Anticipation and cap technique | Pediatric Orthopedic Society of North America (POSNA) (2023)

study guide

Key Points:

  • Epiphysiodesis is the surgical ablation of the genital organ to stop its further growth, usually used to correct a leg length discrepancy
  • Predicting leg length discrepancies at skeletal maturity can be difficult, so several methods have been developed to provide an estimate.
  • The most commonly used technique for permanent epiphysiodesis is percutaneous drilling ablation.


Indications for epiphysiodes include the treatment or prevention of leg length differences in growing children. Epiphysiodesis surgery generally has a low morbidity and low complication rate, making it an excellent option for surgical correction of an LLD protruding 2 to 6 cm in maturity. It usually does not require post-operative immobilization and immobilizes the child only for a short time.

Epiphysiodesis essentially slows down the growth rate of the longer leg to allow the shorter leg to catch up. When used permanently, this technique relies on the ability to predict leg length discrepancies at maturity, not on presentation.


While temporary epiphysiodesis is possible, permanent epiphysiodesis is the most commonly performed, which is an all-or-nothing procedure that completely stops the growth of a given tissue. It is generally accepted that the greatest growth of the lower limbs occurs in the area of ​​the knee joint. After femoral epiphyseal surgery, the leg will generally grow at a slower rate, approximately 27% for the proximal tibia, 38% for the distal femur, and 65% for the combined cap of both plates. (Green, 1947) Since being tall is an advantage, and shorter limbs are more likely to be pathological and can benefit from foot space or support, it is generally better to undercorrect rather than overcorrect. Several methods can be used to predict residual leg growth. Three commonly used methods include Menelaus' arithmetic, or the "hands-on" method, and the multiplier method described by Paley et al. and a Mosley line graph.

The arithmetic method or "rule of thumb" is based on the following statements, which are approximations of the true height pattern described by Green and Anderson: 1. Girls stop growing at 14; 2. Boys stop growing at 16; 3. The distal femoral plate grows 10 mm (3/8 in) per year; 4. The proximal tibial lamina grows 6 mm (1/4 inch) per year; and 5. The divergence increases by 3 mm (1/8 inch) per year. (West, 1981) These approximations are fairly accurate in later years of growth, but are inaccurate for younger children. This method is convenient because it does not use special tools or graphics; however, it uses chronological age rather than skeletal age and is therefore biased for children who grow too early or too late. It is most commonly used to provide families with a quick and approximate estimate of when a future surgery is due in the clinic, and to re-check predictions obtained by other methods.

Moseley described a line charting method in 1978 that is based on two principles: leg height can be plotted using straight lines, and a nomogram can be used to determine the height percentile based on skeletal age and leg length (Moseley, 1978). ). The Moseley chart is also based on the Green and Anderson charts, but was intended to simplify and improve accuracy by including skeletal maturation based on hand and wrist bone membranes, growth retardation, and relative size in the calculations. A straight line graph can be drawn by manipulating the x-axis of the Green and Anderson graphs. Therefore, short and "normal" leg growth is represented by 2 straight lines, and leg length inequality is represented by the vertical distance between the lines. The line corresponding to the height of the shorter leg has a less steep slope, and the effect of epiphysiodesis can be predicted by changing the slope of the "normal" leg by the expected amount. Detailed instructions can be found on Dr. Moseley's website (

The multiplier method described by Paley et al. uses a multiplier table that can predict maturity discrepancy given the current discrepancy and age of the child (Paley, 2000). They derived these multipliers from the graphs of Green and Anderson (Green, 1960), which show the length of legs reached at a given age. Based on these data, it is also possible to determine the proportion of leg lengths in an adult human of any age by simple division. Assuming that birth defects increase in proportion to leg length, it follows that the proportion of final discrepancy is the same as the proportion of final adult length. Paley et al. he then calculated these ratios, inverted them, and provided a table of multipliers that could be used to predict maturity discrepancies. The disadvantage of this method is that it becomes more complex for developmental discrepancies, where the discrepancy does not actually increase in proportion to leg length. These cases require more complex calculations than Paley et al. formulated. This approach has the advantage of requiring only one X-ray and is therefore particularly useful in counseling families of children who initially have birth defects and in setting expectations for future operations. The multiplier method has been shown to be as accurate as the Mosley method for chronological age (Aguilar, 2005; Aguilar, 2005). To facilitate the clinical application of this approach, two popular applications have been developed: "Paley Growth" from the Paley Institute and "Multiplier" from the International Center (Townsend, 2007, Lifebridge Health, 2014).


Clinical Results:

Image research:



The goal of permanent epiphysiodesis is to create a symmetrical bone bridge that holds the epiphysis and prevents future growth. Ablation of the peripheral margins of the medial and lateral epiphyses can create a bone bridge between the epiphysis and metaphysis. Theoretically, the central part of the cap does not require treatment as it is self-closing, although in practice it often perforates. This procedure is indicated in the projected discrepancies in the length of the legs from 2 to 6 cm.

Pemister is credited with first describing the technique of open epiphysiodesis in 1933, and since then many variations of his technique have appeared (Phemister, 1933). Pemister's surgical technique was to remove a rectangular block of bone from the medial and lateral bones, which included two-thirds of the metaphysis and one-third of the epiphyseal plate. He then placed the rectangular block of bone in the reverse position, which would eventually result in a rod through the growth plate.

Percutaneous epiphysiodesis has also been described to prevent unsightly scarring and has gained wide acceptance. It is considered the technique of choice. (Bowen, 1984; Canale, 1986; Olgivie, 1986) This is done with a drill or by drilling through incisions 3 to 10 mm long in the middle and lateral, or only lateral at the level of the epiphyses, located by fluoroscopy. Under fluoroscopy guidance, a drill or bur is inserted into the cap and used to remove the peripheral third of the plaque, leaving the central third of the plaque intact. Particular attention should also be paid to the appropriate ablation of the most peripheral part of the plaque. If necessary, a sagittal epidermis can also be made through the same skin incision on the proximal lateral tibia, but this should be done anteriorly rather than laterally to bypass the peroneal nerve.

Since growth plates are not perfectly flat, the technical challenge is to ensure that the drill tip or burr is in the plate. In the distal femur, the intercondylar notch enters the posterior surface of the distal femoral growth plate and extreme care must be taken not to accidentally enter this notch. Complications of drill epiphysiodes include hematoma, exudate, wound infection, and joint penetration (Edmonds, 2007).

Ultimately, this epiphyseal destruction process is routinely sufficient to ensure that epiphyseal growth is arrested, and it also maintains enough bone strength through residual plaque and surrounding periosteum that postoperative immobilization is not necessary.

Internal immobilization across the body was also used to retard body growth. Blount clamps were used but were complicated by clamp recoil, implant rupture and frontal plane deformations (Blount 1949). The percutaneous epiphysiodesis technique with pedicle screws (PETS) was developed by Métaizeau and has been shown to delay the growth of the knee epiphyses by 89-95% (Metaizeau 1998). The controlled growth technique using tension band plates and screws has also been shown to retard growth compared to staples and PETS (Lykissas 2013). Since these techniques slow growth rather than stopping it abruptly, it is recommended that surgery be performed up to a year earlier as the hardware can be removed once the legs are of equal length (Pendelton 2013).

A minor disadvantage of epiphysiodesis is that it is a compensatory rather than corrective procedure, as it essentially makes a "normal" leg "abnormal". A large amount of shortening can theoretically reduce the expected length of major muscles and weaken them, which is one of the reasons why it is not recommended for large discrepancies. Epiphysiodesis also reduces the patient's height, which may be undesirable.

Long leg epiphysiodesis is a reasonable and commonly used technique for mild limb length disparities of 2 to 6 cm and is mainly limited by the accuracy of the prediction.


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Anticipation and cap technique | Pediatric Orthopedic Society of North America (POSNA) (1)

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