with RC tendinopathy.

PURPOSE OF THE STUDY

This study aimed to evaluate upper limb proprioception during a multijoint task in participants with and without RC tendinopathy and to determine if symptoms, functional limitations, and proprioception are improved after a rehabilitation program.

METHODS

Twenty participants with and 20 without RC tendinopathy were recruited for the cross-sectional study, and 23 participants with RC tendinopathy were recruited for the longitudinal study. Proprioception was evaluated by an active joint-repositioning task: The upper limb was passively moved to a predetermined position, and the participant was asked to actively replicate the movement. The difference between the predetermined position and the replicated position was measured. The mean errors in positions of lateral, medial, and neutral rotation of the shoulder and the global mean error were reported. In addition to the active-repositioning assessment in the longitudinal study, symptoms and functional limitations were evaluated by the Disability of the Arm Shoulder and Hand questionnaire.

RESULTS

Significant deficits in active repositioning (p < .01), independent of the position, were observed in participants with RC tendinopathy compared with controls. The DASH score was improved after rehabilitation intervention (p < .001), and patients with active-repositioning deficits at baseline had reduced repositioning error (p < .05).

CONCLUSIONS

Upper limb active joint repositioning was impaired in participants with RC tendinopathy. Symptoms and functional limitations and active joint repositioning in participants with RC tendinopathy and initial deficits were improved after a 6-week global rehabilitation program.

Assessment of movement coordination strategies to inform health of movement and guide retraining interventions

INTRODUCTION

Exploring characteristics of human movement has long been the focus of clinicians and researchers. Changes in movement coordination strategies have been identified in the presence of pain highlighting the need for assessment in clinical practice. A major development in the understanding of movement related disorders is recognition of individual differences in presentation and consequently the need to tailor interventions based on assessment.

PURPOSE

The purpose of this masterclass is to build a rationale for the clinical assessment of movement coordination strategies, exploring loss of movement choices, coordination variability, and to present a clinical framework for individualised management, including the use of cognitive movement control tests and retraining interventions. An approach for the qualitative rating of movement coordination strategies is presented. A compromised movement system may be one characterised by a lack of ability to access motor abundance and display choice in the use of movement coordination strategies. The identification of lost movement choices revealed during the assessment of movement coordination strategies is proposed as a marker of movement health.

IMPLICATIONS FOR PRACTICE

The health of the movement system may be informed by the ability to display choice in movement coordination strategies. There is evidence that restoring these choices has clinical utility and an influence on pain and improved function. This approach seeks to provide individuals with more flexible problem solving, enabled through a movement system that is robust to each unique challenge of function. This assessment framework sits within a bigger clinical reasoning picture for sustained quality of life.

Quantifying the three-dimensional joint position sense of the shoulder

Joint position sense is important for performing activities of daily living and recreational activities. The objective of this study was to develop new insights into the proprioceptive capabilities of the shoulder using a novel virtual reality paradigm where participants actively recreated shoulder positions in all three dimensions. This allows for better identification of changes in joint position sense across different shoulder postures. Ten males and ten female healthy adults matched a cursor controlled by shoulder rotations calculated from motion capture tracking, to a target shoulder position presented in a virtual environment with the use of a virtual reality headset. Four elevation angles, three plane of elevation angles, and three rotation angles were investigated, totaling thirty-six angles that encompassed the range of motion of the shoulder. Joint position sense was enhanced as the elevation angle was increased, and further enhanced when the arm was more externally rotated and elevated. As elevation angle increased to 90°, joint position sense significantly increased. There was also a significant interaction of external rotation on elevation angle. As elevation angle increased, participants were more accurate when the arm was externally, but exhibited greater variability. These improvements in joint position sense are likely produced by increased tension in muscles and capsuloligamentous mechanoreceptors within the shoulder. As many sports and activities of daily living require joint position sense to complete a task, the ability to elevate and externally rotate is important for adequate shoulder proprioception and control.

Throwing performance in water polo is related to in-water shoulder proprioception

Water polo players require a high level of upper-extremity strength, flexibility and coordination to achieve a peak level of throwing performance. Increased levels of shoulder proprioceptive acuity, strength and range of motion (ROM) have been previously associated with higher sporting performance. A coach-rating scale, used to quantify an athlete's kicking proficiency in soccer; was adapted in the current study to measure each coach's subjective expert opinion regarding athletes' throwing mechanics, velocity, and accuracy. To examine this hypothesis shoulder proprioception acuity of 18 water polo players was measured both in-water and on-land using an AMEDA apparatus and correlated with coach-rated throwing performance and clinical measures of shoulder strength and ROM. There was a moderate positive correlation between the in-water and the on-land proprioception acuity (r = 0.47, p < 0.05). The in-water score showing a strong positive correlation with coach rated throwing mechanics (r = 0.68, p < 0.05) and velocity (r = 0.75, p = 0.02), suggesting that superior proprioception acuity contributed to fast, mechanically-efficient throwing. These findings support the notion that in-water proprioceptive acuity is an important determinant of the throwing performance achieved by water polo athletes and its measurement may be a valuable adjunct to current athlete screening.

Bilateral shoulder proprioception deficit in unilateral anterior shoulder instability

HYPOTHESIS AND BACKGROUND

Proprioception is an important element of shoulder dynamic stability. It has been shown to be affected in cases of capsular or labral injuries of the glenohumeral joint. Therefore, this study was conducted to investigate bilateral shoulder proprioception by active reproduction of joint position both in patients with post-traumatic recurrent unilateral shoulder instability and in normal healthy volunteers.

METHODS

We compared 41 patients, comprising 11 female and 30 male patients with an average age of 25.6 years (range, 18-39 years), with post-traumatic unilateral anterior shoulder instability with a control group of 27 healthy volunteers with no history of shoulder problems and with normal shoulder function during examination. All patients were examined using a high-accuracy computer-controlled electronic goniometer (Propriometer). The error of active reproduction of joint position (EARJP) was measured in abduction, flexion, external rotation, and internal rotation in both shoulders.

RESULTS

We observed a significant deficit in the EARJP in the unstable shoulders within the instability group. Surprisingly, similar results were recorded for the contralateral, unaffected shoulders within this group of patients compared with the control group. Joint acuity increased with higher elevation of the arm position.

CONCLUSION

Unilateral shoulder injuries, resulting in instability, affect proprioception in both shoulders, as demonstrated by an increased EARJP. This is the first report of unilateral shoulder instability coexisting with inferior proprioception in both shoulders.

College Pitchers Demonstrate Directional Differences in Shoulder Joint Position Sense Compared With Controls

CONTEXT

The relationship between overhead throwing and its effect on proprioception is not well understood. It is important to gain a better understanding of how these are related, to protect overhead athletes from an increased risk of injury.

OBJECTIVE

To investigate proprioceptive alterations in the overhead thrower's shoulder.

DESIGN

Cross-sectional study. Independent variables are limb (dominant and nondominant), group (thrower or control), and target angle. Dependent variables are joint position sense and range of motion.

SETTING

An orthopedic biomechanics lab and university athletic training facility.

PARTICIPANTS

Twelve Division I baseball pitchers and 13 nonthrowing control subjects.

INTERVENTION

Shoulder proprioception was assessed using an active joint repositioning task administered with an iPod Touch.

MAIN OUTCOME MEASURE

Root mean square error and constant error of repositioning angles were used to assess accuracy and directional patterns, respectively.

RESULTS

Both groups demonstrated significantly higher joint acuity at the 80° external rotation target angle compared with 60° (1.5° [0.5°], P = .01). There were no differences in accuracy between groups. Constant error revealed differing repositioning patterns between limbs for the pitchers and also between groups for the dominant side. Although the throwing shoulder overshot the target angles by 0.4°, all nonthrowing shoulders undershot by an average of 2.7°.

CONCLUSIONS

There is no difference in shoulder joint position sense accuracy between throwers and nonthrowers, although both groups display increased accuracy closer to their end range of external rotation. The throwing shoulder demonstrates a different repositioning pattern, overshooting the desired target angle, while all other shoulders undershoot.

Shoulder proprioception in patients with subacromial impingement syndrome

BACKGROUND

Recently, proprioception deficits of the rotator cuff and the deltoid muscles have been suggested to play a pivotal role in the subacromial impingement syndrome (SIS). To date, there are no study has been found where the kinesthesia and joint position senses have been evaluated together in SIS.

OBJECTIVE

To investigate the shoulder proprioception in patients with SIS.

METHODS

Sixty-one patients with SIS and 30 healthy controls, aging between 25 and 65 years, were included in the study. Main outcome measure was proprioception, assessed with an isokinetic dynamometer. Kinesthesia, active and passive joint repositioning senses were tested at 0° and 10° external rotation. All tests were repeated 4 times and the mean of angular errors were obtained.

RESULTS

The mean age was 49.14 ± 10.27 and 48.80 ± 11.09 years in patient group and in control group respectively. No significant difference was found between two groups in terms of age, gender and dominance. When involved and uninvolved shoulders of the patient group were compared, kinesthesia, active and passive joint position senses were significantly impaired in involved shoulders at all angles (P < 0.05). When involved shoulders of the patient group were compared to the control group, kinesthesia, active and passive joint position senses were significantly impaired in involved shoulders in patient group at all angles (P < 0.05) except active position sense at 0°. When uninvolved shoulders of the patient group were compared to the control group, kinesthesia at 10° was significantly impaired (P < 0.05).

CONCLUSION

This study showed that shoulder proprioception was impaired in patients with SIS. This proprioceptive impairment was found not only in involved shoulders but also in uninvolved shoulders in patients with SIS.

Proprioceptive deficit after total elbow arthroplasty: an observational study

BACKGROUND

During total elbow arthroplasty (TEA), most of the joint capsule is removed, including many mechanoreceptors important for proprioception, which potentially limits the patient's postoperative functional recovery. We quantified proprioceptive loss by measuring the threshold to detection of passive motion (TTDPM) in patients after unilateral TEA compared with the contralateral side.

METHODS

A continuous passive motion device moving the elbow at 0.5°/s was used to evaluate TTDPM in 8 patients (mean ± standard deviation age, 69.1 ± 9.93 years) at least 1 year after unilateral semiconstricted linked TEA for a range of diagnoses. Elbow function after TEA was assessed using the Mayo Elbow Performance Scale.

RESULTS

Postsurgical Mayo scores revealed 4 excellent results, 2 good, and 2 poor. The TTDPM in the elbows undergoing arthroplasty was still significantly higher compared with the contralateral elbow at 4.2° (15.6  ± 6.9 seconds vs. 7.2  ± 2.6 seconds; D = 3.23, P = .01) equivalent to 8.4 seconds.

CONCLUSIONS

Patients who have had severe joint disease requiring semiconstrained TEA have long-term proprioception deficits. A more conservative technique that maximally preserves insertions and soft tissues, might minimize upper limb proprioceptive deficit.

Differences in humeral retroversion in dominant and nondominant sides of young baseball players

BACKGROUND

The relationship between the disabled throwing shoulder and humeral retroversion has recently attracted a great deal of attention. However, none of the previous studies clarified when the side-to-side difference of humeral retroversion in young baseball players would start. This study aimed to clarify when the difference of humeral retroversion in the dominant and nondominant sides appeared in baseball players.

METHODS

The bicipital-forearm angle in bilateral shoulders of 172 elementary school baseball players was measured by ultrasound. The bicipital-forearm angle was defined as an angle between the perpendicular line to the bicipital groove and the ulnar long axis with the elbow flexed at 90°. The correlation between the bicipital-forearm angle and the grade and the difference of the bicipital-forearm angle between the dominant and nondominant sides were analyzed.

RESULTS

In the nondominant shoulders, the bicipital-forearm angle increased with the grade in school (r = 0.32, P < .0001), but this was not observed in the dominant shoulders. In the fourth to sixth graders, the bicipital-forearm angles were significantly smaller in the dominant shoulders than in the nondominant shoulders.

CONCLUSION

Our findings indicated that humeral retroversion decreased with age in the nonthrowing side but not in the throwing side and that the side-to-side difference of humeral retroversion in the baseball players became obvious from the fourth grade. We assume that the repetitive throwing motion restricts the physiologic humeral derotation process and the difference became apparent from the fourth grade when the growth spurt begins in boys.

Efficacy of Proprioceptive Exercises in Patients with Subacromial Impingement Syndrome: A Single-Blinded Randomized Controlled Study

OBJECTIVE

The objective of this study was to evaluate the effectiveness of proprioceptive exercises on shoulder proprioception, range of motion, pain, muscle strength, and function in patients with subacromial impingement syndrome.

DESIGN

Sixty-one patients with subacromial impingement syndrome participated in this prospective, single-blind randomized controlled trial. All patients were randomly divided into two groups: control group (conventional physiotherapy, n = 30) and intervention group (proprioceptive exercise and conventional physiotherapy, n = 31). The primary outcome measures were sense of kinesthesia and active and passive repositioning for proprioception at 0 degrees and 10 degrees external rotation at 12 wks. The secondary outcome measures were pain at rest, at night, and during activities of daily living with the visual analog scale (0-10 cm), the Western Ontario Rotator Cuff index, the American Shoulder and Elbow Surgeons index, range of motion, and isometric muscle strength at both 6 and 12 wks.

RESULTS

After treatment, significant improvement was found in range of motion, pain, isometric muscle strength, kinesthesia at 0 degrees external rotation, and functional tests in both groups. The intervention group showed a significant improvement in kinesthesia at 10 degrees external rotation and active and passive repositioning at 10 degrees external rotation. When groups were compared, there were no statistically significant differences in any of the parameters at 12 wks.

CONCLUSIONS

Although proprioceptive exercises may provide better proprioceptive acuity, no additional positive effect on other clinical parameters was observed.

Assessing proprioception: A critical review of methods

To control movement, the brain has to integrate proprioceptive information from a variety of mechanoreceptors. The role of proprioception in daily activities, exercise, and sports has been extensively investigated, using different techniques, yet the proprioceptive mechanisms underlying human movement control are still unclear. In the current work we have reviewed understanding of proprioception and the three testing methods: threshold to detection of passive motion, joint position reproduction, and active movement extent discrimination, all of which have been used for assessing proprioception. The origin of the methods, the different testing apparatus, and the procedures and protocols used in each approach are compared and discussed. Recommendations are made for choosing an appropriate technique when assessing proprioceptive mechanisms in different contexts.

Upper limb joint position sense during shoulder flexion in healthy individuals: a pilot study to develop a new assessment method

BACKGROUND

Altered shoulder joint position sense (JPS) following shoulder injury has been demonstrated in the literature and may increase the risk of injury. A JPS assessment targeting the shoulder will provide the clinician with an objective marker. The present study aimed to develop an assessment method of JPS using an active relocation test (ART).

METHODS

In total, 40 healthy participants were recruited. A laser-pointer attached to the index finger during an ART allowed measurement (mm) of JPS by measuring the distance between the target and relocated position. Participants were blindfolded and stood an arm's length (approximately 1 m) away from the wall. Whilst keeping the wrist in neutral and elbow extended, the participant actively moved to the target position (90° glenohumeral flexion), held for 5 seconds, returned their arm to their side and actively returned to the target position. A mean was calculated from three trials to provide an ART score.

RESULTS

The mean (SD) dominant and nondominant ART score was 89.2 (SD 35.5) mm (95% confidence interval = 77.87 mm to 100.5 mm) and 94.1 (34.5) mm (95% confidence interval = 83.1 mm to 105.2 mm), respectively. Arm dominance did not significantly affect ART scores.

CONCLUSIONS

No significant difference was demonstrated between the dominant and nondominant arm using an ART assessing JPS acuity. Further studies are needed to establish inter-rater and intra-rater reliability.

Proprioceptive deficit in patients with complete tearing of the anterior cruciate ligament

Objective

To investigate the existence of proprioceptive deficits between the injured limb and the uninjured (i.e. contralateral normal) limb, in individuals who suffered complete tearing of the anterior cruciate ligament (ACL), using a strength reproduction test.

Methods

Sixteen patients with complete tearing of the ACL participated in the study. A voluntary maximum isometric strength test was performed, with reproduction of the muscle strength in the limb with complete tearing of the ACL and the healthy contralateral limb, with the knee flexed at 60°. The meta-intensity was used for the procedure of 20% of the voluntary maximum isometric strength. The proprioceptive performance was determined by means of absolute error, variable error and constant error values.

Results

Significant differences were found between the control group and ACL group for the variables of absolute error (p = 0.05) and constant error (p = 0.01). No difference was found in relation to variable error (p = 0.83).

Conclusion

Our data corroborate the hypothesis that there is a proprioceptive deficit in subjects with complete tearing of the ACL in an injured limb, in comparison with the uninjured limb, during evaluation of the sense of strength. This deficit can be explained in terms of partial or total loss of the mechanoreceptors of the ACL.

The role of the peripheral and central nervous systems in rotator cuff disease

Rotator cuff (RC) disease is an extremely common condition associated with shoulder pain, reduced functional capacities, and impaired quality of life. It primarily involves alterations in tendon health and mechanical properties that can ultimately lead to tendon failure. RC tendon tears induce progressive muscle changes that have a negative impact on surgical reparability of the RC tendons and clinical outcomes. At the same time, a significant base of clinical data suggests a relatively weak relationship between RC integrity and clinical presentation, emphasizing the multifactorial aspects of RC disease. This review aims to summarize the potential contribution of peripheral, spinal, and supraspinal neural factors that may (1) exacerbate structural and functional muscle changes induced by tendon tear, (2) compromise the reversal of these changes during surgery and rehabilitation, (3) contribute to pain generation and persistence of pain, (4) impair shoulder function through reduced proprioception, kinematics, and muscle recruitment, and (5) help explain interindividual differences and response to treatment. Given the current clinical and scientific interest in peripheral nerve injury in the context of RC disease and surgery, we carefully reviewed this body of literature with a particular emphasis on suprascapular neuropathy that has generated a large number of studies in the past decade. Within this process, we highlight the gaps in current knowledge and suggest research avenues for scientists and clinicians.

Strength training and shoulder proprioception

CONTEXT

Proprioception is essential to motor control and joint stability during daily and sport activities. Recent studies demonstrated that athletes have better joint position sense (JPS) when compared with controls matched for age, suggesting that physical training could have an effect on proprioception.

OBJECTIVE

To evaluate the result of an 8-week strength-training program on shoulder JPS and to verify whether using training intensities that are the same or divergent for the shoulder's dynamic-stabilizer muscles promote different effects on JPS.

DESIGN

Randomized controlled clinical trial.

SETTING

We evaluated JPS in a research laboratory and conducted training in a gymnasium.

PATIENTS OR OTHER PARTICIPANTS

A total of 90 men, right handed and asymptomatic, with no history of any type of injury or shoulder instability.

INTERVENTION(S)

For 8 weeks, the participants performed the strength-training program 3 sessions per week. We used 4 exercises (bench press, lat pull down, shoulder press, and seated row), with 2 sets each.

MAIN OUTCOME MEASURE(S)

We measured shoulder JPS acuity by calculating the absolute error.

RESULTS

We found an interaction between group and time. To examine the interaction, we conducted two 1-way analyses of variance comparing groups at each time. The groups did not differ at pretraining; however, a difference among groups was noted posttraining.

CONCLUSIONS

Strength training using exercises at the same intensity produced an improvement in JPS compared with exercises of varying intensity, suggesting that the former resulted in improvements in the sensitivity of muscle spindles and, hence, better neuromuscular control in the shoulder.

Practice habits and attitudes and behaviors concerning shoulder pain in high school competitive club swimmers

OBJECTIVE

The objective of this study is to describe the practice habits, injury frequency, and attitudes and behaviors concerning shoulder pain in high school-aged competitive swimmers and describe the relationship between attitudes and behaviors.

DESIGN

Cross-sectional research design.

SETTING

Local swimming clubs.

PARTICIPANTS

One hundred two swimmers, aged 13-18 years, at the top training level of their club team were included in the study.

ASSESSMENT OF RISK FACTORS

Participants were given a survey with questions regarding swimming practice and attitudes and behaviors concerning shoulder pain.

MAIN OUTCOME MEASURES

Practice habits (yards/week, practice/week, dry-land and weight/week, and months swimming/year) and attitudes and behaviors concerning shoulder pain.

RESULTS

Subjects completed an average of 6.89 ± 1.41 swimming practices/wk of 6000 to 7000 yd/practice. The majority of swimmers believe that mild and moderate shoulder pain is normal in swimming and should be tolerated to complete practice, while a majority responded that they swim with shoulder pain. Seventy-three percent of swimmers reported using pain medication to manage their shoulder pain. There was a significant correlation between attitude and behaviors of moderate and severe shoulder pain.

CONCLUSIONS

Club swimmers have a high frequency of practices, comparable to collegiate and professional swimmers. They believe that shoulder pain is normal and should be tolerated to complete practice. The association between the swimmers' attitudes and behaviors indicates that the interventions that educate the swimmers, coaches, and parents may be effective in changing their attitudes and ultimately their behaviors, decreasing the number of athletes who train with shoulder pain.

The relationship between anterior glenohumeral laxity and proprioception in collegiate baseball players

OBJECTIVE

To determine if a relationship exists between anterior glenohumeral (GH) laxity and proprioception.

DESIGN

Cross-sectional study.

SETTING

University biomechanics laboratory.

PARTICIPANTS

Thirty asymptomatic collegiate baseball players.

INDEPENDENT VARIABLES

Anterior GH laxity.

MAIN OUTCOME MEASURES

Proprioception (active joint position sense) at positions of 75 degrees of external rotation, 30 degrees of external rotation, and 30 degrees of internal rotation were measured using an isokinetic dynomometer. Anterior GH laxity was measured using an instrumented arthrometer.

RESULTS

Linear regression analyses showed that there were no relationships between anterior GH laxity and active joint position sense at 30 degrees of GH internal rotation and 30 degrees of GH external rotation (r = 0.21, P = 0.13). However, there was a moderate positive relationship between anterior GH laxity and joint position sense at 75 degrees of shoulder external rotation (r = 0.56, P = 0.001).

CONCLUSIONS

These results suggest that shoulder proprioception in 75 degrees of external rotation decreases as anterior GH laxity increases. These results may prove beneficial in the prevention, evaluation, and treatment of various shoulder injuries associated with GH laxity.

Shoulder internal and external rotations torque steadiness in overhead athletes with and without impingement symptoms

OBJECTIVES

This study aimed to investigate torque steadiness of shoulder internal and external rotations in regularly training overhead athletes with and without impingement symptoms.

DESIGN

Cross-sectional laboratory study.

METHODS

Three groups were evaluated: athletes with impingement symptoms (n=21), asymptomatic athletes (n=25) and non-athletes (n=21). To assess torque steadiness, the participants performed 3 submaximal contractions (35% of peak torque) for 10s each, with the arm at 90° of shoulder abduction and 90° of external rotation. The standard deviation, coefficient of variation, mean exerted torque and time to stability were measured from the steadiness trials.

RESULTS

The standard deviation of internal rotation was higher in asymptomatic athletes than in non-athletes (p<0.01); however, there was no difference between the athletes with impingement symptoms and the other groups. The other variables presented no differences among the groups.

CONCLUSIONS

Higher torque fluctuation of shoulder internal rotation in asymptomatic athletes may point to neuromuscular adaptations related to throwing training. However, the steadiness patterns of athletes with impingement symptoms did not differ from those of asymptomatic athletes or non-athletes.

A Comparative Study on Shoulder Rotational Strength, Range of Motion and Proprioception between the Throwing Athletes and Non-athletic Persons

Purpose

The repetitive micro traumatic stresses placed on the athletes shoulder joint complex during the throwing motion challenge the surrounding tissues. The purpose of this study was to compare shoulder rotational strength, range of motion and proprioception between the throwing athletes and non-athletic persons.

Methods

Fifteen throwing athletes and 15 non-athletes participated in a nonrandom case – control study. Strength of shoulder rotational movements was tested with a hand held dynamometer. The ranges of internal and external rotation of shoulder were measured by a standard goniometer. The ability of subjects to replicate the target position and kinesthetic sense was examined on the subjects’ right shoulder by using a continuous passive motion device. Independent and paired t tests were used to statistically analyze between and within group differences.

Results

No significant difference was detected on the range of internal rotation between throwing athletes and non-athletic candidates (P=0.3). The range of external rotation was significantly more in athletic subjects (P=0.03). The results also showed that throwing athletes demonstrated a significantly higher isometric strength of shoulder external and internal rotation than the non-athletic group (P<0.05). However, the comparison of the internal and external rotation strength of dominant side in each group showed that throwing athletes showed a significant lower isometric strength of shoulder external rotation than internal rotation (P<0.001). It was also demonstrated higher joint position acuity in the throwing athletes than non athlete subjects (P=0.01).

Conclusion

The repetitive nature of overhead throwing and the high forces that it causes result in adaptive changes of the dominant extremity. Throwing can lead to mobility, strength and neural adaptation.

Humeral retrotorsion in collegiate baseball pitchers with throwing-related upper extremity injury history

Background:

Collegiate baseball pitchers, as well as position players, exhibit increased humeral retrotorsion compared with individuals with no history of overhead sport participation. Whether the humeral retrotorsion plays a role in the development of throwing-related injuries that are prevalent in collegiate baseball pitchers is unknown.

Hypotheses:

Humeral retrotorsion will be significantly different in collegiate pitchers with throwing-related shoulder or elbow injury history compared with pitchers with no injury history. Humeral retrotorsion can also discriminate participants with and without shoulder or elbow injury.

Study Design:

Cross-sectional study.

Methods:

Comparisons of ultrasonographically-obtained humeral retrotorsion were made between 40 collegiate pitchers with and without history of throwing-related shoulder or elbow injury. The ability of humeral retrotorsion to discriminate injury history was determined from the receiver operating characteristic area under the curve.

Results:

Participants with an elbow injury history demonstrated a greater humeral retrotorsion limb difference (mean difference = 7.2°, P = 0.027) than participants with no history of upper extremity injury. Participants with shoulder injury history showed no differences in humeral torsion compared with participants with no history of injury. Humeral retrotorsion limb difference exhibited a fair ability (receiver operating characteristic area under the curve = 0.74) to discriminate elbow injury history.

Conclusions:

Collegiate pitchers with a history of elbow injury exhibited a greater limb difference in humeral retrotorsion compared with pitchers with no history of injury. No differences in humeral retrotorsion variables were present in participants with and without shoulder injury history.

Clinical Relevance:

Baseball players with a history of elbow injury demonstrated increased humeral retrotorsion, suggesting that the amount of retrotorsion and the development of elbow injury may be associated.

Current concepts in the evaluation and treatment of the shoulder in overhead-throwing athletes, part 1: physical characteristics and clinical examination

The overhead-throwing athlete is a challenging sports medicine patient. The repetitive microtraumatic stresses imposed on the athlete's shoulder joint complex during the throwing motion constantly places the athlete at risk for injury. These stresses may effect several adaptations to normal shoulder range of motion, strength, and scapula position. The clinician should therefore appreciate the unique physical characteristics of the overhead-throwing athlete to accurately evaluate and treat throwing-related injuries.

The impact of rotator cuff tendinopathy on proprioception, measuring force sensation

BACKGROUND

The impact of rotator cuff tendinopathy and related impingement on proprioception is not well understood. Numerous quantitative and qualitative changes in shoulder muscles have been shown in patients with rotator cuff tendinopathy. These findings suggest that control of force might be affected. This investigation wants to evaluate force sensation, a submodality of proprioception, in patients with rotator cuff tendinopathy.

METHODS

Thirty-six patients with rotator cuff tendinopathy and 30 matched healthy subjects performed force reproduction tests to isometric external and internal rotation to investigate how accurately they could reproduce a fixed target (50% MVC). Relative error, constant error, and force steadiness were calculated to evaluate respectively magnitude of error made during the test, direction of this error (overshoot or undershoot), and fluctuations of produced forces.

RESULTS

Patients significantly overshoot the target (mean, 6.04% of target) while healthy subjects underestimate the target (mean, -5.76% of target). Relative error and force steadiness are similar in patients with rotator cuff tendinopathy and healthy subjects. Force reproduction tests, as executed in this study, were found to be highly reliable (ICC 0.849 and 0.909). Errors were significantly larger during external rotation tests, compared to internal rotation.

CONCLUSION

Patients overestimate the target during force reproduction tests. This should be taken into account in the rehabilitation of patients with rotator cuff tendinopathy; however, precision of force sensation and steadiness of force exertion remains unaltered. This might indicate that control of muscle force is preserved.

Joint position sense is not altered during shoulder medial and lateral rotations in female assembly line workers with shoulder impingement syndrome

This study evaluated joint position sense (JPS) during medial and lateral rotations of the shoulder in female workers with and without shoulder impingement syndrome (SIS). Three groups were assessed. The case group consisted of 15 female assembly line workers (35.5, SD 5.8 years) with unilateral SIS. Control group 1 consisted of 15 female assembly line workers asymptomatic for SIS (34.4, SD 5.5 years) and control group 2 consisted of 15 female subjects (33.1, SD 6.2 years) asymptomatic for SIS and with no exposure to activities with the upper limbs. The JPS was evaluated bilaterally during passive (2°/sec) and active (5°/sec) repositioning tests using an isokinetic dynamometer. The target angles were 45° of lateral rotation (achieved by medially rotating the shoulder from 90° of lateral rotation) and 75° of lateral rotation (achieved by laterally rotating the shoulder from neutral rotation). There were no differences between sides for all groups (p  >  0.05). There were no differences in any of the variables between the case group and the control groups (p  >  0.05). The results of this study suggest that JPS during medial and lateral rotations of the shoulder is not altered in female assembly line workers with SIS.

Overuse of training increases mechanoreceptors in supraspinatus tendon of rats SHR

The presence of mechanoreceptors in tendon after overuse activities can be a further step to learn about tendinopathy and overuse. Studies of tendons mechanoreceptors in rats are rare. We studied 12 isogenic spontaneous hypertensive rats (SHR), which underwent an overuse protocol consisting of an hour per daily session of treadmill running at a speed of 17 m/min, 5 times/week for 4 months. Supraspinatus tendons were evaluated with immunohistochemistry using S100 protein antibodies and histological protocol. Supraspinatus tendons at the end of 4 months of overuse protocol had a high number of media mechanoreceptors (4.3) than controls (0.6). The overexpression of S100 protein antibody in overuse activities maybe could represent a adaptative effort to tendon before the tear.

The laser-pointer assisted angle reproduction test for evaluation of proprioceptive shoulder function in patients with instability

INTRODUCTION

Over the last decade, proprioceptive function gained increasing attention in joint disorders such as instability of the shoulder. Common tests for evaluation of proprioception are limited by their complexity and high technical demands. Thus, they are hardly applicable during daily routine. Our hypothesis was that the simplified "laser-pointer assisted angle reproduction test" (LP-ART) presented here allows for clinically feasible assessment of proprioceptive shoulder function.

METHODS

Active angle reproduction capability as an aspect of sensorimotor function was evaluated with the new method in patients with shoulder instability (n = 24) and healthy controls (n = 24). 15 patients had traumatic, 9 non-traumatic anterior instability (6 bilateral), 17 were treated surgically, 13 non-operatively. Tests were performed in flexion and abduction in different angles (55°, 90°, 125°) in randomized order.

RESULTS

Angle reproduction capability was worst below shoulder level (55°) in all groups. Best results were achieved at shoulder level (90°). Healthy controls showed overall better results than patients with instability. Patients after surgical stabilization had better results in 55° and 90° abduction compared to instability patients before surgery.

CONCLUSIONS

The new LP-ART presented here is a technically simple, yet effective instrument for evaluation of the proprioceptive function of the shoulder. In contrast to former test setups it is feasible in daily routine. Compared to healthy controls, patients with unstable shoulder joints show significant proprioceptive disorders that can be quantified by the LP-ART.

Rugby Union on-field position and its relationship to shoulder injury leading to anterior reconstruction for instability

Due to the unique demands of each position on the Rugby Union field, the likelihood of an athlete sustaining a dislocation of their shoulder joint that requires surgical reconstruction may be affected by their position on the field. 166 patients with 184 involved shoulders requiring anterior reconstruction following an on-field Rugby Union injury between January 1996 and September 2008 were analysed. The mean age at time of injury was 18 years with the mean age at time of surgery being 20 years. The most prevalent mechanism of injury was a tackle in 66.3% of players. Players were more likely to suffer injury to their non-dominant shoulder than their dominant side (McNemar's Test, p<0.001). Statistical analysis using chi-squared test of goodness of fit showed there was not a uniform risk of injury for all player positions. Positions with significantly different risk of injury were five-eighth (increased risk) and wing (reduced risk). Although we observed an increased risk in flankers and fullbacks, and a lower risk in second row, these results did not reach statistical significance after application of the Bonferroni correction. This information can be utilized by team staff to assist in pre-season conditioning as well as the development of improved muscle co-ordination programmes for the non-dominant shoulder, and planning a graduated return to sport by the player recovering from surgical reconstruction of the shoulder for instability.

Shoulder joint position sense is not enhanced at end range in an unconstrained task

Shoulder joint position sense (JPS) is important for maintaining stability and contributing to coordinated movements. It is provided by afferent and centrally-derived signals interpreted and integrated by the central nervous system (CNS) for subsequent use. Shoulder JPS is enhanced as the joint approaches end range of motion (ROM) in studies involving internal and external rotation with the arm supported, but this finding has not been confirmed in unconstrained movements. To address this issue, the present study examined the effect of shoulder position in the horizontal plane on JPS at a constant elevation. Twenty-three healthy individuals were recruited from a university campus. Subjects attempted to actively replicate various target positions in both plane and elevation. Target positions consisted of five positions in the horizontal plane, normalized to individual horizontal abduction ROM, at 90° of arm elevation. All target positions were tested three times, and average absolute and variable errors were analyzed for each position. No differences in either absolute (p=.312) or variable (p=.185) errors were observed between positions. These results further support the contention that the muscle spindles are a dominant source of afferent feedback regarding shoulder JPS in unconstrained movements, even approaching end ROM, when the capsuloligamentous receptors are active.

Total shoulder arthroplasty with an uncemented soft-metal-backed glenoid component

BACKGROUND

Loosening associated with cemented polyethylene glenoid components is a major concern following total shoulder arthroplasty (TSA). The purpose of this study was to investigate the clinical and radiographic results associated with use of a novel uncemented soft-metal-backed glenoid component (SMBG), with a minimum follow-up of 2 years.

MATERIALS AND METHODS

Twenty-two patients (19 women) underwent TSA using a uncemented SMBG. The mean age was 68.5 years (range, 49-84). Mean follow-up was 50 months (range, 24-89). Indications for TSA were primary osteoarthritis (10), post-traumatic osteoarthritis (8), steroid-induced avascular necrosis (2), crystalline arthropathy (1), and arthritis secondary to systemic lupus erythematodes (1). Subjective and objective parameters were assessed. Loosening and polyethylene wear were evaluated.

RESULTS

Mean absolute Constant scores improved from 29.1 to 65.9 points (P < .001), age- and sex-adjusted Constant scores improved from 40.1 to 87.7% (P < .001), and subjective shoulder values improved from 35% to 75.2% (P < .001). Mean pain scores improved from 4.2 points to 13.1 (P < .001). Three cases had a fractured glenoid component. Only these 3 had a definite loosening. Polyethylene wear was found in 2 cases.

CONCLUSION

Use of an uncemented SMBG component yields controversial results. Osteointegration appears possible and loosening signs have virtually not been observed. Conversely, the current implant can be associated with a high failure rate (13.6%) because of implant fractures despite short follow-up. As loosening seems absent or minimal but implant stability insufficient, design changes need to be performed and tested in view of solving the implant failure problem while preserving the actually excellent bone-implant interface characteristics.

Effect of posteroinferior capsule tightness on contact pressure and area beneath the coracoacromial arch during pitching motion

BACKGROUND

Tightness of the posteroinferior capsule is assumed to be the cause of internal rotation loss in baseball pitchers. Although the relationship between posterior capsule and subacromial impingement has been recognized, this relationship during the baseball-pitching motion is unclear.

HYPOTHESIS

Contact pressure during baseball-pitching motion increases with posterior capsule tightness.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen shoulders were used. The peak contact pressure and area on the coracoacromial arch were measured on a custom-designed shoulder experimental device capable of 6 degrees of freedom motion. Simultaneously, the sites of peak pressure on the coracoacromial arch and humerus were observed from various angles. The posteroinferior capsule tightness was simulated by plicating the capsule in the region from 6 to 8 o'clock. The static testing positions correlated to the early cocking, late cocking, acceleration, deceleration, and follow-through phases of the pitching motion.

RESULTS

The peak contact pressure during the follow-through phase (0.63 + or - 0.50 MPa) significantly increased with posteroinferior capsule tightness (1.00 + or - 0.65 MPa) (P = .014). Additionally, the contact area on the coracoacromial ligament during the follow-through phase (0.98 + or - 0.67 cm(2)) significantly increased with posteroinferior capsule tightness (1.47 + or - 0.91 cm(2)) (P < .001). The site of the peak contact pressure did not change between the 2 conditions.

CONCLUSION

Our findings demonstrate that posteroinferior capsule tightness leads to higher contact pressure under the subacromial arch and increased contact area, particularly on the coracoacromial ligament during the follow-through phase.

CLINICAL RELEVANCE

This tightness may affect risk of injury of the rotator cuff and its surrounding tissues by increasing subacromial contact during pitching.

Biomechanics of open Bankart and coracoid abutment procedures in a human cadaveric shoulder model

The specific aims of this experiment were (1) to develop a clinically relevant model of anteroinferior shoulder dislocation in the apprehension position to compare the biomechanics of the intact anterior capsuloligamentous structures, and (2) to evaluate the initial strength of an open Bankart and of a coracoid abutment procedure. Fifteen shoulders from deceased donors were used. For the intact shoulders, mean peak load was 486 N, and stiffness was 26,7 N/mm. For the Bankart repair, the mean peak load was 264 N, and mean stiffness was 14.1 N/mm. Transosseous repairs failed by suture pullout through soft tissues. For the coracoid abutment repair, the mean peak load was 607 N and stiffness was 25.57 N/mm. This study reveals that the biomechanical performance of the Bankart and coracoid abutment repairs fails to reproduce the properties of the natural intact state.

Proprioception assessment in subjects with idiopathic loss of shoulder range of motion: joint position sense and a novel proprioceptive feedback index

We examined the effects of elevation range and plane on shoulder joint proprioception in subjects with idiopathic loss of shoulder range of motion (ROM). Joint position sense (JPS) and a novel proprioceptive feedback index (PFI), including difference magnitude and the similarity index, were used to assess proprioception. Twelve subjects (eight male, four female) with involved stiff shoulders and normal opposite shoulders were recruited from a university hospital. Subjects attempted to repeat six target positions. Target positions consisted of arm elevation in three planes (frontal, scapular, and sagittal planes) and two ranges (end/mid range). Six trials of each target position were used to determine acceptable trials for stabilization of the data, less than 5% of the cumulative mean values for at least three successive trials. The data stabilized at the sixth repetition. Compared to control shoulders, involved shoulders had enhanced proprioception during end range movements (p < 0.05). The magnitude of the repositioning error and difference magnitude decreased (1.6 degrees -3.5 degrees for repositioning error and 22.2 degrees -62.1 degrees for difference magnitude), whereas similarity index improved at end range movements compared to mid range movements (p < 0.05) in involved stiff shoulders. Results of JPS and PFI suggest that both capsuloligamentous and musculotendinous mechanoreceptors play an important role in proprioception feedback during active movements in subjects with idiopathic loss of shoulder ROM.