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Proximal humeral replacement- Mutars reverse geometry shoulder (Implantcast)

    Overview

    Learn the Proximal humeral replacement: Mutars reverse geometry shoulder (Implantcast) surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Proximal humeral replacement: Mutars reverse geometry shoulder (Implantcast) surgical procedure.
    After the lungs and liver, the skeleton is the most common site of metastatic disease. Prostate, breast, lung, kidney, and thyroid cancers account for 80% of all skeletal metastases. The femur, spine, humerus, pelvis, ribs, and skull are reported to be the most commonly effected sites, in that order. The prolonged survival of more patients with cancer has led to increasing numbers of individuals with metastatic bone disease.
    Metastatic bone disease is a major contributor to the deterioration of the quality of life of patients with cancer. Impending and actual pathological fractures initiate the period of dependent care for many of them. The majority of metastatic bone lesions are treated effectively with nonsurgical modalities such as radiation therapy, chemotherapy, immunotherapy, hormonal therapy, bone-seeking isotopes, and bisphosphonates.
    Treatment of pathological fractures with closed reduction and immobilisation has been shown to be ineffective. Gainor and Buchert performed a study of 129 pathological fractures of long bones in 123 patients who had been treated with a variety of methods and followed until death or at least one year after the fracture (Gainor & Buchert, Clinical Orthopaedics and Related Research [01 Sep 1983(178):297-302]). They observed fracture-healing in 87% (twenty-six) of thirty patients who were treated with internal fixation and radiation therapy and who survived more than six months compared with 57% (thirteen) of twenty-three patients who had a similar survival time but were treated with cast immobilisation and radiation therapy. As a result, those authors recommended the use of internal fixation and postoperative radiation.
    There are of course exceptions. Patients who have a slow-growing tumour that is responsive to chemotherapy and radiation therapy (such as multiple myeloma) and who have a pathological fracture of a non-weightbearing bone may be initially treated non-operatively. Operative treatment may be required for patients with an existing or impending pathological fracture or with intractable pain that does not respond to any nonoperative procedures.
    Operative intervention for metastatic bone disease is usually a palliative procedure. The goals of surgery are to achieve local tumour control and structural stability of the surgically treated site and to restore function as quickly as possible. Ideally, operative treatment should allow immediate function and weight-bearing with the least possible morbidity and rehabilitation. Operative reconstruction in patients who have bone metastases must also be reliable and durable in accordance with the expected duration of survival, which may be prolonged for patients with breast, prostate, or renal cancer. Failure to achieve one of these goals usually necessitates a second operative intervention, leading to additional impairment of an already compromised quality of life.
    Whilst conventional treatment of metastatic bone lesions has relied on intramedullary stabilisation or internal fixation, followed by external beam radiotherapy, advances in the oncological management of such patients has resulted in increasing numbers outliving these reconstructions. Therefore, there has been in recent years, an expansion in the use of endoprosthetic replacements for the management of osseous metastases, especially those with a good projected prognosis, including lesions arising from haematological malignancies.
    This chapter describes the management of a patient presenting with a pathological fracture through a destructive lesion of the proximal humerus on the background of a new diagnosis of myeloma. Due to the pain from the fracture and the good prognosis from the underlying diagnosis, it was elected, following discussion of the options with the patient, to undertake excision and reconstruction of the proximal humerus.

    Indications

    INDICATIONS
    The indications for operative treatment of long-bone and pelvic girdle metastases include impending and pathological fractures and intractable pain (Bickels et al,Clinical Orthopaedics and Related Research: August 2005, 437, 201-208) . Patients with certain types of cancer who had a solitary bone metastasis were shown to have better survival than patients with similar types of cancer and multiple bone metastases (Althausen et al,Cancer. 1997 Sep 15;80(6):1103-9). However, resection of such lesions was not shown to improve the outcome. Operative treatment of spinal metastases is indicated for patients with spinal instability or spinal cord compression. Patients with a very short life expectancy would not benefit from an operation because of the rapid general deterioration of their functional and physiological status and because of their inability to execute a minimal rehabilitation protocol. Considerations regarding the expected survival, the overall medical status and quality of life, and the magnitude of the operation and rehabilitation potential all contribute to the decision-making process (Am J Clin Oncol. 1982 Dec;5(6):649-55; Schag et al, J Clin Oncol. 1984 Mar;2(3):187-93). It is difficult and impractical to set a rigid time frame, but six to twelve weeks of expected survival is generally the minimum required for relatively simple procedures such as intramedullary nailing, and a minimum of six months is necessary for more complex procedures such as acetabular or endoprosthetic reconstruction.
    Operative treatment of metastatic bone disease cannot be carried out without an established histological diagnosis. When a patient has no previous histological diagnosis of metastatic bone disease, a biopsy is required to establish the diagnosis and exclude tumours that predictably respond to nonoperative treatment (e.g., lymphoma) or that require a different treatment strategy (e.g., sarcoma). Examination of osseous material obtained after reaming a bone lesion may not contribute to an accurate diagnosis, and the results of such an evaluation should be interpreted with caution and an understanding of its limited value. Therefore, where there is debate on the underlying diagnosis, a pre operative biopsy should always be obtained to prevent the inadvertent dissemination of a sarcoma through a whole osseous compartment.
    SYMPTOMS & EXAMINATION
    The commonest feature at presentation of a malignant lesion of bone is pain. This pain often follows a predictable course from functional pain to rest pain and finally night pain. In many cases, the underlying malignancy is known but in some, the development of a lesion of bone may be the first presentation of a new diagnosis of malignancy including haematological malignancy.
    Because of anatomical considerations, the definition of an impending fracture differs among the three major anatomical sites (long bones, acetabulum, and vertebrae) at which operative intervention for metastatic bone disease is often performed. Mirels’s scoring system is based on four parameters (site, radiographic appearance, size, and related pain) for predicting the risk of fracture and for recommending appropriate treatment (Mirels,Clin Orthop Relat Res. 1989 Dec;(249):256-64). Mirels’s system has the advantage of being relatively simple. It is based on clinical evaluation and plain radiographs and has been shown to be reproducible, valid, and more sensitive than clinical judgment across experience levels. A score of 8 or above is suggestive of impending fracture and consideration of prophylactic fixation should be given.
    The medical history should include the current oncological status and related treatments and medications. In cases of spinal metastases, the medical history should focus on sensory and motor dysfunctions, walking ability, and urinary and/or bowel incontinence. The physical examination should include an evaluation of the principal symptomatic area as well as other symptomatic sites. It should focus on the extent of soft tissue tumour extension and its relationship to the neurovascular bundle of the extremity, the neurovascular status of the affected extremity, the presence of limb oedema, muscle strength, and the range of motion of the adjacent joints. Assessment of the sphincter is mandatory for patients who have spinal metastases.
    In patients with a pathological fracture, a careful history should be directed at pre fracture symptoms which may suggest towards a pre fracture lesion. It is clearly of paramount importance that in patients with pre fracture symptoms with injuries that exceed the mechanism of injury should be considered to be pathological and investigations should be directed towards the underlying diagnosis at least initially, prior to surgical intervention which may be inappropriate for certain diagnoses, particularly an undiagnosed sarcoma.
    IMAGING
    When the diagnosis of metastatic bone disease is strongly considered, plain radiographs should be made of the affected site as well as of any other site at which the patient reports bone or joint pain. A computed tomography scan may also be required to detect metastases located in the shoulder girdle, spine, and pelvis because of the complex anatomy of these sites. Metastases located in long bones require biplanar radiographs because a single view may not provide enough information with which to evaluate the full extent of bone involvement. The combined results of these imaging studies will define the extent of bone destruction and soft-tissue extension. The latter may be relevant when the tumour is located in close proximity to a major neurovascular bundle. Metastases located in long bones require plain radiographs of the entire extent of the bone in order to exclude the possibility of additional metastases for the purpose of surgical planning. Missed metastases proximal or distal to the level of fixation could cause pathological fractures on weight-bearing on the operatively treated extremity. Computed tomography scanning of the chest should also be routinely done as a screening study to rule out lung metastases or, alternatively, to determine whether the lung is the site of an unknown primary lesion. A total-body bone scintigraphic evaluation with technetium-99m methylene diphosphonate is recommended prior to operative intervention. It allows detection of additional metastases that may require simultaneous surgical treatment. Bone scanning is highly sensitive for most bone lesions. Tracer uptake, however, is not specific for metastatic bone disease and may spuriously display a large variety of inflammatory, infectious, posttraumatic, and other benign conditions. Therefore, a plain radiograph should be made of any site that is found to be positive on the bone scan. It should be borne in mind that bone scanning is not a substitute for plain radiographs of the entire affected bone or other sites with bone pain because some tumours (such as renal cell carcinoma, multiple myeloma, metastatic melanoma, and thyroid carcinoma) may not be evident on a bone scan. A sagittal, as well as axial and coronal, multilevel T1- weighted magnetic resonance imaging scan with gadolinium enhancement is a useful screening tool for patients who have spinal metastasis.
    ALTERNATIVE OPERATIVE TREATMENT
    Operative intervention for metastatic bone disease is usually a palliative procedure. The goals of surgery are to achieve local tumour control and structural stability of the surgically treated site and to restore function as quickly as possible. Ideally, operative treatment should allow immediate function and weight-bearing with the least possible morbidity and rehabilitation. Operative reconstruction in patients who have bone metastases must also be reliable and durable in accordance with the expected duration of survival, which may be prolonged for patients with breast, prostate, or renal cancer. Failure to achieve one of these goals usually necessitates a second operative intervention, leading to additional impairment of an already compromised quality of life. In their 1958 article, Bremner and Jelliffe stated that: ‘‘Most patients suffering long-bone pathological fracture have widespread disease, but it is wrong and unkind to regard this misfortune as a terminal event warranting only the simplest of symptomatic treatment. Recognition of this state of affairs demands the greatest expedition in returning the patient to comfort and mobility, that he may better enjoy his remaining months.’’ This statement is even more relevant today because of the improved survival of patients who have metastatic bone disease and the newer techniques available for tumour resection and subsequent reconstruction of the defect.
    NON-OPERATIVE MANAGEMENT
    Patients who have a slow-growing tumour that is responsive to chemotherapy and radiation therapy (such as multiple myeloma) and who have a pathological fracture of a non-weightbearing bone may be initially treated non-operatively.
    CONTRAINDICATIONS
    Contraindications may be defined as relative and absolute. Relative contraindications include slow growing, repsonsive lesions in non load bearing bones, as detailed above. Absolute contraindications essentially are those that would result in significant peri-operative morbidity and mortality. In such cases, best supportive care with early involvement of palliative care physicians should be considered.

    Setup

    The risks and benefits of surgical intervention must be explained to the patient in advance.
    Laminer flow theatre.
    Pre op antibiotics.
    Appropriate anaesthesia, including regional nerve blockade to reduce post operative pain.
    Patient positioning: Beach chair with the arm free draped to allow movement intra operatively.

    Operation – 1

    The patient, a 73 year old right hand dominant lady presented with a short onset of pain in the right shoulder. This progressed from functional pain to rest pain and finally night pain. The pain became so severe that she could no longer use her right arm. She was urgently referred to her local hospital where plain X-rays demonstrated a destructive lesion within the right proximal humerus with an associated pathological fracture.

    Subsequent staging CT scan and dedicated CT scan of the proximal humerus demonstrated no evidence of a primary lesion elsewhere and no evidence of further metastatic deposits. The patient underwent biopsy of the proximal humeral lesion which demonstrated features consistent with a plasma cell neoplasm (myeloma or solitary plasma cytoma). Given the destructive extent of the lesion, as seen on CT scan, the patient elected for proximal humeral replacement.

    Patient positioned in a beach chair position with the limb exposed to allow visualisation of the shoulder.

    The limb is prepared with an alcohol based sterilisation fluid. The hand and forearm are prepared and covered to allow them to be freely mobile intra op. Drapes are positioned to allow the shoulder to be visualised. An iodine impregnated skin coverage is also used.

    The skin incision used is for a deltopectoral approach to the shoulder and proximal humerus. The landmarks for the incision are based on the coracoid which is palpable medial to the head of the humerus, and the deltopectoral groove, which is seen as a muscular groove running between the deltoid, laterally and the pectoralis major medially. The cephalic vein lies within this groove.
    This extensile approach allows straightforward distal extension adequate to mobilise the entire humerus if required whilst also giving enough proximal exposure to be able to visualise the glenoid.

    The skin and subcutaneous tissue are incised.

    The cephalic vein is used as a landmark to delineate the plane between the deltoid (laterally) and the pectoralis major (medially). The cephalic vein lies immediately deep to the fascia which once incised, can be easily mobilised. The cephalic vein is mobilised laterally with the deltoid to develop this plane.

    The pectoralis major muscle (A) is elevated by passing an instrument under the muscle and reflecting the muscle off the humerus.
    In the case of proximal humeral replacement, the entire insertion of the pectoralis major muscle needs to be divided away from the humerus. The pectoralis major muscle is identified as it sits medial to the cephalic vein. Its fibres are running medial to lateral in comparison to the deltoid whose fibres are running vertically.

    A stay suture is passed through the pec major prior to its division.
    This can be used to reflect the muscle medially. As the muscle is reflected away from the bone, this is relatively bloodless.

    A finger is then passed underneath pectoralis minor which is then divided to reflect it away from the humerus.
    Pectoralis minor lies immediately deep and slightly proximal to pectoralis major. This muscle forms the anterior wall of the axilla and so care must be taken in the deep dissection as the neurovascular bundle, comprising the axillary vessels and brachial plexus, lie deep to the pectoralis minor.

    At this stage, the long head of biceps can be divided distal to its origin.
    The long head of biceps lies lateral to the short head and takes its origin from the superior aspect of the glenoid. The long head sits within the intertubercular groove covered by a retinaculum. In comparison, the short head of biceps sits much more medially taking origin from the coracoid forming the conjoint tendon with the coracobrachialis muscle. Depending on the amount of tumoral involvement, the long head can either be divided close to its origin or more distally away from the shoulder. Care should be taken when there is concern about involvement of the long head with tumour that the tendon is not divided and the stump allowed to pull out of its groove as potentially, this will contaminate the field. n such cases, the tendon should be divided close to its origin on the glenoid, and distally below the intertubercular groove to allow a segment of the tendon to be excised with the tumour.

    Again, a stay suture is passed through the long head of biceps to allow it to be reflected away from the proximal humerus.

    Having mobilised these muscles from the proximal humerus, the subscapularis tendon which lies over the front of the humeral head can now be divided.
    The subscapularis is easily identified as it is the deepest muscle structure on the front of the shoulder. It forms a retinacular tunnel for the long head of biceps so can be seen lying over the front of the long head.

    A stay suture is passed through the subscapularis prior to its division.

    Having elevated the subscapularis (A), the humeral head is now seen with evidence of the tumour within (B).

    The capsule over the humeral head can now be divided medially to ensure the capsule remains over the humeral head.
    This will form the anterior barrier or margin over the tumour. Approaches to the proximal humerus for non-tumour cases will routinely elevate the capsule laterally to allow subsequent repair. In the case of tumour resection, it is often necessary to elevate the capsule from its origin on the glenoid as this will provide the anterior margin to the tumour.

    The rotator interval, elevating the supraspinatus tendon (A) is now divided to elevate the rotator cuff off the greater tuberosity.
    The rotator interval is the theoretical space between the subscapularis tendon inferiorly and the supraspinatus proximally. It contains the intra-articular portion of the long head of biceps, the superior gleonhumeral ligamnt and the coraco-humeral ligament, The supraspinatus tendon can now be elevated away from its insertion into the greater tuberosity.

    Having mobilised the rotator cuff from the humeral head the distal dissection is completed by reflecting the latisimus dorsi tendon from the humerus.
    The latisimus dorsi takes origin from the back and inserts onto the bicipital groove on the anterior of the humeral shaft. As the insertion is below the level of the main vessels and nerves, this can be safely elevated and reflected off the humerus.

    The humeral head can now be delivered anteriorly. The proximal humerus is abnormal due to the invasion by tumour and the pathological fracture.

    Having delivered the humeral head anteriorly, the posterior capsule (A) can be divided under direct vision.

    Further posterior dissection is completed by reflecting teres minor from the proximal humerus.
    Teres minor inserts onto the posterior aspect of the humerus at the origin of the middle head of triceps. It forms the distal border of the quadrangular space within which lie the circmflex humeral vessels and the axillary nerve. Care should be taken when reflecting the insertion of teres minor to ensure these structures are not damaged.

    The patient, a 73 year old right hand dominant lady, presented with a short onset of pain in the right shoulder. This progressed from functional pain to rest pain and finally night pain. The pain became so severe that she could no longer use her right arm. She was urgently referred to her local hospital where plain X-rays demonstrated a destructive lesion within the right proximal humerus with an associated pathological fracture.

    Further proximal humeral dissection involves reflecting the triceps (A) posteriorly and biceps away from the proximal humerus to circumferentiate the proximal humerus.
    The middle head of triceps takes its origin from the posterior aspect of the humerus at the level of the insertion of teres minor. The medial head of triceps lies medial to this taking its origin from the posterior glenoid and lies away from the dissection. As such the triangular space is often not at risk during this dissection.

    The proximal humerus and humeral head is now delivered and an instrument is passed behind the humeral shaft.

    The humerus is now cut below the level of previously identified tumour infiltration using retractors to protect the surrounding soft tissues.
    By mobilising the proximal humerus and reflecting both the anterior and posterior soft tissue attachments away from the proximal humerus, the major nerves and vessels of the arm are medialised and are well away from the saw blade at the time of osteotomy. However, care should be taken to protect the soft tissues with retractors placed around the humerus at the level of the osteotomy.

    Operation – 2

    Having cut the humerus, the final posterior soft tissues can be divided under direct vision.
    This allows a low energy osteotomy to be performed and the specimen delivered under direct vision without risk of contamination.

    The specimen can now be removed. Where there is extensive soft tissue involvement by tumour or significant destruction of the humeral head, the specimen should be marked to allow orientation by the pathologist. When this is not the case, the specimen need only be sided as the pathologist can orientate the specimen in relation to the resected humeral head.

    The resection specimen demonstrating the abnormal proximal humerus with the tumour within and the pathological fracture covered by a layer of soft tissue. Where there is extensive bone destruction or soft tissue involvement, the reconstruction may not be undertaken and a Tikhoff-Lindberg procedure (extended proximal humeral resection) undertaken. However, invariably, a prosthesis can be inserted if only to maintain length of the upper limb and to act as a spacer for hand, wrist and elbow placement. In cases where there is extensive medial soft tissue involvement where an adequate margin cannot be acheived without sacrifice of the brachial plexus and/or brachial vessels, a shoulder disarticulation or forequarter amputation may need to be considered.

    The resection specimen. The orientation of the specimen can be seen in relation to the humeral head, so long as the side of the resection is known to the pathologist.

    The glenoid (A) is now visualised by placing retractors in front and behind of the glenoid.
    Having washed the resection bed, gloves are changed.
    The retractors are placed in close association to the glenoid and as such there are no structures at risk with retractor placement.

    The centre of the glenoid is marked with diathermy.

    The glenoid preparation begins by placing a guide pin in the centre of the glenoid using a jig.

    The pin is driven into the centre of the glenoid in anatomic retroversion and abduction.
    The pin should be placed centrally within the glenoid in the plane of the scapula. The normal retroversion of the glenoid is approximately 5 degrees whilst the normal abduction angle in relation to the axis of the scapula is approximately 45 degrees.

    Pin placement. The pin should pass centrally along the axis of the scapula.
    The pin should driven enough to engage the bone and hold the pin. If the pin passes out of the bone, this suggests that the angle of insertion is incorrect or the pin has been driven in too far.

    A reamer is then passed over the guide pin and the articular cartilage removed.
    On the Implantcast Mutars system, only one size of glenosphere is available and so a single reamer is used for this step. Care should be taken when reaming the glenoid to ensure a uniform hole is prepared that will exactly match the glenoid component. Sufficient reaming will remove just the articular cartilage and expose the underlying cancellous bone without over reaming and taking away too much bone.

    The reamer is designed to drill a keel hole and remove the articular cartilage.

    The glenoid component is hydroxyappetite coated and with screw holes to reinforce the immediate press-fit.

    The glenoid component is impacted into place.
    The glenoid component will engage the bone with the central keel and should be impacted onto the prepared cancellous bone of the reamed glenoid. Often the glenoid component is primarily stable but should always be reinforced with screws due to the risk of loosening by the torsional forces placed on the implant by the proximal humeral replacement.

    The glenoid component fixation is then reinforced by screws.
    The placement of these screws is determined by the position of the glenoid component so it is important that is placed in such a way that allows screw placement. A guide is then used to guide the screw position. The screws come in locking and non-locking options. The drill size is 2mm in diameter with the non-locking screws being 4mm diameter and the locking screws 4.2mm diameter.
    Whilst there is no minimum number of screws, as many screws as possible, up to a maximum of four, should be inserted. The drill guide allows for divergent screw placement to maximise fixation of the glenoid component.
    Where screws have not been inserted, the screw holes are left empty.

    The glenoid component with 4 locking screws in place. The screw depth is checked with a depth gauge. All screws are self tapping and can be either locking or non-locking.

    A polyethylene glenosphere is now impacted onto the glenoid component.
    The glenosphere is placed free hand onto the glenoid component. The fixation is by means of a snap fit onto the elevated rim of the glenoid component. The glenosphere is impacted with sufficient force using the impactor to snap the glenosphere onto the glenoid component. Fixation is confirmed by seeing whether the glenosphere can be subsequently elevated away from the glenoid component using a MacDonalds elevator or pair of forceps.

    The reconstruction of the glenoid is now complete.

    Preparation of the humerus can now begin.
    A series of rasps are passed antegrade into the remaining humerus.

    Further sequential rasps are then used to the desired diameter.
    The rasps have a hexagonal shape which is designed to create rotational stability for the definitive implant.

    The final rasp is chosen when there is engagement of the rasp on the cortex of the bone.
    If an uncemented fixation is being used, a hexagonal shape to the bone needs to be created by the rasp to allow engagement of the definitive stem. If the fixation is planned to be cemented, a definitive stem 2-4mm smaller than the final rasp is chosen to allow an adequate cement mantle at the time of final fixation.
    Standard stems on the Implantcast system are 120mm long which is invariably adequate for proximal humeral replacement.

    Having rasped the humerus to an appropriate size, the final rasp can be left in situ.
    For native bone, the canal can often simply be prepared with the rasps. On occasion, particularly where there has been previous fracture, reamers are first needed to prepare a canal down which the rasps can be passed.

    Trial components can now be assembled onto the rasp to restore the proximal humerus.
    The modular design of the components allows accurate restoration of length, offset and version. The trial components have an interlocking mechanism (see later) that allows the orientation of the humeral head to be adjusted.

    Having selected the appropriate components, these are locked together with a screw through the components.
    Once the correct orientation is chosen, the trial components can be interlocked with a screw through the head and body which connects all the modular components onto the rasp in the humeral shaft. The image shows the screw being tightened from proximally using a T handle.

    The trial components in situ. A Hey Groves bone holder remains around the proximal humerus to allow it to be manipulated during reduction.

    A trial modular reverse geometry head (A) is now attached to the trial proximal humeral components.
    This is available in a range of offsets (0, +5mm and +10mm) to allow accurate restoration of offset. The trial head is simply screwed onto the modular trial prosthesis.

    Operation – 3

    The trial prosthesis is now reduced and put through a range of movements to ensure the shoulder joint is stable.
    The modularity of the components allows fine tuning of length, offset and version. The orientation of the humeral head should be approximately 30 degrees of retroversion from the long axis of the humerus. This is measured with the elbow flexed to 90 degrees with the hand in a thumb up position. The final orientation position is a composite of the glenoid and humeral retroversion which can be fine tuned for stability using the interlocking mechanism of the prosthesis.

    Having decided on the appropriate components, the trial components are removed.
    The humerus is prepared for cementation by firstly washing the humeral canal with pulsed lavage.

    The bone is then dried with ribbon gauze.

    A double mix of Palacos cement is then inserted retrograde into the humerus. A cement restrictor is not used. Excess cement is removed from the cement before insertion of the prosthesis.

    The stem of the prosthesis is inserted first, the cement allowed to cure and the modular components then assembled onto the stem.
    The intramedullary stem has a collar coated with hydroxyapatite so excess cement at the top end of the humerus should be removed to allow on growth onto the collar.

    Insertion of the intramedullary stem.

    Removal of excess cement.

    The intramedullary stem has an integrated hydroxyapatite collar which sits at the implant bone interface and is designed to encourage bone on-growth and improve fixation.

    The modular silver coated body of the proximal humerus. Grooves can be seen at either end of the body piece which interdigitate with grooves on the cemented stem and the tuberosity piece and allow fine tuning of component version.

    The interlocking screw which is passed through the modular components and harmonise the modular construct.

    Silver coated tuberosity component. Holes are present on the component to allow soft tissue re-attachment where appropriate.

    The interdigitating tuberosity component and body piece.

    The tuberorsity, body piece and screw. A saw tooth design of interlocking grooves can be seen where the body piece and tuberosity component interconnect. This allows rotation and so fine tuning of version prior to final reduction.

    The components are screwed together as previously described. An ante torque handle is passed through the tuberosity component and the T handle screw driver used to lock the components together against the resistance of the ante torque device. This prevents excess torsional force being transmitted to the cement implant interface.

    The proximal humeral component is assembled correcting the appropriate orientation of the prosthesis. The normal degree of retroversion of the humeral head is approximately 30 degrees of retroversion. This can be fine tuned to give maximum stability of the shoulder to prevent dislocation. As described previously, the normal retroversion of the proximal humerus can be orientated according to the long axis of the humerus relative the position of the forearm.

    The definitive modular humeral head. This is available as a 0, +5mm and +10mm offset option to allow correct restoration of offset and soft tissue tension. The head piece simply screws onto the tuberosity component of the prosthesis.

    The modular humeral head is screwed onto the humeral prosthesis.

    The shoulder is reduced and the stability reassessed by putting the shoulder through a range of movement.
    It is often useful to feel humeral head whilst putting the prosthesis through this range of movement to feel for instability, soft tissue tension and evidence of impingement. I often prefer to have the shoulder feel tighter rather than looser. Given the extent of soft tissue dissection, the primary stability of the shoulder is conferred by the implants and as such, it is critical that orientation and offset allow the greatest stability possible.

    The final prosthesis in situ.

    The soft tissue’s are now reattached over the prosthesis. The pec major and minor are reattached to the undersurface of the deltoid. A suction drain is placed deep to this repair.

    The deltoid is then repaired over the front of the prosthesis. The patent cephalic vein (A) can be seen on the lateral side of the deltoid.

    Having completed the deep soft tissue repair, the prosthesis is now completely covered by a soft tissue envelope.

    Further closure in layers is completed using absorbable sutures to subcutaneous tissue and clips to the skin.

    Final closure with drain in situ.

    An adherent dressing is applied.

    Operation – 4

    A pressure dressing is applied and the arm immobilised in a polysling.

    Post operative AP radiograph demonstrating the prosthesis, reduced and in the correct position.

    Lateral post operative radiograph showing a congruent reduction and correct implant orientation.
    The resection histology confirmed a solitary plasmacytoma.

    Post Operative

    Further doses of intravenous antibiotics are given in keeping with hospital protocols. Chemothromboprophylaxis is often not required. A post operative radiograph is taken when the patient is able. The arm is immobilised for the first 5 days. At that stage, hand, wrist and elbow exercises can begin. Passive shoulder exercises commence at 4 weeks and active exercises at 6 weeks. It is convention in our institution to re admit patients at 6 weeks for a week of intensive physiotherapy with both gym activities and hydrotherapy. The resected specimen is reviewed by a specialist musculoskeletal pathologist and discussed in an multidisciplinary team meeting, particularly to discuss the role of adjuvant radiotherapy.

    Recommended Reading

    The optimum method of reconstruction of the shoulder after resection of the proximal humerus remains controversial. Options include the use of a fibular or autoclaved humeral autograft, an osteoarticular allograft, an intercalary allograft prosthesis composite, the clavicula pro humero procedure or an endoprosthesis. Endoprosthetic replacement of the proximal humerus has been criticised as being little more than a prosthetic spacer rather than an articulating reconstruction. Nevertheless, it is the simplest form of reconstruction of the shoulder after resection of tumours of the proximal humerus. Endoprostheses are readily available and this treatment is less expensive than amputation. The principal technical difficulty is in obtaining a wide margin of excision because of the proximity of the neurovascular bundle to the bone, and also in restoring the function of the shoulder, particularly when the rotator cuff and deltoid have been sacrificed as is so often necessary in proximal humeral resections.
    In a retrospective review of proximal humeral endoprosthetic replacements, Kumar et al (J Bone Joint Surg Br. 2003 Jul;85(5):717-22) reported a 10 year limb survival of 93% with a 20 year revision rate for mechanical failure of 86.5%. The mean MSTS was 79%. This represents a very satisfactory, predictable outcome for this method of reconstruction. It should be noted however, that the prostheses used were all conventional monopolar proximal humeral replacements. These prostheses are prone to subluxation, in part due to the extensive soft tissue resection required to remove primary tumours of bone. In an attempt to address this issue, and to improve function, we have utilised reverse geometry prostheses. Kaa et al (Bone Joint J. 2013 Nov;95-B(11):1551-5) reported on the outcomes of reverse geometry prostheses following proximal humeral resection in 10 patients. The authors reported a mean MSTS of 77% with good reported ranges of movement. Two patients suffered a dislocation which was managed by open reduction and alteration of modular components.
    In the case of metastatic bone or haematological malignancy, the benefits of endoprosthetic replacement, including rapid relief of pain, must be offset by the expected reduction in function. Where the rotator cuff and deltoid insertion must be sacrificed, the return of function is often limited due to the lack of muscle attachment to the prosthesis. In our experience, however, this detriment in function is well tolerated by patients and accommodated by adaptive movements at the elbow and wrist.
    The use of endoprosthetic replacement as treatment for metastatic bone disease must be assessed on a case by case basis. In our experience, this is a reliable method of reconstruction particularly in patients with solitary osseous disease and for the treatment of pathological fracture where a rapid resolution of pain can be expected.

    Reference

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