gms | German Medical Science

We present the case of a 69-year-old female patient with severe complication during revision spine surgery. Nine years ago, the patient had to undergo lumbar fusion surgery at the level L4-S1 due to degenerative spine disorder. Afterwards, the patient required several revision surgeries due to adjacent segment disease with additional fusion surgeries up to Th 11. Three years later, the patient recurred with symptoms of thoracic myelopathy with gait disturbance, weakness of the hip flexors and bladder dysfunction. The radiographic evaluation showed a proximal junctional kyphosis with screw loosening and a high grade stenosis with myelon compression at the level of Th 10/11 (Figure 1 [Fig. 1], Figure 2 [Fig. 2]).

We decided for revision surgery. The goal was:

1.

Spinal canal clearance in the stenotic thoracic region with decompressive laminectomy of Th 10 and pedicle screw fixation up to Th 9.

2.

Restore the global spine balance by pedicle subtraction osteotomy (PSO) in the fused flat-back lumbar spine at the level of L4.

The first step was straightforward. Next, the PSO was done by chisel. When we tried to finish the closing maneuver by bending the OR table, we recognized a complete pull-down of the intervertebral oblique cage at the level L3/4, above the osteotomy (Figure 3 [Fig. 3]). So we were not able to close the osteotomy and we created a critical instability at the level above the osteotomy. We decided to perform a staged anterior surgery: stabilization of the anterior column using an expandable cage. Immediately after the posterior surgery, the patient demonstrated a severe paraplegia (ASIA B). The emergency surgery did not show haematoma or myelon compression, neither at the thoracic nor the lumbar level (Figure 4 [Fig. 4]).

Four days later, we performed the anterior reconstruction by minimally invasive cage stabilization (Figure 5 [Fig. 5]). Postoperatively, the neurological deficit improved up to ASIA C. We transferred the patient to neurological rehabilitation. Six months later, the patient was able to walk with crutches, the neurologial symptoms improved up to ASIA D. The radiological follow-up showed a balanced spine without adjacent segment disease and implant problems (Figure 6 [Fig. 6]).

The pedicle subtraction osteotomy (PSO) is a well-described three-column osteotomy to correct fixed sagittal and coronal deformities [1], [2], [3]. PSO is most commonly performed in revision spine surgery in women older than 50 years. 85% had at least one prior spine surgery [4], [5], [6]. PSO is a closing wedge osteotomy with shortening of the posterior column. The main part of this surgery is a sufficient decompression of the neuronal structures to pretend compression during the wedge closing procedure. The osteotomy can be performed by chisel or high-speed burr. It is crucial to preserve the anterior cortex of the vertebral body while the lateral border must be removed under protection of the segmental vessels. The closure of the PSO is achieved by gradual inflection of the OR table and by compression or cantilever maneuver via the posterior instrumentation. Using this technique, the average improvement of lordosis is between 20 and 40 degrees and the sagittal vertical axis (SVA) can be improved up to 13,5 cm [4], [7], [8], [5], [9]. The lower the level the PSO is performed, the higher is the amount of correction. But in general, the level depends on the type of deformity. The goal of deformity correction ist to restore the global alignement with respect to the spinopelvic parameter: SVA<50 mm, PT<25° and LL=PI±10° [10]. The rate of complications after PSO is as high as up to 45%. The most common perioperative complications are massive blood loss, dural tear, nerve root injuries, pseudarthrosis, and neurologic deficits [7], [5]. In a series of 65 patients, Daubs et al. reported three deaths within a 90-day postoperative period [6]. There is a risk of revision surgery after PSO in 25% at 5 years [7]. Our case demonstrates another example of complication during deformity correction using the PSO technique. On the one hand, our patient had a major neurological complication after decompression and fusion of the PJK region. In this level, the thoracic spinal cord is very vulnerable and iatrogenic manipulation can cause severe neurological deficit. As we noticed the problem, we went forward for radiological CT examination and spinal cord revision, immediately. We did not recognize any compression of the spinal cord intraoperatively. Fortunately, the neurological problems improved and recovered. On the other hand, we had to deal with another major problem during the PSO closure procedure as we produced a critical instability above the PSO level. The previous fusion surgery at this level was 5 years ago. The fusion seemed to be solid. There was no hint of pseudarthrosis or missing intersomatic fusion at the level L3/4 in MR imaging or X-ray. But we did not verify it by computed tomography.

There is a reported pseudoarthrosis rate up to 17.5% in deformity correction surgery [11]. The incidence of pseudarthrosis requiring revision after deformity surgery is 3.1% [12]. Symptomatic pseudarthrosis in PSO is described in 10%, mostly at the level of the osteotomy. The lack of solid interbody fusion at adjacent levels is a major risk factor [13], [14]. Therefore, critical assessment of the bony fusion in the adjacent segments is mandatory. X-ray examination is not recommended for the diagnosis of solid fusion, due to its low specificity of 60–62% [15]. Thin-section computed tomography is the modality of choice [16]. CT imaging shows the strongest correlation with an intraoperative assessment of the fusion status [17]. A radiolucent zone greater than 1 mm around the interbody cage at 12-month follow-up is an early predictor of pseudarthrosis [18]. Some authors recommend the PET/CT modality. It additionally provides the localization of an abnormal tracer uptake and is proposed to be the index test for pseudarthrosis [19], [20].

During the osteotomy, we took care of a sufficient decompression and release of the lateral cortex before we started the closing procedure. The osteotomy gap was sufficient, the anterior wall was respected. As we were not able to close the osteotomy, we had to go for a retroperitoneal corpectomy and anterior column stabilization by using an expendable cage. We performed it in a minimally invasive fashion. The patient recovered well, the paraplegia was regressive. The radiological follow-up showed a balanced spine without adjacent segment disease and implant problems.

Revision spine surgery is an upcoming problem not only due to the increasing number of spine surgeries but due to the better understanding of the global spine profile concept. The restoration of an adapted spinopelvic balance is crucial and a lot of deformity correction procedures are described and used frequently. The PSO technique is a useful tool in high grade deformity correction. Even if this technique is well described and often used, this procedure is associated with a high complication rate. An individual analysis of the deformity and planning of the type and location of the correction procedure is mandatory to achieve a balanced global spine and avoid unexpected complications.

The authors declare that they have no competing interests.