title: Comparison between two computer-assisted total knee arthroplasty: gap-balancing versus measured resection technique Joint line restoration after revision total knee arthroplasty. Rotation in total knee arthroplasty: no difference between patient-specific and conventional instrumentation Gap balancing sacrifices joint-line maintenance to improve gap symmetry: a randomized controlled trial comparing gap balancing and measured resection. Effects of the Balanced Gap Technique on Femoral Component Rotation in TKA Prosthesis alignment affects axial rotation motion after total knee replacement: a prospective in vivo study combining computed tomography and fluoroscopic evaluations Comparison of joint line position changes after primary bilateral total knee arthroplasty performed using the navigation-assisted measured gap resection or gap balancing techniques Computer-assisted gap balancing technique improves outcome in total knee arthroplasty, compared with conventional measured resection technique Functional Outcome after Computer-Assisted Total Knee Arthroplasty Using Measured Resection versus Gap Balancing Techniques: A Randomised Controlled Study Is adapted measured resection superior to gap-balancing in determining femoral component rotation in total knee replacement?
abstract: Two surgical strategies are possible in total knee arthroplasty ( TKA ) : a measured resection technique , in which bone l and marks are used to guide resections equal to the distal and posterior thickness of the femoral component , or a gap-balancing approach , in which equal collateral ligament tension in flexion and extension is sought before and as a guide to final bone cuts . In this study performed with computer assisted system , we compared the 2 different methods in 126 patients followed prospect ively in order to analyze the effect of both the techniques on joint-line ( JL ) maintenance , axial limb restoration and components position . The gap technique showed a statistical increase in the post-operative value when compared with the measured resection technique , ( P = 0.008 ) . When comparing the two groups regarding to the pre-operative deformity , we have found a statistical difference ( P = 0.001 ) in case of moderate pre-operative deformity ( less than 10 ° ) , and the measured resection technique showed a slight superiority in preserving a joint line more faithful to the pre-operative . We found an ideal alignment for the mechanical axis ( 180 ° ± 3 ° ) ( 95 % of cases ) . In six cases ( 5 % ) , the mean post-operative value exceeded ( varus or valgus ) the ideal value by more than 3 ° . In the frontal plane , a good alignment was observed for both femoral and tibial components without a significant difference between the two techniques . In the sagittal plane was found more alignment variability due to the different implants used and their ideal starting slope , from 7 ° to 3 ° . Finally , the surgeon can use the approach with which he has more confidence ; however , as the measured resection technique causes less reduction in the post-operative joint-line position , in case of shortening of patellar tendon or patella infera , this technique is preferable In 99 patients , 107 knee replacements were revised in two centers by two surgeons using a single revision total knee arthroplasty system . A retrospective radiographic review of joint line position before and after revision total knee arthroplasty was made , and compared with the joint line position before primary knee arthroplasty . Prospect ively collected Knee Society Clinical Rating Scores were correlated with radiographic findings . The joint line position in unreplaced knee replacements averaged 16 mm , and the joint line position in knee replacements before revision surgery averaged 17 mm . The joint line was elevated by the revision total knee arthroplasty in 85 of 107 knees ( 79 % ) . After the revision total knee replacement , the joint line elevation averaged 24 mm . The Knee Society Clinical Rating Score after revision surgery averaged 131 points . If the joint line position was elevated more than 8 mm , the Knee Society Clinical Rating Score averaged 125 points , if the joint line was elevated less than 8 mm , the score averaged 141 points . Joint line elevation after revision total knee replacement is a problem . Excessive elevation may result in worse clinical outcomes . Distal femoral augments should be used more often and with greater thicknesses . St and ard implants used for revision surgery should have increased distal dimensions Abstract Purpose It was our hypothesis that patient-specific instrumentation ( PSI ) can improve the accuracy of the rotational alignment in TKA based on the concept of the system and on the potential to clearly identify pre-operatively during planning the classical anatomical l and marks that serve as references to set-up the rotation both for the femur and tibia . Material s and methods In this prospect i ve comparative r and omized study , 40 patients ( 20 in each group ) operated in our institution between September 2012 and January 2013 by the 2 senior authors were included . R and omization of patients into one of the two groups was done by the Hospital Informatics Department with the use of a systematic sampling method . All patients received the same cemented high-flex mobile bearing TKA . In the PSI group , implant position was compared to the planed position using previously vali date d dedicated software . The position of the implants ( frontal and sagittal ) was compared in the 2 groups on st and ard X-rays , and the rotational position was analysed on post-operative CT-scan . Results 90 % of the patients add < 2 ° or mm of difference between the planned position of the implants and the obtained position , except for the tibial rotation where the variations were much higher . Mean HKA was 179 ° ( 171–185 ) in the PSI group with 4 outliers ( 2 varus : 171 ° and 172 ° :184 ° and 185 ° ) and 178.3 ° with 2 outliers ( 171 ° and 176 ° ) in the control group . No difference was observed between the two groups concerning the frontal and sagittal position of the implants on the ML and AP X-rays . No significant difference of femoral rotation was observed between the two groups with a mean of 0.4 ° in the PSI group and 0.2 ° in the control group ( p : n.s ) . Mean tibial rotation was 8 ° of internal rotation in the PSI group and 15 ° of internal rotation in the st and ard group ( p : n.s ) . Conclusion Based on our results , we were unable to confirm our hypothesis as PSI can not improve rotation in TKA . More work needs to be done to more clearly define the place of PSI in TKA , to keep on improving the accuracy of the system and to better define the individual targets in TKA in terms of frontal , sagittal and rotational positioning of the implant for each patient . Level of evidence Prospect i ve comparative r and omized study , Level II A total knee arthroplasty can be completed using two techniques ; measured resection or gap balancing . A prospect i ve blinded r and omized controlled trial was completed with 103 patients r and omized to measured resection ( n = 52 ) or gap balancing ( n = 51 ) . Primary outcome measure was femoral component rotation . Secondary outcome measures were joint-line change , gap symmetry and function and quality -of-life outcomes .  Gap balancing result ed in a significantly raised joint-line compared to measured resection .  Gap symmetry was significantly better using gap balancing .  Functional outcomes and quality -of-life were not significantly different at 24 months . Using computer navigation , gap balancing significantly raises the joint-line in order to improve gap symmetry . This does not result in a clinical difference in function or quality of life at 24 months Abstract Femoral component rotation from a  total knee prosthesis  can be determined by either a measured resection technique or a balanced gap technique . With the balanced gap implantation technique , femoral component rotation can vary freely within the restrictions produced by soft tissue structures . Because internal rotation might cause patella problems , the effect of ligament releases on femoral component rotation in a prospect i ve clinical study was studied .  Femoral component rotation  was measured intraoperatively with a tensor applied in flexion at 150 N in 87 knees . Great interpatient variability was found ; femoral component rotation , reference from the posterior condyles , ranged from −4 ° to 13 ° . There was no difference in femoral component rotation of knees with or without ligament releases in extension . However , knees with major medial release had less external femoral component rotation than knees with minor lateral releases . Preoperative alignment had no influence on femoral component rotation . The use of the balanced gap implantation technique theoretically will result in a balanced flexion gap , but the amount of femoral component rotation will be variable owing to patient variability and variation in ligament releases . Level of Evidence : Level II , therapeutic study . See the Guidelines for Authors for a complete description of levels of evidence Background Clinical consequences of alignment errors in  total knee replacement ( TKR ) have led to the rigorous evaluation of surgical alignment techniques . Rotational alignment in the transverse plane has proven particularly problematic , with errors due to component malalignment relative to bone anatomic l and marks and an overall mismatch between the femoral and tibial components ’ relative positions . Ranges of nominal rotational alignment are not well defined , especially for the tibial component and for relative rotational mismatch , and some studies advocate the use of mobile-bearing TKR to accommo date the result ing small rotation errors . However , the relationships between prosthesis rotational alignment and mobile-bearing polyethylene insert motion are poorly understood . This prospect i ve , in vivo study evaluates whether component malalignment and mismatch affect axial rotation motions during passive knee flexion after TKR . Methods Eighty patients were implanted with mobile-bearing TKR .  Rotational alignment of the femoral and tibial components was measured from postoperative CT scans . All TKR were categorized into nominal or outlier groups based on defined norms for surgical rotational alignment relative to bone anatomic l and marks and relative rotational mismatch between the femoral and tibial components . Axial rotation motion of the femoral , tibial and polyethylene bearing components was measured from fluoroscopic images acquired during passive knee flexion . Results Axial rotation motion was generally accomplished in two phases , dominated by polyethylene bearing rotation on the tibial component in early to mid-flexion and then femoral component rotation on the polyethylene articular surface in later flexion . Opposite rotations of the femur-bearing and bearing-baseplate articulations were evident at flexion greater than 80 ° . Knees with outlier alignment had lower magnitudes of axial rotation and distinct transitions from external to internal rotation during mid-flexion . Knees with femoral-tibial rotational mismatch had significantly lower total axial rotation compared to knees with nominal alignment . Conclusions Maintaining relative rotational mismatch within ±5 ° during TKR provided for controlled knee axial rotation during flexion . TKR with rotational alignment outside of defined surgical norms , with either positive or negative mismatch , experienced measurable kinematic differences and presented different patterns of axial rotation motions during passive knee flexion compared to TKR with nominal mismatch . These findings support previous studies linking prosthesis rotational alignment with inferior clinical and functional outcomes .Trial Registration Clinical Trials Purpose This study aim ed to compare the clinical and radiological results of navigation-assisted TKAs performed using the measured gap resection or the gap balancing technique in thirty patients who underwent bilateral primary TKAs . Methods Sixty cases of navigation-assisted TKAs [ 30 TKAs performed using the measured gap resection technique  ( Group A ) and 30 TKAs performed using the gap balancing technique ( Group B ) ] were analyzed prospect ively with minimum follow-up of 2 years . The joint line positions were measured using preoperative and postoperative weight-bearing anteroposterior and lateral radiographs . Clinical results were evaluated using knee scores and functional scores . Results No significant differences in knee scores or functional scores were observed . Polyethylene thickness and flexion/extension gaps were significantly larger in Group B ( P < 0.05 ) . The meaningful proximal shift of the joint line was shown in Group B ( P < 0.05 ) . Conclusion The navigation-assisted TKA with measured gap resection technique could be a useful technique with regard to restoration of the joint line . Level of evidence II Purpose The objective of this prospect i ve study was to compare the functional outcome of conventional measured resection technique and computer-assisted gap balancing technique in TKA . Methods 140 patients were r and omized into two groups . The conventional measured resection technique without computer navigation was performed in Group 1 and the computer-assisted gap balancing technique in Group 2 . Range of motion , clinical laxity assessment with KT-1000 arthrometer , postoperative radiological films and various functional knee scores were documented at 6 months and 2 years . Results At 2 years , there were significantly more patients ( five patients , 7 % ) in the Group 1 with flexion contractures of more than 5 ° ( P = 0.05 ) . There were significantly more outliers in the Group 1 ( eight patients , 11 % ) , who demonstrated anterior tibial translation > 5 mm , than Group 2 ( two patients , 3 % ) ( P = 0.041 ) . The total excursion at 20 ° was significantly higher in Group 1 at 6 months ( P = 0.012 ) and after 2 years ( P = 0.031 ) . Group 2 was able to demonstrate significantly better limb alignment with fewer outliers ( more than 3 ° varus/valgus ) than Group 1 . At 6-month follow-up , Group 2 demonstrated better outcomes in Function Score ( P = 0.040 ) and Total Oxford Score ( P = 0.031 ) . At 2-year review , Group 2 had better outcome in the Total Oxford Score ( 0.030 ) . Conclusion Computer-assisted gap balancing technique was able to achieve more precise soft tissue balance and restoration of limb alignment with better knee scores as compared to the conventional measured resection technique in total knee arthroplasty . Level of evidence Purpose . To compare the 2-year outcome of  total knee arthroplasty ( TKA ) using the measured resection versus the gap balancing techniques . Methods . 21 men and 31 women aged 41 to 89 ( mean , 73 ) years who underwent primary TKA by a single surgeon for osteoarthritis and had an American Society of Anesthesiologists I or II physical status were prospect ively studied . Patients were r and omised to undergo computer-assisted TKA using the measured resection technique ( n=26 ) or the gap balancing technique ( n=26 ) . At the 2-year followup , patients were assessed by a single orthopaedic registrar blinded to the type of surgery using the Knee Society score ( KSS ) , functional Knee Society score ( FKSS ) , and revised Oxford Knee score ( ROKS ) . Results . In the measured resection group , the mean KSS , FKSS , and ROKS increased from 34.3 , 48 , and 21 to 85.9 , 89.6 , and 36.5 , respectively . In the gap balancing group , the respective scores increased from 35.4 , 50 , and 22.5 to 89.1 , 92.4 , and 40.6 . Postoperative with the gap balancing technique ; the respective p values were 0.46 , 0.44 , and 0.12 . Conclusion . Improvements in the knee scores were comparable with the 2 techniques Obtaining a balanced flexion gap with correct femoral component rotation is one of the prerequisites for a successful outcome after total knee replacement ( TKR ) . Different techniques for achieving this have been described . In this study we prospect ively compared gap-balancing versus measured resection in terms of reliability and accuracy for femoral component rotation in 96 primary TKRs performed in 96 patients using the Journey system . In 48 patients ( 18 men and 30 women ) with a mean age of 65 years ( 45 to 85 ) a tensor device was used to determine rotation . In the second group of 48 patients ( 14 men and 34 women ) with a mean age of 64 years ( 41 to 86 ) , an ' adapted ' measured resection technique was used , taking into account the native rotational geometry of the femur as measured on a pre-operative CT scan . Both groups systematic ally reproduced a similar external rotation of the femoral component relative to the surgical transepicondylar axis : 2.4 ° ( SD 2.5 ) in the gap-balancing group and 1.7 ° ( SD 2.1 ) in the measured resection group ( p = 0.134 ) . Both gap-balancing and adapted measured resection techniques proved equally reliable and accurate in determining femoral component rotation after TKR . There was a tendency towards more external rotation in the gap-balancing group , but this difference was not statistically significant ( p = 0.134 ) . The number of outliers for our ' adapted ' measured resection technique was much lower than reported in the literature
target: The meta‐ analysis showed that GB techniques result ed in statistically significant improvements in the restoration of mechanical and rotational alignment and mean Knee Society Scores and Knee Society Function scores two years post‐operatively , but result ed in greater elevation of the position of the joint line .
  There is no significant difference in the other radiographic data .
  Conclusion This study suggests that GB may provide better radiographic and clinical outcomes than MR when used to determine mechanical rotation in TKAs
background: Aims There are two techniques widely used to determine the rotational alignment of the components in total knee arthroplasty ( TKA ) ;  gap balancing ( GB ) and measured resection ( MR ) .
  Which technique is the best remains controversial .
  We aim ed to investigate this in a systematic review and meta‐ analysis .