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Shoulder Fusion

    Overview

    Learn the Shoulder Fusion surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Shoulder Fusion surgical procedure.
    Effective prevention of the causes of paralytic flail shoulder and the introduction of reliable arthroplasty options have led to markedly decreased indications for glenohumeral arthrodesis. However, arthrodesis still remains a valuable and important method of shoulder management particularly in the salvage situation. Glenohumeral arthrodesis provides the stability required for distal elbow and hand function. It is important that patients retain scapulothoracic motion and adequate scapular control is a pre-requisite for surgery. The main indications are currently: Flail shoulder, post tumour resection, infection and salvage following failed shoulder replacement or failed treatment of instability.

    Indications

    Paralytic poliomyelitis is the commonest historical cause of paralytic flail shoulder. The implementation of a worldwide programme of vaccination against poliovirus, has virtually irradiated the condition in developed countries and in modern times, traumatic brachial plexus injuries have become the commonest cause of flail shoulder. Pan-root avulsions remains an unfortunate but relatively common injury pattern associated with motorcycle accidents. This catastrophic injury renders the entire limb flail and in such cases, nerve reconstruction techniques for restoration of shoulder function remain severely limited due to the lack of available donor nerves. In patients with partial plexus injuries involving the upper roots, shoulder function and stability will be lost. With preserved function in the lower plexus roots, nerve transfer options are available and generally reliable in restoring shoulder function in such patients if undertaken early enough. Flail shoulder is still seen in neglected cases or cases where nerve reconstruction has failed and in such cases fusion may be indicated.
    Patients with flail shoulders develop inferior subluxation of the humeral head and this can cause, sometimes severe, aching due to the unsupported weight of the arm. This promotes reliance on slings which hampers potential hand and elbow function and can cause secondary issues with negative postural effects and muscular imbalance. For patients with flail shoulders who have elbow and hand function, shoulder stability becomes a priority as it allows them to position and use the hand in space.
    Total shoulder replacement has established itself as the gold standard treatment of symptomatic glenohumeral arthritis. Arthritis can occur as a result of primary osteoarthritis, inflammatory arthropathy, post trauma, post infective, secondary to rotator cuff tears and instability. Arthrodesis is now generally reserved for salvage following failed arthroplasty rather than a primary treatment for arthritis. There is still a role for arthrodesis following tumour excision and following osteomyelitis/septic arthritis.
    A prerequisite for glenohumeral arthrodesis is retained scapulothoracic movement. If there is good scapular control (i.e. trapezius, rhomboid, elevator scapulae and serratus anterior functioning), then arthrodesis allows adequate stabilization for effective hand function. If these muscles are absent of significantly weakened, function following fusion will be grossly diminished. Additionally, without sufficient scapular motion the arm position becomes too rigid and fixed, and this can become more of an impediment with the patient feeling the arm is permanently in the way.
    Controversy still surrounds the optimal position for fusion. The shoulder should be arthrodesed with enough abduction to clear the axilla, enough internal rotation to reach the midline of the body and enough forward flexion so that the hand can reach the face and head. Conversely, abduction, forward flexion and rotation should not be excessive. The arm should be able to achieve a ‘natural’ position at the patients side without scapula winging, patients should be able to reach a trouser pocket with their hand. Importantly, the patient should be able to sleep comfortably on the side of the arthrodised shoulder. The optimal position for arthrodesis is bespoke to each patient. Modifications based on patient size, body habitus and objectives of fusion are all taken into account. As a general guide the fusion position is 20 degrees of abduction, 20 degrees of forward flexion , and 40 degrees of internal rotation.

    Setup

    The procedure is performed under general anaesthetic. The patient is placed in a lateral position with the affected side uppermost. Pelvic supports and bolsters are positioned to ensure that the trunk alignment is square to the operating table/floor. The operated arm is placed in a multi-directionally adjustable gutter and this allows positioning of the arm in respect to the trunk. The gutter is set so that abduction, forward flexion and internal rotation of the arm are in the desired arthrodesis position. Typical the shoulder should be positioned so that elbow flexion allows the hand to be brought to the mouth and that there is sufficient abduction for axillary hygiene. Prophylactic antibiotics are given at induction of anaesthesia.

    Operation

    This patient is having an arthrodesis of the left shoulder and is positioned in the right lateral position. Once the arm has been positioned in the optimal fusion position the extremity is draped to allow adequate exposure of the spine of scapula as well as the lateral humerus. Regular checks should be made throughout the operation to ensure that the patient’s position on the operating table has not shifted and that the trunk-arm relationship is as desired.

    The incision extends from the spine of the scapula over the top of the acromion and down the lateral aspect of the shaft of the humerus.

    The posterior fibres of trapezius are elevated to expose the spine of the scapula. The acromion process and deltoid muscle are delineated. In cases where the arm is flail due to a nerve injury the spinati and deltoid will be wasted and this makes the exposure easier.

    The deltoid muscle is split in the mid-lateral plane. The anterior branch of the axillary nerve is at risk. In a flail arm, where the axillary nerve and deltoid are non-functioning, the nerve can be sacrificed. However, if fusion is being undertaken for other indications, it may be preferable to preserve the axillary nerve. It is easiest to locate the nerve at the posterior aspect of the quadrangular space. This is found by identifying the inferior border of teres minor which inserts onto the greater tubercle of the humerus. The nerve passes through this space with the posterior circumflex humeral vessels, running from anterior to posterior. Here the nerve is at it’s largest calibre and is dividing into anterior and posterior branches. The anterior branches of the nerve will be seen winding around the surgical neck of the humerus, beneath the deltoid, passing from posterior to anterior.
    Deltoid(D)
    Axillary Nerve *
    Humeral head (H)
    Teres minor (TM)

    The rotator cuff and shoulder capsule are opened to expose the humeral head.

    The glenoid fossa offers only a small area for fusion with the humeral head. Additional fusion area is achieved by obtaining arthrodesis between the acromion and the humeral head. This is done by upwardly subluxing the humeral head and bone grafting into the subacromial space. The rotator cuff, shoulder capsule and subacromial bursal tissue which interposes between the superior humeral head and acromion has to be excised to allow adequate humeral head superior migration.

    De-corticate the undersurface of the acromion with osteotomes.

    With the rotator cuff and superior capsule excised the humeral head can be pushed anteriorly and inferiorly to allow access to the glenoid fossa. The thick fibro-cartilagenous labrum is excised.

    The glenoid is prepared with osteotomes, denuding the articular surface down to sub-chondral bone.

    Reduce the humeral head into it’s desired arthrodesis position. The apposition surfaces with the glenoid and acromion can then be mapped out. These areas are then denuded with osteotomes. It is not necessary to denude the entire humeral head, only the areas which will be fused.

    A large proportion of the posterior humeral head will be redundant. By utilising the redundant humeral head as a source of bone graft, the author avoids having to resort to iliac crest autograft or allograft bone. The bone graft is interposed into the subacromial space.
    Prior to fixation the optimum position is assessed clinically, this has been shown to be accurate to within 10 degrees. Any refinement in arm position can be achieved by placing towels under the arm and re-adjusting the arm support as required. An assistant is asked to maintain this position during the rest of the procedure.

    Reconstruction plates are widely used as they can be relatively easily contoured. A locking compression plate (LCP) is stronger than a recon plate and offers more resistance to bend and torsion once contoured. The long lever arm created by the length of the humerus can concentrate large forces on the plate and for this reason the author’s preference is to use a 3.5mm LCP (Depuy Synthes) when using a single plate construct. An alternative is to use a 2 reconstruction plates, placing a second plate from the posterior scapula spine to the posterior humerus.
    The 3.5mm LCP implant cannot be contoured without the use of a suitable plate bending press. The press is mounted on a side trolley and allows for refined multidirectional contouring, without damaging the locking screw mechanism.
    Implants come in standard lengths up to 22-holes. Depending on the size of the patient plate lengths of 14-holes upward are usually required to allow screws to be place with sufficient cortices across the spine, acromion and humeral shaft.

    Accurate plate contouring is crucial as relatively small errors in plate fitting can lead to significant unintentional changes in the arthrodesis position. Allow plenty of time for this part of the procedure and repeatedly check the plate against the bone until the desired fit is achieved. Intraoperative radiographs are not routinely used.

    Fixing the plate at it’s proximal most and distal most 1-2 holes acts as a ‘first-fix’. Non-locking screws allow for the plate to be seated onto the bone without gaps. If satisfied with the alignment of the arm then attention is turned to achieving compression at the fusion sites.

    Part threaded cannulated screws are used to achieve gleno-humeral compression. Guide wires are positioned, intraoperative radiographs are not routinely used, the glenoid and posterior glenoid neck are easily palpated and trajectory for the wires/screws is relatively easy to ascertain. The screws are passed over the wires. In this case two 6.5mm cannulated screws (Deputy Synthes) were used. The screws are inserted but not initially tightened. Acromio-humeral compression is achieved with non-locking screws passed through the plate into the humeral head. Once the required screws are in position they are then all tightened to achieve the desired compression.

    Locking screws are used to fix the plate proximally and distally through any remaining screw holes.

    The deltoid and trapezius muscles are repaired over the top of the plate.

    The subcutaneous tissue and skin are closed in layers.

    Post operative radiograph showing the proximal position of the humeral head.

    Example of a double plating technique.

    Post Operative

    Shoulder immobilisation is achieved with a polysling and external rotation wedge. Off-the-shelf orthotic wedges are usually used to achieve immobilisation in external rotation, but by adjusting the placement of the wedge on the trunk in a more anterior position, the desired degree of internal rotation is achieved. Scapulothoracic and elbow motion is encouraged as soon as pain allows.
    The plate and screw construct achieves rigid fixation, as a consequence there is frequently little callus formation. Sling and wedge immobilisation is continued continuously for 8 weeks and then at night and in crowds for a further 4 weeks.

    Recommended Reading

    Patient satisfaction after shoulder arthrodesis is reported at around 80% (Clare et al).
    Complications include non-union, humeral fracture and malpositioning. Published rates of nonunion vary according to indications for surgery. It is rare to see a non-union when the indication for fusion has been a brachial plexus lesion. Usually in this situation the bone and joint architecture is normal. In the presence of infection and bone loss, the non-union rates increase accordingly. In Cofield and Briggs’ series of 71 arthrodeses, only 3 resulted in nonunion. These three were successfully fused following a second operative procedure.
    Cofield and Briggs also reported humeral fracture in 10 of their 71 patients. The highest risk appears to be fracture distal to the implant. It is not known whether prophylactic removal of the internal fixation plate can reduce this incidence of fracture.
    Patient satisfaction after shoulder arthrodesis is reported at around 80% (Clare et al).
    Complications include non-union, humeral fracture and malpositioning. Published rates of nonunion vary according to indications for surgery. It is rare to see a non-union when the indication for fusion has been a brachial plexus lesion. Usually in this situation the bone and joint architecture is normal. In the presence of infection and bone loss, the non-union rates increase accordingly. In Cofield and Briggs’ series of 71 arthrodeses, only 3 resulted in nonunion. These three were successfully fused following a second operative procedure.
    Cofield and Briggs also reported humeral fracture in 10 of their 71 patients. The highest risk appears to be fracture distal to the implant. It is not known whether prophylactic removal of the internal fixation plate can reduce this incidence of fracture.
    The most critical complication that may occur is malpositioning of the extremity. Clare et al emphasise that this is primarily the result of excessive abduction and flexion. This has a tendency to produce malrotation or winging of the scapula, which results in a dull, painful ache in the shoulder.
    Cofield RH, Briggs BT. Glenohumeral arthrodesis. Operative and long-term functional results. J Bone Joint Surg Am. 1979;61:668-77
    Clare, D.J., Wirth, M.A., Groh, G.I. and Rockwood Jr, C.A., 2001. Shoulder arthrodesis. JBJS, 83(4), p.593-600

    Reference

    • orthoracle.com

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