Objectives

The anteversion angle of the cup is important for achieving the stability and avoiding the dislocation after total hip arthroplasty (THA). We place the component considering with the change of inclination of pelvis with its posture change. We analyzed the perioperative pelvic inclination angles with posture change and the time course.

Purpose

CentPillar GB HA stem (stryker®) is developed as the stem fitting the Japanese femur, and now there is CentPillar TMZF HA stem (stryker®) as the improvement type of the stem by coating the PureFix HA with plasma spray. We observed the factors which influenced on the stem subsidence between the two-type stems.

Objectives

Few reports were shown about the position of the cup in total hip arthroplasty (THA) with CT-based navigation system. We use minimally invasive surgery (MIS) technique when we perform cementless THA and the correct settings of cups are sometimes difficult in MIS. So we use CT-based navigation system for put implants with correct angles and positions. We evaluated the depth of cup which was shown on intra-operative navigation system.

Objectives

Many reports were shown about the angle of the cup in total hip arthroplasty (THA) with CT-based navigation system. However, there are few reports about the position of the stem. We investigated the position of the stem in navigated THA. We evaluated the position and alignment of stem which were shown on intra-operative navigation system.

ROBODOC is a well known tool for a computer assisted arthroplasty. However, the incision tends to enlarge with the system because of the restriction of range of motion. We have developed the robot system for minimally invasive arthroplasty. This report shows the accuracy of our system composed of original planning software, navigation and bone cutting robot.

We took the DICOM data of cadaver knees from computed tomography. The data were transferred to the workstation for planning. Matching points for registration and cutting planes were determined on the planning software. Cutting tool was the 6th robot which was able to recognize the locations of its apex and the cadaver knee with navigation system. We made five planes for TKA and two planes for UKA on femur. Then we made one plane on tibia. We evaluated the accuracy by measurement the location of cutting plane under navigation system and by CT data.

The registration errors of femur and tibia were less than 1.0mm about cadaver knees. The errors of cutting planes were 1.3 mm about the distal end of femur and 0.5 mm about the proximal end of tibia. The accuracies of the angles of cutting planes were 1.9 degrees and 0.8 degrees compared to the mechanical axis.

The errors of anterior and posterior plane of femur were increased compared to the distal plane. It was because the accuracy of registration were correct in axial direction but was not satisfied in rotational direction. The error was considered by the location of points which decided the rotation alignment. We will make effort to minimize the errors of registration and put it into practical use as soon as possible.

We have devised a combined pillar score (CPS) system, based on the lateral pillar (LP) and the posterior pillar (PP) classifications, together with the age at onset of Perthes’ disease, and examined its correlation with prognosis. The correlation coefficient of the Catterall classification, LP, PP, and CPS systems with the Stulberg system was 0.39, 0.52, 0.50, and 0.70, respectively. Overall 21 of the 22 hips (95.4%) with a CPS of 0 to 1 point had a good outcome and 12 of the 13 hips (92.3%) with a CPS of 3 points or more had a fair or poor outcome. None with a CPS of 2 points, had a poor outcome. The study shows that an accurate prediction of the prognosis is not possible with the LP classification alone for patients classified as belonging to group B (LP height 50% to 100% of contralateral height). The CPS system does allow accurate prediction of outcome.

The authors added a classification of posterior pillars to Herring’s classification of lateral pillars in a retrospective study of 33 patients with Perthes disease. Anteroposterior and frog position lateral radiographs taken approximately two months later from first visit, were evaluated. All patients were treated by a non-weight-bearing method (continuous traction and wheel chair activity). The outcome was evaluated by the Stulberg method.

The mean age at follow-up was 18 years (range,14.2 to 26.9 years).

Thirteen hips were in Catterall group II, 18 were in group III, and two were in group IV. Twenty-five of the 33 hips were in Stulberg class I or II (with good results), and eight hips were class III. Nine hips were in Herring group A, 20 hips were in group B, and four were in group C. Eleven hips were in our group A with the posterior pillar classification, 16 were in group B, and six were in group C. Group A, with a lateral or posterior pillar had good results without exception. Concerning Herring’s classification, all four heads had become aspherical in group C, however, 16 hips were good results and four hips were poor in group B. The outcome was poorly related to the classification in 20 patients with 20 affected hips in Herring group B when only lateral pillars were used in classification. When both lateral and posterior pillars are considered in classification, results can be predicted more accurately than when only lateral pillars are considered. This more accurate prognosis at an early stage of Perthes disease can facilitate effective treatment selection.

Arthrogryposis multiplex congenita (AMC) is a rare disease with multiple joint contractures. It is widely believed that bilaterally dislocated hips should not be reduced since movement is satisfactory and open reduction has had poor results. Since 1977 we have performed a new method of open reduction using an extensive anterolateral approach on ten hips in five children with AMC. The mean age at surgery was 31.5 months (17 to 64) and the mean follow-up was 11.8 years (3.8 to 19.5).

At the final follow-up all children walked without crutches or canes. Two managed independently, one required a long leg brace and two had short leg braces because of knee and/or foot problems. The clinical results were good in eight hips and fair in two and on the Severin classification seven hips were rated as good (group I or group II).

We recommend the extensive anterolateral approach for unilateral or bilateral dislocation of the hip in children with arthrogryposis or developmental dislocation of the hip.

We treated 120 children between the ages of 12 and 31 months with 137 developmental dislocations of the hip and reviewed them at a mean follow-up of 14 years.

We had used two-directional arthrography of all hips before reduction to evaluate the anterior, superior, and posterior portions of the limbus. Of the 137 hips, 64 had no interposed limbus in the AP view of the arthrogram, but 45 of these had an interposed anterior or posterior portion of the limbus. The hips with good stability and no interposed limbus in either AP or lateral arthrograms had excellent results by closed methods; in the other cases the results were less satisfactory.

Our findings suggest that hips suitable for management by closed reduction can be identified by two-directional arthrography. Hips shown to have an interposed limbus are best managed by open reduction.