The effect of degenerative arthritis and prosthetic arthroplasty on shoulder proprioception

Shoulder proprioception changes in postmastectomy patients: an observational study

PURPOSE

Breast cancer surgery can cause changes in the anatomical structure of the shoulder and in shoulder mobility, leading to the increased possibility of long-term arm morbidity such as lymphedema. This study aims to evaluate the active shoulder joint position sense (AJPS) with and without lymphedema in postmastectomy patients.

METHODS

A total of 66 women, including 22 patients with lymphedema, 22 patients without lymphedema, and 22 healthy controls, were enrolled in the study. Pain severity was evaluated with the Numeric Pain Scale and edema severity was measured with circumferentially at 10 cm intervals. The normal range of motion of the shoulder joint was evaluated with the universal goniometer and the AJPS was assessed by active position repetition testing at 55°, 90°, and 125° shoulder flexion targets using the smartphone application "Clinometer."

RESULTS

AJPS at 55°, 90°, and 125° shoulder flexion target angles with and without lymphedema were different in all target angles compared to healthy controls (p < 0.01). There was a difference between the absolute error value of AJPS at 55° flexion (p < 0.05), and no difference at 90° and 125° flexion between the with and without lymphedema groups (p > 0.05).

CONCLUSION

This study shows that the AJPS was negatively affected in with and without lymphedema postmastectomy patients compared to healthy controls. This result emphasizes the importance of adding personalized methods for the restoration of joint position sense in addition to rehabilitation programs generally applied to the patient group.

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.

Relationship between pain and proprioception among individuals with rotator cuff-related shoulder pain

BACKGROUND

Individuals with rotator cuff-related shoulder pain (RCRSP) have altered proprioception. The relationship between shoulder pain and proprioception is not well understood.

PURPOSE

This study aimed to investigate the relationship between shoulder pain and proprioception.

STUDY DESIGN

This was a cross-sectional comparative study.

METHODS

Twenty-two participants with RCRSP (mean age 27.6 ± 4.8 years) and 22 matched pain-free participants (23.4 ± 2.5 years) performed two upper limb active joint position sense tests: (1) the Upper Limb Proprioception Reaching Test (PRO-Reach; reaching toward seven targets) in centimeters and (2) Biodex System at 90% of maximum internal rotation in degrees. Participants performed three memorization and three reproduction trials blindfolded. The proprioception error (PE) is the difference between the memorized and estimation trials. Pain levels were captured pre- and post-evaluation (11-point Likert Numerical Pain Rating Scale). Relationships between PE and pain were investigated using independent t-tests and Spearman rank correlations.

RESULTS

Overall, 22.7% RCRSP participants indicated an increase in pain following the PRO-Reach (X̅ increase of 1.4 ± 1.5 points), while 59% did so with the Biodex (X̅ increase of 2.3 ± 1.8 points), reflecting a clinically important increase in pain. Weak-to-moderate correlations between pain and PEs were found with the Biodex (r = 0.39-0.53) and weak correlations with the PRO-Reach (r = -0.26 to 0.38). Concerning PEs, no significant differences were found between groups with the Biodex (p = 0.32, effect size d = -0.31 [-0.90 to 0.29]). The RCRSP participants demonstrated lower PEs with the PRO-Reach in elevation compared to pain-free participants (global X̅ = 4.6 ± 1.2 cm vs 5.5 ± 1.5 cm; superior 3.8 ± 2.1 cm vs 5.7 ± 2.9 cm; superior-lateral nondominant targets 4.3 ± 2.2 cm vs 6.1 ± 2.8 cm; p = 0.02-0.05, effect size d = 0.72-0.74 [0.12-1.3]).

CONCLUSIONS

Individuals with RCRSP demonstrated better upper limb proprioception in elevation, suggesting a change to interoception (sensory reweighting) in the presence of pain.

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.

Shoulder Proprioception Following Reverse Total Shoulder Arthroplasty for Unreconstructable Upper Third Fractures of the Humerus: 2-Year Outcomes

Background

Proximal humerus fractures may be comminuted in the elderly or after injury with high-energy mechanisms. Reverse total shoulder arthroplasty that may affect shoulder proprioception (rTSA) has also begun to play a part in treating acute proximal humeral fractures. In this study, the authors aimed to evaluate joint position sense (JPS) after rTSA.

Methods

Humac Norm II isokinetic device was used to evaluate the joint position sense. A joint angle was determined and the ability of the patient to create the same value of the angle by the active movement was evaluated. The difference between the pre-determined angle and the patient's measured angle was recorded. For proprioceptive sense, the initial position was 0° and the determination position was 30°, 60°, and 90° for flexion and abduction, and 15° and 30° for internal rotation and external rotation.

Results

While both the mean Constant and ADLEIR scores did not differ between non-operated and operated sides, the mean proprioception differences in all flexion (30°, 60°, and 90°), abduction (30°, 60°, and 90°), internal rotation (15° and 30°), and external rotation (15° and 30°) were significantly higher in the operated side than that in non-operated side (p < 0.01 for each pairwise comparison).

Conclusion

Reverse total shoulder arthroplasty (rTSA) treatment, which has increasingly become a surgical option in un-reconstructable proximal humeral fractures has significant adverse effects on proprioception on the operated side and may pose a risk for long-term instability, premature loosening, and prosthesis mechanical complications, in this context, well-designed prospective controlled studies are required.

Delayed detection of passive motion in shoulders with a rotator cuff tear

The aim of this study was to test whether or not the threshold to the detection of passive motion (TTDPM) and passive joint position sense on the affected shoulder of patients with rotator cuff tear (RCT) was impaired compared to those on the unaffected side and to investigate the relationship between the tear size and changes in the TTDPM and passive joint position sense induced by RCT. This study included 21 patients with unilateral RCT before arthroscopic rotator cuff repair. To investigate proprioception in this study, we measured the TTDPM and passive joint position sense in abduction and external rotation using an isokinetic dynamometer. The tear size was evaluated intraoperatively under direct arthroscopic visualization. The TTDPM in abduction and external rotation was significantly longer on the affected side than on the unaffected side. However, the angular absolute error in passive joint position sense in abduction and external rotation was not significantly different between the limbs. A comparison according to the tear size impaired proprioception of the TTDPM in the larger tear group showed significantly longer values than in the smaller group. There was impaired proprioception of TTDPM in patients with RCT, and the impaired proprioception was related to tear severity. Impaired proprioception of TTDPM may inhibit consistent muscle recruitment to achieve precise control. Our results suggest that clinicians should consider proprioceptive exercises for impaired proprioception in their treatment for conservative or postoperative patients.

Progress of Proprioceptive Training in the Treatment of Traumatic Shoulder Instability

In individuals with traumatic shoulder instability, there is a loss of proprioception. This paper reviews the academic literature on shoulder instability and functional impairment in recent years and combines it with clinical practice experience to summarize several techniques of proprioceptive regeneration following traumatic shoulder instability. Many issues were discovered, including a lack of literature on the role of sensory input, a lack of basic proprioceptive research, insufficient sample size in proprioceptive research, and a lack of systematic and standardized standards for the evaluation and training of proprioception in clinical practice, among others. In the future, we will need to better understand the mechanism of proprioception and conduct research on various groups of people, with a focus on discussing the optimal intensity, frequency, and duration of various training methods, as well as implementing proprioceptive training in stages throughout the rehabilitation process. The reestablishment of shoulder joint function, the restoration of proprioception, and the enhancement of daily activities are all critical.

Long-term results of the uncemented resurfacing shoulder hemiarthroplasty (Global Conservative Anatomic Prosthesis)

BACKGROUND

Treatment with uncemented resurfacing shoulder hemiarthroplasty has proved to be viable for patients with end-stage osteoarthritis at short- and mid-term follow-up. This study was essential to determine whether those outcomes will endure. This study presents the long-term results of the Global Conservative Anatomic Prosthesis (CAP) uncemented resurfacing shoulder hemiarthroplasty (DePuy Synthes, Warsaw, IN, USA).

METHODS

All patients with a diagnosis of glenohumeral osteoarthritis and an intact and clinically sufficient rotator cuff who underwent uncemented resurfacing shoulder hemiarthroplasty between 2007 and 2009 were included. The data of all patients who completed the 10-year follow-up assessments were used for analysis. The visual analog scale pain score, Dutch version of the Simple Shoulder Test score, Constant score, Short Form 12 scores, and physical examination findings were evaluated preoperatively and postoperatively on an annual basis. All complications and revisions were documented. Radiographs were evaluated for loosening, luxation or subluxation, migration, and glenoid erosion.

RESULTS

Of 48 shoulders, 23 (48%, 18 women and 5 men) were available for the 10-year follow-up assessments and their data were used for analysis. The main reasons for dropout were revision (27%) and death (10%). The mean follow-up period of the remaining patients was 10.9 years (range, 9-13 years). The visual analog scale pain score (from 6.5 ± 2.1 to 0.7 ± 1.6, P < .001), Simple Shoulder Test (Dutch version) score (from 22% ± 22% to 79% ± 22%, P < .001), Constant score (from 40 ± 29 to 70 ± 8, P < .001), and Short Form 12 physical score (from 36 ± 7 to 41 ± 12, P = .001) improved significantly compared with preoperative scores. Revision surgery was performed in 13 of the initial 48 shoulders (27%). Most revisions were seen within 7 years postoperatively.

CONCLUSION

Two revisions have been performed in the mid-term to long term because of increased functional outcome scores and the absence of signs of loosening. Nevertheless, the high overall revision rate of 27% between short- and long-term follow-up reflects the need to limit the use of uncemented resurfacing shoulder hemiarthroplasty for the treatment of glenohumeral osteoarthritis.

Is Thumb Proprioception Decreased in Patients With Trapeziometacarpal Joint Osteoarthritis?

Proprioception is thought to be essential for normal joint homeostasis, and its decreased function has been associated with an increased risk of joint diseases. However, only a few studies have been performed on the association between proprioceptive function in the trapeziometacarpal joint (TMCJ) and osteoarthritis. The purpose of this study was to compare TMCJ proprioceptive function in elderly women with radiographic TMCJ osteoarthritis relative to age-matched control women without osteoarthritis. We enrolled 19 women (mean age, 66 years) with symptomatic, radiographic Eaton and Littler grade 2, 3, and 4 TMCJ osteoarthritis and 19 age-matched control women without osteoarthritis. We evaluated thumb proprioception by using a joint-position reproduction test and compared the reposition error (RE) between the groups. We carried out a multivariate analysis for factors potentially associated with increased RE, such as age, body mass index, hand dominance, the presence of diabetes, pain level, and the presence of osteoarthritis. Also, a logistic regression analysis was performed for factors associated with the occurrence of TMCJ osteoarthritis. Patients with TMCJ osteoarthritis had greater RE than did the control patients in the joint-position reproduction test at 20°, 30°, and 40° of thumb palmar abduction. The multivariate analysis indicated that increased RE was associated with the presence of osteoarthritis, but not with the other factors assessed. The occurrence of TMCJ osteoarthritis was associated with increased RE at 20°, 30°, and 40° of thumb palmar abduction. This study showed that decreased proprioceptive function was associated with the presence of osteoarthritis in the TMCJ, although the causality remains unknown. Further studies on the role of proprioception in the pathogenesis of TMCJ osteoarthritis and the potential role of its training for disease prevention or treatment are required.

Shoulder proprioception following reverse total shoulder arthroplasty

Joint replacement affects the proprioception, as shown in knees, elbows, and shoulder studies.

AIM

The aim was to evaluate shoulder joint position sense (JPS) following reverse total shoulder arthroplasty (rTSA) for patients with cuff arthropathy.

METHODS

Twenty-nine patients that underwent unilateral rTSA (19 females, 10 males) and 31 healthy volunteers evaluated for JPS of shoulder using a dedicated high accuracy electronic goniometer. Error of active reproduction of joint position (EARJP) was assessed at the following reference positions: 30°, 60°, 90°, and 120° for forward flexion and abduction and 15°, 30°, and 45° for internal and external rotation in rTSA, contralateral non-operated, and control shoulders.

RESULTS

Results of EPRJP for rTSA, contralateral, and control (respectively) are as follows:Forward flexion: 30° = (8.0 ± 5.7, 9.8 ± 6.1, and 4.9 ± 3.0), 60° = (5.0 ± 2.8, 5.9 ± 2.7, and 5.1 ± 3.2), 90° = (3.1 ± 1.6, 5.5 ± 2.6, and 3.2 ± 1.4), and 120° = (3.4 ± 2.1, 5.6 ± 4.0, and 3.5 ± 1.7)Abduction: 30° = (5.2 ± 2.5, 9.1 ± 6.1, and 4.6 ± 2.3), 60° = (5.2 ± 3.6, 6.6 ± 4.1, and 5.3 ± 3.1), 90° = (3.8 ± 2.0; 7.4 ± 5.5, and 4.1 ± 1.9), and 120° = (5.3 ± 2.9, 7.7 ± 5.3, and 4.2 ± 1.9)Internal rotation: 15° = (4.3 ± 3.1, 6.2 ± 4.4, and 2.8 ± 1.2), 30° = (3.2 ± 1.9, 4.5 ± 2.3, and 3.3 ± 1.4), and 45° = (3.5 ± 2.0, 4.1 ± 1.8, and 2.8 ± 1.0)External rotation: 15° = (3.0 ± 1.7, 4.2 ± 2.2, and 3.6 ± 1.4) and 30° = (3.1 ± 1.5, 3.8 ± 2.6, and 3.4 ± 1.6)The results showed significantly better JPS (lower EPRJP) in shoulders following rTSA and normal control shoulders comparing with the patient's contralateral shoulder. The explanation can be that rTSA improves joint kinematics and stability, which allows better muscular performance and proprioception feedback.

CONCLUSION

Shoulders following rTSA show JPS superior to non-operated contralateral shoulders and comparable with healthy population shoulders. It seems that rTSA restores shoulder proprioception.

Assessment of anatomical and reverse total shoulder arthroplasty with the scapula-weighted Constant-Murley score

AIM OF THE STUDY

To evaluate total (TSA) and reverse total shoulder arthroplasty (RTSA) using the Constant-Murley score (CMS) and the scapula-weighted (SW) CMS, an integrated outcome measure that takes into account the compensatory movements of the scapula.

METHODS

Twenty-five consecutive patients, 12 with TSA and 13 with RTSA, underwent kinematic analysis before and after shoulder replacement. Measurements included flexion (FLEX) and abduction (ABD) for the humerus and Protraction-Retraction (PR-RE), Medio-Lateral rotation (ME-LA), and Posterior-Anterior tilting (P-A) for the scapula. They were recorded at baseline (T0) and at six (T1) and 12 months (T2). Reference data were obtained from 31 control shoulders.

RESULTS

At T1, differences in CMS and SW-CMS were not significant in either group, whereas values at T2 were significantly lower in RTSA patients (p = 0.310 and p = 0.327, respectively). In TSA shoulders, the compensatory scapular movements in FLEX were all reduced from T0 to T2, whereas P-A was increased in ABD. In RTSA patients, the compensatory scapular movements in FLEX showed a general reduction at T1, with an increase in P-A at T2, whereas in ABD, all increased at T1 and decreased at T2 except for P-A, which did not decrease.

DISCUSSION

The SW-CMS showed that the physiological scapulothoracic motion was not restored in TSA and RTSA patients; it may be used as a reference for the gradual progression of deltoid and scapular muscle rehabilitation.

CONCLUSIONS

The worse CMS and SW-CMS scores found in RTSA patients at six months may be due to the biomechanics of the reverse prosthesis and to the weakness of deltoid and periscapular muscles.

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.

How does reverse shoulder replacement change proprioception in patients with cuff tear arthropathy? A prospective optical 3D motion analysis study

BACKGROUND

Reverse total shoulder arthroplasty (RSA) can improve function in cuff tear arthropathy (CTA) shoulders, but limited data are available on the effect of RSA on proprioception. The purpose of this study was the evaluation of the proprioception after RSA.

METHOD

This study included fifteen consecutive patients (n = 15) who received an RSA. We measured an active angle reproduction (AAR) by a novel 3D motion analysis using the Heidelberg upper extremity model (HUX).

RESULTS

The overall proprioception didn't change significantly from 6.2° preoperatively to 6.2° postoperatively.

CONCLUSION

We conclude that, the overall proprioception remained the same or deteriorated for different movements.

Outcome and revision rate of uncemented glenohumeral resurfacing (C.A.P.) after 5-8 years

BACKGROUND

Resurfacing of the glenohumeral joint for patients with glenohumeral arthritis has gained popularity since the first introduction. We report the mid-term results of the Global C.A.P. uncemented resurfacing shoulder prosthesis (DePuy Synthes).

METHODS

From January 2007 to December 2009, 48 humeral cementless resurfacing prostheses in 46 patients were performed. All patients were diagnosed with primary glenohumeral osteoarthritis. Patients were contacted for review; the Constant Score, visual analog pain scale, Dutch Simple Shoulder Test, SF-12 scores and physical examination were assessed both preoperatively and yearly postoperatively. Complications and revision surgery were documented. Radiographs were evaluated for component size, offset, inclination, height, loosening and subluxation.

RESULTS

Forty-six patients (12 males) with a mean age of 72 years old (range 59-89) were included. At a mean 6.4-year follow-up (range 5-8), the Constant Score, visual analog pain scale and the Dutch Simple Shoulder Test scores improved significantly (p < 0.05) from baseline. Three patients were lost to follow-up. One patient died and two patients were not able to attend the follow-up appointments, due to other health-related issues. Eleven patients (23%) had a revision operation.

CONCLUSIONS

The most important findings of this study of the Global C.A.P. shoulder resurfacing arthroplasty were an increase of range of motion, a reduction of pain complaints, but a concerning high rate of revision after mid-term follow-up.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Changes in Driving Performance Following Shoulder Arthroplasty

BACKGROUND

With this study, we sought to quantify perioperative changes in driving performance among patients who underwent anatomic or reverse shoulder arthroplasty.

METHODS

Using a driving simulator, 30 patients (20 anatomic and 10 reverse total shoulder arthroplasties) were tested preoperatively and at 2 weeks (PO2), 6 weeks (PO6), and 12 weeks (PO12) postoperatively. The total number of collisions, centerline crossings, and off-road excursions (when the vehicle traversed the lateral road edge), and scores on a visual analog scale (VAS) for pain and the Shoulder Pain and Disability Index (SPADI) were recorded at each driving trial.

RESULTS

The mean number of collisions increased from 5.9 preoperatively to 7.4 at PO2 and subsequently decreased to 5.6 at PO6 and 4.0 at PO12 (p = 0.0149). In addition, the number of centerline crossings decreased from 21.4 preoperatively to 16.3 at PO12 (p < 0.05). Multivariate analysis of the data demonstrated that increased VAS for pain scores, older age, and less driving experience had a negative impact on driving performance.

CONCLUSIONS

Driving performance returned to preoperative levels at 6 weeks after shoulder arthroplasty. By 12 weeks postoperatively, patients demonstrated improved driving performance compared with preoperative performance. On the basis of our findings, clinicians can suggest a window of 6 to 12 weeks postoperatively for the gradual return to driving. However, for patients of older age, with less driving experience, or with greater pain, a return to driving at closer to 12 weeks postoperatively should be recommended.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Shoulder proprioception - lessons we learned from idiopathic frozen shoulder

Background

Of all the most frequent soft tissue disorders of the shoulder, idiopathic frozen shoulder (IFS) offers the greatest potential for studying proprioception. Studies concerning the presence of proprioception dysfunctions have failed to determine the potential for spontaneous healing of passive shoulder stabilizers (anterior and posterior capsule, middle and inferior gleno-humeral ligaments), its relationship with passive (PJPS) and active (AJPS) shoulder proprioception for internal and external rotation (IR, ER), as well as the isokinetic muscle performance of the internal and external rotators. This study investigates these dependencies in the case of arthroscopic release of IFS.

Methods

The study group comprised 23 patients (average aged 54.2) who underwent arthroscopic release due to IFS and 20 healthy volunteers. The average follow-up time was 29.2 months. The Biodex system was used for proprioception measurement in a modified neutral arm position and isokinetic evaluation. The results were analysed using the T-test, Wilcoxon and interclass correlation coefficient. P-values lower than 0.05 were considered significant.

Results

Statistically significant differences were found between involved (I) and uninvolved (U) shoulders only in the cases of PJPS and AJPS, peak torque, time to peak torque and acceleration time for ER (p < 0.05). No statistically significant difference was noted between PJPS IR and PJPS ER or between AJPS IR and AJPS ER (p > 0.05) for the U shoulders.

Conclusions

The anatomical structure of anterior (capsule, middle and anterior band of inferior gleno-humeral ligament) and posterior (capsule and posterior band of inferior gleno-humeral ligament) passive shoulder restraints has no impact on the difference in PJPS values between ER and IR in a modified neutral shoulder position. The potential for spontaneous healing of the anterior and posterior passive shoulder restraints influences PJPS recovery after arthroscopic release of IFS. ER peak torque deficits negatively affect AJPS values. PJPS and AJPS of ER and IR can be measured with a high level of reproducibility using an isokinetic dynamometer with the arm in a modified neutral shoulder position. Differences greater than 15 % for PJPS and >24 % for AJPS for ER and IR can be helpful for future studies as baseline data for identification of particular passive and active shoulder stabilizers at risk.

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.

Are there differences between stemless and conventional stemmed shoulder prostheses in the treatment of glenohumeral osteoarthritis?

Background

Conventional stemmed anatomical shoulder prostheses are widely used in the treatment of glenohumeral osteoarthritis. The stemless shoulder prosthesis, in contrast, is a new concept, and fewer outcome studies are available. Therefore, the purpose of the study was to investigate the early functional outcome and postoperative proprioception of a stemless prosthesis in comparison with a standard stemmed anatomic shoulder prosthesis.

Methods

Twelve patients (mean age 68.3 years [SD ± 5.4]; 5 female, 7 male) with primary glenohumeral osteoarthritis of the shoulder were enrolled, who underwent total shoulder arthroplasty (TSA) with a stemless total shoulder prosthesis, Total Evolution Shoulder System (TESS®; Biomed, France). The control group consisted of twelve (age and gender matched) patients (mean age 67.8 years; [SD ± 7.1]; 9 female, 3 male), getting a TSA with a standard anatomic stemmed prosthesis, Aequalis® Shoulder (Tournier, Lyon, France). Patients were examined the day before and six months after surgery. The pre- and postoperative Constant Score (CS) was evaluated and proprioception was measured in a 3D video motion analysis study using an active angle-reproduction (AAR) test.

Results

Comparing the postoperative CS, there was no significant difference between the groups treated with the TESS® prosthesis (48.0 ± 13.8 points) and the Aequalis® prosthesis (49.3 ± 8.6 points; p = 0.792). There was no significant difference in postoperative proprioception between the TESS® group (7.2° [SD ± 2.8]) and the Aequalis® group(8.7° [SD ± 2.7]; p = 0.196), either. Comparison of in the results of CS and AAR test pre- and postoperatively showed no significant differences between the groups.

Discussion

In patients with glenohumeral osteoarthritis, treated with TSA, the functional and the proprioceptive outcome is comparable between a stemless and a standard stemmed anatomic shoulder prosthesis at early followup.

Conclusion

Further follow-up is necessary regarding the long-term performance of this prosthesis.

Trial registration

Current Controlled Trials DRKS 00007528. Registered 17 November 2014

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.

Assessing Proprioception: A Systematic Review of Possibilities

Proprioception is a vital aspect of motor control and when degraded or lost can have a profound impact on function in diverse clinical populations. This systematic review aimed to identify clinically related tools to measure proprioceptive acuity, to classify the construct(s) underpinning the tools, and to report on the clinimetric properties of the tools. We searched key databases with the pertinent search terms, and from an initial list of 935 articles, we identified 57 of relevance. These articles described 32 different tools or methods to quantify proprioception. There was wide variation in methods, the joints able to be tested, and the populations sampled. The predominant construct was active or passive joint position detection, followed by passive motion detection and motion direction discrimination. The clinimetric properties were mostly poorly evaluated or reported. The Rivermead Assessment of Somatosensory Perception was generally considered to be a valid and reliable tool but with low precision; other tools with higher precision are potentially not clinically feasible. Clinicians and clinical researchers can use the summary tables to make more informed decisions about which tool to use to match their predominant requirements. Further discussion and research is needed to produce measures of proprioception that have improved validity and utility.

Low preoperative Constant score is a negative predictive factor for postoperative proprioception after total shoulder arthroplasty in osteoarthritis

BACKGROUND

Shoulder proprioception in patients with glenohumeral osteoarthritis and the effect of total shoulder arthroplasty (TSA) on proprioception have been evaluated previously. Measuring proprioception with an active angle reproduction (AAR) test, proprioception remained unchanged or deteriorated in a short follow-up period after shoulder replacement. Therefore, the purpose of this prospective study was to evaluate the influence of the preoperative Constant score (CS) on postoperative proprioceptive outcome after TSA in patients with primary osteoarthritis to address the question of whether the preoperative state of shoulder function influences postoperative proprioceptive outcome.

METHODS

Twenty-four patients who received total shoulder arthroplasty (TSA) (n = 24) for primary osteoarthritis of the shoulder were enrolled. After retrospectively analyzing the preoperative CS for 120 patients with primary osteoarthritis of the shoulder who received TSA, the patient group was divided into three subgroups according to preoperative functional assessment of the shoulder using the CS. Group one consisted of patients with CS < 20, group two patients with CS 20-30, and group three patients with the best preoperative CS (>30). In all patients proprioception was examined 1 day before the operation and 3 months after surgery by 3D motion analysis with an AAR test and also CS.

RESULTS

Postoperatively, proprioception in group one (CS < 20) deteriorated significantly from 5.2° (SD 2.2) to 8.1° (SD 1.8); p = 0.018. In group two, there were no significant changes from preoperative to postoperative status [8.7° (SD 2.1) vs. 9.3° (SD 2.7) (p = 0.554)], likewise in group three [6.3° (SD 2.3) preoperatively vs. 6.9° (SD 3.3) postoperatively (p = 0.617)]. Comparing the postoperative results, the best proprioception [6.9° (SD 3.3)] was found in the group that had the best preoperative CS (group three, CS > 30).

CONCLUSION

In conclusion, a low preoperative CS is a negative predictive factor for postoperative proprioception after TSA. We should keep that in mind when determining the best timepoint for shoulder replacement in patients with glenohumeral osteoarthritis.

The effects of shoulder injury on kinaesthesia: a systematic review and meta-analysis

The aim of this systematic review was to synthesize the evidence for changes for proprioceptive variables consisting of movement and position sense in participants with glenohumeral musculoskeletal disorders. Five databases were searched until 13th August 2013. Methodological quality was assessed and meta-analyses were performed for active and passive joint reposition sense (AJPS and PJPS) and movement sense, determined with threshold to detection of passive motion (TTDPM). The search yielded 17 studies, four of which were classified as having high methodological quality, seven as moderate and six as low quality. For participants with post-traumatic glenohumeral instability, pooled findings indicate moderate evidence for higher TTDPM for involved shoulders compared to control groups and the contralateral uninvolved side, indicating decreased movement sense. For AJPS and PJPS there was moderate to limited evidence for significant increased errors for involved compared to uninvovled shoulders, but not when compared to the control groups. Limited evidence was found for decreased AJPS acuity for patients with chronic rotator cuff pain and for patients with unspecified shoulder pain compared to healthy controls. Movement sense is most likely to be impaired after shoulder injury involving post-traumatic instability when compared to the contralateral shoulder and to controls, while deficits for AJPS and PJPS are more likely to be evident compared to the contralateral shoulder in participants with glenohumeral musculoskeletal disorders.

Elbow joint position sense after total elbow arthroplasty

BACKGROUND

Multiple human experiments have shown that articular lesions can have a negative effect on proprioception. The influence of total elbow arthroplasty on joint position sense has not been reported so far. The purpose of the study was to evaluate proprioception, defined as a joint position sense, after total elbow arthroplasty.

METHODS

The study included 16 patients with unilateral semiconstrained linked total elbow arthroplasty and 21 healthy volunteers. The evaluation included measurement of active and passive reproduction of joint position sense of both elbows after surgery and the control groups. Reference angles included extension to 50° and 70° and flexion to 110°. We also assessed function of the elbow in arthroplasty group using the Mayo Elbow Performance Score, the Disability of the Arm, Shoulder and Hand score, and a visual analog scale for pain level.

RESULTS

The average value of error of passive reproduction of joint position for elbows after arthroplasty was significantly inferior for all evaluated positions compared with the contralateral elbow and with the control group, respectively, at 110° flexion: 4.3°, 2.7°, and 3.2°; at 70° extension: 4.9°, 2.9°, and 2.7°; and at 50° extension: 6.3°, 3.8°, and 3.8°. The average value of error of active reproduction of joint position for the arthroplasty group was also significantly inferior, respectively, at 110° flexion: 3.5°, 1.9° and 2°; and at 50° extension: 4.4°, 3.3°, and 3°.

CONCLUSION

Proprioception in elbows that undergo total arthroplasty is significantly inferior compared with the contralateral site of the patient and in the healthy control group.

Clinical and radiographic mid-term outcomes after shoulder resurfacing in patients aged 50 years old or younger

PURPOSE

Humeral resurfacing is a treatment option to conventional shoulder arthroplasty, conferring the advantages to preserve the bone stock and the normal joint geometry. Aim of the current study was to report clinical and radiographic mid-term outcomes in a population of 60 patients, aged 50 years or younger, who underwent shoulder resurfacing in osteoarthritis.

METHODS

The mean age was 48 ± 8.4, 36 were male and 24 female, dominant arm in 43 cases. Glenoid arthritis was treated in 36 cases (60 %) using a meniscus allograft in 22 cases, biologic patch in 4 cases and microfractures in 10 cases. Clinical and radiographic assessment was performed with Constant-Murley score and standard X-ray.

RESULTS

At an average follow-up of 44 months, the mean values of the constant score increased of 30 points (p < 0.05), the pain decreased of 4.56 points (p < 0.05) and the Simple Shoulder Test increased of 4.3 points (p < 0.05). We found lower scores (p > 0.05) in 9 patients (15 %) treated for glenoid arthritis using homologous meniscus (7 cases) and biologic patch (2 cases). A significant narrowing of joint space (5.92 mm postoperative versus 1.65 mm at 37 months) (p < 0.05) was found in the 22 cases treated with meniscus interposition. In 4 cases with type A2 preoperative glenoid morphology and in 9 cases type B1, we registered significantly lower scores compared with the overall study population (p < 0.01). Five unsatisfied patients (7 %), underwent to meniscus removal and glenoid reaming in 3 cases and conversion in total shoulder arthroplasty in 2 cases.

CONCLUSIONS

Resurfacing arthroplasty is an effective device in young patients with advanced glenohumeral arthropathy; however, the high rate of postoperative glenoid erosion and the failure of biologic allograft lead us to consider glenoid replacement as the best option to improve clinical outcomes.

Proprioception 3 years after shoulder arthroplasty in 3D motion analysis: a prospective study

BACKGROUND

This prospective study evaluated the development of proprioception over the course of 3 years after shoulder arthroplasty.

METHODS

Twenty-one patients were enrolled who underwent total shoulder arthroplasty (n = 10) or hemiarthroplasty (HEMI) (n = 11) for shoulder osteoarthritis. All patients were examined 1 day before the operation, 6 months and 3 years after surgery in a motion analysis study with an active angle-reproduction (AAR) test.

RESULTS

Overall proprioception measured by the AAR deteriorated significantly 3 years after surgery [from 6.6° (SD 3.1) to 10.3° (SD 5.7); p = 0.017] and was significantly worse than in the control group [10.3° (SD 5.7) vs. 7.8° (SD 2.3); p = 0.030). In the HEMI subgroup, 3 years after shoulder replacement, there is a significant deterioration of proprioception at 30° of external rotation [from 3.1° (SD 3.5) to 12.8° (SD 10.7); p = 0.031]. On average, in the TSA subgroup proprioception deteriorated from 7.1° (SD 3.1) to 8.6° (SD 1.4) and in the HEMI subgroup from 6.1° (SD 2.1) to 12.4° (SD 8.3). The comparison of postoperative impairment of proprioception between the TSA and HEMI subgroup showed significantly worse proprioception for the HEMI subgroup at 30° of external rotation [9.8° (SD 10.1) vs. 1.6° (SD 6.3) in the TSA group; p = 0.046].

CONCLUSION

In conclusion, proprioception that was measured by an AAR test remained unchanged or deteriorated 3 years after shoulder arthroplasty. The postoperative deterioration of proprioception was more distinctive in HEMI than in TSA group.

Discrimination of Amount of Spinal Flexion for Movements Made with and without Vision after Lumbar Disc Replacement

Discrimination of differences between small lumbar flexion movements made when standing may differ depending on whether vision is available. Dependence on general vision during trunk movements may be increased following surgery, in which an intervertebral disc is replaced with a prosthetic disc. This study investigated whether the availability of vision changed discrimination of small differences in lumbar forward flexion movement when standing for patients with lumbar disc replacement and healthy peers. 20 volunteers without a history of back pain and 20 with disc replacement undertook a 100-trial sequence of forward flexion movements to a set of physical stops, making an absolute judgement as to the position after each movement. General (nontarget) vision during the movement was available or removed randomly trial by trial. Availability of vision did not affect discrimination of flexion movements of the lumbar spine either in normal healthy individuals or those with disc replacement.

Comparison of lumbar proprioception as measured in unrestrained standing in individuals with disc replacement, with low back pain, and without low back pain

STUDY DESIGN

Cross-sectional laboratory study.

OBJECTIVE

To determine whether individuals with spinal pain and those who have undergone spinal surgery have difficulty discriminating small movement differences using a spinal proprioception test for active flexion movements.

BACKGROUND

Structures contributing to proprioception may be affected during disc replacement surgery. Postsurgical assessment of proprioceptive ability to make discriminations in the range used for maintaining upright postural stability is needed to inform postoperative rehabilitation.

METHODS

Proprioceptive sensitivity to differences between lumbar spine movements of 11 degrees, 13 degrees, 15 degrees, 17 degrees, and 19 degrees of forward flexion was measured in unrestrained standing, with vision of the target obscured. Individuals after disc replacement (n=16), with disc degeneration and discogenic back pain (n=19), and without back pain (n=18) performed 50 movement trials and stated the amount of movement performed for each trial (11 degrees, 13 degrees, 15 degrees, 17 degrees, or 19 degrees).

RESULTS

The pattern of discrimination scores between adjacent lumbar flexion movement pairs shown by the individuals in the discogenic back pain group differed significantly from the disc replacement and healthy control groups (P=.024), which were not significantly different from each other. Although mean discrimination scores averaged over all movement pairs did not differ significantly between the groups, participants with discogenic back pain discriminated between the 2 smallest lumbar flexion movements significantly better than those in the other 2 groups (P=.013).

CONCLUSION

The greater sensitivity of the individuals with disc pain to discriminate between the 2 smallest flexion movements was interpreted as a contrast effect arising from differences between the groups in usual upright posture, with disc replacement restoring the same pattern of posture as seen for healthy controls.

Recovery of shoulder strength and proprioception after open surgery for recurrent anterior instability: a comparison of two surgical techniques

BACKGROUND

Previous studies have documented a decrease in proprioceptive capacity in the unstable shoulder. The degree to which surgical approach affects recovery of strength and proprioception is unknown.

MATERIALS AND METHODS

The recovery of strength and proprioception after open surgery for recurrent anterior glenohumeral instability was compared for 2 surgical procedures. A prospective analysis of 55 consecutive patients with posttraumatic unilateral recurrent anterior glenohumeral instability was performed. Thirty patients (group 1) underwent an open inferior capsular shift with detachment of the subscapularis, and 25 (group 2) underwent an anterior capsulolabral reconstruction.

RESULTS

Mean preoperative proprioception and strength values were significantly lower for the affected shoulders in both groups. At 6 months after surgery, there were no significant differences for mean strength and proprioception values between the unaffected and operative sides for group 2 patients. In group 1 patients, however, there were still significant deficits in mean position sense and strength values. Complete restoration of proprioception and strength, however, was evident by 12 months in group 1.

CONCLUSION

This study demonstrates that there are significant deficits in both strength and proprioception in patients with posttraumatic, recurrent anterior glenohumeral instability. Although both are completely restored by 1 year after surgery, a subscapularis-splitting approach allows for complete recovery of strength and position sense as early as 6 months postoperatively. Detachment of the subscapularis delays recovery of strength and position sense for up to 12 months after surgery.

Can shoulder arthroplasty restore the range of motion in activities of daily living? A prospective 3D video motion analysis study

HYPOTHESIS

There are limited data how total shoulder arthroplasty (TSA) improves shoulder function during activities of daily living (ADL). The hypothesis of this study was that the range of motion (ROM) in ADL gets back to normal after TSA.

MATERIALS AND METHOD

We examined 13 patients before they received TSA for osteoarthritis and 6 months postoperatively with a 3D motion video analysis during 3 ADL and compared them with a control group without any shoulder pathology.

RESULT

Comparing the TSA status preoperatively and postoperatively resulted in a significant increase of the mean values of the ROMs in the ADL in all planes (P < .05). When the postoperative ROM was compared with the controls, TSA was able to restore the ROM in all planes except for abduction in 2 of 3 ADL. The patients were not able to use their maximum active abduction during the course of the ADL.

DISCUSSION

TSA improves the ROM in ADL, but it cannot return completely to normal in abduction after 6 months.

CONCLUSION

This is not related to limitations of active or passive ROM but may be due to impaired proprioception or pathologic movement patterns, or both.

Reduced scapular muscle control and impaired shoulder joint position sense in subjects with chronic shoulder stiffness

The purpose of the present study was to determine (1) if joint position sense (JPS) in subjects with shoulder stiffness (SS) differs from that in controls; (2) if, when JPS is reduced in SS, it is related to scapular muscular activities in the mid/end ranges of motion; and (3) if a person's function is associated with his or her level of JPS. Eighteen subjects with unilateral SS and 18 controls were included. Each subject performed abduction by self-selecting an end/mid range position. The electromagnetic motion-capturing system collected kinematic data while surface electromyography collected muscle activities (upper trapezius, lower trapezius, and serratus anterior muscles). Subjects were asked to move the upper limb to the target position (end/mid range) accurately without visual guidance. Reduced JPS was observed in subjects with SS (2.7 degrees in mid range, p<0.05). The JPS was enhanced by an increased scapula muscular activation level in the end range of motion (R=-0.61 for SS and -0.41 for controls) and by coordination among muscles' activation in the mid-range of motion (R=-0.87 for SS and R=-0.53 for controls). Impaired JPS was also related to self-reported functional status (R=-0.56) in subjects with SS. Shoulder JPS in subjects with chronic SS is impaired in comparison with controls. In the mid-range motion, the coordination of scapula muscular activation is related to shoulder JPS. Impaired JPS is also function-related in subjects with SS. These findings suggest that the coordination among scapula muscles' activation were important to consider in the rehabilitation of patients with chronic SS.

Proprioception in total, hemi- and reverse shoulder arthroplasty in 3D motion analyses: a prospective study

The aim of the study was to assess proprioception after shoulder arthroplasty. Twenty-six patients were enrolled who underwent total shoulder arthroplasty (TSA) (n = 13) or hemi-arthroplasty (n = 8) for shoulder osteoarthritis or reversed arthroplasty (n = 5) for cuff tear arthropathy. All patients were examined before the operation and then again six months thereafter in a motion analysis study with an active angle-reproduction (AAR) test. In all groups the AAR deteriorated at 60 degrees flexion (from 5.5 degrees [SD 2.8] to 7.6 degrees [SD 2.7]; p = 0.007) and at 30 degrees external rotation (ER) (from 6.5 degrees [SD 3.6] to 7.3 degrees [SD 4.8 degrees]; p = 0.023) six months after surgery. In the subgroup of TSA, there was deterioration at 30 degrees ER (p = 0.036). Otherwise, there were no significant changes within or among the subgroups. Proprioception, assessed by the AAR test, remained unchanged or deteriorated six months after shoulder arthroplasty. This might be related to the reduced pain or to the relatively short follow-up period.

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.

Proprioceptive acuity in active rotation movements in healthy knees

OBJECTIVES

To investigate the ability of asymptomatic participants to discriminate between active knee rotation movements of different magnitude and to determine whether proprioceptive acuity of active knee rotation differs between limbs (dominant and nondominant and right and left).

DESIGN

Cross-sectional study.

SETTING

Laboratory in an Australian university.

PARTICIPANTS

Healthy volunteers (N=30) without previous cruciate ligament injury or surgery, previous fracture of the lower limbs, or other lower-limb disorders in the last 3 months.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Knee rotation proprioceptive acuity was determined by using our custom-designed device. The measure of proprioceptive acuity used in this study was the just-noticeable difference (JND). Participants actively rotated the knee (internal or external rotation) to 1 of 4 movement blocks and judged the magnitude of the permitted motion. Proprioceptive acuity scores, representing a participant's ability to detect small differences in magnitude of active knee rotation movements, were then calculated.

RESULTS

The means of the JND for proprioceptive acuity of internal rotation (1.37 degrees +/-.11 degrees ) were significantly (P=.04) lower than for external rotation (1.6 degrees +/-.14 degrees ) regardless of side (right, left) or dominance. No significant difference was found between the mean JND for left and right knee rotations (P=.84) or between the mean JND for dominant and nondominant knee rotation (P=.69).

CONCLUSIONS

Participants perceived smaller differences between active internal rotation movements than external rotation. No significant difference was found between the dominant and nondominant leg or between the left and right leg; therefore, clinicians can establish whether a proprioceptive deficit exists after unilateral injury and can use acuity of the uninjured knee as a normal status for rehabilitation.

Aging of the somatosensory system: a translational perspective

Balance in the elderly population is a major concern given the often catastrophic and disabling consequences of fall-related injuries. Structural and functional declines of the somatosensory system occur with aging and potentially contribute to postural instability in older adults. The objectives of this article are: (1) to discuss the evidence regarding age-related anatomical and physiological changes that occur in the peripheral proprioceptive and cutaneous systems, (2) to relate the basic science research to the current evidence regarding clinical changes associated with normal aging, and (3) to review the evidence regarding age-related proprioceptive and cutaneous clinical changes and relate it to research examining balance performance in older adults. The article is organized by an examination of the receptors responsible for activating afferent pathways (muscle spindle, golgi tendon organ, and articular and cutaneous receptors) and the corresponding sensory afferent fibers and neurons. It integrates basic science laboratory findings with clinical evidence suggesting that advanced aging results in a decline in cutaneous sensation and proprioception. The potential relationship between postural instability and sensory impairments in older adults also is discussed. Current laboratory and clinical evidence suggests that aging results in: (1) diverse and nonuniform declines in the morphology and physiological function of the various sensory structures examined, (2) preferential loss of distal large myelinated sensory fibers and receptors, and (3) impaired distal lower-extremity proprioception, vibration and discriminative touch, and balance. These findings provide foundational knowledge that emphasizes the importance of using reliable and valid sensory testing protocols for older adults and the need for further research that clarifies the relationship between sensory impairment and balance.

Sensorimotor contribution to shoulder stability: effect of injury and rehabilitation

Shoulder joint stability is the humeral head remaining or promptly returning to proper alignment within the glenoid fossa. This is mediated by both mechanical and dynamic restraint mechanisms. Coordination of these restraint systems is required for shoulder joint stability. The sensorimotor system is defined as all of the sensory, motor, and central integration and processing components involved in maintaining joint stability. The sensorimotor system is comprised of several components including proprioception, joint position sense, kinesthesia, sensation of force, and neuromuscular control. With joint injury, not only are the mechanical restraints disrupted (joint capsule, glenoid labrum, etc.) but also, the sensorimotor system is affected. Restoration of the sensorimotor system has been shown to occur through both surgical and conservative intervention and rehabilitation. Surgery has been shown to restore both mechanical restraints and the sensorimotor system. Specific rehabilitation techniques have also been effective at improving the sensorimotor system in healthy and pathological patients.