Partial greater trochanter osteotomy for hip reduction in total hip arthroplasty for high dislocated hip: a preliminary report.

BACKGROUND: Hip reduction in total hip arthroplasty for high dislocated hips is difficult. Various femur osteotomy procedures have been used for hip reduction, but these methods increase operative time and risk of nonunion. We investigated the efficacy of a novel partial greater trochanter osteotomy technique for hip reduction in total hip arthroplasty for patients with high hip dislocation. METHODS: Twenty-one patients (23 hips) with high dislocated hip were treated with total hip arthroplasty that included partial greater trochanter osteotomy, i.e., the upper 2/3 greater trochanter was resected, and the gluteus medius muscle attachment was spared. The clinical outcome was evaluated by comparing the Harris hip scores and radiographic exam results, obtained before surgery and at follow-ups. RESULTS: Follow-ups of 21 patients ranged from 13 to 56 months. The mean Harris hip score increased from preoperative 55.0 (36-69) to postoperative 86.1 (71-93; P = 0.00). The average preoperative leg length discrepancy in patients with unilateral high hip dislocation was 46 mm (28-65 mm); postoperatively leg length discrepancy was less than 1 cm in 11 patients, between 1 and 2 cm in 8 patients, and more than 2 cm in 2 patients. The average leg lengthening at the time of surgery was 36 mm (24-54 mm). Trendelenburg's gait changed from positive to negative in 20 hips by the last follow-up. No nerve injury occurred postoperative. CONCLUSION: Partial greater trochanter osteotomy is an effective method to render hip reduction in total hip arthroplasty for patients with high dislocation of the hip.

In vivo Study on the Corrosion Behavior of Magnesium Alloy Surface Treated with Micro-arc Oxidation and Hydrothermal Deposition.

OBJECTIVE: To study the corrosion behavior of magnesium alloy surface treated with micro-arc oxidation and hydrothermal deposition in living animals. METHODS: A magnesium oxide (MgO) layer was prepared on Mg alloy using micro-arc oxidation technology, and then a composite coating composed of magnesium hydroxide, hydroxyapatite, and MgO was coated on the MgO layer using the hydrothermal deposition method for 2 h and 24 h. Male 3-month-old white New Zealand rabbits (n = 48) weighting 2200-2300 g, were divided into four groups randomly. The prepared Mg alloy samples with composite coatings were implanted into the femoral medullary cavity of rabbits. For the Mg group, bare Mg samples without any treatment were implanted; for the MgO group, bare Mg samples undergoing MAO treatment were implanted; for the HT2h group, samples of the MgO group undergoing hydrothermal treatment (HT) for 2 h were implanted; and for the HT24h group, samples of group MgO undergoing HT for 24 h were implanted. Then the in vivo corrosion behaviors of implants were evaluated by X-ray observation, micro-CT analysis and serum Mg2+ examination. RESULTS: The X-ray showed that samples implanted in animals were decreased as time went by. The micro-CT showed that on the fourth week, the residual volume percentages (RVP) of samples of the Mg, MgO, HT2h, and HT24h groups were 72.81% ± 2.10%, 71.68% ± 1.49%, 81.14% ± 1.54%, and 82.04% ± 0.89%, respectively; on the eighth week, the RVP of four groups were 29.45% ± 1.06%, 41.82% ± 1.13%, 53.92% ± 0.37%, and 62.53% ± 2.06%, respectively; while on the 12th week, RVP were 8.45% ± 0.49%, 9.97% ± 0.75%, 37.09% ± 0.89%, 46.71% ± 1.87%. The RVP of the HT2h group and the HT24h group were higher than for the Mg group and the MgO group for all three time points (P < 0.05); the RVP for HT24h was higher than for HT2h at 8 and 12 weeks, and the differences were significant, indicating that the degradation of Mg alloy slowed down after composite coating. In addition, the composite-coated Mg alloy by 24-h hydrothermal treatment exhibited a slower degradation than that treated by 2 h. Serum Mg2+ concentration results showed that on the second week, the Mg2+ concentrations of the Mg, MgO, HT2h, and HT24h groups were 2.24 ± 0.10 mmol/L, 2.12 ± 0.07 mmol/L, 2.06 ± 0.11 mmol/L, and 2.15 ± 0.12 mmol/L, respectively. On the fourth week, these concentrations were 1.99 ± 0.33 mmol/L, 2.18 ± 0.06 mmol/L, 2.17 ± 0.09 mmol/L, and 2.13 ± 0.14 mmol/L, respectively. On the eighth week, the concentrations were 2.22 ± 0.09 mmol/L, 2.20 ± 0.17 mmol/L, 2.06 ± 0.11 mmol/L, and 2.14 ± 0.07 mmol/L, respectively. On the 12th week, the concentrations were 2.18 ± 0.04 mmol/L, 2.20 ± 0.08 mmol/L, 2.09 ± 0.02 mmol/L, and 2.16 ± 0.11 mmol/L. CONCLUSION: The combination of micro-arc oxidation and hydrothermal deposition can greatly improve the anti-corrosion behavior of Mg alloy, and Mg alloy coated with this composite coating is a promising biomaterial with a satisfactory degradation rate.

[Effects of artificial disc replacement with angles on stress of adjacent intervertebral disc].

OBJECTIVE: To evaluate stress changes of intervertebral space and adjacent intervertebral space after artificial disc replacement with angles. METHODS: Artificial disc replacement with angles were designed according to existing data. Axial pressure, flexion/extension, lateral bending and torsion loading were applied on finite element models of normal cervical discs on C4,5 segments, C4,5 segments with 0 degrees artificial cervical discs and C4,5 segments with 10 degrees artificial cervical discs, then stress changes of C4,5 space was observed. The same loadings were applied on finite element models of normal cervical discs on C4-C6 segments, C4,5 segments with 0 degrees, C4,5 segments with 10 degrees, then stress changes of replaced segments space and adjacent segment space were observed. RESULTS: For C4,5 segments, 80 MPa/0 degrees artificial discs and 80 MPa/10 degrees artificial discs had the similar equivalent shear stress (Se), and were both larger than that of normal discs, when lateral bending were performed, 80 MPa/0 degrees artificial discs were closed to normal discs when axial pressure and flexion/extension were carried out, while 80 MPa/10 degrees artificial discs had a larger Se than that of normal ones,when torsion loading were applied, Szx/Szy stress of 80 MPa/0 degrees and 80 MPa/10 degrees artificial discs were closed to normal ones. For C4-C6 segments, the axial pressure, flexion/extension and lateral bending of C5,6 were all lower than normal discs after C4,5 discs were replaced by 80 MPa/10 degrees artificial discs, while Szx/Szy of torsion loading were closed to normal ones. CONCLUSION: Artificial discs with 10 degrees have less influences on stress of adjacent intervertebral space and closer to mechanical property after being implanted into intervertebral space.

[Effect of estrogen on osteoprotegerin, osteoclast differentiation factor and macrophage colony stimulating factor mRNA expressions in ovariectomized rat bone tissue].

OBJECTIVE: To observe the effect of the estrogen on the mRNA expression of osteoprotegerin (OPG), osteoclast differentiation factor (ODF) and macrophage colony stimulating factor (M-CSF) in bone tissue of ovariectomized rats, and investigate the possible pathway of estrogen in preventing and treating postmenopausal osteoporosis. METHODS; Thirty healthy adult SD rats were randomly divided into sham operation group, ovariectomized group and estrogen-treated group. All rats were ovariectomized except those in the sham operation group. Bone density of the L3-L6 vertebra was detected 12 weeks after the operation. The total RNA were extracted from the femur to examine mRNA expression of OPG, ODF and M-CSF by real-time PCR. RESULTS: Estrogen increased the bone density of the ovariectomized rat lumbar vertebra and up-regulated the expression of OPG, whereas down-regulated the expression of M-CSF and lowered ODF:OPG ratio. CONCLUSION: The effect of estrogen in treating postmenopausal osteoporosis is closely correlated with the regulation of OPG and M-CSF expressions and ODF:OPG ratio.