Introduction. Intra articular distal tibia fractures can lead to post-traumatic osteoarthritis. Joint distraction has shown promise in elective cases. However, its application in acute fractures remains unexplored. This pilot study aims to fill this knowledge gap by investigating the benefits of joint distraction in acute fractures. Materials & Methods. We undertook a restrospective cohort study comprising patients with intra-articular distal tibia and pilon fractures treated with a circular ring fixator (CRF) at a single center. Prospective data collection included radiological assessments, Patient-Reported Outcome Measures (PROM), necessity for additional procedures, and Kellgren and Lawrence grade (KL) for osteoarthritis (OA). 137 patients were included in the study, 30 in the distraction group and 107 in the non-distraction group. There was no significant difference between the groups. Results. Mean follow-up was 3.73 years. There was no significant difference between the groups in overall complications or need for further procedures. There was no significant difference in progression of KL between the groups (1.81 vs 2.0, p=0.38) mean follow up 1.90 years. PROM data was available for 44 patients (6 distraction, 38 non-distraction) with a mean follow-up of 1.71 years. There was no significant difference in EQ5D (p=0.32) and C Olerud-H Molander scores (p=0.17). Conclusions. This pilot study suggests that joint distraction is safe in the acute setting. However, the study's impact is constrained by a relatively small patient cohort and a short-term follow-up period. Future investigations should prioritise longer-term follow-ups and involve a larger patient population to more comprehensively evaluate the potential benefits of joint distraction in acute fractures

Background. Post-operative (postop) lower limb alignment in unicompartmental knee arthroplasty (UKA) has been reported to be an important factor for postop outcomes. Slight under-correction of limb alignment has been recommended to yield a better clinical outcomes than neutral alignment. It is useful if the postop limb alignment can be predicted during surgery, however, little is known about the surgical factors affecting the postop limb alignment in UKA. The purpose of this study was to examine the influence of the medial tibial joint line elevation on postop limb alignment in UKA. Methods. Seventy-four consecutive medial UKAs were enrolled in this study. All the patients received a conventional fixed bearing UKA. Pre-operative (preop) and postop limb alignment was examined using long leg radiograph and lower limb alignment changes were calculated. Femoral and tibial osteotomy thickness were measured during surgery. Medial tibial joint line change was defined as polyethylene thickness minus tibial osteotomy thickness and sawblade thickness (1.27mm). Positive values indicated a tibial joint line elevation. Medial femoral joint line change was defined as femoral distal component thickness (6.5mm) minus femoral distal osteotomy thickness and sawblade thickness. Positive values indicated a femoral joint line reduction. Medial joint distraction width was also calculated by tibial joint line elevation plus femoral joint line reduction. The correlation of lower limb alignment change with polyethylene insert thickness, the medial tibial joint line elevation, femoral joint line reduction, or joint distraction width were analyzed. Results. The mean preop hip-knee-ankle (HKA) angle was 7.1 ± 3.3° in varus and postop was 2.1 ± 3.0° in varus. The mean lower limb alignment change was 5.0 ± 2.6°. The mean polyethylene insert thickness was 8.5 ± 0.8mm, the tibial joint line elevation was 4.4 ± 1.3mm and the medial femoral joint line reduction was 0.0 ± 1.1mm, the joint distraction width was 4.5 ± 1.5mm. The polyethylene insert thickness, the medial tibial joint line elevation, and the joint distraction width were positively correlated with the lower limb alignment change (R=0.27; P<0.05, R=0.47; P<0.001, R=0.53; P<0.001, respectively) (Figure 1a,b,d). There was no correlation between the medial femoral joint line reduction and the lower limb alignment change (Figure 1c). Discussion. The postop limb alignment in total knee arthroplasty (TKA) is determined by the osteotomy angle of the femur and tibia. On the other hand, it has been reported that the postop alignment in UKA is not influenced by the osteotomy angle but by the insert thickness. Our results indicated that the medial tibial joint line elevation and the joint distraction width were more useful to predict lower limb alignment change than the insert thickness itself. Measuring the medial tibial osteotomy thickness during surgery will help surgeon to predict postop lower limb alignment in UKA. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. Accurate soft tissue balancing in knee arthroplasty is essential in order to attain good postoperative clinical results. In mobile-bearing UKA (Oxford Partial Knee unicompartmental knee arthroplasty, Biomet), since determination of the thickness of the spacer block depends on the individual surgeon, it will vary and it will be difficult to attain appropriate knee balancing. The first objective of the present study was to investigate flexion and extension medial unicompartmental knee gap kinematics in conjunction with various joint distraction forces. The second objective of the study was to investigate the accuracy of gap measurement using a spacer block and a tensor device. Methods. A total of 40 knees in 31 subjects (5 men and 26 women) with a mean age of 71.5 years underwent Oxford UKA for knee osteoarthritis and idiopathic osteonecrosis of the medial compartment. According to instructions of Phase 3 Oxford UKA, spacer block technique was used to make the extension gap equal to the flexion gap. Adequate thickness of the spacer block was determined so that the surgeon could easily insert and remove it with no stress. Following osteotomy, the tensor devise was used to measure the medial compartmental gap between the femoral trial prosthesis and the tibial osteotomy surface (joint component gap) (Fig. 1 and 2). The medial gap was measured at 20° of knee flexion (extension gap) and 90° of knee flexion (flexion gap) with 25N, 50N, 75N, 100N, 125N, 150N of joint distraction force. Corresponding size of bearing was determined for the prosthesis. The interplay gap was calculated by subtracting the thickness of the tibial prosthesis and the thickness of the selected size of bearing from the measured extension and flexion gaps. Results. The selected bearing size was 3 mm: 3 knees, 4 mm: 20 knees, 5 mm: 15 knees and 6 mm: 2 knees. The mean flexion gap in the medial compartment was 25N: 8.4 ± 1.6 mm, 50N: 9.4 ± 1.6 mm, 75N: 10.4 ± 1.5 mm, 100N: 11.0 ± 1.4 mm, 125N: 11.6 ± 1.5 mm, 150N: 11.9 ± 1.4 mm. The mean extension gap was 25N: 7.8 ± 1.6 mm, 50N: 8.8 ± 1.6 mm, 75N: 9.7 ± 1.6 mm, 100N: 10.4 ± 1.5 mm, 125N: 11.1 ± 1.5 mm, 150N: 11.4 ± 1.5 mm. The mean flexion interplay gap was 25N: 0.5 ± 1.2 mm, 50N: 1.5 ± 1.2 mm, 75N: 2.4 ± 1.1 mm, 100N: 3.1 ± 1.0 mm, 125N: 3.6 ± 1.1 mm, 150N: 4.0 ± 1.1 mm. The mean extension interplay gap was 25N: −0.2 ± 1.2 mm, 50N: 0.8 ± 1.1 mm, 75N: 1.7 ± 1.2 mm, 100N: 2.5 ± 1.2 mm, 125N: 3.1 ± 1.2 mm, 150N: 3.5 ± 1.2 mm. When flexion and extension of the interplay gap were compared, the extension interplay gap was shown to be significantly smaller compared with the flexion interplay gap at every joint distraction force (p < 0.05). Conclusion. The mean extension interplay gap was shown to be significantly smaller compared with the flexion interplay gap at every joint distraction force even though the extension gap was adjusted to the flexion gap using the spacer block. This suggests that in the actual UKA operative technique using a spacer block there is a potential that the extension gap will be smaller than the flexion gap. Surgeons should be aware of this fact and adjust the flexion and extension gaps with caution when performing mobile-bearing UKA

Objective. Mobile bearing unicompartmental knee arthroplasty (UKA) is an effective and safe treatment for osteoarthritis of the medial compartment. However, mobile-bearing UKA needs accurate ligament balancing of flexion and extension gaps to prevent dislocation of the mobile meniscal bearing. Instability can lead to dislocation of the insert. The phase 3 instruments of the Oxford UKA use a balancing technique for the flexion gap (90° of flexion) and extension gap (20° of flexion), thereby focusing attention on satisfactory soft tissue balancing. With this technique, spacers are used to balance the flexion and extension gap. However, gap kinematics in another flexion angle of mobile-bearing UKA is unclear. We developed UKA tensor for mobile-bearing UKA and we assessed the accurate gap kinematics of UKA. Materials and Methods. Between 2012 and 2013, The Phase 3 Oxford Partial Knee UKA (Biomet Inc., Warsaw, IN) were carried out in 48 patients (71 knees) for unicompartmental knee osteoarthritis or spontaneous osteonecrosis of the medial compartment. The mean age of patients at surgery was 71.6 years and the mean follow-up period was 1.7 years. The mean preoperative coronal plane alignment was 7.4° in varus. The indications for UKA included disabling knee pain with medial compartment disease; intact ACL and collateral ligaments; preoperative contracture of less than 15°; and preoperative deformity of <15°. Each surgery was performed by using different spacer block with 1-mm increments and the meniscal bearing lift-off tests according to surgical technique. We developed newly tensor for mobile bearing UKA which designed to permit surgeons to measure multiple range of the joint medial compartment/joint component gap, while applying a constant joint distraction force (Figure 1). We assessed the intra-operative joint gap measurements at 0, 20, 60, 90 and 120 of flexion with 100N, 125N and 150N of joint distraction forces. Results. The gaps measured were 0°: 8.6 ± 1.6, 20°: 9.2 ± 1.4, 60°: 9.6 ± 1.2, 90°: 11.1 ± 1.3, 120°: 11.6 ± 1.8 in 100 N, 0°: 9.7 ± 1.7, 20°: 11.2 ± 1.3, 60°: 11.4 ± 1.3, 90°: 11.9 ± 1.5, 120°: 10.4 ± 1.6 in 125 N, 0°: 11.3±1.4, 20°: 11.8 ± 1.3, 60°: 11.1 ± 1.2, 90°: 12.5 ± 1.3, 120°: 11.9 ± 1.6 in 150N (Figure 2). There was a significant difference between full extension to extension (20° of flexion) and flexion (90° of flexion) to full flexion (120° of flexion). Conclusion. Mobile bearing UKA instrumentation using a balancing technique by spacer block for the flexion gap (90° of flexion) and extension gap (20° of flexion), full extension gap was significantly smaller than extension gap and flexion gap was significantly smaller than full flexion gap in 100N, 125N and 150N of joint distraction forces

Introduction. Both measured resection technique and gap balancing technique have been important surgical concepts in total knee arthroplasty (TKA). Modified gap technique has been reported to be beneficial for the intra-operative soft tissue balancing in posterior-stabilizing (PS) -TKA. On the other hand, we have found joint distraction force changed soft tissue balance measurement and medial knee instability would be more likely with aiming at perfect ligament balance at extension in modified gap technique. The medial knee stability after TKA was reported to essential for post-operative clinical result. We have developed a new surgical concept named as “medial preserving gap technique” for varus type osteoarthritic (OA) knees to preserve medial knee stability and provide quantitative surgical technique using tensor device. The purpose of this study was to compare post-operative knee stability between medial preserving gap technique (MPGT) and measured resection technique (MRT) in PS-TKA. Material & Method. The subjects were 140 patients underwent primary unilateral PS-TKA for varus type OA knees. The surgical technique was MPGT in 70 patients and MRT in 70 patients. There were no significant differences between two groups in the pre-operative clinical features including age, sex, ROM and deformity. Originally developed off-set type tensor device was used to evaluate both center gap and varus angle with 40 lbs. of joint distraction force. The extension gap preparation was identical in both group. In MPGT group, 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 osteotomy. The knee stabilities at extension and flexion were assessed by stress radiographies; varus-valgus stress test with extension and stress epicondylar view with flexion, at one-month and one-year after TKA. We measured joint opening distance (mm) at medial and lateral compartment at both knee extension and flexion. Joint opening distances were compared between two groups using unpaired t-test, and the difference between medial and lateral compartment in each group was compared using paired t- test (p<0.05). Results. Joint opening distances at medial compartments with both extension and flexion were significantly smaller than lateral in both groups. There were no significant differences in join opening distance between two groups at medial compartment, but those at lateral were significantly smaller in MPGT than MRT with both knee extension and flexion. Discussion. In the present study, we found MPGT resulted in equal postoperative medial knee stability as in MRT, and superior to MRT as for the lateral knee stability. This finding would be the result of different femoral external rotation angle and femoral component size selection between two groups. We used the difference of varus angle and center gap between flexion and extension for the femoral component size selection and external rotation angle in MPGT. Quantitative surgical concept; MPGT, was found to be safer and feasible gap technique in PS-TKA to preserving medial knee stability and control lateral laxity in varus type OA knee. MPGT would be an advantageous gap technique to enhance clinical outcome

Introduction. Although gap balancing technique has been reported to be beneficial for the intra-operative soft tissue balancing in posterior-stabilized (PS)-TKA, excessive release of medial structures for achieving perfect ligament balance would be more likely to result in medial instability, which would deteriorate post-operative clinical results. We have modified conventional gap balancing technique and devised a new surgical concept; named as “medial gap technique” aiming at medial stability with permitting lateral looseness, as physiologically observed in normal knee. Objective. We compared intra-operative soft tissue balance between medial gap technique (MGT) and measured resection technique (MRT) in PS-TKAs. Materials and Methods. The subjects were 210 female patients with varus type osteoarthritic knees, underwent primary PS TKA. The surgical techniques were MGT in 96 patients and MRT in 114 patients. The extension gap was made in the same manners in both groups with medial releases limited until the spacer block could be easily inserted. The residual lateral laxity was permitted. In the MGT group, before posterior femoral osteotomies, varus angles (°) and center gaps (mm) at extension and flexion were measured using an offset type tensor with applying 40 lbs. (177.9N) of joint distraction force. The level and external rotation angle of posterior femoral osteotomies were determined based on the difference of center gaps and varus angles between extension and flexion respectively. Intra-operative joint gap kinematics was measured with femoral trial in place and patello-femoral joint reduced. We measured varus angle and component gap at 8 different knee flexion angles from 0° to 135°. From these component gaps and varus angles, we calculated a medial and lateral compartment gaps (MCG and LCG) by using a trigonometric function. Also we calculated the increase of both compartment gaps from those at full extension, named as joint gap loosening (mm). Both compartment gaps and joint gap loosening were compared between 2 groups using unpaired t-test, and the difference between MCG and LCG in each group were compared using paired t- test (p<0.05). Results. The mean MCGs showed significantly smaller value than LCGs at all flexion angles in both groups (Fig.1). Both medial and lateral joint gap loosening were significantly smaller in MGT group than MRT group from mid-flexion to deep flexion (Fig. 2, 3). Discussion. We have reported the joint distraction force affected varus imbalance due to the stiffness difference between medial and lateral structures. This might be a reason why gap technique was performed less quantitatively and with higher risk of medial instability. In MGT, we allowed persistent lateral looseness and applied the difference in varus angle between extension and flexion to the external rotation angle of femoral component. Results showed no medial looseness were observed in MGT like in MRT. The less joint gap loosening with knee flexion were achieved by MGT because the advantage of conventional gap balancing was also incorporated. We found “medial gap technique” was effective for quantitative soft tissue balancing with more stable joint gap kinematics and no medial looseness

The treatment of medial knee osteoarthritis (OA) in conjunction with anterior knee laxity is an issue of debate. Current treatment options include knee joint distraction, unicompartmental knee replacement (UKR) or high tibial osteotomy with anterior cruciate ligament (ACL) reconstruction or total knee replacement. Bone-conserving options are preferred for younger and active patients with intact lateral and patello-femoral compartment. However, still limited experience exists in the field of combining medial UKR and ACL reconstruction. The aim of this study is to retrospectively evaluate the results of combined fixed-bearing UKR and ACL reconstruction, specifically with regard to patient satisfaction, activity level, and postoperative functional outcomes. The hypothesis was that this represents a safe and viable procedure leading to improved stability and functional outcome in patients affected by isolated unicompartmental OA and concomitant ACL deficiency. Fourteen patients with ACL deficiency and concomitant medial compartment symptomatic osteoarthritis were treated from 2006 to 2010. Twelve of them were followed up for an average time of 7.8 year (range 6–10 years). Assessment included Knee Osteoarthritis Outcome Score (KOOS), Oxford Knee score (OKS), American Knee Society scores (AKSS), WOMAC index of osteoarthritis, Tegner activity level, objective examination including instrumented laxity test with KT-1000 arthrometer and standard X-rays. Wilcoxon test was utilized to compare the pre-operative and follow-up status. Differences with a p value <0.05 were considered statistically significant. KOOS score, OKS, WOMAC index and the AKSS improved significantly at follow-up (p < 0.05). There was no clinical evidence of instability in any of the knees as evaluated with clinical an instrumented laxity testing (p < 0.05). No pathologic radiolucent lines were observed around the components. In one patient a total knee prosthesis was implanted due to the progression of signs of osteoarthritis in the lateral compartment 3 years after primary surgery. UKR combined with ACL reconstruction is a valid therapeutic option for young and active patients with a primary ACL injury who develop secondary OA and confirms subjective and objective clinical improvement up to 8 years after surgery

Objective. Although both accurate component placement and adequate soft tissue balance have been recognized as essential surgical principle in total knee arthroplasty (TKA), the influence of intra-operative soft tissue balance on the post-operative clinical results has not been well investigated. In the present study, newly developed TKA tensor was used to evaluate soft tissue balance quantitatively. We analyzed the influence of soft tissue balance on the post-operative knee extension after posterior-stabilized (PS) TKA. Materials and Methods. Fifty varus type osteoarthritic knees implanted with PS-TKAs were subjected to this study. All TKAs were performed using measured resection technique with anterior reference method. The thickness of resected bone fragments was measured. Following each bony resection and soft tissue releases, we measured soft tissue balance at extension and flexion of the knee using a newly developed offset type tensor. This tensor device enabled quantitative soft tissue balance measurement with femoral trial component in place and patello-femoral (PF) joint repaired (component gap evaluation) in addition to the conventional measurement between osteotomized surfaces (osteotomy gap evaluation). Soft tissue balance was evaluated by the center gap (mm) and ligament balance (°; positive in varus) applying joint distraction forces at 40 lbs (178 N). Active knee extension in spine position was measured by lateral X-ray at 4 weeks post-operatively. The effect of each parameter (soft tissue balance evaluations, thickness of polyethylene insert and resected bone) on the post-operative knee extension was evaluated using simple linear regression analysis. P<0.05 was considered statistically significant. Results. The thickness of resected bone, flexion center gap and ligament balance at extension and flexion had no correlations to the knee extension angle. Thickness of polyethylene insert correlated positively to knee extension (r=0.38, p=0.007). Significant positive correlation were found between extension center gap in both osteotomy and component gap evaluation to the post-operative knee extension. The coefficient of correlations were 0.33 (p=.02) with osteotomy gap and 0.47 (p=0.0007) with component gap evaluation. Discussion and Conclusion. In the present study, extension center gap was found to positively correlate to the early post-operative knee extension. The extension center gap could be considered as the summation of the simultaneous gap from bone resections and the elongation of soft tissue envelope under joint distraction force applied by tensor. The soft tissue with the lower stiffness would be elongated more, and result in the larger center gap. Accordingly, the stiffness of the soft tissue envelope might play an important role on the magnitude of extension center gap and the post-operative knee extension. Furthermore, the center gap in component gap evaluation had higher coefficient of correlation comparing to that in osteotomy gap. Proposed component gap evaluation in soft tissue balance measurement might be more physiological and relevant to the joint condition after TKA, and useful to predict post-operative clinical results

Introduction:. The assumption that symmetric extension-flexion gaps improve the femoral condyle lift-off phenomenon and the patellofemoral joint congruity in total knee arthroplasty (TKA) is now widely accepted. For tease reasons, the balanced gap technique has been developed. However, the management of soft tissue balancing during surgery remains difficult and much is left to the surgeon's feel and experience. Furthermore, little is known about the differences of the soft-tissue stiffness (STS) of medial and lateral compartment in extension and flexion in the both cruciate ligaments sacrificed knee. It has a deep connection with the achievement of appropriate gaps operated according to the balanced gap technique. Therefore, the purpose of this study was to analyze the STS of individual compartment in vivo. Materials and Methods:. The subjects presented 100 osteoarthritic knees with varus deformity underwent primary posterior stabilized (PS) – TKA (NexGen LPS-flex, Zimmer, Warsaw, USA). All subjects completed written informed consent. The patient population was composed of 14 men and 68 women with a mean age of 74.5 ± 7.5 years. The average height, weight, BMI, weight-bearing femorotibial mechanical angle (FTMA), the patella height (T/P ratio), extension and flexion angle of the knee under anesthesia were 151.9 ± 7.8 cm, 62.1 ± 9.4 kg, 26.9 ± 3.7 kg/m. 2. , 167.7 ± 5.6 °, 0.91 ± 0.15 °, −12.0 ± 6.7° and 129.4 ± 13.8°, respectively. After finishing osteotomy and soft tissue balancing, the femoral trial prosthesis was fitted with patello-femoral joint reduction. Then, the medial and lateral compartment gaps (CG) were measured at various distraction forces (89–178 N) using a newly developed versatile tensor device at full extension and 90° flexion positioning, respectively. (Fig. 1) The STS (N/mm) was calculated from a load displacement curve generated by the intra-operative CG data and joint distraction force. Comparisons were made by Wilcoxon signed-ranks test. Correlations were analyzed with Pearson's correlation coefficient. Predictive variables were analyzed with Stepwise regression. A value of p < 0.05 was considered significant. Results:. The CG discrepancy between the medial and the lateral compartments significantly tended to increase as the force dependent manner in the knee at extension (p < 0.0004) and 90° flexion position (p < 0.0001). (Fig. 2) Significant differences (p < 0.0001) were observed in the STS among all compartments respectively; extension medial (71.0 ± ãζζ33.9), flexion medial (26.1 ± 11.6), extension lateral (60.2 ± 36.4) and flexion lateral (19.4 ± 8.2). The ratio of medial to lateral compartment STS (R = −0.54) and the difference of the STS between the medial and lateral compartments (R = 0.385) were significantly correlated with the flexion CG discrepancy (p < 0.0001). The predict variables of the STS could be acquired in extension medial, extension lateral and the ratio of flexion lateral to flexion medial. (Fig. 3). Discussion:. We should notice the significant difference of the STS between the medial and lateral compartments and the ratio of the medial to lateral compartments STS, especially when the balanced gap technique is used. It suggests the importance of refinement of the joint distraction force for individual patients based on their own characteristics of soft tissue

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. The extension and flexion gaps are affected by different factors in total knee arthroplasty (TKA). Flexion but not extension gap measurements are influenced by posterior cruciate ligament (PCL) preservation or resection and patella reduction or eversion and thigh weight. If the flexion gap is measured with the thigh placed on the tibia, the measurement results must include the thigh weight; nevertheless, there is no detailed report regarding the thigh weight influence on the flexion gap. In this study, we investigated how thigh weight affected flexion gap measurement. METHODS. Four knees of whole-body fresh-frozen cadavers (Mongolian race) were investigated. The femur and tibia were dissected with a standard measured resection technique. After the femoral component was set, the flexion gap was measured with a knee balancer. The distraction force of 20, 30, and 40 pounds were loaded at the joint level. For each measurement, the influences of the patella reduced or everted (PR or PE) and the PCL preserved or resected (CR or PS) were estimated. The flexion gap was measured five times in four different categories (CR/PR, CR/PE, PS/PR, PS/PE) and the thigh weight was reduced by weights (0, 0.5, 1.0, 2.0, 3.0 kg) using a string and pulley system. During measurement, the femur was just placed on the tibia, and the knee flexion angle was maintained at 90 degrees with a goniometer. After all measurements, the lower limbs were resected, and the thighs were weighed with a scale. Steel-Dwasstest (non-parametric multiple comparison test) were performed for statistical analysis, and p < 0.05 was considered significant. RESULTS. Flexion gap measurement results show over 10 mm difference between the maximum gap (PS/PE, 40 lbs, 3 kg weight reduction) and the minimum gap (CR/PR, 20 lbs distraction, no weight reduction) in this study. When a 0.5 kg weight reduction was applied, there were no significant flexion gap increases compared to no weight reduction situation in almost all categories except for “CR/PR and 40 lbs distraction”. According to the increase of the weight reduction, the flexion gap became larger in all categories. When a 3 kg weight reduction was applied, there were significant flexion gap increases compared to no weight reduction situation in all categories (Table 1-3). The mean thigh weight was 2.3 kg (2.0–2.6 kg). DISCUSSION. The flexion gap is usually measured with the thigh placed on the tibia in TKA, and the measurement results are considered to include the influence of the thigh weight even though this has not been discussed in the literature. From our results, the influence of the thigh weight reduction on the flexion gap was different according to heaviness of the reduction weight. When the reduction weight was over the thigh weight, flexion gap increase relative to the flexion gap without weight reduction was significant in all categories nevertheless different situations of the PCL, patella position, and joint distraction forces. To estimate adequate flexion gap and avoid post-operative flexion gap looseness, the thigh weight should be reduced when the flexion gap is measured

Introduction / Purpose. Many factors can influence postoperative knee flexion angle after total knee arthroplasty (TKA), and range of flexion is one of the most important clinical outcomes. Although many studies have reported that postoperative knee flexion is influenced by preoperative clinical conditions, the factors which affect postoperative knee flexion angle have not been fully elucidated. As appropriate soft-tissue balancing as well as accurate bony cuts and implantation has traditionally been the focus of TKA success, in this study, we tried to investigate the influence of intraoperative soft-tissue balance on postoperative knee flexion angle after cruciate-retaining (CR) TKA using a navigation system and offset-type tensor. Methods. We retrospectively analyzed 55 patients (43 women, 12 men) with osteoarthritis who underwent TKA using the same mobile-bearing CR-type implant (e.motion; B. Braun Aesculap, Germany). The mean age at the time of surgery was 74.2 (SD 7.3) years. The exclusion criteria for this study included valgus deformity, severe bony defect requiring bone graft or augmentation, revision TKA, active knee joint infection, and bilateral TKA. Intraoperative soft-tissue balance parameters such as varus ligament balance and joint component gap were measured in the navigation system (Orthopilot 4.2; B. Braun Aesculap) while applying 40-lb joint distraction force at 0°, 10°, 30°, 60°, 90°, and 120° of knee flexion using an offset-type tensor with the patella reduced. Varus ligament balance was defined as the angle (degree, positive value in varus imbalance) between the seesaw and platform plates of the tensor that was obtained from the values displayed by the navigation system. To determine clinical outcome, we measured knee flexion angle using a goniometer with the patient in the supine position before and 2 years after surgery. Correlations between the soft-tissue parameters and postoperative knee flexion angle were analyzed using simple linear regression models. Pre- and postoperative knee flexion angle were also analyzed in the same manner. Results. Mean pre- and postoperative flexion angle were 120.5 ± 1.9° and 121.9 ± 1.3°, which did not show significant improvement after surgery. Varus ligament balance at 90° of flexion was positively correlated with postoperative knee flexion angle (R = 0.56, P < 0.001) and calculated joint gap of the lateral compartment at 90° of flexion showed positive correlation with postoperative knee flexion angle (R = 0.51, P < 0.001), while no correlation was found between joint gap of the medial compartment at 90° of flexion and postoperative knee flexion angle. Also, as with some past studies, joint component gap at 90° of flexion was slightly correlated with postoperative knee flexion angle (R = 0.30, P < 0.05) and pre- and postoperative knee flexion angle showed a significant positive correlation (R = 0.63, P < 0.001). Conclusions. Varus ligament balance at mid to deep flexion was a factor that predicted postoperative knee flexion angle after CR-TKA. In addition to preoperative knee flexion angle and joint component gap at 90° of flexion, lateral laxity at 90° of flexion is one of the most important factors affecting postoperative knee flexion angle

Objective. The goal of total knee arthroplasty (TKA) is to achieve a stable and well-aligned tibiofemoral and patello-femoral (PF) joint, aiming at long-term clinical patient satisfaction. The surgical principles of both cruciate retaining (CR) and posterior stabilized (PS) TKA are accurate osteotomy and proper soft tissue balancing. We have developed an offset-type tensor, and measured intra-operative soft tissue balance under more physiological joint conditions with femoral component in place and reduced PF joint. In this study, we measured intra-operative soft tissue balance and assessed the post-operative knee joint stability quantitatively at one month, six months and one year after surgery, and compared these parameters between CR and PS TKAs. Material and Method. Sixty patients with varus osteoarthritis of the knee underwent TKAs (30 CR TKAs: CR and 30 PS TKAs: PS). Mean varus deformity in standing position was 11.1 degrees in CR, and 12.6 degrees in PS. All TKAs were performed by a single surgeon with measured resection technique. The external rotation of posterior femoral condyle osteotomy was performed according to surgical epicondylar axis in pre-operative CT. We measured intra-operative soft tissue balance using an offset-type tensor with 40 lbs of joint distraction force at 0, 10, 30, 45, 60, 90, 120 and 135 degrees of flexion. The joint component gap (mm) and varus angle (degrees) were measured at each flexion angles. One month, six months and one year after surgery, we evaluated the knee stability at extension by varus and valgus stress radiography using Telos (10kg) and at flexion by epicondylar view with 1.5kg weight at the ankle. We measured joint separation distance at medial as medial joint looseness (MJL) and at lateral as lateral joint looseness (LJL). Intra-operative measurements and post-operative joint stabilities were compared between CR and PS using unpaired t-test. The change of joint looseness in each group was analyzed using repeated measures ANOVA. Result. Joint gap kinematics was different between CR and PS (Fig. 1). Joint component gap in PS were significantly higher than CR from 30 to 120 degrees of flexion. Post-operative MJL and LJL changes are shown in figure 2 with knee extension, and in figure 3 with knee flexion. PS showed significantly higher joint looseness than CR at both extension and flexion at three time periods after surgery. There were no significant post-operative changes in both MJL and LJL in CR and PS TKAs. Discussion. We found significant differences in gap kinematics and also in the one year post-operative joint stability between CR and PS. The different characteristics of the intra-operative soft tissue balance between CR and PS TKAs would be a possible reason for the differences in the post-operative knee stability. Our results suggested that TKAs performed by measured resection technique have significantly higher joint stability with CR TKAs comparing to PS TKAs. These findings would be important issues in choosing prosthesis and surgical technique. Conclusion. With measured resection technique, CR TKAs had more consistent joint gap kinematics and higher joint stability after surgery comparing to PS TKAs

Introduction. Appropriate osteotomy alignment and soft tissue balance are essential for the success of total knee arthroplasty (TKA). The management of soft tissue balance still remains difficult and it is left much to the surgeon's subjective feel and experience. We developed an offset type tensor system for TKA. This device enables objective soft tissue balance measurement with more physiological joint conditions with femoral trial component in place and patello-femoral (PF) joint reduced. We have reported femoral component placement decreased extension gap. The purpose of the present study was to analyze the influence of femoral component size selection on the decrease of extension gap in posterior-stabilized (PS) TKA. Material & Method. 120 varus type osteoarthritic knees implanted with PS TKAs (NexGen LPS flex: Zimmer) were subjected to this study. All TKAs were performed using measured resection technique with anterior reference. The femoral component size was evaluated intra-operatively using conventional femoral sizing jig. The selected femoral component size was expressed by the antero-posterior (AP) size increase (mm) comparing to that of original femoral condyles. Gap measurements were performed using a newly developed offset type tensor device applying 40lbs (178N) of joint distraction force. Firstly, conventional osteotomy gaps (mm) were measured at extension and flexion. Secondary, component gaps (mm) after femoral trial placement with PF joint reduced were evaluated at 0° and 90° of knee flexion. To compare conventional osteotomy gaps and component gaps, estimated extension and flexion gaps were calculated by subtracting the femoral component thickness at extension (9mm) and flexion (11mm) from conventional osteotomy gaps respectively. The decrease of gap at extension and flexion were calculated with estimated gaps subtracted by component gaps. The simple linear regression analysis was used to evaluate the influence of selected femoral component size on the decrease of gap after femoral component placement. Results. The mean extension and flexion conventional osteotomy gaps were 25.7 and 28.2 mm, and estimated gaps were 16.7, 17.2 mm respectively. The component gaps were 11.1, 16.9 mm at 0° and 90° of knee flexion respectively. Extension joint gap was significantly decreased as much as 5.6mm after femoral component placement, but flexion gap showed no significant differences. Selected femoral component size showed a positive correlation to the decrease of gap after femoral component placement (Fig 1). Discussion & Conclusion. This result indicates that AP femoral component size variation affects not only flexion gap but also extension gap in PS TKA. With the larger femoral component size selected, the more protrusion of posterior condyles would increase the more tension on the posterior structures and resulted in the more decrease of joint gap after femoral component placement at full extension. This mechanism might play a physiological role on the prevention of knee hyper-extension, and would be affected by flexion contracture. Accordingly, we conclude that the surgeon should aware of the effect of femoral component placement on the gap control, and femoral component size selection affects not only flexion gap but also extension gap after femoral component placement in PS TKA

Purpose. The remplissage procedure may be performed as an adjunct to Bankart repair to address an engaging Hill-Sachs defect. Clinically, it has been reported that the remplissage procedure improves joint stability but that it may also restrict shoulder range of motion. The purpose of this biomechanical study was to examine the effects of the remplissage procedure on shoulder motion and stability. We hypothesized that the remplissage procedure would improve stability and prevent engagement but may have a deleterious effect on motion. Method. Eight cadaveric forequarters were mounted on a custom biomechanical testing apparatus which applied simulated loads independently to the rotator cuff muscles and to the anterior, middle and posterior deltoid. The testing conditions included: intact shoulder, Bankart defect, Bankart repair, 2 Hill-Sachs defects (15%, 30%) with and without remplissage. Joint range of motion and translation were recorded with an optical tracking system. Outcomes measured were internal-external rotation range of motion in adduction and 90 combined abduction, extension range of motion and stability, quantified in terms of joint stiffness and engagement, in abduction. Results. With a 15% Hill-Sachs defect, the remplissage significantly reduced internal-external rotation in adduction (15.111.1, p=0.039), but not in abduction (7.79.0, p=0.380). In a 30% Hill-Sachs defect, the remplissage procedure significantly reduced internal-external rotation in adduction (19.57.8, p=0.001), and in abduction (12.28.6, p=0.03). The remplissage procedure significantly enhanced stability in the 15% Hill-Sachs defect (4.74.0 N/mm, p=0.038), and in the 30% defect (3.93.2 N/mm, P=0.030) compared to the unrepaired defect. All of the unrepaired 30% defects engaged and the remplissage procedure successfully eliminated engagement in each case. However, impingement of the repair on the posterior glenoid with paradoxical posterior pivoting of the humeral head was observed in 50% of the specimens. Conclusion. The remplissage procedure significantly augmented a Bankart repair in 15% and 30% Hill-Sachs defects and, in 30% Hill-Sachs defects, the remplissage successfully prevented engagement of the defect. The remplissage procedure, however, did significantly reduced shoulder internal-external rotation range of motion as reported clinically, and was also found to reduce extension in the two defect groups. During extension the intra-articular soft tissue bumper created by the remplissage procedure was found to impinge on the posterior glenoid rim and cause pivoting, which produced non-physiologic glenohumeral joint distraction. Therefore, the remplissage procedure stabilized the joint to a significantly greater degree than did a Bankart repair alone; however, it also significantly reduced shoulder range of motion

Objective. The goal of total knee arthroplasty (TKA) is to achieve a stable and well-aligned tibiofemoral and patello-femoral (PF) joint, aiming at long-term clinical patient satisfaction. The surgical principles of both cruciate retaining (CR) and posterior stabilized (PS) TKA are accurate osteotomy and proper soft tissue balancing. We have developed an offset-type tensor, and measured intra-operative soft tissue balance under more physiological joint conditions with femoral component in place and reduced PF joint. In this study, we measured intra-operative soft tissue balance and assessed the early post-operative knee joint stability quantitatively, and compared these parameters between CR and PS TKA. Material and Method. Seventy patients with varus osteoarthritis of the knee underwent TKAs (35 CR TKAs: CR and 35 PS TKAs: PS). Mean varus deformity in standing position was 9.8 degrees in CR, and 10.7 degrees in PS (p = 0.45). All TKAs were performed by a single surgeon with measured resection technique. The external rotation of posterior femoral condyle osteotomy was performed according to surgical epicondylar axis (SEA) in pre-operative CT. We measured intra-operative soft tissue balance using an offset-type tensor with 40 lbs of joint distraction force at 0, 10, 30, 45, 60, 90, 120 and 135 degrees of flexion. The joint component gap (mm) and varus angle (degrees) were measured at each flexion angle. Four weeks after operation, we evaluated the knee stability at extension by varus and valgus stress radiography using Telos (10 kg) and at flexion by epicondylar view with 1.5 kg weight at the ankle. We measured joint separation distance at medial as medial joint looseness (MJL) and at lateral as lateral joint looseness (LJL). Joint looseness was defined as the average of MJL and LJL. Intra-operative measurements and post-operative joint stabilities were compared between CR and PS using unpaired t-test. Result. Joint gap kinematics was different between CR and PS (figure 1). Joint component gap in PS were significantly higher than CR from 30 to 120 degrees of flexion. Post-operative joint looseness were 2.7 mm and 3.7 mm at extension (p = 0.001, figure 2), and 1.1 mm and 1.9 mm at flexion (p = 0.021, figure 3) in CR and PS TKAs each respectively. At both extension and flexion, PS showed significantly higher joint looseness, especially with the higher MJL in PS comparing with CR. Discussion. We found significant differences in gap kinematics and also in the early post-operative joint stability between CR and PS. In the PS TKAs, component gaps were significantly larger than those in CR TKAs at mid-flexion to deep flexion of the knee. These different characteristics of the intra-operative soft tissue balance would be a possible reason for the differences in the post-operative joint stability between CR and PS TKAs. Our results suggested that TKAs performed by measured resection technique have significantly higher joint stability with CR than PS. These findings would be important issues in choosing prosthesis and operative technique. Conclusion. With measured resection technique, CR TKAs had more consistent joint gap kinematics and higher joint stability after surgery comparing to PS TKAs

Introduction:. Adjusting joint gaps and establishing mediolateral (ML) soft tissue balance are considered essential interventions for better outcomes in total knee arthroplasty (TKA). However, the relationship between intraoperative laxity measurements and weight-bearing knee kinematics has not been well explored. The goal of this study was to establish how intraoperative joint gaps and ML soft tissue balance affect postoperative kinematics in posterior-stabilized (PS)-TKA. Methods:. We investigated 44 knees with 34 patients who underwent primary PS-TKA. Subjects averaged 71 ± 7 years at the time of surgery, included 8 male and 36 female knees with a preoperative diagnosis of osteoarthritis in 38 knees and rheumatoid arthritis in 6 knees. A single surgeon performed all the surgeries with mini-midvastus approach. After independent bone cutting, soft tissues were released on a case-by-case basis to obtain ML balance. The femoral trial and a tensor were put in place, and the patella was reduced to the original position. A joint distraction force of 40 lb was applied by the tensor, and the central joint gaps and ML tilting angles were measured at 0°, 10°, 30°, 60°, 90°, 120° and 135° flexion (Fig. 1). We defined a “gap difference” as a gap size difference between one gap and another, which represents the gap change between the two knee flexion positions. ML soft tissue balance was assessed by measuring the mean joint gap tilting angle over all flexion angles for each patient. Based on the tilting angle, the 44 knees were classified into three groups: The knees with the mean joint gap tilting of less than −1.0° (13 knees), between −1.0 and 1.0° (14 knees), and over 1.0° (17 knees). At least 1.5 year after surgery, a series of dynamic squat radiographs and 3 static lateral radiographs of straight-leg standing, lunge at maximum flexion, and kneeling at maximum flexion, were taken for each patient. The 3-dimensional position and orientation of the implant components were determined using model-based shape matching techniques (Fig. 2). Correlations between intraoperative measurements and knee kinematics were analyzed. The knee kinematics was also compared among three tilting groups. Results:. Gap difference of 135° minus 0° showed positive correlations with total posterior lateral translation during squatting (r = 0.336, p = 0.042) and total femoral external rotation (r = 0.488, p = 0.002). Gap difference of 135° minus 0° also demonstrated negative correlations with lateral condyle AP position in maximal kneeling (r = −0.501, p = 0.001, Fig. 3), and showed positive correlations with maximal knee flexion during squatting (r = 0.342, p = 0.038) and kneeling (r = 0.355, p = 0.031). Gap differences of 120° minus 90° and 135° minus 90° exhibited positive correlations with femoral external rotation at maximal kneeling and lunge. No correlation was demonstrated between joint tilting angle and post-operative knee kinematics. Also, there were no significant kinematic differences among three tilting groups. Conclusion:. These findings suggest adequate intraoperative joint gaps beyond 90° flexion are important to obtain greater lateral femoral translation and femoral external rotation, both factors for better postoperative flexion, while several degrees of ML imbalance is unlikely to negatively affect postoperative knee kinematics

Introductions. In cruciate-retaining total knee arthroplasty (TKA), among many factors influencing post-operative outcome, increasing the tibial slope has been considered as one of the beneficial factors to gain deep flexion because of leading more consistent femoral rollback and avoiding direct impingement of the insert against the posterior femur. In contrast, whether increasing the tibial slope is useful or not is controversial in posterior-stabilized (PS) TKA, Under such recognition, accurate soft tissue balancing is also essential surgical intervention for acquisition of successful postoperative outcomes in TKA. In order to permit soft tissue balancing under more physiological conditions during TKAs, we developed an offset type tensor to obtain soft tissue balancing throughout the range of motion with reduced patello-femoral(PF) and aligned tibiofemoral joints and have reported the relationship between intra-operative soft tissue balance and flexion angles. In this study, we therefore assessed the relationship between intra-operative soft tissue balance assessed using the tensor and the tibial slope in PS TKA. Materials and methods. Thirty patients aged with a mean 72.6 years were operated PS TKA(NexGen LPS-Flex, Zimmer, Inc. Warsaw, IN) for the varus type osteoarthritis. Following each bony resection and soft tissue release using measure resection technique, the tensor was fixed to the proximal tibia and femoral trial prosthesis was fitted. Assessment of the joint component gap (mm) and the ligament balance in varus (°)was carried out at 0, 10, 45, 90and 135degrees of knee flexion. The joint distraction force was set at 40lbs. Joint component gap change values during 10-0°,45-0°, 90-0°, 135-0° flexion angle were also calculated. The tibial slopes were measured by postoperative lateral radiograph. The correlation between the tibial slope and values of soft tissue balance were assessed using linear regression analysis. Results. Average joint component gaps were 11.2, 14.7, 16.7, 18.4 and 17.0 mm and ligament balance in varus were 2.2, 2.9, 5.3, 6.8 and 6.9°at 0, 10, 45, 90 and 135° of flexion, respectively. Average joint component gap changes were 3.5, 5.6, 7.2 and 5.7 mm at each range of motion between 10–0, 45-0, 90–0 and 135–0° of flexion, respectively. The mean tibial slope was 5.0(1.6–9.6) degrees. Joint component gap at 90 (R = 0.537, p<0.01),135(R=0.463, p<0.05) degrees of flexion, and joint component gap change value of 90–0° (R = 0.433, p<0.05) showed positive correlations with tibial slope. The other factors assessed in this study showed no correlation with tibial slope. Discussions. The joint gap toward mid-range of flexion might be measured at anterior part of the tibiofemoral joint, whereas the values of joint gap at high flexion where the femur shifted posterior due to femoral rollback were measured the widened posterior part of the joint gap. In addition, extensor mechanism as well as tibial slope might influence joint gap at deep flexion. In conclusion, even PS TKA, increasing the posterior tibial slope resulting in larger flexion gap compared to extension gap should be taken into account for the flexion-extension gap balancing

Aims

This study aims to enhance understanding of clinical and radiological consequences and involved mechanisms that led to corrosion of the Precice Stryde (Stryde) intramedullary lengthening nail in the post market surveillance era of the device. Between 2018 and 2021 more than 2,000 Stryde nails have been implanted worldwide. However, the outcome of treatment with the Stryde system is insufficiently reported.