Rotational acetabular osteotomy (RAO), Chiari osteotomy and shelf procedure are important treatments to delay the progression of osteoarthritis in developmental dysplasia of hip (DDH) patients, but their biomechanical differences are still unknown. This study was to evaluate the different biomechanical changes of hip joint after these three surgeries. Sixteen DDH models of 8 human cadaver specimens were reconstructed, and treated by different surgeries, and then strain around femoral head was evaluated by strain gauges. Hip strain value of DDH model was decreased after treated by shelf procedure (Pleft = 0.016 and Pright = 0.021) and rotational acetabular osteotomy (P = 0.004), but not in Chiari osteotomy (P = 0.856). Moreover, the improved ratio of RAO treatment was better than shelf procedure (P = 0.015) and Chiari osteotomy (P = 0.0007), and the descendent range of shelf procedure was greater than Chiari osteotomy (P = 0.018). From biomechanics points, RAO was more effective in relieving hip joint stress compared with shelf procedure and Chiari osteotomy.

https://link.springer.com/content/pdf/10.1186%2F1471-2474-15-47.pdf

The biomechanical differences of rotational acetabular osteotomy, Chiari osteotomy and shelf procedure in developmental dysplasia of hip

Background Total hip arthroplasty (THA) in developmental dysplasia of hip (DDH) is difficult for the abnormal acetabulum. The purpose of this study was to evaluate the difference of anatomic and upward placement of acetabular component during early stage. Methods From April 2014 through June 2015, forty DDH patients (Crowe I to III, 42 hips) were prospectively randomized to either anatomic or upward group. Patient recorded diaries were collected. Radiographs were reviewed. WOMAC and Harris scores were tabulated from pre-operation to 12 months after surgery. Results The patients' characteristics including age and body mass index (BMI) had no significant difference (P > 0.05). There were no statistically differences between two groups for surgery time, intraoperative blood loss, hemoglobin (Hb), blood transfusion, albumin decrease, length of stay-day, but surgery time and blood loss in patients with structural bone graft was much higher in anatomic group. The postoperative limb-length discrepancy (LLD) was also no difference, but limb lengthening was better in anatomic group (P = 0.042). The total hospital costs in the anatomic group were higher, but no significant differences. With regard to Harris and WOMAC score, there were significant improved after surgery in both groups, and the anatomic group was better in the value, but these differences were no statistically significant. Conclusions Acetabular reconstruction for DDH subluxation should be reconstructed as close to the actual acetabular location as possible, but an appropriate (

Cementless acetabular component with or without upward placement in dysplasia hip: Early results from a prospective, randomised study.

Purpose
Both rotational acetabular osteotomy (RAO) and eccentric rotational acetabular osteotomy (ERAO) are effective procedures for young patients with developmental dysplasia of the hip. However, no comparative study of biomechanical changes has been reported following these two procedures. We therefore explored the stress changes on femoral head after RAO and ERAO under different load conditions.

A comparison of biomechanical changes on femoral head following rotational acetabular osteotomy and eccentric rotational acetabular osteotomy in normal cadaveric hip

The centre of rotation of the hip can be displaced in hip dysplasia and revision arthroplasty. This study examined the effect of artificial femoral head load after acetabular component displacement in total hip arthroplasty. Sixteen total hip arthroplasty models of human cadaver specimens were reconstructed, and under different acetabular component position, the load around the femoral head was evaluated by strain gages. The results showed that the load was higher in the same specimens when the cup was moved 2 mm inward or upward, especially after the cup was moved more than 6 mm, and the load had an increasing effect in the inward group. In the upward group, an increasing effect happened at 8 mm upward displacement, but the stress value decreased from 4 mm to 6 mm upward displacement. In the same moving distance, the stress of inward displacement is obviously higher than upward displacement. Altogether, the results suggested that for both inward displacement and upward displacement of the acetabular cup, the load around the femoral head increased gradually, while the distance of the inward displacement and the superior displacement was increased. The greater the displacement, the bigger the loading contact stress. The upward displacement caused less stress change on the femoral head. The stress of the 6 mm upward position was lower than nearby positions; perhaps this site represented a stress buffering zone.

/pdf/upward-and-inward-displacements-of-the-acetabular-component-2fh7mg6ymr.pdf

Upward and inward displacements of the acetabular component increase stress on femoral head in single endoprothesis models

OBJECTIVE
To determine whether one larger or two smaller diameter pins used for tibial tuberosity avulsion fracture (TTAF) stabilization provides greater axial tensile strength and stiffness when subjected to monotonic mechanical load to failure in normal skeletally mature canine cadavers.


STUDY DESIGN
Paired ex vivo biomechanical study.


SAMPLE POPULATION
Eleven pairs of adult cadaveric dog tibias.


METHODS
Twenty-two tibias from 11 dogs were collected to model a TTAF. Each limb of a pair was randomly assigned a one or two-pin fixation. Tibias were subjected to monotonic, axial load to failure. Fixation stiffness, strength, and pin insertion angles were analyzed with parametric testing. Significance was set at p < .05.


RESULTS
The mean strength of the single-pin fixation was 426.2 ± 50.5 N compared to two-pin fixation at 639.2 ± 173.5 N (p = .003). The mean stiffness of the single-pin fixation was 57.3 ± 18.7 N/mm and the two-pin fixation was 71.7 ± 20.5 N/mm (p = .029). The normalized ratio between one and two-pin fixation had a mean stiffness of 68% ± 25.8% and strength of 82.8% ± 24.6%.


CONCLUSIONS
In an ex vivo cadaveric TTAF model, vertically aligned two-pin fixation offers greater strength and stiffness when compared to a single-pin fixation.


CLINICAL SIGNIFICANCE
When repairing TTAF, surgeons should aim to apply two vertically aligned pins rather than a single pin for greater strength and stiffness.

Biomechanical comparison of one pin versus two pin fixation in a canine tibial tuberosity avulsion fracture model.

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Upward and inward displacements of the acetabular component increase stress on femoral head in single endoprothesis models

Biomechanical comparison of one pin versus two pin fixation in a canine tibial tuberosity avulsion fracture model.