Anterior Hyperlordotic Cages: Early Experience and Radiographic Results
Authors: Saville Philip , Kadam Abhijeet , Smith Harvey , Arlet Vincent 
Published: April 2016

Introduction

The mainstay of correction for hypolordotic lumbar deformities has been posterior osteotomies, such as the Smith Petersen, or three column osteotomies (TCO). TCO's while very powerful, are associated with significant neurological complications, variable lordotic correction, pseudarthrosis and loss of correction. We hypothesize that the advent of Hyperlordotic Cages (HLC) (cages with 20 or 30° of built in lordosis) will allow significant restoration of lumbar lordosis, and good predictability of the correction from an anterior approach, thus obviating the need for TCO's.

Material and Methods

We conducted a retrospective review of a single surgeon series of consecutive adult patients, undergoing Anterior Lumbar Interbody Fusion (ALIF) with HLC for degenerative spinal conditions or sagittal imbalance over a 15-month period. Patients had either a standalone ALIF or ALIF followed by posterior instrumented fusion, depending on underlying pathology. The anterior approach involved a retroperitoneal pararectus approach with resection of the anterior longitudinal ligament. Electronic medical records were reviewed for evidence of perioperative complications. Digital lateral spine radiographs were also reviewed to assess for Segmental Lordosis (SL) and its stability over time. Classic deformity measurments were also recorded.

Results

69 HLC's inserted into 41 patients met our inclusion criteria, with a mean follow up of 8 months. Average age of patients was 55 years (23–76), and 29 were female. We implanted twenty-seven 30° HLC's, and forty-two 20° HLC's. The mean pre op lumbar lordosis of our cohort was 39o, post operatively this increased to 59° ( p < 0.01). In 21 levels without spondylolisthesis, the 30° HLC's produced a mean SL of 28° (26–34). In 45 levels without spondylolisthesis the 20° HLC produced a mean SLC of 19°(16–22) p < 0.01. In 7 levels with greater than grade 1 spondylolisthesis, 30° HLCs achieved 19° of SL (14–21) ( p < 0.01). The majority of HLC's were placed in lower lumbar spine, 34 at L5/S1, and 23 at L4/5. Six (9%) HLC's displayed loss of correction (defined as SL loss > 2°). The mean loss of SL was 4.5°(3–10). Complications included two transient neurological deficits (4.4%), one L5 palsy, and one L4 hyperesthesia, both observed after posterior instrumentation, 2 retroperitoneal collections, one requiring incision and debridement, 2 lymphoceles, both requiring laparoscopic fenestrations, and one enterocutaneous fistula requiring intervention. Average blood loss was 240ml(50–900).

Conclusion

Anterior insertion of HLC's is a predictable and reproducible method to correct lordosis, and therefore sagittal balance in complex deformities. The amount of SL obtained with a 30° HLC is comparable to TCO's but the 20% total complication rate is significantly lower than the 58% reported for TCO's in the literature. The ability to implant hyperlordotic cages at lower lumbar levels than traditional L2 or L3 level TCO enables a more anatomic restoration of the lumbar lordosis. Direct lateral cages have failed to demonstrate recreation of lordosis, but anterior insertion does appear to efficiently correct lordosis. Our blood loss (250ml) also compares favorably with reported values for TCO's. The authors therefore advocate the use of HLC's for ALIF to recreate lumbar lordosis.