Tse-Yu Chen1, Wen-Hsien Chen2, Chung-Yuh Tzeng3, Chi-Wei Huang4, Chih-Chang Yang5, Hsien-Te Chen6, Chien-Chun Chang7, Cheng-Ying Lee8, Hsi-Kai Tsou9. 1. Neurological Institute, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China. Electronic address: terry78423@gmail.com. 2. Department of Radiology, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China; Department of Industrial Engineering and Enterprise Information, Tunghai University, Taichung, Taiwan, Republic of China. Electronic address: chenws.tw@gmail.com. 3. Department of Orthopedics, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China; Department of Medicinal Botanicals and Health Applications, Da-Yeh University, Changhua County, Taiwan, Republic of China. Electronic address: tcy0545@gmail.com. 4. Neurological Institute, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China. Electronic address: ty761kimo@gmail.com. 5. Neurological Institute, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China. Electronic address: asunbright@yahoo.com.tw. 6. Department of Sports Medicine, College of Health Care, China Medical University, Taichung, Taiwan, Republic of China; Department of Orthopedic Surgery, China Medical University Hospital, Taichung, Taiwan, Republic of China; Spine Center, China Medical University Hospital, Taichung, Taiwan, Republic of China. Electronic address: bonekid1@gmail.com. 7. Department of Orthopedic Surgery, China Medical University Hospital, Taichung, Taiwan, Republic of China; Spine Center, China Medical University Hospital, Taichung, Taiwan, Republic of China; Ph.D. Degree Program of Biomedical Science and Engineering, National Chiao Tung, University, Hsinchu, Taiwan, Republic of China. Electronic address: Ccchangmd@gmail.com. 8. Neurological Institute, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China. Electronic address: cklove5212@gmail.com. 9. Functional Neurosurgery Division, Neurological Institute, Taichung Veterans General Hospital, 1650 Taiwan Boulevard Sec. 4, Taichung, Taiwan 40705 Republic of China; Department of Rehabilitation, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli County, Taiwan, Republic of China; College of Health, National Taichung University of Science and Technology, Taichung, Taiwan, Republic of China. Electronic address: tsouhsikai@gmail.com.
Abstract
BACKGROUND CONTEXT: Cervical disc arthroplasty (CDA) is an innovative procedure launched in the early 2000s. Compared with anterior cervical discectomy and fusion, many studies show that CDA offers equivalent clinical outcomes while reducing secondary procedures and total cost. PURPOSE: We sought to determine the incidence of anterior bone loss after CDA and the related biomechanical effects. STUDY DESIGN/ SETTING: Retrospective chart review. PATIENT SAMPLE: Patients who underwent CDA with one level Bryan Disc (Medtronic SofamorDanek, Memphis, TN, USA) at one institution. OUTCOME MEASURES: Radiological measurements, including the extent of anterior bone loss, global alignment angle, shell angle, lordotic angle, mean degree of angle of the endplate with the horizontal line, global range of motion (ROM) and ROM of the index level were recorded. The grading of anterior bone loss of the index level was defined as Grade 0, no remodeling; Grade 1, spur disappearance or mild change in body contour; Grade 2, obvious bone regression with Bryan Disc exposure. METHODS: Anatomical measures and ROM were compared by grade of bone loss. RESULTS: Of the 121 patients included in the study, anterior bone loss was found in 53 (43.8%) on the upper adjacent level and 54 (44.6%) on the lower adjacent level. Twenty-nine patients (23.9%) had anterior bone loss in both levels. The majority of cases had Grade 1 anterior bone loss. Grade 2 bone loss was noted in the upper adjacent vertebra in only 5 patients and in 4 patients in the lower adjacent vertebra. Age, sex, operative level, and hybrid surgery had no effect on anterior bone loss. Most radiological assessments, including global alignment angle, lordotic angle, mean degree of angle of the endplate with the horizontal line, global ROM, and ROM of the index level, showed no correlation to anterior bone loss. Shell angle was found to be different in groups with or without remodeling in the upper adjacent level: 5.0 degreesin the Grade 0 group and 7.0 degrees in the Grade 1-2 group, p<.05. CONCLUSIONS: Many more patients than predicted had anterior bone loss. Increasing the shell angle of the artificial disc may increase the incidence of anterior bone loss after CDA. Further study of the biomechanics following CDA should help clarify the mechanisms at work.
BACKGROUND CONTEXT: Cervical disc arthroplasty (CDA) is an innovative procedure launched in the early 2000s. Compared with anterior cervical discectomy and fusion, many studies show that CDA offers equivalent clinical outcomes while reducing secondary procedures and total cost. PURPOSE: We sought to determine the incidence of anterior bone loss after CDA and the related biomechanical effects. STUDY DESIGN/ SETTING: Retrospective chart review. PATIENT SAMPLE: Patients who underwent CDA with one level Bryan Disc (Medtronic SofamorDanek, Memphis, TN, USA) at one institution. OUTCOME MEASURES: Radiological measurements, including the extent of anterior bone loss, global alignment angle, shell angle, lordotic angle, mean degree of angle of the endplate with the horizontal line, global range of motion (ROM) and ROM of the index level were recorded. The grading of anterior bone loss of the index level was defined as Grade 0, no remodeling; Grade 1, spur disappearance or mild change in body contour; Grade 2, obvious bone regression with Bryan Disc exposure. METHODS: Anatomical measures and ROM were compared by grade of bone loss. RESULTS: Of the 121 patients included in the study, anterior bone loss was found in 53 (43.8%) on the upper adjacent level and 54 (44.6%) on the lower adjacent level. Twenty-nine patients (23.9%) had anterior bone loss in both levels. The majority of cases had Grade 1 anterior bone loss. Grade 2 bone loss was noted in the upper adjacent vertebra in only 5 patients and in 4 patients in the lower adjacent vertebra. Age, sex, operative level, and hybrid surgery had no effect on anterior bone loss. Most radiological assessments, including global alignment angle, lordotic angle, mean degree of angle of the endplate with the horizontal line, global ROM, and ROM of the index level, showed no correlation to anterior bone loss. Shell angle was found to be different in groups with or without remodeling in the upper adjacent level: 5.0 degreesin the Grade 0 group and 7.0 degrees in the Grade 1-2 group, p<.05. CONCLUSIONS: Many more patients than predicted had anterior bone loss. Increasing the shell angle of the artificial disc may increase the incidence of anterior bone loss after CDA. Further study of the biomechanics following CDA should help clarify the mechanisms at work.