John D. Koerner

Correlation of growth factor levels at the fusion site of diabetic patients undergoing hindfoot arthrodesis and clinical outcome

BackgroundThe purpose of this study was to quantify the levels of growth factors (platelet-derived growth factor [PDGF] AB, vascular endothelial growth factor [VEGF], insulin-like growth factor [IFG] 1, and transforming growth factor [TGF]- &bgr;1) within bone samples at the fusion site of diabetic patients undergoing hindfoot arthrodesis to determine any correlation with successful fusion. MethodsThe study included 10 adult diabetic patients from one US center, with an average age of 57.9 years (range 49–71 years). Interventions included hindfoot arthrodeses with a fixator (n=8) and pantalar arthrodeses with fixator (n=2). During each procedure, a bony bed sample was taken from the fusion site and frozen. This local bone bed was analyzed for growth factors using ELISA kits. A platelet-rich plasma (PRP) concentration was applied to each fusion site during the procedure. ResultsThree of the ten patients had a nonunion. After normalizing to bicinchoninic acid assay (BCA) total protein levels, a 70% decrease in PDGF-AB (0.044 pg/&mgr;g non-union to 0.149 pg/&mgr;g union; P=0.016) and a 44% decrease in VEGF (0.522 pg/&mgr;g non-union to 0.924 pg/&mgr;g union; P=0.031) were observed in the three nonunion bone samples compared with the arthrodesis group. No difference existed in the levels of IGF-I between the groups. Insignificantly higher levels of TGF-&bgr;1 were detected in the nonunion group (0.199 ng/&mgr;g non-union to 0.142 ng/&mgr;g union; P=0.544). ConclusionsSignificant differences in local growth factor (PDGF, VEGF) levels exist between diabetic patients who achieve union and non-union. Potentially, growth factor levels, PDGF-AB and VEGF, in bone may affect the outcome of successful arthrodesis in diabetic patients. This study supports the concept that growth factor levels within the fusion site of a diabetic patient may affect the outcome of a successful hindfoot arthrodesis.

Septic Arthritis of the Hip Caused by Group B Streptococcus in a Postpartum Patient

Group B streptococcus is the leading cause of neonatal meningitis and sepsis, affecting approximately 9600 newborns in the United States annually1. Classically associated with newborn infection, it is also associated with 50,000 cases of pregnancy-connected morbidity, including urinary tract infection, chorioamnionitis, postpartum endometritis, and bacteremia1,2. Deutscher et al. stated that postpartum women have a “marked predisposition” for group B streptococcal infection3. While rare, cases of septic arthritis of the hip involving group B streptococcus have been reported, including one by Howell and Sheddon4. We present a postpartum woman with group B streptococcal septic arthritis of the right hip. This case highlights the importance of early diagnosis and awareness of septic arthritis in postpartum patients. The patient was informed that data concerning the case would be submitted for publication, and she provided consent. A thirty-eight-year-old woman, seventeen weeks postpartum, presented to the Emergency Department with right-sided hip pain, a progressive limp, and refusal to bear weight on the right lower extremity. Before visiting our Emergency Department, she had been diagnosed with radicular pain and had been prescribed analgesics, which proved ineffective. The pain initially had presented two weeks postpartum and had increased over the next four months. She denied fever, chills, and trauma. She had had an uneventful pregnancy and a vaginal delivery at full term. She was neither tested nor treated for group B streptococcus prior to delivery. She denied current tobacco, alcohol, and drug use but did have a history of cigarette smoking. Medical history and family history were unremarkable. On physical examination, the patient walked a maximum of two paces with an antalgic gait. She had decreased range of motion of the right hip, which worsened with internal rotation and extension. She was afebrile. White blood-cell (WBC) count …

Zinc has insulin-mimetic properties which enhance spinal fusion in a rat model.

BACKGROUND CONTEXT Previous studies have found that insulin or insulin-like growth factor treatment can stimulate fracture healing in diabetic and normal animal models, and increase fusion rates in a rat spinal fusion model. Insulin-mimetic agents, such as zinc, have demonstrated antidiabetic effects in animal and human studies, and these agents that mimic the effects of insulin could produce the same beneficial effects on bone regeneration and spinal fusion. PURPOSE The purpose of this study was to analyze the effects of locally applied zinc on spinal fusion in a rat model. STUDY DESIGN/SETTING Institutional Animal Care and Use Committee-approved animal study using Sprague-Dawley rats was used as the study design. METHODS Thirty Sprague-Dawley rats (450-500 g) underwent L4-L5 posterolateral lumbar fusion (PLF). After decortication and application of approximately 0.3 g of autograft per side, one of three pellets were added to each site: high-dose zinc calcium sulfate (ZnCaSO4), low-dose ZnCaSO4 (half of the high dose), or a control palmitic acid pellet (no Zn dose). Systemic blood glucose levels were measured 24 hours postoperatively. Rats were sacrificed after 8weeks and the PLFs analyzed qualitatively by manual palpation and radiograph review, and quantitatively by micro-computed tomography (CT) analysis of bone volume and trabecular thickness. Statistical analyses with p-values set at .05 were accomplished with analysis of variance, followed by posthoc tests for quantitative data, or Mann-Whitney rank tests for qualitative assessments. RESULTS Compared with controls, the low-dose zinc group demonstrated a significantly higher manual palpation grade (p=.011), radiographic score (p=.045), and bone formation on micro-CT (172.9 mm(3) vs. 126.7 mm(3) for controls) (p<.01). The high-dose zinc also demonstrated a significantly higher radiographic score (p=.017) and bone formation on micro-CT (172.7 mm(3) vs. 126.7 mm(3)) (p<.01) versus controls, and was trending toward higher manual palpation scores (p=.058). CONCLUSIONS This study demonstrates the potential benefit of a locally applied insulin-mimetic agent, such as zinc, in a rat lumbar fusion model. Previous studies have demonstrated the benefits of local insulin application in the same model, and it appears that zinc has similar effects.