Frontal alignment in total knee arthroplasty. Comparative study between radiographic measurement and surgical navigation

OBJECTIVE

To establish the concordance between angulation of the femoro-tibial mechanical axis measured with x-rays and surgical navigation in both the pre and postoperative period after a total knee arthroplasty (TKA) was implanted.

MATERIAL AND METHOD

Pre and postoperative measurements were analyzed in 88 TKA of the same model and all performed with the same surgical navigation system. The mechanical frontal angle (MFA) and femoro-tibial anatomic angle were measured before and after the TKA. The angulation was digitally measured with a teleradiography. In the navigation, the femoro-tibial angle at rest, forced varus and valgus were registered and the average of these three measurements was calculated.

RESULTS

The mean preoperative MFA measured on the radiograph was 4.55°. The mean of the same angle measured on the postoperative radiograph was 1.72°, (p=0.05). The mean of the MFA measured with navigation before TKA was 3.12° and after the implant with navigation was 0.53 (P=.013). The concordance coefficient between the MFA in teleradiography and in navigation was 0.869 (P<.001) preoperatively and 0.709 postoperatively (P=.017).

CONCLUSIONS

We found a strong concordance between radiographic and surgical navigation measurements of the MFA. This may imply that teleradiography is not necessary when using surgical navigation in TKA.

Computer-assisted navigation in total knee arthroplasty without femoral hardware removal

PURPOSE OF THE STUDY

The use of navigation applied to total knee arthroplasty in knees with femoral hardware retained has not been studied.

MATERIAL AND METHODS

We use navigation in six patients to implant a total knee arthroplasty while retaining the femoral hardware. The retained materials were screws in two cases, diaphyseal plates in another two, intramedullary nails in one and supracondylar tube/plate in another one. Preoperative knee scores were within the 46-66 range, whereas the functional scores were within 40-68. The coronal deformity varied between 30° varus and 5° valgus.

RESULTS

The final femoral mechanical axis was between 2° valgus and 3° varus; the axis of the limb was between 4° valgus and 3° varus. Knee scores improved in all cases, with scores between 75 and 90 points (p = 0.028); functional scores were between 64 and 90 points (p = 0.043).The final range of mobility was within the 70°-110° range, with a slight improvement over the preoperative status (p = 0.042). No complications have arisen throughout the follow-up (mean 16 months).

CONCLUSIONS

The use of navigation constitutes a good option in the treatment with total arthroplasties for patients with femoral hardware retained.

Extensively hydroxyapatite-coated stems in revision hip arthroplasty: A radiological mid-term follow-up study

Femoral revision surgery involves the placement of a stable stem and the regeneration of the damaged bone structure. We retrospectively reviewed 36 cases of femoral revision surgery in which an extensively hydroxyapatite-coated porous stem was implanted with a five-year minimum follow-up. Nine of the cases had type I defects, 12 had type II defects, six had III-A defects and nine had III-B defects. The mean follow-up was 7.7 years (range 5-11). No cases of revision surgery, subsidence or displacement were detected. In 35 cases the integration of the stem had been achieved, the bone structure had been restored and there was no fibrous interface visible between the implant and the bone. The fully hydroxyapatite-coated stems thus proved a valuable alternative for femoral revision surgery in mild and moderate bone defects. (Hip International 2005; 15: 38-45).