Generic measures apply to a variety of disease and treatment groups and seek to evaluate multidimensional aspects of health-related function [4]. Originally described by Ware in 1992 to survey health status in the Medical Outcomes Study (MOS) [5], the Medical Outcomes Short Form-36 (SF-36) is the most well known and widely used of these generic outcomes tools. The SF-36 is a 36-item self-administered questionnaire that explores physical and mental health through eight health concepts or domains. These domains include physical functioning, social functioning, general health, mental health, role emotional, role physical, bodily pain, and vitality. From the SF-36 two summary scores can be measured: a physical composite summary score (PCS) and a mental composite summary score (MCS). Using norm-based scoring, all domain scales have a mean of 50 and a standard deviation of 10 based on the general 1998 US population [5]. The SF-36 has been found to be a valid and reliable measure in different disease states, including patients with low back pain [6, 7]. In contrast to other surveys, the SF-36 presents a considerable respondent burden. There are shorter versions available, such as the SF-12 [8] and SF-8 [9], but all items must be answered in order to calculate the PCS and MCS. In addition, the shorter versions do not provide scores across the eight health domains. Lastly, the SF-36, SF-12, and SF-8 require a license to administer and cannot be easily scored in clinic.

Although generic measures translate the effects of treatments across multiple diseases and populations into a numerical value, they do have some limitations. A major disadvantage is that they can miss important components of health evaluation as related to specific diseases or treatments.

Disease-specific measures focus on the effects on HRQOL associated with a specific medical condition. Therefore, these disease-specific measures are more likely to detect the effects of a specific intervention on a disease process. The Oswestry Disability Index (ODI) [10, 11], Roland-Morris Disability Questionnaire (RMDQ) [12], Neck Disability Index (NDI) [13], and Scoliosis Research Society-22R (SRS-22R) [14–17] are examples of spine-specific measures.

The ODI is a self-administered survey measuring “low back-specific function” on a ten-item scale with six response categories each [10, 11, 18]. Each item is scored from 0 to 5 and then transformed into a 0–100-point scale with the higher the score signifying a greater disability experienced by the patient. Patients scoring between 0 and 20 have minimal disability, between 21 and 40 have moderate disability, between 41 and 60 have severe disability, between 61 and 80 are crippled, and between 81 and 100 are bed-bound or exaggerating their symptoms. Relative to RMDQ, it has less of a floor effect and is better used in populations with more severe disability [12]. ODI can be easily administered, scored, and interpreted in the clinic. This allows it to help guide treatment decisions.

The RMDQ is a measure of function and daily activity limitations. There are 12 items answerable by yes or no, giving a score ranging from 0 to 24. A higher score reflects greater disability. Relative to ODI, it has less of a ceiling effect and is better used in evaluating populations with lesser disability [12, 19].

The NDI is a ten-item self-administered survey measuring disability in patients with neck pain. Each item is scored from 0 to 5 for a maximum score of 50 [13]. Similar to ODI and RMDQ, a higher score is associated with a greater disability. Some authors may use a percentage score when one section is missed or is not applicable to what is studied, in which case the range of scores would be from 0 to 100 %.

The SRS-22R is a 22-item questionnaire with five domains, including self-image, pain, activity, mental, and satisfaction, measuring disability specific to scoliosis patients [14, 16, 17]. Each domain is scored from 1 to 5, with higher scores indicating improved outcomes. For patients with either adolescent idiopathic scoliosis or adult spinal deformity, the SRS-22R is the most widely used outcome instrument to measure disease burden and the effect of treatment [20–22].

The visual analogue scale (VAS) [23–26] and numeric rating scales [27, 28] are commonly used pain scales in which the patient subjectively interprets the pain experience and assigns a value to the measurement scale. The VAS is a 100-mm-long horizontal line anchored on the left with “no pain” and on the right with “worst pain experience.” Patients mark on the line the point that they feel best represents their current level of pain. The score is determined by measuring in millimeters from the left-hand side of the line to the point that the patient marks. Numeric rating scales are a variant of the VAS and ask patients to rate their pain levels using numeric values, such as from 0 being no pain at all to 10 being the worst pain imaginable [27]. Advantages of pain scales include a low respondent burden, ease of administration, and a universally accepted tool. Limitations include the difficulty in interpreting objectively the subjective nature of the measurement. Pain scales are also difficult to translate when patients’ pain is in flux and changes depending on the time of day, level of activity, or other extrinsic factors.