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Evaluation of Ventilatory Efficiency During Exercise in Patients With Idiopathic Scoliosis Undergoing Spinal Fusion

Lenke, Lawrence G., MD*; White, Deborah K., RPFT; Kemp, James S., MD; Bridwell, Keith H., MD*; Blanke, Kathy M., RN*; Engsberg, Jack R., PhD§

Exercise Physiology & Functional Outcomes
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Study Design. A prospective evaluation of ventilatory function following spinal fusion in adolescent idiopathic scoliosis.

Objectives. To prospectively evaluate pulmonary function, maximal oxygen uptake, and ventilatory efficiency during exercise in patients with adolescent idiopathic scoliosis before surgery and a minimum of 2 years postoperation.

Summary of Background Data. For reasons that are unclear, patients with untreated adolescent idiopathic scoliosis tend to avoid aerobic exercise. Their reluctance may be the result of low ventilatory efficiency, as they often approach their ventilatory ceiling at maximum oxygen uptake despite forced vital capacities that are near normal. This inefficiency of ventilation with exercise may explain the reluctance of patients with scoliosis to pursue aerobic fitness. No study has evaluated the effect spinal fusion has on the ventilatory function of patients with scoliosis during exercise.

Methods. Forty-two patients with adolescent idiopathic scoliosis (36 female and 6 male) at an average age of 14 ± 3 years (range 10–18 years) underwent spinal fusion. Twenty patients underwent a posterior spinal fusion alone, 20 an anterior spinal fusion alone, and 2 an anterior spinal fusion and posterior spinal fusion. The average Cobb measurement was 55° (range 40–85°). Pulmonary function values (forced vital capacity, total lung capacity, maximum voluntary ventilation), maximum oxygen uptake (VO2max), and ventilatory efficiency were obtained before surgery and a minimum of 2 years postoperation.

Results. For all patients, forced vital capacity percent predicted decreased from 88.1% to 81.4% (P < 0.0001). Total lung capacity also declined from 90.5% to 88.5% but was not statistically significant (P = 0.189). Percent predicted maximum oxygen uptake (VO2max) declined from 93.6% to 85.1% (P = 0.00029). Ventilatory efficiency, as measured by VEmax/maximum voluntary ventilation, improved from 0.76 to 0.68 (P = 0.005), whereas measured by VEmax/FEV1 × 40 was unchanged from 0.69 to 0.70 (P = 0.172) postoperation. The choice of operative approach [anterior (n = 20) versus posterior (n = 20)] or whether rib graft was harvested (n = 33) versus iliac crest graft (n = 7) did not change these results.

Conclusion. Improvement in ventilatory efficiency during exercise does not occur in the majority of patients with adolescent idiopathic scoliosis following spinal fusion and thus cannot be relied on to foster increases in aerobic activity.

From the *Department of Orthopaedic Surgery, Washington University School of Medicine, the

†St. Louis Children’s Hospital Pulmonary Function Lab, the

‡Department of Pediatric Pulmonary Medicine, St. Louis University, and

§Barnes-Jewish Hospital, Human Performance Laboratory, St. Louis, Missouri.

Presented at the Scoliosis Research Society, 36th Annual Meeting (Paper 70), Cleveland, Ohio, September 2001.

Acknowledgment date: October 2, 2001.

First revision date: January 29, 2002.

Acceptance date: March 4, 2002.

Address reprint requests to

Lawrence G. Lenke, MD

Department of Orthopaedic Surgery

Washington University School of Medicine

One Barnes Jewish Hospital Plaza, Suite 11300

St. Louis, MO 63110

E-mail:lenkel@msnotes.wustl.edu

The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.

No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

© 2002 Lippincott Williams & Wilkins, Inc.