Biomechanical analysis of combi-hole locking compression plate during fracture healing: A numerical study of screw configuration.

Locking compression plates (LCPs) have become a widely used option for treating femur bone fractures. However, the optimal screw configuration with combi-holes remains a subject of debate. The study aims to create a time-dependent finite element (FE) model to assess the impacts of different screw configurations on LCP fixation stiffness and healing efficiency across four healing stages during a complete fracture healing process. To simulate the healing process, we integrated a time-dependent callus formation mechanism into a FE model of the LCP with combi-holes. Three screw configuration parameters, namely working length, screw number, and screw position, were investigated. Increasing the working length negatively affected axial stiffness and healing efficiency (p < 0.001), while screw number or position had no significant impact (p > 0.01). The time-dependent model displayed a moderate correlation with the conventional time-independent model for axial stiffness and healing efficiency (ρ ≥ 0.733, p ≤ 0.025). The highest healing efficiency (95.2%) was observed in screw configuration C125 during the 4-8-week period. The results provide insights into managing fractures using LCPs with combi-holes over an extended duration. Under axial compressive loading conditions, the use of the C125 screw configuration can enhance callus formation during the 4-12-week period for transverse fractures. When employing the C12345 configuration, it becomes crucial to avoid overconstraint during the 4-8-week period.

Experimental testing of fracture fixation plates: A review.

Metal and its alloys have been predominantly used in fracture fixation for centuries, but new materials such as composites and polymers have begun to see clinical use for fracture fixation during the past couple of decades. Along with the emerging of new materials, tribological issues, especially debris, have become a growing concern for fracture fixation plates. This article for the first time systematically reviews the most recent biomechanical research, with a focus on experimental testing, of those plates within ScienceDirect and PubMed databases. Based on the search criteria, a total of 5449 papers were retrieved, which were then further filtered to exclude nonrelevant, duplicate or non-accessible full article papers. In the end, a total of 83 papers were reviewed. In experimental testing plates, screws and simulated bones or cadaver bones are employed to build a fixation construct in order to test the strength and stability of different plate and screw configurations. The test set-up conditions and conclusions are well documented and summarised here, including fracture gap size, types of bones deployed, as well as the applied load, test speed and test ending criteria. However, research on long term plate usage was very limited. It is also discovered that there is very limited experimental research around the tribological behaviour particularly on the debris' generation, collection and characterisation. In addition, there is no identified standard studying debris of fracture fixation plate. Therefore, the authors suggested the generation of a suite of tribological testing standards on fracture fixation plate and screws in the aim to answer key questions around the debris from fracture fixation plate of new materials or new design and ultimately to provide an insight on how to reduce the risks of debris-related osteolysis, inflammation and aseptic loosening.

Demystifying Palmar Midcarpal Instability.

Palmar midcarpal instability is an uncommon condition diagnosed clinically with a painful pathognomonic clunk on terminal ulnar deviation of the wrist. Various causes have been described, but congenital laxity of the carpal ligaments is thought to be a key contributor. Treatment commences with conservative measures. This includes proprioceptive training based on more recent concepts on the sensorimotor function of the wrist. When these measures plateau, surgery is considered. The lack of high-level evidence and consensus on its cause continue to hamper our understanding and knowledge of this condition. The purpose of this review is to examine the current evidence to conceptualize this mysterious, yet infrequent phenomenon, and to provide an algorithm on its management.

Biodegradable magnesium alloys for orthopaedic applications.

There is increasing interest in the development of bone repair materials for biomedical applications. Magnesium (Mg)-based alloys have a natural ability to biodegrade because they corrode in aqueous media; they are thus promising materials for orthopaedic device applications in that the need for a secondary surgical operation to remove the implant can be eliminated. Notably, Mg has superior biocompatibility because Mg is found in the human body in abundance. Moreover, Mg alloys have a low elastic modulus, close to that of natural bone, which limits stress shielding. However, there are still some challenges for Mg-based fracture fixation. The degradation of Mg alloys in biological fluids can be too rapid, resulting in a loss of mechanical integrity before complete healing of the bone fracture. In order to achieve an appropriate combination of bio-corrosion and mechanical performance, the microstructure needs to be tailored properly by appropriate alloy design, as well as the use of strengthening processes and manufacturing techniques. This review covers the evolution, current strategies and future perspectives of Mg-based orthopaedic implants.

Using three-dimensional rapid prototyping in the design and development of orthopaedic screws in standardised pull-out tests.

The majority of orthopaedic screws are designed, tested and manufactured by existing orthopaedics companies and are predominantly developed with healthy bone in mind. The timescales and costs involved in the development of a new screw design, for example, for osteoporotic bone, are high. In this study, standard wood screws were used to analyse the concept of using three-dimensional printing, or rapid prototyping, as a viable stage of development in the design of a new bone screw. Six wood screws were reverse engineered and printed in polymeric material using stereolithography. Three of the designs were also printed in Ti6Al4V using direct metal laser sintering; however, these were not of sufficient quality to test further. Both the original metal screws (metal) and polymeric rapid prototyping screws were then tested using standard pull-out tests from low-density polyurethane blocks (Sawbones). Results showed the highest pull-out strengths for screws with the longest thread length and the smallest inner diameter. Of the six screw designs tested, five showed no more than a 17% variance between the metal and rapid prototyping results. A similar pattern of results was shown between the screw designs for both the metal and rapid prototyping screws in five of the six cases. While not producing fully comparable pull-out results to orthopaedic screws, the results from this study do provide evidence of the potential usefulness and cost-effectiveness of rapid prototyping in the early stages of design and testing of orthopaedic screws.

Soft tissue stabilization for palmar midcarpal instability using a palmaris longus tendon graft.

PURPOSE: To report the results of a technique of soft tissue stabilization for palmar midcarpal instability using a palmaris longus graft. METHODS: In patients' symptomatic wrists with palmar midcarpal instability that had failed conservative management, we used a dorsal approach and stabilized the hamate and triquetrum by reconstructing the dorsal triquetrohamate ligament. The palmaris longus tendon graft was fixed with bone anchors. Seven wrists in 6 patients were available for follow-up at a mean of 28 months (range, 17-37 mo). RESULTS: There was an overall meaningful improvement in function (mean preoperative Disabilities of the Arm, Shoulder, and Hand score, 49 preoperatively, 28 postoperatively). There was a significant increase in grip strength from 15 to 21 kg. At final follow-up, 2 patients had moderate pain. The others had mild or no pain. Four patients returned to their previous occupation or activity. Patients retained full pronation and supination. When compared with the normal side, flexion was reduced to 71%, extension to 81%, radial deviation to 90%, and ulnar deviation to 65% of the opposite side. Although the mean results show an improvement, one patient had a poor result with deterioration in Disabilities of the Arm, Shoulder, and Hand score in spite of a clinically stable wrist, and another had clinical evidence of recurrent instability during pregnancy. One patient had residual symptoms from a prominent bone anchor. CONCLUSIONS: Overall, this technique showed good medium-term results in most of our patients. It retained some midcarpal mobility, eliminated clunking in most patients, and provided a noteworthy improvement in grip strength and function. We continue to use this technique for patients with symptomatic midcarpal instability, but it requires further evaluation with larger patient numbers and a longer follow-up to assess its overall value.

Medium-term results of arthroscopic debridement and capsulectomy for the treatment of elbow osteoarthritis.

BACKGROUND: We retrospectively reviewed 20 patients (21 elbows) after arthroscopic debridement and capsulectomy of the elbow for primary osteoarthritis. We aimed to see if there was an improvement in pain, function, and range of movement in the medium-term. MATERIALS AND METHODS: Outcomes of 20 patients (18 men, 2 women) with primary osteoarthritis of the elbow (21 elbows) operated on by the senior surgeon were reviewed at a mean of 5.5 years postoperatively. Inclusion criteria were patients with undergoing arthroscopic debridement and capsulectomy after failure of previous conservative treatment. Exclusion criteria were patients undergoing additional intra-articular procedures at surgery and patients with post-traumatic or inflammatory arthritis. Mean age was 42 years (range, 22-79 years). Preoperatively, osteoarthritis was classified based on plain x-ray images. Functional outcome was assessed using preoperative and postoperative Disabilities of the Arm, Shoulder and Hand (DASH) scores, Mayo scores, and range of movement. RESULTS: Radiographically, osteoarthritis was assessed as class I in 9 elbows, class II in 10 elbows, and class III in 3 elbows. There was a mean significant improvement in DASH score from 34.0 to 12.7 (P < .05). This was true for all grades of osteoarthritis and significant for classes II and III (P < .05). Mayo scores postoperatively were "excellent" in 11 elbows, "good" in 5, "fair" in 4, and "poor" in 1. Nineteen of the 20 patients said they would have had the surgery again. CONCLUSION: Arthroscopic debridement and capsulectomy is an effective procedure for patients with primary osteoarthritis of the elbow. We propose this may work as a partial neurectomy to denervate pain sensation in the joint.

Surgical treatment of complex distal humeral fractures: functional outcome after internal fixation using precontoured anatomic plates.

HYPOTHESIS: Several studies have shown good results with internal fixation of distal humeral fractures; however, few have focused specifically on anatomic parallel plate fixation using the same implant and postoperative regimen. The purpose of this study was to determine the functional outcome after open reduction and internal fixation of these complex fractures using parallel precontoured anatomic plates. MATERIALS AND METHODS: This was a retrospective single-surgeon series involving 16 patients (12 women, 4 men) treated with a double-column parallel plating technique. Clinical assessment included the Mayo Elbow Performance Score (MEPS) and Disabilities of the Arm, Shoulder and Hand Score (DASH). Mean age was 43 years (range, 20-78 years). Average follow-up was 35 months. Four fractures were AO type A and 12 were AO type C. RESULTS: Union was achieved in all patients. There was no superficial or deep infection or hardware failure. Two patients required removal of plates for pain and prominence but not all screws could be completely removed. The mean flexion was 132 degrees and extension was 29 degrees . The mean DASH score was 46.1. Grip strength was 56% of the uninjured side. Mean flexion and extension force was 72% and 70%, respectively, of the uninjured elbow. The mean MEPS score was 72.3. DISCUSSION: Anatomically precontoured parallel plates are effective in achieving bony union with low implant failure with acceptable functional outcomes. However, screw extraction can be difficult when the implant is removed.

Biomechanical comparison of pull-out force of unicortical versus bicortical screws in proximal phalanges of the hand: a human cadaveric study.

BACKGROUND: Bicortical fixation of proximal phalangeal fractures may damage underlying flexor tendons secondary to drilling and screw protrusion in the dorsal-ventral direction. The aim of this study was to measure and compare the pull-out force of unicortical screws compared to bicortical screws in human cadaveric proximal phalanges to identify optimal configuration for internal fixation. METHODS: Forty proximal phalanges were harvested. Bicortical and unicortical self tapping 1.7mm screws were inserted into paired phalanges at the distal and proximal metaphysis and at the mid-diaphysis placed in the dorso-ventral direction. Pull-out force of unicortical and bicortical screws were measured and compared. FINDINGS: Bicortical screw pull-out force is significantly higher than that of unicortical screws in the dorsal-ventral direction. Pull-out strength of unicortical screws at the mid-diaphysis was significantly higher than the pull-out strength of bicortical screws at the proximal metaphysis (181.8N versus 31.5N, P<0.0001). INTERPRETATION: Diaphyseal fixation is stronger than metaphyseal for both unicortical and bicortical configurations. Unicortical mid-diaphyseal is stronger than bicortical proximal metaphyseal screw pull-out strength. This study provides biomechanical data that may be helpful for individualizing fracture fixation techniques at the proximal phalanx.

The mend of the bend-flexor pollicis longus tendon has an additional pulley distal to its point of angulation.

The tendon of flexor pollicis longus angulates at the trapezio-metacarpal joint level. The degree of angulation varies with extent of radial/ulnar deviation (Rack and Ross [1984] J. Physiol. 351:99-110). We report a fibrous pulley at this level that helps stabilize the tendon and facilitates its action. The morphology of the pulley is described. We believe that it has an important role to play in the unique function of the tendon facilitating the movement of the thumb perpendicular to the plane of the thumbnail.

Accuracy of direct magnetic resonance arthrography in the diagnosis of triangular fibrocartilage complex tears of the wrist.

The aim of this study was to assess the value of direct magnetic resonance (MR) arthrography of the wrist for detecting full-thickness tears of the triangular fibrocartilage complex (TFCC). Twenty-four consecutive patients who had ulnar-sided wrist pain and clinical suspicion of TFCC tear were included in the study. All patients underwent direct MR arthrography and then wrist arthroscopy, and the results of MR arthrography were compared with the arthroscopic findings. The positive predictive value of MR arthrography in detecting TFCC full-thickness tear was 0.95, and the negative predictive value was 0.50. The sensitivity of MR arthrography in detecting a TFCC full-thickness tear was 74% (15/19), and specificity was 80% (4/5). The overall accuracy of MR arthrography in detecting a full-thickness tear of the TFCC in our study was 79% (19/24). We believe that diagnosis of tears in the TFCC by direct MR arthrography is not entirely satisfactory, although MR arthrography has a high positive predictive value for detecting TFCC tears. Negative results of MR arthrography in patients with clinical suspicion of TFCC tear should be interpreted with caution.

Can radiological results be surrogate markers of functional outcome in distal radial extra-articular fractures?

The purpose of this study was to evaluate the relationship between radiological and functional results in patients with extra-articular fractures of the distal radius. We conducted a prospective study of radiological and functional assessment in 95 consecutively selected extra-articular distal radius fractures. There were two patient groups: more than 60 and less than 60 years of age. The final fracture union radiographs were analysed for their functional outcome using the Michigan Hand Outcomes Questionnaire (MHQ) and the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire. In patients with acceptable radiological results, 62% (MHQ group) and 72% (DASH group) of patients had satisfactory functional outcome. Analysing patients with satisfactory functional results, 56% (MHQ group) and 59% (DASH group) had satisfactory radiological results. There was a higher proportion of patients with better functional results, despite poor radiological results, in both of the age groups. There was a statistically significant correlation between satisfactory radial tilt and functional outcome in the younger patients. In the older age group, patients with satisfactory radiological results had satisfactory functional outcome (p<0.05). However, in the older age group, satisfactory functional results were achieved, despite unsatisfactory radiological results.

Hook plate fixation for type II fractures of the lateral end of the clavicle.

Management of type II fractures of the lateral end of the clavicle is controversial. Different treatment options have been advocated with varying results. In this paper, we report the results of a group of 22 patients who underwent hook plate fixation for these fractures between 1997 and 2004. The mean follow-up was 39 months. There were 4 significant complications. Twenty-one patients regained their preinjury level of activity, and 19 patients were satisfied with their outcome. We recommend hook plate fixation as an acceptable alternative method for the treatment of type II fractures of the lateral end of the clavicle.