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

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.

Laminoplasty in Motion: Evolving Techniques and Complications

“…Union rates have been documented at 93.8% for autologous spacers, 51% for allograft spacers, and 30 to 75% for hydroxyapatite spacers. 31,34,35,41,42 Union rates were higher with the use of high-porosity hydroxyapatite spacers compared with lowporosity spacers. 41 Metal Plates/Hinge Fracture Plates More recently, a variety of laminoplasty plate implants have been developed to improve laminoplasty stabilization.…”

“…31,34,35,41,42 Union rates were higher with the use of high-porosity hydroxyapatite spacers compared with lowporosity spacers. 41 Metal Plates/Hinge Fracture Plates More recently, a variety of laminoplasty plate implants have been developed to improve laminoplasty stabilization. O'Brien et al first described the technique in 1996 using a repurposed maxillofacial titanium miniplate, which functioned to maintain the laminoplasty door 43 Several studies have shown that miniplate constructs confer equivalent or improved clinical and radiographic outcomes compared with plateless techniques.…”

Changes of laminar angle in cervical double-door laminoplasty -Comparison of conventional method and suture anchor method using computed tomography images

“…The opened lamina is secured with sutures attached to the deep fascia of the paraspinal muscles in the conventional LAMP, but the sutures may come off or loosen during the follow-up period time, which prevents proper laminar opening [10]. Hence, miniplates [11], hydroxyapatite spacers [12], or suture anchors [13] have been developed thus far.…”