Shoulder proprioception - lessons we learned from idiopathic frozen shoulder

Differences in biomechanical and metabolic factors between patients with frozen shoulder and asymptomatic individuals. A cross-sectional study

BACKGROUND

the pathogenesis of frozen shoulder (FS) is thought to be one of inflammation and fibrosis possibly influenced by hyperglycemia. Biomechanical changes of the shoulder joint in terms of muscle strength, scapular kinematics and proprioception might occur in FS.

OBJECTIVES

to compare muscle strength, scapular kinematics, proprioception, and blood glucose levels within patients with FS and to asymptomatic individuals.

DESIGN

cross-sectional study.

METHOD

Thirty-five patients with FS and 35 asymptomatic age and gender-matched individuals underwent physical assessment to determine muscle strength (abduction, external and internal rotation), scapular kinematics (both visually and with a plurimeter), proprioception (joint position sense), and blood glucose level.

RESULTS

Patients with FS showed a decrease in muscle strength in their affected shoulder compared to both the unaffected shoulder and asymptomatic individuals. Significant differences were found between the affected and unaffected shoulder in the FS group and between groups (FS versus controls) in scapular upward rotation (plurimeter) at 30° and 60° abduction. No difference in scapular kinematics (visual observation), proprioception, and blood glucose levels was found neither between shoulders in the FS group nor between groups.

CONCLUSION

A clinically relevant difference in muscle strength and increase in scapular upward rotation were found in the affected shoulder of patients with FS compared to their unaffected side and controls. However, no evidence of different levels of scapular kinematics (visual observation), proprioception, and blood glucose levels in the affected shoulder compared to the unaffected shoulder or controls is lacking.

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.

Shoulder Proprioception: A Review

The purpose of this review is to provide a comprehensive resource for shoulder proprioception assessment and its integration into clinical decision making as well as targeted rehabilitation protocols. Data for this review were acquired from peer-reviewed articles from computerized online databases, namely PubMed and Medline, published between 1906 and 2021. The development of digital/smart phone goniometers can improve shoulder joint range of motion (ROM) measurements and demonstrate comparable measurement accuracy to the universal standard goniometer. The inclinometer offers a portable and cost-effective method for measuring shoulder joint angles and arcs of motion in the vertical plane. Two types of dynamometers, the computerized isokinetic machine and the handheld hydraulic dynamometer, are reliable tools for objective shoulder rotator cuff strength assessment. Motion analysis systems are highly advanced modalities that create three-dimensional models of motion arcs using a series of cameras and reflective beads, offering unparalleled precision in shoulder proprioception measurement; however, they require time-consuming calibration and skilled operators. Advancements in wearable devices and compact mobile technology such as iPhone applications may make three-dimensional motion analysis more affordable and practical for outpatient settings in the future. The complex interplay between proprioception and shoulder dysfunction is not fully understood; however, shoulder proprioception can likely both contribute to and be caused by shoulder pathology. In patients with rotator cuff tears, glenohumeral osteoarthritis, and shoulder instability, clinicians can track proprioception to understand a patient's disease progression or response to treatment. Finally, rehabilitation programs targeting shoulder proprioception have shown promising initial results in restoring function and returning athletes to play.

Ageing and joint position sense of the asymptomatic shoulder: An observational study

PURPOSE

This study aimed to quantify the extent to which age was associated with joint position sense (JPS) of the asymptomatic shoulder as measured by joint position reproduction (JPR) tasks and assess the reproducibility of these tasks.

METHODS

120 Asymptomatic participants aged 18-70 years each performed 10 JPR-tasks. Both contralateral and ipsilateral JPR-tasks were evaluated on accuracy of JPR under active- and passive conditions at two levels within the shoulder forward flexion trajectory. Each task was performed three times. In a subgroup of 40 participants, the reproducibility of JPR-tasks was assessed one week after initial measurement. Reproducibility of JPR-tasks was evaluated by both reliability (intra-class correlation coefficients (ICC's)) and agreement (standard error of measurement (SEM)) measures.

RESULTS

Age was not associated with increased JPR-errors for any of the contralateral or ipsilateral JPR-tasks. ICC's ranged between 0.63 and 0.80 for contralateral JPR-tasks, and from 0.32 to 0.48 for ipsilateral tasks, except for one ipsilateral task where the reliability was similar to contralateral tasks (0.79). The SEM was comparable and small for all JPR-tasks, ranging between 1.1 and 2.1.

CONCLUSION

No age-related decline in JPS of the asymptomatic shoulder was found, and good agreement between test and re-test measurements for all JPR-tasks as indicated by the small SEM.

Is shoulder joint position sense affected in partial and full-thickness supraspinatus tears?

PURPOSE

Neuromuscular control is important for joint stabilization. Supraspinatus muscle plays an essential role in the perception of proprioceptive sense. The aim of this study is to investigate active joint position sense (AJPS) both in patients with partial and full-thickness supraspinatus tears and in healthy participants.

METHODS

Twenty patients with partial supraspinatus tears, 20 patients with full-thickness supraspinatus tears, and 20 healthy participants, aged 40-65 years, were included in the study. Proprioceptive sense was assessed with AJPS measurement. Absolute error was calculated to evaluate joint position sense.

RESULTS

Active joint position sense was decreased in partial and full-thickness tears on both in affected and contralateral shoulders compared to control group (p < 0.05). There was no difference between groups with partial and full-thickness tears on the affected and contralateral shoulders at 40° and 100° elevation (p > 0.05).

CONCLUSION

AJPS was affected after supraspinatus injury. It was seen as proprioceptive deficit in patients with partial and full-thickness tears in both affected and contralateral shoulders.

Positive effects of neuromuscular exercises on pain and active range of motion in idiopathic frozen shoulder: a randomized controlled trial

BACKGROUND AND OBJECTIVES

Frozen shoulder (FS) is characterized by pain and significant loss of active and passive shoulder motion. Strengthening exercises are among the standard exercises used for FS. Neuromuscular exercise (NME) effectively improved pain and the range of motion in shoulder. However, no prior research has looked into the effects of NME compared to strengthening exercises in FS rehabilitation. The aim of the present study was to evaluate the effects of NME compared to strengthening exercises on pain and active range of motion (AROM) in individuals with idiopathic frozen shoulder.

METHODS

Forty individuals with idiopathic frozen shoulder were randomly assigned to either the experimental group (NME with regular physical therapy, n = 20) or the control group (strengthening exercises with regular physical therapy, n = 20). In both groups, the interventions were performed once a day, 5 days a week for 8 weeks. Pain scores on the visual analogue scale (VAS) and AROM of the shoulder were assessed at baseline and after the 8-week treatment. The primary analysis was the group × time interaction.

RESULTS

Two-by-two mixed analysis of variance (ANOVA) revealed a significant group × time interaction for VAS (F = 29.67; p < 0.01); AROM in flexion (F = 12.05; p < 0.01), internal rotation (F = 6.62; p < 0.05) and external rotation (F = 16.93; p < 0.01) in favor of the experimental group. The two-by-two mixed ANOVA revealed a significant main effect of time for VAS (F = 1648.47; p < 0.01); AROM in flexion (F = 591.70; p < 0.01), extension (F = 114.57; p < 0.01), abduction (F = 1602.04; p < 0.01), internal rotation (F = 664.14; p < 0.01) and external rotation (F = 1096.92; p < 0.01). No other significant differences were found.

CONCLUSIONS

NME is superior to strengthening exercises in terms of pain and AROM of shoulder flexion, internal rotation and external rotation in individuals with idiopathic FS. NME could be used to treat individuals with FS.

TRIAL REGISTRATION

Trial registration number: ChiCTR2100054453. Registration date: 17/12/2021.

Assessment of shoulder proprioception in patients with chronic mechanical cervical pain: A comparative study

BACKGROUND

Chronic mechanical cervical pain (CMCP) is a common disabling problem worldwide, interfering with upper extremities function. However studying the impact of CMCP on shoulder proprioception is still lacking.

OBJECTIVE

To investigate the impact of CMCP on shoulder proprioception in young adults compared with normal control (NC) individuals.

METHODS

A comparative study was conducted between two groups; 40 patients with CMCP (mean age 32.28 ± 6.586) and 40 age and sex matched NC (mean age 33.43 ± 9.021). The Biodex isokinetic dynamometer was used to assess shoulder active sense of position at 30∘ external and internal rotations. The absolute angular error was calculated for the dominant and non-dominant shoulders.

RESULTS

The absolute angular error was significantly increased only in the CMCP at both rotation angles for both shoulders, showing a remarkable increase on the dominant shoulder and in the external rotation range compared with NC.

CONCLUSIONS

CMCP can significantly impair shoulder proprioception, particularly on the dominant side and in external rotation range. This could emphasize the careful examination of shoulder proprioception for the early detection of shoulders at risk, to eliminate the possibility of shoulder instability and/or injury in young adults with CMCP.

THE INTER-RATER AND INTRA-RATER RELIABILITY OF GLENOHUMERAL JOINT POSITION AND MOVEMENT SENSE TESTS APPLIED USING AN ISOKINETIC DYNAMOMETER

Purpose: The aim of this study was to test the inter-rater and intra-rater reliability of glenohumeral joint (GHJ) position and movement sense tests of an isokinetic dynamometer in healthy individuals. Methods: The study included 17 healthy subjects. GHJ position and movement sense tests were applied with an isokinetic dynamometer to the dominant extremity. Results: The different error types calculated for position sense were in the range of mean 0.02±1.62 - 5.42±1.74. The ICC value for the different error types was determined in the range of 0.038 - 0.657 for the intra-rater tests, and 0.095 - 0.779 for the inter-rater tests. The movement sense test results for different directions and angles ranged from 9.61±2.61 to 11.18±2.89. The ICC values for movemeent sense were in the range of 0.687 – 0.912 for the intra-rater tests, and 0.844 - 0.925 for the inter-rater tests. Conclusion: The isokinetic dynamometer showed moderate-good intra-rater and inter-rater test reliability in the measurement of the GHJ internal rotation movement sense. The intra-rater test reliability was poor in external rotation but the inter-rater test reliability was moderate-good. However in the measurement of movement sense, the isokinetic dynamometer showed intra-rater and inter-rater test reliability at an excellent level. The conformity of both the position and the movement sense tests, and therefore, the repeatability, was extremely good.

Laser-Pointer assisted angle reproduction test (LP-ART): reliability, performance, and correlation with shoulder pain and disability in patients with subacromial pain syndrome

INTRODUCTION

The proprioception plays an important role in the stability of the shoulder joint. However, clinical practice lacks reliable and user-friendly tools.

OBJECTIVES

To evaluate the intra- and inter-rater reliability of the Laser-Pointer assisted Angle Reproduction Test (LP-ART), to analyze the difference in proprioception between the symptomatic and asymptomatic shoulders, and to investigate if there is a correlation between the LP-ART and the pain intensity assessed by 11-point Numerical Rating Pain Scale (NRPS) and the level of shoulder disability and pain assessed by the Disability Index and Shoulder Pain (SPADI - BR).

METHODS

Fifty patients (age = 56.2 ± 10.4 years) performed the LP-ART at 90° of shoulder flexion.

RESULTS

The intra and interrater reliability of the LP-ART measurements was moderate (Intraclass Correlation Coefficient_2,3 = 0.41 to 0.65) for both shoulders, symptomatic and asymptomatic. There was no difference in the absolute angular deviation between shoulders (mean difference of 0.4°, P = .581). The absolute angular deviation was not significantly correlated with the pain intensity (rs = 0.007, P = .962) and the SPADI - BR (r_s = 0.022, P = .881).

CONCLUSION

The LP-ART measurement showed moderate reliability in participants with subacromial pain syndrome. The active joint position sense was not different between symptomatic and asymptomatic shoulders, and there was no correlation between proprioception and the pain intensity and shoulder pain and disability level.

Proprioception: How is it affected by shoulder pain? A systematic review

INTRODUCTION

Proprioception encompasses the submodalities of joint position sense (JPS), kinesthesia, sense of force, and velocity. Owing to the vast mobility of the shoulder, it heavily relies on an intact sense of proprioception. Moreover, shoulder injuries are associated with a decreased sense of proprioception. What remains unclear is how shoulder proprioception is affected by pain and competing nociceptive senses.

PURPOSE OF THE STUDY

To summarize the literature evaluating the relationship between pain and shoulder proprioception.

METHODS

A literature review was conducted from inception until 22 October 2018, using electronic databases (PubMed, Web of Science, Scopus, EBSCO, CINAHL, and Embase). Retrieved citations were screened for eligibility, and methodological quality was assessed using the Newcastle-Ottawa Scale (NOS).

RESULTS

Eleven studies were included (n = 447 participants with shoulder pain, n = 20 with experimentally induced pain [EIP]/n = 600 painful shoulders and n = 20 [EIP]). The mean methodological quality of the studies was good (76%). Five studies investigated active JPS, four investigated passive JPS, six investigated kinesthesia, sense of force was measured in one study, and no study investigated sense of velocity. There is moderate evidence for impaired kinesthesia and low evidence for reduced sense of force among painful shoulders. Conflicting evidence is seen for the other proprioceptive submodalities.

CONCLUSION

The overall impact of pain on shoulder JPS remains unclear, while moderate evidence for an affected sense of kinesthesia is possible. There is low evidence for an impaired sense of force among painful shoulders. Standardization between studies is lacking, limiting the range of our conclusions. Further investigation is required into well-controlled and pain-induced studies to better understand the influence of pain on shoulder proprioception.

Effectiveness of proprioceptive training and conventional physical therapy in treating adhesive capsulitis

Objective:

To determine effectiveness of proprioceptive training and conventional physical therapy in managing patients with adhesive capsulitis.

Methods:

A pre-test post-test control group study was conducted at Rehman Medical Institute from June to December 2019. Thirty-eight patients, aged 30 to 60 years, with diagnosis of adhesive capsulitis for more than four months were divided into two groups. Subjects in Group-I (conventional group; n=19) received conventional physical therapy protocols for one month while subjects in Group-II (proprioceptive group; n=19) received proprioceptive training along with conventional physical therapy for one month. Disability of Arm Shoulder & Hand questionnaire, Shoulder Pain & Disability Index and goniometer were used at baseline and post-treatment to assess functional activity level, pain & disability and range of motion respectively. Data was analyzed using SPSS version 20.

Results:

The mean age of the participants was 53.13 ± 9.12 years. Baseline characteristics were balanced between the two groups. After the treatment, all measures (functional activity level, pain, disability, ROM) improved in both groups. Post treatment, between group analysis showed that functional activity (DASH) and pain (SPADI pain) significantly (P-value <0.05) improved in proprioceptive group as compared to conventional group. However, there were no significant differences (P-value≥ 0.05) in post treatment SPADI disability, SPADI total and ROM (flexion, abduction, external rotation) scores of both groups.

Conclusion:

Proprioceptive exercises along with conventional physical therapy are more effective in managing pain and improving functional activities in adhesive capsulitis patients as compared to conventional physical therapy alone.

Preoperative and postoperative shoulder position sense in patients who underwent arthroscopic Bankart repair for traumatic shoulder joint instability

Background

Proprioceptive feedback is a reflex dislocation prevention mechanism that contributes to shoulder joint stability. In patients with Bankart lesions, the anteroinferior glenohumeral ligament complex is damaged and reduces the likelihood of tensile stress. As a result, proprioceptive feedback does not work, which leads to instability. Surgical reconstruction is indicated to restore proprioception, but the details of recovery after arthroscopic surgery are unknown. The purpose of this study is to investigate whether arthroscopic Bankart repair can improve the position sense of the shoulder.

Methods

We used the isokinetic dynamometer Biodex System 3 (Biodex, Shirley, NY, USA) to investigate preoperative and postoperative joint position sense in 140 shoulders (137 men, 3 women) undergoing arthroscopic Bankart repair for traumatic shoulder joint instability. The control subjects comprised 40 shoulders of healthy volunteers (all men). Active position sense was measured by setting the shoulder external rotation to 75° based on 90° abduction and neutral internal/external rotation position. Reproductive angle inaccuracy (RAI) was measured thrice, and the mean value was calculated. The RAI was measured preoperatively, 6 months and 1 year postoperatively, and at the final observation (range, 16-96 months; mean, 31.5 months).

Results

Mean RAI was significantly higher (6.4°) preoperatively in the traumatic shoulder instability group than in the control group (5.0°). Mean postoperative RAI changed to 5.0, 4.9, and 4.7° at 6 months, 1 year, and final observation, respectively (mean, 31.5 months). RAI recovered to the same level as the control group at 6 months after the surgery and was maintained the same level until final observation.

Conclusion

Position sense was significantly worse in patients with traumatic shoulder joint instability than in healthy volunteers, and a significant improvement in position sense was observed after reconstruction of the anteroinferior glenohumeral ligament complex by arthroscopic Bankart repair. Therefore, arthroscopic Bankart repair is a favorable procedure that can improve the position sense of the shoulder in patients with traumatic shoulder instability.

Selective Glenohumeral external rotation deficit - sequelae of post-ORIF deltoid adhesions after treatment of the proximal humerus fracture

Background

The deltopectoral approach is commonly used for plate stabilization of proximal humerus fracture. Although adhesions between the deltoid, plate, and humerus are common sequelae of plate ORIF, little is known about their effect on the range of movement and a function of the shoulder. To confirm their impact, the preoperative and intraoperative evaluation of the range of motion (ROM) was measured during the sequential arthroscopic release of adhesions, with special regard to external rotation. Postoperative ROM and subjective shoulder function were also evaluated.

Methods

Eighteen patients treated with ORIF of the proximal humerus were scheduled to the unified arthroscopic procedures comprising sequential limited subacromial bursectomy, removal of the adhesions between the deltoid, plate, and humerus, as well as the plate removal. The ROM of the operated and opposite shoulders were assessed before surgery, intraoperatively and after a minimum two-year follow-up, with special regard to external rotation in adduction (AddER) and abduction (AbdER). Besides, the Constant-Murley score and Subjective Shoulder Value (SSV) were evaluated before a plate removal and after a minimum two-year follow-up after the surgery.

Results

Deltoid adhesion release correlated with considerable and statistically significant improvement of AddER (p < 0.0002) but not with the intraoperative range of AbdER. Significant improvement of AddER, but also of AbdER and other range of motion was noted at the follow-up. The improvement of the affected shoulder function following arthroscopic plate removal was considerable and statistically significant according to the modified Constant-Murley score (p < 0,01) and SSV (p < 0.0000) after a minimum of two-year follow-up.

Conclusions

Our findings are the first to highlight the influence of deltoid muscle, plate, and humerus adhesions on limiting external rotation in adduction after ORIF treatment of proximal humerus fractures. These observations allow the identification of a new shoulder evaluation symptom: Selective Glenohumeral External Rotation Deficit (SGERD) as well as functional deltohumeral space.

Can a Conservative Rehabilitation Strategy Improve Shoulder Proprioception? A Systematic Review

CONTEXT

Proprioception deficits contribute to persistent and recurring physical disability, particularly with shoulder disorders. Proprioceptive training is thus prescribed in clinical practice. It is unclear whether nonsurgical rehabilitation can optimize shoulder proprioception.

OBJECTIVES

To summarize the available evidence of conservative rehabilitation (ie, nonsurgical) on proprioception among individuals with shoulder disorders.

EVIDENCE ACQUISITION

PubMed, Web of Science, and EBSCO were systematically searched, from inception until November 24, 2019. Selected articles were systematically assessed, and the methodological quality was established using the Dutch Cochrane Risk of Bias Tool and the Newcastle-Ottawa Quality Assessment Scale. The Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were utilized for this review. The conservative treatments were categorized as follows: (1) conventional therapy, (2) proprioceptive training, (3) elastic kinesiology tape, and (4) other passive therapies.

EVIDENCE SYNTHESIS

Twelve articles were included, yielding 58 healthy control shoulders and 362 shoulders affected by impingement syndrome, glenohumeral dislocations, nonspecific shoulder pain, rotator cuff dysfunction, or subluxation poststroke. The level of agreement between the evaluators was excellent (84.9%), and the studies were evaluated to be of fair to excellent quality (risk of bias: 28.5%-100%). This review suggests, with moderate evidence, that proprioceptive training (upper-body wobble board or flexible foil training) can improve proprioception in the midterm. No decisive evidence exists to suggest that conventional therapy is of added value to enhance shoulder proprioception. Conflicting evidence was found for the improvement of proprioception with the application of elastic kinesiology tape, while moderate evidence suggests that passive modalities, such as microcurrent electrical stimulation and bracing, are not effective for proprioceptive rehabilitation of the shoulder.

CONCLUSIONS

Proprioceptive training demonstrates the strongest evidence for the effective rehabilitation of individuals with a shoulder proprioceptive deficit. Elastic kinesiology tape does not appear to affect the sense of shoulder proprioception. This review suggests a possible specificity of training effect with shoulder proprioception.

A new method for evaluating joint position sense using oral instructions based on body schema

[Purpose] This study investigated the efficacy of our independently developed method for measuring shoulder joint position sense using oral instructions based on body schema ("schema method") and investigated age-related changes. [Participants and Methods] Forty university students, 19 elderly individuals, and 16 elementary school students were included. Active shoulder abduction was measured in an upright sitting position. Target angles for position sense measurement were 45° of abduction (Target 45) and 90° of abduction (Target 90). The schema method consisted of indicating the target angles through oral instructions alone. The reproduction method and the imitation method were also used to measure angles. Abduction angle, absolute error, and variable error were calculated. [Results] A significant difference in abduction angle at Target 45 was observed between the schema method and the reproduction and imitation methods; no significant differences were observed at Target 90. No significant differences in variable error at Target 90 were observed among the three measurement methods. A significant difference in abduction angle was observed between university students and elderly individuals, and a significant difference in variable error was observed between elementary school students and elderly individuals. [Conclusion] Our body schema-based oral instruction method will be useful for evaluating joint position sense or proprioception.

Shoulder proprioception: How is it measured and is it reliable? A systematic review

STUDY DESIGN

Systematic review.

INTRODUCTION

Constituents of proprioception include our awareness of the position (joint position sense [JPS]) and motion (kinesthesia) of our limbs in space. Proprioceptive deficits are associated with musculoskeletal disorders but remain a challenge to quantify, particularly at the shoulder.

PURPOSE OF THE STUDY

To report the psychometric values of validity, reliability, and responsiveness for shoulder JPS and/or kinesthesia protocols.

METHODS

A review of 5 databases was conducted from inception to July 2016 for studies reporting a psychometric property of a shoulder proprioception protocol. The included studies were evaluated using the QualSyst checklist and COSMIN 4-point scale.

RESULTS

Twenty-one studies were included, yielding 407 participants and 553 evaluated shoulders (n). The included studies support excellent methodological scores using the QualSyst checklist (88.1 ± 9.9%) and good psychometric scores with the COSMIN for reliability (71.1%) and moderate-to-low quality score (50%) for criterion validity. Weighted average intraclass correlation coefficients (ICCs) for intrarater reliability were highest for passive JPS and kinesthesia, ICC = 0.92 ± 0.07 (n = 214) and ICC = 0.92 ± 0.04 (n = 74), respectively. The most reliable movement and tool are internal rotation at 90° of abduction, ICC = 0.88 ± 0.01 (n = 53), and the dynamometer, ICC = 0.92 ± 0.88 (n = 225). Only 2 studies quantify an aspect of validity and no responsiveness indices were reported among the included studies.

CONCLUSION

Based on the results of the included studies, the evaluation of shoulder proprioception is most reliable when using a passive protocol with an isokinetic dynamometer for internal rotation at 90° of shoulder abduction. Standardized protocols addressing the psychometric properties of shoulder proprioception measures are needed.

LEVEL OF EVIDENCE

Level 1a: systematic review.

A new anatomical insight into the aetiology of lateral trunk of suprascapular nerve neuropathy: isolated infraspinatus atrophy

Introduction

Although the pathomechanism of isolated infraspinatus atrophy (ISA) in throwing sports is known to be traction, it is unclear why only some players are affected. One likely explanation is that the infraspinatus pulling force exerted by its contracture generate the compressive resultant component force (Fn) compressing the lateral trunk of the suprascapular nerve (LTSN) against the edge of scapular spine. This paper makes two key assumptions (1) the course of LTSN in relation to the scapular spine, defined as the suprascapular-scapular spine angle (SSSA) is the key individual anatomical feature influencing the Fn magnitude, and thus potentially ISA development (2) SSSA is correlated with scapular notch type.

Materials and methods

The bone landmarks of the LTSN course were identified in 18 formalin-fixed cadaveric shoulders, and the SSSA was measured in 101 dry scapulae. The correlation between the SSSA and suprascapular notch type was evaluated. The Fn value was simulated mathematically based on the values of the SSSA of 101 dry scapulae and the prevalence of ISA in chosen throwing sports, as given in the literature: i.e., beach volleyball − 34% (group A1 − 34%; group A2—remaining 66% of scapulae) and tennis − 52% (group B1 − 52%; group B2—remaining 48% of scapulae).

Results

The mean SSSA value was 44.57° (± 7.9) and Fn 79 N (± 13.1). No statistically significant correlation was revealed between suprascapular notch type and SSSA. Groups A1 and B1 possessed significantly lower SSSA values (p < 0.000) and significantly higher Fn magnitude (p < 0.000) than groups A2 and B2 respectively. The average difference of Fn was 28.1% between group A1 and A2 and 31% between group B1 and B2.

Conclusions

The SSSA has a wide range of values depending on the individual: the angle influencing the magnitude of the compressive resultant force Fn on the LTSN at the lateral edge of the scapular spine via contraction of the infraspinatus muscle. The prevalence of ISA in throwing sports may be correlated with the SSSA of the LTSN. However, further combined clinical, MRI or/and CT studies are needed to confirm this.

Relationship between Joint Position Sense, Force Sense, and Muscle Strength and the Impact of Gymnastic Training on Proprioception

The aims of this study were (1) to assess the relationship between joint position (JPS) and force sense (FS) and muscle strength (MS) and (2) to evaluate the impact of long-term gymnastic training on particular proprioception aspects and their correlations. 17 elite adult gymnasts and 24 untrained, matched controls performed an active reproduction (AR) and passive reproduction (PR) task and a force reproduction (FR) task at the elbow joint. Intergroup differences and the relationship between JPS, FS, and MS were evaluated. While there was no difference in AR or PR between groups, absolute error in the control group was higher during the PR task (7.15 ± 2.72°) than during the AR task (3.1 ± 1.93°). Mean relative error in the control group was 61% higher in the elbow extensors than in the elbow flexors during 50% FR, while the gymnast group had similar results in both reciprocal muscles. There was no linear correlation between JPS and FS in either group; however, FR was negatively correlated with antagonist MS. In conclusion, this study found no evidence for a relationship between the accuracy of FS and JPS at the elbow joint. Long-term gymnastic training improves the JPS and FS of the elbow extensors.