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Biomedical subjects

Wolf Petersen

Publications and source records attributed to Wolf Petersen.

At least 19 recordsLinked to original sources
PubMed2006

Initial fixation strength of a new hybrid technique for femoral ACL graft fixation: the bone wedge technique.

BACKGROUND: Aperture fixation with interference screws matching the diameter of the tunnel is associated with the risk of graft laceration and graft rotation. HYPOTHESIS: A hybrid fixation technique (extracortical and aperture fixation) with undersized interference screw placed behind a bone wedge provides a higher fixation strength as aperture fixation with a screw alone matching the size of the tunnel. STUDY DESIGN: Experimental laboratory study. METHODS: We evaluated the initial fixation strength (single cycle and cyclic loading tests) of hybrid and interference screw aperture fixation using different sized interference screws in porcine knees. RESULTS: Analysis of yield load, maximum load and stiffness in the single cycle loading test showed no statistically significant differences for hybrid fixation with a 1 mm undersized screw and aperture fixation with a screw matching the size of the tunnel. The use of an undersized screw alone resulted in low fixation strength. CONCLUSION: The initial fixation strength of the hybrid technique with undersized screws is comparable to that of interference screw fixation matching the size. CLINICAL RELEVANCE: The new "bone wedge fixation" is an alternative for ACL graft fixation without the risk of graft laceration and graft rotation.

Analysis of Variance↗
PubMed2006

Initial fixation strength of a hybrid technique for femoral ACL graft fixation.

Aperture fixation with interference screws matching the diameter of the tunnel is associated with the risk of graft laceration and graft rotation. A hybrid fixation technique (extracortical and aperture fixation) with undersized interference screws provides a higher fixation strength when compared to an aperture fixation using only a screw matching the size of the tunnel and also reduces the risk of graft laceration. This research is an experimental laboratory study. We evaluated the initial fixation strength at time-zero of an extracortical-, a hybrid- and an aperture fixation in ACL reconstruction using extracortical buttons and different sized interference screws in porcine knees. The tests were performed using a single cycle and cyclic loading protocol. Analysis of yield load, maximum load and stiffness in the single cycle loading test showed no statistically significant differences for hybrid fixation with a 1 mm undersized screw and aperture fixation with a screw matching the size of the tunnel. Cyclic loading tests showed a statistically significant difference between hybrid and aperture fixation. The use of an undersized screw alone in aperture fixation resulted in insufficient fixation strength. The initial fixation strength of the hybrid technique with undersized screws is higher compared to an interference screw fixation alone. The hybrid fixation technique is an alternative for ACL graft fixation.

Absorbable Implants↗
PubMed2006

Anterior cruciate ligament anatomy and function relating to anatomical reconstruction.

Recently, the interest in surgical techniques that reconstruct the anteromedial (AM) and the posterolateral (PL) bundles of the anterior cruciate ligament (ACL) has risen. This review focuses on the structural as well as the mechanical properties of the ACL and the anatomical details of the femoral origin, midsubstance, and tibial insertion of AM and PL bundles of the ACL. The terminology of AM and PL bundles is chosen according to the tibial insertion and determined by their functional tensioning pattern throughout knee flexion. Close to extension the AM is moderately loose and the PL is tight. As the knee is flexed, the femoral attachment of the ACL becomes more horizontally oriented, causing the AM bundle to tighten and the PM bundle to loosen up. The ACL has been described to be restraint to anterior tibial displacement and internal tibial rotation. The rotational component might be represented by the PL bundle. The femoral origin has an oval shape with the center of the AM close to over-the-top position and the center of the PL close to the anterior and inferior cartilage margin. Tibial and femoral insertions of the ACL are over 3.5 times larger when compared to the midsubstance and tunnel placement is more challenging because of the limited size of potential grafts selection of tunnel site placement. For reconstruction, both bone-patellar tendon-bone (BPTB) and quadrupled hamstring grafts are used. Structural properties of a 10 mm wide BPTB or quadrupled hamstring graft have been reported to be comparable with those of the native ACL.

Anterior Cruciate Ligament↗
PubMed2006

The effect of locally applied vascular endothelial growth factor on meniscus healing: gross and histological findings.

INTRODUCTION: Tears in the peripheral part of the menisci have a better healing potential than tears in the central part, because the central two-thirds of the menisci are avascular. We hypothesized that healing of meniscus tears in the avascular zone can be promoted by the local application of the angiogenic factor vascular endothelial growth factor (VEGF). MATERIALS AND METHODS: A tear was created in the avascular zone of the medial meniscus in 18 merino sheep. The tear was then repaired with an uncoated suture (group 1), a suture coated with PDLLA (group 2), and by a suture coated with PDLLA/VEGF (group 3). RESULTS: After 6 weeks, we observed increased immunostaining for factor VIII in the VEGF-treated group 3. However, in this treatment group no meniscus healed completely. In the uncoated suture group and in the PDLLA-coated-suture group, partial healing was observed in three animals and complete healing in three animals, respectively. CONCLUSION: In this experiment the local application of VEGF via PDLLA-coated sutures did not promote meniscus healing. Growth factors might not always be a promising tool for tissue repair.

Animals↗
PubMed2006

Elongation and structural properties of meniscal repair using suture techniques in distraction and shear force scenarios: biomechanical evaluation using a cyclic loading protocol.

BACKGROUND: Most biomechanical studies on meniscal repairs have focused on testing distraction scenarios to evaluate structural properties of the repaired meniscus. An application of shear forces might replicate the in vivo situation more closely. HYPOTHESIS: In the shear force scenario, meniscal repair using a vertical suture technique will result in significantly less elongation when subjected to a cyclic loading protocol than that resulting from a horizontal suture technique. STUDY DESIGN: Controlled laboratory study. METHODS: In fresh-frozen porcine menisci (n = 10 in each group), horizontal and vertical 2.0 Ethibond suturing techniques were tested in distraction and shear force scenarios. Elongation after 1000 cycles between 5 and 20 N and the structural properties such as stiffness, yield load, maximum load to failure, and failure mode were evaluated using a testing machine at a rate of 12.5 mm/s. RESULTS: In the distraction force scenario, no statistically significant difference in elongation after cyclic loading was found between specimens repaired with vertical or horizontal suture techniques. After 1000 cycles of cyclic loading in the shear force scenario, the horizontal suturing revealed significantly less elongation (2.8 +/- 1.1 mm) than did the vertical suture technique (4.6 +/- 2.0 mm). No statistically significant difference in yield and maximum load was found (P > .05). CONCLUSION: The results of the present study do not support the authors' hypothesis. In the shear force test, horizontal sutures were superior to vertical suture techniques. CLINICAL RELEVANCE: Meniscal repair with horizontal suture techniques can withstand elongation due to shear forces more effectively than can vertical mattress sutures.

Animals↗
PubMed2005

Importance of femoral tunnel placement in double-bundle posterior cruciate ligament reconstruction: biomechanical analysis using a robotic/universal force-moment sensor testing system.

BACKGROUND: Previous studies have identified the femoral attachment of the posterior cruciate ligament fibers as one of the primary determinants of fiber tension behavior. In addition, a double-bundle posterior cruciate ligament reconstruction has been shown to restore the intact knee kinematics more closely than does a single-bundle reconstruction. HYPOTHESIS: An anterior tunnel position in double-bundle posterior cruciate ligament reconstruction restores the biomechanics of the normal knee more closely than does a posterior tunnel position. STUDY DESIGN: Controlled laboratory study. METHODS: Kinematics and in situ forces of human knees after double-bundle posterior cruciate ligament reconstruction with 2 different femoral tunnel positions (anterior vs posterior) were evaluated using a robotic/universal force-moment sensor testing system. Within the same specimen, the resulting knee kinematics and in situ forces were compared. For statistical analysis, 2-way analysis of variance repeated measures were performed. RESULTS: The femoral tunnel position of the double-bundle hamstring graft had significant effect on the resulting posterior tibial displacement and in situ forces of the hamstring grafts. The anterior femoral tunnel position provided significantly less posterior tibial translation than did the posterior tunnel position. There was a tendency toward higher in situ forces of grafts fixed in the anterior tunnel when compared to the posterior position, but this difference was statistically not significant. CONCLUSION: An anterior position of the bone tunnels in double-bundle posterior cruciate ligament reconstruction restores the normal knee kinematics more closely than does a posterior position of the tunnels. CLINICAL RELEVANCE: In double-bundle posterior cruciate ligament reconstruction, posterior placement of the tunnel should be avoided.

Aged↗
PubMed2005

Joint kinematics and in situ forces after single bundle PCL reconstruction: a graft placed at the center of the femoral attachment does not restore normal posterior laxity.

INTRODUCTION: Femoral tunnel placement has a great influence on the clinical outcome after PCL reconstruction. MATERIALS AND METHODS: Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of human knees following soft-tissue single bundle PCL reconstruction fixed at the center of the femoral attachment. RESULTS: Posterior tibial translation significantly increased at all flexion angles after transsection of the posterior cruciate ligament (p<0.05). PCL reconstruction resulted in significantly less posterior tibial translation at all flexion angles when compared to the PCL deficient knee (p<0.05). The differences in the in situ force between the intact ligament and the reconstructed graft were statistical significant (p<0.05). CONCLUSION: Single bundle PCL reconstruction with a soft-tissue graft fixed at the center of the femoral attachment is able to reduce the posterior tibial translation significantly. However, it cannot restore kinematics of the intact knee and in situ forces of the intact PCL.

Aged↗
PubMed2005

Symptomatic calcification of the medial collateral ligament of the knee joint: a report about five cases.

Symptomatic calcifications of the rotator cuff tendons is well-known pathologic condition. However, pathologic calcifications may involve other structures of the locomotor system as well. We report about five patients (age 52-66 years) with a painful calcification at the proximal part of the medial collateral ligament of the knee joint. All five patients presented with load-dependent pain pretending meniscus symptoms, but manual valgus stress provoked severe pain at the medial side of the knee. Conventional X-ray examination showed a dense rounded deposit at the proximal part of the medial collateral ligament. Initially all patients were treated conservatively by needling and infiltration with a local anaesthetic. Open resection of the deposit was performed in four patients after unsuccessful conservative treatment. Postoperatively all patients were immediately free of pain. After a mean follow-up of 6 years (patient 1-4) (range=2.5-9.5 years), all patients were still free of pain. Histological evaluation of biopsies obtained during surgery showed nodular deposition of calcium at the collagen fibres, vascular proliferations and inflammative changes. Soft tissue calcifications have to be considered as a rare differential diagnosis in patients presenting with medial knee joint pain. Open resection reduces symptoms immediately. The histological changes seen were comparable to that reported about pathological tendon calcifications of the shoulder. Therefore, both conditions might be of the same aetiology.

Aged↗
PubMed2005

A controlled prospective case control study of a prevention training program in female team handball players: the German experience.

BACKGROUND: Few authors have investigated the effectiveness of preventive intervention in European team handball. PURPOSE: The aim of the present study was to evaluate the effects of a prevention program on the incidence of injuries in female European team handball players. STUDY DESIGN: Prospective controlled study. METHODS: Ten female handball teams (134 players) took part in the prevention program (1. Information about injury mechanism, 2. Balance-board exercises, 3. Jump training) while 10 other teams (142 players) were instructed to train as usual. Over one season all injuries were documented weekly. RESULTS: Ankle sprain was the most frequent diagnosis in both groups with 11 ankle sprains in the control group and 7 ankle sprains in the intervention group (Odds ratio: 0.55, 95% confidence interval: 0.22-1.43). The knee was the second frequent injury site. In the control group 5 of all knee injuries were anterior cruciate ligament (ACL) ruptures (incidence: 0.21 per 1000 h) in comparison with one in the intervention group (incidence: 0.04 per 1000 h). Odds ratio was 0.17 with 95% confidence interval of 0.02-1.5. CONCLUSIONS: This study confirms that proprioceptive and neuromuscular training is appropriate for the prevention of knee and ankle injuries among female European team handball players.

Adult↗
PubMed2005

Locally applied angiogenic factors--a new therapeutic tool for meniscal repair.

Tears in the peripheral part of the menisci have a better healing potential than tears in the central part, because the central two-thirds of the menisci are avascular. The avascular status of the meniscus is maintained by the expression of antiangiogenic factors such as endostatin. The distribution of endostatin in the menisci correlates with the degree of vascularization. Endostatin immunostaining is strong in the avascular zone and reduced in the vascularized outer one-third. Endostatin interacts with signal transduction of the vascular endothelial growth factor (VEGF) by reducing VEGF-induced kinase (Erk1/2) phosphorylation. VEGF plays an important role in angiogenesis in fetal menisci and it is down-regulated in the adult meniscus. We hypothesized that healing of meniscal tears in the avascular zone can be promoted by the local application of the angiogenic factor VEGF. To evaluate this hypothesis a tear was created in the avascular zone of the medial meniscus in 18 merino sheep. The tear was then repaired with an uncoated suture (group 1), a suture coated with PDLLA (group 2), and by a suture coated with PDLLA/VEGF (group 3). After 6 weeks we observed increased factor VIII immunostaining in the VEGF-treated group. However, in this treatment group (VEGF/PDLLA) no meniscus healed. In the uncoated suture group and in the PDLLA-coated suture group partial healing was observed in three animals and complete healing in three animals, respectively. Factor VIII expression is normally restricted to vascular endothelial cells. In this study, however, single endothelial cells could be detected in the menisci of the VEGF/PDLLA group. This finding suggests that the application of VEGF might have stimulated proliferation of vascular endothelial cells but the application of VEGF was not successful in stimulating the more complex process of vasculogenesis. Further immunohistochemical examinations of the specimen have shown that in the VEGF/PDLLA group there is strong immunostaining against matrix metalloproteinase 13 (MMP-13). In vitro studies have shown that VEGF can stimulate chondrocytes to proliferate but also to express MMP-13 via HIF1-alpha induction. Since meniscal fibrochondrocytes express the VEGF receptor 2 (KDR) the induction of MMP expression might be another factor which inhibits healing despite increased angiogenesis. In conclusion, the local application of VEGF via PDLLA-coated sutures does not promote meniscal healing. A single growth factor might not always be a promising tool for the promotion of tissue repair. Further studies have to find out if growth factor combinations (VEGF and angiopoitin) might be more effective in stimulating vasculogenesis during meniscal healing.

Angiostatic Proteins↗
PubMed2005

The influence of biomechanical parameters on the expression of VEGF and endostatin in the bone and joint system.

Many degenerative processes in the skeletal system are induced by mechanical overload. Osteoarthritis and spontaneous tendon ruptures are two examples of mechanically influenced diseases. Incubator-housed compression apparatuses and cyclic strain chambers are adequate models to investigate the cellular processes. Recent studies have shown that growth factors are involved in the transduction pathways of mechanical overload leading to tissue degradation. Vascular endothelial growth factor (VEGF) is a dimerized, 45 kDa peptide that normally attracts endothelial cells in wound healing. VEGF can be detected in the superficial zone of the tibial plateau in osteoarthritic (OA) patients with degenerative changes but not in healthy articular cartilage. Blood vessels are only rarely observed in OA cartilage suggesting that there are other roles for VEGF in cartilage. VEGF is also detectable in ruptured but not in normal tendons. The mechanically induced expression of VEGF in avascular tissues like articular cartilage or fibrocartilage of contact areas from gliding tendons initiates degenerative processes. Chondrocytes from OA cartilage also express the VEGF receptor 2. In vitro assays have shown that VEGF binds the VEGFR-2 leading to a phosphorylation of MAP kinases (ERK1/2) with subsequent transcription factor accumulation (activator protein 1 = AP-1). One of the antagonists of VEGF is endostatin. Endostatin, a fragment of collagen type XVIII, is expressed in avascular tissues and has the potency to decrease VEGF induced effects (ERK1/2 phosphorylation). The increase in matrix metalloproteinase (MMP) production and the decrease in tissue inhibitor metalloproteinase (TIMP) synthesis is a result of the signal transduction cascade activation. MMPs participate in the degradation processes of osteoarthritis whereas TIMPs are inhibitors of the MMPs. Taken together mechanically induced VEGF is involved in the destruction and endostatin in the maintenance of avascular tissues of the bone and joint system.

Biomechanical Phenomena↗
PubMed2005

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

PURPOSE: 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). TYPE OF STUDY: Experimental laboratory study. METHODS: 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. RESULTS: 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. CONCLUSIONS: Our biomechanical data suggest that hamstring graft fixation using a biodegradable PLLA/TCP suspension screw provides an alternative to interference screw fixation. CLINICAL RELEVANCE: Hamstring graft fixation using a suspension screw provides a reasonable alternative to interference screw fixation.

Absorbable Implants↗
PubMed2005

Cyclic loading comparison between biodegradable interference screw fixation and biodegradable double cross-pin fixation of human bone-patellar tendon-bone grafts.

PURPOSE: 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. TYPE OF STUDY: Biomechanical in vitro study. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: 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.

Absorbable Implants↗
PubMed2005

Cyclic testing of flexible all-inside meniscus suture anchors: biomechanical analysis.

BACKGROUND: Flexible meniscus repair devices are designed to combine the benefits of rigid all-inside meniscus anchors with the biomechanical properties of sutures. HYPOTHESIS: Stiffness and pull-out strength of flexible all-inside suture anchors and conventional sutures under cyclic loading conditions will be comparable. STUDY DESIGN: Controlled laboratory study. METHODS: In 50 fresh frozen bovine menisci, artificial meniscus lesions were repaired with different meniscus fixation techniques: horizontal and vertical FasT-Fix, RapidLoc, and horizontal and vertical 2-0 Ethibond sutures. The specimens were cycled 1000 times between 5 and 20 N and then loaded to failure. RESULTS: All devices survived the cyclic loading protocol. There was no significant difference in the displacement between all repair techniques tested (horizontal FasT-Fix, 6.23 mm; vertical FasT-Fix, 5.34 mm; RapidLoc, 6.84 mm; horizontal 2-0 Ethibond, 6.03 mm; vertical 2-0 Ethibond, 5.61 mm (P > .05). Vertical and horizontal FasT-Fix suture anchors had a significantly higher stiffness and pull-out strength (94.1 N and 80.8 N, respectively) than did horizontal sutures (50.2 N) and RapidLoc devices (30.3 N) (P > .05). CONCLUSIONS: In this study, flexible all-inside meniscus anchors (FasT-Fix) had higher pull-out strength than did conventional vertical suture techniques. Biomechanical characteristics of the flexible RapidLoc are comparable to those of horizontal sutures. CLINICAL RELEVANCE: Flexible all-inside meniscus repair devices are an alternative to conventional suture techniques.

Animals↗
PubMed2005

Mechanical comparison of two types of fixation for proximal first metatarsal crescentic osteotomy.

BACKGROUND: The proximal crescentic osteotomy is an effective technique for correcting a widened 1-2 intermetatarsal angle associated with moderate to severe hallux valgus deformities. However, postoperative dorsal malunion at the osteotomy site from loss of fixation has been reported. The purpose of this study was to evaluate the biomechanical characteristics of a new custom-designed plate and compare it to the traditional screw and Kirschner wire construct. METHODS: Twenty identical Sawbone (Pacific Research Laboratories, Vashon, WA) models were used for the study. A proximal crescentic osteotomy was done on each specimen, and 10 were secured with a dorsomedial plate (group I). The remaining 10 models were fixed with a screw and Kirschner wire combination (group II). Physiologic cyclical testing was done using a mechanical testing machine to evaluate dorsal displacement of the metatarsal. Load-to-failure testing was then done on each specimen to evaluate ultimate failure and stiffness of the constructs. Groups I and II were statistically compared using paired t-testing. RESULTS: The mean dorsal displacement of the first metatarsal head after 1000 cycles was 0.19 mm (SD = 0.09 mm) for group I and 0.28 mm (SD = 0.15) for group II, and the difference was not statistically significant (p = 0.08). Group I demonstrated statistically superior ultimate failure strength (95.2 N) and stiffness (26.8 N/mm) compared to group II (73.7 N, 19.4 N/mm). CONCLUSIONS: Based on Sawbone models, dorsal plate fixation of proximal crescentic osteotomy provides a stronger construct than the traditional screw and Kirschner wire construct. The clinical use of the specially-designed plate described in this study may lower the incidence of dorsal malunions that occur postoperatively and may decrease the occurrence of transfer metatarsalgia. Its application may be particularly helpful in patients with poor bone quality.

Biomechanical Phenomena↗
PubMed2004

Soft-tissue graft fixation in posterior cruciate ligament reconstruction: evaluation of the effect of tibial insertion site on joint kinematics and in situ forces using a robotic/UFS testing system.

INTRODUCTION: Surgical reconstruction of the posterior cruciate ligament (PCL) is recommended in acute injuries that result in severe tibial subluxation and instability. The surgical outcome level may be affected by the tibial fixation site. In response to a 110-N posterior tibial load, kinematics and in situ forces of anatomical soft-tissue graft fixation in single-bundle PCL reconstruction using an interference screw fixation are significantly closer to those in the intact knee than with extracortical fixation with two staples. MATERIALS AND METHODS: Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of porcine knees following single-bundle PCL reconstruction fixed at two different tibial fixation sites: anatomical interference screw and extracortical fixation. RESULTS: The site of the tibial graft fixation had significant effect on the resulting posterior displacement and in situ forces of the graft. Both PCL reconstruction techniques reduced the posterior tibial translation significantly. Proximal fixation techniques provided significantly less posterior tibial translation than extracortical fixation. Single-bundle PCL reconstruction with an interference screw showed higher in situ forces of the graft than the extracortical fixation. CONCLUSIONS: The kinematics and in situ forces of a single-bundle PCL reconstruction using an interference screw fixation technique are superior to the primary stability of an extracortical fixation with staples.

Animals↗
PubMed2004

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.

Absorbable Implants↗