Peter P. Koch

Is noncontact ACL injury associated with the posterior tibial and meniscal slope

BackgroundThe risk of noncontact ACL injury reportedly is increased in patients with a greater posterior tibial slope (PTS), but clinical data are inconsistent. It is unclear whether the medial and lateral PTSs have a different impact on this connection. It also is unknown whether the meniscal slope (MS) is associated with ACL injury.Patients/methodsUsing MRI, we compared the medial and lateral PTSs and MSs separately in 55 matched pairs of patients with isolated noncontact ACL injuries and a control group.ResultsNeither the PTS nor the relative difference between the medial and lateral PTSs differed between groups. In contrast, the lateral MS was greater with ACL injuries: 2.0° versus −2.7° in males with and without ACL injury and 1.7° versus −0.9 in females. Uninjured females had a greater PTS than males: 4.9° versus 3.0° in females and males medially, respectively; 5.7° versus 4.0° lateral.ConclusionsThere is no obvious link between the medial or lateral PTSs and ACL injury, and there is no obvious link between the relative difference in the medial and lateral PTSs and noncontact ACL injury. However, a greater lateral MS may indicate a greater risk of injury. The PTS can differ between the genders but the average difference is small.Level of EvidenceLevel II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Femoral and Tibial Torsion Measurements With 3D Models Based on Low-Dose Biplanar Radiographs in Comparison With Standard CT Measurements

OBJECTIVE The purpose of this study was to evaluate the interchangeability of femoral and tibial torsion measurements obtained with 3D models based on low-dose biplanar radiographs and standard CT measurements by testing the following two hypotheses: that there is excellent agreement between the two methods and that there is excellent interreader agreement. MATERIALS AND METHODS Two independent readers used 3D models based on low-dose simultaneous biplanar radiographs and axial CT images to measure femoral and tibial torsion in 35 patients (mean age, 65 years; range, 46-89 years) with osteoarthritis of the knee who were to undergo prosthesis insertion. The two measurements were compared by means of Bland-Altman plots and descriptive statistics. Interreader agreement was quantified with intraclass correlation coefficients. RESULTS The average differences between readers on the CT measurements were 1.3° (range, 0°-11°) for the femur and 1.5° (range, 0°-12°) for the tibia. The average differences for the measurements obtained with the 3D model were 0.1° (range, 0°-9°) for the femur and 0.8° (range, 0°-10°) for the tibia. The average differences between the two methods were 0° (range, -5° to 7°) for the femoral measurements and 3° (range, -12° to 5°) for the tibial measurements. Bland-Altman plots showed no relevant differences between the results of the two measurement modalities. Except for one measurement of femoral torsion and one measurement of tibial torsion, all results based on the 3D models were within the 95% limit of agreement (mean ± 1.96 SD). Interreader agreement was statistically significant (p < 0.001) for all measurements with high intraclass correlation coefficients (> 0.9). CONCLUSION Femoral and tibial torsion measurements obtained with 3D models based on biplanar radiographs are interchangeable with standard CT measurements in patients with osteoarthritis of the knee.

Tensile and Shear Loading Stability of All-Inside Meniscal Repairs An In Vitro Biomechanical Evaluation

Background: Most biomechanical studies for evaluation of the structural properties of meniscal repairs have been performed in tensile loading scenarios perpendicular to the circumferential meniscal fibers. However, meniscal repair constructs are also exposed to shear forces parallel to the circumferential meniscal fibers during healing, particularly in the midportion of the meniscus. Hypothesis: Material properties of meniscal repair devices cannot be extrapolated from tensile to shear load scenarios. Study Design: Controlled laboratory study. Methods: In 84 harvested and isolated bovine lateral menisci following removal of adjacent soft tissue, a standardized vertical lesion was set followed by repair using all-inside flexible (FasT-Fix, FasT-Fix AB, RapidLoc) and rigid (Meniscus Screw, Meniscus Arrow) meniscal repair devices. Vertical and horizontal 2.0 Ethibond sutures were used as controls. The repaired meniscal construct was tested in a tensile (parallel to the axis of the tested repair device) and shear load scenario (perpendicular to the axis of the tested repair device) at 5 mm/min and 37°C environmental temperature. Maximum load to failure, stiffness, and failure mode were recorded. Results: The absolute load to failure values of each repair device in the shear scenario were only marginally different from the tensile load scenario. However, the stiffness of several tested devices was markedly reduced in the shear scenario. In both scenarios, large differences of the load to failure and the stiffness between the implant types up to 5-fold were found (P < .05). The failure mode of several all-inside flexible repair devices was different in the shear versus tensile load scenario, while the failure mode of the rigid systems was similar in both scenarios. Conclusion: All-inside meniscal repair devices exposed to shear load scenarios have comparable maximum loads to failures as tensile load scenarios. However, the stiffness of the majority of the flexible meniscal repair implants in a shear load scenario is markedly reduced. The applied scenario also affects the failure mode in several flexible meniscal repair devices. Clinical Relevance: Meniscal repair devices with sufficient stiffness and stability against shear loads may be favored for meniscal repair, especially within the midportion of the meniscus where shear loads occur during healing.

Complex Osteotomies of Tibial Plateau Malunions Using Computer-Assisted Planning and Patient-Specific Surgical Guides.

Summary: The accurate reduction of tibial plateau malunions can be challenging without guidance. In this work, we report on a novel technique that combines 3-dimensional computer-assisted planning with patient-specific surgical guides for improving reliability and accuracy of complex intraarticular corrective osteotomies. Preoperative planning based on 3-dimensional bone models was performed to simulate fragment mobilization and reduction in 3 cases. Surgical implementation of the preoperative plan using patient-specific cutting and reduction guides was evaluated; benefits and limitations of the approach were identified and discussed. The preliminary results are encouraging and show that complex, intraarticular corrective osteotomies can be accurately performed with this technique. For selective patients with complex malunions around the tibia plateau, this method might be an attractive option, with the potential to facilitate achieving the most accurate correction possible.

Effect of femoral to tibial varus mismatch on the contact area of unicondylar knee prostheses

In unicondylar knee prostheses, the relative angle and congruency of the femoral against the tibial component is not mechanically constrained and may vary with the surgical implantation technique. The contact area between both components was measured with increasing varus (0-20 degrees) and flexion angles (-20 degrees to 90 degrees) in five prosthesis models in the laboratory. The contact area varied with the relative position of the components and was critically reduced up to 70% at a varus range between >5 degrees and <25 degrees. The importance of relative malpositioning of the femoral and tibial components may be underestimated and reduces the contact area of unicondylar prostheses decisively, independent from the limb axis. This increases local pressure and may thus importantly contribute to increased wear and early loosening.

Treatment options for patellofemoral instability in sports traumatology

Patellofemoral instability not only involves lateral patellar dislocation, patellar mal-tracking or subluxation but can also cause a limiting disability for sports activities. Its underlying causes are known as morphological anomalies of the patellofemoral joint or the mechanical axis, femorotibial malrotation, variants of the knee extensor apparatus, and ligamentous insufficiencies often accompanied by poor proprioception. Athletes with such predisposing factors are either suffering from unspecific anterior knee pain or from slightly traumatic or recurrent lateral patellar dislocation Treatment options of patellar instability are vast, and need to be tailored individually depending on the athlete’s history, age, complaints and physical demands. Different conservative and surgical treatment options are reviewed and discussed, especially limited expectations after surgery.

Contact pressure on ACL hamstring grafts in the bone tunnel with interference screw fixation — Dynamic adaptation under load

INTRODUCTION Interference screws used in fixation of anterior cruciate ligament (ACL) hamstring grafts create mechanical hold by forcing the graft into frictional contact with the bone tunnel. We analyzed the resultant graft-tunnel contact pressure using an in vitro model of human cadaver 8mm hamstring grafts. METHODS Contact characteristics were assessed using both pressure sensitive films and a force sensor. Two screw sizes were investigated (8 and 9 mm in an 8mm Sawbone tunnel), both with and without a bone wedge between graft and screw. Separately, time dependent relaxation of contact force was recorded over a one hour epoch and associated tendon water loss was measured. Pullout testing of 8mm tendon grafts from 8mm holes in Sawbone and porcine femora were performed after 1 min and 1h. RESULTS During screw insertion, measured peak pressures (>40 MPa) exceeded the compressive failure stress of metaphyseal bone by more than an order of magnitude. Using a bone wedge between tendon and screw reduced local peak pressure by 85% but produced also inferior average contact pressure. In all approaches, initially achieved graft contact pressure rapidly decreased to approximately 25% within 30 min. Pullout strength was significantly reduced after 1h in comparison to 1 min in porcine bone as well as Sawbone. CONCLUSION Viscoelastic adaptation of the tendon is severe and critically reduces effective graft-bone contact pressure. Consideration of this newly recognized effect may open new and improved approaches for tendon graft fixation.

Lateral patellofemoral ligament reconstruction using a free gracilis autograft.

Medial patellofemoral instability is a rare, disabling condition that is often associated with the wrong indication for lateral retinacular release or overcorrection with medializing tibial tubercle osteotomy. It is an even less common complication after total knee arthroplasty (TKA). The lateral patellofemoral ligament is an important lateral stabilizer of the patella against medial subluxation or dislocation. Until now, no report in the literature has described lateral patellofemoral ligament reconstruction with a free gracilis tendon autograft. Furthermore, there has not been a single case report of lateral patellofemoral ligament reconstruction after TKA. The authors describe a novel technique for reconstruction of the lateral patellofemoral ligament in a symptomatic medial subluxated patella resulting from TKA and extended lateral release in a 62-year-old patient. The result 1 year postoperatively was deemed successful. Clinically, the patella was stable, with correct tracking, and radiologically the patella was correctly positioned. With a technique similar to that used for the medial patellofemoral ligament, the lateral patellofemoral ligament can be reconstructed with a gracilis tendon autograft to permit stabilization independent of resting scar tissue of the lateral retinaculum. This operation can be performed in a minimally invasive way, without opening the joint, therefore decreasing the risk of joint infection. The authors showed a successful clinical and radiologic outcome 1 year after lateral patellofemoral ligament reconstruction in a patient with medial patellar instability after TKA and lateral release.

Assessment of Lower Limb Length and Alignment by Biplanar Linear Radiography: Comparison With Supine CT and Upright Full-Length Radiography

OBJECTIVE The purpose of this article is to compare lower limb length and alignment measurements on supine CT, upright full-length radiography, and 3D models based on upright biplanar linear radiography. SUBJECTS AND METHODS This study involved 51 consecutive patients (22 men and 29 women; mean age, 68.8 years; range, 43-92 years) who were scheduled for total knee replacement. Lower limb length and alignment angle were measured on CT, upright full-length radiography, and 3D models based on biplanar linear radiography with standard and composed leg methods by two independent readers. Descriptive statistics of each modality were calculated. Measurements of different modalities were compared by paired Student t tests. Agreement between readers and modalities was assessed by Bland-Altman analyses. RESULTS Mean (± SD) limb lengths were 783 ± 56.1 mm (range, 639-927 mm), 785 ± 53.0 mm (range, 655-924 mm), 780 ± 55.4 mm (range, 633-921 mm), and 783 ± 55.9 mm (range, 636-924 mm) for CT, upright full-length radiography, and 3D models based on biplanar linear radiography standard and composed leg measurements, respectively. Mean alignment angles were 2.3° ± 5.5° (range, -12° to 20°) for CT, 2.5° ± 6.7° (range, -17° to 18°) for upright full-length radiography, and 3.4° ± 6.6° (range, -14° to 18°) for 3D models based on biplanar linear radiography. No significant differences among modalities for mean limb length were found when using composed leg measurements in biplanar linear radiography. Very small but significant mean differences in angle measurements were seen for CT (-1.1° ± 2.5) and upright full-length radiography (-0.9° ± 3.1) compared with biplanar linear radiography. Bland-Altman analyses showed no significant differences between readers, with the highest agreement for biplanar linear radiography length measurements. CONCLUSION Measurements on 3D models based on upright biplanar linear radiographs allow lower limb length and alignment angle measurements that are interchangeable with supine CT scans and upright full-length radiographs but with superior interreader agreement.

Radiodense ligament markers for radiographic evaluation of anterior cruciate ligament reconstruction

INTRODUCTION Early clinical and radiographic diagnosis of failed or loosened anterior cruciate ligament (ACL) reconstructions can be challenging. The aim of the present study is to retrospectively evaluate the use of radiologically visible markers in the ACL graft, serving as a potential diagnostic tool in ACL graft rupture and insufficiency. METHODS Twenty patients were included in the study. ACL reconstruction was performed with use of a hamstring autograft in hybrid fixation technique. The graft was marked with two radiodense suture knots, one at the tibial and femoral tunnel openings. Radiographs were performed postoperatively, after 6 weeks and 12 months. Four distances between markers and landmarks were measured in anteroposterior and three in lateral radiographic views and the positional change between the timepoints of measurement was calculated. RESULTS Measurements of the marker distances on radiographs showed an excellent interobserver reliability (κ=0.97). In two measured distal anteroposterior distances statistically significant changes could be detected between 6 weeks and 12 months postoperatively in one patient with MRI-documented ACL rerupture and in five patients with ACL elongation defined as anteroposterior-translation with side-to-side difference of ≥3 mm measured with a Rolimeter device. On lateral radiographs, marker distances were highly variable and did not correlate with clinical ACL elongation. CONCLUSION The application of radiodense ACL graft markers is a straight-forward, non-expensive and potentially useful diagnostic tool to identify the position of the transplant and for diagnosis of graft elongation or failure. However, the method is sensitive to the radiological projection, which should be further studied and optimized.