darthroplasty – practical training – wet labs - part 1

WARSAW11-12 November 2016

PART 1www.darthroplasty.com

“Dogs are born with normal hips”

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Alexander, J.W. (1992) The Veterinary Clinics of North America. Vol 22, Number 3

“Embryonically, the hip is laid down as a single unit from mesenchymal tissue,

and it develops normally as long as the components are left in full contact”

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Strayer LM (1943) “The embriology of the human hip joint” Yale J Biol Med 16: 13-26

Human 25 mm embryo (8 weeks)4

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12 days

2 months

8 months

1 month

4 months

2 years

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• 87 dogs from birth to 30 days of age were dissected.

• In 3 of these dogs (all were 30 days old) he found an oedematous femoral head ligament with a few torn fibers with dots of haemorrhage at the point of the tears.

Riser, W (1975) The Dysplastic Hip Joint: Radiologic and Histologic Development Vet Pathol 1975 12: 279

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• In dogs that were 30 to 60 days of age the first signs detected by radiography were femoral head subluxation and a retardation in the development of the craniodorsal acetabular rim.

Riser, W (1975) The Dysplastic Hip Joint: Radiologic and Histologic Development Vet Pathol 1975 12: 279

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5 month old German Shepherd

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• Lust et al used a lineage of Labrador Retrievers with high risk for dysplasia (90% dysplastic offspring) to study the early stage of the disease.

• Most joints studied were from 3 to 6 month olddogs.

• He found a proliferative synovitis (from mild to severe) in all joints studied from the high risk group. In the control group (Labrador Retrievers) 50% of the joints had synovitis, all in the mildest form.

Lust, G; Summers, B. (1981) Early, asymptomatic stage of degenerative joint disease in canine hip joints. Am J Vet Research, vol 42, nr 11, pg 1849-1855.

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“This study provides evidence that synovial fluid and round ligament volume

increase early in the course of osteoarthritis in dogs with incipient hip dysplasia.”

“Microscopically, studies of the synovial membranes support the view that these

changes result from inflammation.”


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Synovitis

Cartilage

damage

Radiographic

signs of disease

The data points to a time sequence of events:

It is therefore very likely that ALL of our patients at the time of radiographic diagnosis have some level of cartilage damage.


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At arthroscopy 96% of the joints had some form of cartilage lesion

50% of the joints had either deep fissuring or full thickness cartilage loss

81% had partial tearing of the femoral head ligament and 7% a complete rupture

93% of the joints had lesions of the labrum (tearing in 44% and avulsion in 49%)

Holsworth, IG, et al (2005) Comparison of arthroscopic and radiographic abnormalities in the hip joints of juvenile dogs

with hip dysplasia JAVMA, vol 227, nr 7: 1091-1094

The authors studied 52 dogs (age 5½ to 15½ months old); Total number of hips = 70

Radiographically, 43% of the joints had NO signs of DJD and 33% considered to have mild signs

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Hip Fluid Sealduring distractive forces helps to generate negative intra-articular pressure resulting in a stabilizing force

– Hip Fluid Seal or Suction Seal – The acetabular labrum constrains the fluid in the joint,

sealing it from fluid extravasion.

during loadingaction over intra-articular fluid pressure

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Ferguson et al. (2003) An in vitro investigation of the acetabular labral seal in hip joint mechanics.

Journal of Biomechanics 36 (2003) 171–178

Hydrostatic fluid pressurisation within the intra-articular space is greater with the labrum than without it.

Cartilage consolidation is quicker without the Labrum

The Labrum adds an extra resistance to the flow path for interstitial fluid expression

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• Resistance to rotation, which reflects articular cartilage friction, was significantly increased following focal labrectomy at 1-3 times Body Weight loading, and following complete labrectomy at all load levels.

• The acetabular labrum appears to maintain a low friction environment, possibly by sealing the joint from fluid exudation.

Yongnam Song et al (2012) Articular cartilage friction increases in hip joints after the removal of acetabular labrum.

Journal of Biomechanics 45 (2012) 524–530

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Nepple et al (2014) The hip fluid seal - Part II: The effect of an acetabular labral tear, repair, resection, and reconstruction on hip stability to distraction. Knee Surg Sports Traumatol Arthrosc (2014) 22: 730–736

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• Surgically executed unilateral eversion of the labrum in 20 Mongrel puppies, 6 week old.

• He observed dysplastic characteristics (subluxation, shallow acetabuli) and gross cartilage abnormalities in all operated joints.

• In his words: “despite the tight closure of the joint capsule after eversion of the acetabular labrum, acetabular dysplasia with subluxation of the femoral head gradually developed following surgery”.

Young-Hoo Kim (1984) Acetabular dysplasia and osteoarthritis developed by an eversion of the acetabular labrum.

Yonsei Medical Journal vol 25, nr 2, 1984

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Coxofemoral joints in which subluxation was demonstrated radiographically had greater synovial fluid and round ligament volumes compared with non-subluxated, normal joints.

• Low prevalence line of dogs: usually free of dysplasia at 9 months of age

• High-dysplastic line: 90% dysplastic at 9 months of age

Lust, G et al (1980) A Relationship between degree of laxity and synovial fluid volume in coxofemoral joints of dogs predisposed

for hip dysplasia. Am J Vet Research, vol 41, nr 1, pg 55-60

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Lust, G et al (1980) A Relationship between degree of laxity and synovial fluid volume in coxofemoral joints of dogs predisposed

for hip dysplasia. Am J Vet Research, vol 41, nr 1, pg 55-60

Subluxation was observed only in the presence of greater than normal synovial fluid and round ligament volumes.

These data indicate that increased synovial fluid volume is one biomechanical component of abnormal laxity and subluxation.

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Riser (1975) Surgically Induced Hip Dysplasia Vet Pathol 12 : 306-315 (1975)

• In 5 dogs the tendons of the obturators (int and ext) and the gemelli were surgically severed at 4 months of age.

• All operated hips became severely dysplastic.

Muscular component destruction also creates dysplasia

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There are several mechanisms acting together and contributing to stability

… …labrum

fluid seal

capsule

muscle / tendon units

neurological networks

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Pountney, T; et al (2006) Hip dislocation in cerebral palsy. BMJ vol 332, 1 APRIL 2006

• In children with cerebral palsy the hip is normal at birth but the effects of delayed motor development lead to dysplasia. Asymmetrical activity of the muscles surrounding the hip and lack of load bearing affect bone development and are the main causes of subluxation and dislocation.

• Lateral migration of the hip (subluxation or partial dislocation) occurs in 30-60% of children with cerebral palsy who are not walking independently at 5 years.

• 92 young dogs (less than 12 months old), hip dysplasia prone on the basis of genealogical records were studied at necropsy

• observed DJD of the Hip in 71%; of the Stifle in 22% and of the Shoulder in 38%

• 40% had Multiple Joints Involved (excludes dogs with only same joint bilaterally affected)

• and the ELBOW was not studied

• “Possibly, there is a systemic basis for joint degeneration with variable expression in different joints”

• This can link hip dysplasia to the other disease that are caused by abnormal progression of endochondral ossification (Shoulder OCD, Elbow Dysplasia, etc ...)

Olsewski, J M; Lust, G; et al (1983) Degenerative Joint Disease: Multiple Joint Involvement in Young and Mature Dogs.

Am J Vet Research, 1983, vol 44, nr 7

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Birgit Lieser (2003); Morphological and biomechanical properties of the hip joint in the Dog (Canis familiaris); Dissertation for the veterinary doctorate - Veterinary

Faculty of the Ludwig Maximilian University of Munich

BODY WEIGHT

25% 50% 75% 100%

150% 200% 250% 300%

400%

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• At low loads and physiological angulation contact areas were mainly found at the peripheral margin of the cranial and caudal part of the facies lunata and caput ossis femoris

• At the cranial roof of the acetabulum a joint space was evident in the loaded specimens up to 75% body weight. Under increasing loads the contact areas expanded towards the joint centre.

• The results of this study established proof of the inhomogeneous load distribution in the canine hip joint. For the first time it was shown that the canine hip joint is not congruous as commonly assumed but maintains a physiological incongruence. This guarantees for an optimal load distribution in the joint and for a better nutrition of the joint cartilage

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The physiological incongruence

may contribute to optimal load distribution specially on

higher load values



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• Micro-fractures of the acetabular rim (Riser)

• Capsule stretching and tearing

• Inflammation

In the young dogpain has been attributed to:

• Degenerative joint disease and its consequences in cartilage and subchondral bone

In the older dogpain has been attributed to:

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C.H. Huang, et al. (2013) The Innervation of Canine Hip Joint Capsule: An Anatomic Study Anat. Histol. Embryol. 42 (2013) 425-431

• The canine hip joint capsule receives multiple innervations from articular branches of 4 nerves. They are articular nerve fibres of femoral, obturator, cranial gluteal and sciatic nerves from the cranioventral, caudoventral, craniolateral and dorsolateral directions of the joint, respectively

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C.H. Huang, et al. (2013) The Innervation of Canine Hip Joint Capsule: An Anatomic Study Anat. Histol. Embryol. 42 (2013) 425-431

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• Does it have an effect on full thickness cartilage loss and nociception by the subchondral bone?NO

• Does it have an effect on the total innervation of the hip capsule?NO

• Is re-inervation a possibility?YES

Hip denervation has been proposed as a palliative measure for hip dysplasia

These questions and others we must ask of the DARTHROPLASTY

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In my opinion there is a class of hip dysplasia affected dogsthat should be called compensated cases on a clinical basis.

Conservative treatment

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Conservative treatment

WARSAW11-12 November 2016

END OF PART 1www.darthroplasty.com

darthroplasty – practical training – wet labs - part 1

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