Abstract

Background: Here, we reviewed the clinical, radiological, and neurological sequelae and treatment when transforaminal lumbar interbody fusion (TLIF) cages migrate into the lumbar spinal canal.

Case Description: A 46-year-old female underwent a TLIF L3-L4. Five months later, she presented with cauda symptoms/signs of dorsal cage migration that warranted surgical removal.

Conclusion: TLIF can be associated with delayed dorsal cage migration into the spinal canal. This adverse event should be clinically recognized, radiologically documented, and appropriately surgically treated to minimize short/long-term neurological sequelae.

Keywords: Anterior lumbar interbody fusion, Posterior cage migration, Risk factor, Transforaminal lumbar interbody fusion

INTRODUCTION

Blume first described a unilateral approach to posterior lumbar interbody fusion (PLIF) in 1981 to minimize complications associated with the traditional bilateral approach.[ 3 ] This technique was later popularized by Harms et al.,[ 5 ] evolving into what is now known as transforaminal lumbar interbody fusion (TLIF). TLIF allows bilateral anterior column support through a unilateral posterolateral approach. When combined with pedicle screw fixation, it ensures both anterior and posterior column stability.[ 9 ] The interbody cage plays a central role by providing anterior support, restoring disc height, and enlarging the neuroforaminal space. However, posterior cage migration (PCM) into the spinal canal or neuroforamen remains a potential complication. Such migration can result in nerve root compression, instrumentation failure, or the need for revision surgery.

Previous studies have identified risk factors for cage migration. In 2010, Aoki et al.[ 1 ] highlighted factors predisposing to this complication, and in 2019, Hu et al.[ 6 ] emphasized the role of cage positioning.

Here, we report the case of a 46-year-old female who developed dorsal cage migration 5 months after TLIF, discussing diagnostic findings, treatment, and risk factors in light of existing literature.

CASE DESCRIPTION

A 46-year-old female underwent a TLIF L3-L4. Five months later, she presented with the new onset of left lower extremity sciatica accompanied by no motor deficits but dysesthesias in the left L3 to L5 dermatomes. Both the computed tomography (CT) and magnetic resonance (MR) studies showed dorsal L3-L4 cage migration into the left side of the lumbar spinal canal (performed 5 months after the TLIF; [ Figures 1 and 2 ]). The cage was removed utilizing an anterior approach and was replaced with an anterior lumbar interbody fusion (ALIF) cage [ Figures 3 and 4 ], obtained during the second surgery). Notably, the right L4 screw was additionally removed due to its slightly medial positioning and because fusion had already been achieved at that level. Postoperatively, the patient was asymptomatic within (the first postoperative day, as documented in [ Figure 5 ]) and remained symptom free at 1 month post-revision, as shown in Figure 6 . Further postoperative imaging – including X-rays, MR, and CT – was performed at three time points: (1) immediately after the initial TLIF surgery [ Figure 7 ], (2) on the 1^st day after the ALIF procedure [ Figure 5 ], and (3) 1 month after ALIF [ Figure 6 ]. These studies documented adequate decompression of the cauda equina and successful positioning and integration of the ALIF cage.

Figure 1:

Computed tomography identifying cage migration.

Figure 2:

Magnetic resonance imaging identifying cage migration.

Figure 3:

Anterior approach: Cage transforaminal lumbar interbody fusion covered by fibrous tissue.

Figure 4:

Anterior approach: Cage transforaminal lumbar interbody fusion being removed after meticulous dissection.

Figure 5:

X-ray after re-approach.

Figure 6:

Axial Magnetic resonance imaging after re-approach.

Figure 7:

X-ray in the immediate transforaminal lumbar interbody fusion postoperative period.

DISCUSSION

A summary of the main studies cited in this discussion is presented in Table 1 . Hu et al. verified in the article that posteriorly located cages and undersized cages and undersized cages are more prone to developing PCM, which may aid surgeons in making optimal decisions during TLIF procedures.[ 6 ]

Table 1:

Summary table of references.

The article by Aoki et al. suggests that the use of a bullet-shaped cage, higher posterior disc height ≥6 mm, the presence of scoliotic curvature, and undersized fusion cages are possible risk factors for cage migration, as well as mentions the potential for postoperative cage migration and limitations of unilateral fixation should be considered by spine surgeons.[ 1 ] That same lead author wrote an article previously, in which he concluded that revision surgery after TLIF appears relatively safe because the migrated cage tends to locate more laterally than in patients with cage migration after PLIF. Further pointed out that cage migration subsequent to TLIF may not cause compression of neural tissues, so conservative treatment may suffice for these patients.[ 2 , 8 ]

Among the risk factors discussed above, the case reported presented 2 of them: The higher posterior disc height ≥6 mm (it was 7.18 mm) and the location of the cage in the posterior region of the intervertebral space [ Figure 7 ].

Despite what was pointed out, the migration of the TLIF cage in this case was extremely symptomatic and required re-approach. Considering the higher posterior disc height as a risk factor for migration of the new cage that would be placed, local fibrosis as a result of the procedure performed previously, and the location of the cage within the canal, the anterior approach was preferred. When this approach is decided in these cases, care must be taken in choosing the material to be used in surgery, as longer and more delicate forceps are necessary to enable the delicate microscopic dissection of the cage surrounded by fibrosis within the vertebral canal, to avoid dural injury, cerebrospinal fluid leak or injury to local noble structures.

Jin et al.[ 7 ] retrospectively evaluated 75 patients who had undergone unilateral instrumented TLIF and found that cages tended to migrate posteriorly or toward the operative side, with less migration occurring when the cage was initially placed closer to the surgical side. They also noted that older patients were more likely than younger individuals to experience cage migration. They presumed that this may be due to older patients having more highly unstable segments and lower bone mineral density (BMD), which could compromise pedicle screw stability. However, they acknowledged that this remained a hypothesis, as BMD was not measured in all patients in their study.[ 7 ]

Hou et al. demonstrated in their meta-analysis of risk factors for cage migration after lumbar fusion surgery (PLIF and TLIF) that bone injury of the endplate, pear-shaped disc, and screw loosening are significantly correlated with cage migration.[ 4 ]

CONCLUSION

Patients undergoing TLIF may develop delayed dorsal cage migration contributing to radicular and/or cauda equina deficits. These patients should undergo timely clinical evaluations, radiological assessment, and appropriate surgical removal of these devices.

Ethical approval:

Institutional review board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

References

1. Aoki Y, Yamagata M, Nakajima F, Ikeda Y, Shimizu K, Yoshihara M. Examining risk factors for posterior migration of fusion cages following transforaminal lumbar interbody fusion: A possible limitation of unilateral pedicle screw fixation. J Neurosurg Spine. 2010. 13: 381-7

2. Aoki Y, Yamagata M, Nakajima F, Ikeda Y, Takahashi K. Posterior migration of fusion cages in degenerative lumbar disease treated with transforaminal lumbar interbody fusion: A report of three patients. Spine (Phila Pa 1976). 2009. 34: E54-8

3. Blume HG, Rojas CH. Unilateral lumbar interbody fusion (posterior approach) utilizing dowel graft. J Neurol Orthop Surg. 1981. 2: 171-5

4. Hou Y, Shi H, Zhao T, Shi J, Shi G. A meta-analysis of risk factors for cage migration after lumbar fusion surgery. World Neurosurg X. 2023. 18: 100152

5. Harms J, Jeszenszky D, Stolze D, editors. True spondylolisthesis reduction and more segmental fusion in spondylolisthesis. The textbook of spinal surgery. Philadelphia, PA: Lippincott-Raven; 1997. p. 1337-47

6. Hu YH, Niu CC, Hsieh MK, Tsai TT, Chen WJ, Lai PL. Cage positioning as a risk factor for posterior cage migration following transforaminal lumbar interbody fusion: An analysis of 953 cases. BMC Musculoskelet Disord. 2019. 20: 260

7. Jin L, Chen Z, Jiang C, Cao Y, Feng Z, Jiang X. Cage migration after unilateral instrumented transforaminal lumbar interbody fusion and associated risk factors: A modified measurement method. J Int Med Res. 2020. 48: 300060519867828

8. Lauber S, Schulte TL, Liljenqvist U, Halm H, Hackenberg L. Clinical and radiologic 2-4-year results of transforaminal lumbar interbody fusion in degenerative and isthmic spondylolisthesis grades 1 and 2. Spine (Phila Pa 1976). 2006. 31: 1693-8

9. Lowe TG, Tahernia AD, O’Brien MF, Smith DA. Unilateral transforaminal posterior lumbar interbody fusion (TLIF): indications, technique, and 2-year results. J Spinal Disord Tech. 2002. 15: 31-8