Reduced invasiveness of myoarchitectonic laminectomy compared with open-door laminoplasty in patients with cervical myelopathy

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1 Reduced invasiveness of myoarchitectonic laminectomy compared with open-door laminoplasty in patients with cervical myelopathy Department of Spinal Surgery 1), Brain Attack Center Ota Memorial Hospital, Fukuyama, Hiroshima, Japan; and Clinical Institute for Spinal Disorders 2), Otsu, Shiga, Japan Tatsuya Ohtonari 1), Nobuharu Nishihara 1), Katsuyasu Suwa 1), Taisei Ota 1), and Tsunemaro Koyama 2)

2 Introduction The ideal posterior cervical decompression 1Necessary and sufficient decompression Excessive decompression from the posterior is unnecessary and may also cause cervical kyphotic deformities. 2Preservation of ligamentomuscular elements The preservation of facet joints and nuchal ligaments is particularly important to prevent postoperative kyphotic deformities. Excessive stripping of the muscles can cause prolonged axial pain. 3The procedure is not a complicated one There is a tendency for the procedure to become complicated when the focus is on soft tissue preservation. 4To use implants as little as possible When implants such as spacer are used, adverse events that defeat the purpose of the surgery, such as dislocation, occur.

3 Objectives We have traditionary performed open-door laminoplasty. However, this surgical method requires significant stripping of the posterior cervical muscles as a preparatory step to create bilateral gutters. We have recently switched to laminectomy, which allows for the preservation of the cervical spine construction. Especially, the preservation of the longitudinal continuity of nuchal ligaments and facets joints capsule. In this presentation, the surgical method of myoarchitectonic laminectomy and its short- to mid-term outcomes are presented. The mid-term outcome of open-door laminoplasty are also reported for comparison. Furthermore, the invasiveness to the deep cervical muscles is evaluated in both surgical methods.

4 Surgical procedure trapezius splenius semispinalis capitis semispinalis cervicis multifidus 1The attachment of the nuchal ligament on the symptom-dominant side of the posterior cervical muscles are dissected in order to preserve the longitudinal continuity of the nuchal ligament. 2Spinous processes of the target decompression area are transected and the posterior cervical muscles on the contralateral side are stripped just beyond the base of the spinous process. 3Laminectomy of about 20 mm in width are performed, with deviation to the side of dominant symptoms.

5 Representative images of a patient who underwent myoarchitectonic laminectomy (entry side is left) Preoperative MRI Postoperative MRI Postoperative CT Postoperative dynamic X-ray

6 Methods 1 Patients with cervical myelopathy caused by degenerative cervical spine diseases were examined, excluding those with OPLL or severe instability. Open-door laminoplasty was performed on 60 patients between January 2005 and August Of these, 43 (33 men, 10 women; mean age, 63.1±11.4 years) were enrolled in this study. Details of the underlying diseases were as follows: spondylosis, 27; canal stenosis, 12; and discopathy, 4. Myoarchitectonic laminectomy was performed for 43 patients between November 2010 and November 2013, with follow-up data available for 34 (23 men, 11 women; mean age, 72.2±10.4 years). Details of the underling diseases were: spondylosis, 16 cases; canal stenosis, 17; and discopathy, 1.

7 Methods 2 The mean ratio of the width between the outermost edges of laminectomy (Fig.1) or bilateral gutters (Fig.2) to the width between the outer edges of bilateral lateral masses at the decompressed lamina was named as the decompression ratio, and it was measured on CT immediately after the operation. The decompression ratio was calculated using the following formula: a/b 100 (%). C7 was excluded from the calculation due to the complexity of its shape. a b Fig.1 b/a 100 (%) a b Fig.2

8 Methods 3 The preoperative and postoperative total volumes of the posterior deep cervical muscles were measured quantatively (cm 2 ) with axial plane at the level of C4 using CT or MRI. The patients who brought printed film-images from another hospital were excluded, because we did not reexamine preoperative images in our hospital and it was difficult to calculate muscle-volume digitally. Under this condition, the measurements were possible for 31 cases of myoarchitectonic laminectomy group (MLG) and 25 cases of open-door laminoplasty group (OLG). The calculation of total volume of muscles: (cm 2 ) Preoperative measurements on MRI or CT Postoperative measurements on MRI or CT

9 Results Myoarchitectonic laminectomy Open-door laminoplasty No. of cases Sex 23 men, 11 women 33 men, 10 women Age (years) 72.2± ± Preop. JOA score 11.0± ± Postop. JOA score 13.8± ± Postop. follow-up period (days) Postop. neurological deterioration Recovery rate of the JOA score (%) Decompression ratio (%) 271.4± ±461.5 <0.001 none Preop.= preoperative; Postop.= postoperative. All data are shown as means±standard deviations. P value less than 0.05 was considered significant. nonee 52.1± ± ± ±4.5 <0.001 SPSS ver. 20, Mann-Whitney U test P

10 The postoperative muscle atrophy in the posterior cervical muscles (%) p=0.014 The rate of muscle atrophy 9.6 p= Open-side in OLG Entry-side in MLG Hinge-side in OLG Contralateral side in MLG OLG= open-door laminoplasty group; MLG= myoarchitectonic laminectomy group. P value less than 0.05 was considered significant. SPSS ver. 20, Mann-Whitney U test

11 Conclusions At the current stage The short- and mid-term outcomes of myoarchitectonic laminectomy The mid-term outcomes of open-door laminoplasty However, myoarchitectonic laminectomy clearly revealed reduced atrophy of the posterior cervical muscles compared with open-door laminoplasty. This laminectomy, which enables almost complete preservation of the nuchal ligament, and contralateral posterior cervical muscles and facets from the entry side, may be preferable, causing less damage in patients with cervical myelopathy due to degenerative cervical spine diseases.

12 Thank you for your attention None of the authors has any potential conflict of interest