To study the outcome of Birmingham mid-head resection (BMHR) arthroplasty of the hip in young and active patients with avascular necrosis of femoral head with gross defects.

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2. Birmingham mid-head resection arthroplasty of hip for avascular
necrosis of femoral head e A minimum follow up of 2 years
K.R. Sharatha,c
, V.C. Boseb,*
ABSTRACT
Aim: To study the outcome of Birmingham mid-head resection (BMHR) arthroplasty of the hip in young and active
patients with avascular necrosis of femoral head with gross defects.
Materials and methods: Study was conducted between Oct 2007 and Dec 2009. Twenty-three hips were operated
upon in this period and data was collected for all patients. Radiographs were obtained in all subjects pre-operatively
and compared to post-operative radiographs to determine migration of the components. Functional outcome was
assessed in all patients using the University of California, Los Angeles (UCLA) scores. Complications, if any were
recorded.
Results: None of the patients were lost to follow up. None of the components migrated. All the patients remained
active with mean UCLA score of 7.23 and there were no failures till our last review.
Conclusion: This study shows promising early results of bone preservation and restoration of the biomechanics of
normal hip in young and active patients with gross defects of the femoral head using BMHR procedure.
Copyright © 2012, Indraprastha Medical Corporation Ltd. All rights reserved.
Keywords: BMHR, AVN, Joint replacement
Modern hip resurfacing is an attractive alternative to total hip
replacement for young and active patients.1
Young and active
patients have always been a challenge for hip arthroplasty
surgeons as the hip is subjected to increased demands and
the implants have to stay functional for a long time. In
patients who are unsuitable for resurfacing due to poor
bone quality in the femoral head, and yet conservative arthro-
plasty is desirable, Birmingham mid-head resection (BMHR)
arthroplasty would be an alternative. Avascular necrosis
(AVN) of femoral head is one such condition which affects
the younger population. Resurfacing arthroplasty in the early
stages of AVN has fared poorly in terms of longevity.1,2
While in other patients in the late stages of AVN, femoral
heads may not be suitable for resurfacing due to the presence
of sub-chondral cysts more than 1 cm and/or gross destruc-
tion. BMHR arthroplasty involves resection of poor quality
bone of femoral head proximal to the described resection
level for resurfacing and retains the distal part of the femoral
head, which participates in load transfer from the stem.3
In
this paper we describe our experience with mid-head resec-
tion device and present our results with a minimum follow
up of 2 years.
MATERIALS AND METHODS
Between Oct 2007 and Dec 2009, we collected data on
twenty consecutive patients (23 hips) who underwent
a
Asst Prof, MS Ramiah Medical College, Bangalore, b
Senior Consultant Orthopedic Surgeon, Apollo Speciality Hospital, Chennai 600035,
Tamil Nadu, India.
*
Corresponding author. email: bose5vijay@hotmail.com
Received: 7.9.2012; Accepted: 5.10.2012; Available online 13.10.2012
c
Study performed when attending a fellowship in joint replacement at Apollo Hospitals, Chennai.
Copyright Ó 2012, Indraprastha Medical Corporation Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.apme.2012.10.001
Apollo Medicine 2012 December
Volume 9, Number 4; pp. 297e302
Original Article

3. BMHR arthroplasty for early stage AVN of the femoral
head. We offered mid-head resection arthroplasty to all
the patients who attended our clinic with MRI diagnosis
of AVN of the femoral head with large cysts or to those
who had collapsed femoral heads (Stage 4 modified Ficat
& Arlet staging).4
Among the 23 hips, four hips that were
posted for resurfacing arthroplasty of the femoral head,
we switched to perform mid-head resection arthroplasty
on the table due to the small size of the femoral heads
(<46 mm).5
In two other hips, we found large sub-chondral
cysts with sclerotic non-viable bone. Patients who were old
(>60 years) with sedentary lifestyles, and patients with
a history of renal failure or renal compromise5
were
excluded from the study. All patients in whom the femoral
head was in the early pre-collapse stage were managed
conservatively, but the subset of these patients who were
severely symptomatic with pain and stiffness underwent
either core decompression or BMHR arthroplasty.
The approval of local ethical committee was obtained
and clinical and radiological data, along with outcome
scores were collected.
OPERATIVE TECHNIQUE
In the lateral position and general anesthesia the hip was
exposed through the posterior approach. Gluteus maximus
tendon was released routinely. Ascending branch of medial
circumflex was sacrificed and short external rotators were
incised without disturbing the joint capsule. Capsule was
then incised close to acetabulum from 12’ O clock to 6’
O clock position to preserve retinacular vessels. Lower
limb was internally rotated up to 90
to visualize the
anterior capsule. Anterior capsule was then incised close
to the labrum. Circumferentially the hip joint capsule was
incised away from the femoral neck preserving the soft
tissue cover over the femoral neck. This neck capsule
approach has been described previously.2
After opening
the hip by neck capsule preserving approach, initial step
would be to determine the minimum size of femoral
component the femur would accommodate (Fig. 4).
Accordingly the acetabulum size also determined. But
reaming of acetabulum will be done independent of femoral
preparation. McMinn jig was positioned to pin placed in
lateral cortex and head preparation was carried out. There
should be intact head neck junction (HNJ) for resurfacing
devices. In case the proportion of defects in head is more
than intact head, BMHR will be the procedure of choice.
Since instrumentation is same for both, decision of switch-
ing to BMHR from BHR can be carried out on the table.
Fig. 1 Method used for calculation of stem shaft angle and
cup inclination.
Fig. 2 Ratio of base of stem diameter and neck diameter.
Fig. 3 Conical reaming using conical reamer.
298 Apollo Medicine 2012 December; Vol. 9, No. 4 Sharath and Bose

4. Napkin ring is placed at HNJ after chamfering of head
was done (Fig. 5) and apple core reamer was used to
ream the head and decision of implanting BMHR was
taken. Proper positioning of ring is very important for leg
length equality. Uppermost part of head was removed
over the ring. Trial implantation was done at this stage
for leg length assessment.
Cone reamer for stem was used to ream the neck (Figs. 3
and 7). Conical uncemented BMHR stem was then placed
over reamed neck. Modular head with 12/14 taper was
then placed over stem (Fig. 6) matching to the size of
implanted acetabular cup.
Procedure is similar to the one described by McMinn.6
Meticulous capsule-to-capsule closure was performed
with No-2 ethibond sutures. Post-operatively drain was
not used routinely.
All patients received three doses of prophylactic antibi-
otic (1 g Cefazolin) perioperatively. Thromboprophylaxis
was in the form of Enoxaparin after 8 h of surgery until
discharge. Thromboembolus deterrent (TED) stockings
and 75 mg aspirin once daily for a duration of 4 weeks
was prescribed at the time of discharge.7
All the patients
were mobilized full weight bearing on the first post-opera-
tive day. Supervised physiotherapy was commenced and
continued throughout the inpatient period. No restrictions
were imposed otherwise except for the use of abduction
pillow when in lateral position for 4 weeks.
Post-operatively, the patients were followed up at 6
weeks, 6 months, 1-year, and then at 2-year intervals. For
the purposes of this study pre-operative functional hip
scores (UCLA hip score) were collected and repeated at
the latest follow up. The antero-posterior (AP) view of
the pelvis was obtained at each follow up.8
For pre and
post-operative hip scores and activity scores, descriptive
statistics were calculated and statistical significance
analyzed using an unpaired Students t-test.
Fig. 5 Napkin ring.
Fig. 6 Implanted BMHR.
Fig. 7 Conical reamer and stem.
Fig. 4 Measuring head size.
BMHR arthroplasty of hip for avascular necrosis of femoral head Original Article 299

5. Radiographic analysis was performed independently by
two observers (VCB and SKR). Points noted were lucent
lines, osteolysis, spot welding, component loosening, and
migration. The inter teardrop line was used as the reference
for cup inclination (Fig. 1). The distance between the
ischial tuberosity and a fixed point on the lesser trochanter
was used to measure leg length and compared to the contra-
lateral side. Angle between lines joining mid-diaphyseal
line and mid-line of implant stem was compared post-oper-
atively and at latest follow up.
RESULTS
The mean follow up was 23.57 months. Twenty patients
were diagnosed to have idiopathic avascular necrosis, of
which 2 were steroid induced and one post-traumatic.
Mean age of patients was 38.7 years with youngest patient
being 19 years and oldest 56 years (Table 1). All patients
were under the care of a senior orthopedic surgeon
(VCB) who performed all the procedures.
Ten patients had bilateral avascular necrosis. Out of
these ten, three of them underwent bilateral BMHR, another
three underwent BHR on one side and BMHR on the oppo-
site side, two of them underwent THR on one side and
BMHR on the opposite side, and the remaining two patients
underwent BMHR on one side and conservative treatment
on the opposite hip. There were no major post-operative
complications like DVT or infection, either superficial or
deep. Two patients required blood transfusion and one
patient had transient urinary symptoms that settled with
antibiotics for a period of 1 week. There was significant
improvement in UCLA scores post-operatively (Table 2).
The mean inclination of the acetabular component was
46.2
as measured on the latest AP pelvis radiograph and
the mean stem shaft angle was 132.8
(Table 3). There
were no radiolucencies or evidence of osteolysis around
the acetabular or the femoral components. Femoral compo-
nent-femoral shaft angle was valgus in seventeen patients,
neutral in six patients compared to original.9
None of the
components were in varus position. Out of 23 hips,
2 hips had V1 stem and the rest got VST stems. Mean
combined abductionevalgus angle (we proposed in our
previous paper) was 184.53
.
DISCUSSION
Birmingham mid-head resection technique is relatively new
and promising for those hips where resurfacing is not
possible yet conservative arthroplasty is desirable. Unce-
mented HA coated proximal stem with porous coated, grit
blasted fluted distal stem helps in good osteo-integration
and rules out the possibility of cement related loosening
and augurs well with recent trends of uncemented arthro-
plasty. Birmingham mid-head resection is more versatile
in equalizing the limb lengths10
and valgus or neutral orien-
tation of femoral components.
Although neck narrowing has been observed in 2 cases
it is unlikely to be an indicator of neck fracture. Neck
fracture is a phenomenon of short term failure and that
which is not seen for first 2 years is highly unlikely to
occur later as explained by Takamura et al.11
There is
association of neck narrowing with valgus orientation of
native neck shaft angle (although not statistically signifi-
cant). Position of femoral stem with respect to neck is
key to survival of prosthesis. Tip of stem should never
touch any of the cortices in both AP and lateral plane
radiographs. We have measured implant tip to lateral
cortex width in post-operative and immediate follow up
X-rays. There is no significant movement of stem either
due to subsidence or varus collapse. For neck thinning
we measured width of implant (femoral component
base) and width of neck (at implant neck) and ratio of
the values were calculated (Fig. 2). Measurement of ratios
helps us to avoid issues of magnification, that are common
with digital X-rays.
Ratios at immediate post-operative and latest follow up
have not changed with respect to statistically significant
values. There was no narrowing or any evidence of stress
shielding of the femoral neck.
In our study no patients had any issues with regard to
metallosis or adverse local tissue reaction (ALTR). No
patient had any local fluid or solid mass or allergic reac-
tion.12
Mean acetabular cup inclination was 43.18
. One
patient had acetabular cup inclination of 55.85
. At the
Table 1 Clinical details of 20 patients (23 hips).
Age (in years) 38.78 (19e57)
Height (in cm) 164 (158e183)
Weight (in kg) 79.7 (57e99)
Male:female 22:1
BMI 27.79 (21.71e36.58)
Table 2 Details of University of California, Los Angeles score
(UCLA).
Pre-operative Post-operative p-Value
UCLA (n ¼ 20)a
4.2 7.9 0.0000012
UCLA (n ¼ 10)b
3.8 7.5 0.000023
a
There were total 20 patients who were administered UCLA score.
b
Ten patients had bilateral involvement and other side hip was operated
in 8 patients (3 BHR, 2 THR, 3 BMHR), 2 patients had conservative
treatment.
UCLA after exclusion of those 10 patients.
300 Apollo Medicine 2012 December; Vol. 9, No. 4 Sharath and Bose

6. latest follow up, the patient is asymptomatic and there are
no radiological evidence to suggest anything amiss with
the implants.
ROM was improved significantly in all patients, but
improvement was more in patients with more pre-operative
range. There were no radiological signs of repetitive
impingement of neck. None of the patients had a post-oper-
ative dislocation at the latest follow up. Gait was normal for
all but one patient, who had had clinical shortening of 1 cm
post-operatively. He was advised shoe modification. No
other patients had any leg length discrepancy. One patient
complained of groin pain anteriorly which was aggravated
by activity. It was treated with short term analgesics. Pain
intensity reduced but was not relieved completely. The
average UCLA score was 7.9 post-operatively when
compared to a pre-operative average score of 4.2, and this
was highly significant (Table 2). This satisfaction is most
likely as a result of high post-operative activity, good
abductor strength and good pain relief.
Migration of well fixed femoral component in resurfaced
patients with osteonecrosis is a known phenomenon due to
continued process of head destruction and enlargement of
existing small cysts in sub-chondral area. In the BMHR
procedure, we remove all the necrotic head while
preserving the vascularity of the retained neck by the use
of modified neck capsule preserving approach.13
As a result
of both of above said reasons, we can expect good osteo-
integration of femoral component.
The present study had some limitations. We used revi-
sion of the prosthesis as end point, but it is possible that
there were some cases in which hip was symptomatic and
was failing but had not yet reached revision. This is
a common limitation of studies that use revision as end
point.14
But since we are considering a small number of
patients with short term study we could get to their symp-
toms or other problems individually during their follow
up. We have not considered metal ion studies either pre-
operatively or post-operatively to screen our patients,
and post-operative MRI/ultrasonography to detect any
asymptomatic fluid collection or pseudotumor formation.
We could not perform these screening procedures as there
are no standard guidelines15e17
available for the same and
cost was a limiting factor in most of our patients.
Overall the results suggest that reliable and durable short
term outcomes may be expected with use of uncemented
COeCr monoblock acetabular cup with uncemented
femoral mid-head resection component. However proper
patient selection and following proper surgical techniques
are sine qua non for the initial behavior of metal compo-
nents. Further long term studies will be useful in ascertain-
ing the eventuality of mid-head resection arthroplasty, in
comparison to conventional total hip arthroplasty for usage
in young and active individuals with gross destruction of
femoral head.
CONFLICTS OF INTEREST
All authors have none to declare.
ACKNOWLEDGMENTS
Mr Jahir Abbas helped us with data collection and Dr Bis-
wajit Dutta Baruah assisted with data assimilation and
statistical analysis.
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Table 3 Details of radiological parameters (mean, range).
Pre-operative Post-operative p-Value
Neck shaft angle 137.48 (129.2e145.3) 145.69 (134.2e156) 0.00032
Acetabular inclination 45.23 (39.01e52.45) 43.18 (37.9e50.85) 0.19
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Neck width ratio 0.248 (0.20e0.36) 0.244 (0.20e0.34) 0.777
Tip to lateral cortex 32.01 (12.0e61.0) 32.23 (12.8e60.46) 0.29
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