J Orthop Sci (2015) 20:143–148 DOI 10.1007/s00776-014-0668-2
ORIGINAL ARTICLE
Femorotibial relationship changes as the posture changes from patellae‑forward stance to preferred toe‑out stance Jung Ho Noh · Dae Kyung Bae · Kyoung Ho Yoon · Sang Jun Song · Young Hak Roh · Chang Hyun Ryu
Received: 14 May 2014 / Accepted: 17 October 2014 / Published online: 5 November 2014 © The Japanese Orthopaedic Association 2014
Abstract Background Full-length standing anteroposterior radiograph is a standard protocol to evaluate the lower limb alignment in frontal plane. However, most people tend to stand or walk with feet pointing outward. The purpose of this study is to assess the femorotibial relationship as the posture changes from patellae-forward stance for the conventional technique of a full-length standing anteroposterior radiograph to a toe-out quiet stance using a fluoroscope. Methods Femoral and tibial rotation and femorotibial rotation were measured in 60 healthy lower limbs using fluoroscopy during postural change from patellae-forward stance to toe-out quiet stance. Results The average toe-out angle was 21.4°. The average femoral, tibial, and femorotibial rotations during postural change were 6.1°, 4.0°, and 2.1°, respectively (p = 0.000). The correlation coefficient for femoral and
J. H. Noh Department of Orthopaedic Surgery, Graduate School of Medicine, Kangwon National University, Chuncheon, South Korea D. K. Bae · K. H. Yoon · S. J. Song Department of Orthopaedic Surgery, Kyunghee University School of Medicine, Seoul, South Korea Y. H. Roh (*) Department of Orthopaedic Surgery, Gachon University School of Medicine, 1198 Kuwol‑dong, Namdong‑gu, Inchon 405‑760, South Korea e-mail: [email protected] C. H. Ryu Department of Orthopaedic Surgery, Kangwon National University Hospital, Chuncheon, South Korea
tibial rotation was 0.747 (p = 0.000). The correlation coefficient for femoral and femorotibial rotation was 0.670 (p = 0.000), and for tibial and femorotibial rotation was 0.006 (p = 0.962). The correlation between toe-out angle and femorotibial rotation was statistically significant (r2 = 0.096, p = 0.016). The correlations between toe-out angle and femoral rotation, and between toe-out angle and tibial rotation were not statistically significant (r2 = 0.047, p = 0.095, and r2 = 0.000, p = 0.9, respectively). Conclusions The subject’s posture significantly affects the femorotibial relationship. When a subject changes posture from a patellae-forward stance to a toe-out quiet stance, the femur rotates internally on the tibia. Level of evidence Diagnostic, level II.
Introduction Assessment of lower limb alignment is important in orthopaedics, especially in total knee arthroplasty and proximal tibial osteotomy. Full-length standing anteroposterior radiograph is a standard protocol to evaluate lower limb alignment in the frontal plane, and in most medical centers, it is taken with the patient facing the radiographic tube and both patellae facing forward [1–3]. This radiographic technique is known to be reproducible [4] and is more accurate than clinical methods for assessing frontal plane deformities of the lower limb [5]. However, many people tend to stand and walk with the feet pointing outward more or less [6–8]. We thought that the femorotibial relationship would be changed when a subject changed their posture from a patellae-forward stance to a toe-out quiet stance, which might affect the mechanical axis of the lower limb. There have been several reports about the effect of rotation on lower limb alignment [9–11]. However, those were about
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rotation of the lower limb, not femorotibial rotation. We are not aware of any report about the relationship between toeout stance and femorotibial rotation. The purpose of this study is to assess the change of the femorotibial relationship as the posture changes from a patellae-forward stance for the conventional technique of a full-length standing anteroposterior radiograph to a toe-out quiet stance using a fluoroscope.
Materials and methods Subjects After approval from the ethics committee of our institution, 30 subjects (60 lower extremities) were recruited with informed consent provided. They had no degenerative changes on plain radiograph of the knee. Exclusion criteria were a past history of trauma or surgery, flexion contracture, subjective symptoms on a lower extremity, female, or leg length discrepancy more than 1 cm or varus/ valgus deformity more than 5° in the mechanical axis on full-length standing anteroposterior radiograph. The subjects with a thigh-foot angle below −5° (internal torsion) or more than 20° (external torsion) were also excluded. The mean age was 20.9 years old (range 19–27). The mean height and weight were 175.4 cm (range 170–184) and 68.8 kg (range 60–88). Average body mass index was 22.4 (range 19.8–29.7). Study design Toe-out angle was measured with the subject’s preferred quiet stance position. The measurement was performed on two separate days for each subject. The toe-out angle was defined as the angle between the sagittal plane and the anteroposterior axis of the foot. The anteroposterior axis of the foot was defined as the line connecting the center of the heel and that of the second toe. First, the subject stood with both patellae pointing straight forward with both knees fully extended (patellae-forward stance). The patellae-forward stance was verified by fluoroscopy (OEC 9800; GE Medical System, Salt Lake, Utah, USA) (commonly called a C-arm image intensifier). The examined knee was placed at the center of rotation of the C-arm image intensifier having a protractor with 0.1° interval. The C-arm image intensifier was set to take a lateral image of the knee with the arm set horizontal (Fig. 1). We set the medial and lateral posterior condyles to overlap each other perfectly as a reference for the femoral rotation (Fig. 2a, b). The reference image of the knee was saved. Next, holding the base of the image intensifier still, the
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Fig. 1 The C-arm which has a protractor with 0.1° interval is set to take a lateral image of the knee and proximal tibia with the arm set horizontal
arm was put down to take the radiograph of the proximal tibia as a reference for the tibial rotation (Fig. 2c), and the reference image of the proximal tibia was saved. After saving the radiographs of the knee and the proximal tibia, the arm of the image intensifier was brought up to the level of the knee. The subject changed the posture to a toe-out quiet stance with the ipsilateral foot not moving and both knees fully extended (Fig. 2d). The stance width, which was defined as the distance between the centers of the heels, was 18 cm [8]. With the subject holding this posture, the arm of the image intensifier was rotated to have the medial and lateral posterior femoral condyles perfectly overlap each other (Fig. 2e). The femoral rotation was calculated as the difference between the angle of the X-ray beam in the patellae-forward stance and that in the toe-out quiet stance. A femoral rotation of more than zero indicated that the internal rotation of the femur based on the ipsilateral foot occurred during the postural change from the patellae-forward stance to the toe-out quiet stance. The arm of the image intensifier was brought down to take the radiograph of the proximal tibia at the same level as the reference. While the subject held the posture, the C-arm was rotated to take an image corresponding to the reference radiograph of the proximal tibia (Fig. 2f). The tibial rotation was also calculated as the difference between the angle of the X-ray beam in the patellae-forward stance and that in the toe-out stance. A tibial rotation of more than zero indicated that the internal rotation of the tibia based on the ipsilateral foot occurred during the postural change from the patellae-forward stance to the toe-out quiet stance. The femorotibial rotation was calculated as the difference between the femoral rotation and tibial rotation. A femorotibial rotation of more than zero indicated that the femur rotated internally on the tibia during the postural change from the patellae-forward stance to the toe-out quiet stance.
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Femorotibial relationship
Fig. 2 a The subject stands with both patellae pointing straight forward, which is usually the posture for the conventional full-length standing anteroposterior radiograph. b A lateral radiograph of the knee on which the medial and lateral posterior condyles of the femur overlap each other perfectly. c A radiograph of the proximal tibia. The reference of the proximal tibia is set as the radiograph on which
the proximal tibia and fibula start overlapping at certain level. The level is indicated by a No.11 surgical blade in this image. d The subject changes the posture to a toe-out stance without moving the ipsilateral foot. e A lateral radiograph of the knee in toe-out stance. f A radiograph of the proximal tibia in toe-out stance
Statistical analysis
(p
ORIGINAL ARTICLE
Femorotibial relationship changes as the posture changes from patellae‑forward stance to preferred toe‑out stance Jung Ho Noh · Dae Kyung Bae · Kyoung Ho Yoon · Sang Jun Song · Young Hak Roh · Chang Hyun Ryu
Received: 14 May 2014 / Accepted: 17 October 2014 / Published online: 5 November 2014 © The Japanese Orthopaedic Association 2014
Abstract Background Full-length standing anteroposterior radiograph is a standard protocol to evaluate the lower limb alignment in frontal plane. However, most people tend to stand or walk with feet pointing outward. The purpose of this study is to assess the femorotibial relationship as the posture changes from patellae-forward stance for the conventional technique of a full-length standing anteroposterior radiograph to a toe-out quiet stance using a fluoroscope. Methods Femoral and tibial rotation and femorotibial rotation were measured in 60 healthy lower limbs using fluoroscopy during postural change from patellae-forward stance to toe-out quiet stance. Results The average toe-out angle was 21.4°. The average femoral, tibial, and femorotibial rotations during postural change were 6.1°, 4.0°, and 2.1°, respectively (p = 0.000). The correlation coefficient for femoral and
J. H. Noh Department of Orthopaedic Surgery, Graduate School of Medicine, Kangwon National University, Chuncheon, South Korea D. K. Bae · K. H. Yoon · S. J. Song Department of Orthopaedic Surgery, Kyunghee University School of Medicine, Seoul, South Korea Y. H. Roh (*) Department of Orthopaedic Surgery, Gachon University School of Medicine, 1198 Kuwol‑dong, Namdong‑gu, Inchon 405‑760, South Korea e-mail: [email protected] C. H. Ryu Department of Orthopaedic Surgery, Kangwon National University Hospital, Chuncheon, South Korea
tibial rotation was 0.747 (p = 0.000). The correlation coefficient for femoral and femorotibial rotation was 0.670 (p = 0.000), and for tibial and femorotibial rotation was 0.006 (p = 0.962). The correlation between toe-out angle and femorotibial rotation was statistically significant (r2 = 0.096, p = 0.016). The correlations between toe-out angle and femoral rotation, and between toe-out angle and tibial rotation were not statistically significant (r2 = 0.047, p = 0.095, and r2 = 0.000, p = 0.9, respectively). Conclusions The subject’s posture significantly affects the femorotibial relationship. When a subject changes posture from a patellae-forward stance to a toe-out quiet stance, the femur rotates internally on the tibia. Level of evidence Diagnostic, level II.
Introduction Assessment of lower limb alignment is important in orthopaedics, especially in total knee arthroplasty and proximal tibial osteotomy. Full-length standing anteroposterior radiograph is a standard protocol to evaluate lower limb alignment in the frontal plane, and in most medical centers, it is taken with the patient facing the radiographic tube and both patellae facing forward [1–3]. This radiographic technique is known to be reproducible [4] and is more accurate than clinical methods for assessing frontal plane deformities of the lower limb [5]. However, many people tend to stand and walk with the feet pointing outward more or less [6–8]. We thought that the femorotibial relationship would be changed when a subject changed their posture from a patellae-forward stance to a toe-out quiet stance, which might affect the mechanical axis of the lower limb. There have been several reports about the effect of rotation on lower limb alignment [9–11]. However, those were about
13
144
J. H. Noh et al.
rotation of the lower limb, not femorotibial rotation. We are not aware of any report about the relationship between toeout stance and femorotibial rotation. The purpose of this study is to assess the change of the femorotibial relationship as the posture changes from a patellae-forward stance for the conventional technique of a full-length standing anteroposterior radiograph to a toe-out quiet stance using a fluoroscope.
Materials and methods Subjects After approval from the ethics committee of our institution, 30 subjects (60 lower extremities) were recruited with informed consent provided. They had no degenerative changes on plain radiograph of the knee. Exclusion criteria were a past history of trauma or surgery, flexion contracture, subjective symptoms on a lower extremity, female, or leg length discrepancy more than 1 cm or varus/ valgus deformity more than 5° in the mechanical axis on full-length standing anteroposterior radiograph. The subjects with a thigh-foot angle below −5° (internal torsion) or more than 20° (external torsion) were also excluded. The mean age was 20.9 years old (range 19–27). The mean height and weight were 175.4 cm (range 170–184) and 68.8 kg (range 60–88). Average body mass index was 22.4 (range 19.8–29.7). Study design Toe-out angle was measured with the subject’s preferred quiet stance position. The measurement was performed on two separate days for each subject. The toe-out angle was defined as the angle between the sagittal plane and the anteroposterior axis of the foot. The anteroposterior axis of the foot was defined as the line connecting the center of the heel and that of the second toe. First, the subject stood with both patellae pointing straight forward with both knees fully extended (patellae-forward stance). The patellae-forward stance was verified by fluoroscopy (OEC 9800; GE Medical System, Salt Lake, Utah, USA) (commonly called a C-arm image intensifier). The examined knee was placed at the center of rotation of the C-arm image intensifier having a protractor with 0.1° interval. The C-arm image intensifier was set to take a lateral image of the knee with the arm set horizontal (Fig. 1). We set the medial and lateral posterior condyles to overlap each other perfectly as a reference for the femoral rotation (Fig. 2a, b). The reference image of the knee was saved. Next, holding the base of the image intensifier still, the
13
Fig. 1 The C-arm which has a protractor with 0.1° interval is set to take a lateral image of the knee and proximal tibia with the arm set horizontal
arm was put down to take the radiograph of the proximal tibia as a reference for the tibial rotation (Fig. 2c), and the reference image of the proximal tibia was saved. After saving the radiographs of the knee and the proximal tibia, the arm of the image intensifier was brought up to the level of the knee. The subject changed the posture to a toe-out quiet stance with the ipsilateral foot not moving and both knees fully extended (Fig. 2d). The stance width, which was defined as the distance between the centers of the heels, was 18 cm [8]. With the subject holding this posture, the arm of the image intensifier was rotated to have the medial and lateral posterior femoral condyles perfectly overlap each other (Fig. 2e). The femoral rotation was calculated as the difference between the angle of the X-ray beam in the patellae-forward stance and that in the toe-out quiet stance. A femoral rotation of more than zero indicated that the internal rotation of the femur based on the ipsilateral foot occurred during the postural change from the patellae-forward stance to the toe-out quiet stance. The arm of the image intensifier was brought down to take the radiograph of the proximal tibia at the same level as the reference. While the subject held the posture, the C-arm was rotated to take an image corresponding to the reference radiograph of the proximal tibia (Fig. 2f). The tibial rotation was also calculated as the difference between the angle of the X-ray beam in the patellae-forward stance and that in the toe-out stance. A tibial rotation of more than zero indicated that the internal rotation of the tibia based on the ipsilateral foot occurred during the postural change from the patellae-forward stance to the toe-out quiet stance. The femorotibial rotation was calculated as the difference between the femoral rotation and tibial rotation. A femorotibial rotation of more than zero indicated that the femur rotated internally on the tibia during the postural change from the patellae-forward stance to the toe-out quiet stance.
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Femorotibial relationship
Fig. 2 a The subject stands with both patellae pointing straight forward, which is usually the posture for the conventional full-length standing anteroposterior radiograph. b A lateral radiograph of the knee on which the medial and lateral posterior condyles of the femur overlap each other perfectly. c A radiograph of the proximal tibia. The reference of the proximal tibia is set as the radiograph on which
the proximal tibia and fibula start overlapping at certain level. The level is indicated by a No.11 surgical blade in this image. d The subject changes the posture to a toe-out stance without moving the ipsilateral foot. e A lateral radiograph of the knee in toe-out stance. f A radiograph of the proximal tibia in toe-out stance
Statistical analysis
(p
