Advantages and disadvantages of nonfusion technology in spine surgery

Biomechanical Effect of Hybrid Dynamic Stabilization Implant on the Segmental Motion and Intradiscal Pressure in Human Lumbar Spine

The hybrid dynamic stabilization system, Dynesys-Transition-Optima, represents a novel pedicle-based construct for the treatment of lumbar degenerative disease. The theoretical advantage of this system is to stabilize the treated segment and preserve the range of motion within the adjacent segment while potentially decreasing the risk of adjacent segment disease following lumbar arthrodesis. Satisfactory short-term outcomes were previously demonstrated in the Dynesys-Transition-Optima system. However, long-term follow-up reported accelerated degeneration of adjacent segments and segmental instability above the fusion level. This study investigated the biomechanical effects of the Dynesys-Transition-Optima system on segment motion and intradiscal pressure at adjacent and implanted levels. Segmental range of motion and intradiscal pressure were evaluated under the conditions of the intact spine, with a static fixator at L4-5, and implanted with DTO at L3-4 (Dynesys fixator) and L4-5 (static fixator) by applying the loading conditions of flexion/extension (±7.5 Nm) and lateral bending (±7.5 Nm), with/without a follower preload of 500 N. Our results showed that the hybrid Dynesys-Transition-Optima system can significantly reduce the ROM at the fusion level (L4-L5), whereas the range of motion at the adjacent level (L3-4) significantly increased. The increase in physiological loading could be an important factor in the increment of IDP at the intervertebral discs at the lumbar spine. The Dynesys-Transition-Optima system can preserve the mobility of the stabilized segments with a lesser range of motion on the transition segment; it may help to prevent the occurrence of adjacent segment degeneration. However, the current study cannot cover all the issues of adjacent segmental diseases. Future investigations of large-scale and long-term follow-ups are needed.

Application of enhanced recovery after surgery care protocol in the perioperative care of patients undergoing lumbar fusion and internal fixation

Background

To explore the effects and deficiencies of the enhanced recovery after surgery (ERAS) care protocol on patients undergoing lumbar fusion and internal fixation in perioperative care.

Methods

A total of 166 patients with lumbar fusion and internal fixation were collected and divided into two groups, among which 86 patients received ERAS care protocol were attributed into ERAS group, while the other 80 patients received traditional perioperative care protocol were assigned to control group. Then, the degree of pain, self-care ability and the degree of recovery were assessed using the visual analogue scale (VAS), Barthel index (BI) rating scale and the Sino-version Oswestry Disability Index (ODI) questionnaire, respectively. Moreover, further analysis was performed based on patients’ different age, gender, body mass index (BMI) and education of patients in ERAS group.

Results

The hospitalization time and the incidence of complication in the ERAS group were obviously lower than those in control group (both, P < 0.05). There was no significant difference in hospitalization expenses between the two groups (P > 0.05). The BI score of the ERAS group was higher than that of the control group (P < 0.05), and the percentage of ODI score in ERAS group was significantly downregulated in comparison with that in control group (P < 0.05). Intra-group analysis in ERAS showed that, compared with older patients, younger patients had higher BI scores (P < 0.05) and lower ODI scores (P < 0.05); meanwhile, overweight patients had lower BI scores (P < 0.05), and the ODI score decreased with the increase in education level of the patients.

Conclusions

ERAS care protocol can significantly shorten the hospitalization time and reduce the occurrence of postoperative complications of patients, significantly enhance the self-care ability of patients after discharge and promote the rapid recovery of patients after surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03099-0.

Effects of posterior lumbar nonfusion surgery with isobar devices versus posterior lumbar interbody fusion surgery on clinical and radiological features in patients with lumbar degenerative diseases: a meta-analysis

Purpose

The aim of this study was to systematically evaluate the efficacy of posterior lumbar isobar nonfusion with isobar devices versus posterior lumbar interbody fusion (PLIF) in the treatment of patients with lumbar degenerative diseases (LDDs).

Materials and method

We performed a literature review and meta-analysis in accordance with the Cochrane methodology. The analysis included a Group Reading Assessment and Diagnostic Evaluation assessments, Jadad Quality Score evaluations, and Risk of Bias in Randomized Studies of Interventions assessments. The PubMed, Ovid, EMBASE, Web of Science, MEDLINE, CNKI, VIP and WanFang databases were searched to collect and compare relevant randomized controlled trials and cohort studies of isobar nonfusion and PLIF in the treatment of lumbar degenerative diseases. The retrieval time was from database inception to June 2021. Two evaluators independently screened the literature, extracted data, and evaluated the quality of the included studies. Outcome measures of interest included low back pain, disability, and radiological features. The protocol for this systematic review was registered on INPLASY (2021110059) and is available in full on inplasy.com (https://inplasy.com/inplasy-2021-11-0059/).

Results

Of the 7 RCTs, 394 patients met the inclusion criteria. The meta-analysis results showed that isobar nonfusion surgery shortened the surgical duration (P = 0.03), reducing intraoperative bleeding (P = 0.001), retained the ROM of surgical segment (P < 0.00001) and the ROM of the lumbar spine (P < 0.00001), and reduced the incidence of ASD (P = 0.0001). However, no significant difference in the postoperative ODI index (P = 0.81), VAS score of LBP (P = 0.59, VAS score of lower limb pain (P = 0.05, and JOA score (P = 0.27) was noted.

Conclusions

Posterior lumbar nonfusion surgery with isobar devices is superior to PLIF in shortening the surgical duration, reducing intraoperative bleeding, retaining the ROM of surgical segments and the lumbar spine to a certain extent, and preventing ASD. Given the possible publication bias, we recommend further large-scale studies.

Investigation into the biomechanics of lumbar spine micro-dynamic pedicle screw

Background

Numerous reports have shown that rigid spinal fixation contributes to a series of unwanted complications in lumbar fusion procedure. This innovative micro-dynamic pedicle screw study was designed to investigate the biomechanical performance of lumbar implants using numerical simulation technique and biomechanical experiment.

Methods

Instrumented finite element models of three configurations (dynamic fixation, rigid fixation and hybrid fixation) using a functional L3-L4 lumbar unit were developed, to compare the range of motion of the lumbar spine and stress values on the endplate and implants. An in vitro experiment was simultaneously conducted using 18 intact porcine lumbar spines and segmental motion analyses were performed as well.

Results

Simulation results indicated that the dynamic fixation and the hybrid fixation models respectively increased the range of motion of the lumbar spine by 95 and 60% in flexion and by 83 and 55% in extension, compared with the rigid fixation model. The use of micro-dynamic pedicle screw led to higher stress on endplates and lower stress on pedicle screws. The outcome of the in vitro experiment demonstrated that the micro-dynamic pedicle screw could provide better range of motion at the instrumented segments than a rigid fixation.

Conclusion

The micro-dynamic pedicle screw has the advantage of providing better range of motion than conventional pedicle screw in flexion-extension, without compromising stabilization, and has the potential of bringing the load transfer behavior of fusional segment closer to normal and also lowers the stress values of pedicle screws.

Characterisation of porous knitted titanium for replacement of intervertebral disc nucleus pulposus

Effective restoration of human intervertebral disc degeneration is challenged by numerous limitations of the currently available spinal fusion and arthroplasty treatment strategies. Consequently, use of artificial biomaterial implant is gaining attention as a potential therapeutic strategy. Our study is aimed at investigating and characterizing a novel knitted titanium (Ti6Al4V) implant for the replacement of nucleus pulposus to treat early stages of chronic intervertebral disc degeneration. Specific knitted geometry of the scaffold with a porosity of 67.67 ± 0.824% was used to overcome tissue integration failures. Furthermore, to improve the wear resistance without impairing original mechanical strength, electro-polishing step was employed. Electro-polishing treatment changed a surface roughness from 15.22 ± 3.28 to 4.35 ± 0.87 µm without affecting its wettability which remained at 81.03 ± 8.5°. Subsequently, cellular responses of human mesenchymal stem cells (SCP1 cell line) and human primary chondrocytes were investigated which showed positive responses in terms of adherence and viability. Surface wettability was further enhanced to super hydrophilic nature by oxygen plasma treatment, which eventually caused substantial increase in the proliferation of SCP1 cells and primary chondrocytes. Our study implies that owing to scaffolds physicochemical and biocompatible properties, it could improve the clinical performance of nucleus pulposus replacement.

The effect of pedicle screw implantation depth and angle on the loading and stiffness of a spinal fusion assembly

BACKGROUND

The increasing prevalence of spine disorders in industrialized environments has impaired the quality of life in the elder population. In an effort to relieve pain, physicians strive to improve treatment through the consideration of patient specific characteristics during preoperative planning of procedures such as spinal fusion.

OBJECTIVE

This study aims at quantifying aspects of spondylodesis to the loading and mobility of the utilized instrumentation, as the use of rigid vs. motion sparing materials as well as implantation angle and depth of the pedicle screws are still subject to controversy among surgeons.

METHODS

A fixation assembly was reverse engineered based on µCT measurements of the involved instrumentation. Two pedicle screws were connected with a rod, thus representing a mono-segmental fixation device. The pedicle screws were embedded in hexahedral structures simulated by bone properties. Upon validation and verification, the response of the model to a compressive and a torsional load was simulated in ANSYS 14, while altering the implantation depth and insertion angle of the pedicle screws along with the rod material.

RESULTS

The mobility of the instrumentation was drastically increased (by up to 390%) when PEEK rods were used in place of traditional Ti ones, a tendency observed at varying extent for all simulated scenarios. Shallow implantation induced a slight stress increase (∼21%) on the implant and a notable distressing of the bony tissue (∼44%), whereas inclined screw positioning was overall beneficial to the developing stress fields in both, with bone profiting a max. stress release of ∼15% during the application of torsion.

CONCLUSIONS

The investigation presented refined insight into the biomechanical response of a spinal fusion device. As expected, rigid fixation seems preferable in fusion oriented instrumentation whereas semi rigid devices should be employed for non-fusion applications. Shallow implantation resulted in a slight posterior offset of the stabilization device, which could be beneficial in the treatment of osteoporotic patients.

Functional and radiological outcomes of semi-rigid dynamic lumbar stabilization adjacent to single-level fusion after 2 years

OBJECTIVE

To prospectively evaluate the functional and radiological outcomes of Isobar semi-rigid dynamic posterior stabilization adjacent to single-level fusion up to and including 24 months postoperatively.

METHOD

A prospective follow-up for 24 months of 36 patients who underwent posterior Isobar dynamic stabilization due to single-level degenerative lumbar discopathy and instability (DLDI) with mild adjacent level degeneration, with collection of functional [visual analog scale (VAS) and Oswestry Disability Index (ODI)] and radiological data (resting, functional X-rays and MRI).

RESULTS

Functional outcomes at 24 months showed significant improvement in mean VAS score by 38.9 points (P < 0.01) and ODI by 22.4 points (P < 0.01). Compared with data preoperatively, disc height at the index and adjacent levels and intervertebral angle (IVA) at the index level showed a slight decreasing trend at each follow-up (P > 0.05), while IVA at the adjacent level showed a slight increasing trend (P > 0.05). Range of motion averaged 2.84° at the index level and remained unchanged at the adjacent level (P > 0.05). The mean Pfirrmann score changed from 2.86 preoperatively to 2.92 at 24 months postoperatively at the index level (P > 0.05), and from 1.92 preoperatively to 1.96 at 24 months postoperatively at the adjacent level (P > 0.05). No reoperation, loosening of screws or infection was recorded.

CONCLUSIONS

Patients with single-level DLDI and mild adjacent level degeneration treated with Isobar stabilization show a clinical improvement after 2 years. However, disc degeneration at the index and adjacent levels seems to continue despite using semi-rigid dynamic stabilization.

Short term outcome of posterior dynamic stabilization system in degenerative lumbar diseases

BACKGROUND

Decompression and fusion is considered as the 'gold standard' for the treatment of degenerative lumbar diseases, however, many disadvantages have been reported in several studies, recently like donor site pain, pseudoarthrosis, nonunion, screw loosening, instrumentation failure, infection, adjacent segment disease (ASDis) and degeneration. Dynamic neutralization system (Dynesys) avoids many of these disadvantages. This system is made up of pedicle screws, polyethylene terephthalate cords, and polycarbonate urethane spacers to stabilize the functional spinal unit and preserve the adjacent motion after surgeries. This was a retrospective cohort study to compare the effect of Dynesys for treating degenerative lumbar diseases with posterior lumbar interbody fusion (PLIF) based on short term followup.

MATERIALS AND METHODS

Seventy five consecutive patients of lumbar degenerative disease operated between October 2010 and November 2012 were studied with a minimum followup of 2 years. Patients were divided into two groups according to the different surgeries. 30 patients underwent decompression and implantation of Dynesys in two levels (n = 29) or three levels (n = 1) and 45 patients underwent PLIF in two levels (n = 39) or three levels (n = 6). Clinical and radiographic outcomes between two groups were reviewed.

RESULTS

Thirty patients (male:17, female:13) with a mean age of 55.96 ± 7.68 years were included in Dynesys group and the PLIF group included 45 patients (male:21, female:24) with a mean age of 54.69 ± 3.26 years. The average followup in Dynesys group and PLIF group was 2.22 ± 0.43 year (range 2-3.5 year) and 2.17 ± 0.76 year (range 2-3 year), respectively. Dynesys group showed a shorter operation time (141.06 ± 11.36 min vs. 176.98 ± 6.72 min, P < 0.001) and less intraoperative blood loss (386.76 ± 19.44 ml vs. 430.11 ± 24.72 ml, P < 0.001). For Dynesys group, visual analogue scale (VAS) for back and leg pain improved from 6.87 ± 0.80 to 2.92 ± 0.18 and 6.99 ± 0.81 to 3.25 ± 0.37, (both P < 0.001) and for PLIF, VAS for back and leg pain also improved significantly (6.97 ± 0.84-3.19 ± 0.19 and 7.26 ± 0.76-3.56 ± 0.38, both P < 0.001). Significant improvement was found at final followup in both groups in Oswestry disability index (ODI) score (both P < 0.001). Besides, Dynesys group showed a greater improvement in ODI and VAS back and leg pain scores compared with the PLIF group (P < 0.001, P = 0.009 and P = 0.031, respectively). For radiological, height of the operated level was found increased in both groups (both P < 0.001), but there was no difference between two groups (P = 0.93). For range of motion (ROM) of operated level, significant decrease was found in both groups (P < 0.001), but Dynesys showed a higher preservation of motion at the operative levels (P < 0.001). However, no significant difference was found in the percentage change of ROM of adjacent levels between Dynesys and PLIF (0.74 ± 8.92% vs. 0.92 ± 4.52%, P = 0.91). Some patients suffered from degeneration of adjacent intervertebral disc at final followup, but there was no significant difference in adjacent intervertebral disc degeneration between two groups (P = 0.71). Moreover, there were no differences in complications between Dynesys and PLIF (P = 0.90), although the incidence of complication in Dynesys was lower than PLIF (16.67% vs. 17.78%).

CONCLUSION

Dynamic stabilization system treating lumbar degenerative disease showed clinical benefits with motion preservation of the operated segments, but does not have the significant advantage on motion preservation at adjacent segments, to avoid the degeneration of adjacent intervertebral disk.

Pedicle-Screw-Based Dynamic Systems and Degenerative Lumbar Diseases: Biomechanical and Clinical Experiences of Dynamic Fusion with Isobar TTL

Dynamic systems in the lumbar spine are believed to reduce main fusion drawbacks such as pseudarthrosis, bone rarefaction, and mechanical failure. Compared to fusion achieved with rigid constructs, biomechanical studies underlined some advantages of dynamic instrumentation including increased load sharing between the instrumentation and interbody bone graft and stresses reduction at bone-to-screw interface. These advantages may result in increased fusion rates, limitation of bone rarefaction, and reduction of mechanical complications with the ultimate objective to reduce reoperations rates. However published clinical evidence for dynamic systems remains limited. In addition to providing biomechanical evaluation of a pedicle-screw-based dynamic system, the present study offers a long-term (average 10.2 years) insight view of the clinical outcomes of 18 patients treated by fusion with dynamic systems for degenerative lumbar spine diseases. The findings outline significant and stable symptoms relief, absence of implant-related complications, no revision surgery, and few adjacent segment degenerative changes. In spite of sample limitations, this is the first long-term report of outcomes of dynamic fusion that opens an interesting perspective for clinical outcomes of dynamic systems that need to be explored at larger scale.

Posterior Transpedicular Dynamic Stabilization versus Total Disc Replacement in the Treatment of Lumbar Painful Degenerative Disc Disease: A Comparison of Clinical Results

Study Design. Prospective clinical study. Objective. This study compares the clinical results of anterior lumbar total disc replacement and posterior transpedicular dynamic stabilization in the treatment of degenerative disc disease. Summary and Background Data. Over the last two decades, both techniques have emerged as alternative treatment options to fusion surgery. Methods. This study was conducted between 2004 and 2010 with a total of 50 patients (25 in each group). The mean age of the patients in total disc prosthesis group was 37,32 years. The mean age of the patients in posterior dynamic transpedicular stabilization was 43,08. Clinical (VAS and Oswestry) and radiological evaluations (lumbar lordosis and segmental lordosis angles) of the patients were carried out prior to the operation and 3, 12, and 24 months after the operation. We compared the average duration of surgery, blood loss during the surgery and the length of hospital stay of both groups. Results. Both techniques offered significant improvements in clinical parameters. There was no significant change in radiologic evaluations after the surgery for both techniques. Conclusion. Both dynamic systems provided spine stability. However, the posterior dynamic system had a slight advantage over anterior disc prosthesis because of its convenient application and fewer possible complications.

Skipping posterior dynamic transpedicular stabilization for distant segment degenerative disease

Objective. To date, there is still no consensus on the treatment of spinal degenerative disease. Current surgical techniques to manage painful spinal disorders are imperfect. In this paper, we aimed to evaluate the prospective results of posterior transpedicular dynamic stabilization, a novel surgical approach that skips the segments that do not produce pain. This technique has been proven biomechanically and radiologically in spinal degenerative diseases. Methods. A prospective study of 18 patients averaging 54.94 years of age with distant spinal segment degenerative disease. Indications consisted of degenerative disc disease (57%), herniated nucleus pulposus (50%), spinal stenosis (14.28%), degenerative spondylolisthesis (14.28%), and foraminal stenosis (7.1%). The Oswestry Low-Back Pain Disability Questionnaire and visual analog scale (VAS) for pain were recorded preoperatively and at the third and twelfth postoperative months. Results. Both the Oswestry and VAS scores showed significant improvement postoperatively (P < 0.05). We observed complications in one patient who had spinal epidural hematoma. Conclusion. We recommend skipping posterior transpedicular dynamic stabilization for surgical treatment of distant segment spinal degenerative disease.

Biomechanical evaluation of pedicle screw-based dynamic stabilization devices for the lumbar spine: a systematic review

Study Design

This study is a systematic review of published biomechanical studies involving pedicle screw-based posterior dynamic stabilization devices (PDS) with a special focus on kinematics and load transmission through the functional spine unit (FSU).

Methods

A literature search was performed via the PubMed online database from 1990 to 2008 using the following key words: “biomechanics,” “lumbar dynamic stabilization,” “Graf system,” “Dynesys,” and “posterior dynamic implant.” Citations were limited to papers describing biomechanics of pedicle screw-based PDS devices currently available for clinical use. Studies describing clinical experience, radiology, and in vivo testing were excluded from the review. Parameters measured included kinematics of the FSU (range of motion (ROM), neutral zone (NZ), and location of the center of rotation) and load transmission through the disk, facets, and instrumentation.

Results

A total of 27 publications were found that concerned the biomechanical evaluation of lumbar pedicle screw-based dynamic stabilization instrumentation. Nine in vitro experimental studies and 4 finite element analyses satisfied the inclusion criteria. The Dynesys implant was the most investigated pedicle screw-based PDS system. In vitro cadaveric studies mainly focused on kinematics comparing ROM of intact versus instrumented spines whereas finite element analyses allowed analysis of load transmission at the instrumented and adjacent levels.

Conclusion

Biomechanical studies demonstrate that pedicle screw-based PDS devices limit intervertebral motion while unloading the intervertebral disk. The implant design and the surgical technique have a significant impact on the biomechanical behavior of the instrumented spinal segment. The posterior placement of such devices results in non-physiologic intervertebral kinematics with a posterior shift of the axis of rotation. Biomechanical studies suggest that the difference at the adjacent level between investigated dynamic devices and rigid stabilization systems may not be as high as reported. Finally, additional investigations of semirigid devices are needed to further evaluate their biomechanical properties compared to soft stabilization PDS systems.

Posterior Dynamic Stabilization as a Salvage Procedure for Lumbar Facet Degeneration Following Total Disc Arthroplasty: Case report

Following an L5-S1 SB Charité disc III implantation, a 37-year-old female patient developed intractable radicular pain in the left L5 distribution. The patient underwent a minimally invasive foraminotomy, and her symptoms improved significantly. However, following recurrence of radicular pain, she showed signs of an L5-S1 facet degeneration and recurrent nerve root compression from hypertrophied synovium. A partial facetectomy was then performed to completely decompress the L5 root with supplemental posterior dynamic stabilization using a pedicle-based flexible titanium rod system. To date, the patient remains free of symptoms. Although posterolateral fusion would have been a viable option, the application of a posterior dynamic system permitted segmental motion preservation.

Measurement error of lumbar total disc replacement range of motion

STUDY DESIGN

A retrospective review of lumbar total disc replacement (TDR) radiographs.

OBJECTIVE

To determine the error and variability in measuring TDR radiographic range of motion (ROM).

SUMMARY OF BACKGROUND DATA

Motion preservation is the driving force behind lumbar TDR technology. In the recent literature, sagittal radiographic TDR ROM as low as 2 degrees has been reported. In these studies, ROM was determined by using the Cobb method to measure TDR sagittal alignment angles in flexion-extension lateral radiographs. However, previous studies in the spinal deformity literature have shown that the Cobb method is very susceptible to measurement error.

METHODS

There were 5 observers, including 2 attending orthopedic spine surgeons, 1 spine fellow, 1 fifth-year resident, and 1 fourth-year resident, who measured the ROM of 50 ProDisc II (Synthes Spine Solutions, New York, NY) TDRs on standard flexion-extension lumbar spine radiograph sets. Repeated measurements were made on 2 occasions using the Cobb method. Measurement variability was calculated using 3 statistical methods.

RESULTS

The 3 statistical methods resulted in extremely similar values for TDR ROM observer variability. Overall, the intraobserver variability of TDR ROM measurement was +/-4.6 degrees, and interobserver variability was +/-5.2 degrees .

CONCLUSIONS

To be 95% certain that an implanted TDR prosthesis has any sagittal motion, a ROM of at least 4.6 degrees must be observed, which is the upper limit of intraobserver measurement variability for a TDR with a true ROM of 0 degrees. To be 95% certain that a change in TDR ROM has occurred between 2 measurements by the same observer, a change in ROM of at least 9.6 degrees must be observed (the entire range of +/-4.6 degrees intraobserver variability). ROM measurement variability should be considered when evaluating the success or failure of motion preservation in lumbar TDR.

Range of motion and adjacent level degeneration after lumbar total disc replacement

BACKGROUND CONTEXT

There are no published studies on the relationship between total disc replacement (TDR) motion and the development of adjacent level degeneration (ALD). Because prevention of ALD is the underlying justification for TDR, studies investigating the validity of this concept are essential.

PURPOSE

To examine the relationship between range of motion (ROM) and ALD 8.7 years after lumbar TDR.

STUDY DESIGN/SETTING

Retrospective radiographic and chart review.

PATIENT SAMPLE

Forty-two patients 8.7 years after lumbar TDR.

OUTCOME MEASURES

Radiographic flexion-extension and ALD. Modified Stauffer-Coventry score. Oswestry Disability Questionnaire. Subjective patient ratings of back pain, leg pain, and disability.

METHODS

We reviewed the flexion-extension radiographs of 42 patients 8.7 years after TDR. Cephalad adjacent levels were evaluated for degeneration: loss of disc space height, anterior osteophyte formation, or dynamic flexion-extension instability. Graphical analysis of motion and the prevalence of ALD was performed. A statistical relationship between ALD and clinical outcome was sought.

RESULTS

Ten of 42 patients evaluated (24%) had radiographic ALD. The mean motion was 3.8 degrees +/-2.0 degrees. The patients with ALD had mean motion of 1.6 degrees +/-1.3 degrees whereas the patients without ALD had motion of 4.7 degrees +/-4.5 degrees (p=.035). A clear relationship between motion and the presence of ALD at 8.7-year follow-up was observed. Patients with motion 5 degrees or greater (n=13) had a 0% prevalence of ALD. Patients with motion less than 5 degrees (n=29) had a 34% prevalence of ALD (p=.021, odds ratio 13.5). ALD had no statistically significant effect on clinical outcome although the sample size was small.

CONCLUSIONS

At 8.7-year follow-up, the prevalence of ALD after TDR is higher in patients with motion less than 5 degrees. The presence of ALD had no significant effect on clinical outcome, but the sample size was small. These data suggest that patients with significant ROM after lumbar TDR may have reduced risk for radiographic ALD.