Abstract
Purpose of Study
Planovalgus deformity in cerebral palsy is disabling for the child in terms of increased energy expenditure during the gait cycle. The lever arm function of the foot is lost due to midfoot break and the achilles tendon is at a disadvantage being unable to lift the body weight during push-off. We evaluated the results of calcaneal lengthening osteotomy in such patients with clinical, radiological and gait parameters.
Methods
17 spastic feet in a sample of 10 children were included in our study. The children were classified according to the GMFCS classification system and clinical parameters such as heel valgus and heel rise tests, radiological angles such as Talo-calcaneal angle and Talo-navicular coverage angle on AP view and Calcaneal pitch angle, calcaneus-5th metatarsal angle and talus-1st metatarsal angle on lateral view were measured. Video gait analysis was performed to observe knee progression angle in mid stance and peak knee flexion angle in mid and terminal stance.
Results
Improvement was noted clinically in the heel valgus angle (preop-12.06°, postop-5.12°) and radiological parameters showed an improved coverage of the talus by navicular with simultaneous lifting of the medial longitudinal arch. Gait analysis showed decreased knee flexion trend in mid and terminal stance phase with better restoration of the knee axis.
Conclusion
Calcaneal lengthening osteotomy with peroneus brevis lengthening corrects almost all aspects of planovalgus deformity with an improved gait pattern without disturbing joint range of motion. It is a safe procedure for GMFCS grade 1 and 2 patients without much complications.
Keywords: Planovalgus deformity, Cerebral palsy, Calcaneal lengthening osteotomy, Gait parameters, Lever arm function
1. Introduction
Planovalgus foot deformity is commonly seen in diplegic and quadriplegic patients of cerebral palsy. During normal gait cycle, the length of the foot from heel to the metatarsal heads, act as a lever arm for the tendino-achilles. In cerebral palsy patients with planovalgus deformity, effective lever arm function of the foot is lost due to midfoot break and the new shorter lever arm available during the push off is from the heel till the midfoot. As a result, the muscles have to generate more amount of force to balance the ground reaction force. Also, the defective lever arm prevents adequate transfer of forces from the ground reaction force (GRF) which falls behind the knee, leading to knee flexion in mid-stance phase and the normal plantarflexion-knee hyperextension coupling is lost. This produces abnormal gait kinematics which is manifested as increased knee flexion and internal rotation at hip.1,2
Conservative treatment can be tried in the form of bracing to anatomically realign the foot skeleton so that the progression of deformity can be stopped. Ground reaction AFO (Ankle Foot Orthosis) is a useful technique to restore the normal ankle plantarflexion-knee hyperextension coupling. Effective bracing with appropriate orthosis can improve foot lever arm function and restore the normal GRF moment anterior to the knee during walking. Surgical treatment is indicated for patients who no longer tolerate orthotics or when lever arm dysfunction interferes with function.3 Surgical procedures described include subtalar extraarticular arthrodesis, triple arthrodesis and arthroereisis of the sinus tarsi.4,5
Calcaneal lengthening osteotomy is currently being used as a standard surgical procedure for correction of valgus heel deformity as it does not disturb the joint function and provides a better weight distribution.6 It is preferred over medial calcaneal slide osteotomy as it corrects all the components of the deformity while the latter produces a second compensatory deformity.7 In this study, we have evaluated the results of calcaneal lengthening osteotomy in cerebral palsy patients with planovalgus deformity using clinical, gait and radiographic parameters.
2. Material and method
We did a prospective observational study on symptomatic patients of spastic planovalgus foot deformity who presented to us in out-patient clinics with sinus tarsi pain, exaggerated shoe-wear and abnormal gait characteristics etc. 17 spastic feet with planovalgus deformity were included in our study after the failure of conservative treatment for a period of six months. All the patients were in the age group of 8–18 years. Patients with tarsal coalition and those with previous surgical procedures done on foot were excluded.
All the children were scaled on the Gross Motor Function Classification System (GMFCS) based on their functional abilities after a detailed history.
Preoperative examination consisted of: 1. Heel valgus angle measurement in relaxed standing foot posture, 2. Single heel rise test, 3. Double heel rise test,4. Ankle joint range of motion, 5. Video assisted gait analysis, 6. Radiographic examination.
Heel valgus was measured using a heel bisector line and the angle it formed with the vertical was measured using a goniometer (Fig. 1a). Single heel rise test was done to assess the muscle strength and tendon function, the patients were asked to repeatedly go on their toes with the heel off the ground and position of the heel was evaluated by looking for correction of heel valgus deformity (Fig. 1b).8 Double heel rise test was done with bilateral heel off the ground simultaneously, the feet were observed for the normal inversion which shows the supinatory potential of the feet (Fig. 1c).9
Fig. 1a.
Measurement of heel valgus angle using heel bisector method.
Fig. 1b.
Single heel rise test.
Fig. 1c.
Double heel rise test.
Gait examination was done using video gait analysis and knee progression angle in mid stance was observed using Edinburgh visual gait scale.10 Knee flexion angle was measured in the mid and terminal stance (Fig. 2a, Fig. 2ba and b).
Fig. 2a.
Still photograph from slow motion video gait analysis showing knee progression angle (external, fully visible knee cap).
Fig. 2b.
Still photograph from slow motion video gait analysis showing peak knee flexion in mid and terminal stance phase.
Preoperative radiographic evaluation with weight bearing anterior-posterior (AP) and lateral views of the foot was done to assess.
-
1.
Talocalcaneal angle and talonavicular coverage angle on AP view (Fig. 3a).
-
2.
Calcaneal pitch angle, calcaneal-5th metatarsal angle and talo-1st metatarsal angle on lateral view (Fig. 3b).11
Fig. 3a.
Weight bearing AP view of foot showing talo-calcaneal angle(TCA) and talo-navicular coverage angle(TNCA).
Fig. 3b.
Weight bearing Lateral view of foot showing calcaneal pitch angle(CPA), talo-1st metatarsal angle(Ta1MTA) and calcaneus-5th metatarsal angle(Ca5MTA) and the calcaneal opening osteotomy (red arrow).
2.1. Surgical technique
Patients were operated in supine position with a pillow under the contralateral buttock to elevate the iliac crest for harvesting the bone graft. Modified Ollier incision was used over the sinus tarsi passing approximately 1 cm proximal to the anterior beak of calcaneus. The peroneus longus and brevis tendons were released from their sheaths and a Z lengthening of peroneus brevis tendon was done while the peroneus longus tendon was retracted plantarwards (Fig. 4a). A 1.5 mm K-wire was inserted on the dorsum of foot from cuboid, passing through the calcaneo-cuboid joint to prevent its subluxation during impaction of graft at the osteotomy site. A lateral opening wedge osteotomy exiting medially between the anterior and the middle facets of calcaneum was performed and it was distracted using kirschner wires (Fig. 4b). A trapezoidal tricortical bone graft of 1.5–2 cm width was obtained from iliac crest and impacted in the osteotomy site to produce distraction. As soon as the graft was press fit in the osteotomy, appearance of the medial arch was noted in the foot.
Fig. 4a.
The two ends of the peroneus brevis tendon after being cut in Z lengthening fashion and the sural nerve isolated and protected in a feeding tube loop.
Fig. 4b.
intra operative photograph showing the K -wires used to distract the osteotomy and another percutaneous K wire holding the calcaneo-cuboid joint.
Post operatively, patients were kept non weight bearing with crutch walking for 6 weeks when the K wire was removed and each patient was given brace (AFO) with medial arch support for 3 months (Fig. 5).
Fig. 5.
Post-operative X ray showing the K wire passing through cuboid (black arrow) and holding the bone graft at the osteotomy site (red arrow).
Follow-up evaluation with clinical, radiological and gait parameters was done at one year by the same surgeon to eliminate the observer bias.
2.2. Statistical analysis
Data analysis was done using SPSS version 21. For quantitative data like clinical parameters (heel valgus) and radiological parameters(AP talocalcaneal angle, AP talonavicular coverage angle, Lateral talus-first metatarsal angle, calcaneal pitch angle, lateral calcaneus-fifth metatarsal angle) mean and standard deviation were calculated and preoperative clinical examination findings and radiographic findings were compared with postoperative follow up findings using appropriate tests. P value < .05 was considered statistically significant.
3. Results
The mean age of the children in study was 11.13 years with following descriptive statistics:
Seven patients (12 feet) were GMFCS grade 1 and three patients (5 feet) were GMFCS grade 2.12 The average heel valgus was 12.06° (range- 10°–18°) and improved to 5.12° (range- 2°–12°) in the postoperative period. This restored the normal hindfoot alignment and placement of sustentaculum tali beneath the talus. The range of motion of the ankle joint was not affected. (Table 1).
Table 1.
Clinical parameters.
| Preoperative | Postoperative | |
|---|---|---|
| Heel Valgus | 12.06° ± 2.384° | 5.12° ± 2.261° |
| APF | 0–30.9° | 0–30.9° |
| ADF | 0–13.8° | 0–13.8° |
∗p value(heel valgus) = <0.001 APF: Ankle plantarflexion, ADF: Ankle dorsiflexion.
Preoperatively, 41.2% patients were able to perform single heel rise test and 47% were able to perform double heel rise test, which improved to 58.8% and 82% respectively in the post-operative period.
Gait parameters such as Knee progression angle in mid stance was observed according to Edinburgh visual gait scale and it was found to be more towards neutral alignment in the post-operative period.13 (Table 2).
Table 2.
Knee progression angle in mid-stance.
| Edinburgh visual scale for Knee progression angle | Preop (frequency in %) | Postop (frequency in %) |
|---|---|---|
| External, fully visible knee cap | 35.2 | 17.6 |
| Neutral, knee cap midline | 47 | 70.58 |
| Internal, all knee cap visible | 11.76 | 5.88 |
| Internal, part knee cap visible | 5.88 | 5.88 |
The peak knee flexion measured in the mid and terminal stance phase of the gait cycle was 7.64° ± 7.72° in the preoperative period and it decreased to 4.7° ± 6.7° in the postoperative period.
Radiologically, the talocalcaneal angle on AP view improved from an average of 34.6° (range- 25°–55°) to 29° (range- 22°–50°) and the talonavicular coverage angle improved from an average of 29.35° (range- 18°–62°) to 21.29° (range- 10°–40°). With the improvement in both these angles, the coronal and transverse plane alignment of the midfoot was restored to near normal. The talus was better covered by the navicular on medial side of the midfoot (Fig. 6a, Fig. 6ba and b).
Fig. 6a.
Pre-operative X ray showing inadequate talonavicular coverage (red arrow).
Fig. 6b.
1 year post-operative follow-up X ray showing improved talo-navicular coverage (red arrow).
Angles measured on the lateral view also showed significant improvement. The arch angle (calcaneus-5th metatarsal angle) improved from 174° (range- 165°–180°) to 169° (range- 160°–180°). Talo-1st metatarsal angle improved from an average of 24.6° (range- 10°–40°) to 12.41° (range- 0°–22°). Thus, the normal alignment of the 1st metatarsal along the talar axis was achieved (Fig. 6c, Fig. 6dc and d). Although, the improvement noted in calcaneal pitch was significant but the postoperative values were not in the normal range for this angle. (Table 3).
Fig. 6c.
Pre-operative X ray with Talar axis facing downwards with respect to 1st metatarsal.
Fig. 6d.
1 year post-operative follow-up X ray showing improved alignment of talar axis with respect to 1st metatarsal.
Table 3.
Radiological parameters.
| AP view | Preoperative | Postoperative |
|---|---|---|
| Talocalcaneal angle | 34.6° ± 8° | 29° ± 7.5° |
| Talo-navicular coverage angle | 29.35° ± 11.6° | 21.29° ± 9° |
| Lateral view | ||
| Calcaneal pitch angle | 5.41° ± 3.4° | 8.41° ± 3.5° |
| Talo-1st metatarsal angle | 24.6° ± 8° | 12.41° ± 5.12° |
| Calcaneus-5th metatarsal angle | 174° ± 5.3° | 169° ± 4° |
∗p value = <.001
We had one patient in the immediate post-operative period with complaint of paresthesia in the region of sural nerve distribution over the lateral aspect of the foot and it was managed successfully with oral vitamin B 12 therapy. We also noted recurrence of deformity in one patient at the time of 1-year follow-up evaluation.
4. Discussion
Forces generated by the muscles during the gait cycle can be best understood in terms of a lever arm system. In a normal functioning foot, during the push-off phase of the gait cycle, Achilles tendon generates the force which acts along the solid lever arm extending from the heel to the metatarsal heads and it lifts the body weight. In cerebral palsy children with planovalgus deformity, this normal functioning lever arm of the foot is lost as there is heel valgus in coronal plane, forefoot abduction in transverse plane and midfoot is broken. Thus, the lever arm of foot in these children is flexible at the midfoot instead of being a normal rigid lever arm. The effort generated by the tendino-achilles during the 3rd rocker in the gait cycle is dissipated at the level of the midfoot across a shorter lever arm and it is inadequate to lift the body weight. As a result, the already contracted tendino-achilles has to generate more amount of force to keep the body moving forwards.14
The triceps surae, being at a disadvantage in such child, fails to cause the GRF moment arm fall anterior to the knee during the mid and terminal stance phase of the gait cycle. So, the normal ankle plantarflexion and knee hyperextension couple is lost and the child has to use his quadriceps muscle during the stance phase to provide knee stability. This increases the energy expenditure and also increases the patellofemoral load causing knee pain in such patients. Lack of stance phase stability in these children produces various symptoms like ankle and midfoot sprains, plantar fasciitis and achilles tendinitis.15
Gait observation combined with clinical and radiological measurements provides a valuable insight into the patho-mechanics of planovalgus deformity and difficulties faced by these children during ambulation. Those patients who continue to have symptoms even after bracing, need surgical treatment. Procedures like arthroeresis and arthrodesis which were popular in the past, are no longer used as the first surgical option due to higher rates of complications such as loosening of the implant, joint effusion or haemarthrosis and contracture of peroneal muscles due to arthroeresis and arthrodesis is known to result in early degenerative arthritis is nearby joints and sometimes pseudoarthrosis formation.16, 17, 18, 19
Osteotomy of the calcaneum combined with soft tissue procedure is the best proven surgical approach now-a-days for the treatment of planovalgus deformity. Previously many attempts have been made in different studies to evaluate the radiological outcome of this osteotomy but, we evaluated clinical parameters also and significant improvement was noted in heel valgus angle which came to near normal range of 5°. A better performance was also noted in the single heel and double heel rise tests in the post-operative period.
Radiologically, our results show that calcaneal osteotomy is effective in achieving adequate coverage of talus by the navicular bone as noted by improvement in the talo-navicular coverage angle. Talo-calcaneal angle correction on AP view also correlates with clinical improvement in the hindfoot valgus.20, 21, 22, 23
On the lateral view, calcaneal osteotomy showed an improvement in the arch angle (Calcaneal-5th Metatarsal angle), Talo-1st metatarsal angle and calcaneal pitch angle, all of which indirectly indicate lifting of the medial longitudinal arch in the foot. Although the calcaneal pitch angle increased in the post-operative readings but it didn’t come in the normal range (mean pre-operative value = 5.41° ± 3.4°, mean post-operative value = 8.41° ± 3.5°). A similar behavior was noted by Sung et al. in their study with a mean calcaneal pitch angle of 7.3° in post-operative readings.24 We didn’t come across calcaneocuboid joint subluxation which is a known complication when the osteotomy is opened up to insert the graft. We believe that inserting a K-wire across the calcaneocuboid joint from the lateral aspect of the foot before distracting the osteotomy site is good technique to prevent joint subluxation.25
We also studied gait parameters including knee progression angle in mid stance and the peak knee flexion in mid and terminal stance phase. Knee progression angle showed a more midline alignment as compared to preoperative readings. The peak knee flexion showed a decreasing trend after the osteotomy indicating a better functioning tendinoachilles across the restored foot lever arm trying to bring the GRF moment in front of the knee in stance phase. These parameters have not been studied simultaneously with clinical and radiological parameters in previous studies.
Foot acts as a key component of the gait cycle and any deformity in foot may produce a secondary compensation proximally at the level of knee. Planovalgus deformity can also produce excessive external rotation of foot thus leading to mal-alignment with the knee axis. Calcaneal osteotomy improves the gait pattern by restoring the lever arm function to near normal and also brings the realignment of the knee axis with respect to foot rotation.
With the restoration of the medial longitudinal arch and increase in the effective length of the calcaneum, the rigid lever arm function of the foot improved during the initial push off phase, making it less energy consuming for the patient. Children walking earlier with a flexed knee gait, jump gait and crouch gait pattern were able to achieve lesser degrees of knee flexion or near complete extension in mid stance phase of the gait cycle. However, the magnitude of improvement was less in patients with higher degrees of knee flexion due to hamstring contractures or those with fixed flexion deformity at knee joint.
In our study, the recurrence rate of deformity was 5.88% (1 out of 17) during a follow-up of 1 year. The child was GMFCS grade 2 with excessive knee flexion in mid stance of gait cycle.
The present study establishes that lateral calcaneal lengthening osteotomy is capable of correcting almost all components of planovalgus deformity effectively in spastic flatfeet of cerebral palsy patients (GMFCS grade 1 and 2). This osteotomy gives prompt result as the appearance of medial arch can be noted on the operating table as soon as the graft is placed in the osteotomy site. The normal weight bearing with the restoration of the heel -metatarsal head lever arm of the foot can be achieved. This procedure is also advantageous over fusion procedures in terms of preservation of subtalar and ankle joint range of motion.
The possible limitations of our study are, a shorter duration of follow-up and a relatively small sample size. Further research with higher number of patients and a longer follow-up with radiographic and gait analysis is required to look for recurrence of deformity and other possible complications.
5. Conclusion
Planovalgus deformity should be treated as a lever arm disease in patients with cerebral palsy with the main focus of treatment being the underlying skeletal deformity rather than muscle imbalance. Calcaneal lengthening osteotomy with concomitant peroneus brevis lengthening significantly corrects the heel valgus and all the radiological parameters of the deformity. It also improves the gait pattern in terms of achieving a stable rigid lever arm of foot for the better functioning of triceps surae muscle. It is a safe procedure for spastic planovalgus foot deformity without much complications in ambulatory GMFCS grade 1 or 2 patients of cerebral palsy.
Funding
Nil.
Statement of informed consent
A complete, fully informed and written consent was taken from the parents of the patients (as the patients were minor) for treatment purpose as well as for the use of their radiographs, photographs and data for the purpose of publication.
Ethical statement
A valid ethical clearance was obtained from the ethical committee of the institution for the purpose of this study.
Declaration of competing interest
On behalf of all the authors, the corresponding author states that there is no conflict of interest.
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