Dislocation following total hip arthroplasty is one of the most common complications, occurring in 1% to 5% of all cases. Several causes for dislocation have been suggested that

Mismatching of cup positioning and stem anteversion

Most often positioning of the stem is anatomically predetermined, while the orientation of the cup is much more flexible. Since July 2005, stem first method has been applied for all cases. During this method, canal preparation and stem trial was done first, and then cup orientation was determined according to the stem direction and impingement. For the bigger cups 34mm or 38mm heads were applied in this series. In the present study dislocation ratio was compared to cup first method.

In the stem fist group (SF), the following procedures were done consequently.

Canal was prepared for the stem. Revelation lateral flare high proximal load transfer stem (DJO) was mainly selected. But for the case with high anteversion over 50 degrees, Modulas; conical distal load transfer stem with modular neck (Lima) was selected.

From October 2002 to July 2008, there were 191 THA cases. There were 81 hips in Standard group and 109 hips in SF group. There were 63 females and 18 males in Standard group and 90 females and 19 males in SF group (p=0.41). Average age was 61.0(22–81) in Standard group and 60.2(29–89) in SF group (p=0.53). In Standard group, 64 were replaced for osteoarthritis, 15 for rheumatoid arthritis and two for avascular necrosis. In SF group, 86 were replaced for osteoarthritis, 17 for rheumatoid arthritis and six for avascular necrosis (p=0.53). As for Crowe’s classification, 61 type I, 18 type II and 2 type III were included in Standard group. And 88 type I, 15type II, 4 type III and 2 type IV were included in SF group (p=0.29). Average anteversion of femoral neck were 23.1(−2 to 70) degree in Standard group and 26.2(−4 to 65) degree in SF group measured with CAT scan (p=0.274). MoM bearing surfaces were used with 71 hips (87.7%) in Standard group and 100 hips (91.7%) in SF group (p=0.35). Only in SF group, big metal head were used in 24hips(22%) with 34mm and in 12hips(11%) as 38mm diameter. Average leg length difference between pre and post operation was 11.5mm(0 to 36) in Standard group and 8.0mm(−18 to 30) in SF group (p< 0.05). Average cup inclination was 43.2(25 to 84) degree in Standard group and 40.9 (22 to 66) degree in SF group (p< 0.05). Average cup anteversion was 8.2 degree (0 to 22.8) in Standard group and 7.1 degree (−12 to 30.5) in SF group (p< 0.05). Average operating time was 111.9min (67–150) in Standard group and 97.5min(60–162) in SF group (p< 0.05). Average intra operative hemorrhage was 744ml(10–2757) in Standard group and 487ml(10–1374) in SF group (p< 0.05). The dislocation rate was decreased from 3.7% (3/81 cases) in Standard group to 0.0% (0/109) in SF group.

In conclusion our study suggested that Stem first method and utilization of big metal head would decrease the dislocation rate in primary cases. More bleeding from canal during accetabular reaming was expected. However less bleeding was observed in SF group.

Introduction: For longer lasting and bone conserving cementless stem fixation, stable and physiological proximal load transfer from the stem to the canal should be one of the most essential factors. According to this understanding, we have been developing a custom stem system with lateral flare and an off-the-shelf (OTS) lateral flare stem system was added to the series. On the other hand, dysplastic hips are often understood that they have larger neck shaft angle as well as larger anteversion. In other words they are in the status called “coxa valga.” From this point of view we had been mainly using custom stems for the dysplastic cases before. After off-the-shelf lateral flare stem system; which is designed to have very high proximal fit and fill to normal femora; was added, we have been using 3D preoperative planning system to determine custom or OTS. Then in most of the cases, OTS stem were suitably selected. Our pilot study of virtual insertion of OTS lateral flare stem into 38 dysplastic femora has shown very tight fit in all 38 cases. The reason was analyzed that the excessive anteversion is twist of proximal part over the distal part and the proximal part has almost normal geometry. In the present study, 59 femora were examined by the 3D preoperative planning system how the excessive anteversion effect to the coxa valga status.

Materials and Methods: Fifty-nine femoral geometry data were examined by the 3D preoperative planning system. Thirty-three hip arithritis, 3 RA, 2 metastatic bone tumours, 5 AVN, 1 knee arthritis, 12 injuries, and 3 normal candidates were included. Among them one arthritic Caucasian and one AVN South American were included. The direction of the femoral landmarks; centre of femoral head (CFH), lesser trochanter (LTR), and asperas in 3 levels (just below LTR, upper 1/3, mid femur; A1-3); were assessed as the angle from knee posterior condylar (PC) line. Neck shaft angle of each case was assessed from the view perpendicular to PC line and neck shaft angle form the view perpendicular to CFH and femoral shaft (i.e. actual neck shaft angle).

Results: Average anteversion was 34.4 +/−9.9 degree. CFH and LTR correlated well (i.e. they rotate together). A1, A2, A3 correlated well (i.e. they rotate together). LTR and A1 correlate just a little, LTR and A2 were independent each other. So the twist existed around A1. Neck shaft angle was 138.7+/−6.6 in PC line view and in actual view 130.3+/−4.4. No excessive neck shaft angle was observed in actual view. Even the case that has the largest actual neck shaft angle (140.4), the virtual insertion showed good fit and fill with the lateral flare stem.

Conclusion: In many high anteversion cases, coxa valga is a product of the observation from non perpendicular direction to CFH-shaft plane. Selection or designation of the stem for high anteversion cases should be carefully determined by 3D observation.

To compare the early result of minimum incision surgery (MIS) to standard incision procedures with use of lateral flare hip replacement (Revelation Hip System, DJO, USA). 38 primary total hip arthroplasty of 36 patients were performed using lateral flare hip system. Lateral flare hip has symmetric contact to medial and lateral cortical bone at high proximal part and it provides definite endpoint of stem insertion. From this point of view, we can say that this system is suitable for MIS. Among the 38 hips, 21 hips were performed by MIS (less than 10cm) and 17 hips were performed by Standard incision. MIS were performed from November 2004 to December 2005. And Standard incisions were performed from June 2004 to December 2005. Two surgeons performed all operations (NW and YT). The main surgeon decided whether MIS was applicable or not for each patient. Anterolateral intra gluteal approach (modified Dall) was applied for all surgeries. The same rehabilitation program was applied on both groups postoperatively. The average follow-up period of MIS patients was 28.6 months and 34.7 months in standard incision. We investigated the early result of these patients.

There was a relationship between patients’ height and the length of skin incision (p< 0.05). No significant difference between two groups was proved in CRP, CPK and D-Dimmer (CRP: 13.9/11.9mg/dl, CPK: 405.5/380.5mg/dl, D-Dimmer: 6.1/5.3mg/dl). Both intraoperative blood loss and operation time were less in MIS group (blood loss 530.9ml vs. 772.8ml, operation time 99min vs. 115.4min) (p< 0.05). The days until the patient was able to do active straight leg raising were 17.3 in MIS group and 22.4 in standard incision group and hospital stay days were 26.7 vs. 29.2. But no significant differences were proved in hospitalization. On roentgenografic findings, the inclination of acetabular cup was 42.0 degree in the MIS group versus 41.2 in the standard incision group and no significant difference was found. In Radiographic findings, one stable fibrous fixation was observed in each group. The other cases were bone ingrowth fixation. Japanese orthopedics association (JOA) hip score was not significant different in each group at the final follow up (88.1 in MIS group and 85.9 in Standard group). Also as the result at the term of 6, 12, 18 and 24 months after operation, JOA hip scores was not significant difference in each group. There were no revision cases in this study until the final follow up.

In the present study, intra-operative hemorrhage and operation time were significantly less in MIS group. It was supposed that at the patient selection, each surgeon decided the candidate of MIS due to patient’s hip condition. But in another situation, no significant difference was found for example in serum CRP, CPK and D-Dimmer levels. Clinical and radiological outcomes were not significantly different between MIS and Standard group in this study.