Suprapatellar Intramedullary Nail (Tibial Nailing)

What It Is

Indications

• Proximal tibia fractures - where achieving an ideal starting point is obstructed in infrapatellar approaches by the patella
• Distal tibia fractures - evidence shows improved sagittal alignment
• Obese patients - the semi-extended position makes imaging and nailing mechanically easier
• Fractures where malalignment is high risk (e.g., where blocking screws alone may be insufficient)

• Rockwood and Green's Fractures in Adults, 10th ed., p. 3192

Surgical Technique

Positioning

• Patient supine on radiolucent table
• Knee supported in ~15-20° of flexion (semi-extended) on a foam/radiolucent triangle placed under the proximal tibia (NOT under the knee or distal femur) to allow slight anterior shift of the tibia relative to the trochlea and the suprapatellar cannula

Incision & Entry

• Midline incision starting at the superior pole of the patella, extending 5 cm proximally
• The quadriceps tendon is split longitudinally
• The knee joint is entered from above (suprapatellar pouch)
• Specialized protective trocars/cannulas are used to protect the patellofemoral articular cartilage from guidewires, reamers, and the nail

Starting Point

Starting Wire Trajectory

• Coronal plane (AP): In line with the long axis of the tibia
• Sagittal plane (lateral): Parallel to the anterior tibial cortex
• A parallel wire guide ("Gatling gun") is helpful for SP nailing since knee flexion is limited - this helps achieve proper sagittal angle
• Alternatively, remove the cannula temporarily while positioning the wire, then carefully replace before reaming

Reaming and Nail Insertion

• Entry reamer opens a path through the proximal tibial metaphysis through the cannula (protecting the joint)
• Sequential reaming to appropriate diameter
• Nail inserted in standard fashion
• Locking screws:
  • Diaphyseal/proximal fractures: Typically 2 distal screws (single may suffice for length-stable patterns); at least 3 proximal screws for proximal patterns
  • Distal fractures: Minimum 3 distal screws, including AP and/or oblique orientation for rotational stability

Advantages Over Infrapatellar Approach

Pitfalls and How to Avoid Them

• Rockwood and Green's Fractures in Adults, 10th ed., p. 3219-3220

Proximal Fracture Malalignment - Key Point

• The patella does not block the ideal starting path
• The semi-extended position reduces pull from the extensor mechanism
• Blocking (Poller) screws can still be added for additional control

Knee Pain After Nailing

• Rockwood and Green's, p. 3228

Recent Evidence (2024-2025)

1. Lu K et al. (2024) - Systematic review comparing suprapatellar, parapatellar, and infrapatellar tibial nailing. [PMID: 39325161] (Arch Orthop Trauma Surg)
2. Hu J & Huang X (2025) - Meta-analysis of RCTs comparing suprapatellar vs. infrapatellar nailing; found suprapatellar had shorter operative time and improved functional (Lysholm) scores. [PMID: 41034881] (BMC Musculoskelet Disord)
3. Xu H et al. (2025) - Systematic review comparing IMN vs. MIPO for proximal tibial fractures. [PMID: 40671027] (J Orthop Surg Res)

Summary

• Nailing proximal or distal tibia fractures where alignment is at risk
• Fluoroscopic access is difficult with the standard hyperflexed position
• You want to minimize deforming forces during nailing

Total Knee Replacement (TKR) - Surgical Technique & Implants

Indications for Surgery

1. Debilitating pain affecting activities of daily living
2. Pain not controlled by conservative measures
3. Medical fitness for surgery
4. No active infection anywhere in the body

• Miller's Review of Orthopaedics, 9th ed., p. 473

Preoperative Planning

Radiographs Required

• Standing bilateral AP views of both knees
• Extension and flexion lateral views
• Sunrise (Merchant) view for patellofemoral assessment
• Standing full-length AP (hip to ankle) when bony angular deformity is present, or extreme height (<60 in / <152 cm or >75 in / >190 cm)

Radiographic Analysis Goals

• Determine femoral and tibial end cuts
• Locate femoral canal entry site
• Identify bone defects and joint subluxation
• Identify ligament stretch-out (order revision system if varus thrust is present)
• Anticipate ligament releases and degree of constraint needed

Surgical Approach

• Midline skin incision
• Medial arthrotomy from the quadriceps tendon, around the medial side of the patella, to the tibial tubercle
• Patella everted or subluxed laterally
• Extrasynovial fat pad may be partially excised for exposure

Alignment Philosophy

Mechanical Alignment (Most Common)

Femoral Cuts

• The anatomic axis of femur (AAF) is defined by the medullary canal
• An intramedullary guide rod is inserted to define this axis
• The valgus cut angle (typically 4-7 degrees) is set into the cutting jig
• This angle = AAF - MAF (mechanical axis of femur)
• Distal femoral cut is made perpendicular to the mechanical axis (MAF)

Tibial Cuts

• The anatomic axis of tibia (AAT) bisects the tibial medullary canal
• Both intramedullary and extramedullary cutting jigs are acceptable
• Proximal tibial cut is made perpendicular to the mechanical axis of the tibia (MAT)
• Tibial slope (posterior slope of ~3-7 degrees) is built into most cutting jigs

Alternative Alignment Philosophies

• Kinematic alignment - cuts made to restore native joint line orientation rather than creating a neutral mechanical axis
• Restricted kinematic alignment - compromise between mechanical and kinematic approaches

Precision Alignment Technologies

Bone Cuts (Sequence)

1. Distal femoral cut - perpendicular to MAF at valgus cut angle (4-7°)
2. Proximal tibial cut - perpendicular to MAT, with posterior slope
3. Anterior femoral cut - parallel to anterior femoral cortex
4. Posterior femoral cut and chamfer cuts - define flexion gap
5. Patellar cut (if resurfacing) - minimum residual patellar thickness 13 mm (below this = fracture risk)

Gap Balancing ("Balancing the Gaps")

Extension Gap

Flexion Gap

Coronal Plane - Ligament Releases for Varus Knee (Medial Tightness)

Coronal Plane - Ligament Releases for Valgus Knee (Lateral Tightness)

Implant Types

1. Cruciate-Retaining (CR)

• PCL retained - provides femoral rollback
• Flatter tibial polyethylene surface
• Requires ability to balance the PCL (within ~1-2 mm)
• Better tolerated when joint line is preserved (sensitive to joint line elevation)
• Technically more demanding; if PCL balance is inadequate, can convert to PS intraoperatively

2. Posterior-Stabilized (PS) - "Cruciate-Substituting"

• PCL excised; cam-and-post mechanism substitutes for PCL function
• Post on tibial insert engages femoral box in flexion to drive rollback
• Box cutout on femoral component removes additional bone
• Tolerates mild joint line elevation better than CR
• Patellar clunk syndrome - fibrous tissue catches in femoral box; reduced with longer trochlear groove designs
• Easier to balance in severe varus/PCL-deficient cases

3. Varus-Valgus Constrained (CCK - Constrained Condylar Knee)

• Enlarged tibial post + deeper femoral box - resists varus/valgus forces
• Does not control hyperextension/recurvatum
• Used for: instability, severe valgus with MCL insufficiency, failed primary TKA
• Typically requires intramedullary stems (cemented or press-fit)
• 10-year survivorship ~97.6% in primary use for complex cases

4. Hinged Prostheses

• Maximum constraint - for massive bone loss, failed prior revisions, tumor resection
• Higher complication rates than other designs

5. Mobile-Bearing / Rotating Platform

• Tibial bearing can rotate relative to tibial tray
• Theoretical advantage: reduced polyethylene stress and potential longer wear
• Often used with CCK designs to dissipate higher torque loads

AAOS 4-Star Evidence Statements (Implant Design)

• No difference in outcomes between PS and CR designs
• No difference with all-polyethylene vs. modular tibial component
• No difference in pain or function with or without patellar resurfacing
• Similar outcomes with cemented vs. cementless tibial fixation

Fixation: Cement vs. Cementless

Patellar Tracking & Resurfacing

• Q angle (tibial tubercle - trochlear groove distance; TT-TG)
• Femoral component rotation (must be parallel to epicondylar axis / Whiteside's line)
• Tibial component rotation (tibial tubercle as reference)
• Joint line level

"No Thumb" Test (Lateral Patellar Tracking)

Patellar Resurfacing

• Minimum remaining bone = 13 mm
• Risk of osteonecrosis if lateral superior genicular artery transected during lateral release
• Blood supply mainly from inferomedial geniculate artery (disrupted with medial arthrotomy)

Perioperative Pearls

Blood Loss Management

• Tranexamic acid (TXA) - IV or topical both effective; reduces blood loss and transfusion; safe in high-risk patients (prior DVT/PE, AF, coronary stents); contraindicated in seizure disorder
• Tourniquet use: reduces intraoperative blood loss but increases short-term postoperative pain; no difference in functional outcomes

Antibiotic Prophylaxis

• Cefazolin is best (24 hr max); good bone penetration
• Non-cefazolin alternatives (vancomycin, clindamycin) have higher infection rates
• 97% of patients with stated penicillin allergy are cefazolin-tolerant on testing

Pain Management (AAOS/AAHKS Strong Recommendations)

• IV/oral acetaminophen: safe, does not increase complications
• NSAIDs (oral preop/early postop) and IV ketorolac: reduce pain and opioid use
• Pregabalin (but not gabapentin): reduces opioid consumption
• Adductor canal block (ACB) + iPACK block = best combination for perioperative analgesia and early ambulation (superior to femoral nerve block for preserving quad strength)
• Periarticular injection (PAB) by surgeon: additive to ACB and iPACK

Intraoperative Complications

Key Design Differences: CR vs. PS Summary

Anteromedial Osteoarthritis (AMOA) of the Knee

Definition & Historical Origin

"Medial compartment full-thickness cartilage and bone erosion centered anteriorly on the tibial plateau, with posterior cartilage preserved, an intact ACL, and functional MCL - producing a correctable varus deformity."

Pathology - The AMOA Lesion

Why Does AMOA Occur? - The ACL Mechanism

• The ACL prevents forward tibial subluxation during gait
• Because the tibia cannot slide forward, contact forces remain in the anterior and central zone of the medial compartment during the mid-stance / extension phase of gait
• The posterior cartilage is never loaded heavily - so it is preserved
• The lateral compartment is similarly unloaded in the coronal plane (the MCL remains at normal tension in flexion)

• The wear pattern extends to the posterior plateau
• Fixed varus deformity develops (unlike the correctable varus of AMOA)
• Lateral compartment degeneration supervenes
• The disease is no longer AMOA - and UKA becomes inappropriate

Clinical Features

• Medial knee pain, worse on loading
• Varus deformity in extension - from bone and cartilage loss medially
• Correctable varus - when knee is flexed to 90°, MCL is tensioned by preserved posterior cartilage, restoring near-normal alignment
• No fixed varus (fixed varus = posterior disease = ACL insufficiency)
• Preserved range of motion - flexion usually >110°
• Fixed flexion deformity <15° typically

Radiological Assessment (Oxford Criteria for UKA)

1. Weight-Bearing AP (or Rosenberg PA 20° flexion view)

• Demonstrates medial bone-on-bone contact (or bone loss)
• Full-thickness medial compartment loss

2. True Lateral View (Femoral Condyles Overlapping)

• Assesses ACL integrity indirectly
• ACL intact = tibial plateau centered under femur, posterior cartilage rim preserved
• ACL deficient = posterior tibial erosion and anterior subluxation of tibia under femur

3. Valgus Stress View (20° Flexion)

• Full-thickness lateral cartilage must be confirmed (lateral joint space opens to normal)
• Confirms correctable varus - if varus corrects to neutral, MCL and soft tissues are functionally intact
• If lateral compartment narrows = lateral disease - UKA contraindicated

Patient Selection for Medial UKA (Oxford Criteria)

Positive Selection Criteria (All Must Be Met)

1. ACL and PCL functionally intact
2. Cartilage/bone erosion limited to anterior and middle medial compartment; posterior medial and lateral compartment have normal cartilage
3. MCL not structurally shortened (varus deformity correctable)
4. Patellofemoral joint damage limited to medial facets (lateral PFJ intact)
5. Fixed flexion deformity <15 degrees
6. Flexion to ≥110 degrees (under anesthesia)
7. Pain causing functional limitation
8. Patient compliance

Features That Do NOT Preclude Oxford UKA

• Isolated medial pain is not required - anterior knee pain does not compromise outcome
• Age, weight, activity level - not exclusion criteria per Oxford data
• Chondrocalcinosis (cartilage calcification on X-ray)
• Lateral marginal osteophytes
• Medial tibial subluxation (corrects once ACL-intact UKA is implanted)
• Full-thickness cartilage loss on non-weight-bearing medial side of lateral femoral condyle

Absolute Contraindications

• Inflammatory arthritis (RA, etc.)
• ACL-deficient knee with clinical instability / posterior tibial erosion
• Fixed varus deformity (posterior disease)
• Lateral compartment full-thickness cartilage loss
• Lateral PFJ subluxation or significant lateral patellar damage
• Severe flexion contracture >15°

Treatment Options

Conservative Management (Early / Moderate Disease)

• Weight loss, physiotherapy, activity modification
• Analgesics, NSAIDs
• Intra-articular corticosteroids (avoid within 2 weeks of planned surgery)
• Bracing (valgus unloading brace)
• High tibial osteotomy (HTO) - for younger patients with varus AMOA and intact ACL, corrects mechanical axis

Surgical Management

1. Medial Unicompartmental Knee Arthroplasty (UKA) - Treatment of Choice for AMOA

• Resurfaces only the medial compartment
• Preserves ACL, PCL, MCL, lateral compartment, patellofemoral joint
• Most commonly used implant: Oxford Phase 3 (mobile-bearing)

• Preserves proprioception and more natural kinematics
• Faster recovery, shorter hospital stay
• Less blood loss
• Better functional scores (Oxford Knee Score, WOMAC, Forgotten Joint Score)
• Patients feel the knee is "more normal"
• Day-of-surgery / outpatient procedure feasible

• 98% at 10 years (Oxford series)
• 93% at 15 years (independent series)
• Average polyethylene wear rate of 0.03 mm/year (mobile bearing)

2. Total Knee Arthroplasty (TKA)

• Indicated when criteria for UKA not met, or patient/surgeon preference
• NICE (UK) stipulates patients with AMOA should be offered a choice of UKA or TKA
• Functional outcomes comparable to UKA in most studies, but UKA superior in patient-reported outcomes in many series (higher Oxford Knee Score, better Forgotten Joint Score)

3. High Tibial Osteotomy (HTO)

• Considered in younger patients (<60 years) with:
  • Varus AMOA
  • Intact ACL
  • Good lateral compartment
  • High physical demands
• Shifts mechanical axis from medial to lateral, reducing medial compartment load

Oxford UKA Surgical Technique (Key Steps)

1. Approach: Minimal medial parapatellar incision (minimally invasive)
2. ACL check: Hook the ACL arthroscopically/directly to confirm integrity before proceeding
3. Osteophyte removal: All osteophytes removed from medial compartment to unmask true ligament lengths
4. Tibial cut:
   • Vertical tibial cut medial to ACL origin (blade angled toward femoral head)
   • Horizontal tibial cut perpendicular to tibial axis with appropriate slope
5. Femoral preparation: Spherical mill used to create curved femoral surface (matching Oxford femoral component's spherical shape)
6. Sizing: Excised tibial plateau used as template to select tibial size
7. Trialing: Gap and stability checked in flexion and extension
8. Implantation: Tibial component, mobile polyethylene bearing, femoral component cemented into position
9. Intraoperative check: Bearing should move freely and not dislocate; knee should be stable and balanced

ACL-Deficient Knee and UKA

• Oxford group have used UKA in clinically stable ACL-deficient patients with selected outcomes
• Fixed-bearing UKA is more commonly used in ACL-deficient cases (less risk of bearing dislocation without posterior constraint)
• Clinically unstable ACL-deficient knee = TKA preferred (altered kinematics risk disease progression)
• ACL-deficiency severity correlates with worse outcomes in fixed-bearing UKA (PMID: 40050997)

Summary: AMOA vs. TKA/UKA Decision at a Glance