SYMPOSIUM: PAPERS PRESENTED AT THE HIP SOCIETY MEETINGS 2009
Osseous Remodeling After Femoral Head-neck Junction
Nader A. Nassif MD, Murat Pekmezci MD,
Gail Pashos BS, Perry L. Schoenecker MD,
John C. Clohisy MD
Published online: 18 September 2009
? The Association of Bone and Joint Surgeons1 2009
is commonly used to treat femoroacetabular impingement,
yet remodeling of the osteochondroplasty site is not well
described. We therefore describe bony remodeling at the
osteochondroplasty site and analyze clinical outcomes and
complications associated with femoral osteochondroplasty.
We retrospectively reviewed 135 patients (150 hips) who
underwent femoral head-neck osteochondroplasty com-
bined with hip arthroscopy, surgical hip dislocation,
periacetabular osteotomy, or proximal femoral osteotomy.
The minimum clinical followup was 10 months (mean,
22.3 months; range, 10–65 months). We assessed the fem-
oral-head neck offset, head-neck offset ratio, alpha angle,
and cortical remodeling. We used the Harris hip score to
determine hip function. We observed an increase in the
head-neck offset, offset ratio, and decrease in the alpha
angle postoperatively and at latest followup. Ninety-eight of
113 (87%) hips had partial or complete recorticalization at
the osteochondroplasty site. The mean Harris hip score
Femoral head-neck junctionosteochondroplasty
hip. There were no femoral neck fractures. The deformity
correction achieved with femoral head-neck osteochon-
droplasty is maintained and recorticalization occurs in the
majority of cases during the first two years.
Level of Evidence: Level IV, therapeutic study. See
Guidelines for Authors for a complete description of levels
Femoroacetabular impingement (FAI) is a recognized
cause of hip dysfunction in the young adult hip and may
result in hip osteoarthritis [2, 19]. Ganz et al. demonstrated
abnormal anatomy results in excessive contact pressures
and microtrauma leading to articular cartilage damage
[2, 19, 24, 38]. Femoroacetabular impingement lesions can
be either femoral-sided (cam impingement) resulting from
a reduced head-neck offset or an aspheric femoral head
[19, 24] or acetabular-sided (pincer impingement) in which
there is excessive acetabular coverage of the femoral head
[19, 25, 37]. Combined femoral and acetabular-sided
lesions are also common [2, 16].
Since recognition of FAI has become more common-
place, efforts have focused on improved methods of
diagnosis and treatment. The best methods of surgical
treatment, however, remain controversial and continue to
be refined. Recontouring of the femoral head-neck junction
to increase the offset is a fundamental aspect of surgical
management for cam-type impingement , whereas ace-
tabular overcoverage is addressed with trimming of the
acetabular rim and infrequently acetabular reorientation
[15, 16, 26]. Several operations have been described to
address the femoral-sided pathology. Ganz et al. described
One or more of the authors have received funding from Award
Number UL1RR024992 from the National Center for Research
Resources (JCC) and the Curing Hip Disease Fund (JCC).
The content is solely the responsibility of the authors and does not
necessarily represent the official views of the National Center for
Research Resources or the National Institutes of Health.
The Institutional Review Board has approved the human protocol for
this investigation, that all investigations were conducted in
conformity with ethical principles of research, and informed consent
N. A. Nassif, M. Pekmezci, G. Pashos, P. L. Schoenecker,
J. C. Clohisy (&)
Department of Orthopaedic Surgery, Washington University
School of Medicine, One Barnes-Jewish Hospital Plaza,
Suite 11300 West Pavilion, St Louis, MO 63110, USA
e-mail: firstname.lastname@example.org; email@example.com
Clin Orthop Relat Res (2010) 468:511–518
a safe and effective surgical hip dislocation that minimizes
the danger of vascular insult to the femoral head, which
allows direct access to the femoral head and neck for
performing the osteochondroplasty . Several others
have also described limited open [11, 27] and entirely
arthroscopic methods [23, 26, 35] for addressing femoral
and/or acetabular lesions. There is a growing body of
evidence that demonstrates improved clinical outcomes
after treatment of FAI [1, 7, 20]. Beaule et al. showed
improvement in the UCLA and WOMAC 3 years after
surgical dislocation and osteochondroplasty , whereas
Byrd et al. reported substantial clinical improvement in the
Harris hip score after arthroscopic osteochondroplasty of
the head-neck junction . These studies thus far suggest a
minimal complication rate with FAI surgery. These studies,
however, provide limited data regarding complications
after recontouring of the femoral head-neck junction and
do not describe bony remodeling of the osteochondroplasty
site [7, 22].
The primary focus of our study was therefore to (1)
describe radiographic bony remodeling after osteochon-
droplasty of the femoral head-neck junction; (2) report
clinical outcomes as they relate to bony remodeling, spe-
cifically recorticalization and change in the alpha angle; (3)
describe the complications and reoperations after osteo-
chondroplasties of the femoral head-neck junction.
Patients and Methods
We retrospectively reviewed 163 patients (178 hips) who
underwent femoral head-neck osteochondroplasty either
exclusively or in association with other procedures from
October 2004 to December 2006 (Fig. 1). The average age
of the included patients at the time of surgery was
32.7 years(range, 15–56 years).Minimum clinical
followup was 10 months (mean, 22.3 months; range, 10–
65 months). Nineteen hips (10.6%) were lost to followup
before 1 year. Four hips (2.2%) were converted to a total
hip or resurfacing arthroplasty in less than 12 months. Two
patients (1.1%) were unable to participate in the study
owing to other medical issues. Three hips (1.6%) with
major proximal femoral head deformity treated with
proximal femoral osteotomies (PFO) and head-neck os-
teochondroplasty were later excluded from the study as a
result of the severity of their deformity. Therefore, we
reviewed 135 patients (150 hips) (Table 1). One hundred
five patients (113 hips) had radiographic and clinical data;
30 additional patients (37 hips) had inadequate radio-
graphic data but full clinical followup. The minimum
radiographic followup was 8 months (mean 20 months;
range, 8–54 months). We obtained prior Institutional
Review Board approval.
Fig. 1 Flow
the included and excluded patients from
the initial group of patients reviewed.
HRA = hip resurfacing arthroplasty.
Table 1. Patient demographics
Patients with radiographic and clinical data (hips) 105 (113)
Patients with clinical followup (hips)30 (37)
Males (%) 70 (51.4%)
Females (%) 65 (48.6%)
Mean age at the time of surgery (years; range)32.7 (15.2–55.5)
ProceduresNumber of hips (%)
Osteochondroplasty (limited open) 90 (60%)
PAO with limited open OCP 40 (26.6%)
Surgical dislocations17 (11.4%)
PAO = periacetabular
PFO = proximal femoral osteotomy.
osteotomy; OCP = osteochondroplasty;
512 Nassif et al.Clinical Orthopaedics and Related Research1
All surgery was performed by one surgeon (JCC).
Ninety hips with isolated FAI were treated with hip
arthroscopy and limited open osteochondroplasty of the
femoral head-neck junction for a cam-type lesion. Forty
hips had a periacetabular osteotomy (PAO) for symptom-
atic acetabular dysplasia with an osteochondroplasty to
prevent secondary impingement [12, 29]. Seventeen hips
underwent surgical hip dislocation to address combined
cam and pincer-type deformity, major pincer abnormali-
ties, or severe femoral head deformities. Three additional
hips with acetabular dysplasia and severe proximal femoral
deformities underwent PAO as well a PFO with reshaping
of the femoral head-neck junction. We performed hip
arthroscopy using standard anterior, anterolateral, and
posterolateral portals [5, 6, 11, 35]. After diagnostic
arthroscopy and de ´bridement of the labrum as necessary,
limited anterior arthrotomy and osteochondroplasty were
performed through a standard anterior approach to the hip.
We performed periacetabular osteotomies as described by
Ganz et al. [8, 9, 18, 28]. After the osteotomy, anterior
arthrotomy and recontouring of the femoral head-neck
junction was carried out to reduce the risk of secondary
impingement. Surgical hip dislocations were performed as
described by Ganz et al. . After the capsule was
opened, the hip was dislocated and examined and the
femoral head-neck offset restored. For all procedures, la-
bral tears were de ´brided and repaired or resected as
necessary. Forty-eight patients had acetabular cartilage
defects for which we performed chondroplasty. Five
patients had microfracture of their acetabular cartilage
defect. Twelve patients had additional acetabular rim
trimming. Intraoperative examination of the range of
motion was performed routinely to ensure adequate
impingement-free range of motion.
Postoperative rehabilitation required patients to be toe-
touch weightbearing for a 6-week period. During that time,
physical therapy focused on gentle range of motion and
isometric exercises. After the 6-week period, patients
progressed to weightbearing as tolerated with increasing
stretching and strengthening. Patients were allowed to
return to full sports activity at 4 months as tolerated.
Radiographic data were available for 105 patients (113
hips). The osteochondroplasty site was analyzed on the
frog lateral radiographs. Ninety-two patients (100 hips) had
preoperative frog lateral radiographs. One hundred five
hips had postoperative radiographs and 109 hips followup
radiographs. Postoperative films were obtained on the first
followup visit rather than immediately after the procedure.
All radiographic variables were measured serially by one
observer (NAN) according to our previously published
techniques [10, 13, 32]. All measurements were performed
using the EVMS Advanced Visualization Software, which
has a measurement precision to the one-hundredth decimal
place (Emageon Inc, Birmingham, AL).
The head-neck offset (HNO) was measured based on the
method previously described by Eijer et al.  on the frog
leg lateral radiograph (Fig. 2). Initially, a line was drawn
so it was parallel and bisected the femoral neck irrespective
of its location on the femoral head. A second line parallel
to the first was drawn tangential to the anterolateral neck on
the frog leg view. A third line, parallel to the first and
second lines, was drawn tangential to the femoral head.
The HNO was determined by measuring the perpendicular
distance between the second and third lines. Postopera-
tively, as a result of the reshaping of the head-neck
junction, the second line was drawn tangential to the
proximal portion of the femoral neck; the third line was
drawn tangential to the most anterolateral aspect of the
femoral head as indicated by a circle template to ensure the
measurement was consistent with the preoperative femoral
head shape. A normal HNO is greater than 9 mm . The
HNO in the preoperative and followup radiographs was
normalized to the femoral head diameter in postoperative
films, which allows for more direct comparisons between
HNO between time points. The head-neck offset ratio
(HNOR) was also calculated to account for error
Fig. 2A–B (A) The head-neck
offset (HNO) was measured in a
preoperative measurement on a
frog leg lateral view. Line 1 is
drawn to bisect the femoral neck.
Parallel lines are draw tangential
to the femoral neck (Line 2) and
the femoral neck (Line 3). The
HNO is the measurement of the
distance between Lines 2 and 3.
(B) An example demonstrates the
measurement of the same patient
after the osteochondroplasty. The
circle template allows for consis-
tent measurement across time
Volume 468, Number 2, February 2010Osseous Remodeling After Osteochondroplasty 513
introduced by magnification differences across time points.
The HNO was divided by the head diameter measured at
every time point (preoperatively, immediately postopera-
tively, and at latest followup). The HNO measurement
reportedly has a high intraobserver and a moderate inter-
observer reliability .
We measured the alpha angle as previously described by
Notzli et al.  at every time point (Fig. 3). A line was
drawn through the longitudinal axis of the femoral neck. A
circular template was drawn to match the diameter of the
femoral head. A line was drawn from the center of the head
through the point where the femoral head deviates from the
circular template. After the osteochondroplasty, the alpha
angle was determined by the point where the femoral head
intersected the circular template. Ideally, this fell at the
intersection of the resected area and femoral neck. The
alpha angle in normal hips is approximately 42?. Mea-
surement of the alpha angle reportedly has high inter- and
intraobserver reliability .
The degree of recorticalization at the osteochondro-
plasty site was also evaluated (Fig. 4). If no evidence of
recorticalization was present when comparing immediate
postoperative films and the latest followup films, it was
graded as ‘‘none.’’ If evidence of sclerosis of the bone
margin was observed but was incomplete, it was graded as
‘‘partial.’’ If there was a continuous cortical line between
the femoral head and head-neck junction, the sample was
graded as ‘‘complete.’’ The degree of heterotopic ossifi-
cation was determined as described by Brooker et al. .
Patients were evaluated at 6 weeks for their first post-
operative followup, then at 12-week, 6-month, 1-year, and
2-year intervals. We obtained Harris hip scores  pre-
operatively and at annual followups. All patients included
had a preoperative Harris hip score and all had an annual
followup hip score. Patients who developed surgical site
infections, fractures, avascular necrosis, or any repeat
surgery were noted.
Longitudinal analyses for HNO, HNOR, and alpha angle
that were measured at more than two time points were
carried out using mixed model repeated measures analyses
of variance with available data from each participant. As a
result of heterogeneity of variance and lack of normality,
Fig. 3A–B (A) The alpha angle
is measured by applying a circular
template to match the diameter of
the femur. A line is drawn along
the longitudinal axis of the fem-
oral neck. A second line is drawn
from the center of the circular
template to the point where the
femoral head deviates from the
circular template. The angle sub-
tended by these lines forms the
alpha angle. (B) Example of
improved alpha angle after rec-
ontouring of the femoral head-
neck junction is shown.
Fig. 4A–C The recorticalization
of the femoral head-neck junction
was assessed by comparing post-
operative and followup films.
They were labeled (A) ‘‘none’’ if
no sclerotic margin was noted at
the resection site and (B) ‘‘par-
tial’’ if sclerosis was present but
was incomplete. (C) If there was
a continuous cortical line between
the femoral head and the head-
neck junction, the sample was
graded as ‘‘complete.’’ The arrow
indicates the location of bone
514 Nassif et al. Clinical Orthopaedics and Related Research1
data were rank-transformed before analysis. The Kruskal-
Wallis test was used to compare the three recorticalization
groups. A paired t-test was used to compare Harris hip
preoperative scores with followup scores. A Spearman
correlation was performed between recorticalization and
Harris hip score as well as alpha angle and Harris hip score.
The data analysis was generated using SAS software
(Version 9.1.3, SAS Institute Inc, Cary, NC).
We observed improvement in all radiographic femoral
based impingement parameters at short-term followup
(Fig. 5). HNO increased (p\0.0001) from 3.7 ± 4.0 mm
preoperatively to 9.6 ± 2.4 mm postoperatively and
increased (p = 0.008) further to 10.3 ± 2.8 mm at latest
followup. The HNOR increased (p\0.0001) from 0.08 ±
0.07 to 0.17 ± 0.04 postoperatively and increased
(p = 0.0009) to 0.19 ± 0.04 at latest followup. The alpha
angle decreased (p\0.0001) from 60? ± 17? to 42? ± 6?
and continued to improve (p = 0.02) to 40? ± 7? in fol-
lowup. At last followup, we observed partial corticalization
in 88 of the 113 hips for which data were available;
complete recorticalization occurred in 10 hips and 15 hips
had no recorticalization. We observed no difference
(p = 0.14) in followup times between those who showed
complete recorticalization (mean 16.58) and those who
showed no recorticalization (mean 18.62).
Overall, the Harris hip score improved from a mean of
64 ± 14 preoperatively to a mean of 85 ± 16 at last fol-
lowup. Six hips (4%) that underwent additional surgery
were excluded from this analysis and are discussed
subsequently. For patients who had radiographic and
clinical data, there was no correlation (p = 0.34) noted
between Harris hip scores and recorticalization (Fig. 6).
p = 0.37) between improvement in Harris hip scores and
postoperative alpha angles. Few major complications were
found in this case series. One patient with Grade II het-
erotopic ossification after a PAO had continued pain for
which we performed surgical excision with good relief.
There were no incidents of deep surgical site infection,
femoral neck fractures, or avascular necrosis of the femoral
head observed over the duration of this study. Five patients
underwent revision surgery for persistent hip pain; in two
of these, we presumed the cause of the pain was persistent
impingement. The first was a 39-year-old man with a his-
tory of FAI who continued to have intermittent hip pain
after his initial hip arthroscopy. He underwent repeat hip
arthroscopy and osteochondroplasty 5 years after his initial
procedure and had complete resolution of pain. The second
patient was a 22-year-old woman with FAI and coxa valga
there wasno correlation(q = ?0.09,
Fig. 5 There was a decrease of the
alpha angle and increase of the head-
neck offset (HNO) and head-neck offset
ratio (HNO ratio).
Fig. 6 We observed no correlation (p = 0.34) between the Harris hip
score and degree of recorticalization.
Volume 468, Number 2, February 2010Osseous Remodeling After Osteochondroplasty 515
who had a varus-producing PFO 6 months after her initial
hip arthroscopy and osteochondroplasty. The PFO was
performed to address excessive anterolateral instability of
the femoral head. We believe instability was a component
of her initial problem, not secondary to the osteochon-
droplasty. One patient had repeat hip arthroscopy for
adhesiolysis of intracapsular scarring. Two patients had
total hip and hip resurfacing at 3 and 4 years, respectively,
for progressive secondary osteoarthritis.
Osteochondroplasty of the femoral head-neck junction is a
common component of hip impingement surgery, yet there
is minimal literature describing the bony remodeling,
clinical consequences, and specific complications associ-
ated with this technique. This study aims to (1) elucidate
bony remodeling after osteochondroplasty of the femoral
head-neck junction; (2) assess the clinical outcomes as it
correlates to evidence of radiographic healing; and (3)
report complications and reoperations after osteochon-
droplasty of the femoral head-neck junction.
This study does have several limitations. First, the het-
erogeneity of the abnormalities and the procedures
performed are confounding variables. Our cohort included
patients with a variety of structural abnormalities. This
may contribute to the large variability in the HNO seen
preoperatively. This heterogeneity, however, does allow
for the generalizability of the results in regard to remod-
eling of head-neck osteochondroplasty because this study
specifically focused on the osteochondroplasty site in
radiographic evaluation. Second, we lost 19 patients (11%)
to followup despite attempts to contact these patients. The
large cohort examined, however, provides adequate data to
support our observations with respect to bony remodeling,
but a longer followup time would be needed to assess the
continued remodeling we observe. Third, because our main
focus was the radiographic evaluation of the osteochon-
droplasty site, acetabular-sided abnormalities, although
commonly addressed during surgery, were not specifically
examined in the setting of healing of the osteochondro-
plasty site. Fourth, the radiographic assessment of recorti-
calization was assessed by only one trained observer. There
are no intraobserver or interobserver reliability data
available for determining the recorticalization of the
chondroplasty site. Slight variations in the xray projection
may also influence the ability to assess recorticalization.
This error is minimized by obtaining our radiographs by
specialized musculoskeletal radiology technicians using
standard techniques and projections.
Our primary objective was to assess the remodeling of
the osteochondroplastysite.The data suggestwe
consistently achieved surgical correction of the head-neck
junction as determined by the HNO and alpha angle. We
also demonstrated partial or complete recorticalization in
87% of the resection sites. Although to our knowledge, no
study has examined recorticalization of the femoral head-
neck junction, one recent study by Neumann et al. exam-
ined the alpha angle correction in a cohort of 45 patients
followed for 2 years . Their study demonstrated a mean
correction to 43?, which was maintained over the 2-year
followup period. Our study demonstrated similar correction
of the alpha angle to an average of 42?. One unexpected
result in our larger cohort of patients, however, was the
continued improvement of the HNO and alpha angle that
was noted at final followup when compared with postop-
erative radiographs. We speculate there will be continued
remodeling and resorption at the osteochondroplasty site
that is ongoing up to 2 years postoperatively. Character-
izing and understanding the mechanism of that remodeling
would merit further investigation.
Several groups have previously demonstrated improved
functional outcomes after treatment of FAI. Patients in
these series were treated with surgical dislocations [1, 3,
15, 16, 33], hip arthroscopy, and combined limited open
osteochondroplasty [11, 27] or all arthroscopic osteo-
chondroplasty [7, 23, 34, 36]. Our data present similar
improvements in hip function scores compared with these
previous reports. The heterogeneity of the groups, how-
ever, does not allow for direct comparisons between this
study and others before it. Additionally, our investigation
failed to show any correlation between radiographic cor-
rection of FAI (ie, alpha angle) and recorticalization with
the Harris hip score. Therefore, the correlation of the
deformity with clinical results has not been firmly estab-
lished in the literature.
We encountered rare (0.7%) major complications and
reoperation rates (3%) were similar to those previously
published. A large case series performed by Larson
investigated outcomes after arthroscopic management of
FAI . In his study of 100 hips, one patient had a
symptomatic heterotopic ossification and 3% underwent
THA. There has been only one recent report in the litera-
ture of femoral neck fracture after osteochondroplasty of
the femoral head neck junction . In a recent review
published by Ilizaliturri et al. , his group reported an
overall complication rate less than 1.5%. They also report
inadequate reshaping is the overwhelming reason for
revision arthroscopy for FAI.
Our study of osseous remodeling of the head-neck
junction after osteochondroplasty demonstrated consistent
correction of cam-type impingement lesions as evaluated
by the HNO, offset ratio, and alpha angle. This correction
was maintained over a mean radiographic followup of
20.1 months. At latest followup, there was continued
516Nassif et al. Clinical Orthopaedics and Related Research1
improvement in the HNO, offset ratio, and alpha angle,
which suggests continued bony remodeling and resorption
may be occurring up to 2 years postoperatively. Bony
recontouring and remodeling does not show evidence of
regrowth and appears to involve recorticalization of the
resected margins in most cases. There was a relatively low
complication rate and minimal reoperation rate for
impingement. Future investigations will focus on deter-
mining optimal parameters for the osteochondroplasty site,
including depth and shape. Additionally, longer-term fol-
lowup will help determine potential long-term hazards of
femoral head-neck osteochondroplasty, which theoretically
could include femoral neck fractures that may develop with
age if complete corticalization is not achieved.
analysis of the data.
We thank Karen Steger May for her statistical
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