The Journal of Arthroplasty xxx (2015) xxx–xxx
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Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty Jerry Yongqiang Chen, MBBS, MRCS (Edin), MMed (Ortho) , Pak Lin Chin, MBBS, FRCS (Edin), Darren Keng Jin Tay, MBBS, FRCS (Edin), Shi-Lu Chia, MBBS, FRCS (Edin), PhD, Ngai Nung Lo, MBBS, FRCS (Edin), FAMS, Seng Jin Yeo, MBBS, FRCS (Edin), FAMS Department of Orthopaedic Surgery, Singapore General Hospital, Singapore
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Article history: Received 31 December 2014 Accepted 6 April 2015 Available online xxxx Keywords: patient-specific instrumentation total knee arthroplasty functional outcome quality of life revision surgery
a b s t r a c t Patient-specific instrumentation (PSI) surgery may represent the next advancement in total knee arthroplasty (TKA). In 2011, 60 patients were prospectively recruited and divided into two groups based on the patient’s choice: (1) PSI surgery; and (2) conventional TKA. At two years after surgery, the Knee Society Function Score, Oxford Knee Score and SF-36 scores were comparable between the two groups. Although the Knee Society Knee Score (KSKS) was 9 ± 3 points better in the PSI group (P = 0.008), the two years improvement in KSKS was comparable between the two groups. None of the patients required revision surgery. These findings cannot justify the additional costs and waiting time incurred by the patients with PSI surgery in the practice of a high volume surgeon. © 2015 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) has proven to be an efficacious and cost-effective treatment modality for severe osteoarthritic knees. Restoration of the mechanical axis of the lower limb and optimal placement of the implants in TKA have proven to reduce the wear and early implant failure rate [1,2]. Perfecting the surgical technique for TKA is hence of paramount importance. More recently, the introduction of patient-specific instrumentation (PSI) surgery may represent the next promising advancement in surgical technique for TKA. This technology allows the ideal implants’ size and alignment to be determined preoperatively, as well as customization of the patient-specific knee cutting jigs with less violation of the intramedullary canal. The promises of PSI surgery are many, including shorter duration of surgery, reduced hospital cost from lesser instrumentation sets used and faster operating room turnover, lesser intraoperative blood loss, fewer outliers in terms of alignment and potentially better clinical outcomes. This wave of early enthusiasm for PSI surgery is followed by a more sober consideration of the inherent issues associated with this technology. In theory, PSI surgery improves efficiency by decreasing operative time, operating room turnover time, sterilization burden, material processing and storage costs. However, when the additional 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.2015.04.007. Reprint requests: Jerry Yongqiang Chen, MBBS, MRCS (Edin), MMed (Ortho), Department of Orthopaedic Surgery, Singapore General Hospital, Outram Road, Academia Building Level 4, Singapore 119228.
expenses incurred by patients for preoperative imaging and fabricating customized jigs are considered, PSI surgery simply transferred the costs from the hospital to the patients. Furthermore, recent meta-analyses have also shown that PSI surgery neither reduces the intraoperative blood loss nor lessens the proportion of outliers in terms of alignment [3–6]. Despite this, “optimized” implants sizing in PSI surgery may confer better clinical outcomes. There is a paucity of published literature on the clinical outcomes after PSI surgery [7–13]. Furthermore, these studies are also limited by their short follow-up periods. With the uncertainty of the effectiveness of PSI surgery in mind, more clinical trials are required. This prospective cohort study aims to compare the clinical outcomes of PSI surgery versus conventional TKA. The authors hypothesize that PSI surgery has better functional outcome and quality of life scores than conventional TKA at two years after surgery. Patients and Methods This study was approved by the hospital’s ethics committee (CIRB: 2011/517/D) and carried out in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. Every patient was given a patient information sheet detailing the conduct of this study and properly counseled before informed consent was provided by the patient. In 2011, 60 patients diagnosed with tricompartmental osteoarthritis of the knee and scheduled for a primary TKA at a tertiary hospital were offered PSI surgery or conventional TKA by an independent healthcare practitioner. The patients decided their choice of surgical technique. Patients with preoperative varus or valgus deformity of more than 11° or preoperative fixed flexion deformity were excluded from this study.
http://dx.doi.org/10.1016/j.arth.2015.04.007 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
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Patients who had undergone previous knee joint surgery or had contraindications to MRI scan were also excluded. Thirty patients underwent PSI surgery using the Zimmer Patient Specific Instruments system (Warsaw, Indiana, United States), based on restoring the mechanical alignment of the lower limb. Six weeks prior to surgery, each patient had an MRI scan of the lower limb from the hip to the ankle as per protocol. Anatomical points such as the center of femoral head, the center of distal femur, the center of proximal tibia and the center of ankle were identified and used to establish the mechanical axes of the femur and the tibia in both the coronal and the sagittal planes. The rotational alignment of the femur was determined using Whiteside line, while the rotational alignment of the tibia was decided from the geometric centers of both the medial and the lateral tibia plateau. The most appropriately sized implants were selected based on the measured dimensions of the knee. The operating surgeon reviewed all of the proposed bone resections as recommended by the manufacturer in three dimensions, without making any adjustment. Customized patient-specific cutting jigs were then manufactured based on the proposed bony resections. The other 30 patients underwent conventional TKA. The distal femur was prepared using an intramedullary rod with a 6° valgus resection cut [14] while the proximal tibia was prepared using an extramedullary jig placed perpendicular to the predicted postoperative mechanical axis of the tibia, which was the line drawn through the center of the talar dome to the center of the resection surface [15]. The medullary canal of the femur was entered 1 cm above the origin of the posterior cruciate ligament and medial to the true center of the intercondylar notch. A bone plug was used to block the femoral medullary cavity after the femoral cuts. Proximal and distal reference points were determined for the tibia extramedullary jig. Proximally, the extramedullary jig should be positioned on the medial one third of the tibia tuberosity. Distally, the sharp anterior crest of the tibia at the level of the malleoli functioned as an anatomical reference point that was independent of any foot or ankle deformity. A senior adult reconstruction surgeon (PLC), who is well-versed in both techniques and has done at least 300 TKAs per annum, performed all the procedures. To minimize performance bias, the authors ensured that the learning curve of PSI surgery was overcome by commencing recruitment of patients only after the mean duration of surgery of 10 consecutive PSI surgeries was similar to the mean duration of surgery of the first five surgeries of this same group of 10. All surgeries were performed using the standard medial parapatellar quadriceps splitting approach with patella subluxation under tourniquet control at 300 mmHg. The surgical aim was to achieve neutral coronal alignment with a 0° mechanical axis and femoral rotation aligned to the transepicondylar axis and checked using Whiteside’s line. All patients had implants from Zimmer Nexgen LPS system (Warsaw, Indiana, United States) and closure of wounds was performed using subcuticular ETHICON MONOCRYL 3-0 suture (Livingston, Scotland, United Kingdom). An independent operating room nurse recorded the duration of surgery for all patients. In accordance with the authors’ hospital standard TKA protocol for postoperative care, the patients underwent early physiotherapy with the aim of early mobilization. Postoperative radiographs were taken when the patients were able to weight bear fully. The authors previously reported a 21% more outliers for lower limb alignment (mechanical axis using hip-knee-ankle angle) in the PSI group compared to the conventional group (P = 0.045) Interestingly, most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group (P = 0.045). However, the proportion of outliers for implant placement was comparable between the two groups [16]. An independent physiotherapist, who was blinded to the surgical technique performed, assessed the patients preoperatively, at six months and two years after surgery. The active range of motion (ROM) of the operated knee, Knee Society Score (KSS), Oxford Knee Score (OKS) and SF-36 scores were recorded. The ROM was measured
using an analog transparent plastic goniometer on the lateral aspect of the leg, with the patients in supine position. For the two arms of the goniometer, the line formed between the greater trochanter and lateral epicondyle represented the reference line for the femur while the line formed between lateral condyle and lateral malleolus represented the reference line for the tibia. Measurements were recorded to the nearest degree (°). The functional outcome scores collected utilized the KSS [17] and OKS [18] as its knee-specific outcome measure. A 200-point scoring system developed by the Knee Society was used: 100 points for Knee Society Function Score (KSFS) and 100 points for Knee Society Knee Score (KSKS). The original OKS devised by Dawson et al used a questionnaire comprising of 12 items on daily activities, which the patient must answer without help from healthcare personnel. Each item was scored from 1 to 5, with 1 representing best outcome/least symptoms. Scores from each item were subsequently added to obtain the global score ranging from 12 to 60 with 12 being the best outcome. In this study, a score of ≤ 18 constitutes a good score while N 18 constitutes a poor score [19]. The quality of life of patients was assessed with the use of SF-36 (Medical Outcomes Trust, Hanover, New Hampshire, United States) [20], which consisted of eight subscales: physical functioning, physical role, bodily pain, general health, vitality, social functioning, emotional role and mental health. Summary scores were developed to aggregate the most highly correlated subscales and to simplify analyses without substantial loss of information. In this study, the medical outcome study (MOS) approach proposed by Ware et al [21] was used to derive two higher-order summary scores: Physical Component Score (PCS) and Mental Component Score (MCS). These two summary scores were found to account for between 80% and 85% of the reliable variance of the standard eight subscales. They have good validity in discriminating among clinically meaningful groups, as well as high internal consistency and test–retest reliability estimates when utilized in a general population [21,22]. Any incidence of postoperative infection or revision surgery during the two years follow-up was also recorded. In this study, superficial infection was defined as surgical site infection [23] while deep infection was defined as prosthetic joint infection based on the American Academy of Orthopaedic Surgeons guidelines [24]. Statistical analysis Power analysis was performed prior to the conduct of this study. At two years after surgery, to detect a difference of 10 points in KSKS from a baseline mean score of 80 with standard deviation of 13, a sample size of 56 patients (28 patients in each group) would be required to achieve a power of 0.80. This calculation was done for a two-sided test with a type I error of 0.05. Hence, this study was designed to include a total of 60 patients (30 patients in each group). Statistical analysis was carried out in consultation with the in-house biostatistician, using SPSS 19.0 (IBM, Armonk, New York, United States). Statistical significance was defined as a P value of ≤0.05. The Student’s unpaired t-test was used to compare the two groups for continuous variables including age, body mass index (BMI), duration of surgery, knee extension and flexion, KSFS, KSKS, OKS, PCS and MCS; while the Pearson chi-square test was used for the analysis of categorical variables such as gender and side of surgery. Results The flow diagram presented outlined this study (Fig. 1). Among the 309 patients assessed for eligibility, 249 of them were excluded: 69 patients met the exclusion criteria, 9 patients declined to participate in this study and 171 patients could not be recruited for predominantly logistical reasons (already registered under another ongoing study, nonavailability of the study surgeon, preoperative decision for a
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
J.Y. Chen et al. / The Journal of Arthroplasty xxx (2015) xxx–xxx
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Fig. 1. Flow diagram displaying the progress of all patients through each stage of the study.
different surgical technique such as computer navigation). One patient in the PSI group had his surgery canceled after the MRI scan as he developed pulmonary embolism two weeks prior to his surgery. Data from the other 59 patients who completed the study were analyzed. There was no difference in age, gender, body mass index and side of operated knee between the two groups (Table 1). None of the patients in the PSI group required intraoperative modification of the surgical plan. The predictability for the implants’ size was 100% and no time was wasted on re-cutting the femur or tibia. The duration of surgery was 58 ± 7 minutes for both groups (P = 0.754). There were no superficial or deep infections in either groups and none of the patients required revision surgery at two years after surgery. The preoperative knee extension and flexion, KSFS, KSKS, OKS and MCS were comparable between the two groups, while the preoperative PCS was significantly better by 7 ± 3 points in the PSI group (P = 0.017). At six months after surgery, there was no difference in the postoperative knee extension and flexion, KSKS, OKS and PCS. The KSFS and MCS were 11 ± 4 and 5 ± 2 points better in the PSI group respectively (P = 0.016 and P = 0.030 respectively). While the six months improvement in KSFS from preoperative score was comparable Table 1 Demographics.
Age (years) Body Mass Index (kg/m2) Gender (male:female) Side of Surgery (left:right)
PSI (n = 29)
Conventional (n = 30)
P Value
65 ± 8 29.4 ± 6.5 9:20 31%:69% 13:16 45%:55%
65 ± 8 28.7 ± 6.0 5:25 17%:83% 14:16 47%:53%
0.747 0.691 0.195 0.887
between the two groups, the six months improvement in MCS from preoperative score remained more by 7 ± 3 points in the PSI group (P = 0.015). At two years after surgery, there was no difference in the postoperative knee extension and flexion, KSFS, OKS, PCS and MCS. The KSKS was 9 ± 3 points better in the PSI group (P = 0.008). However, the two years improvement in KSKS from preoperative score was comparable between the two groups (Table 2). Discussion The main findings of this study include that the postoperative KSKS was significantly better in the PSI group compared to the conventional group at two years after surgery. However, there was no difference in postoperative KSFS, OKS, PCS and MCS contrary to the authors’ hypothesis. There are currently seven commercial manufacturers who offer PSI surgery: (1) Biomet Signature using preoperative MRI or CT scan; (2) ConforMIS iTotal using preoperative CT scan; (3) DePuy TruMatch using preoperative CT scan; (4) Medacta MyKnee using preoperative MRI or CT scan; (5) Smith & Nephew Visionaire using preoperative MRI and long leg radiographs; (6) Wright Medical Prophecy using preoperative MRI or CT scan; and (7) Zimmer Patient Specific Instruments using preoperative MRI scan. Each of these PSI systems in the market is based on one of the three basic alignment goals: (1) restoration of the mechanical axis; (2) restoration of the anatomical axis; and (3) restoration of the kinematic axis. Tilman et al compared MRI-based (Smith & Nephew Visionaire) and CT-based (DePuy TruMatch) PSI surgery with 30 patients each versus conventional TKA in a randomized controlled trial (RCT). At a mean of three months after surgery, they found no difference in Knee Society
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
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Table 2 Functional Outcome and Quality of Life. PSI (n = 29) Knee Extension (°) Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Knee Flexion (°) Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Knee Society Function Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Knee Society Knee Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Oxford Knee Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Physical Component Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Mental Component Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years
8 6 2 3 5
± ± ± ± ±
5 4 5 4 5
116 119 3 121 5
± ± ± ± ±
58 78 20 74 16
Conventional (n = 30)
P Value
9 4 5 1 8
± ± ± ± ±
8 4 8 4 8
0.575 0.221 0.092 0.100 0.069
21 13 32 15 23
119 114 −5 116 −3
± ± ± ± ±
13 14 18 13 16
0.564 0.187 0.098 0.204 0.115
± ± ± ± ±
18 18 21 22 23
54 67 13 73 19
± ± ± ± ±
14 11 15 14 19
0.336 0.016 0.269 0.859 0.816
44 89 45 90 46
± ± ± ± ±
18 10 18 9 19
37 83 46 81 44
± ± ± ± ±
16 12 19 13 15
0.172 0.071 0.862 0.008 0.465
33 18 15 18 15
± ± ± ± ±
10 4 8 7 10
36 19 17 18 18
± ± ± ± ±
7 4 8 3 7
0.258 0.260 0.829 0.772 0.607
39 50 11 48 9
± ± ± ± ±
12 9 10 10 11
32 49 17 48 16
± ± ± ± ±
10 8 12 8 9
0.017 0.597 0.064 0.963 0.056
50 59 9 57 7
± ± ± ± ±
9 7 8 9 8
52 54 2 57 5
± ± ± ± ±
11 9 10 13 12
0.560 0.030 0.015 0.936 0.569
Score (KSS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) between the three groups [7]. There are three other RCTs and one retrospective study evaluating the clinical outcomes of MRI-based PSI surgery versus conventional TKA. Vundelinckx et al prospectively followed up 31 patients who underwent MRI-based PSI surgery (Smith & Nephew Visionaire) for a mean of 200 days and found that the Knee injury and Osteoarthritis Outcome Score (KOOS) and Lysholm score were similar to conventional TKA [8]. The other three studies involved the Zimmer Patient Specific Instruments system, which was also used in this current study. Abdel et al prospectively reviewed 20 patients who underwent MRI-based PSI surgery for three months and reported that the KSS, KOOS, SF-12 and 3-D gait parameters were no difference to conventional TKA [9]. Pietsch et al prospectively evaluated 40 patients who underwent MRI-based PSI surgery and concluded that the KSS was comparable to conventional TKA at three months post surgery [10]. Yaffe et al retrospectively studied 42 patients who underwent MRI-based PSI surgery. At six months after surgery, the PSI group showed a larger improvement in KSFS compared to conventional TKA [11]. Two other studies in the literature studied the clinical outcomes of CT-based PSI surgery versus conventional TKA. Woolson et al followed up 22 patients who underwent CT-based PSI surgery (DePuy TruMatch) for six months and found that KSS was similar to conventional TKA in an RCT [12]. Anderl et al performed a prospectively cohort study on 114 patients who underwent CT-based PSI surgery (Medacta MyKnee) and received mobile-bearing implants. At two years after surgery, the
PSI group had a larger improvement in KSFS compared to conventional TKA. However, the KSKS, OKS and WOMAC were comparable between the two groups [13]. This study also showed a trend toward poorer knee extension in the PSI group. Interestingly, the study by Vundelinckx et al found that 43.3.% of the patients in the PSI group lacked full extension of the knee postoperatively, as compared to 19.4% of the patients in the conventional group [8]. In this study, the duration of surgery was similar between the PSI and conventional groups. This finding is in line with previous metaanalysis reporting no difference in the operative time between the two groups [3]. The proposed advantage of a shorter operative time with PSI surgery may be the result of the ability to customize patientspecific cutting jigs and determine optimal implants size preoperatively, thereby reducing the additional time required for trial implants testing intraoperatively. The authors postulate that trial and resizing of implants intraoperatively is relatively infrequent in the practice of a high volume surgeon; hence, the proposed advantage of a shorter operative time is not observed in this study. When considering the implementation of PSI surgery as an alternative to conventional TKA, it is worthwhile to consider its disadvantages as well. There will be additional costs incurred by the patients for the preoperative scan and fabricating the customized patient-specific cutting jigs, on top of an already significant hospitalization bill. This additional cost has been reported to be in the range of $520 to $1020. However, these numbers can increase to over $1800 [25,26]. As well, the time frame across different commercial manufacturers to deliver the patient-specific cutting jigs varies but has been found to be approximately 23 days [25]. At the hospital where this study is carried out, this additional 23 days is acceptable as caseloads are very high, and the average waiting time for TKA from listing for surgery to operation date is already eight weeks. At hospitals with lower caseloads, the waiting time for TKA will be much shorter, and PSI surgery may not be a viable alternative to conventional TKA. One of the strengths of this study is that it is an adequately powered, prospective trial with the aim of evaluating the clinical outcomes of PSI surgery. Despite the availability of PSI surgery in the market since 1998, there is no prospective study that reports the functional outcome and quality of life of patients at two years after PSI surgery in the current literature. This study represents the longest follow-up available reporting the clinical outcomes of PSI surgery. However, there are limitations to this study. Firstly, the patients in this study were not randomized. Nonetheless, the patients’ demographics were comparable between the PSI and conventional groups in this study. Secondly, this study assesses only a particular PSI design (Zimmer Patient Specific Instruments) but there are several other commercially available systems at the moment. Therefore, the findings of this study may not be applicable to the other systems, especially those based on the model to restore the kinematic axis of the lower limb. Thirdly, the active ROM of the operated knee was measured once at each time point of follow-up. Reliability testing of the measurement with Intraclass Correlation Coefficient (ICC) was not undertaken in this study.
Conclusion In summary, there were no differences in a range of outcomes, including the postoperative KSFS, OKS, PCS and MCS at two years after surgery. Although the two years postoperative KSKS was significantly better with PSI surgery compared to conventional TKA, the two years improvement in KSKS from preoperative score was comparable between the two surgical techniques. These findings, coupled with the lack of literature on the long-term survivorship of PSI surgery, cannot justify the additional costs and waiting time incurred by the patients. The authors cannot recommend the widespread use of this technology in
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
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the practice of a high volume surgeon until further critical appraisal of PSI surgery through larger scale prospective studies can prove otherwise. Acknowledgement The authors thank Hwei Chi Chong and Stephanie Fook-Chong for their technical support. References 1. Wasielewski RC, Galante JO, Leighty RM, et al. Wear patterns on retrieved polyethylene tibial inserts and their relationship to technical considerations during total knee arthroplasty. Clin Orthop Relat Res 1994;299:31. 2. Chin PL, Yang KY, Yeo SJ, et al. Randomized control trial comparing radiographic total knee arthroplasty implant placement using computer navigation versus conventional technique. J Arthroplasty 2005;20(5):618. 3. Voleti PB, Hamula MJ, Baldwin KD, et al. Current data do not support routine use of patient-specific instrumentation in total knee arthroplasty. J Arthroplasty 2014; 29(9):1709. 4. Sassoon A, Nam D, Nunley R, et al. Systematic review of patient-specific instrumentation in total knee arthroplasty: new but not improved. Clin Orthop Relat Res 2014. http://dx.doi.org/10.1007/s11999-014-3804-6. 5. Thienpont E, Schwab PE, Fennema P. A systematic review and meta-analysis of patient-specific instrumentation for improving alignment of the components in total knee replacement. Bone Joint J 2014;96-B(8):1052. 6. Cavaignac E, Pailhé R, Laumond G, et al. Evaluation of the accuracy of patient-specific cutting blocks for total knee arthroplasty: a meta-analysis. Int Orthop 2014. http://dx. doi.org/10.1007/s00264-014-2549-x. 7. Pfitzner T, Abdel MP, von Roth P, et al. Small improvements in mechanical axis alignment achieved with MRI versus CT-based patient-specific instruments in TKA: a randomized clinical trial. Clin Orthop Relat Res 2014;472(10):2913. 8. Vundelinckx BJ, Bruckers L, De Mulder K, et al. Functional and radiographic shortterm outcome evaluation of the Visionaire system, a patient-matched instrumentation system for total knee arthroplasty. J Arthroplasty 2013;28(6):964. 9. Abdel MP, Parratte S, Blanc G, et al. No benefit of patient-specific instrumentation in TKA on functional and gait outcomes: a randomized clinical trial. Clin Orthop Relat Res 2014;472(8):2468. 10. Pietsch M, Djahani O, Zweiger Ch, et al. Custom-fit minimally invasive total knee arthroplasty: effect on blood loss and early clinical outcomes. Knee Surg Sports Traumatol Arthrosc 2013;21(10):2234.
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11. Yaffe M, Luo M, Goyal N, et al. Clinical, functional, and radiographic outcomes following total knee arthroplasty with patient-specific instrumentation, computer-assisted surgery, and manual instrumentation: a short-term follow-up study. Int J Comput Assist Radiol Surg 2014;9(5):837. 12. Woolson ST, Harris AH, Wagner DW, et al. Component alignment during total knee arthroplasty with use of standard or custom instrumentation: a randomized clinical trial using computed tomography for postoperative alignment measurement. J Bone Joint Surg Am 2014;96(5):366. 13. Anderl W, Pauzenberger L, Kölblinger R, et al. Patient-specific instrumentation improved mechanical alignment, while early clinical outcome was comparable to conventional instrumentation in TKA. Knee Surg Sports Traumatol Arthrosc 2014 Oct 19. http://dx.doi.org/10.1007/s00167-014-3345-2. 14. Kharwadkar N, Kent RE, Sharara KH, et al. 5° to 6° of distal femoral cut for uncomplicated primary total knee arthroplasty: is it safe? Knee 2006;13(1):57. 15. Kawano T, Miura H, Nagamine R, et al. Alignment in total knee arthroplasty following failed high tibial osteotomy. J Knee Surg 2003;16:168. 16. Chen JY, Yeo SJ, Yew AK, et al. The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 2014;22(3):630. 17. Insall JN, Dorr LD, Scott RD, et al. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res 1989;248:13. 18. Dawson J, Fitzpatrick R, Murray D, et al. Questionnaire on the perceptions of patients about total knee replacement. J Bone Joint Surg Br 1998;80(1):63. 19. Jenny JY, Diesinger Y. The Oxford Knee Score: compared performance before and after knee replacement. Orthop Traumatol Surg Res 2012;98(4):409. 20. Ware JE, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 1992;30(6):473. 21. Ware JE, Kosinski M, Keller S. SF-36 physical and mental summary scales: a user’s manual. Boston, MA: Health Institute, New England Medical Center; 1994. 22. Ware JE, Kosinski M, Bayliss MS, et al. Comparison of methods for the scoring and statistical analysis of SF-36 health profile and summary measures: summary of results from the Medical Outcomes Study. Med Care 1995;33(4 Suppl):AS264. 23. Mangram AJ, Horan TC, Pearson ML, et al. Guideline for prevention of surgical site infection, 1999. Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol 1999;20(4):250. 24. Della Valle C, Parvizi J, Bauer TW, et al. American Academy of Orthopaedic Surgeons. American Academy of Orthopaedic Surgeons clinical practice guideline on: the diagnosis of periprosthetic joint infections of the hip and knee. J Bone Joint Surg Am 2011; 93(14):1355. 25. Thienpont E, Bellemans J, Delport H, et al. Patient-specific instruments: industry’s innovation with a surgeon’s interest. Knee Surg Sports Traumatol Arthrosc 2013; 21(10):2227. 26. Barrack RL, Ruh EL, Williams BM, et al. Patient specific cutting blocks are currently of no proven value. J Bone Joint Surg Br 2012;94(11 Suppl A):95.
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty Jerry Yongqiang Chen, MBBS, MRCS (Edin), MMed (Ortho) , Pak Lin Chin, MBBS, FRCS (Edin), Darren Keng Jin Tay, MBBS, FRCS (Edin), Shi-Lu Chia, MBBS, FRCS (Edin), PhD, Ngai Nung Lo, MBBS, FRCS (Edin), FAMS, Seng Jin Yeo, MBBS, FRCS (Edin), FAMS Department of Orthopaedic Surgery, Singapore General Hospital, Singapore
a r t i c l e
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Article history: Received 31 December 2014 Accepted 6 April 2015 Available online xxxx Keywords: patient-specific instrumentation total knee arthroplasty functional outcome quality of life revision surgery
a b s t r a c t Patient-specific instrumentation (PSI) surgery may represent the next advancement in total knee arthroplasty (TKA). In 2011, 60 patients were prospectively recruited and divided into two groups based on the patient’s choice: (1) PSI surgery; and (2) conventional TKA. At two years after surgery, the Knee Society Function Score, Oxford Knee Score and SF-36 scores were comparable between the two groups. Although the Knee Society Knee Score (KSKS) was 9 ± 3 points better in the PSI group (P = 0.008), the two years improvement in KSKS was comparable between the two groups. None of the patients required revision surgery. These findings cannot justify the additional costs and waiting time incurred by the patients with PSI surgery in the practice of a high volume surgeon. © 2015 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) has proven to be an efficacious and cost-effective treatment modality for severe osteoarthritic knees. Restoration of the mechanical axis of the lower limb and optimal placement of the implants in TKA have proven to reduce the wear and early implant failure rate [1,2]. Perfecting the surgical technique for TKA is hence of paramount importance. More recently, the introduction of patient-specific instrumentation (PSI) surgery may represent the next promising advancement in surgical technique for TKA. This technology allows the ideal implants’ size and alignment to be determined preoperatively, as well as customization of the patient-specific knee cutting jigs with less violation of the intramedullary canal. The promises of PSI surgery are many, including shorter duration of surgery, reduced hospital cost from lesser instrumentation sets used and faster operating room turnover, lesser intraoperative blood loss, fewer outliers in terms of alignment and potentially better clinical outcomes. This wave of early enthusiasm for PSI surgery is followed by a more sober consideration of the inherent issues associated with this technology. In theory, PSI surgery improves efficiency by decreasing operative time, operating room turnover time, sterilization burden, material processing and storage costs. However, when the additional 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.2015.04.007. Reprint requests: Jerry Yongqiang Chen, MBBS, MRCS (Edin), MMed (Ortho), Department of Orthopaedic Surgery, Singapore General Hospital, Outram Road, Academia Building Level 4, Singapore 119228.
expenses incurred by patients for preoperative imaging and fabricating customized jigs are considered, PSI surgery simply transferred the costs from the hospital to the patients. Furthermore, recent meta-analyses have also shown that PSI surgery neither reduces the intraoperative blood loss nor lessens the proportion of outliers in terms of alignment [3–6]. Despite this, “optimized” implants sizing in PSI surgery may confer better clinical outcomes. There is a paucity of published literature on the clinical outcomes after PSI surgery [7–13]. Furthermore, these studies are also limited by their short follow-up periods. With the uncertainty of the effectiveness of PSI surgery in mind, more clinical trials are required. This prospective cohort study aims to compare the clinical outcomes of PSI surgery versus conventional TKA. The authors hypothesize that PSI surgery has better functional outcome and quality of life scores than conventional TKA at two years after surgery. Patients and Methods This study was approved by the hospital’s ethics committee (CIRB: 2011/517/D) and carried out in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. Every patient was given a patient information sheet detailing the conduct of this study and properly counseled before informed consent was provided by the patient. In 2011, 60 patients diagnosed with tricompartmental osteoarthritis of the knee and scheduled for a primary TKA at a tertiary hospital were offered PSI surgery or conventional TKA by an independent healthcare practitioner. The patients decided their choice of surgical technique. Patients with preoperative varus or valgus deformity of more than 11° or preoperative fixed flexion deformity were excluded from this study.
http://dx.doi.org/10.1016/j.arth.2015.04.007 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
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Patients who had undergone previous knee joint surgery or had contraindications to MRI scan were also excluded. Thirty patients underwent PSI surgery using the Zimmer Patient Specific Instruments system (Warsaw, Indiana, United States), based on restoring the mechanical alignment of the lower limb. Six weeks prior to surgery, each patient had an MRI scan of the lower limb from the hip to the ankle as per protocol. Anatomical points such as the center of femoral head, the center of distal femur, the center of proximal tibia and the center of ankle were identified and used to establish the mechanical axes of the femur and the tibia in both the coronal and the sagittal planes. The rotational alignment of the femur was determined using Whiteside line, while the rotational alignment of the tibia was decided from the geometric centers of both the medial and the lateral tibia plateau. The most appropriately sized implants were selected based on the measured dimensions of the knee. The operating surgeon reviewed all of the proposed bone resections as recommended by the manufacturer in three dimensions, without making any adjustment. Customized patient-specific cutting jigs were then manufactured based on the proposed bony resections. The other 30 patients underwent conventional TKA. The distal femur was prepared using an intramedullary rod with a 6° valgus resection cut [14] while the proximal tibia was prepared using an extramedullary jig placed perpendicular to the predicted postoperative mechanical axis of the tibia, which was the line drawn through the center of the talar dome to the center of the resection surface [15]. The medullary canal of the femur was entered 1 cm above the origin of the posterior cruciate ligament and medial to the true center of the intercondylar notch. A bone plug was used to block the femoral medullary cavity after the femoral cuts. Proximal and distal reference points were determined for the tibia extramedullary jig. Proximally, the extramedullary jig should be positioned on the medial one third of the tibia tuberosity. Distally, the sharp anterior crest of the tibia at the level of the malleoli functioned as an anatomical reference point that was independent of any foot or ankle deformity. A senior adult reconstruction surgeon (PLC), who is well-versed in both techniques and has done at least 300 TKAs per annum, performed all the procedures. To minimize performance bias, the authors ensured that the learning curve of PSI surgery was overcome by commencing recruitment of patients only after the mean duration of surgery of 10 consecutive PSI surgeries was similar to the mean duration of surgery of the first five surgeries of this same group of 10. All surgeries were performed using the standard medial parapatellar quadriceps splitting approach with patella subluxation under tourniquet control at 300 mmHg. The surgical aim was to achieve neutral coronal alignment with a 0° mechanical axis and femoral rotation aligned to the transepicondylar axis and checked using Whiteside’s line. All patients had implants from Zimmer Nexgen LPS system (Warsaw, Indiana, United States) and closure of wounds was performed using subcuticular ETHICON MONOCRYL 3-0 suture (Livingston, Scotland, United Kingdom). An independent operating room nurse recorded the duration of surgery for all patients. In accordance with the authors’ hospital standard TKA protocol for postoperative care, the patients underwent early physiotherapy with the aim of early mobilization. Postoperative radiographs were taken when the patients were able to weight bear fully. The authors previously reported a 21% more outliers for lower limb alignment (mechanical axis using hip-knee-ankle angle) in the PSI group compared to the conventional group (P = 0.045) Interestingly, most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group (P = 0.045). However, the proportion of outliers for implant placement was comparable between the two groups [16]. An independent physiotherapist, who was blinded to the surgical technique performed, assessed the patients preoperatively, at six months and two years after surgery. The active range of motion (ROM) of the operated knee, Knee Society Score (KSS), Oxford Knee Score (OKS) and SF-36 scores were recorded. The ROM was measured
using an analog transparent plastic goniometer on the lateral aspect of the leg, with the patients in supine position. For the two arms of the goniometer, the line formed between the greater trochanter and lateral epicondyle represented the reference line for the femur while the line formed between lateral condyle and lateral malleolus represented the reference line for the tibia. Measurements were recorded to the nearest degree (°). The functional outcome scores collected utilized the KSS [17] and OKS [18] as its knee-specific outcome measure. A 200-point scoring system developed by the Knee Society was used: 100 points for Knee Society Function Score (KSFS) and 100 points for Knee Society Knee Score (KSKS). The original OKS devised by Dawson et al used a questionnaire comprising of 12 items on daily activities, which the patient must answer without help from healthcare personnel. Each item was scored from 1 to 5, with 1 representing best outcome/least symptoms. Scores from each item were subsequently added to obtain the global score ranging from 12 to 60 with 12 being the best outcome. In this study, a score of ≤ 18 constitutes a good score while N 18 constitutes a poor score [19]. The quality of life of patients was assessed with the use of SF-36 (Medical Outcomes Trust, Hanover, New Hampshire, United States) [20], which consisted of eight subscales: physical functioning, physical role, bodily pain, general health, vitality, social functioning, emotional role and mental health. Summary scores were developed to aggregate the most highly correlated subscales and to simplify analyses without substantial loss of information. In this study, the medical outcome study (MOS) approach proposed by Ware et al [21] was used to derive two higher-order summary scores: Physical Component Score (PCS) and Mental Component Score (MCS). These two summary scores were found to account for between 80% and 85% of the reliable variance of the standard eight subscales. They have good validity in discriminating among clinically meaningful groups, as well as high internal consistency and test–retest reliability estimates when utilized in a general population [21,22]. Any incidence of postoperative infection or revision surgery during the two years follow-up was also recorded. In this study, superficial infection was defined as surgical site infection [23] while deep infection was defined as prosthetic joint infection based on the American Academy of Orthopaedic Surgeons guidelines [24]. Statistical analysis Power analysis was performed prior to the conduct of this study. At two years after surgery, to detect a difference of 10 points in KSKS from a baseline mean score of 80 with standard deviation of 13, a sample size of 56 patients (28 patients in each group) would be required to achieve a power of 0.80. This calculation was done for a two-sided test with a type I error of 0.05. Hence, this study was designed to include a total of 60 patients (30 patients in each group). Statistical analysis was carried out in consultation with the in-house biostatistician, using SPSS 19.0 (IBM, Armonk, New York, United States). Statistical significance was defined as a P value of ≤0.05. The Student’s unpaired t-test was used to compare the two groups for continuous variables including age, body mass index (BMI), duration of surgery, knee extension and flexion, KSFS, KSKS, OKS, PCS and MCS; while the Pearson chi-square test was used for the analysis of categorical variables such as gender and side of surgery. Results The flow diagram presented outlined this study (Fig. 1). Among the 309 patients assessed for eligibility, 249 of them were excluded: 69 patients met the exclusion criteria, 9 patients declined to participate in this study and 171 patients could not be recruited for predominantly logistical reasons (already registered under another ongoing study, nonavailability of the study surgeon, preoperative decision for a
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
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Fig. 1. Flow diagram displaying the progress of all patients through each stage of the study.
different surgical technique such as computer navigation). One patient in the PSI group had his surgery canceled after the MRI scan as he developed pulmonary embolism two weeks prior to his surgery. Data from the other 59 patients who completed the study were analyzed. There was no difference in age, gender, body mass index and side of operated knee between the two groups (Table 1). None of the patients in the PSI group required intraoperative modification of the surgical plan. The predictability for the implants’ size was 100% and no time was wasted on re-cutting the femur or tibia. The duration of surgery was 58 ± 7 minutes for both groups (P = 0.754). There were no superficial or deep infections in either groups and none of the patients required revision surgery at two years after surgery. The preoperative knee extension and flexion, KSFS, KSKS, OKS and MCS were comparable between the two groups, while the preoperative PCS was significantly better by 7 ± 3 points in the PSI group (P = 0.017). At six months after surgery, there was no difference in the postoperative knee extension and flexion, KSKS, OKS and PCS. The KSFS and MCS were 11 ± 4 and 5 ± 2 points better in the PSI group respectively (P = 0.016 and P = 0.030 respectively). While the six months improvement in KSFS from preoperative score was comparable Table 1 Demographics.
Age (years) Body Mass Index (kg/m2) Gender (male:female) Side of Surgery (left:right)
PSI (n = 29)
Conventional (n = 30)
P Value
65 ± 8 29.4 ± 6.5 9:20 31%:69% 13:16 45%:55%
65 ± 8 28.7 ± 6.0 5:25 17%:83% 14:16 47%:53%
0.747 0.691 0.195 0.887
between the two groups, the six months improvement in MCS from preoperative score remained more by 7 ± 3 points in the PSI group (P = 0.015). At two years after surgery, there was no difference in the postoperative knee extension and flexion, KSFS, OKS, PCS and MCS. The KSKS was 9 ± 3 points better in the PSI group (P = 0.008). However, the two years improvement in KSKS from preoperative score was comparable between the two groups (Table 2). Discussion The main findings of this study include that the postoperative KSKS was significantly better in the PSI group compared to the conventional group at two years after surgery. However, there was no difference in postoperative KSFS, OKS, PCS and MCS contrary to the authors’ hypothesis. There are currently seven commercial manufacturers who offer PSI surgery: (1) Biomet Signature using preoperative MRI or CT scan; (2) ConforMIS iTotal using preoperative CT scan; (3) DePuy TruMatch using preoperative CT scan; (4) Medacta MyKnee using preoperative MRI or CT scan; (5) Smith & Nephew Visionaire using preoperative MRI and long leg radiographs; (6) Wright Medical Prophecy using preoperative MRI or CT scan; and (7) Zimmer Patient Specific Instruments using preoperative MRI scan. Each of these PSI systems in the market is based on one of the three basic alignment goals: (1) restoration of the mechanical axis; (2) restoration of the anatomical axis; and (3) restoration of the kinematic axis. Tilman et al compared MRI-based (Smith & Nephew Visionaire) and CT-based (DePuy TruMatch) PSI surgery with 30 patients each versus conventional TKA in a randomized controlled trial (RCT). At a mean of three months after surgery, they found no difference in Knee Society
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
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Table 2 Functional Outcome and Quality of Life. PSI (n = 29) Knee Extension (°) Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Knee Flexion (°) Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Knee Society Function Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Knee Society Knee Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Oxford Knee Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Physical Component Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years Mental Component Score Preoperative Six Months Improvement at Six Months Two Years Improvement at Two Years
8 6 2 3 5
± ± ± ± ±
5 4 5 4 5
116 119 3 121 5
± ± ± ± ±
58 78 20 74 16
Conventional (n = 30)
P Value
9 4 5 1 8
± ± ± ± ±
8 4 8 4 8
0.575 0.221 0.092 0.100 0.069
21 13 32 15 23
119 114 −5 116 −3
± ± ± ± ±
13 14 18 13 16
0.564 0.187 0.098 0.204 0.115
± ± ± ± ±
18 18 21 22 23
54 67 13 73 19
± ± ± ± ±
14 11 15 14 19
0.336 0.016 0.269 0.859 0.816
44 89 45 90 46
± ± ± ± ±
18 10 18 9 19
37 83 46 81 44
± ± ± ± ±
16 12 19 13 15
0.172 0.071 0.862 0.008 0.465
33 18 15 18 15
± ± ± ± ±
10 4 8 7 10
36 19 17 18 18
± ± ± ± ±
7 4 8 3 7
0.258 0.260 0.829 0.772 0.607
39 50 11 48 9
± ± ± ± ±
12 9 10 10 11
32 49 17 48 16
± ± ± ± ±
10 8 12 8 9
0.017 0.597 0.064 0.963 0.056
50 59 9 57 7
± ± ± ± ±
9 7 8 9 8
52 54 2 57 5
± ± ± ± ±
11 9 10 13 12
0.560 0.030 0.015 0.936 0.569
Score (KSS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) between the three groups [7]. There are three other RCTs and one retrospective study evaluating the clinical outcomes of MRI-based PSI surgery versus conventional TKA. Vundelinckx et al prospectively followed up 31 patients who underwent MRI-based PSI surgery (Smith & Nephew Visionaire) for a mean of 200 days and found that the Knee injury and Osteoarthritis Outcome Score (KOOS) and Lysholm score were similar to conventional TKA [8]. The other three studies involved the Zimmer Patient Specific Instruments system, which was also used in this current study. Abdel et al prospectively reviewed 20 patients who underwent MRI-based PSI surgery for three months and reported that the KSS, KOOS, SF-12 and 3-D gait parameters were no difference to conventional TKA [9]. Pietsch et al prospectively evaluated 40 patients who underwent MRI-based PSI surgery and concluded that the KSS was comparable to conventional TKA at three months post surgery [10]. Yaffe et al retrospectively studied 42 patients who underwent MRI-based PSI surgery. At six months after surgery, the PSI group showed a larger improvement in KSFS compared to conventional TKA [11]. Two other studies in the literature studied the clinical outcomes of CT-based PSI surgery versus conventional TKA. Woolson et al followed up 22 patients who underwent CT-based PSI surgery (DePuy TruMatch) for six months and found that KSS was similar to conventional TKA in an RCT [12]. Anderl et al performed a prospectively cohort study on 114 patients who underwent CT-based PSI surgery (Medacta MyKnee) and received mobile-bearing implants. At two years after surgery, the
PSI group had a larger improvement in KSFS compared to conventional TKA. However, the KSKS, OKS and WOMAC were comparable between the two groups [13]. This study also showed a trend toward poorer knee extension in the PSI group. Interestingly, the study by Vundelinckx et al found that 43.3.% of the patients in the PSI group lacked full extension of the knee postoperatively, as compared to 19.4% of the patients in the conventional group [8]. In this study, the duration of surgery was similar between the PSI and conventional groups. This finding is in line with previous metaanalysis reporting no difference in the operative time between the two groups [3]. The proposed advantage of a shorter operative time with PSI surgery may be the result of the ability to customize patientspecific cutting jigs and determine optimal implants size preoperatively, thereby reducing the additional time required for trial implants testing intraoperatively. The authors postulate that trial and resizing of implants intraoperatively is relatively infrequent in the practice of a high volume surgeon; hence, the proposed advantage of a shorter operative time is not observed in this study. When considering the implementation of PSI surgery as an alternative to conventional TKA, it is worthwhile to consider its disadvantages as well. There will be additional costs incurred by the patients for the preoperative scan and fabricating the customized patient-specific cutting jigs, on top of an already significant hospitalization bill. This additional cost has been reported to be in the range of $520 to $1020. However, these numbers can increase to over $1800 [25,26]. As well, the time frame across different commercial manufacturers to deliver the patient-specific cutting jigs varies but has been found to be approximately 23 days [25]. At the hospital where this study is carried out, this additional 23 days is acceptable as caseloads are very high, and the average waiting time for TKA from listing for surgery to operation date is already eight weeks. At hospitals with lower caseloads, the waiting time for TKA will be much shorter, and PSI surgery may not be a viable alternative to conventional TKA. One of the strengths of this study is that it is an adequately powered, prospective trial with the aim of evaluating the clinical outcomes of PSI surgery. Despite the availability of PSI surgery in the market since 1998, there is no prospective study that reports the functional outcome and quality of life of patients at two years after PSI surgery in the current literature. This study represents the longest follow-up available reporting the clinical outcomes of PSI surgery. However, there are limitations to this study. Firstly, the patients in this study were not randomized. Nonetheless, the patients’ demographics were comparable between the PSI and conventional groups in this study. Secondly, this study assesses only a particular PSI design (Zimmer Patient Specific Instruments) but there are several other commercially available systems at the moment. Therefore, the findings of this study may not be applicable to the other systems, especially those based on the model to restore the kinematic axis of the lower limb. Thirdly, the active ROM of the operated knee was measured once at each time point of follow-up. Reliability testing of the measurement with Intraclass Correlation Coefficient (ICC) was not undertaken in this study.
Conclusion In summary, there were no differences in a range of outcomes, including the postoperative KSFS, OKS, PCS and MCS at two years after surgery. Although the two years postoperative KSKS was significantly better with PSI surgery compared to conventional TKA, the two years improvement in KSKS from preoperative score was comparable between the two surgical techniques. These findings, coupled with the lack of literature on the long-term survivorship of PSI surgery, cannot justify the additional costs and waiting time incurred by the patients. The authors cannot recommend the widespread use of this technology in
Please cite this article as: Chen JY, et al, Functional Outcome and Quality of Life after Patient-Specific Instrumentation in Total Knee Arthroplasty, J Arthroplasty (2015), http://dx.doi.org/10.1016/j.arth.2015.04.007
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the practice of a high volume surgeon until further critical appraisal of PSI surgery through larger scale prospective studies can prove otherwise. Acknowledgement The authors thank Hwei Chi Chong and Stephanie Fook-Chong for their technical support. References 1. Wasielewski RC, Galante JO, Leighty RM, et al. Wear patterns on retrieved polyethylene tibial inserts and their relationship to technical considerations during total knee arthroplasty. Clin Orthop Relat Res 1994;299:31. 2. Chin PL, Yang KY, Yeo SJ, et al. Randomized control trial comparing radiographic total knee arthroplasty implant placement using computer navigation versus conventional technique. J Arthroplasty 2005;20(5):618. 3. Voleti PB, Hamula MJ, Baldwin KD, et al. Current data do not support routine use of patient-specific instrumentation in total knee arthroplasty. J Arthroplasty 2014; 29(9):1709. 4. Sassoon A, Nam D, Nunley R, et al. Systematic review of patient-specific instrumentation in total knee arthroplasty: new but not improved. Clin Orthop Relat Res 2014. http://dx.doi.org/10.1007/s11999-014-3804-6. 5. Thienpont E, Schwab PE, Fennema P. A systematic review and meta-analysis of patient-specific instrumentation for improving alignment of the components in total knee replacement. Bone Joint J 2014;96-B(8):1052. 6. Cavaignac E, Pailhé R, Laumond G, et al. Evaluation of the accuracy of patient-specific cutting blocks for total knee arthroplasty: a meta-analysis. Int Orthop 2014. http://dx. doi.org/10.1007/s00264-014-2549-x. 7. Pfitzner T, Abdel MP, von Roth P, et al. Small improvements in mechanical axis alignment achieved with MRI versus CT-based patient-specific instruments in TKA: a randomized clinical trial. Clin Orthop Relat Res 2014;472(10):2913. 8. Vundelinckx BJ, Bruckers L, De Mulder K, et al. Functional and radiographic shortterm outcome evaluation of the Visionaire system, a patient-matched instrumentation system for total knee arthroplasty. J Arthroplasty 2013;28(6):964. 9. Abdel MP, Parratte S, Blanc G, et al. No benefit of patient-specific instrumentation in TKA on functional and gait outcomes: a randomized clinical trial. Clin Orthop Relat Res 2014;472(8):2468. 10. Pietsch M, Djahani O, Zweiger Ch, et al. Custom-fit minimally invasive total knee arthroplasty: effect on blood loss and early clinical outcomes. Knee Surg Sports Traumatol Arthrosc 2013;21(10):2234.
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