ORIGINAL ARTICLE
Recurrence of Equinus Foot Deformity After TendoAchilles Lengthening in Patients With Cerebral Palsy Chin Youb Chung, MD,* Ki Hyuk Sung, MD,w Kyoung Min Lee, MD,* Seung Yeol Lee, MD,w In Ho Choi, MD,z Tae-Joon Cho, MD,z Won Joon Yoo, MD,z and Moon Seok Park, MD*
Background: Recurrence of equinus deformity after surgery is common in patients with cerebral palsy. This retrospective study was undertaken to estimate the recurrence rate of the equinus deformity after tendo-Achilles lengthening (TAL) in patients with cerebral palsy and to investigate the risk factors associated with the recurrence. Methods: Two-hundred forty three ambulatory patients with cerebral palsy, who underwent TAL for equinus foot deformity since 1995, and had undergone a preoperative and postoperative 3-dimensional gait analysis, were included. Cox proportional hazards model was used to determine the significant contributing factor for the recurrence of equinus foot deformity. Results: The mean patient age at surgery was 7.8 ± 2.7 years and the mean follow-up duration was 8.1 ± 3.4 years. Equinus deformity recurred in 22 of the 243 patients (9.1%) and the Kaplan-Meier survival estimate was shown to be 89.4% at 10 years not needing repeat surgery. According to the multivariate analysis using the Cox proportional hazard model, preoperative ankle dorsiflexion at initial contact (P = 0.016) was the only significant factor for recurrence of equinus deformity after surgery. Age at surgery and the type of limb involvement were not associated with the recurrence (P = 0.433 and 0.269). The cutoff values of preoperative gait kinematics between the nonrecurrence and recurrence groups were 19 degrees of ankle dorsiflexion at initial contact (P = 0.018). Conclusions: This study showed that the severity of preoperative equinus deformity was a risk factor associated with recurrence after TAL in patients with cerebral palsy. Therefore, surgeons should consider the recurrence and later revision surgery for the patients with severe equinus foot deformity. Level of Evidence: Therapeutic level III.
From the *Department of Orthopaedic Surgery, Seoul National University Bundang Hospital; wDepartment of Orthopaedic Surgery, Myongji Hospital, Kyungki; and zDepartment of Orthopaedic Surgery, Seoul National University Children’s Hospital, Seoul, Korea. Chin Youb Chung, MD and Ki Hyuk Sung, MD are co-first authors. Supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2013R1A1A1012298). The authors declare no conflicts of interest. Reprints: Moon Seok Park, MD, Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, 300 Gumi-Dong, Bundang-Gu, Sungnam, Kyungki 463-707, Korea. E-mail: pms [email protected]. Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 35, Number 4, June 2015
Key Words: equinus foot deformity, recurrence, tendo-Achilles lengthening, cerebral palsy (J Pediatr Orthop 2015;35:419–425)
E
quinus deformity caused by contracture of the triceps surae is one of the most common clinical findings in patients with cerebral palsy (CP).1,2 It leads to a decrease in the stability of the stance phase, loss of smooth transition of the body over the foot, inadequate clearance of the foot in the swing phase, and increase in the forefoot load.3 Failure of conservative treatment such as physiotherapy, ankle foot orthoses, casting, and injections of botulinum toxin A may be an indication for surgical intervention.2,4 A wide variety of procedures has been described for surgical correction of equinus deformity, and tendo-Achilles lengthening (TAL) is the commonly performed procedure in fixed equinus foot deformity.5–7 Recurrence of equinus deformity after surgical intervention is common in patients with CP and reported recurrence rate varies from 0% to 48%.5–22 Risk factors associated with the recurrence include the age at the time of surgery, the type of limb involvement, sex, the type of surgery, and hamstring contracture. Several authors have found that the age at the time of initial surgery and the type of limb involvement were the major factors associated with the recurrence of equinus deformity.5,8,9,11,12,17 However, the risk factors contributing to the recurrence of equinus deformity have not been well-established yet, and this question remains controversial. For instance, several studies have reported that younger children are more likely to have recurrence than older children. In contrast, other studies have reported no relationship between age at surgery and recurrence. Therefore, this study was performed on patients who underwent TAL for the equinus foot deformity and who had undergone preoperative and postoperative 3dimensional (3D) gait analyses to address the following questions: (1) what is the recurrence rate of the equinus deformity after TAL in patients with CP, and (2) what risk factors predispose a CP patient to the recurrence of the equinus deformity.
METHODS This retrospective study was approved by the Institutional Review Board at our institution, which is a www.pedorthopaedics.com |
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
419
J Pediatr Orthop
Chung et al
tertiary referral center for CP. The inclusion criteria were as follows: (1) consecutive ambulatory patients with CP younger than 18 years old, (2) patients who underwent TAL for equinus foot deformity since 1995, and (3) patients who had undergone preoperative 3D gait analysis and postoperative 3D gait analysis with a minimum follow-up of 2 years. The exclusion criteria were as follows: (1) patients with history of previous surgery for equinus deformity or selective dorsal rhizotomy, or (2) patients with a concurrent neuromuscular disease, other than CP. Sex, type of limb involvement, Gross Motor Function Classification System (GMFCS) level, age at the time of surgery, follow-up duration, and details of concomitant surgery were obtained for a review of patients’ medical records.
Operative Protocols TAL by open Z-plasty lengthening was performed as one of the single event multilevel surgery (SEMLS) to improve the gait pattern by 2 pediatric orthopedic surgeons with the same philosophy toward a treatment. TAL was performed based on considerations of both clinical and gait analysis findings. Those were fixed equinus deformity with negative Silfverskiold test and increased plantar flexion in stance.23 The intraoperative goal for the correction was to achieve ankle dorsiflexion of 10 degrees in knee extension. After the surgery, each patient received a postsurgical care as follows. All patients were immobilized in a short leg cast and had a non–weight-bearing period of 3 to 6 weeks after the surgery. Standing and weight bearing were resumed with leaf-spring type ankle foot orthosis, which was worn for 3 months. Subsequently, patients were referred back to a local rehabilitation center to continue muscle-strengthening exercises and gait training. During this period, ankle foot orthoses were recommended only at night to prevent the recurrence of Achilles tightness. At the follow-up examination, the pediatric orthopedic surgeon who performed the initial operation decided whether patients with fixed equinus foot deformity and tiptoeing gait should undergo a second operation.
Acquisition of Kinematic Data and Data Analysis 3D Gait analysis was performed a few days before surgery using a Vicon 370 apparatus (Oxford, UK) equipped with 7 CCD cameras and 2 force plates. Markers were placed as for the Helen Hayes marker set,24 by a single operator with 17 years of experience, who also performed data processing. Patients were asked to walk barefoot on a 9 m walkway >3 times, and 3 trials which represented patients’ typical gait patterns were selected. The averaged kinematic data were archived for the data analysis. 3D gait analysis was repeated for >1 year postoperatively. Kinematic parameters from preoperative 3D gait analysis were compared with those from 1-year postoperative 3D gait analysis. Patients were divided into the nonrecurrence and recurrence groups. When the patients had a second operation, the equinus deformity was con-
420 | www.pedorthopaedics.com
Volume 35, Number 4, June 2015
sidered to have recurred; these patients were classified into the recurrence group. Patient demographics and preoperative gait kinematics in the nonrecurrence group were compared with those in the recurrence group. The cutoff values between the nonrecurrence and recurrence groups were determined based on the preoperative gait kinematics.
Statistical Methods To achieve statistical independence, only data from one limb per patient was included in the statistical analysis.25 For the patients with unilateral involvement, the involved limb was included and for those with bilateral involvement, a randomly selected limb was included. Descriptive statistics were used to summarize the patients’ demographics. A paired t test was used to evaluate differences between the preoperative and postoperative gait kinematics. An independent t test was used to compare the preoperative demographics and gait kinematics between the recurrence group and the nonrecurrence group. The Kaplan-Meier survival estimate was utilized, with the end point defined as reoperation to determine the overall recurrence. The log-rank test was used to compare the recurrence by each variable including sex, GMFCS level, and type of limb involvement. Cox proportional hazards model estimated the significant contributing factors for the recurrence of equinus foot deformity after surgery. After univariate analysis, variables with a P-value < 0.05 were included in multivariate analysis. The receiver operating characteristic curve was used to determine the cutoff values of preoperative gait kinematics between the nonrecurrence and recurrence groups. Statistical analyses were conducted using SPSS for Windows (version 18.0; SPSS, Chicago, IL), and null hypotheses of no difference were rejected if P-values were
Recurrence of Equinus Foot Deformity After TendoAchilles Lengthening in Patients With Cerebral Palsy Chin Youb Chung, MD,* Ki Hyuk Sung, MD,w Kyoung Min Lee, MD,* Seung Yeol Lee, MD,w In Ho Choi, MD,z Tae-Joon Cho, MD,z Won Joon Yoo, MD,z and Moon Seok Park, MD*
Background: Recurrence of equinus deformity after surgery is common in patients with cerebral palsy. This retrospective study was undertaken to estimate the recurrence rate of the equinus deformity after tendo-Achilles lengthening (TAL) in patients with cerebral palsy and to investigate the risk factors associated with the recurrence. Methods: Two-hundred forty three ambulatory patients with cerebral palsy, who underwent TAL for equinus foot deformity since 1995, and had undergone a preoperative and postoperative 3-dimensional gait analysis, were included. Cox proportional hazards model was used to determine the significant contributing factor for the recurrence of equinus foot deformity. Results: The mean patient age at surgery was 7.8 ± 2.7 years and the mean follow-up duration was 8.1 ± 3.4 years. Equinus deformity recurred in 22 of the 243 patients (9.1%) and the Kaplan-Meier survival estimate was shown to be 89.4% at 10 years not needing repeat surgery. According to the multivariate analysis using the Cox proportional hazard model, preoperative ankle dorsiflexion at initial contact (P = 0.016) was the only significant factor for recurrence of equinus deformity after surgery. Age at surgery and the type of limb involvement were not associated with the recurrence (P = 0.433 and 0.269). The cutoff values of preoperative gait kinematics between the nonrecurrence and recurrence groups were 19 degrees of ankle dorsiflexion at initial contact (P = 0.018). Conclusions: This study showed that the severity of preoperative equinus deformity was a risk factor associated with recurrence after TAL in patients with cerebral palsy. Therefore, surgeons should consider the recurrence and later revision surgery for the patients with severe equinus foot deformity. Level of Evidence: Therapeutic level III.
From the *Department of Orthopaedic Surgery, Seoul National University Bundang Hospital; wDepartment of Orthopaedic Surgery, Myongji Hospital, Kyungki; and zDepartment of Orthopaedic Surgery, Seoul National University Children’s Hospital, Seoul, Korea. Chin Youb Chung, MD and Ki Hyuk Sung, MD are co-first authors. Supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2013R1A1A1012298). The authors declare no conflicts of interest. Reprints: Moon Seok Park, MD, Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, 300 Gumi-Dong, Bundang-Gu, Sungnam, Kyungki 463-707, Korea. E-mail: pms [email protected]. Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
J Pediatr Orthop
Volume 35, Number 4, June 2015
Key Words: equinus foot deformity, recurrence, tendo-Achilles lengthening, cerebral palsy (J Pediatr Orthop 2015;35:419–425)
E
quinus deformity caused by contracture of the triceps surae is one of the most common clinical findings in patients with cerebral palsy (CP).1,2 It leads to a decrease in the stability of the stance phase, loss of smooth transition of the body over the foot, inadequate clearance of the foot in the swing phase, and increase in the forefoot load.3 Failure of conservative treatment such as physiotherapy, ankle foot orthoses, casting, and injections of botulinum toxin A may be an indication for surgical intervention.2,4 A wide variety of procedures has been described for surgical correction of equinus deformity, and tendo-Achilles lengthening (TAL) is the commonly performed procedure in fixed equinus foot deformity.5–7 Recurrence of equinus deformity after surgical intervention is common in patients with CP and reported recurrence rate varies from 0% to 48%.5–22 Risk factors associated with the recurrence include the age at the time of surgery, the type of limb involvement, sex, the type of surgery, and hamstring contracture. Several authors have found that the age at the time of initial surgery and the type of limb involvement were the major factors associated with the recurrence of equinus deformity.5,8,9,11,12,17 However, the risk factors contributing to the recurrence of equinus deformity have not been well-established yet, and this question remains controversial. For instance, several studies have reported that younger children are more likely to have recurrence than older children. In contrast, other studies have reported no relationship between age at surgery and recurrence. Therefore, this study was performed on patients who underwent TAL for the equinus foot deformity and who had undergone preoperative and postoperative 3dimensional (3D) gait analyses to address the following questions: (1) what is the recurrence rate of the equinus deformity after TAL in patients with CP, and (2) what risk factors predispose a CP patient to the recurrence of the equinus deformity.
METHODS This retrospective study was approved by the Institutional Review Board at our institution, which is a www.pedorthopaedics.com |
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
419
J Pediatr Orthop
Chung et al
tertiary referral center for CP. The inclusion criteria were as follows: (1) consecutive ambulatory patients with CP younger than 18 years old, (2) patients who underwent TAL for equinus foot deformity since 1995, and (3) patients who had undergone preoperative 3D gait analysis and postoperative 3D gait analysis with a minimum follow-up of 2 years. The exclusion criteria were as follows: (1) patients with history of previous surgery for equinus deformity or selective dorsal rhizotomy, or (2) patients with a concurrent neuromuscular disease, other than CP. Sex, type of limb involvement, Gross Motor Function Classification System (GMFCS) level, age at the time of surgery, follow-up duration, and details of concomitant surgery were obtained for a review of patients’ medical records.
Operative Protocols TAL by open Z-plasty lengthening was performed as one of the single event multilevel surgery (SEMLS) to improve the gait pattern by 2 pediatric orthopedic surgeons with the same philosophy toward a treatment. TAL was performed based on considerations of both clinical and gait analysis findings. Those were fixed equinus deformity with negative Silfverskiold test and increased plantar flexion in stance.23 The intraoperative goal for the correction was to achieve ankle dorsiflexion of 10 degrees in knee extension. After the surgery, each patient received a postsurgical care as follows. All patients were immobilized in a short leg cast and had a non–weight-bearing period of 3 to 6 weeks after the surgery. Standing and weight bearing were resumed with leaf-spring type ankle foot orthosis, which was worn for 3 months. Subsequently, patients were referred back to a local rehabilitation center to continue muscle-strengthening exercises and gait training. During this period, ankle foot orthoses were recommended only at night to prevent the recurrence of Achilles tightness. At the follow-up examination, the pediatric orthopedic surgeon who performed the initial operation decided whether patients with fixed equinus foot deformity and tiptoeing gait should undergo a second operation.
Acquisition of Kinematic Data and Data Analysis 3D Gait analysis was performed a few days before surgery using a Vicon 370 apparatus (Oxford, UK) equipped with 7 CCD cameras and 2 force plates. Markers were placed as for the Helen Hayes marker set,24 by a single operator with 17 years of experience, who also performed data processing. Patients were asked to walk barefoot on a 9 m walkway >3 times, and 3 trials which represented patients’ typical gait patterns were selected. The averaged kinematic data were archived for the data analysis. 3D gait analysis was repeated for >1 year postoperatively. Kinematic parameters from preoperative 3D gait analysis were compared with those from 1-year postoperative 3D gait analysis. Patients were divided into the nonrecurrence and recurrence groups. When the patients had a second operation, the equinus deformity was con-
420 | www.pedorthopaedics.com
Volume 35, Number 4, June 2015
sidered to have recurred; these patients were classified into the recurrence group. Patient demographics and preoperative gait kinematics in the nonrecurrence group were compared with those in the recurrence group. The cutoff values between the nonrecurrence and recurrence groups were determined based on the preoperative gait kinematics.
Statistical Methods To achieve statistical independence, only data from one limb per patient was included in the statistical analysis.25 For the patients with unilateral involvement, the involved limb was included and for those with bilateral involvement, a randomly selected limb was included. Descriptive statistics were used to summarize the patients’ demographics. A paired t test was used to evaluate differences between the preoperative and postoperative gait kinematics. An independent t test was used to compare the preoperative demographics and gait kinematics between the recurrence group and the nonrecurrence group. The Kaplan-Meier survival estimate was utilized, with the end point defined as reoperation to determine the overall recurrence. The log-rank test was used to compare the recurrence by each variable including sex, GMFCS level, and type of limb involvement. Cox proportional hazards model estimated the significant contributing factors for the recurrence of equinus foot deformity after surgery. After univariate analysis, variables with a P-value < 0.05 were included in multivariate analysis. The receiver operating characteristic curve was used to determine the cutoff values of preoperative gait kinematics between the nonrecurrence and recurrence groups. Statistical analyses were conducted using SPSS for Windows (version 18.0; SPSS, Chicago, IL), and null hypotheses of no difference were rejected if P-values were
