Original Research

The Effect of Age on the Benefits of Early Decompression for Cervical Spondylotic Myelopathy

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MATERIALS AND METHODS

Institutional Review Board approval was obtained for this study. Informed consent was waived due to the retrospective nature of the work. The medical records of 212 patients who underwent surgery for CSM by the senior author were reviewed. All surgeries were performed at the University Hospital or the Veterans Administration (VA) between March 2005 and July 2012. CSM was diagnosed by magnetic resonance imaging (MRI) and based on the presence of upper motor signs, clonus, gait abnormalities, or difficulty with fine motor movements such as buttoning a shirt. Nurick score (Table 1) was assessed at presentation and at follow-up, and was the only outcome measure recorded in this cohort. Inclusion criteria were the diagnosis of CSM with a Nurick score, surgical intervention, and at least 2 years of follow-up. Age at presentation, sex, preoperative Nurick score, postoperative Nurick score, duration of symptoms preoperatively, duration of follow-up, procedure performed, approach (anterior vs posterior vs anterior and posterior), prior surgery, number of levels fused, diabetes status, cocaine use, ethanol use, tobacco use, signal change on preoperative MRI, and whether the patient belonged to the VA were recorded. Posterior cervical surgery was performed in patients who had ossification of the posterior longitudinal ligament, had multiple prior anterior cervical procedures, or had involvement of 3 or more levels with anatomy that would make an extensive exposure difficult. Surgeries were performed anteriorly for cases of 1- or 2-level stenosis in the absence of ossification of the posterior longitudinal ligament.

Anterior surgery was also considered in patients with 3-level disease who did not have anatomy that precluded a more extensive exposure.

Patients were stratified according to duration of symptoms by cutoffs of 12 or 24 months and according to age <65 years or >65 years. The age cutoff was chosen because this was the youngest cohort in which stratification revealed a significant difference in change in the Nurick score according to duration of symptoms, and because this age is consistent with the literature. Data were blinded, and outcomes according to duration of symptoms and age were analyzed. The analysis was conducted using simple linear regression and multiple regression.

SURGICAL TECHNIQUE

Patients were evaluated through a complete neurological examination and Nurick scores preoperatively and postoperatively at 6 weeks, 3 months, 6 months, 1 year, and annually thereafter. Decompression procedures performed included single or multilevel corpectomy, anterior decompression with strut grafting and instrumentation, posterior cervical laminoplasty, and posterior cervical laminectomy and fusion. Patients were placed in a Miami J collar (Össur) postoperatively and sent to physical and occupational therapy when able. All procedures were performed by the senior author with the assistance of residents and fellows.

RESULTS

Of the 125 patients who met all the inclusion criteria, 44 were females and 81 were males. The average follow-up duration was 30.9 months (standard deviation [SD], 13.23). The average age of all patients was 55.2 years (range, 27-89 years), and there was no difference in age according to gender (55.0 years for females vs 55.2 years for males). The average preoperative Nurick score was 2.61 (SD, 1.16), and there was no difference in preoperative Nurick score according to cutoff of duration of symptoms. Males had a higher preoperative Nurick score than females (2.73 vs 2.41, P = .12) and a longer but statistically nonsignificant duration of symptoms (25.7 vs 16.9 months, P = .1). There were 97 patients aged ≤65 years (average, 49.6 years) and 28 patients aged >65 years (average, 73.7 years). The younger cohort had a lower preoperative Nurick score than the older cohort, but this difference was not statistically significant (2.52 vs 3.0, P = .06). The younger cohort also had a longer duration of symptoms, but this difference was not significant (21.8 vs 26.2 months, P > .1). The initial analysis of the change in Nurick score in all patients according to duration of symptoms revealed an average change of 1.36 points (SD, 1.13) and a difference in postoperative change in Nurick score for the duration of symptom cutoffs of 12 and 24 months. This pattern was also present when patients were stratified according to age (Tables 2 and 3). The most common procedures performed were anterior cervical discectomy and fusion (ACDF) (58) and corpectomy (49). Data according to the procedure performed are recorded in Table 4. No significant complications were recorded. Simple regression and multiple regression analyses were undertaken to further evaluate these relationships.

Table 1. Nurick Score

0

Signs or symptoms of nerve root involvement by no signs or symptoms of spinal cord involvement

1

Signs of spinal cord compression but no gait abnormalities

2

Gait abnormalities but no interference on employment

3

Gait abnormalities that prevent full time employment

4

Unable to walk without assistance

5

Wheelchair bound or bedbound

Table 2. Change in Nurick According to Threshold of Duration of Symptoms

<12 months

>12 months

<24 months

>24 months

Total

Number

58

67

85

40

125

Preoperative (SD)

2.54 (1.22)

2.70 (1.11)

2.56 (1.19)

2.75 (1.09)

2.61 (1.16)

Change (SD)

1.59 (1.12)

1.17 (1.11)

1.54 (1.21)

0.98 (0.87)

1.36 (1.13)

Abbreviation: SD, standard deviation.

Table 3. Change in Nurick According to Threshold of Duration of Symptoms, by Age

Age <65 Years

Age >65 Years

Months

<12

>12

<24

>24

<12

>12

<24

>24

Number

49

48

69

28

9

19

16

12

Preoperative (SD)

2.53 (1.17)

2.5 (1.11)

2.49 (1.17)

2.57 (1.07)

2.56 (1.51)

3.2 (1.03)

2.88 (1.31)

3.16 (1.11)

Change (SD)

1.61 (1.15)

1.04 (1.11)

1.51 (1.22)

0.89 (0.88)

1.44 (1.01)

1.53 (1.12)

1.69 (1.2)

1.25 (0.87)

Abbreviation: SD, standard deviation.

kusin0918_t1

Abbreviations: ACDF, anterior cervical discectomy and fusion; SD, standard deviation.

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