Factors affecting femoral rotational angle based on the posterior condylar axis in gap-based navigation-assisted total knee arthroplasty for valgus knee

Individualizing a Total Knee Arthroplasty with Three-Dimensional Planning

Total knee arthroplasty (TKA) is evolving from mechanical alignment to more individualized alignment options in an attempt to improve patient satisfaction. Thirteen-year survival of kinematically aligned prostheses has recently been shown to be similar to mechanically aligned TKA, allaying concerns of long-term failure of this newer individualized technique. There is a complex inter-relationship of three-dimensional knee and limb alignment for a TKA. This article will review planning parameters necessary to individualize each knee, along with a discussion of how these parameters are related in three dimensions. Future use of computer software and machine learning has the potential to identify the ideal surgical plan for each patient. In the meantime, the material presented here can assist surgeons as newer individual alignment planning becomes a reality.

Evaluation of painful total knee arthroplasty: an approach based on common etiologies for total knee arthroplasty revision

A differential diagnosis with emphasis on the common indications for revision should be utilized in the workup of painful total knee arthroplasty (TKA). The physician should identify the exact etiology of the patient's pain to maximize outcomes from treatment. Evaluation for infection should be completed using the Musculoskeletal Infection Society (MSIS) criteria. When common causes of revision TKA do not appear to be the cause of the pain, less likely causes should be not be ignored. Further advancements such as pressure sensing devices may be able to improve patient satisfaction and decrease the incidence of pain following TKA.

Is lateral femoral condyle hypoplasia a feature of genu valgum? A morphological computed tomography study of 200 knees

BACKGROUND

Young surgeons are taught that genu valgum deformity is associated with hypoplasia of the lateral femoral condyle, despite the absence of supporting evidence. The objective of this study was to determine whether the lateral condyle was hypoplastic in genu valgum, by assessing the morphological features of the distal femur and their variations according to the severity of the coronal deformity.

HYPOTHESIS

The lateral femoral condyle is not hypoplastic in genu valgum deformity.

MATERIAL AND METHODS

The 200 included patients treated by unilateral total knee arthroplasty were divided into five groups based on their preoperative hip-knee-ankle (HKA) angle. The HKA angle, valgus cut angle (VCA), and anatomical lateral distal femoral angle (aLDFA) were measured on long-leg radiographs. Computed tomography images were then used to measure the medial and lateral anterior-posterior condylar lengths (mAPCL and lAPCL) and condylar thicknesses (mCT and lCT), distal femoral torsion (DFT), medial and lateral posterior condylar heights (mPCH and lPCH), and medial and lateral condylar volumes (mCV and lCV).

RESULTS

No significant differences were demonstrated across the five mechanical-axis groups for mAPCL, lAPCL, mCT, lCT, mPCH, or lPCH. The groups differed significantly regarding the VCA (p<0.0001), aLDFA (p<0.0001), DFT (p<0.0001), and mCV/lCV ratio (p<0.0001). VCA and aLDFA were smaller when the valgus exceeded 10°. DFT was similar in all varus knees (2.2°-2.6°) but significantly greater for knees with moderate (4.0°) or severe (6.2°) valgus. Finally, lCV was greater than mCV in valgus knees compared to varus knees.

CONCLUSION

The presence of lateral condyle hypoplasia in knees with genu valgum seems open to question. Apparent hypoplasia noted during the standard physical examination may be chiefly ascribable to distal valgus of the femoral epiphysis in the coronal plane and, with the knee flexed, to distal epiphyseal torsion, whose severity increases with the degree of valgus deformity. These considerations should be taken into account when performing distal femoral cuts for TKA, to ensure the restoration of normal anatomy in patients with genu valgus.

LEVEL OF EVIDENCE

IV.

Flexion Space Balancing Through Component Positioning and Its Relationship to Traditional Anatomic Rotational Landmarks in Robotic Total Knee Arthroplasty

BACKGROUND

The use of the femoral component position to balance the flexion space and its relationship to the transepicondylar axis (TEA) and posterior condylar angle (PCA) has not been thoroughly evaluated.

METHODS

A total of 233 patients undergoing robotic arm-assisted total knee arthroplasty were evaluated. Native TEA and PCA were established on preoperative computed tomography scans. Femoral component rotation was set in the axial plane to match the native trochlea and native medial femoral condyle to set the flexion gap. Knee flexion space gaps and component position were recorded. The relationship of the femoral component to the native TEA, PCA, and preoperative radiographic landmarks was evaluated.

RESULTS

The intraoperative measured medial flexion space gap did not significantly correlate with the relationship of the femoral component to the PCA or TEA in varus or valgus knees. In varus knees, the preoperative mechanical axis alignment had a positive relationship to femoral component position when compared to the PCA (P = .04) and TEA (P = .002). In valgus knees, there was a positive correlation between the preoperative lateral distal femoral angle and component position when compared to the PCA (P = .04) only.

CONCLUSION

Intraoperative measured flexion space balance through femoral component positioning did not correlate with its relationship to the native TEA or PCA. In varus knees, the preoperative mechanical axis alignment correlated with an increase in femoral component external rotation to the TEA and PCA. In valgus knees, the severity of preoperative lateral distal femoral angle correlated with the rotational relationship of the femoral component to the PCA only.