Percutaneous Distal Femoral or Proximal Tibial Epiphysiodesis for Leg Length Discrepancy



Percutaneous Distal Femoral or Proximal Tibial Epiphysiodesis for Leg Length Discrepancy


Emily R. Dodwell

Roger F. Widmann





ANATOMY



  • The physis is made up of cartilage cells that are replicating and growing away from the physis.



    • The germinal cells are on the epiphyseal side of the physis.


    • The distal femoral physis and proximal tibial physes are undulating and slightly curved.


  • The neurovascular bundle is posterior and midline at the level of the distal femoral physis.


  • The common peroneal nerve at the knee runs obliquely along the lateral side of the popliteal fossa, close to the medial border of the biceps femoris muscle and the lateral head of the gastrocnemius muscle, toward the head of the fibula.



    • The nerve winds posteriorly around the neck of the proximal fibula and passes deep to the peroneus longus muscle, where it divides into the superficial and deep peroneal nerves.


EPIDEMIOLOGY



  • Approximately 25% of people have a leg length discrepancy of 1 cm or more, and the incidence of leg length discrepancy of 2 cm or greater is estimated at 1 in 1000 cases.


  • Epiphysiodesis is the most frequently used operative procedure in North America for the equalization of limb lengths.


PATHOGENESIS



  • The etiology of a limb length discrepancy can be congenital/developmental; related to tumor; neuromuscular disease; skeletal dysplasia; or otherwise acquired through trauma, infection radiation, or other causes. A partial list of causes includes the following:



    • Congenital shortening: proximal focal femoral deficiency, coxa vara, congenital short femur, fibular and tibial hemimelia, hemiatrophy


    • Congenital lengthening: overgrowth syndromes such as hemihypertrophy, Beckwith-Wiedemann syndrome, Klippel-Trenaunay-Weber syndrome, and Parkes-Weber syndrome


    • Skeletal dysplasia or tumor: Multiple hereditary exostoses may result in limb shortening on the affected side, as growth cartilage cells are diverted to the cartilage tumor. Radiation for malignancies adjacent to the physis may result in growth suppression or complete destruction of physeal cartilage cells, resulting in limb length discrepancy or angular deformity.


    • Infection: Physeal destruction may result from physeal invasion from adjacent metaphyseal or epiphyseal bacterial osteomyelitis or direct physeal involvement in the case of intracapsular joint physes such as at the hip and shoulder.


    • Paralysis: Poliomyelitis and cerebral palsy as well as other nervous system afflictions in children typically result in shortening on the more affected side.


    • Trauma: direct injury to growth plate, posttraumatic bone loss or shortening, and overgrowth following femoral fracture


  • Miscellaneous: slipped capital femoral epiphysis, Legg-Calvé-Perthes disease



NATURAL HISTORY



  • Depending on the underlying cause of the leg length discrepancy, a discrepancy may be static or increase or decrease with remaining growth.



    • Congenital limb length discrepancies typically maintain proportional growth over time. For instance, a tibia that is 10% shorter than the normal side at birth will be approximately 10% shorter than the normal side at maturity.


  • Leg length discrepancies under 2 cm are typically well tolerated.



    • Untreated leg length discrepancy of more than 3 cm may result in pelvic obliquity, visual gait disturbance, short-legged gait, or structural/nonstructural scoliosis.


  • Leg length discrepancy greater than 5.5% of the long leg has been shown to decrease the efficiency of gait, as determined from kinetic data.23


  • No causative relationship has been proved between leg length discrepancy and knee or hip pain or arthritis. A large population study has shown an association between leg length discrepancy and knee arthritis, but there was no evidence of causation.9


  • Although scoliosis has been associated with leg length discrepancy, there is no evidence that leg length discrepancy causes structural curvature of the spine. Assessing the spine with a block under the short leg, with the pelvis level, permits assessment of true scoliosis.


  • Following drill epiphysiodesis, bony bridges form between the epiphysis and the metaphysis, preventing further physeal growth. Growth arrest has been documented within 3 months of the procedure using radiostereotactic (RSA) three-dimensional imaging.11


  • Following screw epiphysiodesis, there is compression or tethering across the physis. Physeal closure may be slightly delayed compared to ablative techniques. Growth inhibition has been documented within 6 months of screw epiphysiodesis but has not been measured using RSA or other highly accurate techniques.


PATIENT HISTORY AND PHYSICAL FINDINGS



  • The underlying cause of a leg length discrepancy can typically be elucidated by careful history and physical examination.


  • The common symptoms at presentation are limp, compensatory gait mechanics, pelvic obliquity, and nonstructural scoliosis.


  • Physical findings depend on the etiologic factors.


  • In hemihypertrophy (both syndromic and nonsyndromic), the affected extremity may be larger in both length and girth. In classic hemihypertrophy, upper extremity hypertrophy as well as hemifacial asymmetry may be present. Vascular overgrowth syndromes may be associated with cutaneous or deep hemangiomas, which may alter surgical approaches to attempted limb equalization.


  • Clinically, leg length discrepancy is best measured by the block test, in which the shorter leg is placed on increasingly larger measured blocks until the posterior iliac crest is level. Discrepancies as small as 2 cm are accurately detected by this method, and detection of discrepancies is largely unaffected by patient size or body mass.


  • True leg length is measured from the anterior superior iliac spine to the tip of the medial malleolus. It is important to place the legs in identical positions to measure true leg length, and for this reason, this measurement is less accurate than the block test.



    • If the patient has a 20-degree abduction deformity of right hip, the left hip is placed in 20 degrees of abduction to measure true length.


  • Apparent leg length is measured with the patient supine with the legs parallel to each other. The landmarks are the umbilicus to the tip of medial malleolus. Pelvic obliquity and fixed deformities of the hip and knee affect the reading. This method is also significantly less accurate than block measurement.


  • Range of motion is noted for all joints, primarily the hip, knee, ankle, and subtalar joints. The ankle joint range of motion is measured with the knee in extension and flexion.


IMAGING AND OTHER DIAGNOSTIC STUDIES



  • Plain radiographs have traditionally been used to document the objective measurement of leg length discrepancy.


  • Full-length (hip to ankle) anteroposterior (AP) radiographs are obtained in standing position with both patellae facing directly anteriorly. The appropriate-sized block is placed beneath the shorter leg to level the pelvis. A long x-ray cassette (51-inch) is used with the x-ray beam center focused on the knee from a distance of 10 feet. A radiolucent ruler often is used to assist in calculation of limb discrepancies.



    • A lateral hip to ankle view can be included to further assess length, as contractures in the sagittal plane may result in inaccuracies on AP measurements. This view can also assess for angular deformities in the coronal plane.


    • Computed tomography (CT) scanogram has been the gold standard for low-dose accurate imaging of leg length discrepancy.


    • CT scanogram is as precise in measuring leg length discrepancy as the slit scanogram and it has the added benefit of more easily measuring leg length discrepancy in the setting of joint contractures. Slit scanogram is of historical interest only and is no longer typically used for measuring leg length discrepancy.


    • EOS8 is a low-dose, high-resolution radiologic imaging system that captures standing simultaneous posteroanterior (PA) and lateral radiographs and full-body radiographs.17


    • Recently, EOS biplanar imaging systems have been shown to be equally accurate/reliable with the added benefit of imaging the patient in a standing position such that leg length and alignment can be obtained from a single low-dose image. Radiation exposure is also lower with EOS.6


  • Skeletal age can be determined by a left hand/wrist radiograph in combination with the Greulich and Pyle method.10



    • Alternatively, the Hospital for Special Surgery (HSS) shorthand method can be used. This method was derived from Greulich and Pyle and uses a single radiographic criteria is used for each age, allowing for rapid bone age determination.12


  • The leg length discrepancy at maturity can be predicted in a variety of ways:



    • The arithmetic method18


    • The growth remaining method1, 2


    • The Moseley straight line method20


    • The Paley multiplier technique21


  • Applications/programs that incorporate the Paley multiplication factors are readily available on smartphones/computers for clinical use. These allow calculation of length
    discrepancy at maturity for both congenital and acquired deformities.



    • Parental and sibling height may be useful in interpreting predicted height be the above methods.


    • In leg length discrepancy secondary to physeal growth arrest, graphical or arithmetic methods are helpful in determining appropriate timing of epiphysiodesis.




NONOPERATIVE MANAGEMENT



  • No treatment is required for a predicted limb length discrepancy of less than to 2.5 cm at maturity.


  • A shoe lift can be used as treatment for leg length discrepancies at maturity below 2 cm.



    • Often, a lift is used in children until an appropriate skeletal age is reached to perform an equalization procedure.


SURGICAL MANAGEMENT

Jul 22, 2016 | Posted by in ORTHOPEDIC | Comments Off on Percutaneous Distal Femoral or Proximal Tibial Epiphysiodesis for Leg Length Discrepancy
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