Retrieval Analysis of Neck-Stem Coupling in Modular Hip Prostheses.

BACKGROUND: Dual-taper modular stems have suffered from high revision rates caused by adverse local tissue reactions secondary to fretting and corrosion. We compared the fretting and corrosion behavior of a group of modular neck designs to that of a design that had been recalled for risks associated with fretting and corrosion at the modular neck junction. METHODS: We previously analyzed fretting and corrosion on 60 retrieved Rejuvenate modular neck-stem implants. Here we compare those results to results from 26 retrieved implants from 7 other modular neck designs. For the 26 additional cases, histology slides of tissue collected at revision were reviewed and graded for aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). Multivariate analyses were performed to assess differences in fretting and corrosion, adjusting for confounding factors (eg, length of implantation). RESULTS: The Rejuvenate design had higher damage and corrosion scores than the other 7 designs (P < .01). Histologic samples from the recalled design were 20 times more likely to show ALVAL than samples from the other designs (P < .01). Mixed metal couples had higher fretting (P < .01) and corrosion (P = .02) scores than non-mixed metal couples. CONCLUSION: Fretting and corrosion occurred on all modular neck-stem retrievals regardless of design. However, mixed metal couples suffered more corrosion than homogenous couples. This may be due to the lower modulus of the titanium alloy used for the stem, allowing for increased metal transfer and surface damage when loaded against a cobalt alloy modular neck, which in turn could account for the higher ALVAL and corrosion scores. Due to increased corrosion risk with mixed metals and increased neck fracture risk with non-mixed metal stem and necks, we suggest that clinicians avoid implantation of modular neck-stem systems.

Blood management strategies for total hip arthroplasty in Jehovah's witness patients.

Total hip arthroplasty is associated with extensive blood loss, which is often corrected using allogeneic blood transfusions. However, Jehovah's Witnesses often refuse allogeneic blood transfusions or certain types of autologous blood transfusions due to their religious beliefs. This may represent a tremendous challenge for the orthopaedic surgeon and their team. Performing a total hip arthroplasty on a Jehovah's Witness patient requires a well-trained group of physicians willing to pre-operatively optimize the patient, attempt to minimize the blood loss during the surgery, adequately manage the post-operative period, and be aware of which of the life-saving strategies can be used in these patients during an emergency situation. Ultimately, physicians should be prepared to deal with marked blood loss and respect the patients' wishes, values, and beliefs. This review focuses on studies where primary or revision total hip arthroplasty was performed in Jehovah's Witness patients. Therefore, we will illustrate that with a prepared team and an optimized patient, it is potentially quite safe to perform total hip arthroplasties in Jehovah's Witness patients.

5 points on hip resurfacing.

Hip resurfacing has enjoyed a resurgence in popularity as an alternative to total hip replacement (THR) for the treatment of end-stage arthritis in younger, active patients. However, technical difficulties in implant positioning have been realized, as the procedure has been introduced amongst surgeons new to the concept. Furthermore, as the follow-up interval increases beyond the short-term, it is evident that certain issues with the metal-on-metal bearing surface may lead to complications. These 5 points on hip resurfacing are selected to highlight the factors that will help ensure an optimal outcome.

Adoption of hip resurfacing arthroplasty at hospital for special surgery: a cohort study.

BACKGROUND: Hip resurfacing arthroplasty (HRA) is an alternative to traditional total hip replacement (THR) that allows for the preservation of femoral bone. It is a more technically difficult procedure that has led some researchers to report an unsatisfactory learning curve (Berend et al., J Bone Joint Surg Am Suppl 2:89-92, 2011; Mont et al., Clin Orthop Relat Res 465:63-70, 2007). PURPOSE: The purpose of this study was to investigate the adoption of HRA at our institution, examining the clinical results, revision rate, and modes of failure. Additionally, a comparison of three different implant systems was performed. METHODS: A retrospective review of a consecutive series of HRA performed at our institution between the years 2004 and 2009 was carried out. A total of 820 HRA with a minimum of 2 years of follow-up were included in the study. The majority of included patients were males (70%), with osteoarthritis (92%). The average age was 49.8 years, and the mean BMI was 27.5 kg/m(2). RESULTS: The average Harris hip score improved from 61 to 96.5 postoperatively. Thirteen revisions (1.6%) were performed for femoral neck fracture, femoral head osteonecrosis, acetabular loosening, metal reactivity/metallosis, and metal allergy. The overall Kaplan-Meier survival curve with revision surgery as an endpoint showed 98.5% survival at 5 years. There were no observable differences in clinical scores or revision rates between the different implant systems. CONCLUSIONS: HRA can be successfully adopted with a low complication rate, given careful patient selection, specialized surgical training, and use of good implant design.

Metal-on-metal surface replacement: a triumph of hope over reason: opposes.

Hip resurfacing has been performed for over a decade but still raises controversy as an alternative to traditional total hip arthroplasty (THA). Concerns exist about the potential complications of hip resurfacing, including femoral neck fracture and osteonecrosis of the femoral head. Recently, attention has been given to the metal-on-metal bearing of hip resurfacing with regard to production of metal ions, possible tissue necrosis, and rare instances of metal hypersensitivity. Given the success of the gold-standard THA, it is understandable why some surgeons believe metal-on-metal surface replacement to be "a triumph of hope over reason." However, this article opposes that viewpoint, demonstrating that data exist to justify the practice of preserving bone in younger patients. Hip resurfacing can maintain femoral bone without the expense of removing additional acetabular bone by using modern implants with incremental sizing. Furthermore, many of the problems cited with the bearing couple (such as excess metal production) have been due to poor implant designs, which have now been removed from the market. Finally, we now realize that the metal-on-metal articulation is more sensitive to malposition; thus, good surgical technique and experience can solve many of the problems that have been cited in the past. National registry results confirm that in a select population, hip resurfacing performs comparably to THA, while fulfilling the goal of bone preservation.

Stiffness after TKR: how to avoid repeat surgery.

Stiffness after total knee replacement (TKR) is a frustrating complication that has many possible causes. Although the definition of stiffness has changed over the years, most would agree that flexion <75° and a 15° lack of extension constitutes stiffness. The management of this potentially unsatisfying situation begins preoperatively with guidance of the patient's expectations; it is well-known that preoperative stiffness is strongly correlated with postoperative lack of motion. At the time of surgery, osteophytes must be removed and the components properly sized and aligned and rotated. Soft tissue balancing must be attained in both the flexion/extension and varus/valgus planes. One must avoid overstuffing the tibiofemoral and/or patellofemoral compartments with an inadequate bone resection. Despite these surgical measures and adequate pain control and rehabilitation, certain patients will continue to frustrate our best efforts. These patients likely have a biological predisposition for formation of scar tissue. Other potential causes for the stiff TKR include complex regional pain syndrome or joint infection. Close follow-up of a patient's progress is crucial for the success in return of range of motion. Should motion plateau early in the recovery phase, the patient should be evaluated for manipulation under anesthesia. The results of reoperations for a stiff TKR are variable due to the multiple etiologies. A clear cause of stiffness such as component malposition, malrotation, or overstuffing of the joint has a greater chance of regaining motion than arthrofibrosis without a clear cause. Although surgical treatment with open arthrolysis, isolated component, or complete revision can be used to improve TKR motion, results have been variable and additional procedures are often necessary.

Comparison of bone removed during total hip arthroplasty with a resurfacing or conventional femoral component: a cadaveric study.

We sought to examine the amount of bone removed during total hip arthroplasty with a resurfacing femoral component, compared to with a conventional, stemmed femoral component, by using 6 male and 4 female cadaveric pelves with attached bilateral proximal femora. Using randomized assignment and order, a total hip arthroplasty with a resurfacing femoral implant was performed on one side, and total hip arthroplasty with a cementless, stemmed femoral implant was performed on the contralateral side. The relationship between native femoral head diameter and the implanted acetabular socket was on average within 2 mm for both procedures. No significant difference was observed in the amount of acetabular bone removed (9.8 g for hip resurfacing vs 8.8 g). However, a resurfacing component resulted in approximated 3 x less bone removal from the femur (25.8 g vs 75.1 g). This study shows that the preservation of femoral bone with a resurfacing femoral component does not result in an increased removal of acetabular bone when compared to the use of a conventional, stemmed femoral component.

Network modulation by the subthalamic nucleus in the treatment of Parkinson's disease.

Deep brain stimulation of the subthalamic nucleus (STN DBS) has become an accepted tool for the treatment of Parkinson's disease (PD). Although the precise mechanism of action of this intervention is unknown, its effectiveness has been attributed to the modulation of pathological network activity. We examined this notion using positron emission tomography (PET) to quantify stimulation-induced changes in the expression of a PD-related covariance pattern (PDRP) of regional metabolism. These metabolic changes were also compared with those observed in a similar cohort of patients undergoing STN lesioning. We found that PDRP activity declined significantly (P < 0.02) with STN stimulation. The degree of network modulation with DBS did not differ from that measured following lesioning (P = 0.58). Statistical parametric mapping (SPM) revealed that metabolic reductions in the internal globus pallidus (GPi) and caudal midbrain were common to both STN interventions (P < 0.01), although declines in GPi were more pronounced with lesion. By contrast, elevations in posterior parietal metabolism were common to the two procedures, albeit more pronounced with stimulation. These findings indicate that suppression of abnormal network activity is a feature of both STN stimulation and lesioning. Nonetheless, these two interventions may differ metabolically at a regional level.

Microstructural white matter changes in carriers of the DYT1 gene mutation.

We tested the hypothesis that the DYT1 genotype is associated with a disorder of anatomical connectivity involving primarily the sensorimotor cortex. We used diffusion tensor magnetic resonance imaging (DTI) to assess the microstructure of white matter pathways in mutation carriers and control subjects. Fractional anisotropy (FA), a measure of axonal integrity and coherence, was reduced (p < 0.005) in the subgyral white matter of the sensorimotor cortex of DYT1 carriers. Abnormal anatomical connectivity of the supplementary motor area may contribute to the susceptibility of DYT1 carriers to develop clinical manifestations of dystonia.

Evolving metabolic changes during the first postoperative year after subthalamotomy.

OBJECT: Short-term benefit from unilateral subthalamotomy for advanced Parkinson disease (PD) is associated with metabolic alterations in key targets of subthalamic nucleus (STN) and globus pallidus (GP) output. In this study positron emission tomography (PET) scanning was used to assess these changes and their relation to long-term benefits of subthalamotomy. METHODS: To determine whether the early postoperative changes persisted at longer-term follow up, the authors assessed six patients with advanced PD by using [18F]fluorodeoxyglucose-PET at 3 and 12 months postsurgery. The authors compared each of the postoperative images with baseline studies, and assessed interval changes between the short- and long-term follow-up scans. Clinical improvement at 3 and 12 months was associated with sustained metabolic decreases in the midbrain GP internus (GPi), thalamus, and pons of the lesioned side (p < 0.01). The activity of a PD-related multiregional brain network, which correlated with bradykinesia and rigidity, was reduced at both postoperative time points (p < 0.05). Comparisons of 3- and 12-month images revealed a relative metabolic increase in the GP externus (GPe) (p < 0.001), which was associated with worsening gait, postural stability, and tremor at long-term follow up. CONCLUSIONS: These findings indicate that subthalamotomy may have differential effects on each of the functional pathways that mediate parkinsonian symptomatology. Sustained relief of akinesia and rigidity is associated with suppression of a pathological network involving the GPi and its output. In contrast, the recurrence of tremor may relate to changes in the function of an STN-GPe oscillatory network.