Association of facet tropism with lumbar disc herniation

Purpose

Facet tropism is defined as asymmetry between left and right facet joints and is postulated as a possible cause of disc herniation. In the present study, the authors used a 3-T MRI to investigate the association between facet tropism and lumbar disc herniation at a particular motion segment. They also examined whether the disc herniated towards the side of the more coronally oriented facet joint.

Methods

Sixty patients (18–40 years) with single level disc herniation (L3–L4, L4–L5, or L5–S1) were included in the study. Facet angles were measured using MRI of 3-T using the method described by Karacan et al. Facet tropism was defined as difference of 10° in facet joint angles between right and left sides. Normal disc adjacent to the herniated level was used as control. We also examined if disc herniated towards the side of more coronally oriented facet.

Results

Twenty-five herniations were at L4–L5 level and 35 at L5–S1. Statistical analysis was performed using the Fischer Exact Test. At L4–L5 level, 6/25 cases had tropism compared to 3/35 controls (p = 0.145). At L5–S1 level, 13/35 cases had tropism as compared to 1/21 controls (p = 0.0094). Of 19 cases having tropism, the disc had herniated towards the coronally oriented facet in six (p = 0.11).

Conclusion

The findings of the study suggest that facet tropism is associated with lumbar disc herniation at the L5–S1 motion segment but not at the L4–L5 level.     

Parameters influencing the outcome after total disc replacement at the lumbosacral junction. Part 2: distraction and posterior translation lead to clinical failure after a mean follow-up of 5 years

Purpose

The aim of the second part of the study was to investigate the influence of parameters that lead to increased facet joint contact or capsule tensile forces (disc height, lordosis, and sagittal misalignment) on the clinical outcome after total disc replacement (TDR) at the lumbosacral junction.

Methods

A total of 40 patients of a prospective cohort study who received TDR because of degenerative disc disease or osteochondrosis L5/S1 were invited to an additional follow-up for clinical (ODI and VAS for overall, back, and leg pain) and radiographic analysis (a change in disc height, lordosis, or sagittal vertebral misalignment compared with the preoperative state). Based on the final ODI, patients were retrospectively distributed into groups N (normal: <25 %) or F (failure ≥25 %) for radiographic parameter comparison. A correlation analysis was performed between the clinical and radiological results.

Results

A total of 34 patients were available at a mean follow-up of 59.5 months. Both groups (N = 24; F = 10 patients) presented a significant improvement in overall pain, back pain, and ODI over time. At the final follow-up, higher clinical scores correlated with a larger disc height, increased lordosis, and posterior translation of the superior vertebra, which was also reflected by significant differences in these parameters in the group comparison.

Conclusions

Parameters associated with increased facet joint capsule tensile forces lead to an inferior clinical outcome at mid-term follow-up. When performing TDR, we therefore suggest avoiding iatrogenic posterior translation and overdistraction (and consecutive lordosis).     

Footprint mismatch in total cervical disc arthroplasty

Purpose

Cervical disc arthroplasty has become a commonplace surgery for the treatment of cervical radiculopathy and myelopathy. Most manufacturers derive their implant dimensions from early published cadaver studies. Ideal footprint match of the prosthesis is essential for good surgical outcome.

Methods

We measured the dimensions of cervical vertebrae from computed tomography (CT) scans and to assess the accuracy of match achieved with the most common cervical disc prostheses [Bryan (Medtronic), Prestige LP (Medtronic), Discover (DePuy) Prodisc-C (Synthes)]. A total of 192 endplates in 24 patients (56.3 years) were assessed. The anterior–posterior and mediolateral diameters of the superior and inferior endplates were measured with a digital measuring system.

Results

Overall, 53.5 % of the largest device footprints were smaller in the anterior–posterior diameter and 51.1 % in the mediolateral diameter were smaller than cervical endplate diameters. For levels C5/C6 and C6/C7 an inappropriate size match was noted in 61.9 % as calculated from the anteroposterior diameter. Mismatch at the center mediolateral diameter was noted in 56.8 %. Of the endplates in the current study up to 58.1 % of C5/C6 and C6/C7, and up to 45.3 % of C3/C4 and C4/C5 were larger than the most frequently implanted cervical disc devices.

Conclusion

Surgeons and manufacturers should be aware of the size mismatch in currently available cervical disc prostheses, which may endanger the safety and efficacy of the procedure. Undersizing the prosthetic device may lead to subsidence, loosening, heterotopic ossification and biomechanical failure caused by an incorrect center of rotation and load distribution, affecting the facet joints.     

Lumbar total disc replacement: correlation of clinical outcome and radiological parameters

Background

The objective of this study was to correlate various radiological parameters with clinical outcome in patients who had undergone lumbar total disc replacement (TDR). Lumbar TDR is one possible treatment option in patients with low back pain (LBP), offering an alternative to lumbar fusion. Favourable clinical outcome hinges on a number of radiological parameters, such as mobility, sintering, and—most importantly—accurate positioning of the implant.

Methods

A total of 46 patients received a prosthetic disc because of degenerative lumbar disc disorders. Follow-up evaluation included analysis of radiographs and subjective rating of the clinical status by the patient using the North American Spine Society (NASS) patient questionnaire, visual analogue scale (VAS) for pain and state of health, and the EuroQol EQ-5D. Radiological follow-up took place after 2 years. Coronal and sagittal positions of the prosthesis, intervertebral disc height, facet joint pressure, mobility, sintering, and calcification were evaluated. Optimal positioning of the prosthesis was defined as a central coronal position and a most dorsal position in the sagittal plane. Based on the radiologically determined placement of the prosthesis, the patient population was divided into three groups, i.e., prosthesis ideally placed (<2 mm), discretely shifted (2–3 mm), or suboptimally placed (>3 mm).

Results

Overall, 81 % of patients stated that they would undergo the operation again. Health status was stable at a VAS score of 7.04 points 2 years after TDR, compared to 3.97 points before TDR. Mean working capacity had increased from 53 % preoperatively to 88 % 2 years after TDR. Overall, 39 % of the prostheses were rated as ideally positioned, while 13 % were discretely shifted and 48 % were suboptimally placed with respect to one of the radiological criteria. In 80.4 % of patients, follow-up assessment after ≥2 years indicated good mobility at the operated segment, while calcification was noted in 4 % and sintering was detected in 15 % of the implants.

Conclusions

Our data indicate poor correlation between clinical outcome and position of the prosthesis. Although 48 % of the implants were suboptimally placed in either the coronal or sagittal plane, most of the patients reached a very good clinical outcome. However, suboptimally placed devices appeared to cause significantly more neurological symptoms in long-term follow-up.     

Outcomes of posterior facet versus pedicle screw fixation of circumferential fusion: a cohort study

Purpose

To compare single-level circumferential spinal fusion using pedicle (n = 27) versus low-profile minimally invasive facet screw (n = 35) posterior instrumentation.

Method

A prospective two-arm cohort study with 5-year outcomes as follow-up was conducted. Assessment included back and leg pain, pain drawing, Oswestry disability index (ODI), pain medication usage, self-assessment of procedure success, and >1-year postoperative lumbar magnetic resonance imaging.

Results

Significantly less operative time, estimated blood loss and costs were incurred for the facet group. Clinical improvement was significant for both groups (p < 0.01 for all outcomes scales). Outcomes were significantly better for back pain and ODI for the facet relative to the pedicle group at follow-up periods >1 year (p < 0.05). Postoperative magnetic resonance imaging found that 20 % had progressive adjacent disc degeneration, and posterior muscle changes tended to be greater for the pedicle screw group.

Conclusion

One-level circumferential spinal fusion using facet screws proved superior to pedicle screw instrumentation.     

The translaminar approach for cranially extruded lumbar disc herniations

Objective

To remove extruded disc fragments impinging the exiting root. To spare the interlaminar space and the facet joint.

Indication

Cranially migrated disc herniation.

Contraindication

Severe spinal canal stenosis.

Surgical technique

Microscope from skin to skin, 25 mm skin incision about 5 mm off the midline, conventional subperiosteal route or transmuscular access by blunt splitting the multifidus muscle. A translaminar hole (diameter 10 mm) is drilled off. The epidural exploration starts along the thecal sac until the axilla of the exiting root is reached. An extruded or subligamentous disc fragment(s) is removed. If an extensive annular perforation is detected, the disc space should be cleared (20% of the cases).

Postoperative management

Same day mobilization.

Results

A total of 84 patients (46 men) underwent the translaminar approach. The mean age was 57 years (range 27–80 years). Follow-up examinations by an independent observer at 1 and 6 weeks; 3, 6 and 12 months and once yearly thereafter (mean follow-up 27 months). Extruded (61%) and subligamentous (39%) disc fragments were found. In 4 cases the translaminar hole was enlarged to a laminotomy. In 12 patients the disc space was cleared. The outcome (MacNab criteria) was excellent (67%), good (27%), fair (5%), and poor (1%). The incidence of recurrent disc herniations was 7%.     

The biomechanical impact of facet tropism on the intervertebral disc and facet joints in the cervical spine

Background Context

Facet tropism is defined as the angular difference between the left and the right facet orientation. Facet tropism was suggested to be associated with the disc degeneration and facet degeneration in the lumbar spine. However, little is known about the relationship between facet tropism and pathologic changes in the cervical spine and the mechanism behind.

Artificial total disc replacement versus fusion for lumbar degenerative disc disease: a meta-analysis of randomized controlled trials

Objective

The purpose of this study is to compare the effectiveness and safety of artificial total disc replacement (TDR) with fusion for the treatment of lumbar degenerative disc disease (DDD).

Summary of background data

Spinal fusion is the conventional surgical treatment for lumbar DDD. Recently, TDR has been developed to avoid the negative effects of the fusion by preserving function of the motion segment. Controversy still surrounds regarding whether TDR is better.

Methods

We systematically searched six electronic databases (Medline, Embase, Clinical, Ovid, BIOSIS and Cochrane registry of controlled clinical trials) to identify randomized controlled trials (RCTs) published up to March 2013 in which TDR was compared with the fusion for the treatment of lumbar DDD. Effective data were extracted after the assessment of methodological quality of the trials. Then, we performed the meta-analysis.

Results

Seven relevant RCTs with a total of 1,584 patients were included. TDR was more effective in ODI (MD ?5.09; 95 % CI [?7.33, ?2.84]; P < 0.00001), VAS score (MD ?5.31; 95 % CI [?8.35, ?2.28]; P = 0.0006), shorter duration of hospitalization (MD ?0.82; 95 % CI [?1.38, ?0.26]; P = 0.004) and a greater proportion of willing to choose the same operation again (OR 2.32; 95 % CI [1.69, 3.20]; P < 0.00001). There were no significant differences between the two treatment methods regarding operating time (MD ?44.16; 95 % CI [?94.84, 6.52]; P = 0.09), blood loss (MD ?29.14; 95 % CI [?173.22, 114.94]; P = 0.69), complications (OR 0.72; 95 % CI [0.45, 1.14]; P = 0.16), reoperation rate (OR 0.83; 95 % CI [0.39, 1.77]; P = 0.63) and the proportion of patients who returned to full-time/part-time work (OR 1.10; 95 % CI [0.86, 1.41]; P = 0.47).

Conclusion

TDR showed significant safety and efficacy comparable to lumbar fusion at 2 year follow-up. TDR demonstrated superiorities in improved physical function, reduced pain and shortened duration of hospitalization. The benefits of operating time, blood loss, motion preservation and the long-term complications are still unable to be proved.     

Distal radius fractures and the volar lunate facet fragment: Kirschner wire fixation in addition to volar-locked plating

Background

The volar lunate facet fragment of a distal radius fracture may not be stabilized with volar-locked plating alone due to the small size and distal location of the fragment. Identification and stabilization of this small fragment is critical as unstable fixation may result in radiocarpal and radioulnar joint subluxation. The addition of spring wire fixation with volar plating can provide stable internal fixation of this critical fracture fragment.

Methods

A retrospective review (2006–2011) identified nine patients with distal radius fractures with an associated volar lunate facet fragment that were treated with volar-locked plating and spring wire fixation of the volar lunate facet fragment. Radiographic indices, range of motion, grip strength, and postoperative Patient-related wrist evaluation (PRWE) scores were obtained to assess pain and function.

Results

All distal radius fractures healed, and the volar lunate facet fragment reduction was maintained. The mean follow-up was 54 weeks. Mean active range of motion was 46° wrist flexion, 51° wrist extension, 80° pronation, and 68° supination. The mean grip strength was 21 Kg, achieving 66 % of the uninjured limb. The average PRWE score was 17. No patient required removal of hardware or had evidence of tendon irritation.

Conclusions

The addition of spring wire fixation to volar-locked plating provided stable fixation of the volar lunate facet fragment of distal radius fractures without complication. This technique addresses a limitation of volar-locked plating to control the small volar lunate facet fragment in distal radius fractures otherwise amenable to volar plating.

Level of Evidence

A retrospective case series, Level IV.     

Influence of lumbar intervertebral disc degeneration on the outcome of total lumbar disc replacement: a prospective clinical, histological, X-ray and MRI investigation

Introduction

The role of fusion of lumbar motion segments for the treatment of axial low back pain (LBP) from lumbar degenerative disc disease (DDD) without any true deformities or instabilities remains controversially debated. In an attempt to avoid previously published and fusion-related negative side effects, motion preserving technologies such as total lumbar disc replacement (TDR) have been introduced. The adequate extent of preoperative DDD for TDR remains unknown, the number of previously published studies is scarce and the limited data available reveal contradictory results. The goal of this current analysis was to perform a prospective histological, X-ray and MRI investigation of the index-segment’s degree of DDD and to correlate these data with each patient’s pre- and postoperative clinical outcome parameters from an ongoing prospective clinical trial with ProDisc II (Synthes, Paoli, USA).

Materials and methods

Nucleus pulposus (NP) and annulus fibrosus (AF) changes were evaluated according to a previously validated quantitative histological degeneration score (HDS). X-ray evaluation included assessment of the mean, anterior and posterior disc space height (DSH). MRI investigation of DDD was performed on a 5-scale grading system. The prospective clinical outcome assessment included Visual Analogue Scale (VAS), Oswestry Disability Index (ODI) scores as well as the patient’s subjective satisfaction rates.

Results

Data from 51 patients with an average follow-up of 50.5 months (range 6.1–91.9 months) were included in the study. Postoperative VAS and ODI scores improved significantly in comparison to preoperative levels (p < 0.002). A significant correlation and interdependence was established between various parameters of DDD preoperatively (p < 0.05). Degenerative changes of NP tissue samples were significantly more pronounced in comparison to those of AF material (p < 0.001) with no significant correlation between each other (p > 0.05). Preoperatively, the extent of DDD was not significantly correlated with the patient’s symptomatology (p > 0.05). No negative influence was associated with increasing stages of DDD on the postoperative clinical outcome parameters following TDR (p > 0.05). Increasing stages of DDD in terms of lower DSH scores were not associated with inferior clinical results as outlined by postoperative VAS or ODI scores or the patient’s subjective outcome evaluation at the last FU examination (p > 0.05). Conversely, some potential positive effects on the postoperative outcome were observed in patients with advanced stages of preoperative DDD. Patients with more severe preoperative HDS scores of NP samples demonstrated significantly lower VAS scores during the early postoperative course (p = 0.02).

Conclusion

Increasing stages of DDD did not negatively impact on the outcome following TDR in a highly selected patient population. In particular, no preoperative DDD threshold value was identified from which an inferior postoperative outcome could have been deduced. Conversely, some positive effects on the postoperative outcome were detected in patients with advanced stages of DDD. Combined advantageous effects of progressive morphological structural rigidity of the index segment and restabilizing effects from larger distraction in degenerated segments may compensate for increasing axial rotational instability, one of TDR’s perceived disadvantages. Our data reveal a “therapeutic window” for TDR in a cohort of patients with various stages of DDD as long as preoperative facet joint complaints or degenerative facet arthropathies can be excluded and stringent preoperative decision making criteria are adhered to. Previously published absolute DSH values as contraindication against TDR should be reconsidered.     

The protective role of dynamic stabilization on the adjacent disc to a rigid instrumented level. An in vitro biomechanical analysis

Objectives

To assess the changes of intradiscal pressure at the bridged and at the adjacent levels to a lumbar two-level hybrid instrumentation.

Introduction

The elimination of motion produced by spinal fusion may have potential consequences beyond the index level overloading the juxtaposed spinal motion segments and leading to the appearance of degenerative changes. Degeneration of the segments adjacent to instrumented levels has become a topic of increasing interest in the literature over the last years. In order to prevent degenerative disc changes at the adjacent segments to a fused level, a broad scope of techniques have been developed, one of them is hybrid constructs.

Methods

In 6 human cadaveric lumbosacral specimens, pressure transducers quantified intradiscal pressure changes at three levels (L3–L4, L4–L5 and L5–S1) under axial compression (0–750 N), anterior flexion (+12°) and extension (?12°) in three different situations of spinal stability: intact, L5–S1 rigid rod pedicle screw instrumentation and L4–S1 two-level hybrid instrumentation (rigid at L5–S1 and dynamic at L4–L5).

Results

Once the L5–S1 segment had implanted the rigid instrumentation system (Diapason), the intradiscal pressure at this level decreased by 65 % while the intradiscal pressure at the disc above (L4–L5) increased 20 %. After augmenting the L5–S1 posterior construct with a dynamic stabilization device (Dynesys) at the superior adjacent level, the intradiscal pressure at this level, L4–L5, decreased by 50 % whereas intradiscal pressure at its adjacent level, L3–L4, only experienced a slight increase of 10 %.

Conclusions

The raise of intradiscal pressure at the adjacent segment to a rigid instrumented segment can be reduced when the rigid construct is augmented with a dynamic stabilization device. Hybrid constructs might have a possible protecting role preventing the occurrence of degenerative disc changes at the adjacent segment to a rigid instrumented level. Augmentation with a dynamic stabilization device might protect the disc above a rigid rod pedicle screw construct.     

Correspondence between bone mineral density and intervertebral disc degeneration across age and sex

Summary

The distribution of bone tissue within the vertebra can modulate vertebral strength independently of average density and may change with age and disc degeneration. Our results show that the age-associated decrease in bone density is spatially non-uniform and associated with disc health, suggesting a mechanistic interplay between disc and vertebra.

Purpose

While the decline of bone mineral density (BMD) in the aging spine is well established, the extent to which age influences BMD distribution within the vertebra is less clear. Measures of regional BMD (rBMD) may improve predictions of vertebral strength and suggest how vertebrae might adapt with intervertebral disc degeneration. Thus, we aimed to assess how rBMD values were associated with age, sex, and disc height loss (DHL).

Methods

We measured rBMD in the L3 vertebra of 377 participants from the Framingham Heart Study (41–83 years, 181 M/196 F). Integral (Int.BMD) and trabecular BMD (Tb.BMD) were measured from QCT images. rBMD ratios (anterior/posterior, superior/mid-transverse, inferior/mid-transverse, and central/outer) were calculated from the centrum. A radiologist assigned a DHL severity score to adjacent intervertebral discs (L2–L3 and L3–L4).

Results

Int.BMD and Tb.BMD were both associated with age, though the decrease across age was greater in women (Int.BMD, ??2.6 mg/cm³ per year; Tb.BMD, ??2.6 mg/cm³ per year) than men (Int.BMD, ??0.5 mg/cm³ per year; Tb.BMD, ??1.2 mg/cm³ per year). The central/outer (??0.027/decade) and superior/mid-transverse (??0.018/decade) rBMD ratios were negatively associated with age, with similar trends in men and women. Higher Int.BMD or Tb.BMD was associated with increased odds of DHL after adjusting for age and sex. Low central/outer ratio and high anterior/poster and superior/mid-transverse ratios were also associated with increased odds of DHL.

Conclusions

Our results indicate that the distribution of bone within the L3 vertebra is different across age, but not between sexes, and is associated with disc degeneration.

     

Comparison of alcohol ablation with repeated thermal radiofrequency ablation in medial branch neurotomy for the treatment of recurrent thoracolumbar facet joint pain

Purpose

Chemical denervation is not recommended as part of the routine care of chronic non-cancer pain. Physicians face a dilemma when it comes to repeated interventions in cases of recurrent thoracolumbar facet joint pain after successful thermal radiofrequency ablation (RFA) in medial branch neurotomy. This study was performed to compare the effects of alcohol ablation (AA) with thermal RFA in patients with recurrent thoracolumbar facet joint pain after thermal RFA treatment.

Methods

Forty patients with recurrent thoracolumbar facet joint pain after successful thermal RFA defined as a numeric rating scale (NRS) score of ≥7 or a revised Oswestry disability index (ODI) of ≥22 % were randomly allocated to two groups receiving either the same repeated RFA (n = 20) or AA (n = 20). The recurrence rate was assessed with NRS and ODI during the next 24 months, and adverse events in each group were recorded.

Results

During the 24-month follow-up after RFA and AA, one and 17 patients, respectively, were without recurring thoracolumbar facet joint pain. The median effective periods in the RFA and AA groups were 10.7 (range 5.4–24) and 24 (range 16.8–24) months, respectively (p < 0.000). No significant complications were observed with the exception of injection site pain, which occurred in both groups.

Conclusion

In our patient cohort, alcohol ablation in medial branch neurotomy provided a longer period of pain relief and better quality of life than repeated radiofrequency medial branch neurotomy in the treatment of recurrent thoracolumbar facet joint pain syndrome after successful thermal RFA without significant complications during the 24-month follow-up.     

Optimizing success with lumbar disc arthroplasty

Purpose

This study aimed at determining the variables that may prove useful in predicting clinical outcomes following lumbar disc arthroplasty.

Methods

Pre- and post-operative imaging assessments were obtained for 99 single-level lumbar disc arthroplasty patients from a prospective IDE study. The assessments and patient demographics were tested to identify variables that were significantly associated with clinical outcomes.

Results

Clinical outcome data were available for 85 % of patients at the 5-year follow-up. Numerous assessments made from the pre-operative imaging were found to have statistically significant associations with clinical outcomes at 2 and 5 years. The most notable factors were related to the amount of degeneration at the index level, with patients achieving better outcome scores at 5 years if they have higher grades of degeneration preoperatively.

Conclusions

Several variables may prove effective at optimizing clinical outcomes including a preoperative disc height <8 mm, Modic type 2 changes adjacent to the target disc, a low amount of lordosis present at the treatment level, low levels of fatty replacement of the paraspinal musculature, a prominent amount of facet joint or disc degeneration, and the presence of flat or convex vertebral endplates. There were also post-operative findings associated with better patient outcomes including a larger percent of the endplate covered with the implant, larger implant heights, greater increases in disc space heights, and a larger increase in index level lumbar lordosis. These variables could be explored in other clinical studies to facilitate meta-analyses that could identify effective strategies to optimize clinical outcomes with lumbar disc arthroplasty.     

Motion characteristics of the lumbar spinous processes with degenerative disc disease and degenerative spondylolisthesis

Objective

Recently, interspinous process devices have attracted much attention since they can be implanted between the lumbar spinous processes (LSP) of patients with degenerative disc disease (DDD) and degenerative spondylolisthesis (DLS) using a minimally invasive manner. However, the motion characters of the LSP in the DLS and DDD patients have not been reported. This study is aimed at investigating the kinematics of the lumbar spinous processes in patients with DLS and DDD.

Methods

Ten patients with DDD at L4–S1 and ten patients with DLS at L4–L5 were studied. The positions of the vertebrae (L2–L5) at supine, standing, 45° trunk flexion, and maximal extension positions were determined using MRI-based models and dual fluoroscopic images. The shortest ISP distances were measured and compared with those of healthy subjects that have been previously reported.

Results

The shortest distance of the interspinous processes (ISP) gradually decreased from healthy subjects to DDD and to DLS patients when measured in the supine, standing, and extension positions. During supine-standing and flexion–extension activities, the changes in the shortest ISP distances in DDD patients were 2 ± 1.2 and 4.8 ± 2.1 mm at L4–L5; in DLS patients they were 0.5 ± 0.4 and 2.8 ± 1.7 mm at L4–L5, respectively. The range of motion is increased in DDD patients but decreased in DLS patients when compared with those of the healthy subjects. No significantly different changes were detected at L2–L3 and L3–L4 levels.

Conclusion

At the involved level, the hypermobility of the LSP was seen in DDD and hypomobility of the LSP in DLS patients. The data may be instrumental for improving ISP surgeries that are aimed at reducing post-operative complications such as bony fracture and device dislocations.     

Clinical characteristics of intraspinal facet cysts following microsurgical bilateral decompression via a unilateral approach for treatment of degenerative lumbar disease

Purpose

Primary intraspinal facet cysts in the lumbar spine are uncommon, but it is unclear whether cyst incidence increases following decompression surgery and if these cysts negatively impact clinical outcome. We examined the prevalence, clinical characteristics, and the risk factors associated with intraspinal facet cysts after microsurgical bilateral decompression via a unilateral approach (MBDU).

Methods

We studied 230 patients treated using MBDU for lumbar degenerative disease (133 men and 97 women; mean age 70.3 years). Clinical status, as assessed by the Japanese Orthopedic Association (JOA) score and findings on X-ray and magnetic resonance images, was evaluated prior to surgery and at both 3 months and 1 year after surgery. The prevalence of intraspinal facet cysts was determined and preoperative risk factors were defined by comparing presurgical findings with clinical outcomes.

Results

Thirty-eight patients (16.5 %) developed intraspinal facet cysts within 1 year postoperatively, and 24 exhibited cysts within 3 months. In 10 patients, the cysts resolved spontaneously 1 year postoperatively. In total, 28 patients (12.2 %) had facet cysts 1 year postoperatively. The mean JOA score of patients with cysts 1 year postoperatively was significantly lower than that of patients without cysts. This poor clinical outcome resulted from low back pain that was not improved by conservative treatment. Most cases with spontaneous cyst disappearance were symptom-free 1 year later. The preoperative risk factors for postoperative intraspinal facet cyst formation were instability (OR 2.47, P = 0.26), scoliotic disc wedging (OR 2.23, P = 0.048), and sagittal imbalance (OR 2.22, P = 0.045).

Conclusions

Postoperative intraspinal facet cyst formation is a common cause of poor clinical outcome in patients treated using MBDU.     

Biomechanical evaluation of the Facet Wedge: a refined technique for facet fixation

Purpose

Purpose of this paper is to evaluate the primary stability of a new approach for facet fixation the so-called Facet Wedge (FW) in comparison with established posterior fixation techniques like pedicle screws (PS) and translaminar facet screws (TLS) with and without anterior cage interposition.

Methods

Twenty-four monosegmental fresh frozen non-osteoporotic human motion segments (L2–L3 and L4–L5) were tested in a two-arm biomechanical study using a robot-based spine tester. Facet Wedge was compared with pedicle screws and translaminar screws as a stand-alone device and in combination with an anterior fusion cage.

Results

Pedicle screws, FW and translaminar screws could stabilize an intact motion segment effectively. Facet Wedge was comparable to PS for lateral bending, extension and flexion and slightly superior for axial rotation. Facet Wedge showed a superior kinematic capacity compared to translaminar screws.

Conclusions

Facet Wedge offers a novel posterior approach in achieving primary stability in lumbar spinal fixation. The results of the present study showed that the Facet Wedge has a comparable primary stability to pedicle screws and potential advantages over translaminar screws.     

Radiological study on disc degeneration of thoracolumbar burst fractures treated by percutaneous pedicle screw fixation

Objective

To examine disc degeneration at levels adjacent and next adjacent to the fractured vertebra and to analyses, if the disc degeneration is determined by the endplate fracture.

Summary of background data

Thoracolumbar burst fracture is one of the most common spinal injuries. The diagnostic (clinical and imaging) approach and treatment of a fractured vertebra is well established; however, some controversy remains. The associated disc degeneration is less well known after 9–12 months of the short segment pedicle screw fixations. There is a major controversy whether spinal trauma with vertebral endplate fractures can result in posttraumatic disc degeneration. No study to date, however, has assessed disc degeneration of the AO type A3 thoracolumbar fractures without neurologic deficits after pedicle screw fixations.

Methods

Twenty-six patients with single-level AO type A3 thoracolumbar fractures and no neurological deficit were treated by using postural reduction and short segment percutaneous pedicle screw fixation. No laminectomy and fusion were performed. Implants were removed 9–12 months after the first operation. The thoracolumbar magnetic resonance imaging (MRI) was used to assess disc degeneration at levels adjacent and next adjacent to the fractured vertebra before the first operation and after the second operation in a retrospective study.

Results

After the instrumentation removal, new disc degeneration was usually found at level adjacent to the cranial endplate of fractured vertebra by MRI examination in 24 patients. The average Pfirrmann grade of degenerative discs adjacent to the cranial fractured endplates deteriorated from 2.1 pre-operatively to 3.4 after the second operation. No change of disc degeneration was seen at the caudal disc space adjacent to the fractured vertebra and the levels next adjacent to the fractured vertebra. The discs next adjacent to the fractured vertebra were showed to be relatively normal without changes of degeneration during the study period.

Conclusions

Disc degeneration usually occurs at level adjacent to the fractured endplate of thoracolumbar burst fractures. Endplate fracture is strongly associated with disc degeneration. No correlation between fixation level and disc degeneration is seen in this study.     

Clinical and radiographic outcomes of dynamic cervical implant replacement for treatment of single-level degenerative cervical disc disease: a 24-month follow-up

Purpose

To determine the role of dynamic cervical implant (DCI) replacement for single-level degenerative cervical disc disease in Chinese patients.

Methods

Thirty patients with single-level degenerative cervical disc disease were prospectively enrolled between April 2010 and August 2010 (12 women, 18 men; mean age 56.5 years). All patients underwent anterior cervical decompression, DCI replacement, clinical and radiological assessments preoperatively and at 1, 6, 12, and 24 months postoperatively, and Japanese Orthopaedic Association (JOA), Visual Analogue Scale (VAS), Neck Disability Index (NDI), and Short Form 36 (SF-36) scores. Lateral neutral radiographs provided the intervertebral space height. Lateral dynamic radiographs were taken to measure the range of motion (ROM) of the cervical spine and functional spinal unit (FSU) of the treated segment. We compared the amount of motion of the adjacent vertebral endplate and the intrinsic motion of the implant and calculated a correlation analysis.

Results

DCI showed good clinical and radiographic outcomes. At the final follow-up, JOA, VAS, NDI, and SF-36 average scores improved significantly. The intervertebral space height increased slightly after operation and was maintained during follow up. The ROM of the cervical spine and FSU decreased at early follow-up, but recovered to the preoperative level within 1–2 years. There was a high index of linear correlation between the motion of the adjacent vertebral endplate and the intrinsic motion of the implant.

Conclusions

DCI provided elastic dynamic stability for the targeted segment, and restored and sustained intervertebral space height and ROM of the cervical spine.     

Five-year follow-up of total disc replacement compared to fusion: a randomized controlled trial

Purpose

To evaluate long-term clinical results of lumbar total disc replacement (TDR) compared with posterior lumbar fusion.

Methods

This prospective randomized controlled trial comprised 152 patients; 80 were randomized to TDR and 72 to fusion. All patients had chronic low back pain (CLBP) and had not responded to nonsurgical treatment. Primary outcome measure was global assessment of back pain (GA), secondary outcome measures were back and leg pain, Oswestry Disability Index (ODI), EQ5D, and SF-36. All measures were collected from SweSpine (Swedish national register for spinal surgery) at 1, 2, and 5 years. Follow-up rate at 5 years was 99.3 %.

Results

Both groups showed clinical improvement at 5-year follow-up. For GA, 38 % (30/80) in the TDR group were totally pain free vs. 15 % (11/71) in the fusion group (p < 0.003). Back pain and improvement of back pain were better in the TDR group: VAS back pain at 5 years 23 ± 29 vs. 31 ± 27, p = 0.009, and VAS improvement of back pain at 5 years 40 ± 32 vs. 28 ± 32, p = 0.022. ODI and improvement in ODI were also better in the TDR group: ODI at 5 years 17 ± 19 vs. 23 + 17, p = 0.02 and ODI improvement at 5 years 25 ± 18 vs. 18 ± 19 (p = 0.02). There was no difference in complications and reoperations between the two groups.

Conclusions

Global assessment of low back pain differed between the two surgical groups at all follow-up occasions. Significant differences between groups concerning back pain, pain improvement, and ODI were present at 1 year and disappeared at 2 years, but reappeared at the 5-year follow-up.