Anterior Cruciate Ligament Soft Tissue Graft Fixation in the Elderly: Is There a Reason to Use Interference Screws? A Human Cadaver Study.

PURPOSE: To analyze the ultimate failure load, yield load, stiffness, and cyclic resistance of different anterior cruciate ligament (ACL) soft tissue graft fixation techniques in osteopenic bone. METHODS: In this study, 24 fresh-frozen human cadaveric tibiae (mean age 82.6 years; range 56-96; 6 male and 6 female donors) were used. Quantitative computed tomography was performed to match bone density. Looped porcine flexor tendon grafts were chosen as ACL graft substitutes for tibial graft fixation techniques (n = 8 each): (1) hybrid fixation with an interference screw and extracortical button fixation; (2) extracortical button fixation; and (3) interference screw fixation. In single cycle mode, constructs were loaded to failure to evaluate stiffness, yield load, and maximum load. In cyclic testing, 2,000 cycles (25-100 N) were applied followed by loading to failure. A 1-way analysis of variance was performed with significance set at P = .05. RESULTS: Hybrid fixation resulted in significantly higher yield load (283.4 ± 86.19 N; P = .0037) and maximum load (407.9 ± 102.3 N; P = .0026) than interference screw fixation (yield load 176.4 ± 26.03, max load 231.8 ± 94.06 N) in elderly bone. Yield load after extracortical button fixation (252.9 ± 41.97 N; P = .0286) was also higher than that after interference screw fixation, but stiffness (18.98 ± 9.154 N/mm; P = .0041) was less than that after hybrid fixation (37.28 ± 13.53 N/mm). Of 8 specimens in the interference screw group, 7 did not survive 2,000 cycles and failed by graft slippage, whereas all other specimens in both other groups survived. CONCLUSIONS: Tibial hybrid fixation of ACL soft tissue grafts provides less vertical graft movement than extracortical button fixation and higher primary failure loads than interference screw fixation in elderly bone. CLINICAL RELEVANCE: In this elderly human joint in vitro model, tibial hybrid fixation provides biomechanical advantages over other techniques. Graft fixation with only an interference screw should be avoided in osteopenic bone.

Reverse total shoulder arthroplasty for type I fracture sequelae after internal fixation of proximal humerus fractures.

INTRODUCTION: Complications after internal fixation of proximal humerus fracture are common and may require surgical revision. Reverse total shoulder arthroplasty (RTSA) is frequently performed in such cases. The aim of the present study was to evaluate the functional results and complications after RTSA for the treatment of type I fracture sequelae after internal fixation of proximal humerus fractures. MATERIALS AND METHODS: 26 patients (18 female, 8 male) underwent surgical revision of type I fracture sequelae of the proximal humerus after locking plate (n = 22) or intramedullary nail (n = 4) fixation. The mean age of the patients at the time of the revision was 75 years (range 65-89). After a mean follow-up of 36 months (range 18-58), clinical examination was performed and the age- and gender-related Constant-Murley Score (CMS) and the Oxford Shoulder Score (OSS) were obtained from all patients and compared to the pre-revision values. RESULTS: The mean age- and gender-related CMS of the affected shoulder increased from 44% (range 17-65) to 73% (range 44-97). This difference was statistically significant (p < 0.001). The CMS of the unaffected shoulder was 93% (range 72-98). This relates to a ratio in the CMS of 78% between the affected and the contralateral shoulder. The mean OSS was 28 points (range 12-54) for the operated shoulder and 43 points (range 34-48) for the unaffected side, resulting in 66% ratio. Again, the OSS improved significantly when compared with the preoperative values (p < 0.001). A total of five complications including two periprosthetic fractures were observed and required surgical revision. CONCLUSION: Satisfying results can be obtained with RTSA as a salvage procedure for type I fracture sequelae after previous internal fixation of proximal humerus fractures.

PEEK versus titanium locking plates for proximal humerus fracture fixation: a comparative biomechanical study in two- and three-part fractures.

INTRODUCTION: The high rigidity of metal implants may be a cause of failure after fixation of proximal humerus fractures. Carbon fiber-reinforced polyetheretherketone (PEEK) plates with a modulus similar to human cortical bone may help to overcome this problem. The present study assesses the biomechanical behavior of a PEEK plate compared with a titanium locking plate. MATERIALS AND METHODS: Unstable two- and three-part fractures were simulated in 12 pairs of cadaveric humeri and were fixed with either a PEEK or a titanium locking plate using a pairwise comparison. With an optical motion capture system, the stiffness, failure load, plate bending, and the relative motion at the bone-implant interface and at the fracture site were evaluated. RESULTS: The mean load to failure for two- and three-part fracture fixations was, respectively, 191 N (range 102-356 N) and 142 N (range 102-169 N) in the PEEK plate group compared with 286 N (range 191-395 N) and 258 N (range 155-366 N) in the titanium locking plate group. The PEEK plate showed significantly more bending in both the two- and three-part fractures (p < 0.05), an increased relative motion at the bone-implant interface and lower stiffness values (p < 0.05). CONCLUSION: In this biomechanical study on unstable proximal humerus fractures, fixation with a PEEK plate showed lower fixation strength and increased motion at the bone-implant interface compared with a titanium locking plate.

Biomechanical evaluation of different surgical techniques for treating patellar tendon ruptures.

PURPOSE: The aim of this study was to biomechanically assess patellar tendon repair techniques with additional cable wire or polydioxanone suture (PDS) cord augmentation in comparison with a suture-anchor repair technique. METHODS: Patellar tendon repair was performed in 60 specimens using a porcine bone model. Yield load, maximum load, stiffness and elongation of patellar tendon reconstructions with (1) cable wire augmentation, (2) PDS cord augmentation or (3) suture anchor repair were evaluated using a cyclic loading and load-to-failure test setup. RESULTS: In comparison with suture anchor repair, augmentation of the reconstruction with either cable wires or PDS cords provides significantly higher maximum loads (527 and 460 N vs. 301 N; p < 0.01 and p = 0,012, respectively) under load-to-failure testing and less elongation (8.81 mm ± 1.55 mm and 10.56 mm ± 3.1 mm vs. 18.38 mm ± 7.51 mm; p = 0.037 and p = 0.033, respectively) under cyclic loading conditions. CONCLUSION: Augmentation of a patellar tendon repair with either a cable wire or a PDS cord provides higher primary stability than suture anchor repair in patellar tendon ruptures. The study supports the use of additional augmentation of a tendon repair in the clinical setting in order to prevent loss of reduction and allow for early post-operative mobilisation.

Why does minimally invasive coracoclavicular ligament reconstruction using a flip button repair technique fail? An analysis of risk factors and complications.

PURPOSE: Aim of the present study was to evaluate the risk factors for the failure of coracoclavicular ligament reconstruction using a flip button repair technique and to analyse complications related to this procedure. METHODS: Seventy-one patients (3 female, 68 male) underwent surgical treatment using a flip button repair technique for an acute acromioclavicular joint dislocation. The following factors and its impact on clinical and radiographic outcome were assessed: age at trauma, interval between trauma and surgery, degree of displacement (according to Rockwood's classification), coracoid button position, button migration and post-operative appearance of ossifications. RESULTS: Sixty-three patients were available for follow-up. The overall Constant score was 95.2 points (range 61-100 points) compared to 97 points (range 73-100 points) for the contralateral side (p = 0.05). Nine patients (14.3 %) needed surgical revision. Inappropriate positioning of the coracoid bone tunnel with subsequent button dislocation was the most frequently observed mode of failure (6 cases, 9.5 %). Button migration into the clavicle was associated with loss of reduction (p = 0.02). The patient's age at the time of trauma had a significant impact on the clinical outcome, whereas younger patients achieved better results (p = 0.02). The interval between trauma and surgery did not significantly affect the outcome (n.s.). CONCLUSION: Good to excellent clinical results can be achieved with the presented surgical technique. The age of the patient at trauma had a significant influence on the functional outcome. Furthermore, placement of the coracoid button centrally under the coracoid base is crucial to prevent failure. LEVEL OF EVIDENCE: IV.

Treatment of proximal humerus fractures with a CFR-PEEK plate: 2-year results of a prospective study and comparison to fixation with a conventional locking plate.

BACKGROUND: A radiolucent carbon fiber-reinforced polyetheretherketone (CFR-PEEK) plate was recently introduced for fixation of proximal humerus fractures. Prospective clinical and radiographic results of patients treated with a CFR-PEEK plate are compared with those of patients treated with a conventional locking plate. METHODS: Twenty-nine patients (mean age, 66 years) were treated with a CFR-PEEK plate for a 3- or 4-part proximal humerus fracture. Patients were clinically and radiographically re-examined at 6 weeks, 6 months, 12 months, and 24 months with the Simple Shoulder Test, Constant-Murley score (CMS), and Oxford Shoulder Score (OSS) as well as with simple radiographs. In addition, results were compared with a matched group of patients treated with a conventional locking plate. RESULTS: At the final follow-up examination at 24 months, patients achieved a mean Simple Shoulder Test score of 58%, a mean CMS of 71.3 points (range, 44-97), and a mean OSS of 27.4 points (range, 8-45). Bone union was confirmed in all patients. Compared with patients treated with the conventional locking plate, patients treated with the CFR-PEEK plate achieved significantly better results with regard to the CMS and the OSS (P = .038 and .029, respectively). Furthermore, loss of reduction with subsequent varus deformity was less frequently observed in the CFR-PEEK plate group. CONCLUSION: Fixation of proximal humerus fractures with a CFR-PEEK plate provides satisfying clinical and radiographic results after 2 years of follow-up. The results are comparable to those achieved with conventional locking plates.

Screw augmentation reduces motion at the bone-implant interface: a biomechanical study of locking plate fixation of proximal humeral fractures.

BACKGROUND: Shear forces at the bone-implant interface lead to a loss of reduction after locking plate fixation of proximal humeral fractures. The aim of the study was to analyze the roles of medial support screws and screw augmentation in failure loads and motion at the bone-implant interface after locking plate fixation of proximal humeral fractures. METHODS: Unstable 3-part fractures were simulated in 6 pairs of cadaveric humeri and were fixed with a DiPhos-H locking plate (Lima Corporate, Udine, Italy). An additional medial support screw was implanted in 1 humerus of every donor. The opposite humerus was stabilized with a medial support screw and additional bone cement augmentation of the 2 anteriorly directed head screws. Specimens were loaded in the varus bending position. Stiffness, failure loads, plate bending, and the motion at the bone-implant interface were evaluated using an optical motion capture system. RESULTS: The mean load to failure was 669 N (standard deviation [SD], 117 N) after fixation with medial support screws alone and 706 N (SD, 153 N) after additional head screw augmentation (P = .646). The initial stiffness was 453 N/mm (SD, 4.16 N/mm) and 461 N/mm (SD, 64.3 N/mm), respectively (P = .594). Plate bending did not differ between the 2 groups. However, motion at the bone-implant interface was significantly reduced after head screw augmentation (P < .05). CONCLUSION: The addition of bone cement to augment anteriorly directed head screws does not increase stiffness and failure loads but reduces motion at the bone-implant interface. Thus, the risk of secondary dislocation of the head fragment may be reduced.

Comparison of tension band wiring and precontoured locking compression plate fixation in Mayo type IIA olecranon fractures.

Aim of the present study was to compare the clinical and radiographic outcome of tension band wiring and precontoured locking compression plate fixation in patients treated surgically for an isolated olecranon fractures type IIA according to the Mayo classification. Of 26 patients presenting with an isolated Mayo type IIA olecranon fracture, 13 underwent fixation with a precontoured locking compression plate (group A), 13 patients were treated with tension band wiring (group B). At a mean follow-up of 43 months, patients were clinically and radiographically re-examined using the DASH score, the Mayo Elbow Performance score (MEPS) and anteroposterior and lateral radiographs. The mean DASH score was 14 points in group A and 12.5 points in group B. Regarding the MEPS, 92% of the patients in group A achieved a good to excellent results in comparison to 77% in group B. No significant differences between the two groups could be detected regarding the clinical and radiographic outcome. Implant-related irritations requiring hardware removal occurred more frequently in group B (12 vs. 7). Procedure and implant related costs were significantly higher in group A. Tension band wiring is still a preferable surgical method to treat simple isolated olecranon fractures. The patient must be informed that in all likelihood implant removal will be required once the fracture has healed. Fixation with precontoured locking compression plates does not provide better functional and radiographic outcome but is more expensive than tension band wiring.

Minimally invasive reconstruction of lateral tibial plateau fractures using the jail technique: a biomechanical study.

BACKGROUND: This study described a novel, minimally invasive reconstruction technique of lateral tibial plateau fractures using a three-screw jail technique and compared it to a conventional two-screw osteosynthesis technique. The benefit of an additional screw implanted in the proximal tibia from the anterior at an angle of 90° below the conventional two-screw reconstruction after lateral tibial plateau fracture was evaluated. This new method was called the jail technique. METHODS: The two reconstruction techniques were tested using a porcine model (n = 40). Fracture was simulated using a defined osteotomy of the lateral tibial plateau. Load-to-failure and multiple cyclic loading tests were conducted using a material testing machine. Twenty tibias were used for each reconstruction technique, ten of which were loaded in a load-to-failure protocol and ten cyclically loaded (5000 times) between 200 and 1000 N using a ramp protocol. Displacement, stiffness and yield load were determined from the resulting load displacement curve. Failure was macroscopically documented. RESULTS: In the load-to-failure testing, the jail technique showed a significantly higher mean maximum load (2275.9 N) in comparison to the conventional reconstruction (1796.5 N, p < 0.001). The trend for better outcomes for the novel technique in terms of stiffness and yield load did not reach statistical significance (p > 0.05). In cyclic testing, the jail technique also showed better trends in displacement that were not statistically significant. Failure modes showed a tendency of screws cutting through the bone (cut-out) in the conventional reconstruction. No cut-out but a bending of the lag screws at the site of the additional third screw was observed in the jail technique. CONCLUSIONS: The results of this study indicate that the jail and the conventional technique have seemingly similar biomechanical properties. This suggests that the jail technique may be a feasible alternative to conventional screw osteosynthesis in the minimally invasive reconstruction of lateral tibial plateau fractures. A potential advantage of the jail technique is the prevention of screw cut-outs through the cancellous bone.

Surgical treatment of vertically unstable lateral clavicle fractures (Neer 2b) with locked plate fixation and coracoclavicular ligament reconstruction.

INTRODUCTION: The present study evaluates the outcome of patients treated with a combination of locked plate fixation and minimal-invasive coracoclavicular (CC) ligament reconstruction for unstable lateral clavicle fractures type IIb according to Neer. PATIENTS AND METHODS: Fourteen patients with an unstable lateral clavicle fracture were treated with a combination of locked plate fixation and a minimal-invasive CC ligament reconstruction. At a mean follow-up of 38 months, patients were re-evaluated using the Constant-Murley score, the Acromioclavicular (AC) joint instability score and the TAFT score. Furthermore, anterior-posterior (ap) stress radiographs and axillary views were performed in order to detect any recurrent instability. RESULTS: Bony union was achieved in all cases within 6-10 weeks. The mean Constant-Murley score of the affected shoulder was 93.5 points compared to 97.2 of the contralateral unaffected shoulder. The mean Taft score was 11.2 points and the mean AC joint instability score was 92 points in comparison to 96 points on the unaffected side. The mean CC distance at the time of the injury was 21 mm compared to 8.5 mm after surgery and 12 mm a the final follow-up examination. The CC distance did not differ between the postoperative X-rays and those at the time of follow-up (p = 0.068). Three plates had to be removed because of implant irritation. CONCLUSION: A combination of locked plate fixation and CC ligament augmentation in a minimal-invasive manner can be regarded as suitable for the treatment of vertically unstable lateral clavicle fractures and is associated with excellent clinical and radiological outcomes and a low complication rate.

Reconstruction of the posterior oblique ligament and the posterior cruciate ligament in knees with posteromedial instability.

PURPOSE: Posterior cruciate ligament (PCL) injuries are often associated with injuries of the posteromedial structures of the knee. The motivation for this study was the attempt to test different reconstruction techniques for the structures of the posteromedial corner in a biomechanical experiment. METHODS: Kinematic studies were carried out on 10 cadaveric knees exposed to a 134-N posterior tibial load, 10-Nm valgus torque, and 5-Nm internal torque at 0°, 30°, 60°, and 90° of flexion. The resulting posterior tibial translation (PTT) was determined using a robotic/universal force-moment sensor testing system for (1) intact knees, (2) PCL-deficient knees, (3) knees with deficiency of the PCL and the posteromedial structures, (4) knees with only the PCL reconstructed, (5) knees with the PCL and posterior oblique ligament (POL) reconstructed, and (6) knees with the PCL, medial collateral ligament (MCL), and POL reconstructed. Kinematic data were analyzed by a 2-factor repeated analysis of variance. RESULTS: When both the PCL and the posteromedial structures were cut, PTT increased significantly at all flexion grades under a posterior tibial load (P < .05). Reconstruction of only the PCL could not restore PTT at 0°, 30°, 60°, and 90° of flexion under loading conditions in a knee with combined injury of the PCL and the posteromedial structures (P > .05). Additional reconstruction of the POL improved PTT at all flexion angles in comparison with only the PCL-reconstructed knee. Reconstruction of the MCL had no significant effect on PTT. CONCLUSIONS: This study shows that reconstruction of the POL contributes significantly to the normalization of coupled PTT in knees with combined injury of the PCL and the posteromedial structures under valgus or internal rotational moment. The supplementary reconstruction of the MCL did not provide significant improvement in knee kinematics. CLINICAL RELEVANCE: The POL should be addressed in the patient with combined injuries of the PCL and the posteromedial structures.

Shoulder injuries in polytraumatized patients: an analysis of the TraumaRegister DGU®.

BACKGROUND: The aim of the present study was to analyze the prevalence, epidemiology and relevance of shoulder injuries in polytraumatized patients in a large national trauma database. We hypothesize a high prevalence of shoulder injuries in traffic accidents and a high prevalence of concomitant injuries of the thorax leading to an aggravated clinical course and higher Injury Severity Score (ISS). Furthermore, we hypothesize an increased rate of surgical treatment with the severity of the injury. MATERIALS AND METHODS: The retrospective analysis is based on the database (2002-2013) of the TraumaRegister DGU® and includes statistical data from 608 hospitals. The severity of injuries and trauma were scaled using the Abbreviated Injury Scale (AIS), and the Injury Severity Score (ISS), respectively. Patients with an ISS ≥ 16 were included in the study, and injuries were subdivided according to their anatomical involvement and analyzed with respect to the trauma mechanism and the resulting injuries. RESULTS: In this study, 54,076 cases of patients with an ISS ≥ 16 were analyzed. Shoulder injuries occurred in 15,115 patients (27.9%). Of these, 68.5% were caused by traffic accidents, especially in motorbike, bicycle, and pedestrian accidents. We found more shoulder injuries in blunt trauma mechanisms. Moreover, patients with shoulder injuries spent on average 1.7 more days on the intensive care unit (ICU), or intermediate care unit (IMCU), according to the severity of the injury, and had longer overall hospital stays (26.2 vs. 24.1 days) than patients without shoulder injuries. The overall ISS was increased in patients with shoulder injuries, whereas an increase of mortality could not be identified. Concomitant thoracic injuries occurred significantly more often in patients with shoulder injuries (82.9% vs. 69.6%). Injuries of the abdomen, pelvis, and lower extremity showed no correlation with shoulder injuries, whereas head and spine injuries showed a significant correlation. CONCLUSION: Shoulder injuries are very common in polytraumatized patients. Together with their distinctive concomitant injuries, they have an aggravating impact on the clinical progress. Our data confirm the correlation with thoracic injuries. Furthermore, we identified an increased risk of shoulder injuries in motorbike, bicycle, and pedestrian accidents. An increase in mortality could not be identified.

Biomechanical evaluation of minimally invasive repairs for complete acromioclavicular joint dislocation.

BACKGROUND: The conventional coracoclavicular ligament augmentation with a single polydioxanone loop has been shown to have some pivotal disadvantages. HYPOTHESIS: A minimally invasive flip button/polydioxanone repair provides similar biomechanical properties to the conventional polydioxanone cerclage around the coracoid. However, the authors expected a difference in linear stiffness, ultimate load, and permanent elongation between suture anchor repairs and polydioxanone repairs. STUDY DESIGN: Controlled laboratory study. METHODS: The tensile fixation strength of 4 different minimally invasive repairs was tested in a porcine metatarsal model: (1) 1.3-mm single polydioxanone cerclage with a subcoracoidal flip button fixation, (2) 1.3-mm single polydioxanone cerclage, (3) Twinfix Ti 3.5-mm/Ultrabraid 2-suture anchor, and (4) Twinfix Ti 5.0-mm/Ultrabraid 2-suture anchor. The testing protocol included cyclic superoinferior loading and a subsequent load to failure trial. RESULTS: The flip button repair (646 N) and the conventional polydioxanone banding (663 N) revealed significant higher ultimate loads than did the suture anchor repairs (295 and 331 N, respectively; P < .001), whereas no significant differences were found for the elongation behavior under cyclic loading. CONCLUSION: There was no significant difference between the 2 polydioxanone repairs. The ultimate load of the flip button procedure reaches the level of the native coracoclavicular ligament complex as it has been quantified in the literature. CLINICAL RELEVANCE: Although the biomechanical results comparing a minimally invasive flip button procedure versus a conventional polydioxanone cerclage are similar, the authors recommend the flip button procedure because of its minimally invasive approach and the secure subcoracoidal fixation technique with a minimized risk of anterior loop dislocation and neurovascular damage.

Biomechanical evaluation of different fixation methods for tibial eminence fractures.

BACKGROUND: Tibial eminence fractures have become more common, but the best method of fixing these fractures arthroscopically has not been elucidated. OBJECTIVE: The objective of this study is to assess the stability of different fixation methods for tibial eminence fractures. STUDY DESIGN: Controlled laboratory study. METHODS: The authors evaluated the initial fixation strength of 4 different fixation techniques for tibial eminence fractures (2 screws, 1 screw, suture fixation with 1 mm Ethibond, and suture fixation with No. 5 FiberWire) using single cycle and cyclic loading tests. The tests were performed by loading the knee with an anterior tibial shear force. RESULTS: Suture cerclage with the FiberWire showed significantly higher maximum load (599.6 N) and stiffness (36.99 N/mm) than all other fixation methods tested. The lowest maximum load in the single cycle loading test was observed in the group with 2 screws (1 screw, 371.2 N; 2 screws, 249.8 N). The lowest stiffness was found in the Ethibond group (14.5 N/mm). After 1000 cycles of loading, the maximum load of the FiberWire fixation was significantly higher than the maximum load of the Ethibond fixation (399.4 N), the fixation with 1 screw (354.2 N), and the fixation with 2 screws (301.5 N). CONCLUSION: These biomechanical data suggest that under cyclic loading conditions, suture fixation of tibial eminence fractures provides more fixation strength than screw fixation. CLINICAL RELEVANCE: A second screw has no positive effect on the biomechanical characteristics of screw fixation.

Femoral fixation of hamstring grafts in posterior cruciate ligament reconstruction: biomechanical evaluation of different fixation techniques: is there an acute angle effect?

BACKGROUND: The literature provides little biomechanical data about femoral fixation of hamstring grafts in posterior cruciate ligament reconstruction. HYPOTHESIS: A hybrid fixation technique with use of an undersized screw has sufficient strength to provide secure fixation of posterior cruciate ligament grafts. Additional aperture fixation with a biodegradable interference screw can prevent graft damage that might be caused by an acute angle on the edge of the femoral tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: In part 1, extracortical fixation of posterior cruciate ligament reconstructions with quadrupled porcine flexor digitorum grafts to simulate human hamstring grafts was compared with hybrid fixation methods using 6-, 7-, and 8-mm screws. Groups were tested in cycling loading with the load applied in line with the bone tunnel. In part 2, extracortical fixation was compared with hybrid fixation using a 1-mm undersized screw anterior and posterior to the graft. Structural properties and graft abrasion were evaluated after cyclic loading with the load applied at 90 degrees to the tunnel. In each group, 8 porcine knees were tested. RESULTS: In part 1, stiffness, maximum load, and yield load were significantly higher for hybrid fixation than for extracortical fixation. Hybrid fixation with an 8-mm screw resulted in higher yield load than with a 7-mm screw. In part 2, graft laceration was more pronounced in specimens with extracortical fixation than with hybrid fixation. Posterior screw placement was superior to the anterior position. CONCLUSION: For all parameters, hybrid fixation with an interference screw provided superior structural results. No relevant disadvantages of undersized screws could be found. Graft damage due to abrasion at the edge of the femoral bone tunnel was reduced by use of an interference screw. The posterior screw placement seems favorable. CLINICAL RELEVANCE: Hybrid fixation of hamstring grafts in posterior cruciate ligament reconstruction is superior to extracortical fixation alone with no relevant disadvantages of undersized screws. The results raise the suspicion of an acute angle effect of the femoral bone tunnel.

Biomechanical evaluation of two techniques for double-bundle anterior cruciate ligament reconstruction: one tibial tunnel versus two tibial tunnels.

BACKGROUND: This research was undertaken to determine whether there is a need for a second tibial tunnel in anatomic anterior cruciate ligament reconstruction. HYPOTHESIS: Anatomic two-bundle reconstruction with two tibial tunnels restores knee anterior tibial translation in response to 134 N and to 5-N.m internal tibial torque combined with 10-N.m valgus torque more closely to normal than does double-bundle reconstruction with one tibial tunnel. STUDY DESIGN: Controlled laboratory study. METHODS: Ten cadaveric knees were subjected to a 134-N anterior tibial load at 0 degrees, 30 degrees, 60 degrees, and 90 degrees and to 5-N.m internal tibial torque and 10-N.m valgus torque at 15 degrees and 30 degrees. Resulting knee kinematics and in situ force in the anterior cruciate ligament or replacement graft were determined by using a robotic/universal force-moment sensor testing system for (1) intact, (2) anterior cruciate ligament-deficient, (3) double-bundle/one tibial tunnel, and (4) double-bundle/two tibial tunnels. RESULTS: Anterior tibial translation for the reconstruction with two tibial tunnels was significantly closer to that of the intact knee than was the reconstruction with one tibial tunnel at 0 degrees and 30 degrees of flexion (0 degrees = 3.82 vs 6.0 mm, P < .05; 30 degrees = 7.99 vs 11 mm, P < .05). The in situ force normalized to the intact anterior cruciate ligament for the reconstruction with two tibial tunnels was significantly higher than the in situ force of the reconstruction with one tibial tunnel (30 degrees = 89 vs 82 N, P < .05). With a combined rotatory load, the anterior tibial translation of specimens with a tibial two-tunnel technique was significantly lower than that of specimens with one tunnel (0 degrees = 5.7 vs 8.4 mm, P < .05; 30 degrees = 7.5 vs 9.5 mm, P < .05). CONCLUSIONS: Anatomic reconstruction with two tibial tunnels may produce a better biomechanical outcome, especially close to extension. CLINICAL RELEVANCE: At the time of initial fixation, there appears to be a small biomechanical advantage to the second tibial tunnel in the setting of two-bundle anterior cruciate ligament reconstruction.

Initial and 6 weeks postoperative structural properties of soft tissue anterior cruciate ligament reconstructions with cross-pin or interference screw fixation: an in vivo study in sheep.

PURPOSE: The purpose of this study was to evaluate the detrimental effects of interference screw fixation on soft tissue anterior cruciate ligament (ACL) reconstruction after 6 weeks and compare them with a cross-pin technique. METHODS: In an intra-articular model, ovine soft tissue grafts were fixed with two 3.3-mm biodegradable pins or with interference screws. Maximum load, yield load, and stiffness of the femur-graft-tibia complex were evaluated immediately after surgery and 6 weeks postoperatively. RESULTS: For knees with interference screw fixation, strength deteriorated by 81% and stiffness deteriorated by 67%. For knees with double cross-pin fixation, strength deteriorated by 48% and stiffness improved by 52%. These differences were statistically significant. At the time of surgery, all grafts failed by slippage of the graft past the screw or by cross-pin failure. At 6 weeks postoperatively, the grafts of both groups failed at the tibial or femoral tunnel entrance. CONCLUSIONS: After 6 weeks, the biomechanical characteristics of grafts that were fixed with cross-pins were superior to those of grafts after interference screw fixation. CLINICAL RELEVANCE: Because of significantly inferior biomechanical stability after interference screw fixation, a less aggressive program of rehabilitation might be recommended.

Reducing the "killer turn" in posterior cruciate ligament reconstruction by fixation level and smoothing the tibial aperture.

PURPOSE: The aim of this study was to evaluate the influence of the operative technique on reducing the so called "killer turn" at the tibial bone tunnel exit in posterior cruciate ligament (PCL) reconstruction. METHODS: We investigated the benefit of reducing the sharp edge of the tibial bone tunnel exit using a custom made rasp in combination with extracortical and aperture (interference screw) graft fixation. Grafts were fixed in a porcine tibia model. Ten reconstructions each (sharp and rounded edge) were cyclically loaded (2,000 times) between 50 and 150 N, and another 10 each were subjected to 2,000 cycles between 50 and 300 N force. The surviving PCL reconstructions were loaded to failure using a material testing machine. RESULTS: Being subjected to the sharp edge of the posterior tibia, 5 of 10 extracortical and 8 of 10 aperture fixed grafts survived cyclic loading between 50 and 150 N. All extracortical fixed and 8 of 10 aperture fixed grafts failed before 2,000 cycles when loaded between 50 and 300 N. Structural properties of grafts fixed with interference screw were statistically significant higher when compared to extracortical fixation. After rounding the sharp edge of the tunnel, all grafts survived cycles between 50 and 150 N and 6 out of 10 extracortical and 8 of 10 aperture fixed grafts survived 2,000 cycles between 50 and 300 N. CONCLUSIONS: The results of this study suggest that a rounded posterior aspect of the tunnel exit at the tibial tunnel exit leads to significant less graft damage when compared to the typical sharp edge of the bone tunnel exit ("killer turn"). Additionally, the results show that aperture fixation of soft tissue grafts in PCL reconstruction is superior when compared to an extracortical fixation site. CLINICAL RELEVANCE: Aperture fixation and a rounded tibial bone tunnel exit seem to be a reasonable alternative in PCL reconstruction.

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

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

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

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