TKA Periprosthetic Fractures

Type II or Type III. This is the decision that matters, and it is made on the radiographs before committing to ORIF. A displaced fracture around a loose prosthesis is Type III, and ORIF will fail because it leaves the loosening unaddressed.

• Stable (Types I and II) - no lucency at the bone-cement or cement-implant interface, no subsidence, alignment maintained
• Loose (Type III) - progressive radiolucent lines (over 2mm), subsidence (over 2mm component migration), malalignment (over 3° from neutral)

If in doubt, obtain contralateral TKA radiographs for comparison, or stress fluoroscopy in theatre, before committing to ORIF.

Where Lewis and Rorabeck grades by displacement and prosthetic stability, the Su (Vanderbilt) classification grades supracondylar fractures by location relative to the femoral component. That determines how much distal bone remains for fixation, and therefore whether a plate or nail is feasible or a distal femoral replacement is needed. The Ross and Hoellwarth series cited below both report their results by Su type.

Type I plateau fractures are often associated with component subsidence and need revision arthroplasty with long stems and augments, not simple ORIF. Types III and IV, below the tibial component, can be treated on standard fracture fixation principles.

Two questions. Is the extensor mechanism intact, and is the patellar component fixed? If the patient can straight leg raise against gravity, the extensor mechanism is intact and most periprosthetic patellar fractures can be treated conservatively with a hinged brace and early range of motion. If it is disrupted, surgical repair is mandatory to restore knee extension.

Ortiguera and Berry. The named classification an examiner will ask for sorts these fractures by the same two questions.

Why the patella breaks. Almost all of these fractures occur in a resurfaced patella, and the cause is usually a blood-supply and bone-stock problem rather than trauma:

• Devascularisation - the medial arthrotomy already divides the medial supply, and a lateral release then sacrifices the lateral superior geniculate artery; the combination can leave the patella ischaemic
• Over-resection - a thin residual patella with little bone to carry the component or a fracture
• Large central fixation lugs, maltracking and established osteonecrosis

Many are therefore stress fractures found incidentally on a follow-up radiograph in a comfortable patient. That is the practical argument for leaving a Type I alone, since operative results in thin, ischaemic bone are guarded.

Non-operative treatment, for selected cases. The indications are:

• Elderly, low-demand patient (limited community ambulator)
• Significant medical comorbidities (high anaesthetic risk)
• Minimal displacement (under 2mm shift, under 3° angulation)
• Good bone quality

The protocol is a hinged knee brace locked in extension for 6 weeks and touch weight-bearing with crutches for 8-12 weeks, with radiographs at 2, 6 and 12 weeks to catch displacement, progressing to full weight-bearing at 12 weeks if union is evident. The risks are loss of reduction requiring delayed ORIF in 15-20%, knee stiffness, and nonunion in 5-10% of elderly patients.

Locked lateral plating is for the younger, higher-demand patient with minimal comorbidities, or anyone whose compliance with non-weight-bearing is in doubt. A bridge-plating technique allows early range of motion and progressive weight-bearing (technique below), and function returns in 75-80%.

Which to choose. Examiners often present an 85-year-old with a Type I fracture and ask for management. The safe answer is ORIF with a locked plate in most cases, unless the patient is bedbound or a high anaesthetic risk. Reserve non-operative treatment for very select cases, with shared decision-making about the risk of loss of reduction.

Surgery is required: non-operative treatment of a displaced fracture has an unacceptable failure rate. The choice is between a lateral locked plate and a retrograde nail.

Lateral locked plate (LISS/NCB). The plate works with any implant design and is indicated for:

• A closed-box femoral component, which cannot pass a retrograde nail
• A fracture extending proximally (comminution, proximal third of the femur)
• Poor bone quality, where locking screws provide angular stability
• Patient preference for a shorter operating time

Union is 80-85%, with an average time to union of 4-6 months. Screw pullout complicates 5-10% of cases in osteoporotic bone.

Retrograde intramedullary nail. The nail is indicated for:

• An open-box femoral component, the critical requirement
• Good bone quality
• A fracture about 5cm above the femoral component, leaving adequate distal fixation
• Bilateral periprosthetic fractures, where it allows faster mobilisation

A 9-10mm nail is typical, passed after antegrade reaming if necessary. Union is 85-90%. Nail-implant impingement occurs in 5%, and extension into the joint is rare with modern nails.

Plate or nail. The nail needs less soft-tissue stripping, is biomechanically superior as a load-sharing device and allows faster mobilisation; a lower infection risk is also claimed for it, although the pooled comparison in the evidence section found no significant difference in deep infection. The plate copes better with very distal fractures than the nail and handles comminution better. Poor bone favours the plate over the nail; severe osteoporosis raises revision with cemented stems as the alternative to fixation. A common exam trap is to ask about the nail and then show a closed-box component: decline the nail, and convert to lateral locked plating or revision arthroplasty with stems.

ORIF is contraindicated. The fracture will not heal while the prosthesis is loose. The operation is revision TKA with long cemented stems, the fracture reduced and held with cerclage cables, and the stem providing load-sharing fixation across it (technique below).

Stem length. The stem must pass the fracture apex by at least 100mm or 2 cortical diameters, whichever is longer. Typical Type III fractures need 150-200mm stems.

Cemented stems. In the fracture setting, with osteoporotic bone and a need for immediate stability, cemented stems are preferred. Uncemented press-fit stems risk fracture propagation during insertion.

Augments or sleeves. A contained metaphyseal defect, with a good rim of bone, can accept augments. An uncontained defect with cortical loss needs a press-fit, porous-coated metaphyseal sleeve for additional fixation, and significant cortical deficiency an allograft strut wrapped around the femur and fixed with cerclage. The goal is to restore the joint line and mechanical axis with stable fixation.

Resecting the fractured distal femur and replacing it with a hinged megaprosthesis is a distinct primary option alongside fixation and revision with stems.

When to choose it. The indications are:

• A very low or unreconstructable fracture (Su III) with insufficient distal bone for stable plate or nail fixation
• Severe distal comminution or bone loss, or a coexisting loose or failed femoral component where the distal bone cannot support a revision stem
• A low-demand elderly patient, in whom the decisive advantage is immediate full weight-bearing: a hip-fracture-style "operate once, mobilise now" goal that avoids the prolonged protected weight-bearing and high nonunion risk of ORIF in osteoporotic bone

The trade-off. The replacement bypasses the fracture entirely, which is valuable in frail patients, but it carries a higher deep infection rate than internal fixation (Quinzi). The medium-term burden is substantial: the German EPRD registry (Lützner) found a 4-year revision rate of 19.7%, PJI in 12.8% and 4-year mortality of 32.7%. Late aseptic loosening is the reason to use it cautiously in patients with a longer life expectancy (Ross), and to avoid it where possible in younger, higher-demand patients. Across meta-analysis (Quinzi), complication and reoperation rates are comparable to ORIF and nailing, so it is a selective tool, not a default.

Consent. Warn the patient of:

• Infection - 2-5% superficial, 1-2% deep
• Nonunion, particularly in osteoporotic bone (rates under Complications)
• Malunion - 5-10%, varus or valgus deformity
• Hardware prominence - 10-15%, which may require removal
• Peroneal nerve injury - 1-2%
• Need for revision - 15-20% within 2 years

Equipment. Have ready:

• A LISS or NCB periarticular plate of appropriate length, typically 9-13 holes
• 4.8-5.0mm locking screws, at least 8-10 of them
• Pointed reduction clamps, K-wires and Schanz pins
• A C-arm able to show the full plate length on AP and lateral views
• A revision TKA set on standby in case the prosthesis is found loose intraoperatively

Positioning. Supine on a radiolucent table (Jackson, or a standard table with a radiolucent extension), with a bump under the ipsilateral hip for neutral rotation and the contralateral leg in a well-leg holder. The C-arm comes from the contralateral side for lateral views, with the beam parallel to the floor; confirm adequate AP and lateral imaging of the entire femur before draping, and have the radiographer practise obtaining the femoral component views. Prep and free-drape the leg from hip to ankle, including the contralateral knee if templating may be needed intraoperatively, with impervious stockinette isolating the foot at the ankle.

Incision. Straight lateral, from the lateral femoral epicondyle towards the proximal lateral femur, 8-12cm depending on fracture extent and plate length, centred over the lateral intermuscular septum.

The submuscular space. Incise the fascia lata along the lateral intermuscular septum, identify vastus lateralis anterior to it, and lift the muscle off the septum to create the submuscular space. Ligate or cauterise the perforating vessels.

Reduction. This is bridge plating: do not open the fracture site and do not strip the periosteum. Confirm the fracture by palpating the step-off or gap, and reduce it with traction, manipulation, and K-wires or Schanz pins for provisional alignment. Accept under 5° of varus or valgus and under 5mm of translation on AP and lateral fluoroscopy.

The plate. Create an epiperiosteal tunnel deep to vastus lateralis with a McDonald clamp or the plate insertion guide, and slide the plate proximally, keeping it on the bone surface. It should sit centred on the lateral femoral cortex with its distal end 1-2cm above the femoral component, confirmed on fluoroscopy before fixation. The plate must not impinge on the femoral component, so leave a gap of at least 1cm. If the fracture is very distal (within 5cm of the component), consider revision arthroplasty instead of plating.

Screws. Fix in sequence:

1. Distal locking screws first - 3-4, bicortical
2. Check the reduction on fluoroscopy and adjust it before proximal fixation
3. Proximal locking screws - 4-6, bicortical
4. In osteoporotic bone, fill every available hole for maximal stability

Drill through the locking guide sleeve and measure with a depth gauge (both cortices plus 5mm for safety). Tighten each screw until the head seats in the plate without overtightening, and confirm on fluoroscopy that the threads engage the far cortex.

Final check. AP and lateral fluoroscopy should confirm:

• Reduction maintained
• All screws bicortical
• No screw penetrating the knee joint
• No plate impingement on the femoral component

Manually stress the fracture under fluoroscopy; it should be stable with minimal motion.

Closure. Irrigate the submuscular space with 3L of normal saline, cauterise the perforators, and consider a drain if oozing is significant (removed at 24-48 hours). Close the fascia lata with interrupted 0 Vicryl, watertight to prevent muscle herniation, then 2-0 Vicryl subcuticular to the subcutaneous layer and 3-0 Monocryl or staples to skin, with a sterile dressing and compressive wrap. A hinged knee brace locked in extension gives comfort and protection, with touch weight-bearing on a walker for 6 weeks and range-of-motion exercises from day 1 (see Postoperative Care).

View larger

Confirm the box first. Before starting the case, check the femoral component design on the radiographs or the operation note:

• An open-box design is required for nail passage (confirm on the lateral radiograph)
• Box height - measured on the lateral view, needing at least 10-12mm clearance
• Box width - the anteroposterior dimension, needing 12-14mm for a 9-10mm nail
• Component position - enough space for the nail entry point

If a closed-box design is detected, abandon the nailing plan and convert to a lateral locked plate or revision arthroplasty.

Equipment. Have ready:

• A supracondylar retrograde nail, 9-10mm diameter and 200-300mm long
• Proximal and distal locking screws, typically 2-3 at each end
• A traction table, or an assistant for manual traction
• A C-arm capable of a perfect lateral, which is critical for the entry point
• A lateral plating set on standby if nail passage fails

Positioning. Supine on a radiolucent table (standard or traction table), with the affected leg in a traction boot if a traction table is used or manual traction by an assistant, the contralateral leg in a well-leg holder, and a bump under the ipsilateral hip (15-20° of internal rotation to facilitate lateral imaging). Apply longitudinal traction to reduce the fracture, adjust rotation and varus/valgus on fluoroscopy, and confirm that a perfect lateral of the distal femur and component can be obtained.

Arthrotomy and entry point. A midline anterior incision, 8-10cm and centred over the patella, and a medial parapatellar arthrotomy, splitting the quadriceps tendon if needed for exposure. Evert the patella laterally, inspect the polyethylene insert and confirm the open box under direct vision. The entry point is the centre of the intercondylar notch on the AP and the anterior third of the box on the lateral. Place a K-wire under fluoroscopy, centred to avoid eccentric reaming and aimed towards the fracture and up the femoral canal.

Canal preparation. Open with a cannulated opening reamer (typically 10-12mm) over the K-wire, then hand- or power-ream to 1mm larger than the nail (typically 10-11mm for a 9-10mm nail), up to the proximal femur, confirming passage through the fracture on fluoroscopy.

Nail insertion. Measure the length on fluoroscopy (typically 200-250mm for a supracondylar fracture) and insert the nail over the guidewire with a mallet or inserter. The tip should reach the level of the lesser trochanter for adequate proximal fixation, and the distal end should be buried 5mm below the articular surface so that it cannot impinge on the polyethylene. On the lateral view the nail should be centred in the canal, not eccentric anteriorly or posteriorly.

Locking. Two to three bicortical distal screws (typically 5.0mm) through the aiming jig or freehand, none penetrating the knee joint on the lateral view. Two to three bicortical proximal screws, by fluoroscopy or freehand technique because the target jig is often inaccurate, with good purchase in both cortices. Finish with AP and lateral fluoroscopy confirming reduction, nail position, and all screws bicortical and clear of the joint.

Closure. Inspect the polyethylene insert for damage from reaming or nail insertion. Close the capsule and quadriceps tendon with interrupted 0 Vicryl, checking that the extensor mechanism is intact and patellar tracking normal, then 2-0 Vicryl to the subcutaneous layer and 3-0 Monocryl or staples to skin, a sterile dressing, and a hinged knee brace locked in extension.

Templating. A CT with a metal artefact reduction protocol assesses bone stock and metaphyseal defects.

• Stem length - more than 100mm beyond the fracture apex or 2 cortical diameters, whichever is longer
• Stem diameter - ream to good cortical contact, typically 15-17mm in the femur and 12-15mm in the tibia
• Augments - measure the distal and posterior femoral defects
• Constraint - assess the need for constrained or hinged components if the ligaments are insufficient

Equipment. Have ready:

• A modular revision TKA system
• Long cemented stems, 150-200mm, in multiple diameters
• Block, wedge and step-cut augments (5mm, 10mm, 15mm thicknesses)
• Metaphyseal sleeves for massive femoral or tibial bone loss
• At least 3-4 cerclage cables or wires for provisional fracture fixation
• Bone graft - allograft chips, and femoral strut allografts for cortical deficiency
• High-viscosity antibiotic-loaded PMMA cement

Approach. A medial parapatellar arthrotomy through the old incision. The aim is to see both components without excessive force on the extensor mechanism, and the extensile options are:

• V-Y quadricepsplasty (quadriceps turn-down)
• Tibial tubercle osteotomy, 5-7cm long, preserving the anterior tibial crest
• Rectus snip, a 45° oblique cut through the junction of VMO and the rectus tendon

Component removal. Disrupt the cement-bone interface with an oscillating saw and lift the loose femoral component with osteotomes, taking care not to propagate the fracture and preserving as much bone stock as possible. Remove all cement from the canal with hand instruments and ultrasonic tools so that the stem can pass, without perforating the cortex.

Fracture reduction. Align the fracture with pointed reduction clamps and hold it with 2-3 cerclage cables straddling the fracture, tightened to compress it, confirming reduction on fluoroscopy. K-wires in safe zones, clear of the canal, give rotational control.

Stem preparation. Start with a 12mm reamer and increase in 1mm increments until there is cortical chatter on both cortices, typically at 15-17mm in the femur and 12-15mm in the tibia. Ream to depth, more than 100mm beyond the fracture (150-200mm is typical). Insert the cement restrictor more than 100mm beyond the fracture apex and more than 20mm beyond the stem tip, for third-generation cementation.

Trial. Trial the femoral component (with offset or augments as needed), the stemmed tibial component and a polyethylene thickness that restores the joint line and balance. Check:

• Range of motion - at least 0-100°
• Stability - varus/valgus stress and AP drawer
• Patellar tracking
• Fracture alignment maintained

Cementation. Dry the canal, mix antibiotic-loaded high-viscosity PMMA, and inject it retrograde with a cement gun and nozzle, filling the canal under pressure while a finger plugs the hole in the femoral component. Insert the stem in slight flexion and bring the knee to extension as the cement cures, holding it for 10-12 minutes until fully cured. Seat the components with 5-7° of valgus, neutral rotation and the joint line restored, insert the polyethylene and reduce the knee. Final AP and lateral fluoroscopy confirms alignment, stem position and no cement extruded into the joint.

Why the weight-bearing is staged. Touch weight-bearing for the first 6 weeks allows soft-tissue healing and early callus formation while preventing catastrophic hardware failure. Partial weight-bearing from 6 weeks stimulates further bone healing through controlled mechanical stress (Wolff's law). Full weight-bearing at 12 weeks assumes radiographic union is progressing; if it is not, delay full weight-bearing until 16-20 weeks.