Improved bone bonding of hydroxyapatite spacers with a high porosity in a quantitative computed tomography‐image pixel analysis: A prospective 1‐year comparative study of the consecutive cohort undergoing double‐door cervical laminoplasty. Issue 1 (3rd February 2020)

• Record Type: Journal Article
• Authors: Takeoka, Yoshiki; Yurube, Takashi; Maeno, Koichiro; Kanda, Yutaro; Tsujimoto, Ryu; Miyazaki, Kunihiko; Kakiuchi, Yuji; Miyazaki, Shingo; Zhang, Zhongying; Takada, Toru; Nishida, Kotaro; Doita, Minoru; Kuroda, Ryosuke; Kakutani, Kenichiro
• Is Part Of: JOR spine. Volume 3:Issue 1(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-02-03
• Subjects: bone bonding and absorption -- cervical spine -- computed tomography (CT) -- double‐door laminoplasty -- hydroxyapatite spacer -- porosity and pore size; Spine -- Diseases -- Periodicals; Spine -- Diseases -- Treatment -- Periodicals; Spine -- Wounds and injuries -- Periodicals; Orthopedics -- Periodicals; Electronic journal; Periodicals; 616.73005
• DOI: 10.1002/jsp2.1080
• Languages: English
• ISSNs: 2572-1143

Abstract

Abstract: Laminoplasty using hydroxyapatite (HA) spacers is widely performed in patients with cervical myelopathy. However, spacer dislocation is a critical complication caused by bone absorption and inadequate bone conductivity, and can result in dural damage and restenosis. We thus designed a prospective cohort study to clarify the feasibility of increased porosity HA spacers for double‐door laminoplasty by analyzing computed tomography (CT) images. Forty‐seven patients underwent cervical laminoplasty. Two different types of CERATITE HA spacer were used, either high porosity (50%) or low porosity (35%). These HA spacers were placed in an alternating manner into the laminae in each patient. In total, 85 high‐porosity (50%) HA spacers and 84 low‐porosity (35%) HA spacers were implanted. At postoperative 2 weeks, 3 months, 6 months, and 1 year, CT images were obtained. In both groups, the percentage of bone‐bonding boundary area of the HA spacer in contact with laminae and bone volume of the spinous process relative to the 2‐week value were calculated by a 3D and 2D CT‐image pixel analysis. The bone‐bonding ratio was significantly higher in high‐porosity (50%) than low‐porosity (35%) HA spacers at 3 months and thereafter (1 year, 69.3 ± 27.8% and 49.7 ± 32.9% respectively, P < .01). The bone volume in both groups significantly decreased with time (1 year, 73.2 ± 29.8% and 69.0 ± 30.4% respectively, P < .01), indicating bone absorption. This showed no significant difference between the HA spacers ( P = .15) but was higher in high‐porosity (50%) than low‐porosity (35%) HA spacers throughout the study period. Meanwhile, spacer breakage was found in 4.7% of high‐porosity (50%) HA spacers and 1.2% of low‐porosity (35%) HA spacers ( P = .37). In summary, high‐porosity (50%) HA spacers have the advantages of accelerated bone bonding and relatively decelerated bone absorption compared to low‐porosity (35%) HA spacers; however, possibly more frequent breakage of HA spacers with a high porosity (50%) requires careful, extended postoperative follow‐up. Abstract : Computed tomography (CT)‐image pixel‐based bone‐bonding and bone‐volume analysis was performed in high‐porosity (50%) and low‐porosity (35%) hydroxyapatite (HA) spacers for cervical laminoplasty. A, Helical CT scanning was performed at postoperative 2 weeks, 3 months, 6 months, and 1 year. B, Three‐dimensional (3D) images were reconstructed from the Digital Imaging and Communications in Medicine (DICOM®) data. C, Based on these 3D images, HA spacers were extracted. D, The gap between the inserted HA spacer and split spinous processes was extracted to determine the spacer‐bound area to the bone. E, The boundary between the HA spacer and bone was further extracted as the two‐dimensional (2D) image, pixel in which was counted. Thereafter, the ratio of spacer‐bone contact area was calculated as the bone‐bonding ratio to assess fusion between the spacer and spinous processes. F, The bone volume of the dorsal parts in the split spinous processes in contact with the spacer was measured to assess the progression of time‐dependent bone absorption around HA.