Search

Background: Routine patellar resurfacing during primary total knee arthroplasty (TKA) remains controversial. To our knowledge, there are no studies reporting the long-term performance of a cemented biconvex all-polyethylene inlay component implanted at the time of primary TKA. The purpose of this study was to examine the 15-year survivorship and long-term clinical outcomes of this biconvex inlay patella used at our institution., Methods: We retrospectively reviewed our prospectively collected institutional database and identified 2,530 patients who underwent cemented TKA with a single prosthetic design (from 1996 to 2007) where the patella was resurfaced using this cemented biconvex inlay patella. The mean age at surgery was 68 years (range, 29 to 93). The mean body mass index was 33.0 (range, 16.4 to 76.3), with 61.9% women. At the time of analysis, the mean time from surgery was 20.4 years (range, 15 to 26). We used Kaplan-Meier analysis to calculate survivorship at 15 years. We analyzed clinical outcomes using 3 patient-reported outcome measures collected prospectively., Results: The 15-year survivorship with revision surgery for all causes as the end point was 97.1% (95% confidence interval 96.1 to 98.1%). The 15-year survivorship with revision surgery for a patella-related complication as the end point was 99.7% (95% confidence interval 99.4 to 1.0). At the final follow-up, patients showed significant improvement in scores for the Knee Society Clinical Rating System (P < .001), Western Ontario and McMaster University Osteoarthritis Index (P < .001), and Veterans Rand 12-Item Health Survey physical component (P < .001)., Conclusions: Routine patellar resurfacing using a biconvex inlay patellar component has excellent survivorship and a low rate of complications at 15 years post-TKA., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Bone loss remains an anticipated challenge in revision total knee arthroplasty (rTKA). Recent efforts to enhance rTKA fixation and stability have focused on metaphyseal implants, namely cones and sleeves. We sought to compare cone and sleeve implant survivorship in rTKA., Methods: One hundred eighty patients who underwent rTKA with metaphyseal implants from 2005 to 2018 were retrospectively reviewed. A total of 83 cones (22 femoral, 62 tibial) and 121 sleeves (58 femoral, 63 tibial) were identified. The mean age at the time of surgery was 72 years (range 43-97). Intraoperative Anderson Orthopaedic Research Institute bone loss classifications included the following: type 2A (25), type 2B (98), and type 3 (81). Mean follow-up was 41 months., Results: Revision-free survival for cones was 91.3% vs 92.2% for sleeves (P = .29). Twelve knees (4 cones, 8 sleeves) underwent irrigation, debridement, and polyethylene exchange with metaphyseal implant retention for acute postoperative periprosthetic joint infection (PJI). Development of chronic PJI warranted removal of 7 cones (8.4%), 6 of which were initially placed as part of a 2-stage revision TKA. Eight sleeves (6.6%) were removed for PJI, with all initially placed during a second stage reimplantation. In the absence of infection, survival was 100% and 99.1% for cones and sleeves, respectively. One sleeve was revised for periprosthetic fracture., Conclusion: Metaphyseal cones and sleeves offer equally durable survivorship in revision TKA. PJI was the most common mode of implant failure in this series. Importantly, no cases of cone or sleeve aseptic loosening were observed., (Copyright © 2022 Elsevier Inc. All rights reserved.)

We sought to evaluate wear and kinematics in well-established implants of posterior stabilized (PS) and cruciate retaining (CR) designs. Ninety-one knees implanted for at least five years were examined. The implants were Genesis II PS (Smith & Nephew, Memphis, TN), Sigma PS (DePuy Synthes, Warsaw, IN), or Sigma CR. Radiostereometric analysis (RSA) images were acquired at multiple flexion angles and the 3D positions of the implant components were determined using model-based RSA software. The location of the center of the contact area between the femoral and polyethylene components was used to obtain contact kinematics, and the magnitude of the virtual intersection between the components indicated linear wear. All three groups had paradoxical anterior motion on both condyles, experienced similar net external rotation, and exhibited instances of internal rotation during flexion. The maximum observed wear rate was significantly greater for the Sigma PS than the Genesis II PS on the medial condyle (mean difference = 0.032 mm/year, p = 0.044), but not the lateral condyle, while there was no difference between the Sigma PS and Sigma CR for either condyle. Knees with lateral condylar separation had greater maximum wear rates on the medial condyle (mean difference = 0.033 mm/year, p = 0.001), while those with medial condylar separation had greater maximum wear rates on the lateral condyle (mean difference = 0.044 mm/year, p = 0.014). At long term follow-up in patients with well-functioning implants, there were differences in kinematics and wear resistance between implants. These results suggest that implant design affects long-term kinematics and wear in well-functioning implants and that condylar separation should be avoided to minimize wear., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: Rotating 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., Methods: We 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)., Results: Seventy-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., Conclusion: This 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., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: There is controversy regarding the superiority of posterior-stabilizing (PS) total knee arthroplasty (TKA) and cruciate-retaining (CR) TKA. Substantial work has made comparisons between PS and CR TKA at follow-ups of less than 5 years. It was the goal of the present study to compare the kinematics at greater than 5 years postoperatively between CR and PS TKA, with a secondary goal of comparing patient function., Methods: A total of 42 knees were investigated, with equal representation in the PS and CR TKA groups. Patients underwent radiostereometric analysis imaging at 0°, 20°, 40°, 60° 80°, and 100° of flexion. Contact position, magnitude of excursion, and condylar separation on each condyle were measured. A Timed-Up-and-Go functional test was also performed by patients, with the total test time being measured. Preoperative and postoperative clinical outcome scores were also collected., Results: There were differences in contact position on both the medial and lateral condyles at multiple angles of flexion (P < .05). There was no difference (P = .89) in medial excursion; however, PS TKA had greater lateral excursion than CR TKA (P < .01). No difference (P > .99) was found in frequency of condylar separation. PS TKA was associated with faster (P = .03) total Timed-Up-and-Go test times. There were no differences in clinical outcome scores between the groups preoperatively or postoperatively., Conclusion: We found kinematic and functional differences that favor PS TKA. Our results suggest posterior cruciate ligament insufficiency in CR TKA, indicating that perhaps the cam/post systems in PS TKA better maintain knee kinematics and function long term., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Extensor mechanism disruption after total knee arthroplasty is a serious complication leading to notable patient morbidity. The purpose of this study is to compare the outcomes of extensor mechanism allograft with synthetic graft reconstruction., Methods: We retrospectively identified all patients who underwent extensor mechanism reconstruction using either allograft or synthetic graft from two high-volume academic arthroplasty institutions between 2006 and 2017. We collected extensor lag, need for ambulatory aids, and patient-reported outcome measures, as well as the incidence of postoperative complications and revision surgeries. We evaluated cost differences, considering both material cost and the need for revision surgery., Results: We identified 27 cases. A significantly greater postoperative extensor lag was found in the allograft group (P = 0.05). Graft failure after synthetic reconstruction was zero, with an overall revision surgery rate of 15%. Graft failure was 21%, and the revision surgery rate was 43% after allograft reconstruction. The allograft cost was significantly higher compared with the synthetic graft cost (P = 0.001). The mean total cost was 4,733.08 CAD for the synthetic group and 24,050.40 CAD for the allograft group (P = 0.17)., Discussion: Synthetic reconstruction for extensor mechanism disruption shows benefit in postoperative extensor lag, graft failure, revision surgery, and cost when compared with allograft., Level of Evidence: Level III.

Background: Revision of TKA as a result of polyethylene wear is decreasing, but long-term wear performance of polyethylene is still a topic of interest to surgeons and device manufacturers seeking to improve longevity. Measuring wear of modern, wear-resistant implants has been described using radiostereometric analysis (RSA). Performing in vivo measurements would establish whether implant retrieval studies are representative of wear in well-performing knees., Questions/purposes: For a single knee implant system, we sought to determine (1) the linear wear rate using RSA; (2) the association between demographic factors and wear rate; and (3) the association between limb alignment and wear rate., Methods: A total of 49 patients with a minimum followup of 10 years (median, 12 years; range, 10-20 years) were retrospectively selected. During the examined period, 4082 TKAs were performed of which 2085 were the implant examined in this study. There were 71 of these patients who met the criteria including an available full-leg radiograph postoperatively, and 34 of these patients returned for examination along with 15 additional from a separate RSA study that also met the criteria. All patients received a posterior-stabilized, cobalt-chromium-on-conventional polyethylene total knee implant from a single implant system, which was the most commonly used at our institution at the time. Patients underwent standing RSA examinations from 0° to 120° of flexion at a single time point without the use of marker beads. Linear wear rates (including creep) were measured based on intersections between the femoral component and tibial insert models. Associations between wear and patient age at surgery, sex, height, weight, body mass index, tibial insert size, and limb alignment were examined., Results: Using the maximum linear wear rate from any flexion angle, the lateral rate was 0.047 mm/year (interquartile range [IQR], 0.034-0.066 mm/year) and the medial rate was 0.052 mm/year (IQR, 0.040-0.069 mm/year). Using the median of the linear wear rates across all flexion angles, the lateral rate was 0.027 mm/year (IQR, 0.017-0.046 mm/year) and the medial rate was 0.038 mm/year (IQR, 0.022-0.054 mm/year). This rate for males was 0.049 mm/year medially (IQR, 0.042-0.077 mm/year) and 0.032 mm/year laterally (IQR, 0.026-0.059 mm/year), and for females was 0.027 mm/year medially (0.016-0.039 mm/year) and 0.020 mm/year laterally (IQR, 0.013-0.032 mm/year). The wear rate for males was greater medially (difference = 0.022 mm/year, p < 0.001) and laterally (difference = 0.012 mm/year, p = 0.008). There were associations between greater wear and increasing height (ρ = 0.48, p < 0.001 medially and ρ = 0.30, p = 0.04 laterally), decreasing body mass index (ρ = -0.31, p = 0.03 medially), and greater implant size (ρ = 0.34, p = 0.02 medially). Increasingly varus leg alignment was associated with greater medial wear (ρ = 0.33, p = 0.02)., Conclusions: Greater wear rates were associated with demographic factors and leg alignment. Further RSA wear studies of other modern implant systems would provide complementary information to retrieval studies and valuable data on wear resistance., Clinical Relevance: Good wear resistance was demonstrated by well-performing implants in patients at long-term followup with wear magnitudes in agreement with reported values from retrieval studies.

With utilization of both primary and revision total knee arthroplasty projected to increase in coming decades particularly in younger, more active patients, a determination of best surgical practices is vital to meet the burden of demand. Four challenges in surgical techniques for revision total knee arthroplasty include surgical exposure, careful removal of components, bone deficit management, and fixation options. Surgical exposure may be more complicated in patients presenting for revision who have a history of multiple prior surgeries, infection, scar tissue formation, stiffness, ligamentous deficiency, or vascular compromise. Removal of previous implants while preserving bone stock and ligamentous stabilizers requires adequate exposure of interfaces and visualization, and is facilitated with a variety of tools and techniques. Treatment options for management of bone deficits have expanded in recent years to include a wide range of porous metal sleeves, cones, and augments, in addition to the traditional arsenal of screws, cement, bone graft, metallic augments, offset adapters, and stems in various lengths and geometries. Stem fixation may be noncemented, cemented, or hybrid, with the goal of the stems to load share and enhance the mechanical stability of the reconstruction.

Purpose: To examine implant migration and articular behavior of primary total knee arthroplasty (TKA) at 10 years after index surgery and correlate to implant alignment., Methods: Thirty-five patients underwent a cemented posterior stabilized total knee arthroplasty with a surgical objective of neutral alignment and were enrolled in a long-term radiostereometric analysis (RSA) study. At 10 years after surgery, patients were analyzed for implant migration using RSA as well as radiographic assessment of articular behavior at four positions of knee flexion. Implant position and alignment was measured on full-length radiographs. Patient demographics and reported outcomes were also collected., Results: No difference between patient demographics or patient-reported outcomes were found. When categorized into neutral and varus groupings, no difference in migration was present. If alignment was considered as a continuous variable, there was no correlation between overall leg alignment and migration, however, migration increased with an increasing varus tibial alignment. Although contact location did not differ between neutral and varus groups through a range of motion, condylar liftoff was much more common in the varus group, of which all were lateral liftoff., Conclusions: Increased tibial varus results in increased implant migration. Overall varus limb alignment is correlated with isolated lateral compartment liftoff, and liftoff occurs more commonly than in neutral aligned knees. The increased migration and liftoff raise concerns about the longevity of malaligned total knee replacements. If a goal of overall varus limb alignment is desired for TKA, the tibia should remain neutral., Level of Evidence: Level III.

Aims: The aim of this study was to evaluate the long-term inducible displacement of cemented tibial components ten years after total knee arthroplasty (TKA)., Patients and Methods: A total of 15 patients from a previously reported prospective trial of fixation using radiostereometric analysis (RSA) were examined at a mean of 11 years (10 to 11) postoperatively. Longitudinal supine RSA examinations were acquired at one week, one year, and two years postoperatively and at final follow-up. Weight-bearing RSA examinations were also undertaken with the operated lower limb in neutral and in maximum internal rotation positions. Maximum total point motion (MTPM) was calculated for the longitudinal and inducible displacement examinations (supine versus standing, standing versus internal rotation, and supine versus standing with internal rotation)., Results: All patients showed some inducible displacement. Two patients with radiolucent lines had greater mean standing-supine MTPM displacement (1.35; sd 0.38) compared with the remaining patients (0.68; sd 0.36). These two patients also had a greater mean longitudinal MTPM at ten years (0.64; sd 0.50) compared with the remaining patients (0.39; sd 0.13 mm)., Conclusion: Small inducible displacements in well-fixed cemented tibial components were seen ten years postoperatively, of a similar magnitude to that which has been reported for well-fixed components one to two years postoperatively. Greater displacements were found in components with radiolucent lines. Cite this article: Bone Joint J 2018;100-B:170-5., (©2018 The British Editorial Society of Bone & Joint Surgery.)

Background: Tibial baseplate roughness and polyethylene-insert micromotion resulting from locking-mechanism loosening can lead to polyethylene backside wear in TKAs. However, many retrieval studies examining these variables have evaluated only older TKA implant designs., Questions: We used implant-retrieval analysis to examine if there were differences in: (1) backside damage scores, (2) backside damage modes, and (3) backside linear wear rates in five TKA implant designs owing to differing baseplate surface roughness and locking mechanisms. Additionally, we examined if (4) patient demographics influence backside damage and wear., Methods: Five TKA implant models (four modern and one historical design) were selected with different tibial baseplate and/or locking mechanism designs. Six tibial inserts retrieved at the time of revision from each TKA model were matched for time in vivo, age of the patient at TKA revision, BMI, sex, revision number, and revision reason. Each insert backside was analyzed for: (1) visual total damage score and (2) individual visual damage modes, both by two observers and with an intraclass correlation coefficient of 0.66 (95% CI, 0.39-0.92), and (3) linear wear rate measured by micro-CT. Median primary outcomes were compared among the five designs. For our given sample size among five groups we could detect with 80% power a 10-point difference in damage score and an 0.11-mm per year difference in wear rate., Results: The polished tibial design with a partial peripheral capture locking mechanism and anterior constraint showed a lower total damage score compared with the nonpolished tibial design with only a complete peripheral-rim locking mechanism (median, 12.5; range, 9.5-18.0; 95% CI, 9.58-16.42 versus median, 22.3; range, 15.5-27.0; 95% CI, 17.5-26.5; p = 0.019). The polished baseplate with a tongue-in-groove locking mechanism showed more abrasions than the nonpolished baseplate with a peripheral-rim capture and antirotational island (median, 7.25; range, 0.5-8.0; 95% CI, 2.67-8.99 versus median, 0.75; range, 0-1.5; 95% CI, 0.20-1.47; p = 0.016)). Dimpling was a unique wear mode to the nonpolished baseplates with the peripheral-rim capture and antirotational island (median, 5.5; range, 2.0-9.0; 95% CI, 2.96-8.38) and the peripheral-rim capture alone (median, 9.0; range, 6.0-10.0; 95% CI, 7.29-10.38). Overall, the linear wear rate for polished designs was lower than for nonpolished designs (0.0102 ± 0.0044 mm/year versus 0.0224 ± 0.0119 mm/year; p < 0.001). Two of the polished baseplate designs, the partial peripheral capture with anterior constraint (median, 0.083 mm/year; range, 0.0037-0.0111 mm/year; 95% CI, 0.0050-0.0107 mm versus median, 0.0245 mm/year; range, 0.014-0.046 mm/year; 95% CI, 0.0130-0.0414 mm; p = 0.008) and the tongue-in-groove locking mechanism (median, 0.0085 mm/year; range, 0.005-0.015 mm/year; 95% CI, 0.0045-0.0138 mm; p = 0.032) showed lower polyethylene linear wear rates compared with the nonpolished baseplate design with only a peripheral-rim capture., Conclusions: Total damage scores and linear wear rates were highest involving the nonpolished design with only a peripheral rim capture. There were no differences among the other TKA designs regarding damage and wear, but this finding should be considered in the setting of a relatively small sample size., Clinical Relevance: Our study showed that in the complex interplay between baseplate surface finish and locking mechanism design, a polished baseplate with a robust locking mechanism had the lowest backside damage and linear wear. However, improvements in locking mechanism design in nonpolished baseplates potentially may offset some advantages of a polished baseplate. Further retrieval analyses need to be done to confirm such findings, especially analyzing current crosslinked polyethylene. Additionally, we need mid- and long-term studies comparing TKA revisions attributable to wear and osteolysis among implants before understanding if such design differences are clinically relevant.

Background: The purpose of this study was to examine the 15-year survivorship and long-term clinical outcomes of the GENESIS II total knee arthroplasty (TKA)., Methods: Patients who underwent TKA with the GENESIS II system between 1995 and 1999 were retrieved from our institutional database. We report a Kaplan-Meier survival analysis as well as Western Ontario and McMaster Universities Arthritis Index, the Short Form Health Survey-12 (SF-12), and the Knee Society Scores at a mean of 16 years., Results: Four-hundred sixty-nine TKAs were performed with a mean patient age of 68 years. Patients were followed up prospectively for a mean of 16 years (range, 14.8-19.5 years). The Kaplan-Meier survival analysis at 15 years, with revision for any reason as the end point, was 96.4% (95.5%-97.3%). The Western Ontario and McMaster Universities Arthritis Index and the Knee Society Scores were significantly improved (P < .001) from the preoperative period to the latest follow-up. Patients had a significant improvement (P < .001) from the preoperative to the latest follow-up on the Physical Health Composite Score of the SF-12, but no change was noted on the Mental Health Composite Score of the SF-12., Conclusion: The unique design features of the GENESIS II TKA system have remained a constant over the duration of its clinical use, a rarity for contemporary TKA systems which are often altered before the publication of long-term results. The GENESIS II continues to demonstrate excellent long-term survivorship and improvements in health-related outcomes at a mean of 15 years, representing the standard for TKA systems at our institution., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Coronal plane alignment is one of the contributing factors to polyethylene wear in total knee arthroplasty., Methods: Based on 95 retrieved polyethylene inserts, wear and damage patterns were analyzed in relationship to the overall mechanical alignment and to the position of the tibial component., Results: A progression of wear was observed with progressively mechanical varus alignment. However, there was significantly more damage in the lateral compartment in the mild and moderate varus group compared to the valgus group. No difference in damage was seen between all groups for tibial component positioning in valgus or varus., Conclusion: Progressive wear was observed with progressively varus alignment with more damage at the lateral side. This observation is unique and might be explained by lateral condylar lift-off inducing impact and shear loading in the varus group., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Wear in posterior-stabilized (PS) polyethylene tibial inserts depends on component position, limb alignment, and ligament balancing. Valgus-varus constrained (VVC) inserts are likely to be affected similarly. We aimed to compare wear characteristics of VVC and PS inserts and identify associated factors., Methods: This was a retrieval analysis (macroscopic and radiographic) of all 18 VVC liners collected from patients who underwent revision surgery from 1999 to 2011. These patients were matched to another group with PS inserts who underwent revision in the same time period., Results: There was significantly more damage in the posts of the VVC group (13.0 ± 5.0, compared to 4.7 ± 1.9 in the PS group; P < .001). Within the VVC group, the total damage score and cold flow damage were significantly higher with excessive joint line changes (≥5 mm; P = .01). The excessive joint line elevation was associated with rotational wear pattern of the post (P = .004). Damage scores were increased with femoral component malposition (P = .04), anterior tibial slope (P = .04), and tibial component malposition (P = .04)., Conclusion: Joint line elevation, femoral and tibial component malposition, and anterior tibial slope resulted in significantly more wear in the VVC inserts. Joint line elevation of >5 mm resulted in wear of the medial and lateral aspects of the post, femoral valgus resulted in cold flow wear of the anterior post, and tibial valgus and anterior slope resulted in wear of lateral aspect of the post., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aims: The purpose of the present study was to examine the long-term fixation of a cemented fixed-bearing polished titanium tibial baseplate (Genesis ll)., Patients and Methods: Patients enrolled in a previous two-year prospective trial (n = 35) were recalled at ten years. Available patients (n = 15) underwent radiostereometric analysis (RSA) imaging in a supine position using a conventional RSA protocol. Migration of the tibial component in all planes was compared between initial and ten-year follow-up. Outcome scores including the Knee Society Score, Western Ontario and McMaster Universities Arthritis Index, 12-item Short Form Health Survey, Forgotten Joint Score, and University of California, Los Angeles Activity Score were recorded., Results: At ten years, the mean migration of the tibial component was less than 0.1 mm and 0.1° in all planes relative to the post-operative RSA exam. Maximum total point movement increased with time (p = 0.002) from 0.23 mm (sd 0.18) at six weeks to 0.42 mm (sd 0.20) at ten years., Conclusion: The low level of tibial baseplate migration found in the present study correlates to the low rate of revision for this implant as reported in individual studies and in joint replacement registries., Take Home Message: Overall, the implant was found to be well fixed at ten years, supporting its continued clinical use and the predictive power of RSA for determining long-term fixation of implants. Cite this article: Bone Joint J 2016;98-B:616-21., (©2016 The British Editorial Society of Bone & Joint Surgery.)

This study compared the damage scores and damage patterns in 19 tibial inserts from rotating hinge (RH) implants with 19 inserts from highly constrained (HC) implants. Each insert was divided into 16 damage zones and each zone was subjectively graded from a scale of 0-3 for seven different damage modes. The overall damage scores were comparable for the two groups (RH: 64.1 ± 15.4; HC: 66.1 ± 29.0; P = 0.59). The HC group, however, had greater post damage (compared to the post-hole of RH) while the RH group had greater backside damage. The pattern of damage was also different, with burnishing and cold flow being more common in HC group while pitting, scratching and embedded debris were more common in the RH group., (Copyright © 2016 Elsevier Inc. All rights reserved.)

This study investigated whether subluxation of articulating antibiotic spacers is associated with the bone defects found and constraint required when re-implanting the knee arthroplasty components. Staged revisions for infections of primary total knee arthroplasties between 2004 and 2012 were examined. Radiographic sagittal and coronal subluxations of 72 knees were measured prior to second stage revision. Coronal subluxation was found to be associated with increased requirement for constrained knee systems (P<0.035). Sagittal subluxation was associated with greater tibia bone defects (P<0.037). Careful surgical technique and monitoring of articulating spacers should be done to avoid subluxation after stage 1 revision. If subluxation of the articulating spacer is present, constrained revision knee systems as well as augments should be available at time of re-implantation., (Copyright © 2016 Elsevier Inc. All rights reserved.)

We compared the 10-year survival rates and clinical outcomes of posterior cruciate-retaining (CR) versus posterior cruciate-substituting (CS) total knee arthroplasty (TKA), using the Genesis II knee system (Smith and Nephew, Memphis, TN). Our institutional database identified patients undergoing a primary knee with the Genesis II system between 1995 and 2000. These patients were followed for an average of 12.3years (range 10.2-14.4years). There were 143 (34.5%) CR and 271 (65.5%) CS implants. No significant difference in 10-year survivorship was noted between the two cohorts. The postoperative clinical scores (KSCRS, WOMAC, SF-12) and knee ROM were significantly better for the CS cohort. In this large, long-term, single-implant prospective study, CS performed better than CR in terms of clinical scores and range of motion., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Total knee arthroplasty is a common and immensely successful surgical procedure that reliably relieves pain and improves function. However, early revision rates and patient dissatisfaction are high suggesting that there is need for improvement through careful patient selection and education as well as attention to surgical technique. After ensuring that a patient is an appropriate candidate for the procedure, patient education is critical to ensure appropriate expectations. Careful preoperative planning and achieving appropriate alignment, sizing, and ligament balance are critical for optimal knee function. Careful attention to the cement technique is important for long-term implant fixation. With appropriate patient selection and careful surgical techniques, optimal patient outcomes will be achieved.

Background: Quantitative measurements of damage and wear in orthopaedic components retrieved from patients during revision surgery can provide valuable information. However, to perform these measurements there needs to be an estimate of the original, unworn geometry of the component, often requiring multiple scans of the various sizes of components that have been retrieved. The objective of this study was to determine whether the articular and backside surfaces could be independently segmented from a micro-CT reconstruction of a tibial insert, such that a tibial insert of one thickness could be used as a reference for a tibial insert of a different thickness., Methods: New tibial inserts of a single width but with six different thicknesses were obtained and scanned with micro-CT. An automated method was developed to computationally segment the articular and backside surfaces of the components. Variability between intact and extracted components was determined., Results: The deviations between the comparisons of the extracted surfaces (range, 0.0004 to 0.010 mm) were less (p<0.001) than the baseline deviation between the intact surfaces (range, 0.0002 to 0.053 mm)., Conclusions: An extracted surface from one insert thickness could be used to accurately represent the surface of an insert of a different thickness. This greatly enhances the feasibility of performing retrieval studies using micro-CT as a quantitative tool, by reducing the costs and time associated with acquiring, scanning, and reconstructing multiple reference tibial insert geometries., Clinical Relevance: This will add greater detail to studies of retrieved implants, to better establish how implants are functioning in vivo., (Copyright © 2014 Elsevier B.V. All rights reserved.)

This was a retrieval analysis of 83 PS inserts to assess the effect of limb alignment, implant position and joint line position on the pattern of wear in posterior stabilized (PS) tibial inserts. The total damage score was significantly higher in knees with postoperative varus alignment more than 3° (P = 0.03). The total damage score to the post was significantly more in knees with joint line elevation more than 5 mm (9.7 ± 3.9, compared to 6.5 ± 3.7 in knees with less joint line elevation) (P = 0.05). Limb malalignment and joint line elevation resulted in more damage in PS inserts. An external rotation subluxation damage pattern was found in joint line elevation., (Copyright © 2014 Elsevier Inc. All rights reserved.)

To perform wear measurements on retrieved joint replacement implants, a reference geometry of the implant's original state is required. Since implants are rarely individually scanned before implantation, a different, new implant of the same kind and size is frequently used. However, due to manufacturing variability, errors may be introduced into these measurements, as the dimensions between the retrieved and reference components may not be exactly the same. The hypothesis of this study was that new polyethylene tibial inserts from different manufacturing lots would demonstrate greater variability than those from the same lot. In total, 12 new tibial inserts of the same model and size were obtained, 5 from the same lot and the remainder from different lots. The geometry of each tibial insert was obtained using microcomputed tomography. Measurements of tibial insert volume, thickness, and three-dimensional surface deviations were obtained and compared between tibial inserts from the same and different manufacturing lots. Greater variability was found for the tibial inserts from different manufacturing lots for all types of measurements, including a fourfold difference in volume variability (p < 0.001) and a maximum of 0.21 mm difference in thickness (p < 0.001). Investigators should be aware of this potential confounding error and take steps to minimize it, such as by averaging together the geometries of multiple new components from different manufacturing lots for use as the reference geometry.

Background: High flexion (HF) implants were introduced to increase ROM and patient satisfaction, but design changes to the implant potentially have deleterious effects on polyethylene wear. It is unclear whether the HF implants affect wear., Questions/purposes: We therefore examined whether the design changes between HF and posterior-stabilized (PS) tibial inserts would affect overall damage or damage on their articular surface, backside, and tibial post and whether flexion angle achieved related to damage., Methods: We matched 20 retrieved HF inserts to 20 retrieved PS inserts from the same implant system on the basis of duration of implantation, body mass index, and age. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. Five inserts were scanned using micro-CT to further quantify instances of severe post notching. We determined overall damage with a scoring system., Results: We found greater backside and post damage in the HF group but no difference in the articular surface or overall damage scores. Backside and post damage scores correlated to flexion angle in the HF group. There was no flexion/damage correlation in the PS group. Notch depths around the post in both groups ranged from 0.6 to 1.9 mm., Conclusions: HF inserts are more susceptible to post damage, possibly as a result of higher contact stresses from greater flexion. The increased backside damage was unexpected because the two groups have the same tibial component, locking mechanism, and sterilization method., Clinical Relevance: The introduction of a highly crosslinked HF insert will require close scrutiny as a result of the potential for post damage demonstrated in this series.

Background: Periprosthetic joint infection has been the leading cause of failure following TKA surgery. The gold standard for infection control has been a two-staged revision TKA. There have been few reports on mid- to long-term survivorship, functional outcomes, and fate of patients with a failed two-stage revision TKA., Questions/purposes: Therefore, we determined (1) the mid-term survivorship of two-stage revision TKA, (2) the function of patients in whom infection was controlled, and (3) the outcome of patients with a failed two-stage revision due to recurrent infection., Methods: We retrospectively reviewed 239 patients who underwent 253 two-stage revision TKAs for periprosthetic infection. There were 239 patients (253 knees), 104 men and 135 women, with a mean age of 70 ± 10 years at the time of two-stage revision and a mean BMI of 31.53 ± 6.74 kg/m2. During followup, we obtained WOMAC and The Knee Society Clinical Rating Scores and radiographs. The minimum followup was 1 year (median, 4 years; range, 1-17 years)., Results: Thirty-three patients experienced a failed two-staged TKA. Sixteen patients experienced failure due to recurrent sepsis. There were 17 failures for aseptic causes., Conclusion: The overall infection-free survivorship for two-stage revision TKA was 85% at 5 years and 78% at 10 years., Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Calf serum lubricants consisting of various polypeptide constituent fractions are routinely used in knee wear simulators as part of the standardized test protocol. Three calf sera (bovine, new-born and alpha) were diluted as per the recommendation of ISO 14243-3 and used in displacement-controlled knee wear simulators to investigate their effects on polyethylene wear. Biochemical analyses included measuring total polypeptide degradation, electrophoretic profiles and low-molecular weight polypeptide concentrations to elucidate their involvement in the wear process. The effects of the various calf sera constituent fractions on microbial growth were also explored. The polyethylene wear rates and the results from the biochemical analyses for the three calf serum lubricants were all found to be statistically significantly different from each other. The lubricant derived from the alpha-calf serum was closest in constituent fractions to human synovial fluid. It also showed the lowest polyethylene wear rate (14.38 +/- 0.85 mm3/million cycles) and the lowest amount of polypeptide degradation (7.77 +/- 3.87%). Furthermore, the alpha-calf serum lubricant was associated with the least amount of change in the electrophoretic profile, the least change in low-molecular weight polypeptide concentration, and the lowest microbial growth in the presence of sodium azide (a microbial inhibitor conventionally used in implant wear testing). Replacing sodium azide with a broad spectrum antibiotic-antimycotic eradicated the microbial growth. Some speculation was entertained regarding the effect of alpha-calf serum on colloid-mediated boundary lubrication. Based on the results, it was recommended that ISO 14243-3 be modified to include guidelines on calf serum constituent fractions that would favour using alpha-calf serum in order to improve the fidelity of the simulation in knee implant wear testing.

A six-station displacement-controlled knee simulator with separately controlled left (L) and right (R) banks (three wear implants per bank) was commissioned for a total of three million cycles (Mc) following ISO 14243-3. A commissioning protocol was applied to compare the polyethylene wear among the six wear stations by exchanging the implants between wear stations. Changes in lubricant characteristics during wear testing, such as polypeptide degradation, low-molecular-weight polypeptide concentration, and possible microbial contamination were also assessed. The total mean wear rate for the implants was 23.60 +/- 1.96 mm3/Mc and this was of a similar magnitude to the mean wear rate for the same implant tested under similar conditions by DePuy Orthopaedics Inc. (Warsaw, IN). Repeated run-in wear was observed when the implants were exchanged between wear stations, suggesting that implants should be subjected to the same wear station throughout the duration of a wear test. The total polypeptide degradation for the implants measured 30.53 +/- 3.96 percent; the low-molecular-weight polypeptide concentration of the "used" lubricant for implants (0.131 +/- 0.012 g/L) was 3.3 times greater than the mean polypeptide concentration of the fresh, "unused" lubricant (0.039 +/- 0.004 g/L). This increase in low-molecular weight polypeptide concentration was suggested to be attributable to protein shear in the articulation of the implant, the circulation of the lubricant, and some proteolytic activity. Sodium azide was ineffective in maintaining a sterile environment for wear testing as a single, highly motile Gram-negative micro-organism was identified in the lubricant from wear tests.

Fluid adsorption and the associated mass gain behaviour in tibial inserts of total knee replacements was investigated in polyethylene (PE) manufactured from extruded GUR 1050 resin. Repeatedly removing the PE inserts from the soak fluid for gravimetric assessment (including cleaning, desiccation, and weighing) increased the mass gain. Soaking PE inserts for 46 days or 92 days seemed to give about the same mass gain. PE inserts that were soaked at 37 degrees C gained more mass than PE inserts soaked at room-temperature. Gas-plasma sterilized PE inserts gained less mass than gamma-in-air sterilized PE inserts. No statistically significant differences were detected in mass gain between PE inserts that were of 10mm and 14mm thickness. The mass gain of PE inserts was higher in protein-rich soak fluid compared with low-ion distilled water. Prior to knee simulator wear testing, tibial PE inserts should be conditioned in the same medium and under the same test conditions (gravimetric assessment frequency, fluid protein content, and fluid temperature). This approach would help improve the accuracy and precision of the gravimetrically determined PE wear rate during knee simulator wear testing.

Background: Wear of polyethylene tibial inserts can decrease the longevity of total knee arthroplasty. Wear is currently assessed using laboratory methods that may not permit backside wear measurements or do not quantify surface deviation., Questions/purposes: We developed and validated a technique to quantify polyethylene wear in tibial inserts using microcomputed tomography (micro-CT), a nondestructive high-resolution imaging technique that provides detailed images of surface geometry in addition to volumetric measurements., Methods: Six unworn and six wear-simulated polyethylene tibial inserts were evaluated. Each insert was scanned three times using micro-CT at a resolution of 50 μm. The insert surface was reconstructed for each scan and the insert volume was calculated. Gravimetric analysis was performed for all inserts, and the micro-CT and gravimetric volumes were compared to determine accuracy. We created three-dimensional surface deviation maps., Results: Micro-CT generated high-quality three-dimensional renderings of the insert surface geometry. Between-scan precision was 0.07%; we observed no difference between micro-CT and gravimetric volume measurements., Conclusions: Micro-CT can provide precise and accurate volumetric measurements in addition to quantifiable three-dimensional surface deviation maps for the entire insert surface. The technique has the potential to evaluate wear in wear simulator trials and retrieval studies., Clinical Relevance: This micro-CT technique combines the benefits of volumetric and surface scanning methods to quantify wear across all surfaces of polyethylene components with a single tool. When applied in wear simulator and retrieval studies, these measurements can be used to evaluate and predict the wear properties of the components.

Osteoarthritic human synovial fluid was obtained from the knees of 20 patients and was compared with four different calf sera solutions frequently used as lubricants in knee simulator wear testing. Assuming that the fluid after arthroplasty was the same as the fluid in patients with osteoarthritis, the total protein concentration, protein constituent fractions, osmolality, trace element concentrations, and the thermal stability obtained via differential scanning calorimetry were determined. Human synovial fluid, with an average total protein concentration of 34 g/L, was significantly different from all undiluted calf sera. However, alpha-calf serum and iron-supplemented alpha-calf serum were closest in protein constituent fractions (albumin, alpha-1-globulin, alpha-2-globulin, ss-globulin, and gamma-globulin) to human synovial fluid. Diluting calf sera with low-ion distilled water to a total protein concentration of 17 g/L (as recommended by ISO 14243) produced non-clinically relevant total protein concentration and osmolality levels. Performing the same dilution of iron-supplemented alpha-calf serum with phosphate-buffered saline solution and 1.5 g/L hyaluronic acid produced an artificial lubricant with both a clinically relevant level of osmolality and clinically relevant thermal stability as seen in human synovial fluid from patients with osteoarthritis. The present study suggested that alpha-calf serum, phosphate-buffered saline solution and hyaluronic acid were essential constituents of an artificial lubricant to mimic the major biochemical properties of human synovial fluid for simulator wear testing of total knee replacements., ((c) 2010 Wiley Periodicals, Inc.)

Unlabelled: The range of motion after TKA depends on many patient, surgical technique, and implant factors. Recently, high-flexion designs have been introduced as a means of ensuring or gaining flexion after TKA. We therefore evaluated factors affecting postoperative flexion to determine whether implant design influences longterm flexion. We prospectively collected data on patients receiving a primary Genesis II total knee replacement with a minimum of 1-year followup (mean, 5.4 years; range, 1-13 years). We recorded pre- and postoperative outcome measures, patient demographics, and implant design (cruciate retaining [CR, n = 160], posterior stabilized [PS, n = 1177], high-flex posterior stabilized [HF-PS, n = 197]). Backward stepwise linear regression modeling identified the following factors affecting postoperative flexion: preoperative flexion, gender, body mass index, and implant design. Independent of gender, body mass index, and preoperative flexion, patients who received a HF-PS and PS design implant had a mean of 8 degrees and 5 degrees more flexion, respectively, than those who received a CR implant. Patients with low flexion preoperatively (<100 degrees) were more likely to gain flexion, whereas those with high flexion preoperatively (>120 degrees) were most likely to maintain or lose flexion postoperatively. Controlling for implant design, patients with high flexion preoperatively (>120 degrees) were more likely to gain flexion with the HF-PS design implant (HF-PS = 32.0%; PS = 15.1%; CR = 4.5%)., Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Medial unicompartmental arthroplasties (UKA) are available with mobile- and fixed-bearing designs, with the advantages of one bearing over another unproven. We questioned whether the bearing design influenced clinical outcome, survivorship, the reason for revision, or the timing of failures. We retrospectively reviewed 179 patients (229 knees) who had medial unicompartmental knee arthroplasties between 1990 and 2007; of these 79 knees had a mobile-bearing design and 150 knees a fixed-bearing design. Patients with mobile-bearing UKA had a minimum followup of 1 year (mean, 3.6 years; range, 1-11.3 years); those with fixed-bearing UKA a minimum followup of 1 year (mean, 8.1 years; range, 1-17.8 years). Patients were evaluated with clinical outcome scores and radiographically using the Knee Society rating system. Seven of 79 (9%) mobile-bearing knees underwent revision at a mean of 2.6 years, and 22 of 150 (15%) fixed-bearing knees underwent revision at a mean of 6.9 years. The 5-year cumulative survival rates were 88% (SE +/- 0.47, 95% CI 0.7229-1) and 96% (SE +/- 0.16, 95% CI 0.93-0.9979) for the mobile- and fixed-bearing designs respectively using the endpoint of revision surgery. We observed no differences in the indications or complexity of revision surgery between the groups and none in midterm survivorship., Level of Evidence: Level III, comparative study. See Guidelines for Authors for a complete description of levels of evidence.

This study investigated the change in joint line position after posterior cruciate-retaining and posterior-stabilized total knee arthroplasty with AMK (DePuy, Warsaw, Ind) and Genesis II (Smith & Nephew, Memphis, Tenn) components. A total of 200 primary total knee arthroplasty patients were randomly selected so as to have 50 patients with each of the 4 prosthesis types. Joint line position was measured on preoperative and 2 year postoperative radiographs by both a lateral and an anteroposterior measurement method. Two-year follow-up functional data were assessed. There were no statistically significant differences in the joint line elevation between posterior-stabilized and posterior cruciate-retaining designs within the same implant system as measured on lateral radiographs. There were no differences in clinical functional outcomes in patients with variable joint line elevation.

The purpose of this study is to compare the range of motion and clinical outcomes of a standard posterior-stabilized (PS) vs the high-flex (HF) polyethylene tibial insert of a posterior cruciate substituting total knee arthroplasty system. One hundred patients were entered into a prospective, blinded, randomized clinical trial in which 50 patients received a Genesis II PS insert and 50 patients received a Genesis II HF insert (Smith & Nephew, Memphis, TN). At an average follow-up of 2.7 years (range, 2.3-3.1 years), there were no differences in any outcome measures (Western Ontario and McMaster Universities osteoarthritis index, Short-Form 12, Knee Society clinical rating scores, anterior knee pain). There were no differences (P = .811) in average knee flexion at 2 years (standard, 123 degrees +/- 7 degrees; HF, 124 degrees +/- 7 degrees). In summary, this prospective blinded randomized clinical trial demonstrated no differences between a PS and HF polyethylene design. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.

Unlabelled: The inset biconvex patella component is an alternative form of patella resurfacing in knee arthroplasty. We retrospectively reviewed 433 patients in whom 521 patella prostheses were implanted before April 1997 to determine survivorship, factors associated with failure of the implant, incidence of anterior knee pain, and factors that may be associated with the latter. We had clinical results for 204 surviving patients (242 knees) without failure of their implants with a minimum 10-year followup (mean, 11.4 years; range, 10-17 years). For the remaining 229 patients we used chart or radiographic review to determine if failure of their implant or other complications had occurred. At latest followup, 14 patella components had been revised for aseptic reasons or were radiographically loose. The 10-year Kaplan-Meier survivorship for the entire cohort for aseptic failure was 97.0%. Aseptic failure of the patella component was associated with the presence of osteonecrosis and the absence of a superior rim of bone radiographically. The incidence of anterior knee pain in surviving patients without failure of their implants was 7.8%. No factor examined was associated with anterior knee pain. Survivorship and clinical and radiographic results are equivalent, but not clearly superior, to those reported for other forms of patella resurfacing., Level of Evidence: Level IV, therapeutic study.

The ideal method of stem fixation in revision knee arthroplasty is controversial with advantages and disadvantages for cemented and press-fit designs. Studies have suggested cemented revision knee stems may provide better long-term survival. The aim of this study was to report our experience with press-fit uncemented stems and metaphyseal cement fixation in a selected series of patients undergoing revision total knee arthroplasty. One hundred twenty-seven patients (135 knees) who underwent revision total knee arthroplasty using a press-fit technique (press-fit diaphyseal fixation and cemented metaphyseal fixation) were reviewed. Minimum followup was 2 years (mean, 5 years; range, 2-12 years). A Kaplan-Meier survivorship analysis using an end point of revision surgery or radiographic loosening was used to determine probability of survival at 5 and 10 years. Of the 127 patients (135 knees), 31 patients (36 knees) died and two patients (two knees) were lost to followup. Six patients (six knees) had revisions at a mean of 3.5 years (range, 1-8 years). Kaplan-Meier survivorship analysis revealed a probability of survival free of revision for aseptic loosening of 98% at 12 years. Survivorship of press-fit stems for revision knee arthroplasty is comparable to reported survivorship of cemented stem revision knee arthroplasty. Radiographic analysis has shown continued satisfactory appearances regardless of constraint, stem size, and augmentations.

The purpose of this study was to evaluate the preimplantation surface finish of the femoral component used in total knee arthroplasty. Nine femoral components from various manufacturers were obtained for analysis. All were fixed-bearing, posterior-stabilized implants intended for cemented arthroplasty. Surface characterization involved light profilometry over multiple surface points from the condylar surface, trochlear groove, and the posterior stabilizing cam. Results revealed that the condylar surface roughness was not significantly different when comparing designs with a mean roughness average ranging from 43.6 to 116 nm. The trochlear surface was generally similar to that of the condyles in most implants, although significant differences were seen in 2 implants (P <.05). Of note, the articular surface of the stabilizing cam was uniformly rougher than the condylar surface in all implants and significantly rougher (P <.05) in 6 of the 9 components.

This study compared the midterm results between press-fit and cemented implantation of a highly congruent, all-polyethylene patellar component. We followed prospectively 172 implants (cemented, n = 133; press-fit, n = 39). Average follow up was 6 years (range, 5-8 years). Patellofemoral complications occurred in 4 cemented patellae (2.3%). Two of these patellae required revision. Cemented implants had a significantly higher incidence of patellar maltracking (30% vs 8%; P= .005). No significant differences in the overall Knee Society scores (mean, 165; SD, 27) or any of its components relevant to patellofemoral function were detected between fixation methods. A retrieved specimen showed an intervening fibrous membrane at the implant-bone interface. The potential for macrophage-mediated osteolysis at this site is unknown. No other adverse outcome was associated with press-fit implantation. These results suggest that at midterm follow-up, press-fit implantation of this all-polyethylene patellar component may improve tracking and represents a viable alternative to cement fixation.

Background: With extensive use of posterior stabilized total knee arthroplasty implants, it is increasingly important to assess the mechanical performance of this design alternative. The purpose of this study was to examine the wear patterns at the femoral cam-tibial post interface in a series of posterior stabilized prostheses retrieved at revision arthroplasty., Methods: Qualitative and quantitative wear analysis was performed over the surface of the stabilizing posts from twenty-three retrieved total knee components that had been implanted for a mean of 35.6 months (range, 2.3 to 107.2 months). The implants were designs from four different manufacturers. Digital images of the anterior, posterior, medial, and lateral surfaces of the tibial post were made for quantitative analysis and determination of a post wear score. Wear was characterized with a grading system that isolates adhesive, abrasive, and fatigue wear, inferring a weighted score from an estimation of generated polyethylene debris., Results: Evidence of wear or damage was observed on all twenty-three of the stabilizing posts, including those revised because of infection. On the average, 39.9% (range, 18.5% to 60%) of the post surface demonstrated some form of deformation, with adhesive wear, or burnishing, being the predominant wear mechanism. Seven posts (30%) exhibited severe damage with gross loss of polyethylene. The wear caused premature failure and early revision of two components: one of these failures was related to isolated post wear and the other, to severe post wear and subsequent fracture. Overall, wear was primarily posterior, but wear over the anterior, medial, and lateral surfaces was also notable., Conclusions: The cam-post articulation in posterior stabilized implants can be an additional source of polyethylene wear debris. The variability in wear patterns observed among designs may be due to differences in cam-post mechanics, post location, and post geometry. The surgeon should be aware that the cam-post interface is not an innocuous articulation, and manufacturers should be motivated to produce implants that maintain the function of the post while limiting wear and surface damage.

The effectiveness of an intra-articular injection of bupivacaine, administered before the incision or after closure of the wound, was studied in an effort to decrease the need for postoperative narcotics and to improve analgesia for patients who have elective knee replacement. Eighty-two patients received two intra-articular injections in a random, double blind fashion. Twenty-eight of them received thirty milliliters of 0.5 percent bupivacaine and 1:200,000 epinephrine in saline solution before the incision and an injection of thirty milliliters of plain saline solution after closure of the wound (Group 1). Twenty-seven patients received an injection of thirty milliliters of plain saline solution before the incision and thirty milliliters of 0.5 percent bupivacaine and 1:200,000 epinephrine in saline solution after closure of the wound (Group 2). Twenty-seven patients were given thirty milliliters of plain saline solution (a placebo) for both injections (Group 3). The patients who had received bupivacaine after closure of the wound (Group 2) used less morphine from the patient-controlled analgesia pumps than the patients who had received bupivacaine before the incision (Group 1) and the patients who had received the placebo (Group 3). In the first twenty-four hours after the operation, the administration of morphine (mean and standard deviation) was 59 +/- 27 milligrams for Group 2 compared with 68 +/- 30 milligrams for Group 1 (p = 0.26) and 81 +/- 30 milligrams for Group 3 (p = 0.006). At the time of discharge from the hospital, the patients in Group 2 also had a significantly greater mean range of motion (85.2 +/- 8.0 degrees) compared with that of the patients in Groups 1 (80.6 +/- 6.8 degrees, p = 0.02) and 3 (80.1 +/- 6.2 degrees, p = 0.009). However, there was no difference among the groups with respect to the effectiveness of the analgesia, as measured with use of either the visual-analog or the verbal pain-rating scale, or in the prevalence of side effects, including somnolence, urinary retention, nausea and vomiting, or pruritus. Serum concentrations of bupivacaine were well below toxic levels. It was our conclusion that that and intra-articular injection of thirty milliliters of 0.5 percent bupivacaine and 1:200,000 epinephrine in saline solution after closure of the wound decreases the need for narcotics and increases the range of motion after an elective knee replacement. The clinical importance of the amount of increased motion is questionable and needs long-term monitoring.