Arthroplasty Flashcards

Question

You do this procedure on a healthy 65 yo male. What are all the complications?

Answer 1

* **Femoral Notching** * Jig is placed too low on the femur * Lowers load to failure (fracture) * In bending the fracture extend from the notch creating an oblique fracture * **Peroneal Nerve Palsy** * **PCL deficiency (in a CR knee)** * Will become loose in flexion, knee will feel unstable and femur will start to slide forward * Will get anterior knee pain * Treat with revision to PC or CCK * **Lateral Retinacular Release** * **Patella Fracture** * **Intra-operative MCL injury** * Primary repair with 6 weeks NWB with full ROM (if young) * Recommended treatment is to covert to highly constrained prosthesis * **Arthrofibrosis** * **Post-op Flexion Contracture** * The most important factor of post-op range of motion is pre-op ROM * In a well balanced knee the _gastroc_ is the cause of the flexion contracture * **Severe extra-articular femoral deformity** * Can do a combined osteotomy with TKA with long stem that goes past the osteotomy site * **Osteolysis** * Usually around _8-10 years_ * Gradual increase in effusion with mild warmth but no erythema * Normal lab results and aspiration * Most common place is the _posterior femoral condyle_

Answer 2

8-10 years posterior femoral condyle

Answer 3

* **Functional ROM** * 90 degrees needed to go down stairs * 95 to get up from a chair * **Factors to assess** * Boney resection * patella baja/elevation of joint line * tibial slope (not enought) * posterior osteophytes * patient factors * **Radiography** * Assess joint line based on fibula and patella * Assess alignment of implants * presence of osteophytes * **Treatment** * ****depends on the surgeon, some will take them back if not to 90 by 6 weeks, can be done up to a year * _Manipulation_ * usually at _6 weeks_ * Later manipulation as high rate of fracture * _Scope_ * release adhesions, cement/loose bodies * Arthrotomy * poly exchange, patellar exchange, posterior release, tuberosity transfer, quads snip * Not highly recommended, often fails with recurrent pain and stiffness * _Revision TKA_ * tibial tuberosity osteotomy, V-Y plasty * address tibial slope, patellar height

Answer 4

* Can also occur with lowering of the joint line * **Overview** * _patellar tendon rupture_ is a rare and devastating complication after TKA with an incidence reported ranging from **0.17% to 2.5%** * Quadriceps tendon rupture extremely rare ~1%. * Higher risk with infection, multiple surgeries, hinged prosthesis * _Patellar Fracture_ * Thickness \<12mm * Lateral retinacular release (osteonecrosis) * Due to transection of superior genicular artery * Osteonecrosis * Theoretical risk with removal of fat pad, lateral release, quads turndown * Blood supply comes from the medial to lateral part of the knee * Can also be caused by maltracking or direct trauma * **Quads or patellar tendon rupture** * Overall very poor outcome * **Treatment** * Can treat conservatively if the component is solid and there is no extensor lag * Quads * Drill holes if no patella resurfacing * Suture anchors if there is less bone stalk * Patellar * Primary repair with drill holes or suture anchor does not do well * Component revision if there is enough bone, component resection if not * Allograft or autograft if there is significant extensor lag * Fresh frozen is the prefered choice * Use a detensioning wire (or mersiline tape) for 3 months

Answer 5

* High clinical variability in practice * **Complications** * patellar fracture * malailignment * **Consequences** * Anterior knee pain with higher revision rate * 50% re-operation rates and higher complication rates with no patellar resurfacing - at about 5 years outcomes become the same * Earlier designs had a high failure rate, newer designs have longer survivorship * **Technique** * Indicaitons to resurface * maliagnmnet * minimal wear * inflammatory disease * If you're not resurfacing use a more anatomic design * Patellar cut * Use the caliper before and after * Under resection leads to pain and a tight compartment * Over resection leads to fracture - max thinness is 12mm * Medial-superior placement is ideal * Helps to restore Q angle with fewer tracking complications * Lateral Release * complications * fracture * component dislocation * wear * infection

Answer 6

**Patella Baja** * **Introduction** * A condition manifested by a shortened patellar tendon * Leads to limited flexion due to patellar impingement on the tibia in extremes of flexion * **Causes** * proximal tibial osteotomy * tibial tubercle shift or transfer * proximal tibia previous trauma * **Presentation** * mechanical block to full flexion * **Management** * Operative with TKA * **lowering joint line** * distal femoral augmentation and cutting off more proximal tibia * avoid bone cuts that raise the joint line (raising the joint line will effectively increase the patella baja deformity) * **elevating patella** * use small patellar component and place superiorly * trim bone or polyethylene to reduce impingement * one option in severe deformity is to cut the patella but not to resurface it (this will reduce patellar impingement allowing for more knee flexion)

Answer 7

**RULE OUT INFECTION!!!!!!!!!** * take a complete history around the pain, duration, time pain free, instability, PMHx, smoking * assess for knee stability, contractures, neurological issues, vascular issues * previous inctions * patellar tracking * Get all previous OR notes * ESR, CRP, possible aspiration * Bone scan - fracture, infection * Imaging - AP, lateral WB views, full length standing * compare to previous, assess for further lysis * assess opposite knee * Look at lysis around each component * component alignment, shift * posterior sag tibia = PCL * full alignment of knee * **Goals of revison surgery** * _extraction of components_ with minimal bone loss and destruction * _restoration of bone deficiencies_ * _restoration of joint line_ * _balance knee ligaments_ * _stable revision implants_ * _address patellar malalignment_ * _soft tissue coverage_ * **Exposure****** * Use most lateral incision with multiple incisions * Try to leave skin bridge 6cm if you can't use old incision * Release all adhesions and scar tissue * do not pull off the patellar tendon * If the patella cannot be everted safely * _Quads snip - snip across the quads_ * No need to protect WB * 45 deg angle to arthrotomy * _Patellar turndown - V-Y_ * Associated with weakness * Protect WB with extension brace for 6 weeks * _Tubercle ostotomy_ * Less weakness but can't do if there is patellar baha * 2cm wide, 1cm thick, 6 cm long * start 1cm medial to tubercle with an osillating saw * finish laterally with an osteotome * stemed revision must bipass osteotomy * WBAT with ROMAT * **Prothesis Extraction** * ****Do with as little damage as possible * Contact rep for specific implant removal * ostotomes, punchs, slap hammer, clamps, saw, burr * Take poly out * Free femur with saw and osteotome * don't lever * remove with punch or slaphammer * Similar technique with the tibia * may need to cut the stem * osteotomy for exposure * Patella * can leave, or cut the pegs off and then drill them out * Clear cement, if you are re-cementing you can leave the cement * **Bone Loss****** * _Cause_ * __abrasion, infection, osetolysis, extraction * load sharing to the diaphysis (stem) * stem is cement often, unless you have such sever bone loss you need to go up to the diaphysis (not like a hip) * cavity defect filling * cement * for cavitary defect is \< 1 cm * structural bone grafts * includes metal augments, or modular endoprosthetic devices * indicated for segmental defect \> 1cm**** * **Appropriate implants** * Tibia first, establish joint line * use contralateral films * 2cm above fibular head * _hinged_ * no ligamentous support * multiply revised * hyperextension seen in polio * tumor, infection * charcot (relative) * _CCK/stem_ (constrained condylar knee) * MCL/LCL laxity * flexion gap * ****_CR to PS or CCK_ * **Soft tissue** * ****Medial gastroc is the most reliable * Do not delay closure, should be done at the same time as revision

Answer 8

* **Pain** * pain scores less favorable than primary TKR * activity related pain can be expected for 6 months * **Stiffness** * **Neurovascular problems** * peroneal nerve subject to injury with correction of valgus and flexion deformity * **Infection** * **Skin necrosis** * prior scars should be incorporated into skin incision whenever possible * bloody supply to anterior knee is medially based, so lateral skin edge is more hypoxic * if multiple previous incisions, use most lateral skin incision * can use wound care, skin grafting, or muscle flap coverage (gastroc) for full thickness defects * **Extensor mechanism disruption** * can use extensor mechanism allograft using achilles tendon * Semi-T graft can be used to help augment * Can use this intra-op if you loose the tendon

Answer 9

**KNEE ARTHRODESIS** * **Indications** * painful ankylosis after infection or trauma * neuropathic arthropathy * tumor resection * salvage for failed TKA (most common) * loss of extensor mechanism * **Contraindications** * absolute * active infection * relative * bilateral knee arthrodesis * contralateral leg amputation * significant bone loss * ipsilateral hip or ankle DJD * **Optimal Position** * 5-8° valgus * 0-10° of external rotation (match other leg) * 0-15° of flexion * some limb shortening advantageous for patient self-care

Answer 10

* **Fixation** * _Intramedullary rod fixation_ * can be one long antegrade device or a two part device connected at the knee * patella can be left alone or incorporated into arthrodesis * _External fixation_ * must allow compression of arthrodesis site * done with unilateral external fixation, Ilizarov, or Taylor Spatial Frame * _Plate fixation_ * can be done alone in combination with intramedullary nailing * **Complications** * Nonunion * Infection * Low back pain * Ipsilateral hip degenerative changes * Contralateral knee degenerative changes * Fracture * supracondylar femur or proximal tibial metaphysis fractures

Answer 11

* **Indications** * patients with advanced arthritis and good proximal femoral bone stock * three types of patients for whom hip resurfacing is indicated (Amstutz, et al) * patients with proximal femoral deformity making total hip arthroplasty difficult * patients with high risk of sepsis due to prior infection or immunosuppression * patients with a neuromuscular diagnosis * **Contraindications** * _absolute_ * bone stock deficiency of the femoral head or neck (e.g., cystic degeneration of the femoral head) * \>75% femoral head * abnormal acetabular anatomy (small) * Associated with acetabular loosening * _relative_ * coxa vara * increased risk for neck fractures * significant leg length discrepencies (resurfacing does not allow for leg length corrections) * female gender (controversial) * **Advantages** * preservation of femoral bone stock * improved restoration of hip biomechanics with lower risk of limb length discrepancy * lower dislocation rate * rapid recovery * revision is easier than an intremedullary THA * better stability compared to standard small head (22- to 32-mm) THA * ability to engage in high demand activities * **Disadvantages** * lack of modularity with inability to adjust length or correct offset * requires larger exposure than conventional THA

Answer 12

* variable outcome findings in the literature (79% to 98% success rate) * better results * young * larger males * excellent bone stock treated * osteoarthritis better than for dysplasia or osteonecrosis * some case series have shown survival comparable to conventional THA, while others have reported higher rates of early revision * some products have been removed from the market due to early failure * more recent prospective trials have shown few differences between resurfacing and THA

Answer 13

* **RULE OUT INFECTION** * **Periprosthetic femoral neck fracture** * incidence of 0% to 4% (more common than in THA) * frequent cause for revision in acute post-operative period _(\<20 weeks)_ * mechanism thought to be related to osteonecrosis * _risk factors:_ * notching of the femoral neck * osteoporotic bone * large areas of pre-existing osteonecrosis * femoral neck impingement (from malaligned acetabular component) * female sex * varus positioning of femoral component * presents as groin pain * treatment * _convert to a THA_ * **Implant loosening (aseptic)** * early loosening of the cemented femoral resurfacing component * **Heterotopic ossification** * higher incidence of heterotopic ossification (from wider exposure) * **Elevated metal ion levels in blood and urine from metal debris (unknown significance)** * Metallosis * pseudotumour * ALVAL (Aseptic Lymphocytic Vasculitis Associated Lesions) * Can see this on biopsy * _Treatment is to replace with a THA metal on poly_

Answer 14

* **anteroposterior axis** * defined as a line running from the center of the trochlear groove to the top of the intercondylar notch * a line perpendicular to this defines the neutral rotational axis * **transepicondylar axis** * defined as a line running from the medial and lateral epicondyles * the epicondylar axis is parallel to the tibial surface * A posterior femoral cut parallel to the epicondylar axis will create the appropriate rectangular flexion gap * **posterior condylar axis** * defined as a line running across the tips of the two posterior condyles * this line is in ~ 3 degrees of internal rotation from the transepicondylar axis, the femoral prosthesis should be externally rotated 3 degrees from this axis to produce a rectangular flexion gap * if the lateral femoral condyle is hypoplastic, use of the posterior condylar axis may lead to internal rotation of the femoral component

Answer 15

decreased head-to-neck ratio aspherical femoral head decreased femoral offset femoral neck retroversion

Answer 16

anterosuperior acetabular rim overhang acetabular retroversion acetabular protrusio coxa profunda (deep socket)

Answer 17

* _Technique_ * Hips in 15 deg IR with beam centered between symphysis and ASIS * Assess symmetry of obturator, tear drops; symphysis should be 1-2 cm from the coccyx * _Findings_ * Overall * Tonnis grade - OA * Joint space \< 2mm is a poor prognostic factor * Shenton's line * Acetabulum * **CEA \> 40**, **Tonnis angle \< 0** * Version; **cross over sign,** **ischial spine sign** * Retroversion index \> 33-50% are significant * Assess **protrusio, coxa profunda** * **Posterior wall sign** * Femoral side * Assess coxa vara * Sphericity and contour of femoral head - '**pistol grip deformity**' * _Dunn view_ * **Alpha angle \>50 (cam)** * _Cross-table lateral_ * **Head neck off-set \>8mm (cam)** * _false profile view_ * to assess anterior coverage of the femoral head * standing position at an angle of 65° between the pelvis and the film

Answer 18

* Grade 0 - no signs of OA * Grade 1 - sclerosis with minimal joint space narrowing * Grade 2 - small cysts in head or acetabulum with joint space narrowing * Grade 3 - large cysts in the head with obliteration of joint space and severe head deformation

Answer 19

* **Differential** * ****DDH (+/-cam) * FAI * cam * pincer/retroversion * Residual deformity * SCFE * LCP * **AP View** * _Technique_ * Hips in 15 deg IR with beam centered between symphysis and ASIS * Assess symmetry of obturator, tear drops; symphysis should be 1-2 cm from the coccyx * _Findings_ * Tonnis grade - OA * Joint space \< 2mm is a poor prognostic factor * Shenton's line * Acetabulum * CEA = 25-40 * Tonnis angle 1-10 * Version; cross over sign, ischial spine sign * Retroversion index \> 33-50% are significant * Assess protrusio, coxa profunda * Posterior wall sign * Femoral side * Assess coxa vara/valgus * Sphericity and contour of femoral head - 'pistol grip deformity' * **Dunn view at 45deg** * Alpha angle \>50 (cam) * **Cross-table lateral** * Head neck off-set \>8mm (cam) * **false profile view** * to assess anterior coverage of the femoral head * standing position at an angle of 65° between the pelvis and the film * **Von Rosen** * Flexion, abduction, IR * Helps to assess femoral version * Mimics a true PAO * **Adduction or abduction views** * Can help assess the congruency of the joint * mimics a valgus osteotomy * **CT** * can be used as adjunct to assess for structural abnormalities * Drawback is radiation in a young population * **MRI** * best modality to evaluate for articular cartilage, and labral degeneration and tears * 63% sensitive, 71% specific * can assess anatomy of femoral head/neck junction abnormalities * More accurate to assess the alpha angle * Cam - debonding anterior superior lesion in the cartilage * "outside-in" * Pincer - anterior superior as well, but can be more global * Posterior rim lesions, or 'contrecoup' lesions, should be assessed * **dGEMRIC** * Used to look at the integrity of the cartilage * Not commonly used * **Flouroscopic guide hip injection** * 4-6ml of anesthetic under flouro guidance can help * Have patient assess pain before and after injection * Can be very helpful to determine if pain in intra-articular

Answer 20

**DDH** * **Conservative** * ****first line of treatment * NSAIDS, activity modification * **arthroscopic osteochondroplasty of acetabular rim and/or femoral head reshaping** * reserved for mild to moderate lesions without posterior involvement of the femoral head or neck * Can be done via scope or surgical dislocation (trochanteric slide) * Risk of osteotomy non-union * **periacetabular osteotomy +/- a femoral osteotomy** * _Salter osteotomy (Ganz/Bernese)_ * Most commonly used, allows medialization of the hip joint that reduces hip reaction forces * Lateral rotatation, anterior rotation, with medialization of femoral head * indications * Pain or progressive limp * Adequate ROM * \>90 deg flexion * \>30 deg abduction * concentrically reduces hip/congruent joint * good joint space (tonnis \< 2) * advantages * provides hyaline cartilage coverage * posterior column remains intact and patients can weight bear * Does not change pelvic shape in women of weight bearing age * preserves hip abductors * _salvage pelvic osteotomy (chiari, shelf)_ * Not used as frequently due to improvements in THA * indications * unreduced hip * incongruous joint with obliterated joint space * Can confirm with an abduction view whether the hip is reducible * major goal of procedure * cover femoral head with fibrocartilage (NOT articular cartilage) * Will often need a graft to cover the head anteriorly * Drawback of shelf is that you are not medializing the joint * **Femoral Osteotomy** * Often needed when you don't get enough coverage of the head * Need to use flouro to decide where optimal position is * Don’t close the canal too much because it makes future THA difficult * **Arthrodesis or resection arthroplasty** * Options but not good ones for DDH * Resection arthroplasty might be better for patients with neuromuscular conditions * **total hip arthroplasty (THA)** * _indications_ * treatment of last resort for those with severe arthritis * preferred treatment for older patients (\>50) and those with advanced structural changes * in a patient with bilateral hip dysplasia, there are significant technical challenges that need to be addressed to ensure a successful total hip arthroplasty.

Answer 21

* **Indications - For DDH** * Pain or progressive limp * Adequate ROM * \>90 deg flexion * \>30 deg abduction * concentrically reduces hip/congruent joint * good joint space (tonnis \< 2) * **Contraindicaitons for FAI (reverse PAO)** * Posterior-wall overcoverage * Tonnis \> 2 * Combined pincer/cam

Answer 22

* **Smith-peterson** * **4 cuts** * anterior ischium below the acetabulum * superior pubic ramus * supra-acetabular ilium * posterior column (joining cut number one) * **Re-approximate (for DDH)** * Tilt laterally and anteriorly * Avoid excessive extension and retroversion * Rotate inwardly * Medialize * Fix with k-wires, assess ROM and position with flouro * Secrure with 4.5 cannulated screws * Arthrotomy * Assess head-neck junction and perform osteochondroplasty as necessary

Answer 23

* **Most important factor affecting complications is the surgeons experience** * _Nerve dysfunction_ - most common * LFCN * Less commonly femoral, pudendal and sciatic * _Vascular_ - related to ilioiguinal appraoch * _Non-union_ * Usually the pubis, less commonly the ilium/ishium * Can be treated with bone grafting * _Impingement_ * _High incidence of HO_ * Give indomethecin * _Femoral instability_ * If you don't do associated femoral ostotomy can get recurrence of instability * _Osteolysis_ * Can get osteolysis with excessive stripping * Inferior gluteal artery is the one to be concerned about, comes out below the piriformis

Answer 24

* **PFO can be altered as per what you need** * DDH - varus +/- ER * SCFE (Southwick) - flexion, abduction, IR * Femoral neck nonunion - southwick * Place a k-wire at the level of the ostotomy site * Place a k-wire where the blade should go * This will depend on the angle of the plate * Can also assess whether you will need flex or ex at this time * This should be at least _1.5cm_ away from k-wire1 * 3rd kwire or chisel is used to determine the length of the blade * Use a chisel to make the blade cut along wire number 2 * Mark your version with a k-wire * Osteotomize the femur at Kwire 1 * Remove a wedge if you need to * Remove the chisel * Place the balde, watch this under flouro * Secure the blade to the proximal fragment * Secure the plate to the distal fragement * Check the position on flouro * **Post-op** * Start abduction at 6 weeks * TTWB until 8-12 weeks * Plate may be removed at 1-2 years * **Complications are technical** * Blade protrusion into joint * Fragmentation of distal fragment * Nonunion * **Outcome** * 25% conversion to THA at 15 years * Improved outcomes with less OA

Answer 25

* **ROM** * Test in IR (20) ER (45) in seated position * Test AD (20), AB (45) and flexion (120) in supine * **Gait** * LLD * Trendelenberg * Weak adductors * DDH, anything that medializes the head * Pelvic obliquity * **Arthritis** * Anterior impingement * Roll test - tight and stiff * Patrick test - same as FABER with pain anteriorly * Stinchfeild test - Pain with resisted flexion * **Trendelenberg Test** * **Hip contracture** * Hyperextension of the lumbar spine * During gait lumbar will extend to compensate * **Tompson test** * Flex up both hips to neutralize spine * Then extend each hip indivicually * Rotation of hip is more accurately tested in prone * **FADIR - anterior impingement** * Flexion, adduction and IR * Will cause pain with anterior impingment * **FABER** * Look for SI pain * **Anterior Apprehension** * Extension with ER * Psoas snapping * Passive flexion to 90 * ER with abduction extend the leg, the tendon will snap * **Ober test** * Patient in lateral * Abduct the hip with the knee flexed extend the hip * Pulls the IT band behind the GT * Tight IT - hip won't adduct past neutral * Tight glut med - delay with hip in neutral

Answer 26

* **Residual deformity** * Coxa magna * Asphericity * Coxa plana * Short neck * Acetabulum remodels and becomes dysplastic * **Usually requires** * Osteochondroplasty, neck lengthening, distal trochanteric transfer * **Approaches** * _Anterior approach_ combined with _lateral_ for PFO * Can be extended up to do an acetabular osteotomy if they have instability * _Surgical dislocation_ to do everything * If they need both POA and PFO you can stage it or do it at the same time

Answer 27

* **Indications** * FAI * labral tears * AVN (diagnosis and staging) * loose bodies * synovial disease * chondral injuries * ligamentum teres injuries * snapping hip * mechanical symptoms * impinging osteophytes * **Contraindications** * advanced DJD * hip ankylosis * joint contracture * severe osteoporotic bone * significant protrusio acetabuli

Answer 28

* **Anterolateral portal** * _function_ * primary viewing portal * anterolateral hip joint access * _location and technique_ * located 2 cm anterior and 2cm superior to anterosuperior border of greater trochanter * typically established first under flouroscopic guidance * **Posterolateral portal** * _function_ * posterior hip joint access * _location and technique_ * located 2cm posterior to the tip of the greater trochanter * **Anterior portal** * _function_ * anterior hip joint access * _location and technique_ * located at intersection between * superior ridge of greater trochanter * ASIS * flexion and internal rotation of hip loosens capsule and assists scope insertion

Answer 29

* **Direct injuries** * can occur from scope or cannula placement * most commonly reported complication * _chondral injuries_ * **Neurovascular injury** * traction related * _pudendal nerve injury_ * most common neurovascular complication * due to traction post in groin for traction * neuropraxia or compression injury * _peroneal nerve injury_ * traction neuropraxia * **may prevent traction injuries with** * intermittent release of traction * adequate anesthesia * **anterolateral portal** * risks _superior gluteal nerve_ * **posterolateral portal** * risks _sciatic nerve_ * increased risk with external rotation of hip * **anterior portal** * risks _lateral femoral cutaneous nerve injury_ * risks _femoral neurovascular bundle_ * risks _ascending branch of lateral femoral circumflex artery_

Answer 30

chondral damage

Answer 31

AVN * **Alcoholism** * **steroids** (either endogenous or exogenous) * High the dose the higher the risk * **dysbaric disorders** (decompression sickness, "the bends") * **marrow-replacing diseases** (e.g. Gaucher's disease) * **sickle cell disease** * **hypercoagulable states** * May explain idiopathic disease * **SLE** * **Inflammatory Bowel Disease** * **transplant patient** * **virus** (CMV, hepatitis, HIV, rubella, rubeola, varicella) * **protease inhibitors** (type of HIV medication) * **AVN associated with trauma** * due to injury of femoral head blood supply (medial femoral circumflex) * AVN rates of specific injuries * femoral head fracture: 75-100% * basicervical fracture: 50% * cervicotrochanteric fracture: 25% * hip dislocation: 2-40% (2-10% if reduced within 6 hours of injury) * intertrochanteric fracture: rare

Answer 32

* **Think to get imaging of both hips, 50% of the time is a bilateral disease** * **Radiographs** * AP hip * Double line sign associated with crescent sign * Present in 80% of cases * frog-lateral of the hip - more sensitive * classification systems based largely on radiographic findings (see below) * Size of lesion - % head on AP X % head on lateral * Small - \< 15% * Medium - 15-30% * Large - \> 30% * **MRI - Gold standard** * highest sensitivity and specificity * T1: dark * T2: bright (marrow edema) * Will have evidence of high signal from edema as well as low signal changes * Extent of femoral head involvement * _Kerboul Angle_ * Combine necrotic angles on saggital and coronal * \>200 associated with poorer outcomes

Answer 33

**Transient Osteoporosis of the Hip** * Classic picture is _low signal on T1 and high signal on T2_ with no evidence of low signal in T2 * All the way threw the head, neck and trochanteric region * If there are risk factors or concerns of AVN you can do serial progression, TOH will resolve

Answer 34

* **stage 0:** * plain film: normal * MRI: normal * clinical symptoms: nil * **stage I:** * plain film: normal or minor osteopaenia * _MRI: edema_ * clinical symptoms: pain typically in the groin * **stage II:** * plain film: mixed _osteopenia &/or sclerosis &/or subchondral cysts_, without any subchondral lucency (crescent sign: see below) * MRI: geographic defect * clinical symptoms: pain and stiffness * **stage III:** * plain film: _crescent sign & eventual cortical collapse_ * MRI: same as plain film * clinical symptoms: pain and stiffness+/- radiation to knee and limp * **stage IV:** * plain film: end stage with evidence of _secondary degenerative change_ * MRI: same as plain film * clinical symptoms: pain and limp

Answer 35

**AVN** * **Prognosis** * 80% will collapse * **Bisphosphonates** * indicated for precollapse AVN (Ficat stages 0-II) * trials have shown that alendronate prevents femoral head collapse in osteonecrosis with subchondral lucency * Shock-wave, hyperbaric has been tried, but hasn't been showed to work and there is no evidence behind it * Tantalum rod is an old procedure that was thought to provide support and perhaps revascularization but the outcomes have been shown to be poor * **Core decompression with bone grafting** * _indications_ * for early AVN (FICAT 1, 2), before subchondral collapse occurs * Small lesions (\<15%) * Reversible cause * Now will just do multiple tracks with a smaller drill bit * \*\*Just don’t drill below the less troch region * Not very good results * **Rotational osteotomy** * _indications_ * only for small lesions (\<50%) in which the lesion can be rotated away from a weight bearing surface * Beaule paper * \<45 deg * Kerboul \< 200 * off steroids * _technique_ * typically performed through intertrochanteric region * Japan does a trans-trochanteric that has not become common in NA * Need to be careful because can make conversion to THA more difficult * **vascularized free-fibula transfer** * _indications_ * pre-collapse in patients young and over 40 * Moderate to large lesion * collapsed AVN in young patient * Reversible cause * _technique_ * fibular strut is placed under subchondral bone to help prevent collapse or tamp up small areas of collapse * complications - are related to donor site morbidity * sensory deficit * motor weakness * FHL contracture * tibial stress fracture from side graft is taken * **total hip replacement** * _indications_ * femoral head collapse * acetabular DJD * Advanced collapse in younger patients * _Technique_ * Remember that the bone quality is poor - be gentle with acetabular reaming * Evaluate the femur for previous surgery - core decompression, osteotomy * Use a large head, use a lateral approach * Consider ceramic in younger patients * _Outcomes_ * in young patients with osteonecrosis there is a higher rate of linear wear of the polyethylene liner and a higher rate of osteolysis than when compared to older patients who have THA for osteoarthritis * Should be using uncemented components so they can in-grow * **total hip resurfacing** * _indications_ * in advanced DJD with small, isolated focus of AVN * contraindicated in underlying disease process or chronic steroid use causing AVN (poor bone quality) and renal disease (metal ions from metal-on-metal implant) * **hip arthrodesis** * _indications_ * only consider in the very young patient in a labor intensive occupation

Answer 36

* \> 5mm less chance of progression * Lateral lesion in the weight bearing zone more chance of progression * Keboul angle \> 200deg has increased chance of progression * *Risk of contralateral hip (50%)*

Answer 37

* Use a large head, use a lateral approach * Consider ceramic in younger patients * Remember that the bone quality is poor - be gentle with acetabular reaming * Evaluate the femur for previous surgery - core decompression, osteotomy

Answer 38

* 0 - normal * I - normal XR, abnormal MRI * II - cystic or sclerosis change * III - _crescent sign (subchondral collapse)_ * IV - flattening of femoral head * V - narrowing of joint abnormal * VI - advanced degenerative changes

Answer 39

* **Crowe** * I * Less than 10% Proximal * Less than 50% lateral * II * 10-15% proximal * 50-75% lateral * III * 15-20% proximal * 75-100% lateral * IV * Greater than 20% * Greater than 100% * **Hardofilakidis** * **Dysplasia (Type A)** * Femoral head within acetabulum despite some subluxation. Segmental deficiency of the superior wall. Inadequate true acetabulum depth. * **Low dislocation (Type B)** * Femoral head creates a _false acetabulum_ superior to the true acetabulum. There is complete absence of the superior wall. Inadequate depth of the true acetabulum. * **High dislocation (Type C)** * Femoral head is completely uncovered by the true acetabulum and has _migrated superiorly and posteriorly_. There is a complete deficiency of the acetabulum and excessive anteversion of the true acetabulum.

Answer 40

* Acetabulum * smaller cup, superior migration, false acetabulum * loss of anterior/superior and lateral coverage * Augment with screw fixation * Augment with implant augments * Small cup mean a small femoral head to accommodate sufficient poly * Offset-bore components are available that change the position of the head in the poly to reduce risk of instability * **Femur** * Previous surgeries * Loss of canal * Posterior GT * GT osteotomy or ETO * May need to shorten * 2-4 cm is max without shortening * Soft tissue changes associated with superior migration * Abductors become transverse * Psoas and capsule hypertrophy * Adductor, rectus and hamstring shortening

Answer 41

* **Technique for I** * _Acetabulum_ * can usually use the native acetabulum * size less of an issue * Just consider degree of bone loss * _Femur_ - no need to shorten * Try to go cementless because these patients are young * Minimal deformity - metaphyseal fitting proximally coated stem * Larger deformity - small, DDH stem with minimal flare * Diaphyseal fitting, long coating * Allows correction of version * **Technique for II/III and Hardofilikas B** * _Acetabulum_ * 1) Leave the cup superior (high hip center) * Means you will have a very small cup * May need less shortening * increased stress with early failure * 2) Medialize the cup (acetabuloplasty) at native hip center * Reduces joint reaction forces * 3) Augment with bone graft which is available from the femoral head * Poor results have been published when \> 30% of head is uncovered requiring graft/augment (this is when you would consider leaving the cup more superior) * _Femur_ * Will need a diaphyesal fitting stem with modular components to assess verion * fully porous coated * fluted? * May need to be shortened * \>2-4 cm * GT osteotomy with sequential femoral resection * Canal that is left is poor quality * Need to use a small DDH cemented stem * Subtroch osteotomy is better but harder to do - do this from a posterior approach * make subtroch osteotomy and leave hip in pseudoacetab * prepare the acetab * shorten your femur as necessary, release the head and soft tissues * size your stem * reduce secure the stem with k-wires/allograft as necessary * Risk of nonunion * _Technique IV_ * Put in the native acetabulum * Extra-small cup * The bone will be soft, don't over ream * Do the last reamer on reverse * Posterior approach for femoral shortening osteotomy via GT or subtroch osteotomy

Answer 42

* **Indications** * salvage for failed THA (most common) * young active laborers with painful unilateral ankylosis after infection or trauma * neuropathic arthropathy * tumor resection * **Contraindications** * active infection * delay until no active sinus and normal lab values * severe limb-length discrepancy greater than 2.0 cm. * bilateral hip arthritits * adjacent joint degenerative changes * lumbar spine * contralateral hip * ipsilateral knee * severe osteoporosis * degenerative changes in lumbar spine * contralateral THA * increased failure rate (40%) in THA when there is a contralateral hip arthrodesis

Answer 43

**Hip Arthrodesis** * **Pathomechanics** * _reduces efficiency of gait by ~50%_ * increases pelvic rotation of contralateral hip * increases stress at adjacent joints * **Biochemistry** * increases oxygen consumption * requires _30% more energy expenditure_ for ambulation * **Prognosis** * provides pain relief and reasonable clinical results in most patients * success may be limited by **adjacent joint degeneration** in _60% of patients_ * lumbar spine, ipsilateral knee or contralateral hip may be affected * low back pain and arthritic ipsilateral knee pain are the most common symptoms * may start _within 25 years_ of hip arthrodesis *

Answer 44

**Hip arthrodesis** * **goals** * achieve apposition of arthrodesis surfaces, obtain rigid internal fixation and promote early mobilization * **plan for future THA** * ****preserve the abductors * preserve bone stalk; address missing bone stalk * **optimal position** * _20-35° of flexion_ * Appropriate flexion for sitting, reduce lumbar strain * Too much can exaccerbate LLD * _0°-5° adduction_ * avoid abduction as it creates pelvic obliquity and increased back pain * Too much adduction can make sexual activity and toileting difficult in women * _5-10° external rotation_ * Facilitates putting on shoes and foot care * _Leg length_ * \< 2cm difference is acceptable * Can use abduction to correct 2cm (cannot abduct further than that) * Do not abduct \> 6 deg * \>4 cm stage the procedure and do a second lengthening procedure * **Approach** * _lateral approach with trochanteric osteotomy is preferred_ * important to preserve the abductor complex (used to strip the abductors off the pelvis, now elevate them) * avoid injury to the superior gluteal nerve * _anterior approach to hip is also popular_ * Less risk to the abductors * supine on the operative table makes positioning hip easier * Screw augments the plate - lag screw done first, the plate onto crest up near SI * **Address bone deficiet** * **Instrumentation** * cobra plating * anterior plating * double plating * trochanteric approach * better with excessive bone loss, provides more support * 2 stage - first prepare the joint, second fix the GT back down * improves fusion rates

Answer 45

* **Prognosis** * provides pain relief and reasonable clinical results in most patients * success may be limited by _adjacent joint degeneration in 60% of patients_ * lumbar spine, ipsilateral knee or contralateral hip may be affected * _low back pain_ and _arthritic ipsilateral knee pain_ are the most common symptoms * may start within 25 years of hip arthrodesis * **Conservative treatment** * Consider other causes of low back pain * Do a full hx and neurological exam * ask about progression of the pain and any attempt at conservative treatment * ask about pain in other joints * try to prolong take-down * **Conversion of fusion to THA** * _Indications_ - pain in adjacent joints * severely debilitating back pain (most common - 70%) * severe ipsilateral knee pain with instability * severe contralateral hip pain * Relative: * LLD \> 3 cm * previous nonunion of arthrodesis * _Contraindications_ * unable to cope with large procedure (relative) * active infection - stage procedure) * **Pre-op** * _Full History_ * Pain * Indications and age at initial procedure * Spontaneous vs surgical * Complications following the procedure * _Exam_ * Incisions, palpate abductors * Assess hip position, LLD * Lumbar spine, contralateral hip, ipsilateral knee * Full NV exam * _Rule out infection_ * ESR, CRP * Neutrophil count intra-op * If concerns, take down with prostalac with staged procedure * _Imaging_ * AP/lateral pelvis, full length standing (LLD), judet views * Assess for position of the plate and bone stalk * CT for bone, and alignment * MRI or ECG to access abductors * **Outcomes** * clinical outcome is dependent on abductor complex function * Good outcome patient can expect * Improved back/joint pain * Increased mobility * Resolved leg length discrepancy * the presence of hip abductor complex weakness or dysfunction * requires prolonged rehabilitation (2years) * severe lurching gait may develop

Answer 46

**Hip Arthrodesis conversion to THA** * **Goals** * (1) identify and preserve the hip abductor muscles * (2) accurately identify the hip rotation center of the acetabulum * (3) perform concentric reaming of the acetabular bone bed to achieve medialization and sizing of the component * (4) avoid placement of the acetabular cup in an excessively cephalic position * (5) optimize leg length equalization * (6) restore ideal femoral offset to avoid impingement and instability * **Supine on a radiolucent table** * ****supine easier assessment of acetabulum * will need flouro guidence * **Approach** * _GT osteotomy (more common)_ * Fix with circlage wires or claw plate for weaker bone * _Posteroateral_ * Avoid issues with nonunion of osteotomy site * **Take down osteotomy** * Junction between the ilium and femoral neck is the osteotomy site * Use flouro * Anterior acetabular rim and sciatic notch can also be used * Transverse acetabular ligament if present * **Have allograft or augments** available in case of poor bone stalk or deficiency * **Acetabulum** * Define the acetabulum * Be cognicent of the position of the other hip * Flexion and adduction of the other hip might cause pelvic obliquity and you may antevert the cup * Cup * _Porous coated, multi-hole cup_ or _porous metal (TM)_ * _Large cup_ to allow for a larger poly/head * **Femur** * Want more offset to improve abductor function * Large head (\>36) * Increase ROM, decrease instability * Proximal stem usually ok * Have a revision stem on hand if required * **Post-op** * PWB for 6-8 weeks * Will require can for excessive period of time * Hip precautions or abduction splint * Because poor soft tissue/abductors * At risk of dislocation * **Complications** * _Intra-op_ * pelvic discontinuity * greater trochanteric fracture * femoral perforation * calcar fracture * _Post-operative_ * trochanteric osteotomy nonunion * infection * dislocation * nerve palsy * HO * **Outcomes** * clinical outcome is dependent on abductor complex function * Good outcome patient can expect * Improved back/joint pain * Increased mobility * Resolved leg length discrepancy * the presence of hip abductor complex weakness or dysfunction * requires prolonged rehabilitation (2years) * severe lurching gait may develop

Answer 47

* _Indications_ * severely debilitating back pain (most common - 70%) * severe ipsilateral knee pain with instability * severe contralateral hip pain * Relative: * LLD \> 3 cm * previous nonunion of arthrodesis * _Contraindications_ * unable to cope with large procedure (relative) * active infection - (stage procedure)

Answer 48

* Center of rotation is the center of the femoral head * **Forces threw the hip** * 2.5 X in single leg stance * 3 X with walking * 6 X with running * Cane - takes weight away from the hip * **Decrease joint reaction force** - increase in ratio of A/B (shift center of rotation medially) * _moving the acetabular component as far medial,_ inferior, and anterior * _shifting body weight over affected hip_ * this results in Trendelenburg gait * reduces abductor pull * _increasing offset_ of femoral component * _long stem prosthesis_ * _lateralization of greater trochanter_ * _varus neck-shaft angulation_ * increases shear across joint * _cane in contralateral hand_ * reduces abductor muscle pull and decreases the moment arm between the center of gravity and the femoral head * _carrying load in ipsilateral hand_ * produces additional downward moment on same side of rotational point * **increase joint reaction force** * _valgus neck-shaft angulation_ * decreases shear across joint * _Lateralize cup/liner_ * _decreased offset_

Answer 49

* **Design** * _Pressfit_ * Usually taper with proximal fit * .5-1mm smaller than stem * Fractures due to underreaming * Don't need screws for acetab * _Line to line_ * long cylindrical stem, isn't really used except for revision * Fails distally due to modulus mismatch * Ream to same size * Depends on scratch fit for stem * Need to use screws for acetabulum * **Fixation** * _Bone ingrowth - porous coating_ * Poor size - 50-150 um * Poor depth - deeper is better * Porosity 40-50% * Circumferential coating * _Bone ongrowth - grit blasted_ * Micro-divots created by blasting the surface * Define by surface roughness (depth of pores created) * Bone growth in valleys, microinterdigitation * Always with a press-fit technique, usually with a wedge taper * **Optimizing fixation** * _Minimal Gap_ * \<50um - osteoblast jumping distance * _HA coated_ * Will get ingrowth, but this helps * Osteoconductive * Decreases time to stability * **Complications** * _Intra-op fracture_ if underreamed * _High loosening_ in irradiated bone due to lack of ingrowth * Will last for about 2 years if you don't have ingrowth * _Stress sheilding_ * Can be due to distal fixation and long porous coating * More related to different in modulus * Hoek's law - stiff spring sees more load * Better to have a less stiff component so you get less sheilding * Increased stiffness * Stem diamter (Large stem) * Geometry (Solid stem) * Metallury (cobalt)

Answer 50

* Cement interdigitates into metaphyseal bone, not diaphyseal bone * **Indications** * Better interdigitation into OP bone - mantal should be \>2mm * Limited remodeling potential * Better for irradiated bone * Type C femur - hard to get a tight fit with the pressfit (DORR) * **Technical aspects leading to poor results** * Reduce porosity * Pulse lavage canal * Pressurization * Centralization * Stiff Stem * **Complications** * Cement mantel fracture * Loosening - a stiff stem is better because it will bend less in the cement mantel * **Smooth vs rough** * Smooth will slide threw the cement as the cement undergoes creep and will remain stable over time * Rough although seems like it would be stable at first, will not slide as the cement creeps and can act as sandpaper

Answer 51

* **First** * hand mixed * hand packed * **Second** * Canal lavage/preparation * cement plug * cement gun * **Third** * vacuum-mixing to reduce cement porosity * cement pressurization * femoral canal preparation * pulsatile lavage

Answer 52

* **limited porosity of cement** * leads to reduced stress points in cement * **cement mantle \> 2mm** * increased risk of mantle fractures if \< 2mm mantle * **stiff femoral stem** * flexible stems place stress on cement mantle * **stem centralization** * avoid malpositioning of stem to decrease stress on cement mantle * **smooth femoral stem** * sharp edges produce sites of stress concentration * **absence of mantle defects** * defined as any area where the prosthesis touches cortical bone with no cement between * creates an area of higher concentrated stress and is associated with higher loosening rates * **proper component positioning within femoral canal** * varus or valgus stem positioning increases stress on cement mantle

Answer 53

* **Barrack and Harris grading system - Cement** * _grade A_ * complete filling of medullary canal * "white-out" of cement-bone interface * _grade B_ * slight radiolucency of cement-bone interface * _grade C_ * radiolucencies \> 50% of bone-cement interface or incomplete cement mantles * _grade D_ * gross radiolucencies and/or failure of cement to surround tip of stem * **signs of a well-fixed cementless femoral component** * _spot-welds_ * new endosteal bone that contacts porous surface of implant * _absence of radiolucent lines around porous portion of femoral stem_ * _proximal stress shielding_ in extensively-coated stems * _absence of stem subsidence_ on serial radiographs * **signs of a well-fixed cementless acetabular component** * lack of migration on serial radiographs * lack of progressive radiolucent lines * intact acetabular screws

Answer 54

* **Aseptic loosening** * _causes_ * poor initial fixation * mechanical loss of fixation over time * particle-induced osteolysis * _clinical presentation_ * acetabular loosening * groin/buttock pain * femoral loosening * thigh pain * start-up pain * _evaluation_ * sequential radiographs * bone scan * _treatment_ * revision of loose components * **Stress shielding** * _definition_ * proximal femoral bone loss in the setting of a well-fixed stem * _risk factors_ * stiff femoral stem * most important risk factor * large diameter stem * extensively porous coated stem * greater preoperative osteopenia * _clinical implications_ * clinical implications of proximal stress shielding unknown * **Intraoperative fracture** * _risk factors_ * use of press fit technique * _treatment_ * acetabular fracture * stable cup * add screws for additional fixation * unstable cup * remove cup, stabilize fracture, and reinsert cup with screws * femur fracture * stable prosthesis * consider cerclage cables/wires * limit weight-bearing * unstable prosthesis * remove prosthesis, stabilize fracture, reinsert new stem that bypasses fracture by two cortical diameters

Answer 55

1. particulate debris formation 2. macrophage activated osteolysis 3. prosthesis micromotion * micromotion leads to more wear * elevated N-telopeptide 4. particulate debris dissemination * moves to effective joint space * hydrostatic pressure increases with inflammation * Radiostereometric analysis is the most accurate way to assess wear * particulate size \< 1micron * **Adhesive wear** * most important in osteolytic process * microscopically PE sticks to prosthesis and debris gets pulled off * **abrasive wear** * cheese grater effect of prosthesis scraping off particles * **third body wear** * particles in joint space cause abrasion and wear * **volumetric wear** * _main determinant of number of particles created_ * directly related to square of the radius of the head * volumetric wear more or less creates a cylinder * V=3.14rsquaredw * V is volumetric wear, r is the radius of head, w is linear head wear * _head size is most important factor in predicting particles generated_ * **Linear wear** * is measured by the distance the prosthesis has penetrated into the liner

Answer 56

* **polyethylene** * non-cross linked UHMWPE wear rate is 0.1-0.2 mm/yr * _linear wear rates greater than 0.1 mm/yr_ has been associated with osteolysis and subsequent component loosening * highly-cross linked UHMWPE generates smaller wear particles and is more resistant to wear (but has reduced mechanical properties compared to conventional non-highly cross-linked) * factors increasing wear in THA * thickness \< 6mm * malalignment of components * patients \< 50 yo * men * higher activity level * femoral head size between 22 and 46mm in diameter does not influence wear rates of UHMWPE * **Ceramics** * ceramic bearings have the lowest wear rates of any bearing combination (0.5 to 2.5 µ per component per year) * ceramic-on-polyethylene bearings have varied, ranging from 0 to 150 µ. * has a _unique complication of stripe wear_ occurring from lift-off separation of the head gait * recurrent dislocations or incidental contact of femoral head with metallic shell can cause "lead pencil-like" markings that lead to increased femoral head roughness and polyethylene wear rates. * **Metals** * metal-on-metal produces smaller wear particles as well as lower wear rates than those for metal-on-polyethylene bearings (ranging from 2.5 to 5.0 µ per year) * titanium used for bearing surfaces has a high failure rate because of a poor resistance to wear and notch sensitivity. * metal-on-metal wear stimulates lymphocytes * metal-on-metal serum ion levels greater with cup abduction angle \>55 degrees and smaller component size

Answer 57

* thickness \< 6mm * malalignment of components * patients \< 50 yo * men * higher activity level * femoral head size between 22 and 46mm in diameter DOES NOT influence wear rates of UHMWPE

Answer 58

* **Macrophage activation** * results in macrophage activation and further macrophage recruitment * macrophage releases osteolytic factors (cytokines) including * TNF- alpha * TGF-beta * osteoclast activating factor * oxide radicals * hydrogen peroxide * acid phosphatase * interleukins (Il-1, IL-6) * prostaglandins * **Osteoclast activation and osteolysis** * increase of TNF-alpha increases RANK * increase of VEGF with UHMWPE inhances RANK and RANKL activation * RANKL mediated bone resorption * an increase in production of RANK and RANKL gene transcripts leads to osteolysis

Answer 59

* **poor bone quality** * age * steroid use * rheumatoid arthritis * stress-shielding * **mechanical stress-risers** * screw holes * local osteolysis * stiffness * **neurological disorders** * epilepsy * Parkinson's disease * cerebellar ataxia * myasthenia gravis * polio * cerebral palsy

Answer 60

* **Type I** * Fracture is proximal to the femoral component * **Type II** * Fracture originates at the proximal aspect of the femoral component and extends proximally * **Type III** * Any part of the fracture line is distal to the upper edge of anterior flange of the femoral component

Answer 61

* **antegrade intramedullary nail** * supracondylar fracture proximal to the femoral component (Su Type I) * **retrograde intramedullary nail** * intact/stable prosthesis with open-box design to accommodate nail * fracture proximal to femoral component (Su Type I) * fracture that originates at the proximal femoral component and extends proximally (Su Type II) * **ORIF with fixed angle device** * intact/stable prosthesis * Su Types I or II (described above) unable to accommodate intramedullary device * fracture distal to flange of anterior femoral component (Su Type III) * _techniques_ * condylar buttress plate (non-locking) * locking supracondylar plate * blade plate * dynamic compression screw * _complications_ * nonunion * increased risk in plating via extensile lateral approach compared with submuscular approach * **revision to a long stem prosthesis** * _indications_ * loose femoral component * Su Type III (described above) with poor bone stock * **distal femoral replacement** * _indications_ * elderly patients with loose or malpositioned components and poor bone stock * _advantages_ * immediate weight-bearing * decreased operative time of procedure

Answer 62

prior tibial tubercle osteotomy component loosening component malposition insertion of long-stemmed tibial components

Answer 63

* patellar osteonecrosis * asymmetric resection of patella * inappropriate thickness of patella * implant related * central single peg implant * uncemented fixation * metal backing on patella * inset patellar component

Answer 64

* **Casting in extension** * stable component * intact extensor mechanism * **Operative** * _indications_ * loose patellar component * extensor mechanism disruption * _techniques_ (indications for each have not been clearly defined) * ORIF with or without component revision * partial patellectomy with tendon repair * patellar resection arthroplasty and fixation * total patellectomy

Answer 65

* **PE thickness** * \<8mm * **articular surface design** * flat PE increases contact load * _solution_ * high congruency with less roll back is less anatomic but more load sharing * **kinematics** * excessive femoral rollback * _solution_ * __less femoral rollback * nadir has been move more posterior in most knees * PE sterilization * Oxygen rich environment * subsurface delamination * pitting * fatigue cracking * _Solution_ * sterilize in nitrogen gas or vacum * PE machining * Ram bar extrusion = machine shear forces = stretched PE bands * delamination and fatigue * _Solution_ * direct compression moulding

Answer 66

component design component position soft-tissue tensioning soft tissue function

Answer 67

* **Component design** * _large femoral heads_ * head-neck ratio increased * allow greater arc range of motion prior to impingement * skirts can be avoided * decrease the head-neck ratio * jump-distance is increased * amount of translation prior to dislocation * _femoral offset_ * _elevated rim liner_ * a posteriorly placed elevated rim liner may increase joint stability * _lateralized liner_ * increasing offset * **Component Postition****** * _Acetabular position_ * anteversion - 20° ± 10° * abduction - 45° ± 10° * _Femoral stem position_ * 10°- 15° of anteversion * **Restore offset**t * increasing length of femoral neck * decreasing neck-shaft angle * medializing the femoral neck while increasing femoral neck length * trochanteric advancement * alteration of the acetabular liner (see "component design" above)

Answer 68

* excessive retroversion * posterior dislocation * excessive anteversion * anterior dislocation * excessive abduction (high theta angle, vertical cup) * posterior superior dislocation * eccentric polyethylene wear and late instability * excessive adduction (low theta angle, horizontal cup) * impingement in flexion * inferior dislocation

Answer 69

* **increased offset leads to** * increased soft-tissue tension * decreased impingement * decreased joint reaction force * **deceased offset may lead to** * instability * abductor weakness * gluteus medius lurch * increasing offset improves hip stability

Answer 70

* \>50 * \>1 Tonnis * inflammatory arthritis; * bipolar lesions * uncontained lesion; * inability to perform rigorous postoperative physical therapy regimen

Answer 71

* **unipolar lesion on the femur \< 2cm** * pros * elimination of the need for a second procedure (as in ACI) * contains hyaline cartilage * near-immediate weight bearing * cons * requires hip dislocation * donor site morbidity

Answer 72

* **Femur** * ****\<2cm = "apple bite" following cam resection * microfracture * mosciacplasty * allograft * 2-6cm * micorfracture if found * allograft if known * \>8cm * THA * **Acetabulum** * ****\<6cm * microfracture * \>6cm * THA

Answer 73

* Acetabular loosening * Dissociation of the constrained liner from the shell * Material failure * Disengagment of the constraining ring * Excessive wear due to thin liner

Answer 74

* Pros * best wear characteristics * particles are non-oncogenics * Cons * risk of fracture * 1/5000-1/12000 * 70% with-in 12 months * higher with small, neutral offset heads * Chipping 1.2% * Squeak 0.45% * Stripe wear with edge loading * Fewer prosthetic options * More technically demanding

Answer 75

* complete synovecotmy * can't but ceramic head on damaged trunion * some options are available * best option is ceramic on ceramic * Metal on poly most commonly used but carries risk of accelerated wear from 3rd body debris

Answer 76

* THA rather than a TKA * causative bacteria is known * gram-positive * antibiotic therapy tailored to the causative bacterium is administered for 12 weeks * infection is not polymicrobial ie. single bug * patient factors are optimal (ie. no comorbidities, no immunosuppression)

Answer 77

* water soluble * thermodynamically stable * must have a bactericidal effect * released gradually over an appropriate period of time * evoke minimal local inflammatory reaction

Answer 78

* substantially shorter surgical time * shorter hospital stay * reduced blood loss (during 2nd stage) * decreased transfusion requirements (during 2nd stage) * better interim hip function

Answer 79

Type I - Minimal deformity, intact rim Type IIA - Superior bone lysis with intact superior rim Type IIB - Absent superior rim, superolateral migration Type IIC - Localized destruction of medial wall Type IIIA - Bone loss from 10am-2pm around rim, superolateral cup migration Type IIIB - Bone loss from 9am-5pm around rim, superomedial cup migration

Answer 80

* **Components** * ischial bone loss * tear drop lysis * femoral head center migration * kohlers line (ilioischial line) * **Type I Minimal metaphyseal bone loss** * proximal fitting wedge taper stem * **Type II Extensive metaphyseal bone loss with intact diaphysis** * fully porous coated diaphyseal stem * **Type IIIa Extensive metadiaphyseal bone loss, minimum of 4 cm of intact cortical bone in the diaphysis** * fully porous coated dephyseal stem * **Type IIIb Extensive metadiaphyseal bone loss, less than 4 cm of intact cortical bone in the diaphysis** * ****fully porous coated modular tapered stem with derotational spines * **Type IV Extensive metadiaphyseal bone loss and a nonsupportive diaphysis** * ****APC * step cut into native femur reinforced with circlage wires to help creeping subsitution * risk of disease transmission, benefit is bone in young patients * impaction grafting * clean canal of cement and fibrous tissue, reinforce with mesh * morsalized allograft then cement in revision stem * proximal femoral replacement * instability, loosening, can't reattach soft tissues

Answer 81

* Paprosky 1/2 * porous metal, hemispherical, multi-hole revision cup * can use metal augmets to bolster the cup if there is significant bone loss * allograft is no longer recommended * Paprosk 2c/3a/3b * porous metal cup with metal augments * antiprotrusio cage with cemented liner * if you think the acetabulum won't heal (cancer, pagets) then you don't need to put a cup in because you'll never get ingrowth * does not have good long term outcomes * advantages of cementing liner * can cement liner in proper position * can use antibiotic cement * Distraction cup * jumbo cup is used to distract the disontinuity, need to be careful in poor quality bone * only really good results from paprosky * cup-cage construct * cage has a phalange that goes into the ishium and then secured with screws onto the ilium * custom triphlange cup * made to bridge the defect * porous titanium, HA coated * phalange for ischium, ilium and pubis * expensive, stiff, question of whether it can incorperate