We retrospectively reviewed 45 patients with cerebral palsy who underwent 80 RF distal tendon resections to treat stiff-knee gait between January 2003 and December 2005. The indications for RF surgery were (1) kinematic characteristics of stiff-knee gait; (2) abnormal EMG activity of RF; and/or (3) RF contractures on physical examination. Patients who showed prolonged RF EMG activity without kinematic characteristics of stiff-knee gait did not undergo RF procedures. To be included in the study, patients had to (1) be diagnosed with spastic diplegia related to prematurity; (2) be a functional walker, whether with or without the use of assistive devices; and (3) have had a 3D gait analysis performed before and after surgery. During the study period, we performed RF distal tendon resections on 109 patients. Forty-five patients met the selection criteria and were included in the study. The remaining patients had spastic familiar paraparesis or congenital hemiplegia or were not able to walk enough to obtain a 3D gait analysis. Thirty-five patients underwent bilateral RF procedures, for a total of 80 RF procedures. None of these patients had previous RF surgery. Gender distribution was 27 males and 18 females. Mean age at the time of surgery was 13.3 years (range, 6.1–22.6 years). The minimum followup was 1.5 years (mean, 2.2 years; range, 1.5–3 years). Our hospital institutional review board gave expedited approval and waived the need to obtain written informed consent.
Preoperatively, all patients were functional walkers: 33 patients walked without any assistive devices and 12 patients walked with crutches and used manual wheelchairs for long distances (Table ). We graded function using the Gross Motor Function Classification System (GMFCS) [12
]. We used the GMFCS level as a criterion of inclusion but did not perform a functional assessment to evaluate the functional benefits of the procedure. Similarly, we recorded preoperative EMG, but since EMG studies were not consistently included in postoperative gait analysis, we did not have adequate information regarding changes in RF electrical activity. For each operated limb, we preoperatively determined RF contractures, knee extension in stance, PKF in swing, time to PKF, and knee ROM, as well as patients’ walking velocity and cadence. We estimated RF degree of contracture by measuring the angle of hip flexion, with the patient lying prone with both lower limbs over the edge of the table to bring the pelvis to a neutral position and the knee of the tested limb bent at 90°.
We currently use RF distal tendon resection to treat patients who exhibit kinematic characteristics of stiff-knee gait or RF contractures. Since 2003, this has been the preferred technique at our institution to treat stiff-knee gait. The same two surgeons (GFP, AP) performed the procedure for all patients. The approach for the RF distal tendon resection procedure was similar to that described for RF transfer [19
]. Through a longitudinal anterior approach, proximal to the patella, the muscle was dissected as if a transfer were to be performed. The RF tendon was then released from the patella, proximally transected at the muscular junction, and completely removed (Fig. ). Contrary to the transfer technique description, we paid particular attention to avoid any tendon fibers being left between the muscle and the patella because we have operated on RF transfer relapses and found fibrous tissue causing reattachment of muscle fibers to the patella.
A photograph shows how the RF is dissected from the underlying vasti and transected at the musculotendinous junction.
We performed all the RF procedures as a part of multilevel surgery (Table ). All limbs in this series had medial hamstrings aponeurotic lengthening. Adductor releases (gracilis myotomy with or without adductor longus lengthening) were performed in 67 of the 80 procedures. The third most common soft-tissue procedure was gastrocnemius/soleus lengthening (48 sides). Peroneus brevis lengthening was performed in 20 sides; tibialis anterior transfer was performed in 10 procedures and tibialis posterior lengthening in five. Twenty-seven hips underwent psoas lengthening over the brim of the pelvis. Twenty-eight limbs underwent femoral derotation osteotomy, 21 underwent tibial derotation, and 11 underwent foot surgery (subtalar arthrodesis or lateral column lengthening).
After surgery, the patients followed a standardized rehabilitation program, including two physical therapy sessions a day. The program started the day after surgery and extended for an average of 4 months if only soft-tissue surgery was performed or for 6 months when bony procedures were part of the multilevel surgery.
The patients were seen 6 weeks, 3 months, 6 months, 12 months, and 18 months after surgery. Thereafter, the patients were seen once a year until they were 18 years old. A physical examination including ROM, force, and spasticity assessment was performed at every visit. Video recording and temporal spatial parameters were obtained at 3 and 6 months postoperatively. Full 3D gait analysis was performed at 18 months’ and 3 years’ followup (a few years ago, gait analysis timing was more variable, and thus, these patients had the analyses performed at an average of 2 years’ followup). If bony procedures were performed, radiographs were taken 3 months and 1 year after surgery.
We reviewed patients’ medical records to collect the following clinical data: cerebral palsy pattern, gender, level of motor function (GMFCS), age at surgery, number and type of concomitant surgical procedures, presence of RF contractures, and surgical complications.
The gait analysis data we collected were date of preoperative and postoperative gait analysis, walking velocity and cadence, values of peak knee extension in stance, PKF in swing, knee ROM (defined as the difference between the two last values), time to PKF in swing (measured as percentage of the gait cycle), and presence of RF abnormal EMG pattern in swing.
We based postoperative assessment on physical evaluation and gait analysis data. All patients were available for postoperative gait analysis and final followup visit. The gait analyses included videotaping, 3D kinematics, kinetics, dynamic EMG, and clinical assessment. Postoperative gait analysis did not systematically include EMG recording. Examinations followed the Helen Haynes protocol [7
]. The motion of body segments was recorded in 3D with a six-camera Vicon™ 612 (Oxford Metrics Ltd, Oxford, UK) infrared motion analysis system, at a sampling rate of 50 Hz. Respecting the Vicon™ Plug-in Gait™ biomechanical model (Oxford Metrics Ltd), 13 passive reflecting markers were positioned on various parts of the body. We filtered the data using a second-order Butterworth filter and calculated the Euler angles for the hips, knees, and ankles. We digitized kinetics force plates (Advanced Mechanical Technology, Inc, Watertown, MA) and MA300 EMG system (Motion Lab Systems, Inc, Baton Rouge, LA) data and synchronized them using a 16-bit A/D card with a sample frequency of 1000 Hz. We acquired the EMG signals with MotionLab sensors (Motion Lab Systems, Inc) consisting of two circular stainless steel dry button electrodes. We collected data from five superficial muscles: RF, vastus lateralis, medial hamstrings, tibialis anterior, and lateral gastrocnemius. As the patient walked along a walkway at a self-selected cadence, we collected data from multiple strides; we selected one representative stride for analysis. Preoperatively, all patients showed characteristics of stiff-knee gait (insufficient knee flexion during swing and/or delayed PKF), an overall decrease in knee ROM, RF prolonged activity in swing, and some degree of RF contracture. PKF values were less than 45° in 12 patients (16 sides) and within normal limits for the rest of the patients. Values of gait velocity and cadence were below average for all patients.
The results after operation for knee ROM, peak knee extension in stance, PKF, and time to PKF during swing, temporal spatial parameters, and degree of RF contracture were compared for all patients using paired t tests. The pre- and postoperative PKF values were also compared using paired t tests for the 12 patients with preoperative PKF values of less than 45°.