Georg Schmorl Prize of the German Spine Society (DWG) 2017: correction of spino-pelvic alignment with relordosing mono- and bisegmental TLIF spondylodesis.

Introduction: A balanced ratio of the main parameters of lumbar lordosis (LL) and pelvic incidence (PI) has high clinical relevance. A postoperative mismatch of LL and PI has been described in the literature to be associated with an inferior clinical outcome and higher postoperative revision rates. The aim of this retrospective, radiological study is to evaluate the magnitude of relordosing in mono-/bisegmental TLIF spondylodesis affecting the spino-pelvic alignment and the main contributing factors.

Materials And Methods: 164 patients (pat.) underwent monosegmental (n = 115, G1) and bisegmental (n = 49, G2) TLIF spondylodesis, respectively, for different indications in 2016 in our hospital. Pelvic incidence, lumbar lordosis (preop., postop., 3 months postop.), implanted cage sizes, and the use of additional Smith-Petersen osteotomies were analysed retrospectively. Patients were divided into three groups depending on match of LL/PI (PI-LL < 10° green, PI-LL = 10-20° yellow, PI-LL > 20° red). Furthermore, a differentiation was made between surgeons with more than or less than 10 years of spinal surgery experience, respectively.

Results: 29.6% of pat. in G1 and 16.3% in G2 showed a highly pronounced preoperative spino-pelvic mismatch (red). A high grade of mismatch (yellow) between LL/PI was seen in 29.6% in G1 and in 38.8% in G2. The remaining patients already had a balanced ratio of LL/PI (green). Through relordosing TLIF the LL could be corrected significantly (p < 0.05). Therefore, the number of patients with a balanced sagittal alignment (green) increased from 40.9% preop. to 70.4% postoperative in G1 and from 44.9 to 85.7% in G2 (p < 0.05). The number of pat. with highly pronounced preoperative mismatch (red) could be lowered in G1 from 29.6 to 13.9% and in G2 from 16.3 to 2% postoperative (p < 0.05). In G1, the preoperative LL could be corrected from 46.3° to 53.8° (yellow) and 35.7° to 45.8° (red), while in G2, a correction was possible from 43.4° to 51.5° (yellow) and 36.6° to 50.1° (red) (p < 0.05). No significant difference of segmental/complete LL was found between radiologic measurement immediately postoperative and at the 3-month follow-up. In monosegmental fusion higher cages sizes lead to a better match of LL/PI (p < 0.05). The specific cage lordosis (5° vs. 10°) had no influence on the extent of relordosing. Experienced surgeons had significant higher postoperative matches of LL/PI (p < 0.05) and accomplished more osteotomies (p < 0.05).

Discussion: This retrospective study demonstrates that significant relordosing and, therefore, correction of the spino-pelvic alignment are possible with mono-/bisegmental TLIF spondylodesis. Positive influence of higher cage sizes and surgeon's experience was shown. We conclude that the ratio of LL/PI should be taken into account preoperatively in lumbar fusion surgery when planning mono-/bisegmental TLIF spondylodesis to optimize spino-pelvic alignment. These slides can be retrieved under Electronic Supplementary Material.