Relationship between pre- and post-operative isokinetic strength after ACL reconstruction using hamstring autograft.

BACKGROUND: Anterior cruciate ligament (ACL) ruptures are of major concern in sports. As mostly young and active individuals are affected there is an emphasis on the rapid and safe return to sports (RTS). Strengthening the ventral and dorsal thigh muscles is a prerequisite for a successful RTS after ACL reconstruction (ACLR), as persistent muscle weakness may increase the incidence for secondary injuries and impair performance. Aiming to increase evidence on the importance of preoperative muscle strength and the coaching of patients, the purpose of this study is to compare thigh muscle strength pre- and post-operatively after ACLR. METHODS: We performed a retrospective analysis of 80 patients with primary, isolated ACLR using a four-stranded hamstring autograft. We performed bilateral isokinetic concentric strength measurement (60°/s) before and six months after ACLR. Primary outcomes were the maximal knee extension and flexion torque, hamstrings-to-quadriceps ratio (H/Q ratio) and the corresponding limb symmetry indices (LSI). Pearson correlations were calculated for pre- and post-surgical values. RESULTS: The operated as well as the unaffected leg increased maximal knee extension (+ 18% ± 7% p < 0.05; + 11% ± 5% p < 0.05) and flexion torque (+ 9% ± 5% p < 0.05, + 10% ± 6% p < 0.05) throughout the 6 months of rehabilitation. The H/Q ratio remained unaffected (- 2% ± 3% p = 0.93; - 4% ± 4% p = 0.27). LSI of knee extension strength increased significantly (6% ± 3% p < 0.05), while flexion strength remained unaffected (+ 2% ± 4% p = 0.27). Positive correlations underline the interrelationship between the strength pre- and post-surgery for the knee extension (r = 0.788 p < 0.05) and knee flexion strength (r = 0.637 p < 0.05) after ACLR. CONCLUSIONS: Preoperative leg extension and flexion strength normalized to body mass are strongly correlated to postoperative strength performance after ACLR. Therefore, pre-operative quadriceps and hamstring muscle strength deficits may have a significant negative impact on functional performance following ACLR. This emphasizes the need for intensive preoperative screening and subsequent treatment to achieve the best possible preoperative leg strength before ACLR. TRIAL REGISTRATION: DRKS00020210 .

Lack of response to addition of degradable protein to a low protein diet fed to midlactation dairy cows.

Midlactation Holstein cows (n = 24, 12 primiparous) were subjected to four dietary treatments arranged in six Latin squares. Cows were assigned to squares according to parity and previous production within parity. Diets contained 53 to 55% DM from corn silage, and the remaining DM was from concentrates. The basal diet contained 13.9% CP with 9.5% rumen-degraded and 4.4% undegraded intake protein. Three other treatments were formulated to give one diet with more degradable true protein than the basal (11.9% degraded intake protein, 4.3% undegraded intake protein); another with urea added to the basal (12.2% degraded intake protein, 4.5% undegraded intake protein); and a third with additional undegraded protein added to the basal (8.3% degraded intake protein, 7.2% undegraded intake protein). Milk fat and protein concentration were unaffected by diet in all squares. Only the highest producing cows responded significantly to increased undegraded intake protein; milk production was 30.8, 30.9, 31.6, and 33.2 kg/d for basal, added degradable true protein, added urea, and added undegraded protein, respectively. Corresponding protein productions were 913, 929, 927, and 1004 g/d for these cows. Neither degradable true protein nor degradable N increased milk production in the highest producing cows, suggesting that microbial protein production was not limited by the amount of degradable protein in the basal diet. For midlactation, multiparous, and primiparous cows producing < 30 and 25 kg of milk/d, respectively, the protein content of the basal ration appeared to be adequate.