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Introduction

Although it is desirable to avoid hip replacements in young patients as much as possible, when it comes to choosing a conservative technique the physical and social constraints and the risks incurred by the patient need to be taken into account. The relatively recent progress made in the durability of arthroplasties for young subjects means that the choice of certain surgical techniques whose results are uncertain, preventing a rapid return to social life and sometimes modifying the shape of the upper extremity of the femur with the risk of limiting the chances of success of a subsequent hip replacement, should be avoided.

The object of all the surgical techniques is to relieve the often intense and incapacitating pain caused by osteonecrosis. They should also preserve the range of motion, often near to normal preoperatively.

Conservative techniques

Core decompression of the hip and derived techniques

All coring techniques are extra-articular, do not modify the initial range of joint motion and do not deform the upper extremity of the femur.

Core decompression

The initial technique consists in the resection of a cylindrical core 8 mm in diameter using a serrated trephine penetrating externally into the subtrochanteric region and going to the centre of the necrotic tissue in the subchondral zone, with the aim of decompression in a non extensible bone compartment.

 Procedure

With a percutaneous technique, per and postoperative haemorrhage is negligible, the procedure is not very painful, hospital stay is short, re-education not necessary, and patients are kept off weight-bearing for one month only (Figures 1 to 14).

Figure 1. Core decompression - dorsal decubitus position, monitoring AP X-ray.

Figure 2. 3/4 and lateral X-rays with hip in flexion.

Figure 3. 1 cm incision

Figure 4. Division of tissue with forceps.

Figure 5. 4.5 mm drill bit

Figure 6. Point of entry from the rear in line with the neck, above the thickening of the cortical bone. Gauze plugging of first cortical bone.

Figure 7. Reaming of drill hole at 10mm.

Figure 8. 8 mm trephine

Figure 9. Progressive penetration of the trephine, through percussion with hammer

Figure 10. ...alternating with rotating movements...

Figure 11. ... monitored by the AP amplifier...

Figure 12.  ... 3/4

Figure 13. ...and lateral views, up to the subchondral bone

Figure 14. Monitoring of coring position with CAT scan

Risks

Risk of infection is low. Perforation of the subchondral bone, of the whole necrotic zone, an iterative pertrochanteric fracture following minimal trauma if the point of penetration chosen is too low, are all possible, but not very frequent.

Results

From analysis of recent series with more than ten years follow-up of cases classified according to the ARCO international classification, which in some cases takes into account the volume of osteonecrosis, ⁽¹⁾ it is evident that core decompression is effective for attenuating or getting rid of pain and that the results of core decompression on the rate of radiological stabilisation and on survival without THR is better than that obtained simply by conservative treatment. The most reliable and most evocative criteria is prosthesis implantation: According to Scully the rate of survival is 100 % at stage I, 65% at stage II, 21% at stage III. ⁽²⁾ However, a recent study of 20 control cases at stage II followed up using criteria from MRI, x-ray and CAT scan every two months for two years concluded on a survival rate of 47%. ⁽³⁾.

Core decompression + cancellous autograft

Autografts enable you to both conduct bone rehabilitation and to induce it because they contain stem cells producing growth factors and in particular bone inducing proteins.

Procedure

The technique most used is that of conserving the distal part of the bone core corresponding to samples from the metaphysis and to impact it at the bottom of the coring tract. ⁽⁴⁾ It would appear to be more judicious to percutaneously harvest a cancellous autograft at the iliac crest, because the marrow of the iliac crest is richer than the marrow of the femur metaphysis in a patient with osteonecrosis (Figures 15, 16 and 17).

Figure 15. Harvesting of a cylinder of cancellous bone from the anterosuperior wing of the ilium using an 8mm trephine.

Figure 16. Trephine and extractor.

Figure 17. Graft in the necrotic zone (stage 3 Ficat-4 ARCO): the bone is pushed with the extractor to the proximal part of the tract.

Risks

To the risks of core decompression, need to be added scarring at the harvesting zone in the case of an iliac site, very moderate if a percutaneous technique is used.

Results

Many series do not distinguish between the results of core decompression and those of coring / bone graft; Steinberg grafts systematically after coring; his overall results are significantly better than those of others but it is not possible to say that this difference is directly related to the effect of the graft. ^{(4, 5)}

Core decompression + cortical allograft

The aim is not to obtain full rehabilitation of the cortical allograft which is very long and unpredictable, but to carry out elevation and support of the necrotic bone.

• Procedure: At the end of the procedure, a cortical allograft of fibula calibrated to the diameter of the 12mm coring hole is impacted to the subchondral bone.
• Risks: This technique introduces into the femur head a foreign body of human origin.
  
• Results: Few cases have been reported. It would however seem that the average period before collapse of the femoral head with passage from stage II to stage III is approximately 5 years. ⁽⁶⁾
  

Core decompression + injection of cement

Injection of cement in the coring tract, of the same type as that used in THR, is a technique whose principle remains that of elevating the necrotic segment.

• Procedure: Cement is injected using a cement syringe under pressure.
• Risks: The injection of cement under pressure runs the risk of a pulmonary embolism due to the cement and shock due to the cement as has been observed with cementing in hip arthroplasty. During its polymerisation, the heat given off by the cement is relatively high, from 60° to 90°, which can impair the proteins of collagen and the white non-germline cells remaining in the cancellous bone marrow under the necrotic zone.
• Results: This technique suggested by F. Bresler has not yet been the subject of any publications.
  

Core decompression + injection of bone marrow

The femoral heads of patients with necrosis are particularly poor in marrow. The object of transplantation of red bone marrow is to transplant osteogenic precursors and thus improve repopulation of the osteonecrotic bone ⁽⁷⁾. The aim of this procedure is to combine the pain relieving effect of core decompression with the osteo-inducing effect of the marrow.

• Procedure: The original procedure suggested by Philippe Hernigou consists in multiple coring with a 3 mm trocar in the necrotic zone. 300 ml of autologous marrow are reduced by centrifuging to approximately 40cc environ which will be injected through the coring holes into the head of the femur. This procedure is complex to carry out since you need to have the equipment and personnel necessary to do the centrifuging and it has to be done speedily to maintain full sterile precautions.
• Risks: The risks of infection are low if the technique is carried out with great care. Recovery is speedy.
• Results: P. Hernigou reports 200 cases of necrosis where 42 patients obtained a remission of more than 6 years with eight failures. ⁽⁸⁾
  

Core decompression + injection of bone-inducing proteins

Osteo-inducing proteins are produced by genetic engineering which ensures purity and sterility. ⁽⁹⁾ We can report the results of a pre-study carried out with the aim of assessing the addition of osteo-inducing proteins in a coring tract using Paul Ficat’s initial technique.

• Procedure: The protein dose was 0.1 ml mixed with autologous blood which, after coagulation was placed in the coring tract.
• Risks: the oncological risk of inducing proteins seems to be nil in view of the many experimental works which have not shown any evidence of chromosome anomalies with the multiplication of bone and cartilage cells in contact with inducing proteins. Ossifications, which do not incapacitate, can occur at the level of the coring hole through protein discharge. In the rh-BMP group, 33% of patients had an ectopic calcification, 21% in the control group.
• Results: 43 patients were included in the study, 24 with injection of rh-BMP2 and 19 controls with core decompression only. ⁽³⁾
  

Effect on pain: at 16 weeks the mean Harris score of all the patients was markedly improved, to 82 and 76.5 respectively.

Effect on volume of necrosis: in the rh-BMP2 group, volume of necrosis had decreased on average by 34%, in the control group it had increased on average by 28%, i.e. a difference of 62%. Progression of disease stage: In the rh-BMP2 group, 46% of patients stayed at the same stage of classification two years after inclusion, in the control group 26%. Rate of survival: in the rh-BMP2 group, 25% of patients required total hip arthroplasty, in the control group 47.4%. In relation to the initial volume of necrosis: Volume of necrosis > 60 % BMP 5/10 Controls 3/6; volume of necrosis < 60%, BMP 1/10 (10%), controls 4/9 (44%).

The addition of proteins therefore seems indicated in the treatment by core decompression in necroses at Ficat or ARCO stages I and II where the volume is under 60% of the total volume of the femoral head.

Core decompression + vascularized fibula graft

This technique consists in harvesting a cortical autograft of fibula with its arterial and venous pedicle with the aim of preserving the capital of living bone cells so that they play not just the role of support but also to induce the formation of bone locally.

• Procedure: A portion of fibula is inserted in a wide diameter core using the extra-articular approach and penetrates into the necrotic zone. The blood vessels are attached termino-laterally to the circumflex system (see elsewhere is this edition of Maitrise Orthopédique).
• Risks: This is a technically difficult surgical procedure taking up several hours by a well-trained team of surgeons. There is a price to pay for the removal of 10 cm of fibula. The vascularisation of the inserted piece of fibula is unpredictable, the graft then becoming a simple cortical autograft. Neck fractures have been described. ⁽¹⁰⁾
• Results: One study of 614 hips showed 89% survival without prosthesis at 5 years at Arlet-Ficat stage II and 81% at stage III. ⁽²⁾

Osteotomies

Osteotomies can be extra-articular or intra-articular. They all aim to move the compression load forwards or backwards depending on the technique used in order to decrease the risk of fracture. The disadvantage is that they modify the shape of the upper extremity of the femur, shrinking or lengthening which, depending on the type of osteotomy, can lead to greater or lesser difficulty in carrying out a subsequent primary hip replacement under ideal conditions (Figure 18).

Figure 18: An osteotomy must never compromise the possible subsequent requirement for arthroplasty by deforming the upper extremity of the femur.

Flexion osteotomies

This is an extra-articular trans-trochanteric osteotomy, the principle of which is anteflexion of the upper extremity of the femur, causing a forward rotation of from 20° to 40°. Some authors associate a varus effect or conversely a valgus effect, depending on the position of the graft.

* Risks: This type of procedure causes inward displacement and shrinking of 1 to 2 cm. It can also cause a loss of extension depending theoretically on the extent of flexion, i.e. from 20 to 40°, but in reality less through re-education.

* Results: This procedure is destined in particular for patients who have a well-localized, relatively small necrotic zone, positioned more to the front. The results on short series with 15 years follow-up are in the region of 50% survival but with evolution towards arthrosis in all cases. ^{(11, 12)}

Rotational osteotomies

Two techniques have been described. A forward rotational osteotomy of up to 90° has been proposed by Sugioka who has updated Kramer’s procedure. A backward rotational osteotomy has been proposed by Kempf. The aim is to remove the necrotic zone from the functional support zone of the “ball” of the hip, i.e. 20° either side of the apex. This procedure is aimed at necroses with a volume of not more than one-third the diameter of the femoral head, and preferably before collapse.

* The procedure: This is a surgically difficult technique which requires sectioning around the joint capsule flush with the acetabulum and a judicious choice of plane of bone cuts to avoid displacement, in particular in valgus. It requires trochanteric resection. Recovery involves around 15 days in hospital, followed by 4 months for consolidation and 6 months re-education in all.

* Risks: The risks are the same as for flexion osteotomies. In the case of failure, carrying out arthroplasty is complicated by the 90° rotation of the femur neck which modifies the line of penetration and the direction of the stem of the prosthesis. The hip is no longer in pristine condition which increases the risk of infection. Sectioning the pelvi-trochanteric muscles and the trochanteric resection weaken the stabilising muscles of the hip. Re-education is often lengthy to compensate for the sector of mobility amputated through the principle of the intervention.
* Results: The initial results mentioned by Sugioka were promising. However, those obtained by various other teams around the world who carried out this procedure in the 1980’s showed a high rate of failure, in particular when necrosis accounted for over 30 % of the surface. ^{(13, 14)}

Intra-articular arthroplasty

P. Hernigou suggests using an intra-articular approach to the necrotic zone on an orthopaedic table to restore approximate sphericity of the femoral head using a triangular pin and injection of cement into the dissected subchondral space. Weight-bearing is permitted from the 3rd day post-operatively with crutches abandoned on day 21.
* Risks: This procedure requires arthrotomy and traction on an orthopaedic table. There is a low risk of shock due to the cement.
* Results: The short-term results on pain seem to be good but the percentage of survival at 7 years is in the region of 25 %.

SURGICAL TECHNIQUES USING PROSTHESES

Partial resurfacing arthroplasty

The principle is to remove necrotic bone tissue and cartilage and the corresponding subchondral bone and to compensate the loss of bone and cartilage thus obtained with a partial femoral head implant stabilized with cement. This procedure requires great technical care and a good choice of implant. However, the procedure itself and recovery are as relatively simple as those for total hip replacements but with a lower risk of haemorrhage.

* Risks: Apart from a technical error at the time of positioning the implant, the main risk is that of early destabilisation of said implant due to insufficient support in the remaining bone of the femoral head or insufficient removal of necrotic bone tissue. Subsequently, evolution may be towards arthrosis, as in the case of Moore-type simple cephalic prostheses.

* Results: out of 37 cases with 26 stage III, 10 stage IV, 1 stage II and a mean follow-up of 49 months, 28 implants had been conserved of which 24 with excellent function. ^{(15, 16)}

Total hip replacement

Total hip replacement has been a solution used since the 1970’s to surgically treat necroses with collapse of the femur head from ARCO classification stage III. However, the first results were similar to those for arthroplasty in general. The implant models initially available did not offer great durability. Likewise, for identical models, the evolution of necroses was more unfavourable than that of arthroses. These results are in part due to the terrain, a young, still active patient or, conversely, an impaired terrain, depending on the origin of the necrosis. ⁽¹⁷⁾ It should also be noted that for young patients, in each period, the choice of the latest model implants was not always adequate, in particular in the case of cementless implants which may have compromised results. ⁽¹⁸⁾ At present, hip implant models are developing towards a general consensus whether for cemented or cementless implants. ⁽¹⁹⁾ To limit factors of gravity and increase the durability of the implants, the present tendency for young patients is to use cementless prostheses. Their stability is ensured by their anatomic shape and the effect of their microporous surface with a hydroxylapatite coating and the addition of a friction torque limiting micro-particles such as the metal-metal (metasul) or ceramic-ceramic type. With a reliable surgical technique, the latter can ensure a life-expectancy of several decades (Figures 19 and 20). However, the choice of a cemented stem component is judicious if the femur is very porotic or cylindrical (Figures 21 and 22).

Figure 19. Necrosis Ficat stage 3 –ARCO stage 4.

Figure 20. Cementless THR with Schuster-Omnicase metal-metal Metasul implant.

Figure 21. Bilateral necrosis Ficat stage 4 - Steinberg 5b. Cylindrical femur; Porotic bone.

Figure 22. Bilateral Schuster THR - Omnicase cemented stem

* Procedure: The acetabulum of patients with osteonecrosis of the femoral head does not have the hyperdensity of subchondral bone generally seen in arthrosis. Therefore, the surgeon should ream the acetabulum with prudence so as not to create an unnecessary loss of substance from the “ball” of the hip. Recovery in the case of a standard hip implant involves 15 days hospitalization, and return to domicile is then possible. Peroperative bleeding is moderate and can be compensated by an autotransfusion to avoid the risks of a homologous transfusion, combined eventually with peroperative safeguards. A return to work can be envisaged at the end of the third postoperative month.

* Risks: They are those of arthroplasties: nerve damage, dislocations, infections, loosening. However, today this procedure is commonplace. Most orthopaedic surgeons are trained to carry out the procedure which minimizes the risks. Carrying out an arthroplasty in a patient with necrosis of the femoral head is relatively more straightforward than for arthrosis, the hip remaining, in most cases, well centred and the bony acetabulum apparently intact.

* Results: the recent models of cemented or cementless anatomic implants are responsible for less than 1 % of thigh pain in the early years. The rate of infection is also under 1 %, the rate of dislocation varies from 1 to 3 % depending on the surgeon. The probable survival of these new models of implant is more than 20 years.

Indications

It is the existence or not of collapse of the subchondral bone which will condition the modalities of treatment.

When there is collapse of subchondral bone

Total hip replacement remains the most reliable procedure and the one most easily carried out by all orthopaedic surgeons.

- When there is a large volume of necrotic tissue or associated arthrosis, the indication for total hip replacement must be given with no reservations.

- When sphericity of the femoral head is mostly preserved despite the presence of a slight displacement or a cracked eggshell aspect, total hip replacement can remain systematically indicated in the case of high volume necrosis or for patients who are not able to put a stop to their professional lives for several months on end or to understand the risks of conservative surgery. In the other stage III cases with preservation of sphericity or slight displacement, it is also possible to turn to partial resurfacing arthroplasty,or a vascularized fibula graft, on condition that the technique is very careful and thorough. Osteotomies at this stage have unpredictable results which need to be balanced with deformation of the upper extremity which could influence the good results of a subsequent total hip replacement.

When there is no collapse of subchondral bone

Core decompression is a simple technique able to be carried out by all which provides good relief from pain but which leaves a high percentage of fractures in the early years following the procedure. Vascularized fibula grafting is the conservation technique which provides the best long-term results. However, it is a difficult technique, to be offered to patients only if one is certain of the quality of the procedure. The possibility of grafting the subchondral bone using the coring tract, with subsequent addition of bone marrow or bone-inducing proteins opens the door to conservation techniques which are reliable and accessible to all surgeons. The risk-benefit ratio would certainly be in their favour if proof of their effectiveness were given in the years to come.

Conclusion

For pre-fracture stages, core decompression and its alternatives remain accessible to all surgeons with acceptable results. When a subchondral fracture exists, the vascularized fibula graft seems to be the best conservative solution but at the price of a long and sophisticated procedure; hip replacement remains for many the most rapid and most reliable solution.