Table 8.

Details and results of studies reporting on pseudarthrosis.

Study	Surgical procedure Levels treated (No.)	Method to assess fusion	Radiographic Follow-up	Complication Rates	Summary of Results	Associated Clinical Outcomes
Cho et al. [34]	Single-level PLIF L3/4 (13), L4/5 (60), L5/S1 (13)	1) segmental angulation ≤2° on dynamic x-ray, 2) absence of bridging trabecular bone or peripheral cortication on CT	1 year (XR and CT) and 2 y (XR)	6.17% (5/86)	–Mean lumbar T-scores: -2.8±0.5 (osteoporotic cohort) vs. 0.2±0.9 (normal BMD cohort), p<.001 –No difference in fusion rates at 1 year on X-ray (82.1% vs. 90.6%, p=.273) or CT (83.3% vs. 92.3%, p=.412), or at 2 y on X-ray (92.9% vs. 90.6%, p=.727)	–Fusion rates lower with SL (71.4% vs. 93.9%, p=.038), no differences based on CS (p=.4)
Choi et al. [44]	Single-level TLIF L3/4 (7), L4/5 (47), L5/S1 (25)	Grade 0 (nonunion): lucency visible at one or both endplates on CT Grade 1 (fusion): absence of peri-graft radiolucency Grade 2 (fusion): trabecular bone bridging	Annually to 5 y	* See footnotes	–Mean cohort times to fusion (osteoporosis vs. osteopenia vs. normal BMD) differed based on fusion criteria –Mean time to fusion for absence of peri-graft lucency: 3 y vs. 2 y vs. 0.5 y (p=.003) –Mean time to fusion for trabecular bridging: 5 y vs. 4 y vs. 3 y (p=.001) –Only L1 HU-based categorization [HU cutoffs of 90 and 120] was an independent risk factor for slow trabecular fusion (HR 0.33, p=.003)	N/A
ng , 2019 [32]	Single-level D-LIF L1/2 (1), L2/3 (4), L3/4 (12), L4/5 (67)	1) segmental motion (<3° or 3mm) on dynamic x-ray, 2) intervertebral bridging bone on CT, and 3) no revision or evidence of implant loosening	6 mo (XR and CT), re-evaluation at 12 and 24 mo if nonunion	5.95% (5/84)	–Mean FN T-scores: −1.7 ± 0.4 (osteopenia cohort) vs. −0.6 ± 0.6 (normal BMD cohort), p < 0.001 –No difference in cohort fusion rates at 6 mo (85.4% vs. 93.0%, p=.307), 1 year (90.2% vs. 95.3%, p=.427) or 2 y (92.7% vs. 95.3%, p=.672)	–No significant differences in VAS back or leg pain or ODI between cohorts at 1 and 2 y
Lee et al., [127]	Long posterior fusion [T10-L1 to L5/S1] with ALIF (44) or PLIF (15) Mean 7.4±1.3	3D-CT to assess for presence of trabecular bridging	3, 6, 9, 12, and 24 mo	L5/S1 38.98% (23/59)	–Mean T-scores: −1.31±1.81 (nonunion group) vs. −1.29±1.42 (union group), p=.799	–Patients with fusion had better ODI (p=.017) and VAS back pain (p=.035) scores at last follow-up.
Liu et al., [84]	Single-level PLIF L4/5 (63), L5/S1 (42)	3D-CT to assess for presence of trabecular bridging	At last follow-up (minimum 2 y)	12.38% (13/105)	–Mean BS/TV: 3.09±0.78 (nonunion group) vs. 3.71±0.76 (union group), p<.001) –Mean FN BMD (g/cm2): 0.60±0.1 (nonunion group) vs. 0.76±0.11 (union group), p=.028 –Low BS/TV was the only independent risk factor for nonunion (OR 8.53, p=.032) –ROC analysis: optimal BS/TV cutoff of 3.114 (AUC 0.807) to predict nonunion	–Higher BS/TV associated with better VAS low back and ODI at 1 and 2 y. –No differences in clinical outcome based on fusion status.
Nguyen et al. [130]	L4-S1 Posterolateral fusion	Cases identified by intractable pain with either radiographic or intraoperative evidence of nonunion	1 year	Case (n=10), control (n=10)	–Mean L4/5 HU: 166.98±23.2 (nonunion group) vs. 201.89±36.59 (union group), p=.01	N/A
Otsuki et al. [133]	L4/5 TLIF	1) Segmental dynamic motion ≤3°, 2) visible gap between cage and endplate on CT, 3) no screw loosening	1 year	26% (19/85)	–Mean fusion-level HU: 141.5±53.3 (nonunion group) vs. 141.6±44.4 (union group), p=.99	–Lower postoperative JOA (23.6 vs. 26.3) and recovery rate of JOA in nonunion (62% vs. 82%, p=.01)

Study acronyms are explained in the first footnote to Table 3. Abbreviations: OR, odds ratio; UOR, unit odds ratio; VAS, visual analog scale; ODI, Oswestry disability index; JOA, Japanese Orthopaedic Association score; AUC, area under curve; HR, hazard ratio.

^⁎At 2 years: percentage of patients demonstrating fusion with normal BMD, low BMD, and osteoporosis based on criteria of peri-graft lucency (77.1% vs. 57.2% vs. 44.6%, p=.029) and trabecular bridging (22.7% vs. 11.1%, vs. 4.0%, p=.037), respectively