Gap Balancing Technique Research Articles

Effect of tibia-first, restricted functional alignment technique on gap width changes, and component positioning in robotic arm-assisted total knee arthroplasty.

This study aims to quantitatively assess the predictability of post-resection gap dimensions and the attainment of balanced gaps using robotic arm-assisted total knee arthroplasty (TKA). This retrospective cohort study included 100 consecutive patients who underwent robotic arm-assisted TKA for knee osteoarthritis using a restricted functional alignment (FA) technique. Tibial cuts were performed based on preoperative tibial anatomy within predefined boundaries, followed by femoral component adjustments according to tensioned soft tissues to optimise gap balance. The primary outcome was the proportion of balanced gaps, defined as differential laxities of ≤2 mm, across extension, flexion, lateral, and medial gap measurements. Ligament balancing in lateral and medial compartments was assessed using a robotic system at 10° and 90° flexion to evaluate if restricted FA facilitated a balanced knee. Secondary outcomes included implant alignment, resection depth, and patient-reported outcome measures (PROMs). Significant increases in both lateral and medial gaps at 10° and 90° flexion were observed following tibial and femoral bone resections (p < 0.001). At extension, average gap changes were 0.9 mm (lateral) and 1.6 mm (medial) after tibial cuts, and 0.5 mm (lateral) and 1.2 mm (medial) after femoral cuts. At 90° flexion, changes were 0.3 mm (lateral) and 1.7 mm (medial) following tibial cuts, and 1.0 mm (lateral) and 1.4 mm (medial) after femoral cuts. Despite these variations, the tibia-first, gap-balancing technique achieved overall balance in 98% of gap measurements. The tibial component was placed at an average of 2.1° varus, while the femoral component was positioned at 0.3° varus and 1.3° external rotation relative to the surgical transepicondylar axis. Significant improvements in PROMs were noted between preoperative and one-year postoperative evaluations (all p < 0.05). The tibia-first, restricted FA technique achieved a well-balanced knee in 98% of cases, despite inconsistent gap increments observed between initial assessments and post-resection. Therapeutic Level IV.

A new gap balancing technique with functional alignment in total knee arthroplasty using the MAKO robotic arm system: a preliminary study

BackgroundGap 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.MethodsA 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.ResultsThe 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).ConclusionsThis 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.

Large angular correction of arithmetic coronal alignment is associated with residual lateral laxity after total knee arthroplasty in varus knees for Japanese patients.

One of the most common types of coronal plane alignment of the knee (CPAK) is type I, which is characterised by varus alignment and apex distal joint line obliquity. The purpose of this study was to evaluate the association of changes in arithmetic hip-knee-ankle angle (aHKA) with both postoperative joint laxity and patient-reported outcome measures (PROMs) in patients with CPAK type I following mechanical alignment (MA) total knee arthroplasty (TKA). Of 111 consecutive knees in 92 patients with osteoarthritis who underwent primary TKA, 80 knees (72.0%) with CPAK type I phenotype preoperatively were evaluated. All TKAs were performed to achieve neutral MA by a medial stabilising gap balancing technique. Pre- to postoperative change in aHKA was defined as ΔaHKA. The 80 CPAK type I knees were divided into a larger ΔaHKA group (>7°) and a smaller ΔaHKA group (≤7°). PROMs, including the Knee Society Score and Forgotten Joint Score-12, were assessed before and 2 years after surgery. Pre- and postoperative joint laxity was assessed using a Telos arthrometer. Twenty-two knees showed a larger ΔaHKA, and postoperative lateral joint laxity in varus stress was significantly greater in these patients than in those with a smaller ΔaHKA (6.8° vs. 4.5°, p = 0.006). There were no significant differences between the groups in PROMs (p = n.s.). Postoperative lateral laxity was associated with larger aHKA changes than smaller aHKA changes in CPAK type I knees after TKA. However, no statistically significant differences in PROMs were found according to the amount of change in aHKA. Level III.

Effect of Surgical Technique, Implant Design, and Time of Examination on Contact Kinematics: A Study of Bicruciate-Stabilized and Posterior-Stabilized Total Knee Arthroplasty

BackgroundBicruciate-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. MethodsThe 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. ResultsThere 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). ConclusionsContact 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.

Influence of Preoperative Deformity on Flexion Gap Asymmetry in Measured Resection Technique: A Theoretical Study in Navigated Gap Balancing Total Knee Arthroplasties, Done for Varus Knee Osteoarthritis.

Disagreement exists on (a) achieving a symmetrical flexion gap and (b) the influence of varus deformity on the flexion gap asymmetry (FGA) in measured resection (MR) total knee arthroplasty (TKA). We aimed to determine the FGA and influence of preoperative deformity on the FGA, based on the MR technique, in varus knee osteoarthritis. In 321 navigated TKAs, we released the soft tissues in extension. In 90° flexion, with the tensioner in situ, we calculated the FGA, the angle between the posterior femoral cut (planned 3° external rotation to the posterior condylar line, parallel to the surgical transepicondylar axis, or perpendicular to the Whiteside line) and the proximal tibial resection plane. The FGA values varied widely, and the risk of >2° and >3° FGA was present in at least 60% and 40% knees, respectively. These risks were high in knees with moderate and severe varus deformity. In varus knee osteoarthritis, the risk of FGA (based on the MR technique) was high, especially when the deformity was moderate to severe. Caution is required in MR TKA, and surgeons must consider safer alternatives (gap balancing or hybrid technique) to achieve a symmetrical flexion gap in these knees.

Optimizing femoral component rotation in TKA: The role of posterior condylar angle and condylar twist angle

PurposeFemoral component rotation (FCR) is crucial in total knee arthroplasty (TKA). Currently, the optimal method to select FCR is unknown due to patient anatomy variation. Addressing the variability of femoral component rotation is critical to optimizing TKA outcomes and patient satisfaction. In this study, we aimed to identify outlier frequency and evaluate malrotation risk reduction by setting anatomic limits for FCR selection. MethodsOne hundred patients with end-stage knee osteoarthritis requiring TKA were included and categorized as normal rotation, internal rotation outlier, and external rotation outlier based on their expected FCR calculated intraoperatively using the modified gap balancing technique with a tensioning device. The computed FCR was then referenced to their Posterior Condylar Angle (PCA) and Condylar Twist Angle (CTA). The postoperative FCR and 1, 2-, and 5-years functional scores were also measured. ResultsSeventy-one knees (71%) were within the limits of PCA and CTA. The combined outlier frequency is 29%. The mean computed FCRs are 4.4° (±1.5), −1° (±2.6), and 8.0° (±3.4) for the normal, internal rotation, and external rotation groups, respectively. Whereas after setting the limits, the postoperative FCRs are 3.1° (±1.5), 3.9° (±1.7), and 2.5° (±1.4) for the three groups, respectively. The relative risk reduction against malrotation was 65%. At 1, 2, and 5 years post-TKA, all groups showed significant functional improvement, with no significant differences in functional outcomes between the normal and outlier groups. ConclusionThe use of lower and upper limits for selecting the FCR based on CTA and PCA can be a valuable approach to reducing malrotation risk and achieving satisfactory functional outcomes in TKA. Addressing the individual patient's anatomic limits contributes to improved TKA outcomes and patient-specific component alignment, thus enhancing the overall success of the procedure.

Large Osteophytes over 10 mm at Posterior Medial Femoral Condyle Can Lead to Asymmetric Extension Gap Following Bony Resection in Robotic Arm-Assisted Total Knee Arthroplasty with Pre-Resection Gap Balancing.

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.

Differences in joint line level and posterior condylar offset during total knee replacement with use of gap-balancing and measured resection techniques—matched cohort study

BackgroundTotal knee replacement (TKR) is considered one of the most common elective orthopaedic procedures. The main focus of TKR is to offer patient's symptomatic relief from persistent knee pain. To achieve this it is crucial to restore joint biomechanics by performing proper bone cuts. Some surgeons favor the measured resection technique, others prefer gap balancing technique. The researchers of the presented study performed TKR using these two techniques. The aim of this study was to compare the postoperative change in joint line and posterior condylar offset after TKR with use of anatomic knee design implants between gap balancing and measured resection techniques.MethodsTwo hundred twenty-five X-rays of patients who underwent TKR performed by a single surgeon between 2020 and 2021 were analyzed. The first group of patients (101) was operated with the use of gap balancing technique and the second group (124) was operated with the use of measured resection technique. Patients included in the study were > 50 years of age, had confirmed primary knee osteoarthritis, underwent primary TKR with a PS (posterior stabilized) knee implants without patella resurfacing and had at least 15 degree flexion contracture. T-student test and U Mann–Whitney test were used in statistical analysis of results, according to the normality of distribution examined with the Shapiro–Wilk test. Post-hoc analysis was performed using the Dwass-Steel-Crichtlow-Fligner test (DSCF).ResultsThe postoperative analysis showed a significantly elevated joint line level in the gap balancing group (-2.6 ± 4.1 vs -0.7 ± 4.8, p < 0.0005). In the gap balancing group significantly more patients had joint lines elevated > 2 mm comparing to measured resection technique. The difference between pre- and postoperative PCO (posterior condylar offset) and PCOR (posterior condylar offset ratio) results had no significant differences (100.8 ± 11.8 vs 101 ± 12.5, p > 0.05) between the groups.ConclusionsThe results of the study suggest that when it comes to restoring joint line level measured resection technique seems to be superior in comparison to the gap balancing technique. What is more, results indicate measured resection is equal in terms of restoring posterior condylar offset to the gap balancing technique.Trial registrationNCT04164147, date of registration: November 14, 2019.

Lateral joint tightness in flexion following cementless mobile-bearing total knee arthroplasty decreases patient-reported outcome measures and postoperative range of motion

PurposeThe purpose of this study was to clarify the association between clinical outcomes and the flexion joint gap following rotating concave–convex (Vanguard ROCC) total knee arthroplasty (TKA). MethodsThis consecutive retrospective series included 55 knees that underwent ROCC TKA. All the surgical procedures were performed using a spacer-based gap-balancing technique. To evaluate the medial and lateral flexion gaps, axial radiographs of the distal femur were obtained using the epicondylar view with a distraction force to the lower leg at 6 months postoperatively. Lateral joint tightness was defined as the lateral gap being greater than the medial gap. To evaluate clinical outcomes, patients were asked to complete patient-reported outcome measures (PROMs) questionnaires preoperatively and during at least 1 year of follow-up postoperatively. ResultsThe median follow-up duration was 24.0 months. Overall, 16.0% of patients had postoperative lateral joint tightness in flexion. The postoperative range of motion and PROMs were lower in patients with lateral joint tightness than in those with a balanced flexion gap or lateral joint laxity. No serious complications, including bearing dislocations, occurred during the observation period. ConclusionLateral joint tightness in flexion following ROCC TKA decreases PROMs and postoperative range of motion. Level of evidence4.

Incidence of soft tissue releases in robotic assisted cementless TKA with mechanical alignment and flexion gap balancing

BackgroundTo ensure the success of total knee arthroplasty (TKA), precise bone cuts and a well-balanced soft tissue envelope are crucial. Soft tissue release may be necessary, subject to various factors. Therefore, documenting the type, frequency, and necessity of soft tissue releases can establish a benchmark for comparing different alignment techniques and philosophies and evaluating their outcomes. The purpose of this study was to demonstrate that robotic-assisted knee surgery requires minimal soft tissue release.MethodsWe prospectively documented and retrospectively reviewed the soft tissue releases employed in securing ligament balance in the first 175 patients who received robotic-assisted TKAs at Nepean Hospital. ROSA was utilized in all surgeries with the aim of restoring mechanical coronal alignment, with a flexion gap balancing technique. Surgeries were performed between December 2019 to August 2021 by a single surgeon who used a standard medial parapatellar approach without a tourniquet, and the cementless persona prosthesis. All patients were followed up for a minimum of 6 months post-surgery. Soft tissue releases included any form of medial release for varus knee, posterolateral release for valgus knee and PCL fenestration or sacrifice.ResultsThere were 131 female and 44 male patients, aged between 48 to 89 years (average 60 years). The preoperative HKA ranged from 22 degrees varus to 28 degrees valgus, with 71% of patients presenting with a varus deformity. For the whole group, the no need for soft tissue release was documented in 123 patients (70.3%), small fenestrated releases of PCL in 27 (15.4%), sacrifice of PCL in 8 (4.5%), medial releases in 4 (2.3%) and posterolateral releases in 13 (7.4%). In 29.7% of patients in whom a soft tissue release was necessary for balance, over half were/received minor fenestrations of the PCL. Outcomes to date included no revisions or impending revisions, 2 MUAs (1%), and Oxford knee scores averaged 40 at 6 months.ConclusionWe concluded that Robot technology enhanced the precision of bone cuts and allowed for titration of required soft tissue releases to achieve optimal balance.

The Clinical Outcomes of Measured Resection and Gap Balancing Techniques in Primary Total Knee Arthroplasty: A Meta-analysis.

At present, the clinical efficacy of measured resection (MR) and gap balancing (GB) techniques in total knee arthroplasty (TKA) is still controversial. The objective of this study was to evaluate the clinical outcome indexes of the two surgical methods through a meta-analysis. The literature was systematically searched on PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure (CNKI), WANFANG, Weipu (VIP), and China Biomedical Literature (CBM) electronic databases inception until June 12, 2022. RevMan 5.3 software (the Nordic Cochrane Center, the Cochrane Collaboration, Copenhagen, Denmark) was used to analyze all data of this study. The Cochrane risk bias assessment tool is a risk bias evaluation criterion recommended by the Cochrane Handbook for systematic reviews. Eleven studies involving 1268 knees in total were included. The main outcome indexes showed that the Knee Society Score (KSS) knee score (MD: -1.40; 95% CI: -2.57 to -0.22; p=0.02) and KSS knee function score (MD: -3.11; 95% CI: -3.72 to -2.50; p<0.001) in the GB group were higher 1 year after operation, while femoral component rotation angle (FCRA; MD: -0.75; 95% CI: -1.34 to -0.07; p=0.03) and the osteotomy volume of the posterior medial femoral condyle (MD: -0.76; 95% CI; -1.13 to -0.38; p<0.001) were greater in the GB group. In addition, there was no significant difference in the joint line change (MD: -0.03; 95% CI: -0.07 to 0.01; p=0.16) between the two groups. Secondary outcome results showed that the knee joint range of motion (ROM) in 3 months, and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) score after 1 year were better in the GB group. However, the operation time of the MR group was shorter. In addition, this study revealed no significant differences in post-complications between these two groups. Although the GB technique may not provide better radiographic results or reduce the complication rate, the recovery of joint function showed earlier improvement.

Complications of Bicruciate-Retaining Total Knee Arthroplasty: The Importance of Alignment and Balance.

Bicruciate-retaining total knee arthroplasty (BCR TKA) results in kinematics closer to the native knee and in greater patient satisfaction but information concerning its outcome and complications is lacking.The goal of this study is to report the clinical and radiological outcomes of BCR prosthesis implanted using a spacer-based gap balancing technique and to assess if some preoperative factors are associated with a worse prognosis.A cohort of 207 knees in 194 patients who underwent BCR TKA, with a minimum 1-year follow-up, was retrospectively analyzed.Patients were followed at 6 weeks, 6 months, 1 year, and then every following year postoperatively, and filled questionnaires (Knee Society and Knee injury and Osteoarthritis Outcome Score) at every visit. Clinical and radiological assessments included range of motion, knee alignment, pain, and complications as defined by the Knee Society's Standardized list and definition of Complication of Total Knee Arthroplasty.Forty-three knees (20.8%) suffered major complications. Twenty-one knees (10.1%) underwent revision at an average of 32.1 months after the index procedure. Revision-free survival at 100 months was 85.7%. Revision was performed for aseptic tibial loosening in eight knees (3.9%) and stiffness in five knees (2.4%). There were 29 reoperations other than revision (14.0%), the most frequent procedure being manipulation under anesthesia in 14 knees (6.8%). Minor complications included tendonitis (20.8%), persistent synovitis (6.8%), and superficial wound infections (6.3%).All outcomes scores were greatly improved at the 1-year follow-up compared with preoperatively (p < 0.001). However, maximum flexion at the last follow-up was significantly reduced compared with preoperatively (mean maximum flexion ± standard deviation: 119.9 ± 15.6 vs. 129.9 ± 14.4, p < 0.001). Aseptic tibial loosening was associated with a hypercorrection in varus of preoperative valgus knees (p = 0.012).BCR TKA can give functional results similar to other types of prostheses but involves a substantial risk of complications. Important factors that can explain failed BCR TKA and guide its use were identified, more particularly knee alignment and its role in aseptic tibial loosening.

Component Rotation in Well-Functioning, Gap Balanced Total Knee Arthroplasty Without Navigation

BackgroundMalalignment 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. MethodsThere 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. ResultsThe 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). ConclusionDespite 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 of EvidenceLevel III, Retrospective Cohort Study.

Balancing the flexion gap first in total knee arthroplasty leads to better preservation of posterior condylar offset resulting in better knee flexion.

The purpose of this study is to determine whether the flexion first balancing technique, developed in an attempt to solve the dissatisfaction due to instability in total knee arthroplasties, leads to better restoration of joint line height and medial posterior condylar offset. This might result in better knee flexion, compared to the classic extension first gap balancing technique. The secondary objective is to show non-inferiority of the flexion first balancing technique in terms of clinical outcomes as measured by the Patient Reported Outcome Measurements. A cohort of 40 patients (46 knee replacements) operated using the flexion first balancing technique was retrospectively analyzed and compared with a cohort of 51 patients (52 knee replacements) operated using the classic gap balancing technique. Radiographic analysis of the coronal alignment, joint line height and posterior condylar offset was performed. Clinical and functional outcome data were analyzed pre- and postoperatively and compared between both groups. The two sample t test, Mann-Whitney U test, Chi-square test and a linear mixed model were used for performing statistical analyses, after normality analyses were executed. Radiologic evaluation showed a decrease in posterior condylar offset using the classic gap balancing technique (p = 0.040) versus no change using the flexion first balancing technique (p = n.s.). No statistically significant differences were noted for joint line height and coronal alignment. Using the flexion first balancer technique leads to a greater postoperative range of motion with deeper flexion (p = 0.002) and a better Knee injury and Osteoarthritis Outcome Score (KOOS) (p = 0.025). The Flexion First Balancing technique is a valid and safe technique for TKA, resulting in better preservation of PCO with consequently greater postoperative flexion and better KOOS scores. III.

How does the use of quantified gap-balancing affect component positioning and limb alignment in robotic total knee arthroplasty using functional alignment philosophy? A comparison of two robotic platforms

PurposeThis study aimed to compare the effect of an image-based (MAKO) system using a gap-balancing technique with an imageless (OMNIbot) robotic tool utilising a femur-first measured resection technique.MethodsA retrospective cohort study was performed on patients undergoing primary TKA with a functional alignment philosophy performed by a single surgeon using either the MAKO or OMNIbot robotic systems. In all cases, the surgeon’s goal was to create a balanced knee and correct sagittal deformity (eliminate any fixed flexion deformity). Intra-operative data and patient-reported outcomes (PROMS) were compared.ResultsA total of 207 MAKO TKA and 298 OMNIbot TKAs were analysed. MAKO TKA patients were younger (67 vs 69, p=0.002) than OMNIbot patients. There were no other demographic or pre-operative alignment differences. Regarding implant positioning, in MAKO TKAs the femoral component was more externally rotated in relation to the posterior condylar axis (2.3° vs 0.1°, p<0.001), had less valgus femoral cuts (1.6° vs 2.7° valgus, p<0.001) and more varus tibial cuts (2.4° vs 1.9° varus, p<0.001), and had more bone resected compared to OMNIbot TKAs. OMNIbot cases were more likely to require tibial re-cuts than MAKO (15% vs 2%, p<0.001). There were no differences in femur recut rates, soft tissue releases, or rate of achieving target coronal and sagittal leg alignment between robotic systems. A subgroup analysis of 100 MAKO and 100 OMNIbot propensity-matched TKAs with 12-month follow-up showed no significant difference in OKS (42 vs 43, p=0.7) or OKS PASS scores (83% vs 91%, p=0.1). MAKO TKAs reported significantly better symptoms according to their KOOS symptoms score than patients that had OMNIbot TKAs (87 vs 82, p=0.02) with a higher proportion of KOOS PASS rates, at a slightly longer follow-up time (20 months vs 14 months, p<0.001). There were no other differences in PROMS.ConclusionA gap-balanced technique with an image-based robotic system (MAKO) results in different implant positioning and bone resection and reduces tibial recuts compared to a femur-first measured resection technique with an imageless robotic system (OMNIbot). Both systems achieve equal coronal and sagittal deformity correction and good patient outcomes at short-term follow-ups irrespective of these differences.

Individualized alignment and ligament balancing technique with the ROSA® robotic system for total knee arthroplasty.

Higher patient's expectations and dissatisfaction following total knee arthroplasty are well-documented phenomena. Despite the implications of different patients' related factors both modifiable and nonmodifiable, in the last decade a lot of emphasis has been focused on surgical technique, implant alignment and stability both as a cause and a potential solution of several problems. Different alignment and balancing techniques have been recently described and the introduction of new technologies such as computer and robotic-assisted surgery have been the basis for their optimization. In this paper, the surgical technique of the ROSA Knee System will be described focusing on the potential alignment options and the ligament balancing technique. The current literature available about the system will also be analyzed. The ROSA® robotic system have been recently introduced in the market and presents specific and peculiar features to optimize ligament balancing and an individualized alignment of the implant in a three dimensional prospective. The system is showing a favourable gap balancing technique and the possibility to create an individualized alignment. Preliminary results have now been shown in the literature both on the accuracy of the system and on clinical outcomes. Preliminary results are promising both in terms of accuracy of the system and of clinical outcomes.

Comparison of the Imaging and Clinical Outcomes among the Measured Resection, Gap Balancing, and Hybrid Techniques in Primary Total Knee Arthroplasty.

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). 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. 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. 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.

Femoral Component Rotation in Total Knee Arthroplasty Using a Tibia-First, Gap-Balancing, "Functional Alignment" Technique.

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. 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. 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. 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.

Facteurs extra articulaires du tibia et du fémur influençant l’équilibre du genou dans les prothèses totales de genou implantées selon un alignement mécanique

PurposeAlthough the joint gap distance and compartment loading of the knee are different parameters for obtaining balanced knees in patients with total knee arthroplasty (TKA), the extent to which a balanced knee is achieved in patients with mechanically aligned TKA (MA-TKA) is unclear. This study aimed to investigate the anatomical factors that affect the ligament balancing in MA-TKA according to a gap balancing technique by measured resection technique. MethodsThe relationship between compartment loading, gap distance, and lower limb alignment was analysed in forty-three patients who underwent navigation-assisted MA-TKA with the minimum soft-tissue release. Radiographic parameters included hip-knee-ankle (HKA) angle, femorotibial angle, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle, posterior tibial slope, varus and valgus joint line convergence angle, femoral valgus angle, femoral shaft curve, and tibial shaft curve (TSC). ResultsThe postoperative HKA angle was 0.4°±1.5°, with one coronal alignment outlier (2.3%). The gap distance showed four unbalanced knees for extension (9.3%) and flexion (9.3%), whereas the compartment loading identified 17 unbalanced knees (39.5%) at extension, 8 (18.6%) at 45° flexion, 7 (16.2%) at 90° flexion, and 10 (23.2%) at full flexion in MA-TKA. Mediolateral differentials of compartment loading correlated with femoral valgus angle (0°, 45°, and 90° flexion), mLDFA (45° and 90° flexion), and TSC (45° and 90° flexion). Femoral valgus angle and TSC were risk factors of the mediolateral differentials of compartment loading. ConclusionExtra-articular factors of femoral valgus angle, mLDFA, and TSC were associated with the mediolateral imbalance of compartmental loading, suggesting there is a limit to obtaining balanced knees in MA-TKA due to these unadjustable extra-articular factors. Level of evidenceIV, therapeutic case series.

Comparative study of gap balancing and measured resection technique in patients receiving staged bilateral total knee arthroplasty

Objective: To compare the clinical outcomes of staged total knee arthroplasty (TKA) performed on both knees in the same patient using gap balancing (GB) and measured resection (MR) techniques, respectively. Methods: The clinical data of 57 patients undergoing bilateral staged TKA at the Xi'an Jiaotong University Affiliated Honghui Hospital from July 2018 to January 2020 were analyzed. Using the random number table, MR or GB technique was selected when patients underwent primary TKA, and contralateral procedure was done with another technique. The procedures were performed by one chief surgeon, and the same prosthesis was chosen for all the procedures. The two osteotomy techniques for TKA were compared in terms of surgical status, radiographic data, functional recovery and satisfaction rate. Results: Total of 57 patients, including 16 males and 41 females, were included in the study with a mean age of (68.5±4.6) years (59-79 years) at primary TKA. All patients were followed up for (29.6±4.5) months (22-39 months). The interval between the two procedures was (4.7±3.0) months (0.5-12.0 months). Postoperative drainage was less in the GB side when compared with that in the MR side [(93.6±22.2) ml vs (109.9±36.9) ml, P=0.003]. At the 1-month postoperative follow-up, the visual analogue scale (VAS) of pain was lower on the GB side (3.0±0.8) than on the MR side (3.5±1.2), the range of motion (ROM) was higher on the GB side (105.7°±8.2° vs 100.2°±7.5°), the Knee Society Score (KSS) was higher on the GB side (78.5±5.4 vs 74.2±6.3), and the Western Ontario and McMaster University (WOMAC) score was lower on the GB side (35.4±5.5 vs 38.0±6.3), there were significant differences in the up-mentioned indexes between the two groups (all P<0.05). However, the repeated-measures analysis of variance indicated that there was no significant difference in VAS score, ROM, KSS score and WOMAC score between the two techniques (all P>0.05). The satisfactory rate of GB technique was 84.2%(48/57), ant it was 86.0%(49/57) with MR technique (P=0.446). There was also no significant difference between the two techniques in terms of complications (P=0.754). Conclusion: Both the GB and MR technique result in good knee function with similar clinical outcomes in patients receiving TKA in both knees for osteoarthritis without significant deformity.