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[Computer tomography in the diagnosis and therapy of acetabular fractures].

INTRODUCTION
Acetabular fractures and fracture dislocations of the hip joint are frequently complex, and the precise pathological anatomy is not easily demonstrated by routine radiographs. Conventional radiographs are often supplemented by oblique views [1]. The most commonly used classification of acetabular fractures has been based on conventional radiographs which are, in majority of cases, sufficient to determine the type of acetabular injuries [1-3]. It has been shown that computed tomography is useful method in precise evaluation of the fracture type the soft-tissue damage and integrity of joint space [4-6].


AIM
The aim of the study was to evaluate advantages of computed tomography in diagnosis of complex acetabular fractures.


METHODS
We studied 737 patients with acetabular injuries over the period from 1989 to 1998. Five hundred and seventy five (78%) were males and 162 (22%) females. Eighty patients with acetabular fractures, with and with out hip dislocation, underwent pelvic CT following AP and 45 degrees oblique pelvic radiographs. Each patient was studied while supine, using 5 mm slice thickness at the acetabulum level and 10 mm at other parts of pelvis. Sections were obtained from the iliac crest to the greater trochanter [7].


RESULTS
The causes of acetabular fractures were: 621 (84.3%) patients participated in traffic accidents, 103 (14%) fell from a height, 7 (0.9%) covered in a mine and 6 (0.8%) were wounded. Femur was the most frequently associated injuries of all bones--155 (66.5%) (Graph 1). Permanent growth of acetabular fractures was noted from 1989 to 1993 regarding gender and years (Table 1), but that growth declined in 1993. It can be explained by a lower number of traffic accidents. Traffic, as an aetiological factor is nearly related with economic and energy crisis in our country (Graph 2). There were 176 (23.8%) fractures of the posterior wall, 23 (3.1%) fractures of the posterior column, 14 (1.9%) fractures of the anterior wall, 29 (3.9%) fractures of the anterior column. Transverse fractures were present in 61 patients (8.3%), "T" fractures in 51 (6.9%) patients and 383 (52.1%) were combined fractures. Of 80 patients loose bodies within the hip joint were noted on the CT scan in 77 (96%) patients, and only in 19 (24%) on radiographs. There was a statistically strong difference between methods (chi 2 = 12.376; p < 0.01). There was no significant difference between two methods in fracture of the femoral head detecting (chi 2 = 1.905; p > 0.05), but it has to bee noted that only two patients had fracture of the anterior aspect of the femoral head, both noted on CT but not on radiographs. In 78 (98%) versus 53 (66%) patients chondral defect of acetabulum was detected on radiografs. Difference was significant (chi 2 = 4.372; p < 0.05). Also, stability of the hip joint regarding size and location of the posterior wall fragment was better seen on CT than on radiographs (chi 2 = 5.555; p < 0.05).


DISCUSSION
Our series demonstrates that in many cases details of acetabular fractures are not well visible on conventional radiographs. Because of the complexity of acetabular fractures, precise pathological anatomy is not easily demonstrated by routine radiographs. In a series of Pearson and Shirkhoda et al. [12,13], one third of acetabular fracture was not apparent on the initial radiographs; however, additional views taken three months later demonstrated a fracture. Mossed fractures should decrease with using the CT, which can also reveal the loose bodies in the joint space, occult femoral haed and chondral acetabular impaction. The size of the posterior wall fracture, and thus the stability of the hip, could be better determined by the CT scan than by a conventional radiograph. In conclusion, the information obtained from CT can help the surgeon to decide whether the surgery is necessary, and, if so, the proper approach. We believe that CT is a very helpful supplement to routine AP and 45 degrees oblique views when surgery of acetabular fractures is in question.