Ch 59 Surgery for HD Flashcards
categories for surgical management of canine hip dysplasia are? (3)
1) prophylactic (juvenile pubic symphysiodesis and pelvic osteotomy) goal = prevention of the development of secondary osteoarthritis that is often the sequela to hip joint laxity
2) salvage (Total hip arthroplasty and FHO) replace or eliminate the source of pain and, in the case of total hip arthroplasty, restore function
3) palliative (hip denervation)
Juvenile Pubic Symphysiodesis
anatomy
The pelvic symphysis has three peripheral ligaments: (1) the transverse or oblique fibrous fascia
at the dorsal aspect of the symphysis, which serves to strengthen the symphysis;
(2) the prepubic tendon
inserts at the cranial aspect of the pubic ramus
(3) the arcuate pubic ligament,
crosses the ischial arch and often becomes ossified
What kind of “joint” is the pelvic symphysis?
A synchondrosis which transforms over time to become a synostosis
Which end of the symphysis is larger?
Ischial portion is slightly larger
What kind of cartilage makes up the pelvic synthesis?
Hyaline cartilage - acts as the growth plate
Fibrocartilage - gradually replaced by bone
When does the pelvis symphysis start to ossify?
When is it complete?
Starts to ossify in a caudal to cranial direction beginning at 9-21 months
Completely ossified within 2-6yr
What is a JPS?
indictions? (3)
Application of electrocautery to the hyaline cartilage of the pubic symphysis resulting in heat-induced necrosis of the germinal chondrocytes
- advocated in dogs 12 to 20 weeks of age
- of predisposed breeds
- palpable hip joint laxity
How does a JPS effect acetabular growth?
Results in external rotation of the acetabulum in a ventrolateral axial direction
What is the ideal age for JPS?
12 - 20 weeks
25% treated dogs developed OA vs 83% of sham operated dogs
What muscles are partially elevated from the symphysis for JPS?
Gracilis and adductor muscles
What are the recommended electrosurgical settings for JPS?
500kHz current frequency
40W
- current applied via monopolar probe for 10-30 seconds
- every 2-3mm
- along cranial 1/3 - 1/2 of the symphysis
- sterile wood spatula depressor to protect the urethra OR assistant per rectum deviation of the rectum and urethra.
cranial aspect of the pubic symphyseal brim (pubic tubercle)
Rationale for JPS
- procedure is performed at an age when there is minimal likelihood of existing osteoarthritis
- minimally invasive procedure
studies:
- premature closure of the pubic symphysis results in shortening of the pubic ramus, thereby limiting circumferential growth of the ventral portion of the pelvic canal while dorsal growth remains unrestrained
- result is external rotation of the acetabulae in a ventrolateral axial direction
- increases coverage of the femoral heads
efficacy of JPS
- younger the puppy at the time of the procedure, the greater the change in femoral head coverage (greatest @ 12 weeks)
- hip joint laxity, as described by the PennHIP distraction index, maintained an improvement by 42% compared to control animals
Vezzoni et al
- 217 puppies aged 14 to 22 weeks
- Regardless of initial severity of hip dysplasia, as determined by hip joint laxity, treated puppies had less severe hip dysplasia than the control group at 12 to 18 months of age. The authors concluded that juvenile pubic symphysiodesis was efficacious when performed in patients with mild or moderate hip dysplasia (DI 0.40 to 0.69)
- based on DI, DAR, ortolani
- not effective in puppies with severe hip dysplasia
complications JPS
have not been reported
- excessive ventroversion of the acetabulum, resulting in ventromedial subluxation of the femoral head (if the procedure is performed when too young or no HD)
- pubic rami (shorter and thicker in treated dogs
- long-term complication is lack of efficacy (surgeon error or poor canididate)
What are the aims of TPO/DPO? (3)
- Reducing joint laxity
- Normalising joint stresses
- Improving joint congruence (axial rotation and lateralization of the acetabulum)
goal: prevent the development of phenotypic changes associated with the dysplastic hip
following D/TPO, laxity is expected to diminish
TPO + DPO
- triple pelvic osteotomy includes osteotomies of the pubis, the ischium, and the ilium
- double pelvic osteotomy does not include the osteotomy of the ischium.
- rationale for the development of the double pelvic osteotomy was to reduce the complications
subjective (observational studies and owner assessment) and objective (radiographs, force plate analysis, and kinematic analysis) studies have assessed outcomes following surgery.
biomechanical studies have shown that triple pelvic osteotomy can also reduce the magnitude of the force acting on the load-bearing portions of the acetabular rim and the femoral head and increase the contact area on which the force acts.
DPO patient selection
- laxity, consistent with early stages of hip dysplasia,
- without radiographic evidence of secondary osteoarthritis
- > > advocate for arthroscopic evaluation of the hip> more sensitive than RADS for identification of OA
- patients are younger than 1 year of age, with some authors suggesting a max 10 months
- in skeletally immature dogs, there is a capacity for improvement in joint congruity through uniform cartilage loading, thus preventing or limiting osteoarthritis
- Controversy hip joint laxity but without clinical signs attributable to hip dysplasia
- correlated development of osteoarthritis with early evaluation of hip joint laxity (i.e DI)
- reduction angle less than 15 degrees were unlikely to develop osteoarthritis
Patient Positioning, Approaches, and Procedure
pubic osteotomy
- down to the tendon of origin of the pectineus muscle at the iliopectineal eminence
- The tendinous origin is transected (avoid medial circumflex femoral artery and vein)
- section of pubis is excised (avoid the obturator nerve just caudal)
- sagittal saw, osteotome, or rongeurs
- Dissection of the tendon of insertion of the rectus abdominis muscle at the cranial is limited (risk of the caudal abdominal hernia)
- simultaneous bilateral, the pectineus mm is preserved VS a pubic symphysiotomy
ischial osteotomy (TPO)
- periosteal incision is made along the dorsal border of the ischium
- subperiosteal elevation of the internal obturator muscle (pudendal nerve along dorsal surface also elevated) + origins of the semimembranosus and semitendinosus muscles ventrally
- confirm that the osteotomy is directed toward the obturator foramen
- wire for stabilization is surgeon preference
ilial osteotomy
- gluteal “roll-up” (care cranial gluteal nerve, artery, and vein)
- osteotomy is performed just caudal to the sacroiliac joint, perpendicular to the long axis of the ilium or perpendicular to the long axis of the pelvis
- Caudodorsal angulation > ease lateral rotation of the caudal segment
- perpendicular to the long axis of the pelvis will allow lateral rotation of the acetabulum in the frontal plane, maintaining the alignment of the iliac segments.
- care is taken to protect the lumbosacral trunk as it courses medial to the body, and dorsal as** sciatic n** > protect with sponge or retractor
- Damage to the lumbosacral trunk may also occur during periosteal elevation medial to the iliac body
DPO
- decreased mobility of the caudal iliac segment > helpful to gently lever the caudal iliac segment using a long osteotome
- transection of the sacrotuberous ligament can reportedly ease the rotation
- acetabular ventroversion is generally 5 degrees less than that achieved when performing TPO
Plate fixation
- caudal portion of the plate is secured to the caudal segment, rotation bar screwed in the most cranial hole used to rotate the ilium ventrally while a screw, placed in the most ventral hole of the cranial part of the plate placed
- DPO: 25 and 30 degrees are most common.
What vessels need to be avoided during pubic osteotomy?
Nerve?
Deeper medial circumflex femoral artery and vein
Obturator nerve
What muscles need to be elevated from the ischium for ischial osteotomy of TPO? What structures need to be avoided?
Dorsal
- Internal obturator muscle
- Pudendal nerve
Ventral
- Semimembranosus
- Semitendinosus
- External obtruator muscle
What range of angles are typically available for TPO/DPO plates?
rotation degree?
20 - 45 degrees
The desired degree of rotation is generally 5 degrees greater than the measured angle of subluxation (add another +5 for DPO)
STUDY: Coverage by the DAR does not signifcantly increase over that achieve by a 20 degree plate
Rotation beyong 40 degrees is not advised (3)
- unlikely to yield further improved coverage,
- worsen pelvic canal narrowing
- may result in impingement of the dorsal acetabular rim on the femoral neck
dogs requiring more extreme rotation are not good candidates
locking vs non
- significantly lower incidence of screw pull-out occurs with use of locking plates
- however, risk of en bloc pull-out (i.e., avulsion of the lateral cortex along with the plate and screws)
studies performed before locking plates:
- lower incidence of screw migration is reported with the use of cancellous screws compared with cortical
- 9.2 times greater incidence of screw loosening occurred in hemipelves without a ventral plate
How have the use of locking plate and DPO effected the rates of screw loosening?
- DPO reduced screw loosening to 3.2% (from 6-36%)
- Locking plates reduced the rate of screw loosening to 0.4%
sacral screw purchase
- screw depth in the cranial segment subject of evaluation.
- decreased incidence of screw loosening has been reported when penetrate more deeply (i.e., >27 mm for the cranial two screws or >93% total sacral penetration)
- other studies report a lower incidence of screw loosening when the sacroiliac joint is not entered.
What is the reported complication rate after a TPO? What are the main complications?
35 - 70%
Screw loosening and pelvic canal narrowing
Complications of Pelvic Osteotomy (6)
advantages of DPO over TPO
1) screw pull out
- incidence of screw loosening DPO 3.2%
- compared with TPO 6% - 36%
- compared with locking plate 0.4%
- locking divergent screws, withstand the pull-out forces applied to the caudal part due to the recoil of the twisted ilium and ischium
2) Pelvic canal narrowing-
- greater for increasing rotation angles
- not noted in a retrospective study of DPO (geometry was maintained by the intact ischium)
- narrowing can occur following bilateral TPO (lead to constipation or obstipation)
3) stranguria
- following bilateral TPO
- tends to be a transient phenomenon
- unknown cause (pelvic plexus or pudendal n damage??)
4) Excessive femoral head coverage by the dorsal acetabular rim
- coverage increased over time, 60-80%
- may be due to postoperative increased lateral rotation associated with pelvic canal narrowing
- not seen in DPO
5) Incomplete fracture of the ischial table
6) Ineffective control of hip dysplasia
- progression of osteoarthritis
- improper case selection
- inadequate acetabular ventroversion
Total Hip Arthroplasty
- Despite advances in cementing techniques, concerns about cement failure and associated implant loosening persist
- significant majority of canine total hip implants are cementless prostheses; however, cemented continue to play a significant role in veterinary hip replacement
- design and implantation require consideration of a variety of issues, including implant materials, tribology, means of fixation, and joint kinematics
How do metallic grains effect THR implant strength?
List manufacturing methods of increasing implant strength
The smaller the metallic grain, the stronger the implant
Manufacturing methods to srengthen implants:
- Forging
- Investment casting
- Hot isostatic pressing
- Cold working
- Heat working
Metallic Femoral Stem Materials
- stainless steel, cobalt-chromium alloys, titanium, and titanium alloys
- elasticity of implants is based on their stress-strain curve, and the elastic modulus is measured in pascals
- important not only in terms of the strength and stiffness but also with respect to the interaction of the implants with the bone and bone cement
- greater the elastic modulus mismatch between apposing surfaces, the greater the risk for development of wear debris or stress shielding
- Stainless steel is rarely used in total hip implants today
What is the elastic modulus of stainless steel, cobalt chromium and titanium?
Stainless steel and cobalt chromium = approx 200GPa
Titanium = approx 100GPa
What is stress shielding?
- Occurs when implant is stiffer than bone, preventing adequate load transfer to the bone,
- resulting in bone resorption due to relative disuse atrophy leading to implant loosening
What metals are in 316L stainless steel? (4)
Iron
Chromium
Nickel
Molybdenum
What metals are in cobalt alloys? (3)
What THR implant use this?
Chromium
Molybdenum
Nickel
Implants:
- BioMedtrix (BFX anf CFX)
- Very hard with excellent wear and corrosion resistance
What is the most common titanium alloy?
Which THR implant uses this?
Titanium is highly biocompatible
Ti6Al4V
Stronger, good fatigue resistance compared to pure titanium
More prone to wear debris than cobalt alloys
Implant
- Zurich Cementless (Recently switched to Ti6A14Nb)
- helica
What is tantalum?
A metal that can be fabricated with a porosity and elastic modulus similar to those of cancellous bone
What is tribology?
study of friction, wear, lubrication, and the design of bearings; the science of interacting surfaces in relative motion.
What is the acceptable linear wear rate in people?
0.1mm/year
Dogs showed a significantly lower volumetric wear that is seen in humans however dogs had a more severe bony reaction (osteolysis) to the debris
Bearing Surfaces
hip prostheses have bearing surfaces of polyethylene (on the acetabular side) and metal (on the femoral side)
- development of wear debris at articulating surfaces can result in osteolysis and aseptic loosening
- Implant wear can be evaluated by linear or by volumetric means.
- Linear > measured radiographcally based on a known starting width of the bearing surface.
- Volumetric > based on orthogonal radiographic or three-dimensional CT measurements
- Wear debris can be generated at bearing surfaces by a variety of means: adhesion, abrasion, erosion, corrosion, and fatigue.
Gravimetric testing requires the collection of wear debris
ideal bearing surface? (4)
- low friction,
- low wear debris generation,
- biocompatible,
- damage resistant.
List the 5 main ways in which wear debris can be generated
-
Adhesive wear (material from the softer bearing surface is transferred to the opposing surface and breaks free > cold welding, shear strength of the “cold” weld must be greater than the surface strength of the polyethylene)
2.** Abrasive wear** (irregularity on a hard surface damages the opposing surface or third-body wear/bone particle) - Fatigue wear ( Cyclic loading causing cracks/microcracks or subsurface delamination)
- Erosive wear (Solid particle erosion, impingement wear > if the prosthetic femoral neck contacts either the polyethylene liner or the metallic shell of the acetabular component)
- Corrosive wear ( galvanic corrosion - oxidation that generally results from interactions of disimilar metals)
Polyethylene and PEEK (cups)
primary acetabular bearing surface
- Ultra-high-molecular-weight polyethylene is a good low-friction surface, but it is prone to generation of wear debris
- polyetheretherketone is a semi-crystalline thermoplastic
biomedrix
- Highly Crosslinked and Vitamin E Stabilized UHMWPE
Kyon
- PEEK acetabular inlay
ceramic
Kyon - Zurich
- ceramic head > Zirconia Toughened Alumina
Under what circumstances is the greatest amount of wear debris created?
Titanium bearing surface with a cemented prosthesis
Metals
Cobalt-chromium
- CFX
- implants generate less wear debris than titanium alloys
- wear debris from cobalt-chromium is cytotoxic.
Titanium alloy
- wear debris is more inflammatory than cobalt-chromium
cementless systems now use titanium alloys (kyon, helica, biomedrix)
Surface Coatings for Metallic Heads
Titanium nitride (Ti-N) ceramic
- demonstrated substantial reductions in wear rates
- scratching of the Ti-N coating during surgical implantation and wear-through
Diamond-like carbon
- very low friction, have excellent wear and corrosion resistance, and are biologically inert
used in older generations Zurich Cementless hip
surface coatings for stems
Kyon
- Porous titanium and hydroxyapatite coating
- Calcium phosphate, mineral phase of bone is osteoconductive
Helica
- titanium alloy rough blasted
BFX
- EBM Titanium, , Electron Beam Melting > metal powder is fused layer by layer in a high vacuum using the computer model of the implant.
- porous surface is printed as an integral part of the stem, instead of making use of a spray or coating
histroically: plasma spray (for titanium) and beaded coating (chrome-cobolt) technologies had been used to achieve a stable press-fit
Biologically Active Surface Coatings
Hydroxyapatite
- osteoconductive and provides a calcium phosphate base for the deposition of bone.
- deposited on roughened or porous surfaces by plasma spraying.
- enhance bone ingrowth
- reported to prevent the migration of wear debris
- kyon
Bisphosphonate
- prevent periprosthetic osteoclastic bone resorption. - direct influence on osteoblasts
- dogs used in studies on prevention of aseptic loosening
- not commercial in vet
Ceramics
What forms of ceramic used in THR in dogs?
What are the benefits?
- are harder than metal
- Because of the very high elastic modulus of ceramic (approximately 300 times greater than cancellous bone), metal backing is necessary to prevent aseptic loosening secondary to modulus mismatch.
Zirconia (6th gen Kyon)
Wear products are locally inert
Hydrophilic crating a virtaully frictionless fluid-film lubrication
Metal-on-polyethylene > common commercially available articulation for vet
ceramic -on- PEEK > Kyon
However, production of wear debris and secondary osteolysis and aseptic loosening remain major problems.
metal-on-metal > should have minimal wear debris generation, however concerns regarding metallosis and a form of delayed-type hypersensitivity called aseptic lymphocyte-dominated vasculitis-associated lesion
Methods of Fixation
what (3) immediate methods? and (3) non-press-fit options?
for immediate, initial fixation > cemented (PMMA), cementless, and hybrid systems.
- interfaces between different materials include implant-bone, implant-cement, and cement-bone.
- Load transfer occurs at these interfaces, and the elastic modulus of each component determines how much load each component must bear.
- The differences in elastic modulus result in shear stresses at the interface
- The implant design and means of fixation must be able to withstand these shear stresses.
- (3) immediate methods = cement, press-fit, screw (kyon)/threaded(helica)/lateral bolt (BFX)
cementless
immediate fixation:
- For a press-fit implant, compressive forces at the interface must be greater than the shear stresses.
- This compression occurs as the press-fit implant is impacted or subsides into the bone
- Historically, synonymous with press-fit, an interference fit in which the component being placed is slightly larger than the cavity.
- However, current veterinary achieve it by means other than press-fit > locked screw or threaded systems
long term fixation:
- generally rely on bone ingrowth (osseointegration) or bone ongrowth for long-term stability.
- Bone ingrowth > implants that have a porous surface coating where the bone interdigitates with the implant.
- Bone ongrowth > on surfaces with a roughened surface texture where the bone is directly apposed to the implant surface, without an intervening fibrous membrane
- press-fit > if insufficient friction is achieved to counteract shear stresses, then osseointegration will not be achieved
What environment is necessary for bone ingrowth (osseointegration)? (3)
BFX
Pore size 50 - 400mcm
Micromotion less than 20mcm
Porosity (voids:material) of 30-40% is ideal
porosity is achieved using a sintered bead surface
which (3) cementless systems?
bioMedtrix
- BFX press-fit implant
- BFX press-fit with lateral bolt > applicable to stovepipe shaped femurs (where previously a CFX stem would have been used)
Kyon Zurich
- Cementless system is not press-fit
- the femoral stem counteracts the shear stresses with a locking screw that fixes the femoral implant to the medial cortex of the femur.
- anchorage to only the medial cortex is to uncouple the medial and lateral cortices > should eliminate micromotion
- percentage of bone ingrowth has been reported for the acetabular components as 44% at 12 months after surgery
Innoplant helica
- threaded system > positive profile self-tapping helical threads that screw into bone providing early stabilisation of the implants before bone ingrowth
- femoral neck preserved
What strategies can be imployed to enhance the strength of the cement mantle? (6)
resistance to shear stresses
- Centrifugation and application of a vacuum (Decreases porosity, thus increase strength)
- Pressurisation with injector and intramedullary cement restrictor (improves the distribution of cement and enhances interdigitation)
- Minimum 2mm cement mantle surround stem
- Femoral stem centralisers
- Collared prostheses (helps to pressurize cement within the medullary)
- Minimising blood and fat interposition (pulsatile lavage)
hybrid systems + partial systems
Biomedrix universal
- Hybrid fixation is achieved when one component is cemented and the other is press-fit. The common femoral head is compatible with both the cemented and cementless acetabular cup and femoral stem implants
Kyon Dual Mobility cup
- dogs at a high risk of post-surgical luxation
- Ceramic 19 mm head preassembled inside the 25 mm PEEK articulating head
- wears much faster than normal system
Kyon partial
- permanent solution instead of FHO or THR
- Stem and cup, using patients own acetabulum
- material of the head is Titanium with amorphous diamond-like coating (ADLC)
What is the angle of inclincation?
Angle between the anatomic axis of the femoral neck and femoral shaft
- lower femoral neck angle = varus neck
- higher neck angle = valgus neck.
- The lower the neck angle, the greater the lateralization of the femur but also the greater the bending moment at the neck-shaft junction
What is femoral offset?
Distance between center of rotation of femoral head and anatomical axis of the femur
- angle and the length of the femoral neck determine the femoral offset
- offset lateralizes the femur away from the pelvis
- greater this offset, the greater impingement-free range of motion.
- impingement-free range of motion is described by the angles of flexion, extension, adduction, abduction, external rotation, and internal rotation that can be achieved without contact between the femoral neck and the acetabular rim
longer femoral neck
- longer lever arm > lower force is required to induce luxation
- also provides greater clearance between the femur and the pelvis > less risk of impingement
shorter neck
- lesser the lever arm> greater the force necessary to induce luxation,
- greater risk of impingement
What is femoral neck anteversion?
what are the consequences/risks?
The cranial angulation of the femoral neck in relative to the anatomical axis of the frontal plant of the femur
Increased anteversion can predispose to craniodorsal luxation (during external rotation)
- increased anteversion > internal rotation of the femur, increasing the risk of lateral patella luxation.
- Decreased anteversion > external rotation of the femur and an increased risk of medial patella luxation.
jumping distance
The distance that a femoral head must travel, or subluxate, before luxation will occur
- greater the jumping distance, the greater the resistance to luxation, but at the cost of increasing the production of wear debris
- lateral translation is influenced by the joint reaction force (F) and the angle of lateral opening
position of the acetabular component
- acetabular version
- angle of lateral opening,
- inclination
version
- cranial or caudal angulation of the acetabular component relative to the median or sagittal plane
- angled in a cranial direction is in anteversion
- angled caudally is in retroversion
angle of lateral opening
- angle of the acetabular component relative to the dorsal plane.
- fully open cup > face perpendicular to the dorsal plane is ascribed an angle of 90 degrees
- fully closed cup > face parallel to the dorsal plane is at 0 degrees.
- Truncation of the dorsal rim increases the impingement-free range of motion
angle of inclination
- only for prostheses with a truncated dorsal rim (CFX cup)
- angle between a line connecting the cranial and caudal points of the truncation and the iliac-ischial axis
- Positive inclination is an angle dorsal to the iliac-ischial axis
- negative inclination is an angle ventral to this axis.
What is the recommened version angle of the femoral neck?
15 - 25 degrees anteversion
Acetabular Preparation
- ress-fit and screw-in prostheses, precise preparation is critical
- recognition of the true center of the acetabulum
- dorsal migration of the dorsal acetabular rim can result in positioning the cup in inadequate bone stock
- advanced osteoarthritis will have a false medial acetabular wall > fossa is not visible
- “dish-shaped” acetabulum, the dorsal acetabular rim is not a reliable landmark.
- identification of the cranial and caudal bone columns
- cemented cups, troughs are made by removing cancellous bone to provide interdigitation
Femur Fracture
mechanical failure
- described by the Vancouver classification
press-fit stem
- fissure develop during impaction or subsidence following surgery
- dt failure with compressive loads
- classification B2
Cemented stems
- stress riser at the distal aspect of cement mantle.
- poor implant positioning (varus stem positioning) places tip in contact with caudolateral cortex.
- association with bending forces
- classification C
screw-fixation
- often spiral or long oblique fractures
- fail in torsion
- classification B1
fixation
- Bone plates or cerclage wires, or a combination of the two, repair or prevention fractures.
- prosthesis limits the use of bicortical screws in metaphysis and proximal diaphysis.
- cerclage wire (double-loop) for fissures associated with a press-fit > demonstrated greater resistance to failure compared to intact bone
- high risk for fractures (e.g., thin cortices or when using a press-fit stem) some surgeons advocate for prophylactic application of plates or cerclage wires
Subsidence
mechanical failure
press-fit stem
- occurs prior to osseointegration
- strongly correlated to the surgeon’s learning curve
- Canal fill at the level of the femoral isthmus is necessary for stable press-fit fixation
- subsidence <4 to 5 mm is not of clinical consequence
- substantial subsidence can be catastrophic: fracture, stem retroversion, or luxation
- fissure fractures with the subsidence > double-loop cerclage and a press-fit stem reimplanted
cemented stem
- result of cement failure at the implant-bone or cement-bone interface
- removal of all cement via lateral femoral window, or “coffin lid,” as well as excision of the fibrous tissue membrane
- base of the greater trochanter and extending the length of the cement mantle
calcar femorale is a normal ridge of dense bone that originates from the caudo-medial endosteal surface of the proximal femoral shaft
Surgical Procedure
- partial tenotomy of the tendon of insertion of the deep gluteal muscle, may/may not be needed
- joint capsule is incised parallel with the axis of the femoral neck > second incision, perpendicular to the first, is made in order to gain exposure
- curved Mayo scissors, ligament is transected while externally rotating the femur 90 degrees
osteotomy
- oscillating saw, high-speed burr, osteotome, or rongeur
- removal of entire femoral neck is critical to minimize impingement
- extends from the medial aspect of the greater trochanter proximal-laterally to the lesser trochanter distal-medially.
- Alternatively, a biplanar osteotomy can be performed
- no evidence that removal of the lesser trochanter eliminates impingement, and loss of the insertion point of the iliopsoas muscle may have adverse functional consequences
- techniques to interpose soft tissues: joint capsule closure, deep gluteal or biceps femoris muscle flap
- muscle flaps undergo ischemic necrosis, largely fallen out of favor
Post-op
- Multimodal postoperative pain management > encourage limb use as early as possible
- rehabilitation program: treadmill, weight-shifting exercises, PROM
- Early, consistent activity helps prevent progression of muscle atrophy
FHNE complications
- fairly low risk
- inappropriate approach > damage to the gluteal musculature, increasing postoperative morbidity
- sciatic n. damage
- Poor resection technique can even result in fracture of the femur
- most complications are the result of inadequate resection of the femoral neck > impingement
- limitations in function ought not be associated with discomfort.
- limitations in function > mechanical deficiency associated with a pseudarthrosis joint
Canine total hip replacement using
a cementless threaded cup and stem:
a review of 55 cases
Denny 2018
Helica cementless hip endoprosthesis system.
MATERIALS AND METHODS : Retrospective study of 55 consecutive
first-generation 22 dogs: (39%) experienced complications but (86%) recovered satisfactorily with revisions
second-generation 28 dogs: (32%) experienced complications, but (93%) made satisfactory recoveries, including revisions
Complications: 34·5% most common was aseptic loosening 20%. others: luxation, cup loosening, acetabular #
no risk factors were identified
Follow-up periods ranged from 12 to 63 months, with an average of 30·5 months
first-generation femoral stems are relatively short and are located entirely within the proximal femur.
potential for early osteointegration permits the HHE
to be implanted in dogs from 9 months of age onwards, and 17 of the 50 dogs recorded here were between 9 and 14 months old at the time of surgery.
higher postoperative complication rate than several published reviews of THR outcomes using other systems (Hummel et al . 2010 , Forster et al . 2012 , Henderson et al . 2017 ).
some cases of loosening occurred several years postoperatively, further followup is needed
Poor success rates with double pelvic osteotomy for
craniodorsal luxation of total hip prosthesis in 11 dogs
Thibault 2023
Retrospective case series
craniodorsal luxation of THR and high angle of lateral
opening (ALO) were considered candidates for DPO
Craniodorsal luxation recurred in five dogs and was managed with closed reduction, capsulorrhaphy, or repositioning of the acetabular cup. In the long term,
seven dogs required explantation (five aseptic loosenings, two infections)
Reluxation was frequent after DPO
DPO’s median
decrease in ALO obtained in this study was 11 . This was lower than the mean value of 23 obtained by TPO
three of the five dogs with recurrent luxation
had increased risk factors for THR luxation: two
cases had luxoid hips, and the other had a femoral head and neck excision several months before THR
the initial mispositioning of the cup could result
in impingement between the prosthetic components leading to aseptic loosening.
Outcomes and complications reported from a multiuser canine hip replacement registry over a 10-year period
Allaith 2023
Prospective longitudinal clinical study.
Animals: Dogs (n = 1852).
Kyon (n = 1087, 46%), BioMedtrix CFX (n = 514, 22%), BioMedtrix hybrid (n = 264, 11%), BioMedtrix BFX (n = 221, 9%), and Helica (n = 107, 4.5%).
Veterinary surgeons reported complications in 201/2375 (8.5%) THRs and owners in 107/461 (23%) THRs
BioMedtrix BFX and Helica implants were associated with increased complications (P = .031) when used for revisions of femoral head and neck excisions.
Conclusion: Excellent outcomes, Complications were underreported by veterinary surgeons compared to owners
Minor complications included sciatic neuropraxia
(n = 15/221, 7%), neuropathic pain (n = 1/221, 0.5%), and synoviocoele (n = 1/221, 0.5%). Major complications included luxation (n = 80/221, 36%), fracture (n = 39/221, 18%), aseptic loosening (n = 29/221, 13%), femoral acetabular cup loosening (n = 23/221, 10%), infection (n = 16/2217%), acetabular fracture (n = 5/221, 2%), implant failure
(n = 3/221, 1%), wound dehiscence (n = 1/221, 0. 5%), osteosarcoma (n = 1/221, 0.5%), extraosseous cement
granuloma (n = 1/221, 0.5%), implant displacement
(n = 1/221, 0.5%), and poor function of implant (n = 1/221, 0.5%).
(2%) complications were classified as catastrophic complications.
6% dogs were euthanatized due to complications of the hip replacement or died suddenly due to a catastrophic complication.
It has been well recognized that there is a learning curve associated with THR surgeries and a regular operative caseload is also advisable with this technique.
Given that hip dysplasia and hip oste
oarthritis
are often bilateral but that the majority of dogs
in this study had a unilateral THR, it is possible that OA
in the contralateral hip joints may have contributed to
this rise in LOAD scores postoperatively
Centerline canine cementless total hip arthroplasty as an alternative implant system; results in 17 dogs (2015–2020)
Zuend 2023
Biomedtrix Centerline canine cementless, 17 dogs (20 hips)
15 of 20 (75%) with long term radiographic follow-up had an excellent outcome. 5 hips (25%) had postoperative complications: femoral neck fracture (n = 1; 5%), aseptic loosening (2; 10%), and septic loosening (2; 10%).
complications occurred at a higher rate than recent outcomes of other long-standing THA procedures.
The design of the C-THA is unable to correct for inherent femoral anteversion
no femoral body fractures or subsidence would be identified within this short case series. The short stem design of the implants and preservation of the femoral neck allow for conversion to traditional THA systems if complications do occur post-operatively
Fluoroscopic Categorization of Cementless
Acetabular Component Positioning
Sadowitz 2023
BioMedtrix BFX acetabular
component, which projects as an ellipse at clinically relevant ALO values
Analysis showed perfect (30/30) agreement with a weighted kappa coefficient
of 1 (95% confidence interval: 0.717 to 1).
Clinical Relevance The results demonstrate that accurate categorization of ALO can
be achieved using this fluoroscopic method. This method may prove to be a simple but
effective method of estimating intraoperative ALO.
Currently, few methods exist for intraoperative ALO assessment, making acetabular component positioning one of the most challenging aspects of THA
acetabular components implanted at an
excessively open (ALO>45 degrees) or closed (ALO<45
degrees) ALO have an increased incidence of postoperative luxation.
limitation to the present study is that the acetabular component was evaluated at a single angle of retroversion and inclination
ex vivo, BFX only
Kinetic and Radiographic Outcomes of
Unilateral Double Pelvic Osteotomy in Six Dogs
Prabakaran 2023
Retrospective case series of six dogs that underwent unilateral DPO for
canine hip dysplasia. The untreated limb was unfit for DPO due to radiographic
evidence of osteoarthritis and was therefore managed non-surgically
All untreated hips in this series had increased BVA-HD scores at follow-up, whereas all DPO-treated hips
had reduced BVA-HD scores. This difference was not significant and warrants further studies.
The lack of significant difference between the GLS of treated and untreated hips is likely a type II error (most likely related to power/sample size)
GAITRite system provides a quantitative assessment
of lameness, which is superior to the ability of a clinician to diagnose lameness
Clinical outcomes of DPO have been examined and have shown an increase in femoral head coverage and significantly reduced joint laxity.2 Medium to long-term radiographic outcomes have also been examined,3 demonstrating lower radiographic osteoarthritis scores in DPO-treated hips compared
with untreated hips.
study population had a large age range at initial
presentation with one patient being 13 months old
sensitivity of radiography in detecting osteoarthritic changes in juvenile dogs is inferior to that of arthroscopy
probs
not a life-long study, so can’t rule out developement of OA later in life despite DPO (was always a better hip compared to contralateral)
why no DI??
Type II errors are false negatives, related to the power of the test
Radiographic and CT features of metallosis in a lame dog after
total hip replacement: the cloud sign
Felix Daniel Lucaci
Metallosis represents the accumulation
of metallic debris within the peri-prosthetic tissues and can be responsible for pain and joint effusion.9–Several factors have been concurrent with the presence of metallosis:
(1) using undersized implants,
(2) increased hindlimb bearing due to disease affecting the contralateral limb
(3) oxidation of the polyethylene
CT findings
multiple foci of geographic osteolysis
(Figure 2B) and irregular periosteal reaction of the greater trochanter.
Multiple amorphous mineral-to-metal attenuating foci (821 HU mean)
consistent with “the cloud sign” were diffusely distributed in the
peri-prosthetic soft tissues
Complications and outcomes of total hip arthroplasty
in dogs with luxoid hip dysplasia: 18 cases (2010–2022)
Horwood 2024
Retrospective study, LH vs nonLH
luxoid accounting for 8% of the study population
There were 14 complications
in 13/18 dogs with LH; seven were intraoperative (femoral fissure/fracture) and seven were postoperative (dorsal luxation, n = 5; femoral fracture, n = 1; acetabular cup septic loosening, n = 1). Revisions were performed for all LH dogs that encountered complications; satisfactory outcomes were achieved in 12/13 dogs.
Luxoid hip dysplasia was associated with a higher risk of major complications following THA in dogs, specifically intraoperative fissure/ fracture and postoperative dorsal luxation
palpable laxity and reducibility were not quantified in our study dogs
Most dogs with LH in our study had anatomical distortions as previously described for dogs with chronic luxation,23 including lateralization of the proximomedial femoral cortex and medialization of the greater trochanter.
poor acetabular development and counteracting tension during reduction likely contributed to the increased difficulty > Pre-existing soft tissue tension secondary to chronic
joint displacement may have resulted in excessive loading of the femur during reduction
findings suggest that luxoid dogs may require a more closed position of the acetabular cup.
All dogs with postoperative dorsal luxation underwent implant modification such as cup revision for increasing head size, or neck lengthening.
humans > use of femoral shortening osteotomy to minimize tension to the surrounding soft tissues.
severe muscular and periarticular soft tissue tension due to the marked distal translation of the femur following reduction may be an important predisposing risk factor
modifications could include deeper seating of the acetabular cup, known as the “medial protrusion technique,”41
release of muscles such as the rectus femoris m., hip
external rotators, and/or abductor m., prophylactic iliofemoral suture, and custom THA implants
Case factors for selection of femoral component type in canine hip arthroplasty using a modular system
Meltzer 2022
Retrospective study.
Animals: 128 dogs, 135 THR.
69 BFX, 47 hybrid, and 18 BFX-C were performed
It is possible that longer followup
time would result in increased detection of long-term
complications, such as aseptic loosening, extraosseous cement granuloma, and clinically significant polyethylene
wear
complication rate: 14%
catstrophic: 1.5%
femur fracture in our series (2.9%)
Dogs receiving hybrid THR were older with lower Canal flare index than dogs receiving BFX and BFX-C and heavier than dogs receiving BFX. There
was no difference in complications between groups. Catastrophic complications
and femur fractures occurred less frequently compared to recent studies
of BFX THR.
When compared, cemented and cementless systems
have similar complication rates and outcomes
Hybrid THR, using a cementless acetabular cup and a
cemented femoral stem, has also been described with
comparably favorable outcomes to purely cemented and cementless systems
The implant selected for each case is determined by demographic factors including breed, age, and size and morphologic factors including femoral CFI, femoral cross-sectional area, trabecular bone quality, and cortical thickness.
Implant infection necessitating removal has been reported
to occur in 7.7% and 8.6% of CFX THR.1,18 The use of
PMMA is thought to contribute the risk of infection
BFX-C were markedly lower than for hybrid and BFX.
This resulted in reduced study power and precluded finding
statistically significant differences between groups
Greater trochanter osteotomy as a component of
cementless total hip replacement: Five cases in four dogs
Silveira 2022
in dogs with severe medialization of the greater
trochanter or chronic craniodorsal hip luxation
All five surgical procedures resulted in satisfactory long-term clinical
results at follow-up a median of 48.2 months (range, 34–56 months) after THR.
There were no minor complications and one major complication
Ventral femoral head and neck ostectomy: Standard versus novel K-wire guided technique using a premeasured ostectomy angle in canine cadavers
Sapora 2021
Randomized, controlled, ex vivo study.
Animals: Ten mixed-breed canine cadavers
Residual femoral neck measurements were similar in both groups (p > .75). The average iFHOA in this study was 38.5 degrees.
Guided vFHO took longer (294.5 s, p = .002) than unguided vFHO (166.7 s).
mean iFHOA of 38.5 was less than the previously published 45 degree angulation for vFHOs
benefits vFHO
- sparing the gluteal muscles and dorsal joint capsule
which may provide for added stability and faster
return to limb function
- better visualization of the lesser trochanter which is spared during the osteotomy
- easily perform the procedure bilaterally without having to rotate patient positioning.
Technical challenges
- blind nature of the osteotomy,
- difficulty associated with removal of additional bone following the initial osteotomy,
- proximity of the femoral artery and vein.5,12
had to use osteotome - can’t place saw.
To date, there is no veterinary literature to support
that performing a vFHO is superior to the more traditional craniolateral approach and perceived benefits are speculative. Additional prospective clinical trials
vFHO vs standard comparsion?
ventral FHO approach
A routine ventral approach to the hip
was performed, including a pectineus myotomy at its tendinous origin from the iliopubic eminence.
Treatment Outcomes for Periprosthetic Femoral
Fractures in Cementless Press-Fit Total Hip Replacement
Monotti 2020
preston
retrospective, 28 dogs with fractures
total of 347 THR were performed using a cementless press-fi stem
8 occurred intraoperatively and 20 occurred at a median of 2 days postoperatively. (all occured within 6 weeks)
An oblique or spiral configuration was noted in 19 cases and 15 occurred at the distal end of the femoral stem(type B),
an excellent or good clinical outcome with bone
union can be achieved in a majority of cases that are stabi lized with a lateral plate with proximal screws placed in the greater trochanter and secondary cerclage wires.
Fractures were repaired with nonlocking(
18/28) or locking-platefixation (10/28). Cerclage wirewas appliedaround the plate
and proximal bone segment in 17/28dogs.Major complications occurred in 7/28 cases (five
deep infection, two mechanical failures). Bone healing was noted in 21/23 cases
Return to function was complete in 17
cases, acceptable in 8 cases and unacceptable in 3 cases.
double layer impervious surgical stockinette
was sutured to the dermis following the skin incisions, 5-day course of oral cephalexin (22mg/kg PO BID)
65% (13/20) of postoperative fractures had
a fissure detected during primary surgery and 13/75 fissure progressed to fracture
fractures are challenging to repair due to the scarcity of proximal bone stock available for fixation of both the femoral stem and purchase of implants such as bone screws. Femoral fracture is reported to occur in 2.9% of canine cemented THR and between 5.1 and 13% of uncemented THR.1–6 Identified risk factors for periprosthetic femoral fractures include age, low canal flare index, osteopathy and fissuring during femoral broaching or stem insertion.
Biomechanical studies have compared various repair constructs using cerclage wire, bone screws, cables, struts, compression and locking lateral plates as well as double plating.12
Fracture fixation using a lateral bone plate, proximal unicortical and distal bicortical screws as well as proximal cables or cerclage is themost stable construct for periprosthetic femoral fracture repair when the bone is healthy.
- Biomechanical evaluation of periprosthetic fracture repair in humanmodels has shown that lateral plating with proximal unicortical screws had the best stability
- in people, application of a bone plate that extends
from the greater trochanter to the femoral condyles around a stable stem is recommended - application of secondary stabilizers
in the form of cerclage wire or cables placed around the proximal aspect of the plate and greater trochanter and secured through the plate holes to prevent screw pull out - addition of a cable cerclage doubles the stability of
unicortical screw and plate constructs - Previous reports of femoral fracture occurring despite cerclage stabilization of intra-operative
fissures range from 0 to 45%. - Stabilization with multiple cerclage wires placed at least 1 cm distal to the fissure has been recommended to protect against fracture propagation
locking vs non: benefit of using a non-locking
system for the treatment of these fractures is the ability to direct bone screws in an orientation to maximize bone purchase.
elevated tension may remain in the proximal femur if large stems are impacted when the isthmus has been under reamed
people, type B1 fractures have a 13% incidence of non-union and implant failure due to undetected stem instability and as a result, some surgeons have recommended treating femoral
stems as unstable until proven otherwise
Comparison of femoral stem subsidence between three types of press-fit cementless total hip replacement in dogs
Mitchell 2020
traditional BFX, collared BFX, and BFX lateral bolt stems.
Study design: Retrospective radiographic study.
Sample population: Ninety-three dogs with 101 THR
Subsidence, canal flare index (CFI), stem canal fill (CF), stem orientation, and complications confirmed on radiographs
Subsidence was lower after placement of BFX lateral bolt stems
No differences were identified in CFI or stem orientation in the coronal and sagittal
planes or in complication rates between implants.
likely due to immediately
increased construct stability provided by the bolt early in
the postoperative period, prior to bone ingrowth.
results of this study because similar subsidence was identified
between BFX Collared and traditional BFX
Leaving a small gap of 1 to 2 mm between
the collar and the femoral neck bone helps ensure that the collar coming into contact with the bone does not stop insertion of the stem before a press fit is achieved
Despite the statistically significant difference in
subsidence between groups, all stem groups in this
study subsided on average what would be considered a clinically acceptable magnitude of subsidence in the
postoperative period.
Undersizing the femoral stem has previously been
identified as a factor contributing to postoperative stem subsidence.6,11 The average CF for all of the stem groups in this study was undersized compared with the recommendation of 85% CF;
The results of previous studies have provided evidence to support the idea that dogs with a CFI of less than 1.8 undergoing THR were more likely to experience subsidence»_space;> using bolt/collar may get around this
Early research on press-fit femoral stems has supported
the idea that a small amount of femoral stem subsidence
in the early postoperative period may actually improve
stem stability by allowing the stem to wedge more tightly
into the femur, creating a tighter press fit
> bolt/collar may prevent this.
no study has been published in which the quality of bone ingrowth achieved in canine femurs implanted with a BFX lateral bolt cementless femoral stem has been evaluated;
measuring subsidence is affected by rads positioning etc.»_space; Korani and colleagues13 reported a large
variability in subsidence related to limb positioning
observed on radiographs
small, retro, follow up 42-1008 days
A Biomechanical Comparison of Four Hip
Arthroplasty Designs in a Canine Model
Ordway 2019
evaluate if three alternative implant designs improve
fixation compared with the traditional collarless, tapered stem in the clinically challenging case of moderate canal flare index.
all biomedtrix
Study Design Twenty-four (six/group) laboratory-prepared canine constructs
The collared and collarless stem groups were stiffer in compression
compared with the collarless with a lateral bolt and short-stem groups
Peak failure loads (compressive and torsional) in this study were approximately
four to seven times the simulated gait loading (430 N, 1.6 Nm) regardless of
implant type and highlight the importance of limiting activity level (trotting, jumping)
following hip replacement in the postoperative period and during the osseointegration
of the implant.
for simulated normal gait loading, there were not substantial differences in biomechanical response for the four implant designs.
Even if hip joint loads do not exceed failure levels, our study showed the implantmotion relative to the femur can be appreciablewith a CFI of 1.8 to 2.4 and a limited number of cycles of loading
