Outcome of single level anterior cervical discectomy and fusion using nano-hydroxyapatite/polyamide-66 cage

A Comparison of Corpectomy ACDF Hybrid Procedures with Nano-Hydroxyapatite/Polyamide 66 Cage and Titanium Mesh Cage for Multi-level Degenerative Cervical Myelopathy: A Stepwise Propensity Score Matching Analysis

OBJECTIVE

Previous studies have found satisfactory clinical results with the nano-hydroxyapatite/polyamide 66 (n-HA/PA66) cage to reconstruct the stability of anterior cervical column. However, studies evaluating the long-term outcomes of the n-HA/PA66 cage in multi-level degenerative cervical myelopathy (MDCM) have not been reported. This study aims to compare the outcomes of corpectomy anterior cervical discectomy and fusion (ACDF) hybrid procedures between the n-HA/PA66 cage and titanium mesh cage (TMC) to treat MDCM.

METHODS

After the screening for eligibility, this retrospective study involved 90 patients who underwent corpectomy ACDF hybrid (CACDFH) procedure from June 2013 to June 2018. The CACDFH procedure is the combination of ACDF and anterior cervical corpectomy and fusion (ACCF). According to the cage utilized, we categorized patients into a n-HA/PA66 cage group and a TMC group. Then, stepwise propensity score matching (PSM) was performed to maintain comparable clinical data between groups. All the patients were followed up ≥4 years and the longest follow-up time was 65.43 (±11.49) months. Cage subsidence, adjacent segment degeneration (ASD), segmental height (SH), segmental angle (SA), cervical lordosis (CL), and clinical data (visual analogue scale [VAS] and Japanese Orthopaedic Association [JOA] score) was evaluated preoperatively, at 1 week, and at the final surgery follow-up. The independent student's t test and chi-square test were applied to compare the differences between groups.

RESULTS

Through PSM analysis, 25 patients from the n-HA/PA66 group were matched to 25 patients in the TMC group. The occurrence of ASD was 16.0% (4/25) in the n-HA/PA 66 group, which was significantly less than in the TMC group at 44.0% (11/25) (p = 0.031). Moreover, the cage subsidence rate was significantly higher in the TMC group as compared to the n-HA/PA 66 group (40.0% vs. 12.0%, p = 0.024). But there was no significant difference in SH, SA, and CL at any time after surgery as determined through follow-up. The VAS and JOA scores significantly improved in both groups at 3 months postoperative and at final follow-up. However, there were no significant differences in the VAS and JOA score at any time between the two groups in preoperative (p > 0.05).

CONCLUSION

The n-HA/PA66 cage is associated with lower rate of cage subsidence and ASD than the TMC in the treatment of MDCM. The n-HA/PA66 cage could be superior to the TMC in corpectomy ACDF hybrid procedures.

A novel nanohydroxyapatite/polyamide-66 cage for reducing the subsidence rate after single-level anterior cervical discectomy and fusion: a comparative study of 7-year follow-up

BACKGROUND

A novel nanohydroxyapatite/polyamide-66 cage (n-HA/PA66 cage) with a horseshoe shape was designed to lower the subsidence rate of the traditional hollow cylindrical n-HA/PA66 cage. However, no studies have compared the incidence of subsidence in the two cages. The purpose of this study was to compare the long-term clinical and radiological outcomes of the novel n-HA/PA66 cage with the hollow cylindrical n-HA/PA66 cage after anterior cervical discectomy and fusion (ACDF) to treat single-level cervical degenerative disk disease (CDDD).

METHODS

Fifty-two patients with novel n-HA/PA66 cages (Group A) and fifty-five patients with hollow cylindrical n-HA/PA66 cages (Group B) were included. The radiological parameters included intervertebral height (IH), C2-7 angle (C2-7a), segmental alignment (SA), subsidence rate, and fusion rate. The clinical outcomes were visual analog scale (VAS) scores, Japanese Orthopedic Association (JOA) scores, and patient satisfaction rates.

RESULTS

The pre- and postoperative SA, C2-7a, and fusion rates of the patients in Groups A and B were similar. The preoperative and 6-month postoperative IHs in both groups were comparable. However, the final follow-up IH in Group B was significantly smaller than that in Group A (35.9 mm vs. 36.7 mm). The difference in the subsidence rates at the final follow-up between Group A (5.8%, 3/52) and Group B (18.2%, 10/55) was significant. The VAS score, JOA score, and patient satisfaction rate were not significantly different.

CONCLUSIONS

The novel n-HA/PA66 cage had similar favorable SA, C2-7a, fusion rate, and clinical outcomes compared to the hollow cylindrical n-HA/PA66 cage for treating single-level ACDF. Moreover, the novel n-HA/PA66 cage achieved a lower subsidence rate and higher IH than the hollow cylindrical n-HA/PA66 cage at the final follow-up.

The improved bioactive n-HA/PA66 cage versus the PEEK cage in anterior cervical fusion: results from a 6-year follow-up and a case-matched study

BACKGROUND

The nanohydroxyapatite/polyamide 66 (n-HA/PA66) cage, a bioactive nonmetal cage, is fabricated in a hollow cylindrical shape and has been widely used for decades with good clinical outcomes for anterior cervical fusion. However, there remain some radiological complications, such as a slightly high subsidence rate. To improve the clinical outcomes, the improved n-HA/PA66 cage now has been developed into a trapezoidal and wedge shape, a better biomechanical shape matching the cervical spine that is similar to that of the PEEK cage. However, there have been no long-term comparisons of the improved n-HA/PA66 cage and PEEK cage in anterior cervical reconstruction.

METHODS

Fifty-eight patients who underwent single-level anterior cervical decompression and fusion (ACDF) with the improved n-HA/PA66 cage (n-HA/PA66 group) were matched with patients with the PEEK cage (PEEK group) by clinical presentation, segment, age and sex. All patients underwent a minimum of 6 years of follow-up. The radiographic parameters (cage subsidence, fusion status, cervical lordosis, and segmental sagittal alignment) and clinical parameters (10-point visual analogue scale, Neck Disability Index and Japanese Orthopedic Association scores) from patients were evaluated before surgery, immediately after surgery, and at the latest follow-up.

RESULTS

The n-HA/PA66 and PEEK groups were well matched in terms of clinical presentation, segment, age, and sex at surgery. The n-HA/PA66 and PEEK cages had similar fusion rates at 6 months postoperatively (n-HA/PA66: 58.6% vs. PEEK: 51.7%, P = 0.455) and at the last follow-up (n-HA/PA66: 96.6% vs. PEEK: 93.1%, P = 0.402). The respective cage subsidence rates in the n-HA/PA66 and PEEK groups were 6.9 and 12.1% (P = 0.342). The correction of SA was similar between the groups at the final follow-up (n-HA/PA66: 4.29 ± 1.99 vs. PEEK: 3.99 ± 2.59 P = 0.464). There were no significant differences between the two groups in mean cervical lordosis, visual analogue scale scores of the neck and arm, NDI scores, JOA scores or patients' overall satisfaction at the final follow-up.

CONCLUSION

After single-level ACDF, the improved n-HA/PA66 cage had similar excellent results in both radiological and clinical outcomes compared with the PEEK cage over 6 years of follow-up. According to these results, the improved n-HA/PA66 cage and the PEEK cage could be comparable for ACDF.

Hydroxyapatite Use in Spine Surgery—Molecular and Clinical Aspect

Hydroxyapatite possesses desirable properties as a scaffold in tissue engineering: it is biocompatible at a site of implantation, and it is degradable to non-toxic products. Moreover, its porosity enables infiltration of cells, nutrients and waste products. The outcome of hydroxyapatite implantation highly depends on the extent of the host immune response. Authors emphasise major roles of the chemical, morphological and physical properties of the surface of biomaterial used. A number of techniques have been applied to transform the theoretical osteoconductive features of HAp into spinal fusion systems—from integration of HAp with autograft to synthetic intervertebral implants. The most popular uses of HAp in spine surgery include implants (ACDF), bone grafts in posterolateral lumbar fusion and transpedicular screws coating. In the past, autologous bone graft has been used as an intervertebral cage in ACDF. Due to the morbidity related to autograft harvesting from the iliac bone, a synthetic cage with osteoconductive material such as hydroxyapatite seems to be a good alternative. Regarding posterolateral lumbar fusion, it requires the graft to induce new bone growth and reinforce fusion between the vertebrae. Hydroxyapatite formulations have shown good results in that field. Moreover, the HAp coating has proven to be an efficient method of increasing screw fixation strength. It can decrease the risk of complications such as screw loosening after pedicle screw fixation in osteoporotic patients. The purpose of this literature review is to describe in vivo reaction to HAp implants and to summarise its current application in spine surgery.

Titanium-interlayer mediated hydroxyapatite coating on polyetheretherketone: a prospective study in patients with single-level cervical degenerative disc disease

BACKGROUND

Currently, there are limited reports regarding investigation of the biological properties of polyetheretherketone (PEEK) coated with titanium (Ti) and hydroxyapatite (HA) in human. The objective of this study is to evaluate the in vivo response of the PEEK cages coated with Ti and HA versus uncoated PEEK cages after anterior cervical discectomy and fusion (ACDF) in patients with single-level cervical degenerative disc disease (CDDD).

METHODS

Twenty-four patients with PEEK cages coated with Ti and HA (PEEK/Ti/HA group) were matched one-to-one with patients with uncoated PEEK cages (PEEK group) based on age, gender, and operative segment. All patients had been followed up for more than 2 years. Radiological assessments included intervertebral height (IH), C2-7 angle (C2-7a), segmental alignment (SA), and fusion rate. Clinical parameters included Visual Analogue Scale (VAS) and Japanese Orthopedic Association (JOA) scores.

RESULTS

There was no statistical difference in SA, IH, and C2-7a between the two groups before and after surgery and all these parameters were restored postoperatively. The fusion rate of PEEK/Ti/HA group was significantly higher than PEEK group at 3-month post-operation (87.5% vs. 62.5%). At the last follow-up, the fusion rate of the both groups achieved 100%. The VAS and JOA scores were comparable between two groups and improved postoperatively.

CONCLUSIONS

In patients with single-level ACDF, PEEK cage coated with Ti and HA provided a higher fusion rate than uncoated PEEK cage at 3-month post-operation, while both two cages could achieve solid osseous fusion at the last follow up. Compared with the uncoated PEEK cage, PEEK/Ti/HA cage yielded similar favorable segmental and overall cervical lordosis, IH, and clinical outcomes after the surgery.

In vivo evaluation of porous nanohydroxyapatite/polyamide 66 struts in a goat cervical fusion model

The hollow cylindrical nanohydroxyapatite/polyamide 66 strut (n-HA/PA66) has been used clinically for anterior cervical reconstruction. However, rates of occurrence of a “radiolucent gap” between the dense strut and adjacent endplates were reported. The aim of this in vivo study was to evaluate the viability and advantages of the novel porous n-HA/PA66 strut. The goat C3/4 partial discectomy and fusion model was built, and two groups of n-HA/PA66 struts were implanted into C3/4: group 1, porous n-HA/PA66 strut; and group 2, hollow cylindrical n-HA/PA66 strut filled with autogenous cancellous bone. CT evaluation was performed to assess the fusion status after 12 and 24 weeks. The cervical spines were harvested. Histomorphological analysis was performed to determine new bone formation. Biomechanical testing was performed to determine range of motion (ROM). CT confirmed the disappearance of the boundary of the porous strut and host bone, while the radiolucent gap remained clearly discernible in the dense strut group. The mean CT fusion scores of the porous group were significantly higher. Histologic evaluation showed that the porous struts promoted better osteointegration. Calcein fluorochrome labelling indicated faster bone ingrowth in the porous struts. Biomechanical tests revealed that the porous struts had significantly reduced micromotion. The porous n-HA/PA66 strut could offer interesting potential for cervical reconstruction after corpectomy.

Bone Graft Substitutes in Single- or Double-Level Anterior Cervical Discectomy and Fusion: A Systematic Review

STUDY DESIGN

Systematic review OBJECTIVE.: To undertake a systematic review of published literature to evaluate efficacy of bone graft substitutes on radiographic and clinical outcomes in single- or double-level anterior cervical discectomy and fusion (ACDF) for degenerative disease.

SUMMARY OF BACKGROUND DATA

ACDF is one of the most common spinal surgeries completed in the United States. Today bone graft substitutes including ceramic-based synthetic bone grafts, allografts, bone morphogenetic proteins (BMPs), mesenchymal stem cells, and bone marrow aspirate are widely used to enhance fusions; even though the efficacy of these substitutes is poorly defined. Critical evaluation of these products is necessary to optimize radiographic and clinical outcomes for ACDF in degenerative disease.

METHODS

A systematic literature review of 22 published articles was conducted. All articles reported results on patients who underwent a single- or double-level ACDF performed using a bone graft substitute and reported results on radiographic fusion rates at least 6 months after surgery.

RESULTS

All studies using BMP showed 100% fusion rate despite length of the study or whether additional bone graft substitutes were used. Use of only ceramic-based synthetics had the lowest fusion rate, 80.5%. Use of only mesenchymal stem cells resulted in an average fusion rate of 87.7%. When used alone, allograft resulted in an average fusion rate of 87.3%. This was significantly influenced by one outlier, Kim et al, which when removed, increased the fusion rate to 93.5%. Clinical outcomes were improved postoperatively irrespective of the graft used, although dysphagia was significantly greater in studies using BMP (P < 0.001).

CONCLUSION

Allograft alone has the lowest cost with similar fusion rates and clinical outcomes compared to other bone graft substitutes. Physicians should consider this when choosing to use bone graft substitutes for routine ACDFs.

LEVEL OF EVIDENCE

4.

The n-HA/PA66 Cage Versus the PEEK Cage in Anterior Cervical Fusion with Single-Level Discectomy During 7 Years of Follow-Up

OBJECTIVE

The nano-hydroxyapatite/polyamide66 (n-HA/PA66) cage is a novel biomimetic nonmetal cage, whereas the polyetheretherketone (PEEK) cage has been widely used for decades with excellent clinical outcomes. However, there has been no long-term comparison of these 2 cages in anterior cervical reconstruction.

METHODS

This retrospective study included 98 patients who underwent single-level anterior cervical decompression and fusion (ACDF) from January 2009 to June 2011 with at least 7 years of follow-up; the PEEK cage was used in 51 patients (PEEK group), whereas the n-HA/PA66 cage was used in 47 (n-HA/PA66 group). The groups were compared regarding radiographic (cage subsidence, fusion status, cervical lordosis, and segmental sagittal alignment) and clinical (10-point visual analog scale and Japanese Orthopedic Association scores) parameters preoperatively, postoperatively, and at the final follow-up.

RESULTS

The n-HA/PA66 and PEEK cages had similar fusion rates at the final follow-up (97.9% vs. 98.0%). The respective cage subsidence rates in the PEEK and n-HA/PA66 cage groups were 9.8% and 10.6%. There were no significant differences between the 2 groups in mean cervical lordosis, mean interbody height, segmental sagittal alignment, cervical lordosis, and 10-point visual analog scale and Japanese Orthopedic Association scores at the final follow-up. The n-HA/PA66 cages resulted in high fusion and low subsidence rates during long-term follow-up.

CONCLUSIONS

After single-level ACDF, the n-HA/PA66 cage showed similar radiographic fusion, subsidence rate, and clinical results compared with the PEEK cage during 7 years of follow-up. These results suggest that the n-HA/PA66 cage could be comparable with the PEEK cage for ACDF.

Nanohydroxyapatite Effect on the Degradation, Osteoconduction and Mechanical Properties of Polymeric Bone Tissue Engineered Scaffolds

BACKGROUND

Statistical reports show that every year around the world approximately 15 million bone fractures occur; of which up to 10% fail to heal completely and hence lead to complications of non-union healing. In the past, autografts or allografts were used as the “gold standard” of treating such defects. However, due to various limitations and risks associated with these sources of bone grafts, other avenues have been extensively investigated through which bone tissue engineering; in particular engineering of synthetic bone graft substitutes, has been recognised as a promising alternative to the traditional methods.

METHODS

A selective literature search was performed.

RESULTS

Bone tissue engineering offers unlimited supply, eliminated risk of disease transmission and relatively low cost. It could also lead to patient specific design and manufacture of implants, prosthesis and bone related devices. A potentially promising building block for a suitable scaffold is synthetic nanohydroxyapatite incorporated into synthetic polymers. Incorporation of nanohydroxyapatite into synthetic polymers has shown promising bioactivity, osteoconductivity, mechanical properties and degradation profile compared to other techniques previously considered.

CONCLUSION

Scientific research, through extensive physiochemical characterisation, in vitro and in vivo assessment has brought together the optimum characteristics of nanohydroxyapatite and various types of synthetic polymers in order to develop nanocomposites of suitable nature for bone tissue engineering. The aim of the present article is to review and update various aspects involved in incorporation of synthetic nanohydroxyapatite into synthetic polymers, in terms of their potentials to promote bone growth and regeneration in vitro, in vivo and consequently in clinical applications.

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.

Subsidence as of 12 months after single-level anterior cervical inter-body fusion. Is it related to clinical outcomes?

BACKGROUND

Subsidence is a frequent phenomenon in the interbody fusion process in patients with anterior cervical discectomy and fusion (ACDF). There is little evidence of whether subsidence in the cervical spine has any impact on clinical outcomes.

OBJECTIVES

The purpose of this study is to investigate the correlation of subsidence and clinical outcomes after ACDF and to consider reasons subsidence might not cause unfavorable clinical outcomes.

METHODS

A total of 158 consecutive patients who underwent single-level ACDF were included. The patients were divided into a subsidence group (S-group) and a no subsidence group (N-group), with subsidence defined as a decrease by ≥3 mm in total intervertebral height (TIH). We analyzed outcomes resulting from subsidence, particularly focusing on clinical outcomes and subsequent global and segmental kyphosis using a repeated measure analysis of variance (RM-ANOVA).

RESULTS

Subsidence occurred in 74 patients (46.8%) as of a 12-month follow-up. The S-group included 58.6% with a stand-alone cage for interbody fusion (p = 0.002). Clinical outcomes improved significantly over time (neck pain, RM-ANOVA: F(1.3, 205) = 125.1, p < 0.001; arm pain, RM-ANOVA: F(1.3, 203) = 290.8, p < 0.001). There was no significant difference in interaction with subsidence and clinical outcomes between the S- and N-group (neck pain, RM-ANOVA: F(2,153) = 1.04, p = 0.356, partial η(2) = 0.229; arm pain, RM-ANOVA: F(2,153) = 0.56, p = 0.571, partial η(2) = 0.142). Segmental angle increased in both groups over time and showed a statistically significant difference between the S- and N-groups (RM-ANOVA: F(3,143) = 6.148, p = 0.001, partial η(2) = 0.959). Although, global cervical angle decreased generally and displayed no statically significant difference between the S- and N-group (RM-ANOVA: F(3,119) = 2.361, p = 0.075, partial η(2) = 0.056).

CONCLUSIONS

Radiographic subsidence after ACDF occurred in 46.8% patients as of 12 months after the single-level ACDF. The lack of correlation between bad clinical outcome and radiographic subsidence may be due to segmental kyphosis, preserved posterior height, and maintaining the global cervical angle.

Evaluation of biomechanical strength, stability, bioactivity, and in vivo biocompatibility of a novel calcium deficient hydroxyapatite/poly(amino acid) composite cervical vertebra cage

A new type of cervical vertebra cage was prepared using a novel composite, calcium deficient hydroxyapatite/poly(amino acid) (HA/PAA), and its mechanical properties, in vitro stability and bioactivity, and in vivo biocompatibility were characterized. The results showed that the axial compressive loads of the HA/PAA cage were in the range of 10058-10612 N and the lateral compressive loads were in the range of 1180-2363 N, and varied with the height of the cervical vertebra cages. After immersion in simulated body fluid (SBF) for 16 weeks, the axial compressive loads of the cage decreased from 10058 to 7131 N and the lateral compressive loads decreased from 1180 to 479 N. In addition, the weight loss decreased 6.01%, showing that HA/PAA composites had good stability during the incubation period. The pH value of SBF was also monitored during the whole soaking period; it fluctuated in the range of 6.9-7.4. Scanning electron microscope and energy dispersive spectrometer results showed the cage was bioactive with a new apatite layer attached on the surface. The histological evaluation revealed that new bone tissue bonded tightly with the surfaces of the implants, showing excellent biocompatibility. In conclusion, the HA/PAA cage showed sufficient strength, good stability, bioactivity, and biocompatibility, and has potential applications for clinical cervical vertebrae repair.