Patient-reported outcome after patient-specific unicondylar knee arthroplasty for unicompartmental knee osteoarthritis

Abstract

Background Unicondylar knee arthroplasty was introduced in the late 1960s and remains a topic of controversial discussion. Patient-specific instruments and patient-specific implants are not yet the standard of care. The question remains whether this time-consuming and costly technique can be beneficial for the patient. The aim of this study was to evaluate whether a custom-made unicondylar knee arthroplasty leads to improved patient-reported outcome. Methods This retrospective study evaluates the patient-reported outcome after custom-made unicondylar knee arthroplasty (CM-UKA, ConforMIS™ iUni® G2, ConforMIS Inc., Billerica, MA, USA). We evaluated 29 patients (31 knees) at an average of 2.4 years (range 1.2–3.6 years) after operation for unicondylar osteoarthritis of the knee. The target zone for the postoperative leg axis was a slight under-correction of 0–2° varus. Follow-up evaluation included the Forgotten Joint Score (FJS), the Knee Society Score (KSS), a Visual Analogue Scale (VAS) and a radiographic evaluation including a long-leg radiograph. Primary outcome measure was patient satisfaction based on the Forgotten Joint Score. Results We found an excellent postoperative health-related quality of life with a mean FJS of 76.8 (SD 17.9) indicating a low level of joint awareness after CM-UKA. The mean preoperative KSS was 66.0 (SD 13.71) and 59.4 (17.9) for the KSS function score. The increase was 22.8 points for the KSS knee score (p < 0.0001) and 34.8 points for the KSS function score (p < 0.0001). The VAS for pain decreased from a mean of 5.4 (SD 1.8) to 1.1 (SD 1.2) (p < 0.0001). The malalignment rate with a postoperative deviation of more than 2° in the leg axis was 29%. There was no evidence of component loosening after a mean follow-up of 2.4 years. Conclusions Custom-made unicondylar knee arthroplasty (CM-UKA) can provide improved clinical and functional outcomes for patients with isolated knee osteoarthritis of the medial compartment. We found excellent results regarding patient satisfaction and a low malalignment rate for CM-UKA. Further studies are needed to investigate long-term survivorship of the implant. Level of evidence Level IV. Trial registration Trial Registration number: Z-2014-0389-10 Regensburg Clinical Studies Center (REGCSC) 09/07/2014.

Insufficient evidence to confirm benefits of custom partial knee arthroplasty: a systematic review

“…Of the remaining 30 articles, 13 were not relevant [6, 11, 17, 19, 21, 23, 26, 28, 29, 37, 39, 40, 43], one was a review [41], and one an in‐vitro study [44], which were all excluded after reading their full texts. This left 15 articles that were eligible for data extraction, of which six were on custom UKA [2, 13, 16, 22, 27, 45], six on custom BKA [3, 7, 33, 36, 42, 49], and three on custom PFA [9, 12, 38] (Fig. 1).…”

“…One study [16] on custom UKA reported satisfaction rates of 88% “very satisfied”, 6% “satisfied”, and 6% “neutral” at 12–48 months (Table 3). Two studies on [33, 36] custom BKA reported satisfaction rates of 78–91% “satisfied”, 7–4% “neutral”, and 4–5% “dissatisfied” at 12–72 months A gait analysis study by Wang et al [49] revealed that, compared to OTS TKA, custom BKA enabled larger extensor moments at stance (0.63 versus 0.48 N m/kg, p < 0.05), greater peak extension torques (1.65 versus 1.37 N m/kg, p < 0.05), and larger internal knee rotation (6° versus 3°, p < 0.05).…”

“…Four studies on custom UKA [13, 16, 27, 45] reported coronal limb alignment ranged from 0.6° to 1.9° varus (Table 4). One study [16] reported 13% varus and 16% valgus outliers using a tolerance of ± 2° from neutral.…”

“…Four studies on custom UKA [13, 16, 27, 45] reported coronal limb alignment ranged from 0.6° to 1.9° varus (Table 4). One study [16] reported 13% varus and 16% valgus outliers using a tolerance of ± 2° from neutral. Two studies on custom BKA [3, 36] reported coronal limb alignment ranged from 2.5° valgus to 3.3°varus.…”

“…Anecdotal evidence suggests that, compared to OTS implants, custom implants results in less bone-implant mismatch and that 78-91% of patients are either satisied or very satisied after custom partial knee arthroplasty. [16] iUni® G2 (medial) 14-43 31 0 (0%) [45] iUni® (medial) 0-84 96 29 (25%) [2] iUni® (medial) min, 17 31 0 (0%) 2 (6%) [13] iUni® G1 (lateral) 24-53 33 1 (3%) 1 (3%) Miller-Galante Unicompartmental System 26-109 20 3 (15%) [22] iUni® (medial) BKA (n = 6) [36] iDuo® G2 (medial and lateral) 24-60 26 4 (15%) 1 (4%) [7] iDuo® G2 (medial and lateral) min, 24 73 6 (8%) 2 (3%) [33] n [49] iDuo® (medial and lateral) Persona® TKA Healthy controls [3] iDuo® (medial) [42] iDuo® G2 (medial) min, 12 44 3 (7%) 1 (2%) PFA (n = 3) [12] Custom Performa Knee min, 36 22 3 (14%) 1 (5%) [9] n.r. 2-54 28 9 (32%) 4 (14%) [38] n.r.…”