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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 52 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1021

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the most common cause for late revision (> 2 years post op) total knee arthroplasty?

. Infection
. Polyethylene wear
. Instability
. Patellar complications
. Malalignment

Correct Answer & Explanation

. Infection

Explanation

DISCUSSION: There are multiple causes for failure of total knee arthroplasty, and more than one may exist at the same time. Sharkey and associates reviewed a series of revision total knee arthroplasties, and found that polyethylene failure was the most common cause of failure followed closely by component loosening. The most common cause of early failure (< 2 years post op) was infection. Instability and malalignment are both complications of surgical technique, and if these categories are combined, they would be the most common cause of all total knee failures.REFERENCE: Sharkey PF, Hozack WJ, Rothman RH, et al: Insall Award paper: Why are total knee arthroplasties failing today? Clin Orthop Relat Res 2002;404:7-13.

Question 1022

Topic: 3. Adult Reconstruction (Hip & Knee)

A 78-year-old woman underwent total hip arthroplasty 15 years ago. She reports a recent history of increasing thigh pain prior to a fall and is now unable to ambulate. Radiographs are shown in Figures 87a and 87b. What is the best treatment for this condition?

. Surgical traction for 6 weeks followed by application of a cast brace
. Application of a femoral cable plate
. Femoral revision with a cemented long stem prosthesis
. Application of cerclage wired double allograft femoral struts
. Femoral revision with a cementless long taper fluted modular stem and proximal allograft strut supplementation

Correct Answer & Explanation

. Surgical traction for 6 weeks followed by application of a cast brace

Explanation

DISCUSSION: Severe periprosthetic fractures after total hip arthroplasty with a loose implant and progressive bone loss are difficult problems for orthopaedic surgeons, with a high complication rate. Recent literature favors the use of long fluted tapered stems that have a long distal taper that may optimally engage the remaining femoral shaft isthmus. Plating options are problematic because the ability to use screws with the plate is limited by the intramedullary stem. Although not the only solution to this problem (such as allograft-prosthetic composites, impaction grafting, tumor prostheses), long distally fixed stems circumvent this problem by enhancing fracture healing and create a long-term prosthetic solution in these most difficult cases.REFERENCES: Barrack RL, Booth RE Jr, Lonner JH, et al (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, pp 475503.Kwong LM, Miller AJ, Lubinus P: A modular distal fixation option for proximal bone loss in revision total hiparthroplasty: A 2- to 6-year follow-up study. J Arthroplasty 2003;18:94-97.

Question 1023

Topic: 3. Adult Reconstruction (Hip & Knee)

Which nerve is most commonly injured after total knee arthroplasty?

. Tibial nerve
. Superficial peroneal nerve
. Infrapatellar branch of the saphenous
. nerve52
. Sartorial branch of the saphenous nerve

Correct Answer & Explanation

. Tibial nerve

Explanation

DISCUSSIONThe tibial or peroneal nerves usually are not injured during total knee arthroplasty. Incidence of peroneal nerve damage is highest in knees with a valgus deformity and an associated flexion contracture attributable to nerve stretch. This nerve injury occurs in as many as 9% of patients undergoing knee arthroplasty. Tibial nerve injury is a rare occurrence and usually an iatrogenic transection injury. The infrapatellar branch of the saphenous nerve and its nerve plexus is commonly injured after the medial parapatellar approach, and altered sensation attributable to injury is reported in up to 70% of cases. Injury typically manifests as numbness inferior to the patella. The sartorial branch of the saphenous nerve provides sensation distal to the knee and is uncommonly injured with a medial parapatellar approach. These concepts are illustrated in video 57, “Selective Exposures in Orthopaedic Surgery: The Knee, 2nd Edition.”RECOMMENDED READINGSClarke HD, Bush-Joseph CA, Wolf BR. Selective Exposures in Orthopaedic Surgery: The Knee, 2nd Edition [DVD]. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2012.Hunter LY, Louis DS, Ricciardi JR, O'Connor GA. The saphenous nerve: its course and importance in medial arthrotomy. Am J Sports Med. 1979 Jul-Aug;7(4):227-30. PubMed PMID: 474860.View Abstract at PubMedMistry D, O'Meeghan C. Fate of the infrapatellar branch of the saphenous nerve post total knee arthroplasty. ANZ J Surg. 2005 Sep;75(9):822-4. PubMed PMID: 16174002.View Abstract at PubMedSchinsky MF, Macaulay W, Parks ML, Kiernan H, Nercessian OA. Nerve injury after primary total knee arthroplasty. J Arthroplasty. 2001 Dec;16(8):1048-54. PubMed PMID: 11740762.View Abstract at PubMed

Question 1024

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is not a reported mode of failure for a constrained acetabular component?

. Loosening of the acetabular component
. Disengagement of the constraining ring (with or without redislocation)
. Increased abrasive (polyethylene) wear
. Dissociation of the femoral head from the neck
. Dissociation of the polyethylene liner from the acetabular shell

Correct Answer & Explanation

. Loosening of the acetabular component

Explanation

DISCUSSION: There is no evidence of increased polyethylene wear in constrained acetabular components.  The rates of wear appear to be the same using standard or constrained liners.REFERENCES: Lachiewicz PF, Kelley SS: Constrained components in total hip arthroplasty. J Am Acad Orthop Surg 2002;10:233-238.Anderson MJ, Murray WR, Skinner HB: Constrained acetabular components. J Arthroplasty 1994;9:17-23.Fisher DA, Kiley K: Constrained acetabular cup disassembly. J Arthroplasty 1994;9:325-329.

Question 1025

Topic: 3. Adult Reconstruction (Hip & Knee)

During the implantation of a cementless acetabular component in total hip arthroplasty, placement of a screw in the anterior superior quadrant puts which of the following structures at risk for damage?

. Sciatic nerve
. Internal iliac vessels
. External iliac vessels
. Femoral vessels
. Obturator vessels

Correct Answer & Explanation

. Sciatic nerve

Explanation

DISCUSSION: A knowledge of the safe quadrants for screw placement for acetabular component implantation is essential when performing total hip arthroplasty.  The external iliac vessels are on the inner wall of the pelvis, corresponding to the anterior superior quadrant of the acetabulum.REFERENCES: Keating EM, Ritter MA, Faris PM: Structures at risk from medially placed acetabular screws. J Bone Joint Surg Am 1990;72:509-511.Wasielewski RC, Cooperstein L, Kruger MP, Rubash HE: Acetabular anatomy and the transacetabular fixation of screws in total hip arthroplasty. J Bone Joint Surg Am1990;72:501-508.

Question 1026

Topic: 3. Adult Reconstruction (Hip & Knee)

A 48-year-old woman has knee pain that is worse with weight bearing. She reports no night pain or pain at rest. History reveals that she underwent total knee arthroplasty with cementless components 2 years ago. Examination reveals tenderness along the medial joint line. Figures 12a through 12c show radiographs and a bone scan. What is the most likely cause of the patient’s pain?

. Deep infection
. Malalignment
. Fibrous ingrowth of the femoral component
. Fibrous ingrowth of the tibial component
. Patellar component loosening

Correct Answer & Explanation

. Deep infection

Explanation

DISCUSSION: The radiographs show a halo-like sclerotic margin around the tibial stem and lucency under the baseplate.  The bone scan shows markedly increased uptake under the tibial component, particularly on the medial side (not diffusely through the knee as seen with infection).  These studies indicate lack of bone ingrowth fixation of the cementless porous-coated tibial component.  The recent report of Fehring and associates has identified failure of ingrowth of a porous-coated implant as a dominant mode of early failure of total knee arthroplasties.REFERENCES: Fehring TK, Odum S, Griffin WL, Mason B, Nadaud M: Early failures of total knee arthroplasty. Clin Orthop 2001;392:315-318.Fehring TK: Revision TJA corrects flexion extension gap imbalance. Orthop Today 2002;22:44.

Question 1027

Topic: 3. Adult Reconstruction (Hip & Knee)

What type of cementless femoral fixation results in the highest rate of distal femoral osteolysis?

. Tapered circumferential proximally porous-coated stem
. Hydroxyapatite-coated tapered circumferential proximally porous-coated stem
. Straight circumferential fully porous-coated stem
. Straight modular circumferential proximally porous-coated sleeve and distal fluted stem
. Noncircumferential proximally porous-coated stem

Correct Answer & Explanation

. Tapered circumferential proximally porous-coated stem

Explanation

DISCUSSION: Despite the relatively few problems with porous-coated cementless stems, stress shielding and thigh pain do occur.  One design feature of proximally coated stems that has been associated with a higher incidence of distal osteolysis is the presence of noncircumferential proximal porous coating.  Tapered, modular with sleeve, and hydroxyapatite proximally porous-coated stems have all performed well.  Fully porous-coated straight stems have a high survivorship rate as well.REFERENCES: Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 175-180.Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 417-451.Emerson RH Jr, Sanders SB, Head WC, Higgins L: Effect of circumferential plasma-spray porous coating on the rate of femoral osteolysis after total hip arthroplasty. J Bone Joint Surg Am 1999;81:1291-1298.

Question 1028

Topic: 3. Adult Reconstruction (Hip & Knee)

Which wear mechanism is most likely responsible for the wear damage on the modular tibial insert retrieval shown in Figure 82?

. Adhesive
. Abrasive
. Fatigue
. Creep

Correct Answer & Explanation

. Adhesive

Explanation

DISCUSSIONThe figure shows the top side of a retrieved tibial liner. Pitting and delamination, which are associated with fatigue wear, are noted. Creep is deformation without wear. Adhesive and abrasive wear is associated with removal of material on the back side of modular tibial components.CLINICAL SITUATION FOR QUESTIONS 83 THROUGH 87A bilateral cemented total knee arthroplasty (TKA) was performed on an otherwise healthy 63-year-old woman. The surgery and immediate postsurgical course were uneventful. Two days after surgery, while in physical therapy at the hospital, the patient’s oxygen saturation is noted at 92%.

Question 1029

Topic: 3. Adult Reconstruction (Hip & Knee)

Which laboratory findings would most support a diagnosis of prosthetic joint infection (PJI) in a hip or knee arthroplasty performed 3 weeks ago?

. Erythrocyte sedimentation rate (ESR) higher than 30 mm/h
. C-reactive protein (CRP) level higher than 10 mg/L
. Synovial white blood cell count higher than 10000 cells/µL
. Synovial percentage of polymorphonuclear (PMN) leukocytes higher than 60%

Correct Answer & Explanation

. Erythrocyte sedimentation rate (ESR) higher than 30 mm/h

Explanation

DISCUSSIONThe diagnosis of acute PJI is associated with different criteria than the diagnosis of a chronic PJI. There is no agreed-upon threshold for ESR during the acute period (6 weeks) following total joint arthroplasty. The CRP threshold is higher during the acute period (100 mg/L vs 10 mg/L for a chronic infection). The threshold for synovial fluid analysis for an acute PJI is 10000 cells/µL and more than 90% PMN neutrophils vs 3000 cells/µL and more than 80% PMN neutrophils for a chronic infection.

Question 1030

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures 122a and 122b are the radiographs of a 79-year-old woman with a 2-year history of progressively worsening right hip pain. She had a right total hip arthroplasty 7 years prior. An infection workup is negative. She opts for revision surgery; the most appropriate surgical plan to address her femoral component is

. extended trochanteric osteotomy and revision to a cementless long-stem prosthesis.
. extended trochanteric osteotomy and revision to a cemented long-stem prosthesis.
. revision to a cementless long-stem prosthesis without use of an extended trochanteric osteotomy.
. revision to a cemented long-stem prosthesis without use of an extended trochanteric osteotomy.

Correct Answer & Explanation

. extended trochanteric osteotomy and revision to a cementless long-stem prosthesis.

Explanation

DISCUSSIONThe patient’s radiographs show loosening of the cemented femoral stem and varus remodeling of the femur. An extended trochanteric osteotomy is necessary because attempting to extract the existing prosthesis and implant another prosthesis without an osteotomy is likely to cause a proximal femoral fracture. Also, an osteotomy would facilitate atraumatic removal of the stem and cement. Cementless fixation is likely to produce a more predictable long-term outcome than cemented fixation for the revision implant.

Question 1031

Topic: 3. Adult Reconstruction (Hip & Knee)

When performing a posterior cruciate-substituting total knee revision, trial components are inserted. The knee comes to full extension but is tight in flexion. The surgeon should consider

. flexing the femoral component.
. downsizing the femoral component.
. downsizing the tibial component thickness.
. resecting more distal femur.

Correct Answer & Explanation

. flexing the femoral component.

Explanation

DISCUSSIONIn this scenario, the extension gap is normal and the flexion gap is tight. Increasing the flexion gap without changing the extension gap can be performed by downsizing the femoral component or adding posterior slope to the tibia resection. Flexing the femoral component tightens the flexion gap. Decreasing the tibial component thickness loosens the flexion and extension gaps. Resecting more distal femur only loosens the extension gap.CLINICAL SITUATION FOR QUESTIONS 4 THROUGH 7Figure 4 is the radiograph of a 73-year-old woman who returns for her annual follow-up 14 years after undergoing total hip arthroplasty. She denies pain and has no discomfort upon examination.

Question 1032

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures below show the radiographs, and the CT obtained from a 58-year-old woman who underwent cementless left total hip arthroplasty. Nine months after surgery, she continued to have groin pain when actively flexing her hip. She has trouble walking up stairs and getting out of her car. What is the most likely diagnosis?

. Trochanteric bursitis
. Femoral component loosening
. Iliopsoas tendonitis
. Acetabular component loosening

Correct Answer & Explanation

. Trochanteric bursitis

Explanation

DISCUSSION:Groin pain after total hip replacement has a number of possible causes, and an exact diagnosis may remain elusive in some patients. Infection should be ruled out with laboratory studies and, if indicated, diagnostic aspiration of the hip joint. Implant loosening should be evaluated by plain radiograph and bone scan, if indicated. Synovitis resulting from wear debris should be considered in patients with polyethylene liners who experience late-onset symptoms or in any patient with a metal-on-metal bearing. This patient's symptoms are classic for iliopsoas tendonitis. Physical examination usually reveals pain and weakness with resisted hip flexion. A cross-table lateral radiograph and CT show that the anterior edge of the acetabulum protrudes beyond the anterior wall, thereby acting as a source of iliopsoas tendon irritation. In such cases, acetabular component revision and repositioning are indicated. Fluoroscope-guided iliopsoas cortisone injection can help to establish the diagnosis and relieve groin pain. If the acetabular component is well positioned, then iliopsoas tenotomy should be considered.

Question 1033

Topic: 3. Adult Reconstruction (Hip & Knee)

Figures below depict the radiographs obtained from a 76-year-old woman with a painful total knee arthroplasty. She describes an uneventful recovery with no wound-healing issues and was pain free for the first 10 years. Although reporting no trauma or inciting event, she now describes pain in the entire knee that is most severe with her first few steps. She has begun to notice night pain and, more recently, constant swelling. What is the most appropriate work-up at this time?

. Knee aspiration with cell count/cultures, C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), CT
. Knee aspiration with cell count/cultures, CRP, ESR
. Fresh-frozen specimen at the time of revision knee arthroplasty only
. Technetium-99m bone scan, knee aspiration with cell count/cultures

Correct Answer & Explanation

. Knee aspiration with cell count/cultures, C-reactive protein (CRP) level, erythrocyte sedimentation rate (ESR), CT

Explanation

DISCUSSION:An evaluation of the painful total knee must be supported by an understanding of the potential etiologies of pain. They may include, aseptic loosening, infection, osteolysis, gap imbalance, referred pain, stiffness, and complex regional pain syndrome. In this case, the patient demonstrates start-up pain and had no prior history of infections. Her radiographs show subsidence of the tibia, indicating a loose prosthesis. Knowing that the prosthesis is already loose precludes the need for a bone scan. It is, however, important to rule out infection in this case; therefore, CRP and ESR testing is essential. Aspiration is also recommended when going into knee arthroplasty, and infection is a concern.

Question 1034

Topic: 3. Adult Reconstruction (Hip & Knee)

Figure 10 shows the AP radiograph of an ambulatory 76-year-old patient. What is the most appropriate surgical treatment option for this patient?

. Revision arthroplasty using a cemented femoral component
. Impaction allografting of the femoral component
. Proximal femoral replacement arthroplasty
. Resection arthroplasty
. Hip arthrodesis

Correct Answer & Explanation

. Revision arthroplasty using a cemented femoral component

Explanation

DISCUSSION: The patient has a periprosthetic fracture around a loose cemented femoral component.  The proximal bone stock is poor; therefore, this fracture may be categorized as Vancouver 3-B.  Hip arthrodesis and resection arthroplasty provide suboptimal results, particularly for ambulatory patients.  Although impaction allografting may be an option to restore the bone stock in a younger patient, the latter procedure will be very difficult to perform when the proximal bone is poor in quality and fractured.  Cementing another component into this wide femur is not an option.  The best option for revision of the femoral component in this elderly patient is proximal femoral replacement arthroplasty.REFERENCES: Malkani AL, Settecerri JJ, Sim FH, et al: Long-term results of proximal femoral replacement for non-neoplastic disorders.  J Bone Joint Surg Br 1995;77:351-356.Parvizi J, Sim FH: Proximal femoral replacements with megaprostheses.  Clin Orthop 2004;420:169-175.

Question 1035

Topic: 3. Adult Reconstruction (Hip & Knee)

In total knee arthroplasty, in vitro testing has shown that cross-linking can diminish the rate of polyethylene wear by 30% to 80%. What other change in material properties is possible when polyethylene is highly cross-linked?

. Increased ductility
. Increased wettability
. Diminished fatigue strength
. Decreased resistance to abrasive wear

Correct Answer & Explanation

. Increased ductility

Explanation

DISCUSSION:The most important concern regarding highly cross-linked polyethylene relates to decreased mechanical properties. Cross-linking results in reduced ductility, tensile strength, and fatigue crack propagation resistance. These problems have not been shown to cause implant failure in the most recent clinical trials, but they remain the most important mechanical issues associated with current material processing methods.

Question 1036

Topic: 3. Adult Reconstruction (Hip & Knee)

A 45-year-old man underwent unipolar hemiarthroplasty reconstruction using cementless fixation for nontraumatic osteonecrosis of the femoral head 5 years ago. He now reports buttock and groin pain that is associated with loading activities. What is the most likely cause of his pain?

. Infection
. Stem loosening
. Acetabular osteonecrosis
. Acetabular cartilage degeneration
. Referred pain from the lumbar spine

Correct Answer & Explanation

. Infection

Explanation

DISCUSSION: One of the most common complications of hemiarthroplasty is acetabular cartilage degeneration, resulting in increasing pain.  Conversion total hip arthroplasty generally is successful with placement of an acetabular cup.  Additionally, many patients with osteonecrosis already have degenerative changes of the acetabular cartilage even though radiographic findings may appear normal.REFERENCES: Steinberg ME, Corces A, Fallon M: Acetabular involvement in osteonecrosis of the femoral head. J Bone Joint Surg Am 1999;81:60-65.Dalldorf PG, Banas MP, Hicks DG, Pelligrini VD Jr: Rate of degeneration of human acetabular cartilage after hemiarthroplasty. J Bone Joint Surg Am 1995;77:877-882.

Question 1037

Topic: 3. Adult Reconstruction (Hip & Knee)

Oxidation of polyethylene after sterilization occurs most rapidly when the implant undergoes

. gamma radiation in air.
. gamma radiation in nitrogen.
. gamma radiation in argon.
. gas plasma exposure.
. ethylene oxide exposure.

Correct Answer & Explanation

. gamma radiation in air.

Explanation

DISCUSSION: The use of gamma radiation to sterilize polyethylene will result in the formation of free radicals in the material that increase the susceptibility of the material to oxidation and wear.  The packaging can also have an impact.  If the polyethylene is packaged in air, the oxygen in the packaging can significantly oxidize the material on the shelf prior to clinical use.  Gas plasma and ethylene oxide sterilization do not appear to increase oxidation of polyethylene.REFERENCES: Simon SR (ed): Orthopaedic Basic Science.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 449-486.Wright TM: Ultra-high molecular weight polyethylene, in Morrey BF (ed): Joint Replacement Arthroplasty.  New York, NY, Churchill Livingstone, 1991, pp 37-46.Collier JP, Sutula LC, Currier BH, et al: Overview of polyethylene as a bearing material: Comparison of sterilization methods.  Clin Orthop 1996;333:76-86.FOR ALL MCQS CLICK THE LINK ORTHOMCQ BANK

Question 1038

Topic: 3. Adult Reconstruction (Hip & Knee)

A 46-year-old male construction worker has right hip pain that has failed to respond to nonsurgical management. His body mass index (BMI) is 32, he is 6’2” tall, and he has no other medical comorbidities. AP and lateral radiographs of the right hip are shown in Figures 23a and 23b. The patient inquires about his suitability for metal-on-metal hip resurfacing. The patient should be educated that he is at higher risk for failure secondary to which of the following?

. BMI >30
. Presence of secondary changes of the acetabulum
. Osteonecrosis of the femoral head
. Age of younger than 55 years old
. Male gender

Correct Answer & Explanation

. BMI >30

Explanation

DISCUSSION: This young patient has osteonecrosis of the femoral head with a large area of collapse.The results of hip resurfacing arthroplasty have been reported to be best in young, male patients who are younger than 55 years of age with a diagnosis of osteoarthritis. Although some authors advocate metal- on-metal hip resurfacing as an option for patients with osteonecrosis of the femoral head, in this particular patient, given the size of the necrotic segment, he would be at higher risk for failure and a conventional total hip arthroplasty would be a more conservative option. As the acetabulum is resurfaced in metal- on-metal hip resurfacing, the secondary changes of the acetabulum are not an issue and his BMI is in an acceptable range for the procedure.REFERENCES: Mont MA, Ragland PS, Etienne G, et al: Hip resurfacing arthroplasty. J Am Acad Orthop Surg 2006;14:454-463.Revell MP, McBryde CW, Bhatnagar S, et al: Metal-on-metal hip resurfacing in osteonecrosis of the femoral head. J Bone Joint Surg Am 2006;88:98-103.Buergi ML, Walter WL: Hip resurfacing arthroplasty: The Australian experience. J Arthroplasty 2007;22:61-65. Question 24A 31-year-old woman had disabling right knee pain. An arthroscopic assessment reveals chondromalacia of both the lateral femoral condyle and tibial plateau. The standing femorotibial axis measures 10 degrees of valgus. Theoptimum treatment of this condition should includedistal femoral varus osteotomy.osteoarticular transplant to the lateral femoral condyle.unicondylar arthroplasty.high tibial osteotomy.Fulkerson tibial tubercle transfer. PREFERRED RESPONSE: 1DISCUSSION: The long-term outcome of a distal femoral varus osteotomy has been quite favorable and should remain the primary choice for this young active woman. Sharma and associates have shown that a 5-degree valgus malalignment has a five-fold chance of progressing at least one grade within 18 months, making a corrective osteotomy the most important surgical maneuver.REFERENCES: Sharma L, Song J, Felson DT, et al: The role of knee alignment in disease progression and function decline in knee osteoarthritis. JAMA 2001 ;286:188-195.Murray PB, Rand JA: Symptomatic valgus knee: The surgical options. J Am Acad Orthop Surg 1993; 1:19.Figure 25a Figure 25b Figure 25c

Question 1039

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision total knee arthroplasty (TKA), there is difficulty gaining exposure and a tibial tubercle osteotomy (TTO) is performed. The final components are stable and include a stemmed tibial component that bypasses the osteotomy site. The tibial tubercle is reattached to the osteotomy site with multiple cerclage wires. Following closure of the arthrotomy, the knee is flexed to 90 degrees, and there is no observed displacement of the TTO. What is the best next step in postsurgical rehabilitation?

. Limit flexion to 90 degrees with nonweight-bearing activity with crutches for the first 6 weeks
. Limit flexion to 30 degrees for the first week, progress 10 degrees per week, and allow partial weight-bearing activity with crutches
. The knee should be immobilized in extension; partial weight-bearing activity with crutches may be allowed for the first 6 weeks
. An initial range-of-motion restriction to 90 degrees or weight-bearing restriction is not needed

Correct Answer & Explanation

. Limit flexion to 90 degrees with nonweight-bearing activity with crutches for the first 6 weeks

Explanation

DISCUSSIONTTO is a recognized technique for improving exposure when performing TKA in a stiff knee. TTO has been reported to enhance surgical exposure and not adversely affect outcomes after TKA, but there is a 5% complication rate. The postsurgical routine following TTOincludes full weight-bearing activity and range of motion as tolerated. Caution should be exercised when manipulation is performed to improve knee flexion following a TTO.

Question 1040

Topic: 3. Adult Reconstruction (Hip & Knee)

A 71-year-old woman has a failed revision hip arthroplasty and is undergoing a re-revision hip arthroplasty. Her last hip surgery was 4 years ago with revision of the acetabular component. Radiographs show a well-fixed extensively porous-coated femoral component and a failed acetabular component with proximal and medial migration through the floor of the acetabulum. Preoperative laboratory studies reveal an erythrocyte sedimentation rate (ESR) of 70 mm/h (normal 0-29 mm/h), a C-reactive protein (CRP) of 23.3 (normal 0.2-8.0), and a negative hip aspiration. At the time of surgery, tissues look inflamed and a frozen section shows 20 WBC per high power field; however, a Gram stain is negative. What is the most appropriate action at this point?

. Proceed with the revision as planned
. Obtain cultures and proceed with revision of the acetabulum only
. Obtain cultures and proceed with revision of the femur only
. Obtain cultures, remove the implants, and insert an antibiotic spacer
. Obtain cultures and close

Correct Answer & Explanation

. Proceed with the revision as planned

Explanation

DISCUSSION: Despite the negative aspiration preoperatively, intraoperative findings are suspicious for infection. Additionally, the preoperative blood work is also concerning for infection with an elevated CRP and ESR. The frozen section is also positive. Most important is the unreliability of the Gram stain. Numerous investigators have show high false negative rates for Gram stain in chronic periprosthetic infection. The Gram stain should not be relied on for decision-making in revision surgery, particularly when other investigations point to infection. With the information available, the diagnosis is deep infection. The best course of action is to obtain cultures, remove the implants, and insert an antibiotic spacer. Only obtaining cultures and closing would require a second operation to remove the implants if the cultures are positive.REFERENCES: Sanzen L, Sundberg M: Periprosthetic low-grade hip infections: Erythrocyte sedimentation rate and C-reactive protein in 23 cases. Acta Orthop Scand 1997;68:461-465.Spangehl MJ, Hanssen AD, Osman DR: Diagnosis and treatment of the infected hip arthroplasty, in Morrey BF(edA)L:-MJoaidnetnaRCeopplyacement Arthroplasty, ed 3. Philadelphia, PA, Churchill Livingstone, 2003, pp 856-874. Question 71A 79-year-old patient has a history of peripheral vascular disease and reports chronic knee pain. She has had coronary artery disease treated with angiography and stents on two occasions. Peripheral pulses are absent in both lower extremities, but the patient is disabled by advanced chronic degenerative arthritis in her right knee and would like to proceed with a total knee arthroplasty. The next most appropriate evaluation should include which of the following?Ankle-brachial index of the affected lower extremityFemoral popliteal angiographyVenous Dopplers of both lower extremitiesMRI of the popliteal fossaRadiographs to identify calcified plaques in the femoral arteryDISCUSSION: This question is designed to draw attention to the fact that peripheral vascular disease carries an increased risk of complications for the patient and should be carefully evaluated. The vascular surgeon will make the choice of revascularization or surgical clearance for knee reconstruction based on the initial results of the ankle-brachial index.REFERENCE: Smith DE, McGraw RW, Taylor DC, et al: Arterial complications and total knee arthroplasty. J Am Acad Orthop Surg 2001 ;9:253-257.

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