Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-3496-1
KNEE
Individual valgus correction angle improves accuracy of postoperative limb alignment restoration after total knee arthroplasty Xiaojun Shi · Hai Li · Zongke Zhou · Bin Shen · Jing Yang · Pengde Kang · Fuxing Pei
Received: 15 August 2014 / Accepted: 18 December 2014 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2014
Abstract Purpose The purpose of the current study was to compare and investigate the effect of fixed and individual valgus correction angle (VCA) on postoperative alignment restoration. It is hypothesized that individual VCA would be more accurate than fixed VCA in postoperative limb alignment restoration. Methods Four hundred and fifty-two patients with 546 consecutive uncomplicated primary total knee arthroplasties performed by a single surgeon, with 302 knees that had individual VCA (group A) and 244 knees that had fixed 5° VCA (group B), were enroled in this study. Preoperative and postoperative full-length standing hip-to-ankle radiographs were used to assess limb alignment. Postoperative hip-knee-ankle angle (θ), femoral component angle (α) and tibial component angle (β) were measured and compared between the two groups. Results Mean postoperative θ angle and α angle were 178.9° (SD 1.3°) and 89.1° (SD 1.1°) in the group A, whereas they were 177.8° (SD 1.9°) and 87.9° (SD 1.5°) in the group B. There were significant differences in both parameters between the two groups (p = 0.021 and 0.016, respectively). Mean postoperative β was 89.8° (SD 1.2°) in the group A and 89.7° (SD 1.3°) in the group B, and no significant difference was detected. There were 114 (37.7 %), 221 (73.2 %) and 265 (87.7 %) knees that had restoration of mechanical axis to ±1°, ±2°, ±3° of neutral, respectively, and 37 (12.3 %) outliers (>±3°) in the group A, whereas there were 48 (19.7 %), 122 (50.0 %) and 170 (69.7 %) knees that had restoration of mechanical axis to X. Shi · H. Li · Z. Zhou (*) · B. Shen · J. Yang · P. Kang · F. Pei The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China e-mail: [email protected]
±1°, ±2°, ±3° of neutral, respectively, and 74 (30.3 %) outliers in the group B. Group A had a higher percentage of restoration of limb alignment and fewer outliers than those in the group B, and this difference was statistically significant (p 30°, using restrictive prosthesis and poor quality radiographs that were difficult to measure, were excluded. Preoperative and postoperative full-length standing hipto-ankle radiographs were taken for all patients using a standardized radiographic technique. Postoperative radiographs were taken until knee full extension (≤5° flexion contracture) to avoid measuring errors [15]. Patients were required to stand with their feet 18 in apart, with maximum knee extension, with the patellae and mortise facing forward to prevent limb rotation. Lesser trochanter and the fibular head profiles were important indices to judge the quality of the radiograph. When any one of these two profiles was in excess, this meant the limb was either externally or internally rotated, while these radiographs were being done. Patients in the group A were required to complete full-length standing radiographs again; patients in the group B were excluded from the study [18]. Postoperative full-length standing radiographs were measured (Philips Extended Brilliance™ Workspace) using the onscreen cursor, with an accurate measurement within 0.1°. The initial step of radiographic measurements was definition of reference points and lines (Fig. 1). H is the centre of the femoral head and was identified using Mose’s circles. Kf is the distal endpoint of the femur and was defined as the centre of the femoral intercondylar notch before surgery and as the midpoint between the medial and lateral condyles after surgery. Kt is the upper end of the tibia and was the midpoint of the tibial component base. A is the centre of the ankle and was determined to the centre of the talar dome. HKf and AKt represent the femoral and the tibial mechanical axes, respectively, and lines 1 and 2 were drawn parallel to the tibial tray and tangential to the prosthetic femoral condyles, respectively. Postoperative radiographic measurements included the following: (1) α—the medial angle between the femoral mechanical axes and line 1, the ideal value was 90°. (2) β—the medial angle between the tibial mechanical axes and line 2, the ideal value was 90°. (3) θ—the medial angle between the femoral and tibial mechanical axes, representing the mechanical axis of the limb in coronal plane, the ideal value was 180°. Deviation of measured value away from the ideal value was the alignment error, varus alignment was given a negative value, and valgus alignment was given a positive value. All measurements were performed by a single joint surgeon. In order to identify
the measurement reliability, repetitive measurements were performed for all data by the same observer and another observer after an interval of 2 weeks, and the mean values were denoted as the final valid value. The two sets of data were used to identify intraobserver and interobserver variability using paired and unpaired t tests, respectively. Prior to the study, an approval for this study (No. 2012268) was obtained from the Institutional Review Board of West China Hospital, Sichuan University, and an informed patient consent was also obtained. Statistical analysis A power analysis prior to the study suggested that, with use of a Chi-square test and alpha of 0.05, a sample size of 354 patients would provide 80 % power to detect a difference of 10 % between groups [1]. All data were expressed as mean value (SD) and analysed with the Statistical Package for the Social Sciences (SPSS) version 17.0. All categorical variables were analysed with use of the Chi-square test. Continuous variables were evaluated with use of the Student t test or Mann–Whitney U test, depending on the distribution characteristics of the data. In all comparisons, a p value
KNEE
Individual valgus correction angle improves accuracy of postoperative limb alignment restoration after total knee arthroplasty Xiaojun Shi · Hai Li · Zongke Zhou · Bin Shen · Jing Yang · Pengde Kang · Fuxing Pei
Received: 15 August 2014 / Accepted: 18 December 2014 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2014
Abstract Purpose The purpose of the current study was to compare and investigate the effect of fixed and individual valgus correction angle (VCA) on postoperative alignment restoration. It is hypothesized that individual VCA would be more accurate than fixed VCA in postoperative limb alignment restoration. Methods Four hundred and fifty-two patients with 546 consecutive uncomplicated primary total knee arthroplasties performed by a single surgeon, with 302 knees that had individual VCA (group A) and 244 knees that had fixed 5° VCA (group B), were enroled in this study. Preoperative and postoperative full-length standing hip-to-ankle radiographs were used to assess limb alignment. Postoperative hip-knee-ankle angle (θ), femoral component angle (α) and tibial component angle (β) were measured and compared between the two groups. Results Mean postoperative θ angle and α angle were 178.9° (SD 1.3°) and 89.1° (SD 1.1°) in the group A, whereas they were 177.8° (SD 1.9°) and 87.9° (SD 1.5°) in the group B. There were significant differences in both parameters between the two groups (p = 0.021 and 0.016, respectively). Mean postoperative β was 89.8° (SD 1.2°) in the group A and 89.7° (SD 1.3°) in the group B, and no significant difference was detected. There were 114 (37.7 %), 221 (73.2 %) and 265 (87.7 %) knees that had restoration of mechanical axis to ±1°, ±2°, ±3° of neutral, respectively, and 37 (12.3 %) outliers (>±3°) in the group A, whereas there were 48 (19.7 %), 122 (50.0 %) and 170 (69.7 %) knees that had restoration of mechanical axis to X. Shi · H. Li · Z. Zhou (*) · B. Shen · J. Yang · P. Kang · F. Pei The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China e-mail: [email protected]
±1°, ±2°, ±3° of neutral, respectively, and 74 (30.3 %) outliers in the group B. Group A had a higher percentage of restoration of limb alignment and fewer outliers than those in the group B, and this difference was statistically significant (p 30°, using restrictive prosthesis and poor quality radiographs that were difficult to measure, were excluded. Preoperative and postoperative full-length standing hipto-ankle radiographs were taken for all patients using a standardized radiographic technique. Postoperative radiographs were taken until knee full extension (≤5° flexion contracture) to avoid measuring errors [15]. Patients were required to stand with their feet 18 in apart, with maximum knee extension, with the patellae and mortise facing forward to prevent limb rotation. Lesser trochanter and the fibular head profiles were important indices to judge the quality of the radiograph. When any one of these two profiles was in excess, this meant the limb was either externally or internally rotated, while these radiographs were being done. Patients in the group A were required to complete full-length standing radiographs again; patients in the group B were excluded from the study [18]. Postoperative full-length standing radiographs were measured (Philips Extended Brilliance™ Workspace) using the onscreen cursor, with an accurate measurement within 0.1°. The initial step of radiographic measurements was definition of reference points and lines (Fig. 1). H is the centre of the femoral head and was identified using Mose’s circles. Kf is the distal endpoint of the femur and was defined as the centre of the femoral intercondylar notch before surgery and as the midpoint between the medial and lateral condyles after surgery. Kt is the upper end of the tibia and was the midpoint of the tibial component base. A is the centre of the ankle and was determined to the centre of the talar dome. HKf and AKt represent the femoral and the tibial mechanical axes, respectively, and lines 1 and 2 were drawn parallel to the tibial tray and tangential to the prosthetic femoral condyles, respectively. Postoperative radiographic measurements included the following: (1) α—the medial angle between the femoral mechanical axes and line 1, the ideal value was 90°. (2) β—the medial angle between the tibial mechanical axes and line 2, the ideal value was 90°. (3) θ—the medial angle between the femoral and tibial mechanical axes, representing the mechanical axis of the limb in coronal plane, the ideal value was 180°. Deviation of measured value away from the ideal value was the alignment error, varus alignment was given a negative value, and valgus alignment was given a positive value. All measurements were performed by a single joint surgeon. In order to identify
the measurement reliability, repetitive measurements were performed for all data by the same observer and another observer after an interval of 2 weeks, and the mean values were denoted as the final valid value. The two sets of data were used to identify intraobserver and interobserver variability using paired and unpaired t tests, respectively. Prior to the study, an approval for this study (No. 2012268) was obtained from the Institutional Review Board of West China Hospital, Sichuan University, and an informed patient consent was also obtained. Statistical analysis A power analysis prior to the study suggested that, with use of a Chi-square test and alpha of 0.05, a sample size of 354 patients would provide 80 % power to detect a difference of 10 % between groups [1]. All data were expressed as mean value (SD) and analysed with the Statistical Package for the Social Sciences (SPSS) version 17.0. All categorical variables were analysed with use of the Chi-square test. Continuous variables were evaluated with use of the Student t test or Mann–Whitney U test, depending on the distribution characteristics of the data. In all comparisons, a p value
