Successful outcomes of unilateral vs bilateral pedicle screw fixation for lumbar interbody fusion: A meta-analysis with evidence grading

Table 2 The GRADE evidence quality for each outcome

No of studies	Design	Decrease quality of evidence					Increase quality of evidence			Quality	Importance
		Limitations	Inconsistency	Indirectness	Imprecision	Publication bias	Large effect	Plausible confounding	Does-response
Fusion rate	RCT	No	No	No	No	Unlikely	No	No	No	High (++++)	Critical
Complications	RCT	No	No	No	Serious	Very likely	No	No	No	Very low (+---)	Critical
-Δ VAS	RCT	No	Serious	No	No	Likely	No	No	No	Low (++--)	Important
Δ ODI	RCT	No	Serious	No	No	Likely	No	No	No	Low (++--)	Important
Δ JOA	RCT	No	Serious	No	No	Unlikely	No	No	No	Moderate (+++-)	Important
Total blood loss	RCT	No	Serious	No	No	Very likely	No	No	No	Very low (+---)	Important
Operation time	RCT	No	Serious	No	No	Unlikely	No	No	No	Moderate (+++-)	Important
Length of hospital stay	RCT	No	Serious	No	No	Very likely	No	No	No	Very low (+---)	Important

High quality: Further research is very unlikely to change our confidence in the estimate of effect; Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate; Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate; Very low quality: We are very uncertain about the estimate. VAS: Visual analog scale; ODI: Oswestry disability index; JOA: Japanese Orthopedic Association; RCT: Randomized controlled trial.