The effect of gender, age, BMI and Kellgren-Lawrence grade on functional outcome after Physica ZUK medial unicompartmental knee replacement.

PURPOSE: Several factors influence the outcome of unicompartmental knee replacements. This study investigates the correlation of specific preoperative patient variables with postoperative functional outcomes-measured with the American Knee Society Knee (KS-KS) and Function Scores (KS-FS), as well as the difference in knee flexion pre- and postoperatively. METHODS: In a retrospective study of 242 patients who underwent a medial Physica ZUK unicompartmental knee replacement (UKR), the American KS-KS, KS-FS as well as knee flexion were analyzed preoperatively and at 2-year follow-up. The absolute scores and improvement in scores were calculated per subgroup for gender, age, body mass index (BMI) and Kellgren-Lawrence (KL) radiological grade and compared between the subgroups. RESULTS: All groups had a significant improvement in range of flexion, KS-KS and KS-FS. Female patients had lower preoperative scores and significantly larger improvement in knee flexion and KS-FS. Age does not seem to be associated with the postoperative functional outcome. Patients with a BMI of 30 or higher had a lower postoperative KS-KS and KS-FS as well as knee flexion. Patients with KL grade IV changes had larger gain in KS-KS compared to patients with grade III. CONCLUSION: Overall, KS-KS, KS-FS and knee flexion improve significantly 2 years following a Physica ZUK UKR in all groups. Although excellent results were found in patients with a BMI of 30 or higher, a decrease in BMI was associated with an increase in functional outcome. KL IV grade preoperatively was associated with a better KS-KS improvement compared to the KL III group 2 years postoperatively. This information can aid surgeons in patient selection and to counsel patients on outcomes. EVIDENCE LEVEL: III.

3D, Weightbearing Topographical Study of Periprosthetic Cysts and Alignment in Total Ankle Replacement.

BACKGROUND: We investigated the association between hindfoot residual malalignment assessed on weightbearing computed tomography (WBCT) images and the development of periprosthetic cysts (PPCs) after total ankle replacement (TAR). We hypothesized that PPCs would be found predominantly medially in the varus configuration and laterally in the valgus configuration. METHODS: Cases of primary TAR with available WBCT imaging of the ankle were included in this retrospective study. The location of the PPC was marked and the following volumes were calculated: total (TCV), medial (MCV), central (CCV), and lateral (LCV) cyst volumes. Hindfoot alignment was measured as Foot and Ankle Offset (FAO), with 95% confidence intervals (95% CIs) calculated to define varus (<95% CI) and valgus (>95% CI) groups. Cyst volumes were compared between these 2 groups. The American Orthopaedic Foot & Ankle Society (AOFAS) score at the time of the WBCT was also retrieved. Receiver operating characteristic (ROC) curves were used to determine FAO thresholds for predicting an increased risk of PPC. RESULTS: Forty-eight TARs (mean follow-up, 44.6 months) were included, 81% of which had at least 1 PPC. The mean FAO was 0.12% (95% CI, -1.12 to 1.36). Patients with greater residual malalignment (P < .001) and those with longer follow-up (P < .001) presented with increased TCV. In varus cases, the MCV was greater than the LCV (P = .042), with a threshold FAO value of -2.75% or less predicting an increased MCV. In valgus cases, the LCV was greater than the MCV (P = .049), with a FAO threshold value of 4.5% or more predicting an increased LCV. CONCLUSION: In this series, the PPC volume after primary TAR significantly correlated with postoperative hindfoot malalignment and longer follow-up. LEVEL OF EVIDENCE: Level III, retrospective comparative series.