Caliper-verified unrestricted kinematically aligned total knee arthroplasty in Asian patients showed efficacious mid- to long-term results regardless of postoperative alignment categories.

PURPOSE: There have been insufficient data regarding the long-term results of unrestricted kinematically aligned total knee arthroplasty (unKATKA) in Asian patients. We investigated mid- to long-term clinical and radiological follow-up data of Korean patients after caliper-verified unKATKA of minimum 7.4-10 years including categorised data of postoperative tibial component, limb and knee alignment. Additionally, we analysed the preoperative distribution and postoperative restoration of coronal plane alignment of knee (CPAK) phenotypes. METHODS: This study is a retrospective analysis of 63 patients: 96 osteoarthritic underwent consecutive caliper-verified unKATKA between October 2013 and May 2016 by a single surgeon. Implant survivorship was investigated for revision for any reason. Each knee was categorised into an in-range or outlier group by three postoperative alignment parameters: tibial component, knee and limb alignment. Statistical analyses were done for any significant differences in clinical scores and implant survival rates between groups. Finally, all knees were classified into CPAK classification postoperatively and postoperatively. The CPAK restoration rate was calculated. RESULTS: Among 85 knees in the clinically confirmed group, implant survival was 98.8%. There was one case of revision due to periprosthetic fracture. The percentage postoperatively aligned in the varus (valgus) outlier range was 100% (0%) for tibial component, 16.7% (24.8%) for the knee alignment and 51% (0%) for the limb alignment. All three categories did not affect implant survival or clinical scores. Eighty one out of 96 knees (84.4%) were restored to their CPAK phenotype postoperatively. CONCLUSION: With the limitation of a case series having a small number of patients and gender deviation, our study suggests that caliper-verified unKATKA could be a good option regardless of geographical variation of constitutional alignment in patients with osteoarthritis (OA). LEVEL OF EVIDENCE: Level IV, therapeutic study.

The Morphology of a Kinematically Aligned Distal Femoral Osteotomy Is Different from That Obtained with Mechanical Alignment and Could Have Implications for the Design of Total Knee Arthroplasty.

Background: Kinematically aligned total knee arthroplasty (KA-TKA) may lead to a different pattern of osteotomy from mechanically aligned total knee arthroplasty (MA-TKA). This paper aims to analyze the effects of KA and MA on the morphology of the distal femoral osteotomy surface. Methods: Computed tomography scans of 80 TKA candidates were reconstructed into 3D models. The measurement of bone morphology was performed after the distal femur cut according to two different alignment techniques. The aspect ratio, trapezoidicity ratio, and asymmetry ratio of the distal femur were assessed. Results: The aspect ratio and the asymmetry ratio in the KA group was significantly lower than that in the MA group in the general population (p < 0.001). The trapezoidicity ratio in the KA group was significantly higher than that in the MA group in the general population (p < 0.001). Conclusions: It was found that KA-TKA and MA-TKA presented different morphologies of the distal femoral osteotomy surface, and this difference was also influenced by gender. The surgery pattern of KA-TKA and MA-TKA and gender should be considered when surgeons choose femoral prostheses.

Assessment of the Bone Mineral Density and Microstructure of the Human Femoral Head according to Different Tip-apex Distances Can Guide the Treatment of Intertrochanteric Hip Fractures.

PURPOSE: We analyzed the microstructure and bone mineral density (BMD) of the trabecular bone in the femoral head of patients with osteoporosis. MATERIALS AND METHODS: Sixteen femoral heads with osteoporotic femoral neck fractures underwent micro-computed tomography scanning. In each tip-apex distance (TAD) of 15, 20, and 25 mm, five regions of interest (ROIs) were extracted from the central, anterior, posterior, superior, and inferior sections. A total of 15 ROIs were extracted from TADs of 15, 20, and 25 mm. The measurement parameters included BMD, percent bone volume: bone volume/total volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), structural model index (SMI), and degree of anisotropy (DOA). RESULTS: The lowest BMD and BV/TV values were observed in the inferior region and differed significantly from those in other regions (P<0.05). Lower Tb.Th and Tb.N values were observed in the inferior region compared with those in the central region (P<0.05). The highest SMI value was observed in the inferior region (P<0.05). With TAD of 15 and 20 mm, the DOA values in the inferior region were lower than those in the anterior region (P<0.05). Lower BMD and BV/TV values were observed in the anterior, central, and inferior regions of TAD of 15 mm compared with those in the corresponding regions of TAD of 25 mm (P<0.05). CONCLUSION: Positioning the lag screw between TAD of 20 to 25 mm and in the inferior region is recommended, and TAD of less than 15 mm is not recommended.

Kinematically Aligned TKA Aligns the Ankle Joint Line Closer to Those of the Native Ankle than Mechanically Aligned TKA in Bipedal Stance.

Mechanically aligned total knee arthroplasty (MATKA) aims to make alignment of the hip, knee, and ankle straight unexceptionally. However, emerging evidence suggests that unexceptional straightening the mechanical axis of the lower limb may lead to clinical and radiological problems of the ankle joint. By contrast, kinematically aligned total knee arthroplasty (KATKA) strives to restore the articular surface of the prearthritic knee. In this study, we examined results from KATKA and MATKA to determine which surgery restores the ankle joint orientation closer to the native ankle joint in bipedal stance and hypothesized that KATKA, rather than MATKA, would be more effective. Data from long-leg standing radiographs of 60 healthy adults (control group, n = 120 knees), patients who underwent MATKA (n = 90 knees), and patients who underwent KATKA (n = 90 knees) were retrospectively reviewed. The hip-knee-ankle angle, orientation of the tibial plafond and the talar dome relative to the ground (G-plafond and G-talus, respectively), and orientation of the plafond relative to the mechanical axis of the limb (M-plafond and M-talus, respectively) were measured and analyzed for comparison. Results show that bipedal stance alignment in patients who underwent KATKA (G-plafond: -0.65 ± 3.03 and G-talus: -1.72 ± 4.02) were not significantly different to native ankle joint alignment indicated by the control group. Compared with the native ankle joint measured in the control group (G-plafond: -0.76 ± 2.69 and G-talus: -1.30 ± 3.25), the tibial plafond and talar dome significantly tilted laterally relative to the ground in ankle joints after MATKA (G-plafond: -2.32 ± 3.30 and G-talus: -2.97 ± 3.98, p = 0.001 and p = 0.004, respectively). Thus, postoperative ankle joint line orientation after KATKA was horizontal to the floor and closer to that of native ankle joints than those after MATKA. The level of evidence is Level III.

Mechanical effect of different implant caput-collum-diaphyseal angles on the fracture surface after fixation of an unstable intertrochanteric fracture: A finite element analysis.

BACKGROUND/OBJECTIVE: The choice of implant is one of the most easily controllable factors affecting the outcome of intertrochanteric fractures. While most of the caput-collum-diaphysis (CCD) angles of the femur are within the range of 125° and 130°, there is a shortage of data on whether 125° or 130° implants are preferable. Thus, the present finite element analysis (FEA) aimed to compare the biomechanical effects on the fracture surface when using implants with different CCD angles where the anatomical CCD angle of the femur was between 125° and 130°. METHODS: After establishing a finite element model of an unstable intertrochanteric fracture from the femur with a native CCD angle of 127.3°, proximal femoral nail antirotation (PFNA) models with CCD angles of 125° and 130° were virtually implanted to have the same position of screw tip, respectively. RESULTS: In the one-leg stance during walking, when the implant with 130º CCD angle was used, the magnitude of compressive stress (1.61 and 2.12 MPa in the 130° and 125° model, respectively) was lower and the area of the fracture surface under tensile stress (55% and 5% in 130° and 125° model, respectively), the interfragmentary movements (40.9% more movement in 130° model), and the magnitude of bone deformation (23.5% more deformation in 130° model) were more than those of the 125° model. CONCLUSION: The intertrochanteric fracture fixed with PFNA with a 125º CCD angle revealed less interfragmentary movement on the fracture surface when the native CCD was an in-between angle in the FEA.

Morphological Patterns of Anterior Femoral Condylar Resection in Kinematically and Mechanically Aligned Total Knee Arthroplasty.

BACKGROUND: "Grand-piano sign" has been used as a popular benchmark to facilitate correct rotational alignment during total knee arthroplasty (TKA). The purpose was to quantitatively determine morphological patterns on anterior femoral resection in mechanically aligned (MA) and kinematically aligned (KA) TKA. METHODS: Computed tomography scans of 60 TKA candidates were reconstructed into 3D models. Femurs were virtually cut with a 3D imaging program using various anterior flange flexion angles (AFFAs) of 3°, 5°, and 7°. The anterior femoral resection was performed parallel to the surgical epicondylar axis, at an external rotation and internal rotation of 3° relative to surgical epicondylar axis for MA-TKA, and parallel to the cylindrical axis, at an external rotation and internal rotation of 3° to cylindrical axis for KA-TKA. The ratio of vertical distance from the anterior margin of distal femoral resection to the most proximal peak of each medial and lateral condyle of anterior femoral resection was defined as AC/BC ratio. RESULTS: The mean ratios of AC/BC were 0.57, 0.60, and 0.63 respectively, according to 3°, 5°, and 7° of AFFA with standard MA-TKA method and were 0.73, 0.74, and 0.76, respectively, according to 3°, 5°, and 7° of AFFA with standard KA-TKA method. The AC/BC ratios of malrotated planes were significantly different from those of both standard MA- and KA-TKAs (P-values < .01). CONCLUSION: Surgeons can accessorily use the quantifying method for anterior femoral resection intraoperatively to ensure correct rotational alignment of femoral resection in both mechanically and kinematically aligned TKA.