Drain tip cultures do not predict infections in primary total knee arthroplasty.

BACKGROUND AND AIM: The possibility to predict surgical site infections development could be of high prognostic value. We aimed to investigate whether cultures obtained from the tip of the closed passive wound drain may provide early signs of progression towards periprosthetic joint infections. MATERIALS AND METHODS: We performed an observational study on consecutive primary total knee arthroplasties performed in our department over 4 years by two high volume surgeons (it means they do a lot of arthroplasties/year; it is orthopedics specific). A total of 284 knees in 257 patients were included. Follow up was available for an average of 18.7 months. There were no simultaneous procedures. RESULTS: Nineteen (6.69%) drain tips yielded positive cultures, for a mean duration, from surgery to sample collection, of 1.63 (0.5) days. None of the positive drain tip cultures developed clinical signs of infection and all knees were healed at discharge after a mean of 13.78 days (SD= 3.34; range= 8-18). None of the 7 (2.46%) cases who developed deep infections had positive drain tip cultures. A true positive value of 0 led to a positive predictive value of 0, a negative predictive value of 97.34%, sensitivity of 0% and specificity of 93.14. CONCLUSIONS: The diagnostic use of passive drain tip cultures to detect early infections after total knee replacement is therefore absolutely useless.

Reconstructed ACLs have different cross-sectional areas compared to the native contralaterals on postoperative MRIs. A pilot study.

OBJECTIVE: The current trends in anterior cruciate ligament (ACL) reconstruction aim not only to restore the position and footprint of the native ACL, but also its shape and biomechanical function. The objective of our study was to determine whether the in vivo shape of the healed graft differs from the native ACL. PATIENTS AND METHODS: We performed bilateral MRI examinations on patients with successful unilateral ACL reconstruction for an average period of 3 years. The imaging acquisitions were performed using 1.5 T field strength and T2 FSE axial oblique sequence at 2 mm spacing. We than averaged the ratio between the maximum width and thickness as well as the surface area in pixels using ImageJ (National Institutes for Health) and compared it with the native ACLs using the paired t-test. RESULTS: For both quadrupled hamstrings and B-PT-B neoligaments, the mid-portion area was significantly higher (p < 0.001) than the native contralateral ACL: 41.82/31.39 mm2 and 37.05/32.08 mm2, respectively. The surface area of the neoligaments mid-portion was on average 33.23% higher than the native ACL for the quadrupled hamstrings and 15.49% for the B-PT-B, respectively. The native contralateral ACL was also significantly thinner throughout the mid-portion (p < 0.001) than both B-PT-B and quadrupled hamstrings neoligaments, with a width-thickness ratio of 2.57 vs 1.97 and 2.57 vs 1.39, respectively. CONCLUSIONS: Our study showed that, several years after successful anatomic single bundle ACL reconstruction using an ipsilateral autograft, the mid-portion shape and cross-sectional area are not restored compared to the uninjured contralateral knee. This effect was more prevalent with hamstrings and less prominent when B-PT-B were used.

Anterior cruciate ligament reconstruction and determination of tunnel size and graft obliquity.

OBJECTIVE: Increase in ACL (anterior cruciate ligament) reconstructions has led to a higher prevalence of patients with postoperative symptoms which require investigation. We aimed to investigate the utility of magnetic resonance imaging (MRI) and computer tomography (CT) in determining tunnel size and graft obliquity after single bundle ACL reconstruction. PATIENTS AND METHODS: A retrospective comparison was made on 29 symptomatic knees after anatomic single bundle (trans AM) and transtibial ACL reconstructions which had both MRI and CT scans at an average of 1.3 years postoperatively (2 months-5.7 years). We compared CT and MRI (T2 sequence) tunnel size and graft obliquity estimates using Pearson correlation and t-test. We also compared MRI's of ACL reconstructed knees with hamstrings or patellar autografts, which were confirmed by operative protocol as either antero-medial (AM) technique (n=21) or trans-tibial (TT) technique (n=19). The surgeries were performed for an average of 6.29 (4-10) years for the TT group and 1.3 (0-3) years for the AM group, respectively. The graft inclination was measured relative to the tibial plateau using DICOM software. Statistical analysis used the mean value for each case and the data were processed using the non-parametric Kruskal-Wallis test to determine the difference in graft obliquity and tunnel placement. RESULTS: Tunnel size estimates correlate well between CT and MRI on axial scans: R2=0.795 and 0.630 for femur and tibia respectively. The position of the tunnels and graft obliquity were found to differ on MRI images in both coronal and sagittal planes. Coronal graft obliquity averaged 72.38° (ranging from 69° to 76°) using the AM technique and 75.47° (ranging from 72° to 78°) with TT technique. Sagittal graft inclination angle was 54.5 (51-58.5) and 63.68 (59-69.5) respectively. MRI proves to be the most useful imaging method in determining outcome after ACL reconstruction. However, for a better revision of the ACL reconstructions, CT can offer a clearer image of tunnels and bone stock. A more anatomical graft positioning increases obliquity in coronal and sagittal planes and, thus, becomes difficult to assess both tunnels in a single slice. CONCLUSIONS: The anatomic single bundle reconstruction technique has been found to more accurately reproduce the femoral footprint and the orientation of the graft compared to the TT technique where the appropriate tibial tunnel placement resulted in a more vertical graft.