Aim of study: ‘Dark discs’ (intervertebral discs with normal shape and height but low signal intensity on T2-weighted MRI) are believed by some authors to represent an early stage in the degenerative process although other authors have suggested that they are simply an appearance of the normal aging process. This study addresses the above question by investigating the correlation between disc morphology on MRI of the lumbar spine (‘dark disc’ or obviously degenerative signs such as annular tear, loss of disc height and shape and end plate changes) and the distribution of lower back pain.

Background: It is generally accepted that spinal levels appearing degenerate on MRI may act as ‘pain generators’ either directly or indirectly (by affecting adjacent structures or levels). Furthermore, histopathologic and discographic studies have shown transmition of specific patterns of somatic pain from degenerate spinal levels.

Methods: 231 consecutive patients (mean age: 45 years, SD:15.9) presenting with mechanical lower back pain of more than six months duration completed topographic graphs of the distribution of their back pain (categorised for this study as upper-, mid-, low-lumbar and sacroiliac area pain) and underwent an MRI of the lumbar spine. Chi-square test was used to investigate the association between presence of abnormalities at any spinal level and pain at any of the considered body areas. Two sets of analyses were performed: one including ‘dark discs’ in the ‘pain generators’ group and the other excluding the ‘dark discs’ from this group.

Results: When the ‘dark discs’ were not considered as ‘pain generators’ the only association to reach statistical significance was that between L5/S1 abnormalities and mid-lumbar pain (P=0.02). However, inclusion of the ‘dark discs’ in the ‘pain generators’ group increased the strength of the association between L5/S1 abnormalities and mid-lumbar pain (P< 0.01) and also resulted in the associations between L3/4 and L4/5 level abnormalities and sacroiliac area pain reaching statistical significance (P=0.02 and P< 0.01 respectively).

Conclusion: The significant statistical effect of considering ‘dark discs’ as ‘pain generators’ on the association between specific spinal level abnormalities and presence of back pain in well-defined areas suggests that the MRI appearance of a ‘dark disc’ should be considered an early stage in the degenerative process and not simply an effect of normal aging.

Aims: The aim of the present study was to investigate the correlation between the topography of the reported symptoms of ‘mechanical’ lower back pain and the findings from the MRI of the lumbar spine.

Methods: Topography (‘pain charts’) of the lower back pain (upper, middle, lower lumbar and sacro-iliac areas) and the MRI findings (disc morphology, Modic-type end plate changes, presence and degree of spondylolisthesis) of 230 consecutive patients with ‘mechanical’ lower back pain without neurological symptoms were studied. Chi-square test was used for the statistical analysis.

Results: Analysis showed that the presence of L5/S1 level pathology is associated (p=0.018) with pain in the middle lumbar area. No other statistically significant association between pathology of another level and pain in other lumbar areas was observed.

Conclusions: Contrary to the general belief, pathology of the lowest lumbar spinal level as diagnosed from MRI may be associated with pain in the middle lumbar area while other pathological levels are not necessarily associated with specific areas of pain in the lower back.

Aims: Given that all previous reports on the increased-crystalinity, increased modulus of elasticity, yield strength and density Hylamer polyethylene have been based on observations on uncemented metal-backed acetabular cups, the aim of the present study is to investigate the rate of wear of a cemented Hylamer UHMWPE acetabular cup. Methods: 36 consecutive cases of THA (mean age: 54.7 years) using a cemented Hylamer UHMWPE acetabular cup and a cemented femoral stem were prospectively followed-up with yearly radiographs for an average period of 54.4 months. Two-dimensional femoral head penetration was determined from AP pelvic radiographs, using computeraided uniradiographic methodology. Multiple regression analysis was used to identify all predictor variables that may account for increased average linear and calculated volumetric wear (Kabo’s formula), as well as for increased total area of peri-prosthetic osteolysis on the femoral and acetabular sides. Results: The average linear wear rate was 0.35 mm/year (SD 0.12) with a significantly high average linear wear rate during the initial (‘wear-in’) period (approximately 12–18 months). The average total volumetric wear was calculated to 764.4 mm3 and the average volumetric wear rate to 169.8 mm3/year. Significant osteolysis was seen in an average of 1.5 (range: 0 to 7) out of the 7 Gruen zones on the femoral side and an average of 1 (range: 0 to 3) out of the 3 Charnley-Delee zones on the acetabular side. Conclusions: Increased rate of linear wear and a high rate of peri-prosthetic osteolysis have been observed in the early results of our series of cemented Hylamer UHMWPE acetabular cups.

Aims: To investigate whether normal statistical ßuctuation in the incidence of early complications of primary Knee Arthroplasty (TKA) follows the laws of statistical probability and can thus be amenable to analysis by standard Statistical Quality Control (SQC) methods. The þnal objective is to apply such techniques to distinguish random ßuctuation from real (undetected by traditional p value statistical methods) increase in the incidence of early complications in primary joint Arthroplasty. Methods: We employed statistical quality control charts (X-bar, p, c, u and np) to analyse postoperative complications and length of stay in 1,196 consecutive primary TKAs performed over a 20-quarter time period (October 1995 to September 2000). For all analyses (Minitab 12.1 software) the standard practice of employing ± 3 standard deviation upper and lower control limits and generally accepted criteria for determining the presence or absence of statistical control were used. Results: Deep infection, major thromboembolic incident, total number of complications per case and total number of complicated cases appeared to be in stable statistical control and followed the laws of statistical ßuctuation throughout the entire study period. However, patella mal-tracking, persistent knee stiffness, postoperative length of stay and total number of postoperative complications showed an (undetected by conventional postoperative audit methods) lack of control at various time periods with subsequent return to the statistically-controlled range. Conclusions: SQC methods may be employed in the audit of postoperative events in TKA and can be a valuable tool in continuous assessment of the statistical variability of postoperative complications, with the aim of reducing the variability and improving clinical outcome Arthritic knee imaging

It is generally appreciated that the internal structure and external shape of living bone adapt to mechanical stimuli according to Wolff’s law. However, the precise details of bone adaptation to external forces are not fully understood and there has been no previous investigation of the association between specific loading conditions and the skeletal architecture of a particular anatomical area using case-specific observations in a group of individuals. The aim of the present study was to investigate a previously unreported correlation between the maximum wrist joint reaction force and the volar tilt angle of the distal radius using parameters radiographically obtained parameters from normal wrist joints.

Using free body analysis of the forces acting on the distal radius for the loading condition that corresponds to the lift of a weight using the supinated hand, the wrist joint reaction force F and the angle formed between the vector of F and the long axis of the radius have been expressed as a function of the lifted weight, the lever-arm of the wrist flexor tendons and that of the lifted weight. Measurements of the volar tilt angle of distal radius and the lever-arms of the flexor tendons and the lifted weight were performed from lateral wrist radiographs of 30 normal wrists. Subsequently, using the equations obtained from free body analysis, the maximum wrist joint reaction force F and the angle that the latter forms with the long axis of the radius were calculated for each the cases. Statistical analysis compared the angle of the maximum wrist force and the volar tilt of the distal radius (two-tailed paired t-test) and correlated (a) the angle of the maximum wrist force and the volar tilt angle and (b) the maximum joint reaction force and the volar tilt angle.

Results showed no significant difference (p=0.33, 95% confidence interval −0.64° to 0.22°) but a statistically significant correlation (R² = 0.74, r = 0.86, p < 0.001) between the angle of the maximum wrist force and the volar tilt angle of the distal radius. Additionally, an inverse relationship between the volar tilt angle and the magnitude of the maximum wrist force (R² = 0.71, r =−0.84, p< 0.001) was found.

These observations may explain the mechanism of the phylogenetical development of the volar tilt angle and support the ‘minimum effective strain’ theory of adaptive bone remodeling1. The importance of accurate restoration of the volar tilt during treatment of distal radius fractures, especially in wrists that are normally characterised by a low volar tilt angle, is also emphasized by the results of the present study.

Patient disability and handicap following wrist injuries have been the focus of recent research interest¹. However, the relative importance of each of the commonly-reported and easily-measured clinical outcome parameters such as the range of wrist movement and the grip strength on the level of actual wrist disability following distal radial fractures has not been investigated previously. The present study investigates the correlation between measurements of specific clinical parameters and the patient-rated wrist joint function following wrist fractures.

A prospective assessment of unstable (AO types 23-A2, -A3, -C1 and -C2) fractures of the distal radius treated by closed reduction and percutaneous K-wire fixation followed by cast immobilisation was undertaken. One hundred consecutive observations were made during various follow-up time periods up to one year in a group of twenty-five patients (fifteen female and ten male patients, mean age 43 years – range 18 to 67 years). The clinical parameters tested were the range of wrist dorsiflexion, palmarflexion, pronation and supination (measured using a goniometer) and the mass grip strength (Jamar grip dynamometer) following removal of the plaster cast, expressed as percentage of the affected side relative to the opposite normal side. Additionally, each patient completed the Patient-Rated Wrist Evaluation (PRWE) Score¹. A stepwise multiple regression multivariate model was employed to statistically analyse the relative effect (expressed as the regression coefficient, b) of each clinical parameter on the ‘Function Score’ part of the PRWE Score. Furthermore, the association between each clinical parameter and the Function Score part of the PRWE Score was also investigated using single-patient observations by calculating the correlation coefficient (r).

The results of the statistical analysis (Minitab 12.1) gave the following regression (b) and correlation (r) coefficient values: grip strength (b=0.77, r=0.80), dorsiflexion (b=0.58,r=0.78),pronation (b=0.39,r=0.70),supination (b=0.38, r=0.63), palmarflexion (b=0.32, r=0.62).

The present study shows that grip strength (expressed as percentage that of the unaffected side) is the most reliable index of wrist disability and the most sensitive indicator of return of wrist function, followed by the range of wrist dorsiflexion and pronation. Wrist supination and palmarflexion are the clinical outcome variables showing the weakest correlation with the wrist function as rated by the patients. These observations may facilitate correct interpretation and comparisons of the results of clinical studies on various methods of treatment of wrist trauma.