Both gap balancing and measured resection for TKA will work and these techniques are often combined in TKA. The only difference is really the workflow. The essential difference in gap balancing is that you determine femoral component rotation by cutting the distal femur and the proximal tibia, and then using a spacer to determine femoral rotation. I prefer measured resection because I am, for most cases, a cruciate retaining surgeon. It is not ideal to determine femoral rotation based upon a gap balancing if you retain the cruciate. It is also important to maintain the joint line, especially in cruciate retention, in order to reproduce more normal kinematics and balance the knee throughout the range of flexion and extension. It is my opinion that the soft tissue balancing is easier to do with measured resection and the workflow is easier. The sequence of cuts and soft tissue balance is different if one is a gap balancing surgeon. This is more conducive for people who are cruciate substituters, but more difficult in a varus cruciate retaining knee. In that situation, if you determine femoral rotation by gap balancing with the tibia before you have cleared the posterior medial osteophytes in the varus knee, and remove the last bit of meniscus, you could artificially over rotate the femoral component causing posteromedial laxity. The major difference is that cutting the posterior cruciate will open the flexion space and allow the surgeon easier access to the posteromedial corner of the knee before the posterior femoral cut is made. It is also important to remember that in most cases cruciate substitution surgeons will make the flexion space 2 mm smaller than the extension space to compensate for the flexion space opening when the posterior cruciate is cut. The extensor mechanism plays an important role in flexion balance and should only be tested once the patella is prepared and the patella is back in the trochlear groove. I prefer gap balancing in most revision knees as I am virtually always substituting for the posterior cruciate in that case. My technique for measured resection is to assess the character of the knee prior to surgery. Is it varus? Is it valgus? Does it hyperextend? Does it have a flexion contracture? Would the knee be considered tight or loose? I cut the distal femur first, based upon measured resection. I use anatomic landmarks to determine femoral rotation. My most consistent landmark is the transtrochlear line, which is not always from the top of the notch to the bottom of the trochlea. I will use the medial epicondyle and the posterior reference in a varus knee, but not in a valgus knee. The tibial cut, also by measured resection, is easier once the femur has been prepared. The patellar cut is also a measured resection. Having done a preliminary soft tissue balance based upon the deformity, I will then use trial components to finish the soft tissue balance. In summary, both techniques can be used successfully in a cruciate substituting knee, but measured resection, in my opinion, is preferable especially in varus arthritis when the posterior cruciate is retained

Background. Surgeons generally perform total knee replacement using either a gap balancing or measured resection approach. In gap balancing, ligamentous releases are performed first to create an equal joint space before any bony resections are performed. In measured resection, bony resections are performed first to match anatomical landmarks, and soft tissue releases are subsequently performed to balance the joint space. Previous studies have found a greater rate of coronal instability and femoral component lift-off using the measured resection technique, but it is unknown how potential differences in loading translate into component stability and fixation. Methods. Patients were randomly assigned at the time of referral to a surgeon performing either the gap balancing or measured resection technique (n = 12 knees per group). Both groups received an identical cemented, posterior-stabilized implant. At the time of surgery, marker beads were inserted in the bone around the implants to enable radiostereometeric analysis (RSA) imaging. Patients underwent supine RSA exams at 0–2 weeks, 6 weeks, 3 months, 6 months, and 12 months. Migration of the tibial and femoral components including maximum total point motion (MTPM) was calculated using model-based RSA software. Knee Society Scores were also recorded for each group. Results. At 12 months follow-up, there were no revisions or adverse events. There were no differences in translation or rotation between the measured resection and gap balancing groups at 12 months, including for MTPM of the tibial component (mean 0.67 mm vs. 0.69 mm, p = 0.77, Fig. 1) and the femoral component (mean 0.71 mm vs. 0.51 mm, p = 0.25, Fig. 2). At 6 weeks, tibial components had greater (p = 0.01) anterior tilt in the measured resection group (0.08 deg) while the gap balancing group had greater posterior tilt (0.14 deg), but there were no differences from 3 months onwards (Fig. 3). Patients in both groups improved in Knee Society scores from pre- to post-operatively, with no difference in score between the groups at pre-operation (p = 0.56) or post-operation (p = 0.54). Discussion. Implants in both the gap balancing and measured resection groups were well fixed after 12 months, with no differences in translations or rotations between the two groups as of the latest time points. Both surgical techniques result in adequate fixation for total knee replacement. Future work will include measuring the contact location and possible condylar lift-off with flexion within this cohort. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Computer assisted total knee arthroplasty helps in accurate and reproducible implant positioning, bony alignment, and soft-tissue balancing which are important for the success of the procedure. In TKR, there are two surgical techniques one is measured resection in which bony landmarks are used to guide the bone cuts and the other is gap balancing which equal collateral ligament tension in flexion and extension is done before and as a guide to final bone cuts. Both these procedures have their own advantages and disadvantages. We retrospectively collected the data of 128 consecutive patients who underwent computer-assisted primary TKA using either a gap-balancing technique or measured resection technique. All the operations were performed by a single surgeon using computer navigation system available during a period between June 2016 to October 2016. Inclusion criteria were all patients requiring a primary TKA, male or female patients, and who have given informed consent for participation in the study. All patients requiring revision surgery of a previous implanted TKA or affected by active infection or malignancy, who presented hip ankylosis or arthrodesis, neurological deficit or bone loss or necessity of more constrained implants were excluded from the study. Two groups measured resection and gap balancing was randomly selected. At 1-year follow-up, patients were assessed by a single orthopaedic registrar blinded to the type of surgery using the Knee Society score (KSS) and functional Knee Society score (FKSS). Outcomes of the 2 groups were compared using the paired t test. All the obtained data were analysed. Statistical analysis was performed using SPSS 11.5 statistical software (SPSS Inc. Chicago). Inter-class correlation coefficient (ICC) and paired t-test were used and statistical significance was set at P = 0.05. In the measured resection group, the mean FKSS increased from 48.8769 (SD, 2.3576), to 88.5692 (SD, 2.7178) respectively. In the gap balancing group, the respective scores increased from 48.9333 (SD, 3.6577) to 89.2133(SD, 7.377). Preoperative and Postoperative increases in the respective scores were slightly better with the gap balancing technique; the respective p values were 0.8493 and 0.1045. The primary goal of TKA is restoration of mechanical axis and soft-tissue balance. Improper restoration leads to poor functional outcome and premature prosthesis loosening. Computer navigation enables precise femoral and tibial cuts and controlled soft-tissue release. Well balanced and well aligned knee is important for good results. Mechanical alignment and soft-tissue balance are interlinked and corrected by soft tissue releases and precise proximal tibial and distal femoral cuts. The 2 common techniques used are measured resection and gap balancing techniques. In our study, knee scores of the 2 groups at 1-year follow-up were compared, as most of the improvement occurs within one year, with very little subsequent improvement. Some surgeons favour gap balancing technique, as it provides more consistent soft-tissue tension in TKA

Background. Stability of total knee arthroplasty (TKA) is dependent on correct and precise rotation of the femoral component. Multiple differing surgical techniques are currently utilized to perform total knee arthroplasty. Accurate implant position have been cited as the most important factors of successful TKA. There are two techniques of achieving soft gap balancing in TKA; a measured resection technique and a balanced gap technique. Debate still exists on the choice of surgical technique to achieve the optimal soft tissue balance with opinions divided between the measured resection technique and the gap balance technique. In the measured resection technique, the bone resection depends on size of the prosthesis and is referenced to fixed anatomical landmarks. This technique however may have accompanying problems in imbalanced patients. Prediction of gap balancing technique, tries to overcome these fallacies. Our aim in this study was twofold: 1) To describe our methodology of ROBOTIC TKA using prediction of gap balancing technique. 2) To analyze the clinico-radiological outcome our technique comparison of meseaured resection ROBOTIC TKA after 1year. Methods. Patients that underwent primary TKA using a robotic system were included for this study. Only patients with a diagnosis of primary degenerative osteoarthritis with varus deformity and flexion deformity of were included in this study. Patients with valgus deformity, secondary arthritis, inflammatory arthritis, and severe varus/flexion deformity were excluded. Three hundred ten patients (319 knees) who underwent ROBOTIC TKA using measured resection technique from 2004 – 2009. Two hundred twenty (212 knees) who underwent ROBOTIC TKA using prediction of gap balancing technique from 2010 – 2012. Clinical outcomes including KS and WOMAC scores, and ranges of motion and radiological outcomes including mechanical axis, prosthesis alignments, flexion varus/valgus stabilities were compared after 1year. Results. Leg mechanical axes were significantly different at follow-up 1year versus preoperative values, the mean axes in the Robotic-TKA with measured resection technique and Robotic-TKA with prediction of gap balancing technique improved from 9.6±5.0° of varus to 0.5±1.9° of varus, and from 10.6±5.5° to 0.4±1.3° of varus (p<0.001), respectively. However, no significant intergroup differences were found between mechanical axis or coronal alignments of femoral or tibial prostheses (pï¼ï¿½0.05). Mean varus laxities at 90° of knee flexion in measured resection and gap prediction technique group were 6.4° and 5.3°, respectively, and valgus laxities were 6.2 and 5.2 degrees, respectively, with statistical significance (p=0.045 and 0.032, respectively). KS knee and function scores and WOMAC scores were significantly improved at follow-up 1year (pï¼ï¿½0.05). However, no significant difference was found between the Robotic-TKA with measured resection technique and Robotic-TKA with prediction of gap balancing technique for any clinical outcome parameter at follow-up 1year (pï¼ï¿½0.05). Conclusions. Robotic assisted TKA using measured resection or gap prediction technique provide adequate and practically identical levels of flexion stability at 90° of knee flexion with accurate leg and prosthesis alignment. But, Robotic TKA using measured resection technique have less than flexion stability compared with gap prediction technique with statistical significance after follow-up 1year

The goals of total knee arthroplasty are to restore the mechanical axis of the knee and create equal and symmetric tension on the ligaments throughout an arc of motion. What surgical technique best achieves this goal remains controversial. In gap balancing, the extension space is created (distal femur and proximal tibia) and balanced. The flexion space and femoral component rotation are then set by placing tension on the collateral ligaments. This allows the femoral component to be rotated to create an equal and symmetric flexion gap based on the tension of collateral ligaments rather than arbitrary bony landmarks. In the measured resection technique, fixed bony landmarks are utilised to set femoral component rotation. Bony landmarks are subject to variations in patient's anatomy and inconsistency of the surgeon to reliably and reproducibly locate them during surgery. Fehring et al. demonstrated that 49% of knees using bony landmarks had rotational errors of greater than 3 degrees. A recent study determined that the amount of femoral component rotation necessary to create a balanced flexion gap varied based on the amount of ligament release required, calling into question the validity of using this technique to set femoral component rotation. Additionally, a study by Dennis et al. showed that setting femoral component rotation based solely on bony landmarks leads to asymmetry in the flexion gap and excessive condylar lift-off in flexion in over 60% of knees performed with a measured resection technique

INTRODUCTION. The results of modified gap balancing and measured resection technique have been still controversial. We compared PS-type TKAs for osteoarthritis performed using the modified gap technique and the measured resection to determine if either technique provides superior clinical results. METHODS. The modified gap technique was used in 85 knees, and the measured technique using preoperative CT was used in 70 knees. To compare intra-operative soft tissue balance, bone gap and component gap were measured using original two paddle tensor (20,30,40lb) at 0 degree extension and 90 degrees flexion. To assess the post-operative patella congruency and soft tissue balance, we measured patella tilt, condylar twist angle (CTA) and condylar lift-off angle (LOA) in radiographs. Finally, we evaluated postoperative clinical result (1–5 years) KOOS. Statistical analysis was used by StatView. RESULTS. (1). Component gaps in flexion at measured techniques were bigger than at gap techniques. Lateral flexion-extension gap and lateral-medial balance at 30lb or 40lb in the measured technique were statistically bigger than the gap technique. (2). There were no statistical correlations with patella tilt, CTA and LOA in both techniques. There were no significant differences between each of the two techniques. (3). KOOS of ‘pain during going up or down stairs’ for the measured technique were statistically worse than for the gap technique. DISCUSSION. Intra-operative lateral gap and flexion balance using measured technique were bigger than gap technique, but there were no statistical differences in post-operative LOA and PF congruency in radiographs. Post-operative pain on stairs might be affected by the differences in intra-operative gap and balance between the two techniques with the balanced ligament technique showing more positive results

The goals of total knee arthroplasty are to restore the mechanical axis of the knee and create equal and symmetric tension on the ligaments throughout an arc of motion. What surgical technique best achieves this goal remains controversial. In gap balancing, the extension space is created (distal femur and proximal tibia) and balanced. The flexion space and femoral component rotation are then set by placing tension on the collateral ligaments. This allows the femoral component to be rotated to create an equal and symmetric flexion gap based on the tension of collateral ligaments rather than arbitrary bony landmarks. In the measured resection technique, fixed bony landmarks are utilised to set femoral component rotation. Bony landmarks are subject to variations in patient's anatomy and inconsistency of the surgeon to reliably and reproducibly locate them during surgery. Fehring et al demonstrated that 49% of knees using bony landmarks had rotational errors of greater than 3 degrees. A recent study determined that the amount of femoral component rotation necessary to create a balanced flexion gap varied based on the amount of ligament release required, calling into question the validity of using this technique to set femoral component rotation. Additionally, a study by Dennis et al, showed that setting femoral component rotation based solely on bony landmarks leads to asymmetry in the flexion gap and excessive condylar lift off in flexion in over 60% of knees performed with a measured resection technique

Background. When positioning and rotating the femoral cutting block (AP) on the femur it can either be done according to bony landmarks (measured resection) or by tensioning the flexion gap and positioning it parallel to the tibia (gap balanced technique.) Accurate rotation of the femoral component is essential to ensure a symmetric flexion gap to ensure optimal tibio-femoral kinematics and patello-femoral tracking. Methods. 74 consecutive total knee replacements were assessed intra-operatively for symmetry of the flexion gap by applying a varus and a valgus stress and digitally recording the opening with a computer assisted navigation system. External rotation of the femoral component according to the bony landmarks was measured radiologically. This was compared to the external rotation suggested by the navigation intra-operatively using a gap balanced workflow. Results. The gap balanced technique gave a symmetric flexion gap with less than 3 mm side to side difference in 95% of cases. In 84% of cases (62 of 74) the gap balanced technique was more accurate than the measured resection technique in determining femoral rotation. In 16 % of cases (12 of 74) the same rotation was measured with the two techniques. In no case was the measurement more accurate with the measured resection technique. This result was highly statistically significant. Conclusion. The gap balanced technique is more accurate than measured resection for determining axial rotation of the femoral component in total knee arthroplasty. NO DISCLOSURES

Background. In measured resection (MR) technique it is sometimes not easy to equalize extension gap (EG) and flexion gap (FG) because the size of femoral component is generally determined only depending on the anteroposterior and mediolateral size of femoral condyle in MR technique. In order to equalize the EG and FG, femoral implant size should be determined so that the FG is similar to the EG. We developed the novel sizing technique of femoral component to equalize the EG and FG in MR technique. The purpose of this study was to examine the usefulness of this technique. Methods. Before surgery, the condylar twist angle: CTA (angle between the transepicondylar axis and the posterior condylar axis) was determined for individual knees by transepicondylar view (X ray) or CT. During surgery, after osteophyte was removed EG was made and measured. Knee was flexed in 90° and the specially made tensor which upper paddle has the medial inclination angle (same as the CTA) was inserted to FG before posterior femoral osteotomy. Then, the appropriate traction force was applied to FG. Under this condition, the correct rotational alignment of femur relative to tibia was obtained, and then, the size of femoral component could be determined so that the FG was similar to the EG by measuring the distance between tibial cut surface and posterior cut level of the respective size of femoral conponent. 23 knees that undergone TKA for end stage medial osteoarthritis were examined and the final EG and FG were measured. EG and FG were measured at the mediolateral center of the gap without any trial component. Results. The mean (± SD) and maximum difference between EG and FG was 2.2±0.9 mm (EG>FG) and 3.5 mm, respectively. The mean (± SD) varus-valgus alignment of gap was 2.1 ± 0.8° varus in extension and 0.9 ± 1.2° varus in flexion. Discussion. As the EG was reduced by about 2mm after implantation of femoral components, the difference between DG and FG in this series was thought to be very small after implantation. Although it was reported that gap balancing technique has superior ability to control EG and FG compared to MR technique, it was indicated that EG and FG were well controlled also in MR technique by this novel sizing method. Further study to examine the relationship between the clinical results and this method was definitely required

Measured resection approach (anatomic) is based on the patients' unique anatomy adjusting for worn cartilage or bone loss. The femoral component is aligned around the primary transverse distal femoral axis around which the tibia follows a multi-radius of curvature. The tibia cut is made according to the patient's native anatomy adjusting for worn cartilage and bone loss, and applying an anatomic amount of tibial slope. This technique minimises the need for partial ligamentous releases to a large degree preserving the competence of the patient's soft tissue, though ligament and capsular releases can be used in difficult cases. Adjustments for the varus/valgus (up to 3 degrees) or slope of the tibial bone cut (3–10 degrees) further aids in knee balancing. The final alignment may not agree with a neutral hip-knee-ankle mechanical alignment on full length standing x-rays, leaving varus knees in slight varus, and valgus legs in neutral. Since little balance is required this operation can be performed in less than 40 minutes

Introduction. Surgeons performing a total knee replacement (TKR) have two available techniques available to help them achieve the proper bone resections and ligament tension – gap balancing (GB) and measured resection (MR). GB relies on balancing ligaments prior to bony resections whereas bony resections are made based on anatomical landmarks in MR. Many studies have been done to compare the joint kinematics between the two techniques, however the results have been varied. These studies were not done with anatomically designed prostheses. The Journey II (Smith & Nephew, Memphis, TN) is one such design which attempts to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Given the design differences between anatomical and non-anatomical prostheses, it is important to investigate whether one technique provides superior kinematics when an anatomical design is used. We hypothesize that there will be no difference between the two techniques. Methods. A total of 56 individuals were recruited to receive a Journey II prosthesis and randomized evenly to groups where the GB technique or MR technique is used. For all patients in the study, a series of radiostereometric analysis (RSA) images were acquired at 3-months post-operatively at different knee flexion angles, ranging in 20° increments from 0° to 120°. Model-based RSA software (RSACore, Leiden, Netherlands) was used to obtain the 3D positions and orientations of the femoral and tibial implant components, which were in turn used to obtain kinematic measures (contact locations and magnitude of excursion) for each condyle. Results. Preliminary results for the anterior-posterior (AP) contact locations from 33 patients (18 GB, 15 MR) are displayed in Figure 1. There were no significant differences in medial and lateral contact locations between the GB and MR groups for all angles of flexion. However, the pattern of medial contact for the MR technique displays more paradoxical anterior motion at mid-flexion (40°–60°) than the GB group. There were no significant differences in magnitude of excursion between groups on both medial (mean difference=1.96 mm, p=0.16) and lateral (mean difference=0.21 mm, p=0.79) condyles, indicating that posterior femoral rollback is similar between groups. Conclusions. Early results suggest that the MR technique is associated with slightly more abnormal kinematics than the GB technique when an anatomical prosthesis design is used for TKR. The GB technique may be more appropriate than MR technique for implanting anatomically designed knee replacements. For any figures or tables, please contact authors directly

Introduction:. Total knee arthroplasty (TKA) should aim to adjust the component gap (CG) difference between extension and flexion. However, this difference cannot be measured without placement of a femoral component. The bone gap reportedly decreases in extension after component setting. In contrast, it may be possible to use the mean value of the CG difference in several patients to adjust femoral resection amount beforehand. The purpose of this study is to evaluate the technique of adjusting CG difference using the mean values with measured resection technique (MRT) in TKA. Materials and methods:. The subjects were 222 knees (40 male knees, 182 female knees; mean age 70.4 years). To adjust the CG difference after estimation, the femoral posterior condylar pre-cut technique was used. Extension gap was created by usual bone resection; 4 mm of the femoral posterior condyle was pre-cut, and after all osteophytes and soft tissues had been treated, a pre-cut trial component (thickness of 8 mm for distal femur and 4 mm for posterior condyle without the anterior portion) was mounted, achieving the same condition as the setting of a femoral component in MRT (Fig. 1). When the posterior cruciate ligament (PCL) could be easily preserved by intraoperative gap assessments, the PCL was preserved (190 knees, 86%). Results:. The CG measured intraoperatively were 9.4 ± 2.8 mm (mean ± S.D.) in extension and 12.2 ± 2.8 mm in flexion, and the difference (flexion - extension) was 2.8 ± 2.6 mm. The mean difference was not large but the variation was large (−3 ∼ 11 mm). When the acceptable range of CG difference (flexion - extension) is set at 0 to 3 mm, only 57% of the patients were included within this range; when 2 mm of the distal femur was cut beforehand in all patients considering the mean CG difference of 2.8 mm, 53% of the patients were within the acceptable range and 42% had 3 mm resection (Fig. 2). When the acceptable range was expanded to −2 mm to 3 mm, 64% of the patients were in this range, whereas this figure was 76% with an additional 2 mm resection of the distal femur and 72% with 3 mm resection. Even after expanding the acceptable range for CG difference to 5 mm and adjusting the distal femoral cut, one fourth of the patients were outside of the acceptable range (Fig. 3). Discussion:. This study showed that the CG using MRT was larger in flexion by a mean of 2.8 mm; however, the variation was too large to manage by larger femoral distal cut according to the mean difference beforehand. Although the PCL was preserved in 190 knees, it is anticipated that gaps in flexion will enlarge when PCL resection is selected for all patients, which may further increase the gap requiring adjustment. To resolve such issues, we use the femoral pre-cut technique and pre-cut trial components. With this method, we can control the CG as we want by adjustment of final femoral bone resection in each patient

Background. Proper femoral component placement plays a key role in the success of a total knee replacement (TKR). Controversy exists on which technique should be used to ensure proper femoral component placement. This two-part study compares gap balancing (GB) and measured resection (MR) techniques used in TKR, investigating femoral component position and early clinical outcomes. Methods. Femoral component position was analyzed in 95 consecutive knees that underwent primary TKR. Both GB and MR cutting blocks from the same knee system were sequentially placed on the operative knee, marking the pin sits. A standardized photograph (Figure) was taken prior to making final femoral cuts. Relative rotation was determined based on measurements made from a commercially available software. Clinical comparison was made using 50 consecutive GB patients and 50 consecutive MR patients. Clinical outcome measures were Knee Society Scores (KSS), knee range of motion (ROM), functional ROM (FROM), tourniquet time, and patients having manipulations under anesthesia (MUA). Results. The GB technique resulted in relative external and internal rotation of the femoral component in 41% and 17% knees respectively. Forty 42% of knees had no relative rotation. Mean pre and 1 year post-operative knee ROM for the MR cohort was 116.4±14.3. °. and 115±12.9. °. respectively, with FROM of 103.0±17.2. °. The GB cohort had mean pre and 1 year post-operative knee ROM values of 113.9±10.8. °. and 116.8±13.6. °. respectively, with FROM of 96.0±22.5. °. Mean 1 year pain and function KSS in the MR cohort were 92.5±10.7 and 85.4±18.9. In the GB cohort, the mean 1 year KSS values were 95.7±6.7 and 84.9±19.58 for pain and function respectively. Clinical outcome measures were not statistically different. Conclusion. We found that the GB technique resulted in external rotation relative to the MR technique. Despite these intraoperative findings we found no significant clinical differences

Introduction. Modified gap technique has been reported to be beneficial for the intraoperative soft tissue balancing in posterior-stabilized (PS) -TKA. We have found intraoperative ligament balance changed depending on joint distraction force, which might be controlled according to surgeons' fells. We have developed a new surgical concept named as “medial preserving gap technique (MPGT)” to preserve medial knee stability and provide quantitative surgical technique according to soft tissue balance measurement using a tensor device. The purpose of this study was to compare 3-years postoperative knee stability after PS-TKA in varus type osteoarthritic (OA) knees between MPGT and measured resection technique (MRT). Material & Method. The subjects were 94 patients underwent primary unilateral PS-TKA for varus type OA knees. The surgical technique was MPGT in 47 patients and MRT in 47 patients. An originally developed off-set type tensor device was used to evaluate intraoperative soft tissue balance. In MPGT, medial release was limited until the spacer block corresponding to the bone thickness from proximal lateral tibial plateau could be easily inserted. Femoral component size and external rotation angle were adjusted depending on the differences of center gaps and varus angles between extension and flexion before posterior femoral condylar resection. The knee stabilities at extension and flexion were assessed by stress radiographies at 1 and 3 years after TKA; varus-valgus stress test at extension and stress epicondylar view at flexion. We measured medial and lateral joint openings (MJO, LJO) at both knee extension and flexion. MJOs and LJOs at 2 time periods were compared in each group using paired t-test. Each joint opening distance was compared between 2 groups using unpaired t-test. The significance level was set as P < 0.05. Results. The mean extension MJOs at 1 and 3 years after TKA were 2.4, 2.6 mm in MPGT and 3.2, 3.1 mm in MRT respectively. The mean extension LJOs were 3.5, 3.5 mm in MPGT and 4.6, 4.5 mm in MRT. The mean flexion MJOs were 0.95, 0.77 mm in MPGT and 1.5, 1.2 mm in MRT, and the mean flexion LJOs were 2.2, 2.1 mm in MPGT and 3.0, 2.7 mm in MRT. MJOs were significantly smaller than LJOs in each group at 2 time periods. MJOs at extension and flexion, and LJOs at extension were significantly smaller in MPGT than MRT at 2 time periods. Discussion. Medial knee stabilities had been reported to be essential for postoperative clinical results. We reported medial compartment gap was more stable during mid-to-deep knee flexion in MPGT than MRT. MPGT provided the more stable intraoperative soft tissue balance than MRT in PS-TKA. MPGT was useful to preserve the higher medial knee stability than the lateral as well as MRT, and beneficial to enhance postoperative knee stabilities as long as 3-years after PS-TKA in varus OA knees. MPGT would be an objective and safer gap technique to enhance clinical outcomes

Introduction. Some authors have reported that if PCL is resected, flexion gap(FG) will become wider than extension gap(EG). Sacrifice or sparing of PCL influences the equality of EG and FG. Meanwhile, measured resection technique(MRT) and gap technique(GT) has different system to adjust gap and balance. There are no criteria for choosing between CR or PS component and MRT or GT nevertheless its influences on gap and balance in TKA. Materials and Methods. EG and FG were measured intra-operatively with PCL intact to assess the characteristics of EG and FG. EG was created ordinarily. To measure FG before the final femoral cutting with PCL intact, small temporary FG was created by a pre-cut of the femoral posterior condyle with a 4-in-1 femoral cutting guide bigger than the measured size. After removal of all osteophytes, the gaps were measured by a tension device. To compare both gaps, FG was corrected by the amount of the pre-cut. According to EG and corrected FG, a component type was selected. If there was enough FG with PCL intact, CR component was implanted and if not, PS component was selected. If necessary, soft tissue was released. Finally, the optimal size of the femoral component for adequate EG and FG was estimated and rotation of the femoral component was decided. One hundred and fifty three knees with osteoarthritis were investigated. Results. EG ranged from 8 to 29 (17.5±3.4) mm and corrected FG ranged from 10 to 31 (20.2±3.9) mm. The range of the difference between the two gaps was −4 to 12 (2.7±3.2) mm, and FG was significantly larger than EG. Based on the measured gaps, CR component was used in 118 knees and PS in only 35 knees. The gap increase by PCL resection ranged from 0 to 3 (0.5±0.7) mm in EG and from 0 to 7 (2.5±2.0) mm in FG. FG increase was significantly larger than EG increase. Gap balance in EG and FG were estimated in 131 knees before the final femoral cutting. Extension balance was 1.6±2.0 degree varus and flexion balance was 0.4±3.2 degree valgus on average. Finally, 114 knees were implanted without change of the femoral component rotation as MRT and the rotation was changed in 17 knees. Parallel cut to the tibial surface as GT was performed in 5 knees and the rotation was positioned between MRT and GT in 12 knees. Discussion. Our results indicate that the selection of PS component in all cases would have resulted in a much larger FG in many cases. Given the wide variations in EG, FG, and FG increase, it would be difficult to use only one component, CR or PS, in every case. To attain adequate gaps, better results are achieved by deciding which component to use, CR or PS, based on intra-operative gap measurement. With this technique, MRT and GT could be combined and the femoral component rotation could be decided freely at the final step of the surgery. There is no longer a necessity to distinguish MRT from GT

Computer navigated Total Knee Arthroplasty is routinely performed with gratifying results. New navigation software is now designed to help surgeons balance soft tissues in Total Knee Arthroplasty (TKA). The aim of our study was to compare functional scores at two years between two different techniques of knee balancing. A prospective randomized control study was conducted between February 2007 and February 2008 involving 52 patients. Two different techniques of knee balancing were used namely, measured resection and gap balancing technique. Each group had 26 patients. Oxford and Knee society scores were done at two years to understand if one technique was better than other. Oxford and Knee Society Scores improved significantly in both the groups but gap balancing technique achieved slightly better functional scores which were not significant on statistical analysis. Computer assisted measured resection and gap balancing techniques in TKA reliably improves functional scores postoperatively. Either of the techniques if performed correctly with appropriate patient selection will have satisfactory outcomes

Introduction. Soft tissue releases are often required to correct deformity and achieve gap balance in total knee arthroplasty (TKA). However, the process of releasing soft tissues can be subjective and highly variable and is often perceived as an ‘art’ in TKA surgery. Releasing soft tissues also increases the risk of iatrogenic injury and may be detrimental to the mechanically sensitive afferent nerve fibers which participate in the regulation of knee joint stability. Measured resection TKA approaches typically rely on making bone cuts based off of generic alignment strategies and then releasing soft tissue afterwards to balance gaps. Conversely, gap-balancing techniques allow for pre-emptive adjustment of bone resections to achieve knee balance thereby potentially reducing the amount of ligament releases required. No study to our knowledge has compared the rates of soft tissue release in these two techniques, however. The objective of this study was, therefore, to compare the rates of soft tissue releases required to achieve a balanced knee in tibial-first gap-balancing versus femur-first measured-resection techniques in robotic assisted TKA, and to compare with release rates reported in the literature for conventional, measured resection TKA [1]. Methods. The number and type of soft tissue releases were documented and reviewed in 615 robotic-assisted gap-balancing and 76 robotic-assisted measured-resection TKAs as part of a multicenter study. In the robotic-assisted gap balancing group, a robotic tensioner was inserted into the knee after the tibial resection and the soft tissue envelope was characterized throughout flexion under computer-controlled tension (fig-1). Femoral bone resections were then planned using predictive ligament balance gap profiles throughout the range of motion (fig-2), and executed with a miniature robotic cutting-guide. Soft tissue releases were stratified as a function of the coronal deformity relative to the mechanical axis (varus knees: >1° varus; valgus knees: >1°). Rates of releases were compared between the two groups and to the literature data using the Fischer's exact test. Results. The overall rate of soft tissue release was significantly lower in the robotic gap-balancing group, with 31% of knees requiring one or more releases versus 50% (p=0.001) in the robotic measured resection group and 66% (p<0.001) for conventional measured resection (table-1) [1]. When comparing as a function of coronal deformity, the difference in release rates for robotic gap-balancing was significant when compared to the conventional TKA literature data (p<0.0001) for all deformity categories, but only for varus and valgus deformities for robotic measured resection with the numbers available (varus: 33% vs 50%, p=0.010; neutral 11% vs 50%, p=0.088, valgus 27% vs 53%, p=0.048). Discussion. Robotic-assisted tibial-first gap-balancing techniques allow surgeons to plan and adjust femoral resections to achieve a desired gap balance throughout motion, prior to making any femoral resections. Thus, gap balance can be achieved through adjustment of bone resections, which is accurate to 1mm/degree with robotics, rather than through manual releasing soft tissues which is subjective and less precise. These results demonstrated that the overall rate of soft tissue release is reduced when performing TKA with predictive gap-balancing and a robotic tensioning system. For any figures or tables, please contact authors directly

INTRODUCTION. Mechanical alignment in TKA introduces significant anatomic modifications for many individuals, which may result in unequal medial-lateral or flexion-extension bone resections. The objective of this study was to calculate bone resection thicknesses and resulting gap sizes, simulating a measured resection mechanical alignment technique for TKA. METHODS. Measured resection mechanical alignment bone resections were simulated on 1000 consecutive lower limb CT-Scans from patients undergoing TKA. Bone resections were simulated to reproduce the following measured resection mechanical alignment surgical technique. The distal femoral and proximal tibial cuts were perpendicular to the mechanical axis, setting the resection depth at 8mm from the most distal femoral condyle and from the most proximal tibial plateau (Figure 1). If the resection of the contralateral side was <0mm, the resection level was increased such that the minimum resection was 0mm. An 8mm resection thickness was based on an implant size of 10mm (bone +2mm of cartilage). Femoral rotation was aligned with either the trans-epicondylar axis or with 3 degrees of external rotation to the posterior condyles. After simulation of the bone cuts, media-lateral gap difference and flexion-extension gaps difference were calculated. The gap sizes were calculated as the sum of the femoral and tibial bone resections, with a target bone resection of 16mm (+ cartilage corresponding to the implant thickness). RESULTS. For both the varus and valgus knees, the created gaps in the medial and lateral compartments were reduced in the vast majority of cases (<16mm). The insufficient lateral condyle resection distalises the lateral joint surface by a mean of 2.1mm for the varus and 4.4mm for the valgus knees. The insufficient medial tibial plateau resection proximalises the medial joint surface by 3.3mm for the varus and 1.2mm for the valgus knees. Medio-lateral gap imbalances in the extension space of more than 2mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances of more than 5mm were present in up to 8% of varus and 19% of valgus knees. Higher medio-lateral gap imbalances in the flexion space were created with trans epicondylar axis versus 3 degrees to the posterior condyles (p<0.001). Using trans epicondylar axis, only 49% of varus and 18% of valgus knees had less than 3mm of imbalance in both media-lateral and flexion-extension gaps together. DISCUSSION AND CONCLUSION. A systematic use of the tested measured resection mechanical alignment technique for TKA leads to many cases with medio-lateral or flexion-extension gap asymmetries. Some medio-lateral imbalances may not be correctable surgically and may results in TKA instability. Other versions of the mechanical alignment technique or other alignment methods that better reproduce knee anatomies should be explored. For any figures or tables, please contact the authors directly

In total knee arthroplasty (TKA), rotational alignment of the femoral component is determined by the measured resection technique, in which anatomical landmarks serve as determinants, or by the gap balancing technique, in which the femoral component is positioned relative to the resected aspect of the tibia. The latter technique is considered logically more favorable for obtaining rectangular extension and flexion gaps. However, in patients with severe changes attributed to osteoarthritis and/or a severely limited range of motion, it is difficult to perform adequate posterior clearance (e.g. bone spur excision) before resecting the posterior femoral condyle, often causing unbalanced extension and flexion gaps after resection. Thus, the gap balancing technique is more technically demanding and requires higher skill. We employed a computed tomography (CT)-based navigation system to develop a simple and standardized surgical technique by performing two assessments: Assessment 1, we investigated the relationship between the position of the femoral component determined by the gap balancing technique and anatomical landmarks; and Assessment 2, we placed the femoral component at the position determined by the measured resection technique and within the acceptable gap-balanced range determined in Assessment 1. In Assessment 1, 18 knees with osteoarthritis were treated by posterior stabilized TKA for varus deformity. The extension-flexion balance after resection of the distal femoral condyle and the proximal tibia was within 3° in all cases. Posterior bone resection was performed parallel to the resected aspect of the tibia and at 90° of flexion under constant compression applied using a tensor. In other words, the rotational alignment of the femoral component was determined by the gap balancing technique, and its position relative to the posterior condylar axis (PCA) and clinical transepicondylar axis (CEA), which are landmarks in the measured resection technique, and the condylar twist angle (CTA; the angle between the CEA and PCA) were measured, and their relationships were quantitatively determined. The CTA, which was determined based on the preoperative CT data, was 4.7– 9.6° (mean, 7.05 ± 1.35°), while the aspect of the femoral resection was 3.0–8.3° externally rotated (mean, 5.6 ± 1.6°) to the PCA; a strong positive correlation was found between the rotational alignment of the femoral component and the CTA (p < 0.0001, R. 2. = 0.871). The aspect of the femoral resection was 0.3–2.6° internally rotated (mean, 1.4 ± 0.6°) to the CEA, and no correlation with the CTA was apparent. In Assessment 2, 39 knees with an extension-flexion balance ≤3° were examined to determine the internal-external rotation balance. Based on the results of Assessment 1, we employed the measured resection technique and placed the femoral component by rotationally aligning the target, which was 1.4° internally rotated to the CEA. The final rotational alignment of the femoral component was 2.0 ± 0.6° internally rotated to the CEA; the internal-external rotation balance at 90° of flexion was good and more toward external rotation by 0.72 ± 1.61°. The results demonstrated that the measured resection technique enables placement of the femoral component within an acceptable range of rotational alignment

Arthrofibrosis remains a dominant post-operative complication and reason for returning to the OR following total knee arthroplasty. Trauma induced by ligament releases during TKA soft tissue balancing and soft tissue imbalance are thought to be contributing factors to arthrofibrosis, which is commonly treated by manipulation under anesthesia (MUA). We hypothesized that a robotic-assisted ligament balancing technique where the femoral component position is planned in 3D based on ligament gap data would result in lower MUA rates than a measured resection technique where the implants are planned based solely on boney alignment data and ligaments are released afterwards to achieve balance. We also aimed to determine the degree of mechanical axis deviation from neutral that resulted from the ligament balancing technique. Methods. We retrospectively reviewed 301 consecutive primary TKA cases performed by a single surgeon. The first 102 consecutive cases were performed with a femur-first measured resection technique using computer navigation. The femoral component was positioned in neutral mechanical alignment and at 3° of external rotation relative to the posterior condylar axis. The tibia was resected perpendicular to the mechanical axis and ligaments were released as required until the soft tissues were sufficiently balanced. The subsequent 199 consecutive cases were performed with a tibia-first ligament balancing technique using a robotic-assisted TKA system. The tibia was resected perpendicular to the mechanical axis, and the relative positions of the femur and tibia were recorded in extension and flexion by inserting a spacer block of appropriate height in the medial and lateral compartments. The position, rotation, and size of the femoral component was then planned in all planes such that the ligament gaps were symmetric and balanced to within 1mm (Figure 1). Bone resection values were used to define acceptable limits of implant rotation: Femoral component alignment was adjusted to within 2° of varus or valgus, and within 0–3° of external rotation relative to the posterior condyles. Component flexion, anteroposterior and proximal-distal positioning were also adjusted to achieve balance in the sagittal plane. A robotic-assisted femoral cutting guide was then used to resect the femur according to the plan (Figure 2). CPT billing codes were reviewed to determine how many patients in each group underwent post-operative MUA. Post-operative mechanical alignment was measured in a subset of 50 consecutive patients in the ligament balancing group on standing long-leg radiographs by an independent observer. Results. Post-operative MUA rates were significantly lower in the ligament balancing group (0.5%; 1/199) than in the measured resection group (3.9%; 4/102), p=0.051. 91.3% (42/46) of knees were within 3° and 100% (46/46) were within 4° of neutral alignment to the mechanical axis post-operatively in the ligament balancing group. Conclusions. Gap driven femoral based planning in TKA resulted in a significantly lower post-operative manipulation rate than in the measured resection approach, while maintaining acceptable overall alignment to the mechanical axis