Hinge Total Knee Arthroplasty Research Articles

A novel radiological index uses the inner canal diameter and the Citak classification index to predict risk factor for aseptic loosening following hinged total knee arthroplasty.

It remains unclear if distal femoral morphology should be a key consideration when selecting the implant or fixation strategy. A novel radiological index has been proposed to classify patients' distal femoral morphology. This study aims to evaluate the validity of this classification system in a cohort of patients undergoing hinged Total Knee Arthroplasty (TKA), and to determine if distal femoral morphology is a risk factor for aseptic loosening or all cause revision following hinged TKA. This study was a retrospective analysis of our institutional database. Fifty-nine patients having undergone hinged TKA with adequate radiographs for examination were eligible for inclusion. Radiographic measurements were performed using the Citak radiological index criteria. The proportion of aseptic loosening and all-cause revisions were compared between the different classification groups. The analysis included 41 females (69.5%) and 18 males (30.5%). The mean age of the participants was 71.2 years (SD = 12.6). For inner canal diameter patients were classified as: Type A (31/59, 53%), Type B (19/59, 32%), and Type C (9/59, 15%). For the Index Classification Group, patients were classified as: Group A (26/59, 44%), Group B (20/59, 34%), and Group C (13/59, 22%). There was no significant difference in overall revision rate between the three groups (χ2 = 3.25, P = .197 from a Chi-square test). There was a significantly higher rate of aseptic loosening in Group C compared to Groups A and B, with no significant difference between Groups A and B in terms of aseptic loosening rates (χ2 = 8.72, P = .013 from a Chi-square test). Distal femoral morphology plays an important role in the risk of aseptic loosening following hinged knee replacement, and should be considered when deciding implant type and fixation in these patients.

The Role of a New Hinged Total Knee Arthroplasty System for Use in a Variety of Complex Knee Scenarios: A Case Series.

Hinged knee arthroplasties are commonly used in scenarios where there are major ligament deficiencies or bone loss around the knee. They are applicable in native knees with major deformities and during revisions. They can also be used as a salvage procedure after distal femoral resection. The new modular hinged device system, namely the Triathlon Hinge Knee (THK) System (Stryker, Mahwah, New Jersey), reflects the advancements of third-generation design and enhances surgical flexibility by allowing streamlined integration with the Triathlon Total Stabilized (TS) System (Stryker, Mahwah, New Jersey) and the Global Modular Replacement System (GMRS, Stryker, Mahwah, New Jersey). Additionally, the Triathlon Revision Tibial Baseplate (Stryker, Mahwah, New Jersey) has been launched as part of THK and is compatible with the Modular Rotating Hinge (MRH , Stryker, Mahwah, New Jersey) femur, which allows the Revision Baseplate to replace the existing tibial component while leaving the existing MRH Femoral Component in place. The Triathlon Revision Tibial Baseplate enables orthopaedic surgeons to use constrained or hinged prostheses, including both distal and total femoral replacement options, without changing the Tibial Baseplate. This is because the TS, MRH, THK, and GMRS femurs are compatible with the new Triathlon Revision Tibial Baseplate. Additionally, the system can be augmented with metaphyseal cone constructs to help provide a stable foundation for reconstruction. This report explores the application of a new modular hinged device system in various scenarios, starting with (1) complex primary hinged knee arthroplasty, followed by revision hinged knee arthroplasty cases including (2) failed TKA with medial collateral ligament (MCL) dysfunction, (3) severe arthrofibrosis post-TKA, (4) revisions for prosthetic joint infection, (5) extensor mechanism deficiency, and (6) arthrofibrosis with extensor mechanism disruption, concluding with a case of (7) distal femoral arthroplasty for periprosthetic fracture post-failed TKA.

Use of Hinged Implants for Multistage Revision Knee Arthroplasty for Severe Periprosthetic Joint Infection: Remission Rate and Outcomes After a Minimum Follow-Up of 5 Years

BackgroundIn severe periprosthetic joint infection after total knee arthroplasty (TKA), multistage procedures are indicated for ongoing signs of infection after implant removal during the spacer interval of an intended 2-stage exchange. In these cases, several additional debridement and spacer exchange surgeries may be necessary. Herein, we analyzed the complications, remission rates, and functional outcomes after multistage revision arthroplasty using hinged TKAs. MethodsPatients (n = 79) treated with multistage revision arthroplasty after chronic periprosthetic joint infection of the knee were included (2010 to 2018). During the prosthesis-free interval, a static spacer containing antibiotic-loaded bone cement was implanted. The mean number of surgeries, including implant removal and revision arthroplasty, was 3.8 (range, 3 to 8). The mean duration from implant removal to revision arthroplasty was 83 days (range, 49 to 318). Complications, remission, and mortality were analyzed after a minimum follow-up of 5 years. Outcomes were assessed based on the Knee Society Score (KSS) and the Western Ontario McMasters University Osteoarthritis Index. ResultsDuring follow-up, 24 (30.4%) patients underwent revision surgery, with a mean time to surgical revision of 99 weeks (range, 1 to 261). After follow-up, the infection-free remission rate and overall mortality were 87.3 and 11.4%, respectively. The mean KSS was 74.3 (range, 24 to 99), the KSS Function Score was 60.8 (range, 5 to 100), and the Western Ontario McMasters University Osteoarthritis Index 30.2 (range, 5 to 83). ConclusionsIn difficult-to-treat cases, multistage revision arthroplasty showed high remission rates and low mortality after a follow-up of 5 years. The overall revision rate was comparably high, accounting for early and late reinfections most of the time. In cases of implant survival, functional outcomes comparable to those of revision hinge TKA reported in the literature can be achieved. Therefore, multistage procedures with additional debridement steps should be performed in cases of ongoing infections in intended 2-stage procedures.

Outcomes of rotating versus pure hinge knee arthroplasty in the setting of one-stage exchange for periprosthetic joint infection.

Rotating or pure hinge knee prostheses are often used in case of periprosthetic joint infection (PJI). Five-year survival data of rotating hinge implants ranging from 52 to 90%, whereas pure hinge data are sparse. This study describes the results of both hinge knee prostheses after one-stage septic exchange. One hundred sixty-seven one-stage septic exchanges of a primary unconstrained total knee arthroplasty (TKA) to a cemented hinge prosthesis (117 rotating and 50 pure hinge TKAs) performed between 2008 and 2017 were retrospectively reviewed. Exclusion criteria were stem extensions or augments used in primary TKA, history of extensor mechanism reconstruction, and a follow-up less than twoyears after surgery. Rates of reinfection, mechanical failures, and all-cause revision-free survival data were documented. At fiveyears, the all-cause revision-free survival was 77% (95% CI 69 to 82). Thirty-one patients (19%) had further revision for aseptic reasons. In the rotating hinge group, the mechanical failure rate was more than twice as high as in the pure hinge group (13% vs 6%), significantly influenced by higher body weight. At a mean follow-up of 6.7years, 21 (13%) patients had a reinfection and underwent a further surgery. Reinfection rates did not differ between the two groups. The use of hinge TKA in the revision of PJI shows favourable fiveyear infection-free and all-cause revision-free survival rates of 91% and 77%, respectively. Our study showed poorer results of the rotating hinge design. These results may help surgeons to choose proper implants in case of septic knee revision.

Midterm results of modular hinge total knee arthroplasty using cementless osseointegrating stems: low fixation associated complications and good functional outcome in primary and revision knee arthroplasty.

This study aimed to investigate functional outcome and complications after primary and revision modular H-TKA using hybrid fixation with cementless stems. Between 2015 and 2018, 48 patients with 50 implants were included after hybrid implantation of a single design H-TKA systemusing cementless osseointegrating stems and modular components. Complications and clinical outcome were analysed using Knee Society Score (KSS), the Western Ontario McMasters Universities Osteoarthritis Index (WOMAC) and the Short-Form Health Survey 12 (SF-12) score. Indications for implantation were aseptic revision (n = 29, 58%), primary TKA (n = 19, 38%) and two-stage septic revisions (n = 2, 4%). Complications were reported in 26% (n = 12), whereas complications associated with hybrid fixation occurred in 5 (10%) cases, with 2 (4%) requiring revision surgery for aseptic loosening and 3 (6%) treated with an adapted postoperative protocol for perioperative fractures. Implant survivorship was 84% after a mean follow-up of 54months. Postoperative KSS significantly improved from 51.50 (12-100) to 78.36 (41-99; p < 0.001). The mean WOMAC score was 19.26 (0-55), SF-12 PCS was 41.56 points (22.67-57.66) and SF-12 MCS was 49.21 points (23.87-63.21). Hybrid modular implantation in H-TKA provides satisfactory clinical and functional results in primary and revision TKA. Clinical outcomes significantly improve with reduced pain, increased mobility, and good-to-excellent functional scores after implantation. Whilst implant survival is comparable to previous studies and complications associated with hybrid fixation are low, general complication rates are comparably high.

Can the Current Thresholds for Synovial Cell Count and Neutrophil Percentage to Diagnose Prosthetic Joint Infection be Applied to Metal-on-Metal Rotating Hinge Total Knee Arthroplasty?

BackgroundSynovial leukocyte count analysis is an important tool in the diagnosis of PJI. However, results can be poor if metallosis is present. The issue of metallosis was established for some rotating hinge knee arthroplasty designs. MethodsThis was a retrospective single-center analysis that included 108 patients who had a single-design metal-on-metal rotating hinge knee arthroplasty who underwent revision surgery and had prior synovial fluid analysis performed. The diagnostic accuracy of leukocyte count and the percentage of polymorphonuclear neutrophiles (% PMN) were investigated. ResultsPatients who had a PJI had a higher median leukocyte count and % PMN compared to aseptic revisions (7,905/μL (interquartile range (IQR) 2,419 to 37,400) and 85% (IQR 70.3 to 93.8) versus 450 (IQR 167 to 1,215) and 46% (IQR 28.5 to 67.4%), P < .001). The respective areas under the curves were 0.916 (95% confidence interval 0.862 to 0.970) for leukocyte count and 0.821 (95% confidence interval 0.739 to 0.902) for % PMN. We calculated an optimal cut-off value of 1,200 leukocytes/μL (Sensitivity 94.5%/specificity 75.5%) and 63% PMN (Sensitivity 85.5%/specificity 73.6%) to define PJI. Established thresholds were less sensitive, but more specific. The “infection likely” scenario of the European Bone and Joint Infection Society (EBJIS) definition was closest to the calculated thresholds. ConclusionCurrently used thresholds for leukocyte cell count and %PMN to define PJI were less sensitive and specific in the diagnosis of PJI in metal-on-metal RHK knees. Surgeons must consider lower cut-off values when evaluating such implants for PJI.

Indications, clinical outcome and survival of rotating hinge total knee arthroplasty in a retrospective study of 63 primary and revision cases

PurposeThe purpose of this study is to report and compare outcome data of both primary and revision cases using a rotating hinge knee (RHK) implant.MethodsThis study retrospectively analyzed 63 cases (19 primary, 44 revisions) at a mean follow-up of 34 ± 8 months after RHK implantation. Outcome parameters were stability, range of motion (ROM), loosening, Hospital of Special Surgery Score (HSS), Knee Society Score (KSS), Oxford Knee Score (OKS), EQ-5D-3L, and Visual Analog Scale (VAS) for overall function. Revision rates and implant survival are reported.ResultsEleven percent showed medio-lateral instability < 5 mm, a mean ROM of 115° ± 17° and radiologic loosening occurred in 8% (2% symptomatic). PROMS showed the following results: HSS 79 ± 18, KSS 78 ± 27, OKS 26 ± 10, EQ-5D index 0.741 ± 0.233 and VAS 70 ± 20. Primary cases revealed better outcomes in HHS (p = .035) and OKS (p = 0.047). KSS, EQ-5D index and VAS did not differ between primary and revision cases (p = 0.070; p = 0.377; p = 0.117). Revision rate was 6.3% with an implant survival of 96.8%.ConclusionsRHK arthroplasty can be performed with good clinical outcome and low revision rate in revision and complex primary cases. RHK is an option in cases where standard arthroplasty and even implants with a higher degree of constraint have reached their limits.Level of EvidenceLevel III, retrospective cohort study.

Biomechanical analysis of femoral stems in hinged total knee arthroplasty in physiological and osteoporotic bone

Background and ObjectiveAdequate fixation is a requisite for hinged Total Knee Arthroplasty (TKA): consequently, several stem solutions are currently available. However, there are no evidence-based biomechanical guidelines for surgeons to determine the appropriate stem length and whether to use cemented or press-fit fixation.The objective of this study is therefore to compare, using a validated finite-element model, bone stresses and implant micromotions in different configurations. MethodsThe 3D bone geometries were obtained from CT-scans reconstruction and the 3D model components of an Endo-Model Rotating Hinge (WALDEMAR LINK GmbH & Co. KG, Hamburg, Germany) were generated from industrial designs provided by the manufacturer. Sixteen configurations were investigated considering four stem lengths (50, 95, 120, 160 mm), cemented and press-fit fixation and physiological and osteoporotic bone properties. A further configuration without stem was analyzed as control.Average Von-Mises stresses, risk of fracture and micromotions were extracted in several regions of interest at 0° and 90° of flexion, under physiological load conditions. ResultsGenerally, longer stems guarantee better fixation compared to short ones; however, they induce higher stress-shielding effect in the distal region of the femur (even greater for press-fit stems, with values up to 38.5% greater than cemented ones).The cemented configurations, especially in case of 50 mm and 95 mm lengths, induce lower micromotions (down to 16% lower) compared to their respective press-fit configurations.The osteoporotic RF values were greater than the physiological ones (up to 20.5%), but always below the bone limit of fracture. ConclusionsAccording to this study, when surgeons need to select a femoral stem in a hinged TKA aiming to proper stability and bone stress, the preferable option would be short cemented stems.

Total Knee Arthroplasty in Patients With Prior Ipsilateral Hip Fusion: A Surgical Technique.

In patients with severe osteoarthritis of the knee with prior ipsilateral hip fusion who require total knee arthroplasty (TKA), a controversial issue is whether to first convert the hip fusion to a total hip arthroplasty (THA) or to perform TKA without reconstruction of the hip. Also, immobility of the ipsilateral, fused hip adds significant technical challenge because the usual positioning of the leg requires modification in order to gain access needed for the TKA. In such cases, we position the patient with the knee suspended, similar to how we perform knee arthroscopy. In our experience, the ipsilateral knee has significant deformity and is best addressed with a constrained, hinged TKA. In 3 patients with severe knee osteoarthritis with prior ipsilateral hip fusion-a 72-year-old man and a 79-year-old woman with hip arthrodesis due to posttraumatic arthritis and an 81-year-old woman with hip arthrodesis due to congenital dislocation of the hip-rotating-hinge knee prostheses were implanted due to severe knee instability. All 3 patients had satisfactory results, without complications, after follow-up of 1 to 5 years. We obtained satisfactory results in the short and medium term without previously converting the hip arthrodesis to THA by positioning patients with the knee suspended, in a way similar to when knee arthroscopy is performed, and implanting rotating hinge TKAs due to severe preoperative knee instability.

Patient-reported outcomes after primary rotating hinge total knee arthroplasty: a multi-centre clinical cohort study.

Rotating hinge prostheses for total knee arthroplasty (TKA) are mostly used in revision setting; however, evidence on the use of these constrained devices in primary setting is scarce and inconsistent. Therefore, we aimed to evaluate the functional outcomes after third-generation rotating hinge implants in primary TKA with a minimal follow-up of twoyears in a large dual-centre observational retrospective clinical trial. The hospital databases of two centres were searched for primary rotating hinge arthroplasty from January 2007 to January 2015. A minimum follow-up of at least twoyears was assured. Patients meeting the inclusion criteria were asked to fill out two self-reported functional scores, the Oxford Knee Score (OKS) and Forgotten Joint Score (FJS), to measure the functional status of the knee. In total, 267 primary rotating hinge knee arthroplasties in 242 patients were performed in two centres. The three major indications were axial malalignment (valgus/varus > 15°), 87/267 (33%), persistent ligamentous instability (28%) and neuromuscular disorders (12%). 184 patients with 202 primary rotating hinge knee arthroplasties could be included that provided data of the self-reported outcome measures (OKS and FJS). A mean OKS score of 37.71 (± 9.23) and a mean FJS score of 63.65 (± 31.01) could be obtained. This large clinical study suggests that constrained devices provide the best results when treating bone-on-bone tricompartimental osteoarthritis of the knee with severe axial deviation (valgus/varus > 15°) and/or persistent ligamentous instability.

Retrieval Analysis of Polyethylene Components in Rotating Hinge Knee Arthroplasty Implants

BackgroundThis study examined a cohort of retrieved rotating hinge (RH) total knee arthroplasty implants of four different designs with emphasis on the surface damage observed on the polyethylene components. Our purpose was to determine if differences in polyethylene damage existed among the designs, and if those differences could be explained by differences in design characteristics. Materials and MethodsSeventy-two RH implants from four manufacturers (DePuy LPS/SROM, Zimmer NexGen, Stryker Howmedica MRH, and Biomet Finn-OSS) removed at the time of revision performed between 2002 and 2017 were identified in our institutional retrieval registry. Damage to the surfaces of the polyethylene was assessed using a subjective grading system and evaluated in multiple zones. Design characteristics that were evaluated included the following: location of the dwell point on the polyethylene component, posterior position of the axle, and amount of hyperextension and rotation allowed by the implant. ResultsThere were no differences in total damage scores between the four implant groups (P = .45). The Stryker Howmedica MRH group showed the least backside wear of all implants but significantly more articular-sided wear compared with two of the other three groups. All implants except NexGen showed increased total damage scores in implants revised for mechanical (vs nonmechanical) reasons and in implants with a longer duration of implantation. ConclusionNo single implant design emerged as superior in terms of minimizing polyethylene wear damage. Polyethylene damage existed in various locations but was not different in severity across designs, suggesting that there is no clear superior RH design that minimizes overall articular surface wear compared with other designs.

Complications and failures of non-tumoral hinged total knee arthroplasty in primary and aseptic revision surgery: A review of 290 cases

IntroductionHinged total knee arthroplasty (TKA) implants are a commonly used option during revision or even primary surgery, but their complications are not as well known, due to the rapid adoption of gliding implants. The literature is inconsistent on this topic, with studies having a small sample size, varied follow-up duration and very different indications. This led us to carry out a large multicentre study with a minimum follow-up of 5 years to evaluate the complications after hinged TKA in a non-tumoral context based on the indications of primary arthroplasty, aseptic surgical revision or fracture treatment around the knee. HypothesisHinged TKA was associated with a high complication rate, no matter the indication. Material and methodsTwo hundred and ninety patients (290 knees) were included retrospectively between January 2006 and December 2011 at 17 sites, with a minimum follow-up of 5 years. The patients were separated into three groups: primary surgery (111 patients), aseptic revision surgery (127 patients) and surgery following a recent (<3 months) fracture (52 patients: 13 around the TKA and 39 around the knee treated by hinged TKA). Patients who had an active infection the knee of interest were excluded. All the patients were reviewed based on a standardised computer questionnaire validated by the SOFCOT. ResultsThe mean follow-up was 71±39 months [range, 0 to 188]. Of the 290 patients included in the study, 108 patients (37%) suffered at least one complication and 55 patients (19%) had to undergo revision surgery: 16 in the primary TKA group (16/111, 14% of primary TKA), 28 in the revision surgery group (28/127, 22% of revision TKA) and 11 in the fracture treatment group (11/52, 21% of fracture TKA). The complications due to the hinged TKA for the entire cohort from most to least common were stiffness (41/290, 14%), chronic postoperative pain (37/290, 13%), infection (32/290, 11%), aseptic loosening (23/290, 8%), general complications (20/290, 7%), extensor mechanism complications (19/290, 6%), periprosthetic fracture (9/290, 3%), mechanical failure (2/290, 0.7%). In the primary TKA group, the main complication leading to re-operation was infection (12/111, 11%), while it was loosening for the revision TKA group (15/127, 12%) and infection (8/52, 15%) for the fracture TKA group. DiscussionThe 37% complication rate for hinged TKA implants is high, with 19% of them requiring re-operation. The frequency of complications differed depending on the context in which the hinged implant was used (primary, revision, fracture). The complications requiring revision surgery were major ones that prevented patients from preserving their autonomy (infection, symptomatic loosening, fracture, implant failure). The most found complications – stiffness and chronic pain – rarely led to revision. Level of evidenceIV; retrospective cohort study.

A retrospective comparison of central and posterior hinge joints in 53 total knee arthroplasties

IntroductionThe number of hinged total knee arthroplasty (HTKA) procedures is constantly increasing. There are two hinge types: central (CHTKA) and posterior (PHTKA). The primary purpose of the study was to compare implant survival in patients with CHTKA versus PHTKA. The secondary purpose was to analyse the radiological and clinical results of the implants. HypothesisThere is no difference between the two groups. Materials and methodsThis study involved 53 patients who received a HTKA for either primary, trauma or revision surgery, of these 32 were in the CHTKA group and 21 in the PHTKA group, with a mean age of 69 years (38–89). The exclusion criteria were: etiology of sepsis, incomplete records and refusal to use data. The revision rate, with the replacement of prosthetic components, was the primary endpoint. The secondary outcomes were: mobility, complications, VAS, IKS, Devane, Charnley and Oxford knee scores, and radiological progression. ResultsThe mean follow-up was 51 months (1–139). At 60 months, overall survival rate of the HTKA was 81%, with a confidence interval (CI) of 95% (71–93.2), and there was no difference between CHTKA and PHTKA, 77.7% (95% CI, 63.3–95.4) versus 85.7% (95% CI, 72–100), p=0.625, respectively. Flexion was 101°±15 (80–140) for CHTKA versus 98°±12 (30–130) for PHTKA, p=0.006. VAS was 0.5±16 (0–6) for CHTKA versus 1.6±14 (0–4) for PHTKA, p=0.000008. The IKS was 103±39 (15–180) for CHTKA versus 81±51 (9–200) for PHTKA, p=0.03. There were no differences in either radiological progression, complications or other functional scores. DiscussionNo significant difference was observed between the survival of CHTKA and PHTKA. CHTKA had better flexion, reduced VAS and increased IKS. Surgeons should be aware of these findings and apply careful consideration to their choice of hinge. Level of evidenceIV; retrospective single-centre study.

Incidence of Leg-Length Discrepancy After Index Hinge Total Knee Arthroplasty

BackgroundLeg-length discrepancies are not commonly associated with total knee arthroplasty (TKA); however, hinge TKA is a complex form of knee reconstruction where functionality of all knee ligaments is replaced by the TKA construct. The purpose of this study is to evaluate the incidence of leg-length discrepancies after unilateral index hinge TKA and association with patient outcomes. MethodsA retrospective review was performed of all patients who underwent unilateral index hinge TKA at a single academic institution from 1999 to 2019. Among 671 patients who underwent index hinge TKA, 188 (28%) had full-length standing anteroposterior hip-to-ankle radiographs available for review both preoperatively and postoperatively. All patients with a leg-length change ≥2 cm were also contacted with a standardized questionnaire to assess for complications. The mean age was 65 years, the mean body mass index was 33 kg/m2, and 52% were female. The mean number of prior surgeries was 2 (range, 0-12). ResultsThe absolute mean and median change in leg lengths was 20 mm and 13 mm, respectively (range, 0-130 mm). Lengthening occurred in 119 (63%) patients compared with shortening in 69 (37%) patients. An absolute change in leg lengths ≥1 cm was observed in 109 (58%) patients, ≥2 cm in 63 (34%) patients, and ≥5 cm in 15 (8%) patients. ConclusionLarge changes in the leg length are common after hinge TKA, likely secondary to altered soft-tissue constraints. Surgeons should be cognizant of potential changes in the leg length in the setting of hinge TKA and incorporate this into preoperative planning and patient counseling. Level of EvidenceLevel IV, therapeutic.

Indications, Survivorship, and Clinical Outcomes of a Rotating Hinge Total Knee and Distal Femoral Arthroplasty System

BackgroundRotating hinge knee prostheses (with or without distal femoral replacement) are indicated in cases of unreconstructible bony or soft tissue compromise. Despite their versatility, these implants have demonstrated high rates of mechanical failure. We aimed to review clinical outcomes of a novel hinged knee arthroplasty system. MethodsWe reviewed all cases in a prospective database of hinged total knee arthroplasty (with and without distal femoral arthroplasty) involving a single manufacturer’s implant system at a large tertiary-level academic health sciences center. We collected reasons for surgery, implant survivorship, reasons for revision, and clinical outcomes (Short Form 12, Western Ontario and McMaster Universities Osteoarthritis Index, and Knee Society Scores). ResultsSeventy-six cases of hinged knee implants using the knee system under investigation were performed (39 hinged total knee and 37 distal femoral replacements) between 2011 and 2018, inclusive. Indications for surgery varied, with second-stage reimplantation most common for rotating hinge and fracture most common for distal femoral arthroplasty. There were 6 revisions in the rotating hinge group (none for aseptic loosening) and 5 in the distal femoral arthroplasty group (1 for aseptic loosening). Average follow-up was 2.89 ± 2.09 years. Postoperative Short Form 12 (Physical Component), Western Ontario and McMaster Universities Osteoarthritis Index, and Knee Society Scores were 30.12 ± 10.17, 55.90 ± 21.51, and 115.62 ± 45.20, respectively. ConclusionThis novel hinged knee system is a highly durable option for complex and revision knee arthroplasty. Early failures tend to be secondary to infection. We observed only a single case of aseptic loosening. Although these early results are encouraging, ongoing follow-up is required to determine long-term prognosis in patients receiving this implant.

Acceptable mid- to long-term survival rates and functional outcomes following a single design rotating hinge total knee arthroplasty.

This study first analyzes implant survival of this single design modular rotating hinge knee and identifies potential risk factors for failure and evaluates joint function using the postoperative WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) score, active flexion and extension deficit. 131 prostheses implanted for failure of prior total knee arthroplasty (n = 120) or complex primary procedures (n = 11) using a single modular implant (MUTARS-modular universal tumor and revision system GenuX, Implantcast, Buxtehude, Germany) between 2006 and 2014 including 73 patients treated for periprosthetic joint infection with a two-stage revision protocol were retrospectively identified. Implant survival was assessed using the Kaplan-Meier method; potential risk factors were identified using the log-rank test, as well as non-parametric analysis. Postoperative function was assessed using the WOMAC and measurement of range of motion. After a median follow-up of 62months, 37 implants required implant revision (28%). Five-year survival was 69.7% [95% CI (confidence interval) 60.9-78.5] with periprosthetic (re-) infection being the main cause for failure (15%), followed by aseptic loosening (9%). In cases of periprosthetic infection, infection-free survival was 83% at 5 years (95% CI 74-92) with twelve patients suffering reinfection (16%).While body mass index (p = 0.75), age (p = 0.16) or indication for rotating hinge knee arthroplasty (p = 0.25) had no influence on survival, Charlson comorbidity score (CCI) (p = 0.07) and number of previous revision surgeries (p = 0.05) correlated with implant failure. There was trend (p = 0.1) for improved survival in fully cemented implants. Mean postoperative WOMAC was 127(range 55-191), 11 patients (15%) had limited knee extension. Rotating hinge total knee arthroplasty using a single modular implant shows acceptable survival rates and function compared to previous studies with (re-)infection being the most relevant mode of failure. Patients with a high CCI and multiple previous surgeries are at increased risk for failure. Retrospective cohort study, III.

Primary constrained and hinged total knee arthroplasty: 2- and 5-year revision risk compared with unconstrained total knee arthroplasty: a report on 401 cases from the Norwegian Arthroplasty Register 1994–2017

Background and purpose — The number of primary, highly constrained knee arthroplasty implants has increased with a theoretically increased risk of early failure. Therefore we analyzed the risk of all revision following total knee arthroplasty (TKA) in patients receiving a hinged or condylar constrained knee (CCK) compared with a conventional unconstrained TKA.Patients and methods — The analyses included 401 primary highly constrained or hinged implants from 1994 to 2017. Kaplan–Meier survival curves were used to evaluate time to first revision with a maximum follow-up of 20 years. Cox regression was used to calculate hazard ratio (HR) comparing condylar constrained knee (CCK), hinged, and unconstrained TKA.Results — Kaplan–Meier estimated prosthesis survival after 2 years was 94.8% (95% CI 91.4–98.2) and 93.5% after 5 years for the primary CCK and 91.0% (CI 86.6–95.4) after 2 years and 85.5% after 5 years for the primary hinged TKA. Adjusted for sex, age groups, diagnosis, time period, previous surgery, and surgery time HR was 1.4 (CI 0.8–2.3) for the CCK and 2.4 (CI 1.6–3.7) for the hinged implants. The most common cause of revision in hinged implants was infection: 14 of 22 revisions. When excluding infection as revision cause, there were no differences in survival between the implant types. Estimated survival excluding infection revisions at 5 years was 96% for unconstrained, CCK, and hinged primary TKA implants.Interpretation — Primary rotating hinge total knee arthroplasty had a higher risk of revision compared with conventional TKA after 2 and 5 years’ follow-up. Infection was the most common cause of revision. When excluding infection revisions from the survival analysis, hinged and CCK implants had similar performance to unconstrained TKA.

The survivorship of the link endo-rotational hinge total knee arthroplasty: 5–12-year follow-up of 100 patients

There is a paucity of survival data reporting the medium to long-term outcome of the LINK® Endo-Model® rotational hinge total knee arthroplasty (ERH-TKA). Such information is essential when counselling patients and predictors of survival would help inform patients of their likely outcome. A series of patients, who received an ERH-TKA, with a minimum follow-up of 5years, were retrospectively identified from an established arthroplasty database. Data were collected from paper and electronic patient records. This included patient demographics, indication for surgery, complication rates and revision status. Our primary outcome of interest was joint implant survival. One hundred patients underwent an ERH-TKA over an 11-year period. There were 66 females and 34 males, with a mean age of 73.8years and 67.6years, respectively. Indications were classified into primary (n = 41), aseptic revision (n = 47) and two-stage infective revision (n = 12). The median follow-up was 8.2 (range 5-12) years. One-year implant survival amongst the cohort was 99%, falling to 95% at 5years. Overall, there were eight revisions during the follow-up period. Considering only cases of aseptic failure, survival was 97% at 5years and all failures occurred amongst revision cases. Implant failure was greater following revision arthroplasty but this was not statistically significant (p = 0.97). Cox regression analysis identified male sex to be the only independent predictor of failure (hazard ratio 1.75, 95% CI 1.04-31.82, p = 0.04) after adjusting for confounding variables. The ERH-TKA has a good medium- to long-term survival rate but male patients are nearly twice as likely to undergo revision, compared to females, and should be made aware of this preoperatively.

Operative Time, Length of Stay, Short-Term Readmission, and Complications after Hinged Primary Total Knee Arthroplasty: A Propensity Score Matched Analysis

Despite the wide utilization of total knee arthroplasty (TKA), it can be technically challenging to perform in patients who have concomitant bone loss, ligamentous laxity, or high-grade deformity, whether in a revision situation or due to a primary pathology. Therefore, hinged knee prostheses have been developed to provide more stable fixation in these situations. The purpose of this study was to compare the short-term peri- and postoperative outcomes of patients undergoing primary TKA with and without hinged prosthesis. Specifically, we compared (1) mean operative times, (2) lengths of stay (LOS), (3) 30-day readmissions, and (4) complications. The American College of Surgeons National Surgical Quality Improvement Program database was queried to identify hinged TKAs and 99 procedures were included. They were matched in a 1:3 ratio to primary TKAs without a hinged prosthesis using propensity score matching. Operative time, LOS, discharge disposition, 30-day readmissions, and complications were compared. Adjusted odds ratios (OR) were also calculated. The operative time was significantly higher in hinged cohort compared with the nonhinged cohort (mean difference [MD] = 22 minutes; range, 10-34 minutes, p < 0.001). There were no significant differences between hinged and nonhinged TKAs with respect to LOS (MD= 0.61 days, range, -0.07-1.30 days, p = 0.080), discharge disposition (OR = 1.09, 95% confidence interval [CI], 0.66-1.84), readmissions (OR = 2.67, 95% CI, 0.84-8.24), and any complications (OR = 1.13, 95% CI, 0.55-2.19). Not surprisingly, primary TKAs with hinged prostheses had increased operative times, but had similar LOS, discharge dispositions, and 30-day rates of readmission and complications when compared with TKAs without a hinged prosthesis. One potential contributing factor to the increased operating time is that patients who receive a hinged implant tend to present with more severe deformities. It is reassuring to know that early outcomes were similar between both cohorts (although we await longer follow-up studies), and that hinged implants can be considered in these difficult to treat patients.

High blood metal ion levels in 19 of 22 patients with metal-on-metal hinge knee replacements

Background and purpose — There has been increasing alarm regarding metal-on-metal (MoM) joint replacements leading to elevated levels of metal ions and adverse reactions to metal debris (ARMDs). There is little information available concerning the prevalence of and risk factors for these adverse reactions, except with MoM hip joint replacements. We determined the levels of metal ions in blood and the rate of revision due to ARMDs in patients treated with MoM hinge total knee arthroplasty (TKA).Patients and methods — 22 patients with TKAs and MoM hinge connecting mechanisms were studied for whole-blood chromium and cobalt levels at 6 months, 1 year, and/or ≥2 years after surgery. Possible ARMDs were investigated by MRI. 12 patients with TKAs and metal-on-polyethylene (MoP) connecting mechanisms served as controls.Results — The cobalt levels were over 5 ppb in 19 of the 22 patients in the MoM group and in 1 of the 12 patients in the MoP group. The chromium levels were over 5 ppb in 11 of the 22 patients in the MoM group and in none of the 12 patients in the MoP group. Pseudotumors were operated in 4 of the 22 patients in the MoM group and in none of the patients in the MoP group.Interpretation — Our results clearly show that the MoM hinge TKA carries a high risk of increased levels of systemic metal ions and also local ARMD, leading to complicated knee revisions. We therefore discourage the use of MoM hinge TKA.