The Relaxation of Some Acrylic Bone Cements

The creep and relaxation of acrylic cements during conditions simulating the conditions in the acetabulum have been examined. CMW and Simplex were found to reach stresses of about 10 N/cm² after 1 year whereas Palacos had lost most of its stress after 6 weeks.     

Penetration of Acrylic Bone Cements into Cancellous Bone

The depth of penetration of five commercial acrylic bone cements into cancellous bone was measured in vitro. Under standard, idealized conditions, cement penetration was found to vary significantly with different cements. Penetration was critically influenced by the coarseness of the cancellous bone and increased directly with the effective volume of the “cells” within the osseous matrix. An inverse correlation was determined between the mean cement viscosity during flow into the bone and final penetration depth. The dough time, set time and working time of each acrylic formulation was found to have no significant effect upon the depth of cement penetration.

It is suggested that in addition to the techniques adopted for introduction of cement to the bone, the selection of the bone cement itself may critically influence the incidence of late loosening following total joint replacement.     

Penetration of Acrylic Bone Cements into Cancellous Bone

The depth of penetration of five commercial acrylic bone cements into cancellous bone was measured in vitro. Under standard, idealized conditions, cement penetration was found to vary significantly with different cements. Penetration was critically influenced by the coarseness of the cancellous bone and increased directly with the effective volume of the “cells” within the osseous matrix. An inverse correlation was determined between the mean cement viscosity during flow into the bone and final penetration depth. The dough time, set time and working time of each acrylic formulation was found to have no significant effect upon the depth of cement penetration.

It is suggested that in addition to the techniques adopted for introduction of cement to the bone, the selection of the bone cement itself may critically influence the incidence of late loosening following total joint replacement.     

The Modulus of Elasticity and Flexural Strength of Some Acrylic Bone Cements

The modulus of elasticity and flexural strength were measured for three bone cements, CMW Bone Cement, Surgical Simplex, and Palacos R, with various additions and prepared as in actual use. A distinct afterpolymerization was demonstrated in all three brands. The addition of blood lowered the E-modulus whereas radio-opaque media seemed to render them somewhat stiffer. The rupture values demonstrated the inhomogeneity of the final product in all three brands. The possible clinical significance of the findings is discussed.     

Characterization of Bone Cements

Thirty-seven patients with fractures of the thoracic and lumbar spine treated with Harrington instrumentation were reviewed. Twenty-seven patients with a follow-up time of more than 2 years were summoned for a clinical and radiographic examination. This report presents the results related to reduction, stabilization, return of neural function, spinal posture and mobility, and residual disability. It is concluded that Harrington instrumentation can be performed without a substantial number of complications. Its major advantages are early mobilization and ambulation. The operative technique is discussed with special reference to the preservation of the normal configuration of the back. The value of computerized tomography in the preoperative assessment is stressed.     

Incorporation of Bone Graft Covered with Methylmethacrylate onto Acetabular Wall: An Experimental Study

The acetabular model, as described in the present study, appears to serve as a promising experimental model for grafting procedures since it promotes the acceptance of autogenous grafts and the induction of new bone formation. Further, the biologic and mechanical properties of the femoro-acetabular joint appear permissive to the development of an efficient reparative system even when a foreign material such as methylmethacrylate cement is incorporated into the overall reconstructive procedure. Hence, it is hereby recommended to utilize the biological approach in the frame of replacement arthroplasty of severely damaged acetabulum.     

Polyaxial Locking and Compression Screws Improve Construct Stiffness of Acetabular Cup Fixation: A Biomechanical Study

Bone ingrowth into uncemented acetabular components requires intimate cup-bone contact and rigid fixation, which can be difficult to achieve in revision hip arthroplasty. This study compares polyaxial compression locking screws with non-locked and cancellous screw constructs for acetabular cup fixation. An acetabular cup modified with screw holes to provide both compression and angular stability was implanted into a bone substitute. Coronal lever out, axial torsion and push-out tests were performed with an Instron testing machine, measuring load versus displacement. Polyaxial locking compression screws significantly improved construct stiffness compared with non-locked or cancellous screws. This increased construct stiffness will likely reduce interfacial micromotion. Further research is required to determine whether this will improve bone ingrowth in vivo and reduce cup failure.     

骨水泥填充修复骨缺损在翻修髋臼假体内侧移位松动中的疗效

目的探讨骨水泥填充修复骨缺损结合骨水泥髋臼假体在翻修髋臼假体内侧移位松动中的临床疗效。方法 2006年4月~2011年3月收治16例髋臼假体内侧移位松动患者,均采用骨水泥填充修复骨缺损结合骨水泥聚乙烯髋臼假体翻修松动的髋臼假体,对伴有股骨假体松动的患者,根据患者的骨质情况和骨缺损情况选择骨水泥翻修长柄假体(9例)、非骨水泥型广泛涂层假体(2例)或打压植骨结合骨水泥固定股骨柄假体(1例)。术后进行临床评估及X线评估。结果 16例患者术后平均随访2.6(1.5~6.2)年,未出现臼杯松动病例,Harris评分从术前的35(18~63)分提高到末次随访时的89(60~99)分。结论应用骨水泥填充修复骨缺损结合骨水泥髋臼假体翻修内侧移位松动的髋臼假体是一种有效的手术方法。     

Treatment of Failed Allograft Prosthesis Composites Used for Hip Arthroplasty in the Setting of Severe Proximal Femoral Bone Defects

This study assessed failures of allograft prosthesis composites (APC) and revisions with a new APC. Twenty-one patients with failed APC’s after revision hip arthroplasty with severe proximal femoral bone loss underwent revision with a new APC. Causes of failure were aseptic loosening (18 patients), infection (3 patients). Of these 21 APC revisions, two patients failed (after 60, 156 months). The 5 and 10 year survival rates were 83.5% (95% CI, 79–100%, number at risk 12 and 6 accordingly). In addition, two patients had non-union at the host-allograft bone junction and were augmented with bone autograft and plate. These results suggest that failed APCs may be revised to a new APC with a predictable outcome.     

The Results of a Press-Fit-Only Technique for Acetabular Fixation in Hip Dysplasia

The purpose of the present study was to evaluate the 6- to 11-year follow-up results of hemispherical porous-coated cups implanted into dysplastic hips using press-fit technique without screws focusing on the amount of host bone coverage. There were 87 patients who underwent 98 primary total hip arthroplasties. Bony coverage was measured as the angle between the vertical line and the line drawn from the cup center to the lateral edge of the acetabulum, which was named the cup center-edge angle (cup-CE angle). All 98 cups were judged to be bone ingrown. The minimum cup-CE angle was 8.4° (mean, 26.3°). Bone-cup contact of more than 8.4° of the cup-CE angle was large enough for press-fit cups to resist superior directed loads during this follow-up period.     

The Risk of Acetabular Protrusion Following Prosthetic Replacement of the Femoral Head

A total of 214 patients treated with hemiarthroplasty showed a crude frequency of acetabular protrusion of 26 per cent. Two factors were associated with the development of protrusion: the length of the follow-up period and previous hip operation. The frequency of protrusion was estimated using logistic regression techniques based on information concerning the age of the patients, the length of the follow-up period and any previous hip operation. The frequency ranged from 4.8 per cent for a patient of 75 years or under, with a follow-up period of less than 12 months and no previous hip operation, to 61 per cent for patients of over 75 years, with a follow-up period exceeding 12 months, and a previous hip operation. Patients of over 75 years were 1.7 times more likely to develop protrusion than younger patients, patients previously operated on were 2.3 times more likely to develop protrusion than those not operated on previously, and patients with a follow-up time period exceeding 12 months were 7.9 times more likely to develop protrusion than patients with a shorter follow-up time.     

Wagner SL 翻修型股骨柄在人工髋关节翻修术中的疗效分析简

目的探讨采用WagnerSL翻修型股骨柄在人工髋关节翻修中的方法及疗效。方法自2006年3月至2012年3月,采用Wagner自锁式无骨水泥固定型翻修股骨柄对31例患者（共31髋）行人工髋关节翻修术。其中男性16例,女性15例;年龄41～75岁,平均63．2岁。髋关节翻修术距离初次人工全髋置换的时间是1—20年,平均65．3个月。翻修原因：无菌性假体松动25例,髋关节假体周围感染6例,均为第一次翻修。结果31例均获得了随访,随访时间为0．5—6年,平均为2．7年。患者手术后切口均为I期愈合,无下肢深静脉血栓及坐骨神经损伤等并发症出现。在随访期间没有出现假体松动和感染,假体周围可以看到明显骨长入。有9例患者出现了不同程度的假体下沉,但均无明显的髋部疼痛症状,因此未做特殊处理。末次随访时,Harris评分由（36．24±8．27）分提高到（83．78±4．92）分,MedeD’Aubigne评分由（2．54士5．38）提高到（13．42士3．26）分,VAS疼痛评分由（7．32士0．72）分减低到（1．26±0．61）分,与手术前比较差异具有统计学意义（P〈0．05）。结论使用WagnerS“L”型翻修股骨柄进行人工髋关节翻修术后,近期疗效满意,能明显地缓解疼痛,改善了髋关节的功能。     

Segmental Replacement of the Femur in Baboons with Fiber Metal Implants and Autologous Bone Grafts of Different Particle Size

A study was made of bone ingrowth into fiber metal composite prostheses used to replace large segments of the femur in baboons. Bone grafts of two different types were used to cover the segment: chips of bone with large particle size and ground bone with a smaller particle size. The prosthetic segment was bridged by bone at 3 and 6 months in all cases irrespective of the structure of the transplant. In animals sacrificed at 6 months bone ingrowth occurred, with a marked difference between specimens with the two different grafts. In the ground bone specimens ingrowth occurred over the total surface area, and bone penetrated deep into the composite. With the chip grafts ingrowth was more irregular occurring only in some areas and it was always superficial. The difference is believed to be due to the improved contact between the fiber metal surface and the transplant. The lesser bulk of the ground transplant is advantageous when the soft tissue cover of the bone is thin.     

Improved Antibiotic Impregnated Cement Prosthesis for Treating Deep Hip Infection : A Novel Design Using Hip Compression Screw

A 2-stage revision arthroplasty has been suggested as the optimal treatment for deep infections in the hip joint. Improvement of the surgical technique to increase the interim function is subject to investigation. From 2004 to 2007, we collected a cohort of 15 consecutive patients who were treated by a novel design augmented with a modified hip compression screw. No fracture of the cement spacer occurred. We believe the modified hip compression screw is a good alternative for the functional endoskeleton of an antibiotic loaded cement prosthesis in the treatment of deep hip infection.     

Extrosseous Variations of Temperature During Polymerization of Acrylic Cement in Hip Arthroplasties

In order to evaluate the extraosseous temperature variations during polymerization of acrylic cement being used in hip arthroplasty, measurements were taken on the anterior aspect of the upper part of the femur and also in the ipsilateral iliac vein. No variations were observed in the blood stream. On the external surface of the upper femur, the greatest variations were of the order of 3° C. The significance of these findings is discussed.     

The Influence of Pelvic Tilt on the Anteversion Angle of the Acetabular Prosthesis

The concept of the “safe area” of the acetabular prosthesis has a long history and has been recognized by many scholars. It is generally believed that postoperative hip dislocation rate is low, when the acetabular anteversion angle is placed in the range of 15° ± 10°. Despite this, hip dislocation is a common complication after total hip arthroplasty. In recent years, more and more scholars have paid attention to the influence of pelvic tilt on the acetabular anteversion angle. The concept of acetabular anteversion changes as the pelvic tilt changes, and is challenging the traditional acetabular prosthesis “safe area.” This study summarized the potential influencing factors of pelvic tilt and discussed the influence of the phenomenon on the anteversion angle of total hip arthroplasty (THA) acetabular prosthesis based on the literature review. We conclude that from the supine position to standing, followed by sitting, the pelvis tends to move backward. Pelvic sagittal activity, lumbar disease (ankylosing spondylitis), lumbar fusion (lumbar fusion, spine‐pelvic fusion), and other factors related to the tilt are THA risk factors for postoperative dislocation and revision. With the change of body position, the degree of acetabular anteversion is directly related to the degree of pelvic tilt. The acetabular anteversion varies greatly, which leads to increased hip prosthesis wear and even hip dislocation. The lateral X‐ray of the spine and pelvis is recommended in supine, standing, and sitting positions before THA. In addition, the pelvic tilt should be regarded as a reference of the acetabular prosthesis in the preoperative planning of THA.     

Factors Associated with Heterotopic Bone Formation in Cemented Total Hip Prostheses

A series of 237 total hip replacements were analysed by means of a computer program. High body weight and postoperative fever, as well as several indications of a technically demanding operation, occurred significantly more often in the group of patients which developed paraarticular ossification postoperatively. the results point to a causal relation between tissue trauma and heterotopic bone formation.

We wish to underline the importance of a gentle handling of tissues in the performance of a total hip replacement if the rate of ectopic bone is to be reduced to a minimum.