Lumbar disc herniation (LDH) is one of the most

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Clinical Characteristics and Risk Factors of Recurrent Lumbar Disk Herniation

A Retrospective Analysis of Three Hundred Twenty-One Cases

Zhonghai Li, MD,Hao Yang, MD,^yMozhen Liu, MD,Ming Lu, MD,Jin Chu, MD,Shuxun Hou, MD,^z and Tiesheng Hou, MD^§

Study Design. Retrospective clinical series.

Objective. To investigate the clinical features and the risk factors for recurrent lumbar disc herniation (rLDH) in China.

Summary of Background Data. rLDH is a common cause of poor outcomes after lumbar microdiscectomy surgery. Risk factors for rLDH are increasingly being investigated. However, results in these previous studies were not always consistent.

Methods. Between June 2005 and July 2012, 321 consecutive patients with single-level LDH, who underwent surgery, were enrolled in this study. We divided the patients into the recurrent group (R group) and the nonrecurrent group (N group) and compared their clinical parameters and preoperative radiologic parameters. The relationships between the variables and rLDH were evaluated by univariate analysis and multiple logistic regression analysis.

Results. There was significant difference between groups in sex (P ¼ 0.003), age (P ¼ 0.003), current smoking (P ¼ 0.004), body mass index (BMI) (P ¼ 0.04), occupational lifting (P < 0.001), trauma history (P ¼ 0.04), procedures (P ¼ 0.04), herniation type (P ¼ 0.006), disc height index (DUI) (P ¼ 0.04), facet orientation

(FO) (P ¼ 0.04), facet tropism (FT) (P ¼ 0.04), and sagittal range of motion (from) (P ¼ 0.04). By putting these differences in logistic regression analysis, it showed that being male, young age, current smoking, higher BMI, herniation type (transligamentous extrusion), surgical procedures (bilateral laminectomy or total laminectomy), heavy works, undergoing a traumatic event, a large from, a high DUI, a large FT, and a small FO significantly related with rLDH.

Conclusion. Based on our data, sex, age, current smoking, BMI, occupational lifting, trauma, surgical procedures, herniation type, DUI, FO, FT, and from showed a significant correlation with the incidence of rLDH. Patients with these risk factors should be paid more attention for prevention of recurrence after primary surgery.

Key words: disc height index, facet orientation, facet tropism, recurrent lumbar disc herniation, risk factor, sagittal range of motion.

Level of Evidence: 3 Spine 2018;43:1463–1469

L

umbar disc herniation (LDH) is one of the most frequent disorders of the lumbar spine. The most common surgical procedure performed for the treatment of LDH causing back and leg pain is lumbar discectomy.^1,2However, lumbar discectomy has an unsatisfactory outcome in 5% and 20% of cases.^3–7 The most common cause of ongoing disability after discectomy is recurrent LDH (rLDH), which is reported to occur in 5% to 15%

of cases, with an increasing incidence over time.^{3,5,8 –13} rLDH is defined as ipsilateral or contralateral disc herniation at the same level after a pain-free interval of at least 6 months following conventional discectomy.3,7,8,12–18

rLDH may be caused by further disc material extruding from the disc space, with or without associated scar tissue;

retained disc fragments at the time of the first discectomy; or compression of the neural elements by parts of the disc endplate including bone, annulus, and other reactive tis- sues.^6,19 Secondary surgery will be more difficult due to epidural fibrosis and scarring. Moreover, reoperations lead to physical and psychological suffering for patients and

From theDepartment of Orthopaedics, First Affiliated Hospital of Dalian Medical University, Dalian, People’s Republic of China;^yDepartment of Orthopedics, The First Affiliated Hospital of Kunming Medical University, Kunming, People’s Republic of China;^zDepartment of Orthopaedics, First Affiliated Hospital of PLA General Hospital, Beijing, People’s Republic of China; and^§Department of Orthopedics, Tenth People’s Hospital of TongJi University, Shanghai, People’s Republic of China.

Acknowledgment date: January 23, 2018. First revision date: March 15, 2018. Acceptance date: March 19, 2018.

The manuscript submitted does not contain information about medical device(s)/drug(s).

The Natural Science Foundation of Liaoning Province (20170540294) and Basic Scientific Research Projects of the Universities in Liaoning Province (LQ2017022) funds were received in support of this work.

No relevant financial activities outside the submitted work.

Drs Li and Yang contributed equally to the manuscript and should be considered co-first authors.

Address correspondence and reprint requests to Zhonghai Li, MD, and Mozhen Liu, MD, Department of Orthopaedics, First Affiliated Hospital of Dalian Medical University, Dalian, People’s Republic of China;

E-mail: lizhonghaispine@126.com, lvshunman@sina.com

DOI: 10.1097/BRS.0000000000002655

Spine www.spinejournal.com 1463

C ^LINICAL C ^ASE S ^ERIES

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substantial costs for society. It is important to analyze the risk factors of rLDH to prevent recurrence.

Risk factors for rLDH are increasingly being investigated.3,6,14,20 – 31 Many estimated risk factors have been reported in previous studies, such as age, sex, body mass index (BMI), smoking, herniation type, diabetes, and herniation level. However, results in these previous studies were not always consistent. Because of inconsistent results, reliable conclusions could not be drawn on these risk factors. In addition, data on studies investigated the effects of biomechanical factors, such as disc height index (DHI), sagittal range of motion (sROM), and some pelvic parameters, on rLDH appear only rarely in the literature.^15,20To the best of our knowledge, this study is the first report to investigate preoperative facet joint parameters (facet orientation [FO] and facet tropism [FT] as risk factors for rLDH. In this study, we investigated the frequency of rLDH and evaluated risk factors of rLDH in Chinese population by comparing preoperative clinical and biomechanical parameters.

MATERIALS AND METHODS

Patient Population

This was a retrospective clinical study. From June 2005 to January 2012, 321 patients having single-level LDH at three institutes (First Affiliated Hospital of Dalian Medical Uni- versity, First Affiliated Hospital of PLA General Hospital, and Tenth Affiliated Hospital of Tongji Medical University) were included in this study and who were then observed for a minimum of 6 years postoperatively. All the patients or relatives gave informed consent to participate in this study.

The levels of disk herniation were L4-L5 in 194 cases (60.4%), and L5-S1 in 127 cases (39.6%).

The surgery procedures included discectomy with laminotomy, discectomy with unilateral laminectomy (hemilaminectomy), discectomy with bilateral laminectomy (total laminectomy), and discectomy with bilateral laminectomy and posterolateral noninstrumented fusion. The type of herniation was classified as protrusion, subligamentous extrusion, transligamentous extrusion, and sequestration after the review of the surgical records.

A magnetic resonance imaging (MRI) was recommended for all postoperative patients experiencing persistent or recurrent leg pain. Consequently, due to higher costs of imaging, not all patients in the study received a postoperative MRI and only those with suspected signs and symptoms had MRI. rLDH was defined as a disk herniation at the same level, regardless of ipsilateral or contralateral herniation, in a patient who experienced a pain-free interval of at least 6 months after prior surgery. Patients with herniation recurrence at other level, inability to have MRI examination, recent cerebrovascular arrest or psychological and cognitive disorders, amputation history, active infection, Paget disease or spinal metastasis in the involved segments, severe back arthritis, and neuropathic disease other than diabetes were excluded.

Data Collection and Outcome Evaluations

The patients were divided into a recurrent group (R group) and a nonrecurrent group (N group) in this study. We compared their clinical parameters (age, sex, BMI, diabetes, current smoking, sports activity, occupational lifting, occupational driving, trauma history, preoperative visual analogue scale [VAS], procedures) and preoperative radiologic parameters (herniation type, grade of disc degeneration, DHI, FO, FT, sROM).

The degree of disk degeneration was assessed on T2- weighted sagittal sequences according to modified Pfirr- mann criteria.³²DHI was calculated on lateral radiographs using the Kim method (Figure 1).¹⁵ROM was calculated as the difference in angulation between extension and flexion.

FO is the angle of the facet joint in the transverse plane relative to the sagittal plane. The facet joint angle relative to the sagittal plane at L3-L4, L4-L5, and L5-S1 was measured on the axial computed tomography images, using bone windows by using the method described by Noren et al³³ (Figure 2). On an axial scan that bisected the intervertebral

Figure 1. Calculation of the disc height index. The heights of the vertebral body and disc are measured at the midvertebral line (the line passing through the centers of L4 and L5). The center of each vertebral body is the point where the two diagonal lines joining opposite corners cross each other. Disc height index ¼ ab/bc.

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disc, one line was drawn in the midsagittal plane of the vertebra and one through each facet joint tangential to the superior articular process. FT is defined as asymmetry of the left and right vertebral (zygapophysial) facet-joint angles, with one joint having a more sagittal orientation than the other.³⁴To prevent interobserver variability, measurements were performed three times by the same observer, who was blinded to the operative details.

Statistical Analysis

The Statistical Package for Social Sciences software for Windows (Ver. 17.0, SPSS Inc., Chicago, IL) was used for the analysis. Univariate analysis was performed using an unpaired Student t test and x²test for clinical and radiologic parameters. The Mann-Whitney U test was used to compare group means of continuous data. Multiple logistic regression analysis was used to identify independent risk factors for rLDH. Univariate and multiple logistic regression analysis was used to evaluate the effect of each factor on the rLDH. Results are expressed as the mean standard devia- tion, with a P value of less than 0.05 considered statistically significant.

RESULTS

All cases in the study were followed up for more than 6 years postoperatively (median 98 mo, range 72–150 mo). The R group was composed of 42 men and 16 women, whose ages ranged from 19 to 55 years (35.7 9.9 yr). The N group was composed of 123 men and 140 women, whose ages ranged from 21 to 75 years (48.2 10.4 yr). Patient with rLDH had its onset 32.3 16.5 months (7–90 mo) after primary surgery. Of the 58 rLDH cases, ipsilateral and contralateral rLDH happened in 42 and 16 cases, respectively.

The results of univariate analysis of clinical parameters (age, sex, BMI, diabetes, current smoking, sports activity, occupational lifting, occupational driving, trauma history, preoperative VAS, procedures) and radiologic parameters (herniation type, grade of disc degeneration, DHI, FO, FT, sROM) are summarized in Table 1. Of these factors, sex (P ¼ 0.003), age (P ¼ 0.003), current smoking (P ¼ 0.004), BMI (P ¼ 0.04), occupational lifting (P < 0.001), trauma history (P ¼ 0.04), procedures (P ¼ 0.04), herniation type (P ¼ 0.006), DHI (P ¼ 0.04), FO (P ¼ 0.04), FT (P ¼ 0.04), and sROM (P ¼ 0.04) were found to be significantly associated with incidence of rLDH (P < 0.05).

Average sROMs were 12.158 1.418 and 6.958 1.938 in the R and N groups, respectively; average DHIs were 0.38 0.05 and 0.30 0.04 in the R and N groups, respectively; average FOs were 42.818 4.428 and 48.088 5.988 in the R and N group, respectively; and average FTs were 5.818 1.628 and 3.178 1.598 in the R and N group, respectively. sROM, DHI, FO, and FT were all found to be important predictors of rLDH by univariate analysis.

Univariate and multiple logistic regression analysis was used to evaluate the effect of each factor on the rLDH (Table 2). Univariate logistic regression analyses showed that being male, young age, current smoking, higher BMI, herniation type (transligamentous extrusion), procedures (bilateral laminectomy or total laminectomy), heavy works, undergoing a traumatic event, a large sROM, a large FT, a high DHI, and a low FO were significant risk factors for rLDH. Multiple logistic regression analyses showed that young age and a large FT were significant risk factors for rLDH.

DISCUSSION

rLDH is the most common reason for an unsatisfactory outcome following conventional discectomy for LDH.5,7,8,11,14,18 This study showed that 58 (18.1%) of 321 cases, who underwent microdiscectomy, had rLDH and this frequency was similar to previously reported rates of recurrence.^7,13,14 In reports on rLDH, disk degeneration, smoking, obesity, disk herniation type, young age, being male, large annular defect, and undergoing a traumatic event were reported as risk factors for rLDH (Table 3).

However, some other studies reported that age, sex, smoking, BMI, level of herniation, and symptom duration were not associated with recurrence after discectomy.8,15,25,27,31,35–37 There are many debates regarding the risk factors of rLDH and it is very difficult to define Figure 2. Diagram of the method used to measure the facet joint

angle. The facet line is drawn between the two peaks of each of the superior articular facets (D and E). The midline is drawn through the center of the lumbar vertebral body (O, AO ¼ OB) and the middle point of the base of the spinous process (C). The angle between the midsagittal line and facet line was measured for each side of the lumbar vertebral body (aR ¼ right facet angle, aL ¼ left facet angle).

Facet orientation ¼ (aRþaL)/2; Facet tropism ¼ jaR-aLj.

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them because many clinical and complicated biomechanical parameters are involved.

In this study, we analyzed the occurrence of rLDH in relation to clinical parameters (age, sex, BMI, diabetes, current smoking, sports activity, occupational lifting, occupational driving, trauma history, preoperative VAS, procedures) as well as preoperative radiologic parameters (herniation type, grade of disc degeneration, DHI, FO, FT, sROM). According to our results, sex, age, current smoking, BMI, occupational lifting, trauma, procedures, herniation type, DHI, FO, FT, and sROM were correlated significantly with a high incidence of rLDH. There are some studies about the relationship between sex, age, smoking, BMI, occupational lifting, trauma, procedures, disc degeneration, herniation type, and rLDH. However, data on studies investigated the effects of biomechanical factors, such as DHI, sROM, and some pelvic parameters, on rLDH

appear only rarely in the literature.^15,20To the best of our knowledge, this study is the first report to investigate preoperative facet joint parameters (FO and FT) as risk factors for rLDH.

As an important part of the three-joint complex of the spine, the lumbar facet joint has a far-reaching influence on the spine. With the onset of degeneration in the lumbar spine, increased stress is experienced posteriorly resulting in alterations in the mechanical properties of the facet joints. We believed an analysis of rLDH should include additional biomechanical factors. Consequently, we added some facet joint parameters (FO and FT) and, in addition, other biomechanical parameters (DHI and sROM) in this study, to gain new knowledge about rLDH.

FO is an important structural factor for lumbar degenerative disc diseases.^{33,38 –41}FT defined as asymmetry between TABLE 1.

Risk Factors for Recurrent Lumbar Disc Herniation Using Univariate Analysis

Variable

Recurrent Group (n ¼ 58)

Nonrecurrent Group (n ¼ 263) P

Sex (male:female) 42:16 123:140 <0.0001

Age (yr) 57.71 9.92 40.16 7.41 <0.0001

BMI (kg/m²) 25.84 3.48 24.64 3.21 0.0136

Current smoking, n (%) 33 (56.90%) 78 (29.66%) <0.0001

Alcohol n (%) 9 (15.52%) 40 (15.21%) 0.9529

Diabetes mellitus, n (%) 11 (18.97%) 36 (13.69%) 0.3035

Occupational lifting, n (%) 27 (46.55%) 36 (13.69%) <0.0001

Occupational driving, n (%) 7 (12.07%) 18 (6.84%) 0.1811

Sports activity, n (%) 11 (18.97%) 38 (14.45%) 0.3866

Trauma history, n (%) 37 (63.79%) 55 (20.91%) <0.0001

Preoperative VAS for leg 6.16 1.72 6.16 1.63 0.8813

Preoperative VAS for back 2.03 1.31 2.08 1.23 0.6899

Surgical procedure, n (%) 0.0137

Discectomy with laminotomy 16 (27.59%) 115 (43.73%)

Discectomy with unilateral laminectomy (hemilaminectomy) 16 (27.59%) 83 (31.56%) Discectomy with bilateral laminectomy (total laminectomy) 24 (41.38%) 61 (23.19%) Discectomy with bilateral laminectomy and posterolateral noninstrumented fusion 2 (3.45%) 4 (1.52%)

Disc herniation type, n (%) 0.0023

Protrusion 6 (10.3%) 52 (19.8%)

Subligamentous extrusion 15 (25.9%) 94 (35.7%)

Transligamentous extrusion 29 (50.0%) 66 (25.1%)

Sequestration 8 (13.8%) 51 (19.4%)

Disc degeneration, n (%) 0.1737

Grade I 1 (1.72%) 27 (10.27%)

Grade II 2 (3.45%) 31 (11.79%)

Grade III 22 (37.93%) 72 (27.38%)

Grade IV 19 (32.76%) 66 (25.10%)

Grade V 12 (20.69%) 57 (21.67%)

Grade VI 2 (3.45%) 10 (3.80%)

DHI 0.38 0.05 0.30 0.04 <0.0001

sROM (8) 12.15 1.41 6.95 1.93 <0.0001

FO (8) 42.81 4.42 48.08 5.98 <0.0001

FT (8) 5.81 1.62 3.17 1.59 <0.0001

BMI indicates body mass index; DHI, disc height index; FO, facet orientation; FT, facet tropism; sROM, sagittal range of motion; VAS, visual analogue scale.

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left and right facet joints, has the potential to alter the biomechanics of lumbar movements and expedite the degenerative changes either in the joint or adjacent intervertebral discs.^34,38–45The first hypothesis of Farfan and Sullivan⁴⁴ was that there is a relationship between FT and the development of LDH, but no final conclusion was made after clinical tests.^46–48The role of FO and FT in the pathogenesis of disc degeneration is a contested issue. Some studies report

that the angle of the lumbar facet joint and LDH were significantly related to lumbar facet joint asymmetry and that more severe asymmetry was more likely to cause LDH.38,39,41,42,45 In contrast, other scholars believe that the angle of the lumbar spine and disc herniation do not correlate, and that lumbar facet joint asymmetry is a con- genital structural manifestation, which is not due to age or degeneration.^49–51

TABLE 2.

Risk Factors for Recurrent Lumbar Disc Herniation Using Univariate and Multiple Logistic Regression Analysis

Variable

Univariate Logistic Regression Analysis Multiple Logistic Regression Analysis

OR 95% CI P OR 95% CI P

Sex (male) 0.335 0.179–0.625 0.0006

Age 1.244 1.181–1.310 <0.0001 1.270 1.185–1.360 <0.0001

BMI 1.116 1.023–1.216 0.0130

Current smoking 0.319 0.178–0.572 0.0001

Occupational lifting 0.182 0.098–0.340 <0.0001

Trauma history 0.150 0.081–0.277 <0.0001

Surgical procedure (discectomy with bilateral laminectomy or total laminectomy)

2.828 1.398–5.721 0.0038

Disc herniation type (transligamentous extrusion)

3.808 1.471–9.858 0.0059

DHI >999.999 >999.999–>999.999 <0.0001

sROM 88.832 1.023–1.216 <0.0001

FO 0.825 10.261–769.066 <0.0001

FT 2.456 1.954–3.087 <0.0001 2.698 1.949–3.733 <0.0001

BMI indicates body mass index; DHI, disc height index; FO, facet orientation; FT, facet tropism; sROM, sagittal range of motion; VAS, visual analogue scale.

TABLE 3.

Risk Factors for Recurrent Lumbar Disc Herniation of Previous Studies

References Year Location Risk Factors

Cinotti et al³ 1998 Italy Male, degenerated disk

Suk et al¹⁴ 2001 Korea Male, smoking, trauma

Carragee et al⁶ 2003 USA Annular competence, type of herniation Kara et al²⁷ 2005 Turkey Lack of regular physical exercise McGirt et al²⁶ 2009 USA Larger annular defects, less disc removal

Kim et al¹⁵ 2009 Korea DHI, sROM

Moliterno et al²⁵ 2010 USA Nonobese (lower BMI)

Meredith et al³⁵ 2010 USA Obesity

Matsumoto et al²⁴ 2013 Japan Caudally migrated LDH

Kim et al²³ 2013 Korea Surgical procedure

Shimia et al²¹ 2013 Iran Sex, smoking, heavy works

Miwa et al²² 2015 Japan Current smoking, occupational lifting

Kim et al²⁰ 2015 Korea Male, a large annular defect, moderate disk degeneration, a large sROM, a small RT, a low IHI,

Yao et al²⁸ 2016 China Age (50 yr old), obesity (BMI 25), modic change Yurac et al²⁹ 2016 Chile Age (35 yr old), a subligamentous herniation

Camino Willhuber et al³⁶ 2017 Netherlands DHI, percentage of spinal canal, facet joint degeneration

Yao et al³⁷ 2017 China Age (50 yr old), obesity (BMI 25), learning curve of the surgeon (<200 cases), treatment period, central location of herniation

BMI indicates body mass index; DHI, disc height index; IHI, iliac crest height index; LDH, lumbar disc herniation; sROM, sagittal range of motion; VAS, visual analogue scale.

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At present, there are no reports describing that FO and FT are the risk factors for rLDH. In this study, we compared the FO and TO between the N and R groups, and found that there was a significant correlation between these two parameters and rLDH. We considered that both sides of the facet joints and intervertebral disc together constitute the spinal three-joint complex. When the lumbar spine is flexed and twisted, if both joints are asymmetric, the stress of the three-joint complex is imbalanced. Resistance on the sides of the vertebral body is different, and the vertebral body will deviate from the original trajectory, and thus pulling the rear of the intervertebral disc. Such a loading imbalance may accelerate the degeneration of the facet joints and intervertebral discs. Therefore, facet joint parameters (FO and FT) may play a more important role in the development of rLDH.

Among radiologic parameters, DHI and sROM appeared to be the important risk factor of rLDH in this study.

According to cadaveric and clinical studies, several scholars^52,53reported that sROM increased at the disc with mild and moderate degeneration and then decreased when the disc degenerated severely, whereas others^54,55reported that sROM decreased proportionally to the degree of disc degeneration. These studies agree that degenerated and collapsed discs show severely limited range of motion. Several authors have reported that degenerative segments with preserved disc height had a latent instability compared to segments with collapsed discs. Spinal instability was related with biomechanical stress on the affected disc, which may be related with rLDH. These results suggest that collapsed discs are biomechanically more stable than those with preserved disc height, resulting in a low incidence of rLDH. These reports correspond to our result.

Limitations

Our study has several limitations. First, this was a retrospective nonrandomized case-control study, and the num- ber of patients with rLDH in this study was relatively small. Second, the sROM was checked only from the sagittal view. Multidirectional measurement of the lumbar segment was desirable, but we obtained only flexion and extension views. In addition, our study was limited by geometrical considerations. Even if facet joints often were not planar, our measurements did not take into account the complex three-dimensional geometry of the facet joints and their relationship with the disc and facet joint degeneration. Because of these limitations, future studies should focus on more sophisticated biomechanical factors of the lumbar spine, and further explore the correlation between biomechanical factors and rLDH. In the future, high-quality observational studies and basic experimental studies are still needed to investigate new risk factors for rLDH further.

CONCLUSION

The current study showed that a large sROM, a high DHI, a large FT, and a small FO are biomechanical risk factors of

rLDH. The results also suggested being male, young age, current smoking, higher BMI, herniation type (transligamentous extrusion), primary surgery procedures (bilateral laminectomy or total laminectomy), heavy works and undergoing a traumatic event increase recurrence after discectomy. Patients with these risk factors should be paid more attention for prevention of rLDH. The exact mecha- nism between risk factors and rLDH warrants further investigation. In addition, we found that the postmicrodis- cectomy defect did not automatically lead to a recurrent disc at the original location in this study. It’s an interesting observation and should be closely observed and studied in the future.

Key Points

Univariate logistic regression analyses showed that being male, young age, current smoking, higher BMI, herniation type (transligamentous extrusion), procedures (bilateral laminectomy or total laminectomy), heavy works, undergoing a traumatic event, a large sROM, a large FT, a high DHI, and a low FO were significant risk factors for rLDH.

Multiple logistic regression analyses showed that young age and a large FT were significant risk factors for rLDH.

Facet joint parameters (FO and FT) may play a more important role in the development of rLDH.

Patients with these risk factors should be paid more attention for prevention of recurrence after primary surgery.

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