The effect of medial versus lateral meniscectomy on the stability of the anterior cruciate ligament-deficient knee.
BACKGROUND
The pivot shift is a dynamic test of knee stability that involves a pathologic, multiplanar motion path elicited by a combination of axial load and valgus force during a knee flexion from an extended position.


OBJECTIVE
To assess the stabilizing effect of the medial and lateral meniscus on anterior cruciate ligament-deficient (ACL-D) knees during the pivot shift examination.


METHODS
Controlled laboratory study.


METHODS
A Lachman and a mechanized pivot shift test were performed on 16 fresh-frozen cadaveric hip-to-toe lower extremity specimens. The knee was tested intact, ACL-D, and after sectioning the medial meniscus (ACL/MM-D; n = 8), lateral meniscus (ACL/LM-D; n = 8), and both (ACL/LM/MM-D; n = 16). A navigation system recorded the resultant anterior tibial translations (ATTs). For statistical analysis an analysis of variance was used; significance was set at P < .05.


RESULTS
The ATT significantly increased in the ACL-D knee after lateral meniscectomy (ACL/LM-D; P < .05) during the pivot shift maneuver. In the lateral compartment of the knee, ATT in the ACL-D knee increased by 6 mm after lateral meniscectomy during the pivot shift (16.6 +/- 6.0 vs 10.5 +/- 3.5 mm, P < .01 for ACL/LM out vs ACL out). Medial meniscectomy, conversely, had no significant effect on ATT in the ACL-D knee during pivot shift examination (P > .05). With standardized Lachman examination, however, ATT significantly increased after medial but not lateral meniscectomy compared with the ACL-D knee (P < .001).


CONCLUSIONS
Although the medial meniscus functions as a critical secondary stabilizer to anteriorly directed forces on the tibia during a Lachman examination, the lateral meniscus appears to be a more important restraint to anterior tibial translation during combined valgus and rotatory loads applied during a pivoting maneuver.


CONCLUSIONS
This model may have implications in the evaluation of surgical reconstruction procedures in complex knee injuries.
Musahl
Volker
V
Sports Medicine and Shoulder Service, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA.
Citak
Musa
M
O'Loughlin
Padhraig F
PF
Choi
Daniel
D
Bedi
Asheesh
A
Pearle
Andrew D
AD
D000328:Adult; D016118:Anterior Cruciate Ligament / Q000473:pathology* / Q000601:surgery; D002102:Cadaver; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000601:surgery*; D007719:Knee Joint / Q000473:pathology / Q000601:surgery; D008297:Male; D008592:Menisci, Tibial / Q000601:surgery*; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*