Objectives To evaluate plain radiographs and computed tomography (CT) scans in respect of assessment of articular fragment displacements (step and gap) in displaced acetabular fractures. Methods A retrospective evaluation was done to analyze the CT scans and plain radiographs of 64 patients who had been treated for displaced acetabular fractures in our hospital from January 1998 to May 2003. Of them, 20 met the inclusion criteria. In a blind method, 3 independent reviewers measured step and gap deformities on plain radiographs and CT scans utilizing a standardized measurement technique. The sensitivity and specificity of plain radiographs in detecting step and gap displacements (2 mm and 4 mm) in comparison of those of CT scans were determined. Moreover, intraclass correlation coefficient and intraobserver reliability were also calculated. Results Compared with CT, plain radiographs showed poor sensitivity in detecting step deformity (sensitivity = 44.3%). As far as fracture type was concerned, plain radiographs were particularly poor at detecting step deformity in fractures involving a single column of the acetabulum (sensitivity = 0%). Excellent intraobserver and intraclass reliability existed among the 3 reviewers. Conclusions Compared with CT scans, plain radiographs are poorly sensitive in detection of step and gap deformities in patients with acetabular fractures, and particularly poor at detecting step deformities. Therefore, in treatment of displaced acetabular fractures, CT scans are essential and should not only be used together with plain radiographs in the preoperative evaluation but also be considered in the postoperative assessment of fracture reduction and predicting future outcomes.

BACKGROUND:Reducing blood loss could help to prevent the complications of total knee arthroplasty, relieve the swelling and discomfort postoperatively and accelerate the rehabilitation. OBJECTIVE:To explore the methods for reducing blood loss during total knee arthroplasty. METHODS:Totally 63 patients undergoing primary unilateral total knee arthroplasty were divided into two groups. Group 1 included 27 patients who received the conventional surgical techniques using tourniquet during the whole procedure with wound drainage, as control group. Group 2 included 36 patients who received the modified procedure only using tourniquet during prosthesis implantation without wound drainage, as experimental group. In the experimental group, we stitched the capsule closely. The preoperative and postoperative hemoglobin, decrease of hemoglobin, knee pain score, range of motion blood transfusion rate and wound healing were compared between the two groups. RESULTS AND CONCLUSION:(1) There was no significant difference in preoperative hemoglobin between the two groups. At 1, 4 and 7 days postoperatively, the hemoglobins were significantly lower in the control group than in the experimental group, and the decreases of hemoglobins were significantly lower in the control group than in the experimental group. (2) Knee pain score was not significantly different between the two groups. (3) The range of motion of the knee was significantly larger in the experimental group than in the control group at 7 days. (4) Blood transfusion rate was 18.5%in the control group, and wound healing was poor in one patient. There was no transfused case and wound problem in the experimental group. All wounds were healed normally. (5) There was no infection or hematoma in two groups. (6) With the modified procedure, we could reduce blood loss during total knee arthroplasty without blood transfusion after surgery, which was helpful to postoperative rehabilitation.

OBJECTIVE: To construct a three-dimensional (3D) finite element mechanical model of total hip arthroplasty for comparison of biomechanical differences of the hip joint following capsule repair and postoperative rehabilitation. METHODS: Six frozen specimens of hip joint posterior capsule ligament complex were collected in a bone-capsule-bone manner, and the load-strain curve and other mechanical properties of the specimens were tested using a universal material testing machine. Thin-section CT data of the pelvis and lower limbs obtained from a volunteer were imported into Mimics software to construct a 3D model of the hip joint. Digital models of the cup, femoral prosthesis and joint capsule were created in CATIA software and imported into Mimics to simulate total hip arthroplasty; the assembled data were imported into ABAQUS software. The properties of the capsule were set according to results of the mechanical test, anatomical studies, and constitutive equations, and the biomechanics of the anatomically repaired and conventionally repaired capsules were compared during hip flexion. RESULTS: The results of testing on the 6 capsule specimens showed a mean ultimate tensile strain of (39.21±5.23)% and a mean of ultimate tensile strength of 1.65±0.38 MPa. The stress-strain curve of the finite element model was consistent with the results of mechanical test on the specimens and the biochemical characteristics of the capsule. The stress was distributed evenly in the anatomically repaired capsule during hip flexion but not in the capsule repaired through the conventional approach; the tensile stress in the lower part of the conventionally repaired capsule reached the ultimate tensile stress measured on the capsule specimens at a 90° flexion. CONCLUSIONS The finite element model allows dynamic, quantitative and visual assessment of stress distribution in the hip joint capsule, and compared with the conventional approach, anatomical repair can achieve better biomechanical properties of the capsule.
Arthroplasty, Replacement, Hip ; Biomechanical Phenomena ; Finite Element Analysis ; Hip Joint/surgery* ; Humans ; Prognosis ; Stress, Mechanical