Next-generation soft-tissue-friendly large-diameter femoral head

Large-diameter femoral heads are being used increasingly in total hip arthroplasty (THA) to minimize hip dislocation risk. However, recent studies have shown that conventional large heads can impinge on native soft tissues, particularly the iliopsoas, leading to activity-limiting anterior hip pain. To address this, a novel soft-tissue-friendly anatomically contoured femoral head (ACH) was developed. This paper describes the design rationale and pre-clinical testing of the ACH implant. The test results demonstrate that anatomical contouring of large-diameter femoral heads for soft-tissue relief can be accomplished without affecting dislocation resistance, femoroacetabular contact area, or wear performance in ceramic-on-polyethylene implants.     

Cadaver-Specific Models for Finite-Element Analysis of Iliopsoas Impingement in Dual-Mobility Hip Implants

Background

Joint dislocation is a major cause of failure in total hip arthroplasty. Dual-mobility implants provide a femoral head diameter that can match the native hip size for greater stability against dislocation. However, such large heads are prone to impingement against surrounding soft tissues. To address this concern, the concept of an anatomically contoured dual-mobility implant was evaluated using cadaver-specific finite-element analysis (FEA).

Reducing the distal profile of dual mobility liners can mitigate soft‐tissue impingement and liner entrapment without affecting mechanical performance

Soft‐tissue impingement with dual mobility liners can cause anterior hip pain and intra‐prosthetic dislocation. The hypothesis of this study was that reducing liner profile below the equator (contoured design) can mitigate soft‐tissue impingement without compromising inner‐head pull‐out resistance and hip joint stability. The interaction of conventional and contoured liners with anterior soft tissues was evaluated in cadaver specimens via visual observation and fluoroscopic imaging. Resistance to inner‐head pull‐out was evaluated via finite element analyses, and hip joint stability was evaluated by rigid‐body mechanics simulation of dislocation in two modes (A, B). Cadaveric experiments showed that distal portion of conventional liners impinge on anterior hip capsule and cause iliopsoas tenting at low flexion angles (≤30°). During hip extension, the rotation imparted to the liner from posterior engagement with femoral neck was impeded by anterior soft‐tissue impingement. The iliopsoas tenting was significantly reduced with contoured liners (p ≤ 0.04). Additionally, the contoured and conventional liners had identical inner‐head pull‐out resistance (901 N vs. 909 N), jump distance (9.4 mm mode‐A, 11.7 mm mode‐B) and impingement‐free range of motion (47° mode‐A, 29° mode‐B). Thus, soft‐tissue impingement with conventional dual mobility liners may be mitigated by reducing liner profile below the equator, without affecting mechanical performance. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:889–897, 2016.     

Failure of larger-diameter metal-on-metal total hip arthroplasty resulting from anterior iliopsoas impingement

Anterior iliopsoas impingement is a recognized cause of persistent groin pain after total hip arthroplasty. We report 3 patients with failed total hip arthroplasties resulting from anterior iliopsoas and capsular impingement secondary to a metal femoral ball with a diameter larger than the native femoral head. All patients had the same implant design. Resolution of symptoms occurred in all patients after revision surgery. To our knowledge, this is the first report of this potential failure mechanism with these large-diameter implant designs and should be considered in the appropriate clinical scenario.     

Retroperitoneal Hematoma : An Unusual Cause of Pain After Total Hip Arthroplasty

Pain following total hip arthroplasty due to impingement of the iliopsoas is a recognized complication of the procedure with a reported incidence as high as 4.3%. The pain is most often due to direct mechanical irritation of the iliopsoas due to a malpositioned or oversized acetabular cup. Definitive treatment of iliopsoas impingement often requires surgical revision or iliopsoas tenotomy, although many cases remain undiagnosed or are managed conservatively. We present an unusual case of pain after total hip arthroplasty due to a large retroperitoneal hematoma secondary to acetabular cup irritation of the iliopsoas tendon. This case represents a potentially important complication of undiagnosed or conservatively managed iliopsoas impingement, particularly in patients taking anticoagulants or antiplatelet medications.     

Why large-head metal-on-metal hip replacements are painful: the anatomical basis of psoas impingement on the femoral head-neck junction

Large-head metal-on-metal total hip replacement has a failure rate of almost 8% at five years, three times the revision rate of conventional hip replacement. Unexplained pain remains a feature of this type of arthroplasty. All designs of the femoral component of large-head metal-on-metal total hip replacements share a unique characteristic: a subtended angle of 120° defining the proportion of a sphere that the head represents. Using MRI, we measured the contact area of the iliopsoas tendon on the femoral head in sagittal reconstruction of 20 hips of patients with symptomatic femoroacetabular impingement. We also measured the articular extent of the femoral head on 40 normal hips and ten with cam-type deformities. Finally, we performed virtual hip resurfacing on normal and cam-type hips, avoiding overhang of the metal rim inferomedially. The articular surface of the femoral head has a subtended angle of 120° anteriorly and posteriorly, but only 100° medially. Virtual surgery in a normally shaped femoral head showed a 20° skirt of metal protruding medially where iliopsoas articulates. The excessive extent of the large-diameter femoral components may cause iliopsoas impingement independently of the acetabular component. This may be the cause of postoperative pain with these implants.     

Iliopsoas Tendonitis Caused by Overhang of a Collared Femoral Prosthesis

Pain after total hip arthroplasty can be due to a variety of causes, one of the less common being iliopsoas tendonitis. We report an unusual case of iliopsoas tendonitis caused by overhang of the femoral calcar by a collared femoral prosthesis resulting in impingement on the iliopsoas tendon. An ultrasound-guided corticosteroid and local anesthetic diagnostic injection to the site of impingement confirmed the diagnosis with temporary symptom relief. Revision of the femoral stem to a collarless prosthesis resulted in immediate and complete resolution of symptoms.     

Hip Abduction Can Be Considered the Sole Posterior Precaution Strategy to Lower the Rate of Impingement After Posterior Approach Total Hip Arthroplasty With Large Femoral Head: A Computer Simulation Study

BackgroundStudies suggest that posterior hip precautions are unnecessary after total hip arthroplasty; however, many surgeons and patients choose to follow these precautions to some extent. In this study, we hypothesized that 20° of hip abduction would be sufficient to prevent impingement and dislocation in motions requiring hip flexion when using larger prosthetic heads (≥36 mm) when the acetabular implant is placed within a reasonable orientation (anteversion:15-25° and inclination: 40-60°).MethodsUsing a robotic hip platform, we investigated the effect of hip abduction on prosthetic and bony impingement in 43 patients. For the flexed seated position, anterior pelvic tilt angles of 10 and 20° were chosen, while anterior pelvic tilt angles of 70 and 90° were chosen for the bending forward position. An additional 10° of hip external rotation and 10 or 20° of hip internal rotation were also added to the simulation. One hip received a 32-mm head; otherwise, 36-, 40-mm, or dual-mobility heads were used. The study power was 0.99, and the effect size was 0.644.ResultsIn 65% of the cases, bone-bone impingement between the calcar and anterior-inferior iliac spine was the main type of impingement. The absolute risk of impingement decreased between 0 and 16.3% in both tested positions with the addition of 20° hip abduction.ConclusionWith modern primary total hip arthroplasty stems (low neck diameter) and an overall acceptable cup anteversion angle, small degrees of hip abduction may be the only posterior hip precaution strategy required to lower the risk of dislocation among patients. Future studies can potentially investigate the concept of personalized hip precautions based on preoperative computer simulations, utilized implants, hip-spine relations, and final implant orientation.     

Recurrent Hematomas Within the Iliopsoas Muscle Caused by Impingement After Total Hip Arthroplasty

Impingement of the iliopsoas muscle after total hip arthroplasty is a potential cause of postoperative groin pain. In addition, hematoma within the iliopsoas sheath has been documented as a cause of groin pain in patients on long-term anticoagulation. We present the case of a patient on long-term anticoagulation presenting after total hip arthroplasty with recurrent, symptomatic iliopsoas sheath hematomas. We believe this was due to iliopsoas impingement caused by a malpositioned acetabular component. His pain was relieved after revision of the acetabular component and debridement of the inflamed psoas tendon.     

Extra-articular hip impingement: a narrative review of the literature

There is growing subgroup of patients with poor outcomes after hip arthroscopy for intra-articular pathology suggesting unrecognized cause(s) of impingement may exist. Extra-articular hip impingement (EHI) is an emerging group of conditions that have been associated with intra-articular causes of impingement and may be an unrecognized source of pain. EHI is caused by abnormal contact between the extra-articular regions of the proximal femur and pelvis. This review discusses the most common forms for EHI including: central iliopsoas impingement, subspine impingement, ischiofemoral impingement, and greater trochanteric-pelvic impingement. The clinical presentation of each pathology will be discussed since EHI conditions share similar clinical features as the intra-articular pathology but also contain some unique characteristics.     

Mid-term results of large diameter heads on cross-linked polyethylene liners in total hip replacement

BackgroundHighly cross-linked polyethylene liners in total hip replacement (THR) have allowed the use of larger diameter femoral heads. Larger heads allow for increased range of motion, decreased implant impingement, and protection against dislocation. The purpose of this study is to assess the clinical and radiographic outcomes of patients with large femoral heads THR at 4 years postop.Materials and methodsStudy includes 28 patients who had a primary THR with a 36 mm larger femoral head were retrospectively for minimum 4 years follow-up. All patients received a cementless acetabular shell and a highly cross-linked polyethylene liner with an inner diameter of 36 mm. The median radiographic follow-up was 4 years (range 2.0–6.0), and patients were assessed clinically by Harris hip score.ResultsThe mean follow-up is minimum 4 years (range 2–6 years) results in all operated patients showed marked improvement in Harris hip score from preoperative mean 49.1 to 89.9 at 4 years or more follow-up. The complications include superficial infection (n = 2). No dislocation, or no osteolysis was seen in the pelvis or proximal femur, and no components failed due to aseptic loosening. There was no evidence of cup migration, screw breakage, or eccentric wear on the liner.ConclusionThe mid-term results in this series of patients with LDH using 36 mm femoral head articulating with highly cross linked polyethylene showed excellent clinical, and radiological results, in terms of, joint restoration that replicates the natural anatomy, optimized range of motion without impingement & reduced opportunity for postoperative dislocation.     

Clinical importance of impingement deformities for hip osteoarthritis progression in a Japanese population

Purpose

Femoroacetabular impingement is a new disease concept for hip disorders in young adults suggested as a major cause of primary hip osteoarthritis in Western countries. However, significant controversy exists regarding the prevalence and contribution of impingement deformities to osteoarthritis in Japan, owing to the higher prevalence of developmental dysplasia of the hip. Therefore, the aims of this study were to: (1) determine the prevalence of structural abnormalities associated with hip disorders in patients undergoing total hip replacement and (2) analyse the contribution of impingement deformities to osteoarthritis.

Methods

We analysed 250 patients from two different medical centres who underwent primary total hip replacement except those which were due to femoral head necrosis, posttraumatic osteoarthritis and systemic inflammatory disease. The average patient age at surgery was 64 years (range, 40–89 years), with 35 men and 215 women.

Results

Radiographic abnormality related to developmental dysplasia of the hip was associated with the majority of osteoarthritic hips (62 %). Hips with femoroacetabular impingement deformities were present within the cases categorized as unknown etiology. Cam impingement deformity was present in 22 % of unknown aetiology cases when cases with reactive osteophytes were excluded from all cam deformity cases (pistol grip deformity and aspherical femoral heads).

Conclusions

The prevalence of femoroacetabular impingement within primary osteoarthritis cases and gender predominance of impingement deformities are relatively similar to those reported previously in Western populations. This finding indicates that femoroacetabular impingement deformities are associated with osteoarthritis in the Japanese population, although it has a lower frequency among all hip failure patients.     

Evaluation of Endoscopic Iliopsoas Tenotomy for Treatment of Iliopsoas Impingement After Total Hip Arthroplasty

BackgroundIliopsoas impingement after total hip arthroplasty (THA) occurs in up to 4.3% of patients resulting in functional groin pain. Operative treatment historically has included open iliopsoas tenotomy or acetabulum revision. We present a large single surgeon series of patients treated with endoscopic iliopsoas tenotomy for iliopsoas impingement after THA to evaluate the effectiveness and risks.MethodsA consecutive series of 60 patients with iliopsoas impingement after THA treated with endoscopic iliopsoas tenotomy was retrospectively evaluated. Outcomes assessed were resolution of pain, change in Hip Outcome Score (HOS), and complications. Radiographs were reviewed by a musculoskeletal radiologist to evaluate component positioning and to compare with a control cohort.ResultsAt last follow-up (mean 5.5 months), 93.3% of patients had resolution of pain. The HOS activities of daily living (ADL) subscale mean was 57.5 (range 10.9-89.3, standard deviation [SD] 18.8) preoperatively and 71.6 (range 14.1-100, SD 26.1) postoperatively (P = .005). The HOS sports subscale mean was 37.3 (range 0-83.3, SD 24.0) preoperatively and 58.1 (range 0-100, SD 33.2) postoperatively (P = .002). One complication was reported, a postoperative hematoma managed conservatively. Body mass index and increased offset were associated with iliopsoas symptoms after THA in this series.ConclusionEndoscopic iliopsoas tenotomy after THA had a 93.3% resolution of pain, clinically important improvements in HOS, and low rate of complications. Endoscopic tenotomy should be considered as a treatment option in patients with iliopsoas impingement after THA.     

Range of motion and stability in total hip arthroplasty with 28-, 32-, 38-, and 44-mm femoral head sizes

The purpose of this study was to evaluate, via experimental models, the effect of larger head sizes for total hip arthroplasty on the type of impingement, range of motion (ROM), and joint stability. Testing was conducted using an anatomic full-size hip model (anatomic goniometer) and a novel anatomic dislocation simulator with 28-, 32-, 38-, and 44-mm diameter femoral heads within a 61-mm acetabular shell. Femoral heads >32-mm provided greater ROM and virtually complete elimination of component-to-component impingement. A significant increase in both flexion before dislocation and displacement between the femoral head and acetabulum to produce dislocation occurred with femoral heads >32-mm in diameter. These data indicate that larger femoral heads offer potential in providing greater hip ROM and joint stability.     

Ideal Femoral Head Size in Total Hip Arthroplasty Balances Stability and Volumetric Wear

Background

Over the last several years, a trend towards increasing femoral head size in total hip arthroplasty to improve stability and impingement free range of motion has been observed.

Purpose

The specific questions we sought to answer in our review were: (1) What are the potential advantages and disadvantages of metal-on-metal, ceramic-on-ceramic, and metal-on-polyethylene bearings? (2) What is effect that femoral head size has on joint kinematics? (3) What is the effect that large femoral heads have on bearing surface wear?

Methods

A PubMed search and a review of 2012 Orthopaedic Research Society abstracts was performed and articles were chosen that directly answered components of the specific aims and that reported outcomes with contemporary implant designs or materials.

Results

A review of the literature suggests that increasing femoral head size decreases the risk of postoperative dislocation and improves impingement free range of motion; however, volumetric wear increases with large femoral heads on polyethylene and increases corrosion of the stem in large metal-on-metal modular total hip arthroplasty (THA); however, the risk of potentially developing osteolysis or adverse reactions to metal debris respectively is still unknown. Further, the effect of large femoral heads with ceramic-on-ceramic THA is unclear, due to limited availability and published data.

Conclusions

Surgeons must balance the benefits of larger head size with the increased risk of volumetric wear when determining the appropriate head size for a given patient.     

Use of an anatomical acetabular component for treatment of iliopsoas impingement

Iliopsoas impingement is a known cause of pain after total hip arthroplasty. The author reports on a patient with iliopsoas impingement due to prominence of the anterior aspect of her acetabular hip arthroplasty component successfully treated with revision to an anatomically designed acetabular implant. Use of such an anatomically designed acetabular implant may prove to be beneficial in selected patients with iliopsoas impingement.     

Radiographic Predictors of Hip Pain in Femoroacetabular Impingement

The primary diagnosis of femoroacetabular impingement is based on clinical symptoms, physical exam findings, and radiographic abnormalities. The study objective was to determine the radiographic findings that correlate with and are predictive of hip pain in femoroacetabular impingement (FAI). One hundred prospective patients with unilateral FAI symptoms based on clinical and radiographic findings were included in this study. All patients filled out a WOMAC pain questionnaire. Two independent-blinded surgeons assessed antero-posterior and lateral radiographs for 33 radiographic parameters of FAI. Correlations between pain scores and radiographic findings were calculated. A matched radiographic analysis was performed comparing symptomatic versus asymptomatic hips. Radiograph findings were also compared between males and females. Weak positive correlations were identified between increasing pain scores with radiographic findings of posterior wall dysplasia, presence of a shallow socket, and a more lateral acetabular fossa relative to the Ilioischial line. A symptomatic hip had a lower neck shaft angle, greater distance from Ilioischial line to acetabular fossa and larger distance from cross-over sign to superolateral point of the acetabulum when compared to the asymptomatic hip in the same patient. Symptomatic hips in males had more joint space narrowing, femoral osteophytes, higher alpha angles and larger, more incongruent femoral heads compared to females. Females had more medial acetabular fossa relative to the Ilioischial line and smaller femoral head extrusion index. Similar to other musculoskeletal conditions, radiographic findings of FAI are poor predictors of hip pain.     

The effect of femoral component head size on posterior dislocation of the artificial hip joint

BACKGROUND: Posterior dislocation continues to be a relatively common complication following total hip arthroplasty. In addition to technical and patient-associated factors, prosthetic features have also been shown to influence stability of the artificial hip joint. In this study, a dynamic model of the artificial hip joint was used to examine the influence of the size of the head of the femoral component on the range of motion prior to impingement and posterior dislocation following total hip replacement. METHODS: Six fresh cadaveric specimens were dissected, and an uncemented total hip prosthesis was implanted in each. Each specimen was mounted in a mechanical testing machine and loaded with use of a system of seven cables attached to the femur and pelvis that simulated the action of the major muscle groups crossing the hip joint. The hip was taken through a range of motion similar to that experienced when rising from a seated position. The three-dimensional position of the femur at the points of impingement and dislocation was recorded electronically. The range of joint motion was tested with prosthetic femoral heads of four different diameters (twenty-two, twenty-six, twenty-eight, and thirty-two millimeters). RESULTS: Significant associations were noted between the femoral head size and the degree of flexion at dislocation in ten (p = 0.001), twenty (p < 0.001), and thirty (p = 0.003) degrees of adduction. Increasing the femoral head size from twenty-two to twenty-eight millimeters increased the range of flexion by an average of 5.6 degrees prior to impingement and by an average of 7.6 degrees prior to posterior dislocation; however, increasing the head size from twenty-eight to thirty-two millimeters did not lead to more significant improvement in the range of joint motion. The site of impingement prior to dislocation varied with the size of the femoral head. With a twenty-two-millimeter head, impingement occurred between the neck of the femoral prosthesis and the acetabular liner, whereas with a thirty-two-millimeter head, impingement most frequently occurred between the osseous femur and the pelvis. CONCLUSIONS: With the particular prosthesis that was tested, increasing the diameter of the femoral head component increased the range of motion prior to impingement and dislocation, decreased the prevalence of prosthetic impingement, and increased the prevalence of osseous impingement. CLINICAL RELEVANCE: These results suggest that femoral heads with a twenty-eight-millimeter diameter increase the range of motion after total hip replacement. This may be beneficial when additional factors compromising joint stability are encountered.     

An in vivo model for intraoperative assessment of impingement and dislocation in total hip arthroplasty

We have developed an intraoperative model to quantify total hip arthroplasty impingement and dislocation mechanics using fluoroscopy and shape-matching techniques. Two patient groups were investigated: group 1 consisted of 12 hips using 28- or 32-mm femoral heads and an anterolateral surgical approach, and group 2 consisted of 17 hips using 22- or 26-mm femoral heads and a posterolateral surgical approach. During intraoperative hip stability testing consisting of extension and external rotation motions, group 1 was more unstable, and prosthetic impingement was the major reason for dislocation. With flexion and internal rotation motions, group 2 was more unstable, and superior-lateral impingement or soft tissue traction was the major reason for dislocation. Intraoperative quantitative assessment of hip mechanics provides a safe and clinically relevant method to characterize potential complications and evolve techniques to prevent them.     

Arthroscopic treatment of cam-type femoroacetabular impingement: preliminary report at 2 years minimum follow-up

Femoroacetabular impingement is defined as anterior hip abutment between the acetabular rim and proximal femur. When it is secondary to acetabular overcoverage, it is pincer impingement. When it is secondary to femoral head and neck deformity, it is cam impingement. Open remodeling of impinging deformities is the standard treatment of this condition. We describe arthroscopic treatment of cam impingement in 19 patients using standard hip arthroscopy portals by the lateral approach. Sixteen patients improved their symptoms after the procedure; and 3 patients deteriorated, with 1 needing a total hip arthroplasty at 2 years follow-up. We had no cases with postoperative femoral neck fractures or avascular necrosis. Hip arthroscopy can be successfully used to treat cam impingement. The precautions used in open surgery to preserve femoral neck bone stock and hip vascularity should be followed.