Long-term outcomes of the nano-hydroxyapatite/polyamide-66 cage versus the titanium mesh cage for anterior reconstruction of thoracic and lumbar corpectomy: a retrospective study with at least 7 years of follow-up

BACKGROUND: The nano-hydroxyapatite/polyamide-66 (n-HA/PA66) cage is a biomimetic cage with a lower elastic modulus than the titanium mesh cage (TMC). This study aimed to compare the long-term outcomes of the n-HA/PA66 cage and TMC in the anterior reconstruction of thoracic and lumbar fractures. METHODS: We retrospectively studied 113 patients with acute traumatic thoracic or lumbar burst fractures, comprising 60 patients treated with the TMC and 53 treated with the n-HA/PA66 cage for anterior reconstruction following single-level corpectomy. The radiographic data (cage subsidence, fusion status, segmental sagittal alignment) and clinical data (visual analogue scale (VAS) for pain and Oswestry Disability Index (ODI) for function) were evaluated preoperatively, postoperatively, and at final follow-up after a minimum 7-year period. RESULTS: The n-HA/PA66 and TMC groups had similar final fusion rates (96.2% vs. 95.0%). The cage subsidence at final follow-up was 2.3 ± 1.6 mm with subsidence of more than 3 mm occurring in 24.5% in the n-HA/PA66 group, which was significantly lower than the respective values of 3.9 ± 2.5 mm and 58.3% in the TMC group. The n-HA/PA66 group also had better correction of the bisegmental kyphotic angle than the TMC group (7.1° ± 7.5° vs 1.9° ± 8.6°, p < 0.01), with lower loss of correction (2.9° ± 2.5° vs 5.2° ± 4.1°, p < 0.01). The mean ODI steadily decreased after surgery in both groups. At final follow-up, the ODI and VAS were similar in the TMC and n-HA/PA66 groups. CONCLUSIONS: The n-HA/PA66 cage is associated with excellent radiographic fusion, better maintenance of the height of the fused segment, and better correction of kyphosis than the TMC during 7 years of follow-up after one-level anterior corpectomy. With the added benefit of radiolucency, the n-HA/PA66 cage may be superior to the TMC in anterior reconstruction of thoracic or lumbar fractures.