PKP surgical treatment of OVF can immediately relieve the patient's pain, restore the height of the vertebral body, and correct the kyphosis; moreover, the operation time is short, the trauma is minor, and the surgical skills are easy to master, so it has gradually become one of the main methods for OVF treatment[3–8]. However, some patients still have local pain after the operation, complicated by adjacent vertebral fractures, secondary local instability, and even local kyphotic deformity[10–11]. Takahashi S et al.  reported that the above-mentioned complications were mainly caused by PKP surgery focused solely on the fractured vertebral body itself, ignoring the treatment of the adjacent EDC injury. As the degeneration of the injured IVD accelerates, the local stability of the fracture is lost, and the uneven axial load distribution will eventually result in local chronic pain, adjacent vertebral fractures, and even progressive loss of correction in severe cases. Lin et al.  have shown that 60% of the instability caused by spinal fractures arises from the EDC. Boeree et al. proposed that the integrity of the IVD above the fractured vertebral body is an important factor in maintaining stability. Although the EDC is an important structure for maintaining the integrity of the spine, dispersing axial load, and absorbing shock, there are very few studies of OVF combined with EDC injury. The classification of IVD injury with normal bone mass fracture and IVD injury proposed by Sander et al. is not suitable for patients with osteoporosis. Ortiz et al. reported for the first time the incidence of OVF patients having IVD injury and its impact on the treatment effect, but they did not classify and observe the degree of IVD injury associated with OVF. Tatsuhiko et al. conducted research mainly on whether the healing of OVF in patients with IVD injuries depended on the Sander et al. classification. At present, there is no relevant research on the classification of OVF combined with EDC injury. This study used MRI and CT to observe OVF with combined EDC injury for the first time. The purpose is to establish a new classification to improve communication between spine surgeons and radiologists and facilitate clinical decision making in spine surgery.
Conventional wisdom holds that the trauma that causes OVF is usually minor, and it is not easy to damage adjacent structures. However, the rate of OVF combined with IVD damage in this study is as high as 67.0%, which is slightly higher than the results of Ortiz and Tatsuhiko. This may be because this study used the highly sensitive STIR sequence to observe changes of the IVD signal, in combination with CT MPR technology, to improve the diagnosis rate of EDC injury. This study found that the combined EDC injury in OVF patients occurred mainly on the cranial side of the fractured vertebral body (64.3%), and less often involved the EDC on both sides of the fractured vertebral body. This may be due to the minor trauma of OVF injury.
This study found that the incidence of EDC injury was higher, and the degree of injury more severe, for patients in the thoracolumbar group than for those in the thoracic and lumbar groups. The main reasons are as follows: (1) the thoracolumbar is located at the junction of thoracic kyphosis and lumbar lordosis; (2) the thoracolumbar is in the stress junction area between the thoracic cage and the lumbar spine; and (3) the thoracolumbar vertebral body does not have the thoracic cage and strong psoas major muscle protection. Once it is traumatized, the thoracolumbar vertebral body is prone to fractures, and the degree of fracture and the combined degree of EDC damage are often very serious. In some elderly patients with secondary osteoporosis, the loss of bone mineral and bone matrix and bone microstructure degeneration are very obvious. Severe osteoporosis often occurs, the fragility of the vertebral body is significantly increased, and minor trauma can cause vertebral body fracture. This study found that OVF in patients with severe osteoporosis was associated with a higher incidence and severity of EDC injury, which may be principally because patients with severe osteoporosis have greater bone loss, and consequently their vertebral bodies become more fragile. Once the vertebral body fractures, it is easier to spread to the vertebral body endplates, resulting in IVD damage. The IVD and the adjacent vertebral body are the integral movement unit. Whether it acts on the IVD or the vertebral body, destructive force can easily be transmitted to the adjacent structure and cause damage. Employing the Genant semi-quantitative method, this study found that the degree of vertebral body fracture is almost the same as the degree of EDC injury. The more serious the degree of vertebral body fracture, the higher the incidence of combined EDC injury and the more severe the degree of EDC injury.
PKP surgery is used to treat OVF, which can quickly relieve acute pain and obtain satisfactory clinical effects. However, secondary degeneration of the injured intervertebral disc, local instability, adjacent vertebral body fractures, and secondary kyphosis will significantly affect the patient, and may even require surgical treatment again. Such patients are often elderly, often with multiple organ dysfunction, and it may be difficult for them to tolerate reoperation. Therefore, the first treatment for OVF and the combined injury of the EDC is very important. In OVF patients, if the EDC injury classification is grade 0 or 1, we recommend that the treatment be selected based on the degree of vertebral fracture, without special treatment of the injured IVD. If the EDC injury is grade 2, we recommend PKP to treat OVF as the first choice. In addition, intraoperative bone cement subendplate distribution should be achieved as much as possible to prevent the damaged endplate from collapsing. If the EDC injury is classified as grade 3 or 4, according to the patient's tolerance to surgery, discectomy, reduction of fractured vertebral body and injuried endplate, intervertebral bone grafting, and internal fixation are preferred for the patients. If the patient cannot withstand general anesthesia, percutaneous vertebral body-intervertebral disc cementoplasty may also be one of the effective treatment methods for such patients. However, when injecting bone cement, it is necessary to prevent the bone cement from leaking into the spinal canal through the fracture line of the posterior wall of the vertebral body. Certainly, the above treatment methods need to be combined with standard anti-osteoporosis treatment, brace protection, and enhancement of core muscle strength. As one of the main structures of the spine motor unit, the EDC plays a vital role in maintaining the stability and integrity of the spine, and in protecting the nerves and dispersing the axial load. Especially for OVF patients, there may only be one chance for surgery. Clinicians can carefully screen OVF combined with EDC injuries according to the classification criteria formulated herein and choose individual treatment methods to maximize the therapeutic effect of OVF.
This study is a single-center retrospective study. It deals only with imaging observations. The reliability of guiding the choice of treatment will require long-term clinical observation and follow-up.