Ch 59 Surgery for HD Flashcards

Question

sacral screw purchase

Answer 1

- 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.

Answer 2

35 - 70% Screw loosening and pelvic canal narrowing

Answer 3

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

Answer 4

increase in femoral head coverage and significantly reduced joint laxity (vezzoni from 50 > 70%) Medium to long-term radiographic outcomes > lower OA scores in DPO-treated hips compared with untreated hips (Jenkins 2020) previous studies > progressive osteoarthritis 1 year after TPO

Answer 5

- 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

Answer 6

The smaller the metallic grain, the stronger the implant Manufacturing methods to srengthen implants: - Forging - Investment casting - Hot isostatic pressing - Cold working - Heat working

Answer 7

- 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

Answer 8

Stainless steel and cobalt chromium = approx 200GPa Titanium = approx 100GPa

Answer 9

- 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

Answer 10

Iron Chromium Nickel Molybdenum

Answer 11

Chromium Molybdenum Nickel Implants: - BioMedtrix (BFX anf CFX) - Very hard with excellent wear and corrosion resistance

Answer 12

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

Answer 13

A metal that can be fabricated with a porosity and elastic modulus similar to those of cancellous bone

Answer 14

study of friction, wear, lubrication, and the design of bearings; the science of interacting surfaces in relative motion.

Answer 15

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

Answer 16

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

Answer 17

- low friction, - low wear debris generation, - biocompatible, - damage resistant.

Answer 18

1. **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) 3. **Fatigue wear** ( Cyclic loading causing cracks/microcracks or subsurface delamination) 4. **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) 5. **Corrosive wear** ( galvanic corrosion - oxidation that generally results from interactions of disimilar metals)

Answer 19

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

Answer 20

Kyon - Zurich - ceramic head > Zirconia Toughened Alumina

Answer 21

Titanium bearing surface with a cemented prosthesis

Answer 22

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)**

Answer 23

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

Answer 24

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*

Answer 25

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

Answer 26

- 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

Answer 27

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)

Answer 28

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

Answer 29

Pore size 50 - 400mcm Micromotion less than 20mcm Porosity (voids:material) of 30-40% is ideal | porosity is achieved using a sintered bead surface

Answer 30

**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

Answer 31

**biomedrix CFX** - With a cemented, or bonded, implant, the cement must withstand the shear stresses - require interdigitation of the PMMA with the trabecular bone of the medullary canal and bonding of the cement to the surface of the implant - strength depends on implant design and on cementing techniques. - implant-cement interface can be strengthened by surface roughening (sandblasting or bead blasting) - Grooves in the CFX acetabular component permit interdigitation of cement with the implant - drill holes and troughs aid in cement penetration into the acetabular bone bed STUDY: cemented stem (CFX) and a press-fit stem (BFX) found localized bone resorption at the greater trochanter, as well as generalized decreased periprosthetic bone density, in association with the press-fit stem but no decrease in bone density with the cemented stem (short term study only)

Answer 32

- 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)

Answer 33

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)

Answer 34

successful THR = stable, functional range of motion that is free from impingement - knowledge of the normal anatomy, orientation, and kinematics of the hip joint is needed

Answer 35

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

Answer 36

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

Answer 37

148 and 118 degrees

Answer 38

- angle of inclincation - femoral off-set - neck version - head:neck ratio

Answer 39

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.

Answer 40

ratio of the circumference of the femoral head : neck. - larger the ratio, the greater the range of motion - femoral head size is limited by the size of the acetabular component - too small of a femoral neck circumference will predispose to neck failure or fracture larger femoral head - decrease the risk of luxation - generates more wear debris

Answer 41

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

Answer 42

degree to which range of motion is limited by implant design - fully constrained, semiconstrained, or unconstrained - will affect the impingement-free ROM, resistance to luxation, generation of wear debris, and implant-bone interfacial stresses - Most total hip prostheses are semiconstrained and permit flexion, extension, and rotation. - Translation is generally not permitted > there will be a fixed impingement-free stopping point, and this abrupt stop can lead to interfacial shear stresses - constraint is primarily determined by femoral head coverage - degree of prosthetic head coverage varies with implant system and is also affected by implant positioning.

Answer 43

1. acetabular version 2. angle of lateral opening, 3. 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.

Answer 44

15 - 20 degrees acetabular retroversion

Answer 45

45 degrees lateral opening

Answer 46

15 - 25 degrees anteversion

Answer 47

**indications** - pain and loss of function associated with DJD secondary to hip dysplasia - avascular necrosis of the femoral head - capital femoral physeal fractures - femoral head fractures - acetabular fractures - following femoral head and neck excision or DPO - do not advise surgery unless the clinical signs cannot be adequately controlled by alternative means **contraindications** - Concurrent orthopedic or neurologic disease - if CCLR or LS disease is present, should be addressed prior to THR - lateralization of the femur may exacerbate preexisting medial patellar luxation - acetabular growth plate should be closed - open trochanteric apophysis risk of trochanteric fracture or avulsion - patients with chronic luxation (muscle contracture) increased risk of reluxation - young??? 6 and 10 months demonstrated the safety and efficacy, risk of undersized implants to expected weight - giant-breed dogs, a custom femoral stem may be appropriate

Answer 48

- accurate templating - adequate cement mantle of at least 2 mm around entire CFX stem - BFX stem size is based on maximal fill of the medullary cavity at the diaphyseal isthmus - standard ventrodorsal radiographic projection will present an artifactually foreshortened femur > craniocaudal horizontal beam better - “stovepipe” (cylindrical) versus “champagne flute” (tapered) conformation may determine not only implant size but also the method of implant fixation (e.g., press-fit for a “champagne flute” vs. cement/non-press fit for a “stovepipe” - The size of the acetabular component is chosen based on cranial-to-caudal fill - source of stability of press-fit acetabular components is the cranial and the caudal pole of the acetabulum

Answer 49

- minimize the likelihood of implant malpositioning - lateral recumbency with the patient perpendicular > Fluoroscopy can be used to confirm - craniolateral approach, “L-shaped” tenotomy of the tendon of insertion of the deep gluteal muscle - capsulotomy - Hatt spoon to transect the ligament of femur head

Answer 50

- exception of the Helica hip system, which is a screw-in femoral prosthesis, all total hip arthroplasty systems require some degree of femoral canal preparation - femoral neck excision must extend as far laterally as possible. - Inadequate > malpositioned (varus and caudal tipping) femoral component - series of broaches and/or drill bits and files or rasps - press-fit prostheses, the accuracy of the preparation is critical - femoral neck anteversion is introduced by the surgeon - trial prosthesis is utilized - Cemented prostheses generally have a collar that restricts the subsidence

Answer 51

- 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

Answer 52

- cup is usually placed first, followed by placement of the femoral stem - cup > approximately 45-degree angle of lateral opening and 15- to 20-degree retroversion - stem is placed in 15- to 25-degree anteversion - offset created by the prosthetic head and neck must provide muscle tension and impingement-free ROM - There should be no Barlow sign - tested for resistance to luxation in both a cranial-dorsal and a caudal-ventral direction - Evaluation of impingement > interfering osteophytes are removed.

Answer 53

95% success 5 - 22% complication rate

Answer 54

- Luxation (2 - 17%) - Femoral fracture (2.9% cemented, 5-13% pressfit) - Acetabular fracture - Acetabular cup avulsion - Femoral stem avulsion - Subsidence (less than 4-5mm likely insignificant) - Implant failure - Cement failure

Answer 55

- Aseptic loosening - Septic loosening (1 - 2%) - Stress protection

Answer 56

- ability to accurately assess outcomes for total hip arthroplasty requires the publication of long-term, high-quality, peer-reviewed studies > such studies are lacking - Very few level 1 or level 2 evidence-based studies have been published - Bergh and colleagues: inadequate evidence to support the claim of full return to normal function with any procedure or implant system - Complication rates for total hip arthroplasty have historically been underreported - Most total hip surgeons would not consider lameness that is localized to the hip region to be a successful - proficiency achieved after performing 44 total hip arthroplasty procedures. - broadly classified as either mechanical failure or biological failure - mechanical failure can lead to biologic failure and vice versa

Answer 57

- 2% to 17% - highly dependent on surgeon experience Risk factors: - **excessive anteversion** of the femoral or acetabular component > risk of craniodorsal luxation - **excessive retroversion** of femoral or acetabular component > caudoventral luxation - **excessive angle of lateral opening** (>60 degrees) > craniodorsal luxation - **low angles** of lateral opening (<25 degrees) or a short femoral neck > ventral or caudoventral luxation - malpositioning can decrease the impingement-free range of motion - **luxoid hip** - Preexisting **laxity** > reported as a risk factor - intra-op: re-create the luxation in order to determine the true cause - inspection of acetabular component may reveal damage patient factors that can affect the risk - periarticular osteophytes (impinge on femoral neck) - hip joint conformation (variation in standing angles for different breeds, adducted limb if contralateral limb amputated) - severity of architectural changes

Answer 58

- described by the Vancouver classification press-fit stem - fissure develop during impaction (isthmus has been under reamed) or subsidence following surgery - dt failure with compressive loads - classification B2 - risk factors: age, low canal flare index, osteopathy and fissuring during femoral broaching 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

Answer 59

The Vancouver classification: - Fracture at level of greater trochanter Ag - Fracture of lesser trochanter Al - Fracture with stable prosthesis B1 (screw fixation) - Fracture with unstable prosthesis B2 (press-fit stem) - Fracture with unstable prosthesis, worse prognosis B3 - C describes fractures distal to prosthesis (cemented stems)

Answer 60

- uncommon, there are very few reports - occur as a result of impaction during implantation of a press-fit cup - Bone plate fixation followed by cementing a press-fit cup

Answer 61

- result of inadequate bone support for the implant - inadequate initial press-fit (Imprecise reaming or substantial malpositioning) - primary source of a secure press-fit arises from purchase at the cranial and caudal bone columns (not dorsal coverage) excessive dorsal rim bone loss - Dorsal rim augmentation with bone graft harvested from the excised femoral head, success has been reported though concerns re osseointergration - use of undersized implants - reaming partially through the medial wall in order to medialize the cup and provide greater coverage - contribution of the dorsal rim to implant stability is unknown - StUDY: no significant decrease in resistance to cup avulsion between the intact and dorsal rim loss groups > augmentation not indicated with <50% dorsal rim loss.

Answer 62

press-fit stem - occurs prior to osseointegration - strongly correlated to the surgeon's learning curve - undersizing risk factor > ideally 85% canal fill - 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 - early research > small amount of post-op subsidence may actually improve stem stability by allowing the stem to wedge more tightly 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

Answer 63

- Failure of the metallic component is rare - consequence of excessive cycling dt instability i.e. failure of osseointegration - polyethylene failure from typical wear rates likely dt instability, impingement, or failure of the metal backing mechanical causes of cement failure - fracture of the cement mantle (due to cement preparation > greater porosity creates stress risers at the site of the voids) - debonding at the cement-implant interface (increase risk: exposure to body fluids, titanium stems, and varus positioning) - Loosening at the cement-bone interface (fibrous tissue interposition between the cement and the bone dt residual fat or particulate bone debris or inadequate cement pressurization) *study: mechanical testing revealed 63% of cemented stems were loose, and the primary mode of failure was debonding at the implant-cement interface. Acetabular cups > cement-bone interface*

Answer 64

**(1) wear debris** = primary cause of aseptic loosening - occurring months or years after total hip arthroplasty - may/may not be beyond the control of the surgeon > creation of wear debris the result of impingement in most cases or normal linear wear associated with cyclic loading - Subluxation also likely results in increased wear - crossover between mechanical and biological failure i.e. poor press-fit > micromotion > excessive wear debris. - Once **osseointegration occurs, generally within the first 4 months after surgery** wear debris can be generated by impingement or normal cyclic loading **(2) stress protection** - Loosening that is unrelated to wear debris - associated with the elastic modulus mismatch between the implant and the bone, implant and cement, cement and bone - Stress protection–related bone resorption noted in the region of the calcar Dx - progressive widening of any lucency on serial radiographs suggests loosening - accompanied by clinical lameness, a pain response Treatment - removal of the periprosthetic fibrous membrane is a crucial part of revision. - membrane contains mediators of bone lysis - as early as possible in order to minimize the magnitude of bone loss - cemented prostheses, all cement should be retrieved | progressive widening of lucency on serial rads suggests loosening

Answer 65

Digital radiographic artifact that can make evaluation of periprosthetic lucency challenging

Answer 66

Creation of a bone flap starting at base of greater trochanter and extending the length of the cement mantle. Edges should be beveled and corners should be rounded

Answer 67

Wear-debris mediated osteolysis

Answer 68

Contains **mediators of bone lysis** - Activated macrophages - TNF-a - Oxygen-derived free radicals

Answer 69

- infection - 1% to 2% - association between a positive intraoperative culture and adverse outcomes (i.e., infection) has not been identified - very few reports of successful revision of septic loosening cases in the vet

Answer 70

- present several months following total hip - sclerotic linear opacities that are generally distal to the tip of the femoral stem - STUDY: 14% of cases that included both press-fit and cemented femoral stems. - STUDY: kyon reduced from 19-2.9% with modified technique > reduction of the incidence suggests the endosteal blood supply may be damaged by excessive reaming. - clinical significance is unknown

Answer 71

- consequence of retraction of the femur, generally during acetabular preparation - leakage of polymethylmethacrylate (PMMA), either due to heat or entrapment - incidence in one study was 1.6% - usually self-limiting and generally resolves within 6 weeks

Answer 72

- cemented and press-fit - STUDY: incidence of 82% > only 1/40 case developed clinically relevant consequences (sudden death) - Zurich Cementless hip study > no cases (11) developed PTE - **pressurization** of medullary canal does not occur during Zurich stem implant/prep, suggest pressurization is implicated in the formation of pulmonary fat emboli

Answer 73

acetabular component - Appropriate angle of lateral opening and retroversion angles, with or without inclination angles - ventrodorsal projection > account for pelvic tilt can introduce measurement error - cranial and caudal coverage - full seating of the cup (i.e., no lucency stem - press-fit > canal fill at the isthmus, implant should be intimately associated with the endosteal surface - cemented > minimum 2 mm mantle, stem should be centered - Zurich > stem should contact the medial cortex - accurate calculation of the anteversion angle of the femoral stem is challenging

Answer 74

- salvage procedure - eliminate pain caused by the “bone-on-bone” contact outcomes - Historically, considered inconsistent for dogs more than 20 kg - kinematic and force plate data > patients with more advanced/chronic hip disease have good outcomes regardless of size - case series, good (no lameness) in 38%, satisfactory (slight lameness) in 20%, and poor (persistent mild to severe lameness) in 42% - to worser the OA, the better the outcome (may be in part dt more fibrosis of joint capsule)

Answer 75

- 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

Answer 76

- 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

Answer 77

1)**Hip denervation** - Sensory innervation to Hip: femoral nerve (cranioventral innervation) obturator nerve (caudoventral innervation) cranial gluteal nerve (craniolateral innervation) sciatic nerve (dorsolateral innervation) - studies geneerally show poor ooutcome, i.e only 50% improvement - strip of periosteum is excised from the dorsal surface of the acetabulum 2) **Pectineus myectomy** - transection of the tendon of origin of the pectineus muscle at the iliopectineal eminence - pectineus muscle is an adductor of the femur. - rationale > the muscle creates tension on the hip joint capsule

Answer 78

Helica cementless hip.55. Retrospective. first-gen (39%) complications but (86%) recovered with revisions second-gen (32%) complications, but (93%) satisfactory +/- revision Complications: 34·5% aseptic loosening > 20%. others: luxation, cup loosening, acetabular # no risk factors were identified first-generation femoral stems are relatively short potential for early osteointegration permits the HHE to be implanted in dogs from 9 months of age onwards higher postoperative complication rate than other systems

Answer 79

Retrospective. 11 craniodorsal luxation after THR (cases with high ALO) treated with DPO - ALO reduced: median 66.2° to 55.9°, version angle increased: median 25.6° to 35.3° - craniodorsal luxation reoccurred in 5/11 → closed reduction (1/5), capsulorrhaphy (1/5), cup repositioning (3/5) - long-term complications: 7/11 explantation – 5/7 aseptic loosening, 2/7 infection Reluxation was frequent after DPO three of the five dogs with recurrent luxation had risk factors > luxoid hips + FHNE

Answer 80

Prospective. outcomes and complications from multiuser canine hip replacement registry, n=2375 - post-op LOAD scores improved (21 → 11) - complications: vet-reported 8.5%, owner reported 23% (vet-reported almost all major, underreported others) - major complications: 4% . most common luxation > fracture > loosening. 2% catastrophic. - 6% euthanatized due to complications or died suddenly - no association to weight, age, sex or breed - BFX and Helica → higher complications to revise FHNE system used: Kyon (46%), BioMedtrix CFX (22%), BioMedtrix hybrid (11%), BioMedtrix BFX (9%), and Helica (4.5%). Conclusion: Excellent outcomes 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

Answer 81

Retrospective. pre-closure povidone-iodine lavage was efficacious and had positive cost-benefit in reducing infection after THR - 0.35%PI – 3 minutes low-pressure pulsatile (min 60ml) - infection rate 21/2111 (0.9%) non-PIL, 0/102 PIL - comparative numbers low but cost of revision due to infection → PIL in 2415 cases to 1 revision - breakeven infection rate 0.95%. need prospective comparison to eliminate confounding factors, lavage solution: broad spectrum, is bactericidal but not cytotoxic at concentrations required to diminish the bacterial and biofilm load by 99.9%, rapid onset to full effect. PI: delivering iodine directly to the cell surface where it enters and oxidizes components of the cytoplasmic membranes. safe at 0.35% (cytotoxic >1.4%) | need prospective comparison to eliminate

Answer 82

Retrospective. 195 consecutive cases of BFX lateral bolt stem - complications: intra-op: 11.8% post-op: 13.6%, major 9.2%, minor 4.4% - femoral fracture 3.6%, luxation 3.6% - stem failure, septic loosening, aseptic loosening, acetabular fracture - 2.6% explant (Revision successful in 13/18 (72.2%)) - age associated with post-op fracture - mean stem subsidence at 1m = 1.22±0.16mm - 97.4% return to normal long-term function (longterm success high) THR include: femur fractures (6.8%–13.1%) intraoperative femoral fissures (3.6%–21%), stem migration (2.7%–8.1%) luxation (3%–13.5%). methods to combat subsidence = cerclage to prevent fissure propagation (attempt to restore hoop strength),collared stem, lateral bolt ex vivo biomechanical study, bolt enhanced stability and limited subsidence compared to the traditional BFX femoral stem under cyclical loading.

Answer 83

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

Answer 84

fluoroscopic characterisation of cementless acetabular component position - using circular recess of BFX cup ellipse from standardized reference images - ALO 35° - ellipse barely visible, overlapped by dorsal cup margin - ALO 45° - ellipse bean shaped with 50% coverage by dorsal cup margin - ALO 55° - ellipse more circular with no coverage by dorsal cup margin - perfect agreement with measured ALO | ex vivo, BFX only

Answer 85

Retrospective. 6 dogs. unilateral DPO for The untreated limb had OA OA difference not significant > (most likely related to power/sample size) total pressure index and GAIT4 Dog lameness score equivalent to normal dogs GAITRite (GAIT4Dog) provides a quantitative assessment of lameness > pressure sensitive walkway providing precise canine temporal spatial gait analysis and lameness detection. 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

Answer 86

Retrospective. 22 DPO, 4 no Sx. medium- to long-term radiographically confirmed outcome Follow-up radiographs (median, 4 years) 89% DPO BVA-HD ≤10, 50% nonsurgical cohort had BVAHD >10. 10% not considerably improved/similar to non-sx Laxity index score > 1 was not a contraindication (7 hips) Tx successul All hips mild osteoarthritis according to baseline radiographs > New goal DPO > diminish coxofemoral subluxation to improve function rather than to prevent osteoarthritis. previous studies > progressive osteoarthritis 1 year after TPO Ventroversion shifts the acetabulum closer to the femoral neck causing impingement > explain reduce ROM in this study | prospective studies with objective measures needed

Answer 87

Compared with distraction views, NA is an inaccurate predictor of degenerative joint disease.14 Norberg angle may result in false negatives and false positives,25 and the 105 limit is an inaccurate measure of laxity compared with distraction measurements.14

Answer 88

study is important because it lays important methodological foundations for using precise patient-specific measurements of the native acetabular orientation to allow computer-navigated or robot-assisted orientation of the acetabular component in total hip arthroplasty, as being performed in humans found “that although the mean values for acetabular alignment were generally consistent with clinical guidelines, some dogs in their (sic) study had more extreme values, and there was a wide range of angles across different breeds. Using a standard set of recommended angles across all breeds of dogs may lead to incorrect cup placement and an increased risk of postoperative complications such as luxation.

Answer 89

Lifetime cost of surgical treatment for canine hip osteoarthritis is less than conservative management in dogs under eight years of age aged 1 to 7 years, FHNE had the lowest lifetime cost. Total hip replacement had the second lowest cost until age 4, after which conservative management was lower. > 8 years, conservative management was the most cost-effective. **prevalence of hip dysplasia is 15.6% in all breeds of dogs** weight management, pain management with NSAIDs, and nutritional management via diets high in omega-3 fatty acids all have sufficient evidence to support their use.7–10 There is weak evidence to support other analgesics. anti–nerve growth factor antibody bedinvetmab, the cost of conservative management may soon be much higher than estimated here.

Answer 90

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

Answer 91

Retrospective. 18. THR in luxoid . luxoid 8% of the study population 14 complications: 7 intraop (femoral fissure/fracture) and postoperative (dorsal luxation, n = 5; femoral fracture, n = 1; acetabular cup septic loosening, n = 1). Revisions > satisfactory in 12/13 dogs. Luxoid hip dysplasia was associated with a higher risk of major complications (luxation 25%) anatomical distortions > lateralization of the proximomedial femoral cortex and medialization of the greater trochanter. findings suggest that luxoid dogs may require a more closed position of the acetabular cup. humans > use of femoral shortening osteotomy to minimize tension to the surrounding soft tissues. modifications > deeper seating of the acetabular cup, release of muscles such as the rectus femoris m., prophylactic iliofemoral suture, and custom THA implants

Answer 92

retrospective Cats 44 that underwent THR (n = 56). slipped capital femoral epiphysis (34/56). cemented micro complications (11/56 ~20%) included 9 major complications. Owner satisfaction was reported as “very good” in 30/33 cases (90.9%). prevalence radiographic feline hip (OA) as 69%, Maine Coon is overrepresented, few peer-reviewed long-term outcomes FHNE. THRs that luxated (4/6) suffered a second luxation

Answer 93

prophylactic single loop cerclage distal to femoral neck osteotomy, prox to lesser trochanter - no proximal femoral fracture, 1 fissure, 2 fracture of femoral diaphysis at distal stem level preventing postoperative fissure and stem subsidence is to place a single loop cerclage after stem placement prevent intraoperative and postoperative fissures > prophylactic double-loop cerclage prior to broaching. Increased risk: - proximal femur very (“stovepipe”) or very flared (“champagne flute”) - greater trochanter more centrally over the femur, > broaching and stem placement have a more varus orientation - Abnormal femoral neck structure/prior fracture > bone proliferation more vigorous broaching, STUDY: femora that had a fissure stabilized with double-loop cerclage, hoop strength of the proximal femur was fully restored compared to single-loop

Answer 94

Short-Term Hip Hemi- Arthroplasty in 11 Dogs (kyon cupless) for revision of THR or primary pathology - 10/11 acceptable function based on HCPI - mild lucency of acetabular bed and periarticular sclerosis in 4/11 - clinical significance unknown Sx: acetabulum was reamed. hemi-arthroplasty may have a reduced risk of luxation compared with THR due to its comparatively larger femoral head:neck ratio

Answer 95

post-op complications of DPO, n=458 DPO - complications: overall 8.2% - ischial greenstick fracture 3% - isolated screw loosening 2.8% DPO, 0.5% screws - isolated screw breakage 0.01% DPO, 0.1% screws - incomplete ilial fracture 0.6% - partial caudal plate avulsion 0.6% - sciatic neurapraxia 0.4% - SSI 0.2% - implant-associated pain and lameness 0.4% - major 0.6% - SSI and implant-associated pain cases - risk factors: laterality (left- or right-sided) and body weight (>24kg) - age, breed, plate type, plate angle, sex and bilateral vs unilateral not risk factors - specific DPO plates reduced complications vs DPO with TPO plates - DPO plates → more screw purchase (4 screws with more purchase in the cranial aspect of the caudal segment +/- divergent locking screws vs TPO – more purchase in the cranial segment) - better resistance to pull-out caused by recoil effect from intact ischium | bias of only 2 surgeons

Answer 96

Retrospective. selection of femoral component type, modular system Animals: 128 dogs, 135 THR. 69 BFX, 47 hybrid, and 18 BFX-C were performed longer followup detection of long-term aseptic loosening, wear etc complication rate: 14% catstrophic: 1.5% femur fracture in our series (2.9%) hybrid tended to be higher weight, older and lower mean canal flare index (CFI) - low CFI (stove-pipe) → higher risk of subsidence and femoral fracture with cementless - proposed cutoff for using CFX = ≥7yo, <12kg, ≥50kg, CFI <1.8 cemented and cementless systems have similar complication rates and outcomes Hybrid THR, cementless cup and a cemented stem, compare favorably to purely cemented and cementless systems

Answer 97

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 greater trochanter morphology Grade 1 = lateralized, Grade IV = medialized - trochanter grade associated with post-op stem alignment and frontal plane translation - Grade I → slight valgus stem, Grade II-VI → varus stem

Answer 98

retrospective study initial 21 cases of Zurich for surgeon with experience with other systems had high success rate and low complciations - complications: 2/21 major, 1/21 minor

Answer 99

ex vivo. use of K-wire guided techniqe subjectively improved ventral FHNE - may reduce risk of inappropriate cut angles mean iFHOA of 38.5 (< previously published 45) benefits vFHO - sparing the gluteal muscles and dorsal joint capsule > added stability and faster return to limb function - better visualization of the lesser trochanter - perform 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 - had to use osteotome - can’t place saw. | vFHO vs standard comparsion?

Answer 100

A routine ventral approach to the hip was performed, including a pectineus myotomy at its tendinous origin from the iliopubic eminence.

Answer 101

Retrospective. 13. THR with contralateral pelvic limb amputation satisfactory results in 13/13 (follow up mean 3mths) SHORT TERM - no luxation, 1 failure of osseointegration revised increases in rotational excursion of the pelvis and central placement of the foot > hip adduction > predispose to dorsal luxation. amputee bears 26% to 33% of its body weight in the sole pelvic limb cf 40% bilateral limbs > BFX lateral bolt stem or cemented fixation > offerd more immediate fixation relative contraindication for THR > study reported a postoperative complication rate of 55.6% > 44% early luxation Dual mobility cup recommended for cases with high risk of luxation (success in 50 normal dog THR, no post op luxation)

Answer 102

retrospective, 28. treatment of femoral fracture of cemtnless THR with lateral plate fixation +/- cerclage - achieved bone healing in 21/23 cases - 7/28 (25%) major complication – 5 deep infection, 2 mechanical failure - function complete in 17, acceptable in 8 and unacceptable in 3 347 THR > 8 intraop, 20 median of 2 days (all occured within 6 weeks) oblique or spiral > 19 cases, distal end of the femoral stem(type B) > 15 65% (13/20) of postoperative fractures had a fissure detected during primary surgery and 13/75 fissure progressed to fracture Fracture fixation: lateral bone plate, proximal unicortical and distal bicortical screws + cables or cerclage = most stable construct according to biochem studies. * cerclage/cable prevent screw pull out * fracture occurring despite cerclage stabilization of intra-operative fissures range from 0 to 45%. * 1cm below to prevent propogation * benefit non-locking ability to direct bone screws in an orientation to maximize bone purchase.

Answer 103

Retrospective. subsidence reduced after lateral bolt stem vs collared and traditional BFX, n=101 - no difference between collared and traditional - canal fill, canal fill index, stem orientation and complication rate not associated with increased subsidence - lateral bolt stem → increased early construct stability before subsequent bone ingrowth Leaving a small gap of 1 to 2 mm >ensure bone does not stop insertion of the stem before a press fit is achieved quality of bone ingrowth with a BFX lateral bolt unknown measuring subsidence is affected by rads positioning | small, retro, follow up 42-1008 days

Answer 104

comparison of 4 x BFX implants under simulated load and overload in low canal flare index (stove-pipe) model collared and collarless stem stiffer in compression than collarless with lateral bolt and short-stem - loading above simulated gait → reduction in compressive and torsional stiffness - short-stem implant highest stiffness with high loading - peak failure loads >4-7x simulated gait - exercise restriction important regardless of implant type, - under simulated normal gait loading, there were not substantial differences in biomechanical response for the four implant designs. our study showed the implant motion relative to the femur can be appreciable with a CFI of 1.8 to 2.4 and a limited number of cycles of loading

Answer 105

outcomes and complications of single session bilateral femoral head and neck excision (FHNE) in 39 cats One major complication and five minor complications were reported. cf THR > upt to 20% complication risk. All but one cat returned to normal activity and no owners reported concerns after the 2-week postoperative recheck 14 cats > 4-6wk follow up > two (14.3%) cats had lameness noted, two (14.3%) had muscle atrophy and one (7.1%) had mild hip discomfort. 75% doral approach, 25% ventral.

Answer 106

ground reaction forces in 9 unilateral (THR) compared to 9 (FHO) cats. retrospective. FHO > significantly lower muscle circumference and (ROM) whereas THR showed no statistically significant differences between their hindlimbs. Owner surveys > THR better peak vertical force values were higher in the operated limb THR group than FHO group, resulting in lower symmetry indices (indicating better symmetry) and better loading of the corresponding hindlimb. only one GRF measurement and examination at a previously undefined time postoperatively; therefore, it is not clear whether the results would have been different at another time point. subjective owener surery > cuation interpet results.