Patient-specific pelvic reconstruction for uncontained bone loss when hemispherical revision fixation is not credible
- The implant is only as good as the CT model and the host bone selected for fixation. A custom component does not create viable pelvic bone.
- Plan the hip centre, version, inclination, leg length, offset and liner orientation before ordering the implant; intraoperative improvisation is limited.
- The three flanges are not interchangeable: the iliac flange controls superior fixation, the ischial flange restores the posterior-inferior column and the pubic flange adds anterior control.
- Screw corridors must be planned around the sciatic notch, superior gluteal neurovascular bundle, obturator vessels, bladder and intrapelvic viscera.
- A chronic pelvic discontinuity may need a construct that captures both hemipelvic segments; a cup sitting in one segment can remain mechanically unstable.
- “Custom triflange is a pelvic fixation strategy, not simply a larger revision cup.
- “The design CT must include the whole pelvis and enough distal femur to plan hip centre, limb length and offset.
- “The safest screw is the one planned in a known corridor and checked with fluoroscopy or navigation; the flange should not be used as a licence for long blind screws.
- “The main clinical risks are dislocation, infection, aseptic loosening, sciatic nerve injury, intrapelvic penetration and failure of pelvic union.
Metal artefact, a missed discontinuity, an unrecognised pelvic defect or incorrect side can make an otherwise well-designed component unusable. The surgeon must review the CT segmentation and approve the final design.
A low or medial hip centre may improve coverage but changes abductor tension, leg length and biomechanics. Restore the centre that the remaining bone and soft tissues can tolerate, not an attractive point on a computer model.
Posterior column preparation, ischial flange seating and screw placement occur near the sciatic notch. Avoid excessive retraction, cement extrusion and screws that breach the notch.
A sinus, positive aspiration or infected explant changes the operation. Perform staged debridement and dead-space management rather than placing a definitive custom implant into uncontrolled infection.
Definition, Indications and Alternatives
A custom triflange acetabular component is a patient-specific porous or coated metal reconstruction that uses three pelvic fixation extensions: an iliac flange, an ischial flange and a pubic flange. It bridges severe acetabular bone loss and provides a new hemispherical bearing surface for a revision hip. It is designed from CT rather than selected from a catalogue.
The usual indication is a chronic massive acetabular defect, often Paprosky type IIIB, with or without chronic pelvic discontinuity, when a standard revision shell, augments, a cage or a cup-cage cannot obtain durable fixation. The operation is most credible when the patient has a reconstructable pelvis, tolerable infection biology, viable soft tissue and enough bone for at least two reliable fixation zones.
Indications
- Severe segmental and cavitary acetabular bone loss after repeated revision arthroplasty.
- Chronic pelvic discontinuity with a mobile or non-united superior and inferior hemipelvis.
- Failure of a prior cage, cup-cage, jumbo cup or augment construct when further standard fixation is not credible.
- A pelvic defect in which patient-specific flanges can contact viable iliac, ischial and pubic bone and avoid intrapelvic organs.
- A patient able to tolerate a long revision operation, protected weight bearing and the possibility of further surgery.
Alternatives
- porous metal augments and a revision shell;
- jumbo cup with or without custom or off-the-shelf augments;
- cup-cage reconstruction;
- ilioischial or anti-protrusio cage with a cemented liner;
- acetabular distraction with a highly porous shell;
- structural allograft or an allograft-prosthetic composite in selected centres;
- resection arthroplasty, chronic suppression or hemipelvic salvage when infection, tumour or tissue loss makes reconstruction unsafe.
Custom triflange should not be selected solely because the patient has a large defect. A cage or cup-cage may be faster and more adaptable intraoperatively; a custom component is most useful when the defect can be mapped accurately and the planned flanges provide fixation that other constructs cannot.
Clinical Assessment and Indication Thresholds
History
Document every hip operation, implant, culture, antibiotic course, sinus episode, dislocation, fracture and vascular or abdominal operation. Ask about current mobility, pain, leg-length discrepancy, transfers, shoe lifts, abductor weakness, sciatic symptoms and the patient's desired activity. A custom triflange may restore stability but cannot guarantee normal gait after multiple abductor and approach injuries.
Examination
Skin and approach. Map scars, sinuses, flaps and areas of adherence. A posterior, lateral or direct anterior approach may be limited by prior surgery; the planned approach must leave a viable closure and permit access to the selected flanges.
Leg length and mechanics. Measure from the anterior superior iliac spine to the medial malleolus with the pelvis level, and compare blocks under the short limb when standing. Assess hip abductor power, Trendelenburg sign, flexion contracture, lumbar compensation and the opposite hip and knee.
Neurology. Record sciatic function: ankle dorsiflexion and eversion for the peroneal division, plantar flexion and toe flexion for the tibial division, and sensation in dorsal and plantar distributions. Document pre-existing deficits before counselling.
Vascular and visceral risk. Palpate pulses and assess venous congestion. Prior pelvic surgery, radiation, pelvic fracture, vascular graft or intrapelvic migration increases the need for CT angiography and vascular or general-surgical input. A component that is mechanically feasible but cannot be safely inserted around the external iliac vessels or bladder is not a feasible component.
Infection work-up
Use a composite periprosthetic joint infection assessment: symptoms and sinus, serum inflammatory markers, aspiration with cell count and culture where interpretable, imaging and multiple deep cultures at surgery. If infection is established, remove infected hardware and manage the dead space in a stage that permits later custom reconstruction. A negative aspirate in a chronic low-grade infection does not override a sinus, purulence, histology or multiple positive cultures.
Anatomy and Safe Fixation Corridors
The component must obtain fixation without injuring structures that are hidden behind the thin pelvic walls.
- Ilium: the supra-acetabular and iliac wing bone can provide long screw purchase, but the inner table borders the iliacus and pelvic viscera. The superior gluteal neurovascular bundle exits through the greater sciatic notch and must be respected during posterior and lateral dissection.
- Ischium: the ischial flange sits close to the sciatic notch and the posterior column. The sciatic nerve may be scarred and adherent after repeated surgery. The ischial tuberosity is not a safe target for a screw whose trajectory has not been planned.
- Pubis: the superior pubic ramus and ischiopubic region are near the obturator vessels and nerve, bladder and spermatic or round ligament structures. Small anterior screws can still penetrate the pelvis if the corridor is misread.
- Acetabular rim and columns: the anterior and posterior columns are the remaining structural bridges. A flange should rest on prepared viable bone; a gap filled only by cement or fibrous tissue is not reliable fixation.
- Hip centre and abductor lever arm: a medialised or high centre changes the lever arm and leg length. The cup orientation must be compatible with the femoral component, soft-tissue tension and the chosen dual-mobility or constrained bearing.
- Sciatic nerve: the nerve is particularly vulnerable during posterior exposure, ischial preparation, screw insertion and dislocation manoeuvres. Identify the preoperative deficit and keep the instrument pathway controlled.
Plan each screw in three dimensions. The design engineer's trajectory is a starting plan; intraoperative bone exposure, a reamer, a drill-stop and fluoroscopy or navigation verify the final path.
Imaging and 3D Planning
CT protocol
Request thin-slice CT of the entire pelvis, including both iliac wings, the pubic symphysis, ischia and enough femur to evaluate the existing stem and planned hip centre. Use a metal artefact-reduction protocol when available and reconstruct in axial, coronal and sagittal planes. Include a 3D pelvic model for communication, but never design from a shaded surface model alone; inspect the underlying axial slices.
The CT review must answer:
- Is the discontinuity acute, chronic, mobile or already partly united?
- Which areas of bone are viable and thick enough for screws or flange contact?
- Is the posterior column intact, deficient or internally rotated?
- Are the sciatic notch, superior gluteal vessels, obturator canal, bladder and iliac vessels at risk?
- Where is the current hip centre and where can the new centre sit without excessive leg-lengthening?
- Can the component be inserted through the selected approach without impinging on the greater trochanter, femoral stem or soft tissue?
The design review
The surgeon should approve a side-by-side review of the CT segmentation, proposed resection, flange contact surfaces, screw lengths and trajectories, cup centre, inclination, anteversion, offset and liner option. Check the side, patient identity and the date of the scan. If the pelvis has changed after a spacer, fracture or debridement, obtain a new scan rather than relying on an old model.
Templating measurements
Measure the intended hip centre relative to the teardrop or another reproducible pelvic landmark, the target inclination and version, anticipated leg length and offset, the remaining femoral stem position, the depth of the defect and the length of every planned screw corridor. A plan should identify at least one intraoperative rescue option: change of approach, different liner, additional screw, cup-cage or staged reconstruction.
Implant Selection and Bearing Strategy
A custom triflange may be manufactured with a porous or highly porous bone-contact surface, a hemispherical cup, screw holes and optional augment or buttress features. The precise material and coating are device-specific; the surgical principles are not.
Bearing choices
- A dual-mobility bearing can reduce instability risk in a high-risk revision, but introduces a mobile polyethylene articulation and its own risks, including intraprosthetic dislocation and wear.
- A constrained liner may be needed for severe abductor or soft-tissue deficiency, but transfers high forces to the cup and fixation and should not be used to compensate for an unstable component.
- A large conventional liner may be appropriate when soft-tissue tension and femoral head size are favourable.
Choose the bearing after restoring the hip centre, offset and tension. The liner is not a substitute for correct cup orientation or reliable three-flange fixation.
Operative Technique: PIPADRAW
Custom triflange implantation sequence
- Use a lateral or supine position according to the planned approach, with the pelvis firmly supported and the whole limb free for hip reduction and length assessment.
- Prep from the costal margin to the foot when the approach or vascular rescue may extend; keep the contralateral limb available for comparison.
- Use a urinary catheter and pressure-point protection for a long case; coordinate with anaesthesia for blood loss, cell salvage and neuromonitoring where appropriate.
- Have the approved custom implant, trial or printed model, extraction tools, long drills with stops, navigation or fluoroscopy, backup screws and a cup-cage or cage option available.
- Before incision, confirm the side, implant identifier and the planned flange orientation against the CT model. Never open an implant whose label or side does not match the operative plan.
- Check that fluoroscopy can image the iliac, ischial and pubic corridors; obtain a baseline AP pelvis.
- Administer antibiotics after cultures if infection is suspected and the patient is stable; use the therapeutic plan agreed with the infection team.
- Plan blood conservation, thrombosis prevention and the need for vascular or plastic-surgical support.
- If the case is staged, confirm the criteria for proceeding: healed wound, controlled infection strategy, viable coverage and a current CT model.
- Use the safest previous approach or a planned extensile approach, preserving viable skin bridges and excising any sinus tract en bloc.
- Elevate full-thickness flaps and identify the abductors, external rotators and sciatic nerve according to the approach. Do not strip the entire residual ilium, ischium and pubis just to make the model visible.
- Expose the iliac, ischial and pubic contact surfaces as much as necessary to seat the implant; keep retractors controlled and avoid blind intrapelvic pressure.
- Remove the femoral head, liner, shell, cage, cement and loose screws. Preserve a well-fixed femoral stem only when infection and implant compatibility permit.
- Debride membrane, granuloma and necrotic bone. Obtain multiple separate deep samples before antibiotics when appropriate.
- Identify and protect the sciatic nerve. If the nerve is scarred, limit traction and accept a slower dissection rather than avulsing it from the posterior column.
- Match the exposed bone to the approved model or trial. Remove only obstructing fibrous tissue and non-viable bone; avoid over-reaming the host surface and losing planned flange contact.
- Reduce the hemipelvis and confirm the discontinuity position. Freshen a chronic nonunion only as required to achieve viable contact and correct gross mobility.
- Mark the planned screw corridors on the exposed bone. Use the implant's drill guides or navigation rather than freehanding long screws close to the notch or pelvic cavity.
- Impact the component gently onto all three flanges, confirming full seating without a gap or soft-tissue interposition.
- Use temporary pins or screws and check that the hip centre, cup face and flanges match the CT plan. If the component rocks, stop and find the cause; do not fill a rocking construct with cement.
- Reduce the hemipelvic segments around the component when treating discontinuity, and confirm that both segments are captured by the planned fixation.
- Drill with stops through the planned iliac, ischial and pubic corridors. Measure each screw and confirm the tip remains in bone on orthogonal imaging or navigation.
- Avoid the sciatic notch, superior gluteal bundle, obturator canal, bladder and iliac vessels. A shorter screw with known purchase is safer than an unverified long screw.
- Use locking or variable-angle features according to the implant design and obtain fixation in every viable zone the plan depends on.
- Tighten the screws in a sequence that draws the component onto the prepared bone without levering one flange off its bed.
- Ream or prepare the cup surface only as specified by the implant system, then place the liner at the planned inclination and version.
- Restore femoral head size, offset and length; test stability through flexion, adduction and rotation without excessive force on the reconstructed pelvis.
- Obtain an AP pelvis and orthogonal views of the critical flanges or use a validated navigation record.
- Confirm cup orientation, flange seating, screw length, absence of intrapelvic penetration, femoral stem compatibility and the mechanical hip centre.
- If a screw or flange is unsafe, revise it before closure. Do not rely on postoperative CT to discover a preventable breach.
- Irrigate, achieve haemostasis and close without tension. Coordinate flap or muscle coverage when metal is close to a compromised envelope.
- Use a drain and negative-pressure dressing only when they support the soft-tissue plan; they do not replace dead-space control.
- Protect weight bearing according to fixation and discontinuity stability, commonly with partial or toe-touch loading for four to six weeks, then advance after clinical and radiographic review.
Complications and Failure Management
- Mechanism or clue
- Sinus, drainage, fever, positive cultures or painful loosening
- Immediate response
- Cultures, imaging and infection-team review
- Definitive principle
- Debridement and implant retention only in selected early cases; chronic infection usually requires staged removal and reconstruction
- Mechanism or clue
- Early instability, dual-mobility event or recurrent reduction
- Immediate response
- Urgent reduction and imaging
- Definitive principle
- Correct orientation, offset, liner and soft-tissue cause; revise the construct when fixation or pelvic position is wrong
- Mechanism or clue
- New foot drop, sensory loss or severe postoperative pain
- Immediate response
- Document level, remove compressive dressings and image for screw or retractor cause
- Definitive principle
- Remove or revise a causative screw promptly; avoid traction and coordinate neurologic follow-up
- Mechanism or clue
- New visceral, vascular or neurologic symptoms; breach on CT
- Immediate response
- CT angiography and urgent specialist review
- Definitive principle
- Remove or revise the implant safely; involve vascular or general surgery before extraction if a vessel or organ is at risk
- Mechanism or clue
- Progressive migration, radiolucency or pain after initial stability
- Immediate response
- Exclude infection and assess bone incorporation
- Definitive principle
- Revision requires new viable fixation and may need a different construct; do not simply add a liner
- Mechanism or clue
- Persistent discontinuity motion or pain despite a stable cup
- Immediate response
- CT and dynamic clinical assessment
- Definitive principle
- Freshen and graft the nonunion and augment fixation only if the patient can gain function from revision
- Mechanism or clue
- Acute pain, fracture line around a flange or screw
- Immediate response
- Protect the limb and obtain full pelvic and femoral imaging
- Definitive principle
- Treat the fracture, fixation and infection as one reconstruction problem
Postoperative Care and Follow-up
Protect the reconstruction while allowing safe mobility. Most protocols use toe-touch or partial weight bearing initially, hip precautions tailored to the approach and bearing, thrombosis prevention, culture-directed antibiotics and early physiotherapy. A chronic discontinuity or poor bone quality may need longer protection than an uncomplicated contained defect.
At each review assess wound, fever, drainage, sciatic function, leg length, dislocation symptoms and the ability to transfer. Obtain AP pelvis and appropriate cross-table or oblique views. Look for migration, screw breakage, radiolucency, progressive flange separation, cup inclination change and bridging or incorporation at the discontinuity.
Do not declare biological success from early stable radiographs alone. Osseointegration is gradual; a painful or progressively migrating component needs infection and mechanical reassessment. A dislocation requires a cause analysis: component orientation, femoral offset, abductor deficiency, liner choice, approach and patient movement.
Guidelines, Registries & Global Practice
Global evidence. Custom triflange reconstruction is supported mainly by retrospective series and systematic reviews. Early reports demonstrate high rates of radiographic fixation or pelvic union in selected patients, but also substantial complications, particularly dislocation, infection, aseptic loosening, nerve injury and reoperation. A 2019 systematic review of 579 hips reported a mean complication rate of approximately 48%, illustrating why patient selection and counselling are central rather than quoting a single success percentage [1].
Consensus principles:
- Severe acetabular bone loss should be described by a recognised classification, but the classification does not replace a CT-based three-dimensional plan.
- Chronic pelvic discontinuity requires a construct that stabilises the superior and inferior hemipelvic segments; a shell fixed to one mobile segment is not a solution.
- Infection assessment is composite. A sinus, purulence, histology or multiple positive cultures outweigh a falsely reassuring single marker.
- The hip centre, offset, leg length, cup orientation and soft-tissue tension must be considered together. Over-lengthening the limb to gain coverage can injure the sciatic nerve.
- Screw corridors are planned three-dimensionally and checked intraoperatively. Vascular or visceral risk requires specialist imaging and support.
Registries. Large arthroplasty registries report revision burden and failure modes of standard acetabular components, but custom triflange implants are usually too uncommon and heterogeneous for meaningful registry-specific conclusions. Local implant registries should record implant design, defect pattern, chronic discontinuity, infection status, bearing, reoperation and radiographic incorporation so that future evidence is comparable.
Global practice. In centres with advanced imaging and manufacturing, patient-specific design may shorten the intraoperative search for fixation and improve pelvic coverage. In settings without custom manufacturing, a cup-cage, porous augment or staged cage reconstruction may be safer and more reproducible. The underlying principles are universal: control infection, preserve viable bone, obtain fixation in independent pelvic regions and protect the neurovascular and visceral structures.
MCQ Practice Points
Q: What makes a triflange component "custom"? A: The component is designed from the patient's CT to match the residual ilium, ischium and pubis, with planned screw corridors and a planned hip centre. It is not simply a large off-the-shelf cup.
Q: Which bone-loss pattern is the classic setting for a custom triflange? A: Paprosky type IIIB with severe uncontained loss and chronic pelvic discontinuity is the classic setting, but the decision depends on actual CT-defined host bone and fixation corridors rather than the label alone.
Q: Name the three flanges of a custom triflange component. A: Iliac, ischial and pubic. The three zones distribute fixation around the pelvis and bridge a defect that cannot support a hemispherical shell alone.
Q: What is the highest-risk screw problem with a custom triflange? A: A screw that breaches the sciatic notch, pelvic cavity, obturator region or iliac vessels can cause nerve, vascular or visceral injury. Every critical corridor must be planned and checked.
Q: What failure patterns dominate custom triflange complications? A: Instability and infection dominate reported complications. A stable radiograph does not eliminate dislocation risk when abductors, offset, version or the liner are inappropriate.
Survivorship and clinical outcomes of custom triflange acetabular components in revision total hip arthroplasty: a systematic review
- PRISMA systematic review of custom triflange acetabular components: 579 hips across the included series
- High rates of radiographic fixation and pelvic union in selected patients with severe bone loss or pelvic discontinuity
- A substantial overall complication and reoperation burden, with instability and infection recurring across series
- Heterogeneous follow-up and failure definitions limit pooled survivorship estimates
Pelvic discontinuity treated with custom triflange component: a reliable option
- Multicentre series of chronic pelvic discontinuity reconstructed with patient-specific triflange components
- Durable fixation and improved hip function in selected chronic discontinuity reconstructions
- Complications included dislocation and infection - the construct is not a low-risk operation
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 72-year-old has severe pain and a mobile chronic pelvic discontinuity after three revision THAs. The CT shows a deficient posterior column, a thin but intact iliac wing and a previous pelvic cage. Cultures are negative and the patient can walk with two sticks. How do you plan the reconstruction?”
“Three days after custom triflange implantation, CT shows that an anterior screw projects 8 mm beyond the pelvic cortex near the external iliac vessels. The patient has no pulse deficit but has new groin pain. What do you do?”
“A patient dislocates two weeks after custom triflange reconstruction with a dual-mobility bearing. The radiograph shows no obvious migration. What is your structured assessment?”
Indication
- Severe Paprosky IIIB acetabular loss with uncontained segmental and cavitary defects
- Chronic pelvic discontinuity when a hemispherical shell, augment or cup-cage cannot obtain durable fixation
- Requires viable iliac, ischial and pubic bone, controllable infection and reconstructable soft tissue
- Alternatives: porous augments, cup-cage, distraction, cage, allograft composite or amputation
CT plan
- Thin-slice whole-pelvis CT with metal artefact reduction and slice-by-slice review
- Map discontinuity mobility, columns, flange contact, screw corridors and intrapelvic structures
- Approve side, hip centre, inclination, version, length, offset, bearing and every critical screw
- Have a rescue construct and updated scan if the pelvis changes after staging
PIPADRAW
- Position and expose safely; verify the implant model and side
- Prepare cultures, remove failed hardware and debride to viable bone
- Protect sciatic nerve, vessels and viscera; seat all three flanges without rocking
- Drill with stops or navigation, verify orthogonal images and tighten in a controlled sequence
- Close with durable coverage and protect weight bearing until incorporation
Flanges and risks
- Iliac: superior fixation near inner table and superior gluteal bundle
- Ischial: posterior-inferior fixation near sciatic notch and nerve
- Pubic: anterior fixation near obturator structures and bladder
- Major complications: infection, dislocation, loosening, nerve or vascular injury, nonunion
References
- Mancino F, Cacciola G, Di Matteo V, et al. Reconstruction options and outcomes for acetabular bone loss in revision hip arthroplasty. Orthop Rev (Pavia). 2020;12(Suppl 1):8655. PMID: 32913591.
- Taunton MJ, Fehring TK, Edwards P, Bernasek T, Holt GE, Christie MJ. Pelvic discontinuity treated with custom triflange component: a reliable option. Clin Orthop Relat Res. 2012;470(2):428-434. PMID: 21997785.
- Abolghasemian M, Tangsaraporn S, Drexler M, et al. The challenge of pelvic discontinuity: cup-cage reconstruction does better than conventional cages in mid-term. Bone Joint J. 2014;96-B(2):195-200. PMID: 24493184. DOI: 10.1302/0301-620X.96B2.31907.
- Sheth NP, Melnic CM, Paprosky WG. Acetabular distraction: an alternative for severe acetabular bone loss and chronic pelvic discontinuity. Bone Joint J. 2014;96-B(11 Supple A):36-42. PMID: 25381406. DOI: 10.1302/0301-620X.96B11.34455.
- De Martino I, Strigelli V, Cacciola G, et al. Survivorship and clinical outcomes of custom triflange acetabular components in revision total hip arthroplasty: a systematic review. J Arthroplasty. 2019;34(10):2511-2518. PMID: 31213338. DOI: 10.1016/j.arth.2019.05.032.
- Chiarlone F, Zanirato A, Cavagnaro L, et al. Acetabular custom-made implants for severe acetabular bone defect in revision total hip arthroplasty: a systematic review of the literature. Arch Orthop Trauma Surg. 2020;140(3):415-424. PMID: 31960168. DOI: 10.1007/s00402-020-03334-5.
- Martin CT, Callaghan JJ, Liu SS, et al. Dealing with the deficient acetabulum in revision hip arthroplasty. J Bone Joint Surg Am. 2013;95:2201-2210.
- Paprosky WG, Perona PG, Lawrence JM. Acetabular defect classification and surgical reconstruction in revision arthroplasty. A 6-year follow-up evaluation. J Arthroplasty. 1994;9(1):33-44. PMID: 8163974. DOI: 10.1016/0883-5403(94)90135-x.
- Berry DJ, Lewallen DG, Hanssen AD, et al. Pelvic discontinuity in revision total hip arthroplasty. J Bone Joint Surg Am. 1999;81(12):1692-1702. PMID: 10608380. DOI: 10.2106/00004623-199912000-00006.
- Hogan CA, Ries MD. Treatment of massive acetabular bone loss and pelvic discontinuity with a custom triflange component and ilio-sacral fixation based on preoperative CT templating. A report of 2 cases. Hip Int. 2015;25(6):585-588. PMID: 25952919.