Novel nanohydroxyapatite/ polyamide-66 cage has lower subsidence rate after single-level anterior cervical discectomy and fusion

Zhimou Zeng et al conducted a study 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).

The hollow cylindrical nanohydroxyapatite/polyamide-66 cage (n-HA/PA66, Sichuan National Nano Technology Co., Ltd. Chengdu, Sichuan) is composed of nanohydroxyapatite and polyamide-66, and its biomechanical properties are found to match well with those of natural bone. The high n-HA content in the composites determines the favorable biocompatibility and bioactivity of the n-HA/PA66 cage. However, the n-HA/ PA66 cage has relatively high subsidence rates (10.6%) during long-term follow-up, which could lead to cervical kyphosis, neural foramen stenosis, and yellow ligament folds after surgery.

To decrease the incidence of subsidence, the morphology of the n-HA/PA66 was redesigned. The novel n-HA/PA66 cage is a horseshoe-shaped cage with a more suitable shape and larger bone graft volume than the hollow cylindrical n-HA/PA66 cage.

52 patients with novel n-HA/PA66 cages (Group A) and 55 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.

Key findings of the study were:

• 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.

The authors concluded that – “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.”

Further reading:

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

Zhimou Zeng, Ce Zhu et al

Journal of Orthopaedic Surgery and Research (2023) 18:54

https://doi.org/10.1186/s13018-023-03521-1