HIP International

As the prevalence of total hip replacement is increasing in younger patients, less invasive implants (short stems) are becoming more favourable. However, despite the advantages of these stems, clinical results with a follow-up of more than 10 years are limited to a very few stem designs.

There has been an increase in publications recently – mechanical and clinical studies – concerning the primary stability of short stems. Primary stem stability is an important factor as it reflects final stem stabilisation and is related to the clinical results of the prosthesis.

We conducted a systematic review of the literature to retrieve evidence concerning primary implant stability in short stems – as expressed by implant micromotion and stem subsidence – according to our previously proposed short-stem classification.

Mechanical in vitro studies on stem micromotion are very few and limited to type 2 “partial collum” short stems. The results are comparable to those of stems with a known long-term excellent clinical course.

Clinical results concerning stem migration patterns are also limited to some of the commercially available short stems. Although comparative studies are very few, the results for most of the short stems are similar to those of standard stems.

There are promising results concerning biomechanical studies of the initial micromotion of short stems, as well as clinical results of stem migration patterns. Long-term clinical studies are needed in order to confirm these findings. The existing literature concerns very few of the many commercially available implants.

The objective of this study was to evaluate the mid-term migration pattern of a femoral short stem.

Implant migration of 73 femoral short-stems was assessed by Ein-Bild-Roentgen-Analysis Femoral-Component-Analysis (EBRA-FCA) 5 years after surgery. Migration pattern of the whole group was analysed and compared to the migration pattern of implants “at risk” with a subsidence of more than 1.5 mm 2 years postoperative.

Mean axial subsidence was 1.1 mm (–5.0 mm to 1.5 mm) after 60 months. There was a statistical significant axial migration until 2 years postoperative with settling thereafter. 2 years after surgery 18 of 73 Implants were classified “at risk.” Nevertheless, all stems showed secondary stabilisation in the following period with no implant failure neither in the group of implants with early stabilisation nor the group with extensive early onset migration.

In summary, even in the group of stems with more pronounced early subsidence, delayed settling occurred in all cases. The determination of a threshold of critical early femoral short stem subsidence is necessary because of the differing migration pattern described in this study with delayed settling of the Fitmore stem 2 years postoperatively compared to early settling within the first postoperative year described for conventional stems.

Pseudosubluxation is a transient separation of the prosthetic femoral head from the acetabular liner during the anaesthetic period after total hip arthroplasty (THA). However, little is known about the frequency, pathomechanism, risk factors or natural history.

To determine the incidence, direction of the displacement, risk factors and subsequent instability of pseudosubluxation, we evaluated 1099 primary cementless THAs (943 patients), which were performed during 8 years at one institution. Immediately after THA, postoperative radiographs were obtained for all hips. If a subluxation was noted, the operated hip was examined by fluoroscope within 1 hour of the detection and repeat radiographs were taken on the postoperative day 1.

The pseudosubluxation was identified in 2.6% (28/1059). All of the 28 heads subluxed anteriorly and reduced in flexion-internal rotation. In multivariate analysis: (1) operative decrease of the femoral offset (odds ratio; 1.161 (95% confidence interval [CI]; 1.077–1.251), p = 0.001); and (2) medialisation of acetabular cup (odds ratio; 3.402 (95% CI; 1.482–7.813), p = 0.009) were found as risk factors for pseudosubluxation. None of the 28 hips dislocated during 3- to 8-year follow-up.

Our results provide information about the incidence, risk factors and natural history of pseudosubluxation after primary THA. Surgeons should be aware of the risk of pseudosubluxation when performing THA in patients with coxa vara, who have a large femoral offset, and in those with dysplastic or deficient acetabulum, who have a lateral centre of rotation.

Despite several studies, controversy has prevailed over the rate of complications following 1-stage and 2-stage bilateral total hip arthroplasty (THA). In the current study, we compare the complications and functional outcomes of 1-stage and 2-stage procedures.

One hundred and eighty patients (ASA class I or II) with bilateral hip osteoarthritis were assigned randomly to two equal groups. The two groups were matched in terms of age and sex. All of the surgeries were performed via the Hardinge approach using uncemented implants. In 2-stage procedures, surgeries were performed with a 6-month to 1-year interval. All patients were evaluated 1 year postoperatively.

The Harris Hip Score (HHS) averaged 84.1 and 82.6 in 1-stage and 2-stage groups, respectively (p = 0.528). The hospital stay was significantly longer in the 2-stage group (9.8 days vs. 4.9 days). The cumulative haemoglobin drop and the number of transfused blood units were the same. One patient in each group developed symptomatic deep venous thrombosis which was managed successfully. There was no patient with perioperative death, pulmonary embolism, infection, dislocation, periprosthetic fracture or heterotrophic ossification. No patient required reoperation. Two patients in the 1-stage group developed unilateral temporary peroneal nerve palsy, which was resolved after 3–4 months.

1-stage bilateral THA can be used successfully for patients with bilateral hip disease without increasing the rate of complications. Functional and clinical outcomes are comparable and hospital stay is significantly shorter.

The aim of this study was to analyse the relationship between bony joint orientation and the distribution of hip musculature.

The bone anatomy of the hip (femoral antetorsion (AT), acetabular anteversion (AV), and combined anteversion (AV/AT)) and the muscle volume of the gluteal muscles and the tensor fasciae latae were analysed bilaterally using computed tomography data of 49 patients. Muscle force direction (MFD) was determined for each muscle. The total MFD of the hip musculature was calculated and then correlated with the bony anatomy.

The mean AV, AT, and AV/AT were 21.9° ± 5.9°, 7.22° ± 7.4°, and 29.2° ± 9°, respectively. We found the following mean muscle volumes: gluteus maximus: 780 ± 227 cm3, gluteus medius: 322 ± 82 cm3, gluteus minimus: 85 ± 20 cm3, and tensor fasciae latae: 68 ± 22 cm3. The mean MFD was 18.92° ± 1.29°. We found a uniform distribution of the musculature that was not correlated with the bone anatomy.

This study highlights the variability in native acetabular and femoral anatomy and that bone hip anatomy does not correlate with the distribution of hip musculature. Although native acetabular anteversion matches the suggested targets for cup insertion, native combined anteversion is not related to current implant insertion targets. Understanding native muscular anatomy and the alterations that occur with different surgical approaches can serve as an explanatory model for THAs that has become unstable despite the components being implanted within the safe zone.

We studied whether acetabular bone mineral density (BMD) is better preserved after resurfacing hip arthroplasty (RHA) versus small diameter metal-on-metal total hip arthroplasty (THA).

This randomised controlled trial included 82 patients. BMD was measured in 5 periprosthetic regions of interest (ROI) with dual-energy absorptiometry (DEXA) preoperatively, at 3 and 6 months, 1, 2, 3 and 5 years postoperative. 34 RHA and 26 THA had a complete 5 years follow-up. 1 RHA and 1 THA were revised due to pseudotumour formation, 2 THA were revised because of recurrent dislocations and 1 RHA for avascular necrosis.

Overall an initial decrease in BMD was observed for both implants, stabilising after 2 years. 5 years after RHA a BMD change of +1% in upper cranial, –4% (p < 0.01) in cranial, –8% (p < 0.01) in craniomedial, –7% (p < 0.01) in medial and +4% in caudal ROI compared to baseline values was seen. 5 years after THA a BMD change of –3% (p = 0.01), –13% (p < 0.01), –21% (p < 0.01), –11% (p < 0.01) and –2% for each respective ROI. The observed BMD decrease in different regions was structurally favouring the RHA-cup, with significantly higher levels in the cranial and craniomedial ROI.

Acetabular BMD is better preserved behind a rigid press-fit convex cup in RHA compared to a titanium threaded cup in conventional THA in the cranial and craniomedial ROI. Despite of a theoretical higher stress-shielding behind the stiff acetabular component in RHA, compared to the more elastic threaded titanium THA-cup, bone depletion behind the RHA component does not seem to be of major concern.

EudraCT (2006-005610-12)

The aim of this study was to examine the natural history of lateral femoral cutaneous nerve (LFCN) neuropraxia in a previously reported cohort of individuals after direct anterior approach (DAA).

99 patients (107 hips) with LFCN neuropraxia were identified, out of which 82 patients (87 hips) (83.1%) completed functional outcomes questionnaires at mean follow-up of 5.5 years (4.4–6.9 years). 5 patients were excluded from the study due to intra-articular source of pain and/or revision surgery. The total sample was composed of 77 patients (31 total hip replacements and 51 hip resurfacings) and functional outcomes scores were obtained for all patients.

At average 5.46-year follow-up, 55 patients (60 hips 73%) still reported symptoms of LFCN neuropraxia but their Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were not inferior to those who had resolution for pain, function and stiffness: p values of 0.716, 0.171, and 0.238, respectively. The mean score on visual analogue scale decreased from 2.32 (SD 2.11) to 1.76 (SD 1.99). 1 patient (1.2%) reported his activities were limited by his symptoms.

Although the majority of patients still report symptoms related to LFCN neuropraxia, symptoms do improve over time and there are no functional limitations. Even if LFCN neuropraxia following DAA does not lead to functional limitations, all patients should be made aware in order to alleviate any long-term functional concerns.

Low serum albumin is associated with higher perioperative complications following total hip arthroplasty (THA). The distinct threshold for a significant rise in perioperative complications has not been defined for THA. The purpose of this study was to define the threshold at which perioperative complications rise after THA.

We analysed the American College of Surgeons NSQIP database from 2006 to 2013. Our study cohort included unilateral primary THA with reported preoperative albumin levels. Patients were stratified by albumin level. We analysed mortality and 6 composite complication variables (any complication, any complication without transfusion, wound infection, systemic infection, cardiac/pulmonary complications, and any major complication). All data analysis was executed in STATA statistical software. Multivariable logistic regression analysis was used to adjust for odds ratios.

The final cohort included 24,586 patients who were stratified based upon serum albumin levels. Odds ratios after multivariable regression adjustment for age, gender, race, body mass index, ASA classification, and Charlson Comorbidity Index indicated a trend to elevated odds of complication for all composite complications (3 of which were statistically significant) when serum albumin level was <3.0 g/dL.

Low serum albumin is associated with increased perioperative complications following THA. The threshold associated with an increase in major perioperative complications appears to be an albumin level of <3.0 g/dL. With attempts to correct modifiable risk factors prior to surgery, the threshold value at which perioperative complications increase is important to define.

Perioperative blood transfusion is not without risk and effort should be made to limit patients’ exposure to allogeneic blood. However, there is conflicting data regarding the impact of anaemia on postoperative recovery in patients with repaired hip fractures. It is hypothesised that for a given baseline functional status and fracture type, lower postoperative haemoglobin will increase rehabilitation time and prolong total length of hospital stay.

This is a retrospective study on data collected prospectively on patients entered into the Clinical Pathway aged >65 years admitted to Queen Mary Hospital (QMH) with a fractured neck of femur during 2011–2013. Potential predictor variables were analysed with linear regression with respect to total length of stay and those that reached a significance level of 0.05 were included in further analysis.

1092 patients were admitted to QMH with a suspected fractured neck of femur; data from 747 patients were analysed. The fracture sites were neck of femur (50%), intertrochanteric (48%) and subtrochanteric fracture (2%). Approximately 30% of patients received blood transfusions. Of these only the development of postoperative medical complications statistically prolonged hospital stay. No relationship was seen with haemoglobin levels cut-off above and below 10 g/dl with the result remaining non-significant down to a cut-off of above and below 8 g/dl.

This study revealed that post-surgical haemoglobin level of between 8 g/dl and 10 g/dL did not have an impact on the total length of hospital stay. The development of postoperative medical complications was the only factor that prolonged the total length of stay.

Hemiarthroplasty is the preferred treatment for displaced femoral neck fractures in elderly patients. Recently, short tapered-wedge cementless stems have increasingly been used in this population. However, historic data has consistently shown higher rates of periprosthetic fracture with uncemented stems in hip fracture patients. This study aims to evaluate the rate of periprosthetic fracture requiring re-operation and all-cause mortality between cemented and uncemented femoral stem designs including more recent short tapered-wedge cementless stems in hip fracture patients.

A retrospective chart and radiographic review of patients received bipolar hemiarthroplasty for femoral neck fractures from 2010–2016. Patients biologically (age ≥ 65 years) or physiologically (American Society of Anesthesiologists (ASA) class ≥ 3) elderly were eligible. The uncemented group was subdivided into tapered-wedge stems (a broach only system) and reamed uncemented stems. The primary outcome was periprosthetic fracture requiring re-operation.

We included 657 patients in total, with 296 and 361 patients in the uncemented and cemented stem groups respectively. In the uncemented group there were 197 tapered-wedge and 99 reamed uncemented stems. There was a significantly higher rate of periprosthetic fracture requiring re-operation in the uncemented group (3.0% vs. 0.6%) (p ≤ 0.05). There were no significant differences in rates of all-cause mortality, infection or all-cause re-operation.

Compared to modern uncemented femoral stem designs, cemented stems yield lower rates of periprosthetic fracture requiring re-operation, without increasing risk of all-cause mortality. Tapered-wedge stems had similar rates of re-operation due to periprosthetic fracture as reamed uncemented stems.

The objective was to evaluate clinical and radiological outcomes of Vancouver B2 and B3 periprosthetic femoral fractures in patients older than 65 years treated at our institution from 2000 to 2014. We compared the most common methods of fixation: a modular tapered rectangular titanium stem versus a monoblock tapered stem.

A retrospective review was performed with a minimum follow-up time of 2 years. Patient mobility in the period prior to the fracture and after fracture healing and functional results was assessed according to the Harris Hip Score.

A total of 43 Vancouver B2 and B3 periprosthetic fractures fulfilled the inclusion criteria (31 type B2 and 13 type B3). The mean age was 78 years old (66–88 years). The mean follow-up time was 5 years (range 2–12 years). A Wagner stem was used in 19 patients and a modular rectangular stem was implanted in 24 patients. Although fracture union was achieved in 93% of the cases, the mean Harris Hip Score was 73 (34–87) and 41.9% of the patients did not return to their previous ambulatory levels (p = 0.0049). Dislocation was the most common complication (16.3%). We have found association (p = 0.07) between subsidence with a mean of 4.14 mm and dislocation. No difference was observed between B2 and B3 fractures or between modular and monoblock stems.

Although we reported good results of fracture healing, there were functional impairment and a high rate of complications, especially dislocation, in Vancouver B2 and B3 periprosthetic fractures in elderly patients.

The best treatment of acetabular chondral flaps during surgery for femoroacetabular impingement (FAI) is unknown. We asked if subchondral drilling improves clinical and radiographic outcome and if there are factors predicting failure.

We treated 79 patients with symptomatic FAI and acetabular chondral flaps with surgical hip dislocation between January 2000 and December 2007. Exclusion of all patients with previous hip pathology or trauma resulted in 62 patients (80 hips). The chondral flap was slightly debrided in 43 patients/51 hips (control group). In 28 patients/29 hips (study group), additional osseous drilling was performed. 4 patients (5 hips, 6%) were lost to follow-up. Mean follow-up was 9 years (5–13 years). The groups did not differ in demographic data, radiographic parameters or follow-up. Clinical outcome was assessed with the Merle d’Aubigné score, modified Harris Hip Score and University of California Los Angeles activity score and progression of osteoarthritis with the Tönnis grade.

No patient underwent conversion to total hip arthroplasty (THA) in the drilling group compared to 7 patients (8 hips, 16%) in the control group (p = 0.005); in the remaining hips, clinical scores and progression of Tönnis grade did not differ. Increased acetabular coverage, age and body mass index were univariate predictive factors for conversion to THA. No drilling was as an independent predictive factor for conversion to THA (hazard ratio 58.07, p = 0.009).

Subchondral drilling under acetabular chondral flaps during surgical treatment of FAI is an effective procedure to reduce the rate of conversion to THA.

The goal of this study was to: (1) investigate the association between labral hypertrophy and radiographic and computed tomography (CT) imaging measurements of dysplasia in a femoroacetabular impingement (FAI) cohort; (2) evaluate the association between physical examination parameters suggestive of microinstability and labral hypertrophy.

A retrospective case-control study was performed. Labral hypertrophy was defined as intraoperative labral width measuring greater >4 mm. A control cohort (NL) was matched to the cases. Physical examination parameters and preoperative radiographic and CT imaging studies were reviewed.

231 hip arthroscopies for FAI were reviewed from which 42 cases of labral hypertrophy were identified (LH). In the LH group there was significantly increased hip internal rotation at 90° hip flexion compared to normal controls (13.6° ± 1 0.7° LH vs. 9.3° ± 6.2° NL; p = 0.04). On plain radiographs, the mean lateral centre-edge angle was smaller in the LH group compared to the NL group (27.6° ± 6.00° LH vs. 31.6° ± 6.59° NL; p < 0.001) and the acetabular index was larger in the LH group compared to the NL group (6.61 ± 4.18 LH vs. 4.14 ± 6.13 NL; p = 0.04). On CT imaging coronal sagittal CEA was significantly lower in LH cases compared to NL control (31.8° ± 5.30° LH vs. 35.1° ± 7.67° NL; p = 0.01).

We found that patients with labral hypertrophy have radiographic and CT measurements consistent with subtle but not absolute dysplasia and physical examination findings suggestive of microinstability. We propose that labral hypertrophy can be a useful clinical tool for identifying FAI patients on the dysplasia spectrum.

The aim of this study was to determine the prevalence of asymptomatic radiographic findings of femoroacetabular impingement (FAI) in paediatric football players in different age groups and to investigate aetiological factors.

Paediatric male athletes between 10 and 17 years of age from 8 soccer teams were recruited. In addition to an annual control check-up, anteroposterior pelvis and frog-leg radiographs as well as the curriculum vitae of the athletes, their injuries, and real-time complaints were recorded. The alpha angle, lateral centre-edge angle, Tönnis angle, and collodiaphyseal angle were measured and morphological abnormalities were noted.

There were 214 male football players with a mean age of 13.4 ± 3.2 years included in the study. In the morphological analysis of hips, there was FAI in 30% of the athletes. In the analysis of FAI prevalence in 3 subgroups based on age (Group 1: 10–12 years [n = 25], Group 2: 13–15 years [n = 104], Group 3: 16–17 years [n = 85]), there was 0% FAI in Group 1, 19.1% in Group 2 and 60% in Group 3. In the analysis of aetiological factors, there was no significant difference between the right and left hips of players regarding alpha angles and FAI prevalence. However, the prevalence of FAI was higher in players who had been playing football for 3 years or more and who had been training for 12.5 hours/week or more.

Training for 12.5 hours or more per week in paediatric football players doubled the risk development of FAI morphology.

Little is known about the loading patterns in unilateral hip osteoarthritis (OA) and their relationship to radiographic severity and pain. We aimed to examine the loading patterns at the hips of those with unilateral symptomatic hip OA and identify associations between radiographic severity and pain with loading alterations.

61 subjects with symptomatic unilateral hip OA underwent gait analyses and evaluation for radiographic severity (Kellgren-Lawrence [KL]-grade) and pain (visual analogue scale) at bilateral hips.

Hip OA subjects had greater range of motion and higher hip flexion, adduction, internal and external rotation moments at the contralateral, asymptomatic hip compared to the ipsilateral hip (p < 0.05). Correlations were noted between increasing KL-grade and increasing asymmetry of contralateral to ipsilateral hip loading (p < 0.05). There were no relationships with pain and loading asymmetry.

Unilateral symptomatic hip OA subjects demonstrate asymmetry in loading between the hips, with relatively greater loads at the contralateral hip. These loading asymmetries were directly related to the radiographic severity of symptomatic hip OA and not with pain.

Additional research is needed to determine the role of gait asymmetries in disease progression.

Objective assessment of hip dysplasia patients’ functional hip joint status routinely involves gait analysis or isokinetic dynamometry. However, these methods have shown equivocal results and have not been employed in the same groups of patients and controls.

To assess hip flexor and abductor moments by isokinetic dynamometry in the dysplasia patient and controls, for which we previously reported smaller flexor and slightly larger abductor moments during gait in patients compared to controls.

The study was designed as a prospective cohort study (Level of Evidence II) and conducted in a biomechanics laboratory at Aarhus University, Denmark, during 2011. Participants comprised 32 dysplasia patients and 32 age and gender matched controls. Outcome measures were static peak hip flexion moment at 15, 45 and 75° hip flexion; dynamic eccentric and concentric peak hip flexion moment at 60° and 120°/second; dynamic eccentric and concentric hip abductor moment at 30° and 60°/second.

Hip dysplasia patients had smaller eccentric peak flexion moments and smaller eccentric and concentric peak abduction moments at all tested velocities.

Although dysplasia patients have weaker hip flexion and abductor muscles than controls, their abductor muscles are sufficiently strong to ensure normal function during gait. Hence, gait analysis alone might not reveal the true, subnormal hip joint status in dysplasia patients. We suggest that comprehensive assessment of hip joint function in dysplasia patients should include more strenuous activities than gait, particularly in young(er) patients who are likely to prefer a more active lifestyle.

In the revision setting, intrapelvic acetabular components provide a unique set of challenges for the treating surgeon. Retrieval is complicated by complex anatomical relationships within the pelvis and historically, surgeons have used multiple approaches to safely retrieve the cup.

We present the case of a 53-year-old female with intrapelvic migration of the acetabular components of her total hip arthroplasty. Patient was treated through a novel, single incision approach with utilisation of an anterior inferior iliac spine (AIIS) osteotomy.

An AIIS osteotomy allows for improved visualisation within the pelvis and safe retrieval through a single exposure without compromising the ability to perform definitive, revision reconstruction. At 1-year follow-up, the patient has had no complications related to infection or failure of the implants. Ambulation is performed with the aid of a cane in the community with mild, occasional pain.