Journal of Orthopaedic Surgery 2015;23(1):100-6
Review Article: Patient-specific versus standard instrumentation for total knee arthroplasty Behnam Sharareh, Ran Schwarzkopf
Department Of Orthopaedic Surgery, University of California Irvine, California, USA
ABSTRACT This meta-analysis reviewed 12 studies comparing patient-specific instrumentation (PSI) with standard instrumentation (SI) for total knee arthroplasty in terms of postoperative coronal alignment and operation time. There is no significant difference between PSI and SI in terms of hip-knee-ankle angle (overall coronal alignment or mechanical axis), tibial coronal alignment, and operation time. Key words: arthroplasty, instrumentation
replacement,
knee;
INTRODUCTION In the United States, more than 600 000 total knee arthroplasties (TKAs) are performed yearly.1 By 2030, it is expected to exceed 3.48 million.2 Patient dissatisfaction following TKA is 14% to 19%,3,4 which is higher than that following total hip arthroplasty,
owing to the complexity of the knee joint and the difficulty in retaining the knee anatomy.1 Patientspecific instrumentation (PSI) facilitates patientspecific cutting guides by creating a 3-dimensional model of the knee preoperatively, using computed tomography (CT) or magnetic resonance imaging (MRI) and a full-leg anteroposterior radiograph.5,6 A custom-fit cutting guide takes into account any subtle deformities or osteophytes and enables preoperative planning for bone resection, using the pre-determined implant size, position, and rotation.6 Conventional intramedullary or extramedullary cutting guides to gauge appropriate implant positioning are thus not needed. The patient-specific femoral guides are used to determine the valgus angle, level of resection, alignment, rotation, and size of the femoral component, whereas the patient-specific tibial guides are used to determine tibial alignment, level of resection, and tibial slope and rotation.6 The benefits of PSI include shortened operative time and improved mechanical alignment; this leads to improved implant longevity and clinical outcomes.6,7 This study reviewed 12 studies that compared PSI with standard instrumentation (SI) for TKA in terms
Address correspondence and reprint requests to: Ran Schwarzkopf, Department of Orthopaedic Surgery, University of California Irvine, 101 The City Drive South, Pavilion III, Building 29A, Orange, California, 92868, USA. Email:
[email protected] Vol. 23 No. 1, April 2015
Patient-specific versus standard instrumentation for TKA 101
of coronal alignment and operation time.
for analysis when heterogeneity was present between the PSI and SI groups, whereas the random effects model was used for analysis when there was no heterogeneity. Of the 12 studies, 6 used the Signature Personalized Patient Care system (Biomet, Warsaw [IN], USA), 3 used the VISIONAIRE system (Smith & Nephew, Memphis [TN], USA), one used the Patient Specific Instruments system (Zimmer, Warsaw [IN], USA), one used the TRUMATCH system (DePuy Synthes, Warsaw [IN], USA), and one used all of these 4 systems in 4 sub-groups (Table 1). Seven studies reported the mean postoperative HKA angle with standard deviation (Table 2). The optimal HKA angle is 180º (the neutral angle). The mean deviation from optimal alignment was greater in the PSI arm in 5 studies, greater in the SI arm in one study, and equal in both arms in one study. The test for overall effect size had a Z-score of 2.36 (p=0.02). Regarding heterogeneity, Χ2 was 12.35 (p=0.05). 10 studies reported outliers for postoperative HKA angle. The percentage of outliers was 17.8% in
META-ANALYSIS The PUBMED, EMBASE, and Cochrane Library were searched using the key words ‘patient specific instrumentation knee’, ‘patient matched instrumentation knee’, and ‘patient specific guides knee’. 12 studies that compared PSI with SI for TKA were reviewed (Table 1).8–19 Studies that involved gender-specific guides, unicompartmental knee arthroplasty, or cadaveric/animal studies were excluded, as were studies that only reported outcomes of PSI without comparison to SI, owing to the between-surgeon variability. The mean deviation from optimal alignment in terms of hip-knee-ankle (HKA) angle (also known as the mechanical axis or the overall coronal alignment), femoral coronal alignment (FCA), tibial coronal alignment (TCA), and operation time was recorded; an outlier was defined as a deviation of >3º (Fig.). The fixed model was used
Table 1 Meta-analysis of 12 studies comparing patient-specific instrumentation (PSI) with standard instrumentation (SI) for total knee arthroplasty (TKA) Study
Study type
PSI device
Barrack et al.8
Retrospective
Signature (Biomet)
100
100
Boonen et al.9
Retrospective
Signature (Biomet)
38
35
Daniilidis and Tibesku10 Nunley et al.11
Retrospective
VISIONAIRE (Smith & Nephew) Signature (Biomet)
150
156
50
50
Signature (Biomet)
42
48
All 4 systems
61
64
VISIONAIRE (Smith & Nephew) VISONAIRE (Smith & Nephew)
31
31
39
50
PSI (Zimmer)
40
40
TRUMATCH (DePuy) Signature (Biomet)
26
26
Nunley et al.18
Prospective randomised Retrospective
57
57
Ng et al.19
Retrospective
Signature (Biomet)
105
55
Roh et al.12 Victor et al.
13
Vundelinckx et al.14 Barke et al.15
Retrospective Prospective randomised Prospective randomised Prospective randomised Retrospective
Chareancholvanich Prospective randomised et al.16 Hamilton et al.17
No. of No. of TKAs TKAs using using PSI SI
Results
No significant differences between PSI and SI with respect to component alignment accuracy Improved coronal alignment accuracy and shortened operation time using PSI PSI was superior to SI in terms of fewer outliers in hipknee-ankle angle (9.3% vs. 21.2%) PSI and SI had similar numbers of outliers with respect to hip-knee-ankle angle No significant differences between PSI and SI with respect to component alignment accuracy No significant differences between PSI and SI with respect to component alignment accuracy No significant differences between PSI and SI with respect to functional, clinical, and radiographic outcomes No significant difference between PSI and SI with respect to tibial and femoral component alignment or operation time. SI achieved a hip-knee-ankle angle closer to neutral No significant difference between PSI and SI with respect to hip-knee-ankle angle. Improved accuracy of tibial component alignment and shortened operation time using PSI No significant difference between PSI and SI with respect to operation time No significant difference between PSI and SI with respect to hip-knee-ankle angle and operation time Significant reduction in number of hip-knee-ankle angle outliers using PSI
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102 Sharareh and Schwarzkopf
8.2% in the PSI arms and 7.5% in the SI arms. The test for overall effect size had a Z-value of 0.30 (p=0.77). Regarding heterogeneity, Χ2 was 7.55 (p=0.11). Three studies reported the FCA with standard deviation (Table 4). The optimal FCA is 90º. The mean deviation from optimal alignment was greater in the SI arm in 2 studies and greater in the PSI arm in one study. The test for overall effect size had a Z-score of 2.44 (p=0.01). Regarding heterogeneity, Χ2 was 15.17 (p=0.0005). Five studies reported outliers for postoperative FCA. The percentage of outliers was 5.8% in the PSI arms and 14.2% in the SI arms. The test for overall effect size had a Z-value of 2.82 (p=0.005). Regarding heterogeneity, Χ2 was 11.14 (p=0.02). Five studies reported the operation time with standard deviation (Table 5). The mean operation time was 65.5 minutes in the PSI arms and 67.7 minutes in the SI arms. Four of the 5 studies reported shorter operation time using PSI. The test for overall effect size had a Z-value of 1.23 (p=0.22). Regarding heterogeneity, Χ2 was 19.04 (p=0.0008). Meta-analysis of the 12 articles found no significant difference between PSI and SI except for the FCA favouring PSI. DISCUSSION
Figure The hip-knee-ankle angle, alignment, and tibial coronal alignment.
femoral
coronal
the PSI arms and 21.6% in the SI arms. The overall effect size had a Z-score of 1.58 (p=0.11). Regarding heterogeneity, Χ2 was 17.27 (p=0.04). Five studies reported the mean postoperative TCA with standard deviation (Table 3). The optimal TCA is 90º. The mean deviation from optimal alignment was greater in the SI arm in 3 studies, greater in the PSI arm in one study, and equal in both arms in one study. The test for overall effect size had a Z-score of 1.38 (p=0.17). Regarding heterogeneity, Χ2 was 4.55 (p=0.34). Five studies reported outliers for postoperative TCA. The percentage of outliers was
Neutral coronal alignment is essential for long-term TKA success; poor alignment is a risk factor for implant failure.7,10,19–23 The most important risk factors reported for medial bone collapse (secondary to tibial component failure) were tibial varus alignment of >3º, BMI of >33 kg/m2, and an overall varus mechanical alignment (HKA angle).21 The failure rate increases 4.6 fold for each degree of mechanical varus, and increases to 69 fold for all >3º outliers.22 Postoperative complications such as polyethylene wear, eccentric loading, and implant loosening can be avoided if postoperative alignment is within 3º of the neutral mechanical axis.24,25 In a study using computer navigation to evaluate the accuracy of PSI, 79.3% of the patients achieved postoperative coronal alignment within 3º of optimal alignment.26 PSI is inferior to computer navigation in terms of percentage of patients with accurate HKA angle (70.7% vs. 92.7%), tibial component alignment (87.8% vs. 100%), and femoral component alignment (90.2% vs. 100%).27 PSI is on par with SI. The number of surgical trays, surgical steps, and the intra-operative surgeon-directed changes all affect the operation time. Preparation using PSI could potentially reduce as many as 21 steps during TKA.6 To determine the cost effectiveness of PSI, the
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Patient-specific versus standard instrumentation for TKA 103
Table 2 Postoperative hip-knee-ankle angle for patient-specfic instrumentation (PSI) and standard instrumentation (SI) arms: (a) deviation from optimal alignment (180º), and (b) the number of outliers (>3º from optimal alignment) (a) Study
Barrack et al. Boonen et al.9 Daniilidis and Tibesku10 Nunley et al.11 Roh et al.12 Victor et al.13 Vundelinckx et al.14 8
PSI
SI
Mean SD
Total Mean SD
Total
100 38 150 50 42 61 31
100 35 156 50 48 64 31
20.5% 7.7% 32.2% 10.5% 9.5% 13.1% 6.5%
0.50 (0.22, 0.78) 0.00 (-0.46, 0.46) 0.14 (-0.08, 0.37) 0.24 (-0.16, 0.63) 0.10 (-0.32, 0.51) -0.28 (-0.64, 0.07) 0.12 (-0.38, 0.62)
484
100%
0.15 (0.03, 0.28)
1.7 1.0 1.6 0.7 0.5 0.4 3.0
2.5 4.0 1.5 2.5 2.4 1.7 2.6
0.5 1.0 1.3 0.1 0.3 0.9 2.7
2.3 3.0 2.5 2.5 1.7 1.8 2.4
Total (95% CI) 472 Heterogeneity: Chi2=12.35, df=6 (P=0.05); I2=51% Test for overall effect: Z=2.36 (P=0.02)
Weight Std. mean difference IV, fixed (95% CI)
Std. mean difference IV, fixed (95% CI)
-2 -1 0 1 2 Favours [PSI] Favours [SI]
(b) Study
PSI
SI
Weight
Odds ratio M-H, fixed (95% CI)
Events
Total
Events
Total
31 11 1 14 9 9 9 15 5 15
100 38 40 150 26 105 50 57 42 61
23 16 3 33 8 12 8 10 5 18
100 35 40 156 26 55 50 57 48 64
14.3% 10.7% 2.6% 26.5% 4.7% 13.0% 5.9% 6.6% 3.7% 11.9%
1.50 (0.80, 2.82) 0.48 (0.18, 1.27) 0.32 (0.03, 3.18) 0.38 (0.20, 0.75) 1.19 (0.37, 3.80) 0.34 (0.13, 0.86) 1.15 (0.41, 3.28) 1.68 (0.68, 4.14) 1.16 (0.31, 4.33) 0.83 (0.38, 1.85)
Total (95% CI) 669 Total events 119 136 Heterogeneity: Chi2=17.27, df=9 (P=0.04); I2=48% Test for overall effect: Z=1.58 (P=0.11)
631
100%
0.80 (0.60, 1.06)
Barrack et al. Boonen et al.9 Chareancholvanich et al.16 Daniilidis and Tibesku10 Hamilton et al.17 Ng et al.19 Nunley et al.11 Nunley et al.18 Roh et al.12 Victor et al.13 8
cost of the instrument manufacturing, the operating room time gained, and the cost of MRI/CT should be taken into account. A 2013 study estimated that an additional €78,240 could be made annually (for one THA and 2 minor orthopaedic surgical procedures per week) if the operation time gained with the use of PSI is used to perform other non-TKA orthopaedic procedures.28 However, another study reported that the $322 saving per TKA with reduction in operative time and instrumentation set up was negated by the additional cost of MRI or CT, along with cost of the PSI itself which lead to an overall loss of $1178 per procedure, compared to SI.8 Our meta-analysis did not find any improvement in operation time with the use of PSI over SI. This study has limitations. Only 5 of the 12 studies
Odds ratio M-H, fixed (95% CI)
0.01 0.1 1 10 100 Favours [PSI] Favours [SI]
were prospective randomised trials; the other 7 were retrospective studies. Only one study reported that outliers in terms of the femoral component rotational alignment were significantly fewer for PSI than SI.29 This may be an area of superiority of PSI that could be further explored. Comparison of different PSI systems may be helpful, especially with respect to the use of CT or MRI. A study comparing 4 PSI systems did not find any significant difference in HKA angle, FCA, and TCA, except that the VISONAIRE subgroup had more outliers in terms of HKA angle.13 CONCLUSION No significant difference between PSI and SI with
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104 Sharareh and Schwarzkopf
Table 3 Postoperative tibial coronal alignment for patient-specfic instrumentation (PSI) and standard instrumentation (SI) arms: (a) deviation from optimal alignment (90º), and (b) the number of outliers (>3º from optimal alignment) (a) Study
PSI
1.5 1.0 0.2 0.2 0.3
2.0 2.0 1.2 1.4 1.8
Total Mean
Std. mean difference IV, random (95% CI)
Total
2.1 2.0 1.6 1.1 1.4
50 34 40 48 64
19.4% 16.4% 18.0% 19.6% 26.6%
-0.29 (-0.71, 0.13) 0.00 (-0.46, 0.46) -0.21 (-0.65, 0.23) -0.40 (-0.82, 0.02) 0.12 (-0.23, 0.47)
Total (95% CI) 472 Heterogeneity: Tau2=0.01, Chi2=4.55, df=4 (P=0.34); I2=12% Test for overall effect: Z=1.38 (P=0.17)
484
100%
-0.14 (-0.34, 0.06)
Barrack et al. Boonen et al.9 Chareancholvanich et al.16 Roh et al.12 Victor et al.13
SD
Weight
SD
8
Mean
SI
39 38 40 42 61
2.1 1.0 0.5 0.7 0.1
Std. mean difference IV, random (95% CI)
-4
-2 0 2 Favours [PSI] Favours [SI]
4
(b) Study
PSI
SI
Weight
Odds ratio M-H, fixed (95% CI)
Events
Total
Events
Total
7 0 1 0 9
38 40 26 42 61
7 1 4 2 2
34 40 26 48 64
32.4% 11.2% 18.1% 12.1% 26.2%
0.87 (0.27, 2.80) 0.33 (0.01, 8.22) 0.22 (0.02, 2.12) 0.22 (0.01, 4.69) 5.37 (1.11, 25.94)
Total (95% CI) 207 212 Total events 17 16 Heterogeneity: Tau2=0.89, Chi2=7.55, df=4 (P=0.11); I2=47% Test for overall effect: Z=0.30 (P=0.77)
100%
0.83 (0.24, 2.88)
Boonen et al. Chareancholvanich et al.16 Hamilton et al.17 Roh et al.12 Victor et al.13 9
Odds ratio M-H, fixed (95% CI)
0.01 0.1 1 10 100 Favours [PSI] Favours [SI]
Table 4 Postoperative femoral coronal alignment for patient-specfic instrumentation (PSI) and standard instrumentation (SI) arms: (a) deviation from optimal alignment (90º), and (b) the number of outliers (>3º from optimal alignment) (a) Study or Subgroup
Boonen et al. Roh et al.12 Victor et al.13
9
PSI Mean
SD
0.0 1.0 0.1
2.0 1.4 1.3
SI Total Mean 38 42 61
2.1 0.6 0.7
Weight
Std. mean difference IV, fixed (95% CI)
SD
Total
2.0 1.4 2.0
34 48 64
23.1% 32.2% 44.7%
-0.99 (-1.48, -0.50) 0.28 (-0.13, 0.70) -0.35 (-0.71, 0.00)
484
100%
-0.29 (-0.53, -0.06)
Total (95% CI) 472 Heterogeneity: Chi2=15.17, df=2 (P=0.0005); I2=87% Test for overall effect: Z=2.44 (P=0.01)
Std. mean difference IV, fixed (95% CI)
-4
-2 0 2 Favours [PSI] Favours [SI]
4
(b) Study
PSI
SI
Weight
Odds ratio M-H, fixed (95% CI)
Events
Total
Events
Total
2 0 4 2 4
38 40 26 42 61
12 7 1 1 9
34 40 26 48 64
40.9% 25.2% 2.9% 3.0% 28.0%
0.10 (0.02, 0.50) 0.06 (0.00, 1.00) 4.55 (0.47, 43.78) 2.35 (0.21, 26.89) 0.43 (0.12, 1.47)
Total (95% CI) 207 Total events 12 30 Heterogeneity: Chi2=11.14, df=4 (P=0.02); I2=64% Test for overall effect: Z=2.82 (P=0.005)
212
100%
0.38 (0.19, 0.74)
Boonen et al. Chareancholvanich et al.16 Hamilton et al.17 Roh et al.12 Victor et al.13 9
Odds ratio M-H, fixed (95% CI)
0.01 0.1 1 10 100 Favours [PSI] Favours [SI]
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Patient-specific versus standard instrumentation for TKA 105
Table 5 The operation time (in minutes) for the patient-specific instrumentation (PSI) and standard instrumentation (SI) arms Study
Barke et al.15 Boonen et al.9 Daniilidis and Tibesku10 Hamilton et al.17 Nunley et al.11
PSI Mean
SD
74.4 51.0 50.9 61.8 89.6
11.1 11.0 7.2 5.8 18.2
SI Total Mean 39 40 150 26 57
75.4 61.0 51.1 57.5 93.4
Weight
Std. mean difference IV, fixed (95% CI)
SD
Total
11.1 14.0 7.2 5.0 15.9
50 40 156 26 57
13.9% 11.8% 48.7% 7.6% 18.0%
-0.09 (-0.51, 0.33) -0.79 (-1.24, -0.33) -0.03 (-0.25, 0.20) 0.79 (0.22, 1.36) -0.22 (-0.59, 0.15)
329
100%
-0.10 (-0.25, 0.06)
Total (95% CI) 312 Heterogeneity: Chi2=19.04, df=4 (P=0.0008); I2=79% Test for overall effect: Z=1.23 (P=0.22)
respect to HKA alignment, tibial alignment or operation time. It is unknown whether PSI provides any advantages over conventional methods.
Std. mean difference IV, fixed (95% CI)
-2 -1 0 1 2 Favours [PSI] Favours [SI]
DISCLOSURE No conflicts of interest were declared by the authors.
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