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Excision of osteochondroma from the medial distal femur

    Overview

    Learn the Excision of osteochondroma from the medial distal femur surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Excision of osteochondroma from the medial distal femur surgical procedure.
    Osteochondromas represent approximately 1/3 of all benign bone tumours. They are an exostosis of bone that is covered by cartilage on its external surface. They typically present in the second or third decades of life and most frequently effect the appendicular skeleton, with the lower limbs more commonly effected. They may be solitary or multiple hereditary osteochondromatosis. The risk of sarcomatous change is rare, seen in approximately 1% of solitary osteochondromas, with rates of 1-25% seen in multiple hereditary osteochrondromatosis.
    Surgery for benign osteochondromas should be avoided and only performed if they cause pain, decreased range of motion, pressure on neurovascular structures, tendon irritation or significant bursal formation.
    In this case a young male patient had pain and limitation of deep flexion, which was interfering with his active job. Previously he had suffered a fracture of the stalk of the osteochondroma. A period of conservative management had been tried prior to offering excision. An MRI pre-operatively confirmed there was no suggestion of malignant transformation.

    Indications

    INDICATIONS
    Indications for surgical removal include pain per se, or due to symptomatic compression of local anatomy such as nerve, blood vessels or tendons.
    SYMPTOMS & EXAMINATION
    Classically a discreet, well defined bony mass is noted in the lower or upper limbs. They may well be asymptomatic. If present symptoms will include pain, decreased range of motion, pressure on neurovascular structures, tendon irritation or significant bursal formation. A sudden change in symptoms should prompt re-evaluation and may indicate malignant transformation to a chondrosarcoma.
    Such secondary chondrosarcomas arise in the cartilage cap of a longstanding osteochondroma. Those located in the pelvis and scapula seem to be the most susceptible to malignant change, perhaps because these sites permit undetected growth. Malignant transformation occurs in 1% of solitary osteochondromas and in 4% of patients with multiple osteochondromas (diaphyseal aclasia). This change is often seen in the fourth decade. MO is an autosomal dominant disorder; in almost 90% of MO patients germline mutations in the tumour suppressor genes EXT1 or EXT2 are present.
    IMAGING
    Xray findings are very characteristic and allow quantification and documentation of size and location.
    MRI imaging is used exclude malignant transformation or assist in diagnosis if plain X-Rays are equivocal. A cartilage cap thicker than 1.5 cm when measured with MRI may indicate malignant change and surgical excision



    Setup

    Operation – 1

    AP radiograph of osteochondroma. Note the healed fracture of the proximal “stalk” of the osteochondroma. The osteochondroma arises from the metaphyseal aspect of the distal femur typically projecting away from the epiphysis. The commonest appendicular site for symptomatic osteochondromas is the knee.

    Lateral radiograph of distal femur showing osteochondroma.

    Axial MRI image of the osteochondroma. Note the proximity of the osteochondroma to the medial neurovascular structures. No malignant features are seen.
    The osteochondroma (O) is beneath the vastus medialis(VMO) and lateral to the sartorius (S) muscle seen on this axial view. The vascular bundle (femoral artery and femoral vein) are deeper and lateral to the osteochondroma at this level under adductor magnus (AM). Posterior to the osteochondroma is the semimembranosus muscle.
    The features which should raise the suspicion of possible malignant transformation are :
    A cartilage cap >1.5cm
    Growth of the lesion after skeletal maturity.
    An associated soft tissue mass.
    New lucency or cortical destruction associated with the lesion.
    Pain from the lesion after puberty.


    Coronal MRI of the osteochondroma. The cartilage cap of the osteochondroma is clearly seen. Note the osteochondromas wide base arising from the metaphysis of the medial distal femur. Vastus medialis is seen anteriorly and sartorius (S) seen laterally.

    Prep the skin with 2% Chlorhexidine. After the tourniquet has been applied high in the thigh. A touniquet is not necessary, but can be inflated if bleeding is seen.

    The limb has now been draped and the distal medial femur is exposed, hold the knee slightly flexed to relax the hamstrings.

    Centre the incision over the osteochondroma on the inferior border of the vastus medialis muscle which can be palpated along its inferior border as attaches to superior pole of the patella.Note the dot marked distally is an approximation of the medial epicondyle of the distal femur – representing the axis of the femur.
    The great saphenous vein is on the medial side of the leg, at the level of the knee it is a hands breadth posterior to the medial border of the patella. The incision is anterior to this.

    Incise the skin.as marked.

    Diathermy the bleeding points in the fat layer.

    Incise through the fat in the same line as the skin incision.
    Do this carefully as beneath the fat is a well defined fascial layer.

    Blunt dissect the fat off the fascial layer.

    Incise the fascia in the line of the muscle fibres over the tip of the osteochondroma.Incise the facscia overlying the vastus medialis muscle bulk. The vastus medialis muscle bulk can be identified by palpation, it presents as a well defined bulge superomedially where it attaches to the upper pole of the patella. In cases of osteoarthritis this muscle can be wasted. Vastus medialis is innervated by the femoral nerve.
    Vastus medialis arises from the intertrochanteric line and medially from the linea aspera. It travels distally around the medial side of the femur and combines with vastus intermedius into the quadriceps tendon. Its most distal fibres insert directly into the patellas medial border. The vastus medialis is an important stabiliser of the patella and is one of the main extensors of the knee and is innervated by the femoral nerve.

    Identify the distal border of the vastus medialis muscle. Use your finger to sweep under the muscle belly proximally to identify the plane to be dissected proximally.
    More proximally the Adductor (subsartorial or Hunter’s canal) canal is found. It is a canal formed medially by vastus medialis and the anterior surface of the adductor muscles. It commences below the apex of the femoral triangle. The canal allows the passage of the femoral nerve and vein, saphenous nerve and the nerve to vastus medialis. Sartorius lies on its fascial roof. Adductor longus and brevis form the floor. The femoral artery exits the canal between the adductor magnus and hamstrings to enter the popliteal fossa. The femoral vein is postero-lateral to the artery in the adductor canal.

    Scissors dissect along the inferior border of vastus medialis.

    Continue the dissection under vastus medialis onto the osteochondroma. Start distally where the ostoechondroma arises from the distal femur. This approach is safest as proximally it is closer to the neurovascular structures.
    Reflect the sartorius (the “Tailor’s” muscle) muscle posteriorly, this is obscured by the surgeons finger. The muscle has been retracted posteriorly and at this level the contents of the femoral canal are lateral to the osteochondroma.
    The sartorius muscle is innervated by an anterior branch of the femoral nerve and is the longest muscle in the body. The sartorius muscle arises from the anterior superior iliac spine, travels medially to insert into the upper medial part of the tibia. It inserts anteriorly to the gracilis muscle.
    Sartorius forms the medial border of the femoral triangle proximally and the roof of the adductor (sartorial) canal.
    Sartorius is named the Tailor’s muscle as it causes the thigh to be flexed, externally rotated, abducted and flexes the knee. This position is required to sit cross-legged, as Tailors used to.

    Peel the vastus medialis muscle anteriorly to expose the osteochondroma.

    Identify the inferior border of the osteochondroma.

    Finish the exposure of the osteochondroma both anteriorly and posteriorly.

    Fully expose the osteochondroma prior to excision. Note its cartilagenous cap proximally.

    Carefully identify the base of the osteochondroma as it arises from the femoral cortex.

    Use a wide osteotome to excise the osteochondroma from the femoral cortex, being careful not to notch the femoral cortex.Start in the angle of the osteochondroma as it arises from the cortex as shown.

    Complete the osteotomy taking the whole base of the osteocondroma in one piece. Distally in this case we are well away from the neurovasuclar bundle as the stalk of the osteochondroma arises from the metaphyseal region of the distal medial femur.
    The plane for the osteotomy is at the junction of the osteochondroma and the cortex of the femur. Do not penetrate the femoral cortex with the osteotome.

    Final removal of osteochondroma, use a scalpel to cut any final soft tissue remnants attached to the base of the osteochondroma.

    The excised osteochondroma is sent for Histology.

    The appearance of the base of osteochondroma on medial femoral cortex after osteotomy.

    Operation – 2

    Apply bone wax to the osteotomy site, which helps reduce post-operative bleeding from the bone base.

    Allow the muscle to fall back and cover the bone and close in layers.Wash the cavity with normal saline before closing the fascia. Allow the vastus medialis muscle to rest back over the surgical site.

    The facial layer is closed with 2 vicryl.

    Close the fat layer with 0 vicryl.

    Inject local anaesthetic into the skin.

    Close the skin with a dissolvable suture and apply tissue glue.

    A dressing is applied.

    Wool and crepe bandage applied.

    Post operative radiograph showing complete excision of osteochondroma .

    Post Operative

    Full weight bear
    Histology from specimen
    Remove bandages 24 hours
    Wound check 2 weeks
    Analgesia
    Physiotherapy as needed
    Avoid heavy manual work and impact sports for 3 months.

    Recommended Reading

    Surgical treatment of symptomatic osteochondroma. JBJS Br 2003;85B:1161-5.
    Bottner et al.
    The majority of patients had osteochondroma’s removed for pain. Local recurrence was noted more frequent in cases of mulitple hereditary osteochondroma’s occurring in 3 of 30 verses 1 of 56 solitary osteochondromas excised. Almost 85% of patients were satisfied with the outcome of surgery

    A very comprehensive review of the condition is available open access on the journal RadioGraphics, 2000.
    Imaging of osteochondroma: Varients and complications with radio-pathologic correlation.
    Mark D Murphey et al
    https://pubs.rsna.org/doi/full/10.1148/radiographics.20.5.g00se171407

    Another very useful open access paper is to be found in the journal Human Mutation from 2009.
    Multiple Osteochondromas: Mutation Update and Description of the Multiple Osteochondromas Mutation Database (MOdb)
    Ivy Jennes et al.
    https://onlinelibrary.wiley.com/doi/epdf/10.1002/humu.21123

    Reference

    • orthoracle.com

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