Posterior-stabilized Implants Research Articles

Acquired Idiopathic Stiffness After Contemporary Total Knee Arthroplasty: Incidence, Risk Factors, and Results Over 25 Years

BackgroundAcquired idiopathic stiffness (AIS) remains a common failure mode of contemporary total knee arthroplasties (TKAs). The present study investigated the incidence of AIS and manipulation under anesthesia (MUA) at a single institution over time, determined outcomes of MUAs, and identified risk factors associated with AIS and MUA. MethodsWe identified 9771 patients (12,735 knees) who underwent primary TKAs with cemented, modular metal-backed, posterior-stabilized implants from 2000 to 2016 using our institutional total joint registry. Mean age was 68 years, 57% were female, and mean body mass index was 33 kg/m2. Demographic, surgical, and comorbidity data were investigated via univariate Cox proportional hazard models and fit to an adjusted multivariate model to access risk for AIS and MUA. Mean follow-up was 7 years. ResultsDuring the study period, 456 knees (3.6%) developed AIS and 336 knees (2.6%) underwent MUA. Range of motion (ROM) increased a mean of 34° after the MUA; however, ROM for patients treated with MUA was inferior to patients without AIS at final follow-up (102° vs 116°, P < .0001). Significant risk factors included younger age (HR 2.3, P < .001), increased tourniquet time (HR 1.01, P < .001), general anesthesia (HR 1.3, P = .007), and diabetes (HR 1.5, P = .001). ConclusionAcquired idiopathic stiffness has continued to have an important adverse impact on the outcomes of a subset of patients undergoing primary TKAs. When utilized, MUA improved mean ROM by 34°, but patients treated with MUA still had decreased ROM compared to patients without AIS. Importantly, we identified several significant risk factors associated with AIS and subsequent MUA. Level of EvidenceLevel III, retrospective comparative study.

Secondary Patellar Resurfacing in TKA: A Combined Analysis of Registry Data and Biomechanical Testing.

The German Arthroplasty registry (EPRD) has shown that different prosthesis systems have different rates of secondary patellar resurfacing: four years after implantation, the posterior-stabilized (PS) Vega prosthesis has a 3.2% risk of secondary patellar resurfacing compared to the cruciate-retaining (CR) Columbus prosthesis at 1.0% (both Aesculap AG, Tuttlingen, Germany). We hypothesized that PS implants have increased retropatellar pressure and a decreased retropatellar contact area compared to a CR design, which may lead to an increased likelihood of secondary patellar resurfacing. Eight fresh frozen specimens (cohort 1) were tested with an established knee rig. In addition, a possible influence of the registry-based patient collective (cohort 2) was investigated. No significant differences were found in patient data–cohort 2-(sex, age). A generally lower number of PS system cases is noteworthy. No significant increased patella pressure could be detected with the PS design, but a lower contact area was observed (cohort 1). Lower quadriceps force (100°–130° flexion), increased anterior movement of the tibia (rollback), greater external tilt of the patella, and increasing facet pressure in the Vega PS design indicate a multifactorial cause for a higher rate of secondary resurfacing which was found in the EPRD patient cohort and might be related to the PS’ principle function.

A Prospective Randomized Controlled Trial Comparing Medial-Pivot versus Posterior-Stabilized Total Knee Arthroplasty

BackgroundThe medial-pivot (MP) design for total knee arthroplasty (TKA) aims to restore more natural “ball-and-socket” knee kinematics compared to the traditional posterior-stabilized (PS) implants for TKA. The objective of this study is to determine if there was any difference in functional outcomes between patients undergoing MP-TKA vs PS-TKA. MethodsThis prospective randomized controlled trial consisted of 43 patients undergoing MP-TKA vs 45 patients receiving a single-radius PS-TKA design. The primary outcome was postoperative range of motion (ROM). Secondary outcomes included the Western Ontario and McMaster Universities Arthritis Index, Oxford Knee Score, Knee Society Score (KSS), and radiological outcomes. All study patients were followed-up for 2 years after surgery. ResultsPatients undergoing MP-TKA had comparable ROM at 1 year (114.6° ± 16.3° vs 111.3° ± 17.8° respectively, P = .88) and 2 years after surgery (114.9° ± 15.5° vs 114.9° ± 16.4° respectively, P = .92) compared to PS-TKA. There were also no differences in Western Ontario and McMaster Universities Arthritis Index (26.8 ± 19.84 vs 22.0 ± 12.03 respectively, P = .14), Oxford Knee Score (42.7 ± 8.1 vs 42.3 ± 6.7 respectively, P = .18), KSS clinical scores (82.9 ± 16.96 vs 81.42 ± 10.45 respectively, P = .12) and KSS functional scores (76.2 ± 18.81 vs 73.93 ± 8.53 respectively, P = .62) at 2-year follow-up. There was no difference in postoperative limb alignment or complications. ConclusionThis study demonstrated excellent results in both the single-radius PS-TKA design and MP-TKA design. No differences were identified at 2-year follow-up with respect to postoperative ROM and patient-reported outcome measures.

No difference in the anteroposterior stability between the GRADIUS and multi-radius designs in total knee arthroplasty

BackgroundThis retrospective study aimed to compare stability and clinical and radiological outcomes of total knee arthroplasty (TKA) for the GRADIUS and multi-radius femoral designs after minimum of two-year follow-up. MethodsA total of 142 patients who underwent TKA using ATTUNE posterior stabilized (PS) implants (68 patients, GRADIUS group) or Persona PS implants (74 patients, multi-radius group) for degenerative osteoarthritis were included. After an average of 2-year follow-up, the anteroposterior (AP) stability at 30°, 60°, and 90° was measured using KT 2000 device and compared between the two groups. The clinical outcome measurements included range of motion (ROM) of the knee, patient-reported outcomes and anterior knee pain (AKP). For the clinical evaluation of mid-flexion instability, pain was evaluated using the visual analog scale (VAS) score recorded during climbing up or going down stairs. The radiolucent lines on knee radiographs obtained at final follow-up were evaluated and compared between two groups. ResultsThe average AP stability at 30° knee flexion was 5.7 mm in the GRADIUS group and 5.9 mm in the multi-radius group; however, the difference was not significant. The AP stability at 60° and 90° knee flexion was also similar in both groups. There were no significant differences in the ROM, patient-reported outcomes at follow-up, incidence of AKP and VAS scores between the two groups. There were no differences in the incidence of radiolucency around the components between the two groups. ConclusionThe GRADIUS design did not show any advantage with respect to the stability or clinical outcomes compared with the multi-radius design in TKA.

Safety and efficacy of epsilon aminocaproic acid (EACA) as an antihemorrhagic drug in bilateral one stage total knee arthroplasty: A double-blind randomized controlled trial

BackgroundAntifibrinolytic drugs are widely used to minimize blood loss and transfusion requirements in total knee arthroplasty (TKA). Although tranexamic acid (TXA) has been widely studied for its use in TKA, there are limited studies on epsilon-aminocaproic acid (EACA). MethodsIn a double-blind randomized control trial, all patients (n = 91) operated with bilateral simultaneous TKA were randomly given either intravenous EACA or placebo (normal saline). A single surgeon performed the TKA with posterior-stabilized implants under tourniquet. A suction drain was placed and kept for 48 h postoperatively. The intraoperative blood loss and drain output were calculated. The postoperative hemoglobin (Hb), drop in Hb, total blood loss, and number of blood transfusions in each group were calculated. ResultsBoth of the groups were comparable in terms of age, sex, body mass index, and pre-operative Hb. There was a significant difference between the EACA group and control group in terms of intraoperative blood loss (150 ml vs. 165 ml, P = 0.01), drain output (494 ml vs. 1062 ml, P < 0.001), postoperative Hb (9.9 g/dl vs. 8.6 g/dl, P = 0.002), drop in Hb (2.2 g/dl vs. 3.1 g/dl, P = 0.026) and transfusion rate (median transfusion 0 vs. 1, P < 0.001). The total blood loss, as calculated by the Hb balance method, was significantly less (P < 0.001) in the EACA group (0.99 l) compared with the control group (2.71 l). None of the patients developed any adverse reaction/complication to the drug. ConclusionIntraoperative administration of EACA significantly decreased the blood loss and postoperative transfusion rates compared with no antifibrinolytic therapy in bilateral simultaneous TKA.

Intraoperative Practice Variability in Total Knee Arthroplasty

BackgroundConsiderable practice variability exists among orthopedic surgeons performing total knee arthroplasty (TKA). The purpose of this study is to understand what TKA surgical and perioperative techniques are standard among high-volume academic knee arthroplasty surgeons. MethodsA written survey with 59 questions regarding management preferences in TKA was distributed by the 2018 John N. Insall Traveling Fellows to all arthroplasty-trained attending physicians at 13 medical centers, with 45 responses recorded. ResultsSurveyed surgeons performed unicompartmental knee arthroplasty (88%) and bilateral TKA (87%). Most surveyed surgeons rarely or never performed outpatient primary TKA (71%). Conventional alignment guides and cemented implants were used by 80% of respondents. Most surgeons used posterior-stabilized implants (67%), followed by cruciate-retaining (20%), ultracongruent (20%), and medial congruent or medial pivot designs (17.8%). Surveyed surgeons frequently or always resurfaced the patella (73%), used a tourniquet for the entire case (73%), and used tranexamic acid for all TKAs (91%). The most common locations for intra-articular anesthetic injection were the arthrotomy (91%), the periosteum (84%), and the medial posterior capsule (82%). Saline (62%) and dilute iodine (47%) were the most common irrigation fluids. The arthrotomy was most commonly closed with running barbed suture (60%) followed by interrupted vicryl (40%). Skin closure was predominantly with running monocryl (60%) followed by staples (29%). Anticoagulation for TKA was primarily aspirin 81 mg BID (60%). ConclusionThere was considerable variability among surgeons polled although a strong preference for more conventional and less developmental techniques prevailed.

Fifteen-year survival of the Cedior™ total knee prosthesis.

Total knee arthroplasty (TKA) is an effective treatment for advanced osteoarthritis of the knee. No large and long-term follow-up study has been done about Cedior® prosthesis. The study hypothesis was that 15-year survival for the Cedior™ prosthesis is at least as good as rates reported for other models. A continuous retrospective single-center study included patients managed by Cedior™ TKA with at least 15-year follow-up. The main endpoint was prosthesis survival; secondary objectives were to identify factors for implant revision and to assess functional scores at 15years. In the present series, 15-year all-cause survival for the Cedior® knee prosthesis was 93.03%; comparable to rates in the literature, posterior-stabilized implants showed higher revision rates. No other factors for revision emerged. These findings are comparable with those of the literature.

Uncemented monoblock trabecular metal posterior stabilized high-flex total knee arthroplasty: similar pattern of migration to the cruciate-retaining design — a prospective radiostereometric analysis (RSA) and clinical evaluation of 40 patients (49 knees) 60 years or younger with 9 years’ follow-up

Background and purpose — Uncemented monoblock cruciate retaining (CR) trabecular metal (TM) tibial components in total knee arthroplasty (TKA) work well in the long-term perspective in patients ≤ 60 years. Younger persons expect nearly normal knee flexion after TKA, but CR implants generally achieve less knee flexion compared with posterior stabilized (PS) implants. Cemented PS implants have higher revision rate than CR implants. Can an uncemented monoblock PS TM implant be used safely in younger patients?Patients and methods — 40 patients (49 knees) age ≤ 60 years with primary (20 knees) or posttraumatic osteoarthritis (OA) were operated with a high-flex TKA using an uncemented monoblock PS TM tibial component. Knees were evaluated with radiostereometric analysis (RSA) a mean 3 days (1–5) postoperatively, and thereafter at 6 weeks, 3 months, 1, 2, 5, and 9 years. Clinical outcome was measured with patient-related outcome measures (PROMs).Results — The implants showed a pattern of migration with initial large migration followed by early stabilization lasting up to 9 years, a pattern known to be compatible with good long-term results. Clinical and radiological outcome was excellent with 38 of the 40 patients being satisfied or very satisfied with the procedure and bone apposition to the entire implant surface in 46 of 49 knees. Mean knee flexion was 130°. 1 knee was revised at 3 months due to medial tibial condyle collapse.Interpretation — The uncemented monoblock PS TM implant works well in younger persons operated with TKA due to primary or secondary OA.

Midterm Performance of a Guided-Motion Bicruciate-Stabilized Total Knee System: Results From the International Study of Over 2000 Consecutive Primary Total Knee Arthroplasties

BackgroundThe JOURNEY II Bi-Cruciate Stabilizing Total Knee System (BLINDED) is a second-generation guided-motion knee implant that has been used in over 100,000 primary total knee arthroplasties (TKAs) worldwide. However, performance information is limited. MethodsData for 2059 primary TKAs were abstracted at 7 US and 3 European sites. Estimates of cumulative incidence of revision were compared with registry data for cemented posterior-stabilized implants. ResultsAverage age was 64.3 years (range, 18-91); 58.5% were females; and 12.3% TKAs were in subjects younger than 55 years. Patellae were resurfaced in 95.9%. Median time since primary TKA was 4.2 years; longest was 6.1 years; and 78.9% were 3 years or more since primary TKA. Of 67 revisions (3.2%), 20 (30%) involved femoral or tibial component removal compared to 42% in the Australian Joint Registry (Australian Orthopedic Association National Joint Replacement Registry). All-component revisions accounted for 15 of 67, femoral component only for 2 of 67, tibial component only for 3 of 67, patellar component with/without tibial insert exchange for 17 of 67, and isolated tibial insert exchange for 30 of 67. In addition, there were 18 reoperations without component exchange. Component revision indications were infection (33%), mechanical loosening (21%), fracture of bone around the joint (16%), and instability (15%). Kaplan-Meier revision estimate was 3.1 and 3.6 per 100 TKAs at 3 and 5 years, respectively, compared to Australian Orthopedic Association National Joint Replacement Registry estimates of 3.1 and 4.1 per 100 TKAs. ConclusionThe revision rate for the second-generation implant was similar to cemented posterior-stabilized registry controls.

Effect of polyethylene conformity on total knee arthroplasty early clinical outcomes.

Total knee arthroplasty is a successful procedure in treating subjects with end-stage knee osteoarthritis. The objective of this matched study was to evaluate subjective patient satisfaction and clinical and radiological outcomes in two groups of patients undergoing primary TKA using an identical third-generation design with different conformity in the polyethylene insert. One hundred consecutive patients undergoing TKA because of knee osteoarthritis were randomized in two matched groups. Group A included 50 Posterior-Stabilized (PS) implants, while group B included 50 Medially Congruent (MC) implants. The surgical technique was identical: gap balancing in extension and measured resection in flexion; cruciate ligaments were always removed; the coronal alignment followed the mechanical axis and the tibial slope was set at 3° in the PS group and 5° in the MC. Oxford Knee Score (OKS) and Knee Society Score (KSS) were assessed preoperatively and at 2year minimum follow-up. Two-sample T test statistical analysis was performed. All patients were available at final follow-up: there were no preoperative statistical differences between the two groups in the average preoperative ROM (PS 112°, MC 108°; n.s.), average preoperative KSS (PS 64.4, MC 63.7; n.s.), average preoperative OKS (PS 19.6; MC 19.0; n.s.), and average BMI (PS 34.40, MC 34.60; n.s.). At final follow-up, there were no statistical differences between the two groups in the average OKS (PS 40,5; MC 41.1; n.s.) and in the average KSS (PS 161,5, MC 165,7; n.s.). We found a statistically but not clinically significant difference at final ROM: the average maximum active flexion was 120° in the PS group and 123° in the MC group (s.s.). This study evaluated two biomechanically different polyethylene inserts in the same TKA design, showing that reducing the level of intra-articular conformity had minimal effects on PROMs and objective short-term clinical results but a potentially beneficial effect on ROM. This study suggests that, once a satisfactory intra-operative stability is obtained, the minimal level of constraint should be used. III.

Implant Survivorship and Complication Rates After Total Knee Arthroplasty With a Third-Generation Cemented System: 15-Year Follow-Up

This work is a retrospective cohort study evaluating patients who had undergone third-generation cemented total knee arthroplasty (TKA) with prostheses (NexGen, Zimmer Biomet) utilizing posterior-stabilized (PS) and cruciate-retaining (CR) designs at a single center at their 15-year follow-up. The purpose of this study is to determine the functional knee scores, reoperations, and long-term survivorship for patients with the NexGen Zimmer Biomet Knee system at the 15-year follow-up. In total, 99 patients who had undergone primary TKA were followed for 15 years. At the 15-year follow-up, survivorship in both study groups was similar: 98% for PS TKAs and 100% for CR TKAs. The 2 groups also showed similar functionality: 80% of the PS implants and 89% of the CR implants were associated with no or mild pain (P = .40). Reoperation rates were 2% for the PS group and 0% for the CR group (P = .38). No differences in any of the outcomes analyzed were observed between patients who had CR TKA and those who had undergone PS TKA. Our study found no significant differences in functional outcomes between PS and CR NexGen knee implants. Patients treated by both methods showed excellent longevity and survivorship at the 15-year follow-up.

Medial tilting of the joint line in posterior stabilized total knee arthroplasty increases contact force and stress

BackgroundKinematically aligned total knee arthroplasty is based on the concept to represent the premorbid joint alignment with cruciate-retaining implants, characterized by medial tilt and internal rotation. However, kinematic and kinetic effects of kinematically aligned total knee arthroplasty with posterior-stabilized implants is unknown. The purpose of this study was to examine the effect of medial tilting of the joint line with posterior-stabilized implants. MethodsA mechanical alignment model, and medial tilt 3° and 5° models were constructed. Knee kinematics and contact forces were simulated using a musculoskeletal computer simulation model. Contact stresses on the tibiofemoral joint and the post area were then calculated using finite element analysis. FindingsFrom 0° to 120° of knee flexion, greater external rotation of the femoral component was observed in medial tilt models (−0.6°, 1.8° and 4.2° in mechanical alignment, medial tilt 3° and medial tilt 5° models, respectively). The peak contact stresses on the tibiofemoral joint and the post area at 120° of knee flexion were higher in medial tilt models. The peak contact stresses on the post area in medial tilt 3° and 5° models were 2.2 and 3.8 times greater than that in mechanical alignment model, respectively. InterpretationMedial tilting of the joint line causes greater axial rotation even with posterior-stabilized implants, which can represent near-normal kinematics. However, medial tilting of the joint line in total knee arthroplasty with posterior-stabilized implants may have a higher risk for polyethylene wear at the tibiofemoral joint and post area, leading to subsequent component loosening.

Tibiofemoral Instability After Primary Total Knee Arthroplasty: Posterior-Stabilized Implants for Obese Patients.

Tibiofemoral instability is a common complication after total knee arthroplasty (TKA), accounting for up to 22% of all revision procedures. Instability is the second most common cause of revision in the first 5 years after primary TKA. In this study, 13 knees with tibiofemoral instability after TKA were identified among 693 consecutive primary TKA procedures. Patient demographics, body mass index, clinical symptoms, previous deformity, previous knee surgery, complications, interval between index TKA and first tibiofemoral instability, causes of instability, and interval between index TKA and revision TKA were retrospectively reviewed. Clinical outcomes were assessed with the Lysholm Knee Scoring Scale. All patients were women, and mean body mass index was 37.7 kg/m2 (range, 27.2-52.6 kg/m2). Mean interval between index TKA and first tibiofemoral instability was 23.4 months (range, 9-45 months), and mean interval between index TKA and revision TKA was 25.6 months (range, 14-48 months). All patients had posterior cruciate ligament-retaining implants. Of the 13 knees, 11 had flexion instability and 2 had global instability. In all patients, instability was caused by incompetence of the posterior cruciate ligament; additionally, 1 patient had undersized and malpositioned implants. In 4 knees, the polyethylene insert was broken as well. All patients underwent revision TKA. Lysholm Knee Scoring Scale score had improved from a mean of 35.8 (range, 30-46) to a mean of 68.3 (range, 66-76). All patients included in this study were female and obese. The main cause of instability was secondary posterior cruciate ligament rupture and incompetence. The use of posterior-stabilized implants for primary TKA may prevent secondary instability in obese patients. [Orthopedics. 2017; 40(5):e812-e819.].

Total Knee Replacement in Young Patients: Survival and Causes of Revision in a Registry Population

BackgroundThe incidence of total knee replacements (TKRs) in young patients is increasing. Few reports described encouraging results and acceptable survival rates. However, many concerns still persist, in particular about the high rates of infection and aseptic loosening. Aim of this article was to investigate the survival of TKRs in patients aged 45 years or younger in a registry population. MethodsThe Emilia-Romagna registry RIPO was enquired about TKRs in patients ≤45 years; 238 TKRs were evaluated at a mean follow-up of 5.4 years (range 0-15.6 years), examining the features of the patients involved, the survival rate, and the reasons for revision of the knee implants. ResultsThe TKRs were generally performed in men, in private hospitals, and almost in half of the cases for other causes rather than primary osteoarthritis. The mean age was 40 years. Bicompartmental, cemented posterior-stabilized implants with fixed bearing were preferred. The survival rate was higher than 90% in the first 7 years, and then it decremented. The choice of implant did not apparently influence the survivorship. The final outcomes were acceptable, substantially in line with the previous literature about young patients. Twenty-one revisions occurred (8.8%), in particular 8 cases for aseptic loosening and 7 TKRs for infection. The rate of revision was higher than in overall population and even in some young cohorts. ConclusionTKRs in patients aged 45 years or younger seem a promising procedure, although the high rates of septic and aseptic loosening should be carefully evaluated. Prospective, well-designed studies are required to confirm and investigate these preliminary findings.

Total Knee Arthroplasty Using Bicruciate-Stabilized or Posterior-Stabilized Knee Implants Provided Comparable Outcomes at 2 Years: A Prospective, Multicenter, Randomized, Controlled, Clinical Trial of Patient Outcomes

BackgroundThe bicruciate-stabilized (BCS) knee arthroplasty was developed to replicate normal knee kinematics. We examined the hypothesis that patients with osteoarthritis requiring total knee arthroplasty (TKA) will have better functional outcome and satisfaction with the BCS implant compared with an established posterior cruciate-stabilized implant. MethodsThis multicenter, randomized, controlled trial compared the clinical outcomes of a BCS implant against an established posterior cruciate-stabilized implant with 2-year follow-up. Of the patients awaiting primary knee arthroplasty for osteoarthritis, 228 were randomized to receive either a posterior-stabilized or BCS implant. Primary outcomes were knee flexion and Oxford Knee Score. Secondary outcomes were rate of complications and adverse events (AEs). Tertiary outcomes included Knee Society Score, University of California, Los Angeles, activity score, Patella scores, EQ-5D, 6-minute walk time, and patient satisfaction. ResultsComplete data were recorded for 98 posterior-stabilized implants and 97 BCS implants. Twelve patients had bilateral knee implants. There was no difference between the groups for any of the measures at either 1 or 2 years. At 2 years, knee flexion was 119 ± 0.16 and 120 ± 1.21 degrees for the posterior-stabilized and BCS implants, respectively, (mean, standard error, P = .538) and Oxford Knee Scores were 40.4 ± 0.69 and 40.0 ± 0.67 (P = .828), respectively. There were similar device-related AEs and revisions in each group (AEs 18 vs 22; P = .732; revisions 3 vs 4; P = .618). ConclusionThere was no evidence of clinical superiority of one implant over the other at 2 years.

Comparison of Revision Rates of Non-modular Constrained Versus Posterior Stabilized Total Knee Arthroplasty: a Propensity Score Matched Cohort Study.

Attaining stability during total knee arthroplasty (TKA) is essential for a successful outcome. Although traditional constrained total knee prostheses have generally been used in conjunction with intramedullary stems, some devices have been widely used without the use of stems, referred to as non-modular constrained condylar total knee arthroplasty (NMCCK). The aim of this study was to compare revisions rates after total knee replacement with a non-modular constrained condylar total knee (NMCCK) compared to a posterior-stabilized (PS) design. Between 2007 and 2012, primary PS total knees were compared with NMCCK implants from the same manufacturer. Propensity score matching was performed, and implant survivorship was examined using a Cox proportional hazards model. The cohort consisted of 817 PS knees and 817 NMCCKs matched for patient demographics, surgeon volume, and pre-operative diagnosis. All cause revisions occurred in 11 of 817 (1.35%) in the PS group compared to 28 of 817 (3.43%) in the NMCCK group (p = 0.0168). Excluding revisions for infection and fracture, 8 of 817 (0.98%) PS knees required revision for mechanical failure compared to 18 of 817 (2.20%) NMCCK knees (p = 0.0193). While revisions rates in both cohorts were low, there was a significantly higher revision rate with NMCCKs. Given that cases requiring the use of NMCCK implants are likely more complex than those in which PS implants are used, our findings support the judicious use of NMCCK prostheses.

Total knee implant posterior stabilised by a third condyle: Design evolution and post-operative complications

BackgroundDespite excellent long-term outcomes, posterior stabilisation by a third condyle continues to receive unwarranted criticism regarding patellar complications and instability. HypothesisComplication rates with a tri-condylar posterior-stabilised implant are similar to those with other posterior-stabilised prostheses and have diminished over time due to improvements in prosthesis design. Material and methodsPost-operative complications and revision rates were assessed retrospectively in a prospective cohort of 4189 consecutive patients who had primary total knee arthroplasty (TKA) using a tri-condylar posterior-stabilised implant (Wright-Tornier) and were then followed-up for at least 24 months. The analysis included 2844 knees. The prosthesis generations were HLS1®, n=20; HLS2®, n=220; HLS Evolution®, n=636; HLS Noetos®, n=1373; and HLS KneeTec®, n=595. Complications were compared across generations by applying Fisher's exact test, and survival was compared using the Kaplan-Meier method. ResultsAt last follow-up, there had been 341 (12%) post-operative complications in 306 (10.8%) knees, including 168 (5.9%) related to the implant, 41 (1.4%) infections, and 132 (4.6%) secondary complications unrelated to the implant. Re-operation was required for 200 complications (7%), including 87 (3.1%) consisting in revision of the prosthesis. Implant-related complications were stiffness (n=67, 2.4%), patellar fracture (n=34, 1.2%), patellar clunk syndrome (n=25, 0.9%), patellar loosening (n=3, 0.1%), tibial/femoral loosening (n=15, 0.5%), polyethylene wear (n=3, 0.1%), and implant rupture (n=1, 0.04%). Significant differences across generations were found for stiffness (P<0.0001), patellar fracture (P=0.03), clunk syndrome (P=0.03), and polyethylene wear (P=0.004), whose frequencies declined from one generation to the next. Overall 10-year survival was 92% with no significant difference across generations (P=0.1). DiscussionOutcomes of tri-condylar posterior-stabilised TKA are similar to those obtained using other posterior-stabilised implants. Neither patellar complications nor instability are more common, and improvements in implant design have contributed to correct early flaws. Level of evidenceIV, historical cohort, retrospective assessment of prospectively collected data.

Clinical and Radiographic Results of Attune and PFC Sigma Knee Designs at 2-Year Follow-Up: A Prospective Matched-Pair Analysis

BackgroundAnterior knee pain (AKP) and/or crepitation are important causes of dissatisfaction after total knee arthroplasty (TKA). Aim of this prospective, matched-pair study was to compare 2 different designs of patellofemoral (ie, trochlear groove) TKA. The Attune knee has an anatomic trochlear groove with a medialized dome patellar component vs the PFC Sigma with a single radius trochlear groove with a domed shaped patella. MethodsBetween January 2010 and December 2014, 100 consecutive Attune TKAs were matched to 100 PFC Sigma TKAs based on age, gender, side, and body mass index. All surgeries were performed via medial parapatellar approach and used cemented, posterior-stabilized implants with patellar resurfacing. Clinical evaluations were assessed using Knee Society Scores (KSS) and a patient-administered questionnaire at 2-year follow-up (range, 1.5-3 years). ResultsBased on the KSS clinical rating system, excellent clinical results were achieved in 89.4% and 90.7% of Attune and PFC Sigma TKAs, respectively. There were no significant differences in the KS pain or function scores. The overall incidence of AKP was significantly lower with the Attune knee compared to that of the PFC Sigma (12.5% vs 25.8%; P = .02). The incidence of hearing or feeling noise was also less with the Attune knee (17.7% vs 30.9%; P = .02). The incidence of painful crepitation was low in both groups (1.0% vs 4.1%) with no significant difference between groups (P = .37). Both groups had similar high satisfaction scores of 8.6 and 8.4 for the Attune and PFC groups, respectively (P = .09). ConclusionAt 2-year follow-up, there were no differences between the PFC Sigma and Attune knees in KSS or satisfaction. However, the Attune group had a lesser incidence of AKP and crepitation. Further studies should focus on AKP and noise in cruciate-retaining knees.

The superficial medial collateral ligament is the primary medial restraint to knee laxity after cruciate-retaining or posterior-stabilised total knee arthroplasty: effects of implant type and partial release.

The aim of this study was to quantify the contributions of medial soft tissues to stability following cruciate-retaining (CR) or posterior-stabilised (PS) total knee arthroplasty (TKA). Using a robotic system, eight cadaveric knees were subjected to ±90-N anterior-posterior force, ±5-Nm internal-external and ±8-Nm varus-valgus torques at various flexion angles. The knees were tested intact and then with CR and PS implants, and successive cuts of the deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) quantified the percentage contributions of each structure to restraining the applied loads. In implanted knees, the sMCL restrained valgus rotation (62% across flexion angles), anterior-posterior drawer (24 and 10%, respectively) and internal-external rotation (22 and 37%). Changing from CR TKA to PS TKA increased the load on the sMCL when resisting valgus loads. The dMCL restrained 11% of external and 13% of valgus rotations, and the PMC was significant at low flexion angles. This work has shown that medial release in the varus knee should be minimised, as it may inadvertently result in a combined laxity pattern. There is increasing interest in preserving constitutional varus in TKA, and this work argues for preservation of the sMCL to afford the surgeon consistent restraint and maintain a balanced knee for the patient.

Posterior Stabilized Polyethylene Inserts in Total Knee Arthroplasty: A Retrieval Study Comparing Conventional to High-Flexion Designs

BackgroundHigh-flex (HF) total knee arthroplasties are modified posterior-stabilized (PS) implants designed to accommodate greater flexion. MethodsWe examined differences between HF and PS retrieved tibial inserts with regard to polyethylene surface damage. Twenty HF inserts from each of 3 manufacturers were matched using patient demographics with 20 PS inserts from the same manufacturers. Ranges of motion between matched patients were not different. ResultsBased on subjective damage scores, no differences were detected between HF and PS groups. Differences were found, however, among manufacturers, consistent with design approaches taken for PS and HF implants. ConclusionIn our series, high flexion did not influence damage, although this was likely influenced by the fact that few HF patients in our study had larger range of motions than their PS counterparts.