Biodegradable Interference Screw Research Articles

Hybrid Fixation Improves Structural Properties of a Free Tendon Anterior Cruciate Ligament Reconstruction

This study sought to characterize the structural properties of a combined bioabsorbable interference screw and closed loop and button fixation technique (Hybrid) for femoral fixation of a free tendon graft versus a bioabsorbable interference screw or closed loop and button suspension fixation method alone. Eighteen porcine femora and quadrupled cadaveric flexor tendons were treated in 3 experimental fixation study groups: (1) closed loop and button suspension (CLBS), (2) bioabsorbable interference screw (BIF), and (3) closed loop and button suspension with supplemental biodegradable interference screw (Hybrid). An Instron testing machine (Instron, Canton, MA) was used to quantify each group's structural properties with cyclic loading and tensile load-to-failure. A video digitizing system measured graft deformation during load-to-failure. The Hybrid fixation group had significantly greater structural properties compared with the CLBS or BIF group. Ultimate loads (mean [SEM] in Newtons) were 1184 (88) N, 813 (83) N, and 561 (62) N for the Hybrid fixation group, CLBS group, and BIF group, respectively. Quasi-steady state cyclic stiffness (mean [SEM] in Newtons per millimeter) was also greatest for the Hybrid fixation group at 165 (11) N/mm, compared with CLBS (122 [8] N/mm), and BIF (95 [9] N/mm). Femoral free tendon hybrid fixation provides superior structural properties under tensile and cyclic displacement conditions while preserving the working length of the native anterior cruciate ligament. Hybrid femoral fixation may minimize postoperative laxity for free tendon 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.

Broken Delta interference screw after ACL reconstruction: a report of two cases

We report two cases of an intra-articular dislocation of the proximal part of a broken biodegradable interference screw (Delta screw) used for tibial fixation of a semitendinosis gracilis graft in an unstable knee.

Intraarticular migration of a broken biodegradable interference screw after anterior cruciate ligament reconstruction

Poly-L: -lactic acid biodegradable screws have been used effectively for graft fixation in anterior cruciate ligament (ACL) reconstruction. The overall complication rate associated with the use of this implant is low, although some authors reported complications, such as osteolysis and aseptic effusion of the knee joint. We report a case of a 29-year-old female patient with a failure of a biodegradable interference screw at 22 months after ACL reconstruction using bone-patellar tendon-bone graft. In this illustrated case, the screw broke and migrated into the knee joint. In addition, we performed a detailed review of the medical literature from 1990-2005 to identify possible causes of biodegradable screw failures. We identified six published cases of bioabsorbable interference screw failure with migration into the knee joint. Several authors have reported small diameter of the screw, poor bone quality, bone resorption, and screw divergence as potential causes for intraarticular migration of metallic interference screws. With regard to bioscrews, no specific risk factors for screw breakage and intraarticular migration have been reported. ACL reconstruction with the use of bioabsorbable interference screws for fixation is considered to be reliable. However, we need to be aware of potential problems associated with the use of this implant. Early recognition of bioscrew failure may prevent associated morbidities, such as subsequent cartilage damage.

Hamstring Tendon versus Patellar Tendon Anterior Cruciate Ligament Reconstruction Using Biodegradable Interference Fit Fixation

Background There are still controversies about graft selection for primary anterior cruciate ligament reconstruction, especially with respect to knee stability and functional outcome. Hypothesis Biodegradable interference screw fixation of hamstring tendon grafts provides clinical results similar to those achieved with identical fixation of bone-patellar tendon-bone grafts. Study Design Cohort study; Level of evidence, 2. Methods In 1996 and 1997, primary isolated anterior cruciate ligament reconstruction using a bone-patellar tendon-bone autograft was performed in 72 patients. Since 1998, hamstring tendons were used as routine grafts. Matched patients with a hamstring tendon graft were selected from a database (n = 284). All patients were followed prospectively for a minimum of 2 years with KT-1000 arthrometer testing, International Knee Documentation Committee score, and Lysholm score. Results In the bone-patellar tendon-bone group, 9 patients were excluded because of bilateral rupture of the anterior cruciate ligament, 3 patients (4.2%) had a graft rupture, and 4 patients were lost to follow-up (follow-up rate, 92.1%), leaving 56 patients for a matched-group analysis. In the hamstring tendon database, the graft rupture rate was 5.6% (P = .698). The Lysholm score was 89.7 in the patellar tendon group and 94 in the hamstring tendon group (P = .003). The KT-1000 arthrometer side-to-side difference was 2.6 mm for the patellar tendon group and 2.1 mm for the hamstring tendon group (P = .041). There were significantly less positive pivot-shift test results in the hamstring tendon group (P = .005), and hamstring tendon patients showed lower thigh atrophy (P = .024) and patellofemoral crepitus (P = .003). Overall International Knee Documentation Committee scores were better (P = .001) in the hamstring tendon group (hamstring tendon: 34 × A, 21 × B, 0 × C, 0 × D; bone-patellar tendon-bone: 17 × A, 32 × B, 6 × C, 0 × D). Conclusions In this comparison of anterior cruciate ligament reconstruction with bone-patellar tendon-bone and anatomical hamstring tendon grafts, the hamstring tendon graft was superior in knee stability and function. These findings are partially contrary to previous studies and might be attributable to the use of an anatomical joint line fixation for hamstring tendon grafts. Thus, hamstring tendons are the authors’ primary graft choice for anterior cruciate ligament reconstruction, even in high-level athletes.

Cyclic Loading Comparison Between Biodegradable Interference Screw Fixation and Biodegradable Double Cross-Pin Fixation of Human Bone-Patellar Tendon-Bone Grafts

The aim of this study was to compare ultimate load, yield load, stiffness, and displacement after cyclic loading of a cross-pin technique and an interference screw technique for the fixation of bone-patellar tendon-bone (BPTB) grafts in anterior cruciate ligament (ACL) reconstruction. Biomechanical in vitro study. The devices tested were 2 2.7-mm biodegradable pins (RigidFix; Ethicon, Mitek Division, Norderstedt, Germany) and biodegradable interference screws (Absolute; Innovasive Devices, Marlborough, MA). Each device was used for the fixation of 10 8-mm, 9-mm, or 10-mm sized human BPTB grafts in tunnels drilled in bovine knees. Ultimate load, yield load, stiffness, and displacement after cyclic loading (1,000 cycles between 50 and 250 N) were then evaluated. All 8-mm grafts that were fixed with cross-pins failed after a mean of 124 cycles of load. The 9-mm and 10-mm grafts survived the cyclic loading protocol. Yield load and maximum load of the 10-mm groups (cross-pin and interference screw) were significantly higher than that of the 9-mm groups. There was no significant difference in maximum load, yield load, and stiffness between the cross-pin and interference screw fixation technique for 1 graft size. The biomechanical data suggest that femoral fixation of 9-mm and 10-mm BPTB grafts using 2.7-mm biodegradable cross-pins leads to primary stability that is comparable to that of biodegradable interference screws. Fixation of 8-mm BPTB grafts using 2.7-mm biodegradable cross-pins had poor results. The diameter of the bone block is the limiting factor for the final fixation strength and the cyclical survival when using cross-pins. We strongly recommend not using this technique for bone blocks smaller than 9 mm in diameter.

Soft-Tissue Interference Fixation: Bioabsorbable Screw Versus Metal Screw

To compare the biomechanical properties of eccentrically positioned bioabsorbable and titanium interference screws for quadrupled hamstring tendon graft (QHTG) fixation. In vitro, biomechanical study. In 10 paired cadaveric tibiae and femurs (mean age, 66.5 years; range, 53 to 81 years), QHTG fixation was performed in tunnels sized to within 0.5 mm of QHTG diameter using either a titanium (RCI; Smith & Nephew Donjoy, Carlsbad, CA) or a bioabsorbable (BioScrew; Linvatec, Largo, FL) screw of equal size. Constructs then underwent biomechanical load-to-failure testing on a servo-hydraulic device at 20 mm/min. Load at failure was greater for femoral-side QHTG fixation using the bioabsorbable screw than the titanium screw (486 +/- 223.7 N v 246 +/- 99.1 N, P = .006); however, displacement did not differ (P = .81). There were no statistically significant differences between groups for tibial side load at failure (P = .54), stiffness (P = .44), or displacement (P = .50). Screw thread-induced graft laceration was more frequently observed in the titanium screw group (9 of 10 grafts during femoral-side testing, 0 of 10 grafts during tibial-side testing) than in the bioabsorbable screw group (0 of 10 grafts during femoral-side testing, 1 of 10 grafts during tibial-side testing). BioScrew interference screw fixation was comparable or superior to RCI titanium interference screw fixation. BioScrew interference screw fixation also produced less screw thread-induced laceration of the QHTG during load-to-failure testing. Use of a biodegradable interference screw positioned directly against a soft-tissue graft provides fixation properties similar to those of a metal interference screw.

Biomechanical comparison of posterior cruciate ligament reconstruction techniques using cyclic loading tests

Posterior tibial translation (PTT) of the posterior cruciate ligament (PCL) reconstructed-knee under cyclic loading of 1,000 cycles with a 100-N load was compared between four different procedures, including two reconstructions with patellar tendon graft (transtunnel and inlay techniques) and two reconstructions with hamstring tendon graft (Endobutton and EndoPearl techniques) in twelve fresh-frozen human knees. The EndoPearl technique is a direct tendon fixation using biodegradable interference screws and an anchoring device, while the Endobutton technique is an indirect tendon fixation using a titanium button and surgical tape. The change of PTT after cyclic loading in the Endobutton technique was significantly greater than in the other reconstruction technique. No graft rupture at the killer turn or complete pullout from the bone tunnel was found. The advantage of the inlay technique compared to the transtunnel technique with respect to the posterior stability could not be shown in the current study. Posterior laxity of PCL reconstructed-knees with hamstring tendon graft using the Endobutton technique increased more easily than that with patellar tendon graft. For PCL reconstruction using the hamstring tendon graft, anatomical fixation may be preferable to prevent excessive posterior laxity in the early phase of the rehabilitation protocol.

Fixation of the graft in reconstruction of the anterior cruciate ligament

Methods of reconstruction of the anterior cruciate ligament (ACL) have developed considerably over the last 15 years. Primary repair and extra-articular procedures have failed to reproduce satisfactory stability of the knee[1][1] and the use of prosthetic ligaments has been abandoned.[2][2] These

Development of a perforated biodegradable interference screw

The objective was to develop a perforated biodegradable interference screw to allow for enhanced osseous implant integration without impairing screw stability during insertion. Mechanical testing, followed by animal study. At first, manual perforation of 8 x 23-mm biodegradable poly-(L-co-D,L-lactide) interference screws was performed, using 3 different perforation patterns (clockwise spiral, counter-clockwise spiral, and parallel perforation), followed by torsional tests. Next, parallel perforated screws (n = 6) and unperforated control screws (n = 6) were applied to the proximal tibia of 12 sheep. The sheep were put down after 24 weeks and the screw site was examined histologically. Subsequently, molding of a parallel perforated screw followed by torsional tests was undertaken. The parallel perforated screw presented a torsional strength insignificantly different from the unperforated control screw and well beyond the reported maximum manual insertion torques of biodegradable interference screws in young human bone. When compared with the regular unperforated interference screw, the molded perforated screw exhibited a torsional strength of 91%, indicating a secure surgical application. In contrast to the unperforated screw, histologic evaluations revealed clear bone ingrowth into the perforations including the core of the perforated interference screw. Perforated, "cage-like" interference screws may be promising for the acceleration of osseous implant integration into the bone with a very low risk of screw breakage during insertion. To ameliorate osseous implant integration and possibly enhance ossification of former implant site in anterior cruciate ligament surgery.

Primary stability of hamstring graft fixation with biodegradable suspension versus interference screws

During the early postoperative period, the stability of the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. The aim of this study was to evaluate if the initial fixation strength of a new suspension screw is comparable to that of the biodegradable interference screw fixation technique in the hamstring reconstruction of the anterior cruciate ligament (ACL). Experimental laboratory study. We evaluated the initial fixation strength of a biodegradable poly-L-lactide/tri-calcium phosphate (PLLA/TCP) screw that suspended the graft in the bone tunnel and compared it with the strength of an interference screw for fixation of hamstring grafts in ACL reconstruction using bovine knees. Single-cycle and cyclic loading tests were performed using a materials testing machine. The suspension screw provided a significantly higher yield load and ultimate failure load than the interference screw. There was no significant difference in the stiffness of both techniques. The typical failure mode for the suspension screw was fracture of the screw and for the interference screw it was slippage of the graft past the screw. In cyclic testing, both methods of fixation ran out to 1,000 cycles up to 250 N with a mean displacement of 2.6 mm (range, 1.8 to 3.3 mm) for the suspension screw and 4.1 mm (range, 2.3 to 6.0 mm) for the interference screw. Only the grafts fixed with the suspension screw survived a protocol with 1,000 cycles up to 400 N. Our biomechanical data suggest that hamstring graft fixation using a biodegradable PLLA/TCP suspension screw provides an alternative to interference screw fixation. Hamstring graft fixation using a suspension screw provides a reasonable alternative to interference screw fixation.

Biomechanical evaluation of a new cross-pin technique for the fixation of different sized bone?patellar tendon?bone grafts

To overcome the disadvantages of interference-screw fixation of bone-patellar tendon-bone (BPTB) grafts, new fixation techniques for anterior cruciate ligament (ACL) grafts using biodegradable pins have been developed. The hypothesis of the present study was that cross-pin fixation techniques provide a primary stability that is comparable to that of interference screws. A biomechanical in vitro study was discussed. Human BPTB grafts of 8, 9 and 10 mm diameter were fixed in bovine knees with biodegradable cross pins (diameter: 2.0, 2.7 or 3.2 mm) or biodegradable interference screws. Stiffness and ultimate load were evaluated. For 9 and 10 mm BPTB grafts, no statistically significant difference in maximum load and stiffness was found between the four fixation techniques tested. For 8 mm bone blocks the maximum load of the 3.2 mm pins (274.2 N) was significantly lower than for the 2.0 mm pins (479.8 N) and the interference screws (504.0 N). Predominant failure mode in this group was bone-block fracture. Thicker grafts (9 and 10 mm) fixed with the 2.0 mm pins predominantly failed by implant fracture. Femoral fixation of 8, 9 and 10 mm BPTB grafts using cross pins leads to biomechanical properties that are comparable to biodegradable interference screws when tested by a single-cycle load to failure. Cross pins provide a rigid fixation for 9 and 10 mm BPTB grafts.

Initial Fixation Strength of Two Bioabsorbable Pins for the Fixation of Hamstring Grafts Compared to Interference Screw Fixation

Background During the early postoperative period, the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. Hypothesis The initial fixation strength of a double cross pin fixation technique is comparable with the biodegradable interference screw fixation technique. Study Design Experimental laboratory study. Methods The authors examined the initial fixation strength of two 3.3-mm bioabsorbable pins compared to interference screws for hamstring grafts in bovine knees. Results Analysis of yield load, maximum load, and stiffness in the single-cycle loading test showed no statistically significant differences for cross pin and interference fixation (P< .05). For cross pins and interference screws, the mean displacement under 1000 cycles to 250 N was 5.07 (±1.9) mm and 4.81 (±2.5) mm, stiffness 252 (±78) N/mm and 289 (±148) N/mm. Only grafts fixed with cross pins survived 1000 cycles to 450 N. Conclusion The initial fixation strength of the double cross pin technique is comparable to that of interference screw fixation with a stiffness comparable to that of the native ACL. Clinical Relevance Hamstring graft fixation using two cross pins provides an alternative to bioabsorbable interference screw fixation.

Primary stability of bone-patellar tendon-bone graft fixation with biodegradable pins

Purpose: We evaluated the initial bone-patellar tendon-bone (BPTB) graft fixation strength of biodegradable pins compared with interference screws in anterior cruciate ligament reconstruction using bovine knees. Type of Study: Biomechanical in vitro study. Methods: Ten BPTB grafts from human donors fixed with 2 biodegradable 2.7-mm pins (Rigid Fix; Ethicon, Mitek Division, Norderstedt, Germany) crossing the bone block perpendicular and 10 BPTB grafts fixed with conventional biodegradable interference screws (Absolute Absorbable Interference Screw; Innovasive Devices, Marlborough, MA) underwent ultimate single-cycle failure loading at a rate of 200 mm/min. The grafts were fixed to bovine tibia to simulate young human femoral bone density. Failure mode, displacement before failure, and ultimate failure load were tested with a testing machine. The pullout force was in line with the bone tunnel to simulate a worst case scenario. Results: The failure mode for cross pins was either fracture of the bone block (5 specimens) or fracture of the articular pin (5 specimens). The failure mode for interference screws was slippage past the screw in all specimens. In the single cycle loading test, the mean yield load for the biodegradable pins was 400.2 (± 122.4) N, maximum load, 524.6 (± 136.6) N, with a mean stiffness of 155.2 (± 32.4) N/mm. The yield load at failure for the interference screw was 402.7 (± 143.9) N, maximum load 515.7 (± 168.5) N with a mean stiffness of 168 (± 42) N/mm. Conclusions: Fixation of a BPTB graft with 2 biodegradable 2.7-mm pins (Rigid Fix) leads to primary stability that is comparable to fixation with biodegradable interference screws.

Hamstring insertion site healing after anterior cruciate ligament reconstruction in patients with symptomatic hardware or repeat rupture: a histologic study in 12 patients

Purpose: Our goal was to characterize the type of biologic anchor of hamstring tendons to the femoral tunnel in cases of transfixion fixation for the anterior cruciate ligament (ACL) reconstruction. The histologic bone-hamstring tendon anchorage is not yet clearly understood despite many experimental and some clinical studies. It constitutes the weak point of the ACL reconstruction. The type of fixation, either distant from the joint such as transfixion fixation or at the tunnel entrance such as aperture fixation will determine a specific tendon-bone healing process. Type of study: Histological study. Methods: We performed ACL reconstruction with 4 strands of semitendinosus and gracilis tendons fastened by a transfixion fixation. Femoral fixation was secured by transfixion (Transfix; Arthrex, Naples, CA) and tibia fixation by a biodegradable interference screw and 2 staples. Between 3 and 20 months after surgery, we performed 12 hamstring tendon biopsies (in 9 men and 3 women; mean age, 29 years). Biopsies were performed 2 cm from the femoral outlet in 10 patients undergoing hardware removal or by coring the femoral tunnel in 2 cases of repeat rupture. In 8 cases, the femoral device was removed for persistent lateral pain, in 2 cases for instability of the hardware, and in 2 cases a repeat rupture of the graft occurred. The samples were taken by coring a tunnel 5 mm in diameter, with a tubular harvester, along the femoral Transfix axis. Each fragment was stained with H&E, Solochrome cyanine, or Masson-trichrome, and microscopical examination was performed, including polarized light. Results: At 3 months (in 1 case), a fibrovascular interface was seen between the tendon and uncalcified osteoid with very few collagen fibers. At 5 and 6 months (in 2 cases), some Sharpey-like fibers and less immature woven bone was seen. Maturity of the secondary insertion was seen after at least 10 months in 5 cases. In 2 cases, no contact was seen at the biopsy site despite good clinical stability. The 2 remaining cases underwent repeat rupture at the midsubstance of the graft at 12 and 17 months after surgery. In the first case, the tendon-bone fixation was limited at the outlet of the femoral tunnel with no fixation inside the tunnel. In the second case, the fixation was continuous with Sharpey fibers along the tunnel. Conclusions: According to our histologic results in patients, the time to obtain a mature indirect anchorage at the top of the tunnel was 10 to 12 months, which is much longer than in reported animal models (6 to 24 weeks). To our knowledge, this is the first clinical study reporting the histologic type of femoral ligament insertion 2 cm from the outlet of the tunnel with hamstring autograft for ACL reconstruction.

Paper #61 ACL replacement in sheep with open physes: an evaluation of risk factors for growth disturbances

An in vivo sheep model was used to examine the effect of different transphyseal ACL reconstruction techniques on longitudinal growth. The following risk factors for growth disturbances were analyzed: (1) injury to the perichondral groove of Ranvier on the femoral side, (2) transphyseal bony bridge formation with respect to different graft diameters and (3) transphyseal graft fixation using a biodegradable interference screw on the tibial side.

The effect of outlet fixation on tunnel widening

Purpose: To compare the development of tibial tunnel widening after a standard bone–patellar tendon–bone autograft (BPTB) to a flipped BPTB that allows interference screw outlet fixation with a bone plug at both femoral and tibial tunnels, and to identify any observable clinical effect. The hypothesis of this study was that the outlet fixation achieved by the flipped BPTB technique results in diminished tunnel widening at the site of the bone plug. Type of Study: Nonrandomized control trial. Methods: The postoperative radiographs of 67 BPTB anterior cruciate ligament (ACL) reconstructions were retrospectively reviewed; 31 had conventional BPTBs and 36 had the bone plugs flipped at the tibial end to achieve interference screw fixation of the bone plug at the tibial outlet as well as the femoral outlet. Biodegradable interference screws (PLLA) were used in all cases, which facilitated tunnel measurements. One week after surgery, the maximal tibial bone tunnel widths were measured on anteroposterior and lateral radiographs 1 cm below the tibial plateau. These initial postoperative measurements were compared with measurement from radiographs taken annually thereafter. Clinical information including Lysholm, Tegner, IKDC activity, Lachman, pivot-shift, and range of motion data was also obtained and compared for the 2 groups. Results: In the conventional BPTB group, at an average follow-up of 28 months, 28 of 31 (90%) showed at least a 2-mm increase (20%) in the tibial tunnel width. The mean maximum tunnel width increase was 2.2 mm. In the flipped BPTB group, at an average follow-up of 31 months, none of these 36 showed any increase in tunnel size. In fact, 15 patients had no distinct tibial tunnel remaining and, of the other 21, the average remaining tunnel width was 3 mm. The clinical results evaluating the Tegner, Lysholm, IKDC activity levels, KT, and physical examination parameters showed no significant differences between these 2 groups. The tunnel width decreased during the first year, but remained unchanged after 12 months. No tunnel dilation was observed with bone plug outlet fixation while 90% of the conventional group had at least a 20% increase (P <.001). Conclusions: Outlet fixation with the flipped BPTB technique decreased the tibial tunnel width 1 cm below the plateau while 90% of the conventional BPTB patients demonstrated an average widening of 20%.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 5 (May-June), 2003: pp 485–492

Histological findings of tendon-bone healing following anterior cruciate ligament reconstruction with hamstring grafts.

The purpose of the study was the histological examination of tendon-bone healing of hamstring grafts after anterior cruciate ligament (ACL) reconstruction. During five arthroscopies done 6-14 months after ACL reconstructions, biopsies of the wall of the former drilled femoral canal were obtained. Four patients were primarily operated on using a suspending device (Endobutton, Acufex Microsurgical, Mansfield, MA, USA, and Transfix, Arthrex, Naples, FL, USA) for femoral fixation, one patient was reconstructed with a biodegradable interference screw directly inserted between the tendon and the wall of the canal. Biopsies were obtained using a tube harvester during re-arthroscopy. Three grafts were stable, two grafts were unstable, and revision of the ACL was performed. Histologically, in the four cases of reconstruction with a button or a rectangular pin, biopsies resembled granulation tissue without insertion of fibers between the tendon tissue and the bony wall. A wide area of woven bone was noted adjacent to the pre-existing lamellar bone. In contrast, the tendon-bone junction in the knee reconstructed with a biodegradable interference screw resembled a zone of metaplastic fibrous cartilage between the tendon graft and the lamellar bone. Collagen fibers connecting the tendon-bone interface occurred under polarized light microscopy. We conclude that the use of hamstring grafts for ACL reconstruction can lead to different histological pattern of tendon-bone healing. Micromotion of the hamstring graft inside the drilled canal can be play a role in tendon-bone healing.

Arthroscopic biceps tenodesis with interference screw fixation: The lateral decubitus position

The tendon of the long head of biceps brachii is an important stabilizer within the glenohumeral joint. Bicepstendon pathology commonly occurs in the presence of concomitant shoulder disorders, such as subacromial impingement, and rotator cuff tears. Biceps tenodesis is indicated in the case of a partial tear (≫50%), an unstable biceps tendon due to an incompetent medial sling, and in the presence of a torn subscapularis. This article will describe our technique of arthroscopic biceps tenodesis with biodegradable interference screw fixation. This technique uses a uniquely designed Bio-Tenodesis screw system (Arthrex Inc., Naples, FL) and is performed with the patient in the lateral decubitus position.

The effect of soft-tissue graft fixation in anterior cruciate ligament reconstruction on graft-tunnel motion under anterior tibial loading

Purpose: To compare the motion of an anterior cruciate ligament (ACL) replacement graft within the femoral bone tunnel (graft-tunnel motion) when a soft-tissue graft is secured either by a titanium button and polyester tape (EndoButton fixation; Acufex, Smith & Nephew, Mansfield, MA) or by a biodegradable interference screw (Biointerference fixation; Endo-fix; Acufex, Smith & Nephew) An additional purpose was to evaluate the effect of the graft-tunnel motion on the kinematics of ACL-reconstructed knees and in situ force of the ACL replacement graft. Type of Study: Biomechanical experiment using an in vitro animal model. Methods: ACL reconstruction with a flexor tendon autograft was performed in 8 cadaveric knees of skeletally mature goats. The knee kinematics and the in situ force in the ACL replacement graft in response to anterior tibial loads were evaluated using the robotic/universal force-moment sensor testing system. The longitudinal and transverse graft-tunnel motion during anterior tibial loading was determined based on radiographic measurements parallel and perpendicular to the femoral bone tunnel, respectively. Results: In response to an anterior tibial load of 100 N, the longitudinal graft-tunnel motion for EndoButton fixation and Biointerference fixation was 0.8 ± 0.4 mm and 0.2 ± 0.1 mm, respectively (P < .05), whereas the transverse graft-tunnel motion was 0.5 ± 0.2 mm and 0.1 ± 0.1 mm, respectively (P < .05). Furthermore, the anterior tibial translation for EndoButton fixation (5.3 ± 1.2 mm) was also significantly larger than that for Biointerference fixation (4.2 ± 0.9 mm) (P < .05). With both fixations, however, no significant difference between the in situ forces in the ACL replacement graft and that in the intact ACL could be detected. Conclusions: EndoButton fixation of a soft-tissue graft via an elastic material resulted in significantly larger graft-tunnel motion, and consequently, greater anterior knee laxity compared with more rigid fixation using an interference screw closer to the intra-articular entrance of the bone tunnel. In terms of force distribution, the ACL replacement graft in both fixations still functioned as a primary restraint to an anterior tibial load close to the intact ACL.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 9 (November- December), 2002: pp 960–967