Isometric Graft Research Articles

Medial Patellofemoral Ligament Reconstruction Using Adductor-Transfer and Adductor-Sling at Nonanatomic Femoral Attachment Sites Leads to Unfavorable Graft-Length Change Patterns: A Descriptive Biomechanical Study

To compare the graft length change patterns in nonanatomic adductor-transfer (AT) and adductor-sling (AS) medial patellofemoral ligament (MPFL) reconstruction with those in anatomic MPFL reconstruction (MPFLR) and to investigate the favorable isometric ranges (FIRs) of knee flexion. Eight small fresh-frozen cadaveric knees were mounted in a knee-customized jig with tensioned muscles to measure graft length changes from two patellar points to four femoral attachments using a linear variable displacement transducer. Femoral attachments were at the MPFL footprint center (MPFL-C) in anatomic MPFLR, adductor magnus (AM) footprint center (AM-C) in AT, and at 5-mm (AM-5) or 10-mm (AM-10) points proximal to AM-C in AS. The FIRs of these femoral attachments were determined after zeroing the graft length changes at different initial fixation angles. Anatomic MPFL-C resulted in almost isometric graft length changes from 0° to 90°. At AM-C, the graft length changes displayed an increase from 0° to 45° and significantly greater length changes than those at MPFL-C from 60° to 90°. The graft length changes at both AM-5 and at AM-10 continuously increased with knee flexion angles and presented significantly larger graft length changes than those at MPFL-C and at AM-C from 30° to 90° and 60° to 90°, respectively. After zeroing graft length changes at different fixation angles, the FIRs of the MPFL-C covered all knee flexion angles, regardless of the patellar attachments and initial fixation angles. Moreover, with the smaller FIRs of AM-C observed at any fixation angle when compared with MPFL-C, fixing the graft at 0° to 30° in AT allowed the FIRs to cover the whole functional flexion range. However, the significantly larger graft length changes of both AM-5 and AM-10 resulted in extremely limited FIRs at any fixation angle. Anatomic MPFL-C resulted in a favorable graft length change range (less than 2 mm) at 0° to 90° of knee flexion, which was close to the isometric graft behavior. However, nonanatomic attachments of AM-C in AT, and both AM-5 and AM-10 in AS caused significant anisometric graft length change patterns and limited FIRs. Moreover, AT had a smaller range of graft length change but wider FIRs compared to AS, indicating superior graft behavior for MPFLR. Anatomic MPFLR is preferable for the treatment of in skeletally immature patients, followed in preference by nonanatomic AT. Nonanatomic AS should be performed cautiously.

Biomechanical Analysis of Ideal Knee Flexion Angle for ACL Graft Tensioning Utilizing Multiple Femoral and Tibial Tunnel Locations.

Anterior cruciate ligament (ACL) graft failure rate has been reported to be greater than 5% at 5 years. Our study evaluated ACL excursion with anatomic and nonanatomic femoral and tibial tunnels to determine optimal flexion angle to tension the ACL to minimize excursion. Ten cadaveric knee specimens were used. The ACL was sectioned and the femoral and tibial attachments were marked. A 1/16-inch drill created a tunnel in the center of the ACL footprint on the tibia and femur and additional tunnels were made 5 mm from this. A suture was passed through each tunnel combination and attached to a string potentiometer. The knee was ranged from full extension to 120 degrees of flexion for 10 cycles while mounted in a custom fixture. The change in length (excursion) of the suture during movement was recorded for each combination of femoral and tibial tunnels. Anatomic reconstruction of the ACL with tunnel placement in the center of the femoral and tibial footprint did not result in an isometric graft, with excursion of the ACL during knee motion of 7.46 mm (standard deviation [SD]: 2.7mm), greatest at 2.84 degrees of flexion (SD: 4.22). The tunnel combination that resulted in the least excursion was a femoral footprint 5 mm anterior to the femoral and 5 mm posterior to the tibial footprint (4. 2mm, SD: 1.37 mm). The tunnel combination that resulted in the most excursion utilized femoral footprint 5 mm proximal to the femoral and 5 mm posterior to the tibial footprint (9.81 mm, SD: 2.68 mm). Anatomic ACL reconstruction results in significant excursion of the ACL throughout motion. If not tensioned properly, the ACL can stretch during range of motion, potentially leading to rerupture. To prevent stretching of the graft, the current biomechanical study recommends tensioning an anatomic ACL reconstruction at its point of maximal excursion, or between 0 and 5 degrees of flexion. The level of evidence is IV.

Biomechanical analysis of ideal knee flexion angle for ACL graft tensioning utilizing multiple femoral and tibial tunnel locations

Objectives:Despite more anatomic reconstruction of the ACL, graft failure rate has been reported to be greater than 5% at 5 years. There is concern that anatomic reconstructions may not result in an isometric graft and may predispose the graft to stretching. The current biomechanical study evaluated excursion of the ACL with different drill points for both femoral and tibial tunnels. The purpose was to evaluate the excursion of the ACL with both anatomic and non-anatomic tunnel combinations and determine the optimal flexion angle to tension the ACL to minimize stretching of the graft during motion.Methods:Ten cadaveric knee specimens, mid-femur to mid-tibia, were dissected of skin and subcutaneous tissue. The ACL was sectioned and the femoral and tibial attachments were marked prior to excision. A 1/16 inch drill was used to create a tunnel in the center of the ACL footprint on the tibia and femur and additional tunnels were made 5mm from the original tunnel (Figure 1). A suture was passed through each tunnel combination (Femur A-F; Tibia A-E) and was attached to a string potentiometer. The knee was ranged from full extension to 120 degrees of flexion for 10 cycles while mounted in a custom fixture that measured angle of flexion in the sagittal plane. The change in length (excursion) of the suture during movement was recorded for each combination of femoral and tibial tunnels.Results:Anatomic reconstruction of the ACL with tunnel placement in the center of the femoral (femoral tunnel A) and tibial (tibial tunnel A) footprint did not result in an isometric graft, with excursion of the ACL during knee motion of 7.46mm (SD 2.7mm). The tunnel combination that resulted in the least amount of excursion during knee motion was a reconstruction with a femoral footprint 5mm anterior to the femoral (femoral tunnel D) and 5mm posterior to the tibial footprint (tibial tunnel D) (4.2mm, SD 1.37mm). The tunnel combination that resulted in the most amount of excursion during knee motion was utilized femoral footprint 5mm proximal to the femoral (femoral tunnel F) and 5mm posterior to the tibial footprint (tibial tunnel D) (9.81mm, SD 2.68mm). In an anatomic tunnel placement, we found the angle with the most excursion of the ACL to occur at 2.84 degrees of flexion (SD 4.22).Conclusions:Anatomic ACL reconstruction results in significant excursion of the ACL during range of motion. If not tensioned properly, the ACL can stretch during range of motion, potentially leading to re-rupture. In order to prevent stretching of the graft, the current biomechanical study recommends tensioning an anatomic ACL reconstruction at its point of maximal exertion, or about 10 degrees of flexion. We also determined optimal flexion angles for tensioning the ACL for tunnel combinations that may be non-anatomic.

Comparison of Ligament Isometry and Patellofemoral Contact Pressures for Medial Patellofemoral Ligament Reconstruction Techniques in Skeletally Immature Patients

Background: Adult medial patellofemoral ligament (MPFL) reconstruction techniques are not appropriate for the skeletally immature patient given the proximity of the distal femoral physis. Biomechanical consequences of reconstructions aimed at avoiding the physis have not been adequately studied. Purpose: To quantify the biomechanical effects of MPFL reconstruction techniques intended for skeletally immature patients. Study Design: Controlled laboratory study Methods: Four MPFL reconstruction techniques were evaluated using a computationally augmented cadaveric model: (1) Schoettle point: adult-type reconstruction; (2) epiphyseal: socket distal to the femoral physis; (3) adductor sling: graft wrapped around the adductor tendon; (4) adductor transfer: adductor tendon transferred to patella. A custom testing frame was used to cycle 8 knees for each technique from 10° to 110° of flexion. Patellofemoral kinematics were recorded using a motion camera system, contact stresses were recorded using Tekscan pressure sensors, and MPFL length was computed using an inverse kinematics computational model. Change in MPFL length, patellar facet forces, and patellar kinematics were compared using generalized estimating equation modeling. Results: Schoettle point reconstruction was the most isometric, demonstrating isometry from 10° to 100°. The epiphyseal technique was isometric until 60°, after which the graft loosened with increasing flexion. The adductor sling and adductor transfer techniques were significantly more anisometric from 40° to 110°. Both grafts tightened with knee flexion and resulted in significantly more lateral patellar tilt versus the intact state in early flexion and significantly higher contact forces on the medial facet versus the epiphyseal technique in late flexion. Conclusion: In this cadaveric simulation, the epiphyseal technique allowed for a more isometric ligament until midflexion, when the patella engaged within the trochlear groove. The adductor sling and adductor transfer grafts became tighter in flexion, resulting in potential loss of motion, pain, graft stretching, and failure. Marginal between-condition differences in patellofemoral contact mechanics and patellar kinematics were observed in late flexion. Clinical Relevance: In the skeletally immature patient, using an epiphyseal type MPFL reconstruction with the femoral attachment site distal to the physis results in a more isometric graft compared with techniques with attachment sites proximal to the physis.

Anatomic is better than isometric posterior cruciate ligament tunnel placement based upon in vivo simulation.

To elucidate the effects of various tibial and femoral attachment locations on the theoretical length changes and isometry of PCL grafts in healthy knees during in vivo weightbearing motion. The intact knees of 14 patients were imaged using a combined magnetic resonance and dual fluoroscopic imaging technique while the patient performed a quasi-static lunge (0°-120° of flexion). The theoretical end-to-end distances of the 3-dimensional wrapping paths between 165 femoral attachments, including the anatomic anterolateral bundle (ALB), central attachment and posteromedial bundle (PMB) of the PCL, connected to an anterolateral, central, and posteromedial tibial attachment were simulated and measured. A descriptive heatmap was created to demonstrate the length changes on the medial condyle and formal comparisons were made between the length changes of the anatomic PCL and most isometric grafts. The most isometric graft, with approximately 3% length change between 0° and 120° of flexion, was located proximal to the anatomic femoral PCL attachments. Grafts with femoral attachments proximal to the isometric zone decreased in length with increasing flexion angles, whereas grafts with more distal attachments increased in length with increasing flexion angles. The ALB and central single-bundle graft demonstrated a significant elongation from 0° to 120° of flexion (p < 0.001). The PMB decreased in length between 0° and 60° of flexion after which the bundle increased in length to its maximum length at 120° (p < 0.001). No significant differences in length changes were found between either the ALB or PMB and the central graft, and between the ALB and PMB at flexion angles ≥ 60° (n.s.). The most isometric attachment was proximal to the anatomic PCL footprint and resulted in non-physiological length changes. Moving the femoral attachment locations of the PCL significantly affected length change patterns, whereas moving the tibia locations did not. The importance of anatomically positioned (i.e., distal to the isometric area) femoral PCL reconstruction locations to replicate physiological length changes is highlighted. These data can be used to optimize tunnel positioning in either single- or double-bundle and primary or revision PCL reconstruction cases. IV.

A Novel Medial Collateral Ligament Reconstruction Technique Using Internally Braced Semitendinosus Autograft.

Medial collateral ligament reconstruction is often performed in knees with multiligamentous injury, and numerous techniques have been previously described. A novel method of internally bracing and reconstructing the medial collateral ligament with a semitendinosus autograft is described. This provides several advantages, including reproducible isometric graft placement, optimized fixation strength, and internal bracing. [Orthopedics. 2018; 41(5):e738-e740.].

The Effect of Humeral and Ulnar Tunnel Placement on Achieving UCL Graft Isometry

Objectives:The elbow medial ulnar collateral ligament (UCL) is frequently injured in throwing athletes, most commonly baseball pitchers. When conservative management fails, surgical intervention can allow the athlete to return to sport. While extensive research has been devoted to UCL graft incorporation and outcomes based on varying surgical techniques, there is a paucity of literature available addressing optimal bone tunnel placement in achieving medial UCL graft isometry. The purpose of this study is to assess the effect of humeral and ulnar bone tunnel placement on achieving UCL graft isometry through elbow range-of-motion.Methods:Ten fresh-frozen cadaveric upper extremities were dissected to expose the native UCL in its entirety. Three equidistant humeral and ulnar tunnels were created at each UCL footprint. Suture was passed between nine possible tunnel combinations for each elbow affixed to an isometry guage. Each elbow was moved through a 120-degree arc of motion for each tunnel combination at 0, 30, 60, 90, and 120 degrees. Measured changes in isometry gauge tension were recorded and analyzed using one-way analysis of variance (ANOVA) with Tukey’s HSD for pairwise comparisons. A p-value of 0.05 was used to determine significance for all tests.Results:There was an overall significant effect (p < 0.0001) of tunnel placement at all degrees of flexion measured. Pairwise comparisons revealed increases in displacement between the central and posterior tunnel positions of the medial epicondyle, with significant differences (p=0.0009) occurring when paired with both the central and posterior aspect of the sublime tubercle. Profound differences (p < 0.0001) were noted between the anterior and posterior humeral tunnel positions. No significant differences noted between ulnar tunnel locations at any humeral location. Figure 1: Tunnel placement in the central part of the medial epicondyle (Centralepi) was generally the most isometric grouping, with Centralepi - Anteriortub being the most isometric combination of all. Data are represented as mean +/- SEM.Conclusion:Isometric graft placement of the medial elbow UCL is undoubtedly dependent upon optimal tunnel placement and even slight deviations from the native centroid at either the medial epicondyle or sublime tubercle can possibly lead to early graft failure or abnormal joint kinematics. This information can aid surgeons in performing isometric single bone tunnel UCL reconstruction or repair procedures in the future.

An In Vivo Prediction of Anisometry and Strain in Anterior Cruciate Ligament Reconstruction – A Combined Magnetic Resonance and Dual Fluoroscopic Imaging Analysis

To evaluate the invivo anisometry and strain of theoretical anterior cruciate ligament (ACL) grafts in the healthy knee using various socket locations on both the femur and tibia. Eighteen healthy knees were imaged using magnetic resonance imaging and dual fluoroscopic imaging techniques during a step-up and sit-to-stand motion. The anisometry of the medial aspect of the lateral femoral condyle was mapped using 144 theoretical socket positions connected to an anteromedial, central, and posterolateral attachment site on the tibia. The 3-dimensional wrapping paths of each theoretical graft were measured. Comparisons were made between the anatomic, over the top (OTT), and most-isometric (isometric) femoral socket locations, as well as between tibial insertions. The area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. The most isometric attachment site was found midway on the Blumensaat line with approximately 2% and 6% strain during the step-up and sit-to-stand motion, respectively. Posterior femoral attachments resulted in decreased graft lengths with increasing flexion angles, whereas anterodistal attachments yielded increased lengths with increasing flexion angles. The anisometry of the anatomic, OTT and isometric grafts varied between tibial insertions (P < .001). The anatomic graft was significantly more anisometric than the OTT and isometric graft at deeper flexion angles (P < .001). An area of least anisometry was found in the proximal-distal direction just posterior to the intercondylar notch. ACL reconstruction at the isometric and OTT location resulted in nonanatomic graft behavior, which could overconstrain the knee at deeper flexion angles. Tibial location significantly affected graft strains for the anatomic, OTT, and isometric socket location. CLINICALRELEVANCE: This study improves the knowledge on ACL anisometry and strain and helps surgeons to better understand the consequences of socket positioning during intra-articular ACL reconstruction.

Aircast Award for Basic Science - The Effect of Dynamic Changes in ACL Graft Force on Soft Tissue ACL Graft-Tunnel Incorporation

Objectives:Anterior cruciate ligament grafts that are placed for reconstruction are subject to complex forces with joint motion. Current “anatomic” ACL reconstructions result in greater in situ graft forces. The biologic effect of changing magnitudes of ACL graft force on graft-tunnel osseointegration is not completely understood. The objective of the present study is to determine the effects of dynamic mechanical ACL graft tension or load on graft-tunnel incorporation.Methods:One hundred male Sprague-Dawley rats underwent unilateral ACL resection followed by reconstruction with a soft tissue autograft. The animals were allocated into one of three groups during surgery: (1) ACL reconstruction followed by limb immobilization for the entire duration of the study, (2) ACL reconstruction with a "high-tension" ACL graft and daily knee motion, or (3) ACL reconstruction with an "isometric" low-tension ACL graft and daily knee motion. ACL graft isometry was assessed intraoperatively. External fixators were used to eliminate graft load during cage activity. Daily knee motion was then started on post-operative day 3 for all animals that were allocated to a knee motion group using a custom computerized knee flexion device. Graft-tunnel healing was assessed at 3 and 6 weeks via biomechanical, micro-CT, and histologic analyses. Biomechanical and micro-CT data was analyzed using ANOVA with significance set at p<0.05.Results:Intraoperative ACL graft force measurements demonstrated two distinct ACL graft curves (high-tension versus isometric ACL graft) were achieved with the two different femoral graft tunnel locations. At 90 degrees of knee flexion, there is a 1.6 fold increase in ACL graft force between a high-tension ACL graft and isometric ACL graft at the time of surgery. High ACL graft force with joint motion appeared to be deleterious to early ACL graft-tunnel incorporation. The load to failure for knees with high-tension ACL grafts (5.50 ± 2.30N) was significantly lower when compared to immobilized (10.90 ± 2.78N, p<0.01) and isometric grafts (9.91 ± 3.36N, p=0.01) at 3 weeks. At 6 weeks, isometric ACL grafts coupled with daily knee motion had greater load to failure than immobilized knees (24.16 ± 5.72N versus 16.56 ± 3.51N, p=0.01). Immobilized and isometric grafts had greater femoral bone volume fraction than knees with high-tension grafts at both 3 and 6 weeks (p<0.01 and p<0.001, respectively). Greater cellularity and collagen gaping were seen in loaded ACL graft (those that underwent motion) versus immobilized grafts, particularly within the tibial tunnel. Higher prevalence of osteoclasts were seen along the graft-tunnel interface in high-tension ACL grafts.Conclusion:There is limited data on how the ACL graft mechanical environment affects its healing. We were able to demonstrate that ACL graft-tunnel incorporation is sensitive to dynamic load from joint motion using a novel small animal model. ACL soft tissue grafts that experience higher in situ force have inferior early biomechanical properties. Maintaining graft isometry allows early joint motion without deleterious biomechanical consequences when compared to immobilized grafts in this animal model. Our findings regarding the effects of graft isometry may not only have clinical implications in terms of post-operative rehabilitation with modern anatomic ACL reconstructions, but it also raises questions regarding existing preclinical ACL healing studies where isometry may not have been considered.

Disadvantages and Advantages of Transtibial Technique for Creating the Anterior Cruciate Ligament Femoral Socket

Anterior cruciate ligament (ACL) femoral socket techniques have distinct advantages and disadvantages when considering the following techniques: transtibial, anteromedial portal, outside-in, and outside-in retroconstruction. There is no one perfect technique and we have an incomplete understanding of anatomical, biomechanical, isometry, stability, and clinical outcomes. Our primary focus is transtibial technique for creating the ACL femoral socket. Advantages include less invasive, isometric graft placement, stable Lachman exam, and minimal graft impingement with the tunnel and notch. Disadvantages include nonanatomic vertical graft placement that can cause rotational instability and positive pivot shift, interference screw divergence, graft-tunnel length mismatch, femoral socket constraint, posterior cruciate ligament impingement, and a short, oblique tibial tunnel that may undermine the medial plateau in an attempt to achieve anatomic ACL reconstruction.

Surgery for anterior cruciate ligament deficiency: a historical perspective

The anterior cruciate ligament (ACL) has entertained scientific minds since the Weber brothers provided biomechanical insight into the importance of the ACL in maintaining normal knee kinematics. Robert Adams described the first clinical case of ACL rupture in 1837 some 175years to date, followed by Mayo-Robson of Leeds who performed the first ACL repair in 1895. At that time, most patients presented late and clinicians started to appreciate signs and symptoms and disabilities associated with such injuries. Hey Groves of Bristol provided the initial description of an ACL reconstruction with autologous tissue graft in 1917, almost as we know it today. His knowledge and achievements were, however, not uniformly appreciated during his life time. What followed was a period of startling ingenuity which created an amazing variety of different surgical procedures often based more on surgical fashion and the absence of a satisfactory alternative than any indication that continued refinements were leading to improved results. It is hence not surprising that real inventors were forgotten, good ideas discarded and untried surgical methods adopted with uncritical enthusiasm only to be set aside without further explanation. Over the past 100years, surgeons have experimented with a variety of different graft sources including xenograft, and allografts, whilst autologous tissue has remained the most popular choice. Synthetic graft materials enjoyed temporary popularity in the 1980 and 1990s, in the misguided belief that artificial ligaments may be more durable and better equipped to withstand stresses and strains. Until the 1970s, ACL reconstructions were considered formidable procedures, often so complex and fraught with peril that they remained reserved for a chosen few, never gaining the level of popularity they are enjoying today. The increasing familiarity with arthroscopy, popularised through Jackson and Dandy, and enhancements in surgical technology firmly established ACL reconstruction as a common procedure within the realm of most surgeons' ability. More recently, the principle of anatomic ACL reconstruction, aiming at the functional restoration of native ACL dimensions and insertion sites, has been introduced, superseding the somewhat ill-advised concept of isometric graft placement. Double-bundle reconstruction is gaining in popularity, and combined extra- and intra-articular procedures are seeing a revival, but more accurate and reliable pre- and post-operative assessment tools are required to provide customised treatment options and appropriate evaluation and comparability of long-term results. Modern ACL surgery is united in the common goal of re-establishing joint homoeostasis with normal knee kinematics and function which may ultimately assist in reducing the prevalence of post-operative joint degeneration. This review hopes to provide an insight into the historical developments of ACL surgery and the various controversies surrounding its progress. Level of evidence V.

The use of intra-operative image intensifier control for the ACL surgeon

Tunnel placement during anterior cruciate ligament reconstruction surgery is an important factor in determining the outcome of surgery. Tibial and femoral tunnel placement depends on the experience of the operating surgeon in order to achieve an isometric graft position. We performed a case series to study how often tunnel placement was adequate, as perceived by the surgeon, and if intra-operative image guidance could improve tunnel position. Over 3 years, a single surgeon and his team operated on 55 patients using single bundle patellar tendon bone or hamstring graft. The surgeon placed the guidewires where he felt they would achieve an isometric graft position. A transtibial jig was used for femoral tunnel positioning. At each step, the guidewires were checked using an image intensifier and repositioned as necessary. The number of times that the guidewire position could be improved using the image intensifier was documented. Follow up was between 1 to 3 years. The tibial guidewire was repositioned in 13 out of 55 cases and the femoral guidewire in 16 out of 55 cases. Forty-five out of 55 patients returned to their pre injury state. There were no cases of graft failure in the follow up period. The study concludes that tunnel placement is not always successful despite the surgeon's perception of adequate placement. The use of an intra-operative image intensifier can help the surgeon to achieve accurate and reproducible tunnel placement in ACL reconstruction surgery. We recommend this technique to all surgeons carrying out such procedures.

Biomechanical Comparison of Medial Collateral Ligament Reconstructions Using Computer-Assisted Navigation

Background The medial collateral ligament is a broad ligament that functions as the primary stabilizer against valgus knee stress, particularly at 30° of flexion. Hypothesis A double-bundle reconstruction technique that better restores the native medial collateral ligament anatomy will restore valgus and external rotation stability to a medial collateral ligament–deficient knee. Study Design Controlled laboratory study. Methods Seven fresh-frozen cadaveric knees were studied. A surgical navigation system was used to determine valgus opening and external rotation at 0° and 30° with a 9.8-N·m valgus stress applied to the tibia graft isometry at multiple points on the tibia and femur. Intact and disrupted medial collateral ligament knees were used as controls. Four repair techniques were tested: Bosworth, modified Bosworth, anatomical single bundle, and anatomical double bundle. Results Complete sectioning of the medial collateral ligament resulted in an increase in valgus opening of 5° at 0° and 7.7° at 30°. External rotation increased 4.6° at 0° and 9.7° at 30°. Single-bundle techniques (Bosworth, anatomical single bundle) did not restore valgus laxity at 0° or 30°; the anatomical single bundle did not restore external rotation at 0°. Double-bundle techniques (modified Bosworth, anatomical double bundle) restored valgus laxity and external rotation to the native knee conditions at 0° and 30°. At 30°, the modified Bosworth was 0.3° tighter and the anatomical double bundle 0.2° tighter than was the intact knee. The center of the medial collateral ligament origin on the femur to the proximal insertion of the superficial medial collateral ligament resulted in the most isometric graft position. Conclusion Medial collateral ligament reconstruction configurations that use a double-bundle reconstruction better resist valgus and external rotations in response to valgus stress than do single-bundle techniques. Clinical Relevance Although the medial collateral ligament often heals without surgical intervention, surgical reconstruction is occasionally necessary in grade III medial collateral ligament and combined ligamentous injuries to the knee. Double-bundle reconstruction of the medial collateral ligament better resists valgus forces across the knee and may allow for better surgical outcome after medial collateral ligament reconstruction.

PCL reconstruction

We compared the ability of three different posterior cruciate ligament (PCL) reconstructions to restore normal anteroposterior laxity to the knee from 0 to 130° of knee flexion. Cadaver knees were tested intact, after PCL rupture or after bone-patellar tendon-bone grafting. Grafts were performed isometrically or with a single bundle representing the anatomical anterior PCL fibre bulk (aPC) or with a double bundle that added the posterior PCL fibre bulk (pPC). The grafts were tensioned to restore normal knee laxity at 60° of flexion, except for the pPC which was tensioned at 130°. The isometric graft led to overconstraint as the knee extended resulting in high graft tension in extension and excess laxity in flexion. The aPC graft matched normal laxity from 0 to 60° of flexion but was lax from 90 to 130° of flexion. Only the double-bundled graft could restore normal knee laxity across the full range of flexion.

Knee extension and its relationship to the slope of the intercondylar roof. Implications for positioning the tibial tunnel in anterior cruciate ligament reconstructions.

This study determined that knee extension (range, -30 degrees to 2 degrees) and the slope of the intercondylar roof (range, 26 degrees to 46 degrees) vary widely between knees in both men and women. We found a weak relationship between knee extension and the slope of the intercondylar roof (r2 = 0.207); therefore, roof angle cannot be predicted by clinically measuring knee extension. CLINICAL RELEVANCE; A knee with a given degree of extension can have a variety of different slopes to the intercondylar roof. Knees with the combination of hyperextension and a vertically oriented slope to the intercondylar roof are "unforgiving" because they require a more posterior position for the tibial tunnel to avoid roof impingement and an extensive roofplasty. If the surgical objective is to minimize the extent of the roofplasty and avoid roof impingement, then consideration should be given to customizing the placement of the tibial tunnel to account for variability in knee extension and roof angle when reconstructing the anterior cruciate ligament. Studies have shown that isometric graft placement can be achieved with this surgical approach.

Anterior Cruciate Ligament Reconstruction Stability With Continuous Passive Motion

A comparison was made of the stability of isometric versus nonisometric anterior cruciate ligament (ACL) reconstructions when subjected to immediate postoperative continuous passive motion (CPM). Anterior cruciate ligament reconstructions were performed on 13 anatomic specimen knees using bone/patellar tendon/bone grafts. Nine ACL substitutions were considered isometric with maximum graft length changes of less than 1 mm. Four ACL substitutions were nonisometric with graft length changes of 3 mm or greater resulting from tightening in flexion. The specimens were subjected to CPM through 0 degrees-95 degrees knee flexion. Knee stability was remeasured with a knee arthrometer at three and 14 days after beginning CPM. All four nonisometric specimens had failed within three days, with increased anterior laxity of 2-9 mm in both the Lachman (20 degrees) and anterior drawer (90 degrees) positions. All nine isometric reconstructions successfully retained pre-CPM anterior stability within 1 mm after 14 days of CPM. This investigation illustrates the importance of isometric graft placement for ACL reconstruction success. Continuous passive motion does not appear to adversely affect immediate ACL-substitute integrity or fixation if graft placement is isometric (less than 1 mm of graft excursion through 0 degrees-110 degrees of knee motion). Continuous passive motion may cause graft deformation, fixation failure, or both, with resultant loss of knee stability if the graft is not isometrically positioned (greater than 3 mm of graft excursion resulting from tightening in flexion).

The relationship of the femoral attachment site to the isometric tracking of the anterior cruciate ligament graft.

The large number of reconstructive procedures in the treatment of ACL reflect a lack of consistent clinical success, thus creating the current controversy over the treatment of ACL injuries. The purpose of this study on the relationship of the femoral attachment site to the isometric tracking of the ACL graft was three-fold: 1) to develop a method for evaluating the femoral attachment site for the ideal isometric graft tracking pattern; 2) to develop a reference table comparing femoral attachment sites to graft excursion; and 3) to apply this information to the surgical procedure to allow for stepwise refinement of the attachment site for improved clinical results. To aid in graphic representation, the attachment sites were identified from radiographs by the sclerotic margin of the drill hole in the bone or the bone trough. These attachment sites were transferred to a trace diagram and compiled to form a composite diagram. Three distinct graft tracking patterns were identified. Group I represented the modified "over-the-top" technique with a deep cancellous bone trough and represented the most isometric tracking. Group II represented the modified over-the-top technique with a shallow or no cancellous bone trough and Group III the drill hole technique. Groups II and III were nonisometric. In surgery, palpation of the graft for excursion while performing a range of motion allows for review of isometric graft tracking. Stepwise intraoperative refinement of the femoral attachment site can result in isometric graft tracking.