22. Poor radiographic outcomes after cervical disc replacement

BACKGROUND CONTEXT Cervical disc replacement (CDR) is an effective option for the treatment of herniated cervical discs with radiculopathy or myelopathy. One of the main benefits of CDR is that it maintains physiological range of motion (ROM) and lordosis while achieving decompression. However, there are cases where patients experience loss in segmental ROM or have segmental kyphosis postoperatively. This study analyses the radiographic outcomes of these patients. PURPOSE Analyze the radiographic outcomes of patients who had segmental kyphosis at the operative levels and/or a loss in range of motion after CDR. STUDY DESIGN/SETTING Single-center retrospective cohort study. PATIENT SAMPLE A total of 156 (Poor X-Ray (PXR) Outcomes = 47; Successful X-Ray (SXR) Outcomes = 104). OUTCOME MEASURES Pre- and postoperative segmental and regional sagittal alignment in neutral and flexion/extension, cSVA, disc height, implant distance to the center of the disc, and implant distance to the posterior endplate. METHODS Patients undergoing CDR were included. The cohort was separated into poor X-ray outcomes cases (PXR) and successful X-ray outcomes cases (SXR). The PXR group was defined as patients who had a loss in segmental ROM (≥11° decrease in δ Segmental ROM) after the CDR and/or had postoperative segmental kyphosis at the operative level. Radiographic outcome measures: pre- and postoperative segmental and regional sagittal alignment in neutral and flexion/extension, cSVA, disc height, implant distance to the center of the disc, and implant distance to the posterior endplate. Independent T-test analysis and χ2 test were used to analyze differences in radiographic surgical outcomes, with significance set at p<0.05. RESULTS A total of 151 (PXR=47; SXR=104) patients met the cohort criteria. Pre- and postop segmental lateral cobb angles were more kyphotic in the PXR group (3.50±4.96 vs -1.43±5.17, p<0.001; 2.56±4.07 vs -5.61±5.65, p<0.001). There was a larger δ in segmental lateral cobb angle in the SXR group (-4.18±0.554 vs -0.94±4.40, p<0.001). The PXR group had a larger degree of flexion and a significantly smaller degree of extension at the segment (11.27±7.60 vs 6.54±5.89, p<0.001; -2.21±12.59 vs -6.13±6.05, p=0.049). There was a significant loss in segmental ROM in the PXR group (-5.70±11.6 vs 1.46±7.36, p<0.001). Pre- and postop C2-C7 lateral cobb angles were more kyphotic in the PXR group (-1.22±13.30 vs -9.49±11.8, p<0.001; -2.92±10.96 vs -13.92±10.14, p<0.001). Pre- and postop cSVA were larger in the PXR group (29.64±12.18 vs 25.31±12.41, p = 0.047; 30.10±16.8 vs 22.87±12.88, p=0.004). Subanalysis of patients diagnosed with preop segmental kyphosis vs nonkyphotic patients: higher rate of postop segmental kyphosis in the preop kyphotic group (57.6% vs 17.0%, p<0.001); higher rate of postop C2-C7 kyphosis in the preop kyphotic group (30.5% vs 5.3%, p<0.001); higher rate of poor X-ray outcomes after CDR in the preop kyphotic group (50.8% vs 18.1%, p<0.001). CONCLUSIONS Following CDR, patients who developed postoperative kyphosis or decreased range of motion were more likely to have less segmental and regional C2-7 lordosis and a larger preoperative and postoperative cSVA. Furthermore, patients who had preoperative segmental kyphosis at the operative levels had higher rates of postoperative segmental kyphosis, C2-C7 kyphosis, and poor radiographic outcomes following CDR. Surgeons indicating CDR and counseling patients on the options for anterior cervical discectomy should consider these preoperative parameters. Further studies with long-term follow-up including clinical outcomes are warranted. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs. Cervical disc replacement (CDR) is an effective option for the treatment of herniated cervical discs with radiculopathy or myelopathy. One of the main benefits of CDR is that it maintains physiological range of motion (ROM) and lordosis while achieving decompression. However, there are cases where patients experience loss in segmental ROM or have segmental kyphosis postoperatively. This study analyses the radiographic outcomes of these patients. Analyze the radiographic outcomes of patients who had segmental kyphosis at the operative levels and/or a loss in range of motion after CDR. Single-center retrospective cohort study. A total of 156 (Poor X-Ray (PXR) Outcomes = 47; Successful X-Ray (SXR) Outcomes = 104). Pre- and postoperative segmental and regional sagittal alignment in neutral and flexion/extension, cSVA, disc height, implant distance to the center of the disc, and implant distance to the posterior endplate. Patients undergoing CDR were included. The cohort was separated into poor X-ray outcomes cases (PXR) and successful X-ray outcomes cases (SXR). The PXR group was defined as patients who had a loss in segmental ROM (≥11° decrease in δ Segmental ROM) after the CDR and/or had postoperative segmental kyphosis at the operative level. Radiographic outcome measures: pre- and postoperative segmental and regional sagittal alignment in neutral and flexion/extension, cSVA, disc height, implant distance to the center of the disc, and implant distance to the posterior endplate. Independent T-test analysis and χ2 test were used to analyze differences in radiographic surgical outcomes, with significance set at p<0.05. A total of 151 (PXR=47; SXR=104) patients met the cohort criteria. Pre- and postop segmental lateral cobb angles were more kyphotic in the PXR group (3.50±4.96 vs -1.43±5.17, p<0.001; 2.56±4.07 vs -5.61±5.65, p<0.001). There was a larger δ in segmental lateral cobb angle in the SXR group (-4.18±0.554 vs -0.94±4.40, p<0.001). The PXR group had a larger degree of flexion and a significantly smaller degree of extension at the segment (11.27±7.60 vs 6.54±5.89, p<0.001; -2.21±12.59 vs -6.13±6.05, p=0.049). There was a significant loss in segmental ROM in the PXR group (-5.70±11.6 vs 1.46±7.36, p<0.001). Pre- and postop C2-C7 lateral cobb angles were more kyphotic in the PXR group (-1.22±13.30 vs -9.49±11.8, p<0.001; -2.92±10.96 vs -13.92±10.14, p<0.001). Pre- and postop cSVA were larger in the PXR group (29.64±12.18 vs 25.31±12.41, p = 0.047; 30.10±16.8 vs 22.87±12.88, p=0.004). Subanalysis of patients diagnosed with preop segmental kyphosis vs nonkyphotic patients: higher rate of postop segmental kyphosis in the preop kyphotic group (57.6% vs 17.0%, p<0.001); higher rate of postop C2-C7 kyphosis in the preop kyphotic group (30.5% vs 5.3%, p<0.001); higher rate of poor X-ray outcomes after CDR in the preop kyphotic group (50.8% vs 18.1%, p<0.001). Following CDR, patients who developed postoperative kyphosis or decreased range of motion were more likely to have less segmental and regional C2-7 lordosis and a larger preoperative and postoperative cSVA. Furthermore, patients who had preoperative segmental kyphosis at the operative levels had higher rates of postoperative segmental kyphosis, C2-C7 kyphosis, and poor radiographic outcomes following CDR. Surgeons indicating CDR and counseling patients on the options for anterior cervical discectomy should consider these preoperative parameters. Further studies with long-term follow-up including clinical outcomes are warranted.