The Influence of Spinous Process Union on Clinical Outcomes After Spinous Process Osteotomy for Lumbar Spinal Stenosis After 2 Years: A Secondary Analysis From the NORDSTEN-Study

Sondre Hagerup; Jens Ivar Brox; Hasan Banitalebi; Kari Indrekvam; Tor Åge Myklebust; Erland Hermansen

doi:10.14444/8576

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Figure 1
Illustration of a spinous process osteotomy. The red zone illustrates the focus of decompression.
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Figure 2
Transverse and sagittal computed tomography images of the lumbar spine. A nonunion is shown in the top 2 images and a union in the bottom 2 images.
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Figure 3
Flowchart of the patients in the current study.

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Table 1

Eligibility criteria for the Spinal Stenosis Trial of the NORDSTEN-study.

Inclusion Criteria
1. Clinical symptoms of lumbar spinal stenosis, neurogenic claudication, or bilateral radiating pain.
2. Not responding to at least 3 mo of nonsurgical treatment.
3. Radiological findings corresponding to the clinical symptoms: central stenosis or lateral recess stenosis.
4. Able to give informed consent and to answer the questionnaires.
5. Age >18 y.
6. Able to understand the Norwegian language, both oral and written.

Exclusion Criteria
1. Degenerative lumbar spondylolisthesis with a slip ≥3 mm verified on standing plain x-rays in lateral view.
2. Not willing to participate in the trial.
3. Former surgery in the level of stenosis.
4. Fracture or former fusion in the thoracolumbar region.
5. Age >80 y.
6. ASA classification of 4 or 5.
7. Cauda equina syndrome (bowel or bladder dysfunction) or fixed complete motor deficit.
8. Lumbosacral scoliosis >20°, verified on anteroposterior view.
9. Stenosis in >3 levels.
10. Distinct symptoms in one or both of their legs due to other diseases, such as polyneuropathy, vascular claudication, or osteoarthritis.

Abbreviation: ASA, American Society of Anesthesiologists.

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Table 2

Demographics and baseline pain and function scores in the 3 degree of union groups.

Variable	Total (n = 102)	Nonunion (n = 10)	Partial Union (n = 15)	Complete Union (n = 77)	P
Age, y, mean (SD)	66.2 (8.4) (n = 102)	66.5 (7.2) (n = 10)	65.1 (11.6) (n = 15)	66.3 (8.0) (n = 77)	0.87
Smokers, %	18.6% (n = 19)	20% (n = 2)	40% (n = 6)	14.3% (n = 11)	0.51
Men, %	64.7% (n = 66)	40% (n = 4)	80% (n = 12)	65% (n = 50)	0.12
BMI, mean (SD)	27.4 (4.3) (n = 97)	27.4 (3.8) (n = 10)	28.1 (3.6) (n = 14)	27.3 (4.5) (n = 73)	0.82
ODI, mean (SD)	35.7 (14.5) (n = 101)	41.0 (17.8) (n = 10)	38.6 (17.5) ( n = 15)	34.4 (13.4) (n = 76)	0.28
ZCQ-S, mean (SD)	3.3 (0.5) (n = 98)	3.5 (0.3) (n = 10)	3.3 (0.5) (n = 15)	3.2 (0.5) (n = 73)	0.20
ZCQ-F, mean (SD)	2.5 (0.54) (n = 99)	2.6 (0.4) (n = 10)	2.5 (0.5) (n = 15)	2.4 (0.6) (n = 74)	0.51
LP NRS, mean (SD)	6.3 (1.9) (n = 97)	6.6 (1.8) (n = 10)	6.4 (2.5) (n = 14)	6.3 (1.9) (n = 73)	0.86
LBP NRS, mean (SD)	5.8 (2.2) (n = 98)	7.1 (1.9) (n = 10)	4.9 (2.2) (n = 14)	5.8 (2.2) (n = 74)	0.04
EQ5D, mean (SD)	0.41 (0.30) (n = 100)	0.29 (0.30) (n = 10)	0.43 (0.29) (n = 15)	0.43 (0.30) (n = 75)	0.37

Abbreviations: EQ5D, EuroQol health related quality of life index; LBP, low back pain; LP, leg pain; NRS, numeric rating scale; ODI, Oswestry Disability Index; ZCQ-S/F, Zürich Claudication Questionnaire Symptoms/Function.

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Table 3

Primary outcome of change from baseline to follow-up in the 3 degree of union groups

Outcome Measure	Total (n = 101)	Nonunion (n = 10)	Partial Union (n = 15)	Complete Union (n = 76)	P
ODI, mean (SD)	−20.1 (17.0) (n = 100)	−25.6 (15.9) (n = 10)	−17.3 (20.7) (n = 14)	−19.9 (16.5) (n = 76)	0.49
Success	74% (n = 100)	90% (n = 10)	64.3% (n = 14)	73.7% (n = 76)	0.39

Abbreviation: ODI, Oswestry Disability Index.
Note: Success ≥30% improvement in ODI.

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Table 4

Secondary outcome measures change from baseline to follow-up, mean (SD).

Outcome Measure	Total (n = 101)	Nonunion (n = 10)	Partial Union (n = 15)	Complete Union (n = 76)	P
ZCQ-S	−1.1 (0.9) (n = 98)	−1.4 (0.7) (n = 10)	−1.0 (0.8) (n = 15)	−1.0 (0.9) (n = 73)	0.45
ZCQ-F	−0.9 (0.8) (n = 98)	−0.9 (0.7) (n = 9)	−0.7 (0.7) (n = 15)	−0.9 (0.7) (n = 74)	0.55
LP NRS	−3.6 (3.1) (n = 95)	−3.6 (3.1) (n = 10)	−3.2 (3.3) (n = 13)	−3.6 (3.0) (n = 72)	0.93
LBP NRS	−2.8 (2.5) (n = 97)	−3.6 (2.6) (n = 10)	−1.7 (2.3) (n = 14)	−2.9 (2.5) (n = 73)	0.15
EQ5D	0.34 (0.33) (n = 93)	0.4 (0.3) (n = 10)	0.23 (0.38) (n = 14)	0.34 (0.32) (n = 69)	0.29

Abbreviations: EQ5D, EuroQol health related quality of life index; LBP, low back pain; LP, leg pain; NRS, numeric rating scale; ZCQ-S/F, Zürich Claudication Questionnaire Symptoms/Function.

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Table 5

Primary and secondary outcome measures: change from baseline to follow-up, comparing the complete union group and not complete union group made from merging the nonunion group and partial union group.

Outcome Measure	Not Complete Union (n = 24)	Complete Union (n = 76)	P
ODI	−20.8 (19.0) (n = 24)	−19.9 (16.5) (n = 76)	0.83
Success, %^{^a}	75% (n = 18)	74% (n = 56)	0.90
ZCQ-S	−1.2 (0.8) (n = 25)	−1.0 (0.9) (n = 73)	0.55
ZCQ-F	−0.8 (0.7) (n = 24)	−0.9 (0.7) (n = 74)	0.46
LP NRS	−3.4 (3.1) (n = 23)	−3.6 (3.0) (n = 72)	0.79
LBP NRS	−2.5 (2.6) (n = 24)	−2.9 (2.5) (n = 73)	0.51
EQ5D	0.32 (0.35) (n = 24)	0.34 (0.32) (n = 69)	0.79

Abbreviations: EQ5D, EuroQol health related quality of life index; LBP, Lower Back Pain; LP, leg pain; ODI, Oswestry Disability Index; ZCQ-S/F, Zürich Claudication Questionnaire Symptoms/Function.
Note: Data presented as mean (SD) unless otherwise indicated.
↵a Success ≥30% improvement in ODI.