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.

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

Arthroplasty — MCQs

Arthroplasty — MCQs

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