Tension Band Wiring (TBW) of the Patella

1. Introduction and Anatomy

2. Mechanism of Injury

3. Classification (Descriptive)

4. Clinical Features

• Pain, swelling, bruising over the anterior knee
• Palpable gap over the patella
• Inability to perform straight-leg raise or active knee extension = incompetent extensor mechanism (key sign)
• Haemarthrosis

5. Investigations

• X-ray: AP and lateral views of the knee. Lateral view best shows displacement and articular step-off. Bipartite patella (superolateral location, smooth cortical margins) must be distinguished from fracture.
• CT scan: For comminuted patterns to plan ORIF; better defines articular displacement.
• MRI: Evaluates associated extensor mechanism injuries; usually unnecessary for straightforward fractures.

6. Indications for Surgery

• Displacement >3 mm between fragments
• Articular incongruity >2 mm
• Loss of active knee extension (disrupted extensor mechanism)
• Open fractures

• Nondisplaced fractures with intact extensor mechanism
• Hinged knee brace in extension; progressive flexion after 2-3 weeks

7. Goals of Surgical Treatment

1. Restoration of functional integrity and strength of the extensor mechanism
2. Maximizing articular congruity
3. Preservation of patellar bone stock
4. Stable fixation allowing early ROM and rehabilitation

8. Principle of Tension Band Wiring

• Works best for simple transverse or short oblique fractures
• The anterior surface is the tension side; the posterior (articular) surface is the compression side
• During knee flexion, the wire tightens and compresses the fracture gap

9. Operative Technique: Modified Anterior Tension Band Wiring (AO Technique)

Preoperative Planning

• Radiolucent table; supine position; small bump under the ipsilateral hip
• Tourniquet may be applied but inflated only if needed
• Image intensifier (C-arm) available

Step 1 - Incision and Exposure

• Midline longitudinal incision centered over the patella
• Most versatile; can be extended proximally and distally
• After incising skin and subcutaneous tissue, the articular surface is exposed through the fracture site or through retinacular rents
• Medial and lateral retinacular tears are extended if needed for finger palpation of the articular surface

Step 2 - Joint Irrigation

• Haemarthrosis is evacuated; joint is irrigated
• Fracture surfaces are cleaned of interposed soft tissue and hematoma

Step 3 - Reduction

• Fracture is reduced under direct vision
• Articular congruity is confirmed by finger palpation through the retinacular rent (or by lateral arthrotomy and patellar eversion in comminuted cases)
• Reduction held with a pointed reduction clamp/towel clip

Step 4 - K-Wire Placement

• Two parallel 1.6-mm K-wires are placed perpendicular to the fracture line
• Placed 5 mm below the anterior cortical surface (to allow the tension band to sit flush against bone)
• Wires spaced to divide the patella longitudinally into thirds
• Antegrade technique: wires passed from proximal to distal across the fracture
• Retrograde technique: proximal fragment is flexed 90°, wires started at fracture surface and advanced proximally then distally across the fracture

Step 5 - Tension Band Wire Placement (Figure-of-Eight)

• An 18-gauge stainless steel wire (or braided non-absorbable suture as an alternative) is used
• One end passed posterior to the proximal K-wires from medial to lateral (using a large-bore needle/angiocatheter as a conduit to protect the quadriceps tendon)
• A figure-of-eight configuration is created:
  • The wire is brought diagonally over the anterior patella to the contralateral distal pole
  • Passed posterior to the distal K-wire ends
  • Brought back over the anterior surface to the original superior corner
• Wire is tightened simultaneously from two points using a pliers or needle driver to ensure symmetric, equal tension on both sides
• Wire twisted a minimum of three turns but not over-tightened (risk of articular gapping or wire breakage)
• Wire twist sites ideally placed superiorly where more soft tissue coverage exists

Step 6 - K-Wire Bending and Impaction

• K-wires are cut at both ends and bent acutely 180° posteriorly over the tension band wire
• Ends are gently impacted into the patella using a bone tamp to prevent migration
• Distally, K-wires are bent posteriorly away from skin

Step 7 - Retinacular Repair

• Retinacular tears are repaired with interrupted or figure-of-eight non-absorbable sutures
• Arthrotomy closed in a watertight fashion
• Wound closed in layers

Step 8 - Postoperative Care

• Hinged knee brace; immediate weight-bearing as tolerated
• Early ROM encouraged - this is the main advantage of TBW
• Progressive flexion; quadriceps strengthening

10. Cannulated Screw Tension Band (Modified Technique)

• Same exposure and reduction as above
• Two 4.0-mm cannulated screws are placed perpendicularly across the fracture (guidewires positioned 5 mm below anterior cortex)
• Tension band wire (or braided suture) passed through the cannulated screws in a figure-of-eight configuration
• Biomechanically superior to K-wire technique
• Associated with 50% lower rate of symptomatic hardware requiring reoperation vs K-wires
• The wire should be tensioned over the edge of the patella, not the screw tips (to prevent wire breakage)

11. X-ray showing cannulated screw + tension band technique:

12. Special Situations

13. Complications

14. Outcomes

• Modified anterior tension band wiring: 86% good-to-excellent outcomes reported in historical series
• Cannulated screw tension band: lower reoperation rate for hardware than K-wires alone
• Braided suture alternatives (FiberWire, Ethibond #5): comparable biomechanical strength, lower reoperation rate for hardware removal
• Total patellectomy (reserved for irreparable comminution): 49% reduction in extensor strength; inferior outcomes - avoid wherever possible

15. Key Points for Exam

1. AO principle: anterior surface = tension side; wire converts tensile to compressive forces during knee flexion
2. Displacement criteria: >3 mm separation OR >2 mm articular step-off = operative
3. K-wires placed 5 mm below anterior cortex, dividing patella into thirds
4. Figure-of-eight wire placed posterior to K-wires at both poles
5. Cannulated screw TBW is biomechanically superior with less hardware irritation
6. Most common complication = symptomatic hardware (very high rate; counsel patients)
7. Preserve patella always - even one fragment improves extensor mechanism leverage
8. K-wire migration prevented by bending ends posteriorly into bone
9. Early ROM is the main advantage of TBW over cast immobilization
10. Retinacular repair is mandatory after fixation

Posterior Approach to the Hip (Moore / Southern Approach)

1. Introduction

2. Indications

3. Relevant Surgical Anatomy

Superficial Layer

• Gluteus maximus: The principal landmark. Supplied by the inferior gluteal nerve and artery (enter the muscle from the deep surface, approximately 5 cm from the greater trochanter). The muscle must not be split more than 7 cm from the tip of the trochanter to avoid denervation of its anterosuperior portion.
• Fascia lata / iliotibial band: Incised in line with the skin incision distally.

Deep Layer - Short External Rotators (from superior to inferior)

1. Piriformis - inserts on the tip/superior facet of the greater trochanter
2. Obturator internus (with gemellus superior above and gemellus inferior below)
3. Gemellus superior
4. Gemellus inferior
5. Quadratus femoris - NOT divided; left intact to protect the ascending branch of the medial femoral circumflex artery (MFCA)
6. Obturator externus - NOT divided; lies deep and also protects MFCA

Critical Neurovascular Structures

• Sciatic nerve: Runs posterior to the short external rotators, overlying the quadratus femoris. It is the most important structure at risk. Typically (84%) passes deep/inferior to the piriformis muscle. Must be identified and protected.
  • Anatomic variations of sciatic nerve relative to piriformis:
    • Peroneal division through the piriformis, tibial division below (12%)
    • Entire nerve through the muscle (1%)
    • Peroneal above, tibial below (3%)
• Medial femoral circumflex artery (MFCA): Its ascending branch runs deep to the quadratus femoris and obturator externus. Preserving these two muscles protects the blood supply to the femoral head.
• Superior gluteal nerve and vessels: Exit the greater sciatic notch; at risk if abductors are excessively retracted superiorly.
• Inferior gluteal nerve and artery: Supply gluteus maximus from the deep surface.

4. Surgical Technique (Moore's Approach - Step by Step)

Patient Positioning

• Lateral decubitus (patient on the unaffected side) - standard
• The affected limb is draped free for manipulation
• A small bump under the hip helps control external rotation
• Radiolucent table; C-arm available if needed

Step 1 - Skin Incision

• Begin approximately 10 cm distal to the posterior superior iliac spine (PSIS)
• Extend the incision distally and laterally, parallel to the fibers of the gluteus maximus, toward the posterosuperior angle of the greater trochanter
• Then direct the incision distally 10-13 cm, parallel to the femoral shaft (creating a curved/hockey-stick incision)
• Total length approximately 15-20 cm

Step 2 - Fascial Incision

• Expose and divide the deep fascia (fascia lata) in line with the skin incision

Step 3 - Split Gluteus Maximus

• By blunt dissection, split the fibers of the gluteus maximus in line with its fibers - no more than 7 cm from the tip of the greater trochanter
• This protects branches of the inferior gluteal nerve and artery
• Retract the proximal fibers proximally and the distal fibers distally
• Partially divide the distal insertion of gluteus maximus into the linea aspera to increase exposure

Step 4 - Identify and Protect the Sciatic Nerve

• The sciatic nerve is now visible, overlying the posterior surface of the quadratus femoris
• Identify and protect it throughout the procedure
• Once the surgeon is experienced with this approach, the nerve does not always need to be formally exposed, but during acetabular surgery it must be directly visualised

Step 5 - Internally Rotate the Femur

• The femur is internally rotated - this stretches the short external rotators taut, making them easier to identify and divide
• Internally rotating the thigh also lifts the muscles away from the sciatic nerve

Step 6 - Divide the Short External Rotators

• Identify piriformis, gemellus superior, obturator internus, gemellus inferior
• Tag and divide these tendons 1.5 cm from their insertion into the greater trochanter (to preserve a cuff for later reattachment and to protect the ascending branch of the MFCA)
• Reflect the muscles medially - the reflected muscles act as a natural shield over the sciatic nerve
• Critical: Leave the quadratus femoris and obturator externus intact to protect the ascending branch of the medial circumflex femoral artery (blood supply to the femoral head)

Step 7 - Expose the Joint Capsule

• The posterior hip joint capsule is now fully in view
• Incise the capsule longitudinally from distal to proximal, along the line of the femoral neck, to the rim of the acetabulum
• Detach the distal part of the capsule from the femur
• Further retract the gluteus medius proximally and the quadratus femoris distally for additional exposure

Step 8 - Dislocation of the Hip

• Flex the thigh and knee to 90 degrees
• Internally rotate the thigh
• Adduct the limb
• The hip dislocates posteriorly
• The femoral head and acetabulum are now fully accessible

5. Wound Closure

1. Reduce the hip (or insert prosthesis) and check stability
2. Repair the posterior capsule - with interrupted non-absorbable sutures; watertight repair
3. Reattach the short external rotators (piriformis, obturator internus, gemelli) back to the greater trochanter using drill holes or suture anchors through a non-absorbable suture
4. This posterior soft tissue repair (capsule + external rotators) is mandatory to reduce dislocation risk after posterior approach THA
5. Allow the gluteus maximus to fall back into position (no formal repair needed)
6. Close fascia lata, subcutaneous tissue, and skin in layers

6. Extensions of the Approach (Kocher-Langenbeck for Acetabulum)

• Elevation of gluteus medius and minimus subperiosteally from the posterior and lateral ilium
• Steinmann pins inserted into the ilium above the greater sciatic notch to support retractors
• Trochanteric osteotomy if additional anterior exposure needed - reattached with two 6.5-mm lag screws at closure
• Origin of hamstrings may be reflected from the ischial tuberosity for further exposure

7. Advantages

8. Disadvantages

9. Complications

10. Key Exam Points

1. Eponyms: Moore (Southern exposure) = posterior approach; Kocher-Langenbeck = posterior approach for acetabular fractures
2. Position: Lateral decubitus, affected side up
3. Incision: Curved, from PSIS distally/laterally to posterior trochanter, then distally along femoral shaft
4. Gluteus maximus split must not exceed 7 cm from trochanter tip - protects inferior gluteal nerve
5. Internal rotation of femur stretches short external rotators for easier identification
6. Short external rotators divided 1.5 cm from insertion - tagged for reattachment
7. Quadratus femoris and obturator externus are NOT divided - protect MFCA/femoral head vascularity
8. Sciatic nerve lies on quadratus femoris - must be identified and protected
9. Reflected external rotators shield the sciatic nerve medially
10. Hip dislocation manoeuvre: flex 90°, internally rotate, adduct = posterior dislocation
11. Posterior capsule + short external rotator repair at closure = critical to prevent post-op dislocation
12. Most common complication = posterior dislocation (without soft tissue repair)
13. Sciatic nerve anatomy around piriformis has 4 known variations; the "normal" pattern (nerve runs below piriformis) is present in ~84%

Smith-Petersen Approach (Anterior Iliofemoral Approach) to the Hip

1. Introduction and History

2. Internervous Plane

• The femoral nerve territory (sartorius, rectus femoris) medially
• The superior gluteal nerve territory (TFL, gluteus medius) laterally

3. Indications

4. Relevant Surgical Anatomy

Superficial layer

• Tensor fasciae latae (TFL): Arises from outer lip of iliac crest and ASIS; innervated by the superior gluteal nerve. Lies lateral in the interval.
• Sartorius: Arises from the ASIS; innervated by the femoral nerve. Lies medial in the interval.
• Lateral femoral cutaneous nerve (LFCN): Purely sensory nerve; passes over the sartorius approximately 2.5 cm distal to the ASIS. The key nerve at risk - injury causes meralgia paraesthetica (numbness/dysaesthesia over lateral thigh).

Deep layer

• Rectus femoris: Two heads:
  • Direct head - from the anterior inferior iliac spine (AIIS)
  • Reflected head - from above the acetabular rim
  • Innervated by the femoral nerve; lies medially
• Gluteus medius and minimus: Innervated by the superior gluteal nerve; lie laterally

Vascular

• Ascending branch of the lateral femoral circumflex artery (LFCA): Runs transversely across the deep part of the wound approximately 5 cm distal to the hip joint. Must be identified, clamped, and ligated to avoid significant haemorrhage.

Joint

• Hip joint capsule and iliofemoral ligament (Y-ligament of Bigelow): exposed anteriorly
• Ligamentum teres: may be divided to allow dislocation of the femoral head

5. Patient Positioning

• Supine on a radiolucent operating table
• A small bump may be placed under the ipsilateral hip
• For THA/DAA: often a traction/fracture table is used to facilitate femoral preparation and intraoperative fluoroscopy
• Alternatively, a standard radiolucent table with an adequate assistant to manipulate the limb
• C-arm (image intensifier) is available

6. Surgical Technique (Step by Step)

Step 1 - Skin Incision

• Begin at the middle of the iliac crest (or as far posteriorly as required for more extensive exposure)
• Carry the incision anteriorly to the ASIS
• Then turn the incision distally and slightly laterally for another 10-12 cm, directed toward the fibular head
• For limited DAA (THA/arthroplasty): start 2-3 cm lateral and 2-3 cm distal to the ASIS, incision 10-15 cm long directed toward the fibular head
• A cosmetic "bikini" incision along the inguinal crease can be used in thin female patients

Step 2 - Fascial Incision

• Divide the superficial fascia in line with the skin incision
• Free the attachments of the gluteus medius and tensor fasciae latae from the iliac crest
• With a periosteal elevator, strip the periosteum (along with gluteus medius and minimus attachments) from the lateral surface of the ilium; pack the interval to control bleeding from nutrient vessels

Step 3 - Develop the Superficial Internervous Interval

• Carry dissection through the deep fascia of the thigh
• Develop the interval between:
  • TFL (laterally)
  • Sartorius medially (with the intramuscular septum retracted medially to protect the LFCN)
• The fascia of the TFL is incised just anterior to the perforating vessels (which mark the junction of the TFL and gluteus maximus fascia); this keeps the septum intact and protects the LFCN
• Identify and protect the lateral femoral cutaneous nerve - it crosses over the sartorius 2.5 cm distal to the ASIS; retract it to the medial side

Step 4 - Ligate the Lateral Femoral Circumflex Vessels

• Identify the ascending branch of the lateral femoral circumflex artery running across the deep part of the wound approximately 5 cm distal to the joint
• Clamp, ligate, and divide - failure to do this results in significant haemorrhage

Step 5 - Develop the Deep Internervous Interval

• TFL is retracted laterally; sartorius retracted medially
• Expose the rectus femoris - identify both its direct (from AIIS) and reflected (from above acetabulum) heads
• Separate the reflected head from the acetabulum and capsule, leaving the direct head attached (or detach it if more exposure needed, tagging with suture for reattachment)
• Develop the plane between the rectus femoris (medially) and the anterior hip capsule (posterolaterally)
• A cobra retractor is placed to fully expose the anterior hip capsule

Step 6 - Capsulotomy

• Incise the hip joint capsule:
  • T-shaped capsulotomy - longitudinal limb along the femoral neck, horizontal limb at the level of the acetabular labrum
  • The vertical cut is made parallel to the femoral neck; the horizontal cut opens the joint fully
  • A No. 12 blade (curved) is useful to protect the labrum during capsulotomy
• The posterior capsule is not violated - important for stability

Step 7 - Expose the Hip Joint

• The femoral head and proximal margin of the acetabulum are now visible
• For complete exposure:
  • The ligamentum teres may be divided with a curved knife or scissors
  • The hip is then dislocated - for anterior dislocation, the limb is placed in extension and external rotation
  • All parts of the joint are accessible

Step 8 - Extension of the Approach (Full Iliofemoral)

• The skin incision is extended proximally along the iliac crest
• External oblique attachments are sharply elevated off the iliac crest
• Iliacus is elevated off the inner table of the ilium subperiosteally
• Sartorius can be tagged and released from the ASIS or an ASIS osteotomy performed
• Hip flexion allows the psoas to be retracted medially to expose the anterior acetabular wall
• TFL origin can be peeled back to expose the anterolateral acetabulum

Step 9 - Wound Closure

• Reduce the hip (or insert prosthesis)
• Repair the anterior capsule - with interrupted non-absorbable sutures
• Reattach rectus femoris (both heads) through drill holes in the AIIS or with suture anchors
• Allow the TFL and gluteus medius to fall back into place; no formal repair needed
• Repair the fascia lata/fascial layer
• Close subcutaneous tissue and skin in layers

7. Comparison with Other Hip Approaches (Miller's Review Table)

8. Advantages

1. Truly internervous - the only commonly used approach to the hip that is completely internervous; no muscle is denervated
2. No abductor damage - gluteus medius and minimus are not cut
3. Lowest dislocation rate after THA - anterior structures (capsule/iliofemoral ligament) are repaired; posterior capsule is preserved
4. Rapid functional recovery - no muscle repair needed
5. Excellent access to the anterior acetabulum and femoral head
6. Supine positioning allows easy intraoperative assessment of leg length and limb alignment
7. Fluoroscopy is simple in supine position
8. Extensile - can be extended to a full iliofemoral approach for acetabular/pelvic surgery

9. Disadvantages

1. Difficult femoral canal preparation - requires specialized retractors; the femur is not as easily delivered into the wound as with posterior/lateral approaches
2. Limited posterior acetabular access - cannot visualize the posterior wall through this approach alone
3. May require a specialized orthopaedic (traction) table
4. LFCN at risk - meralgia paraesthetica is the most common complication (numbness over lateral thigh); reportedly occurs in up to 20-40% of DAA THA cases, though often transient
5. Learning curve is steeper than lateral/posterior approaches
6. Restricted access in obese patients
7. Higher risk of proximal femoral fracture during femoral preparation in THA (if femur inadequately elevated)

10. Structures at Risk

11. Modifications

1. Direct Anterior Approach (DAA/Hueter interval): Limited version for THA; starts 2-3 cm distal and lateral to ASIS; no iliac crest dissection; uses traction table
2. Bikini/inguinal crease incision: Cosmetic variant for thin women; same interval but incision along skin crease; slightly limited exposure
3. Somerville approach: For open reduction of CDH in children; ASIS osteotomy with sartorius and rectus release; radial capsulotomy
4. Full Anterior Iliofemoral (Smith-Petersen extended): Includes iliac crest dissection, iliacus elevation, and sometimes sartorius/ASIS osteotomy for acetabular surgery and PAO

12. Key Exam Points

1. Eponym: Smith-Petersen = anterior approach; also called DAA; Hueter first described the interval
2. Internervous plane (must know):
   • Superficial: sartorius (femoral n.) / TFL (superior gluteal n.)
   • Deep: rectus femoris (femoral n.) / gluteus medius (superior gluteal n.)
3. Position: Supine (key differentiator from posterior approach)
4. Incision: From mid-iliac crest → ASIS → distal 10-12 cm along anterolateral thigh
5. LFCN is the most important nerve at risk; passes over sartorius 2.5 cm below ASIS
6. Ascending branch of LFCA must be ligated ~5 cm below joint
7. Capsulotomy: T-shaped or H-shaped; vertical limb along femoral neck
8. Dislocation: Extension + external rotation (vs. flexion + internal rotation for posterior approach)
9. Rectus femoris is tagged and repaired to AIIS at closure
10. Posterior capsule is preserved = lowest dislocation rate of all hip approaches
11. Femoral canal access is the main limitation (specialized retractors needed)
12. LFCN injury (meralgia paraesthetica) is the most common complication