An in vivo injury model of posterolateral knee instability.
BACKGROUND
Posterolateral knee instability is a difficult clinical problem to diagnose and treat. To best evaluate its natural history and the effects of interventional treatments, it is important to develop an in vivo model in an attempt to validate human cadaveric and clinical observational studies.


OBJECTIVE
To develop an in vivo model of posterolateral knee instability in the rabbit and to determine the natural history of untreated posterolateral knee injuries at 6 months postoperatively.


METHODS
Controlled laboratory study.


METHODS
The fibular collateral ligament and popliteus tendon were surgically transected in 1 knee in each of 10 skeletally mature New Zealand White rabbits, with the contralateral knee serving as a control knee. At 6 months postoperatively, the rabbits were euthanized, the knees were removed, and biomechanical testing of knee joint stability was performed. After biomechanical testing, histological sections of each proximal tibia and distal femur were evaluated, and each proximal tibia was graded using an osteoarthritis grading scheme.


RESULTS
Biomechanical testing revealed a statistically significant difference in amount of rotation in the operated knees compared with the unoperated control knees to varus moments at 30 degrees , 60 degrees , and 90 degrees and to external rotation torques at 30 degrees and 60 degrees . Morphological analysis revealed no significant difference in lesions of osteoarthritis in the medial compartment of the operated knees compared with the unoperated knees.


CONCLUSIONS
Although the presence of posterolateral knee instability was validated 6 months after surgery in this model, the authors did not identify significant differences in lesions of osteoarthritis in the operated knees compared with the unoperated control knees.


CONCLUSIONS
This study confirms that posterolateral knee instability can be created in an animal model. It also recapitulates the clinical observation in humans that untreated posterolateral knee injuries do not heal. Similar to animal models of medial collateral ligament sectioning, further studies to validate a posterolateral instability knee model may lead to interventional studies to determine the best way to treat this complex knee instability pattern.
Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue South, R200, Minneapolis, MN 55454, USA. lapra001@umn.edu
Robert F
RF
Laprade
Fred A
FA
Wentorf
Erik J
EJ
Olson
Cathy S
CS
Carlson
D000818:Animals; D016118:Anterior Cruciate Ligament / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D017885:Collateral Ligaments / Q000473:pathology* / Q000503:physiopathology* / Q000601:surgery; D004195:Disease Models, Animal; D005269:Femur / Q000033:anatomy & histology / Q000503:physiopathology; D007593:Joint Instability / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology* / Q000601:surgery; D007718:Knee Injuries / Q000150:complications / Q000473:pathology* / Q000503:physiopathology* / Q000601:surgery; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D019637:Orthopedic Procedures; D010003:Osteoarthritis / Q000209:etiology / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D016119:Posterior Cruciate Ligament / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D011817:Rabbits; D016059:Range of Motion, Articular; D012399:Rotation; D012720:Severity of Illness Index; D013977:Tibia / Q000033:anatomy & histology / Q000503:physiopathology