Autogenic versus allogenic bone grafts in anterior lumbar interbody fusion

Lateral-PLIF for spinal arthrodesis: concept, technique, results, complications, and outcomes

BACKGROUND

Posterior lumbar interbody fusion (PLIF) surgery represents an effective option to treat degenerative conditions in the lumbar spine. To reduce the drawbacks of the classical technique, we developed a variant, so-called Lateral-PLIF, which we then evaluated through a prospective consecutive series of patients.

METHODS

All adult patients treated at our institute with single or double level Lateral-PLIF for lumbar degenerative disease from January to December 2017 were prospectively collected. Exclusion criteria were patients < 18 years of age, traumatic patients, active infection, or malignancy, as well as unavailability of clinical and/or radiological follow-up data. The technique consists of insert the cages bilaterally through the transition zone between the central canal and the intervertebral foramen, just above the lateral recess. Pre- and postoperative (2 years) questionnaires and phone interviews (4 years) assessed pain and functional outcomes. Data related to the surgical procedure, postoperative complications, and radiological findings (1 year) were collected.

RESULTS

One hundred four patients were selected for the final analysis. The median age was 58 years and primary symptoms were mechanical back pain (100, 96.1%) and/or radicular pain (73, 70.2%). We found a high fusion rate (95%). A statistically significant improvement in functional outcome was also noted (ODI p < 0.001, Roland-Morris score p < 0.001). Walking distance increased from 812 m ± 543 m to 3443 m ± 712 m (p < 0.001). Complications included dural tear (6.7%), infection/wound dehiscence (4.8%), and instrument failure (1.9%) but no neurological deterioration.

CONCLUSIONS

Lateral-PLIF is a safe and effective technique for lumbar interbody fusion and may be considered for further comparative study validation with other techniques before extensive use to treat lumbar degenerative disease.

Lumbar degenerative disease treated by percutaneous endoscopic transforaminal lumbar interbody fusion or minimally invasive surgery-transforaminal lumbar interbody fusion: a case-matched comparative study

Purpose

This study aimed to evaluate the clinical efficacy and imaging results of percutaneous endoscopic transforaminal lumbar interbody fusion (PETLIF) through comparing it with minimally invasive surgery-transforaminal lumbar interbody fusion (MISTLIF).

Materials and methods

We performed a retrospective analysis on patients with lumbar degenerative disease treated by PETLIF or MISTLIF from September 2017 to January 2019, and the patients were divided into two groups: the PETLIF group and the MISTLIF group. The clinical and imaging parameters of the two groups were evaluated.

Results

There was no significant difference between the two groups in complication rate. The operative time in the PETLIF group was significantly less than that in the MISTLIF group. Compared with those before operation, the postoperative VAS-L and VAS-B scores were significantly improved after operation in the both groups. In addition, the postoperative VAS-B score of the PETLIF group was significantly lower than that of the MISTLIF group. At the last follow-up, there was no significant difference between the two groups in the VAS-L score, VAS-B score, ODI score, and bony fusion rate.

Conclusions

Both PETLIF and MISTLIF could achieve satisfactory clinical outcomes in the treatment of lumbar degenerative disease, but our study suggested that PETLIF had less damage, rapid recovery after operation, and short discharge time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02841-4.

Nonunion of Transpsoas Lateral Lumbar Interbody Fusion Using an Allograft: Clinical Assessment and Risk Factors

Introduction

This retrospective study was performed to evaluate the clinical influence of - and to identify the risk factors for nonunion of transpsoas lateral lumbar interbody fusion (LLIF) with use of allograft.

Methods

Sixty-three patients who underwent transpsoas LLIF (69.8 ± 8.9 years, 21 males and 42 females, 125 segments) were followed for a minimum 2 years postoperatively. For all LLIF segments, polyetheretherketone (PEEK) cages packed with allogenic bone were applied with supplemental bilateral pedicle screws (PSs). Bone bridge formation was evaluated by computed tomography (CT) 2 years postoperative, and a segment without any bridge formation was determined to be a nonunion. Sixty-one participants (96.8%) were classified into two groups for clinical evacuation: Group N that contained one or more nonunion segments and Group F that contained no nonunion segment. Visual analogue scales (VAS) scores and the effective rates of the five domains of the Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) were compared between Groups N and F. The risk factors for nonunion were determined by univariate and multivariate analyses.

Results

Twenty segments (16%) were diagnosed as nonunion. There were no significant differences in all VAS scores, and the ratio of effective cases in all domains of JOABPEQ between Group N (n = 14) and F (n = 47). Multivariate analysis identified percutaneous PS (PPS) usage (odds ratio [OR]: 3.14, 95% confidence interval: 1.13-8.68, p = 0.028) as a positive risk factor for nonunion.

Conclusions

We should be aware of the higher nonunion rate in the LLIF segments supplemented with PPS, though nonunion does not affect significantly clinical outcomes at 2 years postoperative.

One-stage posterior approaches for treatment of thoracic spinal infection: Transforaminal and costotransversectomy, compared with anterior approach with posterior instrumentation

Treating thoracic infective spondylodiscitis with anterior surgical approaches carry a relatively high risk of perioperative and postoperative complications. Posterior approaches have been reported to result in lower complication rates than anterior procedures, but more evidence is needed to demonstrate the safety and efficacy of 1-stage posterior approaches for treating infectious thoracic spondylodiscitis.Preoperative and postoperative clinical data, of 18 patients who underwent 2 types of 1-stage posterior procedures, costotransversectomy and transforaminal thoracic interbody debridement and fusion and 7 patients who underwent anterior debridement and reconstruction with posterior instrumentation, were retrospectively assessed.The clinical outcomes of patients treated with 1-stage posterior approaches were generally good, with good infection control, back pain relief, kyphotic angle correction, and either partial or solid union for fusion status. Furthermore, they achieved shorter surgical time, fewer postoperative complications, and shorter hospital stay than the patients underwent anterior debridement with posterior instrumentation.The results suggested that treating thoracic spondylodiscitis with a single-stage posterior approach might prevent postoperative complications and avoid respiratory problems associated with anterior approaches. Single-stage posterior approaches would be recommended for thoracic spine infection, especially for patients with medical comorbidities.

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.

Bone substitutes and expanders in Spine Surgery: A review of their fusion efficacies

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

This manuscript intends to provide a review of clinically relevant bone substitutes and bone expanders for spinal surgery in terms of efficacy and associated clinical outcomes, as reported in contemporary spine literature.

SUMMARY OF BACKGROUND DATA

Ever since the introduction of allograft as a substitute for autologous bone in spinal surgery, a sea of literature has surfaced, evaluating both established and newly emerging fusion alternatives. An understanding of the available fusion options and an organized evidence-based approach to their use in spine surgery is essential for achieving optimal results.

METHODS

A Medline search of English language literature published through March 2016 discussing bone graft substitutes and fusion extenders was performed. All clinical studies reporting radiological and/or patient outcomes following the use of bone substitutes were reviewed under the broad categories of Allografts, Demineralized Bone Matrices (DBM), Ceramics, Bone Morphogenic proteins (BMPs), Autologous growth factors (AGFs), Stem cell products and Synthetic Peptides. These were further grouped depending on their application in lumbar and cervical spine surgeries, deformity correction or other miscellaneous procedures viz. trauma, infection or tumors; wherever data was forthcoming. Studies in animal populations and experimental in vitro studies were excluded. Primary endpoints were radiological fusion rates and successful clinical outcomes.

RESULTS

A total of 181 clinical studies were found suitable to be included in the review. More than a third of the published articles (62 studies, 34.25%) focused on BMP. Ceramics (40 studies) and Allografts (39 studies) were the other two highly published groups of bone substitutes. Highest radiographic fusion rates were observed with BMPs, followed by allograft and DBM. There were no significant differences in the reported clinical outcomes across all classes of bone substitutes.

CONCLUSIONS

There is a clear publication bias in the literature, mostly favoring BMP. Based on the available data, BMP is however associated with the highest radiographic fusion rate. Allograft is also very well corroborated in the literature. The use of DBM as a bone expander to augment autograft is supported, especially in the lumbar spine. Ceramics are also utilized as bone graft extenders and results are generally supportive, although limited. The use of autologous growth factors is not substantiated at this time. Cell matrix or stem cell-based products and the synthetic peptides have inadequate data. More comparative studies are needed to evaluate the efficacy of bone graft substitutes overall.

Iliac Crest Bone Graft versus Local Autograft or Allograft for Lumbar Spinal Fusion: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To compare the effectiveness and safety between iliac crest bone graft (ICBG) and local autologous bone and allograft in the lumbar spine.

METHODS

A systematic search of multiple major medical reference databases identified studies evaluating spinal fusion in patients with degenerative joint disease using ICBG, local autograft, or allograft in the thoracolumbar spine.

RESULTS

Six comparative studies met our inclusion criteria. A "low" strength of the overall body of evidence suggested no difference in fusion percentages in the lumbar spine between local autograft and ICBG. We found no difference in fusion percentages based on low evidence comparing allograft with ICBG autograft. There were no differences in pain or functional results comparing local autograft or allograft with ICBG autograft. Donor site pain and hematoma/seroma occurred more frequently in ICBG autograft group for lumbar fusion procedures. There was low evidence around the estimate of patients with donor site pain following ICBG harvesting, ranging from 16.7 to 20%. With respect to revision, low evidence demonstrated no difference between allograft and ICBG autograft. There was no evidence comparing patients receiving allograft with local autograft for fusion, pain, functional, and safety outcomes.

CONCLUSION

In the lumbar spine, ICBG, local autograft, and allograft have similar effectiveness in terms of fusion rates, pain scores, and functional outcomes. However, ICBG is associated with an increased risk for donor site-related complications. Significant limitations exist in the available literature when comparing ICBG, local autograft, and allograft for lumbar fusion, and thus ICBG versus other fusion methods necessitates further investigation.

Comparison of Allograft and Autograft in Lumbar Fusion for Lumbar Degenerative Diseases: A Systematic Review

Purpose/Aim of the study: The purpose of this analysis was to compare the clinical outcomes of vertebral fusion with allograft versus autograft bone.

MATERIALS AND METHODS

Medline, PubMed, Cochrane, EMBASE, and Google Scholar databases were searched until July 27, 2015 using the keywords: lumbar vertebrae, surgery, spondylolisthesis, bone transplantation, allograft, autograft. Inclusion criteria were randomized controlled trials (RCTs), two-arm prospective studies, retrospective studies, and cohort studies comparing the results of autograft and allograft in patients receiving lumbar spinal fusion. The outcomes were changes of Oswestry Disability Index (ODI) and visual analogue scale (VAS) pain scores from baseline at 1, 2, and 3 years after surgery and fusion rates.

RESULTS

Of 154 studies identified in the database searches, five were included in the quantitative analysis (one RCT, one prospective, and three retrospective studies). The mean patient age ranged from approximately 40 to 65 years, and approximately half of the patients were males. The total number of patients who received allografts was 333 and the total that received autografts was 175. The analysis revealed the change of ODI and VAS pain score at 1, 2 and 3 years was similar between the allograft and autograft groups (all, p > .05), as were the fusion rates (p > .05).

CONCLUSIONS

Both allograft and autograft provide acceptable outcomes for spinal fusion.

Mega-granuloma After Using the Universal Clamp for Adolescent Idiopathic Scoliosis: What Is It and Can It Be Prevented?

STUDY DESIGN

Clinical case series.

OBJECTIVE

To characterize the postoperative course and histopathology of peri-implant tissue of adolescent idiopathic scoliosis patients who experienced postoperative development of an aseptic soft tissue reaction, with granulomas adjacent to the sublaminar polyethylene terephthalate strap-titanium clamp used in Zimmer's Universal Clamp (UC) spinal fixation system after spinal surgery.

BACKGROUND SUMMARY

The UC was designed for use with spinal deformity procedures in place of pedicle screws, hooks, or sublaminar wiring in fusion constructs. Recent studies of the UC lack emphasis on implant-related postoperative complications.

METHODS

A total of 26 consecutive patients who underwent spinal deformity correction for scoliosis were reviewed for implant-related postoperative complications. Histology, scanning electron microscopy with energy-dispersive X-ray spectroscopy, fractional culture/biopsy, and Gram stain examination of the peri-implant tissue of patients with complications was performed.

RESULTS

The authors reviewed 26 cases for correction of scoliosis. Two patients with adolescent idiopathic scoliosis who used the UC experienced implant-related complications with development of an aseptic soft tissue reaction with granulomas adjacent to the sublaminar polyethylene terephthalate straps-titanium clamp mechanism of the UC 8 months after AIS correction surgery. There were no signs or symptoms of wound infection. Gram stain revealed no organisms. There were many neutrophils and the surface of the wound revealed rare Staphylococcus aureus but the deep portions of the wounds were negative for organisms. Histopathology revealed extensive granulation tissue and histiocytes with engulfed birefringent particles or debris, and scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis revealed macrophages containing many particles identified as titanium.

CONCLUSIONS

adolescent idiopathic scoliosis patients who use the novel UC construct may develop postoperative foreign-body reaction.

Development of a novel calcium phosphate cement composed mainly of calcium sodium phosphate with high osteoconductivity

Two novel calcium phosphate cements (CPC) have been developed using calcium sodium phosphate (CSP) as the main ingredient. The first of these cements, labeled CAC, contained CSP, α-tricalcium phosphate (TCP), and anhydrous citric acid, whereas the second, labeled CABC, contained CSP, α-TCP, β-TCP, and anhydrous citric acid. Biopex(®)-R (PENTAX, Tokyo, Japan), which is a commercially available CPC (Com-CPC), and OSferion(®) (Olympus Terumo Biomaterials Corp., Tokyo, Japan), which is a commercially available porous β-TCP, were used as reference controls for analysis. In vitro analysis showed that CABC set in 5.7 ± 0.3 min at 22 °C and had a compressive strength of 86.0 ± 9.7 MPa after 5 days. Furthermore, this material had a compressive strength of 26.7 ± 3.7 MPa after 2 h in physiologic saline. CAC showed a statistically significantly lower compressive strength in the presence of physiologic saline and statistically significantly longer setting times than those of CABC. CABC and CAC exhibited apatite-forming abilities in simulated body fluid that were faster than that of Com-CPC. Samples of the materials were implanted into the femoral condyles of rabbits for in vivo analysis, and subsequent histological examinations revealed that CABC exhibited superior osteoconductivity and equivalent bioresorbability compared with Com-CPC, as well as superior osteoconductivity and bioresorbability compared with CAC. CABC could therefore be used as an alternative bone substitute material.

Poly(Epsilon-lysine) dendrons tethered with phosphoserine increase mesenchymal stem cell differentiation potential of calcium phosphate gels

Calcium phosphates (CaP) are considered as biomaterials of choice for the treatment of critical-sized bone defects. Novel injectable CaP materials integrating poly(epsilon-lysine) generation 3 dendrons tethered with phosphoserine were obtained by sol-gel synthesis. This type of dendron was integrated to mimic the biochemical structure of noncollagenous proteins present in the forming osteoids during bone repair. Sol-gel synthesis was coupled with a dialysis process able to equilibrate the materials at a physiological pH value. Fourier transform infrared spectroscopy (FTIR) showed the successful retention of the dendrons after gel dialysis, whereas X-ray diffraction analysis demonstrated both the pH-tuned formation of a hydroxyapatite crystalline phase within the gel and the complete removal of ammonium nitrate deriving from the sol-gel reaction solvent. Scanning electron microscopy images confirmed the presence of crystalline domains in gels synthesized at pH 9.0. Injectability tests showed that the optimized formulations fulfilled the rheological properties required to minimally invasive surgical procedures. Cytotoxicity tests on osteoblast-like MG-63 cells as well as morphology and viability studies showed that the dendrons induced a significantly higher level of cell proliferation at early incubation time. Differentiation of the cell was also clearly enhanced at longer incubation time as demonstrated by both alkaline phosphatase activity and expression of typical markers. Altogether, the data from this work indicate the clinical potential of the osteoid-mimicking CaP cements in minimally invasive bone surgery.

Indications for anterior lumbar interbody fusion

Anterior lumbar interbody fusion (ALIF) has become a widely recognized surgical technique for degenerative pathology of the lumbar spine. Spinal fusion has evolved dramatically ever since the first successful internal fixation by Hadra in 1891 who used a posterior approach to wire adjacent cervical vertebrae in the treatment of fracture-dislocation. Advancements were made to reduce morbidity including bone grafting substitutes, metallic hardware instrumentation and improved surgical technique. The controversy regarding which surgical approach is best for treating various pathologies of the lumbar spine still exists. Despite being an established treatment modality, current indications of ALIF are yet to be clearly defined in the literature. This article discusses the current literature on indications on ALIF surgery.

Complications during anterior surgery of the lumbar spine: an anatomically based study and review

Procedures involving anterior surgical decompression and fusion are being performed with increasing frequency for the treatment of a variety of pathological processes of the spine including trauma, deformity, infection, degenerative disease, failed-back syndrome, discogenic pain, metastases, and primary spinal neoplasms. Because these operations involve anatomy that is often unfamiliar to many neurological and orthopedic surgeons, a significant proportion of the associated complications are not related to the actual decompressive or fusion procedure but instead to the actual exposure itself. To understand the nature of these injuries, a detailed anatomical study and dissection was undertaken in six cadaveric specimens. Critical structures at risk in the abdomen and retroperitoneum were identified, and their anatomical relationships were categorized and photographed. These structures included the psoas muscle, kidneys, ureters, diaphragm and crura, esophageal hiatus, thoracic duct, greater splanchnic nerves, phrenic nerves, sympathetic chains, medial arcuate ligament, superior and inferior hypogastric plexus, segmental and radicular vertebral vessels, aorta, vena cava, median sacral artery, common iliac vessels, iliolumbar veins, lumbosacral plexus, and presacral hypogastric plexus. Based on these dissections and an extensive review of the literature, the authors provide a detailed anatomically based discussion of the complications associated with anterior lumbar surgery.

Posterior lumbar interbody fusion using compressive bone graft with allograft and autograft in the pyogenic discitis

Study Design

This is a retrospective study.

Purpose

To evaluate the advantages and effects of posterior lumbar interbody fusion (PLIF) using allograft and posterior instrumentation in the lumbar pyogenic discitis, which are resistant to antibiotics.

Overview of Literature

To present preliminary results of PLIF using a compressive bone graft with allograft and pedicle screw fixation in the lumbar pyogenic discitis.

Methods

Fifteen patients who had lumbar pyogenic discitis were treated by posterior approach from May 2004 to July 2008. The mean follow-up duration was 27.2 ± 18.68 months. The standing radiographs of the lumbar spine and clinical results were compared and analyzed in order to assess the bony union, the changes in the distance between the two vertebral bodies and the changes in the lordotic angle formed between the fused bodies immediately after surgery and at the final follow-up.

Results

Fifteen solid unions at an average of 15.2 ± 3.5 weeks after operation. The mean preoperative lordotic angle of the affected segments was 14.3 ± 15.1°, compared to 20.3 ± 12.3° after surgery and 19.8 ± 15.2° at last follow-up. For the functional result according to the Kirkaldy-Willis criteria, the outcome was excellent in 9, good in 5, fair in 1, and there were no poor cases. The average visual analogue scale score was decreased from 7.4 before surgery to 3.4 at 2 weeks postoperative.

Conclusions

The main advantage in the procedure of PLIF using compressive bone graft with allograft and post instrumentation is early ambulation. We believe that this is another good procedure for patients with poor general condition because a further autograft bone harvest is not required.

THE HARTSHILL HORSESHOE: THE TREATMENT OF CHRONIC PAIN PATIENTS WITH DISCOGENIC PAIN IN THE ABSENCE OF NEURAL COMPRESSION A PROSPECTIVE 2½- TO 3-YEAR REVIEW

Interbody fusion is a well-recognized technique to achieve spinal fusion. The advantage of using tricortical blocks as opposed to the dowel technique is that intervertebral disc height can be restored. Both techniques can be performed either by the anterior or posterior approach.

The traditional tricortical block technique has advantages over using dowels as it is a more stable construct and can restore intervertebral disc height. However, autologous bone graft has an unpredictable behavior causing potential problems of disc space collapse, forward displacement of the graft and donor bone graft site morbidity.

The Hartshill horseshoe was developed to overcome these autograft problems. It is an implant that is placed within the periphery of the intervertebral disc space where the vertebral end plate is strongest to resist compression forces. It has holes that allow screw fixation of the implant to bone to provide immediate stability and a central area for bone graft where the vertebral body is most vascular to allow incorporation of such a graft.

Previous reports on the Hartshill horseshoe have used autograft (single tricortical graft). This prospective study reports the clinical and radiological results of 19 patients who underwent this procedure using xenograft 2½ to 3 years postoperative. The radiological results do not show any evidence of loosening of the screws or implant nor evidence of intervertebral disc space subsidence. It was not possible to assess the exact incidence of spinal fusion.

Complications following autologous bone graft harvesting from the iliac crest and using the RIA: a systematic review

Bone grafting is a commonly performed surgical procedure to augment bone regeneration in a variety of cases in orthopaedic and maxillofacial surgery. Autologous bone graft remains to be the 'gold standard' and the iliac crest to be the most common harvesting site. The intramedullary canal of long bones represents another potential site for large volume of autologous bone graft harvesting and is recently being used as an alternative donor site. However, harvesting of autologous bone graft is associated with morbidity and a number of complications. The aim of this systematic review was to collect and summarise the existing data on reported complications after harvesting autologous bone from the iliac crest (anterior and posterior) and the long bone intramedullary canal using the RIA device. We searched the PubMed Medline and Ovid Medline databases, from January 1990 to October 2010, to retrieve all relevant articles. A total of 92 articles (6682 patients) were included in the analysis. Overall, the complication rate following RIA was 6% (14 complications in 233 patients) and 19.37% after iliac crest bone graft harvesting (1249 complications in 6449 patients). The rate of each of the reported complications was assessed and, when the donor site was properly documented, comparison within the anterior and posterior iliac crest donor sites was performed. Although the difference of the overall morbidity rates between the two harvesting sites was not statistically significant (p=0.71); the rates of certain complications were found to significantly differ when anterior or posterior iliac crest was used. The rates of infection (p=0.016), haematoma formation (p=0.002), fracture (p=0.017), and hyperthrophic scar (p=0.017) were significantly higher when the donor site was the anterior iliac crest compared to the posterior iliac crest; whereas the rates of chronic donor site pain (p=0.004) and sensory disturbances (p=0.003) were significantly lower. The incidence of bone graft harvesting related complications can be reduced further if certain principles are followed depending on the performed harvesting methods; but overall the use of RIA device as harvesting method seems a promising alternative with a low complication rate.

Biocompatibility and Bone Formation of Flexible, Cotton Wool-like PLGA/Calcium Phosphate Nanocomposites in Sheep

BACKGROUND

The purpose of this preliminary study was to assess the in vivo performance of synthetic, cotton wool-like nanocomposites consisting of a biodegradable poly(lactide-co-glycolide) fibrous matrix and containing either calcium phosphate nanoparticles (PLGA/CaP 60:40) or silver doped CaP nanoparticles (PLGA/Ag-CaP 60:40). Besides its extraordinary in vitro bioactivity the latter biomaterial (0.4 wt% total silver concentration) provides additional antimicrobial properties for treating bone defects exposed to microorganisms.

MATERIALS AND METHODS

Both flexible artificial bone substitutes were implanted into totally 16 epiphyseal and metaphyseal drill hole defects of long bone in sheep and followed for 8 weeks. Histological and histomorphological analyses were conducted to evaluate the biocompatibility and bone formation applying a score system. The influence of silver on the in vivo performance was further investigated.

RESULTS

Semi-quantitative evaluation of histology sections showed for both implant materials an excellent biocompatibility and bone healing with no resorption in the adjacent bone. No signs of inflammation were detectable, either macroscopically or microscopically, as was evident in 5 µm plastic sections by the minimal amount of inflammatory cells. The fibrous biomaterials enabled bone formation directly in the centre of the former defect. The area fraction of new bone formation as determined histomorphometrically after 8 weeks implantation was very similar with 20.5 ± 11.2 % and 22.5 ± 9.2 % for PLGA/CaP and PLGA/Ag-CaP, respectively.

CONCLUSIONS

The cotton wool-like bone substitute material is easily applicable, biocompatible and might be beneficial in minimal invasive surgery for treating bone defects.

Calcium phosphate-based composites as injectable bone substitute materials

A major weakness of current orthopedic implant materials, for instance sintered hydroxyapatite (HA), is that they exist as a hardened form, requiring the surgeon to fit the surgical site around an implant to the desired shape. This can cause an increase in bone loss, trauma to the surrounding tissue, and longer surgical time. A convenient alternative to harden bone filling materials are injectable bone substitutes (IBS). In this article, recent progress in the development and application of calcium phosphate (CP)-based composites use as IBS is reviewed. CP materials have been used widely for bone replacement because of their similarity to the mineral component of bone. The main limitation of bulk CP materials is their brittle nature and poor mechanical properties. There is significant effort to reinforce or improve the mechanical properties and injectability of calcium phosphate cement (CPC) and this review resumes different alternatives presented in this specialized literature.

Symptomatic ectopic bone formation after off-label use of recombinant human bone morphogenetic protein-2 in transforaminal lumbar interbody fusion

OBJECT

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been approved for use in the lumbar spine in conjunction with the lumbar tapered cage. However, off-label use of this osteoinductive agent is observed with anterior fusion applications as well as with both posterior lumbar interbody fusion and transforaminal lumbar interbody fusion (TLIF). Complications using rhBMP-2 in the cervical spine have been reported. Although radiographic evidence of ectopic bone in the lumbar spine has been described following rhBMP-2 use, this finding was not previously believed to be of clinical relevance.

METHODS

This study was a retrospective review of 4 patients who underwent minimally invasive spinal TLIF (MIS-TLIF) in which bone fusion was augmented with rhBMP-2 applied to an absorbable collagen sponge. Case presentations, operative findings, imaging data, and follow-up findings were reviewed.

RESULTS

Four cases with delayed symptomatic neural compression following the off-label use of rhBMP-2 with MIS-TLIF were identified.

CONCLUSIONS

Although previously believed to be only a radiographic finding, the development of ectopic bone following rhBMP-2 use in lumbar fusion can be clinically significant. This paper describes 4 cases of delayed neural compression following MIS-TLIF. The reader should be aware of this potential complication following the off-label use of rhBMP-2 in the lumbar spine.

Allogenic versus autologous cancellous bone in lumbar segmental spondylodesis: a randomized prospective study

The current gold standard in lumbar fusion consists of transpedicular fixation in combination with an interbody interponate of autologous bone from iliac crest. Because of the limited availability of autologous bone as well as the still relevant donor site morbidity after iliac crest grafting the need exists for alternative grafts with a comparable outcome. Forty patients with degenerative spinal disease were treated with a monosegmental spondylodesis (ventrally, 1 PEEK-cage; dorsally, a screw and rod system), and randomly placed in two groups. In group 1, autogenous iliac crest cancellous bone was used as a cage filling. In group 2 the cages were filled with an allogenic cancellous bone graft. Following 3, 6, 9 and 12 months, the clinical outcome was determined on the basis of: the Oswestry Low Back Pain Disability Questionnaire; patient satisfaction; patient willingness to undergo the operation again; and a visual analog scale for pain. The radiological outcome was based on both fusion rate (radiographs, computed tomography), and on the bone mineral density of the grafts. After 6 months, the X-rays of the patients in group 2 had a significantly lower rate of fusion. Aside from this, there were no further significant differences. After 12 months, radiological results showed a similar fusion rate in both groups. Donor site complications consisted of five patients with hematoma, and three patients with persistent pain in group 1. No implant complications were observed. If a bone bank is available for support and accepting the low risk of possible transmission of infectious diseases, freeze-dried allogenic cancellous bone can be used for monosegmental spondylodeses. The results demonstrated an equivalent clinical outcome, as well as similar fusion rates following a 12-month period. This is in despite of a delayed consolidation process.

Structure and mechanical properties of supercritical carbon dioxide processed porous resorbable polymer constructs

Current bone graft substitute materials do not address the complex architectural and biomechanical requirements to achieve a successful spinal fusion. The development of porous, structural constructs for use in spinal fusion surgeries is thus an area of intense interest. Numerous techniques have been introduced to fabricate porous resorbable polymer constructs. However, these techniques have been associated with the use of potentially harmful organic solvents, and resulted in materials with less than optimal properties. Supercritical carbon dioxide (scCO(2)) processing appears to be a promising technique for producing reinforced biodegradable foams. The structure, mechanical properties and water uptake capacity of PDLGA constructs processed with scCO(2) were examined. Porous morphology of the constructs was found to depend strongly on processing temperature and the confinement of the structures after processing. The resulting constructs had a dense "cortical" shell about 15-20 microm thick and an interconnected porous core with pore diameters in the range of 236-239 microm, similar to iliac crest bone grafts currently used in spinal fusion procedures. Mechanical properties and the water uptake capacity of the constructs were found to depend on the glycolic acid content (copolymer composition). Supercritical CO(2) processing is a promising technology to develop porous, resorbable polymer constructs with structural and mechanical properties similar to human bone.

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.

Vascular injury and complication in neurosurgical spine surgery

Vascular injury is an uncommon, but not rare complication of spine surgery. The consequence of vascular injury may be quite devastating, but its incidence can be reduced by understanding the mechanisms of injury. Properly managing vascular injury can reduce mortality and morbidity of patients. A review of the literature was conducted to provide an update on the etiology and management of vascular injury and complication in neurosurgical spine surgery. The vascular injuries were categorized according to each surgical procedure responsible for the injury, i.e., anterior screw fixation of the odontoid fracture, anterior cervical spine surgery, posterior C1-2 arthrodesis, posterior cervical spine surgery, anterolateral approach for thoracolumbar spine fracture, posterior thoracic spine surgery, scoliosis surgery, anterior lumbar interbody fusion (ALIF), lumbar disc arthroplasty, lumbar discectomy, and posterior lumbar spine surgery. The incidence, mechanisms of injury, and reparative measures were discussed for each surgical procedure. Detailed coverage was especially given to vascular injury associated with ALIF, which may have been underestimated. The accumulation of anatomical knowledge and advanced imaging studies has made complex spine surgery safer and more reliable. It is not clear, however, whether the incidence of vascular injury has been reduced significantly in all procedures of spine surgery. Emerging new techniques, such as microendoscopic discectomy and lumbar disc arthroplasty, seem to be promising, but we need to keep in mind their safety issues, including vascular injury and complication.

Safety of transforaminal lumbar interbody fusion and intervertebral recombinant human bone morphogenetic protein-2

OBJECT

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is being increasingly used for spinal fusion. There are few data regarding its clinical safety, effectiveness, and clinical outcome when applied on an absorbable collagen sponge (ACS) in conjunction with allograft for transforaminal lumbar interbody fusion (TLIF).

METHODS

Seventy-four consecutive patients undergoing TLIF for degenerative disc disease were divided into five groups depending on whether the patient underwent a minimally invasive or open approach, as well as the number of spinal levels surgically treated. Surgery-related data, fusion results, complications, and clinical outcome were evaluated. The mean follow-up duration was 20.6 months (range 14-28 months). The radiographic fusion rate was 100% at 12 and 24 months after the surgery. No bone overgrowth or other complications related to BMP use were demonstrated.

CONCLUSIONS

Analysis of the results demonstrated that TLIF combined with a BMP-2-soaked ACS is a feasible, effective, and safe method to promote lumbar fusion. There were no significant intergroup differences in clinical outcome between patients who underwent open compared with minimally invasive procedures. Patient satisfaction rates, however, were higher in the minimally invasive procedure group. The efficacy of BMP-2 was not dependent on which approach was used or the number of spinal levels that were treated.

Strut allograft union and remodeling using rhBMP-2 in a spinal corpectomy model

STUDY DESIGN

Growth factor in a collagen sponge carrier was compared to autograft, both packed within an allograft strut following corpectomy in a bovine spinal model.

OBJECTIVE

To evaluate incorporation of cortical strut allografts after lumbar corpectomy, comparing augmentation with recombinant human bone morphogenetic protein-2 (rhBMP-2) to local autograft.

SUMMARY OF BACKGROUND DATA

Autogenous strut grafts are the gold standard for successful fusion in reconstruction following corpectomy; however, significant donor site morbidity can occur. Recent studies describing consistently successful anterior interbody fusions with BMP augmentation suggest an exciting prospect of unlimited and potent grafting material for these difficult fusions.

METHODS

Sixteen calves underwent L3 corpectomy with instrumented strut allograft reconstruction. The rhBMP-2 impregnated collagen sponges filled the empty medullary canal of the allograft in 8 animals. Eight animals had the allograft strut filled with local autogenous bone. After 4 months, the lumbar spines were harvested for radiographic, biomechanical, and histologic evaluation.

RESULTS

Computerized tomography revealed allograft fusion in 7 of 8 autograft specimens and 8 of 8 BMP specimens. The BMP treated group had denser bone at the ends of the cortical allograft, but a central void persisted. Autograft filled struts maintained a more uniform distribution of less organized bone throughout the strut canal. Histologic assessment verified remodeling and incorporation of the allografts for both groups. Biomechanical testing confirmed no significant difference in fusion strength between groups.

CONCLUSIONS

Large cortical strut allografts (after lumbar corpectomy) supplemented with rhBMP-2 had incorporation and fusion strength comparable to allografts enhanced with cancellous autograft.

In vivo behavior of three different injectable hydraulic calcium phosphate cements

Two dicalcium phosphate dihydrate (DCPD) hydraulic cements and one apatite hydraulic cement were implanted in epiphyseal and metaphyseal, cylindrical bone defects of sheep. The in vivo study was performed to assess the biocompatibility of the DCPD cements, using the apatite cement as control. After time periods of 2, 4 and 6 months the cement samples were clinically and histologically evaluated. Histomorphometrically the amount of new bone formation, fibrous tissue and the area of remaining cement were measured over time. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. All cements were replaced by different amounts of new bone. The two DCPD-cements showed the highest new bone formation and least cement remnants at 6 months, whereas the apatite was almost unchanged over all time periods.

Critical analysis of trends in fusion for degenerative disc disease over the past 20 years: influence of technique on fusion rate and clinical outcome

STUDY DESIGN

Critical analysis of the results reported in published literature.

OBJECTIVES

The purpose of this study was to evaluate whether various technical advancements have affected the outcome of lumbar spinal fusion for degenerative disease by critically analyzing the available literature from the past two decades.

SUMMARY OF BACKGROUND DATA

To improve fusion rate and clinical outcome, various surgical options for lumbar spinal fusion for degenerative disc disorders have been introduced over the past 20 years. However, an important fundamental question still remains: What has been the impact of these new techniques and innovations on surgical results?

METHODS

A comprehensive computer search of the English literature from 1979 to 2000 concerning lumbar/lumbosacral spinal fusion was performed using the keywords degenerative, lumbar, and fusion.

RESULTS

Numerous deficiencies were noted in the reviewed literature. Nearly half of the studies failed to specify methodologic design, and documentation of brace use, graft source, fusion location, and fusion rate was missing in 38, 10, 2, and 4 of the 84 articles reviewed, respectively. From the data gathered, a noticeable trend toward the increasing use of internal fixation was noted, accounting for 23% of fusions in the 1980s versus 41% in the 1990s. Despite this trend, an improvement in overall fusion rate or clinical outcome could not be demonstrated.

CONCLUSIONS

Numerous technologic advancements in lumbar spine fusion have been made over the past 20 years. Future advances in care are dependent on review of reported results. The numerous deficiencies detected in the analyzed literature herald the necessity for a uniform system of outcomes reporting containing a core of critical demographic, perioperative, and postsurgical information. Although a shift toward a greater use of technology was noted in the published literature, the clinical benefit of this trend remains unclear.

Spinal implant debris-induced osteolysis

STUDY DESIGN

Generally, implant-induced osteolysis is a manifestation of an adverse cellular response to phagocytosable particulate wear and corrosion debris. Initially termed "cement disease," particle-induced loosening was recognized by Charnley in the early 1960s. Despite the plethora of information gained over the last 40 years on the basic science of periprosthetic bone loss, much remains unanswered. The effect of unintended debris resulting from wear and corrosion (e.g., micromotion between the interconnection mechanisms in spinal implants) remains a clinical concern. The current study highlights what is known of particle-induced osteolysis and how the presence of spinal implant particulate debris deleteriously influences osseointegration of posterolateral bone graft or disrupts an established posterolateral fusion mass. Tissue explant, animal, and cell culture studies have revealed the complexity of cellular reactivity involved in aseptic particle-induced osteolysis.

OBJECTIVES

The objectives of this study are twofold: 1) to highlight the dominant cellular participants in total joint arthroplasty particle induced osteolysis, which are purportedly the macrophage, osteoblast, fibroblast, and osteoclast and several of the dominant chemical mediators have been identified as well, which include prostaglandin E2, tumor necrosis factor-alpha, interleukin-1, and interleukin-6; and 2) to demonstrate the potential deleterious effects of spinal implant debris using animal models and analysis of soft tissue surrounding spinal implants in symptomatic patients.

METHODS

There are a growing number of proinflammatory and anti-inflammatory cytokines, prostenoids, and enzymes that have been shown to play important roles in the pathology of particle-induced osteolysis. Reports that aseptic granulomatous inflammation typical of that associated with corrosion debris appear to correlate with the complexity of the implant. Titanium particulate material was used to induce effects in 34 New Zealand White rabbits where analysis included serological quantification of systemic cytokines. Postmortem microradiographic, immunocytochemical, and histopathologic assessment of the intertransverse fusion mass quantified the extent of osteolysis, local proinflammatory cytokines, osteoclasts and inflammatory infiltrates. Clinical analysis of 12 patients more than 0.4 years after spinal implants (mean 4.03, range 0.4 to 11 years) presented with late operative site pain.

RESULTS

Currently the etiology of this inflammation around spinal implants resembles particle-induced osteolysis around joint arthroplasties where there typically is a self-perpetuating fibroinflammatory zone adjacent to the implant, where macrophage exhaustion, reactive oxygen intermediates, and pro-inflammatory cytokines affect a host of local cell types and induce a widening zone of soft tissue damage and inflammation. Animal model analysis indicated increased levels of local inflammatory cytokines typically associated with osteolysis-tumor necrosis factor-alpha. Osteoclast cell counts and regions of osteolytic resorption lacunas were higher in the titanium-treated versus autograft-alone groups (P < 0.05), and the extent of cellular apoptosis was markedly higher in the titanium-treated sites at both time intervals. Electron microscopy indicated definitive evidence of phagocytized titanium particles and foci of local, chronic inflammatory changes in the titanium-treated sites.

CLINICAL CASES

11 of 12 clinical cases demonstrated elevated tumor necrosis factor-alpha levels and an increased osteoclastic response in the vicinity of wear debris caused by dry frictional wear particles of titanium or stainless steel. Resection of the wear debris and surrounding fibroinflammatory zone resolved clinical symptoms in all 12 cases.

CONCLUSIONS

More basic science and clinical research is needed to develop novel strategies for gaining knowledge, and developing effective evaluation and treatment of patients with implant debris related osteolysis. Titanium debris simulating that produced by spinal implants introduced at the level of a spinal arthrodesis elicits an inflammatory cytokine mediated particulate-induced response through increased expression of intracellular TNF-alpha, increased osteoclastic activity and cellular apoptosis. This study highlighted the association between spinal implants particulate wear debris and increased potential for osteolysis. Aseptic osteolysis is among the primary reasons for failure of orthopedic implants. Increased awareness of this destructive process is becoming more important with the growing popularity of total disc arthroplasty and highly modular spinal implants.

Revision strategies for lumbar pseudarthrosis

Management and avoidance of lumbar pseudarthrosis are among the most common and challenging tasks faced by reconstructive spine surgeons. The risks of pseudarthrosis can be broadly divided into two categories: those within a surgeon's control and those not within his/her control. These include biological factors, graft choices, site preparation, and surgical design. The authors review the biological factors that affect fusion and how they can be manipulated to avoid or manage lumbar pseudarthrosis. Surgical planning and construct design to prevent or treat pseudarthrosis will also be discussed. Additionally, the importance of restoring sagittal balance will be reviewed.

Surgeon perceptions of the complications and value of threaded fusion cages as a spine fusion technique: results of a consensus survey

BACKGROUND CONTEXT

Threaded cage technology has had a meteoric rise in usage. It has been touted as a procedure with low risk and minimal complications.

PURPOSE

To gauge the spine surgical community's general consensus regarding cage usage and its complications.

STUDY DESIGN/SETTING

A canvassing questionnaire regarding threaded cage usage and complications was sent to members of the North American Spine Society.

PATIENT SAMPLE

A total of 665 doctors reported on their perception of 22,585 cages placed by the second year after pre-market approval from the Food and Drug Administration approval.

OUTCOME MEASURES

A nonscientific canvassing questionnaire was thought to give a consensus of surgical outcome perception in a large number of caregivers with hopes of understanding general trends.

METHODS

Simple statistical measurements were used to report perceived complications by surgeons involved in performing threaded cage surgical procedures.

RESULTS

Sixty-nine percent of doctors reported at least one complication with threaded cages, but the complication incidence was low. Visceral injuries were reported in 0.1%; vascular injuries, 1.0%; cage displacement and dislodgement, 1.4%; temporary and permanent neurologic injuries, 2.25% and 0.56%, respectively; infection 0.34%; retrograde ejaculation 1.2% and revision surgery recorded for 2.7%. Those rating cages as fair to poor (16.5%) were those physicians reporting the longest experience with this technology.

CONCLUSIONS

The general consensus is that threaded cages have low complication rates and high satisfaction rates, 83.5%. The data represent a convenience sampling and is not scientific.

Case report: intraoperative left common iliac occlusion in a scheduled 360-degree spinal fusion

STUDY DESIGN

This is a case report of a left common iliac artery occlusion identified as an intraoperative complication during a planned (combined anterior interbody and posterior fusion) 360 degrees spinal fusion.

OBJECTIVE

The purpose of this report was to document the occurrence of this rare complication during a planned 360 degrees fusion and to increase the awareness of this potential intraoperative vascular complication.

SUMMARY OF BACKGROUND DATA

Several cases of left iliac artery occlusion after anterior spinal surgery have been reported, but there has been no reported case of intraoperative iliac artery occlusion identified during a planned 360 degrees spinal fusion.

METHODS

The patient was a 46-year-old woman with chronic low and mid back pain and left leg pain for several years. She was a 2-pack-a-day cigarette smoker for 30 years. She was diagnosed with internal disc disruption at L3-L4 and L4-L5, unresponsive to nonoperative treatment, and was scheduled for a 360 degrees spinal fusion. During the anterior procedure, the left iliac vessels were retracted with a Wiley retractor during the discectomy and fusion. It was noted that there was no pulse in the left common iliac artery as the anterior procedure neared completion. Intraoperative Doppler showed the left iliac artery was occluded, and a left iliac endarterectomy and thrombectomy were performed immediately.

RESULTS

A significant occlusive plaque was separated distally and transected in a smooth fashion, and fresh thrombus was also removed. The procedure was successfully accomplished without any further complication with excellent restoration of arterial blood flow to the left lower extremity. Doppler study showed good triphasic flow in the iliac artery and all its branches. Because of the arterial repair, the posterior portion of the surgery was not undertaken at that time and was performed 2 weeks later.

CONCLUSIONS

Early recognition and appropriate treatment can prevent serious sequelae. Great care and observation should be given to the patients before surgery, intraoperatively, as well as after surgery.

The effect of bone graft extenders to enhance the performance of iliac crest bone grafts in instrumented lumbar spine fusion

Allograft bone extenders are commonly used in spinal surgery to increase the available graft volume, thereby promoting and achieving a solid fusion mass. We report a single surgeon's use and early results of autologous bone graft and allograft demineralized bone matrix in 65 patients undergoing lumbar spinal fusion. Of the patients included in this study, 59 (91%) patients underwent surgical intervention for lumbar spinal stenosis, three (5%) patients had lumbar spondylolisthesis, two (3%) patients had stenosis, and one (1%) patient had bilateral spondylolysis. Forty-three (64%) women and 22 (36%) men were included in the study. The average patient age was 56 years (20-85 years, SD= +/- 16). Independent radiographic evaluation was performed. Each subsequent radiographic follow-up revealed increased improvement in average Lenke score and was statistically significant between the early (1 month) and recent (12 month) follow-ups. There were statistically significant changes in Lenke score between 1 month and 3 months follow-up (P<.01), between 3 months and 6 months follow-up (P<.001), and between 6 months and 12 months follow-up (P<.01). The gradual and constant increment of improvement in radiographic measurements in this preliminary series may indicate a positive effect of the use of bone graft extenders that may decrease the required amount of autologous bone graft. Bone graft extenders also may minimize the risks and complications associated with the harvesting procedure.

Anterior lumbar interbody fusion with processed sea coral (coralline hydroxyapatite) as part of a circumferential fusion

STUDY DESIGN

A retrospective review of 20 patients undergoing circumferential lumbar fusion with coralline hydroxyapatite blocks anteriorly and autograft with transpedicular or translaminar facet screw fixation posteriorly.

OBJECTIVES

To examine the efficacy of coralline hydroxyapatite as a bone graft substitute for anterior lumbar interbody fusion.

SUMMARY OF BACKGROUND DATA

Autograft is the gold standard for bone grafting in the anterior lumbar spine. Harvesting bone from the iliac crest leads to significant postoperative pain and morbidity. Femoral ring allograft is a widely used alternative to autograft but has some inherent problems. Coralline hydroxyapatite was shown to be 100% successful for anterior cervical fusion when combined with rigid plating.

METHODS

A retrospective review of 20 patients with low back pain and indicated for surgical intervention. A circumferential instrumented fusion was performed with coralline hydroxyapatite blocks anteriorly and transpedicular or translaminar facet fixation and autograft posteriorly. All patients reached a minimum 3-year clinical and radiologic follow-up.

RESULTS

Radiographic follow-up yielded a solid arthrodesis rate of 93.8% by level (30 of 32 disc spaces) and 90% by patient (18 of 20). Clinical follow-up generated a mean pain reduction of 61.8% with clinical success demonstrated in 80% (16 of 20) of all patients who reported good or excellent pain relief. Eight of 12 (66.7%) patients employed before surgery returned to work in some capacity.

CONCLUSIONS

Coralline hydroxyapatite is a practicable anterior lumbar interbody fusion alternative to autograft and allograft as part of a circumferential fusion with rigid posterior fixation. It is not recommended for stand-alone anterior lumbar interbody fusion without further study.

Allograft implants for posterior lumbar interbody fusion: results comparing cylindrical dowels and impacted wedges

OBJECTIVE

With the proliferation of implant types available for use in posterior lumbar interbody fusion (PLIF) procedures, the choices for surgeons have become increasingly complex. The goal of this study was to retrospectively review a series of 49 patients who underwent PLIF with the use of allograft cylindrical threaded cortical bone dowels (TCBDs) and allograft impacted wedges. Nerve root injury rates, fusion rates, and clinical outcomes of the allograft impacted wedge group are compared with those in the allograft cylindrical TCBD group.

METHODS

We performed a retrospective chart and radiographic review of 49 patients. Twenty-seven patients underwent PLIF with impacted allograft wedges, and 22 patients underwent PLIF with allograft cylindrical TCBD. Permanent nerve root injury rates, fusion rates, and clinical outcomes were assessed on the basis of a minimum of 1 year of follow-up data in this nonconsecutive series.

RESULTS

Permanent nerve root injuries in the impacted wedge and TCBD groups were documented with physical examinations conducted pre- and postoperatively. The cylindrical TCBD group showed a 13.6% rate of permanent nerve root injury, and the impacted wedge group demonstrated a 0% rate, and these rates were statistically significant (analysis of variance, P = 0.049). The fusion rate at a mean of 13.9 months of follow-up was 95.4% in patients in whom the cylindrical TCBD was implanted and 88.9% after a mean of 17.4 months of follow-up in patients in whom impacted wedges were used. The fusion rate difference between the TCBD and impacted wedge groups was not significant. The satisfactory outcome rate was 72.7% for the TCBD group and 85.1% for the impacted wedge group, and the impacted wedge group was found to have a significantly higher rate of satisfactory outcomes (P = 0.016, analysis of variance). Analysis of the patient outcomes in the TCBD and impacted wedge groups according to sex, mean length of follow-up, workman's compensation claim rate, and smoking habit yielded no significant difference.

CONCLUSION

With a minimum of 1 year of follow-up in this nonconsecutive series of 49 patients, a comparison of the use of allograft TCBD versus allograft impacted wedges in PLIF procedures reveals a statistically significant increase in permanent nerve root injury rates with the use of cylindrical TCBD implants as compared with impacted allograft wedges. There is no difference between the two groups in terms of fusion rates, and clinical outcomes with the use of impacted wedges were significantly better.

Allograft versus autograft in instrumented posterolateral lumbar spinal fusion: a randomized control trial

STUDY DESIGN

To evaluate the clinical outcome respective of the type of bone graft used, 69 patients undergoing instrumented lumbar spinal fusion were randomized to receive either their own bone (harvested from the iliac crest) or allograft bone (fresh-frozen femoral head from donors undergoing total hip joint arthroplasty). Self-completed questionnaires were administered before surgery and at intervals thereafter.

OBJECTIVES

To compare the clinical outcome of lumbar spinal fusion carried out using either allograft or autograft bone.

SUMMARY OF BACKGROUND DATA

Previous studies have suggested that allograft bone is effective in cervical and thoracic fusion operations but that it is less effective in lumbar spinal fusions. Most of these studies used a radiographic means of determining fusion. However, no reliable radiologic assessment method has yet been agreed upon. It has also been shown that radiographic appearance does not correlate with clinical outcome.

METHODS

A total of 69 patients undergoing instrumented posterolateral lumbar spinal fusion surgery were randomized to receive either allograft bone from the North East of Scotland Blood Transfusion Service or autologous bone from the iliac crest. The patients were then followed up at 1-year intervals over 6 years regarding clinical outcome.

RESULTS

Patients receiving allograft bone had outcome scores similar to those who had received their own bone, except that in the autograft group there was a significant incidence of donor site pain that was persistent in about one sixth of patients.

CONCLUSIONS

Allograft bone, in the form of fresh-frozen human femoral head, gives clinical results at least as good as autograft bone in instrumented posterolateral lumbar spinal fusion and completely avoids any donor site complications.

Advances in posterior lumbar interbody fusion

Since the introduction of the PLIF by Cloward in the 1950s, there have been great improvements in our understanding of the pathophysiology of spinal degenerative diseases and the potential morbidities associated with their surgical management. The advent of durable interbody fusion cages and bone grafting alternatives has lessened the morbidity of bone graft harvesting and disc space collapse and has providing improved stiffness and stability to the affected spinal motion segment. Although criticized by some surgeons for the potential for spinal destabilization and nerve root injuries, newer techniques of posterior interbody access and improved implant designs have led to shortened surgical times, less neurologic injury, and improved overall outcomes. The introduction of the transforaminal lumbar interbody fusion procedure has allowed surgeons to achieve successful fusion without the risk of nerve root tethering that is seen so frequently with standard PLIF techniques. Further study and long-term follow-up regarding its efficacy are necessary before it can be recommended to supplant the more traditional PLIF techniques.

Toxic effect of rifampicin on human osteoblast-like cells

We examined the effects of rifampicin on osteoblast-like cells derived from adult human bone in vitro. Cancellous bone was collected from five different individuals during elective orthopaedic operations and cultured in antibiotic-free media. Total DNA, 3H-thymidine incorporation and alkaline phosphatase (ALP) activity were measured after the cells were cultured for 4 days in media containing concentrations of rifampicin ranging from 0 to 1000 microg/ml. Mean total DNA was decreased at concentrations of 10 microg/ml and above in the cultures obtained from four out of five individuals but these decreases were significant in the cultures from only two individuals. 3H-thymidine incorporation, a more sensitive indicator of change in cell proliferation, and ALP activity were significantly decreased (P < 0.05) in all of the cultures containing 3 and 7 microg/ml, respectively. In the clinical setting, serum concentrations of rifampicin often exceed 10 microg/ml after systemic administration. The present study has shown that rifampicin, at these concentrations, can inhibit the proliferation of osteoblast-like cells in vitro. Further studies should be carried out to assess whether rifampicin is detrimental to the bone repair process in vivo.

Surgical Interbody Research Group–radiographic assessment of interbody fusion devices: fusion criteria for anterior lumbar interbody surgery

The authors present their radiographic criteria for assessing fusion of the lumbar spine after anterior interbody fusion with intradiscal implants. These criteria include the assessment of plain radiographs, dynamic motion radiographs, and thin-cut computerized tomography scans. Fusion within the instrumented spinal motion segment can be determined using radiographic evaluation to assess spinal alignment on sequential examinations, angular and translational changes on dynamic motion studies, and device–host interface, and to identify new bone formation and bone remodeling. Finally, to aid the clinician in assessing fusion, the authors describe the five zones of fusion within the intervertebral disc space.