DOCSLIB.ORG

Patellar Luxation in Dogs

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Patellar Luxation in Dogs VETcpd - Orthopaedics Peer Reviewed Patellar luxation in dogs Part 2: Treatment Surgical treatments for patellar luxation may be broadly categorised into those which reduce the ease with which the patella can exit the trochlear groove, and those which aim to realign the quadriceps mechanism. A number of techniques may be performed to increase the depth of the trochlear groove and implants have become available in recent years to increase the height of the trochlear ridges. Soft tissue release (medially) and imbrication (laterally) may be relied upon, only temporarily, to stabilise a luxating patella. Realignment of the quadriceps mechanism can be performed by moving the insertion of the musculo-tendinous unit (i.e. tibial tuberosity transposition) or anti-rotational suture placement. More advanced procedures to address femoral and tibial deformities may also be considered for certain cases. Phil Witte Key words: Orthopaedics, patella, patellar luxation, quadriceps muscles, surgery BSc BVSc CertAVP(GSAS) DSAS(Orth) MRCVS deepening. Arthurs and Langley-Hobbs RCVS Specialist in Small Introduction In the previous article the (2006) suggested that the frequency of Animal Surgery (Orthopaedics) author discussed the diag- re-luxation was greater without groove Philip graduated from the University of nosis of patellar luxation deepening, Linney et al. (2011) demon- Bristol in 2005. He cut his teeth with and its aetiology, with an strated a reluxation rate of 19.8% without two years in rural mixed practice prior emphasis on the influence groove deepening and Cashmore et al. to a six month stint working with Cape ©istockphoto.com of hind limb anatomy (2014) recognised a 5.1 fold reduction in buffalo in Phalaborwa, South Africa. on quadriceps mechanism alignment. In the rate of patellar luxation with groove He completed a surgical internship in this article the options for management deepening. Groove deepening in the 2009 and an orthopaedic residency at and the reported complications following absence of consideration of quadriceps Southern Counties Veterinary Specialists surgical intervention are discussed. realignment was reported in 46 stifles in a in 2013. He completed the RCVS study of Pomeranians in which 2/46 had Certificate in Advanced Veterinary Surgical treatment options recurrence of luxation within a relatively Practice in September 2013 and the Surgical stabilisation of the femoro- short period of follow-up of 16 weeks RCVS Diploma in Small Animal Surgery patellar joint should restore: (Wangdee et al. 2013). There are a few (Orthopaedics) in 2018. His interests • quadriceps function techniques for increasing trochlear groove include angular limb deformity correction depth and an increasing array of techniques and complex fracture management. (to improve limb function) for realigning the quadriceps mechanism. E: [email protected] • femoro-patellar loading (theoretically slowing the rate of To complete an evidence-based discussion progression of osteoarthritis) of treatment of PL, it should be noted that there is limited evidence that resolution Patellar luxation (PL) is a mechanical of PL has a meaningful influence on the problem with mechanical solutions. A progression of osteoarthritis, although this number of techniques and subsequent would seem intuitive. In fact, in a study of modifications have been proposed. 12 dogs with bilateral PL and unilateral Broadly, these can be divided into surgery, osteoarthritis, as detected radio- procedures that: graphically, had progressed symmetrically a 1. Reduce the ease with which the mean of 33 months following intervention patella can luxate (often involving (Roy et al. 1992). Of course, in that deepening of the trochlear groove) study the more severely affected limb was presumably selected for surgical stabilisa- Or tion, inducing bias in the interpretation of 2. Realign the quadriceps mechanism. the results. Arguably, the latter consideration is of No matter the techniques employed greater importance, however, there is suf- during surgery, the author would empha- ficient evidence to suggest that groove sise that surgeons should never finish a deepening remains an important factor surgery and perform a closure on a PL case SUBSCRIBE TO VETCPD JOURNAL in achieving a stable patella. Three studies in which the patella is not 100% stable. If document patellar luxation surgery in the patella is not stable through a full range Call us on 01225 445561 which tibial tuberosity transposition was of stifle motion on the table, the soft tissue or visit www.vetcpd.co.uk performed (to realign the quadriceps closure cannot be relied upon to prevent mechanism) with or without groove reluxation during convalescence. Page 36 - VETcpd - Vol 6 - Issue 2 VETcpd - Orthopaedics Increasing resistance of two osteotomies (a wedge of triangu- • Wangdee et al. (2015) reported a wedge to patellar luxation lar cross-section) whilst the rectangular recession which was extended proxi- Also termed ‘trochleoplasty’, a few tech- block consists of two parallel osteotomies mally as an excisional trochleoplasty in niques have been described to deepen the connected by a third osteotomy made seven Pomeranian dogs with bidirec- trochlear groove, effectively increasing the deep to the groove using an osteotome tional instability (luxation to either side resistance to luxation of the patella. Groove (Figure 2). Wedges and blocks do not of the groove). deepening has classically been performed require internal fixation, but instead rely • Kite-shield shaped wedge recession by recession of the trochlear groove (see on the frictional interface between the (Katayama et al. 2016) was reported in description below), to effectively elevate two surfaces of cancellous bone and the seven toy breed dogs (10 procedures). the trochlear ridges. More recent innova- compressive force associated with the The technique was called ‘K-wedge’ tions include permanent implants to raise reduced patella. In the case of the rectan- and consists of a wedge in the usual or replace the trochlear ridges. Soft tissue gular block recession trochleoplasty, small position with a third osteotomy made Figure 4: RidgeStop™ is a medical grade, ultra high slivers of bone may be wedged between molecular weight, polyethylene implant fixed in position techniques may aid patellar stabilisation 1A in a dorsal plane at the proximal extent with two or more screws (depending on the size of the and are also mentioned. the block and the trochlear ridge to of the groove to meet the wedge. The implant) to augment the trochlear ridge and reduce the Tibial tuberosity Patella Intercondylar notch Elevated flap of articular increase frictional stability. Johnson et al. resulting wedge/block is removed and ease with which the patella can luxate Abrasion or excisional cartilage with distal base (2001) performed ex vivo experiments recessed. In the study the K-wedge was trochleoplasty involves removal of to show that block recession (initially combined with anti-rotation sutures articular cartilage and subchondral bone, described by Talcott et al. 2000) was (see below) or tibial tuberosity trans- often using a cylindrical file. With this superior to wedge recession in terms position and re-luxation was present technique, the surface on which the patel- of deepening the groove at its proximal (grade I from a grade 3 pre-op) in 1/10. la articulates following healing is likely to extent and improving patellar stabil- • Medial ridge elevation trochleoplasty consist of fibrous and fibrocartilaginous ity with the stifle in extension (when (Fujii et al. 2013) was reported in five material with the potential for ongoing the patella is positioned at the proximal dogs (six stifles) with grade 3 medial retropatellar abrasion and discomfort. extent of the groove). For this reason, the patellar luxation. This technique aims Attempts to resurface the abraded trochlea author prefers rectangular block reces- not to recess the groove, but to elevate with free autogenous periosteal grafts 1B 1C sion (Figure 3). Bone union of a trochlear the medial trochlear ridge by rotating were met with poor results (Hulse et al. wedge was documented from eight weeks o an asymmetrical wedge through 180 . Figure 5: Intra-operative photograph of left 1986). Trochlear abrasion results in slower Figure 1: Chondroplasty performed in a five month old female entire Hungarian Puli with lateral patellar following surgery by Boone et al. (1983). luxation. (A) Articular cartilage is scored with a scalpel blade parallel with and just axial to the trochlear ridges. • Rotation of the entire femoral trochlea stifle and tibia following Kyon Patellar Groove rates of improvement in clinical function Complications specifically associated with The cartilage is elevated from the underlying bone (B) with the intact base of the flap proximal or distal (as has been reported for a single case of Replacement. The distal extent of the lateral in comparison with techniques which these techniques include migration of the femoral condyle and the intracondylar notch are in this case). Note that even in this young dog the articular cartilage is elevated with some subchondral grade 3 medial patellar luxation (Pinna preserve the articular cartilage (Boone et bone remaining adherent to the cartilage (i.e. the surgeon should not expect the articular cartilage to roll off triangular wedge during the early phase apparent distal to the prosthesis. (Distal is left) et al. 2008) in which the primary al. 1983). It is the author’s
Load more

Recommended publications
  • Luxating Patella
    LUXATING PATELLA What is a luxating patella? The patella, or kneecap, is normally located in the center of the knee joint. The term luxating means, “out of place” or “dislocated”. Therefore, a luxating patella is a kneecap that moves out of its normal location. What causes this? The muscles of the thigh attach to the top of the kneecap. There is a ligament, the patellar ligament, running from the bottom of the kneecap to a point on the tibia just below the knee joint. When the thigh muscles contract, force is transmitted through the patella and patellar ligament to a point on the top of the tibia. This results in extension or straightening of the knee. The patella stays in the center of the leg because the point of attachment of the patellar ligament is on the midline and because the patella slides in a groove on the lower end of the femur (the bone between the knee and the hip). The patella luxates because the point of attachment of the patellar ligament is not on the midline of the tibia. It is almost always located too far medial (toward the middle of the body). As the thigh muscles contract, the force is pulled medial. After several months or years of this abnormal movement, the inner side of the groove in the femur wears down. Once the side of the groove wears down, the patella is then free to dislocate. When this occurs, the dog has difficulty bearing weight on the leg. It may learn how to kick the leg and snap the patella back into its normal location.
    [Show full text]
  • Lexique Des Pathologie Du Cheval
    Lexique du cheval, termes Vétérinaires : 1- Pathologies équines - termes de médecine vétérinaire A-C , Equine pathologies, veterinarian terms A-C Français - French - English - Anglais Deutsch - German - Französisch Allemand à vif raw une zone à vif, une plaie à vif a raw spot, a raw wound abattement exhaustion Niedergeschlagenheit abcédation abscessation abcès ; abscess ; die Eiterbeule, die abcès chaud (aigu), abcès froid ; hot (acute) abscess, cold abscess ; Eitergeschwulst l'abcès se collecte ("murit") the abscess matures. abcès de formation lente a slow forming abscess l'abcès s'est rompu the abscess has opened die Eiterbeule hat geöffnet abcès du sabot ; certains les hoof abscess ; hoof abscesses are classent en 4 types : abcès du doigt, of four types : Toe, Sole, Bar and de la sole, des barres et des talons. Heel abscess. abdomen abdoment abdomen aigu acute abdomen abdominal abdominal Bauch- des signes de douleurs abdominales signs of abdominal discomfort des symptômes abdominaux aigus acute abdominal symptoms abondant copious, profuse reichlich des sécrétions abondantes (plur) a copious secretion (sing) abrasion des dents : usure dental abrasion die Zahnabnutzung anormale des dents due à des see : dental wearing away ; dental facteurs mécaniques externes . A attrition différencier de l'usure dentaire ou attrition (cf). Voir auss nivellement acarien mite acide hyaluronique . Certains hyaluronate : some specialists vétérinaires traitent des lésions prone the intralesional hyaluronate tendineuses au stade chronique injection in tendons lesions (lésions persistant après deux mois remaining after 2 months of rest de repos et de traitement and conservative therapy. conservateur) par des injections Hyaluronate would act as an anti- locales d'acide hyaluronique, soit à inflammatory agent and would l'aveugle, soit sous guidage have a direct stimulatory effect on échographique.
    [Show full text]
  • Pelvic Limb Alignment in Small Breed Dogs: a Comparison Between Affected and Free Subjects from Medial Patellar Luxation
    Pelvic limb alignment in small breed dogs: a comparison between affected and free subjects from medial patellar luxation Matteo Olimpo*, Lisa Adele Piras & Bruno Peirone Struttura Didattica Speciale Veterinaria, L.go P. Braccini, 10095 Grugliasco (TO), Italy. * Corresponding author at: Struttura Didattica Speciale Veterinaria, L.go P. Braccini, 10095 Grugliasco (TO), Italy. Tel.: +39 011 6709061, e‑mail: [email protected]. Veterinaria Italiana 2015, 52 (1), 45-50. doi: 10.12834/VetIt.71.206.3 Accepted: 05.08.2015 | Available on line: 17.12.2015 LXVII Meeting of the Italian Society for Veterinary Sciences (SISVet) - Selected papers Keywords Summary Medial patellar luxation, Small breed dogs are 12 times more likely to develop medial patellar luxation (MPL) than Pelvic limb alignment, large breed dogs and breed predisposition has been reported. Many surgical techniques are Small breed dogs. available for correction of patellar luxation in dogs. However, recent studies reported an 8% incidence of reluxation when traditional techniques are used. The relatively high frequency of major complications and patellar reluxation may be partially caused by inadequate appreciation of the underlying skeletal deformity and subsequent incorrect selection and application of traditional techniques. The aims of this study were to report the normal values of the anatomic and mechanical joint angles of the femur and tibia in small breed dogs and to compare these data to a population of small breed dogs affected by different degrees of MPL. Normal values of the anatomic and mechanical angles of the femur are similar to the ones reported in literature in Pomeranian dogs. Normal values of the anatomic and mechanical angles of the tibia have been described for the first time.
    [Show full text]
  • Learning Outcomes Orthopaedics Spring 2013 the Course In
    Learning outcomes Orthopaedics and Hand Surgery Page1 Learning outcomes Orthopaedics Spring 2013 The course in orthopaedics provides students with the fundamental principles for diagnosis and treatment of the diseases and injuries of the musculoskeletal system. The subjects treated in lectures, seminars and group exercises may be prioritised areas for review. The general learning outcomes of the course in orthopaedics are that students shall be able to approach patients in a professional manner obtain a relevant medical history of the patient’s complaint perform an appropriate examination of the musculoskeletal system have knowledge of common diagnostic tools draw up a plan of investigation for the most common diseases of the musculoskeletal system draw up a treatment plan in dialogue with the patient identify disorders that must be treated acutely to avoid a life-long disability On completion of the course, students shall be able to obtain the medical history and perform examination of diseases and injuries of the musculoskeletal system perform primary management, manual repositioning and immobilisation of the injured limb perform an appropriate distal examination make assessments for possible compartmental syndrome make assessments for possible cauda equina syndrome perform infiltration anaesthesia and skin sutures perform joint puncture identify obvious fractures or luxations without X-ray images On completion of the course, students shall demonstrate knowledge of the management principles for patients with multiple injuries the management
    [Show full text]
  • Diseases of the Goat
    Free ebooks ==> www.Ebook777.com www.Ebook777.com k Free ebooks ==> www.Ebook777.com k k www.Ebook777.com k k Diseases of the goat k k k k k k k k Free ebooks ==> www.Ebook777.com Diseases of the goat John Matthews BSc BVMS MRCVS Chalk Street Services Ltd, The Limes Chelmsford, Essex, UK 4TH EDITION k k www.Ebook777.com k k This edition first published 2016 © 2016 by John Wiley & Sons Limited Third edition first published 2009 © 2009 Blackwell Publishing Ltd Registered office: John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial offices: 9600 Garsington Road, Oxford, OX4 2DQ, UK The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK 1606 Golden Aspen Drive, Suites 103 and 104, Ames, Iowa 50010, USA For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Designations used by companies to distinguish their products are often claimed as trademarks.
    [Show full text]
  • Vi STEP by STEP
    Issue 6 t +44 (0)114 258 8530 [email protected] www.vetinst.com Academy Step by Step Patellar Luxation - A Step By Step Guide Patellar luxation is the condition where the patella luxates out of the femoral trochlear sulcus instead of tracking up and down within it. Most commonly the patella luxates medially but lateral luxation also occurs. It can occur in any size or breed of dog but is more common in small breed dogs. Cats have a broad and flat patella and the femoral trochlear sulcus is shallow; therefore the normal cat patella is much more mobile medial to lateral and relatively unstable compared to dogs. Patellar subluxation is common in cats but, clinically significant patellar luxation is uncommon. Patellar luxation is usually a diagnosis made from Grade 3: The patella is always luxated but the patient history and signalment, and by stifle can be returned to the normal position in the manipulation and palpation, rather than from trochlear sulcus by digital manipulation. Once radiographs. This is because the luxating patella such manipulation stops, patellar luxation recurs. is mobile and can change position which can be This causes an abnormality of stifle function i.e. easily palpated but not necessarily appreciated on a inability to extend the stifle and associated hindlimb radiograph. lameness. Surgical correction is beneficial to the Patellar luxation is graded depending on its severity patient as it restores normal stifle function including and there are many ways of doing this. The most the quadriceps ability to extend the stifle. commonly used grading system is the Putnam/ Grade 4: The patella is permanently luxated and Singleton system which can be described as: cannot be reduced to a normal position despite Grade 1: The patella tracks normally but luxates manipulation.
    [Show full text]
  • Alpaca Breed Standard
    British Alpaca Society - ALPACA BREED STANDARD Overview This breed standard has been developed to encourage the objective assessment of the form and function of the alpaca. It is intended as a guide for breeding selection, to promote the pursuit of the alpaca exhibiting high quality fleece traits on a correct frame. The ideal alpaca should not only be fit for function, but be seen as the embodiment of the very best conformational and fleece traits of the breed. An ideal alpaca is one that produces high quality fibre over a long, healthy and productive lifetime. Whilst the breed standard places traits into ‘ideal’ and ‘negative/undesirable traits’, most alpacas will fall somewhere between the two on the continuum of the different characteristics. However, the standard promotes the goal of reaching the ideal through selective breeding, resulting in genetic gain and phenotypical improvement. Consideration should be given to the longevity of the ideal traits and thus the commercial benefits that this brings. Note: Traits are not listed in any particular order - It is acknowledged that some traits, especially those of fleece, will continually improve over time and that this standard is not intended to be static, but to evolve alongside alpaca breeding in the UK. Ideal Negative/Undesirable traits Conformation Phenotype • Alpacas should have a balanced, • Obvious lack of balance proportioned frame, free moving, with a • Light substance of bone strong substance of bone and an alert • Narrow head stance • The head should be carried high Side Profile
    [Show full text]
  • Canine Patellar Luxation Part 2: Treatments and Outcomes
    Vet Times The website for the veterinary profession https://www.vettimes.co.uk Canine patellar luxation part 2: treatments and outcomes Author : Albane Fauron, Karen Perry Categories : Companion animal, Vets Date : April 18, 2016 ABSTRACT The most important decision in cases of canine patellar luxation is whether surgical stabilisation is required. Surgical treatment is generally not recommended for asymptomatic cases. For clinically affected cases, conservative management is unlikely to result in significant improvement and surgical therapy is indicated. Corrective surgical techniques focus on realignment of the quadriceps mechanism and stabilisation of the patella in the trochlea. Cases treated with tibial tuberosity transposition and femoral trochleoplasty have been associated with lower risks of patellar reluxation and major complications, and the use of these techniques should be considered in all developmental cases. In cases where significant skeletal deformities have been identified preoperatively, or in cases that fail to respond to conventional surgical techniques, more advanced imaging and surgery may be required. As discussed in part one (VT46.09), while patellar luxation (PL) is a common condition, not all cases require surgical intervention. Of those needing stabilisation, deciding which deformities require correction to achieve a comfortable and functional outcome is not always straightforward. Corrective surgical techniques used in the management of clinically affected cases focus on realignment of the quadriceps mechanism and stabilisation of the patella in the trochlea. The results of surgical correction vary with the severity of the anatomic abnormalities present, but if appropriate decision-making is employed, for the majority of cases, the outcome should be favourable. 1 / 12 Treatment Decision-making Figure 1.
    [Show full text]
  • Patella Luxation in Dogs and Cats
    Patella Luxation in Dogs and Cats The knee is a complex structure consisting of muscles, ligaments, tendons, cartilage, and bones. These components must align properly and interact harmoniously in order to function properly. Three bones are included in the knee: the femur, the tibia, and the patella (kneecap). Normal Knee Joint of a Dog The patella or kneecap moves up and down in the lower part of the femur called the trochlear groove. In patella luxations, the trochlear groove is usually shallow, causing the kneecap to displace or luxate. Normal Knee Joint of a Dog Showing Muscles, Tendons and Ligaments Normal Exposed Knee Joint of a Dog Symptoms of Patella Luxation Patella luxation (dislocation) is a condition where the kneecap does not align properly with the femur and tibia. The condition can be temporary or permanent and range from complete dislocation to mild patellar instability. The dislocation can occur laterally (toward the outside of the knee joint), medially (toward the inside), or in both directions. There are 4 types of patella luxations. Grade 1 – The patella is positioned normally but can be luxated with slight manual pressure. Grade 2 – Spontaneous luxation occurs; however, it can reduce spontaneously or can be replaced manually. Grade 3 – The patella is luxated most of the time; however it can be replaced manually. Grade 4 – The patella cannot be reduced manually. Most commonly, the disease is a medial luxation and occurs as a result of a congenital (existing at birth) condition in toy and miniature breeds of dogs. Dog breeds most commonly affected by this condition are poodles, Yorkshire terriers, Maltese and bichon frise.
    [Show full text]
  • Luxating Patella Or Kneecap in Dogs
    to Veter n cy H in o en os a r g p r Toronto Veterinary Emergency Hospital er it o a y m l T E 21 Rolark Dr, Toronto, ON, M1R3B1 Phone: 416 247 8387 Fax: 4162873642 Email: [email protected] 24 Hour Emergency & Website: www.tveh.ca Referral Hospital Luxating Patella or Kneecap in Dogs What is a luxating patella? The patella, or "kneecap," is normally located in a groove on the end of the femur, or thigh bone. "Term luxating means 'out of place'." The term luxating means "out of place" or "dislocated". Therefore, a luxating patella is a kneecap that moves out of its normal location. It generally resumes its normal anatomical orientation after only a brief period of luxation in most dogs. What causes a patellar luxation? The large muscles of the thigh (quadriceps) attach to the top of the kneecap. A ligament, known as the patellar ligament, attaches the quadriceps muscle to a point on the center front of tibia (the bone in the lower leg) just below the knee joint. The kneecap sits on the undersurface of this ligament. When the thigh muscles contract, the force is transmitted through the patellar ligament, pulling on the tibia,. This results in extension or straightening of the knee. The patella slides up and down in its groove (the trochlear groove) and helps keep the patellar ligament in place during this movement. "Many toy or small breed dogs...have a genetic predisposition..." Many toy or small breed dogs, including Maltese, Yorkshire terriers, French poodles, and Bichon frise dogs, have a genetic predisposition for a luxating patella due to a congenitally shallow trochlear groove.
    [Show full text]
  • THE LUXATING PATELLA: One Size Does NOT Fit All
    THE LUXATING PATELLA: One size does NOT fit all Synopsis-- Anatomy and the Disease The quadriceps mechanism is the unit of interest when talking about a luxating patella. The condition is a dynamic one, created by predisposing genetics and the resultant development, or by a predisposing anatomy exacerbated by low impact trauma. The patella is supported or encouraged to ride in its groove by several structures. 1) The alignment of the quadriceps muscle/patellar tendon/patella/patellar ligament/tibial tubercle (quadriceps “mechanism”) with the groove; 2) medial and lateral retinacular/joint capsular tension; and 3) depth of groove—probably in that order of importance. IN BREEDS WITH PREDISPOSING GENETICS, we see either a) the mismatch of quadriceps mechanism growth/elongation with bone growth/elongation or b) a wayward tibial tubercle physis that “moves” medially or laterally as it develops as the developmental cause of this condition. When this abnormality is pronounced early in puppyhood, a patella that jumps its track even just a little promotes a vicious cycle of malalignment by the quadriceps mechanism pulling the tibial tubercle physis medially or laterally. In other breeds/mixed breeds, a subtle abnormal anatomy of the quadriceps mechanism can be suddenly turned into a painful luxation with vigorous play, turning, landing, and is best categorized as a catastrophic sprain. The resultant looseness is poorly contained conservatively, and repeated luxations perpetuate the tissue damage preventing healing. PAIN OR DISABILITY associated with a loose patella manifests from several situations. Ongoing pain and consistent lameness is seen when cartilage wear results in subchondral bone exposure, grinding and joint inflammation.
    [Show full text]
  • Tipler, a – Medial Patella Luxation Treatment
    Medial patella luxation treatment Dr Abbie Tipler ATCL BVSc MANZCVS (Surgery) Veterinary Specialist Services 1-15 Lexington Road, Underwood, QLD 4119 Aetiology For a patella to function correctly it needs a proper alignment to the quadriceps muscle group that meets and converges on the patella. With correct alignment, the patella sits in the trochlear groove and this groove develops normally over time. The entire mechanism from pelvis to quadriceps to patella to tibial tuberosity should sit in a relatively straight line. This mechanism is called the extensor apparatus and when aligned with the patella it works to effectively and painlessly extend the knee via contraction of the quadriceps. There can be several facts that can contribute to the abnormal development that is seen in dogs with medial patella luxation (MPL). Puppies are born with normal stifles, however medial malalignment of the quadriceps mechanism leads to abnormal forces on the growth plates during growth and conformational abnormalities result. The conformational abnormalities can typically involve varying degrees of torsion of the tibia with internal rotation, distal femoral varus, hypoplasia of the medial condyle, patella alta and underdevelopment of the trochlear groove. Signalment This is primarily a disease of small breeds such as Chihuahuas, Toy Poodles, Yorkies, Silky Terriers, Papillons and Pomeranians but is also seen in larger breeds such as Labradors, Staffordshires and Bull Terriers. Females tend to be over-represented and it is heritable. Around 50%-60% of the time it is bilateral. Around 80% of luxations are either a grade 2 or a grade 3. Around 10-40% of dogs have a concurrent cruciate ligament rupture.
    [Show full text]