Surgical technique guide for whole and split anterior tibial tendon transfer — SPLATT for relapsed idiopathic clubfoot after Ponseti correction and for dynamic supination in cerebral palsy and stroke, harvest of the TA insertion, rerouting and bony fixation under tension, concurrent tendo-Achilles lengthening
High-yield overview
Transfer of the tibialis anterior tendon to correct dynamic supination deformity | advanced
Surgical Imaging
Anatomy of the tibialis anterior tendon — transferred laterally (e.g. to the lateral cuneiform) to correct dynamic supination in relapsed clubfoot.Credit: AI-generated medical illustration · OrthoVellum
Critical Danger Structures and Exam Traps
Deep Peroneal Nerve and Dorsalis Pedis Artery
Location: The deep peroneal nerve and dorsalis pedis artery run between the EHL and the TA tendon at the ankle joint level, lying deep to the extensor retinaculum.
Risk: During the anterior approach to harvest the TA tendon and during creation of the subcutaneous tunnel from the anterior incision to the lateral foot, the nerve and artery can be stretched, contused or divided. Identify them between EHL and TA before passing the tendon transfer.
Protection: The subcutaneous tunnel must pass superficial to the extensor retinaculum, NOT deep to it. Palpate the nerve pedicle before passing the tendon passer.
Growth Plate Injury — Lateral Cuneiform / Cuboid
Location: The lateral cuneiform and cuboid ossification centres are present in the skeletally immature foot. A drill hole placed too close to the physis violates growth.
Risk: In children (typically aged 3-8 years for SPLATT in clubfoot), a bony tunnel drilled eccentrically near the physis can cause growth arrest, premature physiodesis, or progressive deformity.
Protection: Preoperative planning — use intraoperative fluoroscopy to assess physeal location. Drill the tunnel in the metaphyseal bone or use a metaphyseal suture anchor instead of a transphyseal tunnel.
Extensor Retinaculum Tether
Location: The superior and inferior extensor retinacula of the ankle overlie the anterior compartment tendons. Passing the transferred tendon DEEP to these retinacula restricts excursion.
Risk: A tendon passed deep to the retinaculum will tether — the transfer works against the retinaculum rather than with the excursion of the muscle. The result is limited dorsiflexion and a stiff, ineffectual transfer.
Protection: Pass the transferred tendon superficial to the extensor retinaculum in the subcutaneous plane. The entire rerouting from the anterior incision to the dorsolateral foot should be subcutaneous.
Over-Correction into Valgus — Adverse CTEV
Mechanism: The transferred TA, especially in a whole transfer or when tensioned with the foot in excessive eversion, pulls the foot into a valgus deformity — the opposite problem.
Recognition: Post-operatively the foot sits in a pronated/everted position at rest. On active dorsiflexion the foot adopts a valgus position. The patient (if ambulatory) walks on the medial border of the foot.
Prevention: Tension with the foot in no more than 5 degrees of eversion. Prefer the split transfer (SPLATT) over whole transfer in ambulatory patients. If the peroneals are weak, even a split transfer can over-correct.
Why concurrent TAL is critical: Dynamic supination deformity frequently co-exists with equinus — especially in the relapsed clubfoot and in cerebral palsy. The TA is recruited as a secondary ankle dorsiflexor; after transfer, the equinus contribution of the TA is removed, unmasking a fixed equinus contracture.
The trap: Performing an isolated TA transfer without examining for a Silfverskiöld-positive equinus contracture. If the ankle cannot dorsiflex to neutral with the knee extended, a TAL (or gastrocnemius recession if the contracture is isolated to gastrocnemius) must be performed concurrently to achieve a plantigrade foot.
Test: Silfverskiöld test — dorsiflex the ankle with the knee extended and then flexed. Limited dorsiflexion in both positions = Achilles contracture (need TAL). Limited only with knee extension = gastrocnemius contracture (gastrocnemius recession may suffice).
Peroneal Weakness — Hidden Root of Supination
Pathophysiology: Dynamic supination is a relative imbalance between the tibialis anterior (inverter/everter in dorsiflexion) and the peroneals (evertors). Weakness of the peroneus brevis and/or longus — from nerve injury, myelomeningocoele, or cerebral palsy — unmasks the TA's supination moment.
The exam trap: A patient with what appears to be a pure dynamic supination deformity may have underlying peroneal weakness. If the peroneals are not functioning, even an anatomically perfect SPLATT may produce a stiff transfer that does not restore balanced active eversion.
Prevention: Manual muscle test the peroneals (F-s: foot eversion against resistance) before surgery. If peroneal strength is Medical Research Council grade less than 3, consider a concurrent tendon augmentation or the addition of a posterior tibial tendon transfer.
Mnemonic
T.A.T.TTATT — Key Principles of Tibialis Anterior Tendon Transfer
Mnemonic
S.P.L.A.T.TSPLATT — Patient Selection and Prerequisites
Surgical Indications
Absolute Indications
Dynamic forefoot supination deformity in a relapsed idiopathic clubfoot after Ponseti correction — forefoot-driven supination during the swing phase of gait that does not respond to repeat casting or bracing
Spastic dynamic supination deformity of the foot in cerebral palsy (hemiplegia or diplegia) with a supple, passively correctable foot
Stroke-related dynamic supination with functional impairment during gait — forefoot supination in swing phase causing foot-drop and tripping
Failed non-operative management — bracing, AFO adjustment, botulinum toxin injection to the tibialis anterior have failed to control the deformity
Relative Indications
Mild-to-moderate dynamic supination in the ambulatory CP patient with a Silfverskiöld-negative ankle (no equinus)
Whole transfer for severe recurrent deformity after failed SPLATT
Dynamic supination in myelomeningocoele (lower lumbar level) with supple foot deformity
Combined procedure with calcaneal osteotomy for the rigid cavovarus foot after the osteotomy has corrected the fixed component
Contraindications
Absolute:
Fixed bony deformity — a rigid hindfoot varus, fixed cavus, or fixed equinus that does not correct with passive manipulation. An isolated tendon transfer in this setting will fail. Address the bony deformity with an osteotomy (Dwyer calcaneal osteotomy, lateral column lengthening, first metatarsal dorsiflexion osteotomy) first
Active infection in the surgical field
Non-functioning peroneal musculature (MRC grade less than 3) without a plan for tendon augmentation or alternative reconstruction — the transfer will produce a stiff foot without active eversion
Relative:
Severe spasticity not controlled by botulinum toxin or baclofen — consider selective dorsal rhizotomy or intrathecal baclofen before isolated foot surgery
Non-ambulatory patient without functional goals that the transfer can address — weigh carefully against the simplicity of AFO management
Younger than 2 years — the TA tendon is small, the lateral cuneiform ossific nucleus is small, and the physis is at risk
Previous surgery in the anterior compartment — scarred planes, altered neurovascular anatomy
Evidence for Tendon Transfer
SPLATT for Relapsed Clubfoot
The procedure is the standard of care for dynamic forefoot supination in the Ponseti-treated clubfoot that relapses after initial correction. The incidence of dynamic supination after Ponseti casting ranges from 10% to 30% of treated feet, and SPLATT is indicated when repeat casting and bracing fail
The transfer converts the TA from a supinator into a dorsiflexor-evertor, rebalancing the foot in swing phase
Mubarak and Van Valin (2009, J Pediatr Orthop): a case series of 32 feet treated with SPLATT for relapsed clubfoot after Ponseti treatment showed complete correction in 91% of feet at mean follow-up of 3.5 years, with no recurrence of supination
Thompson et al. (2009, J Pediatr Orthop): retrospective review of SPLATT in 23 children with relapsed clubfoot after Ponseti management — 96% satisfactory outcome at mean 5-year follow-up
SPLATT for Cerebral Palsy
Hoffer et al. (1974): the original description of the split TA transfer — 26 patients with spastic hemiplegia demonstrated durable correction of varus/supination deformity during gait
Barnes and Herring (1991, J Bone Joint Surg Am): 28 patients with CP who underwent combined SPLATT and intramuscular lengthening of the posterior tibial tendon — 82% good-to-excellent results; concurrent TAL performed in 54% of cases
The procedure is most effective in ambulatory children with hemiplegic CP who have a dynamic (not fixed) deformity; the presence of an equinus contracture requiring simultaneous TAL is the rule rather than the exception
Indications and Outcomes — Whole vs Split TA Transfer
Key Evidence
Evidence
The split anterior tibial tendon transfer in the treatment of spastic varus hindfoot of childhood
Level IV
Hoffer MM, Reiswig JA, Garrett AM, Perry J • Orthop Clin North Am
Clinical implication: This seminal description established the SPLATT as the definitive procedure for dynamic supination deformity in cerebral palsy and remains the most widely used tendon transfer for this indication.
Combined split anterior tibial-tendon transfer and intramuscular lengthening of the posterior tibial tendon in spastic cerebral palsy
Level IV
Barnes MJ, Herring JA • J Bone Joint Surg Am
Clinical implication: SPLATT cannot be considered in isolation — the equinus component must be addressed concurrently. This paper established the combined procedure as the standard for the spastic supination deformity.
Source: J Bone Joint Surg Am. 1991 Jun;73(5):734-8
Normalization of Forefoot Supination After Tibialis Anterior Tendon Transfer for Dynamic Clubfoot Recurrence
Level III
Mindler GT, Kranzl A, Radler C • J Pediatr Orthop
Clinical implication: Instrumented gait analysis confirms that TATT normalises forefoot supination in dynamic clubfoot recurrence after Ponseti treatment, approaching the kinematics of age-matched healthy children.
How do different anterior tibial tendon transfer techniques influence forefoot and hindfoot motion?
Level IV
Knutsen AR, Avoian T, Sangiorgio SN, Borkowski SL, Ebramzadeh E • Clin Orthop Relat Res
Clinical implication: Biomechanical evidence supporting SPLATT over whole or medial transfer — the split technique provides the most balanced correction of forefoot supination without over-correcting the hindfoot.
The split anterior tibialis tendon transfer procedure for spastic equinovarus foot in children with cerebral palsy: results and factors associated with a failed outcome
Level IV
Limpaphayom N, Chantarasongsuk B, Osateerakun P, Prasongchin P • Int Orthop
Clinical implication: SPLATT for CP has a high success rate (84%) when patient selection criteria are met — dynamic deformity, good selective motor control, and ambulatory status. Fixed deformity or poor motor control predicts failure.
Origin: Lateral condyle of the tibia, proximal half of the lateral surface of the tibial shaft, the interosseous membrane, and the deep fascia of the leg
Muscle belly: Lies in the anterior compartment of the leg, deep to the extensor retinaculum, alongside the EHL (medially) and EDL (laterally)
Tendon: The TA tendon becomes tendinous in the distal third of the leg, approximately 5-6 cm proximal to the ankle joint. The tendon passes through the superior and inferior extensor retinacula, lying medial to the EHL at the ankle level
Insertion: Primarily into the medial cuneiform (plantar and medial surface) and the base of the first metatarsal. A slip also inserts into the first metatarsal head in some individuals — this variation affects the split-harvest plane
Tendon Dimensions (Clinical Relevance)
Length: 12-15 cm from the musculotendinous junction to the insertion
Width: 8-12 mm at the level of the ankle joint in adults — sufficient for a longitudinal split into two 4-6 mm slips
Excursion: 15-25 mm in the distal segment — the TA has one of the greatest excursions among the anterior compartment tendons
The Anatomical Basis for SPLATT
The tibialis anterior tendon can be split longitudinally into a medial and lateral half. The medial half retains its insertion to the medial cuneiform and base of the first metatarsal — preserving the dorsiflexion and inversion function of the TA. The lateral half is detached from its insertion (which is largely on the medial cuneiform and portions of the first metatarsal) and transferred to the lateral cuneiform or cuboid.
Relationship of the Two Halves
The lateral half of the TA tendon corresponds to the fibres originating from the lateral tibial condyle and lateral tibial shaft — these fibres travel distally along the lateral border of the tendon. The medial half originates from the medial tibial shaft and deeper muscle fibres. The split plane is created by passing a blunt instrument (a fine haemostat or tendon passer) between the fibres from proximal to distal.
Neurovascular Anatomy at Risk
Deep Peroneal Nerve
Course: The deep peroneal nerve (L4, L5, S1) pierces the anterior intermuscular septum and runs between the EHL and TA in the distal third of the leg, lying anterior to the interosseous membrane. At the ankle joint level, it lies between the EHL tendon and the TA tendon, just deep to the extensor retinaculum
Branches: Motor branches to TA, EHL, EDL, peroneus tertius, and the extensor digitorum brevis in the foot (lateral terminal branch). The medial terminal branch provides sensation to the first web space
Risk: The nerve is at risk during two steps: (1) the anterior approach to harvest the TA tendon — deep dissection between EHL and TA must stay lateral to the TA, (2) creation of the subcutaneous tunnel from the anterior incision to the lateral foot — a deep passer can tent or divide the nerve if it is not retracted
Dorsalis Pedis Artery
Course: Continuation of the anterior tibial artery after the ankle joint. It runs between the EHL and EDL, accompanied by the deep peroneal nerve. The artery is palpable (dorsalis pedis pulse) between the EHL (medial) and EDL (lateral) at the ankle
Risk: Same zones as the deep peroneal nerve. Direct injury from the scalpel during the anterior approach is the most common mechanism
Superficial Peroneal Nerve
Course: Emerges in the distal third of the leg between peroneus longus and EDL, becoming subcutaneous. It divides into medial and intermediate dorsal cutaneous nerves to supply the dorsum of the foot (except the first web space)
Risk: At risk during subcutaneous dissection of the lateral incision (access for the bony tunnel) and during passage of the subcutaneous tunnel — a stray blade or a poorly directed passer can lacerate it
The Route of Transfer — Subcutaneous Plane
Superior Extensor Retinaculum
A thickened transverse band of fascia overlying the anterior compartment tendons at the ankle (approximately 4-5 cm proximal to the joint)
The transferred tendon MUST pass superficial to this structure. A tendon tunnelled deep to the retinaculum runs against the retinaculum, loses excursion, and functions poorly
Surgical landmark: Pass the tendon from the anterior incision to the dorsolateral foot in the subcutaneous plane — the tendon should be palpable just under the skin, not fixed to deeper structures
Lateral Cuneiform — Landing Zone
The lateral cuneiform is the preferred fixation site for the transferred tendon because:
It lies in the line of pull from the TA muscle belly (directed dorsolaterally)
It provides a bony tunnel with good bone stock (in children older than 3 years)
The fixation restores the TA as a dorsiflexor-evertor — the lateral cuneiform is dorsal to the axis of the subtalar joint
The cuboid is an alternative site — more lateral position generates more eversion moment but requires a longer subcutaneous tunnel and has thinner bone stock
Physeal consideration in children: The lateral cuneiform ossifies from a single primary centre that appears at approximately 1-2 years of age and fuses in adolescence. The physis is located proximally. A drill hole placed in the central or distal portion of the bone avoids the physis
Positioning and Preparation
Position: Supine. A sandbag is placed under the ipsilateral hip to bring the foot into a neutral or slightly internally rotated position (the foot tends to externally rotate in supine). The contralateral leg is kept extended and abducted to avoid crowding the operative field. The foot should project beyond the end of the operating table to allow the assistant to hold the ankle in the desired position.
Tourniquet: A thigh or calf tourniquet is applied. The thigh tourniquet is preferred for procedures expected to last longer than 60 minutes; a calf tourniquet (300 mmHg) may be used for shorter cases. Exsanguinate with an Esmarch bandage before inflation.
Anaesthesia: General anaesthesia is standard. A popliteal block (sciatic nerve block at the popliteal fossa) provides excellent post-operative analgesia but must be discussed with the anaesthetist — motor blockade of the peroneals may delay early post-operative assessment of active eversion.
Antibiotic prophylaxis: A single dose of a first-generation cephalosporin (e.g. cefazolin) at induction — standard for clean bony surgery with hardware placement (suture-button or interference screw).
Consent: Specific counselling regarding risk of nerve injury (deep peroneal nerve, superficial peroneal nerve — less than 2%), wound issues (5-8%), over-correction into valgus (5-10% in whole transfer), under-correction (3-8%), growth plate injury in children (less than 1% with fluoroscopic guidance), and the planned period of cast immobilisation and non-weight-bearing.
Step-by-Step Surgical Technique
Step 1: Anterior Approach and Tendon Harvest
Incision: Make a longitudinal incision approximately 3-4 cm long over the TA tendon, beginning just proximal to the medial cuneiform and extending distally to the naviculocuneiform joint. The incision is placed just medial to the TA tendon, well away from the deep peroneal nerve and dorsalis pedis artery (which lie laterally between EHL and TA).
Dissection: Incise skin and subcutaneous tissue down to the paratenon of the TA tendon. The paratenon is a thin, glistening, vascularised layer — preserve it if possible (it provides blood supply and gliding). Identify the full width of the TA tendon and trace it to its insertion on the medial cuneiform and base of the first metatarsal.
Identifying the neurovascular bundle: Before any tendon division, identify the deep peroneal nerve and dorsalis pedis artery. Palpate the dorsalis pedis pulse between the EHL (medial) and TA (lateral at the level of the ankle). Gently retract the EHL tendon to expose the neurovascular bundle. Palpation and visual identification before instrumentation is the key step.
Clinical Pearl
Technical Tip: 'I make my incision just medial to the TA tendon, not directly over it. This keeps me away from the neurovascular bundle. I identify the full width of the TA first, then I pass a blunt right-angle forceps from medial to lateral under the TA tendon to define the deep plane. I always palpate the dorsalis pedis pulse — if I cannot feel it I use a Doppler or deflate the tourniquet momentarily to confirm the vessel is intact before I proceed.'
Dangers at this step
Deep peroneal nerve and dorsalis pedis artery — the incision must be medial to the TA, and the dissection must not stray laterally into the interval between EHL and TA
Stripping the paratenon — this compromises the blood supply to the tendon and increases the risk of adhesion formation and tendon rupture
Not defining both borders of the TA tendon before the split — the split plane is between the medial and lateral fibre bundles, and the tendon must be fully exposed to place it correctly
Step 2: Split the TA Tendon (SPLATT)
Identify the split plane: The TA tendon is composed of two fibre bundles — a medial bundle inserting into the medial cuneiform and a lateral bundle inserting primarily into the first metatarsal base (though there is overlap in the insertion). Insert a blunt right-angle forceps between these bundles at the level of the musculotendinous junction (about 5-6 cm proximal to the ankle) and spread gently to create a plane.
Split distally: Pass the forceps distally along the natural fibre split for 4-5 cm, separating the tendon into a medial one-half and a lateral one-half. The split must remain within the tendon substance — peeling one half off at the insertion risks a short stump that is difficult to retain for the preserved medial slip.
Detach the lateral half: Under direct vision, use a number 15 blade to divide the lateral half of the TA tendon at its insertion, leaving a 1-2 mm stump on the medial cuneiform. Grasp the lateral half with a stay suture (2-0 braided polyester or a 2-0 absorbable suture) to control the tendon for the transfer.
Preserve the medial half: Leave the medial half of the TA tendon intact at its insertion. This slip continues to provide active dorsiflexion and inversion.
Clinical Pearl
Technical Tip: 'When I split the TA tendon I pass a right-angle clamp between the fibre bundles starting proximally and push it distally. I can feel the natural split. The lateral half usually represents about 50% of the tendon width. I cut it at its insertion with a distinct blade mark and immediately tag it with a 2-0 suture so I do not lose it in the wound. I then protect the preserved medial slip with a moist gauze while I prepare the tunnel.'
In the whole tendon transfer: For a whole transfer, the entire TA tendon is detached from its insertion. The tendon is then transferred without any retained medial slip. The whole tendon is passed through a larger tunnel (5-6 mm) at the lateral cuneiform or cuboid. The whole transfer generates a greater eversion moment but at the cost of the active dorsiflexion function of the retained medial slip — it is reserved for severe deformity or non-ambulatory patients.
Step 3: Create the Subcutaneous Tunnel
Anticipate the path: The transferred lateral half needs to travel from the anterior incision (medial aspect of the foot) to the lateral cuneiform or cuboid. The path must be in the subcutaneous plane, superficial to the extensor retinaculum.
Make the dorsal incision: Create a second incision — a 2-3 cm longitudinal incision over the lateral cuneiform (located approximately 1 cm distal to the ankle joint and 2 cm distal to the navicular, palpable midway between the base of the second and fourth metatarsals). Cuboid incision is an alternative if the cuboid is preferred as the fixation site (more lateral, more eversion moment).
Pass the tunnel: Use a curved tendon passer, a long clamp, or an aneurysm needle. Pass it from the lateral foot incision, subcutaneously across the dorsum of the foot, emerging from the anterior (medial) incision. The tunnel must be superficial to the extensor retinaculum. Grasp the stay suture on the lateral half of the TA tendon and pull the tendon through the subcutaneous tunnel from medial to lateral.
Confirm the plane: Palpate the dorsum of the foot — the transferred tendon should be palpable subcutaneously, not fixed to the retinaculum or deep to it. If the tendon feels tethered or deep, the tunnel is incorrect — re-pass it superficial to the retinaculum.
Dangers at this step
If the tendon passes deep to the extensor retinaculum, excursion will be limited — re-pass it superficial
The deep peroneal nerve and dorsalis pedis artery lie just deep to the retinaculum — a deep passer can injure them
Excessive subcutaneous tunnelling with a sharp instrument damages the superficial peroneal nerve branches on the dorsum of the foot — use a blunt instrument and pass it gently
Step 4: Prepare the Bony Tunnel
Landing zone: The lateral cuneiform is the most commonly used site. It is identified visually through the lateral incision or with fluoroscopy. In children, use a C-arm image to locate the physis.
Create the tunnel: Use a 4.5 mm or 5.0 mm drill bit (single pass) to create a bone tunnel from dorsolateral to plantaromedial through the lateral cuneiform. In children 3-8 years, use a 3.2 mm or 4.0 mm bit to avoid excessive bone loss. The tunnel is oriented in the line of pull of the transferred tendon (approximately 30-45 degrees from vertical, angled medially and plantarly).
Enlarge the tunnel: If using a pull-out suture technique, the tunnel needs to accommodate the tendon and the suture. A 4.5 mm tunnel accepts most lateral-half TA tendons. For the whole tendon transfer, use a 5.0-6.0 mm tunnel.
Physeal protection: In the growing child, drill under fluoroscopic guidance. Direct the tunnel into the metaphyseal (distal) portion of the lateral cuneiform, avoiding the proximal physis. Confirm that the drill bit remains within the bone on AP and lateral views — the cuneiform is small.
Clinical Pearl
Technical Tip: 'I confirm the lateral cuneiform under fluoroscopy. I drill from dorsal (dorsolateral) to plantar (plantaromedial) in the line of pull of the transferred tendon. In a child I keep the drill parallel to and away from the physis. I then use the same image to confirm that the drill path is within the bone on both views — the lateral cuneiform is narrow mediolaterally and a dorsal entry point placed too far lateral may fall off the bone.'
Step 5: Fix the Transferred Tendon
Pull-out suture technique (the classic method, still the most widely used):
Whip-stitch the end of the transferred tendon with a 2-0 or 0 braided polyester suture on a straight needle
Pass the suture through the bone tunnel from dorsal to plantar (medial to lateral depending on the tunnel orientation)
Pull the tendon into the tunnel until the tendon is snug
The suture exits the plantar skin of the foot and is tied over a felt-padded button (a plantarly placed button guarantees compression of the tendon within the tunnel)
The foot is positioned in neutral dorsiflexion and slight eversion (approximately 5 degrees) before the button is tied
Interference screw technique (alternative):
An absorbable biotendesis screw (5-6 mm in diameter, depending on tunnel size) secures the tendon within the tunnel
The tendon is placed into the tunnel and tensioned, then the screw is advanced alongside the tendon
Advantages: no plantar button, no external suture, no button-related wound problems
Disadvantages: technically more demanding, higher cost, cannot adjust tension after screw insertion
Suture anchor technique (alternative for the small foot in young children):
A single or double 5.0 mm suture anchor (metal or bioabsorbable) is placed in the lateral cuneiform
The tendon is whip-stitched and fixed to the anchor
Advantages: avoids a transosseous tunnel in a small bone with open physis
Disadvantages: lower pull-out strength than a transosseous tunnel
Dangers at this step
Over-tensioning in the pull-out technique — if the button is tied with the foot in excessive eversion or dorsiflexion, the transfer produces valgus deformity. The foot should be in neutral dorsiflexion and no more than 5 degrees of eversion when the suture is tied
Under-tensioning — the tendon must be pulled through the tunnel until the tendon is snug within the cancellous bone. A loose tendon at the tunnel entrance will fill with scar and function poorly
Button complications — painful plantar scar, skin pressure necrosis, button migration. Remove the button at 4-6 weeks
In the interference screw: the screw can split the bone (especially in the small cuneiform of a child) or cut the tendon if the screw diameter is too large relative to the tunnel
Step 6: Wound Closure and Casting
Closure: Close the anterior incision in layers with absorbable sutures (3-0 Vicryl for subcutaneous, 4-0 Monocryl for subcuticular skin). Close the lateral incisions similarly. The pull-out suture exits the plantar skin through a separate stab incision — the plantar button is tied with a felt pad between the button and the skin.
Cast application: Apply a well-padded below-knee cast with the foot in neutral dorsiflexion and the ankle at 90 degrees to the tibia. If a TAL was performed concurrently, the cast position is dictated by the TAL protocol (typically equinus for 3-4 weeks after TAL, then gradually brought to neutral). If no TAL was performed, the foot is casted in the plantigrade position.
Immobilisation period: Non-weight-bearing for 4 weeks, then weight-bearing in a cast for 2 more weeks (total 6 weeks of cast immobilisation). The plantar button and pull-out suture are removed at 4-6 weeks (at the first or second cast change).
Concurrent Procedures
Tendo-Achilles Lengthening (TAL)
The most commonly combined procedure — performed in an estimated 50-70% of all TA transfers
Indication: Silfverskiöld-positive equinus contracture — ankle cannot dorsiflex to neutral with the knee extended
Technique: Either a percutaneous Hoke triple-step-cut TAL (3 hemisections at 3 levels, 180 degrees apart) or an open Z-lengthening of the TA in the sagittal plane, depending on the degree of contracture
Sequence: Perform the TAL first (before the TA transfer) to define the plantigrade position that the TA transfer will be tensioned against
Post-operative: The cast position is determined by the TAL — typically initial equinus (15-20 degrees of plantarflexion) for 3-4 weeks, then neutral for 2-3 weeks
Posterior Tibial Tendon Lengthening
May be combined with SPLATT when there is a spastic varus component from the posterior tibial tendon (PTT)
The Barnes and Herring technique involves intramuscular lengthening of the PTT through a separate medial incision at the ankle, splitting the PTT in the coronal plane and allowing it to slide. This is combined with SPLATT when there is both a dynamic supination (TA-driven) and a spastic varus (PTT-driven) component
Indicated when the foot shows varus in both stance and swing (mixed PTT and TA deformity) rather than pure swing-phase supination from TA alone
Calcaneal Osteotomy
Reserved for the rigid cavovarus foot in which the bony deformity cannot be corrected by a tendon transfer alone
Standard: lateral closing-wedge calcaneal osteotomy (Dwyer) to correct fixed hindfoot varus, or a sliding calcaneal osteotomy
Sequence: Perform the osteotomy first, fix it, then perform the TA transfer against the corrected hindfoot position
Week 0-4: Non-weight-bearing below-knee cast. The foot is held in the plantigrade position (neutral dorsiflexion, slight eversion). If concurrent TAL was performed, the initial cast is in equinus (approximately 15-20 degrees plantarflexion) — this is gradually brought to neutral over the subsequent 2-3 weeks with serial casting. The plantar button (if used) remains buried in the felt-padded dressing. Toe-touch weight-bearing is permitted with crutches.
Week 4-6: The first cast change at 4 weeks — the plantar button and pull-out suture are removed at this point (the tendon should be healed within the bone tunnel). A new below-knee cast is applied in the plantigrade position. Weight-bearing as tolerated in the cast.
Week 6: The cast is removed. Obtain standing AP and lateral foot radiographs. Assess the alignment of the foot — supination should be corrected, the foot should sit plantigrade.
Rehab Phase (Weeks 6-12)
Week 6-8: Transition to a walking boot or a solid AFO. The patient begins active ankle range-of-motion exercises — specifically active dorsiflexion and eversion (the transferred TA function). Gentle passive stretching for any residual equinus. The patient starts active toe flexion and extension to maintain the extrinsic foot muscles.
Week 8-12: Progressive weight-bearing. Wean from the boot to supportive footwear (a stiff-soled shoe or a UCBL insert if there is residual mild deformity). Formal physiotherapy begins — gait training, proprioception exercises, and functional strengthening of the ankle dorsiflexors and evertors.
Beyond 12 weeks: The patient graduates to normal footwear. Active sporting activity is permitted at 4-6 months. Gait analysis may be useful in children with CP or clubfoot to assess the quality of the transfer function. Long-term follow-up (annual) is recommended in children to monitor growth and detect late recurrence.
Casting After Concurrent TAL
If TAL was performed concurrently, the post-operative cast protocol is dictated by the TAL: the foot is cast in equinus (15-20 degrees plantarflexion) for the first 3-4 weeks to protect the lengthened tendon. The foot is then progressively dorsiflexed over the next 2-3 weeks with serial cast changes until neutral is achieved
The TA transfer benefits from early plantigrade positioning but must not compromise the TAL repair — the TAL takes priority in the first 3-4 weeks
Special Case: Relapsed Clubfoot after Ponseti
The Clinical Problem
After successful Ponseti correction (serial casting + percutaneous TAL), approximately 10-30% of children develop dynamic forefoot supination — the foot rolls into supination during the swing phase of gait
The foot is plantigrade at rest and is passively correctable to neutral/valgus — this is the hallmark of a dynamic deformity suitable for SPLATT
Do not confuse this with residual bony deformity (a stiff, uncorrected clubfoot) or with a recurrence of the full clubfoot deformity (equinus, hindfoot varus, midfoot cavus, adductus) — these require repeat casting or a more extensive bony reconstruction
Management Algorithm
Assess with gait observation — the foot is plantigrade in stance but supinates in swing phase
Examine passive range — the foot must be fully correctable to planovalgus; if it is stiff, it is not dynamic and SPLATT is not indicated
Perform Silfverskiöld test — if the ankle cannot dorsiflex to neutral, concurrent TAL is needed
Examine peroneal strength — if the peroneals are weak, consider a whole transfer or augmentation
When to Operate
Most authors recommend SPLATT at age 3-8 years for the relapsed clubfoot
Early intervention (before age 5) prevents adaptive bony deformity — a persistent supination deformity over several years produces a fixed cavovarus foot that later requires an osteotomy
Late presentation (older than 10 years with a fixed supination deformity): a calcaneal osteotomy or triple arthrodesis may be needed in addition to or instead of SPLATT
Special Case: Cerebral Palsy — Hemiplegic Foot
The Clinical Problem
In CP hemiplegia, the foot deformity is typically a dynamic equinovarus or supination-deformity pattern caused by spasticity of the TA (producing supination in swing phase) and often the gastrocnemius-soleus complex (producing equinus in stance)
The classic gait pattern: ankle equinus in stance, foot supination in swing phase, knee hyperextension (crouch or recurvatum pattern)
The deformity is functional: the child walks on the lateral border of the foot, trips on the supinated forefoot, and may fall frequently
Indications for SPLATT in CP
Dynamic supination deformity — if the foot is fixed and rigid, a tendon transfer alone will fail
Ambulatory patient (Gross Motor Function Classification System GMFCS levels I-III) — SPLATT improves gait efficiency and reduces tripping
Non-ambulatory patients: SPLATT is rarely indicated — AFO management or surgical correction of the equinus may be more appropriate
Combined deformity: SPLATT is frequently performed with TAL (most common), posterior tibial tendon lengthening, hamstring lengthening, and/or rectus femoris transfer
Prognostic Factors
Good prognosis: hemiplegic CP, GMFCS I-II, dynamic deformity, plantigrade foot, Silfverskiöld-positive equinus (correctable with TAL)
Poor prognosis: severe spasticity (Ashworth grade 3 or higher), fixed bony deformity, non-ambulatory (GMFCS IV-V), untreated equinus
Special Case: Stroke-Related Equinovarus
Similarities and Differences from CP
The deformity is acquired (not developmental) — the foot was typically normal before the stroke
The neurological deficit is UMN-type spastic hemiplegia — similar pattern to CP but with an insidious onset in adulthood
The supination deformity is caused by unopposed activity of the TA in swing phase — same pathophysiology as CP
The equinus component is often dominant — an isolated TA transfer without TAL is rarely sufficient in the stroke patient
Gait Analysis in Stroke
The classic pattern: the foot drops in swing phase (weak ankle dorsiflexors), the TA contracts to dorsiflex the ankle, but because the peroneals are weak or absent, the TA produces supination rather than pure dorsiflexion
Pre-operative gait analysis (instrumented or observational) is helpful to distinguish:
True TA-driven supination (swing phase)
PTT-driven varus (stance phase)
Mixed pattern
The most common correct pattern is the combined SPLATT + TAL
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
Viva scenarioAdvanced
Clinical prompt
“A 4-year-old boy with a history of Ponseti-corrected idiopathic clubfoot presents with dynamic supination of the forefoot during the swing phase of gait. The foot is plantigrade at rest and can be passively corrected into valgus. His ankle dorsiflexes to neutral with the knee flexed but to 5 degrees of plantarflexion with the knee extended. How do you manage this child?”
Practical approach
This is a classic presentation of relapsed clubfoot with dynamic supination — the foot is passively correctable but the TA produces supination during the swing phase of gait. The Silfverskiöld test is positive for a gastrocnemius-soleus contracture (more equinus with the knee extended than flexed). My management plan is as follows:
**Pre-operative assessment**: I would confirm that the foot is fully supple and that there is no fixed hindfoot varus or fixed equinus — a Coleman block test to rule out forefoot-driven hindfoot varus. I would assess the peroneal strength (MRC grade 4 or greater — adequate for SPLATT). I would obtain standing foot radiographs to document bony alignment and exclude tarsal coalition or other structural deformity.
**Surgical plan**: SPLATT (split anterior tibial tendon transfer to the lateral cuneiform) combined with a gastrocnemius recession (Strayer procedure) or a percutaneous TAL depending on the degree of equinus contracture. I would perform the TAL first to define the plantigrade position, then perform the SPLATT. The transfer would be tensioned with the foot in neutral dorsiflexion and 5 degrees of eversion. I would fix the transferred tendon into a 4.0 mm transosseous tunnel in the lateral cuneiform with a pull-out suture over a plantar button.
**Post-operative care**: Below-knee cast in the equinus position for 3 weeks (to protect the TAL), then serial cast change to neutral at 4-5 weeks. The plantar button and pull-out suture are removed at the first or second cast change. Total cast immobilisation: 6 weeks. After cast removal, the child transitions to a walking boot for 2 weeks, then to normal footwear. Follow-up at 6 months, 1 year, and annually until skeletal maturity for gait assessment and monitoring for recurrence.
**Why not whole transfer?**: The split transfer preserves the medial half of the TA, maintaining active dorsiflexion — important in an ambulatory child who needs balanced ankle motion. A whole transfer would provide more eversion moment but at the cost of losing the active inversion function and increasing the risk of over-correction.
Viva scenarioAdvanced
Clinical prompt
“A 12-year-old boy with spastic diplegic cerebral palsy (GMFCS II, independent community ambulator) presents with a dynamic supination deformity of his right foot. The foot is supple and correctable. There is also an equinus contracture of 10 degrees that is positive on Silfverskiöld testing (gastrocnemius contracture). The peroneals are graded MRC 4. The parents report that he trips frequently when walking outdoors. He has not had any previous surgery. Describe your management.”
Practical approach
This is a classic presentation of the spastic supination deformity in CP hemiplegia/diplegia. The patient is a good candidate for SPLATT because: (1) the deformity is dynamic and fully correctable, (2) he is ambulatory with functional goals, (3) the peroneals are intact. The equinus contracture must be addressed concurrently.
**Pre-operative workup**: I would obtain standing foot radiographs and consider instrumented gait analysis to confirm the swing-phase supination pattern and to assess for concurrent hip/knee pathology (common in CP diplegia). I would examine: (1) GMFCS level, (2) Ashworth grade for spasticity in the ankle plantarflexors and invertors, (3) Selective Motor Control (SMC) score for the TA (the child should be able to activate the TA independently), (4) presence of a hip adduction deformity or hamstring tightness that alters gait.
**Surgical plan**: I would perform a Strayer gastrocnemius recession (or a percutaneous TAL if the Soleus is also contracted — the Silfverskiöld test showed gastrocnemius-only tightness so a Strayer is preferred) combined with SPLATT to the lateral cuneiform. I would use a pull-out suture over a plantar button for fixation. The tensioning principle is the same: neutral dorsiflexion, slight eversion.
**The parents' question about tripping**: I would explain that the SPLATT converts the deforming force from a supinator into a dorsiflexor-evertor, allowing the foot to clear the ground in swing phase without supination. The TAL allows the foot to achieve a plantigrade position in stance. I would set expectations: the GMFCS level does not change after this surgery — the child will still have CP — but gait efficiency and safety improve, tripping frequency decreases, and shoe wear becomes more normal.
**Post-operative plan**: Below-knee cast in equinus for 3-4 weeks then transition to a neutral cast. Total 6 weeks of casting. Then a walking boot for 2-3 weeks, followed by physiotherapy focused on gait retraining and active eversion-dorsiflexion. I would recommend annual follow-up through skeletal maturity to monitor for growth-related recurrence.
**Late effect of the transfer**: The transferred TA continues to function in dorsiflexion — the child will be able to actively dorsiflex the ankle with a slight eversion component (the desired outcome). The preserved medial slip of the TA retains some inversion function, preventing a rigid valgus posture.
Viva scenarioStandard
Clinical prompt
“You have just performed a SPLATT with a pull-out suture over a plantar button for a 6-year-old girl with relapsed clubfoot. The foot was positioned in neutral dorsiflexion and 5 degrees of eversion when the button was tied. At the first cast change (4 weeks), the foot is in 10 degrees of valgus. The button is intact and the wound is clean. What has gone wrong and how do you manage it?”
Practical approach
The foot is 10 degrees into valgus — an over-correction complication. The most likely cause is that the TA transfer was tensioned with the foot in excessive eversion at the time of fixation, or the plantar button was tied with the foot not in the intended position (e.g. the assistant was holding the foot in too much eversion). In a split transfer, this degree of valgus is less common than in a whole transfer, but it can occur.
**Assessment at 4 weeks**: I would examine the foot carefully — confirm that the valgus is passively correctable (i.e. it is a positional deformity from the tension of the transfer, not a fixed bony deformity). I would remove the plantar button and pull-out suture at this visit (as planned — the tendon is healed within the bone tunnel by 4 weeks). I would then apply a new cast with the foot in neutral (not valgus) — the goal is to hold the foot in neutral position and allow the tension to settle. I would keep the cast in neutral for the remaining 2 weeks of the 6-week protocol.
**If the valgus persists at 6 weeks**: After cast removal, I would fit the child with an AFO set in neutral position (not in valgus) to support the foot during gait. I would initiate physiotherapy with a focus on active inversion and plantarflexion (to strengthen the opposing muscles) and gentle passive correction of the valgus. The valgus may improve spontaneously over the next 6-12 months as the child grows and the relative contribution of the transferred tendon decreases.
**If the valgus persists beyond 12 months**: If the valgus is still 10 degrees or more and symptomatic (the child walks on the medial border of the foot, has pain, difficulty with shoe fit), revision surgery may be considered. Options: (1) release of the transferred tendon — a simple tenotomy of the transferred lateral half (the medial half is intact and can still dorsiflex the foot), (2) revision of the transfer with the foot in correct alignment, (3) a medialising calcaneal osteotomy to correct the fixed valgus if adaptive bony deformity has developed.
**Why I would not do the wrong thing**: I would not re-tension the transfer at 4 weeks — removing the button and re-tensioning risks pulling the tendon out of the tunnel or damaging the healed insertion. I would not do nothing — a foot left in 10 degrees of valgus will adapt with growth and produce a fixed deformity. A cast in neutral with an AFO is the most appropriate first step.
Exam day cheat sheet
Tibialis Anterior Tendon Transfer (Whole / Split) — Exam Day Summary
References
Evidence
The split anterior tibial tendon transfer in the treatment of spastic varus hindfoot of childhood
Level IV
Hoffer MM, Reiswig JA, Garrett AM, Perry J • Orthop Clin North Am
Clinical implication: Landmark paper — established SPLATT as the standard procedure for dynamic supination deformity in cerebral palsy.
Combined split anterior tibial-tendon transfer and intramuscular lengthening of the posterior tibial tendon in spastic cerebral palsy
Level IV
Barnes MJ, Herring JA • J Bone Joint Surg Am
Clinical implication: SPLATT should not be performed in isolation — the equinus and varus components from the PTT must be addressed concurrently for optimal outcomes.
Source: J Bone Joint Surg Am. 1991 Jun;73(5):734-8
