CT measures of femoral and tibial version and rotational position of femoral and tibial components of knee replacements: limitations in reliability and suitability for routine clinical practice

Preoperative patellar bone marrow lesions with full thickness cartilage defects correlate with residual anterior knee pain in total knee arthroplasty without patellar resurfacing

PURPOSE

Residual anterior knee pain is one of the most common problems after total knee arthroplasty (TKA). However, the contributing factors affecting postoperative anterior knee pain (AKP) remain poorly understood. This study aimed to evaluate the effect of preoperative patellar bone marrow lesions (BMLs) and patellar cartilage defects on postoperative AKP after patellar non-resurfacing TKA.

METHODS

This retrospective study included 336 patients who underwent unilateral TKA without patella resurfacing. All patients underwent preoperative magnetic resonance imaging (MRI) to assess the presence of BMLs and the degree of cartilage defects in the patella. Patients were categorized into four groups according to the presence of BMLs (with or without BMLs) and the degree of cartilage defects (with or without full thickness cartilage defects). The Kujala Anterior Knee Pain Scale (AKPS) and the Hospital for Special Surgery Knee Rating Scale (HSS) scores at 2 years after TKA were compared among the groups.

RESULTS

Preoperative BMLs in the patella were found in 132 (39.3%) of 336 cases. Among the four groups, the group with both BMLs and full-thickness cartilage defects demonstrated significantly lower AKPS compared to the other groups at 2 years after TKA (p < 0.01), but no significant difference was shown in the HSS scores, between these groups. There were no significant differences in either AKPS or HSS scores among the other three patient groups.

CONCLUSIONS

The presence of preoperative BMLs with full-thickness cartilage defects in the patella was associated with worse postoperative AKP after TKA without patella resurfacing. Patella resurfacing should be considered in this patient group to minimize the risk of developing residual AKP after TKA.

LEVEL OF EVIDENCE

III.

3-dimensional computer tomography is more accurate than traditional long-leg radiographs in the planning and evaluation of coronal alignment in total knee arthroplasty: a prospective study on 121 knees

BACKGROUND AND PURPOSE

Accurate measuring tools are essential in preoperative planning and for the study of the association between postoperative alignment and clinical outcome in total knee arthroplasty (TKA). We aimed to describe a simple method to measure preoperative hip-knee-femoral shaft (HKFS) angle and postoperative coronal alignment in TKA with the use of standard 3D CT and to compare preoperative HKFS angles and postoperative coronal alignment measured with the 3D CT technique and with standing long-leg hip-knee-ankle (HKA) radiographs.

PATIENTS AND METHODS

HKA radiographs and 3D CT were taken preoperatively and 3 months after the operation in 121 knees. The interrater reliability for the 3D CT method was calculated with intra-class correlation coefficient (ICC). The preoperative HKFS angles and the postoperative deformity measured with the 2 methods were compared and illustrated on Bland-Altman plots, frequency tables, and by Cohen's kappa coefficients (k).

RESULTS

The 3D CT method was feasible in all knees and the ICC was excellent. Mean (SD, range) difference in HKFS angle measured on HKA radiographs and on 3D CT was -0.3° (0.9°, -4.1° to 2.4°). Mean (SD, range) difference in postoperative deformity was 0.1° (1.6°, -5° to 6°). The 95% limits of agreement were 1.4° and -2° for HKFS and ±3° for postoperative alignment. The agreement in outlier (≥ 3°) identification was moderate with a k (95% confidence interval) of 0.48 (0.32-0.64).

CONCLUSION

3-dimensional computer tomography was feasible and was shown to be more accurate than traditional long-leg radiographs.

Self-aligned Technique for Tibial Component Placement in Total Knee Arthroplasty Lessening Rotational Malalignment in Measured Resection and Gap-Balancing Techniques

Background

Femorotibial rotational mismatch can occur when there is a rotational malalignment in either the tibial or femoral component. Self-aligned technique was proposed for orienting the tibial component in relation to the femoral prosthesis to reduce rotational malalignment between components. Therefore, we aimed to compare the rotational angle of the femoral and tibial components, as well as the femorotibial rotational mismatch, between the measured resection (MR) and gap-balancing (GB) techniques when combined with a self-aligned technique.

Methods

We conducted a nonrandomized, experimental study with 50 patients in each group. The femoral rotation was set to 3° external rotation relative to the posterior condylar axis in the MR group, whereas the femur was resected to obtain an optimal rectangular flexion gap in the GB group. The self-aligned method was used to set the tibial rotation in both groups. Femoral and tibial rotational alignments were evaluated compared to a surgical transepicondylar axis of the femur using computed tomography. Rotational mismatch was defined as a difference between the femoral and tibial rotational alignments. A positive value indicated that the component was externally rotated relative to the reference line.

Results

The femoral component of the GB group was more externally rotated than that of the MR group (1.52° ± 1.31° vs 0.28° ± 1.16°, p < 0.001). However, the tibial rotational angle was not statistically significantly different between the MR and GB groups (1.28° ± 3.17° vs. 1.86° ± 2.81°, p = 0.220), and the rotational mismatch was 1.00° ± 3.28° and 0.34° ± 2.71°, respectively (p = 0.306).

Conclusions

Although the femoral component of the GB group had a greater degree of external rotation than that of the MR group, the use of a self-aligned technique for tibial component placement resulted in no significant difference in tibial rotational alignment or rotational mismatch. This technique helps align the tibial component with the femoral component and lessen the degree of rotational malalignment in both the MR and GB techniques.