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Biomechanics of the Cranial

Cruciate Ligament-Deficient

Stifle Treated by Tibial

Osteotomies

Antonio Pozzi,Stanley E. Kim, and Selena Tinga

Introduction

Normal tibiofemoral motion is constrained by
articular surfaces, ligaments, joint capsule and
menisci. Cruciate ligament rupture (CR), par-
ticularly rupture of the cranial cruciate liga-
ment (CrCL), alters these constraints and causes
abnormal motion between the articular surfaces
(Anderst & Tashman 2009). Modification in car-
tilage loading caused by the altered surface
interaction initiates progressive osteoarthritis
(Tashmanet al. 2004; Anderst & Tashman 2009;
Kimet al. 2009a). Thus, the goal for CrCL recon-
struction should be the restoration of normal
stifle mechanics, to reestablish biomechanical
homeostasis, and to halt the progression of
osteoarthritis.
Much of the current knowledge regarding
CrCL repair biomechanics in dogs has been
derived fromex vivostudies evaluating nor-
mal, CrCL-deficient and surgically treated sti-
fles under controlled conditions or theoretical
analysis. However,ex vivoand theoretical stud-
ies cannot replicate functional loading, and rep-
resent only the ‘time-zero’ condition, immedi-
ately after surgical fixation (Warzeeet al. 2001;
Shahar & Milgram 2006; Apeltet al. 2007). More
recent investigations conductedin vivosuggest
that the results ofex vivostudies should be

interpreted with much caution as stabilization

techniques fail to provide joint stability in up to

70% of cases (Kimet al. 2012; Skinneret al. 2013;

Reyet al. 2014).

Most clinical and experimental studies eval-

uating surgical techniques for CR adopt static

stability as a measure of the success of the

surgical technique to reestablish normal joint

mechanics (Gambardellaet al. 1981; Slocum &

Slocum 1993; Warzeeet al. 2001). For example,

a persistent positive cranial drawer test after an

extracapsular technique has been traditionally

considered a sign of stifle instability and an

indication of failure of the procedure. A neu-

tralized cranial tibial thrust after tibial plateau

leveling osteotomy (TPLO) has generally been

used as an indication of a ‘stable’ stifle after

reduction of the tibial plateau slope. However,

in both cases, static stability (palpable stability

on orthopaedic examination) may not necessar-

ily correlate with dynamic stability (controlled

alignment of the stifle during activityin vivo).

A key concept is that stifle stability is a

dynamic phenomenon, describing the response

of the neuromusculoskeletal system to a com-

plex combination of body position, muscle

forces, external loads and sensory inputs.

The limited value of palpation tests, such as

cranial drawer and tibial compression tests, for

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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