Reconstructive Review 

Abstract: The emergence of modularity in total hip arthroplasty (THA) in the 1980s and 1990s was based on the fact that the benefit of these design features outweighed the risk. The use of metallic modular junctions presents a unique set of advantages and problems for use in THA. The advantages include improvement in fit and fill of the implant to bone, restoration of joint mechanics, reduced complications in revision surgery and reduction of costly inventory. However, the risks or concerns are a little harder to identify and deal with. Certainly corrosion, and fatigue failure are the two most prevalent concerns but now the specifics of fretting wear and corrosive wear increasing particulate debris and the potential biological response is having an impact on the design and potential longevity of the reconstructed hip. Material and designs are facing a shorter life expectancy than what was previously thought, mostly due to an increasing level of physical activity by the patient. Because there are no accurate laboratory test whereby the service life and performance of these implants can be predicted, early controlled clinical evaluations are necessary. Early publication of testing and clinical impressions should be encouraged in an attempt to reduce exposure to potential at risk patients, implants and material. The reduction and possible elimination of risks will require a balancing of all the variables requiring a multidisciplinary endeavor. This paper is designed to review the risk factors, and benefits of modular junctions in total hip arthroplasty (THA). Also some basic engineering principals that can reduce risk factors and improve functionality of modular junctions.

Abstract: Background: The volume of total knee arthroplasty procedures is growing rapidly and, correspondingly, it is expected that the volume of revision procedures will grow rapidly as well. Revision surgery is most successful when adequate bone remains on both the tibia and femur to allow for the least invasive revision. We hypothesized that total knee arthroplasty with a patient-specific implant would result in significant bone preservation as compared to standard total knee arthroplasty with “off-the-shelf” implants. Methods: We evaluated 100 total knee arthroplasties which utilized patient-specific implants, versus 37 standard posterior stabilized and 32 standard posterior cruciate retaining total knee arthroplasties. Bone resection was quantified utilizing intra-operative measurements of actual resected bone. Additionally we performed a virtual, CAD-based analysis of resections via CT imaging on 15 knees. Findings: We found that patients had significantly less bone resected in all zones measured, on both the femur and tibia, when patient-specific implants with patient-specific jigs were used. When assessed volumetrically with CAD imaging, standard implants resected 12-49% more bone than did patient-specific implants, depending on the size of the implant utilized. Interpretations: Utilizing patient-specific implants in total knee arthroplasty results in significant bone sparing as compared to standard total knee arthroplasty. This has the potential for less invasive revision surgery in the future, possibly obviating the need for dedicated revision implants or augments and other bone substituting devices.

Abstract: This report reviews the findings of a massive pseudotumor detected pre-operatively in a 13-year-old revision total hip arthroplasty. The case is unique in that the bearing involved was a 28mm zirconia ceramic head on a polyethylene liner. We propose that the pseudotumor arose from ultrafine titanium par ticles liberated from the proximal porous coating of the femoral stem. We suspect that the osteolysis produced from polyethylene wear exposed the proximal porous coating and, via a process of mechanical abrasion with the surrounding soft tissues, liberated ultrafine titanium particles. We believe the pseudotumor formed because the patient was pre-sensitized to metal debris based upon a pre-operative lymphocyte T-cell proliferation test (LTT). Based upon this unique case, we feel that pseudotumors more likely form when there is a high rate of ultrafine metal particles generated in a pre-sensitized patient. Finally, we introduce what we believe are the main biologic wear responses in THA. Further research is needed to validate this proposed model.

Abstract: Background: Infection complicates traditional joint reconstruction prostheses in up to 7% of cases, with even higher rates in oncologic cases. Questions / Purposes: The authors ask if prosthetic infection in bone tumor patients is associated with any epidemiologic, treatment, or outcome variables that could influence management of these difficult conditions. Patients and Methods: Authors retrospectively reviewed 329 consecutive bone tumor (malignant and benign) patients treated with hip or knee tumor resection and subsequent joint reconstruction, comparing infected and non-infected cases. Patients were followed for a mean of 34 months.Results: Of lower extremity tumor reconstructions, 13.1% developed periprosthetic infection, with the knee significantly more involved than the hip (20.5% vs 6.1%). The most common organism cultured was Staphylococcus aureus (33%). The diagnosis of sarcoma was associated with a higher infection rate, and infections were associated with a two-fold increase in number of total surgeries. Adjuvant radiation alone and chemotherapy alone (but not in combination) was associated with statistically increased infection rates. Debridement with fixed implant retention achieved a 70% infection remission rate, as opposed to 62% with two-staged treatment, and 100% with amputation. The implants tended to survive longer than the patients.Conclusions: Infection complicates lower extremity prosthetic joint reconstructions in tumor patients more frequently than in non-tumor arthroplasty cases, with eradication rates lower than that of non-tumor patients. Periprosthetic infection correlates with radiation and chemotherapy administration, as well as an overall increase in revision surgery. Single stage debridement procedures result in infection remission rates comparable to two-stage reconstructions.Level of Evidence Level III, Retrospective comparative study.