Progressive spinal destruction secondary to minimal vertebral fracture in a patient with diffuse idiopathic skeletal hyperostosis: a case report

Abstract

Early operative fixation is widely recognized as essential for managing spinal fractures in patients with diffuse idiopathic skeletal hyperostosis (DISH). However, no report to date has addressed the occurrence of minimal vertebral fractures diagnosable only through magnetic resonance imaging (MRI) in these patients and the associated temporal changes in the fracture site. In this report, we describe a rare clinical case involving an 81-year-old man who developed progressive spinal destruction secondary to a minimal vertebral fracture. MRI showed minimum-intensity changes in the T12 vertebral body, whereas X-ray and computed tomography examinations showed DISH and no spinal fracture. Despite experiencing severe low back pain, the patient did not undergo operative therapy for 2 months, resulting in progressive spinal destruction. Spinal fusion with posterior instrumentation was performed, and the patient was followed for 1 year with no symptoms and good functional status. This case emphasizes the importance of clinicians being cautious to avoid overlooking and undervaluing minimal vertebral fractures diagnosable only through MRI in patients with DISH.

Introduction

In 1950, Forestier and Rotes-Querol ¹ reported ankylosing spondylosis as a disease that causes spinal ankylosis due to ossification of the spinal ligaments, mainly the anterior longitudinal ligament. Resnick and Niwayama ² defined diffuse idiopathic spinal hyperostosis (DISH) as bone proliferation not only in the spine but also in general tendons and ligaments of elderly individuals.

The prevalence of DISH in Japanese people reportedly ranges from 12% to 27%. ^{3 , 4} Patients with DISH have a significantly higher risk of spinal fracture than patients without DISH. ⁵ Vertebral fractures in patients with DISH are difficult to treat conservatively because bone union is not achieved in almost all patients. ⁶

Early operative spinal fixation is recommended by spinal surgeons. ^{7 , 8} In some cases, however, doctors underestimate the importance of spinal fractures in patients with DISH, even if they have been correctly diagnosed. Although a few case reports have been published, they mainly focused on surgical techniques and lacked a description of the time course of changes in the bone fracture portion.

We herein describe a patient with DISH who sustained a minimal vertebral fracture and did not receive appropriate care for 2 months, resulting in progressive bony defects.

This study was conducted in conformity with the ethical guidelines for clinical application of human subjects established by the Japanese Ministry of Health, Labour and Welfare. The study protocol was approved by the Research Ethics Committee of North Osaka Housenka Hospital. The patient provided written informed consent for treatment and publication.

Case report

An 81-year-old man with a history of chronic obstructive pulmonary disease and epilepsy fell from a bicycle and was admitted to the hospital for low back pain. Initial X-ray (Figure 1) and computed tomography (CT) (Figure 2) examinations showed continuous ossification of the anterior longitudinal ligament and the intraspinous and supraspinous ligaments in the thoracolumbar spine without evidence of spinal fracture. No inflammatory changes were detected at the sacroiliac joint. However, magnetic resonance imaging (MRI) revealed a minimum-intensity change adjacent to the tail-side endplate of the T12 vertebral body, indicating a fracture (Figure 3). The patient was diagnosed with a fracture of the T12 vertebral body and was treated with a hard thoracolumbar corset, analgesic drugs, and rehabilitation. He was discharged after 4 weeks and was able to walk with a cane. However, 4 days after discharge, he became bedridden in his house because of increasingly severe low back pain.

Figure 1.

Lumbar radiographs soon after injury. (a) Anteroposterior view and (b) Lateral view.

Figure 2.

Lumbar computed tomography images soon after injury. (a) Coronal view. (b) Sagittal view and (c) Sacroiliac joint. The anterior longitudinal ligament and supraspinous ligament were continuously ossified in the thoracolumbar spine, and the fracture was not observed by X-ray or computed tomography at the referring hospital. No inflammatory changes were detected at the sacroiliac joint.

Figure 3.

Lumbar magnetic resonance imaging soon after injury. (a) T1- and (b) T2-weighted sagittal views. (c) T2 STIR image, sagittal view. A minimum-intensity change in the tail-side endplate was observed at the T12 vertebral body, low intensity was observed in the T1-weighted image and the T2-weighted image, and high intensity was observed in the T2 STIR image. No intensity change was recognized in the posterior elements.

The patient was admitted to our hospital almost 2 months after the injury. X-ray and CT examinations showed progressive spinal destruction in the T12 and L1 vertebral bodies and the bone fracture in the ossified intraspinous and supraspinous ligaments (Figure 4). MRI confirmed compression fractures of the T12 and L1 vertebral bodies and the posterior elements with DISH (Figure 5); these were diagnosed as AO classification type C. Therefore, the patient was deemed a surgical candidate for spinal fixation. His HLA-B27 test result was negative. His numerical rating scale score for pain was 10/10, indicating the most severe pain. His Functional Independence Measure (FIM) total score was 56/126, FIM motor score was 21/91, and FIM cognition score was 35/35. Manual muscle tests revealed normal strength in the lower extremities without paralysis, and no urinary disorders were observed. A longer custom-measured hard thoracolumbar corset was designed, and romosozumab injection was administered to stimulate bone formation before the operation.

Figure 4.

Lumbar computed tomography images 2 months after injury. (a) Coronal view. (b) Sagittal view. Vertebral bone defects, posterior intervertebral displacement, and fracture of the ossified intraspinous and supraspinous ligaments occurred between T12 and L1.

Figure 5.

Lumbar magnetic resonance imaging 2 months after injury. (a) T1- and (b) T2-weighted sagittal views. (c) T2 STIR image, sagittal view and (d) T2 STIR image, coronal view. The T1-weighted, T2-weighted, and STIR images showed a wide range of intensity changes in the T12 and L1 vertebral bodies. Low-intensity change in T1-weighted images and high-intensity changes in T2-weighted and T2 STIR images were confirmed in the posterior elements.

Open posterior spinal fixation was performed between the T10 and L3 vertebrae with postural reduction of spinal alignment and vertebral slipping. The operative procedure was conducted with the free-hand technique, and intraoperative X-ray examination was used to ensure the proper direction and position of the markers and screws.

After the surgery, the patient’s intolerable low back pain disappeared and rehabilitation was started, including muscle strengthening exercises, sitting exercises, and standing and walking exercises. The patient was able to stably walk with a cane 6 weeks later.

CT examination showed bone formation in the defect, particularly in the side walls. The romosozumab therapy was stopped after four injections.

The patient was discharged to home with a walking cane at 16 weeks after surgery when he completed the rehabilitation program. One year following the operation, the patient’s scores significantly improved. His numerical rating scale score decreased to 0/10, indicating the absence of pain. His FIM total score and FIM motor score increased to 113/126 and 78/91, respectively, and his FIM cognition score remained at 35/35. No sensory or motor disturbances or urinary disorders were observed. X-ray and CT examinations 1 year after surgery showed bone fusion between the vertebrae, with the side walls tightly united (Figures 6, 7).

Figure 6.

Lumbar radiographs 1 year after surgery. Operative spinal fixation was performed between T10 and L3, and the postoperative course was good. (a) Anteroposterior view and (b) Lateral view.

Figure 7.

Lumbar computed tomography images 1 year after surgery. Intervertebral bone union was confirmed in all areas except the anterior wall, and the side walls exhibited tight union. (a) Coronal view and (b) Sagittal view.

Discussion

In 1976, Resnick and Niwayama ² proposed the following diagnostic criteria for DISH: (a) the presence of “flowing” calcification and ossification along the anterolateral aspects of at least four contiguous vertebral bodies with or without associated localized excrescences at the intervening vertebral body–disc junctions; (b) relative preservation of disc height in the involved areas and the absence of extensive radiographic changes of “degenerative” disc disease, including vacuum phenomena and vertebral body marginal sclerosis; and (c) the absence of apophyseal joint bony ankylosis and sacroiliac joint erosion, sclerosis, or bony fusion. ²

DISH may involve the entire vertebral column, but it most frequently affects the lower thoracic and upper lumbar spine. ⁹ Compression fractures of the spine are most commonly found at the T12 and L1 levels in patients with DISH at an equal frequency of 13%, and fractures extending to the posterior element are observed in 62% of patients. ⁷ Low-energy trauma, such as falls from standing and sitting positions, is detected in 51% of patients, with 40% receiving a delayed diagnosis and 30% developing delayed palsy. ⁷

In the DISH-affected spine, the cortical bone proliferates and thickens, while the spongy bone becomes rough due to stress shielding, causing fragile vertebrae. Ossification of the anterior longitudinal ligament causes the spine to be connected in the longitudinal direction; thus, even minor trauma causes stress to concentrate on the spine, and this is considered to cause the high risk of vertebral fractures. ^{6 , 8}

The fractures in patients with DISH are often three-column injuries that become unstable, increasing the likelihood of dislocation. This is why bone fusion is difficult to achieve with conservative treatment. ⁶ Delayed diagnosis and a prolonged waiting period before surgery are likely to cause delayed nerve palsy, and early internal fixation is recommended. ^{7 , 8}

In one study, the mortality rate 1 year after injury ranged from 0% to 32%. A total of 84% of patients encountered complications, mostly pneumonia, respiratory failure, and pseudoarthrosis. ¹⁰

In other studies, the reoperation rate for vertebral fractures in patients with DISH treated by open surgery with pedicle screws was 25%, ¹¹ and the postoperative backout rate was 23%. ¹² In the present case, we advised the patient not to bend forward, especially when getting up. Additionally, we recommended raising the backrest from a lateral recumbent position with the legs lowered, allowing the patient to sit on the edge of the bed.

Some case reports have described successful treatment with a trunk cast and daily teriparatide injections.^13–17 If this method had been adopted for our patient in the early phase of treatment, bone union could have been achieved.

Our instructive case describes a spinal fracture in a patient with DISH. Some other case reports of fractures recommended early surgical intervention. ^{7 , 8} In these cases, some deformities were observed in the X-ray and/or CT examinations. Our patient showed no deformity in the initial X-ray and CT examination, and minimum-intensity changes were present at the anterior and posterior edges of the caudal endplate in the MRI examination. Therefore, it is important to consider MRI for patients with DISH who develop spinal complications despite no abnormalities on X-ray and CT examinations.

In our case, no intensity change was observed in MRI of the posterior elements of the ankylosed intervertebral joint and ossified intraspinous and supraspinous ligaments at the emergency hospital. These structures were not fractured initially, and they could have served as dependable supporters of the minimally injured spine. However, they could not maintain the spinal structure throughout. Although the ossified posterior structures were fractured in the end, they were able to prevent the development of a crushing spine deformity for 2 months. Therefore, the patient was transferred to our hospital without any neurological deficits.

Conclusions

In this patient with DISH, we found a minimal vertebral fracture that was not detectable by X-ray or CT examinations. Initially, the posterior elements of the ankylosed intervertebral joint and ossified intraspinous and supraspinous ligaments were intact. Although these structures would have ideally maintained spinal stability during the bone union period, progressive spinal destruction occurred, requiring spinal fixation. Fortunately, the patient did not develop spinal cord injury for 2 months. This case highlights the importance of not overlooking or undervaluing the importance of minimal vertebral fractures that are only detectable by MRI in patients with DISH. Early operative fixation should be performed for these spinal fractures.

The reporting of this study conforms to the CARE guidelines. ¹⁸