Ligament reconstruction following multi-ligamentous knee injuries involves graft fixation in bone tunnels using interference screws (IS) or cortical suspensory systems. Risks of IS fixation include graft laceration, cortical fractures, prominent hardware, and inability to adjust tensioning once secured. Closed loop suspensory (CLS) fixation offers an alternative with fewer graft failures and improved graft-to-tunnel incorporation. However, graft tensioning cannot be modified to accommodate errors in tunnel length evaluation. Adjustable loop suspensory (ALS) devices (i.e., Smith & Nephew Ultrabutton) address these concerns and also offer the ability to sequentially tighten each graft, as needed. However, ALS devices may lead to increased graft displacement compared to CLS devices. Therefore, this study aims to report outcomes in a large clinical cohort of patients using both IS and CLS fixation. A retrospective review of radiographic, clinical, and patient-reported outcomes following ligament reconstruction from a Level 1 trauma centre was completed. Eligible patients were identified via electronic medical records using ICD-10 codes. Inclusion criteria were patients 18 years or older undergoing ACL, PCL, MCL, and/or LCL reconstruction between January 2018 and 2020 using IS and/or CLS fixation, with a minimum of six-month post-operative follow-up. Exclusion criteria were follow-up less than six months, incomplete radiographic imaging, and age less than 18 years. Knee dislocations (KD) were classified using the Schenck Classification. The primary outcome measure was implant removal rate. Secondary outcomes were revision surgery rate, deep infection rate, radiographic fixation failure rate, radiographic malposition, Lysholm and Tegner scores, clinical graft failure, and radiographic graft failure. Radiographic malposition was defined as implants over 5 mm off bone or intraosseous deployment of the suspensory fixation device. Clinical graft failure was defined as a grade II or greater Lachman, posterior drawer, varus opening at 20° of knee flexion, and/or valgus opening at 20° of knee flexion. Radiographic failure was defined when over 5 mm, 3.2 mm, and/or 2.7 mm of side-to-side difference occurred using PCL gravity stress views, valgus stress views, and/or varus stress views, respectively. Descriptive statistics were used. Sixty-three consecutive patients (mean age = 41 years, range = 19-58) were included. A total of 266 CLS fixation with Ultrabuttons and 135 IS were used. Mean follow-up duration was 383 days. Most injuries were KD type II and III. Graft revision surgery rate was 1.5%. Intraosseous deployment occurred in 6.2% and 17% had implants secured in soft tissue, rather than on bone. However, the implant removal rate was only 6.2%. Radiographic PCL gravity stress views demonstrated an average of 1.2 mm of side-to-side difference with 6.2% meeting criteria for radiographic failure. A single patient met radiographic failure criteria for collateral grafts. Mean Lysholm and Tegner scores were 87.3 and 4.4, respectively, with follow-up beyond one year. Both IS and CLS fixation demonstrate an extremely low revision surgery rate, a high rate of implant retention, excellent radiographic stability, and satisfactory patient-reported outcome scores. Incorrect implant deployment was seen in a total of 17% of patients, yet none required implant removal. A single patient required graft revision due to implant failure

Introduction: A successful total knee replacement (TKR) relies upon effective soft tissue management. Historically, soft tissue balancing has been difficult to assess and quantify intraoperatively. Computer navigation permits us to accurately assess kinematics during surgery. In a previous study we performed a series of varus and valgus stress measurements in extension to devise an algorithm for soft tissue management. In this study we evaluate the effectiveness of this algorithm. Methods: This prospective study used the Orthopilot® CT-free navigation system during TKR for 57 patients with end-stage arthritis. We collected intraoperative kinematic data for 42 varus knees. Pre- and post-operatively, a varus and valgus stress was applied at maximum extension, recording the mechanical femorotibial (MFT) angle. There were no patellar resurfacings. The following medial releases were performed based upon the kinematics and the algorithm below:. No release–MFT angle not less than −12° with varus stress, greater than 2° with valgus stress, and/or if extension deficit was not greater than 5°. Moderate release–MFT angle less than −12° with varus stress, between −5° and 2° with valgus stress, and/or extension deficit not greater than 5°. Proximal release–MFT angle less than −12° with varus stress, less than −5° with valgus stress, and/or extension deficit greater than 5°. Results: Pre-operatively, the mean MFT angle was −9.6°varus (−3° to −22°) with varus stress and −0.8°varus (4° to −11°) with valgus stress. Post-operatively, the mean MFT angle was −3.5° varus (0° to −5°) with varus stress, and 2.1° valgus (4° to −1°) with valgus stress. Using regressional analysis, there was a strong linear correlation between both varus (r=0.871, p< 0.0001) and valgus (r=0.894, p< 0.0001) stresses and the MFT angle. Post-operatively, the mean MFT angle was maintained within a narrow range (0° to −5° with varus stress, 4° to −1° with valgus stress), with no outliers. There were no extension deficits. Conclusions: Using computer navigation a quantifiable soft tissue management system was introduced. We evaluated this algorithm, and obtained reproducible results within a narrow range and no outliers. This algorithm may provide an effective soft tissue management plan in TKR

Introduction: Accurate soft tissue balancing is an essential part of total knee replacement (TKR), but has been difficult to quantify using traditional instrumentation methods. Computer navigation systems allow us to accurately assess intra-operative kinematics, which are affected by soft tissue management. The aims of this study were to evaluate the role of varus and valgus stress measurements and subsequently devise an algorithm for soft tissue management during TKR. Methods: We used the Orthopilot® CT-free navigation system during TKR for patients with primary end-stage arthritis. This was a prospective study with 71 patients collecting intra-operative kinematic data. 57 knees were varus, 13 valgus, and 1 well aligned. Pre- and post-operatively, the surgeon applied a varus and valgus stress at maximum extension, recording the mechanical femorotibial (MFT) angle. There were no patellar resurfacings. We compared the kinematics of each varus knee. Based upon the kinematics and the surgeon’s experience the following medial releases were performed as usual and divided into three categories:. No release (limited medial approach). Moderate release (postero-medial release including the semimembranosis). Proximal (extensive) release. Results: Pre-operatively, the mean MFT angle was −9.6° (−3° to −22°) with varus stress and −0.8° (4° to −11°) with valgus stress. Post-operatively, the mean MFT angle was −3.7° (−1° to −7°) with varus stress, and 1.1° (4° to −3°) with valgus stress. Using regressional analysis, there was a strong linear correlation between both varus (r=0.742, p< 0.0001) and valgus (r=0.771, p< 0.0001) stresses and the MFT angle. With the following medial releases, these kinematics were found:. No release – MFT angle not less than −12° with varus stress, greater than 2° with valgus stress, and/or if extension deficit was not greater than 5°. Moderate release – MFT angle less than −12° with varus stress, between −5° and 2° with valgus stress, and/or extension deficit not greater than 5°. Proximal release – MFT angle less than −12° with varus stress, less than −5° with valgus stress, and/or extension deficit greater than 5°. The results show that post-operatively, the mean MFT angle is maintained within a narrow range (−1° to −7° with varus stress, 4° to −3° with valgus stress). 5/57(9%) patients had a mean MFT angle of 6.4°(0° to 7°) with valgus stress, and were considered to have been over-corrected. There were no extension deficits. Conclusions: Navigation allows us to quantify soft tissue balancing based upon the initial kinematics with varus and valgus stress testing. From these measurements, an algorithm was developed, which showed that an appropriate release was made in 52/57 (91%) patients, but this may require some adjustment to reduce the number of outlying results

Abstract. Background. Multi-ligament knee injury is a rare but severe injury. Treatment strategies are challenging for most orthopedic surgeons & optimal treatment remains controversial. The purpose of our study was to assess clinico-radiological and functional outcomes after surgical management of multi-ligament knee injuries & to determine factors that could predict outcome of surgery. Materials And Method. It is a prospective observational study of 30 consecutive patients of Multi-ligament knee injury conducted between 2018–2020. All patients were treated surgically with single-stage reconstruction of all injured ligaments and followed standardized postoperative rehabilitation protocol. All patients were evaluated for Clinical (VAS score, laxity stress test, muscle-strength, range of motion), Radiological (stress radiographs) & Functional (Lysholm score) outcomes three times-preoperatively, post-operative 3 & 12 months. Results. At final follow up mean VAS score was 0.86±0.77. The anteroposterior & valgus-varus stress test showed ligament laxity >10mm (GradeD) in 93.3% patient which improved to <3mm (normal, GradeA) in 90% patients. Most patients (83.3%) had preoperative-range <100° and muscle strength of MRC Grade-3 which improved to >120° and muscle strength of MRC grade-5 at final followup. Lysholm score was poor (<64) in all patients preoperatively and improved to good (85–94) in 73.3%, excellent (>95) in 20% & fair (65–84) in 6.6% patients. The stress radiographs showed stable results for anterior/posterior & varus/valgus stress. All patients returned to their previous work. Factors that could predict outcomes of surgery are age, timing of surgery, type of surgery & associated injury. Conclusion. Early complete single stage reconstruction can achieve good functional results with overall restoration of sports & working capacity. Positive predictive factors for good outcome are younger age, early surgery & appropriate rehabilitation

Alignment of total joint replacement in the valgus knee can be done readily with intramedullary alignment and hand-held instruments. Intramedullary alignment instruments usually are used for the femoral resection. The distal femoral surfaces are resected at a valgus angle of 5 degrees. A medialised entry point is advised because the distal femur curves toward valgus in the valgus knee, and the distal surface of the medial femoral condyle is used as reference for distal femoral resection. In the valgus knee, the anteroposterior axis is especially important as a reliable landmark for rotational alignment of the femoral surface cuts because the posterior femoral condyles are in valgus malalignment, and are unreliable for alignment. Rotational alignment of the distal femoral cutting guide is adjusted to resect the anterior and posterior surfaces perpendicular to the anteroposterior axis of the femur. In the valgus knee this almost always results in much greater resection from the medial than from the lateral condyle. Intramedullary alignment instruments are used to resect the proximal tibial surface perpendicular to its long axis. Like the femoral resection, resection of the proximal tibial surface is based on the height of the intact medial bone surface. After correction of the deformity, ligament adjustment is almost always necessary in the valgus knee. Stability is assessed first in flexion by holding the knee at 90 degrees and maximally internally rotating the extremity to stress the medial side of the knee, then maximally externally rotating the extremity to evaluate the lateral side of the knee. Medial opening greater than 4mm, and lateral opening greater than 5mm, is considered abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be abnormally tight. Stability is assessed in full extension by applying varus and valgus stress to the knees. Medial opening greater than 2mm is considered to be abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be too tight. Release of tight structures should be done in a conservative manner. In some cases, direct release from bone attachment is best (popliteus tendon); in others, release with pie-crusting technique is safe and effective. In knees that are too tight laterally in flexion, but not in extension, the LCL is released in continuity with the periosteum and synovial attachments to the bone. When this lateral tightness is associated with internal rotational contracture, the popliteus tendon attachment to the femur is also released. The iliotibial band and lateral posterior capsule should not be released in this situation because they provide lateral stability only in extension. The only structures that provide passive stability in flexion are the LCL and the popliteus tendon complex, so knees that are tight laterally in flexion and extension have popliteus tendon or LCL release (or both). Stability is tested after adjusting tibial thickness to restore ligament tightness on the lateral side of the knee. Additional releases are done only as necessary to achieve ligament balance. Any remaining lateral ligament tightness usually occurs in the extended position only, and is addressed by releasing the iliotibial band first, then the lateral posterior capsule, if needed. The iliotibial band is approached subcutaneously and released extrasynovially, leaving its proximal and distal ends attached to the synovial membrane. In knees initially too tight laterally in extension, but not in flexion, the LCL and popliteus tendon are left intact, and the iliotibial band is released. If this does not loosen the knee enough laterally, the lateral posterior capsule is released. The LCL and popliteus tendon rarely, if ever, are released in this type of knee. Finally, the tibial component thickness is adjusted to achieve proper balance between the medial and lateral sides of the knee. Anteroposterior stability and femoral rollback are assessed, and posterior cruciate substitution is done, if necessary, to achieve acceptable posterior stability

Fibular head avulsion fractures represent a significant injury to the posterolateral corner of the knee. There is a high rate of concomitant injuries including rupture of the cruciate ligaments. Surgical fixation is indicated to restore stability, protect repaired or reconstructed cruciate ligaments and possibly decrease the likelihood of degenerative change. The current presentation describes a novel technique which provides secure fixation to the fibular head, restoring integrity of the posterolateral ligament complex and facilitating early motion. We also present a case series of our experience by a single surgeon at our tertiary referral center. Twenty patients underwent open reduction and internal fixation between 2006 and 2016 using a large fragment cannulated screw and soft tissue washer inserted obliquely from the proximal fibula to tibia. Fixation was augmented with suture repair of the lateral collateral ligament and biceps tendon. The orientation of the fracture was assessed based on preoperative imaging. Repair / reconstruction of concomitant injuries was performed during the same procedure. Early range of motion was initiated at 2 weeks postoperatively under physical therapy guidance. All patients returned for clinical and radiographic assessment (average 3.5 years). All fractures went on to bony union. There were no reoperations for recurrent instability. All patients regained functional range of motion with mean extension of 0.94 degrees and mean flexion of 121.4 degrees. Two patients underwent hardware removal. One patient developed a late local infection, which occurred greater than 5 years after surgery. Eleven patients underwent postoperative varus stress radiographs which demonstrated less than 1 mm difference between the operated and contralateral side. Fracture morphology typically demonstrated an oblique pattern in the coronal plane and a transverse pattern in the sagittal plane. This study represents a novel surgical technique for the repair of fibular head avulsion fractures with a large fragment cannulated screw placed obliquely from the fibula to tibia. Fixation is augmented with a soft tissue washer and suture repair. Our results suggest that this technique allows for early range of motion with maintenance of reduction, high rates of union, and excellent postoperative stability

The preoperative prediction of gap balance after robotic total knee arthroplasty (TKA) is difficult. The purpose of this study was to evaluate the effectiveness of a new method of achieving balanced flexion-extension gaps during robotic TKA. Fifty one osteoarthritic patients undergoing cruciate retaining TKA using robotic system were included in this prospective study. Preoperative planning was based on the amount of lateral laxity in extension and flexion using varus stress radiograph. After complete milling by the robot and soft tissue balancing, intra-operative extension and flexion gaps were measured using a tensioning device. Knees were subdivided into three groups based on lateral laxities in 0° and 90° of flexion, as follows; the tight extension group (≥ 2mm smaller in extension than flexion laxity), the tight flexion group (≥ 2mm smaller in flexion than extension laxity), and the balanced group (< 2mm difference between laxities). In addition, intra-operative gap balance results were classified as acceptable (0–3mm larger in flexion than in extension), tight (larger in extension than in flexion) or loose (> 3mm larger in flexion than in extension) based on differences between extension and flexion gaps. During preoperative planning, 34 cases were allocated to the balanced group, 16 to the tight extension group and 1 case was allocated to the tight flexion group. Intra-operative gap balance was acceptable in 46 cases, 4 cases had a tight result, and one case had a loose flexion gap. We concluded that preoperative planning based on the amount of lateral laxity determined using varus stress radiographs may be useful for predicting intraoperative gap balance and help to achieve precise gap balance during robotic TKA

Introduction. Acquiring adaptive soft-tissue balance is one of the most important factors in total knee arthroplasty (TKA). However, there have been few reports regarding to alteration of tolerability of varus/valgus stress between before and after TKA. In particular, there is no enough data about mid-flexion stability. Based on these backgrounds, it is hypothesized that alteration of varus/valgus tolerance may influence post-operative results in TKA. The purpose of this study is an investigation of in vivo kinematic analyses of tolerability of varus/valgus stress before and after TKA, comparing to clinical results. Materials and Methods. A hundred knees of 88 consecutive patients who had knees of osteoarthritis with varus deformity were investigated in this study. All TKAs (Triathlon, Stryker) were performed using computer assisted navigation system. The kinematic parameters of the soft-tissue balance, and amount of coronal relative movement between femur and tibia were obtained by interpreting kinematics, which display graphs throughout the range of motion (ROM) in the navigation system. Femoro-tibial alignments were recorded under the stress of varus and valgus before the procedure and after implantation of all components. In each ROM (0, 30, 60, 90, 120 degrees), the data of coronal relative movement between femur and tibia (tolerability) were analyzed before and after implantation. Furthermore, correlations between tolerability of varus/valgus and clinical improvement revealed by ROM and Knee society score (KSS) were analyzed by logistic regression analysis. Results. Evaluation of soft tissue balance with navigation system revealed that the tolerance of coronal relative movement between femur and tibia (varus/valgus) after implantation was significantly decreased compared with before implantation even in mid-flexion range. There were no significant correlations between tolerability of coronal relative movement and improvement of extension range and KSS. However, mid-flexion tolerability showed negative correlation with flexion range. Discussion. One of the most important principles for ligament balancing in TKA for varus knees is involved that the medial extension gap should be within 1–3mm to avoid flexion contracture and a feeling of instability, the medial flexion gap should be equal or 1–2mm larger to the medial extension gap, and lateral extension laxity up to 5 degrees is acceptable. However, there have been few reports measuring laxity from 30 to 60 degrees. In this study, the tolerance of coronal relative movement was significantly limited even in mid-flexion. However, mid-flexion tightness was not significantly correlated with clinical results except for flexion range. This result might be suggested that high tolerability of coronal relative movement in mid-flexion range may lead to widening of flexion range of motion of the knee after TKA. For any figures or tables, please contact authors directly

It is recommended in the TKA operation to balance the tension of soft tissues to make the rectangular gap in both flexion and extension because significant imbalance may result in eccentric stress on the polyethylene insert. However, no intensive research has been done on the medial and lateral laxity of the normal knee. X-ray of 50 normal knees were taken under the varus or valgus stress in both extension and flexion at 80 degrees. The angle of lines on the femoral condyles and tibia plateau was measured. The same methods were also done for the 20 osteoarthritis knees. In extension of the normal knees, the mean angle was 5.06 degrees in varus stress and was 2.46 degrees in valgus stress. In flexion of the normal knees, the mean angle was 5.04 degrees in varus stress and was 1.82 degrees in valgus stress. Therefore, the lateral laxity was significantly larger than the medial laxity in both extension and flexion (p< 0.0001). The lateral laxity was significantly larger also in osteoarthritis knees (p< 0.0001). There are some arguments about the priority to make the perfect rectangular gaps. The methods to measure the tension of soft tissues during the operation are not accurate and does not always reflect the post-operative tensions. Furthermore, the tension during the operation may be different from dynamic phase such as walking and standing. The present study showed that the mediolateral laxity was asymmetrical in the normal knees. This imbalance may be necessary for the medial pivot movement of the normal knee. These results suggest that a slight lateral laxity is acceptable during TKA operation and may be beneficial to achieve the normal kinematics especially for the cruciate retaining prosthesis

Purpose of the study: Achieving correct ligament balance for total knee arthroplasty remains a serious challenge, even for the experienced surgeon. Computer-assisted surgery allows real time assessment of the knee joint behavior and gives continuous measures of HKA under stress. Material and methods: Between January 2003 and November 2004, 25 patients with osteoarthritis of the knee joint underwent computer-assisted surgery for implantation of posterior stabilized total knee prosthesis. The series included 13 right knees and 12 left knees in 8 men and 17 women, mean age 73.6±8.1 years, age range 44–84 years. Body mass index was 29±5.5 (range 21.6–42.7). The IKS function score was 35.8±17 (range 5–70) and the IKS knee score was 51.2±8.5 (range 30–73). Measurements were made for varus and valgus stress of 0–30°. Extensive lateral or medial release was also performed for six knees. The medial parapatellar approach with removal of osteophytes was used for all procedures. Results: Preoperatively, four patients presented valgus (185.6±4.7, range 182–191°), one correct alignment and 20 presented varus (174±3.45, range 166–178°). Pre-operatively the mean varus stress angle was 5.13±3.44 (range 0–11°), the mean valgus stress angle was 1.5±1.53, range −4 to 4°). At the end of the procedure, the varus stress angle 1.78±1.59 (0–5°) and the valgus stress angle 1.79±1.6 (0–4°). At 45 days, mean flexion was 115±10° (range 60–126°). There was mobilization in two patients, one with a 5° extension deficit and the other with an extension deficit less than 10°. Discussion: This study demonstrates the usefulness of navigation systems to assess the effect of peripheral release and to limit the extent of release procedures (six of 25 patients). Materializing step by step release of the peripheral structures is helpful in achieving correct release. Conclusion: This work confirms that extensive release is not always necessary. This type of technique should allow better control and fine tuning of ligament balance and tension. This work was supported by work on cadaver specimens measuring the step by step effect of ligament release

Background. In recent literatures, medial instability after TKA was reported to deteriorate early postoperative pain relief and have negative effects on functional outcome. Furthermore, lateral laxity of the knee is physiological, necessary for medial pivot knee kinematics, and important for postoperative knee flexion angle after cruciate-retaining total knee arthroplasty (CR-TKA). However, the influences of knee stability and laxity on postoperative patient satisfaction after CR-TKA are not clearly described. We hypothesized that postoperative knee stability and ligament balance affected patient satisfaction after CR-TKA. In this study, we investigated the effect of early postoperative ligament balance at extension on one-year postoperative patient satisfaction and ambulatory function in CR-TKAs. Materials & Methods. Sixty patients with varus osteoarthritis (OA) of the knee underwent CR-TKAs were included in this study. The mean age was 73.6 years old. Preoperative average varus deformity (HKA angle) was 12.5 degrees with long leg standing radiographs. The knee stability and laxity at extension were assessed by stress radiographies; varus-valgus stress X-ray at one-month after operation. We measured joint separation distance (mm) at medial compartment with valgus stress as medial joint opening (MJO), and distance at lateral compartment with varus stress as lateral joint opening (LJO) at knee extension position. To analyze ligament balance; relative lateral laxity comparing to the medial, varus angle was calculated. New Knee Society Score (NKSS) was used to evaluate the patient satisfaction at one-year after TKA. We measured basic ambulatory functions using 3m timed up and go test (TUG) at one-year after surgery. The influences of stability and laxity parameters (MJO, LJO and varus angle at extension) on one-year patient satisfaction and ambulatory function (TUG) was analyzed using single linear regression analysis (p<0.01). Results. MJOs at knee extension one-month after TKA negatively correlated to patient satisfaction (r=−0.37, p<0.01) and positively correlated to TUG time (r=0.38, p<0.01). LJOs at knee extension had no statistically significant correlations to patient satisfaction and TUG. The extension varus angle had significant positive correlation with patient satisfaction (r=0.40, p<0.01). Discussions. In our study, we have found significant correlations of the early postoperative MJOs at extension to postoperative patient satisfaction and TUG one-year after CR-TKA. Our results suggested that early postoperative medial knee stabilities at extension were important for one-year postoperative patient satisfaction and ambulatory function in CR-TKA. Other interest finding was that postoperative patient satisfaction was positively correlated with extension varus angle. This finding suggested that varus ligament balance; relative lateral laxity to medial stability, was beneficial for postoperative patient satisfaction after CR-TKA. Intra-operative soft tissue balance had been reported to significantly affect postoperative knee stabilities. Therefore, with our findings, surgeons might be better to manage intra-operative soft tissue balance to preserve medial stability at extension with permitting lateral laxity, which would enhance patient satisfaction and ambulatory function after CR-TKA for varus type OA knee. Conclusion. Early postoperative medial knee stability and relative lateral laxity would be beneficial for patient satisfaction and function after CR-TKA

Poor soft tissue balance in total knee arthroplasty (TKA) is one of the most primary causes of dissatisfaction and reduced joint longevity, which are associated with postoperative instability and early implant failure. 1. Therefore, surgical techniques, including mechanical instruments and 3-D guided navigation systems, in TKA aim to achieve optimum soft tissue balancing in the knee to improve postoperative outcome. 2. Patella-in-Place balancing (PIPB) is a novel technique which aims to restore native collateral ligament behaviour by preserving the original state without any release. Moreover, reduction of the joint laxity compensates for the loss of the visco-elastic properties of the cartilage and meniscus. Following its clinical success, we aimed to evaluate the impact of the PIPB technique on collateral ligament strain and laxity behaviour, with the hypothesis that PIPB would restore strains in the collateral ligaments. 3. . Eight fresh-frozen cadaveric legs were obtained (KU Leuven, Belgium, H019 2015-11-04) and CT images were acquired while rigid marker frames were affixed into the femur, and tibia for testing. After carefully removing the soft tissues around the knee joint, while preserving the joint capsule, ligaments, and tendons, digital extensometers (MTS, Minnesota, USA) were attached along the length of the superficial medial collateral ligament (MCL) and lateral collateral ligament (LCL). A handheld digital dynamometer (Mark-10, Copiague, USA) was used to apply an abduction or adduction moment of 10 Nm at fixed knee flexion angles of 0°, 30°, 60° and 90°. A motion capture system (Vicon Motion Systems, UK) was used to record the trajectories of the rigid marker frames while synchronized strain data was collected for MCL/LCL. All motion protocols were applied following TKA was performed using PIPB with a cruciate retaining implant (Stryker Triathlon, MI, USA). Furthermore, tibiofemoral kinematics were calculated. 4. and combined with the strain data. Postoperative tibial varus/valgus stresses and collateral ligament strains were compared to the native condition using the Wilcoxon Signed-Rank Test (p<0.05). Postoperative tibial valgus laxity was lower than the native condition for all flexion angles. Moreover, tibial valgus of TKA was significantly different than the native condition, except for 0° (p=0.32). Although, tibial varus laxity of TKA was lower than the native at all angles, significant difference was only found at 0° (p=0.03) and 90° (p=0.02). No significant differences were observed in postoperative collateral ligament strains, as compared to the native condition, for all flexion angles, except for MCL strain at 30° (p=0.02) and 60° (p=0.01). Results from this experimental study supported our hypotheses, barring MCL strain in mid-flexion, which might be associated with the implant design. Restored collateral ligament strains with reduced joint laxity, demonstrated by the PIPB technique in TKA in vitro, could potentially restore natural joint kinematics, thereby improving patient outcomes. In conclusion, to further prove the success of PIPB, further biomechanical studies are required to evaluate the success rate of PIPB technique in different implant designs

Abstract

Robotic-assisted total knee arthroplasty (TKA) has proven higher accuracy, fewer alignment outliers, and improved short-term clinical outcomes when compared to conventional TKA. However, evidence of cost-effectiveness and individual superiority of one system over another is the subject of further research. Despite its growing adoption rate, published results are still limited and comparative studies are scarce. This review compares characteristics and performance of five currently available systems, focusing on the information and feedback each system provides to the surgeon, what the systems allow the surgeon to modify during the operation, and how each system then aids execution of the surgical plan.

Cite this article: Bone Jt Open 2023;4(1):13–18.

INTRODUCTION. Aseptic loosening is the most common failure mode for Total Elbow Arthroplasty (TEA) and is considered to be associated with accelerated polyethylene bearing wear [1, 2]. This study aimed to evaluate three commercially available implant designs under loads associated with daily living. The hypothesis was that more recent designs (Discovery and Nexel) provide greater articular contact areas resulting in lower polyethylene stresses compared to the Coonrad/Morrey (CM). METHODS. Motion tracking was performed on a healthy volunteer during elbow flexion at 0, 45, and 90° shoulder abduction because most daily activities occur with some shoulder abduction [3] resulting in varus stress about the elbow. This kinematic data was used in an OpenSim upper extremity musculoskeletal model [4] to estimate muscle and joint reaction loads with 5lb in hand, consistent with the common clinical restrictions following TEA. Computer aided assemblies of the smallest size implants for each system were imported to ANSYS for finite element analysis. Metallic components were treated as rigid and polyethylene components were modeled using a nonlinear elastoplastic constitutive model calibrated to material data. Articular contacts were frictional. Physiologic joint reaction forces and moments quantified in OpenSim were applied and the resulting peak articular contact area and peak bearing von Mises stresses were assessed. RESULTS. Simulated deformation patterns of CM bearings corresponded well to those reported in retrievals studies [1, 2] supporting the clinical relevance of the modeling approach. Peak stresses for CM and Nexel were consistently found in the central and side bearings respectively. The central bearing stresses remained 2–2.6 times lower in Nexel compared to CM. Peak stress for all three TEA systems increased with shoulder abduction (Fig.1, 2). Highest peak stresses (Fig.2) were obtained in CM and consistently exceeded the polyethylene yield limit; CM showed the lowest contact area (Fig.3). Nexel and Discovery experienced peak polyethylene stresses 26–34% and 17–39% lower than CM respectively (Fig.2). DISCUSSION. Our results support the hypothesis that newer TEA systems provide increased articular contact area and reduced bearing stresses during physiological loading. The cylindrical CM central bearing carries both the joint reaction force and moment leading to edge loading and high stresses (Fig.1). The design of the Nexel central bearing provides limited resistance to varus-valgus moment, thus transferring the moment to the side bearings and reducing central bearing stresses. The hemispherical Discovery bearing design was confirmed to offer a large articular contact area. However, non-concentricity of the contact spheres can lead to edge loading and high polyethylene stresses under off-axis forces. CM and Discovery utilize conventional polyethylene, whereas Nexel utilizes highly cross-linked Vitamin-E polyethylene. This study does not account for the increased wear resistance of Vitamin-E as compared to conventional polyethylene [5]. Long term clinical data are needed to demonstrate how these wear properties, as well as the geometric design which has been shown to impact stresses and contact patterns, translate to in vivo performance. For figures, please contact authors directly

Severely varus deformed knees are common in Asian countries due to lifestyles such as sitting on the floor. MCL release is essential for encountering severe varus deformity. However, conventional subperiosteal MCL release for severe varus deformity can cause the complete detachment of MCL and it can induce mid-flexion instability. We performed medial epicondylar osteotomy when conventional subperiosteal MCL release couldn't resolve tight medial gap of severely varus deformity. The epicondyle is reattached with #5 nonabsorbable sutures or screws (figure 1). This study evaluated the clinical and radiologic results of medial epicondylar osteotomy for severe varus TKA. From 2004 to 2012, 63 cases (of total 909 cases of primary TKA, 6.9%) with a minimum follow-up of 2 years (24 to 116 months) were included in this study. Two cases of 63 cases were excluded due to the loss of follow up. Intraoperative medial and lateral gap difference in flexion and extension was accepted at less than 2 mm. Average follow up was 50.6±29.8 months (24–116 months). Average clinical knee score was 35.5±17.1 preoperatively and 89.1±8.4 postoperatively. Average function score improved from 48.7±16.0 preoperatively to 88.6±8.0 postoperatively. Average flexion contracture was reduced from 8.5±9.8° preoperatively to 1.0±2.3° postoperatively and range of motion improved from 112.0±21.8° preoperatively to 118.9±13.3° postoperatively. Preoperative femorotibial angle was average varus 10.4±5.7° and mechanical axis was average varus 16.7±5.6°. Postoperative femorotibial angle was average valgus 5.5±3.4° and mechanical axis was average varus 1.0±4.1° (figure 2). Valgus stress radiographs showed average 1.6±0.7 mm gap (femoral implant to liner) and varus stress radiographs revealed average 2.7±1.5 mm gap. The difference with medial and lateral gaps was average 1.2±1.1 mm (figure 2). Unions of bony wafer were 39 bony and 22 fibrotic unions (figure 3). According to the difference with medial and lateral gaps, bony union was average 1.2±1.2 mm and fibrotic union was average 1.2±0.9 mm. There were no significant differences between bony and fibrotic union groups. The clinical and radiological results of medial epicondylar osteotomy are satisfactory in severe varus TKA. The stability with bony and fibrotic unions is not different

The elevation of the joint line is considered a possible cause of mid-flexion instability in total knee arthroplasty (TKA). The authors evaluated the effects of joint line change on mid-flexion stability in cruciate retaining TKA. Seventy-nine knees treated by cruciate retaining TKA using a modified balanced gap technique were included in this prospective study. After prosthesis insertion, valgus and varus stabilities were measured under valgus and varus stress using a navigation system at 0, 30, 60 and 90° of knee flexion. Changes of joint lines were measured preoperatively and postoperatively and compared. The knees were allocated to a “No change group (≤4mm, 62 patients)” or to an “Elevation group (>4mm, 17 patients)”. Medio-lateral stabilities (defined as the sums of valgus and varus stabilities measured intra-operatively) were compared in the two groups. The mean joint line elevation was 4.6mm in the no change group and 1.7mm in the elevation group. Mean medio-lateral stability at 30° of knee flexion was 4.8±2.3 mm in the no change group and 6.3±2.7 mm in the elevation group, and these values were significantly different (p = 0.02). However, no significant differences in medio-lateral stability were observed at other flexion angles (p>0.05). Knees with a < 5mm joint line elevation provide better mid-flexion stability after TKA. The results of this study suggest that a < 5mm elevation in joint line laxity is acceptable for cruciate retaining TKA

Purpose. Locking plate constructs for proximal humerus fractures can fail due to varus collapse, especially in the presence of osteoporosis and comminution of the medial cortex. Augmentation using a fibular allograft as an intramedullary bone peg may strengthen fixation preventing varus collapse. This study compared the ability of the augmented locking plate construct to withstand repetitive varus stresses relative to the non-augmented construct in cadaveric specimens. Method. Proximal humerus fractures with medial comminution were simulated by performing wedge-shaped osteotomies at the surgical neck in cadaveric specimens. For each cadaver (n=8), one humeral fracture was fixated with the locking plate construct alone and the other with the locking plate construct plus ipsilateral fibular autograft augmentation. The humeral head was immobilized and a repetitive, medially-directed load was applied to the humeral shaft until failure (significant construct loosening or humeral head screw pull-out). Results. No augmented construct failed, withstanding either 20 000 cycles or five times the cycles of the contralateral non-augmented construct [average (standard deviation) = 27958 (4633) cycles], while six of the eight non-augmented constructs failed (p=0.007). Failure in the six non-augmented constructs occurred after an average of 5928 (2543) cycles. Conclusion. Fibular allograft augmentation increased the ability of the locking plate construct to withstand repetitive varus loading. Clinically, this may assist proximal humerus fracture fixation in osteoporotic bone with medial cortex comminution

Introduction. This study was performed prospectively and randomly to compare clinical outcomes of modified-Brostrom procedure using single and double suture anchor for chronic lateral ankle instability. Material & Methods. Forty patients were followed up for more than 2 years after modified-Brostrom procedure for chronic lateral ankle instability. Twenty modified-Brostrom procedures with single suture anchor and 20 procedures with double suture anchor randomly assigned were performed by one surgeon. The mean age was 30.6 years, and the mean follow-up period was 2.6 years. The clinical evaluation was performed according to the Karlsson scale and Sefton grading system. The measurement of talar tilt angle and anterior talar translation was performed through anterior and varus stress radiographs. Results. At the last follow-up, the Karlsson scale had improved significantly from preoperative average 45.4 points to 90.5 points in single suture anchor group, from 46.2 points to 91.3 points in double suture anchor group. There were 8 excellent, 10 good, and 2 fair results according to the Sefton grading system in single anchor group, and 9 excellent, 8 good, 3 fair results in double anchor group. Therefore, 18 cases (90%) in single anchor group and 17 cases (85%) in double anchor group achieved satisfactory results. Talar tilt angle had improved significantly from preoperative average 15.7° to 6.1° in single anchor group, from 16.8° to 4.2° in double anchor group. There was significant difference in postoperative talar tilt angle between single and double anchor group. Conclusion. Significant differences in clinical and functional outcomes were not found between single and double suture anchor technique. On stress radiographs for evaluation of mechanical stability, modified-Brostrom procedure using double anchor showed less talar tilt angle than single anchor technique

Introduction. In total knee arthroplasty (TKA), component realignment with bone-based surgical correction (BBSC) can provide soft tissue balance and avoid the unpredictability of soft tissue releases (STR) and potential for more post-operative pain. Robotic-assisted TKA enhances the ability to accurately control bone resection and implant position. The purpose of this study was to identify preoperative and intraoperative predictors for soft tissue release where maximum use of component realignment was desired. Methods. This was a retrospective, single center study comparing 125 robotic-assisted TKAs quantitatively balanced using load-sensing tibial trial components with BBSC and/or STR. A surgical algorithm favoring BBSC with a desired final mechanical alignment of between 3° varus and 2° valgus was utilized. Component realignment adjustments were made during preoperative planning, after varus/valgus stress gaps were assessed after removal of medial and lateral osteophytes (pose capture), and after trialing. STR was performed when a BBSC would not result in knee balance within acceptable alignment parameters. The predictability for STR was assessed at four steps of the procedure: Preoperatively with radiographic analysis, and after assessing static alignment after medial and lateral osteophyte removal, pose capture, and trialing. Cutoff values predictive of release were obtained using receiver operative curve analysis. Results. STR was necessary in 43.5% of cases with medial collateral ligament (MCL) release being the most common. On preoperative radiographs, a medial tibiofemoral angle (mTFA) ≤177° predicted MCL release (AUC = 0.76. p< 0.01) while an mTFA ≥188° predicted ITB release (AUC = 0.79, p <0.01). Intraoperatively after removal of osteophytes, a robotically assessed mechanical alignment (MA) ≥8° varus predicted MCL release (AUC = 0.84. p< 0.01) while a MA ≥2° valgus (AUC = 0.89, p< 0.01) predicted ITB release. During pose-capture, in medially tight knees, an extension gap imbalance ≥2.5mm (AUC = 0.82, p <0.01) and a flexion gap imbalance ≥2.0mm (AUC = 0.78, p <0.01) predicted MCL release while in laterally tight knees, any extension or flexion gap imbalance >0 mm predicted ITB release (AUC = 0.84, p <0.01 and AUC = 0.82, p <0.01 respectively). During trialing, in medially tight knees, a medial>lateral extension load imbalance ≥18 PSI (AUC = 0.84. p< 0.01) and a flexion load imbalance ≥ 35 PSI (AUC = 0.83, p< 0.01) predicted MCL release while, in laterally tight knees, a lateral>medial extension load imbalance ≥3 PSI (AUC = 0.97, p< 0.01) or flexion load imbalance ≥ 9.5 PSI (AUC = 0.86, p< 0.01) predicted ITB release. Of all identified predictors, load imbalance at trialing had the greatest positive predictive value for STR. Conclusion. There are limitations to the extent that TKA imbalance that can be corrected with BBSC alone if one has a range of acceptable alignment parameters. The ability to predict STR improves from pose-capture to trialing stages during detection of load imbalance. Perhaps this may be due to posterior osteophytes that are still present at pose capture. Further investigation of the relationship between the presence, location and size of posterior osteophytes and need for STR during TKA is necessary

Computer-assisted technology has provided surgeons with intra-operative quantitative measurement tools that have led to the development of soft-tissue balancing algorithms based on surgeon-applied varus-valgus stress. Unfortunately these forces tend not to be standardised and the resultant algorithms may at best be surgeon-specific. Furthermore, these techniques are only available intra-operatively and rely on the rigid fixation of trackers to bone. The aim of this study was to develop a non-invasive computer-assisted measurement technique and assess the variation in collateral knee laxity measurements between different clinicians. An image-free navigation system was adapted for non-invasive use by developing external mountings for active infrared trackers. A leg model with rigid tracker mountings was designed and manufactured for comparison. Multiple kinematic registrations of alignment were made for both the model and the right leg of a volunteer to quantify the soft tissue artefacts. Repeatability of the system was assessed by performing two registration processes on eight volunteers. Collateral knee laxity was assessed on a single volunteer by 16 participants of varying experience each applying a maximum varus and valgus knee stress. Two surgeons performed repeated examinations to assess intra-observer variation. For repeated registrations of alignment, the SD of the non-invasive mounting (0.8°) was only a third higher than the leg model (0.6°) and the actual range was only 1° larger. The repeated alignment measurements on the volunteers showed a high level of agreement with an intraclass correlation coefficient of 0.93. Varus-valgus stress values showed poor inter-observer variation with a wide range of angles for both varus (1° to 7°) and valgus stress (0.5° to 5°). A Mann-Whitney test between the two sets of repeated tests showed that both varus stress and overall laxity were significantly different (p< 0.0001) but that valgus stress was marginal (p=0.052). Intra-observer measurements overall appeared more consistent. Soft tissue artefacts did not significantly reduce the repeatability of the assessment of coronal knee alignment using a navigation system and this provided a non-invasive technique for assessing coronal knee laxity. The perception of an ‘end-point’ varied significantly between different clinicians and although there may be a role for surgeon-specific algorithms, to use this quantitative data more widely there is a need to standardise the forces and moments applied