The Journal of Arthroplasty 30 (2015) 126–129
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The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Alteration of Hindfoot Alignment After Total Knee Arthroplasty Using a Novel Hindfoot Alignment View Yusuke Hara, MD, Kazuya Ikoma, MD, PhD , Yuji Arai, MD, PhD, Suzuyo Ohashi, MD, PhD, Masahiro Maki, MD, PhD, Toshikazu Kubo, MD, PhD Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
a r t i c l e
i n f o
Article history: Received 10 March 2014 Accepted 21 July 2014 Keywords: hindfoot TKA coronal alignment hindfoot view X-ray
a b s t r a c t This study examined the coronal alignment of the hindfoot in varus osteoarthritis of the knee before and after total knee arthroplasty (TKA) in 100 legs using a novel imaging method. We categorized the preoperative hindfoot alignment into varus (30 legs) and valgus (70 legs) groups; imaging of the hindfoot was conducted preoperatively and postoperatively, and the varus–valgus angle (VVA) was measured as the hindfoot alignment. The femorotibial angle improved significantly after TKA. We found that the VVA improved significantly after TKA in the hindfoot valgus group (P b 0.001), but not in the varus group (P = 0.554), and we speculate that the hindfoot alignment in the valgus group improved as a result of a residual compensatory capacity in the hindfoot. © 2014 Elsevier Inc. All rights reserved.
The femorotibial angle (FTA) and the line connecting the femoral head to the center of the ankle joint, as determined by full-length radiographs of the lower extremities in a standing position, are used to evaluate the coronal alignment of the lower extremities [1,2]. However, in the lower extremities, motions in the coronal plane involve the participation of not only the hip joint but also the subtalar joint. Therefore, it is important that an assessment of lower limb coronal alignment also includes the hindfoot. Malalignment of the hindfoot is closely associated with deformities of the adjacent forefoot, midfoot, ankle joint, and knee joint, truly emphasizing the importance of evaluating hindfoot alignment. Although various methods can be used to evaluate hindfoot alignment, assessments using plain radiographs are generally the most convenient for clinicians. Accordingly, the Cobey method and related applications are frequently used for the assessment of hindfoot alignment [3–6]. However, owing to the spiral form of the posterior articular surface of the subtalar joint, plain radiographs have a limited capacity for depicting the articular surface [7]. Chandler and Moskal previously reported that deformities in the knee joint and deformities of the foot are related to each other, and that there is a correlation between valgus hindfoot and varus osteoarthritis (OA) (varus deformities) of the knee joint [8]. Moreover, total knee arthroplasty (TKA) has been demonstrated to correct lower extremity alignment (mainly at the knee joint) and is
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.07.026. Reprint requests: Kazuya Ikoma, MD, PhD, Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural, University of Medicine, 465 Kajiicho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, 6028566, Japan. http://dx.doi.org/10.1016/j.arth.2014.07.026 0883-5403/© 2014 Elsevier Inc. All rights reserved.
believed to affect the alignment of the adjacent hindfoot [8,9]; and, accordingly, Mullaji and Shetty reported that preoperative hindfoot alignment showed improvement after TKA [9]. However, the assessment method used in their study was based on the amount of deviation from the center of the knee joint and the straight-line linking of 2 points, namely the center of the femoral head and the point where the calcaneus touches the ground. Because the valgus of the hindfoot was not directly measured, this method is considered insufficient for the assessment of alignment. We have recently developed a new radiological evaluation method for the assessment of the coronal alignment of the hindfoot in the presence of a load based on the inclination of the subtalar joint [10]. This novel method allows for a clear visualization of the posterior middle articular surfaces of the subtalar and talocrural joints by performing plantar flexion of the midfoot and forefoot. Additionally, the inclination of the subtalar joint is determined by the 2 points that form the calcaneus, rather than by the articular surface. Thus, this inclination is considered useful in the assessment of the coronal alignment of the hindfoot. Varus deformities due to diseases of the knee joint are believed to be associated with valgus hindfoot. However, in some cases, the hindfoot can be in varus position before surgery already. We have experienced cases of hindfoot pain newly developing after TKA, and consider that postoperative coronal alignment of the hindfoot was involved in this pain. The association between deformities of the knee joint and the coronal alignment of the hindfoot has not yet been fully explored [11], and, therefore, the purpose of this study was to examine the relationship between hindfoot alignment and varus OA of the knee by measuring preoperative hindfoot alignment in cases of varus OA of the knee using our novel method for imaging the hindfoot.
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A secondary objective of this study was to examine the effects of TKA on hindfoot alignment by classifying the preoperative coronal alignment of the hindfoot into varus and valgus groups and by examining the postoperative changes in coronal alignment in the 2 groups. Materials and Methods Subjects The study was conducted on 100 legs of 82 patients who underwent TKA in our hospital between February 2007 and November 2011 for varus OA of the knee. The mean age at the time of surgery was 74.3 years (range, 58–87 years). Male participants accounted for 14 legs (mean age: 76.9 years), and female participants accounted for 86 legs (mean age: 73.6 years); right legs accounted for 49 cases, and left legs accounted for 51 cases. Patients with valgus OA of the knee, rheumatoid arthritis (RA), and post-traumatic OA, and patients who had previously been subjected to surgery on the knee joint on the same side, such as high tibial osteotomy, were excluded from our analysis. The study was reviewed and conducted in accordance with the ethical standards of our institution. The study protocol was approved by the institutional review board, and, after explaining the study in writing, we obtained written consent from all participants. Surgical method In all cases, TKA was the primary surgery, and was performed by the same surgeon. A midline longitudinal skin incision was made, and expansion was performed using a medial parapatellar or midvastus approach. In all cases, the femoral, tibial, and patellar components were cemented using the following PS-type implants: the Zimmer Nexgen LPS-FLEX mobile bearing (n = 53; Zimmer, Warsaw, USA), the Zimmer Nexgen LPS-FLEX fixed bearing (n = 10; Zimmer, Warsaw, USA), the Stryker Scorpio NRG (n = 31; Stryker Howmedica Osteonics, Mahwah, USA), and the Biomet Vanguard total knee system (n = 2; Biomet, Warsaw, USA) using the measured resection method. Radiological evaluations Full-length radiographs of the entire lower extremity in a standing position and imaging of the hindfoot were performed preoperatively and 3 weeks postoperatively [10]. To study the coronal alignment of the lower limb, the FTA was measured using full-length radiographs of the lower extremity in a standing position. The method used for the imaging of the hindfoot was as follows: the hindfoot was laid flat; an auxiliary tabletop for imaging was used to put the forefoot in 30-degree flexion with the metatarsal region; the participant was instructed to stand on both feet on the auxiliary tabletop for imaging; and an X-ray film was placed vertically on the side of the toes. The direction of the incident X-ray was inclined by 5° from the horizontal plane to the caudal side; imaging of the hindfeet was conducted from behind on both sides. The object distance was 120 cm. Hindfoot alignment was evaluated by measuring the angle between the long axis of the tibia and the line connecting the superior margin of the sustentaculum tali, which was determined from the imaging of the hindfoot to the lateral extremity of the calcaneus at the posterior surface of the talocalcaneal joint (varus–valgus angle, VVA) (Fig. 1). Two board-certified orthopedic surgeons performed the measurements using ImageJ software (NIH). Based on previous studies [10], an average value of 76° was defined as the cut-off value, and the preoperative hindfoot alignments were classified as either hindfoot valgus (VVA N 76°) or hindfoot varus (VVA ≤ 76°); changes in the hindfeet before and after surgery were measured.
Fig. 1. New hindfoot view. (A, B) Line a shows the long axis of tibia. Point b shows the lateral extremity of the calcaneus at the posterior surface of the talocalcaneal joint. Point c shows the superior margin of the sustentaculum tali. Angle d shows varus– valgus angle, VVA.
Statistics Statistical analyses of the changes in FTA and VVA after surgery were conducted using two-tailed paired Student's t-tests. JMP10 (SAS Institute Inc., Cary, NC USA) was used for all analyses, and significant differences were defined as P b 0.05. Results The overall FTA improved from 186.7 ± 4.6° pre-TKA to 174.4 ± 3.1° post-TKA (P b 0.001). The FTA improved in all patients, indicating good correction of the knee joint varus deformities. The mean VVAs were 78.8 ± 5.3° before surgery and 76.8 ± 4.2° after surgery (P b 0.001). Preoperatively, the hindfoot valgus group accounted for 70 legs (35 right legs, 35 left legs; male participants: 10 legs, female participants: 60 legs; mean age: 73.6 ± 7.5 years) and the hindfoot varus group accounted for 30 legs (15 right legs, 15 left legs; male participants: 4 legs, female participants: 26 legs; mean age: 75.0 ± 6.6 years) (Table 1). In the valgus group, the FTA improved significantly from 186.9 ± 4.8° pre-surgery to 174.1 ± 3.1° post-surgery (P b 0.001). In the varus group, the FTA improved from 186.1 ± 4.2° preoperatively to 175.0 ± 2.9° postoperatively (P b 0.001). No significant differences in
Table 1 Subject's Data.
Age (years) Gender FTA (°)
Male Female Preope Postope
Value: Mean ± SD. FTA: femolotibial angle.
Valgus Group (n = 70)
Varus Group (n = 30)
P Value
73.6 ± 7.5 10 60 186.9 ± 4.8 174.1 ± 3.1
75.0 ± 6.6 4 26 186.1 ± 4.2 175.0 ± 2.9
0.33
0.38 0.16
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Y. Hara et al. / The Journal of Arthroplasty 30 (2015) 126–129
Table 2 FTA Before and After TKA.
Valgus group Varus group
Table 3 VVA Before and After TKA. Preope (°)
Postope (°)
P Value
186.9 ± 4.8 186.1 ± 4.2
174.1 ± 3.1 175.0 ± 2.9
b0.001 b0.001
Valgus group Varus group
Preope (°)
Postope (°)
P Value
81.6 ± 3.0 72.3 ± 3.5
78.5 ± 2.7 72.7 ± 4.2
b0.001 0.55
Value: mean ± SD. FTA: femorotibial angle. TKA: total knee arthroplasty.
Value: mean ± SD. VVA: varus–valgus angle. TKA: total knee arthroplasty.
preoperative or postoperative FTAs were noted between the 2 groups (Tables 1 and 2). In the valgus group, the VVA improved significantly from 81.6 ± 3.0° preoperatively to 78.5 ± 2.7° post-surgery (P b 0.001). In the varus group, the VVA showed no change (72.3 ± 3.5° preoperatively and 72.7 ± 4.2° postoperatively; P = 0.554) (Table 3). The valgus and varus deformities were improved in 65 (92.9%) and 11 cases (36.7%), respectively.
In this study, we found that in patients with varus OA of the knee, hindfoot coronal alignments showed not only valgus deformities but also varus deformities in 30% of cases. We hypothesize that the hindfoot valgus alignments in patients with varus OA of the knee occur as a result of compensation for the knee joint deformity by the hindfoot. This situation likely occurs because the subtalar joint, which is capable of moving in the coronal plane, is the only joint that allows for compensation for the changes in the loading axis of the lower limb associated with varus OA of the knee. Hindfoot varus is believed to occur as a result of loss of this compensatory capacity in the hindfoot. Based on the FTA, we confirmed an improvement in lower limb alignment, mainly in the knee joint, after TKA. In addition, hindfoot alignment after TKA was confirmed on the basis of the VVA. The VVA improved significantly after TKA in the hindfoot valgus group, which was consistent with the findings of Mullaji and Shetty and Desai et al [9,11]. The VVA improvement likely resulted from improvements in hindfoot alignment due to the above-mentioned presence of a residual compensatory capacity in the hindfoot. Conversely, the hindfoot alignments revealed no postoperative improvements in the varus group, which we hypothesize might be due to the loss of compensatory capacity in this group. Generally, a valgus foot causes parallel alignment of the midtarsal axes which permits the foot to be flexible and to adapt to different surfaces. A varus foot has subtalar supination which influences the alignment of the two axes of the midtarsal joint, causing them to become non-parallel. This nonparallel alignment of the midtarsal axes permits the foot to become rigid to support the body's weight and to provide rigid lever for propulsion. This biomechanical character of tarsal bones was contributed to a less improvement of varus hindfoot group. There are a number of limitations associated with this study. First, no comparison was made with commonly used techniques for hindfoot radiography, such as the Cobey method. We consider that the varus–valgus angle is more accurate than the deviation for the evaluation of coronal alignment. Because it is difficult to evaluate the angle with the Cobey method, we instead used our novel measurement method in this study. However, comparison between the Cobey method and our method is important, and this needs to be examined in the future. Second, regarding the imaging method used, images of both sides were taken simultaneously, and the load may have been unequal in some cases. It is preferable to take images in a unilateral standing position; however, in this study, to ensure patient safety during the imaging procedure, this was not performed. There was a possibility that load was not enough at the forefoot by reason that forefoot was planterflexed. By contrast, we believe that load was enough at the hindfoot. Lastly, the method that we developed for the evaluation of hindfoot varus–valgus included varus–valgus of the talocrural joint. The talocrural joint has an ankle mortise structure with strong varus– valgus stability. However, in patients with post-injury ankle ligament instabilities and in ankle joints with advanced arthropathic changes, varus or valgus alignment of the talocrural joint may impact the VVA. The hindfoot imaging method performed in this study allowed for assessment of the talocrural joint, and none of the participants had findings suggestive of ankle joint OA. In conclusion, in varus OA of the knee, the hindfoot varus group exhibited no postoperative changes in the coronal alignment of the
Discussion Previous reports have found that although the FTA is frequently used to determine coronal alignment in the presence of a load, it is important that the evaluation of lower limb coronal alignment include that of the hindfoot [8,9,12–14]. Plain radiographs are easy and convenient for clinicians to use to assess alignment. To assess lower limb coronal alignment including the hindfoot, Mullaji and Shetty conducted evaluations measuring the amount of deviation from the center of the knee joint and the straight line joining 2 points consisting of the center of the femoral head and the point where the calcaneus touches the ground [9]. Similarly, Guichet et al and Lee et al also examined lower extremity alignment including the hindfoot and reported that this method was superior to the conventional methods for evaluating lower extremity function and axis [13,14]. To determine the point where the calcaneus touched the ground, Mullaji and Shetty conducted assessments using the wire technique [9], and Guichet et al used a similar method in their study [13]. In their case, the wire technique was used instead of the conventional Cobey method, in which the midpoint of the calcaneus remains unclear due to an overlapping of the subtalar joint and the calcaneus with the midfoot on hindfoot imaging. Moreover, in the upright position, the soft tissue of the foot comes in contact with the ground as a surface, not as a point [3,4]. However, these evaluations based on the amount of deviation require that the height of the foot is taken into consideration in addition to the lengths of the femur and tibia and might be insufficient for use in the assessment of hindfoot alignment [6]. In the hindfoot imaging method developed by our group, images are taken while the hindfoot is in flexion with the midfoot, resulting in reduced overlap of the midfoot and hindfoot and allowing full assessment of the subtalar joint [10]. In this assessment of hindfoot alignment, particular focus is given to the subtalar joint, and problematic issues associated with conventional imaging methods, including the fact that the rotation of the lower extremity affects the depicted image of the subtalar joint, are avoided [14]. In this novel imaging method, points that are less influenced by rotation are confirmed by 3D computed tomography and are used as indicators. Therefore, the influence of rotation is estimated to be small. Previous studies have demonstrated associations between genu varum due to RA of the knee and hindfoot valgus deformities and between genu valgum due to RA of the knee and hindfoot varus deformities [15,16]. In addition, Meding et al reported that, as a result of posterior tibial tendon dysfunction (PTTD), hindfoot valgus can cause implant collapse after TKA surgery [12]. Keenan et al also reported similar findings in their study of patients with RA [17], and concluded that the alignment of the hindfoot is deeply involved with and exerts a strong influence on the knee joint.
Y. Hara et al. / The Journal of Arthroplasty 30 (2015) 126–129
hindfoot after TKA, whereas in the hindfoot valgus group, the coronal alignment of the hindfoot was significantly improved. The improvement in hindfoot alignment in the valgus group as soon as 3 weeks after surgery was hypothesized to be due to a residual compensatory capacity in the hindfoot, whereas the unchanged hindfoot alignment in the varus group was hypothesized to be due to a loss of this residual compensatory capacity. In the future, long-term observations will be needed to examine how hindfoot alignment changes over time and to assess its association with clinical symptoms, such as hindfoot pain. Acknowledgments None. References 1. Deakin AH, Basanagoudar PL, Nunag P, et al. Natural distribution of the femoral mechanical–anatomical angle in an osteoarthritic population and its relevance to total knee arthroplasty. Knee 2012;19:120. 2. Nunley RM, Ellison BS, Zhu J, et al. Do patient-specific guides improve coronal alignment in total knee arthroplasty? Clin Orthop Relat Res 2012;470:895. 3. Cobey JC. Posterior roentgenogram of the foot. Clin Orthop Relat Res 1976;118:202. 4. Cobey JC, Sella E. Standardizing methods of measurement of foot shape by including the effects of subtalar rotation. Foot Ankle 1981;2:30. 5. Saltzman CL, el-Khoury GY. The hindfoot alignment view. Foot Ankle Int 1995;16:572.
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6. Johnson JE, Lamdan R, Granberry WF, et al. Hindfoot coronal alignment: a modified radiographic method. Foot Ankle Int 1999;20:818. 7. Kelikian AS, Sarrafian SK. Sarrafian’s anatomy of the foot and ankle. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011 541. 8. Chandler JT, Moskal JT. Evaluation of knee and hindfoot alignment before and after total knee arthroplasty: a prospective analysis. J Arthroplasty 2004;19:211. 9. Mullaji A, Shetty GM. Persistent hindfoot valgus causes lateral deviation of weightbearing axis after total knee arthroplasty. Clin Orthop Relat Res 2011; 469:1154. 10. Ikoma K, Noguchi M, Nagasawa K, et al. A new radiographic view of the hindfoot. J Foot Ankle Res 2013;6:48. 11. Desai SS, Shetty GM, Song HR, et al. Effect of foot deformity on conventional mechanical axis deviation and ground mechanical axis deviation during single leg stance and two leg stance in genu varum. Knee 2007;14:452. 12. Meding JB, Keating EM, Ritter AM, et al. The planovalgus foot: a harbinger of failure of posterior cruciate-retaining total knee replacement. J Bone Joint Surg Am 2005; 87(Suppl. 2):59. 13. Guichet JM, Javed A, Russell J, et al. Effect of the foot on the mechanical alignment of the lower limbs. Clin Orthop Relat Res 2003;415:193. 14. Lee ST, Song HR, Mahajan R, et al. Development of genu varum in achondroplasia: relation to fibular overgrowth. J Bone Joint Surg (Br) 2007;89:57. 15. Bouysset M, Hugueny P. The rheumatoid foot: pathomechanics clinical and radiological features. Therapeutic conditions. , Foot and ankle in rheumatoid arthritisParis, France: Springer Verlag; 2006. p. 9. 16. Souter WA. Surgical strategy in surgery of the lower limb in rheumatoid arthritis. Foot and ankle in rheumatoid arthritis. Paris, France: Springer Verlag; 2006. p. 229. 17. Keenan MA, Peabody T, Gronley JK, et al. Valgus deformities of the feet and characteristics of gait in patients who have rheumatoid arthritis. J Bone Joint Surg Am 1991;73:237.
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Alteration of Hindfoot Alignment After Total Knee Arthroplasty Using a Novel Hindfoot Alignment View Yusuke Hara, MD, Kazuya Ikoma, MD, PhD , Yuji Arai, MD, PhD, Suzuyo Ohashi, MD, PhD, Masahiro Maki, MD, PhD, Toshikazu Kubo, MD, PhD Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
a r t i c l e
i n f o
Article history: Received 10 March 2014 Accepted 21 July 2014 Keywords: hindfoot TKA coronal alignment hindfoot view X-ray
a b s t r a c t This study examined the coronal alignment of the hindfoot in varus osteoarthritis of the knee before and after total knee arthroplasty (TKA) in 100 legs using a novel imaging method. We categorized the preoperative hindfoot alignment into varus (30 legs) and valgus (70 legs) groups; imaging of the hindfoot was conducted preoperatively and postoperatively, and the varus–valgus angle (VVA) was measured as the hindfoot alignment. The femorotibial angle improved significantly after TKA. We found that the VVA improved significantly after TKA in the hindfoot valgus group (P b 0.001), but not in the varus group (P = 0.554), and we speculate that the hindfoot alignment in the valgus group improved as a result of a residual compensatory capacity in the hindfoot. © 2014 Elsevier Inc. All rights reserved.
The femorotibial angle (FTA) and the line connecting the femoral head to the center of the ankle joint, as determined by full-length radiographs of the lower extremities in a standing position, are used to evaluate the coronal alignment of the lower extremities [1,2]. However, in the lower extremities, motions in the coronal plane involve the participation of not only the hip joint but also the subtalar joint. Therefore, it is important that an assessment of lower limb coronal alignment also includes the hindfoot. Malalignment of the hindfoot is closely associated with deformities of the adjacent forefoot, midfoot, ankle joint, and knee joint, truly emphasizing the importance of evaluating hindfoot alignment. Although various methods can be used to evaluate hindfoot alignment, assessments using plain radiographs are generally the most convenient for clinicians. Accordingly, the Cobey method and related applications are frequently used for the assessment of hindfoot alignment [3–6]. However, owing to the spiral form of the posterior articular surface of the subtalar joint, plain radiographs have a limited capacity for depicting the articular surface [7]. Chandler and Moskal previously reported that deformities in the knee joint and deformities of the foot are related to each other, and that there is a correlation between valgus hindfoot and varus osteoarthritis (OA) (varus deformities) of the knee joint [8]. Moreover, total knee arthroplasty (TKA) has been demonstrated to correct lower extremity alignment (mainly at the knee joint) and is
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.07.026. Reprint requests: Kazuya Ikoma, MD, PhD, Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural, University of Medicine, 465 Kajiicho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, 6028566, Japan. http://dx.doi.org/10.1016/j.arth.2014.07.026 0883-5403/© 2014 Elsevier Inc. All rights reserved.
believed to affect the alignment of the adjacent hindfoot [8,9]; and, accordingly, Mullaji and Shetty reported that preoperative hindfoot alignment showed improvement after TKA [9]. However, the assessment method used in their study was based on the amount of deviation from the center of the knee joint and the straight-line linking of 2 points, namely the center of the femoral head and the point where the calcaneus touches the ground. Because the valgus of the hindfoot was not directly measured, this method is considered insufficient for the assessment of alignment. We have recently developed a new radiological evaluation method for the assessment of the coronal alignment of the hindfoot in the presence of a load based on the inclination of the subtalar joint [10]. This novel method allows for a clear visualization of the posterior middle articular surfaces of the subtalar and talocrural joints by performing plantar flexion of the midfoot and forefoot. Additionally, the inclination of the subtalar joint is determined by the 2 points that form the calcaneus, rather than by the articular surface. Thus, this inclination is considered useful in the assessment of the coronal alignment of the hindfoot. Varus deformities due to diseases of the knee joint are believed to be associated with valgus hindfoot. However, in some cases, the hindfoot can be in varus position before surgery already. We have experienced cases of hindfoot pain newly developing after TKA, and consider that postoperative coronal alignment of the hindfoot was involved in this pain. The association between deformities of the knee joint and the coronal alignment of the hindfoot has not yet been fully explored [11], and, therefore, the purpose of this study was to examine the relationship between hindfoot alignment and varus OA of the knee by measuring preoperative hindfoot alignment in cases of varus OA of the knee using our novel method for imaging the hindfoot.
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A secondary objective of this study was to examine the effects of TKA on hindfoot alignment by classifying the preoperative coronal alignment of the hindfoot into varus and valgus groups and by examining the postoperative changes in coronal alignment in the 2 groups. Materials and Methods Subjects The study was conducted on 100 legs of 82 patients who underwent TKA in our hospital between February 2007 and November 2011 for varus OA of the knee. The mean age at the time of surgery was 74.3 years (range, 58–87 years). Male participants accounted for 14 legs (mean age: 76.9 years), and female participants accounted for 86 legs (mean age: 73.6 years); right legs accounted for 49 cases, and left legs accounted for 51 cases. Patients with valgus OA of the knee, rheumatoid arthritis (RA), and post-traumatic OA, and patients who had previously been subjected to surgery on the knee joint on the same side, such as high tibial osteotomy, were excluded from our analysis. The study was reviewed and conducted in accordance with the ethical standards of our institution. The study protocol was approved by the institutional review board, and, after explaining the study in writing, we obtained written consent from all participants. Surgical method In all cases, TKA was the primary surgery, and was performed by the same surgeon. A midline longitudinal skin incision was made, and expansion was performed using a medial parapatellar or midvastus approach. In all cases, the femoral, tibial, and patellar components were cemented using the following PS-type implants: the Zimmer Nexgen LPS-FLEX mobile bearing (n = 53; Zimmer, Warsaw, USA), the Zimmer Nexgen LPS-FLEX fixed bearing (n = 10; Zimmer, Warsaw, USA), the Stryker Scorpio NRG (n = 31; Stryker Howmedica Osteonics, Mahwah, USA), and the Biomet Vanguard total knee system (n = 2; Biomet, Warsaw, USA) using the measured resection method. Radiological evaluations Full-length radiographs of the entire lower extremity in a standing position and imaging of the hindfoot were performed preoperatively and 3 weeks postoperatively [10]. To study the coronal alignment of the lower limb, the FTA was measured using full-length radiographs of the lower extremity in a standing position. The method used for the imaging of the hindfoot was as follows: the hindfoot was laid flat; an auxiliary tabletop for imaging was used to put the forefoot in 30-degree flexion with the metatarsal region; the participant was instructed to stand on both feet on the auxiliary tabletop for imaging; and an X-ray film was placed vertically on the side of the toes. The direction of the incident X-ray was inclined by 5° from the horizontal plane to the caudal side; imaging of the hindfeet was conducted from behind on both sides. The object distance was 120 cm. Hindfoot alignment was evaluated by measuring the angle between the long axis of the tibia and the line connecting the superior margin of the sustentaculum tali, which was determined from the imaging of the hindfoot to the lateral extremity of the calcaneus at the posterior surface of the talocalcaneal joint (varus–valgus angle, VVA) (Fig. 1). Two board-certified orthopedic surgeons performed the measurements using ImageJ software (NIH). Based on previous studies [10], an average value of 76° was defined as the cut-off value, and the preoperative hindfoot alignments were classified as either hindfoot valgus (VVA N 76°) or hindfoot varus (VVA ≤ 76°); changes in the hindfeet before and after surgery were measured.
Fig. 1. New hindfoot view. (A, B) Line a shows the long axis of tibia. Point b shows the lateral extremity of the calcaneus at the posterior surface of the talocalcaneal joint. Point c shows the superior margin of the sustentaculum tali. Angle d shows varus– valgus angle, VVA.
Statistics Statistical analyses of the changes in FTA and VVA after surgery were conducted using two-tailed paired Student's t-tests. JMP10 (SAS Institute Inc., Cary, NC USA) was used for all analyses, and significant differences were defined as P b 0.05. Results The overall FTA improved from 186.7 ± 4.6° pre-TKA to 174.4 ± 3.1° post-TKA (P b 0.001). The FTA improved in all patients, indicating good correction of the knee joint varus deformities. The mean VVAs were 78.8 ± 5.3° before surgery and 76.8 ± 4.2° after surgery (P b 0.001). Preoperatively, the hindfoot valgus group accounted for 70 legs (35 right legs, 35 left legs; male participants: 10 legs, female participants: 60 legs; mean age: 73.6 ± 7.5 years) and the hindfoot varus group accounted for 30 legs (15 right legs, 15 left legs; male participants: 4 legs, female participants: 26 legs; mean age: 75.0 ± 6.6 years) (Table 1). In the valgus group, the FTA improved significantly from 186.9 ± 4.8° pre-surgery to 174.1 ± 3.1° post-surgery (P b 0.001). In the varus group, the FTA improved from 186.1 ± 4.2° preoperatively to 175.0 ± 2.9° postoperatively (P b 0.001). No significant differences in
Table 1 Subject's Data.
Age (years) Gender FTA (°)
Male Female Preope Postope
Value: Mean ± SD. FTA: femolotibial angle.
Valgus Group (n = 70)
Varus Group (n = 30)
P Value
73.6 ± 7.5 10 60 186.9 ± 4.8 174.1 ± 3.1
75.0 ± 6.6 4 26 186.1 ± 4.2 175.0 ± 2.9
0.33
0.38 0.16
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Y. Hara et al. / The Journal of Arthroplasty 30 (2015) 126–129
Table 2 FTA Before and After TKA.
Valgus group Varus group
Table 3 VVA Before and After TKA. Preope (°)
Postope (°)
P Value
186.9 ± 4.8 186.1 ± 4.2
174.1 ± 3.1 175.0 ± 2.9
b0.001 b0.001
Valgus group Varus group
Preope (°)
Postope (°)
P Value
81.6 ± 3.0 72.3 ± 3.5
78.5 ± 2.7 72.7 ± 4.2
b0.001 0.55
Value: mean ± SD. FTA: femorotibial angle. TKA: total knee arthroplasty.
Value: mean ± SD. VVA: varus–valgus angle. TKA: total knee arthroplasty.
preoperative or postoperative FTAs were noted between the 2 groups (Tables 1 and 2). In the valgus group, the VVA improved significantly from 81.6 ± 3.0° preoperatively to 78.5 ± 2.7° post-surgery (P b 0.001). In the varus group, the VVA showed no change (72.3 ± 3.5° preoperatively and 72.7 ± 4.2° postoperatively; P = 0.554) (Table 3). The valgus and varus deformities were improved in 65 (92.9%) and 11 cases (36.7%), respectively.
In this study, we found that in patients with varus OA of the knee, hindfoot coronal alignments showed not only valgus deformities but also varus deformities in 30% of cases. We hypothesize that the hindfoot valgus alignments in patients with varus OA of the knee occur as a result of compensation for the knee joint deformity by the hindfoot. This situation likely occurs because the subtalar joint, which is capable of moving in the coronal plane, is the only joint that allows for compensation for the changes in the loading axis of the lower limb associated with varus OA of the knee. Hindfoot varus is believed to occur as a result of loss of this compensatory capacity in the hindfoot. Based on the FTA, we confirmed an improvement in lower limb alignment, mainly in the knee joint, after TKA. In addition, hindfoot alignment after TKA was confirmed on the basis of the VVA. The VVA improved significantly after TKA in the hindfoot valgus group, which was consistent with the findings of Mullaji and Shetty and Desai et al [9,11]. The VVA improvement likely resulted from improvements in hindfoot alignment due to the above-mentioned presence of a residual compensatory capacity in the hindfoot. Conversely, the hindfoot alignments revealed no postoperative improvements in the varus group, which we hypothesize might be due to the loss of compensatory capacity in this group. Generally, a valgus foot causes parallel alignment of the midtarsal axes which permits the foot to be flexible and to adapt to different surfaces. A varus foot has subtalar supination which influences the alignment of the two axes of the midtarsal joint, causing them to become non-parallel. This nonparallel alignment of the midtarsal axes permits the foot to become rigid to support the body's weight and to provide rigid lever for propulsion. This biomechanical character of tarsal bones was contributed to a less improvement of varus hindfoot group. There are a number of limitations associated with this study. First, no comparison was made with commonly used techniques for hindfoot radiography, such as the Cobey method. We consider that the varus–valgus angle is more accurate than the deviation for the evaluation of coronal alignment. Because it is difficult to evaluate the angle with the Cobey method, we instead used our novel measurement method in this study. However, comparison between the Cobey method and our method is important, and this needs to be examined in the future. Second, regarding the imaging method used, images of both sides were taken simultaneously, and the load may have been unequal in some cases. It is preferable to take images in a unilateral standing position; however, in this study, to ensure patient safety during the imaging procedure, this was not performed. There was a possibility that load was not enough at the forefoot by reason that forefoot was planterflexed. By contrast, we believe that load was enough at the hindfoot. Lastly, the method that we developed for the evaluation of hindfoot varus–valgus included varus–valgus of the talocrural joint. The talocrural joint has an ankle mortise structure with strong varus– valgus stability. However, in patients with post-injury ankle ligament instabilities and in ankle joints with advanced arthropathic changes, varus or valgus alignment of the talocrural joint may impact the VVA. The hindfoot imaging method performed in this study allowed for assessment of the talocrural joint, and none of the participants had findings suggestive of ankle joint OA. In conclusion, in varus OA of the knee, the hindfoot varus group exhibited no postoperative changes in the coronal alignment of the
Discussion Previous reports have found that although the FTA is frequently used to determine coronal alignment in the presence of a load, it is important that the evaluation of lower limb coronal alignment include that of the hindfoot [8,9,12–14]. Plain radiographs are easy and convenient for clinicians to use to assess alignment. To assess lower limb coronal alignment including the hindfoot, Mullaji and Shetty conducted evaluations measuring the amount of deviation from the center of the knee joint and the straight line joining 2 points consisting of the center of the femoral head and the point where the calcaneus touches the ground [9]. Similarly, Guichet et al and Lee et al also examined lower extremity alignment including the hindfoot and reported that this method was superior to the conventional methods for evaluating lower extremity function and axis [13,14]. To determine the point where the calcaneus touched the ground, Mullaji and Shetty conducted assessments using the wire technique [9], and Guichet et al used a similar method in their study [13]. In their case, the wire technique was used instead of the conventional Cobey method, in which the midpoint of the calcaneus remains unclear due to an overlapping of the subtalar joint and the calcaneus with the midfoot on hindfoot imaging. Moreover, in the upright position, the soft tissue of the foot comes in contact with the ground as a surface, not as a point [3,4]. However, these evaluations based on the amount of deviation require that the height of the foot is taken into consideration in addition to the lengths of the femur and tibia and might be insufficient for use in the assessment of hindfoot alignment [6]. In the hindfoot imaging method developed by our group, images are taken while the hindfoot is in flexion with the midfoot, resulting in reduced overlap of the midfoot and hindfoot and allowing full assessment of the subtalar joint [10]. In this assessment of hindfoot alignment, particular focus is given to the subtalar joint, and problematic issues associated with conventional imaging methods, including the fact that the rotation of the lower extremity affects the depicted image of the subtalar joint, are avoided [14]. In this novel imaging method, points that are less influenced by rotation are confirmed by 3D computed tomography and are used as indicators. Therefore, the influence of rotation is estimated to be small. Previous studies have demonstrated associations between genu varum due to RA of the knee and hindfoot valgus deformities and between genu valgum due to RA of the knee and hindfoot varus deformities [15,16]. In addition, Meding et al reported that, as a result of posterior tibial tendon dysfunction (PTTD), hindfoot valgus can cause implant collapse after TKA surgery [12]. Keenan et al also reported similar findings in their study of patients with RA [17], and concluded that the alignment of the hindfoot is deeply involved with and exerts a strong influence on the knee joint.
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hindfoot after TKA, whereas in the hindfoot valgus group, the coronal alignment of the hindfoot was significantly improved. The improvement in hindfoot alignment in the valgus group as soon as 3 weeks after surgery was hypothesized to be due to a residual compensatory capacity in the hindfoot, whereas the unchanged hindfoot alignment in the varus group was hypothesized to be due to a loss of this residual compensatory capacity. In the future, long-term observations will be needed to examine how hindfoot alignment changes over time and to assess its association with clinical symptoms, such as hindfoot pain. Acknowledgments None. References 1. Deakin AH, Basanagoudar PL, Nunag P, et al. Natural distribution of the femoral mechanical–anatomical angle in an osteoarthritic population and its relevance to total knee arthroplasty. Knee 2012;19:120. 2. Nunley RM, Ellison BS, Zhu J, et al. Do patient-specific guides improve coronal alignment in total knee arthroplasty? Clin Orthop Relat Res 2012;470:895. 3. Cobey JC. Posterior roentgenogram of the foot. Clin Orthop Relat Res 1976;118:202. 4. Cobey JC, Sella E. Standardizing methods of measurement of foot shape by including the effects of subtalar rotation. Foot Ankle 1981;2:30. 5. Saltzman CL, el-Khoury GY. The hindfoot alignment view. Foot Ankle Int 1995;16:572.
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6. Johnson JE, Lamdan R, Granberry WF, et al. Hindfoot coronal alignment: a modified radiographic method. Foot Ankle Int 1999;20:818. 7. Kelikian AS, Sarrafian SK. Sarrafian’s anatomy of the foot and ankle. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2011 541. 8. Chandler JT, Moskal JT. Evaluation of knee and hindfoot alignment before and after total knee arthroplasty: a prospective analysis. J Arthroplasty 2004;19:211. 9. Mullaji A, Shetty GM. Persistent hindfoot valgus causes lateral deviation of weightbearing axis after total knee arthroplasty. Clin Orthop Relat Res 2011; 469:1154. 10. Ikoma K, Noguchi M, Nagasawa K, et al. A new radiographic view of the hindfoot. J Foot Ankle Res 2013;6:48. 11. Desai SS, Shetty GM, Song HR, et al. Effect of foot deformity on conventional mechanical axis deviation and ground mechanical axis deviation during single leg stance and two leg stance in genu varum. Knee 2007;14:452. 12. Meding JB, Keating EM, Ritter AM, et al. The planovalgus foot: a harbinger of failure of posterior cruciate-retaining total knee replacement. J Bone Joint Surg Am 2005; 87(Suppl. 2):59. 13. Guichet JM, Javed A, Russell J, et al. Effect of the foot on the mechanical alignment of the lower limbs. Clin Orthop Relat Res 2003;415:193. 14. Lee ST, Song HR, Mahajan R, et al. Development of genu varum in achondroplasia: relation to fibular overgrowth. J Bone Joint Surg (Br) 2007;89:57. 15. Bouysset M, Hugueny P. The rheumatoid foot: pathomechanics clinical and radiological features. Therapeutic conditions. , Foot and ankle in rheumatoid arthritisParis, France: Springer Verlag; 2006. p. 9. 16. Souter WA. Surgical strategy in surgery of the lower limb in rheumatoid arthritis. Foot and ankle in rheumatoid arthritis. Paris, France: Springer Verlag; 2006. p. 229. 17. Keenan MA, Peabody T, Gronley JK, et al. Valgus deformities of the feet and characteristics of gait in patients who have rheumatoid arthritis. J Bone Joint Surg Am 1991;73:237.
