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Evaluation of Total Knee Arthroplasty Performed With and Without Computer Navigation: A Bilateral Total Knee Arthroplasty Study
The Journal of Arthroplasty 28 (2013) 455–458
Contents lists available at SciVerse ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Evaluation of Total Knee Arthroplasty Performed With and Without Computer Navigation: A Bilateral Total Knee Arthroplasty Study Derek R. Johnson MD a, Douglas A. Dennis MD b, c, d, e, f, Kirk A. Kindsfater MD g, Raymond H. Kim MD b, c, f a
Denver-Vail Orthopedics, Parker, Colorado Colorado Joint Replacement, Denver, Colorado Department of Mechanical and Materials Engineering, University of Denver, Denver, Colorado d Department of Biomedical Engineering, University of Tennessee, Tennessee e University of Colorado School of Medicine, Colorado f Rocky Mountain Musculoskeletal Research Laboratory, Denver, Colorado g Orthopaedic Center of the Rockies, Fort Collins, Colorado b c
a r t i c l e
i n f o
Article history: Received 11 October 2011 Accepted 20 June 2012 Keywords: total knee arthroplasty computer navigation bilateral
a b s t r a c t Sequential bilateral total knee arthroplasty performed on 54 patients utilizing navigation (CAS-TKA) in one knee and traditional instrumentation (T-TKA) in the contralateral knee was reviewed at a mean follow-up duration of 2.5 years. There were no differences with regard to KSS, ROM, postoperative anatomic alignment, mechanical axis, or tibial angle. There was a statistically significant decrease in outliers for the CAS-TKA group with respect to anatomic alignment (3.7% vs. 17.0%, P=0.024), mechanical axis (6.1 vs. 20.4%, P=0.037) and tibial component alignment (0% vs. 7.5%, P=0.042). There is no apparent benefit of CAS-TKA with regards to KSS, ROM, or alignment in the hands of fellowship-trained total joint specialists. The clinical relevance of reduced outliers in the CAS-TKA group is unknown with the current follow-up interval. © 2013 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) is a highly successful procedure with excellent functional outcomes for people with advanced knee arthritis. Results of TKA have demonstrated a 93% to 97% survivorship at 11 years, with 88% to 96% of patients demonstrating good or excellent HSS Scores [1–3]. While excellent results are reported with TKA, patient characteristics, implant design features, surgical technique, and post-operative alignment can affect long-term survival. Post-operative malalignment has been implicated in decreased long-term survival of TKA [4–7]. Improper mechanical alignment has been shown to alter the load distribution on the tibial plateau [8] and lead to increased polyethylene wear in TKA. Despite the improvements in contemporary manual alignment systems over the years, malalignment greater than 3° occurs in up to 26% of TKAs regardless of surgeon experience [9–11]. Concern regarding the failure to achieve ideal alignment in more than one quarter of patients has led to an increase in interest in computer navigation with TKA [11–18]. Most studies have found a clear benefit to computer assisted surgery in decreasing the number of outliers from ideal alignment [11–18]. The overall tendency of these studies shows little difference in the mean limb alignment between those TKAs performed with and without computer navigation, but a The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2012.06.026. Reprint requests: Douglas A. Dennis, MD, Colorado Joint Replacement, 2535 S. Downing St, #100, Denver, CO 80210. 0883-5403/2803-0013$36.00/0 – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2012.06.026
decreased number of outliers in the computer navigation group. One recent study [19], however, did not show a difference in alignment or number of outliers in a series of patients undergoing bilateral TKA in which one knee was performed with computer assistance and one was performed with traditional instrumentation. Our study also compared the functional and radiographic results of a series of patients who underwent sequential bilateral TKA with the first knee performed with computer assistance (CAS-TKA) and the second knee performed with traditional instrumentation (T-TKA). Methods After obtaining IRB approval, 54 consecutive patients were prospectively enrolled undergoing sequential bilateral TKA between October 2004 and April 2009 into the study. All surgeries were carried out by the two senior authors (DAD and KK), both fellowship-trained surgeons in adult reconstruction. Both surgeons were experienced with use of computer navigation with each having performed greater than 150 CAS-TKA. All patients enrolled in the study were available at the time of most recent follow-up (minimum of two-year follow-up). There were no differences between knees with regard to preoperative alignment, range of motion, or knee society scores (KSS). A posterior stabilized rotating platform device (Sigma RP; Depuy, Warsaw, IN) was used in 38 patients, a posterior stabilized rotating platform high-flexion device (Sigma RP-F; Depuy, Warsaw, IN) was used in six patients, and a cruciate retaining rotating platform device
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D.R. Johnson et al. / The Journal of Arthroplasty 28 (2013) 455–458
knee. All surgeries were performed through a standard midline incision with a medial parapatellar arthrotomy. The limb was exsanguinated and tourniquet inflated prior to skin incision and the tourniquet was released prior to closure after the bone cement was fully cured. The computer assisted surgical navigation system (Ci Computer Navigation System; Depuy, Warsaw, IN) used had an optical tracking unit, which detected reflective tracking spheres. The femoral array was placed within the arthrotomy proximal to the distal femoral resection level, while the tibial array was placed through two small stab incisions distal to the arthrotomy. Exsanguination and tourniquet inflation on the T-TKA side were performed a minimum of 10 min after deflation of the tourniquet on the CAS-TKA limb after the anesthesiologist's approval to proceed. While exact operative times of each TKA were not recorded, use of computer navigation typically required an additional 15 min of operative time for both surgeons. Clinical and radiographic follow-up was performed at six weeks, three months, one year, and annually after one year. Clinical data were collected on a prospective basis by the senior authors who performed the surgeries. The evaluators were not blinded to the type of total knee performed. Radiographic evaluation was performed in a nonblinded fashion as well with the AP radiographs being 36-inch films including the femoral head, knee, and ankle (Fig. 1). Six patients in the study did not have 36-inch films available; therefore, we were unable to determine the mechanical axis for these patients. Lateral and skyline views were performed on 14 inch cassettes. Radiographic measurements were recorded according to the recommendation of the Knee Society [20]. Radiographic outliers for tibiofemoral angle were considered to have an angle≥8° or≤3°. Mechanical axis was considered to be an outlier if it was≥3° valgus or varus. Proximal tibial measurements were considered to be outliers if they had an angle≥93° or≤87°. With regards to distal femoral angle, patients were considered to be outliers if their measurement was≥8° or≤3°. After completion of data collection, statistical analysis was performed using Microsoft Excel 2007 (Microsoft Inc.; Redmond, WA). The mean and standard deviation for each data set were calculated and a two-tailed t-test was performed to determine differences between groups using a P-value of 0.05. Results There were 31 males and 23 females enrolled with an average age of 61.9 years. The average height was 67.8 inches and the average weight was 181.8 lb. The diagnosis in 53 patients was osteoarthritis, while one patient had a diagnosis of rheumatoid arthritis. There were 21 right knees and 33 left knees in the CAS-TKA group. The mean duration of follow-up was 2.50 years. Postoperative KSSs were similar between the T-TKA and CAS-TKA groups (Table 1). The T-TKA group had a postoperative KSS of 94.1 compared to a score of 96.3 in the CAS-TKA group (P=0.27). Postoperative range of motion was also similar between the two groups with a range of motion of 126.5° in the CAS-TAK group and a range of motion of 125.7 in the T-TKA group (P=0.4). There was no difference with regards to patient perception of knee function. Sixteen patients considered their CAS-TKA to function better and 12 patients considered their T-TKA to function better, while 26 patients considered both knees to have equal function.
Fig. 1. Thirty-six inch film including femoral head, knee, and ankle after bilateral total knee arthroplasty.
(Sigma RP; Depuy, Warsaw, IN) was used in 10 patients. In each patient the same implant was utilized in both knees. All patients had bilateral lower extremities prepped and draped prior to the procedure and the CAS-TKA was performed on the more symptomatic knee prior to starting the T-TKA in the less symptomatic
Table 1 Radiographic Results.
Mean Mean Mean Mean Mean
femoral–tibial angle distal femoral angle proximal tibial angle posterior tibial slope femoral component flexion
CAS
Traditional
P Value
5.6° 5.5° 89.9° 88.2° 0.7°
5.2° 5.3° 89.6° 88.1° 0.6°
0.115 0.555 0.303 0.843 0.781
D.R. Johnson et al. / The Journal of Arthroplasty 28 (2013) 455–458 Table 2 Clinical Results.
Knee Society Score Postoperative ROM
CAS
Traditional
P Value
96.3 126.5°
94.1 125.7°
0.27 0.4
Radiographic evaluation did not reveal a difference in mean tibiofemoral axis, mechanical axis, proximal tibial angle, or distal femoral angle (Table 2). The mean tibiofemoral axis for the CAS-TKA group was 5.6° compared to 5.2° in the T-TKA group (P=0.115). There was a mean mechanical axis of 0.2° varus in the CAS-TKA group and 0.1° varus in the T-TKA group (P=0.802). The mean proximal tibial angle was 89.9° in the CAS-TKA group compared to 89.6° in the T-TKA group (P=0.303). The mean distal femoral angle was 5.5° in the CASTKA group compared to 5.3° in the T-TKA group (P=0.555). There was also no difference between groups regarding posterior tibial slope or femoral component flexion. Posterior tibial slope was 88.2° and 88.1° in the CAS-TKA and T-TKA groups respectively (P=0.843). Femoral component flexion was 0.7° in the CAS-TKA group compared to 0.6° in the T-TKA group (P=0.781). While there was no difference between groups regarding mean radiographic measurements, there were significantly fewer outliers in the CAS-TKA group with regards to tibiofemoral angle, mechanical axis, and proximal tibial angle and there was a trend towards increase in outliers in the CAS-TKA group regarding the distal femoral angle. There were two (3.7%) outliers in the CAS-TKA group compared to nine (17.0%) outliers in the T-TKA group regarding tibiofemoral angle (P=0.024). The CAS-TKA group had three (6.1%) outliers with regards to mechanical axis, compared to ten (20.4%) in the T-TKA group (P= 0.037). There were zero outliers in the CAS-TKA group and three (7.5%) outliers in the T-TKA group regarding proximal tibial angle (P=0.042). With regards to distal femoral angle, there were eight (14.8%) outliers in the CAS-TKA group, compared to three (7.5%) outliers in the T-TKA group (P=0.238). There were two complications in the CAS-TKA group. One patient developed patellar crepitus which required arthroscopy debridement. Another patient suffered a medial epicondyle fracture while skiing and was managed non-operatively without further complication. There was one complication in the T-TKA group in a patient who developed an acute postoperative infection treated successfully with irrigation and debridement and polyethylene liner exchange. Discussion Obtaining accurate prosthetic alignment in TKA is necessary to prevent early implant failure. Several authors have implicated malalignment greater than 3° as a cause of early failure [4–6]. Many investigators have demonstrated CAS-TKA results in improved coronal alignment compared to T-TKA [11–17]. Previous reports have compared unilateral TKA in differing patients performed with or without computer navigation [11–17]. The current study evaluated CAS-TKA in comparison of T-TKA in patients undergoing sequential bilateral total knee arthroplasty at the same surgical setting. Using this model, each patient serves as their own control and the rehabilitation program is identical and simultaneous for each TKA and equally affected by potential systemic adverse medical events. While we feel our study provides valuable information, we do realize that it has several limitations. The study did not randomize which extremity was performed with CAS and CAS-TKA was always performed on the most symptomatic knee. CAS-TKA was also performed on the first knee, which may have provided information in planning for the T-TKA. We feel that our clinical decision to perform CAS-TKA on the first knee was necessary to decrease the total operative time; however, we realize that this may potentially introduce bias to the study.
457
Another potential weakness of the study was the lack of blinding of the radiographic review. While many studies evaluating CAS-TKA report on blinded radiographic review, it is difficult to perform a blinded review on this type of study due to the fact that the radiographic evidence of the pin tracts for the navigation arrays are often present for several years after surgery. We also failed to obtain full length alignment films on six patients, which decreased our power with regards to assessing the mechanical axis. Similar to previous studies [11–17] on computer navigation, our study found no difference in mean alignment between CAS-TKA and T-TKA, but found a significant decrease in outliers with the use of CASTKA. Anderson and colleagues [12] compared 116 patients who underwent CAS-TKA to 51 patients who underwent T-TKA and found no difference in mean alignment between groups. They did, however, note that 95% of patients in the CAS-TKA group had a mechanical alignment within 3° of neutral compared to 84% in the T-TKA group. A mechanical alignment within 2° of neutral was achieved in 71% of TTKA subjects and 88% of CAS-TKA subjects. No differences were noted in clinical outcome at six-month follow-up. A meta-analysis by Mason et al. [21] demonstrated similar findings. Their analysis of 29 studies comparing CAS-TKA with T-TKA found outliers ≥3° in only 9% of CASTKA, compared to 32% of T-TKA patients. While the majority of the studies available in the literature do not find a difference in mean alignment with regards to CAS-TKA, Weng et al. [18] studied 60 patients undergoing staged bilateral TKA and found a significant difference in both the mean mechanical axis (0.66° vs. 2.55°) and a decrease in the number of outliers greater than 3° (13% vs. 50%) in the CAS-TKA group. The majority of studies in the literature indicate improved accuracy with CAS-TKA; however, a recent study by Kim et al. [19] involving 320 knees found no difference in mean alignment or outliers. In their study of 160 patients undergoing staged bilateral TKA, found 13% of CAS-TKA patients to have a mechanical axis ≥3° from neutral, compared to 19% in the T-TKA group. This trend towards fewer outliers in the CAS-TKA group was not significant (P=0.708). Although the majority of the literature indicate improved accuracy and decreased outliers with CAS-TKA, no navigation studies demonstrate an improvement in clinical outcomes. There is literature, however, that shows increased rates of aseptic loosening and early failure in TKAs with malalignment. Jeffrey et al. [5] found a failure rate of 24% in patients with a mechanical axis ≥3 from neutral compared to a failure rate of only 3% in patients with a mechanical axis within 3° of neutral. Likewise, Ritter and associates [4] found a revision rate of 15% for knees aligned from 4° of anatomic valgus to any degree of varus compared to a revision rate of 1.5% for knees aligned knees from 5° to 8° of anatomic valgus in a review of 421 TKAs. Berend et al. [6] noted medial tibial bone collapse with tibial malalignment of more than 3.0° of varus. Wasielewski et al. [7] also found a significant correlation with increased wear and varus alignment in a study of 55 polyethylene retrievals. The data regarding increased failure with malalignment, coupled with data showing decreased outliers with CAS-TKA may lead one to assume CAS-TKA will lead to decreased failures. We, however, feel that our study, along with the available literature, fails to show a clinical benefit to CAS-TKA with current follow-up. Longer follow-up duration is necessary before implant survival with use of computer navigation can be determined.
References 1. Colizza WA, Insall JN, Scuderi GR. The posterior stabilized total knee prosthesis: assessment of polyethylene damage and osteolysis after a ten-year-minimum follow-up. J Bone Joint Surg Am 1995;77:1713. 2. Dennis DA, Clayton ML, O'Donnell S, et al. Posterior cruciate condylar total knee arthroplasty. average 11-year follow-up evaluation. Clin Orthop Rel Res 1992;281: 168.
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3. Ranawat CS, Luessenhop CP, Rodriguez JS. The press-fit condylar modular total knee system: four to six year results with a posterior-cruciate-substituting design. J Bone Joint Surg Am 1997;79:342. 4. Ritter MA, Farris PM, Keating EM, et al. Postoperative alignment of total knee replacement: its effect on survival. Clin Orthop 1994;299:153. 5. Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. J Bone Joint Surg (Br) 1991;73:709. 6. Berend ME, Ritter MA, Meding JB, et al. Tibial component failure mechanisms in total knee arthroplasty. Clin Orthop 2004;428:26. 7. Wasielewski RC, Galante JO, Leighty R, et al. Wear patterns on retrieved polyethylene inserts and their relationship to technical considerations during total knee arthroplasty. Clin Orthop Relat Res 1994;299:31. 8. Hsu H-P, Garg A, Walker PS, et al. Effect of knee component alignment on tibial load distribution with clinical correlation. Clin Orthop 2005;248:135. 9. Mahaluxmivala J, Bankes MJK, Nicolai P, et al. The effect of surgeon experience on component positioning in 673 PFC posterior cruciate-sacrificing total knee arthroplasties. J Arthroplasty 2001;16:635. 10. Petersen TL, Engh GA. Radiographic assessment of knee alignment after total knee arthroplasty. J Arthroplasty 1988;3:67. 11. Stulberg SD, Loan P, Sarin V. Computer-assisted navigation in total knee replacement: results of an initial experience in thirty-five patients. J Bone Joint Surg Am 2002;84(Suppl 2):90. 12. Anderson KC, Buehler KC, Markel DC. Computer-assisted navigation in total knee arthroplasty: comparison with conventional methods. J Arthroplasty 2005;20(7 Suppl 3):132.
13. Bathis H, Perlick L, Tingart M, et al. Alignment in total knee arthroplasty. A comparison of computer-assisted surgery with the conventional technique. J Bone Joint Surg Br 2004;86:682. 14. Decking R, Markmann Y, Fuchs J, et al. Leg axis after computer-navigated total knee arthroplasty: a prospective randomized trial comparing computer-navigated and manual implantation. J Arthroplasty 2005;20:282. 15. Haaker RG, Stockheim M, Kamp M, et al. Computer-assisted navigation increases precision of component placement in total knee arthroplasty. Clin Orthop 2005;433:152. 16. Kim SJ, MacDonald M, Hernandez J, et al. Computer assisted navigation in total knee arthroplasty: improved coronal alignment. J Arthroplasty 2005;20(7 Suppl 3):123. 17. Seon JK, Song EK. Navigation-assisted less invasive total knee arthroplasty compared with conventional total knee arthroplasty: a randomized prospective trial. J Arthroplasty 2006;21:777. 18. Weng Y, Hsu RW, Hsu W. Comparison of computer-assisted navigation and conventional instrumentation for bilateral total knee arthroplasty. J Arthroplasty 2009;24:668. 19. Kim YH, Kim JS, Choi Y, et al. Computer-assisted navigation does not improve the alignment and orientation of the components in total knee arthroplasty. J Bone Joint Surg 2009;91:14. 20. Insall JN, Dorr LD, Scott RD, et al. Rational of the Knee Society Clinical Rating System. Clin Orthop 1989;248:13. 21. Mason JB, Fehring TK, Estrok R, et al. Meta-analysis of alignment outcomes in computer-assisted total knee arthroplasty surgery. J Arthroplasty 2007;22: 1097.
Contents lists available at SciVerse ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Evaluation of Total Knee Arthroplasty Performed With and Without Computer Navigation: A Bilateral Total Knee Arthroplasty Study Derek R. Johnson MD a, Douglas A. Dennis MD b, c, d, e, f, Kirk A. Kindsfater MD g, Raymond H. Kim MD b, c, f a
Denver-Vail Orthopedics, Parker, Colorado Colorado Joint Replacement, Denver, Colorado Department of Mechanical and Materials Engineering, University of Denver, Denver, Colorado d Department of Biomedical Engineering, University of Tennessee, Tennessee e University of Colorado School of Medicine, Colorado f Rocky Mountain Musculoskeletal Research Laboratory, Denver, Colorado g Orthopaedic Center of the Rockies, Fort Collins, Colorado b c
a r t i c l e
i n f o
Article history: Received 11 October 2011 Accepted 20 June 2012 Keywords: total knee arthroplasty computer navigation bilateral
a b s t r a c t Sequential bilateral total knee arthroplasty performed on 54 patients utilizing navigation (CAS-TKA) in one knee and traditional instrumentation (T-TKA) in the contralateral knee was reviewed at a mean follow-up duration of 2.5 years. There were no differences with regard to KSS, ROM, postoperative anatomic alignment, mechanical axis, or tibial angle. There was a statistically significant decrease in outliers for the CAS-TKA group with respect to anatomic alignment (3.7% vs. 17.0%, P=0.024), mechanical axis (6.1 vs. 20.4%, P=0.037) and tibial component alignment (0% vs. 7.5%, P=0.042). There is no apparent benefit of CAS-TKA with regards to KSS, ROM, or alignment in the hands of fellowship-trained total joint specialists. The clinical relevance of reduced outliers in the CAS-TKA group is unknown with the current follow-up interval. © 2013 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) is a highly successful procedure with excellent functional outcomes for people with advanced knee arthritis. Results of TKA have demonstrated a 93% to 97% survivorship at 11 years, with 88% to 96% of patients demonstrating good or excellent HSS Scores [1–3]. While excellent results are reported with TKA, patient characteristics, implant design features, surgical technique, and post-operative alignment can affect long-term survival. Post-operative malalignment has been implicated in decreased long-term survival of TKA [4–7]. Improper mechanical alignment has been shown to alter the load distribution on the tibial plateau [8] and lead to increased polyethylene wear in TKA. Despite the improvements in contemporary manual alignment systems over the years, malalignment greater than 3° occurs in up to 26% of TKAs regardless of surgeon experience [9–11]. Concern regarding the failure to achieve ideal alignment in more than one quarter of patients has led to an increase in interest in computer navigation with TKA [11–18]. Most studies have found a clear benefit to computer assisted surgery in decreasing the number of outliers from ideal alignment [11–18]. The overall tendency of these studies shows little difference in the mean limb alignment between those TKAs performed with and without computer navigation, but a The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2012.06.026. Reprint requests: Douglas A. Dennis, MD, Colorado Joint Replacement, 2535 S. Downing St, #100, Denver, CO 80210. 0883-5403/2803-0013$36.00/0 – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2012.06.026
decreased number of outliers in the computer navigation group. One recent study [19], however, did not show a difference in alignment or number of outliers in a series of patients undergoing bilateral TKA in which one knee was performed with computer assistance and one was performed with traditional instrumentation. Our study also compared the functional and radiographic results of a series of patients who underwent sequential bilateral TKA with the first knee performed with computer assistance (CAS-TKA) and the second knee performed with traditional instrumentation (T-TKA). Methods After obtaining IRB approval, 54 consecutive patients were prospectively enrolled undergoing sequential bilateral TKA between October 2004 and April 2009 into the study. All surgeries were carried out by the two senior authors (DAD and KK), both fellowship-trained surgeons in adult reconstruction. Both surgeons were experienced with use of computer navigation with each having performed greater than 150 CAS-TKA. All patients enrolled in the study were available at the time of most recent follow-up (minimum of two-year follow-up). There were no differences between knees with regard to preoperative alignment, range of motion, or knee society scores (KSS). A posterior stabilized rotating platform device (Sigma RP; Depuy, Warsaw, IN) was used in 38 patients, a posterior stabilized rotating platform high-flexion device (Sigma RP-F; Depuy, Warsaw, IN) was used in six patients, and a cruciate retaining rotating platform device
456
D.R. Johnson et al. / The Journal of Arthroplasty 28 (2013) 455–458
knee. All surgeries were performed through a standard midline incision with a medial parapatellar arthrotomy. The limb was exsanguinated and tourniquet inflated prior to skin incision and the tourniquet was released prior to closure after the bone cement was fully cured. The computer assisted surgical navigation system (Ci Computer Navigation System; Depuy, Warsaw, IN) used had an optical tracking unit, which detected reflective tracking spheres. The femoral array was placed within the arthrotomy proximal to the distal femoral resection level, while the tibial array was placed through two small stab incisions distal to the arthrotomy. Exsanguination and tourniquet inflation on the T-TKA side were performed a minimum of 10 min after deflation of the tourniquet on the CAS-TKA limb after the anesthesiologist's approval to proceed. While exact operative times of each TKA were not recorded, use of computer navigation typically required an additional 15 min of operative time for both surgeons. Clinical and radiographic follow-up was performed at six weeks, three months, one year, and annually after one year. Clinical data were collected on a prospective basis by the senior authors who performed the surgeries. The evaluators were not blinded to the type of total knee performed. Radiographic evaluation was performed in a nonblinded fashion as well with the AP radiographs being 36-inch films including the femoral head, knee, and ankle (Fig. 1). Six patients in the study did not have 36-inch films available; therefore, we were unable to determine the mechanical axis for these patients. Lateral and skyline views were performed on 14 inch cassettes. Radiographic measurements were recorded according to the recommendation of the Knee Society [20]. Radiographic outliers for tibiofemoral angle were considered to have an angle≥8° or≤3°. Mechanical axis was considered to be an outlier if it was≥3° valgus or varus. Proximal tibial measurements were considered to be outliers if they had an angle≥93° or≤87°. With regards to distal femoral angle, patients were considered to be outliers if their measurement was≥8° or≤3°. After completion of data collection, statistical analysis was performed using Microsoft Excel 2007 (Microsoft Inc.; Redmond, WA). The mean and standard deviation for each data set were calculated and a two-tailed t-test was performed to determine differences between groups using a P-value of 0.05. Results There were 31 males and 23 females enrolled with an average age of 61.9 years. The average height was 67.8 inches and the average weight was 181.8 lb. The diagnosis in 53 patients was osteoarthritis, while one patient had a diagnosis of rheumatoid arthritis. There were 21 right knees and 33 left knees in the CAS-TKA group. The mean duration of follow-up was 2.50 years. Postoperative KSSs were similar between the T-TKA and CAS-TKA groups (Table 1). The T-TKA group had a postoperative KSS of 94.1 compared to a score of 96.3 in the CAS-TKA group (P=0.27). Postoperative range of motion was also similar between the two groups with a range of motion of 126.5° in the CAS-TAK group and a range of motion of 125.7 in the T-TKA group (P=0.4). There was no difference with regards to patient perception of knee function. Sixteen patients considered their CAS-TKA to function better and 12 patients considered their T-TKA to function better, while 26 patients considered both knees to have equal function.
Fig. 1. Thirty-six inch film including femoral head, knee, and ankle after bilateral total knee arthroplasty.
(Sigma RP; Depuy, Warsaw, IN) was used in 10 patients. In each patient the same implant was utilized in both knees. All patients had bilateral lower extremities prepped and draped prior to the procedure and the CAS-TKA was performed on the more symptomatic knee prior to starting the T-TKA in the less symptomatic
Table 1 Radiographic Results.
Mean Mean Mean Mean Mean
femoral–tibial angle distal femoral angle proximal tibial angle posterior tibial slope femoral component flexion
CAS
Traditional
P Value
5.6° 5.5° 89.9° 88.2° 0.7°
5.2° 5.3° 89.6° 88.1° 0.6°
0.115 0.555 0.303 0.843 0.781
D.R. Johnson et al. / The Journal of Arthroplasty 28 (2013) 455–458 Table 2 Clinical Results.
Knee Society Score Postoperative ROM
CAS
Traditional
P Value
96.3 126.5°
94.1 125.7°
0.27 0.4
Radiographic evaluation did not reveal a difference in mean tibiofemoral axis, mechanical axis, proximal tibial angle, or distal femoral angle (Table 2). The mean tibiofemoral axis for the CAS-TKA group was 5.6° compared to 5.2° in the T-TKA group (P=0.115). There was a mean mechanical axis of 0.2° varus in the CAS-TKA group and 0.1° varus in the T-TKA group (P=0.802). The mean proximal tibial angle was 89.9° in the CAS-TKA group compared to 89.6° in the T-TKA group (P=0.303). The mean distal femoral angle was 5.5° in the CASTKA group compared to 5.3° in the T-TKA group (P=0.555). There was also no difference between groups regarding posterior tibial slope or femoral component flexion. Posterior tibial slope was 88.2° and 88.1° in the CAS-TKA and T-TKA groups respectively (P=0.843). Femoral component flexion was 0.7° in the CAS-TKA group compared to 0.6° in the T-TKA group (P=0.781). While there was no difference between groups regarding mean radiographic measurements, there were significantly fewer outliers in the CAS-TKA group with regards to tibiofemoral angle, mechanical axis, and proximal tibial angle and there was a trend towards increase in outliers in the CAS-TKA group regarding the distal femoral angle. There were two (3.7%) outliers in the CAS-TKA group compared to nine (17.0%) outliers in the T-TKA group regarding tibiofemoral angle (P=0.024). The CAS-TKA group had three (6.1%) outliers with regards to mechanical axis, compared to ten (20.4%) in the T-TKA group (P= 0.037). There were zero outliers in the CAS-TKA group and three (7.5%) outliers in the T-TKA group regarding proximal tibial angle (P=0.042). With regards to distal femoral angle, there were eight (14.8%) outliers in the CAS-TKA group, compared to three (7.5%) outliers in the T-TKA group (P=0.238). There were two complications in the CAS-TKA group. One patient developed patellar crepitus which required arthroscopy debridement. Another patient suffered a medial epicondyle fracture while skiing and was managed non-operatively without further complication. There was one complication in the T-TKA group in a patient who developed an acute postoperative infection treated successfully with irrigation and debridement and polyethylene liner exchange. Discussion Obtaining accurate prosthetic alignment in TKA is necessary to prevent early implant failure. Several authors have implicated malalignment greater than 3° as a cause of early failure [4–6]. Many investigators have demonstrated CAS-TKA results in improved coronal alignment compared to T-TKA [11–17]. Previous reports have compared unilateral TKA in differing patients performed with or without computer navigation [11–17]. The current study evaluated CAS-TKA in comparison of T-TKA in patients undergoing sequential bilateral total knee arthroplasty at the same surgical setting. Using this model, each patient serves as their own control and the rehabilitation program is identical and simultaneous for each TKA and equally affected by potential systemic adverse medical events. While we feel our study provides valuable information, we do realize that it has several limitations. The study did not randomize which extremity was performed with CAS and CAS-TKA was always performed on the most symptomatic knee. CAS-TKA was also performed on the first knee, which may have provided information in planning for the T-TKA. We feel that our clinical decision to perform CAS-TKA on the first knee was necessary to decrease the total operative time; however, we realize that this may potentially introduce bias to the study.
457
Another potential weakness of the study was the lack of blinding of the radiographic review. While many studies evaluating CAS-TKA report on blinded radiographic review, it is difficult to perform a blinded review on this type of study due to the fact that the radiographic evidence of the pin tracts for the navigation arrays are often present for several years after surgery. We also failed to obtain full length alignment films on six patients, which decreased our power with regards to assessing the mechanical axis. Similar to previous studies [11–17] on computer navigation, our study found no difference in mean alignment between CAS-TKA and T-TKA, but found a significant decrease in outliers with the use of CASTKA. Anderson and colleagues [12] compared 116 patients who underwent CAS-TKA to 51 patients who underwent T-TKA and found no difference in mean alignment between groups. They did, however, note that 95% of patients in the CAS-TKA group had a mechanical alignment within 3° of neutral compared to 84% in the T-TKA group. A mechanical alignment within 2° of neutral was achieved in 71% of TTKA subjects and 88% of CAS-TKA subjects. No differences were noted in clinical outcome at six-month follow-up. A meta-analysis by Mason et al. [21] demonstrated similar findings. Their analysis of 29 studies comparing CAS-TKA with T-TKA found outliers ≥3° in only 9% of CASTKA, compared to 32% of T-TKA patients. While the majority of the studies available in the literature do not find a difference in mean alignment with regards to CAS-TKA, Weng et al. [18] studied 60 patients undergoing staged bilateral TKA and found a significant difference in both the mean mechanical axis (0.66° vs. 2.55°) and a decrease in the number of outliers greater than 3° (13% vs. 50%) in the CAS-TKA group. The majority of studies in the literature indicate improved accuracy with CAS-TKA; however, a recent study by Kim et al. [19] involving 320 knees found no difference in mean alignment or outliers. In their study of 160 patients undergoing staged bilateral TKA, found 13% of CAS-TKA patients to have a mechanical axis ≥3° from neutral, compared to 19% in the T-TKA group. This trend towards fewer outliers in the CAS-TKA group was not significant (P=0.708). Although the majority of the literature indicate improved accuracy and decreased outliers with CAS-TKA, no navigation studies demonstrate an improvement in clinical outcomes. There is literature, however, that shows increased rates of aseptic loosening and early failure in TKAs with malalignment. Jeffrey et al. [5] found a failure rate of 24% in patients with a mechanical axis ≥3 from neutral compared to a failure rate of only 3% in patients with a mechanical axis within 3° of neutral. Likewise, Ritter and associates [4] found a revision rate of 15% for knees aligned from 4° of anatomic valgus to any degree of varus compared to a revision rate of 1.5% for knees aligned knees from 5° to 8° of anatomic valgus in a review of 421 TKAs. Berend et al. [6] noted medial tibial bone collapse with tibial malalignment of more than 3.0° of varus. Wasielewski et al. [7] also found a significant correlation with increased wear and varus alignment in a study of 55 polyethylene retrievals. The data regarding increased failure with malalignment, coupled with data showing decreased outliers with CAS-TKA may lead one to assume CAS-TKA will lead to decreased failures. We, however, feel that our study, along with the available literature, fails to show a clinical benefit to CAS-TKA with current follow-up. Longer follow-up duration is necessary before implant survival with use of computer navigation can be determined.
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