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Surgical Management of

Cruciate Ligament Rupture

Combined with Patella

Luxation

Anke Langenbachand Denis J. Marcellin-Little

Pathophysiology

Cruciate ligament rupture (CR) predominantly
affects the cranial cruciate ligament (CrCL).
CR and patellar luxation (PL) are two common
causes of dysfunction and lameness in dogs
that are generally independent but can coexist
(Arthurs & Langley-Hobbs 2006). Medial and
lateral PL have been described as risk factors
for CR (Wright 1979; Willauer & Vasseur 1987).
Conversely, CR can predispose dogs to patellar
luxation, particularly in bow-legged dogs. The
prevalence of PL in dogs with CR ranged from
6% to 20% in two reports (Willauer & Vasseur
1987; Gibbonset al. 2006). Pelvic limb lameness
in dogs with combined CR and PL may be
more severe than pelvic limb lameness in dogs
with only CR or only PL. It has been speculated
that the increase in internal rotation resulting
from partial CrCL fiber rupture may increase
clinical signs in dogs with Grade 1 medial
PL and no previous clinical signs. Complete
CR leads to stifle instability, primarily with
cranial tibial thrust but also with an increase
in internal rotation and extension, poten-
tially exacerbating the clinical consequences
of PL.

Patellae that track in an abnormally proximal

position (patella alta) are also a risk factor for

medial PL. In one report, large-breed dogs with

medial PL were found to have a more proxi-

mal patella than large-breed dogs with normal

stifle joints (Johnsonet al. 2006). However, in

another report, patella alta was not identified

in toy poodles with medial PL (Yasukawaet al.

2016). PL has also been reported as an unusual

postoperative complication of CR stabilization

surgery. The proposed mechanism for postoper-

ative PL included a failure of incisional closure

or tearing of the retinacular incision, potentially

combined with muscle atrophy with a result-

ing lack of muscular control. Additional predis-

posing factors include angulation of the prox-

imal or distal portion of the femur, a shallow

trochlear sulcus with poorly developed ridges,

hypoplastic femoral condyles, and torsion of

the tibial tuberosity or bowing of the proxi-

mal tibia. PL after CR stabilization can be either

medial or lateral and can occur after extra-

capsular stabilization, intra-articular stabiliza-

tion, tibial plateau leveling osteotomy (TPLO),

or closing cranial wedge ostectomy (Arthurs &

Langley-Hobbs 2007). An incidence of PL of

1.3% was documented during the development

Advances in the Canine Cranial Cruciate Ligament, Second Edition. Edited by Peter Muir. © 2018 ACVS Foundation.
This Work is a co-publication between the American College of Veterinary Surgeons Foundation and Wiley-Blackwell.

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