Metal-on-metal hip resurfacing: the effect of cup position and component size on range of motion to impingement

The aim of this dry bone study was to determine the range of hip motion to impingement for different hip resurfacing cup positions and component sizes. The maximum angles of hip flexion, extension, abduction, and adduction were calculated from 3-dimensional coordinates for: 1. Cup inclination of 30 degrees , 40 degrees , 50 degrees , 60 degrees , and 70 degrees with fixed anteversion; 2. Cup anteversion of 0 degrees , 10 degrees , 25 degrees , 35 degrees , and 45 degrees with fixed inclination; and 3. 3 different component sizes on the same size dry bones. An acetabular component inclination of 50 degrees and an anteversion of 25 degrees allowed the most physiologic range of hip motion. A larger-diameter femoral component relative to the native femoral neck diameter resulted in a greater range of hip motion to impingement.     

Femoroacetabular cup impingement after resurfacing arthroplasty of the hip

Femoroacetabular cup impingement (FACI), defined as the presence of a bony spur or indentation at the femoral neck corresponding to the abutment site of metallic cup, was observed in 9 (11%) of the 84 hips with contemporary resurfacing arthroplasty of the hip. All FACIs occurred in men after a mean of 14 months (range, 8-24 months) postoperatively. Five patients had persistent groin pain if the hip was moved into flexion, abduction, and external rotation. One patient sustained a late-onset fracture through the femoral neck already weakened by postoperative change of osteonecrosis. Mean postoperative Harris hip score in the FACI group was poorer than that in the non-FACI group (P = .003). Multiple logistic regression analysis showed a significant association of FACI with a low acetabular cup inclination (odds ratio, 1.42; 95% confidence interval, 1.01-1.99; P = .046) and a high cup uncoverage ratio (odds ratio, 1.36; 95% confidence interval, 1.01-1.84; P = .045).     

Metal-on-metal hip resurfacing radiographic evaluation techniques

Hip resurfacing devices require a new radiographic evaluation technique owing to femoral components with short or no stems. Fourteen US surgeons implanted 1148 metal-on-metal hip resurfacing (HR) devices in a US-FDA-IDE clinical trial, which began in 2001. In this multi-center, prospective study, 337 patients (mean age, 50.1 years) were enrolled as a study group of unilateral HR arthroplasties. Radiographs of 292 HR arthroplasties at a minimum 2-year follow-up (maximum 3 years) were reviewed. There were 10 patients with radiographic evidence of femoral component instability beyond 2 years, as evidenced by subsidence > or = 5mm. Of these, 7 did not have clinical symptoms associated with femoral component instability. In the study group, 24 revisions were reported, of which 8 were due to femoral neck fractures, 4 were due to acetabular component loosening, 11 were due to femoral component loosening, and 1 due to dislocation.     

Femoral neck fractures after hip resurfacing

Femoral neck fracture is an important early complication after hip resurfacing. Our aims were firstly to determine the incidence of fracture in an independent series and secondly, in a case control study, to investigate potential risk factors. Fifteen femoral neck fractures occurred in a series of 842 procedures, representing an incidence of 1.8%. No relationship existed between age, sex, and fracture incidence. Mechanical factors such as notching, femoral neck lengthening, and varus alignment of the femoral component were found to have a similar incidence in both fracture and control groups. The proportion of patients that had at least 1 mechanical risk factor was not different between the 2 groups (fracture group, 50%; control group, 41%). Established avascular necrosis of the femoral head was evident in all retrieved femoral heads (n = 9) of patients who sustained postoperative fracture; in none of these patients was avascular necrosis the initial diagnosis. This study suggests that in our practice, mechanical factors, such as neck notching, neck lengthening, or varus angulations, are not the primary cause of femoral neck fractures.     

Impingement and stability of total hip arthroplasty versus femoral head resurfacing using a cadaveric robotics model

We identified and compared the impingent‐free range of motion (ROM) and subluxation potential for native hip, femoral head resurfacing (FHR), and total hip arthroplasty (THA). These constructs were also compared both with and without soft tissue to elucidate the role of the soft tissue. Five fresh‐frozen bilateral hip specimens were mounted to a six‐degree of freedom robotic manipulator. Under load‐control parameters, in vivo mechanics were recreated to evaluate impingement free ROM, and the subluxation potential in two “at risk” positions for native hip, FHR, and THA. Impingement‐free ROM of the skeletonized THA was greater than FHR for the anterior subluxation position. For skeletonized posterior subluxations, stability for THA and FHR constructs were similar, while a different pattern was observed for specimens with soft tissues intact. FHR constructs were more stable than THA constructs for both anterior and posterior subluxations. When the femoral neck is intact the joint has an earlier impingement profile placing the hip at risk for subluxation. However, FHR design was shown to be more stable than THA only when soft tissues were intact. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1108–1115, 2013     

Femoral neck narrowing after metal-on-metal hip resurfacing

We reviewed 40 Corin Cormet 2000 (Corin, Cirencester, UK) metal-on-metal resurfacing hips, in 36 patients, for the presence of femoral neck narrowing. A neck-to-prosthesis ratio was calculated by dividing the diameter of the femoral neck with that of the implant. This ratio was measured on plain anteroposterior pelvis radiographs taken immediately and 2 years postoperation. Subsequent radiographs were measured up to a maximum 7 years (mean, 5.3 years) postoperation. Femoral neck narrowing was observed in 90% of hips at 2 years, with the average neck narrowing ranging from a ratio of 0.865 to 0.811. Importantly, no further narrowing occurred beyond this point up to 7 years postoperation. We described a simple reproducible method of measuring neck narrowing on plain radiographs and discuss possible causal factors for neck narrowing after hip resurfacing.     

股骨偏心距和髋臼旋转中心对人工全髋置换术后关节功能影响的回顾性研究

[目的]通过股骨偏心距及髋臼旋转中心手术后测量,探讨其变化对人工全髋置换术后关节功能的影响。[方法]临床随访本院人工全髋置换术后患者87例(92髋),均为首次行全髋关节置换术患者,平均随访时间2年1个月,测量手术后双髋关节X线片,比较术后假体股骨偏心距、旋转中心与解剖股骨偏心距、旋转中心符合率,对患者术后髋关节功能进行Harris评分并分组进行统计学分析。[结果]股骨偏心距及髋臼旋转中心均恢复(A组)27例(29.35%),(B组)仅FO恢复23例(25.00%),(C组)仅HJC恢复31例(33.70%),(D组)FO及HJC均未恢复11例(11.96%),Harris评分优良率A组96.30%,B组为73.19%,C组为74.19%,D组为27.27%,Harris评分优良率A组与B组(P=0.039),A组与C组(P=0.029),A组与D组(P=0.000)差异均有统计学意义。[结论]股骨偏心距及旋转中心的恢复对人工全髋置换术后关节功能有直接影响。     

全髋表面置换术后发生股骨颈狭窄非手术相关危险因素分析

[目的]探讨全髋表面置换术(resurfacing arthroplasty of the hip,RSAH)术后发生股骨颈狭窄的非手术相关危险因素.[方法]回顾性分析行全髋表面置换术的患者53例(61髋),男31例,女22例;年龄26 ～ 54岁,平均45.3岁;体重指数(RMI)为20.4～37.8,平均为27.4.按病因学分类:股骨头坏死22例(26髋),先天性髋关节发育不良13例(15髋),骨性关节炎10例(12髋)和创伤性关节炎8例(8髋).观察术后股骨颈狭窄发生情况并分组,股骨颈狭窄率≥5％纳入研究组,＜5％列入对照组.对可能导致股骨颈狭窄的17个变量进行单因素分析,对差异有统计学意义的变量进行多因素非条件logistic回归分析.[结果]将37例(43髋)狭窄率＞0％且＜5％和未狭窄的病例纳入对照组;将16例(18髋)狭窄率≥5％的病例,纳入研究组.在研究组中,2例在术后1年于股骨头杯柄周围1、3区出现透光线;1例于术后2年出现假体松动、移位.单因素分析显示,体重指数、患髋疾病、颈干角、头颈比、股骨头囊肿大小及股骨假体柄固定方式6个变量差异有统计学意义(P值均＜0.05);多因素分析显示,患髋疾病、颈干角、头颈比为独立危险因素(P值均＜0.05).[结论]髋关节原发病的诊断、头颈比、颈干角是全髋表面置换术术后股骨颈狭窄发生的非手术独立危险因素.     

Early complications of hip resurfacing

There has been a rapid increase in the number of hip resurfacing procedures for the treatment of symptomatic osteoarthritis over the last decade. We examine our early complications associated with this procedure. Eight hundred forty consecutive hip resurfacing procedures by 1 surgeon using 1 prosthesis were assessed. The complications seen within the first 12-month postoperative period were analyzed. Specific patient selection criteria were used. Complications such as loosening, femoral neck notching, femoral neck fracture, deep vein thrombosis, stress fracture, nerve palsy, and infection were noted. Complications linked with loosening were categorized to either the femoral or acetabular component. A total of 86 early complications were observed in the 840 resurfacings. Twenty-three (2.7%) required operative intervention, and 10 (1.2%) were converted to stemmed hip arthroplasties. Of these 86 complications, the most common complication was deep vein thrombosis, 19 instances (2.26% occurrence in 840), followed by femoral neck fracture, 11 (1.31%); infection, 10 (1.19%); femoral notching, 10 (1.19%); transient nerve palsy, 8 (0.95%); acetabular loosening, 6 (0.71%); hematoma, 5 (0.60%); and stress fracture, 4 (0.48%). The fractures occurred mostly in patients older than 60 years.     

Incidence of heterotopic ossification after hip resurfacing

BACKGROUND: Heterotopic ossification has been noted around total hip arthoplasty in numerous studies. With hip resurfacing growing in popularity, we have prospectively evaluated the incidence in a cohort undergoing hip resurfacing. METHODS: Two hundred and twenty consecutive hip-resurfacing procedures were prospectively reviewed at a minimum of 2 years follow up to assess the incidence of heterotopic ossification and its effect on function and clinical outcome. We also reviewed the preoperative diagnosis, age, sex and previous surgery. RESULTS: The overall percentage of heterotopic ossification was 58.63%. The incidence of Brooker 1 was 37.27%, Brooker 2 was 13.18% and Brooker 3 was 8.18%. Male osteoarthritis had the highest incidence of heterotopic bone formation (HBF). Three men underwent excision of heterotopic bone, two for pain and stiffness and one for decreased range of movement. Both anteroposterior and lateral radiographs were reviewed for evidence of HBF. In all, 12.7% had no evidence of HBF in the first view but clearly had in the second view. CONCLUSIONS: Overall, we found no evidence that HBF affected the clinical or functional outcome of the hip resurfacing at a mean of 3 years follow up. However, in light of the high incidence of HBF seen in a yet unproven long-term prosthesis, we conclude that the Cochrane database recommendations with regard to prophylaxis should be implemented.     

Gait symmetry: a comparison of hip resurfacing and jumbo head total hip arthroplasty patients

Proponents of large femoral head total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) have touted the potential for restoration of more normal hip kinematics. This study examined 20 patients (10 THA and 10 HRA patients) approximately 18 months after surgery. Subjects were evaluated at a self-selected pace, while bilateral spatial-temporal gait variables, hip flexion/extension kinematics, and ground reaction forces were collected. For both groups, swing time was increased on the surgical side, whereas peak hip flexion, peak extension, and flexion at heel strike were decreased. Peak hip extension and peak vertical ground reaction forces were decreased in THA subjects compared with HRA subjects. After a large-diameter THA or HRA, subjects do not display symmetric gait approximately 18 months postoperatively. Total hip arthroplasty subjects demonstrated restricted hip extension and reduced limb loading when compared with HRA subjects.     

Computer navigation experience in hip resurfacing improves femoral component alignment using a conventional jig

Background:

The use of computer navigation has been shown to improve the accuracy of femoral component placement compared to conventional instrumentation in hip resurfacing. Whether exposure to computer navigation improves accuracy when the procedure is subsequently performed with conventional instrumentation without navigation has not been explored. We examined whether femoral component alignment utilizing a conventional jig improves following experience with the use of imageless computer navigation for hip resurfacing.

Materials and Methods:

Between December 2004 and December 2008, 213 consecutive hip resurfacings were performed by a single surgeon. The first 17 (Cohort 1) and the last 9 (Cohort 2) hip resurfacings were performed using a conventional guidewire alignment jig. In 187 cases, the femoral component was implanted using the imageless computer navigation. Cohorts 1 and 2 were compared for femoral component alignment accuracy.

Results:

All components in Cohort 2 achieved the position determined by the preoperative plan. The mean deviation of the stem–shaft angle (SSA) from the preoperatively planned target position was 2.2° in Cohort 2 and 5.6° in Cohort 1 (P = 0.01). Four implants in Cohort 1 were positioned at least 10° varus compared to the target SSA position and another four were retroverted.

Conclusions:

Femoral component placement utilizing conventional instrumentation may be more accurate following experience using imageless computer navigation.     

Hip Flexion After Birmingham Hip Resurfacing : Role of Cup Anteversion,Anterior Femoral Head-Neck Offset,and Head-Neck Ratio

We aimed to investigate the factors affecting range of flexion after hip resurfacing. A total of 82 cases, operated by a single surgeon, were assessed at a mean of 43 months. The Einzel-Bild-Roentgen-Analysis for the acetabular cup software was used to measure socket orientation. Range of flexion had a moderate positive correlation with cup anteversion (R = 0.26, P = .017), weak but significant negative correlation with neck diameter (R = −0.23, P = .042), and none with anterior femoral head-neck offset. Using multivariate analysis that adjusted for age, sex, cup anteversion and inclination, head-neck offset ratio, head-neck ratio, and neck diameter, the only significant correlate of flexion was cup anteversion (P = .017). Care should be taken during cup placement to allow adequate anteversion to be maintained in Birmingham hip resurfacing because this can affect flexion range of motion.     

Optimizing femoral anteversion and offset after total hip arthroplasty, using a modular femoral neck system: an experimental study

To investigate the effectiveness of a modular femoral neck system, consisting of two neutral and four types of retroverted necks for the correction of femoral anteversion and offset in total hip arthroplasty, an experimental study was carried out, using sawbones with four different angles of femoral anteversion (16°, 34°, 47°, and 59°). With the neutral neck, reconstruction of the preoperative anteversion and offset in the normal femur was achieved. While the 15° retroverted long neck was effective for the mildly or moderately anteverted femur, this retroverted neck showed insufficient correction for the severely anteverted femur. This modular neck system proved to be useful for correction of the medial component of femoral offset in femora with anteversion of less than 47°. For patients with greater anteversion, a feature which is rarely seen in the clinical situation, femoral necks with a greater degree of retroversion may be useful. Received: September 3, 1999 / Accepted: March 29, 2000     

Advanced hip joint degeneration associated with femoroacetabular impingement in a retired chiropractor

Femoroacetabular impingement is a relatively new clinical entity only recently described in the orthopedic literature. In this report, we document a severe case of hip joint osteoarthritis associated with cam-type impingement in a retired chiropractor.     

全髋关节表面置换术治疗强直性脊柱炎近期疗效观察

目的 探讨全髋关节表面置换术治疗强直性脊柱炎(AS)的可行性及临床疗效.方法 对12例AS患者行全髋关节表面置换术,术后规范功能锻炼.定期临床随访.结果 所有患者切口均一期临床愈合.12例均获得随访,时间3～7(5±1)个月.早期无股骨颈骨折、感染、关节脱位、血管神经损伤、深静脉栓塞、异位骨化等并发症.术后髋关节活动度明显改善,术后Harris评分由术前平均(36±6)分上升至平均(94±4)分.影像学检查假体位置良好.患者生活质量均明显提高.结论 全髋关节表面置换术治疗AS患者近期临床效果满意.     

Bony impingement affects range of motion after total hip arthroplasty: A subject‐specific approach

Hip range of motion after total hip arthroplasty has been shown to be dependent on prosthetic design and component placement. We hypothesized that bony anatomy would significantly affect range of motion. Computer models of a current generation hip arthroplasty design were virtually implanted in a model of pelvis and femur in various orientations ranging from 35° to 55° cup abduction, 0° to 30° cup anteversion, and 0° to 30° femoral anteversion. Four head sizes ranging from 22.2 to 32 mm and two neck sizes ranging from 10‐mm and 12‐mm diameter were tested. Range of motion was recorded as maximum flexion–extension, abduction–adduction, and axial rotation of the femur before any contact between prosthetic components or bone was detected. Bony impingement preceded component impingement in about 44% of all conditions tested, ranging from 66% in adduction to 22% in extension. Range of motion increased as head size increased. However, increasing head size also increased the propensity for bony impingement, which tended to reduce the beneficial effect of increased head size on range of motion. Reducing neck diameter had a greater effect on prosthetic impingement (mean, 3.5° increase in range of motion) compared to bone impingement (mean, 1.9°). This model allowed for a clinically relevant assessment of range of motion after total hip arthroplasty and may also be used with patient‐specific geometry [such as that obtained from preoperative computed tomography (CT) scans] for more accurate preoperative planning. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:443–452, 2008     

Gait analysis of patients with resurfacing hip arthroplasty compared with hip osteoarthritis and standard total hip arthroplasty

Patients with standard total hip arthroplasties may have reduced hip abduction and extension moments when compared with normal nonosteoarthritic hips. In comparison, patients after resurfacing total hip arthroplasty appear to have a near-normal gait. The authors evaluated temporal-spatial parameters, hip kinematics, and kinetics in hip resurfacing patients compared with patients with unilateral osteoarthritic hips and unilateral standard total hip arthroplasties. Patients with resurfacing walked faster (average 1.26 m/s) and were comparable with normals. There were no significant differences in hip abductor and extensor moments of patients with resurfacing compared with patients in the standard hip arthroplasty group. This study showed more normal hip kinematics and functionality in resurfacing hip arthroplasty, which may be due to the large femoral head.     

髋关节骨性关节炎及髋臼发育不良对髋关节表面置换术中髋臼安装角度的影响

[目的]研究全髋关节表面置换术中,单纯骨性关节炎及髋关节发育不良对髋臼安装角度的影响及两组病例疗效比较。[方法]自2006～2009年,本科共实施全髋表面关节置换术20例23髋,病因包括单纯骨性关节炎10髋及髋关节发育不良13髋。手术假体均采用金属对金属大直径表面置换假体,股骨侧骨水泥固定,髋臼侧生物型固定。[结果]所有患者均获得近期随访(6个月～3年),随访包括临床评估和放射学评估。两组患者术前术后Harris评分均无明显统计学差异。无一发生术后脱位、股骨颈骨折等并发症。其中单纯骨性关节炎患者术后臼杯外展角25.6°～56.0°(平均43.9°±9.9°),平均髋臼覆盖率达95.8%。髋臼发育不良患者术后臼杯外展角22.4°～69.3°(平均46.8°±12.9°),髋臼覆盖率达84.3%。[结论]金属对金属大直径表面置换假体在治疗单纯骨性关节炎及髋关节发育不良早期临床疗效并无明显统计学差异。但是髋关节发育不良患者行髋关节表面置换术中,髋臼假体外展角离散度要明显高于单纯骨性关节炎组,其髋臼杯假体外展角度控制要难于单纯骨性关节炎。