Cartilage status in FAI patients – results from the Danish Hip Arthroscopy Registry (DHAR)
Cartilage status in FAI patients - results from the Danish Hip Arthroscopy
Registry (DHAR). SICOT J
Cartilage status in FAI patients - results from the Danish Hip Arthroscopy Registry (DHAR)
Bent Lund 1
Torsten Grønbech Nielsen 0
Martin Lind 0
0 Department of Orthopaedics, Aarhus University Hospital THG , 8000 Aarhus C , Denmark
1 Department of Orthopaedics, Horsens Regional Hospital , 8700 Horsens , Denmark
- Introduction: The femoroacetabular impingement (FAI) morphology is associated with specific cartilage lesions, which are suspected to be early stages of the osteoarthritic development, which can be the end result of FAI. The cartilage status of FAI afflicted hip joints at the time of arthroscopic management is not fully elucidated. This study from the Danish Hip Arthroscopy Registry (DHAR) will try to show data on the cartilage status from a large cohort. Data from a national registry potentially represent large amounts of population-based epidemiological information from multiple centres and surgeons. Therefore, outcome data might be more reliable for a specific surgical intervention. Methods: This study includes patients operated for symptomatic FAI from January 2012 until December 31st 2013, with a minimum of two-year follow-up and being registered in DHAR. The extent of cartilage damage at the time of surgery is reported and the Patient Related Outcome Measures (PROM) outcome data are presented. Results: Data from a total of 686 FAI procedures in 1082 patients from January 2012 until December 31st 2013 were extracted from DHAR. Cartilage injuries were found in 88% of cases, mainly on the acetabular side. Overall PROM including pain scores improved significantly from preoperative status to follow-up one and two years postoperatively. The Copenhagen Hip and Groin Outcome Score (HAGOS), Hip Sports Activity Scale (HSAS) and global hip function showed less improvements in patients with more severe acetabular cartilage injury. Discussion: The majority of patients with femoroacetabular impingement (FAI) undergoing hip arthroscopy have significant cartilage changes at the time of surgery primarily at the acetabulum and to a lesser degree at the femoral head. During FAI surgery the majority of patients have cartilage debridement performed but rarely cartilage repair. The presence of severe cartilage injury at the time of arthroscopic FAI surgery results in reduced subjective outcome and hip function.
FAI; Cartilage; HAGOS; National Registry
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Several studies have demonstrated evidence supporting the
theory that FAI is a strong risk factor for the development of
secondary osteoarthritis of the hip [
]. FAI morphology is
associated with specific cartilage lesions, which are suspected
to be early stages of the osteoarthritic development. The
cartilage status of FAI afflicted hip joints at the time of arthroscopic
management is not fully elucidated. Similarly there is still
limited knowledge on the impact of cartilage injury on
outcome after arthroscopic management of FAI. A systematic
review from 2013 by Hetaimish et al. states that although
FAI can be managed successfully by arthroscopic techniques,
the current knowledge of the clinical outcome after FAI
surgery is reported with a generally low evidence level mainly
as case studies and with a lack of consistency in outcome
reporting . Cartilage pathology in FAI is believed to be
caused by the impaction of both acetabular and femoral head
cartilage edges onto the cam and pincer deformities of the
FAI affected hip joint. The cartilage injuries in FAI are
characterized by specific changes [
]. Early cartilage changes present
as a bulging cartilage surface at the chondrolabral junction
(wave sign), further lesion development results in a full
thickness delamination and flap formation. Later changes are full
thickness defects in the affected areas [
Presently several surgical strategies exist for the
management of FAI-related cartilage lesions. These range from
debridement of bulging and loose cartilage flaps, suturing
and gluing of cartilage flaps to different repair techniques for
areas of cartilage loss [
]. The repair techniques described
B. Lund et al.: SICOT J 2017, 3, 44
are microfracture, collagen scaffold enhanced microfracture
and different chondrocyte transplantation methods [
National cohort studies have proven very successful for
large-scale investigations of clinical outcome after arthroplasty
and ligament reconstruction [
]. Data from a national
registry potentially represent large amounts of
populationbased epidemiological information from multiple centres and
surgeons. Therefore, outcome data might be more reliable
for a specific surgical intervention. Registry data are
potentially more representative for a specific surgical treatment than
case series that may contain biased data due to selection of
patients and highly dedicated surgeons.
Hip arthroscopy procedures in Denmark have been
registered in the Danish Hip Arthroscopy Registry (DHAR)
since the beginning of 2012. This registry is a voluntary
clinical registry for patients and surgeons, and all of the centres
performing hip arthroscopic procedures in Denmark do report
to the registry [
]. One of the main indications in the registry
for hip arthroscopic surgery is currently femoroacetabular
impingement (FAI). The DHAR contains data on cartilage
and labral pathology, which enables investigations on both
the spectrum of cartilage pathology in FAI patients and the
impact of cartilage status on the clinical outcome of
arthroscopic FAI management.
The purpose of the present study is to present the
intraarticular cartilage pathology in FAI patients and the management
strategies to these cartilage lesions based on data from a
national cohort. Also we shall investigate the impact of cartilage
status on the clinical outcome of arthroscopic FAI management.
The Danish Hip Arthroscopy Registry (DHAR) was
initiated in 2012. Surgeons as well as patients report data
online in an ongoing prospective data registration. For this
study we extracted pre- and perioperative data including
PROMs from DHAR between January 2012 and December
31st 2015. The postoperative patient reported data for this
study were extracted at one and two-year follow-up. The
registry is approved by the Danish Health Authorities, J.nr.
The patient submits the preoperative subjective scores at
registration consisting of various PROM and pain levels.
At one, two and five years postoperatively the patient will be
notified to submit their PROM scores at follow-up. After
surgery, the surgeon reports data from clinical examination,
radiological characteristics and the perioperative data.
Patients in the present study
This study includes patients operated for symptomatic FAI
from January 2012 until December 31st 2013, with a minimum
of two-year follow-up. DHAR uses the three definitions of FAI
types as described by Leunig et al. [
]: cam type, a developed
asphericity of the femoral head and widening of the femoral
neck, pincer type, a developed global or focal overcoverage
on the acetabular side and mixed type, a combination of cam
and pincer. We excluded data from patients without cartilage
data registration, patients who were diagnosed with other
diseases than FAI, previous surgery in the related hip or
incomplete data registrations, patients with hip dysplasia defined as
centre-edge (CE) angle of less than 25 and patients with
revision hip arthroscopy.
Surgical findings and procedures
The operative data reported are the surgical procedure
times including traction times, labral tears, cartilage injury
assessment and surgical technique characteristics such as
anchor usage, depth of rim trimming and cam resections.
The definition of acetabular cartilage injury type used in
DHAR was initially classified by Beck et al. [
], and was later
modified and validated by Konan et al. [
]. We have chosen to
use the classification originally described by Beck, which
is based on the Outerbridge classification. For femoral cartilage
injuries the International Cartilage Repair Society
(ICRS)scale is used which is purely based on the injury depth [
Patient outcome measurements
All PROMs used in DHAR are validated self-assessment
scores and evaluated as suitable for patients undergoing hip
arthroscopy. The used PROM questionnaires are the
Copenhagen Hip and Groin Outcome Score (HAGOS), the EQ-5D
and the Hip Sports Activity Scale (HSAS). The pain score used
is the numeric rating scale (NRS). The HAGOS consists of six
subscales assessing symptoms, pain, function in daily living,
function in sport and recreation, participation in physical
activities and hip and/or groin-related quality of life, each scored
]. HAGOS is a questionnaire (37 questions
in total) aimed for young to middle-aged adults undergoing
nonsurgical treatment or hip arthroscopy, but also patients
presenting with groin pain. The EQ-5D is used as a generic
health-related quality of life instrument, which is translated
and validated into many languages . The HSAS is
recommended as a reliable and valid activity measurement useful for
patients with femoroacetabular impingement [
]. Pain levels
are measured using the NRS pain scores at rest and after
15 min of walking. A global hip function score using visual
analogue scoring (VAS) from 0 to 100 was used, with 100
points being optimal hip function.
The Student t-test was used to analyse the differences
between the preoperative and postoperative PROM values.
P-values below 0.05 were considered statistically significant.
Subgroup analysis was made between patients with acetabular
cartilage injury Beck grade 0–2 and grade 3–4 regarding
PROM values using Student’s t-test for comparisons of PROM
Data from a total of 686 FAI procedures in 1082 patients
from January 2012 until December 31st 2013 were extracted
from DHAR. We excluded 396 procedures due to our
exclusion criteria. Forty-seven patients had bilateral procedures
performed. Forty-eight percent of the patients were female
and 52% male. The average age at the time of surgery was
38.5 years (range, 12–76 years). The majority of the patients
were characterized as mixed type FAI (87.3%). Isolated pincer
type morphology consisted of only 4.9% whereas 7.8% were
characterized as isolated cam type morphology.
The completeness of PROM registrations preoperatively
was 58% and the follow-up completeness at one and two years
was 55% and 52%, respectively. There is an ongoing study that
is looking at data completeness comparing data from DHAR to
the National Registry for Hospital Procedures.
Cartilage injury findings and surgical procedures
Cartilage injuries were found in 88% of cases and the
degree of injury for both acetabulum and femoral head is
shown in Table 1. Normal cartilage was only found in 1.5%
and 24% of the acetabular and femoral head joint surfaces,
respectively. More severe cartilage injury of Beck or ICRS
grade 3–4 was found in 44 and 7% of the acetabular and
femoral head joint surfaces, respectively. Surgery due to
cartilage injury was reported in 523 procedures (76%), with the
most commonly performed surgical intervention being
debridement with shaver or radiofrequency ablation technique.
(Table 2) Cartilage repair procedure in the form of
microfracture was only performed in 7% of cases. Cartilage flap
re-attachment was performed in less than 1% of cases.
Patient related outcome measures (PROM)
Overall PROM including pain scores improved
significantly from preoperative status to follow-up one and two years
postoperatively (Tables 3 and 4). We did not find any
significant improvement in these parameters between one and
two-year follow-up, except the NRS pain score for walking
(p = 0.002). HAGOS demonstrated significant improvements
in all subscales between the preoperative and the postoperative
scores at one-year follow-up.
The impact of having a significant acetabular cartilage
injury of Beck grade 3–4 is presented in Tables 3 and 4. We
found significantly less improvement of the following PROM
parameters when more severe acetabular cartilage injury was
present: HAGOS, HSAS and global hip function.
Key findings in the present study are that patients with
symptomatic FAI in a large national cohort have significant
cartilage changes at the time of surgery, mainly on the
acetabular side. Data from the DHAR shows that 88% of the patients
have cartilage changes and 97% of these were located at the
acetabular side. Seventy-seven percent of patients undergo
some kind of cartilage procedure during the surgical FAI
We also found that patients undergoing FAI surgery do
benefit from hip arthroscopic procedures involving labral
reinsertion, cartilage surgery and removal of cam and pincer bone
deformities within a 2-year follow-up. We also found that
patients with cartilage injury grade 3 to 4 have inferior results
than those with no or minor cartilage injury.
A systematic review by Nwachukwu et al. compared open
vs. arthroscopic FAI surgery and demonstrated excellent and
comparable hip survival rates at medium to long-term
follow-up. Hip arthroscopy showed a statistically significant
improvement in general health-related quality of life, when
compared to open procedures [
]. In the study with THA as
an outcome endpoint, there was an overall survival rate of
93% for open and 90.5% for arthroscopic procedures. A recent
retrospective population-based analysis (n = 7351) by Schairer
et al. showed an overall conversion rate of 12.4% within two
*Significant difference between grade 0–2 and grade 3–4, p < 0.05.
*Significant difference between grade 0–2 and grade 3–4,
p < 0.05.
years of hip arthroscopic surgery [
]. The lowest rate of
conversion was found in the age group younger than 40 years,
at 3%. The highest risk of conversion was seen in the age
group 60 to 69 years, at 35%.
A systematic review by Weber et al. described a rate of
reoperations after hip arthroscopy at 6.3% in a cohort
consisting of more than 6000 from 92 studies [
]. The majority of
these reoperations were, respectively, revision hip arthroscopy
in 1.9% and conversion to THA in 2.9% of the patients.
In a recently published study by Malviya et al. of more
than 6000 hip arthroscopies registered between 2005 and
2013 in the British National Health Service, a revision hip
arthroscopy rate of 4.5% was found [
]. Their conversion rate
to THR was 10.6%. In the present study, revision hip
arthroscopy was performed in 7.3% of cases and conversion to
THA was reported in 1.6% of the cases.
We found that a large proportion (88%) of this FAI cohort
had chondral injuries at the time of surgery. The most common
site of cartilage injury was in the acetabulum and to a minor
degree on the femoral head. Although many of these injuries
were described as full thickness cartilage damage, a repair
procedure was not frequently performed. In the DHAR,
debridement and radiofrequency ablation of cartilage injuries
were the most common procedures compromising more than
91% of all cartilage procedures.
In a large cross-sectional study of a North American FAI
cohort, the most common surgical technique during FAI
surgery was femoral head-neck osteochondroplasty in 91.6% of
the 1130 procedures. However, CAM deformity resection
was not considered a cartilage procedure in the DHAR.
The percentage of acetabular microfracture interventions in
this study was similar to the reported number in DHAR,
respectively, 5.6% and 5.4% [
Several cartilage repair strategies have been suggested
for management of the cartilage lesion found during hip
arthroscopy in FAI patients. Early changes can be managed
by the debridement of bulging and loose cartilage flaps. More
advanced methods are suturing and gluing of cartilage flaps to
different repair techniques for areas of cartilage loss [
The repair techniques described are microfracture, collagen
scaffold enhanced microfracture and different chondrocyte
transplantation methods [
13, 30, 31
]. Microfracture as
described by Steadman et al. [
] is a readily available
cartilage repair technique for hip arthroscopy. The efficacy for
hip cartilage repair has still not been investigated. But
experience from the knee has shown that microfracture can form
fibrocartilage that can result in symptom relief in 70% of
]. One single case series of 24 FAI patients with
microfracture treatment of cartilage lesions and second-look
arthroscopic evaluation of healing found excellent filling in
95% patients. Histologic evaluation of repair tissue from two
patients demonstrated fibrocartilage tissue characteristics [
Microfracture repair can be enhanced with the application
of a collagen scaffold on top of the defect after microfracture
using the so-called autologous matrix-induced chondrogenesis
(AMIC) technique. This technique was compared with
chondrocyte transplantation by Mancini and Fontana describing
good outcomes long-term with both techniques resulting in
38–39 point improvements in modified Harris hip score
without any difference between techniques [
One major problem for investigations of the impact of
cartilage procedures in FAI surgical management is that the
cartilage procedure is secondary to procedures done to remove
the FAI pathology such as removal of cam and pincer
deformities and labral repairs. A recent systematic review on cartilage
injury management by Marquez-Lara et al states that only level
IV and V studies are present and that there is a need for good
level I studies [
The present study and studies previously mentioned show
consistently improved clinical outcomes of hip arthroscopy
in the treatment of FAI and the concurrent labral damage,
especially regarding patient’s quality of life and pain-related
outcome measures. However, the impact of cartilage
debridement and repair is poorly investigated and there is a major
challenge scientifically since the cartilage procedures are
secondary to the FAI procedures. There is a need for good level
I studies comparing different surgical treatment strategies of
FAI with and without cartilage management.
There are limitations in the present study with potential
data quality issues due to the potential diversity in
interpretation of the intraarticular pathology findings done by the
individual surgeons and due to completeness of data in the
Danish Hip Arthroscopy Registry. All data input is voluntary,
both for surgeons and patients. We know from the Danish
National ACL Registry that patient inputs are as low as 35%
but more than 85% from surgeons [
]. The hip arthroscopy
procedure is regulated by the Danish Board of Health and is
therefore limited to the 11 centres with permission to perform
the procedure. The actual number of hip arthroscopic
procedures during this time period in Denmark is not known, but
is being studied in an ongoing validation study. Further studies
based on central healthcare registries are needed to document
the degree of completeness for surgical data. Finally, DHAR
does not include data from patients undergoing nonsurgical
treatments of FAI, which would be of interest for outcome
studies. However, the DHAR utilizes prospective data
collection without potential bias from future study purposes
such as the present study. The high data volume and the
diversity of clinics and surgeons potentially provide data that
to a high degree reflects the true pathology status and outcome
profile of FAI patients.
The majority of patients with femoroacetabular
impingement undergoing hip arthroscopy have significant cartilage
changes at the time of surgery primarily at the acetabulum
and to a lesser degree at the femoral head. During FAI surgery
the majority of patients have cartilage debridement performed
but rarely cartilage repair. The presence of severe cartilage
injury at the time of arthroscopic FAI surgery results in
reduced subjective outcome and hip function.
Conflict of interest
The authors declare no conflict of interest in relation with
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