PHYSEAL DISTRACTION
Experimental aspects and clinical applications.
J de Pablos, M.D., Ph. D.
Orthopaedic Consultant
Hospital of Navarra & Hospital San Juan de Dios
Pamplona, Spain
brupa@ohsjd.es
This technique, likewise called epiphyseal distraction, resulted from the search to find the safest and least invasive way of performing bone lengthening. 
Physeal distraction uses the physis (growth plate) as a "locus minoris resistentiae" of the bone through which a progressive metaphyseal-epiphyseal separation (bone lengthening) can be obtained when distractional forces are applied to its sides. Obviously this technique is to be used in immature patients only.
The first experiments based on these ideas were published by Ring in 1958.
For physeal distraction, we recommend monolateral devices. In our opinion, any apparatus can be used, provided that it allows insertion of the pins in the epiphysis and diaphysis (orthogonal configuration) and it is reliable enough.
The main advantages of physeal distraction as compared to other techniques are its low invasivity and above all the fact that osteotomy is not needed to start lengthening.
Biology of physeal distraction
In order to better understand the biology of physeal distraction, our group carried out an experimental project whose results are summarized in the following points.
- In physeal distraction, lengthening was begun constantly and independently of the distraction rate employed with a physeal fracture (epiphysiolysis). We did not found physeal stimulus or plastic deformation at the distracted grotwh plate.
- Histologically, the reconstruction of the lengthened segment follows three stages which are well differentiated even though they may overlap from one stage to another. Firstly, the physeal fracture gives place to a hematoma which, in approximately 3 weeks, is substituted by a fibrous tissue quite rich in blood vessels, mesenquimal cells and collagen fibers, with significant repair potential. Once the fibrous tissue substitutes the hematoma, it begins to ossify at its ends and in the periphery as well. The type of ossification observed there is a direct one which goes from fibrous tissue to bone tissue with no intermediate cartilaginous cells. This process is more reminiscent of "desmal" ossification than "endochondral" ossification.
- The viability of the growth cartilage after distraction is inversely related to the distraction rate employed and in direct relation to the brusqueness of the initial physeal fracture. The distraction rate which we have found to cause less physeal damage to the distal femoral physis of the lamb has been 0.5 (2 x 0.25) mm/day.
- Physeal bony bridges of a size less than 50% of the total physeal surface can be disrupted with physeal distraction alone without the need for an osteotomy. Fat tissue interposition after disruption can prevent from bridge recurrence.
Applications for physeal distraction
- Simple bone lengthening. Lengthening by physeal distraction can be considered in femoral shortening due to congenital deficiencies or hip disorders. This is so because in physeal distraction of the distal femur, forces are applied distally to the insertion of the adductor muscles, thus minimizing the tendency to varus deformity and also reducing pressure in the hip joint. Nevertheless, its risks overcome the advantages and we have almost abandoned physeal distraction for simple bone lengthening.
- Correction of angular deformities. When an angular deformity of a long bone in an immature patient is located in the vicinity of the growth plate we recommend physeal distraction as the treatment of choice given the additional advantages of this method over other techniques:
- It acts at the level of the deformity.
- Bony bridges (<50% in size) can be disrupted with distraction only (no osteotomy).
- Correction is progressive and adjustable in the postoperative.
- Lengthening can be applied simultaneously if needed.
- In tibia vara, fibular osteotomy is usually not necessary.
This technique, proposed by Cañadell in 1995, uses physeal distraction to separate the epiphysis and physis from a metaphyseal tumoral lesion thus making easier its resection and possibilitating the preservation of the patient’s own epiphysis and joint. In cases of malignant tumors is crucial to make sure that physis and epiphysis are not involved. Due to the concern about local relapse, we personally recommend this technique for benign and para-tumoral lesions where an en-block resection is indicated.
Complications of physeal distraction
Apart from the complications common to all bone lengthening methods, there are other specific hazards involved in its use:
- Risk of septic arthritis due to the vicinity of the epiphyseal pins to the joint. This is of particular concern in femoral distal physeal .
- Risk of damage to the growth plate. Concerning this problem, after experimental and clinical studies, several factors have been identified that have prognostic significance. These include the distraction rate, patient’s age and the condition of the physis prior to distraction. Especifically, physeal viability is more compromised in cases of distraction faster than 0.5 mm/day, older patients and in physes locally damaged (bridges, non-unions, etc.) prior to distraction.
- Stiffness in the joints adjacent to the distraction zone (particularly the knee). In children less than 10-12 y.o., it usually disappears with prompt and adequate physical therapy, once the apparatus has been removed.
Finally we would like to stress what we believe to be the points requiring special attention for minimizing potential complications:
- Ensure that the indication for physeal distraction is correct.
- Use a reliable and versatile fixator-distractor.
- Use this technique in children close to maturity or in those where a complete physeal closure is desirable (i.e. recurrent deformities).
- Do not exceed a rate of 0,5 mm/day, particularly in the first postop. days.
- Meticulous daily nursing is mandatory.
REFERENCES
Azcárate JR, de Pablos J, Cañadell J. Treatment of premature partial physeal closure by means of physeal distraction: An exprimental study. J Pediatr Orthop (B) 1992;1:39-44
Cañadell J, de Pablos J. Breaking bony bridges by physeal distraction. A new approach. International Orthopedics (SICOT) 1985;9:223-229
Cañadell J, de Pablos J. Correction of angular deformities by physeal distraction. Clin Orthop 1992;283:98
De Pablos J (ed.). Surgery of the Growth Plate. Madrid: ERGON, 1998.
De Pablos J, Alfaro J, Barrios C. Treatment of adolescent Blount’s disease by means of asymmetrical physeal distraction. J Pediatr Orthop 1997; 17 : 54-58
De Pablos J, Cañadell J: Experimental physeal distraction in immature sheep. Clin Orthop 1990; 250:73-80
De Pablos J, Franzreb M. Treatment of adolescent tibia vara by asymmetrical physeal distraction. J Bone Joint Surg 1993, 75-B: 592-596
Letts RM, Meadows L: Epiphysiolysis as a method of limb lengthening. Clin Orthop 1978; 133: 230-45
Monticelli G, Spinelli R, Bonucci E: Distraction epiphysiolysis as a method of limb lengthening. Parts I,II,III. Clin Orthop 1981; 154: 256-85
Peltonen J, Alitalo I, Karaharju EO, Helio H: Distraction of the growth plate: experiments in pigs and sheep. Acta Orthop Scand 1984; 55: 359-6
Ring PA: Experimental bone-lengthening by epiphyseal distraction Br J Surg 1958; 49: 169-73
© Creado y diseñado por J.de Pablos /J.A. Bruguera. 2006.