Current literature has not shown if using either allograft or autograft differentially affects postoperative cervical sagittal parameters. The goal of this study was to compare sagittal alignment and patient-reported outcomes following anterior cervical discectomy and fusion (ACDF) with allograft versus autograft.
A retrospective cohort analysis of patients who underwent single-level ACDF was conducted. Preoperative, immediate postoperative, and final follow-up radiographic assessments were conducted and included: change in C2–7 lordosis, T1 slope, levels fused, sagittal vertical axis (SVA), fusion mass lordosis, and proximal and distal adjacent segment degeneration (ASD). Patient-reported outcomes were obtained using the Neck Disability Index and visual analogue scale scores for neck and arm.
A total of 404 patients were assessed; 353 using allograft and 51 using autograft. No significant differences existed in demographics. Cervical lordosis improved in both groups without significant changes in SVA. Autograft group had a significantly greater amount of lordosis at the proximal segment on immediate postoperative radiographs and less overall cervical lordosis at final follow-up. Sagittal parameters were similar at each time point without significant changes between the 3-time points. No significant differences existed in radiographic ASD or reoperation rates. Fusion rates exceeded 96% in both groups. No significant differences existed between preoperative, postoperative, or change in patient-reported outcomes between the 2 groups.
Sagittal alignment is maintained following ACDF when using either allograft or autograft. Radiographic evidence of ASD is present in both groups; however, this was not considered clinically significant, given low rates of pseudarthrosis or reoperation. No significant differences exist between groups in terms of patient-reported outcomes.
Iliac crest bone autograft (ICBG) is the gold standard for anterior cervical discectomy and fusion (ACDF) due to its osteoinductive, osteogenic, and osteoconductive properties [
In addition to recording fusion rates and measuring clinical outcomes according to Odom’s criteria, some investigators have studied additional radiographic measurements, finding that alterations in sagittal radiographic parameters may correlate with changes in patient-reported outcomes. Maintenance or improvement of overall cervical or fusion segment lordosis has been shown to decrease NDI scores, while increased kyphosis may lead to greater VAS scores [
Our study aimed to determine the impact of graft choice (ICBG versus allograft) on various sagittal radiographic parameters in patients undergoing ACDF with plating. In addition to collecting sagittal parameters via radiographic measurements, we recorded NDI and VAS scores at preoperative, immediate postoperative, and final follow-up visits. We hypothesized that there would be no significant difference in sagittal parameters or patient-reported outcomes between ACDF with autograft versus allograft.
We retrospectively reviewed the records of consecutive patients who underwent ACDF between January 1998 and December 2015. This study was approved by the Institutional Review Board of Rush University Medical Center (approval number: 18072091). All surgeries were performed at a single quaternary referral medical center by one of 2 senior surgeons (HSA, EG). Surgery indications included: failure of conservative treatments for radiculopathy, myelopathy, or myeloradiculopathy. Exclusions criteria included: age under 18 years old, previous cervical fusion or concomitant posterior surgery, postoperative follow-up of less than one year, cervical spine fracture, or infection. Of 467 patients originally identified, 404 fulfilled the criteria.
During the study period, senior authors transitioned from the use of autograft to cortico-cancellous allograft. Both surgeons used the following surgical technique. Patients were placed supine on a radiolucent table after induction of general endotracheal anesthesia. Once a bump was placed midline between the scapulae, Gardner-Wells tongs were placed with 15 pounds of traction. Standard Smith-Robinson approach to the anterior cervical spine was utilized. Subsequently, a discectomy was performed in standard fashion. Disc space was distracted with laminar spreaders placed in disc space to allow for adequate visualization and access to perform foraminotomies. The posterior longitudinal ligament was not routinely resected. If the patient was receiving autograft, an incision was made over the iliac crest, and a cortical bone window was created to gain access to the cancellous bone between the outer and inner table of the pelvis. Series of curettes were used to obtain the cancellous bone graft. For patients obtaining an allograft for fusion, after implants were trialed in standard fashion, a fresh-frozen VG2 cortico-cancellous allograft was placed in the disc space, and traction was removed. A rigid (Eagle, DepuySpine, Raynham, MA, USA) or semi-rigid plate (Vuelock, Biomet, Parsippany, NJ, USA) was applied to the anterior cervical spine and screws were then placed. A 3-0 Vicryl suture was used to close the platysma layer and subcutaneous tissue, followed by a 4-0 Vicryl suture and dermabond for the skin.
Postoperatively, all patients were placed into a soft cervical collar and admitted to the hospital for observation. Anteroposterior and lateral cervical spine radiographs were taken at postoperative visit within the first 4 weeks and then again at 3 months, 6 months, and 12 months.
Demographic information collected for all patients included: age, sex, body mass index, diabetes, smoking status, and American Society of Anesthesiologists (ASA) physical status classification system. Preoperative, immediate postoperative, and final follow-up radiographic assessments were conducted and included: C2–7 lordosis, proximal and distal adjacent segment lordosis, height of the fusion mass, adjacent segment degeneration (ASD), T1 angle, SVA, fusion mass lordosis, and the presence of a fusion (
Sagittal parameters were assessed at preoperative, postoperative, and at the final follow-up appointment with the operating spinal surgeon. Preoperative radiographs were obtained in the 1 month preceding operation, postoperative radiographs were taken in the 1 month following the operation, and final follow-up radiographs were obtained at the most recent visit with the surgeon of record.
Postoperative data were collected regarding the presence of new radicular or myelopathic symptoms indicative of pathology at adjacent levels, indicating a clinical diagnosis of ASD. Patient-reported outcomes included NDI scores and VAS scores for neck and arm preoperatively and at the most recent follow-up. Patient charts were also reviewed for evidence of symptomatic pseudarthrosis and any reoperations in the cervical spine.
Baseline patient characteristics were compared using chi-square analysis and independent sample t-tests for categorical and continuous data, respectively. Bivariate and multivariate regressions were applied to compare clinical outcomes between groups. Multivariate analyses controlled for differences in baseline patient characteristics.
A total of 404 patients fulfilled our inclusion criteria; of these, 353 (87.4%) underwent allograft placement, and 51 (12.6%) underwent ICBG (
Cervical lordosis was improved in both groups, without significant changes in SVA (
Clinical outcomes, as measured using VAS Neck, VAS Arm, and NDI scores, were similar between allograft and autograft groups, except preoperative NDI score (
There were no significant differences between groups in radiographic ASD (allograft 19.6%, autograft 29.4%; odds ratio [OR], 1.75; p=0.101) or reoperation rates (allograft 4.3% vs. autograft 7.8%; OR, 1.98, p=0.250) at final follow-up (
Although allograft is regularly utilized by surgeons performing ACDF with anterior plating, the superiority of allograft or autograft in maintaining or improving sagittal alignment has yet to be determined. It is also not well known if choosing allograft or autograft affects patient-reported outcomes. Our study determined that patients receiving autograft had significantly more lordosis at the proximal segment on immediate postoperative radiographs, but had significantly less overall cervical lordosis than the allograft group on final follow-up radiographs. We also found that there were no significant differences between groups in VAS Neck, VAS Arm, or NDI scores, nor significant differences in rates of fusion, subsidence, reoperations, or ASD when using allograft or autograft in ACDF.
Gum et al. [
When we evaluated changes in sagittal alignment from preto postoperative period, and from postoperative to final follow-up, we found no significant differences between groups. In a 2012 investigation of 38 patients, Kim et al. [
VAS Arm, VAS Neck, and NDI measurements all improved in both allograft and autograft groups, although neither graft option showed a significant benefit over the other. We could not find studies which directly measured patient-reported outcomes comparing allograft and autograft in ACDF, though most studies recorded fusion rate, clinical outcomes according to Odom’s criteria, rate of subsidence, or rate of graft collapse [
Patients who underwent ACDF with anterior plating using autograft or allograft had similar rates of fusion, reoperation, ASD, and subsidence. Both allograft group and autograft group had high rates of fusion (97.4% and 96.1%, respectively). This high level of fusion is similar to previously published research comparing allograft and autograft in ACDF with anterior plating [
There are several limitations to this study. The study was retrospective, so patients were not randomly assigned to either group. During the study period, senior authors transitioned from use of autograft to allograft. However, the remaining fundamental techniques did not change. Although this could influence outcomes, the demographic variables were very similar in both groups, other than percentage of female patients, and all demographic variables were controlled for during multivariate statistical analysis. Another limitation is the short follow-up length in comparison to similar studies. Additionally, follow-up radiographs were not taken at specific intervals, but rather radiographs were selected based on their status as preoperative, immediate postoperative, or final follow-up radiographs. Instrumentation was somewhat varied between patients, based on surgeon preference which may impact outcomes. Half of the patients in the cohort received semi-rigid plates, while the other half received rigid plates.
Before this investigation, it was unknown if use of allograft or autograft in ACDF with anterior plating would lead to significant differences in sagittal parameters or patient-reported outcomes. By multivariate analysis, we found that while autograft use leads to significantly greater proximal segment lordosis in the immediate postoperative period, the use of autograft leads to significantly less cervical lordosis at final follow-up. Besides there was no difference between groups in terms of VAS Arm, VAS Neck, or NDI scores, nor did we find significant differences between groups in fusion rate, subsidence, reoperation rate, or rate of ASD. Overall, both graft choices are acceptable treatments for maintaining cervical sagittal parameters and improving patient-reported outcomes in patients undergoing ACDF for cervical radiculopathy or myelopathy.
The authors have nothing to disclose.
Lateral cervical plain radiographs are taken 12 months following a 2-level ACDF in a 56-year-old male who underwent ACDF with iliac crest bone autograft (A) and a 54-year-old male that underwent ACDF with fresh-frozen cortico-cancellous allograft (B). ACDF, anterior cervical discectomy and fusion.
Demographics
Demographic | Allograft (n = 353) | Autograft (n = 51) | All patients (n = 404) | p-value |
---|---|---|---|---|
Age (yr) | 49.6 ± 10.8 | 52.4 ± 12.5 | 49.9 ± 11.1 | 0.094 |
Female sex | 49.70 | 49.00 | 49.60 | 0.926 |
BMI (kg/m2) | 28.7 ± 6.2 | 28.7 ± 6.9 | 28.7 ± 6.3 | 0.963 |
Smoking | 20.40 | 11.80 | 19.30 | 0.144 |
Diabetes | 11.30 | 14.00 | 11.70 | 0.582 |
ASA grade ≥ III | 19.30 | 19.60 | 19.30 | 0.896 |
No. of levels | 0.026 |
|||
1 | 33.1 | 25.5 | 32.2 | |
2 | 47.6 | 47.1 | 47.5 | |
3 | 19.0 | 23.5 | 19.6 | |
4 | 0.3 | 3.9 | 0.7 |
Values are presented as mean±standard deviation or %.
BMI, body mass index; ASA, American Society of Anesthesiologists physical status classification system.
p<0.05, statistically significant differences.
Preoperative and postoperative sagittal parameters
Variable | Allograft | Autograft | All patients | Bivariate |
Multivariate |
||
---|---|---|---|---|---|---|---|
Beta | p-value | Beta | p-value | ||||
Preoperative | |||||||
Lordosis (°) | 4.7 ± 11.5 | 2.6 ± 10.9 | 4.4 ± 11.5 | -2.1 | 0.238 | -3.0 | 0.083 |
SVA (mm) | 27.4 ± 11.1 | 27.6 ± 12.3 | 27.4 ± 11.2 | 0.2 | 0.919 | -0.4 | 0.816 |
Fusion seg lordosis (°) | -0.1 ± 7.1 | 0.6 ± 8.4 | 0.0 ± 7.3 | 0.7 | 0.530 | 0.3 | 0.784 |
T1 slope (°) | 26.0 ± 8.5 | 25.2 ± 7.9 | 25.9 ± 8.4 | -0.8 | 0.603 | -1.3 | 0.413 |
Proximal lordosis (°) | 1.4 ± 7.4 | 4.1 ± 11.1 | 1.7 ± 8.0 | 2.7 | 0.031 |
1.7 | 0.145 |
Distal lordosis (°) | 3.9 ± 4.4 | 2.4 ± 5.1 | 3.7 ± 4.5 | -1.5 | 0.099 | -1.2 | 0.190 |
Immediate postoperative | |||||||
Lordosis (°) | 7.7 ± 10.0 | 6.0 ± 10.2 | 7.5 ± 10.0 | -1.7 | 0.265 | -2.8 | 0.050 |
SVA (mm) | 29.4 ± 10.7 | 31.6 ± 10.5 | 29.7 ± 10.7 | 2.1 | 0.189 | 2.0 | 0.189 |
Fusion seg lordosis (°) | 6.26 ± 5.6 | 7.4 ± 6.8 | 6.4 ± 5.8 | 1.1 | 0.199 | 0.3 | 0.689 |
T1 slope (°) | 27.9 ± 7.5 | 28.2 ± 1.5 | 27.9 ± 0.5 | 0.4 | 0.801 | -0.4 | 0.769 |
Proximal lordosis (°) | 0.8 ± 7.8 | 4.5 ± 12.2 | 1.2 ± 8.5 | 3.7 | 0.004 |
3.0 | 0.015 |
Distal lordosis (°) | 2.6 ± 4.6 | 1.6 ± 6.1 | 2.5 ± 4.8 | -1.0 | 0.244 | -0.7 | 0.470 |
Final | |||||||
Lordosis (°) | 9.5 ± 10.1 | 6.6 ± 9.6 | 9.1 ± 10.1 | -2.9 | 0.054 | -3.8 | 0.010 |
SVA (mm) | 27.1 ± 10.2 | 28.6 ± 12.7 | 27.3 ± 10.5 | 1.5 | 0.347 | 0.9 | 0.548 |
Fusion seg lordosis (°) | 5.8 ± 5.8 | 6.0 ± 6.2 | 5.9 ± 5.8 | 0.2 | 0.841 | -0.4 | 0.606 |
T1 slope (°) | 28.7 ± 7.7 | 28.1 ± 8.0 | 28.6 ± 7.7 | -0.6 | 0.683 | -0.6 | 0.688 |
Proximal lordosis (°) | 1.8 ± 7.7 | 4.6 ± 11.2 | 2.1 ± 8.3 | 2.8 | 0.025 |
2.0 | 0.093 |
Distal lordosis (°) | 3.7 ± 5.0 | 2.2 ± 5.6 | 3.5 ± 5.1 | -1.5 | 0.105 | -1.1 | 0.262 |
Values are presented as mean±standard deviation.
SVA, sagittal vertical axis.
p<0.05, statistically significant differences.
Change in parameters at different time points
Variable | Allograft | Autograft | All patients | Bivariate |
Multivariate |
||
---|---|---|---|---|---|---|---|
Beta | p-value | Beta | p-value | ||||
Change preoperative to postoperative | |||||||
Lordosis (°) | 3.1 ± 8.0 | 3.0 ± 8.4 | 3.1 ± 8.1 | -0.1 | 0.949 | -0.4 | 0.717 |
SVA (mm) | 2.2 ± 7.5 | 4.1 ± 9.1 | 2.4 ± 7.8 | 2.0 | 0.118 | 1.9 | 0.121 |
Fusion seg lordosis (°) | 6.4 ± 6.5 | 6.6 ± 6.6 | 6.4 ± 6.5 | 0.3 | 0.781 | 0.0 | 0.970 |
T1 slope (°) | 2.0 ± 5.3 | 3.2 ± 6.5 | 2.2 ± 5.5 | 1.2 | 0.289 | 0.6 | 0.576 |
Proximal lordosis (°) | -0.5 ± 3.9 | 0.3 ± 4.3 | -0.4 ± 4.0 | 0.8 | 0.169 | 0.8 | 0.214 |
Distal lordosis (°) | -1.4 ± 4.1 | -0.4 ± 5.6 | -1.2 ± 4.3 | 1.0 | 0.254 | 1.0 | 0.261 |
Change postoperative to final | |||||||
Lordosis (°) | 1.7 ± 5.6 | 0.6 ± 5.8 | 1.5 ± 5.6 | -1.1 | 0.182 | -0.8 | 0.317 |
SVA (mm) | -2.7 ± 7.2 | -3.7 ± 7.5 | -2.8 ± 7.3 | -1.1 | 0.343 | -1.4 | 0.209 |
Fusion seg lordosis (°) | -0.4 ± 3.7 | -1.4 ± 3.8 | -0.6 ± 3.7 | -0.9 | 0.099 | -0.8 | 0.175 |
T1 slope (°) | -0.2 ± 5.9 | -0.3 ± 4.4 | -0.1 ± 5.7 | -0.2 | 0.860 | 0.0 | 0.977 |
Proximal lordosis (°) | 1.1 ± 3.7 | 0.1 ± 3.9 | 1.0 ± 3.8 | -1.0 | 0.081 | -1.0 | 0.080 |
Distal lordosis (°) | 1.1 ± 3.8 | 0.5 ± 4.3 | 1.0 ± 3.9 | -0.6 | 0.413 | -0.4 | 0.575 |
Change preoperative to final | |||||||
Lordosis (°) | 4.8 ± 8.0 | 3.7 ± 6.6 | 4.7 ± 7.8 | -1.1 | 0.364 | -1.0 | 0.395 |
SVA (mm) | -0.4 ± 8.1 | 0.5 ± 7.3 | -0.3 ± 8.0 | 0.9 | 0.460 | 0.7 | 0.588 |
Fusion seg lordosis (°) | 5.9 ± 6.7 | 5.2 ± 6.4 | 5.8 ± 6.7 | -0.7 | 0.492 | -0.7 | 0.462 |
T1 slope (°) | 2.1 ± 7.0 | 2.9 ± 5.2 | 2.2 ± 6.8 | 0.8 | 0.572 | 0.8 | 0.590 |
Proximal lordosis (°) | 0.6 ± 4.6 | 0.6 ± 4.8 | 0.6 ± 4.6 | 0.0 | 0.992 | -0.1 | 0.930 |
Distal lordosis (°) | -0.3 ± 4.3 | -0.5 ± 5.0 | -0.3 ± 4.4 | -0.2 | 0.780 | 0.0 | 0.970 |
Values are presented as mean±standard deviation.
SVA, sagittal vertical axis.
Comparing clinical outcomes
Variable | Allograft | Autograft | All patients | Bivariate |
Multivariate |
||
---|---|---|---|---|---|---|---|
Beta | p-value | Beta | p-value | ||||
Preoperative | |||||||
VAS neck | 7.0 ± 3.3 | 7.1 ± 2.7 | 7.1 ± 3.2 | 0.0 | 0.969 | 0.2 | 0.819 |
VAS arm | 5.7 ± 3.8 | 4.7 ± 3.8 | 5.6 ± 3.8 | -1.0 | 0.329 | -0.8 | 0.460 |
NDI | 48.2 ± 20.5 | 36.8 ± 16.4 | 46.4 ± 20.3 | -11.4 | 0.038 |
-8.0 | 0.141 |
Final | |||||||
VAS neck | 2.0 ± 2.4 | 2.1 ± 2.3 | 2.1 ± 2.4 | 0.1 | 0.922 | -0.2 | 0.735 |
VAS arm | 1.6 ± 2.6 | 2.1 ± 3.1 | 1.7 ± 2.7 | 0.5 | 0.421 | 0.3 | 0.647 |
NDI | 21.8 ± 20.7 | 17.0 ± 20.3 | 20.9 ± 20.6 | -4.8 | 0.343 | -5.2 | 0.311 |
Change preoperative to final | |||||||
VAS neck | 5.1 ± 3.9 | 5.5 ± 3.6 | 5.1 ± 3.8 | 0.5 | 0.669 | 0.9 | 0.434 |
VAS arm | 4.2 ± 3.8 | 3.0 ± 3.9 | 4.1 ± 3.8 | -1.2 | 0.280 | -0.6 | 0.586 |
NDI | 27.5 ± 25.4 | 22.9 ± 17.5 | 26.7 ± 24.2 | -4.6 | 0.492 | -1.1 | 0.866 |
Values are presented as mean±standard deviation (score).
VAS, visual analogue scale; NDI, Neck Disability Index.
p<0.05, statistically significant differences.
Comparison of ASD, reoperations, fusion, and subsidence
Variable | Allograft (%) | Autograft (%) | All patients (%) | Bivariate |
Multivariate |
||
---|---|---|---|---|---|---|---|
OR |
p-value | OR |
p-value | ||||
Any ASD | 19.60 | 29.41 | 20.84 | 1.71 | 0.110 | 1.75 | 0.101 |
Proximal | 14.49 | 21.57 | 15.38 | 1.62 | 0.194 | 1.69 | 0.171 |
Distal | 9.38 | 13.73 | 9.93 | 1.54 | 0.335 | 1.48 | 0.390 |
Proximal and distal | 4.26 | 5.88 | 4.47 | 1.40 | 0.602 | 1.32 | 0.678 |
Reoperations | 4.26 | 7.84 | 4.71 | 1.91 | 0.267 | 1.98 | 0.250 |
Fusion | 97.44 | 96.08 | 97.27 | 0.64 | 0.579 | 0.61 | 0.551 |
Subsidence | 5.97 | 9.80 | 6.45 | 1.71 | 0.302 | 2.02 | 0.199 |
ASD, radiographic evidence of adjacent segment degeneration.
Subsidence as measured by a decrease in intervertebral disc height of ≥2 mm from immediate postoperative radiographs to final follow-up radiographs.
Odds ratio (OR) represents odds of ASD per one-unit increase in each sagittal parameter.