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The AAHKS Clinical Research Award: Are Minimum Two-Year Patient-Reported Outcome Measures Necessary for Accurate Assessment of Patient Outcomes After Primary Total Knee Arthroplasty?

Published:February 10, 2022DOI:https://doi.org/10.1016/j.arth.2022.02.016

      Abstract

      Background

      The two-year minimum follow-up after total knee arthroplasty (TKA) required by most academic journals is based on implant survivorship studies rather than patient-reported outcome measures (PROMs). Additionally, the COVID-19 pandemic placed an unprecedented burden on patients and staff and halted asymptomatic surveillance clinic visits to minimize exposure. The purpose of this study was to determine if clinically meaningful differences were observed in PROMs beyond one year after TKA.

      Methods

      A retrospective review was performed on prospectively collected PROMs after 1093 primary TKAs at a suburban academic center. PROMs related to pain, function, activity level, and satisfaction were compared by subsequent follow-up intervals preoperatively, at 4 months, 1 year, and minimum 2 years using paired data analysis techniques.

      Results

      Pain with level walking and while climbing stairs improved from preoperative levels to 4-month, 1-year, and minimum 2-year follow-up. The University of California Los Angeles activity level and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement improved over the same intervals. Patient satisfaction improved over postoperative follow-up intervals (84.0%, 87.3%, and 90.9%). While PROMs improved with statistical and clinical significance preoperatively to 4-month to 1-year follow-up, improvements from 1-year to minimum 2-year follow-up were small and did not reach minimum clinically important differences for nearly all PROMs, demonstrating significant overlap of the 95% confidence intervals.

      Conclusion

      While long-term follow-up after TKA remains important for implant survivorship, it appears that one-year PROMs are as clinically reliable and meaningful as two-year PROMs. Therefore, it is reasonable to question the currently accepted 2-year minimum follow-up requirement used in peer-reviewed research involving PROMs.

      Level of Evidence

      Level III.

      Keywords

      Total knee arthroplasty (TKA) outcomes are frequently assessed with patient-reported outcome measures (PROMs). Collection of PROMs is often performed prospectively before and after surgery at various follow-up intervals. Collection of PROMs adds additional cost and burden to patients and clinical staff [
      • Samuelsson K.
      • Magnussen R.A.
      • Alentorn-Geli E.
      • Krupic F.
      • Spindler K.P.
      • Johansson C.
      • et al.
      Equivalent knee injury and osteoarthritis outcome scores 12 and 24 months after anterior cruciate ligament reconstruction: results from the Swedish national knee ligament register.
      ], with one study finding that maximal effort in PROM collection led to a 76% response rate, compared to 44% with minimal effort or automated collection [
      • Pronk Y.
      • Pilot P.
      • Brinkman J.M.
      • van Heerwaarden R.J.
      • van der Weegen W.
      Response rate and costs for automated patient-reported outcomes collection alone compared to combined automated and manual collection.
      ]. Nonetheless, PROMs have become an important tool in clinical research, with retrospective and prospective studies utilizing PROMs as primary or secondary outcomes. Many orthopedic surgery journals require a minimum of 2-year follow-up for publication of clinical research [
      • Ramkumar P.N.
      • Navarro S.M.
      • Haeberle H.S.
      • Ng M.
      • Piuzzi N.S.
      • Spindler K.P.
      No difference in outcomes 12 and 24 months after lower extremity total joint arthroplasty: a systematic review and meta-analysis.
      ], accentuating the burden of PROM data collection. This minimum requirement for follow-up has evolved from implant survivorship studies, and the value and necessity of long-term PROM collection are yet to be fully understood [
      • Flannery O.
      • Harley O.
      • Badge R.
      • Birch A.
      • Nuttall D.
      • Trail I.A.
      Matortho proximal interphalangeal joint arthroplasty: minimum 2-year follow-up.
      ]. While most agree that patient follow-up and surveillance are critical, the utility of long-term PROMs remains uncertain.
      The push to reduce health care costs over the past decade has left no area of medicine untouched. Additional office visits place additional burden on patients, physicians, and the health care system. Estimating the added cost of extra visits is difficult, but a small prospective study following patients after TKA and total hip arthroplasty (THA) estimated the average cost of additional visits at $117 ± 60, with only 9% of visits resulting in some change in patient care [
      • Hendricks T.J.
      • Chong A.C.M.
      • Cusick R.P.
      The cost of routine follow-up in total joint arthroplasty and the influence of these visits on treatment plans.
      ]. With the onset of the COVID-19 pandemic, routine clinic follow-up faced a new challenge, as many physicians had to adapt to a virtual office model. This development added difficulty to routine collection of PROMs, with recent studies finding decreased rates of PROM collection and overall contact with physician offices during the pandemic [
      • Lee D.
      • Lencer A.J.
      • Gibbs B.S.
      • Paul R.W.
      • Tjoumakaris F.P.
      Disruptions in standard care: anterior cruciate ligament reconstruction outcomes during the Sars-Cov2 pandemic.
      ,
      • Bargon C.A.
      • Batenburg M.C.T.
      • van Stam L.E.
      • Mink van der Molen D.R.
      • van Dam I.E.
      • van der Leij F.
      • et al.
      Impact of the COVID-19 pandemic on patient-reported outcomes of breast cancer patients and survivors.
      ]. Additionally, many long-term or routine asymptomatic office visits were halted altogether to minimize contagion exposure and reduce burden on patients and staff. The additional cost and added burden of office visits for virtual or electronic capture for long-term PROM collection must be carefully considered against the value of collecting PROMs up to 2 years or more after surgery.
      The purpose of the current study was to evaluate changes in PROMs between preoperative baseline, 4-month, 1-year, and minimum 2-year follow-up periods following primary TKA. The null hypothesis was that there would be no statistically significant changes in PROMs between 1-year and minimum 2-year follow-up.

      Materials and Methods

      Study Design

      The study was a retrospective review of prospectively collected data on all primary TKAs performed by a single fellowship-trained arthroplasty surgeon at a single institution between September 2010 and September 2018. Institutional review board approval was obtained for the study. A total of 1187 TKAs were initially identified during this catchment period. Ninety-four TKAs were excluded (Table 1), leaving 1093 TKAs available for analysis.
      Table 1Exclusions.
      ReasonN
      Hybrid cementation technique15
      Unresurfaced patella15
      Medically complex
      Medically complex cases involved those with hematologic cancer, thromboembolic disease, and severe dementia.
      10
      Orthopedically complex
      Orthopedically complex cases involved those with tibial augments, revision type baseplates, and prior osteotomies.
      16
      Any procedure after index TKA30
      Deaths unrelated to TKA7
      Extensor mechanism reconstruction1
      Total94
      TKA, total knee arthroplasty.
      a Medically complex cases involved those with hematologic cancer, thromboembolic disease, and severe dementia.
      b Orthopedically complex cases involved those with tibial augments, revision type baseplates, and prior osteotomies.

      Data Collection

      PROMs were routinely collected at the preoperative visit and during postoperative visits at 4 months, 1 year, and every year thereafter if the patient returned to the clinic. The PROMs included the following: University of California Los Angeles (UCLA) activity level, components of the modern Knee Society Score (KSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS JR), and overall satisfaction. The UCLA activity level score asks patients to choose their highest level of current activity, ranging from 0 (wholly inactive: dependent on others, cannot leave residence) to 10 (regularly participate in impact sports such as jogging, tennis, skiing, acrobatics, ballet, heavy labor, or backpacking) [
      • Zahiri C.A.
      • Schmalzried T.P.
      • Szuszczewicz E.S.
      • Amstutz H.C.
      Assessing activity in joint replacement patients.
      ]. Individual items from the KSS questionnaire included pain with walking on a level surface, pain with stair climbing (both scored 0 for none to 10 for severe), and the question “does this knee feel normal to you?” (KSS knee normal: always, sometimes, or never) [
      • Scuderi G.R.
      • Bourne R.B.
      • Noble P.C.
      • Benjamin J.B.
      • Lonner J.H.
      • Scott W.N.
      The new knee society knee scoring system.
      ]. The KOOS JR is the short-form version of the original long-form KOOS outcome measure for TKA that focuses on stiffness, pain, and activities of daily living characterizing overall knee joint health (scores range from 0 indicating total knee disability to 100 indicating perfect knee health) [
      • Lyman S.
      • Lee Y.Y.
      • Franklin P.D.
      • Li W.
      • Cross M.B.
      • Padgett D.E.
      Validation of the Koos, Jr: a short-form knee arthroplasty outcomes survey.
      ]. Overall satisfaction was assessed with the question “what is your current level of satisfaction with your knee replacement?” scored on a five-point scale (very satisfied, satisfied, neutral, dissatisfied, or very dissatisfied).
      Follow-up intervals were operationally defined as preoperative (<0.0 months), 4-month (3.0-5.0 months), 1-year (8.5-15.4 months), and minimum 2-year (≥20.5 months) intervals. Medical and demographic covariates were collected via chart review in the electronic medical record. Demographic information included age, gender, and body mass index. Medical covariates related to PROMs included American Society of Anesthesiologists Physical Status score, lumbar spine disease, fibromyalgia, systemic lupus erythematosus, rheumatoid arthritis, psoriatic arthritis, depression, and preoperative narcotic use (as needed [prn] or scheduled). Surgery-specific covariates were also collected including posterior cruciate ligament status, implant type, and fixation type (cemented or cementless).
      In addition to statistical significance, clinical significance using empirically derived MCIDs (the minimum clinically important difference patients perceive as meaningful) was included in our analysis. MCIDs for the various PROMs used in total joint arthroplasty (TJA) have been studied extensively to better understand the significance of changes in PROMs after surgery, as statistical significance does not necessarily equate to clinical meaningfulness. The MCID used for the UCLA activity level was 0.92 [
      • Copay A.G.
      • Eyberg B.
      • Chung A.S.
      • Zurcher K.S.
      • Chutkan N.
      • Spangehl M.J.
      Minimum clinically important difference: current trends in the orthopaedic literature, part II: lower extremity: a systematic review.
      ]. For KSS pain with level walking and pain with stair climbing, MCIDs of 0.61 and 2.0 were evaluated for both scores [
      • Lee W.C.
      • Kwan Y.H.
      • Chong H.C.
      • Yeo S.J.
      The minimal clinically important difference for knee society clinical rating system after total knee arthroplasty for primary osteoarthritis.
      ,
      • Salaffi F.
      • Stancati A.
      • Silvestri C.A.
      • Ciapetti A.
      • Grassi W.
      Minimal clinically important changes in chronic musculoskeletal pain intensity measured on a numerical rating scale.
      ]. For KSS “knee normal” scores, an improvement of 33% was considered clinically meaningful [
      • Salaffi F.
      • Stancati A.
      • Silvestri C.A.
      • Ciapetti A.
      • Grassi W.
      Minimal clinically important changes in chronic musculoskeletal pain intensity measured on a numerical rating scale.
      ]. The MCID for KOOS JR was defined as 6.0 [
      • Lyman S.
      • Lee Y.Y.
      • McLawhorn A.S.
      • Islam W.
      • MacLean C.H.
      What are the minimal and substantial improvements in the Hoos and Koos and Jr versions after total joint replacement?.
      ].

      Statistical Analysis

      Statistical analysis was performed with Minitab 19 (State College, PA). Outliers were evaluated with Dixon’s ratio test based on the sample size of the analysis group. Paired two-sample t-tests (t) were used to compare means between follow-up intervals. McNemar’s test was used to compare proportions of 2 × 2 paired data groups. A significance level of 0.050 was considered statistically significant.

      Results

      Patient Demographics and Covariates

      Sixty-seven percent (735/1093) of the 1093 patients were female with a mean age and body mass index of 65.6 ± 9.2 years and 34.2 ± 7.0 kg/m2, respectively. Most patients had a TKA with posterior cruciate ligament preservation (77%) and cement fixation (87%). All patients received either a Triathlon (Stryker, Mahwah, NJ) or EMPOWR 3D (DJO Surgical, Lewisville, TX) knee. Sample demographics and covariates are shown in Table 2. Patient demographics and covariates had little effect on PROMs and remained constant for paired data analysis.
      Table 2Cohort Demographics and Covariates.
      VariableNMean (SD)MinMax
      Age, y109365.6 (9.2)33.191.4
      BMI, kg/m2109334.2 (7.0)16.559.3
      Gender1093Female (67.2%)Male (32.8%)
      ASA-PS class1093I (1.1%)II (36.5%)III (60.1%)IV (2.3%)
      PCL status1091
      2 cases missing status of PCL.
      Partial or full release (23.3%)Fully preserved (76.7%)
      Implant used1093EMPOWR 3D (50.3%)Triathlon (49.7%)
      Fixation1093Cemented (86.5%)Cementless (13.5%)
      Lumbar spine disease109314.6%
      Fibromyalgia or SLE10934.4%
      RA or PA10937.2%
      Depression109324.3%
      Pre-op narcotic use109324.5%
      SD, standard deviation; BMI, body mass index; ASA-PS, American Society of Anesthesiologists Physical Status; PCL, posterior cruciate ligament; SLE, systemic lupus erythematosus; RA, rheumatoid arthritis; PA, psoriatic arthritis.
      a 2 cases missing status of PCL.

      Patient-Reported Outcome Measures

      Response rates for preoperative, 4-month, 1-year, and minimum 2-year PROMs were 88.2%, 69.9%, 63.6%, and 55.7%, respectively. The mean minimum 2-year follow-up for PROMs was 29.1 months (range = 20.5-85.0 months). The within-patient UCLA activity level (Fig. 1) significantly improved from preoperative baseline to 4-month follow-up (paired mean difference = 0.90, 95% confidence interval [CI] = 0.77-1.03, P < .001) and from 4-month to 1-year follow-up (paired mean difference = 0.33, 95% CI = 0.19-0.47, P < .001). However, there was not a statistically or clinically significant change in the mean UCLA activity level from 1-year to minimum 2-year follow-up (paired mean difference = 0.08, 95% CI = −0.07 to 0.23, P = .307).
      Figure thumbnail gr1
      Fig. 1Statistically and clinically meaningful paired group differences were detected in UCLA activity level, KSS pain with level walking, and KSS pain with climbing stairs from preoperative baseline to 4-month and 4-month to 1-year follow-up, but not between 1-year and minimum 2-year follow-up. Error bars represent the 95% confidence intervals. UCLA, University of California Los Angeles; KSS, Knee Society Score.
      Similarly, mean KSS pain while walking on a level surface (Fig. 1) showed statistically and clinically significant improvement from preoperative baseline to 4-month follow-up (mean difference of −4.3, 95% CI = −4.5 to −4.1, P < .001) and between 4-month and 1-year follow-up (paired mean difference of −0.41, 95% CI = −0.57 to −0.25, P < .001). Again, there was not a statistically or clinically significant change in pain with level walking between 1-year and minimum 2-year follow-up (paired mean difference = −0.10, 95% CI = −0.08 to 0.27, P = .266). Similar results were observed for mean KSS pain with stair climbing scores (Fig. 1), with significant and clinically meaningful improvement observed from preoperative baseline to 4-month follow-up (paired mean difference = −4.8, 95% CI = −5.1 to −4.6, P < .001) and 4-month to 1-year follow-up (paired mean difference = −0.82, 95% CI = −1.00 to −0.64, P < .001) and no such change between 1-year and minimum 2-year follow-up (paired mean difference = −0.08, 95% CI = −0.29 to 0.14, P = .474).
      There were significant improvements both statistically and clinically in mean KOOS JR scores (Fig. 2) from preoperative baseline to 4-month follow-up (paired mean difference = 26.7, 95% CI = 25.0-28.3, P < .001) and 4-month to 1-year follow-up (paired mean difference = 8.2, 95% CI = 7.0-9.5, P < .001). There was a statistically significant improvement between 1-year and minimum 2-year follow-up, but the mean change did not reach the defined MCID of 6.0 (paired mean difference of 2.9, 95% CI = 1.5-4.4 points, P < .001).
      Figure thumbnail gr2
      Fig. 2Statistically and clinically meaningful paired group differences were detected in KOOS JR total scores from preoperative baseline to 4-month and 4-month to 1-year follow-up, but the statistically significant difference between 1-year and minimum 2-year follow-up did not meet the threshold for the MCID. Error bars represent the 95% confidence intervals. KOOS JR, Knee Injury and Osteoarthritis Outcome Score; MCID, minimum clinically important difference.
      There was continual increase in the proportion of patients “very satisfied or satisfied” after TKA from 4-month to 1-year to minimum 2-year follow-up (Fig. 3). However, improvements between both periods were modest at approximately 3.5% (P ≥ .088). While the change in satisfaction between 4-month and 1-year follow-up may be considered noteworthy (P = .088) with “trending significance,” it was not a clinically significant change. Similarly, the change between 1-year and minimum 2-year follow-up was not statistically or clinically significant (estimated paired increase = 0.0%, 95% CI = −3.2% to 3.2%, P = 1.000). KSS ‘knee normal’ scores followed the same pattern as satisfaction scores with statistically significant improvements in the proportion of patients who reported their knee always feels normal from preoperative baseline to 4-month follow-up and between 4-month and 1-year follow-up intervals (Fig. 3, increase of 29.4% [95% CI = 25.9%-33.0%] and 17.5% [95% CI = 12.5%-22.4%], respectively, P < .001); however, the MCID was only reached in the upper limit of the 95% CI for the change between preoperative baseline to 4-month follow-up and not between 4-month to 1-year time points. Furthermore, there was a statistically significant increase between 1-year and minimum 2-year follow-up (P < .001), but the estimated proportional difference did not reach the established MCID of 33% (Fig. 3, estimated paired increase of 14.0%, 95% CI = 8.7%-19.3%).
      Figure thumbnail gr3
      Fig. 3Global satisfaction increased from 4-month to 1-year to minimum 2-year follow-up; however, increases were likely not clinically significant. Likewise, patients reporting their knee to “always” feel normal increased preoperatively to 4-month to 1-year to minimum 2-year follow-up, but did not reach the MCID beyond 1-year follow-up. MCID, minimum clinically important difference.
      As expected, a significantly higher proportion of patients achieved established MCIDs between preoperative to 4-month follow-up (≥90.4% met the MCID) than the proportion of patients meeting MCIDs between 4-month and 1-year and 1-year to minimum 2-year follow-up (P < .001). However, the proportion of patients which achieved the MCID at subsequent follow-up intervals diminished between 4-month and 1-year follow-up (≤52.6%) and further diminished between 1-year to minimum 2-year follow-up (≤39.8%). In addition, the proportions of patients meeting MCIDs from preoperative baseline to 1-year follow-up compared with proportions of patients meeting MCIDs from preoperative baseline to minimum 2-year follow-up were not different for the PROMs evaluated (P ≥ .581).

      Discussion

      This study investigated changes in PROMs following primary TKA between preoperative baseline, 4-month, 1-year, and minimum 2-year follow-up. Overall, we could not reject the null hypothesis of no significant changes in PROMs between 1-year and minimum 2-year follow-up, and in the two instances in which the null hypothesis could be rejected (KOOS JR and KSS knee normal scores), established MCIDs were not met. Significant improvements from preoperative baseline values to 4-month follow-up and from 4-month to 1-year follow-up were observed for all PROMs except global satisfaction. Thereafter, there were no significant changes defined by MCIDs after 1-year follow-up in UCLA activity level, KSS pain while walking on a level surface, KSS pain with stair climbing, KOOS JR scores, KSS ‘knee normal’ scores, or global satisfaction scores.
      These findings support the few studies which similarly found no difference in PROMs comparing those collected at 1-year and 2-year follow-up [
      • Samuelsson K.
      • Magnussen R.A.
      • Alentorn-Geli E.
      • Krupic F.
      • Spindler K.P.
      • Johansson C.
      • et al.
      Equivalent knee injury and osteoarthritis outcome scores 12 and 24 months after anterior cruciate ligament reconstruction: results from the Swedish national knee ligament register.
      ,
      • Ramkumar P.N.
      • Navarro S.M.
      • Haeberle H.S.
      • Ng M.
      • Piuzzi N.S.
      • Spindler K.P.
      No difference in outcomes 12 and 24 months after lower extremity total joint arthroplasty: a systematic review and meta-analysis.
      ,
      • Piuzzi N.S.
      Patient-reported outcomes at 1 and 2 Years after total hip and knee arthroplasty: what is the minimum required follow-up?.
      ]. A cohort study of 23,952 patients undergoing anterior cruciate ligament reconstruction found equivalent results at 1-year and 2-year follow-up for KOOS [
      • Samuelsson K.
      • Magnussen R.A.
      • Alentorn-Geli E.
      • Krupic F.
      • Spindler K.P.
      • Johansson C.
      • et al.
      Equivalent knee injury and osteoarthritis outcome scores 12 and 24 months after anterior cruciate ligament reconstruction: results from the Swedish national knee ligament register.
      ]. This study showed that knee outcome scores improved significantly within the first year after anterior cruciate ligament reconstruction, with no significant change or improvement observed between the 1-year to 2-year follow-up period. Another study by Mathijjsen et al [
      • Mathijssen N.M.C.
      • Verburg H.
      • London N.J.
      • Landsiedl M.
      • Dominkus M.
      Patient reported outcomes and implant survivorship after total knee arthroplasty with the persona knee implant system: two year follow up.
      ] studied PROMs after TKA at 6-week, 6-month, 1-year, and 2-year follow-up periods. The authors reported no significant changes in PROMs between 1-year and 2-year follow-up. Additionally, they showed minimal change in PROMs between 6-month and 1-year follow-up. A meta-analysis studying 1564 TKAs and 740 THAs showed no significant difference in four different PROMs between 1-year and 2-year follow-up [
      • Ramkumar P.N.
      • Navarro S.M.
      • Haeberle H.S.
      • Ng M.
      • Piuzzi N.S.
      • Spindler K.P.
      No difference in outcomes 12 and 24 months after lower extremity total joint arthroplasty: a systematic review and meta-analysis.
      ]. Several other studies comparing PROMs in TJA also note minimal changes between 6-month, 1-year, 2-year, and even 3-year follow-up periods [
      • Piuzzi N.S.
      Patient-reported outcomes at 1 and 2 Years after total hip and knee arthroplasty: what is the minimum required follow-up?.
      ,
      • Zeni Jr., J.A.
      • Snyder-Mackler L.
      Early postoperative measures predict 1- and 2-year outcomes after unilateral total knee arthroplasty: importance of contralateral limb strength.
      ,
      • Schotanus M.G.M.
      • Pilot P.
      • Vos R.
      • Kort N.P.
      No difference in joint awareness after mobile- and fixed-bearing total knee arthroplasty: 3-year follow-up of a randomized controlled trial.
      ,
      • Gauthier-Kwan O.Y.
      • Dobransky J.S.
      • Dervin G.F.
      Quality of recovery, postdischarge hospital utilization, and 2-year functional outcomes after an outpatient total knee arthroplasty program.
      ]. There is generally a significant improvement in PROMs during the first 3 to 6 months following TJA, but, as noted earlier, the necessity and value of collecting long-term PROMs remain uncertain [
      • Rosenlund S.
      • Broeng L.
      • Holsgaard-Larsen A.
      • Jensen C.
      • Overgaard S.
      Patient-reported outcome after total hip arthroplasty: comparison between lateral and posterior approach.
      ]. While these studies conclude minimal change was observed in PROMs between 1-year and 2-year follow-up after surgery, these studies did not specifically interpret their results in the setting of MCIDs which the current study took into consideration.
      The conventionally accepted criterion of minimum 2-year follow-up was established during the early evolution of knee systems in the 1980s and 1990s when implant survivorship hovered at approximately 80%-90% [
      • Ranawat C.S.
      • Boachie-Adjei O.
      Survivorship analysis and results of total condylar knee arthroplasty. Eight- to 11-year follow-up period.
      ,
      • Scuderi G.R.
      • Insall J.N.
      • Windsor R.E.
      • Moran M.C.
      Survivorship of cemented knee replacements.
      ,
      • Rand J.A.
      • Ilstrup D.M.
      Survivorship analysis of total knee arthroplasty. Cumulative rates of survival of 9200 total knee arthroplasties.
      ,
      • Rinonapoli E.
      • Mancini G.B.
      • Azzará A.
      • Aglietti P.
      • Santucci C.
      Survivorship of the total condylar I prosthesis: results of a series of 100 total knee arthroplasties.
      ,
      • Buechel Sr., F.F.
      • Buechel Jr., F.F.
      • Pappas M.J.
      • Dalessio J.
      Twenty-year evaluation of the New Jersey LCS rotating platform knee replacement.
      ]. For modern implants, 2-year follow-up is most likely not as relevant given the extremely low cumulative incidence of revision for primary TKAs of less than 2% (98% survivorship) [
      AAOS
      American Joint Replacement Registry (AJRR) Annual Report.
      ]. Consequently, a greater focus on patient outcomes is emphasized today. One systematic review identified 47 different PROMs used in evaluation of patient outcomes [
      • Ramkumar P.N.
      • Harris J.D.
      • Noble P.C.
      Patient-reported outcome measures after total knee arthroplasty: a systematic review.
      ]. The PROMs analyzed in our study are among some of the more common PROMs collected after TKA. One factor to consider when analyzing PROMs in this context is the ceiling effect. The ceiling effect refers to a clustering of participants' scores toward the upper limit of a scale, thereby limiting the instrument’s ability to detect change beyond a certain point. Ceiling effects have been shown for some of the PROMs analyzed in our study, such as KOOS JR at 1 year postoperatively [
      • Eckhard L.
      • Munir S.
      • Wood D.
      • Talbot S.
      • Brighton R.
      • Walter B.
      • et al.
      The ceiling effects of patient reported outcome measures for total knee arthroplasty.
      ]. This may further explain the insignificant changes noted in our study beyond 1-year postoperative follow-up. Another possible explanation to there being no significant change in PROMs beyond 1-year follow-up is that of the already aging population of patients who underwent TKA. These patients may be experiencing deterioration related to overall health and quality of life rather than knee-specific health evaluated in this study. Later complications of aseptic loosening could also contribute to lower PROMs at minimum 2-year follow-up although all patients included in the current study analysis were not revised at the time of any PROM collection.
      This study should be considered in the context of its limitations. First, the retrospective nature of this study comes with the potential for bias; however, all PROMs were prospectively collected. Next, the overall number of outcome measures evaluated is a limitation. This limitation is likely due to the single institution included in this study as we only collect a specific set of PROMs at our institution to limit the patient burden for collecting PROMs. Reducing the number of outcome measures evaluated helps balance the need for robust outcome collection with high data response rates while also limiting patient burden during clinic office visits. There are several other routinely collected and validated PROMs that have been reported in TKA literature that were not included in this study. Outcomes such as the Western Ontario and McMaster Universities Osteoarthritis index [
      • Bellamy N.
      • Buchanan W.W.
      • Goldsmith C.H.
      • Campbell J.
      • Stitt L.W.
      Validation study of Womac: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
      ] and Oxford Knee Score [
      • Dawson J.
      • Fitzpatrick R.
      • Murray D.
      • Carr A.
      Questionnaire on the perceptions of patients about total knee replacement.
      ] are two other commonly reported and validated TKA outcome measures. Inclusion of additional outcome measures would strengthen the conclusions being drawn from this study. Another limitation to this study was the use of only two implants by one surgeon at a single academic institution which could limit generalizability of these results. Furthermore, decreasing response rates for PROMs over time is another limitation. Although the study’s highest response rate of 88.2% preoperatively is excellent, and its lowest response rate of 55.7% at minimum 2-year follow-up approaches the minimum 60% response rate needed to evaluate THA patient outcomes [
      • Pronk Y.
      • van der Weegen W.
      • Vos R.
      • Brinkman J.-M.
      • van Heerwaarden R.J.
      • Pilot P.
      What is the minimum response rate on patient-reported outcome measures needed to adequately evaluate total hip arthroplasties?.
      ], the associated bias is most likely not significantly increased when compared with response rates achieving the 70%-80% range [
      Value in research: achieving validated outcome measurements while mitigating follow-up cost.
      ].
      Given patient burdens and health care costs associated with collecting long-term PROMs following total joint replacement, careful consideration is warranted to evaluate the utility of long-term PROM collection. The COVID-19 pandemic has added additional burden to patients and clinic staff for both routine follow-up and outcome data collection. Current study findings and similar findings from other studies [
      • Samuelsson K.
      • Magnussen R.A.
      • Alentorn-Geli E.
      • Krupic F.
      • Spindler K.P.
      • Johansson C.
      • et al.
      Equivalent knee injury and osteoarthritis outcome scores 12 and 24 months after anterior cruciate ligament reconstruction: results from the Swedish national knee ligament register.
      ,
      • Ramkumar P.N.
      • Navarro S.M.
      • Haeberle H.S.
      • Ng M.
      • Piuzzi N.S.
      • Spindler K.P.
      No difference in outcomes 12 and 24 months after lower extremity total joint arthroplasty: a systematic review and meta-analysis.
      ,
      • Piuzzi N.S.
      Patient-reported outcomes at 1 and 2 Years after total hip and knee arthroplasty: what is the minimum required follow-up?.
      ] suggest that the cost benefit ratio of long-term PROM data collection deserves increased investigation and consideration, especially in this epoch of value-driven health care. Understanding the limitations of current PROMs to detect patient-related sources of failure is also important to understanding the value of long-term PROM collection. To date, no PROM exists that is dedicated to identifying sources of failure such as instability, aseptic loosening, or late-onset prosthetic joint infection.
      While long-term follow-up after TKA remains important for implant survivorship, it appears that one-year PROMs are as clinically reliable and meaningful as two-year PROMs. Therefore, it is reasonable to question the currently accepted 2-year minimum follow-up requirement used in peer-reviewed research involving PROMs.

      Appendix A. Supplementary Data

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