Does the sizing of current cervical disc arthroplasty systems match Chinese cervical anatomic dimensions?

The Impact of Endplate Coverage on Heterotopic Ossification Following Cervical Disc Replacement: A Systematic Review and Meta Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

Describe the impact of endplate coverage on HO in cervical disc replacement (CDR).

SUMMARY OF BACKGROUND DATA

CDR is a motion-sparing alternative to anterior cervical discectomy and fusion. However, the high prevalence of heterotopic ossification threatens to diminish range of motion and limit this benefit associated with CDR.

MATERIALS AND METHODS

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. EMBASE and PubMed databases were queried. Results were deduplicated and screened. Relevant studies were included. All metrics that were reported in ≥3 studies were aggregated for analysis. SPSS was used to perform the meta-analysis.

RESULTS

A total of 10 studies were included in the systematic review. Endplate coverage was assessed using a wide variety of measurements, including anteroposterior implant depth (ID), endplate depth (ED), exposed endplate depth (EED), implant depth to endplate depth ratio (ID:ED), EED to ED ratio (EED:ED), implant width (IW) to endplate width (EW) ratio (IW:EW), and the implant area (IA) to endplate area (EA) ratio (IA:EA). No evidence has linked ID (three studies) to HO. Mixed evidence has linked ID:ED (3/5) and IW:ED (1/2) to HO. All available evidence has linked ED (2), EED (4), EED:ED (2), and IA:EA (1) to HO. In our meta-analysis, ID was not found to be a significant risk factor for HO. However, EED and ID:ED were found to be significant risk factors for HO formation.

CONCLUSIONS

Exposed endplate, especially as assessed by EED and ID:ED, is a significant risk factor for HO. Surgeons should focus on preoperative planning and intraoperative implant selection to maximize endplate coverage. While optimizing technique and implant selection is crucial, improved implant design may also be necessary to ensure that appropriate implant-endplate footprint matching is possible across the anatomic spectrum.

The footprint mismatch of cervical disc arthroplasty comes from degenerative factor besides ethnic factor

A mismatch in footprints of cervical total disc arthroplasty (CTDA) implants occasionally occurred in Asian population and it had been attributed solely to ethnic factor. Yet, cervical degeneration process may play a role. Our purpose was to compare the cervical vertebra morphometric data with and without degeneration. The study included patients with CT scans of cervical spine from our hospital between January, 2019, and September, 2021. The total cervical degenerative index (TCDI) of each patient were collected by adding CDI score for 5 disc-levels. Patients were categorized into normal (TCDI 0-5) and degeneration groups (TCDI 6-60). Various measurements of the C3-C7 vertebral body and endplate were taken. Forty-nine patients in the normal group and 55 in the degeneration group were included. No significant difference was noted in gender, BH, BW, or BMI except age and TCDI (p < .001). During degeneration, disproportional endplate size changes were observed, with an increment ratio of 12-20% in the anteroposterior and 5-17% in the mediolateral plane throughout C3-C7, while vertebral body height remained constant. In conclusion, degeneration process, besides ethnic factor, causes the endplate size and shape mismatch. This information can help spine surgeon choose appropriate implants in CTDA surgery.

Measurement of anatomical parameters of anterior transpedicular root screw intervertebral fusion system of cervical spine

OBJECTIVE

This study aims to investigate the feasibility of the anterior transpedicular root screw (ATPRS) intervertebral fusion system for the cervical spine and provide a basis for the design of the ATPRS intervertebral fusion system.

METHODS

A total of 60 healthy adult cervical spine CT images examined from our hospital were selected, including 30 males and 30 females, with an average age of 39.6 ± 4.8 years. The image data was imported into Mimics 21.0 software in DICOM format for 3D model reconstruction. Simulated screw insertion was performed on both sides of the midline of the intervertebral space. The entry point (P1) was determined when the upper and lower screw paths did not overlap. When the screw was tangent to the medial edge of the Luschka joint, the insertion point was determined as the entry point (P2). Measurements were taken and recorded for the following parameters: distance from the screw entry point to the midline of the intervertebral space (DPM), the simulated screw length, inclination angle, cranial/caudal tilted angle, the anterior-posterior (AP) and mediolateral (ML) diameters of the cervical intervertebral space, the heights of the anterior, middle, and posterior edges of the cervical intervertebral space, and the curvature diameter of the lower end plate of the cervical vertebral body. Statistical analysis was performed on the measurement results.

RESULTS

The screw entry area (P1P2) showed an increasing trend from C3-C7 in both male (2.92-6.08 mm) and female (2.32-5.12 mm) groups. There were statistical differences between men and women at the same level (P < 0.05). The average screw length of men and women was greater than 20 mm, and the upper and lower screw lengths showed an increasing trend from C3 to C7. In the area where screws could be inserted, the range of screw inclination was as follows: male group upper screw (47.73-66.76°), lower screw (48.05-65.35°); female group upper screw (49.15-65.66°) and lower screw (49.42-63.29°); The range of cranial/caudal tilted angle of the screw was as follows: male group upper screw (32.06-39.56°), lower screw (29.12-36.95°); female group upper screw (30.97-38.92°) and lower screw (27.29-37.20°). The anterior-posterior diameter and mediolateral diameter of the cervical intervertebral space showed an increasing trend from C3 to C7 in both male and female groups. The middle height (MH) of the cervical intervertebral space was greater than the anterior edge height (AH) and posterior edge height (PD), with statistical differences (P < 0.05).

CONCLUSIONS

Through the study of CT images of the cervical spine, it was determined that the ATPRS intervertebral fusion system has a feasible area for screw insertion in the cervical intervertebral space.