Two or more batches of rats are castrated and given no treatment and respectively some AAS of interest. The LA/VP ratio for an AAS is calculated as the ratio of LA/VP weight gains produced by the treatment with that compound using castrated but untreated rats as baseline: (LAc,t–LAc)/(VPc,t–VPc). The LA/VP weight gain ratio from rat experiments is not unitary for testosterone (typically 0.3–0.4), but it is normalized for presentation purposes, and used as basis of comparison for other AAS, which have their androgenic:anabolic ratios scaled accordingly (as shown in the table above). In the early 2000s, this procedure was standardized and generalized throughout OECD in what is now known as the Hershberger assay. Body composition and strength improvements
Body weight in men may increase by 2 to 5 kg as a result of short-term (<10 weeks) AAS use, which may be attributed mainly to an increase of lean mass. Animal studies also found that fat mass was reduced, but most studies in humans failed to elucidate significant fat mass decrements. The effects on lean body mass have been shown to be dose-dependent. Both muscle hypertrophy and the formation of new muscle fibers have been observed. The hydration of lean mass remains unaffected by AAS use, although small increments of blood volume cannot be ruled out.The upper region of the body (thorax, neck, shoulders, and upper arm) seems to be more susceptible for AAS than other body regions because of predominance of ARs in the upper body.
Treatment
It is sometimes possible to correct the problem with surgery, though this has high failure rates for treatment of post-traumatic radioulnar synostosis. Indication for the surgical treatment of congenital radioulnar synostosis include severe disability due to bilateral disorder or hyperpronation ≥90 [1]

References
External links
Radioulnar synostosis at eMedicine