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Simple bone cyst of the proximal femur- Curettage and plating with Synthes 4.5 mm DCP plate

    Overview

    Learn the Simple bone cyst of the proximal femur: Curettage and plating with Synthes 45 mm DCP plate surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Simple bone cyst of the proximal femur: Curettage and plating with Synthes 45 mm DCP plate surgical procedure.
    Unicameral bone cysts (UBC) or simple bone cysts were reported by Virchow in 1876 and despite therefore the considerable length of experience with this tumour many factors related to it, including pathogenesis and treatment, continue to be under debate. They represent about 3% of all bone tumors and there is a prevalence of males / female of 2:1. Malignant transformation has not been documented in these tumours.
    Around 75% of all UBCs occur in children and adolescents and usually these cysts are reported in the metaphyseal areas of long bones with open physes. Most of the time they are solitary lesions and there are not associated with syndromes. The proximal humerus and femur account for almost 90% of these cases. UBCs in the proximal humerus develop more frequently during childhood and tend to disappear after puberty. On the other hand proximal femoral UBCs tend to present in adolescent patients.
    The etiology of this tumor remains unclear. Many hypotheses, including disturbance in bone growth, inflammatory and dysplastic processes, traumatic events or blockage in the venous drainage, are described.
    UBC diagnosis is based characteristic plane X-ray images in the main and most of time does not require biopsy. However one should include as differential diagnoses aneurysmal bone cyst, fibrous dysplasia, enchondroma and eosinophlic granuloma. If I am not sure that I am dealing with an UBC I will confirm the diagnosis through histology.
    The main therapeutic options for simple bone cysts are immobilisation and observation, percutaneous decompression, percutaneous aspiration plus injection of corticosteroids or intralesional surgery.
    Readers will also find of interest the following OrthOracle technique:
    Unicameral bone cyst (proximal femur) : curettage , bone grafting and plating.



    Indications

    INDICATIONS
    Most of the UBC will be treated with non invasive or percutaneous treatment. Surgery is only indicated in select cases. My main indications for surgical treatment are:
    Pathological fracture in the lower extremities
    Proximal femoral location
    Mechanical pain during activity
    UBC in adolescent patients
    No healing after a pathological fracture of the upper extremity.
    No healing after 3 steroid injections in any area.
    Recurrence after conservative treatment.
    UBC of the proximal femur represents a challenging situation, because of the high risk of pathological fracture and their presentation in mainly adolescent patients. A subtrochanteric location is usually associated with mechanical pain and for me is one of the main indications for surgical treatment including an aggressive curettage, bone grafting and plating in order to allow immediate weight bearing.
    SYMPTOMS & EXAMINATION
    Although in the vast majority of patients these lesions are asymptomatic, discovered incidentally and resolve spontaneously, a small percentage may present with pain, swelling or joint stiffness (depending upon location) or associated with a pathological fractures.
    It is important to understand that although a pathological fracture could be regarded as a positive factor for healing, reports, including papers by Ahn and also Hiroshi, reflect that non invasive treatment (immobilisation and observation) is actually associated with high rate of recurrence or not healing ( up to 50%).
    The patient’s age has an important influence on the clinical presentation and prognosis of the bone cysts and the risk of recurrence has been described as high as 35%. Dormans and Pill highlighted that age and type of treatment are the most important factors for UBC healing. Patients older than 10 years heal at a higher rate (90%) than do younger patients (60%).
    IMAGING
    The most important imaging studies for diagnosis of an UBC are the Plain X-rays.
    AP and lateral views demonstrate the main characteristics of the UBC, which are:
    A well defined geographic lucent lesions with a narrow zone of transition
    A central location in the medullary cavity with long axis parallel to length of bone.
    No periosteal reaction or soft tissue component
    The cortex is thinned but typically is not compromised
    If there is a fracture through this lesion a dependent bony fragment may be seen, and this is known as the fallen fragment sign.
    MRI can help to clarify the diagnosis, exclude other possible benign lesions and is especially important when we have an UBC in an unusual location such as the pelvis. Although commonly only plain X-rays are used to confirm the diagnosis of UBCs, I personally recommend adding an MRI to the diagnostic protocol for UBC.
    The typical MRI findings demonstrate the presence of fluid and confirms its cystic nature. It also gives information on the local aggressiveness, with detail of features such as fracture, local expansion or cortical erosion. A UBCs main characteristics on MRI are low signal intensity on T1-weighted sequences and high signal intensity on T2-weighted.
    On occasion a CT scan is indicated could help to get a better definition of the bone effected, but considering the age of the patients and the radiation exposure, I do not recommend it as a routine study and only rarely is it required.
    ALTERNATIVE OPERATIVE TREATMENT
    Surgical treatment is indicated in those patients with an UBC that presented with a pathological or impending fracture of the lower extremity, mechanical pain or those cyst that has enlargement during the observation period. Diferente surgical alternatives have been proposed including:
    Curettage and Bone Grafting with allograft.
    Decompression Techniques: Based on Cohen’s hypothesis, in which venous obstruction leads to intramedullary accumulation of interstitial fluid that results in cavity formation, a UBC can be decompressed by violating the wall of the cyst and draining its contents, allowing native marrow to enter the cavity. Decompression can be achieved using needles, curets, or implants (eg, intramedullary nails, cannulated screws, Kirschner wires).
    Combination of both techniques. This is the alternative we most prefer. After doing the aggressive curettage of the cyst and before doing the reconstructions we always do an intramedullary decompression using a reammer or angled curet.

    NON-OPERATIVE MANAGEMENT
    Nonsurgical treatment is recommended for UBCs that are diagnosed incidentally in young children and in asymptomatic patients. These patients could be treated with close observation if there is a low risk of suffering a pathological fracture.
    In patients with a pathologic fracture in a non weight bearing bone (most frequently the proximal humerus) initial nonsurgical treatment with immobilisation for 4 to 6 weeks is appropriate. However, consolidation and bone restoration of a UBC after a pathological fracture is below 20%, as reported by Wilkins.
    There is good published evidence that percutaneous treatment with injections can help to achieve healing of the cyst and should be considered as part of the non operative treatment management for UBC. Several agents have been described for intra-lesional injection including steroids (methylprednisolone was the first one reported by by Scaglietti during the ’70s), autologous bone marrow, calcium phosphate bone substitute material and demineralized bone marrow or combinations of all of these.
    Pretell-Mazzini et al in their comprehensive review recommend that although the use of biologic and synthetic injections have yielded promising results, additional large, long-term studies are required to prove the superiority of these agents over steroids.
    In my personal experience, I recommend at least 3 intra-lesional injections with steroids before considering a surgical procedure, location dependant.
    CONTRAINDICATIONS
    Percutaneous injections are procedures that most of the times do not require general anaesthesia. However, hypersensitivity or allergy to one of the components (mainly steroids) could be considered a contraindication.
    References
    Ahn JI et al: Pathological fractures secondary to unicameral bone cysts. Int Orthop 1994, 18(1):20–22.
    Hiroshi Urakawa et al. Clinical factors affecting pathological fracture and healing of unicameral bone cysts. BMC Musculoskelet Disord. 2014 May 17;15:159.
    J. Dormans, S. Pill, Fractures through bone cysts: unicameral bone cysts, aneurysmal bone cysts, fibrous cortical defects, and non-ossifying fibromas, Instr. Course Lect. 51 (2002) 457.
    Wilkins RM: Unicameral bone cysts. J Am Acad Orthop Surg 2000;8(4):217-224
    Scaglietti O: L’azione osteogenetica dell acetate di metilprednisolone. Bull Sci Med (Bologna) 1974;146:15-17.
    Cohen J: Etiology of simple bone cyst. J Bone Joint Surg Am 1970;52(7): 1493-1497
    Juan Pretell-Mazzini et al. Unicameral Bone Cysts: General Characteristics and Management Controversies. J Am Acad Orthop Surg 2014 May;22(5):295-303.

    Setup

    Operation

    A 20 year old female patient presented with right hip pain, associated with the physical activity, mainly during her gym activities, and a normal examination.
    Preoperative AP X-rays shows a well circumscribed lytic lesion in the sub-trochanteric area of the right femur, with no cortical erosion or soft tissue extension. Those features on the plain X- ray plus the clinical history make us think in a benign bone tumor.
    When we compare the right side with the left side, we can appreciate more clearly the lytic bone lesion and its extension through the subtrochanteric area to the proximal diaphysis.
    It is always important in benign bone lesion evaluation to compare the effected side with the normal side to improve our diagnosis.

    MRI helps to confirm the diagnosis and exclude other possible benign lesions, mainly an aneurysmal bone cyst or fibrous dysplasia.
    The other important reason to do an MRI is to evaluate in detail the aggressiveness of the lesion, demonstrated more clearly with MRI, with features such as cortex disruption, soft tissue extension or an impending pathological fracture.
    The MRI suggest a SBC here because of the high signal intensity in T2-weighted that confirms the presence of fluid and cystic nature with no presence of solid components.

    Surgical instruments necessary to perform the surgery correctly.
    It is important to have curettes of different sizes and angles for the correct intralesional resection. This is an importan fact because will allow us to access to all the cyst.
    It is also important to have multiple impactors for the bone reconstruction. I recommend different sizes and forms (circular and rectangular). This is the set that I use.

    The skin incision is centred on the greater trochanter, extending gently posteriorly 3-4 cm and distally in a direct line 10-15 cmWhen centering the incision for the posterolateral approach it is important to palpate tip of greater trochanter. Palpation of the trochanter can be facilitated by abduction and adduction of the hip.
    The incision should run longitudinally through the middle line of the lateral aspect of the femur.
    It is important to gently curve the incision at the proximal part. This little gesture will help during the dissection and mobilization of the soft tissue structures.
    If you need to extend the incision proximally for better visualization (in case that the tumor extends to the neck) you must take care of the superior gluteal nerve, artery and vein that cross 3-5 cm proximal to the tip of the greater trochanter and run over the piriformis between the gluteus medius and minimus. I recommend not to dissect beyond this point.
    For our case, it is not necessary to extend the incision above the tip of the trochanter because we do not need to get access to the hip.

    A posterolateral approach approach to the proximal femur is used.Patient is positioned left side down, right side up. Pre-operatively the patient has routine hip props, anteriorly and posteriorly. An initial pre-prep of the skin using alcoholic chlorhexidine is performed.
    I use a 3m Ioban Antimicrobial Incise Drape for the surgical field. Always include in the hip props and prep the entire leg, so you will be available to do internal and external rotation of the hip that will be necessary during the surgery.

    The skin is incised from the greater trochanter distally in the line of the femur.A posterolateral approach approach to the proximal femur is used.
    Incise the skin with knife. Continue through the fat in the same line but using electrocautery. Pay attention to to cauterize subcutaneous vessels and take your time at this point which will help you to have a clean surgical area.
    Blunt dissect of the fat off the fascial layer.A Cobb elevator could helps this step.
    Clear identification of the tensor fascia lata is key, following which it is incised at the greater trochanter and this extended distally over the lateral femoral shaft.
    There is no internervous plane in this approach.the fascia lata is held open with retractors.
    Next proceed to the deep dissection and identify the fascia over the vastus lateralis. The fascia must be incised longitudinally. I highly recommend to do it with scalpel or scissors.

    The fascia lata is opened in the line of the femur and vastus lateralis identified beneath itAfter opening the fascia, we will find the vastus lateralis muscle running longitudinally from the trochanter to the knee, all along the lateral side of the femur.
    Elevate it from its origin in a submuscular manner along the posterior intermuscular septum. We do not need to remove its insertion from the trochanter.
    It is helpful to place a Homans retractor over the posterior aspect of femur in order to visualise the intermuscular septum.
    Position the retractor between the femur and intermuscular septum, Bear in mind that the sciatic nerve runs over the adductor muscles. Despite being protected by the gluteal maximus and biceps, it is advisable not exert too much traction.
    Pay attention in this anatomical area to the small perforating vastus lateralis vessels. You should identify and coagulate these using electrocautery in order to prevent bleeding, which will impede our visualisation of the surgical field and can be difficult to control.
    We can also need to manage the perforating arteries that perforate the adductor muscles to reach the back of the thigh. The first perforating artery (arteria perforans prima) that runs between the pectineus and upper margin of the adductor longus and to the second perforating artery (arteria perforans secunda) runs along the upper margin of the adductor brevis. All perforating arteries together provide blood supply to the posterior muscle group of the thigh and partly to the medial muscle group of the thigh.



    Impact the graft to achieve a stable reconstruction. It is important to use different impactors in order to fill cyst cavity completely. We recommend to have in the surgical table different impactors in terms of size and angle. I usually use 2 types of impactors: rectangular and round.

    After the bone graft reconstruction, relocate the bone window. You should impact it carefully.

    The De Puy-Synthes 4.5 mm Locking Compression Plate (LCP) plates.
    I prefer to use an LCP plate because of the ability to use cortical and locked screws
    I will use the plate only to stabilise the bone window, so do not need to do use interfragmentary compression

    Elevate the vastus lateralis from the posterior intermuscular septum, and carefully position a Homans rectractor between the femur and septum.Dissection should be done through the lateral intermuscular septum of the vastus lateralis / gluteus maximus / biceps femoris.
    The lateral femoral intermuscular septum extends from the insertion of the Gluteus maximus to the lateral condyle, separates the vastus lateralis anteriorly from the short head of the Biceps femoris posteriorly, and gives partial origin to these muscles.
    Lift vastus lateralis off the intermuscular septum. Try not to split the vastus lateralis fibers.
    Retract the vastus lateralis to the anterior zone. The use of a Hoffman retractor will be help to achieve a great exposure of the femoral diaphysis. The retractor must be placed between the femur and the muscle mass.
    Perform this step carefully and take you time, always palpating the bone. Be careful not to go medially and injure part of the femoral vascular structures.
    Expose the desired area of femur with subperiosteal dissection. Once you do this, a great exposure of the femoral bone will be achieved (A).
    It is not necessary to dissect the gluteus medius tendon insertion over the trochanter or remove the gluteus maximus insertion in the linea aspera. Remember that we do not need to access to the hip so we do not need to extend the deep dissection proximally.

    Plan and cut the bone window to access to the medullary cavity of the femur.The procedure is done with a surgical drill (Colibri / Depuy-Synthes). It is important to have a different sizes of saws to do the osteotomies. Care must be taken at the vertices of the osteotomies, so as not exceed and weaken the bone.
    To perform the bone window:
    1- Mark the area with the electrocautery according to the preoporative planning.
    2- Do the osteotomies with the saw, starting with the posterior and anterior ones.
    3- Change to a small saw for the upper and lower osteotomies.
    The critical area of bone window are the corners or vertices. You must be very meticulous at this point so as not to pass through and weaken the bone. If you don’t feel confident using the oscillating saw a good surgical tip is to drill the corners of the rectangle (window) before doing the osteotomies.
    A really key point is that the bone window should not exceed the 25% of the circumference of the femur.

    Remove the bone window and do an aggressive curettageRemove the bone window and you will have full access to the medullary cavity which is full of fluid.
    One needs to do an aggressive curettage and it is important to have different angle curettes in order to access to all the cyst. One must “feel” the cyst walls and curet them.
    Although we are sure that we are dealing with a benign tumor, send material to histology to confirm the diagnosis.

    Fragmented frozen bone allograft chips are prepared.
    The chips were obtained from a donor femoral head, that has been screened and correctly processed.

    Reconstruction of the bone defect is done with fragmented bone allograft to fill in completely the cavity, which is then impacted.

    Replace the bone window and stabilise the reconstruction with the 4.5 mm LCP plateIt is important first to position the plate on the lateral diaphysis of the femur, making sure the window is covered by the plate. Using the LCP drill sleeve can helps us during the position procedure of the plate. (A)
    Firstly fix the cortical screws above and below the osteotomies. These screws will let us to apply the plate to the one and keep the bone window in place.
    The steps to follow are:
    Press the spring-loaded guide against the bone in the DC part of the LCP hole. The inner sleeve retracts. The rounded end of the outer sleeve slides along the hole angle into neutral position. Drill.
    Measure the screw length with the depth gauge.
    Using the screwdriver, manually insert and tighten a standard headed screw of the measured length.
    Once the 2 cortex screws are inserted I add a locking screw.
    Locking screws should be inserted using the correct technique.
    Carefully screw the LCP drill sleeve into the desired LCP hole until it is accurately and completely engaged by its threads. The use of the LCP drill sleeve is mandatory in order to ensure that the locking screw is drilled in the proper perpendicular angle and correctly locked into the plate.
    Carefully drill the screw hole using an appropriate LCP Drill Bit 4.3 mm
    Determine screw length. Read the drilled depth directly from the laser mark on the drill bit or you can use depth gauge.
    Screw insertion with a power tool. To insert the locking screw using a power tool, fit a torque limiter to the power tool. Then insert the screw- driver shaft into the torque limiter.

    Final plate stabilisation with 1 screw above (A) and 2 screws below (B) the bone window.
    The implant on the lateral side of the femur bridges the cortical window.
    I do not recommend to put a screw through the window as it is very thin, and easily fractures. This level of fixation is enough to give support to the bone window for healing.

    This step it is really import. Do a very carefully soft tissue reconstruction.
    Reattach the vastus lateralis to the gluteus maximus fascia. This step will let us cover the plate and reconstruct the intermuscular plane.

    Reattach the vastus lateralis to the fascia of the gluteus maximus in order to restore the intermuscular plane.Soft tissue coverage of the osteosynthesis.

    Meticulous closure of the fascia. I use vicryl 1 with a continuous suture.
    For deep subcutaneous plane I use vicryl 0 and vicryl 2.0 for the superficial subcutaneous plane.
    It is important to do a meticulous plane closure to try to reduce haematoma formation and wound complications.

    Finally close the skin with intradermal suture, we prefer resorbable vicryl rapid so we do not need to remove the suture.
    Over the close skin we put steristrips to help to reduce the tension of the wound and have a better ciactrization.

    Immediate postoperative X-rays showing the reconstruction with fragmented allograft (chips) and the stabilization with the LCP 4.5

    Post Operative

    Post operative protocol. It is important to coordinate with the rehabilitation team in orden to do the proper exersices
    Full range movement of the hip and knee is allow.
    No weight bearing for 6 weeks until we achieve consolidation of the bone window.
    Patient is allowed to mobilize with crutches.

    Recommended Reading

    The meta-analysis of published literature by Muayad Kadhim et al in 2014 on UBC treatment indicates improved healing rates among treated patients relative to the observational management.
    Healing rate was found to be comparable in studies that utilized bone marrow injection or methylprednisolone acetate, and higher rate of healing was found when demineralized bone matrix was added.
    Surgical curettage resulted in healing rate of 90 % with the utilization of autograft, allograft or any bone substitution material. Healing rate was also high with the utilization of IM nails.
    Muayad Kadhim 1 , Mihir Thacker, Amjed Kadhim, Laurens Holmes Jr. Treatment of unicameral bone cyst: systematic review and meta analysis. J Child Orthop. 2014 Mar;8(2):171-91.

    Reference

    • orthoracle.com

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