An in vitro biomechanical study of a hinged external fixator applied to an unstable elbow

Orthopaedic Biomechanics Laboratory, Mayo Clinic, Rochester, MN 55905, USA.
Journal of Shoulder and Elbow Surgery (Impact Factor: 2.29). 07/2005; 14(4):429-32. DOI: 10.1016/j.jse.2004.09.012
Source: PubMed


Details of the mechanical properties of hinged external fixators are essential to use the fixator properly in the clinical setting. A hinged external fixator (Dynamic Joint Distractor 2) was attached to the lateral side of 7 cadaveric elbows. Cantilever lateral bending tests were performed at 3 flexion angles in varus and valgus directions. Varied states of joint contact and axial loading were studied. Stiffness of the construct was calculated with uniaxial loading. Stiffness decreased with increased elbow flexion. Gap creation made the system less stiff. Axial loading made the system stiffer, especially in valgus testing. Stiffness in varus was approximately 4 times that in valgus. Lateral fixator application with half pins is most effective for protecting against varus-producing forces. When using the external fixator for unstable elbows, attention should be paid to the status of the articular surfaces and the integrity of the ligaments, and this should also be noted for elbow position during rehabilitation.

2 Reads
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Elbow contracture is a recognized sequela of elbow injuries in children and adolescents, but previous studies of operative treatment with formal capsular release have demonstrated unpredictable outcomes and unfavorable results. Over a period of five years, fourteen children and adolescents with a mean age of fourteen years who had posttraumatic stiffness of the elbow were managed according to a prospective protocol. Eleven patients had undergone a mean of three previous operative procedures before the index operation. After intraoperative distraction with an external fixator, there was a relaxation phase for six days followed by mobilization of the elbow joint under distraction in the fixator for a mean of seven weeks. Intraoperative range of motion under distraction reached a mean of 100 degrees. Open arthrolysis was not performed, but in four children impinging heterotopic bone was removed through a limited approach. Decompression of the ulnar nerve was performed in seven patients. The mean preoperative arc of total elbow motion was 37 degrees. The mean pronation was 46 degrees, and the mean supination was 56 degrees. After a mean duration of follow-up of thirty-four months, all patients but two had achieved a functional arc of motion of 100 degrees. The mean arc of flexion-extension was 108 degrees (range, 75 degrees to 130 degrees). The mean range of pronation was 73 degrees (range, 20 degrees to 90 degrees), and the mean range of supination was 75 degrees (range, 10 degrees to 90 degrees). There were no pin-track infections or deep infections, and all elbows were stable. At the time of follow-up, three patients had radiographic evidence of humeroulnar degeneration. Closed distraction of the elbow joint with use of a monolateral external fixation frame with motion capacity yields more favorable results than other previously reported options for the treatment of posttraumatic elbow contractures in children and adolescents.
    The Journal of Bone and Joint Surgery 06/2006; 88(5):1011-21. DOI:10.2106/JBJS.D.02090 · 5.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose of review: Recent advances in the treatment and classification of fractures of the proximal ulna will be reviewed, with an emphasis on injury patterns rather than on fracture locations. Recent findings: For the terrible triad injury, a protocol has been created that addresses all bony and soft tissue injuries, recognizing that the lateral collateral ligament complex rarely remains intact. The coronoid process is also repaired, and new data emphasize the role of the coronoid in varus stability. Recent work has also shown that the type of coronoid fracture can to a great extent be predicted by the mechanism of injury. Varus overload results in medial facet fractures, posterior dislocations result in coronoid tip fractures, and trans-olecranon fracture-dislocations result in large coronoid base fractures. Some attention has also been paid to defining the trans-olecranon fracture-dislocation as a distinct entity from Monteggia lesions. Results with trans-olecranon fractures have been poor despite aggressive surgical management, particularly with concomitant radial head or neck injuries. Summary: The recognition of specific injury patterns involving fractures of the proximal ulna has led to advances in the management and classification of these injuries.
    Current Opinion in Orthopaedics 07/2006; 17(4):355-363. DOI:10.1097/
  • [Show abstract] [Hide abstract]
    ABSTRACT: HintergrundDie frhfunktionelle Nachbehandlung komplexer Verletzungen des Ellenbogens mit einem Bewegungsfixateur ist, definiert durch eine monozentrische Achsenfhrung des Fixateur externe, ein neues Konzept der Gelenktransfixation mit kontrolliertem Bewegungsspielraum. Biomechanische Untersuchungen an Kadavergelenken konnten den Nachweis der Funktionsfhigkeit der monozentrischen Fhrung einer externen Fixation belegen, die bereits zu einem frheren postoperativen Zeitpunkt eine operative Versorgung komplexer osteoligamentrer Verletzungen und Revisionseingriffe erlaubt.Patienten und MethodeVon 1997–2004 wurden 23Patienten mit komplexen Frakturen des Ellenbogengelenks nach operativer Versorgung der frhfunktionellen Nachbehandlung im Bewegungsfixateur zugefhrt. Die frhfunktionelle Behandlung begann im Mittel nach 6,4Tagen, der anfngliche Bewegungsradius (ROM) fr Extension/Flexion betrug durchschnittlich 58.ErgebnisseDie Behandlung im Bewegungsfixateur wurde mit einem mittleren ROM von 71 im Mittel fr 34,7Tage fortgefhrt – 18Patienten erreichten dabei eine weitere Steigerung des Bewegungsausmaes, in 4Fllen konnte der anfngliche Bewegungsspielraum erhalten werden, in 1Fall wurde eine Verringerung des ROM um 5 beobachtet. Nachuntersuchungsergebnisse ergaben einen mittleren Bewegungsspielraum von 88 nach durchschnittlich 10Monaten.SchlussfolgerungIn bereinstimmung mit der Literatur zeigen die Ergebnisse, dass eine frhfunktionelle Nachbehandlung operativ versorgter komplexer osteoligamentrer Ellenbogenverletzungen im Bewegungsfixateur positive Frhresultate erzielt und Vorteile fr die langfristige Restitution der Gebrauchsfhigkeit erwarten lsst.BackgroundThe treatment of complex injuries of the elbow joint by a hinged fixator is a new concept of external transfixation with guided movement in a defined monocentric axis. Biomechanical investigations using cadaver specimens showed that the monocentric guidance ensures additional stability in these unstable osteoligamentous injuries, allows early functional treatment, and can be used in primary but also in revision surgery.Patients and methodsBetween 1997 and 2004, 23 patients with complex fractures of the elbow joint were treated with a hinged monocentric external fixator after open reduction and internal fixation. The early functional treatment started 6.4days (mean) postoperatively; the average range of motion (ROM) was 58.ResultsThe early functional treatment using a hinged fixator resulted in a mean increase in the range of motion of up to 71 within an average time course of 34.7days. In 18 patients a significant increase in the ROM was seen; in 4 patients no improvement in the ROM could be achieved. Only one patient showed a decrease in ROM (5). Follow-up examinations after 10months revealed a mean ROM of 88.ConclusionIn agreement with the literature, our results provide evidence that the use of a hinged monocentric external fixator in combination with early functional therapy results in an increase in the ROM and represents a beneficial device and concept in the treatment of complex injuries of the elbow joint.
    Der Unfallchirurg 03/2007; 110(4):320-326. DOI:10.1007/s00113-006-1223-1 · 0.65 Impact Factor
Show more