Background The transepicondylar axis is often used for positioning of the femoral component in knee replacement.
MethodsWe studied the reproducibility of the intra-operative palpation of the transepicondylar axis for rotational alignment of the femoral component in 20 total knee replacement (TKR) implantations with a non-image-based navigation system. 2 surgeons defined the transepicondylar axis 3 times each without changing the reference plane.Results The angle between the reference plane and the transepicondylar axis was measured by the navigation system. The mean intra-observer ranges of variation were 5° and 6° for both surgeons, with a maximum of 15°. The mean inter-observer range of variation was 9°, with a maximum of 15°. Variations occurred in either internal or external rotation. Intra-observer agreement was considered good for one surgeon and poor for the other. There was no agreement between the two observers.Interpretation To define the rotational alignment of the femoral component of a TKR according to the intra-operative palpation of the transepicondylar axis may not be as reproducible as expected. However, the exact effect of this variability on the outcome after TKR should be studied.
We studied a consecutive series of 40 patients presenting a septic knee arthritis, with a mean age of 49 +/- 20 (range 19-81) years. The aetiologies were: 18 postoperative arthritis, 12 haematogenous infections, 7 arthritis following aspiration or infiltration, and 3 articular wounds. The most common organisms were Staphylococcus aureus and epidermidis (23 cases). Surgical procedures consisted in 20 arthroscopic debridements, 6 open debridements, 14 synovectomies. According to Gächter's classification, there were 8 stage I, 18 stage II, 11 stage III and 3 stage IV cases. Fifteen patients had to be reoperated after the index procedure at our institution: one open debridement, six open synovectomies, one open arthrolysis, one arthrodesis and six total knee arthroplasties (TKA). Final examination was performed after 22 +/- 26 (range 12-96) months. All cases were considered free of infection. Good functional result was present by 19/33 cases (excluding arthrodesis and TKA). The delay between the onset of symptoms and surgery was the major prognostic factor of success (P=0.023). This delay was correlated with Gächter's staging of the intra-articular lesions. The diagnosis of septic knee arthritis must be suspected at the early stage of the disease, and diagnostic joint aspiration must be immediately performed when the diagnosis is suspected. We suggest that the treatment should be more aggressive than generally advocated. Needle aspiration should be only performed at the very early stages. Arthroscopic debridement should be the routine treatment. Synovectomy should be considered even as a primary procedure when significant synovial hypertrophy is present (Gächter stage III and IV) or when a more conservative treatment did not lead to a fast improvement.
The accuracy of implantation is an accepted prognostic factor for the long-term survival of unicompartmental knee prostheses (UKP). We developed a non-image-guided navigation system for UKP implantation without any extramedullary or intramedullary guiding device. The 30 patients operated on with the navigation system (group A) were matched to 30 patients operated on with the conventional technique (group B) using age, sex, body mass index, preoperative coronal mechanical femorotibial angle, and severity of the preoperative degenerative changes. All patients had a complete radiological examination in the first 3 months after the index procedure, with anteroposterior and lateral plain knee radiographs and anteroposterior and lateral long leg radiographs. Coronal femorotibial mechanical angle and both coronal and sagittal orientations of the femoral and tibial components were measured. There were no significant differences in the mean numerical values of all measured angles except for the sagittal orientation of the tibial component, with a significant excessive posterior tibial slope in group B. There was a significant increase in the rate of prostheses implanted in the desired angular range for all criteria except the coronal mechanical femorotibial angle in group A. An optimal implantation with all optimal items was obtained by 18 cases in group A and 6 cases in group B. Navigated implantation of a UKP with the used, non-image-based system improved the accuracy of the radiological implantation without any significant inconvenience and with little change in the conventional operative technique. The only inconvenience was a 20-min longer operative time. This improvement could be related to a longer survival of such implanted prostheses.
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