Incidence and Risk Factors for Facet Joint Violation in Open Versus Minimally Invasive Procedures During Pedicle Screw Placement in Patients with Trauma

Highlights

• Overall facet joint violation rate was found in 39.0%.

• Higher risk of facet joint violation in the lumbar spine than in the thoracic spine.

• The use of a side-loading device is associated with a facet joint violation.

• Open instrumentation reduces the risk of facet joint violation.

• Age, gender, and BMI do not affect the incidence of facet joint violation.

Objective

A possible risk factor for premature facet joint degeneration or adjacent segment degeneration after surgical treatment of spine fractures is facet joint violation (FV) during insertion of pedicle screws. The aim of this study was to determine risk factors for FV in the thoracic and lumbar spine after minimally invasive screw insertion or open instrumentation (OI).

Methods

A retrospective analysis of all patients with spine fractures requiring posterior stabilization was performed. After patients were allocated to the thoracic/lumbar group, FV was defined as an involvement caused by the positioning of a pedicle screw and its severity as determined by computed tomography was assessed by using a customized scoring system. Gender, age, and body mass index as well as segmental facet joint angle and the instrumentation system used (side-loading [SL] vs. top-loading) were considered as individual factors.

Results

In total, 1099 pedicle screws were evaluated and an FV was identified in 433 instrumentations (39.0%). OI was used in 61.1% (n = 671) and an SL system was inserted in 45.0% (n = 494). In both, the thoracic (odds ratio [OR], 1.663; 95% confidence interval [CI], 1.119–2.472; P = 0.012) and the lumbar spine (OR, 0.494; 95% CI, 0.317–0.771; P = 0.002), OI was associated with a lower risk of FV. The violation rate was significantly higher when using a SL system (thoracic spine: OR, 1.822; 95% CI, 1.163–2.854; P = 0.009; lumbar spine: OR, 0.311; 95% CI, 0.203–0.477; P ≤ 0.001).

Conclusions

FV is a common complication after thoracic and lumbar spine surgery. Although both, the SL instrumentation and a minimally invasive procedure increases its occurrence, the patient characteristics do not affect the rate of FV.

Introduction

Fractures of the thoracolumbar spine are relatively common injuries. The operative management varies from minimally invasive procedures to open surgery. The general aim is posterior reduction and to restore correct spinal alignment. When handling AOSpine type B lesions or unstable burst fractures, pedicle screw/rod-based devices can be used as a stand-alone technique.¹ Traditional open pedicle screw procedure is a widely accepted treatment option but it is being gradually replaced by minimally invasive procedures as indications for the latter are expanded. Less blood loss, lower infection rates, reduced postoperative pain, early mobilization, and fast recovery to work are the advantages of percutaneous pedicle screw placement compared with open surgery.2, 3, 4, 5

Although the standard midline approach provides wide exposure to the facet joint complex, minimally invasive screw insertion (MIS) renders the direct visualization of the relevant anatomic landmarks impossible. Posterior MIS has been described previously1, 6, 7, 8 and in this regard, the owl's eye and the true anteroposterior (AP) and lateral techniques are well known. Generally, percutaneous screw instrumentation is performed with the aid of intraoperative C-arm fluoroscopy in 2 planes (AP and lateral) to ensure that the relevant spinal anatomy is visible.

When performing the open procedure, additional intersegmental fusion is possible, although this is not the case in minimally invasive percutaneous screw placement. In most cases, the implant removal is performed after 6–12 months to release the motion segment. In this regard, it is most important that the facet joints of the segments under consideration are not severely altered as a result of worse screw positioning. Degenerative processes, in particular adjacent segment degeneration, might be the consequence. Because facet joints and intervertebral discs are the primary load-bearing and stabilizing structures in the physiologic spine, degenerative processes of the facets resulting from their violation might lead to increased sagittal-plane instability, especially in flexion,⁹ which in turn leads to more degeneration, initiating a vicious circle. However, the facet joints are at risk for iatrogenic damage within the instrumented segment during screw instrumentation, irrespective of an additional fusion procedure being performed or not.

Although several studies have focused on facet joint violation (FV) after pedicle screw instrumentation in the lumbar spine for degenerative indications,10, 11, 12, 13 little is known about the effects of FV at the thoracic spine and in trauma cases. Tannous et al.¹⁴ analyzed 2 different techniques in screw placement within the thoracic and lumbar spine (T2-L5) in a cadaver study. These investigators found that the lateral-to-medial technique reduced the risk for iatrogenic FV. In their retrospective analysis, Tromme et al.¹⁵ found a moderate rate of FV within the thoracolumbar spine (15.4%) and stated that the implant can be safely removed and the facet joint complex preserved. It is against this background that the present study aimed 1) to examine the incidence of FV in the thoracic and the lumbar spine and 2) to analyze implant-related and patient-related factors associated with FV.

The aim of the present study is to 1) examine the incidence of FV in the thoracic and the lumbar spine, 2) to analyze implant-dependent and 3) to analyze patient-dependent factors associated with FV including the assessment of pedicle screw accuracy referring to the classification system according to Zdichavsky et al.¹⁶