Fixation of periprosthetic femur fractures with the less invasive stabilization system (LISS)--a new minimally invasive treatment with locked fixed-angle screws

The Less Invasive Stabilization System (LISS) is a minimally invasive technique indicated for fixation of periprosthetic fractures. This new system allows percutaneous placement of cortical-shaft screws and fixation of the fracture with fixed-angle locked screws with minimal surgical exposure of the mostly osteoporotic bone and without disturbance of the existing total joint replacement. Immediate range-of-motion exercises are begun postoperatively. A retrospective clinical review of 5 patients (2 total hip arthroplasties, 3 total knee arthroplasties) was performed to describe indications, surgical technique, intra- and postoperative complications and patient follow-up. Indications are periprosthetic distal femur fractures, per- and supracondylar fractures. Contraindications are none, except existing medical comorbidities. Extraarticular fractures were treated via stab incisions over the lateral femoral condyle. Fractures with intraarticular displacement were fixed via an anterolateral parapatellar approach to the knee joint. After anatomic reduction of femoral condyles, articular fragments are fixed with Kirschner wires, followed by closed reduction aligning the articular fragments controlling length, axis and rotation. The LISS is introduced proximally under the M. vastus lateralis along the femur. It is fixed with self-drilling cortical shaft screws, locked fixed-angle screws both proximally and distally. Range-of-motion exercises are begun on the second day postoperatively. Time to full weight bearing averaged 6-8 weeks depending on clinical and radiological findings. Benefits of the LISS technique include the minimally invasive approach with increased primary stability using monocortical fixings thus eliminating the need for spongiosaplasty and blood transfusion. Disadvantages of the percutaneous placement of the LISS include malplacement on the femur, proximal screw pull-out and postoperative rotational and axial malalignment.     

Distal femoral fractures and LISS stabilization

In recent years, the technique of surgical stabilization in the distal femur has changed. This change decreased the number of non unions and the need for bone grafting. Minimally invasive surgical techniques with a submuscular plate placement have replaced the emphasis on anatomical reduction in the shaft area. Reconstruction of complex articular injuries has been simplified by more direct visualization of the articular surface with the lateral peripatellar approach. Problems remaining are surgical technique and implant considerations. The Less Invasive Stabilization System (LISS) simplifies the surgical technique for percutaneous plate osteosynthesis. An insertion guide is used to insert monocortical, self-tapping screws through a stab incision. A thread in the plate provides the angular stability for the anchoring of these screws. In extra-articular fractures and simple intra-articular fractures, the distal femoral nail permits intramedullary stabilization. A spiral blade improves fixation of the distal femoral condylar block. Despite the enhanced surgical technique and implant possibilities, a great number of patients show a functional deficiency. These are particularly patients with complex intra-articular fractures. The 'fatigue failure' of the osteoporotic implant-bone construct is a problem in elderly patients. The LISS represents a good option to avoid the addition of bone cement to an osteosynthesis.     

LISS钢板治疗股骨远端C型骨折

目的 探讨LISS钢板固定治疗股骨远端C型骨折的临床疗效及手术要点.方法对22例股骨远端C型骨折患者采用LISS钢板固定,骨缺损者一期植骨.结果 22例均获随访,时间12~24个月,骨折均愈合.膝关节功能按Kolmert评分标准：优8例,良11例,可3例.结论 对股骨远端C型骨折采用LISS钢板固定,既能使骨折达到关节面解剖复位,又提供有效稳定的固定,是治疗股骨远端C型骨折的良好方法.     

Biomechanical evaluation of the less invasive stabilization system and the 95-degree angled blade plate for the internal fixation of distal femur Fractures in human cadaveric bones with high bone mineral density

BACKGROUND: The less invasive stabilization system (LISS) is an internal fixator that utilizes unicortical locked screws for fixation of distal femur fractures. A question is whether locked unicortical screw fixation is sufficient, when compared with a standard implant such as a blade plate. METHODS: Eight matched pairs of fresh-frozen cadaveric femora were instrumented with either the LISS or a 95-degree blade plate. A 4-cm supracondylar gap fracture model was created and all bone-implant constructs were tested to failure in axial loading. RESULTS: All constructs failed by plastic deformation of the implant. There was no significant difference between the LISS and the blade plate constructs with respect to load to failure. CONCLUSIONS: Despite unicortical fixation axial loading to failure of the LISS did not result in implant/screw pull-out neither proximally nor distally. However, there does not appear to be a biomechanical advantage of using the LISS as opposed to a blade plate in bones with high bone mineral density.     

Operative stabilization of supracondylar femur fractures above total knee arthroplasty: a comparison of four treatment methods

Periprosthetic fractures of the distal femur above a total knee arthroplasty present a challenging surgical problem for orthopedic surgeons. Numerous operative and nonoperative treatment options exist including casting, Rush rods, supracondylar nails, and plate fixation. Potentially significant complications are associated with all current treatment alternatives. Plate or nail constructs frequently achieve limited distal fixation, leading to loss of fixation and varus angulation. This complication was not observed with the Less Invasive Stabilization System (LISS). In addition, our early results demonstrate the superiority of LISS treatment with low infection rates, no requirement for acute bone grafting, and secure fixation allowing for immediate postoperative mobilization. LISS fixation may offer a superior surgical treatment option for periprosthetic distal femur fractures.     

Distal femoral fracture fixation utilizing the Less Invasive Stabilization System (L.I.S.S.): the technique and early results

The treatment of supracondylar femoral fractures in the past three decades has evolved from non-operative to operative treatment. While operative fixation utilizing either plate fixation or rigid intramedullary nail fixation has improved patient outcomes, the problems of malunion, nonunion, need for bone grafting, joint stiffness, and infection persist. An emphasis on maintenance of the soft tissue envelope around fractures has improved efficacy in increasing osseous healing and decreasing infection. Out of this movement grew the concept of submuscular plating for distal femoral fractures, and subsequently L.I.S.S. fixation (Less Invasive Stabilization System) for distal femoral fractures. The technique and early results utilizing the L.I.S.S. for distal femoral fractures is described. The technique of L.I.S.S. fixation first begins with traditional direct visualization and internal fixation of the articular surface. Closed reduction is then performed on the metaphyseal / diaphyseal component of the fracture, followed by submuscular fixation utilizing the L.I.S.S. fixation. The L.I.S.S. can best be thought as an "internal" external fixator.     

LISS钢板治疗股骨远端骨折疗效分析

目的总结LISS钢板内固定治疗股骨远端闭合性骨折的疗效。方法34例股骨远端骨折患者,按AO分型：A型19例,B型5例,C型10例。股骨髁间骨折12例,股骨髁上骨折22例,均行LISS钢板内固定。结果本组术后发生深部感染1例,经切开引流、抗感染及再次钢板固定治愈;并发膝外翻1例,于术后4个月进行翻修治愈。本组均获随访,平均15（10～34）个月,骨折平均愈合时间为4．5（3～10）个月。疗效评价按HSS膝关节评分：优26例,良4例,可2例,差2例;优良率为88．2％。结论LISS钢板内固定治疗股骨远端骨折可以获得令人满意的疗效。     

Distal femur fractures with complex articular involvement: management by articular exposure and submuscular fixation

The A.O./O.T.A. C3 distal femur fracture is characterized by complex articular involvement and is often accompanied by a very short distal femur segment, small osteochondral fragments, and high-energy soft tissue disruption. Current fixation strategies do not provide for optimal visualization/reduction of the articular surface in conjunction with stable fixation of the distal femoral block. Malunion, loss of fixation, need for supplemental fixation, and need for bone grafting is common in the treatment of the C3 distal femur fracture. The transarticular percutaneous osteosynthesis technique, popularized by Krettek, et al, utilizes a lateral peripatellar approach for optimal articular visualization and submuscular fixation for minimal devitalization. In this article, its use is described, as well as reduction and fixation strategies for the articular surface.     

Treatment of distal femur fractures using the less invasive stabilization system: surgical experience and early clinical results in 103 fractures

OBJECTIVE: To summarize the complications and early clinical results of 123 distal femur fractures treated with the Less Invasive Stabilization System (LISS; Synthes, Paoli, PA). DESIGN: Retrospective analysis of prospectively enrolled patients. SETTING: Two academic level I trauma centers. SUBJECTS AND PARTICIPANTS: One hundred nineteen consecutive patients with 123 distal femur fractures (OTA type 33 and distal type 32 fractures) treated by 3 surgeons. One hundred three fractures (68 closed fractures and 35 open fractures) in 99 patients were followed up at least until union (mean follow-up = 14 months, range: 3-50 months). INTERVENTION: Surgical reduction and fixation of distal femur fractures. MAIN OUTCOME MEASUREMENTS: Perioperative complications, radiographic union, infection rate, loss of fixation, alignment, and range of motion. RESULTS: Ninety-six (93%) of 103 fractures healed without bone grafting. All fractures eventually healed with secondary procedures, including bone grafting (1 of 68 closed fractures and 6 of 35 open fractures). There were 5 losses of proximal fixation, 2 nonunions, and 3 acute infections. No cases of varus collapse or screw loosening in the distal femoral fragment were observed. Malreductions of the femoral fracture were seen in 6 fractures (6%). The mean range of knee motion was 1 degrees to 109 degrees . CONCLUSIONS: Treatment of distal femur fractures with the LISS is associated with high union rates without autogenous bone grafting (93%), a low incidence of infection (3%), and maintenance of distal femoral fixation (100%). No loss of fixation in the distal femoral condyles was observed despite the treatment of 30 patients older than 65 years. The LISS is an acceptable surgical option for treatment of distal femoral fractures.     

Operative treatment of acute distal femur fractures: systematic review of 2 comparative studies and 45 case series (1989 to 2005)

BACKGROUND: The incidence of distal femur fractures is approximately 37 per 100,000 person-years. Typically, distal femur fractures are caused by a high-energy injury mechanism in young men or a low-energy mechanism in elderly women. Managing these fractures can be a challenging task. Most surgeons agree that distal femur fractures need to be treated operatively to achieve optimal patient outcomes. The articular fracture component is usually treated with open reduction and internal lag screw fixation or external tension wire fixation (Illizarov). However, there is no consensus on the type of implant for the fixation of the metaphyseal-diaphyseal fracture component. OBJECTIVE: The aim of this study is to systematically summarize and compare the results of different fixation techniques (traditional compression plating, antegrade nailing, retrograde nailing, submuscular locked internal fixation, and external fixation) in the operative management of acute nonperiprosthetic distal femur fractures (AO/OTA type 33A and C) and the characteristics of the fractures for each treatment (articular/nonarticular and open/closed). Additionally an attempt was made to evaluate the impact of surgical experience on nonunion rate, fixation failure rate, deep infection rate, and secondary surgical procedure rate. In the context of this article compression plating relates to techniques/implants that require compression of the implant to the femoral shaft-it does not relate to interfragmentary compression.     

Successful results of minimally invasive surgery for comminuted supracondylar femoral fractures with LISS: comparative study of multiply injured and isolated femoral fractures

Background The aim of this prospective study was to compare the outcomes of distal femoral fractures treated by the Less Invasive Stabilization System (LISS) in multiply injured and isolated fracture cases. Methods This study comprised 26 patients (16 men, 10 women), who had 27 distal femoral fractures. Patients were divided into two groups; multiple injuries (group I) or isolated distal femoral fracture (group II). The average Injury Severity Score of group I was 26.7. Operations were performed according to biological fixation principles in a submuscular manner. No bone grafting was performed to enhance the healing. The cases were evaluated based on the criteria of Schatzker–Lambert and the modified Hospital for Special Surgery (HSS) scoring system. Results The mean follow-up period was 25.8 months. Union was achieved in all cases. Two patients in group I required débridement procedures due to deep infection. One of them healed completely but the other did not. The average range of knee motion of groups I and II at the last control were 112.8° and 121.8°, respectively. The mean modified HSS scores were 73.9 and 79.9, respectively. There was no significant difference in the HSS scores or the range of knee motion. The time to full weight bearing was longer in group I owing to the concomitant injuries. Conclusions We concluded that LISS is a useful method for comminuted supracondylar fractures with multiple trauma patients as the results showed no significant differences when compared with those of patients with isolated femoral fractures.     

LISS固定系统治疗股骨远端骨折

目的：探讨应用AO微创内固定系统（tass）治疗股骨远端骨折的临床效果。方法：应用LISS治疗股骨远端骨折15例,33-A2骨折2例,33-A3骨折5例,33-C2骨折5例,33-C3骨折3例;其中9例开放骨折均为Ⅱ～Ⅲ级,有4例患者为多发骨折患者,伤后4d（2～7d）应用LISS行内固定治疗。结果：所有患者随访3—19个月,骨折均连接,骨折愈合时间8～18周,未出现钢板螺钉松动移位、骨折塌陷、复位丢失等。股骨远端骨折15例,HSS评分优5例;良7例;可3例。膝关节活动范围70°-140°,所有患者膝关节行走无疼痛。结论：LISS能有效治疗各种分型的股骨远端骨折。     

Management of supracondylar fractures of the femur with the GSH intramedullary nail: preliminary report

The GSH supracondylar nail is a closed section rigid intramedullary device that combines the biomechanical advantages of intramedullary fixation with the stability of rigid internal fixation for the management of supracondylar fractures of the femur. The use of this implant is indicated in the management of distal comminuted nonarticular fractures and fractures with intraarticular extension. Intramedullary fixation provides improved fracture stabilization in both elderly patients with osteoporotic metaphyseal bone and in younger patients with extensively comminuted fractures. The experience with the GSH supracondylar nail has shown that it provides better results than supracondylar plating for the stabilization of acute fractures or revision of failed internal fixation.     

The use of tibial Less Invasive Stabilization System (LISS) plate [AO-ASIF] for the treatment of paediatric supracondylar fracture of femur: a case report

Paediatric supracondylar fractures of the femur are not common. The treatment options depend on the age of child, the site of the fracture, the pattern of injury and the surgeon's preference. We report a case of an 11-year old boy who sustained a comminuted displaced supracondylar fracture of the femur and was treated with indirect reduction and internal fixation with the Less Invasive Stabilization System (LISS) tibial plate.     

应用LISS治疗下肢骨不连的初步报告

目的报告应用微创内固定系统(LISS)治疗股骨及胫骨骨不连的初步临床效果。方法自2003年2月～2004午8月间，应用LISS固定与植骨治疗5例股骨下段骨折小连接，4例胫骨上段骨折不愈台；其中内固定失效7例，外固定治疗火败和感染各1例；病程10～111个月，平均29个月。结果个部患随访6～16个月，平均8个月；骨折均住术后4～6个月牢固连接，平均愈合时间4．7个月，无内植入物松动等并发症。结论LISS因其先进的设计，能有效治疗股骨下段和胫骨上段骨折不连接。     

Intra-articular Fracture Pattern in Intercondylar Distal Femur Fractures: An Analysis of Frequency and Major Fracture Fragments

IntroductionThe treatment of intercondylar distal femur fractures requires anatomic reduction of intra-articular fragments and absolute fixation. Preoperative planning is necessary to understand fracture morphology. All fracture lines need to be recognized as the primary implant may not capture all articular fragments, mainly when coronal plane fractures are present. Oftentimes, independent interfragmentary compression screws are necessary. No recent studies have visually mapped out the distal femur articular fracture fragments necessary for absolute fixation. The objectives of this study are to determine the frequency of coronal plane fractures in intercondylar distal femur fractures and describe the pattern of intra-articular fracture fragments.Materials and MethodsThe hospital's trauma registry was queried for distal femur ORIF CPT codes logged in the past four years. A retrospective chart review was performed using the EMR and CT scans. Demographics and mechanisms of injury were analyzed. Fracture fragments were surveyed and drawn out by hand on a template for easy organization. Patients’ fractures were categorized into the following groups: fractures with no intra-articular coronal plane fractures, those with medial coronal fractures, those with lateral coronal fractures, or those with both medial and lateral coronal fractures. Major fracture fragments were identified.ResultsA total of 55 patients were included. 26 patients (47%) were found to have no intra-articular coronal plane fractures; 6 patients (11%) were found to have medial coronal plane fractures; 15 patients (27%) were found to have lateral coronal plane fractures, and 8 patients (15%) had medial and lateral coronal plane fractures. Collectively, intra-articular coronal plane fractures were identified in 29 patients (53%) with intercondylar distal femur fractures. Four major fracture fragments along with intercondylar and condylar comminution sites were identified.DiscussionDistal femur intra-articular coronal plane fractures can yield large anterior and posterior condylar fracture fragments of either the medial condyle, lateral condyle, or both condyles. Coronal plane fracture fragments must be identified to obtain absolute fixation. Our study found a higher coronal plane fracture line frequency (52.7%) than prior commonly cited studies. Surgeons must be on the lookout for anterior fracture fragments, posterior fracture fragments, and articular comminution when treating intercondylar femur fractures.     

Internal Fixation of Distal Femur Fractures with the Less Invasive Stabilizing System (LISS)

Objective Stable internal fixation of distal femur with an implant resisting angular forces. The technique is minimally invasive, relies on a monocortical screw fixation and obviates the need for bone grafting. Indications Distal femur fractures of types A and C according to the AO classification. Periprosthetic femur fractures after total knee and hip arthroplasty. Contraindications Local infection, osteitis. Surgical Technique For intraarticular fractures: anterolateral parapatellar approach to the knee joint, anatomic reduction and temporary fixation of the articular fragments with Kirschner wires. Closed reduction aligning the block of articular fragments with the shaft. Submuscular introduction of the LISS plate with the help of an aiming device and its adaptation of the femur. Through stab incisions the screws are inserted leading to a stable anochorage of the plate. For extraarticular fractures: stab incisions over the lateral femoral condyle. Results In a prospective study, results of 54 fresh fractures of the distal femur in 51 patients (28 men, 23 women) operated between February 1997 and February 2000 could be assessed. The patients' average age at the time of infury was 53 (20-93) years. 48 patients suffered from type 33 fractures. Six type 32 fractures were encountered. Ten fractures were open. Six patients fractured their femur above or below a total joint replacement. We noted the following complications: one heterotopic ossification, two deep thrombophlebites with lung embolism and three infections. A loosening of the proximal screws occurred in four patients. 40 patients could be followed up clinically and radiologically, of these 32 after more than 6 months and 27 after more than 1 year. The Neer score of the 27 patients examined after >1 year amounted to an average of 73.9 (33-88) points, with six excellent, 14 satisfactory, six unsatisfactory results and one poor result. The Lysholm score amounted to 80.5 (40-100) points.     

The effect of plate rotation on the stiffness of femoral LISS: a mechanical study

OBJECTIVE: Malposition of the femoral Less Invasive Stabilization System (LISS) plate may alter its biomechanical behavior. This study compares the mechanical stability of "correctly" affixed LISS plates matching the slope of the lateral femoral condyle to "incorrectly" placed LISS plates fixed in external rotation relative to the distal femur. METHODS: A fracture gap model was created to simulate a comminuted supracondylar femur fracture (AO/OTA33-A3). Fixation was achieved using two different plate positions: the LISS plate was either placed "correctly" by internally rotating the plate to match the slope of the lateral femoral condyle, or "incorrectly" by externally rotating the plate relative to the distal femur. Following fixation, the constructs were loaded in axial, torsional, and cyclical axial modes in a material testing machine. MAIN OUTCOME MEASUREMENT: Stiffness in axial and torsional loading; total deformation and irreversible (plastic) deformation in cyclical axial loading. RESULTS: The mean axial stiffness for the correctly placed LISS constructs was 21.5% greater than the externally rotated LISS constructs (62.7 N/mm vs. 49.3 N/mm; P = 0.0007). No significant difference was found in torsional stiffness between the two groups. Cyclical axial loading caused significantly less (P < 0.0001) plastic deformation in the correct group (0.6 mm) compared with externally rotated group (1.3 mm). All the constructs in the incorrect group failed, where failure was defined as a complete closure of the medial fracture gap, prior to completion of the test cycles. CONCLUSION: Correct positioning of the LISS plate for fixation of distal femur fractures results in improved mechanical stability as reflected by an increased stiffness in axial loading and decreased plastic deformation at the bone-screw interface.     

Nailing versus plating for comminuted fractures of the distal femur: a comparative biomechanical in vitro study of three implants

Purpose

The purpose of our study was to determine the biomechanical properties of three different implants utilized for internal fixation of a supracondylar femur fracture. The retrograde supracondylar nail (SCN), the less invasive stabilization system plate (LISS) and the distal femoral nail (DFN) were tested and their biomechanical properties compared.

Methods

Twenty pairs of fresh-frozen human femura were used. Each femur was osteotomised to simulate a comminuted supracondylar fracture (AO/OTA 33.A3) and then randomized to fracture fixation with either SCN (n=9) or LISS (n=9). Each contralateral femur was stabilized with DFN as a control (n=18). Two femur pairs were spent on pretesting. All femura were subjected to axial (10–500 N) and torsional (0.1–14 Nm) loading.

Results

Eighteen matched femur pairs were analyzed. The post-loading median residual values were 49.78, 41.25 and 33.51% of the axial stiffness of the intact femur and 59.04, 62.37 and 46.72% of the torsional stiffness of the intact femur in the SCN, LISS and DFN groups. There were no significant differences between the three implants concerning axial and torsional stiffness.

Conclusions

All implants had sufficient biomechanical stability under physiological torsional and axial loading. All three implants have different mechanisms for distal locking. The SCN nail with the four-screw distal interlocking had the best combined axial and torsional stiffness whereas the LISS plate had the highest torsional stiffness.     

LISS--不仅仅是一项骨折微创内固定的技术

生物学固定技术概念的提出,应运而生了很多内固定设计,其中LISS是“生物力学固定技术(BO)”的典型代表。LISS实现了微创,明显提高了手术治疗股骨远端、胫骨近端、假体周围及骨质疏松性骨折的临床效果。然而LISS的应用的手术技巧还需提高,LISS的应用适应证和适应范围还有待探索,LISS内固定的改善、骨折愈合的机制还有待于研究。