Your concern is very valid. Untreated limb length discrepancy can result in abnormal curvature of the spine. This may lead to chronic backache beyond 50 years. However, severe scoliosis usually results when the limb lengths are markedly different. All degrees of discrepancy need not be corrected. The criteria that has followed for correction is as follows:
1. Upto 2 cm of difference, the body compensates without any adverse affect.
2. From 2 to 4 cm difference, the patient can be given a shoe raise. The shoe raise need not be like a heel if you go to a good shoe fitter the shoe raise can be inside the shoe without any obvious evidence of its presence. You need not even compensate the full extent. You could compensate half or 2/3 of difference.
3. If limb length difference is more than 4 cm, then compensation may not be adequate with shoe raise and if the patient is keen he can have limb lengthening.
In your case, with a difference of only 4 cm I would recommend that you could manage comfortably with a 2 cm shoe raise. This should not cause any increase in your deformity in the spine.