Soft tissue balance is important for good clinical outcome and good stability after TKA. Ligament balancer is one of the devices to measure the soft tissue balance. The objective of this study is to clarify the effect of the difference in the rotational position of the TKA balancer on medial and lateral soft tissue balance. This study included with 50 knees of the 43 patients (6 males, 37 females) who had undergone TKA with ADLER GENUS system from March 2015 to January 2017. The mean age was 71.1±8.1 years. All patients were diagnosed with medial osteoarthritis of the knee. All implants was cruciate substituted type (CS type) and mobile bearing insert. We developed a new ligament balancer that could be fixed to the tibia with keel and insert trial could be rotated on the paddle. We measured the medial and lateral soft tissue balance during TKA with the new balancer. The A-P position of the balancer was fixed on tibia in parallel with the Akagi line (A-P axis 0 group) and 20 degrees internal rotation (IR group) and 20 degrees external rotation (ER group). Soft tissue balance was measured in extension and 90 degrees of knee flexion on each rotational position. The mean angle of valgus and varus in IR group, 0 group and ER group were 4.6±2.2 degrees varus, 1.9±1.6 degrees varus and 0.4±2.4 degrees varus respectively in extension, and 5.5±3.0 degrees varus, 2.1±2.2 degrees varus and 0.7±3.2 degrees varus respectively in 90 degrees of knee flexion. There were significant differences between three groups in extension (p<0.0001) and flexion (p<0.0001). In other words, when the balancer was fixed on tibia with internal rotation against the Akagi line, the soft tissue balance indicated medial tightness. Conversely, when the balancer was fixed on tibia with external rotation against the Akagi line, the soft tissue balance showed lateral tightness. The insert trial significantly rotated to opposite side against the position of balancer fixed.Materials and Methods
Results
The objective of this study is to compare three dimensional (3D) postoperative motion between metal and ceramic bipolar hip hemiarthroplasty for femoral neck fracture. This study was conducted with forty cases (20 cases of metal bipolar hemiarthroplasty (4 males, 16 females), 20 cases of ceramic bipolar hemiarthroplasty (2 males, 18 females)) from November 2012 to November 2014. Average age was 80.8±7.5 years for the metal bipolar group and 79.3±10.5 years for the ceramic bipolar group. We obtained motion pictures from standing position to maximum abduction in flexion by fluoroscopy then analyzed by 2D–3D image matching method. The motion range of the “Shell angle”, “Stem neck angle” and the “Stem neck and shell angle” has been compared between the metal bipolar group and the ceramic bipolar group (Fig. 1). Metal bipolar showed greater variability of the Stem neck angle and Shell angle than ceramic bipolar. Six of the twenty cases reached unilateral oscillation angle of 37 degrees in metal bipolar. In other words, 30% of metal bipolar group revealed neck-shell impingement. No case reached oscillation angle of 58 degrees in ceramic bipolar group. There was no significant difference between the metal bipolar group and the ceramic bipolar group with respect to the difference of minimum and maximum angle of Stem neck angle (movement range of the stem neck) and Shell angle (movement range of the bipolar cup). On the other hand, difference of minimum and maximum angle of the Stem neck and shell angle (movement range of the inner head) was significantly greater in the metal bipolar group than the ceramic bipolar group. Movement, range of bipolar shell was significantly greater than that of inner head in both groups (Table 1).Materials and Methods
Results
