Can Idiopathic Scoliosis Fusion Improve Aerobic Efficiency During Exercise?

Washington University School of Medicine, Dept of Orthopaedic Surgery
Barnes-Jewish Hospital, Pulmonary Function Lab
Barnes-Jewish Hospital, Human Performance Laboratory
St. Louis University Hospital; St. Louis, MO, USA

INTRODUCTION:
For reasons that are unclear, untreated adolescent idiopathic scoliosis (AIS) patients approach their ventilatory ceiling during maximal aerobic exercise despite only small restrictions in forced vital capacity (FVC) and forced expiratory volume in one second (FEV₁). This inefficiency of ventilation with exercise may explain the reluctance of AIS patients to pursue aerobic fitness.

PURPOSE:
To prospectively evaluate pulmonary function, maximal O₂ consumption and ventilatory efficiency during exercise in AIS patients preop and a minimum 2 years postop, to see if aerobic inefficiency can be improved following surgery.

METHODS:
42 AIS patients were prospectively evaluated preop and a minimum of 2 years following spinal fusion. There were 36 females and 6 males with an average age of 14+3 (range 10+7 through 17+11). 17 underwent PSF alone, 20 an ASF alone, 5 both an ASF and PSF. All patients had standard spirometry for evaluation of FVC and total lung capacity (TLC), as well as cycle ergometry to assess aerobic capacities via maximal oxygen consumption (VO₂max), and aerobic efficiency at VO₂max (V_E/MVV). Preop and postop results were compared by paired T-tests.

RESULTS:

There was a statistical decline in FVC, without any change in TLC. The RV/TLC ratio suggests air trapping in the spirometry results. Although the absolute value of VO₂max was unchanged, the % Predicted VO₂max statistically declined following surgery. In addition, aerobic efficiency as measured by efficiency of ventilation (V_E/MVV) declined at 2 years postop. Evaluation using an Oxygen uptake efficiency slope (OUES) which reflects ventilatory efficiency with exercise independent of effort, demonstrated that these aerobic inefficiencies could not be accounted for solely based on poor patient effort.

CONCLUSIONS:
Although there was no difference in absolute maximum oxygen consumption during exercise, aerobic efficiency of ventilation during exercise statistically declined following AIS fusion surgery. Measures should be investigated to improve aerobic fitness in postop AIS patients long-term.