A narrative review and content analysis of functional and quality of life measures used to evaluate the outcome after TSA: an ICF linking application

The high prevalence of shoulder pain (7–21%) in the general population results in high, and increasing, levels of disability and health-care costs [1, 2]. Glenohumeral arthritis is the primary cause of shoulder pain and dysfunction in an aging population [1]. Psychological issues such as depression, anxiety, and decreased quality of life (QoL) are associated with chronic musculoskeletal pain [1‐4]. The combined physical and psychosocial impacts of shoulder pain are complex and contribute to lower quality of life [2].

Total shoulder arthroplasty (TSA) is reconstructive surgeries that can provide pain relief and restore function in severely damaged arthritic shoulders [5‐8]. Such treatments have a predictable outcome for patients with joint destruction arising from pathologies such as osteoarthritis, rheumatoid arthritisand proximal humeral head fracture [8‐10]. Previous studies indicated significant improvement of both psychological status and health-related quality of life (HRQoL) by 3-months after surgery [2, 11]. However, implant issues, such as loosened glenoid components can lead to poorer outcomes over the longer-term [3, 7]. While improvement can be expected, normal function cannot be restored and the outcome achieved is variable and dependent on many factors including different surgical indications, soft tissue recovery, subscapularis integrity, and post-operative rehabilitation [5, 12].

To evaluate surgery outcomes, many clinicians and researchers are aware of the importance of measuring pain, functional outcomes, biopsychological health, QoL, and HRQoL [13]. Since the 1990s, numerous patient-reported outcome measures (PROMs) have been developed and validated to assess outcomes in shoulder conditions [14‐16]. Researchers have established acceptable levels of reliability, validity, and responsiveness of PROMs such as the American Shoulder and Elbow Society score (ASES) and the Simple Shoulder Test (SST), and synthesized the evidence of psychometric properties in a systematic way [7, 13, 17, 18].

Content validity is a fundamental property of PROM, but relatively unintended to in the literature. Although standard definitions exist for functioning, disability, and health (FDH), rather than HRQoL or QoL [19‐21], there is overlap in these concepts and insufficient precision by developers and users with respect to these terms [20]. The absence of a theoretical framework or conceptual definition leads to difficulty of interpreting study results using different outcome measures, since it can be unclear which domains of health are affected by the intervention, and whether differences in outcomes relate to the intervention or the measure [5]. Since few developers provide clear definitions of their latent constructs or how items were mapped to these constructs it is important to do a retrospective evaluation to inform content validation and understand differences in constructs evaluated by commonly used measures.

The World Health Organization (WHO) definitions provided in the International Classification of Functioning, Disability and Health (ICF) and the manual of WHO-Quality of Life brief version (WHOQOL-BREF) [21‐24] provided internationally used frameworks, definitions and coding language to describe the impact of health conditions on function, disability and health [21]. With the ICF framework, the concept of FDH refers to the biopsychosocial components and interactions among body structures and function, and activities and participation in the context of the environment and personal factors [25‐28]. The QoL is defined by WHO as “a person’s perception of their position in life affected by the culture and value system in which they live and in relation to goals, expectations, standards, and concerns [21, 23].”

However, the terminology HRQoL, remains variably defined by different sources [20]. In HRQoL is specific focus on how QoL is influenced by a health condition [20, 23]. While culture, politics and economic context also affect QoL, those influences are generally not addressed in HRQoL measures or health-related PROM [20]. See Table 1 for orgnizations of the concepts for FDH, QoL, and HRQoL.

Using the ICF framework, researchers can evaluate individual items of content, by a standardized coding, or “linking” procedure [29, 30]. According to the ICF linking rules, a second level codes start with the letters b, s, d and representing the classification of body function and structure, activity, participation, environmental factors and personal factors followed by a numeric code for the chapter number (one digit) and another two digits as the second level [29]. The linking process is a universal language that can be used to define the content of items and describe their meaningful contructs [26]. A systematic review conducted in 2013 evaluated the content of 475 shoulder related outcome measures by linking invidual items to ICF codes [18]. This work provided some evidence on content validity of shoulder PROM. We are building on this work by focusing on shoulder arthroplasty to understand the use of PROM in this area of practice, providing an updated assessment of PROM usage, and classifying the conceptual framework according to standard definitions.

The objective of the current study was to analyze the classification and content of functional and quality of life measures used to evaluate the outcome after TSA using the ICF framework by (1) identifying the PROMs used for patients after TSA; (2) mapping the content of the individual items using second level ICF codes; (3) summarizing the focus of these PROMs based on ICF domains; and (4) providing an updated assessment of PROM usage and summarizing the predominant application of included PROMs based on ICF linking and pre-defined concepts of FDH, HRQoL, and QoL.

This study found variation between commonly used PROM used to assess the outcomes of TSA in terms of their overall latent construct and the item level content, although most were more focused on activity and participation than patients perceptions of body structure and function. Overall, the content covered by the PROM included 10 s level ICF codes under the domain of body functions and structures, and 23 codes belong to activities and participation. This is consistent with the fact that PROMs focus on the patient be experience and uniquely able to assess how a person functions in their own life; whereas impairments in body structure and function can be better measured with clinical tests. Only two categories under Environmental factors were mentioned. Other content analysis of PROMs has noted a similar lack of attention to the environment [18]. Even where environment is not explicitly addressed, we expect it to be an important factor in disability that may partially explain why patients with similar impairments experiences different disability.

Pain is a primary concern for patients with TSA surgery [6]. This is consistent with that one category the sensation of pain (b280), was ranked as the most frequently used code. Although pain is considered an impairment in ICF, it also a subjective experience and as such typically captured by PROM. The second most linked code under body function domain was muscle power function (b730), which belongs to the impairment domain under the ICF framework. Strength can be assessed by clinicians using dynamometers or other devices; or can be self-reported by patients. Typically, we expect that PROM would focus on functional items and that pain, motion and strength might all interfere with functional performance. However, some PROMs do ask questions that specifically target muscle strength. Generally, these questions must be fairly generic rather than target specific muscle groups as might be assessed by dynamometers For example, questions from SST that ask participants to rate the difficulty of lifting task with three pre-defined weight levels ranging from one lb. to 20 lbs., assess strength, but do not identify particular muscle groups or adaptations.

Activity was the predominant ICF domain, accounting for 41% of the items [21, 28]. Hand and arm use and lifting and carrying objects are the most commonly linked ICF codes under the activity domain. This suggests a consistent recognition of the importance of these tasks in patients with shoulder arthritis, requiring TSA. However, on the other hand, the ICF categories related to mental function such as sleep function, emotional function, and energy and drive were infrequently linked suggesting less agreement that these are central to TSA outcomes. Given the importance of psychological health [18, 35] in post-surgical patients, one might consider this as under-representation, especially if the instrument is intended to measure QoL. However, outcome instrument developers often try to focus on a clear construct, and it would be the responsibility of researchers to include measures of physical health and psychologic health within their studies, since summing different construct together may not always be appropriate. Further, developers may consider psychological factors as mediators of outcomes rather than the outcomes themselves. Ideally, developers would be explicitly explaining these conceptual assumptions.

Recreation and leisure (d920) and Remunerative employment (d850) were ranked as third and fourth order among all the linked items. This high ranking is consistent with a previous systematic review focusing PROMs of shoulder pain and functioning [18]. Most PROMs such as ASES, DASH, and Oxford Shoulder Scale (OSS) imply these concepts by formulating questions as leisure activities and usual work. Overall, these items and others that fit within participation comprise 24% of the total items. The concept of participation defined by the ICF framework is subject to qualifiers that describe what a person does in their usual life. That means subjects’ response to such questions might be modified by the usual roles or environmental factors, but these are not directly measured.

According to the WHO, different PROMs used for patients after TSA share areas of content and purposes of application. The single item measure SANE, and SSV, that investigate to what extent a patient would rate their shoulder as being normal, was classified as HRQoL perspective since it address a global evaluation, whereas researchers and clinicians commonly use it as a functional outcome since it assumed to be rating physical function on a scale of 0–100% [36]. A previous study found that patients have a lot of confusion about what is being calibrated when responding to this questions, which reflect the ambiguity in its definition [37]. It is important to have a conceptual distinction between measures designed to assess HRQoL which is intended to be comprehensive, versus those designed to measure physical functioning which a smaller construct that might affect QoL. The confusion we found in conceptual clarity and content of items across many of these measures emphasizes the importance for instrument developers to define their conceptual framework so that users of outcome measures can match the measurement purpose is to a specific conceptual framework.

Patients satisfaction is important, but often variably measured in health research. Satisfaction with care is a process measure; whereas as satisfaction with health/shoulder status can be considered as an HRQoL measure. However, by asking about the satisfaction with surgery and care, this scale mixes evaluation of the process of care or Quality of Care [34], with outcome evaluation. Researchers and clinicians should be more explicit about whether they are measuring process or outcome satisfaction; and ensuring their selected measure reflects that choice.

A key issue in the literature was the vague and imprecise terminology used to for different outcome measures and the definition of the FDH, QoL, and HRQoL. For researchers, clearly defined concepts within PROMs help them detect the most appropriate and precise latent construct. For clinicians, in both research and daily practice work, appropriate selection of the outcomes measures is not only depend on the psychometric properties and intention of the application, but also on the precise understanding of the content informed by an unified conceptual framework [25]. Developers rarely provide a strong conceptual framework, and users rarely state their measurement rationale or the content validity of the tools they selected for the constructs of interest. Rather justification of PROMs within studies tend to focus on psychometric properties like reliability, which do not reflect content validity. Some measures mix different constructs. For example, The DASH provides a comprehensive set of items and is defined an as FDH instrument but contains items that fall within a HRQoL construct. Terms are often used incorrectly, for example health status measures and functional measures are often referred to as QoL measures. The use of terms like clinical outcome measures or functional outcomes happens without clear distinction about what these terms mean [11, 38]. The conceptual analysis performed in the current study may help resolve the issue by precisely categorizing the retrieved PROMs into three types as: (1) FDH (the capacity, performance, presence / absence, frequency, severity, or other biopsychosocial domains), (2) HRQoL (the expectations, standards, or concerns about individual health), and (3) QoL (the patient’s personal assessment of their position in life). Mapping the ICF domains within PROM can help researchers and clinicians to select the most appropriate PROMs for their context (and research question). That is considering the impacts of shoulder joint destruction (or indications for TSA) and expected impacts of TSA (outcomes) should drive the PROM that have the best conceptual match. Further, this can identify when important constructs are missing, and supplemental measures might be needed. This would complement, not replace, considering important psychometric properties like reliability and responsiveness.

TSA outcomes measures should be developed under a clear conceptual framework. Many of the consensus panels that attempt to achieve consensus on outcome measurement start with defining the core constructs that should be measured for a given health problem, and then choose the best measure within those constructs [25, 33, 39]. Our findings could support such a process. A better understanding of the latent construct evaluated within PROM is essential to enables clinicians and researchers to make valid conclusions. For those validated PROMs, clinician should also be cautious to use them in different conditions such as other language versions. The cross-cultural adaption might not be able to ensure the content validity with the consideration of the various culture background, healthcare systems.

We found confusion in conceptual definitions on PROMs, and wide variation in PROM content and use. Despite the variability there were some common constructs evident in measurement of pain, hand and arm use, recreational activities work and employment, lifting and carrying. Mental function components such as emotional function, and energy and drive were rarely covered reflecting the focus on physical recovery following TSA. Users evaluated in these constructs may require supplemental PROM. Efforts to the consensus on the key constructs that should be measured following TSA are needed.