[Minimally invasive anterior approach]. / Der minimal-invasive anteriore Zugang.

The minimally invasive direct anterior approach for total hip arthroplasty (THA) was first published in 1985. Since then the technique has been further improved and the indications have been extended. The approach utilizes the muscle gap between the tensor fasciae latae muscle on the lateral side and the sartorius muscle on the medial side. This muscle gap allows a direct and quick approach to the hip joint with good muscle preservation. During preparation of the femur the tensor fasciae latae muscle is at risk of being damaged. The lateral cutaneous nerve of the thigh (NCFL) and its branches are also in danger of being damaged during skin incision and dissection of the subcutaneous tissue. In this article the technique, risks and current clinical results of THA using the minimally invasive direct anterior approach are described. The results from the literature, as well as own results are compared to the traditional transgluteal lateral Bauer approach and discussed. Reviewing the literature, special attention has been given to the incidence of NCFL lesions, damage of the tensor fasciae latae muscle and positioning of the cup. Especially for the latter, the general view is hindered in the minimally invasive technique.

Do varus or valgus outliers have higher forces in the medial or lateral compartments than those which are in-range after a kinematically aligned total knee arthroplasty? limb and joint line alignment after kinematically aligned total knee arthroplasty.

AIMS: The aims of this study were to determine the proportion of patients with outlier varus or valgus alignment in kinematically aligned total knee arthroplasty (TKA), whether those with outlier varus or valgus alignment have higher forces in the medial or lateral compartments of the knee than those with in-range alignment and whether measurements of the alignment of the limb, knee and components predict compartment forces. PATIENTS AND METHODS: The intra-operative forces in the medial and lateral compartments were measured with an instrumented tibial insert in 67 patients who underwent a kinematically aligned TKA during passive movement. The mean of the forces at full extension, 45° and 90° of flexion determined the force in the medial and lateral compartments. Measurements of the alignment of the limb and the components included the hip-knee-ankle (HKA) angle, proximal medial tibial angle (PMTA), and distal lateral femoral angle (DLFA). Measurements of the alignment of the knee and the components included the tibiofemoral angle (TFA), tibial component angle (TCA) and femoral component angle (FCA). Alignment was measured on post-operative, non-weight-bearing anteroposterior (AP) scanograms and categorised as varus or valgus outlier or in-range in relation to mechanically aligned criteria. RESULTS: The proportion of patients with outlier varus or valgus alignment was 16%/24% for the HKA angle, 55%/0% for the PMTA, 0%/57% for the DLFA, 25%/12% for the TFA, 100%/0% for the TCA, and 0%/64% for the FCA. In general, the forces in the medial and lateral compartments of those with outlier alignment were not different from those with in-range alignment except for the TFA, in which patients with outlier varus alignment had a mean paradoxical force which was 6 lb higher in the lateral compartment than those with in-range alignment. None of the measurements of alignment of the limb, knee and components predicted the force in the medial or lateral compartment. CONCLUSION: Although kinematically aligned TKA has a high proportion of varus or valgus outliers using mechanically aligned criteria, the intra-operative forces in the medial and lateral compartments of patients with outlier alignment were comparable with those with in-range alignment, with no evidence of overload of the medial or lateral compartment of the knee. Cite this article: Bone Joint J 2017;99-B:1319-28.