Cerebral Palsy | Dynamic vs Fixed Deformity | SPLATT | Tendon Transfers | Gait Analysis
DEFORMITY CLASSIFICATION
Critical Must-Knows
- Equinovarus = ankle plantarflexion + hindfoot varus + forefoot supination from spastic muscle imbalance
- Tibialis posterior overactivity drives hindfoot varus; tibialis anterior drives forefoot supination and first ray plantarflexion
- Distinguish dynamic (supple under anaesthesia) from fixed deformity before choosing surgery
- SPLATT (split tibialis anterior transfer) is the workhorse operation for dynamic forefoot supination
- Single-event multilevel surgery (SEMLS) is the modern paradigm combining all corrections in one procedure
Clinical Pearls
- "Dynamic equinovarus is correctable under GA; fixed is not - this distinction changes the operation
- "SPLATT splits the TA tendon, half stays anterior, half passes through the interosseous membrane to the peroneal side
- "GMFCS level is the single most important prognostic factor for ambulatory outcome
- "Gait analysis (3-D) guides surgical planning by quantifying which muscles are overactive and when in the gait cycle
Clinical Imaging
Spastic Equinovarus Foot Deformity in Cerebral Palsy
Images for this topic are sourced separately via the dedicated image pipeline.
Critical Equinovarus Exam Points
Anatomy
Tibialis posterior inverts and plantarflexes the hindfoot. Tibialis anterior dorsiflexes and inverts (supinates) the forefoot. Overactivity of either or both muscles creates the equinovarus pattern. The peroneus longus and brevis are the antagonists (evertors).
Dynamic vs Fixed
Dynamic deformity corrects under general anaesthesia - spasticity alone. Fixed deformity persists under GA - contracture or bony change. This distinction is critical: dynamic deformity may respond to BTX-A or tendon transfer; fixed deformity requires lengthening, release, or osteotomy.
Surgical Hierarchy
Address equinus first (gastrocnemius recession or TAL), then varus (TP release or transfer), then forefoot supination (SPLATT). Plan all levels in one sitting (SEMLS principle) to avoid repeated anaesthetics and cast immobilisation in children.
GMFCS Prognosis
GMFCS I-II: Community ambulators, excellent surgical outcomes. GMFCS III: Household ambulators with assistive devices, good outcomes with careful selection. GMFCS IV-V: Limited ambulation, surgery focused on comfort, bracing, and seating. Always state GMFCS level in your exam answer.
Quick Decision Guide
| Presentation | Diagnosis | Treatment | Key Pearl |
|---|---|---|---|
| Dynamic equinovarus, GMFCS I-II, ambulatory child | Correctable under GA, 3-D gait analysis shows premature heel rise | Gastrocnemius recession + SPLATT ± TP intramuscular lengthening | Single-event multilevel surgery (SEMLS) preferred |
| Fixed hindfoot varus with equinus, GMFCS II-III | Not correctable under GA, weight-bearing lateral X-ray shows varus | TAL + TP Z-lengthening or transfer + SPLATT | Must distinguish TA-driven from TP-driven varus |
| Severe rigid deformity, GMFCS IV-V, non-ambulatory | Fixed deformity with skin breakdown risk, seating issues | Talectomy or subtalar fusion for positioning | Goals shift from gait to comfort and hygiene |
STEPMuscles Driving Equinovarus
| S | Soleus and gastrocnemius Spastic equinus from plantarflexion overactivity |
| T | Tibialis posterior Hindfoot varus from inversion overactivity |
| E | Extensor hallucis longus Great toe clawing from recruitment during swing |
| P | Peroneals (weak) Weak or underactive evertors fail to oppose inversion |
| S | Soleus and gastrocnemius Spastic equinus from plantarflexion overactivity | E | Extensor hallucis longus Great toe clawing from recruitment during swing |
| T | Tibialis posterior Hindfoot varus from inversion overactivity | P | Peroneals (weak) Weak or underactive evertors fail to oppose inversion |
Hook:STEP through the equinovarus muscles: Soleus for equinus, Tibialis posterior for varus, EHL for claw toe, Peroneals too weak to resist!
GRABSSurgical Options for Equinovarus
| G | Gastrocnemius recession Proximal release for isolated spastic equinus (first step) |
| R | Rectify varus (TP lengthening or transfer) Tibialis posterior intramuscular lengthening or split transfer to peroneal brevis |
| A | Anterior tibialis transfer (SPLATT) Split transfer of TA to lateral cuneiform or cuboid for forefoot supination |
| B | Botox (BTX-A) Chemical denervation for dynamic deformity; temporising but repeatable |
| S | SEMLS Single-event multilevel surgery: address all levels in one operative sitting |
| G | Gastrocnemius recession Proximal release for isolated spastic equinus (first step) | B | Botox (BTX-A) Chemical denervation for dynamic deformity; temporising but repeatable |
| R | Rectify varus (TP lengthening or transfer) Tibialis posterior intramuscular lengthening or split transfer to peroneal brevis | S | SEMLS Single-event multilevel surgery: address all levels in one operative sitting |
| A | Anterior tibialis transfer (SPLATT) Split transfer of TA to lateral cuneiform or cuboid for forefoot supination |
Hook:GRABS the equinovarus: Gastrocnemius recession, Rectify varus, Anterior tibialis transfer, Botox, SEMLS!
STAGGait Analysis Phases in Equinovarus
| S | Swing phase TA overactivity causes foot inversion and forefoot supination during clearance |
| T | Terminal swing Premature heel rise or toe-first contact from equinus |
| A | Absence of heel strike Equinus prevents normal first rocker; patient lands on lateral border |
| G | Ground reaction vector 3-D analysis shows deviated GRF producing knee hyperextension moment |
| S | Swing phase TA overactivity causes foot inversion and forefoot supination during clearance | A | Absence of heel strike Equinus prevents normal first rocker; patient lands on lateral border |
| T | Terminal swing Premature heel rise or toe-first contact from equinus | G | Ground reaction vector 3-D analysis shows deviated GRF producing knee hyperextension moment |
Hook:STAGger through gait analysis: Swing phase inversion, Terminal swing toe-strike, Absent heel strike, Ground reaction deviation!
Overview and Epidemiology
Why This Matters
Spastic equinovarus is the most common foot deformity in cerebral palsy and a high-yield FRACS/FRCS paediatric orthopaedic topic. It exemplifies the principle of muscle imbalance: spastic overactivity of invertors and plantarflexors overwhelms weak evertors and dorsiflexors. The surgical management requires a systematic approach - distinguishing dynamic from fixed deformity, identifying which muscles are overactive and when in the gait cycle, and planning single-event multilevel surgery.
Epidemiology
- Cerebral palsy is the most common motor disability in childhood, with an incidence of approximately 2 to 3 per 1000 live births globally
- Equinovarus deformity affects roughly 15 to 30 percent of children with spastic CP, making it the most prevalent foot deformity
- Spastic diplegia (bilateral CP) carries the highest prevalence of equinovarus, followed by hemiplegia
- Unilateral involvement (hemiplegia) often shows more severe varus due to unopposed tibialis posterior spasticity
Clinical Impact
- Gait disturbance: Toe-walking, lateral border weight-bearing, tripping, and poor push-off
- Pain: Lateral foot pain from overloaded peroneal tubercle and fifth metatarsal base
- Skin breakdown: Callus formation over lateral border, risk of ulceration in severe cases
- Bracing difficulty: AFOs cannot adequately control dynamic varus, leading to poor compliance
- Progression: Untreated dynamic deformity progresses to fixed contracture with secondary bony changes
Pathophysiology
Muscle Imbalance Mechanism in Spastic Equinovarus
The equinovarus deformity results from spastic overactivity of plantarflexors and invertors combined with relative weakness of dorsiflexors and evertors. The key muscles driving the deformity are:
- Gastrocnemius-soleus complex: Spastic equinus (ankle plantarflexion)
- Tibialis posterior: Spastic hindfoot inversion (varus); active in both stance and swing
- Tibialis anterior: Spastic forefoot supination and first ray plantarflexion; most active in swing phase
The antagonists (peroneus longus, peroneus brevis, extensor digitorum longus) are typically weak or underactive, failing to counterbalance the invertors. Over time, dynamic spasticity leads to muscle contracture, ligamentous shortening, and eventually bony deformation of the growing foot.
Muscle Contributions to Equinovarus Deformity
| Muscle | Spastic Action | Deformity Produced | Phase of Overactivity |
|---|---|---|---|
| Gastrocnemius-soleus | Ankle plantarflexion | Equinus (toe-walking) | Stance phase (premature heel rise) |
| Tibialis posterior | Hindfoot inversion + plantarflexion | Hindfoot varus | Stance and swing (persistent) |
| Tibialis anterior | Forefoot supination + first ray plantarflexion | Forefoot varus / supination | Swing phase (foot clearance) |
| Extensor hallucis longus | Great toe hyperextension | Claw great toe (recruited for dorsiflexion) | Swing phase (compensatory) |
| Peroneus longus and brevis | Foot eversion (antagonists, weak) | Cannot oppose inversion | Underactive throughout gait cycle |
Dynamic Deformity
Definition: Deformity present during activity but correctable passively and under anaesthesia
Mechanism: Spasticity alone without contracture
Key test: Examine under GA - full passive correction achieved
Management: BTX-A injections, AFO bracing, physical therapy, or tendon transfers (no lengthening needed)
Fixed Deformity
Definition: Deformity persists even under general anaesthesia
Mechanism: Muscle contracture, joint capsule shortening, bony deformation
Key test: Examine under GA - passive correction incomplete or absent
Management: Surgical lengthening, release, osteotomy, or arthrodesis
Classification and Types
Gross Motor Function Classification System
The GMFCS level is the single most important prognostic factor in CP foot surgery. It determines treatment goals and expected outcomes.
| GMFCS Level | Ambulation | Surgical Goals | Expected Outcome |
|---|---|---|---|
| Level I | Walks without limitations | Normalise gait pattern, improve efficiency | Excellent - near-normal gait achievable |
| Level II | Walks with limitations (no devices) | Improve gait, prevent progressive deformity | Very good - meaningful gait improvement |
| Level III | Walks with assistive devices | Maintain or improve community ambulation | Good - functional gains with realistic expectations |
| Level IV | Self-mobility with limitations, may use powered mobility | Comfort, positioning, bracing tolerance, seating | Modest - focus shifts from gait to comfort |
| Level V | Transported manually | Comfort, hygiene, prevent skin breakdown | Limited - positioning procedures |
Always state the GMFCS level when discussing surgical plans in exams. Surgical outcomes deteriorate significantly with higher GMFCS levels.
Clinical Assessment
History
- Birth history: Prematurity, birth asphyxia, neonatal complications
- Motor milestones: Delayed sitting, crawling, walking
- CP classification: Topography (hemiplegia, diplegia, quadriplegia), GMFCS level
- Gait pattern: Toe-walking onset, tripping frequency, falling pattern
- Previous treatment: BTX-A injections, AFO use, prior surgeries
- Functional level: Community ambulation distance, assistive devices used
- Patient and family goals: Realistic expectations discussion is essential
Physical Examination
- Inspect: Standing posture, foot progression angle, toe-walking pattern, lateral border callus
- Look: From behind - too many toes sign (hindfoot valgus) vs no toes visible (varus); from side - heel contact pattern
- Feel: Tibialis posterior tendon during inversion (overactive? palpable spasm?); peroneal tendon bulk
- Move: Passive ROM ankle (equinus), subtalar (varus correctability), forefoot (supination)
- Silfverskiold test: Distinguish gastrocnemius (improves with knee flexion) from soleus equinus (no change with knee flexion)
- Spasticity grading: Modified Ashworth Scale for TA, TP, gastrocnemius-soleus
Silfverskiold Test: Essential for Equinus Assessment
Technique: Passive ankle dorsiflexion measured with the knee extended and then flexed to 90 degrees.
Gastrocnemius tightness (positive Silfverskiold): Dorsiflexion improves by more than 10 degrees when the knee is flexed (relaxes gastrocnemius which crosses the knee joint).
Soleus tightness: Dorsiflexion does not significantly improve with knee flexion (soleus does not cross the knee).
Clinical implication: Isolated gastrocnemius tightness is treated with gastrocnemius recession (proximal release). Combined gastrocnemius-soleus tightness may require percutaneous or open TAL (Achilles tendon lengthening). Over-lengthening the Achilles in an ambulatory child must be avoided as it causes calcaneus gait (crouch gait).
Clinical Tests for Equinovarus Assessment
| Test | Technique | Positive Finding | Significance |
|---|---|---|---|
| Silfverskiold test | Passive DF with knee extended vs flexed 90 degrees | Greater than 10 degrees improvement with knee flexion | Isolated gastrocnemius tightness = recession, not TAL |
| TP block test | Inject TP with local anaesthetic, reassess gait | Varus corrects after block | TP is dominant varus driver, consider TP lengthening or transfer |
| Observation under GA | Examine foot passive ROM under general anaesthesia | Full correction (dynamic) vs residual deformity (fixed) | Determines whether soft tissue surgery alone suffices |
| Modified Ashworth Scale | Passive stretch of target muscle, grade 0 to 4 | Grade 3 or above = considerable spasticity | Guides BTX-A dosing and surgical planning |
Differential Diagnosis of Paediatric Equinovarus
| Condition | Key Features | Discriminating Finding | Management Difference |
|---|---|---|---|
| Spastic equinovarus (CP) | Spasticity, hyperreflexia, upper motor neuron signs, dynamic component | CP diagnosis established, GMFCS graded, dynamic deformity pattern | SEMLS, BTX-A, tendon transfers |
| Idiopathic clubfoot (congenital talipes equinovarus) | Present at birth, no neurological findings, fixed deformity from birth | Congenital onset, Pirani scoring, no spasticity or hyperreflexia | Ponseti casting, posteromedial release if recurrent |
| Hereditary motor sensory neuropathy (Charcot-Marie-Tooth) | Progressive cavovarus, peroneal muscle wasting, sensory changes | Bilateral cavovarus, family history, nerve conduction studies abnormal | Tendon transfers, osteotomies, genetic counselling |
| Habitual toe-walker (idiopathic) | Bilateral toe-walking, no neurological signs, normal development | Can walk heel-toe on request, normal neurological exam, no spasticity | Observation, serial casting if persistent, no tendon surgery |
| Spinal cord pathology (tethered cord, syrinx) | Progressive foot deformity, bowel or bladder changes, back pain | Deteriorating neurological signs, MRI spine abnormality | Neurosurgical decompression first, then orthopaedic correction |
Do Not Miss
Always examine the spine in a child with progressive equinovarus. A tethered cord or syrinx can mimic or coexist with CP. Deteriorating gait, new bowel or bladder dysfunction, or asymmetric neurological findings warrant urgent MRI of the entire neuroaxis. Operating on a foot deformity caused by untreated spinal pathology is a critical error.
Investigations
Investigation Protocol
Clinical examination: Silfverskiold test, passive ROM, spasticity grading, observation of gait pattern
3-D instrumented gait analysis: The gold standard for surgical planning. Quantifies joint angles, moments, powers, and EMG timing of individual muscles through the gait cycle. Identifies which muscles are overactive and when, guiding the choice between SPLATT, TP lengthening, or both.
Video gait analysis: Useful when 3-D analysis is unavailable (common in limited-resource settings)
Views: Standing AP and lateral of the foot and ankle; saltarelli view (dorsiflexion lateral) if equinus severe
Look for: Talar flattening, navicular-medial malleular overlap (subtalar subluxation), calcaneal pitch, Meary angle (talar-first metatarsal angle), hindfoot alignment
Clinical correlation: Radiographs are most useful in fixed deformity to assess bony changes and plan osteotomies
Indication: Progressive deformity, bowel or bladder changes, asymmetric signs, absent CP diagnosis
Findings: Tethered cord, syrinx, diastematomyelia, lipoma
Critical: Neurosurgical intervention may halt progression and change orthopaedic management
Investigation Pearl
3-D gait analysis has been shown to change the surgical plan in approximately 40 to 60 percent of cases compared with clinical examination alone. In the exam, mention it as the gold standard for surgical planning in ambulatory children (GMFCS I-III). It is not required for non-ambulatory children (GMFCS IV-V) where goals are positioning and comfort.
Management Algorithm
Conservative Management
Goal: Delay or prevent surgery, maintain ROM, optimise gait while the child grows
Conservative Protocol
Stretching programme: Daily gastrocnemius-soleus stretching, TP stretching, ankle ROM exercises
Strengthening: Peroneal strengthening (evertors), tibialis anterior strengthening for eccentric control
Functional training: Gait training, balance exercises, task-specific practice
Evidence: Therapy alone rarely corrects established equinovarus but maintains ROM and delays surgery
Mechanism: Botulinum toxin type A blocks acetylcholine release at the neuromuscular junction, reducing spasticity for approximately 3 to 4 months per injection
Targets: Gastrocnemius, tibialis posterior, tibialis anterior (guided by gait analysis)
Dose: Typically 4 to 6 units per kilogram per muscle (total dose up to 15 to 20 units per kilogram per session)
Evidence: Effective for dynamic deformity; delays surgery but does not prevent eventual need in most cases
Limitation: Repeated injections may cause antibody formation and reduced efficacy; does not address fixed contracture
Solid AFO: Controls equinus and partially controls varus in stance; best for fixed equinus
Hinged AFO: Allows some dorsiflexion while controlling equinus; preferred for ambulatory children to permit third rocker
Ground reaction AFO: Anterior tibial shell controls crouch gait and equinus simultaneously
Supramalleolar orthosis (SMO): Controls subtalar varus while allowing ankle movement; useful when varus is the primary problem
Key principle: Bracing compensates for deformity but does not correct it; most children require surgery as they grow
Indication: Short-term correction of dynamic equinus, often combined with BTX-A
Technique: Above-knee cast changed weekly, gradually correcting equinus and varus
Limitation: Short-lived benefit; deformity recurs once cast removed if underlying spasticity persists
Conservative Management Pearl
Non-operative treatment is the first line for dynamic equinovarus in young children (typically under 6 years). However, it is a temporising strategy. Approximately 70 to 80 percent of children with spastic equinovarus will eventually require surgery. The goal of conservative care is to maintain ROM and optimise the timing of single-event multilevel surgery (SEMLS), typically performed between ages 6 and 10 years.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Recurrent deformity | 10 to 30 percent over 5 to 10 years | Younger age at surgery, higher GMFCS, growth remaining | Revision SEMLS; consider repeat gait analysis |
| Overcorrection (calcaneus / valgus) | 5 to 15 percent after TAL or TP transfer | Over-lengthening Achilles, over-transfer of TP | Avoided by careful intraoperative tensioning; bracing if mild |
| Crouch gait (calcaneus gait) | 10 to 20 percent after TAL in diplegics | Excessive Achilles lengthening, especially in GMFCS II-III | Ground reaction AFO; revision with gastrocnemius advancement |
| Wound breakdown or infection | 2 to 5 percent | Multiple incisions, poor nutrition, GMFCS IV-V | Standard wound care; delayed rehabilitation |
| Stiffness (loss of ROM) | Variable, more common with bony procedures | Prolonged immobilisation, multiple simultaneous procedures | Early mobilisation protocol, intensive post-op therapy |
| Tendon transfer failure | 5 to 10 percent | Poor tendon quality, inadequate fixation, early loading | Revision transfer or alternative procedure |
Over-lengthening the Achilles: A Preventable Complication
Over-lengthening the Achilles tendon is one of the most significant complications in CP foot surgery. It produces calcaneus gait (heel-strike with absence of push-off) and can progress to crouch gait in diplegic children. Prevention strategies include: using gastrocnemius recession (Baumann or Strayer) rather than TAL whenever the Silfverskiold test is positive; avoiding percutaneous TAL in ambulatory children; and meticulous intraoperative tensioning. Once established, calcaneus gait is difficult to salvage and may require gastrocnemius advancement or tendon transfer.
Outcomes and Prognosis
Outcomes by GMFCS Level and Procedure
| GMFCS Level | Typical Procedure | Expected Outcome | Long-term Function |
|---|---|---|---|
| Level I | SEMLS (GR + SPLATT ± TP lengthening) | Near-normal gait, excellent satisfaction | Community ambulation, sport participation possible |
| Level II | SEMLS (GR + SPLATT + TP procedure) | Significant gait improvement, reduced tripping | Independent community ambulation maintained |
| Level III | SEMLS (comprehensive, may include bony) | Improved gait efficiency, reduced assistive device need | Maintained household to community ambulation |
| Level IV | Positioning procedures, talectomy or fusion | Improved comfort and bracing tolerance | Comfortable sitting, standing transfers |
| Level V | Palliative (release, talectomy for positioning) | Comfort, hygiene, skin breakdown prevention | Pain-free positioning |
Prognostic Factors
Best prognosis: GMFCS I-II, dynamic deformity, ambulatory, good selective motor control, good balance, age 7 to 10 at surgery, compliant with post-operative therapy
Poor prognosis: GMFCS IV-V, fixed bony deformity, poor selective motor control, absent balance reactions, age under 5 at surgery (high recurrence), poor compliance with rehabilitation
Key message: SEMLS produces durable results in GMFCS I-III, with approximately 80 to 90 percent maintaining improved gait at 5-year follow-up. Recurrence is the main concern in younger children and higher GMFCS levels.
Evidence Base
The split anterior tibialis tendon transfer procedure for spastic equinovarus foot in children with cerebral palsy: results and factors associated with a failed outcome
- SPLATT achieved correction in most children but younger age at surgery and severe spasticity predicted poorer outcomes and recurrence
Split tibialis posterior tendon transfer for correction of spastic equinovarus hindfoot deformity
- Split TP transfer reliably corrected spastic equinovarus hindfoot deformity with good maintenance of correction at follow-up
Modified split tendon transfer of posterior tibialis muscle in the treatment of spastic equinovarus foot deformity: long-term results and comparison with the standard procedure
- Modified split TP transfer demonstrated durable long-term correction comparable to standard split transfer with low recurrence rates
Correction of severe crouch gait in patients with spastic diplegia with use of multilevel orthopaedic surgery
- Multilevel orthopaedic surgery including foot procedures produced significant and sustained improvements in gait parameters at mean 3-year follow-up in spastic diplegia
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Dynamic Equinovarus in Ambulatory Child
"A 7-year-old girl with spastic diplegia, GMFCS II, presents with progressive toe-walking and tripping. On examination, she has bilateral equinovarus with hindfoot varus worse on the right. Passive correction is possible but deformity recurs immediately with activity. Silfverskiold test is positive. She has been using hinged AFOs and had BTX-A injections to the gastrocnemius twice with temporary benefit. 3-D gait analysis shows premature heel rise, tibialis posterior active in midstance, and tibialis anterior overactivity in swing. How would you manage this?"
Scenario 2: Fixed Equinovarus in a Teenager
"A 14-year-old boy with spastic hemiplegia, GMFCS I, presents with a progressive right equinovarus foot deformity. He has had no prior surgical treatment. On examination, he has a fixed hindfoot varus with equinus that does not correct under examination. Weight-bearing lateral X-ray shows talar flattening and decreased calcaneal pitch. He walks on the lateral border of his right foot with pain over the base of the fifth metatarsal. How would you investigate and manage this?"
MCQ Practice Points
Anatomy Question
Q: Which muscle is the primary driver of hindfoot varus in spastic CP equinovarus? A: Tibialis posterior. The TP inverts the subtalar joint and is normally silent during midstance. In spastic CP, TP overactivity during stance produces hindfoot varus. The TA primarily drives forefoot supination and first ray plantarflexion. Distinguishing which muscle dominates the varus is essential for surgical planning.
Diagnosis Question
Q: What is the significance of the Silfverskiold test in equinovarus surgery? A: The Silfverskiold test distinguishes isolated gastrocnemius tightness (dorsiflexion improves by more than 10 degrees with knee flexion) from combined gastrocnemius-soleus tightness (no improvement with knee flexion). A positive test supports gastrocnemius recession rather than TAL, which reduces the risk of over-lengthening and calcaneus gait in ambulatory children.
Classification Question
Q: What is the most important prognostic factor for outcome after SEMLS in CP? A: GMFCS level. GMFCS I-II children have excellent outcomes with durable gait improvement. GMFCS III children have good but more variable outcomes. GMFCS IV-V children have limited ambulatory goals, and surgery focuses on comfort and positioning. Always state the GMFCS level when discussing treatment plans.
Surgical Question
Q: Describe the SPLATT procedure and its key anatomical steps. A: SPLATT (split tibialis anterior tendon transfer) splits the TA tendon longitudinally. The medial half remains in situ, preserving dorsiflexion power. The lateral half is passed through the interosseous membrane from anterior to posterior, then routed subcutaneously to insert on the lateral cuneiform or cuboid using a suture anchor or bone tunnel. This converts the lateral half from an invertor to an evertor, correcting dynamic forefoot supination.
Complications Question
Q: What is the most significant preventable complication of Achilles tendon lengthening in CP? A: Over-lengthening causing calcaneus gait. This occurs when TAL is performed instead of gastrocnemius recession in a child with isolated gastrocnemius tightness (positive Silfverskiold). The calcaneus gait results in loss of push-off power and can progress to crouch gait in diplegics. Prevention requires using the Silfverskiold test to select the appropriate procedure and meticulous intraoperative tensioning.
Guidelines, Registries & Global Practice
Global Epidemiology
- Cerebral palsy affects approximately 2 to 3 per 1000 live births worldwide, with higher rates in preterm and low-birth-weight infants
- Equinovarus is the most common foot deformity in CP, affecting approximately 15 to 30 percent of children with spastic subtypes
- Spastic diplegia has the highest association with bilateral equinovarus; hemiplegia typically produces unilateral deformity
- Global variation: Higher CP prevalence in low-resource settings due to higher preterm birth rates and limited perinatal care; however, access to gait analysis and SEMLS is concentrated in high-resource centres
Practice Variation by Resource Setting
- High-resource centres: 3-D gait analysis before SEMLS, custom AFOs, BTX-A programmes, specialist CP gait laboratories
- Middle-resource: Clinical gait analysis, BTX-A available, surgical SEMLS performed but with limited gait lab guidance
- Low-resource: Limited BTX-A access, clinical examination-based surgical decisions, limited post-operative rehabilitation, higher recurrence rates
- Universal principle: The surgical principles (dynamic vs fixed, TA vs TP driven, avoid over-lengthening) apply regardless of resource setting
Society and Reference Guidance (Side by Side)
| Source | Assessment Emphasis | Surgical Approach | Key Recommendation |
|---|---|---|---|
| AACPDM (American Academy for Cerebral Palsy) | 3-D gait analysis gold standard for surgical planning; GMFCS-based goals | SEMLS preferred over staged procedures; gastrocnemius recession over TAL when possible | Evidence-based care pathway: conservative first, then SEMLS at age 6 to 10 |
| BOA / BSCOS (UK) | Gait analysis before SEMLS in GMFCS I-III; careful dynamic vs fixed assessment | Gastrocnemius recession preferred; TAL reserved for fixed equinus; SEMLS model standard | Multidisciplinary team: orthopaedic surgeon, physiatrist, physiotherapist, orthotist |
| POSNA / AOPO (North American Paediatric Ortho) | Gait analysis changes surgical plan in 40 to 60 percent of cases | SPLATT for TA-driven, TP procedures for TP-driven; address all levels simultaneously | Post-operative intensive rehabilitation is mandatory for outcome |
| European CP consensus (CPUP surveillance) | Standardised follow-up with GMFCS, gait classification, and repeated assessment | Conservative until age 6 to 7, then SEMLS if progressive despite BTX-A and bracing | Population-based registry tracking outcomes across Scandinavia |
Registry and Evidence Note
The CPUP (Cerebral Palsy Follow-Up Programme) in Sweden and Scandinavia is the most comprehensive CP surveillance registry, tracking GMFCS, gait classification, interventions, and outcomes from diagnosis through adulthood. It has demonstrated that early and standardised intervention reduces the proportion of children requiring major orthopaedic surgery. The evidence base for CP foot surgery is predominantly Level III-IV (retrospective and prospective cohort studies), with few randomised trials. The SEMLS concept, while widely adopted, is supported by consistent observational evidence rather than RCT data.
Documentation Essentials (Globally Applicable)
Record in every pre-operative CP foot assessment:
- GMFCS level and topographic CP classification (hemiplegia, diplegia, quadriplegia)
- Dynamic vs fixed deformity at each level (equinus, hindfoot, forefoot)
- Silfverskiold test result (positive or negative)
- 3-D gait analysis findings (if available) - which muscles are overactive and when
- Prior treatments: BTX-A (number, timing, response), AFO type and compliance, physiotherapy
- Patient and family goals with realistic expectations documented
Missed TP overactivity (addressing only TA-driven varus with SPLATT without managing the TP) is a common cause of persistent varus and reoperation. Always evaluate both muscles.
Controversies & Areas of Uncertainty
Timing of SEMLS
The optimal age for SEMLS is debated. Most surgeons operate between ages 6 and 10 years. Earlier surgery (under 6) has higher recurrence rates due to continued growth and spasticity. Later surgery (over 12) risks fixed bony changes. The trend is toward operating when gait deterioration is documented rather than at a fixed age.
Gastrocnemius Recession vs TAL
Gastrocnemius recession is preferred when the Silfverskiold test is positive, as it preserves soleus push-off power and reduces calcaneus gait risk. However, some surgeons argue that the distinction is less important than meticulous intraoperative tensioning. The consensus in high-resource practice favours recession for dynamic equinus.
Split vs Full Tendon Transfer
Split transfers (SPLATT, SPOTT) are generally preferred over full transfers because they preserve some native function. However, in severe deformity, full TP transfer may provide greater corrective power. No head-to-head trials exist; choice is guided by severity and surgeon preference.
BTX-A as Definitive Treatment
BTX-A is effective for dynamic deformity but does not prevent eventual surgery in most children. The controversy centres on whether repeated BTX-A cycles delay surgery unnecessarily or provide genuine benefit during growth. Current consensus: BTX-A is a bridge to surgery, not a substitute.
SPASTIC EQUINOVARUS FOOT (CP)
Clinical summary
Key Anatomy & Pathophysiology
- •Gastrocnemius-soleus spasticity drives equinus; TP drives hindfoot varus; TA drives forefoot supination
- •Peroneals (evertors) are weak antagonists that cannot oppose inversion
- •Dynamic deformity corrects under GA (spasticity alone); fixed deformity persists (contracture and bone)
- •Untreated dynamic deformity progresses to fixed contracture with secondary bony deformation
Assessment
- •Silfverskiold test: positive = isolated gastrocnemius tightness (do recession, not TAL)
- •Examine under GA: confirms dynamic vs fixed at each level
- •3-D gait analysis: gold standard; changes surgical plan in 40 to 60 percent of cases
- •GMFCS level: single most important prognostic factor - always state it
Surgical Algorithm (SEMLS)
- •Equinus: Gastrocnemius recession (dynamic) or TAL (fixed); avoid over-lengthening
- •Hindfoot varus (TP-driven): TP intramuscular lengthening (dynamic) or Z-lengthening / split transfer (fixed)
- •Forefoot supination (TA-driven): SPLATT - split TA, lateral half through interosseous membrane to cuboid
- •Timing: SEMLS at age 6 to 10 years; all levels in one sitting; 6 to 12 months post-op rehabilitation
Complications to Avoid
- •Over-lengthening Achilles = calcaneus gait (use Silfverskiold to choose recession over TAL)
- •Recurrent deformity = 10 to 30 percent over 5 to 10 years, higher in younger children and higher GMFCS
- •Missed TP overactivity = persistent varus after SPLATT alone
- •Crouch gait = over-lengthened Achilles in diplegics, requires ground reaction AFO or revision