Degenerative rotator cuff tear, repair or not repair? A review of current evidence.

INTRODUCTION: We review the literature and highlight the important factors to consider when counselling patients with non-traumatic rotator cuff tears on which route to take. Factors include the clinical outcomes of surgical and non-surgical routes, tendon healing rates with surgery (radiological outcome) and natural history of the tears if treated non-operatively. METHODS: A PRISMA-compliant search was carried out, including the online databases PubMed and Embase™ from 1960 to the end of June 2018. FINDINGS: A total of 49 of the 743 (579 PubMed and 164 Embase™) results yielded by the preliminary search were included in the review. There is no doubt that the non-surgical route with an appropriate physiotherapy programme has a role in the management of degenerative rotator cuff tears. This is especially the case in patients with significant risk factors for surgery, those who do not wish to go through a surgical treatment and those with small, partial and irreparable tears. However, rotator cuff repair has a good clinical outcome with significant improvements in pain, range of motion, strength, quality of life and sleep patterns.

The influence of the mechanical environment on remodelling of the patellar tendon.

An understanding of the remodelling of tendon is crucial for the development of scientific methods of treatment and rehabilitation. This study tested the hypothesis that tendon adapts structurally in response to changes in functional loading. A novel model allowed manipulation of the mechanical environment of the patellar tendon in the presence of normal joint movement via the application of an adjustable external fixator mechanism between the patella and the tibia in sheep, while avoiding exposure of the patellar tendon itself. Stress shielding caused a significant reduction in the structural and material properties of stiffness (79%), ultimate load (69%), energy absorbed (61%), elastic modulus (76%) and ultimate stress (72%) of the tendon compared with controls. Compared with the material properties the structural properties exhibited better recovery after re-stressing with stiffness 97%, ultimate load 92%, energy absorbed 96%, elastic modulus 79% and ultimate stress 80%. The cross-sectional area of the re-stressed tendons was significantly greater than that of stress-shielded tendons. The remodelling phenomena exhibited in this study are consistent with a putative feedback mechanism under strain control. This study provides a basis from which to explore the interactions of tendon remodelling and mechanical environment.

Collagenous microstructure of the glenoid labrum and biceps anchor.

The glenoid labrum is a significant passive stabilizer of the shoulder joint. However, its microstructural form remains largely unappreciated, particularly in the context of its variety of functions. The focus of labral microscopy has often been histology and, as such, there is very little appreciation of collagen composition and arrangement of the labrum, and hence the micromechanics of the structure. On transmission electron microscopy, significant differences in diameter, area and perimeter were noted in the two gross histological groups of collagen fibril visualized; this suggests a heterogeneous collagenous composition with potentially distinct mechanical function. Scanning electron microscopy demonstrated three distinct zones of interest: a superficial mesh, a dense circumferential braided core potentially able to accommodate hoop stresses, and a loosely packed peri-core zone. Confocal microscopy revealed an articular surface fine fibrillar mesh potentially able to reduce surface friction, bundles of circumferential encapsulated fibres in the bulk of the tissue, and bone anchoring fibres at the osseous interface. Varying microstructure throughout the depth of the labrum suggests a role in accommodating different types of loading. An understanding of the labral microstructure can lead to development of hypotheses based upon an appreciation of this component of material property. This may aid an educated approach to surgical timing and repair.

Qualitative and quantitative descriptions of glenohumeral motion.

Joint modelling plays an important role in qualitative and quantitative descriptions of both normal and abnormal joints, as well as predicting outcomes of alterations to joints in orthopaedic practice and research. Contemporary efforts in modelling have focussed upon the major articulations of the lower limb. Well-constrained arthrokinematics can form the basis of manageable kinetic and dynamic mathematical predictions. In order to contain computation of shoulder complex modelling, glenohumeral joint representations in both limited and complete shoulder girdle models have undergone a generic simplification. As such, glenohumeral joint models are often based upon kinematic descriptions of inadequate degrees of freedom (DOF) for clinical purposes and applications. Qualitative descriptions of glenohumeral motion range from the parody of a hinge joint to the complex realism of a spatial joint. In developing a model, a clear idea of intention is required in order to achieve a required application. Clinical applicability of a model requires both descriptive and predictive output potentials, and as such, a high level of validation is required. Without sufficient appreciation of the clinical intention of the arthrokinematic foundation to a model, error is all too easily introduced. Mathematical description of joint motion serves to quantify all relevant clinical parameters. Commonly, both the Euler angle and helical (screw) axis methods have been applied to the glenohumeral joint, although concordance between these methods and classical anatomical appreciation of joint motion is limited, resulting in miscommunication between clinician and engineer. Compounding these inconsistencies in motion quantification is gimbal lock and sequence dependency.

Tensile properties of the human glenoid labrum.

Human fresh-frozen cadaveric glenoid labrae from 16 donors were harvested and ten of these had no gross degeneration. These ten were divided into eight equal circumferential sections. Each section was cut to produce test-samples from the core layer with a cross-section of 1 x 1 mm. Tensile testing was performed within a controlled environment unit at 37 +/- 1 degrees C and 100% relative humidity. Each test-sample was precycled to a quasi-static state to alleviate the effects of deep-freezing, prior to final testing. The tangent modulus was calculated for each test-sample before and after a 5-min period of stress relaxation and at yield. The mean elastic modulus and yield stress of the glenoid labrum were 22.8 +/- 11.4 and 2.5 +/- 2.1 MPa, respectively. The anterosuperior portion had a lower elastic modulus and lower yield stress than the inferior portion (both P < 0.02). The pre-stress relaxation tangent modulus was significantly lower than the post-stress relaxation tangent modulus for all portions of the labrum. The glenoid labrum has similar tensile material properties to articular cartilage. Its elastic modulus varies around its circumference. This suggests that the labrum may encounter different forces at different positions.

Glenohumeral motion: review of measurement techniques.

Measurement of upper limb motion is problematic, not least because of the large range of path dependent description of motion of the joints, and the multiple non-cyclical unstandardised motion tasks measured. Furthermore, appreciation of shoulder motion specifically is obscured by overlying soft tissue. In order to satisfy the complexity of a clinically useful model of the movement of the joint, input data must be acquired from a set of pre-determined movements using a non-invasive technique with a high level of accuracy. Descriptive and predictive modeling of the glenohumeral joint requires input of high-fidelity data into a 6 degree of freedom representation, without which, the application of the tool is of limited clinical significance to the advancement of both operative and non-operative management of shoulder pathology. Electromagnetic, linkage and radiographic techniques have previously been used, however, an optimal solution is yet to be described.

Mechanical factors in the initiation and propagation of tears of the rotator cuff. Quantification of strains of the supraspinatus tendon in vitro.

Differential strain has been proposed to be a causative factor in failure of the supraspinatus tendon. We quantified the strains on the joint and bursal sides of the supraspinatus tendon with increasing load (20 to 200 N) and during 120 degrees of glenohumeral abduction with a constant tensile load (20 to 100 N). We tested ten fresh frozen cadaver shoulders on a purpose-built rig. Differential variable reluctance extensometers allowed calculation of the strain. Static loading to 100 N or more increased strains on the joint side significantly more than on the bursal side. During glenohumeral abduction an increasing and significant difference in strain was measured between the joint and bursal sides of the supraspinatus tendon, which reached a maximum of 10.6% at abduction of 120 degrees. The joint side strain of 7.5% reached values which were previously reported to cause failure. Differential strain causes shearing between the layers of the supraspinatus tendon, which may contribute to the propagation of intratendinous defects that are initiated by high joint side strains.

Magic angle imaging of the achilles tendon in patients with chronic tendonopathy.

AIMS: To assess the Achilles tendon in patients with chronic tendonopathy using magnetic resonance (MR) magic angle imaging, and to compare the appearances and uptake of contrast medium in abnormal tendons with those in normal tendons. MATERIAL AND METHODS: Eight patients with chronic Achilles tendonopathy and five normal controls were examined with the long axis of the tendon placed at 55 degrees and at 0 degrees to the main magnetic field. Conventional two-dimensional (2D) multi-slice images were obtained and T1 values were calculated before, and for up to 1h after the administration of intravenous gadodiamide. Both the unenhanced appearance and the pattern of enhancement in the tendon were compared. RESULTS: In the patients with tendonopathy, high signal intensity areas were evident on the short T1 inversion recovery (STIR) images obtained at 55 degrees in all tendons. Contrast medium enhancement was seen in six tendons and was most obvious on the images obtained at the magic angle. This was initially focal and then spread more diffusely within the tendon. After contrast medium administration, T1 values were significantly reduced in the tendonopathy group compared with normal controls (p<0.01). On the late post-contrast medium images obtained at 55 degrees, enhancement was evident in most of the tendon and correlated well with high signal intensity seen on STIR images. CONCLUSION: The use of magic angle MR imaging improved the demonstration of signal changes in the Achilles tendon in chronic tendonopathy. The STIR images obtained at the magic angle showed more obvious signal change than those obtained at 0 degrees. The changes due to enhancement were much more evident on images obtained at 55 degrees than at 0 degrees. The uptake of contrast medium was greater in the patients than in normal controls.

Magnetic resonance: magic angle imaging of the Achilles tendon.

Tendons do not normally produce detectable signals with conventional magnetic-resonance techniques and are recognised as dark signal voids. However, if tendons are examined at 55 degrees to the static magnetic field (the "magic angle"), signals become detectable and the tendons can become the brightest structure on the image. We have used this approach to establish tendon relaxation times and magnetisation transfer ratios and to show contrast enhancement. We have also shown more detail of acute and chronic tendon rupture by this method compared with images made with the tendon parallel to the static magnetic field.

Electrothermal shrinkage reduces laxity but alters creep behavior in a lapine ligament model.

Thermal denaturation of collagen in ligament tissue has the potential to enhance arthroscopic shoulder stabilization. Previous studies have shown that laser energy produces significant capsular shortening without alteration of viscoelastic properties, but little information is available on the effects of radio frequency electrothermal energy. We assessed the acute effects of radio frequency shrinkage with use of the lapine medial collateral ligament model, in which the tibial insertion was shifted proximally to produce abnormal laxity. Thermal treatment resulted in restoration of laxity from 3.33 +/- 0.25 mm to 0.66 +/- 0.31 mm, which was not significantly different from medial collateral ligaments replaced anatomically (0.50 +/- 0.34 mm). When tested at 4.1 megapascals, cyclic and static creep strains were increased twofold to threefold in thermally-treated ligaments (P <.01), and partial failure occurred in 2 of 8 cases. We conclude that radio frequency electrothermal shrinkage is effective at reducing laxity but significantly alters viscoelastic properties, posing a risk of recurrent stretching-out at "physiological" loads.

Structural properties of the intact and the reconstructed coracoclavicular ligament complex.

Numerous procedures have been described for the operative management of acromioclavicular joint injuries, but surprisingly little information is available on the ultimate mechanical behavior of the native coracoclavicular ligament complex or on the various methods of reconstruction. We tested 19 fresh-frozen cadaveric bone-ligament-bone preparations of the coracoclavicular ligament in uniaxial tension at 25 mm/min until failure. Seven specimens were left intact, six had the trapezoid ligament sectioned, and six had the conoid ligament sectioned. Reconstruction of the coracoclavicular ligament was achieved using coracoacromial ligament transfers, woven polyester slings, suture anchors, and Bosworth screws; all reconstructions were also tested to failure. The intact coracoclavicular ligament failed by avulsion or midsubstance tear at 500 (+/-134) N, with a stiffness of 103 (+/-30) N/mm and elongation to failure of 7.7 (+/-1.9) mm. There was no significant difference between the contributions of the conoid or trapezoid ligaments in this loading configuration. Coracoclavicular slings and suture anchors provided strength similar to that of the coracoclavicular ligament, but with significantly greater deformations (14 to 26 mm). Screw fixation resulted in comparable stiffness and superior strength to the coracoclavicular ligament, but only if bicortical purchase was obtained. Coracoacromial ligament transfers were the weakest and least stiff, and augmentation with another form of coracoclavicular fixation is recommended. These results provide a useful baseline for comparison of the initial performance of reconstructive techniques with the performance of the native coracoclavicular ligament.

Resurfacing of the glenoid in total shoulder arthroplasty. A comparison, at a mean of five years, of prostheses inserted with and without cement.

BACKGROUND: Clinically evident loosening of a glenoid component inserted with cement in total shoulder arthroplasty is infrequent, but radiographic changes that indicate loosening at the implant-bone interface are common and have been associated with functional limitation. We compared the results of total shoulder arthroplasties in which the glenoid implant had been inserted with cement with those of arthroplasties in which a bone-ingrowth glenoid implant had been inserted without cement. METHODS: The results of eighty-six consecutive total shoulder arthroplasties, performed by the same surgeon, were retrospectively reviewed between four and seven years after the operation. Fifty-eight shoulders in which the primary glenoid implant was in situ were assessed with use of the Simple Shoulder Test and Short Form-36 questionnaires, clinical examination, and fluoroscopic imaging of the glenoid implant-bone interface. Thirty-two of the glenoid components had been fixed with cement and twenty-six, without cement. RESULTS: Complications occurred in 16 percent (fourteen) of the eighty-six shoulders, and 9 percent (eight) of the shoulders needed a revision operation. None of the revisions were done because of loosening of the glenoid component. Five of the eight revisions involved implants that had been inserted without cement. Three of these implants were revised because of early instability and two, because the polyethylene component had separated from the metal tray of the glenoid implant. With the numbers available, we could not detect any significant differences between the groups with respect to pain, range of motion, function of the shoulder, or general health. Radiographic analysis demonstrated a high level of interobserver agreement (kappa = 0.89). Radiolucent lines were observed after 41 percent (thirteen) of the thirty-two arthroplasties performed with cement compared with 23 percent (six) of the twenty-six arthroplasties performed without cement. The proportion of implants classified as probably loose was approximately three times greater in the group in which cement had been used. Eccentric wear of the posterior rim of the metal tray and focal osteolysis under the metal tray were observed in the group in which the component had been inserted without cement; these findings may indicate a potential for progression of radiographic loosening with increased durations of follow-up. CONCLUSIONS: We concluded that, despite the higher rate of early complications, the intermediate-term outcomes of arthroplasties in which the glenoid implant is inserted without cement are comparable with those of arthroplasties with cementing of the glenoid component.

Intraoperative assessment of tibiofemoral contact stresses in total knee arthroplasty.

The production of polyethylene wear debris in total knee arthroplasty (TKA) is due to multiple factors. In particular, inadequate implant alignment and high bearing surface contact stresses are associated with polyethylene failure. Optimal implant placement and soft tissue balancing may contribute to reducing wear and the production of polyethylene particles. We present a case in which a quantitative technique was used to measure tibiofemoral contact stresses during implantation of a total knee prosthesis in vivo. In a knee with preoperative varus and fixed flexion deformity, medial compartment contact stresses after initial resection were reduced from 14.3 MPa to 11.3 MPa in neutral alignment by additional bone resection. Posterior cruciate release was required to reduce contact stresses further and to provide satisfactory balance between medial and lateral compartments, as determined by the operating surgeon, and was confirmed by the measurement system (3.8 MPa medially; 3.0 MPa laterally). This technique has potential to fine-tune implant positioning and ligament balancing during TKA.

The interosseous membrane in radio-ulnar dissociation.

In severe forearm injuries, the diagnosis of disruption of the interosseous membrane is frequently delayed and sometimes missed, giving difficulties in the salvage of forearm stability. We studied the structure and function of the interosseous membrane in 11 cadaver preparations, using mechanical and histological analysis. Seven of the specimens tested in uniaxial tension sustained a mid-substance tear of the central band of the membrane at a mean peak load of 1038 +/- 308 N. The axial stiffness was 190 +/- 44 N/mm with elongation to failure of 10.34 +/- 2.46 mm. These results provide criteria for the evaluation of reconstructive methods. A preliminary clinical investigation of the use of ultrasound suggests that this may be of value in the screening of patients with complex fractures of the forearm, and for investigating the natural history of tears of the interosseous membrane.

The design and performance of an experimental external fixation device with load transducers.

It is becoming increasingly common that fracture healing is modelled in the laboratory with an osteotomy in the diaphysis of the ovine tibia. External fixation is often used to hold the bones in these models, presenting the problem that the loads on such devices are poorly understood. To help investigate this, a unilateral device has been developed which is capable of measuring the two components of load considered to be the most important, that of axial compression and bending in the plane of the fixator. The device was found to be a rigid system and easy to apply, with the in-vivo measurements being straightforward. The estimated limits of error of the compression transducer are +37.9 N and -21.4 N and those of the bending transducer are +3.6 Nm and -4.2 Nm. Preliminary measurements showed the maximum load during normal walking to 345 N compression and 28 Nm in-plane bending.

Measurement of serum angiogenic factor in devascularized experimental tibial fractures.

Early recovery of the vasculature is of profound importance in healing fractures, but the exact role of the regenerating endothelium remains controversial. Serum activity of endothelial cell-stimulating angiogenesis factor (ESAF) was measured after tibial osteotomy in two groups of sheep over a period of 42 days. Each osteotomy was held in an instrumented external fixator, and in one group the musculoperiosteal vasculature was excluded from the osteotomy site. In the well-vascularized group (n = 4), ESAF activity was significantly higher 2-5 days after osteotomy, with a peak at 4 days (21.1 +/- 5.4, p < 0.05), and displayed a biphasic pattern of secretion with a second peak at 7 days (24.3 +/- 5.5). In the devascularized group (n = 4) overall activity was lower, with only a single peak occurring at 9 days (17.5 +/- 3.2). These findings were correlated with significant differences in structural properties and on histological examination. The early detection of such regional vascular responses may prove to be of significant clinical value in high-energy trauma, enabling prediction of those fractures at risk of delayed or nonunion.