2010 Adult Reconstruction

1. 2010 Adult Reconstruction

4. Answer: 5 Indications for surgical intervention for periprosthetic osteolysis include (1) first-time presentation of advanced osteolysis in the presence of an identifiable cause of wear particle production or in the presence of associated bone loss that places the structural integrity of the bone or fixation of the components at risk, (2) bearing surface wear in the presence of impending wear-through or related mechanical symptoms, (3) progressive osteolysis in an active individual, and (4) symptoms of wear debris�related synovitis that are refractory to conservative treatment.

5. 1,4- Acetabular revision, femoral and acetabular revision: Despite extensive loss of bone in the pelvis, the porous-coated acetabular component can remain rigidly fixed by so-called pods of bone. Removal of a stable shell often leads to destruction of these pods, further compromising the reconstruction. Similarly, removal of a socket stabilized by bone ingrowth can result in a defect of the medial wall of the acetabulum; extensive damage to the anterior and posterior columns; and, in some cases, pelvic discontinuity. If the metal shell has been markedly damaged by the femoral head, the locking mechanism for the polyethylene liner is not intact, or a satisfactory replacement liner is not available, then revision of the porous-coated acetabular component is Indicated. 2- Follow-up in 1 year: Neglect of wear and significant osteolysis only delays the need for what may become more difficult surgery, as lesions progress in size and/or complete failure of the bearing with metal-on metal contact precludes simple bearing exchange. 3- Initiation of alendronate sodium therapy: This will not reverse the cause of the osteolysis, which is a biological reaction to wear debris.

6. 15- Which of the following is the strongest independent risk factor for dislocation after total hip arthroplasty? 1- Female gender 2- Diabetes mellitus 3- Height of over 6 feet 4- BMI of greater than 35 5- Age greater than 75 years

7. 15) A: 1- Female gender Approximately 60-70% of dislocations occur in the first 6 weeks after surgery. Most studies have found a 2:1 to 3:1 higher risk of dislocation in women, with the greatest discrepancies in first time dislocators after 5 years. One large review study found an overall relative risk of 2.1 in women. Patient ager great than 75 years is often referred to as a known risk factor for dislocation but the evidence for age as an independent risk factor for instability is rather weak. RR in patients > 70 was 1.3 in a large series study compared to those <70. Obese patient may develop soft tissue impingement sooner because of increased limb girth contacting the prominent abdomen leading to greater ease of dislocation. Tall patient with longer limbs have a greater lever arm that increases forces at the hip, which may affect the tendency to dislocate. The most significant preexisting risk factor for dislocation is prior hip surgery. Most likely due to impaired muscle strength or dysfunction, damaged soft tissue attachments to the proximal femur and the adverse impact these factors have on soft tissue tension and dynamic control of the joint.

8. Question 26 A 66-year-old woman falls 2 weeks after undergoing primary total hip arthroplasty and sustains a Vancouver B2 periprosthetic fracture. What is the preferred treatment? 1) Protected weight bearing for 6-8 weeks 2) Fixation with a locking-cable plate system 3) Fixation with an allograft strut and cables 4) Revision with a long stem implant 5) Revision with a proximal femoral allograft and a long stem implant

9. 4. Revision with a long stem implant

10. 4) Revision with a long stem implant Non operative treatment is only for type A Fixation with locking cable and plate system is most likely b1 Fixation with an allograft strut and cable- could be B3 The technique proposed in the reference article is for the treatment of B2 fractures, using cerclage wires to reconstruct the fractures, then implantation of a longstem uncemented femoral component followed by cable attachment of femoral allograft struts to reconstruct the biomechanical properties of the proximal part of the femur. Revision with a long stem implant and allograft is for B3

11. 39 Use of a metal-on-metal bearing compared with use of a metal-on-cross linked polyethylene bearing of the same diameter will result in which of the following?

12. 39 Use of a metal-on-metal bearing compared with use of a metal-on-cross linked polyethylene bearing of the same diameter will result in which of the following?Response # 1

13. 39 Use of a metal-on-metal bearing compared with use of a metal-on-cross linked polyethylene bearing of the same diameter will result in which of the following?

14. 54 Compared with a static antibiotic spacer, an articulating antibiotic spacer inserted following resection of a septic total knee arthroplasty demonstrates 1. A greater chance of infection recurrence 2. A greater retention of host bone 3. An improved rate of infection eradication 4. Decreased exposure time during reimplantation 5. Decreased wound healing complications

15. 54 Answer 4. Decreased exposure time during reimplantation 1. Although you are able to use larger doses of antibiotics with static spacers they have been shown to have similar rates of infection recurrence 2. Static Spacers have also been found to have increased not decreased bone loss compared to mobile spacers 3. Rates of eradication are statistically similar with either static or mobile 4. Exposure at the time of the second stage of the revision is made easier due to retained joint motion, this may also lead to better ROM after the final surgery 5. Wound healing complications can be higher with mobile spacers

16. 54 Mobile Cement spacers Come in three flavors Cement on Cement, Cement on Poly, Cement on Metal Benefits: Limited ability for patient to use leg, able to do PT with spacer, better final ROM, less bone loss, easier reimplantation surgery Drawbacks: Possibility of cement fracture, problems with wound healing

17. 62) Following a total knee arthroplasty for a varus knee, a patient is unable to extend her toes and cannot dorsiflex or evert her ankle. Plantar flexion strength is intact. What is the most likely cause of the weakness? 1- Aberrant retractor placemen 2- Ischemia from a prolonged tourniquet time 3- Correction of a preoperative flexion contracture 4- Peroneal nerve transection 5- Excessive medial release

18. 62) Answer 1) Aberrant Retractor Placement All answers are correct, just pick most common. 3 is most common in valgus not varus knee. Could not find any information on aberrant retractor placement incidence, probably why question got tossed. Peroneal Nerve Palsy post TKA Peroneal Nerve (L2-S2, branch of sciatic) Motor: CPN (short head biceps), SPN (peroneals), DPN (EHL, TA, EDL, EDB) Sensory: Sural n. (lateral leg), SPN (lateral leg and dorsal foot), DPN (1st dorsal webspace) Incidence: 0.3-1.3% may be underdiagnosed Prognosis: Most studies show >50% achieve full recovery Treatment Removal of restrictive dressings Knee flexion EMG if no improvement in 1 mo Chronic: Dropfoot brace and ROM exercises Delayed exploration and decompression at 3-4 mo Also possible nerve graft of Post tib transfer

19. 62) Answer 1: Aberrant retractor placement Predisposing factors for Peroneal Nerve Palsy Valgus Deformity > 10 - 15 � and Flexion Contracture > 20 � Traction injury: axon damage seen with 4 - 11 % elongation and microcirculatory damage with 8% elongation More extensive soft tissue dissection Postop Epidural Anesthesia Usually delayed presentation Previous Neuropathy or Spinal Surgery �Double-crush� phenomenon. Secondary insult to already diseased nerve. Can be central (stenosis, radiculopathy) or peripheral Diabetes not shown to have association Rheumatoid Arthritis Slowed motor n. conduction velocity and abnormal sensory conduction in superficial peroneal n. distribution seen in asymptomatic pts Tourniquet > 120 min Linked, but not proven. EMG changes shown in studies, plus lots of bad things can happen with extended tourniquet time so use with caution Hematoma (Theoretical) Constrictive Dressing (Theoretical) Previous Proximal Tibial Osteotomy: stretch/traction/scarring

22. 108 Allograft strut fixation is most appropriately indicated as an adjunct to a lateral plate for what type of periprosthetic femoral fracture associated with a total hip arthroplasty? 1. Trochanteric fracture (Vancouver type A) 2. Shaft fracture at the tip of the stem with a well-fixed stem (Vancouver type B1) 3. Shaft fracture at the tip of a loose stem (Vancouver type B2) 4. Shaft fracture at the tip of a loose stem associated with bone loss (Vancouver type B3) 5. Fracture distal to the stem (Vancouver type C)

23. Question 108 - Preferred answer: 4 Type AG (fracture in greater trochanter) - treat symptomatically with protected weight bearing; limit abduction. Consider ORIF if fracture is displaced > 2.5 cm or if there is pain, instability, or abductor weakness due to trochanteric nonunion. Type AL (fracture in lesser trochanter) - treat symptomatically with protected weight bearing even if fracture is displaced. Treat surgically only if a large portion of the medial cortex is attached. Type B1 (fracture is around or just distal to the femoral stem and the stem is well fixed) - ORIF with fixation in 2 planes (lateral and anterior). Type B2 (fracture is around or just distal to the femoral stem, the stem is loose, and there is good bone stock in the proximal femur) - long-stem revision. Consider cortical strut grafts to improve stability and enhance bone stock. Type B3 (fracture is around or just distal to the femoral stem, the stem is loose, and there is poor bone stock in the proximal femur) - long-stem revision. Consider allograft-prosthetic composite in a young patient to help augment bone stock. Consider proximal femoral replacement (tumor-type) component in elderly or low-demand patients.

24. 108 Type C (fracture located well below the femoral stem) - ORIF. Manage with blade plate, condylar screw plate, or locking supracondylar plate (e.g. LISS). Overlap plate and stem to avoid creation of a stress riser. Use screws to secure plate distal to the stem. Use cerclage wires around the plate at the level of the stem. May consider treatment with a retrograde IMN, but this may create a stress riser between the femoral stem tip and the nail.

25. 108: Vancouver Classification of periprosthetic fractures

26. 108 Recommended readings: Ricci WM, Bolhofner BR, Loftus T, Cox C, Mitchell S, Borrelli J Jr. Indirect reduction and plate fixation, without grafting, for periprosthetic femoral shaft fractures about a stable intramedullary implant. Surgical Technique. J Bone Joint Surg Am. 2006 Sep;88 Suppl 1 Pt 2:275-82. PubMed PMID: 16951099. Ricci WM, Haidukeqych GJ. Periprosthetic femoral fractures. Instr Course Lect. 2009;58:105-15. PubMed PMID 19385524.

27. 109 The routine use of a continuous passive motion device following total knee arthroplasty compared with a structured physical therapy program results in which of the following? 1. Increased length of hospitalization 2. Decreased need for narcotic medication 3. Equivalent early range of motion 4. Improved range of motion at 1 year 5. Improved knee society scores.

28. 109 � Preferred answer: 3 Leach et al. performed a randomized prospective study to study the effects of continuous passive motion on knee range of motion, pain levels, and analgesia use. Patients were evaluated at time of discharge from hospital, 6 weeks, 6 and 12 months postoperatively. They concluded that continuous passive motion following total knee arthroplasty does not influence outcome of range of motion or reported pain. Bourne performed a review of various randomized controlled trials, controlled clinical trials, case-control studies, or cohort studies comparing CPM with placebo, no treatment, or active interventions. He concluded that in patients who have had total knee arthroplasty, CPM plus PT increases active knee flexion more than PT alone 2 weeks after surgery and reduces hospital length of stay. Other range-of-motion outcomes are not significantly different between CPM and PT. Outcomes are also no different when comparing CPM with splinting (except for knee flexion) or comparing different CPM applications.

29. 111 What process is used to fabricate ultra-high molecular weight polyethylene by directly molding the resin into the finished part? 1. Net shape 2. Ram extrusion 3. Annealing 4. Porosity reduction 5. High-density branching

30. 111. Preferred answer: 1 Net shape compression molding (AKA direct compression molding) the resin is directly molded into the finished part. One advantage of net shape compression molding is the extremely smooth surface finish obtained with a complete absence of machining marks at the articulating surface. Better wear of UHMWPE has been consistently achieved with the direct compression molding process. In ram extrusion, the resin is extruded through a die under heat and pressure to form a cylindrical bar that in turn is machined into the final shape. Annealing is the process of heating PE close to the melting point to remove free radicals. If the heating is kept below the melting point, there is little reordering of the PE structure. If the heating is taken above the melting point, there is structural reordering of the PE chains, which can increase the crystallinity of the PE with certain techniques.

31. Porosity reduction is a process to decrease pore size in cement to 200 to 400 micrometers, mostly via centrifugation or vacuum mixing. Controversy remains as to the benefit of porosity reduction. In vitro studies demonstrate increased fatigue strength with porosity reduction. However, clinical studies question the significance of porosity reduction in the face of surface irregularities. High density branching or cross-linking of UHMWPE improves resistance to adhesive and abrasive wear, which improves wear rates. UHMWPE treated with low-dose irradiation in an inert environment without oxygen favors cross-linking of PE.

34. Question #147 Figures 147a through 147d show the radiographs of a 71-year-old woman who presents for a second opinion. She has a well-functioning right total knee arthroplasty (TKA) and underwent left TKA 5 months ago. Following surgery on the left knee, she reports severe pain with passive range of motion from -5� to 105�. Work-up for infection is normal. What is the most appropriate management? 1- Hinged knee orthosis 2- Aggressive physical therapy 3- Closed manipulation of the knee 4- Revision total knee arthroplasty 5- Arthroscopy and synovial d�bridement

35. Question #147 Images Page 1 of 2 1- Hinged knee orthosis 2- Aggressive physical therapy 3- Closed manipulation of the knee 4- Revision total knee arthroplasty 5- Arthroscopy and synovial d�bridement

36. Question #147 Page 2 of 2 Images 1- Hinged knee orthosis 2- Aggressive physical therapy 3- Closed manipulation of the knee 4- Revision total knee arthroplasty 5- Arthroscopy and synovial d�bridement

37. Question #147: Answer: 4 Revision TKA There are lots of clues in the question without even looking at the picture. She has good (but painful) range of motion and there is no mention of instability. Three answers, physical therapy, manipulation, and arthroscopy and debridement are usually therapies for poor range of motion. This leaves an orthosis and revision, given no instability, a revision TKA would be the best choice. Images then confirm this, looking at the long leg she is in too much valgus.

38. 160. A patient perceives a limb-length discrepancy after undergoing a total hip arthroplasty. He feels that the operated leg is too long. Aside from an actual limb-length difference, what is a possible cause of this perception? Quadriceps weakness An external rotation contracture A hip flexion contracture A hip adduction contracture Weakness of the hip abductors

39. 5: Weakness of the hip abductors Hip abductors function to keep the pelvis level during stance When the abductors are weak the contralateral side of the pelvis drops (Trendelenburg Sign) giving the perception that the affected side is longer None of the other choices would give the perception that the operative side is longer A hip flexion contracture or adduction contracture may give the perception of the operative side being short

40. 172. After a standard medial parapatellar approach to the knee with excision of the fat pad and lateral meniscus, what artery is likely the only remaining blood supply to the patella?  1- Superior lateral genicular 2- Inferior lateral genicular 3- anterior recurrent tibial 4- superior medial genicular 5- inferior medial genicular

41. 172 Preferred Response: 1) superior lateral genicular Medial vessels will likely be disrupted due to the initial approach. Superior and inferior lateral genicular arteries are important remaining vessels to the patella, but the anterior tibial recurrent passes superiorly along the patellar tendon and supplies it and mostly skin overlying patella Lateral retinacular release along with fat pad excision and lateral meniscus resection will likely disrupt the inferior lateral genicular artery, which anastamoses with the anterior tib recurrent artery. It passes deep to lateral collateral ligament at level of the joint passing superficial to the popliteus tendon and then passes over the lateral limb of the arcuate ligament and popliteal musculotendinous junction and the lateral meniscus This would leave superior lateral genicular as the last artery standing, and it does anastomose with the descending branch of lateral femoral circumflex artery

43. #181 Adult Reconstruction In total knee arthroplasty, appropriate femoral component rotation achieves which of the following? Creation of a rectangular extension gap Creation of a rectangular flexion gap Ensures appropriate tibial rotation Correction of a varus deformity Maximizes the amount of knee extension that can be obtained.

44. #181 Answer: 2. Creation of a rectangular flexion gap This is a gap balancing question. When approaching these questions remember distal femoral cuts effect the extension gap only and femoral component size (the AP dimension of the component) effects only the flexion gap. Appropriate femoral component rotation creates a rectangular flexion gap (see figure below) Creation of a rectangular extension gap requires an appropriate distal femoral cut which is made parallel to the tibial cut (as well as soft tissue balance) Femoral component rotation will not correct a coronal plane deformity (varus/valgus) Achieving full knee extension has to do with the extension gap which is dependent on the distal femoral and tibial cuts (as well as soft tissue balancing)

47. Answer-2

49. Answer-4

52. Answer 5: Rupture of the PCL Figures show a CR knee From the vignette, patient has A/P laxity. Unable to rise from chair = quadriceps active test. Climbing stairs = flexion instability PCL-retaining TKAs with PCL insufficiency show a posterior tibial�sag, a positive posterior drawer test, and a positive 90��quadriceps active test. X-ray rules out quad tendon rupture (no patella alta) and varus malpositioning. Flexion/extension mismatch is a general term and could be a possible answer but she would have had the problem since surgery When the PCL is inadvertently cut or improperly�balanced, flexion instability in the AP plane can occur. Delayed�rupture of a PCL also can cause flexion instability Gonzalez MH, Mekhail AO. The failed total knee arthroplasty: evaluation and etiology. J Am Acad Orthop Surg. 2004 Nov-Dec;12(6):436-46. Review. PubMed PMID: 15615509.

54. 210.5- Lateral collateral ligament The most common structures on the lateral side of the knee to be released in a valgus knee iliotibial band posterolateral capsule lateral collateral ligament popliteal tendon lateral head of the gastrocnemius. Releasing the LCL, popliteus, lateral gastroc, and IT band give <5 degrees of correction in extension. Addition of PCL release gets a total of 9-degrees of correction. Releasing the LCL first allows for a more gradual correction. If the other structures are released first with inadequate correction, subsequent release of the LCL may lead to over correction and instability. If lateral side tight In both extension and flexion = release LCL In only extension = release IT band or popliteus In only flexion = release posterolateral capsule and popliteofibular ligament Favorito PJ, Mihalko WM, Krackow KA. Total knee arthroplasty in the valgus knee. J Am Acad Orthop Surg. 2002 Jan-Feb;10(1):16-24. Review. PubMed PMID: 11809047. Krackow KA, Jones MM, Teeny SM, Hungerford DS. Primary total knee arthroplasty in patients with fixed valgus deformity. Clin Orthop Relat Res. 1991 Dec;(273):9-18. PubMed PMID: 1959292.

55. #214. The routine use of antibiotics in the bone cement for primary total joint arthroplasty is associated with which of the following risks? 1- Reduced risk of aseptic loosening 2- Reduced risk of aseptic loosening and infection 3- Increased risk of aseptic loosening 4- Increased risk of renal insufficiency 5- Increased risk of a resistant organism

56. 3. Increased chance of aseptic loosening Antibiotic cement has shown to decrease acute and chronic infections following total joint arthroplasty for up to 2 years following revision TKA Aseptic loosening is a complication of any cemented implant whether antibiotic cement or nonantibiotic cement is used. Reduction of aseptic loosening rates is incorrect, see above Reduction of aseptic loosening and infection is also incorrect. It has not been shown to reduce infection in primary total joint arthroplasty. Joints Chiu, Fang-Yao et al, Atibiotic-Impregnated Cement in Revision Total Knee Arthroplasty; JBJS, 2009;91-623-33.

57. 236 Hip precautions following the anterolateral approach to the hip for total hip arthroplasty would include avoiding 1- flexion and internal rotation. 2- flexion and external rotation. 3- internal rotation in midflexion. 4- extension and external rotation. 5- extension and internal rotation.

58. 236 4 � extension and external rotation Postop hip precautions generally apply to posterior and anterolateral approaches for total hip arthroplasty. The references were not helpful for this question. In order to answer appropriately, you have to consider where the soft tissue structures are violated with the various approaches and then determine what hip position would put the femoral head at risk of dislocation. Anterolateral (Watson-Jones) approach to the hip utilizes the interval b/w tensor fasciae latae and gluteus medius. This approach has been shown to reduce postop dislocation rates. Postop hip precautions include avoiding extension and external rotation.

59. 236 Posterior approach to the hip has no true internervous interval. Slightly higher dislocation rate than anterolateral approach. Post-op hip precautions involve avoiding flexion and internal rotation (1).

62. 259. (Joints) In total hip arthroplasty, what is the linear wear rate of conventional polyethylene that is considered the threshold above which osteolysis is likely to occur? 1- 1 micrometer per year 2- 0.1 millimeter per year 3- 0.5 millimeter per year 4- 1 millimeter per year 5- 2 millimeters per year

63. 2- 0.1 millimeter per year Fact. Just know this. It�s a commonly asked question on exams and by attendings. Osteolysis is a hystiocytic response to wear debris that incites macrophage activation, dissolution of bone from the prosthesis, micromotion, more wear debris, and loosening. Wear rate of less than 0.1mm/yr, as with UHMWPE, are believed to cause less osteolysis than conventional polyethylene. Other poly facts: Sterilization using gamma radiation in air crosslinks the poly, but generates free radicals that increases oxidative degradation and wear. Radiating in inert environments and remelting prevents formation of free radicals. Lin