a 61-year male presented to the emergency department with a history of road traffic accident . he arrived hemodynamically stable with a blood pressure of 126/76 mmhg and a heart rate of 78 beats per minute . on plain radiograph ( fig . 1a ) anteroposterior and two judet 45 oblique view1 ) and computed tomography ( ct ) scan of pelvis ( fig . 1b ) , the findings revealed both column fracture of acetabulum without hip dislocation , but no presence of femoral head fracture or onfh . buttress plating through ilioinguinal approach was performed using a reconstruction plate , which was supplemented by a compact hand plate . the patient was transfused 8 units of whole blood , 3 units of fresh frozen plasma and 8 units of packed red blood cells . intra - operative hb was 9.7 gm% ; the average mean arterial pressure was 91.82 mmhg during the operative procedure . post - operatively the patient was transfused 2 units of whole blood and 1 unit of fresh frozen plasma . the hb postoperatively was 10.3 gm% , the patient was shifted to intensive care unit for a day , later was transferred to the ward . the post - operative x - ray ( fig . 2a ) and ct scan revealed an acceptable reduction of the fracture fragments and a concentric hip . sitting up was performed on the first postoperative day ; the patient subsequently began formal physical therapy and active range of motion exercises . partial toe touch weight bearing ( 20 to 30 lb ; 9 to 13.6 kg ) with a walker was maintained for 6 - 8 weeks . progression to full weight bearing was started on the basis of the follow - up radiographs . the patient 's 4-month postoperative x - ray revealed a radiolucent lesion in the superolateral part of femoral head , crescent sign , and sclerosis . 2b ) showed collapse and sclerosis , findings consistent with onfh . a ct scan ( fig . on was diagnosed only when the radiographic findings provided a clear differentiation from wear of the femoral head2 ) . the joint pain increased due to the onfh , we performed a total hip replacement ( fig . 3b ) 12 months after the index surgery . late complications of acetabulum fractures include heterotopic ossification and onfh , which are present in less than 10% of the population3 ) . the incidence of onfh is known to be high in transverse and posterior wall fractures associated with posterior dislocation6 ) . on also occurs in conjunction with approximately 3% of anterior hip dislocations and in more than 13% of posterior hip dislocations . in a recent meta analysis of 3,670 surgically treated displaced acetabular fractures the incidence of onfh showed an overall incidence of 5.6%3 ) , suggesting that it is grossly overestimated and that most of the observed changes in the head of the femur are probably due to osteoarthritis5 ) . onfh is caused by inadequate blood supply to the affected segment of the subchondral bone . when posterior surgical approaches have been used , on rates as high as 42% within the first year after surgery have been reported7 ) . many systemic conditions are associated with on , but 25% of all cases are described as idiopathic and can contributes as a cause9 ) . trauma is one of the most common causes of on , interruption of the blood supply to the affected segment of the bone being the cause of ischemia . in this case the exact cause of onfh eludes us , especially in the absence of any patient related predisposing risk factors , except presence of fracture without hip dislocation and subsequent intervention by an ilio - inguinal approach . a probable theory of etiology could be the intra - operative hypovolaemia , low mean arterial pressure , causing compromised flow to the femoral head being so as to act as the final blow . alteration of the blood supply to vital organs during hypovolaemia is well established . with mean arterial pressure usually in the range of 50 to 60 mmhg , the flow to the femoral head is potentially compromised10 ) so as to act in an accumulative stress theory , as suggested by kenzora and glimcher9 ) . it is questionable as to whether this alone would be enough to explain the development of on .
osteonecrosis in isolated fractures of the acetabulum without dislocation of hip seems to be a known complication , but to our knowledge it has not been reported adequately . 
 the causative nature of post - traumatic femoral head osteonecrosis has not been studied critically . 
 the pathophysiology of osteonecrosis in this case also eludes us . striking evidence points towards the intra - operative blood loss and low mean arterial pressure possibly leading to hypo - perfusion of femoral head leading to osteonecrosis . 
 fractures of the acetabulum pose a difficult problem for the patient and the surgeon because of possible complications . 
 thus any surgeon involved in surgery for fractures of the acetabulum should be aware of the possibility of this potential complication . here 
 is a 61-year male , who sustained a complex fracture of the acetabulum without hip dislocation , subsequently was treated surgically with internal fixation using an anterior approach , 10 months after surgery patient developed osteonecrosis of the femoral head .