Incidence of postoperative progressive segment degeneration at decompression and adjacent segments after minimally invasive lumbar decompression surgery: a 5-year follow-up study

Hasibullah Habibi Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Hiromitsu Toyoda Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Hidetomi Terai Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Kentaro Yamada Department of Orthopaedic Surgery, PL Hospital, Osaka, Japan

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Masatoshi Hoshino Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Akinobu Suzuki Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Shinji Takahashi Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Koji Tamai Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Hamidullah Salimi Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Yusuke Hori Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Akito Yabu Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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Hiroaki Nakamura Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, Osaka; and

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OBJECTIVE

There are several reported studies on the incidence of adjacent segment disease (ASD) after lumbar fusion surgery; however, the incidence of ASD after decompression surgery has not been well studied. In this study the authors aimed to investigate the incidence of progressive segment degeneration (PSD) at the decompression and adjacent segments 5 years after minimally invasive lumbar decompression surgery.

METHODS

We investigated data from 168 patients (mean age, 69.5 ± 9.2 years) who underwent bilateral microscopic or microendoscopic decompression surgery via a unilateral approach and were followed up for more than 5 years. Outcomes were self-reported visual analog scale (VAS) scores for low-back pain, leg pain, and leg numbness and physician-assessed Japanese Orthopaedic Association (JOA) scores for back pain. Changes in the disc height and movement of the adjacent lumbar segments were compared using preoperative and 5-year postoperative lateral full-length standing whole-spine radiographic images. PSD was defined as loss of disc height > 3 mm and progression of anterior or posterior slippage > 3 mm. The incidence and clinical impact of PSD were investigated.

RESULTS

The mean JOA score improved significantly in all patients from 13.4 points before surgery to 24.1 points at the latest follow-up (mean recovery rate 67.8%). PSD at the decompression site was observed in 43.5% (73/168) of the patients. The proportions of patients with loss of disc height > 3 mm and slippage progression were 16.1% (27/168) and 36.9%, respectively (62/168: 41 anterior and 21 posterior). The proportion of patients with PSD at the adjacent segment was 20.5% (35/168), with 5.4% (9/168) of the patients with loss of disc height > 3 mm and 16.0% (27/168: 13 anterior and 14 posterior) with slippage progression. There was no significant difference in the clinical outcomes between patients with and those without PSD.

CONCLUSIONS

Radiological ASD was observed even in the case of decompression surgery alone. However, there was no correlation with symptom deterioration, measured by the VAS and JOA scores.

ABBREVIATIONS

ASA = American Society of Anesthesiologists; ASD = adjacent segment disease; JOA = Japanese Orthopaedic Association; LBP = low-back pain; LSS = lumbar spinal stenosis; PLIF = posterior lumbar interbody fusion; PSD = progressive segment degeneration; VAS = visual analog scale.

OBJECTIVE

There are several reported studies on the incidence of adjacent segment disease (ASD) after lumbar fusion surgery; however, the incidence of ASD after decompression surgery has not been well studied. In this study the authors aimed to investigate the incidence of progressive segment degeneration (PSD) at the decompression and adjacent segments 5 years after minimally invasive lumbar decompression surgery.

METHODS

We investigated data from 168 patients (mean age, 69.5 ± 9.2 years) who underwent bilateral microscopic or microendoscopic decompression surgery via a unilateral approach and were followed up for more than 5 years. Outcomes were self-reported visual analog scale (VAS) scores for low-back pain, leg pain, and leg numbness and physician-assessed Japanese Orthopaedic Association (JOA) scores for back pain. Changes in the disc height and movement of the adjacent lumbar segments were compared using preoperative and 5-year postoperative lateral full-length standing whole-spine radiographic images. PSD was defined as loss of disc height > 3 mm and progression of anterior or posterior slippage > 3 mm. The incidence and clinical impact of PSD were investigated.

RESULTS

The mean JOA score improved significantly in all patients from 13.4 points before surgery to 24.1 points at the latest follow-up (mean recovery rate 67.8%). PSD at the decompression site was observed in 43.5% (73/168) of the patients. The proportions of patients with loss of disc height > 3 mm and slippage progression were 16.1% (27/168) and 36.9%, respectively (62/168: 41 anterior and 21 posterior). The proportion of patients with PSD at the adjacent segment was 20.5% (35/168), with 5.4% (9/168) of the patients with loss of disc height > 3 mm and 16.0% (27/168: 13 anterior and 14 posterior) with slippage progression. There was no significant difference in the clinical outcomes between patients with and those without PSD.

CONCLUSIONS

Radiological ASD was observed even in the case of decompression surgery alone. However, there was no correlation with symptom deterioration, measured by the VAS and JOA scores.

The standard surgical procedure for lumbar spinal stenosis (LSS) is decompression of the stenosis. Although satisfactory surgical outcomes have been reported, instability following the procedure has become a great concern among surgeons due to symptom progression.1,2 In cases of spinal instability, additional fusion surgery is considered. The advent of a minimally invasive midline-sparing method using microsurgical or endoscopic procedures that allow for bilateral decompression of the neural elements has further reduced the risk of iatrogenic instability, removing the need for fusion.3,4

Both decompression and additional fusion surgery pose a risk for revision surgery. However, the indications for revision vary and include the progression of slippage or disc degeneration. Same-segment diseases, including disc herniation and recurrent stenosis, are the major cause of revision after decompression, while symptomatic adjacent segment disease (ASD) is a major cause of revision surgery after fusion surgery.5 ASD and postoperative progressive segment degeneration (PSD) are defined by the narrowing of disc height > 3 mm, a posterior opening > 5°, and progression of slippage > 3 mm compared with preoperative flexion and extension lateral radiographs.6,7 There are several published studies on the incidence of ASD after fusion surgery,810 and limited evidence exists on the incidence of ASD and PSD in the decompression segment. We performed an analysis of radiographic changes in disc degeneration and clinical outcomes after minimally invasive decompression surgery for LSS using preoperative and 5-year follow-up data. We aimed to clarify the incidence of postoperative PSD at the decompression site and adjacent levels after decompression surgery.

Methods

Patient Population

We conducted a retrospective analysis of prospectively collected data from patients who underwent minimally invasive lumbar decompression surgery for LSS. All participants provided informed consent, and the study protocol was approved by our institutional review board. No funding was received in support of this study. We reviewed the data of 244 patients with > 5 years’ postoperative follow-up period. Patients were excluded if any of the 5-year follow-up data, such as full-length standing whole-spine radiographs, were missing (n = 75) or if they had a vertebral fracture (n = 1). In total, 168 patients were included in the final analysis.

Surgical Indication and Procedure

The clinical indications for surgery were leg pain and/or leg numbness inducing intermittent claudication (rather than back pain), mainly derived from spinal canal stenosis. Therefore, we proactively performed minimally invasive lumbar decompression surgery as the optimal first-line surgical treatment for patients with LSS. We excluded patients with a Cobb angle > 25°, severe low-back pain (LBP), changes in segmental disc wedging between the standing and prone position > 5°, or changes in lateral disc slippage > 3 mm.

All minimally invasive lumbar decompression surgeries were performed using bilateral decompression via a unilateral approach to decompress the central and bilateral lateral recesses using a microscope or a microendoscopic discectomy system (METRx Medtronic Sofamor Danek), as previously described.4,11 Single-level or two-level decompression was principally performed with the microendoscope. Multiple-level decompression or facet-angle sagittalization was performed with a microscope.

Clinical Evaluation

Patients were clinically assessed preoperatively and 5 years postoperatively using the Japanese Orthopaedic Association (JOA) score,12,13 a physician-administered patient evaluation score for back pain. The pre- and postoperative differences in the JOA score (%) were calculated as follows: (postoperative JOA score − preoperative JOA score)/(29 − preoperative JOA score) × 100. Additionally, self-reported scores for back pain, leg pain, and leg numbness using the visual analog scale (VAS) were included.13,14 The VAS score for pain or numbness intensity ranged from 0 mm (no pain or numbness) to 100 mm (worst imaginable pain or numbness). Data were collected on baseline patient characteristics, including age, sex, body mass index (BMI), and American Society of Anesthesiologists (ASA) physical status classification system score.

Definition of PSD

On lateral full-length standing whole-spine radiographs, we measured the intervertebral disc height (in mm, between the midpoints of the upper and lower endplates) and the degree of slip distance (in mm, between the posterior lower portion of the upper vertebral body and the posterior border of the lower vertebral body) from levels L1–2 to L5–S1 in a standardized method preoperatively and at the 5-year follow-up (Fig. 1).15,16 Images were independently assessed by two spine surgeons (H.H. and K.Y.), with 10 and 18 years of experience, respectively, in spine radiography, who were blinded to the outcomes. The films were evaluated using imaging analysis software for Windows (Surgimap, Nemaris, Inc.). Any differences in the evaluations were settled by the consensus of the two assessors. Radiographic PSD was defined as either the development of an antero- or retrolisthesis > 3 mm or a decrease in disc height > 3 mm during the 5-year follow-up.

FIG. 1.
FIG. 1.

Representative sagittal radiographs showing a lateral full-length standing whole-spine radiograph obtained preoperatively (left) and postoperatively (right) showing measurements of the intervertebral disc height and degree of slip distance (mm) from levels L1–2 to L5–S1 (white arrows) at the 5-year follow-up.

To evaluate the impacts of decompression surgery, all intervertebral discs were classified into two groups depending on whether decompression surgery was performed (operated disc levels and nonoperated disc levels).

The adjacent segment is defined as the disc at the cephalad segment adjacent to the decompression segment. For example, in a case with L4–5 single-level decompression, the decompression level indicated the L4–5 level, and the adjacent level indicated the L3–4 level. In a case with L3–5 two-level decompression, the decompression levels were L3–5, and the adjacent level was only the L2–3 level. In the case of multilevel decompression, the incidence of PSD at the decompression level was defined as an occurrence in at least one level.

Statistical Analysis

The preoperative and 5-year postoperative radiological and clinical data were analyzed using the Mann-Whitney U-test for the univariate analyses and Pearson’s chi-square test for multivariate analysis. For all analyses, p values < 0.05 were considered statistically significant. The analyses were conducted using SPSS software version 25.0 (SPSS).

Results

Patient Demographics

The preoperative demographic and clinical characteristics of 168 patients are listed in Table 1. The mean age and BMI of patients were 69.5 ± 9.2 years and 24.2 ± 3.6 kg/m2, respectively. One-level decompression was performed in 116 (69%) patients, two-level in 40 (23.8%), and three-level in 12 (7.1%). The mean preoperative VAS scores for LBP, leg pain, and leg numbness were 48.1 ± 31.3, 62.9 ± 28.0, and 61.3 ± 27.9, respectively, and the JOA score was 13.4 ± 4.5. The 5-year postoperative VAS scores for LBP, leg pain, and leg numbness improved to 24.4 ± 26.9, 17.9 ± 25.8, and 31.3 ± 29.3, respectively, and the JOA score increased to 24.1 ± 4.4. The JOA score improvement rate was 67.8% ± 27.3%.

TABLE 1.

Patient demographic data

Demographic VariableValue
No. of pts 168
Age, yrs69.5 ± 9.2
Male sex87 (51.8)
BMI24.2 ± 3.6
Smoking status
 Current31 (13.5)
 Past9 (5.4)
 Never128 (76.2)
Comorbidities
 Cardiovascular disease*85 (50.6)
 Diabetes31 (18.5)
 Respiratory disease7 (4.2)
 Chronic kidney disease8 (4.8)
 Chronic liver disease6 (3.6)
 Hypothyroidism6 (3.6)
 Autoimmune disease6 (3.6)
 Malignancy14 (8.3)
 Other61 (36.3)
ASA class
 I28 (16.7)
 II134 (79.8)
 III4 (2.4)
Microendoscopy106 (63.1)
No. of decompression segments
 1116 (69.0)
 240 (23.8)
 312 (7.1)
Assessment scores
 Preop
  VAS LBP 48.1 ± 31.3
  VAS leg pain 62.9 ± 28.0
  VAS leg numbness61.3 ± 27.9
  JOA score13.4 ± 4.5
 5-yr FU
  VAS LBP 24.4 ± 26.9
  VAS leg pain 17.9 ± 25.8
  VAS leg numbness31.3 ± 29.3
  JOA score24.1 ± 4.4
  JOA score improvement ratio 67.8 ± 27.3

FU = follow-up; pt = patient.

Data are presented as number (%) of patients or mean ± SD.

Cardiovascular disease included hypertension, coronary artery disease, and arrhythmia.

Respiratory disease included chronic obstructive pulmonary disease and asthma.

Disc Height Loss at 5-Year Follow-Up

The details on disc height are shown in Table 2. The disc heights at L2–3, L3–4, L4–5, and L5–S1 were significantly reduced by decompression during the 5-year follow-up. However, the incidence of disc height loss > 3 mm at each level was not significantly different between the treatment groups.

TABLE 2.

Progression of disc height loss during the 5-year follow-up period

L1–2p ValueL2–3p ValueL3–4p ValueL4–5p ValueL5–S1p Value
Decompression opYes NoYes NoYes NoYes NoYes No
No. of pts116712156631051383017151
Disc height, mm
 Preop8.367.62 ± 1.560.6397.48 ± 1.857.95 ± 1.950.4257.92 ± 2.028.60 ± 2.080.0408.12 ± 1.86 7.74 ± 2.410.4216.88 ± 2.456.88 ± 1.661.00
 5-yr FU7.927.12 ± 1.650.6345.72 ± 2.067.27 ± 2.060.0135.87 ± 2.117.20 ± 2.09<0.0015.81 ± 1.946.55 ± 2.230.0715.03 ± 2.656.07 ± 1.630.131
 Change0.440.52 ± 0.620.8991.76 ± 0.460.72 ± 0.55<0.0012.13 ± 0.891.43 ± 0.91<0.0012.34 ± 1.061.19 ± 0.79<0.0011.85 ± 0.830.84 ± 1.150.001
Loss of disc height >3 mm 0 (0)2 (1.2)0.9120 (0)1 (0.6)0.7819 (14.3)8 (7.6)0.19122 (16.9)1 (3.3)0.0691 (5.9)5 (3.3)0.593

Data are presented as number (%) of patients or mean ± SD unless otherwise indicated. Boldface type indicates statistical significance.

Anterior and Posterior Slippage at the 5-Year Follow-Up

The data on slippage are shown in Table 3. For all levels, there were no significant differences in the change of slip distance during the 5 years in patients with or without decompression surgery. The incidence of slip progression > 3 mm at the L5-S1 level was significantly higher in the operated disc levels than in the nonoperated disc levels. The incidence of slip progression > 3 mm at the other levels was not significantly different between the treatment groups. However, there was a certain percentage of cases with anterior or posterior slip progression during the 5-year follow-up, regardless of decompression surgery.

TABLE 3.

Progression of anterior or posterior slippage during the 5-year follow-up period

L1–2p ValueL2–3p ValueL3–4p ValueL4–5p ValueL5–S1p Value
Decompression opYes NoYes NoYes NoYes NoYes No
No. of pts116712156631051383017151
Slip, mm
 Preop000.817−0.50 ± 0.92−0.67 ± 1.260.6470.49 ± 2.27−0.53 ± 1.33<0.0011.93 ± 2.510.62 ± 1.520.0070.51 ± 1.500.06 ± 0.510.235
 5-yr FU000.841−1.24 ± 2.07−0.61 ± 2.010.3001.07 ± 3.43−0.82 ± 2.20<0.0012.95 ± 4.091.31 ± 2.330.0360.57 ± 2.630.26 ± 1.180.638
 Change 0−0.10.937−0.74 ± 1.980.05 ± 1.880.1600.57 ± 3.25−0.28 ± 2.0060.0621.09 ± 2.860.68 ± 1.510.3720.05 ± 1.940.20 ± 1.210.667
>3-mm slip progress
 Ant0 (0)1 (0.6)0.9880 (0)11 (7.1)0.60810 (15.9)8 (7.6)0.17130 (21.7)4 (13.3)0.2622 (11.8)8 (5.3)0.040
 None1 (100)163 (97.6)11 (91.7)136 (87.2)45 (71.4)87 (82.9)95 (68.8)25 (83.3)13 (76.5)140 (92.7)
 Pst0 (0)3 (1.8)1 (8.3)9 (5.8)8 (12.7)10 (9.5)13 (9.4)1 (3.3)2 (11.8)3 (2.0)

Ant = anterior; progress = progression; pst = posterior.

Data are presented as number (%) of patients or mean ± SD unless otherwise indicated. Boldface type indicates statistical significance.

During the 5-year follow-up, anterior slip progression > 3 mm at L3–4 occurred in 15.9% of patients (10/63) at the operated disc levels and 7.6% of patients (8/105) at the nonoperated disc levels. In addition, > 3 mm of anterior slip progression at L3–4 occurred in 12.7% of patients at the operated disc levels and 9.5% of patients at the nonoperated disc levels.

Regarding L4–5, anterior slip progression > 3 mm during the 5-year follow-up occurred in 21.7% of patients (30/138) at the operated disc levels and 13.3% of patients (4/30) at the nonoperated disc levels. Posterior slip progression > 3 mm occurred in 9.4% of patients at the operated disc levels and 3.3% of patients at the nonoperated disc levels.

PSD at the Decompression and Adjacent Segments

At the 5-year follow-up, loss of disc height > 3 mm was observed in 16.1% (27/168) of patients at the decompression segment and 5.4% (9/168) at the adjacent segment (Table 4). The rates of progression of anterior slippage were 24.4% (41/168 patients) and 17.7% (13/168 patients) at the decompression and adjacent segments, respectively. In contrast, the rates of posterior slippage progression at the 5-year follow-up were 12.5% (21/168 patients) and 8.3% (14/168 patients) at the decompression and adjacent segments, respectively. Overall, PSD was observed in 43.5% and 20.5% of patients at the decompressed and adjacent segments, respectively.

TABLE 4.

Incidence of PSD at the decompression and adjacent segments

Level
DecompressionAdjacent
All pts (n = 168)
 Loss of disc height, 3 mm27 (16.1)9 (5.4)
 Progress of ant slippage, 3 mm41 (24.4)13 (7.7)
 Progress of pst slippage, 3 mm21 (12.5)14 (8.3)
 PSD*73 (43.5)35 (20.5)
L4–5 single decompression (n = 88)
 Loss of disc height, 3 mm14 (15.9)6 (6.8)
 Progress of ant slippage, 3 mm20 (22.7)6 (6.8)
 Progress of pst slippage, 3 mm8 (9.1)8 (9.1)
 PSD*39 (44.3)19 (21.6)

Data are presented as number (%) of patients.

Development of antero- or retrolisthesis > 3 mm or decrease in disc height > 3 mm.

We performed a data subanalysis using only L4–5 single-level decompression (n = 88). Loss of disc height > 3 mm at the 5-year follow-up was observed in 15.9% (14/88) and 6.8% (6/88) of patients at the decompression and adjacent segments, respectively. Anterior slippage progression at the 5-year follow-up was observed in 22.7% (20/88) and 6.8% (6/88) of patients at the decompression and adjacent segments, respectively. Progression of posterior slippage at the 5-year follow-up was observed in 9.1% (8/88) of patients in the decompression and adjacent segments, respectively. Overall, the incidence rates of PSD in patients with L4–5 single-level decompression were 44.3% and 21.6% in the decompression and adjacent segments, respectively (Fig. 2).

FIG. 2.
FIG. 2.

Representative radiographic changes after L4–5 single-level decompression. A, C, and E: Before surgery. B, D, and F: Five years after surgery. A and B: Significant change is not observed. C and D: PSD at the decompression segment is shown. E and F: PSD at both the decompression and adjacent segments is shown.

Clinical Outcomes in Patients With PSD

Changes in VAS (LBP, leg pain, and leg numbness) and JOA scores are shown in Table 5 according to PSD at the decompression or adjacent segment. No significant differences in smoking status or comorbidities were observed. Similarly, there were no significant differences in the clinical outcomes at the 5-year follow-up in patients with PSD between the decompression and adjacent segments. In total, 20 patients underwent reoperation, of which 8 surgeries (4.8%) were performed at the same level and 12 (7.1%) at different levels. There were no significant differences in the incidence rates of revision surgery between patients with and those without PSD at either the decompression or adjacent segments.

TABLE 5.

Comparison of clinical outcomes between patients with and those without PSD at the decompression or adjacent segments

PSD at Decompression Levelp ValuePSD at Adjacent Levelp Value
YesNoYesNo
No. of pts739535133
Age, yrs69.5 ± 9.069.5 ± 9.40.99271.3 ± 8.669.0 ± 9.40.167
Male sex44 (60.3)43 (45.3)0.06217 (48.6)70 (52.6)0.707
BMI24.4 ± 3.424.0 ± 3.80.46324.0 ± 3.324.2 ± 3.70.731
Smoking status0.3520.200
 Current13 (17.8)18 (18.9)6 (17.1)25 (18.8)
 Past6 (8.2)3 (3.2)4 (11.4)5 (3.8)
 Never54 (74.0)74 (77.925 (71.4)103 (77.4)
Comorbidities
 Cardiovascular disease*37 (50.7)48 (50.5)0.55421 (60.0)64 (48.1)0.144
 Diabetes13 (17.8)18 (18.9)0.5079 (25.7)22 (16.5)0.158
 Respiratory disease2 (2.7)5 (5.3)0.3433 (8.6)4 (3.0)0.159
 Chronic kidney disease3 (4.1)5 (5.3)0.5131 (2.9)7 (5.3)0.475
 Chronic liver disease1 (1.4)5 (5.3)0.1791 (2.9)5 (3.8)0.635
 Hypothyroidism2 (2.7)4 (4.3)0.4670 (0)6 (4.5)0.238
 Autoimmune disease5 (6.8)1 (1.1)0.0580 (0)6 (4.5)0.238
 Malignancy4 (5.5)10 (10.6)0.1822 (5.7)12 (9.1)0.405
 Other29 (39.7)32 (33.7)0.2599 (25.7)52 (39.1)0.101
ASA class
 I14 (19.2)14 (14.7)0.285 (14.3)23 (17.3)0.747
 II56 (76.6)78 (82.1)28 (80.0)106 (79.7)
 III1 (1.4)3 (3.2)1 (2.9)3 (2.3)
Microendoscopy41 (56.2)65 (68.4)0.07120 (57.1)86 (64.7)0.265
Assessment scores
 Preop
  VAS LBP 46.3 ± 30.949.4 ± 31.70.53259.0 ± 33.545.2 ± 30.20.025
  VAS leg pain 58.1 ± 29.865.9 ± 26.40.11266.1 ± 29.062.1 ± 27.70.459
  VAS leg numbness60.0 ± 28.462.2 ± 27.60.61460.7 ± 28.861.4 ± 27.70.893
  JOA13.6 ± 4.513.3 ± 4.40.68813.3 ± 5.113.5 ± 4.30.856
 5-yr FU
  VAS LBP 25.2 ± 28.123.7 ± 26.00.74426.9 ± 25.623.8 ± 27.30.581
  VAS leg pain 20.9 ± 27.115.3 ± 24.40.20415.2 ± 26.018.6 ± 25.80.528
  VAS leg numbness29.8 ± 28.132.6 ± 30.40.58834.8 ± 31.230.3 ± 28.90.464
  JOA 24.5 ± 4.623.8 ± 4.30.40224.8 ± 3.223.9 ± 4.70.360
 JOA score improvement ratio 70.4 ± 27.365.7 ± 27.40.31771.0 ± 19.366.7 ± 29.20.381
Reoperation
 Same level2 (2.7)6 (6.3)0.2811 (2.9)7 (5.3)0.552
 Other level4 (5.5)8 (8.4)0.4532 (5.7)10 (7.5)0.712
 Total6 (8.2)14 (14.7)0.1963 (8.6)17 (12.8)0.494

Data are presented as number (%) of patients or mean ± SD unless otherwise indicated. Boldface type indicates statistical significance.

Cardiovascular disease included hypertension, coronary artery disease, and arrhythmia.

Respiratory disease included chronic obstructive pulmonary disease and asthma.

Discussion

PSD-like ASD was observed not only at the decompression segment, but also at the adjacent segment after decompression surgery alone. Our results show that ASD was observed postoperatively even after decompression surgery, although less frequently than after fusion surgery. We speculated that PSD may naturally occur in patients with LSS and demonstrated that the occurrence of PSD at either the decompression or adjacent segments did not affect patient clinical outcomes or reoperation rates.

Regarding the loss of disc height, a few recent studies have used radiography to examine the natural history of lumbar spine disc degeneration. Hassett et al. used lateral lumbar spine radiography for a semiquantitative study in a population-based inception cohort of women and reported that the progression rates for disc height loss over the course of 9 years were 3% per year and that peak disc height loss occurred at L4–5 at a rate of 27%.17 Jarraya et al. demonstrated that the progression of disc height loss over a 6-year period increased with age, ranging from 26%–36% in patients 60–69 years old and 29%–43% among patients 70–89 years old using a semiquantitative method based on computed tomography.18 Teraguchi et al. performed a longitudinal population-based cohort study using the Pfirrmann classification system with spine magnetic resonance imaging and reported that lumbar disc degeneration was observed in 52.0% and 60.4% of men and women, respectively, during a 4-year follow-up.19 In the present study, the incidence of loss of disc height > 3 mm in the nonoperated disc levels was 1.2% at L1–2, 0.6% at L2–3, 7.6% at L3–4, 3.3% at L4–5, and 3.3% at L5–S1. Although the method used to evaluate disc degeneration is different for each study, our findings demonstrated a disc height loss > 3 mm even in the nonoperated disc levels, suggesting that this outcome might be attributable to the natural course of degeneration in patients with LSS. The rate of loss of disc height > 3 mm in the operated disc levels was 0% at L1–2, 0% at L2–3, 14.3% at L3–4, 16.9% at L4–5, and 5.9% at L5–S1. These results indicate that even minimally invasive decompression surgery affected the loss of disc height postoperatively.

Spondylolisthesis progression or de novo spondylolisthesis can be partially attributed to age-related disc degeneration. According to a large population-based longitudinal cohort study among older patients, Denard et al. reported that spondylolisthesis progressed in 12% of male patients, and de novo spondylolisthesis appeared in 12% of elderly men at an approximate 5-year follow-up.20 The results from a 4-year follow-up study by Wáng et al. were similar, reporting that spondylolisthesis progressed in 13.0% of men, and de novo spondylolisthesis appeared in 12.4%, while spondylolisthesis progressed in 16.5% of women, and de novo spondylolisthesis appeared in 12.7% of the study population.21 In these studies, anterior and posterior slippage were not separated and considered together as spondylolisthesis. We investigated anterior and posterior slippage separately and revealed that progression of anterior slippage > 3 mm in the nonoperated disc levels was 0% at L1–2, 7.1% at L2–3, 7.6% at L3–4, 13.3% at L4–5, and 5.3% at L5–S1. Anterior slippage progression > 3 mm in the operated disc levels was 0% at L1–2, 0% at L2–3, 15.9% at L3–4, 21.7% at L4–5, and 11.8% at L5–S1. Although there were no significant differences between lumbar segments in the number of slippages from baseline to the 5-year follow-up, we speculated that even minimally invasive decompression surgery affected spondylolisthesis progression or de novo spondylolisthesis postoperatively. We observed not only anterior slippage, but also some cases of segment degeneration with progressive posterior slippage.

ASD is associated with fusion surgery, which can induce abnormal intradiscal pressure and excessive movement at the adjacent spinal levels. A systematic review revealed that the incidence of radiologically diagnosed ASD ranged from 5.3% to 100% during 36 to 369 months of follow-up, and the incidence of symptomatic ASD ranged from 5.2% to 18.5% during 44.8 to 164 months of follow-up.10 In a study of 128 patients with a 10-year follow-up period, Okuda et al. demonstrated that the rates of radiologically assessed ASD at 2, 5, and 10 years were 19%, 49%, and 79%, respectively, after primary posterior lumbar interbody fusion (PLIF) surgery.9 Based on our results and findings, the rates of segment degeneration at the decompression and adjacent levels were 43.5% and 20.5%, respectively, after 5 years of minimally invasive lumbar decompression surgery. ASD was observed even after decompression surgery, although less frequently than after fusion surgery. However, PSD-like ASD was commonly observed at the decompression level, in which the incidence of PSD at the decompression segment in our study was roughly similar to that of ASD after fusion surgery, as in previous reports. In contrast, the incidence of PSD in the adjacent segment was similar to the natural course of LSS, which has been previously reported.

Our finding on the occurrence of slippage progression > 3 mm in 5 years in 36.9% of the patients is unexpected and contrary to common practice after minimally invasive decompression. Additionally, Ravinsky et al. reported that spondylolisthesis slip percentage increased in 55.4% of patients after minimally invasive surgical decompression for low-grade degenerative lumbar spondylolisthesis during 1.7 years of follow up.22 Since the present study was retrospective, it is unclear whether a midline-sparing method using microsurgical or endoscopic procedures can reduce the risk of iatrogenic instability compared to standard decompression surgery. The risk of PSD might include not only surgical approach, but also genetic and environmental factors. In the present study, there were no significant differences in the incidence of disc height loss > 3 mm and slip progression > 3 mm in patients at each level with or without decompression surgery during the 5-year follow-up. It has been suggested that ASD after fusion is a natural process that is not related to fusion surgery.23 Recently reported studies have shown that the risk factors of ASD include not only abnormal intradiscal pressure after fusion surgery, but also the number of instrumented levels, preexisting degenerative conditions at an adjacent motion segment, sagittal alignment change, and older age.6

Okuda et al. demonstrated that symptomatic ASD after one-level PLIF surgery was significantly correlated with worse clinical outcomes,9 which is not consistent with our results and those of other studies demonstrating that asymptomatic ASD is not correlated with clinical outcomes.7,10 Postoperative degenerative changes include both radiographic and symptomatic ASD. Radiographic ASD can develop into symptomatic ASD, leading to serious pain, dysfunction, or need for additional surgery. Regarding slip progression in degenerative lumbar spondylolisthesis following minimally invasive decompression surgery, Ravinsky et al. concluded that there was no correlation with symptom worsening, as measured by the Oswestry Disability Index, despite a small degree of slip progression in the majority of patients.22 We speculate that most postoperative degenerative changes after decompression surgery were related to radiological ASD.

The present study has several limitations. First, this study has a retrospective design; therefore, we could not include all possible risk factors for radiological ASD in the analysis. Second, the distribution of the number of patients in the operated disc levels and nonoperated disc levels was not equal even though our data can provide important information to surgeons. Third, we could not include a control group and could only compare results with those of previous studies. Fourth, we had a low follow-up rate for patients because of incomplete postoperative data.

Conclusions

In conclusion, radiologically assessed ASD was observed not only after fusion surgery, but also after minimally invasive decompression surgery. There was no correlation with worse symptoms, as measured by VAS and JOA scores, regardless of the occurrence of ASD. PSD-like radiological ASD occurred not only in the decompression segments but also in the segments without decompression.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Toyoda, Habibi, Terai. Acquisition of data: Toyoda, Yamada, Hoshino, Suzuki, Salimi. Analysis and interpretation of data: Toyoda, Habibi, Yamada. Drafting the article: Toyoda, Habibi, Terai. Critically revising the article: Hoshino, Suzuki, Tamai, Hori, Yabu. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Toyoda. Statistical analysis: Toyoda, Takahashi, Tamai. Study supervision: Toyoda, Nakamura.

References

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    Szpalski M, Gunzburg R. Lumbar spinal stenosis in the elderly: an overview. Eur Spine J. 2003;12(2)(suppl 2):S170S175.

  • 2

    Herkowitz HN, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis. J Bone Joint Surg Am. 1991;73(6):802808.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Bridwell KH, Sedgewick TA, O’Brien MF, Lenke LG, Baldus C. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord. 1993;6(6):461472.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Toyoda H, Nakamura H, Konishi S, Dohzono S, Kato M, Matsuda H. Clinical outcome of microsurgical bilateral decompression via unilateral approach for lumbar canal stenosis: minimum five-year follow-up. Spine (Phila Pa 1976). 2011;36(5):410415.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Lang Z, Li JS, Yang F, et al. Reoperation of decompression alone or decompression plus fusion surgeries for degenerative lumbar diseases: a systematic review. Eur Spine J. 2019;28(6):13711385.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Wang T, Ding W. Risk factors for adjacent segment degeneration after posterior lumbar fusion surgery in treatment for degenerative lumbar disorders: a meta-analysis. J Orthop Surg Res. 2020;15(1):582.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Okuda S, Iwasaki M, Miyauchi A, Aono H, Morita M, Yamamoto T. Risk factors for adjacent segment degeneration after PLIF. Spine (Phila Pa 1976). 2004;29(14):15351540.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Okuda S, Yamashita T, Matsumoto T, et al. Adjacent segment disease after posterior lumbar interbody fusion: a case series of 1000 patients. Global Spine J. 2018;8(7):722727.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Okuda S, Nagamoto Y, Matsumoto T, Sugiura T, Takahashi Y, Iwasaki M. Adjacent segment disease after single segment posterior lumbar interbody fusion for degenerative spondylolisthesis: minimum 10 years follow-up. Spine (Phila Pa 1976). 2018;43(23):E1384E1388.

    • Crossref
    • PubMed
    • Search Google Scholar
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  • 10

    Park P, Garton HJ, Gala VC, Hoff JT, McGillicuddy JE. Adjacent segment disease after lumbar or lumbosacral fusion: review of the literature. Spine (Phila Pa 1976). 2004;29(17):19381944.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Dohzono S, Toyoda H, Matsumoto T, Suzuki A, Terai H, Nakamura H. The influence of preoperative spinal sagittal balance on clinical outcomes after microendoscopic laminotomy in patients with lumbar spinal canal stenosis. J Neurosurg Spine. 2015;23(1):4954.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Fukui M, Chiba K, Kawakami M, et al. Japanese Orthopaedic Association Back Pain Evaluation Questionnaire. Part 2. Verification of its reliability: The Subcommittee on Low Back Pain and Cervical Myelopathy Evaluation of the Clinical Outcome Committee of the Japanese Orthopaedic Association. J Orthop Sci. 2007;12(6):526532.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Habibi H, Suzuki A, Tamai K, et al. The severity of cervical disc degeneration does not impact 2-year postoperative outcomes in patients with cervical spondylotic myelopathy who underwent laminoplasty. Spine (Phila Pa 1976). 2020;45(18):E1142E1149.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Bijur PE, Silver W, Gallagher EJ. Reliability of the visual analog scale for measurement of acute pain. Acad Emerg Med. 2001;8(12):11531157.

  • 15

    Ha KY, Shin JH, Kim KW, Na KH. The fate of anterior autogenous bone graft after anterior radical surgery with or without posterior instrumentation in the treatment of pyogenic lumbar spondylodiscitis. Spine (Phila Pa 1976). 2007;32(17):18561864.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Makino T, Honda H, Fujiwara H, Yoshikawa H, Yonenobu K, Kaito T. Low incidence of adjacent segment disease after posterior lumbar interbody fusion with minimum disc distraction. Medicine (Baltimore). 2018;97(2):e9631.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17

    Hassett G, Hart DJ, Manek NJ, Doyle DV, Spector TD. Risk factors for progression of lumbar spine disc degeneration: the Chingford Study. Arthritis Rheum. 2003;48(11):31123117.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Jarraya M, Guermazi A, Lorbergs AL, et al. A longitudinal study of disc height narrowing and facet joint osteoarthritis at the thoracic and lumbar spine, evaluated by computed tomography: the Framingham Study. Spine J. 2018;18(11):20652073.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Teraguchi M, Yoshimura N, Hashizume H, et al. Progression, incidence, and risk factors for intervertebral disc degeneration in a longitudinal population-based cohort: the Wakayama Spine Study. Osteoarthritis Cartilage. 2017;25(7):11221131.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Denard PJ, Holton KF, Miller J, et al. Lumbar spondylolisthesis among elderly men: prevalence, correlates, and progression. Spine (Phila Pa 1976). 2010;35(10):10721078.

  • 21

    Wáng YXJ, Deng M, Griffith JF, et al. Lumbar spondylolisthesis progression and de novo spondylolisthesis in elderly Chinese men and women: a year-4 follow-up study. Spine (Phila Pa 1976). 2016;41(13):10961103.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Ravinsky RA, Crawford EJ, Reda LA, Rampersaud YR. Slip progression in degenerative lumbar spondylolisthesis following minimally invasive decompression surgery is not associated with increased functional disability. Eur Spine J. 2020;29(4):896903.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Battié MC, Videman T. Lumbar disc degeneration: epidemiology and genetics. J Bone Joint Surg Am. 2006;88(suppl 2):39.

  • Collapse
  • Expand

Illustration from Kong et al. (pp 4–12). Copyright Qing-Jie Kong. Used with permission.

  • FIG. 1.

    Representative sagittal radiographs showing a lateral full-length standing whole-spine radiograph obtained preoperatively (left) and postoperatively (right) showing measurements of the intervertebral disc height and degree of slip distance (mm) from levels L1–2 to L5–S1 (white arrows) at the 5-year follow-up.

  • FIG. 2.

    Representative radiographic changes after L4–5 single-level decompression. A, C, and E: Before surgery. B, D, and F: Five years after surgery. A and B: Significant change is not observed. C and D: PSD at the decompression segment is shown. E and F: PSD at both the decompression and adjacent segments is shown.

  • 1

    Szpalski M, Gunzburg R. Lumbar spinal stenosis in the elderly: an overview. Eur Spine J. 2003;12(2)(suppl 2):S170S175.

  • 2

    Herkowitz HN, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis. J Bone Joint Surg Am. 1991;73(6):802808.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Bridwell KH, Sedgewick TA, O’Brien MF, Lenke LG, Baldus C. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord. 1993;6(6):461472.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Toyoda H, Nakamura H, Konishi S, Dohzono S, Kato M, Matsuda H. Clinical outcome of microsurgical bilateral decompression via unilateral approach for lumbar canal stenosis: minimum five-year follow-up. Spine (Phila Pa 1976). 2011;36(5):410415.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Lang Z, Li JS, Yang F, et al. Reoperation of decompression alone or decompression plus fusion surgeries for degenerative lumbar diseases: a systematic review. Eur Spine J. 2019;28(6):13711385.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Wang T, Ding W. Risk factors for adjacent segment degeneration after posterior lumbar fusion surgery in treatment for degenerative lumbar disorders: a meta-analysis. J Orthop Surg Res. 2020;15(1):582.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Okuda S, Iwasaki M, Miyauchi A, Aono H, Morita M, Yamamoto T. Risk factors for adjacent segment degeneration after PLIF. Spine (Phila Pa 1976). 2004;29(14):15351540.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Okuda S, Yamashita T, Matsumoto T, et al. Adjacent segment disease after posterior lumbar interbody fusion: a case series of 1000 patients. Global Spine J. 2018;8(7):722727.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Okuda S, Nagamoto Y, Matsumoto T, Sugiura T, Takahashi Y, Iwasaki M. Adjacent segment disease after single segment posterior lumbar interbody fusion for degenerative spondylolisthesis: minimum 10 years follow-up. Spine (Phila Pa 1976). 2018;43(23):E1384E1388.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Park P, Garton HJ, Gala VC, Hoff JT, McGillicuddy JE. Adjacent segment disease after lumbar or lumbosacral fusion: review of the literature. Spine (Phila Pa 1976). 2004;29(17):19381944.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Dohzono S, Toyoda H, Matsumoto T, Suzuki A, Terai H, Nakamura H. The influence of preoperative spinal sagittal balance on clinical outcomes after microendoscopic laminotomy in patients with lumbar spinal canal stenosis. J Neurosurg Spine. 2015;23(1):4954.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Fukui M, Chiba K, Kawakami M, et al. Japanese Orthopaedic Association Back Pain Evaluation Questionnaire. Part 2. Verification of its reliability: The Subcommittee on Low Back Pain and Cervical Myelopathy Evaluation of the Clinical Outcome Committee of the Japanese Orthopaedic Association. J Orthop Sci. 2007;12(6):526532.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Habibi H, Suzuki A, Tamai K, et al. The severity of cervical disc degeneration does not impact 2-year postoperative outcomes in patients with cervical spondylotic myelopathy who underwent laminoplasty. Spine (Phila Pa 1976). 2020;45(18):E1142E1149.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Bijur PE, Silver W, Gallagher EJ. Reliability of the visual analog scale for measurement of acute pain. Acad Emerg Med. 2001;8(12):11531157.

  • 15

    Ha KY, Shin JH, Kim KW, Na KH. The fate of anterior autogenous bone graft after anterior radical surgery with or without posterior instrumentation in the treatment of pyogenic lumbar spondylodiscitis. Spine (Phila Pa 1976). 2007;32(17):18561864.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Makino T, Honda H, Fujiwara H, Yoshikawa H, Yonenobu K, Kaito T. Low incidence of adjacent segment disease after posterior lumbar interbody fusion with minimum disc distraction. Medicine (Baltimore). 2018;97(2):e9631.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17

    Hassett G, Hart DJ, Manek NJ, Doyle DV, Spector TD. Risk factors for progression of lumbar spine disc degeneration: the Chingford Study. Arthritis Rheum. 2003;48(11):31123117.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Jarraya M, Guermazi A, Lorbergs AL, et al. A longitudinal study of disc height narrowing and facet joint osteoarthritis at the thoracic and lumbar spine, evaluated by computed tomography: the Framingham Study. Spine J. 2018;18(11):20652073.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Teraguchi M, Yoshimura N, Hashizume H, et al. Progression, incidence, and risk factors for intervertebral disc degeneration in a longitudinal population-based cohort: the Wakayama Spine Study. Osteoarthritis Cartilage. 2017;25(7):11221131.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Denard PJ, Holton KF, Miller J, et al. Lumbar spondylolisthesis among elderly men: prevalence, correlates, and progression. Spine (Phila Pa 1976). 2010;35(10):10721078.

  • 21

    Wáng YXJ, Deng M, Griffith JF, et al. Lumbar spondylolisthesis progression and de novo spondylolisthesis in elderly Chinese men and women: a year-4 follow-up study. Spine (Phila Pa 1976). 2016;41(13):10961103.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Ravinsky RA, Crawford EJ, Reda LA, Rampersaud YR. Slip progression in degenerative lumbar spondylolisthesis following minimally invasive decompression surgery is not associated with increased functional disability. Eur Spine J. 2020;29(4):896903.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Battié MC, Videman T. Lumbar disc degeneration: epidemiology and genetics. J Bone Joint Surg Am. 2006;88(suppl 2):39.

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