2. Pre-operative planning:
a. Exclusion of infection.
This should be carried out along conventional lines. It is often not possible to exclude infection pre-operatively, though every effortshould be made to do so.

b. Analysis of bone deficiencies
The site(s) of major bone stock loss in the femur should be clarified from X-rays, as far as possible, before surgery starts. For example, anterior femoral deficiencies are difficult to deal with unless the anterior aspect of the femur can be fully exposed.

c. Templating:
A.P. and Lateral Films should include the whole of the femoral component and should extend distally down to the normal diaphysis beyond the femoral component.

From these films are determined: (Fig. 1)

- The position and size of the distal plug. The plug should be placed at least 2cm beyond the most distal lytic area in the femur.

- The distance of the plug down the femoral canal against an appropriate anatomical landmark, e.g. the tip of the greater trochanter. The distance can be measured using the plug templates, and is used with the plug introducer and guide wire to position the plug at the appropriate depth.

The plug will need to be inserted at least 19cm from the proposed centre of the femoral head which is normally at the level of the tip of the greater trochanter.

- An estimate of the size of the Exeterª stem to be used. Superimpose the appropriate X-change¨ template on the plug template with the Exeter stem at the appropriate position. Final stem sizing is best delayed until the situation is clarified intra-operatively.

  
4. Surgical exposure via the posterior approach:
a. Incision:
The incision should be made through a pre-existing scar wherever possible. A long incision extending up the lateral aspect of the femur and extending posteriorly from the tip of the greater trochanter is favoured.

b. Fascial incision:
Initially this should be through an area of fascia lata that has not been involved in previous exposures of the hip. This may be very distal, but allows the development of the subfascial plane that is later important in repairing the fascia. The tendinous part of the gluteus maximus at its insertion into the femur always requires division in this approach.

c. Identification, exposure and protection of the sciatic nerve:
This is a wise step at this stage. Identification should start relatively distal, where the nerve is usually free of scar tissue, and proceed proximally. Where distal exposure is not feasible, the sciatic notch may be identified proximally, and the nerve found where it enters the notch, and then traced distally. The nerve may run a very tortuous course, and can be drawn up very close to the trochanteric ridge at times.

d. Aspiration of the hip:
This should be repeated at this stage to obtain fluid for gram stain in order to exclude the presence of excess neutrophils or organisms.

e. Capsular exposure and incision:
Generally, the capsule and remnants of the external rotators are incised with cutting diathermy close to their attachments to the posterior aspect of the trochanter and trochanteric ridge. They are reflected as a flap backwards from the femur, the proximal margin of the flap running along the lower border of gluteus minimus to the posterior margin of the socket,and the distal margin being the postero-inferior aspect of the capsule. Traction sutures can then be used to hold the flap back to the posterior margin of the fascia lata. Where the capsule is very thick and scarred, the deeper portions are excised, leaving a thinner flap that is very useful for reattachment to the femur during closure. The Psoas tendon should be released from the lesser trochanter.

f. Dislocation:
After the mobilisation of the posterior capsular flap, the head of the prosthesis is visible. Further superior, inferior and anterior resection continues with gradual and gentle mobilisation of the femur. A large blunt hook or long gauze swab can be passed around the neck of the prosthesis, and dislocation achieved by lifting the head and neck posteriorly using the hook or the swab, rather than by rotating the femur through the lower leg. With serious bone stock deficiencies, this phase of the operation carries a risk of fracture of the femur and great care is needed in achieving dislocation with generous soft tissue release as necessary, especially from the anterior aspect of the femoral neck.

6. Further mobilisation of the femur:
a. Circumferential capsulotomy:
Always essential to achieve adequate mobilisation and delivery of the proximal femur, with subsequent restoration of leg length. Superiorly and inferiorly this is usually straightforward. Often, with gross capsular thickening,much of the capsule requires excision rather than incision. Anteriorly, there may be more difficulty, especially where scarring has been marked. It is then wise to expose the anterior aspect of the femur, and excise the anterior capsule under direct vision.

b. Anterior exposure:

• Externally rotate the leg.
• A direct lateral approach is carried out in the conventional manner, taking care to protect the neurovascular bundle at the proximal end.
• Anterior femoral deficiencies can be exposed by reflecting the proximal part of quadriceps by taking it off the anterior aspect of the femur below the trochanteric level.

c. Proximal exposure of the femur:
The proximal part of the greater trochanter must be exposed sufficiently to allow the insertion of the guide wire down the medullary canal in the midline axis of the canal, and the subsequent insertion of the proximal impactor. This means the ‘neomedullary canal’ that is formed by the graft is in neutral alignment within the femur, and not in varus or valgus. The width of these instruments is such as to require opening of the proximal aspect of  the trochanter to approximately 1cm lateral to the midline axis of the canal, when this is projected proximally through the trochanteric region.

7. Preparation of the graft:
a. Fresh frozen cancellous allograft is recommended.
A,B,O compatibility between graft donor and recipient is not necessary. Rhesus compatibility is important when the patient is a Rhesus negative woman of child bearing age.Autogenous cancellous chips may be mixed with the allograft if the surgeon so wishes.

b. Allograft chips are prepared by passing the bone through a mill. The size of the chips that are needed is such as to give the compressed chips some ‘body’ (eg 4 – 6mm). Bone slurry is not satisfactory because its consistency is too low. Larger chips up to 10mm in size can be mixed with the smaller chips for packing of the proximal femoral canal around the phantom.

c. At least two femoral heads should be available, and more if femoral bone stock loss is severe and/or the acetabulum requires grafting

8. Preparation of the femoral canal:
a. Removal of cement:
Cement removal must be total with one exception: If the existing distal cement plug is greater than 2cm beyond the most distal lytic area in the femur and is solidly fixed, and there is definitely no infection, it may be left in position.

b. Removal of all granulomata and fibrous membrane:
This must be complete and thorough, and followed by copious irrigation of the canal. Membrane remnants should be used for frozen section and microbiological examination.

c. Repair of defects in the femur: (see section 9)
The success of this revision technique depends on adequate physical constraint for the graft.
Structural defects in the femoral diaphysis must therefore be made good before impacting the graft.
For technical details of the methods of repair, see appendix (below).

It is essential that the proximal femur is reconstructed up to a level that corresponds to the level of neck section preferred at a primary hip replacement. As a guide, the femoral component should never be positioned so that the lowest of the marks on the anterior and posterior aspects at the base of the neck lie above the level of the graft. (see section 9)

d. Prophylactic cerclage wiring of the femur:
This is recommended where the femoral cortex is especially flimsy. Under such circumstances, vigorous packing of the canal can produce a split in the diaphysis. This is more easily managed if cerclage wires have been applied before the split occurs. Overtightening of the wire may crush the femur when its structure is seriously compromised.

9. The repair of femoral cortical defects:
a. Diaphyseal defects:
If these are small and completely sealed at their margins by soft tissues, they can be ignored and simply packed with chips from within. Larger defects should be exposed surgically, their margins clearly defined, and all associated granulomatous material and fibrous tissue removed. These defects are repaired by using a combination of stainless steel mesh and cerclage wires. Once the defect has been closed in this way, the operation proceeds as though no defect were present. Cortical healing can be anticipated. Large defects particularly near the tip of the prosthesis, should be bridged either by a long stem implant, a femoral plate or strut grafts.

b. Metaphyseal defects:
These are best repaired following trial reduction, performing the reconstruction with the proximal impactor in position, ensuring an adequate gap between mesh and prosthesis.
The defect must be repaired in such a way that the proximal allograft chips can be fully constrained, and thus made capable of taking some load. This is achieved by applying the X-change® mesh, held in position with a suitable cerclage technique.(see appendix)

10. Distal occlusion of the femur: There are three possibilities:
a. Where a new (threaded) Intramedullary plug is to be used: (Fig. 3)
The threaded I.M. plug is screwed onto the guide wire. The plug introducer sleeve is passed over the guide rod. The guide rod introducer is then assembled onto the handle assembly and the plug is impacted to the appropriate level.

Typically, this should be to a depth of at least 19cm from the proposed centre of the femoral head and 2cm distal to the most distal lytic area, whichever is the greater. The minimum plug depth is marked on the guide wire.
The plug must be a tight fit.

b. Where there is a suitable cement plug which is to be left in situ: (ref: 8a) (Fig. 4)
The largest impactor that will fit is placed down to the level of the plug, to act as a drill centraliser. The I.M. drill is passed through the impactor and the cement drilled. The I.M. drill will require replacing after repeated use.
The guide wire is then passed through the impactor and screwed into the pre-drilled hole using the T-handle. The impactor is then removed.

c. Where a new (threaded) intramedullary plug is required beyond the isthmus:
A 2mm K-Wire is drilled through both cortices at the desired level. The pointed end of the X-change® plug is cut off to make a flat end. It is then inserted into the canal and placed on top of the K-Wire.

12.Impaction of the graft:
a. Wash and suck out the distal canal to remove any debris.

b. Sizing the distal impactors: (Fig. 5)
Before using the impactors to impact the bone chips, it is important to establish the distance that each size of impactor can be passed into the femoral canal without jamming against the walls of the canal. Driving the impactors beyond this point runs the risk of splitting the femur. Take each impactor in turn, pass it over the wire, noting the depth of insertion, by clipping a marker onto the groove opposite the tip of the greater trochanter, or equivalent mark. (Fig. 5a) Subsequently, when impacting the bone chips, do not drive each impactor beyond its marker clip (Fig. 6). (It will be necessary to replace the marker clips after repeated use).
If the plug is noticed to be migrating during impaction, as indicated by the depth markings on the guide wire, skewer it with a percutaneous K-Wire.

c. Introduce allograft chips proximally around the guide wire. Push as far distally as possible using your fingers then use the large impactors handheld to push the bone chips further down the canal. 1cm of graft should be packed on top of the plug by using the distal impactors by hand, before starting to use the sliding hammer. This prevents distal migration of the plug. At this stage, the impactor should be carried on the handle assembly and the sliding hammer should be used. (Fig. 7) Continue this process by introducing and impacting more chips, using progressively larger impactors in relation to canal diameter. Check the depth of the guide wire after each instrument has been used to make sure the plug is not migrating. Continue this process of packing until the distal impactor cannot be introduced beyond the ‘distal impaction’ line.* (Fig. 7-9)

* Note Distal Impaction Line

The surgeon should start using the proximal impactors when the distal impaction line is reached. This point is marked by the end of the polished area on the distal impactors (for standard length stems).
The distal impaction line is the depth that the tip of the stem will reach on implantation. For the core range of stems (with offsets of 37.5mm, 44mm and 50mm), the distal impaction line is 155mm from the eventual centre of the femoral head. For the 205mm Long Tapered Stem, the distal impaction line is at 205mm and this should be indicated by clipping a marker on the distal impactor in the groove immediately above the ‘20’ mark. For the smaller stems of offsets 30mm, 33mm and 35.5mm, three rings marked within the polished region indicate the respective lengths of these stems.

It is important not to continue with distal impaction other than by hand beyond the distal impaction line as this might make it impossible to insert the proximal impactor to the correct depth.

d. Mount the appropriate proximal impactor on the handle assembly and pass it over the guide wire. (Fig. 10)
Load graft into the proximal femur. Using the sliding hammer, drive the proximal impactor distally into the chips to force them up against the walls of the canal. Use the handle assembly to control the rotational position of the proximal impactor, and ensure that the ‘neo-medullary canal’ so formed is in the correct anteversion*. The proximal impactor should be driven vigorously into the chips. (Fig. 11)

e. Withdraw the proximal impactor from over the guide wire, insert more chips and then impact them, using the distal impactors by hand. (Fig. 12)

Continue to use the distal impactors by hand, alternating them with the proximal impactor, until you are happy that the graft in the mid-stem region is adequately packed.

f. As the canal is filled from below upwards, continue to insert the proximal impactor over the guide wire, and again drive the proximal impactor into the chips, using the sliding hammer. (Fig. 13)
The proximal impactor should now be getting tighter. If it is not then look for fractures.

g. The proximal impactor should be driven into the desired depth as indicated by templating. Final proximal packing is achieved using the block and ‘half moon’ impactors. Larger chips should be mixed with the smaller chips. (Figs. 14 & 15)
If the graft is so tight that the proximal impactor cannot be introduced fully, use one size smaller for final impaction. Select the stem size on the basis of the size of the proximal impactor that is used for the final packing.

h. The surgeon must ensure absolute axial and torsional stability of the proximal impactor at the conclusion of packing. It is emphasised that it should be impossible to withdraw the proximal impactor without using the sliding hammer. (Fig. 16)

i. It is normally possible to do a trial reduction with the guide wire in place. If not possible then the guide wire is unscrewed from the plug and withdrawn from the femur. (Fig. 17)
* Note that the small guide rod from the Exeter™ cup introducer may be inserted into the threaded hole in the upper flange of the handle to improve assessment of anteversion.

13.Trial reduction:
This allows assessment of stability and leg length, and acts as a further guide for the depth of stem insertion.

a. The hip is reduced with the appropriate trial head in place. (Fig. 18)

b. Any changes to the depth of insertion of the stem can now be estimated by the relative leg lengths of the patient. If the leg is short, impaction is continued to further build up the femur.

c. Carefully redislocate the hip. Remove the trial head.

d. Once you are happy with your stem position and trial reduction, remove the guide wire using the ‘T’ handle.

e. If a metaphyseal defect is present, this is the appropriate time to apply X-change® mesh.

f. Attach a spigot protector accurately over the trial stem spigot, and assemble the stem introducer (with leg-length gauge) onto it. (Fig. 19)

g. Adjust the “traveller” on the leg-length gauge to a convenient position in relation to the upper end of the femur.

h. Mark the position of the distal end of the “traveller” on the femur by marking with diathermy and methylene blue dye. The mark on the femur not only helps achieve the desired leg length but is a useful guide to indicating correct alignment. The “traveller” will not be parallel to the mark if the stem is in varus or valgus.

i. In addition, the marks on the stem can also be used to gauge and check stem insertion depth.

j. Carefully remove the stem introducer, and avoid disturbing the position of the leg-length gauge.

k. Ensure that the connection on the shoulder of the proximal impactor is clear of bone graft debris or soft tissue and replace the impactor connector in preparation for removal of the proximal impactor prior to cement insertion. (Fig. 20)

14.Cement insertion and stem introduction:
a. Leave the impactor in position until just before cement insertion. This keeps the graft compressed and the canal can be sucked dry by a catheter placed down the trial lumen.

b. Remove the wings from the Exeter™ stem centraliser and hold it in position on the stem tip. (Fig. 21). V40™ stems are packaged with a winged and wingless centraliser.

c. Insert Simplex® cement retrograde from the cement gun, using the tapered gun spout (Fig.22).
The time of insertion will depend upon the type of cement being used. Relatively low viscosity cement is recommended, to ensure adequate penetration of the graft. Two 40g mixes of Simplex are required to allow adequate cement for continuous pressurisation prior to stem insertion.

d. Once the canal has been filled retrograde, apply the proximal femoral seal, cut off the nozzle at the level of the seal and  pressurise the Simplex cement into the graft. (Fig. 23)

e. Maintain pressurisation until the viscosity of the Simplex cement is appropriate for stem insertion.

f. Insert the Exeter™ stem to its predetermined position by using the leg-length gauge. Attention must be paid to the alignment of the stem during insertion. (Fig. 24) The surgeon must use his thumb to occlude the exit from the medullary canal on the medial side of the stem, and thus maintain pressure on the cement throughout insertion.

g. As soon as the desired insertion depth is achieved, the stem introducer is removed. Apply the stem seal around the proximal stem, and maintain pressure on the seal until the cement has polymerised, ensuring that the stem does not back out during polymerisation. (Fig. 25)

Indication
The X-change® Revision Instruments System for Long Stems is supplied as an extension to the basic X-change technique to be used in conjunction with an Exeter™ Long Stem for cases with lysis or bone stock deficiency at or beyond the tip of a primary length Exeter stem.

There are two types of Exeter Long Stem: those based on the 44mm offset No. 3 stem with a cylindrical extension to give lengths of 200mm, 220mm, 240mm and 260mm; and the 205mm  fully Tapered Long Stem (based on the 44mm offset No. 2 stem). The X-change Revision Instruments System for Long Stems may be used for the 205mm Long Tapered Stem and the full range of Long Stems.

Preparation and distal impaction for 200, 220, 240 and 260mm Exeter™ Long Stems
The surgical protocol is identical to that for the basic X-change Revision Instruments System up to and including impaction of the graft to the 'distal impaction line'. However, the X-change Long Stem Guide Wire, which has a smaller diameter than the Standard Guide Wire for use with the Graft Corer, must be used. It can be recognised by its length and the area of polishing below the first mark at 19cm. As with the primary instruments, the Intramedullary Plug should be inserted to a depth 2cm distal to the tip of the stem to be used (Fig 1).

With the X-change® Revision Instruments System for Long Stems, impaction of the graft to the 'distal impaction line' (Fig2a) is carried out for all types of Long Stem. Proximal impaction is then carried out before making a space for the distal cylindrical portion of the stem.

Proximal impaction for 200mm, 220mm, 240mm and 260mm Exeter™ Long Stems
Mount the X-change Proximal Starter Impactor on the Handle Assembly and thread it over the Guide Wire. Using the Sliding Hammer, drive the Proximal Impactor distally into the chips to force them up against the walls of the canal (Fig 2b). Use the Handle Assembly to control the rotational position of the Proximal Impactor, and ensure that the 'neo-medullary canal' so formed is in the correct anteversion. The Proximal Starter Impactor should be driven vigorously into the chips. If proximal bone quality is poor, a cerclage wire should be placed around the calcar before proximal impaction.

Withdraw the Proximal Starter Impactor from over the Guide Wire, insert more chips and then impact them, using the Distal Impactors by hand.

Continue to use the Distal Impactors by hand, alternating them with the Proximal Starter Impactor attached to the Sliding Hammer.

The Proximal Starter Impactor should now be getting tighter. If it is not then look for fractures and fix as appropriate with cerclage wires to achieve stability. Impaction should continue until the Proximal Starter Impactor is absolutely rigid in the neomedullary canal.

The Proximal Starter Impactor should be driven into the desired depth as indicated by templating. At this stage it is useful to perform a preliminary trial reduction.

Coring of cylinder for distal portion of Long Stem
The X-change® Graft Corer should now be assembled. Thread the Graft Corer over the Guide Wire and push the internal piston down until the locking nut touches the handle. Advance the Graft Corer into the graft by hand with an oscillating rotary motion of about half a turn in one direction and then the other. As the Graft Corer descends and fills with graft, the piston will rise (Fig 2c). When a mark on the shaft of the piston becomes visible, withdraw the Graft Corer and expel the graft by depressing the piston (often a Mallet is needed), taking care to retain the graft for later use. Re-insert the Graft Corer and continue to advance to the required depth.

Depth marks are provided on the Graft Corer corresponding to the length of stem which is to be implanted. The mark should be aligned with the tip of the greater trochanter, or equivalent mark identifying the final position of the femoral head. The marks for the long stems are identified by the length of the stem.

A single mark at 205mm is given for both the 200mm Long Stem and the 205mm Long Tapered Stem.

When graft has been removed to the correct depth, withdraw the Graft Corer, mount the appropriate long stemmed Proximal Impactor on the Handle Assembly and thread it over the Guide Wire. Insert the Proximal Impactor to the required depth in the 'neo-medullary' canal already formed (Fig 2d). If necessary, add more graft to the canal and impact with the Proximal Impactor to raise it to the required depth if this is not at first achieved. Re-use the pellets of graft from the Graft Corer as required. After sound impaction, the Proximal Impactor can only just reach the desired depth, back off the impactor 1-2cm and using the ‘half moon’ impactors. Pack large bone chips around the Proximal Impactor. Again, hammer the Proximal Impactor to its fully seated position and continue the proximal packing.

The surgeon must ensure absolute axial and torsional stability of the Proximal Impactor at the conclusion of packing. It should be emphasised that it must be impossible to withdraw the Proximal Impactor without using the Sliding Hammer.

It is usually possible to do a trial reduction with the Guide Wire in place. If this is not possible, then the connector is removed and the Guide Wire is unscrewed from the plug and withdrawn from the femur.

Return to the surgical protocol for the basic

X-change® Revision Instruments System for guidance on the trial reduction and the subsequent operative steps.

Impaction technique for 205mm Fully Tapered Long Stem
Follow the impaction technique for the standard instruments up to the 'distal impaction line' (Fig 4a).

Assemble the X-change® Graft Corer. Thread the Graft Corer over the Guide Wire and push the internal piston down until the Locking Nut touches the handle. Advance the Graft Corer into the graft by hand with an oscillating rotary motion of about half a turn in one direction and then the other. As the Graft Corer descends and fills with graft, the piston will rise (Fig 4b). When a mark on the shaft of the piston becomes visible, withdraw the Graft Corer and expel the graft by depressing the piston, taking care to retain the graft for later use. Re-insert the Graft Corer and continue to advance to the required depth.

Depth marks are provided on the Graft Corer corresponding to the length of stem which is to be implanted. The mark should be aligned with the tip of the greater trochanter, or equivalent mark identifying the final position of the femoral head. The marks for the long stems are identified by the length of the stem. A single mark at 205mm is given for both the 200mm Long Stem and the 205mm Long Tapered Stem (marks are also provided for shorter stems but these are not relevant to the present technique).

When graft has been removed to the correct depth, withdraw the Graft Corer, mount the appropriate Proximal Impactor on the Handle Assembly and thread it over the Guide Wire (Fig 4c).

Continue with the technique for proximal impaction outlined in the surgical protocol for the basic X-change® Revision Instruments System.

Indications for the use of Long Stems
The long stem should be used to bypass areas of lysis, poor bone quality or fracture.

The 205mm fully tapered Long Stem can be used for the indication of bypassing weakened areas of bone. It is not appropriate to use this stem in cases of femoral fracture. In addition, if there is a danger that the distal portion of the stem may be more rigidly fixed than the proximal portion, then the use of this stem is contra-indicated. This situation may occur, for instance, where there is a tight diaphysis beneath an expanded proximal femur, the latter having resulted from endosteal lysis around a shorter stem. In these cases it may be appropriate to ream up the diaphysis to allow for a complete mantle of graft around the 205mm Long Stem. If there has been inadequate packing of the proximal femur there is a danger that the distal portion of the stem may be more rigidly fixed than the proximal portion. If this situation is allowed to occur then there is a danger that the fully tapered long stem may fracture. It is essential that packing of the proximal femur should result in absolute axial and torsional stability of the implant.