The MMP3 gene in musculoskeletal soft tissue injury risk profiling: A study in two independent sample groups

Matrix metalloproteinase-3 (MMP3) is a mediator of matrix remodelling and a proposed susceptibility locus in the genetic profile of musculoskeletal soft tissue injuries. Therefore, this study aimed to validate the MMP3 gene as a risk marker for these injuries by conducting a case control genetic association study in two independent samples groups. Three previously investigated MMP3 variants (rs679620, rs591058 and rs650108) in addition to the functional promoter variant (rs3025058) were genotyped in 195 Australian control participants and 79 Australian individuals with chronic Achilles tendinopathy. Similarly, 234 South African individuals with acute anterior cruciate ligament ruptures and 232 matched control participants were also analysed. Based on high linkage with the previously associated MMP3 variant rs679620, rs3025058 was inferred and found to be associated with increased risk for Achilles tendinopathy within the South African group (P = 0.012; OR: 2.88; 95% CI: 1.4 to 6.1). Lastly, the 6A-G-C-G haplotype, constructed from the investigated variants, was significantly associated with reduced risk for Achilles tendinopathy (29% CON vs. 20% TEN, P = 0.037) in the Australian group. In conclusion, a signal surrounding MMP3 is apparent with respect to Achilles tendinopathy. However, whether the investigated variants are contributing to injury susceptibility or whether they are merely linked to the risk conferring variants mapping elsewhere within the MMP gene cluster on chromosome 11, still requires refining.

Computational modelling of mobile bearing TKA anterior-posterior dislocation

Anterior-posterior stability in an unconstrained mobile-bearing total knee arthroplasty (TKA) and one with rotational constraints is compared in a computational model based on an ASTM test. Both TKA designs dislocate at loads greater than reported maximum in vivo forces. The posterior drawer forces (mean: 3027 N vs. 1817 N) needed to induce subluxation increase with a greater anterior jump distance (12 mm vs. 7 mm; refers to the vertical height of the anterior or posterior border of the tibial insert's articulating surface). The posterior jump distance for both tested TKA differed by 1.5 mm and had minimal effect on the magnitude of the anterior drawer forces at dislocation in mid-flexion (unconstrained vs. constrained: 445 N vs. 412 N). The unconstrained insert dislocated by means of spin-out whereas in the constrained TKA the femur dislocated from the bearing during posterior drawer and the bearing from the baseplate during anterior drawer. MCL function is an important consideration during ligament balancing since a ± 10% variation in MCL tension affects dislocation forces by ± 20%. The simulation platform provided the means to investigate TKA designs in terms of anterior-posterior stability as a function of knee flexion, collateral ligament function and mechanical morphology.

ELN and FBN2 gene variants as risk factors for two sports-related musculoskeletal injuries

The proteins ELN and FBN2 are important in extracellular matrix function. The ELN rs2071307 and FBN2 rs331079 gene variants have been associated with soft tissue pathologies. We aimed to determine whether these variants were predisposing factors for both Achilles tendinopathy (AT) and anterior cruciate ligament (ACL) ruptures. For the AT study, 135 cases (TEN group) and 239 asymptomatic controls were recruited. For the ACL rupture study our cohort consisted of 141 cases (ACL group) and 219 controls. Samples were genotyped for both the ELN rs2071307 and FBN2 rs331079 variants using TaqMan assays. Analysis of variance and chi-squared tests were used to determine whether either variant was associated with AT or ACL rupture with significance set at p<0.05. The GG genotype of the FBN2 variant was significantly over-represented within the TEN group (p=0.035; OR=1.83; 95% CI 1.04-3.25) compared to the CON group. We also found that the frequency of the G allele was significantly different between the TEN (p=0.017; OR=1.90; 95% CI 1.11-3.27) and ACL groups (p=0.047; OR=1.76; 95% CI 1.00-3.10) compared to controls. The ELN rs207137 variant was not associated with either AT or ACL rupture. In conclusion, DNA sequence variation within the FBN2 gene is associated with both AT and ACL rupture.

The GDF5 gene and anterior cruciate ligament rupture

A recent genetic association study has revealed that a variant (rs143383) within the 5'-untranslated region of the growth differentiation factor 5 gene (GDF5) associates with the risk of Achilles tendon pathology. The aim of this study was to determine whether this variant associates with the risk of ACL rupture. A cohort of 126 Caucasians with ACL rupture (ACL group), including 51 subjects who ruptured their ACL through a non-contact mechanism (NON sub-group), and 214 controls (CON group) were genotyped for the rs143383 variant. We report no significant GDF5 rs143383 genotype (P=0.396) or allele (P=0.810) frequency differences between the ACL (TT genotype, n=37, 29%; CT genotype, n=72, 57%; CC genotype, n=17, 14%) and CON (TT genotype, n=73, 34%; CT genotype, n=106, 50%; CC genotype, n=35, 16%) groups. There were also no significant differences between the NON sub-group and the CON group (allele; P=0.710, genotype; P=0.771). Furthermore, in gender specific analysis we found no association between rs143383 and ACL in either males (allele; P=0.988, genotype; P=0.407) or females (allele; P=0.643, genotype; P=0.885), respectively. Nor were there any gender specific associations between the NON sub-group and either genotype or allele. In conclusion, the rs143383 variant was not found to associate with the risk of ACL rupture.

Knee rotational laxity: an investigation of bilateral asymmetry for comparison with the contralateral uninjured knee

BACKGROUND

Instability associated with anterior cruciate ligament injury is commonly evaluated against the patient's contralateral knee. The objectives of this study were, therefore, to assess symmetry of rotational knee laxity in vivo under passive torsional loading in uninjured subjects, and to compare mean rotation of this control group with the contralateral, intact knees of anterior cruciate ligament deficient patients.

METHODS

Axial knee rotation was measured in 29 patients with unilateral anterior cruciate ligament injury and 15 uninjured age and gender-matched control subjects using an imaging-compatible torsional loading device. Side-to-side differences in internal, external, and range of knee rotation were assessed in the control group and mean bilateral knee rotation was compared to the patients' contralateral knee data at both full extension and 30° of flexion.

FINDINGS

Statistically significant differences in symmetry were found in three of the six measures of transverse plane rotation in the uninjured knees; a mean side-to-side difference of 2.2° in range of rotation was detected in the flexed position. No significant differences were observed between the mean values of the healthy control group and the contralateral knees of the anterior cruciate ligament deficient patients.

INTERPRETATION

Bilateral asymmetry of rotational laxity occurs in healthy individuals. Nevertheless, comparability of rotational knee laxity between the contralateral limbs of patients and the uninjured population was evidence that rotational laxity was not inherent or developed in the contralateral knees of the anterior cruciate ligament deficient participants.

Double-bundle ACL surgery demonstrates superior rotational kinematics to single-bundle technique during dynamic task

BACKGROUND

While traditional surgical repair of the anterior cruciate ligament is able to restore anterior-posterior knee stability, laxity in the transverse plane remains. Double-bundle reconstruction has demonstrated greater rotational restraint than the single-bundle technique under passive loading conditions; however, no comparison has been made under physiological weight-bearing conditions. The purpose of this study was to determine differences in rotational knee kinematics during a dynamic task in patients who had received either a single- or double-bundle reconstruction.

METHODS

Twenty-two patients exhibiting isolated anterior cruciate ligament rupture were randomly allocated either a single or double-bundle reconstruction. Three-dimensional knee kinematics were measured during a dynamic cutting activity prior to and following surgery. Functional range of rotation was compared between groups pre- and post-operatively and kinematics were assessed against uninjured control subjects.

FINDINGS

No difference in overall range of rotation was found under physiological loading conditions. However, a significant interaction of the midpoint of the range of movement was observed; a greater external rotational shift in the single-bundle group followed reconstruction, while the kinematics of the double-bundle patient group shifted closer to those of the control group.

INTERPRETATION

The double-bundle reconstruction demonstrated superior outcome in rotational kinematics to the single-bundle technique.

Intra-operative pneumatic tourniquet--perceptions of use and complications in the orthopaedic community of South Africa

OBJECTIVES

To assess views on use, maintenance and side-effects of the pneumatic tourniquet in the South African orthopaedic community.

METHODS

A census-type questionnaire study was conducted of all 475 orthopaedic surgeons registered with the Orthopaedic Association of South Africa during 1993/94. The chi-square test was used to determine statistical significance between different groups of respondents.

RESULTS

Seventy-seven per cent of the questionnaires were returned. Ninety-nine per cent of respondents used a pneumatic tourniquet. Eighty-four per cent believed that the tourniquet may damage underlying tissue both as a result of applied pressure effects and ischaemic consequences. Fifty-four per cent of respondents personally checked the calibration of the pneumatic tourniquet, although 76% of respondents believe that the apparatus needs to be checked at least once per month. More respondents who did not check the tourniquet apparatus than respondents who did check it believe that applied pressure does not cause tissue damage (P < 0.001), that the operating room technician or hospital engineer should be responsible for checking equipment (P < 0.001), and that equipment did not need to be checked more than once every 6 months (P < 0.001).

CONCLUSIONS

Although most orthopaedic surgeons are aware of the pneumatic tourniquet's side-effects, a minority appear to be unaware of the hazards of excessive applied pressure alone or excessive applied pressure caused by use of faulty equipment. It needs to be emphasised to these surgeons that regular checking of the pneumatic tourniquet apparatus is necessary in order to prevent postoperative complications ascribed to use of the tourniquet.

Hospital admissions for adverse reactions to drugs and deliberate self-poisoning

In a prospective study of 300 patients, 14 admissions (4,6%) were considered to be related to adverse drug reactions. A further 29 admissions (9,6%) were due to self-poisoning with drugs prescribed for therapeutic purposes. Agents causing adverse reactions were predominantly cardio-active drugs and anticoagulants. Mean duration of hospital stay in this group of patients was 8,3 days (range 2-18 days); there were no deaths. Tranquilizers and antidepressants were most commonly used for self-poisoning. Duration of admission in these patients was much shorter than in the previous group--mean 1,8 days (range 1-5 days), and there was 1 death. To the best of our knowledge, this is the first reported series of such cases in South Africa. It shows that drugs are an important cause of morbidity in hospital patients in the RSA.

Hepatic enzymes, their induction and usefulness in predicting maximal serum bilirubin levels in premature newborn infants

Sixty-seven babies were utilized to (a) document the serum bilirubin lowering effect and safety of a phenobarbitone and nikethamide combination in neonatal hyperbilirubinaemia of non-hemolytic origin; (b) determine whether birthweight and/or SGOT, SGPT or SGGT activity on day one of life correlated with the maximum serum bilirubin level achieved; and (c) investigate the pattern of hepatic enzyme levels in serum under normal conditions anf following drug induction. Results indicate a significantly lower serum bilirubin level in the treated group of babies. Birthweight and day one SGGT levels, and SGGT/birthweight ratio correlated well with the maximum serum bilirubin reached, the latter ratio being particularly useful in predicting the degree of hyperbilirubinaemia.