Peter K. Sculco

Assessment of femoral head and head-neck junction perfusion following surgical hip dislocation using gadolinium-enhanced magnetic resonance imaging: a cadaveric study.

BACKGROUND The purpose of the present study was to quantify perfusion to the femoral head and head-neck junction using gadolinium-enhanced magnetic resonance imaging following three surgical dislocations of the hip (trochanteric flip osteotomy, standard posterior approach, and modified posterior approach). METHODS The medial femoral circumflex artery was cannulated in fifty fresh-frozen cadaveric hips (twenty-five pelvic specimens). One hip on each pelvic specimen was randomly chosen to undergo one of the three surgical dislocations, and the contralateral hip was used as a control. Gadolinium enhancement on the magnetic resonance imaging scan was quantified in both the femoral head and head-neck junction by volumetric analysis using custom magnetic resonance imaging analysis software. A polyurethane compound was then injected, and gross dissection was performed to assess the extraosseous vasculature. RESULTS Magnetic resonance imaging quantification revealed that the trochanteric flip osteotomy group maintained almost full perfusion (mean, 96% for the femoral head and 98% for the head-neck junction). The standard posterior approach almost completely compromised perfusion (mean, 4% for the femoral head and 8% for the head-neck junction). Six specimens in the modified posterior approach group demonstrated partial perfusion (mean, 32% in the femoral head and 26% in the head-neck junction). Three specimens in the modified posterior approach group demonstrated almost full perfusion (mean, 96% in the femoral head and 97% in the head-neck junction). Gross dissection revealed that all specimens in the standard posterior approach group and seven of ten in the modified posterior approach group sustained disruption of the ascending branch of the medial femoral circumflex artery. All specimens in the standard posterior approach group demonstrated disruption of the inferior retinacular artery. The inferior retinacular artery remained intact in nine of ten specimens in the modified posterior approach group. One specimen in the modified posterior approach group that had disruption of both the ascending medial femoral circumflex artery and inferior retinacular artery demonstrated a substantial decrease in perfusion (7% in the femoral head and 5% in the head-neck junction). CONCLUSIONS The trochanteric flip osteotomy preserves the vascular supply to the femoral head and head-neck junction. The standard posterior approach disrupts the vascular supply and should be completely abandoned for surgical hip dislocation. Despite reduced enhancement, substantial perfusion of the femoral head and head-neck junction was present in the modified posterior approach group, likely because of the preservation of the inferior retinacular artery. The modified posterior approach produced variable results, indicating that improvement to the modified posterior approach is needed. CLINICAL RELEVANCE Our study provides previously unreported quantitative magnetic resonance imaging data on the perfusion to the femoral head and head-neck junction during common surgical approaches to the hip.

Periprosthetic Knee Infections Treated with Irrigation and Debridement: Outcomes and Preoperative Predictive Factors

The role of irrigation and debridement (I&D) in the treatment of periprosthetic joint infections (PJI) of the knee remains controversial. Our purpose was to identify the success rate and factors determining outcome of I&D in those patients. Clinical characteristics of 78 patients with PJI of the knee treated with I&D were retrospectively reviewed. Implant retention at final follow-up was achieved in 43 patients (55.1%). Logistic regression analysis revealed that duration of symptoms >5days and thyroid disease were independent predictors of I&D failure. Patients with methicillin-resistant staphylococcal infections had a success rate of 45.5% and significantly lower odds of success compared to patients with negative cultures. In selected patients, I&D is a reasonable option in the context of acute PJI of the knee.

Risk Factors for Recurrence of Periprosthetic Knee Infection

We retrospectively reviewed 110 patients who underwent two-stage revision surgery in order to identify potential risk factors for recurrence of periprosthetic infection. We found that patients with inflammatory arthritis (P=0.0125), perioperative hematoma formation (P=0.0422), wound dehiscence (P=0.042), and those who are chronic Staphylococcus carriers (P=0.0177) were associated with an increased incidence of re-infection. The duration of intravenous antibiotic therapy less than 6 weeks was associated with a reduced risk of reinfection to greater than 6 weeks (P=0.03). Multivariate analysis indicated that wound dehiscence (odds ratio [OR], 5.119; 95% confidence interval [CI], 1.367-19.17), and Staphylococcus carriers (OR, 11.419; 95% CI, 1.376-94.727) are significant predictors of recurrence (P=0.0153 and 0.0241, respectively).

The effect of a low radiation CT protocol on accuracy of CT guided implant migration measurement: A cadaver study.

The current study compared the impact of low radiation CT protocols on the accuracy, repeatability, and inter‐ and intra‐observer variability of implant migration studies in total hip arthroplasty. Two total hip replacements were performed in two human cadavers and six tantalum beads were inserted into the femur similar to radiostereometric analysis. Six different 28 mm heads (−3 mm, 0 mm, 2.5 mm, 5.0 mm, 7.5 mm, and 10 mm) were added to simulate five reproducible translations (maximum total point migration) of the center of the head. Three CT scans with varying levels of radiation were performed for each head position. The effective dose (mSv) was 3.8 mSv for Protocol A (standard protocol), 0.7 mSv for Protocol B and 1.6 mSv for Protocol C. Implant migration was measured in a 3‐D analysis software (Geomagic Studio 7). The accuracy was 0.16 mm for CT Protocol A, 0.13 mm for Protocol B and 0.14 mm for Protocol C; The repeatability was 0.22 mm for CT Protocol A, 0.18 mm for Protocol B and 0.20 mm for Protocol C; ICC for inter observer reliability was 0.89, intra observer reliability was 0.95. The difference in accuracy between standard protocol A and the two low radiation protocols (B, C) was less than 0.05 mm. The accuracy, inter‐ and intra‐observer reliability of all three CT protocols is comparable to radiostereometric analysis. Reducing the CT radiation exposure to numbers similar to an AP Pelvis radiograph (0.7 mSv protocol B) does not affect the accuracy of implant migration measurements. Keywords: Radiation dose, CT, migration analysis, cadaver.

Multiple Irrigation and Debridements for Periprosthetic Joint Infections: Facing a Necessity or Just Prolonging the Inevitable?

Irrigation and debridement (I&D) may be a viable option in selected cases of periprosthetic joint infections (PJI). Our aim was to investigate the role of multiple I&Ds. Among 141 patients with PJI treated with I&D in our institution, 19 were subjected to additional procedures. Their clinical characteristics were retrospectively reviewed and compared to the remaining patients treated with a single I&D. The probability of treatment failure (removal of implants) was not significantly different among the two groups. The interval between serial I&Ds was a significant factor determining outcomes. Patients treated with multiple I&Ds had a significantly higher prevalence of peripheral vascular disease. The decision to proceed with repeat of I&D should be made with caution.