Implant Removal – Acetabulum

Faculty Operative Technique & Master Lecture: Safe Removal of Well-Fixed and Failed Acetabular Components in Revision Total Hip Arthroplasty (Douglas E. Padgett, MD).

1. High-Yield Summary

• Primary Clinical Indications: Explantation of an acetabular component is indicated for chronic periprosthetic joint infection (PJI) requiring two-stage exchange arthroplasty, progressive symptomatic aseptic loosening with circumferential osteolysis or migration, catastrophic polyethylene liner failure with metallic shell damage, recurrent prosthetic instability driven by severe component malorientation (>55 degrees inclination or excessive anteversion/retroversion), and adverse local tissue reactions (ALTR) associated with trunnionosis or modular interface corrosion.
• The Critical Move: Controlled tangential shearing of the bone-implant interface using specialized curved acetabular osteotomes or cylindrical Explant blades that strictly match the outer convex radius of the shell. Blades must hug the metallic implant contour throughout 360 degrees of rotation, initiating with short blades and progressing to full-depth blades to achieve complete circumferential release before applying any extraction force.
• The Catastrophic Technical Error: Applying high-torque cantilever or levering forces across an incompletely released, well-fixed porous component. This error propagates stress concentrations into structural pelvic columns, precipitating iatrogenic acetabular column fracture, acute pelvic discontinuity, or medial wall blowout with perilous intrapelvic instrument displacement into the external iliac or obturator vascular corridors.
• Host Bone Preservation Principle: Revision reconstruction durability depends directly on the quantity and structural viability of remaining host acetabular bone. Preservation of greater than 50% viable host bone contact permits stable biological fixation using porous hemispherical cups or modular porous augments, avoiding complex custom triflange cages or structural allografts.

2. Indications

Indications and Contraindications

Surgical decision-making regarding whether to retain or remove an acetabular component during revision total hip arthroplasty requires careful evaluation of component stability, position, locking mechanism integrity, and underlying pathology:

• Absolute Indications:
  • Chronic periprosthetic joint infection (PJI) requiring complete implant and cement removal for biofilm eradication during two-stage exchange arthroplasty.
  • Gross mechanical loosening evidenced by progressive radiographic migration, broken fixation screws, or complete circumferential radiolucent lines (>2 mm) across DeLee and Charnley zones I, II, and III.
  • Recurrent prosthetic dislocation secondary to severe acetabular malposition (inclination >55 degrees, anteversion <10 degrees or >30 degrees) where modular elevated-rim or face-changing liners cannot re-establish a stable impingement-free arc of motion.
  • Catastrophic mechanical failure, including complete polyethylene wear-through with severe metallic shell grooving, locking mechanism destruction, or shell fracture.
  • Extensive retroacetabular osteolysis threatening structural column support beneath an unstable or compromised component.
• Relative Indications:
  • Adverse local tissue reaction (ALTR) or metallosis from dual-modular neck taper corrosion or metal-on-metal articulation requiring component exchange to eliminate incompatible geometries or optimize orientation.
  • Well-fixed cup in a patient with recurrent instability where exchange to a dual-mobility construct or constrained liner is planned, but the existing shell locking mechanism is obsolete, unidentifiable, or incompatible with contemporary cemented liner interfaces.
• Contraindications:
  • A well-fixed, well-oriented cementless shell with an intact, undamaged locking mechanism in an aseptic revision setting where modular liner exchange alone accomplishes stability, bearing replacement, or osteolysis debridement.
  • Medically unstable patient with profound systemic comorbidities unable to tolerate extended operative duration or anticipated blood loss.
  • Active pelvic discontinuity where isolated component extraction without structural column stabilization and plating would induce catastrophic pelvic collapse.

3. Preoperative Planning

Imaging Review

Preoperative radiographic assessment requires a structured, multiplanar imaging protocol to define component fixation, orientation, remaining bone stock, and column integrity:

• Standard Radiographic Series: A low anteroposterior (AP) pelvis centered over the pubic symphysis, a true cross-table lateral of the affected hip, and 45-degree Judet iliac and obturator oblique views. The iliac oblique view profiles the posterior column and anterior acetabular rim; the obturator oblique view details the anterior column, posterior rim, and obturator foramen.
• Radiographic Signs of Looseness: Progression of radiolucent lines >2 mm in all three DeLee and Charnley zones, broken or bent transacetabular fixation screws, migration >2 mm superiorly or medially, change in abduction angle >5 degrees, or visible fracture of the surrounding cement mantle. Conversely, the absence of radiolucent lines and presence of stress-shielding osteopenia in Zone II with medial trabecular remodeling suggest rigid osseointegration.
• Advanced Metal-Artifact Reduction CT (MARS-CT): High-resolution CT imaging with 3D multiplanar reconstructions is essential in all revision acetabular cases. MARS-CT quantifies residual anterior and posterior column dimensions, detects retroacetabular cavitary defects hidden on plain radiographs, confirms medial wall breakthrough, tracks screw trajectories relative to retroperitoneal vessels, and rules out pelvic discontinuity by assessing cortical continuity across the sciatic notch and obturator ring.

Equipment Checklist

The operating room must be equipped with specialized explantation tooling and comprehensive revision reconstructive implants prior to incision:

Instrument / Implant Category	Specific System / Tools Required	Intraoperative Function & Purpose
Curved Explantation Blades	Mechanical Explant System (Zimmer/Centerpulse) with full size-matched short and long cylindrical blades	Low-profile circumferential shearing of bone-implant interface hugging the outer metallic shell radius.
Manual Osteotomes & Gouges	Charnley and Moreland curved acetabular osteotomes, flexible thin osteotomes, 1/4-inch straight osteotomes	Controlled peripheral interface disruption, clearing bone overgrowth, and tangential cement mantle sectioning.
High-Speed Burrs	Midas Rex or pneumatic high-speed motor with carbide pencil burrs, egg-shaped burrs, and diamond burrs	Decorticating osteophytes, sectioning polyethylene liners, cutting stripped screws, and trimming cement.
Hardware Removal Set	Universal screw extraction system, reverse-helix conical extractors, trephines, square/hex drivers	Engagement and extraction of stripped, damaged, or deeply countersunk acetabular fixation screws.
Polyethylene Extraction Tools	Modular liner pullers, 3.5 mm self-tapping cortical screws with drill, threaded extraction pins, U-hooks	Disengaging locked polyethylene liners from the metallic shell without damaging host columns.
Revision Reconstruction Armamentarium	Highly porous titanium/trabecular metal revision shells, modular porous augments, revision screws, reconstruction cages	Immediate definitive reconstruction of anticipated Paprosky Type I through Type III acetabular bone defects.

Examination Under Anesthesia (EUA)

Following induction of anesthesia and prior to sterile preparation, perform systematic manual examination of the affected extremity:

• Palpate pelvic stability and test for gross motion across the hemipelvis to identify unappreciated pelvic discontinuity.
• Record baseline passive hip range of motion, assessing fixed flexion, adduction, or rotational contractures that dictate extensive soft-tissue release.
• Verify baseline limb length discrepancies and soft-tissue tension across the abductor complex to guide subsequent reconstructive restoration.

4. Patient Positioning & Setup

Patient positioning must guarantee rigid pelvic stability while permitting full excursion of revision instruments and intraoperative fluoroscopy:

• Lateral Decubitus Position: Position the patient in the lateral decubitus position on a radiolucent operating table supported by a rigid pegboard or adjustable anterior and posterior pelvic positioners. Secure the anterior positioner firmly against the pubic symphysis and the posterior pad against the sacrum, avoiding lumbar lordosis or pelvic tilt that distorts visual orientation.
• Table Alignment Check: Ensure the long axis of the pelvis is strictly perpendicular to the floor. Subtle tilt into extension or flexion alters functional acetabular anteversion and inclination angles during component extraction and subsequent trial re-implantation.
• Peripheral Nerve and Pressure Padding: Place an axillary roll inferior to the dependent axilla to protect the brachial plexus. Pad the dependent peroneal nerve at the fibular neck and place protective gel padding between the lower extremities to prevent pressure necrosis.

Safety Check

Bring the C-arm fluoroscopy unit into the sterile field before final draping to confirm that unobstructed AP pelvis and Judet oblique views can be acquired without colliding with pelvic positioners or table attachments. Verify that high-volume suction, cell saver autotransfusion tubing, and rapid infusers are operational prior to skin incision.

5. Approach

The posterior approach (Kocher-Langenbeck / Moore) is the primary surgical workhorse for revision acetabular surgery, providing comprehensive circumferential exposure of the acetabular rim, posterior column, and retroacetabular space:

• Internervous and Intermuscular Boundaries: Dissection proceeds through the fascia lata and splits the gluteus maximus along its muscle fibers, which are innervated by the inferior gluteal nerve. The plane between the gluteus medius (superior gluteal nerve) and tensor fasciae latae is preserved superiorly. The piriformis, superior gemellus, obturator internus, and inferior gemellus are identified and reflected with stay sutures.
• Sciatic Nerve Mobilization and Protection: The sciatic nerve courses directly posterior to the short external rotators in the retrotrochanteric gutter. In revision procedures, extensive scar tissue frequently tethers the nerve directly to the posterior capsule or extruded cement. The sciatic nerve must be formally identified by palpation and direct visualization, mobilized from surrounding adhesions, and protected with a broad, dull malleable retractor or soft-tissue pad. The knee must be maintained in 30 to 45 degrees of flexion throughout the procedure to relax tension on the nerve trunk.
• Extended Exposure Corridors: If exposure of the acetabulum is obstructed by a retained femoral stem, perform an extended trochanteric osteotomy (ETO) or anterior capsular release to allow safe anterior displacement of the proximal femur without avulsing the abductor mechanism.

6. Technique

Step 1: Exposure and Soft-Tissue Mobilization

Achieving 360-degree visualization of the true acetabular rim is an absolute prerequisite before initiating component extraction:

• Incise the pseudocapsule circumferentially, resecting hypertrophic fibrous tissue and excessive scar envelope.
• Excise all retroacetabular osteophytes and overhanging bone lips using a rongeur or curved osteotome. Retained peripheral osteophytes mechanically entrap the shell rim, preventing axial dislodgement and forcing surgeons into dangerous levering motions.
• Position Retractors: Place an anterior Hohmann retractor over the anterior acetabular rim, maintaining bone contact to avoid femoral neurovascular injury. Position a superior Hohmann into the iliac wing above the dome, and place a bent Hohmann or Meyerding retractor inferiorly beneath the transverse acetabular ligament or into the obturator foramen.

Step 2: Liner and Hardware Removal

Component extraction must proceed in an orderly, stepwise fashion from bearing insert to underlying hardware:

• Extract the Polyethylene Liner: If the locking mechanism does not disengage with standard osteotome tapping, drill a 3.5 mm pilot hole in the non-articular dome of the insert. Drive a 4.5 mm or 6.5 mm cortical screw through the polyethylene until its tip contacts the metallic shell base. Advancing the screw acts as an internal jack, forcing the liner out of the locking rim. Alternatively, section the liner into quadrants with a high-speed pencil burr.
• Locate and Inspect All Screws: Clear fibrous tissue, bone ingrowth, and debris from screw head drive recesses using a fine curette or pick. Completely seat the appropriate screwdriver before applying torque.
• Back Out Supplemental Screws: Remove all transacetabular fixation screws. If a screw head is stripped, apply a reverse-threaded conical screw extractor with axial impaction, or trephine around the screw shank using a hollow core drill. Absolute Safety Check: Never attempt shell explantation until every screw has been confirmed completely removed; attempting extraction over a retained screw causes catastrophic column avulsion.

Step 3: Interface Disruption and Bone Preservation

The method of bone-implant interface disruption depends on whether the component is cementless or cemented:

• Well-Fixed Cementless Components (Explant System Technique):
  • Select the cylindrical Explant blade whose curvature exactly matches the outer diameter of the shell.
  • Anchor the central alignment mandrel into the apex dome hole or central driver thread of the shell to maintain concentric rotation.
  • Engage the short blade first. Oscillate the blade back and forth while maintaining constant gentle inward pressure, keeping the cutting edge flush against the metal shell substrate. The blade shears trabecular osseointegration within 1 to 2 mm of the implant surface.
  • Once the short blade reaches its maximum depth, swap to the longer curved blade to complete equatorial and polar release across the dome.
• Well-Fixed Cementless Components (Manual Curved Osteotome Technique):
  • Utilize thin, flexible curved osteotomes (Charnley or Moreland). Orient the bevel of the osteotome toward the metallic shell and away from the host bone to direct cutting forces along the implant interface.
  • Work circumferentially around the rim in 10- to 15-degree increments, advancing the osteotome only 5 to 10 mm per pass. Avoid driving osteotomes deep in a single quadrant, which risks cortical perforation.
• Cemented Acetabular Cups:
  • Section the all-polyethylene cup into four quadrants using an osteotome or burr, then collapse and remove the segments.
  • Create controlled radial stress-riser grooves in the cement mantle with narrow 5 mm osteotomes.
  • Extract cement fragments tangentially using small gouges and curettes, fragmenting the mantle away from the underlying cancellous trabeculae without prying directly against the thin medial acetabular wall.

Step 4: Cup Extraction and Defect Assessment

Once circumferential interface release is complete, thread the revision cup inserter or vice grip securely onto the component rim or dome. Apply gentle rotational oscillations in internal and external rotation. The shell should rotate freely within the acetabular bed. Deliver the component axially without exerting cantilever levering against the peripheral rim.

Following extraction, thoroughly debride nonviable fibrous tissue, pseudomembrane, and particulate debris with curettes and pulsatile lavage to expose viable, bleeding host cancellous bone. Systematically evaluate remaining acetabular architecture to grade the defect according to the Paprosky Classification.

Critical Move

The single critical move is the continuous visual and tactile verification that the cutting blade remains strictly flush against the outer convex contour of the metallic shell throughout 360 degrees of rotation. The point of no return occurs during equatorial blade advancement: any outward deflection directs the blade away from the implant and deep into the structural bone of the anterior or posterior column, converting an easily manageable Paprosky Type I or II defect into an unstable Type III column loss or catastrophic pelvic discontinuity.

7. Pearls and Pitfalls

Category	Technical Nuance / Strategy	Clinical & Biomechanical Rationale
Surgical Pearl	Pre-drill a 3.5 mm hole and drive a 4.5 mm cortical screw into the polyethylene dome against the metallic shell base.	Generates an internal jacking force that reliably pops stubborn, captured polyethylene liners out of intact locking mechanisms without rim damage.
Surgical Pearl	Maintain continuous sterile saline irrigation on Explant blades during motorized or manual oscillating passes.	Dissipates frictional thermal heat, preventing thermal osteonecrosis of adjacent host trabecular bone and extending blade sharpness.
Surgical Pearl	Advance the short Explant blade fully around 360 degrees before engaging the long blade.	Creates a concentric guide channel that prevents the longer blade from skiving obliquely into structural pelvic bone.
Surgical Pearl	Orient the bevel of manual curved osteotomes toward the metal implant rather than host bone.	Directs the cutting vector inward against the metallic surface, minimizing bone resection to a thin layer <1 mm.
Technical Pitfall	Applying heavy levering torque with a cup extractor when the component remains partially bound.	Induces massive posterior column fracture, converts stable walls into pelvic discontinuity, or causes catastrophic medial wall blowout.
Technical Pitfall	Attempting component extraction with an undetected or sheared screw shank still seated in bone.	Acts as an unyielding mechanical anchor that avulses a massive wedge of host bone when traction is applied.
Technical Pitfall	Using straight osteotomes tangentially across the acetabular rim to free deep polar ingrowth.	Straight blades cannot conform to spherical cup geometry and inevitably exit through the medial or posterior column cortex.
Technical Pitfall	Failing to identify and release peripheral retroacetabular osteophytes prior to shell extraction.	Creates a mechanical bottleneck that traps the equatorial diameter of the cup, resisting extraction even after complete interface release.

8. Postoperative Care

Immediate Postoperative Protocol

Postoperative management is governed by the structural stability of the subsequent acetabular reconstruction:

• Weight-Bearing Status: If a rigid press-fit revision shell with robust multi-screw fixation was achieved in an intact acetabular bed (Paprosky Type I or II), patients may initiate weight-bearing as tolerated (WBAT) with a walker. If structural bone grafting, modular porous metal augments, or reconstruction cages were required for column loss (Paprosky Type III), restrict weight-bearing to flat-foot touch-down weight-bearing (TDWB, <20 lbs) for 6 to 12 weeks to protect biological osseointegration.
• Venous Thromboembolism (VTE) Prophylaxis: Administer dual-modality thromboprophylaxis combining intermittent pneumatic compression devices with direct oral anticoagulants (DOAC, e.g., apixaban 2.5 mg BID) or low-molecular-weight heparin (enoxaparin 40 mg daily) for 35 days postoperatively.
• Dislocation Precautions: Maintain standard posterior hip precautions (avoiding flexion >90 degrees, internal rotation, and adduction across the midline) for 6 to 12 weeks, especially in patients revised for recurrent instability or abductor compromise.

Rehabilitation Protocol

Rehabilitation Phase	Timeline	Weight-Bearing & Activity Restrictions	Therapeutic Exercise Goals
Phase I: Protection	Weeks 0 to 6	Touch-down weight-bearing (TDWB) or WBAT per reconstructive stability; walker/crutches	Ankle pumps, isometric quadriceps/gluteal sets, gentle active-assisted hip ROM within safety precautions.
Phase II: Transition	Weeks 6 to 12	Advance to partial weight-bearing (50%), progressing to full weight-bearing with cane by week 10	Closed-kinetic-chain strengthening, stationary cycling with high seat, abductor strengthening, balance exercises.
Phase III: Strengthening	Weeks 12 to 24	Full weight-bearing without assistive devices; unconstrained community ambulation	Progressive resistive hip exercises, core stabilization, gait retraining, low-impact aerobic conditioning.
Phase IV: Maintenance	>24 Weeks	Full unrestricted daily activities; avoidance of high-impact ballistic sports	Long-term functional maintenance, joint protection education, annual clinical and radiographic follow-up.

9. Outcome

Clinical and radiographic outcomes following acetabular component revision correlate directly with the amount of viable host bone preserved during explantation:

• Host Bone Preservation and Implant Survivorship: Preservation of greater than 50% viable host bone contact allows biological hemispherical press-fit fixation, yielding 10-year survivorship free from aseptic loosening exceeding 92% to 95%. When excessive host bone is sacrificed during explantation requiring structural allografts or massive cages, 10-year failure rates increase significantly, with mechanical failure reported in 15% to 25% of complex reconstructions.
• Functional Outcome Scores: Patients successfully revised with bone-preserving techniques achieve substantial gains in validated outcome metrics, with mean Harris Hip Scores improving from 45 to 52 preoperatively to 82 to 88 at mid-term follow-up. Pain relief is achieved in over 90% of patients without pelvic discontinuity.
• Comparative Explantation System Efficacy: Clinical studies evaluating mechanical curved blade explantation systems demonstrate significantly reduced operative time (mean reduction of 20 to 35 minutes) and significantly lower rates of structural column fractures compared to manual straight osteotome extraction techniques.

10. Complications

Acetabular explantation is associated with significant potential intraoperative and perioperative morbidities:

Complication	Incidence Rate	Primary Mechanism & Risk Factors	Prevention & Rescue Strategy
Acetabular Column Fracture	2.0% to 5.0%	Excessive cantilever levering against unreleased cups; eccentric osteotome advancement.	Use matched curved blades; identify resistance immediately; stabilize fracture with posterior column plates or modular augments.
Pelvic Discontinuity	1.0% to 3.0%	Deep bone loss across the anterior and posterior columns connecting to the obturator ring.	Recognize discontinuity on CT; reconstruct with dual-column structural plating, porous distraction augments, or custom triflange cages.
Sciatic Nerve Neuropraxia	1.5% to 3.5%	Excessive retractor traction, direct thermal injury from burrs, or entrapment in scar.	Formally mobilize nerve; maintain knee at 45 degrees flexion; avoid posterior retractor levering; release traction intermittently.
Major Vascular Laceration	<0.5%	Medial wall perforation or anterior retractor displacement into external iliac vessels.	Stay within safe Waschke zones; keep retractors directly on bone; avoid driving osteotomes through the medial quadrilateral plate.
Excessive Host Bone Loss	4.0% to 8.0%	Straight osteotome skiving; aggressive high-speed reaming of well-fixed shells.	Utilize circumferential Explant system; shear bone within 1 mm of implant interface; assess defect before revision reaming.
Recurrent Instability / Dislocation	5.0% to 10.0%	Abductor insufficiency, extensive capsular debridement, or revision component malorientation.	Restore native center of rotation and offset; verify 40-degree inclination and 20-degree anteversion; consider dual-mobility bearings.

11. Anatomic Danger Zones & Pelvic Neurovascular Safety

Safe navigation of the acetabular perimeter during screw removal and blade explantation requires mastery of pelvic quadrant anatomy based on the Waschke coordinate system:

• Waschke Quadrant System: Constructed by drawing a primary line from the anterior superior iliac spine (ASIS) through the center of the acetabulum to the fovea, and a secondary perpendicular line bisecting the primary axis. This divides the socket into four distinct quadrants:
  • Posterosuperior Quadrant (Safe Zone): Contains the thickest bone stock of the posterior column and iliac wing. Transacetabular screws can be placed safely up to 35 to 50 mm without exiting cortical bone. However, over-penetration beyond the sciatic notch endangers the superior gluteal neurovascular bundle.
  • Posteroinferior Quadrant (Caution Zone): Contains the ischial bone bed. Screws placed here must not exceed 25 mm to prevent penetration into the lesser sciatic notch, which endangers the internal pudendal vessels and sciatic nerve.
  • Anterosuperior Quadrant (Danger Zone): Directly abuts the external iliac artery and vein lying on the inner pelvic brim. Retractors placed over the anterior rim must never penetrate the iliopsoas belly. No fixation screws should ever be directed into this quadrant.
  • Anteroinferior Quadrant (Danger Zone): Overlies the obturator canal containing the obturator nerve, artery, and vein. Screws directed here risk vascular laceration and catastrophic intrapelvic hemorrhage.
• Medial Wall (Quadrilateral Plate) Danger Zone: The medial acetabular wall is paper-thin (<2 to 3 mm) in dysplastic or osteolytic hips. Aggressive impaction of osteotomes or unguided burr debridement risks violating the quadrilateral plate, displacing instruments into the retroperitoneal space adjacent to the bladder and internal iliac venous plexus.

12. Acetabular Bone Loss & Defect Classification

Following successful explantation, acetabular bone deficiency must be classified to guide appropriate reconstructive strategy. The Paprosky Classification serves as the international standard:

Paprosky Defect Type	Anatomic Characteristics & Rim Status	Ischial Lysis / Kohler’s Line	Recommended Reconstructive Strategy
Type I	Hemispherical rim fully intact; minor focal cavitary defects; columns rigid.	No ischial lysis; Kohler’s line intact; <1 cm migration.	Standard cementless hemispherical porous shell with multi-screw fixation.
Type IIA	Superior-medial rim distortion; intact columns; cavitary lysis <2 cm.	Mild ischial osteolysis; Kohler’s line intact; <2 cm superior migration.	High-hip center placement or standard porous shell with screw fixation and particulate bone grafting.
Type IIB	Superior-lateral rim deficiency <one-third circumference; columns intact.	No teardrop migration; Kohler’s line intact; <2 cm migration.	Jumbo hemispherical porous cup (≥62 mm) or modular porous metal buttress augment.
Type IIC	Medial wall blowout/deficiency; intact peripheral rim and columns.	Teardrop destruction; Kohler’s line breached; medial migration.	Porocoat/trabecular metal cup with medial impaction bone grafting or porous mesh.
Type IIIA	Severe superior rim loss (one-third to one-half circumference); posterior column intact.	Moderate teardrop lysis; ischial lysis <1.5 cm; 2 to 3 cm “up-and-out” migration.	Modular porous metal augments, porous revision shell, structural trabecular buttress.
Type IIIB	Massive column destruction (>one-half circumference); severe anterior and posterior column deficiency.	Severe ischial osteolysis (>1.5 cm); Kohler’s line disrupted; >3 cm “up-and-in” migration.	Cup-cage construct, custom triflange acetabular component (CTAC), or dual-column plating with augments.
Pelvic Discontinuity	Complete transverse fracture separating superior ilium from inferior ischiopubic segment.	Complete mobility of inferior hemipelvis; severe gap across posterior column.	Distraction porous augments with plating, double-column locking plate fixation, or custom triflange cage.

13. Evidence-Based Synthesis

Modern clinical decision-making is grounded in high-quality randomized controlled trials and prospective registry analyses, corroborated by seminal biomechanical and anatomical descriptions.

Clinical Question / Investigation	Level of Evidence	Pivotal Landmark Study	Study Design & Methodology	Cohort Size / Follow-up	Primary Outcome / Effect Size	DOI
What are the comparative mechanisms, efficacy, and bone-loss profiles of modern acetabular removal systems?	Level IV	Njoku I, Surace P, Piuzzi NS et al (2023)	Systematic Surgical Review	Comprehensive systematic review of modern mechanical explantation devices	Identifies curved blade removal systems as significantly reducing operative time and minimizing host bone loss compared to straight osteotomes.	DOI
How do bone preservation and complication rates compare between curved osteotomes and the Explant system during well-fixed cup removal?	Level III	Adelani MA, Goodman SB, Maloney WJ et al (2016)	Comparative Cohort Study	Comparative cohort of 68 patients undergoing well-fixed cementless acetabular component revision	Demonstrated that mechanical explant systems preserved host bone stock with lower rates of intraoperative acetabular column fracture.	DOI
What surgical techniques preserve acetabular bone stock during component removal in revision total hip arthroplasty?	Level IV	Paprosky WG, Weeden SH, Bowling JW Jr (2001)	Seminal Surgical Technique & Classification Series	143 revision total hip arthroplasties evaluated for component removal and defect reconstruction	Established foundational classification of acetabular bone loss and safe explantation techniques avoiding pelvic discontinuity.	DOI
How effective is the Explant system in extracting monoblock or thin-walled well-fixed resurfacing cups without extensive pelvic osteotomy?	Level V	Bhutta MA, Gambhir A (2009)	Technical Innovation & Clinical Report	Technical series of challenging monoblock metal-on-metal cup explantations	Successful extraction of thin-walled well-fixed components with complete preservation of the native acetabular rim and columns.	DOI
What sequential surgical techniques optimize bone preservation during explantation of well-fixed cemented acetabular cups?	Level V	Stevens J, Macpherson G, Howie C (2018)	Surgical Technique & Biomechanical Review	Biomechanical and surgical analysis of controlled crack propagation and cement fragmentation	Controlled tangential cement fragmentation prevents deep column crack propagation and maintains stable structural bone bed.	DOI

14. References

• Njoku I, Surace P, Piuzzi NS et al. Acetabular Component Removal Systems. JBJS Rev. 2023. doi:10.2106/JBJS.RVW.22.00246 [Level IV: Systematic Surgical Review]
• Adelani MA, Goodman SB, Maloney WJ et al. Removal of Well-Fixed Cementless Acetabular Components in Revision Total Hip Arthroplasty. Orthopedics. 2016. doi:10.3928/01477447-20160129-04 [Level III: Comparative Cohort Study]
• Paprosky WG, Weeden SH, Bowling JW Jr. Component removal in revision total hip arthroplasty. Clin Orthop Relat Res. 2001. doi:10.1097/00003086-200112000-00021 [Level IV: Seminal Surgical Technique & Classification Series]
• Bhutta MA, Gambhir A. Using the Explant Acetabular Cup Removal System for removing a well-fixed resurfacing cementless acetabular component. Ann R Coll Surg Engl. 2009. doi:10.1308/rcsann.2009.91.4.344a [Level V: Technical Innovation & Clinical Report]
• Stevens J, Macpherson G, Howie C. Bone preserving techniques for explanting the well-fixed cemented acetabular component. J Orthop. 2018. doi:10.1016/j.jor.2018.03.037 [Level V: Surgical Technique & Biomechanical Review]

15. Master Class Pro-Tip

When explanting a rigidly ingrown porous acetabular component, the master surgeon never uses the extraction handle as a lever against the peripheral bone rim. If resistance persists after completing circumferential blade passes, do not increase extraction torque. Stop and inspect the inner dome for hidden, sheared screw shanks or localized hydroxyapatite bridges anchoring the polar shell. Use a 2 mm pencil carbide burr to precisely disconnect stubborn osseous bridges at the bone-metal interface under direct vision. Preserving 2 millimeters of native subchondral bone stock converts what would be a complex custom triflange cage or structural allograft procedure into a straightforward biological jumbo cup reconstruction.

Master Class Surgical Pearl: Acetabular Component Explantation and Bone Preservation