BACKGROUND Sarcopenia refers to a chronic loss of skeletal muscle mass, often associated with hypovitaminosis D and advanced age, which involves a greater risk of falls and fractures. The association of sarcopenia and osteoporosis defines osteo-sarcopenia. In this work, the authors analyzed the osteometabolic profile and the loco-regional muscular state of patients undergoing major orthopedic surgery, in order to define the incidence of district osteosarcopenic states, linked to a condition of disuse. METHODS 19 patients (10M-9F), between 15 and 85 years old, underwent major orthopedic surgery (15 resection prosthesis and custom made, 2 resection and reconstruction with transplant) were evaluated, of which 9 on an oncological basis. In all patients, the phospho-calcium metabolism was assessed by blood tests and intraoperative muscle biopsy was performed at the intervention site and contralaterally; in 3 cases a densitometric comparative study of the affected/contralateral limb was performed. RESULTS Results shows 5 patients with hypovitaminosis D; 7 pcs with hypocalcemia; 5 with PTH rise; 4pcs with ALP increase. In 100% of cases, the biopsy revealed sarcopenic patterns exclusively on the affected limb. 2 out of 3 DEXAs (66%) showed loco-regional osteoporosis compared to the contralateral. CONCLUSIONS The fact that in our sample sarcopenia is unilateral affecting only the pathological limb, that it is frequently associated with osteoporosis which is also unilateral and that for the most part it is not associated with vitamin D deficiency, suggests that it is an independent condition, with etiopathogenetic mechanisms different from osteosarcopenia itself. In major orthopedic surgery, bone integration and muscle status are both essential for achieving and lasting positive results. Considering the high incidence of district osteosarcopenia, an integrated surgical, pharmacological, and rehabilitative approach is desirable for the optimization of results, as well as more studies for the definition of the etiopathogenesis of this pathological condition.