Comparison of torsional strengths of bioabsorbable screws for anterior cruciate ligament reconstruction

Bailout Options for Intra-operative Implant and Instrumentation Related Incidents and Complications During Arthroscopic Knee Surgery-A Retrospective Study

Background

Arthroscopic knee procedures are one amongst the common surgical interventions for problems in the knee. It is technically more demanding than an open procedure and is associated with several potential complications. During arthroscopy procedures, several technical challenges may arise, and even experienced surgeons may encounter new issues. However, careful attention to the surgical technique can help prevent or resolve them.

Methodology

The study was conducted on all patients who underwent knee arthroscopy procedure during study period. We recorded details of the implants used and any unexpected situations related to them, as well as how they were managed. Instrumentation-related parameters such as screwdriver issues, radiofrequency ablator issues, scope damages, shaver complications, probe complications, and meniscus suture passing devices were also assessed.

Results

In total, there were 12 (3.73%) implant and instrument-related incidents and complications, of which 5 (1.55%) were implant-related and 7 (2.17%) were instrument related. Among the instrumentation-related incidents and complications, two (0.62%) were screwdriver breakage incidents, two (0.62%) were radiofrequency ablator-related incidents, one was arthroscopic probe (0.31%) related incident, one (0.31%) was meniscus suture passing device related complication and one (0.31%) was arthroscope related incident.

Conclusion

Surgeons must be ready to anticipate and effectively manage any technical difficulties that may arise during the procedure, maintaining composure in the face of unexpected challenges and guiding the team. In most cases, incidents can be addressed intra operatively and may not have long-term effects on patient outcomes. It is crucial to have multiple implant and instrument backup options available for successful surgery.

The Development and Biomechanical Analysis of an Allograft Interference Screw for Anterior Cruciate Ligament Reconstruction

Graft fixation during cruciate ligament reconstruction using interference screws is a common and frequently used surgical technique. These interference screws are usually made of metal or bioabsorbable materials. This paper describes the development of an allograft interference screw from cortical human bone. During the design of the screw, particular attention was paid to the choice of the screw drive and the screw shape, as well as the thread shape. Based on these parameters, a prototype was designed and manufactured. Subsequently, the first biomechanical tests using a bovine model were performed. The test procedure comprised a torsion test to determine the ultimate failure torque of the screw and the insertion torque during graft fixation, as well as a pull-out test to asses the ultimate failure load of the graft fixation. The results of the biomechanical analysis showed that the mean value of the ultimate failure torque was 2633 Nmm, whereas the mean occurring insertion torque during graft fixation was only 1125 Nmm. The mean ultimate failure load of the graft fixation was approximately 235 N. The results of this work show a good overall performance of the allograft screw compared to conventional screws, and should serve as a starting point for further detailed investigations and studies.

Redesigning Metal Interference Screws Can Improve Ease of Insertion While Maintaining Fixation of Soft-Tissue Anterior Cruciate Ligament Reconstruction Grafts

Purpose

To compare the fixation strength and loads on insertion of a titanium alloy interference screw with a modified tip against a conventional titanium interference screw.

Methods

Slippage of bovine digital extensor tendons (as substitutes for human tendon grafts) under cyclic loading and interference fixation strength under a pullout test were recorded in 10 cadaveric knees, with 2 tunnels drilled in each femur and tibia to provide pair-wise comparisons between the modified-tip screw (MS) and conventional screw (CS). To analyze screw insertion, 10 surgeons blindly inserted pairs of the MS and CS into bone-substitute blocks (with polyester shoelaces as graft substitutes), with insertion loads measured using a force/torque sensor.

Results

No differences were found between the MS and CS either in graft slippage from the femur (P = .661) or tibia (P = .950) or in ultimate load to failure from the femur (P = .952) or tibia (P = .126). On insertion, the MS required less axial force application (78 ± 38 N, P = .001) and fewer attempted turns (2 ± 1, P < .001) to engage with the bone tunnel than the CS (99 ± 43 N and 4 ± 4, respectively). In 90% of the paired insertion tests, the screw identified by the surgeon as being easier to initially insert was the MS.

Conclusions

The MS was found to be easier to engage with the bone tunnel and initially insert than the CS while still achieving similar immediate postsurgical fixation strength.

Clinical Relevance

The study shows that screw designs can be improved to ease insertion into a bone tunnel, which should reduce any likelihood of ligament reconstruction graft damage.

Femoral Interference Screw Fixation in ACL Reconstruction Using Bone-Patellar Tendon-Bone Grafts

» Anterior cruciate ligament (ACL) reconstruction is a commonly performed orthopaedic procedure with numerous reconstructive graft and fixation options. Interference screws have become one of the most commonly utilized methods of securing ACL grafts such as bone-patellar tendon-bone (BPTB) autografts. » The composition of interference screws has undergone substantial evolution over the past several decades, and numerous advantages and disadvantages are associated with each design. » The composition, geometry, and insertional torque of interference screws have important implications for screw biomechanics and may ultimately influence the strength, stability of graft fixation, and biologic healing in ACL reconstruction. » This article reviews the development and biomechanical properties of interference screws while examining outcomes, complications, and gaps in knowledge that are associated with the use of femoral interference screws during BPTB ACL reconstruction.

Complications after tendon transfers in the foot and ankle using bioabsorbable screws

BACKGROUND

Tendon transfers are commonly used for correction of pathology or deformity of the foot and ankle. Bioabsorbable implants have been developed as an alternative to metal interference screws. The purpose of this study was to document complications following tendon transfers of the foot and ankle using bioabsorbable poly-L-lactide interference screws.

METHODS

A retrospective chart review was used to identify patients in whom either of the 2 senior authors had performed a tendon transfer of the foot and ankle using a bioabsorbable interference screw between 1999 and 2005. A minimum of 6 months of follow-up was required for inclusion in the study. In all, 31 patients were identified who met the inclusion criteria with an average follow-up of 75 weeks. All screws were made of poly-L-lactide (PLLA).

RESULTS

Complications were identified in 12 (39%) of patients. All of the complications reported were known complications of the tendon transfer procedure itself, and were not directly related to the bioabsorbable screw.

CONCLUSIONS

Based on these early results, PLLA implants appear safe and effective for tendon transfers of the foot and ankle. However, until long-term outcomes are available, judicious use of these implants is recommended.

Biomechanical testing of implant free wedge shaped bone block fixation for bone patellar tendon bone anterior cruciate ligament reconstruction in a bovine model

Background

The use of an interference fit wedged bone plug to provide fixation in the tibial tunnel when using bone-patellar tendon-bone autograft for anterior cruciate ligament reconstruction offers many theoretic advantages including the potential to offer a more economical and biological alternative to screw fixation. This technique has not been subjected to biomechanical testing. We hypothesised that a wedged bone plug fixation technique provides equivalent tensile load to failure as titanium interference screw fixation.

Methods

In a controlled laboratory setting, anterior cruciate ligament reconstruction was performed in 36 bovine knees using bone-patella-bone autograft. In 20 knees tibial fixation relied upon a standard cuboid bone block and interference screw. In eight knees a wedge shaped bone block with an 11 mm by 10 mm base without a screw was used. In a further eight knees a similar wedge with a 13 mm by 10 mm base was used. Each specimen used a standard 10 mm tibial tunnel. The reconstructions were tested biomechanically in a physiological environment using an Instron machine to compare ultimate failure loads and modes of failure.

Results

Statistical analysis revealed no significant difference between wedge fixation and screw fixation (p = 0.16), or between individual groups (interference screw versus 11 mm versus 13 mm wedge fixation) (P = 0.35).

Conclusions

Tibial tunnel fixation using an impacted wedge shaped bone block in anterior cruciate ligament reconstruction has comparable ultimate tensile strength to titanium interference screw fixation.

Torsional stability of interference screws derived from bovine bone--a biomechanical study

Background

In the present biomechanical study, the torsional stability of different interference screws, made of bovine bone, was tested. Interference screws derived from bovine bone are a possible biological alternative to conventional metallic or bioabsorbable polymer interference screws.

Methods

In the first part of the study we compared the torsional stability of self-made 8 mm Interference screws (BC) and a commercial 8 mm interference screw (Tutofix^®). Furthermore, we compared the torsional strength of BC screws with different diameters. For screwing in, a hexagon head and an octagon head were tested. Maximum breaking torques in polymethyl methacrylate resin were recorded by means of an electronic torque screw driver. In the second part of the study the tibial part of a bone-patellar tendon-bone graft was fixed in porcine test specimens using an 8 mm BC screw and the maximum insertion torques were recorded. Each interference screw type was tested 5 times.

Results

There was no statistically significant difference between the different 8 mm interference screws (p = 0.121). Pairwise comparisons did not reveal statistically significant differences, either. It was demonstrated for the BC screws, that a larger screw diameter significantly leads to higher torsional stability (p = 9.779 × 10^-5). Pairwise comparisons showed a significantly lower torsional stability for the 7 mm BC screw than for the 8 mm BC screw (p = 0.0079) and the 9 mm BC screw (p = 0.0079). Statistically significant differences between the 8 mm and the 9 mm BC screw could not be found (p = 0.15). During screwing into the tibial graft channel of the porcine specimens, insertion torques between 0.5 Nm and 3.2 Nm were recorded. In one case the hexagon head of a BC screw broke off during the last turn.

Conclusions

The BC screws show comparable torsional stability to Tutofix^® interference screws. As expected the torsional strength of the screws increases significantly with the diameter. The safety and in vivo performance of products derived from xenogeneic bone should be the focus of further investigations.

The migration of a BioScrew as a differential diagnosis of knee pain, locking after ACL reconstruction: a report of two cases

INTRODUCTION

Problems with the initial fixation strength and widening of the femoral and tibial canal after ACL reconstruction using a triple or quadruple semitendinosus autograft have led to the introduction of the so-called Hybrid fixation with the additional use of interference screws. Pain and intraarticular migration have been reported with metal interference screws requiring implant removal (Am J Knee Surg 11:32-34, 2000, Arthroscopy 11:289-291, 1995) but not yet with bioabsorbable screws.

MATERIALS AND METHODS

We report on two cases were the intraarticular position of a bioabsorbable interference screw possibly due to migration in the early postoperative period lead to symptoms, the need for further surgery, and implant removal.

RESULTS

A preoperative MRI revealed the diagnosis. After removal of the tibial interference screw both knees were settling down, albeit with residual instability and only a moderate clinical result.

DISCUSSION

Despite the attractiveness of bioabsorbable screws due to the very fact that they are being reabsorbed over time, there is a slight risk of migration in the first month after the operation. In any suspicious case an MRI will easily clarify the diagnosis.

Influence of thread design on bioabsorbable interference screw insertion torque during retrograde fixation of a soft-tissue graft in synthetic bone

PURPOSE

Bioabsorbable interference screw design may influence biomechanical characteristics. This study compared the insertion torque and load at failure characteristics of 2 types of screws during retrograde fixation of a soft-tissue graft.

TYPE OF STUDY

Biomechanical study.

METHODS

Eight matched pairs of doubled 100-mm long tibialis anterior allografts were prepared and fixed in appropriately sized tunnels created in 10 lb/ft 3 (0.16 g/cm3) dense synthetic bone blocks using screws of similar length and root and thread diameter designed with either a large buttress thread with a smaller taper or small buttress thread with a larger taper. Insertion torque was measured at one-third, two-thirds, and full screw insertion. After the graft fixation constructs were mounted in a servohydraulic-testing device with the loading axis aligned directly with the tunnel and preloaded to 25 N, they were cycled 3 times from 0 to 50 N, and then subjected to a 20 mm/minute traction force to failure.

RESULTS

All constructs failed by graft slippage past the screw. Mean maximum load at failure (360.5 +/- 68 N v 341.6 +/- 58 N, P = .2) and stiffness (63.6 +/- 16 N/mm 2 v 66.4 +/- 14 N/mm 2 , P = .89) was similar between constructs fixed with a large buttress thread small-taper screw and small buttress thread large-taper screw, respectively. The small buttress thread screw with a large taper displayed greater mean insertion torque at one-third insertion (4.1 +/- 0.57 in-lb v 3.2 +/- 0.49 in-lb, P = .03), whereas the large buttress thread screw with a small taper displayed greater mean insertion torque at full insertion (11.1 +/- 0.74 in-lb v 9.4 +/- 1.3 in-lb, P = .012). Mean differences were not observed at two-thirds screw insertion (P = .12).

CONCLUSIONS

Large buttress thread small-taper screws displayed biomechanical fixation characteristics comparable to small buttress thread large-taper screws.

CLINICAL RELEVANCE

Given reports of superior screw-graft-bone tunnel contact area, these biomechanical results suggest that use of a large buttress screw with a small taper may be preferable for retrograde soft-tissue graft fixation.

Development of a perforated biodegradable interference screw

PURPOSE

The objective was to develop a perforated biodegradable interference screw to allow for enhanced osseous implant integration without impairing screw stability during insertion.

TYPE OF STUDY

Mechanical testing, followed by animal study.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

CLINICAL RELEVANCE

To ameliorate osseous implant integration and possibly enhance ossification of former implant site in anterior cruciate ligament surgery.

Transtibial tubercle fixation without hardware for anterior cruciate ligament and posterior cruciate ligament reconstruction: A new technique

Tibial fixation with implants for both anterior and posterior cruciate ligament reconstructions (ACLR and PCLR) can be associated with a wide variety of problems. Common problems encountered include graft-tunnel mismatch when using grafts with bone blocks, graft damage or poor graft fixation using metal or absorbable implants, painful retained hardware requiring removal, and hardware interference during revision surgery. A new technique is presented using transosseous graft suture passage across the tibial tubercle followed by knot tying over a bone bridge. The technique provides a quick, simple, safe, and reproducible alternative for primary or supplemental tibial graft fixation without hardware in ACLR and PCLR.

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.

Foam-reinforced elderly human tibia approximates young human tibia better than porcine tibia: a study of the structural properties of three soft tissue fixation devices

BACKGROUND

Because there is an insufficient supply of young human knees, an alternative is needed for evaluating anterior cruciate ligament reconstructions. The authors determined whether an elderly human tibia reinforced with foam is a better substitute for a young human tibia than a porcine tibia in this study of the tibialfixation of a soft tissue anterior cruciate ligament graft using 3 devices.

HYPOTHESIS

A foam-reinforced elderly human tibia more closely approximates the performance of a young human tibia than porcine tibia.

STUDY DESIGN

Biomechanical study.

METHODS

Failure mode, stiffness, yield, and slippage were determined for a double-looped tendon graft fixed with either an interference screw, WasherLoc, or tandem washers in young human tibiae, foam-reinforced tibiae from elderly humans, and porcine tibiae.

RESULTS

The stiffness and yield of interference screw and WasherLoc fixation in foam-reinforced tibiae more closely approximate those in young human tibiae than in porcine tibiae. Slippage of all combinations of tibiae and fixation devices was similar

CONCLUSIONS

A foam-reinforced human tibia more closely approximates the performance of a young human tibia than that of porcine tibia in this study.

CLINICAL RELEVANCE

Fixation devices should be tested in foam-reinforced tibiae from elderly humans rather than tibiae from large farm animals when the supply of young human knees is insufficient.