Minimally invasive compared with traditional transgluteal approach for total hip arthroplasty: a comparative gait analysis.

BACKGROUND: Minimally invasive total hip arthroplasty is purported to allow an improved and faster rehabilitation in the immediate postoperative period because of reduced soft-tissue damage compared with total hip arthroplasty performed with use of a standard approach. In the present study, a minimally invasive approach was compared with a traditional standard approach in terms of the effect on gait kinematics as demonstrated with gait analysis and electromyography. METHODS: Twenty randomized patients who underwent a primary total hip replacement with use of a minimally invasive modified Watson-Jones approach (minimally invasive group) were compared with a group of twenty patients who underwent a total hip arthroplasty with use of a standard transgluteal Hardinge approach (standard group). All patients received the same cementless implant, inserted with use of standard instruments, and all operations were performed by a single, experienced surgeon. The patients were evaluated with use of three-dimensional gait analysis and dynamic electromyograms at three time points: preoperatively, ten days postoperatively, and twelve weeks postoperatively. Temporospatial and joint-kinematic parameters were evaluated. RESULTS: There were no significant differences between the two groups with regard to the temporospatial variables of velocity, cadence, step length, and stride length at any tested time point. With regard to the range of motion of the operatively treated hip, the minimally invasive group had a smaller decrease at the ten-day time point in comparison with the standard group. However, this finding was not significant. The reduction in the range of motion was mainly caused by reduced hip extension. A compensatory increase in the pelvic tilt was observed in both groups. One patient in the standard group showed a positive Trendelenburg gait ten days postoperatively; it had disappeared completely at the twelve-week time point. CONCLUSIONS: With regard to gait kinematics in the early postoperative period (three months), the present study showed no significant benefit for patients who underwent a total hip arthroplasty through a minimally invasive Watson-Jones approach in comparison with those who were managed with a standard transgluteal approach.

Retrieval analyses of highly cross-linked polyethylene acetabular liners four and five years after implantation.

Two Durasul highly crosslinked polyethylene liners were exchanged during revision surgery four and five years after implantation, respectively. The retrieved liners were evaluated macroscopically and surface analysis was performed using optical and electron microscopy. A sample of each liner was used to determine the oxidation of the material by Fourier transform infrared spectroscopy. Samples of the capsule were examined histologically. The annual wear rate was found to be 0.010 and 0.015 mm/year, respectively. Surface analysis showed very little loss of material caused by wear. Histological evaluation revealed a continuous neosynovial lining with single multinucleated foreign-body giant cells. Our findings showed no unexpected patterns of wear on the articulating surfaces up to five years after implantation and no obvious failure of material.

Cementless total hip arthroplasty using a threaded cup and a rectangular tapered stem. Follow-up for ten to 17 years.

We carried out a clinical and radiological review of 103 cementless primary hip arthroplasties with a tapered rectangular grit-blasted titanium press-fit femoral component and a threaded conical titanium acetabular component at a mean follow-up of 14.4 years (10.2 to 17.1). The mean Harris hip score at the last follow-up was 89.2 (32 to 100). No early loosening and no fracture of the implant were found. One patient needed revision surgery because of a late deep infection. In 11 hips (10.7%), the reason for revision was progressive wear of the polyethylene liner. Exchange of the acetabular component because of aseptic loosening without detectable liner wear was carried out in three hips (2.9%). After 15 years the survivorship with aseptic loosening as the definition for failure was 95.6% for the acetabular component and 100% for the femoral component.

Tribological considerations for a new hip system.

PURPOSE OF THE STUDY: This paper was initiated to evaluate a new total hip system based on cementless fixation and focusing options for different articulations within a single hip system. MATERIAL AND METHODS: 100 patients provided with the cementless Variall hip system were evaluated clinically and radiographically. The 59 female and 41 male patients were followed for a minimum of 3 years postoperative. They were clinically evaluated using the Harris Hip Score. Radiographic analysis was based on plain x-rays at the latest follow-up evaluation. RESULTS: The evaluated patients achieved an excellent clinical result with an average Harris Hip Score of 94,3 points after an average follow-up of 42 months. The radiographic evaluation of the threaded cup did not exhibit any migration of the implant nor could we find radiolucencies. All tapered stems were radiographically stable. Due to the modified proximal design and the macrostructure an improved stem bone interface was found during the follow-up period. DISCUSSION The new cementless cup with its cylindrical threads and the spherical floor achieves an anatomic fit within the acetabulum and provides excellent primary stability. The design of the gamma inlay offers the fixation of ceramic and metal articulations without polyethylene interface. Additionally, options for conventional and cross-linked polyethylenes are available. These facts make the cup a cost-effective device. The design of the new uncemented stem guarantees a high degree of primary stability and excellent rotational stability due its rectangular cross section. This pressfit is further enhanced by the proximal macrostructure of the implant, again ensuring an excellent bond between prosthesis and bone. CONCLUSION: Thanks to the versatility of all the components this comprehensive new total hip prosthesis offers many options for a long-term successful implant. Additionally, it is a cost-effective solution - an important fact of nowadays strained financial situation in public health care.

Experimental investigation of threaded cup performance during insertion in total hip replacement.

Cementless threaded cups are often used in Europe on the acetabular side of a total hip arthroplasty (THA), with some products achieving excellent clinical results. Titanium and titanium alloys are nowadays accepted as the materials of choice for these implants. In contrast, however, there is no consensus about the ideal thread design. This in vitro and human cadaver study aimed to compare the insertion torques of commercially available threaded cups during insertion. The aims were (1) to see whether the clinical experience of surgeons using these cups specifically related to insertion torque could be reproduced in the experiment and (2) to assess whether or not the cup size and thread design has a statistically significant influence on the insertion torque. Using a biaxial testing machine the cups were screwed into pre-machined polyurethane blocks and the insertion torque was recorded by an appropriate sensor. Clear differences were seen between the four different designs. A variance analysis using statistical software showed that both the cup size (p=0.003) and the thread design (p=0.0009) significantly affect the insertion torque. The human cadaver study allowing a right-left comparison of two different cups within the same specimen confirmed the insertion torque data of the experimental study. In addition, the trends observed during the course of the insertion agreed with the clinical experience of the orthopaedic surgeons consulted as part of this study. (Hip International 2004; 14: 11-7).