Complex regional pain syndrome (CRPS) is a persistent, painful, and disabling condition that usually manifests in response to acute trauma or surgery [1]. It is a multifactorial condition with a complex cause and with a challenging diagnosis as the signs and symptoms vary over time, resulting in severe pain and disability [2]. Incidence rates from 5.46 to 26.2 per 100,000 person-years have been reported, however they were variable and dependent upon the different diagnostic criteria used in the studies [3,4]. Two types of CRPS exist: CRPS type I occurs without a nerve lesion and CRPS type II has a detectable nerve lesion. It is even more challenging to diagnose CRPS type I which is not accompanied by any peripheral neuropathy [5]. Likewise, although a debate regarding the diagnosis of CRPS still exists, adiagnosis of CRPS is made based on clinical examination and by using the “Budapest” diagnostic criteria, which were approved by the International Association for the Study of Pain [6].

CRPS has a significant impact on the activity of daily living (ADL) and the quality of life (QoL) of patients due to intractable chronic pain. In particular, chronic CRPS is a challenging and complex bio-psychosocial condition which requires a comprehensive and multidisciplinary approach from direct pain management to physical and psychosocial rehabilitation [7]. Therefore, different types of interventions should be applied together and they could include appropriate medication, invasive therapies, as well as continuous rehabilitation (physical therapy and occupational therapy) [8-14].

A lot of research on the multifactorial origin and maintenance of CRPS are underway and they include studies on new or existing agents that target the different mechanisms of action. Various medications are being explored, including but not limited to steroids, non-steroid antiinflammatory drugs, bisphosphonate, calcitonin, N-methyl-d-aspartate receptor antagonist, as well as immunomodulation therapy and botulinum toxin A [15]. Nevertheless, CRPS is still difficult to treat and it usually evolves into a chronic disease. One of the causes for this progression may be related to the lack of adequate physical and occupational treatment that should be included as a first-line of treatment for CPRS patients [16].

Rehabilitative interventions for CRPS mainly consist of several types of physical and occupational therapy targeted at decreasing pain and edema, increasing range of motion (ROM), promoting normal sensitization, and maximizing limb or body function [12]. Rehabilitative treatments that are aimed at improving limb function and desensitization to pain are a crucial part of CRPS management. However, patients do not receive appropriate or sufficient rehabilitation treatments consistently, despite their needs. Unmet needs are defined as the gap between the needs of patients and the actual receipt of services [17]. Unmet needs for rehabilitative treatments and potential barriers to treatment access should be assessed in patients with CRPS, but their rehabilitation needs have rarely been investigated [18]. A previous qualitative study reported that a lack of access to accurate information was a major unmet need in patients with CRPS [19]. In Korea, rehabilitative treatment is not provided appropriately to patients with CRPS due to a lack of awareness of rehabilitation options available for both patients and healthcare professionals. Although physical and occupational therapy should be considered as the first-line treatment for every CRPS patient, comprehensive rehabilitation therapy is not being applied widely in clinical settings [16]. While rehabilitation for other disabilities is being well developed comparatively, institutional and policy limitations do not allow appropriate rehabilitation services for chronic pain.

Therefore, this study aimed to evaluate the current status of pain severity, pain-related disability and QoL in patients with CRPS in Korea, and to assess both their perceived needs and unmet needs for rehabilitation services.

This study describes the current status of pain severity, QoL and its relationship with disease symptoms, and both the subjective needs and unmet needs for rehabilitation services of 47 patients with CRPS. CRPS symptoms were found to interfere significantly with patients’ life, daily functioning, and QoL.

The QoL of CRPS patients was shown to deteriorate more when compared with other populations with activity limitations reported in previous studies [28,30]. The average EQ-5D-5L index and WHODAS-II values were 0.39 and 70.49, respectively, in this study; however, the EQ-5D-5L index measured in another study to compare treatment effects in 56 CRPS patients was 0.53 or 0.47 before treatment [31]. In one study evaluating the QoL of Korean polio survivors, the EQ-5D-5L index was 0.68 [28]. The other study of evaluating QoL in patients with traumatic brain injury (TBI) and spinal cord injury (SCI) in Thailand, WHODAS-II overall score was 66.38 for TBI patients and 52.00 for SCI patients [30]. CRPS patients in our study had the lowest level of QoL when compared to CRPS patients from other countries and other patients with severe disability. As a result, a more comprehensive and improved rehabilitation treatment approach would be necessary to further improve QoL and recovering function of patients living with CRPS. Nonetheless, although rehabilitation treatment is strongly recommended to CRPS patients, current rehabilitation specialists mainly provide only pain management therapy, instead of a coordinated multidimensional program for these patients to learn to cope with their various other symptoms and disabilities [32] (Fig. 1). Various approaches to physical and occupational therapy have been considered as key components in the management of CRPS [2,9]. Usual physical therapy has been shown to help overcome pain and pain-related symptoms such as kinesiophobia, and it improves functional use of the limb. Examples include ROM exercises, contrast baths, functional electrical stimulation, massage, and isometric strengthening exercises to overcome pain. Occupational therapy to increase the use of the affected limb in ADL, along with mirror therapy and applying garments for reducing edema or sensory overload have also been administrated [8].

The unmet needs of rehabilitation treatments in CRPS patients were 48.07% overall, although there was a difference in each item. Considering that the unmet need for pain is as low as 17.78%, unmet needs for other problems are quite high (32.43%–83.33%). Currently, it is difficult to compare directly unmet needs with other studies because there have been no studies reporting the unmet needs of rehabilitation services in CRPS patients as far as we know. However, a study conducted in Denmark reported about 20% of unmet needs in cancer rehabilitation [33]. The unmet needs for medical services of SCI patients in Korea were reported as 24.8% [27]. Compared to these studies, our study reported that the unmet needs of CRPS patients in Korea are higher than those of patients with other diseases.

In Korea, even CRPS patients who did receive rehabilitation treatment were found to have low satisfaction of said treatment. Satisfaction with treatment was 53.30% overall, though variable according to each domain (28.57%–73.33%). Regarding the rehabilitation treatment for pain, which is characterized by relatively low unmet needs, satisfaction was still low (40.54%). When investigating what treatment was given to CRPS patients, most were pain-related medications or procedures. Patients with CRPS have complex combined physical, psychological, behavioral, and emotional disabilities. CRPS rehabilitation is a process supported by therapists, family members, and carers to achieve patients’ maximum potential for each domain [32]. However, CRPS treatments in Korea have focused mainly on managing pain and pain-related symptoms. Some therapists are not aware of “learned disuse” (marked disability developed as a means of avoiding pain) and its management, and they focus only on pain treatments. Our study also reported that the unmet needs in several other domains are quite high. The unmet need for pain is only 17.78%, which is the lowest, but no satisfactory improvement is seen through treatment thereof, resulting in poor satisfaction.

Characteristically, the unmet needs of weight management and memory impairment were high at 72.0% and 83.3%, respectively. In contrast, satisfaction showed opposite results; weight management 28.57%, memory impairment 60.00%. There may be several reasons for weight gain, but we surmise that limitations on activity resulted in an increase in body weight. In the domain of memory impairment, excessive use of analgesics is thought to adversely affect cognitive performance [34]. In the case of satisfaction, result interpretation is limited because a very small number of the patients actually received the treatment in respective domain (weight management=7; memory impairment=5). In this study, the absence of objective figures for weight changes and memory impairment also make result interpretation difficult. Future studies should further evaluate weight-related problems and cognitive performance of CRPS patients using specific evaluation tools.

Regression analysis was performed to clarify factors affecting unmet needs and QoL in CRPS patients. All other factors, including demographic factors, were not correlated. Only the BPI average score influenced QoL (EQ-5D-5L). Thus, pain control was found to be important as related to QoL of CRPS patients. Most rehabilitation treatments and efforts aim to control patients’ pain, but satisfaction is low as confirmed in this study (40.54%). The reasons for low satisfaction should be further investigated, and we should attempt to find and apply effective treatment methods. For example, graded motor imaginary therapy has been highlighted as a mechanismbased approach for the treatment of CRPS [35]. In a recent systematic review, graded motor imaginary therapy and mirror therapy may provide clinically meaningful improvements in patients with CRPS, although the quality of the supporting evidence is very low [9]. The logistic regression analysis to find the causes of the unmet needs suggests that only “education level” affects the unmet need of “decreased physical performance”. Reasons for unmet needs for rehabilitation are multi-dimensional and complex. Many studies indicate that barriers to accessing medical services, educational levels, and household income were essential determinants of unmet needs [27,28,36]. Our research also supports that lower educational attainment increases the unmet need of a health care system. Educational level affects those with lower socio-economic status more, and this implies that individuals with lower educational levels have more barriers to overcome to access medical systems [29,37].