Screening for Nuclear Replacement Candidates in Patients With Lumbar Degenerative Disc Disease

BACKGROUND Nuclear replacement is an emerging surgical treatment for degenerative disc disease (DDD) and low back pain (LBP). While clinical experience is most extensive with the prosthetic disc nucleus PDN (Raymedica, Minneapolis, Minnesota), strict indications apply for the implantation of this device. The purpose of this study was to ascertain what percentage of patients treated surgically for degenerative disc disease with other surgical procedures would have been candidates for nuclear replacement implantation. METHODS The charts and films of 85 consecutive patients with failed conservative management for LBP treated surgically with fusion, disc replacement, or annuloplasty were retrospectively reviewed. There were 53 patients with 1-level disease and 32 with 2-level disease, accounting for 117 treated levels. Patients with the following radiographic contraindications to nuclear replacement were serially eliminated: (1) Schmorl's nodes and > 50% collapse of the disc space, (2) irregular/convex endplates on the MRI, (3) complete tears and large annular defects (ie, both incomplete tears and complete tears were eliminated, but patients with local annular deficiency were deemed eligible for nuclear replacement), and (4) a BMI > 30. RESULTS Fifty-nine levels (50.4%) had no radiographic contraindications to treatment with a nuclear replacement device. Twelve levels in 10 patients with a BMI > 30 were excluded. Overall, 47 out of 117 levels (40.2%) had no contraindications to a prosthetic nucleus device. The L5-S1 level was the most commonly treated level (55 out of 117, 47%), but only 25.5% had no radiographic contraindications, and overall only 21.8% of the levels were suitable for a nuclear replacement device. Upper lumbar levels (L3-4 and L4-5) had no radiographic contraindications in a higher percentage of cases (68.8% and 72.7%, respectively). The inclusion of the BMI criteria reduced these percentages to 50% and 59.1%, respectively. CONCLUSIONS The surgeon has to assess endplate integrity, disc height, endplate shape, annular integrity, and BMI when offering nuclear replacement as treatment for patients with DDD.