The effect of interlaminar Coflex stabilization in the topping-off procedure on local and global spinal sagittal alignment

Abstract

Purpose: To investigate the effect of interlaminar Coflex stabilization (ICS) at various segments in the topping-off procedure on local and global spinal sagittal alignment.

Methods: Eighty-nine consecutive patients with degenerative lumbar spinal stenosis (DLSS) who underwent ICS and transforaminal lumbar interbody fusion (TLIF) were retrospectively reviewed. They were divided into Group A (L4-L5 ICS + L5-S1 TLIF), Group B (L3-L4 ICS + L4-S1 TLIF), and Group C (L2-L3 ICS + L3-S1 TLIF) according to their fusion levels. The measured local sagittal parameters included the implanted segmental angle (ISA), intervertebral disc angle (IDA), intervertebral foreman height (IFH), and disc height. The assessed global sagittal parameters included thoracic kyphosis, lumbar lordosis (LL), the fused segment angle (FSA), the sacral slope, the pelvic tilt, pelvic incidence, and the sagittal vertical axis. The Oswestry Disability Index (ODI) and visual analog scales (VAS) were recorded to evaluate the clinical outcomes.

Results: Regarding the local alignment parameters, the ISA and IDA decreased immediately after surgery in Groups A and B, followed by an increase at the last follow-up (all, P < 0.05). Conversely, the IFH of Groups A and B first increased after surgery and then decreased to approximately the original value (all, P < 0.05). No significant differences were evident between the local sagittal parameters at different time points in Group C. Regarding the global sagittal profiles, the LL and FSA exhibited a significant postoperative increase (both at P < 0.05) in all the groups. All three groups displayed significant improvements in the ODI, VAS-back pain, and VAS-leg pain. Furthermore, 4.5% (4/89) of the patients exhibited radiographic adjacent segment degeneration (ASD) at the last follow-up.

Conclusion: ICS during topping-off surgery led to a temporary loss of local lordosis, especially in the lower lumbar segment, while the intervertebral space realigned after middle-term follow-up. The topping-off procedure with ICS is a feasible and promising surgical option of DLSS since it reduces fusion levels and prevents ASD development.

Keywords: Coflex; Degenerative lumbar spinal stenosis; Interlaminar dynamic stabilization; Sagittal spinal alignment; Topping-off procedure.

Fig. 1

Schematic diagram of interlaminar Coflex insertion

Fig. 2

Radiographic evaluation of the spinal sagittal parameters. A SVA indicates sagittal vertical axis, TK indicates thoracic kyphosis, LL indicates lumbar lordosis, SS indicates sacral slope, PI indicates pelvic incidence, PT indicates pelvic tilt. B PDH indicates posterior disc height, ADH indicates anterior disc height. C IFH indicates intervertebral foramen height. D FSA indicates fused segment angle, IDA indicates intervertebral disc angle. E ISA indicates implanted segment angle

Fig. 3

Illustration of the variations in lordosis distribution index (LDI) of the implanted or fused segment in three groups after surgery. A Variations in LDI of the implanted segment (left) and the fused segment (right) in Group A. B Variations in LDI of the implanted segment (left) and the fused segment (right) in Group B. C Variations in LDI of the implanted segment (left) and the fused segment (right) in Group C

Fig. 4

A 69-year-old female patient underwent L4-L5 ICS and L5-S1 TLIF with a 15-month follow-up. A Preoperative ISA, FSA, and LL was 14.5°, 18.9°, and 30.2°, respectively. B ISA decreased from 14.5° to 9.6° after surgery, while postoperative FSA and LL increased to 21.2° and 32.5°, respectively. C At the last follow-up, the ISA, FSA, and LL was 15.4°, 20.8°, and 36.8°, respectively

Fig. 5

A 68-year-old male patient underwent L3-L4 ICS and L4-S1 TLIF with a 16-month follow-up. A Preoperative ISA, FSA, and LL was 6.7°, 18.1°, and 27.7°, respectively. B ISA decreased from 6.7° to 1.5° after surgery, while postoperative FSA and LL increased to 22.1° and 29.7°, respectively. C At the last follow-up, the ISA, FSA, and LL was 3.6°, 22.7°, and 30.5°, respectively

Fig. 6

A 73-year-old female patient underwent L2-L3 ICS and L3-S1 TLIF with a 15-month follow-up. A Preoperative ISA, FSA, and LL was 4.4°, 33.8°, and 40.1°, respectively. B Postoperative ISA, FSA, and LL was 3.4°, 39.9°, and 47.4°, respectively. C At the last follow-up, the ISA, FSA, and LL was 4.2°, 40.6°, and 46.4°, respectively