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Tibialis posterior transfer (for foot drop)

    Overview

    Learn the Tibialis posterior transfer (for foot drop) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Tibialis posterior transfer (for foot drop) surgical procedure.
    Historically the Tibialis posterior transfer for foot drop has been the main intervention for patients intolerant of, or requiring better function than is afforded by , a simple stabilising Ankle Foot Orthosis (AFO).
    Significant improvements in non-operative management options, both with energy returning carbon fibre foot drop splints and FES (functional electrical stimulation) have made this a far less commonly performed operation for an isolated and flexible foot drop deformity.
    In patients with other co-existing pathologies which can accompany the foot drop (such as Achilles contracture or a varus heel) which make conservative management less effective, there remains a strong indication for the operation.

    Indications

    SYMPTOMS & EXAMINATION:
    There are very disparate pathologies which can result in the functional weakness of phasic foot and ankle dorsiflexion and eversion which produces a foot drop. These different pathologies will have their own associated symptoms which may vary cause to cause. Most cases will either be part of a Cavus/Cavo-varus or an isolated problem with the common peroneal nerve. The latter may be due to local trauma to the nerve at the knee (such as seen after a traumatic dislocation of the joint or iatrogenic injury at the time of knee replacement) or a more proximal injury to the sciatic nerve (a rare complication of the posterior approach to the hip). Causes of the Cavus foot can be considered either central (eg CVA, Cerebral Palsy,MS) , spinal (eg polio , spinal cord injury) ,peripheral nerve (eg HSMN , Leprosy) or muscular ( eg muscular dystrophy). The foot drop itself will produce a weakness, instability and clumsiness during gait. If part of a cavus foot there may be characteristic symptoms from this also.
    Most patients will present to the surgeon already with a diagnosis and having been diagnostically worked up. If this is not the case then a thorough neurological examination (including recording of power, reflexes and the presence of spasticity ) needs to be performed. The opinion of a neurologist should also be sought.
    A careful assessment of the opposing neuromuscular units is always required .How to proceed surgically depends on the balance of power of the agonist/antagonist muscle groups , their absolute strength(judged by the MRC scale) and also the passive correctibility of components of the deformity. On the MRC grading scale no muscular contraction is graded as 0 , contraction but no movement as 1, active movement that cannot overcome gravity 2, active movement that can overcome gravity 3 ,active movement against gravity and resistance 4, normal muscle muscle strength 5. It should be remembered that in transferring a muscle to a different position and function it is expected that its MRC grading will fall by 1 or 2 points on the MRC scale , which makes transferring an MRC 1 or 2 power muscle of dubious value. It is also key that flexibility (and passive correctibility) of any deformity is present otherwise a tendon transfer alone will not be sufficient to produce a meaningful correction. In the context of a neuromuscular cause plantar flexion of the 1st ray, a varus heel, Achilles and plantar fascia contracture may also require correction.
    Even if the Tibialis Posterior has near normal power prior to transfer it is not predictable to be able to determine that a transfer will result in a phasic unit which contracts at the appropriate stage of the gait cycle , resulting in optimal function. The patient should be prepared for the fact that all that may result post-operatively is a strong but static restraint to the foot drop. If this is the case then supplementary orthotic management may be required. An optimum result will be a phasic response from the transfer and this in most cases requires also appropriate gait re-education as well as an appropriate response from the transferred Tibialis posterior.
    One cause of a foot drop self-evidently requiring a different operative management is rupture of the Tibialis anterior and this should be looked for.
    It should be understood that neurological compromise is not an all or nothing phenomenon. A”foot-drop” may be more a “tendency towards a foot drop” if useful, though reduced, power is present within the peroneal tendons and tibialis anterior (compared to a more powerful tibialis posterior and Achilles). In this type of patient a full transfer may not be required, rather a recession of the musculo-tendinous junction considered.
    The overall function of both the limb and patient themselves are also important things to consider. In a non-ambulatory (or non-standing) patient with an unopposed and over active Tibialis Posterior a simple division of the tendon to allow more comfortable positioning in an AFO splint for a balanced foot position during sitting maybe at that is required.
    NON-OPERATIVE ALTERNATIVES:
    Ankle Foot Orthosis(AFO): The most basic stabilising device which simply holds the foot and ankle in neutral alignment.
    Shoewear :This is really in combination with the AFO to provide an appropriate rocker-type platform on which to forward progress during gait.
    Carbon-fibre (energy return) Foot drop type splint: These are ideally custom fitted to the patient and in many allow a much more naturalistic gait.
    Functional electrical stimulation.
    OPERATIVE ALTERNATIVES:
    These are more by the way of additional interventions, rather than alternatives, for the other components of a cavo-varus foot or if an Achilles contracture has developed.
    A corrective arthrodesis is for consideration if the transfer fails or there are considerable fixed or arthritic components to the deformity at the time of presentation.
    Calcaneal osteotomy :To correct a varus heel
    Achilles release: Open or as a triple cut depending on the extent of contracture
    Dorsiflexing 1st Ray basal osteotomy: To deal with a destabilising plantar flexed first ray.
    Postero-medial muscle recession: If the deformity is a flexible one , not too severe , and also with some useful Peroneal and Tibialis anterior function , then a recession of the postero-medial tendons may be an adequate intervention. This involves selectively sectioning muscle fibres off their musculo-tendinous junction.
    Arthrodesis: The level(s) will be determined by the joints effected .

    Setup

    Operation carried out with the patient supine
    The incisions used are postero-medial & anterior as shown in the technique.
    One or two side supports should be placed on the operated side at thigh and trunk level whilst several sandbags are placed under the opposite buttock , thus turning the operated leg into 90 degrees of external rotation
    The further addition of rolled up sterile towels allow an extra element of helpful rotation and access to the back and lateral aspects of the tendon
    Thigh tourniquet to be used
    Prophylactic antibiotics and LMWHeparin peri-operatively & post-operatively
    Bipolar diathermy

    Operation – 1

    The Tibialis posterior tendon (1) is harvested with a generous incision from just below the medial malleolus (marked in yellow) down to its insertion at the navicular.
    There is usually a reasonable sized leash of vessels sitting in the fat layer at the point of Tibialis Posterior insertion.

    As much length as possible is required of the tendon. The Tibialis Posterior has a wide insertion and as much of this as can be harvested under direct vision is taken(1). The arrow shows the direction that the sub-periosteal dissection needs to take on the inferior aspect of the Navicular insertion to get maximum length.

    The detached end of the Tibialis Posterior tendon(1).

    The tendon next needs to be dissected out and identified proximally in preparation for transfer from the posterior flexor compartment to the anterior extensor compartment. This point is approximately a hands breadth above the medial malleolus.

    A proximal and longitudinal incision(1) is made behind the posterior border of the tibia(2) a hands breadth above the medial malleolus.The deep fascia is visible with beneath it the muscle belly of Flexor Digitorum Longus(FDL, 3) once the fat layer has been blunt dissected away with a swab. In the anterior aspect of the wound the Saphenous vein and nerve may be encountered.

    The deep fascia is next split(1,3). At this level the most superficial structure is the FDL muscle and tendon(2).

    Once the FDL is retracted(1) the Tibialis posterior tendon can be seen beneath it(2).The posterior border of the tibia is marked 3.

    That the Tibialis Posterior tendon has been correctly identified is confirmed by pulling proximally (2) and observing movement of the tendon end distally(1).

    The Tibilais Posterior tendon needs to be delivered through the proximal wound. This is achieved with proximal traction upon the tendon using a tendon hook.
    Quite a lot of force maybe be required so it is key before applying this that the distal tendon end is debulked to allow a smooth passage.

    Distally guiding the stump through its sheath behind the medial malleolus. It may require the distal stump to be debulked to allow it to pass.

    The Tibialis posterior (1) now delivered proximally and ready for transfer into the anterior compartment.

    The tendon needs to be transferred behind the tibia , from the deep flexor compartment to the extensor compartment.The posterior surface of the tibia is identified with finger tip dissection (1). A channel for the tendon across the back of the Tibia is most easily started in the correct and deepest plane by inserting a strong and controlled orthopaedic finger which should keep in direct contact with the bony posterior surface of the Tibia.
    Prior to this the deep fascia should to be freed proximal to the apex of the skin incision (2) to allow easy passage of the Tibialis posterior muscle belly. This is best done by elevating the proximal wound with a large Langenbecks’ retractor and under direct vision pushing the almost closed tips of a large pair of dissecting scissors proximally along the deep fascia.

    A channel along the posterior surface of the tibia , up to the deep surface of the interosseous membrane (between Tibia and Fibula) has now been created(3) by firm digital dissection. The posterior border of the tibia(2) and Tibialis Posterior tendon(1) are also visible .

    A large curved Coley forceps(1) is now required.

    This is placed into the channel and kept closely applied to the bone of the posterior tibia as it is advanced into the interosseous membrane, tips closed. The interosseous membrane is identifiable with the tips of the Coley forceps between the posterior aspect of Tibia and Fibula.

    The interosseous membrane is identified by feel and is breached by pushing the forceps through ,tips closed.Once through the membrane the tips are opened and the forceps pulled back , creating a larger defect, sufficient to allow the Tibialis posterior tendon to be passed.

    The Coleys’ forceps are now once again passed along the track , tips closed(2). They are pushed into the anterior compartment through the breech in the Interosseous membrane. The forceps are angled to keep in contact with the tibial bone, exiting in the deeper soft tissues immediately adjacent to anterior crest of the tibia(1). It is best not to exit these large forceps through the anterior tibial neuro-vascular bundle, which is only slightly lateral to the anterior tibial crest so it is important to keep the tips of the forceps in close contact with Tibial crest bone as they are pushed anteriorly).

    The tips of the Coleys’ forceps are dissected directly down onto as they tent the extensor fascia anteriorly (1).
    Distal sits to the left of this image and medial is superior

    With the deep fascia(1) opened the Tibialis anterior tendon is identified (2) and the interval between it and the crest of the tibia(3) is defined ,through which the tendon will be passed.

    The Tibialis anterior tendon(1)is retracted a little to allow blunt scissors dissection between it and the subcutaneous border of the tibia(2) to complete the channel for tendon transfer(3).

    The Coleys forceps(1) are next passed back through the extensor compartment under direct vision, and beneath the tibia to the medial compartment(2) to pick up the tibialis posterior tendon and then pull it back through into the extensor compartment.

    The Tibialis posterior tendon(1), delivered into the extensor compartment and medial to the Tibialis anterior tendon(2).
    It should pass easily and be of appropriate length. If you are struggling with this check back that the deep fascia is adequately released in the proximal part of the medial wound.

    The final incision is made onto the dorsal midfoot , to where the tendon will be reattached. This is either midline or midline/lateral.
    The extensor retinaculum should be identified beneath the fat layer as the transfer should pass beneath it.
    The Tibialis Posterior is kept moist wrapped in a saline soaked large swab.

    A tendon passing forcep(1) is routed underneath the extensor retinaculum from distal wound to proximal wound to catch the Tib Post tendon(2). The line of its passage should be kept superficial and in direct contact with the under surface of the retinaculum to avoid damage to the anterior Tibial neurovascular bundle.
    The line of transfer should also avoid the Anterior Tibial neuro-vascular bundle.

    The tendon grasped.

    Operation – 2

    The tendon delivered distally(1).

    The long extensor tendons retracted(1) to allow access to the dorsal midfoot, in the approximate midline.
    Subperiosteal dissection to identify a midfoot bone of appropriate size into which a suture anchor is placed(2). Most commonly the lateral Cuneiform.
    Other points of attachment can be the Extensor digitorum brevis or in cases with no hindfoot varus the Tibialis anterior can also be used.

    A starting hole being made (2) for the suture anchor. The Extensors(1) retracted.

    The Tibialis posterior tendon(2) being reattached using the Arthrex Bio-corkscrew anchor(3) in this case lateral to the long extensor tendons(1).
    As with all tendon transfers it is important that the tendon is reattached under appropriate tension (the foot should be placed into dorsiflexion when the graft tension is being set).

    Post Operative

    6 weeks in below knee cast post-operatively non-weight-bear
    The position in cast should be in a degree of eversion.
    Initial 2 weeks in back-slab to allow for swelling
    Dressing changes at 1 & 2 weeks
    Long Air-cast boot to follow
    Of upmost importance through-out the post-operative period is that the wound is looked after . Wound infection and small areas of breakdown occur easily in a freshly healed wound that is allowed to rub on socks/shoewear.
    Any exudate from the wound which is allowed prolonged contact with the wound will further excacerbate any skin breakdown . Dressing changes may therefore need to be frequent if such a complication ensues.
    Once out of cast I advise another month of daytime dressings when in shoes and also nocturnal dressings whilst any of the wound remains unhealed
    Showering & bathing is from when out of cast
    Increase weight bearing as comfortable in boot , likely able to come off crutches by 7-8 weeks post op
    Commence weight-bearing rehab (strength & balance from then)
    Commence range of motion excercises and non-weight bear strengthening routine from when out of cast
    Gait re-education regime is required. Rehabilitation with specialist neuro-physiotherapist if available.

    Recommended Reading

    Posterior tibial tendon transfer for foot drop:20 cases followed for 1-5 years.
    Acta Orthop Scand.1998.69(6);608-10.
    L.M.Hove , P.T.Nilsen
    Transfer through Interosseous membrane and split into 2 tails for a wider insertion into EHL and EDBr.
    20 cases reported with a 10% revision rate (for graft tensioning issues). All could walk without orthotic and all had active ankle dorsiflexion (with median of 5 degrees).
    Interosseous transfer of Tibialis posterior for common peroneal nerve palsy.
    J Bone Joint Surg.1989.71-B.834-837.
    M.Richard.
    39 patients with Leprosy as the aetiology of the foot drop. Tendon ( with minimum of MRC 4/5) routed through interosseous membrane and split into 2 insertion points
    If passive dorsi-flexion not to 20 degrees then TA lengthening added (14 of 39 legs).
    Tibialis posterior transfer for the correction of foot drop in Leprosy-Long term outcome.
    J Bone Joint Surg (Br)1996 ;78-B:61-2
    D Soares
    A comparison of the interosseous route (43 patients) against the medial circumtibial route(26 patients) for transferring Tibialis posterior. 69 feet of which 63 also had elongation of the Achilles tendon. Of the 26 patients 22 noted to be suffering with recurrent inversion deformity at follow up whereas only 1 of the 43 transferred by interosseous route did. The follow up however was longer for the circumtibial route compared to interosseous by a number of years.
    In both groups the tendon was split and anchored both laterally and medially. The lateral point of attachment was into either Extensor digitorum Longus or the Peroneals in almost equal numbers(and sutured with the foot held in 20 Degrees of dorsiflexion). Medially attachment was to the Tibialis anterior whilst the foot was held in neutral.
    Rehabilitation started after 3 weeks post-operatively with active contraction excercises for the Tibialis posterior into dorsiflexion and eversion out of cast . No weight bearing until 6 weeks post op.

    Reference

    • orthoracle.com

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