Keywords
tibial plateau slope - epiphysiodesis - growing dogs - Salter–Harris II fracture
Introduction
Fractures of the proximal tibia are identified in about 7% of all canine tibial fractures.[1]
[2]
[3]
[4] Avulsion of the tibial tuberosity and Salter–Harris type I or II fractures of the
proximal physis are the most reported in immature dogs.[1]
[2]
[3] Avulsion of the tibial tuberosity may occur either independently or in association
with fracture-separation of the tibial epiphysis. Incidence reported in the literature
varies from rare to common.[5]
[6]
[7]
[8] Small breed dogs, particularly terriers, seem predisposed to the latter.[5]
[7]
[8]
[9]
[10] This association of fractures has been reported in dogs aged between 3.5 and 8 months.[7]
[9]
[10] The typical distocaudal displacement of the proximal segment is of concern as it
is accompanied by subsequent increased tibial plateau angle. This predisposes to increased
stress on the cranial cruciate ligament, possibly leading to its rupture.[11]
Currently, there are several ways to manage proximal tibial epiphyseal fractures in
puppies. Kirschner wires with or without tension band are mostly used,[7]
[8] reduction and fixation being performed either by open technique or percutaneously.[12]
[13]
Proximal tibial epiphysiodesis has been described as a therapy for growing dogs with
cranial cruciate ligament deficient stifles. It aims at closing the cranial part of
the proximal tibial physis with a cancellous screw.[14]
[15] This case report describes a hitherto unreported use of proximal tibial epiphysiodesis
as mini-invasive treatment of a displaced Salter–Harris II proximal tibial fracture,
associated with a tibial tuberosity avulsion, in a puppy.
Clinical Report
A 13.8-kg, 4.5-month-old, female, Airedale Terrier was presented with a right hindlimb
lameness after trauma while playing with another dog, 10 days earlier. Faced with
no improvement after conservative management, the dog was referred at the ‘Clinique
Vétérinaire Universitaire of Liège University’. General physical examination and neurological
assessment were within normal limits. A numerical lameness scale (0–5), as previously
described, was utilized.[16] Orthopaedic examination revealed a severe weight-bearing lameness (⅘). In comparison
with the contralateral thigh, low-grade amyotrophy of the right thigh was present.
Deep static pressure caused pain at the level of the tibial crest, but no crepitation
could be elicited upon stifle mobilization. Direct and indirect drawer signs were
negative. Patella was in normal position and stable within the trochlea. Radiographs
of the affected stifle joint revealed soft tissue swelling cranial to the right tibial
tuberosity and a Salter–Harris type II fracture of the right tibial proximal epiphysis
associated with tibial tuberosity avulsion. The tibial plateau and tibial tuberosity
were displaced as a single block, with the first being caudodistally tilted and the
latest cranioproximally elevated with the presence of several mineralized nuclei distal
to it ([Fig. 1]). The tibial plateau angle was 40°. It was measured on the mediolateral view according
to the method described by Slocum.[17]
Sedation was obtained with methadone (0.2 mg/kg, intravenous [IV]) and midazolam (0.2
mg/kg, IV). Anaesthesia was induced with propofol (2–6 mg/kg, IV) given to effect
and maintained with isoflurane. A peridural locoregional analgesia was performed (morphine
0.2 mg/kg and levobupivacaine 1 mg/kg).
The surgical procedure was based on the one described by Vezzoni and colleagues.[14] The lateral skin incision extended from slightly distally to the patella to the
tibial tuberosity. The patellar ligament was reclined medially to allow, under a fluoroscopic
guidance, the intra-articular insertion of a 32 mm × 3.5 mm cancellous screw in a
positional mode. The desired point of insertion was the mediolateral centre of the
most proximal part of the tibial plateau. The joint was lavaged with saline. The surgical
wound was routinely closed. Postoperative radiographs confirmed appropriate placement
of the screw. Immediate postoperative tibial plateau angle was 36° ([Fig. 2]).
Cephalexin was administered 20 mg/kg perioperatively, methadone 0.2 mg/kg every 4
hours 24 hours postoperatively and carprofen 2 mg/kg twice a day for 5 days. Cold
packs were applied on the stifle four to six times a day for 5 minutes for 4 days.
The dog was discharged from the hospital the day after surgery with a 5-day carprofen
2 mg/kg twice a day and 3-day tramadol 2 mg/kg twice a day prescription. Strict exercise
restriction was recommended until re-evaluation.
At recheck 3 weeks postoperatively, owners mentioned a decrease in the lameness at
home. The dog still presented a stiff gait and a mild right hindlimb lameness (⅖)
but no stifle pain. Direct and indirect drawer signs remained negative. Radiographs
revealed patellar ligament thickening and joint swelling. Ongoing bone healing of
tibial tuberosity fracture was present. Tibial plateau angle was 32°. Leash walking
and passive mobilization of the right stifle were advocated.
Six-week postoperative follow-up revealed a dog free of lameness, pain-free mobilization
of the stifle, normal range of motion and negative drawer signs. Healing of the tibial
tuberosity avulsion fracture was progressing well on radiographs. Tibial plateau angle
was 21°. The dog was re-evaluated 12 weeks after surgery. The tibial tuberosity growth
plate was nearly closed on radiographs. Tibial plateau angle was 9°.
Last follow-up evaluation was performed 8 months postoperatively. The dog presented
no lameness, and thighs' muscle masses were symmetrical. The operated stifle was stable
and pain-free upon manipulation. Radiographs showed complete healing of the tibial
tuberosity avulsion fracture and full closure of the tibial plateau growth plate.
The screw head was covered by smooth, regular, new formed bone. The proximal tibia
exhibited a tibial plateau caudally displaced, creating an overhang. There were no
radiographical signs of osteoarthritis. Final tibial plateau angle was 7° ([Fig. 3]). At telephone follow-up 18 months postoperatively, owners reported sustained and
full functional recovery of the dog.
Discussion
This report illustrates the use of the proximal tibial epiphysiodesis as described
by Vezzoni and colleagues[14] for the successful treatment of a proximal tibial Salter–Harris type II fracture
associated with avulsion of the tibial tuberosity in a 4.5-month-old Airedale Terrier.
Reduction and stabilization of a proximal tibial physeal fracture can be challenging,
and several ways of treatment have been proposed.[7]
[8]
[12]
[13]
[18]
Our elected method of treatment was based on the combination of several fracture features;
that is, displacement of the fragments with a 40° tibial plateau angle, undisrupted
connection between tibial plateau and tuberosity, a growing patient, a 10-day period
of time elapsed since the fracture occurrence, leading to a rather good stability
of the fracture site. An attempt to reduce the tibial tuberosity would have disrupted
soft tissues and early callus. Since the displacement was moderate, no functional
handicap was expected. Non-surgical management is usually recommended as the initial
treatment for dogs with minimally displaced tibial tuberosity avulsion fracture.[19]
The difference between pre- and immediate postoperative tibial plateau angles may
be explained by the fact that although the screw was initially inserted in a neutral
mode, it must have slightly displaced the tibial plateau in relation with the proximal
tibial metaphysis.
Proximal tibial epiphysiodesis is a mini-invasive technique described by Vezzoni and
colleagues[14] to treat puppies affected by cranial cruciate ligament deficiency. The screw inserted
in the centre of the cranial part of the tibial plateau arrests the cranial part of
the tibial plateau growth. Consequently, the tibial plateau slope progressively decreases
during the residual growth. Alternatively, proximal tibial epiphysiodesis by electrocauterization
has been recently described.[20]
[21] This procedure is thought to be less invasive than the screw technique, with a lower
morbidity. It seems to provide the same final tibial plateau angle in a shorter time.[21] However, we considered it non-applicable in our case as electrocauterizing the early
callus could have affected the fracture healing process. Moreover, the screw contributed
to the maintenance of reduction, and added stability.
We acknowledge the fact that using one single position screw to stabilize a type II
Salter–Harris proximal tibial fracture might be seen as risky. When proposed by Vezzoni
and colleagues,[14] the epiphyseal screw had no role of stabilization and was only placed to prevent
further growth of the cranial tibial plateau. We were not able to quantify, on one
hand, the shear force that could be applied to the tibial plateau and, on the other,
the shear strength of one 3.5 mm cancellous screw. Although guidelines for evaluating
mechanical properties of implants are provided by the American Society for Testing
and Materials, realistic clinical conditions evolving complex cortical geometry, cancellous
architecture or bone properties cannot be fully duplicated.[22] We nevertheless assumed that due to the 10-day period of time elapsed between the
fracture and the surgical treatment, and given the very young age of the patient,
some fibrous callus had already developed, hence some stability was already regained,
mimicking more closely the use of one epiphysiodesis position screw, as previously
described.
As mentioned by Vezzoni and colleagues,[14] screw removal may be required in very young dogs. Occurrence of physis closure is
in fact individual and breed related. The potential of remaining growth should be
evaluated by looking at the physis width on pre- and post-op radiographs.[14]
[15] A radiographical follow-up allows monitoring of the decreasing tibial slope. In
case of overcorrection, the screw should be removed before the end of the growth phase.
No screw removal was necessary in our case. Our final tibial plateau angle was 7°,
an optimal result to prevent excessive strain on the cranial cruciate ligament, according
to in vitro experimental testing.[23]
Radiographical follow-up is recommended for early diagnosis of angulation deformities
secondary to epiphysiodesis screw insertion. Physeal closure can be symmetrical or
asymmetrical.[24] Angulation deformities have been found to be more frequent with a medial than with
a lateral approach.[14] Hence, our choice for a lateral approach with no final angulation observed. Screw
position is essential, and the use of intraoperative fluoroscopy or radiographs is
highly recommended. Despite a slight eccentricity of the screw observed on the postoperative
radiograph, we could not detect any adverse consequence throughout the follow-up period.
No radiographical signs of osteoarthritis appeared during the growth of the dog. This
highlights a major advantage of the mini-invasive procedure and suggests a stable
knee joint and a cranial cruciate ligament integrity over time.
The noticeable increase in caudal overhang of the proximal tibial epiphysis is probably
due to the proximal tibial plateau pivoting around the screw insertion point. This
is also noticeable on the cases described by Vezzoni and colleagues,[14] yet not reported previously.
To our knowledge, this is the first documented case of epiphysiodesis to treat a displaced
proximal tibial physeal fracture in a growing dog. Thus, this is another indication
of this technique, which, in this case, yielded excellent long-term outcome. As overcorrection
could be a possible complication, radiographic follow-up is essential, allowing to
decide whether and when screw removal may be required.
Based on this report, authors believe that epiphysiodesis has its place in the treatment
arsenal of sub-acute, moderately displaced, Salter–Harris I or II proximal tibial
fractures. Further cases are needed to demonstrate the efficiency of a single screw
epiphysiodesis in the treatment of various types of proximal metaphyseal tibial fractures.
Fig. 1 Preoperative radiographs showing a moderately displaced Salter–Harris II fracture
of the right tibial proximal epiphysis associated with tibial tuberosity avulsion.
Fig. 2 Immediate postoperative radiographs showing adequate screw position.
Fig. 3 Bilateral follow-up radiograph 8 months after surgery. (A) Operated side: No signs of osteoarthritis are visible. The final plateau angle is
7° with caudal overhang of the proximal tibial epiphysis. (B) Contralateral side without overhang of the proximal tibial epiphysis.
