Carolina Veterinary Surgical Service

Case Presentation

 

 

Signalment "Lobo" , a 400 gram, 13 year old, male Greater Mouse Lemur (Mirza coquerli)
History Acute left hindlimb disuse approximately 4-5 days prior to presentation 
Clinical Exam Grade V lame, left hindlimb.  Significant swelling of the left thigh with crepitation noted on palpation of the mid femur.  Radiographic examination revealed the presence of a left femur fracture.
Diagnosis Left femur fracture: distal diaphysis, caudomedial displacement, non-comminuted
Procedure Open reduction through a craniolateral approach to the left femur, combination of internal and external fixation

 

 

 

 

Mouse Lemur

  Pre-operative medio-lateral view of left thigh   IM Pin tied into the Type I ESF frame
         
   
Application of ESF bonding agent   Post-operative craniocaudal view   Patient photograph taken shortly after extubation.  Note weight-bearing stance on operated limb.

 

 

Comments:

This case presents several challenges to the surgeon, including anesthetic management, implant selection and application,  and designing the appropriate aftercare plan.

In general, the forces which must be addressed when dealing with a short oblique diaphyseal fracture include bending, shear (collapse), and rotation.  Bone plating is often the preferred method of treating such fractures in the skeletally mature patient.  However, in this case, patient size is too small for even the smallest bone plate and screws.  Application of an intramedullary (IM) pin is appropriate for neutralizing bending forces, but is inadequate in addressing the rotational instability.  The short length of the obliquity precludes the proper application of multiple cerclage wires, and as a result, an external skeletal fixator (ESF) was chosen to supplement the IM pin.   When inserting a ESF pin into the bone which contains an IM pin, care must be taken to avoid iatrogenic fracture - careful selection of IM pin and ESF pin diameter is important.  Tying in the IM pin to the ESF increases frame rigidity and helps minimize the risk of IM pin migration.  Additionally, staged reduction of the ESF with IM pin removal as the final step is made easier where the IM pin has been externalized.  The size of this patient dictated the use of the smallest available orthopedic pins (.035").

Activity during convalescence is difficult to control in exotic species.  Though classified as a quadruped, Mouse lemurs place a greater proportion of their weight on the hindlimbs during ambulation as compared with domestic animals.  Consequently, it is expected that the fracture repair will be significantly stressed during convalescence.  While crate confinement is recommended until complete bony union is present, the physical and behavioral effects of severe activity restriction are unknown, and must be monitored closely. 

Mouse lemurs are an endangered species, primarily due to habitat destruction and hunting in their homeland of Madagscar.  As a breeding male, the patient presented in this case is  valuable to the conservation efforts of the Duke University Lemur Center, which is dedicated to the goal of re-introducing lemurs to protected areas within Madagascar.  Severe orthopedic debilitation, as would be expected for this patient if managed conservatively, would negatively affect the breeding value of this individual. 

The prognosis for uncomplicated healing is guarded due to the uncertainties relating to post-operative activity and patient toleration of the ESF.

Recheck examinations:

2-week:  Suture removal.  Fully weight-bearing, ambulation within area of confinement.

6-week:  Complete bony union, normal usage

 

Special thanks to Dr. Cathy Williams and Kelly Glenn of the Duke University Lemur Center for referring Lobo to CVSS and for their participation in his peri-operative managment.

 

If you have any comments or questions regarding this case, please contact Dr. Clary.

 

 

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