Arthroplasty Practice Questions

Q: Which of the following is considered a fenestrated hip prosthesis?

Austin Moore prosthesis. **Explanation:** The correct answer is **Austin Moore prosthesis**. In orthopaedic surgery, a **fenestrated prosthesis** refers to an implant with "windows" or openings in its stem. These holes allow for bone to grow through the prosthesis (biological fixation), providing long-term stability. **1. Why Austin Moore is correct:** The Austin Moore prosthesis is a unipolar hemiarthroplasty implant used for femoral neck fractures. Its defining feature is a **fenestrated stem**. During surgery, bone chips are often packed into these fenestrations; over time, bone grows through these holes (osseointegration), anchoring the prosthesis to the femoral shaft without the need for bone cement. **2. Why the other options are incorrect:** * **Thompson prosthesis:** This is also a unipolar prosthesis, but it has a **solid (non-fenestrated) stem**. It is designed to be used with bone cement (Polymethylmethacrylate - PMMA) for fixation. * **Bipolar prosthesis:** This refers to an implant with two points of articulation (one at the acetabulum and one within the prosthetic head). While the stem design can vary, the term "bipolar" describes the head mechanism, not the presence of fenestrations. **High-Yield Clinical Pearls for NEET-PG:** * **Fixation:** Austin Moore = **Uncemented** (Press-fit/Biological); Thompson = **Cemented**. * **Indications:** Austin Moore is preferred in patients with good bone quality; Thompson is preferred in osteoporotic patients where cement provides immediate stability. * **Calcar:** The Austin Moore prosthesis has a collar that rests on the calcar femorale to prevent subsidence. * **Complication:** A common complication of unipolar prostheses (Moore/Thompson) is **acetabular erosion** (protrusio acetabuli) because the metal head rubs directly against the native cartilage.

Q: A patient with an orthopaedic hip implant is to undergo dental extraction. What antibiotic prophylaxis is recommended?

Antibiotic prophylaxis is not required. **Explanation:** The correct answer is **D. Antibiotic prophylaxis is not required.** **1. Underlying Medical Concept:** Historically, it was believed that dental procedures could cause transient bacteremia leading to Late Prosthetic Joint Infection (PJI). However, current evidence-based guidelines from the **American Academy of Orthopaedic Surgeons (AAOS)** and the **American Dental Association (ADA)** state that there is no direct link between dental procedures and PJI. Routine antibiotic prophylaxis is **not recommended** for patients with prosthetic joint replacements undergoing dental procedures. The risks of antibiotic use (allergic reactions, *C. difficile* infection, and antimicrobial resistance) outweigh the unproven benefits of preventing joint infection. **2. Why Incorrect Options are Wrong:** * **Options A and B:** Prophylaxis is never administered for multiple days or a full day before a procedure. If prophylaxis were indicated (e.g., for infective endocarditis), it would be a single pre-operative dose. * **Option C:** While IV antibiotics are used for surgical prophylaxis (like during the arthroplasty itself), they are not indicated for dental work in patients with joint implants. **3. Clinical Pearls for NEET-PG:** * **Exception:** Prophylaxis may be considered only in **severely immunocompromised** patients (e.g., stage 3 AIDS, chemotherapy, or recent organ transplant) with poorly controlled oral infections, and even then, only after consultation between the dentist and the orthopedic surgeon. * **Timing:** If prophylaxis is deemed necessary for other reasons (like high-risk cardiac conditions), the standard dose is **2g Amoxicillin orally 30-60 minutes before** the procedure. * **High-Yield Fact:** The most common cause of Late PJI is hematogenous spread, but the source is usually skin or urinary tract infections, not dental flora.

Q: Who is considered the father of joint replacement surgery?

Charnley. **Explanation:** **Sir John Charnley** is universally recognized as the **"Father of Modern Joint Replacement"** for his pioneering work in Total Hip Arthroplasty (THA). In the early 1960s, he revolutionized the field by introducing the **Low Friction Arthroplasty (LFA)**. His three landmark contributions include: 1. The use of **Ultra-High-Molecular-Weight Polyethylene (UHMWPE)** for the socket. 2. The use of **Polymethylmethacrylate (PMMA)** bone cement for stable fixation. 3. The concept of a **small diameter femoral head (22.25 mm)** to reduce torque and wear. **Analysis of Incorrect Options:** * **Manning:** Not associated with the development of joint replacement; likely a distractor in the context of orthopedic history. * **Girdlestone:** Known for the **Girdlestone excision arthroplasty**, which involves removing the femoral head and neck without replacement. It is now primarily used as a salvage procedure for infected hip replacements. * **Ponseti:** Famous for the **Ponseti technique**, the gold standard non-operative treatment for Congenital Talipes Equinovarus (CTEV/Clubfoot) using serial casting. **High-Yield Clinical Pearls for NEET-PG:** * **Charnley’s Triad:** Low friction principle, Bone cement (PMMA), and UHMWPE. * **PMMA:** Acts as a grout (filler), not a glue. A common complication during its insertion is **Bone Cement Implantation Syndrome (BCIS)**, characterized by hypoxia and hypotension. * **Clean Air Rooms:** Charnley also pioneered the use of laminar airflow in operating theaters to reduce surgical site infections.

Q: Patellar clunk is a known complication of which surgery?

Total knee replacement. **Explanation:** **Patellar Clunk Syndrome** is a specific complication associated with **Total Knee Replacement (TKR)**, particularly in Posterior-Stabilized (PS) designs. It occurs due to the formation of a painful fibrous nodule at the superior pole of the patella (at the junction of the quadriceps tendon and the proximal patellar button). When the knee moves from flexion to extension (typically between 30° and 45°), this nodule gets caught in the intercondylar notch of the femoral component and then "pops" or "clunks" out as the knee straightens. **Analysis of Options:** * **Option A & D:** Corrective osteotomies and proximal tibia plating involve extra-articular or intra-articular bone realignment/fixation. While they may cause stiffness or patellofemoral pain, they do not involve the prosthetic intercondylar notch necessary to produce a "clunk." * **Option C:** MPFL reconstruction addresses patellar instability. While it can lead to over-tightening or restricted motion, it does not involve the specific fibrous-prosthetic impingement seen in TKR. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factor:** More common in **Posterior-Stabilized (PS)** knee designs because the "box" (intercondylar notch) provides a space for the nodule to entrap. * **Clinical Presentation:** A painful "catch" or audible "thud" during active knee extension. * **Management:** Initial treatment is conservative, but definitive treatment is **arthroscopic debridement** (resection of the fibrous nodule). * **Prevention:** Modern TKR designs have a more "anatomical" femoral trochlea and a superiorly placed box to reduce this impingement.

Q: A Baker's cyst is a type of:

Pulsion diverticulum of the knee joint. **Explanation:** A **Baker’s cyst** (also known as a popliteal cyst) is not a true cyst but rather a **pulsion diverticulum** of the synovial membrane of the knee joint. 1. **Why Option A is Correct:** The cyst is formed by the herniation of the synovial membrane through the posterior capsule of the knee, typically between the medial head of the gastrocnemius and the semimembranosus tendons. It occurs due to increased intra-articular pressure (pulsion) caused by underlying joint pathology (e.g., osteoarthritis or meniscal tears). A one-way valve mechanism allows synovial fluid to enter the cyst but prevents it from returning to the joint. 2. **Why other options are incorrect:** * **Retention Cyst:** These occur due to the obstruction of a gland's duct (e.g., sebaceous cyst). Baker’s cysts are formed by pressure-driven herniation, not ductal blockage. * **Bursitis:** While a Baker’s cyst often involves the gastrocnemio-semimembranosus bursa, it is specifically a communication/herniation of the joint space rather than simple primary inflammation of a bursa. * **Benign Tumor:** It is a fluid-filled reactive sac, not a neoplastic growth of cells. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** Most commonly found in the **posteromedial** aspect of the popliteal fossa. * **Associated Conditions:** In adults, it is usually secondary to **Osteoarthritis** (most common) or Rheumatoid Arthritis. In children, it is often primary and idiopathic. * **Foucher’s Sign:** The cyst becomes firm on knee extension and soft on flexion (helps differentiate it from a popliteal artery aneurysm). * **Complication:** Rupture of the cyst can mimic **Deep Vein Thrombosis (DVT)**, presenting with sudden calf pain and swelling (Pseudothrombophlebitis).

Q: What is the best treatment for a fracture neck of femur in a 65-year-old lady?

Hemireplacement arthroplasty. **Explanation:** The management of a fracture of the neck of the femur is primarily determined by the **age of the patient** and the **displacement of the fracture**. In an elderly patient (typically >60–65 years), the blood supply to the femoral head (via the retinacular vessels) is highly precarious. Displaced fractures carry a high risk of **Avascular Necrosis (AVN)** and non-union. **Why Hemireplacement Arthroplasty is correct:** For a 65-year-old patient, the goal is early mobilization to prevent complications of prolonged bed rest (like DVT or pneumonia). Hemireplacement arthroplasty (e.g., Austin Moore or Bipolar prosthesis) allows for immediate weight-bearing and avoids the high failure rate associated with internal fixation in osteoporotic elderly bone. **Analysis of Incorrect Options:** * **A. Pop cast:** Hip fractures are "unstable" and cannot be managed by immobilization in a cast. This leads to malunion and fatal complications of recumbency. * **B. Gleohy:** This appears to be a typographical error (likely intended to be Girdlestone excision arthroplasty or a similar term). Regardless, excision arthroplasty is a salvage procedure, not a primary treatment. * **C. Bone grafting and compression:** This is generally reserved for younger patients ( 65 yrs) & Sedentary:** Hemireplacement Arthroplasty. * **Elderly (>65 yrs) & Active:** Total Hip Arthroplasty (THA) is preferred over Hemireplacement to provide better long-term functional outcomes. * **Garden Classification:** Used to grade displacement; Stages III and IV have the highest risk of AVN.

Q: Aseptic loosening in cemented total hip replacement occurs as a result of a hypersensitivity response to which of the following?

High-density polyethylene debris. **Explanation:** **Aseptic loosening** is the most common cause of long-term failure in total hip replacement (THR). The primary pathophysiology involves a biological response to wear debris, known as **"Particle Disease."** 1. **Why High-density polyethylene (HDPE) is correct:** The repetitive motion of the metal femoral head against the polyethylene liner produces microscopic wear particles. These particles (specifically those sized 0.1–10 μm) are phagocytosed by **macrophages**. This triggers an inflammatory cascade involving the release of cytokines (IL-1, IL-6, TNF-α) and RANKL. This process leads to **osteoclast activation**, resulting in periprosthetic bone resorption (osteolysis) and subsequent loosening of the implant. 2. **Analysis of Incorrect Options:** * **Titanium debris:** While metal debris can cause "metallosis," polyethylene wear is the dominant cause of osteolysis in conventional cemented THR. * **N,N-Dimethyltryptamine (DMT):** This is a hallucinogenic drug and has no clinical relevance to orthopaedic implants or aseptic loosening. (Note: The chemical used in bone cement is Methylmethacrylate; DMT is likely a distractor for N,N-dimethyl-p-toluidine, an accelerator in cement). * **Free radicals:** While oxidative stress occurs during inflammation, they are secondary products and not the primary inciting agent for the hypersensitivity/osteolytic response. **Clinical Pearls for NEET-PG:** * **Interface:** In cemented THR, loosening most commonly occurs at the **cement-bone interface**. * **Gold Standard:** The most effective way to reduce polyethylene wear is the use of **Highly Cross-Linked Polyethylene (HXLPE)**. * **Radiographic Sign:** Look for "linear osteolysis" or "lucent lines" >2mm wide around the prosthesis (Gruen zones for femur, DeLee and Charnley zones for acetabulum).

Question 1

Which of the following is considered a fenestrated hip prosthesis?

Accepted Answer

Austin Moore prosthesis

Answer

Bipolar prosthesis

Answer

Thompson prosthesis

Answer

All of the above

Question 2

A patient with an orthopaedic hip implant is to undergo dental extraction. What antibiotic prophylaxis is recommended?

Accepted Answer

Antibiotic prophylaxis is not required

Answer

Amoxicillin 3 times a day for 3 days before the procedure

Answer

Amoxicillin 3 times a day for 1 day before the procedure

Answer

Amoxicillin intravenously 1 hour before the procedure

Question 3

Who is considered the father of joint replacement surgery?

Accepted Answer

Charnley

Answer

Manning

Answer

Gridlestone

Answer

Ponseti

Question 4

During hip replacement surgery, loss of joint and ligament receptors leads to which of the following outcomes regarding sensation and proprioception?

Accepted Answer

No significant loss of joint sensation or proprioception.

Answer

Complete loss of all joint sensations and proprioception.

Answer

Joint sensation is lost only in unstable positions.

Answer

A decrease in proprioception and a decrease in motor control.

Question 5

Which of the following are major indications for arthroplasty?

Accepted Answer

Osteoarthritis of the hip

Answer

Ankylosis of the elbow

Answer

Ununited tibial fracture

Answer

Ununited femoral neck fracture

Question 6

Patellar clunk is a known complication of which surgery?

Accepted Answer

Total knee replacement

Answer

Corrective osteotomy for genu valgum

Answer

Medial patellofemoral ligament reconstruction

Answer

Bicondylar plating of proximal tibia fracture

Question 7

A Baker's cyst is a type of:

Accepted Answer

Pulsion diverticulum of the knee joint

Answer

Retention cyst

Answer

Bursitis

Answer

Benign tumor

Question 8

What is the best treatment for a fracture neck of femur in a 65-year-old lady?

Accepted Answer

Hemireplacement arthroplasty

Answer

Pop cast

Answer

Gleohy - I suspect this is a typo and should be 'Galeal tendon' which doesn't fit here, or potentially a less common fracture treatment term. I will assume it's a typo and leave it as is for now, but it is highly suspect.

Answer

Bone grafting and compression

Question 9

Aseptic loosening in cemented total hip replacement occurs as a result of a hypersensitivity response to which of the following?

Accepted Answer

High-density polyethylene debris

Answer

Titanium debris

Answer

N,N-Dimethyltryptamine (DMT)

Answer

Free radicals

Question 10

The Watson-Jones approach is indicated for which of the following conditions?

Accepted Answer

Hip replacement

Answer

Neglected club foot

Answer

Muscle paralysis

Answer

Valgus deformity

Arthroplasty — MCQs

Arthroplasty — MCQs

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