Revision anterior cruciate ligament surgery

Nonirradiated versus irradiated Achilles allograft: in vivo failure comparison

BACKGROUND

Many studies suggest that gamma irradiation decreases allograft strength in a dose-dependent manner. No study has demonstrated that this decrease in strength translates into higher clinical failures.

HYPOTHESIS

Irradiation of allograft tissue will lead to higher early clinical failure in anterior cruciate ligament (ACL) reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Medical records were reviewed for 90 consecutive patients who had received Achilles allograft reconstruction for unilateral primary ACL injuries at one institution between July 2001 and June 2002. One half of patients received nonirradiated Achilles allograft and the other half received irradiated Achilles allograft at a dose range of 2.0 to 2.5 Mrad. The ACL allograft reconstructions were performed using the same surgical technique. The rehabilitation program was identical for both groups. All clinical failures were recorded.

RESULTS

At least 6 months' follow-up was available on 42 subjects in the nonirradiated group and 33 subjects in the irradiated group. A significant difference was noted in early failure rates between the groups (P <.01). The nonirradiated group had 1 in 42 (2.4%) catastrophic failure. In the irradiated group, 11 of 33 (33%) Achilles tendon grafts failed.

CONCLUSIONS

Less than satisfactory results led the senior authors to discontinue the use of irradiated allografts in ACL surgery. Continued research into alternatives to gamma irradiation is needed.

Primary versus single-stage revision anterior cruciate ligament reconstruction using autologous hamstring tendon grafts: a prospective matched-group analysis

BACKGROUND

There is a low level of evidence about clinical results after anterior cruciate ligament (ACL) revision reconstruction using autologous hamstring tendon grafts.

HYPOTHESIS

Anterior cruciate ligament revision reconstruction improves knee stability but shows inferior results for functional and subjective outcome and knee stability compared with primary reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Between October 1997 and July 2005, 166 single-stage or 2-stage revision ACL reconstructions were done using different graft types. One hundred twenty-four cases underwent a single-stage revision reconstruction with autologous hamstring tendon grafts. At the time of data analysis, 67 cases fulfilled the criteria of minimum 2-year follow-up. Five patients were lost to follow-up (follow-up rate, 91%). Four patients (6%) who experienced graft rupture were counted as failures but not subjected to further detailed analysis. Because of loss to follow-up and exclusion criteria (n = 12), 50 patients were included in the study. For a comparative matched-group analysis, patients with a primary hamstring tendon graft ACL reconstruction were selected out of a database with minimum 2 years' follow-up (N = 284). Patients were followed using the International Knee Documentation Committee (IKDC) and Lysholm scores, KT-1000 arthrometer testing, and additional functional tests.

RESULTS

Four of 62 available patients (6.5%) in the revision group experienced graft failure, which was comparable to 16 of 284 (5.6%) in the primary reconstruction group. When the 2 matched groups of 50 patients were further compared, postoperative IKDC results showed no significant differences between groups. The manual maximum KT-1000 arthrometer side-to-side difference was 2.1 +/- 1.6 mm for the revision group and 2.2 +/- 1.1 mm for the primary reconstruction group. The Lysholm score was significantly better in the primary reconstruction group (P = .014). The incidence of postoperative positive pivot-shift test results was not significantly different. The primary reconstruction group showed significantly less extension deficits. Functional testing revealed significantly better results for the primary reconstruction group for stair climbing, squatting, knee bending, and duck walk.

CONCLUSIONS

In our patient series, primary ACL reconstruction showed significantly better results in Lysholm score, although the IKDC score and objective knee stability showed no significant difference between the groups. Thus, parameters other than measurable knee stability must be responsible for the inferior results of the revision reconstruction group.

Development of controlled matrix heterogeneity on a triphasic scaffold for orthopedic interface tissue engineering

Biological fixation of orthopedic soft tissue grafts to bone poses a significant clinical challenge. The clinical success of soft tissue-based grafts for anterior cruciate ligament (ACL) reconstruction is limited by the lack of functional graft integration with subchondral bone. Soft tissues such as the ACL connect to subchondral bone via a complex interface whereby three distinct tissue regions (ligament, fibrocartilage, and bone) work in concert to facilitate load transfer from soft to hard tissue while minimizing stress concentration at the interface. Although a fibrovascular tissue forms at the graft-to-bone interface following surgery, this tissue is nonphysiologic and represents a weak link between the graft and bone. We propose that the re-establishment of the native multi-tissue interface is essential for biological graft fixation. In vivo observations and our in vitro monolayer co-culture results suggest that osteoblast-fibroblast interaction is important for interface regeneration. This study focuses on the design of a triphasic scaffold system mimicking the multi-tissue organization of the native ACL-to-bone interface and the evaluation of osteoblast-fibroblast interactions during three-dimensional co-culture on the triphasic scaffold. We found that the triphasic scaffold supported cell proliferation, migration and phenotypic matrix production while maintaining distinct cellular regions and phase-specific extracellular matrix deposition over time. This triphasic scaffold is designed to guide the eventual reestablishment of an anatomically oriented and mechanically functional fibrocartilage interfacial region directly on biological and synthetic soft tissue grafts. The results of this study demonstrate the feasibility of multi-tissue regeneration on a single scaffold, and the potential of interface tissue engineering to enable the biological fixation of soft tissue grafts to bone.

A new harvest site for bone graft in anterior cruciate ligament revision surgery

During revision anterior cruciate ligament (ACL) surgery, femoral interference screws frequently require removal. This may lead to significant tunnel widening and possible graft fixation failure as a result. Solutions include drilling the revision tunnel in a different location, using stacked interference screws, or using bone graft to fill the defect. Autogenous iliac crest graft and allograft are both used, but there are significant comorbidities associated with each. We developed a new technique for harvesting autogenous bone graft that avoids many of the complications associated with other graft sources. By use of the existing surgical incision from the initial harvest of the bone-patellar tendon-bone autograft, bone from the medial tibial metaphyseal safe zone is harvested via an OATS tube harvester (Arthrex, Naples, FL). A bone plug 1 mm larger in size than the femoral defect is harvested and arthroscopically inserted via a press-fit technique. At 3 months after bone grafting, patients undergo revision ACL reconstruction. The proximal tibial metaphysis is a safe bone graft harvest site in revision ACL surgery and offers an effective method for filling large bony defects, allowing anatomic reconstruction of the ACL after bone healing has occurred. Furthermore, it eliminates the problems associated with allograft or use of a remote graft donor site.

Effects of low-intensity pulsed ultrasound on tendon-bone healing in an intra-articular sheep knee model

PURPOSE

This study reports the mechanical and histologic properties of intra-articular tendon-bone healing with the application of low-intensity pulsed ultrasound (LIPUS) in an ovine knee model.

METHODS

A single digital extensor tendon autograft from the right hoof was used as the graft in 89 adult sheep. Femoral fixation was achieved with an EndoButton (Smith & Nephew Endoscopy, Andover, MA) and tibial fixation by tying over a bony post. LIPUS treatment was performed daily for 20 minutes over the femoral and tibial tunnels until sacrifice in all groups, apart from the 26-week group, which was treated only for the first 12 weeks. Histology was performed at 3, 6, 12, and 26 weeks. Mechanical testing was performed at 6, 12, and 26 weeks.

RESULTS

The LIPUS-treated group showed increased cellular activity at the tendon-bone interface and general improvement in tendon-bone integration and vascularity. Stiffness and peak load were greater compared with the control group at 26 weeks after surgery (P < .05).

CONCLUSIONS

The application of LIPUS appears to improve healing at the tendon-bone interface for soft tissue grafts fixed with a suspensory fixation technique. Histology supports a benefit based on increased integration between tendon and bone and a biologically more active interface, which would account for the improved mechanical properties.

CLINICAL RELEVANCE

The indications of LIPUS may be expanded to include tendon-bone healing, for example, in anterior cruciate ligament reconstruction.

Proliferation of anterior cruciate ligament cells in vitro by photo-immobilized epidermal growth factor

The purpose of this study was to explore the early treatment potential of anterior cruciate ligament (ACL) injuries using artificial juxtacrine stimulation by photo-immobilization of a growth factor. A photo-reactive epidermal growth factor complex (EGF-Az) was synthesized by conjugating EGF with N-(4-azidobenzoyloxy) succinimide followed by immobilization onto polystyrene culture plates using UV irradiation. ACL cells from human tissues (1 x 10(5)cells, 100 microl/well) were cultured as follows: control, no EGF; 50 microl native EGF; 50 microl EGF-Az immobilized; and 100 microl EGF-Az immobilized. The ACL cells were cultured long-term and evaluated for possible differences in their responses to EGF. An in vitro wound closure assay was developed to enable examination of cellular proliferation and migration. ACL cell proliferation was most evident in the photo-immobilized EGF culture group and was seen to increase in proportion to the amount of added EGF. In the in vitro wound closure assay, the lesioned area at 72 h after culture initiation was indistinguishable in the photo-immobilized cultures, but remained clearly visible in the controls. We conclude that photo-immobilized EGF induced rapid proliferation of ACL fibroblast cells by artificial juxtacrine stimulation and speculate that similar EGF immobilization onto bioabsorbable material (e.g., polyglycolic acid or polylactic acid) might contribute to a new therapy for the treatment of ACL injuries.

Revision anterior cruciate ligament reconstruction due to knee instability

Introduction. The primary goal of anterior cruciate ligament reconstruction is to provide stability to the knee and regain full range of motion. Although great improvement has been achieved in surgical techniques and rehabilitation, some patients are not completely satisfied with the results of surgery and a revision anterior cruciate ligament reconstruction is necessary. Material and Methods. Revision arthroscopic anterior cruciate ligament reconstruction was carried out in eleven patients with bone-tendon-bone autografts. The surgery was performed in a standard manner and the graft was taken from the opposite knee. Eight men and three women were evaluated. The mean age of patients was 26 (17-34) years. Repeated instability of the knee was caused by injury in five patients, while six patients were unsatisfied with the position of the graft. Results. The follow up was 4,2 years (2-8) respectively. The mean Lysholm and Gillquist score after operation was 88 (65-90). Preoperative and postoperative tibial shift was 9mm (6-15) and 2mm (0-4), respectively. The preoperative pivot shift test was grade 2 and 3 in all patients. Postoperative pivot shift test was negative in seven patients, in three it was grade 1 and grade 2 in one patient. According to the IKDC scale, preoperative results were abnormal in three patients and in eight they were severely abnormal. Postoperative IKDC score was normal in five patients, in four nearly normal, and in one patient the score was still abnormal. Five patients continued to be active in sports activities, four patients decreased the level of sports activity and two stopped all sports activities. Conclusion. Success of revision anterior cruciate ligament reconstruction requires detailed preoperative evaluation of the repeated instability of the knee. The treatment plan is then decided upon. The patients must be preoperatively informed about the real possibilities of revision surgery. Only a mutual collaboration between the patient, physiatrist and a surgeon is a key for successful treatment and return to previous level of sports activities.

Intraarticular rupture pattern of the ACL

To date, the intraarticular rupture pattern of the anterior cruciate ligament (ACL) has not been reported. The ACL is a complex structure consisting of two functionally synergistic structures: the anteromedial (AM) and posterolateral (PL) bundle. The purpose of our study was to evaluate the intraarticular rupture pattern of the ACL with regard to its two functional bundles. We examined ACL rupture patterns with regard to the integrity of AM and PL bundle in 121 consecutive patients undergoing anterior cruciate ligament reconstruction surgery within 120 days after injury. The intraarticular pattern was observed by one experienced surgeon. In 25% of the patients a partial rupture of the ACL was found, whereas in the remaining 75% a complete rupture of AM and PL bundles was seen. A partial rupture could only be detected by careful dissection of the ligament. In 44% of all patients the AM and PL bundles did not rupture at the same location. In 12% of the patients the PL bundle showed no signs of rupture. When performing ACL reconstruction, care should be taken when dissecting down the ACL remnants to evaluate intact fiber bundles of the ACL.

Anatomy of the anterior cruciate ligament with regard to its two bundles

The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial and posterolateral bundle. When the knee is extended, the posterolateral bundle (PL) is tight and the anteromedial (AM) bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes a more horizontal orientation; causing the AM bundle to tighten and the PL bundle to relax. There is some degree of variability for the femoral origin of the anterome-dial and posterolateral bundle. The anteromedial bundle is located proximal and anterior in the femoral ACL origin (high and deep in the notch when the knee is flexed at 90 degrees ); the posterolateral bundle starts in the distal and posterior aspect of the femoral ACL origin (shallow and low when the knee is flexed at 90 degrees ). In the frontal plane the anteromedial bundle origin is in the 10:30 clock position and the postero-lateral bundle origin in the 9:30 clock position. At the tibial insertion the ACL fans out to form the foot region. The anteromedial bundle insertion is in the anterior part of the tibial ACL footprint, the posterolateral bundle in the posterior part. While the anteromedial bundle is the primary restraint against anterior tibial translation, the posterolateral bundle tends to stabilize the knee near full extension, particularly against rotatory loads.

Elastographic imaging of strain distribution in the anterior cruciate ligament and at the ligament-bone insertions

The anterior cruciate ligament (ACL) functions as a mechanical stabilizer in the tibiofemoral joint, and is the most commonly injured knee ligament. To improve the clinical outcome of tendon grafts used for ACL reconstructions, our long-term goal is to promote graft-bone integration via the regeneration of the native ligament-bone interface. An understanding of strain distribution at this interface is crucial for functional scaffold design and clinical evaluation. Experimental determination, however, has been difficult due to the small length scale of the insertion sites. This study utilizes ultrasound elastography to characterize the response of the ACL and ACL-bone interface under tension. Specifically, bovine tibiofemoral joints were mounted on a material testing system and loaded in tension while radiofrequency (RF) data were acquired at 5 MHz. Axial strain elastograms between RF frames and a reference frame were generated using crosscorrelation and recorrelation techniques. Elastographic analyses revealed that when the joint was loaded in tension, complex strains with both compressive and tensile components occurred at the tibial insertion, with higher strains found at the insertion sites. In addition, the displacement was greatest at the ACL proper and decreased in value gradually from ligament to bone, likely a reflection of the matrix organization at the ligament-bone interface. Our results indicate that elastography is a novel method that can be readily used to characterize the mechanical properties of the ACL and its insertions into bone.

Biomechanics and anterior cruciate ligament reconstruction

For years, bioengineers and orthopaedic surgeons have applied the principles of mechanics to gain valuable information about the complex function of the anterior cruciate ligament (ACL). The results of these investigations have provided scientific data for surgeons to improve methods of ACL reconstruction and postoperative rehabilitation. This review paper will present specific examples of how the field of biomechanics has impacted the evolution of ACL research. The anatomy and biomechanics of the ACL as well as the discovery of new tools in ACL-related biomechanical study are first introduced. Some important factors affecting the surgical outcome of ACL reconstruction, including graft selection, tunnel placement, initial graft tension, graft fixation, graft tunnel motion and healing, are then discussed. The scientific basis for the new surgical procedure, i.e., anatomic double bundle ACL reconstruction, designed to regain rotatory stability of the knee, is presented. To conclude, the future role of biomechanics in gaining valuable in-vivo data that can further advance the understanding of the ACL and ACL graft function in order to improve the patient outcome following ACL reconstruction is suggested.

Anatomy of the anterior cruciate ligament double bundle structure: a macroscopic evaluation

INTRODUCTION

Traditional anterior cruciate ligament (ACL) surgery has demonstrated good results, but there is still a subset of unsatisfactory outcomes. Trends in reconstruction technique have changed from bone-patella-tendon-bone to hamstring refixation, and the next step appears to be the double bundle concept.

METHODS

We examined six fresh-frozen cadaver knees to evaluate the double bundle structure, dynamic motion characteristics and the relationship of knee flexion and relative position of the femoral insertion sites of the ACL.

RESULTS

In all knees, we identified an anteromedial (AM) and posterolateral (PL) bundle. The motion pattern demonstrated that the AM and PL bundles are oriented near parallel with the knee extended, and twist around each other as the knee is flexed. The visualization of the femoral footprint anatomy differs with knee flexion.

DISCUSSION

The double bundle model facilitates restoration of the original footprint anatomy and biomechanics more easily than the concept of the ACL as a one-bundle structure and the use of the o'clock position. It is essential to be aware of the degree of knee flexion when drilling the femoral tunnels.

PERSPECTIVE

Anatomic ACL reconstruction is a concept, not a technique, and allows a more refined surgical approach to ACL reconstruction including revision cases and partial ACL tears.

Anterior cruciate ligament revision: double-bundle augmentation of primary vertical graft

A variety of factors contribute to the failure of primary anterior cruciate ligament (ACL) reconstruction; most commonly, it is technical error related to tunnel placement. Recently, the increasing popularity of the all-endoscopic ACL reconstruction and concern about graft impingement may have led to more posterior placement of the tibial tunnel by surgeons. Working through a tibial tunnel placed too posterior makes it more difficult to recognize the correct starting position on the femur, and more likely to start the femoral tunnel in a central 12 o'clock position. The combination of subtle posterior placement of the tibial tunnel and central placement of the femoral tunnel results in a graft that is malpositioned in both the sagittal and coronal planes--a "vertical graft." We present a novel method of ACL revision surgery applicable to a specific subset of ACL revision patients with an intact "vertical graft" and instability that is rotational more than translational. In these patients, a double-bundle revision ACL augmentation technique can be used, leaving the original graft in place. A new tibial tunnel is placed anterior to the original and a new femoral tunnel lateral to the original. Reconstruction is performed with allograft and the combined ACL construct provides robust translational and rotational stability to the tibiofemoral joint.

Comparison of initial mechanical properties of 4 hamstring graft femoral fixation systems using nonpermanent hardware for anterior cruciate ligament reconstruction: an in vitro animal study

PURPOSE

To compare the initial mechanical characteristics of 4 systems used to fix tendons to the femur during anterior cruciate ligament reconstruction.

METHODS

A total of 32 porcine femurs were used to study the following fixation systems: Bioabsorbable interference screw (Stryker, Kalamazoo, MI), Bio-Transfix Cross-pin (Arthrex, Naples, FL), Biosteon Cross-pin (Stryker), and a fixation technique based on wrapping the graft around the femoral condyle itself, thus allowing it to be fixed in place without the use of any hardware. The mechanical characteristics of each system were obtained by a preconditioned failure tensile test.

RESULTS

The yield load values (990.9 +/- 242.6 N for Bio-Transfix, 905.1 +/- 158.8 N for Biosteon Cross-pin, 684.4 +/- 119.7 N for the without-hardware system (WHS), and 369.4 +/- 120.1 N for the interference screw) revealed significant differences between the techniques that used cross-pins and the other 2 techniques (P < .006) on the one hand, and between the without hardware technique and the interference screw (P < .004) on the other. The stiffness of the 2 cross-pin fixation systems (117.6 +/- 22.5 N for Bio-Transfix and 112.6 +/- 22.5 N for Biosteon) was greater (P < .01) than those of the other systems (79.4 +/- 15.2 N for the WHS and 68.5 +/- 13 N for the interference screw).

CONCLUSIONS

The initial biomechanical properties of the 2 cross-pin fixation systems proved to be superior to those of the other 2 systems studied. The WHS fixation system exhibited better mechanical properties than its interference screw counterpart.

CLINICAL RELEVANCE

The better initial mechanical characteristics encountered using the Bio-Transfix and Biosteon Cross-pin systems indicate that these systems are better equipped to bear the loads generated by aggressive rehabilitation. The WHS fixation system provides an alternative to interference screw fixation.

Femoral press-fit fixation technique in anterior cruciate ligament reconstruction using bone-patellar tendon-bone graft: a prospective clinical evaluation of 285 patients

BACKGROUND

The security of the graft fixation is an important factor of anterior cruciate ligament reconstruction, especially in the early postoperative period.

HYPOTHESIS

The femoral press-fit fixation technique is a safe, alternative technique for the fixation of the bone-patellar tendon-bone graft.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between January 1, 1998, and June 30, 2002, 285 patients, with a mean age of 29.1 years, underwent operation and observation in our department. All patients had arthroscopic anterior cruciate ligament reconstruction using bone-patellar tendon-bone graft with femoral press-fit and tibial interference screw fixation. The mean follow-up period was 35.8 months (range, 24-77 months). During each patient's evaluation, a physical examination, a subjective evaluation, the International Knee Documentation Committee and Lysholm scores, KT-1000 arthrometer testing, and radiological evaluation were performed. The paired Student t test or chi(2) test was used for statistical analysis.

RESULTS

According to the International Knee Documentation Committee score, 241 patients (85%) had good (46 normal and 195 nearly normal) results, whereas 39 patients had abnormal and 5 patients had severely abnormal overall results. The preoperative mean Lysholm score was 63.5 +/- 12.7 points. At the final examination, the mean value was 93.5 +/- 7.8 points (P < .01). One hundred ninety-seven athletes could return to their previous sports activity level, whereas 13 patients gave up their sports career. The KT-1000 arthrometer results showed a side-to-side difference of 1.91 +/- 2.1 mm at the maximum manual strength tests.

CONCLUSION

The femoral press-fit fixation is an alternative fixation method for the bone-patellar tendon-bone graft and provides good stability for the anterior cruciate ligament reconstruction. The use of press-fit fixation technique avoids most interference screw or other hardware-induced complications at the femoral side.

Revision anterior cruciate ligament reconstruction using a 2-stage technique with bone grafting of the tibial tunnel

BACKGROUND

Revision anterior cruciate ligament surgery is often considered a salvage procedure with limited goals. However, this limitation need not be the case. Similar to primary reconstruction, the goal should be to choose an appropriate graft and place it in an anatomical position in a good quality bone. The issue of good quality bone seems to have been ignored.

HYPOTHESIS

A 2-stage anterior cruciate ligament revision reconstruction with bone grafting of the tibial tunnel and the use of a different femoral tunnel will produce measured knee laxity and International Knee Documentation Committee scores similar to a primary anterior cruciate ligament reconstruction.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

This prospective study involved 49 consecutive 2-stage anterior cruciate ligament revisions (group R) performed by a single surgeon from 1993 to 2000. Two-stage revision surgery was performed if the tibial tunnel from a previous reconstruction surgery would overlap (either partially or fully) the correctly placed revision tunnel. The first stage consisted of removal of the old graft and interfering metalwork, together with bone grafting of the tibial tunnel. After ensuring adequate bone graft incorporation using computed tomography scan, the second stage revision was undertaken. This stage comprised harvesting the autograft, its anatomical placement, and its adequate fixation. The results were compared with the results of a matched group of patients with primary anterior cruciate ligament reconstruction (group P).

RESULTS

In group R, as meniscal and chondral lesions were more common, the International Knee Documentation Committee scores were lower than those of group P (61.2 for group R and 72.8 for group P; P = .006). Objective laxity measurement was similar in both groups (1.36 mm for group R and 1.2 mm for group P; P = .25).

CONCLUSION

This study establishes that the laxity measurements achieved with a 2-stage revision anterior cruciate ligament reconstruction can be similar to those achieved after primary anterior cruciate ligament reconstruction, although the International Knee Documentation Committee rating is lower.

Effect of patellar tendon shortening on tracking of the patella

BACKGROUND

Although 10% postoperative patellar tendon shortening after bone-patellar tendon-bone autograft reconstruction of the anterior cruciate ligament has been reported, there are no published studies assessing the effect of shortening on patellofemoral joint biomechanics under physiological loading conditions.

PURPOSE

To investigate the influence of patellar tendon shortening on patellofemoral joint biomechanics.

STUDY DESIGN

Controlled laboratory study.

METHODS

The authors evaluated the patellofemoral contact area, the location of contact, and the patellofemoral joint reaction force and contact stresses in 7 cadaveric knees before and after 10% patellar tendon shortening. Shortening was achieved using a specially designed device. Experimental conditions simulating those occurring during level walking were employed: physiological quadriceps loads and corresponding angles of tibial rotation were applied at 15 degrees , 30 degrees , and 60 degrees flexion of the knee. Patellofemoral joint contact areas were measured before and after shortening using the silicone oil-carbon black powder suspension squeeze technique.

RESULTS

After patellar tendon shortening, patellofemoral joint contact areas were displaced proximally on the patellar surface and distally on the femoral surface. Although the contact area increased by 18% at 15 degrees of knee flexion (P = .04), no significant change occurred at 30 degrees or 60 degrees of knee flexion (P > .05). Patellofemoral contact stress remained unchanged after patellar tendon shortening (P > .05) at each flexion angle.

CONCLUSION

Our results suggest that a 10% shortening of the patellar tendon does not alter patellar contact stresses during locomotion. It is not clear whether apparent changes in contact location in all positions and contact area at 15 degrees would have clinical consequences.

Management of bony deficiency in revision anterior cruciate ligament reconstruction using allograft bone dowels: surgical technique

Revision anterior cruciate ligament (ACL) reconstruction surgery has become increasingly common over the past decade and its popularity is likely to rise further as the number of primary ACL reconstructions increases each year. More than 75% of all cases of failed ACL reconstruction are the result of technical error and, of these, more than 70% are attributed specifically to malpositioned tunnels. Management of tunnel malposition in revision surgery often requires innovative approaches for dealing with the resultant bony defects. In addition, tunnel osteolysis may create bone loss that interferes with desired tunnel placement. A number of options have been described for handling these bony deficiencies, many of which are technically difficult and time consuming. We describe a novel technique to address bony defects during revision ACL reconstruction using freeze-dried allograft bone dowels. These allografts are readily available and can be used easily to fill deficiencies resulting from previous tunnels or osteolysis. The grafts provide sufficient structural support for redrilling of new tunnels through or next to the bony plug, allowing uncompromised tunnel placement.

Computed tomography-guided and arthroscopically controlled en bloc retrograde resection of a juxta-articular osteoid osteoma of the tibial plateau

Osteoid osteoma represents approximately 10% to 11% of all the benign bone tumors. The localization at the articular and juxta-articular level of the knee is an atypical picture that causes both diagnostic and therapeutic problems. We present the case of an osteoid osteoma of the lateral tibial plateau just beneath the joint level. The lesion was removed by a rear-entry computed tomography (CT)-guided drill under arthroscopic control and the bony defect filled with bone graft harvested from the proximal tibial metaphysis. Postoperative CT scans at 3 months, and 1 and 2 years were performed. The result of the kneeling test to evaluate donor-site morbidity 1 year after the surgery was negative. There were no immediate or delayed complications. Currently (2 years postoperatively), the patient has no pain and has gone back to his normal active daily lifestyle and routines. The follow-up CT scan 2 years after surgery showed complete excision of the lesion and perfect positioning of the bone graft. This new approach/technique enabled us to avoid damaging the proximal structures, to examine the lesion, and to fill the bony defect. Moreover, as shown by CT scan at follow-up, iatrogenic lesions to the cartilage of the tibial plateau were not reported.

Analysis of forces of ACL reconstructions at the tunnel entrance: is tunnel enlargement a biomechanical problem?

Bone tunnel enlargement is a common phenomenon following reconstruction of the anterior cruciate ligament (ACL). Biomechanical and biological factors have been reported as potential causes of this problem. However, there is no analysis of forces between the graft and bone, as the graft changes direction at the bone tunnel entrance. The purpose of this study was to study these 'redirecting forces'. Magnetic resonance images of 10 patients with an ACL reconstruction (age: 26+/-6.8 years) were used to determine the angle between graft and drill holes. Vector analysis was used to calculate the direction and magnitude of the perpendicular component of the force between the bone tunnel and the graft at the entrance of the bone tunnel. Force components were projected into the radiographically important sagittal and coronal planes. Tension of ACL reconstructions was recorded during passive knee motion in 10 cadaveric knee experiments (age: 28.9+/-10.6 years) and the tension multiplied with the force component for each plane. Results are reported for the coronal and sagittal planes, respectively: For -10 degrees of extension, the percentages of graft tension were determined to be 17+/-7 (max: 26; min: 7%) and 26+/-9 (max: 39; min: 16%) for the tibia. They were 59+/-6 (max: 66; min: 48%) and 99+/-1 (max: 1.00; min: 99%) for the femur. Force components were 14.68+/-6.54 and 25.73+/-12.96 N for the tibial tunnel. For the femoral tunnel, they were 52.48+/-19.03 and 90.77+/-32.06 N. Percentages of graft tension and force components were significantly higher for the femoral tunnel compared with the tibial tunnel. Moreover, in the sagittal direction, force components for the femoral tunnel were significantly higher compared with the coronal plane (Wilcoxon test, p < 0.01). The differences in force components calculated in this study corresponds with the amount of tunnel enlargement in the radiographic planes in the literature providing evidence that biomechanical forces play a key role in postoperative tunnel expansion.

Biomechanical evaluation of press-fit femoral fixation technique in ACL reconstruction

In this experimental study, the authors evaluated the biomechanical properties of the femoral press-fit graft fixation technique in ACL reconstruction. 20 fresh frozen distal femurs, patellae and patellar ligaments were used from 10 cadaver specimens. Three bone-patellar tendon grafts of 10 mm width were prepared from each sample; altogether 60 bone-patellar tendon grafts were prepared for the experiment. Three 9 mm wide tunnels were drilled in each distal femur at different angles (0, 15, 30, 45, and 60 degrees). This means that 60 tunnels were drilled into the 20 femurs, 12 at each angle. The trapezoid bone blocks were impacted into the holes. The primary stability and stiffness of this press-fit fixation method were measured with a Zwick 020 computer-controlled testing device using maximum-failure tensile-strength tests. The ultimate tensile strength was the greatest at 45 degrees (534+/-20 N, range 507-554), with 118+/-10 N/mm (range 99-126) stiffness, followed by 485+/-35 N (range 416-510) with 122+/-13 N/mm (range 104-136) stiffness at 30 degrees, 353+/-18 N (range 320-371) with 113+/-13 N/mm (range 83-124) stiffness at 15 degrees, and 312+/-30 N (range 261-343) with 89+/-14 N/mm (ranged:68-103) stiffness at 0 degrees. In the cases of 0, 15, 30 and 45 degrees the bone blocks were pulled out of the drilled holes, but at 60 degrees rupture of the patellar tendon or breakage of the bone block occurred more frequently. It can be seen that the ultimate tensile strength increased with the angle between the loading direction and the bone block. When compared to data in the literature, these data showed similar and satisfying biomechanical properties of femoral press-fit fixation. Because of the known advantages of an implantation-free fixation technique, the femoral press-fit fixation technique can be a good alternative in ACL surgery. These results provide the basis for future studies involving the postoperative healing process of this femoral press-fit fixation technique in porcine knees.

Fixation strength of a novel bioabsorbable expansion bolt for patellar tendon bone graft fixation: an experimental study in calf tibial bone

This biomechanical study compares the initial fixation strength of a novel bioabsorbable two-shell expansion bolt (EB) with that of a well-established interference-screw technique in bone-patellar tendon-bone (BPTB) reconstruction in a calf model. Thirty tibia plateaus (age 5-6 months) were assigned to three groups: In groups I and II, trapezoidal bone plugs of BPTB grafts were fixed with bioabsorbable poly-L-lactide interference screws (8 x 23 mm) or titanium interference screws (8 x 25 mm) respectively. In group III, semicircular grafts were fixed using bioabsorbable poly-D, L-lactide expansion bolts (5.8/8.7 x 10 x 35 mm). The tensile axis was parallel to the bone tunnel, and the construction was loaded until failure applying a displacement rate of 1 mm per second. In group II the mean ultimate loads to failure (713 N+/-218 N) were found to be significantly higher than those of groups I (487 N+/-205 N) and III (510 N+/-133 N). Measurement of stiffness showed 45 N/mm+/-13.3 in group I, 58 N/mm+/-17.4 in group II and 46 N/mm+/-6.9 in group III, and did not demonstrate significant differences. We found a correlation between insertion torque and wedge insertion force and ultimate loads to failure in all groups (r=0.53 in group I, r =0.54 in group II, and r =0.57 in group III). Cross-section planes of bone tunnel increased by 51%, 30% and 31% respectively, following insertion of screws or expansion of bolts (p<0.05). We conclude that ACL graft fixation by means of the presented expansion bolt demonstrates a fixation strength similar to the established bioabsorbable screw fixation, and is a reasonable alternative fixation method, especially since some of the specific pitfalls of screw fixation can be avoided.

Semitendinosus regrowth: biochemical, ultrastructural, and physiological characterization of the regenerate tendon

BACKGROUND

Previous studies have suggested that hamstring tendons can regenerate following harvesting for anterior cruciate ligament reconstruction.

HYPOTHESIS

This "neo-tendon" is a true, functional tendon, not scar tissue.

STUDY DESIGN

Controlled laboratory study.

METHODS

Semitendinosus tendons were harvested from 35 New Zealand white rabbits using a standard tendon stripper. The rabbits were sacrificed 9 to 12 months following the index procedure and thoroughly evaluated.

RESULTS

Thirty-one rabbits were available at the time of sacrifice. The neo-tendon was present in 26 rabbits but was highly variable in size and location of its tibial insertion. Histologic and immunohistochemical staining confirmed that the regenerate tissue was indeed tendon with normal cellularity, organization, and immunolocalization of type I collagen. Electron microscopy showed regeneration of organized collagen tissue that simulated native tendon but with a smaller cross-sectional diameter. Functionally, the neo-tendon was able to transmit force across the musculotendinous junction but at a significantly slower rate than the opposite, control leg. Biomechanical properties of the neo-tendon were significantly less than the control side. Biochemical analysis revealed that the neo-tendons contained glycosaminoglycans and collagen, but levels were significantly lower than normal tendons.

CONCLUSIONS

Semitendinosus tendons regenerate with biologically reactive tendinous tissues in an animal model. This tissue has many of the characteristics of a normal tendon but appears to be inferior to the original musculotendinous unit at 9- to 12-month evaluation. Further characterization of the "lizard tail phenomenon" is still needed.

CLINICAL RELEVANCE

Hamstring tendon regrowth may have a dramatic impact on postoperative function of patients who undergo anterior cruciate ligament reconstruction with these tendons. Further modulation of this regeneration may further reduce graft harvesting morbidity.

Tunnel enlargement after anterior cruciate ligament surgery

Bone tunnel enlargement has been reported after anterior cruciate ligament (ACL) reconstruction surgery. Although the long-term outcome of this phenomenon is not yet known, tunnel lysis or expansion may be clinically significant in revision surgery because the enlarged tunnels may complicate graft placement and fixation. There any many proposed theories for tunnel lysis. The most accurate statement is that this condition has a multifactorial etiology. Mechanical and biological causes have been reported, and both contribute to enlarged graft tunnels. This article describes the multiple causes of bone tunnel enlargement after ACL surgery. Future techniques and advances in primary ACL surgery must seek to eliminate this phenomenon.

Bioabsorbable expansion bolt fixation in anterior cruciate ligament reconstruction

The current study evaluated initial fixation strength of a bioabsorbable expansion bolt compared with interference screw fixation in anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft. Thirty calf tibial plateaus with adjacent patella and extensor ligaments were used. Bioabsorbable poly-L-lactide interference screws were used for graft fixation in Group I, titanium screws in Group II, and bioabsorbable poly-DL-lactide expansion bolts were used in Group III. The mean force-to-failure (+/- standard deviation) in the three groups was 487 +/- 205 N, 713 +/- 218 N, and 594 +/- 224 N, respectively. The differences between Groups I and II were significant. No statistical differences were found regarding stiffness. Graft damage was significantly less in Group III compared with screw fixation. The fixation concept of an expansion bolt shows similar fixation strength and less graft damage compared with the established interference screw fixation. Because of the total absence of torque forces in contrast to bioabsorbable screws, the risk of implant breakage is minimized.

Revision anterior cruciate ligament reconstruction using autografts with a polyester fixation device

Twenty-nine patients who had undergone anterior cruciate ligament (ACL) revision were evaluated retrospectively between 1992 and 2000. A similar surgical technique was used in all cases. Twenty-six patients underwent revision following failed primary and revision surgery with the ABC scaffold ligament. There were 2 failed primary semitendinosus/gracilis (STG) autografts and one failed bone patella tendon bone (BPTB) autograft. Autologous hamstring tendons (STG) were used in 26 knees, quadriceps tendon in 2 and BPTB autograft in 1 knee. The Mark I Soffix soft tissue fixation device was used in 16 patients and 13 patients underwent reconstruction with the Mark II BH (Button Hole ) Soffix. Follow up evaluation included clinical examination, KT 2000 arthrometric side to side difference (SSD) assessment, Lysholm, Tegner and IKDC scoring. The average follow up time was 50+/-22 months. The overall SSD was 1.66+/-1.5 mm, a mean Lysholm score of 87.2+/-12.5 was obtained and 22 patients had an IKDC score of nearly normal (B). In the Mark II (BH Soffix) group knees were significantly tighter than in the Mark I Soffix group (P<0.05) with a mean SSD of 1.23+/-1.3 and 2.0+/-1.6 mm, respectively. However there were no significant differences in the other measured parameters between the two fixation devices. Multiply re-operated knees tended to have lower IKDC and Lysholm scores (not statistically significant). We concluded that the technique reported in this study can restore stability to the knee following failed primary or revision ACL reconstruction and the results in the non-multiply operated knees are comparable to primary reconstruction.

Current opinion on computer-aided surgical navigation and robotics: role in the treatment of sports-related injuries

Computer-assisted surgery (CAS) may allow surgeons to be more precise and minimally invasive, in addition to being an excellent research tool. Medical imaging, such as magnetic resonance and computed tomography is not only an important diagnostic tool, but also a necessary planning tool. In orthopaedic sports medicine, precision is needed when placing tunnels for soft tissue fixation of replacement grafts. Two types of CAS systems -- passive and active -- have been developed. Passive systems, or surgical navigation systems, provide the surgeon with additional information prior to and during the surgical procedure (in real time). Active systems have the ability of performing certain surgical steps autonomously. Both active and passive CAS systems are currently a subject of basic science and clinical investigations and will be discussed and commented on in this article. In summary, passive navigation systems can provide additional information to the surgeon and can therefore lead to more precise tunnel placement. Active robotic technology seems to be accurate and feasible with promising initial results from Europe. However, active and passive CAS can only be as precise as the surgeon who plans the procedure. Therefore, future studies have to focus on integrating, arthroscopy, 3-D image-enhanced computer navigation, and virtual kinematics, as well as to increase precision in surgical techniques.