Patients demonstrate distinct trajectories of recovery after THA. The purpose of this study was to assess the impact of adjacent muscle quality on postoperative hip kinematics. We hypothesized that patients with better adjacent muscle quality (less fatty infiltration) would have greater early biomechanical improvement.

Adults undergoing primary THA were recruited. Preoperative MRI was obtained and evaluated via Scoring Hip Osteoarthritis with MRI Scores (SHOMRI, Lee, 2015). Muscle quality was assessed by measuring fat fraction [FF] from water-fat sequences. Biomechanics were assessed preoperatively and six weeks postoperatively during a staggered stance sit-to-stand using the Kinematic Deviation Index (KDI, Halvorson, 2022). Spearman's rho was used to assess correlations between muscle quality and function.

Ten adults (5M, 5F) were recruited (average age: 60.1, BMI: 23.79, SHOMRI: 40.6, KDI: 2.96). Nine underwent a direct anterior approach and one a posterior approach. Preoperatively, better biomechanical function was very strongly correlated with lower medius FF (rho=0.89), strongly correlated with lower FF in the minimus (rho=0.75) and tensor fascia lata (TFL) FF (rho=0.70), and weakly correlated with SHOMRI (rho=0.29). At six weeks, greater biomechanical improvement was strongly correlated with lower minimus FF (rho=0.63), moderately correlated with medius FF (rho=0.59), and weakly correlated with TFL FF (rho=0.26) and SHOMRI (rho=0.39). Lastly, medius FF was moderately correlated with SHOMRI (rho=0.42) with negligible correlations between SHOMRI and FF in the minimus and TFL.

These findings suggest adjacent muscle quality may be related to postoperative function following THA, explaining some of the variability and supporting specialized muscle rehabilitation or regeneration therapy to improve outcomes.

Background: Evidence on pre and post- prophylactic antibiotics given with open orthopaedic procedures is limited. It is common practice to use cefuroxime in many UK orthopaedic units despite a strong causative association with Clostridium Difficile (C.diff) infection, particularly in elderly patients who form a significant proportion of total orthopaedic patients. Prior to April 2009 our hospital guidelines recommended cefuroxime 1.5g IV at induction and a further 750mg IV cefuroxime 8 and 16 hours post procedure. Subsequent changes in guidelines recommended a single dose of 750mg IV cefuroxime at induction with no post operative doses. The aim of this study was to evaluate the impact of this change in antibiotic guidelines on overall post-operative infection rates.

Methods: We identified 2 age and sex matched procedural cohorts: cohort 1 included 912 procedures pre-formed between December 2007 and March 2008, while cohort 2 included 836 procedures preformed between December 2008 and March 2009, both pre-formed in the same orthopaedic trauma theatres at our level I trauma centerI. The hospital results server was reviewed for evidence of post operative infection. Data on positive wound swabs, bacteraemia and C.diff was collected for the first 50 days post-procedure.

Results: There was no significant difference in overall post operative wound infection (10.1% vs. 6.1%; ns) and bacteraemia rate (0.3% vs. 0.7%; ns) after guideline change. However, a significant reduction in post operative C.diff infection rate after guideline change was noted (2.4% vs. 0.5%; p=0.03).

Discussion: We have demonstrated a significant reduction in post operative C.diff infection rates without a resultant increase in overall infection rate, after a recent change in hospital antibiotic policy. The change in antibiotic guidelines is clearly a positive step reducing C.diff rates and therefore morbidity and mortality relating to the infection. There is also likely to be an associated cost reduction. Moreover these results question the need for prophylactic antibiotics given that most orthopaedic procedures are clean, further work in this field is needed.