Purpose Robotic arm-assisted unicompartmental knee arthroplasty (RA-UKA) has been shown to improve component placement, reduce intraoperative variability, increase patient satisfaction and improve short-term survivorship results. The aim of this retrospective study was to determine the incidence of revision and the clinical performance at a minimum of 5-year follow-up for a cohort of patients who received a medial RA-UKA. Methods Between April 2011 and July 2013, a total of 254 patients underwent medial RA-UKA at a single centre. Clinical performance was investigated using the Forgotten Joint Score-12 (FJS-12) and a 5-level Likert scale made of five items to assess joint perception and patient satisfaction. Kaplan-Meier implant survivorship was calculated and reasons for revision were collected. The effect of age, gender and body mass index (BMI) on the probability of reporting high FJS-12 and satisfaction were assessed. Results After considering exclusion criteria and loss to follow-up, a total of 216 patients (224 medial RA-UKAs) were assessed at a mean 5.9 years of follow-up. Five RA-UKAs underwent implant revision, resulting in an overall Kaplan-Meier survivorship of 97.8%. Unexplained knee pain (0.9%) was the most common reason for RA-UKA revision. Good-to-excellent FJS-12 scores and high satisfaction levels were reported at mid-term follow-up. Male patients had higher probability of having FJS-12 > 90 (p < 0.05) and high satisfaction levels (p < 0.05). Conclusions RA-UKAs demonstrated high survivorship and good-to-excellent patient-reported outcome measures and satisfaction levels at minimum 5-year follow-up. Results for male patients had improved clinical performance when compared to female subjects. Level of evidence IV.

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PurposeTo investigate the femoral component alignment in patients undergoing soft tissue‐guided, navigated total knee arthroplasty (TKA). It was hypothesized that with a mechanically aligned tibial component, the soft tissues tensioned and symmetric medial and lateral gaps in flexion/extension, the femoral component would be aligned to the preoperative distal femoral joint line, as measured on knee radiographs. MethodsBetween 2015 and 2017, 77 patients (78 knees) underwent navigated soft tissue‐guided TKA at a single centre. Pre and postoperative radiographs were collected and varus knees were taken into account. The tibial cut was performed with navigation in neutral alignment. The femoral cuts were adjusted based on tensioned soft tissues, aiming for equal medial and lateral gaps in flexion and extension. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and Knee Society Score (KSS) were collected pre and postoperatively as a secondary outcome measure. ResultsA total of 58 TKAs on varus knees were assessed. On average, the femoral component was placed at 1.7° (SD 1.7) varus in the coronal plane. The comparison between the radiographic native distal femoral alignment and the orientation of the femoral component coronal cut demonstrated a statistically significant (p < 0.0001), linear inverse relationship (r = 0.5). Satisfactory knee function and excellent pain remission were demonstrated by KOOS and KSS scores at a mean of 2.8 years (SD 0.5) follow‐up. One TKA was revised, resulting in a 98.3% survivorship at three years. ConclusionThe proposed soft tissue‐guided, navigated technique, aiming to preserve the integrity of the ligaments and a neutrally aligned tibial cut, provided a joint line respecting femoral coronal cut and encouraging short‐term clinical results. Level of evidenceIII.

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