Disability Trajectories in Patients With Complaints of Arm, Neck, and Shoulder (CANS) in Primary Care: Prospective Cohort Study

Main Results

To our knowledge, this is the first prospective cohort study of patients in primary care with a new episode of CANS in which disability trajectories were analyzed over a 2-year period, together with their prognostic indicators. This cohort can be regarded as representative for Dutch patients with CANS because the numbers of participating practices and GPs were large enough to account for possible local variations in patient groups, the initial response to participate was very high, and relatively low nonresponse rates at follow-up were observed. There were no indications that patients with CANS in the southwest region of the Netherlands differ much from those of other regions.

Three disability trajectories were differentiated: fast recovery (67.6%), modest recovery (23.6%), and continuous high disability (8.8%). The proportion of patients with DASH scores comparable to those of the normal population (<11)^49,50 increased from 44% at 6-month follow-up to 58% at 2-year follow-up. A slightly higher proportion (54%–62%) indicated complete recovery or much improvement at all follow-up measurements. However, only 43% of the patients indicated absence of complaints at 2-year follow-up.

The fast recovery trajectory represents the majority of patients who had an improved outcome at 2-year follow-up (most already at 6 months after baseline); in this group, the number of recurrences was low. The modest recovery trajectory consists of patients with persisting disability at a lower level compared with baseline, as well as patients with relapses and recurrent disabilities after initial improvement. This conclusion is supported by the fact that, at all follow-up measurements, the proportion of patients without complete recovery or much improvement (46%–38%) or a normal level of disability (56%–42%) was considerably higher than the proportion of patients in the high disability trajectory (8.8%). Therefore, many of these patients must be in the modest recovery trajectory.

We present several demographical, complaint-related, physical, and psychosocial characteristics that have predictive value for the high disability and modest recovery trajectories. These characteristics can be identified using screening methods that capture information obtained through patient history and administering validated measures, such as the 4DSQ and Tampa scale. This approach implies the feasibility for clinicians to differentiate subgroups of patients within the larger group with nonspecific complaints who might have a different prognosis based on appropriate adaptation of therapeutic management focusing on the identified predictors. This option for differentiation is especially relevant for physical therapists because the GPs referred 63% of all patients to physical therapists during the 2-year follow-up. However, the exact performance of these predictive variables in this subgroup still has to be studied.

Limitations

The present study had some limitations. First, at the different follow-up measurements, loss to follow-up ranged from 10% to 22% of the cohort, and no follow-up data were available for 5% of the initial cohort. Nevertheless, for a follow-up study with a large initial cohort, these data are very acceptable.⁵¹ Furthermore, the LCGM analysis provides estimates for missing data during follow-up, and the nonresponse analysis yielded only small differences. Overall, of the prognostic indicators present in the final models, the responders are slightly less likely to be of older age or male.

Second, a patient-reported outcome measure (DASH) was used to assess disabilities, and no physical tests were performed. However, the DASH is a widely used and well-validated measure for CANS, both in total and at specific body regions.^31,33,49

Third, the GPs' diagnosis at the first consultation was used to differentiate between specific CANS (59%) and nonspecific CANS (41%). However, as the CANS model had not yet been published and no classification criteria were available at that time, some misclassification may have occurred. In our analysis, a specific diagnosis is not associated with any trajectory. However, optimal classification may slightly alter this association.

Fourth, some predictor variables were assessed with measures or questions with limited or unknown validity, such as history of trauma of neck or upper extremity, musculoskeletal or nonmusculoskeletal comorbidity, health locus of control, social support, and catastrophizing. This limitation might have influenced their association with the disability trajectories.

Fifth, the presented model has less explained variance (0.544) than a full model including all variables of Table 3 (0.574) or a model resulting from using a backward step procedure with P<.157 (0.552). In the latter model, the only difference is the inclusion of the not significantly associated variable of region with most complaints. A more parsimonious model including half the number of prognostic indicators would explain already 46% of the variance.

Finally, although LCGM is a well-established method to analyze distinct trajectories, the decision regarding the optimal number of classes and the use of a model with pooled or fixed variance remains to some extent arbitrary⁵²; however, the number of cases and allocation to the respective trajectories proved to be good. The advantage of LCGM is that the course of CANS can be examined over time; moreover, especially the category of patients with continuous high disability can be identified, resulting in an analysis of the prognostic indicators for this specific trajectory.

Prognostic Indicators Compared With Other Studies

The present study is unique in its description of disability trajectories for the whole group of patients with CANS and the analysis of prognostic indicators of disability. All other studies reviewed used a single endpoint of recovery after one specific follow-up period (generally between 6 months and 5 years). Also, most earlier studies investigated only one region, mostly the neck or shoulder (eTab. 6).

With regard to psychosocial characteristics, somatization was identified as an important prognostic indicator for continuous high disability, as also described for the CANS cohort in a physical therapy setting.^14–16 Only one other primary care study¹⁸ also looked at the predictive value of somatization in shoulder disorders but showed no association with persistent shoulder symptoms (46% of the initial group at 6-month follow-up, although there was an association in their univariate analysis). Our results show a significant association of somatization with the high disability trajectory and a trend of association with modest recovery. Earlier, in both CANS cohorts, an association of “high catastrophizing” and “high kinesiophobia” with unfavorable outcome was shown at some follow-up measurements, especially in nonspecific disorders.^13–15 This association was confirmed in the present study. Previously, an association with catastrophizing was found in relation to recovery of chronic shoulder complaints¹⁹ and neck complaints.¹⁶ With regard to kinesiophobia, earlier studies showed no association with recovery in patients with neck complaints^16,53,54 or shoulder complaints.¹⁸ In our cohort, we also identified low social support as a prognostic indicator for both trajectories with worse outcome, whereas other authors found no such association.^14–16,54 The variable of distress was investigated in both CANS cohorts (and a subgroup with neck pain) and in several cohorts with shoulder disorders; however, no association with outcome was observed.^16–18 Also, in both CANS cohorts, no association with general mental limitations or low health locus of control was found.^12,14,15

With regard to physical characteristics, our study shows that musculoskeletal comorbidity is an important prognostic indicator, which is in line with other studies.^{17,18,53,55,56} Poor self-perceived general health is consistently related to unfavorable outcome.^53,55 A history of trauma or injury in the region of complaints was associated with unfavorable outcome in some studies^53,55 and in our study, but not in other studies.^14–16,57 Depending on the interpretation of “trauma” or “injury” and the formulation of the question, preceding trauma can be indicated occasionally by respondents who experience (for instance) bumping, pulling, or arm strain. However, such a history is difficult to link to the complaints under study when patients with diagnoses indicating a traumatic cause (eg, contusion, distortion, whiplash) have been excluded. For nonmusculoskeletal comorbidity, the evidence is inconclusive; however, there is much variation in the applied definitions. Also, evidence for an association of physical limitations at baseline with unfavorable outcome is inconclusive. In the present study, because the outcome of interest was disability, the baseline value was not included in the analysis.

Within the group of complaint characteristics, >3 months complaint duration at baseline was identified as a prognostic indicator, which is similar to other studies.^{15–18,20,55,56,58} Furthermore, we identified complaints that are widespread over the arm-neck-shoulder region as a prognostic indicator. However, the main location of the complaints or having a specific diagnosis was not associated with any disability trajectory; this finding is similar to the earlier CANS cohort.^14,15 In the present study (and in other studies^17–20,55), high complaint severity or pain intensity at baseline was associated with unfavorable outcome. However, this association was not present at 6-month follow-up in our cohort, at 2-year follow-up in the earlier CANS cohort,^12,15 or in 3 studies on neck complaints.^16,53,56 For recurrent complaints as a possible prognostic indicator, the evidence is inconsistent. In the present study, we found no association with any disability trajectory.

Examining the demographical and participation characteristics revealed that female sex and low educational level were associated with both disability trajectories. Older age was associated with only the modest recovery trajectory; however, the associations with both disability trajectories might be underestimated due to the fact that nonresponse was higher among older people. Although results for these variables vary among different studies, the absence of an association is consistent for shoulder disorders.^17–20 Regarding sports participation, no association with any disability trajectory or recovery was present in the 2 CANS cohorts. This finding confirms the results of other studies in which physical exercise or activity at baseline was included as a possible prognostic indicator.^{14,15,18,19,55}

With regard to unemployment, we previously found an association with nonrecovery at 6 months follow-up.¹² However, in the present study, a relationship between unemployment and both disability trajectories was found only in the univariate analysis. In other studies in which unemployment was included as a possible prognostic indicator, no association was found with unfavorable outcome.^{14,15,20,53,55,58}

In conclusion, this study revealed 3 trajectories that describe the course of disabilities due to CANS over a 2-year follow-up: fast recovery, modest recovery, and continuous high disability. We identified several sociodemographic, complaint-related, physical, and psychosocial prognostic indicators that can easily be recognized in a primary care setting. It is important to identify patients at risk for continuous high disability at an early disease stage. Some prognostic indicators related to this particular outcome may be amenable for change (eg, the psychosocial factors of somatization, kinesiophobia, and catastrophizing and the physical factors of poor general health and musculoskeletal comorbidity). Thus, in view of the considerable numbers of patients following a trajectory of chronic disabilities in CANS, establishing a clear prognosis can be valuable to mitigate this course. We recommend checking the indicators identified in this study at an early stage of CANS before giving advice about treatment options. The presence of these indicators may lead to a decision for more intensive or additional interventions. For psychosocial indicators, the involvement of a psychosomatic physical therapist or psychologist or a multidisciplinary approach can be considered, and, for physical indicators, more intensive therapy may be appropriate. A similar management approach in patients with nonspecific low back pain, using a screening method to identify patients at high risk for persistent disability and providing psychologically informed physical therapy, has already shown to have promising effects compared with usual management by physical therapists.^59–61 Further research focusing on the use of these prognostic indicators in treatment decision making is needed to further substantiate their predictive value and may result in a screening tool that can be applied in patients with CANS.