Cement fixation has been the most commonly used method for total knee arthroplasty (TKA) implant fixation. Although cemented TKAs have been shown to have excellent survivorship,1–4 some studies have reported bone resorption, osteolysis, and aseptic loosening at the bone–cement interface,5–9 especially in younger patients.2,10 As the incidence of TKA in younger patients has increased, the indications for surgery have also expanded.11 Moreover, younger patients who undergo TKA are also usually more active,2,4 which places them at a higher risk for requiring revision surgery later in life. Therefore, to defer or potentially even prevent revision surgery, these patients would greatly benefit from long-term implant survivorship.12,13
Cementless fixation in TKA was initially developed to potentially preserve bone stock, to increase implant survivorship, and to decrease cement-related implant failures.5,14–16 However, the original cementless implants had high early failure rates that resulted from osteolysis and aseptic loosening, especially with the tibial component.17–20 Despite the problems reported with the original implants, current innovations in implant designs and newer biomaterials have been shown to have improved fixation and osseointegration, which may ultimately lead to improved longer-term cementless implant survivorship.14,16,21,22
These new advances warrant an updated analysis of modern cementless prostheses. Therefore, the purpose of this review was to evaluate the most recent literature on cementless TKA. Specifically, this review reports (1) a comparison of original and newer cementless implants; (2) outcomes of newer designs; (3) a risk–benefit analysis; and (4) a comparison of cementless vs cemented TKAs.
Original and Newer Cementless Implants
Cementless fixation, unlike cement, allows the bone and implant surface to form a biological bond that may respond more favorably to stress.14,15 The original cementless designs, however, were complicated by implant failure due to patchy porous coatings, design flaws, metallosis from metal-backed patellar failures, low-quality polyethylenes, and tibial tray subsidence from poor surgical technique.16,23,24 In addition, the original cementless designs with matte or gritblasted coatings showed poor biological fixation, and some implants were recalled. Similar to the prior coatings, highly porous tantalum-coated implants have had mixed results, with early failures leading to some implants being recalled.21,25
In contrast to these results,26 newer cementless implant designs have bioactive surface coatings that may facilitate both bone ingrowth and ongrowth.7 One implant design consists of a highly crystal-line solution form of hydroxyapatite that 3-dimensionally coats cobalt-chromium beads.27 Hydroxyapatite has been shown to improve both femoral and tibial implant fixation to bone and to decrease implant micromotion.28,29 Another design consists of highly porous titanium that is produced from commercially pure titanium and 3-dimensionally coats the bone apposition area of the implant.30–32 Highly porous titanium has a biologically inspired micro- and macrostructure,30 which allowed for a higher fixation strength and more bone ingrowth in a canine model,32 and may lead to more stability and decreased micromotion.27,33
Outcomes of Newer Cementless Designs
Since 2000, there have been several studies, including 3 randomized clinical trials (Table 1), 8 case–control studies (Table 2), and 20 cohort studies (Table 3), that have reported on the outcomes of newer cementless TKA designs.1,2,7,12,13,27,34–58
Randomized Clinical Trials
In a prospective randomized clinical study, Fricka et al34 described 47 patients who had a mean age of 60 years (range, 43–72 years) and received a cementless TKA and 46 patients who had a mean age of 59 years (range, 43–72 years) and received a cemented TKA, with at least 2 years of follow-up. Although the cemented group had better Knee Society Scores (KSS) than the cementless group (mean, 96 vs 92 points, P=.03), there was no significant difference in the KSS functional scores (mean, 95 vs 92 points, P=.14). Additionally, there was 1 septic failure in the cemented group and 1 aseptic failure in the cementless group, but there were no differences between the 2 groups in terms of patient satisfaction (P=.59) or pain control (P=.31).
In a recent study comparing the implant coatings of newer cementless TKAs, Harwin et al7 evaluated 805 beaded periapatite-coated cementless TKAs in patients who had a mean age of 67 years and 219 highly porous titanium-coated cementless TKAs in patients who had a mean age of 66 years. At a mean follow-up of 4.4 years, there were no differences between the beaded periapatite-coated and the highly porous titanium-coated TKAs in terms of KSS functional scores (mean, 85 vs 85 points, P=.766) or pain scores (mean, 93 vs 93 points, P=.9). Moreover, the authors reported that the all-cause survivorship in both groups was 99.5%. In the periapatite-coated group, there were 3 septic failures and 1 aseptic failure due to subsidence that required tibial component revision. In the highly porous titanium-coated group, there were only 2 aseptic failures that underwent revision—1 for subsidence and 1 for radiolucency. Although no statistical difference (P=.936) was seen between the highly porous titanium-coated group and the periapatite-coated group, the highly porous titanium-coated group still had an overall lower revision rate. In another study, Ouanezar et al36 described 87 cementless TKAs performed with computer-assisted surgery and 51 cementless TKAs performed conventionally in patients who had a mean age of 70 years and were followed for a mean of 10.5 years. Patient satisfaction was not significantly different between the conventional and the computer-assisted groups (98% vs 89%, P>.05), and there were no differences in KSS knee score (mean, 92 vs 91 points, P>.05) or KSS functional score (mean, 71 vs 73 points, P>.05). The authors also mentioned that, for both groups, the 10-year survivorship for aseptic loosening was 100%.
Although cementless TKAs were initially intended for younger patients, there have been successful outcomes in the elderly as well. A recent study27 reported on a cohort of 134 patients (142 knees) older than 75 years (mean, 80 years) who underwent cementless TKA and had a mean follow-up of 4 years (range, 2–8 years). The aseptic survivorship was 99.3%, and the all-cause implant survivorship was 98.6%. There was 1 aseptic revision due to aseptic loosening of the tibial baseplate, and 1 septic revision. Patients who have inflammatory arthropathies may also benefit from cementless TKAs. Buchheit et al45 evaluated 23 patients (34 knees) who had chronic inflammatory arthritis, had a mean age of 55 years (range, 26–78 years), underwent cementless TKA, and were followed for a mean of 6 years (range, 3–12 years). The survivorship was 97%, with 1 revision being performed for aseptic loosening and 1 because of a periprosthetic joint infection. Additionally, at the latest follow-up, 96% of patients reported being very satisfied or satisfied with the results of their surgery. Various other studies have reported excellent short-term outcomes of cementless designs.1,13,37,49,50
In summary, although initially intended for younger patients who undergo TKA, the newer cementless TKA designs have shown excellent survivorship, functional outcomes, and satisfaction rates in not only young but also elderly populations. Having 1 implant type that can appropriately manage 2 distinct patient populations further adds to an orthopedic surgeon's ability to best manage each individual patient.
One of the many advantages of cementless TKA fixation is the biological bond that forms between the interface of the bone and the implant. With highly porous titanium, the higher porosity allows for an increased amount of and rapid bone ingrowth in the canine model, which might explain its higher tensile strength.32 As evidenced in the canine study, hydroxyapatite-coated cobalt-chromium creates a milieu that is suitable for bone formation,32 thereby hastening bone ingrowth and fixation.22 In a study by Hansson et al59 comparing porous beaded fixation coated implants with hydroxyapatite-coated implants, the latter had significantly less tibial subsidence at 2-year follow-up.
Another advantage of cementless TKA is that this technique has been shown to decrease tourniquet and operative times. Unlike cemented TKA, cementless prostheses do not require complete exposure of trabecular bone, and the surgeon does not have to wait for the cement to dry.60 Kamath et al40 reported that, compared with patients who underwent cementless fixation, patients who underwent cemented TKA had a mean operative time that was 12 minutes longer (mean, 61 vs 73 minutes, P<.01). One study reported that the operating room charges are $1500 per 15-minute interval for cemented cases, and that an average of 20 minutes is spent on the cementing portion of the TKA; therefore, $3000 is saved per cementless TKA case.12
The use of cementless TKA has been questioned in those patients with poor bone quality and potentially decreased remodeling capacity of bone, which could potentially affect fixation of the implant.61,62 Li and Nilsson62 used radiostereometry to measure migration of the tibial implant in 28 knees that received either cementless or cemented TKAs. The authors noted that in the cementless TKAs, the preoperative bone quality influenced the amount of tibial component migration; in addition, during the early postoperative period, cemented fixation can compensate for differences in bone quality. Despite the fact that elderly patients can have poor bone quality, this is not always the case. Elderly patients with good bone quality might benefit from these implants, as evidenced by the study by Newman et al,27 which had 99.3% survivorship.
Also, it has been reported that compared with cemented TKA, cementless fixation can be associated with greater blood loss. Porteous et al63 evaluated 100 patients who underwent TKA and received a cemented, cementless, or hybrid prosthesis. The authors reported that compared with the cemented group, the total mean drainage was higher in the cementless group (1220 vs 754 mL, P<.001) and the hybrid group (1035 vs 754 mL, P<.05). Similarly, in a smaller study, Mylod et al64 described 34 patients (48 knees) who received either cementless or cemented TKAs. They found that compared with the cemented group, the cementless group had significantly more blood loss (P<.01) and had a higher transfusion rate (P<.025) in the first 48 hours postoperatively. However, in a study by Nam et al,1 there were no significant differences between the cementless and the cemented groups in terms of blood loss (202 vs 192 mL, P=.7).
Although the component costs for cementless TKAs have been reported to be higher24 (sometimes up to 3 times higher than those for cemented TKA),65 fewer resources are used during cementless surgery; hence, the total cost per procedure may more likely be lower.40 Kamath et al40 reported that with the money saved from not using additionally required cement-related supplies and the shorter operative times, the difference in cost between cementless and cemented TKAs was $150.
Comparison of Outcomes for Cementless and Cemented TKAs
Several studies have compared the outcomes of cementless TKAs with the outcomes of cemented TKAs at various time points. Short- to mid-term outcome studies analyzed patients with newer implant designs, whereas longer-term studies analyzed patients with similar but slightly older implant designs. Nevertheless, in most studies, similar findings have been noted between cementless and cemented cohorts at the different time points.
Nam et al1 analyzed 128 patients who had a mean age of 63 years. Sixty-six patients (66 knees) received a cementless TKA, and 62 patients (62 knees) received a cemented TKA. At a mean follow-up of 1.4 years, the implant survivorship was 100% in both groups. Furthermore, there was no difference in patient satisfaction between the groups (P=.4). Fricka et al34 performed a prospective randomized trial that compared 50 patients with trabecular metal with 50 patients with cement. At 2-year follow-up, they found that the KSS clinical scores were significantly lower in the cementless group compared with the cemented group (mean, 92 vs 96 points, P=.03), but there was no difference in the KSS functional scores (mean, 92 vs 95 points, P=.14). Additionally, there were no differences between the groups in terms of survivorship. Similarly, Park and Kim41 reviewed 50 patients (100 knees) with a mean age of 58 years (range, 51–67 years) who underwent simultaneous bilateral TKA and received a cementless implant in 1 knee and a cemented implant in the other. At a mean follow-up of 2 years, there were no differences between the cementless and cemented TKAs for KSS knee scores (mean, 98 vs 96 points, P=.350), KSS functional scores (mean, 88 vs 86, P=.627), or Western Ontario and McMaster Universities Osteoarthritis Index scores (mean, 35.6 vs 34.5 points, P=.191). There were also no differences in patient satisfaction scores between the cementless TKA and the cemented TKA (mean, 8.3 vs 8.1 points, P=.728). The authors reported that the femoral component survivorship was 100% for both but that the cementless tibial component survivorship was 98%. Of note, this study evaluated primarily Korean patients. Additionally, the cementless cohort had a significantly greater postoperative blood loss than the cemented cohort (mean, 1686.9 vs 1021.9 mL, P=.005).
Other studies have reported on the mid-term outcomes of cementless and cemented TKA. Bagsby et al37 reviewed 144 obese patients (145 knees) with a mean age of 63, years who received a cementless TKA (144 posterior-stabilized knees and 1 cruciate-retaining knee) and were followed for a mean of 3.6 years, and 149 patients (154 knees) with a mean age of 59, years who received a cemented TKA (96 posterior-stabilized knees, 58 cruciate-retaining knees) and were followed for a mean of 6.1 years. Compared with the cemented group, the cementless group had better KSS function scores (mean, 79 vs 55 points, P<.0001) and KSS pain scores (mean, 93 vs 88, points, P=.0001). The survivorship for aseptic loosening at 8 years was 100% for the cementless TKA, 93.8% for the cemented posterior-stabilized TKA, and 94.8% for the cruciate-retaining TKA. In another study, Kamath et al40 evaluated 100 patients (100 knees) younger than 55 years who underwent cementless TKA, and 312 patients (312 knees) with a mean age of 63 years who underwent cemented TKA. At a mean follow-up of more than 5 years, there were no differences between the cementless and cemented TKAs in KSS knee score (mean, 94.7 vs 91.3 points, P>.05) or functional score (mean, 88.4 vs 86.1 points, P>.05). In the cementless group, there were 3 failures, but none were related to implant fixation; however, in the cemented group, 2 revisions were performed for aseptic loosening.
For longer-term outcomes, Choy et al35 evaluated 126 patients (168 knees) with a mean age of 68 years (range, 49–80 years) who underwent TKA. Six patients who underwent bilateral TKAs had cemented fixation in 1 knee and cementless in the other. Eighty-two knees received cementless and 86 knees received cemented TKAs. At a mean follow-up of 9 years, there were no significant differences between the cementless and cemented groups in terms of KSS knee scores (mean, 94 vs 94 points, P=.90), KSS functional scores (mean, 78 vs 77 points, P=.92), or Western Ontario and McMaster Universities Osteoarthritis Index scores (mean, 26.8 vs 24.7, P=.19). The authors also reported that the survivorship with loosening or revision was 100% for both groups.
Additionally, Kim et al2 reported on the longer-term outcomes of a randomized clinical trial that included 80 patients (160 knees) with a mean age of 54.3 years (range, 49–55 years) who underwent simultaneous bilateral TKA with a cementless implant placed in 1 knee and a cemented implant placed in the other. At a mean follow-up of 16.6 years, there were no significant differences between the cementless and cemented TKAs for KSS knee scores (mean, 96 vs 97 points, P=.319) or Western Ontario and McMaster Universities Osteoarthritis Index scores (mean, 25.4 vs 25.9 points, P=.189). Additionally, they reported that patient satisfaction was similar between the cementless and cemented TKAs (mean, 8.1 vs 8.3 points, P=.698). At 17 years, the tibial component survivorship in the cementless group was 98.7%, with 1 being revised for aseptic loosening, but the femoral component survivorship was 100%. In the cemented group, the survivorship was 100% for both the femoral and tibial components.
A Cochrane review evaluated all studies performed through 2011 reporting on different component fixation options for TKA, including cementless, cemented, and hybrid fixation. The analysis, which included 3 studies that described 216 patients, used an instability classification that was based on radiographic measurements. It was determined that more displacement occurred in the cementless tibial components compared with the cemented components. Additionally, the risk of aseptic loosening with cemented fixation was twice that of cementless fixation.66 However, implant survivorship and patient-reported outcomes were not analyzed.
On the basis of the above studies, cemented and cementless TKA patients had similar outcomes at various postoperative time points. Patient satisfaction and functional outcome scores were also similarly positive among all cohorts. Therefore, cementless TKA appears to be just as effective as cemented TKA.
A subanalysis on rotating platforms was also completed. Only 1 study satisfied the current authors' inclusion criteria. Napier et al67 compared 98 patients (100 TKAs) with a mean age of 65 years (range, 54–79 years) who were morbidly obese (50 TKAs) or nonobese (50 TKAs) and received cementless rotating platform TKAs. The intraoperative anesthetic times were similar between the morbidly obese and nonobese cohorts (mean, 36 vs 31 minutes, P>.05). They also found a significant range of motion difference between the morbidly obese and nonobese patients preoperatively (mean, 99.0° vs 113.0°, P<.001) and at 1 year postoperatively (mean, 99.3° vs 104.3°, P<.033). They found Short-Form 12 outcome differences between the cohorts to be similar both preoperatively (mean, 42 vs 42 points, P>.05) and 1 year postoperatively (mean, 47 vs 50, P>.05). There were no revision surgeries. However, 4 patients developed superficial wound infections and 2 patients developed deep wound infections and were treated with irrigation and debridement with component retention. Therefore, on the basis of these results, both morbidly obese and nonobese patients who receive rotating platform implants can potentially achieve improved 1-year outcomes.
Subanalysis—Cementless Patella Fixation
A total of 7 studies met the inclusion criteria for cementless patella fixation. All 7 of the studies had a minimum of 2-year follow-up, with the overall mean follow-up time of all studies being 8 years.
Gerscovich et al25 performed a minimum 10-year follow-up study involving a group of 95 patients (108 TKAs) who had a mean age of 65 years and underwent cementless TKA. A total of 47 patients (58 TKAs) were available at 11-year follow-up. They reported a 97% survivorship for the tibial and femoral components. There were 2 cases of patellar revisions for loose components. At a mean follow-up of 6 years, Chan and Giori42 evaluated 29 patients (30 TKAs) with a mean age of 51 years who underwent cementless TKA with a cementless metal-backed titanium patella. At the follow-up visit, patellar fractures had occurred in 6 knees (20%). Although 4 TKAs required reoperations, Chan and Giori did not attribute the revision surgeries to the patellar component fractures. Harwin et al13 described 951 patients (1024 knees) who underwent cementless TKAs and were followed for a mean of 4 years. They reported that 1 patient had dislodgment of the patellar implant during a manipulation under anesthesia at 6 weeks postoperatively. Due to the dislodgment, a cemented patellar component was then implanted.
Additionally, Nodzo et al68 reviewed the radiographs of 101 TKAs that had cementless patella components and 50 TKAs with cemented patella components. At a minimum follow-up of 2 years, the survivorship was 100% in both groups, and there were no signs of patellar instability. However, compared with the cemented group, 45% of the knees in the cementless group had small areas of lower trabecular bone density around the patellar pegs. Kwong et al12 described 105 patients (115 knees) with a mean age of 67 years who underwent cementless TKA and were followed for a mean of 7 years. They reported survivorship of 96%, no radiographic evidence of osteolysis, and no revisions for aseptic loosening. There was 1 intraoperative patellar fracture and 1 postoperative patellar fracture from a fall. The latter was treated nonoperatively, and the patient has done well without any changes in the patellar component position.
Yamanaka et al69 evaluated 31 patients with rheumatoid arthritis and a mean age of 64 years who underwent cementless TKA with a cementless all-polyethylene patellar component and were followed for a mean of 8 years. None of the patellae had radiolucent lines, and the implant survivorship at 12 years was 97%. Ritter and Meneghini57 described 47 patients (73 knees) with a mean age of 59 years who underwent cementless TKA with a metal-backed cementless patella. Fifteen failures occurred, with 12 revision surgeries performed for failure of the metal-backed patellar components and metallosis. The mean time to failure was 9 years.
These studies reveal favorable outcomes of cementless fixation for the patellar component. Overall, 1359 patients (1482 TKAs) were analyzed. There were 25 adverse postoperative events (2%) related to the patella. These events ranged from patellar fracture due to traumatic fall, which was treated nonoperatively, to component dislodgment during manipulation under anesthesia. Therefore, based on the above results, cementless fixation of the patellar component is a potentially successful option.
Survivorship of TKAs depends, in part, on the ability of the bone and implant to maintain fixation. The most commonly used method has been with cement. However, with younger patients undergoing TKA, alternative fixation techniques have been developed to improve implant longevity.
Studies have compared cohorts of patients who received cementless TKAs regarding screw fixation, obesity, and computer-assisted surgery.36,39,70 However, as newer cementless designs have been marketed, there is a paucity of literature comparing their different types of coatings.7 At a mean follow-up of 4.4 years, Harwin et al7 found no differences between cementless TKAs coated with highly porous titanium vs beaded periapatite in terms of survivorship, function, or complication rates. Moreover, additional studies focusing on comparing different types of highly porous metal coatings and other bioactive coatings would be beneficial.
In the current health care environment, where payers are pressuring hospitals to substantiate the costs of surgery, the financial burden associated with TKA has become increasingly important.71 Moreover, one of the largest expenses associated with TKA is the cost of the implants, which has been shown to vary between hospitals and surgeons.72 Therefore, to determine the cost-effectiveness of cementless TKA, there needs to be a reduction in the variability of pricing. Although surgery may be faster in cementless TKA, there are other variables that may influence the cost, such as the implant and transfusion.
This review had some limitations. Specifically, the authors did not discuss hybrid fixation, having a cemented component along with a cementless component, which has been proposed due to the strength of the high osteoconductive properties of the modern coatings. Because this study focused on only cementless fixation of both TKA components, this design type was not included. Additionally, the subanalyses performed on rotating platform implants and cementless patella fixation were limited by the number of studies currently available in the literature. Future studies should analyze the uses, clinical and radiographic outcomes, patient-reported outcomes, and costs of different implant and fixation modalities.