Article Figures & Data
Figures
- Figure 1
Illustration showing the surgical steps of haplo-paraspinal-muscle-preserving (HMP) technique in laminoplasty. (A) Representative image showing the structure of the cervical vertebra and its posteriorly attached muscle. (B) The main difference between the HMP technique and traditional laminoplasty is that only half of the laminae that are to be opened during the laminoplasty procedure are exposed. The paraspinal muscle is only dissected on the left side of the spinous process, and the right side of the paraspinal muscle remains intact. (C) After exposure, the left sides of the laminae are opened and flipped using a small vertebral spreader. During the opening, the spreader slowly separates the laminae to prevent hinge side laminae fracture. (D) After opening the spinal canal, an ARCH plate is fixed to maintain the canal enlargement. PSM, paraspinal muscles; SL, spinous process–attached ligaments; SM, spinous process–attached muscles.
- Figure 2
The surgical view, radiographic outcome, and intraoperative images showing the process of laminoplasty using the haplo-paraspinal-muscle-preserving (HMP) technique. (A) Only one side of the laminae is exposed and the paraspinal muscles, as well as spinous process–attached ligaments and muscles of the other side, were prevented from being dissected. (B) The laminae were cut to create an opening of the spinal canal with the assistance of a small vertebral spreader. (C) ARCH plates were used after the opening to finish the laminoplasty procedure. The radiological images show the preoperative magnetic resonance images (D), preoperative reconstructed computed tomography (E), and postoperative reconstructed computed tomography (F) of the same patient that received HMP laminoplasty. Note that the spinal canal is significantly enlarged after the surgery. LA, laminae; LM, dissected laminae–attached muscles; SP, spinous process.
- Figure 3
Computed tomography (CT) images showing the typical characteristics of hinge side fractures in different laminoplasty techniques. Typical CT images of a hinge side fracture in the C4 level of an haplo-paraspinal-muscle-preserving laminoplasty–treated patient (A–C). Stenosis is observed preoperatively (A), and the spinal canal enlarged significantly after the surgery (B), with a fracture in the cortical bone of the ventral side of the hinge laminar while the dorsal side of the hinge remained intact. The fracture is healed 6 mo after the surgery, with no sign of cortical bone fracture of the hinge side (C). Typical CT images of hinge side fractures in the C3 (D) and C4 (E) levels of a traditional laminoplasty–treated patient. The C5 (F) level is intact. Both ventral and dorsal sides of the hinge side laminae were compromised when the fracture occurred (D–E); typically, the dorsal side of the hinge is thinned due to the removal of cortical bone to form a hinge (F).
- Figure 4
Magnetic resonance images (MRIs) showing the posterior cervical paravertebral muscle volumes between different laminoplasty groups. Case example of a 55-year-old female patient who received traditional laminoplasty, with the T2-weighted axial MRI showing the paravertebral muscle volumes (A) preoperation, (B) 3 days postoperation, and (C) 1 year postoperation. Case example of a 57-year-old male patient who received haplo-paraspinal-muscle-preserving laminoplasty, the T2-weighted axial MRI showing the paravertebral muscle volumes (D) preoperation, (E) 3 days postoperation, and (F) 1 year postoperation.
Tables
Demographics MP Group LP Group P Value Number 22 46 – Age 61.2 ± 6.4 60.9 ± 5.9 0.85 Gender (male:female) (14:8) (29:17) 0.96 BMI 26.6 ± 3.0 27.7 ± 2.7 0.08 Disc herniation (patients) 19 39 – OPLL (patients) 8 20 – Operation level 0.74 C3–C6 4 8 – C3–C7 16 29 – C2–C6 1 4 – C2–C7 1 5 – Preoperative JOA 9.1 ± 7.9 8.7 ± 7.2 0.84 Preoperative VAS 5.2 ± 2.5 5.4 ± 2.3 0.75 Follow-up period (mo) 15.8 ± 3.8 16.8 ± 3.2 0.55 Note: Data are shown as the mean ± SD; ‘-’ represents values were not compared for differences.
BMI, body mass index; JOA, Japanese Orthopaedic Association; LP Group, traditional open-door laminoplasty-treated patients; MP Group, haplo-paraspinal-muscle-preserving laminoplasty-treated patients; OPLL, ossification of posterior longitudinal ligament; VAS, visual analog scale.
Surgical Parameters MP Group LP Group P Value Time of surgery, min 50.5 ± 12.8 74.0 ± 17.8 0.01 Blood loss volume, mL 92.5 ± 49.3 189.4 ± 62.7 <0.01 Spinal canal expansion, mm 3.9 ± 1.3 4.2 ± 1.2 0.35 CSF leakagea 0 1 0.68 Note: Spinal cord expansion was measured and compared using preoperative and postoperative computed tomography. Data expressed as mean ± SD. Boldface indicates statistically significant findings.
↵a The CSF leakage here represents leakage that was found during the surgery.
CSF, cerebrospinal fluid; LP Group, traditional open-door laminoplasty-treated patients; MP Group, haplo-paraspinal-muscle-preserving laminoplasty-treated patients.
Postoperative Clinical Data MP Group LP Group P Value JOA score Before surgery 9.1 ± 7.9 8.7 ± 7.2 0.84 6 mo after surgery 12.6 ± 2.2 12.7 ± 2.4 0.87 12 mo after surgery 13.8 ± 3.1 13.6 ± 2.8 0.64 IR (%) 59.5 ± 9.2 59.0 ± 8.9 0.23 VAS Before surgery 5.3 ± 2.6 5.2 ± 2.7 0.75 6 mo after surgery 2.5 ± 1.6 3.8 ± 1.6 <0.01 12 mo after surgery 2.1 ± 1.5 2.7 ± 1.6 0.15 C2–C7 Cobb angle, degree Before surgery 10.2 ± 2.8 10.8 ± 2.6 0.65 6 mo after surgery 11.4 ± 2.8 10.6 ± 2.7 0.05 12 mo after surgery 10.7 ± 2.3 9.2 ± 2.4 <0.01 Loss of lordosis (final follow-up) 0.7 ± 1.1 1.4 ± 1.2 <0.01 Postoperative complications, n (%) Persistent axial neck pain 2 (9.1) 7 (15.2) 0.75 C5 nerve root palsy 0 (0.0) 1 (2.2) 0.68 CSF leakage 1 (4.5) 4 (8.7) 0.91 Note: Data presented as mean ± SD except where otherwise noted. Boldface indicates statistically significant findings.
CSF, cerebrospinal fluid; IR, improvement rate; JOA, Japanese Orthopaedic Association; LP Group, traditional open-door laminoplasty-treated patients; MP Group, haplo-paraspinal-muscle-preserving laminoplasty-treated patients; VAS, visual analog scale.
Hinge Fracture Type MP Group
(107 levels)LP Group
(227 levels)P Value Ventral cortex fracture 67 (59.8%) 57 (25.1%) <0.01 Dorsal cortex fracture 9 (8.4%) - - Complete fracture 9 (8.4%) 57 (25.1%) <0.01 Hinge side displacement 0 (0.0%) 3 (1.3%) 0.31 Note: Data presented as number of levels (%). Boldface indicates statistically significant findings
LP Group, traditional open-door laminoplasty-treated patients; MP Group, haplo-paraspinal-muscle-preserving laminoplasty-treated patients.
Muscle Volume (cm2) MP Group
(n = 22)LP Group
(n = 46)P Value Open-door side Preoperation 76.84 ± 6.23 77.69 ± 7.21 0.82 Postoperation 65.23 ± 5.22 66.79 ± 4.67 0.42 1-year follow-up 72.61 ± 5.24 73.23 ± 5.12 0.79 Hinge side Preoperation 76.62 ± 6.11 77.42 ± 6.75 0.78 Postoperation 75.27 ± 5.83 68.54 ± 5.48 <0.01 1-year follow-up 76.22 ± 4.96 74.63 ± 6.74 <0.01 Note: Data are expressed as the mean ± SD. Boldface indicates statistically significant findings.
LP Group, traditional open-door laminoplasty-treated patients; MP Group, haplo-paraspinal-muscle-preserving laminoplasty-treated patients.
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