MSC WEEK 8 THA/TSA

What are the four components of a total hip replacement?

Femoral head, femoral stem, acetabular liner, acetabular cup. (bonus 5th component can be a screw)

Where is the femoral head inserted during a posterior hip replacement?

Posterior superior

What is the normal femoral neck angle?

120°-135° (approximately 124° average)

What is coxa vara?

Neck angle <120° (around 115°), shortened leg, decreased offset.

What is coxa valga?

Neck angle >135° (around 140°), increased leg length.

Where is the head center located?

At the center of the femoral head

What is femoral offset?

Horizontal distance from the femoral head center to the femoral shaft axis.

Why is femoral offset important?

Restores soft tissue tension and hip stability.

What is femoral neck length?

Distance from the femoral neck resection to the femoral head center.

What is femoral leg length?

Distance from the medial neck resection (calcar) to the femoral head center.

Where should the neck resection generally occur?

Around one finger width above the lesser trochanter.

Why template the opposite hip?

To restore normal anatomy and build the new hip correctly.

Normal femoral anteversion?

10-20°

Recommended femoral stem anteversion?

10-20°

Why is proper femoral anteversion important?

Prevents impingement and reduces dislocation risk

Recommended cup anteversion?

20-25°

Recommended cup abduction/inclination?

40-45°.

What is the most common cementless stem?

Tapered wedge.

What coating does the tapered wedge stem commonly use?

Plasma spray.

What is the purpose of plasma spray?

Bone ongrowth.

What is bone ongrowth?

Bone attaches onto the implant surface (plasma spray).

What is bone ingrowth?

Bone grows into a porous implant surface in 3D

Which component commonly uses ingrowth?

Acetabular shell.

Which component commonly uses plasma spray ongrowth?

Femoral stem.

Advantages of cobalt chrome stems?

Stronger and stiffer; commonly cemented.

Advantages of titanium alloy stems?

Elastic modulus closer to bone; commonly press-fit/cementless.

When are cemented stems commonly used?

Poor bone quality.

Advantages of cementless stems?

Biological fixation through bone ingrowth/ongrowth

Benefit of a collared stem?

Extra support, especially in osteoporotic bone.

Benefit of a collarless stem?

Easier insertion during minimally invasive surgery.

DORR classification: Type A femur?

Thick cortices; champagne-flute canal

DORR Classification: Type B femur?

Moderate cortical thickness.

DORR Classification: Type C femur?

Thin cortices; stovepipe canal.

Gold standard hip approach?

Posterior. 60-70% of cases

the three traditional THA approaches

-Anterior: 15-35% of cases
- Posterior: 60-70% of cases
- Lateral: 10% of cases

Which approach is muscle-sparing? (minimally invasive surgery)

Direct anterior.

Which approach is growing the fastest?

Direct anterior

Purpose of broaching?

Shapes femoral canal, matches implant geometry, sequential sizing, creates press-fit fixation.

Common reasons for revision THA?

Aseptic loosening, infection, fracture, instability/dislocation, implant wear, implant breakage, pain.

Non-reimbursed injections?

PRP and Bone Marrow Concentrate (BMC).

Reimbursed injections?

Corticosteroids and hyaluronic acid (viscosupplementation).

Normal humeral retroversion?

20-30°.

Normal humeral neck angle?

135°.

The four rotator cuff muscles? (SITS)

Supraspinatus, Infraspinatus, Teres Minor, Subscapularis.

Supraspinatus function?

Initiates abduction.

Infraspinatus function?

External rotation.

Teres Minor function?

External rotation and adduction.

Subscapularis function?

Internal rotation.

What is scapulohumeral rhythm?

2:1 ratio of glenohumeral motion to scapular rotation

During 180° of shoulder abduction, how much comes from the glenohumeral joint?

120

How much comes from scapular rotation?

60°.

Primary glenohumeral ligaments?

Superior, Middle, Inferior.

Coracohumeral ligament function?

Prevents inferior translation and excessive external rotation.

Transverse humeral ligament function?

Holds the long head of the biceps tendon.

Strongest ligament in the body?

liofemoral ligament (Y ligament of Bigelow).

Pubofemoral ligament prevents?

Excessive abduction and extension.

Ischiofemoral ligament prevents?

Excessive extension.

Zona orbicularis function?

Encircles femoral neck to resist distraction.

What is Wolff's Law?

Bone remodels and becomes stronger in response to mechanical stress

Ceramic liners can have an elevated lip.

False. Ceramic liners cannot have an elevated lip.

What is AVN?

Avascular necrosis—loss of blood supply causing bone death.

What is the "Chili Pepper" stem design?

A cementless stem geometry that preserves proximal bone, uses different medial curvatures, and works well with direct anterior approaches.