Systematic use of short unicortical epiphyseal locking screws versus full-length unicortical locking screws in distal radius fracture volar plating: A prospective and comparative study.

PURPOSE: Volar locking plates, used in distal radius fracture (DRF), present a risk of injuring extensor tendons with screws penetrating the dorsal cortex of the radius. Actually, even when aiming to use maximum-length unicortical locking screws, some still could be bicortical. We hypothesize the use of only short unicortical screws would allow a proper stabilization of the radial epiphysis without the risk of dorsal cortex penetration. MATERIALS AND METHODS: A prospective monocentric non-randomized study was conducted. Patients with DRF (excepted for partial dorsal joint fractures) were treated in group A with short locking epiphyseal screws (16 mm for females, 18 mm for males) and in group B with full-length unicortical locking screws. Ultrasound was done 3 months postoperatively to evaluate the number and length of prominent dorsal screws. X-rays were performed after 6 weeks to assess stability according to volar tilt and radial inclination variations. RESULTS: There were 37 patients in group A and 39 in group B with 148 and 156 epiphyseal screws, respectively. In group A, there were 0% of dorsal penetrating screws against 6.5% (10 screws from 8 patients) in group B (p < 0.05). There was no significant difference for the stability between the groups: mean volar tilt variation ( - 0.6° vs. - 0.7°) and mean radial inclination variation ( - 0.4° vs. - 0.4°). CONCLUSION: For a same stability with volar locking plates for DRF, short epiphyseal locking screws should be preferred to full-length unicortical screws in order to prevent extensor tendon injuries. Based on 75% of distal radial average anteroposterior width for each sex, screw lengths of 16 mm for females and 18 mm for males seem to be the length to use. LEVEL OF EVIDENCE 2: Prospective, Comparisons made, non-randomized.

The differentiation of prehypertrophic into hypertrophic chondrocytes drives an OA-remodeling program and IL-34 expression.

OBJECTIVES: We hypothesize that chondrocytes from the deepest articular cartilage layer are pivotal in maintaining cartilage integrity and that the modification of their prehypertrophic phenotype to a hypertrophic phenotype will drive cartilage degradation in osteoarthritis. DESIGN: Murine immature articular chondrocytes (iMACs) were successively cultured into three different culture media to induce a progressive hypertrophic differentiation. Chondrocyte were phenotypically characterized by whole-genome microarray analysis. The expression of IL-34 and its receptors PTPRZ1 and CSF1R in chondrocytes and in human osteoarthritis tissues was assessed by RT-qPCR, ELISA and immunohistochemistry. The expression of bone remodeling and angiogenesis factors and the cell response to IL-1ß and IL-34 were investigated by RT-qPCR and ELISA. RESULTS: Whole-genome microarray analysis showed that iMACs, prehypertrophic and hypertrophic chondrocytes each displayed a specific phenotype. IL-1ß induced a stronger catabolic effect in prehypertrophic chondrocytes than in iMACs. Hypertrophic differentiation of prehypertrophic chondrocytes increased Bmp-2 (95%CI [0.78; 1.98]), Bmp-4 (95%CI [0.89; 1.59]), Cxcl12 (95%CI [2.19; 5.41]), CCL2 (95%CI [3.59; 11.86]), Mmp 3 (95%CI [10.29; 32.14]) and Vegf mRNA expression (95%CI [0.20; 1.74]). Microarray analysis identified IL-34, PTPRZ1 and CSFR1 as being strongly overexpressed in hypertrophic chondrocytes. IL-34 was released by human osteoarthritis cartilage; its receptors were expressed in human osteoarthritis tissues. IL-34 stimulated CCL2 and MMP13 in osteoblasts and hypertrophic chondrocytes but not in iMACs or prehypertrophic chondrocytes. CONCLUSION: Our results identify prehypertrophic chondrocytes as being potentially pivotal in the control of cartilage and subchondral bone integrity. Their differentiation into hypertrophic chondrocytes initiates a remodeling program in which IL-34 may be involved.

Balloon humeroplasty reconstruction for acute Hill-Sachs injury: A technical note.

Posterior Hill-Sachs humeral defects are present in 80% to 100% of cases of anterior shoulder dislocation and are a factor in recurrent instability. Several techniques have been described to fill the defect and avoid recurrence. We developed a percutaneous technique to fill the newly created defect in which a percutaneous balloon, analogous to the one used in vertebral kyphoplasty, is used to reduce the defect, which is then filled with calcium phosphate cement. One patient with an acute anterior dislocation of the shoulder with no previous history was treated using this method. Early imaging results showed adequate reduction of the defect and no cement resorption. The patient was followed for 12 months; he had normal function of the shoulder and no recurrent dislocation. Shoulder computed tomography (CT) arthrography with contrast after 3 months showed an intact capsule and no recurrence of the defect. While this technique is certainly in its infancy, we have demonstrated that emergency reduction of the defect in acute first occurrence anterior shoulder dislocation is feasible, helps to restore normal anatomy of the humeral head and leads to good clinical results. Whether it can improve clinical results and prevent recurrent shoulder dislocation remains to be evaluated.

New modalities of pain treatment after outpatient orthopaedic surgery.

Postoperative pain relief is one of the cornerstones of success of orthopaedic surgery. Development of new minimally-invasive surgical procedures, as well as improvements in pharmacological and local and regional techniques should result in optimal postoperative pain control for all patients. The analgesic strategy has to be efficient, with minimal side effects, and be easy to manage at home. Multimodal analgesia allows for a reduction of opiate use and thereby its side effects. Local and regional analgesia is a major component of this multimodal strategy, associated with optimal pain relief, even upon mobilization, and it has beneficial effects on postoperative recovery. Ultrasound guidance improves the success rate of distal nerve blocks and makes distal selective blockade possible, helping to preserve the limb's motility. Besides peripheral nerve blocks, local infiltration (incisional and/or intra-articular) is also important to consider. Duration of the nerve blockade is limited after a single injection. This must be taken into consideration to avoid the recurrence of pain when the patient returns home. Continuous perineural blocks using catheters are an option that can be easily managed at home with monitoring by home-care nurses. Extended-release liposomal bupivacaine and adjuvants such as dexamethasone could significantly enhance the duration of the sensory block, thereby reducing the indications for pain pumps. Non-pharmacological approaches, such as cryotherapy, hypnosis and acupuncture should not be ignored.

Characterization of diabetic osteoarthritic cartilage and role of high glucose environment on chondrocyte activation: toward pathophysiological delineation of diabetes mellitus-related osteoarthritis.

OBJECTIVE: To examine the relationship between osteoarthritis (OA) and type 2 diabetes mellitus (DM). METHODS: OA cartilage from DM and non-DM patients undergoing knee replacement were stimulated by IL-1ß for 24 h and release of interleukin-6 (IL-6) and prostaglandin E2 (PGE2) was measured. Primary cultured murine chondrocytes were stimulated for 24 and 72 h with or without IL-1ß (5 ng/mL) under normal-glucose (5.5 mM) or high-glucose (25 mM) conditions. The expression and release of pro-inflammatory mediators (IL-6, cyclooxygenase 2 [COX2]/PGE2) were analyzed by quantitative RT-PCR and ELISA/EIA. Glucose uptake was assessed with ((14)C)-2-deoxyglucose. Reactive oxygen species (ROS) and nitric oxide (NO) production were measured. To analyze the mechanism of IL-1ß-induced inflammation, cells were pretreated or treated with inhibitors of glucose transport (cytochalasin B), the polyol pathway (epalrestat), mitochondrial oxidative stress (MitoTEMPO) or nitric oxide synthase (l-NAME). RESULTS: With IL-1ß stimulation, IL-6 and PGE2 release was greater in human DM than non-DM OA cartilage (2.7- and 3-fold, respectively) (P < 0.05). In vitro, with IL-1ß stimulation, IL-6 and COX2 mRNA expression, IL-6 and PGE2 release, and ROS and NO production were greater under high-than normal-glucose conditions in cultured chondrocytes. IL-1ß-increased IL-6 release was reduced with cytochalasin B, epalrestat, L-NAME or MitoTEMPO treatment (-45%, -62%, -38% and -40%, respectively). CONCLUSION: OA cartilages from DM patients showed increased responsiveness to IL-1ß-induced inflammation. Accordingly, high glucose enhanced IL-1ß-induced inflammation in cultured chondrocytes via oxidative stress and the polyol pathway. High glucose and diabetes may thus participate in the increased inflammation in OA.

Comparison of fondaparinux with low molecular weight heparin for venous thromboembolism prevention in patients requiring rigid or semi-rigid immobilization for isolated non-surgical below-knee injury.

BACKGROUND: In several small studies, anticoagulant therapy reduced the incidence of venous thromboembolism (VTE) in patients with isolated lower-limb injuries. OBJECTIVES: To compare the efficacy and safety of fondaparinux 2.5 mg (1.5 mg in patients with a creatinine clearance between 30 and 50 mL min(-1) ) over nadroparin 2850 anti-factor Xa IU. PATIENTS AND METHODS: In this international, multicenter, randomized, open-label study, patients with an isolated non-surgical unilateral below-knee injury having at least one additional major risk factor for VTE and requiring, in the Investigator's opinion, rigid or semi-rigid immobilization for 21-45 days with thromboprophylaxis up to complete mobilization received subcutaneously once-daily either fondaparinux or nadroparin. The primary efficacy outcome was the composite of VTE (symptomatic or ultrasonographically detected asymptomatic deep vein thrombosis of the lower limb or symptomatic pulmonary embolism) and death up to complete mobilization. The main safety outcome was major bleeding. RESULTS: We randomized 1349 patients (mean age 46 years): 88.7% had a bone fracture, and 83.8% had a plaster cast fitted (mean duration of immobilization, 34 days). The primary efficacy outcome occurred in 15 of 584 patients (2.6%) in the fondaparinux group and 48 of 586 patients (8.2%) in the nadroparin group (odds ratio, 0.30; 95% confidence interval [CI], 0.15-0.54; P < 0.001). A single major bleed was experienced by fondaparinux-treated patients and none by nadroparin-treated patients. These results were maintained up to the end of follow-up. CONCLUSIONS: Fondaparinux 2.5 mg day(-1) may be a valuable therapeutic option over nadroparin 2850 anti-FXa IU day(-1) for preventing VTE after below-knee injury requiring prolonged immobilization in patients with additional risk factors.

Stress-induced signaling pathways in hyalin chondrocytes: inhibition by Avocado-Soybean Unsaponifiables (ASU).

OBJECTIVE: Avocado-Soybean Unsaponifiables (ASU) represent one of the most commonly used drugs for symptomatic osteoarthritis (OA). The mechanisms of its activities are still poorly understood. We investigate here the effects of ASU on signaling pathways in mouse or human chondrocytes. METHODS: Mouse or human chondrocytes stimulated with interleukin-1beta (IL1beta, 10 ng/ml) and cartilage submitted to a compressive mechanical stress (MS) were studied in the presence or absence of ASU (10 microg/ml). Nuclear factor kappaB (NF-kappaB) activation was assessed by immunoblot, using an I-kappa B alpha antibody, nuclear translocation of NF-kappaB using p65 antibody, and extra-cellular signal-regulated kinase (ERK)1/2 activation using phospho and ERK1/2 antibodies. The binding of the p50/p65 complex on DNA was studied by electrophoretic mobility shift assay. RESULTS: ASU decrease matrix metalloproteinases-3 and -13 expressions and Prostaglandin E(2) (PGE(2)) release in our model. The degradation of I-kappa B alpha is prevented in the presence of ASU as shown by the persistent expression of I-kappa B alpha protein in the cytosol when chondrocytes are stimulated by IL1beta or MS. Nuclear translocation of the NF-kappaB complex is shown by the decrease of the p65 protein from the cytosol, whereas p65 appears in the nucleus under IL1beta stimulation. This translocation is abolished in the presence of ASU. Moreover, bandshift experiments show an inhibition of the IL1beta-induced binding of p50/p65 complexes to NF-kappaB responsive elements in response to ASU. Finally, among the different mitogen-activated protein kinases known to be induced by IL1beta, ERK1/2 was the sole kinase inhibited by ASU. CONCLUSION: These results demonstrate that ASU express a unique range of activities, which could counteract deleterious processes involved in OA, such as inflammation.

[Total knee arthroplasty for recent severe fracture of the proximal tibial epiphysis in the elderly subject]. / Arthroplastie totale de genou pour fracture récente grave de l'épiphyse tibiale proximale chez le sujet âgé.

PURPOSE OF THE STUDY: Bone comminution, serious cartilage damage, and the poor mechanical quality of osteoporotic bone create a difficult challenge for osteosynthesis of joint fractures in the elderly subject. Poor results with certain hip, elbow and shoulder fractures have lead certain authors to propose emergency arthroplasty in selected cases. We report our experience with four knee arthroplasties implanted for recent severe fracture of the proximal tibial epiphysis in elderly subjects. MATERIAL AND METHODS: Four independent patients aged over 75 years presented a severe comminutive fracture of the proximal epiphysis of the tibia (Three Schatzker 5, one Schatzker 4). After obtaining the patients' informed consent, early knee arthroplasty was performed. A long-stem cemented tibial piece was used on which the epiphysis was reconstructed. Implants providing support for ligament deficits were used in all cases. Immediate weight-bearing was authorized. RESULTS: Follow-up ranged from two to seven years. The IKS function score (15, 60, 100, 100) depended on the patient's general status. The IKS knee score was excellent for three knees (90, 95, 95), and fair in one (45). Re-operations were not needed in any of the patients. All x-rays showed bone healing with correctly aligned limbs (less than 2 degrees deformation). There were no lucent lines at last follow-up. DISCUSSION: Early arthroplasty for complex fractures of the proximal epiphysis of the tibia is a realistic option. Using a cemented long-stem tibial piece ensures primary stability sufficient for early weight-bearing before bone healing. Use of a constrained prosthesis, or better a hinged prosthesis, can be questioned but avoids the difficulty of ligament balance on an osteoporotic knee with a destroyed joint surface. None of the patients required reoperation and the results in terms of pain were excellent. The overall outcome depends on the general status of the patient.

[Quality of information transfer for informed consent: an experimental study in 21 patients]. / Difficultés du transfert d'information en vue d'un consentement éclairé: etude expérimentale chez 21 patients.

PURPOSE OF THE STUDY: Delivering information to the patient, an ethical obligation recognized for years, has recently become a legal obligation. Proof of information delivery has become the legal responsibility of the surgeon. We conducted a prospective study to evaluate the quality of information transfer by assessing patient comprehension of information delivered in an orthopedic surgery unit. MATERIAL AND METHODS: All patients attending consultations before undergoing arthroscopic treatment for rotator cuff tendinopathy were enrolled in this study when the consultation was conducted in the presence of an observer. Two questionnaires, one for the patient and one for the surgeon, were used to collect given information about the pathological condition, the modalities of treatment, and the expected results of the treatment and its complications. RESULTS: All 21 patients included in the study considered they had been well informed and that they had understood their pathological condition as well as the complications of the proposed treatment. However, agreement between their stated comprehension and the information delivered was poor, varying from 15 to 50%. Furthermore, 90% of the patients stated they had understood the potential complications of the surgical procedure, despite the fact that the consulting surgeons had not (generally) provided information on such complications. DISCUSSION: There is a gap between what the surgeon says (or thinks he/she says) and what the patient understands. Potential biases in this study (non-unbiased observer) might explain this discordance which was probably related to the unequal relationship between the patient and the physician for any consultation. Therefore, the basis of informed consent cannot be found in the details concerning complications actually delivered to the patient. Surgeons must become aware that the patients understand very little of their explanations. This does not mean that the information should not be delivered but on the contrary that it must be. The important point is not necessarily the information content but rather the quality of the human relationship enabling information transfer.

[Reactive synovitis: MRI features with arthroscopic correlation]. / Synovites réactionnelles: aspects en IRM et corrélations arthroscopiques.

OBJECTIVES: To evaluate MR imaging in detecting and characterizing secondary reactive synovitis and correlate the results with arthroscopy. MATERIALS AND METHODS: Retrospective study of 10 patients referred for MR imaging and arthroscopy of the knee or shoulder. The diagnosis of reactive synovitis was confirmed by arthroscopy and pathological examination. Synovial thickening was graded at MRI as follows. Grade 0: normal; grade 1: diffuse synovial thickening; grade 2: nodular synovial hypertrophy; grade 3: pseudotumoral synovial mass. RESULTS: Synovitis was described at MRI in 8 cases. There were 2 false negative results on MR imaging for the knee. Synovitis was secondary to knee trauma and rotator cuff tear or surgery of the shoulder. On arthroscopy, all synovial lesions were detected and confirmed at pathology. Synovitis was not detected at MRI (grade 0) in 20% of cases. Synovitis appeared diffuse (grade 1) in 30%, nodular (grade 2) in 30% and pseudotumoral (grade 3) in 20%. Bony erosions were adjacent to synovial thickening in 5 cases. CONCLUSION: Reactive synovitis can occur after trauma. MR imaging is useful in detecting and evaluating secondary reactive synovitis. Arthroscopy and synovial biopsy are necessary to exclude infectious or tumoral synovitis.

[Soft-tissue chondroma of the hand: a case report and analysis of diagnostic procedures for extra-osseous cartilaginous lesions of the hand]. / Chondrome des parties molles de la main: diagnostic des lésions cartilagineuses extra-osseuses à la main (à propos d'un cas).

We report a case of a chondroma found in the soft tissues of the hand. Reports in the literature show that this cartilaginous tumor is a rare slowly-evolving benign tumor. Diagnosis is difficult as standard x-rays show variable images depending on the degree of calcification. Magnetic resonance imaging is helpful in orienting the diagnosis and delimiting the tumor but is not always useful in determining its exact origin. Positive diagnosis is provided by the pathology examination, but confirmation may be difficult to establish. We stress the importance of repeated microtrauma in the development of soft-tissue chondroma. Surgical treatment is the only successful solution but recurrence is not exceptional.

[En bloc resection of the hip via a simultaneous double approach]. / Résection monobloc de hanche par double abord simultané

The pelvis is not an uncommon localization for primary or secondary tumors. Progress in chemotherapy has reduced the risk of metastasis and advances in reconstruction surgery using prostheses or allografts has made it possible to preserve a functional limb. We describe our method for en bloc resection of the hip. We use a double simultaneous approach for en bloc resection of the hip. The posterior Kocher-Langenbeck approach is associated with a anterior iliocrural approach. Each approach is performed by a separate team. We analyzed the advantages and disadvantages of this method, describing three recent cases. The double-simultaneous approach allowed greater safety for en bloc carcinological resection of the hip for patients with malignant tumors or aggressive intra-articular extension. Reconstruction was achieved with a total hip arthroplasty, reducing the duration of the operation and in theory, blood loss and risk of secondary infection. This method would not be indicated for patients without pelvic involvement nor for patients with a small-sized tumor (<5 cm).

[Impact factor or do we have to choose between the impact factor and the Revue de Chirurgie Orthopédique?]. / Le facteur d'impact ou pour publier faut-il choisir entre la Revue de Chirurgie Orthopédique et l'impact factor?

It is common practice to evaluate the scientific value of a candidate for a university or hospital position using the mean of the impact factors of the journals he/she has published in. This shows that the true composition and true meaning of the impact factor are not sufficiently understood. The impact factor was invented in the 60s to help librarians choose the most read journals. The impact factor provides an accurate definition of the distribution of a journal, but in no case the quality of its publications. Moreover, the impact factor has many technical limitations that are detailed in this article. This strongly limits the accuracy of the impact factor to compare between journals of different specialties. There is no correlation between the scientific value of a single author and the impact factor of the journals he/she has published in. Eugene Garfield, the inventor of the impact factor, has emphasized that it should not be used to judge the scientific value of a candidate.

Radiocarpal dislocations: classification and proposal for treatment. A review of twenty-seven cases.

BACKGROUND: The radiographic characteristics and treatment of radiocarpal dislocation are not well defined. There have been only two reported series of more than eight patients. Thus, there are many questions concerning treatment and functional results. METHODS: Two groups of patients were defined. Group 1 included all patients with pure radiocarpal dislocation and patients with only a fracture of the tip of the radial styloid process. Group 2 included patients with radiocarpal dislocation and an associated fracture of the radial styloid process that involved more than one-third of the width of the scaphoid fossa. A retrospective review and a clinical evaluation were performed. RESULTS: From 1975 to 1998, we observed twenty-seven cases of radiocarpal dislocation. Four were displaced volarly, and twenty-three were displaced dorsally. Fourteen patients presented with associated lesions. Four patients were treated with closed reduction and immobilization in a plaster cast; five, with percutaneous Kirschner wire fixation and cast immobilization; and two, with an external fixator. Eleven patients had open reduction with Kirschner wire fixation and cast immobilization. The seven patients in Group 1 had a highly unstable injury, and four of the seven patients presented with ulnar translation of the carpus. At the time of follow-up, at an average of 26.8 months, pronation averaged 76 degrees; supination, 66 degrees; wrist flexion, 54 degrees; wrist extension, 54 degrees; radial inclination, 15 degrees; and ulnar inclination, 18 degrees. The average grip strength was 27 kg. Group 2 included twenty patients. Only thirteen, with dorsal dislocation, were evaluated at the time of follow-up, which averaged fifty-one months. At that time, six reported no pain; four, slight pain; and two, moderate pain. Pronation averaged 63 degrees; supination, 76 degrees; wrist flexion, 51 degrees; wrist extension, 56 degrees; radial inclination, 21 degrees; and ulnar inclination, 39 degrees. Grip strength averaged 38 kg. Seven patients had complications. CONCLUSIONS: On the basis of our experience and a review of the literature, we believe that patients with pure radiocarpal dislocation or with radiocarpal dislocation with a fracture of the tip of the radial styloid process should be treated with reattachment of the ligaments through a volar approach. In patients with radiocarpal dislocation and a fracture of the radial styloid process that involves more than one-third of the width of the scaphoid fossa, the ligaments are still attached to the radial fragment. We believe that in this group of patients, exact articular reduction should be performed through a dorsal approach. Additional studies are needed to support these hypotheses.

Haemodynamic stability during moderate hypotensive anaesthesia for spinal surgery. A comparison between desflurane and isoflurane.

BACKGROUND: The aim of this study was to compare desflurane and isoflurane for spinal procedures requiring moderate levels of controlled arterial hypotension, when these agents were administered via a semi-closed circuit at 1 l x min(-1) fresh gas flow. METHODS: After ethics committee approval and written informed consent, 20 ASA I or II patients were randomly allocated to receive either desflurane (n=10) or isoflurane (n=10), in O2/ N2O (1:1) for maintenance of anaesthesia. Induction of anaesthesia, fentanyl dosing and volume loading were standardized. Blood pressure was invasively monitored and maintained within a target systolic blood pressure (SBP) range of 80 to 100 mmHg during the study period. Results were presented as medians and interquartiles, and non-parametric statistical methods were used. RESULTS: Patient demographic data, SBP and heart rate prior to surgery, and duration of the procedure were similar between the two groups. During the study period, tighter arterial blood pressure control was maintained with desflurane as compared with isoflurane. SBP was 21.2% (9.5-41.7) of time outside the range 80-100 mmHg with isoflurane and 5.1% (0.6-10.3) with desflurane (P<0.01). CONCLUSIONS: Desflurane, administered via a semi-closed circuit at 1 l x min(-1) fresh gas flow, maintained better haemodynamic stability in spinal surgery requiring moderate arterial hypotension than isoflurane.

[Posterior shoulder instability in athletes: surgical treatment with iliac bone block. Apropos of 6 case reports]. / Instabilité postérieure de l'épaule chez le sportif traitée par butée iliaque. A propos de 6 observations.

PURPOSE OF THE STUDY: Sports activities requiring antepulsion, adduction and medial rotation can favor the development of posterior instability of the shoulder. Conservative treatment is indicated, but many techniques have been proposed in case of failure. All do not allow recovery of the same sports level. We report our experience with six cases of posterior shoulder instability treated with a Gosset posterior bone block. MATERIAL AND METHODS: We retrospectively reviewed cases treated between 1974 and 1995. Six athletes, aged 17 to 34 years (mean 25 years) underwent posterior bone block surgery using the Gosset procedure on their dominant shoulder. Three of the patients had experienced involuntary dislocation and three others involuntary and voluntary dislocation. One patient had a multidirectional hyperlaxity. Five patients had participated in rehabilitation programs for at least five months. Two patients had undergone unsuccessful bone block surgery in another unit. RESULTS: Stability and pain relief were achieved in all cases. Three patients recovered complete mobility. In the three others, mean limitation of mobility for the different sectors was 15 degrees. There has been no sign of osteoarthrosis at three years follow-up. All patients have resumed their sports activities, three at the same level. DISCUSSION: In our experience, most surgical techniques proposed for the treatment of posterior shoulder instability are unsuccessful. The Gosset iliac bone block prolongs the articular surface. After consolidation, it allows sports activities requiring shoulder force and provides satisfactory mobility.