The hip joint capsule passively restrains extreme range of motion protecting against impingement, dislocation and possibly edge loading. These functions would be advantageous following total hip arthroplasty (THA) however the degree of capsular excision, preservation and/or repair greatly varies between surgeons/approaches. Therefore, we asked: how does THA affect capsular ligamentous biomechanics? Which factors have the biggest influence? For this laboratory based, cadaveric model, THA was performed through the acetabular medial wall, thus preserving the entire hip capsule. A previously published testing rig was used to measure capsular function by internally and externally rotating the hip in each of five hip positions (standing, sitting, gait heel strike, and two impingement risk positions, full flexion with adduction & extension with abduction). N=8 hips were tested both before and after THA allowing for repeated measurements between the native and replaced hip. The ROM before the capsule engaged increased following THA Following THA, the capsular ligaments were no longer able to wrap around the smaller femoral head thereby limiting their ability to restrain excessive hip movement. The anterior capsule is affected less than the posterior, and may benefit from being preserved length. A repair to the posterior capsule should compensate for the reduced THA head size in order to restore function.
Cam and pincer morphologies are potential precursors to hip osteoarthritis and important contributors to non-arthritic hip pain. However, only some hips with these pathomorphologies develop symptoms and joint degeneration, and it is not clear why. Anterior impingement between the femoral head-neck contour and acetabular rim in positions of hip flexion combined with rotation is a proposed pathomechanism in these hips, but this has not been studied in active postures. Our aim was to assess the anterior impingement pathomechanism in both active and passive postures with high hip flexion that are thought to provoke impingement. We recruited nine participants with cam and/or pincer morphologies and with pain, 13 participants with cam and/or pincer morphologies and without pain, and 11 controls from a population-based cohort. We scanned hips in active squatting and passive sitting flexion, adduction, and internal rotation using open MRI and quantified anterior femoroacetabular clearance using the β angle.Aims
Methods
Femoroacetabular impingement (FAI) is a morphological hip joint deformity associated with pain and early degenerative changes. Cam-type FAI is prevalent in young male athletes. While biomechanical deficiencies (decreased hip muscle strength and range of motion (ROM)) have been associated with symptomatic cam-type FAI (sFAI), results have been conflicting and little is known about biomechanical characteristics during dynamic tasks. (1) Compare coronal-plane hip muscle strength, activation and joint rotation during movement tasks in sFAI hips against healthy controls. (2) Investigate the effect of hip internal rotation ROM (IR-ROM) on these outcomes.Introduction
Objectives
It has been well documented in the arthroplasty literature that lumbar degenerative disc disease (DDD) contributes to abnormal spinopelvic motion. However, the relationship between the severity or pattern of hip osteoarthritis (OA) as measured on an anteroposterior (AP) pelvic view and spinopelvic biomechanics has not been well investigated. Therefore, the aim of the study is to examine the association between the severity and pattern of hip OA and spinopelvic motion. A retrospective chart review was conducted to identify patients undergoing primary total hip arthroplasty (THA). Plain AP pelvic radiographs were reviewed to document the morphological characteristic of osteoarthritic hips. Lateral spine-pelvis-hip sitting and standing plain radiographs were used to measure sacral slope (SS) and pelvic femoral angle (PFA) in each position. Lumbar disc spaces were measured to determine the presence of DDD. The difference between sitting and standing SS and PFA were calculated to quantify spinopelvic motion (ΔSS) and hip motion (ΔPFA), respectively. Univariate analysis and Pearson correlation were used to identify morphological hip characteristics associated with changes in spinopelvic motion.Aims
Methods
Robotic assisted surgery aims to reduce surgical errors in implant positioning and better restore native hip biomechanics compared to conventional techniques for total hip arthroplasty (THA). The primary objective of this study was to compare accuracy in restoring the native centre of hip rotation in patients undergoing conventional manual THA versus robotic-arm assisted THA. Secondary objectives were to determine differences between these treatment techniques for THA in achieving the planned combined offset, cup inclination, cup version, and leg-length correction. This prospective cohort study included 50 patients undergoing conventional manual THA and 25 patients receiving robotic-arm assisted THA. All operative procedures were undertaken by a single surgeon using the minimally-invasive posterior approach. Two independent blinded observers recoded all radiological outcomes of interest using plain radiographs. Patients in both treatment groups were well-matched for age, gender, body mass index, laterality of surgery, and ASA scores. Interclass correlation coefficient was 0.92 (95% CI: 0.84 – 0.95) for intra-observer agreement and 0.88 (95% CI: 0.82–0.94) for inter-observer agreement in all study outcomes. Robotic THA was associated with improved accuracy in restoring the native horizontal (p<0.001) and vertical (p<0.001) centres of rotation, and improved preservation of the patient's native combined offset (P<0.001) compared to conventional THA. Robotic THA improved accuracy in positioning of the acetabular cup within the combined safe zones of inclination and anteversion described by Lewinnek et al (p=0.02) and Callanan et al (p=0.01) compared to conventional THA (figures 1–2). There was no difference between the two treatment groups in achieving the planned leg-length correction (p=0.10). Robotic-arm assisted THA was associated with improved accuracy in restoring the native centre of rotation, better preservation of the combined offset, and more precise acetabular cup positioning within the safe zones of inclination and anteversion compared to conventional manual THA. Robotic-arm assisted THA enables improved preservation of native hip biomechanics compared to conventional manual THA. For any figures or tables, please contact authors directly:
Hip arthroplasty aims to accurately recreate joint biomechanics. Considerable attention has been paid to vertical and horizontal offset, but femoral head centre in the anteroposterior (AP) plane has received little attention. This study investigates the accuracy of restoration of joint centre of rotation in the AP plane. Postoperative CT scans of 40 patients who underwent unilateral uncemented total hip arthroplasty were analyzed. Anteroposterior offset (APO) and femoral anteversion were measured on both the operated and non-operated sides. Sagittal tilt of the femoral stem was also measured. APO measured on axial slices was defined as the perpendicular distance between a line drawn from the anterior most point of the proximal femur (anterior reference line) to the centre of the femoral head. The anterior reference line was made parallel to the posterior condylar axis of the knee to correct for rotation.Aims
Methods
Hip arthroplasty does not always restore normal anatomy. This is due to inaccurate surgery or lack of stem sizes. We evaluated the aptitude of four total hip arthroplasty systems to restore an anatomical and medialized hip rotation centre. Using 3D templating software in 49 CT scans of non-deformed femora, we virtually implanted: 1) small uncemented calcar-guided stems with two offset options (Optimys, Mathys), 2) uncemented straight stems with two offset options (Summit, DePuy Synthes), 3) cemented undersized stems (Exeter philosophy) with three offset options (CPT, ZimmerBiomet), and 4) cemented line-to-line stems (Kerboul philosophy) with proportional offsets (Centris, Mathys). We measured the distance between the templated and the anatomical and 5 mm medialized hip rotation centre.Aims
Methods
Legg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition. Finite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP.Objectives
Methods
In this study we used subject-specific finite
element analysis to investigate the mechanical effects of rotational acetabular
osteotomy (RAO) on the hip joint and analysed the correlation between
various radiological measurements and mechanical stress in the hip
joint. We evaluated 13 hips in 12 patients (two men and ten women, mean
age at surgery 32.0 years; 19 to 46) with developmental dysplasia
of the hip (DDH) who were treated by RAO. Subject-specific finite element models were constructed from
CT data. The centre–edge (CE) angle, acetabular head index (AHI),
acetabular angle and acetabular roof angle (ARA) were measured on
anteroposterior pelvic radiographs taken before and after RAO. The
relationship between equivalent stress in the hip joint and radiological measurements
was analysed. The equivalent stress in the acetabulum decreased from 4.1 MPa
(2.7 to 6.5) pre-operatively to 2.8 MPa (1.8 to 3.6) post-operatively
(p <
0.01). There was a moderate correlation between equivalent
stress in the acetabulum and the radiological measurements: CE angle
(R = –0.645, p <
0.01); AHI (R = –0.603, p <
0.01); acetabular
angle (R = 0.484, p = 0.02); and ARA (R = 0.572, p <
0.01). The equivalent stress in the acetabulum of patients with DDH
decreased after RAO. Correction of the CE angle, AHI and ARA was
considered to be important in reducing the mechanical stress in
the hip joint. Cite this article:
In In a hip fracture experiment, nine pairs of human cadaver femurs
were tested in a paired study design. The femurs were then re-matched
according to BMD, creating two new test groups. Intra-pair variance
and paired correlations in fixation stability were calculated. A
hypothetical power analysis was then performed to explore the required sample
size for the two types of group allocation. Objective
Methods
Cementless femoral stems are currently preferred
for total hip replacement (THR) in the United States. Improvements
in stem design, instrumentation and surgical technique have made
this technology highly successful, reproducible, and applicable
to the vast majority of patients requiring a THR. However, there
are ongoing developments in some aspects of stem design that influence
clinical results, the incidence of complications and their inherent adaptability
in accommodating the needs of individual patients. Here we examine
some of these design features. Cite this article:
Progressive retroversion of a cemented stem is
predictive of early loosening and failure. We assessed the relationship
between direct post-operative stem anteversion, measured with CT,
and the resulting rotational stability, measured with repeated radiostereometric
analysis over ten years. The study comprised 60 cemented total hip
replacements using one of two types of matt collared stem with a
rounded cross-section. The patients were divided into three groups
depending on their measured post-operative anteversion (<
10°,
10° to 25°, >
25°). There was a strong correlation between direct
post-operative anteversion and later posterior rotation. At one
year the <
10° group showed significantly more progressive retroversion
together with distal migration, and this persisted to the ten-year
follow-up. In the <
10° group four of ten stems (40%) had been
revised at ten years, and an additional two stems (20%) were radiologically
loose. In the ‘normal’ (10° to 25°) anteversion group there was
one revised (3%) and one loose stem (3%) of a total of 30 stems,
and in the >
25° group one stem (5%) was revised and another loose (5%)
out of 20 stems. This poor outcome is partly dependent on the design
of this prosthesis, but the results strongly suggest that the initial
rotational position of cemented stems during surgery affects the
subsequent progressive retroversion, subsidence and eventual loosening.
The degree of retroversion may be sensitive to prosthetic design
and stem size, but <
10° of anteversion appears deleterious to
the long-term outcome for cemented hip prosthetic stems. Cite this article:
Patients demonstrate distinct trajectories of recovery after THA. The purpose of this study was to assess the impact of adjacent muscle quality on postoperative hip kinematics. We hypothesized that patients with better adjacent muscle quality (less fatty infiltration) would have greater early biomechanical improvement. Adults undergoing primary THA were recruited. Preoperative MRI was obtained and evaluated via Scoring Hip Osteoarthritis with MRI Scores (SHOMRI, Lee, 2015). Muscle quality was assessed by measuring fat fraction [FF] from water-fat sequences.
The aim of this study was to evaluate the suitability of the tapered cone stem in total hip arthroplasty (THA) in patients with excessive femoral anteversion and after femoral osteotomy. We included patients who underwent THA using Wagner Cone due to proximal femur anatomical abnormalities between August 2014 and January 2019 at a single institution. We investigated implant survival time using the endpoint of dislocation and revision, and compared the prevalence of prosthetic impingements between the Wagner Cone, a tapered cone stem, and the Taperloc, a tapered wedge stem, through simulation. We also collected Oxford Hip Score (OHS), visual analogue scale (VAS) satisfaction, and VAS pain by postal survey in August 2023 and explored variables associated with those scores.Aims
Methods
In the native hip, the hip capsular ligaments tighten at the limits of range of hip motion and may provide a passive stabilizing force to protect the hip against edge loading. In this study we quantified the stabilizing force vectors generated by capsular ligaments at extreme range of motion (ROM), and examined their ability to prevent edge loading. Torque-rotation curves were obtained from nine cadaveric hips to define the rotational restraint contributions of the capsular ligaments in 36 positions. A ligament model was developed to determine the line-of-action and effective moment arms of the medial/lateral iliofemoral, ischiofemoral, and pubofemoral ligaments in all positions. The functioning ligament forces and stiffness were determined at 5 Nm rotational restraint. In each position, the contribution of engaged capsular ligaments to the joint reaction force was used to evaluate the net force vector generated by the capsule.Aims
Methods
Custom flange acetabular components (CFACs) are a patient-specific option for addressing large acetabular defects at revision total hip arthroplasty (THA), but patient and implant characteristics that affect survivorship remain unknown. This study aimed to identify patient and design factors related to survivorship. A retrospective review of 91 patients who underwent revision THA using 96 CFACs was undertaken, comparing features between radiologically failed and successful cases. Patient characteristics (demographic, clinical, and radiological) and implant features (design characteristics and intraoperative features) were collected. There were 74 women and 22 men; their mean age was 62 years (31 to 85). The mean follow-up was 24.9 months (Aims
Patients and Methods
The hip’s capsular ligaments passively restrain extreme range of movement (ROM) by wrapping around the native femoral head/neck. We determined the effect of hip resurfacing arthroplasty (HRA), dual-mobility total hip arthroplasty (DM-THA), conventional THA, and surgical approach on ligament function. Eight paired cadaveric hip joints were skeletonized but retained the hip capsule. Capsular ROM restraint during controlled internal rotation (IR) and external rotation (ER) was measured before and after HRA, DM-THA, and conventional THA, with a posterior (right hips) and anterior capsulotomy (left hips).Aims
Materials and Methods
Our aim was to evaluate the radiographic characteristics of patients
undergoing total hip arthroplasty (THA) for the potential of posterior
bony impingement using CT simulations. Virtual CT data from 112 patients who underwent THA were analysed.
There were 40 men and 72 women. Their mean age was 59.1 years (41
to 76). Associations between radiographic characteristics and posterior
bony impingement and the range of external rotation of the hip were
evaluated. In addition, we investigated the effects of pelvic tilt
and the neck/shaft angle and femoral offset on posterior bony impingement.Aims
Patients and Methods
We evaluated the accuracy with which a custom-made
acetabular component could be positioned at revision arthroplasty
of the hip in patients with a Paprosky type 3 acetabular defect. A total of 16 patients with a Paprosky type 3 defect underwent
revision surgery using a custom-made trabecular titanium implant.
There were four men and 12 women with a median age of 67 years (48
to 79). The planned inclination (INCL), anteversion (AV), rotation
and centre of rotation (COR) of the implant were compared with the post-operative
position using CT scans. A total of seven implants were malpositioned in one or more parameters:
one with respect to INCL, three with respect to AV, four with respect
to rotation and five with respect to the COR. To the best of our knowledge, this is the first study in which
CT data acquired for the pre-operative planning of a custom-made
revision acetabular implant have been compared with CT data on the
post-operative position. The results are encouraging. Cite this article:
Many different lengths of stem are available
for use in primary total hip replacement, and the morphology of
the proximal femur varies greatly. The more recently developed shortened
stems provide a distribution of stress which closely mimics that
of the native femur. Shortening the femoral component potentially
comes at the cost of decreased initial stability. Clinical studies
on the performance of shortened cemented and cementless stems are promising,
although long-term follow-up studies are lacking. We provide an
overview of the current literature on the anatomical features of
the proximal femur and the biomechanical aspects and clinical outcomes
associated with the length of the femoral component in primary hip
replacement, and suggest a classification system for the length
of femoral stems. Cite this article:
