Comparison with Navigation of a Novel Three-Step Technique for Improving Accuracy of the Distal Femoral Resection during Conventional TKA: A Case-Control Study

Assessment and quantification of ipsilateral and contralateral ankle joint alignment changes after unilateral total knee arthroplasty for knee osteoarthritis with varus deformity: a retrospective cohort study

PURPOSE

The study's primary objective was to assess and quantify the ipsilateral (side A) and contralateral (side B) ankle joint line orientation (AJLO) changes after unilateral total knee arthroplasty (TKA) for primary knee osteoarthritis (OA) with varus deformity. The secondary objectives were to detect if there was a correlation between the knee deformity correction and AJLO changes and if the knee and ankle clinical outcomes on the TKA side correlate with joint alignment changes.

METHODS

This retrospective cohort study included 70 patients with a mean age of 61.76 ± 5.96 years. The lower limb alignment was evaluated using the hip-knee-ankle (HKA) angle, while the AJLO was assessed using the tibial plafond to horizontal line angle (TPHA). The functional outcomes for side A were evaluated at a median follow-up of 18 (interquartile range (IQR): 12-46.2) months using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and The American Orthopaedic Foot and Ankle Society (AOFAS) score for the knee and ankle joints, respectively.

RESULTS

In side A, the HKA significantly improved from 167.49 ± 6.25 to 177.08 ± 4.39 (p < 0.001). No difference in AJLO was found between both sides preoperatively (p = 0.329). At the last follow-up, in side A, the AJLO changed significantly into less varus from -7.11 ± 5.44° to -1.10 ± 4.91° (p < 0.001); in side B, the AJLO showed no significant changes (-6.38 ± 6.10° versus -6.65 ± 6.50°, p = 0.970). For side A, the KOOS and AOFAS showed significant improvement, 45.20 ± 14.94 versus 75.72 ± 13.28 (p < 0.001) and 70 (65-75) versus 90 (80-90; p < 0.001), respectively. The preoperative HKA and AJLO on side A and side B showed significant positive correlations (r = 0.591, p < 0.001 and r = 0.611, p < 0.001, respectively). On side A, the postoperative HKA and AJLO showed a significant positive correlation (r = 0.298, p = 0.012). The preoperative and postoperative AJLO and AOFAS on side A showed nonsignificant negative correlations (r = -0.202, p = 0.277 and r = -0.115, p = 0.537, respectively). The preoperative and postoperative HKA and AOFAS on side A showed nonsignificant positive correlations (r = 0.126, p = 0.499 and r = 0.331, p = 0.069, respectively). The linear regression analysis indicated that for every 1° correction in HKA, the AJLO changed by 0.5° (R2 = 0.241, 95% confidence interval (CI) 0.298-0.747, p < 0.001).

CONCLUSIONS

The ipsilateral ankle joint realigned to a less varus position after ipsilateral TKA for managing knee OA with varus deformity, with an estimated half a degree of less varus AJLO after HKA correction by a degree. No changes occurred in the contralateral ankle joint. The ankle joint function improvement was not correlated to the HKA or AJLO changes.

Valgus arthritic knees can be classified into nine phenotypes

PURPOSE

It is not shown whether anatomical variations exist in valgus arthritic limbs as to support individualized component and limb alignment. The null hypothesis was that there was no phenotypic variation of coronal femoro-tibial morphology in valgus knees. The aim was to determine whether distinct phenotypes of valgus knees could be identified to help surgical planning and classifying valgus knees for outcome studies.

METHODS

Full-leg weight-bearing radiographs of 233 knees (182 preoperative; 51 of contralateral arthritic knee) were measured for HKA (hip-knee-ankle angle), VCA (valgus correction angle), mLDFA (lateral mechanical distal femoral angle), aLDFA (lateral anatomical distal femoral angle), MPTA (medial proximal tibial angle), MNSA (medial neck shaft angle), TAMA (angle between tibial mechanical and anatomical axes), and TBA (tibial bowing angle).

RESULTS

Nine phenotypes were identified encompassing all 233 knees which could be clubbed into 4 broad types. Type 1 Neutral knees (12.5%) had almost normal values (mean VCA 5.3°, mLDFA 86.9°, aLDFA 81.1°). Type 2 'Intra-articular valgus' (22.7%) showed lateral compartment bone loss (mean mLDFA 83.9°; MPTA 90.2°). Type 3 'Extra-articular valgus' (35.2%) had extra-articular deformity: 3a showed valgus femoral bowing (mean VCA 2.7°); 3b valgus tibial bowing; 3c showed valgus tibial bowing with lateral femoral condyle wear (mean mLDFA 84.3°). Type 4 'Varus' type (29.6%) had features of varus knees: 4a had varus femoral bowing (VCA 8.3°); distal femur in 4b was akin to varus knees (mean mLDFA 89.3°) with lateral tibial bone loss (mean MPTA 91.2°). 4c had varus tibial bowing and deficient lateral femoral condyle (mLDFA 83.7°). 4d had varus tibial bowing and lateral tibial bone loss (mean MPTA 89.8°).

CONCLUSIONS

The study identified four broad groups of valgus arthritic knees with nine phenotypes based on coronal plane variations in femoro-tibial morphology. This study may be of value in planning and performing corrective osteotomies, and planning the optimal position of femoral and tibial components in unicompartmental and total knee arthroplasty. The classification presented in this study may aid in categorizing valgus knees for outcome studies.

LEVEL OF EVIDENCE

IV.