3. Adult Reconstruction (Hip & Knee) MCQs

A knee that is symmetric but tight in flexion requires more space in the flexion gap. This can be achieved by decreasing the anteroposterior dimension of the femur (downsizing the femoral component or anteriorizing the component if using anterior referencing) or by increasing the posterior slope of the tibial cut. Increasing the posterior slope opens the flexion gap without significantly affecting the extension gap.

The superior gluteal nerve innervates the gluteus medius, gluteus minimus, and tensor fasciae latae, which are the primary hip abductors. Injury results in abductor weakness and a Trendelenburg gait. While a direct posterior approach typically protects this nerve, overzealous retraction superiorly or extending the approach too far proximally into the gluteus medius can injure it.

A knee that is tight in flexion and balanced in extension has an isolated tight flexion gap. Using an anterior referencing system, downsizing the femoral component shifts the posterior femoral condylar cut anteriorly (resecting more posterior bone). This effectively increases (loosens) the flexion gap without affecting the extension gap.

Macrophages are the primary effector cells that phagocytose polyethylene wear debris in periprosthetic osteolysis. Upon activation, they release pro-inflammatory cytokines (such as TNF-alpha, IL-1, and IL-6) that upregulate RANKL expression. This ultimately stimulates osteoclast-mediated bone resorption.

A tight flexion gap with a balanced extension gap implies that the anteroposterior (AP) dimension of the femoral component is too large. Downsizing the femoral component (shifting the posterior condylar cut anteriorly) will increase the size of the flexion gap without affecting the extension gap.

The patient has a chronic periprosthetic joint infection. In North America, the gold standard for managing chronic PJI is a two-stage revision arthroplasty involving component removal, placement of an antibiotic spacer, and delayed reimplantation.

Irradiation of polyethylene cross-links the material to reduce wear, but generates free radicals that can cause oxidative degradation over time. Thermal treatments like annealing (heating below melting point) or remelting are utilized to extinguish these free radicals and stabilize the liner.

DISCUSSION:Dislocation after total hip arthroplasty is a multifactorial problem. Numerous risk factors may act independently or cumulatively to increase the risk of this complication. Previous hip surgery of any kind is associated with a twofold increased risk for dislocation. Other risk factors include female gender, impaired mental status, inflammatory arthritis, and older age. Numerous studies have shown a lower dislocation rate with a direct lateral approach, although surgical techniques such as capsular repair have significantly lowered the incidence of dislocation after using the posterior approach. Metal-on-metal bearings have been associated with other complications such as adverse tissue reactions but are often used with larger-diameter bearings, which pose a lower risk of dislocation.Question 2A patient has pain 2 years after undergoing a metal-on-metal (MOM) left total hip arthroplasty (THA). Whichtest(s) best correlate with a prognosis if this patient is having a reaction to metal debris?A. Erythrocyte sedimentation rate, C-reactive protein, and white blood cell countB. Serum cobalt and chromium ion levelsC. MRI with metal artifact reduction sequence (MARS) D. CT of pelvisCORRECT ANSWER: C DISCUSSION:Painful MOM THA and taper corrosion can cause substantial damage to a patient's hip if left untreated. In this case, the workup for a painful MOM THA starts the same as a workup for a painful metal-on- polyethylene bearing couple. Infection must be ruled out in every case with a set of inflammatory markers. If these markers are remotely elevated, this is an indication for joint aspiration. In patients with metal debris, the pathology report often indicates too many cells to count or cellular debris. Metal ion levels do not seem to correlate with prognosis. There are well-functioning patients with high ion levels and poor- functioning patients with low ion levels. Advanced imaging with MARS MRI to evaluate for peritrochanteric fluid collection, a soft-tissue mass, or synovial/capsular hypertrophy will reveal signs of a metal reaction that indicate the need for a revision discussion. A CT scan can show more advanced bony destruction as an indicator of poor prognosis. These films can be used to determine the need for a structural graft or augments for reconstruction of bone loss attributable to metal debris.Question 3Figuresbelowdemonstratetheradiographsobtainedfroma35-year-oldwomanwithend-stagedebilitatingosteoarthritisoftherighthip.Sheiscontemplatingtotalhiparthroplasty(THA).Shehasa historyofrighthipdysplasiaandunderwenthiposteotomyasanadolescent.Overtheyears,nonsurgical treatment,includingweightloss,activitymodifications,andintra-articularinjections,hasfailed.Her infectionwork-uprevealslaboratoryfindingswithindefinedlimits.Afurtherwork-uprevealselevations inserumcobaltandchromiumlevelsandfluidcollectionssurroundingthehiponMRIwithMARS. RevisionTHAisrecommended.Themostcommoncomplicationfollowingrevisionofafailedmetal-on- metalhiparthroplastyisA.infection. B.instability. C.loosening.D. periprosthetic fracture.CORRECT ANSWER: B DISCUSSION:THA has proven durable and reliable for pain relief and improving function for patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A metal-on- metal articulation is associated with excellent wear rates in vitro. With its capacity to offer a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis with potential transfer of metal ions across the placental barrier make metal-on-metal bearings less desirable and relatively contraindicated for younger women of child- bearing age. The workup of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including sedimentation rate, CRP, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging including MARS MRI should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so, when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cellcounts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following revision of failed metal-on-metal hip replacements.Question 4Figure 1 shows the radiograph and Figure 2 shows the MRI scan obtained from a 37-year-old woman with a2-month history of left hip pain. Which combination of a single symptom and examination finding is most likely in this scenario?A. Pain during sitting; flexion abduction and external rotation of the hipB. Groin pain; pain with internal rotation and adduction while supine with the hip and knee flexed 90°C. Clicking; abductor lurchD. Buttock pain; pain with hip extension, adduction, and external rotation while proneCORRECT ANSWER: B DISCUSSION:MRI reveals an anterior labral tear, and the radiograph shows minimal arthritis with possible dysplasia. The most common location of pain in patients with a labral tear is the groin, and the most common physical finding is a positive impingement test result. Pain during sitting, clicking, and buttock pain are frequently described by patients with a labral tear, but these symptoms are less common than groin pain. A positive posterior impingement test finding is more common in patients with a posterior labral tear. Although age over 40 years and a body mass index higher than 30 can adversely affect clinical outcomes after joint preservation procedures such as PAO, hip arthroscopy, and femoral acetabular impingement surgery, the presence of hip arthritis on presurgical radiographs is the most commonly mentioned cause of failed hip joint preservation surgery. Tönnis grade is a radiographic measure of hip arthritis. A higher Outerbridge score is associated with more frequent poor outcomes after hip arthroscopy; however, the Outerbridge cartilage score is determined by direct visualization at the time of surgery. The Outerbridge score cannot be determined presurgically.Question 5Figures1and2demonstratetheradiographsobtainedfroma35-year-oldwomanwithend-stagedebilitatingosteoarthritisoftherighthip.Sheiscontemplatingtotalhiparthroplasty(THA).Shehasa historyofrighthipdysplasiaandunderwenthiposteotomyasanadolescent.Overtheyears,nonsurgical treatment,includingweightloss,activitymodifications,andintra-articularinjections,hasfailed.Her infectionwork-uprevealslaboratoryfindingswithindefinedlimits.Thepatientundergoessuccessful primaryTHAwithametal-on-metalbearing.At1-yearfollow-up,shereportsnopainandishighly satisfiedwiththeprocedure.However,3yearsaftertheindexprocedure,shereportsatraumaticrighthip painthatworsenswithactivities.Radiographsrevealtheimplantsingoodpositionwithnosignof looseningorlysis.AninitiallaboratoryevaluationrevealsanormalsedimentationrateandC-reactive protein(CRP)level.ThemostappropriatenextdiagnosticstepisA.MRIwithmetalartifactreductionsequence(MARS)only. B.serumcobaltonly.C.serumcobaltandchromiumlevels.D. serum cobalt and chromium levels and MRI with MARS.CORRECT ANSWER: DDISCUSSION:THA has proven to be durable and reliable for pain relief and improvement of function in patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. Ametal-on-metal articulation is associated with excellent wear rates in vitro. Because it offers a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions—including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis after the possible transfer of metal ions across the placental barrier—make metal-on-metal bearings less desirable and relatively contraindicated for younger women of child-bearing age.The work-up of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including the erythrocyte sedimentation rate, C-reactive protein (CRP) level, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging, including MRI with MARS, should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following a revision of failed metal-on-metal hip replacements.Question 6A59-year-oldwomanwithahistoryofosteoporosisisinvolvedinahigh-speedmotorvehicleaccident,resultinginlefthippainanddeformity.TheinitialradiographfromthetraumabayisshowninFigure1/. PostreductionCTisshowninFigures2through4.Whatisthemostappropriatedefinitivesurgical treatment?A.Openreductionandinternalfixation(ORIF)oftheacetabularfracturewithconcomitantacute totalhiparthroplastyB.ORIFoftheacetabularfractureandORIFofthefemoralheadfracturefragmentsC.ORIFoftheacetabularfractureandhemiarthroplastyD. Skeletal traction with delayed total hip arthroplasty after the acetabular fracture has healedCORRECT ANSWER: ADISCUSSION:The radiograph shows a posterior wall acetabular fracture-dislocation. Post reduction CT indicates a large comminuted posterior wall fracture with marginal impaction of the articular surface. A comminuted femoral head fracture also is seen extending to the superior weight-bearing surface. Given the marginalimpaction of the acetabulum and the considerable comminution of the femoral head (which is likely unreconstructible), this injury would have a high risk of causing posttraumatic arthritis if treated with ORIF of the fractures alone. Considering this fact and the patient’s age, ORIF of the posterior wall and acute total hip arthroplasty would likely have the best functional result and the lowest risk of reoperation. Hemiarthroplasty is inappropriate for this injury considering the acetabular fracture. Skeletal traction currently plays a limited role in the definitive treatment of acetabular fractures.Question 7Figuresbelowshowtheradiographs,MRI,andMRarthrogramobtainedfroma25-year-oldcollegiatesoccerplayerwhohasnew-onsetleftgroinpain.Heplayedcompetitivesoccerfromayoungageandhas competedorpracticed5to6timesperweeksincetheageof10.Hedeniesanyspecifichipinjurythat necessitatedtreatment,buthistrainercontendsthathehadagroinpull.Hereportsgroinpainwithpassive flexionandinternalrotationofthelefthip,andhishiphaslessinternalrotationthanhisasymptomatic righthip.Heisotherwisehealthy.Whatistheprimarycauseofacamdeformity?A.AgeneticproblemB.RepetitiveactivitiesinvolvinganopenproximalfemoralphysisC.EarlyclosureoftheproximalfemoralphysisD. Hip dysplasiaCORRECT ANSWER: B DISCUSSION:Multiple studies have confirmed that cam or pincer anatomy is commonly present in asymptomatic hips. According to a large systematic review, cam deformities are present in approximately one-third of asymptomatic hips in young adults, and the proportion is higher than 50% in the subgroup of athletes. Ganz and associates proposed that femoral acetabular impingement is the root cause of osteoarthritis in most nontraumatic, nondysplastic hips, and functional improvement with surgical correction of the deformity has been demonstrated. Despite the link between cam deformity and hip osteoarthritis, a corresponding link between the correction of the deformity and prevention of osteoarthritis has never been proven. The results of cam deformity correction, typically including repair of the degenerative labral tear, are much poorer when substantial joint space loss is present. A typical joint space cutoff of 2 mm or less is used to recommend against hip preservation surgery.Question 8FiguresAdult Reconstructive Surgery of the Hip and Knee Scored andRecorded Self-Assessment Examination 2019

Painful MOM THA and taper corrosion can cause substantial damage to a patient's hip if left untreated. In this case, the workup for a painful MOM THA starts the same as a workup for a painful metal-on- polyethylene bearing couple. Infection must be ruled out in every case with a set of inflammatory markers. If these markers are remotely elevated, this is an indication for joint aspiration. In patients with metal debris, the pathology report often indicates too many cells to count or cellular debris. Metal ion levels do not seem to correlate with prognosis. There are well-functioning patients with high ion levels and poor- functioning patients with low ion levels. Advanced imaging with MARS MRI to evaluate for peritrochanteric fluid collection, a soft-tissue mass, or synovial/capsular hypertrophy will reveal signs of a metal reaction that indicate the need for a revision discussion. A CT scan can show more advanced bony destruction as an indicator of poor prognosis. These films can be used to determine the need for a structural graft or augments for reconstruction of bone loss attributable to metal debris.

THA has proven durable and reliable for pain relief and improving function for patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. A metal-on- metal articulation is associated with excellent wear rates in vitro. With its capacity to offer a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis with potential transfer of metal ions across the placental barrier make metal-on-metal bearings less desirable and relatively contraindicated for younger women of child- bearing age. The workup of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including sedimentation rate, CRP, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging including MARS MRI should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so, when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cellcounts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following revision of failed metal-on-metal hip replacements.

THA has proven to be durable and reliable for pain relief and improvement of function in patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. Ametal-on-metal articulation is associated with excellent wear rates in vitro. Because it offers a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions—including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis after the possible transfer of metal ions across the placental barrier—make metal-on-metal bearings less desirable and relatively contraindicated for younger women of child-bearing age.The work-up of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including the erythrocyte sedimentation rate, C-reactive protein (CRP) level, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging, including MRI with MARS, should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following a revision of failed metal-on-metal hip replacements.

The recent experience of a large clinical cohort revealed the most likely risk factors as being female gender, age younger than 40, small components, and a diagnosis of hip dysplasia causing osteoarthritis. Failure was least likely among men and after procedures involving larger components. These data have prompted some authors to caution against using metal-on-metal hip resurfacing in women and to primarily target candidates who are men younger than age 50. Small components may be more prone to failure because of malpositioning and edge loading, which have been noted to be more common in dysplasia cases.

This patient presents with HO 4 months after undergoing THA. Symptomatic HO may complicate nearly7% of primary THA cases. Improvement in pain is expected within 6 months, and most patients will not need surgical treatment. Surgical excision may be warranted for symptomatic patients after full maturation of the HO, usually 6 to 18 months after the surgery. Patients can be followed with repeated serum alkaline phosphatase levels, which are elevated initially and should return to normal upon maturation of the HO. Alternatively, a bone scan can show decreased activity after the HO has matured. Twenty-five milligrams of indomethacin 3 times daily for 6 weeks or 1 dose of irradiation at 700 to 800 Gy is effective in the prevention of HO but not for the treatment of established HO.

The radiograph shows that this patient has a high offset varus femoral morphology of both hips. Preoperative templating would identify this, and the surgeon should choose an implant system that has extended offset options to help match the native anatomy and biomechanics and minimize the risk of instability. Trialing a high offset neck, rather than a standard offset neck, is the next most appropriate step. Depending on the design of the implant system, this step can be accomplished by direct medialization of the femoral head, which would not affect leg length, or by lowering the neck angle, which would affect the leg length and would require a longer femoral head, because the leg lengths had previously been equal. Placement of a longer femoral head would likely improve hip stability but would also make the leg length uneven, which is a common cause of dissatisfaction after total hip arthroplasty. An offset acetabular liner also increases the leg length and does not correct the issue, which is on the femoral side. Trochantericadvancement is sometimes used as a treatment for instability but would be inappropriate as the next step in this setting.

The obesity epidemic is increasing, and the number of patients with a BMI higher than 35 undergoing THA and TKA also is growing. Controversy exists over the optimal BMI cutoff and the ability to perform joint replacements safely in patients who are morbidly obese. Several clinical series and national database analyses have shown that morbidly obese patients undergoing THA or TKA are at increased risk for wound complications as well as 30-day and 90-day readmissions. These patients’ incisions are typically larger because of the size of the soft-tissue envelope. Although the clinical scores following successful THA or TKA often are lower than the scores of controls, the overall changes in clinical function and satisfaction are equivalent in nonobese and obese patients.

intravenous antibioticsDISCUSSION:This patient clearly has a chronically infected total hip arthroplasty, indicated by the open, draining sinus, as well as trochanteric bone resorption on radiographs, and two years of pain. Recently, specific guidelines have been published to better help the clinician define infection. Repeating the hip aspiration is unnecessary, because infection is already evident. Initiating a wound care consult would not address the underlying infection. The determination whether to retain the components or perform a two-stage exchange is based more on the acuity of infection. In this particular case, the patient is chronically infected. Irrigation and debridement with a liner exchange and retention of the components are reserved for the acute setting.

Periprosthetic fracture is the third most common reason (after loosening and infection) for revision surgery after total hip arthroplasty (THA). Late periprosthetic fracture risk is 0.4% to 1.1% after primaryTHA and 2.1% to 4% after revision THA. Risk factors for periprosthetic fracture include age over 70 years, decreasing bone mass, and loosening of implants and osteolysis. The risk of concomitant infection in the presence of a periprosthetic fracture is 11%, according to Chevillotte and associates. Obtaining presurgical aspiration or intrasurgical tissue for culture is recommended if concomitant infection is suspected.

Gamma irradiation produces free radicals. Although these free radicals can form cross-links with other polyethylene chains, the free radicals can also form a bond with oxygen, resulting in early oxidation. Gamma irradiation in air produces the highest risk for oxidized polyethylene, resulting in the highest risk for wear, delamination, and subsequent osteolysis. This patient demonstrates severe periarticular osteolysis. When she is asymptomatic, this suggests the acetabular and femoral components remain well fixed to the bone. Consequently, she can be treated by removing the wear generator (polyethylene exchange), along with bone grafting of the osteolytic defect. Considering the extensive amount of osteolysis indefinite observation would not be appropriate. A foot drop develops 2 days after surgery. As a result, it can be assumed that the nerve was not injured directly during the surgical procedure. Although MRI or CT may be indicated to identify an evolving hematoma, the immediate concern is to minimize pressure on the sciatic nerve. Tension on the nerve can be reduced by flexing the surgical knee and positioning the bed flat.

First-time early dislocations are often treated successfully without revision surgery, especially when no component malalignment is present. In this clinical scenario, it appears the patient would benefit from better education about dislocation precautions. Hip orthoses are of questionable benefit unless the patient is cognitively impaired. Revision surgery can be successful but is usually reserved for patients with recurrent dislocations.

Given a well-fixed acetabular metal shell and a localized osteolytic lesion, good outcomes can be expected from liner revision in this clinical scenario with retention of the metal socket, assuming no damage to the components or other unexpected findings arise during revision surgery. Here, complete cup revision is not warranted, considering the appropriate implant position. Beaulé and associates reviewed 83 consecutive patients (90 hips) in whom a well-fixed acetabular component was retained in a clinical scenario such as the one described. No hip showed recurrence or expansion of periacetabular osteolytic lesions.