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Abstract Background Gap tension is an important factor influencing the clinical outcomes of total knee arthroplasty (TKA). Traditional mechanical alignment (MA) places importance on neutral alignment and often requires additional soft tissue releases, which may be related to patient dissatisfaction. Conversely, the functional alignment requires less soft tissue release to achieve gap balance. Conventional gap tension instruments present several shortcomings in practice. The aim of this study is to introduce a new gap balancing technique with FA using the modified spacer-based gap tool and the MAKO robotic arm system. Methods A total of 22 consecutive patients underwent primary TKA using the MAKO robotic arm system. The gap tension was assessed and adjusted with the modified spacer-based gap tool during the operation. Patient satisfaction was evaluated post-operatively with a 5-point Likert scale. Clinical outcomes including lower limb alignment, Knee Society Score (KSS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) were recorded before surgery, 3 months and 1 year after surgery. Results The range of motion (ROM) was significantly increased (p

Aims: The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases. Methods: Patients who underwent RA-TKA between January and December 2022 for primary varus osteoarthritis were included. Safe boundaries for E-rKA were defined. Residual medial compartment tightness was compared following virtual surgical planning using E-rKA and MA, in the same set of knees. Soft-tissue releases were documented. Errors in postoperative alignment in relation to planned alignment were compared between patients who did (group A) and did not (group B) require soft-tissue releases. Results: The use of E-rKA helped restore all knees within the predefined boundaries, with appropriate soft-tissue balancing. E-rKA compared with MA resulted in reduced residual medial tightness following surgical planning, in full extension (2.71 mm (SD 1.66) vs 5.16 mm (SD 3.10), respectively; p < 0.001), and 90° of flexion (2.52 mm (SD 1.63) vs 6.27 mm (SD 3.11), respectively; p < 0.001). Among the study population, 156 patients (78%) were managed with minor adjustments in component positioning alone, while 44 (22%) required additional soft-tissue releases. The mean errors in postoperative alignment were 0.53 mm and 0.26 mm among patients in group A and group B, respectively (p = 0.328). Conclusion: E-rKA is an effective and reproducible alignment strategy during RA-TKA, permitting a large proportion of patients to be managed without soft-tissue releases. The execution of minor alterations in component positioning within predefined multiplanar boundaries is a better starting point for gap management than soft-tissue releases. Cite this article: Bone Jt Open 2024;5(8):628–636.

Abstract Objective In total knee arthroplasty (TKA), achieving soft-tissue balance while retaining acceptable lower limb alignment is sometimes difficult and may lead to patient dissatisfaction. Theoretically, patient-specific implants can bring great benefits, while the lack of precise surgical tools may hinder the improvement of outcomes. The objective of this study was to illustrate surgical techniques and evaluate kinematics and early clinical outcomes of robotic-assisted TKA using patient-specific implants. Methods Based on preoperative CT scan, femoral and tibial components were 3D printed. Medial and lateral tibial liners were separate with different thicknesses, posterior slopes and conformity. TiRobot Recon Robot was used for surgery, and was armed with smart tools that quantify gap, force and femoral-tibial track. We collected data on demographics, intraoperative gap balance and femoral-tibial motion. In the follow-up, we evaluated the range of motion, Visual Analogue Scale (VAS), forgotten joint score (FJS), Knee injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR) score. Radiological data were also harvested. Results Fifteen patients (17 knees) were enrolled with a mean age of 64.6 ± 6.4 (53–76) years. In 5 knees, we used symmetric tibial liners, the rest were asymmetric. After surgery, the average alignment was 1.6 ± 2.0 (-3–5) degrees varus. The average follow-up lasted 6.7 ± 4.2 (1–14) months. The mean visual analogue scale was 0.8 ± 0.7 (0–2), FJS was 62.4 ± 25.3 (0–87), KOOS was 86.5 ± 9.4 (57–97). 11 patients were “very satisfied”, 3 were “satisfied" with the result, and one patient was neutral due to restricted extension and unsatisfactory rehabilitation at five months’ follow-up. Conclusions With patient-specific implants and robotics, TKA could be performed by a mathematical way, which was dubbed a “differential” TKA. Intraoperative kinematics was excellent in terms of gap-force balancing and femoral-tibial relative motion. Preliminary clinical outcomes were overall satisfactory.

Background: Gap tension is an important factor influencing the clinical outcomes of total knee arthroplasty (TKA). Traditional mechanical alignment (MA) places importance on neutral alignment and often requires additional soft tissue releases, which may be related to patient dissatisfaction. Conversely, the functional alignment requires less soft tissue release to achieve gap balance. Conventional gap tension instruments present several shortcomings in practice. The aim of this study is to introduce a new gap balancing technique with FA using the modified spacer-based gap tool and the MAKO robotic arm system. Methods: A total of 22 consecutive patients underwent primary TKA using the MAKO robotic arm system. The gap tension was assessed and adjusted with the modified spacer-based gap tool during the operation. Patient satisfaction was evaluated post-operatively with a 5-point Likert scale. Clinical outcomes including lower limb alignment, Knee Society Score (KSS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) were recorded before surgery, 3 months and 1 year after surgery. Results: The range of motion (ROM) was significantly increased (p < 0.001) and no patients presented flexion contracture after the surgery. KSS and WOMAC score were significantly improved at 3 months and 1 year follow-up (p < 0.001 for all). During the surgery, the adjusted tibial cut showed more varus than planned and the adjusted femoral cut presented more external rotation than planned (p < 0.05 for both). The final hip-knee-ankle angle (HKA) was also more varus than planned (p < 0.05). Conclusions: This kind of spacer-based gap balancing technique accompanied with the MAKO robotic arm system could promise controlled lower limb alignment and improved functional outcomes after TKA. [ABSTRACT FROM AUTHOR]

Understanding alignment and gap balancing in Total Knee Arthroplasty (TKA) can be challenging for trainee and experienced orthopedic surgeons. Traditional learning methods may not effectively translate to real-life scenarios. The advent of advanced technologies like robotic surgery and navigation systems has revolutionized intraoperative understanding of gap balancing techniques. This trial aims to investigate the effectiveness of robotic TKA planning software in educating trainees about alignment and ligament balancing. We hypothesize that a single session with the software will significantly enhance trainees' understanding of these techniques. This UK-based single-center, two-arm, group parallel randomized controlled trial was conducted during a national robotic arthroplasty symposium. It aims to evaluate the effect of robotic knee arthroplasty software training on understanding TKA alignment and gap balancing principles using Multiple Choice Questions (MCQs). The MCQ test was crafted based on established guidelines from a different institution with expert consensus in the field. Our study revealed that baseline knowledge of gap balancing and alignment principles was generally low among all participants. However, the intervention group, which received comprehensive robotic software training, demonstrated a significant improvement in their MCQ scores compared to the control group, which did not undergo the training. In conclusion, our study demonstrates that robotic arthroplasty software training significantly improves the understanding of TKA alignment and balancing principles among orthopedic trainees. Level of Evidence II. [ABSTRACT FROM AUTHOR]

Background: Advanced osteoarthritis of knees with varus deformity consists of attenuation of lateral structures with contracture of the posteromedial structures and formation of medial osteophytes. The conventional step-wise medial and posteromedial release with measured resection may sometimes hinder achievement of perfectly balanced flexion and extension gaps with maintenance of flexion stability, without the use of a constrained prosthesis. Medial femoral epicondylar sliding osteotomy tailors the balancing to the need of the kinematics of the native knee and precludes the use of a constrained implant. Methods: 15 patients with Ahlbäck Grades III through V osteoarthritic changes at Howrah Orthopaedic Hospital were included in a prospective cohort case series with a minimum period of follow-up being 12 months. Physical examination, clinical questionnaire and radiographic evaluation were done post-operatively for objectification by functional Knee Society and Oxford Knee Scores respectively. Results and Analysis: The mean post-operative femorotibial angulation ameliorated to a value of 3.73 ± 1.58° from 18.67 ± 4.2° in the pre-operative stage. The mean overall Range of Motion of operated knee was 109.87 ± 6.86° with no residual frontal laxity and/or laxity in the coronal plane. The mean amount of resection of tibial plateau in patients with severe varus deformity was kept to a minimum, 6.56 mm from the least deficient portion of the lateral condyle. There were no complications as regards component loosening and/or surgical-site infection. Conclusion: The main objective of balancing a severely varus-afflicted knee is to preserve as much of the Medial Collateral Ligament as possible, to retain its check rein function and not jeopardise the stability. This is ensured by distalisation and posteriorizing the medial epicondyle by an incomplete osteotomy in addition to modest tibial resection fetching a non-isometric point of knee flexion. All osteotomies united by bony union and restoration of kinematic alignment. The limitation of this study however includes the lack of long-term results, such as late instability and polyethylene wear. [ABSTRACT FROM AUTHOR]

Bicruciate-stabilized (BCS) total knee arthroplasty (TKA) designs attempt to approximate natural knee mechanics. Multiple surgical techniques, including gap balancing (GB) and measured resection (MR), have been developed to provide optimal implant positioning and soft-tissue balance. The goal of this study was to determine the effect of surgical technique on BCS TKA contact kinematics. Secondary goals included investigating the change of kinematics over time and comparing BCS TKA kinematics to a posterior-stabilized (PS) design. The study included the BCS-GB, BCS-MR, and PS-MR groups. The BCS-GB and BCS-MR groups underwent weight-bearing radiostereometric analysis for multiple knee flexion angles at 3 months and 1 year postoperatively, whereas the PS-MR group was imaged at 1 year postoperatively. The medial and lateral contact kinematics were determined from implant poses. There were no differences in BCS TKA kinematics between the GB and MR techniques. There were differences in the mid-flexion ranges when comparing the 3-month and 1-year kinematics of the BCS design; however, they were less than 1.5 mm. Differences existed between the kinematics of the BCS and PS designs at all flexion angles for the medial condyle (P <.0006) and at 0° of flexion on the lateral condyle (P <.0001). Contact kinematics for a BCS design were similar for both surgical techniques, suggesting both are appropriate for this design. Small, likely clinically insignificant differences were found between 3-month and 1-year kinematics. The BCS TKA kinematics differed from the PS design; however, it is unclear whether these differences improve clinical outcomes. [ABSTRACT FROM AUTHOR]

Background: Instability is a common cause of (total knee arthroplasty) TKA failure, which can be prevented by achieving proper gap balance during surgery. There is no consensus on the ideal gap balance in TKA, and different alignment philosophies result in varying soft-tissue tightness. Traditional TKA aims for symmetric compartment balance, while kinematic alignment (KA) restores anatomy and accepts asymmetric flexion gaps. This study evaluated the impact of these philosophies on the flexion gap balance and clinical outcomes. Methods: A retrospective review of 167 patients who received true or restricted KA robotic-assisted TKA with at least one year of follow-up was conducted. The groups were based on intraoperative flexion gap differences: symmetric (0–1 mm) (n = 94) and asymmetric (2–5 mm) (n = 73). Results: Preoperative demographics and postoperative clinical and functional scores were compared. Both groups were similar in demographics and preoperative scores. True KA alignment was more likely to result in an asymmetric flexion gap, while restricted KA produced symmetric gaps. Conclusions: The study found no adverse effects from the physiological asymmetric flexion gap, with clinical and functional outcomes comparable to symmetric gaps. A 5 mm difference between the medial and lateral gap width did not negatively impact the outcomes. True KA more frequently results in a physiological asymmetric flexion gap. [ABSTRACT FROM AUTHOR]

Objective: In total knee arthroplasty (TKA), achieving soft-tissue balance while retaining acceptable lower limb alignment is sometimes difficult and may lead to patient dissatisfaction. Theoretically, patient-specific implants can bring great benefits, while the lack of precise surgical tools may hinder the improvement of outcomes. The objective of this study was to illustrate surgical techniques and evaluate kinematics and early clinical outcomes of robotic-assisted TKA using patient-specific implants. Methods: Based on preoperative CT scan, femoral and tibial components were 3D printed. Medial and lateral tibial liners were separate with different thicknesses, posterior slopes and conformity. TiRobot Recon Robot was used for surgery, and was armed with smart tools that quantify gap, force and femoral-tibial track. We collected data on demographics, intraoperative gap balance and femoral-tibial motion. In the follow-up, we evaluated the range of motion, Visual Analogue Scale (VAS), forgotten joint score (FJS), Knee injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR) score. Radiological data were also harvested. Results: Fifteen patients (17 knees) were enrolled with a mean age of 64.6 ± 6.4 (53–76) years. In 5 knees, we used symmetric tibial liners, the rest were asymmetric. After surgery, the average alignment was 1.6 ± 2.0 (-3–5) degrees varus. The average follow-up lasted 6.7 ± 4.2 (1–14) months. The mean visual analogue scale was 0.8 ± 0.7 (0–2), FJS was 62.4 ± 25.3 (0–87), KOOS was 86.5 ± 9.4 (57–97). 11 patients were "very satisfied", 3 were "satisfied" with the result, and one patient was neutral due to restricted extension and unsatisfactory rehabilitation at five months' follow-up. Conclusions: With patient-specific implants and robotics, TKA could be performed by a mathematical way, which was dubbed a "differential" TKA. Intraoperative kinematics was excellent in terms of gap-force balancing and femoral-tibial relative motion. Preliminary clinical outcomes were overall satisfactory. [ABSTRACT FROM AUTHOR]

Purpose: Loose flexion gaps are associated with poor functional outcomes and instability in total knee arthroplasty (TKA). The effect of a trapezoidal flexion gap in a functionally aligned TKA remains unknown. The aim of this study was to investigate the effect of a larger lateral flexion gap in a robotic‐assisted (RA), functionally aligned (FA) and cruciate‐retaining (CR) TKA on clinical outcomes. Methods: Data from 527 TKA in 478 patients from 2018 to 2020 were collected. All patients underwent an RA (MAKO, Stryker), FA and CR TKA. Gap measurements were collected intraoperatively. Patient‐reported outcome measures (PROMs), pain Visual analogue score (VAS) and range of motion were collected postoperatively. Patients were also asked about the ease of stair ascent and descent and kneeling on a 5‐point scale. The minimum follow‐up was 2 years. Patients were stratified into three groups based on lateral flexion laxity. Results: At 2 years postoperatively, the group with a looser gap (3–6 mm) had higher mean PROMs when compared with the group with a gap of 2–3 mm. There were no differences detected in any other outcomes at 2 years. A total of 70.9% of patients in the group with a 3–6 mm gap reported being able to walk down a flight of stairs 'easily', compared with 56.7% in the 2–3 mm group and 54% in the <2 mm group (p = 0.04). Conclusion: The study shows that a loose lateral flexion gap in functionally aligned CR TKA does not adversely affect outcomes in the short term. Level of Evidence: Level III, retrospective cohort study. [ABSTRACT FROM AUTHOR]

Background: Robotic-assisted total knee arthroplasty (RA-TKA) allows surgeons to perform intraoperative soft tissue laxity assessments prior to bone resections and is used to alter resections to achieve gap balance. This study compared 2 techniques for flexion gap laxity assessment during RA-TKA. Methods: A prospective study of 50 primary RA-TKAs performed by a single surgeon was conducted between February and October 2023. Following full exposure, anterior tibial dislocation, and osteophyte removal, maximal medial and lateral compartment flexion laxity was quantified to the nearest 0.5 mm by the robotic system using a dynamic, surgeon-applied stress (SURGEON). This data was used to plan a balanced flexion gap by adjusting the femoral component size, rotation, and anterior-posterior translation. Flexion laxity was quantified again after distal femoral and proximal tibial resections using a ligament tensor instrument (TENSOR). These new data were used to plan for the same desired flexion gap using the same variables. Paired-samples t-tests and a simple linear regression were used for analysis. Results: Both methods produced near-identical recommendations for femoral component sizing (mean deviation 0.06 sizes, range −1 to +1 size; P = .569), rotation (deviation mean 1.0°, range −3.0° to +3.0°; P = .741), and anterior-posterior translation (deviation mean 0.13 mm, range −0.5 to +0.5 mm, P = .785). SURGEON femoral component rotation predicted TENSOR rotation (R2 = 0.157; 95% confidence interval = 0.124, 0.633; P = .004). Conclusions: Assessing flexion laxity with a surgeon-applied stress vs a ligament tensor produced near-identical laxity data in RA-TKA, suggesting surgeons may comfortably choose either technique as a reliable method. Level of Evidence: Level III.

Purpose: The aim of this study was to identify if constitutional alignment and preoperative radiologic parameters determined whether medial gap balancing was required in mechanically aligned total knee arthroplasty (TKA). Methods: Two hundred and sixty three patients with 394 consecutive knees who underwent primary TKAs were retrospectively analysed in this study. Selective sequential multiple needle puncturing (MNP) was performed for medial ligament balancing when required. Constitutional alignment, which was determined using the Coronal Plane Alignment of the Knee (CPAK) classification, as well as preoperative and postoperative radiologic parameters was evaluated to identify factors which predicted the need for MNP. Results: One hundred and fifty eight (40.1%) knees required medial ligament balancing with MNP. Patients who required MNP during surgery had significantly more constitutional varus, more varus preoperative mechanical Hip–Knee–Ankle angle (mHKA), smaller preoperative medial proximal tibial angle (MPTA) and a larger change in mHKA and MPTA after surgery than those who did not. Patients with constitutional varus also had a higher incidence of having had MNP to both anterior and posterior superficial medial collateral ligament (sMCL) fibres. There was no significant difference in preoperative lateral distal femoral angle (LDFA), posterior tibial slope (PTS) and varus–valgus difference (VVD) between groups. Conclusion: Ligament balancing using MNP was determined by constitutional alignment rather than medial soft tissue contracture. Patients with constitutional varus who had a larger medio-lateral gap difference in extension also had a higher incidence of having had MNP to both anterior and posterior sMCL fibres. Level of evidence: Retrospective comparative study, level IV. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this prospective study was to compare femoral component rotation (FCR) values when adjusted with 'gap balancing' (GB) and 'measured resection' (MR) techniques following total knee arthroplasty (TKA). The study hypothesis was that the GB technique would be better on FCR than MR in TKA. Methods: From a total of 93 unilateral TKAs performed between August 2019 and November 2020, the FCR values were adjusted by GB in 46 cases and MR in 47. Post-TKA magnetic resonance imaging (MRI) was applied for FCR assessment. Orthoroentgenograms and lateral knee radiographs were taken to determine the mechanical axis and posterior condylar offset (PCO) ratio, respectively. Both groups were compared radiologically. The Western Ontario and Mcmaster Universities Osteoarthritis Index (WOMAC), Knee Society Score (KSS), and Hospital for Special Surgery (HSS) patella scores were calculated and compared between the groups preoperatively and at the end of 6 months, and 1 and 2 years postoperatively. Results: There was no difference between the groups in respect of the demographic data. The mean HSS patella score was 86.4 ± 4.1 in the GB group and 84.6 ± 3.8 in the MR group in the 2nd year (p = 0.047). A higher degree of external rotation in the FC was determined in the GB group [2.2° (1.7°–4.3°)] compared to the MR group [1.7° (0.8°–3.0°)] (p = 0.009). The postoperative increase in PCO ratio was higher in the GB group (p = 0.005). All other variables were similar in both groups. Conclusion: The results of this study showed that at the end of the 2nd year, the HSS patella scores were better, FCs were more externally rotated and PCO ratios were higher in TKAs using the GB technique. However, taking into account that the difference between the 2nd year HSS patella scores was too small to be considered clinically significant, it was shown that both the GB and MR techniques can be used for FCR in clinical practice without any hesitation. [ABSTRACT FROM AUTHOR]

Robotic arm–assisted total knee arthroplasty (TKA) involves a pre-resection gap balancing technique to obtain the desired gap. However, the expected gap may change owing to the soft-tissue release effect of unreachable osteophytes. This study evaluated the effect of unreachable osteophytes of the posterior medial femoral condyle on gap changes following bony resection. We retrospectively analysed 129 robotic arm–assisted TKAs performed for varus knee osteoarthritis. Knees were classified according to the size of osteophytes on the posterior medial femoral condyle using preoperative computed tomography measurement. After the removal of reachable osteophytes, the robotic system measured pre- and post-resection medial extension (ME), lateral extension (LE), medial flexion (MF), and lateral flexion (LF) gaps. No extension gap changes were observed for 25 (19.4%), and no flexion gap changes were observed 41 (31.8%) knees, following bone cuts. ME, LE, MF, and LF gaps increased with the osteophyte size (p < 0.05). For osteophytes <10 mm, all the gaps increased symmetrically. However, for osteophytes >10 mm, the ME gap increased asymmetrically more than LE, MF, and LF gaps (p < 0.05). The gap changes due to bony resection were correlated to the osteophyte sizes of the posterior medial femoral condyle. Surgeons should plan a slightly tight medial extension gap to attain the desired gaps for >10 mm osteophytes. [ABSTRACT FROM AUTHOR]

Objective Although many studies have compared the measured resection (MR) technique to the gap balancing (GB) technique, few studies have investigated the hybrid technique. In this study, we compared imaging and clinical outcomes of the MR, GB, and hybrid techniques in primary total knee arthroplasty (TKA). Methods From January 2016 to January 2019, we conducted a retrospective study on 90 patients who underwent unilateral primary TKA; 30 received the MR technique, 30 received the GB technique, and 30 received the hybrid technique. Radiological outcomes, including joint line level, mechanical alignment of the lower limb, positions of the femoral and tibial components, and rotation of the femoral component, and clinical outcomes, including the visual analog scale score for pain, the Knee Society Score, and the range of motion, were assessed among the three groups. One‐way analysis of variance and Dunnett's test were performed for normally distributed data. Kruskal–Wallis H test and Dunn–Bonferroni test were conducted for non‐normally distributed data. Results No significant difference in the mechanical alignment (p = 0.151) and the positions of the tibial and femoral components (p = 0.230 for α angle, p = 0.517 for β angle, p = 0.686 for femoral flexion angle, and p = 0.918 for tibial slope angle) was found among the three groups. No significant difference in the elevation of the joint line between the MR and the hybrid groups was found (2.1 ± 0.3 mm vs 2.1 ± 0.1 mm, p = 0.627), but the GB group (2.8 ± 0.2 mm) differed significantly from the other two groups (p 0.05), although the results in the hybrid group were slightly higher. Conclusion The hybrid technique helped to restore the mechanical alignment of the lower limb and realize optimal positions of the femoral and tibial components without significant differences relative to the MR and GB techniques. The hybrid technique was more helpful for maintaining the original height of the joint line, which was similar to the MR technique. Additionally, although the improvement in the clinical outcomes in the hybrid group was slightly higher, it was not significantly different among the three groups.

Malalignment of total knee arthroplasty (TKA) components is a potential cause of clinical failure following TKA. Since the goal of a gap balancing (GB) technique is equal flexion and extension gaps secondary to soft-tissue balancing, and not necessarily component alignment, variation in component placement may exist. Our purpose was (1) to evaluate precision of component alignment in well-functioning GB TKAs performed without the aid of navigation using computed tomographic evaluation and (2) to determine any relationship between femoral version and/or tibial torsion and TKA component positioning. There were 93 well-functioning TKAs performed with an extension gap first GB technique with a minimum 2-year follow-up evaluated using computed tomography to assess component rotational alignment, as well as osseous femoral version and tibial torsion. Femoral and tibial rotational alignment was assessed by previously described methods. The mean Knee Society Score was 185.7 ± 21.7. The mean range of motion was 128.5 ± 7.8°. Femoral posterocondylar axis (relative to the transepicondylar axis) values ranged from −8.3 to 4.1° with a mean of −0.78 ± 2.7° (internal rotation). Mean tibial rotation was 17.2 ± 7.9° internal rotation relative to the tibial tubercle. No correlation was found between native femoral version and femoral component rotational alignment (Pearson's correlation coefficient, r , 0.007). Weak correlation was found between native tibial torsion and tibial component alignment (r = 0.24). Despite being only a secondary objective with the GB technique, most components evaluated were within the desired range of rotation. Alignment was not influenced by native osseous rotational geometry. Level III, Retrospective Cohort Study. [ABSTRACT FROM AUTHOR]

This study evaluated the ability to achieve the targeted soft-tissue balance in terms of medio-lateral (ML) laxity and gap values when using a computer-assisted orthopedic surgery (CAOS) system featuring an intra-articular force-controlled distractor and assessed learning curves associated with the adoption of this technology. The first 273 cases using this technology were reported without exclusions comparing 1) final ML laxity and 2) final average gap to their predefined targets. For both parameters, the signed and unsigned differentials were reported. The linear mixed model was used to evaluate laxity curve differences between surgeons. A cumulative sum control chart (CUSUM) was applied to assess surgeon learning curves regarding surgical time. Both the average signed ML laxity and gap differentials were neutral throughout the full arc of motion. Both the average unsigned ML laxity and gap differentials were linear. Signature of ML laxity and gap differential curves tended to be surgeon-specific. The CUSUM analyses of surgical times demonstrated either a short learning curve or the absence of a discernible learning pattern for surgeons. Data from all users involved with the pilot release of the balancing device were considered to capture variability in familiarity with the technique and learning curve cases were included. A high ability to achieve targeted gap balance throughout the arc of motion using the proposed method was observed. [ABSTRACT FROM AUTHOR]

Background: Recent developments in intra-operative sensor technology provide surgeons with predictive and real-time feedback on joint balance. It remains unknown, however, whether these technologies are better suited to femur-first or tibia-first workflows. This study investigates the balance accuracy, precision and early patient outcomes between the femur-first and tibial-first workflows using a digital gap-balancing tool. Methods: One-hundred six patients had posterior cruciate ligament sacrificing total knee arthroplasty using a digital joint tensioner. The participants were divided into 4 groups with different visibility to balance data 1) Femur-first blinded data, 2) Femur-first not blinded data, 3) Tibia-first blinded data, 4) Tibia-first not blinded data with predictive balancing. Knee Injury and Osteoarthritis Outcome Score and University of California at Los Angeles activity level were recorded at 1-year. Results: Group 4 reported less midflexion imbalance (40°) compared to all other groups (1: 1.5 mm, 2: 1.7 mm, 3: 1.6 mm, 4: 1.0 mm, P < .031) and reduced variance compared to all other groups at 40° and 90° (P < .012), resulting in an increased frequency of joints balanced within 2 mm throughout flexion in group 4 (1: 69%, 2: 65%, 3: 67%, 4: 91%, P < .006). No differences were found between 3-month, 6-month, or 1-year outcome scores between technique. Conclusions: Improvements in balance were observed in midflexion instability and balance variability throughout flexion when a tibia-first approach in combination with a digital balancing tool was used. The combination of a digital balancing tool and a tibia-first approach allowed a target joint balance to be achieved more accurately compared to a non-sensor augmented or femur-first approach.

Introduction: Alignment goals in total knee replacement (TKR) is a topical subject. This study compares the short-term functional outcomes and patient reported outcome measures (PROMs) of two philosophies for knee arthroplasty alignment: measured resection (MR) and an individualised alignment philosophy, with the tibia mechanically aligned and an instrumented gap balancer (GB) to align the femur in both flexion and extension. Patients and methods: 94 knees were enrolled in this randomised controlled trial. The surgical protocol used a MR technique for mechanical alignment or a GB technique for individualised alignment. Primary outcome was quadriceps strength. Secondary outcomes included validated functional tests and PROMs as well as patient satisfaction. Outcomes were assessed pre-operatively, at 6 weeks, 3, 6 and 12 months post-operatively. Results: At 12-month follow-up, there was no significant difference in the change from baseline mean quadriceps peak torque between the two groups (p = 0.988). Significant improvement in the change in range of motion (ROM) in the GB group compared to the MR group at 3 months (13° vs 6° p = 0.028) but this improvement was not significant at 1 year (20° vs 17° p = 0.21). The functional test of balance showed statistically significant improvement at 6 weeks (p = 0.03) in the GB group but this difference was not maintained. PROMs favoured the GB group, with the KOOS pain scoring statistically better (p ≤ 0.05) at 6 weeks, 3, 6 and 12 months. Conclusions: Individualised alignment philosophy utilising a GB technique did not demonstrate an improvement in the primary outcome measure quadriceps peak torque. Improvement was seen in the GB group in PROM pain scores that was significant, both statistically and clinically, out to at least 1 year. Gains that were seen in functional assessment with GB, although significant at some time points, were no longer significant at 1 year and no difference was seen in quads strength. Compared to a MR technique, the individualised GB technique appears to confer some improvement in pain, ROM and some functional tests following TKR in the short-term. [ABSTRACT FROM AUTHOR]

Background: To understand the extent and frequency of soft-tissue adjustment required to achieve mediolateral (ML) balance in measured resection (MR) vs gap-balancing (GB) total knee arthroplasty, this study compared ML balance and joint laxity throughout flexion between the 2 techniques. The precision of predictive GB in achieving ML balance and laxity was also assessed. Methods: Two surgeons performed 95 robot-assisted GB total knee arthroplasties with predictive balancing, limiting tibial varus to 3° and adjusting femoral positioning to optimize balance. A robotic ligament tensioner measured joint laxity. Planned MR (pMR) was simulated by applying neutral tibial and femoral coronal resections and 3° of external femoral rotation. ML balance, laxity, component alignment, and resection depths were compared between planned GB (pGB) and pMR. ML balance and laxity were compared between pGB and final GB (fGB). Results: The proportion of knees with >2 mm of ML imbalance in flexion or extension ranged from 3% to 18% for pGB vs 50% to 53% for pMR (P < .001). Rates of ML imbalance >3 mm ranged from 0% to 9% for pGB and 30% to 38% for MR (P < .001). The mean pMR laxity was 1.9 mm tighter medially and 1.1 mm tighter laterally than pGB throughout flexion. The mean fGB laxity was greater than the mean pGB laxity by 0.5 mm medially and 1.2 mm laterally (P < .001). Conclusion: MR led to tighter joints than GB, with ML gap imbalances >3 mm in 30% of knees. GB planning improved ML balance throughout flexion but increased femoral posterior rotation variability and bone resection compared to MR. fGB laxity was likely not clinically significantly different than pGB.

Objective: Although many studies have compared the measured resection (MR) technique to the gap balancing (GB) technique, few studies have investigated the hybrid technique. In this study, we compared imaging and clinical outcomes of the MR, GB, and hybrid techniques in primary total knee arthroplasty (TKA). Methods: From January 2016 to January 2019, we conducted a retrospective study on 90 patients who underwent unilateral primary TKA; 30 received the MR technique, 30 received the GB technique, and 30 received the hybrid technique. Radiological outcomes, including joint line level, mechanical alignment of the lower limb, positions of the femoral and tibial components, and rotation of the femoral component, and clinical outcomes, including the visual analog scale score for pain, the Knee Society Score, and the range of motion, were assessed among the three groups. One‐way analysis of variance and Dunnett's test were performed for normally distributed data. Kruskal–Wallis H test and Dunn–Bonferroni test were conducted for non‐normally distributed data. Results: No significant difference in the mechanical alignment (p = 0.151) and the positions of the tibial and femoral components (p = 0.230 for α angle, p = 0.517 for β angle, p = 0.686 for femoral flexion angle, and p = 0.918 for tibial slope angle) was found among the three groups. No significant difference in the elevation of the joint line between the MR and the hybrid groups was found (2.1 ± 0.3 mm vs 2.1 ± 0.1 mm, p = 0.627), but the GB group (2.8 ± 0.2 mm) differed significantly from the other two groups (p < 0.001). Although rotation of the femoral component in the GB group was larger than that of the MR and hybrid groups, the difference was not significant (1.8° ± 0.2° vs 1.7° ± 0.3° vs. 1.7° ± 0.2°, p = 0.101). The clinical outcomes were not significantly different (p > 0.05), although the results in the hybrid group were slightly higher. Conclusion: The hybrid technique helped to restore the mechanical alignment of the lower limb and realize optimal positions of the femoral and tibial components without significant differences relative to the MR and GB techniques. The hybrid technique was more helpful for maintaining the original height of the joint line, which was similar to the MR technique. Additionally, although the improvement in the clinical outcomes in the hybrid group was slightly higher, it was not significantly different among the three groups. [ABSTRACT FROM AUTHOR]

Background: Both restricted inverse kinematic alignment (iKA) and gap balancing aim for a balanced total knee arthroplasty by adjusting femoral component position based on ligamentous gaps. However, iKA targets a native tibial joint line vs resecting perpendicular to the mechanical axis. This study compares how these 2 techniques impact the balance and laxity throughout flexion and joint line obliquity (JLO), arithmetic hip-knee-ankle angle (aHKA), and the coronal plane alignment of the knee (CPAK). Methods: Two surgeons performed 75 robot-assisted iKA total knee arthroplasties. A digital joint tensioner collected laxity data throughout flexion before femoral resection. The femoral component position was determined using predictive gap-planning to optimize the balance throughout flexion. Planned gap balancing (pGB) simulations were performed for each case using neutral tibial resections. Mediolateral balance, laxity, and CPAK were compared among pGB, planned iKA (piKA), and final iKA. Results: Both piKA and pGB had similar mediolateral balance and laxity, with mean differences .05) between pGB and piKA. piKA recreated a more native CPAK distribution, with types I-V being the most common ones, while most pGB knees were of type V, VII, and III. Final iKA and piKA had similar mediolateral balance and laxity, with a root-mean-square error

Background: The purpose of this study was to describe the femoral component rotation in total knee arthroplasty (TKA) using a tibia-first, gap-balancing, "functional alignment" technique. Methods: Ninety-seven patients with osteoarthritis received a TKA using computer navigation. The tibial resection was performed according to the kinematic alignment (KA) principles, while the femoral rotation was set according to the gap-balancing technique. Preoperative MRIs and intraoperative resection depth data were used to calculate the following rotational axes: the transepicondylar axis (TEA), the posterior condylar axis (PCA) and the prosthetic posterior condylar axis (rPCA). The angles between the PCA and the TEA (PCA/TEA), between the rPCA and the PCA (rPCA/PCA) and between the rPCA and the TEA (rPCA/TEA) were measured. Data regarding patellar maltracking and PROMs were collected for 24 months postoperatively. Results: The mean PCA/TEA, rPCA/TEA and rPCA/PCA angles were −5.1° ± 2.1°, −4.8° ± 2.6° and −0.4° ± 1.7°, respectively (the negative values denote the internal rotation of the PCA to the TEA, rPCA to TEA and rPCA to PCA, respectively). There was no need for lateral release and no cases of patellar maltracking. Conclusions: A tibia-first, gap-balancing, "functional alignment" approach allows incorporating a gap-balancing technique with kinematic principles. Sagittal complexities in the proximal tibia (variable medial and lateral slopes) can be accounted for, as the tibial resection is completed prior to setting the femoral rotation. The prosthetic femoral rotation is internally rotated relative to the TEA, almost parallel to the PCA, similar to the femoral rotation of the KA-TKA technique. This technique did not result in patellar maltracking. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to compare ligament balance and laxity profiles achieved throughout flexion in restricted kinematic alignment (rKA) and gap balancing (GB). rKA and GB both aim to improve soft tissue balance and reduce ligament releases in total knee arthroplasty (TKA). Methods: One surgeon performed 68 rKA, another performed 73 GB TKAs using the same CR implant and robotic system. rKA limited femoral valgus and tibial varus to 6°, with tibial recuts performed to achieve balance. GB limited tibial varus and femoral valgus to 2°, with femoral resections adjusted to achieve mediolateral balance throughout flexion using predictive-gap planning software. Final joint laxity was measured using a robotic ligament tensioner. Statistical analyses were performed to compare differences in mediolateral balance and joint laxity throughout flexion. Further analyses compared alignment, joint line elevation and orientation (JLO), and frequency of ligament releases and bone recuts. Results: Both techniques reported greater lateral laxity throughout flexion, with GB reporting improved mediolateral balance from 10° to 45° flexion. GB resected 1.7 mm more distal femur (p ≤ 0.001) and had greater overall laxity than rKA throughout flexion (p ≤ 0.01). rKA increased JLO by 2.5° and 3° on the femur and tibia (p ≤ 0.001). Pre-operative and post-operative coronal alignment were similar across both techniques. rKA had a higher tibial recut rate: 26.5% vs 1.4%, p < 0.001. Conclusions: rKA and GB both report lateral laxity but with different JLO and elevation. Use of a predictive-gap GB workflow resulted in greater mediolateral gap symmetry with fewer recuts. Level of evidence: III, retrospective cohort study. [ABSTRACT FROM AUTHOR]

Background: To increase total knee arthroplasty procedure satisfaction, surgeons are exploring improvements in surgical technique. The impact of gap balancing or measured resection approach on posterior condylar offset (PCO) is not well understood. Methods: We reviewed the clinical and radiographic results of 498 unilateral posterior stabilized total knee arthroplasties. Radiographs were assessed to measure the primary endpoints of anterior-posterior width, PCO, and anterior condylar offset. Clinical outcome measures were used to assess patient improvement measures. Multiple linear regression analyses were performed to determine the clinical factors related to our primary endpoints. Results: No significant difference was observed between groups in anterior-posterior width (P = .24) and PCO (P = .78). Significant positive correlations were observed between postoperative PCO and knee range of motion (r = 0.12, P = .04) and total Knee Society Scores (r = 0.14, P = .02). Conclusion: No impact of surgical technique on PCO was observed. Correlations were observed between postoperative PCO and the functional subscore and total Knee Society Score. All patients reported clinical improvements at 1 year postoperatively.

Abstract Background Which technique, gap balancing or measured resection, can obtain better femoral component alignment and soft tissue balance in total knee arthroplasty (TKA) is still controversial. This study aimed to determine whether the gap balancing technique using a modified spacer block in TKA can result in better postoperative clinical outcomes than the measured resection technique. Methods A total of 124 patients who underwent consecutive primary TKA between May 2016 and August 2018 were retrospectively reviewed. The gap balancing technique assisted by a modified spacer block was used in 61 patients, and the measured resection technique was used in 63 patients. The surgical, imaging and knee function outcomes of the two groups were compared. Results The thickness of the posterior medial condyle bone resection using the modified spacer block tool in gap balancing was significantly larger than that of the MR technique (P = 0.001). Compared with the measured resection group, the gap balancing group had a greater external rotation resection angle of the femur (4.06 ± 1.10° vs. 3.19 ± 0.59°, P

Background: Achieving coronal plane balance in total knee arthroplasty (TKA) is of paramount importance. There is concern that obtaining balancing before removal of posterior osteophytes may lead to asymmetrical extension balance once removed. We hypothesized that there is a particular posterior osteophyte size and location that does not result in significant change in coronal gap balancing.Methods: In this study of 245 robotic arm-assisted TKAs, the size and location of posterior osteophytes were obtained from preoperative computer tomography scans. Gap measurements at 10°-25° and 90° flexion after removal of medial and lateral osteophytes, before and after posterior osteophyte removal and bone resection were compared with respect to the size and location of posterior osteophytes.Results: The largest size posterior osteophytes measured >10 mm in 8.2% of cases, 5-10 mm in 34.7%, <5 mm in 23.7%, and 23.7% had no osteophytes. The mean osteophyte size was 5.7 mm. The cohorts with and without posterior osteophytes were both found to have significant but similar changes in all gaps after osteophyte removal and bone resection (mean 0.8-1.4 mm, P < .0001 and mean 0.7-1.7 mm, P < .0001, respectively). Osteophyte size and location had no significant effect on the change in postresection gaps. This included osteophytes greater than 10 mm, but their incidence was small.Conclusion: There is a small significant change in gaps between initial assessment and subsequent TKA bone resections, with or without posterior osteophytes. Our study found that where the surgeon thoroughly removes the medial and lateral osteophytes on initial exposure, posterior osteophytes <10 mm can be ignored during initial knee coronal balancing. [ABSTRACT FROM AUTHOR]

Total knee arthroplasty is a common procedure performed to improve pain and dysfunction attributed to arthritis, yet postoperative patient dissatisfaction rates remain relatively high. Patient satisfaction and outcomes have been linked to successful joint gap balancing in the coronal and sagittal planes intraoperatively. In previously described balancing techniques, the fulcrum used for alignment changes is customarily centered on the intramedullary axis generating symmetric changes in medial and lateral gaps. We propose a novel technique in the literature that, with the use of robotic-arm assisted technology or similar systems, allows manipulation of the fulcrum center of rotation during pre-resection planning and intraoperative gap establishment before bony cuts to asymmetrically influence medial and lateral, flexion and extension gaps to aid in balancing during total knee arthroplasty.

Abstract Objective We compared the measured resection (MR) technique and the gap balancing (GB) technique in patients with knee osteoarthritis after primary total knee arthroplasty (TKA) in China to understand the effects of the two techniques on knee function and squat function. Methods From March 2017 to September 2019, a prospective randomized controlled trial was conducted with 96 patients with knee osteoarthritis undergoing primary TKA from March 2017 to September 2019 randomized to GB group (n = 48) and MR group (n = 48). Intraoperative indicators (operation time, osteotomy volume of medial and lateral of posterior femoral condyles, external rotation angle) were recorded during operation. At 1, 3, 6, and 12 months after surgery, all the patients came to the hospital for review and underwent the pain severity, Western Ontario and McMaster University Osteoarthritis Index (WOMAC), knee joint range of motion, Oxford Knee Score (OKS), and American Knee Society Score (AKSS) tests. All patients were followed up for more than 1 year. Results The osteotomy volume of the medial femoral condyle in the GB group was higher than that in the MR group (P

Background: There is no consensus regarding superiority between gap balancing (GB) and measured resection (MR) techniques to implant total knee arthroplasties. In a multicenter setup, we compared both techniques using the same prosthesis. Methods: We included 262 balanSys posterior-stabilized total knee arthroplasties from 4 centers: 3 using the MR (n = 162) and one using the GB technique (n = 100), without navigation. Results: There was no significant difference in the Knee Society Score or visual analog scale pain at 2- and 7-year follow-up. The visual analog scale for satisfaction was significantly better in the MR group at 2 but not at 7 years. We found a significantly higher average valgus in the GB group, but the overall alignment was within 2° of neutral on the full-leg radiographs. There were no significant differences concerning radiolucency and survival. Conclusions: We found no significant differences in the functional outcome, pain, alignment, or survival, but a tendency toward better function using MR and better survival with GB.

Introduction: Recently, some studies showed assessment of the component gap is important for determination of the implant-inserted condition during total knee arthroplasty (TKA). We perform the modified gap technique with adjustment of the virtual gap which estimated by computer-aided design (CAD) using navigation system. The purpose of this study was to compare the virtual gap (CAD-gap) with the actual gap after inserting a femoral trial component (Trial-gap), and examine the usefulness of the surgical technique. Materials and methods: The subjects were 35 patients who underwent primary TKA using a navigation system and posterior-stabilized type TKA. The surgical procedure was to produce an extension gap, confirm the flexed CAD-gap on the navigation screen based on CAD data, and plan osteotomy of the femur. After osteotomy, the femoral component was inserted and the gap balance was measured. A tensor was used to adjust and measure the gap balance. Initial alignment, rotation of the femoral component, soft tissue balance in extension, final alignment after fixing all components, and the CAD- and Trial-gaps in both extension and flexion were evaluated. Results: The mean initial alignment angle, rotation angle of the femoral component, soft tissue balance angle and final alignment angle were 8.1 ± 4.2° varus, 3.5 ± 1.3°external rotation, 2.7 ± 2.5° varus and 0.4 ± 1.4° varus respectively. The mean medial and lateral CAD-gaps in extension were 10.8 ± 2.5 and 13.7 ± 2.5 mm, and the mean medial and lateral CAD-gaps in flexion were 12.2 ± 2.2 and 13.9 ± 2.7 mm. The equivalent Trial-gaps in extension and flexion were 10.5 ± 2.6 and 11.4 ± 3.1 mm, and 12.2 ± 2.5 and 14.4 ± 2.8 mm. The CAD- and Trial-gaps differed significantly only for lateral gaps in extension. Conclusion: In comparing the CAD-gap and the Trial-gap, only small difference was found in the lateral gap of extension. The other gaps in both extension and flexion were well maintained. We concluded adjustment of the CAD-gap during surgery using a navigation system can be used to adjust the actual component gap especially in the medial side.

Purpose: This study aimed to compare the reliability of two gap assessment methods (component and bone surface gap measurement vs. planned gap balance) and identify the contributors to component gaps other than planned gaps. Methods: The prospectively collected data for 122 consecutive primary total knee arthroplasties (TKAs; 114 patients). After femoral planning for gap balancing, the medial and lateral planned gaps were calculated (planned gap). The established medial extension and flexion gaps (MEG and MFG, respectively) and lateral extension and flexion gaps (LEG and LFG, respectively) were measured with and without the TKA components (bone surface and component gaps) at 0° and 90° flexion. The intraclass and Pearson correlation coefficients for each gap measurement method were assessed using planned gap values, and multiple linear regression analyses were performed to identify the contributors to component gaps. Results: Compared with the bone surface gap measurement, the component gap measurement showed higher reliability and stronger correlation with the planned gap balance for each gap. The changes in the medial posterior femoral offset contributed to the MEG and LEG, whereas those in the joint line height contributed to the LEG. The changes in the hip–knee–ankle angle and lateral posterior femoral offset contributed to the LFG. Conclusion: Component gap measurements of the established gap more accurately and reliably reflect the planned gap balance than do bone surface gap measurements. The established gaps are affected by several factors other than femoral planning. [ABSTRACT FROM AUTHOR]

Background: The goal of this study is to investigate the migration and inducible displacement of a bicruciate-stabilized (BCS) total knee arthroplasty implanted using gap balancing (GB) or measured resection (MR) surgical techniques. We hypothesized equal migration and displacement between the techniques.Methods: The study is a single-blinded, prospective, randomized controlled trial, with allocation of 71 patients to either GB or MR groups. Fifteen patients were withdrawn, resulting in 31 patients in the GB group and 25 in the MR group. Patients received the JOURNEY II™ BCS implant. Migration and inducible displacement were evaluated using radiostereometric analysis and patient examinations were performed at a 2-week baseline, and at 6 weeks, 3 months, 6 months, 1 year, and 2 years postoperation.Results: No differences (P > .05) existed between GB and MR groups for any measurement of tibial or femoral migration. Both groups had tibial migrations below 0.5 mm from baseline to 6 months, and below 0.2 mm from both 6 months to 1 year and 1-2 years postoperation. No differences (P > .05) were found between GB and MR groups for inducible displacement.Conclusion: No differences were found in implant migration or inducible displacement between GB and MR groups. The BCS implant can be expected to have migration risks on par with industry standards and both surgical techniques are safe and effective options for implantation of this implant design. [ABSTRACT FROM AUTHOR]

Background: Which technique, gap balancing or measured resection, can obtain better femoral component alignment and soft tissue balance in total knee arthroplasty (TKA) is still controversial. This study aimed to determine whether the gap balancing technique using a modified spacer block in TKA can result in better postoperative clinical outcomes than the measured resection technique. Methods: A total of 124 patients who underwent consecutive primary TKA between May 2016 and August 2018 were retrospectively reviewed. The gap balancing technique assisted by a modified spacer block was used in 61 patients, and the measured resection technique was used in 63 patients. The surgical, imaging and knee function outcomes of the two groups were compared. Results: The thickness of the posterior medial condyle bone resection using the modified spacer block tool in gap balancing was significantly larger than that of the MR technique (P = 0.001). Compared with the measured resection group, the gap balancing group had a greater external rotation resection angle of the femur (4.06 ± 1.10° vs. 3.19 ± 0.59°, P < 0.001°). Despite these differences, the mean ROM, KSS scores, and WOMAC scores at the 6-week, 1-year, and 2-year follow-ups were not significantly different. Postoperatively, there was no significant difference between the two groups in mechanical axis measurements (P = 0.275), the number of HKA outliers (P = 0.795) or the joint line displacement (P = 0.270). Conclusion: The functional outcomes of the gap balancing technique based on the modified spacer are similar to those of measured resection at 3 years. Compared with the MR technique, the GB technique resulted in a greater external rotation resection angle and thicker posterior medial condylar cuts in TKA with knee varus. [ABSTRACT FROM AUTHOR]

Abstract Background Measured resection and gap balancing are two distinct methods for proper femoral component alignment in total knee arthroplasty. Decision-making between the two techniques is controversial. The aim of this systematic review and meta-analysis was to compare measured resection and gap balancing with regard to the radiological and clinical benefits, and to examine whether this change the conclusions from previous trails. Methods A systematic literature search of the medical literature from January 1990 to February 2015 was performed. We selected six randomized controlled trials and five prospective cohort studies comparing gap balancing and measured resection in patients undergoing primary total knee arthroplasty. Data from included studies were pooled with use of fixed-effects and random-effects models with standard mean differences and risk ratios for continuous and dichotomous variables, respectively. Heterogeneity across studies was assessed with calculation of the I2 statistic. Results A total of 857 knees from 11 trials were included. Four hundred and forty-one knees were treated with gap balancing and 416 were treated with measured resection. In contrast to previous studies, we found that gap balancing demonstrated better patient-reported outcomes with regard to Knee Society score for pain (WMD 2.75, p = 0.004) and Knee Society score for function (WMD 5.47, p

Objective: We compared the measured resection (MR) technique and the gap balancing (GB) technique in patients with knee osteoarthritis after primary total knee arthroplasty (TKA) in China to understand the effects of the two techniques on knee function and squat function. Methods: From March 2017 to September 2019, a prospective randomized controlled trial was conducted with 96 patients with knee osteoarthritis undergoing primary TKA from March 2017 to September 2019 randomized to GB group (n = 48) and MR group (n = 48). Intraoperative indicators (operation time, osteotomy volume of medial and lateral of posterior femoral condyles, external rotation angle) were recorded during operation. At 1, 3, 6, and 12 months after surgery, all the patients came to the hospital for review and underwent the pain severity, Western Ontario and McMaster University Osteoarthritis Index (WOMAC), knee joint range of motion, Oxford Knee Score (OKS), and American Knee Society Score (AKSS) tests. All patients were followed up for more than 1 year. Results: The osteotomy volume of the medial femoral condyle in the GB group was higher than that in the MR group (P<0.05), and the operation time in the GB group was shorter than that in the MR group (P<0.05). At 1, 3, 6, and 12 months after surgery, the pain severity in the GB group was lower than that in the MR group (P<0.05), the knee range of motion in the GB group was larger than that in the MR group (P<0.05), the WOMAC of the GB group was lower than that of the MR group (P<0.05), the OKS of the GB group was higher than that of the MR group (P<0.05), the AKSS of the GB group was higher than that of the MR group. The incidence of postoperative complications in the GB group (4.17%) was significantly lower than that in the MR group (18.75%) (P<0.05). Conclusion: The GB technique can effectively shorten the operation time, relieve pain, improve knee range of motion, improve squat function and knee function, reduce osteoarthritis index, and reduce the occurrence of complications, which is worthy of clinical popularization and application. [ABSTRACT FROM AUTHOR]

Aim For a successful total knee arthroplasty (TKA), bone cuts and soft tissue envelope must be balanced to ensure equal flexion and extension gaps. The study aims to assess if preoperative computed tomography (CT) scans and planning software reduce soft tissue release. Methodology A retrospective analysis was conducted for the first 100 consecutive robotic-assisted (RA) TKA (RA-TKA) patients between March 2022 and May 2023. All patients underwent preoperative leg CT scans utilizing a fully automated Cuvis Joint robot. Planning software determined implant sizes and bone resections to achieve a 180° hip-knee-ankle axis. A posterior-stabilized knee design was implanted during surgery by the same surgical team using a medial parapatellar approach. The study hypothesis was, that RA-TKA with preoperative CT scans and planning does not reduce soft tissue release incidence, comparing it with the historical control cohort using chi-square tests ( P  < 0.05 considered significant). Results The study consisted of 89 women and 11 males, with an average age of 65.3 ± 12 years. The average body mass index of the patients was 27.4 ± 5.2 kg/m 2 . Ninety-four individuals had varus knees, while six had valgus knee deformity. Varus deformity ranged between 7° and 18°, and valgus knee deformity ranged from 6° to 14° preoperatively. Twelve patients (12.77%) of 94 varus knees (versus historic control 29%,  P -value = 0.0047) and one out of 6 (16.67%) valgus knees (versus historic control 84%, P  < 0.0001) required posteromedial and posterolateral release for appropriate knee balance. Conclusions The study negates the null hypothesis and indicates that RA-TKA with preoperative CT scans and planning reduces the incidence of soft tissue releases to achieve a well-balanced knee., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. N/A issued approval N/A. This study adhered to ethical guidelines, and all patients provided written informed consent prior to the surgery. This study was not sponsored by any or our Institute and our Local Research Ethics Committee does not mandate review of the retrospective study. Due to the retrospective nature of the study, the Local Research Ethics Committee waived the approval. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Londhe et al.)

Introduction: To achieve the most desirable post-operative results, operation techniques and procedures for total knee arthroplasty (TKA) are highly standardized. However, debates persist whether patients having undergone a gap balancing technique (GB) perform better than those having undergone measured resection (MR) technique. Therefore, a meta-analysis study was conducted to investigate advantages of GB compared to the MR. The focus of the present study was on clinical and functional scores, radiological measurements and further complications.Materials and Methods: The present meta-analysis was conducted according to the PRISMA checklist. In November 2019, literature search was performed. All clinical studies comparing measured resection technique versus gap balancing technique for primary total knee arthroplasty were considered for inclusion. Only articles reporting quantitative data under the outcomes of interest were eligible for inclusion. The methodological quality assessment and statistical analyses were performed through the Review Manager Software version 5.3 (The Cochrane Collaboration, Copenhagen).Results: Data from 25 clinical trials (2971 procedures) were collected. Patient baseline demonstrated a good comparability. No difference among the two cohorts was found in terms of SF-12 Mental and Physical, ROM, KSS, KSS Function, OKS, WOMAC. No difference was found in the alignment of mechanical axis and femoral rotation. During the knee motion, no difference was found between the medial and lateral gaps among the two techniques. The GB showed a significant elevated joint line (P < 0.0001), along with a longer duration of the operating time (P = 0.001). No differences were found in terms of revision surgery, aseptic loosening or prosthetic infections.Conclusion: GB and MR achieve similar outcomes for TKA. In the GB group, a proximalisation of the joint line and extended operating time was detected. Regarding the additional outcomes of interest, the present analysis showed comparability between both groups, MR and GB. [ABSTRACT FROM AUTHOR]

Purpose: Femoral rotation in total knee arthroplasty (TKA) is hypothesized to vary in the same knee depending on the method used to establish it.Methods: Thirty-eight patients who underwent TKA surgery using a measured resection technique (RT) were compared with 40 patients who underwent a flexion-gap balancing technique with computer-assisted (for navigation) surgery (FB-CAS) to assess clinical and radiographic alignment differences at two years postoperatively. In 36 of the 40 patients in the FB-CAS group, both methods were used. Intraoperatively, the transepicondylar femoral rotation (TEFR) in reference to the transepicondylar axis was established as the rotation that balanced the flexion gap. Once the TEFR was obtained, an analogous rotation as measured by a posterior reference femoral rotation (PRFR) cutting guide was determined.Results: Femoral component rotation determined by the TEFR and PRFR methods differed in each of the knees. The median TEFR was 0.08°±0.6° (range - 1.5°, 1.5°), and the median PRFR was 0.06°±2.8° (range - 6°, 5°). The mean difference in the rotational alignment between the TEFR and PRFR techniques was 0.01° ± 3.1°. The 95% limits of agreement between the mean differences in measurements were between 6.2° external rotation and - 6.1° internal rotation. At 2 years postoperatively, we found no differences in the radiographic or clinical American Knee Society score between the two groups.Conclusion: Rotation of the femoral component in TKA can vary in the same knee depending on the surgical method used to establish it. This variation in femoral rotation is sufficiently small enough to have no apparent effect on the 2-year clinical outcome score.Level Of Evidence: II. [ABSTRACT FROM AUTHOR]

BACKGROUND: Total knee arthroplasty is effective in managing end-stage knee disease. Measured resection and gap balancing are two different techniques． Both of two have advantages and disadvantages. A technique has been developed that combines the benefits of measured resection and gap balancing to optimize the clinical effect of total knee arthroplasty. OBJECTIVE: To evaluate the operation and early clinical effect in total knee arthroplasty about the combination of measured resection and gap balancing technique used in femoral component rotation. METHODS: Totally 30 patients were treated with the combination of measured resection and gap balancing technique in total knee arthroplasty from September 2016 to December 2018, including 4 males and 26 females, at the age of 46-81 years. There were 24 cases of osteoarthritis with varus and 2 cases of osteoarthritis with valgus. There were 4 cases of rheumatoid arthritis with valgus. All patients signed the informed consent. This study was approved by the Hospital Ethics Committee. Effects were evaluated by Visual Analogue Scale, Hospital for Special Surgery score, femorotibial angle and range of motion before surgery and during final follow-up. RESULTS AND CONCLUSION: (1) The incision healed in the first stage after operation. No early complications occurred, such as infection, vascular nerve injury, deep venous thrombosis of the lower extremities and periprosthetic fracture. (2) Totally 30 patients were followed up for 6-30 months. (3) Visual Analogue Scale, Hospital for Special Surgery score, range of motion and femorotibial angle were improved during final follow-up compared with those before surgery (P < 0.05). (4) Surgeons should be familiar with measured resection and gap balancing technique in total knee arthroplasty, and then use the combination of two techniques based on the specific situation of patients to obtain better soft tissue balance and prosthesis position. The combination technique is easy to master and can be operated with traditional osteotomy tools. Thus, good short-term effect can be achieved. [ABSTRACT FROM AUTHOR]

Purpose: Total knee arthroplasty is a successful procedure in treating subjects with end-stage knee osteoarthritis. The objective of this matched study was to evaluate subjective patient satisfaction and clinical and radiological outcomes in two groups of patients undergoing primary TKA using an identical third-generation design with different conformity in the polyethylene insert.Methods: One hundred consecutive patients undergoing TKA because of knee osteoarthritis were randomized in two matched groups. Group A included 50 Posterior-Stabilized (PS) implants, while group B included 50 Medially Congruent (MC) implants. The surgical technique was identical: gap balancing in extension and measured resection in flexion; cruciate ligaments were always removed; the coronal alignment followed the mechanical axis and the tibial slope was set at 3° in the PS group and 5° in the MC. Oxford Knee Score (OKS) and Knee Society Score (KSS) were assessed preoperatively and at 2 year minimum follow-up. Two-sample T test statistical analysis was performed.Results: All patients were available at final follow-up: there were no preoperative statistical differences between the two groups in the average preoperative ROM (PS 112°, MC 108°; n.s.), average preoperative KSS (PS 64.4, MC 63.7; n.s.), average preoperative OKS (PS 19.6; MC 19.0; n.s.), and average BMI (PS 34.40, MC 34.60; n.s.). At final follow-up, there were no statistical differences between the two groups in the average OKS (PS 40,5; MC 41.1; n.s.) and in the average KSS (PS 161,5, MC 165,7; n.s.). We found a statistically but not clinically significant difference at final ROM: the average maximum active flexion was 120° in the PS group and 123° in the MC group (s.s.).Conclusion: This study evaluated two biomechanically different polyethylene inserts in the same TKA design, showing that reducing the level of intra-articular conformity had minimal effects on PROMs and objective short-term clinical results but a potentially beneficial effect on ROM. This study suggests that, once a satisfactory intra-operative stability is obtained, the minimal level of constraint should be used.Level Of Evidence: III. [ABSTRACT FROM AUTHOR]