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Open reduction and soft tissue correction of a congenitally dislocated knee

    Overview

    Learn the Open reduction and soft tissue correction of a congenitally dislocated knee surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Open reduction and soft tissue correction of a congenitally dislocated knee surgical procedure.
    Congenital dislocation of the knee (CDK) is rare occurring in 1 in 100,000 live births. Approximately 50% of cases are associated with other conditions including myelodysplasia, arthrogryposis and Larsen’s syndrome.
    The severity of the condition is fairly variable. Milder cases can often be managed with serial casting where as the most severe cases require aggressive lengthening of the quadriceps extensor mechanism and an open release of the knee joint, which is shown in the case detailed here.
    Surgery is best performed before 1 year of age and patients with associated syndromes will generally have a poorer prognosis.

    Indications

    INDICATIONS
    Congenital dislocation of the knee (CDK) is rare, occurring in 1 in 100,000 live births. This is approximately 1ooth the incidence of developmental dysplasia of the hip (DDH). Half of patients have neuromuscular or musculoskeletal pathologies, the most common being myelodysplasia, arthrogryposis and Larsen’s syndrome.
    SYMPTOMS & EXAMINATION
    Patients with CDK are generally identified at birth. They present with a hyperextended knee (often up to 90 degrees) such that the foot is frequently in close proximity to the face. Frequently associated abnormalities include Developmental dysplasia of the hip (DDH) and congenital talipes equinovarus (CTEV). These occur in 40-50% of cases. Sixty percent of cases of CDK are bilateral.
    Early examination (first 24 hrs) is useful in deciding on treatment strategy. The Tarek classification is determined by the amount of passive knee flexion that is possible:
    Grade I: Knees will allow passive flexion of the knee to 90 degrees (recurvatum).
    Grade II: Knees will allow 30-90 degrees passive flexion (generally these knees will be subluxed).
    Grade III: Knees have less than 30 degrees passive flexion. These are generally the true dislocations with no contact between the tibial plateau and the femoral condyles.
    IMAGING
    Hip ultrasound is mandatory to rule out DDH. Ultrasound of the knee is also useful since it will help to determine whether the knee is truly dislocated (in which case the tibia lies in front of the femur), subluxed, or simply hyper extended (recurvatum). X ray can also be helpful although much of the knee is unossified in the new born period.
    ALTERNATIVE OPERATIVE TREATMENT
    The most severe (gradeIII) knees may still be trialed with serial casting but failure rates are high, particularly in syndromic cases. Some of the milder grade III and the majority of grade II knees will partially respond to casting and casting can be followed by percutaneous quadriceps recession (PQR). This has been shown to be effective and is much less invasive than a formal open release.
    The underlying problem is that the quadriceps mechanism is too short in CDK. An alternative option is to perform femoral shortening osteotomy. Reports of this technique are relatively few but this is a technique that can be particularly effective for recurrent cases.
    NON-OPERATIVE MANAGEMENT
    Non operative management involves serial casting until 90 degrees of knee flexion is possible. At this point a Pavlik harness can be applied. This is the method of choice for Tarek grade I and grade II knees. Treatment should start within the first few days of life.
    CONTRAINDICATIONS
    Open release is contra indicated for knees that respond to serial casting. If it is clear that the knee is not reducing after 2-3 casts then open surgery should be considered. Radiographs in cast can be helpful in deciding whether the knee is reducing.

    Setup

    Surgery is performed under general anaesthetic. Caudal anaesthetic block is recommended for analgesia. The condition is generally bilateral and both knees should have surgery at the same sitting. The patient is placed in supine position. Tourniquet is not indicated since there will not be sufficient room and application of tourniquet would tether the extensor mechanism.
    A single shot of broad spectrum antibiotic is administered prior to surgery and monocular diathermy should be available.

    Operation

    Define the anatomy and locate the front of the knee.
    The first step in the procedure is to define the anatomy. It is easy to mistake the front of the knee for the popliteal fossa. The patella is small at this age and often hypoplastic. Draw a circle around the patella as shown.
    Note the association with talipes equinovarus in this case, which is common. This patient also has bilateral DDH.

    Assess the range of knee flexion whilst palpating front of knee and femoral condyles posteriorlyAssess the range of knee flexion. If the knee will flex beyond neutral a combination of serial casting +/- percutaneous tenotomy of quadriceps would be indicated.
    In this case the knee is stuck in hyper extension and formal open release is indicated. Passive flexion is to just short of neutral (Tarek grade III).
    Note that the femoral condyles will feel very prominent in the popliteal fossa. They should also be identified with a marker pen.

    Pre operative imaging can be helpful. It is easy to misinterpret images however. In this x ray the epiphyses are not yet visible. The front of the knee is marked (A) and posterior aspect (B).

    Mark skin incision anterolateral and extending proximal to midpoint of femur and distal as far as proximal tibia.Prepare skin up to the groin. The skin incision is anterolateral and may need to be extended to the proximal femur. It will be necessary to access both the medial and lateral side of the quadriceps. The drapes have to be applied as high as possible which excludes use of tourniquet.

    After skin incision use sharp dissection towards the midline anteriorlyProceed with sharp dissection and diathermy to maintain a blood free field of view. Aim to keep dissection toward the midline. Structures will initially be difficult to identify since the extensor mechanism will often be very scarred. Muscle fibres of the quadriceps will often appear quite fibrosed and care must be taken to avoid damage to them. The quadriceps will seem to merge with the hamstrings medially and laterally.

    Identify medial and lateral hamstrings and extensor mechanismWork laterally and medially from the midline. The medial hamstrings (marked with hypodermic needle, A) and ileotibial band will have subluxed forward. They will in effect be knee extensors. Do not lengthen/divide the hamstrings. The quadriceps mechanism will form one indistinct unit (B). It will not be possible to differentiate the vastus medialis, lateralis or rectus.

    The ileotibial band (A) may be very closely applied to the quadriceps. The quadriceps itself distally is quite hypoplasitc. The muscle fibres of the vasti and rectus will not extend as far as the patella and the distal quadriceps may be a relatively thin sheet of fibrotic tissue

    Divide the ileotibial band distally.The ileotibial band will need to be divided but this must be done with great care since the common peroneal nerve will lie just posterior to it, distally running around the neck of the fibula. It is often not possible to visualise the nerve.

    Identify the biceps femoris tendon running toward fibula head.Once the ileotibial band has been divided the biceps femoris tendon (A) and lateral hamstrings will be visible.
    Trace the biceps femoris tendon towards the fibula head (B) but do not divide the tendon. It is important to preserve function in the hamstrings.

    Separate the distal quadriceps from the hamstrings.It is very important to delineate and define the junction between the quadriceps and the adjacent hamstrings. They may be fibrosed together and should be separated. Note how the distal quadriceps is a thin sheet of fibrotic tissue (A) separated from medial hamstrings (B) and lateral hamstrings (C).

    Mark the proposed incision for a V-Y plasty in extensor mechanismThe quadriceps is lengthened using a V-Y technique. The ‘tongue’ in the V will need to be much longer than you anticipate. It will frequently need to be up to half the length of the whole quadriceps. The central portion of the V will extend into the fibrosed muscle belly of quadriceps.
    Mark the incision clearly with a pen before starting the dissection. The patella (A) may be very hypoplastic and is more distal than one would expect

    Incise the extensor mechanism in a V fashion, to enter the knee joint distally.An extended ‘tongue of muscle and tendon is elevated with its distal attachment to the patella. A size 15 scalpel blade is recommended for this.

    As the distal tongue of tendon is elevated the knee joint will be entered.

    Release the anterior joint capsule.A McDonalds elevator is inserted into the joint with the concave surface placed over the trochlea of the distal femoral condyles.
    The anterolateral and anteromedial capsule of the joint is released, with a scalpel or scissors, as far as the collateral ligaments.

    As the front of the knee is released, flex the knee to reduce the tibia will onto the femur.Release of the collateral ligaments should be avoided if possible although the ligaments are often not identifiable structures. As the knee reduces the medial and lateral hamstrings should ‘flip’ behind the axis of rotation and become knee flexors. Cruciate ligaments will often be absent.

    Elevate the lateral quadriceps off underlying femoral shaft.As the tibia reduces onto the femur the vastus lateralis and medialis will be displaced posteriorly. They will need to be elevated off the underlying femur in order to reconstruct the extensor mechanism. Here vastus laterals (A) is being elevated off the femur to allow it to be advanced distally and medially. Note how lateral hamstrings (B) now lie posterior to the axis of flexion of the joint.

    The vasti are carefully elevated until they can be mobilised to meet the distal tongue of tissue. The original descriptions of Curtis (1969) and later Bell (1987) suggested that it is sometimes necessary to elevate the whole of the quadriceps off the femur. It is generally not possible to repair the extensor mechanism with the knee at 90 degrees of flexion since the distal and proximal segments of quadriceps will not meet. In most cases 30-40 degrees of flexion is the most the can be attained.

    Bell MJ, Atkins RM, Sharrard WJ. Irreducible congenital dislocation of the knee. Aetiology and treatment. J Bone Joint Surg 1987; 69-B(3): 403-406.
    Curtis BH, Fisher RL. Congenital hyperextension with anterior subluxation of the knee: surgical treatment and long term observations. J Bone Joint Surg (Am) 1969; 51(A): 255-259.

    Repair vastus lateralis to the distal tongue of the extensor mechanismVastus lateralis (A) is sutured to the distal tongue of tissue (B) with 0 vicryl interrupted sutures. This is typically performed with knee flexed approximately30- 45 degrees.

    Repair of vests medialis to the distal tongue of the extensor mechanismVastus medialis (A) is next elevated and advanced and sutured both to the distal tissue and to vastus lateralis.

    Check that the knee remains enlocated with extensor mechanism intact.It is frequently not possible to advance the vasti as far as the patella itself. This is not mandatory providing the extensor mechanism is in continuity. The distal extensor mechanism will be very narrow and appear quite flimsy. It should lie centrally within the trochlea. Ensure that the knee remains enlocated. Too much flexion and the extensor mechanism will not be repairable. Too little flexion and the hamstrings will sublet forward and the knee redislocate.

    The wound is closed in layers. 3/0 vicryl to fat and 4/0 subcuticular vicryl or monocryl to skin.

    Apply an above knee cast with the knee flexed to approximately 45 degrees.At the conclusion of the operation the knee should be kept flexed to maintain reduction of the tibia onto the femur. Flexion should not be excessive since this will rupture the repair. Inadequate flexion will lead to resubluxation of the knee joint. Note how the wound which was originally anterolateral is not on the lateral aspect of the leg. A full above knee cast is applied.

    A post operative radiograph is mandatory to ensure that the joint remains enlocated. Anterior (A), Posterior (B).

    Post Operative

    A full above knee cast should be applied. This can be difficult if there is coexisting CTEV.
    Cast changes may be needed at 2 weeks to check viability of the skin. This also provides an opportunity to check that the knee remains enlocated. The urge to increase knee flexion should be avoided unless the knee is very unstable.
    Total time in cast is 5-6 weeks.
    DDH and CTEV frequently co exist. Ponseti casting may be trialed at the same time as casting to improve knee flexion. However, if the knee does not flex Ponseti casting is likely to fail. DDH is the newborn period is generally treated in Pavlik harness or brace but this is not possible until the knees are in flexion.
    Most surgeons would address the knee deformity first followed by CTEV (Ponseti or posteromedial release) and finally DDH.

    Recommended Reading

    Functional results are highly dependent upon the severity of dislocation, patients with underlying conditions tending to have worse outcomes. Very few series have been published and the numbers in those published are small.
    Most patients who have grade III CDK will attain a reduced joint with surgery. The majority should as a result be able to mobilise independently without aids or supports. However, a knee extensor lag is almost universal and knee flexion beyond 90 degrees is unusual from grade III cases. Patients will also often have a degree if cruciate and collateral instability, although few require further intervention.

    Congenital dislocation of the knee: a protocol for management based on degree of knee flexion.
    Abdelaziz TH, Samir S. J Childrens Orthopaedics. 2011; 5(2):143-149

    Irreducible congenital dislocation of the knee. Aetiology and treatment.
    Bell MJ, Atkins RM, Sharrard WJ. J Bone Joint Surg 1987; 69-B(3): 403-406.

    Congenital hyperextension with anterior subluxation of the knee: surgical treatment and long term observations.
    Curtis BH, Fisher RL. J Bone Joint Surg (Am) 1969; 51(A): 255-259.

    Reference

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