[Effectiveness of nano-hydroxyapatite/polyamide-66 Cage in interbody fusion for degenerative lumbar scoliosis]

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.

Efficacy of NHP66 Bioactive Cage on Patients with Cervical Spine Injury in Short-Track Speed Skating

Background

Short-track speed skating (STSS) is an extreme sport in pursuit of extreme speed and explosive force. In such a sport, once athletes fall down, they are susceptible to serious cervical spine injury (CSI) under the inertia of high-velocity movement. Nanohydroxyapatite/polyamide 66 (NHP66) bioactive cage is a high-tech product of nanotechnology in the medical field in recent years. With a structure similar to that of human cortical bone, NHP66 bioactive cage has extremely high toughness and strength, which tailors to the needs of STSS.

Objective

This study mainly analyzed the therapeutic effect of NHP66 on patients with CSI in STSS, aiming to provide new opportunities for the treatment of this patient population.

Methods

A total of 51 patients with CSI treated in our hospital were enrolled, including 19 cases of short-track speed skaters (observation group) and 32 cases of car accidents, falls from heights, or collision injuries (control group). The relevant surgical indicators (operation time, intraoperative blood loss, etc.), the incidence of adverse reactions, the Cobb angle of cervical lordosis before and after surgery, and the fusion segment height of the cage were observed and compared between the two groups. Postoperative pain was evaluated by the visual analog scale (VAS), improvement of spinal cord injury was assessed by the American Spinal Cord Injury Association (ASIA) Impairment Scale, and bone fusion, bone subsidence, and other motor functions were assessed by the Japanese Orthopaedic Association (JOA) score rating system.

Results

The operation time, intraoperative blood loss, and incidence of adverse reactions in the observation group were significantly lower than those in the control group. The Cobb angle of cervical lordosis and the fusion segment height of cage increased significantly higher in both groups after surgery. In addition, the VAS scores of the observation group 2 h and 3 d after operation were significantly lower than those of the control group. In terms of improvement of spinal cord injury, ASIA and JOA scores in the observation group were significantly higher than those before treatment and in the control group. There was no significant difference in bone fusion activity between the two groups.

Conclusions

In this study, it is found through experiments that NHP66 has higher safety and application value than autogenous iliac bone, confirming that NHP66 can achieve significant results as a cage for anterior cervical decompression and iliac bone graft fusion and internal fixation in short-track speed skaters after CSI.

Risk Factors and Scoring System of Cage Retropulsion after Posterior Lumbar Interbody Fusion: A Retrospective Observational Study

Objective

To investigate risk factors of cage retropulsion after posterior lumbar interbody fusion (PLIF) in China and to establish a scoring system of cage retropulsion.

Methods

The retrospective analysis was based on two hospital databases. The medical data records of posterior lumbar interbody fusion with cage retropulsion were selected from August 2009 to August 2019. Inclusion and exclusion criteria were set in advance. Risk factors including patients' baseline demographics (age, gender, operation diagnosis time difference), preoperative neurological symptoms, whether the fusion involves single or double segments, screw type, intraoperative compression, preoperative bone mineral density, whether there are neurological symptoms before surgery, whether there is urine dysfunction before surgery, disease type, complete removal of the endplate, and patient's education level. The research endpoint was the retropulsion of fusion cages. The Kaplan–Meier (K‐M) method was used to analyze potential risk factors, and multivariate Cox regression was used to identify independent risk factors (P < 0.05). The Statistical Package for the Social Sciences (version 22.0; SPSS, IBM, Chicago, IL, USA) software was used for statistical analysis, and univariate analysis was used to screen out the factors related to cage retropulsion. All independent risk factors were included to predict the survival time of the retropulsion of cage.

Results

This study included a total of 32 patients with PLIF between 2009 to 2019. All patients were residents of China. Univariate analysis showed that there were 13 patients over 60 years old and 19 patients under 60 years old. There were 20 male patients and 12 female patients. The surgical diagnosis time was seven patients within 1 month, 17 patients within 1 to 3 months, and eight patients over 3 months. The disease type was 18 cases of lumbar disc herniation, 10 cases of lumbar spinal stenosis, four cases of lumbar spondylolisthesis. The fusion segment was 18 cases of single segment, 14 cases of double segment. The intraoperative compression was seven cases of compression, 25 cases of no compression. The preoperative bone mineral density was 10 cases of low density, 18 cases of normal, four cases of osteoporosis. The screw type was 27 cases of universal screw, five cases of one‐way screw. Preoperative neurological symptoms were found in 25 cases and not in seven cases. Preoperative urination dysfunction occurred in 8 cases, whereas 24 cases did not have this dysfunction. The endplate was completely removed in 10 cases and not in 22 cases. Education level was nine cases of primary school education, 10 cases of secondary school, 13 cases of university level. Cox regression analysis showed that intraoperative pressure (hazard ratio [HR] = 4.604, P = 0.015) and complete removal of the endplate (HR = 0.205, P = 0.027) are associated with the time of cage retropulsion. According to the HR of each factor, the scoring rules were formulated, and the patients were divided into the low‐risk group, moderate‐risk group, and high‐risk group according to the final score. The three median survival times of the three groups were 66 days in the low‐risk group, 55 days in the moderate‐risk group, and 45 days in the high‐risk group, with statistical significance (P < 0.05).

Conclusion

Intraoperative pressure and complete removal of the intraoperative endplate can be helpful to evaluating the expected time of cage retropulsion in patients with PLIF, and this clinical model guided the selection of postoperative prevention and follow‐up treatment.

Single approach to double-channel core decompression and bone grafting with structural bone support for treating osteonecrosis of the femoral head in different stages

BACKGROUND

We created a novel method-single approach to double-channel core decompression and bone grafting with structural bone support (SDBS)-to treat early-stage osteonecrosis of the femoral head (ONFH) by improving the Phemister technique. This study aimed to evaluate the results of SDBS for early-stage ONFH.

METHODS

Altogether, 53 patients (73 hips) were treated using SDBS during 2016-2018. Bilateral (20 patients) and unilateral (33 patients = 18 left hips, 15 right hips) ONFH was diagnosed. According to the Association Research Circulation Osseous classification stages, the femoral heads were staged as IIB (n = 15), IIC (n = 19), IIIA (n = 34), IIIB (n = 4), and IIIC (n = 1). The Harris hip score was used to evaluate the hips' clinical function, computed tomography to evaluate subchondral fractures, and plain radiography to assess the extent of femoral head collapse.

RESULTS

The average follow-up was 20.71 ± 6.65 months (6-36 months). At the patients' last follow-up, 4 hips were found to require arthroplasty. Thus, the overall femoral head survival rate was 94.52% (69/73). Also, the overall Harris score (84.44 ± 14.57) was significantly higher than that preoperatively (77.67 ± 14.37) (P = 0.000). The combined excellent and good rate (76.71%) was significantly higher than that preoperatively (38.36%) (P = 0.000). Imaging showed that 16 femoral heads had some ONFH progression. The average length of stay was 6.15 ± 0.86 days. The average incision measured 2.69 ± 0.30 cm. Intraoperative blood loss was 61.20 ± 4.81 ml. There were no complications during or after the operation.

CONCLUSION

SDBS is an effective method for treating early-stage ONFH. It is a hip-preserving surgical approach to slow/prevent ONFH progression.