Cervical Footprint Anthropometry in Indian Population: Implications on Design of Artificial Disc Replacement Devices

STUDY DESIGN: Cross-sectional study. PURPOSE: To accurately measure the dimensions of cervical endplates based on computed tomography (CT) scans in Indian population and assess accuracy of match with currently available cervical disc prostheses. OVERVIEW OF LITERATURE: The dimensions of currently available cervical disc replacement implants are based on early published geometrical measurements of vertebrae endplates for Caucasian population. To author's knowledge, similar study has not been published for patients from Indian subcontinent. METHODS: CT scans of cervical spine of patients from Indian subcontinent were collected and reviewed. Seventy patients (54 men and 16 women; aged 18-56 years with average of 37 years) who underwent CT scans of cervical spine were included in study. 3D CT scans of sub axial cervical spine (C3 to C7) were analyzed. The anterior-posterior (AP) and central mediolateral (CML) dimensions of superior and inferior endplates from C3 to C7 were measured using digital measuring system. RESULTS: A total of 560 endplates of 70 patients were included in the study. The AP diameter of cervical endplates ranged from 0.87 to 2.47 cm. The CML diameters ranged from 0.84 to 2.98 cm. For levels C3/C4 and C4/C5 for AP dimension Prestige-LP (90.5%) and Prodisc-C (89%) discs showed higher percentage of matching than Discover discs (58.5%). For CML diameter, Prestige-LP (69.5%), Prodisc-C (70%) and Discover (39.5%) discs showed almost similar matching with measured endplates. For levels C5/C6 and C6/C7 for AP dimension, Prestige-LP (67.25%), Prodisc-C (49.35%) and Discover (51.5%) discs showed similar matching. For CML diameter Prestige-LP (32%), Prodisc-C (27.5%) and Discover (42.2%) discs showed poor matching with measured endplates. CONCLUSIONS: This study indicates need for redesign of cervical disc prostheses to match Indian patients. The collected anthropometric dimensions from this study may be used to design and develop indigenous artificial total disc replacement prosthesis and even cervical cages in India. With the present study being a small pilot study, the authors recommend anthropometric CT measurements in larger number of Indian patients in order to validate footprint dimensions for designing better-matched prosthesis.

A Broken Drill-bit Fragment Causing Severe Radiating Pain after Cervical Total Disc Replacement: A Case Report

This is a case report of a 38-year-old man with severe radiating pain on upper extremity after cervical total disc replacement (TDR). We faced an unusual complication that has not been reported yet. He underwent cervical TDR for left central disc protrusion on C5-6. After the surgery, preoperative symptom disappeared. However, at postoperative 1 year, he complained severe right-sided radiating pain that had a sudden onset. On postoperative X-ray, a metal fragment which seemed like a broken drill bit was shown within the spinal canal. To remove that, right-sided anterior microforaminotomy on C5-6 was performed and the metal fragment was removed successfully. After that, anterior fusion was done because the motion of the artificial disc was minimal and the removed structure seemed to attenuate stability during cervical motion. The operation resulted in prompt symptomatic relief. During cervical TDR, particular attention should be paid to the procedures that require using drill-bits.