Initial fixation strength of interference nail fixation for anterior cruciate ligament reconstruction with patellar tendon graft (experimental study)

The objective of this study was to evaluate initial fixation strength of a new interference nail fixation in anterior cruciate ligament reconstruction using bone-patellar tendon-bone graft. Human cadaver knees were used. Fixation strengths ranged from 500 N to 600 N (mean 550 N). This corresponds to loads in the graft during aggressive rehabilitation. No slippage occurred at fixation site of specimens. Most of the failures appeared from the femoral side with tendon ruptures. With respect to primary fixation strength, interference nail fixation is a reasonable alternative for anterior cruciate ligament reconstruction with bone-patellar tendon-bone graft.     

Determination of time of biologic fixation after anterior cruciate ligament reconstruction with hamstring tendons

BACKGROUND: It has been unclear when a hamstring tendon graft becomes biologically fixed in the bone tunnel after anterior cruciate ligament reconstruction. HYPOTHESIS: Postoperative biomechanical testing and magnetic resonance images can indicate biologic fixation of the graft in the femoral bone tunnel. STUDY DESIGN: Prospective cohort study. METHODS: Sixty-four patients were evaluated by serial biomechanical testing, magnetic resonance imaging, and second-look arthroscopy 2 years after surgery. Biologic fixation of the graft was confirmed radiographically by injecting a contrast medium into the femoral bone tunnel. RESULTS: Forty-two stable knees with graft fixation maintained a high stiffness (120% of normal) and showed low signal intensity in an early postoperative magnetic resonance image (12 +/- 8 months). Fourteen stable knees without graft fixation had gradually increased anterior displacement with nearly normal stiffness and high signal intensity. Five unstable knees with graft fixation retained low stiffness (70%) and showed late low signal intensity at 20 +/- 9 months. Three unstable knees without biologic fixation had rapidly increased anterior displacement, with half the stiffness of a normal knee. CONCLUSION: Postoperative low stiffness and high signal intensity might indicate late biologic graft fixation, predicting a possibility of postoperative anterior knee instability.     

Reconstruction of the coracoclavicular ligaments with tendon grafts: a comparative biomechanical study

BACKGROUND: Numerous surgical techniques have been described to address injuries to the coracoclavicular ligaments. PURPOSE: To compare the biomechanical properties of tendon graft reconstructions with those of the native coracoclavicular ligaments and various other repair methods. STUDY DESIGN: Controlled laboratory study. METHODS: Eleven fresh-frozen human cadaveric shoulders were tensile tested to failure to compare the biomechanical properties of the native coracoclavicular ligaments, coracoacromial ligament transfer, No. 5 Mersilene suture repair, 5-mm Mersilene tape repair, and tendon graft reconstructions with gracilis, semitendinosus, and long toe extensor tendons. RESULTS: Reconstructions with semitendinosus, gracilis, or long toe extensor tendon grafts were found to have superior initial biomechanical properties compared with coracoacromial ligament transfer; failure strengths were as strong as those of the native coracoclavicular ligaments. Failure of the tendon grafts occurred through the midsubstance of the tendon graft, not at the fixation site. CONCLUSIONS: Tendon graft reconstruction may be an alternative to coracoacromial ligament transfer and may provide a permanent biologic reconstruction with superior initial biomechanical properties, including that of tensile strength. Clinical Relevance: Use of tendon graft reconstruction may limit the need for postoperative immobilization and lead to an accelerated rehabilitation program.     

Allografts in the treatment of anterior cruciate ligament injuries

Symptomatic knee instability is a common complaint among athletic individuals after a torn anterior cruciate ligament (ACL) of the knee. Allograft ACL reconstruction has gained popularity for primary and revision reconstructions. This graft choice has become popular with good intermediate term results combined with decreased operative times, hospital costs, and improved immediate postoperative pain and function. Intermediate follow-up has demonstrated similar results with autograft reconstructions, without the addition of donor site morbidity. Multiple allograft options exist for ACL reconstruction. The most commonly selected grafts include patellar tendon, Achilles tendon, and tibialis allografts. The use of a tibialis allograft provides a stout graft for reconstruction, while minimizing bone tunnel size. Bone-patella-bone allografts provide bone to bone fixation options with flexibility in tunnel selection sizing.     

Equal tension in all four strands of a semitendinosus graft with a low profile tibial fixation device (Cobra LFD)

The article introduces a novel tibia fixation device, the Cobra Ligament Fixation Device (Cobra LFD), for anterior cruciate ligament reconstruction. The Cobra LFD has a low profile and is hooked upon the cortical bone of tibia. It is useful either for primary ACL reconstruction or for ACL revision surgery, mainly for fixation of hamstring grafts. Fixation in the cortical bone is of great importance, in particular for revision cases. Besides technical aspects, we also present the 4-year follow-up of 15 cases of ACL revision surgery, where the Cobra LFD has been used for the tibia fixation.     

Anterior cruciate ligament reconstruction using the Bio-TransFix femoral fixation device and anteromedial portal technique

The cross-pin femoral fixation technique for soft tissue grafts is a popular option in anterior cruciate ligament (ACL) reconstruction. One of these devices is the Bio-TransFix (Arthrex Inc., Naples, FL, USA) which provides high fixation strength. According to the manufacturer, the femoral tunnel is created by placing the femoral aiming device through the tibial tunnel (transtibial technique). However, using this technique it is very difficult or even impossible to place the graft at the anatomical ACL attachment site at the “10 o’clock” position. In this report, we describe the use of the Bio-TransFix device with an anteromedial portal technique. Using this technique, the surgeon has more freedom to place the graft in an anatomical position, while combining the advantages of the excellent biomechanical properties of this device.     

Bone graft fixation in anterior cruciate ligament reconstruction evaluated by radiostereometric analysis

For most anterior cruciate ligament reconstruction techniques, the tensile strength of the ligament substitutes and the surgical methods of fixation have been examined. In the present study seven consecutive patients with a chronic anterior cruciate ligament deficiency, who were reconstructed with a bone-patellar tendon-bone graft, were followed. The migration of the bone blocks was examined with radiostereometric analysis immediately postoperatively and after 3 and 12 months. The median migration of the bone blocks in the femur was 0.4 mm and in the tibia 0.4 mm. Clinical examination was undertaken preoperatively and one year postoperatively. We conclude that the use of interference screws seems to be a reliable method for fixation in anterior cruciate reconstruction and that healing of the bone blocks occurs during the first three postoperative months.     

A new interference nail fixation for anterior cruciate ligament soft tissue grafts

We present a new device for femoral and tibial fixation in anterior cruciate ligament reconstruction using soft tissue. We evaluated the method biomechanically in pullout tests using human cadaver knee joints. Fixation strengths ranged from 300 ± 60 to 600 ± 50 N (mean 400 ± 50 N). This corresponds to loads in the graft during aggressive rehabilitation although cadaveric specimens were used. With respect to primary fixation strength this implant is a reasonable alternative for anterior cruciate ligament graft fixation. Received: 6 October 1999 Accepted: 5 March 2000     

Press-fit fixation in reconstruction of anterior cruciate ligament,using bone–patellar tendon–bone graft

We studied arthroscopic reconstruction of the anterior cruciate ligament (ACL) using patellar ligament-bone graft fixed to the femur by press-fit technique. The main feature of this technique was a stable bony fixation on the femoral site without using interference screws or other fixation devices. We treated 42 patients with ACL rupture by this technique; clinical examination was carried out preoperatively and at 3 months, 6 months, and then every 6 months using the standard criteria for evaluation of the IKDC (mean follow-up 29 months, 22–41). CT and MRI were performed 6 months postoperatively. According to IKDC score 37 knee (88%) were graded as normal or nearly normal, 4 (10%) as abnormal, and one (2%) as severely abnormal, none of the poor results was due to instability. Reconstruction of the ACL by press-fit technique is a more anatomically oriented method of fixation without the complications of interference screws at the femoral attachment of the graft.     

Insertion of autologous tendon grafts to the bone: a histological and immunohistochemical study of hamstring and patellar tendon grafts

This study examined the structure of the insertion of autologous tendon grafts used for anterior cruciate ligament reconstruction. Biopsy specimens of the femoral ¶and tibial bone graft interface were obtained at revision surgery in 14 patients (6 with hamstring grafts, 8 with a patella tendon graft). The specimens were analyzed by light microscopy and immunohistochemistry (confirming type I, type II, and type III collagen). The insertions of hamstring autografts to the bone tunnel have three characteristic histological zones. Zone 1 is composed of the dense connective tissue of the graft. The collagen fibers of the graft enter the bone under oblique angles. Zone 2 is composed of woven bone with ¶a sharp transition to the lamellar bone of the tibia (zone 3). Immunohistochemistry revealed the presence of type I and type III collagen within the dense connective tissue of the graft. The woven and lamellar bone showed positive immunostaining for antibodies against type I collagen only. This structure resembled a fibrous ligament or tendon insertion. In the majority of patients with a patella tendon graft the structure of the insertion resembled a chondral enthesis. The chondral insertion of the graft to the bone is composed of four characteristic zones. Between the dense connective tissue of the graft (zone 1) and bone (zone 4) there is a zone of fibrocartilage (zone 2). Close to the bone the fibrocartilage is mineralized (zone 3). Within the fibrocartilage the immunohistochemical analysis confirmed type II collagen. This structure resembled the chondral enthesis of the normal anterior cruciate ligament. However, in cases in which the distal bone bloc has been fixated outside the tibial tunnel, the tibial insertion of the patellar tendon graft resembled a fibrous insertion. While both types of tendon grafts heal to the bone of femur and tibia, the insertion of patella tendon grafts healing by bone plug incorporation resembles the chondral insertion of the normal anterior cruciate ligament and may have a more physiological connection to the bone than hamstring grafts.     

A comparison of five tibial-fixation systems in hamstring-graft anterior cruciate ligament reconstruction

The weak point in an ACL reconstruction immediately after surgery is the tibial fixation of the graft. This factor will often limit the return to load-inducing activities. Many new hamstring-graft fixation devices have been introduced for cruciate ligament reconstruction, but there is little comparative data on their performance. This work tested the hypotheses that some of these devices will resist graft slippage under cyclic loads better than others, and that some will have higher ultimate strength than others. Five devices were tested: WasherLoc, Intrafix fastener; and RCI, Delta Tapered, and Bicortical interference screws. Cyclic loads representing normal walking activity (1000 cycles from 70 to 220 N) and ultimate strength tests were done, using calf tibiae (similar bone density to young human tibiae) and four-strand tendon grafts, with eight tests of each device for each of cyclic and ultimate tensile strength tests. A series of graft creep tests under cyclic loads was also done. The results showed that there was no significant difference in graft construct elongation under cyclic loads (range 0.7–1.3 mm) after allowing for 0.4 mm mean graft creep. The WasherLoc gave the highest ultimate strength (945 N, p <0.001, range 490–945 N). We concluded that all devices performed well under cyclic loads that represented normal walking activity, but the ultimate strengths differed. The performance under cyclic load was better than has been published for conventional interference screws. This evidence suggests that it may now be safe to mobilise younger patients less cautiously immediately after hamstring-graft ACL reconstruction.     

Intraarticular anterior cruciate ligament graft placement on the average most isometric line on the femur. Does it reproducibly restore knee kinematics?

In the past, there has been a plausible hypothesis that anterior cruciate ligament graft placement at isometric sites, such that the tibial and femoral attachment sites remain equidistant from each other throughout knee range of motion, would increase the likelihood of a satisfactory outcome. For a given tibial placement we wanted to determine whether placing the graft on the average of the most isometric femoral line, a fixed distance from the outlet of the intercondylar notch, would return normal laxity to all knees. The three-dimensional kinematics of seven cadaveric knees were measured for angles from full extension to 90 degrees of flexion at 15 degrees increments. Physiologic levels of quadriceps muscle forces were applied to the intact knee, after transection of the anterior cruciate ligament, and after ligament reconstruction with a patellar tendon graft. On average, the reconstruction was found to return anterior-posterior translation, internal-external rotation, and varus-valgus rotation to levels not significantly different from those of the intact knee. However, the ranges of the translation and rotations were large. Placing the graft on the average most isometric femoral line did not restore knee laxity to normal in all knees. This supports the need to customize graft placement in each knee at the time of surgery.     

Augmentation of autologous hamstring graft during anterior cruciate ligament reconstruction using the bone chip technique

The use of autologous quadrupled hamstring tendon graft is a well-known technique for anterior cruciate ligament reconstruction. In cases where the diameter of the graft is inadequate, the stability of graft fixation and subsequent bone to tendon healing may be compromised. We describe a new technique to augment the autologous double looped hamstring tendon graft during anterior cruciate ligament reconstruction using cancellous bone chips. This simple technique effectively enhances graft fixation and stability.     

Hamstring anterior cruciate ligament reconstruction using femoral cross pin fixation

Surgical reconstruction of the anterior cruciate ligament (ACL) with bone-patella tendon-bone (BPTB) graft hasbecome the most commonly performed procedure for the unstable cruciate-deficient knee. The use of BPTB has been complicated by chronic anterior knee pain, loss of extension, patella tendon rupture, and patella fractures. The TransFix technique uses a double-looped semitendinosis and gracilis (DLSG) graft that is stronger than BPTB, and has less graft site and operative morbidity. This technique uses cross-pin femoral fixation and tibial interference screw fixation in the tibia that allows immediate weight bearing and an aggressive rehabilitation program. Results are equal to those previously reported for BPTB.     

A biomechanical evaluation of transcondylar femoral fixation of anterior cruciate ligament grafts

BACKGROUND: Interference screw fixation of the graft in anterior cruciate ligament reconstruction is considered the gold standard, but limited clinical experience suggests that transcondylar fixation is equally effective. PURPOSE: To compare transcondylar and interference screw fixation. STUDY DESIGN: Ex vivo biomechanical study. METHODS: Twenty pairs of unembalmed knees underwent anterior cruciate ligament reconstruction with patellar tendon autografts. In 1 knee of each pair, the bone plug was stabilized in the femoral tunnel with standard interference screws; in the other knee, transcondylar screws were used. Testing to failure occurred immediately or after 1000 cycles of sinusoidal loading (30 to 150 N) (20 paired reconstructions each). Fixation stiffness, strength, graft creep, displacement amplitude, and change in amplitude were measured and compared (repeated measures anaylsis of variance with Tukey test; P <.05). RESULTS: There was no significant difference in acute strength, maximum load within 3 mm, or stiffness between transcondylar fixation (410 +/- 164 N, 183 +/- 93 N, and 49.6 +/- 28 N/mm, respectively) and interference fixation (497 +/- 216 N, 206 +/- 115 N, and 61 +/- 37.8 N/mm, respectively). Similarly, there was no significant difference in cyclic strength, maximum load within 3 mm, or stiffness between transcondylar fixation (496 +/- 214 N, 357 +/- 82.9 N, and 110 +/- 27.4 N/mm, respectively) and interference fixation (552 +/- 233 N, 357 +/- 76.2 N, and 112 +/- 26.8 N/mm, respectively). Predominant modes of failure were bone plug pullout (transcondylar fixation) and tendon failure or bone plug fracture (interference fixation). CONCLUSIONS: Transcondylar screw fixation of the patellar tendon autograft into the femoral tunnel performed mechanically as well as interference screw fixation. CLINICAL RELEVANCE: The results suggest that transcondylar and interference screws provide similar fixation for anterior cruciate ligament reconstruction.     

Soft tissue graft interference fit fixation: observations on graft insertion site healing and tunnel remodeling 2 years after ACL reconstruction in sheep

Using soft tissue grafts for anterior cruciate ligament (ACL) reconstruction, insertion site healing plays a crucial role in the long-term fate of the graft. It has been shown in an experimental animal study that using a soft tissue graft and anatomic graft fixation, a direct ligamentous insertion alike the native ACL developed 24 weeks postoperatively. Yet there are no reports on the long-term insertion site healing of anatomically fixed soft tissue grafts. The objective of this study was to evaluate graft insertion site healing, the intra-tunnel fate of the graft and its osseous replacement 2 years after ACL reconstruction in sheep. The left ACLs of six sheep were replaced by an autologous flexor tendon split graft and anatomically fixed with biodegradable poly-(d, l-lactide) interference screws. Animals received polychromic sequential labeling at different points in time to determine bone apposition per period. For evaluation of the insertion site healing and intra-tunnel changes, MRI scans were taken in vivo. Following sacrifice, radiographic imaging, conventional histology and fluorescence microscopy was undertaken. Most of the specimens showed a wide direct ligamentous insertion. It showed patterns alike the direct ligament insertion seen in intact ACLs. The intra-tunnel part of the graft had completely lost its tendon-like structure and in two cases, it was separated from the graft insertion by a thick bony layer. The biodegradable interference screw was fully degraded in all specimens. Ossification of the former drill tunnels was intense, showing only partial-length tunnel remnants in one femoral and three tibial specimens. As the graft heals to the joint surface and the aperture site is closed with soft tissue, mechanical stress of the intra-tunnel part of the graft is eliminated and the bone tunnel is protected from synovial fluid, resulting in osseous bridging of the tunnel aperture site, accelerated intra-tunnel graft resorption and its osseous replacement.     

Compaction versus extraction drilling for fixation of the hamstring tendon graft in anterior cruciate ligament reconstruction

Initial strength of quadrupled hamstring tendon grafts fixed with titanium interference screws was assessed in 30 pairs of porcine tibiae. Bone tunnels were drilled with either compaction drilling (stepped routers) or conventional extraction drilling (cannulated drill bits). Fifteen pairs of specimens were subjected to a single-cycle load-to-failure test, while the rest underwent a cyclic-loading test to further assess the quality of the fixation. No significant difference between the two drilling techniques was found with regard to yield load, displacement at yield load, stiffness, or mode of failure. Porcine trabecular bone mineral density was determined using peripheral quantitative computed tomography and compared with that of young women and men at a site corresponding to that of the tibial bone drill hole of an anterior cruciate ligament reconstruction. There was a significant difference between the two species (210 +/- 45 mg/cm(3) in porcine tibial bone versus 129 +/- 30 mg/cm(3) in women and 134 +/- 34 mg/cm(3) in men), suggesting that porcine knee specimens may have limitations in studies of graft fixation in anterior cruciate ligament reconstruction. We found no difference between extraction and compaction drilling in initial fixation strength of a hamstring tendon graft for anterior cruciate ligament reconstruction using a porcine model.     

A biomechanical comparison of different surgical techniques of graft fixation in anterior cruciate ligament reconstruction

Different surgical methods of graft fixation in ACL reconstruction were examined to determine the effects on mechanical properties of the reconstructed ACL. Ten human cadavers were used in this study. Six different types of grafts were studied. The tendon grafts were removed from each cadaver and fixed to femurs and tibias as ACL substitutes with different surgical fixation methods, leaving femur-reconstructed graft-tibia preparations. The surgical techniques used were staple fixation, tying sutures over buttons, and screw fixation. In the latter, the screws were introduced through femoral and tibial drill holes from the outside in order to achieve interference fit as described by Lambert. Tensile testing demonstrated that the original ACL is significantly stronger than the graft used for reconstruction in linear load, stiffness, and maximum tensile strength. All of the failures of the reconstructed ACL grafts occurred at the fixation site, indicating that the mechanically weak link of the reconstructed graft is located at the fixation site. Among the different methods of fixation, one-third of the patellar tendon secured with a cancellous screw, especially with a custom designed large diameter screw, showed significantly higher values. Although many other factors affect the success of ACL reconstruction, our study indicates that the method of surgical fixation is the major factor influencing the graft's mechanical properties in the immediate postoperative period.     

How four weeks of implantation affect the strength and stiffness of a tendon graft in a bone tunnel: a study of two fixation devices in an extraarticular model in ovine

BACKGROUND: For a tendon graft to function as an anterior cruciate ligament, the tendon must heal to the bone tunnel. We studied the effect of 4 weeks of implantation on the strength and stiffness of a tendon in a bone tunnel using two different fixation devices in an ovine model. HYPOTHESIS: The type of fixation device in anterior cruciate ligament reconstruction may affect early healing, which can be measured as the strength and stiffness of a tendon in a bone tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: An extraarticular tendon graft reconstruction was performed in ovine tibias. The graft was fixed with either a bioresorbable interference screw or a WasherLoc. After 4 weeks of implantation the strength and stiffness of the complex and the tendon graft-bone tunnel interface were determined by incrementally loading specimens to failure. RESULTS: For the interference screw, the strength deteriorated 63% and the stiffness deteriorated 40%. For the WasherLoc, the strength was similar and the stiffness improved 136%. CONCLUSIONS: The type of fixation device determines whether the strength and stiffness of a tendon in a bone tunnel increases or decreases after implantation. Clinical Relevance: The pace of rehabilitation may need to be adjusted based on the type of fixation device used to secure a soft tissue graft.     

Biomechanical analysis of femoral tunnel pull-out angles for anterior cruciate ligament reconstruction with bioabsorbable and metal interference screws

BACKGROUND: Fixation strength of metal and bioabsorbable interference screws has not been evaluated while varying the anterior cruciate ligament graft tension angle. HYPOTHESIS: There is no difference in fixation strength between 2 types of interference screws for anterior cruciate ligament graft fixation while the graft tension angle is varied relative to the femoral tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-eight anterior cruciate ligament reconstructions were performed using immature porcine femurs stripped of soft tissue and doubled-over porcine flexor digitorum profundus tendon grafts. Specimens were randomized to bioabsorbable or titanium interference screw fixation. Specimens were randomized to one of three pull angles (0 degrees , 30 degrees , 60 degrees ) representing loading at different knee flexion angles (n = 8/group). Reconstructed ligaments were tensioned to 10 N followed by 200 loading cycles between 10 and 150 N and a final failure test. Construct elongation (mm) at 100 and 200 cycles and failure load (N) were analyzed using a 2-way analysis of variance (P < .05). RESULTS: Screw material interacted significantly with graft tension angle, as the bioabsorbable screw specimens demonstrated significantly greater fixation strength when tensioned at greater angles. Specimens fixed with bioabsorbable screws showed significantly less elongation at both 100 and 200 cycles and significantly greater failure load compared with titanium screws. CONCLUSION: Bioabsorbable interference screws acutely have increased fixation strength compared with titanium interference screws for anterior cruciate ligament grafts loaded at greater tension angles. CLINICAL RELEVANCE: The strength of anterior cruciate ligament reconstruction fixation increases with increasing divergence between the tension angle and femoral tunnel, a condition seen when the knee approaches full extension.