Cement mantle retention: filling the hole

[Postoperative imaging of the hip]

CLINICAL ISSUE

To assess postoperative imaging of the hip joint regarding possible complications, it is indispensable to have in-depth knowledge of commonly used surgical techniques, access routes, and the implanted materials.

STANDARD RADIOLOGICAL METHODS

While radiography is used to evaluate the position of foreign material and to rule out periprosthetic fractures that have occurred intraoperatively, follow-up examinations might show signs of material failure, aseptic loosening, prosthesis infections, or the occurrence of heterotopic ossifications. If radiographic findings are ambiguous, computed tomography (CT) may be used to clarify findings, whereas magnetic resonance imaging (MRI) is helpful to identify intra- and periarticular soft tissue pathologies such as surgery-associated cartilage and ligament damage, muscle insufficiency, or metallosis.

METHODOLOGICAL INNOVATION AND EVALUATION

To guide clinical decision making in common postoperative complications, various classification systems are available, e.g., for periprosthetic fractures, aseptic loosening, or heterotopic ossification. However, the differentiation between aseptic material loosening and septic endoprosthesis infection remains challenging if based on imaging alone.

PRACTICAL RECOMMENDATIONS

The assessment of postoperative hip imaging should be closely linked to the respective surgical technique and the implanted foreign material, whereby different probabilities of specific complications can be derived.

Acetabular reconstruction using a composite layer of impacted cancellous allograft bone and cement: minimum 5-year follow-up study

BACKGROUND

Revision total hip arthroplasty (rTHA) is often complex and has a less reliable outcome than primary total hip arthroplasty. Acetabular reconstruction remains a challenge because of the variable amount of bone loss. This study describes and evaluates a novel technique of acetabular reconstruction using composite bone grafting.

PATIENTS AND METHODS

Between June 2005 and January 2012, 108 consecutive patients underwent revision hip arthroplasty in which the acetabular component was revised using composite bone grafting. Of these, 24 were lost to follow-up leaving 84 in the study with a minimum 5-year follow-up. There were 54 women and 30 men with a mean age of 70.1 (31-91) years. All patients were assessed clinically and radiologically after a minimum of 5 years. The primary outcome measures were rate of re-revision, patient-reported outcomes and radiological evidence of loosening.

RESULTS

The mean follow-up after revision surgery was 6.9 years (5-10). At operation, 60 patients had an acetabular defect of AAOS stage 3 or more. There was no evidence of loosening in 69 revision acetabular components; 12 showed evidence of non-progressive loosening and 3 patients underwent a re-revision procedure (2 for infection, 1 recurrent dislocation).The mean postoperative Hip Disability and Osteoarthritis Outcome Score (HOOS) was 89.11/100 (95% CI, 87.8-90.5). Scores were significantly improved in patients with a more extensive preoperative defect (p = 0.006). The overall patient satisfaction rate at final follow-up was very high.

CONCLUSIONS

Composite impaction grafting using a layered cement and bone graft technique can give satisfactory clinical and radiological outcomes in the medium- to long-term.

Management of femoral bone loss in revision total hip arthroplasty

Femoral bone loss is frequently encountered during revision total hip arthroplasty. The quality and quantity of remaining bone helps determine the best method for reconstruction. Extensively porous-coated cylindrical stems or titanium fluted tapered devices that achieve fixation in the diaphysis have both demonstrated excellent long-term survivorship. Titanium fluted tapered stems with a modular proximal body allow for more accurate leg length, offset, and version adjustments independent of the distal stem which may optimise hip biomechanics. Intraoperative fractures are more common with cylindrical stems and subsidence with tapered stems, particularly monoblock designs and in both dislocation continues to be one of the most common postoperative complications. In salvage situations in which an ectatic femoral canal is unable to support an uncemented device, impaction bone grafting, allograft-prosthetic composite, or a segmental proximal femoral replacement may be required.

Factors affecting flexural strength in cement within cement revisions

Cement within cement revisions provide substantial benefits for conventional revision yet remains uncommon possibly because of the perceived weakness of the cement-cement interface. This study investigated the flexural strength of beams composed of 2 different cements, exploring the factors of pore size, fracture location, viscosity, and the surface roughness of the interface. We found no significant difference when comparing combinations of different cements (P = .30), varying pore sizes (P = .13), or surface roughness (P = .39). Differences in fracture locations and viscosity combinations approached statistical significance (P = .08 and .05, respectively). Our findings suggest strong bonding between cements at the interface, with other factors being more important causes of weakness. Thus, we recommend that the strength of the cement-cement interface should not be a factor when considering such revisions.