Surgery performed in low-volume centres has been associated with longer operating time, longer hospital stays, lower functional outcomes, and higher rates of revision surgery, complications, and mortality. This has been reported consistently in the arthroplasty literature, but there is a paucity of data regarding the relationship between surgical volume and outcome following anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare the ACL reconstruction failure rate between hospitals performing different annual surgical volumes. The hypothesis was that ACL reconstructions performed at low-volume hospitals would be associated with higher failure rates than those performed at high-volume centres.

This level-II cohort study included all patients from the Norwegian Knee Ligament Registry that underwent isolated primary autograft ACL reconstruction between 2004 and 2016. Hospital volume was divided into quintiles based on the number of ACL reconstructions performed annually, defined arbitrarily as: 1–12 (V1), 13–24 (V2), 25–49 (V3), 50–99 (V4), and ≥100 (V5) annual procedures. Kaplan-Meier estimated survival curves and survival percentages were calculated with revision ACL reconstruction as the end point. Mean change in Knee Injury and Osteoarthritis Outcome Score (KOOS) Quality of Life and Sport subsections from pre-operative to two-year follow-up were compared using t-test.

19,204 patients met the inclusion criteria and 1,103 (5.7%) underwent subsequent revision ACL reconstruction over the study period. Patients in the lower volume categories (V1-3) were more often male (58–59% vs. 54–55% p=<0.001) and older (27 years vs. 24–25 years, p=<0.001) compared to the higher volume hospitals (V4-5). Concomitant meniscal injuries (52% vs. 40%) and participation in pivoting sports (63% vs. 56%) were most common in V5 compared with V1 (p=<0.001). Median operative time decreased as hospital volume increased, ranging from 90 minutes at V1 hospitals to 56 minutes at V5 hospitals (p=<0.005). Complications occurred at a rate of 3.8% at low-volume (V1) hospitals versus 1.9% at high-volume (V5) hospitals (p=<0.001). Unadjusted 10-year survival with 95% confidence intervals for each hospital volume category were: V1 – 95.1% (93.7–96.5%), V2 – 94.1% (93.1–95.1%), V3 – 94.2% (93.6–94.8%), V4 – 92.6% (91.8–93.4%), and V5 – 91.9% (90.9–92.9%). There was no difference in improvement between pre-operative and two-year follow-up KOOS scores between hospital volume categories.

Patients having ACL reconstruction at lower volume hospitals did not have inferior clinical or patient reported outcomes, and actually demonstrated a lower revision rate. Complications occurred more frequently however, and operative duration was longer. The decreased revision rate is an interesting finding that may be partly explained by the fact that patients being treated in these small, often rural hospitals, may be of lower demand as suggested by the increased age and decreased participation in pivoting sports. In addition, patients with more complicated pathology such as meniscal tears were more commonly treated in the larger volume hospitals. The most significant limitation of this study is that provider volume was not assessed, and the number of surgeons dividing up the surgical volume at each hospital is not known.

Aim

This study aimed to identify risk factors for development of deep periprosthetic joint infection (PJI) in patients following surgical treatment of neck of femur fracture.

A randomised controlled trial was conducted using a rabbit model of a complex contaminated extremity war wound. Compared to saline soaked gauze dressings Inadine (iodine) and Acticoat (nanocrystalline silver) had significantly lower levels of Staphylococcus aureus after 7 days while Activon Tulle (Manuka honey) had significantly higher levels.

Molecular level analysis of the wound was conducted. Plasma cytokines of interest were assayed using ELISA and levels of expression of relevant tissue genes measured using PCR following RNA extraction.

Appreciable levels of Interleukins 4 and 6 and Tumour Necrosis Factor-α were identified in plasma with significantly higher levels of IL-4 and TNFα detected in the Activon Tulle group. In tissue TNFα, Matrix metalloproteinase-3 and the ratio of Matrix metalloproteinase-9 to Tissue Inhibitor of Matrix metalloproteinase-1 were significantly higher in tissue injured limbs than the uninjured limbs with no significant differences between groups.

Interpretation of these results is challenging. IL-4 has been associated with transition from pathological inflammation to repair and TNFα with impaired healing. However, Activon Tulle had significantly higher levels of S. aureus and we found no differences in observational, histology, haematology or tissue gene expression outcomes over 7 days which would correlate with these molecular biology results.

A randomised controlled pre-clinical trial utilising an existing extremity war wound model compared the efficacy of saline soaked gauze to commercial dressings. The Flexor Carpi Ulnaris of anaesthetised New Zealand rabbits was exposed to high-energy trauma using computer-controlled jig and inoculated with 10⁶Staphylococcus aureus 3 hours prior to application of dressing. After 7 days the animals were culled. Quantitative microbiological assessment of post-mortem specimens demonstrated statistically significantly reduced S aureus counts in groups treated with iodine or silver based dressings (2-way ANOVA p< 0.05).

Clinical observations and haematology were performed during the study. Histopathological assessment of post-mortem muscle specimens included image analysis of digitally scanned haematoxylin and eosin stained tissue sections and subjective semi-quantitative assessment of pathology severity using light microscopy to grade muscle injury and lymph node activation. Tissue samples were also examined using scanning electron microscopy to determine the presence of bacteria and biofilm formation within the injured muscle. Non-parametric data were compared using Kruskal-Wallis.

There were no bacteraemias, significantly raised white cell counts, abscesses, purulent discharge or evidence of contralateral axillary lymph node activation. All injured muscle specimens showed evidence of haemorrhage, inflammatory cell infiltration and fibrosis. All ipsilateral axillary lymph nodes were activated. There were no significant differences in the amount of muscle loss, size of the activated lymph nodes or in subjective semi-quantitative scoring criteria for muscle injury or lymph node activation. There was no evidence of bacterial penetration or biofilm formation.

This study demonstrated statistically significant reductions in Staphylococcus aureus counts associated with iodine and silver dressings, and no evidence that these dressings cause harm. This was a time-limited study which was primarily powered to detect reduction in bacterial counts; however, there was no significant variation in secondary outcome measures of local or systemic infection over 7 days.

Extremity injury and complications such as wound infection remain a significant problem for the military. This study investigates the anti-microbial efficacy of four dressings used in militarily relevant complex extremity injury.

Under general anaesthesia, the flexor carpi ulnaris of 24 New Zealand White rabbits was exposed to a high-energy impact and then inoculated with 10⁶ colony forming units of Staphylococcus aureus. Dressings: gauze soaked in saline, Chlorhexidine, Betadine or Acticoat¯, were randomised and applied 3 hours post injury, to replicate casualty evacuation. Once recovered, animals were checked at least twice daily and body temperature recorded. Analgesia was administered once a day. At 48hrs animals were culled, the muscle harvested and analyzed by a blinded investigator. Group sizes of 6 were required to detect a statistically significant effect of a mean one log reduction in bacterial counts at 48 hours.

No dressing gave a significant reduction in bacterial counts at 48 hours. A paired t-test of contamination versus recovered dose gave p values of 0.903, 0.648, 0.396 and 0.336 for saline, Acticoat¯, chlorhexidine and iodine respectively. Contamination dose between groups compared using ANOVA showed no significant difference (p=0.566). Recovered bacterial loads between groups revealed no significant difference (p=0.280).

This study indicates that over a 48 hour period, dressings with reported anti-bacterial properties offer no advantage over saline soaked gauze in reducing the bacterial burden in a contaminated soft tissue injury. Future work will extend the study temporally and introduce multiple contaminants.