Total Knee Arthroplasty Implants Research Articles

No Difference in Implant Micromotion Between Hybrid Fixation and Fully Cemented Revision Total Knee Arthroplasty: A Randomized Controlled Trial with Radiostereometric Analysis of Patients with Mild-to-Moderate Bone Loss.

In revision total knee arthroplasty (TKA), the femoral component and tibial baseplate are usually cemented. However, stems can be fixed either with cement or with a press-fit technique, with the latter resulting in hybrid fixation. There is no consensus on the preferred stem fixation technique. Therefore, we compared the stability of cemented TKA implants with the stability of TKA implants fixed with the hybrid technique in a prospective randomized trial using radiostereometric analysis (RSA). Thirty-two patients with a Type-I or II bone defect who needed revision TKA and were randomly allocated at the time of surgery into either the cemented or hybrid-fixation group were included in the study. The radiographs for the RSA were obtained during hospitalization (baseline); at 6 weeks; and at 3, 6, 12, and 24 months. Migration of the femoral and tibial implants was measured using model-based RSA and expressed along or around the 3 orthogonal axes and as total translation (TT) and total rotation (TR). Clinical results were evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), active flexion, and visual analog scale (VAS) scores for pain and satisfaction. Mann-Whitney and chi-square tests were used to compare migration and clinical outcomes between the cement and hybrid techniques. At 24 months, no difference in median migration or the number of migrating components was found between the cemented and hybrid-fixation groups. In each group, approximately one-third of the tibial components had total rotation of >1°. The clinical scores did not differ between the techniques. At 24 months after revision TKAs, cemented and hybrid-fixation replacements were equally stable. Unexpectedly, both groups had implants with >1 mm or >1° of micromotion although there were no clinical or radiographic signs of loosening. Whether these findings indicate the possibility of loosening with longer follow-up remains to be investigated. Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Patellar tendon length during knee flexion of meniscal-bearing and rotating total knee arthroplasty implants.

The length of the patellar tendon after total knee arthroplasty (TKA) has most commonly been compared with preoperative measurements. However, there are no reports that discuss changes in the length of the patellar tendon during knee flexion after TKA. The purpose of this study was to evaluate changes in the length of the patellar tendon during knee flexion and to clarify the impact of changes in patellar tendon strain on the length of the patellar tendon and post-operative range of motion (ROM) after TKA. Thirty-six patients undergoing sequential bilateral TKA for osteoarthritis were evaluated. Patients received a meniscal-bearing (MB) implant on one side and a rotating platform (RP) implant on the other and were followed for a median of 115months (range 60-211months). The lengths of the patellar tendon at maximum extension, 30°, 60°, 90° and maximum flexion were measured, and the post-operative ROM of both knees were assessed. The effects of implant design and the knee flexion angle on the length of the patellar tendon were analysed using a linear mixed-effects model. The relationship between patellar tendon strain and post-operative knee ROM was assessed using Pearson's correlation coefficients. Post-operative clinical scores were similar for MB and RP implants. Neither the implant design nor the knee flexion angle significantly affected the length of the patellar tendon. The ROMs in the two designs at final follow-up were equivocal (114° in MB, 113° in RP). There was no correlation between patellar tendon strain and ROM in knees with either implant type. Patellar tendon lengths after mobile-bearing TKA with implants that permitted different anteroposterior constraints were relatively constant at varying degrees of knee flexion. Differences in patellar tendon strain may not impact ROM. These results provide conclusive evidence that the quality of the patellar tendon may play a less important role in ROM after TKA. Therapeutic study, Level II.

Impact of preoperative antithrombotic therapy on blood management after implantation of primary total knee arthroplasty.

Red blood cell concentrates (RCC) substitution after total knee arthroplasty (TKA) is correlated with multifold of complications and an independent predictor for higher postoperative mortality. TKA is mainly performed in elderly patients with pre-existing polymorbidity, often requiring permanent preoperative antithrombotic therapy (PAT). The aim of this retrospective analysis was to investigate the impact of demand for PAT on inpatient blood management in patients undergoing TKA. In this study 200 patients were retrospectively evaluated after TKA for differences between PAT and non-PAT regarding demographic parameters, preoperative ASA score > 2, duration of operation, pre-, and intraoperative hemoglobin level, and postoperative parameters including amount of wound drainage, RCC requirement, and inpatient time. In a multivariate logistic regression analysis the independent influences of PAT, demographic parameters, ASA score > 2, and duration of the operation on RCC demand following TKA were analyzed. Patients with PAT were significantly older, more often had an ASA > 2 at surgery, needed a higher number of RCCs units and more frequently and had lower perioperative hemoglobin levels. Multivariate logistic regression revealed PAT was an independent predictor for RCC requirement. PAT patients are more likely to require RCC following TKA and should be accurately monitored with respect to postoperative blood loss.

Tibial Tray Thickness Significantly Increases Medial Tibial Bone Resorption in Cobalt–Chromium Total Knee Arthroplasty Implants

BackgroundStress shielding is an uncommon complication associated with primary total knee arthroplasty. Patients are frequently identified radiographically with minimal clinical symptoms. Very few studies have evaluated risk factors for postoperative medial tibial bone loss. We hypothesized that thicker cobalt–chromium tibial trays are associated with increased bone loss. MethodsWe performed a retrospective review of 100 posterior stabilized, fixed-bearing total knee arthroplasty where 50 patients had a 4-mm-thick tibial tray (thick tray cohort) and 50 patients had a 2.7-mm-thick tibial tray (thin tray cohort). A clinical evaluation and a radiographic assessment of medial tibial bone loss were performed on both cohorts at a minimum of 2 years postoperatively. ResultsMean medial tibial bone loss was significantly higher in the thick tray cohort (1.07 vs 0.16 mm; P = .0001). In addition, there were significantly more patients with medial tibial bone loss in the thick tray group compared with the thin tray group (44% vs 10%, P = .0002). Despite these differences, there were no statistically significant differences in range of motion, knee society score, complications, or revision surgeries performed. ConclusionA thicker cobalt–chromium tray was associated with significantly more medial tibial bone loss. Despite these radiographic findings, we found no discernable differences in clinical outcomes in our patient cohort. Further study and longer follow-up are needed to understand the effects and clinical significance of medial tibial bone loss.

Changes in the rotational axes of the tibiofemoral joint caused by resection of the anterior cruciate ligament.

Kinematic alignment is a method of aligning implants in total knee arthroplasty (TKA) that strives to restore the native flexion-extension (F-E) and longitudinal rotation (LR) axes of the tibiofemoral joint. The anterior cruciate ligament (ACL) is typically resected at the time of TKA, which might change the position, and orientation of these axes from that of the native knee. Our objective was to determine whether resecting the ACL causes changes in the F-E and LR axes. A custom designed and validated instrumented spatial linkage (ISL) measured the F-E and LR axes in nine cadaveric knees before and after ACL resection. Changes in these axes were computed for knee flexion from 0° to 120°. For the F-E axis, the two statistically significant yet relatively small changes were internal rotation of 0.5° (p = 0.02) and posterior translation of 0.3 mm (p = 0.04). For the LR axis, the statistically significant and relatively large change was medial translation of 2.1 mm (p = 0.01). Changes to the LR axis in both medial-lateral position and varus-valgus orientation varied widely; 77% of a population of knees would have a medial-lateral position change greater than 1 mm, and 53% of a population of knees would have a varus-valgus orientation change greater than 1°. Knowledge of changes of the F-E and LR axes caused by resecting the ACL provides an important baseline for determining the changes in these axes caused by kinematic alignment and mechanical alignment of bi-cruciate retaining, posterior cruciate retaining, and posterior cruciate substituting implants. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:886-893, 2017.

Clinical and Biomechanical Evaluations of Staged Bilateral Total Knee Arthroplasty Patients with Two Different Implant Designs.

Background:Various implants of total knee arthroplasty (TKA) are used in clinical practice and each presents specific design characteristics. No implant managed this day to reproduce perfectly the biomechanics of the natural knee during gait.Objectives:We therefore asked whether (1) differences in tridimensional (3D) kinematic data during gait could be observed in two different designs of TKA on the same patients, (2) if those gait kinematic data are comparable with those of asymptomatic knees and (3) if difference in clinical subjective scores can be observed between the two TKA designs on the same patient.Methods:We performed knee kinematic analysis on 15 patients (30 TKAs) with two different TKA implant designs (Nexgen, Zimmer and Triathlon, Stryker) on each knee and on 25 asymptomatic subjects (35 knees). Clinical evaluation included range of motion, weight bearing radiographs, questionnaire of joint perception, KOOS, WOMAC and SF-12.Results:Comparison between TKAs and asymptomatic knees revealed that asymptomatic knees had significantly less knee flexion at initial contact (p < 0.04) and more flexion for most of the swing phase (p between 0.004 and 0.04). Asymptomatic knees also had less varus at loading response, during stance phase and during most of the swing phase (p between 0.001 - 0.05). Transverse plane analysis showed a tendency for asymptomatic knees to be more in internal rotation during stance phase (p 0.02 - 0.04). Comparing both TKA designs, NexgenTM implant had significantly more flexion at the end of swing phase (p = 0.04) compared to knees with the TriathlonTM implant. In frontal plane, from initial contact to maximum mid stance angle and between the mean mid stance angle and initial contact NexgenTM TKA had significantly more adduction (varus, p =0.02 – 0.03). Clinical scores of both TKAs did not have significant difference.Conclusions:TKA with the tested implants did not reproduce natural knee kinematics during gait. In our cohort of patients, TKA implant design translated in limited kinematics differences during gait and on clinical results.

Does BMI influence clinical outcomes after total knee arthroplasty?

Obesity is a common problem in the western European countries. Since the association between obesity and the emergence of gonarthrosis is approved, it is more important to gain reliable information about this patient group. The aim of the present retrospective study is to evaluate clinical outcomes of German obese patients after total knee arthroplasty (TKA). Between 2001 and 2009 a total of 199 patients with 230 TKA were included in the present study. The collective was divided into four groups in relation to their Body-Mass-Index (BMI); group 1: BMI < 25 kg/m2, n = 24; group 2: BMI 25-30 kg/m2, n = 80, group 3: BMI 30-40 kg/m2, n = 109; group 4: BMI> 40 kg/m2, n = 17. Clinical outcome measurement was scored postoperatively using the knee society score (KSS), hospital for special surgery score (HSS) and the visual analogue scale (VAS). Furthermore complications and subjective patient satisfaction were noted. We did not detect any significant differences in the clinical scores between the BMI-subgroups. However we measured statistically significant worse results in case of infection and instability in all BMI subgroups (p> 0.01). While infection and instability may have a negative influence for the clinical outcome, we did not detect any significant correlation between obesity and exiting complications. Obesity has no significant correlation to influence the outcome after TKA implantation negatively.

Midterm Results After Coated and Uncoated TKA: A Randomized Controlled Study.

Patients undergoing total knee arthroplasty (TKA) who have hypersensitivity to metals usually receive hypoallergenic TKA implants. Coating of a standard implant is a common solution. Although in vitro tests have demonstrated reduction in polyethylene wear for these coatings, it is unknown whether these costly implants have a clinical benefit for patients. One hundred twenty patients undergoing TKA were randomly assigned to receive a novel 7-layer-coating implant or a standard TKA implant. One revision occurred in the standard group, resulting in a calculated 5-year survival of 100% in the coated group and 98.1% in the standard group. The Oxford Knee Score improved substantially in both groups from a mean of 21.6 points preoperatively in the coated group and 21.9 points in the standard group to 39.2 points and 39.2 points, respectively. The current authors observed no adverse effects with the new coating during midterm follow-up. However, longer follow-up time is needed to evaluate possible advantages of this coating. [Orthopedics. 2016; 39(3):S13-S17.].

Postoperative Radiographic Assessment of the Vega Posterior-Stabilized TKA.

Different biomechanical designs are incorporated into various total knee arthroplasty (TKA) implants. The posterior-stabilized prosthesis design utilizes a polyethylene post and femoral cam in place of the posterior cruciate ligament. This produces a more stable component interface, increased range of motion, and potentially a less technical procedure. This study aimed to assess the short-term (>2 year) outcomes associated with the Vega System posterior-stabilized knee prosthesis (Aesculap Implant Systems, Center Valley, Pennsylvania) based on postoperative radiographs using the Knee Society Roentgenographic Evaluation and Scoring System (KSRESS). Thirty-seven TKA patients who had received the Vega posterior-stabilized knee prosthesis and had postoperative radiographs at each follow-up for a minimum of 2 years were enrolled, retrospectively. Two independent observers evaluated the radiographs using KSRESS. Descriptive statistics were used to analyze the data. The average age and body mass index of patients enrolled was 67 years (range, 51-89 years) and 38.5 kg/m(2) (range, 21.2-54 kg/m(2)), respectively. Patients had radiographic follow-up for an average of 36 months (range, 24-58 months). Comparison between first and last available postoperative radiographs revealed a stable femoral and tibial interface with no significant change in prosthesis alignment over the follow-up period. Assessment of the short-term survivorship of the Vega posterior-stabilized prosthesis using KSRESS revealed no significant change in alignment after 2 years of follow-up; however, mid- to long-term studies assessing this junction are needed. A future prospective study using KSRESS in combination with clinical follow-up is recommended to allow comparison of the Vega posterior-stabilized to other prostheses. [Orthopedics. 2016; 39(3):S56-S60.].

Bone Preservation in a Novel Patient Specific Total Knee Replacement.

Background: The volume of total knee arthroplasty procedures is growing rapidly and, correspondingly, it is expected that the volume of revision procedures will grow rapidly as well. Revision surgery is most successful when adequate bone remains on both the tibia and femur to allow for the least invasive revision. We hypothesized that total knee arthroplasty with a patient-specific implant would result in significant bone preservation as compared to standard total knee arthroplasty with “off-the-shelf” implants. Methods: We evaluated 100 total knee arthroplasties which utilized patient-specific implants, versus 37 standard posterior stabilized and 32 standard posterior cruciate retaining total knee arthroplasties. Bone resection was quantified utilizing intra-operative measurements of actual resected bone. Additionally we performed a virtual, CAD-based analysis of resections via CT imaging on 15 knees. Findings: We found that patients had significantly less bone resected in all zones measured, on both the femur and tibia, when patient-specific implants with patient-specific jigs were used. When assessed volumetrically with CAD imaging, standard implants resected 12-49% more bone than did patient-specific implants, depending on the size of the implant utilized. Interpretations: Utilizing patient-specific implants in total knee arthroplasty results in significant bone sparing as compared to standard total knee arthroplasty. This has the potential for less invasive revision surgery in the future, possibly obviating the need for dedicated revision implants or augments and other bone substituting devices.

No difference between fixed- and mobile-bearing total knee arthroplasty in activities of daily living and pain: a randomized clinical trial.

Until now, there are no definitive conclusions regarding functional differences related to middle- and long-term everyday activities and patient pain following implantation of mobile- and fixed-platform tibial prostheses. The aim of this study was to determine whether there are middle-term differences in knee function and pain in patients undergoing fixed- and mobile-bearing total knee arthroplasty (TKA). Eligible patients were randomized into two groups: the first group received TKA implantation with a fixed tibial platform (group A); the second group received TKA with a mobile tibial platform (group B). Patients were followed up (2years), and their symptoms and limitations in daily living activities were evaluated using the Knee Outcome Survey-Activities of Daily Living Scale (ADLS), in addition to pain evaluation assessed using the pain visual analogue scale (VAS). There were no significant differences in function and symptoms in the ADLS and VAS between the study groups. The type of platform used in TKA (fixed vs. mobile) does not change the symptoms, function or pain of patients 2years post-surgery. Although mobile TKAs may have better short-term results, at medium- and long-term follow-up they do not present important clinical differences compared with fixed-platform TKAs. This information is important so that surgeons can choose the most suitable implant for each patient. Randomized clinical trial, Level I.

Tibiofemoral forces for the native and post-arthroplasty knee: relationship to maximal laxity through a functional arc of motion

Accurate soft tissue balance must be achieved to improve functional outcome after total knee arthroplasty (TKA). Sensor-integrated tibial trials have been introduced that allow real-time measurement of tibiofemoral kinematics during TKA. This study examined the interplay between tibiofemoral force and laxity, under defined intraoperative conditions, so as to quantify the kinematic behaviour of the CR femoral single-radius knee. TKA was undertaken in eight loaded cadaveric specimens. Computer navigation in combination with sensor data defined laxity and tibiofemoral contact force, respectively, during manual laxity testing. Fixed-effect linear modelling allowed quantification of the effect for flexion angle, direction of movement and TKA implantation upon the knee. An inverse relationship between laxity and contact force was demonstrated. With flexion, laxity increased as contact force decreased under manual stress. Change in laxity was significant beyond 30° for coronal plane laxity and beyond 60° for rotatory laxity (p<0.01). Rotational stress in mid-flexion demonstrated the greatest mismatch in inter-compartmental forces. Contact point position over the tibial sensor demonstrated paradoxical roll-forward with knee flexion. Traditional balancing techniques may not reliably equate to uniform laxity or contact forces across the tibiofemoral joint through a range of flexion and argue for the role of per-operative sensor use to aid final balancing of the knee.

Morphological evaluation of the sagittal plane femoral load-bearing surface in computer-simulated virtual total knee arthroplasty implantation at different flexion angles.

To examine the effect of implantation of the femoral component of a total knee arthroplasty (TKA) system in 0°, 3°, and 6° of flexion on the sagittal plane morphology of the femoral load-bearing surfaces. It was hypothesized that increasing the flexion angle would result in undersizing of the anterior surface without changing the flexion gap. Computer simulation of a TKA using three-dimensional models of 10 healthy knees, matched to three different sized femoral components. Size discrepancy in the sagittal plane anterior, distal, and posterior joint surfaces between the native and prosthetic knees was calculated at 0°, 3°, and 6° of flexion. The required component size varied with the angle of implantation: 0°, size 3/size 4 (N=7/3), 3°, size 3 (N=10); and 6°, size 2/size 3 (N=4/6). Component undersizing ranged between 4.4-6.3mm at the anterior lateral surface, with a significant difference between 0° and 6° (p<0.05), and 1.2-3.5mm at the anterior medial surface. Component oversizing of the distal surface of the lateral condyle (2.9mm) and undersizing of the medial surface of the posterior condyle (1.6-2.3mm) were comparable at all three flexion angles of component implantation. Increasing the flexion angle of implantation increased the incidence of using a smaller size of femoral component without significant interference with the flexion gap. However, the effect of a smaller femoral component on undersizing of the anterior surface of the condyle and the impact on the extensor mechanism need to be considered.

An Algorithmic, Pie-Crusting Medial Soft Tissue Release Reduces the Need for Constrained Inserts Patients With Severe Varus Deformity Undergoing Total Knee Arthroplasty

BackgroundWe studied the need to use a constrained insert for residual intraoperative instability and the 1-year result of patients undergoing total knee arthroplasty (TKA) for a varus deformity. In a control group, a “classic” subperiosteal release of the medial soft tissue sleeve was performed as popularized by pioneers of TKA. In the study group, an algorithmic approach that selectively releases and pie-crusts posteromedial structures in extension and anteromedial structures in flexion was used. MethodsAll surgeries were performed by a single surgeon using measured resection technique, and posterior-stabilized, cemented implants. There were 228 TKAs in the control group and 188 in the study group. Outcome variables included the use of a constrained insert, and the Knee Society Score at 6 weeks, 4 months, and 1 year postoperatively. The effect of the release technique on use of constrained inserts and clinical outcomes were analyzed in a multivariate model controlling for age, sex, body mass index, and severity of deformity. ResultsThe use of constrained inserts was significantly lower in study than in control patients (8% vs 18%; P = .002). There was no difference in the Knee Society Score and range of motion between the groups at last follow-up. No patient developed postoperative medial instability. ConclusionThis algorithmic, pie-crusting release technique resulted in a significant reduction in the use of constrained inserts with no detrimental effects in clinical results, joint function, and stability. As constrained TKA implants are more costly than nonconstrained ones, if the adopted technique proves to be safe in the long term, it may cause a positive shift in value for hospitals and cost savings in the health care system.

Stemless constrained total knee arthroplasty: An obsolete concept or a contemporary solution?

Achieving a balanced total knee arthroplasty (TKA) can be challenging when addressing fixed deformities with bone deficiencies and a compromised soft issue envelope. Efforts to achieve ligamentous stability without violating the medullary canal led to the introduction of stemless constrained implants. While a stemless constrained implant is bone conserving and efficient, there are biomechanical concerns of higher failure rates due to increased stresses at the bone–implant interface. The purpose of this study is to review the current literature on stemless constrained implants in TKA and address the controversy around their use.

Regional differences in temperature course after knee arthroplasty.

During wound healing after surgery, physiological inflammation leads to an increase in soft tissue perfusion. This is reflected by a characteristic temperature course in the skin. Although local surgical trauma also influences soft tissue perfusion, no data have been available on the regional temperature distribution after knee arthroplasty to date. This study aims at testing the hypothesis that the greatest regional difference in the temperature course is on the site of the maximum surgical trauma (medially) after knee arthroplasty implantation. This is to our knowledge the first study to present regional differences in the temperature course after TKA which would limit the diagnostic value of thermography. Forty-two subjects who were to receive a surface replacement of the knee joint due to primary varus gonarthrosis were included in the study. In all cases, a medial parapatellar approach was chosen. Patients who underwent lateral release or a release of the lateral ligament structures were excluded. In all patients, a thermographic temperature determination was carried out on the operated knee joint every day up to the seventh post-operative day. On the medial side, there was no significant change in temperature between day one 34.9°±0.2° (34.6-35.3°C) and seven after surgery. Thereafter, the temperature remained constant here up to the seventh day after the operation. In contrast to this, on the lateral side there was an increase in skin temperature from the second 35.0±0.2°C (34.7-35.4°C) to the fifth 34.6°±0.2° (34.1-34.9°C) post-operative day (p=0.002). Thereafter, the temperature remained constant here up to the seventh day after the operation. This study refutes the hypothesis that the greatest regional difference in the temperature course is on the site of maximum surgical trauma (medially) after knee arthroplasty implantation. It is shown to the contrary that there is the least regional difference in the temperature course on the site of maximum surgical trauma (medially) after total knee arthroplasty implantation. It is on the site of the minimal trauma (laterally) where marked differences in the temperature course appeared. The normal temporary temperature increase typical of physiological wound healing could only be shown at a distance from the site of soft tissue preparation. This may be the result of a local compromise of perfusion. Consequently, the post-operative diagnostic application of thermography remains limited to regions distant from the surgical site. This may prevent misinterpretation of post-operative thermographic measurements for scientific or clinical reasons. II.

The effect of tibial component alignment on periprosthetic bone remodeling after total knee arthroplasty

Introduction Total knee arthroplasty (TKA) implantation alters mechanical loading of both femur and tibia and leads to local bone loss which can compromise the prosthesis survival and present problems at revision arthroplasty. The aim of this study is to assess the effect of tibial component alignment on periprosthetic bone remodeling after TKA. Patients and methods A prospective study was conducted involving 60 patients (90 knees) who underwent primary cemented posterior stabilized fixed platform TKA. Tibial component alignment was measured in the immediate postoperative X-ray, and patients were divided into three groups: group I with less than 10° of malalignment, group II with 10–15° of varus malalignment, and group III with more than 15°. Dual-energy X-ray absorptiometry (DEXA) was done within 1 week postoperatively and repeated after 12 and 24 months. Three regions of interest (ROIs) were measured: ROI 1 for the lateral tibial plateau, ROI 2 for the medial tibial plateau, and ROI 3 just distal to the tip of the prosthesis. Results The results of DEXA showed statistically insignificantdifferenceinboneremodelingbetweengroup Iandgroup II and statistically significant difference in group III compared to group I and II, with increased bone loss in ROI 1 in group III and increased bone loss in ROI 2 in groups I and II. Conclusion Marked tibial component malalignment more than 15° significantly alters periprosthetic bone remodeling after total knee arthroplasty; however, the effect of this abnormalremodelingonprostheticsurvivalneedslongerfollow-up.

Patient-Specific Total Knees Demonstrate a Higher Manipulation Rate Compared to “Off-the-Shelf Implants”

Patient-specific total knee replacements have been designed in hopes of providing better functional outcomes compared to “off-the-shelf” implants in primary total knee arthroplasty (TKA). We prospectively evaluated manipulation rates and clinical outcomes of 21 patient-specific TKAs matched with 42 posterior-stabilized and 11 cruciate-retaining “off-the-shelf” TKAs. Postoperatively, the patient-specific group had a range of motion significantly less than both control groups (P<0.01). Six of the 21 (28.6%) patient-specific TKAs required manipulation to improve range of motion. No manipulations were reported in either control groups. At minimum two-year follow-up the patient-specific TKAs had similar motion, but worse satisfaction and KSS pain scores. Radiographic analysis provided no insight to the cause of stiffness. Early manipulation is recommended for stiffness with patient-specific TKA.

Platelet-rich plasma does not decrease blood loss in total knee arthroplasty.

This study was designed to assess the use of platelet-rich plasma (PRP) during primary total knee arthroplasty (TKA). The authors hypothesized that this would result in less blood loss and greater hemoglobin and hematocrit levels at discharge and would potentially decrease the length of hospital stay. Leukocyte rich PRP was used during the procedure and at wound closure. Two surgeons performed all procedures in a similar fashion. Two different TKA implants were used. Each surgeon used the same implant throughout the study. A limited medial parapatellar approach was used and drains were used at closure. No tranexamic acid preparations were used. Continuous passive motion machines were used in all patients during their hospital stay. A total of 102 consecutive TKAs were performed. The study group (n=46) consecutively received the PRP injections during the TKA, whereas the control group (n=47) did not. Hemoglobin and hematocrit levels were obtained pre- and postoperatively. Estimated blood loss was recorded during surgery, and the auto-collection reinfusion drain system output was measured. The length of hospital stay was collected and recorded. The study showed that hemoglobin and hematocrit levels were not different when comparing study and control groups. Age and sex differences were insignificant. Finally, no statistical difference was seen for the estimated blood loss and hospital stay between the 2 groups. Platelet-rich plasma use during TKA does not decrease hospital stay or reduce estimated blood loss in the perioperative period.

Survival and functional results after a mean follow-up of 9 years with the Ceragyr® highly congruent mobile-bearing TKA

IntroductionFixed-bearing total knee arthroplasty (TKA) implants have excellent long-term survival. Mobile-bearing implants were developed to reduce bone–implant interface stresses and polyethylene insert wear. The primary objective of this study was to analyze the survival rate of a highly congruent mobile-bearing TKA implant (Ceragyr®) in patients having a minimum follow-up of 7years. We hypothesized that the survival rate would be 95–100% at that time point. Patients and methodsA single-center prospective study included all the patients operated for a primary TKA procedure with a Ceragyr® implant between 2000 and 2003. All the implants were cemented. Patellar resurfacing was not carried out systematically, but could be carried out secondarily in cases of persistent anterior knee pain. Clinical and radiological data were collected before the surgery, at 3months postoperative, at 1year and then at a minimum follow-up of 7years. The primary endpoint was the overall revision-free survival rate. Secondary endpoints were the survival without mechanical failure, IKS scores, knee range of motion and implant positioning. ResultsOne hundred and thirty-four patients (143 Ceragyr® TKA cases) were included; 9 patients (10 TKA) were lost to follow-up (6.7%) and the remaining 125 patients (133 TKA) were contacted. At the final review, 7 of the 133 TKA cases (5.3%) had been revised (6 men, 1 women; P=0.002), 2 (1.5%) because of mechanical failure and 5 (3.8%) because of an infection. The overall revision-free survival rate was 94.8% [95% CI: 89.3–97.5]; survival was 98.4% [95% CI: 93.8–99.6] with mechanical failure as an endpoint. An in-person assessment was conducted on 76 patients (80 TKA cases) (49 women; 27 men) who had an average age of 70.3±8.4years at the time of the arthroplasty procedure. The patella had been resurfaced during the initial procedure in 49 cases, and was either not resurfaced or secondarily resurfaced in 31 cases. The average follow-up was 8.7±1.1years. The IKS score had significantly improved relative to the preoperative values (P<0.00001). Knee flexion and the IKS knee score remained stable over time (P>0.05). Patients who underwent patella resurfacing during the initial TKA procedure had better clinical results (P=0.03). ConclusionAfter a minimum follow-up of 7years, the overall revision-free survival rate for the Ceragyr® was 94.8%; the survival was 98.4% with mechanical failure as an endpoint. The results were stable over time. Level of evidenceIV, retrospective study of prospectively collected data.