Correlation between paraspinal muscle atrophy, morphological changes of facet joints and adjacent segment degeneration after lumbar fusion / 中华骨科杂志

ABSTRACT

Objective:To investigate the correlation between paraspinal muscle atrophy, morphological changes of facet joints and adjacent segment disease (ASDis) after lumbar fusion operation.Methods:A retrospective study was conducted among 195 patients who underwent posterior lumbar fusion again for ASDis at this institution from January 2014 to December 2020, including 29 patients with ASDis whose initial surgical fusion segment was L 4,5. According to Roussouly's staging, there were 5 cases of type I, 9 cases of type II, 10 cases of type III, and 5 cases of type IV. Another 29 cases were selected from patients without ASDis after lumbar fusion as a control group. The control group was paired 1∶1 with the ASDis group according to gender, fusion segment, and Roussouly typing of the lumbar spine. The cross-sectional area (CSA) and fat infiltration (FI) of paravertebral muscle, facet joint angle (F-J) and pedicle facet (P-F) angle before the first (second) operation were measured and compared between the two groups. Then logistic regression analysis was used to determine the predictors of ASDis after posterior lumbar fusion. Finally, the receiver operation characteristic (ROC) curve was described, and the area under the curve (AUC) and cut-off point were calculated. At the same time, the paraspinal muscle atrophy before the second operation in ASDis group was measured. Results:The average follow-up time of 98 patients was 59.25±6.38 months (range, 49-73 months). The average body mass index (BMI) of ASDis group was 24.76±3.64 kg/m 2, which was higher than that in control group (22.24±2.92 kg/m 2) ( t=2.481, P=0.041). The average CSA and relative cross-sectional area (rCSA) of paraspinal muscle in ASDis group were 3 214.32± 421.15 mm 2 and 1.69±0.36 respectively, which were less than 3 978.91±459.87 mm 2 and 2.26±0.29 in control group ( t=10.22, P=0.012; t=9.47, P=0.038). The FI degree of paraspinal muscle in ASDis group (21.95%±5.89%) was significantly higher than that in control group (14.64%±7.11%) ( t=7.32, P=0.002). The F-J angle in ASDis group was 35.06°±3.45°, which was less than 38.39°±4.67° in control group ( t=4.76, P=0.027). The P-F angle in ASDis group was 117.39°±8.13°, which was greater than 111.32°±4.78° in control group ( t=5.25, P=0.031). Multivariate logistic regression analysis showed that higher BMI ( OR=1.34, P=0.038), smaller rCSA of paraspinal muscle ( OR=0.02, P=0.017) and higher FI of paraspinal muscle ( OR=1.58, P=0.032) were the risk factors of postoperative ASDis. The ROC curve showed that the AUC of BMI was 0.680 and the cut-off point was 22.58 kg/m 2; The AUC of the FI of paraspinal muscle was 0.716 and the cut-off point was 15.69%; The AUC of rCSA of paraspinal muscle was 0.227 and the cut-off point was 1.92. For ASDis patients, the paraspinal muscle before the second operation had a higher degree of FI (25.47%±6.59% vs. 21.95%±5.89%, t=3.99, P=0.042) and a smaller rCSA (1.52±0.28 vs. 1.69±0.36, t=3.85, P=0.038) than that before the first operation. The difference between the FI degree of paraspinal muscle before the second operation and the first operation was negatively correlated with the occurrence time of ASDis ( r=-0.53, P=0.039) , and the difference of rCSA was positively correlated with the occurrence time of ASDis ( r=0.64, P=0.043) . Conclusion:When BMI >22.58 kg/m 2, FI of paraspinal muscle >15.69%, and rCSA of paraspinal muscle <1.92, it suggests that ASDis is more likely to occur after operation. And the more obvious paraspinal muscle atrophy after the first operation, the earlier ASDis may occur. Morphological changes of facet joints cannot be used as an index to predict the occurrence of ASDis.