Summary of Individual Studies
The duration of intervention, change score for each intervention group, and whether a statistical significance was found for each of the included articles are summarized in Table 2
Across the 7 studies that met the inclusion criteria, all intervention groups demonstrated a reduction in shoulder pain as determined by a decrease in WUSPI score. Three studies3,13,15 performed between-group comparisons: Curtis et al3 compared an HEP to no intervention—those who received the HEP indicated a WUSPI change score of −8.3, while those receiving no intervention indicated a −0.4 WUSPI change score; Mulroy et al13 compared an HEP to an attention control group—the HEP group WUSPI change score was −36.3 while the attention control group actually increased by 0.2; finally, Nawoczenski et al15 compared an HEP to an asymptomatic control group—the HEP group WUSPI change score was −22.85, while the asymptomatic control group change score was +2.01. The between-group comparisons for Mulroy et al13 and Nawoczenski et al15 were statistically significant, but the P values for Curtis et al3 for main effect of treatment group and interaction between group and time were not significant. Middaugh et al12 reported WUSPI change scores associated with both an HEP group and a group receiving an HEP coupled with EMG biofeedback (HEP+EMG). The HEP WUSPI change score was −11.9 (P = 0.42) while the HEP+EMG was −37.0 (P = 0.02). The HEP+EMG change score was significant, but the change score for the HEP alone was not.
Several authors have reported outcomes associated with the study interventions with no between-group comparisons.14,16,17 Nash et al14 employed a circuit resistance training program that produced a WUSPI change score of −26.8 (statistically significant). Norrbrink et al16 utilized a program consisting solely of double-poling upper body ergometry, producing a change score of −19.0, but the statistical significance was not reported for this study. Van Straaten et al17 utilized an HEP with videoconferencing for feedback and progression during the intervention period, producing a WUSPI change score of −10.3 (P = 0.007).
In reviewing the literature available for manual wheelchair users with SCI, we set out to evaluate the effectiveness of exercise programs that have been developed to manage shoulder pain. Although the studies identified were heterogenous in regard to type of study and interventions investigated, each intervention was effectively and safely implemented and resulted in a decreased score on the WUSPI. The articles reviewed consistently demonstrated a reduction in WUSPI scores following an intervention period based on the studies' parameters. The reduction in WUSPI score exceeded the minimal detectable change of 5.10,9 indicating a clinically important change in shoulder pain. There were no adverse events reported in any of the studies that were directly attributable to the exercise intervention.
It is important to consider differences among the studies with regard to the time periods over which the exercise interventions were applied. The durations of study interventions ranged from 8 weeks12,15 to 6 months.3 Because of heterogeneity in interventions applied, baseline WUSPI scores of the participants, and comparators across the 7 studies, it is not possible to conclude whether a longer intervention time frame is more beneficial in reducing pain scores. To determine the most effective duration of exercise intervention, a future randomized controlled trial comparing different intervention periods is needed, utilizing an identical intervention across the different time groups and controlling for differences in baseline shoulder pain.
Across the 7 studies reviewed, there were both similarities and differences in exercise prescription. Of the 6 studies that evaluated stretching interventions, 5 utilized anterior shoulder joint or pectoralis stretching,3,12,13,15,17 3 utilized biceps stretching,3,12,15 3 utilized upper trapezius stretching,12,13,15 3 utilized posterior capsule stretching,13,15,17 and 1 utilized cervical rotation stretching.12 There were 7 studies that evaluated strengthening interventions. Two studies utilized arm ergometry as a form of endurance strengthening intervention,14,16 with 1 of these 2 alternating arm ergometry with resistance training. The other 5 studies provided strengthening exercises without incorporating arm ergometry.3,12,13,15,17 Of these studies, all five utilized a shoulder external rotation exercise,3,12,13,15,17 4 utilized scapular retraction,3,12,13,17 3 studies utilized shoulder adduction exercises,3,12,13 1 utilized a shoulder extension exercise.12 One study utilized a shoulder elevation in the scaption plane exercise,13 1 utilized a middle and lower trap,15 and 2 utilized a serratus anterior exercise.15,17 Two studies utilized EMG biofeedback in the intervention.12,15 One study12 used EMG biofeedback in the HEP + EMG biofeedback intervention group before introducing the HEP to train the participant to utilize the correct muscles and demonstrated improvement in the effectiveness of the exercises. The other study15 utilizing EMG biofeedback introduced it early as a technique to train the muscles and again at follow-up if needed for each participant. Based on the common exercises that improve the WUSPI and pain in this population, a standardized shoulder program could be created.
Despite the variability among studies noted earlier, based on some commonalities among studies, general recommendations for exercises can be forwarded for this population, from which further RCTs might be developed. The evidence reviewed indicates a number of potential combinations of strengthening exercises targeting the posterior shoulder musculature for power and endurance, and stretching targeting the muscles of the anterior shoulder joint structures. Three studies utilized unilateral, shoulder external rotation with the elbow at 90° of flexion, and the shoulder in a neutral position.3,12,13 This exercise was to be performed using a resistance band. Two studies utilized simultaneous, bilateral external rotation with a resistance band with the elbows at 90° of flexion and neutral positioning of the shoulders.15,17 These exercises specifically targeted the external rotator as part of the posterior shoulder musculature. These strengthening exercises and stretching, possibly in combination with EMG biofeedback training and arm ergometry, could be used to create a program targeting the management and treatment of shoulder pain in this population. Furthermore, there may be value in understanding whether a home-based exercise program could be effective for improving strength and reducing pain.19
There is concern about exacerbating shoulder pain with exercises in manual wheelchair users with SCI. Overuse injuries may result from inappropriate strengthening programs. Although no explanation was given for the increased pain scores at the 2-month time period in Curtis et al,3 this is the only study that included exercise on a daily basis. As such, we cannot ignore the possibility that increased intensity of exercise may have contributed to increased pain. To effectively implement a new strengthening and stretching exercise program for manual wheelchair users, customization of the program to suit the unique needs of each individual is necessary. This is particularly important with regard to the amount of resistance, the number of sets and repetitions, rest time, and modification of mechanics. This could be achieved by developing a standardized set of exercises from which a therapist selects the exercises appropriate to a specific individual. For example, in the studies by Mulroy et al13 and Nash et al,14 each participant was given a different level of resistance to utilize in strengthening exercises based on initial evaluation of individual repetition maximum. In Nawoczenski et al,15 follow-up visits with a physical therapist after initiation of the exercise program were used to ensure correct form and progress resistance, intensity, and duration for each participant. These 3 studies demonstrated the highest WUSPI change scores.13–15 In addition, Van Straaten et al17 provided modifications in position, resistance (isometric vs isotonic), and the number of repetitions; exercises were then advanced through videoconference feedback throughout the intervention time frame. This highlights the importance of and need for further research for evaluating baseline exercise capabilities in manual wheelchair users with SCI, identifying the most critical individual exercises for improvement of shoulder pain, and tailoring exercise programs specifically to suit individual needs and prevent pain exacerbation.
Limitations of the Review
Our systematic review is not without limitations. We excluded non-English language publications, so there may be informative studies that we did not identify. Our selection of the WUSPI as the primary outcome of interest may have decreased our opportunity to identify other relevant research related to the management and treatment of shoulder pain that did not use the WUSPI. We only considered studies that used exercise programs as an intervention of interest, but there are other interventions such as wheelchair propulsion and positioning strategies, acupuncture, and surgical options that may play a role in the treatment of wheelchair-associated shoulder pain among individuals with SCI.
Additional limitations to this review include small sample sizes of the primary studies; a limited number of eligible studies; a heterogenous mix of study designs and differences in reporting raw data, change scores, and statistical significance of outcomes. Baseline pain scores of participants varied across the eligible studies, which may have influenced the relative degree of pain reduction that could be achieved. For example, in Curtis et al,3 the presence of pain was not an inclusion criterion and only 50% of the participants had shoulder pain at the start of the study. Furthermore, Nawoczenski et al15 had an asymptomatic control group while the treatment group had levels of shoulder pain at baseline that were in the low to moderate severity range. Another limitation pertains to study participants: 3 articles included some participants who did not have SCI but had a different reason for using a manual wheelchair, these included 2 participants with amputation, 2 participants with cerebral palsy, 3 participants with postpolio syndrome, 1 participant with multiple sclerosis, and 1 participant with spina bifida.3,15,17
Of the studies that included only participants with SCI, the participants had various levels of injury. Within 1 study some participants may have had full innervation and use of the upper extremities while other participants did not. The prevalence and intensity of shoulder pain with performance of functional activities are significantly higher in those with tetraplegia than in those with paraplegia, and the report of bilateral shoulder pain is higher in those with tetraplegia as well.20,21 This is to be expected, considering the greater involvement of the upper extremities in those with tetraplegia. The pathology underlying shoulder pain is likely to be different among persons with paraplegia and persons with tetraplegia, considering the impairments of muscle balance caused by paralysis, decreased range of motion, and spasticity present in those with tetraplegia. In the study by Silfverskiold and Waters,21 more than 75% of persons with tetraplegia had shoulder pain in the first 6 months after SCI. In addition, in participants with shoulder pain that was initially associated with spasticity, the pain persisted at the time of follow-up.21 In 3 studies, the PC-WUSPI was used in an attempt to correct for activities that participants could not perform because of level of injury3,12,15; however, it is a limitation of our review that we were unable to compare differences among participants with paraplegia versus participants with tetraplegia.
It has been reported that subjects with tetraplegia also decrease their performance of functional activities with advancement of age resulting in functional disability.20 Performance of activities that provoke pain results in less frequent performance of those activities. This may account for differences in PC-WUSPI scores reported with advancing age, a time when a greater duration of wheelchair use and exacerbation of shoulder pain and dysfunction is more likely to occur, resulting in less frequent performance of activities that provoke pain.20 While both people with paraplegia and those with tetraplegia seem likely to benefit from a strengthening and stretching program, ability to perform some of the exercises may be limited in persons with tetraplegia. It is unclear whether both SCI groups would have the same response to an exercise program.
Finally, the methodological quality of the studies available for review varied greatly. The current paucity of high-quality randomized controlled trials and the lack of consistency in reporting outcomes across studies preclude meta-analysis to calculated pooled effect sizes. Study participants demonstrated variability in improved pain ratings, which makes it difficult to determine magnitude of response to intervention. Regarding long-term outcomes, none of the included articles provided more than 6-month intervention3 or more than 6-month follow-up,12,17 which makes it difficult to predict effectiveness of interventions beyond this time frame. Many unanswered questions remain to be considered in future clinical trials.
Current literature supports the use of various exercise programs to reduce shoulder pain and increase daily function over time in manual wheelchair users with SCI, with the caveat that the existing literature reports on findings from exercise programs that differ across published studies. The studies included in this review support the effectiveness of various therapeutic interventions on the management and treatment of shoulder pain, as demonstrated by a clinically meaningful reduction in self-reported WUSPI scores. Exercise is a feasible, conservative, and therapeutic intervention for the treatment of shoulder pain in our population of interest. Additional high-quality studies are needed to further evaluate and differentiate techniques for the reduction of shoulder pain. Further studies should also focus on determining the most efficient and effective time frame of intervention with the potential to develop a standardized set of exercises for initial consideration that can be customized to specific needs of the individual wheelchair user.
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