Does design change in total knee arthroplasty implants affect patient-reported outcomes?

PURPOSE: The purpose of this study is to compare the early results of patient-reported outcomes between two generations of a total knee system. METHODS: Between June 2018 and April 2020, 121 first-generation, cemented TKAs (89 patients) and 123 s-generation, cemented TKAs (98 patients) were performed by a single surgeon. Demographic and surgical data were collected from all patients. Starting at the 6-month follow-up, patient-reported outcome measures Knee Injury and Osteoarthritis Outcome Score, Joint Reconstruction (KOOS-JR) and Knee Society (KS) clinical and radiographic scores were prospectively recorded. This study represents a retrospective review of these prospectively collected data. RESULTS: There were no statistically significant differences between the two groups in terms of demographic variables such as age, body mass index, gender and race. KOOS-JR and Knee Society (KS) scores improved significantly (p < 0.001) from their preoperative values in both device generations. There were no differences, pre-operatively, between the two groups in terms of KOOS-JR, KS functional, KS objective, patient satisfaction, and expectation scores; however, there were statistically significant (p < 0.001) lower values of KOOS-JR and KS functional scores for first versus second generation at 6 months (81 vs. 89 and 69 vs. 74, respectively). CONCLUSION: While significant improvement in KS objective, subjective, and patient satisfaction scores were noted with both knee systems, KOOS-JR and KS function scores were significantly higher at the early (6-month) follow-up in the second-generation group. Patients responded acutely to the design change as evidenced by significantly improved patient-reported outcome scores for the second generation.

Cementless and Cemented Dual-Pivot Total Knee Arthroplasty: A Matched Comparison With a Minimum Two-Year Follow-Up.

BACKGROUND: With the use of newer biomaterials, many authors have reported similar results between cementless and cemented total knee arthroplasty (TKA). The purpose of this study was to compare the early clinical and radiographic outcomes of cementless and cemented TKA using the same dual-pivot articulation. METHODS: A consecutive series of 806 TKAs were implanted by a single surgeon using the same dual-pivot articulation. There were 634 TKAs (79%) cemented and 172 (21%) uncemented. One patient in the cementless group was lost before two years. The remaining 171 cementless TKAs were matched 1:1 with cemented TKAs with respect to age, sex, and body mass index. All patients were followed for a minimum of two years (range, 24-66 months) using the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement , and Knee Society clinical and radiographic evaluation. The average follow-up was 3.8 years (range, 24-66 months) in the cemented group and 3.4 years (range, 24-56 months) in the cementless group. RESULTS: At final follow-up, the average Knee Injury and Osteoarthritis Outcome Score for Joint Replacement was higher in the cementless group (86 points (range, 64-100) versus 80 points (range, 57-100). Postoperative Knee Society scores (including pain and function) were similar. There was one deep infection (cemented TKA). The manipulation rate was 1.2% in the cementless group and 2.4% in the cemented TKA group. Excluding infection, two knees (1.2%) were revised in each group. No cases of femoral or tibial component loosening were identified. CONCLUSION: Patients implanted with either a cemented or cementless TKA using the same conforming dual-pivot articulation design had similar early outcomes and functional improvements. The type of fixation did not appear to influence the early clinical results.

Custom Triflange Acetabular Implants: Average 10-Year Follow-Up.

BACKGROUND: Acetabular reconstruction options in the setting of substantial bone deficiency (Paprosky 3A and 3B) remain limited. Custom triflange acetabular implants are one choice for this challenging problem. However, few studies have reported on survivorship beyond 3 to 5 years. The purpose of this study was to report our 6 to 13-year clinical results using these custom-made acetabular components. METHODS: Between 2008 and March 2015, 42 revision total hip arthroplasties (41 patients) were performed at our institution with a custom triflange acetabular component. All revisions involved either Paprosky 3A or 3B acetabular defects. Two patients died before the five-year follow-up. Harris Hip Scores were obtained at 6 months, 1 year, and every 2 to 3 years thereafter. The average follow-up in the remaining 40 revision total hip arthroplasties was 10 years (range, 6 to 13 years). RESULTS: At the final follow-up, the mean Harris score was 74 points. There were two deep infections (5%). One custom implant was removed for deep infection (2.5%). Three hips (7.5%) experienced a total of four dislocations necessitating revision in one hip (femoral component only). One custom implant was judged to be loose. There were no cases of femoral nerve palsy. At final follow-up, 38 (95%) of the custom acetabular implants were considered radiographically stable. CONCLUSION: Instability and infection remain a major concern and cause of failure in these complex reconstructions. At an average follow-up of 10 years, however, custom triflange acetabular implants appear to work at least as well as jumbo cups and cup/cage constructs in the setting of extensive erosion of acetabular bone.

Instability After Primary Total Hip Arthroplasty: Dual Mobility Versus Jumbo Femoral Heads.

BACKGROUND: The use of dual mobility (DM) articulations has grown substantially over the last decade to help minimize dislocation risk. The purpose of this study is to compare the results of DM articulations to jumbo femoral heads of equivalent sizes as they relate to postoperative dislocation. METHODS: This is a retrospective cohort study of primary total hip arthroplasties (THAs) performed at a single institution between 2005 and 2018. DM articulations and large-diameter metal-on-metal femoral heads were included. Patients were followed with Harris Hip Scores and standard radiographs. Complications were prospectively recorded. Statistical analyses included chi-squared and Brown-Forsythe tests. RESULTS: In total, 1,288 Magnum femoral head THAs and 365 Active Articulation DM THAs were included for analysis. The same monoblock cup was implanted via a posterior approach in all cases. Age, gender, body mass index, and diagnosis were similar between groups. Average follow-up in the DM group was 49 months, and 126 months in the jumbo head group. The average head sizes in the DM and jumbo head groups were 50 mm. There were no dislocations in the DM hips and only 2 (0.2%) in the jumbo femoral head group. Both groups had significant improvements in Harris Hip Score from their preoperative baseline. CONCLUSION: Our study found similarly low dislocation rates in DM and jumbo femoral heads in primary THA. No evidence currently exists showing a benefit of the DM articulation beyond that of the large effective head size, and we recommend making every attempt at maximizing head size prior to using DM articulations.

Press-Fit Dual-Pivot Total Knee Arthroplasty: Early Results With a Minimum 2-Year Follow-Up.

BACKGROUND: Ultracongruent (UC) tibial bearings are being used with increasing frequency in the United States. Evidence suggests that the use of certain UC bearings may lead to improved patient satisfaction when compared with using conventional inserts. However, little is known as to what effect the use of UC tibial inserts has on bone ingrowth in uncemented total knee arthroplasty (TKA). The purpose of this study was to determine the early clinical and radiographic results of TKA using a press-fit dual-pivot design. METHODS: Between 2017 and 2019, a consecutive series of 232 TKAs were implanted using a press-fit tibial and femoral component and a UC dual-pivot tibial insert. Sixty-two percent of patients were male. The average age was 56 years. Patients were followed for a minimum of 2 years (range, 24-42 months) using KOOS-JR and Knee Society clinical and radiographic evaluation. RESULTS: No patient had more than mild knee stiffness at the final follow-up. Two patients reported moderate knee pain with stair climbing. All other patients reported either mild or no pain with activity. Knee Society pain scores averaged 42 points. Flexion averaged 118 degrees. Three knees (1.3%) were revised (one each for flexion instability, tibial plateau fracture, and suspected femoral component loosening). No other cases of femoral or tibial loosening were identified. CONCLUSION: Although the success of uncemented TKA is determined by a variety of factors, the use of this dual-pivot knee design did not appear to influence tibial or femoral component fixation at early follow-up, yielding acceptable clinical and radiographic outcomes.

Progressive Tibial Bearing Sagittal Plane Conformity in Cruciate-Retaining Total Knee Arthroplasty.

BACKGROUND: We hypothesized that when the posterior cruciate ligament (PCL) is found deficient at total knee arthroplasty (TKA), using an anterior-stabilized (AS) tibial insert would provide similar function and survivorship when compared to using a more traditional cruciate-retaining (CR) bearing when the (PCL) is balanced. METHODS: A total of 1731 TKAs were performed using the same TKA design. Of them, 868 TKAs had a standard CR insert implanted (CR-S), 480 TKAs used a lipped CR insert (CR-L), and 383 TKAs used an AS insert. If the PCL was considered nonfunctional or absent, an AS bearing was placed. When the PCL was balanced, a CR-S or CR-L bearing was used. Follow-up was performed using the Knee Society scoring system. Kaplan-Meier survivorship was used with failure defined as aseptic loosening. RESULTS: At final follow-up, there were no significant differences in knee flexion, pain, function, or stair scores. Walking scores were significantly lower in the AS group. Posterior instability was higher in the CR-S group, whereas the manipulation rate was highest in the CR-L group (1.7%, 1.3%, and 0% for CR-L, CR-S, and AS groups, respectively). Kaplan-Meier survivorship at 5 years demonstrated no significant difference between the 3 groups (99% 100%, and 99% for CR-S, CR-L, and AS groups, respectively). CONCLUSION: Using an AS insert provided similar function and 5-year survivorship as compared to using a CR-S and CR-L tibial insert when the PCL was balanced. Using an ultracongruent AS dished tibial component appears to be a reasonable option when the PCL is completely released or found deficient at operation.

Bilateral Total Hip and Knee Arthroplasties: Average 10-Year Follow-Up.

BACKGROUND: The present study investigates the clinical and radiographic outcomes in patients with all 4 major lower extremity joints replaced. METHODS: A retrospective review of our institution's database identified 125 patients in whom both hips and both knees were replaced. The mean time between the first and last arthroplasty was 6.6 years. Preoperative diagnoses included osteoarthritis in 80% and rheumatoid arthritis in 20%. The average age at the time of the first arthroplasty was 63.7 years. The mean follow-up for all arthroplasties was 10.5 years (range 2-31 years). Patients were then matched according to age, gender, diagnosis, prosthesis, and follow-up, to patients with single or bilateral total hip or total knee arthroplasty. RESULTS: There were 11 aseptic hip revisions (4.4%) and 3 aseptic knee revisions (1.2%). At final follow-up, 86% of hips and 83% of knees were rated with no or mild pain, 68% of patients rated walking as unlimited, and 98% of patients were able to satisfactorily negotiate stairs. Aseptic survivorship for all joint arthroplasties was 93.8% at 15 years. No statistical differences were noted in pain, function, stair, and walking scores between the matched groups. CONCLUSION: This report demonstrated excellent clinical, functional, and radiographic outcomes in patients with all 4 major lower extremity joints replaced. Walking aids were needed in 15% of patients, however. At final follow-up, this selected group of patients appears to fare just as well as patients with single or bilateral hip or knee arthroplasty with respect to pain and function.

Characterization of Femoral Component Initial Stability and Cortical Strain in a Reduced Stem-Length Design.

BACKGROUND: Short-stemmed femoral components facilitate reduced exposure surgical techniques while preserving native bone. A clinically successful stem should ideally reduce risk for stress shielding while maintaining adequate primary stability for biological fixation. We asked (1) how stem-length changes cortical strain distribution in the proximal femur in a fit-and-fill geometry and (2) if short-stemmed components exhibit primary stability on par with clinically successful designs. METHODS: Cortical strain was assessed via digital image correlation in composite femurs implanted with long, medium, and short metaphyseal fit-and-fill stem designs in a single-leg stance loading model. Strain was compared to a loaded, unimplanted femur. Bone-implant micromotion was then compared with reduced lateral shoulder short stem and short tapered-wedge designs in cyclic axial and torsional testing. RESULTS: Femurs implanted with short-stemmed components exhibited cortical strain response most closely matching that of the intact femur model, theoretically reducing the potential for proximal stress shielding. In micromotion testing, no difference in primary stability was observed as a function of reduced stem length within the same component design. CONCLUSION: Our findings demonstrate that within this fit-and-fill stem design, reduction in stem length improved proximal cortical strain distribution and maintained axial and torsional stability on par with other stem designs in a composite femur model. Short-stemmed implants may accommodate less invasive surgical techniques while facilitating more physiological femoral loading without sacrificing primary implant stability.

Twenty-year followup of an uncemented stem in primary THA.

BACKGROUND: Uncemented stems have been used in THA for well over two decades, but there are relatively few studies reporting on the results after 20 years. QUESTIONS/PURPOSES: The purpose of this study was to evaluate at a minimum followup of 20 years (1) hip scores; (2) radiographic findings, including stem fixation and osteolysis; (3) reoperations; and (4) survivorship free from aseptic loosening in a group of patients who underwent primary THA using a proximally porous-coated, plasma-sprayed, straight-stemmed, titanium-alloy femoral component. METHODS: Between 1987 and 1993, we performed 1517 primary THAs, of which 447 were cementless, and 157 used the implant under study here (representing 10% of the THAs during the period in question). General indications for the use of the study stem included (1) younger age with relatively stronger bone (average age 55 years in this study); (2) patients not involved in another study protocol (as were the 278 other cementless hips implanted during this time); and (3) patients who, at the surgeon's discretion, would be compliant with protected weightbearing. Of those, 111 were available for followup at a minimum of 20 years (mean, 20 years), whereas 36 had died and nine (6%) were lost to followup or declined participation. The primary diagnosis was osteoarthritis in 77 hips (69%). The mean age at operation was 55 years. The clinical result was evaluated on the basis of the Harris hip score. Radiographic analysis was performed at each followup visit for distal cortical hypertrophy, spot welds, radiolucencies, stem subsidence, varus or valgus shift, osteolysis, and femoral component loosening. Kaplan-Meier analysis was performed to evaluate the survival of the femoral component. RESULTS: The mean Harris hip score improved from 46 points to 87 points (of a possible 100 points) at the most recent followup. All hips had evidence of proximal femoral remodeling consistent with osseous ingrowth. Femoral osteolyis was seen in 22 hips (20%). One stem was revised as a result of a periprosthetic fracture. No femoral component had evidence of loosening, and none was revised. Thirty-three acetabular components (30%) were revised. CONCLUSIONS: This femoral component provided durable long-term fixation for over two decades after THA. The porous stem geometry is still in use today and will continue to be studied into the third decade of use. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Acetabular cup design influences deformational response in total hip arthroplasty.

BACKGROUND: Press-fit acetabular components are susceptible to deformation in an underreamed socket, with excessive deformation of metal-on-metal (MOM) components potentially leading to increased torsional friction and micromotion. Specifically, however, it remains unclear how cup diameter, design, and time from implantation affect shell deformation. QUESTIONS/PURPOSES: We asked whether (1) changes in component geometry and material altered maximum shell deformation and (2) time-dependent deformational relaxation processes occurred. METHODS: Diametral deformation was quantified after press-fit implantation of metal shells into a previously validated polyurethane model. Experimental groups (n = 6-8) consisted of 48-, 54-, 60-, and 66-mm MOM cups of 6-mm wall thickness, 58-mm cups of 10-mm wall thickness, and CoCrMo and Ti6Al4V 58-mm modular cups. RESULTS: Greater cup diameter, thinner wall construction, and Ti6Al4V modular designs generated conditions for maximum shell deformation ranging from 0.047 to 0.267 mm. Relaxation (18%-32%) was observed 120 hours postimplantation in thin-walled and modular designs. CONCLUSIONS: Our findings demonstrate a reduction of shell deformation over time and suggest, under physiologic loading, early component deformation varies with design. CLINICAL RELEVANCE: Component deformation should be a design consideration regardless of bearing surface. Designs neglecting to adequately address deformational changes in vivo could be susceptible to diminished cup survival, increased wear, and premature revision.

Pain relief and functional improvement remain 20 years after knee arthroplasty.

BACKGROUND: TKA provides demonstrable pain relief and improved health-related quality of life. Yet, a decline in physical function may occur over the long term despite the absence of implant-related problems. QUESTIONS/PURPOSES: (1) Does pain relief diminish over 20 years after TKA? (2) Does function decline over 20 years in terms of Knee Society function, knee, and walking scores? And (3) what is the patient-reported activity level at most recent followup? PATIENTS AND METHODS: We retrospectively identified 1471 patients with 1757 primary cruciate-retaining TKAs implanted between 1975 and 1989 and identified 128 living patients (8.7%) with 171 TKAs. Ninety-three patients were women. We determined Knee Society scores prospectively and UCLA scores retrospectively. Minimum followup was 20 years (average, 21.1 years; range, 20-27 years). Average age at last followup was 82.3 years (range, 45-103 years). Of the 128 patients, 66 (73 TKAs) died after 20-year followup. RESULTS: Pain scores did not diminish over time (average, 49; range, 20-50). Average knee score was 78 (range, 39-97). Function, stair, and walking scores diminished over time. Average function score was 70 (range, 5-100), primarily due to an average stair score of 35 (range, 0-50); average walking score was 37 (range, 10-50). All but two patients (two TKAs) could negotiate stairs; 95 patients (124 TKAs) could walk at least five blocks; three patients (three TKAs) were housebound. Of the 62 patients still living (98 TKAs), the average UCLA activity score was 8.3 (range, 5-10). CONCLUSIONS: Although aging may cause a gradual decline in physical activity, an improved functional capacity and activity level continue 20 years or more after TKA.

Low incidence of groin pain and early failure with large metal articulation total hip arthroplasty.

BACKGROUND: Large-diameter metal-on-metal articulations reportedly improve stability and wear in THAs. However, some reports suggest some patients have unexplained hip and early failures with these implants. Thus, the potential benefits may be offset by these concerns. However, the incidence of these problems is not clearly established. QUESTIONS/PURPOSES: We therefore assessed hip pain, function, osteolysis, and complications in patients with large-diameter metal-on-metal THA. PATIENTS AND METHODS: We retrospectively reviewed 611 patients who had 681 large-diameter metal-on-metal THAs with the same cup and head design. The average age at operation was 62 years, 53% of the THAs were in men, and the average body mass index was 32 kg/m(2). The diagnosis was osteoarthritis in 92% of the THAs. The minimum followup was 24 months (mean, 37 months; range, 24-60 months). RESULTS: Nine of the 611 patients (1.5%) experienced moderate or severe pain in the hip region that we considered to be coming from an extraarticular source in each case. Harris hip scores for pain averaged 42 points. Total Harris hip scores averaged 93 points. Cup abduction averaged 42°, and cup anteversion averaged 26°. There were no infections. Three cups (0.4%) were considered radiographically loose. All were secondary to inadequate seating of the shell. CONCLUSION: Our observations suggest with this implant the concerns of higher incidences of groin pain, early failures, and adverse tissue reactions were not confirmed. Early successes or failures with large-diameter metal-on-metal articulations may be implant specific. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Acetabular UHMWPE survival and wear changes with different manufacturing techniques.

BACKGROUND: Polyethylene wear may be affected by the type of polyethylene resin, manufacturing technique, degree of thermal stabilization, and sterilization technique. QUESTIONS/PURPOSES: We therefore compared femoral head penetration into the PE and cup survival using the same cup system with different PE resins, manufacturing, and sterilization techniques. METHODS: Our study group consisted of 1912 THAs performed using the same uncemented cup and identical 28-mm cobalt-chrome heads. The polyethylene varied as follows: Group 1 (94 cups), GUR 4150 resin, ram-extruded, sterilized in air, no barrier packaging; Group 2 (74 cups), same as Group 1 but sterilized in argon; Group 3 (75 cups), Himont 1900 resin, compression-molded bar stock, sterilized in argon, no barrier packaging; Group 4 (620 cups), same as Group 3 except with barrier packing; Group 5 (711 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon gas with barrier packaging; and Group 6 (338 cups), GUR 1050 resin, compression-molded bar stock, sterilized in argon with barrier packaging, irradiated with 50 kGy, heated below melting temperature, machined, and finally placed in nonbarrier packaging with gas plasma sterilization. Minimum followup was 2 years (average, 7 years; range, 2-17 years). RESULTS: Femoral head penetration averaged 0.05 mm per year for Groups 5 and 6 and was substantially lower than for Groups 1 to 4. Cup survival was higher at seven years in Groups 3, 4, and 5, and at 10 years in group 4 when compared to groups 1, 2, and 3. CONCLUSIONS: We observed lower FHP rates and higher cup survival with polyethylene machined from direct compression-molded bar stock, sterilized in argon gas, with barrier packaging. LEVEL OF EVIDENCE: Level III Therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Does high tibial osteotomy affect the success or survival of a total knee replacement?

BACKGROUND: Whether a previous high tibial osteotomy (HTO) influences the long-term function or survival of a total knee arthroplasty (TKA) is controversial. QUESTIONS/PURPOSES: We compared long-term functional scores and survival of bilateral TKAs in patients who had a previous HTO in one of the knees. PATIENTS AND METHODS: From 1980 to 1995, we performed 5043 primary TKAs; 39 of these patients had bilateral TKAs at an average of 8.7 years after unilateral HTO. Surgery was simultaneous in 32 patients and staged in seven. There were 12 women and 27 men with an average age of 66.9 years at the time of surgery. At last followup, 19 of the 39 patients were living and had been reevaluated since our previous study. We determined function with Knee Society scores. The length of followup for patients who had HTOs averaged 14 years (range, 3-21 years); for patients without HTOs, the average followup was 13.9 years (range, 3-22 years). RESULTS: We observed no differences in Knee Society function and radiographic and pain scores between the knees without and with previous HTO. Terminal extension and flexion, arc of motion, and knee alignment were similar between the knees. There were no femorotibial revisions in either group of knees. Survival at 15 years was 100% for knees without previous HTO and 97% for knees with previous HTO. CONCLUSIONS: Our observations suggest a previous high tibial osteotomy does not influence the function or survival of a knee long term. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Intramedullary vs extramedullary femoral alignment guides: a 15-year follow-up of survivorship.

The influence of intramedullary (IM) and extramedullary (EM) femoral cutting guides on survivorship of total knee arthroplasty was studied in 6726 total knee arthroplasty guided by either an IM (4993 knees) or EM (1733 knees) system. Fifteen-year survivorship of the 2 cohorts showed no statistically significant difference (EM 97.9% vs IM 98.5%; P = .2500, log rank). Medial bone collapse comprised the highest proportion of all failure modes for both groups (0.35% vs 0.40%, respectively, P = .6731, Cox regression). Mean tibiofemoral (overall) anatomical alignment was statistically more accurate in the IM group (IM 4.6° [± 2.2°] valgus vs EM 5.1° [± 3.1°] valgus; P < .0001). The mean tibial alignment was 90.5° (± 3.0) and 90.3° (± 2.2) (P = .0077). The EM group had a significantly larger tibial component alignment variance (SD(2)) than the IM group. No statistical difference in postoperative Knee Society scores, pain, or stair-climbing abilities was found. The choice of either alignment system should be determined by the patient's anatomy; however, the overall alignment is not as precise using the extramedullary system.

High survival of uncemented proximally porous-coated titanium alloy femoral stems in osteoporotic bone.

UNLABELLED: Because the initial fixation of an uncemented stem may be compromised in patients with osteoporotic bone (Class C, Dorr et al.), many surgeons prefer a cemented stem in this setting. We therefore determined the survival of an uncemented, proximally porous-coated, straight-stemmed, titanium alloy femoral component in patients with Class C bone when compared with Class A and B bone. We implanted proximally plasma-sprayed, straight-stemmed titanium alloy stems in 1994 patients (2321 hips). Of these, 625 hips (27%), 1569 hips (67%), and 127 hips (6%) were classified as Classes A, B, and C, respectively. Minimum followup was 2 years (mean, 5.9 years; range, 2-19.5 years). We identified no differences in Harris hip scores, pain, radiolucencies, or osteolysis among Classes A, B, and C hips. Stem survival at 5, 10, and 15 years for aseptic loosening (failure) was 100% in all patients with Class A bone; 99+% in all patients with Class B bone; and 100% in all patients with Class C bone. Initial stability and durable fixation can be achieved with the use of this uncemented stem in patients in whom a cemented stem traditionally has been preferred as a result of poor bone quality. LEVEL OF EVIDENCE: Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Total knee arthroplasty with 4.4 mm of tibial polyethylene an update.

Three hundred eighty-seven one-piece, 8-mm tibial components were implanted in 313 patients. All tibial prostheses were manufactured with 4.4 mm of polyethylene. From this group, 116 patients underwent simultaneous bilateral total knee arthroplasty with an 8-mm tibial component on one side and a tibial component with at least 6.4 mm of polyethylene on the other side. Follow-up averaged 11.8 years. The average Knee Society knee score was 81, and the average pain score was 46. No polyethylene wear or osteolysis was identified radiographically. There were 7 knees with tibial radiolucencies, 5 knees with polyethylene failure of metal-backed patellae, and 1 tibial component failure. Survival rates for loosening or revision of any component for any reason were 98.9%, 97.5%, 95.1%, and 93.2% at 5-, 10-, 15-, and 18-years, respectively.