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Fractional Tendon Lengthening and Swanson Silastic Metacarpophalangeal Joint Replacement (Wright Medical) for Spasticity

    Overview

    Learn the Fractional Tendon Lengthening and Swanson Silastic Metacarpophalangeal Joint Replacement (Wright Medical) for Spasticity surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Fractional Tendon Lengthening and Swanson Silastic Metacarpophalangeal Joint Replacement (Wright Medical) for Spasticity surgical procedure.
    The following procedure demonstrates the application of the Swanson silastic joint arthroplasty in the treatment of a longstanding, fixed flexion, MCPJ contracture resulting from spasticity. These implants have a well established role in the surgical treatment of the rheumatoid hand but they remain a versatile implant with a wider range of useful indications.
    The adult spastic hand commonly results from traumatic brain injury or anoxic insult resulting in an upper motor neurone lesion.
    In mild cases this may result in loss of dexterity or coordination. In severe cases, spasticity within extrinsic and/or intrinsic muscle groups results in contractures of the wrist or digits. The most severe contractures present with a clasped hand, fixed skeletal deformities and joint subluxation. They are often associated with poor hygiene and an associated risk of skin breakdown.
    The management of this unique group of patients requires a careful evaluation of the factors driving the deformity, the potential reversibility of each, and any residual function that may be expected. An understanding of the patients specific expectations is central to a satisfactory outcome.
    The surgical technique demonstrated here is only one possible technique, and was very much tailored to the unique nursing and functional needs of this particular patient. There is clearly great variation between patients with spasticity affecting hand function.
    The implants used in this case are the Swanson small finger joints manufactured by Wright Medical.


    Indications


    INDICATIONS:
    Initial treatment of spasticity may involve non-surgical modalities such as stretching, and serial static splinting in combination with pharmacological agents that reduce muscle tone.
    It has been difficult to clearly establish the optimal timing for any surgical treatment since the time course for neurological recovery following the onset of an upper motor neurone lesion remains variable. There is evidence to suggest that ongoing neurologic recovery may be seen for 12 months following an ischaemic stroke and for 18 months following a head injury. Opheim et al. have shown that early spasticity at 4 weeks following a stroke was the best predictor for future severe spasticity.
    Surgical modalities for the spastic hand include distal intrinsic release, lateral band transection or translocation, fractional lengthening of extrinsics, tenotomy, superficialis to profundus transfer, and selective neurectomy. Bony procedures that may be required in severe deformities include wrist arthrodesis, proximal row carpectomy, metacarpal head excision or metacarpohalangeal joint arthroplasty.
    The use of intramuscular Botulinum toxin type A is a useful diagnostic adjunct that may help identify muscle groups that may be driving the contracture and are potentially reversible through surgery.
    The patient in this case was a 70 year old woman who had a background of mild cerebral palsy with a more recent stroke that had occurred in the last 5-10 years.

    SYMPTOMS & ASSESSMENT:
    She presented with a unilateral clasped hand that had some useful function in the index finger and thumb. The middle and ring metacarpophalangeal joints (MCPJs) were fixed in full flexion of 95 degrees and the little MCPJ was fixed at 60 degrees. All demonstrated fixed volar subluxation but no ulnar or radial drift. A degree of volitional FDS and FDP control was present clinically and on electromyography. The proximal interphalangeal joints (PIPJs) were also fixed in a flexed position with a rotational deformity affecting the little and ring PIPJs.
    None of the deformities were passively correctable.
    There was evidence of poor soft tissue support around the MCPJs, including a contracted volar soft tissue.
    Skin quality in the palm was poor due to poor access for hygiene and difficulty in trimming the fingernails.
    The patients main aim was to open the hand out to permit hygeine but she was keen to regain any grasp function that could be preserved.
    A functional assessment by a hand therapist was performed.
    INVESTIGATION:
    The initial assessment of the patient involves liaison with other members of a multidisciplinary team including a neurologist, hand therapist and a neurophysiologist. X-rays revealed subluxed MCPJs with advanced degenerative changes. The radiographs are important to assess the degree of bone erosion and cavitation and to plan implant size. EMGs revealed a degree of volitional long flexor control despite the significant spasticity present. Clinical examination in combination with neurophysiology testing confirmed that the predominant driving force behind deformity was longstanding spasticity within FDS and FDP and there was minimal intrinisic muscle involvement. This suggested that fractional lengthening of FDS and FDP would allow release the shortened muscle tendon unit whilst retaining some possible function.
    OPERATIVE ALTERNATIVES:
    Alternatives to MCPJ arthroplasty include metacarpal head excision or arthrodesis.
    In this patient with a degree of residual control but poor local soft tissue support, a constrained implant such as the Swansons arthroplasty is better suited than many of the alternatives. A silastic implant acts primarily as a spacer that restores joint space and alignment and may allow some active motion if the patient retains some volitional control.
    The disadvantage of silastic implants is their propensity to piston within the medullary canal during flexion and extension. This is thought to contribute to the generation of wear particles that may set up a local foreign body reaction, ultimately causing bone resorption and subsidence.
    There are many alternatives to fractional lengthening of the long finger flexors that have been described elsewhere. They include superficialis to profundus transfer or selective neurectomy of the long flexors. Neither was suitable in the context of this patients longstanding tight contracture and hope of regaining some active control of finger flexion.
    NON-OPERATIVE ALTERNATIVES:
    Non-operative alternatives had already been exhausted by this patient but the patient may be managed with ongoing attempts to maintain hygiene with close attention to nail and skin care and regular nursing input.
    CONTRAINDICATIONS:
    Apart from the usual contraindications to surgery, one must ensure that the expectations of the patient, as well as those of their carers are realistic and in line with the aims of the treating surgeon. A good hand therapist is invaluable in this scenario as is the ability to reassess the patient at different intervals. Any acute infection is a contraindication to arthroplasty and skin condition must be optimised before embarking on such a procedure.

    Setup

    This procedure was performed under general anaesthesia but many patients may be suitable for regional anaesthesia. The patient is positioned supine with an arm table and an upper arm tourniquet.
    The patient is given a dose of prophylactic antibiotics at induction. Local policy on thromboprophylaxis should be followed.
    The availability of all potential implant sizes should be checked beforehand.
    Fluoroscopy is not routinely needed.

    Operation – 1

    Pre-operative radiographs demonstrate the skeletal deformity, and the the current positions of the digits. It also demonstrates the bony architecture including the presence of osteophytes. The thumb and index MCPJs have normal alignment here and the remaining digits are in varying degrees of MCPJ flexion with volar subluxation of the proximal phalanges.

    When applying skin prep, the clasped hand can present a difficult problem. A useful technique is to pass a medium sized swab soaked in chlorhexidine through difficult to reach ares within the palm or web spaces.
    The hand is positioned on a rolled up towel and incisions are marked out.

    A transverse incision may be used for multiple MCPJ replacements but here, with a significant fixed flexion and volar subluxation, a series of extensile longitudinal incisions were deemed more suitable.
    The skin is incised exposing a very thin soft tissue coverage overlying the prominent metacarpal head.
    Superficial veins are cauterised, dorsal cutaneous nerves, if seen, are protected.
    The extensor hood is divided in the midline and retracted.


    The joint is exposed and the metacarpal head is is very tightly fixed to the base of the proximal phalanx.
    It is initially very difficult to gain access to the metacarpal head and neck to make the first bone cut to remove the head and create some space.
    Here the collateral ligamants are sequentially recessed at their metacarpal insertion. The soft tissues in general are noted to be thinned out and fragile. The collaterals here may be completely detached if required.
    With such a severe contracture the final neck cut on the metacarpal is much larger than for a typical arthroplasty procedure for example in rheumatoid arthritis. The neck may eventually be cut proximal to the collateral ligament insertion.

    Once the metacarpal head and neck can be accessed, the position of the neck cut is marked out.
    This is intially very conservative and as mentioned above will likely need to be a more aggressive resection to allow for the severity of the joint contracture.

    The cut is made using an oscillating power saw with irrigation. A McDonald elevator to protect the distal joint surface.
    This image also demonstrates the complete loss of articular cartilage over all but the most volar aspect of the matacarpal head.

    The neck cut is assessed. The face of the cut should be flat and even. Any peripheral osteophytes may be trimmed.
    Note that the phalangeal articular surface remains in a a volar, subluxed position.

    An attempt is made to see whether the proximal phalanx can be brought into a more dorsal, extended position.
    Applying traction gives an idea of the soft tissue contracture that is restricting correction.

    A partial correction is possible.
    A further cut of the metacarpal neck will be required to create space for joint surfaces to face each other in full extension with an intervening silastic joint replacement.

    A further cut is made.
    Again, perpendicular to the long axis of the metacarpal.
    Sequential cuts, taking 2-3mm of neck away at each occasion allow repeated assessment to ensure enough bone is removed without taking too much.

    Once the volar surface of the proximal phalanx becomes accessible, the volar plate can be partly detached from its distal insertion, to aid realignment of the joint surfaces.
    The volar plate is likely to be severely contracted.
    In this case a reasonably good release was obtained after a few mm of resection and the distal most attachment of the volar plate was kept intact.
    The articular surface of the proximal phalanx is removed with a bone nibbler.

    The remaining contribution to tightness was within the forearm, and the long finger flexors, FDP and FDS.
    The muscle bellies of these muscles are now approached through a longitudinal incision made between FCR and FCU.
    One must be approximately 5cm proximal to the wrist crease to ensure that the musculo-tendinous junction is clearly identifiable.

    A judgment must be made about how much lengthening is required as well as which muscles need to be addressed.
    In this case I felt that FDS was very tight even under anaesthesia and the MCPJ position could not be fully corrected until this was released. FDP demonstrated some tightness to a much lesser degree.

    This image demonstrates the technique of fractional lengthening where the tendinous component within the distal muscle belly is divided sharply leaving the surrounding muscle fibres intact. An immediate gain in length is apparent although the muscle-tendon unit is kept in continuity and will continue to function at a longer resting length.

    Fractional lengthening of FDP was therefore combined with tenotomies of the ulnar sided FDS tendons which were rather tight and preventing correction of MCP joint position at this stage.
    As mentioned earlier, the PIPJs of these digits were fixed in flexion with no active or passive movement.

    The preceding steps have allowed the joint to sit in a corrected position.
    Some surgeons may perform metacarpal head excision for such hands, particularly where minimal function is expected.
    A silastic arthroplasty will hold the joint surfaces in a fixed relationship whilst allowing the possibility of active movement if residual muscle function and control remains.
    Of course the existence of any useful residual function may not be possible to assess with any great reliability in the pre-operative, contracted state.
    Here the proximal phalanx is entered with a sharp awl. The bone was as soft as seen in any rheumatoid patient and great care must be taken to prevent perforating the cortex and to form a well aligned canal.
    Making the proximal phalangeal tunnel slightly volar, and the corresponding metacarpal tunnel slightly dorsal, helps counteract the propensity of the to surfaces to sit in their original position of volar subluxation.

    As above, the sharp awl is now used to make an entry into the metacarpal canal. As explained above, in this situation this is made slightly dorsal to the mid-point.
    A further point worth mentioning here is the rectangular profile of the awl as well as the subsequent reamers described later.
    This matches the morphology of the stems of the final implant. If there is a rotational deformity across the joint, this can be counteracted by inserting the awl with a rotational correction ‘dialled in’. The final implant will therefore correct the rotational deformity as it is seated into the stem.

    The Swanson implant tray carries a series of reamers, that may now be used to ream the canal in order that it may accept the stem of the silastic implant.
    The reamers are marked D (distal) for the phalanx and P (proximal) for the metacarpal.

    Here metacarpal reaming is underway.
    Great care is taken to ensure correct alignment of each reamer so that the shape and direction of the canal matches that of the implant. This is easy to get wrong as the reamer will often want to follow its own path into the shaft.

    A mallet can be used if required. Often this is only needed once the larger sized reamers are used.

    A series of trial implants are on the tray and are colour coded.
    A trial of the appropriate fit is inserted and checked.
    It is important to ensure that the stem of the implant fits completely into the canal so that the midsection is in contact with the bone on either end. Clearly this is is much more difficult to achieve here than in an arthroplasty that is performed for arthritis.
    The trial is moved through a full range of motion.
    It should remain in position without dislocation.
    Any impingement in extension suggests that the bone cuts are inadequate and should be addressed before proceeding to the next stage.

    As for an arthritic case, the end of the implant must sit freely without contacting the end of the reamed canal at either end. It me be necessary to shorten the stem of the implant to achieve this.
    Non toothed forceps are used to handle the trial and the implant. Here they are used to guide the trial spacer into the phalangeal canal.

    Once each of the the three joints has been prepared, the trial spacers are removed.
    At this stage all wounds undergo a thorough irrigation with normal saline. The tourniquet is also released at this stage and careful haemostasis performed.
    Each trial spacer is replaced by an implant of the same size.
    The titanium grommets are not used. The evidence for their benefit is not well establishes although in theory they protect the implant at the bone-implant interface. Trail et al. reported no obvious benefit in their large series, whilst there are reports of metallosis being caused particularly when joint stability is not perfect.
    The implant is first inserted into the metacarpal using non-toothed forceps and a no-touch technique.

    Slight traction on the distal digit allows the distal stem of the implant to be flexed and inserted into the proximal phalangeal shaft.
    There should be no implant impingement or escape during full range of passive MCPJ motion.

    Further irrigation follows.
    The extensor hood is repaired using a running 4/0 PDS suture.

    Operation – 2

    This is the final corrected position of the hand prior to skin closure.
    The hand has opened up to a reasonable degree to allow for nursing and hygeine. If volitional flexion is maintained this patient may be able to grasp objects in the palm.
    The PIPJs remain an area of stiffness and the little finger PIPJ remains fixed in a degree of rotation and flexion.

    The skin is closed with running 4/0 monocryl sutures.

    The wound edges are supported with steristrips.

    A volar resting slab to support the new resting position is applied.
    Plenty of soft padding here is important.
    The patient may be able to go home the same day providing adequate nursing support is available but clearly this depends on local circumstances.
    Close attention to distal circulation and analgesia are vital in the first 24 hours.

    Post Operative

    This group of patients are all rather different to each other and a bespoke surgical plan and post-operative regime is to be expected.
    In this case the patient stayed in hospital for one night before returning home. A wound check in the dressing clinic was performed at 1 week.
    The plaster was removed and replaced with a thermoplastic splint at 1 week. This splint remained in place for an initial six weeks followed by intermittent splinting with range of motion and strengthening exercises.
    The splint was completely discarded at 3 months although the patient decided that she preferred to keep a night time splint in place for a further 4 weeks.

    Recommended Reading

    Most results for silastic MCPJ replacements come from groups of rheumatoid patients.
    Trail et al report outcomes for Swanson joint replacement in a large cohort of rheumatoid patients. The report an overall implant survivorship of 63% at 17 years.
    There are no studies looking at silastic MCPJ replacement in spasticity. However Lundborgs group reported outcomes for an osseointegrated flexible hinge implant for 68 patients, 3 of which were for spasticity. Overall results are excellent with significant improvements in function, pain and cosmesis.
    Keenan et al reported results of fractional lengthening of long finger flexors. In their large cohort they reported good results. Their overall results report 91% of patients with improved function and 9% reporting loss of grip strength due to overlengthening.
    Keenan MA, Matzon JL: Upper extremity dysfunction after stroke or brain injury, in Wolfe SW, Hotchkiss RN, Pederson WC, Kozin SH, eds: Green’s Operative Hand Surgery, ed 6. Philadelphia, PA, Churchill Livingstone, 2011, vol 2, pp 1184-1205.
    Keenan MA: Management of the spastic upper extremity in the neurologically impaired adult. Clin Orthop Relat Res 1988;233:116-125.
    Early prediction of long-term upper limb spasticity after stroke: part of the SALGOT study.
    Opheim A, Danielsson A, Alt Murphy M, Persson HC, Sunnerhagen KS.
    Neurology. 2015 Sep 8;85(10):873-80.
    Results of fractional lengthening of the finger flexors in adults with upper extremity spasticity. Keenan MA, Abrams RA, Garland DE, Waters RL.
    J Hand Surg Am. 1987 Jul;12(4):575-81.
    Metacarpophalangeal joint arthroplasty based on the osseointegration concept.
    Lundborg G1, Brånemark PI, Carlsson I. J Hand Surg Br. 1993 Dec;18(6):693-703.

    Reference

    • orthoracle.com

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