Equinus deformity is commonly encountered in children with spastic cerebral palsy (CP). It might cause problems in gait, including lack of normal equilibrium, metatarsal head callosities, unstable ankle, pelvis tilting, and high energy consumption 1,2. Current options for the treatment of equinus deformity in children with CP include serial casting 3,4, orthotic devices 5,6, botulinum toxin A injection 7,8, selective fascicular neurotomy 9, calcaneal tendon transfer 10, and several different methods of Achilles tendon lengthening (ATL), such as percutaneous lengthening 11,12, Vulpius 13, Baker 14,15, White 16, Baumann 17, and Z-lengthening 18,19 procedures. The current consensus is that the better surgical option for equinus contracture in most children with CP is lengthening the gastrocnemius aponeurosis rather than lengthening the Achilles tendon. Two types of procedures are commonly used by most orthopedic surgeons: the sliding lengthening (Vulpius, Baker, or Strayer procedure) and the sectional (Z-lengthening) procedures. The surgical options vary depending on the degree of deformity and contracture. The sectional (Z-lengthening) procedure is often used for fixed contractures 18,19.
The immobilization period after operation varies from 3 to 7 weeks to ensure healing before returning to full function or exercise 20. Blaiser and White have reported that 3 weeks of immobilization after sliding lengthening may be sufficient 20, whereas some authors have suggested 4 weeks of short leg cast immobilization after Z-lengthening of the Achilles tendon 21. Renshaw et al. 22 have recommended 6 weeks of a short leg cast after triple-cut sliding lengthening. There has been a recent interest in avoiding prolonged immobilization following operative treatment because of the disadvantages of muscle weakness, joint contracture, slow recovery and rehabilitation, and delayed return to unrestricted daily activity. The goals are to prevent the musculoskeletal changes associated with immobilization, to reduce the time needed for rehabilitation, and to facilitate an early return to daily activities.
In the present study, we aimed to report the surgical techniques and preliminary results of a new method of sliding procedure, the ‘mesh ATL procedure’, which might provide decreased immobilization and lead to quicker recovery. Because Vulpius ATL and Z-lengthening are the most common procedures performed at our institution for equinus contracture, these procedures were selected for comparison in this study. The clinical efficacy of the mesh ATL procedure was analyzed for the treatment of equinus deformity in patients with spastic CP.
Materials and methods
The study was carried out after obtaining informed consent from all patients and their parents. The patients with equinus contracture who failed conservative treatment were chosen for surgical lengthening of the Achilles tendon. Those who had gastrocnemius equinus contracture were treated either with the mesh ATL technique or with the Vulpius procedure, whereas patients with fixed equinus contracture underwent Z-lengthening of the Achilles tendon. From June 1997 to March 2004, 55 CP patients (93 limbs) received surgeries for correcting the equinus foot deformity in our institution. Three different methods of ATL were performed for these patients: the mesh ATL, Vulpius ATL, and Z-lengthening of the Achilles tendon. Forty-two patients without a fixed contracture of the gastrocnemius and soleus (dorsiflexion of the foot to neutral but not more than 10° past neutral with the knee in flexion and in extension under anesthesia) were assigned to undergo the mesh ATL procedure (22 patients, 36 tendons) or Vulpius ATL (20 patients, 33 tendons) randomly. Thirteen patients (24 tendons) with a fixed contracture of the gastrocnemius and soleus (lack of dorsiflexion of the foot to neutral even with the knee in flexion under anesthesia) underwent Z-lengthening of the Achilles tendon. If residual ankle varus deformity or claw toe deformity was identified following the Achilles tendon procedure, lengthening of the tibialis posterior, flexor hallucis longus, or flexor digitorum longus was performed accordingly. As required, the psoas was lengthened at the brim of the pelvis for hip flexion contracture; the hamstrings were lengthened for knee flexion; and the adductor longus and gracilis were released for scissoring gait. All the procedures were performed by one senior pediatric orthopedic surgeon. The maximal passive dorsiflexion angles of the ankle at full extension of the knee were evaluated across the three groups using a goniometer preoperatively, postoperatively, and 2 years after the correction. The angles of surgical correction and long-term correction were also compared.
Mesh Achilles tendon lengthening
All patients were placed in a supine position after receiving general anesthesia. After skin preparation, sterilizing, and draping, the affected limb was exsanguinated for reduced bleeding. A posteromedial longitudinal skin incision, 3–4 cm long, was made at the junction of the middle and lower thirds of the lower leg. By blunt dissection, the musculotendinous junction of the gastrocnemius was exposed. Mesh tenotomy of the tendinous potion of gastrocnemius and soleus fascia was performed. The mesh tenotomy included multiple transverse cuts for 5–8 mm, around 5×5 cuts (row×column), with at least 3–5 mm apart between cuts. After tenotomy, the ankle was gently dorsiflexed, yielding a 4–6 mm longitudinal gap for each cut, and 20–30 mm lengthening of the Achilles tendon was gained (Fig. 1). After careful hemostasis, the incision was closed in layers. After surgery, a long leg splint was applied with the ankle in a neutral position.
Vulpius and Z-lengthening procedures
These procedures followed the commonly accepted protocol 13,18,19,23. We used identical types of incisions for all three procedures. However, the incision was longer in some cases to expose the entire tendon.
After surgery, all patients in the mesh ATL and Vulpius groups received below-knee casts, which were removed at 1 week. The below-knee casts were applied in the Z-lengthening group, but were removed after 4 weeks. A custom-made long leg plaster-splint was then used to maintain knee extension during resting periods, which also provided passive knee extension in the stance phase of gait. The splint was used until muscle balance at the knee was established and the muscle power in the calf was sufficient to stabilize the knee during stance. Daily physiotherapy, rehabilitation, and gait training could begin after removal of the cast, once the pain could be tolerated, the muscle power was adequate, and muscle balance was achieved. We collected information about each patient’s postoperative recovery from evaluation of clinic follow-up and medical records.
One-way analysis of variance was used to compare the maximal passive dorsiflexion angles of the ankle at full extension of the knee between the three study groups. Both the dorsiflexion angles of surgical correction and long-term correction were compared. In addition, the time required for rehabilitation, to return to walking training, and to acquire improved speed and stability was also compared using one-way analysis of variance.
Gait analysis was performed in the mesh ATL group. The testing laboratory was equipped with a motion analysis system (Motion Analysis Corp., Santa Rosa, California, USA) that included six charge-coupled device (CCD) cameras, two video processors (VP320), a SUN workstation, and 21 pieces of retroreflective markers (Helen Hays Simplified Marker Set) 24. Two Kistler force plates (60×40 cm, 9281B) and an eight-charge amplifier (9865B) were used to collect ground reaction forces synchronized by a photocell trigger. Gait parameters, including spatiotemporal parameters, kinematics, and kinetics, were analyzed 25. Angles of the ankle and knee were measured during the stance and swing periods. From the ankle dorsiflexion–plantarflexion plots, we obtained the angles of dorsiflexion and plantar flexion of the ankle during the stance and swing periods. From the knee flexion–extension plots, we also determined the flexion angles of the knee.
The demographics of the three groups are shown in Table 1. The average age of the patients in the Z-lengthening group (7.2 years) was older than the average ages in the mesh ATL and the Vulpius groups (6.2 and 6.5 years, P>0.05, respectively). There a lower number of children who could walk independently (GMFCS I+II) in the Z-lengthening group (69%) compared with the mesh ATL and the Vulpius groups (82 and 85%, P>0.05, respectively). The maximal passive dorsiflexion angles of the ankle and the angles of correction were evaluated preoperatively, postoperatively, and again 2 years after the operation. The angles of surgical correction and long-term correction were also compared. The results are summarized in Table 2. The Z-lengthening group had smaller massive passive dorsiflexion angles of the ankle at full extension of the knee than the remaining groups. There was no statistical difference between the three groups in the postoperative massive passive dorsiflexion angles of the ankle at full extension of the knee. At the 2-year follow-ups, no statistically significant difference was found between the mesh ATL and the Vulpius ATL groups in the dorsiflexion angles, whereas the angles in both the groups were significantly smaller than those of the Z-lengthening group. In terms of the surgical correction angles and the 2-year long-term correction angles, there were no statistically significant differences between the mesh ATL group and the Vulpius ATL group, but they were smaller than those of the Z-lengthening group.
The data on patients’ recovery after surgical corrections are summarized in Table 3. The time needed for patients in the mesh ATL group to begin rehabilitation, and walking training, and to gain stability for running, and to perform one-legged hopping was found to be significantly less than that for both the Vulpius ATL group and the Z-lengthening group.
The changes in the ankle angles in kinematics during gait analysis before and after the mesh ATL procedure are shown by a representative case in Fig. 2a. Before surgery, the ankle angles showed plantarflexion (10–20°) in both the stance (0–60% gait cycle) and the swing (60–100% gait cycle) phases. After the mesh ATL procedure, the ankle angles showed dorsiflexion (0–10°) that resembled that in a normal gait pattern. The results of the knee angles in kinematics are shown in Fig. 2b. We found that the knee angles before and after the mesh ATL procedure were similar. This indicated that the mesh ATL procedure had little effect on the motion of the knee.
CP spasticity results in inhibition of longitudinal muscle growth and movement, limiting muscle stretching in daily activities, and leading to the development of muscle and joint deformities. Equinus of the ankle is the most common deformity encountered in children with CP. There are several surgical options for ATL for the treatment of equinus deformity and spasticity. The sliding procedure lengthens the biarticular gastrocnemius muscle and the sectional procedure (Z-lengthening) lengthens both the biarticular gastrocnemius muscle and the monoarticular soleus muscle. Gage 26 reported that the spasticity inherent in CP seems to primarily affect the biarticular muscles. In the current study, we reported the clinical efficacy of the newly designed mesh ATL procedure, an innovative method of selective sliding lengthening in the gastrocnemius tendon and soleus fascia.
Muscle weakness is one of the major concerns in the treatment of an equinus deformity in patients with CP. Calcaneal gait is a significant iatrogenic complication after ATL procedures. It usually results from overlengthening or muscle weakness. Segal et al. 27 defined a calcaneal gait as more than 14° of the mean ankle dorsiflexion during the stance phase. He reported, by gait analysis, a higher prevalence (30%) of calcaneal gait than that in previous reports (1–12%). Delp et al. 28 suggested that independent lengthening of the contracted gastrocnemius and soleus, rather than lengthening of their common tendon, may be a more effective method of restoring range of motion and maintaining the power of plantar flexion. In our study, no calcaneal gait was observed in the mesh ATL group. The mesh ATL procedure does not sever the gastrocnemius completely: the fascia receives multiple separated small cuts in a mesh. This weakens the aponeurosis without completely disconnecting it and decreases the risk of overlengthening of the gastroc–soleus unit, which may occur with ATL or the Vulpius procedure, with the possible complications of loss of plantar flexion power and calcaneal gait.
Recurrence of equinus deformity is another concern. Sala et al. 29 reported a recurrence rate of 22% in patients after they underwent ATL. Rattey et al. 21 reported a recurrence rate of 18% for diplegic patients and 41% for hemiplegic patients. Koman et al. 30 reviewed 31 studies and found that hemiplegic patients and children younger than 7 years of age at the time of surgery had a higher recurrence rate. In our study, there was no recurrence in the latest follow-up (2 years after surgery). However, mid-term or long-term follow-up is required for further evaluation of the recurrence rate.
Yngve and Chambers 19 evaluated the ankle function in gait after 22 Vulpius lengthenings and 27 Z-lengthenings for equinus deformity in patients with CP. The ankle movements improved to an almost normal function for most patients in each group. The patients in the Vulpius group showed a notable presence of abnormal midstance work initially and a significant decrease at follow-up. The patients in the Z-lengthening group showed a notable presence of equinus and a lack of push-off work initially, which improved significantly at follow-up. There were no significant differences between both the groups at the final follow-up in any of the parameters. In our study, the mesh ATL group had correction angles similar to the Vulpius group immediately after the operation and during the 2-year follow-up, but both the groups had smaller correction angles than the Z-lengthening group. However, the recovery time (e.g. time to return to rehabilitation and to achieve better stability) in our mesh ATL group was significantly shorter than that of the other two groups.
Although the study yielded successful results, caution is advised in drawing conclusions from this single study. The number of patients in this study was small, with a relatively short follow-up period. The method of evaluation of recovery was limited. It is a challenge to study children with CP because there is a wide variability in each child’s involvement, and the growth pattern may affect the results of the intervention. Given these constraints, this study was designed simply as a pilot investigation. Controlled, randomized, double-blind studies with more patients and detailed evaluation are necessary to clarify the role of the mesh ATL procedure. Most importantly, future studies should include more long-term follow-up as recurrence might occur after 2 years from surgery.
The mesh ATL procedure, with soft tissue release performed through a mesh-like series of small cuts, has the advantage of preserving the gastrocnemius without complete section. The present study shows that it confers greater antigravity stability and facilitates quicker recovery, and also achieves adequate correction of the equinus deformity in spastic CP, which is as effective as that of the Vulpius procedure.
Conflicts of interest
There are no conflicts of interest.
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