Achondroplasia with seronegative spondyloarthropathy resulting in recurrent spinal stenosis : A case report

INTRODUCTION

Achondroplasia an autosomal dominant caused by a mutation of the G380 gene encoding fibroblast growth factor receptor 3 on chromosome 4P.[1] The clinical findings include rhizomelic extremities (humerus shorter than forearm and femur shorter than tibia), cranial frontal bossing, and often cervical, thoracic, and lumbar spinal stenosis with attendant cord compression.[3] Degenerative changes at these levels typically occur at an earlier age and include disc herniations, degenerative spondylosis, and other arthritic findings. Here, a 36-year-old male with achondroplasia and seronegative spondyloarthropathy presented with recurrent L3-L4 lumbar canal restenosis 9 years following an initial L2-S1 laminectomy for stenosis.

CASE PRESENTATION

A 36-year-old male with achondroplasia (113 cm and weight 43 kg [BMI-33.7] with forehead prominence) presented with low back pain and right lower extremity sciatica of 6 months duration. On examination, the patient was wheelchair bound, had difficulty standing, and could not walk independently (4/5 motor dysfunction diffusely throughout both lower extremities and diffuse hypoesthesia in the L3, L4 distributions). Nine years ago, he had undergone a L2-S1 decompressive laminectomy for stenosis with good resolution of his symptoms. New radiographic studies now showed recurrent L3-L4 lumbar stenosis. Plain lumbar X-rays demonstrated fusion between the L1-L3 and L3-L5 lumbar levels, with osseous fusion of the right sacroiliac joint accompanied by irregularity of the left S1 joint cortex due to advanced seronegative spondyloarthropathy [Figures 1-4].

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Figure 1:: Preoperative X-ray of lumbosacral spine (anteroposterior and lateral): X-ray suggestive of degenerative changes of lumbar spine and osseous fusion of the right SI joint with irregularity of cortex in the left SI joint. (b) Postoperative X-ray lumbosacral spine (anteroposterior and lateral): posterior decompression at L3-4 and fusion was achieved with the right side unilateral instrumented stabilization and interbody fusion with bone graft.

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Figure 2:: CT scan sagittal view: L3-4 unfused segment with fused dorsolumbar segments showing advanced seronegative changes.

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Figure 3:: MRI scan of lumbosacral spine sagittal view: lumbar canal stenosis is seen at L3-4 level due to diffuse disc bulge, facetal arthropathy, and osseous malformation of L3 and L4 vertebral bodies.

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Figure 4:: MRI scan of lumbosacral spine axial view: bilateral L3-4 foraminal narrowing and lumbar canal stenosis are seen causing bilateral L3 nerve root compression.

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Surgery

The patient underwent a wide bilateral microscope-assisted decompressive L3-L4 laminectomy for resection of L3-L4 bony spurs, L3-4 discectomy, interbody fusion using local autograft, and L3-L4 right-sided instrumented stabilization [Table 1]. At surgery, it was difficult to identify the pedicles of L3-4 due to the distorted anatomy, hypertrophic scar, and dense fibrous bridges between the respective facet joints.

Table 1:: Surgical outcomes.

Postoperative outcomes

Postoperatively, the patient neurologically improved; he walked with a walker on the day of surgery and was able to return to work 6 weeks later. One year postoperatively, his motor deficit fully resolved (i.e. to 5/5) [Table 2].

Table 2:: Patient scores.

DISCUSSION

Patients with achondroplasia and congenitally shortened pedicles are susceptible to developing cervical, thoracic, and/or lumbar stenosis. Patients typically become symptomatic in their 30s though 50s due to accelerated disc degeneration, lumbar kyphosis, hypertrophy of ligamentum flavum, bone spurs, and thickened laminae/facet joints.[2,5]

There is often a need for revision spine surgery in these patients attributed to their accelerated facet hypertrophy associated with their genetic defect (i.e., an exaggerated response to normal motion leading to early degeneration)[4,6] [Table 3]. Ain et al. further reported recurrent stenosis occurring in these as well.[1] Further, repeat surgery may successfully reduce pain and neurological symptoms/signs. In the case presented of a 36-year-old male with achondroplasia, 9 years following an original L2-S1 laminectomy for stenosis, repeated decompression and fusion at the L3-L4 level addressing recurrent stenosis were successful.

Table 3:: Review of revision spine surgeries in achondroplasia.

CONCLUSION

Patients with achondroplasia who have previously undergone lumbar decompressive surgery may develop recurrent lumbar stenosis that responds well to repeated surgical intervention.