Lumbar total disc replacement: correlation of clinical outcome and radiological parameters

Influence of positioning of L4-5 disc prostheses on functional outcomes and sagittal balance: 2-year follow-up of a cohort of 38 patients

OBJECTIVE

The main objective of this study was to evaluate the influence of L4-5 total disc replacement (TDR) positioning on functional outcome at the 2-year follow-up. The secondary objective was to assess its influence on sagittal balance.

METHODS

Prospective data were compiled for 38 single-level L4-5 ProDisc-O TDRs. Anteroposterior placement (APP) was the distance between the center of the implant and the center of the L5 endplate divided by the total length of the L5 endplate. This ratio was expressed as a percentage (APP 0%-49%, anterior off-centering; 50%, perfect centering; and 51%-100%, posterior off-centering). The patients were divided into 3 groups depending on the APP and using quartile values: group 1, anterior placement (APP 0%-46%); group 2, central placement (APP 46.1%-52%, the 2 central quartiles); and group 3, posterior placement (APP 52.1%-100%). The sagittal balance parameters assessed were overall lordosis, segmental lordosis, and pelvic incidence. Adequate lordosis was defined for each patient according to their pelvic incidence. The Oswestry Disability Index and visual analog scale (VAS) scores for back and leg pain were assessed.

RESULTS

The average APP was 48% (range 40%-64%). There were 10 patients in group 1, 18 in group 2, and 10 in group 3. There was a significant difference in functional outcomes among the 3 groups. APP influenced the VAS back (p = 0.04) and VAS leg (p = 0.05) scores. Group 1 consistently showed the highest performance scores. No significant association between APP and the sagittal balance parameters was found. Patients who had preoperative sagittal imbalance or those who significantly modified their balance after the surgery had the poorest outcomes.

CONCLUSIONS

Disc prostheses at L4-5 seem to provide better functional outcome when they are positioned anteriorly to the center of the vertebral body.

Long-term clinical results following Charite III lumbar total disc replacement

BACKGROUND CONTEXT

Lumbar total disc replacement (TDR) operation represents an alternative to lumbar fusion for the treatment of symptomatic lumbar intervertebral disc degeneration and has gained increasing attention in recent years.

PURPOSE

This study aimed to assess clinical outcomes in a cohort of patients with TDR and the long-term survival rate of the prostheses.

STUDY DESIGN

This is a retrospective, single-center clinical study.

PATIENT SAMPLE

The sample comprised 30 patients, giving a total of 35 prostheses after an average follow-up (FU) of 15.2 years following TDR, which was performed for the treatment of lumbar degenerative disc disease.

OUTCOME MEASURES

Clinical evaluation included visual analog scale (VAS) and the Oswestry Disability Index (ODI). Radiological parameters of intervertebral disc height (IDH), range of motion (ROM), lumbar lordosis, lumbar scoliosis, and prosthesis position were evaluated in surgical and adjacent levels. Complications and re-operation rates were also assessed.

METHODS

Clinical evaluation and radiological parameters were evaluated preoperatively and at final FU. All data were collected by members of our department, including research assistants and nurses who were not involved in the decision making of this study.

RESULTS

Thirty of the 35 patients participated in the final FU. The cumulative survival rate of the prosthesis at a mean FU of 15.4 years was 100%. The clinical success rate was 93.3%. The VAS and ODI scores at final FU were significantly lower than preoperatively (p<.001). The average ROM of the operated and superior adjacent segment decreased significantly at the final FU, whereas the inferior adjacent segment was not affected. The IDH of all surgical and adjacent levels were well maintained at the final FU. Ten patients had a lumbar scoliosis >3° and the mean angle was 8.5°, of which 7 had left convex curvature. Three prostheses were offset more than 5 mm from the midline on the coronal plane. Four prostheses showed subsidence. Twenty-six operative segments and five adjacent segments showed heterotopic ossification. Two patients of the total 35-patient cohort underwent a secondary operation.

CONCLUSIONS

Satisfactory clinical results and good prosthesis survival can be achieved in the long term. Lumbar TDR surgeries also have the potential to reduce the incidence of adjacent segment disease.

Patient-reported Outcomes and Revision Rates at a Mean Follow-up of 10 Years After Lumbar Total Disc Replacement

STUDY DESIGN

Prospective observational cohort study.

OBJECTIVE

The aim of this study was to determine the long-term clinical results and prosthesis survival in patients treated with lumbar total disc replacement (TDR).

SUMMARY OF BACKGROUND DATA

Fusion has become the current standard surgical treatment for lumbar degenerative disease. TDR is an alternative treatment that seeks to avoid fusion-related adverse events, specifically adjacent segment disease.

METHODS

Sixty-eight consecutive patients treated with TDR from 2003 to 2008 were invited to follow-up and complete a Visual Analog Scale (VAS) for back and leg pain, the Dallas Pain Questionnaire (DPQ), and the Short Form-36. These surveys were also administered to the subjects before their index TDRs. Data on reoperation were collected from the patients' medical records.

RESULTS

Fifty-seven (84%) patients were available for follow-up at a mean 10.6 years post-operatively (range 8.1-12.6 years). There was a significant improvement from preop to latest follow-up in VAS (6.8 vs. 3.2, P < 0.000) and DPQ (63.2 vs. 45.6, P = 0.000) in the entire cohort. Nineteen patients (33%) had a revision fusion surgery after their index TDR. Patients who had revision surgery had statistically significant worse outcome scores at last follow-up than patients who had no revision. Thirty patients (52.6%) would choose the same treatment again if they were faced with the same problem.

CONCLUSION

This study demonstrated significant improvement in long-term clinical outcomes, similar to previously published studies, and two-thirds of the discus prostheses were still functioning at follow-up. However, there is still a lack of well-designed long-term studies, thus requiring further investigation.

LEVEL OF EVIDENCE

3.

A New CT Method for Assessing 3D Movements in Lumbar Facet Joints and Vertebrae in Patients before and after TDR

This study describes a 3D-CT method for analyzing facet joint motion and vertebral rotation in the lumbar spine after TDR. Ten patients were examined before and then three years after surgery, each time with two CT scans: provoked flexion and provoked extension. After 3D registration, the facet joint 3D translation and segmental vertebral 3D rotation were analyzed at the operated level (L5-S1) and adjacent level (L4-L5). Pain was evaluated using VAS. The median (±SD) 3D movement in the operated level for the left facet joint was 3.2 mm (±1.9 mm) before and 3.5 mm (±1.7 mm) after surgery and for the right facet joint was 3.0 mm (±1.0 mm) before and 3.6 mm (±1.4 mm) after surgery. The median vertebral rotation in the sagittal plane at the operated level was 5.4° (±2.3°) before surgery and 6.8° (±1.7°) after surgery and in the adjacent level was 7.7° (±4.0°) before and 9.2° (±2.7°) after surgery. The median VAS was reduced from 6 (range 5–8) to 3 (range 2–8) in extension and from 4 (range 2–6) to 2 (range 1–3) in flexion.

Rotation effect and anatomic landmark accuracy for midline placement of lumbar artificial disc under fluoroscopy

PURPOSE

Total disc arthroplasty can be a viable alternative to fusion for degenerative disc disease of the lumbar spine. The correct placement of the prosthesis within 3 mm from midline is critical for optimal function. Intra-operative radiographic error could lead to malposition of the prosthesis. The objective of this study was first to measure the effect of fluoroscopy angle on the placement of prosthesis under fluoroscopy. Secondly, determine the visual accuracy of the placement of artificial discs using different anatomical landmarks (pedicle, waist, endplate, spinous process) under fluoroscopy.

METHODS

Artificial discs were implanted into three cadaver specimens at L2-3, L3-4, and L4-L5. Fluoroscopic images were obtained at 0°, 2.5°, 5°, 7.5°, 10°, and 15° from the mid axis. Computerized tomography (CT) scans were obtained after the procedure. Distances were measured from each of the anatomic landmarks to the center of the implant on both fluoroscopy and CT. The difference between fluoroscopy and CT scans was compared to evaluate the position of prosthesis to each anatomic landmark at different angles.

RESULTS

The differences between the fluoroscopy to CT measurements from the implant to pedicle was 1.31 mm, p < 0.01; implant to waist was 1.72 mm, p < 0.01; implant to endplate was 1.99 mm, p < 0.01; implant to spinous process was 3.14 mm, p < 0.01. When the fluoroscopy angle was greater than 7.5°, the difference between fluoroscopy and CT measurements was greater than 3 mm for all landmarks.

CONCLUSIONS

A fluoroscopy angle of 7.5° or more can lead to implant malposition greater than 3 mm. The pedicle is the most accurate of the anatomic landmarks studied for placement of total artificial discs in the lumbar spine.

An 11-year minimum follow-up of the Charite III lumbar disc replacement for the treatment of symptomatic degenerative disc disease

PURPOSE

To report our 11-year minimum clinical and radiological outcomes, as well as complications of the Charite III total disc replacement (TDR).

METHODS

A total of 35 patients indicated for total disc replacement were implanted with the Charite III prosthesis. Clinical evaluation included visual analog scale (VAS) for back pain and the Oswestry disability index (ODI). Radiological parameters of intervertebral disc height (IDH), range of motion (ROM), lumbar lordosis, lumbar scoliosis and prosthesis position were evaluated. Complications and reoperation rates were also assessed.

RESULTS

Thirty-two patients had a minimum 11-year follow-up, and 33 prostheses were implanted. The mean follow-up time was 11.8 years, ranging from 11.3 to 13.8 years. Twenty-eight patients (87.5 %) had a successful outcome, as defined by the FDA. Reoperation was performed in 2 patients for adjacent segment degeneration and pedicle fracture (1 case each). Both VAS and ODI scores showed significant improvement compared to baseline. At the final follow-up, the ROM of both the index- and adjacent-level showed an obvious decrease. The IDH of the index level showed a tendency to decrease, but the difference was not significant. The IDH of adjacent levels were not significantly affected by the surgery. Mean lumbar lordosis was increased at the final follow-up, and lumbar scoliosis over 3° was observed in 12 patients (37.5%), with a mean angle of 5.6° (range 3°-12°). Of all 35 prostheses, 15 were left-shifted, 3 were right-shifted and 14 were just in the middle. In the coronal plane, 25 were rated as ideally placed, 5 were discretely shifted, 4 were slightly shifted and 1 was markedly shifted. In the sagittal plane, only 12 prostheses were rated as ideally placed, 14 were discretely shifted and 9 were suboptimally placed. Prosthesis subsidence was noted in 3 (9.4%) patients (the subsidence distances were 3.1, 4.2 and 2.8 mm, respectively). Heterotopic ossification was detected in 25 segments (71.4%), consisting of Class-I heterotopic ossification in 7 segments (20.0%), Class-II in 9 segments (25.7%), and Class-III in 9 segments (25.7%). Class-IV heterotopic ossification was not observed.

CONCLUSION

The cumulative survival was 100% at a mean follow-up of 11.8 years. Clinical and radiological results were satisfactory and long-term clinical results were maintained for a mean follow-up of 11.8 years. Reoperation and complication rates are acceptable, and our study does not substantiate the fear of reoperation or late complications. The results of our long-term follow-up indicate that, with strict indication, TDR is a safe and effective procedure as an alternative to lumbar fusion.

ISASS Policy Statement - Lumbar Artificial Disc

PURPOSE

The primary goal of this Policy Statement is to educate patients, physicians, medical providers, reviewers, adjustors, case managers, insurers, and all others involved or affected by insurance coverage decisions regarding lumbar disc replacement surgery.

PROCEDURES

This Policy Statement was developed by a panel of physicians selected by the Board of Directors of ISASS for their expertise and experience with lumbar TDR. The panel's recommendation was entirely based on the best evidence-based scientific research available regarding the safety and effectiveness of lumbar TDR.

Five-year results of lumbar disc prostheses in the SWISSspine registry

PURPOSE

The Swiss Federal Office of Public Health demanded a nationwide HTA registry for lumbar total disc arthroplasty (TDA), to decide about its reimbursement. The goal of the SWISS spine registry is to generate evidence about the safety and efficiency of lumbar TDA.

METHODS

Two hundred forty-eight cases treated between 3-2005 and 6-2006, who were eligible for the 5-year follow-up were included in the study. Follow-up rates for 3-6 months, 1, 2 and 5 years were 85.9, 77.0, 44.0 and 51.2 %, respectively. Outcome measures were back and leg pain, medication consumption, quality of life, intraoperative and postoperative complication and revision rates. Additionally, segmental mobility, ossification, adjacent and distant segment degeneration were analysed at the 5-year follow-up.

RESULTS

There was a significant, clinically relevant and lasting reduction of back (preop/postop 73/29 VAS points) and leg pain (preop/postop VAS 55/22) and a consequently decreased analgesics consumption and quality of life improvement (preop/postop 0.30/0.76 EQ-5D score points) until 5 years after surgery. The rates for intraoperative and early postoperative complications were 4.4 and 3.2 %, respectively. The overall complication rate during five postoperative years was 23.4 %, and the adjacent segment degeneration rate was 10.7 %. In 4.4 % of patients, a revision surgery was performed. Cumulative survivorship probability for a revision/re-intervention-free 5-year postoperative course was 90.4 %. At the 5-year follow-up, the average range of motion of the mobile segments (86.8 %) was 9.7°. In 43.9 % of patients, osteophytes at least potentially affecting the range of motion were seen.

CONCLUSIONS

Lumbar TDA appeared as efficient in long-term pain alleviation, consequent reduction of pain medication consumption and improvement of quality of life. The procedure also appeared sufficiently safe, but surgeons have to be aware of a list of potential adverse events. The outcome is stable over the 5-year postoperative period. The vast majority of treated segments remained mobile after 5 years, although almost half of patients showed osteophytes.