Long-term survivorship of cemented bipolar hemiarthroplasty for fracture of the femoral neck

Cemented bipolar hemiarthroplasty commonly is used to treat displaced fractures of the femoral neck in elderly patients. The purpose of the current study was to review the results and survivorship of 212 bipolar hemiarthroplasties done in 205 patients for acute femoral neck fracture between 1976 and 1985. The mean age of the patients at the time of surgery was 79 years (range, 61-100 years). The mean followup for the patients who were alive was 11.7 years (range, 5.3-16.8 years) and 5.8 years (range, 51 days-19.4 years) for the entire group. Ten hips (4.7%) were revised or removed: five for aseptic femoral component loosening, one for acetabular erosion, one for chronic dislocation, and three for infection. In living patients with surviving implants, 96.2% had no or slight pain. Ten-year survivorship free of reoperation for any reason was 93.6%, free of revision surgery for aseptic femoral loosening or acetabular cartilage wear was 95.9%, free of revision surgery for aseptic femoral loosening was 96.5%, and free of revision surgery for acetabular cartilage wear was 99.4%. Cemented bipolar hemiarthroplasty for acute femoral neck fracture is associated with excellent component survivorship in elderly patients. The rate of complications was low, and the arthroplasty provided satisfactory pain relief for the lifetime of the majority of elderly patients.     

Initial femoral stem position in cementless bipolar hemiarthroplasty for femoral neck fracture in elderly patients is associated with early implant subsidence: A radiographic analysis

BackgroundBipolar hemiarthroplasty is a well-established treatment for displaced femoral neck fracture in elderly patients. Implant subsidence is a potential complication with cementless femoral stems, and smaller canal fill ratio has been reported as a radiographic risk factor. We aimed to determine the risk factors for subsidence, particularly the initial implant position relative to the resected medial calcar of proximal femur.MethodsWe retrospectively reviewed all cementless bipolar hemiarthroplasties performed using a single proximally hydroxyapatite-coated femoral stem in patients with a minimum radiographic follow-up of 12 weeks between January 2017 and December 2018. The amount of subsidence (significant subsidence defined as ≥ 5 mm), canal fill ratio, and implant position relative to the point of resected medial calcar (position A: medial and superior to calcar; position B: lateral and superior to calcar; position C: lateral and inferior to calcar) were measured and analyzed.ResultsOne-hundred eighty patients were identified (mean age: 80.9 years). Significant subsidence was observed in 52 patients (28.9%). On multivariate analysis, older age, lower canal fill ratio, implant position B, C, and less medial overhang of stem were independent risk factors for early implant subsidence. The risk ratio of position B and C to position A was 5.13 (95% confidence interval, 2.23-11.80).ConclusionIn our analysis, older age and lower canal fill ratio were associated with increased risk of subsidence, whereas implant with position A and more medial overhang were less prone to subsidence with the tapered proximally hydroxyapatite-coated implant.     

Fractures of the femoral neck treated with cemented bipolar hemiarthroplasty

Seven of 59 (12%) bipolar hemiarthroplasties for displaced femoral neck fracture were classified as failures at the 3-year follow-up examination. Two prostheses dislocated, 4 had loose femoral stems, and 1 was revised to a total hip arthroplasty because of pain. No patients developed acetabular erosion or deep infection. Only four of 15 patients examined by fluoroscopy shared movement between outer metal/cartilage and inner metal/polyethylene surfaces. All movement occurred at the outer metal/cartilage surface in the remaining nine patients. We conclude that the low failure rate, which compares favorably with the best results after internal fixation, is caused by the optimal selection of patients for this operation (high age, low activity level) and the use of bone cement. The bipolar design is less important, since most of these prostheses function as ordinary unipolar prostheses after some time.     

Lower reoperation rate for cemented hemiarthroplasty than for uncemented hemiarthroplasty and internal fixation following femoral neck fracture

Background and purpose Elderly patients with displaced femoral neck fractures are commonly treated with a hemiarthroplasty (HA), but little is known about the long-term failure of this treatment. We compared reoperation rates for patients aged at least 75 years with displaced femoral neck fractures treated with either internal fixation (IF), cemented HA, or uncemented HA (with or without hydroxyapatite coating), after 12–19 years of follow-up.

Methods 4 hospitals with clearly defined guidelines for the treatment of 75+ year-old patients with a displaced femoral neck fracture were included. Cohort 1 (1991–1993) with 180 patients had undergone IF; cohort 2 (1991–1995) with 203 patients had received an uncemented bipolar Ultima HA stem (Austin-Moore); cohort 3 (1991–1995) with 209 patients had received a cemented Charnley-Hastings HA; and cohort 4 (1991–1998) with 158 patients had received an uncemented hydroxyapatite-coated Furlong HA. Data were retrieved from patient files, from the region-based patient administrative system, and from the National Registry of Patients at the end of 2010. We performed survival analysis with adjustment for comorbidity, age, and sex.

Results Cemented HA had a reoperation rate (RR) of 5% and was used as reference in the Cox regression analysis, which showed significantly higher hazard ratios (HRs) for IF (HR = 3.8, 95% CI: 1.9–7.5; RR = 18%), uncemented HA (HR = 2.2, CI: 1.1–4.5; RR = 11%) and uncemented hydroxyapatite-coated HA (HR = 3.6, CI: 1.8–7.4; RR = 16%).

Interpretation Cemented HA has a superior long-term hip survival rate compared to IF and uncemented HA (with and without hydroxyapatite coating) in patients aged 75 years or more with displaced femoral neck fractures.     

Hip fractures in elderly patients treated with bipolar hemiarthroplasty: comparison between cemented and cementless implants

Abstract A prospective, randomised study was conducted to evaluate the clinical and functional outcomes at 12 months of followup in two groups of patients affected by femoral neck fractures and treated with cemented or cementless bipolar hemiarthroplasty. Fifty-three cemented and 53 cementless prostheses were implanted on alternate days in 106 consecutive patients. We considered general demographic variables (age, sex, side of injury), operative delay, number of pre-existing conditions, ASA score, haemoglobin levels at admission and pre- and postoperatively, number of blood units transfused perioperatively, duration of operation, clinical complications, hospital stay and mortality within one year after discharge. At follow-up, a Total Functional Score (from 0 to 18 points) was used to evaluate walking ability and personal and daily activity. Furthermore, the economic costs of hospital care (medical and nursing staff, drugs, diagnostic procedures, blood transfusions, hospital stay) and prostheses in the 2 groups of patients were considered. There was no significant difference between the 2 groups of patients regarding most variables, except for postoperative haemoglobin value (9.60±1.88 g/dl in cemented group vs 8.80±8.70 g/dl in cementless group, p=0.018) and duration of operation (75.00±22.43 min in cemented group and 56.98±55.00 min in cementless group, p<0.001). Furthermore, there was no difference regarding 1-year mortality (24.5% in cemented group and 26.4% in cementless group) or in total functional score (9.13±6.02 in cemented group and 8.95±5.86 in cementless group). Economic evaluation revealed that the cementless implant costs 1980 euro while the cemented one costs 1065 euro. In our study, the morbility rate for elderly patients with femoral neck fracture was higher than in the literature. The mortality rate and functional outcome at 12 months of follow-up were similar in the two groups of patients. Considering the higher cost for the cementless prosthesis, the use of cementless bipolar hemiarthropalsy does not seem to be justified in daily orthopaedic practice for the treatment of femoral neck fractures in elderly patients.     

Uni- and bipolar hemiarthroplasty with a modern cemented femoral component provides elderly patients with displaced femoral neck fractures with equal functional outcome and survivorship at medium-term follow-up

Introduction

The choice between unipolar and bipolar hemiarthroplasty for treatment of displaced intracapsular femoral neck fractures in elderly patients still remains controversial. Our objective was to compare series of elderly individuals with a displaced femoral neck fracture treated with either a cemented, modular unipolar or bipolar prosthesis with the same femoral component.

Materials and methods

A prospective, randomized controlled trial of 175 displaced intracapsular femoral neck fractures in patients over 65 years was randomly allocated to unipolar (88) and to bipolar (87) hemiarthroplasty group. The primary end point was implant survival. Secondary end points included difference in ambulatory ability and mortality. Follow-up evaluations were performed at 2 months, at 1, 3 and 5 years. Implant and patient survival were followed until 2/2012. Survival analyses were performed using Kaplan–Meier curves with log-rank test. Data were analyzed using Chi-square test and Student’s t test.

Results

Unipolar hemiarthroplasty group had a significantly higher dislocation rate when compared with bipolar hemiarthroplasty group. This did not translate into difference in revision rates at 8 years. Prosthetic survival ship was 0.98 (95 % Cl 0.94–1.00) in the unipolar group and 0.97 (95 % Cl 0.93–1.00) in the bipolar group. There were no statistically significant differences in ambulatory ability, possibility to return home mortality or early radiological acetabular erosion. There were significantly more one-time dislocations in the unipolar group, but there was no difference in incidence of revisions due to recurrent dislocations. The overall mortality rate was 6 % at 30 days, 9 % at 90 days, 16 % at 12 months, and 53 % at 5 years. There was no difference in mortality between the groups.

Conclusions

Unipolar hemiarthroplasty group had a significantly higher dislocation rate when compared with bipolar hemiarthroplasty group. However, both provide elderly patients with equal ambulatory ability and low revision rate at medium-term follow-up.     

High incidence of cardiorespiratory deterioration in patients receiving cemented hip hemiarthroplasty for femoral neck fracture

BACKGROUND: Anesthesia for patients who undergo surgery for femoral neck fractures can be associated with severe cardiopulmonary complications. METHODS: We retrospectively studied 361 consecutive patients who underwent surgery for femoral neck fractures. Dividing patients into three groups according to type of surgery-hip hemiarthroplasty (n=134), compression hip screw (n=123) or gamma nail (n=104)--we calculated the incidences of cardiorespiratory deterioration during anesthesia and examined factors associated with it. RESULTS: Among hemiarthroplasty patients, six (4.5%) encountered cardiorespiratory deterioration; four (3.0%) experienced profound hypotension, bradycardia or cardiac arrest immediately after implantation of the bone cement or insertion of the prosthesis into the femoral bone; and two (1.5%) developed hypoxia and angina pectoris during the late phase of surgery. Patients who underwent compression hip screw or gamma nail had no cardiorespiratory deterioration. No difference was found in patient characteristics or type of anesthesia used among the three surgery groups. Time of surgery and amount of blood loss both were significantly greater in patients undergoing hemiarthroplasty. CONCLUSIONS: The surgical techniques selected for hip hemiarthroplasty, which is associate with an increase in intramedullary pressure, may be a significant risk factor for cardiorespiratory deterioration from anesthesia in patients undergoing surgery for femoral neck fracture.     

骨水泥与非骨水泥微创半髋关节置换术治疗老年股骨颈骨折的疗效分析

目的回顾性比较骨水泥和非骨水泥微创半髋关节置换术(MIS-HA)治疗老年股骨颈骨折的短期临床疗效。方法自2012-01—2013-04采用前外侧入路分别行骨水泥(70例70髋,骨水泥组)和非骨水泥(70例70髋,非骨水泥组)MIS-HA治疗140例老年移位股骨颈骨折,比较2组手术时间、术中出血量、术后引流量、总失血量、输血率、并发症、髋关节功能Harris评分。结果非骨水泥组70例获得随访,平均随访23(14~28)个月;骨水泥组术中因肺栓塞死亡1例,69例获得随访,平均随访20(14~28)个月。2组术中Sp O295%者、舒张压下降≥20 mm Hg者、术后引流量、输血率比较,差异无统计学意义(P0.05);与骨水泥组相比,非骨水泥组手术时间较短、术中出血量较少、总失血量较少,差异有统计学意义(P0.05);2组在术后3、6、12个月比较髋关节功能Harris评分,差异无统计学意义(P0.05)。2组均无血管神经损伤,并发症比较差异无统计学意义(P0.05)。结论前外侧入路MIS-HA治疗老年股骨颈骨折具有创伤小、并发症少、恢复快等优点,骨水泥和非骨水泥型MIS-HA均可获得良好的临床结果。     

Primary hemiarthroplasty in old patients with displaced femoral neck fracture

103 patients with displaced femoral neck fractures (Garden 3–4) treated with primary hemiarthroplasty in the Department of Orthopedics, Malmö University Hospital, Sweden 1998–1999 were followed in a prospective, consecutive study for 1 year. Inclusion criteria were age of at least 80 years, signs of mental changes and/or residence in an institution. The control group consisted of 69 patients with internal fixation (Hansson hook pins).

The arthroplasty group required more blood transfusions, a longer operation and had more superficial infections. No differences were detected as regards other complications, length of hospital stay, in-hospital mortality or ability to return home. The 1-year mortality rates were similar in the arthroplasty (29/103) and control groups (28/69). Within 1 year, we found a lower failure rate in the arthroplasty group (6/103) than in the control group (18/69). In the arthroplasty group, 2/103 had dislocations. Of the surviving arthroplasty patients at 12 months, 31/74 could walk as well as before the fracture and 55/74 had no pain.

We recommend primary hemiarthroplasty for demented and/or institutionalized patients over 80 years with displaced femoral neck fractures.     

Pulmonary haemodynamics and right ventricular function during cemented hemiarthroplasty for femoral neck fracture

Background: Bone cement implantation syndrome (BCIS) is characterised by hypoxia, hypotension and loss of consciousness occurring early after bone cementation. The haemodynamic perturbations during BCIS have not been extensively studied, particularly not in patients with femoral neck fracture. We evaluated the effects of cemented hemiarthroplasty, in these patients, on pulmonary haemodynamics, right ventricular performance, intrapulmonary shunting and physiological dead space. Methods: Fifteen patients undergoing cemented hemiarthroplasty because of femoral neck fracture were included. Surgery was performed under total intravenous anaesthesia in the lateral position. All patients were catheterised with a radial and pulmonary artery catheter, for continuous measurements of mean arterial pressure (MAP), pulmonary arterial pressure (PAP), cardiac output, mixed venous oxygen saturation, right ventricular end‐diastolic volume (RVEDV) and right ventricular ejection fraction (RVEF). Haemodynamic measurements and blood gas analyses were performed after induction of anaesthesia, during surgical stimulation before and immediately after bone cementation and prosthesis insertion, 10 and 20 min after insertion and during skin closure. Results: After bone cementation and prosthesis insertion, MAP (?10%), cardiac index (?10%) and stroke volume index (?10%) decreased, while PAPs (10–15%) and the pulmonary vascular resistance index (45%) increased. RVEF decreased by 10–20%, while the RVEDV index increased by 10%. Pulmonary haemodynamic and RV variables changed progressively with time, while intra‐pulmonary shunting and physiological dead space increased immediately after prosthesis insertion and then returned to baseline. Conclusions: Cemented hemiarthroplasty in patients with femoral neck fracture causes a pronounced pulmonary vasoconstriction and an impairment of RV function accompanied by pulmonary ventilation/perfusion abnormalities.     

高龄老年人股骨颈骨折人工全髋与半髋关节置换术的选择

目的探讨全髋关节置换术与半髋关节置换术在高龄老年人（≥85岁）股骨颈骨折中的疗效比较。方法本组在2004年至2007年共收治67例股骨颈骨折的高龄患者,其中17例采用全髋关节置换术治疗;其余50例采用半髋关节置换术治疗。随访3个月～4年,平均3．1年。对两组患者的手术时间、手术出血量、住院时间、住院费用、并发症、关节功能等进行比较。结果全髋关节置换组的平均手术时间、术中出血量、住院费用等明显要多于半髋关节置换组,差异有统计学意义（P〈0．05）。住院时间、并发症、关节功能等比较,差异无统计学意义（P〉0．05）。结论对高龄老年人（≥85岁）股骨颈骨折的治疗尽可能采用简单有效的手术方法,半髋关节置换术完全可以满足该类患者的需求。     

A piriformis-preserving posterior approach reduces dislocation rate of the hemiarthroplasty in patients with femoral neck fracture

IntroductionThe posterior approach (PA) for hemiarthroplasty (HA) in patients with femoral neck fracture (FFN) has a high risk of dislocation; however, by preserving the piriformis muscle, the dislocation rate could be lowered considerably. The aim of this study was to compare the surgical complications of the piriformis-preserving posterior approach (PPPA) and the PA in patients with FNF treated with HA.MethodsOn 1 January 2019, the PPPA was introduced at two hospitals as the new treatment standard. The sample size was calculated based on a 5 percentage point dislocation reduction and 25% censoring; a sample of 264 patients per group was determined. An approximately 2-year inclusion period with 1-year follow-up was estimated, including a historical cohort from 2 years before the PPPA introduction. Data were retrieved from health care records and X-ray images from the hospitals’ administrative databases. Relative risk (RR) and 95% confidence intervals were calculated using Cox regression and adjusted for age, sex, comorbidity, smoking, surgeon experience and implant type.ResultsThere were 527 patients included in the study, of which 72% were women and 43% were above 85 years old. There were no baseline differences between the PPPA and PA groups in sex, age, comorbidity, body mass index, smoking, alcohol, mobility, length of surgery, blood loss or implant positioning, but there were differences in 30-day mortality, surgeon experience and implant type.The dislocation rate reduced from 11.6% in the PA group to 4.7% in the PPPA group (p = 0.004), with an RR of 2.5 (1.2; 5.1). The reoperation rate reduced from 6.8% with the PA to 3.3% with the PPPA (p = 0.022), with an RR of 2.1 (0.9; 5.2), and total surgery-related complications reduced from 14.7% with the PA to 6.9% with the PPPA (p = 0.003), with an RR of 2.4 (1.3; 4.4).InterpretationChanging from PA to PPPA in patients with FNF treated with HA resulted in a more than 50% reduction in dislocation and reoperation rates. This approach was easily introduced and may enable further lowering of dislocation rates through the sparing of all short external rotators.     

生物型加长柄关节置换治疗高龄股骨转子间骨折

 目的 探讨应用Zweym俟ller生物型加长柄关节置换治疗高龄股骨转子间骨折的手术可行性、实用性和疗效。方法 回顾性分析2006 年6 月至2010 年6 月应用Zweym俟ller生物型加长柄关节置换治疗91 例高龄股骨转子间骨折患者资料, 男35 例, 女56 例;年龄75~94 岁, 平均81.2 岁。股骨转子间骨折按Evans-Jensen 分型: III型36 例, IV型55 例。骨质疏松按Singh 指数分级: III级51 例, II级40 例。损伤至手术时间2~10 d, 平均3.5 d。全部采用Zweym俟ller 生物型加长柄股骨假体。根据Harris 评分评价髋关节功能。结果 手术时间30~50 min, 平均39 min ;出血量320~610 ml, 平均405ml。术后91 例患者切口均一期愈合, 住: 时间14~21 d, 平均16.5 d。2例于术后第3 天发生呼吸系统感染, 经抗感染、化痰、平喘、机械通气等治疗痊愈;3 例发生深静脉栓塞, 经介入科在下腔静脉植入滤网溶栓治疗后痊愈;2 例发生肺梗死, 其中1例在发病2 h内死亡, 另1 例急诊CT 血管造影检查确诊后转入ICU行溶栓治疗后康复。55 例患者获得随访, 其中18 例在此期间因其他疾病死亡, 实际37 例获得随访, 随访时间15~38 个月, 平均24.5 个月。末次随访时Harris 评分为40~96 分, 其中优13 例, 良18 例, 可4 例, 差2例, 优良率83.8豫(31/37)。无一例发生骨溶解、异位骨化、假体松动下沉;1 例患者术后6 个月摔倒致假体周围斜型骨折, 行切开复位捆绑带固定15 d后出: 。结论 Zweym俟ller生物型加长柄关节置换是治疗高龄股骨转子间骨折的一种有效方法, 术后患者可早期下地负重活动, 功能恢复良好。     

Evaluation of femoral neck fracture treatment with hemiarthroplasty in elderly patients]

The authors reviewed the medical records of 457 patients who underwent a hemiarthroplasty procedure for the treatment of displaced femoral neck fracture. The age of the patients ranged from 60 to 103 years (mean age: 83 years). Follow-up evaluation of 331 patients was done 4-114 months post-op (mean follow-up time 52 months). 19 patients (4.2%) died in hospital, 67 patients (14.6%) developed systemic conditions during hospitalisation. 12 months post-op the mortality rate was 15.7%. Mean survival was 36.5 months. According to the Merle d'Aubigne-Postel evaluation system there were 154 satisfactory results (75.9%). Cemented or uncemented implantation techniques had no influence on long term results. 94 patients (4.2%) achieved pre-injury mobility. The reoperation rate was 8.1%. Poor general conditions at admission that postponed surgery and impaired mobility were strong negative prognostic factors.     

骨水泥型双极人工股骨头置换治疗高龄股骨颈骨折

目的探讨骨水泥型双极人工股骨头置换治疗高龄股骨颈骨折的临床疗效。方法采用髋关节后外侧改良Gibson入路对25例高龄股骨颈骨折行骨水泥型双极人工股骨头置换。结果25例均获随访,时间6～24个月。髋关节功能按Harris评分：优8例,良14例,可3例。结论骨水泥型双极人工股骨头置换治疗高龄股骨颈骨折可早期活动,关节功能恢复满意,提高生存质量。     

骨水泥型与非骨水泥型人工半髋关节置换术治疗高龄股骨颈骨折患者的对比研究

目的对比骨水泥型与非骨水泥非骨水泥型人工半髋关节置换术在高龄股骨颈骨折患者中的治疗效果。 方法前瞻性收集2014年1月至2018年12月期间行唐县人民医院收治的112例高龄股骨颈骨折患者为研究对象，采用随机数字表法将患者分为骨水泥组、非骨水泥组，每组各56例。骨水泥组患者给予骨水泥型人工半髋置换手术治疗，男26例，女30例，年龄（72±4）岁。非骨水泥组给予非骨水泥人工半髋关节置换术治疗，男31例，女25例，年龄（73±4）岁。对比两组患者围术期相关指标、手术效果、并发症发生率，并对两组患者术后进行为期3年的随访观察，对患者在随访期间的Harris髋关节功能评分、不良事件发生率等进行统计对比。 结果112例患者获得完整随访，随访时间（36±5）个月。两组患者手术时间、术中失血量、引流量等差异无统计学意义（P>0.05），而骨水泥组患者的住院时间[（14±3）d]、开始负重时间[（41±9）d]均低于非骨水泥组[（17±3）d、（46±10）d]（t=4.353，2.856，P<0.05）。骨水泥组手术优良率为87.50%（49/56），高于非骨水泥组71.43%（40/56）（χ²=4.432，P<0.05）。骨水泥组术后并发症发生率为7.14%（4/56），低于非骨水泥组的21.43%（12/56）（χ²=4.667，P<0.05）。骨水泥组患者的Harris评分在术后6个月[（82±14）分]、12个月[（86±8）分]、24个月[（91±7）分]、36个月[（95±4）分]均优于非骨水泥组[（76±11、81±9、87±8、91±6）分]。骨水泥组不良事件发生率为8.93%（5/56），低于非骨水泥组的23.21%（13/56）（χ²=4.236，P<0.05）。 结论相较于非骨水泥型人工半髋关节，骨水泥型人工半髋关节置换术对于高龄股骨颈骨折患者的手术效果更好，术后关节功能恢复好，值得临床推荐。     

Bipolar cemented hip hemiarthroplasty in patients with femoral neck fracture who are on hemodialysis is associated with risk of stem migration

Background and purpose Femoral neck fractures are considerably more common in patients on hemodialysis than in the general population. We determined the outcome of bipolar hemiarthroplasty for hip fracture in patients with long-term hemodialysis and compared it with that of a matched-paired group of patients with intact renal function.Methods We analyzed 26 bipolar hemiarthroplasties in 23 hemodialysed patients with a mean age of 56 (41–78) years who were followed for mean 3.6 (1–8) years. These cases were matched for age, sex, and BMI with 26 patients with femoral neck fractures and normal renal function. The mean follow-up time in the control group was 7 (5–10) years. As primary surgery for their femoral neck fracture, all patients had a bipolar hemiarthroplasty with a 28-mm metal-polyethylene internal articulation and a cemented stem.Results The mortality rate was 21% in the hemodialysed group and 4% in the control group (p = 0.005). The bipolar head migrated in 1 patient in the hemodialysed group but in none of the patients in the case-matched group. In the hemodialysed group, 8 stems migrated and 3 of these were revised, whereas in the control group 3 stems migrated and 2 were revised. The stem migration in the hemodialysed group was not preceded by the development of osteolysis or radiolucent lines at the bone-cement interface. The cumulative survival for prosthesis migration as endpoint was 44% at 5 years in the hemodialysed group and 96% in the control group (p = 0.03).Interpretation The main mode of failure of cemented bipolar hemiarthroplasties in hemodialysed patients is stem migration, due to failure of the bone-cement interface.     

Minimally invasive intermuscular approach does not improve outcomes in bipolar hemiarthroplasty for femoral neck fracture

Background  

Optimal acetabular cup position is an important determinant of the success of total hip arthroplasty (THA), and navigation systems have been developed and applied to improve placement precision. However, the registration method touching bony landmarks through soft tissues may decrease the accuracy in obese cases and in patients with acetabular dysplasia.