Pseudofusion Dilemma

History

A 53-year-old, nonsmoking woman came to the clinic with increasing back and right leg pain despite undergoing an L4-S1 Transforaminal Lumbar Interbody Fusion (TLIF) and lateral mass fusion with Bone Morphogenetic Protein (BMP) just 8 months prior. She initially had surgery for severe degenerative disc disease at L4-5 and a Grade I spondylolisthesis with stenosis at L5-S1. This procedure provided good relief of her pain. Her past surgical history also includes a retroperitoneal approach pelvic floor reconstruction for uterine and rectal prolapse and bladder neck suspension.

Examination

The physical exam revealed dorsiflexion weakness in the ankle, as well as decreased sensation in the L5 dermatome bilaterally. The patient’s pain was reproduced with forward flexion. At this time, plain film imaging demonstrated pseudofusion at both levels as confirmed by CT scan. 

Prior Treatment

The patient’s treatment to-date was the TLIF and fusion with BMP 8 months prior and while she initially received relief from her pain, her back and right leg pain has returned and is worsening.

Images

The images include a lateral plain film, demonstrating lack of bone growth at either disc space [Fig. 1] and a Sagittal CT scan confirming pseudofusion at both interspaces.

Figure 1 Lateral plain film showing lack of bone growth at both disc spaces.	Figure 2 Sagittal CT scan confirming pseudofusion at both interspaces
Figure 3 Coronal CT showing lack of lateral mass fusion at either level

Discussion of Treatment Options and Recommendation

Imaging should be conducted to investigate whether there is there is any continued posterior compressive pathology causing the leg pain (MRI lumbar spine with contrast or a CT myelogram). Additionally, EMG and nerve conduction could be helpful in delineating the cause for leg pain.

If it is determined that there is posterior continued stenosis, then a foraminal steroid injection could help as a diagnostic and therapeutic maneuver. However, if that fails, a redo minimally-invasive posterior foraminotomy could alleviate any continued stenosis.

This patient also has pseudoarthrosis, for which I would suggest ALIF at L4-S1 with cages and BMP. I also would recommend a redo retroperitoneal approach or a transperitoneal approach, with the assistance of a vascular surgeon.

Selected Treatment

Editor’s note: In this particular case, you the readers brought to our attention that we may not have included all possible treatment options. Dr Reginald Knight of Kirkland, Washington, suggested that he would "perform no additional surgery." We appreciate the feedback and, based on readers' feedback, from now on we are including "Other" as a treatment option.

Having failed conservative therapy and despite her previous abdominal surgeries we elected to undergo an anterior approach.  With the help of a vascular surgeon we performed a transperitoneal exposure of L4-S1.  This avoided the difficulty of scar tissue impeding a retroperitoneal approach.  After performing an anterior discectomy, both cages were easily harvested and an aggressive preparation of the endplates was carried out.  We then placed threaded interbody cages with BMP using an ALIF technique at each level.  As there was no hallowing around the screws we elected to leave the posterior instrumentation. The patient tolerated the procedure well with minimal blood loss and no further complications.

Outcome

One week postoperatively, the patient reported marked improvement in her leg pain with moderate improvement in her back pain (Figure 4). She still required pain management for her back pain but reported it was improved by the surgery. At 6 months postoperatively,  the patient demonstrated solid bony fusion at both levels as witnessed by CT imaging (Figure 5).

Figure 4 Postoperative film showing threaded cylindrical cages in interspace at L4-5 and L5-S1.

Figure 5 At 6 months postoperatively, the patient demonstrated solid bony fusion at both levels as witnessed by CT imaging.