Summary

A novel in vivo animal model to establish new surgical interventions for patients with ACL insufficiency.

Although proximal tibia vara is physiologically and pathologically observed, it is difficult to measure the varus angle accurately and reproducibly due to inaccuracy of the radiograph because of rotational and/or torsional deformities. Since tibial coronal alignment in TKA gives influence on implant longevity, intra- or extra-medurally cutting guide should be set carefully especially in cases with severe tibia vara. In this context, we measured the proximal tibial varus angle by introducing 3D-coordinate system.

Bi-cruciate substituting total knee arthroplasty (TKA) having two post-cam mechanisms was developed to substitute for cruciate ligament function after surgery. A previous study has shown many of these knees achieve high functional flexion. However, there is little information provided to differentiate between knees able to flex deeply and those that could not, although this is a major concern for surgeons. This study was conducted to compare the kinematic pathway from 0° to 90° in both groups.

Twenty five knees were included in this study. All knees were diagnosed with osteoarthritis (OA) and all TKAs were performed by the same surgeon (WR) from November 2005 to September 2006. A mini mid-vastus surgical approach with posterior cruciate ligament (PCL) resection and patellar resurfacing was used in all cases. Computer navigation was used to guide bone cuts in all the cases. Patients' age averaged 63 years (range, 43–73) at the time of surgery. The study observations were performed at an average of 53 (SD 4) months after surgery. Knee motions were recorded using video-fluoroscopy while subjects performed stair up and down, and lunge activities. The three-dimensional position and orientation of the implant components were determined using model-based shape-matching techniques. This initial manual solution was refined using nonlinear least-squares optimization to maximize image-edge correspondence. Joint kinematics were determined from the three-dimensional pose of each implant component using Cardan/Euler angles. TKAs were divided into two groups according to the maximum lunge angles; TKAs achieved larger than 130° were defined as high flexion group (H group) and the ones from 110° to 130° were defined as moderate flexion group (M group). Tibial internal position and the AP locations of medial and lateral condyles were examined.

Two TKAs were excluded since their maximum flexion was less than 110°. Twelve and eleven TKAs were defined as the H group (High flexing, average 137°, SD 4°) and the M group (Moderate flexing, average 121°, SD 5°), respectively. Tibial internal rotation averaged 10° (SD 4°) and 9° (SD 3°), respectively, at lunge position. The medial and the lateral condyles were located at 9 mm (SD 2 mm) and 17 mm (SD 3 mm) posterior to the tibial centerline during the lunge activity in the M group and at 11 mm (SD 2 mm) and 21 mm (SD 3 mm) in the H group. Tibial rotation was not statistically different (Figure 1), while AP position of the lateral condyle translated more backward in H group at 90° (Figure 2). The TKAs in the M group exhibited femoral forward motion from 0° to 20° flexion, while the H group moved backward (Figure 2).

Our results revealed the post-cam mechanisms worked effectively in the H group TKA. The TKAs which acquired deep flexion successfully prevented the “roll forward motion” and had greater femoral posterior translation at 90° where the posterior post-cam mechanism engages. It appears adequate femoral posterior translation may be important to acquire deep flexion after TKA.

Although optimal alignment is essential for improved function and implant longevity after TKA, we have less bony landmarks of tibia relative to femur. Trans-malleolar axis (TMA) is a reference line of distal tibia in the axial plane, which externally rotated relative to a ML axis of proximal tibia. We originally defined another reference axis associated with the orientation of tibial plafond, and then measured tibial torsion in the 3D-coordinate system.

Three-dimensional CAD models of 20 tibiae were reconstructed based on pre-operative CT data from OA patients (16 females and 4 males, 73.8 ± 6.9 years old). TMA was a line connecting each apex of medial and lateral malleolus. The plafond axis (PLA) that we originally defined in this study was a line connecting each midpoint of medial and lateral margin of talocrural facet. In terms of interobserver correlation coefficiency and mean errors of the designated points to define those axes, TMA was found out to be 0.982, 3.14 ± 0.47 mm (medial), and 0.988, 4.88 ± 0.59 mm (lateral). Those of PLA were 0.997, 1.97 ± 0.53 mm (medial), and 0.995, 2.02 ± 0.44 mm (lateral). The tibial torsion was 16.3 ± 6.3°with reference to TMA, and 10.2 ± 8.4°to PLA.

Based on these results, as for the rotational reference axis in the axial plain of distal tibia, we consider the plafond axis to be another reliable and reproducible axis, which is expected to be applicable in preoperative planning in TKA to reduce outliers of coronal alignment.

In the light of the increasing popularity of femoral resurfacing implants, there has been growing concern regarding femoral neck fracture. This paper presents a detailed investigation of femoral neck anatomy, the knowledge of which is essential to optimise the surgical outcome of hip resurfacing as well as short hip stem implantation.

Three-dimensional lower limb models were reconstructed from the CT-scan data by using the Mimics (Materialise NV, Leuven, Belgium). We included the CT data for 22 females and nine males with average age of 60.7 years [standard deviation: 16.4]. A local coordinate system based on anatomical landmarks was defined and the measurements were made on the unaffected side of the models.

First, the centre of the femoral head was identified by fitting an optimal sphere to the femoral head surface. Then, two reference points, one each on the superior and the inferior surface of the base of femoral neck were marked to define the neck resection line, to which an initial temporary neck axis was set perpendicular. Cross-sectional contours of the cancellous/cortical border were defined along the initial neck axis. For each cross-sectional contour, a least-square fitted ellipse was determined. The line that connects the centre of the ellipse at the base of the femoral neck and the centre of the femoral head was defined as the new neck axis. The above process was repeated to reduce variances in the estimation of the initial neck axis. The neck isthmus was identified according to the axial distributions of the cross-sectional ellipse parameters.

The short axis of the ellipse decreased monotonically since it was calculated from the center of the femoral head to the neck resection level (base of neck), whereas the long axis changed with the local minima. The cross section at which the long axis of the fitted ellipse had the local minima was determined as the neck isthmus.

The following measurements were made on the proximal part of the femur. The neck axis length measured from the center of the femoral head to the lateral endosteal border of the proximal femur was 67.3 mm [6.4]. The length between the center of the femoral head and the neck isthmus was 22.5 mm [2.7]. The diameter of the ellipse long axis at the neck isthmus was 27.6 mm [3.5] and was 23.6 mm [3.3] for the short axis.

The center of the neck isthmus did not align with the neck axis. The deviation of the isthmus from the neck axis which we defined as the isthmus offset was 0.7 mm [0.4].

If an alternative neck axis was defined between the center of the femoral head and the center of the neck isthmus, there would be a certain degree of angular shift with respect to the original neck axis. An angular shift of 1.8 degrees between the two axes can be expected for a 0.7-mm isthmus offset. In the worst case, an angular shift of 4.59 degrees was estimated for a subject with the largest isthmus offset of 1.93 mm.

Further investigations would be necessary to determine the axis configuration that represents the clinically relevant centre of the femoral neck. In order to reduce the deviations in the three-dimensional determination of the femoral neck axis, the reference anatomical landmarks and methods of evaluation should be carefully selected.

Background: Deformity of the femoral head after open reduction for developmental dislocation of the hip (DDH) influences the outcome of pelvic osteotomy as a final correction for residual dysplasia to prevent secondary osteoarthritis. The purpose of this study was to review long-term outcomes after open reduction using a medial approach for DDH. The correlation between age at the time of operation and femoral head deformity at skeletal maturity was specifically evaluated.

Methods: Forty-two hips in 40 patients with more than 10 years of follow-up were assessed radiologically. The mean age at the time of surgery was 14.3 (range, 6–31) months, and the postoperative follow-up period ranged from 10 to 27 (mean, 15.8) years. The round and enlargement indices of the femoral head were measured on follow-up radiographs to evaluate deformity and enlargement of the femoral head at skeletal maturity.

Results: Severin classification was I and II in 16 hips; III, IV, and V in 23; and II at the final follow-up in the 3 hips treated by osteotomy less than 10 years after open reduction. Mean round index at follow-up was 58.3 ± 8.3 (range, 47–79); it showed correlation with age at the time of operation (r = 0.68, p < 0.001). Mean enlargement index at follow-up was 113.4 ± 11.8 (range, 93–137) and showed no correlation with age at the time of operation (r = 0.009, p = 0.96).

Conclusions: At more than 10 years’ follow-up, the occurrence of deformity of the femoral head correlated with increased age at the time of operation. Indications for use of a medial approach in the correction of DDH in older patients must take into account the risk of subsequent femoral head deformity at skeletal maturity.

The outcomes of various operative methods for osteochondritis dissecans of the femoral condyles were reviewed, and choice of these operative methods were discussed.

Twenty-four cases (19 males and 5 females) which underwent operative treatments were reviewed. The operative methods included drilling, repositioning and fixation of the osteochodral fragment, and bone graft or osteochondral graft. The minimum follow-up period was two years. The medial femoral condyle was involved in 17 cases, and the lateral, in seven. Lateral discoid meniscus or meniscal injury was combined in all the 7 cases in the lateral. The operative methods were decided from the condition of the cartilage. Drilling was performed in cases with no or minimal cartilage damages (10 cases). Repositioning (if required) and fixation of the fragment using absorbable pins was carried out in cases with a partial or total fragmentation (7 cases). Bone graft or osteochondral graft was performed when the original site was already degenerated (7 cases). Partial meniscectomy was added when the meniscal injury was combined.

In patients who received drilling, the lesion healed radiographically in all the cases and they complained of no or minimal symptoms. In patients who received the fragment fixation, re-union of the fragment was observed in 71% and the clinical outcomes were satisfactory in most of the cases. In patients who received bone graft or osteochondral graft, although union of the graft was observed in all the cases radiographically, 71% of the patients complained of residual pain.

From the results, drilling is sufficient if the cartilage surface is not damaged. When the fragmentation occurred already, the fragment should be repositioned and fixed to the original site before degenerated, as its clinical symptoms were much better than those with bone graft or osteochondral graft.