Antibiotics are an integral part of infection prophylaxis in orthopaedic surgery, and tourniquets are widely used during many of those same surgeries. The timing of antibiotic administration in relation to tourniquet use has long been debated. Hanberg et al. explore this “balancing act” in the November 4, 2020 issue of The Journal in a carefully performed animal study.
The researchers anesthetized 24 female pigs and surgically exposed both of their hind calcanei. They then placed microdialysis catheters through drill holes in each calcaneus and also into the subcutaneous adipose tissue in the hind feet. Tourniquets were applied to one hind leg on each animal, and each pig was then randomized into 1 of 3 groups, based on when the animal received 1.5 gm of cefuroxime intravenously:
- Group A –15 minutes prior to tourniquet inflation
- Group B – 45 minutes prior to tourniquet inflation
- Group C – At the time of tourniquet release
Hanberg et al. inflated the tourniquets for 90 minutes in all 3 groups, and then they measured the concentrations of cefuroxime and ischemic markers at regular intervals between the time of tourniquet inflation and up to 480 minutes afterward.
The authors found that in both Groups A and B, cefuroxime concentrations were maintained above the minimum inhibitory concentration (MIC) for Staphylococcus aureus in cancellous bone and adipose tissue throughout the 90 minutes of tourniquet inflation. In addition, injecting cefuroxime at the time of tourniquet deflation (Group C) kept the tissue-antibiotic levels above the MIC on the tourniquet side for 3.5 hours after tourniquet release.
There were no differences in the time above MIC in bone or adipose tissue between the 3 groups, but the researchers noted a trend toward shorter time above MIC in bone in Group A vs. Group C (p=0.08). There was also a tendency toward higher time above MIC in bone on the tourniquet side compared to no-tourniquet side in Group B (p=0.08) and Group C (p=0.06). The researchers also found that, in all the animals, tissue ischemia persisted for 2.5 hours after tourniquet deflation in bone, while the adipose tissue recovered immediately.
This animal study provides useful data and prompts us to ponder ideas for further investigation regarding the interplay between tourniquets and antibiotic perfusion. For example, I think the prolonged ischemia in cancellous bone is a topic that warrants further investigation, and I am also curious whether adding antibiotics at the time of tourniquet release might help combat the potentially negative effects of that ischemia.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
Osteonecrosis of the femoral head is a dreaded complication for patients with a slipped capital femoral epiphysis (SCFE). This complication is far more common with acutely displaced and unstable slips. Safely reducing the femoral head back on the neck while preserving blood supply can often be accomplished with closed reduction maintained by in situ cannulated screw fixation, although some recent efforts to treat SCFE have focused on open approaches.
In the June 15, 2016 edition of The Journal, Schrader et al. demonstrate the benefits of using a simple intracranial pressure (ICP) monitoring probe (see photo) inserted through the cannulated screw to measure femoral head perfusion. While using this technique intraoperatively on 26 hips with SCFE, the authors encountered six hips in which there was no blood flow to the femoral head after closed reduction and screw stabilization. In these situations, they performed percutaneous capsular decompression.
The fact that all patients—even those with no initial femoral head perfusion—left the operating room with measurable blood flow confirms the long-held principle that lack of perfusion can be treated with capsulotomy. The ICP device uses waveforms to measure blood flow and is an accurate gauge of perfusion. Moreover, the technology is available in most hospitals with trauma centers or neurosurgery services.
Having researched femoral head perfusion myself as a young orthopaedist and having kept abreast of more recent findings in this area, I think the monitoring protocol described by Schrader et al. is the best yet published to limit the devastating complication of hip osteonecrosis. I feel that if ICP monitors are available, this protocol should be adopted by all centers treating patients with acute SCFE.
Marc Swiontkowski, MD