Screw-augmented fixation of acetabular components: A mechanical model to determine optimal screw placement

Sixteen embalmed hemipelves were used to determine the optimal acetabular screw placement to provide maximal screw pull-out strength in unicortical and bicortical screw fixation. The anterior column, superior ilium, posterior column, ischium, and pubis regions of the pelvis were tested using 6.5-mm titanium alloy screws and a hydraulic servo-controlled 1321 Instron testing machine. Force vs displacement data were acquired. Bicortical fixation was stronger than unicortical fixation in the four zones compared. This difference was significant in the superior ilium, posterior column, and ischium. The anterior column could not accept unicortical screws due to inadequate bone depth, which ranged between only 6 mm and 10 mm. Bicortical fixation was significantly greater in the superior ilium, posterior column, and ischium than in the anterior column or pubis. Unicortical fixation was greatest in the superior ilium. This information may aid decisions concerning the positioning of screws to augment acetabular component fixation.     

Midterm results of 506 solid trispiked reflection cementless acetabular components for primary total hip arthroplasty

The purpose of this prospective study was to evaluate the outcomes and survivorship of a trispiked, sintered bead-coated titanium shell with a polished inner surface, no screw holes, and an improved locking mechanism. A total of 506 total hip arthroplasties with a minimum 5-year follow-up were available for review at a mean of 7 years (range, 5-11 years). Three sockets (0.6%) were revised for reasons other than aseptic loosening, and 14 (2.8%) polyethylene liners were exchanged. There was no difference in revision rate between non-cross-linked and highly cross-linked liners (P = .4). There were no cases of radiographic loosening. Retroacetabular osteolysis was identified in 2%. The overall 5-year and 10-year Kaplan-Meier survivorship was 97.5% and 97.4%, respectively, whereas survivorship of the shell was 99.8%.     

髋臼假体安装位置与无菌性松动的相关分析

[目的]探讨髋臼假体安放位置与假体松动的相关性.[方法]回顾性分析2010年9月-2017年3月采用改良Har-dinge入路初次全髋关节置换术符合纳入排除标准136例患者的临床资料,患者均顺利手术,随访20个月以上,按是否发生松动将患者分为两组,采用单因素分析和二元多因素逻辑分析假体松动的相关因素.[结果]末次随访时...     

The minimum 10-year results of a second-generation cementless acetabular shell with a polished inner surface

The purpose of this prospective study was to evaluate the minimum 10-year outcomes and survivorship of the Reflection shell with a polished inner surface and an improved locking mechanism. Three hundred sixty-three total hip replacements with a mean follow-up of 11.6 years (range, 10.0-15.1) were evaluated. The mean Harris Hip and WOMAC scores at last follow-up were 87 and 77, respectively. Four cups were revised: 2 for infection and 2 for aseptic loosening. Thirteen cases underwent liner exchange for wear. Radiographic review of remaining cups identified 8.8% with identifiable peri-acetabular osteolysis and no cases of loosening. The overall 10- and 15-year Kaplan-Meier survivorship was 94% and 90% for the total hip arthroplasty system while the survivorship of the shell remained 99.4% at 15 years.     

Multidirectional deformation in fully congruent acetabular components

Most clinical studies have used femoral head migration as an index of acetabular wear, but a previous study showed multiple wear vectors in 30% of retrieved acetabular components with noncongruent liners. The origin of multiple wear vectors is unclear, and it has been suggested that polyethylene creep in a noncongruent shell might influence deformation on the articular surface. We used shadowgraph and volumetric methods to evaluate the extent and direction of surface deformation of 37 retrieved polyethylene liners that were fully congruent to a single design of metal backing. The results show that multiple deformation vectors are relatively common in retrieved acetabular cups (27% in this study) and are independent of congruency between liner and metal backing, rim impingement, and backside creep. Polyethylene liners with multiple wear vectors were significantly thinner than those of cups with a single vector. The origin of multiple vectors is still unclear, but clinical and laboratory studies measuring linear wear alone without recognizing multiple vectors underestimate total in vivo volumetric wear.     

A comparison of the outcome of cemented all-polyethylene and cementless metal-backed acetabular sockets in primary total hip arthroplasty

We compared, after a 10-year-minimum follow-up, the outcome of 50 cemented all-polyethylene Charnley acetabular sockets with that of 51 cementless metal-backed sockets in 2 comparable cohorts of young patients. Although the revision rate for the cemented and cementless group was 28% and 35%, respectively, the revision rate for aseptic loosening was 28% for the cemented and 12% for the cementless group. The mean polyethylene wear was 0.112 and 0.114 mm/y, respectively, for the 2 groups. Linear osteolysis was observed in 18 of 50 cemented sockets. Expansile osteolysis presented in 10 of 51 cementless sockets and only in one of the cemented sockets. In conclusion, cementless components had more durable fixation than cemented components. However, they presented more aggressive expansile osteolysis caused by the coexistence of polyethylene and metal debris.     

Acetabular micromotion as a measure of initial implant stability in primary hip arthroplasty: An in vitro comparison of different methods of intial acetabular component fixation

Micromotion has been shown to affect bony ingrowth into cementless components. This study was designed both to quantitate initial micromotion at the prosthesis-periacetabular bony interface and to compare different methods of commonly employed acetabular component fixations, ie, a press-fit hemispherical titanium cup, a press-fit hemispherical titanium cup with one and two dome screws, a press-fit titanium hemispherical cup with three spikes, and a cemented chromium-cobalt cup. The press-fit component without screws demonstrated the greatest motion equaling 162 μm at the ilium, 97 μm at the pubis, and 54 μm at the ischium. With one and two screws placed into the dome, the mean ileal displacement decreased by 28 μm (17%) and 36 μm (22%), respectively. Dome screw placement demonstrated a minimal effect at the pubis and ischium. Compared to the press-fit component without augmentation, the tri-spike motion was less at the pubis and ischium. The cemented prosthesis provided the least amount of motion in all three areas tested. This experiment demonstrates that the ilium provides the least amount of support to immediate acetabular fixation, while the pubis (anterior column) and ischium (posterior column) provide more stability. One dome screw does not afect the stability of a hemispherical prosthetic cup significantly. A two dome screw fixation provides an added method of support at the ilium, but fails to decrease motion at the pubis or ischium significantly. The tri-spike fixation does not restrict motion at the ilium to the extent as the dome screws, but its effect at the ischium and pubis is much more pronounced. The obvious difference between initial motion seen with cemented versus uncemented components may suggest that before surgery, patients may need a period of protected weight bearing until ingrowth has occurred.     

髋臼翻修术治疗THA术后单纯髋臼假体松动的临床研究

目的比较单纯髋臼翻修术治疗单纯髋臼假体松动与全髋关节翻修术治疗全髋假体松动的疗效。方法回顾性分析自2006年1月~2012年1月收治的44例单侧全髋关节置换(THA)术后假体松动,分成2组(各22例),研究组采用单纯髋臼翻修术治疗单纯髋臼假体松动,对照组采用全髋关节翻修术治疗全髋假体松动。比较两组术中出血量、手术时间及术后1.5、3、6、12个月Harris评分改善情况。结果研究组平均手术时间、术中出血量明显少于对照组,差异有统计学意义(P<0.05)。术后1.5、3个月研究组Harris评分改善情况优于对照组,差异有统计学意义(P<0.05);术后6、12个月两组Harris评分改善情况差异无统计学意义(P>0.05)。结论单纯髋臼翻修术后患者髋关节功能恢复情况短期内(3个月内)优于全髋关节翻修术。     

Effect of screw fixation on acetabular component alignment change in total hip arthroplasty

Purpose

The use of screws can enhance immediate cup fixation, but the influence of screw insertion on cup position has not previously been measured. The purpose of this study was to quantitatively evaluate the effect of intra-operative screw fixation on acetabular component alignment that has been inserted with the use of a navigation system.

Methods

We used a navigation system to measure cup alignment at the time of press-fit and after screw fixation in 144 hips undergoing total hip arthroplasty. We also compared those findings with factors measured from postoperative radiographs.

Results

The mean intra-operative change of cup position was 1.78° for inclination and 1.81° for anteversion. The intra-operative change of anteversion correlated with the number of screws. The intra-operative change of inclination also correlated with medial hip centre.

Conclusion

The insertion of screws can induce changes in cup alignment, especially when multiple screws are used or if a more medial hip centre is required for rigid acetabular fixation.     

Removal of the acetabular component minimizing destruction of the bone bed

Removal of a well-fixed acetabular component can be difficult and may produce destruction of the acetabular bone bed. The authors describe a technique for removal of such a component with minimal bone destruction that involves the use of an offset punch and breaking the fixation interface in tension. This technique obviates the need for prying at the interface and fracturing the bone bed.     

The relationship between increased hip range of motion, wear, and locking mechanism failure in the Harris-Galante acetabular component

We performed both clinical and radiographic evaluations of 178 patients (190 hips) who had undergone cementless total hip arthroplasties using Harris-Galante I/II porous cups after an average 12-year follow-up period (range, 8-18 years). We revised 15 Harris-Galante I/II porous cups (7.8%), and the locking mechanism was broken in 10 revised cups (67%). There was a significant association between locking mechanism failure and linear polyethylene wear. We observed a significant positive correlation between linear polyethylene wear and increased ranges of motion such as flexion, adduction, and external rotation at the last follow-up visit after the primary operation. Increased ranges of motion seen in Asians induced higher linear polyethylene wear and locking mechanism failure due to impingement of the neck and cup.     

传统手术方法安放髋臼假体角度准确性的三维CT研究

[目的]通过对全髋置换术后髋臼假体角度的CT测量,总结使用传统手术方法安放髋臼假体角度的临床现状,评估使用传统手术方法安放髋臼假体角度的准确性,并就医生经验对安放髋臼假体角度准确性的影响进行研究。[方法]对2011年9月20日～11月20日在本院进行全髋置换的206髋进行了前瞻性研究,所有手术均采用侧卧位后外侧入路和传统手术方法,没有借助任何定向器等辅助器械,手术由12名医生完成,其中6名高级职称医生完成131髋,6名主治医生完成75髋。术后1周内进行了CT测量,使用三维CT方法测量了髋臼假体的倾斜角和前倾角,并对研究中使用的三维CT方法进行了准确性研究。将测量的倾斜角和前倾角数据与Lewinneck提出的理想范围:倾斜角(40±10)°,前倾角(15±10)°进行比较分析,评估使用传统手术方法安放髋臼假体角度的准确性。将高级职称医生组的数据与主治医生组的数据进行比较,研究医生经验对安放髋臼假体角度准确性的影响。[结果]本研究中使用的三维CT方法测量髋臼倾斜角和前倾角在组内测量和组间测量中均有很高的准确性,ICC>0.99。在206例髋关节中,倾斜角平均为(36.07±6.72)°,78.16%的病例在安全范围内;前倾角平均为(16.27±8.26)°,76.21%的病例在安全范围内;倾斜角和前倾角均在安全范围内的占总病例数的60.19%。高级医生组与主治医生组完成的手术在髋臼假体角度方面没有显著区别(P>0.05)。[结论]三维CT测量髋臼角度是准确可靠的。目前本院使用传统全髋置换技术安放髋臼假体时,倾斜角为(36.07±6.72)°,前倾角为(16.27±8.26)°;安放髋臼假体角度的准确性不理想,有60.19%的髋臼安放在Lewinneck安全区。使用传统手术方法,医生经验并不能显著提高安放髋臼假体角度的准确性。     

Catastrophic progression of the disassembly of a modular acetabular component

Disassembly of a metal-backed modular acetabular component used for total hip arthroplasty is becoming more common. If the acetabular disassembly is detected early, the revision procedures are relatively simple. In the case of long-term sustained disassembly, however, there are more complicated problems, and more difficult revision procedures are needed. We report a case of long-term sustained disassembly of a modular acetabular component in order to alert orthopaedic surgeons of the catastrophic progression to more severe complications, such as the loosening of the metal-acetabular component and severe acetabular osteolysis.     

Impaction grafting using a cemented porous-coated modular acetabular component

Reconstruction of major acetabular defects continues to challenge surgeons. There are many surgical options for these situations, including oversized hemispherical cups, oblong cups, acetabular cages, bulk allografts, and impaction allografting. We present the case of a modification to the impaction grafting technique for acetabular reconstruction. In our case, a porous-coated modular titanium acetabular component was cemented in place instead of an all-polyethylene acetabular component, which is the standard technique for impaction grafting reconstruction. The use of the modular component allowed a greater number of surgical options at the time of surgery. At 5 years from surgery, the patient has a successful reconstruction and the radiographs continue to look excellent.     

Total hip arthroplasty for posttraumatic arthritis after acetabular fracture

Total hip arthroplasty (THA) outcomes for posttraumatic arthritis after acetabular fracture have yielded inferior results compared to primary nontraumatic THA. Recently, improved results have been demonstrated using cementless acetabular reconstruction. Thirty-two patients underwent THA for posttraumatic arthritis after acetabular fracture; 24 were treated with open reduction internal fixation, and 8 were managed conservatively. Time from fracture to THA was 36 months (6-227 months). Average follow-up was 4.7 years (2.0-9.7 years). Harris Hip score increased from 28 (0-56) to 82 points (20-100). Six patients required revision. Five-year survival with revision, loosening, dislocation, or infection as an end point was 79%. Survival for aseptic acetabular loosening was 97%. Revision surgery correlated with nonanatomic restoration of the hip center and a history of infection (P < .05). Despite obvious challenges, advances in fracture management and cementless acetabular fixation in THA demonstrate improved results for posttraumatic arthritis following acetabular fracture.     

重建钢板内固定治疗髋关节后脱位伴髋臼后壁骨折

目的探讨重建钢板内固定治疗髋关节后脱位伴髋臼后壁骨折的临床疗效及影响预后的相关因素。方法对35例髋关节后脱位伴髋臼后壁骨折的患者采用K-L入路、AO重建钢板内固定治疗。结果 35例均获随访,时间2年～5年4个月。采用改良Merle d’Aubingne-Postel评分系统评价:优16例,良12例,一般4例,差3例。Matta影像学分级:优13例,好16例,一般5例,差1例。临床结果与X线分级呈显著正相关。患者年龄≥55岁、复位时间≥12 h及复杂性骨折患者中临床评分明显降低。结论对于髋关节后脱位伴髋臼后壁骨折,及时确诊和满意复位、恢复髋臼的连续性和稳定性是取得满意手术疗效的关键;患者年龄、复位时间、骨折类型是影响患者预后的重要因素。     

Cementing acetabular sockets into metal-backed acetabular components and antiprotrusio cages: a technical tip

Cementing a polyethylene socket or acetabular liner into a well-fixed metal-backed acetabular shell has become a useful procedure in selected complex primary and revision hip arthroplasties. Polyethylene sockets are frequently cemented into antiprotrusio cages as well. Frequently, these metallic devices are fixed to host bone with acetabular screws. Unfortunately, when polyethylene sockets are cemented into such devices, the cement fills the recess within the screw head and makes subsequent screw removal extremely difficult should the device need to be removed or revised. The author describes a technique of filling the screw heads with bone wax and gel foam before cementation. This keeps the recess within the screw head relatively patent and allows easier removal of the screw in the future should it become necessary.     

Cementless hemispheric acetabular component for acetabular revision arthroplasty: a 5- to 19-year follow-up study

This study evaluated the 5- to 19-year clinical and radiographic results of cementless acetabular revision. Between 1986 and 1998, 130 hips (125 patients) underwent cementless acetabular revisions. Ten patients were lost to follow-up; 6 patients died. One hundred nine patients (114 hips) were reviewed at a mean follow-up of 8.8 years. The mean Harris hip score improved from 62.1 to 90.7 at final follow-up. Two hips underwent repeat revision. Twenty-two hips developed cavitary osteolysis. Kaplan-Meier survivorship at 121 months was 98.2% with repeat revision for any reason as the end point and 89.5% with repeat revision or radiographic loosening as the end point. Cementless acetabular revision provides favorable clinical and radiographic results, and the initial disease and age may adversely affect the outcomes.