Outcomes comparison between novel hydroxyapatite enhanced polyetheretherketone and titanium implants after anterior lumbar interbody fusion.

Background: Interbody implants have evolved to reduce the risk of nonunion with polyetheretherketone (PEEK) and subsidence with titanium devices. Two novel anterior lumbar interbody fusion (ALIF) implants, hydroxyapatite (HA) infused PEEK (HA PEEK) and titanium alloy with microtextured HA infused surface [titanium hydroxyapatite (TiHA)] may overcome these inherent risks. The primary objective of this study was to compare subsidence and fusion rates between HA PEEK and TiHA implants. Secondarily, reoperation rates and changes in patient reported outcomes were compared. Methods: In this multicenter retrospective analysis, data was extracted for adult circumferential ALIF ≤3 levels using HA PEEK or TiHA implants. Primary outcomes included rates of subsidence at 12 months and fusion at 6 and 12 months. Secondary outcomes included reoperation rates up to 12 months and changes in ODI and VAS back pain scores at 12 months. Fusion and subsidence were evaluated using an automated, computer vision-based analysis of radiographs. Fusion was defined as <3° of angular motion and subsidence was defined as ≥2 mm of disc space height loss. Analysis compared outcomes between implant groups to test for differences. Results: Of 181 patients (48.1% HA PEEK, 51.9% TiHA), 273 levels were treated, 47.8% of patients were males, and the median age was 55 years. At 6 months, the majority of levels were fused in both groups (94.2% HA PEEK, 99.3% TiHA, P=0.04). Fusion at 6 months was strongly predictive of 12-month fusion (92% HA PEEK, 98% TiHA, P=0.02). At 12 months, subsidence was minimal in both groups (4.1% HA PEEK, 0.7% TiHA, P=0.10). No difference was found in reoperation rates between implant groups (9% HA PEEK, 11% TiHA, P=0.10). Reduction in ODI scores (-29.0 HA PEEK, -22.7 TiHA, P=0.049) and VAS back pain scores (-40 HA PEEK, -25 TiHA, P=0.02) trended better in the HA PEEK group at 12 months. Conclusions: Surface-enhanced PEEK and titanium ALIF implants demonstrated high fusion rates, low rates of subsidence and reoperation, and clinically meaningful improvements in disability and back pain at 12 months. These results suggest that modern surface-enhanced interbody implants may mitigate the historical nonunion risk of untreated PEEK and subsidence risk of untreated titanium, allowing implant selection to be guided by surgeon preference and case-specific factors rather than performance.