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Core decompression of femoral head for avascular necrosis

    Overview

    Learn the Core decompression of femoral head for avascular necrosis surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Core decompression of femoral head for avascular necrosis surgical procedure.
    Avascular necrosis (AVN) most commonly affects the hip joint. It accounts for between 5 and 12% of total hip arthroplasties. This equates to approximately 15,000 new cases in the US each year. The aetiology and pathogenesis are still unclear but a number of risk factors have been identified. These include trauma (intra capsular neck of femur), smoking, corticosteroids, alcohol abuse, haemaglobinopathy, autoimmune disease, Gauchers disease and Caisson disease. Corticosteroids and alcohol account for up to 90% of non traumatic cases.
    Several joint preserving techniques have been described. There is little evidence to prove that any single technique has a clear advantage. Core decompression is the most simple and associated with the least morbidity.
    The results of all joint preservation techniques for AVN are better for small lesions and early stage disease.

    Indications

    INDICATIONS
    Avascular necrosis of femoral head. Best results in pre collapse stages. The necessity for restricted weight bearing post surgery means that unilateral cases are easier to treat. Bilateral procedures can be undertaken but patients would then probably require a wheelchair post operatively.
    SYMPTOMS & EXAMINATION
    Early avascular disease may be asymptomatic. Since AVN is bilateral in up to 50% of cases asymptomatic hips are generally only identified during the investigation or follow up of symptomatic disease in the opposite hip.
    The first symptom is usually pain in the groin which may radiate to the knee or buttock. Once collapse of the femoral head commences there will usually be restricted range of motion.
    IMAGING
    Diagnosis and staging of AVN is made on Anteroposterior and frog lateral radiographs plus MRI. A number of staging classifications have been described including those of Ficat, Steinberg and ARCO (Association research circulation osseous). The original description by Ficat and Arlet was proposed in 1964. This was prior to MRI and the classification was based on stages 1-4. A further pre clinical stage was proposed in 1985 and the classification extended to grades 0-4.
    Stage 0 – pre clinical – suspected when definite diagnosis in the opposite hip.
    Stage 1 – Pre radiographic. Pain but normal x ray (MRI/bone scan positive)
    Stage 2 – increased density/cystic changes on plain radiograph (subsequently split into IIa and IIb depending on whether crescent sign is present)
    Stage 3 – disruption of the round contour/accumulation of sequestrum/increased joint space
    Stage 4 – collapse of femoral head/ loss of joint space
    The extent of disease has been quantified by determining the Kerboul angle. This is calculated by summating the angle of involvement in 2 orthogonal planes.
    Both the stage of disease and area of involvement are prognostic. Best results if stage <3 and Kerboul angle <190 degrees.

    ALTERNATIVE OPERATIVE TREATMENT
    Many different treatment options have been proposed. Medical treatment with bisphosphonates has been suggested for early disease (0-II) but is unproven. The combination of bone grafting and bone marrow mesenchymal cells (BMMC) in conjunction with core decompression have been described and may improve results although long term studies are lacking as yet.
    Osteotomy to rotate an uneffected area of the femoral head may be considered but is only appropriate when a small area (<15%) of the femoral head is involved. These operations are technically demanding and may compromise subsequent total joint arthroplasty.
    Vascularised Fibula strut grafting has good results (80% survival at 5-10 years) in expert hands but requires considerable experience and there is potential donor site morbidity.
    The trap door procedure requires surgical dislocation of the hip. The articular cartilage in the area of involvement is elevated as a ‘trap door’ and the necrotic bone derided and replaced with cancellous bone graft. This is ideally is suited to small areas of collapse. Surgical dislocation is a major undertaking and also associated with potential morbidity.
    Although core decompression is not guaranteed to be efficacious it is popular because it is simple and associated with minimal morbidity. There is therefore a tendency for its indications to be expanded more so than more complex procedures.

    NON-OPERATIVE MANAGEMENT
    Restricted weight bearing and physiotherapy may help symptoms. Progression in early stage disease is not inevitable.
    CONTRAINDICATIONS
    Results are significantly worse for grade III and IV disease. In these cases total hip replacement is the only viable option unless very small area of involvement.

    Setup

    Core decompression can be performed either on traction (fracture) table or supine on standard (radiolucent) operating table.
    Surgery is performed under general anaesthetic. Nerve block not necessary.
    Image intensifier necessary throughout.

    Operation

    Most patients will have been diagnosed using plain radiographs. This radiograph shows classic changes of sclerosis in both femoral heads. There are definite signs of collapse in the right femoral head (stage 3). Core decompression very unlikely to be effective.
    On the left side the femoral head remains relatively spherical. Further imaging required to asses suitability for core decompression.

    MRI confirms extensive involvement of femoral head. This is a poor prognostic sign. However, no significant collapse of femoral head.

    CT can also be helpful. This confirms significant collapse of articular surface on right side (grade 3).
    On left there is early collapse. This is grade 2/3. This will mitigate against good result but is not a contraindication.

    Core decompression is performed percutaneously.
    Historically a large diameter single core is made using 7-8mm cannulated drill. More recently there has been a trend towards 2-3 passes of smaller diameter drills or guide wires typically 3-5mm.

    The patient is placed in a supine position on a radiolucent operating table. Prior to skin preparation and draping it is advisable to ensure that it is possible to acquire suitable anteroposterior and lateral images per operatively. Frog lateral images are acquired by flexing and abducting the hip.

    It is important to verify that an adequate lateral as well as AP projection can be obtained with image intensifier before starting the case.It is important to verify that an adequate lateral projection can be obtained. An alternative approach would be to place the patient on a standard traction table and then move the ‘C’ arm of the image intensifier to obtain a lateral view. However, this is time consuming and research has shown that the overall dose of radiation is greater than moving the leg and keeping the image intensifier still.

    The patient is draped with the leg free and image intensifier screens in easily accessible position.

    A guide wire is placed over the front of the hip to determine the entrance point for the guide wire.A guide wire is placed over the front of the hip to determine the entrance point for the guide wire.

    Adjust the guide wire position until a clear path to the centre of the lesion is identified.Adjust the guide wire position until a clear path to the centre of the lesion is identified. The entrance point in the lateral cortex should not be below the lesser trochanter since this reduces risk of pathological fracture. Once an acceptable position has been identified use a marker pen to draw along the guide wire on the skin to give an approximate angle of wire insertion.

    When making the initial incision use a size 15 blade to make a small 3-4mm incision. If the positioning of this cut is subsequently found to be incorrect a more significant incision is avoided.

    A stout guide wire (2.5mm or greater) is inserted under II control.This can be threaded or unthreaded. Since the average femoral version is approximately 15-20 degrees it is generally easier to find the correct angle of insertion by internally rotating the hip by 15-20 degrees. This reduces the chance of the guide wire slipping off the trochanter. The entrance point may need to be slightly posterior to the midline to access a straight path into the anterior part of the femoral head. Note that initial entrance wound in this case was too anterior/inferior.

    Advance the guide wire until contact is made with the lateral cortex and check the position with image intensifier.Advance the guide wire until contact is made with the lateral cortex and check the position with image intensifier.

    It is imperative to perform a lateral view on the image intensifier before advancing the guide wire too far.Inadvertent penetration of the joint will result in a bent or broken wire (and chondral damage) when the leg is placed in flexion abduction and external rotation.
    The guide wire passes through the Tensor fascia lata to access the femur. As the hip is repositioned to achieve a lateral projection there is a tendency for the wire to bend. This is more likely for thinner wires and a guide wire of 2mm or greater is recommended. By placing ones finger on the wire whilst moving the leg the bending moment is minimised.
    A bent wire is difficult or impossible to advance and even small kinks in the wire can result in the wire breaking when over drilled. This is a particularly common problem for narrow wires.

    Check lateral projection with image intensifierThe lateral projection confirms that the guide wire is within the femoral neck and heading towards the centre of the necrotic area.

    Advance the guide wire until it is just short of the articular surface in both AP and lateral views.As the wire is over drilled there is a tendency for the wire to advance so leave it 5mm short of the joint surface.

    Make 1cm skin incision around guide wire.Once the desired guide wire position is achieved enlarge the skin incision to approximately 1cm.

    Free up soft tissues around guide wireSlide a pair of metzenbaum scissors (with the blads just open) along the guide wire to free up the soft tissues.

    Protect soft tissues with a guide if a drill is usedIf a cannulated drill is used a drill guide will protect the soft tissues.

    Ensure that the guide wire is not advanced across the joint by the drill Ensure that the guide wire is not advanced across the joint by the drill (see step 13).

    A further 1-2 drill passes should be made if small diameter core decompression is being performed.A single pass is sufficient if a large diameter drill (7-8mm) is being used. The same entrance point should be used on the lateral cortex to reduce risk of pathological fracture. A stiff large diameter guid wire (minimum 2.5mm) helps since with smaller wires there is a tendency for the same path to be followed. Larger wires are more easy to redirect.

    Use image intensifier to ensure passes of drill are separated adequatelyTry to spread the drill as much as possible whilst staying within the area of involvement.

    10-15ml of long acting local anaesthetic is instilled along surgical tract.

    Subcuticular suture for closureWound less than 2cm long. No fat stitch required. Subcuticular dissolvable monofilament suture.

    Post Operative

    Thromboprophylaxis with subcutaneous low molecular weight heparin for 3-4 weeks.
    Early passive range of movement is advisable. Hydrotherapy.
    Partial weight bearing (maximum 50% weight) for six weeks.
    At this point further plain radiographs performed.
    Patients will frequently still have discomfort at this stage but gradual weaning of crutches over course of 2-3 weeks is instituted.
    It may take a further 3-4 months to establish whether surgery has been successful. Failure of technique would generally be an indication for total joint replacement if further collapse of the femoral head is evident and the patient symptomatic.

    Recommended Reading

    The results of core decompression correlate well with both the stage of the disease and the size of the involved area. Across all treatment modalities results are better for the pre collapse stages of disease.
    There are very few long term studies of core decompression. Fairbank (1995) reported 96% 10 year survival in grade I disease, 74% survival in grade 2 and 35% in grade III.
    Fairbank AC, Bhatia D, Jinnah RH, Hungerford DS. Long-term results of core decompression for ischaemic necrosis of the femoral head. J Bone Joint Surg Br. 1995 Jan;77(1):42-9.
    Mont reported similar results at mean follow up of 12 years. He quotes 59% survival in Steinberg grade III and 8% survival in grade IV (post collapse). These authors also found that central and lateral lesions had worse outcomes than medial lesions. AA combined Kerboul necrotic angle of >250 degrees also correlated with poor outcome.
    Mont MA, Jones LC, Pacheco I, Hungerford DS. Radiographic predictors of outcome of core decompression for hips with osteonecrosis stage III. Clin Orthop Relat Res. 1998 Sep;(354):159-68.
    Song et al (2007) reported results of the multiple drill technique. At minimum 5 year follow up 79% of stage I and 77% of stage II patients required no further sugery. All patients with <25% involvement were successful and 84% of those with lesions 25-50% of the femoral head.
    Song WS, Yoo JJ, Kim YM, Kim HJ. Results of multiple drilling compared with those of conventional methods of core decompression. Clin Orthop Relat Res. 2007 Jan;454:139-46.

    Reference

    • orthoracle.com

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