J Korean Neurosurg Soc.  2012 Jul;52(1):27-31. 10.3340/jkns.2012.52.1.27.

Midline-Splitting Open Door Laminoplasty Using Hydroxyapatite Spacers : Comparison between Two Different Shaped Spacers

• Park JH
• Jeon SR

• KMID: 2190519
• DOI: http://doi.org/10.3340/jkns.2012.52.1.27

Abstract

OBJECTIVE
Although hydroxyapatite (HA) spacer has been used for laminoplasty, there have been no reports on factors associated with fusion and on the effects of HA shape.
METHODS
During January 2004 and January 2010, 45 patients with compressive cervical myelopathy underwent midline-splitting open door laminoplasty with winged (33 cases) and wingless (12 cases) HAs by a single surgeon. Minimal and mean follow up times were 12 and 28.1 months, respectively. Japanese Orthopedic Association (JOA) score was used for clinical outcome measurement. Cervical X-rays were taken preoperatively, immediately post-operatively, and after 3, 6, and 12 months and computed tomography scans were performed preoperatively, immediately post-operatively and after 12 months. Cervical lordosis, canal dimension, fusion between lamina and HA, and affecting factors of fusion were analyzed.
RESULTS
All surgeries were performed on 142 levels, 99 in the winged and 43 in the wingless HA groups. JOA scores of the winged group changed from 10.4+/-2.94 to 13.3+/-2.35 and scores of the wingless group changed from 10.8+/-2.87 to 13.8+/-3.05. There was no significant difference on lordotic and canal dimensional change between two groups. Post-operative 12 month fusion rate between lamina and HA was significantly lower in the winged group (18.2 vs. 48.8% p=0.001). Multivariate analysis showed that ossification of the posterior longitudinal ligament, male gender, and wingless type HA were significantly associated with fusion.
CONCLUSION
Clinical outcome was similar in patients receiving winged and wingless HA, but the wingless type was associated with a higher rate of fusion between HA and lamina at 12 months post-operatively.

Keyword

Cervcial myelopathy; Fusion rate; Hydroxyapatite; Laminoplasty; Midline splitting; Shape

MeSH Terms

Animals
Asian Continental Ancestry Group
Durapatite
Follow-Up Studies
Humans
Longitudinal Ligaments
Lordosis
Male
Multivariate Analysis
Orthopedics
Spinal Cord Diseases
Durapatite

Figure

• 

  Fig. 1 Types of HA. A : Winged type. B : Wingless type. HA : hydroxyapatite.

• 

  Fig. 2 A : Cervical lordosis, defined as the angle between C2 and C7 inferior end plates. B : Changes in cervical lordosis in the winged and wingless groups. Lordosis changed from 11.73 to 10.95 degrees in the winged type group and from 12.27 to 18.11 degrees in the wingless type group (p=0.135).

• 

  Fig. 3 A : Spinal canal dimension measurements. B : The spinal canal dimensions increased immediately post-operatively in both groups, from 190.76 to 291.46 in the winged group and from 189.25 to 290.60 in the winged group, but decreased to 276.77 and 276.93, respectively, after 12 months (p=0.970).

• 

  Fig. 4 A : AP distance, as measured on CT axial image. (Upper image) immediate post-operative AP distance; (lower image) AP distance after 12 months. B : The AP distance of the spinal canal increased immediately after surgery from 11.52 mm to 19.22 mm in the wingless group and from 11.59 mm to 18.18 mm in the winged type group. After 12 months, the AP distances were 18.67 mm and 17.93 mm in the wingless and winged groups, respectively (p=0.021). AP : anterior-posterior, CT : computed tomography.

• 

  Fig. 5 A : Immediate post-operative axial CT image in the winged type group showing good touch status. B : Post-operative 12 month axial CT in the same patient showing non-fusion and spinous process resorption. C : Immediate post-operative axial CT image in the wingless type group showing good touch status. D : Post-operative 12 month axial CT in the same patient showing fusion, but spinous process resorption. CT : computed tomography.

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