Degenerative lumbar spondylolisthesis (DLS) is a common condition of the lumbar spine.1,2 Surgery should be considered in patients experiencing from recalcitrant back pain or nerve irritation, as well as in patients in whom conservative therapy has failed.3–5 While planning the operation, neurosurgeons should determine whether the patient’s condition is accompanied by lumbar instability (LI).6–9 At present, lateral flexion-extension (LFE) standing radiographs are the most widely used tool for evaluating lumbar stability.10 However, the quality of these images is frequently decreased because patient cooperation has a large effect on functional radiographic imaging, and different degrees of patient pain tolerance and cooperation may lead to variations in examination results.11–13
In recent years, both auxiliary examination methods for LI and the accuracy of radiographic positioning have developed rapidly, giving rise to technologies such as traction positioning during radiographic examination and supine scanning using CT or MRI. However, these examination methods are expensive and may be cumbersome, and hence they cannot be widely performed in the clinical setting.13–16 In an effort to deal with this problem, we have developed a new standardized technique for evaluating lumbar stability, performing LFE radiographs with a fulcrum for patient support during positioning. In this study, we evaluated whether the use of this technique can improve the detection rate of LI in patients with DLS.
Methods
Design and Manufacture of the Fulcrum
The fulcrum includes three parts (Fig. 1A and B). The upper part is the support platform (height 30 cm), which includes the semiarc leaning bench with an armrest on both sides. The semiarc leaning bench is made of polyethylene, which allows the penetration of rays to ensure that the film is clear and measurable. The armrest can be adjusted according to the degree of patient bending required and may help the patient stand steadily during the examination process. This support system may also reduce patient anxiety. The middle of the fulcrum has an adjustable lifting platform with a wheel on the side that allows height adjustment (height range 9–35 cm). The operation is simple and convenient. At the bottom of the leaning bench there is a four-corner bracket that stabilizes the whole apparatus (height 30 cm).
A and B: The fulcrum consists of three parts. The top is the support platform, including the semiarc leaning tool with armrests on both sides. The patient can hold the armrest with both hands to maintain body balance. The middle part is a lifting platform that can be adjusted according to the height of the patient. The bottom layer is a four-corner base that provides the stability of the fulcrum. C and D: During the flexion radiographs, the patient stood upright facing the fulcrum from a close distance. The patient held the armrest on both sides of the fulcrum and bent forward to the maximum extent. At this time, the stress flexion radiographs were taken. E and F: Then the patient turned their body and held the armrests on the two sides of the fulcrum with both hands to maintain body balance with the body tilted back as much as they could. At this time, the stress extension radiographs were taken. Figure is available in color online only.
Study Patients
A total of 67 patients with L4–5 DLS underwent surgery in our hospital from January 2021 to December 2021 (40 men and 27 women; mean age 58.49 ± 15.10 years). The inclusion criteria were as follows: 1) single-level grade 1 lumbar spondylolisthesis (L4–5) demonstrated by standard lumbar radiographs, including anteroposterior and lateral radiographs; 2) presentation with persistent mechanical low-back and radicular leg pain after more than 6 months of conservative treatment; and 3) CT imaging taken after admission. Exclusion criteria included positive history of any of the following: previous thoracolumbar surgery, acute spinal trauma, tumor, spondylolysis, ankylosing spondylitis, multilevel lumbar spondylolisthesis, and severe scoliosis. This study was reviewed and approved by the ethics committee of the hospital, and written informed consent was obtained from all participants in this study. After admission, all patients underwent lumbar spine radiography that included traditional (LFE) radiographs and LFE with fulcrum (LFEF) radiographs.
Inspection Method
The fulcrum was 1 m away from and perpendicular to the radioactive source. During the flexion radiographs (Fig. 1C and D), the patient stood upright facing the fulcrum from a close distance, and the height of the fulcrum was adjusted to the level of the bilateral iliac crest. The patient held the armrest on both sides of the fulcrum with both hands to maintain body balance, and then bent forward to the maximum extent. At this time, the stress flexion radiographs were taken. The patient then turned their body and stayed close to the fulcrum, holding the armrests on the two sides of the fulcrum with both hands to maintain body balance with the body tilted back as much as possible without discomfort. At this time, the stress extension radiographs (Fig. 1E and F) were taken.
Data Measurement
All radiographs were taken by two radiologists with 5 years of experience in musculoskeletal system imaging. Three spine surgeons with more than 10 years of experience completed the measurements independently. All the spine surgeons were blinded to the patients and the device. The average values of the measured data were the final data. All data were measured using radiology software (Neusoft PACS/RIS) to reduce variability. Measurements were taken with the patient in the neutral position, extension position, flexion position, stress extension position, and stress flexion position (Fig. 2A and B). Sagittal translation (ST), segmental angulation (SA), posterior opening (PO), and change in lumbar lordosis (CLL) were also measured. LI was defined as ST ≥ 3 mm or SA ≥ 20° on flexion-extension radiographs, or PO ≥ 5° on flexion radiographs.17,18 The whole and relative data of ST, SA, and PO and the detection rates on LFEF radiographs were compared with those of LFE. In addition, the amount of flexion-extension was assessed through the CLL on flexion-extension radiographs and compared between LFE and LFEF radiographs.
A and B: Measurement used in the study. For ST, the anterior translation of L4 was recorded with positive numbers, and the posterior translation was recorded with negative numbers. The difference between the two distances was defined as the amount of ST (a − a1). For SA, the difference of intervertebral angles between flexion and extension radiographs was calculated (β1 − β). For PO, the intervertebral angle on the flexion radiograph was measured (−β). Next, to determine the CLL, LL was measured as the angle between the cranial L1 and cranial S1 vertebral endplates (α, α1). After that, the difference of LL angles between flexion and extension radiographs was calculated (α1 − α). C–F: The flexion and extension images of a patient aged 40–49 years showed higher segmental translation when obtained with the fulcrum (E and F) than without the fulcrum (C and D) (3.74 vs 0.95 mm, respectively). Furthermore, SA and CLL measured with patients supported by the fulcrum were larger than those measured without the fulcrum (16° vs 2°, and 53° vs 22°, respectively). A PO of 7° was noted in the flexion image with the fulcrum. Figure is available in color online only.
Data Analysis
All statistical tests were conducted using IBM SPSS version 20.0 (IBM Corp.). Continuous variables are presented as mean ± standard deviation. A paired t-test was used to assess the SA, CLL, ST, and PO differences between LFEF and LFE. A chi-square test or Fisher exact test was used to compare the ratios of the PO ≥ 5° and LI between LFEF and LFE; p < 0.05 was considered significant.
Results
A total of 67 patients with L4–5 grade 1 DLS were enrolled in this study (40 men and 27 women with an average age of 58.49 ± 15.10 years). The measurement of ST revealed an absolute value of 1.32 ± 1.05 mm in LFE and 2.64 ± 1.45 mm in LFEF radiographs, with a significant difference between them (p < 0.05; Table 1). There were 6 patients (8.96%) with an ST ≥ 3 mm in LFE and 20 patients (29.85%) with an ST ≥ 3 mm in LFEF radiographs. The value of SA in LFE was 5.76° ± 3.72°, and the value of SA in LFEF radiographs was 9.96° ± 4.00°, with the difference being significant (p < 0.05; Table 1). One of 67 patients (1.49%) showed an SA ≥ 20° in LFEF radiographs, and this patient was also one of the patients who showed an ST ≥ 3 mm in LFEF radiographs. No patients showed an SA ≥ 20° in LFE radiographs.
ST, SA, PO, and CLL measured in flexion-extension radiographs taken with or without a fulcrum for patient support
| Variable | Fulcrum | t | p Value | |
|---|---|---|---|---|
| w/ | w/o | |||
| ST, mm | 2.64 ± 1.45 | 1.32 ± 1.05 | −9.329 | <0.001 |
| SA, ° | 9.96 ± 4.00 | 5.76 ± 3.72 | −8.097 | <0.001 |
| CLL, ° | 37.07 ± 13.16 | 27.31 ± 11.96 | −7.075 | <0.001 |
| PO, ° | −0.55 ± 3.83 | −2.07 ± 3.45 | −5.360 | <0.001 |
Values are presented as mean ± SD unless otherwise indicated. For all variables, values measured with the fulcrum were significantly higher than those measured without the fulcrum.
The results of PO measurement were −2.07° ± 3.45° in LFE and −0.55° ± 3.83° in LFEF radiographs, with a significant difference between these values (p < 0.05; Table 1). Four of 67 patients (6.0%) showed a PO ≥ 5° in LFEF, and none showed a PO ≥ 5° in LFE radiographs. The number of patients with LI was 7 (10.4%) in LFE and 21 (31.3%) in LFEF. Four of 67 patients (5.97%) showed a PO ≥ 5° in LFEF, and none met this threshold in LFE radiographs (Table 2). Of the 4 patients with a PO ≥ 5° in LFEF, 3 patients showed an ST ≥ 3 mm in LFEF, and 1 patient did not meet the conditions of ST and SA LI in LFEF radiographs, indicating that the PO should be a separate factor in the process of LI detection.
Comparison of PO and LI in flexion-extension radiographs taken with or without a fulcrum for patient support
| Radiography Results (n = 67) | p Value | ||
|---|---|---|---|
| Yes | No | ||
| LI | |||
| w/ fulcrum | 21 (31.3) | 46 (687) | <0.001* |
| w/o fulcrum | 7 (10.4) | 60 (89.6) | |
| PO, ≥5° | |||
| w/ fulcrum | 4 (6.0) | 63 (94.0) | 0.119† |
| w/o fulcrum | 0 | 67 (100) | |
Values are presented as number (%) of patients unless otherwise indicated.
Chi-square test; chi-square value = 17.122.
Fisher exact test.
The mean CLL measurements were 27.31° ± 11.96° in LFE and 37.07° ± 13.16° in LFEF, with a significant difference between these values (p < 0.05; Table 1). This result indicated that the range of motion changes measured for lumbar lordosis (LL) were significantly increased in LFEF compared with LFE radiographs. There were 7 patients (10.4%) with LI in LFE and 21 (31.3%) with LI in LFEF, and this difference was also significant (p < 0.05; Table 2). LFEF radiographs can decrease the false-negative rate compared with that for imaging without the fulcrum. There were 14 patients with LI detected in LFEF radiographs who had false-negative results in LFE radiographs taken without the fulcrum. When asked about discomfort during the radiographic examinations, 64 patients felt more comfortable with the fulcrum. Three patients with severe back pain who reported unbearable pain when they extended and flexed their waist slightly reported feeling little difference between the two methods.
The flexion and extension images of these patients, aged 40–49 years, showed higher segmental translation in LFEF radiographs than in LFE radiographs taken without the fulcrum (3.74 vs 0.95 mm). Furthermore, SA and CLL measurements were larger when taken while patients were supported with the fulcrum than without fulcrum support (16° vs 2° and 53° vs 22°, respectively). A PO of 7° was noted in the flexion image taken with fulcrum support (Fig. 2C–F).
Discussion
In our study, we tested a new method of obtaining lumbar LFE radiographs with the patient support provided by a fulcrum, which may be useful as a standardized technique for evaluating abnormal lumbar activity and lumbar stability. The fulcrum includes three parts to provide support to the patient for leaning forward and backward and can be disassembled to facilitate handling. When lumbar LFEF radiographs are being taken, patients can hold the armrest in the support platform, which can reduce the fear of falling and allow patients to better complete the process of obtaining the radiographs. In this study, we have formulated the specifications and processes for taking lumbar LFEF radiographs and demonstrated that this method can reduce interference of human factors in the process of obtaining accurate radiographic data with good repeatability.
To the best of our knowledge, LI does not have specific symptoms or signs, and there are as of yet no unified diagnostic criteria to detect this condition.19–22 Flexion-extension lateral radiographs taken with the patient in the standing position are the most widely used tools to evaluate radiological lumbar stability. However, the details of performing this imaging method may vary across institutions. In addition, spinal surgeons have various viewpoints regarding the definition of abnormal mobility in LI.8,9,23,24 In the past few years, great progress has been made in the radiological examination and evaluation of lumbar stability. Landi et al. studied the use of dynamic projections in standing and recumbent positions in 200 patients with LI.25 The detection rates of instability in L4–5 radiographs were 14.3% with the patient in a standing position and 11.6% with the patient in a recumbent position. In our study, there were 21 patients (31.3%) with abnormal instability detected in LFEF radiographs. This detection rate was higher than that reported by Landi et al. Tarpada et al. demonstrated that the addition of a supine radiograph to the standard spondylolisthesis evaluation shows more reduction in anterolisthesis than an extension radiograph.26 Flexion-supine radiographs show more vertebral mobility and reduction and thus may be more appropriate for the initial evaluation of lumbar spondylolisthesis than flexion-extension radiographs. The mean mobility with flexion-supine radiographs reported by Tarpada et al. was 7.83% ± 4.67%. Morita et al. analyzed flexion-extension radiographs in patients led by hand to provide assistance with positioning and those not led by hand.18 The measurement of ST indicated an absolute value of 3.8 ± 1.7 mm in patients with this positioning assistance and 2.2 ± 1.3 mm in patients without it.
Study findings determined with LFE radiographs are frequently questioned because patient cooperation has an important effect on functional radiographic imaging, and different degrees of pain tolerance and cooperation in the patient may cause different examination results. Therefore, a rapid, convenient, and less cumbersome detection tool is urgently needed. In an effort to resolve this issue, we designed a fulcrum for patient positioning during radiography as a tool for enhancing detection of LI and tested its use in this study. The height of the positioning fulcrum can be adjusted to the height of the patient, so that the highest point of the auxiliary detection platform is parallel to the level of the bilateral iliac crests. The standardized application of this process can reduce measurement deviations on radiographs to the greatest extent. In this study, we found that low-back pain or poor posture may lead to underestimation of LI in patients who undergo LFE radiography without support. When LFEF radiographs were taken of the same patients while supported with the fulcrum, the burden on muscles and ligaments used by the patient to maintain the position of extension or flexion in the waist and back was reduced. Thus, the symptoms of lumbar pain were greatly relieved. This improvement in the comfort of patients during radiography led to more successful results.
Our study included 67 patients with L4–5 DLS. The measurement of ST revealed an absolute value of 2.64 ± 1.45 mm in LFEF radiographs, which was significantly higher than that in LFE radiographs. There were 6 patients (8.96%) with an ST ≥ 3 mm in LFE and 20 patients (29.85%) with an ST ≥ 3 mm in LFEF. This difference indicated that flexion-extension radiographs obtained with fulcrum support of the patient can display ST instability more clearly. Meanwhile, we also obtained results showing that compared with LFE, LFEF can significantly improve the measurement of SA and PO. Four of 67 patients (5.97%) showed a PO ≥ 5° in LFEF, and 1 patient did not meet the conditions of ST and SA LI in LFEF radiographs. These findings indicate that the PO should be treated as a separate factor in the process of LI detection. The changes of LL were significantly greater in LFEF than in LFE without fulcrum radiographs, which indicates that patients can complete the lumbar activities needed to obtain accurate radiographs more safely and comfortably with assistance of this auxiliary tool. LI was detected in 7 patients (10.4%) with LFE radiographs obtained without the fulcrum and 21 patients (31.3%) with LFEF radiographs, and this difference was also significant. In the present study, the detection rate of LI was improved by use of a fulcrum for patient support (31.3% vs 10.4%), and missed diagnosis of LI caused by low-back pain and the inability of the patient to cooperate with the examination without auxiliary support was avoided.
There are also some limitations to this study. First, our sample of 67 patients was small. Furthermore, the definition of instability (ST ≥ 3 mm or SA ≥ 20° on flexion-extension radiographs, or PO ≥ 5° in this study) was calculated with the data of standard flexion-extension radiography without the use of a fulcrum. Our next step is to measure the lumbar spine values of healthy individuals without spinal pain or instability using standard flexion-extension radiography with a fulcrum with the goal of formulating the reference values for LI measured with fulcrum support of the study participants.
Conclusions
This study shows that compared with traditional LFE radiographs obtained without support provided for patient positioning, LFEF radiographs with integrated patient positioning support can make the process safer and more comfortable by reducing the patient’s fear and back pain, which leads to improved positioning and more accurate results. The findings show that the ST, SA, and PO measurements on LFEF radiographs were significantly greater than those on LFE radiographs obtained without fulcrum support. The LFEF method enables the acquisition of accurate hyperextension and flexion images and is thus worthy of further clinical application and promotion.
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: all authors. Acquisition of data: Lin, Zhiqiang Zhou, Li, Shan, Zhentao Zhou, Sun. Analysis and interpretation of data: X Zhou, Lin, Zhiqiang Zhou, Li. Drafting the article: X Zhou, Lin, Zhiqiang Zhou, Li. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: X Zhou. Statistical analysis: Lin, Zhiqiang Zhou, Li. Administrative/technical/material support: Lin, Zhiqiang Zhou, Li, Shan, Zhentao Zhou, Sun. Study supervision: Lin, Zhiqiang Zhou, Li.
References
- 1↑
Allegri M, Montella S, Salici F, et al. Mechanisms of low back pain: a guide for diagnosis and therapy. F1000Res. 2016;5:F1000 Faculty Rev-1530.
- 2↑
Huang M, Buchholz A, Goyal A, et al. Impact of surgeon and hospital factors on surgical decision-making for grade 1 degenerative lumbar spondylolisthesis: a Quality Outcomes Database analysis. J Neurosurg Spine. 2021;34(5):768–778.
- 3↑
Bisson EF, Guan J, Bydon M, et al. Patient-reported outcome improvements at 24-month follow-up after fusion added to decompression for grade I degenerative lumbar spondylolisthesis: a multicenter study using the Quality Outcomes Database. J Neurosurg Spine. 2021;35(1):42–51.
- 4
Chan AK, Bisson EF, Bydon M, et al. A comparison of minimally invasive and open transforaminal lumbar interbody fusion for grade 1 degenerative lumbar spondylolisthesis: an analysis of the prospective Quality Outcomes Database. Neurosurgery. 2020;87(3):555–562.
- 5↑
Haddas R, Sandu CD, Mar D, Block A, Lieberman I. Lumbar decompression and interbody fusion improves gait performance, pain, and psychosocial factors of patients with degenerative lumbar spondylolisthesis. Global Spine J. 2021;11(4):472–479.
- 6↑
Ghogawala Z, Dziura J, Butler WE, et al. Laminectomy plus fusion versus laminectomy alone for lumbar spondylolisthesis. N Engl J Med. 2016;374(15):1424–1434.
- 7
Austevoll IM, Gjestad R, Brox JI, et al. The effectiveness of decompression alone compared with additional fusion for lumbar spinal stenosis with degenerative spondylolisthesis: a pragmatic comparative non-inferiority observational study from the Norwegian Registry for Spine Surgery. Eur Spine J. 2017;26(2):404–413.
- 8↑
Försth P, Ólafsson G, Carlsson T, et al. A randomized, controlled trial of fusion surgery for lumbar spinal stenosis. N Engl J Med. 2016;374(15):1413–1423.
- 9↑
Sigmundsson FG, Jönsson B, Strömqvist B. Outcome of decompression with and without fusion in spinal stenosis with degenerative spondylolisthesis in relation to preoperative pain pattern: a register study of 1,624 patients. Spine J. 2015;15(4):638–646.
- 10↑
Wood KB, Popp CA, Transfeldt EE, Geissele AE. Radiographic evaluation of instability in spondylolisthesis. Spine (Phila Pa 1976). 1994;19(15):1697–1703.
- 11↑
Zhou QS, Sun X, Chen X, et al. Utility of natural sitting lateral radiograph in the diagnosis of segmental instability for patients with degenerative lumbar spondylolisthesis. Clin Orthop Relat Res. 2021;479(4):817–825.
- 12
Temes B, Karas S, Manwill J. Assessment of lumbar spine instability using C-arm fluoroscopy. J Orthop Sports Phys Ther. 2016;46(9):810.
- 13↑
Hey HW, Lau ET, Lim JL, et al. Slump sitting X-ray of the lumbar spine is superior to the conventional flexion view in assessing lumbar spine instability. Spine J. 2017;17(3):360–368.
- 14
Cho IY, Park SY, Park JH, Suh SW, Lee SH. MRI findings of lumbar spine instability in degenerative spondylolisthesis. J Orthop Surg (Hong Kong). 2017;25(2):2309499017718907.
- 15
Kao Y, Liu Z, Leng J, et al. A preoperative predictive model of lower lumbar spine instability based on three-dimensional computed tomography: a retrospective case-control pilot study. Orthop Surg. 2021;13(2):484–492.
- 16↑
Charest-Morin R, Zhang H, Shewchuk JR, et al. Dynamic morphometric changes in degenerative lumbar spondylolisthesis: a pilot study of upright magnetic resonance imaging. J Clin Neurosci. 2021;91:152–158.
- 17↑
Yoshimoto M, Miyakawa T, Takebayashi T, et al. Microendoscopy-assisted muscle-preserving interlaminar decompression for lumbar spinal stenosis: clinical results of consecutive 105 cases with more than 3-year follow-up. Spine (Phila Pa 1976). 2014;39(5):E318–E325.
- 18↑
Morita T, Yoshimoto M, Terashima Y, et al. Do we have adequate flexion-extension radiographs for evaluating instability in patients with lumbar spondylolisthesis? Spine (Phila Pa 1976). 2020;45(1):48–54.
- 19↑
Alyazedi FM, Lohman EB, Wesley Swen R, Bahjri K. The inter-rater reliability of clinical tests that best predict the subclassification of lumbar segmental instability: structural, functional and combined instability. J Manual Manip Ther. 2015;23(4):197–204.
- 20
Areeudomwong P, Jirarattanaphochai K, Ruanjai T, Buttagat V. Clinical utility of a cluster of tests as a diagnostic support tool for clinical lumbar instability. Musculoskelet Sci Pract. 2020;50:102224.
- 21
Sriphirom P, Siramanakul C, Chaipanha P, Saepoo C. Clinical outcomes of interlaminar percutaneous endoscopic decompression for degenerative lumbar spondylolisthesis with spinal stenosis. Brain Sci. 2021;11(1):E83.
- 22↑
Dombrowski ME, Rynearson B, LeVasseur C, et al. ISSLS Prize in Bioengineering Science 2018: dynamic imaging of degenerative spondylolisthesis reveals mid-range dynamic lumbar instability not evident on static clinical radiographs. Eur Spine J. 2018;27(4):752–762.
- 23↑
Iyer S, Lenke LG, Nemani VM, et al. Variations in sagittal alignment parameters based on age: a prospective study of asymptomatic volunteers using full-body radiographs. Spine (Phila Pa 1976). 2016;41(23):1826–1836.
- 24↑
Viswanathan VK, Hatef J, Aghili-Mehrizi S, Minnema AJ, Farhadi HF. Comparative utility of dynamic and static imaging in the management of lumbar spondylolisthesis. World Neurosurg. 2018;117:e507–e513.
- 25↑
Landi A, Gregori F, Marotta N, Donnarumma P, Delfini R. Hidden spondylolisthesis: unrecognized cause of low back pain? Prospective study about the use of dynamic projections in standing and recumbent position for the individuation of lumbar instability. Neuroradiology. 2015;57(6):583–588.
- 26↑
Tarpada SP, Cho W, Chen F, Amorosa LF. Utility of supine lateral radiographs for assessment of lumbar segmental instability in degenerative lumbar spondylolisthesis. Spine (Phila Pa 1976). 2018;43(18):1275–1280.
