Cerebral Palsy Gait and SEMLS

The modern literature is consistent on the core message: cerebral palsy gait should be understood as a whole-limb mechanical problem, not as a list of tight muscles. SEMLS studies, gait-analysis reviews and crouch-gait papers repeatedly support the same practical sequence: define the functional goal, classify the gait pattern, identify fixed deformity and lever-arm dysfunction, choose procedures that match the drivers, and plan rehabilitation as part of the treatment.

Cerebral palsy gait is a dynamic, multiplanar orthopaedic problem. The brain lesion is non-progressive, but the musculoskeletal consequences progress because the child grows through abnormal tone, muscle imbalance, weakness, impaired motor control and altered loading. A toddler with dynamic equinus may become a school-aged child with fixed calf contracture, tibial torsion, planovalgus, knee flexion contracture, patella alta and increasing energy cost.

The central idea is that CP gait is rarely a single tight muscle. A visible abnormality may be the primary pathology, a compensation, or the only mechanism keeping the child upright.

SEMLS developed to avoid repeated isolated operations. Treating equinus one year, hamstrings another year and femoral anteversion later can create sequential imbalance and repeated rehabilitation cycles. SEMLS aims to correct clinically important fixed deformities and lever-arm dysfunctions together, once the gait pattern is sufficiently understood and the child can participate in rehabilitation.

Cerebral palsy is the most common cause of lifelong physical disability beginning in childhood. Orthopaedic gait surgery mainly concerns ambulant children, particularly those with spastic diplegia or hemiplegia and GMFCS I to III function. In non-ambulant children, orthopaedic priorities often shift toward hip surveillance, sitting, hygiene, pain, skin protection, transfers and care.

The practical learning sequence is:

1. Define the functional problem.
2. Classify function and gait pattern.
3. Identify dynamic tone, fixed contracture, weakness, torsion, foot deformity and compensation.
4. Decide whether non-operative care, tone management, orthoses, surgery or surveillance best matches the goal.
5. If surgery is required, plan the whole limb and rehabilitation pathway.

Single-event multilevel surgery is the planned correction of clinically important musculoskeletal deformities at multiple anatomical levels during one operative episode. In ambulant CP, it is usually planned from clinical examination, radiographs, rotational assessment and instrumented gait analysis.

A concise definition:

SEMLS is a gait-analysis-informed single-stage strategy for ambulant children with cerebral palsy, designed to correct fixed soft-tissue contractures and bony lever-arm dysfunctions at the hip, knee, tibia, ankle and foot, with one coordinated rehabilitation pathway.

The phrase "single-event" does not mean every abnormality must be treated. It means the clinically relevant fixed deformities that drive the gait problem are corrected together where this is safer and more logical than serial isolated surgery.

This topic is organised around the decisions that make cerebral palsy gait assessment safe and useful:

1. Explain why CP gait deteriorates despite a static neurological lesion.
2. Classify common gait patterns in spastic diplegia and hemiplegia.
3. Distinguish true equinus, jump gait, apparent equinus and crouch gait.
4. Describe how GMFCS is assigned from function.
5. Interpret the major outputs of instrumented gait analysis.
6. Match SEMLS procedures to deformity, gait pattern and lever-arm dysfunction.
7. Avoid the major overcorrection traps: calcaneus after Achilles lengthening and worsening crouch after inappropriate lengthening.
8. Explain SEMLS to a family in practical terms.

Normal gait cycle

Normal gait is usually divided into stance and swing. Stance occupies roughly 60 percent of the gait cycle and includes initial contact, loading response, midstance, terminal stance and pre-swing. Swing occupies roughly 40 percent and includes initial swing, mid-swing and terminal swing.

Efficient gait needs:

• Heel strike or controlled initial contact.
• Controlled tibial progression over a stable foot.
• Adequate stance-phase knee extension without recurvatum or collapse.
• Hip extension in terminal stance.
• Heel rise and plantarflexion power in terminal stance and pre-swing.
• Adequate knee flexion in swing for foot clearance.
• Controlled terminal swing knee extension.
• Balanced pelvic motion with limited compensatory trunk movement.

Why CP disrupts gait

The child with CP loses gait efficiency when tone, weakness, contracture and skeletal alignment disturb the normal sequence.

CP gait is a kinetic-chain problem

A deformity at one level changes the apparent problem elsewhere.

Distribution and movement disorder

Begin by describing the child, not the operation.

• Spastic hemiplegia: one side predominantly involved, often with equinus or equinovarus, drop foot in swing, stiff knee gait or internal rotation gait.
• Spastic diplegia: both lower limbs involved, usually with relative upper limb sparing, commonly showing equinus, jump gait, apparent equinus, crouch, scissoring, internal rotation and planovalgus.
• Quadriplegia: all four limbs involved; gait surgery is less often the primary goal and orthopaedic care commonly focuses on hips, sitting, spine, hygiene, comfort and transfers.
• Dyskinetic or dystonic CP: variable posture and tone may make SEMLS outcomes less predictable if dystonia is dominant.

GMFCS from real-world function

GMFCS is assigned or confirmed from observed and reported function. It is based on what the child can do in daily life, with emphasis on sitting, transfers and mobility.

Build the level from functional questions:

• Does the child walk indoors, outdoors and at school?
• Are stairs possible, and is a rail required?
• Does the child use AFOs, crutches, a walker or a wheelchair?
• How far can the child walk before fatigue?
• Does the child fall?
• Can the child keep up with peers?
• Are transfers independent?
• Has function declined with growth?
• Is pain limiting walking?

Then classify:

• GMFCS I: walks without major limitations, but speed, balance, running and jumping may be impaired.
• GMFCS II: walks without handheld mobility devices but has limitations with distance, uneven ground, crowds, inclines or speed.
• GMFCS III: walks with a handheld mobility device and often uses wheeled mobility for longer distances.
• GMFCS IV: self-mobility is limited; powered mobility or substantial assistance is often required.
• GMFCS V: transported in a manual wheelchair, with severe limitations in head and trunk control.

The common gait-improvement SEMLS group is ambulant CP, especially GMFCS I to III. GMFCS IV and V children may still need orthopaedic surgery, but the goals are usually comfort, sitting, hygiene, hip containment, standing transfers and care rather than efficient community walking.

CP gait abnormalities arise from neurological and musculoskeletal factors acting together.

Neurological contributors

• Spasticity: velocity-dependent resistance to stretch.
• Dystonia: involuntary fluctuating postures or movements.
• Co-contraction: simultaneous activation of antagonists, reducing smooth motion.
• Poor selective motor control: inability to isolate hip, knee, ankle and foot movement.
• Weakness: particularly hip extensors, hip abductors, quadriceps, dorsiflexors and plantarflexors.
• Impaired balance: abnormal trunk and pelvic strategies.
• Motor learning differences: persistence of inefficient movement patterns after deformity correction.

Musculoskeletal contributors

• Muscle-tendon contracture.
• Joint contracture.
• Femoral anteversion.
• Tibial torsion.
• Patella alta and extensor mechanism insufficiency.
• Planovalgus or equinovarus foot deformity.
• Hip displacement and pelvic obliquity.
• Scoliosis or spinal imbalance.

Lever-arm dysfunction

Muscles need stable skeletal levers. Even strong muscles cannot work efficiently if the lever is malaligned.

• Femoral anteversion changes hip rotation and reduces efficient abductor mechanics.
• External tibial torsion externally rotates the foot lever and weakens the plantarflexion-knee-extension couple.
• Planovalgus shortens and destabilises the foot lever.
• Midfoot break allows collapse rather than push-off.
• Patella alta reduces the effectiveness of the quadriceps mechanism and contributes to extensor lag.

This is why bony correction and foot reconstruction may be more important than additional soft-tissue lengthening in selected children.

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The Rodda and Graham sagittal classification is useful because it links observed gait to treatment reasoning. It should not replace full assessment.

Hemiplegic gait is commonly described using the Winters, Gage and Hicks pattern. The value is not memorising labels; it is linking the involved levels to treatment.

History: define the lived problem

The history should explain why the child is presenting now.

• Main concern: tripping, fatigue, pain, loss of walking, brace intolerance, cosmetic concern, hygiene, transfers or school participation.
• Function: indoor walking, outdoor walking, stairs, playground, sport, endurance and community mobility.
• Mobility aids: AFO type, walker, crutches, wheelchair, night splints and tolerance.
• Falls: frequency, direction, triggers and injuries.
• Pain: hip, knee, foot, back, brace pressure or post-activity pain.
• Fatigue: distance before stopping, end-of-day deterioration and recovery time.
• Development: prematurity, neonatal history, milestones and cognitive or communication needs.
• Neurology: seizures, dystonia, medication, selective control concerns and tone management.
• Previous treatment: physiotherapy, strengthening, botulinum toxin, serial casting, orthoses, baclofen, intrathecal baclofen, selective dorsal rhizotomy and prior orthopaedic surgery.
• Growth: recent growth spurt, worsening contracture or new functional decline.
• Goals: what change would make treatment worthwhile?
• Rehabilitation reality: school support, therapy access, transport, home setup and family capacity.

Observation

Observe before touching the limb. Watch transfers, standing balance, shoes, braces and spontaneous walking. Then observe barefoot and braced gait from the side, front and behind.

Record:

• Walking speed and endurance.
• Initial contact: heel, flat foot or toe.
• Knee position in stance.
• Hip flexion and pelvic tilt.
• Foot progression angle.
• Step length and symmetry.
• Base width and scissoring.
• Trunk lean, arm posture and balance.
• Compensations: vaulting, circumduction, hip hiking and excessive pelvic rotation.

Physical examination

The examination should explain the gait, not merely document range.

Key tests

• Thomas test: hip flexion contracture.
• Hip abduction in flexion and extension: adductor tightness and hip surveillance relevance.
• Popliteal angle: hamstring length.
• Duncan-Ely or prone rectus test: rectus femoris tightness or overactivity clue.
• Silfverskiold test: gastrocnemius versus soleus contribution to equinus.
• Patellar height and extensor lag: extensor mechanism insufficiency.
• Rotational profile: femoral anteversion and tibial torsion.
• Foot assessment: hindfoot, midfoot, forefoot, subtalar flexibility and braceability.
• Strength and selective motor control: essential before lengthening decisions.

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Plain radiographs

• AP pelvis: migration percentage, acetabular index, femoral head shape, neck-shaft angle, hip subluxation, pelvic obliquity and pain source.
• Standing long-leg radiographs: coronal alignment and mechanical axis when deformity is suspected.
• Foot radiographs: weight-bearing AP and lateral views for planovalgus, cavovarus, midfoot break, talonavicular coverage and calcaneal pitch.
• Spine radiographs: scoliosis or pelvic obliquity when clinically relevant.
• Patellar height imaging: useful when crouch, extensor lag or anterior knee pain is present.

CT and MRI

CT may help quantify femoral anteversion or tibial torsion when clinical and gait findings are unclear. CT should support the decision; it should not replace functional assessment.

MRI brain is not routinely required for established CP gait planning, but may be appropriate if the neurological diagnosis is unclear, progressive or atypical.

Instrumented gait analysis

Instrumented gait analysis is most useful in complex ambulant CP, especially before SEMLS. It combines video, kinematics, kinetics, dynamic EMG, plantar pressure and temporospatial measures.

What gait lab does not replace

Gait analysis cannot decide whether the family can manage rehabilitation, whether pain is the main complaint, whether school planning is realistic, or whether surgery matches the child's priorities. The report must be reconciled with examination, radiographs and shared decision-making.

Management is matched to function, age, gait pattern, impairments, goals and rehabilitation capacity.

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The exact SEMLS package is individualised. The procedures below are common options; they are not a mandatory list.

Hip-level procedures

Adductor lengthening

Indications include adductor contracture, scissoring, reduced abduction, selected hip-at-risk patterns and hygiene/care needs in non-ambulant children. Commonly addressed muscles include adductor longus, gracilis and adductor brevis. Avoid destabilising the hip by treating adductors without considering hip containment.

Iliopsoas lengthening

Indications include hip flexion contracture, excessive anterior pelvic tilt, jump gait and persistent hip flexion in stance. Overlengthening can weaken hip flexion and impair swing advancement.

Femoral derotation osteotomy

Indications include excessive femoral anteversion with internal rotation gait, patellar maltracking or lever-arm dysfunction. Correction should be based on clinical rotational profile and gait, not CT numbers alone. Avoid overcorrection into external rotation.

Knee-level procedures

Medial hamstring lengthening

Indications include true hamstring contracture, increased popliteal angle, knee flexion contracture and excessive knee flexion in stance where hamstrings are a major driver. It is not the default treatment for all crouch gait.

Rectus femoris transfer

Indicated for selected stiff-knee gait with reduced or delayed swing-phase knee flexion and inappropriate rectus femoris activity. Dynamic EMG and kinematics are important. Poor selective control, weak push-off or lever-arm dysfunction may also cause poor knee flexion and should not be mistaken for isolated rectus overactivity.

Distal femoral extension osteotomy

Considered for severe crouch with fixed knee flexion deformity, especially in older children and adolescents. It corrects sagittal knee alignment and is often combined with patellar tendon advancement or shortening when extensor mechanism insufficiency is present.

Patellar tendon advancement or shortening

Indicated when patella alta and extensor lag contribute to crouch. If knee flexion deformity is corrected but patella alta is ignored, crouch may persist.

Tibial-level procedures

Tibial derotation osteotomy

Indications include clinically significant internal or external tibial torsion with abnormal foot progression and lever-arm dysfunction. External tibial torsion is especially important in crouch because it weakens the effective foot-ankle lever.

Calf and ankle procedures

Gastrocnemius recession

Considered when equinus is gastrocnemius-driven with a positive Silfverskiold pattern. In diplegia, gastrocnemius recession may preserve soleus better than tendo-Achilles lengthening.

Tendo-Achilles lengthening

Considered for fixed gastrocsoleus equinus in selected children, more commonly in hemiplegic fixed equinus than diplegic crouch-prone patterns. Risks include overlengthening, calcaneus, weak push-off and worsening crouch.

Foot procedures

Planovalgus correction

Indications include pain, brace intolerance, midfoot break, progressive deformity and lever-arm failure. Options include calcaneal lengthening osteotomy, medial column procedures, subtalar fusion or triple fusion in older severe rigid deformity.

Equinovarus correction

Indications include lateral border weight-bearing, recurrent sprains, brace difficulty and pressure callosity. Options include split tibialis anterior transfer, split tibialis posterior transfer, tendon lengthening, osteotomy or fusion in severe rigid deformity.

True equinus

Decide whether the equinus is dynamic or fixed, gastrocnemius-only or gastrocsoleus, unilateral or bilateral, and whether it provides stance stability.

• Dynamic equinus: therapy, orthoses, botulinum toxin or serial casting.
• Fixed gastrocnemius contracture: gastrocnemius recession may be considered.
• Fixed gastrocsoleus contracture: Achilles lengthening may be considered with caution.
• Apparent equinus: do not lengthen the Achilles.

Jump gait

Jump gait is a multilevel flexed pattern with equinus. Treatment may require hip flexor, hamstring, calf, rotational or foot-level correction depending on findings. Isolated calf surgery is often incomplete.

Apparent equinus

The ankle is not the primary problem. Treat proximal flexion drivers, lever arms, weakness and gait pattern. Achilles lengthening here can create avoidable crouch.

Crouch gait

Crouch is a high-energy flexed gait pattern. Treatment depends on the drivers:

• Flexible mild crouch: strengthening, endurance work and selected orthoses.
• Hamstring-driven crouch: selected hamstring lengthening.
• Lever-arm crouch: correct femoral anteversion, tibial torsion, planovalgus or foot collapse.
• Extensor mechanism crouch: consider distal femoral extension osteotomy and patellar tendon advancement/shortening when indicated.
• Calcaneus or weak plantarflexor crouch: avoid further calf lengthening and focus on support, strengthening and lever arms.

Stiff-knee gait

The problem is reduced or delayed swing knee flexion. Rectus femoris transfer is considered only when the gait-lab and clinical pattern support inappropriate rectus activity. Circumduction, hip hiking and vaulting may be compensations for poor clearance.

Scissoring

Assess adductor tone, hip abduction range, hip displacement risk, balance and selective control. Do not treat scissoring in isolation without understanding the hip and functional goal.

Rehabilitation is part of the indication. A child who cannot complete the rehabilitation pathway may not benefit from the operation.

Preoperative phase

• Define functional goals.
• Explain the timeline to the family and school.
• Optimise strength, nutrition, skin and equipment.
• Plan wheelchair, walking aids, orthoses and home transfers.
• Prepare for pain, casts, braces and reduced independence.

Early postoperative phase

• Pain and spasm control.
• Neurovascular and wound monitoring.
• Cast and pressure-area care.
• Transfers and safe positioning.
• Protection of osteotomies and tendon procedures.
• Family training.

Recovery phase

• Restore safe range without overstretching repairs.
• Begin muscle activation.
• Progress weight bearing according to procedures and fixation.
• Optimise orthoses.
• Strengthen hip extensors, abductors, quadriceps and plantarflexors.

Gait retraining phase

• Relearn walking with corrected alignment.
• Progress aids and endurance.
• Reintroduce stairs and school participation.
• Monitor recurrence, weakness, pain and brace fit.

Maximum functional benefit may take 12 to 24 months.

General complications

• Pain and delayed recovery.
• Blood loss.
• Wound problems or infection.
• Cast pressure sores.
• Neurovascular injury.
• Delayed union or nonunion after osteotomy.
• Hardware irritation.
• Rehabilitation failure.
• Loss of confidence or temporary loss of walking independence.
• Residual deformity, recurrence or need for revision surgery.

Procedure-specific complications

High-risk clinical reasoning errors

• Treating every toe-walker as true equinus.
• Lengthening Achilles for apparent equinus.
• Treating every crouch gait with hamstring lengthening.
• Ignoring weak plantarflexors.
• Ignoring patella alta and extensor lag.
• Ignoring planovalgus as a lever-arm problem.
• Planning from CT torsion numbers alone.
• Planning SEMLS without rehabilitation.

Initial approach to a child with CP gait concern

"I would assess this child in a multidisciplinary cerebral palsy gait clinic. I would define the functional concern, family goals, distribution of involvement, movement disorder, GMFCS level, dynamic versus fixed deformity, strength, selective motor control and lever-arm dysfunction. I would not plan surgery from visual gait alone. For complex ambulant CP, especially before SEMLS, I would combine clinical examination, radiographs, rotational assessment and instrumented gait analysis."

If shown a toe-walking video

"I would first distinguish true equinus from apparent equinus. True equinus is ankle plantarflexion relative to the tibia. Apparent equinus may be caused by hip and knee flexion with a relatively plantigrade ankle. The distinction is critical because Achilles lengthening in apparent equinus can weaken the plantarflexors and worsen crouch."

Explaining what SEMLS means

"SEMLS is single-event multilevel surgery. It is the planned correction of clinically significant fixed soft-tissue contractures and bony lever-arm abnormalities affecting gait in one operative episode, usually informed by instrumented gait analysis, with one coordinated rehabilitation pathway."

Choosing investigations

"I would obtain radiographs relevant to the clinical problem: pelvis for hip surveillance, feet for planovalgus or cavovarus, long-leg alignment if coronal deformity is suspected, and rotational imaging only where it changes planning. For complex ambulant gait, I would use instrumented gait analysis including video, kinematics, kinetics, dynamic EMG, plantar pressure and temporospatial data."

Main danger in CP gait surgery

"The biggest danger is treating the visible compensation rather than the primary driver. Examples include Achilles lengthening for apparent equinus and isolated hamstring lengthening for crouch without addressing plantarflexor weakness, patella alta, external tibial torsion or planovalgus."

Pitfall 1: Toe walking means Achilles lengthening

Incorrect. Toe walking may be true equinus, jump gait, apparent equinus, dystonia or compensation.

Pitfall 2: Crouch means tight hamstrings

Incorrect. Crouch may be driven by weak plantarflexors, patella alta, planovalgus, external tibial torsion, prior Achilles overlengthening, weak quadriceps, hamstring contracture or fixed knee flexion deformity.

Pitfall 3: CT version decides femoral osteotomy

Incorrect. CT can quantify version, but clinical gait and instrumented gait analysis determine whether rotation is functionally important.

Pitfall 4: Rectus transfer for any stiff knee

Incorrect. Confirm inappropriate rectus femoris activity and the correct kinematic pattern. Poor push-off, weakness and poor selective control can also reduce swing knee flexion.

Pitfall 5: SEMLS is just multiple releases

Incorrect. Modern SEMLS may include soft-tissue balancing, tendon transfers, osteotomies, patellar tendon procedures and foot reconstruction, all linked to one rehabilitation plan.

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