Comparison of single-level L4-L5 versus L5-S1 lumbar disc replacement: results and prognostic factors

Abstract

The aim of our prospective non-randomized clinical study was to analyze operative data, short-term results, safety, efficacy, complications, and prognostic factors for single-level total lumbar disc replacement (TLDR), and to compare results between different levels (L4-L5 vs. L5-S1). Thirty-six patients with single-level L4-L5 or L5-S1 TLDR, with 1-year minimum follow-up (FU), had complete clinical [SF36, visual analog scale (VAS), Oswestry Disability Index (ODI)] and radiological data, and were included in our study. Mean FU was 38.67 +/- 17.34 months. Replaced level was L4-L5 in 12 (33.3%) cases, and L5-S1 in 24 cases (66.7%). Mean age at diagnosis was 41.17 +/- 7.14 years. 24 (66.7%) were females and 12 (33.3%) were males. Statistical analyses were assessed using t tests or Mann-Whitney test for continuous variables and Chi-square test or Fisher's exact test analyses for categorical variables. Univariate linear regression and binary logistic regression analyses were utilized to evaluate the relationship between surgical outcomes and covariates (gender, age, etiology, treated level, pre-operative SF36, ODI, and VAS). Mean operative time was 147.03 +/- 30.03 min. Mean hospital stay was 9.69 +/- 5.39 days, and mean return to ambulation was 4.31 +/- 1.17 days. At 1-year FU, patients revealed a statistical significant improvement in VAS pain (P = 0.000), ODI lumbar function (P = 0.000), and SF36 general health status (P = 0.000). Single-level TLDR is a good alternative to fusion for chronic discogenic low back pain refractory to conservative measures. Our study confirmed satisfactory clinical results for monosegmental L4-L5 and L5-S1 disc prosthesis, with no difference between the two different levels for SF36 (P = 0.217), ODI (P = 0.527), and VAS (P = 0.269). However, replacement of the L4-L5 disc is affected by an increased risk of complication (P = 0.000). There were no prognostic factors for intraoperative blood loss or return to ambulation. Age (P = 0.034) was the only prognostic factor for operative time. Hospital stay was affected by level (P = 0.036) and pre-op VAS (P = 0.006), while complications were affected by the level (P = 0.000) and pre-op ODI (P = 0.049). Complete pre-operative assessment (in particular VAS and ODI questionnaires) is important because more debilitating patients will have more hospital stay and higher complications or complaints. Patients had to be informed that complications, possibly severe, are particularly frequent (80.6%).

Fig. 1

Comparison of SF36, VAS, and ODI clinical outcomes for TLDR at different levels. a SF36 health survey (P = 0.003 in L4–L5, and P = 0.000 in L5–S1), b ODI lumbar function (P = 0.002 in L4–L5, and P = 0.000 in L5–S1), and c VAS lumbar pain (P = 0.001 in L4–L5, and P = 0.000 in L5–S1) showed statistical significant improvement between pre-op and 1-year FU. There was no statistical significance difference between the two different levels (P = 0.217 for SF36; P = 0.527 for ODI; P = 0.269 for VAS)

Fig. 2

Five-year follow-up (FU) anteroposterior (a) and lateral (b) standard X-rays of a 48-year-old man with a L4–L5 TLDR. He was completely satisfied, with an important improvement in SF36 health status (from 56 pre-op to 93 at 5-year FU), in ODI lumbar function (from 50 pre-op to 0 at 5-year FU), and VAS lumbar pain (14 pre-op, 0 5-year FU). Dynamic X-rays (c, d) showed a prosthetic disc ROM of 18° in flexion–extension

Fig. 3

After 1 year from L5–S1 TLDR (a, b), a 35-year-old woman was completely satisfied. She had an improvement in SF36 health status (from 71 pre-op to 94 at 1-year FU), in ODI lumbar function (40 pre-op, 6 1-year FU), and VAS lumbar pain (90 pre-op, 0 1-year FU). Flexion–extension L5–S1 prosthetic disc ROM was 6° at dynamic radiographs (c, d)

Fig. 4

After 2 years from the L5–S1 disc replacement, a patient complained for persistent radiculitis in malpositioning of the implant (a, b). He was submitted to a 270° fusion with removal of the disc prosthesis (c, d). After 3-year FU, one from the second operation, he revealed partial but not sufficient improvement in SF36 health status (34), ODI lumbar function (66) and VAS lumbar pain (80)

Fig. 5

A 35-year-old woman after 4 years from L5–S1 disc arthroplasty (a, b) complained for right lumbar pain (located on the right L4–L5 posterior facets space). She had a left L4–L5 bone union (a), and developed a superior junctional pathology: right L4–L5 facets degeneration secondary to overload (c). She was then submitted to L4–L5 segmental posterior fusion (d, e), with complete remission of the right lumbar pain, and the functional impairment