With the accelerating pace of population aging, osteoporosis has been identified by the World Health Organization (WHO) as one of the 10 most common chronic conditions posing a major threat to the health of older adults (1, 2). Among its complications, osteoporotic vertebral compression fracture (OVCF) is the most frequent, affecting nearly 40.0% of postmenopausal women with at least one fragility fracture over their lifetime, thereby creating a significant burden on families and society (3, 4).

OVCF often leads to debilitating thoracic or lumbar back pain, progressive spinal kyphotic deformity, and, in advanced cases, impairment of cardiopulmonary and gastrointestinal functions, resulting in a marked decline in patients’ quality of life (5, 6). Although some individuals experience relief through conservative approaches—including bed rest, oral non-steroidal anti-inflammatory drugs, brace support, and anti-osteoporotic therapy—more than one-third eventually require surgical treatment (7, 8). Owing to the advanced age, complex comorbidities, and severe bone loss in these patients, outcomes following traditional open reduction and internal fixation are often unsatisfactory (9, 10).

In 1987, Galibert first introduced bone cement injection into the vertebral body for treating vertebral hemangiomas, yielding favorable clinical outcomes (11). Percutaneous vertebroplasty (PVP), developed subsequently, stabilizes vertebral fractures by injecting bone cement, which rapidly restores spinal integrity and provides substantial relief of thoracolumbar pain (12, 13). However, PVP shows limited ability to restore vertebral height and is often inadequate in correcting kyphotic deformities (13, 14). Furthermore, the use of high-pressure cement injection is associated with a high incidence of cement leakage (15, 16). To overcome these limitations, Reiley et al. and Belkoff et al. proposed a balloon-assisted technique to expand the compressed vertebral body and create a cavity for cement injection (17). This method improves the correction of spinal kyphosis and, by compressing surrounding trabecular bone, helps seal fracture lines, thereby significantly lowering the risk of cement leakage (18, 19). Due to these advantages, percutaneous kyphoplasty (PKP) has increasingly become the preferred surgical intervention for OVCF. Nevertheless, recent studies have highlighted several drawbacks of PKP. First, balloon dilation often results in uneven or localized cement accumulation within the vertebral body, which can lead to stress concentration and increase the risk of re-fracturing the treated vertebra or adjacent segments (20–23). Second, excessive attempts to restore vertebral height during balloon inflation may rupture the cortical bone, leading to severe complications such as delayed cement displacement or extrusion (24, 25). Moreover, the use of balloon-expandable instruments adds significantly to the overall treatment cost.

The comparative therapeutic PVP and PKP for OVCF remains debated, with the internal distribution of bone cement identified as a pivotal factor influencing long-term outcomes. Prior research suggests that a diffuse cement distribution with strong anchorage to trabecular bone is more effective in sustaining spinal alignment and reducing the risk of cement migration and extrusion. Current literature mainly relies on subjective, morphology-based grading systems to assess cement distribution, which lack reproducible quantification and fail to directly reflect biomechanical integration at the trabecular level. This study introduces a novel approach using 3D reconstruction and quantitative parameters for an objective evaluation of cement dispersion. This method allows for comparison of distribution patterns between PVP and PKP and establishes a direct, clinically relevant link between these parameters and key clinical outcomes. This study examines how bone cement distribution in PVP and PKP procedures affects vertebral height, Cobb angle correction, and symptom recurrence. The findings are clinically significant, guiding surgical technique choices and cement injection protocols to enhance long-term stability and reduce complications like adjacent fractures and correction loss.

PVP and PKP surgeries involve the injection of bone cement into the vertebral body through minimal trauma to stabilize the fractured ends within the vertebra and reconstruct spinal stability, thereby providing immediate relief from chest or back pain in patients (7, 8). Initially, PVP was the preferred treatment for osteoporotic vertebral compression fractures (OVCF). Subsequently, Reiley et al. and Belkoff et al. introduced modifications to the PVP procedure by incorporating balloon kyphoplasty before bone cement injection (17). This approach effectively restored vertebral height and corrected spinal kyphosis. More importantly, numerous studies suggest that balloon expansion can effectively compress and seal fracture lines within the vertebra, reducing bone cement leakage (18, 19). Consequently, despite the significantly higher medical costs associated with PKP compared to PVP, PKP has become the primary surgical approach for treating OVCF.

The choice between unilateral and bilateral surgical approaches warrants consideration. In our institution, the unilateral puncture technique was primarily employed, with contralateral supplementation reserved for cases demonstrating inadequate cement dispersion across the vertebral midline on postoperative CT evaluation. This strategy aimed to minimize surgical trauma and radiation exposure while ensuring adequate cement distribution. The comparable rates of supplemental contralateral puncture in both groups (9.90% in PVP vs. 8.42% in PKP) suggest that most patients achieved satisfactory outcomes through the unilateral approach alone. The unilateral technique offers advantages including reduced operative time, decreased tissue damage, and lower radiation exposure. However, when cement distribution is suboptimal, supplemental contralateral puncture becomes necessary to enhance biomechanical stability and reduce the risk of correction loss.

With the global dissemination of PKP, many studies have found that although PKP achieves more pronounced short-term vertebral height restoration, the excessive aggregation of bone cement leads to increased stress, making patients more susceptible to re-fracture of the augmented vertebra or adjacent vertebral fractures postoperatively (20–23). Many studies posit that while the balloon used in PKP can expand the vertebral body and correct kyphosis, the cavity formed by balloon expansion confines bone cement distribution primarily within the expanded area, preventing effective interdigitation with the surrounding trabecular bone (24, 25). Furthermore, the stiffness of the solidified bone cement significantly exceeds that of the osteoporotic vertebra, thereby increasing the likelihood of re-fracture in the augmented vertebra or adjacent vertebrae following PKP.

Through retrospective analysis, this study found that both PKP and PVP surgeries significantly alleviated thoracic and back pain in patients in the short term. Compared to PVP, PKP demonstrated superior efficacy in restoring anterior vertebral height and improving local Cobb angle in the short term, consistent with findings from previous studies (14–16). However, during the follow-up period, this study observed a significant loss of anterior vertebral height restoration and Cobb angle correction in the PKP group. Concurrently, patients in the PKP group experienced recurrent exacerbation of thoracic and back pain and ODI dysfunction at the final follow-up. Further analysis of postoperative imaging data revealed that, according to Liu et al’s bone cement distribution score, the PVP group exhibited significantly better bone cement distribution than the PKP group. However, Liu et al’s method, like many others, evaluates bone cement distribution based on its morphology, which is highly subjective and exhibits poor interobserver agreement (29–32). Moreover, factors such as bone cement texture, temperature, viscosity, injection technique, and vertebral fracture morphology influence bone cement morphology within the vertebra, limiting the clinical value of evaluating bone cement distribution solely based on its shape. Subsequently, scholars proposed using the ratio of bone cement volume to vertebral volume to assess bone cement distribution (33, 34). However, due to the influence of bone cement’s fluid properties and the pressure within the cavity containing the bone cement, even when the same volume of bone cement is injected, its actual volume within the vertebra may vary. Most importantly, solely pursuing the volume of bone cement within the vertebra without considering its distribution pattern is unscientific.

To overcome the limitations of previous bone cement distribution evaluation methods, this study innovatively employed Mimics software to measure the surface area and volume of bone cement within the vertebra postoperatively, using the ratio of bone cement surface area to volume to evaluate bone cement distribution. This approach allows for the calculation of the surface area of bone cement in contact with vertebral bone per unit volume, providing a more intuitive and precise quantification of the contact area between bone cement and trabecular bone. Furthermore, this study analyzed the correlation between bone cement distribution and loss of correction in PKP patients using both Liu et al’s scoring method and the proposed approach. The findings revealed that a larger relative surface area of bone cement correlated with stronger ability to maintain correction. Compared to PKP patients, PVP patients exhibited better bone cement distribution patterns and larger contact areas between bone cement and trabecular bone, which may explain the absence of significant correction loss in PVP patients postoperatively.

The distribution pattern of bone cement within the vertebra not only influences deformity correction but also contributes significantly to re-fracture of the augmented vertebra and adjacent vertebral fractures (35–37). This study found that the incidence of re-fracture in the augmented vertebra and adjacent vertebral fractures was higher in the PKP group than in the PVP group. Previous literature suggests that after balloon kyphoplasty in PKP creates a cavity within the vertebra, bone cement tends to aggregate into clumps, failing to interdigitate with trabecular bone and even forming necrotic bone areas between the bone cement and vertebral bone (24, 25). Consequently, when the augmented vertebra is subjected to mechanical stress again, the highly rigid bone cement can easily cause fractures in the fragile vertebral bone. Additionally, the aggregated bone cement in PKP significantly increases the stiffness of the operated vertebra, particularly when larger volumes of bone cement are injected, leading to increased stress on adjacent vertebrae and a higher incidence of adjacent vertebral fractures. In contrast, in the PVP group, the extensive interaction area between bone cement and trabecular bone may disperse stress more effectively, potentially explaining the lower incidence of re-fracture in the augmented vertebra and adjacent vertebral fractures in this group. However, further confirmation through biomechanical experiments and finite element analysis is necessary to validate these findings.

The difference in long-term outcomes likely stems from variations in biological integration and mechanical load transfer at the “cement-bone interface” between the two methods. Ideally, cement augmentation should achieve maximum microscopic interlocking with the bone trabeculae. In PVP, injecting cement under moderate pressure enhances its penetration into trabecular spaces, creating strong microscopic mechanical interlocking, as supported by experimental models (38). This “infiltrative” distribution increases contact area and enhances bond strength through microscopic interlocking. In contrast, during PKP, balloon expansion compresses and disrupts the surrounding bone’s architecture, creating a smooth, dense cavity wall. Cement solidifies into an isolated mass, relying on macroscopic congruence rather than microscopic interlocking. Li et al. (24) noted that post-PKP, cement coalesces, hindering interdigitation and potentially causing bone necrosis at the interface, compromising integration (24). A poorly integrated interface can lead to micromotion and fatigue failure under long-term cyclic loading, affecting mechanical load transfer. Efficient load transfer through the augmented vertebra is crucial for handling spinal load. PVP’s diffuse cement network interweaves with trabeculae, allowing seamless stress transfer and preventing local stress concentration, thus protecting vertebral integrity and reducing stress on adjacent segments. In contrast, PKP forms a central cement mass with a higher elastic modulus than the surrounding bone, creating a “stress riser” that concentrates stress at the cement-bone interface and causes uneven load distribution on the superior endplate. This offers a clear mechanical explanation for why PKP is more prone to postoperative refractures and fractures in nearby vertebrae. Finite element analysis shows that uneven cement clumps cause abnormal load transfer and stress concentration in adjacent vertebrae (39). Moreover, biomechanical tests show that strengthening a vertebral body raises the risk of adjacent vertebrae failing (40). Frankel et al. (20) clinically demonstrated that PKP significantly increases the short-term risk of adjacent fractures compared to PVP (20).In essence, PVP’s cement distribution is superior due to its enhanced biological integration and mechanical behavior, leading to better interfacial interlocking and stress dispersion. This underpins its long-term stability and lower complication rates. Although PKP initially restores height more effectively, its interfacial properties may lead to long-term mechanical issues.

However, this study’s findings should be interpreted with caution due to several limitations. This single-center retrospective study, conducted by a consistent surgical team in one orthopedic department, ensures consistent techniques but limits generalizability. Differences in patient selection, surgical methods, materials, and rehabilitation across centers could affect outcomes. Future prospective multi-center studies with standardized protocols are needed for validation. Second, the study uses a non-randomized design, allowing patients to choose between PVP and PKP after thorough counseling. This respects patient autonomy and mirrors real-world decisions but introduces selection bias. Choices may be influenced by factors like socioeconomic status, insurance, preference for newer technology, or cost sensitivity. Wealthier patients might opt for the costlier PKP, differing in baseline characteristics from those choosing PVP. These unmeasured factors could partly explain the PKP group’s higher rates of re-fracture and adjacent vertebral fracture. Therefore, the comparisons of the long-term effectiveness of the two procedures should be seen as observational associations within a specific context, rather than definitive causal conclusions. While an innovative imaging method was employed to measure cement distribution, the assessment metrics could be improved. The study did not directly measure complex biomechanical factors like microscopic bond strength at the cement-trabeculae interface or detailed stress distribution within the cemented vertebra. These insights are essential for fully understanding the impact of cement distribution on vertebral biomechanics and long-term stability. In summary, recognizing these limitations enhances the study’s value by providing context. The findings offer key hypotheses and guide future research. Further studies should address these limitations with prospective, multi-center, randomized controlled trials and advanced biomechanical tools to clarify the long-term benefits of PVP and PKP in treating OVCF.

Both PVP and PKP are widely used in the management of OVCF and are capable of delivering favorable short-term clinical outcomes and anatomical correction. However, PKP involves a longer operative duration, greater radiation exposure, and higher treatment costs than PVP. Over the long term, due to the less optimal cement distribution achieved during PKP, patients in this group are more likely to experience a decline in deformity correction and may suffer recurrent thoracic or back pain symptoms. Therefore, PVP may be superior to PKP in maintaining long-term correction, particularly when bone cement distribution is optimized.