Short-Segment Bone Cement-Augmented Pedicle Screw Fixation Combined with Bone Grafting for Management of Kümmell Disease with Segmental Instability

Introduction

Kümmell disease is a condition characterized by osteonecrosis and nonunion following osteoporotic vertebral fractures. Its incidence has increased in parallel with the rising prevalence of osteoporosis in recent years. The exact pathogenesis of this disease remains unclear, although it is commonly believed to result from post-fracture bone ischemia. Previous studies have indicated that approximately 10% of osteoporotic vertebral fractures can progress to Kümmell disease [1,2]. However, this estimate may underestimate the true incidence, as a certain proportion of cases are asymptomatic [3]. The widespread use of advanced imaging modalities in recent years has led to an increased detection rate of such cases [4].

For most Kümmell disease cases, percutaneous vertebroplasty (PVP) and kyphoplasty (PKP) have been demonstrated to be effective minimally invasive procedures, offering significant pain relief and functional improvement [5,6]. However, clinical experience suggests that these interventions may not always yield satisfactory outcomes, particularly in cases involving segmental instability. Persistent pain in such cases is primarily attributed to mechanical instability, which must be addressed to achieve effective pain control. Posterolateral fusion with instrumentation can effectively stabilize the affected spinal segment, thereby providing substantial pain relief. Given that Kümmell disease is often accompanied by severe osteoporosis, there is an elevated risk of internal fixation failure [7]. Therefore, bone cement-augmented pedicle screw fixation was used in this study.

To the best of our knowledge, Kümmell disease associated with segmental instability has not been specifically addressed in previous literature. The concept of segmental instability was originally derived from studies on degenerative lumbar disorders, in which a sagittal angular motion exceeding 10° has been commonly used as a diagnostic threshold for instability [8,9]. This criterion has gained widespread acceptance among spinal surgeons. Drawing upon these established diagnostic standards and conceptual frameworks, we propose, for the first time, the definition and diagnostic criteria for segmental instability in the context of Kümmell disease. This study aims to evaluate the feasibility and efficacy of short-segment bone cement-augmented pedicle screw fixation combined with bone grafting for the treatment of Kümmell disease with segmental instability, thereby offering clinical guidance for therapeutic decision-making.

Material and Methods

ETHICS STATEMENT:

The study was approved by Ethics Committee of the Honghui Hospital, Xi’an Jiaotong University. Written informed consent was obtained from all participants. All procedures were conducted in accordance with the principles outlined in the Declaration of Helsinki.

GENERAL INFORMATION:

The study was conducted from January 2021 to January 2024, and cases of Kümmell disease with segmental instability were included in our center. The inclusion criteria were as follows: (1) fulfillment of the diagnostic criteria for Kümmell disease with segmental instability as specified below; (2) involvement of only 1 vertebral body; and (3) complete data availability with a follow-up duration exceeding 12 months. Patients who have previously undergone spinal surgery, and those with infections, tumors, and mental or psychological disorders were excluded. General data such as age, sex, bone mineral density, cause of trauma, disease duration, fundamental diseases, involved segment, and follow-up time were also recorded. All surgeries were performed by the same senior attending physician.

DIAGNOSTIC CRITERIA OF INSTABILITY:

The angle of posterior convexity of the injured vertebra was measured as the angle between the line of the inferior endplate of the superior body of the injured vertebra and the line of the inferior endplate of the injured vertebra when the superior endplate of the injured vertebra was collapsed (Figure 1A), or the angle between the line of the superior endplate of the inferior body of the injured vertebra and the superior endplate of the injured vertebra when the inferior endplate of the injured vertebra was collapsed (Figure 1B). The posterior convexity angle of the injured spine was measured respectively on standing lateral radiographs and the supine median sagittal computed tomography (CT) films, according to the above methods. A change of ≥11° in the posterior convexity angle of the injured vertebra in both positions was defined as instability.

SURGICAL PROCEDURES:

All patients were carefully positioned in the prone position on a sterile operating table and secured to ensure stability throughout the procedure. General anesthesia was administered to maintain unconsciousness and ensure pain-free conditions during the entire surgical intervention. A posterior midline approach was used to precisely expose the spinous processes, vertebral laminae, and articular facets, thereby revealing the detailed anatomical structure of the spine. Pedicle screws were accurately inserted into the fractured vertebra as well as into the adjacent vertebrae – 1 level above and 1 level below – to achieve stable fixation. During the bone cement application phase, polymethylmethacrylate bone cement was slowly and continuously injected into the pedicle screws of the affected vertebra via a fine puncture needle. This process was conducted under continuous fluoroscopic monitoring in the lateral projection, allowing real-time visualization of cement distribution. Cement injection was terminated once adequate diffusion within the vertebral body and around the screws was confirmed radiologically. Six pedicle screws were connected using 2 longitudinal rods, to ensure proper alignment and structural support. Under fluoroscopic guidance, even dispersion of the bone cement was observed, accompanied by a notable restoration of vertebral body height. The facet joints of the affected vertebra and the posterior lateral implant bed were carefully prepared, followed by posterior lateral fusion using allograft bone to promote effective bone healing and fusion. The surgical wound was extensively irrigated with saline solution to remove debris, and thorough hemostasis was achieved to minimize the risk of postoperative complications. Finally, the incision was closed in layers with meticulous attention to detail to facilitate a smooth recovery, and the surgical procedure was concluded successfully.

POSTOPERATIVE MANAGEMENT:

For the first 48 h after surgery, cefoxitin sodium was used to prevent infection, and nonsteroidal anti-inflammatory drugs were used for pain relief within 24 h. On postoperative day 1, bed exercises were performed under a physician’s guidance. On days 2 and 3, drainage tubes were removed, and patients began walking while wearing a brace. Braces were worn for the next 3 months, and back muscles were gradually strengthened with exercises. Patients were required to receive osteoporosis treatment for at least 6 months.

EVALUATION OF CLINICAL AND RADIOLOGICAL RESULTS:

The visual analog scale (VAS) score was used to assess low back pain, and the Oswestry Disability Index (ODI) score was used to assess the impact on the patient’s daily life. The rate of vertebral height loss and the localized kyphotic Cobb angle were measured using lateral radiographs. Vertebral height loss rate=(1-anterior vertebral height/posterior vertebral height)×100% (Figure 1C) [10]. The localized kyphotic Cobb angle is the angle between the upper endplate of the upper vertebra and the lower endplate of the lower vertebra (Figure 1D) [11]. All of the above data were evaluated preoperatively, 1 week postoperatively, and at final follow-up. All patients underwent preoperative frontal and lateral spine X-ray, CT and magnetic resonance imaging (MRI), and X-ray during follow-up. Postoperative CT and MRI examinations were performed on an elective basis depending on the patient’s condition. In addition, operative time, blood loss, hospitalization time, and complications were recorded.

STATISTICAL ANALYSIS:

Statistical analysis was performed using SPSS 23.0 software (IBM Corp, Armonk, NY, USA). Multivariate regression models were used to adjust for confounders, ensuring that the observed effects were not affected by other variables. Measurement data (age, medical history, follow-up time, bone mineral density, operative time, blood loss, hospitalization time, VAS scores, ODI scores, vertebral height loss rate, and kyphosis angle) were represented by mean±standard deviation, and counting data (sex, involved segment, fundamental disease, and complications) were represented by the number of cases and percentage. The repeated measures analysis of variance was used to compare the differences in the indicators (VAS scores, ODI scores, vertebral height loss rate, and kyphosis angle) between the 2 time points. P<0.05 was considered statistically significant.

Results

BASELINE AND PERIOPERATIVE INDICATORS:

A total of 23 patients were included in this study. There were 10 men and 13 women, with a mean age of 66.5±6.6 years (56–82 years). The lumbar spine bone mineral density T score ranged from −2.5 to −4.5 standard deviations, with mean of −3.2±0.6 standard deviations. Nineteen patients had minor injuries (10 due to falls and 9 from lifting weights), and 4 patients had no history of trauma. The symptom duration in 23 patients ranged from 2 to 8 months, with a mean of 4.0±1.4 months. Seven patients had hypertension, 3 patients had diabetes mellitus, and 2 patients had heart disease. The levels of diseased vertebrae were as follows: L2 (3 cases), L1 (7 cases), T12 (8 cases), T11 (4 cases), and T10 (1 case). The mean duration of follow-up was 23.9±7.4 months (12–36 months). The mean operative time was 130.3±7.5 min (120–155 min), mean blood loss was 222.3±16.1 mL (200–250 mL), and mean hospital stay was 7.7±1.3 days (6–12 days). The general data of the patients are shown in Table 1.

CLINICAL EFFICACY AND IMAGING RESULTS:

The results showed that the differences of VAS scores, ODI scores, vertebral height loss rate, and kyphotic Cobb angles showed statistically significant differences between preoperative and 1 week postoperative measurements, and between preoperative and final follow-up measurements (P<0.05; Table 2). VAS and ODI scores at the final follow-up were lower than those measured 1 week before surgery (P<0.05; Table 2), but no significant difference was found in the vertebral height loss rate and kyphotic Cobb angles (P>0.05; Table 2). Based on postoperative CT results, 21 patients (91.3%) achieved solid fusion at final follow-up.

COMPLICATIONS:

No serious complications were found. Two patients developed cement leakage but were asymptomatic postoperatively. One patient developed a urinary tract infection that resolved with conservative treatment. No postoperative nerve injury was found, and no cement migration occurred during follow-up. No loosening, displacement, or fracture of the internal fixation occurred at final follow-up (Figure 2).

Discussion

Treatment options for Kümmell disease have remained a subject of debate in recent years. Although a universally accepted standard treatment has not yet been established, several guiding principles are widely recognized among surgeons. For patients presenting with neurological injury, decompression combined with spinal fixation is generally considered the fundamental approach, with the dual objectives of relieving nerve compression and achieving spinal stabilization. In the absence of neurological deficits, treatment decisions should be based on multiple factors, including the severity of osteoporosis, which can significantly affect bone healing and implant stability; local spinal stability, which is essential for identifying the pain source and determining the necessity of internal fixation; presence of comorbidities such as diabetes or cardiovascular disease, which can influence surgical risk and postoperative recovery; and patient age, as older individuals can exhibit varying tolerances to surgical intervention and rehabilitation [12]. Existing studies have indicated that conventional conservative treatments, such as pharmacological pain management and physical therapy, are often insufficient in providing long-term relief, which supports the recommendation of surgical intervention for this condition [13]. The selection of specific surgical approaches – ranging from PKP/PVP, to spinal fixation and fusion – constitutes a central focus of this study.

Kümmell disease without neurological impairment is classified as either stable or unstable based on whether the kyphotic Cobb angle changes by more than 11° when comparing standing lateral lumbar spine radiographs with recumbent lumbar spine CT scans. For stable Kümmell disease, minimally invasive procedures, such as PVP or PKP, are typically used. These techniques involve the precise injection of bone cement into the vertebral body to fill and stabilize the affected vertebra. The efficacy of PVP and PKP in relieving pain, improving functional status, restoring vertebral height, and correcting spinal deformities has been well documented in numerous studies [14,15]. Since chronic pain in Kümmell disease primarily arises from abnormal vertebral mobility, the injection of bone cement into the vacuum-like intravertebral space effectively alleviates pain by stabilizing the vertebra and reducing motion-induced discomfort. However, clinical practice has shown that these minimally invasive procedures are not universally effective, particularly in cases of Kümmell disease with segmental instability. The persistent pain associated with segmental instability in Kümmell disease is typically sharp and throbbing, radiating to the affected region and significantly impairing the patient’s quality of life. This pain stems primarily from intersegmental instability rather than intrinsic vertebral pathology. Consequently, achieving adequate pain relief requires addressing the root cause by eliminating segmental instability through stabilization of the affected spinal segments to restore proper alignment and function. To the best of our knowledge, this condition has not been previously recognized in the literature. The unsuitability of PKP and PVP for the case series in the present study can be attributed to the following reasons. For Kümmell disease with posterior wall rupture, PKP and PVP carry increased risk of cement leakage and have long been considered relative contraindications [16,17]. Additionally, severe segmental instability can generate excessive stress at the cement-vertebral interface, thereby increasing the risk of delayed cement displacement, further vertebral collapse, and the potential need for revision surgery [18]. Thus, standalone PKP and PVP are not suitable for Kümmell disease with segmental instability.

Once the instability-related source of back pain is identified, the treatment strategy for Kümmell disease with segmental instability becomes clear: posterolateral rigid fusion with internal fixation can effectively eliminate segmental instability, thereby achieving satisfactory pain relief. Given that the Kümmell disease cases in this study were associated with severe osteoporosis, a risk factor for internal fixation failure, we injected bone cement around the internal fixation devices to enhance their holding strength and ultimately reduce the risk of failure. This bone cement augmentation technique for internal fixation has been widely applied in clinical practice. For Kümmell disease with posterior wall rupture, measures must be implemented to minimize the risk of bone cement leakage. First, the procedure is performed under strict fluoroscopic guidance; if signs of cement leakage appear, injection is paused and the direction is immediately adjusted. Second, we typically inject the cement during its doughy phase, which significantly reduces the risk of leakage. Previous research has demonstrated the excellent clinical efficacy, safety, and feasibility of this approach [3,7]. Furthermore, considering the adverse effects of osteoporosis on patient outcomes, we recommend the administration of effective anti-osteoporotic medications in the early postoperative period. This is crucial for improving bone mineral density, enhancing patient quality of life, and reducing the risk of internal fixation failure. In the present study, all patients received systematic anti-osteoporotic treatment, and no cases of internal fixation failure were observed during follow-up, further emphasizing the importance of proactive osteoporosis management in preventing such complications.

The surgical technique used in this study offers several advantages over traditional long-segment fixation. First, effective posterolateral bone graft fusion combined with short-segment pedicle screw fixation can effectively eliminate segmental instability, thereby achieving excellent postoperative pain relief. The graft material, typically allogeneic bone, integrates seamlessly with the host bone, facilitating robust osseointegration and enhanced stability. Second, the risk of postoperative screw loosening or displacement is significantly reduced, as cement-augmented pedicle screws have demonstrated superior anchoring strength. The bone cement functions as an adhesive, ensuring firm fixation of the screws within the vertebral body. Third, short-segment fixation is associated with less surgical trauma, shorter operative duration, and reduced blood loss – factors that are particularly critical for elderly patients who may not tolerate extensive surgical procedures. Additionally, the minimally invasive nature of the approach minimizes the need for large incisions, contributing to faster recovery and a lower risk of infection. Fourth, the rate of cement leakage is significantly reduced, thereby substantially lowering the risk of nerve injury. Precise cement application minimizes extravasation beyond the target area, protecting vulnerable neural structures. Fifth, compared with long-segment fixation, short-segment fixation exerts less adverse impact on adjacent spinal segments, which can significantly reduce the risk of adjacent segment degeneration [19]. Currently, various internal fixation and reconstructive surgical techniques are used in the management of Kümmell disease. However, previous literature has indicated that these procedures are often associated with a relatively high incidence of complications, posing a major challenge in the surgical treatment of this condition [20–22]. In contrast, only 3 complications were observed in the present study, including 2 cases of asymptomatic cement leakage and 1 case of urinary tract infection. These findings suggest that posterolateral bone grafting combined with cement-augmented short-segment fixation is associated with fewer complications. This may be primarily attributed to the less invasive nature of the procedure and reduced blood loss. However, the small sample size and limited follow-up duration in our study should also be considered as potential confounding factors. A 2024 study identified several risk factors for bone cement displacement after PKP, including a high patient body mass index, high degree of Cobb angle correction, large distance between the cement and the vertebral endplate, and cement leakage [23]. Therefore, early identification and management of these risk factors may effectively reduce potential postoperative complications, such as cement displacement.

However, several previous studies have indicated that the postoperative improvements in vertebral height and kyphotic angle tend to diminish over time. This phenomenon may be attributed to progressive osteoporosis, which could increase the risk of further local kyphosis progression [3,24,25]. In the present study, compared with the outcomes at 1 week after surgery, the kyphotic angle and height of the affected vertebrae showed slight reductions at the final follow-up; however, these differences were not statistically significant (P>0.05). Additionally, at the final follow-up, the degree of loss in the kyphotic angle and height of the affected vertebrae did not differ significantly from that observed with traditional anterior or posterior fixation. This finding may be associated with the short follow-up duration and small sample size of the present study, thus necessitating further observation to validate the results. In this study, posterolateral bone graft fusion required a certain period to achieve consolidation, during which the stability of the vertebrae depended on posterior internal fixation. Due to the severe instability of the affected vertebrae, the stress on the posterior internal fixation was significantly increased. Despite the application of bone cement in this study, there remained a risk of loosening, displacement, and fracture of the internal fixation devices. Therefore, close follow-up is essential until the posterior bone graft achieves firm fusion.

This study has several limitations. First, the main limitation of this study is the lack of a control group, which makes it impossible to compare with surgical methods such as PVP and PKP or long-segment internal fixation. The lack of a control group can also have a negative impact on the accuracy and reliability of the research results. Second, it was a retrospective, single-center study, which may have introduced bias and limited data representation. Third, a small sample size and short follow-up periods may affect the reliability of the results and prevent the observation of long-term clinical effects or complications. In the future, large-sample and long-term follow-up studies are needed. Lastly, a prospective, multicenter, randomized controlled study would more effectively assess the clinical efficacy of posterolateral bone grafting combined with bone cement–enhanced short-segment fixation for Kümmell disease with segmental instability. These aspects will be the focus of our future research.

Conclusions

Short-segment bone cement-augmented pedicle screw fixation combined with bone grafting is a safe and effective surgical method for the treatment of Kümmell disease with segmental instability. This method can achieve satisfactory pain relief, functional improvement, and correction of kyphosis and vertebral height, and causes few complications. However, further evaluation is required to determine long-term clinical and radiological outcomes. We plan to conduct large-scale multicenter randomized controlled trials to verify the reliability of the research results.