The Use of Nitinol Rods in Surgical Treatment of Degenerative Scoliosis. 2.5-YEAR Follow-Up

Abstract

Objectives: To compare the outcomes of surgical treatment with lumbar fixation using nitinol rods without fusion and with standard lumbar fixation with titanium rods and interbody fusion. Methods: Treatment results of 70 patients with degenerative lumbar scoliosis aged 40 to 82 were analyzed. In all cases pedicle screws and nitinol rods with a diameter of 5.5 mm were used. Thirty patients underwent fixation at L1-S1 and 40 patients underwent fixation at L1-L5. Spinal fusion was not performed. All patients had radiography, CT and MRI performed. The results were assessed according to the Oswestry scale, SRS 22, SF 36 and VAS. The minimum follow-up period for all patients was 2.5 years. For the control group, consisting of 72 patients, pedicle fixation with titanium rods and interbody fusion in the lumbosacral region were performed. Results: The average level of deformity correction equaled 25° (10° - 38°). The analysis of X-ray and CT-scans revealed a single patient with implant instability, two patients with bone resorption around the screws and one patient with rod fractures. Functional radiography 2.5 years after surgery showed an average mobility of the lumbar spine of 21° (15° - 30°). There were no problems at the adjacent levels. Conclusions: The use of nitinol rods in spinal deformity surgery is promising. This technology is an alternative to rigid fixation. Continued gathering of clinical data and its further evaluation is necessary.

Nitinol Spinal Vertebrae: A Favorable New Substitute

“…Equiatomic Ni-Ti alloy called Nitinol combines strength, softness, pseudo-elasticity and biocompatibility [7,25]. With less than 49.4 atom% Ti, the alloy becomes hard and brittle due to the Ni3Ti intermetallic phase.…”

“…Recent studies on anatomical models, tissue specifications, surgical implants and prostheses fabrication by 3D manufacturing have specified promising results [72][73][74][75]. By using neuroimaging, patients anatomy information and software processing, an appropriate implant can be obtained [7], [72]. Work on producing wrist prostheses by 3D printing has gained satisfactory results [21].…”

“…With Nitinol usage, due to good interaction, decrease in the risk of failure has lowered [12]. A comparison of Nitinol with Ti rods applied to 70 patients to improve their degradative lumbar scoliosis showed better spinal deformation correction by the former [7]. Nitinol did not cause spinal canal inflammation and any lymph (and other organs) particle detachment [11].…”

“…Treating the back-pain is distressing and expensive [5] because the backbone column is a complicated system having vertebras and cartilages which protect the spinal cord. When noninvasive methods have not been successful, the surgery is recommended [6,7]. Disc replacement, spinal fusion [8,9] and vertebral implantation are *Corresponding Author Email: sadrnezh@sharif.edu (S. K. Sadrnezhaad) increasingly implemented year by year.…”

“…During the past five decades, metallic orthopaedic devices have been used for spinal shape correction in scoliosis disease [7,[11][12][13][14]. Despite good strength, Young's moduli of metals are higher than bone.…”