Risk factors for high-grade heterotopic ossification after single-level cervical disc replacement with Prestige LP disc

English Keywords:Cervical disc replacement  Heterotopic ossification  Risk factor  Sagittal alignment

English Abstract:

  【Abstract】 Objectives: To evaluate the risk factors of high-grade heterotopic ossification(HO) after single-level cervical disc replacement with Prestige LP disc. Methods: 61 patients(24 males and 37 females) underwent single-level Prestige LP cervical disc replacement from February 2008 to December 2016 were retrospectively included in this study. The mean age was 43.6±7.8 (26-63) years old. The clinical data (such as Japanese Orthopedic Association score and visual analogue score) were collected before surgery and at the last follow-up. Radiological data including cervical sagittal alignment parameters (C2-C7 cervical lordosis, segmental lordosis, disc angle, and C2-C7 sagittal vertical axis), disc height index at the surgical level, C2-C7 range of motion, and segmental range of motion at the surgical level were collected before surgery and at 3-day, 3-month, 12-month and at the last follow-up after surgery. McAfee classification system was used to evaluate the grade of heterotopic ossification. Patients were divided into high-grade HO group (group A, McAfee grade Ⅲ-Ⅳ) and non high-grade HO group (group B without HO and McAfee gradeⅠ-Ⅱ). Student t-test and chi-square test were used to evaluate the difference between the two groups. Paired t-test was used to compare preoperative and post-operative clinical outcomes. Implant size was analyzed using the rank sum test. Univariate logistic regression analysis was used to assess the risk factors for high-grade HO. Results: The clinical results of both groups were significantly improved. There was no significant difference in the improvement of clinical results between the two groups. There was no obvious impact of the implant size on the development of high-grade HO. The mean follow-up time for gourp A and group B was 59.7±28.4m and 47.6±20.6m respectively, the difference was not statistically significant(P=0.097). For the motion function, the global range of motion before surgery for group A and group B was 47.3°±15.4° and 54.1°±15.1° respectively, but the difference was not statistically significant(P=0.168). The segmental range of motion at the surgical level before surgery for group A and group B was 8.7°±4.7° and 11.1°±4.6° respectively, but the difference was not statistically significant(P=0.106). For the cervical sagittal alignments, the C2-C7 cervical lordosis at the 3-month follow-up for group A and group B was 2.8°±9.4° and 10.9°±10.2° respectively, and there was significant difference between two groups(P=0.015). The C2-C7 SVA at the 3-month follow-up for group A and group B was 21.7±8.8mm and 16.2±7.3mm, and and there was significant difference between two groups(P=0.029). Conclusions: Poor cervical sagittal alignment in the early period after surgery could increase the risk of high-grade HO after single-level Prestige LP cervical disc replacement.