Restoring segmental lumbar lordosis after failed previous fusion at the same level

Introduction

The restoration of lumbar lordosis is mandatory during lumbar fusion surgery for degenerative disc disease, since not restoring lumbar lordosis adequately may adversely affect surgical outcomes and the patient’s quality of life in the follow-up (1,2).

Preoperative planning and measuring radiographic spinopelvic parameters are the key to better outcomes of lumbar fusion surgery (3,4). While a minor extent of segmental lordosis correction during lumbar fusion is normally easy to perform, dealing with a severe loss of lordosis is a real problem. Revision surgery to restore segmental lordosis at the level of previous spinal fusion is extremely difficult to do and its performance is usually inferior to that of primary surgery (5).

We report a surgical technique to restore segmental lordosis via a posterior approach, which is especially important after failed previous fusion at the same lumbar level. We present this article in accordance with the SUPER reporting checklist (available at https://jss.amegroups.com/article/view/10.21037/jss-24-169/rc).

Preoperative preparations and requirements

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images/video. A copy of the written consent is available for review by the editorial office of this journal.

Indications and contraindication

The main indications for this technique are:

• The restoration of segmental lordosis at one of the levels L3–L4, L4–L5 or L5–S1 on a non-operated segment, on an operated segment after prior lumbar fusion at the same level or on an adjacent segment;
• Need for a major extent of segmental lordosis restoration, but having any contraindication to or the inability to perform osteotomy like Schwab type-3-6 procedures (6).

The main contraindications for this technique are:

• Complete interbody fusion after previous surgery at the level of surgery. Because any increase in the mobility of complete interbody fusion is traumatic and dangerous, alternative types of osteotomy should be considered (7).
• Low bone mineral density of the lumbar vertebrae makes it difficult to perform corrective manipulations with them (8).
• If none of the approaches used in the previous lumbar fusion surgery were the posterior one, cages shall not be removed through the posterior approach.

Specific perioperative considerations

This technique should be used after a detailed planning of the surgical management of the patients. Preoperative sagittal and frontal full-body X-rays are critical. Global evaluation of the entire spine and the measurement of the regional sagittal balance will allow surgeons to determine the extent of correction to be achieved during surgery. Therefore, preoperative sagittal and frontal full-body X-rays are essential. Magnetic resonance imaging (MRI) and computed tomography (CT) scans are also required. MRI allows visualization of vertebral disc elements as well as paravertebral and neural structures of the spinal canal. Changes in bone tissue, vertebral elements, and localization of implants are assessed by CT.

Patient positioning

Under tracheal intubation anaesthesia, the patient is placed prone with the abdomen free on a radio-lucent table, permitting anterior-posterior and lateral imaging using uniplanar or biplanar X-ray. Hip pads at the level of the posterior superior iliac spine help with lumbar lordosis.

Step-by-step description

The key steps are demonstrated in the accompanying video (Video 1). Written informed consent was obtained from the patient for publication of this article and accompanying video.

The patient is placed prone on an operating table. Once the surgical trajectory has been determined under C-arm fluoroscopy, a standard middle-line posterior approach is performed, detaching paravertebral muscles to gain access to the posterior spinal column. The previous rods are removed; if the pedicle screws are found to be loosened or misplaced, they are replaced by new ones installed correctly.

Segment release

If neither laminectomy nor bilateral foraminotomy had been performed during previous surgery, they have to be done at this point. The dural sac and nerve roots are released from epidural fibrotic scar tissue. The temporary rods are put in place, their length being sufficient to distract the segment, then the maximum possible distraction is achieved and the segment is temporarily fixed in that position.

The intervertebral disc space is released by dissection of the posterior longitudinal ligament and the posterior annulus fibrosus. The intervertebral cage, if there is one, is released from all sides and removed. All disc fragments are removed and the vertebral endplates are prepared.

In order to have access to and expose the anterior intervertebral disc space, the screw heads should be moved further apart on the rod and fixed temporarily to facilitate segmental distraction (Figure 1).

Figure 1 Stage of segmental distraction at the L4–L5 level. (A) Schematic of segmental distraction (the arrows indicate the direction of the force vector for the purpose of distraction of the interbody space). (B) The distractor is set on the screw heads on the left side. (C) C-arm-based intraoperative sagittal image of the lumbar spine with distraction at L4–L5.

The next step is induction of the maximum segmental release under C-arm fluoroscopy. The lateral and the anterior annulus fibrosus are dissected with a Cobb dissector. The perimeter of the annulus fibrosus is cut until it feels like a hollow space is reached. To save the anterior longitudinal ligament and to prevent vascular injury, the Cobb dissector’s tip should not extend more than 5 mm beyond the vertebral body margin (Figure 2).

Figure 2 Stage of release of the anterior annulus fibrosus at the L4–L5 level. (A) Schematic of positioning the Cobb dissector to release the anterior annulus fibrosus. (B) Cobb dissector placed in the intervertebral disc space for dissecting the annulus fibrosus. (C) C-arm-based intraoperative sagittal image of the lumbar spine showing the Cobb dissector positioned for anterior annulus fibrosus release at L4–L5.

Restoring segmental lordosis

The totally released lumbar segment is ready for the restoration of segmental lordosis. At the first step, maximum segmental distraction is achieved for cage placement. The cage is placed into the anterior third of the intervertebral disc space under C-arm fluoroscopy. The middle and posterior thirds of the intervertebral disc space are filled with osteoinductive material.

The next step is performed on an operating table. The screws are loosened and the operating table is set so that the patient placed prone on it assumes a head-up feet-up position. While the patient is in this position, the temporary fixation rods are replaced with permanent rods on both sides and the screw heads are put closer together by the surgeon to achieve an additional contraction of the lumbar segment. The amount of correction achieved is estimated using C-arm fluoroscopy. After ensuring that the extent of lordosis correction is satisfactory and the nerve roots are not compressed, final tightening is performed (Figure 3).

Figure 3 Final stage of lordosis correction at the L4–L5 level. (A) Schematic of the final segmental lordosis after final segmental contraction. (B) C-arm-based intraoperative sagittal image of the lumbar spine with posterior cage migration after failed previous fusion at L4–L5. (C) C-arm-based intraoperative sagittal image of the final segmental lordosis at L4–L5.

The developed technique allows to reduce the risk of сage subsidence and migration and to avoid loss of segmental lumbar lordosis before the solid interbody fusion occurs (Figure 4).

Figure 4 The outcome of restoring segmental lumbar lordosis after a failed previous fusion at the L4–L5 level. (A) Preoperative CT scan. Cage migration after failed previous fusion at L4–L5. Segmental lumbar lordosis is 0°. (B) Postoperative CT scan: segmental lumbar lordosis restored to 15.1°. (C) Postoperative CT scan follow-up after 3 months. Segmental lumbar lordosis is 14.7°. CT, computed tomography.

Postoperative considerations and tasks

The postoperative period includes early mobilization, proper nutrition and multimodal anesthesia. Patients are encouraged to mobilize the day of surgery or first postoperative day after surgery. No additional specific postoperative patient care is required. The length of stay depends on several factors such as the number of levels, patient comorbidities.

Tips and pearls

Hip pads at the level of the posterior superior iliac spine or slightly lower are useful. This helps to achieve better fixation of the lumbar lordosis. The dissection of the lateral and anterior annulus fibrosus to achieve maximum segmental release is guided by C-arm fluoroscopy rather than direct visual control. First, strict adherence to the technique and not allowing the Cobb dissector’s tip to extend beyond the vertebral body margin farther out than 5 mm will prevent vascular injury. Secondly and finally, the protection of the nerve roots prevents damage during dissection of the lateral annulus fibrosus.

An injury to the anterior longitudinal ligament can cause anterior cage migration. Should this happen, an additional anterior approach will be taken to fix the lumbar segment. Patients should be informed of the possibility of an additional anterior approach.

Some other general risks, such as infection, postoperative hemorrhage or incidental durotomy, need to be communicated to the patient in advance.

Discussion

Lumbar hypolordosis following short-segment fusion can lead to the development of an iatrogenic deformity in the adjacent segment, which is a significant risk factor for subsequent surgery and can worsen postoperative clinical outcomes (1,2). The restoration of lumbar lordosis, especially at the L4–S1 level, is a major goal of re-operation after failed previous surgery. Traditionally, pedicle subtraction osteotomy (PSO) has been used to significantly restore lumbar lordosis (6). These surgeries are challenging and carry high morbidity rates. When PSO is performed, it is necessary to expand the instrumentation area. The complication rates reach 48.1%, and re-operation is required in 36.7% of cases (9). Another strategy is the 540 degree fusion procedure (back-front-back). For this type of surgery, anterior column realignment (ACR) using hyperlordotic implants is performed (7,10). A surgeon must have excellent ventral surgery skills in order to perform ACR. The length of surgery and hospital stay are significantly increased with ACR and PSO.

One of the serious potential complications of posterior discectomy is the retroperitoneal injury to vessels due to their close adjoining with the anterior lumbar spine (11). In 75% of cases, this complication occurs at the L4–L5 disc level (12). According to Goel A. and the co-workers, “most reported cases of abdominal vascular injury were caused by the pituitary rongeur pushed too far ventrally as to perforate the annulus fibrosus and anterior longitudinal ligament” (12). A factor that increases the risk of vascular injury is previous surgery on the intervertebral discs or abdomen, which are associated with fibrosis and adhesions between the anterior parts of vertebral bodies and retroperitoneal vessels. The vascular surgeons and access to endovascular equipment in a single hospital will facilitate conversion surgery rapidly in case of vascular complications (11-13). It is important to know that injury to retroperitoneal vessels may occur with any correction surgery on the lumbar spine, such as PSO, vertebral column resection (VCR), ACR (anterior lumbar interbody fusion, oblique lateral interbody fusion), especially if it is revision surgery. Our technique of restoring segmental lumbar lordosis after a failed previous fusion at the same level has the same risks. It is also important to inform the patient about the possibility of this adverse event. It is necessary to conduct further follow-ups to determine the long-term clinical outcomes, bone union and the rate of cage subsidence after surgery.

Navigation assist is a useful additional option that has several advantages: a better accuracy of pedicle screw insertion, decreased blood loss and operation time, reduced radiation exposure, improved functional outcomes, less complications, and higher fusion rates (14-17). Although navigation assist is used in primary minimally invasive surgery (MIS) surgeries, it is useful in revision surgeries, too. Performing our proposed technique with navigation assist provides better control of the Cobb dissector insertion depth during the release of the anterior annulus fibrosus as well as an accurate positioning of the cage in the interbody space. We recommend navigation assist for use with our technique.

Maximum segmental mobility is achieved by dissection of the lateral and the anterior annulus fibrosus, yet with safety to the anterior longitudinal ligament. The cage design is not a factor for the restoration of segmental lordosis (18-22). The cage offers reliable support between vertebrae and contributes to interbody fusion.

Conclusions

We have introduced a new method for restoring segmental lumbar lordosis after failed previous fusion at the same level. A major advantage of developed technique is that it makes a large extent of segmental lordosis achievable in only one posterior approach per surgical session. The next one is the ability to restore lumbar lordosis by acting only on the failed previous fusion, without extending the area of instrumentation. It is necessary to conduct further follow-ups to determine the long-term clinical outcomes, bone union and the rate of cage subsidence after surgery.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the SUPER reporting checklist. Available at https://jss.amegroups.com/article/view/10.21037/jss-24-169/rc

Peer Review File: Available at https://jss.amegroups.com/article/view/10.21037/jss-24-169/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-24-169/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images/video. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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