Authors: Junyu Li, Lizhi Xu, Yinhao Liu, Zhuoran Sun, Yongqiang Wang, Miao Yu, Weishi Li, Yan Zeng
Categories: Review Articles, Neurologic Impairment, Open Surgical Correction, Osteoporosis Vertebral Compression Fractures, Osteotomy, Quality of Life, Spinal Kyphosis, Review Article
Source: Orthopaedic Surgery
Doi: 10.1111/os.13822
With an aging population, the osteoporotic vertebral compression fracture (OVCF) has become a constant concern for its physical and neurological complications, such as spinal kyphosis and refractory pains. Compared with traditional conservative treatments, the open surgery is more superior in some ways because of its direct decompression and correction. Various operation methods applying to different indications have been developed to deal with different fracture situations, including anterior, posterior, and combined surgery. In this review, we have concluded the latest developments of the surgery treating OVCF and the internal fixation as references for spinal surgeons of the choice of suitable treatments.
Keywords: Osteoporosis Vertebral Compression Fractures, Spinal Kyphosis, Open Surgical Correction, Osteotomy, Quality of Life, Neurologic Impairment
With an aging population, the incidence of osteoporotic vertebral compression fractures (OVCF) is gradually increasing, as is the number of patients seen for acute and chronic pain and progressive spinal deformities. ^1^ In OVCF patients, the fractured vertebrae remain in a state of constant compression and slight displacement due to prolonged activity, resulting in constant irritation of the peripheral vertebral nerves and consequent long‐lasting pain. ^2^ In addition, the healing function of the fracture site stops under certain conditions, and in 14% of patients, the fracture site forms a pseudarthrosis, which can cause nerve damage in severe cases. ^3^ , ^4^ Therefore, for OVCF patients, physicians should choose reasonable treatment methods to avoid further compression of the fractured vertebrae, correct kyphosis, and avoid nerve injuries.
There are several different treatment strategies available at conservative treatment, traditional surgery, and minimally invasive surgery. ^6^ The choice of treatment depends on the type of fracture and the purpose of the treatment. Traditional conservative treatments of OVCF requires prolonged bed rest, oral analgesics, and bracing, which is relatively low risk but suffers from complications associated with bed rest, medication side effects, and poor tolerance of bracing in the elderly. If the conservative treatment does not relieve the patient's pain, minimally invasive vertebro/kyphoplasty can be considered to perform. In patients with severe compression fractures with kyphosis and neurological deficits, the above treatment modalities usually neither correct the deformity nor restore the stability of the fractured segment, making it difficult to relieve refractory low back pain and neurological compression, so open surgery is often the best treatment option for such patients.
There is still no consensus on the open surgery indications for OVCF, but some guidelines are available for reference. It is observed that some of the non‐traumatic OVCF population seek medical help only when the complications develop to a concerning level, ^5^ such as progressing and intolerant pain, suggesting that we may need to focus on the relief of neurological symptoms and the improvement of the quality of life. Generally, if the deformity is not severe (vertebral kyphosis <25°, height loss <25%) and the patient has mild or moderate pain, conservative treatment such as back brace immobilization and analgesic medication can be used. ^6^ Compared to sham procedure, percutaneous vertebro/kyphoplasty, though often used, seems to have little significant effect in terms of pain, disability, quality of life, or treatment success according high‐ to moderate‐quality evidence. ^7^ The use of internal fixation alone can only delay the progression of the disease, instead of getting complete relief. ^8^ Besides, its use on OVCF patients is difficult to achieve good results because of bone loss. So, an open surgery with or without osetotomy be performed when severe pain or nerve disorders occur. However, the indicating role of angle of kyphosis to open surgery remains indefinite because there is no significant correlation between kyphotic angles and neurological symptoms. ^9^ National Institute for Health and Care Excellence (NICE) has proposed that the indications for surgical treatment are unstable fractures with >35° of kyphosis and neurological deficits. ^10^ In patients with severe compression fractures and kyphosis, the goals of treatments are usually focused on (1) complete release of spinal cord and nerve compression, (2) restoration of the spinal alignment and maximal correction of kyphosis, (3) restoration of the stability of the fractured vertebra and reduction of lower back pain and postoperative complications. ^11^
Depending on the degree of the vertebral compression fracture and the severity of the deformity, a variety of surgical approaches are anterior surgery, posterior surgery, combined anterior and posterior surgery, etc. In the following article, we will review the above surgical approaches.
Neurological deficits are caused by impingement and compression of the ventral side of the spinal cord in most patients with OVCF. Vertebral compression fractures tend to occur anteriorly in the vertebral body and the spinal cord compression originates from the ventral aspect of the spinal cord. The advantage of anterior surgery is that it can remove the fracture fragments directly from the posterior edge of the vertebral body anteriorly, therefore achieving direct decompression of the injured spinal cord or nerve roots with fewer steps, and to reconstruct the anterior spinal structures by implanting support grafts while preserving the integrity of the posterior spinal structures to enhance spinal stability. ^12^ , ^13^ , ^14^ Sudo et al. ^3^ suggested that anterior reconstruction is important in OVCF in a retrospective study that included 50 patients with OVCF, because anterior structures, especially at the thoracolumbar junction, play an important role in weight bearing, and reconstruction of the anterior and middle columns of the spine is important in postoperative spinal stability as well as successful fusion. In a study of 28 patients with OVCF who underwent anterior expandable titanium cage replacement, Uchida et al. ^15^ suggested that this procedure yielded good clinical results in patients with type I vertebral collapse with middle and posterior columns in a relatively good condition. Kanayama et al. ^16^ performed anterior Kaneda internal fixation in 31 patients with OVCF and neurological deficits. The result suggested that this procedure allows for safe and reliable decompression and that 80% of patients can be successfully treated with anterior spinal reconstruction only.
However, a large number of cases cannot be treated via an anterior approach alone. ^14^ Some studies suggest that the vertebral bodies of osteoporotic patients are fragile and that using anterior vertebral body internal fixition is insufficient for initial stability. ^17^ Some reports suggest that 20%–30% of patients with OVCF receiving simple anterior fusion require additional posterior reinforcement due to severe multi‐segmental osteoporosis, progression of kyphosis, or screw loosening. ^3^ , ^16^ , ^18^ In addition, anterior surgery often requires thoracotomy and a retroperitoneal approach. Diaphragmatic separation is also required in many patients with vertebral fractures occurring in the thoracolumbar segment. ^14^ Therefore, in older patients or those with more comorbidities, anterior surgery is highly invasive and carries a greater surgical risk. ^19^ , ^20^ In conclusion, for patients with single segment fracture, fracture near the caudal end, and relatively mild osteoporosis, the anterior surgery can directly address the compressed fractured segment and obtain better results.
The posterior surgery is currently a mainstream surgical procedure. The anatomy of the posterior spinal approach is usually more familiar to surgeons and decompression procedures are simpler via the posterior approach. For patients, the posterior approach causes less trauma, and is also able to avoid potential thoracoabdominal organ or vascular complications which may happen during or after the anterior surgery. ^21^ Although anterior and posterior approaches provide similar corrections, ^3^ posterior spinal fusion with internal fixation is more advantageous in obtaining better postoperative spine stability, especially in patients with osteoporosis or multi‐segmental compression fractures with kyphosis. It has been shown that direct decompression of the middle column can be accomplished via a posterior approach, and for some simple cases, posterior surgery can achieve similar results to the combined anterior and posterior approach. ^22^ For older patients, the posterior approach may be a more desirable surgical option. A study by Ataka et al. ^23^ suggested that posterior short‐segment fusion without nerve decompression could improve nerve function and relieve back pain without major complications in patients with incomplete neurological deficiency after osteoporotic thoracolumbar vertebral compression fractures. This not only demonstrates the importance of posterior surgery for spinal stability reconstruction, but also shows that one of the main points of treatment for OVCF is to improve instability at the fracture site. Nakano et al. ^24^ in a study suggested that posterior short‐segment fusion combined with additional anchoring, such as spinous process plates, also yielded good results. In addition, OVCF is often combined with posterior compression such as ossified or hypertrophied ligamenta flava, which can be treated together when performing surgery from a posterior approach. ^14^
However, the limited ability to perform decompression in the spinal canal is one of the disadvantages of posterior surgery. For example, when there is severe vertebral body comminution or collapse, large fracture fragments may extend into the spinal canal and cause compression of the spinal cord. Treating injuries above the L1 level also carries a higher risk because of the proximity to the spinal cord. ^17^ Additionally, inadequate anterior support after a posterior distractive reduction for severe collapsed vertebral body may lead to correction failure or implant failure. ^17^ Watanabe et al. ^12^ concluded that, according to the concept of load bearing and load sharing, posterior vertebral fusions can generate posterior stresses through flexion moments in standing or sitting positions, leading to a higher risk of internal fixation failure because of lack of anterior support, and thus longer segmental internal fixation fusions are required. Therefore, the length of the selected segment for posterior fusion is also a topic of discussion. In a study that included 238 patients with OVCF, Xu et al. ^2^ classified these patients into grades I‐V based on clinical features and imaging. The appropriate surgical approach was developed according to the classification and the corresponding fusion segments were selected with good results. Therefore, we concluded that for old vertebral fractures with local instability, short‐segment posterior fusion can achieve desired results. In the case of old vertebral fractures with spinal stenosis, long‐segment posterior decompression and fusion should be used.
A combined anterior‐posterior approach is used to obtain optimal biomechanical results through anteriorly supported bone grafts and posterior pedicle screw fixations. The anterior approach allows correction of kyphosis and direct decompression at the OVCF site. ^12^ , ^25^ It has been shown that anterior decompression of the spinal canal is twice as effective as posterior decompression. ^26^ Posterior fixation can also be accomplished without damage to the paravertebral muscles. ^17^ The strength of the fixation in combined approach is superior to that of anterior or posterior surgery alone, especially in patients with severe osteoporosis. ^26^ , ^27^ In a multicenter clinical study of 93 patients with OVCF at six hospitals, Nakashima et al. ^25^ compared combined anterior and posterior surgery with posterior spinal fusion vertebroplasty, suggesting that combined surgery is significantly superior to posterior surgery in terms of maintenance of correction rates during follow‐up periods and incidence of postoperative mechanical complications. ^17^ , ^22^ , ^26^ Machino et al. ^26^ evaluated the surgical treatment with posterior internal fixation, anterior decompression, and cage implantation in a study of 100 patients, the result suggesting that this procedure allows for short‐segment internal fixation, resulting in good correction and a higher postoperative fusion rate, while avoiding the risk of progression of kyphosis and screw loosening after anterior surgeries. Xia et al. ^28^ performed combined anterior and posterior surgery in 34 patients with thoracic fracture and dislocation that could not be adequately treated by anterior or posterior surgery alone. The result showed that all patients had no deterioration in neurological function, while the neurological status of 24 patients with preoperative incomplete paralysis improved by at least one grade according to the classification of the American Spinal Injury Association (ASIA), suggesting that combined anterior and posterior surgery may be more effective for this type of severe injury.
However, the combined anterior and posterior approach is relatively more invasive, has a higher chance of intraoperative blood loss, and takes longer to perform than the simple anterior or posterior surgery alone. Moreover, the lateral position during surgery makes the posterior operation of the surgery technically more difficult to perform, especially when inserting pedicle screws. The higher risk of combined anterior and posterior surgery in medically compromised elderly patients is an important factor limiting its application. ^3^ , ^16^ Therefore, the use of advanced auxiliary techniques or surgical devices to minimize the risk of surgery is a common endeavor for future scholars and surgeons.
With the gradual development of osteotomy and the widespread use of piezosurgery and other equipment, posterior surgery with esteotomy is gradually able to achieve similar correction results as anterior surgery and has more advantages on operation time and postoperative complications. Mainstream posterior osteotomy procedures include Ponte/SPO osteotomy (Smith‐Peterson Osteotomy), pedicle subtraction osteotomy (PSO), bone‐disc‐bone osteotomy (BDBO), and vertebral column resection (VCR), etc.
SPO osteotomy has a more limited ability to correct kyphosis and is therefore less widely used. ^11^ The three‐columns osteotomy (e.g., PSO) has the advantage of kyphosis correction and direct decompression, ^14^ , ^29^ , ^30^ which is the widely accepted treatment for vertebral compression fractures with progressive kyphosis and sagittal imbalance. Zhou et al. ^31^ reviewed 11 patients with old OVCF kyphosis combined with neurological injury and sagittal imbalance who underwent anterior column reconstruction via pedicle osteotomy, suggesting a better clinical outcome. However, to perform PSO, the anterior vertebral body needs to be preserved as a hinge, which may be infeasible due to lack of adequate bone mass in osteoporosis patients, making PSO technically impossible. Therefore, it has been suggested that PSO is not suitable for patients with severe osteoporosis. ^32^ Three‐columns osteotomy is also one of the invasive procedures because it removes both the anterior and posterior columns and thus causes a higher risk of neurological injuries. ^14^ , ^29^ Kim et al. ^33^ evaluated the use of modified PSO (mPSO) in patients with OVCF with kyphosis, and the results suggested that despite the limited correction of the kyphotic angle, patients recovered satisfactorily symptomatically after mPSO (Figure 1).
Figure 1 A schematic diagram of modified pedicle subtraction osteotomy (mPSO). Compared to traditional PSO, intervertebral disc and part of the pedicle are removed for more corrective angle and better bone‐to‐bone fusion and sagittal stability.
Meanwhile, posterior closed wedge osteotomy has been widely used clinically. In a study that included 26 patients with OVCF, Suk et al. ^34^ suggested that compared to combined anterior and posterior surgery, posterior closed wedge osteotomy has better surgical results, significantly reduced mean operative time and mean blood loss. For patients with OVCF combined with neurological impairments, it is potentionally a better option than combined anterior and posterior surgery, despite the high technical requirements.
For severe kyphosis, some researchers have also attempted to correct the sagittal imbalance of the patient using VCR. In a two‐center retrospective study that included 17 patients with OVCF treated with simple PVCR, the results suggested a significant improvement in segmental kyphosis and visual analog scale(VAS). ^35^ In a 5‐year study of 109 patients with OVCF, Pehlivanoglu et al. ^32^ suggested that subtotal PVCR combined with implantation of an expandable titanium cage was a safe and effective procedure, which significantly improved clinical and imaging outcomes by decompressing the spinal canal and reconstructing the resected segmental vertebra. The expandable titanium cage provides some support to the anterior approach, minimizing stress on the posterior pedicle screw and improving fusion rates. ^36^ However, compared to PSO, VCR requires a higher level of surgical skill and a longer learning curve for the surgeons. ^37^
Patil et al. ^38^ retrospectively studied 40 consecutively operated patients with OVCFs with nonunion and adopted different surgical approaches according to different fracture types. The results suggested that when the patients had kyphosis less than 30° with vertebral instability and spinal cord compression causing neurological deficit, Ponte osteotomy or SPO could be used; PSO could be used when the patients had vertebral instability with spinal cord compression causing neurological deficit and kyphosis greater than 30°; VCR is used when patients have neurological deficits and intervertebral instability due to endplate fractures. All of the above osteotomies have achieved good clinical and imaging results. This lay the foundation for the development of an osteotomy strategy for OVCF.
Notably, posterior shortening requires particular attention to potential postoperative spinal cord deformities, especially when posterior shortening is performed above the L1 segment. Tomita et al. ^39^ suggested that spinal shortening can be divided into three Stage 1 (safe range) includes spinal shortening up to 1/3 of a segment, characterized by no deformity of the dural sac or spinal cord; Stage 2 (warning range) includes spinal shortening from 1/3 to 2/3 of a segment, characterized by contraction and curvature of the dural sac and no deformity of the spinal cord; and Stage 3 (dangerous range) includes spinal segment shortening beyond 2/3 of a segment, which causes deformity of the spinal cord, dural sac and spinal cord. This causes deformity of the spinal cord, curvature of the dura and compression of the spinal cord, and possibly more severe neurological deficits.
In conclusion, the selection of the most appropriate osteotomy option depends on an assessment of the bone condition, the extent of the deformity, prior interventions, the type of reconstruction required, the patient's medical condition, and the operator's skill proficiency. ^21^
For patients with OVCF, how to enhance the stability of postoperative internal fixation, maintain the correction effect better, and reduce the occurrence of postoperative complications is the hot issue of current research. ^6^ There are several internal fixation systems available currently, with the most widely used being the pedicle screw system. Pedicle screws provide good initial stability with good coronal and sagittal correction capabilities. However, there is a direct negative correlation between the degree of osteoporosis and the holding power of the screw. ^40^ When pedicle screw fixation is used in elderly patients who have developed osteoporosis, failure of internal fixation, especially pedicle screw fixation, is the most common complication and also a critical factor in surgery. ^41^
Presently, operators can use different strategies to limit these risks. One option is anterior cortical fixation of the vertebral body with double cortical support, ^42^ but anterior cortical structures carry a risk of injuries of the paracortical structures, especially in thoracolumbar structures. Therefore, it is mainly used in sacrum. Second, it has also been suggested that appropriate changes in screw length and diameter or the use of cancellous bone to fill screw tunnel may improve screw holding power. ^43^ , ^44^ Another approach is to use multiple screw anchorage points to better distribute the load over the implant, for example by placing long fixations on either side of the deformity while ensuring that the fixation does not terminate in the area of kyphosis. ^45^
Recently, some researchers have proposed the idea of strengthening screws with hydroxyapatite‐coated screws or expansion screws to increase extraction strength. It has also been proposed that screws can be reinforced with bone cement in the vertebral body, ^40^ , ^46^ where the bone cement can be injected prior to screw insertion or, if fenestrated screws are used, after screw positioning. For the latter, PMMA bone cement can be injected into the vertebral body once inserted, which diffuses to the end of the screw, increasing the pullout strength of the screws. This option is suitable for both open and percutaneous procedures, with the fenestrations of the screw preferably located in the middle of the vertebral body. ^11^ In a prospective multicenter study, Katsumi et al. ^46^ reported that posterior vertebral fusion using bone cement without neural decompression can be adopted in patients with OVCF with <40% intraspinal compression. In a retrospective study, Ma et al. ^11^ suggested that VCR combined with cement‐enhanced pedicle screw fixation could restore the spinal alignment in patients with severe vertebral compression fractures combined with kyphotic deformity with good clinical outcomes. Therefore, posterior fusion with bone cement screw can be widely used as a standard procedure for OVCF patients with severe osteoporosis. But it has limited ability to correct the kyphosis, which can be corrected with osteotomy when patients have sagittal imbalance. ^12^
At the same time, there are risks associated with cemented screws; if the screws are too long, there is a risk of anterior cement leakage which may causing pulmonary embolism. Conversely, too short screws increase the risk of cement leakage in the spinal canal or foramen. ^47^ Therefore, knowing the indications for cemented screws and selecting the appropriate cemented screws are the keys to successful postoperative internal fixation.
OVCF is becoming increasingly prevalent in society as a public health problem. Understanding the characteristics of normal aging and osteoporosis is essential to develop appropriate treatment strategies. The various treatment options (conservative, minimally invasive surgery, open surgery) are essential for surgeons to understand and master. The best treatment option requires a thorough preoperative analysis of the patient, anticipation of potential complications, and targeted prevention before starting treatment.
Junyu Li: Manuscript conceptualization, article screening, manuscript writing and editing. Lizhi Xu: Article screening, manuscript writing, editing, and revising. Yinhao Liu, Zhuoran Sun, Yongqiang Wang, Miao Yu, and Weishi Li: Manuscript writing and editing. Yan Zeng: Manuscript conceptualization, manuscript writing, and editing.
This article is funded by the National Natural Science Foundation of China (82272540).
The authors declare that they have no affiliations with or involvement in any organization or entity with any competing interest in the subject matter or materials discussed in this manuscript.