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

Restricted kinematically aligned total knee arthroplasty with an anatomically designed implant can restore constitutional coronal lower limb alignment

PURPOSE

Restricted kinematically aligned total knee arthroplasty (rKA-TKA) may not restore the constitutional varus alignment in most patients with knee osteoarthritis. This study aimed to investigate (1) the extent to which constitutional lower limb alignment can be restored by rKA-TKA using an anatomically designed implant and (2) which lower limb alignment parameters are associated with patient-reported outcome measures (PROMs).

METHODS

This study included 60 patients who underwent rKA-TKA using an anatomically designed implant. Radiographic alignment parameters, including mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), coronal hip-knee-ankle angle (HKA), coronal joint line obliquity (JLO), posterior tibial slope (PTS), single-leg standing knee flexion angle (KFA), sagittal JLO, and arithmetic HKA (aHKA), were evaluated preoperatively and postoperatively. The Western Ontario and McMaster Universities Arthritis Index (WOMAC) was used for clinical evaluation.

RESULTS

The mLDFA, MPTA, and aHKA showed no significant differences before and after surgery. Coronal HKA and PTS have significantly changed from 8.1 ± 8.7° and 9.9 ± 8.6° preoperatively to 3.5 ± 3.1° and 2.5 ± 2.0° postoperatively, respectively (p < 0.001 for each comparison). The postoperative WOMAC total score was significantly correlated with the KFA (r = 0.4063, p = 0.0034) and sagittal JLO (r = -0.3435, p = 0.0157). Postoperative KFA is a causal factor for the increased postoperative WOMAC total score (r = 1.416, 95% confidence interval: 0.491-2.342, p = 0.003).

CONCLUSION

rKA-TKA using an anatomically designed implant can restore constitutional coronal lower limb alignment, while postoperative KFA and sagittal JLO were associated with poor PROMs. Care should be taken for the postoperative KFA because it is a risk factor for poor PROMs.

LEVEL OF EVIDENCE

Level III, case-control study.

Constitutional alignment predicts medial ligament balancing in mechanically aligned total knee arthroplasty for varus knees

PURPOSE

The aim of this study was to identify if constitutional alignment and preoperative radiologic parameters determined whether medial gap balancing was required in mechanically aligned total knee arthroplasty (TKA).

METHODS

Two hundred and sixty three patients with 394 consecutive knees who underwent primary TKAs were retrospectively analysed in this study. Selective sequential multiple needle puncturing (MNP) was performed for medial ligament balancing when required. Constitutional alignment, which was determined using the Coronal Plane Alignment of the Knee (CPAK) classification, as well as preoperative and postoperative radiologic parameters was evaluated to identify factors which predicted the need for MNP.

RESULTS

One hundred and fifty eight (40.1%) knees required medial ligament balancing with MNP. Patients who required MNP during surgery had significantly more constitutional varus, more varus preoperative mechanical Hip-Knee-Ankle angle (mHKA), smaller preoperative medial proximal tibial angle (MPTA) and a larger change in mHKA and MPTA after surgery than those who did not. Patients with constitutional varus also had a higher incidence of having had MNP to both anterior and posterior superficial medial collateral ligament (sMCL) fibres. There was no significant difference in preoperative lateral distal femoral angle (LDFA), posterior tibial slope (PTS) and varus-valgus difference (VVD) between groups.

CONCLUSION

Ligament balancing using MNP was determined by constitutional alignment rather than medial soft tissue contracture. Patients with constitutional varus who had a larger medio-lateral gap difference in extension also had a higher incidence of having had MNP to both anterior and posterior sMCL fibres.

LEVEL OF EVIDENCE

Retrospective comparative study, level IV.

A Comparative Study of Clinical Outcomes Between Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty: A Propensity Score-Matched Cohort Study

INTRODUCTION

We investigated a comparison of clinical outcomes between cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty. However, it is still controversial which design leads to better clinical results. In clinical settings, choosing either CR or PS is likely based on the surgeon's preferences. In this study, short-term clinical outcomes between CR and PS in patients who received a single knee prosthesis were compared using propensity score matching.

METHODS

Two hundred and twelve CR and 43 PS of a single knee prosthesis were enrolled in this study. After propensity score matching, 34 knees each in the CR and PS groups were chosen and were without significant differences in age at operation, gender, BMI, preoperative range of motion (ROM), preoperative femorotibial angle (FTA), and presence or absence of patellar replacement. Clinical scores, including ROM, Knee Society score (KSS), knee injury and osteoarthritis outcome score (KOOS), except for the sports subscale, were compared between the CR and PS groups preoperatively and two years postoperatively.

RESULTS

Postoperatively, there were no significant differences in FTA, ROM, or KSS. Preoperative scores for the KOOS except for the pain subscale were comparable between the groups. Postoperatively, however, the PS group had a significantly higher score in the ADL subscale compared to the CR group (PS: 89.5 vs. CR: 80.8, p = 0.017). The KOOS subscales other than activities of daily living (ADL) were comparable between the groups.

CONCLUSIONS

In this propensity score-matched cohort study, PS showed a better outcome for the ADL than the CR design. These findings suggest that choosing either CR or PS should not depend on the surgeon's preferences. A PS design may be preferable to CR for elderly patients.