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.

One of the most important characteristic of the developmental dysplastic hip (DDH) is high anteversion in femoral neck. Neck-shaft angle is also understood to be higher (i.e. coxa-valga) in DDH femora. From this understanding many DDH intended stems were designed having larger neck shaft angle.

According to the result of our prior study; reported in ISTA 2005 etc.; using computer 3-D virtual surgery of high fit-and-fill lateral flare stem into high anteversion patients, it was revealed that the geometry of proximal femur itself does not have big difference from normal femora but they are only rotated blow lessertrochanter.

It is very important to know what anteversion is, and where anteversion is located, to design a better stem and to decide more proper surgical procedures for DDH cases with high anteversion.

In the present study, the geometry of 57 femora was assessed in detail to reveal the geometry of anteversion and its location in the DDH femora.

Fifty seven CAT scan data with many causes were analyzed. Thirty-two DDH, 3 Rheumatic Arthritis (RA), 2 metastatic bone tumors, 4 avascular necrosis (AVN), 1 knee arthritis, 12 injuries, and 3 normal candidates were included. Whole femoral geometries were obtained from CAT scan DICOM data and transferred to CAD geometry data format. All the following landmarks were measured its direction by the angle from posterior condylar line. The assessed landmarks were

anteversion,

All the directions were measured by the angle from the medial of the femur.

The direction of anteversion and lesser trochanter were well correlated, (R=0.55, Y=0.56X−35) i.e. femoral head and lesser trochanter were rotated together.

The direction of lesser trochanter and aspera in upper 1/6 section had no relation even they are located very close with only several cm distance, (R=−0.03, Y=−0.02X−88) i.e. however the lesser trochanter was rotated, the upper most aspera was located almost at the same direction (−87.5+/−7.58 degree).

The direction of aspera at upper 1/6 and middle femur were strongly correlated. (R=0.63, Y=0.81X-22) i.e. they stay at the same direction.

The results mean that the anteversion is a twist between normal proximal femur (from femoral head and lesser trochanter) and normal distal femur. The twist was located just blow lesser trochanter within several centimeter.

The anteversion has been understood as the abnormal mutual position between femoral neck and femoral shaft. In high anteversion hips the neck shaft angle was also believed to be higher, so several DDH oriented stems have higher neck shaft angle i.e. coxa-valga geometries. It has been believed that the location of the anteversion was around neck part. This study revealed that the deformity was located in the very narrow part just below lesser trochanter. It has been discussed that DDH oriented stems should have fit to different canal geometries, but understanding the biomechanics of abnormal anteversion and its treatment should be more important.

Introduction: The success of cemenntless THA (total hip arthroplasty) mainly depends on the choices of stem, its size and accuracy of stem orientation. Selection of the optimal stem judging only by plain X-ray is not so easy. Because deformity varies in each case and it is impossible to obtain profile view of the hip. As osteoarthritic patients tend to develop external rotation contractures, radiographic position of the patients with correct rotation is very difficult. To override these problems, we have been using 3-D preoperative planning system. As for the stem selection, we have been mainly using Revelation stem, because it has a structure called lateral flare that provide proximal physiological load transfer. In the present study, the usefulness of our preoperative planning system especially for the determination of the size and stem orientation with Revelation stem.

Materials and Method: Pre-operative planning was performed in 55 osteoarthritic hips in 50 patients (10 male and 40 females), and the mean age at the operation was 64.05 years old. The 3-dimensinal geometries of the femora femora were reconstructed from the CAT scan DICOM data. The geometry of femur and components were placed on the same coordinate. Cross-sectional images from many directions were observed, and the optimal location and the size of the stem were selected. According to the result, actual operations were done. Planed sizes and selected sizes at the surgeries were compared. For several patients, post-operative CAT scans were performed, then planed stem position and actual stem position were compared.

Result: Stems preoperatively defined were used in 50hips (90.9%),1 size large ones were used in 2 hips (3.6%) and 1 size large ones were used in 3 hips (5.5%).

Discussion: As Revelation stems have very high proximal fit-and-fill, the end point of the stem insertion is very definite. The characteristics made the accuracy of the preoperative planning. So it was not so difficult to perform THA according to the preoperative planning as it had been imagined.

Since 1993, we have been developing preoperative planning system based on CAT scan data. In early period it was used to decide cup diameter and orientation for Total Hip Arthroplasty (THA). It was done using hemisphere object locating proper position and orientation. According to our progress, we have started using it for custom stem designing, stem selection and stem size planning too since 1995. Since 2001, we have been using it for almost all THA cases. We also have started use it for any case we have question about 3D geometries. Since 2005 we started computer planed 2 staged THA after leg elongation for high riding hips and reported at ISTA 2007 too. Now our policy became that every tiny question we have, we shall analyze and plan preoperatively.

In our population, the incidence of the developmental dysplastic hips is higher. The necks often have bigger anteversion, and less acetabular coverage. So we often use screws for cup fixation. The screw direction allowed in thin shell thickness is limited and less bone coverage makes good cup fixation difficult. With highly defected cases and with revision cases the situation is more difficult.

In the present study, we have developed acetabular 3D preoperative planning method with screw direction, length, and for the cases with defect, cup supporter pre-shaping with models and prediction of the allograft volume.

For the less defect cases, geometries of cup with screw holes were requested to the maker and were provided for us. Screws were attached perpendicular to each screw hole. Screw geometries have marks at every 5mm to plan proper length. The cup was located as much as closer to the original acetabular edge, keeping in the limit to avoid dislocation. Small space above the cup was accepted if anterior and posterior cup edge could be supported by original bone. Then the cup was rotated until we can obtain proper screw fixation.

For the cases with severe defects, we use cup supporters and allografts. Cup supporters are designed to be bent and fit to the pelvis during the surgery. But to shape it a properly; for good coverage and strong support; is very difficult and takes long through the limited window with fatty gloves. And mean while we get more bleeding. The geometries were obtained by CAT scan of the devices. Then proper size was determined as cup size. Chemiwood model was made and proper size supporter was opened and bent preoperatively using the model. It was scanned again and compared to the pelvic geometry again.

Using cluster cups, no dangerous screw was found as long as normal cup orientation was decided and screws were less than 30mm. Posterior screws were often too short then rotated anterior and found to have good fixation. Pre-bending could reduce surgical time remarkably.

As long as we could know, no navigation system can control the cup rotation. But acetabular preoperative planning was very useful and could reduce operative invasion. It could be done easily without using navigation system.

It is frequently difficult to diagnose and treat of malignant sacral bone tumors. This tumor is diagnosed with lumbar disc hernia, instability coccygitis, hemorrhoids. We reviewed the surgical treatment of primary malignant (14) and secondary (metastatic) sacral tumors (11) in 25 patients from 1983 to 2000. Primary tumors consisted of chordoma in 11 patients, chordoma with spindle cell sarcoma, malignant peripheral nerve sheath tumor (MPNST), giant cell tumor of bone in 1 patient each. The secondary tumors consisted of invading carcinoma in 7 patients, metastatic carcinoma in 4 patients. Location of the sacral tumor was showed total sacrum in 2 patients, below S2 in 18, S3 in 2 and S4 in 3. Preserving nerves were L5 in 1 patient, S1 in 17, S2 in 2, S3 in 3, and 2 performed curettage. Posterior approach was used in 8 patients, and an anterior and posterior combined approach in 17. Sacrectomy only in 7 patients, and sacrectomy and colostomy in 8, including with rectum was performed in 8, and 2 patients had extensive curettage and bone graft or hydroxyapatite (HA) transplantation. Six tumor excisions were used modified T-saw which pass through the sacral canal preserving nerve roots. Surgical margin of chordoma in primary sacral tumors had wide in 10, wide excision with partial contamination in 2, except curettage in 1. MPNST had curettage and giant cell tumor of bone had marginal in 1 each. Secondary sacral tumors had wide in 9, marginal in 2.

Adjuvant therapy was used radiation therapy in 3 patients and chemotherapy in 2 and ethanol in 1. Musculocutaneous flap was reconstracted tensor fascia lata flap and gluteal muscle flap in 2 patients. Interval between initial chief complaints and diagnosis of chordoma detected from 6 months to 10 years, avarage 5 years 3 months by rectal examination, radiogram, genital ultra echo and MRI; invading carcinoma from 2 months to 3 years, avarage 8 months, and metastatic carcinoma from 2 months to 4 months, average 3 months. Six of 12 patients of chordoma in primary sacral tumors are alive from 6 months to 18 years, average 4 years 6 months; remaining patients were died 6 month to 8 years, average 3 years 2 months, except 2 patient died with infection. The patient with a MPNST died after 2 years 6 months, and a giant cell tumor of bone had no recurrence or lung metastases in 10 years.

One of 11 patients of secondary sacral tumor (initial surgery) is alive in 14 years 6 months, remaining 10 patients died 3 months to 4 years 6 months, average 1 year 10 months, except 2 patients died with infection. Complications were much bleeding, infection, skin slough, nerve injury. We recommend better surgical method that anterior and posterir approach use above S3, and posterior approach blow S4, A modified T-saw performed an osteotomy of the pars lateral of the sacrum, proved to be easier and faster than osteotomies performed using the old method.