Poly L-lactide co-glycolide/ß-tricalcium phosphate interference screw fixation for bone-patellar tendon bone anterior cruciate ligament reconstruction.

The objective of this study was to prospectively evaluate the clinical effectiveness and radiographic response of a poly (l-lactide co-glycolide)/ß-tricalcium phosphate (PlLA/PGA/ß-TCP) interference screw used in bone-patellar tendon-bone (BPTB) anterior cruciate ligament (ACL) reconstruction. A prospective, consecutive series of 104 patellar tendon bone-tendon-bone ACL reconstructions fixed with PLLA/PGA/ß-TCP biocomposite screws were studied. After receiving the approval from the Institutional Review Board, the following data were collected preoperatively from all patients: physical examination, Lysholm score, Cincinnati, and International Knee Documentation Committee (IKDC) activity scores, and standard knee radiographs. In addition to these, follow-up assessments included Lachman and pivot-shift tests, Tegner scores, and KT side-to-side differences. Surgical failure was defined by a 2+ Lachman test, positive pivot-shift test, side-to-side KT difference of greater than 5 mm or subsequent ACL revision surgery. Approximately 95% of patients (99 of 104) with an average follow-up of 36 months (range, 24 to 68) are reported. The average age was 30 years (range, 13 to 57 years). Postoperatively, four patients demonstrated +1 Lachman score and one patient demonstrated a +2 Lachman score. Postoperative pivot-shift tests were a trace positive in one patients and +1 in two patients. The average KT side-to-side difference was 0.65 mm. All, but five patients, demonstrated KT side-to-side measurements of 3 mm or less and those five demonstrated measurements of 5 mm or less. No revision reconstructions were performed. Significant improvements in Cincinnati score (41 to 85 postoperative) and Lysholm score (46 to 90) were observed. The average postoperative Tegner score was 7. IKDC activity score increased from 2.3 to 3.1. Approximately 4% of patients (4 of 99) met the criteria for failure. A PLLA/PGA/ß-TCP biocomposite interference fixation screw provides good graft fixation, with good radiographic incorporation, without adverse events.The level of evidence of the study is IV.

Loose body following cross-pin fixation for anterior cruciate ligament reconstruction.

We report a case of loosening of a bioabsorbable cross-pin fixation device for anterior cruciate ligament reconstruction. Forty-two months following a bone tendon bone reconstruction of the anterior cruciate ligament, the patient presented with a subcutaneous collection in the medial side of the knee. At subsequent surgery, a RIGIDFIX cross-pin fixator (Mitek, Westwood, MA, USA) was retrieved, intact, from the sterile fluctuant mass around the superomedial aspect of the knee. The graft was stable both radiologically and clinically, and the patient remains symptom free. This case raises concern about the use of this smooth cross-pin fixator and the consequences of backing out and the resultant intraarticular loose body. We suggest consideration of a loose body if the patient becomes symptomatic postoperatively, and early intervention to prevent chondral damage is recommended.

Isokinetic muscle strength and knee function associated with double femoral pin fixation and fixation with interference screw in anterior cruciate ligament reconstruction.

PURPOSE: Intensive scheduling in sports requires athletes to resume physical activity shortly after injury. The purpose of this study was to investigate early isokinetic muscle strength and knee function on bone-patellar tendon-bone (BPTB) ACL reconstruction with double femoral pin fixation or interference screw technique. METHODS: A prospective study was conducted from 2008 to 2009, with 48 athletes who received femoral BPTB fixation with interference screw (n = 26) or double pin (n = 22). Clinical (IKDC objective score and hop test) and isokinetic muscle strength (peak torque (PT), PT/body weight and flexion/extension rate (F/E) in 60 and 240°/s) were analyzed at 6 months of follow-up. RESULTS: Analysis at baseline showed no differences between groups before surgery related to age, gender, associated injury, Tegner or Lysholm score; thus showing that groups were similar. During follow-up, however, there were significant differences between the two groups in some of the isokinetic muscle strength: PT/BW 60°/s (Double Pin = 200% ± 13% vs. Interference Screw = 253% ± 16%*, *P = 0.01); F/E 60°/s (Double Pin = 89% ± 29%* vs. Interference Screw = 74% ± 12%, *P = 0.04). No statistical differences between groups were observed on IKDC objective score, hop test and complications. CONCLUSION: The significant muscle strength outcome of the interference screw group found in this study gives initial evidence that this fixation technique is useful for athletes that may need accelerated rehabilitation. Early return to sports ability signaled by isokinetic muscle strength is of clinical relevance as it is one of the main goals for athletes' rehabilitation.

Long-term degradation of a poly-lactide co-glycolide/ß-tricalcium phosphate biocomposite interference screw.

PURPOSE: To evaluate the long-term in vivo degradation of biodegradable interference screws made of poly-L-lactide co-glycolide (poly-L-lactic acid [PLLA]/polyglycolic acid [PGA]) and ß-tricalcium phosphate (ß-TCP). METHODS: To study in vivo the biological behavior of a PLLA/PGA/ß-TCP biocomposite screw (Milagro; DePuy Mitek, Raynham, MA), an institutional review board-approved program using anterior cruciate ligament (ACL) interference fixation screws was initiated in 2005. Thirteen patients who had bone-patellar tendon-bone ACL reconstruction fixed at both the femur and tibia with PLLA/PGA/ß-TCP screws at least 24 months earlier were evaluated by physical, radiographic, and computed tomography (CT) evaluations. Lysholm, Tegner, Cincinnati, and International Knee Documentation Committee scores were also obtained. Radiographs and CT scans of the operated knee were obtained. CT scan data measured in Hounsfield units (HU) evaluated the material density at the screw and bone plug sites. Soft-tissue and cancellous and cortical bone site readings were also taken. Osteoconductivity scores were determined at the screw sites by use of an ossification quality score (range, 1 to 4). RESULTS: Eleven men and two women were evaluated at a mean of 38 months after surgery (range, 24 to 49 months). CT scans and radiographs showed the bone plug fused to the tunnel wall with no PLLA/PGA/ß-TCP screw remaining. The screws were replaced with material that was calcified and non-trabecular. Osteoconductivity was present in 21 of 26 tunnels (81%) and complete (type 4 ossification) in 5 of 26 (19%). Mean screw site densities (femoral, 159 HU; tibial, 157 HU) were not different from the mean cancellous bone density (femoral, 146 HU; tibial, 140 HU). No positive pivot-shift tests were found. Lysholm, Tegner, and Cincinnati scores improved from 44, 3.7, and 37 preoperatively to 93, 6, and 87 at follow-up, respectively. The mean KT arthrometer (MEDmetric, San Diego, CA) difference was 0.8 mm. CONCLUSIONS: The PLLA/PGA/ß-TCP interference screw completely degraded, and no remnant was present 3 years after implantation for a bone-patellar tendon-bone graft ACL reconstruction. Osteoconductivity was confirmed in 21 of 26 screw sites (81%) and completely filled the site in 5 of 26 (19%). The PLLA/PGA/ß-TCP biocomposite interference screw is osteoconductive. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Does graft construct lengthening at the fixations cause an increase in anterior laxity following anterior cruciate ligament reconstruction in vivo?

A millimeter-for-millimeter relation between an increase in length of an anterior cruciate ligament graft construct and an increase in anterior laxity has been demonstrated in multiple in vitro studies. Based on this relation, a 3 mm increase in length of the graft construct following surgery could manifest as a 3 mm increase in anterior laxity in vivo, which is considered clinically unstable. Hence, the two primary objectives were to determine whether the millimeter-for-millimeter relation exists in vivo for slippage-resistant fixation of a soft-tissue graft and, if it does not exist, then to what extent the increase in stiffness caused by biologic healing of the graft to the bone tunnel offsets the potential increase in anterior laxity resulting from lengthening at the sites of fixation. Sixteen subjects were treated with a fresh-frozen, nonirradiated, nonchemically processed tibialis allograft. Tantalum markers were injected into the graft, fixation devices, and bones. On the day of surgery and at 1, 2, 3, and 4 months, Roentgen stereophotogrammetric analysis was used to compute anterior laxity at 150 N of anterior force and the total slippage from both sites of fixation. A simple linear regression was performed to determine whether the millimeter-for-millimeter relation existed and a springs-in-series model of the graft construct was used to determine the extent to which the increase in stiffness caused by biological healing of the graft to the bone tunnel offset the increase in anterior laxity resulting from lengthening at the sites of fixation. There was no correlation between lengthening at the sites of fixation and the increase in anterior laxity at 1 month (R(2)=0.0, slope=0.2). Also, the increase in stiffness of the graft construct caused by biologic healing of the graft to the bone tunnel offset 0.7 mm of the 1.5 mm potential increase in anterior laxity resulting from lengthening at the sites of fixation. This relatively large offset of nearly 50% occurred because lengthening at the sites of fixation was small.

Biomechanical evaluation of a novel application of a fixation device for bone-tendon-bone graft (EndoButton CL BTB) to soft-tissue grafts in anatomic double-bundle anterior cruciate ligament reconstruction.

PURPOSE: The purpose of this biomechanical study was to compare the structural properties of the flexor tendon graft connected to the EndoButton CL BTB (ECL-BTB) (Smith & Nephew Endoscopy, Andover, MA), which is newly developed to fix the bone-tendon-bone graft, with those of the same graft connected to the EndoButton CL (ECL) (Smith & Nephew Endoscopy), which is commonly used as a standard fixation device. METHODS: We randomly divided 40 porcine flexor digitorum profundus tendons into 4 groups. An ECL and an ECL-BTB were attached to the doubled tendon measuring 6 mm in diameter in groups I and II, respectively. An ECL and an ECL-BTB were attached to the doubled tendon measuring 7 mm in diameter in the same manner in groups III and IV, respectively. Tensile testing was performed with a tensile tester. RESULTS: The linear stiffness of the tendon-device composite (mean +/- SD) was 131.8 +/- 18.3 N/mm, 109.7 +/- 14.9 N/mm, 132.4 +/- 20.5 N/mm, and 123.8 +/- 10.7 N/mm in groups I, II, III, and IV, respectively. The 2-way analysis of variance (ANOVA) showed a significant difference (P = .0058) between the ECL and the ECL-BTB. Concerning the maximum load and the elongation at failure of the tendon-device composite, the 2-way ANOVA showed no significant difference between the 2 fixation devices. Regarding the cross-sectional area, the 2-way ANOVA indicated no significant difference between the 2 fixation devices. CONCLUSIONS: This study has shown that the maximum load of the flexor tendon graft connected to the ECL-BTB is similar to that of the ECL whereas the stiffness of the ECL-BTB is inferior to that of the ECL. CLINICAL RELEVANCE: This study has suggested that patients should not be permitted to perform vigorous activities in the early period after anterior cruciate ligament reconstruction by use of the ECL-BTB fixation technique, because of its low stiffness compared with the ECL device.

The relationship of lateral anatomic structures to exiting guide pins during femoral tunnel preparation utilizing an accessory medial portal.

Anatomic reconstruction of the anterior cruciate ligament through an accessory medial portal has become increasingly popular. The purpose of this study is to describe the relationship of guide pin exit points to the lateral anatomic structures when preparing the anterior cruciate ligament femoral tunnel through an accessory medial portal. We utilized seven fresh frozen cadaveric knees. Utilizing an anteromedial approach, a guide wire was placed into the center of each bundle's footprint. Each guide wire was advanced through the lateral femoral cortex. The guide pins were passed at 90, 110, and 130 degrees of knee flexion. The distances from each guide pin to the closest relevant structures on the lateral side of the knee were measured. At 90 degrees the posterolateral bundle guide pin was closest to the lateral condyle articular cartilage (mean 5.4 +/- 2.2 mm) and gastrocnemius tendon (mean 5.7 +/- 2.1 mm). At 110 degrees the posterolateral bundle pin was closest to the gastrocnemius tendon (mean 4.5 +/- 3.4 mm). At 130 degrees the posterolateral bundle pin was closest to the gastrocnemius tendon (mean 7.2 +/- 5.5 mm) and lateral collateral ligament (mean 6.8 +/- 2.1 mm). At 90 degrees the anteromedial bundle guide pin was closest to the articular cartilage (mean 2.0 +/- 2.0 mm). At 110 degrees the anteromedial bundle pin was closest to the articular cartilage (mean 7.4 +/- 3.5 mm) and gastrocnemius tendon (mean 12.3 +/- 3.1 mm). At 130 degrees the AM bundle pin was closest to the gastrocnemius tendon (mean 8.2 +/- 3.2 mm) and LCL (mean 15.1 +/- 2.9 mm). Neither guide pin (anteromedial or posterolateral bundle) put the peroneal nerve at risk at any knee flexion angle. At low knee flexion angles the anteromedial and posterolateral bundle guide pins closely approximated multiple lateral structures when using an accessory medial arthroscopic portal. Utilizing higher flexion angles increases the margin of error when preparing both femoral tunnels. During preparation of the anterior cruciate ligament femoral tunnel through an accessory anteromedial portal the tunnels should be drilled in at least 110 degrees of knee flexion in order to move guide pin exit points away from important lateral knee structures.

Comparison between bovine bone and titanium interference screws for implant fixation in ACL reconstruction: a biomechanical study.

INTRODUCTION: The application of interference screws for the fixation of bone-patellar tendon-bone (BPTB) grafts is a well-established technique in anterior-cruciate ligament reconstruction. Interference screws derived from bovine compact bone are a biological alternative to metallic or biodegradable polymer interference screws. MATERIALS AND METHODS: In 60 porcine specimens, the tibial part of an anterior-cruciate ligament reconstruction was performed using a BPTB graft. To secure the graft, either an 8-mm titanium interference screw or a self-made bovine interference screw (BC), or a commercial bovine compact bone screw (Tutofix) was used. The maximum failure load was determined by means of a universal testing machine with computer interface at a testing speed of 50 mm/min. In a second test series, cyclic sub-maximal load was applied to the test specimen from 40 to 400 N with a number of 1,000 load cycles and a frequency of 1 Hz. Subsequently, the maximum failure load was determined. The stiffness of the test specimen was investigated in both test series. Each type of interference screw was tested 10 times. RESULTS: A secure fixation of the grafts was achieved with all interference screws. In the experiments on the maximum load to failures, the titanium screws showed significantly higher failure loads than the Tutofix screws (P = 0.005). The stiffness of the grafts fixed with BC screws was significantly higher as compared to the fixation with Tutofix screws (P = 0.005). After cyclic sub-maximal loading, the maximum failure load of the titanium screws was significantly higher than that of the Tutofix screws (P = 0.033). The fixation of the BC screws showed a significantly higher failure load (P = 0.021) and stiffness (P = 0.032) than the Tutofix screw fixation. Except for two screw head fractures and two intra-tendinous graft ruptures, the failure mode was slippage in the interface between interference screw and bone plug. CONCLUSION: Interference screws derived from bovine compact bone show similar good results as the titanium interference screws. Therefore, the safety and in vivo performance of products derived from xenogenic bone should be the focus of further investigations.

Implant-free press-fit fixation for bone-patellar tendon-bone ACL reconstruction: 10-year results.

OBJECTIVE: The aim of this study is to determine the outcome of anterior cruciate ligament (ACL) reconstruction without foreign material with patellar tendon bone graft in the fixation with bone dowels near the native insertion. MATERIALS AND METHODS: Between 1998 and 1999, 189 patients were operated with ACL reconstruction with BTB patellar tendon graft. In a prospective study, 148 (78%) (91M, 57F) patients could be seen for a mean follow-up of 10.3 years. All had foreign material-free press-fit and a bottom-to-top (BTT) fixation in 120 degrees knee flexion. All patients were evaluated with detailed history, clinical examinations, radiographic examination with weight bearing which could be compared to the time of surgery in 64 (43%) patients. Laxity testing was performed in Lachman position with the Rolimeter and pivot shift. All patients were graded according to the IKDC and Tegner activity score. RESULTS: 87% of the patients achieved an IKDC score of A/B. The subjective IKDC score was A/B in 94.6% of the subjects. The average side-to-side difference was 1.42 +/- 0.88 mm for the Lachman test, 97% of the patients were rated between 0 and 2 mm. The pivot-shift test was negative in 90% and was observed with a glide in 7% of the patients. Radiological joint space narrowing was found in the medial compartment in 8 (12.4%) cases, and laterally in 9 (14.1%) cases. All these patients had partial or total meniscus resections. The patello-femoral joint space was reduced in 21 (23%) cases. The Tegner activity score changed from 6.9 pre-injury to 5.0 at the 10-year follow-up. CONCLUSION: The implant-free fixation of the graft with bone dowels and BTT implantation has good and excellent results after 10 years in more than 80% of the patients. Loss of the meniscus is a main factor contributing to osteoarthritis. Advantages of patellar tendon bone press-fit fixation include anatomical positioning and fast bone-to-bone healing, ease for revision surgery and cost effectiveness.

CALAXO osteoconductive interference screw: the value of postmarket surveillance.

The CALAXO osteoconductive interference screw was recalled in August 2007 due to reports of increased numbers of postoperative complications associated with screw swelling and prominence leading to the need for surgical debridement. This study reviews complications associated with CALAXO screw use in a consecutive cohort of patients undergoing anterior cruciate ligament reconstruction surgery by the senior author at the authors' institution. Over a 12-month period, 226 CALAXO interference screws, either of 20 mm length or 25 mm length, were implanted in 112 patients, and postoperative complications were noted. The 25-mm tibial screw was over 5 times (RR 5.2, 95% CI 1.8 to 15.3) more likely to be prominent than the 20-mm screw (p value=.002). Four surgical debridements were required in the 25-mm tibial screw group; none were required in the 20-mm group. The authors hypothesize that the inability to bury the longer screw length into the bone tunnel is associated with postoperative complications associated with the CALAXO screw.

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

¼ 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. ¼ The composition of interference screws has undergone substantial evolution over the past several decades, and numerous advantages and disadvantages are associated with each design. ¼ 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. ¼ 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.

A biomechanical analysis of tibial ACL reconstruction with graft length mismatch.

INTRODUCTION: The incidence of graft length mismatch (GLM) during anterior cruciate ligament (ACL) reconstruction is reported to be up to 13%, with a rate of 20% when using bone-patellar tendon-bone (BPTB) allografts. Multiple techniques have been described to accommodate for the longer BPTB graft. As no study has compared the biomechanical properties of these methods (with cyclic loading), we evaluated the strength of four different surgical techniques used to accommodate for GLM during ACL reconstruction. METHODS: A total of 32 fresh-frozen bovine tibiae and patellar tendons were divided into four groups based on the method of tibial graft fixation: (1) sutures tied over a post, (2) bone staples, (3) screws and washers, and (4) soft-tissue conversion with interference screw. Biomechanical testing was performed comparing the tensile properties of graft fixation techniques under cyclic loading. Ability to withstand 1500 cycles of load, the maximum tensile strength at load-to-failure, and the mode-of-failure were evaluated. RESULTS: Only group 4 had all grafts intact after 1500 loading cycles, while the other groups had one graft failure at 338 (group 1), 240 (group 2), and 309 (group 3) cycles. The highest mean load-to-failure was observed in group 3 at 762 ± 173 N, which was found to be significantly higher than the other groups. The mean loads to failure in groups 1-4 were 453 ± 86 N, 485 ± 246 N, 762 ± 173 N, and 458 ± 128 N. CONCLUSION: While there are multiple viable techniques for fixation of a BPTB graft in the case of GLM, this study demonstrated that direct screw fixation offers the strongest construct.

Femoral press-fit fixation technique in anterior cruciate ligament reconstruction using bone-patellar tendon-bone graft: a prospective clinical evaluation of 285 patients.

BACKGROUND: The security of the graft fixation is an important factor of anterior cruciate ligament reconstruction, especially in the early postoperative period. HYPOTHESIS: The femoral press-fit fixation technique is a safe, alternative technique for the fixation of the bone-patellar tendon-bone graft. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Between January 1, 1998, and June 30, 2002, 285 patients, with a mean age of 29.1 years, underwent operation and observation in our department. All patients had arthroscopic anterior cruciate ligament reconstruction using bone-patellar tendon-bone graft with femoral press-fit and tibial interference screw fixation. The mean follow-up period was 35.8 months (range, 24-77 months). During each patient's evaluation, a physical examination, a subjective evaluation, the International Knee Documentation Committee and Lysholm scores, KT-1000 arthrometer testing, and radiological evaluation were performed. The paired Student t test or chi(2) test was used for statistical analysis. RESULTS: According to the International Knee Documentation Committee score, 241 patients (85%) had good (46 normal and 195 nearly normal) results, whereas 39 patients had abnormal and 5 patients had severely abnormal overall results. The preoperative mean Lysholm score was 63.5 +/- 12.7 points. At the final examination, the mean value was 93.5 +/- 7.8 points (P < .01). One hundred ninety-seven athletes could return to their previous sports activity level, whereas 13 patients gave up their sports career. The KT-1000 arthrometer results showed a side-to-side difference of 1.91 +/- 2.1 mm at the maximum manual strength tests. CONCLUSION: The femoral press-fit fixation is an alternative fixation method for the bone-patellar tendon-bone graft and provides good stability for the anterior cruciate ligament reconstruction. The use of press-fit fixation technique avoids most interference screw or other hardware-induced complications at the femoral side.

All-inside meniscal repair using a new flexible, tensionable device.

BACKGROUND: A new generation of flexible all-inside meniscal repair devices is available, but clinical studies with these devices are lacking. HYPOTHESIS: The RapidLoc has an intermediate-term meniscal healing rate that is equivalent to literature reports of inside-out suture technique in patients undergoing concurrent anterior cruciate ligament reconstruction. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Retrospective analysis was performed for 75 meniscal tears in 66 consecutive patients undergoing anterior cruciate ligament reconstruction who underwent meniscal repair with the RapidLoc. Patients with at least 2 years' follow-up were evaluated for symptoms suggestive of a meniscal tear and were assessed with the International Knee Documentation Committee form and the Knee Disorders Subjective History visual analog scale. Subjects were asked to return for a clinical examination to include evaluation for an effusion and joint line tenderness as well as McMurray test and KT-1000 arthrometry readings. Patients with symptoms consistent with meniscal repair failure underwent magnetic resonance arthrography and repeat arthroscopy. RESULTS: Twenty patients with 21 meniscal tears were excluded, resulting in 54 meniscal tears in 46 patients. At a mean follow-up of 34.8 months, the clinical success rate for meniscal repair was 90.7% (49/54), with 5 failures requiring meniscectomy. Univariate analysis revealed predictive variables for failure: bucket-handle configuration, multiplanar tears, tear length greater than 2 cm, and chronicity longer than 3 months. Non-predictive variables included compartment, zone, ligament graft choice, gender, age, follow-up, and visual analog scale score. Analysis of healed patients revealed a negative correlation between chronicity of tear and International Knee Documentation Committee score. CONCLUSIONS: The RapidLoc has an acceptable intermediate-term clinical healing rate in patients undergoing concurrent anterior cruciate ligament reconstruction. Predictive variables for failure should be considered during operative decision making.

The effect of interference screw diameter on soft tissue graft fixation.

Tibial fixation of soft-tissue grafts is a weak link in anterior cruciate ligament reconstruction. Previous studies have examined varying interference screw lengths, screw types and tunnel sizes as means to improve graft fixation. We hypothesized that increasing interference screw diameter would significantly increase the maximum load to failure of the graft and decrease the graft's initial slippage. Seventy tibialis anterior and tibialis posterior tendons were divided, looped, trimmed, and sutured to simulate 4-strand hamstring grafts. These grafts were then inserted into composite bone blocks having pre-drilled 8 mm holes and fixed with 8 mm, 9 mm, 10 mm, 11 mm, or 12 mm interference screws. Fourteen grafts were tested for each screw size. The graft was first cyclically loaded from 50 N to 250 N at 0.3 Hz for 100 cycles to measure graft slippage. The graft was then tested to failure at 0.5 mm/sec to determine the maximum load to failure and mode of failure. Graft slippage was not affected by screw diameter. Maximum load to failure increased with increasing screw diameter up to 11 mm; 11 mm screw fixation was 20% stronger than 8 mm screw fixation. In this model, no increase in graft fixation was seen in by increasing interference screw diameter beyond 3 mm of the tunnel diameter.

The interaction between the whipstitch sutures of multi-strand ACL grafts and interference screw fixation.

In a recent experiment examining the effect of interference screw sizing on the fixation stability of multi-strand anterior cruciate ligament grafts, we noticed a large variation in fixation strengths and attributed it to the suturing of the grafts and its interaction with the screw. We performed an experiment using interference screws for fixation of hamstring grafts within a bone tunnel model to compare how the presence of sutures affected graft fixation. We found that having sutures along the region of the graft that contacts the screw within the bone tunnel can increase graft fixation strength 100%.

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.

Effect of tibial tunnel position on arthroscopically assisted anterior cruciate ligament reconstruction using bone-patellar tendon-bone grafts: a prospective study.

INTRODUCTION: The aim of this research was to study the effect of the tibial tunnel position in anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon-bone (BPTB) grafts in ensuring optimal knee functioning. METHODS: A prospective study was conducted on 41 patients who underwent arthroscopically assisted ACL reconstruction using a BPTB graft and who were followed up for a minimum period of two years. The radiographic position of the tibial tunnel was compared with the clinical outcome using the International Knee Documentation Committee (IKDC) and modified Lysholm knee scores at two years after surgery. RESULTS: Six out of eight patients with a fair outcome based on the modified Lysholm score and five out of eight patients with an abnormal outcome based on the IKDC score had their tibial tunnel within the 10 percent to 25 percent anteroposterior width of the tibial plateau. The tibial tunnel of patients with a fair Lysholm outcome (mean 22.2 percent) was significantly anterior compared to that of those with an excellent (mean 38.1 percent) and good (mean 34.1 percent) outcome (p is less than 0.01). The analysis using the IKDC score showed a similar trend. CONCLUSION: Placing the tibial tunnel in the anterior 25 percent of the tibial plateau is associated with a poor knee outcome. More predictable results can be achieved through 35 percent to 46 percent anteroposterior placement of the tibial tunnel.

Biomechanical evaluation of bioabsorbable versus metallic screws for posterior cruciate ligament inlay graft fixation: a comparative study.

BACKGROUND: Although a tibial inlay technique for posterior cruciate ligament reconstruction is advantageous, metallic screw fixation of the bone block is required. This may pose problems for future surgery (eg, osteotomies, total knee replacement). HYPOTHESIS: There is no significant difference in the biomechanical integrity of bone block fixation using stainless steel versus bioabsorbable screw fixation of the tibial inlay graft in posterior cruciate ligament reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: Fourteen human cadaveric knees were randomized to receive either stainless steel or bioabsorbable screw fixation of a bone-patellar tendon-bone graft. Cyclic tensile testing of each construct was performed, followed by a load-to-failure test. Digital video digitization was used to optically determine tendon graft deformation. RESULTS: Cyclic creep deformation showed no significant difference between the 2 groups (P = .8). The failure load (stainless steel, 461 +/- 231 N; bioabsorbable, 638 +/- 492 N; P = .7) and linear stiffness (stainless steel, 116 +/- 22 N/mm, bioabsorbable, 106 +/- 44 N/mm; P = .6) also showed no significant difference between the 2 groups. Optically measured graft deformation was not significant for distal (P = .7) and midsubstance (P = .8) regions, while proximal deformation was significantly higher for bioabsorbable fixation (P = .02). All samples failed at the tibial insertion site with the tibial bone block fracturing at the screws. CONCLUSION: Bioabsorbable screw fixation using a tibial inlay technique does not compromise the strength and stiffness characteristics afforded by metallic fixation. From a biomechanical perspective, bioabsorbable screws are a viable alternative to metal in the context of tibial inlay reconstruction. CLINICAL RELEVANCE: Use of bioabsorbable fixation can potentially eliminate future hardware problems after posterior cruciate ligament reconstruction using a tibial inlay technique.