INTRODUCTION
Achondroplasia is a congenital skeletal dysplasia characterized by spinal canal narrowing due to short pedicles, thickened ligamentum flavum, and early-onset degenerative changes. These anatomical abnormalities predispose patients to lumbar spinal stenosis (LSS), leading to neurogenic claudication and functional impairment. While traditional open decompression remains the primary treatment, it is associated with significant soft tissue disruption and potential spinal instability.
Endoscopic unilateral laminotomy for bilateral decompression (ULBD) is a minimally invasive technique that preserves spinal stability while achieving effective neural decompression. However, its application in achondroplasia patients remains underreported. This case report presents a 48-year-old male with symptomatic multilevel LSS who underwent staged endoscopic ULBD, highlighting the technical challenges and clinical outcomes.
CASE REPORT
A 48-year-old male with achondroplasia presented with progressive bilateral neurogenic claudication and lower extremity radiculopathy. His symptoms included lower back pain, numbness, and weakness, with a visual analogue scale (VAS) score of 10/10 on the right and 8/10 on the left. He required frequent rest breaks while walking and was unable to sleep in a supine position (Figure 1).
His medical history included diabetes mellitus, hypertension, and hyperlipidemia, managed with metformin (250 mg), teneligliptin (20 mg), telmisartan (20 mg), aspirin (100 mg), rosuvastatin (10 mg), tramadol SR (100 mg), pregabalin (75 mg), and lansoprazole (100 mg).
Neurological examination revealed weakness in great toe dorsiflexion (3/5 bilaterally) and ankle dorsiflexion (3/5 bilaterally), while knee and plantar flexion remained intact. Magnetic resonance imaging demonstrated severe LSS at L1–2, L2–3, L3–4, and L4–5, with the most significant stenosis at L2–3 and L4–5 (Figure 2). A staged surgical approach was planned, with initial endoscopic ULBD at L2–3 and L4–5, followed by decompression at L1–2 and L3–4 one week later.
This study was conducted in compliance with the Declaration of Helsinki. Informed consent was obtained from the patient.
SURGICAL TECHNIQUE
The surgical procedure was performed under epidural anesthesia with additional inhalation sedation via mask for optimal patient comfort. The patient was positioned prone on the operating table in accordance with standard spine surgery protocols. The biportal endoscopic ULBD approach was utilized, employing 2 separate portals: 1.5- to 2.0-cm working port and 1.0- to 1.5-cm viewing port for endoscopic visualization (Figure 3).
The standard endoscopic spine surgery instrumentation set was employed, consistent with typical unilateral biportal endoscopic procedures. However, several technical modifications and careful considerations were necessary due to the unique anatomical characteristics of achondroplasia. The reduced spinal canal dimensions, comparable to those of pediatric patients, demanded exceptionally precise portal placement to avoid facet violation. This was particularly crucial given the altered anatomical relationships typical in achondroplasia patients.
The decompression procedure followed the principles of conventional ULBD, with several technical challenges specific to this case. The shortened pedicles characteristic of achondroplasia created additional difficulty in tissue dissection and root manipulation around the pedicle region. Furthermore, the ligamentum flavum demonstrated significantly more severe adhesion compared to typical cases, requiring meticulous dissection. Particular attention was paid during the decompression process due to the apparently weakened dural surface, which presented an elevated risk of durotomy. Despite these challenges, complete bilateral flavectomy was achieved, and both traversing nerve roots were adequately decompressed (Figure 4).
Each level required approximately 40 minutes of operative time, reflecting the careful attention needed to navigate the modified anatomy while ensuring adequate decompression. The procedure successfully achieved the surgical objectives of neural decompression while maintaining spinal stability through preservation of critical anatomical structures.
A staged approach, addressing 2 levels per surgery, was selected rather than performing all 4 levels simultaneously, considering anatomical complexity, limited experience with achondroplasia, and patient comorbidities (hypertension, diabetes mellitus, and hyperlipidemia) that could increase anesthesia-related risks. Additionally, the surgery was performed from the left side due to anatomical advantages for right-handed surgeon, where the upper lamina overlaps the lower lamina, allowing more precise and efficient surgical manipulation and thereby minimizing operative time and systemic risks.
RESULTS AND OUTCOMES
The patient's recovery followed a staged pattern corresponding to the 2 surgical interventions. Following the initial endoscopic ULBD at L2–3 and L4–5 levels, the patient reported moderate symptom improvement, with the VAS score for pain decreasing from 10 to 7. However, the neurological deficits, particularly the weakness in bilateral ankle and toe movement, showed minimal subjective immediate improvement during this period.
During the second surgical procedure one week later, endoscopic exploration of the previously operated L2–3 level revealed an unexpected finding: a linear durotomy approximately 1.5 cm in length along the midline of the dura (Figure 5). Notably, the arachnoid membrane remained intact with no evidence of rootlet herniation. This dural defect was likely a secondary development, presumably resulting from the expansion of the previously compressed, notably thin and weakened dura following adequate decompression. The finding was particularly significant given that no immediate evidence of durotomy was observed during the initial procedure. The compromised area was reinforced with dural sealing matrix application (Figure 5).
At 1-week follow-up after the second surgery, significant clinical improvement was observed. The patient's motor strength in bilateral ankle and toe movement improved from grade 3/5 to 4/5. Pain levels showed substantial reduction, with VAS scores decreasing to 3 during daily activities. A notable functional improvement was observed in sleeping patterns—while the patient still experienced some limitations in maintaining a fully supine position throughout the night, intermittent supine sleeping became possible, marking a significant improvement from the preoperative state where sitting position was required for sleep.
These outcomes suggest that despite the technical challenges and the occurrence of a delayed durotomy, the staged endoscopic ULBD procedures achieved meaningful clinical improvement in this achondroplasia patient with complex multilevel spinal stenosis.
The decision to explore the surgical site again was prompted by an observation during the routine postoperative assessment at the conclusion of the surgery, where insufficient thecal sac expansion was noted upon cessation of continuous water flow. Further exploration unexpectedly revealed the dural tear from the first procedure, allowing for immediate management.
DISCUSSION
The surgical management of LSS in achondroplasia patients presents unique challenges that demand careful consideration of both surgical approach and timing. While traditional open decompression has been the standard treatment, Abu Al-Rub et al. [1] reported that while most patients benefit from decompression alone, approximately 3% required fusion procedures, and 9% showed no improvement in symptoms. Our experience with endoscopic ULBD demonstrates the potential advantages of this minimally invasive approach, particularly in achieving adequate decompression while minimizing structural disruption. The endoscopic technique's ability to preserve the posterior tension band and minimize tissue disruption may help prevent postoperative kyphosis, a significant concern in achondroplasia patients [2].
The staged surgical approach employed in this case offers several notable advantages for treating multilevel stenosis in achondroplasia patients. Each level required only 30–40 minutes of operative time, with minimal blood loss compared to traditional open procedures [3]. Furthermore, the small incision size (1.5- to 2.0-cm working port and 1.0- to 1.5-cm viewing port) significantly reduces the risk of surgical site infection and minimizes damage to supporting musculature and ligamentous structures. The discovery of a delayed durotomy during the second procedure highlights an important consideration in achondroplasia patients: the potential for dural vulnerability that may not be immediately apparent during the initial surgery. This finding suggests that staged procedures may offer an additional advantage in allowing for early detection and management of such complications through routine exploration of previously operated levels without requiring additional incisions.
The technical aspects of endoscopic ULBD in achondroplasia patients deserve special attention. As noted by Sienkiel et al. [4], the altered anatomy in these patients necessitates particularly careful dissection techniques. Our experience suggests that the natural hydrodissection effect created by the endoscopic irrigation system, combined with high-resolution visualization, provides significant advantages over open surgery in performing the fine dissection required in these cases. The enhanced visualization allows for more precise identification and preservation of neural structures, which is particularly crucial given the anatomical variations present in achondroplasia patients [5].
While our initial results are encouraging, several limitations must be acknowledged. Long-term follow-up is essential to evaluate the durability of clinical improvement and to monitor for potential late complications such as progressive kyphosis or instability [6]. Additionally, our experience with a single case, while informative, cannot definitively establish the superiority of this approach over traditional techniques. Future studies with larger patient cohorts and longer follow-up periods will be necessary to validate these findings and better define the role of endoscopic ULBD in treating LSS in achondroplasia patients. Nevertheless, our experience suggests that staged endoscopic ULBD may represent a valuable addition to the surgical armamentarium for treating this challenging patient population.
CONCLUSION
This case demonstrates that endoscopic ULBD can be a viable surgical option for treating LSS in achondroplasia patients, offering the benefits of minimal tissue disruption while achieving adequate decompression. The staged approach not only allows for careful management of multiple stenotic levels but also provides an opportunity for early detection and treatment of potential complications. While careful attention to technical details is essential, particularly regarding dural handling and fine dissection techniques, the enhanced visualization and precise manipulation afforded by the endoscopic approach may make it particularly suitable for the unique anatomical challenges presented by achondroplasia patients. Further studies with larger patient cohorts will be necessary to fully establish the long-term efficacy and safety of this technique in this specific patient population.
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