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 841
Topic: 3. Adult Reconstruction (Hip & Knee)
What is the most common cause for late revision (> 2 years post op) total knee arthroplasty?
Correct Answer & Explanation
. Polyethylene wear
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 842
Topic: 3. Adult Reconstruction (Hip & Knee)
Which component position is associated with poor patellar tracking during total knee arthroplasty (TKA)?
Correct Answer & Explanation
. Internal rotation of the tibial component
Explanation
DISCUSSION: Internal malrotation of the femoral or tibial component is associated with lateral tracking of the patella in TKA. Lateral placement of the femoral component and medial placement of the patellar component can aid in preventing lateral tracking of the patella. Varus alignment of the proximal tibia has not been associated with patella maltracking.
Question 843
Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following is considered the most common complication of the impaction grafting technique for femoral revision surgery?
Correct Answer & Explanation
. Early stem subsidence
Explanation
DISCUSSION: Impaction grafting technique for femoral revision surgery has become increasingly popular over the past decade. This technique is designed to address cavitary deficiencies of the femur. The femoral stem is inserted with cement fixation. Its clinical efficacy has not been shown to be superior to extensively porous-coated stems. Early subsidence of the stem has been reported in more than 50% of the patients. However, loss of fixation has occurred infrequently (5%) in reported series conducted by experienced surgeons. It has not been shown to have a higher infection rate. REFERENCES: Gie GA, Linder L, Ling RS, Simon JP, Slooff TH, Timperley AJ: Impacted cancellous allografts and cement for revision total hip arthroplasty. J Bone Joint Surg Br 1993;75:14-21. Meding JB, Ritter MA, Keating ME, Faris PM: Impaction bone-grafting before insertion of a femoral stem with cement in revision total hip arthroplasty: A minimum two-year follow-up study. J Bone Joint Surg Am 1998;79:1834-1841.
Question 844
Topic: Total Hip Arthroplasty (THA)
A 59-year-old active woman undergoes elective total hip replacement in which a posterior approach is used. She has minimal pain and is discharged to home 2 days after surgery. Four weeks later, she dislocates her hip while shaving her legs. She undergoes a closed reduction in the emergency department. Postreduction radiographs show a reduced hip with well-fixed components in satisfactory alignment. What is the most appropriate management of this condition from this point forward?
Correct Answer & Explanation
. Observation and patient education regarding hip dislocation precautions
Explanation
DISCUSSION: 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.
Question 845
Topic: 3. Adult Reconstruction (Hip & Knee)
Figures below depict the radiographs obtained from a 60-year-old man with instability and pain 1 year after primary right total knee arthroplasty. He states that he had surgery on two occasions for a tendon rupture that was repaired with sutures but that his knee popped again, and now the leg is unable to hold his weight. On examination, he is in no acute distress. His height is 6'3", and he weighs 240 pounds. He is ambulatory with crutches. Range of motion of the right knee is 50° to 120° actively and 0° to 120° passively. More than 10° of varus/valgus laxity and more than 5 mm of anteroposterior drawer are present. A palpable defect is observed in the tissue just proximal to the patella. The incision is well healed. The erythrocyte sedimentation rate is 46 mm/h (reference range 0 to 20 mm/h) and the C-reactive protein level is 2.04 mg/L (reference range 0.08 to 3.1 mg/L). Aspiration of the right knee reveals hazy yellow fluid with a white blood cell count of 120 and 1% neutrophils. No growth of organisms is seen on routine culture. What is the best next step?
Correct Answer & Explanation
. Revision total knee arthroplasty with extensor mechanism allograft
Explanation
DISCUSSION: This patient has a chronic quadriceps tendon rupture after total knee arthroplasty. Two previous primary repair attempts have failed, which is not surprising based on the poor results of primary repair reported in the literature. The patient also has an unstable knee and will require revision of some or all of the prosthesis to achieve a stable knee. Revision total knee arthroplasty with extensor mechanism allograft allows an allograft reconstruction of the ruptured quadriceps tendon. The other option is to utilize a synthetic mesh extensor mechanism reconstruction. These are likely to have the best result in this situation. Revision total knee arthroplasty with liner change and primary quadriceps repair is not the best form of management, because it involves a third attempt at primary tendon repair, which will likely fail again. Resection knee arthroplasty and arthrodesis with antegrade nail is a possible option but is not the best, because it would likely make driving and other daily activities difficult. Two-stage revision total knee arthroplasty with extensor mechanism allograft is not the best option because the laboratory results show no signs of infection, so a single-stage procedure is preferred.
Question 846
Topic: 3. Adult Reconstruction (Hip & Knee)
The most appropriate next surgical procedure is
Correct Answer & Explanation
. conversion to total knee arthroplasty (TKA).
Explanation
DISCUSSIONThis patient’s arthritis likely has progressed to the lateral compartment. The location and degree of local pain and tenderness are the most important physical findings. History and physical findings indicate arthritis progression to the lateral and anterior compartments. This scenario suggests the need for conversion of the unicompartmental arthroplasty to TKA.
Question 847
Topic: 3. Adult Reconstruction (Hip & Knee)
Which of the following abnormalities has been observed in a higher than expected frequency in patients with metal-on-metal hip bearings?
Correct Answer & Explanation
. Leukocyte chromosomal aberrations
Explanation
DISCUSSION: Metal-on-metal hip bearings have been associated with very low rates of wear and are commonly used in North America and Europe. Patients with these bearings have higher levels of metal ions (particularly cobalt and chromium) in the bloodstream than patients with bearings made of other materials. Although many researchers have been concerned that these ions may predispose to cancer, there has been no evidence that patients with metal-on-metal bearings are developing sarcomas or carcinomas with higher frequency than the general population. However, there has been mixed data as to whether hematopoietic malignancies are slightly more prevalent in patients with metal-on-metal bearings. Two recent reports have found chromosomal abnormalities, such as translocations and aneuploidy, to be increased in patients with metal-on-metal hip bearings. The clinical consequences of these changes, if any, remain unknown. REFERENCES: Dunstan E, Ladon D, Whittingham-Jones P, et al: Chromosomal aberrations in the peripheral blood of patients with metal-on-metal hip bearings. J Bone Joint Surg Am 2008;90:517-522. Ladon D, Doherty A, Newson R, et al: Changes in metal levels and chromosome aberrations in the peripheral blood of patients after metal-on-metal hip arthroplasty. J Arthroplasty 2004:19:78-83. Visuri T, Pukkala E, Paavolainen P, et al: Cancer risk after metal on metal and polyethylene on metal total hip arthroplasty. Clin Orthop Relat Res 1996:329:S280-S289.
Question 848
Topic: 3. Adult Reconstruction (Hip & Knee)
The knee arthroplasty type associated with the highest 5-year revision rate is
Correct Answer & Explanation
. patellofemoral arthroplasty.
Explanation
DISCUSSION: Revision rates for UKA at 10 years are lower than 5% at specialty centers. However, the 10-year revision rate associated with UKA in registries such as the National Joint Registry for England and Wales is 2 to 3 times that of TKA. Among partial knee replacements, patellofemoral arthroplasty is associated with the highest revision rate at every time interval.
Question 849
Topic: 3. Adult Reconstruction (Hip & Knee)
Figures 136a through 136c are the weight-bearing anteroposterior and lateral radiographs of a 28-year-old construction worker who has had 6 months of progressive knee pain isolated to the medial aspect of his right knee. The pain has not responded to nonsurgical treatment. His body mass index is 26. He has knee range of motion from 0 to 125 degrees, and his knee is stable to ligament examination. What is the most appropriate surgical treatment?
Correct Answer & Explanation
. Proximal tibial osteotomy
Explanation
DISCUSSIONProximal tibial osteotomy is the best option for this young patient who has good range of motion and arthritis isolated to the medial compartment. Distal femoral osteotomy is more appropriate for correction of valgus deformity. In the setting of most varus deformities as shown in this patient’s radiographs, there is varus angulation of the proximal tibial. Correction of alignment at the femur results in obliquity of the joint line and abnormal loading. Medialunicompartmental knee arthroplasty and TKA are less optimal in this setting because of this patient’s young age and high demands as a laborer. Unicompartmental knee arthroplasty and TKA are not preferred options for this patient because risk for premature failure is high.
Question 850
Topic: 3. Adult Reconstruction (Hip & Knee)
Figures below demonstrate the radiographs obtained from a 35-year-old woman with end-stage debilitating osteoarthritis of the right hip. She is contemplating total hip arthroplasty (THA). She has a history of right hip dysplasia and underwent hip osteotomy as an adolescent. Over the years, nonsurgical treatment, including weight loss, activity modifications, and intra-articular injections, has failed. Her infection work-up reveals laboratory findings within defined limits. A further work-up reveals elevations in serum cobalt and chromium levels and fluid collections surrounding the hip on MRI with MARS. Revision THA is recommended. The most common complication following revision of a failed metal-on- metal hip arthroplasty is
Correct Answer & Explanation
. periprosthetic fracture.
Explanation
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 851
Topic: 3. Adult Reconstruction (Hip & Knee)
A 65-year-old male presents with groin pain 5 years after a primary total hip arthroplasty (THA). The implant uses a metal-on-polyethylene bearing. Aspiration is negative for infection, but serum Cobalt and Chromium levels are significantly elevated, and MRI demonstrates a large adverse local tissue reaction (ALTR) around the hip. Which of the following component design factors most increases the risk of this specific complication?
Correct Answer & Explanation
. Increased horizontal femoral offset
Explanation
This patient has trunnionosis, a form of mechanically assisted crevice corrosion occurring at the modular head-neck junction. High horizontal femoral offset increases the lever arm and bending moments at the trunnion, which significantly increases micromotion, fretting, and subsequent corrosion. Large metal heads and increased horizontal offset are known mechanical risk factors for trunnionosis in metal-on-polyethylene THA.
Question 852
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female presents 1 year after a posterior-stabilized (PS) total knee arthroplasty (TKA) with a painful catching sensation in her anterior knee as she actively extends the knee from a flexed position. Which of the following implant design features or surgical techniques is the primary cause of this phenomenon?
Correct Answer & Explanation
. A prominent anterior-superior aspect of the intercondylar box
Explanation
The patient is experiencing patellar clunk syndrome, which occurs when a fibronodular tissue mass develops on the undersurface of the quadriceps tendon just proximal to the patella. As the knee extends, this nodule catches on the anterior-superior edge of the intercondylar box of a posterior-stabilized femoral component. Modern PS designs have modified (rounded or lowered) the anterior box edge to decrease this complication.
Question 853
Topic: Total Hip Arthroplasty (THA)
You are planning a deformity correction for a patient with a tibial malunion. During pre-operative templating, you determine the Center of Rotation of Angulation (CORA). If you perform your closing wedge osteotomy at a level proximal to the CORA and only correct the angular deformity (without any translation at the osteotomy site), what will be the effect on the mechanical axis?
Correct Answer & Explanation
. Secondary translational deformity of the bone and mechanical axis
Explanation
According to the rules of osteotomy formulated by Paley: If an osteotomy is performed at the CORA, angulation corrects the deformity fully. If the osteotomy is performed at a level different from the CORA, correcting the angular deformity without concurrent translation at the osteotomy site will result in a secondary translational deformity (the anatomical axis will end up with a zigzag or parallel shift).
Question 854
Topic: 3. Adult Reconstruction (Hip & Knee)
During a revision total hip arthroplasty, pre-operative radiographs demonstrate superior migration of the hip center by 3.5 cm. Intraoperatively, there is destruction of the teardrop and severe ischial osteolysis. However, Kohler's line remains intact. According to the Paprosky Acetabular Defect Classification, what is the defect type?
Correct Answer & Explanation
. Paprosky 3B
Explanation
Paprosky Type 3 defects involve severe bone loss with superior migration > 3 cm. Type 3A defects have an intact Kohler's line (no massive medial migration), though the teardrop and ischium are severely compromised. Type 3B defects are characterized by disruption of Kohler's line indicating massive medial migration (pelvic discontinuity may also be present).
Question 855
Topic: 3. Adult Reconstruction (Hip & Knee)
A 70-year-old female sustains a complete patellar tendon rupture 2 years following a primary total knee arthroplasty. The diagnosis was delayed, and the patella is significantly retracted. Soft tissue quality is poor. What is the most reliable reconstructive option for this chronic extensor mechanism disruption?
Correct Answer & Explanation
. Extensor mechanism allograft utilizing an Achilles tendon with a calcaneal bone block
Explanation
Chronic, retracted extensor mechanism ruptures post-TKA have dismal outcomes with primary repair. The gold standard for reconstruction in this setting involves a complete extensor mechanism allograft (using Achilles tendon with calcaneal bone block press-fit into the tibia, or a whole extensor mechanism allograft) or synthetic mesh reconstruction to restore the structural integrity of the extensor apparatus.
Question 856
Topic: 3. Adult Reconstruction (Hip & Knee)
A patient presents with a painful total knee arthroplasty. Serum ESR and CRP are moderately elevated. A synovial aspiration yields 2,500 WBC/uL with 65% neutrophils. Because this fluid profile is equivocal, which of the following synovial fluid biomarkers provides the highest specificity for diagnosing a periprosthetic joint infection (PJI)?
Correct Answer & Explanation
. Alpha-defensin
Explanation
Alpha-defensin is an antimicrobial peptide released by neutrophils in response to pathogens. In the setting of PJI, synovial fluid alpha-defensin has been shown to have extremely high sensitivity and specificity (often >95%), making it an excellent adjunctive test, especially in cases where cell counts are borderline or equivocal.
Question 857
Topic: 3. Adult Reconstruction (Hip & Knee)
During pre-operative templating for a total hip arthroplasty, the surgeon plans to place the acetabular component in a more medialized position compared to the native anatomy. What is the primary biomechanical effect of medializing the center of rotation of the hip?
Correct Answer & Explanation
. Decreases the body weight lever arm
Explanation
The hip joint acts as a class 1 lever. The joint reaction force is determined by the abductor force and body weight. Medializing the acetabular component moves the center of rotation closer to the body's center of gravity. This decreases the body weight lever arm, which effectively decreases the abductor force required to maintain a level pelvis, thereby decreasing the overall joint reaction force on the hip.
Question 858
Topic: 3. Adult Reconstruction (Hip & Knee)
A 55-year-old male presents with isolated medial compartment knee pain. Radiographs demonstrate bone-on-bone medial osteoarthritis. Which of the following conditions is considered a classic absolute contraindication for performing a medial Unicompartmental Knee Arthroplasty (UKA)?
Inflammatory arthropathies (like Rheumatoid Arthritis) cause global synovial disease and systemic cartilage destruction, making them an absolute contraindication for UKA due to the high risk of rapid progression in the retained compartments. Historical contraindications like younger age (<60) and heavier weight (>90 kg) have been largely abandoned. An intact ACL is a prerequisite for a standard UKA.
Question 859
Topic: 3. Adult Reconstruction (Hip & Knee)
A 65-year-old female presents with groin pain and swelling three years following a metal-on-metal total hip arthroplasty. Serum cobalt and chromium levels are significantly elevated. Aspiration yields sterile, cloudy fluid. Histological examination of the periprosthetic tissue reveals a dense perivascular lymphocytic infiltrate with macrophages and focal tissue necrosis. This adverse local tissue reaction (ALTR) is primarily mediated by which of the following immunologic mechanisms?
Correct Answer & Explanation
. Type IV hypersensitivity (delayed-type cell-mediated)
Explanation
Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) is the histological hallmark of an adverse local tissue reaction (ALTR) in metal-on-metal implants. It is characterized by a delayed-type (Type IV) hypersensitivity response mediated by T-lymphocytes reacting to metal ions (typically cobalt or chromium) acting as haptens.
Question 860
Topic: 3. Adult Reconstruction (Hip & Knee)
A 68-year-old female presents with a painful catching sensation in her knee 18 months after a primary posterior-stabilized (PS) total knee arthroplasty. The catching predictably occurs as the knee extends from 45 degrees to 30 degrees of flexion. Radiographs show well-fixed components with appropriate sizing. What is the most likely etiology of her symptoms?
Correct Answer & Explanation
. Entrapment of a fibrous nodule within the intercondylar notch of the femoral component
Explanation
This presentation is classic for Patellar Clunk Syndrome, a well-described complication of older posterior-stabilized (PS) TKA designs. A fibrous nodule forms at the superior pole of the patella. As the knee extends from flexion, the nodule catches within the intercondylar box of the femoral component, then suddenly pops out (clunks) at around 30 to 45 degrees of extension.
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