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Koga et al. Minimal laminectomy with the interlaminar approach for PELD

(SAP), are directly removed by using the Kerrison significant difference between the 2 groups in the AP
rongeur. In such cases, after detachment of the yellow size ratio, operation time, postoperative hospital stay,
ligament from the bone margin, the cutting edge of the blood loss, follow-up period, and operative outcome.
Kerrison rongeur is sledded into the detached space We observed no intraoperative complications in this
(case 4, Supplementary Video 1). As exposure of a study [Table 1].
small part of the protruded vertebral disc is sufficient to
remove it, we only perform minimum removal of bone Two recurrent cases (cases 1 and 5) received minimal
and yellow ligament (final stage of Supplementary laminectomy for exposure of the fresh margin of the
Video 1: the white protruded disc surface at the vertebral laminae and yellow ligament. One case
shoulder area of the nerve root can be seen). (case 2) received minimal laminectomy to perform
ILA underan inappropriate endoscope insertion due
RESULTS to a high level of obesity (body mass index 39.4).
Generally, the endoscope is introduced from the caudal
Thirteen patients were registered for this study; 10 to the cephalic direction toward the interlaminar space;
underwent the ILA via the shoulder (cases 1-10) and however, we could not maintain this slope because
three underwent the ILA via the axilla (cases 11-13). of the thickness of soft tissue in this case. We had
The mean patient age was 46.3 years (range 17-82 to remove the CM-UVL, which is one workaround for
years), and the most affected vertebral level was L5/ inappropriate endoscope insertion.
S1 (11 cases), followed by L4/5 (2 cases). The LDH
location, AP size ratio, width of the interlaminar space, Furthermore, we radiologically analyzed each case
operation time, postoperative hospital stay, blood loss, that received laminectomy, including the shape of the
and operative outcome (mJOA and NRS scores) for upper vertebral laminae, extent of migration, and area
each case are shown in Table 1. Compared with our of laminectomy [Table 2].
previous ILA data[laminectomy (-) group], the width
of the interlaminar space in the cases that received Four of 10 cases (cases 4, 6, 9, and 12) showed an
laminectomy was significantly narrower (25.95 mm interlaminar space with a width of < 20 mm, and a
vs. 22.46 mm, P = 0.003). However, there was no small extent of SAP removal was mainly required. The

Figure 1: Preoperative radiographic findings on the migration and shape of the upper vertebral laminae. The extent of migration was
evaluated by using T2-weighted sagittal magnetic resonance imaging. (A) Low-grade migration: defined as a migration extent smaller than
the height of the disc space (case 2); (B) high-grade migration: defined as a migration extent exceeding the height of the disc space (case
11); (C) concave (-): caudal margin of the upper vertebral laminae (CM-UVL) is straight, as evaluated by using three-dimensional computed
tomography (case 8); (D) concave (+): CM-UVL has a measurable concave and the superior articular process is easy to access (case 9)
58 Mini-invasive Surgery ¦ Volume 1 ¦ June 30, 2017