Kelly J. Hendricks

The "Gull Sign": a harbinger of failure for internal fixation of geriatric acetabular fractures.

Objectives To identify factors affecting the outcomes of surgery for acetabular fracture in patients over the age of 60 years. Design Retrospective review of records and radiographs; current examination, radiographs and outcome surveys when possible. Setting Academic, Level 1 trauma center. Patients/Participants Forty-eight patients over age 60 with displaced acetabulum fractures. Intervention Surgical reduction and fixation. Main Outcome Measurements Clinical ratings and radiographic evaluations, Short Musculoskeletal Functional Assessment survey (SMFA), SF-36, and hip-specific questions. Radiographs were evaluated using the criteria of Matta. Results Ten patients died since surgery. Four were lost to follow-up. Seven had >12 months of follow-up information in the chart. Twenty-seven had current evaluations for the study. Average follow-up was 37 months, range 1–114 months. The average age at surgery was 71.6 years (range 61–88). No perioperative deaths occurred. Initial reductions achieved: 61% anatomic, 34% imperfect, and 5% poor. A specific radiographic finding (superomedial dome impaction) predictive of failure was identified. This was designated the “Gull Sign.” These patients had inadequate reduction, early fixation failure, or medial/superior joint narrowing and subluxation. Functional outcomes in patients with current examination were similar to age-matched controls. Radiographic outcomes: 30% excellent, 30% good, 9% fair, 23% poor, and 7% arthroplasty. Anatomic reduction was closely related to good or excellent radiographic result. Conclusions While some patients over sixty years of age can have satisfactory functional outcomes after acetabular fracture fixation, a significant number will have failure of the procedure. Osteopenic patients with superomedial dome impaction (the Gull Sign) did not benefit from attempted open reduction and internal fixation in this series.

High placement of noncemented acetabular components in revision total hip arthroplasty. A concise follow-up, at a minimum of fifteen years, of a previous report.

We previously reported the average ten-year results associated with the use of porous-coated noncemented acetabular shells that were placed at a high hip center at the time of revision total hip arthroplasty in thirty-four patients (thirty-six hips) with severe acetabular bone loss. We now report the average 16.8-year results for twenty-one patients (twenty-three hips). Of the original cohort of forty-four patients (forty-six hips), thirty-nine patients (forty-one hips; 89%) retained the shell. Two shells (4.3%) were revised because of aseptic loosening, and three (6.5%) were revised because of infection. Six femoral components were revised because of femoral osteolysis, and seven were revised because of aseptic loosening without osteolysis. On the basis of our results after an average duration of follow-up of 16.8 years, we believe that the placement of an uncemented acetabular component at a high hip center continues to be an excellent technique for revision total hip arthroplasty in selected patients with severe acetabular bone loss.

Synergy between Staphylococcus aureus and Pseudomonas aeruginosa in a rat model of complex orthopaedic wounds

Background: We observed an interaction in animals inoculated concomitantly with Staphylococcus aureus andPseudomonas aeruginosa during a study of the efficacy of surfactants for disinfection of orthopaedic wounds. This led us to investigate whether synergy could be demonstrated between Staphylococcus aureus and Pseudomonas aeruginosa in a rat model of complex orthopaedic wounds. Methods: A wire was implanted into the spinous process of a lumbar vertebra of Sprague-Dawley rats through a dorsal incision. Animals were divided into two groups: group one was inoculated with either Staphylococcus aureus or Pseudomonas aeruginosa, and group two received a polymicrobial inoculation with both test organisms in varying concentrations. After inoculation, the wounds were irrigated and closed. On postoperative day 14, all animals were killed and specimens from the wounds were cultured. The number of colony-forming units (CFU) of Staphylococcus aureus or Pseudomonas aeruginosa needed to cause infection in 50% of the animals (ID50) was determined with use of the Reed-Muench method. The infection rate associated with each inoculum combination was calculated, and the two groups were compared. Results: The ID50 was 2.8 ¥ 104 CFU for Staphylococcus aureus and 4.8 ¥ 105 CFU for Pseudomonas aeruginosa. The combination of 103 CFU of Staphylococcus aureus with low concentrations (102, 103, or 104 CFU) of Pseudomonas aeruginosa yielded infection rates that were higher than those found with either organism alone at the same concentrations. The combination of 103 CFU of Staphylococcus aureus and 103 CFU of Pseudomonas aeruginosa yielded a 75% infection rate, which was significantly higher (p = 0.004) than that associated with 103 CFU of either organism alone. As the Pseudomonas aeruginosa concentration was increased (to 105, 106, and 107 CFU), this trend reversed, and the infection rate decreased to 33% (p = 0.004). Low concentrations of Pseudomonas aeruginosa (0 to 105 CFU) combined with 106 CFU of Staphylococcus aureus yielded infection rates ranging from 83% to 100%. At the higher concentrations of Pseudomonas aeruginosa (106 and 107 CFU), however, the infection rate again decreased, to 33% (p = 0.005). Only Staphylococcus aureus was isolated from the cultures of the specimens from the animals that had received a polymicrobial inoculum. Conclusions: Synergy between Staphylococcus aureus and Pseudomonas aeruginosa was demonstrated when low levels of each organism were present in the wound. As the Pseudomonas aeruginosa concentration was increased, the infection rates fell well below what would be anticipated, suggesting that low concentrations of Pseudomonas aeruginosa enhance the ability of Staphylococcus aureus to cause infection in this orthopaedic wound model. At the same time, the presence of Staphylococcus aureus in the ratios tested decreased the rate of infection by Pseudomonas aeruginosa. Clinical Relevance: Staphylococcus aureus is a pathogen commonly seen in orthopaedic patients. The pathogenicity of Staphylococcus aureus was shown to be increased in the presence of anaerobic bacteria. This study is the first one that we are aware of that demonstrated synergy between Staphylococcus aureus and Pseudomonas aeruginosa, at low concentrations, in a wound model while at the same time showing that Staphylococcus aureus lowers the rate of Pseudomonas aeruginosa infection.

Short segment bone-on-bone instrumentation for single curve idiopathic scoliosis.

Study Design. Retrospective case series review. Objectives. To evaluate the outcomes of a new short segment anterior scoliosis technique with complete removal of the discs, bone-on-bone apposition of the vertebral bodies, and dual rod instrumentation. To evaluate a new preop planning technique for scoliosis instrumentation. Summary of Background Data. Scoliosis surgery traditionally was performed via a posterior approach, but anterior scoliosis instrumentation has proven to be superior regarding the amount of curve correction and the number of segments saved from instrumentation. Methods. Thirty-one patients with single curve idiopathic scoliosis less than 75° were operated using the bone-on-bone surgical technique with dual rod instrumentation (Kaneda Anterior Scoliosis System, Depuy AcroMed, Raynham, MA from 1996 until 2001). Average follow-up was 40 months (range 15–77 months). Results. Surgical correction of the major curve averaged 73.9% over the instrumented levels and 51.4% over the entire curve. The average number of discs fused was 4.6 for thoracic curves and 3.3 for thoracolumbar and lumbar curves. There were no implant-related complications or nonunions. The compensatory curves spontaneously improved by an average of 38.6%. Uneventful healing of all fusions occurred—most within 8 to 12 weeks. One compensatory thoracic curve progressed and posterior instrumentation was done 28 months after correction of the major thoracolumbar curve. Conclusions. Surgical correction was achieved in over half the levels that would have been operated by standard posterior segmental fixation. Bony healing due to the bone-on-bone apposition was achieved uneventfully after apical correction of the spinal curvature in all patients. Use of dual rod instrumentation (Kaneda Anterior Scoliosis System) is fundamental in maintaining the correction of the curvature achieved in the operating room. The preoperative planning technique worked well.

Revision of failed acetabular components with use of so-called jumbo noncemented components. A concise follow-up of a previous report.

Acetabular revision in the presence of major bone-stock deficiency is a difficult clinical and surgical problem. Of an original pool of twenty-four consecutive patients treated with an acetabular revision with a so-called jumbo (>65-mm) cementless hemispherical acetabular component, fifteen were followed for an average of seven years in our previous study. The current report presents the results for the twelve patients in this group who were alive at a minimum of twelve years (mean, 13.9 years) postoperatively and agreed to return for follow-up. The average final Harris hip score was 79 points. No acetabular shell had been revised because of aseptic loosening, and none was loose as seen radiographically. The complication rate was high but was largely related to infection. In the patients without infection, the fixation of these large sockets remained excellent at the time of long-term follow-up.

Increasing the elution of vancomycin from high-dose antibiotic-loaded bone cement: a novel preparation technique.

BACKGROUND Antibiotic bone cement is commonly used in staged revision arthroplasty as well as the treatment of open fractures. Multiple factors affect antibiotic elution from bone cement. This study was performed to investigate the effect of two variables, the quantity of liquid monomer and the timing of antibiotic addition, on the ultimate elution of antibiotic from bone cement. METHODS Vancomycin-loaded Simplex P and SmartSet MV bone cement was prepared with three different methods: a common surgical technique, a mixing technique that doubled the amount of liquid monomer, and a novel technique that delayed antibiotic addition until after thirty seconds of polymerization. Cylinders of a standardized size were created from each preparation. The elution profiles of five cylinders from each preparation were measured over six weeks with use of high-performance liquid chromatography. Cylinders were tested in compression to quantify strength. RESULTS Delayed antibiotic addition resulted in significantly greater cumulative elution over six weeks (p < 0.0001), with minimal reduction in strength, compared with the other groups. Doubling the liquid monomer significantly reduced cumulative elution over six weeks compared with either of the other techniques (p < 0.0001). Vancomycin elution from Simplex P was 52%greater and vancomycin elution from SmartSet MV was 25% greater in the delayed-antibiotic-addition groups than it was in the corresponding standard surgical technique groups. The majority of the antibiotic was released over the first week in all groups. : High-dose-antibiotic bone cement prepared with delayed antibiotic addition increased vancomycin elution compared with the standard surgical preparation. Incorporating additional liquid monomer decreased vancomycin elution from high-dose-antibiotic cement. We recommend preparing high-dose-antibiotic bone cement with the delayed-antibiotic addition technique and not incorporating additional liquid monomer. CLINICAL RELEVANCE Both the relative volume of liquid monomer and the timing of antibiotic addition have substantial effects on the elution of antibiotic from bone cement.

Surfactant wound irrigation for the treatment of staphylococcal clinical isolates.

Deep wound infection involving an implanted biomaterial is a devastating complication in orthopaedic surgery. Two-thirds of such infections are monomicrobial and the most commonly isolated bacteria in human osteomyelitis and orthopaedic device infection are Staphylococcus aureus and Staphylococcus epidermidis. The purpose of the current study was to examine the effectiveness of the previously reported sequential surfactant irrigation protocol against human-isolated clinical strains of Staphylococcus aureus and Staphylococcus epidermidis in the rat model of orthopaedic implant contamination. The infectivity rate of human-isolated clinical strains of Staphylococcus aureus in a contaminated complex orthopaedic wound was reduced effectively by a sequential surfactant irrigation protocol. Also, in this model, the infectivity of Staphylococcus epidermidis was reduced by normal saline irrigation alone when compared with no irrigation. Therefore, the sequential surfactant irrigation protocol may represent an effective method of wound irrigation in monomicrobial Staphylococcus aureus orthopaedic implant contamination, and normal saline irrigation may suffice in cases of monomicrobial Staphylococcus epidermidis contamination. Additional studies are necessary to determine the clinical use of surfactant irrigation.

In vitro elution of tobramycin from bioabsorbable polycaprolactone beads.

Objectives To compare the in vitro elution characteristics of tobramycin impregnated beads made of polycaprolactone (PCL) and polymethylmethacrylate (PMMA). Design Six-millimeter PCL and PMMA beads with 6% tobramycin were formed and placed in phosphate-buffered saline or newborn calf serum and incubated at room temperature or 37°C. Aliquots were taken at intervals for eight weeks. Tobramycin levels were determined by fluorescent assay and antibacterial efficacy was assessed by measuring the zones of inhibition against Staphylococcus aureus and Pseudomonas aeruginosa on agar diffusion plates. Results Tobramycin elution rates at room temperature were similar up to three weeks. At three weeks, elution rates from PCL beads were twice those from PMMA beads, and at eight weeks, elution from PCL was quadruple that from PMMA. At 37°C, tobramycin elution rates from PCL were eight times greater than those from PMMA by eight weeks. Total tobramycin eluted from PCL beads was 38.9% and 20% in PMMA beads. All samples showed bacteriostatic activity against S. aureus and P. aeruginosa at eight weeks. Conclusions These in vitro results show that PCL has superior antibiotic elution characteristics compared with PMMA, and this may translate into a more effective antibiotic delivery vehicle. In addition, PCL is a bioabsorbable polymer, which may decrease the need for a second surgical procedure to remove retained beads.

Compression Strength and Porosity of Single-Antibiotic Cement Vacuum-Mixed With Vancomycin

We evaluated the ultimate compression strength (UCS), porosity, and fracture surface roughness of 2 commercially available single-antibiotic bone cements vacuum-mixed with additional amounts of vancomycin (2, 4, 6, and 8 g). At least 8 g could be added to Palacos R + 0.5 g gentamicin (UCS = 75.04 +/- 6.64 MPa) and no more than 6 g to Simplex P + 1 g tobramycin (UCS = 78.93 +/- 4.98 MPa) to maintain a UCS above the International Organization for Standardization minimum standard (70 MPa). Increasing vancomycin concentration correlated with a decrease in porosity but showed a trend towards greater fracture surface roughness.

Eradication by surfactant irrigation of Staphylococcus aureus from infected complex wounds.

Treatment of infected orthopaedic hardware usually requires the removal of the appliance. When the device is removed and immediately replaced, persistent infection frequently complicates this exchange procedure. We modeled the exchange procedure in rats by passing a wire suture through a posterior spinous process and then contaminating the wound with Staphylococcus aureus. We then investigated whether a sequence of surfactant enriched irrigation solutions (Castile soap followed by benzalkonium chloride, sequential surfactant irrigation) had a greater capacity to eradicate Staphylococcus aureus from the experimental wound than did the standard wound irrigant, normal saline. When we left the wire in place through the 2-week course of the study, sequential surfactant irrigation showed only a modest advantage over normal saline (staphylococci recovered from 39% versus 58% of wound cultures respectively). Simple removal of the wire 24 hours after implantation and bacterial contamination prevented wound infection in most animals (with the wire removed, 38% of the animals remained infected versus 85% with the wire left in place), without regard to the irrigation solution. Alternatively, when we removed the wire after 24 hours, irrigated the wound, and then placed a fresh wire back into the wound, sequential surfactant irrigation showed a significant advantage over NS (54% of the animals irrigated with sequential surfactants remained infected versus 100% of the animals irrigated with normal saline). Our findings confirm the importance of a contaminated medical device for promoting foreign body infection; our findings also show that sequential surfactant irrigation has therapeutic value in a rat model of orthopaedic device infection; this irrigation protocol should be studied further as a potential agent for the treatment of infected orthopaedic wounds.