Distal femoral phenotypes in Asian varus osteoarthritic knees

Femoral and tibial phenotypes of varus alignment in a Southeast Asian arthritic population: a descriptive study

INTRODUCTION

Knowledge of femoral and tibial morphology is important for patient-specific surgery in both joint reconstruction and preservation procedures. Studies evaluating morphological variance in femoral and tibial alignments in Asian populations are scarce. This is the first descriptive study evaluating the femoral and tibial phenotypes of varus alignment in a Southeast Asian population.

METHODS

Long-leg coronal standing radiographs of 2021 limbs were obtained, and the hip-knee-ankle angle, mechanical lateral distal femoral angle, medial proximal tibial angle and joint line convergence angle were measured. Joint line obliquity was calculated, and the knees were classified according to the Coronal Plane Alignment of Knee (CPAK) classification. Descriptive analyses on alignment parameters and demographic data (age, gender, ethnicity and body mass index [BMI]) were performed and entered into a linear regression model.

RESULTS

The highest frequency of limb alignment in the population was found to be CPAK type I (52.71%, n = 1003). Tibial varus was the largest contributor of varus malignment. Of the varus knees (n = 1247), varus deformity was found solely in the tibia (68.60%), solely in the femur (2.07%) and was contributed by both the femur and the tibia (4.97%). In the linear regression model, BMI was found to be a strong determinant for femoral varus (P = 0.004) and joint line incongruence (P < 0.001).

CONCLUSION

The findings of this study will be important to surgeons during planning for joint preservation procedures (such as corrective osteotomies) and joint arthroplasties to restore alignment.

How Do the Morphological Abnormalities of Femoral Head and Neck, Femoral Shaft and Femoral Condyle Affect the Occurrence and Development of Medial Knee Osteoarthritis

OBJECTIVE

At present, the main viewpoint is that tibial varus is the main reason of medial knee osteoarthritis (OA), and high tibial osteotomy (HTO) is also the main alignment correction method to correct medial knee OA. In contrast, the impact of the anatomical alignment of the femur on medial knee OA is often overlooked. We evaluated the increased risk for medial knee OA because a varus alignment could be attributed to the anatomical reasons that include hip anatomy, femoral shaft bowing (FSB) and femoral condylar dysplasia.

METHODS

The present research adopted a cross-sectional study method. We selected 62 patients with HTO in the Third Hospital of Hebei Medical University from June 2021 to March 2022 as the HTO group and 55 healthy volunteers as the control group. Femoral neck-shaft angle (NSA), lateral FSB, mechanical lateral distal femoral angle (mLDFA) and hip-knee-ankle (HKA) was radiographically examined within the two groups. The femoral neck length and offset were also measured, and the ratio is represented by the ratio of the femoral neck length to off-set (N/O). The 2-tailed Student t-test was used to compare the differences between groups when the data were in accordance with a normal distribution. Otherwise, the Mann-Whitney U tests was used to compare the differences between groups.

RESULT

Compared to the control group, the HTO group had a higher offset (p < 0.05), greater femoral neck length (p < 0.05), and decreased (more varus) NSA (p < 0.05). The HKA in the HTO group was 172.20 ° (3.50°), which was significantly lower than that of the control group 177.00° (3.05°), (p < 0.001), while the medial OA was associated with more varus HKA. The mean mLDFA was 89.10 ° (2.35°) and 87.50° (2.85°) in the HTO and control groups (p < 0.005), respectively. The mean lateral FSB values of the full-length radiographs were larger (p < 0.001) in the HTO group (4.24° ± 3.25°) than that in control group (1.16° ± 2.32°).

CONCLUSION

The reduction of NSA (coxa vara) and the increase of the mLDFA can lead to medial knee OA, while the lateral FSB also affects medial OA. We believe that femoral deformity is also one of the cause of the medial knee OA. Therefore, it is necessary to evaluate the joint deformity of the femur and tibia before surgery in order to determine whether to use HTO alone to correct the lower limb alignment.

Comparison of both lower leg bone mineral density in single limb knee osteoarthritis patients

PURPOSE

The relationship between knee osteoarthritis (OA), bone mineral density (BMD), and alignment has not yet been clarified. This study aimed to investigate the relationship between the two limbs in patients with single-limb knee OA.

METHODS

Patients who underwent single-limb total knee arthroplasty between March 2019 and February 2021 were retrospectively analyzed. Only patients with Kellgren-Lawrence (KL) grades III and IV on the operated side and KL I and II on the opposite side were included. Patients with traumatic OA, a surgery that could change the alignment of both lower extremities and previous fractures were excluded. The proximal femur BMD on the OA and non-OA sides were compared. In addition, the difference in BMD was compared between a group with a difference in alignment of both lower extremities (> 5°) and a group without a difference (< 5°).

RESULTS

In total, 149 patients were included. The BMD T-score of the femoral neck on the OA side was lower than that of the non-OA side (p < 0.001). There was no correlation between BMD and alignment, and there was no difference in BMD according to the difference in alignment.

CONCLUSION

The femoral neck BMD of the leg on the side with knee OA was lower than that on the side without OA. However, the alignment difference between the legs did not affect BMD. BMD was lowered because of OA and not because of alignment.

Kinematically Aligned Oxford Unicompartmental Knee Arthroplasty Using the Microplasty Instrumentation System

This technical note demonstrates kinematically aligned Oxford unicompartmental knee arthroplasty using the Microplasty instrumentation system with custom-made devices. The medial joint line is evaluated preoperatively; if it is aligned and parallel with the lateral joint line, they are considered to comprise the coronal knee joint line (CJL). In this case, the coronal inclination of a spoon gauge inserted into the medial joint space indicates the CJL. Otherwise, an accessory spoon is inserted and connected to the medial spoon to refer to the posterior condylar line, which is considered the CJL. The tibial cutting block is then connected without changing the inclination of the spoon and the coronal tilt of the tibial extramedullary rod is adjusted, which is implemented with a custom-made ankle yoke. The remainder of the steps is then identical to the conventional Microplasty procedure. This technique can imitate the cutting line to the CJL, which might be considered ideal from mechanical and kinematic perspectives.

The impact of postoperative inclination of the joint line on clinical outcomes in total knee arthroplasty using a prosthesis with anatomical geometry

The goal of this study was to investigate the impact of postoperative inclination of the joint line on clinical results after total knee arthroplasty (TKA) using a prosthesis with anatomical geometry. This study included 145 primary cruciate-retaining type of knee prosthesis with anatomical geometry. Three years postoperatively, clinical outcomes including the patient-reported outcomes (PROs) were recorded. Limb alignment was evaluated by the hip-knee-ankle (HKA) axis and inclination of the joint line was assessed by the joint line orientation angle (JLOA). Knees were divided into two groups according to the HKA: in-range (- 3 to 3°) and outlier group (< - 3° or > 3°) or the JLOA: in-range (2-4°) and outlier group (< 2° or > 4°), and clinical outcomes were compared between the groups. Postoperative Knee Society Function Score (KS-FS) was significantly higher in the HKA in-range group than the outlier group (p = 0.01). The Knee Society Knee Score and all subscales of the Knee injury Osteoarthritis Outcome Score were comparable between the groups. A multivariate analysis revealed a significant association between age at operation and postoperative KS-FS > of 80 points. Neither HKA in-range nor JLOA in-range were associated with the higher knee function. In conclusion, TKA-postoperative inclination of the joint line was not relevant to the short-term PROs. Treatment strategies that attempt to make joint line inclination in order to improve postoperative PROs should be avoided, and alignment goals such as kinematic alignment should be considered carefully.

Effects of Severe Varus Deformity on Soft Tissue Balancing in Total Knee Arthroplasty

This study aimed to establish the effect of severe varus deformity on soft tissue balance in total knee arthroplasty (TKA), which is not yet well established. We retrospectively enrolled 205 patients (270 knees) who underwent primary TKA using the measured resection technique. Four intraoperatively measured TKA gaps and gap differences were compared between the severe varus deformity group (Hip-knee-ankle [HKA] varus angle ≥ 10°) and the mild varus deformity group (HKA varus angle < 10°). Pearson’s correlation analysis and multiple linear regression analysis were used to investigate the factors affecting flexion and extension gap differences (FGD and EGD). A receiver operating characteristic curve was applied to assess the cut-off value of the HKA varus angle to discriminate the rectangular gap. The FGD (1.42 ± 1.35 mm vs. 1.05 ± 1.16 mm, p = 0.019) and the EGD (1.45 ± 1.32 mm vs. 0.97 ± 1.53 mm, p = 0.006) were significantly larger in severe varus deformity group than in mild varus deformity group. The HKA varus angle was positively correlated with both FGD (r = 0.264, p < 0.001) and EGD (r = 0.319, p < 0.001) and was an influencing factor for FGD (β = 0.232, p = 0.040) and EGD (β = 0.229, p = 0.037). A preoperative HKA angle of 12.4° was selected as the cutoff value to discriminate between rectangular and trapezoidal gaps. Thus, the severity of varus deformity (HKA varus angle) was found to be a significant factor affecting the mediolateral gap difference in TKA. When performing TKA in a knee with an HKA varus angle ≥ 12.4°, a trapezoidal gap is more likely to be expected. Level of evidence III, case−control study.

Coronal plane femoral bowing in Far East Asians: implications for the strategy of distal femoral resection in total knee arthroplasty

Background

The accuracy of distal femoral resection in intramedullary (IM) guided total knee arthroplasty (TKA) depends on femoral morphology and varies according to individual anatomy. This study aimed to characterise coronal plane femoral bowing in Far East Asians according to age, sex, and severity of varus deformity to identify optimal strategies for distal femoral resection in TKA.

Method

Femoral anatomical parameters in 656 patients (M/F = 232:424) were assessed using standing long-leg anteroposterior radiography which was fulfilling strict standard. The femur was divided into three longitudinal segments to measure the segmental anatomical axial deviation from the mechanical axis and intersegmental bowing. Coronal plane femoral bowing pattern was categorised based on combined gross bowing and distal bowing.

Results

Mean hip–knee–ankle angle; neck–shaft angle; proximal, middle, and distal segmental axial differences; mechanical lateral distal femoral angle; and femur length were 6.7 ± 6.8°, 125.0 ± 5.5°, 5.9 ± 1.7°, 6.1 ± 1.1°, 5.3 ± 1.6°, 88.4 ± 2.6°, and 432.3 ± 23.9 mm in male and 8.4 ± 5.5°, 126.4 ± 5.6°, 5.4 ± 1.5°, 6.6 ± 0.9°, 5.6 ± 1.6°, 89.3 ± 2.6°, and 410.6 ± 23.3 mm in female, respectively. Mean proximal, distal, and gross femoral bowing was 0.3 ± 1.8°, − 0.8 ± 1.8°, and − 0.5 ± 2.9° in male and 1.2 ± 1.6°, − 1.0 ± 1.6°, and 0.2 ± 2.7° in female, respectively.

Conclusions

Grossly straight femur with a straight distal part was the most common femoral bowing pattern in Far East Asians. Distal bowing was proved to be a key factor to choose method for distal femoral resection in TKA. Using IM-guide to achieve accurate distal femoral resection in the femora with distal segmental axial deviation between 4–8° and distal bowing less than ± 1° is considered feasible.

Deformity analysis of the lower limb on the coronal plane in patients with rheumatoid arthritis and osteoarthritis

OBJECTIVES

To evaluate joint orientation angles of the coronal plane in patients with rheumatoid arthritis (RA) in comparison with osteoarthritis (OA).

METHODS

In total, 72 patients with RA (90 knees) and 76 patients with OA (90 knees) who underwent total knee arthroplasty were enrolled. The hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and joint line convergence angle (JLCA) were measured on preoperative long-leg radiographs in the standing position. Student's t-test was used to assess differences in radiographic data between patients with RA and OA.

RESULTS

In knees with RA and OA, the mean HKA was -3.4 ± 9.4° and -10.6 ± 8.0°, the mean mLDFA was 86.6 ± 3.7° and 88.2 ± 2.7°, the mean mMPTA was 85.9 ± 4.0° and 84.3 ± 3.7°, and the mean JLCA was 2.7 ± 4.2° and 6.8 ± 4.1°. All parameters in the knees with RA were more valgus than those with OA.

CONCLUSIONS

Knees with RA had a great variability in joint orientation angles on the coronal plane; the whole lower limb alignment and the femur, tibia, and joint were more valgus in knees with RA than with OA.