Cerclage performance analysis - a biomechanical comparison of different techniques and materials.

BACKGROUND: Wire cerclages play a fundamental role in fracture fixation. With an increasing variety of designs being commercially available the question arises which cerclage should be used. This study investigates the biomechanical properties of metallic and non-metallic cerclages and their different application-types. Furthermore, potential influence of muscular interposition between bone and cerclage constructs was tested. METHODS: Samples of the following four different cerclage types were tested on 3D printed models of human humeri as well as on human cadaveric humeri with and without muscular interposition: Titanium Cable Cerclage (CC), Steel Wire Cerclage (SWC), Suture Tape (ST), Suture Tape Cerclage (STC) with both single- (sSTC) and double-loop application (dSTC). A preinstalled self-locking mechanism secured by the provided tensioner in the STCs being the main difference to the STs. Cyclic loading was performed to 1 kN and then linearly to a maximum load of 3 kN. Statistical analysis was performed using either one-way ANOVA and post-hoc Tukey or Kruskal-Wallis and post-hoc Dunn test depending on normalization of data (p < 0.05). RESULTS: Whilst all cerclage options could withstand high loads during failure testing, only within the CC and dSTC group, all samples reached the maximal testing load of 3000 N without any failure. The SWC reached 2977.5 ± 63.6 N, the ST 1970.8 ± 145.9 N, and the sSTC 1617.0 ± 341.6 N on average. Neither muscular interposition nor bone quality showed to have a negative influence on the biomechanical properties of the cerclage constructs, presenting no significant differences. CONCLUSION: All tested cerclage constructs produce reliable stability but differ in their resulting compression forces, in a simplified fracture model. Therefore, non-metallic cerclage alternatives can provide similar stability with less compression and stiffness to metallic cable constructs, but they may offer several advantages and could possibly provide future benefits. Especially, by offering more elasticity without losing overall stability, may offer a biologic benefit. Installing any cerclage constructs should be performed carefully, especially if poor bone quality is present, as the tightening process leads to high forces on the construct.

Primary stability of single-stage revision reconstruction of the anterior cruciate ligament in case of failure of dynamic intraligamentary stabilization depends on implant position during ACL repair.

INTRODUCTION: The object of this study was to evaluate the primary stability of tibial interference screw (IFS) fixation in single-stage revision surgery of the anterior cruciate ligament (ACL) in the case of recurrent instability after ACL repair with dynamic intraligamentary stabilization (DIS), dependent on the implant position during DIS. MATERIALS AND METHODS: Tibial aperture fixation in ACL reconstruction (ACL-R) was performed in a porcine knee model using an IFS. Native ACL-R was performed in the control group (n = 15). In the intervention groups DIS and subsequent implant removal were performed prior to single-stage revision ACL-R. A distance of 20 mm in group R-DIS1 (n = 15) and 5 mm in group R-DIS2 (n = 15) was left between the joint line and the implant during DIS. Specimens were mounted in a material-testing machine and load-to-failure was applied in a worst-case-scenario. RESULTS: Load to failure was 454 ± 111 N in the R-DIS1 group, 154 ± 71 N in the R-DIS2 group and 405 ± 105 N in the primary ACL-R group. Load-to-failure, stiffness and elongation of the group R-DIS2 were significantly inferior in comparison to R-DIS1 and ACL-R respectively (p < 0.001). No significant difference was found between load-to-failure, stiffness and elongation of R-DIS1 and the control group. CONCLUSION: Primary stability of tibial aperture fixation in single-stage revision ACL-R in case of recurrent instability after DIS depends on monobloc position during ACL repair. Primary stability is comparable to aperture fixation in primary ACL-R, if a bone stock of 20 mm is left between the monobloc and the tibial joint line during the initial procedure.

[Periprosthetic fractures: basics, classification and treatment principles]. / Periprothetische Frakturen: Grundlagen, Klassifikation und Therapieprinzipien.

Periprosthetic fractures (PPFx) are becoming an increasingly important topic in orthopedics and trauma surgery due to the rising number of endoprosthetic joint replacements. The recently published unified classification system (UCS) has replaced numerous historical classification systems and can be applied to all PPFx regardless of the bone or joint involved. The treatment of PPFx requires individual therapeutic concepts taking patient-dependent and patient-independent factors into consideration. The conservative treatment of PPFx is only justified in exceptional situations. In contrast, the choice between operative treatment and deciding between osteosynthesis or revision arthroplasty is particularly based on the assessment of the implant stability. In order to achieve fracture consolidation and also a good functional outcome, knowledge of the basic biomechanical principles of operative (osteosynthesis or endoprosthesis) treatment of periprosthetic fractures is necessary.

[Periprosthetic fractures of the shoulder girdle]. / Periprothetische Frakturen des Schultergürtels.

Periprosthetic fractures of the shoulder girdle will increasingly become part of routine clinical practice due to rising numbers of joint replacements and the demographic changes. Diagnostically, the status of the rotator cuff, bed of the implant (stable or loose), type of shoulder arthroplasty as well as exclusion of joint infections are crucial for therapeutic decision-making. Novel imaging tools, such as dual-energy computed tomography provide improved preoperative planning options. The unified classification system describes the fracture location, stability of the prosthesis and quality of the bone. While nonoperative treatment is reserved for patients with severe pre-existing conditions and nondisplaced fractures, the standard treatment of fractures with a stable bed include fixation with cerclage wiring and angular stable plates. Modern implant systems with variable angle screw holes, attachment plates and hinges enable secure fixation around the stem. In cases of a loose stem revision arthroplasty is necessary. There are currently only a limited number of clinical studies with only few patients that analyzed clinical and radiological results. Thus, increased research efforts are indispensable in order to compare treatment options and improve treatment quality.

Converting round tendons to flat tendon constructs: Does the preparation process have an influence on the structural properties?

PURPOSE: The structural properties of hamstring tendon grafts were evaluated in a porcine model, after processing it to a flat shape, to better replace or augment anatomic flat structures (e.g. ACL, MPFL or MCL). METHODS: In this biomechanical study, porcine flexor tendons were used which have a comparable shape to semitendinosus and gracilis tendons. One part of the tendon was prepared to a flat tendon construct by splitting the tendon longitudinally with a knife to half of the diameter of the tendon. The semi-split tendon was scratched out to a flat shape. The other matched part was tested in its original round shape. The tendons (n = 40) have been fixed in a uniaxial testing machine (Zwick/Roell) by cryo-clamps after preparing the fixed ends by 2-0 polyester sutures (2-0 Ethibond® EXCEL, Ethicon, Somerville, NJ). In every specimen, there was a free 60-mm tendon part between both clamps. The tendons have been loaded to failure to evaluate typical biomechanical parameters such as stiffness, yield load and maximum load. RESULTS: No statistically significant differences (n.s.) regarding stiffness, yield load and maximum load between natively round and processed flat tendons could be detected. CONCLUSION: A prepared flat-shaped tendon does not show any different structural properties compared with an original round tendon. Therefore, a flat tendon seems to be a biomechanical stable graft option for anatomic reconstruction or augmentation of injured natively flat-shaped structures such as MCL, MPFL or ACL.

Surgical treatment of acute acromioclavicular joint dislocations: hook plate versus minimally invasive reconstruction.

PURPOSE: This study was performed to compare the clinical results of a minimally invasive technique for acute acromioclavicular (AC) joint dislocation repair with the traditional hook plate fixation. METHODS: Forty-four patients with an acute (within 2 weeks after trauma) complete AC joint separation (35 male, nine female; median age 36.2 years, range 18-56) underwent surgical repair with either a minimally invasive AC joint repair or a conventional hook plate. Functional outcome was evaluated using the Constant-Murley Score (CMS), the TAFT score and the AC joint instability score (ACJI). Radiographic evaluation was performed with bilateral anterior-posterior (a.p.) stress and Alexander views. RESULTS: All patients were available after a median follow-up of 32 months (range 24-51). There were no significant differences in the mean CMS, Taft score and the ACJI between the two groups. The radiological assessment revealed no significant difference in the coracoclavicular distance. In both groups, a slight loss of reduction was observed. Periarticular ossification was seen in 11 patients of the minimally invasive AC joint repair and eight patients of the hook plate group but this did not affect the final outcome. Hook plates were removed after a median interval of 11.9 weeks (range 10-13). CONCLUSION: Good clinical results can be achieved with both minimally invasive AC joint repair and hook plate fixation. However, in the hook plate group a second operation is mandatory for plate removal. LEVEL OF EVIDENCE: III.

The Müller acetabular reinforcement ring--still an option in acetabular revision of Paprosky 2 defects? Longterm results after 10 years.

BACKGROUND: Aim of this study was to measure the clinical and radiological longterm outcome after acetabular revision arthroplasty (RTHA) using the Müller acetabular reinforcement ring. MATERIAL AND METHODS: 86 patients with 90 revision arthroplasties and a mean age of 68 years (41 to 84) were included. The mean follow-up was 10 years (range 7-12). The Harris Hip Score and the WOMAC Index were used to assess pain and functional outcome. Furthermore clinical examination of range of motion and radiologic examinations were performed in 34 patients. RESULTS: The radiologic analysis reports no signs of loosening in 79%, 15% showed possibly loosening and 6% probable loosening. Definite radiologic loosening has not been detected. In the meantime 12 patients (13.3%) of 90 revision total hip arthroplasty underwent a revision of the acetabulum with change of the acetabular component which means a survival rate of 86.7% after 10 years follow-up. The mean center of rotation of the hip moved 0.15 cm (SD 0.74 cm) laterally and 0.1 cm (SD 0.97 cm) cranially based on the geometrically reconstructed center of rotation. A mean score of 58 points for the Harris Hip Score (range 14-93) indicated a poor functional outcome, while a mean value of 96 points (range 0-223) for the WOMAC Index indicated good results for functional outcome in daily living. CONCLUSIONS: The revision arthroplasty in cases with acetabular defects using the Müller acetabular reinforcement ring shows acceptable longterm results. LEVEL OF EVIDENCE: Level IV.

[Dynamic intraligamentary stabilization of the anterior cruciate ligament. Operative technique and short-term clinical results]. / Dynamische intraligamentäre Stabilisierung des vorderen Kreuzbandes. Operationstechnik und klinische Kurzzeitergebnisse.

BACKGROUND: Reconstruction of tears in the anterior cruciate ligament with a tendon graft is the current gold standard. OBJECTIVES: Dynamic intraligamentary stabilization is a new technique for preservation of the anterior cruciate ligament. METHODS: This article describes the indications, operative technique, rehabilitation and preliminary results after dynamic intraligamentary stabilization for acute anterior cruciate ligament ruptures. RESULTS: A total of 24 women and 31 men with an acute anterior cruciate ligament tear were included in a prospective clinical trial. Of the patients 26 had already been followed-up for 12 months and satisfying values for the Lysholm, Tegner and International Knee Documentation Committee (IKDC) outcome scores were achieved. High subjective patient satisfaction was also achieved. The Lachman test showed a mean anterior translation difference to the healthy side of 1.7 mm. CONCLUSION: Dynamic intraligamentary stabilization in combination with microfracturing of the notch can provide biomechanical and biological conditions for self-healing of the anterior cruciate ligament. Further clinical and biomechanical research is needed to identify appropriate patients and rupture types suitable for this new technique.

Comparison of outside-in and inside-out technique for tibial fixation of a soft-tissue graft in ACL reconstruction using the Shim technique.

INTRODUCTION: The aim of this study was to compare the biomechanical properties of tibial fixation of a free tendon graft in ACL reconstruction using the Shim, a new wedge-shaped implant, in an outside-in technique to fixation by the Shim used in an inside-out technique and fixation by interference screw in a porcine model. MATERIALS AND METHODS: Porcine tibia and flexor tendons were used. In Group 1, the Shim was applied outside-in. In Group 2, the Shim was inserted inside-out. In the Group 3, an 8-mm interference screw was used. Ten specimens were tested in each group. Load-to-failure, elongation, stiffness and failure mode were recorded. Cyclic loading was performed between 5 and 250 N for 1,000 cycles, followed by a load to failure testing. RESULTS: Mean maximum load-to-failure was 629.53 N in Group 1,648.54 N in Group 2 and 749.53 N in Group 3. There was no significant difference between the groups. Stiffness varied between 127.34 N/mm in Group 1, 151.27 N/mm in Group 2 and 182.25 N/mm in Group 3. No significant differences were found between outside-in Shim and interference screw fixation. No significant difference was found for elongation among the three groups. The main failure mode was a rupture of the tendon in the IFS group and a slippage of either the implant or the tendon in both groups using the Shim. CONCLUSIONS: As no statistically significant difference could be seen concerning load to failure, stiffness and elongation between the inside-out and the outside-in techniques, the Shim can be used for tibial fixation in an outside-in or inside-out technique depending on the preference of the surgeon. To prevent slippage of the graft a hybrid fixation should be considered.

[Treatment of periprosthetic fractures : new concepts in operative treatment]. / Versorgung periprothetischer Frakturen : Neue Konzepte in der operativen Therapie.

BACKGROUND: Periprosthetic fractures represent a common and complex challenge in the clinical practice in orthopedics and trauma surgery. Due to demographic changes characterized by increased life expectancy and higher numbers of primary arthroplasties, the number of periprosthetic fractures is increasing as well. Factors such as osteoporosis, multimorbidity and a highly active aging population additionally increase the complexity of periprosthetic fractures. INJURY PATTERNS: Most periprosthetic fractures affect the proximal and distal femur; however, periprosthetic fractures of the tibial head, the ankle, shoulders and the upper extremities as well as complex interprosthetic fractures pose an increasing challenge for orthopedic and trauma surgeons. THERAPY: Many therapeutic options exist and the number of implants especially designed to treat periprosthetic fractures is steadily rising. Principally, loosened prostheses are indicative for replacement operations whereas for periprosthetic fractures of well-anchored prostheses as a rule osteosynthesis is necessary. A standardized treatment algorithm does not yet exist and usually the decision of how to treat these fractures has to be made on an individual basis. PERSPECTIVES: The present article demonstrates the current state of open reduction and internal fixation of periprosthetic fractures with respect to biomechanical principles and furthermore provides an overview on implant augmentation.

Evaluation of immobilization in external rotation after primary traumatic anterior shoulder dislocation: 5-year results.

BACKGROUND: It is still not clear which method is the most efficient for treating primary traumatic anterior shoulder dislocation. Immobilization in external rotation has become increasingly discussed within the last 10 years. The aim of this study was to evaluate the rate of recurrence and clinical outcome of the immobilization in external rotation after primary traumatic anterior dislocation within a midterm period of 5 years. Additionally, a summary of literature is given according to the present knowledge of this issue. METHODS: From May 2004 to May 2006, 28 patients with primary traumatic anterior shoulder dislocations were included in a prospective MRI-controlled study. After a follow-up of 5 years, the recurrence rate and clinical outcomes of the patients were evaluated using clinical scores (Constant and Murley score, Western Ontario Shoulder Instability Index, Rowe score). RESULTS: After 5 years, 26 patients (93 %; males, n = 25; female, n = 1; mean age, 29.3 years) were interviewed concerning re-dislocations. In the meantime, four patients (15 %) experienced a re-dislocation (ø 12.2 months) after the end of the immobilization. Overall, 21 patients (75 %) were included in a clinical follow-up (CM score: ø 92.8 points; Western Ontario Shoulder Instability Index: ø 87 %; Rowe score (in 17 patients): ø 94.2 points). Upon clinical examination, unidirectional anterior instability was found in one patient, which corresponds to an overall instability rate of 19 % within the examined patient population including the re-dislocations. CONCLUSIONS: Immobilization in external rotation shows satisfactory results after 5 years in regard to recurrence and instability rates and clinical outcomes. The data show that with immobilization in external rotation, re-dislocations occur within the first 2 years.

Complex fractures of the proximal humerus in the elderly--outcome and complications after locking plate fixation.

Open reduction and internal fixation (ORIF) with locking plates or primary arthroplasty remains a controversial issue in the management of complex proximal humerus fractures. Aim of this study was to evaluate the surgeon- and patient-based outcome of patients older than 65 years who underwent ORIF using locking plate fixation of a 3- or 4-part fracture of the proximal humerus. Twenty-seven patients older than 65 years were treated with locking plate fixation (PHILOS, Fa. Synthes, Umkirch, Germany). At an average follow-up of 44 months, the clinical and the subjective outcome were evaluated, and complications were analyzed. The mean age- and gender-related Constant score was 70% (30­100%) compared with 92% (47­108%) of the contralateral non-injured shoulder. The mean DASH score was 29 points (0­71). Five patients (18.5%) showed clinical signs of an impingement, which was related to malpositioning of the plate in 3 cases. Screw cutout was seen in 22.2% (6 patients). Avascular necrosis of the head or the tubercula was found in 8 patients (29.6%). The revision rate was 29.6%. However, the patients considered the functional status of their shoulder as "good" or "satisfactory." The functional and patient-orientated results of the locking plate fixation of complex displaced proximal humerus fractures in the elderly are comparable to those of primary arthroplasty and minimally invasive treatment. Proper surgical technique (screw length, plate position) is mandatory for reducing the revision rate.

Structural properties of a new fixation strategy in double bundle ACL reconstruction: the MiniShim.

INTRODUCTION: Double-bundle reconstruction of the ACL has become the focus of scientific and clinical interest in the last years. However, there is still a discussion about the most appropriate technique for graft fixation. Both, extracortical fixation systems like the Endobutton and aperture fixation by interference screws have advantages as well as disadvantages. Aim of this study was to analyze the biomechanical properties of a new small wedge shaped implant (MiniShim, Karl Storz, Germany) for the fixation of a soft tissue graft in double bundle ACL reconstruction and to compare it to an aperture fixation by interference screw and an extracortical fixation. METHODS: Porcine knees and flexor tendons were used for this study. 5 and 6 mm tunnels were drilled. The following fixation strategies were tested: 4 and 5 mm MiniShim (Karl Storz Germany), 6 mm interference screw (MegaFix, Karl Storz, Germany), hybridfixation by FlippTack (FlippTack, Karl Storz, Germany) and MiniShim and hybridfixation by FlippTack and 6 mm interference screw. All fixation strategies were tested with a 5 and 6 mm tendon graft. Maximum load, yield load and stiffness were recorded using a material testing machine. Load was applied in line with the bone tunnel. Grafts were cyclically preconditioned between 0 and 20 N for 10 cycles before the graft-bone-complex was loaded to failure. Statistical evaluation was performed using SPSS Version 11.0. RESULTS: Load to failure for the 5 mm graft was 81.1 and 118.0 N for the 4 and 5 mm MiniShims. Fixation by interference screw reached 237.4 N. The extracortical fixation resulted in a load to failure of 471.7 N. Load to failure for the 6 mm tendon grafts was 52.0 and 92.8 N for the 4 and 5 mm MiniShims. Fixation by interference screw resulted in a load to failure of 214.0 N. Extracortical fixation failed at 451.7 N. The difference between MiniShim and interference screw was statistically significant. Load to failure was significantly higher for extracortical fixation compared to fixation by MiniShim or interference screw. Hybrid fixation showed higher fixation strength compared to fixation by interference screw or MiniShim alone. This difference was statistically significant. Stiffness was significantly higher for fixation by interference screw compared to extracortical fixation and fixation by MiniShim. Four different modes of failure could be seen. All 4 mm MiniShims failed by slippage of the tendon past the MiniShim. In the 5 mm group the fixation failed by pullout of the MiniShim or the tendon past the MiniShim. Hybrid fixation failed by rupture of the linkage material. When the graft was fixed by an interference screw failure occurred by rupture of the tendon at the fixation side. CONCLUSION: Hybrid fixation using the MiniShim provides biomechanical properties strong enough to withstand the forces occurring during rehabilitation and comparable to the fixation strength provided by interference screw. While fixation by MiniShim alone does not provide sufficient fixation strength in double bundle ACL reconstruction, hybridfixation using a cortical fixation by FlippTack is an alternative to aperture fixation by interference screw concerning primary stability.

[Tibial head fractures in the elderly]. / Tibiakopffrakturen im Alter.

In contrast to younger patients, tibial head fractures of the elderly usually result from minor trauma. In these patients, fractures of the tibial plateau are frequently seen and classified according to the Tscherne classification. In addition to plain radiographs which consist of an a.p. and a lateral view, a CT-scan is an obligatory part of the preoperative diagnostic. The therapeutic management is strongly depending on the psychic and physical condition of the patient, the fracture morphology, the decreased bone mineralization and the soft tissue damage. Low bone density requires rigid implants to provide a stable osteosynthesis. Metaphyseal defects have to be augmented with synthetic bone substitutes to avoid secondary loss of reduction. Early mobilization should be achieved to decrease the risk of serious complications.

[Bipolar hemiarthroplasty in femoral neck fractures--impact of duration of surgery, time of day and the surgeon's experience on the complication rate]. / Die Duokopfprothese zur Therapie der Schenkelhalsfraktur--Einfluss von OP-Dauer, Tageszeit und Erfahrung des Operateurs auf die Komplikationsrate.

AIM: Bipolar hemiarthroplasty is frequently used in femoral neck fractures. There is only little evidence regarding differences in complication rates if the procedure is performed by either a junior or senior surgeon. METHODS: 360 bipolar hemiarthroplasties were retrospectively investigated. Complication rates for junior and senior surgeons were evaluated as well as differences between daytime and nightshift surgery. We also assessed the duration of surgery for the two groups and its impact on the complication rate. RESULTS: The average duration of the procedure was 67 minutes (23-194) with statistically significant differences between junior and senior surgeons (77 vs. 61 minutes, p < 0.001). Complications occurred in 27 (7.5%) of all cases. Postoperative infections were most frequently found (3.1% of all complications), followed by haematomas and dislocations of the implant (1.7% and 1.1 %, respectively). 25 patients required revision operations. More complications were found in cases performed by junior surgeons (9.56% vs. 6.25%). This difference was not significant (p = 0.248). During on-call duty we also observed more complications compared to daytime surgery (11% vs. 7%). There was no coherence between the duration of surgery and the incidence of complications. CONCLUSIONS: Bipolar hemiarthroplasty is a reliable treatment option for femoral neck fractures even when performed by a junior surgeon. The higher incidence of complications during nighttime surgery should be a reason to perform those cases that are not urgent during the daytime shift.

[Immobilisation of the shoulder in external rotation after traumatic first-time dislocation--what is reasonable? A retrospective survey]. / Die Ruhigstellung der Schulter in Aussenrotation nach traumatischer Erstluxation--Was kann man seinen Patienten zumuten? Eine retrospektive Patientenbefragung.

BACKGROUND: Immobilisation in external rotation has become a new option in the therapy of the traumatically dislocated shoulder. Brace comfort and patient's satisfaction with this kind of conservative treatment are evaluated in a retrospective survey. METHODS: 34 patients with a traumatic first-time anterior shoulder dislocation were immobilised in an external rotation brace for three weeks. Afterwards they were asked to complete a questionnaire regarding brace comfort and how they managed their daily life with one arm immobilised in external rotation. RESULTS: 29 questionnaires could be evaluated. 26 patients (90%) were satisfied with the new therapy. 24 patients (83%) would prefer the conservative treatment in an external rotation brace in case of another dislocation under similar circumstances. The impact of the brace therapy on daily live was reasonable. 79% of the patients (23) wore the brace more than 20 hours daily (average 22 hours, min.15, max. 24 hours). CONCLUSION: Despite the uncomfortable arm position during immobilisation the therapy in an external rotation brace showed a high acceptance. In addition to previous results regarding reposition of the labroligamentous complex it appears to be proven a suitable therapy for first-time traumatic anterior shoulder dislocation.