Results of the biocompatible osteoconductive polymer (BOP) as an intersomatic graft in anterior cervical surgery

Dosing Strategy for Osteobiologics Used in ACDF Surgery: Influence on Fusion Rates and Associated Complications. A Systematic Literature Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To assess the available evidence related to dose-dependent effectiveness (i.e., bone fusion) and morbidity of osteobiologics used in anterior cervical discectomy and fusion (ACDF).

METHODS

Studies with more than 9 adult patients with degenerated/herniated cervical discs operated for one-to four-levels ACDF reporting used osteobiologics doses, fusion rates at six months or later, and related comorbidities were included. PubMed, EMBASE, ClinicalTrials, and Cochrane were searched through September 2021. Data extracted in spread sheet and risk of bias assessed using MINORS and Rob-2.

RESULTS

Sixteen studies were selected and sub-grouped into BMP and non-BMP osteobiologics. For the 10 BMP studies, doses varied from 0.26 to 2.1 mg in 649 patients with fusion rates of 95.3 to 100% at 12 months. For other osteobiologics, each of six studies reported one type of osteobiologic in certain dose/concentration/volume in a total of 580 patients with fusion rates of 6.8 to 96.9% at 12 months. Risk of bias was low in three of the 13 non-randomized (18.75%) and in all the three randomized studies (100%).

CONCLUSIONS

Taking into account the inconsistent reporting within available literature, for BMP usage in ACDF, doses lower than 0.7 mg per level can achieve equal successful fusion rates as higher doses, and there is no complication-free dose proved yet. It seems that the lower the dose the lower the incidence of serious complications. As for non-BMP osteobiologics the studies are very limited for each osteobiologic and thus conclusions must be drawn individually and with caution.

Extrusion of Biocompatible Osteoconductive Polymer (BOP) Causing Cervical Myelopathy

BACKGROUND

As the prevalence of spinal fusion surgery has increased, reliable and safe bone graft substitutes have been developed in response. Biocompatible osteoconductive polymer (BOP) has been used as a bone graft alternative for spine surgery. We present a case of cervical myelopathy due to extrusion of BOP 23 years after surgery and discuss the pathophysiology in terms of spinal fusion.

CASE DESCRIPTION

A 65-year-old man presented with a 3-month history of cervical myelopathic symptoms. Twenty-three years earlier, the patient had undergone cervical surgery for a C6-7 herniated disc with the use of BOP. Imaging studies of the cervical spine showed cord compression due to extruded BOP at C6-7. He underwent corpectomy of the C7 vertebral body and removal of the BOP for the neural decompression, combined with interbody fusion by use of an iliac bone graft and plate fixation. During the operation, crumbly fibers of the BOP were easily removed. His myelopathic symptoms improved immediately after surgery. Postoperative magnetic resonance imaging also showed successful decompression of the spinal cord. Histologically, a foreign body reaction and bony degeneration were found around the synthetic fibers of the BOP.

CONCLUSIONS

Spine surgeons should recognize the pathophysiology of the BOP used for spine fusion surgery. Although BOP is not currently used for spinal surgery, patients undergoing previous surgery with the BOP can present with related complications. Revision surgery is recommended to remove the unincorporated BOP and achieve solid spine fusion.

Usefulness of polyetheretherketone (PEEK) cage with plate augmentation for anterior arthrodesis in traumatic cervical spine injury

BACKGROUND CONTEXT

Even though many clinical reports about cages have been documented in patients with degenerative disorders, reports were scarce for traumatic injury cases, and those cases using metal cages were restricted to only one-level injury.

PURPOSE

To evaluate the usefulness of polyetheretherketone (PEEK) cage and plate construction in anterior interbody fusions (AIF) for traumatic cervical spine injuries by analyzing radiographic changes and clinical outcomes.

STUDY DESIGN/SETTING

Retrospective study.

PATIENT SAMPLE

Fifty-eight patients (91 levels) underwent cage and plate construction for treatment of traumatic cervical spine injury.

OUTCOME MEASURES

The fusion rate, fusion time, changes of Cobb angle, subsidence rate, and adjacent level changes were assessed as a radiographic outcome. Clinical analysis includes the recovery rate on the American Spinal Injury Association (ASIA) impairment scale and the presence of the complications.

METHODS

We evaluated 58 patients (91 levels) who underwent surgery and had at least 24 months in follow-up study. Radiographic evaluation included the assessment of interbody fusion rate, fusion time, changes of Cobb angle, subsidence rate, and adjacent level changes. Clinical assessment was done by analyzing recovery state of ASIA impairment scale from preoperative period to the last follow-up and by evaluating complications.

RESULTS

Fifty-four cases showed bony fusion within 3 months after the surgery. The mean Cobb angle between the vertebral bodies was 2.54 degrees before operation, 9.13 degrees after operation, and 8.39 degrees at the latest follow-up. The mean intervertebral disc height was increased by 3.01 mm after the operation, but the mean height was 2.17 mm shorter at the last follow-up than after postoperation. In terms of clinical results, five Grade A cases and one Grade B case as assessed by the ASIA impairment scale were unchanged until the last follow-up. Twenty-three cases of Grade C, 16 cases of Grade D, and 13 cases of Grade E improved to seven cases, 26 cases, and 19 cases, respectively. Three cases went through additional surgery, two posterior fusions for delayed union and posterior instability and one AIF for adjacent level disease.

CONCLUSION

The PEEK cage and additional plate fixation is a surgical procedure that decreases donor site morbidity, obtains high fusion rate with rigid fixation, and provides satisfactory clinical outcome for traumatic cervical spine injuries, regardless of the numbers of the involved levels.

Bone graft substitutes in anterior cervical discectomy and fusion

Anterior cervical discectomy with fusion is a common surgical procedure for patients suffering pain and/or neurological deficits and unresponsive to conservative management. For decades, autologous bone grafted from the iliac crest has been used as a substrate for cervical arthrodesis. However patient dissatisfaction with donor site morbidity has led to the search for alternative techniques. We present a literature review examining the progress of available grafting options as assessed in human clinical trials, considering allograft-based, synthetic, factor- and cell-based technologies.

Diagnosing cervical fusion: a comprehensive literature review

Study Design

Comprehensive literature review.

Purpose

To document the criteria for fusion utilized in these studies to determine if a consensus on the definition of a solid fusion exists.

Overview of Literature

Numerous studies have reported on fusion rates following anterior cervical arthrodesis. There is a wide discrepancy in the fusion rates in these studies. While factors such as graft type, Instrumentation, and technique play a factor in fusion rate, another reason for the difference may be a result of differences in the definition of fusion following anterior cervical spine surgery.

Methods

A comprehensive English Medline literature review from 1966 to 2004 using the key words "anterior," "cervical," and "fusion" was performed. We divided these into two groups: newer studies done between 2000 and 2004, and earlier studies done between 1966 and 2000. These articles were then analyzed for the number of patients, follow-up period, graft type, and levels fused. Moreover, all of the articles were examined for their definition of fusion along with their fusion rate.

Results

In the earlier studies from 1966 to 2000, there was no consensus for what constituted a solid fusion. Only fifteen percent of these studies employed the most stringent definition of a solid fusion which was the presence of bridging bone and the absence of motion on flexion and extension radiographs. On the other hand, the later studies (2000 to 2004) used such a definition a majority (63%) of the time, suggesting that a consensus opinion for the definition of fusion is beginning to form.

Conclusions

Our study suggests that over the past several years, a consensus definition of fusion is beginning to form. However, a large percentage of studies are still being published without using stringent fusion criteria. To that end, we recommend that all studies reporting on fusion rates use the most stringent criteria for solid fusion following anterior cervical spine surgery: the absence of motion on flexion/extension views and presence of bridging trabeculae on lateral x-rays. We believe that a universal adoption of such uniform criteria will help to standardize such studies and make it more possible to compare one study with another.

[Posterior extrusion of Biocompatible Orthopaedic Polymer (BOP) graft mimicking a calcified lumbar disc herniation: case report]

OBJECTIVE AND IMPORTANCE

We present a case of intracanalar extrusion of a L5S1 Biocompatible Orthopaedic Polymer (BOP) graft associated with a L4L5 disc herniation 19 years after a lumbar intersomatic fusion for a L5S1 disc herniation. Radiological aspect of this complication should be recognized by neurosurgeons.

CLINICAL PRESENTATION

A 55-year old man presented with a right L5 sciatic pain. Neurological examination found a severe weakness in dorsal flexion of the foot. A lumbar CT scanner disclosed aspects consistent with right L4L5 and huge calcified L5S1 lumbar disc herniation.

INTERVENTION

The patient was operated via a bilateral paravertebral approach and a L5 laminectomy. A dense and extensive epidural scarring was seen. The right L4L5 herniated disc was excised. At the left L5S1 level, fibres from a BOP graft had separated into large fragments extruded into the vertebral canal through the dura. The fibres could only be removed partially because of nerve roots adherence. The patient developed postoperative cerebrospinal fluid (CSF) leakage that required a second operation for dural closure. The postoperative course was uneventful and the patient recovered the right L5 root deficit.

CONCLUSION

Neurosurgeons should be aware of the radiological aspect of this complication. If it is recognized on CT scan and asymptomatic, conservative management should be proposed because of the risk of nerve roots injury or postoperative CSF leakage.

Solis cage (PEEK) for anterior cervical fusion: preliminary radiological results with emphasis on fusion and subsidence

BACKGROUND CONTEXT

Recent literature has raised some apprehensions with regard to the usage of cervical cages.

PURPOSE

Radiological review of cases performed at our institution with a novel cage made of polyetheretherketone (PEEK).

STUDY DESIGN

Retrospective study.

METHODS

A retrospective review of the first 15 consecutive cases of single-level anterior cervical interbody fusion using the Solis cage (PEEK material) for cervical spondylotic radiculopathy or myelopathy was performed. The follow-up ranged from 12 to 35 months (average 18 months). Anteroposterior and lateral radiographs were taken immediately after the surgery and at intervals of 3, 6, 12, and 24 months after surgery. Anterior disc height (ADH), posterior disc height (PDH), interbody height ratio (IBHR), distance between the posterior margin of the cage and the posterior wall of the vertebral body (D-CPW), and interbody angle (IBA) were measured on the lateral radiographs and compared. Fusion was assessed by examining for trabecular continuity, bridging of bone across the disc space, and sclerosis at the vertebral end plates on both sides. The parameters assessed were time for fusion, subsidence, segmental sagittal alignment of the operated segment, and presence/absence of migration of the cage. Data were analyzed using the Mann-Whitney nonparametric test.

RESULTS

Fusion was evident at 3-6 months postsurgery in all cases except one (93.33% fusion rate at 6 months). At the last follow-up, fusion was maintained in all cases. The immediate postoperative ADH and PDH was significantly greater than the respective preoperative values and was maintained at the last follow-up though there was a significant amount of subsidence when the follow-up radiographs were compared with the immediate postoperative X-rays. The immediate postoperative IBHR was significantly greater than the preoperative IBHR, and was maintained at the last follow-up, but not statistically significant. The immediate postoperative IBA (lordotic angle) was greater than the preoperative IBA but was not statistically significant. The IBA at the last follow-up was lesser than the preoperative value but with no statistical significance. The IBA measured at the last follow-up was less than the value at the immediate postoperative period, but not statistically significant. There was no migration or extrusion of the cage at latest follow-up.

CONCLUSIONS

The high fusion rate, low subsidence, stability provided by the cage, and facilitation of radiological assessment are the result of the physical properties of the PEEK material as well as the design of the cage.

High rate of fusion in sheep cervical spines following anterior interbody surgery with absorbable and nonabsorbable implant devices

STUDY DESIGN

Fourteen sheep were fused using anterior interbody implants at C2-C3 and C4-C5 and followed for 6 months.

OBJECTIVE

To evaluate the effect of absorbable and nonabsorbable implants on fusion rate, cage migration, and implant integrity.

SUMMARY OF BACKGROUND DATA

Despite the high clinical success rate with metallic plates and interbody grafting, complications such as dysphagia, imaging artifacts, and revision difficulties exist. Less permanent and lower profile implants could minimize these problems.

METHODS

Four treatments were studied: 1) carbon fiber-reinforced polymer (CFRP) cage alone, 2) CFRP cage with an absorbable tension band, 3) absorbable cage with an absorbable tension band, and 4) absorbable cage with a titanium plate. Fusion was assessed using radiographs, biomechanical testing, and micro-CT analysis.

RESULTS

Treatments with the CFRP cage alone had the lowest fusion rate at 3 months (2/6) and 6 months (4/6). The CFRP cage with the absorbable strap treatments had 5/6 fusions at 6 months. The absorbable cage with absorbable strap also had 5/6 fusions, but two of the cages fractured. The absorbable cage with titanium plate had 5/6 fusions, but the one partial fusion was attributed to poor screw and plate placement.

CONCLUSION

Using both absorbable and nonabsorbable implants, high fusion rates were achieved in the challenging sheep cervical spine model. However, the absorbable cages were not able to withstand the mechanical forces during the 6-month survival period.

A prospective randomized comparison of rectangular titanium cage fusion and iliac crest autograft fusion in patients undergoing anterior cervical discectomy

Object

The authors compare clinical outcome and fusion rates after iliac crest autograft (ICAG)– and rectangular titanium cage (RTC)–augmented fusion in patients undergoing anterior cervical discectomy (ACD).

Methods

One hundred consecutive patients with 127 levels of cervical disc disease refractory to conservative treatment were randomized into one of the two treatment groups (ICAG/RTC fusion). The visual analog scale was used by the patient to rate overall pain and head, neck, arm, and donor site pain separately. Myelopathy was documented according to Japanese Orthopaedic Association and Nurick grading systems. Outcome was analyzed using Odom criteria, the 36-Item Short Form (SF-36), and Patient Satisfaction Index scales. Fusion rates were assessed on standard and flexion–extension radiographs. Follow-up data of at least 12 months' duration were available for 95 patients.

More residual overall pain after 12 months was documented in patients who underwent ICAG fusion (3.3 ± 2.5 [ICAG] and 2.2 ± 2.4 [RTC]; p < 0.05). Although arm and head pain were minimal in both groups, neck pain proved to be the predominant symptom (2.7 ± 2.5 [ICAG] and 1.9 ± 2.1 [RTC]), which resolved in only 67 and 48% of RTC-and ICAG-treated patients, respectively (p < 0.05). Myelopathy improved comparably in both groups. Regardless of increased pain in ICAG-treated patients, PSI and SF-36 scores were not significantly different between groups (only four [8%] of 47 ICAG-treated patients and five [10%] of 48 RTC-treated patients were unsatisfied). Good to excellent functional recovery according to Odom criteria was observed in 75 and 79% of ICAG- and RTC-treated patients, respectively. Fusion rates were 81 and 74%, respectively (p = 0.51).

Conclusions

Fusion rates and clinical outcome at 12 months after ACD were comparable between patients who underwent ICAG and RTC fusion. The use of rectangular cages, however, avoids donor site morbidity and reduces overall pain and, thus, seems to be an advantageous treatment alternative.

[HAC-titanium as an implant for interbody fusion in spinal canal stenosis of the cervical spine. Six-year clinical trial]

A total of 102 patients were operated on in 134 levels because of an isolated spondylotic cervical stenosis in 6 years. A titanium implant coated with hydroxyapatite ceramic (HAC) was inserted. The average age of the patients was 53 years. The final clinical and radiological follow-up was performed after 15 months. The functional outcome was classified as good to excellent (Odoms's score) in 83.8% of the patients. Implant-related complications requiring revision surgery included two dislocated dowels and one vertebral collapse in a bisegmental operation. After 6 weeks beginning of bony growth around the implant was seen in 38% of all inserted titanium cages on roentgenograms. A complete solid bony incorporation was shown in 91.2% of the fused segments after 6 months and in 96% after 12 months or at follow-up, respectively. These results illustrate the efficacy of the easy to handle HAC titanium implant, demonstrating that this technique achieves good clinical outcome with the same complication rate as comparable techniques.

Integrated outcome assessment after anterior cervical discectomy and fusion: myelocompression but not adjacent instability affect patient-reported quality of life and cervical spine symptoms

STUDY DESIGN

The authors conducted a cross-sectional study.

OBJECTIVE

Integrated assessment of adjacent instability (AI), myelocompression (MC), magnetic resonance imaging (MRI) signs of myelopathy (MRISM), physician-assessed clinical signs and symptoms, including clinical signs of myelopathy (CSM), patients' self-reported symptoms and quality of life after anterior cervical discectomy and fusion (ACDF).

MATERIALS AND METHODS

Fifty-four patients who had ACDF between 1986 and 1995 received MRI scans, conventional and flexion/extension radiographs to assess myelocompression, MRISM, fusion, and AI. Clinical outcome was assessed using signs and symptoms based on selected items of Odom's criteria, Oswestry low back pain disability questionnaire, and the neck disability index. Patients reported their quality of life (QL) on a standardized instrument (Profiles of QL of Chronically Ill [PLC]) and by a specific validated Cervical Spine Symptom Scale (CSSS).

RESULTS

Myelocompression was found more frequently than expected (24%). MRISM were seen in 2 patients (4%). One of the 2 patients developed CSM. Fusion was achieved in 94% (with kyphosis in 17%). AI was found in 30%. However, only myelocompression but not AI was associated with statistically significant decreases in most QL scores (i.e., everyday capabilities, positive mood) and high cervical spine symptom burden (all P's < 0.05).

CONCLUSIONS

The study results underline the need for a better understanding of the biomechanical changes in the adjacent unfused segments. Consensus is needed on postoperative follow-up guidelines, including pain management strategies. Future studies on the outcome of ACDF will profit from an integrated outcome approach, including assessments based on imaging, physicians, and patients.

A prospective randomized comparison of coralline hydroxyapatite with autograft in cervical interbody fusion

STUDY DESIGN

A prospective randomized trial with independent clinical and radiographic outcome review of patients receiving either hydroxyapatite or tricortical iliac crest graft for cervical interbody fusion was conducted.

OBJECTIVE

To determine whether coralline-derived hydroxyapatite is a suitable bone graft substitute in cervical interbody fusion.

SUMMARY OF BACKGROUND DATA

Tricortical iliac crest bone is the "gold standard" graft material for cervical interbody fusion. Various bone substitutes have been used for this procedure to avoid potential donor site morbidity. ProOsteon 200 is a coralline-derived hydroxyapatite product, the use of which remains unclear for cervical interbody fusion.

METHODS

In this study, 29 patients undergoing anterior cervical fusion and plating were randomized to receive either ProOsteon 200 or iliac crest grafts. The SF-36 and Oswestry Disability Index were used to measure clinical outcome. Postoperative radiographs were analyzed for graft fragmentation, loss of height, angular alignment, and hardware failure to assess structural integrity of the graft material. Plain radiographs and computed tomography scans were used to evaluate fusion.

RESULTS

Both the ProOsteon 200 and iliac crest groups demonstrated significant improvement in clinical outcome scores. There was no significant difference in clinical outcome or fusion rates between the two groups. Graft fragmentation occurred in 89% of the hydroxyapatite grafts and 11% of the autografts (P = 0.001). Significant graft settling occurred in 50% of the hydroxyapatite grafts, as compared with 11% of the autografts (P = 0. 009). One patient in the ProOsteon 200 group required revision surgery for graft failure.

CONCLUSIONS

ProOsteon 200 does not possess adequate structural integrity to resist axial loading and maintain disc height or segmental lordosis during cervical interbody fusion.

Prospective controlled study of rectangular titanium cage fusion compared with iliac crest autograft fusion in anterior cervical discectomy

Object

The complications of autogenous bone grafting compel spine surgeons to seek alternative methods for cervical spinal fusion. This prospective study was conducted to evaluate the safety and efficacy of using rectangular titanium cage fusion compared with the widely performed iliac crest autograft fusion.

Methods

A total of 36 patients with cervical disc disease in whom an anterior approach was indicated for discectomy were included in this prospective controlled study. The first 18 consecutive patients received iliac crest autograft; the next 18 consecutive patients received rectangular titanium cages. The intergroup demographic and clinical data were comparable. All patients attended follow up for 1 year. According to Odom criteria, 15 (83%) of 18 patients in both groups experienced good to excellent functional recovery. According to the Patient Satisfaction Index, 17 (94%) of 18 patients in both groups were satisfied. The evaluation of neck pain and arm pain did not indicate statistically significant differences between either group. Fusion was present after 1 year in 16 (89%) of 18 patients who received iliac crest autografts and in 15 (83%) of 18 patients who received rectangular titanium cages. In the autograft group, a pseudarthrosis was present in one patient and marked hip pain was observed in three patients. In the cage group, there was one case of temporary vocal cord paresis but no implant-related complications.

Conclusions

The authors conclude that the use of titanium cages in anterior cervical discectomy constitutes a safe and efficient alternative to iliac crest bone autograft.

Anterior cervical interbody fusion with hydroxyapatite graft and plate system

Object

In cases of spondylosis or spine trauma, cervical interbody grafts are sometimes required after anterior discectomy. To avoid morbidity related to the harvesting of iliac crest bone, numerous materials have been developed such as allografts, methylmethacrylate, biocompatible osteoconductive polymer, and coralline grafts or cages. Some of these materials, however, are inefficient for fusion or are associated with specific complications. Conversely, hydroxyapatite (HA) grafts have numerous advantages. For example, their mechanical properties provide adequate load resistance and their porosity allows infiltration by newly formed bone, leading to complete fusion. The authors studied the results of using HA grafts combined with plating in patients who underwent anterior cervical discectomy.

Methods

Fifty-four patients underwent 68 cervical interbody fusion procedures in which an HA graft and plating were used. Indications for surgery were radiculopathy (caused by soft-disc herniation or spondylosis) in 46 cases, spondylotic myelopathy in two cases, and spinal trauma in six cases. Postoperatively the patients were followed for a mean of 24.6 months. Patients underwent radiography to evaluate fusion, intervertebral disc height, and the degree of lordosis.

Clinically, excellent or good results (based on the Odon classification) were demonstrated in 91% of patients who presented with radiculopathy. Complete interbody fusion was achieved in 99% of all cases. Preoperative kyphotic deformities were corrected in all cases after surgery. Intervertebral disc height was maintained throughout follow up. Surgery-related morbidity was low; only one patient suffered from a permanent dysphagia. Graft deterioration was observed in 13 cases and two graft fractures occurred but without adversely affecting fusion. There were no cases of graft extrusion.

Conclusions

Hydroxyapatite grafts are very efficient in achieving cervical fusion, maintaining intervertebral disc height, and restoring lordosis. When combined with the placement of a cervical plate, immediate stability is achieved and graft displacement is prevented.

Nonautologous interbody fusion materials in cervical spine surgery: how strong is the evidence to justify their use?

STUDY DESIGN

A review of the literature concerning the use of interbody fusion devices and materials in anterior cervical surgery.

OBJECTIVES

To examine the evidence supporting the use of interbody fusion devices as an alternative to autologous bone after anterior cervical discectomy.

SUMMARY OF BACKGROUND DATA

Concerns over the morbidity associated with harvesting autologous bone and the risk of transmissible infectious from allografts and xenografts have prompted the search for alternative methods of achieving interbody fusion. Several of these methods have been associated with an unacceptable rate of complications. The clinical and health economic implications of the widespread introduction of interbody fusion devices in the absence of sound evidence cannot be ignored.

METHODS

A systematic review of the literature relating to cervical interbody fusion was undertaken. Studies were assessed critically with respect to their methodology, results, and conclusions.

RESULTS

Thirty-two clinical studies and 10 laboratory studies were analyzed. Methodologic weaknesses were identified in the majority. Only four clinical reports were either randomized or blinded or involved independent assessment of their outcomes. Fewer than half of the studies included a valid statistical analysis. Radiologic evidence of fusion was limited in many cases. There was little evidence that nonautologous fusion devices offered a reduction in the length of hospital stay. Autologous bone was as effective as, or superior to, many other fusion devices. The early results of some new fusion techniques used alone or in combination showed promise.

CONCLUSIONS

There is limited evidence supporting the use of a cervical interbody fusion device in place of autologous bone. There is a need to standardize the testing of implants with good quality laboratory work preceding clinical use. Certain devices including cages, some forms of hydroxyapatite, and bone morphogenic proteins merit further study.