Pyrocarbon unipolar radial head prosthesis: clinical and radiologic outcomes at long-term follow-up.

BACKGROUND: Several studies have already reported good short-term results with a pyrocarbon unipolar radial head prosthesis (Pyc-uRHP). The aim was to evaluate the evolution from mid- to long-term clinical and radiographic outcomes of a Pyc-uRHP. METHODS: This was a retrospective, single-center study. We followed up all the patients who underwent Pyc-uRHP surgery in our original study at 2 years of follow-up (52 patients), reaching a minimum of 7 years of clinical and radiologic follow-up. This study included 26 patients who underwent a clinical examination assessing mobility, the Mayo Elbow Performance Score, and the visual analog scale score and radiologic evaluation with anteroposterior and profile radiographs at a mean follow-up of 110 months (range, 78-162 months). The radiologic study analyzed signs of proximal osteolysis, stem loosening, capitellar wear, and humeroulnar osteoarthritis. RESULTS: No patients required revision. Eight patients required reoperation: coronoid screw removal in 1 and arthrolysis for stiffness in 7. The mean time to reoperation was 11 months. The mean Mayo Elbow Performance Score at last follow-up was 96 ± 9 (of 100), with a pain score of 42 ± 7 (of 45), mobility score of 19 ± 2 (of 20), stability score of 10 (of 10), and function score of 25 (of 25). Comparison with clinical data from the mid-term delay did not reveal any significant difference. All patients presented with proximal osteolysis around the neck but without progression. No stem loosening was noted. The rates of humeroulnar osteoarthritis (12% at mid-term vs. 80% at last follow-up, P < .0001) and capitellar lesions (34% at mid-term vs. 80% at last follow-up, P = .001) increased significantly. CONCLUSION: We have shown that a Pyc-uRHP at 9 years' follow-up provided stable and satisfactory clinical results. Osteolysis of the radial neck was always present but it did not evolve, and no stem loosening was noted. Finally, we have shown a clear worsening of radiologic humeroulnar osteoarthritis and capitellar lesions that remained asymptomatic.

Results of radial head prostheses implanted during Essex-Lopresti syndrome in multicentric study.

AIMS: The aim was to evaluate the results of radial head prostheses (RHP) in Essex-Lopresti injury (ELI) and to compare results after RHP between acute and chronic ELI. PATIENTS AND METHODS: Thirty-one patients treated with RHP for ELI were selected from a multicenter retrospective series of 310 RHP, with follow-up greater than two years. Two groups were acute ELI group (n=19, average diagnosis = 5+/-9 days) and chronic ELI group (n=12, average diagnosis 8.4+/-7.1 months). RHP was associated in some cases with K-wires: during acute ELI to stabilize the distal radio-ulnar joint (n=4) or during chronic ELI with ulnar osteotomy or palliative surgery (n=4). Clinical and radiologic evaluation was performed including analysis of the complications and revisions rates, pain level, range of motion, and MEPS (Mayo Elbow Performance Score) and DASH score (Disabilities of the Arm, Shoulder and Hand). RESULTS: At last follow-up (71+/-38 months), survival of RHP in the acute ELI group was 84% (16/19) and 92% (11/12) in the chronic ELI group without statistically significant difference. Flexion (acute=131degrees+/-13.4 vs chronic=22+/-12.8, p=0.041) and supination (ELI=71+/-16.8 vs chronic=58+/-17.4; p=0.045) were better in acute ELI group. The DASH score was also better in the acute group (15+/-9.1 versus 24+/-15.2, p=0.048). There was more advanced stage of humero-radial osteoarthritis in the chronic ELI group (0.7+/-0.5 versus 1.4+/-0.6, p=0.041). CONCLUSION: RHP in acute ELIs provide better clinical results, although RHPs are part of the therapeutic arsenal to treat chronic ELI.

Clinical and radiologic outcomes of pyrocarbon radial head prosthesis: midterm results.

BACKGROUND: The modular pyrocarbon (MoPyC) radial head prosthesis (Tornier, Saint-Ismier, France) is a monoblock modular radial head prosthesis. This study assessed midterm outcomes after implantation of the prosthesis. MATERIALS: A retrospective study was conducted of a consecutive cohort of 65 patients who underwent radial head replacement with the MoPyC prosthesis from January 2006 to April 2013. Indications were fractures, early or late failures from orthopedic or fixation treatments, and revisions after another implant. Patients were observed for >2 years for range of motion, pain, and stability; function by the Mayo Elbow Performance Score (total score, 100) and grip strength were assessed. Quality of stem implantation, bone resorption around the neck, and periprosthetic lucency were noted and quantified on radiographs. Capitellum shape and density as well as humeroulnar aspect (river delta sign) were evaluated. Complications and revision procedures were noted. RESULTS: We evaluated 52 of 65 patients (mean follow-up, 46 ± 20 months; range, 24-108). The Mayo Elbow Performance Score was 96 ± 7; pain score, 42 ± 7/45; and motion score, 18 ± 2/20. Function and stability were excellent. Radiology revealed 92% of patients with cortical resorption around the neck without mechanical failure. Bone resorption was mostly anterior and lateral; it resolved within the first year and thereafter was stable. Eight patients underwent revision surgery for stiffness. No implant failures were noted. CONCLUSION: Results of the MoPyC radial head prosthesis appear to be satisfactory. Bone resorption around the neck (stress shielding) is frequent and stable after 1 year and does not impair stem fixation. The MoPyC prosthesis appears to be a reliable solution for replacing the radial head.

Stability of cluster solutions in a cooperative consumer chain model.

We study a cooperative consumer chain model which consists of one producer and two consumers. It is an extension of the Schnakenberg model suggested in Gierer and Meinhardt [Kybernetik (Berlin), 12:30-39, 1972] and Schnakenberg (J Theor Biol, 81:389-400, 1979) for which there is only one producer and one consumer. In this consumer chain model there is a middle component which plays a hybrid role: it acts both as consumer and as producer. It is assumed that the producer diffuses much faster than the first consumer and the first consumer much faster than the second consumer. The system also serves as a model for a sequence of irreversible autocatalytic reactions in a container which is in contact with a well-stirred reservoir. In the small diffusion limit we construct cluster solutions in an interval which have the following properties: The spatial profile of the third component is a spike. The profile for the middle component is that of two partial spikes connected by a thin transition layer. The first component in leading order is given by a Green's function. In this profile multiple scales are involved: The spikes for the middle component are on the small scale, the spike for the third on the very small scale, the width of the transition layer for the middle component is between the small and the very small scale. The first component acts on the large scale. To the best of our knowledge, this type of spiky pattern has never before been studied rigorously. It is shown that, if the feedrates are small enough, there exist two such patterns which differ by their amplitudes.We also study the stability properties of these cluster solutions. We use a rigorous analysis to investigate the linearized operator around cluster solutions which is based on nonlocal eigenvalue problems and rigorous asymptotic analysis. The following result is established: If the time-relaxation constants are small enough, one cluster solution is stable and the other one is unstable. The instability arises through large eigenvalues of order O1. Further, there are small eigenvalues of order o1 which do not cause any instabilities. Our approach requires some new ideas: (i) The analysis of the large eigenvalues of order O1 leads to a novel system of nonlocal eigenvalue problems with inhomogeneous Robin boundary conditions whose stability properties have been investigated rigorously. (ii) The analysis of the small eigenvalues of order o1 needs a careful study of the interaction of two small length scales and is based on a suitable inner/outer expansion with rigorous error analysis. It is found that the order of these small eigenvalues is given by the smallest diffusion constant ε2(2).

Can surgeons predict what makes a good hemiarthroplasty for fracture?

BACKGROUND: The purposes of this study were (1) to identify the risk factors for tuberosity complications and poor functional outcomes and (2) to compare a standard humeral stem with a fracture-specific humeral stem in hemiarthroplasty for the treatment of 3- and 4-part proximal humeral fractures. METHODS: We retrospectively reviewed the cases of 60 consecutively operated patients (61 shoulders) using radiographs and computed tomography scans. There were 56 displaced four-part and 5 three-part fractures. The technique was standardized for prosthesis positioning in height and retroversion and for tuberosity fixation. A conventional standard stem was implanted in the first 31 shoulders (group A), and a specific fracture stem was implanted in the next 30 shoulders (group B). The sample size needed for comparison was predetermined with an a priori power analysis. The mean follow-up period was 64 months (range, 24 to 150 months). RESULTS: At the last follow-up, the greater tuberosity was healed in an adequate (anatomic) position in 45% of the patients in group A (14 of 31) and 87% of those in group B (26 of 30) (P = .0001). Active forward elevation, active external rotation, and the Constant score were significantly better with fracture stems (136°, 34°, and 68 points, respectively) than with conventional stems (113°, 23°, and 58 points, respectively) (P < .0001). Regardless of the type of implant used, patients aged 75 years or older and women had significantly lower functional results and higher rates of tuberosity complications (P < .0001). CONCLUSION: Good functional outcomes can be anticipated after hemiarthroplasty for proximal humeral fractures if the greater tuberosity is anatomically positioned (ie, lateral to the stem) and healed around the prosthesis. The use of a specific fracture stem allows to double the rate of tuberosity healing compared to a conventional stem (87% vs. 45%), decreases complications and improves shoulder function. Risk factors associated with poor functional results and anatomic failures are (1) patient age (≥75 years), (2) patient gender (women), and (3) use of a conventional (bulky) stem.

Comparative study of a Y- anatomical and innovative locking plate versus double plate for supracondylar humeral fracture.

INTRODUCTION: There is no "gold standard" for the type of plate to be used for distal extra-articular humeral fractures; the most used is plating of each column. The objective was to evaluate the short-term clinical and radiological results of a Y- anatomical and innovative locking plate (YALP). HYPOTHESIS: The hypothesis is: this anatomical and innovative locking plate will produce satisfactory and reliable results on extra-articular distal humerus fracture superior to double plate fixation. MATERIALS AND METHODS: In a retrospective observational multicenter study, all patients with a distal humerus fracture type 13 A2.2 according to AO classification fixed with a new Y-plate (YALP) were compared to the results of double plate fixation for the same type of fracture. With a follow-up of more than 12 months, the objective and subjective clinical elbow criteria as well as the overall function of the upper limb and radiological assessment were collected. RESULTS: With an average follow up of 24±11 months, 26 patients met the inclusion criteria and received a YALP and 24 patients received double plate. All patients whose fracture had healed except one were pain-free (mean VAS 0.3±0.6). All patients had good subjective results (mean SEV 96%±4). Elbow function was excellent (mean total MEPS 96±4) with normal triceps strength (23/24 patients had a triceps strength graded 5/5 and one patient 4/5) and range of motion (flexion 139±8, extension -7±8 and pronosupination greater than 155 degrees). The operating time was shorter in the YALP group (84 ± 23minutes versus 97 ± 28minutes, p=0.03). The double plate group had more complications; the overall complication rate was significantly higher (p=0.02) in the double 90-degree plate group (12/24, 50%) with four nonunions, four symptomatic ulnar nerves, three hardware removals for pain and one radial nerve injury versus 5/26 complications (19%, p=0.02) in the Y-plate group: one iliac graft for nonunion, 1 plate removal due to functional discomfort, 1 twisted YALP, 1 broke interfragmentary screw and one symptomatic ulnar nerve. DASH, SEV, MEPS scores and flexion-extension range were better in the YALP group. DISCUSSION: YALP produces satisfactory results in supracondylar fractures of the distal humerus. The results of YALP appear to be better than the results with two 90° plates for the same fracture type with a shorter operative time and easier management of fractures with proximal diaphyseal extension. LEVEL OF EVIDENCE: III; case control study.

Flow-distributed spikes for Schnakenberg kinetics.

We study a system of reaction-diffusion-convection equations which combine a reaction-diffusion system with Schnakenberg kinetics and the convective flow equations. It serves as a simple model for flow-distributed pattern formation. We show how the choice of boundary conditions and the size of the flow influence the positions of the emerging spiky patterns and give conditions when they are shifted to the right or to the left. Further, we analyze the shape and prove the stability of the spikes. This paper is the first providing a rigorous analysis of spiky patterns for reaction-diffusion systems coupled with convective flow. The importance of these results for biological applications, in particular the formation of left-right asymmetry in the mouse, is indicated.

Double incision repair technique with immediate mobilization for acute distal biceps tendon ruptures provides good results after 2 years in active patients.

INTRODUCTION: Surgical treatment of distal biceps tendon ruptures is recommended in an active population to avoid loss of strength, especially in supination and flexion. HYPOTHESIS: A double incision repair technique with immediate postoperative mobilization for acute distal biceps tendon ruptures is safe and provides good results after 2 years in active patients. MATERIAL AND METHODS: Seventy-four men (47±7 years) with acute tears of the distal biceps tendon tears were included in this retrospective single-center study. All patients were operated using the double-incision repair technique described by Morrey. The tendon was inserted with transosseous sutures into the biceps tuberosity. Patients were allowed to perform immediate postoperative active mobilization. A minimum follow-up of two years was required including clinical and radiological evaluation. RESULTS: Sixteen patients were lost to follow up leaving 58 (78%) patients for analysis with a mean follow-up of 53±19 months. At final follow-up, the mean evaluation for pain on the VAS scale was 0.22±0.7. Mean range of motion results included extension -1°±2°, flexion 138°±6°, pronation 72°±16° and supination 81°±10°. The strength ratio in flexion was 94±8% and in supination 90.5±12% compared to the contralateral limb. Subjective elbow value and DASH score were respectively 94±6% and 7.5±9%. All patients were satisfied or very satisfied and all except one returned to their previous sport. We noticed 2 heterotopic ossifications and one patient needed a reoperation for a radioulnar synostosis. Neither re-rupture nor nerve injury were observed. DISCUSSION: A double incision technique for distal biceps tendon repair is a minimally invasive procedure with reliable results. Morrey's modification of the initial procedure associated with early mobilization is associated with a low rate of complications and limited the occurrence of synostosis or ossifications. LEVEL OF EVIDENCE: IV, case series, with no comparison group.

Stable spike clusters for the precursor Gierer-Meinhardt system in R 2.

We consider the Gierer-Meinhardt system with small inhibitor diffusivity, very small activator diffusivity and a precursor inhomogeneity. For any given positive integer k we construct a spike cluster consisting of k spikes which all approach the same nondegenerate local minimum point of the precursor inhomogeneity. We show that this spike cluster can be linearly stable. In particular, we show the existence of spike clusters for spikes located at the vertices of a polygon with or without centre. Further, the cluster without centre is stable for up to three spikes, whereas the cluster with centre is stable for up to six spikes. The main idea underpinning these stable spike clusters is the following: due to the small inhibitor diffusivity the interaction between spikes is repulsive, and the spikes are attracted towards the local minimum point of the precursor inhomogeneity. Combining these two effects can lead to an equilibrium of spike positions within the cluster such that the cluster is linearly stable.

The intermetatarsal articular facet of the first metatarsal bone in humans: a derived trait unique within primates.

The occurrence and morphology of an intermetatarsal facet of the first metatarsal bone have been investigated in a series of 306 nonhuman primates representative of 40 genera, and in a series of 412 human metatarsal bones (dried bones) (215 left, 197 right). In nonhuman primates, no case of intermetatarsal facet was observed in the 306 first metatarsal bones studied. In humans, a well-defined intermetatarsal facet was observed in 127 out of the 412 bones (30.8%); no significant difference was observed between the left and right sides. The shape of the facet was elliptical, more or less elongated; it had a mean major axis (height) of 10.7 mm, and a mean minor axis (width) of 6.1 mm (extremes: 5 x 3 mm and 17 x 10 mm). The facet was located in the dorsal third of the lateral side of the first metatarsal in 103 out of 127 cases (81.1%), and in the middle third in 24 out of 127 cases (18.9%); it was never observed in the plantar third. The intermetatarsal facet was in connection with the proximal articular facet for the medial cuneiform in 68 out of 127 cases (53.5%), and it was separated from the proximal facet by a small nonarticular area or groove in 59 out of 127 cases (46.5%). The present observations suggest that the human first intermetatarsal facet is a derived trait unique within primates (autapomorphy) which is present in approximately one third of individuals. The appearance of this new articular facet in human evolution seems clearly related to the morphological modifications of the foot due to the acquisition of bipedalism, and more particularly to the loss of abductability of the hallux and its permanent adduction.