C. Van Der Straeten

Metal ion levels from well-functioning Birmingham Hip Resurfacings decline significantly at ten years

A retrospective study was conducted to investigate the changes in metal ion levels in a consecutive series of Birmingham Hip Resurfacings (BHRs) at a minimum ten-year follow-up. We reviewed 250 BHRs implanted in 232 patients between 1998 and 2001. Implant survival, clinical outcome (Harris hip score), radiographs and serum chromium (Cr) and cobalt (Co) ion levels were assessed. Of 232 patients, 18 were dead (five bilateral BHRs), 15 lost to follow-up and ten had been revised. The remaining 202 BHRs in 190 patients (136 men and 54 women; mean age at surgery 50.5 years (17 to 76)) were evaluated at a minimum follow-up of ten years (mean 10.8 years (10 to 13.6)). The overall implant survival at 13.2 years was 92.4% (95% confidence interval 90.8 to 94.0). The mean Harris hip score was 97.7 (median 100; 65 to 100). Median and mean ion levels were low for unilateral resurfacings (Cr: median 1.3 µg/l, mean 1.95 µg/l (< 0.5 to 16.2); Co: median 1.0 µg/l, mean 1.62 µg/l (< 0.5 to 17.3)) and bilateral resurfacings (Cr: median 3.2 µg/l, mean 3.46 µg/l (< 0.5 to 10.0); Co: median 2.3 µg/l, mean 2.66 µg/l (< 0.5 to 9.5)). In 80 unilateral BHRs with sequential ion measurements, Cr and Co levels were found to decrease significantly (p < 0.001) from the initial assessment at a median of six years (4 to 8) to the last assessment at a median of 11 years (9 to 13), with a mean reduction of 1.24 µg/l for Cr and 0.88 µg/l for Co. Three female patients had a > 2.5 µg/l increase of Co ions, associated with head sizes ≤ 50 mm, clinical symptoms and osteolysis. Overall, there was no significant difference in change of ion levels between genders (Cr, p = 0.845; Co, p = 0.310) or component sizes (Cr, p = 0.505; Co, p = 0.370). Higher acetabular component inclination angles correlated with greater change in ion levels (Cr, p = 0.013; Co, p = 0.002). Patients with increased ion levels had lower Harris hip scores (p = 0.038). In conclusion, in well-functioning BHRs the metal ion levels decreased significantly at ten years. An increase > 2.5 µg/l was associated with poor function.

Clinical outcome in MPFL reconstruction with and without tuberositas transposition

AbstractPurposeThere are several surgical options for recurrent patella dislocations. As the reconstruction of the medial patellofemoral ligament (MPFL) has been proven to restore stability, it has become more accepted. Aim of this study was to investigate the clinical outcome after MPFL reconstruction as an isolated procedure or in association with a transposition of the tibial tubercle (in case of patella alta or an excessive TT–TG) in a large prospective cohort study. Additionally, the effect on patellar height was analysed radiographically using the Caton–Deschamps index.MethodsnIn a large prospective cohort study of 129 knees in 124 patients (81 females, 48 males, mean age 22.8xa0±xa07.7xa0years), 91 knees received primary MPFL reconstruction (group 1) and 38 were a combination with a transposition of the tibial tubercle (group 2). The clinical follow-up was evaluated using KOOS and Kujala scores preoperatively and 1xa0year postoperatively. Patient satisfaction, complications and revision surgery were recorded.ResultsOverall, Kujala improved significantly from 53.5 (SD 22.7) preoperatively to 74.7 (SD 20.5) postoperatively (pxa0<xa00.01). All KOOS subdomains improved significantly (pxa0<xa00.01). No significant difference for Kujala score between groups was noticed. Revision rate was (5/129) 3.9xa0%. Reconstruction was supplemented with a transfer of the tibial tuberosity in (38/129) 29.4xa0% of the cases and shows a comparable outcome.ConclusionMPFL reconstruction is a viable treatment option for episodic patellar dislocation. A concomitant tuberositas transposition is useful in selected patients.Level of evidenceI.

Design issues and comparison of hip resurfacing prostheses

Abstract: There are 15 hip resurfacings described in detail in this book. This chapter provides an overview of their design advantages and limitations from the point of view of an experienced hip resurfacing surgeon. Many of the observations come from first-hand knowledge obtained during a multi-implant comparison study performed by the authors.

The practical application of metal ion level measurement in evaluating hip resurfacing

Abstract: This chapter highlights the practical implications relating to the methodology of metal ion analysis and the interpretation of results based on the long-standing experience and the large metal ions database of a high-volume hip resurfacing surgeon.

Comparing hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA)

Abstract: The comparison of hip resurfacing arthroplasty (HRA) with total hip arthroplasty (THA) seems straightforward since both procedures are performed to treat diseases of the hip joint. However, besides biomechanical distinctions, differences in indications, treatment timing, surgical experience and technique have been demonstrated. This chapter compares the outcomes of HRA and THA from a clinical, radiographic and survivorship point of view focusing especially on the group of young and/or active patients for whom HRA was primarily developed. Objective, multi-factorial weighing of the current knowledge leads to the conclusion that hip resurfacing is the better reconstructive option for specific patient groups such as young and active males with osteoarthritis. Other patient groups such as females or patients with anatomic deformities should be assessed thoroughly and considered as HRA candidates with certain reservations.

Acoustic phenomena in hip resurfacing

Abstract: Squeaking is not commonly reported in hip resurfacing studies. In hard-on-hard bearings, an increase in friction produces a vibration by the stick–slip phenomenon. This vibration is then amplified by the resonance of the metallic components. Edge loading is known to increase wear and friction, and retrieved squeaking hips have been found to have edge loading wear. This may prove to be an important mechanism in squeaking hips. To manage a patient with a squeaking or clicking resurfacing, we recommend excluding component malposition, checking for sequelae of high wear, and counseling patients to avoid certain activities if necessary. Patients with squeaking hips should be followed up regularly since some cases may be associated with high wear-related problems.

Comparing surgical techniques in hip resurfacing

Abstract: Adequate surgical exposure of the hip is important for correct positioning of the hip resurfacing components. In this chapter several possible approaches are discussed. The posterior approach is known to yield the best exposure to the hip. The modified posterior approach ensures soft tissue preservation to protect the vascularisation of the femoral head and correct application of cement, avoiding thermal damage to the bone. The modified lateral approach, trochanteric flip approach and (Hueter) anterior approach are used by some surgeons to preserve the femoral circumflex arteries and thus avoid avascular necrosis of the femoral head.

Metallkonzentrationen bei Patienten mit Metall-Metall-Gleitpaarungs-Prothese@@@Metal ion concentrations in patients with metal-metal bearings in prostheses

ZusammenfassungErhöhter Verschleiß von Prothesen mit Metall-Metall-Gleitpaarungen führt bei betroffenen Patienten zu erhöhten systemischen und lokalen Metallkonzentrationen. Die lokalen Metallbelastungen in der Nähe des Implantats (z.xa0B. Gelenkpunktat/Gewebe) sind dabei um ein Vielfaches höher als die systemischen Belastungen (z.xa0B. im Blut/Serum). In Folge der erhöhten Metallbelastung kann es zu lokalen und systemischen Wirkungen, wie z.xa0B. Osteolysen, Pseudotumoren, lokal-allergischen Reaktionen oder in seltenen Fällen zu Intoxikationen kommen. Die Bestimmung der systemischen Metallkonzentrationen hat sich mittlerweile etabliert, obwohl die genaue Definition eines Grenz- oder Schwellenwerts zur Diagnose eines klinischen Problems aufgrund der geringen Sensitivität schwierig ist. Derzeit wird ein Schwellenwert für Kobalt oder Chrom in der Größenordnung zwischen 4 und 7xa0µg/l diskutiert. Sehr hohe Konzentrationen (≥u200920xa0µg/l) oder die sukzessive Zunahme der Metallkonzentration sollten als alarmierende Zeichen gewertet werden. Nichtsdestotrotz sollte die Metallkonzentration nicht im Sinne eines isolierten diagnostischen Verfahrens, sondern im Gesamtkontext der klinischen und radiologischen Untersuchungen (Metal-artifact-reduction-sequence[MARS]-MRT, Ultraschall und CT) bewertet werden.AbstractIncreased wear leads to elevated systemic and local metal ion concentrations for patients treated with metal-on-metal bearings. The local metal ion content in the close environment of the joint replacement (e.g. joint aspirate or tissue) is several times higher compared to the systemic metal content (e.g. in blood or serum). As a result of increased metal ion levels, local and systemic effects, such as osteolysis, pseudotumors, sensitization or in rare cases toxicity may occur. Although the definition of a specific threshold to define clinical problems is difficult due to a lack of sensitivity, the systemic metal concentration is frequently measured clinically. Currently a threshold for cobalt and chromium between 4xa0µg/l and 7xa0µg/l is under debate. Very high levels (≥u200920xa0µg/l) or a steady increase over time should be a warning sign; however, metal ion levels should not be interpreted as a single diagnostic tool but rather in the entire context of the clinical, radiological and cross-sectional imaging, metal artefact reduction sequence (MARS) magnetic resonance imaging (MRI), ultrasound and computed tomography (CT) findings.Increased wear leads to elevated systemic and local metal ion concentrations for patients treated with metal-on-metal bearings. The local metal ion content in the close environment of the joint replacement (e.g. joint aspirate or tissue) is several times higher compared to the systemic metal content (e.g. in blood or serum). As a result of increased metal ion levels, local and systemic effects, such as osteolysis, pseudotumors, sensitization or in rare cases toxicity may occur. Although the definition of a specific threshold to define clinical problems is difficult due to a lack of sensitivity, the systemic metal concentration is frequently measured clinically. Currently a threshold for cobalt and chromium between 4xa0µg/l and 7xa0µg/l is under debate. Very high levels (≥u200920xa0µg/l) or a steady increase over time should be a warning sign; however, metal ion levels should not be interpreted as a single diagnostic tool but rather in the entire context of the clinical, radiological and cross-sectional imaging, metal artefact reduction sequence (MARS) magnetic resonance imaging (MRI), ultrasound and computed tomography (CT) findings.