Peter Reilly

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.

Methylenetetrahydrofolate Reductase 677 C→T Mutation and Coronary Heart Disease Risk in UK Indian Asians

Plasma homocysteine concentrations are elevated in UK Indian Asians and may contribute to twice as many coronary heart disease (CHD) deaths in this group compared with European whites. The mechanisms underlying elevated homocysteine concentrations among Indian Asians are not well understood. In this study, we have investigated the extent to which the methylenetetrahydrofolate reductase (MTHFR) 677 C →T mutation accounts for elevated plasma homocysteine and increased CHD risk in Indian Asians compared with European whites. We investigated 454 male cases (with myocardial infarction or angiographically proven CHD: 224 Indian Asians, 230 European whites) and 805 healthy male controls (381 Indian Asians, 424 European whites). Fasting homocysteine concentrations, MTHFR 677 C →T genotype, and conventional CHD risk factors were measured. The prevalence of homozygous MTHFR 677 T in Indian Asian controls was less than one third that in European white controls (3.1% versus 9.7%, P <0.001). In Indian Asians, the TT MTHFR genotype was not associated with homocysteine concentrations and was not present in any of the Asian controls with hyperhomocysteinemia (>15 &mgr;mol/L). In contrast, among European whites, the TT MTHFR genotype was strongly related to elevated plasma homocysteine concentrations and was found in 27% of the European controls with hyperhomocysteinemia. Elevated homocysteine in Indian Asian compared with European white controls was accounted for by their reduced levels of B vitamins but not by the MTHFR 677 T genotype. However, neither the TT MTHFR genotype nor B vitamin levels explained the elevated homocysteine concentrations in CHD cases compared with controls. TT MTHFR was not a risk factor for early-onset CHD in Indian Asians (odds ratio, 0.5; 95% confidence interval, 0.1 to 2.4;P =0.39), unlike in European whites (odds ratio, 2.1; 95% confidence interval, 1.1 to 4.1;P =0.02). We conclude that the MTHFR 677 T mutation does not contribute to elevated plasma homocysteine concentrations or increased CHD risk in Indian Asians compared with European whites. Our results suggest that novel genetic defects and/or environmental factors influence homocysteine metabolism in Indian Asians residing in the United Kingdom.

Validation of orthopaedic bench models for trauma surgery

The aim of this study was to validate the use of three models of fracture fixation in the assessment of technical skills. We recruited 21 subjects (six experts, seven intermediates, and eight novices) to perform three procedures: application of a dynamic compression plate on a cadaver porcine model, insertion of an unreamed tibial intramedullary nail, and application of a forearm external fixator, both on synthetic bone models. The primary outcome measures were the Objective Structural Assessment of technical skills global rating scale on video recordings of the procedures which were scored by two independent expert observers, and the hand movements of the surgeons which were analysed using the Imperial College Surgical Assessment Device. The video scores were significantly different for the three groups in all three procedures (p < 0.05), with excellent inter-rater reliability (alpha = 0.88). The novice and intermediate groups specifically were significantly different in their performance with dynamic compression plate and intramedullary nails (p < 0.05). Movement analysis distinguished between the three groups in the dynamic compression plate model, but a ceiling effect was demonstrated in the intramedullary nail and external fixator procedures, where intermediates and experts performed to comparable standards (p > 0.6). A total of 85% (18 of 21) of the subjects found the dynamic compression model and 57% (12 of 21) found all the models acceptable tools of assessment. This study has validated a low-cost, high-fidelity porcine dynamic compression plate model using video rating scores for skills assessment and movement analysis. It has also demonstrated that Synbone models for the application of and intramedullary nail and an external fixator are less sensitive and should be improved for further assessment of surgical skills in trauma. The availability of valid objective tools of assessment of surgical skills allows further studies into improving methods of training.

Coracoacromial ligament tension in vivo

Tension in the coracoacromial (CA) ligament has been postulated as the mechanism of acromial spur formation. Five patients (mean age, 58 years) undergoing open rotator cuff repair were recruited. A differential variable reluctance transducer (DVRT) was inserted into the CA ligament parallel to the fiber orientation. The DVRT measured linear displacement as the glenohumeral joint was moved through 90 degrees of abduction and full internal/external rotation. The CA ligament was then removed with the DVRT in situ. The specimen was mounted on a material-testing machine. Load was applied in the line of the CA ligament fibers, and the DVRT output recorded. The CA ligament was found to be under tension, which was lowest with the arm adducted (mean, 8.9 N; range, 3.7-22 N) and highest in abduction (mean, 15.7 N; range, 6.5-38 N). This study confirms CA ligament tension in vivo as a possible stimulus for acromial spur formation.

Mechanical factors in the initiation and propagation of tears of the rotator cuff

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.

Rotator cuff repair failure in vivo: a radiostereometric measurement study

BACKGROUNDnThe prevalence of failure among repairs of the rotator cuff is well known, but very few objective data exist regarding either the scale or timing of this complication. The aim of this study was to use a previously validated modified technique of roentgen stereophotogrammetric analysis to monitor the behavior of the rotator cuff after repair to establish at what point failure may occur.nnnMATERIALS AND METHODSnA series of 10 patients had metal beads and wire sutures embedded into the humeral greater tuberosity and supraspinatus tendon, respectively, during open cuff repair procedures. Roentgen stereophotogrammetric analysis imaging of the repaired rotator cuffs was performed at set intervals during the first year after surgery.nnnRESULTSnThe mean distance between the tendon and bone markers did not increase significantly between the time of surgery and 3 to 4 weeks. There was then a significant increase of 7.0 mm in the distance between the tendon and bone markers, with the largest increase occurring between 3 to 4 weeks and 12 to 14 weeks after surgery, as well as a further small but significant increase of 1.7 mm between 12 to 14 weeks and 1 year. These results were compared with clinical examination and ultrasound findings.nnnCONCLUSIONnMost tendon marker movement was seen during the most intensive period of physiotherapy, in the second and third months after surgery. Significantly more movement was seen in the tendon markers of those patients in whom the repair failed.

A novel technique to measure active tendon forces: application to the subscapularis tendon

This paper describes the design and use of a novel system for quantification of active tendon forces. An arthroscopically implantable force probe (AIFP) was inserted arthroscopically into the subscapularis tendon of the shoulder in vivo. The output response of this device was calibrated in situ with known forces applied to the tendon using an arthroscopic technique. On recovery of motor control following interscalene regional anaesthesia, the force within the tendon during active muscle contraction was measured. The AIFP was then retrieved through an arthroscopic portal. The technique showed that the subscapularis may produce forces of 250xa0N during maximum internal rotation of the shoulder.

A comparison of the degree of retraction of full-thickness supraspinatus tears with the Goutallier grading system

BACKGROUNDnTears of the supraspinatus are common and incompletely understood. The degree of fatty infiltration into the muscle is perceived to be a determining factor of successful surgical repair and postoperative function. It is the hypothesis of this study that the degree of central tendon retraction (CTR) as seen on magnetic resonance imaging corresponds to the amount of fatty infiltration classified according to the Goutallier grading system.nnnMATERIALS AND METHODSnMagnetic resonance imaging scans of the supraspinatus were reviewed in 2 identifiable groups: 143 scans with no tear (NT) and 148 scans with a full-thickness tear (FTT) and CTR. The degree of CTR and the corresponding Goutallier grade were measured. The difference in Goutallier grade between the NT and FTT groups was measured with the Mann-Whitney test. The relationship between Goutallier grade and increasing amount of CTR was described by use of Spearman rank correlation. Studying the difference between the Goutallier grades and CTR was achieved by use of Mann-Whitney tests.nnnRESULTSnOf NT scans, 100% showed Goutallier grade 0 or 1. Among FTT scans, 2 showed grade 0, 21 showed grade 1, 35 showed grade 2, 14 showed grade 3, and 76 showed grade 4. The difference was statistically significant (P < .001) between the Goutallier grade 3 and 4 scans, and the degree of Goutallier grade increased with increasing CTR (P < .001).nnnCONCLUSIONnFatty infiltration can be directly linked to CTR and, as such, may help to determine surgical intervention between groups.

Measurement of migration of soft tissue by modified Roentgen stereophotogrammetric analysis (RSA): validation of a new technique to monitor rotator cuff tears

The purpose of this study was to develop a technique to use Roentgen stereophotogrammetric analysis (RSA) to measure migration of soft-tissue structures after rotator cuff repair. RSA stereo films were obtained; images were analysed using a semi-automatic software program allowing 3D viewing of results. RSA imaging experiments were performed to validate the technique, using a glass phantom with implanted RSA beads and an animal model with steel sutures as RSA markers which were moved known distances. Repeated measurements allowed assessment of inter- and intra-observer variability at a maximum of 1.06u2009mm. RSA analysis of the phantom showed a variation up to 0.22u2009mm for static and 0.28u2009mm for dynamic studies. The ovine tissue specimen demonstrated that using steel sutures as RSA markers in soft tissue is feasible, although less accurate than when measuring bone motion. This novel application of RSA to measure soft tissue migration is practicable and can be extended to inu2009vivo studies.

Heterogeneity of the definition of elderly age in current orthopaedic research

Medical research often defines a person as elderly when they are 65xa0years of age or above, however defining elderly age by chronology alone has its limitations. Moreover, potential variability in definitions of elderly age can make interpretation of the collective body of evidence within a particular field of research confusing. Our research goals were to (1) evaluate published orthopaedic research and determine whether there is variability in proposed definitions of an elderly person, and (2) to determine whether variability exists within the important research sub-group of hip fractures. A defined search protocol was used within PubMed, EMBASE and the Cochrane Library that identified orthopaedic research articles published in 2012 that stated within their objective, intent to examine an intervention in an elderly population. 80 studies that included 271,470 patients were identified and subject to analysis. Four (5xa0%) studies failed to define their elderly population. The remaining 76 (95xa0%) studies all defined elderly age by chronology alone. Definitions of an elderly person ranged from 50 to 80xa0years and above. The most commonly used age to define an elderly person was 65, however this accounted for only 38 (47.5xa0%) of studies. Orthopedic research appears to favor defining elderly age by chronology alone, and there is considerable heterogeneity amongst these definitions. This may confuse interpretation of the evidence base in areas of orthopaedic research that focus on elderly patients. The findings of this study underline the importance of future research in orthopaedics adopting validated frailty index measures so that population descriptions in older patients are more uniform and clinically relevant.