Influence of transcutaneous electrical stimulation on heterotopic ossification: an experimental study in Wistar rats

Heterotopic ossification (HO) is a metaplastic biological process in which there isnewly formed bone in soft tissues, resulting in joint mobility deficit and pain.Different treatment modalities have been tried to prevent HO development, but thereis no consensus on a therapeutic approach. Since electrical stimulation is a widelyused resource in physiotherapy practice to stimulate joint mobility, with analgesicand anti-inflammatory effects, its usefulness for HO treatment was investigated. Weaimed to identify the influence of electrical stimulation on induced HO in Wistarrats. Thirty-six male rats (350-390 g) were used, and all animals were anesthetizedfor blood sampling before HO induction, to quantify the serum alkaline phosphatase.HO induction was performed by bone marrow implantation in both quadriceps of theanimals, which were then divided into 3 groups: control (CG), transcutaneouselectrical nerve stimulation (TENS) group (TG), and functional electrical stimulation(FES) group (FG) with 12 rats each. All animals were anesthetized and electricallystimulated twice per week, for 35 days from induction day. After this period, anotherblood sample was collected and quadriceps muscles were bilaterally removed forhistological and calcium analysis and the rats were killed. Calcium levels in musclesshowed significantly lower results when comparing TG and FG (P<0.001) and betweenTG and CG (P<0.001). Qualitative histological analyses confirmed 100% HO in FG andCG, while in TG the HO was detected in 54.5% of the animals. The effects of themuscle contractions caused by FES increased HO, while anti-inflammatory effects ofTENS reduced HO.