The effect of calcar contact on femoral component micromovement. A mechanical study.

Extra-long-neck, large-stem Trapezoidal-28 femoral components with standard and modified large flanges were cemented into fresh cadaver femora and measurements were made of the movement of the prostheses relative to the bone as load was applied to the head of the prosthesis. In the presence of collar-calcar femoral contact, the prosthesis subsided very little under load; displacements for a load of 2000 newtons were less than 0.1 millimeter. Removal of bone and acrylic support beneath the undersurface of the flange by sawing a thin gap caused no increase in the displacement of the stem tip in most specimens, but the displacements of the collar relative to bone for the standard flange design increased by an average of 0.014 millimeter (8 to 28 per cent) under a 2000-newton force when contact was removed, while the displacements for the prostheses with a modified large flange that extended to the cortical rim of the resected neck increased 0.047 to 0.060 millimeter (56 to 432 per cent), indicating greater support from the collar due to the increased area of contact. An increase of the stem-flange angle of 22 degrees (from 30 to 52 degrees), making the flange more horizontal, had no significant effect on the results for large-flanged units. Prostheses with a standard flange and a one to two-millimeter Silastic liner between cement and bone subsided as much as twenty times more than rigidly cemented units. In the presence of the liner, removal of collar-calcar contact increased the collar displacement by 29 to 75 per cent, indicating a possibly important function of the flange for components cemented in soft bone or components that may become loose or be surrounded by a fibrous membrane. Repacking of the gap between the collar and bone with acrylic after removal of part of the calcar femoral reduced subsidence in one specimen, while the acrylic in a second specimen cracked out during reloading. Based on our laboratory experience with sixteen specimens, we believe that it would be extremely difficult to achieve an effective degree of uniform calcar femorale-collar contact at operation and that one or two localized contact areas would be the more common situation after total hip replacement.

Mechanical stability of the greater trochanter following osteotomy and reattachment by wiring.

Greater trochanters of fresh and formalin-perserved cadaver femora were osteotomized, rewired using techniques described by Amstutz, Charnley, Coventry and Harris, and then mechanically tested. Force simulating abductor muscle pull was applied to the trochanter in the plane of section while its displacement was measured continuously with an extensometer. Although many trochanters appeared rigidly fixed when stressed manually, all displaced visibly when 27 kg load was first applied. When released, permanent sets averaging 0.1 mm (Charnley and Harris) to 3--4 mm (Coventry) were measured. Subsequent repeated loadings (0--27 kg) from this new "rest" position produced recoverable cyclic "functional" displacements averaging 0.7 mm (Charnley and Harris) to 2.3 mm (Coventry). With the exception of the specimens wired by the Coventry technique, results for a simulated 45 degrees anterior pull were generally comparable to those for a neutral pull. Ultimate failure loads of the trochanteric fixation were on the order of 110 kg for selected fresh specimens.

The treatment of arthritis of the shoulder joint by double osteotomy.

This paper presents the new operations of double osteotomy of the shoulder for the treatment of painful arthritis. The procedure consists of osteotomy without displacement of the necks of both the scapula and the humerus. Sixteen patients who have had this operation have been followed for one to nine years (average 2 years 11 months). The results show good or excellent pain relief in 13 patients and a substantial increase in active abduction in 13 patients. Complications were few and none were serious. A possible reason for the reduction of pain is suggested and the advantages of this operation over arthrodesis and total shoulder replacement are discussed.

A comparison of the treatment of trochanteric fractures of the femur by internal fixation with a nail plate and the Ender technique.

In our experience, trochanteric fractures fixed with Ender nails achieved a degree of success similar to those treated by nail plating, but the risk of wound infection was much less with the former method. The results of 78 trochanteric fractures of the femur internally fixed with Ender nails have been analysed and compared with the results in 100 similar patients treated by nail plate fixation. The Ender method has advantages over existing operative methods, in that in our series the infection rate was zero and we found that the operation produced less shock. We consider that this method, although technically more difficult, can be used for most intertrochanteric fractures and merits further trial.

Effect of excising Freund's adjuvant granuloma on subsequent development of experimental allergic arthritis.

Rabbits were immunized with antigen in Freund's complete adjuvant. Several weeks later the granuloma which developed was excised one day before joint challenge with antigen. The subsequent development of experimental allergic arthritis (EAA) was not affected, which argues against the chronicity of the disease being maintained by continuous recruitment of mycobacterial debris to EAA joints.