The influence of femoral offset on health-related quality of life after total hip replacement.

Several factors have been implicated in unsatisfactory results after total hip replacement (THR). We examined whether femoral offset, as measured on digitised post-operative radiographs, was associated with pain after THR. The routine post-operative radiographs of 362 patients (230 women and 132 men, mean age 70.0 years (35.2 to 90.5)) who received primary unilateral THRs of varying designs were measured after calibration. The femoral offset was calculated using the known dimensions of the implants to control for femoral rotation. Femoral offset was categorised into three groups: normal offset (within 5 mm of the height-adjusted femoral offset), low offset and high offset. We determined the associations to the absolute final score and the improvement in the mean Western Ontario and McMaster Universities osteoarthritis index (WOMAC) pain subscale scores at three, six, 12 and 24 months, adjusting for confounding variables. The amount of femoral offset was associated with the mean WOMAC pain subscale score at all points of follow-up, with the low-offset group reporting less WOMAC pain than the normal or high-offset groups (six months: 7.01 (sd 11.69) vs 12.26 (sd 15.10) vs 13.10 (sd 16.20), p = 0.006; 12 months: 6.55 (sd 11.09) vs 9.73 (sd 13.76) vs 13.46 (sd 18.39), p = 0.010; 24 months: 5.84 (sd 10.23) vs 9.60 (sd 14.43) vs 13.12 (sd 17.43), p = 0.004). When adjusting for confounding variables, including age and gender, the greatest improvement was seen in the low-offset group, with the normal-offset group demonstrating more improvement than the high-offset group.

The significance of an asymmetric extension gap on routine radiographs after total knee replacement: A new sign and its clinical significance.

We investigated whether an asymmetric extension gap seen on routine post-operative radiographs after primary total knee replacement (TKR) is associated with pain at three, six, 12 and 24 months' follow-up. On radiographs of 277 patients after primary TKR we measured the distance between the tibial tray and the femoral condyle on both the medial and lateral sides. A difference was defined as an asymmetric extension gap. We considered three groups (no asymmetric gap, medial-opening and lateral-opening gap) and calculated the associations with the Western Ontario and McMaster Universities osteoarthritis index pain scores over time. Those with an asymmetric extension gap of ≥ 1.5 mm had a significant association with pain scores at three months' follow-up; patients with a medial-opening extension gap reported more pain and patients with a lateral-opening extension gap reported less pain (p = 0.036). This effect was still significant at six months (p = 0.044), but had lost significance by 12 months (p = 0.924). When adjusting for multiple cofounders the improvement in pain was more pronounced in patients with a lateral-opening extension gap than in those with a medial-opening extension gap at three (p = 0.037) and six months' (p = 0.027) follow-up.

Using the patient's perspective to develop function short forms specific to total hip and knee replacement based on WOMAC function items.

Although the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index was originally developed for the assessment of non-operative treatment, it is commonly used to evaluate patients undergoing either total hip (THR) or total knee replacement (TKR). We assessed the importance of the 17 WOMAC function items from the perspective of 1198 patients who underwent either THR (n = 704) or TKR (n = 494) in order to develop joint-specific short forms. After these patients were administered the WOMAC pre-operatively and at three, six, 12 and 24 months' follow-up, they were asked to nominate an item of the function scale that was most important to them. The items chosen were significantly different between patients undergoing THR and those undergoing TKR (p < 0.001), and there was a shift in the priorities after surgery in both groups. Setting a threshold for prioritised items of ≥ 5% across all follow-up, eight items were selected for THR and seven for TKR, of which six items were common to both. The items comprising specific WOMAC-THR and TKR function short forms were found to be equally responsive compared with the original WOMAC function form.

[The minimally invasive unicompartmental knee system "Preservation"First clinical results and analysis of complications]. / Der minimal-invasive Halbschlitten "Preservation" Erste klinische Ergebnisse und Komplikationsanalyse.

The Preservation uni knee system is a minimally invasive procedure for implantation of a unicompartmental knee prosthesis. The early results show that the rehabilitation process is quick; the postoperative pain and blood loss is less than after conventional knee arthroplasty. Still there are some pitfalls. The implantation of the tibial mobile-bearing component requires a sound operative technique; otherwise complications will occur. The combination of the available navigation system with the Preservation uni will improve operative accuracy.

Transcranial magnetic stimulation of extrastriate cortex degrades human motion direction discrimination.

The human temporo-parieto-occipital junction is an extrastriate visual area that may mediate motion vision processing. We determined if transcranial magnetic stimulation (TMS) delivered over this extrastriate area would degrade motion discrimination, similar to the transient decrease in spatial acuity observed when TMS is delivered over striate cortex. TMS was delivered 50-250 msec after the onset of a brief, random dot, motion direction discrimination task or a spatial acuity task. TMS significantly reduced correct motion discrimination when delivered 100-150 msec after the random dot stimulus. During the same time window TMS did not significantly effect spatial acuity. TMS over the left extrastriate cortex reduced motion discrimination in both hemifields and its effect had a crude topographical organization. TMS safely perturbs extrastriate visual areas and may reveal the temporal sequence of higher perceptual processing.

Problems with the sterilisation and the maintenance of sterility of arthroscopic instruments: a comparison of different types of camera drapes.

Case reports of gas gangrene following arthroscopy using instruments sterilised with glutaraldehyde demonstrate the inadequacy of this sterilisation method. A safer way to achieve sterility is to combine gas-sterilised arthroscopes and a non-sterile camera covered with a sterile drape. Several different types of camera drapes are available; their different safety aspects are discussed.

[Antetorsion of the femur neck. A variable of the trochanter minor?]. / Die Antetorsion des Schenkelhalses. Eine Variable des Trochanter minor?

The antetorsion angle (beta) of the femoral neck and the "retrotorsion" angle (alpha) of the lesser trochanter were measured in 52 female and 34 male femora taken from 46 human cadavers (age at death 80.3 +/- 8.67 years). In addition, the diameter of the femoral head (d) and the length of the femur (l) were measured. As expected, the antetorsion angle varied over a wide range (beta = 10.5 degrees +/- 9.22 degrees). Measurements on right and left demonstrated an asymmetry: beta right = 8.2 degrees +/- 9.14 degrees; beta left = 12.6 degrees +/- 8.99 degrees. The measurements for retrotorsion of the lesser trochanter also varied in a similar way: alpha total = 31.5 degrees +/- 11.8 degrees; alpha right = 35 degrees +/- 10.7 degrees; alpha left = -28 degrees +/- 11.9 degrees. If alpha and beta are combined to couples, a strong regression is visible (r = 0.7657): beta = 29.5 degrees +/- 0.6 . alpha. Thus, the antetorsion angle depends on the retrotorsion angle or vice versa. The measurements of d and l show marked symmetry: d total = 47.4 +/- 3.6 mm; d right = 47.6 +/- 3.6 mm; d left = 47.2 +/- 3.5 mm; l total = 442.7 +/- 24.6 mm; l right = 441.3 +/- 24.4 mm; l left = 444.0 +/- 24.8 mm. Thus, d and l also vary in dependence on each other (r = 0.578). As the length of the femur is determined by body height, there must be a correlation between the diameter of the femoral head and height; that is to say, a short patient will have a small femoral head.

[Comparative theoretical study of various external fixation devices for the stabilization of distal radius fractures]. / Vergleichende theoretische Untersuchung verschiedener Montagen des Fixateur externe zur Stabilisierung der distalen Radiusfraktur.

In the treatment of comminuted Colles' fractures different types of external fixation devices are used. Three main types are compared: (1) Fixation with two pins in each plane: Ace-Colles' type; (2) fixation with four or more parallel pins in one plane: Wagner/Hoffmann type; (3) fixation with four pins in one plane, two pins on each side of the fracture forming an angle of 60 degrees: ASIF-type fixator. These three types are compared with reference to the different forces that have to be neutralized by the seating of the pin in the bone. To minimize these forces with the aim of preventing pin-loosening, the theoretical results are used as the basis of practical surgical advice: (1) The distance between skin and fixator should be as short as possible. (2) The fixator should be fixed as close as possible to the fracture. (3) The diameter of the pins should be as great as possible. (4) If more than two pins per plane are used (Hoffmann/Wagner type), the pins should be wide apart. (5) If only two pins per plane are used (Ace-Colles Type) the bending stress on each pin is high (6) If more than two parallel pins per plane are used (Hoffmann/Wagner type), the axial forces on each pin are high. (7) The pins should be fixed at right angles to the fractured bone. Pins at other angles do more harm than good.

[The coxal end of the femur. An architecture following strict rules]. / Das koxale Fermurende. Eine Architektur nach strengen Regeln.

In order to combine the dynamic hip screw with a plate that anchors the greater trochanter, detailed measurements of the greater trochanter are necessary and its relation to the femoral head and neck must be studied. The hips in 200 X-ray films in the AP view were measured. The radiographs were obtained from 46 males and 87 females (69.2 +/- 16.9 years old) without hip disease. Concerning the neck shaft angle, no selection was done. The axis of the femoral head and neck was drawn; a second horizontal line passed through the apex of the lesser trochanter. Both lines intersected the lateral cortex of the femur. The distance between those two intersections was measured: d = 0.41 +/- 0.28 cm. In the next step, 74 human femora were obtained from 21 females and 17 males (79.9 +/- 9.0 years old). A special gauge was fixed at the lateral site of the femur. Using this gauge, the size and shape of the greater trochanter were measured: (1) the apex of the greater trochanter lay exactly on the line, which was determined by the lateral cortex of the femoral shaft (+/- 0.4 cm); (2) the maximum lateral extension of the greater trochanter was measured half-way from the lesser trochanter niveau to the apex of the greater trochanter (minor-major distance: 6.09 +/- 0.82 cm; minor-lateral maximum distance: 3.03 +/- 0.59 cm); (3) the maximum lateral extension of the greater trochanter measured 11.4 +/- 3 mm.

Zn2+ regulation of ornithine transcarbamoylase. II. Metal binding site.

Two types of conformational changes are mediated in Escherichia coli ornithine transcarbamoylase by the metal ion zinc. Upon binding of zinc in rapid equilibrium, the enzyme undergoes an allosteric transition. In the absence of substrates, the zinc-bound enzyme further undergoes a slow isomerization with a concomitant activity loss. Three metal ions are tightly complexed in the isomerized enzyme as determined by gel chromatography and atomic absorption spectroscopy. Since the enzyme is a trimer composed of identical subunits, one zinc ion is bound per enzyme monomer. With the application of site-directed mutagenesis, the cysteinyl residue at position 273 of the enzyme has been identified as a metal ligand. When this residue is replaced by an alanine, zinc is no longer a tight-binding inhibitor and does not promote isomerization. The alteration in the action of zinc on the mutant enzyme is attributed to a reduced metal affinity. The mutant enzyme, when saturated by the metal, displays an intrinsic allostery unchanged from that of the wild-type; an identical Hill coefficient of 1.5 is found for zinc binding to the Ala273 and wild-type enzymes. Cys273 is also a binding site of L-ornithine. At pH 8.5, the Ala273 enzyme binds the substrate analog L-norvaline ten times more weakly and exhibits a kcat/Kmorn that is 27 times less than that of the wild-type enzyme. This finding supports our earlier interpretation that the zinc-induced ornithine co-operativity of ornithine transcarbamoylase is caused by direct competition between L-ornithine and the metal for the same site. As controls, each of the remaining three cysteinyl residues of the bacterial ornithine transcarbamoylase has also been replaced with alanine. These sulfhydryl groups are found not to be related to zinc complexation, ornithine binding or enzyme allostery.

Substrate specificity and protonation state of ornithine transcarbamoylase as determined by pH studies.

The ornithine transcarbamoylase catalyzed reaction and its inhibition by L-norvaline have been investigated between pH 5.5 and 10.5. The steady-state turnover rate (kcat) of the enzyme from Escherichia coli increases with pH and plateaus above pH 9. Its change with pH conforms to a single protonation process with an apparent pKa of 7.3. The effect of pH on the apparent Michaelis constant (KMapp) of L-ornithine suggests that this diamino acid in its cationic form is not the substrate. Treating only the zwitterions of ornithine as substrate, the pH profile of the pseudo-first-order rate constant (kcat/KMz) of the reaction is a bell-shaped curve characterized by pKa's of 6.2 and 9.1 and asymptotic slopes of +/- 1. Similar pKa's (6.3 and 9.3) are obtained for the pKi profile of zwitterionic L-norvaline, a competitive inhibitor. The pKi profile further indicates that the alpha-amino group of the inhibitor must be charged for binding. Together, these pH profiles provide sufficient information to suggest that only the minor zwitterionic species of ornithine, H2N(CH2)3CH(NH3+)COO-, binds the enzyme productively. The selection of this substrate form by the enzyme leads to a Michaelis complex in which ornithine is poised for nucleophilic attack. Following such binding, the need for deprotonation of the delta-NH3+ group is avoided, and transcarbamoylation becomes energetically more feasible. Reaction schemes accounting for the effects of pH are proposed for the enzymic reaction.

On the inhibition of microsomal drug metabolism by polychlorinated biphenyls (PCB) and related phenolic compounds.

The in vitro metabolism of p-nitroanisole, aminopyrine, and aniline by rat liver microsomal monoxygenases were studied in the presence of different polychlorinated biphenyl (PCB) mixtures and some related hydroxybiphenyls. The tested PCB mixtures contained preferably dichloro- (di-CB), tetrachloro- (tetra-CB), or hexachlorobiphenyls (hexa-CB). All PCB were competitive inhibitors of only aminopyrine demethylation by normal microsomes (Ki 22-39 micron). In microsomes of PCB-pretreated rats the aminopyrine demethylation was inhibited noncompetitively by di-CB and hexa-CB whereas tetra-CB remained a competitive inhibitor (Ki 12 micron). Moreover, after PCB pretreatment all PCB were competitive inhibitors of p-nitroanisole demethylation. 2-OH-biphenyl and 4-OH-biphenyl caused competitive inhibition of aminopyrine demethylation and aniline hydroxylation but failed to inhibit p-nitroanisole metabolism by normal microsomes. Chlorinated 4-hydroxybiphenyls inhibited competitively the metabolism of both type I and type II substrates. However, after PCB pretreatment all phenolic compounds caused uncompetitive inhibition of aniline hydroxylation.