J Korean Soc Spine Surg.  2014 Dec;21(4):160-166. 10.4184/jkss.2014.21.4.160.

Change of Lumbar Isometric Extensor Strengths after Posterior Lumbar Interbody Fusion in Patients with Lumbar Degenerative Disease

• Seo YG
• Lee CS
• Kang KC
• Park WH

• KMID: 2097866
• DOI: http://doi.org/10.4184/jkss.2014.21.4.160

Abstract

STUDY DESIGN: Prospective cohort study.
OBJECTIVES
This study was undertaken to examine changes in lumbar isometric extensor strength after posterior lumbar interbody fusion (PLIF) surgery. SUMMARY OF LITERATURE REVIEW: In most reports, the patients that have undergone PLIF surgery have been shown to have muscle weakness and atrophy. However, the research conducted regarding the changes in muscle strength throughout a follow up period is insufficient.
MATERIALS AND METHODS
Forty-nine patients (mean age, 65 years (range, 45 to 77)), scheduled for posterior lumbar interbody fusion due to symptomatic degenerative diseases, were enrolled. Preoperatively and 3, 6, and 12 month after surgery, lumbar isometric extensor strength was assessed using a MedX instrument in 7 angular positions (0-72degrees). The mean isometric strength and rate of increase were calculated. Isometric strengths were compared according to patients' age (<60, 60-70, and > or =70 years) and fusion level (short: <3; and long: > or =3) and the respective relationships were analyzed.
RESULTS
The mean isometric strength changed from 89.0 preoperatively to 85.3, 110.4, and 120.8 ft-lb at each follow-up, respectively. The rate of increase of strength was significantly greater at 0degrees(36.1 %) than at 72degrees(24.2 %) (p=0.019). Preoperative isometric strengths were similar in each age and fusion level group, but isometric strengths at the final follow-up were significantly lower in older patients and in the long level fusion group (p=0.002 and 0.043, respectively). Mean isometric strength at the last follow-up showed significant associations with age and fusion level (r=-0.431 and -0.317, p=0.002 and 0.030, respectively).
CONCLUSION
After lumbar fusion surgery, back muscle strength slightly decreased until 3 months and then significantly increased. However, postoperative strength increases were lower in older patients and those in the long level (>3) fusion group. These results could be basic data for a rehabilitation program after lumbar fusion.

Keyword

Lumbar degenerative disease; Posterior lumbar interbody fusion; Lumbar isometric extensor strength

MeSH Terms

Atrophy
Back Muscles
Cohort Studies
Follow-Up Studies
Humans
Muscle Strength
Muscle Weakness
Prospective Studies
Rehabilitation

Figure

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  Fig. 1. Restraining mechanism of the Medx lumbar extension machine.

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  Fig. 2. After lumbar fusion surgery, the isometric strengths were maintained or slightly decreased without significance until 3 months and then increased until 12 months. In particular, significant increases were obseved between at postoperative 3 and 6 months* (p<0.001). The isometric strengths were stronger in higer flexion angular positions.

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  Fig. 3. After lumbar fusion surgery, the mean isometric extension strength increased significantly and the mean ratio of 72°/0° isometric strength decreased significantly, particularly between postoperative 3 and 6 months* (p<0.001 and 0.007, respectively). The mean isometric strength showed a significant negative association with the ratio of 72°/0° isometric strength (r=-0.371, p<0.001).

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  Fig. 4. In comparisons of the mean isometric strength according to patients’ age and fusion level groups, preoperative isometric strengths were not significantly different, but the increases of isometric strengths were lower in older patients and long level fusion group (*p<0.05).

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  Fig. 5. After lumbar fusion sugery, the ODI and VAS for back decreased gradually until postoperative 12 months and significant decreases were obseved between preoperative and at postoperative 3 months* (p=0.045 and 0.022, respectively).

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