Lateral patellar luxation in nine small breed dogs

Abstract

The objective of this paper was to describe the clinical features, the management and the outcome of nine small breed dogs affected with lateral patella luxation referred during the period between January 2010 and December 2014. Patellar luxations were classified according to: breed, age, sex, weight, and grade of patellar luxation, as well as if unilateral or bilateral, and concurrent cranial cruciate ligament lesion. In affected dogs, surgical correction consisted in the combination of tibial tuberosity transposition and soft tissue procedure. Adjunctive condroplasty or trochleoplasty was performed as needing. The outcome was found positive after surgical management with low complication rate and complications have been easily managed with high success rate.

Full text

Open Veterinary Journal, (2016), Vol. 6(3): 255-258
ISSN: 2226-4485 (Print)
Short Communication
ISSN: 2218-6050 (Online)
DOI: http://dx.doi.org/10.4314/ovj.v6i3.16
________________________________________________________________________________________________________
*Corresponding Author: Francesco Di Dona. Department of Veterinary Medicine and Animal Productions, University of
Napoli “Federico II”. Via Federico Delpino, 1 – 80138 Napoli, Italy. Email: francesco.didona@unina.it
255
_____________________________________________________________________________________
Submitted: 01/08/2016
Accepted: 04/12/2016
Published: 21/12/2016
Lateral patellar luxation in nine small breed dogs
F. Di Dona1,*, G. Della Valle1, C. Balestriere1, B. Lamagna1, L. Meomartino2, G. Napoleone1, F. Lamagna1 and
G. Fatone1
1Department of Veterinary Medicine and Animal Productions, University of Napoli “Federico II”, Italy
2Interdepartmental Center of Veterinary Radiology, University of Napoli “Federico II”, Italy
_____________________________________________________________________________________________
Abstract
The objective of this paper was to describe the clinical features, the management and the outcome of nine small breed
dogs affected with lateral patella luxation referred during the period between January 2010 and December 2014.
Patellar luxations were classified according to: breed, age, sex, weight, and grade of patellar luxation, as well as if
unilateral or bilateral, and concurrent cranial cruciate ligament lesion. In affected dogs, surgical correction consisted
in the combination of tibial tuberosity transposition and soft tissue procedure. Adjunctive condroplasty or
trochleoplasty was performed as needing. The outcome was found positive after surgical management with low
complication rate and complications have been easily managed with high success rate.
Keywords: Dog, Lateral, Luxation, Patellar.
_____________________________________________________________________________________________
Introduction
Patellar luxation (PL) is one of the most common
orthopedic disease in dogs, and can affect both large
and small dogs and may be seen in cats as well
(Nunamaker, 1985; DeAngelis, 1996; Ness et al., 1996;
Linney et al., 2011). Lateral patellar luxation (LPL)
occurs less frequently than does medial patellar
luxation (MPL) (Roush, 1993). LPL is commonly
diagnosed in large or giant breed dogs, especially the
St. Bernard, while it seems to be an unusual occurrence
in small breed dogs (Roush, 1993; Hayes et al., 1994;
LaFond et al., 2002; L’Eplattenier and Montavon,
2002; Harasen, 2006). In a recent study, which
evaluated retrospectively 65 dogs of all breeds with
LPL, medium and large breed dogs were more affected;
and less than 10% (6/65) of all dogs were small breed
dogs (Kalff et al., 2014).
The purpose of this paper is to describe clinical
presentation, radiographic findings, management and
outcome of 9 small breed dogs with a diagnosis of LPL.
Materials and Methods
Medical records of small breed dogs with confirmed
diagnosis of LPL admitted to the Veterinary Teaching
Hospital at the University of Napoli (2010–2014) were
identified. According to Kennel Club standards for
weight, dogs with a physical weight less than 9 kg were
considered small breed (Priester, 1972; Hayes et al.,
1994; Bound et al., 2009). Data collection included:
breed, age, sex, weight, grade of PL, as well as if
unilateral or bilateral, and concurrent cranial cruciate
ligament (CrCL) lesion. Grade of PL was determined
by referencing the description of PL to a simplified
grading system by Roush (1993). Grade I: Patella can
be manually luxated but returns to normal position
when released. Grade II: Patella luxates with stifle
flexion or on manual manipulation and remains luxated
until stifle extension or manual replacement occurs.
Grade III: Patella luxated continually, and can be
manually replaced but will reluxate spontaneously
when manual pressure is removed. Grade IV: Patella
luxated continually and cannot be manually replaced.
Orthopedic examination consisted in gait evaluation by
visual inspection, joint flexion-extension movements
and range of motion evaluation, and grade of PL.
Radiographic images in both medio-lateral and cranio-
caudal projections were taken. All dogs were treated
surgically and were evaluated at clinical follow-up.
Surgery
All surgical procedures were executed throughout a
cranio-medial, parapatellar, incision to the stifle joint.
The surgical techniques used in dogs with LPL were
grouped in soft tissue procedures (STP) and osseous
procedures (medial tibial tuberosity transposition
[TTT]; femoral recession trochleoplasty or
chondroplasty). The soft tissue techniques included
lateral retinacular release and medial imbrication
(Roush, 1993); the deep fascia was released laterally
and imbricated medially in order to produce slight
medial tension. The osseous procedures included TTT,
femoral recession trochleoplasty (TP) or chondroplasty
(CP). TTT consisted in osteotomy of the tuberosity with
intact distal attachment; tibial crest was then moved
medially a sufficient distance to provide straight
alignment of the quadriceps mechanism and was
stabilized with two Kirschner wires (0.8 to 1.5 mm;
Alcyon Italia S.p.A., Italy) without using tension band

http://www.openveterinaryjournal.com
F. Di Dona et al. Open Veterinary Journal, (2016), Vol. 6(3): 255-258
________________________________________________________________________________________________________
256
fixation. Femoral recession trochleoplasty was
performed when the trochlear sulcus was shallow or
absent; trochlear block recession was performed
through elevating an osteochondral block from the
patellar groove, removing bone from the bottom of the
incised block to deepen the sulcus, and then replace the
osteochondral block (Priester, 1972; Bound et al.,
2009). In young dogs (less than 8 months)
chondroplasty was performed by elevating the hyaline
cartilage and removing subcondral bone beneath the
cartilage flap (Roush, 1993). The adjunctive surgical
technique used in dogs with concurrent CrCL injury
consisted in the medial and lateral fabellae suturing
(FS) (DeAngelis and Lau, 1970; Shaver et al., 2014).
Two unilateral-session surgeries were performed in
dogs bilaterally affected.
Pre- and post-operative care
All dogs were premedicated with intramuscular
administration of methadone (0.3 mg/kg; Eptadone: L.
Molteni & C. S.p.A., Italy) or morphine (0.4 mg/kg;
Morfina cloridrato: L. Molteni & C. S.p.A., Italy) and
dexmedetomidine (5μg/kg; Dexdomitor: Vetoquinol
Italia S.r.l., Italy). Intravenous administration of
propofol (4-6 mg/kg; Propovet: Esteve S.p.A., Italy)
was used to induce anesthesia, then maintained via
gaseous mixture of oxygen and isoflurane (Isoflurane
Vet: Merial Italia S.p.A., Italy). Peripheral sciatic and
femoral nerve block with lidocaine (2 mg/kg; Lidocaina
Cloridrato: A.T.I. S.r.l., Italy) was obtained.
Perioperative antibiotic therapy included intravenous
administration of cephazolin (22 mg/kg; Cefazolina
Teva: Teva Italia S.r.l., Italy). Postoperative analgesia
included intramuscular administration of methadone
(0.3 mg/kg; Eptadone: L. Molteni & C. S.p.A., Italy) as
required for up to 48h and either carprofen (2 mg/kg
SID; Rimadyl: Pfizer Italia S.r.l., Italy) or firocoxib (5
mg/kg SID; Previcox: Merial Italia S.p.A., Italy) for 6
to 10 days following surgery. Dogs were dismissed
from the hospital 24-48h following surgery.
Outcome and Complications
Clinical follow was performed for each dog at 7 and 14
days, then at 4 to 12 weeks following surgery, and
thereafter by telephone interview. The outcome of
surgical correction was classified, according to dogs’
status, in: excellent (no gait abnormality), good (mild
or intermittent gait abnormality), fair (moderate gait
abnormality), and poor (severe gait abnormality).
Frequency and type of postoperative complication
associated with LPL stabilization were registered. Dogs
that underwent a revision surgery were considered as
having a major complication. Whereas complication
did not required additional treatments were classified as
minor.
Statistical analysis
All statistical analyses were performed using
commercial software (Prism GraphPad Software, Inc,
USA). Descriptive statistics were calculated and data
were reported as median and range. Categorical data
were expressed as frequencies. Statistical power was
inadequate to compare outcome measures or incidence
of complications with signalment or surgical variables.
Results and Discussion
Of the one hundred thirty-seven dogs with a diagnosis
of PL in the reference period, LPL was present in
fourteen dogs. However only nine of them met the
inclusion criteria and were classified as small breed
dogs. Seven dogs were female (one neutered) and the
remaining two were intact male. Dogs ranged in age
from 5 to 132 months (median = 18 months). Body
weight ranged from 1.3 to 8.8 kg (median = 4 kg). The
following breed were registered: Poodle (n=3),
Pinscher (n=2), Pekingese, Yorkshire, Cavalier King
Charles Spaniel and mixed-breed. Five dogs had a
diagnosis of grade III luxation and one of them was
bilaterally affected. The remaining four dogs were
equally affected with grade I and II luxation, whereas
none of the dogs had a diagnosis of a grade IV luxation.
One dog had a history of vehicular trauma, while
another one experienced an acute lameness due to a
CrCL injury.
Surgical correction was performed in 10 stifles and
consisted in TTT and STP for all the dogs included.
Two dogs received adjunctive chondroplasty because
of their young age, whereas in other three dogs, the
deepening of the trochlear groove was obtained through
a block recession trochleoplasty. One dog was managed
in a single session surgery for both LPL and CrCL
injury, through medial TTT and subsequently FS.
Major complications were observed only in two dogs
that experienced a lateral reluxation, and were managed
with a second soft tissue procedure to improve medial
tension. Two dogs had implant migration and
concomitant seroma, and were considered as having a
minor complication. Follow-up was performed for all
dogs. Four dogs with five stifles treated were classified
as having excellent outcome; three dogs as having good
outcome; and two dogs as having fair outcome. These
last two dogs with moderate gait abnormalities at last
examination were both affected by concurrent injuries
(CrCL injury; aftereffects of a pelvic trauma) (Table 1).
PL is a common stifle disorder in dogs, and MPL occurs
more frequently than does LPL, especially in small
breed dogs (Nunamaker, 1985; Vasseur, 2003; Shaver
et al., 2014).
The clinical picture of the population referred to our
hospital is dominated by MPL, while LPL occurred in
10.2% of the dogs. According to the literature, lateral
dislocation has been observed approximately in 5% to
12% of dogs with PL, however, this was increased in
large and giant breed dogs to reach 17% to 33% (Hayes
et al., 1994; Arthurs and Langley-Hobbs, 2006; Alam
et al., 2007; Shaver et al., 2014).

http://www.openveterinaryjournal.com
F. Di Dona et al. Open Veterinary Journal, (2016), Vol. 6(3): 255-258
________________________________________________________________________________________________________
257
Table 1. Distribution of lateral patellar luxation. Surgical management, complications, and outcome.
Cases
Breed
Sex
Age
(months)
Weight
(kg)
Grade
CrCL
Surgery
Complications
Outcome
1*
Poodle
F
5
2.2
3
TTT, STP, CP
excellent
2
Poodle
F**
36
3
3
TTT, STP, TP
Seroma; implant migration
good
3
Poodle
F
7
5.2
3
TTT, STP, CP
excellent
4
Cavalier King
Charles Spaniel
M
48
7.9
1
Yes
TTT, STP, FS
Seroma; implant migration
fair
5
Mixed-breed
M
36
8.8
1
TTT, STP
excellent
6
Pekingese
F
84
6.8
2
TTT, STP
excellent
7
Pinscher
F
132
2.3
3
TTT, STP, TP
Reluxation
fair
8
Pinscher
F
12
4
2
TTT, STP
good
9
Yorkshire
F
18
1.3
3
TTT, STP, TP
Reluxation
Good
(TTT): Tibial tuberosity transposition; (STP): Soft tissue procedure; (CP): Condroplasty; (TP): Throcleoplasty; (FS): Fabellar suture.
* With bilateral patellar luxation. ** Neutered.
Most of dogs included were young at the time of
examination, which is consistent with previous reports
(Hayes et al., 1994; Arthurs and Langley-Hobbs, 2006;
Kalff et al., 2014; Shaver et al., 2014). The young age
was frequently associated to grade III or IV of lateral
luxation due to congenital reasons as a result of under-
development of the trochlear groove. However, the
disease may be diagnosed in older dogs, as low-grade
luxations are usually asymptomatic in early stages
(Kalff et al., 2014).
Surgical treatment was advised for all dogs with a
diagnosis of PL. TTT may be the most important
component of surgical treatment for dogs with PL since
quadriceps malalignment is a key feature in the
development of all grades of PL (Robins, 1990). A
previous study evaluated the effect of the sole TTT
without trochlear groove deepening in 91 dogs with
MPL, and concluded that trochlear groove deepening
procedures are not always necessary, and patients that
undergo these techniques should be carefully selected
(Linney et al., 2011). Dog included in this report
received adjunctive trochlear groove deepening when a
clinical and radiographic evidence of shallow groove
was observed.
Complications after surgical treatment of LPL have
been previously reported, however one of the major
limitation was the highly variable nature of surgical
correction of LPL, which made impossible to draw
conclusions about the effect of specific treatments
(Shaver et al., 2014). The population reported here was
managed with the same techniques (TTT and STP),
with adjunctive procedures as needing, and our results
support the effectiveness of the procedure that can
result in definitive stabilization of the patella in its
trochlear groove.
In the present case series, reluxation is the most
important complication after surgical correction and
occurred in 20% of stifle joints treated. Arthurs and
Langley-Hobbs (2006) and Shaver et al. (2014) found
respectively that 17% and 21.3% of stifle joints with
LPL have reluxated, and this data is comparable with
the percentage reported here. Kalff et al. (2014),
accounting this complication in 6/65 of the dogs
treated, reported the lower incidence of lateral
reluxation. Minor complications included the migration
of the pins and the following development of a seroma,
and were easily managed through pins removal. Even
though pin migration requires a minor surgical
procedure for removing the Kirschner wires, it has been
classified as minor complication (Kalff et al., 2014).
Previous studies detected a correlation between body
weight and a higher risk of complications and
reluxation after corrective surgery (Arthurs and
Langley-Hobbs, 2006; Gibbons et al., 2006; Cashmore
et al., 2014). Because the dogs included are
lightweight, probably stresses on stifle joints are lower,
and the response to surgery may be better; furthermore
the young age of affected dogs may play a central role
in better recovery, due to the great tendency of tissues
to have fast healing, and also for the absence of chronic
degenerative joint lesions.
Shaver et al. (2014) stated that bilateral surgery during
a single session was the only variable significantly
associated with reluxation, accounting odds of
reluxation 12.5 times higher than dogs that had
unilateral surgery. We cannot confirm this data as most
of the dogs were unilaterally affected, and the only one
dog with a bilateral luxation was managed in double
session surgery. Moreover, the limited number of stifles
studied is a main limitation. Wangdee et al. (2013)
evaluating the surgical management of MPL in
Pomeranian dogs, established that grade II luxation had
good outcome with a 100% success rate following
surgery. Dogs with grade III luxation had recurrent PL
in about 11% of the stifle joints treated; while dogs with
grade IV luxation had higher rate of reluxation,
accounting 36% of the dogs subjected to surgery,
because varying degree of skeletal deformities.

http://www.openveterinaryjournal.com
F. Di Dona et al. Open Veterinary Journal, (2016), Vol. 6(3): 255-258
________________________________________________________________________________________________________
258
Most of the dogs included in this sample had positive
outcome. Whereas our hypothesis about the two dogs
that experienced fair outcome is that it may be more
linked to the concurrent CrCL and pelvic injuries than
to the PL.
The knowledge about LPL in the dog is still limited.
The present report suggests that small breed dogs seems
to be affected as well as medium, large and giant breed
dogs. It can be concluded that previous studies analyzed
populations with different prevalence of each breed and
data obtained cannot be compared, LPL is a growing
disease in small breed dogs and that LPL in small breed
dogs is underestimated.
___________________________________________
References
Alam, M.R., Lee, J.I., Kang, H.S., Kim, I.S., Park, S.Y.,
Lee, K.C. and Kim, N.S. 2007. Frequency and
distribution of patellar luxation in dogs. 134 cases
(2000 to 2005). Vet. Comp. Orthop. Traumatol. 20,
59-64.
Arthurs, G.I. and Langley-Hobbs, S.J. 2006.
Complications associated with corrective surgery
for patellar luxation in 109 dogs. Vet. Surg. 35, 559-
566.
Bound, N., Zakai, D., Butterworth, S.J. and Pead, M.
2009. The prevalence of canine patellar luxation in
three centres. Clinical features and radiographic
evidence of limb deviation. Vet. Comp. Orthop.
Traumatol. 22, 32-37.
Cashmore, R.G., Havlicek, M., Perkins, N.R., James,
D.R., Fearnside, S.M., Marchevsky, A.M. and
Black, A.P. 2014. Major complications and risk
factors associated with surgical correction of
congenital medial patellar luxation in 124 dogs.
Vet. Comp. Orthop. Traumatol. 27, 263-270.
DeAngelis, M. 1996. Patellar luxation in dogs. Vet.
Clin. North Am. Small Anim. Pract. 1, 403-415.
DeAngelis, M. and Lau, R.E. 1970. A lateral retinacular
imbrication technique for the surgical correction of
anterior cruciate ligament rupture in the dog. J. Am.
Vet. Med. Assoc. 157, 79-84.
Gibbons, S.E., Macias, C., Tonzing, M.A., Pinchbeck,
G.L. and McKee, W.M. 2006. Patellar luxation in
70 large breed dogs. J. Small Anim. Pract. 47, 3-9.
Harasen, G. 2006. Patellar luxation: Pathogenesis and
surgical correction. Can. Vet. J. 47, 1037-1039.
Hayes, A.G., Boudrieau, R.J. and Hungerford, L.L.
1994. Frequency and distribution of medial and
lateral patellar luxation in dogs: 124 cases (1982-
1992). J. Am. Vet. Med. Assoc. 205, 716-720.
Kalff, S., Butterworth, S.J., Miller, A., Keeley, B.,
Baines, S. and McKee, W.M. 2014. Lateral patellar
luxation in dogs: a retrospective study of 65 dogs.
Vet. Comp. Orthop. Traumatol. 27, 130-134.
LaFond, E., Breur, G.J. and Austin, C.C. 2002. Breed
susceptibility for developmental orthopedic
diseases in dogs. J. Am. Anim. Hosp. Assoc. 38,
467-477.
L'Eplattenier, H.F. and Montavon, P. 2002. Patellar
luxation in dogs and cats: management and
prevention. Comp. Cont. Edu. Pract. Vet. 24, 292-
300.
Linney, W.R., Hammer, D.L. and Shott, S. 2011.
Surgical treatment of medial patellar luxation
without femoral trochlear groove deepening
procedures in dogs: 91 cases (1998– 2009). J. Am.
Vet. Med. Assoc. 238, 1168-1172.
Ness, M.G., Abercromby, R.H., May, C., Turner, B.M.
and Carmichael, S. 1996. A survey of orthopaedic
conditions in small animal veterinary practice in
Britain. Vet. Comp. Orthop. Traumatol. 9, 43-52.
Nunamaker, D.M. 1985. Patellar luxation. In Textbook
of Small Animal Orthopaedics, Eds., Newton, C.D.
and Nunamaker, D.M.: Lippincott, Philadelphia,
pp: 941-947.
Priester, W.A. 1972. Sex, size, and breed as risk factors
in canine patellar luxation. J. Am. Vet. Med. Assoc.
4, 633-636.
Robins, G.M. 1990. The canine stifle joint. In Canine
Orthopedics, Ed., Whittick, W.G.: Lea and Febiger,
Philadelphia, pp: 693-760.
Roush, J.K. 1993. Canine patellar luxation. Vet. Clin.
North Am. Small Anim. Pract. 23, 855-868.
Shaver, S.L., Mayhew, K.N., Sutton, J.S., Mayhew,
P.D., Runge, J.J., Brown, D.C. and Kass, P.H. 2014.
Complications after corrective surgery for lateral
patellar luxation in dogs: 36 cases (2000–2011). J.
Am. Vet. Med. Assoc. 244, 444-448.
Vasseur, P.B. 2003. Stifle joint. In Textbook of Small
Animal Surgery, Ed., Slatter, D.S.: Saunders,
Philadelphia, pp: 2090-2133.
Wangdee, C., Theyse, L.F.H., Techakumphu, M.,
Soontornvipart, K. and Hazewinkel, H.A. 2013.
Evaluation of surgical treatment of medial patellar
luxation in Pomeranian dogs. Vet. Comp. Orthop.
Traumatol. 26, 435-439.