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Os Naviculare excision and tibialis posterior advancement

    Overview

    Learn the Os Naviculare excision and tibialis posterior advancement surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Os Naviculare excision and tibialis posterior advancement surgical procedure.
    An Os Naviculare is a medial midfoot bony prominence at the point of the Tibialis Posterior insertion that presents with localised pain (and possibly swelling) in both adults and children.
    If activity restriction and orthotic management fails to control symptoms simple excision of the bony prominence is indicated.
    An Os Naviculare can be present in a foot with a normal arch profile or a pes planus. If in the latter a calcaneal osteotomy at the time of surgery may be indicated. Strong evidence for re-routing the insertion of the Tibialis posterior through the navicular to improve the medial arch profile (known as the Kidner procedure) is lacking.


    Indications

    INDICATIONS.
    A symptomatic Os Naviculare that has failed to settle with conservative management.
    SYMPTOMS AND EXAMINATION .
    This condition develops during childhood/adolescence and may present then or may remain asymptomatic till some minor ankle or foot injury later in life. The primary issue is pain localised to the medial midfoot and the region of the navicular which is associated with the local prominence. The condition may be associated with an entirely normal arch profile or varying degrees of plano-valgus. In an acute case the features of tibialis posterior dysfunction may be present and this should be considered as one of the differential diagnoses in the adult. Rarely the condition can co-exist with a tarsal coalition and the flexibility of a pes planus should be always assessed.
    INVESTIGATION.
    The commonly used classification for the Os Naviculare is based on the plain X-Ray appearance, as described by Geist in 1914 (when bigger things were happening and it didn’t get the coverage it deserved).
    Type 1 is a small circular area of ossification within the tendon insertion. Type 2 a triangular bony prominence which articulates directly with the medial aspect of the navicular and type 3 a prominent hooked medial aspect of the navicular in bony continuity with the rest of the navicular.
    There is nothing especially prognostic about the classification.
    Weight bearing X-Rays allow the angular measurement of various bony relationships when the foot is at its flattest. This does not help in surgical decision making (above and beyond a clinical examination) but potentially allows objective documentation of any improvement in the weight-bearing profile of the foot post-operatively.
    It is however more useful to image using MRI or CT which allow a better “3D” appreciation of where the bone to be excised lies. The state of the tendon itself is also visualised if MRI is chosen and whether the interface between Os and bone is inflammed or whether the Os itself is inflammed or both. These investigations also on occasion will turn up other inter-current pathologies associated with pes planus that may require treatment as well (and as such are better identified pre-surgery), such as tarsal coalitions.
    NON-OPERATIVE MANAGEMENT.
    Initial management should be activity modification , “detensioning” the Tibialis Posterior with a functional foot orthotic and possibly a period of off-load in a long post-operative boot.
    If the interface between Os and Navicular is particularly oedematous then an ultrasound guided injection may be a worthwhile additional procedure.
    ALTERNATE/ADDITIONAL OPERATIVE MANAGEMENT.
    There is some debate on whether the Tibialis Posterior insertion should be entirely detached and then re-routed through a plantar bony tunnel in the Navicular (the Kidner procedure). The altered line of pull has theoretical advantages with respect to improving the medial longitudinal arch. The efficacy of this does not appear to be strongly supported by the literature (see results section).
    If a pes planus deformity is present then the addition of a medialising calcaneal osteotomy should be considered. Whether to add this in depends on the degree of the pes planus and also location of symptoms. If there are lateral hindfoot symptoms due to fibula tip impingement or medial arch symptoms in addition to those directly located at the Os Naviculare then a calcaneal osteotomy to improve the weight bearing profile of the foot and its loading characteristics should be considered.
    A more recently reported alternative to improve the correction of an associated plano-valgus deformity is the addition of an Arthroresis implant into the sinus tarsi region of the subtalar joint
    As with any planovalgus deformity the tightness of the gastrosoleus complex should be assessed and release of one of its components considered depending upon findings. See Hari Harans excellent explanation on this in his own Os naviculare excision technique.

    Setup

    The operation is carried out with the patient supine
    The incision used most is a direct one onto the tendon insertion and extending proximally a few inches.
    One or two side supports should be placed on the operated side at thigh and trunk level whilst a sandbag is placed under the opposite buttock , thus turning the operated leg into a degree of external rotation
    The further addition of rolled up sterile towels allow an extra element of helpful rotation and access .
    Thigh tourniquet to be used and Flowtron on non-operated calf.
    Prophylactic antibiotics and LMWHeparin peri-operatively & post-operatively
    Bipolar diathermy.

    Operation

    A large Os trigonum. More usually they are smaller and getting an appreciation of their location is best done with an MRI. The sagittal images are most useful in localising for surgical excision.

    A more prominent navicular (2) than normal, typical of an Os Naviculare. Here however it is almost as prominent medially as the medial malleolus (1) which is unusual.

    The skin incision is made in the line of the Tibialis Posterior tendon (3). It runs between the Medial Malleolus (1) and the prominent medial aspect of the Navicular (2). It of course can be extended superiorly if indicated.
    Once through the skin there is usually a prominent leash of vessels in the fat layer near the tendons’ insertion.
    Small branches of the saphenous nerve may be present superiorly and posteriorly the cutaneous innervation is also the saphenous nerve.

    The insertion of the Tibilais Posterior (1) should be inspected for tendinitis and tendinosis which may require debridement. The paratenon is usually inflammed and should be excised.
    Distal to the medial malleolus the local anatomy is that the tibialis posterior (Tib Post) and flexor digitorum longus (FDL) sit in separate sheaths, the tibialis posterior above the sustentaculum tali and the FDL immediately beneath it. Inferior again is the flexor hallucis longus and between the two flexors is the neurovascular bundle.

    The deep aspect of the tibialis posterior tendon should also be viewed by displacing the tendon with an appropriate blunt instrument , such as a McDonalds(1).
    Some attempt can also be made at this stage to identify the interface between the Os Naviculare and the body of the Navicular which will not be immediately obvious. This can be done by both exerting traction through the tendon insertion and also direct probing the medial aspect of the Navicular (2) and looking for differential movement within the periosteal sleeve.
    It is always worth studying the pre-op MRI (in particular the axial and saggital cuts) to get a better appreciation of where the Os Naviculare actually sits.
    It is worth remembering that the tibialis posterior tendon does not just insert onto the navicular tuberosity. It has three defined terminations, anterior ,middle and posterior. Only the anterior inserts into the navicular tuberosity. The two other parts insert diffusely, including into the intermediate & lateral cuneiforms, cuboid and sustentaculum tali.

    Once some movement has been identified (in a type 1 & 2 Os Naviculare) this guides the plane of sharp dissection.
    If no movement is detectable (for example with a type 3 deformity) then a longitudinal incision in the midline of the tendon is used and deep dissection carried on in this line until bone of the Navicular is encountered. Any bony prominence should simply be dissected around using the same subperiosteal reflection technique before resecting the appropriate amount of bone.

    The insertional fibres of the tendon( 2) which attach to the Os Naviculare (1) are dissected free of the bone by a combination of knife and periosteal elevator dissection(shown here). The fibrous joint between the Os Naviculare and the main body of the Navicular (3) is inter-currently dissected free.

    The body of the navicular (3) with its thick periosteal covering intact following removal of the Os (1) and preservation of as much of the Tibialis Posterior insertion(2) as possible. With a large Os little more than a peripheral shell of tendon is left attached once the bone is removed.
    Once the bone is removed the underlying spring (Talo-calcaneo-navicular) ligament should be inspected, in particular in the presence of a pes planus. If it appears either torn or attenuated then it can be repaired/tightened at the same time, though this is an unusual eventuality.
    The tendon itself (and its more proximal extent) may require a debridement which will most likely entail longitudinal incisions between its fibres after stripping away thickened paratenon. Any large areas so treated may require repair using a continuous 2.0 Vicryl suture.

    Clearly visible proximal to the thin, preserved sleeve of the Tibialis Posterior (1) is a more structural element of the tendon. The tendon insertion needs to be closely re-opposed to the navicular.
    A suture anchor such as the Arthrex 5.5mm Bio-Corkscrew implanted into the navicular is ideally suited to this. Anchoring the tendon like this makes advancing the insertion and tightening it a straightforward procedure. No matter how well anchored this will not be suitable for immediate weight-bearing. Deciding what an appropriate tension is for the tendon requires some judgement. In a foot with a flatter medial arch profile leaving the foot in a degree of supination after tendon advancement (and possibly adding a medialising Calcaneal osteotomy) is probably appropriate.
    In cases with a smaller area of bone to be removed a direct closure of the tendon defect produced may be appropriate.

    Once the suture anchor is implanted (1) it is straightforward to advance the tibialis posterior (2) onto it, thus closing the cavity created by removing the bone and at the same time tightening the tendon.

    The Tibialis Posterior tendon after an appropriate re-attachment.
    Interrupted heavy Vicryl sutures (1) are used in addition to the central core sutures of the anchor in reattaching it.

    Post Operative

    The first four weeks are spent in a lightweight cast , non- weight bearing.
    Dressing changes are at 2 & 4 weeks.
    After four weeks into long post-operative boot and commence light weight bearing using crutches if the operation has just involved a tendon advancement.
    Usually by the end of 5 to 6weeks post op it is comfortable to weight-bear just in the boot without the need for crutches.
    Once weight-bearing commences the addition of a semi-rigid orthotic to support the medial arch profile is of use.
    From 6 weeks commence weight-bearing rehabilitation (strength & balance work) and non-weight bear strengthening and range of motion excercises.
    Static bike from earliest 6 weeks
    Cross-training from earliest 8 weeks
    Light Full weight bearing jog on treadmill from 12 weeks
    (sooner on Alter-G treadmill or in pool)
    Of great 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/shoe-wear.
    Any exudate from the wound which is allowed prolonged contact with the wound will further exacerbate 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.
    If a Calcaneal osteotomy has been performed then an X-ray is required post operatively and at 5-6 weeks and weight bearing should not be commenced until after this. From week 6-12 the patient will be in a post-operative boot and progressing to full weight bearing by 8-9 weeks. Once this has been achieved rehabilitation can commence as detailed above.

    Recommended Reading

    Surgical treatment of the symptomatic accessory Navicular. The Journal of Bone and Joint Surgery 1984 .Vol 66-B. No 2. 218-226.
    M F MacNicol, S Voutsinas.
    26 patients were treated surgically with the Kidner procedure and 21 with simple excision of the Os Naviculare (though the groups treated were not strictly comparable).
    15 patients with a normal weight bearing profile lost all symptoms after simple excision as did 4 of 6 feet with pes planus. Mean follow up here was 10 years.
    The Kidner procedure was used in an exclusively pes planus group and successfully in 19 patients. 4 recurrences of the Os Naviculare were noted. Mean follow up in this group 12 years.
    Kidner procedure for symptomatic accessory Navicular and its relation to pes planus. Foot Ankle Int.1995.Aug 16(8);500-3. S Prichasuk, O Sinphurmsukskul .
    28 patients with symptomatic Os Naviculare underwent excision and Kidner procedure. Good results in 27 re pain relief however only 3 patients displayed any improvement in the medal arch profile of the foot. Mean 3 year follow up.
    Simple excision vs the Kidner procedure for type 2 accessory Navicular associated with flat foot in the paediatric population.
    Foot Ankle Int 2o13. 34(2) 167-72. SM Cha et al
    25 patients treated with simple excision and 25 with the Kidner procudure. No difference between the groups re arch profile , though both groups had improved calcaneal pitch.
    Outcome of modified Kidner procedure with subtalar arthroresis for painful accessory navicular associated with planovalgus deformity . Foot & Ankle Intl .2012 .33(11). Garras DN, Hansen PL, Miller AG, Raikin SM.
    20 patients of average age 18 years with a type 2 Os Naviculare and associated planovalgus deformity were treated with a Kidner type operation supplemented by the implantation of an Arthroresis implant into the subtalar joint.
    After follow up for a mean of just over 4 years 19 of the patients reported good or excellent outcomes, widespread improvements in the weight-bearing profile of the feet was noted and no subtalar arthritic change .3 implants were removed due to pain with no loss of correction.
    Medial displacement calcaneal osteotomy with posterior tibial tendon reconstruction for the flexible flat foot. J Foot Ankle Surg 2014 .53(5): 539-43. HH Chao et al
    21 feet , heel valgus corrected in all. All patients pain free from 6 months.

    Reference

    • orthoracle.com

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