Valgus stress knee radiographs accurately anticipate the bone resection in medial unicompartmental knee arthroplasty: Protocol validation using an image-based robotic system.

PURPOSE: The objective of this study was to describe a planning method for medial unicompartmental knee arthroplasty (UKA) implantation using preoperative stress radiographs to measure the thickness of tibial and femoral bone resections and to validate this method with data from an image-based robotic surgery system. Having such method for preoperative planning would be of interest for surgeons performing UKA in order to anticipate optimal bone resection on both tibia and femoral sides. METHODS: A new planning method for medial UKA based on valgus stress knee radiographs validated it with an image-based robotic surgery system (Restoris MCK, MAKO®, Stryker Corporation) was proposed. This retrospective study involved radiographic measurements of 76 patients who underwent image-based robotic medial UKA between April 2022 and February 2023. Preoperative anteroposterior stress radiographs of the knee were used to simulate UKA implantation. The UKA technique was based on Cartier's angle and aimed at restoring the joint line. The total dimension measured was 14 mm (8 mm for minimal tibial component and polyethylene insert + 4 mm for femoral component + 2 mm for safety laxity). Bone resections were measured in the preoperative valgus stress radiographs and then against the intraoperative bone resection data provided by the robotic system. Inter- and intra-observer reliability was assessed using 25 measurements. RESULTS: The mean planned tibial resection measured in the radiographs was 4.3 ± 0.4 [2.9-5.8], while the mean robotic resection was 4.2 ± 0.5 [2.7-5.8] (mean difference = 0.15 mm, 95% confidence interval [CI] [-0.27 to 0.57]). There was a strong correlation between these two values (Pearson's rank R = 0.79, p < 0.001). Intra- and inter-observer reliability were also very strong (Pearson's rank R = 0.91, p < 0.001, and Pearson's rank R = 0.82, p < 0.001, respectively). The mean planned femoral bone resection measured in the radiographs was 2.7 ± 0.7 mm [1-4.5], while the mean robotic resection was 2.5 ± 0.9 [1-5] (mean difference = 0.21 mm, 95% CI [-0.66 to 1.08]). There was a strong correlation between these two values (Pearson's rank R = 0.82, p < 0.001). Intra- and inter-observer reliability were also strong (Pearson's rank R = 0.88, p < 0.001, and Pearson's rank R = 0.84, p < 0.001, respectively). CONCLUSION: This study describes and validates with robotic information a simple and reproducible preoperative planning method to determine femoral and tibial bone resection for medial UKA implantation using antero-posterior valgus stress knee radiographs, leaving a medial safety laxity of 2 mm. It represents a very valuable contribution to the understanding of UKA principles, which can serve to extend its indications and increase reproducibility of the surgical technique. LEVEL OF EVIDENCE: III. Retrospective cohort study.

Enhancing robotic precision in medial UKA: Image-based robot-assisted system had higher accuracy in implant positioning than imageless robot-assisted system across 292 knees.

PURPOSE: The objective of this study was to compare the degree of accuracy in implant positioning and limb alignment offered by two robot-assisted (RA) systems: an image-based robot-assisted (IBRA) versus an imageless robot-assisted (ILRA) system for the treatment of medial knee osteoarthritis with unicompartmental knee arthroplasty (UKA). METHODS: This retrospective radiographic study included medial UKAs performed between 2011 and 2023. Radiographic measurements taken preoperatively and at 1-year postoperative control visit focusing on hip-knee-ankle angle (HKA), posterior tibial slope (PTS), tibial component coronal alignment relative to Cartier's angle and restoration of proper joint line (JL) height were analyzed. Outliers for postoperative measurements were defined as follows: HKA <175° or >180°, PTS <2° or >8°, >3° or <-3° alterations in Cartier's angle and ±2 mm changes in the height of the joint line. RESULTS: The final sample consisted of 292 medial UKAs: 95 (32.5%) with an IBRA system and 197 (67.5%) with an ILRA system. Implant positioning and limb alignment were more accurate in the group of patients treated with IBRA, HKA (77.9% vs. 67.5%, p = 0.07), PTS (93.7% vs. 82.7%, p = 0.01), restoration of tibial varus relative to Cartier's angle (87.4% vs. 65%, p < 0.001) and restoration of JL height (81.1% vs. 69.5%, p = 0.04). CONCLUSION: Medial UKA surgery using an IBRA system was associated with a higher degree of accuracy in implant positioning and postoperative limb alignment as compared to an ILRA system. This is a valuable contribution to help communicate the advantages of using this surgical technique and improve its reproducibility. LEVEL OF EVIDENCE: Level III, Retrospective cohort study.

Associated patellofemoral osteoarthritis is not a contraindication for unicompartmental knee replacement. Report of one hundred ten prostheses with an average 6-year follow-up.

INTRODUCTION: Associated patellofemoral joint osteoarthritis (APFJ-OA) has typically been considered a contraindication for unicompartmental knee arthroplasty (UKA) in the treatment of femorotibial joint osteoarthritis. However, this contraindication is being challenged. The aim of this study was to assess clinical and functional outcomes, complications, and implant survival in medial or lateral UKA, regardless of clinical symptoms or radiographic signs of APFJ-OA. METHODS: This retrospective, comparative study included patients treated with medial or lateral UKA regardless of preoperative symptoms or signs of APFJ-OA, with a minimum 2-year follow-up. Intraoperatively, knees were subdivided based on APFJ-OA grade, according to the Outerbridge classification. Clinical and functional outcomes were analyzed using the 2011 Knee Society Score (KSS) at the last follow-up control. APFJ-OA was treated systematically, in a tailored, stepwise fashion according to its severity. Complications and implant survival rates were evaluated. Two-sided paired T-test, ANOVA, and Kruskal-Wallis tests were used with a significance level of 5%. RESULTS: Finally, 110 UKAs were assessed 81 (73.6%) medial and 29 (26.4%) laterals. The average follow-up was 6 years (2-19.5). According to Outerbridge, 22 knees (20%) were in grade 2, 59 (53.6%) were in grade 3, and 29 (26.4%) were in grade 4. All three groups showed a statistically significant increase in KSS scores and range of motion. There were no significant differences in clinical KSS improvement and flexion contracture between Outerbridge groups (average 35.7 and -4.9, respectively). Group 3 showed statistically significant improvement in functional KSS when compared to group 2 (68.8 vs 61.2). In maximum flexion, groups 3 and 4 did significantly better than group 2 (20° vs 15°). Three prostheses (2.7%) needed revision after 7, 8.6, and 12 years due to aseptic tibial loosening. Implant survival was 100% at 5 (64 of 64), 97% at 7 (30 of 31), 93% at 9 (14 of 15), and 89% at 12 years, respectively (8 of 9). CONCLUSION: Clinical and functional results, complications, and survival of medial or lateral UKA were not negatively affected by APFJ-OA assessed intraoperatively using the Outerbridge classification after an average follow-up of 6 years. We consider that APFJ-OA is not a contraindication for UKA when treated systematically according to its severity. LEVEL OF EVIDENCE: IV.

Reemplazo unicompartimental bilateral de rodilla en un tiempo quirúrgico. Resultados a mediano plazo de 86 prótesis con un seguimiento promedio de 6.2 años / Bilateral simultaneous unicompartmental knee arthroplasty. Medium-term outcomes in 86 arthroplasties with an average follow-up of 6.2 years

Objetivo: Evaluar los resultados funcionales, las complicaciones y la supervivencia a mediano plazo de la prótesis unicompartimental bilateral medial o lateral de rodilla en un tiempo quirúrgico. Materiales y Métodos: Estudio retrospectivo de pacientes con prótesis unicompartimental bilateral medial o lateral de rodilla colocada en un tiempo quirúrgico por gonartrosis entre abril de 2004 y abril de 2020, seguimiento mínimo 1 año. Se evaluaron los resultados clínico-funcionales con el KSS 2011. Se determinaron los tiempos quirúrgico total y de internación, y el requerimiento de transfusiones. Se analizaron las complicaciones a corto y mediano plazo, y las tasas de revisión y de supervivencia de la prótesis. Resultados: Se evaluaron 86 prótesis unicompartimentales en 43 pacientes (seguimiento promedio 6.1 años). El KSS clínico y funcional aumentó de 46,1 ± 10,2 a 80,9 ± 15,9 y de 22,8 ± 11,9 a 89,8 ± 18,9, respectivamente. La flexión máxima mejoró de 106,3° ± 5,2° a 125,1° ± 4,2° y la contractura en flexión, de 7,5° ± 2,2° a 2,3° ± 1,6°. La cirugía duró 178.6 min y la internación, 39.8 h. Dos pacientes requirieron transfusión. La tasa de complicaciones fue del 6,9%, todas menores. Tres rodillas tuvieron un aflojamiento mecánico aséptico y requirieron revisión a prótesis total de rodilla o nueva prótesis unicompartimental tras 12, 8.6 y 7 años. La supervivencia de la prótesis fue del 96,5%. Conclusión: La prótesis unicompartimental bilateral medial o lateral en un tiempo quirúrgico para la gonartrosis unicompartimental de rodilla proporciona excelentes resultados clínico-funcionales, con bajas tasas de complicaciones. Nivel de Evidencia: IV

Objective: The purpose of this article is to examine the functional outcomes, complications, and medium-term survivorship of medial or lateral bilateral simultaneous unicompartmental knee arthroplasty (bUKA) for the treatment of bilateral knee osteoarthritis. Materials and Methods: Retrospective report of patients who underwent a medial or lateral bUKA for treatment of bilateral knee osteoarthritis between April 2004 and April 2020, with a minimum follow-up of 1 year. The KSS 2011 was used for the clinical-functional evaluation of each patient. The duration of surgery, length of hospital stay, and transfusion requirements were determined. The short-term and medium-term complications were analyzed, as well as the revision rate and the prosthesis survivorship. Results: We evaluated 86 bUKAs in 43 patients with a mean follow-up of 6.1 years. The clinical and functional KSS improved from 46.1 ± 10.2 to 80.9 ± 15.9 and 22.8 ± 11.9 to 89.8 ± 18.9 respectively. Postoperative maximal flexion improved from 106.3º ± 5.2º to 125.1º ± 4.2º and flexion contracture improved from 7.5º ± 2.2º to 2.3º ± 1.6º. The mean surgical time was 178.6 minutes and the hospital stay was 39.8 hours. Two patients required transfusions. The complication rate was 6.9%. Three knees (3.5%) required revision surgery for aseptic loosening after 7, 8.6 and 12 years. The survivorship rate was 96.5%. Conclusion: Simultaneous medial or lateral bUKA provides excellent clinical-functional outcomes with a low rate of complications in patients with bilateral knee osteoarthritis. Level of Evidence: IV

Prótesis unicompartimental lateral de rodilla en el tratamiento del genu valgo artrósico. Resultados en 29 artroplastias con un seguimiento promedio de 6.2 años / Lateral unicompartmental knee arthroplasty for the treatment of lateral knee osteoarthritis. Results in 29 arthroplasties with an average follow-up of 6.2 years

Objetivo: Evaluar, de manera retrospectiva, los resultados funcionales y la supervivencia a mediano plazo de la prótesis unicompartimental lateral de rodilla para tratar el genu valgo artrósico. materiales y métodos: Estudio observacional retrospectivo. Se analizaron los casos operados con prótesis unicompartimental lateral de rodilla por genu valgo artrósico entre enero de 1999 y enero de 2019, seguimiento mínimo de un año. Se evaluaron los resultados clínicos y funcionales mediante el KSS 2011, el grado de artrosis en el compartimento externo y su progresión en el compartimento contralateral con la clasificación de Kellgren y Lawrence, y la condropatía femororrotuliana mediante la clasificación de Outerbridge modificada. Se determinaron la incidencia de complicaciones y la supervivencia de la prótesis. Resultados: Se evaluaron 29 prótesis unicompartimentales laterales de rodilla en 27 pacientes, con un seguimiento promedio de 6.2 años. El KSS clínico y funcional se incrementó de 56,5 ± 9,8 a 91,9 ± 5,3 y de 33,9 ± 13,7 a 91,4 ± 10,3, respectivamente, (p <0,001). La flexión máxima mejoró de 106,6º ± 6,7º a 124,2º ± 2,4º y la contractura en flexión, de 5,2º ± 3,2º a 1º ± 1,6º (p <0,001). El eje preoperatorio fue de 12,3º ± 4,1º de valgo, para un posoperatorio de 5,2º ± 3,1º de valgo (p <0,001). La supervivencia de la prótesis fue del 100%, con un caso de progresión artrósica en el compartimento medial (3,4%). Conclusión: La prótesis unicompartimental lateral de rodilla representa una alternativa válida y definitiva para tratar la patología artrósica femorotibial externa. Nivel de Evidencia: IV

Objective: The purpose of this article is to examine the medium-term functional outcomes and survivorship of lateral unicompartmental knee arthroplasty in the treatment of lateral knee osteoarthritis. Materials and Methods: Retrospective report. We selected and analyzed all patients who had undergone a lateral unicompartmental knee arthroplasty for the treatment of lateral knee osteoarthritis between January 1999 and January 2019, with a minimum follow-up of 1 year. The KSS score system 2011, the Kellgren-Lawrence osteoarthritis classification, the Outerbridge femoropatellar chondropathy classification and serial radiographs were used in the evaluation of each patient. The complication and prosthesis survivorship rates were assessed. Results: We identified 29 lateral unicompartmental knee arthroplasties in 27 patients with a follow-up of 6.2 years (1-19.5). The clinical and functional KSS improved from 56.5 ± 9.8 to 91.9 ± 5.3 and 33.9 ± 13.7 to 91.4 ± 10.3 respectively (p<0.001). Postoperative maximal flexion improved from 106º ± 6.7º to 124.2º ± 2.4º and flexion contracture improved from 5.2º ± 3.2º to 1º ± 1.6º (p<0.001). The average preoperative alignment was 12.3º ± 4.1º of valgus angulation, which was corrected to 5.2º ± 3.1º of valgus (p<0.001). The survivorship rate was 100% and only one patient showed osteoarthritic changes in the medial compartment (3.4%). Conclusion: Lateral unicompartmental knee arthroplasty provides excellent medium-term results. It represents a reliable and definitive option in the treatment of the isolated lateral knee osteoarthritis. Level of Evidence: IV