Loss of pin fixation in displaced supracondylar humeral fractures in children: causes and prevention.
BACKGROUND
Although the results are generally good following pin fixation of supracondylar humeral fractures in children, occasionally there is postoperative displacement. The purposes of the present study were to identify the causes leading to loss of fixation after pin fixation and to present methods for prevention.


METHODS
We evaluated 322 displaced supracondylar humeral fractures that had been treated with percutaneous pin fixation. We examined fracture classification, pin configuration, intraoperative alignment after fixation, change in alignment after fixation, details of additional procedures, and final radiographic and clinical outcomes.


RESULTS
Adequate radiographs were available for 279 of the 322 fractures. Eight (2.9%) of the 279 fractures were associated with postoperative loss of fixation; all eight were Gartland type-III fractures. Seven of these eight fractures initially had been treated with two lateral-entry pins, and one had been treated with two crossed pins. In patients with Gartland type-III fractures, loss of fixation was successfully avoided more often when three pins were used (with fixation being maintained in thirty-seven of thirty-seven patients) as opposed to when two lateral-entry pins were used (with fixation being maintained in thirty-five of forty-two patients) (p = 0.01). In all cases, loss of fixation was due to technical errors that were identifiable on the intraoperative fluoroscopic images and that could have been prevented with proper technique. We identified three types of pin-fixation errors: (1) failure to engage both fragments with two pins or more, (2) failure to achieve bicortical fixation with two pins or more, and (3) failure to achieve adequate pin separation (>2 mm) at the fracture site.


CONCLUSIONS
Postoperative displacement following pin fixation of supracondylar humeral fractures in children is uncommon. In the present series, loss of fixation was most likely to occur when Gartland type-III fractures were treated with two lateral-entry pins. There were no failures when three pins were used. In all cases of failure, there were identifiable technical errors in pin placement.


METHODS
Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.
Sankar
Wudbhav N
WN
Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Wood Building, 2nd Floor, 34th and Civic Center Boulevard, Philadelphia, PA 19104, USA.
Hebela
Nader M
NM
Skaggs
David L
DL
Flynn
John M
JM
D000293:Adolescent; D001858:Bone Nails; D002648:Child; D002675:Child, Preschool; D004868:Equipment Failure; D005592:Fracture Fixation; D006801:Humans; D006810:Humeral Fractures / Q000601:surgery*; D007223:Infant; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control