Due to the aging tendency of population, LCF’s incidence is increasing rapidly. Approximately 1.5 million adults are affected by LCF each year in the United States24. BMD gradually decreases with age, and almost half of normal axial bone mass is lost by age 80(24). For those older than 80, approximately 16% of men and 33% of women suffer from osteoporotic vertebral fractures25. In addition to the classic low back pain, it can also cause complications such as progressive spinal deformity, pulmonary dysfunction, severe back pain, deep vein thrombosis, muscle atrophy, pressure ulcers, sleep disturbance, depression, intestinal obstruction and, sometimes is easily overlooked, LSS. Many studies thus far were concerned with the relationship between lumbar burst fractures and LSS12, 26, 27, but few studies have investigated LSS in patients with the LCF, although it has a higher morbidity28. We speculate that lumbar VCF and burst fractures may have some similarities in the pathogenesis of LSS, such as the deformation of the vertebral body directly compressing the spinal canal29 or the loss of vertebral body height and the intervertebral foramen leading to lower extremity symptoms30. And now we can say our results are broadly consistent with this view.
For LCF with LSS, the first challenge of clinicians is to diagnose it. This is sometimes easily overlooked because these patients often have severe low back pain, which may mask some lower extremity symptoms. This requires clinicians to not only pay attention to X-rays, but also CT and MR examinations2. Through more detailed imaging examinations, clinicians can more accurately diagnose LSS and access its severity. Ishimoto et al. found that the most severe central spinal stenosis is closely associated with typical LSS symptoms, while mild radiographic spinal stenosis is likely to be atypical. The author also emphasizes that the lumbar vertebral osteoporotic compression fractures can cause nerve root radiating pain and claudication even if there is no obvious spinal canal compression31. It is notable that in our study, some patients with no obvious stenosis on MR but still have lower extremity symptoms that seriously limited their life confirmed this view. So, a complete clinical examination is also always necessary.
In this study, we found that patients with severe/extreme LSS had a higher BMI, a higher proportion of history of trauma and lower extremity symptoms. Radiographically, the patient had a higher grading of fracture and a lower PI. First, an increase in BMI increases the load on the vertebral body and intervertebral disc simultaneously, so body weight itself is an important risk factor for both LCF and LSS7. A study of spinal balance in patients with lumbar fractures by Fechtenbaum et al showed that there was no statistically significant difference in PI between fracture patients and controls32.Meanwhile ,Farrokhi et al. found that patients with lower PI had greater degenerative changes in the lumbar spine33. This suggests that PI may be independent of lumbar fractures, but accelerate the occurrence of LSS in fractured patients. Trauma as a common cause of LCF, is not surprising that it occurred more frequently in the more severe stenosis group. On one hand ,patient has LSS due to degeneration and other reasons, the typical gait changes will greatly increase the probability 34. On the other hand, the force can cause the vertebral body to be displaced dorsally, similar to burst fractures35. Among all 134 patients in this study, 98 (73%) had LSS caused by the posterior displacement of the vertebral body of the fractured segment, which suggests that the most important factor affecting LSS in patients with fractures is the degree of the fracture itself such as retropulsion of the superior portion of the posterior wall. Our results demonstrated that that when we face severe lumbar vertebral compression fractures, it is necessary to determine whether there is LSS at the vertebral body or adjacent disc level.
After confirming that the patient has LCF with LSS, the next step is to choose the best surgical approach for the patient. We recognized that most of the patients have achieved satisfactory postoperative outcomes evaluated by VAS, ODI, and JOA compared with those at preoperative admission regardless of which surgical method was chose Table 5 .According to our statistics in Fig. 1, when the preoperative imaging indicates that the LSS is more severe, clinicians are more inclined to perform decompression surgery. However, the results in our study don’t seem to support this tendency Table 7 .This is in line with the North American Spine Society (NASS) Guideline of LSS and some other studies that there is insufficient evidence for a correlation between clinical symptoms or function and anatomic stenosis of the spinal canal on imaging36–38. Sangbong et al. compared ODI and VAS before and 3 years after surgery in patients with different degrees of sttly enosis(without fracture), and they also did not find a statistically significant difference in the prognosis of these patients39. But meanwhile ,we found that the prognosis of patients with preoperative lower extremity symptoms who choose decompression surgery is better than non-decompression surgery. In contrast, there are some studies that suggest that PKP is a sufficiently safe and effective option for patients with LCF combined with radiculopathy29, 30. Their theory is PKP can increase in segmental stability provided by the cement augmentation and decrease in retropulsion and foraminal narrowing secondary to some degree of fracture reduction and height restoration 40.But the patients selected in those two studies were all undergoing PKP, and there was no comparison with other surgeries. The study by Masaaki et al also showed that decompression surgery has a satisfactory effect on the relief of lower extremity symptoms in patients with LSS-OVF, but the problem that cannot be ignored is that the authors pointed out that these patients developed many complications such as wound infection, delirium, respiratory complications, pedicle screw loosening and adjacent vertebral fracture41. Furthermore, some other surgical methods such as spinal endoscopy or interspinous spacer40, 42 have also been reported to have good therapeutic effects, but the number of cases is still small and needs further study. Overall, the choice of surgery is a comprehensive issue, except for LSS ,the patient's surgical tolerance, life expectancy, and economic situation must be taken into account, which requires the clinician to exercise their own judgment.
This study has several limitations. First, we reviewed the postoperative images of the patients, but most of the patients only had X-rays after surgery, lacking MR examination results, and it was impossible to evaluate and compare the degree of spinal stenosis before and after surgery. Second, the follow-up time of this study is only 2–3 years. Considering that LSS is a chronic degenerative disease, some long-term changes could not be included in our study. Furthermore, this was a retrospective study lacking strict randomized control. Thus, further large-scale, randomized controlled study with longer follow-up time is recommended.