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Excision of synovial chondromatosis using a posterior approach to the knee

    Overview

    Learn the Excision of synovial chondromatosis using a posterior approach to the knee 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 synovial chondromatosis using a posterior approach to the knee surgical procedure.
    Primary synovial chondromatosis is a benign, metaplastic and chondrogenic disorder of the synovium most commonly involving the knee, in two-thirds of cases, of middle aged patients. Extra-articular synovial chondromatosis may occasionally be encountered in hand and feet. Symptoms include firm articular swellings, which my be painful or associated with mechanical locking, restriction or crepitus. Radiographs and CT highlight small rounded calcifications at the periphery of the joint. The standard initial treatment for symptomatic patients includes joint-preserving arthroscopic or open resection by way of synovectomy. Incomplete removal will likely result in local recurrence, reported in up-to 25% cases. If asymptomatic, clinical and radiological surveillance may be acceptable to both patient and surgeon.
    Secondary synovial chondromatosis, characterised by loose bodies within degenerative synovial joints, is associated with degenerative joint disease for which the management is the same as the primary aetiology i.e. non-operative management of osteoarthritis prior to joint replacement surgery.
    Rarely, secondary synovial chondrosarcoma has been reported to arise in primary synovial chondromatosis; symptom progression over several months (82%), rapid recurrence after complete resection (30%), and medullary canal invasion (43%) are associated with malignant change (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481616/).
    When there is anxiety regarding diagnosis, disease extent or malignant transformation, referral to a specialist orthopaedic oncology centre may be preferred, but the majority of cases can be managed in non-oncology units.

    Author : Mr Jonathan Stevenson FRCS (Tr & Orth).
    Institution: The Royal Orthopaedic hospital, Birmingham, UK.
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    Indications

    Indications:
    Relative indications for surgical excision of primary synovial chondromatosis include pain, swelling and mechanical symptoms such as stiffness or locking from the effected joint. An absolute indication for surgery is evidence of malignant transformation to secondary chondrosarcoma. Symptomatically this is suggested by sudden symptom onset, rapid recurrence after primary treatment and radiographically evidence of medullary canal invasion.
    Symptoms in clinical assessment:
    Routine examination of the knee may identify an effusion and restriction of the joint (as in this case, with limited knee flexion beyond 80 degrees) and a bony hard mass at the posterior aspect of the knee in the popliteal fossa. Clinical assessment should also include neurovascular assessment distally to compare to post-operatively.
    Investigations:
    Patients have plain radiographs which may show synovial based masses with ‘popcorn-like’ calcifications and bone erosions in almost 50% of cases. MRI is routinely undertaken to delineate the exact location of the synovial masses and their anatomical relationships to neurovascular structures. The calcifications are represented by a signal void on the MR imaging. Benign & malignant synovial chondromatosis share non-specific features including soft tissue mass, joint effusion, joint space destruction, osseous erosion and local recurrence. Concerning features include large size, rapid clinical progression of pain, local recurrence within 12 months after complete resection, soft-tissue infiltration and invasion of the medullary canal (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481616/).
    Operative alternatives:
    If the patient is asymptomatic and there are no imaging characteristics suggestive of malignancy, observation alone may be sufficient. For discrete lesions of the anterior knee, hip and shoulder arthroscopic resection may be feasible; in the present case the patient had already undergone a complete open anterior synovectomy and now warranted open posterior capsular synovectomy due to the extent of disease.
    Contraindications:
    Contraindications for surgery include medical co-morbidities deeming general anaesthesia unsafe.

    Setup

    Operation – 1

    Lateral pre-operative radiograph which unusually does not show popcorn calcifications at the periphery of the posterior capsule. Given the symptoms of pain, swelling and limitation of motion, MRI is indicated to investigate further.

    Sagittal T2 weighted MRI highlighting the primary synovial chondromatosis arising in the posterior capsule, posterior to the posterior cruciate ligament, extending posterior to the proximal tibia, deep to the popliteal neuromuscular bundle. This patient had already had an open anterior synovectomy performed eight months previously.

    Axial T2 MRI at the level of the femoral condyles showing the synovial chondromatosis posterior to the condyles medial to lateral, and the immediate relationship to the popliteal vessels between the two gastrocnemii.

    Axial T2 MRI at the level of the proximal tibia-fibular joint showing the synovial chondromatosis posterior to the proximal tibial metaphysis and deep to the trifurcation of the popliteal vessels. The popliteal artery bifurcates into the anterior tibial artery and the tibio-fibular trunk which immediately divides into the posterior tibial and peroneal arteries.

    Position the patient prone with pressure area protection.The patient is positioned prone under a general anaesthetic with a thigh-high tourniquet and exclusion drape applied, as shown in the photograph. The distal tibia and ankle is rested on a bolster so that the knee is partially flexed to 15o. Intravenous antibiotics are given as the joint will be opened during the procedure.

    Mark the skin incision.An S-shaped surgical incision is marked on the skin. The ascending limb runs up the lateral side of the popliteal fossa overlying the biceps femoris tendon so that the common peroneal nerve can be identified on the lateral side of the popliteal fossa. The middle portion of the incision is marked in a skinfold traversing the fossa and the descending portion of the incision runs down the medial aspect of the posterior calf.

    Viewed from the lateral side the ascending portion of the incision is marked. The fibula head is marked out with the likely anatomical location of the common peroneal nerve wrapping around the fibula neck.

    Skin preparation and drape.After alcoholic chlorhexidine skin preparation the limb is isolated with sterile drapes. A bowel bag is wrapped around the foot so that any muscle contractions can be visualised during the procedure and neuro-vascular status assessed. The skin is covered with Ioban incisional drapes.

    S shaped skin incision in popliteal fossa.The incision is made along the marked skin incision across the popliteal fossa, and diathermy is used to cauterise any bleeding vessels.

    Elevate full thickness skin flaps.Viewed from the medial side, full thickness skin flaps are elevated down to the deep fascia which is visible here. Full thickness skin flaps are preferable to optimise wound healing.

    Identify the short saphenous vein.The (SSV) short saphenous vein is identified as it pierces this deep fascia in the centre of the popliteal fossa. The deep fascia is then incised in line with the skin incision.

    The (SSV) short saphenous vein is identified as it pierces this deep fascia in the centre of the popliteal fossa. This is a marker to identify the popliteal vein which it drains into, thus identifying the popliteal neuovascular structures. The most superficial are the tibial and peroneal nerves, then the vein and the artery is deepest adjacent to the joint capsule.

    Identify the common peroneal nerve.Now viewed from the lateral side: Dissection is deepened to find the (P) common peroneal nerve posterior to the (BF) biceps femoris. The nerve is very close to the deep fascia and should be identified with careful blunt dissection also show is the (SSV) short saphenous vein, which has been dissected. Tracing the short saphenous vein proximally will identify the popliteal vein which has the tibial nerve superficial to it and the popliteal artery deep to it.

    Sloop the common peroneal nerve.Viewed from the lateral side of the knee: A vascular sloop is placed beneath the common peroneal nerve to control and aid atraumatic handling of the nerve. Medial to this the next neurovascular structure to identify in the popliteal fossa is the tibial nerve.

    A sloop is now placed underneath the (T) tibial nerve, in addition to the (P) peroneal nerve, as shown. Identification is made easier by the previous dissection and ligation of the short saphenous vein which leads us to the popliteal vein and therefore artery.

    Sloop the tibial nerve.The sloop around the tibial nerve is used to gently retract the tibial nerve laterally allowing deeper dissection on to the popliteal vein, artery and medial head of the gastrocnemius muscle down to its origin on the posterior distal femur.
    The medial head of the gastrocnemius is elevated with a retractor, as shown, which reveals the posterior joint capsule at the level of the posterior femoral condyles.

    Elevate the medial head of gastrocnemius. The (MG) medial head of gastrocnemius muscle is elevated and retracted off the white posterior capsule of the joint. I prefer to use a small Cobb elevator to do so. This view is permitted by the gentle retraction of the (T) tibial nerve, superficial to the vein and artery not shown.

    The (MG) medial gastrocnemius has been elevated and retracted off the (PC) posterior capsule of the joint revealing the bulky prominence of the synovial chondromatosis.

    Longitudinal arthrotomy.Carefully a longitudinal arthrotomy incision is made using a 15 blade into the posterior joint capsule gaining entry to the synovial joint to assess the synovial chondromatosis. Care is made not to damage the chondral surface of the posterior condyle.

    The posterior capsule has now been opened and the posterior femoral condyle and its chondral surface are visible inside the synovial joint.

    Excise synovial chondromatosis. The pearlescent white synovial chondromatosis tissue shown in the centre of the photograph is carefully excised from the synovial layer via the arthrotomy. A combination of blunt dissection using McIndoe’s and small nibblers to maintain tension on the excised tissue and diathermy to cauterise bleeding vessels completes the job. The knee in maintained in the same position with careful retraction of the neurovascular bundle and medial gastrocnemius.

    Nibblers are used to grasp the tissue and McIndoe’s scissors are used to dissect the synovial layer to enable all of the synovial chondromatosis to be excised from the posterior portion of the knee joint.

    The posterior capsule is now clear of the synovial chondromatosis. Also visualised in this photograph is the neurovascular bundle containing the (A) peroneal artery and (V) vein which are deep to the slooped (T) tibial nerve. The vessels are between the capsule and the tibial nerve in the photograph.

    Clinical photograph showing all of the excised synovial chondromatosis taken out. This tissue is sent fresh for histological analysis to exclude the rare possibility of malignant change.

    Capsular closure and skin flap approximation.After closure of the capsule with interrupted 1.0 Vicryl sutures the skin flaps are approximated and the deep fascia closed with interrupted Vicryl. A vacuum drain is placed in the plain between the vessels, capsule and gastrocnemius in the popliteal fossa.

    Operation – 2

    Skin closure in layers.After closure of the deep fascia with interrupted Vicryl the deep dermis is closed with interrupted 2.0 Vicryl sutures and clips are applied to the skin.

    Apply dressings.Aquacel dressing and a Mepore dressing for the drain are applied.

    Post Operative

    Distal neurovascular observations post-operatively (motor and sensory function and vascular status of the limb distally to be documented)
    24-hours of IV antibiotics (Flucloxacillin)
    VTE: early mobilisation protective weight bearing with crutches and mechanical thrombo prophylaxis with foot pumps and TED stockings for six weeks, chemical thrombo prophylaxis with low molecular weight Heparin from six hours post-operatively for two weeks.
    Removal of clips at 14 days
    Outpatient physiotherapy aiming to achieve 90o flexion within five days

    Recommended Reading

    This patient was walking without pain nor analgesia with improved range of motion and return to work by six weeks post-operatively. Local recurrence is associated with incomplete excision and occurs in up-to 25% of cases. Consequently post-operative surveillance for recurrence should involve clinical and radiological review for several years post-operatively.
    Synovial chondromatosis can rarely undergo a malignant transformation. There are a limited number of case reports, since this was first reported in 1957. However, about half were reported to be high grade and half low grade and associated with a 30% risk of recurrence arising in the knee (50%), hip (33%), ankle (6%) and shoulder (4%). Multiple surgeries have been described, culminating in amputation in 61% of cases. Pre-operatively, malignant transformation is suggested by a rapid recurrence after previous resection and invasion of the medullary canal on imaging (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481616/).
    In 2017 The Mayo Clinic, Rochester, described the outcomes of 20 patients who underwent total knee replacements for synovial chondromatosis. Five patients suffered recurrence and were treated with further synovectomy and revision surgery or amputation in three of those five. There was a high risk of complications with knee replacement with this condition including stiffness in 45% and amputation in 10% and revision in 15% (https://www.sciencedirect.com/science/article/pii/S0883540317301584).

    Reference

    • orthoracle.com

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