**General Session: Cervical Motion Preservation**

**Presented by:** J.Y. Lazennec - View Audio/Video Presentation (Members Only)

**Author(s):**

J.Y. Lazennec(1), J.P. Rakover(2), O. Ricart(3), S. Ramare(2), M.A. Rousseau(4)

(1) Pitie Hospital UPMC, Orthopedic Surgery, Paris, France

(2) Clinique du Pre, Orthopedic Surgery, Le Mans, France

(3) Kirchberg Hospital, Orthopedic Surgery, Luxembourg, Luxembourg

(4) Beaujon Hospital, Orthopedic Surgery, Clichy, France

### Abstract

**Introduction:** The ESP prosthesis is a one-piece deformable but cohesive interbody spacer. The viscoelastic prosthesis achieves 6 degrees of freedom including vertical translation to provide shock absorption. The rotation center can vary freely during motion. The prosthesis geometry allows limited rotation and translation with resistance to motion aimed at avoiding overload of the posterior facets.

**Material and Methods:** Surgeries were performed by 2 senior surgeons in 46 women and 30 men. Average age was 42 (SD: 7). Average BMI was 24.2kg/m² (SD: 4.9). Clinical data and X-rays were collected at the preoperative time and at 60 months post-op. The analysis was performed by a single observer independent from the selection of patients and from the surgical procedure. We measured the ROM and the location of mean center of rotation of the implanted and adjacent levels (Spine View software).The MCR is considered to reflect the quality of movement of a segment; it is localized thanks its co-ordinates. X is expressed as a percentage of the length of the vertebral end plate, and Y as a percentage of the height of the posterior wall. The usual location of the MCR is in a circle, whose center is placed between 30 and 50% of the superior vertebral endplate, and whose diameter is 70% of the vertebral endplate size. According to the Tournier paper for normal discs (18 patients) X-CMR location is 39.4% for L5-S1,32,5% for L4-L5 and 24% for L3-L4.Y-CMR is 33,9% for L5-S1, 5,5% for L4-L5 and -2 % for L3-L4.

**Results:** We did not observe device-related complications. All clinical outcomes significantly improved. Globally the mean ROM was 6,3° (SD 3,2) at the implanted level, 6,7°(5,2) at above level , 7°(4,9) at below level. • Mean x-MCR value at the implanted level was 33.1%±20.8 % and mean y-MCR value -12,41% ±30.1%. • Mean x- MCR value at the above level was 25,7%± 30.1% and mean y-MCR value 16%±39.4%. • Mean x- MCR value at the below level were 31.1%±29.8 % and mean y-MCR value - 0,61%±46.8%. For L5-S1 disc replacements, the mean ROM was 6,1° (SD 4,7) at the implanted level and 7,6°(4,7) at above level. • Mean x-MCR value at the implanted level was 26.1%±31.5 % and mean y-MCR value -15,7%± 31,5%. • Mean x- MCR value at the above level was 36.8%±17.9% and mean y-MCR value -15%±33.9%. For L4-L5 disc replacements, the mean ROM was 6,9° (SD 4) at the implanted level, 7,5°(4,9) at above level , 8°(5,4) at below level. • Mean x-MCR value at the implanted level was 24.7%±29.2 % and mean y-MCR value -2,86%±26.2%. • Mean x- MCR value at the above level was 31.1%±20.9% and mean y-MCR value - 7,9 %±24.7%. Mean x- MCR value at the below level was 30,2±22,2 and mean y-MCR value - 0,61%±46.1%.

**Conclusion:** The concept of the viscoelastic ESP prosthesis is different from that of “first generation” disc implants. This study confirms the encouraging clinical and radiological results previously reported since the first cases implanted in 2004.Radiological results of the kinematic behavior seem promising especially because the MCR locations appear similar to those of the natural disc described in the literature.