Toxic effects of local anesthetics on rat fibroblasts: An in-vitro study.

BACKGROUND: Infusion catheters facilitate a controlled infusion of local anesthetic (LA) for pain control after surgery. However, their potential effects on healing fibroblasts are unspecified. METHODS: Rat synovial fibroblasts were cultured in 12-well plates. Dilutions were prepared in a solution containing reduced-serum media and 0.9% sodium chloride in 1:1 concentration. Each well was treated with 500 µl of the appropriate LA dilution or normal saline for 15- or 30-min. LA dilutions included: 0.5% ropivacaine HCl, 0.2% ropivacaine HCl, 1% lidocaine HCl and epinephrine 1:100,000, 1% lidocaine HCl, 0.5% bupivacaine HCl and epinephrine 1:200,000, and 0.5% bupivacaine HCl. This was replicated three times. Dilution of each LA whereby 50% of the cells were unviable (Lethal dose 50 [LD50]) was analyzed. RESULTS: LD50 was reached for lidocaine and bupivacaine, but not ropivacaine. Lidocaine 1% with epinephrine is toxic at 30-min at 1/4 and 1/2 sample dilutions. Bupivacaine 0.5% was found to be toxic at 30-min at 1/2 sample dilution. Bupivacaine 0.5% with epinephrine was found to be toxic at 15- and 30-min at 1/4 sample dilution. Lidocaine 1% was found to be toxic at 15- and 30-min at 1/2 sample dilution. Ropivacaine 0.2% and 0.5% remained below LD50 at all time-points and concentrations, with 0.2% demonstrating the least cell death. CONCLUSIONS: Though pain pumps are generally efficacious, LAs may inhibit fibroblasts, including perineural fibroblast and endoneurial fibroblast-like cells, which may contribute to persistent nerve deficits, delayed neurogenic pain, and negatively impact healing. Should a continuous infusion be used, our data supports ropivacaine 0.2%. LEVEL OF EVIDENCE: Basic Science Study; Animal model.

Patient-specific targeting guides compared with traditional instrumentation for glenoid component placement in shoulder arthroplasty: a multi-surgeon study in 70 arthritic cadaver specimens.

HYPOTHESIS AND BACKGROUND: The purpose of this study was to compare the accuracy of patient-specific guides for total shoulder arthroplasty (TSA) with traditional instrumentation in arthritic cadaver shoulders. We hypothesized that the patient-specific guides would place components more accurately than standard instrumentation. MATERIALS AND METHODS: Seventy cadaver shoulders with radiographically confirmed arthritis were randomized in equal groups to 5 surgeons of varying experience levels who were not involved in development of the patient-specific guidance system. Specimens were then randomized to patient-specific guides based off of computed tomography scanning, standard instrumentation, and anatomic TSA or reverse TSA. Variances in version or inclination of more than 10° and more than 4 mm in starting point were considered indications of significant component malposition. RESULTS: TSA glenoid components placed with patient-specific guides averaged 5° of deviation from the intended position in version and 3° in inclination; those with standard instrumentation averaged 8° of deviation in version and 7° in inclination. These differences were significant for version (P = .04) and inclination (P = .01). Multivariate analysis of variance to compare the overall accuracy for the entire cohort (TSA and reverse TSA) revealed patient-specific guides to be significantly more accurate (P = .01) for the combined vectors of version and inclination. Patient-specific guides also had fewer instances of significant component malposition than standard instrumentation did. CONCLUSION: Patient-specific targeting guides were more accurate than traditional instrumentation and had fewer instances of component malposition for glenoid component placement in this multi-surgeon cadaver study of arthritic shoulders. Long-term clinical studies are needed to determine if these improvements produce improved functional outcomes.

Return to athletic activity after plate fixation of displaced midshaft clavicle fractures.

BACKGROUND: Recent data support primary plate fixation of displaced midshaft clavicle fractures. The safety and efficacy of this practice have not been well documented in athletes. HYPOTHESIS: Plate fixation of clavicle fractures in athletes is a safe and effective procedure, resulting in a reliable and timely return to play. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A total of 29 patients with displaced midshaft clavicle fractures from athletic activity were treated with plate fixation between January 1, 2003 and December 31, 2008, including 1 patient treated for each clavicle for separate injuries. All 29 patients were contacted for follow-up. At a mean follow-up of 21 months, patients completed a questionnaire focused on the time to return to athletics and treatment course. Patients also completed the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) questionnaire. Radiographs were reviewed to identify fracture comminution, displacement, shortening, and angulation; radiographic union time; and malunion. RESULTS: All of the patients (30/30 cases) returned to sports after open reduction internal fixation of their fracture. The mean time to return to play was 83 days with a range of 13 to 277 days. Seven (23%) of the cases returned to athletics at ≤6 weeks after surgery, and a total of 20 patients (67%) returned at ≤12 weeks after surgery. All patients (100%) were satisfied with their treatment. The QuickDASH scores revealed almost perfect recovery (mean score, 0.8 of 100). Four minor complications were identified. No patient had a refracture, plate fracture, loss of fixation, nonunion, malunion, or deep wound infection. CONCLUSION: Plate fixation of displaced clavicle fractures in athletes is a safe procedure, resulting in a high satisfaction rating and minimal disability to the upper extremity. An early return (<6 weeks) to sports is possible after this treatment; however, the time to return is highly variable.