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Comparative Incidence of Patellofemoral Complications Between 2 Total Knee Arthroplasty Systems in a Multicenter, Prospective Clinical Study
The Journal of Arthroplasty xxx (2017) 1e6
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Comparative Incidence of Patellofemoral Complications Between 2 Total Knee Arthroplasty Systems in a Multicenter, Prospective Clinical Study Sean D. Toomey, MD a, *, Juan A. Daccach, MD b, Jinesh C. Shah, MS b, Sam E. Himden, BA, CCRA b, James P. Lesko, PhD b, William G. Hamilton, MD c a b c
Orthopedic Physician Associates, Seattle, Washington DePuy Synthes, Warsaw, Indiana Anderson Orthopaedic Research Institute, Alexandria, Virginia
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a b s t r a c t
Article history: Received 8 December 2016 Received in revised form 31 March 2017 Accepted 10 April 2017 Available online xxx
Background: Cumulative incidence rates (CIRs) of patellofemoral complications (PCCs) and patellofemoral symptomatic crepitus (SC) using a new knee systemetotal knee arthroplasty (NEW-TKA) were compared with those of a currently available productetotal knee arthroplasty (CA-TKA). Methods: Twenty-two investigators prospectively enrolled 704 patients into a study using CA-TKA; 364 received a posterior-stabilized configuration. Twenty-three investigators (19 from the CA-TKA study) enrolled 1138 patients with NEW-TKA; 584 received a posterior-stabilized configuration. CIRs were estimated with Kaplan-Meier methods. Results: CA-TKA had 32 PCCs (6.15% CIR at 1 year and 8.26% at 2 years). NEW-TKA had 19 PCCs (3.15% CIR at 1 year and 4.11% at 2 years). CA-TKA had 15 SCs, 12 before 2 years (CIR ¼ 3.67%); NEW-TKA had 5 SCs before 2 years (CIR ¼ 1.21%). NEW-TKA had a statistically lower CIR of overall PCC and SC (log-rank P values ¼ .018 for PCC and .017 for SC). Conclusion: Interim 1- and 2-year CIRs of PCC and SC in NEW-TKA were less than half of those for CATKA, which is a promising trend for this new implant. © 2017 Elsevier Inc. All rights reserved.
Level of Evidence: Level III Keywords: total knee arthroplasty patellofemoral complications patellofemoral crepitus symptomatic crepitus complication pain
Primary total knee arthroplasties (TKAs), and posteriorstabilized (PS) knee arthroplasties specifically, have demonstrated excellent survivorship, yet, not all patients are fully satisfied [1e3]. Many factors can influence satisfaction and most center on pain and lack of function [4]. Prior studies have documented the most common reasons for revision, but there are other conditions that can lead to suboptimal outcomes and subsequent reoperation [5,6]. There remains some variability regarding the postoperative incidence of undesirable outcomes such as anterior knee pain, symptomatic crepitus (SC), and symptomatic patellar clunk. The lack of consensus is likely due to a combination of issues such as
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2017.04.014. * Reprint requests: Sean D. Toomey, MD, Orthopedic Physician Associates, 601 Broadway, Suite 600, Seattle, WA 98122-5330. http://dx.doi.org/10.1016/j.arth.2017.04.014 0883-5403/© 2017 Elsevier Inc. All rights reserved.
inconsistent outcomes measurement collection (physician vs patient reported), the varying definitions of clunk and crepitus, and differences in reporting observations (symptomatic vs asymptomatic). Differences in implant design and variability in surgical technique may also influence these outcomes [7]. Fibrous peripatellar scar tissue formation has been identified as causing a varying degree of knee symptoms after TKA. Although this condition was first noted by Insall et al [8] in a case report in 1982, it was not until 1989 that Hozack et al [9], defined this type of occurrence as “patellar clunk syndrome” by relating the pathophysiology of a discrete fibrous nodule impinging on the femoral implant, creating a clunking sensation when the knee goes from extension into flexion. Since this time, multiple authors have reported on this disease process, which seems to be most prevalent in PS TKAs with incidence ranging from 0% to 21% [10e17]. This condition can lead to a spectrum of symptoms ranging from painless crepitus to painful crepitus, and painful clunking when extending the knee from a flexed position. Patients may report audible sounds from the anterior aspect of the knee. One type of
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sound is commonly referred to as “crepitus,” which is described as a grating, grinding, or crunching sound generally believed to be due to soft-tissue impingement in the anterior flange of the femoral component during knee flexion [18]. Crepitus may or may not be symptomatic (painful), and may be treated, either openly, or more commonly, arthroscopically [19,20]. A second type of sound is “patellar clunk,” believed to be due to a suprapatellar fibrous nodule that develops at the junction between the superior patella and the quadriceps tendon. Patellar clunk is a palpable and sometimes audible phenomenon often associated with a jumping motion that is typically observed at a discrete point in the flexion arc as the knee extends [9]. Causation appears multifactorial, as there are many reported factors contributing to the relative risk of development of patellar clunk or crepitus. Surgical technique (patellar positioning, joint line elevation, femoral component positioning, patellar sizing, patellar thickness, patellar tilt, anterior placement of the tibial tray, mini subvastus approach, and so forth) and femoral implant design (eg, increased intracondylar box ratio, anterior flange geometry, and trochlear groove geometry) can also influence these clinical outcomes [21e23]. Crepitus or clunk usually occurs anywhere from 2 months to 2 years after TKA [23]. The incidence of this clinical outcome is ill-defined in part due to confusion between crepitus and patellar clunk, lack of reporting clarity with respect to symptomatic as opposed to asymptomatic crepitus, and inadequate reporting of relevant surgical technique covariates. In addition, most reports on this topic are retrospective evaluations. The purpose of this analysis was to evaluate and compare the incidence of patellofemoral SC using the ATTUNE Knee System (DePuy Synthes, Warsaw, IN) with that of the P.F.C. SIGMA Knee System (DePuy Synthes, Warsaw, IN). We hypothesize that design modifications to the femoral component with ATTUNE could reduce the overall incidence of patellofemoral SC and/or clunk and the subsequent need for a secondary surgery.
Materials and Methods
Currently Available ProducteTotal Knee Arthroplasty From October 2011 to March 2015, 22 investigators (from the United States, United Kingdom, Australia, and New Zealand) enrolled 845 patients (845 primary TKAs) equally across all 4 configurations (cruciate-retaining [CR] fixed bearing, CR rotating platform [RP], PS fixed bearing, and PS rotating platform [RP]) with a combination of CAPs, of which 704 received the CA-TKA reported in this article, the P.F.C. SIGMA System. Of these 704 (89%) patients, 364 received a PS configuration, 97.8% with a resurfaced patella. Surgeons were allowed to choose the type of implant they would commonly use in their standard practice and implant only 1 of the 4 knee configurations. Because patellar clunk and crepitus is predominantly reported with PS knees, this article focused on the PS subset. This cohort was registered on clinicaltrials.gov under the registration number: NCT01497730.
New Knee SystemeTotal Knee Arthroplasty From November 2012 to May 2015, 23 investigators (19 of whom also participated in the CA-TKA study) enrolled 1138 patients (1138 primary TKAs) across the same configurations with the NEW-TKA. Centers that did not enroll into the CA-TKA cohort were allowed to implant in only 1 of the 4 knee configurations. Centers that had previously enrolled into the CA-TKA cohort remained in their previously selected configuration with the exception of 1 site that contributed to another configuration to help the study team complete enrollment. NEW-TKA was the ATTUNE Knee System, a primary, cemented, multiradius TKA system. Patellofemoral design attributes for NEW-TKA vs CA-TKA that are relevant to this evaluation of patellofemoral complications (PCCs) included narrower and thinner anterior flange, proportional intracondylar box, finer increments of patellar thickness, and an extended trochlear groove. A total of 584 (51%) NEW-TKA patients received a PS configuration, 98.5% with a resurfaced patella. Similar to the CA-TKA cohort, analyses in this article focused on the PS subset. This cohort was registered on clinicaltrials.gov under the registration number: NCT01746524.
Study Groups A total of 1983 primary TKAs were prospectively enrolled in a multicenter clinical study. Before enrollment in the study, approval was granted from each participating center’s institutional review board or ethics committee. Written informed consent was provided by all study patients before their inclusion in the study. The study enrolled patients aged 22-80 years, inclusive with noninflammatory degenerative joint disease that was suitable candidates for cemented primary TKA. Treatment assignment was not randomized. Enrolled patients were both willing and able to perform study procedures and meet follow-up requirements. Exclusion criteria consisted of patients who had inflammatory arthritis, psychosocial disorders limiting rehabilitation, previous knee arthroplasty (including unicompartmental, bicompartmental, or patellofemoral joint arthroplasty), prior patellectomy, prior high tibial osteotomy, or primary TKA in the affected knee. Other exclusion criteria included patients with a contralateral TKA, which was previously entered in the study, those experiencing radicular pain from the spine, or a patient who was pregnant or lactating. Participating centers were instructed to follow their standard of care regarding the surgical process and with respect to patellar resurfacing. Patients were evaluated preoperatively, at <1 year (1303 days), minimum 1 year (304-668 days), and minimum 2 years (669-1763 days) after surgery.
Definition of PCC and SC PCCs were collected on an adverse event form by the examiner and included both crepitus (asymptomatic and SC) and patellar clunk. Crepitus was identified on physical examination as the presence of a consistent grinding/crunching sound localized to the front of the knee when the patients extended their knee from a flexed position. Clunk was a phenomenon of similar pathology regarding the scar tissue process, manifesting as patellar catching with a visible “popping” of the patella at a discrete point in the arc of motion. SC excluding patellar clunk was noted as an event where the patient was aware of, or had pain/discomfort, which could be verified during examination. The coauthors of this article critically reviewed all PCCs and queried investigators as needed resulting in a consistent and accurate analysis for this report.
Passive Flexion Flexion was measured by the surgeons (or their medically trained team members) using a goniometer. Flexion at last observed follow-up for each subject was dichotomized at 110 , and the odds ratios of PCCs were compared for subjects who had a low flexion (<110 ) vs a high flexion (110 ).
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Statistical Methods Given the different enrollment periods, CA-TKA had the potential for a longer follow-up and adverse event reporting compared with NEW-TKA. Thus, a direct comparison of proportions would be biased. To overcome this bias, the cumulative incidence rates (CIRs) were compared postoperatively using the Kaplan-Meier (KM) time to event methodology. The time variable was time to first observation of the event, or last clinical follow-up or death if there was no event. CIR was defined as 100% minus KM (absence of the event) estimate. KM CIR was estimated for PS subjects in which at least 40 subjects had later follow-up. A logistic regression analysis was performed to calculate the odds of PCC events for subjects with a flexion of 110 compared to subjects with a flexion of <110 . Because the days to follow-up varied between subjects, the length to last observed follow-up was controlled for in the model.
Results Disposition of subjects in both study cohorts is presented in Figure 1. Demographics were similar (SIGMA PS vs ATTUNE PS: mean [standard deviation, SD] age 65.5 [8.5] vs 65.6 [8.0] years; female, 62.9% vs 59.1%; mean [SD] body mass index, 31.9 [6.4] vs 32.0 [6.1] kg/m2; diagnosis [osteoarthritis], 98.1% vs 99.0%); however, CA-TKA had a longer length of follow-up (mean [SD], 1.94 [0.73] vs 1.23 [0.66] days) because the enrollment period was earlier than for NEW-TKA. In SIGMA, 21 PCCs occurred before 1 year postoperatively, whereas cumulatively 27 occurred before 2 years postoperatively. Ten SCs occurred before 1 year postoperatively and cumulatively 12 occurred before 2 years postoperatively. Of the 9 SCs that received treatment, 1 patient received physical therapy, 4 were treated with arthroscopy, and 4 received steroid injections. In ATTUNE, 16 PCCs occurred before 1 year postoperatively, whereas cumulatively 18 occurred before 2 years postoperatively.
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Four SCs occurred before 1 year postoperatively and cumulatively 5 occurred before 2 years postoperatively. The 2 SC cases that received treatment underwent arthroscopy. KM plots of CIRs for PCC and SC and their respective estimates along with 95% confidence intervals demonstrated a higher CIR for PCC and SC for the patients implanted with SIGMA (Figs. 2 and 3, respectively). A log-rank test was performed using these interim data to compare differences in the point-wise estimates of CIRs for PCC and SC, respectively. The P value was .018 for PCC, and .017 for SC. In SIGMA, it was observed that subjects with a flexion 110 had an odds of PCCs which was approximately 5.1 times the odds of PCCs for subjects with <110 of flexion (P value ¼ .1152). In contrast, for ATTUNE, it was observed that subjects with a flexion 110 had an odds of PCCs which was approximately equal to the odds of PCCs for subjects with <110 of flexion (P value ¼ .9955). These odds ratio estimates were at the last observed follow-up with these interim data. The proportions of subjects with low and high flexion for both SIGMA and ATTUNE (PS knees only) along with their odds ratios and 95% confidence intervals are reported in Figure 4.
Discussion The purpose of this article was to determine if modifications made in designing the ATTUNE Knee TKA System reduced the incidence of patellar crepitus or clunk when compared with a currently available implant, the P.F.C. SIGMA design. There are several weaknesses of this comparison that should be acknowledged. This comparison is a nonrandomized, matched, case-control design with the SIGMA cases performed 1-2 years before the ATTUNE cases. Changes in surgical technique or perioperative protocols over time may have influenced the incidence of crepitus or clunk. We believe this is unlikely given the close sequential timing of the 2 cohorts and the consistency of surgeons and perioperative protocols during this timeframe. Furthermore, the incidence of crepitus or clunk was dependent on surgeons
CA-TKA
NEW-TKA
All Enrolled Subjects (N = 845) minus minus
Remove non-PS Subjects (N= 423)
Remove Screen Failures (N = 0)
All PS subjects (N = 422)
minus
Remove non-PS Subjects (N= 553)
minus
Remove Screen Failures (N = 1)
All PS subjects (N = 584)
®
1 Year or later Follow-up 2 Year or later Follow-up
SIGMA Only – PS Subjects (N = 364)
1 Year or later Follow-up 2 Year or later Follow-up
All Enrolled Subjects (N = 1138)
N = 842 N = 353
N = 323 N = 220
Fig. 1. Patient flowchart. CA-TKA, currently available productetotal knee arthroplasty; NEW-TKA, new knee systemetotal knee arthroplasty; PS, posterior stabilized.
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<110o Flexion ATTUNE® – PS (561 of 584 flexion measurements available)
SIGMA® - PS (356 of 364 flexion measurements available)
PCC – No (N = 542) PCC – Yes (N = 19) PCC – No (N = 324) PCC – Yes (N = 32)
84 (96.55%)
≥110o Flexion
Odds Rao (95% CI) p-value
458 (96.62%)
3 (3.45%)
16 (3.38%)
47 (97.92%)
277 (89.94%)
1 (2.08%)
31 (10.06%)
1.00 (0.28, 3.53) p-value = 0.9955 5.07 (0.67, 31.13) p-value = 0.1152
Fig. 4. Odds ratio estimates for overall (including symptomatic and asymptomatic) PCCs (crepitus and/or clunk) by Flexion for ATTUNE Knee vs P.F.C. SIGMA.
Fig. 2. Kaplan-Meier (KM) plot of the cumulative incidence rate for overall (including symptomatic and asymptomatic) patellofemoral complications (PCCs; crepitus and/or clunk). CI, confidence intervals.
identifying and reporting this complication. There may have been differences in surgeons’ definition of this diagnosis or threshold to report the complication from center to center, although training for investigators was provided before the study to minimize this
Fig. 3. KM plot of the cumulative incidence rate of symptomatic crepitus (SC) only.
possibility. The coauthors thoroughly reviewed and queried all PCCs to enhance the quality of the analysis. Furthermore, any differences that persisted should have remained generally consistent between the 2 arms of the study and should not have changed our ability to detect a difference between the implants studied. The follow-up of this study is relatively short, although most publications that describe this complication report a mean time for presentation of crepitus or clunk of <1 year [7,24e26]. Results from both cohorts are interim, and the planned further follow-up may help identify these late presenting cases. Although we intended to capture several different manufacturers’ designs in the cohort of currently available TKAs (CA-TKA), the majority of the cases were primarily of one design (SIGMA), which led us to focus on a comparison between the DePuy SIGMA and ATTUNE designs. Finally, other than to define an incidence of this complication, we did not make radiographic measurements or examine patient characteristics that may have better elucidated the etiology of this complication. This may be the emphasis of a future investigation. There are also several strengths of this study. This was a prospective study that was designed in part to identify the incidence of clunk and crepitus throughout the duration of the study. All surgeons were instructed via study training, as well as with adverse event forms, to report all noises emanating from the front of the knee, as well as any anterior (patellofemoral) symptoms in general. Each site had a research coordinator that reviewed the medical records to ensure that any adverse events that were reported in the patient’s medical record were also reported as an adverse event to study personnel. Research coordinators also contacted patients to maximize follow-up and minimize patients lost to follow-up. We believe that this type of study design and attentive oversight has the best chance of reporting an accurate incidence of any complication, especially when compared with a retrospective database review, which appears to be the most frequently reported study design on this topic. Several studies have evaluated the incidence of patellar clunk or crepitus using the P.F.C. SIGMA knee system. The definitions from study to study are quite variable, so it is critical when evaluating each study to understand what is being reported (crepitus vs clunk, symptomatic vs asymptomatic, and operative vs nonoperative cases) as well as the design of each study (ie, prospective vs retrospective). Furthermore, there are several variations of the SIGMA design (fixed vs mobile bearing, PS vs CR, and standard vs high flex) as well as a change to the intracondylar box that was made to the femoral component circa 2008 to deepen the trochlear groove and smooth the transition to the intracondylar box [27]. All these factors can dramatically influence the figures reported. This comparison of CA-TKA and NEW-TKA cohorts was designed to capture comprehensive data on these implants including all instances of noise emanating from the front of the knee. This will likely yield figures that, while higher than other studies reported, represent the most accurate incidence of this complication. There are several studies that have reported on the rates of crepitus and clunk using the SIGMA knee system. Agarwal et al retrospectively reviewed 107 patients with the P.F.C. SIGMA RP-F
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design (high flex mobile bearing; DePuy Synthes) [24]; Sixteen of 107 patients (15.0%) were diagnosed with patellar clunk (patellar crepitus was not described in this report) of which 11 went on to operative debridement (10.3%), whereas 5 patients responded to conservative management. No recurrences were reported in this study. Costanzo et al [26] performed a retrospective review of 2713 DePuy P.F.C. SIGMA cruciate-substituting knees and identified 75 knees (2.76%) that required arthroscopy for patellar clunk. Patellar crepitus was not described in this study, nor was the incidence of crepitus or clunk that was managed nonoperatively. Four patients were noted to have recurrence of the patellar clunk [26]. In a study comparing 62 patients with the DePuy Synthes P.F.C. SIGMA PS RP (standard mobile bearing) vs 66 patients with the RP-F (mobile bearing high flex), Hamilton et al [28] reported patellar SC in 3.2% of the RP vs 16.7% in the RP-F group. One patient in the RP group (1.6%) and 2 patients in the RP-F group (3.2%) required arthroscopic debridement [28]. Rajshekhar et al [29] also reported on a series of 130 TKAs using the enhanced trochlear design of the SIGMA PS femur. They reported a rate of patellar clunk in 3 of 130 knees (2%). There have been several studies that have documented an improvement in patellar clunk or crepitus with implant design modifications. In a study of the SIGMA PS design, Frye et al [27] compared the rate of crepitus and clunk before and after modifications were made to the femoral trochlea, which included deepening the trochlear groove and smoothing the transition to the intercondylar box. In 108 TKAs before the trochlear modification, 13 (12%) TKAs were found to have crepitus (9 cases) or clunk (4 cases), whereas 0% of the 136 TKAs reported this complication after the modification was made. Although the pathophysiology of patellar noise is incompletely understood, prior studies have attempted to identify factors that predispose to crepitus or clunk using the SIGMA PS design. Dennis et al [7] examined 60 TKAs that required arthroscopic nodule removal for symptomatic crepitus or clunk and matched them to a control group. They found several factors that increased the risk of developing symptomatic crepitus or clunk which included shortened patellar tendon length, the use of smaller patellar components, decreased patellar composite thickness, and increased posterior femoral condylar offset [7]. In a similar study, Costanzo et al [26] identified 75 cases of patellar clunk managed with arthroscopic nodule removal and matched them with controls and performed radiographic measures. The factors that increased the risk of developing clunk in their article included a thicker preoperative patella, a smaller patellar component, and a longer patellar length [24]. Finally, flexion has also been investigated as a predictor of PCCs in previously published literature, specifically flexion 110 . In a study of 570 TKAs using the Genesis II system (Smith & Nephew), Peralta-Molero et al [30] reported an incidence of patellar crepitus and clunk in 34 knees (6%) of which 6 patients (1.1%) required arthroscopic debridement. They found that for every degree of increasing postoperative flexion, the likelihood of developing a clunk or crepitus increased 4.2%. Our odds ratio analysis for CA-TKA yielded similar results (Fig. 4). However, for ATTUNE, our analysis showed no difference for high flexion vs low flexion. In summary, this prospective study reported a CIR of symptomatic crepitus at 2 years of 3.67% with the SIGMA of which 9 of the 15 patients required treatment (1 received physical therapy, 4 were treated with arthroscopy, and 4 received steroid injections) and 1.21% with the ATTUNE implants, of which 2 of the 5 patients required arthroscopic debridement. Although the complication rates are low with both implants, the trend toward reducing this complication is reassuring for surgeons and patients alike. This comparison shows that the implant design changes included in this
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study may improve patient outcomes with this frustrating complication. In addition to the results regarding SC, this comparison reported the overall CIR of all (symptomatic and asymptomatic) PCCs of SIGMA (8.26%) vs ATTUNE (4.11%) at 2 years. It is our observation that modifications to knee component design, while not completely eliminating patellofemoral soft-tissue concerns which is clearly a multifactorial problem, can help reduce SC and asymptomatic crepitus. Further follow-up, which is ongoing, will help to confirm the trends that have been seen in these interim data.
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[25] Choi WC, Ryu K-J, Lee S, Seong SC, Lee MC. Painful patellar clunk or crepitation of contemporary knee prostheses. Clin Orthopaedics Relat Res 2013;471:1512e22. [26] Costanzo JA, Aynardi MC, Peters JD, Kopolovich DM, Purtill JJ. Patellar clunk syndrome after total knee arthroplasty; risk factors and functional outcomes of arthroscopic treatment. J Arthroplasty 2014;29(9 Suppl.):201e4. [27] Frye BM, Floyd MW, Pham DC, Feldman JJ, Hamlin BR. Effect of femoral component design on patellofemoral crepitance and patella clunk syndrome after posterior-stabilized total knee arthroplasty. J Arthroplasty 2012;27: 1166e70.
[28] Hamilton WG, Sritulanondha S, Engh CA. Prospective randomized comparison of high-flex and standard rotating platform total knee arthroplasty. J Arthroplasty 2011;26(Suppl. 6):28e34. [29] Rajshekhar KT, Kumar MN, Venugopal P, Chandy T. Patellar clunk in total knee arthroplasty using modified Sigma posterior stabilized femoral component. J Clin Orthopaedics Trauma 2014;5:211e4. [30] Peralta-Molero JV, Gladnick BP, Lee Y-Y, Ferrer AV, Lyman S, Gonzalez Della Valle A. Patellofemoral crepitation and clunk following modern, fixed-bearing total knee arthroplasty. J Arthroplasty 2014;29:535e40.
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Comparative Incidence of Patellofemoral Complications Between 2 Total Knee Arthroplasty Systems in a Multicenter, Prospective Clinical Study Sean D. Toomey, MD a, *, Juan A. Daccach, MD b, Jinesh C. Shah, MS b, Sam E. Himden, BA, CCRA b, James P. Lesko, PhD b, William G. Hamilton, MD c a b c
Orthopedic Physician Associates, Seattle, Washington DePuy Synthes, Warsaw, Indiana Anderson Orthopaedic Research Institute, Alexandria, Virginia
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 December 2016 Received in revised form 31 March 2017 Accepted 10 April 2017 Available online xxx
Background: Cumulative incidence rates (CIRs) of patellofemoral complications (PCCs) and patellofemoral symptomatic crepitus (SC) using a new knee systemetotal knee arthroplasty (NEW-TKA) were compared with those of a currently available productetotal knee arthroplasty (CA-TKA). Methods: Twenty-two investigators prospectively enrolled 704 patients into a study using CA-TKA; 364 received a posterior-stabilized configuration. Twenty-three investigators (19 from the CA-TKA study) enrolled 1138 patients with NEW-TKA; 584 received a posterior-stabilized configuration. CIRs were estimated with Kaplan-Meier methods. Results: CA-TKA had 32 PCCs (6.15% CIR at 1 year and 8.26% at 2 years). NEW-TKA had 19 PCCs (3.15% CIR at 1 year and 4.11% at 2 years). CA-TKA had 15 SCs, 12 before 2 years (CIR ¼ 3.67%); NEW-TKA had 5 SCs before 2 years (CIR ¼ 1.21%). NEW-TKA had a statistically lower CIR of overall PCC and SC (log-rank P values ¼ .018 for PCC and .017 for SC). Conclusion: Interim 1- and 2-year CIRs of PCC and SC in NEW-TKA were less than half of those for CATKA, which is a promising trend for this new implant. © 2017 Elsevier Inc. All rights reserved.
Level of Evidence: Level III Keywords: total knee arthroplasty patellofemoral complications patellofemoral crepitus symptomatic crepitus complication pain
Primary total knee arthroplasties (TKAs), and posteriorstabilized (PS) knee arthroplasties specifically, have demonstrated excellent survivorship, yet, not all patients are fully satisfied [1e3]. Many factors can influence satisfaction and most center on pain and lack of function [4]. Prior studies have documented the most common reasons for revision, but there are other conditions that can lead to suboptimal outcomes and subsequent reoperation [5,6]. There remains some variability regarding the postoperative incidence of undesirable outcomes such as anterior knee pain, symptomatic crepitus (SC), and symptomatic patellar clunk. The lack of consensus is likely due to a combination of issues such as
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2017.04.014. * Reprint requests: Sean D. Toomey, MD, Orthopedic Physician Associates, 601 Broadway, Suite 600, Seattle, WA 98122-5330. http://dx.doi.org/10.1016/j.arth.2017.04.014 0883-5403/© 2017 Elsevier Inc. All rights reserved.
inconsistent outcomes measurement collection (physician vs patient reported), the varying definitions of clunk and crepitus, and differences in reporting observations (symptomatic vs asymptomatic). Differences in implant design and variability in surgical technique may also influence these outcomes [7]. Fibrous peripatellar scar tissue formation has been identified as causing a varying degree of knee symptoms after TKA. Although this condition was first noted by Insall et al [8] in a case report in 1982, it was not until 1989 that Hozack et al [9], defined this type of occurrence as “patellar clunk syndrome” by relating the pathophysiology of a discrete fibrous nodule impinging on the femoral implant, creating a clunking sensation when the knee goes from extension into flexion. Since this time, multiple authors have reported on this disease process, which seems to be most prevalent in PS TKAs with incidence ranging from 0% to 21% [10e17]. This condition can lead to a spectrum of symptoms ranging from painless crepitus to painful crepitus, and painful clunking when extending the knee from a flexed position. Patients may report audible sounds from the anterior aspect of the knee. One type of
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sound is commonly referred to as “crepitus,” which is described as a grating, grinding, or crunching sound generally believed to be due to soft-tissue impingement in the anterior flange of the femoral component during knee flexion [18]. Crepitus may or may not be symptomatic (painful), and may be treated, either openly, or more commonly, arthroscopically [19,20]. A second type of sound is “patellar clunk,” believed to be due to a suprapatellar fibrous nodule that develops at the junction between the superior patella and the quadriceps tendon. Patellar clunk is a palpable and sometimes audible phenomenon often associated with a jumping motion that is typically observed at a discrete point in the flexion arc as the knee extends [9]. Causation appears multifactorial, as there are many reported factors contributing to the relative risk of development of patellar clunk or crepitus. Surgical technique (patellar positioning, joint line elevation, femoral component positioning, patellar sizing, patellar thickness, patellar tilt, anterior placement of the tibial tray, mini subvastus approach, and so forth) and femoral implant design (eg, increased intracondylar box ratio, anterior flange geometry, and trochlear groove geometry) can also influence these clinical outcomes [21e23]. Crepitus or clunk usually occurs anywhere from 2 months to 2 years after TKA [23]. The incidence of this clinical outcome is ill-defined in part due to confusion between crepitus and patellar clunk, lack of reporting clarity with respect to symptomatic as opposed to asymptomatic crepitus, and inadequate reporting of relevant surgical technique covariates. In addition, most reports on this topic are retrospective evaluations. The purpose of this analysis was to evaluate and compare the incidence of patellofemoral SC using the ATTUNE Knee System (DePuy Synthes, Warsaw, IN) with that of the P.F.C. SIGMA Knee System (DePuy Synthes, Warsaw, IN). We hypothesize that design modifications to the femoral component with ATTUNE could reduce the overall incidence of patellofemoral SC and/or clunk and the subsequent need for a secondary surgery.
Materials and Methods
Currently Available ProducteTotal Knee Arthroplasty From October 2011 to March 2015, 22 investigators (from the United States, United Kingdom, Australia, and New Zealand) enrolled 845 patients (845 primary TKAs) equally across all 4 configurations (cruciate-retaining [CR] fixed bearing, CR rotating platform [RP], PS fixed bearing, and PS rotating platform [RP]) with a combination of CAPs, of which 704 received the CA-TKA reported in this article, the P.F.C. SIGMA System. Of these 704 (89%) patients, 364 received a PS configuration, 97.8% with a resurfaced patella. Surgeons were allowed to choose the type of implant they would commonly use in their standard practice and implant only 1 of the 4 knee configurations. Because patellar clunk and crepitus is predominantly reported with PS knees, this article focused on the PS subset. This cohort was registered on clinicaltrials.gov under the registration number: NCT01497730.
New Knee SystemeTotal Knee Arthroplasty From November 2012 to May 2015, 23 investigators (19 of whom also participated in the CA-TKA study) enrolled 1138 patients (1138 primary TKAs) across the same configurations with the NEW-TKA. Centers that did not enroll into the CA-TKA cohort were allowed to implant in only 1 of the 4 knee configurations. Centers that had previously enrolled into the CA-TKA cohort remained in their previously selected configuration with the exception of 1 site that contributed to another configuration to help the study team complete enrollment. NEW-TKA was the ATTUNE Knee System, a primary, cemented, multiradius TKA system. Patellofemoral design attributes for NEW-TKA vs CA-TKA that are relevant to this evaluation of patellofemoral complications (PCCs) included narrower and thinner anterior flange, proportional intracondylar box, finer increments of patellar thickness, and an extended trochlear groove. A total of 584 (51%) NEW-TKA patients received a PS configuration, 98.5% with a resurfaced patella. Similar to the CA-TKA cohort, analyses in this article focused on the PS subset. This cohort was registered on clinicaltrials.gov under the registration number: NCT01746524.
Study Groups A total of 1983 primary TKAs were prospectively enrolled in a multicenter clinical study. Before enrollment in the study, approval was granted from each participating center’s institutional review board or ethics committee. Written informed consent was provided by all study patients before their inclusion in the study. The study enrolled patients aged 22-80 years, inclusive with noninflammatory degenerative joint disease that was suitable candidates for cemented primary TKA. Treatment assignment was not randomized. Enrolled patients were both willing and able to perform study procedures and meet follow-up requirements. Exclusion criteria consisted of patients who had inflammatory arthritis, psychosocial disorders limiting rehabilitation, previous knee arthroplasty (including unicompartmental, bicompartmental, or patellofemoral joint arthroplasty), prior patellectomy, prior high tibial osteotomy, or primary TKA in the affected knee. Other exclusion criteria included patients with a contralateral TKA, which was previously entered in the study, those experiencing radicular pain from the spine, or a patient who was pregnant or lactating. Participating centers were instructed to follow their standard of care regarding the surgical process and with respect to patellar resurfacing. Patients were evaluated preoperatively, at <1 year (1303 days), minimum 1 year (304-668 days), and minimum 2 years (669-1763 days) after surgery.
Definition of PCC and SC PCCs were collected on an adverse event form by the examiner and included both crepitus (asymptomatic and SC) and patellar clunk. Crepitus was identified on physical examination as the presence of a consistent grinding/crunching sound localized to the front of the knee when the patients extended their knee from a flexed position. Clunk was a phenomenon of similar pathology regarding the scar tissue process, manifesting as patellar catching with a visible “popping” of the patella at a discrete point in the arc of motion. SC excluding patellar clunk was noted as an event where the patient was aware of, or had pain/discomfort, which could be verified during examination. The coauthors of this article critically reviewed all PCCs and queried investigators as needed resulting in a consistent and accurate analysis for this report.
Passive Flexion Flexion was measured by the surgeons (or their medically trained team members) using a goniometer. Flexion at last observed follow-up for each subject was dichotomized at 110 , and the odds ratios of PCCs were compared for subjects who had a low flexion (<110 ) vs a high flexion (110 ).
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Statistical Methods Given the different enrollment periods, CA-TKA had the potential for a longer follow-up and adverse event reporting compared with NEW-TKA. Thus, a direct comparison of proportions would be biased. To overcome this bias, the cumulative incidence rates (CIRs) were compared postoperatively using the Kaplan-Meier (KM) time to event methodology. The time variable was time to first observation of the event, or last clinical follow-up or death if there was no event. CIR was defined as 100% minus KM (absence of the event) estimate. KM CIR was estimated for PS subjects in which at least 40 subjects had later follow-up. A logistic regression analysis was performed to calculate the odds of PCC events for subjects with a flexion of 110 compared to subjects with a flexion of <110 . Because the days to follow-up varied between subjects, the length to last observed follow-up was controlled for in the model.
Results Disposition of subjects in both study cohorts is presented in Figure 1. Demographics were similar (SIGMA PS vs ATTUNE PS: mean [standard deviation, SD] age 65.5 [8.5] vs 65.6 [8.0] years; female, 62.9% vs 59.1%; mean [SD] body mass index, 31.9 [6.4] vs 32.0 [6.1] kg/m2; diagnosis [osteoarthritis], 98.1% vs 99.0%); however, CA-TKA had a longer length of follow-up (mean [SD], 1.94 [0.73] vs 1.23 [0.66] days) because the enrollment period was earlier than for NEW-TKA. In SIGMA, 21 PCCs occurred before 1 year postoperatively, whereas cumulatively 27 occurred before 2 years postoperatively. Ten SCs occurred before 1 year postoperatively and cumulatively 12 occurred before 2 years postoperatively. Of the 9 SCs that received treatment, 1 patient received physical therapy, 4 were treated with arthroscopy, and 4 received steroid injections. In ATTUNE, 16 PCCs occurred before 1 year postoperatively, whereas cumulatively 18 occurred before 2 years postoperatively.
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Four SCs occurred before 1 year postoperatively and cumulatively 5 occurred before 2 years postoperatively. The 2 SC cases that received treatment underwent arthroscopy. KM plots of CIRs for PCC and SC and their respective estimates along with 95% confidence intervals demonstrated a higher CIR for PCC and SC for the patients implanted with SIGMA (Figs. 2 and 3, respectively). A log-rank test was performed using these interim data to compare differences in the point-wise estimates of CIRs for PCC and SC, respectively. The P value was .018 for PCC, and .017 for SC. In SIGMA, it was observed that subjects with a flexion 110 had an odds of PCCs which was approximately 5.1 times the odds of PCCs for subjects with <110 of flexion (P value ¼ .1152). In contrast, for ATTUNE, it was observed that subjects with a flexion 110 had an odds of PCCs which was approximately equal to the odds of PCCs for subjects with <110 of flexion (P value ¼ .9955). These odds ratio estimates were at the last observed follow-up with these interim data. The proportions of subjects with low and high flexion for both SIGMA and ATTUNE (PS knees only) along with their odds ratios and 95% confidence intervals are reported in Figure 4.
Discussion The purpose of this article was to determine if modifications made in designing the ATTUNE Knee TKA System reduced the incidence of patellar crepitus or clunk when compared with a currently available implant, the P.F.C. SIGMA design. There are several weaknesses of this comparison that should be acknowledged. This comparison is a nonrandomized, matched, case-control design with the SIGMA cases performed 1-2 years before the ATTUNE cases. Changes in surgical technique or perioperative protocols over time may have influenced the incidence of crepitus or clunk. We believe this is unlikely given the close sequential timing of the 2 cohorts and the consistency of surgeons and perioperative protocols during this timeframe. Furthermore, the incidence of crepitus or clunk was dependent on surgeons
CA-TKA
NEW-TKA
All Enrolled Subjects (N = 845) minus minus
Remove non-PS Subjects (N= 423)
Remove Screen Failures (N = 0)
All PS subjects (N = 422)
minus
Remove non-PS Subjects (N= 553)
minus
Remove Screen Failures (N = 1)
All PS subjects (N = 584)
®
1 Year or later Follow-up 2 Year or later Follow-up
SIGMA Only – PS Subjects (N = 364)
1 Year or later Follow-up 2 Year or later Follow-up
All Enrolled Subjects (N = 1138)
N = 842 N = 353
N = 323 N = 220
Fig. 1. Patient flowchart. CA-TKA, currently available productetotal knee arthroplasty; NEW-TKA, new knee systemetotal knee arthroplasty; PS, posterior stabilized.
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<110o Flexion ATTUNE® – PS (561 of 584 flexion measurements available)
SIGMA® - PS (356 of 364 flexion measurements available)
PCC – No (N = 542) PCC – Yes (N = 19) PCC – No (N = 324) PCC – Yes (N = 32)
84 (96.55%)
≥110o Flexion
Odds Rao (95% CI) p-value
458 (96.62%)
3 (3.45%)
16 (3.38%)
47 (97.92%)
277 (89.94%)
1 (2.08%)
31 (10.06%)
1.00 (0.28, 3.53) p-value = 0.9955 5.07 (0.67, 31.13) p-value = 0.1152
Fig. 4. Odds ratio estimates for overall (including symptomatic and asymptomatic) PCCs (crepitus and/or clunk) by Flexion for ATTUNE Knee vs P.F.C. SIGMA.
Fig. 2. Kaplan-Meier (KM) plot of the cumulative incidence rate for overall (including symptomatic and asymptomatic) patellofemoral complications (PCCs; crepitus and/or clunk). CI, confidence intervals.
identifying and reporting this complication. There may have been differences in surgeons’ definition of this diagnosis or threshold to report the complication from center to center, although training for investigators was provided before the study to minimize this
Fig. 3. KM plot of the cumulative incidence rate of symptomatic crepitus (SC) only.
possibility. The coauthors thoroughly reviewed and queried all PCCs to enhance the quality of the analysis. Furthermore, any differences that persisted should have remained generally consistent between the 2 arms of the study and should not have changed our ability to detect a difference between the implants studied. The follow-up of this study is relatively short, although most publications that describe this complication report a mean time for presentation of crepitus or clunk of <1 year [7,24e26]. Results from both cohorts are interim, and the planned further follow-up may help identify these late presenting cases. Although we intended to capture several different manufacturers’ designs in the cohort of currently available TKAs (CA-TKA), the majority of the cases were primarily of one design (SIGMA), which led us to focus on a comparison between the DePuy SIGMA and ATTUNE designs. Finally, other than to define an incidence of this complication, we did not make radiographic measurements or examine patient characteristics that may have better elucidated the etiology of this complication. This may be the emphasis of a future investigation. There are also several strengths of this study. This was a prospective study that was designed in part to identify the incidence of clunk and crepitus throughout the duration of the study. All surgeons were instructed via study training, as well as with adverse event forms, to report all noises emanating from the front of the knee, as well as any anterior (patellofemoral) symptoms in general. Each site had a research coordinator that reviewed the medical records to ensure that any adverse events that were reported in the patient’s medical record were also reported as an adverse event to study personnel. Research coordinators also contacted patients to maximize follow-up and minimize patients lost to follow-up. We believe that this type of study design and attentive oversight has the best chance of reporting an accurate incidence of any complication, especially when compared with a retrospective database review, which appears to be the most frequently reported study design on this topic. Several studies have evaluated the incidence of patellar clunk or crepitus using the P.F.C. SIGMA knee system. The definitions from study to study are quite variable, so it is critical when evaluating each study to understand what is being reported (crepitus vs clunk, symptomatic vs asymptomatic, and operative vs nonoperative cases) as well as the design of each study (ie, prospective vs retrospective). Furthermore, there are several variations of the SIGMA design (fixed vs mobile bearing, PS vs CR, and standard vs high flex) as well as a change to the intracondylar box that was made to the femoral component circa 2008 to deepen the trochlear groove and smooth the transition to the intracondylar box [27]. All these factors can dramatically influence the figures reported. This comparison of CA-TKA and NEW-TKA cohorts was designed to capture comprehensive data on these implants including all instances of noise emanating from the front of the knee. This will likely yield figures that, while higher than other studies reported, represent the most accurate incidence of this complication. There are several studies that have reported on the rates of crepitus and clunk using the SIGMA knee system. Agarwal et al retrospectively reviewed 107 patients with the P.F.C. SIGMA RP-F
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design (high flex mobile bearing; DePuy Synthes) [24]; Sixteen of 107 patients (15.0%) were diagnosed with patellar clunk (patellar crepitus was not described in this report) of which 11 went on to operative debridement (10.3%), whereas 5 patients responded to conservative management. No recurrences were reported in this study. Costanzo et al [26] performed a retrospective review of 2713 DePuy P.F.C. SIGMA cruciate-substituting knees and identified 75 knees (2.76%) that required arthroscopy for patellar clunk. Patellar crepitus was not described in this study, nor was the incidence of crepitus or clunk that was managed nonoperatively. Four patients were noted to have recurrence of the patellar clunk [26]. In a study comparing 62 patients with the DePuy Synthes P.F.C. SIGMA PS RP (standard mobile bearing) vs 66 patients with the RP-F (mobile bearing high flex), Hamilton et al [28] reported patellar SC in 3.2% of the RP vs 16.7% in the RP-F group. One patient in the RP group (1.6%) and 2 patients in the RP-F group (3.2%) required arthroscopic debridement [28]. Rajshekhar et al [29] also reported on a series of 130 TKAs using the enhanced trochlear design of the SIGMA PS femur. They reported a rate of patellar clunk in 3 of 130 knees (2%). There have been several studies that have documented an improvement in patellar clunk or crepitus with implant design modifications. In a study of the SIGMA PS design, Frye et al [27] compared the rate of crepitus and clunk before and after modifications were made to the femoral trochlea, which included deepening the trochlear groove and smoothing the transition to the intercondylar box. In 108 TKAs before the trochlear modification, 13 (12%) TKAs were found to have crepitus (9 cases) or clunk (4 cases), whereas 0% of the 136 TKAs reported this complication after the modification was made. Although the pathophysiology of patellar noise is incompletely understood, prior studies have attempted to identify factors that predispose to crepitus or clunk using the SIGMA PS design. Dennis et al [7] examined 60 TKAs that required arthroscopic nodule removal for symptomatic crepitus or clunk and matched them to a control group. They found several factors that increased the risk of developing symptomatic crepitus or clunk which included shortened patellar tendon length, the use of smaller patellar components, decreased patellar composite thickness, and increased posterior femoral condylar offset [7]. In a similar study, Costanzo et al [26] identified 75 cases of patellar clunk managed with arthroscopic nodule removal and matched them with controls and performed radiographic measures. The factors that increased the risk of developing clunk in their article included a thicker preoperative patella, a smaller patellar component, and a longer patellar length [24]. Finally, flexion has also been investigated as a predictor of PCCs in previously published literature, specifically flexion 110 . In a study of 570 TKAs using the Genesis II system (Smith & Nephew), Peralta-Molero et al [30] reported an incidence of patellar crepitus and clunk in 34 knees (6%) of which 6 patients (1.1%) required arthroscopic debridement. They found that for every degree of increasing postoperative flexion, the likelihood of developing a clunk or crepitus increased 4.2%. Our odds ratio analysis for CA-TKA yielded similar results (Fig. 4). However, for ATTUNE, our analysis showed no difference for high flexion vs low flexion. In summary, this prospective study reported a CIR of symptomatic crepitus at 2 years of 3.67% with the SIGMA of which 9 of the 15 patients required treatment (1 received physical therapy, 4 were treated with arthroscopy, and 4 received steroid injections) and 1.21% with the ATTUNE implants, of which 2 of the 5 patients required arthroscopic debridement. Although the complication rates are low with both implants, the trend toward reducing this complication is reassuring for surgeons and patients alike. This comparison shows that the implant design changes included in this
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study may improve patient outcomes with this frustrating complication. In addition to the results regarding SC, this comparison reported the overall CIR of all (symptomatic and asymptomatic) PCCs of SIGMA (8.26%) vs ATTUNE (4.11%) at 2 years. It is our observation that modifications to knee component design, while not completely eliminating patellofemoral soft-tissue concerns which is clearly a multifactorial problem, can help reduce SC and asymptomatic crepitus. Further follow-up, which is ongoing, will help to confirm the trends that have been seen in these interim data.
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[25] Choi WC, Ryu K-J, Lee S, Seong SC, Lee MC. Painful patellar clunk or crepitation of contemporary knee prostheses. Clin Orthopaedics Relat Res 2013;471:1512e22. [26] Costanzo JA, Aynardi MC, Peters JD, Kopolovich DM, Purtill JJ. Patellar clunk syndrome after total knee arthroplasty; risk factors and functional outcomes of arthroscopic treatment. J Arthroplasty 2014;29(9 Suppl.):201e4. [27] Frye BM, Floyd MW, Pham DC, Feldman JJ, Hamlin BR. Effect of femoral component design on patellofemoral crepitance and patella clunk syndrome after posterior-stabilized total knee arthroplasty. J Arthroplasty 2012;27: 1166e70.
[28] Hamilton WG, Sritulanondha S, Engh CA. Prospective randomized comparison of high-flex and standard rotating platform total knee arthroplasty. J Arthroplasty 2011;26(Suppl. 6):28e34. [29] Rajshekhar KT, Kumar MN, Venugopal P, Chandy T. Patellar clunk in total knee arthroplasty using modified Sigma posterior stabilized femoral component. J Clin Orthopaedics Trauma 2014;5:211e4. [30] Peralta-Molero JV, Gladnick BP, Lee Y-Y, Ferrer AV, Lyman S, Gonzalez Della Valle A. Patellofemoral crepitation and clunk following modern, fixed-bearing total knee arthroplasty. J Arthroplasty 2014;29:535e40.