Removal of the lateral or medial third of patellar tendon alters the patellofemoral contact pressure and area: an in vitro experimental study in dogs.
OBJECTIVE
To compare patellofemoral contact pressure and areas after immediate removal of the lateral, central, or medial third of patellar tendon.


METHODS
In vitro experiment in 12 dogs.


BACKGROUND
Alteration of the vector sum of the quadriceps muscle contraction after removal of partial patellar tendon might result in changes of patellar tracking in the trochlea.


METHODS
Patellofemoral contact pressure and areas were recorded using Fuji pressure-sensitive film at 45 degrees, 60 degrees, and 90 degrees of knee flexion under an isometric quadriceps force of 100% body weight. The patellofemoral contact imprint from the intact knees were obtained as control, and the lateral (n=4), central (n=4), and medial (n=4) third of the patellar tendon were subsequently removed and the patellofemoral contact imprint was recorded.


RESULTS
The patellofemoral contact area was found to increase with increasing knee flexion angles. No change in patellofemoral contact pressure and areas was found after removal of the central third patellar tendon. However, after removal of either lateral or medial third of patellar tendon, the patellofemoral contact was rotated with increasing knee flexion angles. This was due to the altered vector sum of the quadriceps force, resulting in significantly decreased patellofemoral contact areas and simultaneously a significantly increased contact pressure, characterized with concentration of patellofemoral contact pressure on both lateral and medial facets of the patellofemoral joint.


CONCLUSIONS
The results suggest that removal of the central third of patellar tendon may not alter the patellofemoral contact pressure and areas as compared with removal of either lateral or medial third of patellar tendon that may result in an altered postoperative tracking mechanism of the patellofemoral joint immediately after operation.


CONCLUSIONS
Findings of this in vitro animal study supports the use of central third of patellar tendon as autograft for anterior cruciate ligament reconstruction. However, further experimental studies are needed to investigate how the postoperative healing of the host patellar tendon will influence the findings obtained from this in vitro study.
Chan
K M
KM
Department of Orthopaedics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin N.T., Hong Kong, People's Republic of China.
Qin
L
L
Li
C K
CK
Hung
L K
LK
Tang
C Y
CY
Rolf
C
C
D000818:Animals; D004285:Dogs; D005269:Femur / Q000503:physiopathology*; D006614:Hindlimb / Q000503:physiopathology; D066298:In Vitro Techniques; D007596:Joints / Q000503:physiopathology* / Q000601:surgery*; D010329:Patella / Q000503:physiopathology*; D011312:Pressure; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D013710:Tendons / Q000503:physiopathology* / Q000601:surgery*