COMMENTARY
Biomechanical analysis of pinning techniques for pediatric supracondylar humerus fractures.
Larson L, Firoozbakhsh K, Passarelli R, Bosch P.
J Pediatr Orthop A 2006;25(5):573–578.
Closed reduction and percutaneous pinning is the treatment of choice for most Gartland type 2 and 3 supracondylar humerus fractures. As reviewed in the article, previously published large series of supracondylar humerus fractures showed that treatment with lateral pins is acceptable.
The authors in this current study used synthetic humeri to evaluate the torsional stability of various pin configurations in the setting of medial column comminution.
Angular deformity associated with supracondylar fractures has decreased with modern fixation techniques. Cubitus varus is the most common deformity; it is more often the result of malunion of the distal fragment and not growth disturbance or avascular necrosis (Voss et al.). True coronal plane varus is the major component of cubitus varus, with any additional internal rotation worsening the deformity (Chess et al.). This is important to understand intraoperatively when trying to identify residual deformity, as an accurate reduction of the fracture is likely the most important factor in preventing varus collapse. This current study tested pin configurations using internal rotation stress only. This technique disregards the primary direction of deformity for these fractures, which is varus. Medial column comminution removes the inherent medial side support, implying that the additional rotational stress is not required for subsequent varus collapse. An additional group or groups with varus stress would have provided valuable information.
The paper describes and illustrates the pin configurations employed. All arrangements depict low placement within the columns and crossing at the typical fracture site or within the olecranon fossa. True column pins are positioned higher, which gives better control. Additionally, medial and lateral pins should cross above the fracture to provide adequate stability. The authors used relatively small K-wires in their testing; most textbooks and papers recommend 1.8- or 2.0-mm K-wires for additional stability.
The authors wanted to test torsional stability for various pin configurations. Adding varus stress would have recreated in vivo stresses; additionally, pin placement and size are variables that further limit support for use of three lateral pins over standard crossed pins in fractures with medial comminution. Although difficult to apply the authors’ outcomes to those fractures, they are applicable to injuries without comminution, as some rotation of the distal fragment is required for varus collapse when the column is intact. Thus, this is another paper that supports the clinical success rates of lateral-only pin fixation.
Reviewed by Judith A. Siegel, M.D.
Department of Orthopaedic Surgery Boston University School of Medicine
Boston Medical Center; Boston, Massachusetts
References:
Voss F, Kasser J, Trepman E, Simmons E, Hall J. Uniplanar supracondylar humeral osteotomy with preset Kirschner wires for posttraumatic cubitus varus. J Pediatr Orthop 1994;14(4):471–478.
Chess D, Leahey J, Hyndman J. Cubitus varus: Significant factors. J Pediatr Orthop 1994;14(2):190–192.
