Survivorship analysis of 150 consecutive patients with DIAM™ implantation for surgery of lumbar spinal stenosis and disc herniation

Brief review

*Title: Survivorship analysis of 150 consecutive patients with DIAM™ implantation for surgery of lumbar spinal stenosis and disc herniation

요추 협착증과 디스크 탈출증으로 DIAM 이식술을 시행한 150명의 환자에 대한 생존 분석

*Authors: Yoo-Joon Sur, Chae-Gwan Kong, Jong-Beom Park

*Bibliography: EurSpine J (2011) 20: 280-288

Background of data

The Device for Intervertebral Assisted Motion (DIAM™) has been introduced for surgery of degenerative lumbar disc diseases.

Purpose

To determine the survivorship of DIAM™ implantation for degenerative lumbar disc diseases and risk factors for reoperation.

Methods

▶Subjects: 150 patients who underwent laminectomy or discectomy with DIAM™ implantation (84 males + 66 females)

▶Mean age: 46.5 years;

▶Mean follow-up period: 23 months (range 1–48 months)

▶Indications: 96 spinal stenosis and 54 disc herniations

▶Index level: 146 one-level (L4–5: 115/ L5–6: 31) and 4 two-level (L4–5 and L5–6)

▶Evaluating methods:

1. Kaplan–Meier analysis: To determine the cumulative reoperation rate and survival time

2. The log-rank test and Cox regression model: To evaluate the effect of age, gender, diagnosis, location, and level of DIAM™ implantation

-Reoperations of the DIAM™ implantation level or adjacent levels were defined as a failure and used as the end point for determining survivorship.

Results

▶Reoperation rate: 4.7% (total 7 patients- only implantation level)

▶The causes of reoperation:

1. recurrent spinal stenosis (n=3)

2. recurrent disc herniation (n=2)

3. post-laminectomy spondylolisthesis (n=1)

4. delayed deep wound infection (n=1)

▶The mean time interval (from 1st to 2nd surgery): 13.4 months (range 2–29 months)

▶Kaplan–Meier analysis: predicted an 8% cumulative reoperation rate 4 years post-operatively.

Survival time was predicted to be 45.6 ± 0.9 months.

▶In Log-rank test, the reoperation rate: L5–6 > L4–5 (p = 0.002)

two-level > one-level (p = 0.01)

-Gender, age, diagnosis did not significantly affect the reoperation rate of DIAM™ implantation.

-Based on a Cox regression model, L5–6 and two-level DIAM™ implantation were also significant variables associated with a higher reoperation rate.

(L5–6: hazard ratio (HR) 10.3, 95% CI, 1.7–63.0; p = 0.01 / HR, 10.4; 95% CI, 1.2–90.2; p = 0.04)

-Survival time was significantly lower in L5–6 (47 vs. 22 months, p = 0.002) and two-level DIAM™ implantation (46 vs. 18 months, p = 0.01) compared with L4–5 and one-level DIAM™ implantation.

Conclusions

-8% patients who have a DIAM™ implantation for primary lumbar spinal stenosis or disc herniation are expected to undergo reoperation at the same level within 4 years after surgery.

-DIAM™ implantation at L5–6 and two-level are significant risk factors for reoperation.