Periprosthetic fractures, management of the hip and the knee

AAOS classifications¹⁰  use five main defect types and three sub-types:

I. Segmental defect
II. Cavitary defect
III. Combined segmental and cavitary defect
IV. Pelvic discontinuity
A. With mild segmental or cavitary loss
B. With moderate to severe segmental or cavitary loss
C. With prior pelvic irradiation
V. Hip arthrodesis (fusion)

The Paprosky Classification system for acetabular bone¹¹

The Paprosky classification system is also widely used. While this only specifies three main classes, i.e., degrees of severity, Type II includes three sub-types and Type III includes two. To arrive at a classification, we evaluate the defect based on four variables: femoral head migration, ischial osteoporosis, the Kohler line, and the teardrop.

Correcting for acetabular bone defects

Impaction grafting

For simple segmental or combined structural bone defects (AAOC I, III; Paprosky IIA, B, C) , impaction grafting and cementation can be used with a metal mesh to contain and strengthen the bone-deficient areas. In addition to restoring the bone stock, the mesh allows the surgeon to cement a polyethylene liner into place.

Non-cemented hemispherical acetabular reconstruction

Another possibility is a non-cemented hemispherical acetabular reconstruction. This requires column and partial rim support, e.g., via screws, as well as supplemental fixation. Various fixation options, including porous metal implants, are available to enhance stability and promote biological fixation. Structural allografts are also possible.¹²

Structural allograft reconstruction

A third possibility, where the host acetabular bone is inadequate for stable component fixation, is structural allograft reconstruction.¹³  For hip acetabular reconstruction, allografts have largely been replaced by porous metal augmentations; however, if those are unavailable, allografts still offer satisfactory mid- and long-term results.

Modular porous metal augments

For Paprosky types II, IIIA and IIIB (superior rim defects), non-cemented hemispheric or elliptical components are indicated, in combination with modular augments. This type of augment both supports the acetabular component while bone grows in.¹⁴

Oblong cup implant

For Paprosky types IIB and IIIA, an oblong cup provides mechanical stability on the host bone, with relatively little bone removal required to match the defect.¹⁵   However, bear in mind that an oblong cup covers and replaces the defective bone rather than reconstructing it. Therefore, if any future revision is necessary, the surgeon will have much less bone to work with.

Ring and Case reconstruction

In contrast to the oblong cup, the roof reinforcement ring (e.g., a Ganz ring) and the antiprotrusio cage (e.g., a Burch-Schneider cage) are designed both to provide a scaffold for bone growth and to protect allografted tissue during the remodeling phase. These are recommended for AAOS Types III and IV.

As well as allowing a liner to be positioned independently of the ring position using antibiotic-treated cement, this system facilitates the elution of antibiotics from that cement. However, roughly 20% of cages fracture or loosen within 10 years.¹⁶

Kerboull-Tanaka plate and allograft

The Kerboulli-Tanaka plate is an excellent choice for acetabular reconstruction. Designed by Kerboulli and modified by Tanaka, this plate guides reconstruction of bone stock, particularly in the hip center. This is advantageous if revision becomes necessary. A long-term reliability study by Kim et al. (2015) indicated 10-year survival rates >94%.¹⁷

Summary:

Revision surgery in acetabular and femoral bone defect demands an evaluation of the bone loss.

Key treatment concerns are good bone restoration and rigid fixation of the component.

Bone loss may be addressed via an acetabular revision system or a (cemented or cementless) stem system with morselized or structural allograft.

Periprosthetic Joint Infection (PJI)

As the number of people who need arthroplasty is increasing, so is the number of infections. Outcomes include morbidity and mortality. In areas where few people have health insurance, treatment is also very expensive.

Dealing efficiently with an infection requires a combination of knowledge and experience. So, for surgeons who only see a small number of infections per year, it is essential to read and understand the literature and to participate either in webinars or in actual operations whenever possible.

Additional team members will be necessary

Tackling this type of problem requires a high level of teamwork. In addition to the usual surgical team members, an infection team includes a microbiologist, a histobiologist experienced with joint and bone infection, and a pathophysiologist to identify the origin of whatever is found. Clear radiological images and a full set of laboratory results will also be necessary.

That is, finding a reliable diagnosis for PJI requires a combination of clinical evidence. Once we are certain the joint is infected, we need to identify the organism responsible, its origin and route. Then we can choose the appropriate antibiotics both to treat it and to prevent its recurrence.

Preoperative testing

Preoperative exploration requires hematological testing. For example, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) tests will give important information on inflammation, as will medical imaging, including X-rays and PET scans. The synovial fluid will need to be tested. If a culture can be identified, is it gram-positive or -negative? Leukocyte and leukocyte esterase counts will also be necessary.

Intraoperative testing

Intraoperative tissue samples can provide vital histopathology and gram information. There are also several new methods that can be very useful. In Indonesia, for example, surgeons have access to polymerase chain reaction (PCR), but not sonication, microcalorimetry or mass spectrometry.

International Consensus Group (ICG) criteria

The International Consensus Group offers a similar set of criteria. While their major criteria are that same as those of the MSIS, their scoring system is simpler: The presence of any three of the five minor criteria indicates an infection. ¹⁸

Preventive preoperative antibiotics: Timing is important

According to WHO guidelines, preventive preoperative antibiotics should be started one hour before surgery, then discontinued after 24 hours.

Intraoperative cultures are still necessary

Very early Tsukuyama Type I¹⁹ infections may not yield positive preoperative test results. Therefore, intraoperative tissue samples should be taken from multiple locations. If a notable infection is detected, it may be necessary to procede with the operation in stages.

For longer-term infections, the Zimmerli classification system may be more useful.

Route of infection

Infections can be introduced via wounds, during surgery, or hematogenously. Hematogenic infections commonly originate in the mouth. Among diabetics, infections of the extremities also commonly spread to other parts of the body.

DAIR:

Where infection is present, a combination of debridement, antibiotics, and implant retention (DAIR) is recommended. Following Zimmerli’s algorithm (below), for infections more that 3 weeks old, a multi-stage approach may also be necessary. In some cases, the only possibility is a salvage operation.

Most common choice with PJI: 2-stage exchange

Where an infection is present, the most common choice among surgeons is a two-stage exchange. In the first stage, they remove the implant, debride the site and install an antibiotic-impregnated cement spacer. After waiting for the antibiotics to take effect (2-6 weeks, depending on the institution), the new prosthesis can be implanted and the tissue biopsied. In all cases, the patient should take oral antibiotics for six weeks.

Special patient considerations

Certain patient conditions, e.g., immunosuppression or cognitive decline, require special consideration.

Country-specific considerations

In developing countries, because of financial concerns, patients often arrive at a very advanced state of infection, and may opt for only the first part of a multi-stage treatment. Also, certain antibiotics may not be available. For example, at the time of this lecture, Daptomycin and Tobramycin were unavailable in Indonesia.