1. Introduction

Spinal cord compression is associated with considerable morbidity and mortality [1]. A variety of etiologies in spinal cord compression are known. Severe angular kyphosis is one of the uncommon etiologies of spinal cord compression that is usually caused by congenital kyphosis. Yet, other etiologies such as post-tuberculous kyphosis and posttraumatic kyphosis are also acknowledged. Severe angular kyphosis may lead to compressive myelopathy, a rare and disastrous pathology with challenging surgical treatment, particularly for those with neurologic deficits. The surgical intervention might impose mechanical stress to an already “sick spinal cord,” resulting in further neurologic damages and more complicated treatments [2-4].

Despite the difficult management of compressive myelopathy in severe angular kyphosis, many aspects of this disorder are obscure, including its incidence, prognosis, and potential adverse neurologic outcomes of the different surgical approaches [2, 5]. This is mainly due to the rare occurrence of such disorder and the limited number of papers concerning the compressive myelopathy in severe angular kyphosis. In earlier literature, the outcome of surgical treatment of compressive myelopathy in severe angular kyphosis has only been reported in a small number of case series and it is unclear to what extent the patients will benefit from the surgical intervention. Moreover, in a subset of patients, the neurological status has reported being deteriorated after the operation [2].

In this retrospective study, we report a series of 12 patients with compressive myelopathy caused by severe angular kyphosis, as well as the results of surgical decompression and kyphosis correction.

2. Methods

This retrospective study was approved by the Review Board of our institute and the written informed consent was obtained from all patients to use their data for publication. We included patients with compressive myelopathy caused by severe angular kyphosis between 2011 to 2017. The inclusion criteria were the progressive or the sudden onset of paraplegia. Computed Tomography (CT) scanning was used to precisely identify the abnormality and fusion. Magnetic Resonance Imaging (MRI) was used to identify cord compression and the extent of signal intensity alteration. Anteroposterior and lateral radiographs were obtained to assess the balance of the spine in different planes. 

Neurological status of the patients was evaluated with the international standards for neurological and functional classification of spinal cord injury published by the American Spinal Injury Association (ASIA) [6], designed in five grades of A. (complete: no sensory or motor function is preserved); B. (sensory incomplete); C. (motor incomplete with a muscle grade less than 3); D. (motor incomplete with a muscle grade more than 3); and E. (normal). Neurological status was recorded once before the surgery and at four stages after the surgery (after 1 day, after 1 week, after 6 months, after 1 year).

Main surgical interventions included Anterior Spinal Fusion (ASF) with or without instrumentation and with or without decompression, Posterior Spinal Fusion (PSF) with or without instrumentation and with or without decompression, and anterior corpectomy. All operations were done by one senior spinal surgeon. Intraoperative wake-up test, motor evoked potentials, and somatosensory evoked potential monitoring was not used for any patients. The demographic and clinical characteristics of the patients were extracted from the patients’ medical files.

3. Results

A total of 12 cases of compressive myelopathy caused by severe angular kyphosis were identified during the study period. The study population comprised 4 males (33.3%) and 8 females (66.7%) with the Mean±SD age of 41.9±16.4 years, ranging from 14 to 59 years. The etiology of myelopathy was congenital kyphosis in 10 patients (83.3%). The level of paralysis ranged from T10 to L2 vertebra. The Mean±SD duration of paralysis was 6.4 ±6.6 months, ranging from 1 to 24 months. The Babinski sign was upward in 7 patients (58.3%) and downward in 5 patients (41.7%). The Mean±SD percentage of cord thinning at the apex was 61.7±17.5% ranging from 40% to 90%. The clinical and demographic characteristics of the patients are presented in detail in Table 1.


 

One-stage surgery was performed in 5 patients (41.7%), while the surgery was performed in two stages in the other 7 patients (58.3%) (Figure 1-3).








The detailed surgical intervention and outcome are provided in Table 2.



The Mean±SD preoperative kyphosis angle was 92.1±28 degrees that reduced to 50.2±38.5 degrees after the surgery. The Mean±SD preoperative scoliosis angle was 23.5±24.1 degrees that reduced to 9.4±11.4 degrees after the surgery. Before the operation, 6 patients (50%) had bowel or bladder dysfunction which was resolved in 5 of these patients after the operation. One year after the operation, the ASIA typing was improved in 9 patients (75%) and remained the same as preoperative status in 3 patients (25%). No ASIA typing deterioration was observed in our series (Table 2).

4. Discussion

Considering the rare incidence of severe angular kyphosis, the beneficial effects of surgical treatment of compressive myelopathy in these patients is not well-understood. It is unclear to what extent the patients would benefit from surgical intervention. In a subset of patients, the neurologic status might even deteriorate after the surgery, which further complicates the current uncertainties. In this situation, reports of the outcome of surgical treatment in these patients could be regarded as a valuable approach to resolve the existing concerns.  

According to the study results, congenital kyphosis was the most frequent etiology of compressive myelopathy in severe angular kyphosis. Surgical intervention results in the improvement of neurological symptoms in the majority of patients, including their bowel/bladder dysfunction. In this respect, bowel or bladder dysfunction resolved in 5 (83.3%) out of 6 patients after the surgery. Besides, the neurological status improved in 9 (75%) out of 12 patients and remained the same as preoperative status in 3 patients (25%). No neurological symptoms deterioration was observed in patients of the current series.

To date, compressive myelopathy in severe angular kyphosis has only been reported in a small number of case series. 

In the study of Zhang et al., 10 patients with severe angular kyphosis and a progressive or a sudden onset of paraplegia were surgically treated [2]. Song et al. [3] and Chang et al. [4] also reported a series of 17 and 16 patients with compressive myelopathy in angular kyphosis of the thoracic spine, respectively. While the dominant etiology was congenital kyphosis in Zhang’s study (8 out of 10 cases) as well as ours (10 out of 12 cases). Pott’s kyphosis was the most common diagnosis in the study of Song et al. as well as Chang et al. (7 out of 16 cases and 11 out of 17 cases, respectively). The most common apex of the kyphosis was the lower thoracic spine in the study of Song et al. (10 out of 16 cases) as well as Change el. (14 out of 17 cases). Yet, the most common apex of kyphosis was upper thoracic spine (6 out of 10 cases) in the study of Zhang et al. The apex of kyphosis was equally distributed between lower thoracic spine and upper lumbar spine in our series.

KY and YH reported the outcome of the treatment of neurological deficit in 36 patients with severe angular kyphosis caused by spondylitis secondary to tuberculosis. An improvement of the neurological symptoms, evaluated by the ASIA impairment scale, occurred in 4 out of 9 patients (44.4%) who were treated surgically [7].

The mean age of patients in the current series was 41.9 years. The onset of the neurological deficit was more than 16 years of age in 9 out of 10 cases of congenital kyphosis that was not in accordance with the earlier investigations [2, 8, 9]. 

The reduction of spinal cord diameter at the apex was 40%-80% in the study of Zhang et al. This level of cord thinning in patients with congenital kyphosis presented with paraplegia was in accordance with the earlier investigations [10-12]. The percentage of spinal cord thinning ranged from 40% to 90% in our patients at the time of presentation. 

Correction of spinal deformity has been reported as a risk factor of spinal cord injury in many investigations [13-15]. In this respect, the ASIA typing deteriorated in one of the cases of the study of Zhang et al. Yet, no ASIA type deterioration was recorded in our series. Several factors might affect the outcome of spinal correction surgery, including the intraoperative spinal cord vessels or neural tissue distortion, spinal cord impingement at the edges of decompression, blood loss, etc. [13]. The ASIA typing improved in all patients of the studies of Song et al. and Chang et al. but not in some patients with ASIA type A. The ASIA typing improved in 9 cases of our series. The initial ASIA type was D in these patients and remained the same in the last follow-up.

Atici et al. analyzed the complications of Posterior Vertebral Column Resection (PVCR) for the treatment of 17 patients with severe angular kyphosis > 100°. Complications occurred in 12 patients (70.6%), comprising spinal shock (n=4), hemothorax (n=3), postoperative infection (n=2), dural laceration (n=2), neurological deficit (n=2), the shifted cage (n=2), and rod fracture (n=2). Neurological events occurred in 6 patients (35%) which were temporary in 5 patients and permanent in the other one. They concluded that although PVCR is an efficient technique for the correction of severe angular kyphosis, it is associated with several major complications [16].

Zhang et al. suggested factors such as the patient’s age (over 20 years old), the kyphosis angulation (over 120 degrees), and gradual onset of paraplegia as the indicators of poor prognosis in congenital kyphosis after surgery. Particularly, the preoperative duration of paraplegia and the severity of paraplegia before the surgery were mentioned as the key factors for adverse postoperative neurological prognosis [2]. Yet, these factors did not seem to be determinative of the outcome in our series. However, to prevent further neurological defects, it is safer to perform decompression surgery when spinal cord compression and cord thinning at the apex are seen in MRI and adequate decompression can be achieved surgically.

This study was not without limitations. The retrospective design and a small number of patients could be regarded as the main limitations of this study. However, it should be noted that available case series are the best way to gather information regarding the outcome of surgical treatment of compressive myelopathy in patients with severe angular kyphosis. 

Altogether, our study reveals that severe angular congenital kyphosis could result in compressive myelopathy with serious neurological impairments. As the surgical decompression is shown to correct the neurological symptoms in the majority of cases, it is suggested to perform surgical intervention as soon as the spinal cord compression is detected. Delay in surgery might lead to a more complicated operation and impose a further risk of neurological damages to an already vulnerable patient. Yet, it should be noticed that complete recovery might not be achievable and this should be discussed with the patients and their families.

Ethical Considerations

Compliance with ethical guidelines

All ethical principles are considered in this article. The participants were informed about the purpose of the research and its implementation stages; they were also assured about the confidentiality of their information; moreover, they were free to leave the study whenever they wished, and if desired, the research results would be available to them.

Funding

This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors. 

Authors' contributions

All authors contributed in preparing this article.

Conflict of interest

The authors declared no conflict of interest.


 

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