Radiographic characteristics on conventional radiographs after posterior lumbar interbody fusion: comparative study between radiotranslucent and radiopaque cages

Technical Feasibility and Early Clinical Outcome of Biportal Endoscopic Transforaminal Lumbar Interbody Fusion Using Larger Cage

BACKGROUND

Transforaminal lumbar interbody fusion with biportal endoscopic guidance (BE-TLIF) has been previously reported with promising clinical results. However, complications such as delayed union or subsidence occurred as with open surgery. We assumed using larger cages would result in less occurrence of such complications. We aimed to analyze the clinical outcome and technical feasibility of BE-TLIF using larger cages, initially designed for oblique lumbar interbody fusion.

METHODS

We enrolled cases that underwent single-level BE-TLIF between January 2021 and January 2022. Polyetheretherketone cages that were larger than the conventional size were used. Diagnoses were degenerative spondylolisthesis or isthmic spondylolisthesis. Visual analog scale scores of the back and leg and Oswestry Disability Index were collected perioperatively. Modified Macnab criteria were used to evaluate the patients at the final follow-up. Radiologic outcome of interbody fusion rate and perioperative complications were analyzed.

RESULTS

A total of 35 cases were included in this study. The mean age was 67.5 ± 8.4 and consisted of 13 male patients, and the mean follow-up duration was 18.3 ± 3.7 months. The majority (32/35, 91.3%) of the index level was located within the lower lumbar region, L4-S1. Oswestry Disability Index scores improved from 65.4 ± 5.4 preoperatively to 15.4 ± 6.1 at the final follow-up (P < 0.001). Visual analog scale scores of the leg decreased from 7.9 ± 1.5 to 1.7 ± 1.5 at the final follow-up (P < 0.001). Per the modified Macnab criteria on the final follow-up, 94% of the patients reported good/excellent. Most (94.2%) of the patients showed fusion grade I and II at the 1-year follow-up. No patient showed subsidence or other postoperative complication.

CONCLUSIONS

BE-TLIF using a larger cage was safely performed without risk of subsidence during the 1-year follow-up. A cage with a larger footprint may be advantageous in BE-TLIF in the aspect of interbody fusion and subsidence.

Evolution of polyetheretherketone (PEEK) and titanium interbody devices for spinal procedures: a comprehensive review of the literature

INTRODUCTION

Interbody fusion is commonly utilized for arthrodesis and stability among patients undergoing spine surgery. Over the last few decades, interbody device materials, such as titanium and polyetheretherketone (PEEK), have been replacing traditional autografts and allografts for interbody fusion. As such, with the exponential growth of bioengineering, a large variety cage surface technologies exist. Different combinations of cage component materials and surface modifications have been created to optimize interbody constructs for surgical use. This review aims to provide a comprehensive overview of common surface technologies, their performance in the clinical setting, and recent modifications and material combinations.

MATERIALS AND METHODS

We performed a comprehensive review of the literature on titanium and PEEK as medical devices between 1964 and 2021. We searched five major databases, resulting in 4974 records. Articles were screened for inclusion manually by two independent reviewers, resulting in 237 articles included for review.

CONCLUSION

Interbody devices have rapidly evolved over the last few decades. Biomaterial and biomechanical modifications have allowed for continued design optimization. While titanium has a high osseointegrative capacity, it also has a high elastic modulus and is radio-opaque. PEEK, on the other hand, has a lower elastic modulus and is radiolucent, though PEEK has poor osseointegrative capacity. Surface modifications, material development advancements, and hybrid material devices have been utilized in search of an optimal spinal implant which maximizes the advantages and minimizes the disadvantages of each interbody material.

Augmenting posterolateral fusion with transforaminal lumbar interbody fusion cage improves clinical outcome, but not fusion rate, of posterior decompression

Objective

This study was performed to compare fusion rates and clinical outcomes of posterior decompression by posterolateral fusion (PLF) versus transforaminal lumbar interbody fusion (TLIF) for treatment of lumbar spinal stenosis.

Methods

This retrospective cohort study involved 157 patients with lumbar spinal stenosis treated with instrumented PLF alone or instrumented PLF combined with TLIF from 2010 to 2018. The patients were divided into two groups: the PLF group (Group A), in which posterior decompression with instrumented PLF was performed, and the cage-augmented group (Group B), in which TLIF was added to the procedures described for the PLF group. Patient outcomes (Oswestry Disability Index, visual analog scale score, and 36-Item Short-Form Health Survey scores) and fusion rates were compared.

Results

The fusion rate was similar between the two groups. Among patients with two- and three-level fusion, improvements in the clinical outcome scores were significantly greater in Group B than Group A.

Conclusion

Combining TLIF with PLF provides better clinical outcomes than PLF alone when multilevel fusion is indicated. TLIF augmentation does not improve the fusion rates in either single- or multi-level surgery.

Vertebral instability of lumbar spine and its neurological presentations

 Background. The research results of data of 57 patients with vertebral instability of lumbar spine with neurological presentations are presented. Patients were on in-patient treatment at the Vertebral surgery department of Institute of Traumatology and Orthopedics (Kyiv) in 2010–2014. Research object. The aim of the research was to determine the features of clinical signs and X-ray measures depending on type and stage of instability in lumbar spine. Materials and methods. The research is based on the analysis of management of 57 patients with lumbar spine instability. The management consisted of anamnesis, examination of patients, X-ray of spine, MRI and CT. The majority of patients were males. There were 35 (61.4 %) males, 22 (38.6 %) females among all of the patients. Due to the data of the research it was inquired that the spine instability was detected frequently in the most employable age, from 20 to 44 years – 30 (52.6 %) cases. Results and discussion. The spine instability is clinical and radiographic manifestation of pathological removability of contiguous vertebras due to each other. This resulted in lesion of vertebras and adjoined vessels and nerves, caused by inadequate supporting system of spinal motion segments. Failure of spinal motion segments develops mainly in degenerative and dystrophic disorders resulted in acute or chronic congestions influenced by microtraumas. Development of secondary lesions of spine and spinal radixes are affected by deformation of spine and spinal channel. Emerging of pathological processes is accompanied by orthopedic and neurological presentations, that requiring surgical correction. Conclusions. Instability of VMS is caused by structure alteration of intervertebral discs, aquatics and processes joints and a part of vertebral arc between joints. Clinical signs depend on the level of localization and the stage of spine instability. Among patients with spine instability the manifestation of radixes lesions were on the 1st place – 29 (50.9 %) cases, on the 2nd place – lesions of lumbago – 19 (33.3 %) cases. X-ray features of instability are: enlargement of linear displacement of vertebral body in sagittal plane more than 4.5 mm, segmental axial rotation of vertebra – more than 40°.

Factors Associated With Clinical Outcomes After Lumbar Interbody Fusion With a Porous Nitinol Implant

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

The aim of this study is to assess the association of demographic and perioperative factors with clinical outcomes of lumbar interbody fusion with a porous nitinol (TiNi) implant for degenerative disc disease.

METHODS

Forty-one patients with degenerative lumbar disease were prospectively followed for a mean of 4.8 years. All patients were instrumented with porous TiNi interbody fusion devices. The Oswestry Disability Index (ODI) and return to work were used to assess clinical outcomes. Factors including age, body mass index, smoking status, insurance status, number of comorbidities, duration of surgery, estimated blood loss, number of levels fused, time since surgery, and preoperative ODI score were assessed. A multiple linear regression analysis was performed to look for demographic and perioperative factors associated with clinical outcome.

RESULTS

All patients except one (98%) showed complete fusion on radiography at 1 year. Estimated blood loss and duration of surgery were significantly associated with higher postoperative ODI scores (P = .002 and P = .019, respectively). Smoking status, salary insurance status, age, body mass index, number of comorbidities, number of levels fused, time since surgery, and preoperative ODI score were not significantly associated with outcome.

CONCLUSIONS

Porous nitinol permitted fusion rates similar to those reported in the literature for alternative fusion cages. Poor functional outcome of patients was strongly associated with intraoperative blood loss and duration of surgery. We believe that estimated blood loss should be carefully evaluated in studies of postoperative outcome, as it may affect midterm outcomes.

LEVEL OF EVIDENCE

Level 3.

Results of lumbar spondylodeses using different bone grafting materials after transforaminal lumbar interbody fusion (TLIF)

PURPOSE

Can a mixture of hydroxyapatite (HA) and autologous bone from decompression sites produce similar results when used for transforaminal lumbar interbody fusion (TLIF)? In the current literature, autologous iliac crest bone grafts (ICBGs) have been reported the gold standard for this procedure. Indeed, to date, no clinical data have confirmed that a mixture of equal volumes of HA and local autologous bone produce similar results in term of fusion as the same volume of autologous ICBG alone.

METHODS

Study design/setting This study was approved by the local ethics committee and completed in a prospective, randomized, single-blinded manner. The results of lumbar fusion using TLIF and different bone grafting materials were compared. Patient sample The patient sample included patients with spinal lumbar degenerative disease. Outcome measures The clinical outcome was determined using the Oswestry Low Back Pain Disability Questionnaire (ODI) and Visual Analog Scale (VAS). The radiological outcomes and fusion rates were determined with radiographs evaluated using the McAfee criteria and computed tomography (CT) data evaluated by the Williams criteria. Three blinded investigators (one radiologist and two orthopedic surgeons) assessed the data. The secondary variables included donor site morbidity. Methods The patients were admitted to our department for orthopedic surgery with degenerative lumbar pathologies (L2-S1) that required stabilization in one or two segments using a TLIF procedure. The patients were 18-80 years old. Only those patients who had degenerative lumbar pathologies and agreed to be educated about the study were included. The patients were divided into the following two randomized groups: group A: TLIF procedure using autologous ICBGs alone; and group B: TLIF procedure using local bone from decompression site mixed with hydroxyapatite. Each group received equal graft volumes. The mixture in group B consisted of equal volumes of local autograft (5 cc) and synthetic bone (5 cc). A graft volume of 10 cc was used at each fusion level. The patients were followed up at three appointments at 1.5, 6 and 12 months postoperatively. Every patient received detailed education about the course of the study.

RESULTS

Forty-eight patients finished the study (2 patients dropped out). The radiographic fusion rate did not significantly differ between the two groups. Based on the CT criteria, 83.3% of the patients showed fusion in both groups after 12 months. Furthermore, 95.3% of the patients in group A and 91.7% of the patients in group B showed bony spondylodeses according to the radiographic criteria at the 12-month follow-up. The donor site morbidity consisted of one patient with a wound infection and one with a hematoma in group A and two patients with persistent pain in group B. Group A also included one patient with cage subsidence of 4 mm and archived fusion after 12 months. In group B, one patient had a pedicle screw breakage and achieved fusion after 6 months. The clinical outcomes were similar between the two groups. In both groups, the VAS and ODI data improved during the follow-up period (p < 0.05). No patients required additional surgeries.

CONCLUSIONS

Both groups demonstrated equivalent clinical outcomes. HA and autologous bone from decompression sites can achieve similar fusion rates to those achieved with identical volumes of the gold standard autologous graft. The graft mixture can be used for one- or two-level lumbar spondylodeses to avoid donor site morbidity.

Outcomes of autograft alone versus PEEK+ autograft interbody fusion in the treatment of adult lumbar isthmic spondylolisthesis

OBJECTIVES

Bone resulting from a complete resection of the posterior arch can be cut into an autograft bone that contains the facet joint structure and morselised bone for interbody fusion. However, whether a strut autograft that contains this trimmed facet joint can produce the same clinical and radiographic outcomes as a cage for interbody fusion remains unclear. The aim of this study was to compare the outcomes of a local facet joint autograft alone to those of polyetheretherketone (PEEK)+autograft for posterior lumbar interbody fusion (PLIF) in the treatment of adult isthmic spondylolisthesis.

PATIENTS AND METHODS

A retrospective analysis was performed on 84 patients with single lumbar isthmic spondylolisthesis who were treated with a local facet joint autograft alone (group A; n=44) or PEEK+autograft (group B; n=40) in PLIF with a minimum follow-up period of 24 months. Pain and disability were assessed using the visual analogue scale, Oswestry disability index and Kirkaldy-Willis criteria. In the radiological evaluation, disc height, slippage reduction, and fusion status were examined. Postoperative complications were also monitored.

RESULTS

At the last follow-up examination, 84.1% (37/44) of the patients in group A and 82.5% (33/40) of the patients in group B had a good outcome, and there were no significant differences between the two groups. Boh Methods led to significant improvements in disc height, and while PEEK+autograft produced a smaller loss in disc height, the difference was insignificant. The improvements in slippage and the fusion and complication rates between the two groups were similar.

CONCLUSION

There were no significant differences in the clinical outcomes or radiographic improvements of both fusion methods in the treatment of adult isthmic spondylolisthesis. An autograft excised from a complete posterior arch containing a facet joint for interbody fusion is effective and affordable for treating isthmic spondylolisthesis.

Suitability of carbon fiber–reinforced polyetheretherketone cages for use as anterior struts following corpectomy

OBJECTIVE

Fibular allograft remains a widely used strut for corpectomy surgeries. The amount of graft material that can be packed into an allograft strut has not been quantified. Cages are an alternative to fibular allograft for fusion surgeries. The authors of this study assessed the suitability of carbon fiber–reinforced polyetheretherketone (CFRP) cages for anterior corpectomy surgeries. They further explored the parameters known to affect fusion rates in clinical practice.

METHODS

Six fibular allografts were tested at standard lengths. Three sets of carbon fiber cages (Bengal, DePuy Spine), each with a different footprint size but the same lengths, were tested. The allografts and cages were wrapped in adhesive, fluid-tight transparent barriers and filled with oil. The volume and weight of the oil instilled as well as the implant footprints were measured. The fibular allografts and cages were tested at 20-, 40-, and 50-mm lengths. Two investigators independently performed all measurements 5 times. Five CFRP cubes (1 × 1 × 1 cm) were tested under pure compression, and load versus displacement curves were plotted to determine the modulus of elasticity.

RESULTS

Significantly more oil fit in the CFRP cages than in the fibular allografts (p < 0.0001). The weight and volume of oil was 4–6 times greater in the cages. Interobserver (r = 0.991) and intraobserver (r = 0.993) reliability was excellent. The modulus of elasticity for CFRP was 16.44 ± 2.07 GPa.

CONCLUSIONS

Carbon fiber–reinforced polyetheretherketone cages can accommodate much more graft material than can fibular allografts. In clinical practice, the ability to deliver greater amounts of graft material following a corpectomy may improve fusion rates.

Interbody Fusion in Low Grade Lumbar Spondylolsithesis: Clinical Outcome Does Not Correalte with Slip Reduction and Neural Foraminal Dimension

Study Design

Prospective nonrandomized study.

Purpose

To find a possible correlation between clinical outcome and extent of lumbar spondylolisthesis reduction.

Overview of Literature

There is no consensus in the literature concerning whether a beneficial effect of reduction on outcome can be expected following reduction and surgical fusion for low grade lumbar spondylolisthesis.

Methods

Forty six patients with a mean age of 37.5 years (age, 17–48 years) with isthmic spondylolisthesis underwent interbody fusion with cages with posterior instrumentation (TLIF). Clinical outcome was measured using visual analogue score (VAS) and Oswestry disability index (ODI). Foraminal dimensions and disc heights were measured in standard digital radiographs. These were analyzed at baseline and 1 year after surgery and changes were compared. Radiographic fusion was judged with computed tomography scans at 1 year.

Results

Ninety percent of the patients had good or very good clinical results with fusion and instrumentation. Baseline and one-year postoperative mean VAS score was 6.33 (range, 5–8) and 0.76 (range, 0–3), respectively (p=0.004). Baseline and one-year postoperative, mean ODI score was 48 (range, 32–62) and 10 (range, 6–16), respectively (p<0.001). A mean spondylolisthesis slip of 32.1% was reduced to 6.7% at 1 year. Average anterior disc height, posterior disc height, vertical foraminal dimension), and foraminal) diameter improved from 9.8 to 11.7 mm (p=0.005), 4.5 to 5.8 mm (p=0.004), 11.3 to 12.6 mm (p=0.002), and 18.6 to 20.0 mm (p<0.001), respectively. The fusion rate was 75% with TLIF. There is no significant correlation between the improvements of ODI scores and the extent of slip reduction.

Conclusions

Neural decompression and interbody fusion can significantly improve pain and disability but the clinical outcome does not correlate with radiological improvement in the neural foraminal dimension.

Mechanical, thermal and bio-compatibility studies of PAEK-hydroxyapatite nanocomposites

In this study high performance bone analogue has been developed using poly(aryl ether) ketone, poly(dimethyl siloxane) and reinforced with nanohydroxyapatite as biocompatible filler. Compressive, tensile and flexural properties have shown sustained improvement up to 7% of nanohydroxyapatite loading. The mechanical properties were further analyzed using micromechanical theories for good interfacial adhesion between matrix and filler. The composites are cytocompatible and revealed multiple layers of apatite formation in simulated body fluid. The thickness of apatite layer increased with increase in nanohydroxyapatite loading in the composite. Poly(dimethyl siloxane) has been grafted with phosphate group to enhance compatibility with nanohydroxyapatite. Nanohydroxyapatite has been treated with silane to enhance compatibility and facilitate dispersion in the matrix as observed through transmission electron microscopy, scanning electron microscopy and X-Ray diffraction studies.

Application of titanium and polyetheretherketone cages in the treatment of pyogenic spondylodiscitis

OBJECTIVE

Surgical treatment of a pyogenic spondylodiscitis (PSD) involves a fixation and debridement of the affected segment combined with a specific antibiotic therapy. To achieve a proper stability and to avoid pseudarthrosis and kyphotic malposition many surgeons favour the interposition of an anterior graft. Besides autologous bone grafts titanium (TTN) cages have gained acceptance in the treatment of PSD. Polyetheretherketone (PEEK) cages have a more favourable modulus of elasticity than TTN. We compared both cage types. Primary endpoints were the rate of reinfection and radiological results.

METHODS

From 2004 to 2013 51 patients underwent surgery for PSD with fixation and TTN or PEEK cage-implantation. While lumbar patients underwent a partial discectomy by the posterior approach, discs of the cervical and thoracic patients had been totally removed from anterior. Clinical and radiological parameters were assessed in 37 eligible patients after a mean of 20.4 months. 21 patients received a PEEK- and 16 patients a TTN-cage.

RESULTS

A reinfection after surgery and 3 months of antibiotic therapy was not observed. Solid arthrodesis was found in 90.5% of the PEEK-group and 100% of the TTN-group. A segmental correction could be achieved in both groups. Nonetheless, a cage subsidence was observed in 70.3% of all cases. Comparison of radiological results revealed no differences between both groups.

CONCLUSIONS

A debridement and fixation with anterior column support in combination with an antibiotic therapy appear to be the key points for successful treatment of PSD. The application of TTN- or PEEK-cages does not appear to influence the radiological outcome or risk of reinfection, neither does the extent of disc removal in this clinical subset.

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 5: correlation between radiographic outcome and function

In an effort to diminish pain or progressive instability, due to either the pathological process or as a result of surgical decompression, one of the primary goals of a fusion procedure is to achieve a solid arthrodesis. Assuming that pain and disability result from lost mechanical integrity of the spine, the objective of a fusion across an unstable segment is to eliminate pathological motion and improve clinical outcome. However, conclusive evidence of this correlation, between successful fusion and clinical outcome, remains elusive, and thus the necessity of documenting successful arthrodesis through radiographic analysis remains debatable. Although a definitive cause and effect relationship has not been demonstrated, there is moderate evidence that demonstrates a positive association between radiographic presence of fusion and improved clinical outcome. Due to this growing body of literature, it is recommended that strategies intended to enhance the potential for radiographic fusion are considered when performing a lumbar arthrodesis for degenerative spine disease.

No correlation between slip reduction in low-grade spondylolisthesis or change in neuroforaminal morphology and clinical outcome

Background

In instrumented posterolateral fusion reduction of a spondylolisthesis is appealing on theoretical grounds since this may lead to indirect decompression of the entrapped nerve roots. However, there is no consensus in the literature whether a beneficial effect of reduction on outcome can be expected. The objective of the current study was to evaluate whether a correlation between the extent of listhesis reduction and clinical improvement could be established.

Methods

From two ongoing prospective studies 72 patients with a single-level instrumented posterolateral lumbar fusion for low-grade spondylolisthesis (isthmic/degenerative 51/21) were evaluated. Radiographs and clinical outcome scores were available at baseline, 6 weeks and 1 year after surgery. Changes in neuroforaminal morphology were measured on calibrated radiographs. These changes in radiographic parameters were correlated to clinical outcome (Visual Analogue Score (VAS) leg pain, Oswestry Disability Index (ODI)). Fusion status was assessed on Computed Tomography-scan at one year.

Results

A mean spondylolisthesis of 25 percent was reduced to 15 percent at 6 weeks with some loss of reduction to 17 percent at one year. The VAS and ODI significantly improved at both time intervals after surgery (p < 0.001). No significant correlations could be established between the extent of slip reduction and improvement in VAS or ODI (Pearson’s correlation −0.2 and 0.07 respectively at one year); this also accounted for the other radiographic parameters. A fusion rate of 64 percent was seen on CT-scan.

Conclusions

Clinical outcome was not related to the obtained radiographic reduction of the slipped vertebra in patients with a lumbar fusion for low grade spondylolisthesis. Loss of reduction or non-union on CT-scans had no effect on the clinical outcome. Reduction of a low-grade spondylolisthesis in spinal fusion is appealing, however, there is no evidence that it positively affects clinical outcome on the short term.

Trial registration

ISRCTN43648350

Changes in bone mineral density in the intertransverse fusion mass after instrumented single-level lumbar fusion: a prospective 1-year follow-up

STUDY DESIGN

Prospective cohort.

OBJECTIVE

The purpose of this study was to evaluate changes in bone mineral density (BMD) in the intertransverse fusion mass as representative for the process of bone remodeling after spinal fusion.

SUMMARY OF BACKGROUND DATA

Intertransverse bone graft is frequently applied to facilitate bony fusion between 2 spinal levels. The biological process of bone graft remodeling leading to eventual fusion is, however, poorly understood.

METHODS

In 20 patients with a single-level instrumented posterolateral lumbar fusion for low-grade spondylolisthesis, radiographs, and clinical outcome scores (visual analogue scale for back and leg pain, Oswestry Disability Index, Short Form-36) were obtained. Locally harvested laminectomy bone was used as intertransverse bone graft. The BMD in selected "regions of interest" at both intertransverse fusion areas was assessed on days 4 and 3, after a period of 6 and 12 months after surgery using dual-energy x-ray absorptiometry scans. Eventual fusion status was assessed on computed tomographic scan at 12 months.

RESULTS

All clinical outcome scores significantly improved at the final follow-up (P < 0.05). Baseline BMD in both paraspinal fusion areas was expressed as 100%, which significantly decreased from 81% to 75% and 77% to 70% at 3 and 6 months, for regions of interest 1 and 2, respectively (P < 0.001). From 6 to 12 months, there was an increase in BMD from 90% to 80%, for regions of interest 1 and 2 (P = 0.296). On computed tomography scan a complete fusion was noticed in 70% of the patients.

CONCLUSION

Repeated dual-energy x-ray absorptiometry was able to elucidate the biological process of bone graft remodeling in the intertransverse fusion mass. An active bone remodeling process was quantified with profound resorption or demineralization of the graft during the first 6 months, followed by subsequent bone apposition and restoration of BMD at the final follow-up. No difference in trend in BMD change between patients with and without fusion could be established; however, no firm conclusions can be drawn from small patient numbers.

Bone union rate with autologous iliac bone versus local bone graft in posterior lumbar interbody fusion (PLIF): a multicenter study

PURPOSE

The purpose of this study is to compare bone union rate between autologous iliac bone and local bone graft in patients treated by posterior lumbar interbody fusion (PLIF) using carbon cage for single level interbody fusion.

METHODS

The subjects were 106 patients whose course could be observed for at least 2 years. The diagnosis was lumbar spinal canal stenosis in 46 patients, herniated lumbar disk in 12 patients and degenerative spondylolisthesis in 51 patients. Single interbody PLIF was done using iliac bone graft in 53 patients and local bone graft in 56 patients. Existence of pseudo-arthrosis on X-P (AP and lateral view) was investigated during the same follow up period.

RESULTS

No significant differences were found in operation time and blood loss. Significant differences were also not observed in fusion grade at any follow up period or in fusion progression between the two groups. Donor site pain continued for more than 3 months in five cases (9%). The final fusion rate was 96.3 versus 98.3%.

CONCLUSIONS

Almost the same results in fusion were obtained from both the local bone group and the autologous iliac bone group. Fusion progression was almost the same. Complications at donor sites were seen in 19% of the cases. From the above results, it was concluded that local bone graft is as beneficial as autologous iliac bone graft for PLIF at a single level.

Anterior cervical discectomy and fusion: comparison of titanium and polyetheretherketone cages

BACKGROUND

Titanium (TTN) cages have a higher modulus of elasticity when compared with polyetheretherketone (PEEK) cages. This suggests that TTN-cages could show more frequent cage subsidence after anterior cervical discectomy and fusion (ACDF) and therefore might lead to a higher loss of correction. We compared the long term results of stand-alone PEEK- and TTN-cages in a comparable patient collective that was operated under identical operative settings.

METHODS

From 2002 to 2007 154 patients underwent single-level ACDF for degenerative disc disease (DDD). Clinical and radiological outcome were assessed in 86 eligible patients after a mean of 28.4 months. 44 patients received a TTN- and 42 patients a PEEK-cage.

RESULTS

Solid arthrodesis was found in 93.2% of the TTN-group and 88.1% of the PEEK-group. Cage subsidence was observed in 20.5% of the TTN- and 14.3% of the PEEK-group. A significant segmental lordotic correction was achieved by both cage-types. Even though a loss of correction was found at the last follow-up in both groups, it did not reach the level of statistical significance. Statistical analysis of these results revealed no differences between the TTN- and PEEK-group.When assessed with the neck disability index (NDI), the visual analogue scale (VAS) of neck and arm pain and Odom's criteria the clinical data showed no significant differences between the groups.

CONCLUSIONS

Clinical and radiological outcomes of ACDF with TTN- or PEEK-cages do not appear to be influenced by the chosen synthetic graft. The modulus of elasticity represents only one of many physical properties of a cage. Design, shape, size, surface architecture of a cage as well as bone density, endplate preparation and applied distraction during surgery need to be considered as further important factors.

Bone union rate with autologous iliac bone versus local bone graft in posterior lumbar interbody fusion

STUDY DESIGN

A retrospective clinical study with a long-term follow-up in a single facility.

OBJECTIVE

The purpose of this study is to compare bone union rate between autologous iliac crest bone graft and local bone graft in patients treated by posterior lumbar interbody fusion (PLIF) using carbon cage for single-level interbody fusion.

SUMMARY OF BACKGROUND DATA

Recently, a number of authors have reported on local bone grafting using bone that is obtained from laminectomy, and have indicated that the achieved fusion rate is similar to that of autologous iliac bone grafting. However, there is no report comparing the fusion rates between autologous iliac bone and local bone graft with a detailed follow-up of fusion progression.

METHODS

The subjects were 101 patients whose course could be observed for at least 2 years. The diagnosis was lumbar spinal canal stenosis in 14 patients, herniated lumbar disc in 19 patients, and degenerative spondylolisthesis in 68 patients. Single interbody PLIF was performed using iliac bone graft in 54 patients and local bone graft in 47 patients. Existence of pseudarthrosis on X-P (anteroposterior and lateral view) was investigated during the same follow-up period.

RESULTS

No significant differences were found in operation time and blood loss. Significant differences were also not observed in fusion grade at any follow-up period or in fusion progression between the 2 groups. Donor site pain continued for more than 3 months in 6 cases (11%). The final fusion rate was 94.5% versus 95.8%.

CONCLUSION

Fusion results from the local bone group and the autologous iliac bone group were nearly identical. Furthermore, fusion progression was nearly identical. Complications at donor sites were seen in 17% of the cases. From the aforementioned results, it was concluded that local bone graft is as beneficial as autologous iliac bone graft for PLIF at a single level.

Fusion criteria for posterior lumbar interbody fusion with intervertebral cages : the significance of traction spur

OBJECTIVE

The purpose of this study was to establish new fusion criteria to complement existing Brantigan-Steffee fusion criteria. The primary purpose of intervertebral cage placement is to create a proper biomechanical environment through successful fusion. The existence of a traction spur is an essential predictable radiologic factor which shows that there is instability of a fusion segment. We studied the relationship between the existence of a traction spur and fusion after a posterior lumbar interbody fusion (PLIF) procedure.

METHODS

This study was conducted using retrospective radiological findings from patients who underwent a PLIF procedure with the use of a cage without posterior fixation between 1993 and 1997 at a single institution. We enrolled 183 patients who were followed for a minimum of five years after the procedure, and used the Brantigan-Steffee classification to confirm the fusion. These criteria include a denser and more mature bone fusion area than originally achieved during surgery, no interspace between the cage and the vertebral body, and mature bony trabeculae bridging the fusion area. We also confirmed the existence of traction spurs on fusion segments and non-fusion segments.

RESULTS

The PLIF procedure was done on a total of 251 segments in 183 patients (71 men and 112 women). The average follow-up period was 80.4 +/- 12.7 months. The mean age at the time of surgery was 48.3 +/- 11.3 years (range, 25 to 84 years). Among the 251 segments, 213 segments (84.9%) were fused after five years. The remaining 38 segments (15.1%) were not fused. An analysis of the 38 segments that were not fused found traction spur formation in 20 of those segments (52.6%). No segments had traction spur formation with fusion.

CONCLUSION

A new parameter should be added to the fusion criteria. These criteria should be referred to as 'no traction spur formation' and should be used to confirm fusion after a PLIF procedure.

Instrumented posterior lumbar interbody fusion in adult spondylolisthesis

It is unclear whether using artificial cages increases fusion rates compared with use of bone chips alone in posterior lumbar interbody fusion for patients with lumbar spondylolisthesis. We hypothesized artificial cages for posterior lumbar interbody fusion would provide better clinical and radiographic outcomes than bone chips alone. We assumed solid fusion would provide good clinical outcomes. We clinically and radiographically followed 34 patients with spondylolisthesis having posterior lumbar interbody fusion with mixed autogenous and allogeneic bone chips alone and 42 patients having posterior lumbar interbody fusion with implantation of artificial cages packed with morselized bone graft. Patients with the artificial cage had better functional improvement in the Oswestry disability index than those with bone chips alone, whereas pain score, patient satisfaction, and fusion rate were similar in the two groups. Postoperative disc height ratio, slip ratio, and segmental lordosis all decreased at final followup in the patients with bone chips alone but remained unchanged in the artificial cage group. The functional outcome correlated with radiographic fusion status. We conclude artificial cages provide better functional outcomes and radiographic improvement than bone chips alone in posterior lumbar interbody fusion for lumbar spondylolisthesis, although both techniques achieved comparable fusion rates.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

The distribution of mineral density in the cervical vertebral endplates

Subsidence of various constructs into the vertebral body is a well-known complication in anterior fusion. Information on bone structure is needed, as a basis for improving these procedures. There are, however, no data available on the distribution of mineral density within vertebral endplates. In this study the regional distribution of mineralization within the cervical endplates with respect to endplate orientation (inferior and superior endplate) and level distribution (C3-C7) was examined by means of computed tomographic osteoabsorptiometry (CT-OAM). The distribution of mineralization in 80 cervical endplates of 8 spinal columns (4 male, 4 female, age range 38-62 years) in vertebrae C3-C7 was investigated by CT osteoabsorptiometry (CT-OAM). The subchondral mineralization distribution revealed considerable topographic differences within each endplate, whereby the areas of greatest density were found in the peripheral marginal zones with maxima in the posterolateral surface, whereas mineralization density was much lower in the central areas. The superior endplates showed an additional posteromedial maximum, whereas the inferior endplates showed an additional anterior mineralization maximum. Comparison of the distribution patters of inferior and superior endplates at different levels from C3 to C7 reveals a uniform increase of mineralization in the anterior portions from cranial to caudal. The mineralization distribution showed characteristic reproducible patterns. The maximal values occurred in the posterolateral parts, and can thus be considered a morphological substrate of high long-term loading. This can serve as a basis for improved prosthesis design and the anchorage point for various fusion techniques.

Quantitative analysis in outcome assessment of instrumented lumbosacral arthrodesis

The outcome assessment in instrumented lumbosacral fusion mostly focuses on clinical criteria, complications and scores, with a high variability of imaging means, methods of fusion grading and parameters describing degenerative changes, making comparisons between studies difficult. The aim of this retrospective evaluation was to evaluate the interest of quantified radiographic analysis of lumbar spine in global outcome assessment and to highlight the key biomechanical factors involved. Clinical data and Beaujon-Lassale scores were collected for 49 patients who underwent lumbosacral arthrodesis after prior lumbar discectomy (mean follow-up: 5 years). Sagittal standing and lumbar flexion-extension X-ray films allowed quantifying vertebral, lumbar, pelvic and kinematic parameters of the lumbar spine, which were compared to reference values. Statistics were performed to assess evolution for all variables. At long-term follow-up, 90% of patients presented satisfactory clinical outcomes, associated to normal sagittal alignment; vertebral parameters objectified adjacent level degeneration in four cases (8%). Clinical outcome was correlated (r = 0.8) with fusion that was confirmed in 80% of cases, doubtful in 16% and pseudarthrosis seemed to occur in 4% (2) of cases. In addition to clinical data (outcomes comparable to the literature), quantitative analysis accurately described lumbar spine geometry and kinematics, highlighting parameters related to adjacent level's degeneration and a significant correlation between clinical outcome and fusion. Furthermore, criteria proposed to quantitatively evaluate fusion from lumbar dynamic radiographs seem to be appropriate and in agreement with surgeon's qualitative grading in 87% of cases.

Comparison of polyetheretherketone cages with femoral cortical bone allograft as a single-piece interbody spacer in transforaminal lumbar interbody fusion

OBJECT

Transforaminal lumbar interbody fusion (TLIF) is an accepted alternative to circumferential fusion of the lumbar spine in the treatment of degenerative disc disease, spondylolisthesis, and recurrent disc herniation. To maintain disc height while arthrodesis takes place, the technique requires the use of an interbody spacer. Although titanium cages are used in this capacity, the two most common spacers are polyetheretherketone (PEEK) cages and femoral cortical allografts (FCAs). The authors compared the clinical and radiographic outcomes of patients who underwent TLIF with pedicle screw fixation, in whom either a PEEK cage or an FCA was placed as an interbody spacer.

METHODS

The charts and x-ray films obtained in 39 patients (age range 33-68 years, mean 44.7 years) who underwent single-level TLIF between October 2001 and April 2004 and in whom either a PEEK cage (18 patients) or FCA (21 patients) was placed as an interbody spacer were evaluated in a retrospective study. Radiological outcome was based on fusion rate and a comparison of the initial postoperative lordotic angle on standing lateral radiographs with that at long-term follow up (mean follow up 15.1 months, minimum 12 months). To control for variations in radiographic magnification, the authors used lordotic angle as an indirect measure of disc space height. Clinical outcome was assessed using the Oswestry Disability Index (ODI). There were no major complications in either group. Radiographically documented fusion occurred in all patients in the PEEK group and 95.2% of those in the FCA group. Pseudarthrosis developed in one patient in the FCA group, and this patient underwent additional surgery. In both groups, the mean lordotic angle changed by less than 2.20 degrees during the postoperative period, and the mean postoperative ODI score was more than 40 points lower than the mean preoperative score. There was no significant difference between the two groups in mean change in lordotic angle (p = 0.415) and mean change in ODI score (p = 0.491).

CONCLUSIONS

Both PEEK cages and FCAs are highly effective in promoting interbody fusion, maintaining postoperative disc space height, and achieving desirable clinical outcomes in patients who undergo TLIF with pedicle screw fixation. The advantages of PEEK cages include a lower incidence of subsidence and their radiolucency, which permits easier visualization of bone growth.

Is High Level of Disability an Indication for Spinal Fusion?

OBJECTIVE

Posterior lumbar interbody fusion is a recognized procedure for the treatment of back pain associated with degenerative disc disease and segmental instability. It allows decompression of the spinal canal and circumferential fusion through a single posterior incision.

METHODS

Sixty-five consecutive patients who underwent posterior lumbar interbody fusion using carbon cages and pedicle fixation between 1993 and 2000 were recruited and contacted with a postal survey. Clinical outcome was assessed by the postoperative clinical findings and complications and the fusion rate, which was assessed using the scoring system described by Brantigan and Steffee. Functional outcome was measured by using improvement in the Oswestry Disability Index, return to work, and satisfaction with the surgical outcome. The determinants of functional relief were analyzed against the improvement in disability using multiple regression analysis.

RESULTS

The mean postoperative duration at the time of the study was 4.4 years. Overall radiologic fusion rate was 98%. There was a significant improvement in Oswestry Disability Index (P < 0.01). There was 84% satisfaction with the surgical procedure and 61% return to predisease activity level and full employment. We found preoperative level of disability to be the best determinant of functional recovery irrespective of age or the degree of psychological morbidity and litigation (P < 0.01).

CONCLUSION

The combination of posterior lumbar interbody fusion and posterior instrumented fusion is a safe and effective method of achieving circumferential segmental fusion. A direct relationship between preoperative level of disability and functional recovery suggests that disability should be measured preoperatively and spinal fusion should be performed to alleviate disability caused by degenerative spine.

Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 5: correlation between radiographic and functional outcome

At the present time, there is no Class I or II medical evidence to indicate that the appearance of a radiographic fusion is significantly associated with improved functional outcomes. The majority of Class III medical evidence does suggest that successful radiographic fusion is associated with improved clinical outcomes. It is widely acknowledged that this relationship is not perfect.

Experimental anterior lumbar interbody fusion with an osteoinductive bovine bone collagen extract

STUDY DESIGN

A randomized experimental porcine anterior lumbar interbody fusion.

OBJECTIVE

To determine the osteoinductive potential of a bovine bone derived collagen lyophilisate for anterior interbody spinal fusion in an animal model.

SUMMARY OF BACKGROUND DATA

Complications associated with autologous bone graft harvesting are still major concerns when performing spinal fusion surgery. A new formulation of bovine bone collagen-protein extracts (Colloss) has been shown to be effective in animal studies as a bone graft enhancer. The present study further tested its osteogenic potential in the anterior spinal fusion cage in a controlled animal study.

METHODS

Twelve normal Danish landrace pigs of 50 kg each were chosen as experimental animals. Lumbar spine interbody fusion of L3-L4, L4-L5 using titanium alloy cages was performed on each pig with pedicle screws instrumentation. Cages packed with either autograft or Colloss were randomly assigned to the two levels. Pigs were followed up to 3 months. After termination, the spine segments were evaluated by radiograph, micro-CT, and histomorphometry

RESULTS

Ten pigs completed the study. Implant breakage, loosening, or spinal deformity was not observed after 12 weeks on radiograph examination. Micro-CT evaluations demonstrated that cages with Colloss had the same fusion rate (9 of 10) as those with autograft, further evaluation of bone volume (BV/TV), and trabecular thickness (Tb Th) also showed no different between them. Histologically, both autograft and Colloss levels had 80% (8 of 10) fusion rate. Histomorphometric results revealed that the only difference was the Colloss-filled cages had a higher cartilage tissue volume (P < 0.04).

CONCLUSION

Colloss was effective as a bone graft substitute. It achieved the same fusion rate and the samepercentage of new bone formation as that of autologous iliac bone graft in this demanding porcine anterior spinal fusion model after 12 weeks.

Radiological changes in the bone fusion site after posterior lumbar interbody fusion using carbon cages impacted with laminar bone chips: follow-up study over more than 4 years

STUDY DESIGN

A retrospective clinical study with a follow-up of more than 4 years was conducted.

OBJECTIVES

To know the radiologic changes in the interbody bone fusion site in patients who had received posterior lumbar interbody fusion (PLIF) using carbon fiber cages.

SUMMARY OF BACKGROUND DATA

PLIF using cages is a popular surgical method for treating degenerative lumbar spinal diseases. However, there are few reports on the radiologic changes in the bone fusion site after this procedure.

METHOD

Forty-one patients were observed (male-to-female ratio 12:29; mean age 51 years; 1-level-to-2-level PLIF 37:4) for 56 months (range 48-78). Anteroposterior and lateral radiograph films were taken from all patients immediately after bone fusion, at 6 and 12 months after surgery, and at follow-up. The extent of the bone fusion was classified as: only inside the cage; around the cage; extending to the vertebral cortical margin; and overgrowth beyond the vertebral cortical margin. The extent of bone fusion was observed anterior and posterior to the cages.

RESULTS

Of the 45 fusion levels examined in these 41 patients, successful bone fusion was observed in 40 levels of 36 patients (88%). All the successful fusions occurred inside and posterior to the cages. Of the 40 successful fusion levels at 6 and 12 months after surgery, 10% and 35% of the levels showed the fusion mass to be both inside and around the cages, while the remaining 90% and 65% of the levels showed the fusion mass only inside the cages, respectively. More than 4 years after surgery, 82% of the levels showed the fusion mass extending to the posterior cortical margin, and 2 levels (5%) with shallowly inserted cages showed bony overgrowth into the spinal canal.

CONCLUSION

All the intervertebral bone fusion after PLIF occurred inside the cages and in the posterior intervertebral space. We suggest the complete removal of discmaterial and deep insertion of the cages to create sufficient posterior intervertebral space for bone growth. PLIF using cages impacted with laminar bone chips is a useful method when considering the time required for surgery and the morbidity of the autograft donor sites.

Clinical outcomes and complications associated with pedicle screw fixation—augmented lumbar interbody fusion

Object. The authors conducted a prospective study to evaluate the clinical and radiological outcomes and complications associated with uni- and bilateral transforaminal lumbar interbody fusion (TLIF) performed using carbon fiber Brantigan I/F Cages and pedicle screw fixation.

Methods. Forty-two consecutive patients who had undergone uni- or bilateral TLIF between February 1999 and July 2000 were prospectively evaluated. Clinical outcome was graded using a modified Prolo Scale, the McGill Pain Index Scale, a follow-up questionnaire, and charts. An independent radiologist assessed radiological outcomes. All patients were followed for at least 1 year.

Based on Prolo Scale scores, an excellent or good 1-year outcome was achieved in 73% of patients; 90% of patients responded that they would undergo the procedure again. At 1 year, radiographic fusion was demonstrated in 74% and was statistically related to clinical outcome (p < 0.05).

There were no deaths or major hardware failures. Complications requiring repeated surgery included one case of cerebrospinal fluid (CSF) leakage and one case in which the hemovac drain was retained. There were four cases involving minor wound infections, eight involving CSF leaks, and none requiring repeated surgery. On routine follow-up radiography one pedicle screw was found to be broken; the patient remained asymptomatic and fusion occurred.

Conclusions. Unilateral and bilateral TLIF involving placement of carbon fiber cages and pedicle screw fixation are effective treatment options in patients with indications for lumbar arthrodesis. The procedures result in acceptable rates of fusion and clinical success, and a minimal incidence of morbidity when performed by an experienced surgeon.

The importance of the endplate for interbody cages in the lumbar spine

Intervertebral cages in the lumbar spine represent an advancement in spinal fusion to relieve low back pain. Different implant designs require different endplate preparations, but the question of to what extent preservation of the bony endplate might be necessary remains unanswered. In this study the effects of endplate properties and their distribution on stresses in a lumbar functional spinal unit were investigated using finite-element analyses. Three-dimensional finite-element models of L2-L3 with and without a cage were used. An anterior approach for a monobloc, box-shaped cage was modelled. The results showed that inserting a cage increased the maximum von Mises stress and changed the load distribution in the adjacent structures. A harder endplate led to increased concentration of the stress peaks and high stresses were propagated further into the vertebral body, into areas that would usually not experience such stresses. This may cause structural changes and provide an explanation for the damage occurring to the underlying bone, as well as for the subsequent subsidence of the cage. Stress distributions were similar for the two endplate preparation techniques of complete endplate preservation and partial endplate removal from the centre. It can be concluded that cages should be designed such that they rely on the strong peripheral part of the endplate for support and offer a large volume for the graft. Furthermore, the adjacent vertebrae should be assessed to ensure that they show sufficient density in the peripheral regions to tolerate the altered load transfer following cage insertion until an adequate adaptation to the new loading situation is produced by the remodelling process.