Preliminary report on the flexible rod technique for prevention of proximal junctional kyphosis following long-segment fusion to the sacrum in adult spinal deformity

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OBJECTIVE

The incidence of proximal junctional kyphosis (PJK) after long-segment fixation in patients with adult spinal deformity (ASD) has been reported to range from 17% to 61.7%. Recent studies have reported using “hybrid” techniques in which semirigid fixation is introduced between the fused and flexible segments at the proximal level to allow a more gradual transition. The authors used these hybrid techniques in a clinical setting and analyzed PJK to evaluate the usefulness of the flexible rod (FR) technique.

METHODS

The authors retrospectively selected 77 patients with lumbar degenerative kyphosis (LDK) who underwent sagittal correction and long-segment fixation and had follow-up for > 1 year. An FR was used in 30 of the 77 patients. PJK development and spinal sagittal changes were analyzed in the FR and non-FR groups, and the predictive factors of PJK between a PJK group and a non-PJK group were compared.

RESULTS

The patient population comprised 77 patients (75 females and 2 males) with a mean (± SD) follow-up of 32.0 ± 12.7 months (36.7 ± 9.8 months in the non-FR group and 16.8 ± 4.7 months in the FR group) and mean (± SD) age of 71.7 ± 5.1 years. Sagittal balance was well maintained at final follow-up (10.5 and 1.5 mm) in the non-FR and FR groups, respectively. Thoracic kyphosis (TK) and lumbar lordosis (LL) were improved in both groups, without significant differences between the two (p > 0.05). PJK occurred in 28 cases (36.4%) in total, 3 (10%) in the FR and 25 (53.2%) in the non-FR group (p < 0.001). Postoperatively, PJK was observed at an average of 8.9 months in the non-FR group and 1 month in the FR group. No significant differences in the incidence of PJK regarding patient factors or radiological parameters were found between the PJK group and non-PJK group (p > 0.05). However, FR (vs non-FR) and interbody fusion except L5–S1 using oblique lumbar interbody fusion (vs non–oblique lumbar interbody fusion), demonstrated a significantly lower PJK prevalence (p < 0.001 and p = 0.044) among the surgical factors.

CONCLUSIONS

PJK was reduced after surgical treatment with the FR in the patients with LDK. Solid long-segment fixation and the use of the FR may become another surgical option for spine surgeons who plan and make decisions regarding spine reconstruction surgery for patients with ASD.

ABBREVIATIONS ALIF = anterior lumbar interbody fusion; ASD = adult spinal deformity; BMD = bone mineral density; BMDT = BMD T-score; FR = flexible rod; LDK = lumbar degenerative kyphosis; LL = lumbar lordosis; OLIF = oblique lumbar interbody fusion; PI = pelvic incidence; PI-LL = PI − LL; PJA = proximal junctional angle; PJK = proximal junctional kyphosis; PLIF = posterior lumbar interbody fusion; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; SS = sacral slope; SVA = sagittal vertical axis; TK = thoracic kyphosis; UIV = uppermost instrumented vertebra.
Article Information

Contributor Notes

Correspondence Jung-Hee Lee: Graduate School, College of Medicine, Kyung Hee University, Seoul, Korea. ljhspine@gmail.com.INCLUDE WHEN CITING Published online July 12, 2019; DOI: 10.3171/2019.4.SPINE1915.Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
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