Mehmet Serhan Er

Biomechanical evaluation of syndesmotic screw position: a finite-element analysis.

Objectives: To evaluate the stresses in syndesmotic screws and widening of syndesmosis under loading after placement of the screws at different levels from the ankle joint line and to determine the optimal level. Methods: From a set of computed tomographic data of an ankle, a 3-dimensional finite-element model was reconstructed. Six fixation configurations of the syndesmosis with placement of 3.5 or 4.5 mm single tricortical screws at 20–45 mm from the tibiotalar joint were performed on this model. Physiological loads approximating those during both midstance and heel-off states of stance phase of normal walking were applied to evaluate the stress in the screw and widening of the syndesmosis. Results: Among the 6 fixation configurations, the lowest von Mises stress was found in the screws placed 30–40 mm above the joint line (373.31–380.17 MPa for 3.5 mm cortical screw and 284.06–327.31 MPa for 4.5 mm cortical screw in midstance phases), whereas the least syndesmosis widening was determined when the screw was placed 30 mm above the tibial plafond (0.005 mm) for 3.5 mm cortical screw and 20, 25, and 30 mm above the tibial plafond (0.004 mm for each, respectively) for 4.5 mm cortical screw during midstance phases. Conclusions: This study showed that syndesmosis fixation at the level of 30–40 mm above the tibiotalar joint has advantages with regard to stress in screws in comparison with the other evaluated levels.

Anatomical evaluation and stress distribution of intact canine femur.

In the biomedical field, three‐dimensional (3D) modeling and analysis of bones and tissues has steadily gained in importance. The aim of this study was to produce more accurate 3D models of the canine femur derived from computed tomography (CT) data by using several modeling software programs and two different methods.

Femoral neck stress fracture in children: a case report, up-to-date review, and diagnostic algorithm.

Stress fracture of the femoral neck in skeletally immature individuals is a rare condition and generally seen as compressive type. Because the condition may lead to disastrous complications, femoral neck stress fracture must also be kept in mind in the differential diagnosis of pediatric hip pain. We present a case of compressive-type stress fracture of the femoral neck in a 10-year-old girl with left hip pain that was sustained for 4 weeks and emphasize the difficulty of early diagnosis with only a radiographic evaluation and put forward an algorithm for diagnosis and treatment.

Biomechanical Evaluation of Syndesmotic Screw Design via Finite Element Analysis and Taguchi's Method

BACKGROUND Screw fixation of syndesmotic injuries facilitates ligament healing and restoration of ankle stability, but failure of the screw might threaten the success of the treatment. Screw design parameters, such as outer diameter, inner diameter, thread pitch, leading edge radius, trailing edge radius, leading edge angle, and trailing edge angle, might have effects on the stresses that occur in the screws. This is the first study, to our knowledge, to investigate which geometric screw parameters play key roles in stresses that occur in screws used for syndesmotic fixation. METHODS A three-dimensional finite element model of an ankle was reconstructed. Four different types of titanium screws—4.5-mm malleolar, 4-mm cancellous, 4-mm machine, and 3.5-mm cortical—were placed on this model. Physiologic load was applied to evaluate the stress in the screw. Then the contribution of each design factor to stress in the screws was analyzed systematically by Taguchis robust design method. RESULTS The maximum equivalent ductile failure (von Mises equivalent stress) value was found in the 4-mm cancellous screw (402 MPa). Taguchis analysis showed that the descending order of contribution of the design factors to stress emerging on the screw is inner diameter, leading edge angle, thread pitch, outer diameter, and trailing edge angle. CONCLUSIONS Stress that occurs in syndesmotic screws is closely related to their geometry and dimensions. According to the results, a 3.5-mm cortical screw with the ideal screw design regarding optimal parameters to resist against stresses in the syndesmosis seems more reasonable to choose in syndesmotic fixation.

An assessment of sleep quality in patients undergoing total knee arthroplasty before and after surgery.

OBJECTIVE The aim of this study was to compare the sleep quality of patients who underwent total knee arthroplasty before and after the surgery and analyze the effect of total knee arthroplasty on sleep quality. METHODS The study included 42 patients (32 females, 10 males) who underwent total knee arthroplasty for primary knee osteoarthritis. For each patient the preoperative 1 day and postoperative 3 months results of Pittsburgh Sleep Quality Index (PSQI) and 100-mm visual analogue scale (VAS) were compared. RESULTS The preoperative mean PSQI was 9. VAS score decreased in 97.6% of the patients, while sleep quality increased in 78.6%. 85.7% of the patients reported to have less episodes of pain related sleep disturbances. While both the PSQI and VAS improved after the surgery, there was no correlation between the parameters (p>0.05). CONCLUSION Our results suggested that total knee arthroplasty surgery relieves pain and improves sleep quality. The improvement in sleep quality does not appear to be related to pain relief.

Three-dimensional finite element analysis used to compare six different methods of syndesmosis fixation with 3.5- or 4.5-mm titanium screws: a biomechanical study.

BACKGROUND Use of thicker and longer (four cortices) screws or of multiple screws seems to be more stable and efficient for syndesmosis fixation. METHODS A three-dimensional finite element model of an ankle was constructed from serial axial sections from an existing two-dimensional computed tomographic image. Constructions of syndesmosis fixation with 3.5-mm single tricortical, 3.5-mm single quadricortical, 3.5-mm double tricortical, 3.5-mm double quadricortical, 4.5-mm single tricortical, and 4.5-mm single quadricortical screws were performed on this model. Physiologic loads approximating those during stance phase normal walking were applied to this ankle system. Stress values on the screws using the six fixation methods were compared. RESULTS The highest maximum stress was determined over 3.5-mm cortical screws applied as single quadricortical, and the lowest maximum stress was determined over the 4.5-mm cortical screw applied as single quadricortical. Stress on the 3.5-mm single screw with quadricortical application was found to be higher than that with tricortical application and also compared with the 4.5-mm quadricortical screw application. Differences between the 4.5-mm single tricortical and quadricortical screws and between the 3.5-mm single tricortical and 3.5-mm double tricortical screw applications were not significant. CONCLUSIONS Quadricortical application of 3.5-mm single screws and tricortical application of 3.5-mm double cortical screws are not good choices for syndesmosis fixation. If the plan is tricortical application, a 3.5-mm single cortical screw is adequate. If quadricortical application of syndesmosis fixation is planned, a 4.5-mm cortical screw should be used.

Hallux valgus deformity correction without fusion in children with cerebral palsy.

This study aimed to evaluate the outcomes of nonarthrodesis surgical treatment of hallux valgus (HV) deformity in children with cerebral palsy using radiographic and gait analysis parameters. There were 25 patients who had hallux valgus correction in 39 feet. The mean age at surgery was 15±2.8 years and the mean follow-up duration was 14.6 months. The first metatarsal osteotomy was performed in nine feet, bunionectomy in 25 feet, and Aiken osteotomy in 32 feet. None had metatarsophalangeal joint fusion. We observed a significant correlation between HV correction and other foot and ankle gait parameters. Our study showed correction of HV deformity at short-term follow-up without fusion of the metatarsophalangeal joint. Level of evidence: Level IV Therapeutic Studies.

Diagnostic efficacy of standard knee magnetic resonance imaging and radiography in evaluating integrity of anterior cruciate ligament before unicompartmental knee arthroplasty

OBJECTIVE The purpose of this study was to investigate the diagnostic efficacy of standard magnetic resonance imaging (MRI) and plain radiographs in determining the status of anterior cruciate ligament (ACL) for surgical decision-making processes in cases of medial unicompartmental knee arthroplasty (UKA). METHODS A total of 59 knees of 36 consecutive patients who underwent knee replacement surgery were analyzed retrospectively. MRI scans were assessed independently by 3 observers (radiologists), while the plain radiographs were evaluated by an independent radiologist. Results were compared with the intraoperative ACL status. Cross tabulation was used for descriptive statistics to analyze sensitivity, specificity, and accuracy of MRI and plain radiographs. RESULTS When the same observer assessed and classified the MRI twice, the reproducibility of the classification system varied from moderate to excellent. However, the interobserver concordance was moderate. The sensitivity of MRI was 73% and the specificity was 81%, while the sensitivity and specificity of plain radiographs was 36% and 79%, respectively. The accuracy of MRI was 80%, while that of the radiographs was 71%. CONCLUSION Detection of intact ACL may be possible on available plain radiographs without necessity for additional means such as MRI, which may cause increase costs and loss of time. In cases where there is uncertainty regarding ACL integrity in degenerative knees, although standard MRI provides additional information on ACL status, it is not of sufficient diagnostic value.

Comment on "compression screw fixation of the syndesmosis".

Dear Editor, We read with interest the article titled “Compression Screw Fixation of the Syndesmosis” by Darwish et al. The authors conducted a study to determine whether lag screws would generate greater syndesmosis compression and maintain a smaller medial clear space than tricortical screws during the course of cyclically applied mechanical challenges to the fixation. They also investigated if 4.5-mm or 3.5-mm lag screws would show better performance for measures of reduction. We believe that this is an important topic for study, but question some of the basic study design methodology. They stated that because in clinical practice the limb is largely protected from weight-bearing postoperatively, they chose a more direct method of medial and lateral cyclic loading for provoking diastasis to focus on the resistance of the screws to pulling out. First of all, we believe that this point of view is not exactly true. Many studies suggest that screws should be removed 6 to 8 weeks after a 4-cortical fixation, and even routine removal is probably not necessary after a 3-cortical fixation. If a stable osteosynthesis is achieved with placement of a syndesmotic screw, weight-bearing in plaster cast could be allowed. Moreover the authors stated that they did not use a model of axial compression, because the syndesmosis does not undergo any loading during the period of immobilization in cast. Suggesting that the point of view is true, the syndesmosis does not undergo any kind of stresses as described in the text, either. Even with ankle dorsiflexion, the distal fibula moves proximally and posteriorly and rotates externally. Physiological loads occur under anatomical circumstances, thus simulations for those should also contain the appropriate model of physiological loading. In addition, in our opinion authors applied maximum torque as much as possible to tighten the lag screws, but in clinical practice it is inappropriate because overtightening the syndesmosis may cause complications such as restricted range of motion (ROM) of ankle, fibular fracture, and so on. Besides, because the anterior aspect of the talus is wider than the posterior aspect, many textbooks describe fixation of the syndesmosis with the foot in dorsiflexion to prevent overcompression. Aim of syndesmosis fixation is not compression of syndesmosis, but holding the distal tibiofibular joint in reduced position during the healing of disrupted ligaments. This can be achieved by the screw that can optimally resist both deformation and pull-out forces generated during passive ROM and partial weight-bearing as well. It is a well-known fact that the pull-out strength of a screw is directly proportional to the thread diameter of it. Moreover, there is not any evidence-based data that more compression leads to better clinical results. Thus, we believe that the results found by the authors are not feasible in clinical practice.