Aims The aim of this study was to assess the effectiveness of perioperative essential amino acid (EAA) supplementation to prevent rectus femoris muscle atrophy and facilitate early recovery of function after total knee arthroplasty (TKA). Methods The study involved 60 patients who underwent unilateral TKA for primary knee osteo-arthritis (OA). This was a double-blind, placebo-controlled, randomized control trial with patients randomly allocated to two groups, 30 patients each: the essential amino acid supplementation (9 g daily) and placebo (lactose powder, 9 g daily) groups. Supplementation and placebo were provided from one week before to two weeks after surgery. The area of the rectus femoris muscle were measured by ultrasound imaging one month before surgery and one, two, three, and four weeks postoperatively. The serum albumin level, a visual analogue knee pain score, and mobility were also measured at each time point. The time to recovery of activities of daily living (ADLs) was recorded. Postoperative nutrition and physiotherapy were identical in both groups. Results The mean relative change from baseline was as follows for the amino acid group: 116% in rectus femoris muscle area (71% to 206%); 95% in serum albumin (80% to 115%) and 39% in VAS pain (0% to 100%) at four weeks after surgery. These values in the placebo group were: 97% in muscle area (68 to 155); 89% in serum albumin (71% to 100%) and 56% in VAS pain four weeks after surgery (0% to 100%). All changes were statistically significant (p < 0.05). The mean time to recovery of ADLs was shorter in the amino acid group compared with the placebo group (p = 0.005). Conclusion Perioperative essential amino acid supplementation prevents rectus femoris muscle atrophy and accelerates early functional recovery after TKA. Cite this article: Bone Joint J 2020;102-B(6 Supple A):10–18.

Background: This study aimed to clarify differences in clinical results, including in patients' joint awareness, between cruciate-substituting (CS) and cruciate-retaining (CR) medial pivot total knee arthroplasty (TKA) over a 10-year follow-up. Methods: A total of 333 TKAs were included in this study. There were 257 cases of CS and 76 cases of CR TKAs. Knee range of motion, Knee Society Score, and radiological outcomes were assessed. The patients' joint awareness was evaluated using the Forgotten Joint Score-12 at the final follow-up. The survival rate with respect to reoperation or revision was analyzed. Results: The mean follow-up period was 10 ± 1.7 years, and the loss to follow-up was 5.4%. All clinical outcomes improved significantly after surgery in both groups (P < .001). Postoperative knee flexion was 118 ± 13 in the CS group and 116 ± 10 in the CR group (P ¼ .10). The mean Forgotten Joint Score-12 scores were 57 ± 27 points in the CS group and 56 ± 28 points in the CR group (P ¼ .59). Ten years after the operation, the survival rates for reoperation were 96.3% in the CS group and 94.2% in the CR group (P ¼ .61), and those for revision were 98.4% and 98.7% in the CS and CR groups, respectively (P ¼ .87). Other postoperative clinical results did not differ between the 2 groups. Conclusion: In this 10-year follow-up study, medial pivot TKA, regardless of polyethylene insert type, showed a high survival rate and good patient awareness of the prosthetic joint.

Background: Perioperative essential amino acid (EAA) supplementation suppresses lower-limb muscle atrophy and promotes functional improvement in the first 4 weeks after total knee arthroplasty (TKA). However, its effect on the recovery of muscle volume and strength in the intermediate term is unclear. The aim of this study was to evaluate the effect of perioperative EAA supplementation on the recovery of lower-limb muscle volume and strength in the 2 years after TKA.Methods: Sixty patients who underwent unilateral TKA for primary knee osteoarthritis were included in this double-blinded randomized controlled trial. After excluding dropouts, 26 patients assigned to the EAA group (9 g/day) and 26 assigned to the placebo group (powdered lactose, 9 g/day) were available for analysis. Patients received EAA supplementation or a placebo from 1 week prior to surgery to 2 weeks after it. The rectus femoris muscle area was measured using ultrasonography and quadriceps muscle strength was measured isometrically with a handheld dynamometer, preoperatively and periodically up to 2 years postoperatively. Knee pain, knee range of motion, functional mobility, and Knee Society Score 2011 subjective scores were measured at each time point. Perioperative management, except for supplementation, was identical in the 2 groups.Results: Taking the baseline as 100%, the mean values in the EAA and placebo groups were 134% ± 31% and 114% ± 27%, respectively, for the rectus femoris muscle area and 159% ± 54% and 125% ± 40% for the quadriceps muscle strength, respectively, at 2 years after surgery. The differences were significant (p < 0.05). Clinical outcomes were not significantly different between the 2 groups.Conclusions: Perioperative EAA supplementation contributes to the recovery of rectus femoris muscle volume and quadriceps muscle strength in the 2 years after TKA. The EAA supplementation did not impact clinical outcomes.

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Background:Medial-pivot total knee arthroplasty (TKA) is designed with high articular conformity in the medial compartment in order to achieve stability. The subjective outcome of patients has been reported to be good postoperatively; however, the association between the objective and subjective knee stability and the influence of subjective stability on the overall outcomes of TKA remained unknown. Our hypothesis was that postoperative flexion joint-gap imbalance could affect subjective knee instability following TKA in medial-pivot prostheses. The purpose of this study was to analyze the association between the joint gap in flexion and subjective knee instability and between subjective knee instability and outcomes following medial-pivot TKA.Methods:A total of 769 patients who underwent primary TKA with use of medial-pivot prostheses were enrolled. Clinical outcomes included knee range of motion, Knee Society Score-2011 (KSS-2011), Forgotten Joint Score-12 (FJS-12), patient-reported subjective knee instability, and axial knee radiography to assess flexion joint-gap balance measured at the final follow-up. Clinical outcomes were compared between patients with and without subjective knee instability. Moreover, associated factors were analyzed for postoperative subjective knee instability.Results:Overall, 177 patients (23%) reported experiencing postoperative subjective knee instability. Knee flexion (p = 0.04); KSS-2011 symptom (p<0.001), satisfaction (p<0.001), expectation (p=0.008), and activity (p<0.001) subscales; and FJS-12 (p < 0.001) were significantly worse in patients with subjective knee instability. The KSS-2011 subjective score differences were greater than the minimal clinically important difference. Older age at the time of surgery (odds ratio, 1.04; p = 0.04) and a wider postoperative joint gap in flexion on the medial side (odds ratio, 1.21; p = 0.001) were significant risk factors for subjective knee instability. A gap angle of −2.9° (i.e., medial laxity) was the threshold to predict postoperative knee instability (sensitivity, 0.29; specificity, 0.91).Conclusions:Postoperative flexion joint-gap laxity on the medial side following medial-pivot TKA affected the patient-reported subjective knee instability scores. Postoperative KSS-2011 subjective scores following medial-pivot TKA were poorer in patients with subjective knee instability.Level of Evidence:Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.