Effects of microprocessor-controlled prosthetic knees on self-reported mobility, quality of life, and psychological states in patients with transfemoral amputations.

OBJECTIVE: This study aimed to determine the effects of the microprocessor-controlled prosthetic knee (MPK) joint on self-mobility, body perceptions, depression, and quality of life in patients with unilateral transfemoral amputations (TFAs). METHODS: Thirty consecutive patients (28 males, mean age=38.5 years, age range=22-57) who had previously used non-MPKs and who were approved to use swing and stance phase-control MPKs were included in this 12-week clinical study. Before the MPK use and after the three-month follow-up, prosthetic use and locomotor capabilities were evaluated using the Houghton Scale and the Locomotor Capabilities Index (LCI-5), respectively. Body perception was assessed using the Amputee Body Image Scale (ABIS). The depressive symptoms and quality of life were evaluated using the Beck Depression Inventory (BDI) score and the 36-Item Short- Form Health Survey (SF-36), respectively. RESULTS: After MPK use, statistically significant ameliorations were observed in all outcome measures. The basic and advanced LCI-5 increased from 26.7±2.2 and 24.8±5.2 to 27.6±1.2 (p=0.007) and 27±2.1 (p=0.004), respectively. Houghton scores improved from 9±1 to 10.3±0.8 (p=0.000). The ABIS and BDI scores decreased from 43.2±10.9 and 5.7±6.6 to 37.1±8.9 (p=0.000) and 3.8±4.5 (p=0.015), respectively. Also, the SF-36 physical function and vitality subscales increased from 71.2±24.0 and 75.5±14.6 to 85.6±16.6 (p=0.001) and 81.7±14.1 (p=0.015), respectively. CONCLUSION: MPK use provides significant improvements in the locomotor capabilities, quality of life, and activities of daily living to patients with TFAs as well as improves their body image perceptions and depressive symptoms. LEVEL OF EVIDENCE: Level III, Self controlled study.

The Effect of Prosthesis Design on Blood Loss in Simultaneous Bilateral Total Knee Arthroplasty: Closed-Box versus Open-Box Prosthesis.

BACKGROUND: Various pre- and perioperative risk factors have been reported in association with blood loss in knee arthroplasty. However, the effect of the uncovered cancellous surface on blood loss in simultaneous bilateral total knee arthroplasty (SBTKA) by different prosthetic designs is not well elucidated. Therefore, this study aimed to compare the blood loss and transfusion rate between different knee prostheses in SBTKA and to identify risk factors that influence blood loss and transfusion after SBTKA. METHODS: Demographic and perioperative data of patients who underwent SBTKA using either a closed-box or an open-box femoral component of posterior-stabilized fixed-bearing (PS FB) knee system were retrospectively reviewed. The calculated blood loss (CBL) and blood transfusion rate were compared by using Student t-test and confirmed with multivariate regression analysis. RESULTS: There was no significant difference in preoperative parameters between 54 closed-box and 56 open-box PS FB TKAs. The CBL of the closed-box TKA group was 135.23 mL less (95% confidence interval [CI], -215.30 to -55.16; p = 0.001) than that of the open-box TKA group. However, the blood transfusion rates of the closed- and open-box TKA groups were not significantly different (24.1% and 38.5%, p = 0.11). For each additional minute of total operative time, 3.75 mL (95% CI, 1.75 to 5.76; p < 0.001) of blood loss was anticipated. For each additional mg/dL of preoperative hemoglobin, 71% (p < 0.001) reduction of blood transfusion probability was predicted. CONCLUSIONS: The use of closed- and open-box knee prostheses resulted in a significant difference in blood loss in SBTKA. Prolonged operative time also significantly increased CBL. Therefore, strategies to control the bleeding surface and shorten operative duration may be considered if blood loss is of special concern. The preoperative hemoglobin was the only factor that affects the probability of blood transfusion in SBTKA.

Sagittal profile has a significant impact on the explantability of well-fixed cemented stems in revision knee arthroplasty: a biomechanical comparison study of five established knee implant models.

BACKGROUND: Easy revisability is gaining increasingly in importance. The removal of well-fixed cemented stems is very demanding and is often associated with increased operative morbidity. Implant design may be here a decisive impact factor, and the best way to ascertain it is experimentally. Aim of this study is to assess different cemented stems of established knee revision implants in regard to their removal capability. METHODS: Based on their sagittal profile, five stem extensions from known manufacturers were divided in conical, conical-cylindrical and cylindrical designs. The pedicles were also characterized in respect to their cross section, diameter and surface roughness. The cemented stems were dismounted six times each in a reproducible biomechanical setup. The explantation energy required was determined and statistical analyzed. RESULTS: The conical shaft needed significantly the slightest explantation energy with 19.2 joules (p = 0.004). There was a strong negative linear correlation between conicity proportion and explantation energy of the cemented stems (R2 = 0.983). The removal of the three purely cylindrical shafts-regardless of their differences in diameter, cross-sectional design and surface- was the most demanding (98.3, 105, and 116.7 joules) with only secondary differences between them. CONCLUSION: The longitudinal stem profile may have a primary impact on the explantability of well-fixed cemented shafts with conical designs showing superiority. Cross-sectional profile and surface roughness had here a less decisive influence on the explantability. Surgeons can choose proper implants and removal techniques depending on potential implant-associated revision risks and re-revisions to be expected.

Mid-term results of total knee replacement with single-radius versus multi-radius posterior-stabilized implants.

OBJECTIVE: Single-radius femoral total knee endoprosthesis designs were introduced with the promise of better clinical and functional results by means of superior biomechanical characteristics. The aim of this study was to compare the mid-term clinical, functional, radiologic, and survivorship outcomes of 2 types of posterior-stabilized knee replacement systems: the single-radius Scorpio® (Stryker®, Mahwah, NJ, USA) and the multi-radius NexGen® (Zimmer®, Warsaw, IN, USA). METHODS: This retrospective observational study included 139 patients (164 knees) that underwent total knee replacement (TKR) between October 2004 and December 2010: 94 knees (75 patients) with Scorpio® and 70 knees (64 patients) with NexGen®. The 2 patient groups were similar in terms of age, gender ratio, diagnosis, disease stage, and knee joint alignment. Mean follow-up times were 35 (range: 12-112) months and 32 (range: 13-75) months, respectively. Evaluation was based on the Knee Society scores (KSS) and the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System, with survival data compiled using Kaplan-Meier survival analysis. RESULTS: Clinical and functional improvements were recorded in all cases, with no statistically significant differences between the 2 patient groups. Survivorship was 95.8% (95% confidence interval [CI]: 91.8-99.8%) for the multi-radius implant at 60 months and 92.7% (95% CI: 87.7-97.7%) for the single-radius implant at 84 months, with no significant difference (p=0.31). CONCLUSION: This study demonstrates that both single-radius and multi-radius posterior-stabilized knee endoprostheses can significantly reduce pain and improve knee joint function in patients if used with a proper technique, with the additional benefit of good mid-term survivorship.

[Dorsal sagittal knee joint stability after endoprosthetic knee arthroplasty : Influence of preoperative joint stability and the type of implanted prosthesis]. / Dorsale sagittale Kniegelenkstabilität nach endoprothetischem Kniegelenkersatz : Einfluss der präoperativen Gelenkstabilität und des implantierten Prothesentyps.

BACKGROUND: Anterior knee pain is a known complication after implantation of a prosthesis and a possible reason is a posterior knee joint instability; however, the influence on postoperative stability is just as unknown as the possible influence of the type of prosthesis on postoperative stability. AIM: This study investigated two possible preoperative and intraoperative influencing factors by determination of the preoperative joint stability and type of prosthesis.

RSA prediction of high failure rate for the uncoated Interax TKA confirmed by meta-analysis.

BACKGROUND AND PURPOSE: In a previous radiostereometric (RSA) trial the uncoated, uncemented, Interax tibial components showed excessive migration within 2 years compared to HA-coated and cemented tibial components. It was predicted that this type of fixation would have a high failure rate. The purpose of this systematic review and meta-analysis was to investigate whether this RSA prediction was correct. MATERIALS AND METHODS: We performed a systematic review and meta-analysis to determine the revision rate for aseptic loosening of the uncoated and cemented Interax tibial components. RESULTS: 3 studies were included, involving 349 Interax total knee arthroplasties (TKAs) for the comparison of uncoated and cemented fixation. There were 30 revisions: 27 uncoated and 3 cemented components. There was a 3-times higher revision rate for the uncoated Interax components than that for cemented Interax components (OR = 3; 95% CI: 1.4-7.2). INTERPRETATION: This meta-analysis confirms the prediction of a previous RSA trial. The uncoated Interax components showed the highest migration and turned out to have the highest revision rate for aseptic loosening. RSA appears to enable efficient detection of an inferior design as early as 2 years postoperatively in a small group of patients.

Changes in lower extremity 3-dimensional load-bearing axes before and after mobile-bearing total knee arthroplasty.

This study evaluated changes in the lower extremity 3-dimensional load-bearing mechanical axes in the anteroposterior and mediolateral directions before and at 3 weeks after mobile-bearing total knee arthroplasty. The effects of the degrees of anteroposterior constraint of the designs on the location of the load-bearing mechanical axis at the knee joint level were also assessed. We evaluated 151 knees from 134 patients with 74 knees receiving meniscal bearing-type and 77 knees receiving rotating platform-type prostheses. In the mediolateral direction, both designs showed significant improvements, whereas in the anteroposterior direction, they revealed no improvements postoperatively and were worsened significantly in meniscal bearing type. Differences in the degree of bone and soft tissue involvement for the correction of alignment may explain the findings.

Impact of stance phase microprocessor-controlled knee prosthesis on ramp negotiation and community walking function in K2 level transfemoral amputees.

BACKGROUND: Microprocessor controlled prosthetic knees (MPK) offer opportunities for improved walking stability and function, but some devices' swing phase features may exceed needs of users with invariable cadence. One MPK offers computerized control of only stance (C-Leg Compact). OBJECTIVE: To assess Medicare Functional Classification Level K2 walkers' ramp negotiation performance, function and balance while using a non-MPK (NMPK) compared to the C-Leg Compact. STUDY DESIGN: Crossover. METHODS: Gait while ascending and descending a ramp (stride characteristics, kinematics, electromyography) and function were assessed in participant's existing NMPK and again in the C-Leg Compact following accommodation. RESULTS: Ramp ascent and descent were markedly faster in the C-Leg Compact compared to the NMPK (p ≤ 0.006), owing to increases in stride length (p ≤ 0.020) and cadence (p ≤ 0.020). Residual limb peak knee flexion and ankle dorsiflexion were significantly greater (12.9° and 4.9° more, respectively) during single limb support while using the C-Leg Compact to descend ramps. Electromyography (mean, peak) did not differ significantly between prosthesis. Function improved in the C-Leg Compact as evidenced by a significantly faster Timed Up and Go and higher functional questionnaire scores. CONCLUSIONS: Transfemoral K2 walkers exhibited significantly improved function and balance while using the stance-phase only MPK compared to their traditional NMPK.

Twenty-year survival analysis in total knee arthroplasty by a single surgeon.

Between January 1988 and December 2006, a total of 3014 primary total knee arthroplasties (TKAs) in 2042 patients were performed, and survivorship analysis was performed. Survivorship analysis showed a 10-year survival of 93.8% and a 20-year survival of 70.9%. There was no significant difference in the survival rate according to sex and diagnosis (P = .142 and .443, respectively). The survival rate was higher in the patients older than 60 years (P < .001). The survival rate of Total Condylar IV (TC-IV) was higher than that of Ortholoc (Dow Corning Wright Medical, Arlington, Tenn) (P < .001). Total knee arthroplasty results in satisfactory long-term survival rates. However, the survival rate decreases over time. The risk of requiring revision TKA was related to age and type of implants. Careful consideration is necessary to decide the time for TKA and select type of implants.

Long-term comparison of mobile-bearing vs fixed-bearing total knee arthroplasty.

Few published reports have been published regarding a comparison of the long-term outcomes between mobile- (MB) and fixed-bearing component designs for knee arthroplasty. The minimum 10-year clinical and radiologic follow-up of an unselected consecutive series of 89 patients (107 knees) who were randomized to have one of these different designs for primary arthroplasty was done. Twenty-six patients (30 knees) who had a fixed-bearing design and 24 patients (33 knees) who had an MB prosthesis were available for follow-up. Two MB knees were revised for aseptic loosening of a tibial component in one and femoral component fracture in the other. In patients who did not have revision surgery, there were no differences between the groups with respect to mean Knee Society scores, knee flexion, or pain scores.

Meta-analysis and systematic review of clinical outcomes comparing mobile bearing and fixed bearing total knee arthroplasty.

Mobile bearing (MB) knee replacements were designed with the goal of increased conformity and decreased bearing wear. We conducted a meta-analysis and systematic review of randomized controlled trials comparing outcomes of MB and fixed bearing (FB) total knee arthroplasty (TKA). We identified 14 studies reporting our primary outcome of Knee Society Scores (KSS). We also pooled data for post-operative range of motion (ROM) and Hospital for Special Surgery scores (HSS). The standard difference in mean outcome scores for KSS and HSS demonstrated no difference between groups (P = .902, and P = .426 respectively). Similarly, the pooled data for ROM showed no difference between groups (P = .265). The results of this study found no significant differences between clinical outcomes of MB and FB TKA.

The natural history of anterior knee pain in 2 posterior-stabilized, modular total knee arthroplasty designs.

Anterior knee pain (AKP) has been a persistent complaint after total knee arthroplasty; however, the natural course of this complaint has not been fully investigated. This is a 10-year follow-up report of a prospective, randomized study between the Insall-Burstein II (Zimmer, Warsaw, IN) and the Press Fit Condylar Modular (Johnson & Johnson, Raynham, MA) knees. Up to one third of total knee arthroplasties will experience mild to moderate AKP at 1-year follow-up, which will persist in approximately 30% of these previously symptomatic knees at 10-year follow-up. New-onset AKP will develop in approximately 10% of previously asymptomatic knees.

[Imaging of knee prostheses]. / Imagerie des prothèses du genou.

The authors present a pictorial essay illustrating the different types of knee prostheses, their normal appearances, as well as the imaging features (radiographs, CT, US) of the main complications that may occur.

Incidence and risk factors for surgical infection after total knee replacement.

Surgical site infection (SSI) after total knee replacement (TKR) is a devastating complication. We performed a retrospective study of all consecutive TKRs performed during a 2-y period. Surgical site infection (SSI) was defined by standard criteria. All patients were examined 1 y following surgery. Of 180 patients undergoing TKR, 10 (5.6%) developed a superficial (3, 1.7%) or deep (7, 3.9%) SSI. Two independent risk factors for SSI were detected: left knees became infected more often (9/ 92, 9.8%) than right knees (1/88, 1.1%) (Relative Risk 6.7 +/- 95% CI 1.7-26.8); and 7/72 (9.7%) patients receiving a type-1 prosthesis developed infection versus 3/104 (3.1%) receiving a type-2 prosthesis (RR 4.7, 95% CI 1.18-18.4). Investigation of the operating room revealed 3 problems: there was significant traffic through the door on the left of the patient; a nonstandard horizontal-flow air conditioner had been installed above that door; a tool-washing sink was in use on the other side of that door. Infection control guidelines were rehearsed: the sink was removed, the air conditioner was disconnected, and the door was locked. In a prospective survey performed 2 y later only 1/45 patients (2.2%) undergoing TKR developed a superficial SSI (p = 0.5). Correction of independent risk factors for infection following TKR led to a decrease in SSI rate.

[Revision surgery for knee prostheses using the DRG system]. / Wechseloperationen in der Kniegelenkendoprothetik im DRG-System.

Due to an increasing life expectancy and earlier primary implantation of total knee replacements, the number of patients requiring revision surgery in Germany is increasing by 7% every year. These revision cases belong to the most treatment and cost intensive operations in joint replacement surgery. Presently, the description of these procedures in the German DRG system, which defines the financial reimbursement for the hospitals, is changing yearly with the development of new catalogues. The changes made from 2003 to 2005 are outlined in the following article. A correct depiction of the treatment and procedures required in such cases is a prerequisite for an adequate reimbursement. In the long-term, hospitals will only be able to offer such complex treatment forms if the financial compensation correctly reflects the costs incurred.

Estudio multicéntrico sobre la repercusión de las lesiones meniscales y de ligamento cruzado anterior previas a la cirugía protésica en pacientes intervenidos de prótesis de rodilla / Multi-center study on the repercussion of meniscal and ACL injuries prior to prosthetic replacement in patients undergoing TKR

Objetivo. Evaluar la incidencia y repercusión de las lesiones e intervenciones previas en la articulación de la rodilla en pacientes operados de prótesis de rodilla. Material y método. Se registraron 474 pacientes diagnosticados de gonartrosis intervenidos con una prótesis total de rodilla (PTR) primaria en 5 centros españoles, durante 12 meses, analizando sus características morfológicas y las lesiones e intervenciones previas sufridas en la articulación de la rodilla comparado con una población aleatoria de 129 pacientes intervenidos, en los mismos centros y en el mismo período de tiempo, de prótesis total de cadera (PTC) primaria. En cada paciente analizamos la edad, el sexo, el lado intervenido, el peso, la talla y el índice de masa corporal (IMC: kg/m2), las prótesis previas en la articulación contralateral o en otras articulaciones y el año de su colocación. Los parámetros evaluados fueron la alineación de la rodilla, la actividad laboral desempeñada previamente y en el momento de la intervención, la actividad física, las enfermedades e intervenciones generales previas a la intervención, los traumatismos padecidos, las intervenciones en la articulación de la rodilla y el estado óseo. Resultados. No hemos encontrado diferencias estadísticamente significativas entre el grupo PTR y PTC comparando los traumatismos previos, la actividad laboral, las intervenciones del sistema musculoesquelético previas ni tampoco la alineación de la rodilla. En el grupo de las PTR no encontramos diferencias estadísticamente significativas entre las lesiones de rodilla previas con la edad, el peso, la talla o el IMC ni entre la técnica quirúrgica previa de la articulación de la rodilla con la edad, el peso, la talla o el IMC. Sin embargo, en el grupo PTR hubo un mayor número de lesiones meniscales y un mayor IMC que entre los operados de PTC. Además, en las PTR las mujeres presentaron un IMC mayor (p < 0,006). Las amas de casa tenían el IMC más elevado (p < 0,02) entre todos los grupos laborales. Conclusiones. Se constató una correlación significativa entre artrosis de rodilla y obesidad, y también una correlación baja entre meniscectomía previa y artrosis de rodilla. Por ello, el tratamiento de la obesidad debe ser una medida preventiva de la artrosis de rodilla, y por tanto de los PTR. Los pacientes operados de meniscectomía o rotura de ligamento cruzado anterior deben ser estudiados con mayor detenimiento (AU)

Purpose. To assess the incidence and repercussion of previous lesions to and procedures in the knee joint in patients undergoing TKR. Materials and methods. 474 subjects were included, who had undergone primary TKR with a diagnosis of gonarthrosis in 5 Spanish hospitals. The patients were followed up over a period of 12 months, during which their morphological characteristics as well as the earlier lesions and procedures they had had in the knee joint were analyzed. A comparison was made with a random control population of 129 patients who underwent a primary THR. For each patient we analyzed the following factors: age, gender, the operated side, weight, height and body mass index (BMI: kg/m2), any prior prostheses in the contralateral ¬ or any other - joint and the year it/they had been implanted. Other parameters assessed were: knee alignment, occupational profile of the patient at and prior to the time of operation, their degree of physical activity, any diseases or general operations suffered prior to the procedure, any trauma experienced, any surgery to the knee joint as well as the overall bone stock condition. Results. We did not find statistically significant differences between the TKR and the THR groups as regards previous trauma, occupational profile, previous surgery to the musculoskeletal system or knee alignment. In the TKR group, we did not find statistically significant differences between the previously sustained knee injuries and the patients' age, weight, height or BMI; or between the surgical technique used in any previous surgery to the knee joint and the patients' age, weight, height or BMI. Nonetheless, there was a larger number of meniscal lesions as well as a higher BMI in the TKR group than in the THR patients. Furthermore, in TKRs female patients showed a higher BMI (p<0,006), given that housewives had a higher BMI (p<0,02) then any of the other occupational groups. Conclusions. A significant correlation was found between knee osteoarthritis and obesity as well as a low correlation between previous meniscectomy and knee osteoarthritis. For that reason, obesity treatment should be a preventive measure against knee osteoarthritis and therefore it should be employed prior to a TKR. Patients undergoing a meniscectomy or ACL repair surgery should be considered more carefully (AU)

Vástagos cementados en recambio de prótesis de rodilla. Nuestra experiencia / Cemented stems for revision knee arthroplasty. Our experience

Objetivo: Nuestro objetivo es analizar los resultados clínicos y radiológicos de los vástagos de revisión cementados del modelo Natural I y II (Centerpulse) intervenidos en el servicio desde 1992 hasta 2002. Material y Métodos: Para ello se hace una valoración clínica y radiológica de la última consulta realizada en el hospital utilizando la base de datos Orthocom (Centerpulse) y una encuesta telefónica para determinar el estado de salud (SF-12) así como el grado de satisfacción del paciente. Un 75% de la muestra eran mujeres. LA edad media era 71+/- 5 años (60-83). El seguimiento medio ha sido de 3,5 +/- 2 años (1,3-9). Resultados: La causa más frecuente de recambio ha sido el aflojamiento aséptico de los componentes (15 casos) predominando el aflojamiento el componente tibial con delaminación de la bandeja de polietileno, seguido de infección en 5 casos, inestabilidades en varo: 2 casos y en valgo: 2 casos, y 1 caso de artrofibrosis. En un caso la prótesis fracasó con una inestabilidad en valgo, por lo que fue necesario un segundo recambio. Discusión: Existen pocas series publicadas, con un seguimiento muy limitado. En este trabajo hemos encontrado que los pacientes con vástagos cementados en recambio de prótesis de rodilla tienen unos resultados clínicos aceptables a medio plazo, pero con una tasa de segundo recambio de un 13% a casi 4 años, hecho que nos preocupa

Objective: The purpose of the study was to review the clinical and radiographic outcome of revision total knee arthroplasty using cemented component fixation with Natural I and II stems between 1992 and 2002 (Centerpulse). Material and Methods: We study the clinical and radiographic outcome of the last visit in our office and use the Orthocom database (Centerpulse). We do a questions list by phone to determine the SF-12 and the satisfaction of the patient. A 75% of the patients were females. The mean age was 71+/-5 years (range 60-83). Patients were followed for a mena of 3,5+/-2 years (range: 1,3-9). Results: The majority of the revisions (15 patients) were for aseptic loosening of components, mainly tibial component with polyethylene delamination. Infection occurred in 5 cases, instability in varus: 2 cases and in valgus: 2 cases, and 1 case of arthrofibrosis. A case of instability in valgus was re-vised. Discussion: There are few studies, most with limited follow-up that have been published regarding uncemented and cemented intramedullary stems in revision total knee arthroplatsy. This study found that patients with cemented components in revision knew arthroplasty has acceptable midterm clinical results, but the rate of re-revision, 13% at almost 4 years, is a concern

Biomecánica de las prótesis de rodilla / Biomechanics of the knee prosthesis

Las prótesis totales de rodilla constituyen uno de los implantesmás colocados en el ámbito de la ortopedia. El númerode modelos existentes en el mercado es muy elevadoy todos tienen sus características. A pesar de ello podemosagrupar las artroplastias de rodilla por estas caracterísricas,siendo las prótesis de platillo móvil el grupo más novedoso.Revisamos la bibliogrfía más reciente sobre la biomecánicade las prótesis totales de rodilla, englobando aspectos comolos materiales, el polietileno, la fijación, la geometría ola presencia del ligamento cruzado posterior para entenderen profundidad el funcionemiento de una PTR

Total knee prostheses (TKAs) are one of the most frequentimplants we use like orthpaedists. There are a largenumber of models and all of them have their characteristics.Despite of it we can group TKAs in avery few ones inwhich mobile-bearing arthroplasty in the newness. We reviewthe literature about biomechanics of TKAs includingmaterials, UHMWPE, fixation of the prostheses, geometryor presence of the cruciate posterior ligament to really understandarthroplasty working

Rodillas protésicas. Clasificación e indicaciones clínicas / Prosthitic knees. Clasification and clinical prescription

La rodilla protésica es uno de los elementos claves en el diseño de las prótesis modulares y la aparición de nuevos mecanismos junto con la proliferación de rodillas ha complicado su clasificación y prescripción. En este trabajo revisamos los distintos mecanismos de rodillas, los agrupamos según su mecanismo de acción y proponemos al lector una guía orientativa para su prescripción. Para ello hemos realizado una revisión bibliográfica en la base de datos médica Medline y hemos recabado información de la industria ortoprotésica. Para aquellos puntos en que no existen criterios firmes exponemos el criterio que seguimos según nuestra experiencia (AU)

Medical devices; reclassification of the knee joint patellofemorotibial metal/polymer porous-coated uncemented prosthesis and the knee joint femorotibial (unicompartmental) metal/polymer porous-coated uncemented prosthesis. Final rule.

The Food and Drug Administration (FDA) is announcing that it has reclassified two fixed-bearing knee joint prostheses, the knee joint patellofemorotibial metal/polymer porous-coated uncemented prosthesis, which is intended to be implanted to replace a knee joint, and the knee joint femorotibial (uni-compartmental) metal/polymer porous-coated uncemented prosthesis, which is intended to be implanted to replace part of a knee joint. FDA has reclassified the devices from class III (premarket approval) into class II (special controls). The special control that will apply is a guidance document entitled "Class II Special Controls Guidance Document: Knee Joint Patellofemorotibial and Femorotibial Metal/Polymer Porous-Coated Uncemented Prostheses; Guidance for Industry and FDA." The agency is reclassifying these devices into class II because special controls, in addition to general controls, will provide reasonable assurance of the safety and effectiveness of the devices, and there is sufficient information to establish special controls. The agency is also announcing that it has issued an order in the form of a letter to the Orthopedic Surgical Manufacturers Association (OSMA) reclassifying the devices.