Objectives

This study investigated the biomechanical performance of decellularized porcine superflexor tendon (pSFT) grafts of varying diameters when utilized in conjunction with contemporary ACL graft fixation systems. This aimed to produce a range of ‘off-the-shelf’ products with predictable mechanical performance, depending on the individual requirements of the patient.

In the UK we have many surgeon inventors – surgeons who innovate and create new ways of doing things, who invent operations, who design new instruments to facilitate surgery or design new implants for using in patients. However truly successful surgeon inventors are a rare breed and they need to develop additional knowledge and skills during their career in order to push forward their devices and innovations. This article reviews my own experiences as a surgeon inventor and the highs and lows over the whole of my surgical career.

The biomechanical function of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL) remains controversial. Some studies report that the AM bundle stabilises the knee joint in anteroposterior (AP) translation and rotational movement (both internal and external) to the same extent as the PL bundle. Others conclude that the PL bundle is more important than the AM in controlling rotational movement.

The objective of this randomised cohort study involving 60 patients (39 men and 21 women) with a mean age of 32.9 years (18 to 53) was to evaluate the function of the AM and the PL bundles of the ACL in both AP and rotational movements of the knee joint after single-bundle and double-bundle ACL reconstruction using a computer navigation system. In the double-bundle group the patients were also randomised to have the AM or the PL bundle tensioned first, with knee laxity measured after each stage of reconstruction. All patients had isolated complete ACL tears, and the presence of a meniscal injury was the only supplementary pathology permitted for inclusion in the trial. The KT-1000 arthrometer was used to apply a constant load to evaluate the AP translation and the rolimeter was used to apply a constant rotational force. For the single-bundle group deviation was measured before and after ACL reconstruction. In the double-bundle group deviation was measured for the ACL-deficient, AM- or PL-reconstructed first conditions and for the total reconstruction.

We found that the AM bundle in the double-bundle group controlled rotation as much as the single-bundle technique, and to a greater extent than the PL bundle in the double-bundle technique. The double-bundle technique increases AP translation and rotational stability in internal rotation more than the single-bundle technique.

Objectives. We hypothesise that a long-term bioresorbable hydrophilic silkworm silk device, the SeriACL(tm) scaffold, can support the development and remodelling of native functional ligament tissue if designed to anticipate the remodelling curve of an ACL graft. This study evaluated the SeriACL scaffold for ACL replacement in a goat model at 3, 6 and 12 months. Methods. The ACL of 43 goats was replaced in an arthroscopically assisted procedure. The ACL was excised, a guide pin driven into the femur and 6mm diameter antegrade drilling performed. The tibial tunnel was drilled under direct visualisation. The graft was anchored around a post on the femur, tensioned to 50N and cycled 30x before tibial fixation with a staple and sutures around a post. Animals were clinically, mechanically and histologically evaluated. Results. The SeriACL graft did not induce acute inflammation, swelling or initial scar formation as indicated by rapidly declining pain and knee size scores. All animals were weight bearing at 3, 6 and 12 months, with 95% returning to normal gait by 6 months. Lachman showed the majority of knees were clinically stable with a normal range of motion at all times. No gross cartilaginous damage, synovitis or particulate debris in lymph nodes was observed. Collagen development throughout the graft and bone tunnels increased with time. Conversely, inflammation and device mass decreased with time. Fluoroscopy indicated no abnormal bone tunnel findings. Total IgG levels did not increase from pre-surgery levels. AP laxity indicated joint stability at all times. Implant abrasion was observed to varying extents yet mechanical testing revealed tissue development supported increased load bearing over time. Conclusions. The SeriACL graft supported autologous development of a mechanically robust, biologically viable ligament which stabilised the goat joint over a 12 month period. Mechanical, clinical and histological results indicated SeriACL graft safety with initial indications of efficacy

Anterior cruciate ligament (ACL) reconstruction allows overall good results, but there is still a significant rate of failure. It is well accepted that the main reason for ACL reconstruction failure is a misplacement of tibial or femoral tunnels. Conventional techniques rely mainly on surgical skill for intra-operative tunnel placement. It has been demonstrated that, even by experienced surgeons, there was a significant variation in the accuracy of tunnel placement with conventional techniques. Navigation systems might enhance the accuracy of ACL replacement. 10 cadaver knees with intact soft-tissue and without any intra-articular abnormalities were studied. We used a non image based navigation system (OrthoPilot ®, Aesculap, Tuttlingen, FRG). Localizers were fixed on bicortical screws on the distal femur and on the proximal tibia. Both kinematic and anatomic registration of the knee joint were performed by moving the knee joint in flexion-extension and palpating relevant intra- and extra-articular landmarks with a navigated stylus. The most anterior, posterior, medial and lateral point of both tibial and femoral attachment of the ACL were marked with metallic pins. The navigated stylus was positioned on these points, and the system recorded its position in comparison to the bone contours. Subsequently, we performed conventional plain AP and lateral X-rays and a CT-scan, and measured the position of the pins in comparison to the bone contours. Finally, all measurements were made again with a caliper after disarticulating the knee joint. We calculated the center of the footprint as the mid-point between the four pins of both tibial and femoral attachment for each measurement technique. All measurements were expressed as percentages of the bone size to compensate for the different sizes. There were no significant difference in the paired measurements of the location of the ACL footprints on both femur and tibia between anatomic, radiographic, CT-scan and navigated measurements. There was a significant correlation between the paired measurements of the location of the ACL footprints on both femur and tibia with either measurement techniques. Anatomic measurement is the gold standard experimental technique for the positioning of the ACL foot-print, and CT-scan measurement is currently the gold standard technique in clinical situation. According to this reference, the position of ACL attachments on the tibia and on the femur can be accurately defined by the navigation system. Intra-operative measurement of the location of the bone tunnels during ACL replacement with this navigation system should be accurate as well

Objectives: Advances in biomedical engineering have led to a thorough understanding of the body’s own capacity for ACL healing if provided the correct impetus—a long-term bioresorbable graft scaffold that anticipates the defect site’s biological and mechanical requirements. We hypothesize that by providing a structural scaffold which anticipates ACL repair mechanisms, “engineered” autologous ligament with excellent functional integrity can be developed by the body itself. This study evaluated the SeriACL™ graft, a non-mammalian derived long-term bioresorbable multi-bundled silk-based implant, for ACL replacement in a goat model at 3, 6 and 12 months post-operatively. Methods: The ACL of 43 goats was replaced with the SeriACL graft in an arthroscopically assisted procedure. The ACL was excised, a guide pin driven into the femur and 6mm diameter antegrade drilling performed. The tibial tunnel was drilled under direct visualization. The SeriACL, designed to mimic hamstring grafts, was anchored around a post on the femur. The graft was tensioned to 50N and cycled 30x before tibial fixation with a staple and sutures around a post. Animals were clinically, mechanically and histomorphometrically evaluated at 3, 6 and 12 months. Results: The SeriACL graft or surgical procedure did not induce early signs of acute inflammation, swelling or initial scar formation as indicated by rapidly declining scores for pain and knee size. All animals were weight bearing at 3, 6 and 12 months, with 95% returning to normal gait by 6 months. Lachmann showed the majority of knees were clinically stable at all points. Range of motion assessment indicated the knees maintained a normal range flexion and extension at all points. No gross cartilaginous damage, synovitis or particulate debris in lymph nodes was observed at any time point. Organized collagen and aligned fibroblasts in a crimp pattern were observed in the periphery of the ligament structure, adjacent to and attached to the remaining SeriACL device at all necropsy times. Collagen development throughout the graft and bone tunnels increased with time. Conversely, inflammation and device mass loss decreased with time. Fluoroscopy indicated no abnormal bone tunnel findings. Total plasma IgG levels did not increase from pre-surgery levels at any time. AP laxity indicated joint stability at all time points. Implant abrasion was observed to varying extents yet mechanical testing revealed tissue development supported increased load bearing over time. Conclusions: Results clearly demonstrate the potential of a scaffold-first strategy in engineering viable autologous ACL tissue that may serve over the patient’s life time. The SeriACL graft supported autologous development of a mechanically robust, biologically viable ligament which stabilized the joint over a 12 mo period. Mechanical, clinical and histological results indicated the safety of the SeriACL with initial indications of efficacy. Thus, the implant may offer the potential of an ACL replacement graft without the deleterious side-effects associated with donor-site morbidity and allogenic and xenogenic grafts

Introduction: Navigation systems might enhance the accuracy of ACL replacement. Methods: The authors used a non image based navigation system with both kinematic and anatomic registration. Navigated aimers were positioned to simulate the intra-articular hole of both femoral and tibial tunnels. The system displayed the position of the guide wire, the expected isometricity of the graft and the potential impingement within the intercondylar notch. 40 patients were operated on for an arthroscopic assisted bone – patellar tendon – bone ACL replacement with an outside-in femoral tunnel. The guide wires were placed according to the standard technique, and their position recorded by the system. The recorded position was compared:. to the conventional radiographic measurement of the position of the tunnels on plain antero-posterior and lateral X-rays,. and to the 3D measurement of the position of the tunnels on a CT-scan. Results: There was a significant difference in the paired absolute values of the mediolateral position of the tibial tunnel between radiographic and navigated measurements (p = 0.008). However there was a significant correlation between these two measurements (p = 0.05). There was no significant difference in the paired absolute values of the mediolateral position of the tibial tunnel or of the antero-posterior position of the femoral tunnel between radiographic and navigated measurements. There was no significant difference in the paired absolute values of the antero-posterior and medio-lateral position of the tibial tunnel or of the antero-posterior position of the femoral tunnel between CT and navigated measurements. Discussion: CT-scan measurement of the positioning of the ACL replacement tunnels is currently the gold standard technique. According to this reference, the antero-posterior position of both the femoral and the tibial tunnels can be accurately assessed by the navigation system used. The X–ray measurement is less accurate and should not be considered as a confident control of the accuracy of the tunnel placement. Summary: The antero-posterior position of both the femoral and the tibial tunnels can be accurately assessed by the system

Purpose: The use of allografts for anterior cruciate ligament (ACL) reconstruction has gained increased popularity. The major benefits of allograft for ACL replacement include decreased morbidity, easier patient rehabilitation and include ease of surgical procedure, decreased harvest site morbidity and easier patient rehabilitation. Further, allografts have improved appeal because of better sterilization techniques, improve graft availability and decreased hospital costs.|The objective of this study was to perform mechanical testing on various types of allograft. Specimens for allograft reconstruction of the anterior cruciate ligament included tibialis anterior tendon, tibialis posterior tendon, Achilles tendon and bone patella tendon tissues. Methods: The allografts tested were used for deployment in patients suffering with anterior cruciate ligament disruptions. A total of fifty grafts were analyzed. The breakdown of graft types included 15 tibialis anterior tendon, 15 tibialis posterior tendon, 10 Achilles tendon and 10 bone patella tendon tissues. The test techniques included: cutting the tendons to a set thickness and length. The tendons were then mounted in a cryogrip and frozen with liquid Nitrogen to below zero. They were mounted into a servo-hydraulic testing machine and pre-loaded and pre-conditioned. The specimens were then stretched to failure at a set strain rate. Results: No difference was found between the mechanical/material properties of the various tendon allografts – these included tensile strength and a high stress linear modulus assessments. The mechanical (structural properties) of the allografts were more dependant on the cross sectional area of the allograft than the type of allograft tissue.The greater the cross-sectional area of the allograft, the greater the strength and stiffness of the graft. Conclusions: These findings have considerable clinical applicability in choosing an allograft for anterior cruciate ligament reconstruction

Introduction: This biomechanical study evaluates the consequences of a mid-third BPTB-autograft excision on patellofemoral biomechanics and knee kinematics. Of particular interest was the potential role of a BPTB-autograft excision on postoperative anterior knee pain in ACL replacement surgery. Methods: Isokinetic knee extension from 120 of flexion to full extension was simulated on 9 human knee cadaver specimens (5 male, 4 female, average age at death 43 years). Joint kinematics was evaluated by ultrasound sensors (CMS 100TM, Zebris, Isny, Germany), and retro-patellar contact pressure was measured using a thin-film resistive ink pressure system (K-ScanTM 4000, Tekscan, Boston). All data were taken before and after excision of a mid-third BPTB-autograft. Results: Following excision of a mid-third patella tendon autograft we found a significant (p< 0.05) proximalization of the patella (average: 0.5 mm) and a significant decrease of patella flexion in the sagittal plane (average: 1). Patella tilt, -rotation (frontal plane), -translation (medial/lateral) and tibiarotation (external-/internal), -axis (varus-/valgus position) remained unchanged. Patellofemoral contact pressure and -area decreased significantly near knee extension (p< 0.05). Conclusions: We conclude that an excision of a mid-third patella tendon autograft results in a lengthening of the tendon with a proximalization of the patella. As the patellofemoral pressure decreases and the patella remains centralized, postoperative anterior knee pain following ACL-replacement using a BPTB autograft can not be explained by the results of our study

Aim. The purpose of this paper is to report on the results of ACL hamstring reconstruction using a novel fixation device. Patients-Methods. We reviewed a total of 132 patients with anterior cruciate ligament reconstruction, operated between 1998 and 2002, with a mean follow up time of 51 ± 9 months. A uniform arthroscopically assisted surgical technique with an instrument guided impingement free tibial tunnel placement and “over the top” femoral routing was employed. An autologous four strand semitendinosus-gracilis tendon graft in combination with a polyester graft suspension tape and cortical fixation device was used. An accelerated rehabilitation was instructed. All patients were examined in a dedicated Research Clinic on a 6 month basis. IKDC, Lysholm and Tegner scoring were employed to validate the end results. Arthrometric evaluation was performed with the KT 2000 device. Results. The over all analysis showed a mean side to side difference of 2.9 mm ± 1.8 and the International Knee Documentation Committee score rating was 91.6 % normal or nearly normal (121 patients). Complications included one graft rupture, one deep infection and 5 case of loosening. Conclusion. These findings suggest that the described method of anterior cruciate ligament replacement produces good early functional results and restores knee stability

We excised the anterior cruciate ligament from the left stifle of 24 sheep and replaced it by a polyester fibre implant routed 'over the top' of the femoral condyle and fixed, using grommets and screws. All the joints were sound, and the animals moved normally until they were killed at six, 12 and 24 months after operation. We found that the implants were always covered by host tissue, which matured into bundles with a histological appearance similar to the natural ligament. The implants were joined to the bones by organised fibrous tissue and there was no anchorage loosening. There was no synovitis, but the operated joints showed progressive cartilage degeneration. The reconstructed joints became less stable immediately after operation, but regained normal stability as the neoligaments developed. The neoligaments lost strength with time, despite tissue ingrowth. The good functional, biomechanical, and histological results justify clinical trials of this type of implant.

We report the two- to four-year results following the insertion of the Leeds-Keio prosthetic ligament for chronic anterior cruciate deficiency. Virtually all the 20 patients were less disabled by instability, but objective results were good or excellent in only two-thirds and under anaesthesia the pivot shift sign was still positive in half. Arthroscopic and histological assessment in 16 patients failed to show the development of a functional neoligament, and the common appearance of a synovitic reaction to polyester particles gave concern.

The anteroposterior stability of cadaveric knees was investigated. There was a wide range of normal laxity; knees were more stable at 90 degrees than at 20 degrees flexion. Anterior cruciate ligament implants with different stiffnesses were inserted; normal stability could always be restored, and the stiffness or extensibility of implants did not affect knee behaviour significantly. The tightness of implants was critical--small tensioning errors caused subluxation, inhibited knee extension and allowed damagingly high implant tensions. It is concluded that the tension of ligament implants could not be adjusted simply with a pre-set instrument; the procedure will remain critically dependent on the judgment of the operating surgeon.

The anterior cruciate ligament was replaced in rabbits, using implants of carbon or polyester filaments with known mechanical properties. The biocompatibility of the implants was assessed in detail using light microscopy, and scanning and transmission electron microscopy. Mechanical tests were made of stability, in comparison with normal joints and controls after excision of the ligament. Some carbon fibre implants broke down in vivo, allowing instability; the fragments caused chronic inflammation. Intact carbon implants did not induce the formation of neoligaments; they were covered by tissue, but there was no ingrowth. Polyester did not degrade mechanically and supported early collagenous ingrowth within the implant, even in the mid-joint space. It was concluded that there was no justification for the use of carbon fibres as anterior cruciate replacements; polyester appeared to be suitable