Anterior Slope Research Articles

Human jaw joint hypermobility: Diagnosis and biomechanical modelling.

Patients with hypermobility disorders of the jaw joint experience joint sounds and jerky movements of the jaw. In severe cases, a subluxation or luxation can occur. Clinically, hypermobility disorders should be differentiated from disc displacements. With biomechanical modelling, we previously identified the anterior slope angle of the eminence and the orientation of the jaw closers to potentially contribute to hypermobility disorders. Using cone-beam computed tomography (CBCT), we constructed patient-specific models of the masticatory system to incorporate these aspects. It is not known whether the clinical diagnosis of hypermobility disorders is associated with the prediction of hypermobility by a patient-specific biomechanical model. Fifteen patients and eleven controls, matched for gender and age, were enrolled in the study. Clinical diagnosis was performed according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and additional testing to differentiate hypermobility from disc displacements. Forward simulations with patient-specific biomechanical models were performed for maximum opening and subsequent closing of the jaw. This predicted a hypermobility disorder (luxation) or a control (normal closing). We found no association between the clinical diagnosis and predictions of hypermobility disorders. The biomechanical models overestimated the number of patients, yielding a low specificity. The role of the collagenous structures remains unclear; therefore, the articular disc and the ligaments should be modelled in greater detail. This also holds for the fanned shape of the temporalis muscle. However, for the osseous structures, we determined post hoc that the anterior slope angle of the articular eminence is steeper in patients than in controls.

The arthroscopic Bankart repair procedure enables complete quantitative labrum restoration in long-term assessments.

The restoration of the labrum complex and the influence on secondary osteoarthritis after arthroscopic Bankart repair on magnetic resonance imaging (MRI) remain unclear. Twenty-one patients were retrospectively followed after unilateral primary arthroscopic Bankart repair with knot-tying suture anchors (8.8 ± 2.5years after surgery, age 25.3 ± 6.3years). Bilateral structural MRI was performed to assess labrum-glenoid restoration by measurements of the labrum slope angle, height index, and labrum interior morphology according to the Randelli classification. Osteoarthritic status was bilaterally assessed by a modified assessment based on the Samilson-Prieto classification. MRI assessment revealed full labrum-glenoid complex restoration with equivalent parameters for anterior slope angle (mean ± SD: 21.3° ± 2.6° after Bankart repair vs. 21.9° ± 2.6° control) and height index (2.34 ± 0.4 vs. 2.44 ± 0.4), as well as the inferior slope angle (23.1° ± 2.9° vs. 23.3° ± 2.1°) and height index (2.21 ± 0.3 vs. 2.21 ± 0.3) (all n.s.). The labrum morphology showed only for the anterior labrum significant alterations (1.4 ± 0.9 vs. 0.6 ± 0.7, p < 0.05), the inferior labrum occurred similarly (1.3 ± 0.8 vs. 0.8 ± 0.5, n.s.). Osteoarthritic changes were significantly increased after Bankart repair compared to the uninjured shoulder (4.8 ± 5.1mm vs. 2.5 ± 1.0mm; p < 0.05), with a significant correlation of osteoarthritis status between both shoulders (p < 0.05). Scores generally decreased after Bankart repair (constant 84.6 ± 9.5 vs. 94.5 ± 4.9 control, p < 0.05; Rowe 84.5 ± 6.5 vs. 96.2 ± 4.2, p < 0.05; Walch-Duplay 82.4 ± 7.0 vs. 94.3 ± 4.0, p < 0.05) with a strong correlation with osteoarthritis status (p < 0.05). Arthroscopic Bankart repair enabled good clinical outcomes and complete quantitative labrum restoration parameters. Next to several well-known parameters, secondary osteoarthritis after arthroscopic Bankart repair significantly correlated with osteoarthritic status of the uninjured contralateral shoulder but was not influenced by quantitative labrum restoration. The recommendation for arthroscopic Bankart repair should be based on clinical parameters and not on prevention of secondary osteoarthritis. Case series. IV.

Predicted osteotomy planes are accurate when using patient-specific instrumentation for total knee arthroplasty in cadavers: a descriptive analysis

PurposeMalalignment of implants is a major source of failure during total knee arthroplasty. To achieve more accurate 3D planning and execution of the osteotomy cuts during surgery, the Signature (Biomet, Warsaw) patient-specific instrumentation (PSI) was used to produce pin guides for the positioning of the osteotomy blocks by means of computer-aided manufacture based on CT scan images. The research question of this study is: what is the transfer accuracy of osteotomy planes predicted by the Signature PSI system for preoperative 3D planning and intraoperative block-guided pin placement to perform total knee arthroplasty procedures?MethodsThe transfer accuracy achieved by using the Signature PSI system was evaluated by comparing the osteotomy planes predicted preoperatively with the osteotomy planes seen intraoperatively in human cadaveric legs. Outcomes were measured in terms of translational and rotational errors (varus, valgus, flexion, extension and axial rotation) for both tibia and femur osteotomies.ResultsAverage translational errors between the osteotomy planes predicted using the Signature system and the actual osteotomy planes achieved was 0.8 mm (± 0.5 mm) for the tibia and 0.7 mm (± 4.0 mm) for the femur. Average rotational errors in relation to predicted and achieved osteotomy planes were 0.1° (± 1.2°) of varus and 0.4° (± 1.7°) of anterior slope (extension) for the tibia, and 2.8° (± 2.0°) of varus and 0.9° (± 2.7°) of flexion and 1.4° (± 2.2°) of external rotation for the femur.ConclusionThe similarity between osteotomy planes predicted using the Signature system and osteotomy planes actually achieved was excellent for the tibia although some discrepancies were seen for the femur. The use of 3D system techniques in TKA surgery can provide accurate intraoperative guidance, especially for patients with deformed bone, tailored to individual patients and ensure better placement of the implant.

Revision of partial knee to total knee arthroplasty with use of patient-specific instruments results in acceptable femoral rotation.

Patient-specific instruments (PSI) were initially developed for the alignment of both total knee- (TKA) and partial knee arthroplasty (PKA). We hypothesize that CT-based PSI for PKA-to-TKA revision surgery can restore biomechanical limb alignment and prosthetic component positioning in vivo as calculated pre-operatively, resulting in a limited percentages of outliers. An imaging analysis was performed using CT-based 3D measurement methods based on a pre- and post-revision CT scan. Imaging data were gathered on 10 patients who were operated for PKA-to-TKA revision with the use of PSI based on CT imaging. The planned femur and tibia component position in vivo were compared with the pre-revision planned component position. Outliers were defined as deviations >3.0° from pre-revision planned position for the individual implant components. Adjustments (e.g. resection level and implant size) during surgery were recorded. The HKA axis was restored accurately in all patients with a mean post-operative HKA axis of 178.1° (1.4°). Five femoral (2 varus, 2 internal rotation and 1 extension) and 14 tibial guides (2 varus, 6 anterior slope, 3 internal rotation and 3 external rotation) on a total of 60 outcome measures were identified as outliers. During surgery, an intraoperative tibial resection of 2mm extra was performed in three patients. In 80 and 70% for, respectively, the femur and tibia, the surgeon-planned size was implanted during surgery. All patient-specific guides fitted well in all patients. No intraoperative or post-operative complications related to surgery were registered. This study introduced a unique new concept regarding PSI, PKA-to-TKA revision surgery. Based on the results, we were unable to fully confirm our hypothesis. PSI as a "new" tool for PKA-to-TKA revision surgery appears to be an accurate tool for the alignment of the TKA femur component. The tibial guide seems more susceptible to errors, resulting in a substantial percentage of outliers. Prospective cohort study, Level II.

Medial Open Wedge High Tibial Osteotomy for Varus Malunited Tibial Plateau Fractures

To analyze radiologic and functional outcomes of varus malunited tibial plateau fractures managed with medial open wedge high tibial osteotomy (MOHTO). Eighteen patients with symptomatic varus malunited tibial plateau fractures with less than stage II arthritic changes managed from July 2009 to October 2013 were included. Patients with complex intra-articular step malunions and severe arthritic changes (stage III and IV) were excluded. Initially, diagnostic arthroscopy was performed followed by MOHTO stabilized with locking plate and tricortical autograft (n= 11, 61%) or a Puddu plate and allograft (n= 7, 39%). Patients were evaluated radiologically for union, medial proximal tibial angle, and tibial slope angle, and functional assessment was performed with a knee outcome survey based on activities of daily living. The mean follow-up duration was 41.7 ± 12.1months (range 25-61); all patients achieved radiologic union by a mean duration of 4.3 ± 1.2months (range 3-8). The mean medial proximal tibial angle improved from 75.3° ± 3.7° (range 70.5°-85.2°) to a postoperative angle of 83.8° ± 3.6° (range 77.5°-90.4°) (P < .001). In 12 patients, an abnormal mean anterior slope of-5.5° ± 3.0° (range-1.1° to-13°) was corrected to a postoperative posterior slope of 5.8° ± 4.4° (range-1.1° to 14.1°) (P < .001). In 6 patients, a mean posterior slope of 17.4° ± 10.5° (range 1.4°-33°) was corrected to a postoperative posterior slope of 14.08° ± 5.6° (range 7.4-21.3) (P = .214). The mean knee outcome survey scores preoperatively were 25% ± 9.68% (range 8%-48%) and postoperatively were 85% ± 11.18% (range-52% to 98%, P < .001). MOTHO for varus malunited tibial plateau fractures is safe and effective procedure that provides excellent functional outcomes, acceptable radiologic outcomes, and carries minimal complications. Level IV, therapeutic case series.

Factors Affecting Wear of Constrained Polyethylene Tibial Inserts in Total Knee Arthroplasty

BackgroundWear in posterior-stabilized (PS) polyethylene tibial inserts depends on component position, limb alignment, and ligament balancing. Valgus-varus constrained (VVC) inserts are likely to be affected similarly. We aimed to compare wear characteristics of VVC and PS inserts and identify associated factors. MethodsThis was a retrieval analysis (macroscopic and radiographic) of all 18 VVC liners collected from patients who underwent revision surgery from 1999 to 2011. These patients were matched to another group with PS inserts who underwent revision in the same time period. ResultsThere was significantly more damage in the posts of the VVC group (13.0 ± 5.0, compared to 4.7 ± 1.9 in the PS group; P < .001). Within the VVC group, the total damage score and cold flow damage were significantly higher with excessive joint line changes (≥5 mm; P = .01). The excessive joint line elevation was associated with rotational wear pattern of the post (P = .004). Damage scores were increased with femoral component malposition (P = .04), anterior tibial slope (P = .04), and tibial component malposition (P = .04). ConclusionJoint line elevation, femoral and tibial component malposition, and anterior tibial slope resulted in significantly more wear in the VVC inserts. Joint line elevation of >5 mm resulted in wear of the medial and lateral aspects of the post, femoral valgus resulted in cold flow wear of the anterior post, and tibial valgus and anterior slope resulted in wear of lateral aspect of the post.

How muscle relaxation and laterotrusion resolve open locks of the temporomandibular joint. Forward dynamic 3D-modeling of the human masticatory system

Patients with symptomatic hypermobility of the temporomandibular joint report problems with the closing movement of their jaw. Some are even unable to close their mouth opening wide (open lock). Clinical experience suggests that relaxing the jaw muscles or performing a jaw movement to one side (laterotrusion) might be a solution. The aim of our study was to assess the potential of these strategies for resolving an open lock and we hypothesised that both strategies work equally well in resolving open locks. We assessed the interplay of muscle forces, joint reaction forces and their moments during closing of mouth, following maximal mouth opening. We used a 3D biomechanical model of the masticatory system with a joint shape and muscle orientation that predispose for an open lock. In a forward dynamics approach, the effect of relaxation and laterotrusion strategies was assessed. Performing a laterotrusion movement was predicted to release an open lock for a steeper anterior slope of the articular eminence than relaxing the jaw-closing muscles, herewith we rejected our hypothesis. Both strategies could provide a net jaw closing moment, but only the laterotrusion strategy was able to provide a net posterior force for steeper anterior slope angles. For both strategies, the temporalis muscle appeared pivotal to retrieve the mandibular condyles to the glenoid fossa, due to its’ more dorsally oriented working lines.

Effect of simultaneous stretching of the wrist and finger extensors for lateral epicondylitis: a gross anatomical study of the tendinous origins of the extensor carpi radialis brevis and extensor digitorum communis

BackgroundPulling the wrist into flexion with the elbow in extension and forearm in pronation has been used as the stretching technique of wrist extensors for lateral epicondylitis. Simultaneous stretching of the fingers in addition to the wrist flexion has also been applied. However, the mechanism of this simultaneous stretching has not been clarified. This study is designed to clarify the mechanism underlying this simultaneous stretching technique based on the anatomical features of the origins of the extensor carpi radialis brevis (ECRB) and extensor digitorum communis (EDC). MethodsThirty-nine arms from formalin-embalmed Japanese human specimens were dissected. The features of the origins of the ECRB and EDC were macroscopically observed, and the locations of each origin on the lateral epicondyle were measured. ResultsThe ECRB had a long and wide, purely tendinous origin which originated from the anterior slope of the lateral epicondyle. The tendinous origin of the index finger of the EDC (EDC-IF) arose from the posterior aspect of the ECRB tendinous origin, with a coexisting muscular portion observed at the level of the proximal forearm. The middle finger of the EDC (EDC-MF) had a short tendinous origin with an associated muscular portion and originated proximo-laterally to the origin of the ECRB on the lateral epicondyle. In addition, the muscular origin of the EDC-MF arose on the superficial and posterior aspect of the ECRB tendinous origin. In contrast, the ring and little fingers of the EDC originated from the tendinous septum of the extensor digiti minimi and extensor carpi ulnaris, and had no connection with the ECRB tendinous origin. ConclusionsOn the basis of our anatomical findings, simultaneous stretching of the wrist extensors by wrist, index and middle fingers flexion could provide stretching force to both the tendinous origins of the ECRB and EDC through the EDC-IF and EDC-MF.

Study of Condylar Asymmetry in Angle Class III Malocclusion With Mandibular Deviation

Differences in the condylar between both sides in class III cases with mandibular deviated are important for the diagnosis, treatment, and retention in this kind of patient. To detect the subtle differences, we analyzed the size, shape, and bone density with three-dimensional reconstructed technology. The symmetry group and the asymmetry group each with 20 cases were chosen according to some standards. The computed tomographic data obtained and three-dimensional model were built with SimPlant software. The distance and angle were measured in the three-dimensional model, and the bone density was measured with the SimPlant software. The differences between the separated side in each group and the difference between the 2 groups were analyzed. In the asymmetry group, some measurement projects of the bilateral condyles showed significant differences, such as the ramal height, condylar perpendicular height, the area of maximum cross section of condylar, condylar medialateral diameter, length of posterior slope, and angle of posterior slope. When the asymmetry group was compared with the symmetry group, the condyles of the asymmetry group showed more asymmetrical variations in morphology, such as the ramal height, the condylar perpendicular height, the area of maximum cross section of condylar, the medialateral diameter, the length of anterior slope, and angle of posterior slope. The bone mineral density of the condylar anterior and condylar medial point was higher in the nondeviated side, and the bone mineral density of the condylar posterior was higher in the deviated side, and no statistically significant difference was found in the symmetry group. In class III malocclusion with mandibular deviation patients, the three-dimensional morphology and bone density of condylar on the deviated side differ from the nondeviated side, which indicates the association between asymmetrical jaw function and joint remodeling.

Twice cutting method reduces tibial cutting error in unicompartmental knee arthroplasty

BackgroundBone cutting error can be one of the causes of malalignment in unicompartmental knee arthroplasty (UKA). The amount of cutting error in total knee arthroplasty has been reported. However, none have investigated cutting error in UKA. The purpose of this study was to reveal the amount of cutting error in UKA when open cutting guide was used and clarify whether cutting the tibia horizontally twice using the same cutting guide reduced the cutting errors in UKA. MethodsWe measured the alignment of the tibial cutting guides, the first-cut cutting surfaces and the second cut cutting surfaces using the navigation system in 50 UKAs. Cutting error was defined as the angular difference between the cutting guide and cutting surface. ResultsThe mean absolute first-cut cutting error was 1.9° (1.1° varus) in the coronal plane and 1.1° (0.6° anterior slope) in the sagittal plane, whereas the mean absolute second-cut cutting error was 1.1° (0.6° varus) in the coronal plane and 1.1° (0.4° anterior slope) in the sagittal plane. Cutting the tibia horizontally twice reduced the cutting errors in the coronal plane significantly (P<0.05). ConclusionOur study demonstrated that in UKA, cutting the tibia horizontally twice using the same cutting guide reduced cutting error in the coronal plane.

Osteoartritis sub-astragalina posterior

La circunstancia de harber encontrado un caso de osteo-artritis subastragalina posterior, -lesión cuya rareza explica las pocas referencias anotadas en la literatura- y el hecho de las derivaciones clínicas y terapéuticas que comporta su diagnóstico, nos ha llevado a hacer una revisión de su conocimiento en el momento actual, dar cuenta de la feliz evolución del caso por nosotros anotado y, en fin, discutir ciertos aspectos fisiológicos y su relación con otros procesos afines. En especial, queremos señalar la posibilidad de que, con los recursos actuales, es posible controlar la evolución de estas infecciones en sólo la porción posterior de la articulación ya dicho, evitando así su difusión a la vertiente anterior y las articulaciones mediotarsianas.

Comment on Conteduca et al.: Patient-specific instruments in total knee arthroplasty

Dear Editor, The recently published article on “Patient-specific instruments in total knee arthroplasty” [1] caught our attention. Contemporary techniques like custom cutting blocks (CCB), computer-assisted surgery (CAS) etc. are being promoted and developed for improving the mechanical alignment of the limb in total knee arthroplasty (TKA), which has so far not been achievable [2]. It is also not yet proven if achieving a near normal mechanical alignment improves the survival of the TKA and has any significant clinical repercussion [3]. We are however convinced CCB may offer certain other advantages like decreased operative time [2] and bleeding [4] and faster recovery [4]. The major disadvantages of CCB include increased cost and delay in their procurement for surgery. In our set-up, typically this lag time has been reduced to five to seven working days and the cost for a single knee block has come down to about US$400 [4]. We believe that the additional cost of CCB can be offset by decreased operative time, less need for blood transfusion and reduction of number of trays used with CCB [2] and less need for sterilisation of the trays used in the surgery. It could also potentially lead to decreased change over time in a high volume set-up. We also have the following concerns about the results in the article: The authors state that “the mean deviation of the EM tibial guides from the ideal alignment (0°) was 0.7° ± 0.39 and of the VISIONAIRE was 129° ± 1.55 (P = 0.22).” There seems to be a significant oversight in the data for VISIONAIRE as the variations from ideal alignment cannot be 129°. The authors state that the EM guide group had a mean posterior tibial slope of −1.62 and the patient-specific had a slope of +1.16, an anterior slope. This seems contrary to other studies published which measured the component alignment between conventional and patient-specific jigs [5] and reported a posterior slope in both groups. The problem of not being able to reproduce the posterior slope may be inherent to the magnetic resonance imaging (MRI)-based jig of VISIONAIRE. Chotanaphuti et al. [5] in their study comparing component alignment in both sagittal and coronal planes used computed tomography (CT)-based custom jigs and were able to reproduce the posterior slopes. It is possible to predetermine and reproduce the tibial slope in CCB by CT-based techniques like PrePlan (Stryker). Koch et al. [6] in their review of 301 TKA performed with CT-based custom jigs reported a posterior tibial slope in both computer-assisted and patient-specific instrumentation (PSI). Whether this advantage is inherent to the CT-based PSI needs further exploration. We believe that CT-based manufacturing of CCB may prove to be superior to MRI-based techniques. We hope that with further developments in computer analysis of CT images, manufacturing techniques of CCB and clinical experience of the surgeons their accuracy will be enhanced and it may be possible to provide a near normal mechanical alignment of limbs after TKA.

Mandibular asymmetry: a three-dimensional quantification of bilateral condyles

IntroductionThe shape and volume of the condyle is considered to play an important role in the pathogenesis of the mandibular deviation. Curvature analysis is informative for objectively assess whether the shape of the condyles matches that of the glenoid fossa. In this study, a three-dimensional (3-D) quantification of bilateral asymmetrical condyles was firstly conducted to identify the specific role of 3-D condylar configuration for mandibular asymmetry.Methods55 adult patients, 26 males (26 ± 5 yrs) and 29 females (26 ± 5 yrs), diagnosed with mandibular asymmetry were included. The examination of deviation of chin point, deviation of dental midlines, inclination of occlusal plane, and depth of the mandibular occlusal plane were conducted. After the clinical investigation, computed tomography images from the patients were used to reconstruct the 3-D mandibular models. Then the condylar volume, surface size, surface curvature and bone mineral density were evaluated independently for each patient on non-deviated and deviated sides of temporomandibular joint.ResultsBoth the condylar surface size and volume were significantly larger on deviated side (surface size: 1666.14 ± 318.3 mm2, volume: 1981.5 ± 418.3 mm3). The anterior slope of the condyle was flatter (0.12 ± 0.06) and the posterior slope (0.39 ± 0.08) was prominently convex on the deviated side. The corresponding bone mineral density values were 523.01 ±118.1 HU and 549.07 ±120. 6 HU on anterior and posterior slopes.ConclusionsThe incongruence presented on the deviated side resulted in a reduction in contact areas and, thus, an increase in contact stresses and changes of bone density. All aforementioned results suggest that the difference existing between deviated and non-deviated condyles correlates with facial asymmetrical development. In mandibular asymmetry patients, the 3-D morphology of condyle on deviated side differ from the non-deviated side, which indicates the association between asymmetrical jaw function and joint remodeling.

Increase of tibial slope reduces backside wear in medial mobile bearing unicompartmental knee arthroplasty

BackgroundUnicondylar knee arthroplasty is a good alternative for patients in monocompartmental osteoarthritis. The revision rate in unicondylar knee arthroplasty is higher than in total knee arthroplasty. The influence of the tibial slope on wear in unicondylar knee arthroplasty has not been investigated so far. MethodsThe influence of the tibial slope on wear was investigated in mobile bearing unicondylar knee prosthesis. This was positioned with four different tibial slopes (−4°, 0°, 4°, 8°) in a knee wear simulator simulating the human gait in a plane according to ISO 14243-2:2002(E). After this a kinematic analysis was performed and the inlays were observed under reflected-light-microscopy. FindingsWear was significantly reduced with an increasing tibial slope (0°: 3.46mg/millioncycles, SD: 0.59, 4° slope: 1.52mg/millioncycles, SD: 0.06, 8° slope group: 0.99mg/millioncycles, SD: 0.42). An anterior slope of −4° also reduced wear (2.08mg/millioncycles, SD: 0.37). Kinematic analysis revealed a reduced translation between the inlay and the tibia with an increasing tibial slope. The backside of the inlays of the 4° and 8° slope group showed less wear pattern when observed under reflected-light microscopy. InterpretationIncreasing the tibial slope led to a reduced translation between the inlay and the prosthesis in the analysed mobile-bearing unicondylar knee arthroplasty and with this to a reduced backside wear. A tibial slope between 4 and 8° can be recommended in mobile UKA to reduce wear, however, the influence on the ligaments has to be considered and needs to be investigated in further studies.

Relationship of Alignment and Tibial Cortical Coverage to Hypertrophic Bone Formation in Salto Talaris® Total Ankle Arthroplasty

A retrospective analysis of 107 Salto Talaris® total ankle replacements was performed to determine the effect of alignment and tibial cortical coverage on the formation of heterotopic bone. The radiographic parameters were studied for at least 18 months to detect any changes over time. The angle of insertion of the implant was most often in varus and with a positive anterior slope. A slight increase was seen in the slope over time (p < .0001) but was not clinically relevant. The mean percentage of cortical coverage of the tibial component was 89%, and only 7 patients had complete coverage of both the anterior and the posterior cortices. The percentage of patients who had hypertrophic bone growth increased over time (p < .0001). As the slope of the implant increased, there was a negative correlation with the degree of tibial coverage (p = .007). There was also an increase in the extent of hypertrophic bone as the tibial coverage decreased. None of the patients had symptoms that required an additional surgical procedure. The results of the present study indicate a high incidence of hypertrophic bone proliferation when the dimensions of the tibial component do not match the anteroposterior depth of the tibia at the plane of resection. Despite the high occurrence rate, the clinical relevance of hypertrophic bone is obscure.

Biomechanical modeling of open locks of the human temporomandibular joint

BackgroundPatients with hypermobility of the temporomandibular joint may have problems closing their mouth after opening widely. In the worst case, the mandibular condyles become trapped in front of the articular eminences and the jaw muscles cannot reposition them into the fossae (open lock). The difference in ease of closing the jaw between patients and non-patients is presently not well understood. MethodsWide opening and subsequent jaw closing were simulated with a biomechanical model in a forward dynamics approach. The effect of anterior slope angle and orientation of jaw-closing muscles on condylar travel was determined. FindingsThe mandibular condyles traveled anterior of the eminences and back into the fossae uneventfully with backwardly oriented jaw closers and eminences with a gentle anterior slope. However, combinations of relatively forward oriented jaw closers and a steep anterior slope caused the condyles to continue traveling anteriorly upon jaw-closing attempts, ending in an open lock position. InterpretationOur results indicate that for the masticatory system to reach an open lock, various unfavorable combinations of jaw-closer orientation and anterior slope angle exist within normal physiological ranges. These findings could be relevant for maxillofacial surgeons, both for the diagnostic process and for clinical decisions, regarding patients suffering from open locks.

In Vivo Evidence for Tibial Plateau Slope as a Risk Factor for Anterior Cruciate Ligament Injury

Background: In vivo studies reporting tibial plateau slope as a risk factor for anterior cruciate ligament (ACL) injury have been published with greatly increasing frequency. Purpose: To examine and summarize the in vivo evidence comparing tibial slope in ACL-injured and uninjured populations. Study Design: Systematic review and meta-analysis. Methods: We reviewed publications in Scopus, SPORTDiscus, CINAHL, and PubMed to identify all studies reporting a measure of tibial plateau slope between ACL-injured groups and controls. A meta-analysis was performed including calculation of effect size and 95% confidence interval as well as 95% confidence intervals for the mean values of the measurement in each study. Results: Fourteen studies met our inclusion/exclusion criteria. Five of 6 radiographic studies reporting medial tibial plateau slope (MTPS) demonstrated significant differences between controls and ACL-injured groups, while only 1 of 7 magnetic resonance imaging (MRI) studies reported significant differences between groups. Mean MTPS measurements and standard deviations reported for controls ranged from 2.9° ± 2.8° anterior to 9.5° ± 3° posterior. For ACL-injured patients, MTPS ranged from 1.8° ± 3.5° anterior to 12.1° ± 3.3° posterior. Lateral tibial plateau slope (LTPS) was reported to be significantly greater in ACL-injured groups in all 5 MRI-based studies reporting group comparisons. Mean values for LTPS in controls ranged from 0.3° ± 3.6° anterior slope to 9° ± 4° posterior slope. In ACL-injured groups, mean reported LTPS values ranged from 1.8° ± 3.2° to 11.5° ± 3.54° posterior slope. Conclusion: Despite high measures of reliability for the various methods reported in current studies, there is vast disagreement regarding the actual values of the slope that would be considered “at risk.” Reported tibial slope values for control groups vary greatly between studies. In many cases, the study-to-study differences in “normal” tibial slope exceed the difference between controls and ACL-injured patients. The clinical utility of imaging-based measurement methods for the determination of ACL injury risk requires more reliable techniques that demonstrate consistency between studies.

Are MRI-based, patient matched cutting jigs as accurate as the tibial guides?

The aim of this study is to evaluate the accuracy of VISIONAIRE (Smith & Nephew Inc., Memphis, TN, USA) Patient Matched cutting tibial jigs in comparison with extramedullary (EM) tibial instrumentation by analysing data as detected by intra-operative use of VectorVision knee navigation software from BrainLAB (Redwood City, CA, USA). Twelve patients were selected for unilateral total knee replacement (TKR). They underwent a full-length weight-bearing anteroposterior (AP) radiograph and magnetic resonance imaging (MRI). During surgery, once the EM guides were placed and fixed on the tibia, the orientation in the coronal and sagittal planes was checked by the navigator and then compared with the data obtained by measuring the orientation of VISIONAIRE Patient Matched cutting tibial jigs. An unsatisfactory result was considered an error ≥2° in both coronal and sagittal planes for the tibial component as a possible error of 4° could result. In the coronal plane the mean deviation of the EM tibial guides from the ideal alignment (0°) was 0.7 ± 0.39° and of the VISIONAIRE was 129 ± 1.55° (P = 0.22). In the sagittal plane the mean deviation of the EM tibial guides from 3° of posterior slope was -1.62 ± 1.78° and of the VISIONAIRE was +1.16 ± 4.29° (P < 0.05). Negative values indicate a more posterior slope from the ideal and positive values an anterior slope. This preliminary study documented only a fair accuracy of the method with a consistent risk of error of more of 3° especially in the sagittal plane. We could speculate that the problem in the sagittal plane was due to the fact that the pre-operative protocol does not include a lateral X-ray projection of the knee and only includes an AP standing X-ray of the straight leg and MRI.

MRI assessment of the structural labrum integrity after Bankart repair using knotless bio-anchors

Adequate labral restorations after Bankart repair have been demonstrated in cadaver models for knot-tying and knotless anchors and in vivo by magnetic resonance imaging for knot tying. The influence of glenoidal bio-degradation on clinical outcome, and conclusions regarding drill hole enlargement and foreign body reactions remain controversial. The labrum was analyzed in magnetic resonance images for 37 consecutive patients with Bankart repair using knotless PLLA anchors and for 31 volunteers as radiologic controls. The labrum was assessed regarding slope, height index (quotient between labral height to the glenoid height), and labrum morphology in axial and coronal T2 images. Glenoidal bio-degradation was graded in terms of the drill hole configuration in T1 images and the corresponding osseous reaction in T2 images. Constant-Murley, Walch-Duplay, and Rowe scoring were carried out preoperatively and at follow-up. At 15months after arthroscopy, the anterior slope (24.8°), height index (3.0), inferior slope (25.4°), and height index (2.5) were not significantly different from control values. Morphologic analysis revealed significant changes in the Bankart group (P<0.05) that were influenced by the number of preoperative dislocations. Bio-degradation proceeded slowly with no evidence of drill hole enlargement. Osseous reactions were significantly greater in inferior compared to superior implants. The clinical scores were excellent and were not influenced by bio-degradation. Knotless anchors facilitate labral restoration that is comparable to the knot-tying approach. Bio-degradation proceeds slowly without clinical or radiologic evidence of foreign body reactions. III.

The accuracy of intramedullary tibial guide of sagittal alignment of PCL-substituting total knee arthroplasty

Experimental and clinical studies on the accuracy of the intramedullary alignment method have produced different results, and few have addressed accuracy in the sagittal plane. Reported deviations are not only attributable to the alignment method but also to radiological errors. The purpose of this study was to evaluate the accuracy of the intramedullary alignment method in the sagittal plane using computed tomography (CT) and 3-dimensional imaging software. Thirty-one TKAs were performed using an intramedullary alignment method involving the insertion of a long 8-mm diameter rod into the medullary canal to the distal metaphysis of the tibia. All alignment instruments were set to achieve an ideal varus/valgus angle of 0° in the coronal plane and a tibial slope of 0° in the sagittal plane. The accuracy of the intramedullary alignment system was assessed by measuring the coronal tibial component angle and sagittal tibial slope angles, i.e., angles between the tibial anatomical axis and the tangent to the medial and lateral tibial plateau or the cut-surface. The mean coronal tibial component angle was 88.5°±1.2° and the mean tibial component slope in the sagittal plane was 1.6°±1.2° without anterior slope. Our intramedullary tibial alignment method, which involves passing an 8-mm diameter long rod through the tibial shaft isthmus, showed good accuracy (less than 3 degrees of variation and no anterior slope) in the sagittal plane in neutral or varus knees.