Most studies about hemi-arthroplasty of hip have focused on clinical aspects. Design features of various implants of hemi-arthroplasty have not been studied extensively. The aim was to investigate the relationships between radiological variables and possible mode of failure in various hemiarthroplasty implants in intracapsular neck of femur fractures. A retrospective review of 42 hemi hip arthroplasties, Austin Moore and Thompson prosthesis by Biomet, Medical Product Service (Tipsan) and Smit Medimed (SMPL) used in our hospital. Controversy exists between indication for a particular design in an unselected series of patients once excluding the choice of cementing or uncementing the prosthesis. In monoblock prosthesis not only the head-neck region affects the stability but also the stem fit in proximal femur. Surgeon preference to technique and approach excluded. Premorbidly all patients were mobilising independently. 5 criteria reviewed. 1) head size of prosthesis 2) neck length 3) prosthesis stem shaft angle 4) stem-cortical distance ratio and 5) shape of the femoral canal as classified by Dorr. Head size compared in AP views of involved hip and normal head size compared with that of prosthesis. A difference <2 mm or >3 mm indicative of incorrect size. Neck length measured by the vertical distance from center of head to superior aspect greater trochanter was zero. A range of +/− 5 mm was acceptable. Neck shaft angle with a difference of >5 degrees was indicative of varus position of the stem. Canals of the proximal femoral categorized as a) stove pipe b) champagne c) fluted varieties radiologically. X-ray magnification corrected. All measurements were done on immediate postoperative radiographs. Stability of various design features of straight stemmed and curved implants are dependant on the anterior bowing angle and canal ratio of femur to prosthesis. A prospective study with CT from selected shapes of the proximal femoral is being carried out. Inappropriate head size as reported by Thompson or neck length was related to incidence of dislocation resulting in failure. Our findings emphasise importance of careful selection of a particular implant design towards the morphology of the femoral canal.
Mini-incision total hip arthroplasty seeks to eliminate some complications of traditional extensile exposure and also facilitates more rapid post-operative rehabilitation. Posterior approach has been associated with increased risk of posterior dislocation. Thus, a modified mini-incision lateral approach of Hardinge was described not only to overcome this problem by preserving the posterior capsule, but also allows adequate access for orientation of the implant. The author has modified the Hardinge approach by a V-shaped incision where the apex is centered over the tip of the greater trochanter with the one limb extending proximally along the fibers of the gluteus medius muscle and the distal limb extending across the proximal part of vastus lateralis. This innovative surgical approach is described in this article. Larger incisions and surgical approaches have been associated with larger blood loss, greater need for perioperative transfusion, use of more postoperative analgesics, a longer hospital stay, and a slower recovery. In this modified approach, the gluteus medius is left intact. The postoperative strength of the abductors of the operated side was the same as that on the non-operated side and functionally, the direct lateral approach was a safe alternative to other approaches in decreasing the trendelenburg gait and incidence of heterotrophic ossification.Conclusion
Stress shielding of the proximal femur occurs in stemmed implants. Resurfacing implant does not invade the intramedullary region. We studied the stress patterns in conventional and nonstemmed designs. FE model geometry was based on standard femur from the international Society of Biomechanics Mesh Repository. Loading simulated for one- legged stance with body weight of 826 N. 2 regions were defined, R1 (40 mm from tip of head) and R2 41 mm–150 mm) of the intramedullary part of the stemmed model's interface with bone. 2 different loading conditions bending and torsion were compared for stress and strain. The FE model was solved with ANSYS version 6.1 on a single processor NT station. With conventional implants, stem shields cortical bone from being loaded. In nonstemmed implants, Von Misses stress contours show a similar distribution as intact bone, transferring loads to the cortical shell but with higher stresses and a maximum displacement of 17.39% higher than that of intact bone. 15–23 mm proximal to R2 and around 110 mm, region of the stem tip, there were higher stress and strain concentrations.Methods
Results
Core decompression is used in precollapse lesions to forestall disease progression in avascular necrosis (AVN) of femoral head (FH). The author reports a new technique using reverse bone graft technique to effectuate core decompression. To prevent precollapse in Ficat Type 1&2 and revascularization using synthetic bone graft material.Introduction
Aim
CAN TKR is aimed to improve accuracy in realignment with balanced knee joint. Variability in the force exerted during tissue tensioning depends on the viscoelastic nature of soft tissues.
Relationships between OT/UT analyzed by Spearman rank ratio p<
0.001.
