Abstract
Purpose
To compare the outcomes of decompression alone and fusion for L4–5 DLS in different age cohorts (< 70 years, ≥ 70 years).
Methods
This retrospective cohort study included patients who underwent minimally invasive decompression or fusion for L4–5 DLS and had a minimum of 1-year follow-up. Outcome measures were: (1) patient-reported outcome measures (PROMs) (Oswestry Disability Index, ODI; Visual Analog Scale back and leg, VAS; 12-Item Short Form Survey Physical Component Score, SF-12 PCS), (2) minimal clinically important difference (MCID), (3) patient acceptable symptom state (PASS), (4) response on the global rating change (GRC) scale, and (5) complication rates. The decompression and fusion groups were compared for outcomes separately in the < 70-year and ≥ 70-year age cohorts.
Results
233 patients were included, out of which 52% were < 70 years. Patients < 70 years showed non-significant improvement in SF-12 PCS and significantly lower MCID achievement rates for VAS back after decompression compared to fusion. Analysis of the ≥ 70-year age cohort showed no significant differences between the decompression and fusion groups in the improvement in PROMs, MCID/PASS achievement rates, and responses on GRC. Patients ≥ 70 years undergoing fusion had significantly higher in-hospital complication rates. When analyzed irrespective of the surgery type, both < 70-year and ≥ 70-year age cohorts showed significant improvement in PROMs with no significant difference.
Conclusions
Patients < 70 years undergoing decompression alone did not show significant improvement in physical function and had significantly less MCID achievement rate for back pain compared to fusion. Patients ≥ 70 years showed no difference in outcomes between decompression alone and fusion.
Keywords: Degenerative spondylolisthesis, Fusion, Decompression, Age, Association, Outcomes, Younger, Older
Introduction
Degenerative lumbar spondylolisthesis (DLS) is a common spinal pathology that often causes symptoms in patients. In cases where conservative measures fail to provide relief, surgery can be indicated. Surgical treatment of DLS has been shown to improve outcomes compared to nonoperative treatment [1]. Two types of surgeries are mainly considered: decompression alone and fusion. Multiple studies have been conducted comparing the effectiveness of the two surgeries with contrasting evidence [2–6].
Although there is ample data in the literature on the topic of decompression alone versus fusion for DLS, no study has been conducted examining the possible impact of age on the comparison of outcomes after the two surgeries. This is despite the fact that age is a common factor determining the choice of surgery for DLS, as demonstrated by multiple previous studies [7–9]. The objective of this study was, therefore, to compare the outcomes of decompression alone and fusion for L4–5 DLS in two different age cohorts (< 70 years, ≥ 70 years) and assess if age impacts how the two surgeries fare against each other. A secondary objective was to compare the outcomes of surgical treatment of L4–5 DLS between < 70-year and ≥ 70-year age cohorts, irrespective of the surgery type. Since DLS is most commonly seen at L4–5, we selectively chose this level to maintain the homogeneity of our cohort.
Methods
Study design and patient cohort
This Institutional Review Board-approved retrospective cohort study included patients who underwent primary minimally invasive tubular decompression (unilateral laminotomy for bilateral decompression, ULBD) or instrumented interbody fusion (tubular transforaminal lumbar interbody fusion, TLIF; lateral lumbar interbody fusion, LLIF; anterior lumbar interbody fusion; ALIF) (Qureshi-Louie class 1 or 2) [10] for L4–5 degenerative spondylolisthesis of at least 3 mm between April 2017 and January 2022. All patients had a minimum of 1-year follow-up. Patients were stratified into two cohorts based on age: < 70 years and ≥ 70 years. This threshold of 70 years to broadly classify patients into younger and older cohorts is well-established in the literature and has been utilized by various studies related to degenerative conditions of the lumbar spine [11–13].
Surgical selection and technique
All included patients underwent primary surgery for L4–5 DLS with lumbar radiculopathy, neurogenic claudication, or low back pain not responding to conservative measures. L4–5 was recognized as the affected level causing symptoms based on localizing signs, diagnostic injections, and radiological correlation. Revision surgeries were excluded. Patients needing > 1 level surgery for symptomatic stenosis or spondylolisthesis at adjacent levels were excluded. Indications of interbody fusion surgery were unstable spondylolisthesis, high-grade spondylolisthesis (grade 3 or above), up-down foraminal stenosis causing exiting root compression symptoms, spondylolisthesis in combination with a facet cyst, need for alignment restoration, and anticipated removal of > 50% of the facet joint. In the absence of these indications, tubular ULBD surgery without fusion was performed.
Amongst interbody fusion techniques, ALIF and LLIF were preferred in cases where greater lordosis restoration or coronal realignment was needed. Vascular anatomy and psoas morphology were assessed before selecting patients for ALIF and LLIF. ALIF and LLIF relied upon restoration of the disc and foraminal heights and indirect decompression for symptomatic relief. TLIF with direct decompression (ULBD) was preferred in cases with severe central stenosis. All TLIFs were supplemented with pedicle screw instrumentation. It is important to note here that the choice of interbody fusion technique depended heavily on surgeon preference. Surgeries were performed at a single academic institution by multiple fellowship-trained spine surgeons. Surgical techniques were as previously described in the literature [14–21].
Data collection
Following data were collected and managed using REDCap (Research Electronic Data Capture) [22, 23] hosted at Weill Cornell Medicine Clinical and Translational Science Center supported by the National Center For Advancing Translational Science of the National Institute of Health under award number: UL1 TR002384:
Preoperative data age, gender, body mass index (BMI), American Society of Anesthesiologists (ASA) class, age-adjusted Charlson Comorbidity Index (CCI), patient reported outcome measures (PROMs) (Oswestry Disability Index, ODI; Visual Analog Scale, VAS back and leg; 12-Item Short Form Survey Physical Component Score, SF-12 PCS).
Operative data type of surgery (decompression or fusion).
- Postoperative data (outcome measures) Data were collected at 2 weeks, 6 weeks, 12 weeks, 6 months, 1 year, and 2 years after the surgery. Two postoperative time-points—early (< 6 months) and late (≥ 6 months)—were defined for analyses. These timepoints utilized the latest available PROMs data for each patient within their specified range, such that the early timepoint used the latest of the 2-week, 6-week, and 12-week data, and the late timepoint used the latest available 6-month, 1-year, and 2-year data. This methodology allowed us to analyze the data with the maximum follow-up and is well-established in the literature having been utilized previously by multiple studies [24–27].
- PROMs (ODI, VAS back and leg, SF-12 PCS) at < 6 months and ≥ 6 months.
- Minimal clinically important difference (MCID)—it is defined as the minimal change (postoperative minus preoperative) which is perceivable as clinical improvement by the patient. The thresholds utilized for ODI, VAS back, VAS leg, SF-12 PCS were 12.8, 1.2, 1.6, and 4.9, respectively, as described by Copay et al. [28]. This was assessed at < 6 months and ≥ 6 months postoperatively.
- Patient acceptable symptom state (PASS)—it is defined as an absolute postoperative ODI score below which the patient can be expected to have achieved an acceptable symptom state. The cutoff utilized was postoperative ODI score of 25.2, as described by Shahi et al. [29]. This was assessed at ≥ 6 months postoperatively.
- Global rating change (GRC)—it entails a single question: “Compared to preoperative, you feel (1) better, (2) same, or (3) worse?)” [30]. This was assessed at < 6 months and ≥ 6 months postoperatively.
- Complications—intraoperative complications, in-hospital complications, and reoperation rates were analyzed.
Statistical analysis
The decompression and fusion groups were compared for outcomes separately in the < 70-year and ≥ 70-year age cohorts. As a secondary analysis, the < 70-year and ≥ 70-year age cohorts were also compared for outcomes, not specific to the surgery type. Following statistical tests were applied:
Demographic factors: unpaired t-tests and Chi-square tests.
Preoperative and postoperative PROMs and their differences: unpaired t-tests.
MCID/PASS achievement rates, responses on the GRC scale, complication and reoperation rates: Chi-square tests.
Changes in VAS back, ODI, and SF-12 PCS from preoperative values were analyzed with the paired t-tests. Significance was defined at p ≤ 0.05. All analyses were performed using the IBM Statistical Package for the Social Sciences (SPSS) version 25 (IBM Corp., Armonk, NY).
Results
233 patients were included. 121 patients (51.9%) were < 70 years, 112 patients (48.1%) were ≥ 70 years. In the < 70-year age cohort, 27 patients (22.3%) underwent decompression alone and 94 patients (77.7%) underwent fusion. In the ≥ 70-year age cohort, 60 patients (53.6%) underwent decompression alone and 52 patients (46.4%) underwent fusion. Out of the 146 total patients who had fusion surgery, 130 underwent TLIF (89%), 14 underwent LLIF (9.6%), and 2 underwent ALIF (1.4%). In the < 70-year age cohort, age (62.7 vs. 58.1 years; p = 0.01) and age-adjusted CCI (2.5 vs. 1.8; p = 0.001) were significantly higher in the decompression group compared to fusion. There were no significant differences in gender, BMI, and ASA class between the two groups. In the ≥ 70-year age cohort, age was significantly higher (77.7 vs. 74.2 years; p = 0.002) in the decompression group while there were no significant differences in gender, BMI, age-adjusted CCI, and ASA class (Table 1).
Table 1.
Decompression versus fusion for demographic factors and spondylolisthesis grade in the < 70-year and ≥ 70-year age cohorts
| < 70 years | ≥ 70 years | |||||
|---|---|---|---|---|---|---|
| Decompression (n = 27) | Fusion (n = 94) | p | Decompression (n = 60) | Fusion (n = 52) | p | |
| Age | 62.7 ± 8.44 | 58.14 ± 7.9 | 0.01 | 77.7 ± 6.36 | 74.17 ± 4.97 | 0.002 |
| Gender | 0.86 | 0.836 | ||||
| Female | 15 (55.5%) | 54 (57.4%) | 38 (63.3%) | 31 (59.6%) | ||
| Male | 12 (44.5%) | 40 (42.6%) | 22 (36.7%) | 21 (40.4%) | ||
| BMI | 27.73 ± 5.69 | 28.99 ± 6.62 | 0.37 | 25.92 ± 4.66 | 27.63 ± 5.64 | 0.08 |
| Ageadjusted CCI | 2.55 ± 0.89 | 1.83 ± 1.3 | 0.01 | 4.23 ± 1.33 | 4.13 ± 1.32 | 0.7 |
| ASA class | 0.43 | 0.42 | ||||
| I | 1 (3.7%) | 12 (12.8%) | 0 | 1 (1.9%) | ||
| II | 23 (85.2%) | 72 (76.6%) | 49 (81.7%) | 44 (84.6%) | ||
| III | 3 (11.1%) | 10 (10.6%) | 11 (18.3%) | 7 (13.5%) | ||
| Spondylolisthesis grade | 0.26 | 0.72 | ||||
| I | 26 (96.3%) | 84 (89.4%) | 52 (86.7%) | 44 (84.6%) | ||
| II | 1 (3.7%) | 10 (10.6%) | 8 (13.3%) | 8 (15.4%) | ||
Bold values indicate a significant p value. BMI body mass index, CCI Charlson Comorbidity Index, ASA American Society of Anesthesiologists
Decompression versus fusion in < 70 years
Analysis of the < 70-year age cohort showed that patients who underwent decompression did not achieve statistically significant improvement in SF-12 PCS at < 6 months (37.2 vs. 36.1; p = 0.56) and ≥ 6 months (44 vs. 36.1; p = 0.07) compared to the preoperative baseline. However, they showed significant improvement in the other PROMs (ODI, VAS back, VAS leg) at both timepoints. The fusion group, on the other hand, showed significant improvement in all PROMs at both timepoints (Tables 2, 3).
Table 2.
Comparison of PROMs between the decompression and fusion groups in the < 70-year and ≥ 70-year age cohorts preoperatively and at < 6 months and ≥ 6 months after surgery
| < 70 years | ≥ 70 years | |||||
|---|---|---|---|---|---|---|
| Decompression | Fusion | p * | Decompression | Fusion | p * | |
| ODI | ||||||
| Preop | 36.17 ± 17.12 | 39.59 ± 18.34 | 0.43 | 40.56 ± 17.26 | 33.25 ± 16.65 | 0.02 |
| < 6 m | 19.19 ± 12.1 (p < 0.001)# |
23.71 ± 19.53 (p < 0.001)# |
0.26 | 25.12 ± 20.28 (p < 0.001)# |
19.07 ± 15.71 (p < 0.001)# |
0.08 |
| ≥ 6 m | 14.06 ± 12.04 (p < 0.001)# |
17.99 ± 19.61 (p < 0.001)# |
0.45 | 21.32 ± 20.34 (p < 0.001)# |
19.18 ± 16.99 (p < 0.001)# |
0.59 |
| VAS back | ||||||
| Preop | 5.18 ± 2.9 | 5.63 ± 2.73 | 0.5 | 5.14 ± 3.01 | 4.75 ± 3.06 | 0.49 |
| < 6 m | 2.51 ± 2.23 (p < 0.001)# |
2.65 ± 2.27 (p < 0.001)# |
0.78 | 2.67 ± 2.71 (p < 0.001)# |
1.91 ± 1.6 (p < 0.001)# |
0.07 |
| ≥ 6 m | 2.07 ± 1.81 (p = 0.03)# |
2.27 ± 2.39 (p < 0.001)# |
0.76 | 2.1 ± 2.39 (p < 0.001)# |
2.27 ± 2.44 (p < 0.001)# |
0.75 |
| VAS leg | ||||||
| Preop | 5.7 ± 2.67 | 5.7 ± 2.67 | 0.99 | 5.52 ± 3.08 | 5.62 ± 2.9 | 0.86 |
| < 6 m | 2.75 ± 3.04 (p = 0.003)# |
2.32 ± 2.91 (p < 0.001)# |
0.53 | 2.88 ± 3 (p < 0.001)# |
2 ± 2.24 (p < 0.001)# |
0.08 |
| ≥ 6 m | 1.57 ± 1.45 (p < 0.001)# |
2.3 ± 3.11 (p < 0.001)# |
0.39 | 2.07 ± 2.64 (p < 0.001)# |
2.18 ± 2.42 (p < 0.001)# |
0.85 |
| SF12 PCS | ||||||
| Preop | 36.1 ± 9.61 | 32.44 ± 8.77 | 0.1 | 30.37 ± 7.26 | 33.07 ± 8.03 | 0.07 |
| < 6 m | 37.24 ± 7.19 (p = 0.562)# |
37.97 ± 10.52 (p < 0.001)# |
0.77 | 37.71 ± 10.78 (p < 0.001)# |
40.21 ± 9.09 (p = 0.001)# |
0.19 |
| ≥ 6 m | 44.05 ± 9.08 (p = 0.07)# |
43.47 ± 13.05 (p < 0.001)# |
0.87 |
39.81 ± 11.47
(p < 0.001) # |
40.86 ± 10.96 (p < 0.001)# |
0.68 |
represents p value comparing the preoperative to the postoperative values
represents p value comparing the decompression and fusion groups, bold values represent a significant p value. PROMs patient-reported outcome measures, VAS Visual Analog Scale, ODI Oswestry Disability Index, SF-12 PCS 12-Item Short Form Survey Physical Component Score, pre-op preoperative, m months
Table 3.
Comparison of the magnitude of improvement in PROMs between the decompression and fusion groups in the < 70-year and ≥ 70-year age cohorts at < 6 months and ≥ 6 months after surgery
| < 70 years | ≥ 70 years | |||||
|---|---|---|---|---|---|---|
| Decompression | Fusion | p | Decompression | Fusion | p | |
| ΔOΔI | ||||||
| < 6 m | 15.7 ± 16.54 | 16.41 ± 22.31 | 0.89 | 15.69 ± 17.94 | 13.47 ± 17.12 | 0.51 |
| ≥ 6 m | 20.32 ± 14.09 | 20.31 ± 20.06 | 0.99 | 18.53 ± 17.97 | 13.34 ± 18.65 | 0.22 |
| ΔςAΣ βαχκ | ||||||
| < 6 m | 2.55 ± 2.52 | 2.96 ± 3.14 | 0.58 | 2.46 ± 3.72 | 2.7 ± 3.02 | 0.71 |
| ≥ 6 m | 2.28 ± 3.58 | 3.12 ± 3.04 | 0.36 | 2.52 ± 2.6 | 2.35 ± 3.36 | 0.8 |
| ΔςAΣ λεγ | ||||||
| < 6 m | 2.83 ± 3.82 | 3.4 ± 3.99 | 0.55 | 2.65 ± 4.33 | 3.55 ± 3.2 | 0.22 |
| ≥ 6 m | 3.32 ± 2.01 | 3.25 ± 4.04 | 0.95 | 3.16 ± 3.07 | 3.2 ± 3.7 | 0.95 |
| ΔΠXΣ | ||||||
| < 6 m | 1.19 ± 8.84 | 5.58 ± 11.01 | 0.11 | 6.24 ± 9.66 | 6.32 ± 10.64 | 0.97 |
| ≥ 6 m | 6.17 ± 11.2 | 11.15 ± 13.35 | 0.21 | 9.33 ± 9.42 | 7.21 ± 11.74 | 0.43 |
Δ represents change score (preoperative minus postoperative). PROMs patient-reported outcome measures, VAS Visual Analog Scale, ODI Oswestry Disability Index, SF-12 PCS 12-Item Short Form Survey Physical Component Score, m months
Patients < 70 years undergoing decompression also showed significantly lower MCID achievement rates for VAS back at < 6 months (50% vs. 72%; p = 0.02) and ≥ 6 months (47% vs 76%; p = 0.02) compared to fusion. There were no significant differences between the two groups in MCID achievement rates for ODI, VAS leg, and SF-12 PCS. PASS achievement rates and responses on the GRC scale did not show any significant differences between the decompression and fusion groups (Table 4).
Table 4.
Comparison of MCID/PASS achievement rates and responses on the GRC scale between the decompression and fusion groups in the < 70-year and ≥ 70-year age cohorts at < 6 months and ≥ 6 months after surgery
| < 70 years | ≥ 70 years | |||||
|---|---|---|---|---|---|---|
| Decompression | Fusion | p | Decompression | Fusion | p | |
| ODI MCID | ||||||
| < 6 months | 51.60% | 52.40% | 0.93 | 56.60% | 45.30% | 0.24 |
| ≥ 6 months | 80% | 66.70% | 0.3 | 60.60% | 54.80% | 0.61 |
| VAS back MCID | ||||||
| < 6 months | 50% | 72.10% | 0.02 | 64.20% | 57.70% | 0.49 |
| ≥ 6 months | 46.70% | 75.60% | 0.02 | 70.60% | 52.40% | 0.1 |
| VAS leg MCID | ||||||
| < 6 months | 60% | 65.40% | 0.58 | 60.40% | 67.30% | 0.46 |
| ≥ 6 months | 80% | 64.10% | 0.23 | 70.60% | 64.30% | 0.56 |
| SF12 PCS MCID | ||||||
| < 6 months | 38.50% | 48.50% | 0.36 | 51.10% | 49% | 0.84 |
| ≥ 6 months | 50% | 71.20% | 0.11 | 63% | 54.80% | 0.5 |
| PASS | 87.50% | 73.20% | 0.22 | 70% | 68.90% | 0.91 |
| GRC < 6 months | 0.47 | 0.51 | ||||
| Better | 90.50% | 85.10% | 85.70% | 80% | ||
| Same | 9.50% | 8.10% | 9.50% | 17.50% | ||
| Worse | 0 | 6.80% | 4.80% | 2.50% | ||
| GRC ≥ 6 months | 0.44 | 0.19 | ||||
| Better | 92.80% | 89.50% | 76.70% | 77.80% | ||
| Same | 7.20% | 3% | 16.70% | 5.50% | ||
| Worse | 0 | 7.50% | 6.70% | 16.70% | ||
Bold values represent a significant p value. MCID minimal clinically important difference, PASS patient acceptable symptom state, GRC global rating change, VAS Visual Analog Scale, ODI Oswestry Disability Index, SF-12 PCS 12-Item Short Form Survey Physical Component Score
There was no significant difference between the decompression and fusion groups in the < 70-year age cohort in intraoperative complication rates (0 in both groups), in-hospital complication rates (3.7% decompression, 12.7% fusion; p = 0.18), and reoperation rates (7.4% decompression, 8.5% fusion; p = 0.85) (Table 5).
Table 5.
Comparison of intraoperative and in-hospital complication rates and reoperation rates between the decompression and fusion groups in the < 70-year and ≥ 70-year age cohorts
| < 70 years | ≥ 70 years | |||||
|---|---|---|---|---|---|---|
| Decompression | Fusion | p | Decompression | Fusion | p | |
| Intra-op complications | 0 | 0 | - | 4 (6.7%) (all durotomies) | 2 (3.8%) (1 durotomy, 1 screw cut out) | 0.5 |
| In-hospital complications | 1 (3.7%) (POUR) | 12 (12.7%) (4 PONV, 4 POUR, 3 acute blood loss anemia, 1 hyponatremia) | 0.18 | 4 (6.7%) (3 POUR, 1 hyponatremia) | 12 (23.1%) (3 PONV, 3 POUR, 2 motor deficit, 2 acute blood loss anemia, 1 ileus, 1 hyponatremia) | 0.01 |
| Reoperations | 2 (7.4%) (both recurrent stenosis) | 8 (8.5%) (4 pseudarthrosis, 3 ASD, 1 SSI) | 0.85 | 5 (8.3%) (all recurrent stenosis) | 3 (5.7%) (2 pseudarthrosis, 1 ASD) | 0.6 |
Bold values indicate significant p value. POUR postoperative urinary retention, PONV postoperative nausea and vomiting, ASD adjacent segment disease, SSI surgical site infection
Decompression versus fusion in ≥ 70 years
Analysis of the ≥ 70-year age cohort showed that both decompression and fusion groups attained significant improvement in all PROMs at < 6 and ≥ 6 months compared to the preoperative baseline with no significant difference in the magnitude of improvement between the two groups (Tables 2, 3). MCID achievement rates for all PROMs, PASS achievement rates, and responses on the GRC scale did not show any significant differences between the decompression and fusion groups (Table 4). The fusion group in the ≥ 70-year age cohort had a significantly higher in-hospital complication rate (23.1% vs. 6.7% after decompression, p = 0.01). There was no significant difference between the decompression and fusion groups in intraoperative complication rates (0 in both groups) and reoperation rates (7.4% decompression, 8.5% fusion; p = 0.85) (Table 5).
<70-year age cohort versus ≥ 70-year age cohort (not specific to surgery type)
The mean age in the < 70-year and ≥ 70-year age cohorts was 76.1 and 59.2 years, respectively. The ≥ 70-year age cohort had significantly significantly lower BMI (26.7 vs. 28.7 kg/m2, p = 0.01), and significantly higher age-adjusted CCI (4.2 vs. 2, p < 0.001) (Table 6).
Table 6.
Comparison of demographic factors between the < 70-year and ≥ 70-year age cohorts
| < 70 years (n = 121) |
≥ 70 years (n = 112) |
p | |
|---|---|---|---|
| Age | 59.16 ± 8.21 | 76.08 ± 6 | < 0.001 |
| Gender | 0.459 | ||
| Female | 69 (57%) | 69 (61.6%) | |
| Male | 52 (43%) | 43 (38.4%) | |
| BMI | 28.71 ± 6.42 | 26.71 ± 5.18 | 0.01 |
| Ageadjusted CCI | 1.99 ± 1.25 | 4.18 ± 1.32 | < 0.001 |
| ASA class | 0.007 | ||
| I | 13 (10.7%) | 1 (0.9%) | |
| II | 95 (78.5%) | 93 (83%) | |
| III | 13 (10.7%) | 18 (16.1%) |
Bold values represent a significant p value. BMI body mass index, CCI Charlson Comorbidity Index, ASA American Society of Anesthesiologists
Both age cohorts, however, showed significant improvement in all PROMs at both timepoints with no significant difference in the magnitude of improvement (Tables 7, 8). There were no significant differences between the age cohorts in MCID/PASS achievement rates and responses on the GRC at any timepoint (Table 9).
Table 7.
Comparison of PROMs between the < 70-year and ≥ 70-year age cohorts preoperatively and at < 6 months and ≥ 6 months after surgery
| < 70 years | ≥ 70 years | p* | |
|---|---|---|---|
| ODI | |||
| Preoperative | 38.85 ± 18.06 | 38.03 ± 17.63 | 0.755 |
| < 6 months | 22.59 ± 18.03 (p# < 0.001) |
22.45 ± 17.66 (p# < 0.001) |
0.956 |
| ≥ 6 months | 17.3 ± 18.5 (p# < 0.001) |
20.58 ± 18.52 (p# < 0.001) |
0.262 |
| VAS back | |||
| Preoperative | 5.53 ± 2.76 | 4.82 ± 2.97 | 0.093 |
| < 6 months | 2.62 ± 2.25 (p# < 0.001) |
2.27 ± 2.26 (p# < 0.001) |
0.284 |
| ≥ 6 months | 2.23 ± 2.3 (p# < 0.001) |
2.19 ± 2.42 (p# < 0.001) |
0.896 |
| VAS leg | |||
| Preoperative | 5.7 ± 3.07 | 5.43 ± 3.15 | 0.561 |
| < 6 months | 2.41 ± 2.93 (p# < 0.001) |
2.43 ± 2.67 (p# < 0.001) |
0.963 |
| ≥ 6 months | 2.18 ± 2.91 (p# < 0.001) |
2.06 ± 2.41 (p# < 0.001) |
0.793 |
| SF12 PCS | |||
| Preoperative | 33.2 ± 9.02 | 31.67 ± 8.23 | 0.25 |
| < 6 months | 37.83 ± 9.93 (p# < 0.001) |
38.86 ± 10.23 (p# < 0.001) |
0.495 |
| ≥ 6 months | 43.57 ± 12.41 (p# < 0.001) |
40.33 ± 11.04 (p# < 0.001) |
0.099 |
p# represents p value for difference between preoperative and postoperative scores; p* represents p value for difference in the change scores between the two age cohorts; bold values represent significant p values (p ≤ 0.05). PROM patient-reported outcome measure, VAS Visual Analog Scale, ODI Oswestry Disability Index, SF-12 PCS 12-Item Short Form Survey Physical Component Score
Table 8.
Comparison of the magnitude of improvement in PROMs between the < 70-year and ≥ 70-year age cohorts at < 6 months and ≥ 6 months after surgery
| < 70 years | ≥ 70 years | p | |
|---|---|---|---|
| ΔODI | |||
| < 6 months | 16.25 ± 21.07 | 15.44 ± 16.85 | 0.779 |
| ≥ 6 months | 20.31 ± 19.09 | 16.05 ± 18.73 | 0.175 |
| ΔVAS back | |||
| < 6 months | 2.87 ± 3.01 | 2.5 ± 3.31 | 0.429 |
| ≥ 6 months | 2.98 ± 3.13 | 2.35 ± 3.05 | 0.218 |
| ΔVAS leg | |||
| < 6 months | 3.28 ± 3.94 | 2.95 ± 3.71 | 0.574 |
| ≥ 6 months | 3.26 ± 3.76 | 3.27 ± 3.36 | 0.981 |
| ΔSF-12 PCS | |||
| < 6 months | 4.68 ± 10.7 | 6.39 ± 10.33 | 0.297 |
| ≥ 6 months | 10.3 ± 13.08 | 8.5 ± 10.82 | 0.385 |
Δ represents change score (preoperative minus postoperative). PROM patient-reported outcome measure, VAS Visual Analog Scale, ODI Oswestry Disability Index, SF-12 PCS 12-Item Short Form Survey Physical Component Score
Table 9.
Comparison of MCID/PASS achievement rates and responses on the GRC scale between the < 70-year and ≥ 70-year age cohorts at < 6 months and ≥ 6 months after surgery
| < 70 years | ≥ 70 years | p | |
|---|---|---|---|
| MCID ODI | |||
| < 6 months | 58.20% | 50.60% | 0.313 |
| ≥ 6 months | 66.70% | 56.70% | 0.214 |
| MCID VAS back | |||
| < 6 months | 69.40% | 60% | 0.191 |
| ≥ 6 months | 69.10% | 58.80% | 0.19 |
| MCID VAS leg | |||
| < 6 months | 65.30% | 63.80% | 0.829 |
| ≥ 6 months | 65.40% | 67.60% | 0.775 |
| MCID SF12 PCS | |||
| < 6 months | 46.20% | 50% | 0.626 |
| ≥ 6 months | 68.40% | 58.70% | 0.236 |
| PASS | 75.30% | 67.50% | 0.274 |
| GRC < 6 months | 0.285 | ||
| Better | 84.70% | 83.90% | |
| Same | 8.50% | 14.30% | |
| Worse | 6.80% | 1.80% | |
| GRC ≥ 6 months | 0.067 | ||
| Better | 91.40% | 77.90% | |
| Same | 2.80% | 12.10% | |
| Worse | 2.80% | 10.30% |
MCID minimal clinically important difference, PASS patient acceptable symptom state, GRC global rating change, VAS Visual Analog Scale, ODI Oswestry Disability Index, SF-12 PCS 12-Item Short Form Survey Physical Component Score
Discussion
This study attempted to assess if age impacts the comparative outcomes of decompression alone versus decompression with interbody fusion for the surgical treatment of L4–5 DLS. We found that decompression alone had inferior outcomes to fusion in patients < 70 years and similar outcomes in patients ≥ 70 years. Although surgical decision-making for DLS involves multiple factors, we believe that the finding of our study stresses on the importance of appropriate patient selection, especially in the younger cohort.
Age has been demonstrated to be a decision-making factor for decompression alone versus fusion for the surgical treatment of DLS. In a survey of 223 spine surgeons conducted by Schroeder et al., age was found to affect the recommended treatment, with older patients being significantly less likely to be offered a fusion procedure [7]. Another survey conducted by Morse et al. found age > 65 years to be an important variable for the decision-making of fusion versus decompression [8]. A multicenter retrospective Canadian study found that decreasing age increased the odds of a fusion procedure [9]. Likewise, in the current study, majority of younger patients underwent a fusion procedure and majority of older patients underwent decompression alone. Importantly, our findings demonstrated that patients < 70 years undergoing decompression alone did not show significant improvement in their physical function and had significantly less MCID achievement rates in back pain compared to patients who underwent fusion. In addition, patients ≥ 70 years undergoing fusion had significantly higher in-hospital complication rates compared to patients who underwent decompression alone. These findings serve to support the preference towards fusion in younger patients and fusion in older patients in the setting of degenerative spondylolisthesis, obviously after due consideration of other more important radiological and clinical criteria in this decision-making.
The fact that this study shows inferior outcomes of decompression alone in patients < 70 years and similar outcomes of decompression alone and fusion in patients ≥ 70 years suggests an age demarcation in the comparative outcomes of decompression alone versus fusion for DLS. This has not been shown in the literature before. The possible explanation behind inferior outcomes of decompression alone in patients < 70 years is that since these patients are younger (average age of 59 years in our cohort), they are likely to be more active, have healthier and better maintained discs, and have an overall lesser degree of degeneration. These patients, therefore, are more likely to develop some motion in the affected spinal segment over time if they undergo decompression alone, even though there might not have been any signs of instability before the index procedure. Contrastingly, patients over 70 years (average age of 76 years in our cohort) are likely to be less active and have a higher degree of degeneration. This provides inherent stiffness and stability to the affected spinal segment, thus decreasing the likelihood of any motion even when decompressed alone.
Leaving the confounding role of age aside, multiple studies have performed the overall comparison between the outcomes of decompression alone versus fusion for the treatment of DLS. A randomized controlled trial (RCT) of 66 patients conducted by Ghogawala et al. demonstrated slightly greater improvement in overall physical health-related quality of life following fusion compared to decompression alone [2]. Similar to our SF-12 PCS finding, they reported significantly greater improvement in SF-36 PCS at 2 years, 3 years, and 4 years after fusion compared to decompression alone. An RCT conducted by Inose et al. that included L4–5 DLS patients under 75 years of age (n = 85) demonstrated greater improvements in the SF-36 subscale scores of vitality (VT), social functioning (SF), role limitations—emotional (RE), and mental health (MH) after fusion compared to decompression alone [3]. Contrastingly, Austevoll et al., in their RCT of 267 patients, showed that laminectomy alone was non-inferior to fusion in outcomes at 2 years [4]. A retrospective cohort study conducted by Bovonratwet et al. reported similar improvements in pain and physical function after minimally invasive decompression alone and fusion for DLS [5]. A meta-analysis by Koenig et al. also showed similar outcomes after the two procedures and could not firmly support one surgical treatment over the other [6]. Forsth et al. conducted an RCT of 247 patients between 50 and 80 years of age with lumbar stenosis undergoing decompression with fusion or decompression alone surgery [31]. Randomization was stratified based on the presence of degenerative spondylolisthesis (n = 135). Outcomes in the form of PROMs, 6-min walk test, and health economic evaluation were assessed at 2 years and 5 years. None of the outcome measures had any significant difference at 2 years and 5 years between the decompression with fusion and decompression alone groups. Reoperation rates were also found to be similar (22% after fusion, 21% after decompression alone) with a mean follow-up period of 6.5 years. Although these studies compared the outcomes of decompression and fusion for DLS, there is no data on how age impacts this comparison, even though age is an important decision-making factor for the choice of surgery. To the best of our knowledge, this is the first study comparing decompression alone and fusion separately in younger and older age cohorts.
Our study also demonstrated no significant differences in outcomes between the < 70-year and ≥ 70-year age cohorts, when analyzed irrespective of the surgery type. Improvement in PROMs, MCID/PASS achievement rates, and the responses on the GRC scale were similar in the two age cohorts following surgical treatment for L4–5 DLS. Although the impact of age on spine surgery outcomes is well-studied [32, 33], only two studies have attempted to analyze this association with postoperative outcomes specifically in DLS patients [34, 35]. Karsy et al. performed a prospective database analysis including 608 patients who underwent surgical treatment for grade I DLS and reported significant improvement in all PROMs, regardless of age [34]. Liao et al. conducted a retrospective study of 76 patients following surgical treatment for DLS and found that patients over 80 years had similar clinical results in terms of their ODI and VAS scores as patients who were 65–79 years old [35].
There are several limitations of this study. The retrospective and single-center study design limits the level of evidence and the generalizability of the findings, respectively. Patients included in this study were not randomized to undergo decompression or fusion. Rather the selection process was dependent on criteria including age, comorbidity burden, surgical fitness, disc height, facet diastasis/effusion, and the predominant presenting complaint. This selection bias could have impacted the findings. The minimum follow-up required for inclusion in the study was 1 year (maximum follow-up of 2 years). Studies with longer follow-ups are required to better analyze the impact of age on comparative outcomes of decompression and fusion in DLS over the long term. We included patients only with L4–5 degenerative spondylolisthesis since this is the most commonly affected level and a similar inclusion criterion has been utilized by various prior studies [3, 36, 37]. Although this methodology helps maintain the homogeneity of the cohort and hence the validity of the findings, it does decrease the applicability for comparison between decompression alone and fusion surgeries for degenerative spondylolisthesis at other levels. The study lacked a control group of patients with degenerative spondylolisthesis who were managed conservatively. Although having such a control group would have enabled us to compare non-operative versus operative treatment, this analysis has been performed by multiple previous studies [1, 38, 39] and the focus of this study was to analyze differences between decompression alone and fusion surgeries in two different age cohorts. Age-adjusted CCI was significantly different between the decompression and fusion groups in the < 70-year age cohort. However, we lacked the numbers to do additional analysis to control for these differences. Confounding variables like degree of degeneration, spinal alignment, duration of preoperative symptoms, and psychosocial factors were not accounted for. Our outcome measures of MCID/PASS and GRC have been criticized for dependence on preoperative PROM scores and recall bias, respectively [40–42]. Although we studied improvement in back pain, the type of pain (muscular, discogenic, facetogenic, neurogenic, sacroiliac) was not specified. Additionally, functional outcomes such as change in posture and walking distance were not analyzed.
In conclusion, patients < 70 years undergoing decompression alone did not show significant improvement in physical function and had significantly less MCID achievement rate for back pain compared to fusion. Patients ≥ 70 years showed no difference in outcomes between decompression alone and fusion. When analyzed irrespective of the surgery type, the < 70-year and ≥ 70-year age cohorts demonstrated similar outcomes following surgical treatment for degenerative spondylolisthesis.
Funding
No direct funding was received for this study. However, this study used REDCap (Research Electronic Data Capture) hosted at Weill Cornell Medicine Clinical and Translational Science Center supported by the National Center For Advancing Translational Science of the National Institute of Health under award number: UL1 TR002384.
Conflict of interest
Sheeraz A. Qureshi: Royalties: Stryker K2M, Globus Medical, Inc.; Globus Medical, Inc.: HS2, LLC; Private Investments: Tissue Differentiation Intelligence; Consulting: Stryker K2M, Globus Medical, Inc.; Speaking and/or Teaching Arrangements: AMOpportunities, Globus Medical, Inc.; Board of Directors: Society of Minimally Invasive Spine Surgery; Scientific Advisory Board/Other Office: International Society for the Advancement of Spine Surgery, Cervical Spine Research Society, Lumbar Spine Research Society, North American Spine Society, Association of Bone and Joint Surgeons, Simplify Medical, Inc., LifeLink.com Inc., Society of Minimally Invasive Spine Surgery, Minimally Invasive Spine Study Group, Spinal Simplicity, LLC, Contemporary Spine Surgery, Annals of Translational Medicine. Sravisht Iyer: Innovasis (Research Support), Globus Medical (Speaker’s Bureau), Healthgrades (Advisory Board Member), Stryker (Speaker’s Bureau). Rest of the authors: None.
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