Fusion via transpsoas lateral approach: considerations and initial results

Clinical efficacy and safety of a new flexible interbody spacer system

BACKGROUND

Patients with lumbar degenerative disk disease (DDD) often require an interbody fusion. Several spacer systems have been developed to achieve an adequate fusion. The newly developed flexible interbody spacer system (Luna®, Benvenue Medical Inc.) expands to the disk space and is adjustable to the patient's anatomy.

OBJECTIVE

Prospective monocentric evaluation of interbody fusions performed with the new system in patients with DDD to assess the device's efficacy and safety.

METHODS

The study includes patients with DDD of one or two contiguous lumbar levels. All patients were treated with the new flexible cage system. To evaluate the clinical outcome, examinations were conducted preoperatively, 6 weeks, 6 months and 12 months postoperatively. At each study visit possible implant loosening was assessed by plain radiography and any adverse events were documented. Furthermore, back pain was evaluated using the visual analogue scale (VAS), functional impairment using the Oswestry-Disability-Index (ODI) and quality of life using the SF36.

RESULTS

A total of 30 patients (age: 52.8 ± 11 years, gender: 53% male) were included. None of the patients showed signs of implant loosening and the total number of adverse events was low (3%). The VAS improved significantly from 81.2 ± 9.5 mm at baseline to 28 ± 26.2 mm after 12-months (p ≤ 0.0001). The ODI also improved significantly from 57.9 ± 9.6% at baseline to 20 ± 15.6% after 12-months (p ≤ 0.0001). The physical component score (PCS) of the SF36 improved significantly ongoing from 29.2 ± 9.3 at baseline to 56.1 ± 14.9 after 12-months (p = 0.0079) and the mental component score (MCS) improved significantly from 49.2 ± 20.7 at baseline to 62.8 ± 18.9 after 12 months (p = 0.013).

CONCLUSIONS

Minimal-invasive lumbar interbody fusion with the new flexible system is a safe and effective treatment method for patients with DDD. Complication rates are low and treatment leads to an improvement of pain, functional impairment and quality of life.

IN WHICH PATIENTS IS IT POSSIBLE TO PERFORM STANDALONE LATERAL LUMBAR INTERBODY FUSION WITHOUT CAGE SUBSIDENCE?

ABSTRACT Objective: To identify the factors related to the non-occurrence of cage subsidence in standalone lateral lumbar interbody fusion procedures. Methods: Case-control study of single level standalone lateral lumbar interbody fusion (LLIF) including 86 cases. Patients without cage subsidence composed the control group (C), while those in the subsidence group (S) developed cage subsidence. Preoperative data were examined to create a risk score based on correlation factors with S group. The proven risk factors were part of an evaluation score. Results: Of the 86 cases included, 72 were in group C and 14 in group S. The following risk factors were more prevalent in group S compared to C group: spondylolisthesis (93% vs 18%; p<0.001); scoliosis (31% vs 12%; p=0.033); women (79% vs 38%; p=0.007); older patients (average 57.0 vs 68.4 years; p=0.001). These risk factors were used in a score (0-4) to evaluate the risk in each case. The patients with higher risk scores had greater subsidence (p<0.001). Scores ≥2 were predictive of subsidence with 92% sensitivity and 72% specificity. Conclusions: It was possible to correlate the degree of subsidence in standalone LLIF procedures using demographic (age and gender) and pathological (spondylolisthesis and scoliosis) data. With a score based on risk factors and considering any score <2, the probability of non-occurrence of subsidence following standalone LLIF (negative predictive value) was 98%.