Analysis of the Postoperative Absorption Process of Unsintered Hydroxyapatite Particles/Poly L-Lactide Composite Device (OSTEOTRANS MX®) for Facial Bone Fractures in 13 Cases

INTRODUCTION AND PURPOSE: Absorptive devices are often used to treat facial bone fractures in Japan. Few reports have investigated whether the plate used was absorbed.¹ We used the OSTEOTRANS MX^® (Takiron Co., Ltd.) in 13 patients with facial bone fractures. In patients in whom the OSTEOTRANS MX^® has been used, it takes 5-6 years until absorption is complete, and then, the device is no longer visible on computed tomography (CT) scans; however, some patients had the device removed due to infection.² We describe the decomposition behavior of the extracted plate and screw from patients in whom removal was necessary.

 

METHODS: Between August 2008 and June 2014, the OSTEOTRANS MX^® was used in 78 patients with facial bone fracture or posterior malignant tumor reconstruction. Among them, 13 patients (16.7%) required plate removal due to complications from postoperative plate infection. Image observation with a scanning electron microscope (SEM) and elemental analysis by energy dispersive X-ray spectrometry (EDX) were performed. The viscosity average molecular weight and crystallinity were retrospectively measured by an automatic viscometer and differential scanning calorimetry (DSC), respectively.

 

RESULTS: Age at surgery ranged from 14 to 80 years (average, 52±20.1 years); there were 8 men and 5 women. The OSTEOTRANS MX^® was removed at the shortest duration, 1 month postoperatively, and at the longest duration, 4 years 6 months after the first operation (average, 16±16.1 months). We did not observe a patient in whom the device was completely absorbed or replaced with the bone, or its shape disappeared. The molecular weight of poly l-lactide (PLLA) decreased with time. The unsintered hydroxyapatite (u-HA) was released from the plate, which created a pore, and the decomposition generally progressed smoothly based on the measurement of crystallinity by DSC.

 

CONCLUSIONS: According to the elemental analysis by EDX, the u-HA content was low in the hypodense part, as confirmed by the SEM, and this part had many pores from which u-HA was released. We infer that the u-HA detached from the plate’s fine pores, and it adhered to the bone on the plate. Additionally, we presume that the bone tissue did not migrate to the plate due to the force during plate removal. Absorption and bone substitution progressed favorably where the plate was in close contact with the cortical bone compared with where the plate was not in close contact with the cortical bone. Skill may be necessary to close and fix the plate. Although PLLA is absorbed with time, the u-HA requires more time for bone replacement; in many cases, the u-HA remains visible on images for at least up to 5-6 years. Follow-up observation is needed.

 

References

1. Hayashi M, Muramatsu H, Sato M, et al. Surgical treatment of facial by using unsintered hydroxyapatite particles/poly L-Lactide composite device (OSTEOTRANS MX(®)): a clinical study on 17 cases. J Craniomaxillofac Surg. 2013;41(8):783-788.
2. Shikinami Y, Matsusue Y, Nakamura T. The complete process of bioresorption and bone replacement using devices made of forged composites of raw hydroxyapatite particles/ poly l-lactide (F-u-HA/PLLA). Biomaterials. 2005;26(27):5542-5551.