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

doi:10.1016/j.arthro.2003.10.023

Arthroscopy: The Journal of Arthroscopic & Related Surgery

Volume 19, Issue 10, December 2003, Pages 1097-1102

https://doi.org/10.1016/j.arthro.2003.10.023 Get rights and content

Abstract

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.

Section snippets

Biomechanical model

In this study, 10 pairs of fresh bovine knees were used to simulate young human femoral density as described by Weiler et al.17, 18 In this model, the screw insertion site represents a trabecular bone density of 0.8 g/cm³,17, 18 similar to what is expected in young human femora.21, 22

The mean age of the animals was 28 weeks ± 2 weeks. The material was obtained from a local abattoir, fresh frozen at −20° and thawed for 12 hours at room temperature before testing. The muscles and soft tissues

Results

A typical load-elongation curve is shown in Fig 5. The mean yield load in the cross pin group (Rigid Fix) was 400.2 (± 122.4) N and 402.7 (± 143.7) N in the biodegradable interference screw group. The maximum load at failure was 524.6 (± 136.6) N in the cross pin group and 515.7 N (± 168.5 N) in the interference screw group. Cross pin fixation resulted in a linear stiffness of 155 (± 32) N/mm and interference fixation in 168 (± 42) N/mm. All these measurements were not significantly different (

Discussion

In ACL reconstruction with BPTB grafts, bone block healing occurs between 4 and 12 weeks after surgery.5 In a study by Clancy et al.,6 the bone blocks were histologically incorporated at 8 weeks after surgery in a Rhesus monkey. Until biological fixation has occurred, a stable fixation of the graft is necessary if the patient underwent an aggressive rehabilitation protocol.3 Therefore, fixation strength is integral to the success of ACL reconstruction.20

The initial fixation strength required

Acknowledgements

We want to thank Mr. M. Vogiatzis, Mr. S. Zander, and Mr. A. Studt for their expert technical assistance. The implants used in this study were kindly provided by Ethicon, Mitek Division (Norderstedt, Germany). However, none of the authors received financial support from any commercial party.

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Cited by (26)

Improvement of primary stability in ACL reconstruction by mesh augmentation of an established method of free tendon graft fixation. A biomechanical study on a porcine model
2013, Knee
Citation Excerpt :
To simulate a moderate level of activity in the early rehabilitation period we chose a loading regime from 20 to 150 N as Milano et al. did [24]. In several biomechanical studies the displacement rate is described with 150 mm/min [35,36] or 200 mm/min [13,14,17] but there is still no common sense. Perhaps it would have been better to choose a displacement rate of 200 mm/min for a better comparison of our results to other studies.
The aim of the present study was to compare primary stability in ACL reconstruction and ultimate load to failure of a mesh augmented hamstring tendon graft fixed with two cross pins to established hamstrings and bone-patellar-tendon-bone (BTB) graft fixation methods.
Forty fresh porcine femora were divided into four groups: (A): BTB graft fixed with two RigidFix® pins, (B): hamstring tendon graft fixed with a Milagro® interference screw, (C): hamstring tendon graft fixed with two RigidFix® pins, and (D): hamstring tendon graft augmented with Ultrapro® mesh fixed with two RigidFix® pins. Each graft underwent cyclic loading in tension and load to failure. Elastic and plastic displacements were measured by 3-dimensional digital image correlation. Groups were compared by one-way ANOVA and Tukey–Kramer post-hoc tests.
After 1000 cycles, the mean plastic displacement was lowest in the BTB graft (p < 0.001). Plastic displacement was significantly lower in the mesh augmented group compared to the plain hamstring graft and the Milagro screw group (p < 0.05). Load to failure was highest in the mesh-augmented group; significant to the hamstring tendon (p = 0.023).
Although the BTB-graft represented the most stable construct against plastic displacement in our study, mesh augmentation of free tendon grafts significantly increased primary stability and reduced plastic displacement of femoral cross pin fixation. This new augmentation device may better protect the hamstrings graft from secondary elongation during postoperative rehabilitation.
Mesh augmentation seems to be an effective technique to stabilise free hamstring tendon autografts during postoperative rehabilitation with significant reduction of graft slippage.
The Biomechanical Performance of Bone Block and Soft-Tissue Posterior Cruciate Ligament Graft Fixation With Interference Screw and Cross-Pin Techniques
2009, Arthroscopy - Journal of Arthroscopic and Related Surgery
Citation Excerpt :
To simulate PCL reconstruction in the operating room, young to middle-aged human cadaveric knees were used for biomechanical testing and the operative procedures were the same, as was the surgeon. The testing model was similar to that in previous studies of ACL reconstruction.17,19,20 However, we created the tibial tunnel with the same transtibial technique because tunnel length and BMD may have an influence on the biomechanical performance of hybrid fixation.
The purpose of this study was to evaluate the biomechanical properties of 4 different graft fixation constructs on the tibial side of the posterior cruciate ligament with reconstruction by use of an Achilles tendon graft.
Biomechanical testing of 4 different fixation techniques was performed on 20 human cadaveric tibias and Achilles tendons. Cross-pin fixation with bone blocks (group A), interference screw fixation with bone blocks (group B), cross-pin fixation of soft tissue with backup fixation (group C), and interference screw fixation of soft tissue with backup fixation (group D) were tested. The tibia-graft fixation complex was cyclically loaded between 50 N and 250 N at 1 Hz for 1,000 cycles. After cycling, the amount of graft displacement was determined by measuring the change in grip-to-grip distance. The complex was then loaded to failure at 1 mm/s, and maximum failure load, stiffness, and mode of failure were determined.
Group C had a higher maximum failure load and stiffness than groups A and B (P < .05 and P < .001, respectively) but poor results for displacement (P < .05 and P < .05, respectively). The failure modes were bone block fracture, graft laceration, or cross-pin fracture in the cross-pin groups and graft pullout in the interference screw groups.
Our study suggests that maximum failure load and stiffness of hybrid fixation for Achilles tendon graft are comparable to those of both single calcaneal bone plug fixation methods that we studied. However, tendon graft displacement was significantly greater regardless of fixation method when compared with bone plug fixation.
Hybrid fixation for soft-tissue graft on the tibial fixation site provides comparable biomechanical properties of bone-to-bone fixation.
A pilot clinical evaluation comparing the Mitek bone-tendon-bone cross pin and bioabsorbable screw in anterior cruciate ligament reconstruction fixation, a randomized double blind controlled trial
2008, Knee
Citation Excerpt :
Several biomechanical studies have revealed that cross pins have comparable initial stability to interference screws [19,24]. Weimann et al. reported the mean yield load for the RIGIDfix pins was 400 N, the ultimate load at failure was 525 N while the mean stiffness was 155 N/mm [19]. Failure modes for the two fixation devices were quite different.
To compare the clinical efficacy of ACL reconstruction using the Mitek bone–tendon–bone cross pin (RIGIDfix) to the Linvatec Bioscrew (control device).
Forty subjects were randomized into one of two groups: the RIGIDfix or control group. Eligible subjects were male and female, 18years of age and older, with an ACL injury of at least 3weeks duration and no evidence of ACL insufficiency on the contralateral side. Subjects were followed for 24-month post-operatively. Evaluations included the International Knee Documentation Committee (IKDC) Knee Ligament Standard Evaluation, Mohtadi's ACL Deficiency Quality of Life (ACL-QOL) questionnaire and the attainment of six rehabilitation milestones. Subjects and assessors were blinded to the surgical device used.
Four subjects in the RIGIDfix group and four controls were lost to follow-up. The change in final IKDC scores did not differ significantly between groups with the majority demonstrating an improvement of one to two grades. The change in ACL-QOL scores did not differ significantly between the RIGIDfix subjects (40.0 + 4.4) and controls (46.0 + 3.6). Furthermore, the number of weeks that the RIGIDfix subjects versus controls attained full active extension, functional range of motion, normal gait, stair climbing, running gait and sprinting did not differ significantly.
The RIGIDfix results in a similar post-operative course to the control device and is efficacious for the reconstruction of the ACL. No adverse events were associated with the use of the RIGIDfix. The results of this study should be considered preliminary due to the small sample size.
Initial and 6 Weeks Postoperative Structural Properties of Soft Tissue Anterior Cruciate Ligament Reconstructions With Cross-Pin or Interference Screw Fixation: An In Vivo Study in Sheep
2007, Arthroscopy - Journal of Arthroscopic and Related Surgery
Purpose: The purpose of this study was to evaluate the detrimental effects of interference screw fixation on soft tissue anterior cruciate ligament (ACL) reconstruction after 6 weeks and compare them with a cross-pin technique. Methods: In an intra-articular model, ovine soft tissue grafts were fixed with two 3.3-mm biodegradable pins or with interference screws. Maximum load, yield load, and stiffness of the femur–graft–tibia complex were evaluated immediately after surgery and 6 weeks postoperatively. Results: For knees with interference screw fixation, strength deteriorated by 81% and stiffness deteriorated by 67%. For knees with double cross-pin fixation, strength deteriorated by 48% and stiffness improved by 52%. These differences were statistically significant. At the time of surgery, all grafts failed by slippage of the graft past the screw or by cross-pin failure. At 6 weeks postoperatively, the grafts of both groups failed at the tibial or femoral tunnel entrance. Conclusions: After 6 weeks, the biomechanical characteristics of grafts that were fixed with cross-pins were superior to those of grafts after interference screw fixation. Clinical Relevance: Because of significantly inferior biomechanical stability after interference screw fixation, a less aggressive program of rehabilitation might be recommended.
Cyclic loading comparison between biodegradable interference screw fixation and biodegradable double cross-pin fixation of human bone-patellar tendon-bone grafts
2005, Arthroscopy - Journal of Arthroscopic and Related Surgery
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.
Arthroscopic anterior cruciate ligament reconstruction using quadriceps tendon autograft and bioabsorbable cross-pin fixation
2005, Arthroscopy - Journal of Arthroscopic and Related Surgery
We describe a technique for arthroscopic anterior cruciate ligament (ACL) reconstruction using the middle third of the quadriceps tendon without a patellar bone block and absorbable tibial and femoral cross-pin fixation. The central part of the quadriceps tendon is harvested through a 5-cm long anterior skin incision without a patellar bone block. Tibial and femoral tunnels are prepared, the graft is passed up the tunnels, and is fixed both in the femur and the tibia using absorbable cross pins (Rigid Fix; Mitek, Johnson & Johnson, Norwood, MA). In this way, the graft is stabilized near the joint line, providing outlet fixation. In our practice, very good results have been obtained with the use of this technique.

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Original articlePrimary stability of bone-patellar tendon-bone graft fixation with biodegradable pins

Abstract

Section snippets

Biomechanical model

Results

Discussion

Acknowledgements

Arthroscopy

Arthroscopy

Arthroscopy

J Biomech

J Biomech

Arthroscopy

Arthroscopy

The science of reconstruction of the anterior cruciate ligament

J Bone joint Surg Am

Current trends in anterior cruciate ligament reconstruction. Part II: Operative procedures and clinical correlations

Am J Sports Med

Accelerated rehabilitation after anterior cruciate ligament reconstruction

Am J Sports Med

Patellofemoral problems after anterior cruciate ligament reconstruction

Clin Orthop

Failure of anterior cruciate ligament reconstructionThe biological basis

Clin Orthop Rel Res

Anterior and posterior cruciate ligament reconstruction in rhesus monkeys

J Bone Joint Surg Am

Vascularized patellar tendon graft with rigid internal fixation for anterior cruciate ligament insufficiency

Clin Orthop

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

Am J Sports Med

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