THA after acetabular fracture fixation: is frozen section necessary?

BACKGROUND: Infection is uncommon after THA performed for failed acetabular fracture repair, despite a high reported incidence of culture-positive fixation implants. The use of frozen section analysis at the time of THA after acetabular fracture fixation surgery is unknown. QUESTIONS/PURPOSES: We asked whether frozen section analysis predicted occult infection after THA performed after acetabular fracture repair. METHODS: We retrospectively reviewed the charts of 43 of 49 patients with prior acetabular fracture fixation who had intraoperative frozen section and culture data from a conversion THA between 2002 and 2010. The average age of patients at fracture was 53 years; conversion was performed after an average of 553 days (median, 369 days; range, 51-2951 days). Five patients had an infection after acetabular fracture surgery (three deep, two superficial). At conversion we obtained an average of three frozen section specimens per patient; 10 specimens in eight patients contained greater than 10 polymorphonuclear cells/high-power field. The minimum followup was 51 days (median, 256 days; range, 51-2085 days). RESULTS: Five patients had positive intraoperative cultures, three of whom had a positive frozen section. All patients who had prior deep infection developed positive intraoperative cultures. The sensitivity, specificity, positive predictive value, and negative predictive value of frozen section analysis were 0.60, 0.87, 0.38, and 0.94, respectively. CONCLUSION: Infection complicating THA after acetabular fracture repair is uncommon. A history of deep infection complicating the acetabular fracture surgery was the strongest predictor of infection. Frozen section analysis has a high specificity and negative predictive value. LEVEL OF EVIDENCE: Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Gap formation in transpatellar patellar tendon repair: pretensioning Krackow sutures versus standard repair in a cadaver model.

BACKGROUND: Postfixation loosening within the Krackow stitch-tendon construct may be associated with gap formation in patellar tendon repair. HYPOTHESIS: Pretensioning the Krackow stitch-tendon construct decreases postfixation gap formation in transpatellar patellar tendon repair. STUDY DESIGN: Controlled laboratory study. METHODS: Patellar tendon rupture was simulated in 8 pairs of cadaveric knees. Standard manual traction was used in all specimens to remove Krackow stitch slack. In the experimental group, specimens were pretensioned with a simulated active concentric quadriceps contraction with cycling of the knee 10 times from 90 degrees to 5 degrees of flexion. All specimens were then cycled at 0.25 Hz from 90 degrees to 5 degrees for 1000 cycles until failure, which was defined as 3 or 5 mm of gap formation. RESULTS: A 3-mm gap occurred at 1 cycle (mean, 3.5 mm) and 35 cycles (4.0 mm) in the control and experimental groups, respectively. Gapping of 5 mm occurred at 35 (5.9 mm) and 100 cycles (5.0 mm) in the control and experimental specimens, respectively. Gap formation was smaller in the experimental group through 100 cycles (P < .05). CONCLUSION: Gapping was lower with pretensioning in the early cycling stages. However, significant gapping occurred in both groups with repetitive concentric active loading ranging from 90 degrees to 5 degrees of flexion. CLINICAL RELEVANCE: Tightening of the Krackow stitch as done in this study does not result in a clinically important decrease in gapping. This observation may be generalizable to other applications of the Krackow stitch.

Distal biceps tendon rupture: biomechanical analysis of repair strength of the Bio-Tenodesis screw versus suture anchors.

The purpose of this study was to compare the strength and stiffness of distal biceps tendon ruptures repaired with either a Bio-Tenodesis screw or suture anchor technique in a cadaveric model. Ten matched pairs of cadaveric arms underwent simulated distal biceps tendon ruptures and were repaired with either a Bio-Tenodesis screw or suture anchor technique. We analyzed pullout strength, stiffness, and mode of failure for each construct. The mean pullout strength of the repair with a Bio-Tenodesis screw was significantly higher (192 N [SD, 42.5 N] vs 147 N [SD, 29.5 N], P < .013). Use of the Bio-Tenodesis screw is an effective means of repairing distal biceps tendon ruptures. It provides significantly more initial pullout strength compared with suture anchors. This could potentially allow more aggressive rehabilitation and faster return to function.