The optimal method of tibial fixation when using a hamstring tendon autograft in anterior cruciate ligament (ACL) reconstruction is unclear. This study aimed to compare the risk of revision ACL reconstruction between suspensory and interference devices on the tibial side. Prospective data on primary ACL reconstructions recorded in the New Zealand ACL Registry between April 2014 and December 2019 were analyzed. Only patients with a hamstring tendon autograft fixed with a suspensory device on the femoral side were included. The rate of revision ACL reconstruction was compared between suspensory and interference devices on the tibial side. Univariate Chi-Square test and multivariate Cox regression was performed to compute hazard ratios (HR) and 95% confidence intervals (CI) with adjustment for age, gender, time-to-surgery, activity at the time of injury, number of graft strands and graft diameter. 6145 cases were analyzed, of which 59.6% were fixed with a suspensory device on the tibial side (n = 3662), 17.6% fixed with an interference screw with a sheath (n = 1079) and 22.8% fixed with an interference screw without a sheath (n = 1404). When compared to suspensory devices (revision rate = 3.4%), a higher risk of revision was observed when using an interference screw with a sheath (revision rate = 6.2%, adjusted HR = 2.05, 95% CI 1.20 – 3.52, p = 0.009) and without a sheath (revision rate = 4.6%, adjusted HR = 1.81, 95% CI 1.02 – 3.23, p = 0.044). The number of graft strands and a graft diameter of ≥8 mm did not influence the risk of revision. When reconstructing the ACL with a hamstring tendon autograft, the use of an interference screw, with or without a sheath, on the tibial side has a higher risk of revision when compared to a suspensory device

We compared self-reported pain and function, complications and revision rates, and radiographic outcomes of hydroxylapatite(HA) or cemented tibial fixation in the first five years following primary total knee arthroplasty. This was a randomised clinical trial of eighty-one patients. Prospective, randomised clinical trial. Patients less than seventy years of age with non-inflammatory knee arthritis. Eighty-one patients were randomised at the time of surgery to receive HA or cemented tibial fixation. Subjects were evaluated preoperatively, six months, one and five years postoperatively by a physical therapist who was blinded to group allocation. X-rays were evaluated by an experienced arthroplasty surgeon who did not perform any of the surgeries. Self-reported pain and function, the primary outcomes, were measured by the Western Ontario McMaster (WOMAC) Osteoarthritis Index and the RAND 36-item Health Services Inventory (RAND-36). Complications and revision rates were determined through hospital record review and at each patient evaluation. The Knee Society Radiological Score was used to evaluate plain radiographs at each assessment. There was slightly more pain in HA group at six months as measured by both the WOMAC and RAND-36, a difference that disappeared by the one-year assessment. There were no differences in function, radiographic findings or complications at any time. Finally, no subjects required revision of the tibial prosthesis during the study. Overall, no significant differences were seen between groups. The initial difference in self-reported pain disappeared by twelve-months postoperatively. At five-years postoperatively, there is no advantage to HA tibial fixation over cemented tibial fixation

This prospective, randomized clinical comparison of tibial fixation in 4-bundle hamstring ACL reconstruction, evaluated mechanical results (laxity) between BioScrew XtraLok® (Linvatec) and Intrafix® (Mitek Products) at six months. One hundred and three sequential patients undergoing ACL reconstruction by three surgeons with identical technique were recruited. KT-1000 arthrometer manual maximum measurements were taken at six weeks, six and six months post-operatively. At six weeks and three months, KT-1000 side-to-side differences between the groups are not statistically significant (student-t test, p=0.87 and p=0.34, respectively). In clinical results at six months, tibial fixation with Bioscrew XtraLok has significantly decreased laxity compared to the Intrafix device (p=0.017). This prospective, randomized clinical comparison of tibial fixation in hamstring ACL reconstruction evaluated mechanical results (laxity) between BioScrew XtraLok® (Linvatec, Largo, FL) and Intrafix® (Mitek Products, Norwood, MA) at six months. After Ethics Review Board approval and sample-size calculation, one hundred and three sequential patients undergoing ACL reconstruction were recruited. Inclusion criteria were: absence of other ligamentous injury or previous knee surgery, and a normal contralateral knee. After drilling tunnels, patients were allocated to a study arm (XtraLok® or Intrafix®) by a computer-generated randomization table. In all patients, EndoButton® (Smith & Nephew, Andover, MA) was used for femoral fixation and the Mitek tensioner was employed. The patients were assessed with KT-1000 arthrometer manual maximum measurements taken at six weeks, three and six months post-operatively by independent clinicians. Mean measurements between the two groups were compared using the student-t test at the above intervals. At six months, eighty-seven of one hundred and three (84%) patients were available for follow-up; 43 XtraLok (XL), and forty-four Intrafix (IF). There was no significant difference between groups in mean age and gender. KT-1000 arthrometer side-to-side differences at six weeks were 1.04mm (XL) versus 1.14mm (IF), and 0.96mm (XL) versus 1.38mm (IF) at three months. At these intervals, differences between the groups are not statistically significant (p=0.87 and p=0.34, respectively). At six months, KT-1000 side-to-side difference was 1.26mm (XL) versus 2.41mm (IF), which is statistically significant (p=0.017). In clinical results at six months, ACL fixation with Bioscrew XtraLok shows decreased laxity compared to the Intrafix device

Background Female patients undergoing arthroscopic anterior cruciate ligament reconstruction with hamstring tendon graft developed increased post-operative laxity compared to male and female patients who had been reconstructed using patellar tendon graft. Hypothesis Supplementary tibial fixation in female patients will reduce laxity. Study Design Prospective, randomized, double-blinded clinical trial. Methods Fifty-six female patients divided into two groups (standard tibial fixation versus supplementary staple fixation) were followed for 2 years. Results After 2 years the mean side-to-side difference utilizing KT-1000 arthrometer manual maximum measurements was 1.8 mm (standard group) and 1.1 mm (staple group) (p=0.05). A Grade 0 Lachman test was present in 63% of the standard group and 86% of the staple group (p=0.04). Kneeling pain was experienced by 7% of the standard group and 29% of the staple group (p=0.05). Conclusions Supplementary tibial fixation in female patients undergoing ACL reconstruction with hamstring tendon graft and interference screw fixation with a single screw size significantly improves laxity measurements and clinical stability assessment 2 years postoperatively. However, this is at the cost of increased kneeling pain

The purpose of this study was to quantify tibial tunnel enlargement at 3-, 6- and 12-months post-anterior cruciate ligament reconstruction (ACLR), and evaluate the magnitude of tunnel widening with use of a Poly (L-lactic Acid) interference screw (PLLA (Bioscrew XtraLok, Conmed, New York)) compared to a Poly (L-lactic Acid) + tricalcium phosphate interference screw (PLLA+TCP (GENESYS Matryx screw comprised of microTCP and 96L/4D PLA, Conmed, New York)). This was a prospective randomized controlled trial with two parallel groups. Eighty unilateral ACL-deficient participants awaiting ACLR surgery were recruited between 2013 and 2017 from the clinic of a sole fellowship trained orthopaedic surgeon. Patients had to be skeletally mature and less than 45 years old, with no concomitant knee ligament injuries requiring surgery, chondromalacia, or previous history of ipsilateral knee joint pathology, surgery or trauma to the knee. Participants were randomized intra-operatively into either the PLLA or PLLA+TCP tibial interference screw fixation group. Study time points were pre-, 3-, 6-, and 12-months post ACLR. Participants underwent x-rays with a 25 mm calibration ball, IKDC knee assessment, and completed the ACL-Quality of Life score (ACL-QOL) at each visit. Measurement (mm) of the most proximal and distal extents as well as the widest point of the tibial tunnel were taken using efilm (IBM Watson Health) and were standardized relative to the calibration ball. A contrast inverter was used to determine clear borders based on contrast between normal and drilled bone. In addition, a subjective evaluation of the tunnel was conducted looking for bowing of the borders of the tunnel or change in tunnel shape, categorizing the tunnel as widened or not widened. Differences between groups at each time point were evaluated using independent t-tests corrected for multiple comparisons. Tunnel width was also compared as a percentage of actual screw size at 12-months post-operative. Categorical data were compared using Fisher's Exact Test. Forty participants were randomized to each group with mean age (SD) of 29.7 (7.6) and 29.8 (9.1), for PLLA and PLLA+TCP, respectively. There were no differences between groups in age, gender or ACL-QOL. There were no differences found between groups at any time point in either tunnel width measurements or tunnel width as a percentage of actual screw size. The greatest difference between groups was noted in the measurement of the widest point on lateral x-ray view with a mean difference of 11%. Based on subjective evaluation of tunnel shape, three participants had visible widening in the PLLA group, and two in the PLLA+TCP group (p=NS). No differences in tunnel widening were identified between ACL reconstruction patients using a PLLA interference screw compared to a PLLA+TCP screw for tibial fixation up to 12-months post-operative

Purpose: The purpose of this study was to analyse the clinical and MRI results of anterior cruciate ligament (ACL) grafts using the patellar tendon with a tibial fixation by th resorbable interference screw PLA 98 (Phusis(r)). Material and methods: ACL grafts were performed in 182 patients between 1994 and 1997. A unique graft was used in 85 cases (Kenneth Jones), and association with Lemaire plasty in 97. The tibial fixation was achieved with the resorbable screw in all cases. Clinical and radiological data were recorded before surgery, and at one and five years. Among the 110 patients with an MRI at one year, 62 also had an MRI control at five years (57%). The antero-posteior and mediolateral tibial position was evaluated on the horizontal slices. We defined a method for evaluating the femoral position on the horizontal MRI slices. The aspect of the graft was analysed at one and five years. Results: There were three failures (Trillat-Lachmann test). Mean residual differential laxity was 2.6 mm (Telos). At five years, 92% of patients practiced sports at a moderate or intensive level. The tibial position was good and highly reproducible (SD=0.06). Five femoral positions were not satisfactory but were not related with failure. All screws were resorbed at five years. There were two bone reactions at one year, with no relation with screw absorption (one contusion and one reflex dystrophy). At one year, the MRI with gadolinium injection visualised peripheral enhancement of the graft. At five years three transplants appeared heterogeneous, corresponding to three ruptures. Segmentary heterogenic aspects were not found to have any pathological significance. Discussion: Evaluation of the femoral position is difficult on the MRI sagittal views. Our analysis method based on horizontal slices allowed reliable reproducible analysis. Analysis of the graft should take into consideration the time since surgery and the sequence used. There was no problem with fixation or screw absorption. Conclusion: MRI follow-up of ACL grafts enables an analysis of the transplant positions, to follow the evolution of the graft, and to confirm the reliability and safety of the resorbable screw fixation

Introduction: This study addresses the long term results of 1225 uncomplicated primary total knee arthroplasties performed between 1986 and 1995, using one design with various tibial fixation methods. Methods: 1225 primary total knees were performed using a press fit total condylar cruciate retaining design. 108 cases were eliminated because of death and 171 due to lack of follow up leaving a group of 946 knees. Mean time insitu is 9.2 years. 500 knees had both the tray and stem cemented, 374 had only the tray cemented, and 72 used no cement. Both clinical and radiographic Knee Society Scores were tabulated preoperatively and annually thereafter. The SF-36 has been recorded both pre and postoperatively since 1993. Results: Overall revision rates for the cemented, tray only and non-cemented groups were 1.0%, 3.4% and 12.5%, respectively. A combined 20 cases had the tibial component revised due to polywear and osteolysis with 0.6% from the cemented group, 2.4% from the tray only group and 11.1% from the tray only group. The joint portion of the Knee Society score was comparable for the cemented and tray only groups (88.9 and 88.3, respectively) but only 80.9 for the non-cemented group. Discussion and conclusion: Using a component design that meets the needs of the majority of patients regardless of bone quality has proven to be successful and cost effective for this institution. The authors believe these excellent results and low revision rate for loosening indicate this design has much to offer with its flexibility of tibial fixation

The purpose of this study is to biomechanically compare Evolgate and Intrafix using cyclic loading with final pull-out tests. Five pairs of double looped bovine digital extensor tendons and 10 porcine tibias were used. We evaluated the displacement at 1, 10, 100, 250, 500, 1000 and 1500 cycles. We used cyclic tests (1500 cycles between 50 and 200 N with final pull-out). Biomechanical tests were performed with use of a Zwick-Roell Z010 mechanical testing machine (Zwick-Roell, Germany), and the testing data were recorded with the accompanying software package (Testexpert 8.1, Zwick-Roell). A paired t-test was performed for statistical evaluation. There was no statistically significant difference in slippage between the two devices. The mean ultimate failure load at pull-out after 1500 cycles was 832±156 N for Intrafix and 1058±130 N for the Evolgate.The mean stiffness at pull-out was 269±86 for Intrafix and 247±44 for the Evolgate, and there were no statistically significant differences (p> 0.05). At statistical evaluation there was a difference in ultimate failure load between the IF and the EV (p< 0.05). Although further studies are needed to investigate bone growth into the tibia tunnel, Evolgate seems to be a good choice for tibial fixation of hamstring tendons. Moreover, Evolgate has higher values of strength than Intrafix

Anterior Cruciate Ligament (ACL) reconstruction is a well established procedure for restoration of stability following ACL rupture. Several methods exist for fixation of soft tissue grafts on the tibia, without general agreement about the optimal method. This study compared two different methods of tibial fixation using hamstring grafts in ACL reconstruction. 113 consecutive patients were randomized into two groups at the time of surgery. In group one, fixation was with a metal interference screw (RCI) and staples and in group two, with a polyethylene screw and sheath (Intrafix). Evaluation of outcomes was conducted using KT-1000 arthrometer, Lysholm, IKDC subjective and Mohtadi scores. 7 reinjuries occurred within the time frame of the study, mostly related to sporting injuries, with 5 in group 2. 81% of remaining participants were successfully followed at 2 years post surgery. No significant difference in mean KT-1000 side-to-side measurements was found between groups at an average follow-up of 30 months (1.5 ± 1.9mm and 1.8 ± 1.9mm, respectively; p > 0.05). The mean Lysholm score for group one was 65.2 ± 15.5 preoperatively and 90.8 ± 9.5 postoperatively; for group two these scores were 62.0 ± 20.7 preoperatively and 88.8 ± 14.3 postoperatively. This improvement in scores after surgery was similar for both groups and was not significantly different between groups (p > 0.05). Both the IKDC subjective and Mohtadi scores showed significant (p < 0.05) improvements postoperatively compared with pre-operatively but no significant difference between fixation groups. There were no significant differences between the two groups for any outcome value, with both methods of graft fixation producing good results. The newer Intra-fix device had a higher reinjury rate but this was not significantly different from the screw and staple fixation, and on all other outcome measures the Intrafix device was equivalent to an interference screw and staples for tibial-sided graft fixation in ACL reconstruction

Aims

Total knee arthroplasty is an established treatment for knee osteoarthritis with excellent long-term results, but there remains controversy about the role of uncemented prostheses. We present the long-term results of a randomized trial comparing an uncemented tantalum metal tibial component with a conventional cemented component of the same implant design.

Traditional procedures for orthopedic total joint replacements have relied upon bone cement to achieve long-term implant fixation. This remains the gold standard in number of procedures including TKR and PKR. In many cases however, implants fixed with cement have proven susceptible to aseptic loosening and 3^rd body wear concerns. These issues have led to a shift away from cement fixation and towards devices that rely on the natural osteoconductive properties of bone and the ability of porous-coated implants to initiate on-growth and in-growth at the bone interface, leading to more reliable fixation.

To facilitate long-term fixation through osseointegration, several mechanical means have been utilized as supplemental mechanism to aid in stabilizing the prostheses. These methods have included integrated keels and bone screws. The intent of these components is to limit implant movement and provide a stable environment for bone ingrowth to occur. Both methods have demonstrated limitations on safety and performance including bone fracture due keel induced stresses, loosening due to inconsistent pressfit of the keel, screw-thread stripping in cancellous bone, head-stripping, screw fracture, screw loosening, and screw pullout. An alternative method of fixation utilizing blade-based anchoring has been developed to overcome these limitations.

The bladed-based fixation concept consists of a titanium alloy anchor with a “T-shaped” cross-section and sharped-leading end that can be impacted directly into bone. The profile is configured to have a bladed region on the horizontal crossbar of the “T” for engagement into bone and a solid rail at the other end to mates with a conforming slot on the primary body of the prosthesis. A biased chisel tip is added to the surface of the leading blade edge to draw the bone between the anchor's horizontal surface and surface of the implant, thus generating a compressive force at the bone-to-prothesis interface. The anchoring mechanism has been successfully been integrated into the tibial tray component of a partial knee replacement; an implant component that has a clinical history of revision due to loosening.

A detailed investigation into the pulloff strength, wear debris generation, compressive-force properties, and susceptibility to tibial bone fracture was carried out on the anchor technology when integrated in a standard tibial tray of a partial knee replacement. When tested in rigid polyurethane bone foam (Sawbones, Grade 15) the pulloff strength of the construct increased by 360% when utilizing the anchor. The tibial tray and anchor construct were cycled under compressive loading and demonstrated no evidence of interface corrosion or wear debris generation after 1 million cycles. In addition, the anchor mechanism was shown to generate 340N of compressive force at the tibial tray-to-bone interface when evaluated with pressure sensitive film (Fuji Prescale, Medium Grade). Finally, the ultimate compressive load to induce tibial fracture was shown to increase by 17% for the anchored tray as compared to a traditional keeled tray when tested in an anatomic tibial sawbones model; and by 19% when evaluated in human cadaveric tibias.

For any figures or tables, please contact authors directly.

Aims

The introduction of a novel design of total knee arthroplasty (TKA) must achieve outcomes at least as good as existing designs. A novel design of TKA with a reducing radius of the femoral component and a modified cam-post articulation has been released and requires assessment of the fixation to bone. Radiostereometric analysis (RSA) of the components within the first two postoperative years has been shown to be predictive of medium- to long-term fixation. The aim of this study was to assess the stability of the tibial component of this system during this period of time using RSA.

Purpose

The purpose of this study was to assess radiologically the absorption of a poly L-lactide bioabsorbable interference screw used in anterior ligament reconstruction.

The purpose of this paper is to investigate the relative contribution of each component in the ultimate strength and stiffness of the Evolgate (Citieffe), which is presently a widely used fixation device in DGST ACL reconstruction. The three components of the Evolgate were tested using fresh frozen animal tissue stored at −20° Celsius. Common extensor tendons were harvested from 20-month-old bovine forelimbs. Twenty-four tests were performed for each of the following configurations: six tests using Evolgate complete, six tests using screw alone, six tests using screw and washer and six tests using screw and coil. A randomised t-test was used; differences were considered significant when p< 0.05. The mean strength was: Evolgate complete 1314±194N; coil and screw 700±152N; screw alone 408±86N; and screw and washer 333±93N. There was a significant difference between fixation strength of Evolgate and the other devices, none between screw alone and screw and washer. The mean slippage of the Evolgate was significantly lower than the other devices. The mean stiffness of the Evolgate (269±14 N/mm) was significantly greater than the other devices. On the basis of the results of the present study, the coil appears to be the most important component of the Evolgate, resulting in a significant increase of the fixation strength of the screw. However, it is important to note that, as the washer alone does not improve the strength of the screw, if a washer is associated with a coil a further significant increase in strength and stiffness of the device is observed.

Introduction and Aims: Good clinical outcome can be expected following cementless total knee arthroplasty (TKA) provided there is early stability and bone ingrowth. Screws give excellent initial stability but provide a path for osteolysis. Screws also cause an irregularity of the tibial component surface which limits their use as a mobile bearing component. We hypothesise that early stability can be obtained with four peripheral pegs rather than screws. We present the results of such a tibial component at a minimum of two years in a cementless mobile-bearing TKA.

Materials and Methods: We evaluated 200 knees in 173 patients. The average age at surgery was 72 years (range, 45–91 years) with 61% of cases in women. Patients were followed up for an average of 45.7 months (range 24 to 69 months). All radiographic and clinical scores were performed prospectively and recorded on a relational database. The components used were the cementless Low Contact Stress femoral component with the DuoFix MBT tibial tray (Depuy, Warsaw, Indiana, USA). The tibial tray was manufactured from cobalt-chrome with a central polished stem and four peripheral pegs. The underside, including the pegs, had a porous surface coated with 50 microns of hydroxyapatite.

Results: After excluding patients who had died, or lost to follow up, 164 cases had a minimum 2-year follow-up. None of the tibial components have required revision. One patient (0.6%) required revision of the femoral component at 22 months for failure of bone ingrowth. There was one superficial infection which resolved with intravenous antibiotics. Two patients developed deep infections (1.2%) which resolved with arthroscopic lavage and antibiotics. One patient presented with bearing spin out at 3 months following surgery, and an exchange to a thicker tibial insert was performed. Average flexion at follow up was to 110°. The patients stated that they were satisfied with their knees in 141 out of 155 cases (91%). The mean score for pain at rest was 0.9 (0–10) and for activity related pain was 1.3. The average HSS score was 86/100 with 90% good or excellent results, compared with a preoperative score of 54/100. Lucent lines were seen in one tibial zone in ten knees (7%), and two zones in three knees (2.1%). There were lucent lines in one femoral zone in 13 cases and two zones in two cases. None of the lines were progressive, and all the surviving components were bone ingrown. Osteolysis was present in a single zone around one (0.7%) tibial component. One patient showed some femoral osteolysis in one zone (0.7%) and also had patellar osteolysis in one zone. Two patients had osteolysis in a single zone of the patella.

Conclusion: This study shows that this design of mobile bearing tibial component provides good primary stability and bone ingrowth.

Introduction. Aseptic loosening is one of the highest causes for revision in total knee arthroplasty (TKA). With growing interest in anatomically aligned (AA) TKA, it is important to understand if this surgical technique affects cemented tibial fixation any differently than mechanical alignment (MA). Previous studies have shown that lipid/marrow infiltration (LMI) during implantation may significantly reduce fixation of tibial implants to bone analogs [1]. This study aims to investigate the effect of surgical alignment on fixation failure load after physiological loading. Methods. Alignment specific physiological loading was determined using telemetric tibial implant data from Orthoload [2] and applying it to a validated finite element lower limb model developed by the University of Denver [3]. Two high demand activities were selected for the loading section of this study: step down (SD) and deep knee bend (DKB). Using the lower limb model, hip and ankle external boundary conditions were applied to the ATTUNE. ®. knee system for both MA and AA techniques. The 6 degree of freedom kinetics and kinematics for each activity were then extracted from the model for each alignment type. Mechanical alignment (MA) was considered to be neutral alignment (0° Hip Knee Ankle Angle (HKA), 0° Joint Line (JL)) and AA was chosen to be 3° varus HKA, 5° JL. It is important not to exceed the limits of safety when using AA as such it is noted that DePuy Synthes recommends staying within 3º varus HKA and 3º JL. The use of 5º JL was used in this study to account for surgical variation [Depuy-Synthes surgical technique DSUS/JRC/0617/2179]. Following a similar method described by Maag et al [1] ATTUNE tibial implants were cemented into a bone analog with 2 mL of bone marrow in the distal cavity and an additional reservoir of lipid adjacent to the posterior edge of the implant. Tibial implant constructs were then subjected to intra-operative ROM/stability evaluation, followed by a hyperextension activity until 15 minutes of cement curing time, and finally 3 additional ROM/stability evaluations were performed using an AMTI VIVO simulator. The alignment specific loading parameters were then applied to the tibial implants using an AMTI VIVO simulator. Each sample was subjected to 50,000 DKB cycles and 120,000 SD cycles at 0.8 Hz in series; approximating 2 years of physiological activity. After physiological loading the samples were tested for fixation failure load by axial pull off. Results. Following alignment specific physiological loading the average fixation pull-off load for MA was 3289 ± 400 N and for AA was 3378 ± 133 N (Figure 1). There was no statistically significant difference fixation failure load by axial pull-off between the two alignment types (p=0.740). Conclusion. This study indicated that anatomic alignment, as defined with the alignment limits of this study, does not adversely affect the fixation failure load of ATTUNE tibial implants. For any figures or tables, please contact the authors directly

A paper was presented two years ago reviewing evidence of absorption of the Bio Interference screw and tunnel widening at three, six and 12 months following anterior cruciate ligament reconstruction using double-stranded hamstrings. The femoral fixation was with an Endobutton with a double loop of Mercylene tape with a Bio Interference screw and an extra small staple for the distal fixation. This paper presents further magnet resonance imaging (MRI) studies at least two years after surgery on 10 of those patients to assess if there was any MRI evidence of absorption of the Bio Interference screw or tunnel widening (in particular ganglion formation) in the femoral or tibial tunnels.

The results showed that at least two years after surgery there was little evidence of Bio Interference screw absorption. There was no evidence of tunnel widening.

Introduction. Beneath infection, instability and malalignment, aseptic tibial component loosening remains a major cause of failure in total knee arthroplasty (TKA) [1]. This emphasizes the need for stable primary and long-term secondary fixation of tibial baseplates. To evaluate the primary stability of cemented tibial baseplates, different pre-clinical test methods have been undergone: finite element analysis [2], static push-out [3,4] or dynamic compression-shear loading [5] until interface failure. However, these test conditions do not reflect the long-term endurance under in vivo loading modes, where the tibial baseplate is predominantly subjected to compression and shear forces in a cyclic profile [5,6]. To distinguish between design parameters the aim of our study was to develop suitable pre-clinical test methods to evaluate the endurance of the implant-cement-bone interface fixation for tibial baseplates under severe anterior (method I) and internal-external torsional (method II) shear test conditions. Materials & Methods. To create a clinically relevant cement penetration pattern a 4. th. generation composite bone model was customised with a cancellous core (12.5 PCF cellular rigid PU foam) to enable for high cycle endurance testing. VEGA System. ®. PS & Columbus. ®. CRA/PSA ZrN-multilayer coated tibial baseplates (2×12) were implanted in the customised bone model using Palacos. ®. R HV bone cement (Figure 1). An anterior compression-shear test (method II) was conducted at 2500 N for 10 million cycles and continued at 3000 N & 3500 N for each 1 million cycles (total: 12 million cycles) simulating post-cam engagement at 45° flexion. An internal-external torsional shear test (method II) was executed in an exaggeration of clinically relevant rotations [7,8] with ±17.2° for 1 million cycles at 3000 N tibio-femoral load in extension. After endurance testing either under anterior shear or internal-external torsion each tibial baseplate was mounted into a testing frame and maximum push-out strength was determined [3]. Results. The cement penetration depth and characteristic pattern were comparable to 3D-CT scans of 24 cemented human tibiae from a previous study [5]. From the final push-out testing, no statistical significant differences could be found for anterior compression-shear testing (method I) with VEGA System. ®. PS (2674 ± 754 N) and Columbus. ®. CRA/PSA (2177 ± 429 N) (p = 0.191), as well as internal-external torsional shear testing (method II) between VEGA System. ®. PS (2561 ± 519 N) and Columbus. ®. CRA/PSA (2825 ± 515 N) tibial baseplates (p = 0.399). Discussion. The newly developed methods allow the evaluation of the endurance behaviour of the implant-cement-bone interface fixation for tibial baseplates in comparison to clinically long-term established knee systems, based on a combination of a suitable artificial bone model and severe anterior and internal-external torsional high cycle shear test conditions

Aim of the study: To evaluate whether additional aperture fixation to distal fixation (two-point fixation or 2P) may diminish tibial tunnel enlargement compared to distal fixation alone (one-point fixation or1P). Methods: Two groups of patients were evaluated. In group 1P (44pts.) the grafts were fixed on the tibial side, using two 4 mm Mersilene tapes tied over a 10 mm bone bridge created in the anterior cortex. In group 2P, an additional fixation, using 1 absorbable cross pin in 27 pts. and 2 absorbable cross pins (Rigid fix, Mitek) in 24 pts., was performed. AP and lateral radiographs as well as patients evaluation were performed 3, 6 and 12 months post-op. Tibial tunnel size was measured at the widest diameter in both AP and lateral radiographs. Results: Tunnel enlargement occurred in both groups at 3 months post-op, but not thereafter. In the lateral radiographs, tunnel enlargement was significantly less in group 2P compared to group 1P (p< 0.05). No statistical relationship was found between tunnel enlargement and gender, age, IKDC, and KT 1000 side-to-side difference. Conclusion: Additional tibial graft fixation with cross-pins seems to diminish tibial tunnel enlargement in the sagital plane. This may be explained by the fact that the cross pins inserted in the coronal plane, reduce tibial graft movements mainly in the sagital plane. The study supports the hypothesis that tibial graft micro-movements during the period of tendon healing to bone (up to 3m) play a role in tibial tunnel enlargement after ACL reconstruction using hamstrings

This study was to evaluate the stability of a delta keel tibial tray using a block prosthesis and to determine whether a long intramedullary stem is a necessary adjunct to augment construct stability. An experimental technique was used employing strain gauges and deflection transducers to assess the stiffness and principle strains conferred to human cadaveric tibiae under various axial loading conditions.

As a control measure, tests were conducted in the absence of any bone loss, and repeated in a simulated bone defect treated with a metal block. The latter was analysed with and without augmentation of the tibial tray with an intramedullary stem. With axial loading of 2000N, the tray and block configuration resulted in 21% less proximal bone strain than the tray alone. The combined tray, block and stem resulted in 35% less proximal bone strain than the tray alone. Using the tray and block produced 1.06 times more deflection of the tibial tray and using the tray, block and stem 1.03 times more deflection of the tibial tray than the tray alone in the absence of a bony defect.

There was no statistical difference in overall construct stability (p < 0.05) despite the large strain-offsetting effect recorded using the tibial tray in conjunction with the block and stem

These results suggest that isolated bone defects that can be dealt with using a single block and modern standard tibial tray may not require additional supplementation with a long intramedullary stem.