Koen De Smet

Histological Features of Pseudotumor-like Tissues From Metal-on-Metal Hips

BackgroundPseudotumor-like periprosthetic tissue reactions around metal-on-metal (M-M) hip replacements can cause pain and lead to revision surgery. The cause of these reactions is not well understood but could be due to excessive wear, or metal hypersensitivity or an as-yet unknown cause. The tissue features may help distinguish reactions to high wear from those with suspected metal hypersensitivity.Questions/purposesWe therefore examined the synovial lining integrity, inflammatory cell infiltrates, tissue organization, necrosis and metal wear particles of pseudotumor-like tissues from M-M hips revised for suspected high wear related and suspected metal hypersensitivity causes.MethodsTissue samples from 32 revised hip replacements with pseudotumor-like reactions were studied. A 10-point histological score was used to rank the degree of aseptic lymphocytic vasculitis-associated lesions (ALVAL) by examination of synovial lining integrity, inflammatory cell infiltrates, and tissue organization. Lymphocytes, macrophages, plasma cells, giant cells, necrosis and metal wear particles were semiquantitatively rated. Implant wear was measured with a coordinate measuring machine. The cases were divided into those suspected of having high wear and those suspected of having metal hypersensitivity based on clinical, radiographic and retrieval findings. The Mann-Whitney test was used to compare the histological features in these two groups.ResultsThe tissues from patients revised for suspected high wear had a lower ALVAL score, fewer lymphocytes, but more macrophages and metal particles than those tissues from hips revised for pain and suspected metal hypersensitivity. The highest ALVAL scores occurred in patients who were revised for pain and suspected metal hypersensitivity. Component wear was lower in that group.ConclusionsPseudotumor-like reactions can be caused by high wear, but may also occur around implants with low wear, likely because of a metal hypersensitivity reaction. Histologic features including synovial integrity, inflammatory cell infiltrates, tissue organization, and metal particles may help differentiate these causes.Clinical RelevancePainful hips with periprosthetic masses may be caused by high wear, but if this can be ruled out, metal hypersensitivity should be considered.

The 2012 Otto Aufranc Award: The interpretation of metal ion levels in unilateral and bilateral hip resurfacing.

BackgroundThe interpretation of metal ion concentrations and their role in clinical management of patients with metal-on-metal implants is still controversial.Questions/PurposesWe questioned whether patients undergoing hip resurfacing with no clinical problems could be differentiated from those with clinical (pain, loss of function) and/or radiographic (component malpositioning, migration, bone loss), problems based on metal ion levels, and if there was a threshold metal level that predicted the need for clinical intervention. Furthermore, we asked if patient and implant factors differed between these functional groups.MethodsWe retrospectively identified 453 unilateral and 139 bilateral patients with ion measurements at minimum followup of 12 months (mean, 4.3 years; range, 1–12.9 years). Patients were designated as well functioning or poorly functioning based on strict criteria. The acceptable upper levels within the well-functioning group were determined from the 75th percentile plus 1.5× interquartile range. The sensitivity and specificity of these levels to predict clinical problems were calculated.ResultsWell-functioning group ions were lower than the poorly functioning group ion levels. The acceptable upper levels were: chromium (Cr) 4.6 μg/L, cobalt (Co) 4.0 μg/L unilateral and Cr 7.4 μg/L, Co 5.0 μg/L bilateral. The specificity of these levels in predicting poor function was high (95%) and sensitivity was low (25%). There were more males in the well-functioning group and more females and smaller femoral components in the poorly functioning group.ConclusionsMetal levels higher than these proposed safe upper limits can predict problems with metal-on-metal resurfacings and are important parameters in the management of at-risk patients.Level of EvidenceLevel II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Revisions of Metal-on-Metal Hip Resurfacing: Lessons Learned and Improved Outcome

This retrospective, consecutive case series of a single surgeon performed between 2001 and 2010 assesses the outcome following revision of metal-on-metal hip resurfacing arthroplasties (N = 113). Mean time to revision was 31 months (0-101) after primary hip resurfacing. Malpositioning of the components with associated wear-induced soft tissue fluid collections was the most frequent factor leading to failure of a hip resurfacing arthroplasty. The mid-term outcome of the revisions was satisfactory; complications occurred in 11 patients (9.7%). Six of these patients underwent a re-revision.

Failure Modes of 433 Metal-on-Metal Hip Implants: How, Why, and Wear

Metal-on-metal total hip replacements (THRs) and hip resurfacings are coming under increasing scrutiny in light of concerns that they fail because of high wear and elevated metal ions. The aim of this study was to investigate the modes of failure in a collection of 433 metal-on-metal THRs and hip resurfacings and to examine the correlations between the reasons for revision and a range of patient and implant variables considered relevant to implant wear.

Reducing Metal Ion Release Following Hip Resurfacing Arthroplasty

Recent guidelines have suggested that routine postoperative care of patients with metal-on-metal hip prostheses should involve metal ion analysis. This study sought to investigate the relationship between bearing surface wear rates of metal components and serum metal ion analysis and also to quantify the incidence of excessive increases in serum metal ion concentrations post-hip resurfacing arthroplasty.

Complications Encountered With the Use of Constrained Acetabular Prostheses in Total Hip Arthroplasty

At our department, 46 constrained acetabular components in 38 patients were placed successively for a period of 4 years. Indications included recurrent dislocation, septic and aseptic loosening with extensive bone loss, tumor surgery with extensive bone resection, and instability due to neurologic impairment. Because 2 cup failures and 10 dislocations were observed with the constrained devices at 4 to 7 years of follow-up, the authors started to use large-diameter metal-on-metal bearings for similar indications. A series of 36 such bearings in 38 patients revealed only one cup failure and one dislocation at 2 to 4 years of follow-up. Although the 2 series are different and therefore difficult to compare, the authors recommend judicious use of constrained devices because of the high failure rate (26%) and consideration of alternative options such as the use of large-diameter metal-on-metal bearings.

A Modified Posterior Approach Preserves Femoral Head Oxgenation During Hip Resurfacing

In 11 patients, the oxygenation was measured in the superolateral quadrant of the femoral head during resurfacing with a modified posterior approach, designed to preserve the blood supply, using a gas-sensitive electrode. These were compared with measures from 10 patients in whom the standard posterior approach was used. The modified approach patients maintained a significantly (P < .005) higher amount of relative oxygenation after the approach, 78% (standard deviation [SD], 45%) vs 38% (SD, 26%), and acetabular component implantation, 74% (SD, 56%) vs 20% (SD, 28%). The modified posterior approach, unlike the standard extended approach, does not significantly compromise the blood supply to the head; and we recommend this approach be considered for hip resurfacing.

Does Intraoperative Cell Salvage Remove Cobalt and Chromium from Reinfused Blood

In 12 patients undergoing a revision hip arthroplasty after a failed metal-on-metal primary hip arthroplasty, the effectiveness of intraoperative cell salvage (ICS) in removing metal ions was investigated. Samples of blood collected during surgery were filtered using 2 ICS devices. The samples had the concentrations of cobalt (Co) and chromium (Cr) measured before and after filtration. There was an average reduction of 76.3% for Cr concentration and 78.6% for Co concentration after ICS filtering. The Co-to-Cr ratio before and after filtration was similar. At the present time, these salvage systems should be used with caution in the patient undergoing revision of metal-on-metal bearing surfaces.

Italian Version of University of California at Los Angeles (UCLA) Activity Score: Cross-Cultural Adaptation

Over the last 10 years, patient-oriented evaluations using questionnaires have become an important aspect of clinical outcome studies. Any questionnaire must be translated and culturally adapted in order to be used with different language groups, and the translated version must then be evaluated for reliability, validity and responsiveness which are fundamental attributes of any measurement tool. The aim of this study is the validation, translation and cross-cultural adaptation of the Italian version of UCLA activity Score, following the Guillemin criteria. The results show that our Italian version of the UCLA score has the following: reproducibility expressed as ICC=0.994, an internal consistency calculated as Spearman-Brown coefficient=0.754 and finally the construct validity has demonstrated a significant Pearsons correlation coefficient with other validated hip questionnaires.

Hip resurfacing arthroplasty complicated by mismatched implant components

Metal-on-metal hip resurfacing has gained popularity as a feasible treatment option for young and active patients with hip osteoarthritis and high functional expectations. This procedure should only be performed by surgeons who have trained specifically in this technique. Preoperative planning is essential for hip resurfacing in order to execute a successful operation and preview any technical problems. The authors present a case of a man who underwent a resurfacing arthroplasty for osteoarthritis of the left hip that was complicated by mismatched implant components that were revised three days afterwards for severe pain and leg length discrepancy. Such mistakes, although rare, can be prevented by educating operating room staff in the size and colour code tables provided by the companies on their prostheses or implant boxes.