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Apollo Medicine 2012 DecemberVolume 9, Number 4; pp. 297e302 Original Article

Birmingham mid-head resection arthroplasty of hip for avascularnecrosis of femoral head e A minimum follow up of 2 years

K.R. Sharatha,c, V.C. Boseb,*

aAsstTamil*CorreReceivc StudyCopyrihttp://d

ABSTRACT

Aim: To study the outcome of Birmingham mid-head resection (BMHR) arthroplasty of the hip in young and activepatients 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 operatedupon in this period and data was collected for all patients. Radiographs were obtained in all subjects pre-operativelyand compared to post-operative radiographs to determine migration of the components. Functional outcome wasassessed in all patients using the University of California, Los Angeles (UCLA) scores. Complications, if any wererecorded.

Results: None of the patients were lost to follow up. None of the components migrated. All the patients remainedactive 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 ofnormal 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 hipreplacement for young and active patients.1 Young and activepatients have always been a challenge for hip arthroplastysurgeons as the hip is subjected to increased demands andthe implants have to stay functional for a long time. Inpatients who are unsuitable for resurfacing due to poorbone quality in the femoral head, and yet conservative arthro-plasty is desirable, Birminghammid-head resection (BMHR)arthroplasty would be an alternative. Avascular necrosis(AVN) of femoral head is one such condition which affectsthe younger population. Resurfacing arthroplasty in the earlystages of AVN has fared poorly in terms of longevity.1,2

While in other patients in the late stages of AVN, femoralheads may not be suitable for resurfacing due to the presence

Prof, MS Ramiah Medical College, Bangalore, bSenior ConsultantNadu, India.sponding author. email: bose5vijay@hotmail.com

ed: 7.9.2012; Accepted: 5.10.2012; Available online 13.10.2012performed when attending a fellowship in joint replacement at Apoll

ght � 2012, Indraprastha Medical Corporation Ltd. All rights reservedx.doi.org/10.1016/j.apme.2012.10.001

of sub-chondral cysts more than 1 cm and/or gross destruc-tion. BMHR arthroplasty involves resection of poor qualitybone of femoral head proximal to the described resectionlevel for resurfacing and retains the distal part of the femoralhead, which participates in load transfer from the stem.3 Inthis paper we describe our experience with mid-head resec-tion device and present our results with a minimum followup of 2 years.

MATERIALS AND METHODS

Between Oct 2007 and Dec 2009, we collected data ontwenty consecutive patients (23 hips) who underwent

Orthopedic Surgeon, Apollo Speciality Hospital, Chennai 600035,

o Hospitals, Chennai..

Fig. 2 Ratio of base of stem diameter and neck diameter.

298 Apollo Medicine 2012 December; Vol. 9, No. 4 Sharath and Bose

BMHR arthroplasty for early stage AVN of the femoralhead. We offered mid-head resection arthroplasty to allthe patients who attended our clinic with MRI diagnosisof AVN of the femoral head with large cysts or to thosewho had collapsed femoral heads (Stage 4 modified Ficat& Arlet staging).4 Among the 23 hips, four hips that wereposted for resurfacing arthroplasty of the femoral head,we switched to perform mid-head resection arthroplastyon the table due to the small size of the femoral heads(<46 mm).5 In two other hips, we found large sub-chondralcysts with sclerotic non-viable bone. Patients who were old(>60 years) with sedentary lifestyles, and patients witha history of renal failure or renal compromise5 wereexcluded from the study. All patients in whom the femoralhead was in the early pre-collapse stage were managedconservatively, but the subset of these patients who wereseverely symptomatic with pain and stiffness underwenteither core decompression or BMHR arthroplasty.

The approval of local ethical committee was obtainedand clinical and radiological data, along with outcomescores were collected.

OPERATIVE TECHNIQUE

In the lateral position and general anesthesia the hip wasexposed through the posterior approach. Gluteus maximustendon was released routinely. Ascending branch of medialcircumflex was sacrificed and short external rotators wereincised without disturbing the joint capsule. Capsule wasthen incised close to acetabulum from 12’ O clock to 6’O clock position to preserve retinacular vessels. Lowerlimb was internally rotated up to 90� to visualize the

Fig. 1 Method used for calculation of stem shaft angle andcup inclination.

anterior capsule. Anterior capsule was then incised closeto the labrum. Circumferentially the hip joint capsule wasincised away from the femoral neck preserving the softtissue cover over the femoral neck. This neck capsuleapproach has been described previously.2 After openingthe hip by neck capsule preserving approach, initial stepwould be to determine the minimum size of femoralcomponent the femur would accommodate (Fig. 4).Accordingly the acetabulum size also determined. Butreaming of acetabulum will be done independent of femoralpreparation. McMinn jig was positioned to pin placed inlateral cortex and head preparation was carried out. Thereshould be intact head neck junction (HNJ) for resurfacingdevices. In case the proportion of defects in head is morethan 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. 3 Conical reaming using conical reamer.

Fig. 6 Implanted BMHR.Fig. 4 Measuring head size.

BMHR arthroplasty of hip for avascular necrosis of femoral head Original Article 299

Napkin ring is placed at HNJ after chamfering of headwas done (Fig. 5) and apple core reamer was used toream the head and decision of implanting BMHR wastaken. Proper positioning of ring is very important for leglength equality. Uppermost part of head was removedover the ring. Trial implantation was done at this stagefor leg length assessment.

Cone reamer for stem was used to ream the neck (Figs. 3and 7). Conical uncemented BMHR stem was then placedover reamed neck. Modular head with 12/14 taper wasthen placed over stem (Fig. 6) matching to the size ofimplanted acetabular cup.

Procedure is similar to the one described by McMinn.6

Meticulous capsule-to-capsule closure was performedwith No-2 ethibond sutures. Post-operatively drain wasnot used routinely.

All patients received three doses of prophylactic antibi-otic (1 g Cefazolin) perioperatively. Thromboprophylaxis

Fig. 5 Napkin ring.

was in the form of Enoxaparin after 8 h of surgery untildischarge. Thromboembolus deterrent (TED) stockingsand 75 mg aspirin once daily for a duration of 4 weekswas prescribed at the time of discharge.7 All the patientswere mobilized full weight bearing on the first post-opera-tive day. Supervised physiotherapy was commenced andcontinued throughout the inpatient period. No restrictionswere imposed otherwise except for the use of abductionpillow when in lateral position for 4 weeks.

Post-operatively, the patients were followed up at 6weeks, 6 months, 1-year, and then at 2-year intervals. Forthe purposes of this study pre-operative functional hipscores (UCLA hip score) were collected and repeated atthe latest follow up. The antero-posterior (AP) view ofthe pelvis was obtained at each follow up.8 For pre andpost-operative hip scores and activity scores, descriptivestatistics were calculated and statistical significanceanalyzed using an unpaired Students t-test.

Fig. 7 Conical reamer and stem.

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 0.0000012UCLA (n ¼ 10)b 3.8 7.5 0.000023a There were total 20 patients who were administered UCLA score.b Ten patients had bilateral involvement and other side hip was operatedin 8 patients (3 BHR, 2 THR, 3 BMHR), 2 patients had conservativetreatment.

UCLA after exclusion of those 10 patients.

300 Apollo Medicine 2012 December; Vol. 9, No. 4 Sharath and Bose

Radiographic analysis was performed independently bytwo observers (VCB and SKR). Points noted were lucentlines, osteolysis, spot welding, component loosening, andmigration. The inter teardrop line was used as the referencefor cup inclination (Fig. 1). The distance between theischial tuberosity and a fixed point on the lesser trochanterwas used to measure leg length and compared to the contra-lateral side. Angle between lines joining mid-diaphysealline 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 patientswere diagnosed to have idiopathic avascular necrosis, ofwhich 2 were steroid induced and one post-traumatic.Mean age of patients was 38.7 years with youngest patientbeing 19 years and oldest 56 years (Table 1). All patientswere under the care of a senior orthopedic surgeon(VCB) who performed all the procedures.

Ten patients had bilateral avascular necrosis. Out ofthese ten, three of them underwent bilateral BMHR, anotherthree underwent BHR on one side and BMHR on the oppo-site side, two of them underwent THR on one side andBMHR on the opposite side, and the remaining two patientsunderwent BMHR on one side and conservative treatmenton the opposite hip. There were no major post-operativecomplications like DVT or infection, either superficial ordeep. Two patients required blood transfusion and onepatient had transient urinary symptoms that settled withantibiotics for a period of 1 week. There was significantimprovement in UCLA scores post-operatively (Table 2).The mean inclination of the acetabular component was46.2� as measured on the latest AP pelvis radiograph andthe mean stem shaft angle was 132.8� (Table 3). Therewere no radiolucencies or evidence of osteolysis aroundthe 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 thecomponents were in varus position. Out of 23 hips,2 hips had V1 stem and the rest got VST stems. Meancombined abductionevalgus angle (we proposed in ourprevious paper) was 184.53�.

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 22:1BMI 27.79 (21.71e36.58)

DISCUSSION

Birmingham mid-head resection technique is relatively newand promising for those hips where resurfacing is notpossible yet conservative arthroplasty is desirable. Unce-mented HA coated proximal stem with porous coated, gritblasted fluted distal stem helps in good osteo-integrationand rules out the possibility of cement related looseningand augurs well with recent trends of uncemented arthro-plasty. Birmingham mid-head resection is more versatilein equalizing the limb lengths10 and valgus or neutral orien-tation of femoral components.

Although neck narrowing has been observed in 2 casesit is unlikely to be an indicator of neck fracture. Neckfracture is a phenomenon of short term failure and thatwhich is not seen for first 2 years is highly unlikely tooccur later as explained by Takamura et al.11 There isassociation of neck narrowing with valgus orientation ofnative neck shaft angle (although not statistically signifi-cant). Position of femoral stem with respect to neck iskey to survival of prosthesis. Tip of stem should nevertouch any of the cortices in both AP and lateral planeradiographs. We have measured implant tip to lateralcortex width in post-operative and immediate follow upX-rays. There is no significant movement of stem eitherdue to subsidence or varus collapse. For neck thinningwe measured width of implant (femoral componentbase) and width of neck (at implant neck) and ratio ofthe values were calculated (Fig. 2). Measurement of ratioshelps us to avoid issues of magnification, that are commonwith digital X-rays.

Ratios at immediate post-operative and latest follow uphave not changed with respect to statistically significantvalues. There was no narrowing or any evidence of stressshielding of the femoral neck.

In our study no patients had any issues with regard tometallosis or adverse local tissue reaction (ALTR). Nopatient had any local fluid or solid mass or allergic reac-tion.12 Mean acetabular cup inclination was 43.18�. Onepatient had acetabular cup inclination of 55.85�. At the

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) 0.00032Acetabular inclination 45.23 (39.01e52.45) 43.18 (37.9e50.85) 0.19

Immediate post-operative Latest follow up p-Value

Acetabular inclination 43.18 (37.9e55.85) 43.05 (37.3e55.85) 0.75Neck shaft angle 145.69 (134.2e156) 144.98 (134.8e155.87) 0.678Neck width ratio 0.248 (0.20e0.36) 0.244 (0.20e0.34) 0.777Tip to lateral cortex 32.01 (12.0e61.0) 32.23 (12.8e60.46) 0.29

BMHR arthroplasty of hip for avascular necrosis of femoral head Original Article 301

latest follow up, the patient is asymptomatic and there areno radiological evidence to suggest anything amiss withthe implants.

ROM was improved significantly in all patients, butimprovement was more in patients with more pre-operativerange. There were no radiological signs of repetitiveimpingement of neck. None of the patients had a post-oper-ative dislocation at the latest follow up. Gait was normal forall but one patient, who had had clinical shortening of 1 cmpost-operatively. He was advised shoe modification. Noother patients had any leg length discrepancy. One patientcomplained of groin pain anteriorly which was aggravatedby activity. It was treated with short term analgesics. Painintensity reduced but was not relieved completely. Theaverage UCLA score was 7.9 post-operatively whencompared to a pre-operative average score of 4.2, and thiswas highly significant (Table 2). This satisfaction is mostlikely as a result of high post-operative activity, goodabductor strength and good pain relief.

Migration of well fixed femoral component in resurfacedpatients with osteonecrosis is a known phenomenon due tocontinued process of head destruction and enlargement ofexisting small cysts in sub-chondral area. In the BMHRprocedure, we remove all the necrotic head whilepreserving the vascularity of the retained neck by the useof modified neck capsule preserving approach.13 As a resultof 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 thatthere were some cases in which hip was symptomatic andwas failing but had not yet reached revision. This isa common limitation of studies that use revision as endpoint.14 But since we are considering a small number ofpatients with short term study we could get to their symp-toms or other problems individually during their followup. 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 thereare no standard guidelines15e17 available for the same andcost was a limiting factor in most of our patients.

Overall the results suggest that reliable and durable shortterm outcomes may be expected with use of uncementedCOeCr monoblock acetabular cup with uncementedfemoral mid-head resection component. However properpatient selection and following proper surgical techniquesare 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, incomparison to conventional total hip arthroplasty for usagein young and active individuals with gross destruction offemoral 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 andstatistical analysis.

REFERENCES

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