Chih-Chien Hu

Continuous intra-articular infusion of bupivacaine for post-operative pain relief after total hip arthroplasty: A randomized, placebo-controlled, double-blind study

Background: Instillation of local anesthetics into a surgical site has been gaining popularity in post‐operative pain management.

Finite element analysis of different repair methods of Vancouver B1 periprosthetic fractures after total hip arthroplasty.

OBJECTIVE To use finite element analysis to study the stability of different fixation methods used to repair Vancouver type B1 periprosthetic fractures occurring after total hip arthroplasty (THA). METHODS An artificial femur was used as the basis for the solid model; U2 series femoral stem (United Orthopedic Corporation, Hsinchu, Taiwan) was used for modelling of the prosthesis; and the modelling of the cable plate, wires and screws was based on information given in the manufacturers catalogue (Zimmer, Warsaw, IN, USA). The analysis model was constructed using the ANSYS software, and all material settings were based on literature values. A six-orifice cable plate, unicortical screws (20mm long and 4.5mm in diameter) and bicortical screws (50mm long and 4.5mm in diameter) were constructed. Four analysis models were defined. The basic model had a plate and three cable wires above the fracture line and two bicortical screws below the fracture line. In the second model, two unicortical screws were added above the fracture line. In the third model, three wires were added below the fracture line. In the fourth model, both the proximal screws of the second model and the distal wires of the third model were added to the basic model. To ensure that the numerical values produced by analysis reached convergence, mesh convergence was tested. RESULTS Adding two proximal unicortical screws to the basic Ogden construct (plate, proximal wires and distal screws) lessened displacement of the fracture and decreased the von Mises stress on the repair. Adding three distal wires to the basic construct had no noticeable effect. CONCLUSION Better fixation power is achieved by using both proximal and distal screws (the locking-plate concept) in treating Vancouver type B1 periprosthetic fracture after THA.

Vancomycin and Ceftazidime in Bone Cement as a Potentially Effective Treatment for Knee Periprosthetic Joint Infection

Background: The aim of this study was to determine the optimal formulation of antibiotic-loaded bone cement for knee periprosthetic joint infection. We used both in vitro and in vivo models incorporating various broad-spectrum antibiotics and tested their efficacy against gram-positive and gram-negative bacteria. Methods: Bone cement specimens loaded with 4 g of either vancomycin or teicoplanin and 4 g of ceftazidime, imipenem, or aztreonam were studied to measure their in vitro antibiotic release characteristics and antibacterial capacities against methicillin-susceptible Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli. Bone cement spacers loaded with the antibiotics with the superior in vitro antibacterial capacity were then implanted into 8 patients (4 women and 4 men between 51 and 79 years of age) diagnosed with chronic knee periprosthetic joint infection. The antibiotic concentrations and antibacterial activities in the joint fluid at the site of the infection were measured following spacer implantation. Results: Cement samples loaded with vancomycin and ceftazidime exhibited in vitro antibacterial activity against the test microorganisms that lasted for as long as or longer than that of cement loaded with the other antibiotic combinations. Joint fluid samples exhibited activity against bacteria including American Type Culture Collection (ATCC) strains and clinically isolated strains. Conclusions: Bone cement loaded with vancomycin and ceftazidime provided broad-spectrum antibacterial capacity both in vitro and in vivo and was shown to be a potentially effective therapeutic measure in the treatment of knee periprosthetic joint infections. Clinical Relevance: This study confirmed the potential effectiveness of drug delivery from bone cement spacers impregnated with vancomycin and ceftazidime.

Acute Delirium and Poor Compliance in Total Hip Arthroplasty Patients With Substance Abuse Disorders

From the joint registry of 2831 primary total hip arthroplasties (2351 patients) performed between 1998 and 2003, we identified 15 patients (16 hips) who had a documented history of substance abuse disorders at the time of the index surgery. The patients included 13 men (14 hips) and 2 women (2 hips), with the mean age of 49 years (range, 29-65 years). On the basis of the criteria specified in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, 13 patients had alcohol abuse disorders, 1 had amphetamine abuse disorder, and 1 had heroin abuse disorder. We found high rates of postoperative substance withdrawal delirium and psychosis (46%), late complication (25%), and lost to follow-up (27%) in these patients. Because patients with substance abuse disorders have unexpected perioperative psychotic episodes, poor compliance, and a tendency to not follow medical advice after surgery and show early discontinuation of follow-up, we suggest that surgeons should work with other medical professionals and carefully perform total hip arthroplasty in such patients.

Biomechanical consideration of total hip arthroplasty following failed fixation of femoral intertrochanteric fractures – A finite element analysis

OBJECTIVE The current study aimed to perform a biomechanical analysis of the effect and distribution of stress and strain values in the femur and its residual screw holes from the implantation of different lengths of total hip prostheses following failed dynamic hip screw (DHS) fixation of AO type A1.1 and A1.3 intertrochanteric fractures. METHODS Medical image processing, computer-assisted engineering design, and finite element analysis were combined for the analysis and the reliability of the model confirmed by convergence testing and comparison with a physical model. Using finite element analysis, patterns of stress from implantation of total hip prostheses with different stem length were obtained. RESULTS Stress distribution was concentrated over the third and fourth residual screw holes, especially in the models with shorter stem length. Fracture type (AO type A1.1 or A1.3) did not alter its distribution. In proximal cancellous bone, a stress-shielding effect was seen at the region of the residual fracture fragment, especially in the A1.1 fracture. In the fracture fixed with 2 cable wires, the maximum von Mises stress was in the proximal cable wire. CONCLUSION The results suggest that an increase in the original stem length equal to the diameter of the femoral isthmus, or a distance between the most distal residual screw hole and the end of the femoral prosthesis, provide improved stress distribution.

Metal ion concentrations and semen quality in patients undergoing hip arthroplasty: A prospective comparison between metal-on-metal and metal-on-polyethylene implants.

Purpose: The widespread usage of metal‐on‐metal (MoM) articulations in total hip arthroplasty (THA) has been tempered by concerns of increased metal ion production. The purpose of the study is to evaluate the influence of metal ion exposure on semen quality in young male patients undergoing THA. Methods: Male patients who were scheduled for unilateral THA and aged between 20 and 45 years were prospectively enrolled. Patients were sorted into MoM and metal‐on‐polyethylene (MoP) groups with equal case number. Semen and blood metal ion levels were measured and sperm analysis was performed before, 6 months after, and 1 year after surgery. Results: Compared to preoperative baseline, patients (n = 50) in both groups had increased cobalt (Co) and chromium (Cr) concentrations in blood and seminal fluid after surgery. Between‐group comparisons at 6 months and 1 year after surgery showed that patients in the MoM group both had a greater Co concentration in blood and semen and a greater Cr concentration in blood and semen. Patients receiving MoM prosthesis had a reduced percentage of morphologically normal sperm, and decreases from the preoperative level (44.7%) were significant at 6 months (36.8%, p = 0.03) and 1 year (33.8%, p = 0.004). Conclusions: Our data shows a significantly greater concentration of metal ion in blood and semen in patients with MoM prosthesis with a reduced percentage of morphologically normal sperm. Despite small effects on sperm quality, some concerns remain. Further studies are necessary to determine sources of metal ion and to investigate effects on male fertility.

Two-stage revision arthroplasty for Mycobacterium Tuberculosis periprosthetic joint infection: An outcome analysis

Background Mycobacterium tuberculosis periprosthetic joint infection (TBPJI) is a rare complication of hip/knee joint arthroplasty. The outcomes of hip/knee TBPJI treatment are still unreported. The objective of this study was to investigate the outcomes of hip/knee TBPJI following treatment with two-stage exchange arthroplasty. Materials and methods From 2003 to 2013, 11 patients with TBPJI (six hips and five knees) were treated with two-stage exchange arthroplasty at our institution. We collected and analyzed variables including demographic data, comorbidities, microbiological data, duration of symptoms, and types of antibiotic used in bone cement. Results At the most recent follow-up, the success rate of two-stage exchange arthroplasty was 63.3% (7 of 11). All five knee treatments resulted in infection eradication and successful prosthesis reimplantation. However, only two hip TBPJI treatments resulted in successful outcomes; two patients died and two experienced chronic infection. Overall, secondary bacterial infections were common in patients with TBPJI (5 of 11 cases, 45.5%). Streptomycin in bone cement increased the success rate (83.33% vs. 40%). Conclusion More than one third of the patients treated with two-stage exchange arthroplasty for TBPJI showed infection relapse or uncontrolled infection. Streptomycin-loaded interim cement spacers appeared to help ensure successful treatment. Routine M. tuberculosis culture is recommended when treating TBPJI in areas of high tuberculosis prevalence.

Surgical Approach May Influence Survival of Large-Diameter Head Metal-on-Metal Total Hip Arthroplasty: A 6- to 10-Year Follow-Up Study

Large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA) has lost popularity because of metal allergy or ALTRs (adverse local tissue reactions) in the past decade. Whether the surgical approach may influence the survival of LDH-MoM-THA has not been reported. From 2006 to 2009, we performed 96 LDH-MoM-THAs on 80 patients using an in situ head-neck assembly technique through a modified Watson-Jones approach. With a mean follow-up of 8.4 years (range, 6.3–10.1 years), the implant survival rate was 100%. All patients were satisfied with the results and the Harris Hip Score improved from 52 points to 98 points. No ALTRs were found, but 17.7% of the 96 hips (17 adverse events) experienced adverse events related to the cup, including 5 cases of outlier cup malposition, 11 cases of inadequate cup seating, and 1 acetabular fracture. The tissue tension that was improved by a muscle-sparing approach might lessen the chance of microseparation or edge-loading that is taken as the major risk for early implant failure. Further investigation of whether these LDH-MoM-THAs would fail or not would require a longer follow-up or even retrieval analysis in the future.