"Acquired" Type Castellvi-IIIa Lumbarization Transformed From Castellvi-IIa Following Discectomy and Fusion at Lumbosacral Level: A Case Report.

STUDY DESIGN: A retrospective case report.

OBJECTIVE: To report a case that transformed from type Castellvi-IIa sacralization to type Castellvi-IIIa after decompression and fusion surgery at transitional disc (TD).

SUMMARY OF BACKGROUND DATA: Traditionally, lumbosacral transitional vertebra has been regarded as a congenital anomaly. No literature has ever reported that transformation from one type lumbosacral transitional vertebra to another would happen after birth.

METHODS: A 60-year-old man presented to our department with the complaint of low back pain and left sciatic pain, and was diagnosed of lumbar disc herniation at L4-5 and L5-S1 levels. Lumbar digital radiography revealed an anomalous articulation formed between sacrum and enlarged right L5 transverse process, exhibiting a typical Castellvi-IIa sacralization. Dynamic lateral radiographs showed mobilization existed at L5-S1 disc which was TD. The patient received posterior lumbar interbody fusion (PLIF) surgery at L4-5 and L5-S1 levels. Postoperative computed tomography examinations were taken to identify the progress of solid fusion at the operated segments.

RESULTS: After surgery, the patient's symptoms alleviated obviously. As solid fusion developed at intended interbody regions with time, we found that bony bridge passed through the patient's anomalous articulation region gradually, and finally, complete osseous fusion of the right L5 transverse process to the sacrum developed 1 year after surgery.

CONCLUSION: Following PLIF surgery at TD segment on a Castellvi-IIa Sacralization case, "acquired" transformation to Castellvi-IIIa might develop.

LEVEL OF EVIDENCE: 5.