Intervertebral mobility in the progressive degenerative process. A radiostereometric analysis

The Three-Step Approach for Lumbar Disk Herniation with Anatomical Insights Tailored for the Next Generation of Young Spine Surgeons

Background/Objectives: Lumbar disc herniation, a complex challenge in spinal health, significantly impacts individuals across diverse age groups. This article delves into the intricacies of this condition, emphasising the pivotal role of anatomical considerations in its understanding and management. Additionally, lumbar discectomy might be considered an "easy" surgery; nevertheless, it carries significant risks. The aim of the study was to present a groundbreaking "three-step approach" with some anatomical insight derived from our comprehensive clinical experiences, designed to systematise the surgical approach and optimise the outcomes, especially for young spine surgeons. We highlighted the purpose of the study and introduced our research question(s) and the context surrounding them. Methods: This retrospective study involved patients treated for lumbar disc herniation at a single institution. The patient demographics, surgical details, and postoperative assessments were meticulously recorded. All surgeries were performed by a consistent surgical team. Results: A total of 847 patients of the 998 patients initially included completed the follow-up period. A three-step approach was performed for every patient. The recurrence rate was 1.89%. Furthermore, the incidence of lumbar instability and the need for reoperation were carefully examined, presenting a holistic view of the outcomes. Conclusions: The three-step approach emerged as a robust and effective strategy for addressing lumbar disc herniation. This structured approach ensures a safe and educational experience for young spinal surgeons.

Lumbar lordosis and sacral slope do not differ in two types of postoperative lumbar disc re-herniation: a cross-sectional observational study

BACKGROUND

To identify the differences of lumbar lordosis (LL) and sacral slope (SS) angles between two types of postoperative lumbar disc re-herniation, including the recurrence of same level and adjacent segment herniation (ASH).

METHODS

We searched the medical records of lumbar disc herniation (LDH) patients with re-herniation with complete imaging data (n = 58) from January 1, 2013 to December 30, 2020 in our hospital. After matching for age and sex, 58 patients with LDH without re-herniation from the same period operated by the same treatment group in our hospital were served as a control group. Re-herniation patients were divided into two groups, same-level recurrent lumbar disc herniation group (rLDHG) and adjacent segment herniation group with or without recurrence (ASHG). The preoperative, postoperative and one month after operation LL and SS were measured on standing radiographs and compared with the control group by using t-test, ANOVA, and rank-sum test. Next, we calculated the odds ratios (ORs) by unconditional logistic regression, progressively adjusted for other confounding factors.

RESULTS

Compared with the control group, the postoperative LL and SS were significantly lower in LDH patients with re-herniation. However, there were no differences in LL and SS between ASHG and rLDHG at any stage. After progressive adjustment for confounding factors, no matter what stage is, LL and SS remained unassociated with the two types of re-herniation.

CONCLUSIONS

Low postoperative LL and SS angles are associated with degeneration of the remaining disc. Low LL and SS may be independent risk factors for re-herniation but cannot determine type of recurrence (same or adjacent disc level).

Biomechanical repercussion of sitting posture on lumbar intervertebral discs: A systematic review

BACKGROUND

The static sitting position contributes to increased pressure on the lumbar intervertebral disc, which can lead to dehydration and decreased disc height.

OBJECTIVE

To systematically investigate the of sitting posture on degeneration of the lumbar intervertebral disc.

MATERIALS AND METHODS

One researcher carried out a systematic literature search of articles with no language or time limits. Studies from 2006 to 2018 were found. The searches in all databases were carried out on January 28, 2022, using the following databases: Pubmed, Scopus, Embase, Cochrane, and Physiotherapy Evidence Database (PEDro) databases, and for the grey literature: Google scholar, CAPES Thesis and Dissertation Bank, and Open Grey. The acronym PECOS was used to formulate the question focus of this study: P (population) - male and female subjects; E (exposure) - sitting posture; C (comparison) - other posture or sitting posture in different periods; O (outcomes) - height and degeneration of the lumbar intervertebral disc(s), imaging exam; and S (study) - cross-sectional and case control.

RESULTS

The risk of bias was in its moderate totality in its outcome: height and degeneration of the lumbar intervertebral disc(s) - imaging. Of the four selected studies, three found a decrease in the height of the disc(s) in sitting posture.

CONCLUSION

The individual data from the manuscripts suggest that the sitting posture causes a reduction in the height of the lumbar intervertebral disc. It was also concluded that there is a need for new primary studies with a more in-depth design and sample size.

Comparison of Clinical and Radiographic Outcomes Between Transforaminal Endoscopic Lumbar Discectomy and Microdiscectomy: A Follow-up Exceeding 5 Years

OBJECTIVE

To compare the long-term clinical and radiographic outcomes of transforaminal endoscopic lumbar discectomy (TELD) versus microdiscectomy (MD).

METHODS

The data of 154 patients with lumbar disc herniation (LDH) who underwent TELD (n = 89) or MD (n = 65) were retrospectively analyzed. The patients' clinical outcomes were evaluated using visual analogue scales for leg and low back pain, the Japanese Orthopaedic Association (JOA) score, and the Oswestry Disability Index (ODI). The evolution of radiographic manifestations was observed during follow-up. Potential risk factors for a poor clinical outcome were investigated.

RESULTS

During a mean follow-up of 5.5 years (range, 5-7 years), the recurrence rate was 4.49% in the TELD group and 1.54% in the MD group. All scores significantly improved from preoperatively to postoperatively in both groups (p < 0.01). The improvement in the ODI and JOA scores was significantly greater in the TELD than MD group (p < 0.05). Forty-seven patients (52.8%) in the TELD group and 32 (49.2%) in the MD group had Modic changes before surgery, most of which showed no changes at the last follow-up. The degeneration grades of 292 discs (71.0%) were unchanged at the last follow-up, while 86 (20.9%) showed improvement, mostly at the upper adjacent segment. No significant difference was observed in the intervertebral height index or paraspinal muscle-disc ratio.

CONCLUSION

Both TELD and MD provide generally satisfactory long-term clinical outcomes for patients with LDH. TELD can be used as a reliable alternative to MD with less surgical trauma. Modic type II changes, decreased preoperative intervertebral height, and a high body mass index are predictors of a poor prognosis.

Analysis of Clinical Pattern of Musculoskeletal Disorders in the Cervical and Cervico-Thoracic Regions of the Spine

Background: Cervical spine disorders (CSDs) are a common cause of neck pain. Proper diagnosis is of great importance in planning the management of a patient with neck pain. Hence, the aim of this study is to provide an overview of the clinical pattern of early-stage functional disorders affecting the cervical and cervico-thoracic regions of the spine, considering the age and sex of the subjects. Methods: Two hundred adult volunteers were included in the study. Manual examination of segments C0/C1-Th3/Th4 was performed according to the methodology of the Katenborn-Evjenth manual therapy concept and the spine curvatures were assessed (cervical lordosis and thoracic kyphosis). Results: The most common restricted movement was lateral flexion to the left, and the least disturbed movement were observed in the sagittal plane (flexion and extension). The most affected segment was C7/Th1 (71.5% participants had problems in this segment), and the least affected segment was Th3/Th4 (69.5% participants had no mobility disorders in this segment). The number of disturbed segments did not differ between men and women (p > 0.05), but increased with age (r = 0.14, p = 0.04). Conclusions: Cervical mobility in adult population is frequently restricted. The number of affected segments increased with age and was not sex-dependent.

Analogy of Lumbar Disc: Retained, Residual, or Recurrent Disc?

Discectomy is a standard surgery for disc herniation performed by senior, experienced as well as young trainee spine surgeons. Yet, they both have patients returning with radicular pain. Sometimes, it is attributed to insufficient decompression in the primary surgery, sometimes to re-herniation at the same level, and sometimes thought as new disc herniation at a different level. The primary surgery is often blamed for the recurrence of the pain, without an assessment of the clinical condition of the patient. Surgeons use the terms recurrent, residual, and retained disc interchangeably as per their convenience without understanding the actual disc pathology. This causes errors in further treatment and dissatisfaction in patients. In this short review, we intend to clear the baffling terminologies pertaining to discectomy and help the readers to identify the exact nodus of the patient’s plight. The optimal extent of disc excision for a satisfactory outcome is not strictly defined [1]. Two main types of discectomy are subtotal discectomy, in which the annulus is opened and all accessible disc material is removed by curettage of the endplate; and limited discectomy, in which only the loose fragments are removed [1]. Patients who undergo subtotal discectomy experience progressive degeneration and back pain at the operated level compared with patients who undergo limited discectomy, which may eventually require spinal fusion at that level [2, 3] The problem with limited discectomy, on the other hand, is the higher recurrence rate due to the remaining disc material herniating later [2]. The surgical method may also have a bearing on the results. Open discectomy is based on direct visualization of decompression of the nerve root, whereas newer techniques such as microscopic and percutaneous endoscopic discectomy use indirect methods to confirm the adequacy of decompression, such as checking the free mobility of the traversing nerve root, the free mobility of the probe in the epidural space, and the removal of loose fragments which were identified on pre-operative magnetic resonance imaging (MRI) [1]. Percutaneous endoscopic discectomy allows for smaller incisions, less soft-tissue trauma, and faster recovery, resulting in greater relief of back pain and allowing an earlier return to work [4]. However, studies have shown that up to 2.8–15% of patients treated with limited discectomy using percutaneous endoscopic disc removal had residual disc material on immediate post-operative MRI examination [5]. Therefore, these techniques are subjective and dependent on the surgeon’s experience and skill and may result in inadequate decompression. Post-operatively, these patients may not experience the expected pain relief and continue to have radicular symptoms. In some patients, pain may be relieved for a short period of time, after which the same symptoms may recur, either due to re-herniation at the same level or at adjacent levels. Hence, it is very important to know the types of inefficiencies in disc removal, namely recurrence, retained, residual, and relapsed disc. Distinguishing the causes of pain after surgery can help surgeons do better pre-operative planning and make better intraoperative decisions, thereby helping them to choose a clear endpoint for decompression. This can also help patients by preventing the need for reoperation and achieving better functional outcomes after surgery. Recurrent Disc A disc recurrence is defined as a re-herniation of disc material at the previously operated level with the recurrence of similar pain after a period of relief of minimum 6 months and MRI confirmation, which may occur on the same or contralateral side (Fig. 1) [6-9]. In up to 5–15% patients, disc herniation can recur [10]. However, if stricter definition of recurrence is used, with cases restricted to recurrence at the same level and side as previous operation, the recurrence rate was found to be 2–5%. [9, 10] Risk factors for recurrence of a lumbar disc prolapse include disc degeneration, modic changes in the endplate, trauma to back, advanced age, and smoking [11] Radiological features such as increased disc height, lumbosacral transitional vertebrae, and segmental instability may also predict recurrence [4, 12]. It has been suggested that contralateral nucleus pulposus herniation may occur if the annulus on the opposite side is damaged during primary discectomy and only limited fragments are removed. In the case of a recurrent disc herniation on the opposite side, removal of the opposite annulus and disc material may damage the posterior longitudinal ligament and affect lumbar biomechanics and spinal stability. The average time between primary surgery and recurrent disc herniation symptoms was reported to be 17 ± 21 months by Eun et al. [4]. Surgical management of recurrence is debatable due to a need for high-level evidence [8]. Repeat discectomy remains the main procedure for it, with only minimal improvement often reported in the patient’s clinical condition as compared to the primary surgery [13]. There also remains risk of further instability. Therefore, many authors advocate the use of instrumented spinal fusion with repeat discectomy, despite the absence of instability at the time of recurrence [14]. Residual Disc A residual disc is defined as the disc material that remains at the symptomatic operated level after the extruded fragment has been removed and enough decompression has been achieved (Fig. 2). The residual disc material may cause painful radicular symptoms to persist post-operatively, with patients complaining of inadequate relief. Such patients require re-operation. Discectomy usually involves removal of only the herniated disc material and decompression of the nerve roots, leaving the remaining disc in situ. However, this may cause more disc material to come out and recompress or inflame the nerve roots [15]. To deal with this, Aoyama et al. used intraoperative ultrasound to differentiate between nerve roots and disc material in 30 patients. By this method, they were able to confirm the adequacy of decompression in all 30 patients and also identified residual disc material in 2 patients which they were able to remove satisfactorily [15]. However, it was found to be more useful for patients with a large surgical field undergoing procedures such as removal of spinal tumors or arachnoid cysts to check the remaining fragments [16]. In 2.8–15% of patients undergoing percutaneous endoscopic lumbar discectomy (PELD), residual disc fragments were observed on immediate post-operative MRI [5]. Although the presence of a residual disc fragment with persistent compression is a reason for reoperation, not all residual disc fragments observed on immediate post-operative MRI are symptomatic (i.e., they are clinically silent). Only 1.3% of patients with residual disc tissue had to go for repeat discectomy [17]. In a retrospective study by Baek et al., the long-term clinical outcomes of PELD patients in whom complete disc fragment removal was achieved (complete group) were compared with those in whom residual fragments were detected on post-operative MRI (residual group). Early reoperation (within the first 3 post-operative months) was performed in 3 patients in the residual group (7.9%) and 4 patients in the complete group (2.1%). They concluded that in patients with asymptomatic disc remnants, “watchful waiting” can be performed instead of immediate re-exploration [17]. Careful examination of post-operative MRI findings (within 24 h of surgery) revealed that some of the disc-like material was actually edematous tissue due to the fluid used during surgery. Therefore, analysis of T1-weighted MRI images is preferable, before taking up the patient for an unnecessary repeat surgery [18]. Retained Disc Retained disc is the one at same level where only nerve root decompression or deroofing was considered assuming that it should give symptomatic relief. Also retained disc can be dealing with two level discs where only one level disc is removed or decompressed and the other disc is kept as it assuming it will not create symptoms. (Fig. 3) In both the above mentioned scenarios, the discs which were untreated/ retained creates symptoms after a while because of worsening of disc or extrusion. Though this was thought to be uncommon, this entity is seen at many instances which is the Retained disc variation. Therefore, supervised neglect of the retained disc carries its risks. Careful clinical examination is important to differentiate retained disc from recurrence. . Conclusion: Clinical examination of the patient plays a crucial role in identifying the level of radiculopathy. Dermatomal pain in the same region after discectomy often indicates recurrence, whereas pain in an adjacent or new dermatomal distribution could be due to the retained disc. MRI findings help to confirm the pathological level and differentiate between a recurrent and retained disc. Understanding the different types of disc re-herniations is important in deciding treatment options such as physiotherapy, nerve root block, and surgical modalities.

Lumbar Facet Joint Effusion on Magnetic Resonance Imaging: Do Different Joint Effusion Images Have Different Clinical Values?

OBJECTIVE

The objective of the study was to explore the significance of the distribution of lumbar facet joint effusion (unilateral or bilateral) and the amount of joint effusion in the process of lumbar degeneration.

METHODS

A total of 142 patients with L4-5 lumbar facet joint effusion in our hospital from December 2020 to December 2021 were analyzed retrospectively, including 69 cases of unilateral facet joint effusion and 73 cases of bilateral facet joint effusion. The correlation between joint effusion width, effusion area and lumbar stability, facet joint degeneration grade, lumbar intervertebral disc degeneration index, and lumbosacral angle (LSA) was analyzed. To study the significance of the distribution of joint effusion, the patients were divided into unilateral and bilateral effusion groups.

RESULTS

The size of the LSA in the bilateral effusion group was significantly larger than that in the unilateral effusion group (t = 3.6634, P < 0.05). There was a significant difference in the proportion of stability between both groups (P < 0.05). The width of the joint effusion was positively correlated with lumbar stability and the LSA. When the width of the joint effusion was 2 mm, the probability of lumbar instability was 58.1%. The area of joint effusion was positively correlated with lumbar stability and the LSA. When the area of effusion was 0.2 cm2, the probability of lumbar instability was 58.9%.

CONCLUSIONS

A bilateral effusion signal is more likely to indicate lumbar instability than a unilateral effusion signal. The distribution width and area of effusion were positively correlated with lumbar stability and LSA.

Vertebral stabilisation for thoracolumbar vertebral instability associated with cranial and caudal articular process anomalies in pugs: Seven cases (2010-2019)

OBJECTIVES

To describe the diagnostic findings, surgical technique and outcomes in seven pugs with thoracolumbar vertebral instability due to articular process anomalies.

MATERIALS AND METHODS

Records (2010 to 2019) of pugs with thoracolumbar vertebral instability associated with articular process anomalies that underwent decompressive laminectomy and vertebral stabilisation were reviewed. Data on preoperative and postoperative neurologic status, diagnostic findings, surgical techniques and outcomes were retrieved.

RESULTS

Seven dogs were presented with ambulatory or non-ambulatory paraparesis. Caudal articular process anomalies (three dogs) and concomitant cranial and caudal articular process anomalies (four dogs) were noted. Myelography (six dogs) or magnetic resonance imaging (one dog) showed none to severe spinal cord compression. Dynamic myelography in six dogs demonstrated nine distinct sites of spinal cord dimension reduction positioned in extension and/or flexion (mean reduction: 16.0%, range: 8.5 to 24.0%). These dynamic compressions were located at sites with articular process anomalies (seven sites) and sites with no articular process anomalies (two sites). Vertebral instability was confirmed by intraoperative spinal manipulation in all dogs. All dogs remained ambulatory with improved (five dogs) or static (two dogs) neurological deficits at the last follow-up (median: 16 months; range: 1.5 to 66 months).

CLINICAL SIGNIFICANCE

Dynamic myelography and/or intraoperative spinal manipulation demonstrated vertebral instabilities at sites with or without articular process anomalies on imaging. Decompressive laminectomy with vertebral stabilisation resulted in long-term neurological improvement in most dogs.

Comparable dislocation and revision rates for patients undergoing total hip arthroplasty with subsequent or prior lumbar spinal fusion: a meta-analysis and systematic review

BACKGROUND

There is a known correlation between the procedures of lumbar spinal fusion (LSF), total hip arthroplasty (THA) and the complication of hip dislocation and revision occurring in patients. However there is no consensus as to whether the risk of this complication is higher if THA is performed before or after LSF. This meta-analysis aims to determine the influence of surgical sequence of lumbar spinal fusion and total hip arthroplasty on the rates of hip dislocation and revisions.

METHODS

A meta-analysis was conducted with a multi-database search (PubMed, OVID, EMBASE, Medline) according to PRISMA guidelines on 27th May 2020. Data from all published literature meeting inclusion criteria were extracted and analyzed with an inverse variance statistical model.

FINDINGS

A total of 25,558 subsequent LSF and 43,880 prior LSF THA patients were included in this study. There was no statistically significant difference in all-cause revisions (OR = 0.86, 95%CI: 0.48-1.54, p = 0.61), dislocation (OR = 0.82, 95%CI: 0.25-2.72, p = 0.75) or aseptic loosening (OR = 1.14, 95%CI: 0.94-1.38, p = 0.17) when comparing patients receiving LSF subsequent versus prior to THA.

CONCLUSION

Lumbar spinal fusion remains a risk factor for dislocation and revision of total hip arthroplasties regardless of whether it is performed prior to or after THA. Further preoperative assessment and altered surgical technique may be required in patients having THA who have previously undergone or are likely to undergo LSF in the future.

EVIDENCE LEVEL

Level II, Meta-analysis of homogeneous studies.

Radiological predictors of recurrent lumbar disc herniation: a systematic review and meta-analysis

OBJECTIVE

Lumbar discectomy for the management of lumbar radiculopathy is a commonly performed procedure with generally excellent patient outcomes. However, recurrent lumbar disc herniation (rLDH) remains one of the most common complications of the procedure, often necessitating repeat surgery. rLDH is known to be influenced by a variety of factors, and in this systematic review the authors aimed to explore the radiological predictors of recurrence.

METHODS

A systematic review and meta-analysis was conducted to identify studies analyzing radiological predictors of recurrent herniation, both ipsilateral and contralateral. A search was conducted on Medline and EMBASE. Both retrospective and prospective comparative studies were included, measuring radiological parameters of lumbar discectomy patients. All factors were considered irrespective of imaging modality, and a meta-analysis of the data was performed in which 5 or more studies were identified analyzing the same parameter.

RESULTS

In total, 1626 reported studies were screened, with 23 being included in this review, of which 13 were appropriate for meta-analysis. Three factors, namely disc height index, Modic changes, and sagittal range of motion, were determined to be significantly correlated with an increased rate of rLDH. Some variables were considered in only 1 or 2 different studies, and the authors have included a narrative review of these novel findings.

CONCLUSIONS

The findings of associations between the radiological parameters and rLDH implicates the role of instability in the development of recurrence. Understanding the physiological factors associated with instability is important, because although early degenerative disc changes may predispose patients to herniation recurrence, more advanced degeneration likely reduces segmental motion and concurrently risk of recurrence.

The degenerative lumbar disc: not a disease, but still an important consideration for OMPT practice: a review of the history and science of discogenic instability

BACKGROUND

A recent AAOMPT position paper was published that opposed the use of the term 'degenerative disc disease' (DDD), in large part because it appears to be a common age-related finding. While common, there are significant physiologic and biomechanical changes that occur as a result of discogenic degeneration, which are relevant to consider during the practice of manual therapy.

METHODS

A narrative review provides an overview of these considerations, including a historical perspective of discogenic instability, the role of the disc as a pain generator, the basic science of a combined biomechanical and physiologic cycle of degeneration and subsequent discogenic instability, the influence of rotation on the degenerative segment, the implications of these factors for manual therapy practice, and a perspective on an evidence-based treatment approach to patients with concurrent low back pain and discogenic degeneration.

CONCLUSIONS

As we consider the role of imaging findings such as DDD, we pose the following question: Do our manual interventions reflect the scientifically proven biomechanical aspects of DDD, or have we chosen to ignore the helpful science as we discard the harmful diagnostic label?

An in vivo study exploring correlations between early-to-moderate disc degeneration and flexion mobility in the lumbar spine

PURPOSE

Early disc degeneration (DD) has been thought to be associated with loss of spine stability. However, before this can be understood in relation to back pain, it is necessary to know the relationship between DD and intervertebral motion in people without pain. This study aimed to find out if early-to-moderate DD is associated with intervertebral motion in people without back pain.

METHODS

Ten pain-free adults, aged 51-71, received recumbent and weight bearing MRI scans and quantitative fluoroscopy (QF) screenings during recumbent and upright lumbar flexion. Forty individual level and 10 composite (L2-S1) radiographic and MRI DD gradings were recorded and correlated with intervertebral flexion ROM, translation, laxity and motion sharing inequality and variability for both positions.

RESULTS

Kinematic values were similar to previous control studies. DD was evidenced up to moderate levels by both radiographic and MRI grading. Disc height loss correlated slightly, but negatively with flexion during weight bearing flexion (R =  - 0.356, p = 0.0.025). Composite MRI DD and T2 signal loss evidenced similar relationships (R =  - 0.305, R =  - 0.267) but did not reach statistical significance (p = 0.056, p = 0.096). No significant relationships between any other kinematic variables and DD were found.

CONCLUSION

This study found only small, indefinite associations between early-to-moderate DD and intervertebral motion in healthy controls. Motion sharing in the absence of pain was also not related to early DD, consistent with previous control studies. Further research is needed to investigate these relationships in patients.

Recurrent disc herniation following percutaneous endoscopic lumbar discectomy preferentially occurs when Modic changes are present

Objective

To investigate the relationship between Modic changes (MCs) and recurrent lumbar disc herniation (rLDH) and that between the herniated disc component and rLDH following percutaneous endoscopic lumbar discectomy (PELD).

Methods

We included 102 (65 males, 37 females, aged 20–66 years) inpatients who underwent PELD from August 2013 to August 2016. All patients underwent CT and MRI preoperatively. The presence and type of Modic changes were assessed. During surgery, the herniated disc component of each patient was classified into two groups: nucleus pulposus group and hyaline cartilage group. The association of herniated disc component with Modic changes was investigated. The incidence of rLDH was assessed based on a more than 2-year follow-up.

Results

In total, 11 patients were lost to follow-up; the other 91 were followed up during 24–60 months. Of the 91 patients, 99 discs underwent PELD; 28/99 (28.3%) had MCs. Type I and II MCs were seen in 9 (9.1%) and 19 (19.2%), respectively; no type III MCs were found. Among 28 endplates with MCs, according to the herniated disc component, 18/28 (64.3%) showed evidence of hyaline cartilage in the intraoperative specimens, including 6/9 and 12/19 endplates with type I and II MCs, respectively. Among 71 endplates without MCs, 14/71 (19.7%) showed evidence of hyaline cartilage in the intraoperative specimens. Hyaline cartilage was more common in patients with MCs (P < 0.05). We found 2 cases of rLDH in the non-MC group (n = 71); 6 cases of rLDH were found in the MC group (n = 28), including 2 and 4 cases for types I and II, respectively. There was no significant difference between types I and II (P > 0.05). rLDH was more common in patients with MCs (P < 0.05). We found 5 rLDH cases in the hyaline cartilage group (n = 32); 3 rLDH cases were found in the nucleus pulposus group (n = 67). rLDH was more common in the hyaline cartilage group (P < 0.05).

Conclusions

rLDH following PELD preferentially occurs when MCs or herniated cartilage are present.

Predictive Scoring and Risk Factors of Early Recurrence after Percutaneous Endoscopic Lumbar Discectomy

Purpose

To predict the early recurrence after full endoscopic lumbar discectomy, we analyzed factors related to demographic factor anatomical factors, operative method, and postoperative management, and predicted the possibility of recurrence according to the scoring system.

Materials and Methods

In this prospective study, we enrolled 300 patients who underwent 1 out of 3 surgical procedures. The patients were randomized into one of the following groups: group A (n = 100), transforaminal inside-out approach; group B (n = 100), transforaminal outside-in approach; and group C (n = 100), interlaminar approach. The clinical results were evaluated by a visual analogue scale (VAS). Related factors evaluated with points of (A) demographic factors: (1) age, (2) gender, (3) BMI, (B) anatomical factors: (4) disc degeneration scale, (5) modic change, (6) number of involved disc herniation, (7) history of discectomy (first, recurred), (8) herniated disc level, (9) disc height, (10) segmental dynamic motion, (11) disc location, (C) operation factors: (12) annulus preservation along the disc protrusion, (13) approach method (transforaminal inside-out, transforaminal outside-in, interlaminar); (D) postoperative care factors: (14) early ambulation, (15) spinal orthosis (corset) application. Among these, we analyzed statistically significant recurrence risk factors after PELD in all patients and early recurrence predicting score ratio was obtained.

Results

The overall recurrence rate was 9.33%. The recurrence rate was 11%, 10%, and 7% for groups A, B, and C, respectively. Average early recurrence time was 3.26 months. The change in preoperative and postoperative VAS score was from 8.07 to 1.39, 8.34 to 1.34, and 8.14 to 1.86 in groups A, B, and C, respectively. The recurrence rate based on the (1) age was <40 years: 5.22% (6/115), 41–60 years: 16.1% (20/124), and >61 years: 3.07% (2/65); (2) gender was male: 13/139 (9.35%), female: 15/161 (9.32%); (3) BMI was obese: 17.57% (13/74), overweight: 11.6% (9/77), underweight: 6.35% (4/63), and normal weight: 2.33% (2/86); (4) degeneration scale was grades 1–2: 2% (1/50), grade 3: 7.4% (10/135), and grades 4–5: 14.8% (17/115); (5) modic change was type I: 25% (3/12), type II: 14.3% (1/7), type III: 33% (1/3), and no modic change: 8.27% (23/278); (6) number of involved disc herniation was 1 level: 3.9% (5/128), 2 level: 10.4% (13/125), 3 levels: 18.9% (7/37), and 4 levels: 30% (3/10); (7) history of discectomy was first: 8.83% (25/283) and repeated: 17.65% (3/17); (8) herniated disc level was L1–L2/L2–L3/L3–L4: 3.95% (3/76) and L4–L5: 14.6% (18/123); (9) disc height was <80%: 17.14% (6/35), 81%–100%: 8.16% (12/147), and >101%: 8.5% (10/118); (10) segmental dynamic motion was 1–10°: 8.58% (20/233) and 11–20° : 11.9% (8/67); (11) disc location was central: 7.41% (2/27), foraminal: 3.03% (2/66), and inferior/superior/paracentral: 11.59% (24/207); (12) radical annulotomy was 8.05% (7/87) vs. 9.86% (21/213); (13) approach method was transforaminal (inside-out): 11% (11/100), transforaminal (outside-in): 10% (10/100), and interlaminar: 7% (7/100); (14) early ambulation was 16.42% (23/140) vs. 3.13% (5/160); and (15) spinal orthosis application was 7.35% (10/136) vs. 10.98% (18/164). According to the above results, after summation of all scores, the early recurrence predicting score: recurrence rate ratio was 1–4: 0% (0/23), 5–8: 7.1% (13/183), 9–12: 8% (6/75) and 13–16 100% (10/10).

Conclusions

Early recurrence after PELD is associated with several risk factors such as BMI, degeneration scale, combined HNP, and early ambulation. If we use the predicting score, we can postulate the occurrence of early recurrence after PELD. Knowing the predictive factors prior to surgical intervention will allow us to decrease the early recurrence rate after PELD.

Timing of Lumbar Spinal Fusion Affects Total Hip Arthroplasty Outcomes

Many patients are affected by concurrent disease of the hip and spine, undergoing both total hip arthroplasty (THA) and lumbar spinal fusion (LSF). Recent literature demonstrates increased prosthetic dislocation rates in patients with THA done after LSF. Evidence is lacking on which surgery to do first to minimize complications. The purpose of this study was to evaluate the effect of timing between the two procedures on postoperative outcomes.

Risk factors for recurrent lumbar disc herniation after discectomy

PURPOSE

There are many reports about the risk factors for recurrence after lumbar disc surgery. However, there are none about whether lumbosacral transitional vertebrae (LSTV) are associated with recurrent lumbar disc herniation (LDH). We investigated various risk factors for recurrent LDH after discectomy including LSTV.

METHODS

A total of 119 patients who had undergone a discectomy for L4-5 disc herniation were evaluated with a minimum follow-up of two years. Clinical parameters including age, gender, body mass index (BMI), and smoking status, and radiological parameters including type of herniated disc, degree of disc degeneration, LSTV, and sagittal range of motion (SROM) in flexion-extension radiography were evaluated. SROM was measured by the difference of the lordotic angle between the flexion and extension view.

RESULTS

Recurrent disc herniation at L4-5 developed in 21 (17.6%) of the 119 patients. The mean period between primary surgery and recurrence was 17.6 ± 21.1 months. LSTV was found in 11 (52.4%) of the 21 patients who had recurrence and seven (7.1%) of the 98 patients in the non-recurrent group. SROM at L4-5 was 11.68 ± 4.24° in the recurrent group and 9.04 ± 3.65° in the non-recurrent group with a significant difference (p = 0.004). Multiple logistic regression analyses confirmed that LSTV and a larger SROM were significant risk factors for recurrent disc herniation at L4-5.

CONCLUSIONS

Lumbosacral transitional vertebrae and a hypermobile disc in flexion-extension radiography were found to be risk factors for recurrent lumbar disc herniation.

Anterior spinal instrumentation combining a prosthetic disc nucleus with a flexible stabilization device: Manufacture and use in intervertebral disc repair

Artificial disc replacement alone is unable to completely cure cervical degenerative diseases; thus, a stabilization device markedly improves patient recovery. In order to meet this requirement, an anterior spinal instrumentation combining a prosthetic disc nucleus with a flexible stabilization device (ASI combining PDN/FD) was developed. An artificial disc was designed and manufactured using polyvinyl alcohol hydrogel (PVA-H) with a repeated freeze-melting technique, and subsequently the dehydration and swelling properties of the PVA-H were investigated. A canine animal model was then used to compare the differences in the degeneration of cervical discs adjacent to the operative segment with PDN/FD against a plate fixation system, without the interferences of brace intensity, which was ensured by pressure monitoring the dog's intervertebral disc adjacent to operative segments. The in vivo results demonstrated a clear decrease in the degeneration of the adjacent disc with the use of PDN/FD as compared with the plate fixation system. In conclusion, PDN/FD may offer a promising method for the treatment of cervical degenerative disease.

Dynamic MRI in the evaluation of the spine: state of the art

INTRODUCTION

Degenerative disease of the spine is a generic term encompassing a wide range of different disease processes, which leads to spinal instability; traumatic/neoplastic events can accelerate this aging process. Therefore, the dynamic nature of the spine and its mobility across multiple segments is difficult to depict with any single imaging modality.

METHODS

A review of PubMed databases for articles published about kMRI in patients with cervical and lumbar spinal desease was performed. We focused on the physiopathological changes in the transition from supine to upright position in spine instability.

DISCUSSION

Until a few years ago, X-ray was the only imaging modality for the spine in the upright position. Of the imaging techniques currently available, MRI provides the greatest range of information and the most accurate delineation of soft-tissue and osseous structures. Conventional MRI examinations of the spine usually are performed in supine position, in functional rest, but the lumbar spine instability is often shown only by upright standing. This can result in negative findings, even in the presence of symptoms. Regardless, the final result is distorted. To overcome this limitation, Kinetic MRI (kMRI) can image patients in a weight-bearing position and in flexed and extended positions, thus revealing abnormalities that are missed by traditional MRI studies.

CONCLUSION

Despite some limitations, the upright MRI can be a complementary investigation to the traditional methods when there are negative results in conventional MRI in symptomatic patients or when surgical therapy is scheduled.

RSA in Spine: A Review

STUDY DESIGN

Systematic review of literature.

OBJECTIVES

This systematic review was conducted to investigate the accuracy of radiostereometric analysis (RSA), its assessment of spinal motion and disorders, and to investigate the limitations of this technique in spine assessment.

METHODS

Systematic review in all current literature to invesigate the role of RSA in spine.

RESULTS

The results of this review concluded that RSA is a very powerful tool to detect small changes between 2 rigid bodies such as a vertebral segment. The technique is described for animal and human studies for cervical and lumbar spine and can be used to analyze range of motion, inducible displacement, and fusion of segments. However, there are a few disadvantages with the technique; RSA percutaneous procedure needs to be performed to implant the markers (and cannot be used preoperatively), one needs a specific knowledge to handle data and interpret the results, and is relatively time consuming and expensive.

CONCLUSIONS

RSA should be looked at as a very powerful research instrument and there are many questions suitable for RSA studies.

Lumbar Retrolisthesis in Aging Spine: What are the Associated Factors?

STUDY DESIGN

A retrospective radiographic study.

OBJECTIVE

The aim of this study is to demonstrate that lumbar retrolisthesis serves as an important compensatory mechanism and to identify the possible factor related to lumbar retrolisthesis.

SUMMARY OF BACKGROUND DATA

Lumbar instability is one of the common degenerative changes, which presents as 2 radiologic features: anterolisthesis and retrolisthesis. Compared with the extensive studies on anterolisthesis, limit data are available on the characteristics and clinical relevance of lumbar retrolisthesis.

MATERIALS AND METHODS

In this study, 105 adult patients with low back pain were prospectively recruited, of which 60 patients had retrolisthesis (group 1) and 45 patients had anterolisthesis (group 2). Another 40 healthy age-matched adults (group 3) were also included to serve as the control group. Sagittal spinopelvic parameters were measured from the standing lateral radiograph, including thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), pelvic incidence (PI), sacrum slope (SS), pelvic tilt (PT), sagittal vertical axis (SVA), spinosacral angle (SSA), and C7 tilt (C7T). In addition, disk degeneration was quantitatively evaluated by Pfirrmann score on T2-weighted magnetic resonance images in patients with retrolisthesis.

RESULTS

For all the sagittal parameters, SVA, PI, SS, and LL in retrolisthesis group were found to be significantly lower than those in the anterolisthesis group and in the control group, respectively (P<0.05), whereas TLK in retrolisthesis group was significantly larger than other 2 groups (P<0.01). In addition, the average Pfirrmann disk score was 2.11 at levels with retrolisthesis indicating that the disks were not severely degenerated.

CONCLUSIONS

Lumbar retrolisthesis, together with thoracolumbar kyphosis, appears to be associated with mechanisms associated with regulation of sagittal balance. Low PI and disk instability due to degeneration may contribute to the development and progression of retrolisthesis.

Preoperative estimation of disc herniation recurrence after microdiscectomy: predictive value of a multivariate model based on radiographic parameters

BACKGROUND CONTEXT

Recurrence of lumbar disc herniation (rLDH) is one of the unfavorable outcomes after microdiscectomy. Prediction of the patient population with increased risk of rLDH is important because patients may benefit from preventive measures or other surgical options.

PURPOSE

The study assessed preoperative factors associated with rLDH after microdiscectomy and created a mathematical model for estimation of chances for rLDH.

STUDY DESIGN/SETTING

This is a retrospective case-control study.

PATIENT SAMPLE

The study includes patients who underwent microdiscectomy for LDH.

OUTCOME MEASURES

Lumbar disc herniation recurrence was determined using magnetic resonance imaging.

METHODS

The study included 350 patients with LDH and a minimum of 3 years of follow-up. Patients underwent microdiscectomy for LDH at the L4-L5 and L5-S1 levels from 2008 to 2012. Patients were divided into two groups to identify predictors of recurrence: those who developed rLDH (n=50) within 3 years and those who did not develop rLDH (n=300) within the same follow-up period. Multivariate analysis was performed using patient baseline clinical and radiography data. Non-linear, multivariate, logistic regression analysis was used to build a predictive model.

RESULTS

Recurrence of LDH occurred within 1 to 48 months after microdiscectomy. Preoperatively, patients who developed rLDH were smokers (70% vs. 27%, p<.01; odds ratio [OR]=6.31, 95% confidence interval [CI]: 3.27-12.16) and had higher body mass index (29.0±6.1 vs. 27.0±4.3, p=.03; OR=1.09 per 0.01 unit change). Radiological parameters that were associated with rLDH were higher disc height index (0.35±0.007 vs. 0.26±0.002, p<.001), higher segmental range of motion (9.8±0.28° vs. 7.6±0.11°, p<.001; OR=0.53 per 0.01 unit change), and lower central angle of lumbar lordosis (33.4±0.81° vs. 47.1±0.47°, p<.001; OR=0.53 per 0.01 unit change). Additionally, Pfirrmann grade 3 (OR=16.62, 95% CI: 8.10-34.11), protrusion type of LDH (OR=5.90, 95% CI: 3.06-11.36), and Grogan sclerosis grades 3 and 4 (OR=4.81, 95% CI: 2.50-9.22) were also associated with rLDH. Multivariate non-linear modeling allowed for more accurate prediction of rLDH (90% correct prediction of rLDH; 99% correct prediction of no rLDH) than other univariate logit models.

CONCLUSIONS

Preoperative radiographic parameters in patients with LDH can be used to assess the risk of recurrence after microdiscectomy. The multifactorial non-linear model provided more accurate rLDH probability estimation than the univariate analyses. The software developed from this model may be implemented during patient counseling or decision making when choosing the type of primary surgery for LDH.

Quantification of intervertebral displacement with a novel MRI-based modeling technique: Assessing measurement bias and reliability with a porcine spine model

The purpose of this study was to develop a novel magnetic resonance imaging (MRI)-based modeling technique for measuring intervertebral displacements. Here, we present the measurement bias and reliability of the developmental work using a porcine spine model. Porcine lumbar vertebral segments were fitted in a custom-built apparatus placed within an externally calibrated imaging volume of an open-MRI scanner. The apparatus allowed movement of the vertebrae through pre-assigned magnitudes of sagittal and coronal translation and rotation. The induced displacements were imaged with static (T₁) and fast dynamic (2D HYCE S) pulse sequences. These images were imported into animation software, in which these images formed a background 'scene'. Three-dimensional models of vertebrae were created using static axial scans from the specimen and then transferred into the animation environment. In the animation environment, the user manually moved the models (rotoscoping) to perform model-to-'scene' matching to fit the models to their image silhouettes and assigned anatomical joint axes to the motion-segments. The animation protocol quantified the experimental translation and rotation displacements between the vertebral models. Accuracy of the technique was calculated as 'bias' using a linear mixed effects model, average percentage error and root mean square errors. Between-session reliability was examined by computing intra-class correlation coefficients (ICC) and the coefficient of variations (CV). For translation trials, a constant bias (β₀) of 0.35 (±0.11) mm was detected for the 2D HYCE S sequence (p=0.01). The model did not demonstrate significant additional bias with each mm increase in experimental translation (β₁Displacement=0.01mm; p=0.69). Using the T₁ sequence for the same assessments did not significantly change the bias (p>0.05). ICC values for the T₁ and 2D HYCE S pulse sequences were 0.98 and 0.97, respectively. For rotation trials, a constant bias (β₀) of 0.62 (±0.12)° was detected for the 2D HYCE S sequence (p<0.01). The model also demonstrated an additional bias (β₁Displacement) of 0.05° with each degree increase in the experimental rotation (p<0.01). Using T₁ sequence for the same assessments did not significantly change the bias (p>0.05). ICC values for the T₁ and 2D HYCE S pulse sequences were recorded 0.97 and 0.91, respectively. This novel quasi-static approach to quantifying intervertebral relationship demonstrates a reasonable degree of accuracy and reliability using the model-to-image matching technique with both static and dynamic sequences in a porcine model. Future work is required to explore multi-planar assessment of real-time spine motion and to examine the reliability of our approach in humans.

The impact of generalized joint laxity (GJL) on the posterior neck pain, cervical disc herniation, and cervical disc degeneration in the cervical spine

BACKGROUND CONTEXT

Generalized joint laxity (GJL) can have a negative impact on lumbar spine pathology, including low back pain, disc degeneration, and disc herniation, but the relationship between GJL and cervical spine conditions remains unknown.

PURPOSE

To investigate the relationship between GJL and cervical spine conditions, including the prevalence of posterior neck pain (PNP), cervical disc herniation (CDH), and cervical disc degeneration (CDD), in a young, active population.

STUDY DESIGN

Retrospective 1:2 matched cohort (case-control) study from prospectively collected data PATIENT SAMPLE: Of a total of 1853 individuals reviewed, 73 individuals with GJL (study group, gruop A) and 146 without GJL (control group, Group B) were included in the study according to a 1:2 case-control matched design for age, sex, and body mass index.

OUTCOME MEASURE

The primary outcome measure was the prevalence and intensity of PNP at enrollment based on a visual analogue scale score for pain. The secondary outcome measures were (1) clinical outcomes as measured with the neck disability index (NDI) and 12-item short form health survey (SF-12) at enrollment, and (2) radiological outcomes of CDH and CDD at enrollment.

METHODS

We compared baseline data between groups. Descriptive statistical analyses were performed to compare the 2 groups in terms of the outcome measures.

RESULTS

The prevalence and intensity of PNP were significantly greater in group A (patients with GJL) than in group B (patients without GJL) (prevalence: p=.02; intensity: p=.001). Clinical outcomes as measured with NDI and SF-12 did not differ significantly between groups. For radiologic outcomes, the prevalence of CDD was significantly greater in group A than in group B (p=.04), whereas the prevalence of CDH did not differ significantly between groups (p=.91).

CONCLUSIONS

The current study revealed that GJL was closely related to the prevalence and intensity of PNP, suggesting that GJL may be a causative factor for PNP. In addition, GJL may contribute to the occurrence of CDD, but not CDH. Spine surgeons should screen for GJL in patientswith PNP and inform patients of its potential negative impact on disc degeneration of the cervical spine.

Development of a morphology-based modeling technique for tracking solid-body displacements: examining the reliability of a potential MRI-only approach for joint kinematics assessment

Background

Single or biplanar video radiography and Roentgen stereophotogrammetry (RSA) techniques used for the assessment of in-vivo joint kinematics involves application of ionizing radiation, which is a limitation for clinical research involving human subjects. To overcome this limitation, our long-term goal is to develop a magnetic resonance imaging (MRI)-only, three dimensional (3-D) modeling technique that permits dynamic imaging of joint motion in humans. Here, we present our initial findings, as well as reliability data, for an MRI-only protocol and modeling technique.

Methods

We developed a morphology-based motion-analysis technique that uses MRI of custom-built solid-body objects to animate and quantify experimental displacements between them. The technique involved four major steps. First, the imaging volume was calibrated using a custom-built grid. Second, 3-D models were segmented from axial scans of two custom-built solid-body cubes. Third, these cubes were positioned at pre-determined relative displacements (translation and rotation) in the magnetic resonance coil and scanned with a T₁ and a fast contrast-enhanced pulse sequences. The digital imaging and communications in medicine (DICOM) images were then processed for animation. The fourth step involved importing these processed images into an animation software, where they were displayed as background scenes. In the same step, 3-D models of the cubes were imported into the animation software, where the user manipulated the models to match their outlines in the scene (rotoscoping) and registered the models into an anatomical joint system. Measurements of displacements obtained from two different rotoscoping sessions were tested for reliability using coefficient of variations (CV), intraclass correlation coefficients (ICC), Bland-Altman plots, and Limits of Agreement analyses.

Results

Between-session reliability was high for both the T₁ and the contrast-enhanced sequences. Specifically, the average CVs for translation were 4.31 % and 5.26 % for the two pulse sequences, respectively, while the ICCs were 0.99 for both. For rotation measures, the CVs were 3.19 % and 2.44 % for the two pulse sequences with the ICCs being 0.98 and 0.97, respectively. A novel biplanar imaging approach also yielded high reliability with mean CVs of 2.66 % and 3.39 % for translation in the x- and z-planes, respectively, and ICCs of 0.97 in both planes.

Conclusions

This work provides basic proof-of-concept for a reliable marker-less non-ionizing-radiation-based quasi-dynamic motion quantification technique that can potentially be developed into a tool for real-time joint kinematics analysis.

The Compensatory Relationship of Upper and Subaxial Cervical Motion in the Presence of Cervical Spondylosis

STUDY DESIGN

This study was an in vivo kinematic magnetic resonance imaging analysis of cervical spinal motion in human subjects.

OBJECTIVE

The objective of the study was to identify associations between disk degeneration in the subaxial cervical spine and upper cervical spinal motion in patients with general age-related cervical spondylosis.

SUMMARY OF BACKGROUND DATA

The kinematic relationship between the occipital-atlantoaxial complex and subaxial cervical spine in patients with cervical spondylosis and decreased cervical motion is not well understood.

METHODS

A total of 446 symptomatic patients who had neck pain with and without neurogenic symptoms were included in this study. Kinematic magnetic resonance imaging was performed with dynamic motion of the cervical spine in upright, weight-bearing neutral, flexion, and extension positions. Intervertebral disk degeneration for each segment from C2-3 to C7-T1 and sagittal angular motion between flexion and extension for each segment from Oc-C1 to C7-T1 was evaluated. Depending on the amount of sagittal subaxial angular motion, the patients were classified into 3 groups by sagittal angular motion using cutoff points based on tertile (<36-degree group: 149 cases; 36-47-degree group: 148 cases; and >47-degree group: 149 cases).

RESULTS

A significant correlation was found between subaxial angular motion and intervertebral disk degeneration, indicating that the subaxial motion decreases according to the degree of disk degeneration. Mean angular motion of the occipital-atlantoaxial complex, especially of Oc-C1, was significantly higher in the <36-degree and 36-47-degree group than in the >47-degree group, whereas no significant difference was found at C1-C2.

CONCLUSIONS

Our study demonstrates that decreased subaxial cervical spinal motion is associated with intervertebral disk degeneration in a symptomatic population. This decrease in mobility at the subaxial cervical spine is compensated for by an increase in angular mobility of the upper cervical spine at the occipital-atlantoaxial complex, especially at Oc-C1.

Generalized Joint Laxity is Associated with Primary Occurrence and Treatment Outcome of Lumbar Disc Herniation

BACKGROUND

We investigated relationships between generalized joint laxity and primary lumbar disc herniation occurrence and compared clinical outcomes after conservative treatment in lumbar disc herniation patients with and without generalized joint laxity.

METHODS

The study group included 128 men, and the control group included 276 men matched for age and body mass index with the study group. The primary outcome measure was the presence or absence of generalized joint laxity using the Beighton scale. Clinical outcomes measured by the visual analog scale and the Oswestry disability index 2 years after conservative treatment were the secondary outcome measure.

RESULTS

Generalized joint laxity prevalence was 13.2% in the study group and 5.1% in the control group, a significant difference (P=0.01). Spearman correlation analysis revealed that weight (r=0.162, P=0.03), body mass index (r=0.131, P=0.03), and generalized joint laxity (r=0.372, P<0.01) significantly correlated with lumbar disc herniation occurrence. In multivariate regression analysis, generalized joint laxity was the only significant lumbar disc herniation predictor (P=0.002; 95% confidence interval, 1.08 to 5.26). Generalized joint laxity in lumbar disc herniation patients was associated with worse clinical outcomes after conservative treatment measured by visual analog scale scores for lower extremity pain (P=0.02), lower back pain (P=0.03), and Oswestry disability index scores (P=0.03).

CONCLUSION

Generalized joint laxity might be associated with lumbar disc herniation occurrence and might also be a negative predictor of worse clinical outcomes after conservative treatment.

Simulation of a Bead Placement Protocol for Follow-up of Thoracic Spinal Fusion Using Radiostereometric Analysis

STUDY DESIGN

Computer simulation to detect intervertebral motion enabling future follow-up of spinal fusions performed on patients with multilevel thoracic scoliosis.

OBJECTIVES

To propose a method using computer simulation to evaluate a radiostereometric analysis (RSA) marker placement protocol for visibility and redundancy and validate the performance of the developed RSA system in detecting intervertebral motion.

SUMMARY OF BACKGROUND DATA

Radiostereometric analysis is a stereo x-ray technique in which clusters of tantalum markers are implanted to label well-defined landmarks and measure the relative motion between rigid bodies.

METHODS

A model of the spine with the instrumentation and the RSA markers was developed. The vertebrae were aligned to mimic multilevel thoracic scoliosis after correction. The researchers performed virtual segment motion to validate the performance of the developed system. X-ray images were simulated and RSA was used to evaluate the proposed marker placement protocol and detect virtual motion. The authors performed a physical phantom study to evaluate marker visibility.

RESULTS

All markers were located and matched between simulations and the condition numbers were well below the recommended value of 100. Based on computer simulation, average translational accuracy was 0.14, 0.01, and 0.24 mm along the x, y, and z axes, respectively, and average rotational accuracy was 0.23°, 0.12°, and 0.11° about the x, y, and z axes, respectively. The translational and rotational precision of the simulated RSA system was generally high. The physical phantom study agreed with the computer simulation and validated marker visibility.

CONCLUSIONS

Computer simulation is a powerful tool that can be used to facilitate the development and refinement of an RSA system before its application in patients, particularly when the anatomy involved is complex. The proposed marker placement protocol yielded translational and rotational accuracy below the limits of clinical significance, which enables future follow-up of multilevel thoracic scoliosis with Lenke classification 1AN.

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

BACKGROUND CONTEXT

Patients with spinal stenosis with concomitant degenerative spondylolisthesis (DS) and predominant back pain (PBP) have been shown to have inferior outcome after surgery. Studies comparing outcome according to preoperative pain predominance and treatment received are lacking.

PURPOSE

The purpose was to study if adding spinal fusion to the decompression in DS affects outcome in patients with PBP (back pain [BP] Visual Analog Scale [VAS] more than or equal to leg pain [LP] VAS) compared with predominant leg pain (PLP) (BP VAS less than LP VAS).

PATIENT SAMPLE

The Swedish Spine Register was used and included 1,624 patients operated for DS at the L4-L5 level.

OUTCOME MEASURES

Self-reported measures were used, including a VAS for BP and LP, the EuroQol-5D (EQ-5D), and the physical and mental component summaries of the Short-Form 36 to estimate health-related quality of life and the Oswestry disability index (ODI) to estimate function.

METHODS

Inclusion criterion was single-level DS operated on with either decompression only (D) or decompression and instrumented posterolateral fusion (DF). Based on preoperative LP and BP scores, the patients were assigned to one of the two groups: LP predominance or BP predominance. The patients completed the outcome protocol at 1- and 2-year follow-ups. Statistical analysis was performed using linear regression adjusting for multiple potential confounders.

RESULTS

In the adjusted outcome at the 1-year follow-up, patients with PLP reported a 7.9-mm more improvement on the VAS for BP with fusion, compared with D (95% confidence interval [CI], 0.7-15.2), p=.03. Despite more change in the fused group, the reported BP levels remained similar in the D versus decompressed and fused at the 1-year follow-up (28 vs. 24, p=.77). The patients with PBP benefited from adding fusion in terms of BP 7.1 (95% CI, 0.3-13.9, p=.04), LP 8.8 (2-15.7, p=.01), the ODI 5.7 (1.6-9.9, p=.006), and the EQ-5D 0.09 (1.7-0.02, p=.02) at the 1-year follow-up as the DF group reported greater change in the outcome compared with the D group. At the 2-year follow-up, no significant differences were found between D and decompressed and fused in either the LP or the PBP groups.

CONCLUSIONS

Patients with PBP operated with DF report better outcomes in terms of pain, function, and health-related quality of life than patients with D. Although these differences are significant on a group level, they may fail to reach minimal clinical significant difference. Patients with PLP report significantly more improvement in terms of BP with DF compared with D, but because of baseline differences in preoperative BP, these improvements may not be explained by the added fusion per se. At the 2-year follow-up, no significant differences were observed between the D and DF patients in either the PBP or PLP groups, but greater loss to follow-up in the DF groups could potentially bias these findings.

The effect of disc degeneration on anterior shear translation in the lumbar spine

Many pathologies involving disc degeneration are treated with surgery and spinal implants. It is important to understand how the spine behaves mechanically as a function of disc degeneration. Shear loading is especially relevant in the natural and surgically stabilized lumbar spine. The objective of our study was to determine the effect of disc degeneration on anterior translation of the lumbar spine under shear loading. We tested 30 human cadaveric functional spinal units (L3-4 and L4-5) in anterior shear loading. First, the specimens were imaged in a 1.5 T magnetic resonance scanner. The discs were graded according to the Pfirrmann classification. The specimens were then loaded up to 250 N in anterior shear with an axial compression force of 300 N. Motion of the vertebrae was captured with an optoelectronic camera system. Inter- and intra-observer reliability for disc grading was determined (Cohen's and Fleiss' Kappa), and a non-parametric test was performed on the translation data to characterize the effect of disc degeneration on this parameter. We found fair to moderate agreement between and within observers for the disc grading. We found no significant effect of disc degeneration on anterior shear translation (Kruskal-Wallis ANOVA). Our results indicate that disc degeneration, as classified with the Pfirrmann scale, does not predict lumbar spinal motion in shear.

Effect of disc degeneration on lumbar segmental mobility analyzed by kinetic magnetic resonance imaging

STUDY DESIGN

Retrospective radiographical study.

OBJECTIVE

To define the relationship between the grade of disc degeneration and the motion of the lumbar spine by using kinetic magnetic resonance imaging.

SUMMARY OF BACKGROUND DATA

Disc degeneration is common after middle age. Lumbar instability has generally been recognized as a potential risk factor of low back pain. However, correlations between the grade of disc degeneration and the motion of the lumbar spine need more investigation.

METHODS

Kinetic magnetic resonance imaging was performed in 162 patients with symptomatic low back pain without prior history of surgery. The lumbar intervertebral discs were graded by spine surgeons according to the degenerative grading system (grades I-V). Translational motion and angular variation were measured at each segment from L1-L2 through L5-S1. The relationship between the degree of lumbar disc degeneration and extent of lumbar spine mobility was analyzed.

RESULTS

The translational motion in discs with grade I through IV increased gradually, but decreased with grade V. Compared with other less degenerative grades, grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). The angular variation in discs with grade I through IV was fairly constant, but decreased with grade V. Compared with other degenerative grades (I-IV), grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). For less degenerative grades I and II discs, the L2-L3 and L3-L4 segmental units contributed the majority of total angular mobility of the spine. However, for the severely degenerated segments, grade V discs, the contributions of the L2-L3 and L3-L4 significantly decreased (P < 0.01).

CONCLUSION

As disc degeneration developed from the normal to an increasingly severe stage, the motion of lumbar spine progressed from the normal stage to an unstable phase with higher mobility and finally to an ankylosed stage where stability was increased.

LEVEL OF EVIDENCE

3.

Distribution of Schmorl nodes in the lumbar spine and their relationship with lumbar disk degeneration and range of motion

STUDY DESIGN

A kinematic magnetic resonance imaging study.

OBJECTIVE

To investigate the distribution of Schmorl nodes (SNs) in the lumbar spine in healthy adults, and determine the association with lumbar disk degeneration and lumbar spine motion.

SUMMARY OF BACKGROUND DATA

SNs have been associated with several pathologies of the lumbar spine, although it has been demonstrated that they also occur in the healthy adult population without a clearly identified cause. A thorough understanding of SN distribution may help reveal reasons for their formation. How disk degeneration and lumbar spine motion relate to SNs is poorly understood.

METHODS

Kinematic magnetic resonance images (0.6 T) were available for 1179 healthy individuals from 15 to 85 years of age. Spine specialists performed computer-based measurements. All parameters were measured and calculated automatically using the eRAD PACS Viewer (eRAD Inc., version 6.2.1.1). Lumbar disk degeneration was documented according to the Pfirrmann classification system. Lumbar spine lordosis was quantified as the angle between the inferior endplate of L1 and superior endplate of S1. The level of significance was defined as P ≤ 0.05. The distribution of SNs along the lumbar spine and their relationship with age and sex was investigated using the single factor analysis of variance χ test. The relationship between SNs, age group, disk location, and overall grades of lumbar disk degeneration were investigated by multiple logistic regression analysis. Lumbar spine motion was compared between patients with and without SNs via independent t test among 585 individuals with qualified kinematic images. Multiple logistic regression analysis was performed on associations of lumbar motion range among the SN population.

RESULTS

The prevalence of SNs in our study population was 28.4%, and SNs were observed to be present more frequently in males (34.6%) than in females (20.2%) (ρ< 0.01). There was no significant difference in the incidence of SNs between age groups (ρ= 0.18). SNs were more common at the L2 and L3 vertebral bodies (14.3% and 14.4%), whereas SNs were least common at S1 vertebral bodies (1.5%). The highest incidences of SNs presentation was on disks with degeneration grade III (41.9%) and grade IV (45.3%). SN occurrence, aging, and disk location were positively correlated with lumbar disk degeneration grade. The lumbar spine range of motion was significantly different between individuals with and without SNs (31.4° vs. 37.9°, ρ< 0.01). The frequency of SNs was associated with decreased lumbar range of motion in all age groups except 51 to 60 years and 61 to 70 years.

CONCLUSION

SNs have a high incidence in individuals without persistent lumbar disorders and were found in disks at all degrees of degeneration. SNs occurrence were positively associated with lumbar disk degeneration In addition, the presence of SNs was correlated with decreased overall lumbar motion across all age groups.

The impact of generalized joint laxity on the occurrence and disease course of primary lumbar disc herniation

BACKGROUND CONTEXT

Generalized joint laxity (GJL) has been associated with spine-related disorders such as low back pain, accelerated disc degeneration, and recurrence after discectomy surgery for primary lumbar disc herniation (p-LDH). Generalized joint laxity might be a causative factor of p-LDH, but this relationship is poorly understood. In addition, the impact of GJL on outcomes after the treatment for p-LDH has not been reported.

PURPOSE

To explore relationship between GJL and p-LDH and to compare clinical and radiological outcomes post-therapy in p-LDH patients with or without GJL.

STUDY DESIGN

A retrospective comparative study.

PATIENT SAMPLE

The study group included 203 males, and the control group included 362 males who were matched for age, race, and body mass index with the study group.

OUTCOME MEASURES

The primary outcome was the presence or absence of GJL according to the Beighton scale. The secondary outcome measures included the clinical outcome according to a visual analog scale and the Oswestry disability index and the radiological outcome.

METHODS

We compared baseline data between groups, and we evaluated the impact of GJL on outcomes after different types of several treatment for LDH.

RESULTS

The prevalence of GJL was significantly higher in the study group (10.8%) than in the matched control group (4.4%) (p=.003). In multivariate logistic regression analysis, GJL was the only significant predictor (p=.012). For all treatment methods, patients with GJL had worse clinical outcomes than did patients without GJL. In the patients treated with lumbar discectomy surgery, the differential Cobb value at the last follow-up was higher in the GJL patients than in the non-GJL patients (p=.001).

CONCLUSIONS

Generalized joint laxity was closely related to p-LDH and may be a causative factor. In addition, patients with GJL had worse clinical and radiological outcomes than patients without GJL. Consequently, GJL should be evaluated preoperatively, and this information should be communicated to p-LDH patients with GJL.

Coronal curvature and spinal imbalance in degenerative lumbar scoliosis: disc degeneration is associated

STUDY DESIGN

A retrospective radiographical study.

OBJECTIVE

To determine the association between disc degeneration and spinal malalignment on both coronal and sagittal planes in patients with degenerative lumbar scoliosis (DLS).

SUMMARY OF BACKGROUND DATA

In recent years, a thorough understanding of spinal coronal balance and sagittal alignment has become more and more important in treating patients with DLS. Although degeneration of discs has been generally accepted as the main cause of DLS, to date no study has documented the relationships between disc degeneration and the curve magnitude as well as spinal imbalance.

METHODS

In this study, 57 patients with DLS were recruited. Degeneration of the apical disc, lower end vertebral (EV) discs and regional lumbar discs (L1-L2 and L5-S1) were quantitatively evaluated by the Pfirrmann score based on T2-weighted magnetic resonance images. Radiographical parameters including Cobb angle, coronal trunk shift, sagittal vertical axis (SVA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence, pelvic tilt, and sacral slope were measured from long-cassette standing upright radiographs. Subjects were assigned to 4 groups: both coronal and sagittal balanced (C+ S+); coronal imbalanced but sagittal balanced (C- S+); coronal balanced but sagittal imbalanced (C+ S-); and both coronal and sagittal imbalanced (C- S-). The Spearman correlation was used to identify the relationship between the Pfirrmann score of disc degeneration and radiographical parameters. Analysis of variance 2×2 factorial design was performed to identify the decisive factors affecting coronal and sagittal balance.

RESULTS

On the basis of the criteria for each group, 19 patients were assigned to group A (C+ S+), 10 patients to group B (C- S+), 11 patients to group C (C+ S-), and 17 patients to group D (C- S-). The Pfirrmann score of regional lumbar disc degeneration strongly correlated with Cobb angle, SVA, TK, and LL (r = -0.364, -0.386, 0.283, and 0.479, respectively, P < 0.01). Specifically, the Pfirrmann score of apical disc degeneration correlated with Cobb angle, whereas degeneration of lower EV discs correlated with SVA, TK, and LL. On the basis of analysis of variance 2 × 2 factorial design, the score of the lower EV disc degeneration significantly correlated with sagittal balance (P < 0.05).

CONCLUSION

This study demonstrated that the lower EV disc degeneration strongly correlated with sagittal imbalance in patients with DLS, implying that disc degeneration may be regarded as a potential risk factor for sagittal imbalance. This result strengthened the importance of not selecting the lower EV as the lower instrumented vertebra during the surgical decision making, which may lead to deterioration of sagittal balance. Disc degeneration was also strongly correlated with sagittal malalignment, as demonstrated by a more positive SVA, decreased TK and LL, providing insight into reasons for low quality of life in elderly patients with DLS.

Effects of sagittal endplate shape on lumbar segmental mobility as evaluated by kinetic magnetic resonance imaging

STUDY DESIGN

Retrospective analysis using kinetic magnetic resonance imaging.

OBJECTIVE

To investigate relationships between vertebral endplate remodeling, Modic changes, disc degeneration, and lumbar segmental mobility.

SUMMARY OF BACKGROUND DATA

Previous studies have shown that disc degeneration and vertebral endplate Modic changes are associated with differences in spinal motion, however, the effects of vertebral endplate morphology on lumbar segmental motion have not been fully investigated.

METHODS

A total of 420 patients underwent kinetic magnetic resonance imaging of 2100 lumbar motion segments. Sagittal endplate shapes (concave, flat, irregular), Modic changes (types, 0-3), and disc degeneration (grade, I-V) were assessed along with translational and angular motion of vertebral segments in flexion, extension, and neutral positions.

RESULTS

The most common findings were concave endplate shape (63.24%), type 2 Modic change (71.79%), and grade II disc degeneration (40.33%). Flat, irregular endplates were more common at L1-L2, L4-L5, and L5-S1 than L2-L3 and L3-L4. Types 1, 2, and 3 Modic changes increased in frequency according to endplate shape: concave less than flat less than irregular. Type 0 was observed to decrease with the change of endplate shape from flat to concave to irregular. Vertebral levels with irregular endplates had more disc generation than those with flat; levels with flat endplates had significantly more disc degeneration than those with concave. Translational motion of the lumbar segment was greatest at levels with irregular endplates and decreased at those with flat and then concaves endplates. Angular motion was least at levels with irregular endplates and increased at levels with flat, then concave endplates.

CONCLUSION

The degree of pathogenic lumbar segmental motion is associated with remodeling of the sagittal endplate. Endplate remodeling may occur as an adaptation to restrain abnormal movement of the lumbar segment.

LEVEL OF EVIDENCE

N/A.

Hemilaminectomy and vertebral stabilization for thoracolumbar intervertebral disc associated dynamic compression in 11 dogs

OBJECTIVE

To describe the diagnostic findings, surgical technique and outcome in dogs with thoracolumbar intervertebral disc-associated dynamic compression.

STUDY DESIGN

Retrospective case series.

ANIMALS

Client owned dogs (n = 11).

METHODS

Medical records (2005-2010) of dogs with a stress myelographic diagnosis of spinal cord injury due to thoracolumbar intervertebral disc-associated dynamic compression with inconclusive compression in the neutral myelographic views that had hemilaminectomy and vertebral stabilization were reviewed. Data on pre- and postoperative neurologic status, diagnostic findings, surgical techniques and outcomes were retrieved. Follow-up clinical and radiographic evaluations were performed immediately, and at approximately one, two, and six months postoperatively as well as at annual follow-up examinations.

RESULTS

The stress myelography demonstrated distinct ventral dynamic compression due to bulging of the disc and additional dorsal compression due to infolding of the ligamentum flavum in some cases. The median percentage of post-stress reduction in spinal cord height on the lateral view was 18.0% (9.8-27.2%). All dogs recovered after surgery and at follow-up examinations were still ambulatory (median: 45 months, range: 7 to 94 months).

CONCLUSIONS AND CLINICAL RELEVANCE

Thoracolumbar intervertebral disc degeneration may result in disc-associated dynamic compression. Stress myelography was an effective means of diagnosing this condition and hemilaminectomy with vertebral stabilization was an effective treatment resulting in long-term neurological improvement in all dogs.

Parameters that effect spine biomechanics following cervical disc replacement

Total disc replacement (TDR) is expected to provide a more physiologic alternative to fusion. However, long-term clinical data proving the efficacy of the implants is lacking. Limited clinical data suggest somewhat of a disagreement between the in vitro biomechanical studies and in vivo assessments. This conceptual paper presents the potential biomechanical challenges affecting the TDR that should be addressed with a hope to improve the clinical outcomes and our understanding of the devices. Appropriate literature and our own research findings comparing the biomechanics of different disc designs are presented to highlight the need for additional investigations. The biomechanical effects of various surgical procedures are analyzed, reiterating the importance of parameters like preserving uncinate processes, disc placement and its orientation within the cervical spine. Moreover, the need for a 360° dynamic system for disc recipients who may experience whiplash injuries is explored. Probabilistic studies as performed already in the lumbar spine may explore high risk combinations of different parameters and explain the differences between "standard" biomechanical investigations and clinical studies. Development of a patient specific optimized finite element model that takes muscle forces into consideration may help resolve the discrepancies between biomechanics of TDR and the clinical studies. Factors affecting long-term performance such as bone remodeling, subsidence, and wear are elaborated. In vivo assessment of segmental spine motion has been, and continues to be, a challenge. In general, clinical studies while reporting the data have placed lesser emphasis on kinematics following intervertebral disc replacements. Evaluation of in vivo kinematics following TDR to analyze the quality and quantity of motion using stereoradiogrammetric technique may be needed.

Grade three disc degeneration is a critical stage for anterior spondylolisthesis in lumbar spine

INTRODUCTION

Little is known about when and how progressive spondylolisthesis occurs. In this report segmental motion related to age and disc degeneration at L4/5 disc was investigated.

MATERIALS AND METHODS

637 patients with low back and/or leg pain underwent radiologic and MRI examinations simultaneously. Because 190 patients with conditions which might impede accurate measurement were excluded, 447 patients, comprising 268 men and 179 women, were included; age range, was 10-86 (mean: 53) years. Three radiologic parameters slip in neutral position (mm), sagittal translation (mm), and segmental angulation (degrees) were examined at the L4/5 segment. On T2-weighted MRI, severity of disc degeneration at L4/5 was classified by Pfirrmann's criteria, grade 1-5.

RESULTS

Results showed stage of disc degeneration that progressed according to aging with significant differences except for between grades 4 and 5. Amount of anterior slip was small among grades 1 to 3; however, it greatly increased between grades 3 and 4 and between grades 4 and 5, suggesting that grade 3 disc degeneration has a potential risk of future progression of anterior slip. This finding may also suggest that once significant slip occurs, it will progress to the final grade. Furthermore, the grade 3 degeneration group exhibited large amounts of motion in both angulation and translation, suggesting it was the most unstable group.

CONCLUSION

Our results with radiography and MRI indicate that grade 3 disc degeneration is a critical stage for the progression of lumbar spondylolisthesis at L4/5 segment.

Effects of lumbar artificial disc design on intervertebral mobility: in vivo comparison between mobile-core and fixed-core

Although in theory, the differences in design between fixed-core and mobile-core prostheses should influence motion restoration, in vivo kinematic differences linked with prosthesis design remained unclear. The aim of this study was to investigate the rationale that the mobile-core design seems more likely to restore physiological motion since the translation of the core could help to mimic the kinematic effects of the natural nucleus. In vivo intervertebral motion characteristics of levels implanted with the mobile-core prosthesis were compared with untreated levels of the same population, levels treated by a fixed-core prosthesis, and normal levels (data from literature). Patients had a single-level implantation at L4L5 or L5S1 including 72 levels with a mobile-core prosthesis and 33 levels with a fixed-core prosthesis. Intervertebral mobility characteristics included the range of motion (ROM), the motion distribution between flexion and extension, the prosthesis core translation (CT), and the intervertebral translation (VT). A method adapted to the implanted segments was developed to measure the VT: metal landmarks were used instead of the bony landmarks. The reliability assessment of the VT measurement method showed no difference between three observers (p < 0.001), a high level of agreement (ICC = 0.908) and an interobserver precision of 0.2 mm. Based on this accurate method, this in vivo study demonstrated that the mobile-core prosthesis replicated physiological VT at L4L5 levels but not at L5S1 levels, and that the fixed-core prosthesis did not replicate physiological VT at any level by increasing VT. As the VT decreased when the CT increased (p < 0.001) it was proven that the core mobility minimized the VT. Furthermore, some physiologic mechanical behaviors seemed to be maintained: the VT was higher at implanted the L4L5 level than at the implanted L5S1 level, and the CT appeared lower at the L4L5 level than at the L5S1 level. ROM and motion distribution were not different between the mobile-core prosthesis and the fixed-core prosthesis implanted levels. This study validated in vivo the concept that a mobile-core helps to restore some physiological mechanical characteristics of the VT at the implanted L4L5 level, but also showed that the minimizing effect of core mobility on the VT was not sufficient at the L5S1 level.

The influence of sagittal instability factors on clinical lumbar spinal symptoms

STUDY DESIGN

Cross-sectional and prospective study.

OBJECTIVE

To find the critical order of 3 radiographic factors observed in standing flexion-extension films and to discover their combined effect on lumbar symptoms.

SUMMARY OF BACKGROUND DATA

Many previous reports have described relationships between degenerative change in the lumbar disc and segmental instability; however, few reports have attempted to show any relationship between instability and symptoms. Little is known about which type of instability is the most critical in the sagittal plane of the lumbar spine.

METHODS

Excessive segmental motion (factors): >3 mm slip, >3 mm translation, and >10 degrees angulation, at the L4/5 segment in 880 patients (389 men and 491 women; mean age, 49.4 y) with low back and/or leg pain were investigated at initial visit. Symptoms of low back and leg pain, and walking ability were evaluated at initial visit and 4.6-year follow-up using Japanese Orthopaedic Association's scoring system. Severity and continuity of symptoms were evaluated and compared among the groups according to various combinations of excessive motion.

RESULTS

Of the 3 factors, patients with >3 mm slip had the lowest scores, and patients with >10 degrees angulation had the highest, both at initial visit and follow-up (P<0.001). In the comparative study of various factors, the groups with >3 mm slip had significantly lower scores than the group with no factors, and these groups had significantly lower scores in leg pain and walking ability than the nonfactor group (P<0.05).

CONCLUSIONS

Of the 3 factors, >3 mm slip had the strongest effect on symptoms followed by >3 mm translation and then >10 degrees angulation. Therefore, patients with low back and/or leg pain at initial visit and >3 mm slip, may expect symptoms of a duration exceeding 4 years. More than 10 degrees angulation had the least effect on symptoms as shown by the similarity in scores with the nonfactor group.

Disc height and segmental motion as risk factors for recurrent lumbar disc herniation

STUDY DESIGN

Retrospective review and multivariate analysis.

OBJECTIVES

Recurrent lumbar disc herniation (rLDH) is a repeated disc herniation at a previously operated disc level in patients who experienced a pain-free interval of at least 6 months after surgery. We investigated whether the preoperative radiologic biomechanical factors (disc height index [DHI] and sagittal range of motion [sROM]) have any effect on rLDH.

SUMMARY OF BACKGROUND DATA

rLDH has been reported in 5% to 15% of patients. There have been many studies suggesting various risk factors for rLDH, such as disc degeneration, trauma, age, smoking, gender, and obesity. However, these factors did not reflect a biomechanical effect on the affected joint directly. Investigation of DHI and sROM would be helpful to understand the biomechanical impact on the occurrence of rLDH.

METHODS

This study enrolled 157 patients who underwent surgery for L4-L5 LDH. We divided the patients into the recurrent and the nonrecurrent group and compared their clinical parameters (age, sex, body-mass index, symptom duration, diabetes, smoking, herniation type, preoperative visual analogue scale) and preoperative radiologic parameters (disc degeneration, DHI, sROM).

RESULTS

rLDH occurred at 40.8+/-15.5 months (7-70 months) after primary surgery. Mean DHI was 0.37+/-0.09 and 0.29+/-0.09 in the recurrent and the nonrecurrent group, respectively (P<0.05). Mean sROM was 11.3 degrees+/-2.9 degrees and 5.9 degrees+/-3.7 degrees in the recurrent and the nonrecurrent group, respectively (P<0.05). Both smoking and disc degeneration were related with the development of rLDH (P<0.05).

CONCLUSION

Together with our data, DHI and sROM showed a significant correlation with the incidence of recurrent lumbar disc herniation, suggesting that preoperative biomechanical conditions of the spine can be an important pathogenic factor in the site of lumbar disc surgery.

Lumbar segmental mobility according to the grade of the disc, the facet joint, the muscle, and the ligament pathology by using kinetic magnetic resonance imaging

STUDY DESIGN

The kinematic study of human lumbar spinal movements.

OBJECTIVE

To investigate how disc degeneration and the degeneration of facet joint, ligaments, and paraspinal muscles are associated with lumbar segmental mobility.

SUMMARY OF BACKGROUND DATA

Previous studies revealed relationship between spinal motion and osteoarthritic changes of facet joint as well as disc degeneration; however, little is known about the association of disc, facet joint, ligament, and muscle degeneration with lumbar segmental motion characteristics.

METHODS

The 1580 lumbar motion segments from 316 patients (200 male, 116 female) underwent Kinetic magnetic resonance imaging, which were used to assess disc degeneration (grade I-V) and facet joint degeneration (grade 1-4), interspinous ligament (ISL) degeneration (grade 1-4), ligamentum flavum hypertrophy (LFH), and fatty degeneration of muscles. Segmental translational and angular motion in the flexion, extension, and neutral postures were digitally automatically measured by MR analyzer.

RESULTS

Grade II (46.77%) disc, grade 1 (48.35%) facet joint degeneration, and grade 1 (64.1%) ISL were most common. LFH was most common in L4-L5 (49/330, 14.8%). In younger age (<35), grade I disc and grade 1 facet joint were predominant compared with the older age (35< or = and <45) in which grade III, IV, and V disc and grade 2 facet joint were predominant (P < 0.05). Translational motion increased significantly in high grade of disc and facet joint (except grade V disc and grade 4 facet joint) and with LFH in L1-L5 (P < 0.05). Angular motion significantly decreased in grade V disc, grade 4 ISL, and without LFH in L1-L5 (P < 0.05). According to muscle fatty degeneration, translational and angular motions were not significantly changed.

CONCLUSION

Our results support that facet joint degeneration is followed by disc degeneration according to age. Increased translational movements of the lumbar segments occurred in severe disc degeneration accompanied by facet joint degeneration or the presence of LFH even if the movements were stabilized in the advanced status. Therefore, the current status of the intervertebral discs, facet joints, and ligamentum flavum should be taken into consideration when evaluating stability within the lumbar spine.

Accuracy of dynamic computed tomography to calculate rotation occurring at lumbar spinal motion segments

STUDY DESIGN

Reliability study comparing computed tomography (CT) to biomechanics.

OBJECTIVE

To measure the accuracy and precision of such measurements in comparison with a standard method.

SUMMARY OF BACKGROUND DATA

Rotations of lumbar spinal motion segments can be measured with dynamic CT imaging. This may be a useful tool to measure intersegmental motion. Validation of its use is lacking.

METHODS

Human cadaveric lumbar spines were fixed in a rigid rotation device and rotated, whereas rotation at each level was measured with extensiometers. Rotation at each level was calculated as a percent of total rotation. The spines were placed in a CT scanner and imaged after rotation of the spine in each direction. The percent of total rotation that occurred at each level was calculated with a software program. Accuracy of the CT method was calculated as the average difference between methods. Precision was measured as the standard deviation of the CT measurement. Biomechanical testing and CT were repeated after the posterior anulus fibrosus at L3-L4 was incised with a scalpel. The power of the CT method to detect a change in rotation was tested by calculating the difference between the pre- and postsurgery rotation at L3-L4 and testing it for significance with a Student t test of paired samples.

RESULTS

Differences between CT and biomechanical measurements averaged 0.2%. Precision was 6.0% (Table 1). Postanular injury, percent rotation at the L3-L4 level increased, whereas it decreased at the other 4 levels. The change at L3-L4 was statistically significant (P = 0.047).

CONCLUSION

Dynamic CT measures vertebral rotations sufficiently accurately to study the effect of a radial tear on axial rotation can.

Twelve-Month Follow-up of Lumbar Spine Range of Motion Following Intervertebral Disc Replacement Using Radiostereometric Analysis

Background

Many clinical studies have focused on clinical pain scores and less on kinematics following intervertebral disc replacement. Although flexion and extension of the motion segment can be measured on lateral X-rays, measuring lateral bending and axial rotation of the device is extremely difficult on plain radiography. This study was designed to measure, using radiostereometric analysis (RSA), the postoperative range of motion of the spinal segment following placement of ProDisc-L interbody device (Synthes Spine, West Chester, Pennsylvania).

Methods

Twelve patients (15 discs) with a ProDisc-L intervertebral disc replacement were followed postoperatively at 1.5, 3, 6, and 12 months with both clinical and RSA examinations. For follow-up RSA analysis, 4 to 5 tantalum beads were inserted into the vertebrae adjacent to the surgical level during surgery. Standing biplanar films were collected during follow-up, and the ranges of motion (ROM) (sagittal and coronal bending) of the adjacent vertebrae were determined by RSA.

Results

Based on the clinical surveys, this group of patients had similar outcomes compared to larger clinical populations. The flexion/extension ROM with the disc replacement averaged 2.5° at 6 weeks and increased over the follow-up period to 6.6° at 6 months. The lateral bending ROM with the disc replacement remained consistent over the 4 time points and averaged 3.0°. The motion at the level of the L4-5 vertebrae following disc replacement was greater across all time points than the motion at the L5-S1 level for both sagittal (5.9° versus 2.1°) and coronal (4.2° versus 0.6°) bending.

Conclusions

In this study, the amount of RSA-measured segmental flexion/extension ROM for those with disc replacement was similar to other studies using plain radiography. In lateral bending, the amount of motion with disc replacement was less than the typical 6°–16° reported for normal ROM.

Clinical Relevance

This is the first published study evaluating the in vivo kinematics of artificial disc replacement using RSA.

Kinematic analysis of the relationship between the grade of disc degeneration and motion unit of the cervical spine

STUDY DESIGN

Kinetic MRIs of cervical spines were obtained and analyzed according to the amount of motion and the degenerative grade of the intervertebral disc.

OBJECTIVE

To define the relationship between the grade of disc degeneration and the motion unit of the cervical spine and elucidate changes in the role of each cervical spine unit during flexion-extension motion caused by degeneration.

SUMMARY OF BACKGROUND DATA

Degenerative changes in the cervical disc occur with age. The correlation between the degree of cervical disc degeneration and extent of cervical spine mobility has not yet been determined. The effect of degeneration on the overall motion of the functional spinal unit also remains undefined.

METHODS

We studied 164 patients with symptomatic neck pain. The cervical intervertebral discs were graded by spine surgeons according to the degenerative grading system (Grades I to V). All radiologic data from kinetic MRIs were recorded on a computer for subsequent measurements. All measurements and calculations for translational motion and angular variation of each segment were automatically performed by a computer analyzer.

RESULTS

The translational motion in discs with Grade II degeneration (mild degeneration) increased to Grade III degeneration (higher degeneration). However, the translational motion and angular variation significantly decreased for the Grade V (severe degeneration). For patients with relatively low grades of degeneration, Grades I and II discs, the C4-C5 and C5-C6 segmental units contributed the majority of total angular mobility of the spine. However, for the severely degenerated segments, Grade V discs, the contributions of the C4-C5 and C5-C6 U significantly decreased.

CONCLUSION

The changes that occur with disc degeneration progress from the normal state to an unstable phase with higher mobility and subsequently to an ankylosed stage. This study evaluated the contribution of different levels to the changes in overall motion that occur with degeneration.

Lumbar intervertebral instability: a review

Intervertebral instability of the lumbar spine is thought to be a possible pathomechanical mechanism underlying low back pain and sciatica and is often an important factor in determining surgical indication for spinal fusion and decompression. Instability of the lumbar spine, however, remains a controversial and poorly understood topic. At present, much controversy exists regarding the proper definition of the condition, the best diagnostic methods, and the most efficacious treatment approaches. Clinical presentation is not specific, and the relationship between radiologic evidence of instability and its symptoms is controversial. Because of its simplicity, low expense, and pervasive availability, functional flexion-extension radiography is the most thoroughly studied and the most widely used method in the imaging diagnosis of lumbar intervertebral instability. In this article, we provide an overview of the current concepts of vertebral instability, focusing on degenerative lumbar intervertebral instability, and review the different imaging modalities most indicated in diagnosing vertebral instability.