Clinical outcomes for andersson lesion in patients with ankylosing spondylitis by transforaminal thoracolumbar intervertebral fusion surgery

Abstract

BACKGROUND:

Andersson lesion (AL) is a rare complication of ankylosing spondylitis (AS). Its clinical outcome of surgical treatment needs further exploration.

OBJECTIVE:

To evaluate the clinical and radiological outcomes of transforaminal thoracolumbar intervertebral fusion (TTIF) in the treatment of AS patients with thoracolumbar AL.

METHODS:

Fourteen patients with thoracolumbar AL who suffered from back pain, spinal instability or kyphotic deformity were retrospectively recruited. The clinical outcomes were evaluated with Visual Analog Scale (VAS) and Oswestry Disability Index (ODI). Radiological outcomes were measured with local kyphotic (LK) angle and general kyphotic (GK) angle.

RESULTS:

Before surgical treatment for the AL patients, their VAS score and ODI score was 8.0 $\pm$ 0.2 and 64.0 $\pm$ 6.9, respectively. After TTIF surgery, VAS score of the patients was improved to 2.4 $\pm$ 0.5 ( $p<$ 0.01) and ODI score was decreased to 17.0 $\pm$ 3.7 ( $p<$ 0.01). One patient with neurological deficit showed an improvement in the Frankel grade from C to D and all others were grated E-level before and after surgery. For radiological outcomes, patients’ LK angle was reduced from 18.5 $\pm$ 7.2 to 11.0 $\pm$ 6.4 ( $p<$ 0.01) and GK angle was reduced to 38.6 $\pm$ 8.8 from 42.8 $\pm$ 10.4 ( $p<$ 0.01) at the 1-year follow-up.

CONCLUSION:

For AS patients with thoracolumbar AL, we propose that TTIF is an effective and safe operative treatment, which can achieve good fusion, satisfactory radiological and clinical outcomes.

Keywords

Vertebral fusion andersson lesion ankylosing spondylitis kyphosis

1. Introduction

Andersson lesion (AL) is a rare complication occurring in the late stage of ankylosing spondylitis (AS) with a prevalence rate of about 1.5% to 28% [1, 2, 3]. AL was first described by Dr. Andersson in 1937 and Cawley et al. categorized it into three groups according to whether it involved the discal surface of the vertebral rim or the cartilaginous part of the vertebral end plate [4, 5]. The most commonly affected site of AL is the thoracolumbar junction which attributes to the fact that this region is a transitional zone with high stress risers. AL leads to an increasing sharp, localized pain which worsens with activity and relieves with rest. Besides, kyphotic deformity is also a common complication of AL. Furthermore, rapid progression may happen after minor trauma, which would have a great impact on a patient’s life [6].

Though with limited evidence, it is generally believed that surgical management is necessary when AL leads to severe back pain, neurological dysfunction and aggravated kyphotic deformity [7]. The ultimate goal of surgery in AL patients is to not only decompress the spinal canal and alleviate back pain, but also restore spinal stability and facilitate fusion of the lesion. However, considerable adverse effects such as neurological symptoms, nonunion and progressive kyphotic deformity could occur after surgical treatment [8, 9, 10].

Some researchers have investigated whether AL should be conservatively or surgically treated. Different kinds of surgical strategies, including anterior spinal fusion, short segment posterior spinal fusion, long segment posterior spinal fusion, and combined anterior and posterior spinal fusion have been described [11, 12, 13, 14, 15, 16]. However, no consensus has been achieved considering the approach or the fusion criteria. According to our knowledge, the appliance of transforaminal thoracolumbar intervertebral fusion (TTIF) for the treatment of trans-disc type AL has not been reported. In the past three years, we recruited 14 trans-disc type AL patients and managed with TTIF and posterior internal fixation and followed them up for at least 1 year. The data of radiological outcome, clinical efficacy and complications before and after the operation were collected and analyzed to evaluate the outcome of TTIF in the treatment of AS patients with thoracolumbar AL.

2. Materials and methods

2.1 Patient selection and data collection

The data were retrospectively collected of 14 patients who were diagnosed with AS combined with thoracolumbar AL at Spinal Surgery Department of Guanghua Hospital affiliated to Shanghai University of Traditional Chinese Medicine from 2019 to 2021. All patients underwent plain radiography, computed tomography (CT), magnetic resonance imaging (MRI), areal bone mineral density (BMD) (g/cm ${}^{2}$ ) measurements using dual-energy X-ray absorptiometry (DEXA) on the lumbar spine, and physical examination by a spinal surgeon after admission. They all exhibited radiological features of ankylosed ‘bamboo’ spine and fused sacroiliac joints, indicating severe advanced AS.

A CT scan provided the bony anatomy and deformity of the lesion and an MRI scan revealed the fractural condition and the compression extent of the spinal cord. All preoperative imaging examinations confirmed the diagnosis of trans-disc type AL. Our indications for TTIF were as follows: (1) the lesion was located in T10-L2; (2) spinal instability threatening neurological deficit; (3) progressively worsening pain and deformity. Age, gender, clinical manifestations, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), human leukocyte antigen-B27 (HLA-B27), T score of BMD (L1-L5), duration of symptoms before surgery, lesion location, fixed segments, surgery duration and hemorrhage volume was recorded. In addition, the preoperative and 1-year follow-up back pain levels using the Visual Analog Scale (VAS), patient’s function level using the Oswestry Disability Index (ODI), neurological status using Frankel grading and kyphotic status using local and general kyphotic angle and the condition of fusion and complications were also recorded. This study was approved by the Ethics Committee of Guanghua Hospital affiliated to Shanghai University of Traditional Chinese Medicine (approval number: 2019-K-04) and informed consent was obtained from all patients.

Table 1
Baseline characteristics of included patients

List	Gender	Age	Surgery indications	ESR mm/h	CRP mg/L	HLA- B27	BMD (T score)	Symptom duration before surgery
(month)	Lesion segment	Fixed segment	Surgery time (min)	Hemorrhage volume (ml)
1	F	41	Pain, kyphotic deformity	5	4.5	$+$	$-$ 3.5	3	T11/12	T10-L1	180	500
2	M	71	Pain, instability	23	10.3	$+$	$-$ 2.5	6	T10/11	T9-T12	160	300
3	F	64	Pain, instability, kyphotic deformity	40	33.1	$+$	$-$ 2.2	12	L1/2	T12-L3	200	550
4	M	46	Pain, instability	9	12.9	$+$	$-$ 2.0	2	T11/12	T10-L1	110	400
5	F	55	Pain, instability	25	10.2	$+$	$-$ 2.6	3	T12/L1	T11-L2	130	200
6	F	54	Pain, instability	36	20.9	$+$	$-$ 1.6	1	T11/12	T10-L1	100	250
7	M	64	Pain, instability	35	18.4	$+$	$-$ 2.2	1	T10/11	T9-T12	100	150
8	F	82	Pain, instability	19	9.2	$+$	$-$ 3.8	1	T10/11	T8-L1	125	200
9	M	68	Pain, instability, neurological deficit	38	9.7	$+$	$-$ 2.8	12	T11/12	T9-L2	120	200
10	M	32	Pain, kyphotic deformity	11	22.2	$+$	$-$ 3.3	0.5	T12/L1	T11-L2	90	100
11	M	31	Pain, instability	19	31.6	$+$	$-$ 2.8	9	L1/2	T12-L3	120	200
12	M	48	Pain, instability, kyphotic deformity	26	10.8	$+$	$-$ 2.6	12	L1/2	T12-L3	170	150
13	M	38	Pain, instability, kyphotic deformity	21	10.4	$+$	$-$ 1.9	6	T11/12	T10-L1	100	150
14	F	53	Pain, instability, kyphotic deformity	28	41.9	$+$	$-$ 2.2	48	T11/12	T9-L2	120	200

M: male, F: female.

Table 2

Clinical outcomes of TTIL for AS, VAS and ODI and complications at 12 months after the surgery

List	Preoperative	1-year follow up	Preoperative	1-year follow up	Preoperative	1-year follow up	Complications
	VAS		ODI		Frankel grade
1	7.5	2	61	15	E	E	N
2	8.5	3	67	16	E	E	N
3	7.5	2	62	18	E	E	N
4	7.5	2	70	17	E	E	N
5	8.5	2	63	19	E	E	N
6	7.5	2	56	20	E	E	N
7	9.5	3	75	22	E	E	Delayed healing
8	9.5	3	72	26	E	E	N
9	9.5	2	74	14	C	D	N
10	7.5	2	63	13	E	E	N
11	7.5	2	60	13	E	E	N
12	6.5	3	52	16	E	E	N
13	7.5	2	64	14	E	E	N
14	7.5	3	57	15	E	E	N

2.2 Surgical methods

Patients were placed on the operating table in the prone position. After general anesthesia and target segment was located by C-arm X-ray, a midline incision was made and the paraspinal muscle was separated from the lamina bilaterally. Suitable pedicle screws were inserted into the upper and lower 2–3 vertebrae. Smith-Peterson ostomy (SPO) was operated to remove the appropriate range of spinal posterior structure according to the angle designed preoperatively. Intervertebral disc as well as compressive materials, such as ossified posterior longitudinal ligament or fracture fragments were transforaminally removed and the best conditions for the bony fusion were achieved. The height of the intervertebral space was measured by a tryout cage, and then a correct-sized bone from the ilium or intervertebral cage packed with granulated autogenous bone was inserted into the intervertebral space. Next, the rods were installed to restore the height and realign the spinal sequence, and the position of the internal instruments was confirmed by C-arm X-ray. All patients were mobilized after surgery in 1 week as per the pain tolerance. They were also fitted with custom-made molded braces for at least 12 weeks postoperatively.

Table 3
Comparison of local kyphotic angle, general kyphotic angle between preoperatively and 1-year follow-up

	Local kyphotic angle		General kyphotic angle		Birdwell grade
List	Preoperative	1-year follow up	Preoperative	1-year follow up	1-year follow up
1	15	8.5	29.9	26.4	I
2	16.2	11.6	36	31.3	I
3	38.6	31.6	40.9	35.5	I
4	25.3	9.2	70.6	56.8	I
5	16.3	7.1	30.2	24.7	I
6	8.8	5.3	52.3	51	I
7	12.4	6.2	40.6	38.7	II
8	17.3	10.8	39.8	35.5	II
9	19.5	13.2	45.1	40.9	I
10	14.8	7.5	42.6	39.8	I
11	13.2	10.7	36.5	34.6	I
12	20.3	11.2	37.4	35.6	I
13	19.6	9.3	47.9	44.4	I
14	22	11.2	49.5	45.6	I

2.3 Measurements

Full-length anteroposterior and lateral films of the spine were collected preoperatively and at 1-year follow-up. Radiological measurements included local and general kyphotic angles. Local kyphosis (LK) angle referred to the angle between the end plate connection of the upper normal vertebra and the lower normal vertebra of AL, and general kyphosis (GK) angle was the angle between the end plate connection of T5 upper vertebra and S1 lower vertebra. The fusion evaluation was assessed by the Bridwell intervertebral fusion grading system [17] and by a computed tomography (CT) scan that was conducted at 12 months postoperatively.

2.4 Statistical analysis

The difference between preoperative and postoperative differences was compared by pairing sample $t$ -test. $P<$ 0.05 were regarded as statistically significant. All statistical analyses were completed using SPSS software (version 25.0; IBM Corp., Armonk, NY, USA).

3. Results

Among all 14 patients who underwent TTIF for AL, 8 were men and 6 were women, with an average age of 53.36 years old. Twelve of the 14 patients suffered from instability (85.7%) and 6 of them had severe kyphotic deformity (42.9%). In the preoperative CT scan or MRI, the lesions were all found involving all the three spinal columns. The average ESR was 23.9 mm/h and the average CRP was 17.6 mg/L preoperatively. HLA-B27 positivity was found in all cases and their average T score of BMD in lumbar spine was $-$ 2.6. The symptom duration ranged from 0.5 month to 4 years and all lesions were located in the thoracolumbar region (T10-L2), including 3 in T10/11 and L1/2 (both 21.4%), 6 in T11/12 (42.9%), 2 in T12/L1 (14.3%). The operating time ranged from 90 to 200 min. In addition, the intraoperative bleeding volume was 100 to 500 ml. Intraoperative tissue samples sent for aerobic and anaerobic cultures did not isolate any organism in the series. Dura mater laceration and cerebrospinal fluid leak happened (Table 1).

All patients were satisfied with the surgical results. Back pain was reduced in all the patients which was shown by the improvement in VAS from 8.0 $\pm$ 0.2 preoperatively to 2.4 $\pm$ 0.5 at the 1-year follow-up ( $p<$ 0.01). The ODI score improved from 64.0 $\pm$ 6.9 to 17.0 $\pm$ 3.7 ( $p<$ 0.01). As for Frankel grading, 13 patients were graded E-level before and after the surgery. In the immediate postoperative period, 1 patient had incomplete neurological deficit which gradually improved before discharge. Another patient with neurological deficit showed an improvement in the Frankel grade from C to D. Only one patient suffered from delayed incision healing 20 days after the operation and recovered after debridement and dressings for 2 weeks. No other complications such as prosthesis joint formation, pedicle screw fracture or internal fixation looseness occurred. None of the patients received biologic drug therapy and were using only non-steroidal anti-inflammatory drugs for pain relief (Table 2).

All patients had achieved union at 1-year follow-up and there was no recurrence of the lesion, progressive deformity or loss of correction and no implant failure occurred in any patient. Compared with preoperative value, both local kyphotic angle and general kyphotic angle at 1-year follow-up were statistically significant improved. The average LK angle was corrected from 18.5 $\pm$ 7.2 to 11.0 $\pm$ 6.4 ( $p<$ 0.01); GK angle decreased from 42.8 $\pm$ 10.4 preoperatively to 38.6 $\pm$ 8.8 ( $p<$ 0.01). All patients experienced fusion by the end of 1 year. After CT scan at the 1-year follow up, 12 patients obtained grade I and 2 patients were grade II in Birdwell intervertebral fusion grading system (Table 3). In addition, no patients required revision surgery and all the patients reported good symptomatic relief clinically. Pictures of 2 representative patients are showed in Figs 1 and 2.

Figure 1.

T11-T12 Andersson lesions with 4 vertebrae fixed: a and b are the preoperative anteroposterior and lateral plain radiographs of the spine respectively. c and d are the coronal and sagittal computed tomography preoperatively. e is an intraoperative photograph shows that surgical treatment was performed. f and g are the anteroposterior and lateral plain radiographs 1 year after the surgery, showing a good position of fixation, and restoration of local kyphotic angle. h and i are the coronal and sagittal computed tomography after 1 year of the surgery, showing full vertebral fusion.

Figure 2.

T11-T12 Andersson lesions with 6 vertebrae fixed: a and b are the preoperative anteroposterior and lateral plain radiographs of the spine respectively. c and d are the sagittal and coronal computed tomography preoperatively. e and f are the sagittal T1-weighted image and sagittal short inversion time inversion recovery (STIR) sequence images of MR, respectively. g and h are the anteroposterior and lateral plain radiographs 1 year after the surgery, showing a good restoration of local kyphotic angle. i and j are the coronal and sagittal computed tomography after 1 year of the surgery, showing full vertebral fusion.

4. Discussion

AL is a chronic inflammatory lesion of the fused disc or vertebra in patients with late stage AS and AL was classified into three categories by Cawley [3, 16, 18]. Type 1 involved the central portion of the discovertebral junction which was covered by cartilage; Type 2 lesions involved the peripheral portion of discovertebral junction which was not covered by cartilaginous endplate and Type 3 involved both the peripheral and central portions. Among them, type I and II lesions were in the early stage of ankylosing spondylitis, while in lesions at type III, inflammatory damage was widespread and usually found in the late stage of AS.

Although AL is well described, it is commonly misdiagnosed as infective discitis, spinal tuberculosis or different kinds of tumorous conditions. In our series, one patient was initially diagnosed tuberculosis and received anti-tubercular treatment before he came to our institute. In patients with AS who have localized vertebral or discovertebral lesions without soft tissue swelling or paravertebral masses, AL should be considered at the first place. But it is still not easy for physicians, surgeons and radiologists to make an early diagnosis due to its characteristics and complexity. Non-infective inflammation and traumatic factors are widely accepted as the main reason for the occurrence and progression of AL. Park et al. believed that differentiation between inflammatory damage and traumatic lesions is of vital significance [19]. Inflammatory lesions often located in multiple vertebrae, which are part of the pathophysiological process of AS, while traumatic lesions are commonly occurred in the late stage of AS and accompanied with a history of slight trauma and posterior fractures with local pseudoarthrosis formation. Bron et al. divided AL into three categories: (1) focal lesions which were generally caused by inflammation; (2) extensive lesions without fractured posterior elements. These lesions caused by a combination of inflammatory reaction and mechanical factors and are associated with unfused facet joints; (3) extensive lesions with fractured posterior elements resulting from mechanical factors with transdiscal or transvertebral location [20]. The last 2 categories commonly result in pseudoarthrosis. Besides, Bron et al. believed that surgical treatment is mandatory to achieve neurological decompression, correct kyphotic deformity and restore spinal stability, thereby facilitating bone healing and fusion of the lesion.

As the etiology, imaging findings and even diagnosis of AL are controversial, the best treatment strategy for AL is still under discussion. Most researchers believed that surgical fusion treatment is a necessity for thoracolumbar and lumbar AL with spinal instability, progressive kyphotic deformity, sagittal imbalance and neurological deficit [21]. The objective of surgical management is to relieve spinal stenosis and cord compression, restore spinal stability and sagittal balance and promote graft bone fusion on the basis of rigid internal fixation [22]. However, till now no single surgical option can be considered ideal.

Various surgical methods and strategies have been demonstrated such as anterior spinal fusion, combined anterior and posterior fusion, posterior fusion with correction of the lesion, posterior single segment fixation with bone grafting [9, 10, 11, 12, 13, 14]. In early stage, some scholars believed that anterior approach surgical option can help remove necrotic lesions directly which is more conforming to the biomechanical features of spine. Fang et al. [23] reported that 16 patients with neurological deficit received anterior debridement and reconstruction with autogenic bone grafting within anterior defect. 2 patients suffered from pseudoarthrosis and 1 patients required another posterior operation after a follow-up more than 5 years. The radiological outcomes of kyphosis have not been documented. However, spinal sagittal imbalance cannot be corrected through anterior approach. Besides, anterior bone graft fusion cannot provide rigid fixation as most AS patients are combined with severe osteoporosis [10, 24].

Chen et al. treated 8 AL patients with kyphotic deformity using anterior and posterior approach combined surgery [25]. Symptoms were significantly alleviated, kyphotic deformity was corrected on average of 18.6 degrees, and strong fusion were achieved postoperatively. As a matter of fact, restricted lung function is one of the most common complications of AS, therefore, the anterior approach via thoracic cavity showed obvious disadvantages in these patients since the anterior approach operation is much more complicated and accompanied with more complications [26]. Thus posterior approach operation has been extensively used.

Rajoli et al. [16] reported that 20 patients with AL whom presented with instability, back pain or neurological deficit were managed by single stage posterior approach with long segment pedicle screw fixation and anterior vertebral reconstruction. The mean anterior column defect was 1.6 $\pm$ 0.6 cm and the mean follow-up was 2.1 years. All patients had achieved radiological union at a mean 7.2 $\pm$ 4.6 months. The mean regional kyphotic angle was 27 ${}^{\circ}$ preoperatively, 16.7 ${}^{\circ}$ postoperatively and 18.1 ${}^{\circ}$ at the final follow-up. He believed that Posterior stabilization and anterior reconstruction through an all-posterior approach was safe and could achieve good results in AL.

Shaik et al. [27] analyzed 18 patients with AL who were treated with posterior long segment spinal fusion without any anterior intervertebral grafting or posterior osteotomy. The results showed that most patients experienced fusion by the end of 1 year, and the fusion mass could be observed as early as 4 months. Patients reported good symptomatic relief and Whiteclouds’ outcome analysis score at the latest follow-up revealed good-to-excellent outcomes in all patients. He proposed that ALs could be treated using the posterior-only approach with long segment fixation and posterior spinal fusion which proved to be a safe, simple, and quick procedure that prevent the morbidity of anterior surgery. In our study, TTIF surgery was performed to remove lesions and fuse vertebrae with autogenous bone graft. After 1-year follow-up, both VAS and ODI scores improved significantly compared to the preoperative value. Besides, local and general kyphotic angles were corrected as well. One patient with neurological deficit showed an improvement in the Frankel grade from C to D and all others were grated E-level before and after the surgery. Chang et al. [28] considered that the neurological symptoms were mainly from the spinal stenosis caused by hyperplasia and ossification of ligamentum flavum and facet joint. Thus the neurological symptoms can be more effectively improved by posterior surgical resection and decompression.

In addition, Langlois et al. [29] proposed that the spinal cord cannot be compressed by the intervertebral disc in itself, but the accompanying vertebral instability led to dynamic compression of spinal cord. We believed that there is a large bone defect in the anterior spinal column which will be a threatening vertebral instability factor after simple posterior orthopedic surgery, thus increasing the stress of the internal fixation system [30]. Therefore, we used autologous bone for intervertebral bone grafting after a complete curettage of necrotic and ossified tissue. Moreover, most spinal surgeon are more accustomed to posterior surgical approach which can help reduce operation time and intraoperative bleeding volume, and is also conducive to early functional exercise [31].

It has been reported that 5.7–9.6% AS patients had a poor incision healing after surgery [28, 32]. In this study, only one patient had a complication of delayed incision healing, which might be caused by poorer skin and subcutaneous tissue vitality. The patient received debridement procedure at the 20th day after surgery, then fully recovered after 14 days of dressings. In addition, all 14 patients obtained satisfactory intervertebral fusion and no other complications occurred after the surgery.

There were several limitations in our study. First, it was a retrospectively, single center study without randomized controlled design. Second, the wide variations in the clinical and radiological parameters and the small patient sample considering the rarity of the lesion restrained us from drawing a strong conclusion.

5. Conclusion

TTIF surgery is a safe and effective technique to manage AL in AS patients with unbearable pain, progressive kyphotic deformity or neurological deficits. This management could effectively achieve symptoms improvement, neurological decompression, kyphotic deformity correction and spinal stability restoration. In addition, it was proved safe and reliable to transforaminally remove lesions and plant intervertebral cage to achieve successful bone fusion.

Funding

This work was supported by the National Natural Science Foundation of China (grant number 81972118), Sailing Plan of Shanghai Science and Technology Committee (grant number 21YF1439000), Shanghai Municipal Commission of Science and Technology (grant number 20Y21903200), Shanghai Municipal Health Bureau (grant number 20204Y0395) and Shanghai Changning District Doctoral Innovation Base Project (grant number RCJD2021B06).

Ethical approval

This study was approved by the Ethics Committee of Guanghua Hospital affiliated to Shanghai University of Traditional Chinese Medicine (Ethical approval number: 2019-K-04).

Informed consent

All patients and their families were explained the purpose, necessity, possible risks and complications of TTIF, as well as the conditions of this study after informed consent was signed.

Author contributions

Zheng Huang and Ji Guo analyzed and interpreted the patient data. Yongwei Jia and Zheng Huang operated all the surgical procedures. All the other authors were responsible for data collection and processing. Zheng Huang and Ji Guo were major contributors in writing the manuscript. All authors read and approved the final manuscript.

Footnotes

Conflict of interest

No potential conflict of interest relevant to this article was reported.

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Slot

Anderson

, et al. Spinal osteotomy in patients with ankylosing spondylitis: Complications during first postoperative year. Spine (PhilaPa 1976). 2005; 30: 101–107.

Clinical outcomes for andersson lesion in patients with ankylosing spondylitis by transforaminal thoracolumbar intervertebral fusion surgery

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSION:

Keywords

1. Introduction

2. Materials and methods

2.1 Patient selection and data collection

Table 1 Baseline characteristics of included patients

Table 3 Comparison of local kyphotic angle, general kyphotic angle between preoperatively and 1-year follow-up

2.4 Statistical analysis

3. Results

5. Conclusion

Funding

Ethical approval

Informed consent

Author contributions

Footnotes

Conflict of interest

References

Table 1
Baseline characteristics of included patients

Table 3
Comparison of local kyphotic angle, general kyphotic angle between preoperatively and 1-year follow-up