Custom Triflange Acetabular Components

• Paprosky IIIA and IIIB defects where a stable hemispherical construct (even with porous metal augments) cannot be achieved
• Chronic pelvic discontinuity — the strongest and most established indication; the rigid monoblock bridges the discontinuity
• Failed prior cage or cup-cage reconstruction with progressive bone loss
• Massive irradiation-associated bone loss (post pelvic radiotherapy osteonecrosis) — dead, sclerotic bone will not support conventional ingrowth cups; triflange distributes load to remaining viable bone
• Failed prior triflange or structural allograft with defect beyond salvage by off-the-shelf means
• Selected tumour resection reconstructions (periacetabular resection with custom hemipelvis-type implants — a related but distinct workflow)

1. Trial with the supplied patient-specific trial; confirm it seats fully on all three flanges — rocking indicates retained soft tissue or bone not removed per plan (use the model to identify the offending area)
2. Seat the definitive implant; confirm flush contact iliac and ischial flanges
3. Ischial screws first — locks the inferior hemipelvis and, in discontinuity, compresses/controls the fracture line
4. Iliac flange screws — multiple, long, into sciatic buttress and towards the sacroiliac joint per plan
5. Dome/cup screws (if designed) and pubic fixation last
6. Impact or lock the planned liner — dual mobility or constrained in most modern series
7. Trial reduction: assess stability through range, leg length, impingement; the femoral side often needs revision to a high-offset or modular stem to restore tension against the pre-set hip centre

Aftercare: protected weight-bearing (touch to partial) for 6 to 12 weeks, especially with discontinuity; hip precautions per articulation; serial radiographs for screw integrity and flange position; thromboprophylaxis and heterotopic ossification prophylaxis considered given extensile exposure.

• Sciatic nerve — ischial dissection and screws; reported palsy in several percent of series
• Superior gluteal neurovascular bundle — proximal iliac dissection through the greater sciatic notch region
• Obturator vessels/nerve — pubic flange work
• Intrapelvic vessels (external iliac, corona mortis) — mitigated by pre-planned screw lengths and trajectories
• Pitfall: incomplete flange seating — the commonest technical error; leads to malposition of the entire construct because the cup position is slaved to the flanges
• Pitfall: failing to revise the femur — a restored (often distalised) hip centre changes leg length and soft-tissue tension; anticipate femoral revision
• Salvage of intra-operative non-fit: limited bone recontouring per model, or bail-out to cup-cage/distraction construct — always have a plan B on the shelf

• Most published series report aseptic survivorship in the region of 80 to 95 percent at 5 to 10 years, remarkable given the severity of the defects treated
• Radiographic healing of pelvic discontinuity is reported in the majority of cases
• Failure modes: instability requiring revision, deep infection, aseptic loosening (screw breakage, flange lift-off, migration); catastrophic flange fracture is rare

• Dislocation — the leading complication, roughly 10 to 20 percent in older series with conventional bearings; markedly reduced with dual mobility or constrained liners designed into the implant, large heads and careful pre-planned version
• Deep infection — around 5 to 10 percent in many series, reflecting long multiply-revised operations; managed by DAIR with liner exchange early, or explantation (very destructive) for chronic infection
• Sciatic nerve palsy — a few percent; mostly ischial-side traction/dissection; usually partial, often recovers incompletely
• Aseptic loosening — watch serial films for broken ischial screws (a classic early sign of failing inferior fixation and non-healing discontinuity)
• Intra-operative fracture, haemorrhage, heterotopic ossification, leg-length inequality