Disease occurring under 21-years of age is termed ‘adolescent’[12-14]. But at what age there is a relevant distinction from adult disease is unclear. Great care should be taken when operating on the immature spine due to that it is unknown whether operating on the immature spine may increase their risk for having spinal surgery in the future. Additionally, delaying surgery for conservative treatment is warranted, but for how long remains unclear.
Appropriate conservative treatment including (bed rest, physical therapy and (NSAIDs) is the first choice for adolescents, but the young patients do not respond as well to nonsurgical treatment as adults due to adolescent disk material often remains well hydrated[13-15]. The surgical aim of treatment for ALDH is achieving of appreciable pain relief and function improvement. Mixter and Barr , published the first report of a herniated nucleus pulposus in a child in 1934, with another report of surgical treatment for a 12-year-old boy by Wahren in 1945 . Traditionally, open discectomy (OD) and microendoscopy discectomy (MED) was employed as the standard operation for ALDH [18,19].
In recent years, minimally invasive techniques are an attractive alternative to open discectomy (OD) and microendoscopy discectomy (MED) with a view to improving management of ALDH patients[18,19]. Endoscopic techniques have been widely used for ALDH since the first introduction by Ruetten et al . It has unique advantages of minimizing trauma to the normal spinal structures, reducing intraoperative bleeding and allowing earlier return to work. Most studies[10,12,13] have since been published on the surgical management of single level (especially L4–L5 or L5-S1) disk herniation in children and adolescents. Due to the sample size of 2 contiguous level ALDH is relatively small and rarity of its incidence, even though FELD has rapidly evolved and gained popularity, but, the efficacy of FELD is still debatable for contiguous ALDH. To our knowledge, currently, those studies had not mentioned one-stage operation of full-endoscopic lumbar discectomy for 2 contiguous level ALDH simultaneously[9-14].
Anatomically, inclination of L5–S1 disc spaces steeper than the L4–L5, which making single entry puncture point is enough to perform PELD at both the L4–L5 and L5–S1 levels. According to described technique[5,10], in cases of L4/L5- L5/S1 ALDH, under fluoroscopic guidance the meeting point of two lines crossing the L5 and S1 facet joint, indicating the point through which the surgeon can perform PELD for two level ALDH. In case of L3/L4-L4/L5 herniation, a small single skin puncture point is also possible, which rely on the technique of rod adjustment of a working cannula and targeted fragmentectomy. The favorable indications for one-stage operation of transforaminal full-endoscopic lumbar discectomy are same-side two level lumbar disc herniations causing unilateral radicular leg pain. However, the transforaminal approach at L5–S1 has limitations in cases of high iliac crests, small intervertebral foramen, large migrated disc herniations and different side lumbar disc herniations. In this study, 2 patients underwent one level transforaminal endoscopic lumbar discectomy combine one level endoscopic interlaminar discectomy. Because of this 2 pantients indicated different side lumbar disc herniations causing bilateral radicular leg pain.
ALDH is a rare disease with an incidence of only 1%-5%. Approximately 93% of symptomatic disk herniations occur predominantly at vertebral levels L4/L5 and L5/S1, other levels and 2 contiguous level disease recognized, but uncommon. Wang et al.  revealed that among 121 adolescents patients, L4/5 disease accounted for 50.4% (n = 61) of patients, L5/S1 for 34.7% (42/61), L3/4 for 3.3% (4/61), L4/5 + L5/S1 for 10.7% (13/61), and L3/4 + L4/5 for 0.8%. However, this cases have undertook the single level traditional open discectomy such as open discectomy (OD) and microendoscopy discectomy (MED).
The distinguishing feature of adult LDH was a result of age-related degenerative process of the spine. However, ALDH must be explained another cause such as micro-trauma, because degeneration is infrequent in adolescents[22-24]. But in actual fact the pathogenesis of ALDH is unclear, trauma or sports-related incidents, genetics and dysfunctional bio-mechanical conditions ( being overweight, or being tall, congenital lumbosacral malformations ) are likely contributory [21-25]. This study indicated that students accounted for 77.7%, we speculate that hours spent sitting is a major risk factor due to increased axial load. In our study, flattening of the sagittal lumbar curvature happened in 7 cases (63.6%). Other studies demonstrated that flattened spines are often associated with degeneration of multiple discs and back muscle weakness, which further significantly decreases spinal flexibility and stability[25,26,27] .
Several points should be kept in mind. (1) placement and rod adjustment of working cannula precisely, (2) toward the target compressing element of the disc directly, (3) require proper training and suitable patient selection.
Despite the sample size is relatively small because of rarity of its incidence with retrospective design, the absence of a control group and the follow-up period is too short to comment on the subsequent degeneration of the disc, our study suggests that one-stage operation of full-endoscopic lumbar discectomy for 2 contiguous level ALDH is an effective and less invasive method. To overcome the limitations, further studies are wanted to determine long-term therapeutic effect of one-stage operation of full-endoscopic lumbar discectomy for 2 contiguous level ALDH.