Long-term magnetic resonance imaging evaluation of bioresorbable anterior cervical plate resorption following fusion for degenerative and traumatic disk disruption

The effectiveness of biodegradable instrumentation in the treatment of spinal fractures

INTRODUCTION

A variety of biodegradable implants (screws, rods, plates and cages) are available which are composed of many different biodegradable polymers with varying characteristics. The present review of animal and clinical studies examines the efficacy and safety of biodegradable implants in spinal fracture intervention.

METHODS

A review of the literature through March 2018 was performed using PubMed and Cochrane databases. Success rates were calculated according to sufficient tissue biocompatibility, solid clinical fusion and propensity for osseointegration.

RESULTS

49 articles (24 animal and 25 human studies) were included. In animal experiments, the overall success rate for spinal fusion was 60.3%, while the mean success rate regarding the cervical spine was 51.8% compared to 68.1% for the lumbar spine (p = 0.002). In studies involving control group(s): the mean bioabsorbable implant success rate for spinal fusion was 42% compared to 57% for conventional implants (p = 0.0016). In the lumbar spine pL-lactide acid (PLLA) had 75.2% success rate compared to poly (L-lactide-co-DL-lactide) (PLDLLA) at 53.4% (p = 0.003). In clinical studies, the overall mean success rate was 89%, while the mean success rate regarding the cervical spine was 92%, as compared to 83.6% for the lumbar spine (p = 0.001). In studies involving control group(s): the mean bioabsorbable implant success rate was 75% compared to a conventional implant mean success rate of 97% (p<0.0001). In the cervical spine PLLA had a 98.7% success rate compared to 90% with PLDLLA (p = 0.015). In the lumbar spine PLDLLA had 84.7% success rate compared to 63.6% for poly-glycolic acid (PGA) (p = 0.085).

DISCUSSION

Studies combined biodegradable and conventional implants. Polymers were used in various combinations and surface modification of the implants also varied. Comparison studies were of small sample size. Animal and clinical studies diverged. The current data are not encouraging. The end-point of assessing osseointegration varies in the studies and is indeterminate. In early stages the structure comparison of osseous restoration using biodegradable implants appears inferior to utilization of conventional cages and instrumentation. There is no statistically significant evidence supporting the efficacy of biodegradable implants replacing traditional instrumentation. There is a lack of prospective clinical trials with long-term follow-up regarding utilization of biodegradable implants and the available data does not support their routine use in spinal fracture intervention.

Outcomes observed during a 1-year clinical and radiographic follow-up of patients treated for 1- or 2-level cervical degenerative disease using a biodegradable anterior cervical plate

OBJECTIVE The purpose of this study was to present an initial surgical experience in the management of 1- or 2-level degenerative disc disease of the cervical spine using biodegradable anterior cervical plates (bACPs) in anterior cervical discectomy and fusion (ACDF). The authors also aimed to provide insight into this critical and controversial clinical issue by clarifying outcomes for patients receiving bACPs and by comparing their outcomes with those achieved using a traditional metallic anterior cervical plate (mACP) implant. METHODS A retrospective review was conducted for 2 series of patients who had undergone ACDF using either bACP (31 patients, 38 segments) or mACP (47 patients, 57 segments) instrumentation. The patients were followed up for a mean 13.5 ± 0.9 months (range 12-18 months) in the bACP group and 14.8 ± 1.5 months (range 14-22 months) in the mACP group. Clinical outcomes were determined according to scores on the visual analog scale (VAS), the modified Japanese Orthopaedic Association (mJOA) scoring system, and Odom's criteria. Radiological images were used to assess fusion rates, intervertebral height, Cobb's angle, and the width of prevertebral soft tissue. RESULTS Both VAS and mJOA scores were significantly improved at each follow-up in both groups. Excellent or good results according to Odom's criteria were achieved in 93.5% (29/31) of patients in the bACP group and 93.6% (44/47) of patients in the mACP group. At 6 months postoperatively, the fusion rate was 94.7% (36/38) in the bACP group and 96.5% (55/57) in the mACP group, but subsidence of the intervertebral space at the surgical level was more evident in the bACP group. Angulation, as measured by Cobb's angle, demonstrated obvious healing in both groups, while better maintenance was observed in the mACP group. The local inflammatory reaction was uneventful during follow-up. Dysphonia and dysphagia were observed in both groups during the follow-up. CONCLUSIONS The relatively comparable early clinical and radiographic outcomes and the overall acceptable complication rates for bACP and mACP use suggest that bACPs could be used as alternative instruments in ACDF. Mild graft resorption was noted without evidence of symptoms. However, the prospective efficacy of biodegradable instrumentation can only be elucidated with longer-term observation.

A Novel Shape Memory Plate Osteosynthesis for Noninvasive Modulation of Fixation Stiffness in a Rabbit Tibia Osteotomy Model

Nickel-titanium shape memory alloy (NiTi-SMA) implants might allow modulating fracture healing, changing their stiffness through alteration of both elastic modulus and cross-sectional shape by employing the shape memory effect (SME). Hypotheses: a novel NiTi-SMA plate stabilizes tibia osteotomies in rabbits. After noninvasive electromagnetic induction heating the alloy exhibits the SME and the plate changes towards higher stiffness (inverse dynamization) resulting in increased fixation stiffness and equal or better bony healing. In 14 rabbits, 1.0 mm tibia osteotomies were fixed with our experimental plate. Animals were randomised for control or induction heating at three weeks postoperatively. Repetitive X-ray imaging and in vivo measurements of bending stiffness were performed. After sacrifice at 8 weeks, macroscopic evaluation, µCT, and post mortem bending tests of the tibiae were carried out. One death and one early implant dislocation occurred. Following electromagnetic induction heating, radiographic and macroscopic changes of the implant proved successful SME activation. All osteotomies healed. In the treatment group, bending stiffness increased over time. Differences between groups were not significant. In conclusion, we demonstrated successful healing of rabbit tibia osteotomies using our novel NiTi-SMA plate. We demonstrated shape-changing SME in-vivo through transcutaneous electromagnetic induction heating. Thus, future orthopaedic implants could be modified without additional surgery.

A giant periosteal chondroma of the distal femur successfully reconstructed with synthetic bone grafts and a bioresorbable plate: a case report

Periosteal chondromas are rare benign cartilaginous tumors that arise adjacent to the cortex beneath the periosteum. These lesions are usually slow-growing and rarely exceed 3 cm in the greatest dimension. Here, we describe a 17-year-old boy who had a giant periosteal chondroma of the right distal femur, which was treated with intralesional resection and intensive curettage. In addition, we report a novel application of a bioresorbable plate in the management of the large bone defect after resection of a benign bone tumor.

Bioabsorbable instrumentation for single-level cervical degenerative disc disease: a radiological and clinical outcome study

Object

The authors present the radiological and clinical outcome data obtained in patients who underwent single-level anterior cervical discectomy and fusion (ACDF) for cervical spondylosis and/or disc herniation; bioabsorbable plates were used for instrumentation. The use of metallic plates in ACDF has gained acceptance as a stabilizing part of the procedure to increase fusion rates, but when complications occur with these devices, the overall effectiveness of the procedure is compromised. As a possible solution, bioabsorbable implants for ACDF have been developed. This study investigates the feasibility and radiological and clinical outcomes of the bioabsorbable plates for ACDF.

Methods

The radiological and clinical outcomes of 30 patients were investigated retrospectively. All patients presented with cervical radiculopathy or myelopathy and underwent single-level ACDF in which a bioabsorbable anterior cervical plate and an allograft bone spacer were placed at a level between C-3 and C-7. Radiological outcome was assessed based on the fusion rate, subsidence, and Cobb angle of the surgical level. Clinical outcome was determined by using a visual analog scale, the Neck Disability Index, and the Odom criteria.

Results

There were no intraoperative complications, and no hardware failure was observed. No signs or symptoms of adverse tissue reaction caused by the implant were seen. Two reoperations were necessary due to postoperative blood collections. The overall complication rate was 16.7%. After 6 months, radiographic fusion was seen in 92.3% of patients. Subsidence at 11.3 ± 7.2 months was 3.1 ± 5.8 mm (an 8.2% change over the immediately postoperative results), and the change in the sagittal curvature was –2.7 ± 2.7°. The visual analog scale score for neck and arm pain and Neck Disability Index improved significantly after surgery (p < 0.001). Overall at 19.5 months postoperatively, 83% of the patients had favorable outcomes based on the Odom criteria.

Conclusions

Absorbable instrumentation provides better stability than the absence of a plate but graft subsidence and deformity rates may be higher than those associated with metal implants. There were no device-related complications, but adverse late effects cannot be excluded. The fusion rate and outcome are comparable to the results achieved with metallic plates. The authors were satisfied with the use of bioabsorbable plates as a reasonable alternative to metal, avoiding the need for lifelong metallic implants.

Correlation of radiostereometric measured cervical range of motion with clinical radiographic findings after anterior cervical discectomy and fusion

STUDY DESIGN

Prospective clinical study.

OBJECTIVE

To evaluate the correlation between clinical radiographic findings and sagittal range of motion (ROM) measured using radiostereometric analysis (RSA) after anterior cervical discectomy and fusion (ACDF).

SUMMARY OF BACKGROUND DATA

Evaluation of fusion after ACDF continues to be difficult. Radiographic films including flexion/extension views are routinely used for this purpose. Unfortunately, routine radiographs are insensitive in demonstrating pseudarthrosis. RSA is an accurate technique that can be used in evaluation of segmental motion in vivo and can potentially be used in evaluation of spinal fusion.

METHODS

Sixteen patients who underwent multi-level ACDF were enrolled in this study. The procedure was performed in the routine fashion; cervical plates were utilized in each case. Intraoperatively, 3 to 5 tantalum beads were inserted into each vertebral body. At the 1-year follow-up period, sagittal ROM of the operated segments was measured with RSA. In addition, each segment was clinically evaluated for evidence of radiographic fusion by using a 3-point grading system (fused, uncertain, pseudarthrosis) and by measuring the interspinous widening on flexion/extension films. The correlation between the radiographic findings and RSA measured sagittal ROM was evaluated.

RESULTS

Fourteen 2-level and two 3-level procedures representing 31 motion segments were analyzed. The average sagittal ROM of all segments as measured by RSA was 1.3 +/- 1.4 degrees . The sagittal ROM of the segments with less than 2 mm of interspinous widening on clinical flexion/extension radiographs was measured at 1.1 degrees +/- 1.0 degrees with RSA, whereas the sagittal ROM of the segments with greater than 2 mm of interspinous widening was measured at 3.4 degrees +/- 2.9 degrees ; a significant correlation was noted between the 2-point grading method and the sagittal ROM (Pearson coefficient, r = 0.504, P = 0.004). Using the 3-point grading system, there were 20 levels graded as fused (0.8 degrees +/- 0.9 degrees ), 6 levels were graded as uncertain (1.7 degrees +/- 1.0 degrees ), and 4 levels were graded as pseudarthrosis (3.5 degrees +/- 2.7 degrees ). The pseudarthrosis group showed significantly greater motion than the fusion group (P = 0.005); a significant correlation was noted between the 3-point grading method and the sagittal ROM (Pearson coefficient, r = 0.561, P = 0.001).

CONCLUSION

In this study, we evaluated the utility of RSA in evaluating segmental motion after ACDF and demonstrated a significant difference between segments that demonstrated radiographic evidence of fusion when compared with segments that demonstrated evidence of pseudarthrosis. RSA appears to be a quantitative technique capable of assisting in the evaluation of fusion.

[Anterior cervical fusion in the lower cervical spine. Locked vs nonlocked screw plate, pure cancellous bone vs tricortical strut]

Physical alterations in cervical fusions endanger healing. Experimentally we determined less stability loss in fixations using cancellous bone grafts than in those using tricortical grafts. Four hundred eighty-five Patients underwent anterior cervical fusion, for a total of 700 Segments. Patients were divided into four groups: (1) nonlocked H plate with autogenous cancellous bone, (2) nonlocked H plate with autogenous tricortical graft, (3) locked cervical plate with tricortical graft, and (4) stand-alone cage with cancellous bone. Evaluations included X-ray and random CT scan examinations. Our results suggest that anterior cervical fusions using nonlocked H screw plate systems with pure autogenous cancellous bone grafts provide the fastest (6 weeks) and most secure bone healing (P=0.00001), whereas fixations using nonlocked or locked screw plate systems and tricortical autograft require prolonged healing and develop nonunions more frequently. Complete consolidation was achieved using stand-alone cages filled with pure autogenous cancellous bone, but bony healing was delayed due to the cage. Rate of nonunions were: groups 1 and 4 0%, and groups 2 and 3 4.5% and 21%, respectively.