Clinical trial of exercise for shoulder pain in chronic spinal injury.

Shoulder musculoskeletal disorders have been linked to occupations or activities that require repetitive use or sustained elevated shoulder postures. (1,2) In many cases, people exposed to routine overhead work, such as construction workers, welders, or athletes whose sports involve frequent overhead arm use, have high rates of shoulder pain that frequently progresses to functional loss and disability. (3-6) Through the nature of their functional routines and the increased demands placed on the upper limbs, people with spinal cord injury (SCI) may be considered at a similar risk for the development of shoulder pain. The prevalence of shoulder pain, reported to range between 30% and 50% in people with paraplegia, (7-11) may be related to the repetitive and nearly exclusive use of the upper limbs during self-care, weight-relief raises, transfers, and wheelchair mobility. Although shoulder pain may not initially limit an individual's ability to perform functional activities, if mobility is lost because of disabling shoulder pain, the physical, social, and vocational consequences for wheelchair users are significant. (12)

Subacromial impingement is considered to be one of the primary underlying factors related to shoulder pain in SCI. (7,8,13) The pain associated with impingement has been linked to the functional compromise of the subacromial space and the structures within the space: rotator cuff, long head of the biceps muscle, and bursae. (14-16) In the general clinical setting, factors thought to contribute to impingement include anatomic abnormalities, such as changes in acromial shape and slope, (17,18) poor rotator cuff or scapular muscle function or muscle fatigue (or both), (19) and posterior capsule or pectoralis minor tightness. (20,21) In addition to anatomic and soft-tissue factors, altered kinematics of the shoulder complex are believed to exacerbate the impingement condition. (16,22-24) Specific kinematic changes have been identified during elevation of the arm in subjects who have shoulder impingement but who do not have SCI. (22,23,25) The motions that bring the greater tuberosity in closer contact with the coracoacromial arch are considered particularly problematic. These include excessive superior or anterior translations of the humeral head on the glenoid, inadequate external rotation of the humerus, (26) and decreases in scapular posterior tilting and upward rotation. (22,23) Even subtle kinematic deviations that result in a reduction in the available subacromial space may contribute to the initiation or progression of impingement symptoms. (16,24,27) This process would be worsened by inflammation, fibrosis or thickening of the tendons or bursae, or bony osteophyte formations, all of which may develop with chronic impingement. (15,16)

The demands associated with upper-extremity weight-bearing tasks place people with SCI at even greater risk for the development of shoulder pain. (7,28-31) During wheelchair-related activities of daily living assessed in subjects who were able-bodied, both weight-relief raise and transfer activities resulted in scapular and humeral positions believed to negatively influence the subacromial space in people with shoulder impingement. (31) When evaluating mechanical loading at the shoulder, van Drongelen and colleagues (30,32) found that these same activities resulted in greater glenohumeral contact forces than level wheelchair propulsion.

Past clinical trials have shown positive effects of exercise for subjects with shoulder pain related to impingement, rotator cuff disease, or pain of local mechanical origin in the general orthopedic setting. (33-43) Brox et al (34) reported significant improvements in pain and function in subjects who had shoulder impingement and who were randomly assigned to an exercise group compared with a placebo group. In a randomized clinical trial of people with shoulder pain believed to be of local mechanical origin, Ginn and Cohen (40) reported significant improvements in shoulder function in a physical therapy exercise intervention group compared with a control group. Ludewig and Borstad (37) also reported significant improvements in shoulder impingement symptoms in a home exercise intervention group compared with a control group. This latter investigation was unique in that the exercise program specifically targeted previously identified altered motion and muscle activity patterns in construction workers with shoulder pain.

In a study that examined the effect of an exercise intervention on self-reported pain in subjects with shoulder pain and SCI, Curtis et al (44) used a combination of stretching for the anterior shoulder and strengthening for the posterior shoulder musculature. Following a 6-month home exercise program, subjects in the shoulder pain group reported improvements in shoulder pain during the performance of activities of daily living. However, the Wheelchair User's Shoulder Pain Index (WUSPI) changes were not significantly different from those in the control group.

Consistent among several of the intervention studies to date is that the exercise protocols either combine global (ie, nonspecific) strengthening of the scapular muscles with glenohumeral strengthening or do not address the scapular muscles at all. In the present study, we tested the efficacy of a series of therapeutic exercises designed to address shoulder pain in people who are long-term wheelchair users. The exercise program used in this study was targeted to known detrimental kinematic deviations previously identified in people who are able-bodied but have shoulder pain, including scapular and humeral motion abnormalities and muscle activity alterations. (21-24,45-47) Specific muscle groups were emphasized because of their purported impact on scapular movement. (21,23,48) The strengthening protocol addressed the serratus, middle and lower trapezius, and glenohumeral external rotator muscles. The stretching protocol focused on soft tissue structures that are frequently tightened in people who are long-term wheelchair users: the pectoralis muscles, the long head of the biceps muscle, the upper trapezius muscle, and the posterior glenohumeral joint capsule. (44,49,50) The selective combination of strengthening and stretching is believed to have the greatest potential to effectively reduce pain and improve function in people with SCI and symptoms of shoulder impingement.

The purpose of this study was to determine the effects of a controlled 8-week, scapula-focused exercise intervention on shoulder pain and functional disability in people with SCI and symptoms of shoulder impingement. We hypothesized that subjects in the intervention group would show significant improvements over time, whereas subjects in the asymptomatic control group would retain stable functional status over time, as measured with the WUSPI, the Shoulder Rating Questionnaire (SRQ), and patient satisfaction scores.

Method

Subjects

The study design was a clinical trial with an asymptomatic control group. The population for this study consisted of manual wheelchair users with SCI (paraplegia and incomplete tetraplegia) and spina bifida (1 subject). People with and people without current self-reported shoulder pain were recruited through local clinics and SCI support groups, resulting in a sample of convenience. Data collection took place in the Movement Analysis Laboratory in the Department of Physical Therapy at Ithaca College-Rochester Campus and in the Orthopaedic Biomechanics Laboratory at the University of Minnesota. All subjects signed a written informed consent document prior to participation.

Demographic and medical data were collected from each subject and included specific details regarding shoulder pain, if present, and the number of transfers and hours spent in the wheelchair per day. Inclusion criteria for the study required subjects to be at least 1 year after spinal injury in order to ensure exposure to repetitive or sustained shoulder use. Additional inclusion criteria for the intervention group subjects included a current history of unilateral or bilateral shoulder pain lasting 3 months or longer and localized to the proximal anterolateral shoulder region; at least 2 positive results from the following impingement tests: Neer, (15) Hawkins-Kennedy, Jobe, and Speeds (51-53); at least 2 of the following findings: painful arc on active scapular plane abduction, pain with resisted shoulder motions (flexion, abduction, or internal or external rotation with arm at side and at 90[degrees]), or painful palpation around the shoulder joint (anteriorly, posteriorly, or at greater and lesser tubercles); and shoulder pain during transfers, weight-relief raises, or wheelchair propulsion. People were excluded from the study if they had reproduction of symptoms during a cervical screening examination, a history of onset of symptoms attributable to traumatic injury to the glenohumeral or acromioclavicular joint, surgery on the shoulder, or denervation of any of the scapular muscles. Asymptomatic control group subjects did not have a history of shoulder pain within the preceding 3 months and had negative findings for clinical testing in the categories listed above.

Forty-one subjects met the inclusion criteria and were placed into either the intervention (n=21) or the asymptomatic control (n=20) group on the basis of the results of the musculoskeletal examination. The past literature is not fully consistent; however, the clinical diagnostic tests used generally have either high sensitivity (Neer, Hawkins-Kennedy) or high specificity (painful arc, resisted external rotation with arm at side) when used in isolation. (15,51,53,54) When multiple diagnostic tests are found to be positive, diagnostic accuracy has been shown to be greater than that of arthroscopic confirmation. (54) Our inclusion criteria were most similar to the categorization of Park et al, (54) in which at least 2 of the following tests were positive: Hawkins-Kennedy, painful arc, and external rotation with the arm at the side (infraspinatus muscle test). In the clinical diagnosis of impingement syndrome, this categorization had a 90% posttest probability for arthroscopic confirmation of impingement. (54) Group demographic data are shown in Table 1.

Outcome Measures

All subjects who met the inclusion criteria completed the WUSPI and the SRQ and provided patient satisfaction scores. (55-57) The WUSPI is a 15-item self-report survey specifically designed to assess shoulder pain in wheel chair users during daily functional activities with a 10-point visual analog scale (Appendix 1). The SRQ is an outcome tool that is more typically used in the general orthopedic setting. The SRQ overall score reflects the severity of symptoms and the functional status of the shoulder and comprises various domains: global assessment, pain, daily activities, recreational and athletic activities, and work. The satisfaction score, used as the third outcome measure in this study, is an additional item in the SRQ that is not used in the calculation of the SRQ overall score. Appendix 2 shows a full version of the SRQ. The psychometric properties (reliability, validity, responsiveness, and internal consistency) of the WUSPI and the SRQ for people with shoulder pathology were previously reported. (55,57)

Experimental Procedure for Intervention Group

After the preintervention outcome measures were completed (pretest), subjects in the intervention group were given a home exercise program consisting of stretching and strengthening exercises with elastic band resistance (Figs. 1 and 2). The subjects were provided with a customized exercise pamphlet with their photographs inserted into a written program. They also were asked to complete a daily adherence log. Subjects were called each week to review the exercises and clarify any questions about the techniques. At 4 weeks, or sooner if deemed necessary to modify the exercises, the subjects returned to augment the exercise program with either increasing elastic band resistance or increasing repetitions or both. For example, if subjects were at the lower band resistances (ie, green or blue bands) and were able to complete 3 sets of 10 repetitions, they were given the next level of band resistance. If they were at the highest level of band resistance for this exercise program (ie, black band), they were asked to increase the number of repetitions (ie, 3 sets of 20 repetitions) for the duration of the program. At the conclusion of 8 weeks, subjects in both the asymptomatic control and the intervention groups returned to complete WUSPI, SRQ, and satisfaction outcome measures (posttest).

Figure 1.
Stretching exercises. The stretching exercises were performed every
day.

Upper Trapezius Muscle

While maintaining good sitting posture, use
one arm to stabilize the trunk and the other
arm to gently bend the head to one side.
Avoid rotating the head during the stretch.

Pectoralis Muscle

Position the wheelchair in the doorway and
place the forearm on the doorjamb, keeping
the elbow below 90[degrees]. Slowly rotate the chair
away from the doorjamb.

Long Head of the Biceps Muscle

Position the wheelchair in the doorway and,
with the arm slightly abducted, place the
forearm on the doorjamb. Slowly rotate the
chair away from the doorjamb. It is
important to maintain scapular retraction and
depression during the stretch.

Posterior Capsule

Lay partially between supine and side lying
on the side to be stretched in order to
stabilize the scapula (stretch is shown for
right side in this image). Place a pillow
underneath the opposite scapula. Gently pull
the arm across the body with the opposite
arm without rotating the shoulder.

Figure 2.

Strengthening exercises. The strengthening exercises were performed
every other day. For all exercises, subjects were instructed to
minimize activity of the upper trapezius by keeping the shoulders
relaxed. The method for the trapezius muscle strengthening was
selected based on the subject's ability to selectively activate these
muscles via electromyographic biofeedback.

Middle and Lower Trapezius Muscles:
Method 1

While maintaining good sitting posture and
with the arms slightly abducted and
externally rotated, squeeze the shoulder
blades down and together. This exercise
should precede the shoulder external
rotation exercise with the resistance band.

Middle and Lower Trapezius Muscles:
Method 2

While lying in a supine position with the
arms at approximately 45[degrees] of abduction,
pinch the shoulder blades down and
together. Extend the arms against the mat
for resistance.

Serratus Anterior Muscle

Attach a resistance band to the back the
wheelchair or the knob of a door on the side
to be strengthened. Start with the shoulder
blades pinched down and together, then
punch the arm forward.

Shoulder External Rotators

Place a towel roll between the trunk and
each arm. While keeping elbows bent to
90[degrees], grasp the resistance band. Pinch
shoulder blades down and together, and
then slowly pull hands apart.

Adherence to the exercise program was established through self-report written adherence logs and weekly verbal communication. Subjects were judged to be highly adherent if they completed 75% or more of the exercise program at the prescribed frequency. Moderate adherence was judged as completion at 25% to 75% frequency, and nonadherence was judged as completion at less than 25% frequency.

Exercise Intervention

Electromyographic (EMG) biofeedback was used during the initial session and, if needed, at the 4-week visit to ensure selective activation, relaxation, or both of targeted muscles. Bipolar surface electrodes were placed over the serratus anterior, pectoralis major, and upper, middle, and lower trapezius muscles. These electrode placements were described in previous investigations. (23,58,59) The surface electrodes were used to provide visual and auditory feedback to the subjects as they were performing the exercises, thereby allowing the subjects to modify the exercise technique until it was properly done.

The exercise protocol consisted of 3 or 4 stretching exercises and 3 or 4 strengthening exercises. The stretching exercises focused on the upper trapezius muscle, the pectoralis major and minor muscles, the long head of the biceps muscle (if tightness was evident), and the posterior capsule of the glenohumeral joint (Fig. 1). The strengthening exercises targeted the serratus anterior muscle, the middle and lower trapezius muscles, and the shoulder external rotator muscle (Fig. 2). Emphasis was placed on selectively activating these muscles while at the same time minimizing the activity of the upper trapezius and pectoralis muscles. As each exercise was given, the subjects also were shown the anatomy of each structure with a skeletal model or textbook (or both). If a subject could not selectively target a muscle or muscle group without considerable unwanted EMG activity from the upper trapezius and pectoralis muscles or if the exercise reproduced shoulder pain, the exercise was not given. This procedure resulted in a final exercise program comprising 6 to 8 exercises.

The exercises were performed with the shoulder flexed to 90 degrees or less in order to avoid positions that might aggravate symptoms further. Subjects were informed that slight muscle soreness might occur but that the exercises should not cause increased or persistent pain. They were instructed to stop all exercises and call the study investigators if increased pain occurred.

Data Reduction

The WUSPI was scored with methods previously described by Curtis et al. (56) The score on the WUSPI ranges from 0 to 150. If a question was not applicable, if a subject did not answer 1 or more questions, or if both of these situations occurred, then a performance corrected score was applied (PC-WUSPI). (12) This PC-WUSPI score (range, 0-150) then was used in final statistical calculations. A lower score on the WUSPI indicates decreased pain and increased function. The SRQ was scored as described by L'Insalata et al, (57) resulting in scores ranging from 17 to 100. A higher score indicates greater shoulder function and fewer shoulder impingement symptoms. The weighting system multiplies the global assessment rating by 1.5, the pain score by 4, the daily activity score by 2, the recreational and athletic activity score by 1.5, and the work score by 1. (57) The satisfaction score is a single item that specifically asks an individual the following question: "How would you rate your overall degree of satisfaction with your shoulder?" It is not used to calculate the SRQ overall score and can range from 2 to 10, with a higher score indicating greater satisfaction.

Data Analysis

Normality was assessed for each of the 3 dependent variables (WUSPI, SRQ, and satisfaction scores). In the presence of an abnormal distribution, a square root transformation was performed. A 2-way mixed-model analysis of variance was used for each normalized dependent variable to determine the main effects of group (asymptomatic control or intervention) or time (pretest and posttest) and any interaction effects. The group factor was a between-subjects comparison, and the time factor was a within-subjects comparison. The significance level was set at .05. Significant interactions were expected, with anticipated improvements in function and reductions in pain for the intervention group over time, and stable values were expected over time for the asymptomatic control group. In the presence of significant interactions, post hoc analyses with Tukey-Kramer adjustments were completed to test for differences between groups in both pretest and posttest scores as well as within groups over time.

Possible confounding effects were assessed by completing independent group t tests of demographic variables (Tab. 1) and computing Pearson correlation matrices between the demographic variables (age, body mass index, years since injury, average transfers per day, and average hours in the chair per day) and the dependent variables. Although age and years since injury were significantly different between groups, no demographic variable reached a correlation with any dependent variable of greater than .52; therefore, none was included as a covariate in the analysis. An r value of greater than .60 has been suggested as an appropriate threshold for use in an analysis of covariance. (60)

The analysis included all subjects initially enrolled, regardless of their level of adherence to the exercise program, in an "intention-to-treat" analysis. (61) Missing posttest data for the 2 subjects lost to follow-up were replaced with imputed values based on the pretest scores for those subjects. This is a conservative approach assuming that data for subjects lost to follow-up did not change from pretest to posttest. (61)

Descriptive data were determined for average changes (posttest minus pretest) by group for the WUSPI, SRQ, and satisfaction scores. Because the WUSPI was the primary survey tool for this population of people who were wheelchair users, descriptive statistics ([bar.X] and SE) also were calculated for each question on the WUSPI. This strategy allowed for a secondary descriptive interpretation of areas in which function was most affected or in which the greatest improvements in function were obtained.

Results

Ninety-five percent of all subjects returned at 8 weeks. All subjects in the asymptomatic control group returned for 8-week visits. Two subjects in the intervention group were lost to follow-up, despite multiple attempts to contact the subjects by telephone and letter. Of the 19 subjects in the intervention group who returned for the 8-week follow-up, 14 were determined to be highly adherent, 3 were determined to be moderately adherent, and 2 were determined to be non-adherent.

The WUSPI scores were abnormally distributed and therefore were transformed prior to the statistical analysis. Consistent with the hypothesis, subjects in the intervention group showed significant improvements in their WUSPI scores from pretest to posttest, whereas asymptomatic control group subjects remained stable. Statistically, these data represented an interaction of group and time (F=10.70; df=l,39; P=.002) (Fig. 3). Follow-up testing verified the significant changes in the intervention group over time as well as significant differences between the 2 groups at pretest. At posttest, although improved, the average WUSPI scores of the intervention group subjects remained significantly above those of the asymptomatic control group subjects.

[FIGURE 3 OMITTED]

The SRQ scores also were abnormally distributed and therefore were transformed. Again, there was a significant interaction of group and time (F=24.64; df=1,39; P<.001) (Fig. 4), with subjects in the intervention group showing significant improvements in their SRQ scores from pretest to posttest, whereas asymptomatic control group subjects did not show significant changes over time. Follow-up testing verified the significant changes in the intervention group over time as well as significant differences between the 2 groups at pretest. Again, at posttest, the average SRQ scores of the intervention group subjects remained significantly below those of the asymptomatic control group subjects.

[FIGURE 4 OMITTED]

Satisfaction scores further demonstrated a significant interaction of group and time, with significant improvements in satisfaction scores in the intervention group subjects over time (F=19.10; df=1, 39; P<.001) (Fig. 5). The asymptomatic control group subjects showed no significant changes in satisfaction scores from pretest to posttest. The intervention group scores were significantly lower than the asymptomatic control group scores at pretest. At posttest, the satisfaction scores of the intervention group remained significantly lower than those of the asymptomatic control group.

[FIGURE 5 OMITTED]

Descriptive statistics for average change scores by group are shown in Table 2. On average, the intervention group showed improvements of 20% for the WUSPI and 29% for the SRQ. Figure 6 shows the pretest and posttest scores for the 15 WUSPI items. Pushing up ramps, overhead lifting, and washing the back were the items with the greatest functional limitations at pretest and showed substantial improvements from pretest to posttest.

[FIGURE 6 OMITTED]

Discussion

The present study assessed the benefits of an exercise program designed to selectively stretch and strengthen specific scapular and rotator cuff muscles in people with spinal injury who were wheelchair users and experiencing shoulder pain consistent with rotator cuff dysfunction. The results showed that a selective 8-week home exercise program is effective in reducing pain and improving function and satisfaction in this population. Over time, the intervention group showed significant, positive changes related to pain, function, and satisfaction, whereas the asymptomatic control group remained essentially stable.

Although past clinical trials showed positive effects of exercise for subjects with shoulder pain related to impingement or rotator cuff disease, (33,34,36-38,42-44) the majority of these studies assessed outcomes in subjects who were able-bodied. Additionally, most investigations included general shoulder stretching and strengthening exercises rather than exercises targeted toward the correction of specific identified movement deviations. The present study targeted specific movement deviations presumed to be present in people with SCI on the basis of existing literature. In a randomized controlled trial, Ludewig and Borstad (37) showed significant improvements in shoulder impingement symptoms following an 8-week home exercise intervention pro gram in construction workers who had regular exposure to overhead work conditions. This exercise program was based on previously identified scapular motion and muscle activity deviations in construction workers. (23) McClure et al (38) evaluated the effects of a 6-week exercise program on shoulder function and 3-dimensional shoulder kinematics in a general orthopedic setting of subjects with impingement syndrome. Interventions included exercises designed to increase strength and improve the flexibility and posture of the shoulder complex and trunk, with the majority of exercises focusing on glenohumeral motion. The positive changes found after 6 weeks in relation to pain, satisfaction, and shoulder function also were maintained at the 6-month follow-up.

To date, only 1 study has examined the effects of exercise intervention in subjects with shoulder pain and SCI. Curtis et al (44) used a combination of stretching and strengthening exercises over a 6-month period for 42 people who were wheelchair users who were randomly assigned to a control group (n=21) and a treatment group (n=21). The subjects had a range of disabilities, including 10 subjects with paraplegia. Two static stretching exercises were given to increase the flexibility of the pectoralis and biceps muscles, similar to the anterior shoulder stretches used in the present study. Two of the 3 strengthening exercises were targeted to the shoulder external rotator and shoulder adductor muscles, and the third exercise was prescribed for scapular retraction to be performed in a "rowing" motion. The glenohumeral external rotation exercise would be considered comparable to that given to subjects in the present study. Without the use of EMG to verify muscle activation, it is difficult to ascertain which muscles were specifically targeted during the scapular retraction exercise used in the study of Curtis et al, (44) minimizing the ability to compare that investigation with the present investigation.

No significant differences between the treatment group and the control group or interactions of group and time were identified in the study of Curtis et al. (44) The 10 subjects with paraplegia in the treatment group reported a 12-point reduction in PC-WUSPI scores, compared with a 1.5-point reduction in 11 control group subjects (a reduction in scores indicates improvement) over the 6-month intervention. However, as these reductions were not statistically significant between groups, chance sampling errors cannot be ruled out. It is interesting to note that subjects actually showed poorer PC-WUSPI scores at the 8-week point of the study. The authors did not report adherence to the exercise protocol, making it difficult to ascertain whether the reduction in symptoms over the 6-month period represented the effects of the intervention, a modification in the activity level, or the natural course of tissue healing.

The success of our therapeutic intervention, compared with the nonsignificant results of Curtis et al, (44) may be attributable to a number of factors, such as a smaller treatment effect (average change of 12 WUSPI points in the paraplegic treatment group in the study of Curtis et al versus 21 points in the present study) or greater variation in how subjects responded to the intervention. Additionally, the average WUSPI scores were lower at baseline in that study than in the present study, reflecting a lower level of disability. This difference is likely attributable in part to the fact that 50% of the treatment and control group subjects in the study of Curtis et al (44) were asymptomatic for shoulder pain at the time of the study. Subjects who were asymptomatic for shoulder pain and subjects who were symptomatic for shoulder pain were randomly assigned to treatment and control groups, thus likely reducing the potential for a significant treatment effect. The differences between study findings also may have resulted from the attempt in the present study to design an exercise protocol to specifically target musculature believed to be contributory to abnormal scapular movement patterns identified in subjects who were able-bodied. (21-24,47,62,63)

Scapular movement patterns that include increased anterior tipping, downward rotation, and internal rotation as well as glenohumeral internal rotation have been considered to be particularly detrimental to the subacromial space. (23,27,64) These scapular movement patterns have been shown to be magnified during functional tasks such as weight-relief raises and transfers, weight-bearing tasks that are performed routinely in people with SCI. (31) Additionally, in the non-weight-bearing shoulder, these kinematic alterations in scapular motion have been associated with decreases in serratus muscle activity, increases in upper trapezius muscle activity, or a shortened pectoralis minor muscle. (21,23) These aforementioned scapular kinematic and muscle activity findings provided the basis for the exercise protocol used in the present study.

Specific muscle groups were emphasized because of their purported impact on scapular movement. The lower and middle divisions of the serratus anterior muscle are key contributors to normal and abnormal scapular motion and control. (48) The insertion of the serratus anterior muscle into the scapular vertebral border and inferior angle results in larger moment arms for the production of scapular upward rotation and posterior tipping than any of the other muscles linking the scapula and the thorax. (48) The serratus anterior muscle is also unique among the scapulothoracic muscles in that it has the ability to contribute to all components of the normal 3-dimensional movement of the scapula on the thorax during elevation of the arm. Specifically, this muscle can produce scapular upward rotation, posterior tipping, and external rotation while at the same time stabilizing the vertebral border and inferior angle of the scapula in contact with the thorax. The importance of the serratus anterior muscle is evidenced further by the presence of abnormal muscle activation in various shoulder pathologies. (23,65,66) Reduced serratus anterior muscle EMG activity has been demonstrated in throwers with glenohumeral instability, (65) construction workers with shoulder impingement, (23) and swimmers with shoulder pain. (66) As a result of these findings, increased emphasis was placed on serratus muscle strengthening for rehabilitation and prevention of shoulder dysfunction.

In addition to serratus muscle strengthening, the middle and lower trapezius muscles also were addressed with a progressive resistance program because of their presumed role in balancing the lateral translatory force of the serratus muscle and the elevation forces of the upper trapezius muscle. (48,67) Rotator cuff strengthening for the external rotator muscles is based on the critical function of these muscles in controlling the translation of the humeral head on the glenoid (19) and on identified muscle imbalances in people with SCI. (10,50)

The stretching protocol addressed the posterior capsule and the upper trapezius and pectoralis muscles. Posterior capsule stretching was incorporated into the proposed exercise intervention on the basis of identified excess anterior humeral translations in subjects with impingement and the association of these abnormal translations with tightness of the posterior capsule. (45,68) Upper trapezius and pectoralis muscle stretches were incorporated because of the potentially detrimental restriction of the normal posterior tilting and external rotation of the scapula if these muscles are tight as well as documented excess activation in subjects with impingement. (21-23) Interventions targeted to the scapula may effectively minimize the progression of shoulder impingement symptoms and ultimately the secondary disability associated with shoulder pain.

The results of the present study showed significant positive effects on pain, function, and satisfaction despite the fact that only 6 to 8 exercises were completed during a home exercise program. A number of factors may have contributed to the effectiveness of the intervention. Performance and problems were monitored by weekly telephone calls, and exercise performance was reviewed, corrected, and augmented at the 4-week follow-up. With the exception of 2 subjects who were eventually classified as nonadherent, all subjects were able to progress at the 4-week follow-up, as demonstrated by an increase in the elastic band resistance level, an increase in the number of repetitions, or both. The exercise protocol was standardized in terms of the selection of exercises yet was subject specific in terms of using EMG biofeedback for instruction and allowing modifications based on a subject's ability to activate the desired muscles or muscle groups. The inclusion of an educational component related to shoulder anatomy, shoulder pain, and impingement also may have contributed to the adherence to and effectiveness of the intervention.

Adherence to the exercise program was assessed by written adherence logs and demonstration and verbal understanding of the exercises. Fourteen of the subjects were determined to be highly adherent (75% or greater frequency of completion of the exercise program), 3 were determined to be moderately adherent (25%-75% frequency of completion), and 2 were determined to be nonadherent. When informally asked about their lack of adherence, subjects cited lack of time as the main factor preventing higher levels of adherence. As most subjects were highly adherent, there is a lack of data from which to assess whether adherence was related to the various levels of improvement experienced by subjects in the intervention group. However, when subjects were grouped in terms of high adherence versus no or moderate adherence, average difference scores (posttest minus pretest) on the WUSPI were -28.40 points (a negative value reflects a reduction in pain) for highly adherent subjects versus only -4.08 points for subjects with no or moderate adherence. The SRQ and satisfaction difference scores, however, were similar between these subgroups and similar to the overall intervention group change scores provided in Table 2. Although at the 4-week visit the subjects were able to accurately demonstrate the exercise program to the investigators, the adherence data should be interpreted cautiously because the accuracy of the logs is dependent on subject self-report.

With a significant overall group effect, it is also of interest to determine the magnitude of the effect relative to the smallest real difference (SRD) (69) and the numbers of individual subjects demonstrating significant improvements. The SRD represents the smallest measurement change for an individual subject that can be interpreted as a real difference (at a 95% confidence level, SRD=SEM x [square roof of 2 x 1.96, where SEM is the standard error of the measurement). (69) On the basis of the previously published psychometric properties of the WUSPI, (55) the SEM can be determined to be SD x [square root of (l-r)], or 2.8 WUSPI points. The SRD at a 95% confidence level therefore is 7.8 WUSPI points. (69) The mean change in the WUSPI scores for the intervention group subjects (-22.9) therefore was nearly 3 times the SRD. When values for individual subjects were considered, 57% of the intervention group subjects demonstrated improvements on the WUSPI at posttest that were at or above the SRD threshold.

This investigation included an asymptomatic control group; therefore, significant changes found over time in the symptomatic group are known to be beyond the natural variability of the outcome measures across time. However, because subjects and therapists were not unaware of the group designation and because the control group was asymptomatic, natural improvements over time independent of the intervention, placebo effects, and bias are limitations of the present study that should be considered. With regard to the natural history of the disease over time and placebo effects, other controlled studies for shoulder pain consistently showed a lack of significant improvements over time in asymptomatic control or placebo groups. (34,37,70,71) Therefore, these potential confounders are unlikely explanations for the findings in the present study.

The generalizability of the results of the present study should be limited to people who have full scapular muscle innervation. People with tetraplegia may not be able to fully activate the serratus muscle, and exercise programs would need to be modified to minimize abnormal scapular movement patterns. The present study also assessed long-term wheelchair users. The effects of this exercise protocol on acute shoulder pain (ie, lasting <1 year) are not known. When results of clinical trials are applied to clinical practice, study inclusion and exclusion criteria are always important considerations.

Although significant improvements were obtained for the intervention group at the 8-week follow-up, this group remained different from the asymptomatic control group in terms of WUSPI and SRQ scores. That is, maximum recovery was not yet achieved. This finding is similar to the findings of a previous study of people who were able-bodied that compared an intervention group with an asymptomatic control group (37) and stresses the need for continued investigations that will enable subjects to achieve the greatest recovery. For example, enhanced outcomes may be obtained from a more intense exercise program, one incorporating greater supervision, a larger number of glenohumeral exercises, or adjuncts to the exercise program, such as manual therapy (33) or medication. Little is known regarding optimal exercise parameters and dose-response relationships, such as how many repetitions should be used and what threshold of force or muscle activation should be targeted to alter functional movement patterns and maximally reduce symptoms. Given the 8-week duration of the study and the amount of resistance used, subjects likely did not increase muscle hypertrophy. Greater understanding of potential subclassifications of shoulder pain and refined clinical diagnostic tests may be needed in order to match the most suitable interventions to the most appropriate subjects. Furthermore, there is a need for a better understanding of the mechanisms underlying the symptomatic changes, both positive and negative, that alter pain and function. To date, improvements in symptoms in shoulder intervention studies have not been shown to be associated with substantial improvements in the underlying movement abnormalities thought to be related to the original development of the pathology. (38) Research regarding kinematic alterations before and after exercise interventions in subjects with shoulder pain and spinal injury is ongoing.

Four of the 6 to 8 exercises used for each subject were targeted to scapular muscles; therefore, the exercise program was described as scapula focused. However, we are not advocating ignoring the literature evidence for glenohumeral joint contributing factors. We incorporated rotator cuff elastic band resistance exercises and posterior capsule stretching in the exercise program as well. We believe that a focus on the scapula is a critical element for optimizing upper-extremity function in people with shoulder pain but may be inadvertently overlooked in exercise protocols for people with spinal injury who were wheelchair users. The scapula often is supported, obscured, or both by the back height of the wheelchair, thereby minimizing active stabilization efforts during routine exercises or activities. Additionally, because of the muscle activation requirements associated with wheelchair-related activities, (72-74) glenohumeral strengthening may be emphasized without proper scapular stabilization to prevent anterior tilting or loss of contact of the scapular medial border or inferior angle with the thorax during exercise routines. In the present study, the scapula was observed as subjects performed a glenohumeral external rotation exercise with elastic band resistance (Fig. 2). If excessive scapular mobility was noted and subjects were unable to maintain scapular retraction or depression during the exercise, then elastic band resistance was either decreased or eliminated until the scapula could be controlled adequately throughout the exercise. The goal of preventing the long-term complications and loss of mobility associated with shoulder pain may be best achieved through continued development and refinement of shoulder rehabilitation protocols for long-term wheelchair users.

Conclusion

A specifically targeted, scapula-focused exercise program resulted in significant improvements in shoulder function and reductions in shoulder pain over 8 weeks in wheelchair users with spinal injury and shoulder pain compared with the results obtained for the control group. Satisfaction scores also were positive for this exercise program. Further investigation is needed for a better understanding of the mechanisms underlying the development of and rehabilitation for the disabling shoulder pain commonly seen in this population.

Appendix 1.

Wheelchair User's Shoulder Pain Index Items (a)

During the past week, how much shoulder pain did you experience when:

1. Transferring from a bed to a wheelchair?

2. Transferring from a wheelchair to a car?

3. Transferring from a wheelchair to the tub or shower?

4. Loading your wheelchair into a car?

5. Pushing your chair for 10 min or more?

6. Pushing up ramps or inclines outdoors?

7. Lifting objects down from an overhead shelf?

8. Putting on pants?

9. Putting on a T-shirt or pullover?

10. Putting on a button-down shirt?

11. Washing your back?

12. Performing usual daily activities at work or school?

13. Driving?

14. Performing household chores?

15. Sleeping?

(a) Subjects answered each question by marking an "X" on a 10-cm visual analog scale anchored at "no pain" to "worst pain ever experienced." If a question did not apply, subjects were asked to mark "NA."

Appendix 2.

Shoulder Rating Questionnaire (a)

Please answer the following questions regarding the shoulder for which you have been evaluated or treated. If a question does not apply to you, leave that question blank. If you indicated that both shoulders have been evaluated or treated, please complete a separate questionnaire for each shoulder and mark the corresponding side (right or left) at the top of each form.

1. Considering all the ways that your shoulder affects you, circle a number on the scale below for how well you are doing. Very poorly { 1 2 3 4 5 6 7 8 9 10 } Very well The following questions refer to pain.

2. During the past month, how would you describe the usual pain in your shoulder at rest?

A) Very severe

B) Severe

C) Moderate

D) Mild

E) None

3. During the past month, how would you describe the usual pain in your shoulder during activities?

4. During the past month, how often did the pain in your shoulder make it difficult for you to sleep at night?

A) Every day

B) Several days per week

C) 1 day per week

D) Less than 1 day per week

E) Never

5. During the past month, how often have you had severe pain in your shoulder?

The following questions refer to daily activities.

6. Considering all the ways you use your shoulder during personal and household activities leg, dressing, washing, driving, household chores), how would you describe your ability to use your shoulder? A) Very severe limitation; unable

B) Severe limitation

C) Moderate limitation

D) Mild limitation

E) No limitation

Questions 7-11: During the past month, how much difficulty have you had in each of the following activities due to your shoulder?

7. Putting on or removing a pullover sweater or shirt

A) Unable

B) Severe difficulty

C) Moderate difficulty

D) Mild difficulty

E) No difficulty

8. Combing or brushing your hair

9. Reaching shelves that are above your head

10. Scratching or washing your lower back with your hand

11. Lifting or carrying a full bag of groceries (8-10 lb)

The following questions refer to recreational or athletic activities. 12. Considering all the ways you use your shoulder during recreational or athletic activities leg, baseball, golf, aerobics, gardening), how would you describe the function of your shoulder?

A) Very severe limitation; unable

B) Severe limitation

C) Moderate limitation

D) Mild limitation

E) No limitation

13. During the past month, how much difficulty have you had throwing a ball overhand or serving in tennis due to your shoulder?

14. List one activity (recreational or athletic) that you particularly enjoy and then select the degree of limitation you have, if any, due to your shoulder. Activity The following questions refer to work.

15. During the past month, what has been your main form of work?

A) Paid work (list type of work)

B) Housework

C) Schoolwork

D) Unemployed

E) Disabled due to your shoulder

F) Disabled secondary to other causes

G) Retired

If you answered D, E, F, or G to the above question, please skip questions 16-19 and go on to question 20. 16. During the past month, how often were you unable to do any of your usual work because of your shoulder?

A) All days

B) Several days per week

C) 1 day per week

D) Less than 1 day per week

E) Never

17. During the past month, on the days that you did work, how often were you unable to do your work as carefully or as efficiently as you would like because of your shoulder?

18. During the past month, on the days that you did work, how often did you have to work a shorter day because of your shoulder?

19. During the past month, on the days that you did work, how often did you have to change_ the way that your usual work is done because of your shoulder? The following questions refer to satisfaction and areas for improvement.

20. During the past month, how would you rate your overall degree of satisfaction with your shoulder?

A) Poor

B) Fair

C) Good

D) Very good

E) Excellent

21. Please rank the 2 areas in which you would most like to see (place a 1 for the most important, a 2 for the second most important). Pain -- Daily personal and household activities -- Recreational or athletic activities Work --

(a) For subsequent questions that use the same answer format, these answer formats are not repeated in this presentation of the questionnaire. Adapted with permission from L'Insalata JC, Warren RF, Cohen SB, et al. A self-administered questionnaire for assessment of symptoms and function of the shoulder. J Bone Joint Surg Am. 1997;79:738-748. Copyright 1997, The Journal of Bone and Joint Surgery Inc.

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This article was received January 3, 2006, and was accepted August 7, 2006.

DOI: 10.2522/ptj.20060001

DA Nawoczenski, PT, PhD, is Professor, Department of Physical Therapy, Ithaca College-Rochester Campus, 1100 S Goodman St, Rochester, NY 14620 (USA). Address all correspondence to Dr Nawoczenski at: [e-mail].

JM Ritter-Soronen, PT, DPT, is Staff Physical Therapist, Adventist Rehabilitation Hospital of Maryland, Rockville, Md.

CM Wilson, PT, DPT, is Staff Physical Therapist, Christiana Care Center for Rehabilitation, Wilmington Hospital, Wilmington, Del.

BA Howe, PT, MSPT, is Graduate Research Assistant, Department of Physical Therapy, Ithaca College-Rochester Campus.

PM Ludewig, PT, PhD, is Associate Professor, Program in Physical Therapy, Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, Minn.

Dr Nawoczenski provided concept/idea/research design, writing, data collection and analysis, project management, fund procurement, and facilities/equipment. Ms Ritter-Soronen and Dr Wilson provided data collection and project management. Mr Howe provided data collection and analysis. Dr Ludewig provided concept/research design, writing, data analysis, subjects, and facilities.

This study was approved by the institutional review boards of Ithaca College-Rochester Campus and the University of Minnesota.

This study was funded by the Spinal Cord Research Foundation (grant no. 2251-01) and National Institutes of Health grant no. R15HD41379.

Table 1.

Subject Demographics (a)

                                         Asymptomatic
                          Intervention   Control
                          Group          Group
Variable                  (n=21)         (n=20)          P

Age, y, [bar.X] (SD)      47.1 (11.7)    38.1 (7.6)      .006

Sex
  Male                    15             13
  Female                   6              7

BMI, [bar.X] (SD)         24.7 (5.8)     27.0 (6.4)      NS

Years since injury,       17.0 (13.3)    9.2 (5.8)       .02
  [bar.X] (SD)

No. of transfers/d,       20.7 (21.3)    16.5 (7.5)      NS
  [bar.X] (SD)

Hours in wheelchair/d,    12.4 (3.8)     14.3 (2.8)      NS
  [bar.X] (SD)

Level of injury
  Cervical (incomplete)    3              0
  Thoracic
    High (T2-T7)           7              7
    Low (T8-T12)           7             12
  Lumbar                   4              1

Extent of injury
  Incomplete              13              6
  Complete                 8             14

(a) BMI=body mass index, NS=not significant (P > .05). Data are
reported as number of subjects unless otherwise indicated.

Table 2.

Change (Pretest to Posttest) Scores

                                               Range of
                                               Possible
Measurement Tool                Variable        Scores

Wheelchair User's
  Shoulder Pain Index (a)   Difference score     0-150
Shoulder Rating
  Questionnaire (b)         Difference score    17-100
Satisfaction score (c)      Difference score     2-10

                            [bar.X] (SE) for:

                            Intervention       Asymptomatic
                                Group          Control Group
Measurement Tool               (n=21)             (n=20)

Wheelchair User's
  Shoulder Pain Index (a)   -22.85 (7.59)      2.01 (1.31)
Shoulder Rating
  Questionnaire (b)          15.62 (3.20)     -1.75 (1.37)
Satisfaction score (c)        2.38 (0.47)     -0.10 (0.31)

(a) A negative score indicates a reduction in pain
and improved function.

(b) A positive score indicates a reduction in shoulder
symptoms and improved shoulder function.

(c) A higher score indicates greater satisfaction.