https://orcid.org/0000-0002-3118-9366
Abstract
Both pyogenic spondylitis and diffuse idiopathic skeletal hyperostosis (DISH) can develop in the thoracolumbar spine of older adults. Among patients with pyogenic spondylitis, those with DISH reportedly have a significantly higher mortality rate than those without DISH. However, the reasons for this increased mortality and effective strategies for preventing fatal outcomes remain to be determined. Here, we report three cases of pyogenic spondylitis affecting non-ankylotic lesions in older patients with DISH. These patients were successfully treated with anterior and posterior fixation using penetrating endplate screws, which provide strong fixation and are particularly advantageous in DISH. In cases of pyogenic spondylitis involving non-ankylotic lesions in DISH, early spinal fixation with penetrating endplate screws, guided using computed tomography and magnetic resonance imaging, may help prevent older adult patients from becoming bedridden.
Introduction
With increasing numbers of older and immunocompromised patients, cases of pyogenic spondylitis are more prevalent [1, 2]. Concurrently, the incidence of diffuse idiopathic skeletal hyperostosis (DISH), characterized with ossification of the anterior longitudinal ligament across ≥4 vertebrae, is rising in this aging population [3, 4].
The lumbar spine is the most common site of infection in pyogenic spondylitis, followed by the thoracic spine [5, 6]. The mid-to-lower thoracic spine, which is the most frequently affected region in DISH, often overlaps with these infection sites [7]. Fractures in the thoracolumbar transition region are highly susceptible to instability, and spinal fixation using pedicle screws (PSs) is an effective stabilization method [8]. In cases of pyogenic spondylitis with associated instability, early surgical intervention is recommended, particularly for patients with neurological deficits, sepsis, or significant bone destruction [9, 10]. Stabilizing the spine can facilitate infection control [11]. Furthermore, pyogenic spondylitis in non-ankylosing DISH lesions tends to be more severe owing to mechanical stress concentration, which exacerbates instability [12].
Magnetic resonance imaging (MRI) is useful for detecting pyogenic spondylitis [12]. Computed tomography (CT) is valuable for evaluating vertebral fractures and determining treatment strategies in patients with DISH [7, 13]. MRI is less effective in detecting DISH, but in combination with CT it can provide additional diagnostic insights [14].
Among patients with pyogenic spondylitis, those with DISH have a significantly higher mortality rate than those without DISH, establishing DISH as a recognized risk factor for mortality [15]. However, the underlying causes of this increased mortality and the most effective interventions for reducing mortality need clarification. We report three cases of pyogenic spondylitis with bone destruction in non-ankylotic lesions of DISH. These patients underwent anterior and posterior fixation using penetrating endplate screws (PESs), particularly double-endplate penetrating screws (DEPS), which offer strong fixation and are advantageous in DISH. This approach aimed to prevent prolonged bed rest and facilitate early mobilization, leading to favorable outcomes.
Case presentation
The patient characteristics are summarized in Table 1. Three men (mean age: 84.3 ± 3.5 years) were admitted to our facility with fever and lower back pain, with blood test results showing inflammatory changes. Each patient was diagnosed with pyogenic spondylitis and an iliopsoas hypostatic abscess originating from an infected intervertebral disc based on MRI findings (Fig. 1). CT imaging revealed an ankylotic spine with DISH and pyogenic spondylitis, along with bone destruction at the endplate in the non-ankylotic region. Two patients exhibited bony bridging on both the cranial and caudal sides of the affected region (Fig. 2A and B), whereas one patient had bridging only on the cranial side (Fig. 2C).
Clinical characteristics of the patients.
| Characteristic | Case A | Case B | Case C |
|---|---|---|---|
| Age (years) | 88 | 84 | 81 |
| Mean age ± SD | 84.3 ± 3.5 | ||
| Sex | Male | Male | Male |
| Affected vertebral levels | L1–L2 | T12–L1 | L3–L4 |
| Blood culture result | Corynebacterium striatum | Gemella morbillorum | Bacteroides fragilis |
| Iliopsoas abscess | Present | Present | Present |
| Surgical approach | Two-stage | One-stage | Two-stage |
| Bone graft source | Rib | Rib | Ilium |
| Characteristic | Case A | Case B | Case C |
|---|---|---|---|
| Age (years) | 88 | 84 | 81 |
| Mean age ± SD | 84.3 ± 3.5 | ||
| Sex | Male | Male | Male |
| Affected vertebral levels | L1–L2 | T12–L1 | L3–L4 |
| Blood culture result | Corynebacterium striatum | Gemella morbillorum | Bacteroides fragilis |
| Iliopsoas abscess | Present | Present | Present |
| Surgical approach | Two-stage | One-stage | Two-stage |
| Bone graft source | Rib | Rib | Ilium |
Abbreviation: SD, standard deviation.
Clinical characteristics of the patients.
| Characteristic | Case A | Case B | Case C |
|---|---|---|---|
| Age (years) | 88 | 84 | 81 |
| Mean age ± SD | 84.3 ± 3.5 | ||
| Sex | Male | Male | Male |
| Affected vertebral levels | L1–L2 | T12–L1 | L3–L4 |
| Blood culture result | Corynebacterium striatum | Gemella morbillorum | Bacteroides fragilis |
| Iliopsoas abscess | Present | Present | Present |
| Surgical approach | Two-stage | One-stage | Two-stage |
| Bone graft source | Rib | Rib | Ilium |
| Characteristic | Case A | Case B | Case C |
|---|---|---|---|
| Age (years) | 88 | 84 | 81 |
| Mean age ± SD | 84.3 ± 3.5 | ||
| Sex | Male | Male | Male |
| Affected vertebral levels | L1–L2 | T12–L1 | L3–L4 |
| Blood culture result | Corynebacterium striatum | Gemella morbillorum | Bacteroides fragilis |
| Iliopsoas abscess | Present | Present | Present |
| Surgical approach | Two-stage | One-stage | Two-stage |
| Bone graft source | Rib | Rib | Ilium |
Abbreviation: SD, standard deviation.
MRI with sagittal short TI inversion recovery and axial T2-weighted images in Cases A–C. Arrowheads indicate infected lesions.
CT with sagittal (sag) and coronal (cor) views in Cases A–C. Arrowheads indicate infected lesions.
All patients initially received antibiotic therapy. While inflammatory markers improved, the patients remained immobile with persistent lower back pain. Consequently, surgical intervention was planned and performed to prevent prolonged bed rest and facilitate early mobilization. The surgical approach involved debridement combined with autogenous bone grafting from the rib or iliac bone via an anterior approach, followed by posterior screw and rod fixation using PESs. The posterior fixation spanned two segments above and two segments below the ankylotic region. If MRI signal changes indicated vertebral infection, conventional PSs were inserted. Two patients underwent a two-stage procedure (Fig. 3A and B), whereas one patient had a single-stage surgery (Fig. 3C). Postoperatively, all patients were able to get out of bed, and their inflammatory markers improved rapidly (Fig. 4). Effective antibiotic therapy was continued for at least 6 weeks. A CT scan performed 12-months postoperatively confirmed bony fusion of the grafted bone at the lesion site (Fig. 5A and B).
Postoperative images (Cases A–C) showing anterior debridement with autogenous bone grafting and posterior fixation using PESs. Conventional PSs were placed in MRI-identified infected vertebrae. Arrowheads indicate grafted bone.
Perioperative changes in serum C-reactive protein levels in all cases.
‘0’ on the horizontal axis of the graph represents the date of surgery, or the surgical period in cases of staged surgery.
CT images of Cases A and B 1 year post-surgery. Arrowheads indicate bony fusion.
Discussion
Pyogenic spondylitis is likely to develop in non-ankylosing lesions of DISH owing to concentrated mechanical stress and increased instability. MRI and CT are valuable diagnostic tools in such cases, while PESs can reduce the posterior fixation range compared with conventional PSs and should be used proactively.
In non-ankylosing DISH lesions, pyogenic spondylitis tends to be more severe because of mechanical stress, leading to instability beyond fractures [12]. Early spinal fusion is particularly beneficial for older adult patients, as early mobilization helps prevent complications. However, no previous reports have documented pyogenic spondylitis in non-ankylosing DISH lesions leading to instability and bone destruction. In such patients, early spinal stabilization should be prioritized to facilitate early mobilization, while PESs, which provide strong fixation forces while allowing for a reduced posterior fixation range in pyogenic spondylitis with DISH, should be used proactively. Additionally, because DISH frequently affects the thoracolumbar junction, ribs harvested during an anterior approach can serve as bone grafts to enhance spinal fusion.
In spinal fractures associated with DISH, stress is concentrated at the fracture site, leading to instability. Consequently, when using conventional PSs, posterior fixation at least three levels above and below the fractured vertebra is required [16, 17]. PESs offer superior fixation compared with conventional PSs, and dual expandable pedicle screws (DEPSs) provide even greater fixation [18, 19]. Using PESs for the fixation of ankylotic vertebrae can reduce bleeding, minimize the fixation range, and decrease the risk of screw loosening [20, 21]. In addition to fractures, PESs have been successfully employed to provide strong fixation in cases of instability resulting from spinal metastases in patients with DISH, further supporting their efficacy [22]. In our cases of pyogenic spondylitis with DISH, PESs effectively reduced the posterior fixation range (Fig. 6).
Schematic diagrams illustrate posterior fixation using PSs (left) and PESs (right), with PESs reducing the fixation range.
Pyogenic spondylitis in ankylosed vertebrae in a patient with ankylosing spondylitis has been reported [23]. The treatment strategy we outline here may also be beneficial in such cases. Overall, early spinal fixation is particularly advantageous, especially in older adult patients. However, these findings are based on data from a small number of patients. Larger studies and long-term follow-up are needed to validate these results.
In conclusion, pyogenic spondylitis can develop in non-ankylosing lesions of DISH, leading to severe instability and bone destruction. In such cases, posterior fixation using PESs should be actively considered, particularly in older adult patients, to facilitate early mobilization and prevent complications.
Conflict of interest statement
There are no conflicts of interest to declare.
Funding
The funding source had no involvement in this work.
Ethical statement
All clinical investigations in this case report were conducted following The Code of Ethics of the World Medical Association (Declaration of Helsinki) and its later amendments. Ethics committee approval was not required for this study. All patients were informed that their data and images would be used in this case report, with written informed consent obtained.
