Association of intraoperative medial joint gap laxity in the flexion position with subjective knee instability after fixed-bearing posterior-stabilised total knee arthroplasty.

BACKGROUND: Postoperative subjective knee instability is an important clinical outcome after total knee arthroplasty (TKA), however the association with intraoperative soft tissue balance remains unclear. This study aimed to assess the association between intraoperative soft tissue balance and postoperative subjective knee instability in fixed-bearing posterior-stabilised (PS) TKA. METHODS: This retrospective case-control study included 457 patients who underwent fixed-bearing PS TKA. Intra-articular distraction force was quantitatively applied to measure the gap parameters (length and angle) during surgery. The intraoperative joint gap parameters and postoperative clinical outcomes between the patients with (n = 90) and without (n = 367) subjective knee instability were compared. The risk factors for subjective postoperative knee instability were analysed using multivariate logistic regression analysis. RESULTS: The patients with subjective knee instability demonstrated a medially wider intra-articular gap angle and worse Knee Society Score 2011 symptoms (18 vs. 21; p < 0.01), satisfaction (27 vs. 30; p < 0.01), functional activity (55 vs. 65; p < 0.01), and Forgotten Joint Score 12 items (51 vs. 65; p < 0.01) than those in the patients without subjective knee instability. The use of measured resection technique (odds ratio, 2.3; 95% CI, 1.1-4.8; p = 0.02) and the medial laxity of joint gap balance in the flexion position (odds ratio, 1.2; 95% CI, 1.0-1.4; p = 0.04) were detected as risk factors for postoperative subjective knee instability. CONCLUSION: In fixed-bearing PS TKA, intraoperative medial joint laxity in the flexion position was associated with postoperative subjective knee instability, and surgical techniques to achieve sufficient soft tissue balance contributed to improve postoperative subjective clinical outcomes. LEVEL OF EVIDENCE: Ⅲ (case-control study).

Usefulness of non-surgical treatment without weight bearing restriction versus surgical treatment for maintaining activities of daily living in patients with peri-prosthetic femoral fractures.

PURPOSE: Non-surgical treatment without weight-bearing restriction, even in the early post-injury phase, may have a favourable effect on the activities of daily living (ADLs) in elderly patients with peri-prosthetic femoral fractures (PFFs). This study aimed to assess the effectiveness of surgical and non-surgical treatments for PFFs in terms of ADL maintenance and clinical safety. METHODS: This retrospective cohort study included 44 patients with PFFs proximal to the stem fixation site without stem loosening. Rehabilitation with weight bearing was initiated after internal fixation of the fracture site in the surgical group (n = 12) and immediately after the injury in the non-surgical group (n = 32). Clinical and radiological outcomes, including time until the first weight-bearing exercise, time until independent walking, ADL deterioration, and bone union rate, were compared between groups. Independent risk factors for ADL deterioration were also evaluated. RESULTS: The time until first weight-bearing exercise was shorter and the ADL deterioration rate was smaller in the non-surgical group than in the surgical group (8.8 ± 9.2 vs. 21 ± 13 days, P = 0.004; 6.2% vs. 12.5%, P = 0.04, respectively). Bone union rates were similar between groups (91% vs. 83%, P = 0.42), and aseptic loosening of the stem was not observed. Time until first weight-bearing exercise was identified as an independent risk factor for ADL deterioration (odds ratio, 1.13; 95% confidence interval, 1.01-1.26; P = 0.03). CONCLUSION: Non-surgical treatment of PFFs proximal to the stem fixation site without stem loosening, which does not restrict early weight-bearing exercise after injury, is an effective and safe treatment procedure that maintains ADL performance in elderly patients.

Clinical outcomes and radiolucent line analysis in cementless mobile-bearing total knee arthroplasty: a prospective multicentre study in Japan.

The objective of this study was to assess radiolucent lines (RLLs) and to determine their effect on clinical outcomes of the newly introduced cementless mobile-bearing total knee arthroplasty (TKA) system. This was prospective, multicentre study. Seventy-eight patients with knee osteoarthritis who underwent primary TKA were enrolled. Patient-reported outcome measures (PROMs) and radiographic assessments were evaluated at preoperative baseline and at 6 weeks, 1 year, and 2 years after surgery. KOOS, PKIP, 2011KSS, EQ-5D-3L and SKO improved from preoperative baseline to all postoperative timepoints, with no loosening of components. No RLLs were detected at 6 weeks after surgery. However, RLLs ≥ 1 mm developed in 2.8% of the patients for the femur and 9.7% for the tibia at 1 year after surgery, and values were 5.7% and 10.9%, respectively, at 2 years after surgery. RLL incidence was not correlated with PROMs. Age, sex, body mass index, range of motion knee flexion, posterior cruciate ligament treatment and ß angle did not impact the occurrence of RLLs. There were no intraoperative complications, revisions or reoperations. This TKA system improved PROMs and showed less incidence of RLLs compared to the previous reported TKA without implant-related complications.

Early Postoperative Functional Recovery in Older Patients With Periprosthetic Femoral Fractures: Comparison Between Cemented and Cementless Stem Revisions.

Background: Early postoperative functional recovery is important in older patients with lower-extremity fractures to prevent disuse, and periprosthetic femoral fractures (PFFs) are no exception. This study aimed to compare the postoperative functional recovery in the early phase after revision for PFF with loose stems between cemented and cementless stems. Methods: Eighteen patients with Unified Classification System type B2 PFF were included in this retrospective cohort study with a follow-up period of about 2 years. All patients underwent stem revision and were divided into 2 groups: the cemented stem group (n = 9) and the cementless stem group (n = 9). In postrevision, functional independence measure score, independent walk rate, activities of daily living recovery rate to the original level at 2 weeks postoperatively, the Beals and Tower classification for radiological status, and survival rate for readmission as endpoints were compared between the 2 groups. Results: Patients in the cemented group recovered functional mobility earlier than in the cementless group, with higher postoperative functional independence measure functional subscale values (73 vs 50 points, P = .02), higher independent walk rate (89 vs 11%, P < .01), and more postoperative activities of daily living recovery (100% vs 44%, P = .03) at 2 weeks postoperatively. The Beals and Tower classification and survival rates were similar in both groups. Conclusions: Revision using a cemented stem for PFF in older patients was a useful surgical procedure in terms of early postoperative functional recovery. Cemented stem revision was comparable with cementless in bone union and safety at 2 years postoperatively.

Simultaneous Post and Cone Fractures of a Polyethylene Insert in a Mobile-Bearing Posterior-Stabilized Total Knee Arthroplasty.

We report a novel case of the simultaneous post and cone fractures of a polyethylene (PE) insert in a mobile-bearing posterior-stabilized total knee arthroplasty. Twelve years after the primary total knee arthroplasty, the 72-year-old male patient presented with a recurring right knee instability and was diagnosed with the wear of the PE insert based on physical and radiological examinations. Revision surgery was performed. The post and cone of the PE insert had fractured simultaneously. Moreover, the femoral and tibial components were in direct contact with each other. One year post-revision, knee function had improved. To diagnose a PE breakage, such as a post or cone fracture, surgeons should consider the possibility of PE breakage even in the absence of pain since patients might complain of subjective instability only.

Improvement of rotational arc during deep flexion range of a novel designed polyethylene insert for posterior-stabilised total knee arthroplasty.

BACKGROUND: One of the remaining issues in total knee arthroplasty (TKA) is achieving sufficient rotational arc during deep flexion range of the knee for specific postures such as the 'seiza' or cross-legged sitting. This study aimed to evaluate whether there was a change in the actual in vivo rotational arc during deep flexion range before and after a design change of polyethylene (PE) inserts. METHODS: In 50 posterior-stabilised TKA cases, knee kinematics, including rotational movement, were measured intraoperatively using an image-free navigation system to compare a newly designed PE insert with reduced the posterior lip with a conventional PE insert. Femoral-tibial rotational angles at 30°, 45°, 60°, 90°, 120°, and 130° knee flexion were evaluated. Varus/valgus instability, knee range of motion, and femoral rollback were also measured. Obtained parameters were compared between new and conventional PE inserts. The independent factors associated with rotational arc during deep flexion range (120° and 130° knee flexion) were analysed using multivariate analysis. RESULTS: The newly designed PE insert demonstrated a significant increase in the rotational arc at 120° (22.9 ± 8.7° vs. 30.1 ± 11.9°, P < 0.001) and 130° (24.3 ± 9.5° vs. 32.5 ± 12.4°, P < 0.001) knee flexion compared with that with the conventionally designed posterior-stabilised insert. Multivariate analysis demonstrated that using the newly designed PE insert was an independent predictor of improved rotational arc during deep flexion range: regression coefficient was 11.2 (95% confidence interval 7.1-15.3, P < 0.001). CONCLUSION: The design change, which reduced the posterior lip of the PE insert, contributed to improved rotational arc in 120° and 130° deep flexion ranges.

Mobile-bearing prosthesis suppresses the postoperative rotational mismatch and improves patient-reported outcome measurements better than fixed-bearing prosthesis: rotational analysis by 3D measurement in total knee arthroplasty.

INTRODUCTION: It is preferable to reduce postoperative excessive rotational mismatch between the femur and tibia that causes poor clinical results following total knee arthroplasty (TKA). The aim of this study is to compare postoperative rotational mismatches and clinical outcomes with mobile- and fixed-bearing prostheses. MATERIALS AND METHODS: This study classified 190 TKAs into two groups equally by propensity score matching: mobile-bearing group (n = 95) and fixed-bearing group (n = 95). Computed tomography images of the whole leg were taken at 2 weeks postoperatively. The component alignments, rotational mismatches between the femur and tibia, and rotations among components were measured three-dimensionally. The knee range of motion, New Knee Society Score (KSS) subjective sores, and Forgotten Joint Score (FJS-12) were assessed at the final follow-up. RESULTS: Rotational mismatch between the femur and tibia was significantly less in the mobile- (- 0.8° ± 7.3°) than in the fixed-bearing (3.3° ± 8.5°, p < 0.001) group. New KSS functional activity score was significantly poorer in patients with excessive rotational mismatch (61.3 ± 21.4) than in those without it (49.5 ± 20.6, p = 0.02). Comparing mobile-bearing prosthesis, the use of fixed-bearing prosthesis was a risk factor for postoperative excessive rotational mismatch (odds ratio: 2.32, p = 0.03). CONCLUSION: When compared to a fixed-bearing prosthesis, TKA using a mobile-bearing prosthesis could suppress the postoperative rotational mismatch between the femur and tibia that causes poor subjective functional activity score. However, since this study was conducted for PS-TKA, the results might not be applicable to other models.

Long-term clinical results of alumina ceramic medial pivot total knee arthroplasty: a 10-year follow-up study.

BACKGROUND: The newly-designed alumina ceramic medial pivot total knee prosthesis was introduced to reduce polyethylene wear and better fit the anatomical morphology of the Asian population. This study aimed to clarify the long-term clinical results of alumina medial pivot total knee arthroplasty over a minimum follow-up period of 10 years. METHODS: The data of 135 consecutive patients who underwent primary alumina medial pivot total knee arthroplasty were analyzed in this retrospective cohort study. Patients were examined over a minimum 10-year follow-up period. The knee range of motion, Knee Society Score (KSS) knee score, Knee Society Score function score, and radiological parameters were assessed. The survival rate was also evaluated by using reoperation and revision as endpoints. RESULTS: The mean follow-up period lasted 11.8 ± 1.4 years. Patients who were not followed accounted for 7.4% of the total cohort. Knee and function scores of KSS improved significantly following total knee arthroplasty (P < 0.001). In 27 individuals (28.1%), a radiolucent line was observed. Aseptic loosening occurred in three cases (3.1%). The survival rates for reoperation and revision were 94.8% and 95.8% 10 years after the operation, respectively. CONCLUSIONS: During a minimum 10-year follow-up period, the present model of alumina medial pivot total knee arthroplasty showed good clinical outcomes and survival rates.

Three-dimensional adipose-derived stem cell spheroids exert potent therapeutic effects on rat femur osteochondral defects.

BACKGROUND: Spheroids can allow three-dimensional (3D) cell culture without scaffolds, potentially promoting the production of growth factors from adipose-derived stem cells (ADSCs). We hypothesized that ADSC spheroids exert more favourable effects on osteochondral defects than ADSCs in two-dimensional (2D) cultures. The purpose of this study was to compare the therapeutic effects of 2D and 3D cultures of ADSCs on osteochondral defects using animal models. METHODS: Rat femoral osteochondral defects were created. When creating osteochondral defects, phosphate-buffered saline, 2D ADSCs, or ADSC spheroids as a 3D culture were administered on to the lesion. At 2, 4, 6, 8, 10 and 12 weeks post-surgery, knee tissues were harvested and evaluated via histological examination. The expression of genes related to growth factors and apoptosis were compared between 2D and 3D ADSCs. RESULTS: Histologically, the repair of osteochondral defects was significantly enhanced in 3D ADSCs than in 2D ADSCs in terms of the Wakitani score and cartilage repair rate. In 3D ADSCs, TGF-ß1, VEGF, HGF and BMP-2 were significantly upregulated, while apoptosis was suppressed in the early phase. CONCLUSION: The therapeutic effects of 3D ADSC spheroids on osteochondral defects were more potent than those of 2D ADSCs. The upregulated expression of growth factors and suppression of apoptosis could contribute to promoting these therapeutic effects. Overall, ADSC spheroids can help treat osteochondral defects.

Perioperative Essential Amino Acid Supplementation Facilitates Quadriceps Muscle Strength and Volume Recovery After TKA: A Double-Blinded Randomized Controlled Trial.

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. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Clinical usefulness and safety in the early phase after a newly designed rotating-platform total knee arthroplasty: A prospective multicentre cohort study with a 2-year follow up.

BACKGROUND: This study aimed to assess the clinical results and safety of a newly designed rotating-platform posterior-stabilised total knee arthroplasty (TKA) in the early postoperative phase, within 2 years of follow up. METHODS: This prospective, multicentre cohort study included 100 consecutive patients who underwent rotating-platform posterior-stabilised (PS) TKA (Vanguard PSRP). After excluding dropouts, 93 patients were analysed. The objective Knee Society Score (KSS)-2011, subjective KSS-2011, knee range of motion, EuroQol 5 Dimension index, complications, and survival rates were assessed before TKA and at 6 months, 1 year, and 2 years postoperatively. The scores at each time-point were compared, and the survival rate was assessed with revision as the endpoint. To demonstrate non-inferiority, the clinical outcomes of patients who underwent rotating-platform PS TKA were compared with those collected retrospectively from 50 patients who underwent fixed-PS TKA (Vanguard PS), defined as the control group. RESULTS: All clinical outcomes at the final follow up significantly improved compared with their preoperative values (P < 0.001). The objective KSS-2011 was 90.0 ± 8.2 points, subjective KSS-2011 satisfaction was 30.7 ± 8.6 points, expectation was 10.4 ± 2.1 points, and functional activity was 74.0 ± 18.5 points at 2 years postoperatively. Complications included knee dislocation in one patient and surgical site infection in one patient. The survival rate was 99% at 2 years postoperatively. Clinical outcomes, complications, and survival rates of newly designed TKA were not statistically different compared with the control group. CONCLUSION: The newly designed rotating-platform PS TKA showed good clinical results and suitable safety during the early postoperative phase in this prospective multicentre cohort study.

Association of a Wider Medial Gap (Medial Laxity) in Flexion with Self-Reported Knee Instability After Medial-Pivot Total Knee Arthroplasty.

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.

No Difference in Postoperative Knee Flexion and Patient Joint Awareness Between Cruciate-Substituting and Cruciate-Retaining Medial Pivot Total Knee Prostheses: A 10-Year Follow-Up Study.

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 = .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 = .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 = .61), and those for revision were 98.4% and 98.7% in the CS and CR groups, respectively (P = .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.

Comparison of postoperative knee flexion and patient satisfaction between newly and conventionally designed medial pivot total knee arthroplasty: a 5-year follow-up matched cohort study.

INTRODUCTION: The medial pivot total knee arthroplasty (TKA) has good patients' satisfaction; however, there is likely the restriction of postoperative knee flexion. The 2nd generation medial pivot TKA prosthesis was designed to improve postoperative knee flexion. This study aimed to compare the clinical outcomes and patient satisfaction between the 2nd generation and 1st generation medial pivot TKA prostheses. MATERIALS AND METHODS: We conducted a retrospective study of 472 consecutive TKAs, performed using either the 2nd generation (EVOLUTION™), having smaller posterior femoral condyle and asymmetrical tibial tray, or 1st generation (ADVANCE™) prosthesis. The use of each system was historically determined. Patient age, sex and body mass index were matched between the two groups, with 157 cases ultimately included in each group. Measured clinical outcomes included: knee range of motion, the Knee Society Score, the rate of re-operation, and radiological parameters. Patient satisfaction was evaluated using the 12-item Forgotten Joint Score (FJS-12). RESULTS: The average follow-up period was 5.0 (3.7-6.3) years for the 2nd generation group and 8.7 (6.1-12.8) years for the 1st generation group (p < 0.01). The postoperative knee flexion range was 127° (80°-140°) for the 2nd generation and 118° (90°-135°) for the 1st generation at final follow-up (p < 0.01). On multivariate regression analysis, use of the 2nd generation prosthesis predicted greater postoperative knee flexion. The average FJS-12 score was 64 (0-100) for the 2nd generation and mean 57 (0-100) for the 1st generation (p < 0.01). Other clinical outcomes were similar between the two groups. CONCLUSIONS: Compared to the 1st generation, the 2nd generation medial pivot prosthesis provides greater postoperative knee flexion and patient satisfaction.

Topical co-administration of zoledronate with recombinant human bone morphogenetic protein-2 can induce and maintain bone formation in the bone marrow environment.

BACKGROUND: Bone morphogenetic proteins (BMPs) induce osteogenesis in various environments. However, when BMPs are used alone in the bone marrow environment, the maintenance of new bone formation is difficult owing to vigorous bone resorption. This is because BMPs stimulate the differentiation of not only osteoblast precursor cells but also osteoclast precursor cells. The present study aimed to induce and maintain new bone formation using the topical co-administration of recombinant human BMP-2 (rh-BMP-2) and zoledronate (ZOL) on beta-tricalcium phosphate (ß-TCP) composite. METHODS: ß-TCP columns were impregnated with both rh-BMP-2 (30 µg) and ZOL (5 µg), rh-BMP-2 alone, or ZOL alone, and implanted into the left femur canal of New Zealand white rabbits (n = 56). The implanted ß-TCP columns were harvested and evaluated at 3 and 6 weeks after implantation. These harvested ß-TCP columns were evaluated radiologically using plane radiograph, and histologically using haematoxylin/eosin (H&E) and Masson's trichrome (MT) staining. In addition, micro-computed tomography (CT) was performed for qualitative analysis of bone formation in each group (n = 7). RESULTS: Tissue sections stained with H&E and MT dyes revealed that new bone formation inside the ß-TCP composite was significantly greater in those impregnated with both rh-BMP-2 and ZOL than in those from the other experimental groups at 3 and 6 weeks after implantations (p < 0.05). Micro-CT data also demonstrated that the bone volume and the bone mineral density inside the ß-TCP columns were significantly greater in those impregnated with both rh-BMP-2 and ZOL than in those from the other experimental groups at 3 and 6 weeks after implantations (p < 0.05). CONCLUSIONS: The topical co-administration of both rh-BMP-2 and ZOL on ß-TCP composite promoted and maintained newly formed bone structure in the bone marrow environment.

Four-Millimeter Additional Bone Resection in the Distal Femur Does Not Result in an Equivalent Increase in the Extension Joint Gap in Total Knee Arthroplasty.

BACKGROUND: Additional bone resection in the distal femur is performed to increase the extension joint gap in total knee arthroplasty (TKA). The present study aimed to analyze the relationship between the amount of additional bone resection in the distal femur and the increase in the extension joint gap in TKA. METHODS: Fifty knees undergoing TKA for varus osteoarthritis were evaluated. Two femoral trial component models were prepared: (1) a normal model with 9-mm-thick distal and posterior femoral components and (2) an additional bone resection model with a 5-mm-thick distal femoral component (9 mm to 4 mm) and a 9-mm-thick posterior femoral component, which simulated an additional bone cut in the distal femur of 4 mm. The femoral trial component models were set before implantation, and the extension joint gap was measured using a tensor device that had a shape identical to that of the fixed-bearing tibial insert. RESULTS: The additional bone resection model had a larger joint gap than the normal model (P < .01). The mean extension gap increase in the additional bone resection model was 2 (standard deviation 1) mm, which was less than the thickness of the additional bone resection (4 mm) (P < .01). CONCLUSION: The amount of additional bone resection in the distal femur was not equal to the increase in the extension joint gap. Additional bone resection of 4 mm in the distal femur only increased the extension joint gap by a mean of 2 mm.

Long-term clinical outcomes of medial pivot total knee arthroplasty for Asian patients: A mean 10-year follow-up study.

BACKGROUND: Many Asian populations have a unique floor-based lifestyle that might cause mechanical stress of the knees. It is important to clarify the longevity of a medial pivot total knee arthroplasty, as its prosthetic design could cause mechanical stress onto the insert. The purpose of this study was to clarify the clinical results of medial pivot total knee arthroplasty for Asian patients in a 10-year follow-up study. METHODS: Consecutive, primary total knee arthroplasties (n = 257) were analyzed in the study using the medial pivot knee system. The clinical outcomes were assessed preoperatively and at the final follow-up. The patient-reported Forgotten Joint Score-12 and radiological outcomes were measured at the final follow-up. The survival rate was assessed with reoperation or revision as the end-point. RESULTS: The mean follow-up period was 10.1 ± 1.7 years. The lost to follow-up was 4.5%. All clinical outcomes improved significantly after surgery (p < 0.001). The mean postoperative knee flexion was 118° ± 11° and the mean Forgotten Joint Score-12 was 59.7 ± 27 points. The radiolucent line was observed in 29 patients (11.3%), however there was no aseptic loosening noted. The survival rates with reoperation or revision were 96.3% or 98.4% at 10 years after the operation. CONCLUSIONS: Medial pivot total knee arthroplasty used for Asian patients showed good longevity and patient-reported outcome measurement in a mean 10-year follow-up study. Medial pivot total knee arthroplasty has long-term stability among patients who have a floor-based lifestyle. LEVEL OF EVIDENCE: III.

Vitamin E-infused highly cross-linked polyethylene did not reduce the number of in vivo wear particles in total knee arthroplasty.

AIMS: Vitamin E-infused highly cross-linked polyethylene (E1) has recently been introduced in total knee arthroplasty (TKA). An in vitro wear simulator study showed that E1 reduced polyethylene wear. However there is no published information regarding in vivo wear. Previous reports suggest that newly introduced materials which reduce in vitro polyethylene wear do not necessarily reduce in vivo polyethylene wear. To assist in the evaluation of the newly introduced material before widespread use, we established an in vivo polyethylene wear particle analysis for TKA. The aim of this study was to compare in vivo polyethylene wear particle generation between E1 and conventional polyethylene (ArCom) in TKA. METHODS: A total of 34 knees undergoing TKA (17 each with ArCom or E1) were investigated. Except for the polyethylene insert material, the prostheses used for both groups were identical. Synovial fluid was obtained at a mean of 3.4 years (SD 1.3) postoperatively. The in vivo polyethylene wear particles were isolated from the synovial fluid using a previously validated method and examined by scanning electron microscopy. RESULTS: The total number of polyethylene wear particles obtained from the knees with E1 (mean 6.9, SD 4.0 × 107 counts/knee) was greater than that obtained from those with ArCom (mean 2.2, SD 2.6 × 107 counts/knee) (p = 0.001). The particle size (equivalent circle of diameter) from the knees with E1 was smaller (mean 0.5 µm, SD 0.1) than that of knees with ArCom (mean 1.5, SD 0.3 µm) (p = 0.001). The aspect ratio of particles from the knees with E1 (mean 1.3, SD 0.1) was smaller than that with ArCom (mean 1.4, SD 0.1) (p < 0.001 ). CONCLUSION: This is the first report of in vivo wear particle analysis of E1. E1 polyethylene did not reduce the number of in vivo polyethylene wear particles compared with ArCom in early clinical stage. Further careful follow-up of newly introduced E1 for TKA should be carried out. Cite this article: Bone Joint J 2020;102-B(11):1527-1534.

2020 Chitranjan S. Ranawat Award: Perioperative essential amino acid supplementation suppresses rectus femoris muscle atrophy and accelerates early functional recovery following total knee arthroplasty.

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.