Knee strength measurement: Can we switch between isokinetic dynamometers?

BACKGROUND: Isokinetic evaluation is considered the gold standard in muscle strength measurement due to its sensitivity, intra-dynamometer reproducibility and usefulness in the injury prevention screening and follow up of subjects with musculoskeletal pathologies, neurological disease or after surgical operation. However, can one switch among different isokinetic dynamometers for the purpose of knee muscles evaluation? OBJECTIVES: To comprehensively evaluate the compatibility of the isokinetic short concentric and eccentric strength evaluation protocol and of the fatigability resistance evaluation between three different isokinetic devices. METHODS: Eighteen recreationally active men underwent three isokinetic knee testing sessions on three different isokinetic devices with 7–10 days of rest between each session. Relative (Pearson’s r product-moment correlation coefficient – PCC) and absolute (standard error of measurement – SEM, Cohen effect sizes (d) and probabilistic inferences – MBI) parameters of reproducibility were determined to assess the inter-dynamometer agreement. RESULTS: For the short concentric and eccentric strength evaluation protocol, the extensors in concentric mode and the flexors in eccentric mode can be compared (eventually with transposition formulas provided) between Biodex, Con-Trex and Cybex (almost all PCC ⩾ 0.80). The DCR could be compared between Con-Trex and Cybex and between Biodex and Cybex pairs (eventually with transposition formula provided). For the fatigability resistance evaluation protocol, the total sum can be compared for extensors (eventually with transposition formulas provided) for PM for all dynamometer pairs considered and, in the case of MW, only for Biodex and Con-Trex (PCC ⩾ 0.80). CONCLUSIONS: Only some of the parameters derived either from the short concentric and eccentric strength evaluation protocol or the fatigability resistance evaluation protocol may be interchangeable providing transposition formulas are applied. Otherwise, isokinetic findings are largely system-dependent save some specific instances.

PO 18121 - Reconstruction of peroneus brevis tendon tears by semitendinosus tendon autograft

Introduction: Reconstruction for irreparable tears of the peroneal brevis tendon (PBT) using tendon allograft has provided satisfactory clinical results. The aim of this study is to present the surgical technique for reconstruction of PBT tears using semitendinosus tendon autograft (SA) as an alternative to allograft and its early results. Methods: We describe the surgical technique for the reconstruction of irreparable tears of the PBT using SA performed in 3 patients, from December 2016 to May 2017, and early results. Two patients were male and one female, with a mean age of 46.6 years and a mean follow-up of 21 months. The indication for reconstruction was the presence of degenerative tissue that involved more than 50% of the cross-sectional area of the PBT. Preoperative planning included a clinical and imaging evaluation to search for conditions such as ankle instability, cavovarus foot, low-lying muscle belly of the PBT and peroneus quartus tendon. In the pre and postoperative period, they were prospectively assessed using visual analog scale (VAS) scores for pain and the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score. At 6 months, they were submitted to an isokinetic evaluation of the strength of both feet. Results: At the final follow-up, the mean VAS score was 8,7 preoperatively and 0 postoperatively. The mean AOFAS score was 43 preoperatively and 98,7 postoperatively. The 3 patients had different conditions associated with the lesions: a peroneus quartus tendon, a low-lying muscle belly and a cavovarus foot. They were addressed with resection of the peroneus quartus, resection of the low-lying muscle belly and with a lateral sliding calcaneal osteotomy. At 3 months, they were pain free and able to resume labor activities. At 6 months, they were able to return to sports. The isokinetic evaluation showed no eversion strength deficits compared with the contralateral side. At a mean follow-up of 21 months, they remain asymptomatic and fully active. Conclusion: Reconstruction of PBT tears with SA may be an effective alternative to allograft tissues. It can decrease pain and restore PBT function.