Table 4. Summary of pre- and postoperative JOA score in relation to the levels involved.

No. of levels	No. of patients	Mean follow-up (months)	Preop JOA score	Last postop JOA score	Mean increase in JOA score
1-level	133	102.4±26.5 (60–186)	10.7±1.8	14.5±2.2	3.8±1.3
C4	14	114.3±32.4 (72–186)	10.7±1.7	13.9±2.3	3.1±1.5
C5	85	101.3±26.0 (60–178)	10.6±1.9	14.4±2.4	3.7±1.3
C6	32	99.5±24.6 (60–153)	10.8±1.7	14.8±1.6	4.0±1.2
C7	2	112.5±36.1 (87–138)	10.0±1.4	14.5±0.7	4.5±0.7
2-level	12	99.1±19.8 (60–130)	10.8±2.1	14.8±1.4	3.9±1.1
C4–5	7	95.3±21.1 (60–126)	10.3±2.1	14.4±1.5	4.1±1.1
C5–6	5	104.4±18.7 (86–130)	11.6±2.1	15.2±1.1	3.6±1.1

No., number; JOA, the Japanese Orthopedic Association; Preop, preoperative; Postop, postoperative.