Research in spinal surgery: Evaluation and practice of evidence-based medicine

Table 1 Types of study design

Design type	Advantages	Disadvantages
Case series	Suitable for rare diseases or new treatments	No comparison group
		Retrospective nature
Case control	Small sample size	Presence of confounding
	Short duration	Retrospective nature
Cohort studies	Evaluates risk factors	Presence of confounding
	Compares two treatments
	May be prospective
Randomized controlled trials	Prospective in nature	Limited generalizability
	Reduce confounding and bias	Potential for low recruitment and high crossover
		High cost and administrative oversight
Systematic review	Provides summation of available literature	Dependent on quality of individual studies

Adapted from Fisher et al[5].

Table 2 Levels of evidence

Evidence level	Therapeutic studies: Evaluating results of treatment	Prognostic studies: Evaluating outcome of disease
I	RCT	Prospective study (> 80% follow-up)
	Systematic review of level 1 RCTs	Systematic review of level I studies
II	Prospective cohort study	Retrospective study
	Poor quality RCT (e.g., < 80% follow-up)	Systematic review of level II studies
	Systematic review of level III studies
III	Case control study
	Retrospective cohort study
	Systematic review of level III studies
IV	Case series	Case series
V	Expert opinion	Expert opinion

Adapted from Wright et al[8]. RCT: Randomized controlled trial.

Table 3 Outcome tools in spinal surgery

Topic	Tool	Notes
Pain	VAS	May be used for generalized or localized pain
Disability	ODI, NDI	Evaluates multiple life experiences
		The NDI is an adaptation of ODI for patients with neck disability
Myelopathy	JOA, mJOA	Evaluates motor function, sensation, and bladder function
Quality of life	SRS-22, EQ-5D-5L, SF-36	SRS-22 developed for patients with spinal deformity

VAS: Visual analog scale; NDI: Neck disability index; ODI: Oswestry disability index; JOA: Japanese Orthopaedic Association; mJOA: Modified JOA; SRS-22: Scoliosis Research Society-22; SF-36: Short Form-36.