When is a tibial (tibia) stem indicated in knee replacement surgery?

Indications for Tibial Stem Use in Primary Total Knee Arthroplasty

Tibial stems should be used in primary total knee arthroplasty when patients have compromised bone quality (osteoporosis or structurally altered bone), obesity (particularly BMI >30-35), severe varus deformity >10-15 degrees, tibial bone defects or stress fractures, or inflammatory arthritis—while standard stemless components are appropriate for patients with healthy bone stock and normal anatomy. 1, 2

Primary Indications for Tibial Stem Use

Compromised Bone Quality

• Use tibial stems when bone has diminished structural properties or osteoporosis, as biomechanical analysis demonstrates that stems reduce compression fatigue by nearly 50% in structurally altered bone and provide enhanced stability and fixation 2
• In healthy bone with good structural properties, stems are unnecessary in primary TKA and may introduce stress-shielding effects 2

Obesity

• Tibial stems are indicated in obese patients, representing the most common indication in contemporary practice, though specific BMI thresholds vary between studies (typically BMI >30-35 kg/m²) 1
• Stems help distribute increased mechanical loads and reduce stress on the tibial component in higher-weight patients 1

Severe Deformity

• Use stems in cases of severe varus deformity (typically >10-15 degrees), as they provide additional stability and reduce complications related to abnormal load distribution 1
• Stems resist shear forces and reduce tibial lift-off in the setting of significant malalignment 3

Bone Defects and Fractures

• Tibial stems are effective in osteoarthritis with associated tibial stress fractures or plateau fractures, improving implant stability and reducing complications 1
• For contained tibial defects, short cemented stems combined with impaction bone grafting provide excellent stability with immediate weight-bearing capability 4

Inflammatory Arthritis

• Consider stems in patients with inflammatory arthritis due to typically compromised bone quality and increased risk of component loosening 1

Stem Selection Algorithm

Short Cemented Stems (30-50mm)

• Short cemented stems are the preferred choice for most complex primary TKA cases requiring stem augmentation, as they preserve bone stock, optimize load transmission, and minimize stress-shielding while providing adequate stability 1, 2
• Short stems offer a balance between reduced micromotion and more proximal bone deformation, reducing stress-shielding potential compared to long stems 5
• Particularly beneficial in obesity, moderate deformity, and mild-to-moderate bone quality compromise 1

When NOT to Use Stems

• Do not use tibial stems in primary TKA when bone is healthy with good structural properties and normal anatomy, as standard configurations offer sufficient stability and excellent long-term survivorship without introducing unnecessary stress-shielding 2
• The AAOS guideline provides strong evidence supporting no difference in outcomes between cemented and non-cemented tibial component fixation in routine primary TKA 6

Biomechanical Considerations

Advantages of Stems

• Stems provide resistance to shear forces, reduce tibial lift-off, and increase stability by reducing micromotion at the bone-implant interface 3
• Enhanced mechanical stability of tibial components, particularly important in revision scenarios with bone loss 3
• Dynamic compression analysis shows slightly better results with tibial stems in both healthy and degraded bone 2

Disadvantages and Risks

• Stress-shielding along stem length with associated reduction in bone density, creating theoretical risk of subsidence, loosening, and end-of-stem pain 3
• Long stems (>100mm) are generally unattractive in primary TKA due to excessive stress-shielding, though they become desirable in revision surgery with significant bone loss 3
• Risk of peri-prosthetic fracture, particularly with longer stems 3

Common Pitfalls to Avoid

• Avoid using long stems (>100mm) in primary TKA unless dealing with extensive bone defects, as they introduce excessive stress-shielding and distal fixation issues without added benefit 3, 5
• Do not add stems routinely to all primary TKA cases—reserve for specific indications where bone quality or patient factors warrant additional stability 2
• Avoid stemless components in patients with known osteoporosis or severe obesity, as inadequate initial fixation may lead to early loosening 1, 2
• Do not assume that adding a stem always improves outcomes—in healthy bone, standard configurations provide equivalent or superior results without stress-shielding complications 6, 2