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Guided Growth: The Importance of a Single Tether. An Experimental Study

Sanpera, Ignacio Jr MD, PhD*; Raluy-Collado, David MD*; Frontera-Juan, Guillem MD; Tejada-Gavela, Silvia PhD; Ramos-Asensio, Rafael MD§

Journal of Pediatric Orthopaedics: December 2012 - Volume 32 - Issue 8 - p 815–820
doi: 10.1097/BPO.0b013e31824b755a

Background: During the last few years, the use of the 8-plate as a technique for hemiepiphysiodesis has gained wide acceptance, as it has been shown that it works in a more physiological way than other methods such as staples or transphyseal screws. It has mechanically been compared with a tension band plate, and for this reason, only a single plate is needed. The following study was undertaken to test the 8-plate against the staples and assess factors that can influence the difference in results.

Methods: A prospective experimental study was designed to compare the ability of 2 hemiepiphysiodesis methods, the 8-plate and the double staple, to produce angular deformity in the rabbit’s tibia (group I). The variable studied was the variations in the articular line-diaphysis angle at 6 weeks. As the results showed that the 8-plate produced a bigger deformity, a second group was designed (group II) comparing single against double staple, under the hypothesis that the differences observed in the first group could be related to the number of anchors put across the physis and consequently depend on the volume of physis involved by the staples.

Results: In group I, the 8-plate produced a bigger angulation at 6 weeks’ time than the 2 staples (a difference of 6.5 degrees, P=0.03). Similarly, in group II, the single staple produced a greater angulation than the 2 staples (difference 6 degrees, P=0.08). When both groups were compared, no differences in the angulation produced by the 8-plate and the single staple with respect to the 2 staples were found.

Conclusions: These results suggest that one of the reasons why the 8-plate may act in a more “physiological way” (vs. the traditional 2-staple or 3-staple hemiepiphysiodesis) could be the fact that the growth plate is tethered only at a single point. Therefore, the physis retains a major potential for growth and deformity.

Clinical relevance: The 8-plate is superior in producing/correcting angular deformity when compared with the traditionally used staples (2 or more) but not when compared with a single staple.

*Pediatric Orthopaedic Department

Research Department

§Morbid Anatomy Department, Hospital Universitari Son Espases

Fundació Hospital Son Llatzer, Palma de Mallorca, Spain

Supported by a national grant for basic medical research from the Instituto de Salud Carlos III from the Spanish Science and Innovation Department (PI08-90917). No other benefits or indirect gains were obtained from the study (The “Instituto de Salud Carlos III, is a Spanish NIH).

The authors declare no conflict of interest.

Reprints: Ignacio Sanpera Jr, MD, PhD, Servei de Ortopèdia i Traumatologia Infantil, Hospital Universitari Son Espases, Crta de Valldemosa 77, 07010 Palma de Mallorca, Spain. E-mail:

© 2012 Lippincott Williams & Wilkins, Inc.