Eur J Orthop Surg Traumatol DOI 10.1007/s00590-015-1638-x
ORIGINAL ARTICLE • KNEE - ARTHROPLASTY
Evaluation of alignment in total knee arthroplasty: a prospective study K. S. Manjunath1,2
•
K. G. Gopalakrishna1,3 • G. Vineeth1
Received: 15 March 2015 / Accepted: 7 April 2015 Springer-Verlag France 2015
Abstract Background Successful results of knee arthroplasty demand precise surgical technique, sound implant design, kinematics, appropriate materials and patient compliance with rehabilitation. The precision with which the implants are placed directly affects patient outcome as implant position and alignment influence the stability, durability and patellar tracking. Evaluating the alignment in total knee arthroplasty and functional outcome with respect to the alignment is the need of the hour. Aim and objective of the study (1) To evaluate the accuracy of the overall limb alignment and component alignment in jig-assisted TKR. (2) To evaluate the functional outcome with respect to the alignment parameters. Methodology This is a prospective study of 120 knees in 80 patients that underwent total knee replacement at Victoria and Bowring and Lady Curzon hospitals. Patients were selected according to the inclusion and exclusion criteria and evaluated using knee society score at regular follow-up. Preoperative and postoperative standing ‘longleg radiographs’ and postoperative CT scans were taken & K. S. Manjunath [email protected] K. G. Gopalakrishna [email protected]
from all the patients. In our study, we had 54 female patients and 26 male patients. Indications were OA in 72 and RA in 48 knees. The average follow-up period was 36 months. Results Preoperatively, all the patients had moderate to severe pain. Mechanical and tibiofemoral axes were outside the acceptable range. Postoperatively, with respect to mechanical axis, the inliers had significantly better knee score (p = 0.026) compared to the outliers. But the functional score did not show any significant difference between these two groups (p = 0.2093). Inliers in tibiofemoral axis alignment parameter had extremely significant better knee score (p = 0.0001) and also functional score (p = 0.0082) compared to outliers group. Sagittal and rotational femoral component angles in all 120 cases were coming within the ‘inliers group’. Similarly, the sagittal, the coronal and the rotational component angles of tibia were also coming under inliers group in all 120 replaced knees. Conclusion Aligning the mechanical axis, tibiofemoral angle within (0 ± 3) and placement of prostheses within (0 ± 3) to the normal alignment in all the three planes significantly produce excellent result with respect to functional outcome. Keywords Total knee arthroplasty Knee society score Mechanical axis Rotational axis Alignment
G. Vineeth [email protected] 1
Department of Orthopaedics, Bangalore Medical College and Research Institute, Fort, K. R. Road, Bangalore 560002, India
Introduction
2
No: 44/10/3, 11th A Main Road, 18th Cross, Padmanabhanagar, Bangalore 560061, India
3
Flat No: 106, Ideal Apartments, 16th Cross, Ideal Home Township, Rajarajeshwarinagar, Bangalore 560098, India
The goals of the total knee arthroplasty (TKA) are threefold: pain relief, restoration of normal limb alignment and restoration of a functional range of motion. A successful result demands precise surgical technique, sound implant
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design and kinematics, appropriate materials and patient compliance with rehabilitation. This approach can be applied to implantation of any well-designed prosthesis. The shapes of the reconstructed femur and tibia, particularly in the sagittal plane, dictate the kinematics of the reconstructed knee. Accurate component placement in knee replacement surgery is important. The precision with which the implants are placed directly affects the patient outcome as implant position and alignment influence the stability, durability and patellar tracking. The ability to measure the accuracy of implantation of knee replacement components is valuable in assessing and evaluating the quality of the technique. Numerous studies have shown a correlation between long-term success of TKA and restoration of near-normal limb alignment. Malalignment of total knee prostheses has been implicated in long-term difficulties, including tibiofemoral instability, patellofemoral instability, patellar fracture, stiffness, accelerated polyethylene wear and implant loosening. Hence, the use of accurate instrumentation and an understanding of the basic principles inherent to the instruments are necessary to implant reproducibly the wellaligned prostheses.
Standard postoperative protocol was followed to develop quadriceps muscle and to improve the range of motion and early weight-bearing ambulation. Clinical follow-up was done at 2 weeks and at 1, 3, 6, 12 months. Radiological evaluation was done at 2 weeks postoperative using plain radiograph, scanogram and CT scan. All the data and observations were documented. Final evaluation was done using KSS scoring system. Statistical derivation was done using the suitable tools.
Radiological evaluation Coronal alignment The mechanical axis alignment was determined by ‘the angle between a line connecting the centers of the femoral head and knee (femoral mechanical axis) and a line connecting the centers of the knee and ankle (tibial femoral axis)’ [10]. This is 0 in the normal knee and post-operated knee. The outcome was defined as an ‘‘inlier’’ when it was within the optimum value ±3 and an ‘‘outlier’’ when it was outside the optimum value ±3 [1] (Fig. 1).
Methodology We did a prospective study on the accuracy of alignment and the functional outcome of 120 knees that underwent total knee replacement at Victoria and Bowring and Lady Curzon hospitals. Most of the indications belong to osteoarthritis (72 knees, 60 %) and rheumatoid arthritis (48 knees, 40 %) of the knees. All our patients were above 50 years, mean age being 61.6 years. There were 67 % of female and 33 % of male patients. Forty patients underwent bilateral total knee replacement and 40 patients unilateral TKA. In bilateral knees, 20 were of OA (50 %) and 20 were of RA (50 %). In unilateral knees, 32 were of OA (80 %) and 8 were of RA (20 %) patients. Twenty patients were having only hypertension, 12 patients had morbid obesity, 8 patients had DM, 8 patients had CVD and 44 patients had multiple comorbid conditions. All the 120 knees had poor knee society score of \60 preoperatively. Surgery was performed under spinal and epidural anesthesia in all except in 8 patients. The TKA was performed using standard midline approach and medial parapatellar arthrotomy. Resection of femur and tibia was done at primary level. Patellar resurfacement was not done in any patient. The alignment, soft tissue and gap balancing were achieved by appropriate release and resection. They were checked both in extension and in flexion. Components were placed in proper alignment. Joint line position was measured. Patellar tracking was noticed normal in all.
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Fig. 1 Radiograph showing the mechanical axis in the coronal plane. The alignment of the femoral and tibial components was measured by the angle subtended at the intersection of a line drawn across the base of each component in frontal (coronal) plane and the mechanical axis (a, FFC angle, b-frontal tibial component angle)
Eur J Orthop Surg Traumatol
The tibiofemoral angle, i.e., ‘the angle between femoral and tibial anatomical axes’ was measured (Fig. 2). The frontal femoral component (FFC) angle and the frontal tibial component (FTC) angles were measured with respect to mechanical axis of femur and tibia, respectively, which should be 90. The LFC (lateral femoral component) angle was measured between the anterior cortex of the distal femur and the shield of the femoral component. The LTC (lateral tibial component) angle was measured in relation to the posterior tibial cortex. This is 3 in femur and 3 posterior slope in tibia as recommended by the manufacturer. Postoperative CT scan was carried out using a multislice scanner to determine the rotational alignment of the components. The scan sequence was started at the superior pole of the patella and ended at the tibial tuberosity, in contiguous slices of 2.5 mm. The rotation of the femoral component was determined in relation to the transepicondylar axis. An axial image of the distal femur was chosen, which most clearly demonstrated the medial epicondylar sulcus, when the sulcus was present, or the central point of the medial epicondyle, when no sulcus was found, and the lateral epicondylar prominence. A line was drawn between these two points, thereby establishing the surgical epicondylar axis. A second line was drawn across the middle of the posterior condyles of the femoral component. The angle between these represented the rotation of the component [1] (Figs. 3, 4).
Fig. 3 Rotational femoral and tibial component alignment: CT showing measurement of axial rotation of the femoral component in relation to the transepicondylar axis (A–A) and posterior femoral component condylar line (B–B)
Fig. 4 Rotational femoral and tibial component alignment: CT showing measurement of axial rotation of the tibial component in relation to the posterior margins of medial and lateral plateau (A–A) and to the medial and lateral edges of the tibial component (B–B)
Fig. 2 Radiograph showing the measurement of flexion and extension of the femoral component and measurement of the posterior slope of the tibial component. A, Sagittal femoral angle measured by an angle subtended between the anterior femoral cortical line and a line perpendicular to the base of the component; B, sagittal tibial angle measured by an angle subtended between the posterior tibial cortical line and a line parallel to the tibial base plate
The rotation of the tibial component was determined relative to the posterior margin of the proximal tibia. A line was drawn between the posterior margins of the medial and lateral tibial plateau. A second line was drawn between the medial and lateral edges of the peg/fin of the tibial component. The angle between these represented the rotation of the tibial component [1].
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This should be 0. The outcome was defined as an ‘‘inlier’’ when it was within the optimum value ±3 and an ‘‘outlier’’ when it was over the optimum value ±3 [2]. Functional evaluation was done preoperatively and 6 week postoperatively using ‘knee society score’. Statistical analysis Results were compared using an unpaired Student’s t test and paired t test with the assumption of homogeneity of variance used as appropriate.
Results and discussion We have analyzed our observation parameters like mechanical axis, tibiofemoral angle and individual component angles for their accuracy like ‘inlier and outlier’ and their significance with reference to ‘knee society score’ which include knee score and functional score (Table 1; Fig. 5). We had most of the indications in osteoarthritis (72 knees, 60 %) and rheumatoid arthritis (48 knees, 40 %). Normann Scott reports 88 knees OA (73.9 %), 22 knees RA (18.5 %), osteonecrosis 4 (3.36 %) and traumatic arthritis 5 (4.2 %) [3]. Rand et al. [4] report OA in 68 %, RA in 31 % and traumatic arthritis in \1 %. Robert et al. [5] report that nearly 90 % (86.8 %) of the patients had osteoarthritis. Our male/female ratio was 1:2 with 54 female (67 %) and 26 male (33 %) patients. The sex of the patients affects the cumulative rates of survival. Ranawat et al. report 20 % males and 80 % females. Male survivorship at 15 years was 83.3 %, and in female it was 95.3 %. However, he opines that there was 75 % female and less number of males, and hence, the survivorship analysis with respect to sex is less reliable [6]. Jain et al.
[7] report that female who undergone TKA in 1990–2000 is 62.6 %. Robert et al. [5] report that about two-thirds (65.4 %) of the patients were women in their study. Our study includes 40 patients belong to age 50–60 years, 36 patients from 61–70 years and 4 patients [70 years (Fig. 6). Ranawat et al. report the average age of 65 years in their study [6]. Ole kristensen et al. report the average age of 52 years in their study [8]. Normann Scott et al. report the average age of 66.9 years in their study [2, 7]. Robert et al. [5] report the average age of the patients at the time of surgery was 67.5 years. Forty of our patients underwent bilateral TKA, and the other 40 had unilateral TKA. In bilateral cases, 40 were of OA (50 %) and 40 were of RA (50 %). In unilateral cases, 32 were of OA (80 %) and 8 were of RA (20 %) (Fig. 7). Normann Scott [3] reported 23.75 % left knee, 27.5 % right knee and 48.75 % bilateral in his study. William. F Donaldson III reported 48.1 % right, 28 % left and 24 % bilateral [9]. In our 40 unilateral knees, 18 were male and 22 were female, and in 40 bilateral cases, 32 were female and 8 were male.
40 females males
30 20 10 0
Table 1 Indications—120 knees Indications
51-60
61-70
Rheumatoid arthritis
48
Osteoarthritis
72
indications
Fig. 6 Mean age in our study is 61.6 years
80
40
60
Osteoarthritis 60%
Fig. 5 Indications—120 knees [1]
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>70
No. of knees
Rheumatoid arthritis 40%
40
32
20
8
0
UNILATERAL
40
BI LATERAL
Rheumatoid arthritis
Fig. 7 Laterality indications—120 cases
Osteoarthritis
Eur J Orthop Surg Traumatol
Knee society score
100
Knee score: all the 120 knees had poor knee score of \60 preoperatively. Postoperatively, 100 knees had excellent score (80–100), 12 knees with good score (70–79), 4 knees with fair score (60–69) and 4 knees with poor score (\60). Preoperative mean score of 17.73 points was increased to 80.86 points postoperatively with p value of 0.0001, indicating significant improvement in ‘knee score’ following total knee replacement (Table 2; Fig. 8). In OA knees, the preoperative mean ‘knee score’ of 23.39 was increased to 86.27 postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement. In RA knees, preoperative mean ‘knee score’ of 9.25 was increased to 72.75 postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement (Fig. 9). Functional score In overall functional score of 80 patients, 76 had poor (\60) and 4 patients had fair functional score (60–69) preoperatively. Postoperatively, 64 patients had excellent (80–100), 12 had good (70–79), and 4 had poor score (\60) (Table 3; Fig. 10). The preoperative mean ‘functional score’ of 23.5 points was increased to 78.16 points postoperatively with p value
80 60 40
OA
20
RA
0 pre
post
Fig. 9 Knee score improvement versus indications
Table 3 Functional score 80 patients Functional score
Preoperative
Postoperative
80–100
Excellent
0
64
70–79
Good
0
12
60–69
Fair
4
0
\60
Poor
76
4
Functional Score
100 80 60 40
Table 2 Knee score—120 knees Knee score
20
Preoperative
Postoperative
80–100
Excellent
0
100
70–79
Good
0
12
60–69
Fair
0
4
\60
Poor
120
4
100
Knee Score
80 60 40 20
knee score 0 mean pre op
mean post op
Fig. 8 Mean preoperative and postoperative knee scores
functional score 0 pre op
post op
Fig. 10 Functional score (preoperative vs. postoperative)
of 0.0001, indicating significant improvement in functional score following total knee replacement. In osteoarthritic knee, preoperative mean ‘functional score’ of 32.78 points was increased to 84.44 points postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement. In RA knee, preoperative mean ‘functional score’ of 9.58 points was increased to 68.75 points postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement. The result of our study was comparable with the study of 524 knees done by Elke et al. in 1995 in which the knee score rose in the OA group from a mean of 28–89 points after 1 year and in RA from 21 points to 90 points after 1 year Kim et al. [1] reported the mean preoperative hospital for special surgery knee score and knee society knee and functional scores were 42, 41 and 42, respectively, and postoperatively, they were 84, 90 and 84 points,
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respectively. The preoperative and postoperative total WOMAC scores were 73 and 84 points, respectively. Mechanical axis In 120 knees, the mechanical axis alignment of 96 knees (80 %) was in the inliers group (\±3), and in 24 knees (20 %), it was outside the normal range ([±3) and hence the outliers group (Table 4; Fig. 11). Comparison of outcome between inliers and outliers group with respect to mechanical axis alignment Our observation is supported by a study of Ba¨this et al. in 2004 which reported 80 patients having the postoperative axis of the limb exceeded 3 of varus/valgus deviation in their 22 % of the patients who were operated by conventional technique. Mielke et al. [11] and Petersen and Engh [12] observed in their independent studies that although an improvement in the mechanical alignment, the conventional implantation technique fails to restore the mechanical limb axis within the range of ±3 of the varus or valgus in up to 30 %. Our study is also in agreement with the results of Ek et al. published in 2008, wherein 50 patients underwent conventional primary TKA. In their conventional group, the mean mechanical axis (coronal) alignment was 0.67. There were 5 TKAs with a deviation of [5 and 31 TKAs within 3 of neutral.
Table 4 Mechanical axis—120 knees No.
Knee score
Functional score
Mean
Mean
SD
80.20
15.42
70
24.49
Inliers (\±3)
96
83.58
Outliers ([±3)
24
70 p = 0.026
SD 7.59 24.49
p = 0.209
The mean knee score was 83.58 points in ‘inliers’ and 70 points in ‘outliers’ group (p = 0.026), which is statistically significant. Rand and Coventry reported a 10-year survival rate in 90 % of the knees when the leg alignment was between 0 and 4 valgus, but it was 71 and 73 % when it was higher than the 4 valgus and varus alignment, respectively [14]. Jeffery et al. reported a 24 % rate of prosthetic loosening when the mechanical axis was over ±3 deviation. The acceptable range for the postoperative leg alignment in a TKA is still controversial [15]. However, a postoperative limb axis within a range of ±3 varus or valgus was found to be associated with a lower rate of aseptic component loosening in many studies. The mean functional score was 80.2 points in ‘inliers’ and 70 points in ‘outliers’ group (p = 0.2093), which is not significant statistically. We opine that the accuracy in mechanical axis alignment improves the anatomical and radiological alignment although it does not influence the functional outcome. This observation was supported by the study of Tew and Waugh et al. [16] in 1982, who previously suggested that the postoperative limb alignment was not the only factor for determining durability but factors other than alignment might also be more important for determining long-term survival and functional outcome following total knee arthroplasty. In a large retrospective clinical series of Parratte et al. [17] in 2010 reported that a postoperative mechanical axis of 0 ± 3 did not improve implant survival at the time of the fifteen-year follow-up for those 398 modern, cemented, condylar total knee replacements. Efforts to more consistently achieve mechanical axis alignment of 0 ± 3, as is currently done with contemporary computer navigation systems, seem unlikely to be rewarded with substantial improvements in implant survival following TKA as compared with that achieved when traditional total knee instruments are employed mindfully. Percentage of inliers in our study (80 %) is comparable to various previous studies as mentioned in Table 5. Tibio femoral axis
85
In 120 knees, the tibiofemoral axis of 112 knees (93.34 %) was inside inliers group (\±3), and in 8 knees (6.66 %), it was outside the normal range ([±3), which was considered as outliers group (Table 6; Fig. 12).
80 75 70
KS FS
65 60
inliers
outliers
Fig. 11 Inliers versus outliers group (mechanical axis)
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Comparison of outcome between inliers and outliers group with respect to tibiofemoral angle These results agree with those of Petersen and Engh [12] and Mahaluxmivala et al. [19] who found that up to 26 and
Eur J Orthop Surg Traumatol Table 5 Clinical studies of conventional manual surgical techniques placing limb alignment within ±3 of the mechanical axis of the lower extremity [18] References
Number
Percent of inliers
Haaker et al. (2005)
100
75
Sparmann et al. (2003)
120
78
Victor and Hoste (2004) Jenny et al. (2005)
50 235
74 74
Jenny and Boeri (2001)
30, 30
70
Kim et al. (2005)
69, 78
58
Perlick et al. (2004)
40
75
Seon and Song (2005)
47, 50
76
Bathis et al. [10]
160
78
Perlick et al. (2004)
50
72
Hart et al. (2003)
60
70
Anderson et al. (2005)
116, 51
Average
Component alignment Frontal plane Frontal femoral component angle in 116 knees (96.67 %) was in the inliers group (\90 ± 3) and 4 knees (3.33 %) was in outliers group ([90 ± 3). Mean FFC angle was 89.67 (Table 7; Fig. 13). Comparison of outcome between inliers and outliers group with respect to component alignment
84 74
Source Table 115-1, Clinical Studies That Compare Conventional Manual Surgical Techniques With Computer Navigation In Placing The Limb Alignment Within ±3 Degrees Of The Mechanical Axis Of The Lower Extremity. Chapter 115, Section 12, page no. 1204, 5th edition, Scot and Insal (http://www.expertconsult.com) Table 6 Tibiofemoral angle No.
Inliers (\±3) Outliers ([±3)
112 8
Knee score
Functional score
Mean
SD
Mean
SD
83.32
6.88
80.35
14.2
46.5
37.47
47.5
38.89
p = 0.0001
extremely statistically significant. The mean functional score was 80.35 points and 47.5 points for inliers and outliers group, respectively, (p = 0.0082), which is very statistically significant.
p = 0.0081
90 80 70 60 50 40 30 20 10 0
The mean knee score was 82.96 for inliers and 20 for outliers group with respect to FFC angle. The mean functional score was 80.17 for inliers and 20 for outliers group, which is statistically significant p = 0.0001. Coronal component angle of tibia in all 120 knees (100 %) was inside inliers group. The mean angle was 89.55. The mean knee score was 80.86, and the mean functional score was 78.16 with respect to coronal component angle of tibia. Statistical significance of this parameter in our study cannot be evaluated since there were no outliers. Ek et al. [13] studied 50 knees (conventional technique) in 2008 in which the mean tibial axis (coronal) alignment was 89.6 and the mean femoral axis (coronal) alignment was 88.9. Kim et al. [1], in their study of 100 knees in 2007, showed frontal femoral angle outliers ([±3) were only 9 % and frontal tibial angle outliers ([±3) were only 7 %. The study of Seon et al. in 2004 showed that the Table 7 Inliers versus outliers group (FFC angle)
KS FS inliers
Inliers (\90 ± 3) Outliers ([90 ± 3)
No
KS
116
82.96
80.17
20
20
4
FS
outliers
Fig. 12 Inliers versus outliers group (tibiofemoral angle)
25 % of their patients, respectively, had the deviation. Postoperative tibiofemoral angle exceeded 3 of varus/valgus deviation up to 18 % of the patients in the study of Kim et al. [1] in 2007. In Jenny and Boeri et al. [20] study, a tibiofemoral angle of ±3 varus/valgus was achieved in 78 % using a conventional technique. The mean knee score in our study was 83.32 points and 46.5 points for ‘inliers’ and ‘outliers’ group, respectively, (p = 0.0001) with respect to tibiofemoral angle, which is
90 80 70 60 50 40 30 20 10 0
KS FS
inliers
outliers
Fig. 13 Inliers versus outliers group (frontal femoral component angle)
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coronal component angle of femur had 17 (42.5 %) and 2 (5.6 %) outliers in navigation and conventional methods, respectively, and the mean value of this angle was 87.1 ± 2.4 and 88.7 ± 1.7, respectively. The coronal inclination of the tibial component on the anteroposterior radiographs showed no outliers. The mean value was 90.7 ± 0.8 [2]. Ba¨this et al. [10] study in 2004 had 69 (86 %) inliers in the FFC and 75 (94 %) inliers in the FTC alignment. Sagittal plane Sagittal femoral component angle in all 120 knees (100 %) was inside inliers group. The mean sagittal femoral component angle is 4.15 flexion (85.85). The mean knee score was 80.86 points, and the mean functional score was 78.16 points with respect to sagittal femoral component angle. Sagittal component angle of tibia in all 120 knees (100 %) was inside inliers group. The mean sagittal tibial component angle was 88.4 [19]. The mean knee score was 80.86 points, and the mean functional score was 78.16 points with respect to sagittal tibial component angle. Ek et al. [13] studied 50 knees (conventional technique) in 2008 in which the mean tibial slopes (sagittal alignments) were 85.8 (the optimal being 87) and the mean femoral slopes (sagittal alignments) were 87.8 (1.2) of flexion). Kim et al. [1] study of 100 knees in 2007 showed that sagittal femoral angle outliers ([±3) were only 33 % and sagittal tibial angle outliers ([±3) were only 9 %. The study of Seon et al. [2] in 2004 showed that the sagittal component angle of femur had no outliers. The coronal inclination of the tibial component on the anteroposterior radiographs showed no outliers. And the outliers in the inclination of the tibial component were found in 16 knees (40 %). The mean value was 90. 09. Ba¨this et al. [10] study in 2004 reported that the mean lateral tibial component angle was 87 ± 4.5 in conventional group. Rotational plane Rotational femoral component angle in all 120 knees (100 %) was inside inliers group. The mean rotational femoral component angle is 0.92 of external rotation. The mean knee score was 80.86 points, and the mean functional score was 78.16 points. Rotational component angle of tibia in all 120 knees (100 %) was inside inliers group. The mean rotational tibial component angle is degree 0.98. The mean knee score was 80.86 points, and the mean functional score was 78.16 points. Harman [21] study in 2012 showed that there were 16 (24 %) TKR with isolated malrotation of the tibial component and 4 (6 %) TKR with isolated malrotation of the femoral component. Kim et al. [1] study of 100 knees in
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Table 8 Summary of the results Determinants
Preoperative
Postoperative
Mean
Range
Mean
9.64
Range
1
Tibiofemoral angle ()
2.1–27
2.83
2
Mechanical axis ()
10.34
3.6–23.8
1.83
0.2–23.7 0–27.6
3
Knee score
17.73
2–40
80.86
20–94
4
Functional score
23.5
0–45
78.1
20–100
5
Femoral component ()
89.6
87–95.1
6
Tibial component ()
89.55
82–92
7 8
Femoral component () Tibial component ()
4.15 88.42
2–6.7 85.9–90
9
Femoral component ()
0.92
0.02–1.84
10
Tibial component ()
0.98
0.11–1.94
2007 showed that femoral rotation angle outliers ([±3) were only 15 % and tibial rotation angle ([±3) were found in up to 49 % of patients. Berger and coworkers in 1988 noted that normal rotation of the femoral condyles is 0.3 ± 1.2 0 of internal in comparison with the surgical epicondylar axis [22] (Table 8).
Conclusion Total knee arthroplasty is a well-proven procedure. Although it usually produces excellent results, proper axial alignment is of paramount importance for the longevity of the implant. Even minor malpositioning can lead to early loosening, increased polyethylene wear and poor function. Malalignment of the components in any anatomical plane can cause major complications. Malrotation of either the femoral or the tibial component will critically affect patellar tracking and can lead to patellar subluxation or dislocation. We opine that the accuracy in mechanical axis alignment improves the anatomical and radiological alignment, although it does not influence the functional outcome. Our view is strengthened by the fact that the other determinants like component alignment which influences the functional outcome have been within the normal limit, thereby giving the exclusivity to the mechanical axis in our study. Nevertheless, aligning the mechanical axis, tibiofemoral angle within (0 ± 3) postoperatively significantly produces excellent result, and the components alignment in all the three planes is equally important and decisive for final outcome. Good results with respect to alignment can be achieved even without assistance of navigational technique as shown in our study.
Conflict of interest
None.
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References 1. Kim YH (2007) Alignment and orientation of the components in total knee replacement with and without navigation support. J Bone Joint Surg 89:471–476 2. Seon JK (2004) The accuracy of lower extremity alignment in a total knee arthroplasty using computer-assisted navigation system. J Korean Orthop Assoc 39:566–571 3. Scot WN et al (1988) Results after knee replacement with a posterior cruciate substituting prosthesis. J Bone Joint Surg 70A:1163 4. Rand JA et al (1991) Survivorship analysis of TKA. J Bone Joint Surg 73A:397 5. Kane RL, Saleh KJ, Wilt TJ, Bershadsky B (2005) J Bone Joint Surg (87) 8–12 6. Kristensen O et al (1992) Long term results of TCK arthroplasty in RA. J Bone Joint Surg 74B:803 7. Jain NB, Higgins LD, Ozumba D, Guller U, Neil MC (1990–2000) Trends in epidemiology of knee arthroplasty in the United States, American registry 8. Dennis DA et al (1992) Posterior cruciate condylar total knee arthroplasty-average 11 year follow-up. Clin Orthop Relat Res 281:168 9. Scuderi GR et al (1992) Total knee arthroplasty current clinical prospective. Clin Orthop Relat Res 276:26 10. Ba¨this H (2004) Orthopaedic surgeon alignment in total knee arthroplasty a comparison of computer-assisted surgery with the conventional technique. J Bone Joint Surg [Br] 86:682–687 11. Mielke RK, Clemens U, Jens JH, Kershally S (2001) Navigation in knee endoprosthesis implantation-preliminary experiences and prospective comparative study with conventional implantation technique. Z Orthop Ihre Grenzgeb 139:106–116
12. Petersen TL, Engh GA (1988) Radiographic assessment of knee alignment after total knee arthroplasty. J Arthroplasty 3:67–72 13. Ek ETH, Dowsey MM, Tse LF (2008) J Orthop Surg 16(2):192–196 14. Rand JA, Coventry MB (1988) Ten-year evaluation of geometric total knee arthroplasty. Clin Orthop Relat Res 232:168–173 15. Jeffery RS, Morris RW, Denham RA (1991) Coronal alignment after total knee replacement. J Bone Joint Surg Br 73:709–714 16. Tew M, Waugh W (1982) Estimating the survival time of knee replacement. J Bone Joint Surg Br 64:579–582 17. Parratte S, Pagnano MW (2010) Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern cemented total knee replacements. J Bone Joint Surg Am 92:2143–2149 18. Abdel Fatah EE, Mahfouz MR, Merkl B et al (2013) Threedimensional morphology of the knee biomechanics. Insall and scott surgery of knee 5th edition Mosby Elsevier.12 19. Mahaluxmivala J, Bankes MJ, Nicolai P, Aldam CJH, Allen PW (2001) The effect of surgeon experience on component positioning in 673 press fit condylar posterior cruciate-sacrificing total knee arthroplasties. J Arthroplasty 16:635–640 20. Jenny JY, Boeri C (2001) Navigated implantation of total knee endoprosthesis: a comparative study with conventional instrument. Z Orthop Ihre Grenzgeb 139:117 21. Harman MK, Banks SA (2012) Prosthesis alignment affects axial rotation motion after total knee replacement: a prospective in vivo study combining computed tomography and fluoroscopic evaluations Harman. BMC Musculoskelet Disord 13:206 22. Berger RA, Crossett LS, Jacobs JJ, Rubash HE (1998) Malrotation causing patellofemoral complications after total knee arthroplasty. Clin Orthop Relat Res 356:144–153
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ORIGINAL ARTICLE • KNEE - ARTHROPLASTY
Evaluation of alignment in total knee arthroplasty: a prospective study K. S. Manjunath1,2
•
K. G. Gopalakrishna1,3 • G. Vineeth1
Received: 15 March 2015 / Accepted: 7 April 2015 Springer-Verlag France 2015
Abstract Background Successful results of knee arthroplasty demand precise surgical technique, sound implant design, kinematics, appropriate materials and patient compliance with rehabilitation. The precision with which the implants are placed directly affects patient outcome as implant position and alignment influence the stability, durability and patellar tracking. Evaluating the alignment in total knee arthroplasty and functional outcome with respect to the alignment is the need of the hour. Aim and objective of the study (1) To evaluate the accuracy of the overall limb alignment and component alignment in jig-assisted TKR. (2) To evaluate the functional outcome with respect to the alignment parameters. Methodology This is a prospective study of 120 knees in 80 patients that underwent total knee replacement at Victoria and Bowring and Lady Curzon hospitals. Patients were selected according to the inclusion and exclusion criteria and evaluated using knee society score at regular follow-up. Preoperative and postoperative standing ‘longleg radiographs’ and postoperative CT scans were taken & K. S. Manjunath [email protected] K. G. Gopalakrishna [email protected]
from all the patients. In our study, we had 54 female patients and 26 male patients. Indications were OA in 72 and RA in 48 knees. The average follow-up period was 36 months. Results Preoperatively, all the patients had moderate to severe pain. Mechanical and tibiofemoral axes were outside the acceptable range. Postoperatively, with respect to mechanical axis, the inliers had significantly better knee score (p = 0.026) compared to the outliers. But the functional score did not show any significant difference between these two groups (p = 0.2093). Inliers in tibiofemoral axis alignment parameter had extremely significant better knee score (p = 0.0001) and also functional score (p = 0.0082) compared to outliers group. Sagittal and rotational femoral component angles in all 120 cases were coming within the ‘inliers group’. Similarly, the sagittal, the coronal and the rotational component angles of tibia were also coming under inliers group in all 120 replaced knees. Conclusion Aligning the mechanical axis, tibiofemoral angle within (0 ± 3) and placement of prostheses within (0 ± 3) to the normal alignment in all the three planes significantly produce excellent result with respect to functional outcome. Keywords Total knee arthroplasty Knee society score Mechanical axis Rotational axis Alignment
G. Vineeth [email protected] 1
Department of Orthopaedics, Bangalore Medical College and Research Institute, Fort, K. R. Road, Bangalore 560002, India
Introduction
2
No: 44/10/3, 11th A Main Road, 18th Cross, Padmanabhanagar, Bangalore 560061, India
3
Flat No: 106, Ideal Apartments, 16th Cross, Ideal Home Township, Rajarajeshwarinagar, Bangalore 560098, India
The goals of the total knee arthroplasty (TKA) are threefold: pain relief, restoration of normal limb alignment and restoration of a functional range of motion. A successful result demands precise surgical technique, sound implant
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design and kinematics, appropriate materials and patient compliance with rehabilitation. This approach can be applied to implantation of any well-designed prosthesis. The shapes of the reconstructed femur and tibia, particularly in the sagittal plane, dictate the kinematics of the reconstructed knee. Accurate component placement in knee replacement surgery is important. The precision with which the implants are placed directly affects the patient outcome as implant position and alignment influence the stability, durability and patellar tracking. The ability to measure the accuracy of implantation of knee replacement components is valuable in assessing and evaluating the quality of the technique. Numerous studies have shown a correlation between long-term success of TKA and restoration of near-normal limb alignment. Malalignment of total knee prostheses has been implicated in long-term difficulties, including tibiofemoral instability, patellofemoral instability, patellar fracture, stiffness, accelerated polyethylene wear and implant loosening. Hence, the use of accurate instrumentation and an understanding of the basic principles inherent to the instruments are necessary to implant reproducibly the wellaligned prostheses.
Standard postoperative protocol was followed to develop quadriceps muscle and to improve the range of motion and early weight-bearing ambulation. Clinical follow-up was done at 2 weeks and at 1, 3, 6, 12 months. Radiological evaluation was done at 2 weeks postoperative using plain radiograph, scanogram and CT scan. All the data and observations were documented. Final evaluation was done using KSS scoring system. Statistical derivation was done using the suitable tools.
Radiological evaluation Coronal alignment The mechanical axis alignment was determined by ‘the angle between a line connecting the centers of the femoral head and knee (femoral mechanical axis) and a line connecting the centers of the knee and ankle (tibial femoral axis)’ [10]. This is 0 in the normal knee and post-operated knee. The outcome was defined as an ‘‘inlier’’ when it was within the optimum value ±3 and an ‘‘outlier’’ when it was outside the optimum value ±3 [1] (Fig. 1).
Methodology We did a prospective study on the accuracy of alignment and the functional outcome of 120 knees that underwent total knee replacement at Victoria and Bowring and Lady Curzon hospitals. Most of the indications belong to osteoarthritis (72 knees, 60 %) and rheumatoid arthritis (48 knees, 40 %) of the knees. All our patients were above 50 years, mean age being 61.6 years. There were 67 % of female and 33 % of male patients. Forty patients underwent bilateral total knee replacement and 40 patients unilateral TKA. In bilateral knees, 20 were of OA (50 %) and 20 were of RA (50 %). In unilateral knees, 32 were of OA (80 %) and 8 were of RA (20 %) patients. Twenty patients were having only hypertension, 12 patients had morbid obesity, 8 patients had DM, 8 patients had CVD and 44 patients had multiple comorbid conditions. All the 120 knees had poor knee society score of \60 preoperatively. Surgery was performed under spinal and epidural anesthesia in all except in 8 patients. The TKA was performed using standard midline approach and medial parapatellar arthrotomy. Resection of femur and tibia was done at primary level. Patellar resurfacement was not done in any patient. The alignment, soft tissue and gap balancing were achieved by appropriate release and resection. They were checked both in extension and in flexion. Components were placed in proper alignment. Joint line position was measured. Patellar tracking was noticed normal in all.
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Fig. 1 Radiograph showing the mechanical axis in the coronal plane. The alignment of the femoral and tibial components was measured by the angle subtended at the intersection of a line drawn across the base of each component in frontal (coronal) plane and the mechanical axis (a, FFC angle, b-frontal tibial component angle)
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The tibiofemoral angle, i.e., ‘the angle between femoral and tibial anatomical axes’ was measured (Fig. 2). The frontal femoral component (FFC) angle and the frontal tibial component (FTC) angles were measured with respect to mechanical axis of femur and tibia, respectively, which should be 90. The LFC (lateral femoral component) angle was measured between the anterior cortex of the distal femur and the shield of the femoral component. The LTC (lateral tibial component) angle was measured in relation to the posterior tibial cortex. This is 3 in femur and 3 posterior slope in tibia as recommended by the manufacturer. Postoperative CT scan was carried out using a multislice scanner to determine the rotational alignment of the components. The scan sequence was started at the superior pole of the patella and ended at the tibial tuberosity, in contiguous slices of 2.5 mm. The rotation of the femoral component was determined in relation to the transepicondylar axis. An axial image of the distal femur was chosen, which most clearly demonstrated the medial epicondylar sulcus, when the sulcus was present, or the central point of the medial epicondyle, when no sulcus was found, and the lateral epicondylar prominence. A line was drawn between these two points, thereby establishing the surgical epicondylar axis. A second line was drawn across the middle of the posterior condyles of the femoral component. The angle between these represented the rotation of the component [1] (Figs. 3, 4).
Fig. 3 Rotational femoral and tibial component alignment: CT showing measurement of axial rotation of the femoral component in relation to the transepicondylar axis (A–A) and posterior femoral component condylar line (B–B)
Fig. 4 Rotational femoral and tibial component alignment: CT showing measurement of axial rotation of the tibial component in relation to the posterior margins of medial and lateral plateau (A–A) and to the medial and lateral edges of the tibial component (B–B)
Fig. 2 Radiograph showing the measurement of flexion and extension of the femoral component and measurement of the posterior slope of the tibial component. A, Sagittal femoral angle measured by an angle subtended between the anterior femoral cortical line and a line perpendicular to the base of the component; B, sagittal tibial angle measured by an angle subtended between the posterior tibial cortical line and a line parallel to the tibial base plate
The rotation of the tibial component was determined relative to the posterior margin of the proximal tibia. A line was drawn between the posterior margins of the medial and lateral tibial plateau. A second line was drawn between the medial and lateral edges of the peg/fin of the tibial component. The angle between these represented the rotation of the tibial component [1].
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This should be 0. The outcome was defined as an ‘‘inlier’’ when it was within the optimum value ±3 and an ‘‘outlier’’ when it was over the optimum value ±3 [2]. Functional evaluation was done preoperatively and 6 week postoperatively using ‘knee society score’. Statistical analysis Results were compared using an unpaired Student’s t test and paired t test with the assumption of homogeneity of variance used as appropriate.
Results and discussion We have analyzed our observation parameters like mechanical axis, tibiofemoral angle and individual component angles for their accuracy like ‘inlier and outlier’ and their significance with reference to ‘knee society score’ which include knee score and functional score (Table 1; Fig. 5). We had most of the indications in osteoarthritis (72 knees, 60 %) and rheumatoid arthritis (48 knees, 40 %). Normann Scott reports 88 knees OA (73.9 %), 22 knees RA (18.5 %), osteonecrosis 4 (3.36 %) and traumatic arthritis 5 (4.2 %) [3]. Rand et al. [4] report OA in 68 %, RA in 31 % and traumatic arthritis in \1 %. Robert et al. [5] report that nearly 90 % (86.8 %) of the patients had osteoarthritis. Our male/female ratio was 1:2 with 54 female (67 %) and 26 male (33 %) patients. The sex of the patients affects the cumulative rates of survival. Ranawat et al. report 20 % males and 80 % females. Male survivorship at 15 years was 83.3 %, and in female it was 95.3 %. However, he opines that there was 75 % female and less number of males, and hence, the survivorship analysis with respect to sex is less reliable [6]. Jain et al.
[7] report that female who undergone TKA in 1990–2000 is 62.6 %. Robert et al. [5] report that about two-thirds (65.4 %) of the patients were women in their study. Our study includes 40 patients belong to age 50–60 years, 36 patients from 61–70 years and 4 patients [70 years (Fig. 6). Ranawat et al. report the average age of 65 years in their study [6]. Ole kristensen et al. report the average age of 52 years in their study [8]. Normann Scott et al. report the average age of 66.9 years in their study [2, 7]. Robert et al. [5] report the average age of the patients at the time of surgery was 67.5 years. Forty of our patients underwent bilateral TKA, and the other 40 had unilateral TKA. In bilateral cases, 40 were of OA (50 %) and 40 were of RA (50 %). In unilateral cases, 32 were of OA (80 %) and 8 were of RA (20 %) (Fig. 7). Normann Scott [3] reported 23.75 % left knee, 27.5 % right knee and 48.75 % bilateral in his study. William. F Donaldson III reported 48.1 % right, 28 % left and 24 % bilateral [9]. In our 40 unilateral knees, 18 were male and 22 were female, and in 40 bilateral cases, 32 were female and 8 were male.
40 females males
30 20 10 0
Table 1 Indications—120 knees Indications
51-60
61-70
Rheumatoid arthritis
48
Osteoarthritis
72
indications
Fig. 6 Mean age in our study is 61.6 years
80
40
60
Osteoarthritis 60%
Fig. 5 Indications—120 knees [1]
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>70
No. of knees
Rheumatoid arthritis 40%
40
32
20
8
0
UNILATERAL
40
BI LATERAL
Rheumatoid arthritis
Fig. 7 Laterality indications—120 cases
Osteoarthritis
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Knee society score
100
Knee score: all the 120 knees had poor knee score of \60 preoperatively. Postoperatively, 100 knees had excellent score (80–100), 12 knees with good score (70–79), 4 knees with fair score (60–69) and 4 knees with poor score (\60). Preoperative mean score of 17.73 points was increased to 80.86 points postoperatively with p value of 0.0001, indicating significant improvement in ‘knee score’ following total knee replacement (Table 2; Fig. 8). In OA knees, the preoperative mean ‘knee score’ of 23.39 was increased to 86.27 postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement. In RA knees, preoperative mean ‘knee score’ of 9.25 was increased to 72.75 postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement (Fig. 9). Functional score In overall functional score of 80 patients, 76 had poor (\60) and 4 patients had fair functional score (60–69) preoperatively. Postoperatively, 64 patients had excellent (80–100), 12 had good (70–79), and 4 had poor score (\60) (Table 3; Fig. 10). The preoperative mean ‘functional score’ of 23.5 points was increased to 78.16 points postoperatively with p value
80 60 40
OA
20
RA
0 pre
post
Fig. 9 Knee score improvement versus indications
Table 3 Functional score 80 patients Functional score
Preoperative
Postoperative
80–100
Excellent
0
64
70–79
Good
0
12
60–69
Fair
4
0
\60
Poor
76
4
Functional Score
100 80 60 40
Table 2 Knee score—120 knees Knee score
20
Preoperative
Postoperative
80–100
Excellent
0
100
70–79
Good
0
12
60–69
Fair
0
4
\60
Poor
120
4
100
Knee Score
80 60 40 20
knee score 0 mean pre op
mean post op
Fig. 8 Mean preoperative and postoperative knee scores
functional score 0 pre op
post op
Fig. 10 Functional score (preoperative vs. postoperative)
of 0.0001, indicating significant improvement in functional score following total knee replacement. In osteoarthritic knee, preoperative mean ‘functional score’ of 32.78 points was increased to 84.44 points postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement. In RA knee, preoperative mean ‘functional score’ of 9.58 points was increased to 68.75 points postoperatively with p value of 0.0001, indicating significant improvement following total knee replacement. The result of our study was comparable with the study of 524 knees done by Elke et al. in 1995 in which the knee score rose in the OA group from a mean of 28–89 points after 1 year and in RA from 21 points to 90 points after 1 year Kim et al. [1] reported the mean preoperative hospital for special surgery knee score and knee society knee and functional scores were 42, 41 and 42, respectively, and postoperatively, they were 84, 90 and 84 points,
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respectively. The preoperative and postoperative total WOMAC scores were 73 and 84 points, respectively. Mechanical axis In 120 knees, the mechanical axis alignment of 96 knees (80 %) was in the inliers group (\±3), and in 24 knees (20 %), it was outside the normal range ([±3) and hence the outliers group (Table 4; Fig. 11). Comparison of outcome between inliers and outliers group with respect to mechanical axis alignment Our observation is supported by a study of Ba¨this et al. in 2004 which reported 80 patients having the postoperative axis of the limb exceeded 3 of varus/valgus deviation in their 22 % of the patients who were operated by conventional technique. Mielke et al. [11] and Petersen and Engh [12] observed in their independent studies that although an improvement in the mechanical alignment, the conventional implantation technique fails to restore the mechanical limb axis within the range of ±3 of the varus or valgus in up to 30 %. Our study is also in agreement with the results of Ek et al. published in 2008, wherein 50 patients underwent conventional primary TKA. In their conventional group, the mean mechanical axis (coronal) alignment was 0.67. There were 5 TKAs with a deviation of [5 and 31 TKAs within 3 of neutral.
Table 4 Mechanical axis—120 knees No.
Knee score
Functional score
Mean
Mean
SD
80.20
15.42
70
24.49
Inliers (\±3)
96
83.58
Outliers ([±3)
24
70 p = 0.026
SD 7.59 24.49
p = 0.209
The mean knee score was 83.58 points in ‘inliers’ and 70 points in ‘outliers’ group (p = 0.026), which is statistically significant. Rand and Coventry reported a 10-year survival rate in 90 % of the knees when the leg alignment was between 0 and 4 valgus, but it was 71 and 73 % when it was higher than the 4 valgus and varus alignment, respectively [14]. Jeffery et al. reported a 24 % rate of prosthetic loosening when the mechanical axis was over ±3 deviation. The acceptable range for the postoperative leg alignment in a TKA is still controversial [15]. However, a postoperative limb axis within a range of ±3 varus or valgus was found to be associated with a lower rate of aseptic component loosening in many studies. The mean functional score was 80.2 points in ‘inliers’ and 70 points in ‘outliers’ group (p = 0.2093), which is not significant statistically. We opine that the accuracy in mechanical axis alignment improves the anatomical and radiological alignment although it does not influence the functional outcome. This observation was supported by the study of Tew and Waugh et al. [16] in 1982, who previously suggested that the postoperative limb alignment was not the only factor for determining durability but factors other than alignment might also be more important for determining long-term survival and functional outcome following total knee arthroplasty. In a large retrospective clinical series of Parratte et al. [17] in 2010 reported that a postoperative mechanical axis of 0 ± 3 did not improve implant survival at the time of the fifteen-year follow-up for those 398 modern, cemented, condylar total knee replacements. Efforts to more consistently achieve mechanical axis alignment of 0 ± 3, as is currently done with contemporary computer navigation systems, seem unlikely to be rewarded with substantial improvements in implant survival following TKA as compared with that achieved when traditional total knee instruments are employed mindfully. Percentage of inliers in our study (80 %) is comparable to various previous studies as mentioned in Table 5. Tibio femoral axis
85
In 120 knees, the tibiofemoral axis of 112 knees (93.34 %) was inside inliers group (\±3), and in 8 knees (6.66 %), it was outside the normal range ([±3), which was considered as outliers group (Table 6; Fig. 12).
80 75 70
KS FS
65 60
inliers
outliers
Fig. 11 Inliers versus outliers group (mechanical axis)
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Comparison of outcome between inliers and outliers group with respect to tibiofemoral angle These results agree with those of Petersen and Engh [12] and Mahaluxmivala et al. [19] who found that up to 26 and
Eur J Orthop Surg Traumatol Table 5 Clinical studies of conventional manual surgical techniques placing limb alignment within ±3 of the mechanical axis of the lower extremity [18] References
Number
Percent of inliers
Haaker et al. (2005)
100
75
Sparmann et al. (2003)
120
78
Victor and Hoste (2004) Jenny et al. (2005)
50 235
74 74
Jenny and Boeri (2001)
30, 30
70
Kim et al. (2005)
69, 78
58
Perlick et al. (2004)
40
75
Seon and Song (2005)
47, 50
76
Bathis et al. [10]
160
78
Perlick et al. (2004)
50
72
Hart et al. (2003)
60
70
Anderson et al. (2005)
116, 51
Average
Component alignment Frontal plane Frontal femoral component angle in 116 knees (96.67 %) was in the inliers group (\90 ± 3) and 4 knees (3.33 %) was in outliers group ([90 ± 3). Mean FFC angle was 89.67 (Table 7; Fig. 13). Comparison of outcome between inliers and outliers group with respect to component alignment
84 74
Source Table 115-1, Clinical Studies That Compare Conventional Manual Surgical Techniques With Computer Navigation In Placing The Limb Alignment Within ±3 Degrees Of The Mechanical Axis Of The Lower Extremity. Chapter 115, Section 12, page no. 1204, 5th edition, Scot and Insal (http://www.expertconsult.com) Table 6 Tibiofemoral angle No.
Inliers (\±3) Outliers ([±3)
112 8
Knee score
Functional score
Mean
SD
Mean
SD
83.32
6.88
80.35
14.2
46.5
37.47
47.5
38.89
p = 0.0001
extremely statistically significant. The mean functional score was 80.35 points and 47.5 points for inliers and outliers group, respectively, (p = 0.0082), which is very statistically significant.
p = 0.0081
90 80 70 60 50 40 30 20 10 0
The mean knee score was 82.96 for inliers and 20 for outliers group with respect to FFC angle. The mean functional score was 80.17 for inliers and 20 for outliers group, which is statistically significant p = 0.0001. Coronal component angle of tibia in all 120 knees (100 %) was inside inliers group. The mean angle was 89.55. The mean knee score was 80.86, and the mean functional score was 78.16 with respect to coronal component angle of tibia. Statistical significance of this parameter in our study cannot be evaluated since there were no outliers. Ek et al. [13] studied 50 knees (conventional technique) in 2008 in which the mean tibial axis (coronal) alignment was 89.6 and the mean femoral axis (coronal) alignment was 88.9. Kim et al. [1], in their study of 100 knees in 2007, showed frontal femoral angle outliers ([±3) were only 9 % and frontal tibial angle outliers ([±3) were only 7 %. The study of Seon et al. in 2004 showed that the Table 7 Inliers versus outliers group (FFC angle)
KS FS inliers
Inliers (\90 ± 3) Outliers ([90 ± 3)
No
KS
116
82.96
80.17
20
20
4
FS
outliers
Fig. 12 Inliers versus outliers group (tibiofemoral angle)
25 % of their patients, respectively, had the deviation. Postoperative tibiofemoral angle exceeded 3 of varus/valgus deviation up to 18 % of the patients in the study of Kim et al. [1] in 2007. In Jenny and Boeri et al. [20] study, a tibiofemoral angle of ±3 varus/valgus was achieved in 78 % using a conventional technique. The mean knee score in our study was 83.32 points and 46.5 points for ‘inliers’ and ‘outliers’ group, respectively, (p = 0.0001) with respect to tibiofemoral angle, which is
90 80 70 60 50 40 30 20 10 0
KS FS
inliers
outliers
Fig. 13 Inliers versus outliers group (frontal femoral component angle)
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coronal component angle of femur had 17 (42.5 %) and 2 (5.6 %) outliers in navigation and conventional methods, respectively, and the mean value of this angle was 87.1 ± 2.4 and 88.7 ± 1.7, respectively. The coronal inclination of the tibial component on the anteroposterior radiographs showed no outliers. The mean value was 90.7 ± 0.8 [2]. Ba¨this et al. [10] study in 2004 had 69 (86 %) inliers in the FFC and 75 (94 %) inliers in the FTC alignment. Sagittal plane Sagittal femoral component angle in all 120 knees (100 %) was inside inliers group. The mean sagittal femoral component angle is 4.15 flexion (85.85). The mean knee score was 80.86 points, and the mean functional score was 78.16 points with respect to sagittal femoral component angle. Sagittal component angle of tibia in all 120 knees (100 %) was inside inliers group. The mean sagittal tibial component angle was 88.4 [19]. The mean knee score was 80.86 points, and the mean functional score was 78.16 points with respect to sagittal tibial component angle. Ek et al. [13] studied 50 knees (conventional technique) in 2008 in which the mean tibial slopes (sagittal alignments) were 85.8 (the optimal being 87) and the mean femoral slopes (sagittal alignments) were 87.8 (1.2) of flexion). Kim et al. [1] study of 100 knees in 2007 showed that sagittal femoral angle outliers ([±3) were only 33 % and sagittal tibial angle outliers ([±3) were only 9 %. The study of Seon et al. [2] in 2004 showed that the sagittal component angle of femur had no outliers. The coronal inclination of the tibial component on the anteroposterior radiographs showed no outliers. And the outliers in the inclination of the tibial component were found in 16 knees (40 %). The mean value was 90. 09. Ba¨this et al. [10] study in 2004 reported that the mean lateral tibial component angle was 87 ± 4.5 in conventional group. Rotational plane Rotational femoral component angle in all 120 knees (100 %) was inside inliers group. The mean rotational femoral component angle is 0.92 of external rotation. The mean knee score was 80.86 points, and the mean functional score was 78.16 points. Rotational component angle of tibia in all 120 knees (100 %) was inside inliers group. The mean rotational tibial component angle is degree 0.98. The mean knee score was 80.86 points, and the mean functional score was 78.16 points. Harman [21] study in 2012 showed that there were 16 (24 %) TKR with isolated malrotation of the tibial component and 4 (6 %) TKR with isolated malrotation of the femoral component. Kim et al. [1] study of 100 knees in
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Table 8 Summary of the results Determinants
Preoperative
Postoperative
Mean
Range
Mean
9.64
Range
1
Tibiofemoral angle ()
2.1–27
2.83
2
Mechanical axis ()
10.34
3.6–23.8
1.83
0.2–23.7 0–27.6
3
Knee score
17.73
2–40
80.86
20–94
4
Functional score
23.5
0–45
78.1
20–100
5
Femoral component ()
89.6
87–95.1
6
Tibial component ()
89.55
82–92
7 8
Femoral component () Tibial component ()
4.15 88.42
2–6.7 85.9–90
9
Femoral component ()
0.92
0.02–1.84
10
Tibial component ()
0.98
0.11–1.94
2007 showed that femoral rotation angle outliers ([±3) were only 15 % and tibial rotation angle ([±3) were found in up to 49 % of patients. Berger and coworkers in 1988 noted that normal rotation of the femoral condyles is 0.3 ± 1.2 0 of internal in comparison with the surgical epicondylar axis [22] (Table 8).
Conclusion Total knee arthroplasty is a well-proven procedure. Although it usually produces excellent results, proper axial alignment is of paramount importance for the longevity of the implant. Even minor malpositioning can lead to early loosening, increased polyethylene wear and poor function. Malalignment of the components in any anatomical plane can cause major complications. Malrotation of either the femoral or the tibial component will critically affect patellar tracking and can lead to patellar subluxation or dislocation. We opine that the accuracy in mechanical axis alignment improves the anatomical and radiological alignment, although it does not influence the functional outcome. Our view is strengthened by the fact that the other determinants like component alignment which influences the functional outcome have been within the normal limit, thereby giving the exclusivity to the mechanical axis in our study. Nevertheless, aligning the mechanical axis, tibiofemoral angle within (0 ± 3) postoperatively significantly produces excellent result, and the components alignment in all the three planes is equally important and decisive for final outcome. Good results with respect to alignment can be achieved even without assistance of navigational technique as shown in our study.
Conflict of interest
None.
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12. Petersen TL, Engh GA (1988) Radiographic assessment of knee alignment after total knee arthroplasty. J Arthroplasty 3:67–72 13. Ek ETH, Dowsey MM, Tse LF (2008) J Orthop Surg 16(2):192–196 14. Rand JA, Coventry MB (1988) Ten-year evaluation of geometric total knee arthroplasty. Clin Orthop Relat Res 232:168–173 15. Jeffery RS, Morris RW, Denham RA (1991) Coronal alignment after total knee replacement. J Bone Joint Surg Br 73:709–714 16. Tew M, Waugh W (1982) Estimating the survival time of knee replacement. J Bone Joint Surg Br 64:579–582 17. Parratte S, Pagnano MW (2010) Effect of postoperative mechanical axis alignment on the fifteen-year survival of modern cemented total knee replacements. J Bone Joint Surg Am 92:2143–2149 18. Abdel Fatah EE, Mahfouz MR, Merkl B et al (2013) Threedimensional morphology of the knee biomechanics. Insall and scott surgery of knee 5th edition Mosby Elsevier.12 19. Mahaluxmivala J, Bankes MJ, Nicolai P, Aldam CJH, Allen PW (2001) The effect of surgeon experience on component positioning in 673 press fit condylar posterior cruciate-sacrificing total knee arthroplasties. J Arthroplasty 16:635–640 20. Jenny JY, Boeri C (2001) Navigated implantation of total knee endoprosthesis: a comparative study with conventional instrument. Z Orthop Ihre Grenzgeb 139:117 21. Harman MK, Banks SA (2012) Prosthesis alignment affects axial rotation motion after total knee replacement: a prospective in vivo study combining computed tomography and fluoroscopic evaluations Harman. BMC Musculoskelet Disord 13:206 22. Berger RA, Crossett LS, Jacobs JJ, Rubash HE (1998) Malrotation causing patellofemoral complications after total knee arthroplasty. Clin Orthop Relat Res 356:144–153
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