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.
Sports Medicine and Shoulder Service, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA.
Volker
V
Musahl
Musa
M
Citak
Padhraig F
PF
O'Loughlin
Daniel
D
Choi
Asheesh
A
Bedi
Andrew D
AD
Pearle
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*