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Background: There is currently a lack of evidence to identify the optimal patellar implant design in total knee arthroplasty (TKA). The aim of this study was to assess clinical, intraoperative, radiographic, and scintigraphic differences between inlay (IN), onlay round (OR), and onlay oval (OO) patellar implants. Methods: A parallel-group, double-blinded, randomized trial compared IN, OR, and OO patellar implants using the same posterior-stabilized TKA prosthesis for each. Patient outcomes were prospectively followed for a minimum of 2 years, with survivorship outcomes followed for a mean of 5 years. The primary outcome was the between-group differences in the mean Kujala score change from preoperatively to 2 years postoperatively. The secondary outcomes included differences in other knee-specific and general health outcomes, intraoperative characteristics, radiographic parameters, patellar vascularity, and implant survivorship. Results: A total of 121 participants (40 in the IN group, 41 in OR group, 40 in the OO group) were allocated to 1 of 3 implant designs. At 2 years postoperatively, there were no significant differences in Kujala score changes between groups (p = 0.7; Kruskal-Wallis test). Compared with the IN group, the OR group showed greater improvements in Knee injury and Osteoarthritis Outcome Score (KOOS) Activities of Daily Living and in KOOS Quality of Life compared with the OO group. However, the OO design exhibited better bone coverage and lower lateral facetectomy rates compared with the IN and OR designs. The IN group had more lateral contact compared with the OO group (p = 0.02; Fisher exact test), but the overall value for lateral contact was not significant (p = 0.09; chi-square test). There were no differences in postoperative scintigraphic vascularity (p = 0.8; chi-square test). There was 1 revision for infection at 3 years postoperatively in the OO group, and no revision in the other groups. Conclusions: Patellar design did not influence patellofemoral outcomes or survivorship. However, OR implants showed improvements in some secondary patient-reported outcome measures, and OO implants exhibited superior bone coverage and improvements in several intraoperative, radiographic, and scintigraphic outcomes. These findings, combined with superior long-term implant survivorship from previous studies, add support for the use of onlay designs in TKA. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]

Background: The accuracy of surgeon-defined assessment (SDA) of soft tissue balance in total knee arthroplasty (TKA) is poorly understood despite balance being considered a significant determinant of surgical success. The study's hypothesis was that intra-operative SDA is a poor predictor of coronal balance in TKA. Methods: A prospective, multicenter study assessing accuracy of SDA of balance was conducted in 250 patients (285 TKAs). Eight surgeons and thirteen trainees participated, and all were blinded to sensor measurements. The primary outcome was test accuracy of SDA measured at 10°, 45° and 90° compared to sensor measures as the gold standard test. Cohen's kappa coefficient was calculated to determine chance-corrected agreement. Secondary outcomes include the relationship of SDA to level of surgical experience, analysis of between-surgeon differences, and the influence of patient and operative factors on SDA accuracy. Results: Average accuracy of SDA was 58.3%, 61.2% and 66.5% at 10°, 45° and 90° respectively. Cohen's kappa coefficient was 0.18 at all angles and rated as "slight agreement". SDA sensitivities to correctly identify a balanced knee (76.2% at 10°; 82.6% at 45°; 83.2% at 90°) were approximately twice specificities to correctly identify an unbalanced knee (42.6% at 10°; 34.1% at 45°; 41.4% at 90°). Surgical experience (surgeon versus trainee) had no effect on capacity to determine balance. Considerable between-surgeon variability was found (33–65% at 10°, 41–73% at 45°, 55–89% at 90°). Conclusion: SDA was a poor predictor of balance, particularly when assessing the unbalanced TKA. Surgeon experience had no effect on test accuracy and considerable between-surgeon variability was recorded. These findings question the accuracy of SDA in TKA. Trial Registration Number: ACTRN# 12618000817246. [ABSTRACT FROM AUTHOR]

Aims: This study examined windswept deformity (WSD) of the knee, comparing prevalence and contributing factors in healthy and osteoarthritic (OA) cohorts., Methods: A case-control radiological study was undertaken comparing 500 healthy knees (250 adults) with a consecutive sample of 710 OA knees (355 adults) undergoing bilateral total knee arthroplasty. The mechanical hip-knee-ankle angle (mHKA), medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were determined for each knee, and the arithmetic hip-knee-ankle angle (aHKA), joint line obliquity, and Coronal Plane Alignment of the Knee (CPAK) types were calculated. WSD was defined as a varus mHKA of < -2° in one limb and a valgus mHKA of > 2° in the contralateral limb. The primary outcome was the proportional difference in WSD prevalence between healthy and OA groups. Secondary outcomes were the proportional difference in WSD prevalence between constitutional varus and valgus CPAK types, and to explore associations between predefined variables and WSD within the OA group., Results: WSD was more prevalent in the OA group compared to the healthy group (7.9% vs 0.4%; p < 0.001, relative risk (RR) 19.8). There was a significant difference in means and variance between the mHKA of the healthy and OA groups (mean -1.3° (SD 2.3°) vs mean -3.8°(SD 6.6°) respectively; p < 0.001). No significant differences existed in MPTA and LDFA between the groups, with a minimal difference in aHKA (mean -0.9° healthy vs -0.5° OA; p < 0.001). Backwards logistic regression identified meniscectomy, rheumatoid arthritis, and osteotomy as predictors of WSD (odds ratio (OR) 4.1 (95% CI 1.7 to 10.0), p = 0.002; OR 11.9 (95% CI 1.3 to 89.3); p = 0.016; OR 41.6 (95% CI 5.4 to 432.9), p ≤ 0.001, respectively)., Conclusion: This study found a 20-fold greater prevalence of WSD in OA populations. The development of WSD is associated with meniscectomy, rheumatoid arthritis, and osteotomy. These findings support WSD being mostly an acquired condition following skeletal maturity., Competing Interests: D. B. Chen and S. J. MacDessi report research fellowship funding and a collaborative multi-study research agreement to evaluate functional knee alignment techniques with Mako robotic total knee arthroplasty from Stryker, which is related to this work; and consulting fees from Stryker, Amplitude SAS, and MicroPort Orthopedics; speakers’ bureau/paid presentations for Stryker, all of which are unrelated. In addition, S. J. MacDessi reports being an editorial board member of The Bone and Joint Journal, which is also unrelated. W. Colyn declares that being a Belgian Knee Society board member is also unrelated to this manuscript., (© 2024 Moore et al.)

Aims: Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies., Methods: In 137 robotic-assisted TKAs, extension and flexion stressed gap laxities and bone resections were measured. The primary outcome was the proportion and magnitude of medial and lateral SPI (gap differential > 2.0 mm) for KA, MA, and FA. Secondary outcomes were the proportion of knees with severe (> 4.0 mm) SPI, and resection thicknesses for each technique, with KA as reference., Results: FA showed significantly lower rates of medial and lateral SPI (2.9% and 2.2%) compared to KA (45.3%; p < 0.001, and 25.5%; p < 0.001) and compared to MA (52.6%; p < 0.001 and 29.9%; p < 0.001). There was no difference in medial and lateral SPI between KA and MA (p = 0.228 and p = 0.417, respectively). FA showed significantly lower rates of severe medial and lateral SPI (0 and 0%) compared to KA (8.0%; p < 0.001 and 7.3%; p = 0.001) and compared to MA (10.2%; p < 0.001 and 4.4%; p = 0.013). There was no difference in severe medial and lateral SPI between KA and MA (p = 0.527 and p = 0.307, respectively). MA resulted in thinner resections than KA in medial extension (mean difference (MD) 1.4 mm, SD 1.9; p < 0.001), medial flexion (MD 1.5 mm, SD 1.8; p < 0.001), and lateral extension (MD 1.1 mm, SD 1.9; p < 0.001). FA resulted in thinner resections than KA in medial extension (MD 1.6 mm, SD 1.4; p < 0.001) and lateral extension (MD 2.0 mm, SD 1.6; p < 0.001), but in thicker medial flexion resections (MD 0.8 mm, SD 1.4; p < 0.001)., Conclusion: Mechanical and kinematic alignment (measured resection techniques) result in high rates of SPI. Pre-resection angular and translational adjustments with functional alignment, with typically smaller distal than posterior femoral resection, address this issue., Competing Interests: S. J. MacDessi and D. B. Chen report receiving research support from Stryker, Smith & Nephew, and Zimmer Biomet; research fellowship funding from the Ramsay Hospital Research Fund; reimbursement for presentations from Stryker and Smith & Nephew; and paid consultations from Stryker and Amplitude, all of which are unrelated to this study. T. S. Shen declares consulting fees from Zimmer Biomet and HSS Innovation Center, which are also unrelated., (© 2024 van de Graaf et al.)

The aim of mechanical alignment in total knee arthroplasty is to align all knees into a fixed neutral position, even though not all knees are the same. As a result, mechanical alignment often alters a patient's constitutional alignment and joint line obliquity, resulting in soft-tissue imbalance. This annotation provides an overview of how the Coronal Plane Alignment of the Knee (CPAK) classification can be used to predict imbalance with mechanical alignment, and then offers practical guidance for bone balancing, minimizing the need for soft-tissue releases., Competing Interests: J. Bellemans reports royalties or licenses and consulting fees from Smith & Nephew and Corin, consulting fees and payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing or educational events from Smith & Nephew, Corin, and Medacta, and multiple patents, all of which are unrelated to the study. D. B. Chen and S. J. MacDessi report research fellowship funding from Smith & Nephew, Stryker, and Zimmer Biomet, and a collaborative multi-study research agreement to evaluate functional knee alignment techniques from Stryker. D. B. Chen and S. J. MacDessi also report consulting fees from Stryker and Amplitude, and speakers' bureau payments from Stryker, all of which are unrelated to this study. D. B. Chen and S. J. MacDessi have also applied for a patent lodged on IP pertaining to this study. S. J. MacDessi is an editorial board member of The Bone & Joint Journal., (© 2024 The British Editorial Society of Bone & Joint Surgery.)

Purpose: To establish the effect of the addition of suture tape to the hamstring graft construct through measurement of instrumented sagittal plane knee laxity at 6 months after anterior cruciate ligament reconstruction (ACLR)., Methods: A retrospective analysis was undertaken of a consecutive series of primary ACLR performed between May 2017 and June 2019. Patients with concomitant or historic contralateral knee injury were excluded. Suture tape was included in the graft construct from the midpoint of the study period (May 2018). Sagittal plane knee laxity was quantified using the KT2000 arthrometer at 6 postoperative months. Mean side-to-side differences in sagittal plane laxity between the operated and contralateral, uninjured knees were compared for grafts with and without suture tape. Additional outcomes included comparison between suture tape application techniques (graft reinforcement versus augmentation), comparison between suture tape with and without iliotibial band (ITB) tenodesis and documentation of complications necessitating further surgery., Results: A total of 169 patients were eligible for inclusion. Seventy-two grafts included suture tape and 84 patients underwent concomitant ITB tenodesis. There was no significant difference in mean laxity between grafts containing suture tape (mean difference: 1.2 mm, SD: 2.6 mm) and those without (mean difference: 1.3 mm, SD: 2.1 mm), P  = .83 (CI -.92 to 1.13). Neither were there significant differences in laxity when using suture tape with concomitant ITB tenodesis (mean difference: 1.1 mm, SD: 2.1 mm), P  = .75 (CI -.79 to 1.09), or when comparing techniques: graft reinforcement (mean difference .9 mm, SD 2.6 mm); graft augmentation (mean difference: 1.5 mm, SD: 2.5 mm) P  = .52 (CI -2.29 to 1.16). There were no complications associated with suture tape., Conclusions: The addition of suture tape to an autologous hamstring graft construct did not reduce instrumented sagittal knee laxity in the first 6 months after ACL reconstruction. As such, the clinical relevance of its use remains unknown., Level of Evidence: Level III, retrospective cohort study., (© 2021 The Authors.)