SAS journal最新文献

Background: Maintenance of segmental motion following lumbar total disc replacement (LTDR) is one of the theoretical advantages of spinal arthroplasty. This in vivo study examined paradoxical and coupled motions during sagittal plane movements following disc arthroplasty and compared these motions with those measured following lumbar discectomy.

Methods: Ten patients following LTDR using ProDisc-L (Synthes, Inc., West Chester, Pennsylvania) and 8 patients following lumbar discectomy (LD) were enrolled. At 1-month, 1-year and 2-year postoperative time-points, patients performed flexion/extension starting from a neutral position, and the intervertebral rotations were determined with radiostereometric analysis. The amount of intended and coupled motion was compared in each group and at each postoperative time. The frequency of paradoxical motion was compared between the 2 groups, and the effects of intended motion, operative-level, number of levels, and postoperative time-point were examined.

Results: The intended and coupled motions following LTDR and LD did not change over time and did not differ from each other for the flexion and total sagittal movements. The sagittal range of motion (ROM) of LTDR was significantly smaller than that of LD in extension (-0.6° ± 1.1° vs -2.2° ± 1.6°). LTDR exhibited a significantly higher rate of paradoxical motion when compared to LD (26.4% vs 6.7%). In LTDR, the rate of paradoxical motion at 1 month (40%) was significantly higher than at 1-year (21.1%) or at 2-year (25.0%). The presence of paradoxical motion was significantly less frequent at L4-5 (19.2%) when compared to L5-S1 (31.3%) or L2-3 (36.4%).

Conclusion: The overall sagittal ROM of LTDR was 3.5° ± 2.4° and not significantly different than LD. The current study did not demonstrate a difference in coupled motions between LTDR and LD. The rate of paradoxical motion was significantly higher in LTDR than in LD. In LTDR, there was a significantly lower rate of paradoxical motion seen at L4-5 and significantly higher rate seen in the earlier postoperative period.

Level of evidence: Prospective cohort study with good follow-up (level 1b).

Background: Degenerative spondylolisthesis is associated with a significant segmental kyphosis at the level of the listhesis. We treated 7 disc spaces with Grade 2 listhesis and/or kyphosis of the slipped disc level with Kineflex disc replacement.

Methods: Out of a single-center prospective registry, involving 310 lumbar disc replacement patients, 7 patients underwent a single-level Kineflex disc replacement at the level of a degenerative spondylolisthesis with either segmental kyphosis or a Grade 2 slip. Preoperative and follow-up radiological parameters studied were: pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis L1-S1, degree of segmental listhesis, segmental lordosis, and range of motion (ROM). Clinical outcome measures were Visual Analog Scale pain score (VAS), Oswestry Disability Index (ODI), and patient satisfaction.

Results: Five replacements were performed at the L4-L5 level, and 2 were performed at a L3-4 level, above a pre-existing L4-S1 posterolateral fusion. Mean age was 50 (32-62) years. Average follow-up was 23.8 ± 13.1 months. Six of 7 patients considered their outcome as good or excellent. The mean VAS score decreased from 8.4 ± 1.9 to 2.7 ± 2.2 (P < .01). The ODI decreased from 45.2 ± 9.9 preoperatively to 19.7 ± 12.8 (P < .01). There were increases in lumbar lordosis (from 47.4o ± 10.6 to 61.3o ± 8.0 (P < .03)), in segmental lordosis (from 0.17° ± 7.0° to 16.4° ± 2.0° (P < .03)), and in sacral slope (from 34.5° ± 4.8° to 40.7° ± 4.5° (P < .03)). There were decreases in pelvic tilt (from 22.6° ± 6.3° to 15.5° ± 5.9° (P < .05)), and degree of segmental listhesis (from 24.4% ± 7.7 to 3.7% ± 3.4 (P < .03)). Pelvic incidence and ROM did not change.

Conclusions: Disc replacement resulted in significant improvement in clinical outcome and excellent sagittal balance and slip correction. However, the influence of improved sagittal spinal alignment on clinical outcomes needs to be investigated in larger studies including a control group.

Clinical relevance: This study is the first focused on disc replacement in degenerative spondylolisthesis.

Background: This is a retrospective study to assess the prognostic factors influencing the postoperative motion dynamics and clinical outcome following cervical arthroplasty with a Bryan disc.

Methods: Twenty-seven patients (30 levels) consecutively underwent cervical arthroplasty using a Bryan disc (Medtronic Sofamor Danek, Memphis, Tennessee). Motion dynamics and clinical outcome (visual analogue score (VAS) and neck disability index (NDI) score) were examined preoperatively and at 1 month, 1 year, and final follow-up (average: 25 months). The prognostic factors influencing clinical outcome and postoperative motion dynamics were assessed.

Results: At last follow-up, mean VAS and NDI scores were significantly decreased from 8.33 ± 1.52 to 1.10 ± 0.99 (P = .001) and from 25.0 ± 15.9 to 9.2 ± 5.9 (P = .001), respectively. In a comparative study of pre- and postoperative motion changes at operated segments, mean segmental range of motion (ROM) increased from 6.96° ± 2.03° to 8.93° ± 3.53° (P = .014), and mean segmental angle decreased from 2.85° ± 3.27° to 1.21° ± 5.93° (P = .126). Mean global angle increased significantly from 14.54° ± 10.32° to 18.36° ± 11.10° (P = .003), and ROM increased non-significantly from 40.25° ± 13.51° to 41.56° ± 12.53° (P = .654). At upper and lower segments, ROMs did not change significantly postoperatively. The heights of functional segment units showed no change postoperatively (3.51 ± 0.21 to 3.49 ± 0.22, P = .701). No significant relationships were found between VAS and NDI improvement and changes in ROMs or segmental angles at last follow-up. Statistically, the postoperative functional segment unit (FSU) ROM decreased as the age of the patients increased (Spearman r = 0.391, P = .048). The gender and preoperative segmental ROM did not influence FSU ROM.

Conclusions: Our results demonstrate that cervical arthroplasty with the Bryan disc for the treatment of cervical degenerative provides a good clinical outcome and preserves motion postoperatively. The age of the patients and the preoperative segmental ROM significantly affect the postoperative FSU ROM. These factors however do not relate to the clinical outcome. The relationship between long-term outcome and these variables should be verified by a larger cohort study.

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.