Risk factors for an adverse event included diagnosis of a myeloproliferative disorder,,obe sity,or diss intravasc ular coagulation.In genera .howe ver.when comp cations do occur they tend to be minor,mainly consisting of bleeding at the biopsy/aspiration site or infection (table 3). Bleeding Hemorrhage from bone marrow aspiration can occur at any site is more likely in the individual with thrombocytopenia and/or abnormal platele function,and is associated most commonly with the myeloproliferative disorders 147-501 Of interest the risk of hemorrhage has not been found to be associated with operato ce48. In most cases,bleeding is controlled by manual application of pressure to the site.Pressure dressings should be applied to the site following the procedure may have to be given if the patientis severely thrombocytopenic,or if platelet function is compromised. There have been rare reports of retroperitoneal hemorrhage[14.51.521 gluteal artery laceration or pseudoaneurysm with gluteal compartment syndrome [48,53],and internal iliac artery pseudoaneurysm [52].These are presumed due to penetration of the needle through the inner cortex of the iliac bone.In a cT-based cadaver study.these complications.as well as penetration of the t,appeared less likely to occur wh n the needle inserted into the posterior superior iliac spine was pointed in the direction of the ipsilateral anterior superior iliac spine,rather than when it was pointed in a perpendicular direction [40].(See 'Posterior iliac crest'above.) Infection-Infections are usually minor,requiring only topical medications More serious infections may occur in immunocompromised patients.There is a potential risk of contracting infections from a patient,and some recommend double-gloving.However,universal precautions should be applied in all nd the operator should always take care to avoid dle e penetration Tumorseeding -There have been rare case reports of tumor seeding from the bone marow into theneedle track (eg.into muscle.sub taneous tissue skin)following bone marrow biopsy,in patients with small cell lung carcinoma, multiple myeloma,and lymphoma [54-56]. Needle breakage- -Rarely,a bone marrow needle may break.If this occurs an attempt to extract the distal segment with a hemostat should be made.If this maneuver is unsuccessful,a surgeon should be consulted. Local radiologic changes- -There may be abnormal radiologic studies of the pelvis post-biopsy,including lytic lesions surrounded by a sclerotic border Risk factors for an adverse event included diagnosis of a myeloproliferative disorder, treatment with aspirin or warfarin, obesity, or disseminated intravascular coagulation. In general, however, when complications do occur, they tend to be minor, mainly consisting of bleeding at the biopsy/aspiration site or infection (table 3). Bleeding — Hemorrhage from bone marrow aspiration can occur at any site, is more likely in the individual with thrombocytopenia and/or abnormal platelet function, and is associated most commonly with the myeloproliferative disorders [47-50]. Of interest, the risk of hemorrhage has not been found to be associated with operator experience [48]. In most cases, bleeding is controlled by manual application of pressure to the site. Pressure dressings should be applied to the site following the procedure in patients with thrombocytopenia. If bleeding continues, platelet transfusions may have to be given if the patient is severely thrombocytopenic, or if platelet function is compromised. There have been rare reports of retroperitoneal hemorrhage [14,51,52], gluteal artery laceration or pseudoaneurysm with gluteal compartment syndrome [48,53], and internal iliac artery pseudoaneurysm [52]. These are presumed due to penetration of the needle through the inner cortex of the iliac bone. In a CT-based cadaver study, these complications, as well as penetration of the sacroiliac joint, appeared less likely to occur when the needle inserted into the posterior superior iliac spine was pointed in the direction of the ipsilateral anterior superior iliac spine, rather than when it was pointed in a perpendicular direction [40]. (See 'Posterior iliac crest' above.) Infection — Infections are usually minor, requiring only topical medications. More serious infections may occur in immunocompromised patients. There is a potential risk of contracting infections from a patient, and some recommend double-gloving. However, universal precautions should be applied in all cases, and the operator should always take care to avoid needle penetration of the skin. Tumor seeding — There have been rare case reports of tumor seeding from the bone marrow into the needle track (eg, into muscle, subcutaneous tissue, skin) following bone marrow biopsy, in patients with small cell lung carcinoma, multiple myeloma, and lymphoma [54-56]. Needle breakage — Rarely, a bone marrow needle may break. If this occurs, an attempt to extract the distal segment with a hemostat should be made. If this maneuver is unsuccessful, a surgeon should be consulted. Local radiologic changes — There may be abnormal radiologic studies of the pelvis post-biopsy, including lytic lesions surrounded by a sclerotic border