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Achilles Reconstruction -Flexor Hallucis Longus tendon transfer using Arthrex Biotenodesis screw

    Overview

    Learn the Achilles Reconstruction :Flexor Hallucis Longus tendon transfer using Arthrex Biotenodesis screw surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Achilles Reconstruction :Flexor Hallucis Longus tendon transfer using Arthrex Biotenodesis screw surgical procedure.
    The Flexor Hallucis Longus transfer for Achilles reconstruction is a straight-forward and effective operation for salvaging various situations which have resulted in a deficient and de-functioned Achilles tendon.
    The flexor hallucis longus tendon is easily accessed sitting just anterior to the Achilles tendon and can be safely harvested as long as care is taken to identify and avoid the posterior tibial neuro-vascular bundle. It has not been my experience in performing this procedure for over 15 years that any more than a single incision is required to access and harvest adequate length of the FHL for reconstruction. If the tendon is slightly too short for a bone anchor it can be woven into the native Achilles insertion and sutured.
    The Arthrex Biotenodesis screw is a useful implant to anchor the harvested tendon into the calcaneus, though the tendon can be woven into the native Achilles insertion also. The key is appropriate tensioning of the transfer.
    Despite the slightly more involved nature of surgery compared to primary Achilles repair the period of immobilisation and recovery and outcome are little different.



    Indications

    INDICATIONS
    1)Delayed presenting Achilles rupture within the first three months: For cases where tendon ends cannot be opposed or tissue to be repaired is very poor quality.
    2)Any delayed presentation Achilles ruptures after 3 months.
    3)As a reconstruction after radical Achilles debridement: Where debridement results in significant loss of tendon tissue the transfer has a definite role. These will be cases of tendinosis with exceptionally poor tendon quality(which is rare), chronic infection & widespread gouty infiltration of the tendon.
    4)As a salvage after a failed primary debridement for tendinosis: Most cases of tendinosis irrespective of degree of severity are appropriately dealt with by a primary debridement .On rare occasions this fails to resolve symptoms and more minor degrees of tendinotic change are then radically excised. Again this is a rare situation.
    5)An over-lengthened Achilles: A way of “tightening” an over-lengthened but intact Achilles, as can occur after non-presentation at the time of rupture or over-zealous early range of movement rehabilitation after Achilles rupture.
    SYMPTOMS & EXAMINATION
    The classical presentation occurs in most patients with the sensation of being kicked in the Achilles , on occasion this includes an audible “crack”. Patients are almost always unable to continue any meaningful weight-bearing on the effected leg and a fair degree of bruising and swelling ensues rapidly. The bruising is however not invariable as a proportion of patients who rupture do not tear the sheath and all haematoma remains contained post rupture leading to no bruising. Peoples proclivity for seeking early medical advice does vary. By 2 weeks there is little residual local Achilles pain, though function will be invariably reduced, and the injury may be mis-recalled as an ankle sprain. A low index of suspicion should be had for all ankle injuries presenting late and Achilles rupture looked for in all. Reported symptoms may include instability , anterior ankle pain (due to poorly counter-balanced ankle dorsi-flexion), calf pain, significantly reduced function, a newly acquired limp and ankle swelling .
    On examination the patient will not be able to perform a single heel rise , but a double heel rise (with weight bearing upon the uninjured side) will be possible and is therefore a useless test to perform. It may be possible to palpate a defect in the tendon but swelling may preclude this. With the patient relaxed and supine gentle dorsi-flexion on the injured side should produce a significant increase in the detectable movement given the Achilles is a major passive posterior restraint to ankle dorsi-flexion. With the patient prone a calf squeeze will not produce ankle plantar-flexion if the Achilles tendon is ruptured. The amount of movement resulting even when the tendon is intact can be subtle and so the un-injured side should be examined first.
    INVESTIGATION:
    Ultrasound:An ultrasound scan is the investigation of choice with the acute rupture In skilled hands this will allow not only confirmation of diagnosis but also whether the tendon ends sit it good apposition.
    A further benefit of ultrasound is the fact that the deep calf veins can be imaged for DVT at the same sitting .There is a recognised increased incidence of DVT associated with Achilles rupture (as well as cast immobilisation).
    In the revision situation, which is by enlarge what the FHL transfer is used for, an MRI would be my preference in most cases.
    MRI: In the revision situation an MRI is a more objective investigation to interpret and as a “route map” for a surgeon intra-operatively is more easily interpreted.
    ALTERNATE OPERATIONS
    Tendon Allograft: Consider Wright Graft-jacket. Appropriate tendon re-tensioning is of paramount importance again.
    Othre tendon transfers: The peroneals are considerably smaller muscles compared to FHL though also in the neighbourhood. The Flexor Digitorum Longus has also been used in this situation as has peroneus brevis.
    Turn-down Achilles technique. Dependent on the quality of the Achilles tendon.
    Synthetic materials. Both Carbon fibre and Dacron are described.

    CONTRAINDICATIONS
    Caution needs to be exercised in patients with poor vascularity , poor skin quality , Diabetes and immuno-suppresive medications or steroids .The operation is not contra-indicated but the chance of wound infection or break down higher and patients should be consented appropriately. Protracted wound healing and the requirement for secondary reconstructive plastic surgery are rare eventualities that patients need to be aware of and Surgeons need to be realistic about.
    In patients with previous Achilles surgery the old scars should generally be re-used to avoid the risk of producing a narrow skin bridge between two scars which may result in skin necrosis.
    In low demand patients a deficient Achilles may be best managed with an AFO type splint and appropriate rocker soled footwear.
    Patients must be able to manage the post-operative protocol.

    Setup

    Almost all Achilles repairs can be carried out with the patient supine
    The incision used is postero-medial between the Achilles and the medial malleolus.
    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 and flowtron calf compression pump on non operated calf.
    Prophylactic antibiotics and LMWHeparin peri-operatively & post-operatively
    Bipolar diathermy only is used.

    Operation

    A right sided chronic Achilles rupture, viewed from posteriorly. Note the lack of tendon definition in the midline and the inability to perform a single heel rise (a double heel rise is however usually possible )

    An Achilles tendon that has been significantly and comprehensively infiltrated with gouty tophus. Apart from very superficially (posteriorly) there is almost no normal tendon tissue visible. The tendons dimensions are grossly abnormal (1 – 2).
    This requires radical debridment and will then need an FHL transfer to restore function.

    The axial view confirms the almost complete lack of normal tendon tissue (1-2)

    A long posteromedial skin incision is made, midway between the anterior border of the achilles tendon and the posterior aspect of the medial malleolus. The patient can be supine but needs to be rolled/tilted towards the operated side and the lower limb thus externally rotated approximately 80 or 90 degrees. The patient needs to be supported with side supports and the non-operated buttock elevated with several sandbags placed securely beneath.

    After the skin and superficial fat has been divided
    further dissection is with carful scissor and blunt swab dissection, being careful not to penetrate the deep fascia.The skin edges should not be undermined, and if a self-retaining retractor used (rather than assistants) it should be frequently released and placed well beneath the fat to minimise trauma to the skin edges.

    The deep fascia is a very well defined layer in most and the neurovascular bundle easily identified beneath it.The FHL also sits beneath this layer, but more posteriorly placed.
    It helps to appreciate where the bundle sits, though it need not be explicitly exposed.
    The deeper dissection onto the Achilles tendon will proceed using scissors posterior to this deep fascia initially as marked 1.

    The Achilles tendon is carefully dissected around, mobilising it from adhesions, the aim is to define the deep fascia immediately anterior to it (4), beneath which sits the Flexor Hallucis longus(FHL) muscle belly .The orientation of the patient is that they have been placed prone, so the Achilles sits uppermost in the field of vision. I used to position this way but no longer do & haven’t found an issue with surgical access.
    The deeper dissection shown here is from this separate case than the earlier approach steps.
    The full thickness skin flap (3) is evident should then be developed with scissors dissection down onto the Achilles (1,2). The tendon has an investing sheath which has already been opened in this case.
    How easy this stage is depends on when you are doing it and for what. If the situation is a missed Achilles rupture there can be a significant amount of adhesions and the normal planes can be more difficult to define so proceed carefully, the exposure may need to be worked for.
    The area marked 5 denotes approximately where the neuro-vascular bundle sits beneath the deep investing fascia. If this has been defined as in the previous slide there is less guess work in avoiding it.
    The deep fascia(4) overlying the FHL muscle belly should be opened in the midline, well away from its medial aspect , thus avoiding damage to the posterior tibial nerve which is deep to this deep fascial layer.


    The deep fascia is split in the mid-line, immediately beneath which is the FHL muscle belly(2). This should be exposed proximally by extending the cut in the fascia using long dissecting scissors.The next step is to identify the posterior Tibial nerve(3) so that it can be avoided. If the nerve is exposed by dissecting just medial to FHL muscle then it is found easily in quite a dense fatty layer. Its location is often initially best found by palpation and rolling it beneath the finger tips before further carefully dissecting just a little through the fat using tenotomy scissors.
    If one approaches the posterior tibial nerve from posteriorly through the deep aspect of the fascia as here then the Nerve overlies the posterior Tibial vessels which are slightly more anterior and will therefore not be seen .
    Before proceeding it is worth making a few points about how to handle operating on and around a significant nerve such as the Posterior Tibial nerve. The scissors used need to have fine tips, such as a pair of tenotomy scissors, and the forceps used are best fine and non toothed. Once the nerve is identified keep it in sight at all times and dissect confluently along its course , rather than jumping along to a guessed next location (on this point be aware of the expected anatomy and its variations rather than embarking on a blind exploration). Keep the nerve and branches moist at all times (local anaesthetic works well for this) and if retracting be gentle and use only short periods of traction even with vascular sloops. Diathermy must be bipolar and used sparingly away from the direct vicinity of the nerve. Finally spend time throughout the dissection, from the skin incision onwards, ensuring that any bleeding all vessels encountered is cauterised / controlled in a safe fashion.

    It is necessary to free the muscle belly of the FHL(1) off the back of the tibia and also the inter-muscular septum(2) by finger and scissors dissection. If this is not done then the transfer can be tight.The Tendo-Achilles (2) is retracted to reveal the FHL , once the deep fascia over FHL has been carefully opened. Beneath the FHL muscle belly is the posterior surface of the Tibia(3).
    What can also be noted here is how the FHL converges distally onto its tendon (1), seen here heading towards its fibro-osseous tunnel into the sole of the foot. There are variations in the anatomy of which you should be aware. The main ones that make this more laborious are if the FHL has two muscle bellies or if it has a low lying and more extensive muscle belly. The muscle belly needs to be mobile as well as the tendon and the distal tendon needs not to have extensive muscle attached. There is no harm in debriding excess muscle but one must ensure that any bleeding points are diathermised.
    The Posterior Tibial nerve (4) also sits beneath the deep fascia and has been identified here.
    It should also be appreciated that in its distal course behind the ankle the posterior tibial nerve converges very close towards the FHL tendon in the region of its fibro-osseous tunnel.
    As soon as I have identified the nerve I start to moisten it with 0.25% marcaine which I continue through-out the procedure. This results in a very dense block and a very comfortable patient.

    The FHL Tendon (2) is traced distally into its fibro-osseous tunnel in preparation for being harvested. The posterior Tibial nerve (3) is very close to the tendon at this point and has converged upon it compared to its location more proximally in the calf. The distal end of FHL is cut with a knife, angled away from the nerve.It can be even less benign in its location with respect to the tendon and sit almost directly over the FHL. In this circumstance it will need to be carefully retracted using vascular sloops.
    When the tendon it harvested this is done fairly deeply in the tunnel with a narrow number 11 scalpel blade. Given the location of the nerve the direction of the detaching cut needs to be away from the nerve and into the tunnel and only under direct vision.
    Using this single incision technique there is rarely any “spare” tendon and maximum possible length should be harvested. This is aided by ensuring an assistant maximally plantar-flexes both the ankle and the Hallux as well as placing proximally directed traction upon the FHL muscle belly (1).
    A 2 incision technique is also described using a second incision distally to harvest the FHL tendon but it’s not something I’ve ever found the need to do by following the described technique for harvesting.

    The harvested FHL tendon(3) has its end sewn through with a robust Arthrex size 2 fibre wire “whip stitch” and is then sized with the Arthrex sizing paddle.In this case a chronic Achilles rupture(2) is being reconstructed.
    The FHL tendon is next sized with the Arthrex paddle and the Bio-tenodesis screw of closest size chosen accordingly. This is often a 5.5 mm screw which is 10mm long.
    The next step is not shown. This involves a guide wire being drilled into the posterior Calcaneus at a point anterior to the Achilles insertion (1) on the medial face of the Calcaneus. This point should be chosen so that there is adequate depth for the implant to sit and adequate good bone stock around the drilled hole also.
    The same sized cannulated drill is chosen(or 1mm larger) than the implant diameter and drilled to 2mm deeper than the implant.

    Dependent upon the screw used an appropriate sized”blind-ended” tunnel (3) is drilled at right angles to the insertion of the Achilles(1). This orientation with the Biotenodesis screw gives it maximum pull out strength.In this case it has been possible to route the FHL (2) easily through a big defect in the Achilles which is effectively in continuity. Some thought needs to be given to how the FHL transfer interfaces with the remaining Achilles. It is better if it is routed directly through existing Achilles tendon both sides of the defect. It is important to ensure that the FHL muscle belly is not constricted on its passage through the old tendon, to avoid strangulating portion of the muscle. The tendon path should also be kept as direct as possible.

    Measuring from the most distal point of the tendon a mark is made with a surgical marker at 10mm. The object is that this mark sits at the mouth of the tunnel with 10mm of tendon implanted.The FHL tendon (3) is appropriately tensioned (with the ankle at neutral or deliberately in sight equinus) at the point of its re-insertion. The length of the implant to be used (and depth of the hole drilled ) is 10-12mm and this much tendon will therefore be implanted into the tunnel(4).
    If the mark on the tendon sits distal to the tunnel (4) as is shown here then the transfer is too long (which is not common) and some tendon should be excised otherwise the transfer will be slack. The tendon would then be remarked to confirm appropriate tension again.

    The FHL transfer is routed proximally and distally through the Achilles remnant and the Biotenodesis screw roped onto the most distal part of the FHL tendon.The FHL tendon(1) is controlled by the anchoring whip stitch and the Bio-tenodesis screw(2) is “roped”onto the tendon in preparation for implanting the 10mm marked portion of the tendon into the tunnel.
    Consult the Arthrex Biotenodesis technique for explanation of the “roping” step. Essentially there is a loop of small gauge Fibre-wire routed into the end of the cannulated Bio-tenodesis screw that protrudes from this distal end of the screw and is pulled taught and controlled from the proximal end of the attached screw driver.
    Getting the tendon well into the tunnel to the appropriate depth (thus ensuring appropriate tension) is easiest done by plantar-flexing the ankle first and encouraging the tendon in without much resistance. The screw can then be driven home into the tunnel, ensuring that the ankle assumes a position of neutral(or slightly less than neutral) before the screw is fully implanted.
    An alternate (& much easier technique still using the Biotenodesis screw ) is to drill the initial guide pin just out of the lateral aspect of the Calcaneus (avoiding sural nerve territory) before over-drilling the incomplete tunnel for the screw to the appropriate size and depth.
    The FHL tendon is pulled into the tunnel using the whip stitch which is itself pulled out of the lateral aspect of the Calcaneus having mounted it on the flexible tendon passing wire supplied in the kit. This allows very easy and precise tensioning of the tendon transfer , which is a key step in the operation.

    The FHL tendon is guided into the tunnel on the end of the Biotenodesis screw.It is not only important that the appropriate amount of tendon is in the tunnel, ensuring appropriate tension of the transfer, but that the screw(3) to tendon(2) interference fit is good.
    If one is unlucky the fit may be poor, especially if bone quality is not good. If this form of fixation fails then it is entirely appropriate to suture the FHL transfer directly into the distal stump of the Achilles. It should be “woven” into the Achilles and fixed at multiple points with heavy duty sutures. Again it is critical that the tension is adequate and commensurate with the resting tension of the opposite side.


    Additional sutures should be used between the Achilles remnants and the FHL transfer. These should be 1 vicryl absorbable sutures and are used as back-up fixation. The suturing should only be between tendinous tissue and not include muscle.1-The “whip stitch ” suture end
    2-End of Biotenodesis screw stitch (1 and 2 are now tied together and the ends cut short).
    3-Transferred FHL tendon
    4-FHLmuscle belly filling the defect in the Achilles tendon.

    This is a chronically infected Achilles tendon with deep infection throughout wide areas of tendon as well as both medial and lateral sinuses.
    This unusual case is the sort that will require radical and extensive debridement , producing a defect that the well vascularised FHL musculo-tendinous graft will be indicated for.

    A T2 weighted saggital MRI hinting at the extensive nature of the infection (with evidence of retained non-absorbable sutures within the infective mass)

    A T2 weighted saggital MRI which shows well the significant dimensions to which the Achilles has developed due to the chronic soft tissue infection.

    The axial MRI reveals the “through and through” nature of the infection with both medial and lateral sinuses evident.

    Post Operative

    5-6 weeks in below knee cast post-operatively non-weight-bear
    The initial 2 weeks foot position may be slight equinus if needed ( if transfer tight ) but aim for neutral position of foot by 2 weeks .
    Dressing changes at 1 & 2 weeks
    Long Air-cast boot to follow after 5-6 weeks
    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/shoe-wear after a patient is out of cast.
    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 routinely advise another month of daytime dressings when in shoes and also nocturnal dressings whilst any of the wound remains unhealed
    Showering & bathing is allowed from when out of cast
    Commence range of motion excercises and non-weight bear strengthening regieme from when out of cast
    Avoid pushing Ankle dors-iflexion range early as this risks over-lengthening/stretching the newly repaired tendon
    Increase weight bearing as comfortable in boot , likely able to come off crutches by 8 weeks post op
    Commence weight-bearing rehab (strength & balance) from when able to full weight bear.
    Static bike from 7 weeks
    Cross-training from 9 weeks
    Light Full weight bearing jog on treadmill from 11-12 weeks
    (sooner on Alter-G treadmill or in pool)

    Recommended Reading

    Flexor Hallucis longus transfer in treatment of Achilles tendinosis.
    J Bone Joint Surg (Am) 2013. 95(1):54-60.
    L C Schon et al
    An older surgical population , average age in the mid 50s, in whom the FHL transfer was used to supplement Achilles debridement (which itself has a good outcome). 24 month follow up revealed significant improvement in function and pain (within 3 to 6 months of operation though continuing to improve). Single heel raise was the slowest aspect to improve. 2/3 rds of patients observed no alteration in balance due to loss of FHL function (but 1/3 rd did).
    Flexor Hallucis Longus transfer for treatment of chronically ruptured Achilles tendons.
    Journal of Orthopaedic Surgery 2009 .17(2).194-8
    R H Mahajan , R B Dalal.
    36 patients (& 38 ruptures) in a population with mean age of 70 years and Chronic Achilles ruptures(all in excess of 12 weeks).
    A slightly unusual technique described in that the location of rupture was not exposed rather the tendon harvested at knot of Henry and muscle belly of FHL sutured to Gastro-soleus proximally.
    Reviewed at 12 months 33 /38 could stand on tip toe , 28 excellent and 8 fair results. 5 wound healing complications and 3 patients with reduced push off.
    A good paper because it reports on a patient group with one pathology (Chronic Achilles rupture) in whom there would be little debate about the indication and appropriateness of the operation.
    Operative treatment of chronic irreparable Achilles tendon ruptures with large flexor hallucis longus transfers.
    Foot & Ankle Intl. 2013. 34(8):1100-10.
    S Rahm et al
    24 feet (22 patients , mean age 52 ) were treated with a “trans-tendinous” technique who were followed for a mean of 72 months and in whom the AOFAS improved from 66 mean to 89 mean though isokinetic power was only 75% of the normal side.
    A second group of 18 feet (in 18 patients, mean age ) underwent intra-osseous anchoring. Follow up was 35 months and AOFAS improved from 59 mean to 85 mean and isokinetic power was reduced at follow up to 77% of the normal side.

    Reference

    • orthoracle.com

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