Migration of Rod: A Case Report of Rare Complication of Minimal Invasive Surgery in Spinal Trauma with Narrative Review of Literature.

INTRODUCTION: Traumatic spine injury is one of the leading causes of morbidity and mortality in trauma patients. Open surgical procedure is associated with increased blood loss, surgical trauma, and increased recovery period. The goal of minimally invasive surgery (MIS) is to minimize iatrogenic trauma caused by open surgery. CASE REPORT: A 39-year-old female patient presented to us with complaints of severe pain in back following a fall from ten feet height 1-day back. She was diagnosed with L1 burst fracture and was managed by indirect fracture reduction and posterior instrumented stabilization from D12 to L2 by MIS. She presented to us with complaints of pain over back after 3 months of index surgery. Neurology was intact, and ESR and quantitative CRPH were normal. X-ray showed downward and outward displacement of left connecting rod with pedicle screws in situ.
CONCLUSION: Minimal invasive surgery in spine is associated with steep-learning curve and technical challenges. Mechanical complications associated with implants should be always kept in mind while planning the surgery. Copyright: © Indian Orthopaedic Research Group.

Mechanical complications associated with implants should be always kept in mind while planning Minimal invasive surgery in spine trauma.

Introduction

Traumatic spine injury (TSI) is one of the leading causes of morbidity and mortality in trauma patients. Global incidence for TSI was 10.5 cases per 100,000 persons (95% CI 8.6–12.84 cases/100,000) that resulted in an estimated 768,473–790,695 cases of TSI worldwide each year as reported by Kumar et al. [1]. Spinal trauma is traditionally managed by decompression and fixation by instrumentation. Open surgical procedure is usually associated with increased blood loss, surgical trauma, and increased recovery period [2]. Significant devascularization and denervation of spinal musculature cause chronic pain after open surgery. The goal of minimally invasive surgery (MIS) is to minimize iatrogenic trauma caused by open surgery. MIS causes decreased denervation and muscle atrophy [3].

Wiltse et al. reported muscle-splitting approach in 1968, with same exposure to perform far-lateral discectomy, insertion of pedicle screws, and ipsi-contralateral decompression in lumbar spine, which formed the basic philosophy of minimal invasive surgery in spine [4]. MIS for spinal trauma was initially reported as endoscopic guided anterior approach in 2005 by Beisse et al. [5].

Assaker et al. presented the use of minimal access spinal techniques for the management of thoracolumbar trauma at Eurospine, Barcelona, Spain, 2005. He has described posterior approach as a stand-alone technique or in combination with an anterior endoscopic approach [6]. First report of a percutaneous transforaminal endoscopic approach combined with percutaneous pedicle screw fixation for the correction of altered sagittal plane alignment in thoracolumbar burst fractures was published in 2014 by Wang et al. [7].

Due to decreased morbidity and postoperative hospital stay compared to open surgeries, which involve extensive sub-periosteal stripping and prolonged retraction of soft-tissues resulting in significant ischemic necrosis of the paraspinal muscles and chronic back pain [8], MIS is gaining popularity over past two decades. Nonetheless, application of MIS principles in spine trauma still remains to be explored and, as per current evidence, has been reported to have a number of hardware-related complications [9].

We are reporting an unusual complication of migration of connecting rod that has been published only once in literature related to spine trauma [10], and in that process, we intend to present a narrative review of literature on failure of implants-related complications in MIS for thoracolumbar spinal injuries.

Case Presentation

A 39-year-old female patient presented to us with complaints of severe pain in back following a fall from ten feet height 1-day back. No history of back pain before trauma. Clinical examination did not reveal any neurologic deficit. Radiologic examination showed burst fracture of L1 (AO type A4) with 15 degrees of segmental kyphosis and thirty percent canal compromise (Fig. 1). She was managed with indirect fracture reduction and posterior instrumented stabilization from D12 to L2 by MIS (Fig. 2). Her further hospital stay was uneventful. She was mobilized full weight bearing with customized thoracic lumbar sacral orthotic (TLSO) brace on post-operative day 1 and was discharged on day 2. Her surgical site staples were removed on post-operative day 14 and there were no wound related complications.

Figure 1

Pre-operative X-ray showing L1 burst fracture.

Figure 2

Immediate post-operative X-ray showing pedicle screws and connecting rod in position.

She presented to us with complaints of pain over back after 3 months of index surgery. On examination mild tenderness was present over surgical site without any sign of infection or inflammation. Neurology was intact, and ESR and quantitative CRPH were normal. X-ray showed downward and outward displacement of left connecting rod with pedicle screws in situ (Fig. 3). Patient was planned for removal of implant.

Figure 3

X-ray showing connecting rod migration, pedicle screws were in situ.

Intraoperatively, pedicle screws were found to be loose, but the cap was found to be tight. No collection or bony changes was found intraoperatively. The displaced rod was traced and removed through a subcutaneous tunnel, without extending the incision, along-with ipsilateral pedicle screws and contralateral connecting rod and pedicle screws. There were no radiologic signs of instability intraoperatively after implant removal. Postoperatively patient started on full weight bearing mobilization with customized TLSO brace and was not having any neurological deficit. Three months after the second surgery, patient is pain-free with Oswestry Disability Index of 30 %.

Discussion

Due to limited work-space available in MISS, there is obvious difficulty in locating anatomical landmarks that can result in injury to facet capsule, nerve root, dura, and cord. Such a complication may necessitate open or revision procedures. Although less morbid, minimal invasive surgery is reported to be associated with certain hardware related complications [10].

We can divide these broadly into two categories: Organ injuries from hardware and failure of implant. The list includes, though not exclusive of, intraoperative guidewire breakage, abdominal aorta injury, dura mater injury, pedicle screw misplacement, screw breakage, plug screw falling off, connecting rod loosening, and poor reduction [10]. Complication rates for MIS and open surgeries did not differ significantly [11].

A number of recent studies have compared outcomes of open versus MIS and complication rates in both modalities.

In a study of 424 percutaneous placed pedicle screws done by Raley and Mobbs, post-operative CT scans demonstrated 41 misplaced screws (9.7%). Lateral cortical breaches were more common (n = 30) than medial breaches (n = 11), and neurological injury as a result of these breaches occurred with two screws (0.5%) [12].

Kramer et al. reported hardware failure, in the form of loss of correction or progressive increase in kyphosis, in 4 of 11 thoracolumbar fractures treated with short-segment fixation performed through a standard open approach with posterolateral fusion within a 2-year follow-up [13].

Biomechanical investigation comparing construct bending stiffness, torsional stiffness, and cycles to failure were done between patients who have undergone MIS versus universal spine stabilization system (USS) by Kubosch et al. [14] shows that construct in MIS is showing significant loss of correction compared to USS.

Le et al. did a retrospective study on 101 patients who have underwent minimally invasive lateral interbody fusion for trauma and other degenerative conditions and found that hardware related complications were 5.9% [15].

In our patient, mechanical failure seems to be the reason for loosening of implants. Even though bony union was achieved, construct got weakened on cyclical load from activities of daily living over. The unique features of this case is that the dislodged connecting rod is asymptomatic and without neurological impairment. Even though the construct became weak, bony union was achieved. Patient did not need any revision procedure for stabilization. We removed the implants and postoperatively patient had no neurological deficit and was mobilized full weight bearing with brace.

Implant-related complications can be avoided with proper surgical technique and selecting appropriate implants. Timely identification of complications and revision surgeries helps in improving outcome. Percentage of various complications in the studies, we analyzed are compiles in Table 1. A compilation of most relevant latest studies on MIS in spinal trauma and the complications in those studies is shown in Table 2.

Table 1

Complications in reviewed literature.

Table 2

Representative publications on implant related complications in MIS in traumatic spine injuries

Conclusion

Minimal invasive surgery in spine is associated with long learning curve and technical challenges. Mechanical complications associated with implants should be always kept in mind while planning the surgery. Careful selection of patients and implants with proper technique of MIS in spine will be advantageous than open surgeries.

Migration of connecting rod is an extremely rare and unusual complication in MIS spine surgery that has been published only once in literature related to spine trauma. We are adding another such case to the literature.