Surgical techniques 2022, Dec, 21 | 12:00 am

Revision Total Hip Arthroplasty With Acetabular Bone Loss: Impaction Allografting

 

 

 

DEFINITION

  • Acetabular bone loss remains a challenge to the joint reconstruction surgeon.

  • Bone loss may be the result of trauma, acetabular dysplasia, tumor, infection, implant loosening, or osteolysis.

  • Primary reconstruction methods often are inadequate to restore bone loss.

  • Acetabular impaction grafting restores bone stock by using tightly impacted, well-contained cancellous bone graft.

  • The goal of impaction bone-grafting is to achieve immediate implant stability with the use of compacted, morselized bone graft. In turn, this allows the restoration of bone stock through bone remodeling.

  • Impaction bone grafting is suitable for simple cavitary defects as well as extensive segmental defects.

    • Stainless steel mesh is used to convert segmental defects (medial wall or peripheral) into contained cavitary defects suitable for impaction grafting.

  • Impacted bone graft provides an excellent bed for cement interdigitation, which confers immediate mechanical stability and acts as a substrate promoting bone remodeling, allowing bone stock restoration.

  • Acetabular impaction grafting has shown good long term results.7–10

  • Standard implants and current cement techniques often are used.

     

    ANATOMY

  • The acetabulum is a complex three-dimensional structure.

  • It is important to identify relevant landmarks intraopera-tively, such as the transverse acetabular ligament, medial wall, anterior and posterior walls and columns, and superior dome (FIG 1).

  • Bone impaction grafting combined with a cemented polyethylene cup allows for the restoration of the hip center and normal hip biomechanics.

     

    PATHOGENESIS

  • Animal studies show that impacted, morselized fresh-frozen allograft bone incorporates into new bone.6

  • Twenty-four acetabular bone biopsy specimens were obtained from 20 patients who had undergone acetabular reconstruction with impaction bone grafting.11

    • Biopsy specimens were obtained at 3 months to 15 years.

    • Histology showed rapid revascularization of the graft followed by osteoclastic resorption and woven bone formation on the graft remnants.

    • A mixture of graft, new bone, and fibrin remodeled completely into a new trabecular structure, with normal lamel-

  • Localized areas of nonincorporated bone graft surrounded by fibrous tissue remained, irrespective of the follow-up period.

  • Large nonincorporated fragments of cartilage also were found, particularly in cases in which femoral head bone chips were produced by a bone mill.

  • Despite the contact between bone graft and cement, the bone graft retains its biologic and mechanical viability and healing potential.5

    NATURAL HISTORY

  • Reports on acetabular impaction grafting show promising intermediate and long-term results.4,7–10

     

    PATIENT HISTORY AND PHYSICAL FINDINGS

  • It is important to obtain a thorough history from the patient with a failed acetabular component.

    • A history of persistent infection should be ruled out.

  • Physical examination should include examination of previous incisions, sinus tracts, range of motion, leg-length discrepancy, neurovascular status, and contractures.

  • Records of previous surgeries should be obtained.

     

    IMAGING AND OTHER DIAGNOSTIC STUDIES

     

     

  • The initial diagnostic imaging examination should begin with standard AP pelvis and AP and lateral radiographs of the affected hip.

 

Rectus femoris tendon

 

Acetabular labrum

 

Transverse acetabular ligament

lar bone and only scarce remnants of graft material. FIG 1 • Anatomy of the acetabulum.

 

 

 

 

 

  • A CT scan may useful in identifying bone loss and structural defects.

  • The actual bone defects or bone loss may be more severe than preoperative radiographic studies reveal.12

  • A preoperative work-up for infection should be performed.

    • Laboratory studies, including a complete blood cell count with differential, erythrocyte sedimentation rate, and C-re-active protein, should be obtained.

    • If laboratory values are elevated or suspicious for infection, a fluoroscopic guided aspiration should be perfromed and sent for cell count, Gram stain, and cultures to rule out infection.

      DIFFERENTIAL DIAGNOSIS

  • Alternative methods of fixation include cemented acetabular revision, revision with structural allograft, uncemented acetabular components with structural allograft, uncemented components with metal augments, jumbo acetabular components, and trabecular metal acetabular components.

  • In cases of pelvic discontinuity or severe anterior or posterior column defects, alternative techniques of reconstructions such as cages, plates and screws, or trabecular metal implants may be necessary.

    NONOPERATIVE MANAGEMENT

  • No nonoperative techniques are available for reconstruction of the failed acetabulum.

    SURGICAL MANAGEMENT

    Preoperative Planning

  • Precise preoperative templating is necessary to restore the acetabular component to its anatomic position to reestablish the native hip center.

    Positioning

  • The patient is positioned according to the surgeon’s preference and planned surgical approach. This technique is applicable to most patient positions and surgical techniques.

    Approach

  • Any surgical approach that allows full acetabular exposure can be used. It is important that the surgeon use an approach that is both familiar and extensile.

  • Wide exposure and identification of the major landmarks of the acetabulum are necessary.

     

     

    TECHNIQUES

     

    ACETABULAR EXPOSURE

    • A wide exposure of the acetabulum is necessary. The femur may be mobilized or a femoral osteotomy performed to improve acetabular exposure. Removal of the femoral stem may be necessary to gain unimpeded exposure of the acetabulum.

      • Circumferential capsulotomy often is necessary.

      • Iliopsoas release may be necessary.

 

  • The previous acetabular components are removed using traditional implant removal techniques and care must be taken to avoid additional bone damage.

  • Any residual cement must be removed.

  • Fibrous tissue and necrotic bone are débrided until viable bleeding bone is encountered.

  • Acetabular bone defects are identified.

     

    ACETABULAR PREPARATION

    • An acetabular reamer is used to remove sclerotic cortical bone to expose bleeding trabecular bone. Multiple drill holes (2 mm) may be used to create bleeding in areas of extremely sclerotic bone.

    • The acetabulum is irrigated with pulsatile lavage.

    • The anatomic position for the acetabular component is identified.

      • Because there may be severe anterior, posterior, or superior bony deficiencies, this is best done by first locating the inferior portion of the acetabulum and transverse acetabular ligament.

      • A trial acetabular component may be used to identify bone deficiencies and estimate the amount and location of bone graft needed.

    • Segmental defects are converted into cavitary defects with flexible wire mesh and screws (X-change Revision Instrument System, Stryker Orthopaedics, Mahwah NJ).

      • This mesh is precontoured but may be trimmed and adapted to fit the identified acetabular defects.

         

  • Medial segmental defects may be covered with metal mesh.

    • Usually the mesh is stable without screws; however, small screws may be used for initial mesh stability.

    • If the medial wall is found to be intact but weak, mesh may be used to prevent fracture or medial graft migration during impaction (TECH FIG 1A).

  • Peripheral wall defects are identified.

    • Complete exposure of the peripheral rim with sub-periosteal dissection is performed to avoid injury to surrounding neurovascular structures such as the superior gluteal nerve and vessels.

    • Peripheral mesh is applied to the outer side of the acetabular rim with bicortical screws at a minimum of three points (TECH FIG 1B).

    • If necessary, the wire mesh may be applied to the inner surface of the acetabulum and fixed with screws.

       

       

       

       

      Defect

      Stainless steel mesh

       

       

      TECHNIQUES

       

      Stainless steel mesh

       

      Superolateral wall defect

       

       

      A Medial wall defect B

      TECH FIG 1 • After removal of a failed acetabular component, stainless steel wire mesh and screws are used to reconstruct a central medial wall defect (A) and a peripheral superolateral defect (B).

       

      PREPARATION OF BONE GRAFT

    • Allograft bone from fresh-frozen femoral heads is used. If autogenous bone is available, this may be mixed with the allograft bone. Usually at least two femoral heads are needed. Large defects require more graft material. The allograft is thawed and débrided of all soft tissue before it is used.

    • A 7- to 10-mm bone chip is recommended,1 in contrast to the smaller bone graft size used with femoral impaction grafting.

    • Soft tissue and cartilage must be removed from the bone graft.

       

    • The femoral head is divided into four parts with a saw and morselized using a rongeur into 7- to 10-mm bone chips.

    • Alternatively, commercially available bone mills may be used. Most bone mills produce graft sized for femoral impaction grafting, which may be too small for acetabular impaction grafting.

  • Larger bone graft size and the removal of excess fat and soft tissue with mechanical débridement and warm saline lavage enhances initial stability.1,3

     

    ACETABULAR BONE RECONSTRUCTION

    • The acetabulum is irrigated with pulsatile lavage.

    • Small cavitary defects are first packed with graft. Then bone graft is impacted into the acetabular cavity layer by layer to construct an anatomically located neoacetabulum.

      • Vigorous impaction using specialized impactors is necessary. A small impactor should be used initially for graft impaction and gross acetabular reconstruction, and then progressively larger impactors should be used to shape the neoacetabulum (TECH FIG 2).

      • Reverse reaming with an acetabular reamer should be avoided, because this technique has shown inferior results.2

  • When performed correctly, the bone graft will be stable in the acetabulum even after the impactors are removed.

    • At least 5 mm of impacted graft is necessary to prevent overpenetration of cement into the host bone–graft interface.

  • The last impactor should be approximately 4 mm larger than the acetabular cup to be placed. This allows for an adequate cement mantle.

  • Once impacted, the bone graft and bed should not be irrigated with pulsatile lavage.

     

     

     

    TECHNIQUES

     

    Stainless steel mesh

     

     

    Stainless steel mesh

     

     

    Cancellous bone chips

    Cancellous bone chips

     

    Impactor

     

    A B

    TECH FIG 2 • A. The defect is filled with allograft bone chips. B. The bone chips are vigorously impacted using specialized bone impactors of progressively larger size

     

    CEMENTED CUP INSERTION

    • The acetabular bed is thoroughly dried. Hydrogen peroxide may be used to clean and dry the acetabular bed.

    • Vacuum-mixed antibiotic-loaded cement is prepared using the technique of choice. While still in a relatively viscous state, the cement is placed in the acetabular bed. A cement pressurizer is used to introduce the cement into the impacted bone graft (TECH FIG 3A).

       

  • An all-polyethylene cup is implanted using the alignment guide and insertion handle of the surgeon’s choice (TECH FIG 3B). The cup is held in position with a cup pusher until the cement hardens.

     

     

    Stainless steel mesh

    Cancellous bone chips Cement

    Cancellous bone chips

    Stainless steel mesh

     

    Cement

     

     

    Polyethylene cup

     

    A B

    TECH FIG 3 • A. After a stable bone graft thickness of at least 5 mm has been obtained, antibiotic-impregnated cement is pressurized into the bone graft. B. An all-polyethylene cup is then inserted into the cement mantle.

     

     

     

     

    PEARLS AND PITFALLS

    Acetabular exposure ■ Wide acetabular exposure is necessary to identify and contain bone defects with wire

    mesh. Be cautious of neurovascular structures.

    Acetabular preparation ■ Sclerotic bone should be reamed or drilled with a 2-mm drill. Bone graft preparation ■ Fresh-frozen bone femoral head is the ideal graft.

    • Remove all soft tissue and cartilage.

    • Bone graft should be 7 to 10 mm3.

    • Commercial bone mills often produce smaller graft sizes.

    • Irrigate graft with warm saline prior to impaction.

    • Do not irrigate the graft once it is impacted.

      Acetabular bone reconstruction ■ Vigorous impaction with specially designed impactors is necessary to provide initial me-

      chanical stability of the graft.

    • Overimpaction may cause fractures.

    • Reverse reaming with acetabular reamers should be avoided.

    Cemented cup insertion ■ Optimal cup placment is necessary to restore the anatomic center, thereby limiting instability.

     

     

    POSTOPERATIVE CARE

    • Postoperative protocols are according to the surgeon’s preference. Anticoagulation and periooperative antibiotics are recommended.

    • Prophylaxis for heterotopic ossification should be considered.

    • Patients are toe-touch weight-bearing for 6 weeks, followed by partial weight bearing with crutches or a walker for another 6 weeks.

    • Interval-appropriate radiographs are recommended.

      OUTCOMES

    • Schreurs and Bolder7 reported on 62 consecutive acetabular revisions in 58 patients with acetabular impaction bone grafting and a cemented cup at an average follow-up of 16.5 years and found an overall survival rate of 79% and a 84% survival rate when aseptic loosening was used as an endpoint.

    • Schreurs and Busch8 reported a 20-year survival rate of 91% with aseptic loosening as an endpoint in patients younger than 50 years of age. The overall survival in this patient population was 80% when acetabular revision for any reason was evaluated.

    • Schreurs and Thien,10 using a similar technique in 35 hips in patients with rheumatoid arthritis, demonstrated a prosthetic survival rate with aseptic loosening as the endpoint of 90% at 8 years.

    • Pitto4 reported on 81 patients treated with impaction bone grafting and reinforcement rings. At an average of 6.5 years, only one patient had a revision because of dislocation. All grafts demonstrated graft incorporation at 3 months.

      COMPLICATIONS

    • Complications generally related to revision hip arthroplasty, such as infection, instability, hematoma, and neurovascular injury, can occur.

    • Wide acetabular exposure puts neurovascular structures such as the superior gluteal nerve and vessels at risk.

    • Intraoperative fractures may occur due to overimpaction of the bone graft.

    • Potential infection or graft-versus-host disease theoretically may occur as a result of the bone graft material. Eradication of infection may require resection arthroplasty.

REFERENCES

  1. Arts JJ, Verdonschot N, Buma P, et al. Larger bone graft size and washing of bone grafts prior to impaction enhances the initial stability of cemented cups: experiments using a synthetic acetabular model. Acta Orthop 2006;77:227–233.

  2. Bolder SB, Schreurs BW, Verdonschot N, et al. Particle size of bone graft and method of impaction affect initial stability of cemented cups: human cadaveric and synthetic pelvic specimen studies. Acta Orthop Scand 2003;74:652–657.

  3. Dunlop DG, Brewster NT, Madabhushi SP, et al. Techniques to improve the shear strength of impacted bone graft: the effect of particle size and washing of the graft. J Bone Joint Surg Am 2003;85A: 639–646.

  4. Pitto RP, Di Muria GV, Hohmann D. Impaction grafting and acetabular reinforcement in revision hip replacement. Int Orthop 1998;22: 161–164.

  5. Roffman M, Silbermann M, Mendes DG. Viability and osteogenicity of bone graft coated with methylmethacrylate cement. Acta Orthop Scand 1982;53:513–519.

  6. Schimmel JW, Buma P, Versleyen D, et al. Acetabular reconstruction with impacted morselized cancellous allografts in cemented hip arthroplasty: a histological and biomechanical study on the goat. J Arthroplasty 1998;13:438–448.

  7. Schreurs BW, Bolder SB, Gardeniers JW, et al. Acetabular revision with impacted morsellised cancellous bone grafting and a cemented cup: a 15- to 20-year follow-up. J Bone Joint Surg Br 2004;86B: 492–497.

  8. Schreurs BW, Busch VJ, Welten ML, et al. Acetabular reconstruction with impaction bone-grafting and a cemented cup in patients younger than fifty years old. J Bone Joint Surg Am 2004;86A: 2385–2392.

  9. Schreurs BW, Slooff TJ, Buma P, et al. Acetabular reconstruction with impacted morsellised cancellous bone graft and cement: a 10- to 15-year follow-up of 60 revision arthroplasties. J Bone Joint Surg Br 1998;80B:391–395.

  10. Schreurs BW, Thien TM, de Waal Malefijt MC, et al. Acetabular revision with impacted morselized cancellous bone graft and a cemented cup in patients with rheumatoid arthritis: three to fourteen-year follow-up. J Bone Joint Surg Am 2003;85A:647–652.

  11. van der Donk S, Buma P, Slooff TJ, et al. Incorporation of morselized bone grafts: a study of 24 acetabular biopsy specimens. Clin Orthop Rel Res 2002:131–141.

  12. Walde TA, Weiland DE, Leung SB, et al. Comparison of CT, MRI, and radiographs in assessing pelvic osteolysis: a cadaveric study. Clin Orthop Relat Res 2005;(437):138–144.