Effects of Botulinum Toxin Type a Injection into Vastus Lateralis in Patients with Patellar Lateral Subluxation

Patellofemoral pain syndrome (PFPS) often occurs in athletes and young women. One of the major factors resulting in PFPS is patellar lateral subluxation (PLS), which is mainly caused by abnormal bony structure and muscle imbalance of lower extremity. The femur with flattened trochlear groove, forward tilting or pronation are the possible abnormal bony structure issues. The muscular issue is caused by the muscle tone imbalance between vastus medialis obliquus (VMO) and vastus lateralis (VL). If the patients do not receive proper treatment, the symptoms will result in patellofemoral arthritis and affect the patient’s ADL. In addition to oral none-steroid anti-inflammatory drug , conservative rehabilitative exercise and surgery are prescribed to treat the patients with PLS clinically. On the basis of biomechanical concept, these treatments attempt to reduce the lateral traction force of patella, and thus decrease the lateral sliding of patella. However, the outcome of therapeutic exercise was not satisfactory. Previous reports also suggested that the outcome of lateral patellar retinaculum release were not good as expected and usually accompanied complications. Botulinum Toxin type A (BTA) is widely used to treat the spasticity of muscular dystonia. If BTA can be used to alter the biomechanical mechanism of PLS, i.e. inhibit the muscle tone of VL and enhance the muscular activation of VMO by exercise training, the PLS will likely be improved. Therefore, the purpose of this study are: (1) to investigate the effects of BTA injection into VL in patients with PLS due to larger sulcus angle, larger Q angle, and VMO/VL imbalance respectively; (2) to investigate the effects of combining BTA injection into VL and closed-chain exercise in the patients with PLS due to VMO/VL imbalance. The first year of this project is a prospective case-control study. Fifteen patients with PLS will be recruited respectively in three subgroups, which are patients with larger sulcus angle, larger Q angle, and VMO/VL imbalance. Another 15 healthy patients will be recruited as control group. The second year of this project is a prospective, double-blind, randomized controlled trial. Thirty patients with PLS due to VMO/VL imbalance will be recruited and assigned into two groups randomly. In addition to closed-chain exercise, experimental group will receive BTA injection and control group will receive normal saline injection into VL. Subjects will be evaluated with a series of test (clinical questionnaire, Numeric rating scale for pain, Lequesne Index, WOMAC, X-ray image studies, isokinetic and surface electromyographic assessment ) before intervention and at 4, 8, 12 and 24 weeks after intervention. We expect that in patients with PLS due to VMO/VL imbalance, BTA injection will present extraordinary efficacy. And the effect will be further enhanced with the combination of closed-chain exercise. We hope the results of this study can provide another alternative in treating the patients with PLS.

Project ID:PC10301-0560
External Project ID:NSC102-2314-B182-011-MY2