Comparison of metal ion concentrations and implant survival after total hip arthroplasty with metal-on-metal versus metal-on-polyethylene articulations.

Background and purpose - Large metal-on-metal (MoM) articulations are associated with metal wear and corrosion, leading to increased metal ion concentrations and unacceptable revision rates. There are few comparative studies of 28-mm MoM articulations with conventional metal-on-polyethylene (MoP) couplings. We present a long-term follow-up of a randomized controlled trial comparing MoM versus MoP 28-mm articulations, focused on metal ions and implant survival. Patients and methods - 85 patients with a mean age of 65 years at surgery were randomized to a MoM (Metasul) or a MoP (Protasul) bearing. After 16 years, 38 patients had died and 4 had undergone revision surgery. 13 patients were unavailable for clinical follow-up, leaving 30 patients (n = 14 MoM and n = 16 MoP) for analysis of metal ion concentrations and clinical outcome. Results - 15-year implant survival was similar in both groups (MoM 96% [95% CI 88-100] versus MoP 97% [95% CI 91-100]). The mean serum cobalt concentration was 4-fold higher in the MoM (1.5 µg/L) compared with the MoP cohort (0.4 µg/L, p < 0.001) and the mean chromium concentration was double in the MoM (2.2 µg/L) compared with the MoP cohort (1.0 µg/L, p = 0.05). Mean creatinine levels were similar in both groups (MoM 93 µmol/L versus MoP 92 µmol/L). Harris hip scores differed only marginally between the MoM and MoP cohorts. Interpretation - This is the longest follow-up of a randomized trial on 28-mm MoM articulations, and although implant survival in the 2 groups was similar, metal ion concentrations remained elevated in the MoM cohort even in the long term.

Axial load weightbearing radiography in determining lateral malleolus fracture stability: a cadaveric study.

BACKGROUND: Ankle fractures are the most common fracture treated by orthopaedic surgeons in the United States. Isolated lateral malleolus fractures are treated nonoperatively, while associated deltoid disruption injuries are unstable and usually treated by fixation of the fracture. Various stress radiographs and MRI have been used to determine deltoid competency and the subsequent need for operative stabilization of lateral malleolus fractures. To date, no standardization of stress radiography has been performed. The aim of this study was to evaluate the ability of weightbearing ankle X-rays to determine stability and their reliability. METHODS: This study sought to utilize simulated weightbearing radiography as a potential method to determine the need for lateral malleolus fixation. Twelve cadaveric ankle specimens were tested by obtaining ankle mortise radiographs for interpretation of medial clear space. Each ankle was tested with 0, 25, 36, and 50 kg of axially applied weight. The groups of measurements obtained were: intact ankles (Group A), ankles with an isolated oblique fibular osteotomy (Group B), and osteotomized ankles after complete deltoid ligament transaction (Group C). Three authors measured the medial clear space for every ankle using PACSR software. Instability of the ankle mortise was defined as medial clear space widening of greater than 2 mm from the intact ankle. RESULTS: An isolated lateral malleolus fracture (Group B) and a lateral malleolus fracture with an incompetent deltoid ligament (Group C) showed no statistical medial clear space widening with simulated axial weightbearing radiography when compared to intact ankles (Group A). ANOVA's between Group A and B had p < 0.001, and between Group A and C of p < 0.001. CONCLUSION: Our model did not find instability with an osteotomized fibula and a disrupted deltoid. CLINICAL RELEVANCE: This study suggests a weightbearing radiograph of an isolated lateral malleolus fracture cannot determine deltoid ligament integrity and thus need for fibular operative fixation.

A quantitative analysis of tension band plating of the femur diaphysis.

OBJECTIVES: To measure quantitatively the strains in the concave and convex sides of a femur to substantiate the Arbeitsgemeinschaft für Osteosynthesefragen (AO) tension band principle. METHODS: Eight cadaveric fresh-frozen femurs were cleaned of soft tissue and prepared for mounting the strain gages (Vishay, Raleigh, NC). The student strain gages were mounted at the anterior, lateral and medial surfaces of a femur. They were loaded at 100, 250, 500, 1,000 and 1,500 N axial forces in a mechanical testing machine (Instron Model 4202, Norwood, MA) and the micro strains were measured for intact and after fixation of a simulated fracture by an eight hole broad 4.5 mm stainless steel compression plate (Synthes LCP). In order to simulate the fracture conditions, where all eight screw holes might not be filled, three different arrangements were tested: 8 screws, 4 screws and 2 screws. The microstrains under different loads were analyzed by Analysis of Variance (ANOVA) with Holm-Sidak multiple comparison method. RESULTS: At the same gage location micro strains were not significantly different between the intact, and the femur fixated by 8, 4 and 2 screws. For intact bones at 1,500 N the strain ratio between the tension to compression sides was -0.21 proximally and -0.04 distally. The comparison of these strain ratios at different loads did not show any significant differences at p = 0.05 and power of 0.8. CONCLUSIONS: The data showed a trend validating the tension band principle as tensile strains lowered and compressive strains increased after placement of the plate.

Minimizing Opioids After Joint Operation: Protocol to Decrease Postoperative Opioid Use After Primary Total Knee Arthroplasty.

BACKGROUND: For decades, opioids have been the mainstay in pain management after total joint arthroplasty despite evidence that their use should be curtailed. To limit unnecessary prescribing of opioids, the US Department of Veterans Affairs (VA) Portland Health Care System Total Joints Service implemented the Minimizing Opioids After Joint Operation (MOJO) postoperative pain protocol in 2018 to reduce opioid use following total knee arthroplasty (TKA). This protocol included reductions of inpatient and outpatient opioid prescribing, preoperative optimization, use of perioperative nerve blocks, and surgery without a tourniquet. METHODS: We performed a retrospective chart review that compared the first 20 consecutive patients undergoing TKA using the MOJO protocol with the last 20 patients using the prior routine. Outcomes included total inpatient opioid use, daily opioid use, emergency department (ED) visits or readmissions within 90 days, phone calls for pain or medication refills, length of stay (LOS), and pain during inpatient hospital stay. RESULTS: There were significant differences between the pre-MOJO and the MOJO groups with regard to daily inpatient morphine equivalent dose (MED) (82 mg vs 31 mg, P < .01) and total inpatient MEDs (306 mg vs 33 mg, P < .01). There was less self-reported pain on postoperative day 1 in the MOJO group (5.5 vs 4.1, P = .01), decreased LOS (4.4 days vs 1.1 days, P < .01), fewer total ED visits (6 vs 2, P < .07), and fewer discharges to skilled nursing facilities (12 vs 0, P < .01). CONCLUSIONS: The MOJO protocol reduced postoperative opioid use after TKA in the VA setting without compromising pain control or increasing ED visits. The framework and routines described are potentially applicable to other institutions and surgical specialties.

Primary cortical brain cells influence osteoblast activity.

The presence of neuropeptides and neuroreceptors in the bone have been reported in several studies. Bone turn-over seems to be controlled by the nervous system. The actual pathway or the control mechanism is still under investigation. In this study we investigate the changes in osteoblast cells if they are in co-culture with primary cortical brain cells. After seven days in co-culture with the primary fetal brain cells the osteoblast cells exhibited hypertrophic morphological changes and showed stronger ALP activity.

Elevated serum concentrations of cobalt, chromium, nickel, and manganese after metal-on-metal alloarthroplasty of the hip: a prospective randomized study.

In this prospective randomized study, we investigate metal ion concentrations and clinical outcome 2 years after metal-on-metal (28 patients) or metal-on-polyethylene (26 patients) hip arthroplasty with 28-mm modular heads. Metal ion concentrations in patient serum were analyzed by high-resolution plasma mass spectrometry. The clinical outcome was almost identical in both groups with respect to the Harris hip score and the Medical Outcome Study Short Form-36; and on plain radiography, no signs of loosening occurred in any group. In the metal-on-metal group, concentrations of all investigated ions increased significantly when compared with preoperative values: cobalt, 15.3-fold (95% confidence interval [CI], 9.4-21.2); chromium, 5.2-fold (CI, 3.5-7.0); nickel, 2.1-fold (CI, 1.2-3.0); and manganese, 1.6-fold (CI, 1.3-2.0). In the metal-on-polyethylene group, a smaller but significant increase in the concentrations of cobalt and nickel occurred, whereas concentrations of the other ions did not change significantly.

A new biodegradable polyester elastomer for cartilage tissue engineering.

The objective of this study is to assess whether a new biodegradable elastomer, poly(1,8-octanediol citrate) (POC), would be a suitable material to engineer elastomeric scaffolds for cartilage tissue engineering. Porous POC scaffolds were prepared via the salt-leaching method and initially assessed for their ability to rapidly recover from compressive deformation (% recovery ratio). Controls consisted of scaffolds made from other materials commonly used in cartilage tissue engineering, including 2% agarose, 4% alginate, non woven poly(glycolic acid) (PGA) meshes, and non woven poly(L-lactide-co-glycolide) (PLGA) meshes. Articular chondrocytes from bovine knee were isolated and seeded onto porous disk-shaped POC scaffolds, which were subsequently cultured in vitro for up to 28 days. POC scaffolds completely recover from compressive deformation, and the stress-strain curve is typical of an elastomer (recovery ratio>98%). Agarose gel (2%) scaffolds broke during the compression test. The recovery ratio of 4% alginate gel scaffolds, PLLA, and PGA were 72, 85, and 88%, respectively. The Young's modulus of POC-chondrocyte constructs and cell-free POC scaffolds cultured for 28 days were 12.02+/-2.26 kPa and 3.27+/-0.72 kPa, respectively. After 28 days of culture, the recovery ratio of POC-chondrocyte constructs and cell-free POC scaffolds were 93% and 99%, respectively. The glycosaminoglycan (GAG) and collagen content at day 28 was 36% and 26% of that found in bovine knee cartilage explants. Histology/immunohistochemistry evaluations confirm that chondrocytes were able to attach to the pore walls within the scaffold, maintain cell phenotype, and form a cartilaginous tissue during the 28 days of culture.

Subcutaneous methylnaltrexone for treatment of acute opioid-induced constipation: phase 2 study in rehabilitation after orthopedic surgery.

BACKGROUND: Methylnaltrexone has been shown to be effective for treating opioid-induced constipation (OIC) in chronic settings, but its effects on acute OIC have not been studied. OBJECTIVE: To assess safety and efficacy of subcutaneous methylnaltrexone in patients with acute OIC after orthopedic procedures. DESIGN: Double-blind, randomized, parallel-group, placebo-controlled, hypothesis-generating phase 2 study. SETTING: Sixteen US hospitals and rehabilitation facilities. PATIENTS: Adult patients with acute OIC after orthopedic surgical procedure, expected to require opioids for at least 7 days postrandomization. INTERVENTIONS: Patients received once-daily subcutaneous methylnaltrexone 12 mg or placebo for up to 4 or 7 days. MEASUREMENTS: All endpoints were exploratory and included the percentage of patients achieving laxation within 2 and 4 hours of first dose and time to laxation. RESULTS: Thirty-three patients received at least 1 dose of study drug (methylnaltrexone, n = 18; placebo, n = 15). Within 2 and 4 hours, significantly more patients receiving methylnaltrexone achieved laxation (2 hours: 33.3% vs 0%, P = 0.021; 4 hours: 38.9% vs 6.7%, P = 0.046) compared with placebo. Time to laxation was significantly shorter with methylnaltrexone (median = 15.8 hours) versus placebo (median = 50.9 hours), P = 0.0197. The most common adverse events related to the gastrointestinal tract. Pain scores remained stable and were similar to those of placebo, and signs and symptoms of opioid withdrawal did not emerge in patients receiving methylnaltrexone. CONCLUSIONS: Methylnaltrexone was generally well tolerated and was active in inducing laxation in this study of patients experiencing acute OIC following orthopedic surgery.

New technique for humerus shaft fracture retrograde intramedullary nailing.

Humeral shaft fracture intramedullary nailing is less invasive than plates and screws. Antegrade technique has postoperative shoulder pain, increased rehab time, and frequent reoperation for rod removal. Published retrograde technique is not collinear with the shaft, has insertion site fractures (5% to 15%), and radial nerve palsies (5%). Our retrograde technique is collinear with the humerus shaft, simpler, and decreases operative fracture risk. The supine patient's elbow is fully flexed. A guide pin is inserted through the triceps tendon to the olecranon fossa roof, aligned with the humerus shaft, and drilled thought the cortex followed by the 6.5 mm cannulated drill through a small triceps splitting incision. The guide pin is passed along the humerus shaft and across the fracture. A small incision is made to identify and protect the radial nerve during reduction, reaming, and rod insertion. Flexible reamers are used and the nail placed and locked at least distally to prevent distal migration. An institutional review broad approved retrospective review of Louisiana State University Health Sciences Center adult humeral shaft fractures with retrograde technique from 1999 to January of 2009 was carried out. Sixteen patients were treated without perioperative fracture or nerve palsy.

Biomechanics of humerus fracture fixation by locking, cortical, and hybrid plating systems in a cadaver model.

The goal of this study was to discover how locking or cortical screws or a hybrid of both would perform in stabilizing a simulated humerus fracture. We simulated stripping of screw threads or poor bone quality by overdrilling the screw hole, and also studied a control group with no overdrilling. A total of 38 fresh frozen cadaver humeri were divided into 2 groups: 16 undergoing overdrilling with a drill bit 0.3 mm less than the diameter of the screw and 22 undergoing no overdrilling. A 4-point bending test followed torsional fatigue of 1000 cycles with an amplitude of +/-10 degrees. The post-fatigued samples were retested in the same way after tightening the loose screws if necessary. Finally, each fatigued specimen was tested for failure in torsion at 0.5 Hz by applying a maximum rotational displacement of 60 degrees .The bending stiffness values (Nm/mm) of cortical and locking screws, with the exception of the hybrid system, were significantly higher for the overdrilled group than the non-overdrilled (cortical, 6.9 vs 5.6; locking, 9.1 vs 6.3; hybrid, 8.4 vs 6.8). Fatigue had no effect on the bending stiffness of all the screw/plate systems (cortical, 6.9 vs 7.4; locking, 9.1 vs 8.8; hybrid, 8.5 vs 8.1). The overdrilling had no effect on the failure loads and displacements for all the screws except cortical screws, where the failure displacement was significantly higher for the overdrilling group. The torsional stiffness retentions after 1000 cycles were significantly different for overdrilled specimens in the cortical screws group only.Overdrilling had a minimal effect on bending and torsional properties. The results of the locking and hybrid were close, and the cortical screw had only slightly lower bending stiffness.

Low IGF-I in synovial fluid and serum in patients with aseptic prosthesis loosening.

BACKGROUND: We have previously shown that proliferation in primary cultures of human osteoblast-like cells is lower after exposure to synovial fluid from patients with aseptic prosthesis loosening than after exposure to synovial fluid from patients with osteoarthrosis. MATERIALS AND METHODS: Insulin-like growth factors (IGF) I and II and IGF binding proteins (IGFBP) 3-6, were measured with radioimmunoassy in synovial fluid and in serum from patients with aseptic prosthesis loosening or osteoarthrosis. Proliferation in osteoblast-like MG-63 cells was studied with the CyQUANT assay. RESULTS: IGF-I and IGFBP-4 concentrations were lower whereas the concentration of IGFBP-6 was higher in synovial fluids from patients with prosthesis loosening than in synovial fluid from patients with osteoarthrosis. IGF-I concentrations in serum from patients with prosthesis loosening were also lower than in the osteoarthrosis group, and were even below the normal range in most cases (72%). Synovial fluid from patients with aseptic loosening had a weaker stimulatory effect on MG63 osteoblast-like cell proliferation than synovial fluid from patients with osteoarthrosis, but there was no difference between the two groups when a human IGF-I antibody was added. INTERPRETATION: Low levels of IGF-I in synovial fluid possibly result from low serum levels and may be a mechanism leading to aseptic prosthesis loosening.

Cobalt ions influence proliferation and function of human osteoblast-like cells.

Cobalt is the major component in many orthopedic implants and the introduction of a second generation of metal on metal bearing prosthesis systems actualizes the toxicity and biocompatibility of this compound. We studied the effect of cobalt ions on primary cultures of human osteoblast-like cells. Cobalt ions dissolved in cell culture medium caused a dose-dependent decrease in proliferation of human osteoblasts measured as (3H)thymidine incorporation. We also found that cobalt ion-enriched medium increased the production of interleukin-6 from the osteoblast-like cells. Furthermore, incubation of osteoblasts with cobalt ion-enriched medium reduced collagen type I and osteocalcin production in a dose-dependent manner when 1,25 dihydroxyvitamin-D3 was added to the culture medium. Cobalt concentrations below 10 microg/mL or 0.17 mmollmL in the cell culture medium had no significant effect on human osteoblast proliferation and function.