Polyethylene Luxation in an Oxinium Fixed-bearing Unicompartmental Knee Replacement Leading to Metallosis: A Case Reports for an Early and a Late Presentation.

Introduction: Polyethylene (PE) subluxation is a rare complication after fixed-bearing unicompartmental knee replacement. We present two cases of PE luxation with a rapid onset of metallosis in a unicompartmental knee replacement made of Oxinium, one early presentation 3 months after surgery and the other case 6 years after. Case Report: Case 1: A 84-year-old male underwent a fixed-bearing medial unicompartmental knee replacement in his left knee. Standard surgery was carried out with robotic assistance. Three months after surgery, he felt acute pain in the anterior portion of his knee. Radiographs showed that the PE was luxated anteriorly and a radiopaque "cloud" that blurs the vision of the implants suggesting metallosis. In the revision surgery, abundant blackish liquid and metallic-like debris were deposited in the synovial tissue and capsule around the knee. The tibial and femoral components presented extensive wear areas, suggesting extensive metal-to-metal contact. Both components were removed, and a posterior stabilized total knee prosthesis was placed. Case 2: A 50-year-old male patient underwent a fixed-bearing medial unicompartmental knee replacement. After 6 years, he complained of insidious pain in the posteromedial side of his knee. During the physical examination, significant joint effusion, a loss of extension, and a limited flexion were observed, with flexion reaching only up to 80°. The patient did not report systemic symptoms associated with metallosis, and no signs of systemic involvement were found. Radiographs show similar findings than in case 1, but the radiopaque "cloud" was limited to the knee. In the revision surgery, both components were removed. The tibial and femur components had extensive wear, especially in the posterior-central portion. A posterior stabilized total knee prosthesis was used. Conclusion: Emphasis on careful engagement between the PE and the tibial component is a must, checking that no tissue or cement gets in the way of the anchoring system. Furthermore, prosthesis designs must look for models with a more friendly, engaging system to prevent early presentation. The radiographs assessing the height of the PE - especially in the posterior area - must be carried out. In the case of metallosis and PE luxation, we suggest performing a revision surgery with total knee arthroplasty; however, there is little evidence for a strong recommendation.

Robotic-assisted vs conventional surgery in medial unicompartmental knee arthroplasty: a clinical and radiological study.

BACKGROUND: The use of unicompartmental knee arthroplasty (UKA) has increased and new technologies have been developed to improve patient survival and satisfaction, soft tissue balance, alignment, and component size. Robot-assisted systems offer an increase in surgical precision and accuracy. The purpose of this study is to evaluate the precision of component position using five radiological parameters in conventional and robotic-assisted medial UKA using the NAVIO system. METHODS: A cohort study was designed for patients who underwent medial UKA between April 2017 and March 2019 in a single center. Patients were allocated in the conventional (UKA-C) or robotic-assisted (UKA-R) group. The variables analyzed were age, gender, affected knee side, length of hospital stay, surgical time, and radiological measurements such as anatomical medial distal femoral angle (aMDFA), anatomical medial proximal tibial angle (aMPTA), tibial slope, the sagittal femoral angle, and the component size. A target was defined for each measurement, and a successful UKA was defined if at least four radiological measures were on target after surgery. Also, patients' reported outcomes were evaluated using the Oxford Knee Score (OKS) and a numeric rating scale (NRS) for pain. RESULTS: Thirty-four patients were included, 18 of them underwent UKA-R. The success rate for UKA in the UKA-R group was 87%; meanwhile, in the UKA-C group this was 28%, this difference was significant and powered (Fisher's exact test, p = 0.001; 1 - ß = 0.95). Also, a 5-point difference in favor of the UKA-R group in the median OKS (p = 0.01), and a significantly lower median NRS for pain (p < 0.000) were found after surgery. CONCLUSIONS: UKA-R achieved more precision in the radiological parameters' measure in this study. Also, UKA-R has a trend towards a better OKS and a lower NRS for pain at short-term follow-up.

Robot-Assisted Unicompartmental Knee Arthroplasty: Increasing Surgical Accuracy? A Cadaveric Study.

Unicompartmental knee arthroplasty (UKA) represents 10% of knee arthroplasties. Advantages are better functional results, quicker recovery, shorter hospitalization time, and lower blood loss, among others. However, revision rates are larger than total knee arthroplasty. Among the most important factors that explain this are the implant position and alignment, and the correct surgical indication. Greater accuracy in the implant placement may improve clinical results and increase the rate of implant survival. The objective of this study is to evaluate the precision of the Navio robot-assisted system in the position and alignment of medial UKA compared with the conventional technique. This is an experimental pilot study. Twenty-six cadaveric models were randomized into 2 groups: Robot-Assisted surgery (R) and Conventional Surgery (C). Radiological study was performed pre- and post-surgery, evaluating the medial distal femoral angle (MDFA), medial proximal tibial angle (MPTA), tibial slope, tibiofemoral angle (TFA), sagittal femoral angle (SFA), and size of the femoral and tibial components. The main result measurement was the change in postoperative angulation. The results of this study are MDFA median of 1.07° (0.19-4.5) for group R and 0.12° (0.03-10.4) with a significant difference in variances; a Welch t-test of p = 0.013; and an MPTA of 1.28° (0.05-5.87) for R and 1.3°(0.08-14.1) for C with significantly different variances (p = 0.0064). Size of the femoral component has a difference of p < 0.05 between groups. No differences for dispersion of TFA nor for the size of the tibial component were observed. In conclusion, using robot-assisted UKA allows for greater accuracy in the positioning of the implants and in the prediction of the size of the femoral component.

Robotic-assisted surgery in medial unicompartmental knee arthroplasty: does it improve the precision of the surgery and its clinical outcomes? Systematic review.

There is a high prevalence of knee osteoarthritis that affects only the medial tibiofemoral compartment. In this group of patients with severe disease, the medial unicompartmental knee arthroplasty (UKA) is an excellent choice. However, this technique has a great learning curve due to the lower tolerance of improper positioning and alignment. In this context, the robotic-assisted surgery (RAS) arises as an option to improve the accuracy and secondarily enhance the clinical outcomes related to the UKA. The objective in this study is to determine if there are significant advantages with the use of RAS over conventional surgery (CS). In the systematic review of the literature, classification of the results in three main subjects: (A) precision and alignment; (B) functional results and clinical parameters; (C) survivorship. We found 272 studies, of which 15 meet the inclusion and exclusion criteria. There is mostly described that RAS significantly improves the accuracy in position (80-100% of planned versus performed P < 0.05), alignment (2-3 times less error variance P < 0.05) and selection of the proper size of the implants (69.23% of correct size femoral implants versus 16.67% using CS P < 0.0154). Recently, there is mild evidence about benefits in the early rehabilitation and post-operative pain, but in all studies reviewed, there is no advantages of RAS in the long-term functional evaluation. There is no strong literature that supports a longer survival of the prothesis with RAS, being the longest mean follow-up reported of 29.6 months. RAS is a useful tool in increasing the precision of the medial UKA implant placement. However, there is still a lack of evidence that properly correlates this improvement in accuracy with better clinical, functional and survival results.

Robotic-assisted Unicompartmental knee Arthroplasty optimizes joint line restitution better than conventional surgery.

PURPOSE: To compare joint line restoration after unicompartmental knee arthroplasty (UKA) between conventional and robotic-assisted surgery. Previous studies have shown that joint line distalization can lead to higher failure rates. The hypothesis was that robotic-assisted UKA is associated with less femoral component distalization and a precise tibial cut, which allows a more anatomical restitution of the knee joint line. METHODS: Retrospective cohort study of patients undergoing medial or lateral UKA between May 2018 and March 2020. Preoperative and postoperative radiologic assessment of the joint line was performed by two observers, using three different methods, one for tibial slope and one for tibial resection. Robotic assisted UKA and conventional UKA groups were compared. RESULTS: Sixty UKA were included, of which 48 (77.42%) were medial. Robotic-assisted UKA were 40 (64.52%) and 22(35.48%) were conventional The distalization of the femoral component was higher in the conventional group despite the method of measurement used In both Weber methods, the difference was statistically different: Conventional 2.3 (0.9 to 5.6) v/s Robotic 1.5 (- 1.1 to 4.1) (p =0.0025*). A higher proportion of patients achieved a femoral component position ≤ two millimeters from the joint line using robotic-assisted UKA compared to the conventional technique . No statistical difference between robotic-assisted and conventional UKA was found in tibial resection and slope. CONCLUSION: Robotic-assisted UKA shows a better rate of joint line restoration due to less femoral component distalization than conventional UKA. No difference was found in the amount of tibial resection between groups in this study. LEVEL OF EVIDENCE: III.

Cirugía robótica en artroplastia de rodilla / Robotic surgery in knee arthroplasty

La cirugía protésica de rodilla es un procedimiento ampliamente aceptado como etapa final del tratamiento de la artrosis de rodilla, con sobrevida que supera el 90% a 10­15 años. Dentro de las principales causas de fallo, se encuentran la infección (20,4%) y el aflojamiento mecánico (20,3%). El uso de ayudas tecnológicas en cirugía está en constante desarrollo, con el objetivo de mejorar la precisión del acto quirúrgico. En ese escenario, la Cirugía Asistida por Computador (CAS) en artroplastia de rodilla, crece de forma exponencial, y apunta a mejorar el posicionamiento y selección del tamaño de los componentes protésicos, aumentar la precisión de las resecciones óseas y mejorar el balance de los tejidos blandos, logrando así una mayor sobrevida del implante. En comparación a las técnicas convencionales, la cirugía robótica ha mostrado mejores resultados funcionales, al primer año de seguimiento, en términos de rango articular, menor dolor post-operatorio y menor tiempo de estadía hospitalaria. Pero todavía es necesario establecer si, a largo plazo, esas diferencias funcionales se traducirán en mejores resultados clínicos que permitan, de forma consistente, inclinar la balanza en favor de la técnica asistida por robot por sobre las técnicas tradicionales.

Prosthetic knee surgery is a widely accepted procedure as the final stage in the treatment of knee osteoarthritis, with survival rate over 90% at 10 - 15 years. Among the main causes of failure are infection (20.4%) and mechanical loosening (20.3%). The use of technological aids in surgery is in constant development, with the aim of improving the accuracy of the surgical act. In this scenario, Computer-Aided Surgery (CAS) in knee arthroplasty grows exponentially, and aims to improve the positioning and selection of the size of the prosthetic components, increase the accuracy of bone resections and improve the balance of soft tissues, thus achieving a greater survival of the implant. Compared to conventional techniques, robotic surgery has shown better functional results at the first year of follow-up, in terms of joint range, less post-operative pain and shorter hospital stay. It is still necessary to establish whether, in the long term, these functional differences will result in better clinical results that will allow - in a consistent manner - to tip the balance in favor of robot-assisted technique over traditional techniques.

Meniscal Ramp Lesion Repair Using an All-Inside Technique.

Posteromedial meniscotibial ligament lesions, known as meniscal ramp lesions, are typically associated with ACL injuries, but frequently underdiagnosed. When correctly diagnosed, repair is mandatory in most cases. Retraction of the soft tissues makes it difficult to repair and leads to suture failure. Previously described techniques include all-inside and inside-out meniscal sutures, but do not ensure correct meniscotibial closure because of the soft tissue retraction. The purpose of this Technical Note is to describe a meniscal ramp lesion arthroscopic repair with an all-inside technique with the Fast-Fix 360 device, detailing the use of the accessory posteromedial portal, and the addition of an arthroscopic grasper that raises the retracted meniscotibial ligament, to allow correct fixation.

Lesiones meniscales ramp, y lesiones del ligamento meniscotibial posteromedial / Meniscal ramp lesions, and posteromedial meniscotibial ligament lesions

Las lesiones meniscales son las lesiones más frecuentemente asociadas a lesiones del Ligamento Cruzado anterior (LCA), encontrándose 9,3 a 16,9% en el segmento posteromedial y comprometiendo el ligamento meniscotibial. Descritas por Strobel por su apariencia artroscópica de rampa, se ha presentado su importancia dado el subdiagnóstico y el efecto biomecánico de una lesión posteromedial del menisco sobre el LCA y que su reparación restaura la traslación nativa de la tibia en conjunto con la reconstrucción del pivote central. Se ha demostrado que la mejor forma para diagnosticar lesiones ramp, es por visiones artroscópicas accesorias, una a través del surco intercondíleo y la otra por un portal posteromedial, logrando diagnosticar y manejar aquellas lesiones que sean inestables, a través de suturas dentro tanto por el portal anterior como por el posterior. Los resultados quirúrgicos son buenos, con mayor riesgo de falla en casos que la lesión se extiende al cuerpo meniscal. Es una lesión que debe buscarse bajo lupa, ya que pasarla por alto puede llevar a progresión de la lesión y a un mayor riesgo de rerotura del ligamento cruzado reconstruido.

Meniscal tears are the most frequently associated lesions in Anterior Cruciate Ligament (ACL) rupture, 9.3 to 16.9% on them in the posteromedial segment compromising the meniscotibial ligament. Described by Strobel for its arthroscopic ramp appearance, has gained importance given the underdiagnosis and biomechanical effect of a posteromedial meniscal lesion on the ACL, and that its repair restores the native anterior tibial translation when the central pivot is also reconstructed. It has been shown that the best way to diagnose ramp lesions is by accessory portals, one through the intercondylar notch and the other through a posteromedial portal, useful to diagnose and repair those lesions that are unstable, through all-inside sutures within both Anterior and posterior portals. Surgical results are good, with increased risk of failure in cases where the lesion extends to the meniscal body. It is a lesion that must be looked for in a direct way, since misdiagnosing it can lead to ramp lesion progression and increased risk of re rupture of the reconstructed ACL.

Biomechanical and histological comparison between the cryopreserved and the lyophilized Gracilis tendon allograft for MPFL reconstruction, a cadaveric experimental study.

BACKGROUND: Medial patellofemoral ligament (MPFL) is the main restrictor of lateral shifting of the patella, contributing by 60 % in the first 20° flexion of the knee. MPFL reconstruction has been performed in order to restore the stability of the patella with good results.Lyophilized Gracilis tendon allograft (LGA) compared to Cryopreserved Gracilis tendon allograft (CGA) has a lower cost, does not require to maintain cooling chain or preparation. The purpose of this study is to compare the histological and biomechanical characteristics of an experimental model of reconstruction of the MPFL in porcine patellas with LGA versus CGA. METHODS: Randomized controlled experimental study in porcine model conducted on 36 porcine patellas in which 18 were intervened with LGA and 18 were intervened with CGA. The confluent tunnel technique was used for MPFL reconstruction. Maximum tensile force, allograft elongation and stiffness of the construct were measured. The cellularity and collagen tissue distribution were evaluated in the allografts. The histological and biomechanical characteristics of the LGA were compared to those of the CGA. RESULTS: The median of the maximum tensile force for the LGA group was 299.63 N and 280.86 N for the CGA group (p = 0.45). The median of the stiffness was 57.86 N/mm for the LGA and 54.23 N/mm for the CGA (p = 0.2). The median of the elongation for the LGA was 5.95 mm and 6.12 mm for the CGA (p = 0,29). The bone bridge failed in 88.88 % of the constructs with LGA and 94.44 % in those with CGA (p = 0.5). CONCLUSIONS: No differences were observed between the LGA group and the CGA group in maximum tensile force, elongation, stiffness, site of rupture and histological characteristics. The use of a lyophilized Gracilis tendon allograft for MPFL reconstruction confers the same histological and biomechanical characteristics as a cryopreserved Gracilis tendon allograft.