PMC10232900_01
Postoperative lumbar radiograph and CT images taken on 26 and 27 December 2019, respectively. AP (A) and lateral view (B) of the lumbar radiograph. Postoperative CT images (C-G) detected the majority of calcified fragments that were removed. The calcified base at the posterolateral corner of the L5 inferior endplate was left asymptomatic (soft tissue window), and the calcified shell of the herniated S1-2 disc and osteophytes from the inferior endplate of S1 within the S1-2 foramen was also not removed. (C) Sagittal reconstructed CT image through the left paracentral plane. (D) Sagittal reconstructed CT image through the left recess. (E) Sagittal reconstructed CT image through the left foramen plane. (F) Raw transverse CT image through L5S1 level. (G) Raw transverse CT image through S1-2 level. (Arrow 1) Residual osteophytes at the posterolateral corner of the L5 inferior endplate. (Arrow 2) A residual calcified shell of the herniated S1-2 disc and osteophytes from the inferior endplate of S1 within the intervertebral foramen.
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F1
LDHs at the two lowest free levels. LDH at the lowest level was a shoulder type, and that at the penultimate level mainly was an axillary type (Figure 1). The shoulder space to the S2 nerve was exposed first as the S2 nerve had been displaced medially by the herniated S1-2 disc which resulted in a narrowed axillary region and widened shoulder region (Figure 1D).
MRI of the lumbar spine taken on 22 September 2019, revealed huge LDHs at the lowest two free levels at the left side, which was later confirmed to be L5S1 and lumbarized S1-2 disc [type IV TD (lumbosacral transitional disc) according to Wigh et al.'s classification based on the following whole spinal images]. (A) Sagittal plane through the left lateral recess (T1WI). (B) Sagittal plane through the left lateral recess (T2WI). (C) Transverse plane through the L5S1 disc (T2WI) showed an axillary type LDH. (D) Transverse plane through the well-developed S1-2 disc (T2WI) showed a shoulder type LDH.
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F2
Both L5S1 and S1-2 levels had a wide laminar space, defined as the interlaminar window distance between the cranial and caudal laminae and between the middle line and mediodorsal border of the inferior articular process (IAP) at either level which exceeded 10 mm (Figure 2C). Both calcified disc tissues and formed osteophytes were left-sided (Figure 2). L5S1 level was chosen as the first decompression target, as the herniated tissues at this level were mainly soft and might be the major source of the patient's complaints (Figure 2).
Preoperative whole spinal radiograph and CT images taken on 23 September 2019. (A-E) The whole spine radiograph revealed a complete LZ according to Lee's classification and also type IB LZ according to Castellvi's classification. Anteroposterior (AP) view of the cervical (A), thoracic (B), and lumbar spine (C) and lateral view of the lumbar spine at flexion (D) and extension (E). The space of the interlaminar window at the sagittal or transverse direction at L5S1 and S1-2 met the criteria demand (>6 mm) for PEID (C). (F-N) CT scanning revealed CLDH at L5S1 and lumbarized S1-2 levels with osteophyte formation at adjacent posterior edges, L5S1 had scattered calcified disc tissues, and S1-2 had a calcified shell at the posterior edge of herniated tissues. (F) Coronal reconstructed image at the bone window confirmed type IB LZ. Sagittal reconstructed CT image through the left lateral recess plane at the soft tissue (G) and bone tissue windows (K) detected huge soft LDH at L5S1 level with osteophyte formation at the posterior edge of the inferior endplate of L5 and a calcified shell of the herniated S1-2 disc connected with osteophytes from the posterior edge of the inferior endplate of S1 while still separated from the superior endplate of S2. Sagittal reconstructed CT image lateral to the medial border of the left pedicle at the soft tissue (H) and bone windows (L) detected scattered calcified disc tissues at L5S1 level and a calcified shell of the herniated S1-2 disc connected with osteophytes from the posterior edge of S1. Raw transverse CT image adjacent to the inferior endplate of L5 at the soft tissue (I) and bone windows (M) detected calcified tissues from the herniated L5S1 disc at the lateral region, which was separated from the L5 vertebra (black concave arrow). Raw transverse CT image at the superior endplate level of the S2 vertebra at the soft tissue (J) and bone windows (N) detected a calcified shell of the herniated S1-2 disc separated from the S2 vertebra at the left lateral margin (black concave arrow) while no osteophyte was found at the non-herniated right side.
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F3
The patient was placed in the prone position, and the L5S1 and S1-2 levels were confirmed under C-arm guidance (Figure 3A). The skin entrance points were marked (with reference to the medial pedicular line on AP and spino-laminar line on lateral view) (Figure 3B). In addition, 5-10 mL of 0.5% lidocaine was infiltrated around the periosteum and the ligamentum flavum (LF) to prevent pain from following LF splitting (Figure 3C). After optimal positioning of the working channel under C-arm guidance (Figure 3D), a 30  endoscope was inserted. The most inferolateral LF connected to this corner was exposed and split longitudinally using a probe and resected in the same direction using a punch to open a 5-mm-long window to expose the epidural space, which is located at the axilla area of the traversing S1 nerve (Figure 3E). The working cannula was then moved to the shoulder space of the S1 nerve after soft retraction of the S1 nerve medially to remove the residual herniated disc shoulder ventral to the S1 nerve (Figure 3E-I). After insertion of the working cannula, the tip of the working cannula was adjusted toward the bony corner formed by the inferior edge of the superior lamina turning to the base of the inferior process from the S1 vertebra under C-arm guidance (Figures 3J,K).
PEID performed on 25 December 2019. (A) AP view on C-arm fluoroscopy to determine the skin incision positions. (B) Skin marks for entrance points. (C) The location of the puncture needle tip at L5S1 level confirmed on AP fluoroscopy ("V" point: the intersection of the ligamentum flavum, IAP, and SAP). (D) The location of the working cannula's beveled end adjusted to the inferolateral corner formed by the medial edge of SAP and the superior edge of the lamina from S1. (E) LF at the latero-inferior corner of the L5S1 interlaminar space was split longitudinally exposing fragments of the herniated L5S1 disc at the axillary region. (F) Hard and soft fragments of the herniated disc axillary to the S1 nerve were resected using angled forceps, the dura mater was at the 12 o'clock direction, and the S1 was at the 6 o'clock direction beyond endoscopic visualization. (G) Free space after herniated disc fragments at the axillary region of the S1 nerve was resected, and the S1 nerve appeared at the 6 o'clock direction. (H) Herniated disc fragments shoulder to the S1 nerve. (I) Free space at the shoulder space shoulder to S1 after the herniated disc at this region was removed. (J) The location of the puncture needle tip at S1-2 level. (K) The location of the working cannula's beveled end pointed to the superolateral corner formed by the medial edge of IAP and the inferior edge of the lamina from S1. (L) Calcified fragments of LDH shoulder to the S2 nerve were removed using an angled forceps. (M) Calcified fragments of the herniated S1-2 disc shoulder to the S2 nerve were shaved off by rotating and migrating the beveled end of the working cannula as an end-bit trephine exposing free space shoulder to the traversing S2 nerve. (N) Residual calcified shell and submerged soft tissues of the herniated S1-2 disc axillary to the S2 nerve. (O) Free space beneath the dura mac at S1-2 level after decompression; the S2 nerve was at the 6 o'clock direction but beyond the endoscopic visualization. (P) One day postoperatively, on 26 December 2019, the patient began to walk without any discomfort; 12 o'clock was the medial direction, and 9 o'clock was the cranial direction.
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F4
The residual disc tissues at the axillary region were removed when pushing the S2 nerve laterally (Figures 4l-O). The calcified shell of CLDH and osteophytes within the S1-2 foramen, which are all located at the inferior portion of the foramen, were removed, produced no compression to neural elements nearby, and were left undisturbed (Figure 4G). In addition, the calcified shell of the herniated S1-2 disc and osteophytes were removed completely from the inferior endplate of S1 within the spinal canal, while those at the inferior portion of S1-2 foramen were left but produced no compression on neural elements (Figure 4).