118 Day B (12/9 A 7 B 12/10) Daily Mastery Plan

Front 1

Patella baja is a known problem commonly encountered intraoperatively when converting which of the following patients to a total knee arthroplasty. 1-Previous medial compartment unicompartmental arthroplasty; 2-Previous medial proximal tibial opening wedge osteotomy; 3-Previous lateral distal femoral closing wedge osteotomy; 4-Previous patello-fem unicompar arthroplasty; 5-Patella baja is not assoc w/any of the presented options

Back 1

the cause of patella baja when converting a previous medial proximal tibial osteotomy to total knee arthroplasty is scarring from the previous surgery. In addition, the opening wedge changes the position of the tibial tubercle in relation to the joint line, resulting in patella baja. Conversion of a previous lateral distal femoral osteotomy often results in patella alta. Conversion of uni-compartmental (either tibio-femoral or patello-femoral) arthroplasties does not show an association with patella baja.Ans2

Front 2

Hx: 70yo F has persistent anterior knee pain and stiffness 10 mths s/pTKA w/associated lateral patellar release. xrays before and p/ surgery Fig A & B. Pre-op, her Insall-Savati ratio = 0.95, compared to 0.76 post-op. Which of the following is the most likely cause of her xray abnormality and pain? 1- Notching of the femur; 2-Excessive resection of the distal femur and lateral release of the patella; 3. Preop patella baja; 4-Excessive release of the patellar lig from the tibial tubercle; 5-Excessive resection of the prox tibia

Back 2

iatrogenic patella baja and an elevated joint line caused by excessive resection of the distal femur and contracture of the patellar tendon likely as a result of lateral patellar release. Figure A does not demonstrate pre-operative patellar baja, and answer choices 4 and 5 would lead to patella alta. The Insall-Savati ratio, shown in Illustration A, is the ratio of the patella tendon length to the length of the patella. A value <0.8 is cosistent with patella baja, and a value >1.2 is consistent with patella alta.Ans2

Front 3

All of the following are contraindications to medial unicondylar knee arthroplasty EXCEPT: 1-Flexion contracture > 10 deg; 2-Varus deformity >10 deg not correctable with stress testing; 3-Lateral knee jlt
4-RA; 5-Osteonecrosis of the medial femoral condyle

Back 3

Contraindications to performing a unicompartmental/unicondylar knee arthroplasty include: inflammatory arthritis, fixed varus/valgus deformity more than 10 degrees, flexion contracture more than 10 degrees, less than 90 degrees of flexion pre-operatively, ACL insufficiency, significant arthritis in the other compartments, and joint subluxation of more than 5mm.Ans5

Front 4

All of the following are contraindications for a medial unicompartmental knee replacement EXCEPT? 1-ACL deficiency; 2-Anterior compartment osteophytes and pain beneath the patella; 3-Medial sided knee pain with med & lat compartment osteophytes and 3 deg of varus defmty; 4-Lateral sided knee pain with OA changes isolated to the medial compart & 7 deg of varus defm; 5-Flex contracture of 3 deg

Back 4

Unicompartmental knees rely on normal knee biomechanics to preserve motion and stability at the knee. The indications for unicondylar knee replacements are evolving. Using the original published criteria, indications for unicondylar replacement include: non-inflammatory arthritis, mechanical axis deviation <10 degrees from neutral in varus or 5 degrees in valgus, intact ACL, flexion contracture <15 degrees, no patellofemoral symptoms (although radiographic arthritis alone at the PF joint is not a contraindication), flexion to 90 degrees or greater, age >60, low activity demand, and weight <82 kilograms.

In a study of 10 year follow up, Murray et al, defined the following indications for UKA: fixed flexion deformity <15 degrees, correctable varus deformity (indicating a competent medial collateral ligament), full-thickness cartilage in the lateral compartment, and non-inflammatory arthritis. Patellofemoral arthritis is not a contraindication, nor is moderate obesity.Ans5

Front 5

Hx57yo M c/o knee pain that is exacerbated with Wb & ambulation. He underwent surgery on his knee 10 yrs ago following MVA. PE =mjlt & ljlt and no instability. xrays are provided in fig A and B. Conservative therapy w/ NSAID's and viscosupplementation is initiated. If he continues to develop further OA changes and needs arthroplasty what type of implant should be utilized? 1-Unicompartmental mobile bearing knee arthroplasty; 2-Posterior cruciate retaining TKA
3-Posterior stabilized TKA; 4-Constrained nonhinged TKA; 5-Constrained hinged TKA

Back 5

he radiographs and clinical presentation are consistent with a patient who has undergone a previous patellectomy and is now developing degenerative arthritis of the knee. Patellectomy is an indication to use a posterior stabilized implant. The PS implant will offer better femoral rollback and reduce the risk of potential anteroposterior instability that may occur with use a cruciate retaining prosthesis.Ans3

Front 6

Hx:55yo F with a long hx of DM presents for evaluation of chronic knee pain. xray in Fig A. Which of the following knee prostheses, shown in Fig B through E, would be most appropriate in the initial tx of this pt?1-A cruciate retaining TKA; 2-A hinged prosthesis; 3-A posterior stabilized TKA;
4- condylar constrained knee prosthesis
5-unicompartmental knee arthroplasty

Back 6

neuropathic arthropathy, which can occur in the setting of chronic diabetes mellitus. The main problem with these patients after total knee arthroplasty is persistant instability that occurs secondary to ligamentous laxity. Therefore, a semiconstrained prosthesis is indicated in the surgical treatment of these patients.
pt w severe, neurosyphilitic Charcot arthropathy in nineteen knees. A cemented condylar constrained knee prosthesis was implanted in all but two knees. 16% aseptic loosening rate, which required salvage by arthrodesis. They concluded that although Charcot arthropathy is not an absolute contraindication to total knee replacement, there is a high incidence of serious complications.Ans4

Front 7

Figure A demonstrates a total knee prosthesis design. Which of the following motions is constrained in this particular design: 1-Complete anterior-posterior translation constraint only
2-Partial varus-valgus angulation constraint only
3-Partial varus-valgus angulation and partial internal-external rotation constraint
4-Complete internal-external rotation constraint only; 5-Complete varus-valgus angulation and anterior-posterior translation constraint

Back 7

non-linked, constrained total knee arthroplasty prosthesis. This drawing depicts the degree of coronal plane and rotational constraint provided by the tall, wide tibial spine in the deep femoral box. This design constrains varus-valgus (allows 2°-3°) and internal-external rotation (allows 2°). A linked, rotating-hinge prosthesis (Illustration A) constrains anterior-posterior translation in addition to varus-valgus and internal-external rotation.

The article by Scuderi reports that in revision TKA, the goal is to restore the original anatomy, restore function, and provide a stable joint. To this point of stability, it is preferable to implant the prosthesis that provides adequate stability with the least mechanical constraint possible to avoid bone-implant stresses that may cause early loosening. Therefore, it is preferable to use a posterior-stabilized (cruciate substituting) articulation (Illustration B) if the knee remains stable without constrained components.ans3

Front 8

A 64-year-old female with rheumatoid arthritis is undergoing a left total knee arthroplasty. During the tibial cut, a ligament is transected by a reciprocating saw. The ligament is not able to be repaired. The surgeon is balancing the tibial and femoral cuts with sizing blocks and finds that the knee has valgus instability greater than 1cm in full extension. Which implant offers the most appropriate level of constraint while limiting the amount of implant-host interface stresses? 1. Unlinked constrained (varus-valgus constrained)
2. Fixed bearing PCL-substituting (posterior-stabilized); 3. Mobile bearing PCL-substituting (posterior-stabilized) ;4. PCL-retaining (cruciate-retaining) ;5. Rotating-hinge constrained

Back 8

The history, examination, and image is consistent with an iatrogenic MCL injury that is irreparable. An unlinked constrained (varus-valgus constrained) prosthesis has a tall tibial post and a deep femoral box, which provide more inherent coronal plane stability than do standard cruciate retaining or cruciate-substituting prostheses. Because there is no axle connecting the tibial and femoral components, these implants are sometimes referred to as unlinked constrained implants. Ans1

Front 9

With regards to unicompartmental knee arthroplasty, all of the following are true EXCEPT: 1. Females have > revision rate; 2-BMI > 32 is not a risk factor for early implant failure; 3-Presence of osteopenia contributes to premature implant failure; 4-Lateral compt arthroplasties >failure rates than medial compart arthroplasties
5-Progressive OA within the remaining compartments of the knee is low 5 years post-op

Back 9

Lateral compartment arthroplasties have NOTbeen shown to have > failure rates than medial compartment arthroplasties. NO statistically significant difference in the need for revision was demonstrated between those knees in which a medial as compared with a lateral compartmental arthroplasty had been performed. Female gender > RR compared to men. They also found that the average patient requiring revision had a BMI of 32.6 kg/m2, and an association between obesity (wt >81kg) and revision was statistically significant. However more recent data, summarized below, has called this particular finding into question.Ans4

Front 10

When compared to the standard medial parapatellar approach for revision TKA, the oblique rectus snip approach showed impairment in which of the following post-op outcomes? 1-ROM; 2-pt satisfaction; 3-pain; 4-WOMAC function score;5-no difference in outcomes

Back 10

The WOMAC function, pain, stiffness and satisfaction scores demonstrated no statistical difference. They concluded that use of a rectus snip as an extensile procedure had NO adverse effect on outcome.Ans5

Front 11

In total knee arthroplasty, what would be a difference with use of the tibial component shown in Fig A compared to Fig B? 1-> ductility of the polyethylene; 2->wear on the articular side of the polyethylene; 3-Less wear on the articular side of the polyethylene; 4-More wear at the backside of the polyethylene; 5-Less wear at the backside of the polyethylene

Back 11

Adding a polyethylene-metal interface by making it modular leads to more wear on the backside, not the articular surface, Modularity with metal tibial base plates has the advantage of being able to customize implants intraoperatively. However, a disadvantage of modularity is increased rates of osteolysis and backside polyethylene wear due to micromotion between tibial baseplate and undersurface of polyethylene that occurs during loading. A monoblock tibial component creates intraoperative challenges as determination of tibial component size is done prior to cementing.Ans4